Adhesion molecule knockouts: one step forward and one step backward.

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P A Ward

Somatic cell gene therapy for a trait as complex as hypertension?

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J A Martinez, D T O'Connor

Impaired muscle fat metabolism: a cause or effect of visceral obesity?

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R R Henry

Gap junction-mediated cell-to-cell communication in bovine and human adrenal cells. A process whereby cells increase their responsiveness to physiological corticotropin concentrations.

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We have studied the role of gap junction-mediated intercellular communication on the steroidogenic response of bovine (BAC) and human (HAC) adrenal fasciculo-reticularis cells in culture to corticotropin (ACTH). Indirect immunofluorescence analyses showed that intact human and bovine adreno-cortical tissue as well as HAC and BAC in culture expressed the gap junction protein connexin43 (also termed alpha 1 connexin). Both HAC and BAC were functionally coupled through gap junctions as demonstrated by microinjection of a low molecular mass fluorescent probe, Lucifer yellow. The cell-to-cell transfer of the probe was blocked by 18 alpha-glycyrrhetinic acid (GA), an inhibitor of gap junction-mediated intercellular communication. GA markedly decreased the steroidogenic response (cortisol production) of both HAC and BAC to low (10 pM) but not to high (5 nM) concentrations of ACTH. GA had no inhibitory effect on the steroidogenic response to 8 Br-cAMP (at either low or high concentrations) and did neither modify the binding of 125I-ACTH to its receptor nor the ACTH-induced cAMP production. BAC cultured at high or low cell densities (2.4 x 10(5) vs. 0.24 x 10(5) cells/cm2) exhibited distinct levels of intercellular communication and were differently responsive to sub-maximal ACTH concentrations. The ACTH ED50 values for cortisol production were 8.5 +/- 1.3 and 45 +/- 14 pM (P < 0.02) for BAC cultured at high and low density, respectively. In the presence of GA, there was a shift of the ACTH concentration-response curves in the two culture conditions. The ACTH ED50 of high density and low density cultured BAC increased 25- and 5-fold, respectively, and became similar (220 +/- 90 and 250 +/- 120 pM). These results demonstrate that gap junction-mediated communication between hormone-responsive and nonresponsive cells is one mechanism by which adrenal cells increase their responsiveness to low ACTH concentrations.

Authors

Y Munari-Silem, M C Lebrethon, I Morand, B Rousset, J M Saez

Alkaline phosphatase: placental and tissue-nonspecific isoenzymes hydrolyze phosphoethanolamine, inorganic pyrophosphate, and pyridoxal 5'-phosphate. Substrate accumulation in carriers of hypophosphatasia corrects during pregnancy.

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Hypophosphatasia features selective deficiency of activity of the tissue-nonspecific (liver/bone/kidney) alkaline phosphatase (ALP) isoenzyme (TNSALP); placental and intestinal ALP isoenzyme (PALP and IALP, respectively) activity is not reduced. Three phosphocompounds (phosphoethanolamine [PEA], inorganic pyrophosphate [PPi], and pyridoxal 5'-phosphate [PLP]) accumulate endogenously and appear, therefore, to be natural substrates for TNSALP. Carriers for hypophosphatasia may have decreased serum ALP activity and elevated substrate levels. To test whether human PALP and TNSALP are physiologically active toward the same substrates, we studied PEA, PPi, and PLP levels during and after pregnancy in three women who are carriers for hypophosphatasia. Hypophosphatasemia corrected during the third trimester because of PALP in maternal blood. Blood or urine concentrations of PEA, PPi, and PLP diminished substantially during that time. After childbirth, maternal circulating levels of PALP decreased, and PEA, PPi, and PLP levels abruptly increased. In serum, unremarkable concentrations of IALP and low levels of TNSALP did not change during the study period. We conclude that PALP, like TNSALP, is physiologically active toward PEA, PPi, and PLP in humans. We speculate from molecular/crystallographic information, indicating significant similarity of structure of the substrate-binding site of ALPs throughout nature, that all ALP isoenzymes recognize these same three phosphocompound substrates.

Authors

M P Whyte, M Landt, L M Ryan, R A Mulivor, P S Henthorn, K N Fedde, J D Mahuren, S P Coburn

Overexpression of the rat inducible 70-kD heat stress protein in a transgenic mouse increases the resistance of the heart to ischemic injury.

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Myocardial protection and changes in gene expression follow whole body heat stress. Circumstantial evidence suggests that an inducible 70-kD heat shock protein (hsp70i), increased markedly by whole body heat stress, contributes to the protection. Transgenic mouse lines were constructed with a cytomegalovirus enhancer and beta-actin promoter driving rat hsp70i expression in heterozygote animals. Unstressed, transgene positive mice expressed higher levels of myocardial hsp70i than transgene negative mice after whole body heat stress. This high level of expression occurred without apparent detrimental effect. The hearts harvested from transgene positive mice and transgene negative littermates were Langendorff perfused and subjected to 20 min of warm (37 degrees C) zero-flow ischemia and up to 120 min of reflow while contractile recovery and creatine kinase efflux were measured. Myocardial infarction was demarcated by triphenyltetrazolium. In transgene positive compared with transgene negative hearts, the zone of infarction was reduced by 40%, contractile function at 30 min of reflow was doubled, and efflux of creatine kinase was reduced by approximately 50%. Our findings suggest for the first time that increased myocardial hsp70i expression results in protection of the heart against ischemic injury and that the antiischemic properties of hsp70i have possible therapeutic relevance.

Authors

M S Marber, R Mestril, S H Chi, M R Sayen, D M Yellon, W H Dillmann

Regulation of G-protein alpha i2 subunit expression by oxidized low-density lipoprotein.

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Oxidized low-density lipoprotein (LDL) inhibits signalling pathways mediated by pertussis toxin-sensitive guanine nucleotide-binding proteins (Gi proteins). To determine whether this inhibition is due to altered G protein alpha i subunit expression, mRNA and protein levels of alpha i isoforms were assessed in bovine aortic endothelial cells treated with oxidized LDL (0-100 micrograms/ml, 0-72 h). Oxidized LDL did not affect the expression of alpha i3, but did cause time- and concentration-dependent decrease in alpha i2 mRNA and protein resulting in a 3.2- and 3.5-fold reduction, respectively, after 72 h. This decrease in alpha i2 coincided with a 86% decrease in alpha i2 GTPase activity. Nuclear run-off studies did not show any significant effect of oxidized LDL on alpha i2 or alpha i3 transcription. In the presence of actinomycin D, oxidized LDL shortened the t1/2 of alpha i2 mRNA from 16 h to 8 h which was attenuated by cycloheximide. In addition, pulse-chase labelling with [35S]methionine revealed that oxidized LDL reduced the t1/2 of alpha i2 protein from 27 to 14 h. Our results indicate that oxidized LDL can modulate receptor-Gi coupling by downregulating the expression of alpha i2, but not alpha i3. The mechanism involves both mRNA destabilization and protein degradation.

Authors

J K Liao, S L Clark

24-hour glucose profiles during continuous or oscillatory insulin infusion. Demonstration of the functional significance of ultradian insulin oscillations.

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Under basal and stimulated conditions, normal insulin secretion oscillates with periods in the ultradian 100-150-min range. To test the hypothesis that oscillatory insulin delivery is more efficient in reducing blood glucose levels than continuous administration, nine normal young men were each studied on two occasions during a 28-h period including a period of polygraphically recorded sleep. Endogenous insulin secretion was suppressed by somatostatin, a constant intravenous glucose infusion was administered, and exogenous insulin was infused either at a constant rate or in a sinusoidal pattern with a period of 120 min. The mean glucose level over the 28-h period was 0.72 +/- 0.31 mmol/liter lower when insulin was infused in an oscillatory pattern than when the rate of infusion was constant (P < 0.05). The greater hypoglycemic effect of oscillatory versus constant infusion was particularly marked during the daytime, with the difference averaging 1.04 +/- 0.38 mmol/liter (P < 0.03). Serum insulin levels tended to be lower during oscillatory than constant infusion, although the same amount of exogenous insulin was administered under both conditions. Ultradian insulin oscillations appear to promote more efficient glucose utilization.

Authors

J Sturis, A J Scheen, R Leproult, K S Polonsky, E van Cauter

Ethanol impairs post-prandial hepatic protein metabolism.

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The effects of acute ethanol ingestion on whole body and hepatic protein metabolism in humans are not known. To simulate social drinking, we compared the effects of the association of a mixed meal (632 kcal, 17% amino acids, 50% glucose, 33% lipids) with a bottle of either table wine (ethanol content 71 g) or water on the estimates ([1-14C]-leucine infusion) of whole body protein breakdown, oxidation, and synthesis, and on the intravascular fractional secretory rates (FSR) of hepatically (albumin, fibrinogen) and extrahepatically (IgG) synthesized plasma proteins in two randomized groups (ethanol n = 7, water n = 7) of healthy nonalcoholic volunteers. Each study was carried out for 8 h. Protein kinetics were measured in the overnight post-absorptive state, over the first 4 h, and during a meal infusion (via a nasogastric feeding tube at constant rate) combined with the oral ingestion of wine or water, over the last 4 h. When compared with water, wine ingestion during the meal reduced (P < 0.03) by 24% the rate of leucine oxidation, did not modify the estimates of whole body protein breakdown and synthesis, reduced (P < 0.01) by approximately 30% the FSR of albumin and fibrinogen, but did not affect IgG FSR. In conclusion, 70 g of ethanol, an amount usual among social drinkers, impairs hepatic protein metabolism. The habitual consumption of such amounts by reducing the synthesis and/or secretion of hepatic proteins might lead to the progressive development of liver injury and to hypoalbuminemia also in the absence of protein malnutrition.

Authors

P De Feo, E Volpi, P Lucidi, G Cruciani, F Monacchia, G Reboldi, F Santeusanio, G B Bolli, P Brunetti

Intracellular acidification associated with changes in free cytosolic calcium. Evidence for Ca2+/H+ exchange via a plasma membrane Ca(2+)-ATPase in vascular smooth muscle cells.

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The purpose of this study was to define the mechanism whereby agonists that increase free cytosolic calcium (Cai2+) affect intracellular pH (pHi) in smooth muscle. Rat aortic vascular smooth muscle cells grown on coverslips were loaded with BCECF/AM or fura-2/AM for continuous monitoring of pHi or Cai2+, respectively, in a HCO3-/CO2- containing medium. Recovery from rapid increases in Cai2+ produced by 1 microM angiotensin (Ang) II (delta Cai2+ -229 +/- 43 nM) or 1 microM ionomycin (delta Cai2+ -148 +/- 19 nM) was accompanied by a fall in pHi (delta pHi, -0.064 +/- 0.0085 P < 0.01, and -0.05 +/- 0.012 pH units, P < 0.01, respectively). Neither the fall in pHi nor the rise in Cai2+ elicited by Ang II was prevented by pretreatment with agents which block the action of this agonist on pHi via the stimulation of the Cl/HCo3 exchangers (DIDS, 50 microM) or the Na+/H+ antiporter (EIPA, 50 microM). In the presence of DIDS and EIPA, Ang II produced a fall in pHi (delta pHi, -0.050 +/- 0.014, P < 0.01) and a rise in Cai2+ (delta Ca2+ 252 +/- 157 nM, P < 0.01). That the change in pHi was secondary to changes in Cai2+ was inferred from the finding that, when the rise in Cai2+ elicited by Ang II was prevented by preincubation with a Ca2+ buffer, BAPTA (60 microM), the fall in pHi was abolished as well (delta pHi, 0.0014 +/- 0.0046). The pHi fall produced by Ang II and ionomycin was prevented by cadmium at a very low concentration (20 nM) which is known to inhibit plasma membrane Ca(2+)-ATPase activity (delta pHi -0.002 +/- 0.0006 and -0.0016 pH units, respectively). Cadmium also blunted Cai2+ recovery after Ang II and ionomycin. These findings suggest that the fall in pHi produced by these agents is due to H+ entry coupled to Ca2+ extrusion via the plasma membrane Ca(2+)-ATPase. Our results indicate that agonists that increase Cai2+ cause intracellular acidification as a result of Ca2+/H+ exchange across the plasma membrane. This process appears to be mediated by a plasma membrane Ca(2+)-ATPase which, in the process of extruding Ca2+ from the cell, brings in [H+] and thus acidifies the cell.

Authors

J T Daugirdas, J Arrieta, M Ye, G Flores, D C Battle

The effect of cyclic-AMP on the regulation of c-myc expression in T lymphoma cells.

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Myc is implicated in the control of growth in a variety of cell types. I investigated c-myc gene expression in several lymphoid cell lines to determine the response to cyclic AMP. Cyclic AMP causes a precipitous decline in c-myc message concentration that precedes G1 cell cycle arrest in wild type S49 cells but not in KIN- cells that lack cAMP dependent PKA activity. In wild-type S49 cells washout of cyclic AMP restores c-myc message levels within 2 h but does not relieve the G1 arrest until 10 h later. Transcription runoff studies demonstrate inhibition of both transcriptional initiation and prolongation of initiated transcripts. However, the degree of inhibition is insufficient to explain the absence of detectable myc message suggesting that the predominant effect of cyclic AMP is to destabilize the c-myc message. In contrast to wild-type cells, the "Deathless" mutant S49 cell line is viable when arrested in G1 by exposure to cyclic AMP and has preserved c-myc expression. Thus, in S49 cells down regulation of c-myc expression appears to be associated with loss of viability rather than G1 cell cycle arrest. Interestingly, CEM human T lymphoma cells do not arrest in G1 phase when exposed to cyclic AMP in spite of losing detectable c-myc gene expression. This suggests that in some T lymphoma cells c-myc gene expression may not be necessary for cell cycle progression and proliferation.

Authors

D A Albert

Unexpected inhibition of cholesterol 7 alpha-hydroxylase by cholesterol in New Zealand white and Watanabe heritable hyperlipidemic rabbits.

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We investigated the effect of cholesterol feeding on plasma cholesterol concentrations, hepatic activities and mRNA levels of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase and hepatic LDL receptor function and mRNA levels in 23 New Zealand White (NZW) and 17 Watanabe heritable hyperlipidemic (WHHL) rabbits. Plasma cholesterol concentrations were 9.9 times greater in WHHL than NZW rabbits and rose significantly in both groups when cholesterol was fed. Baseline liver cholesterol levels were 50% higher but rose only 26% in WHHL as compared with 3.6-fold increase with the cholesterol diet in NZW rabbits. In both rabbit groups, hepatic total HMG-CoA reductase activity was similar and declined > 60% without changing enzyme mRNA levels after cholesterol was fed. In NZW rabbits, cholesterol feeding inhibited LDL receptor function but not mRNA levels. As expected, receptor-mediated LDL binding was reduced in WHHL rabbits. Hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels were 2.8 and 10.4 times greater in NZW than WHHL rabbits. Unexpectedly, cholesterol 7 alpha-hydroxylase activity was reduced 53% and mRNA levels were reduced 79% in NZW rabbits with 2% cholesterol feeding. These results demonstrate that WHHL as compared with NZW rabbits have markedly elevated plasma and higher liver cholesterol concentrations, less hepatic LDL receptor function, and very low hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels. Feeding cholesterol to NZW rabbits increased plasma and hepatic concentrations greatly, inhibited LDL receptor-mediated binding, and unexpectedly suppressed cholesterol 7 alpha-hydroxylase activity and mRNA to minimum levels similar to WHHL rabbits. Dietary cholesterol accumulates in the plasma of NZW rabbits, and WHHL rabbits are hypercholesterolemic because reduced LDL receptor function is combined with decreased catabolism of cholesterol to bile acids.

Authors

G Xu, G Salen, S Shefer, G C Ness, L B Nguyen, T S Parker, T S Chen, Z Zhao, T M Donnelly, G S Tint

Glutamate decarboxylase-, insulin-, and islet cell-antibodies and HLA typing to detect diabetes in a general population-based study of Swedish children.

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Most autoimmune diabetes occurs in those without a diabetic relative, but few cases are identifiable prospectively. To model general population prediction, 491 consecutive newly diabetic children from all of Sweden were tested for autoantibodies to glutamate decarboxylase (GAD65ab), insulin (IAA), and islet cells (ICA), and for HLA-DQ genotypes by PCR; 415 matched control children were tested in parallel. GAD65ab sensitivity/specificity was 70/96%, versus 84/96% for ICA, 56/97% for IAA, 93/93% (any positive), 39/99.7% (all positive), and 41/99.7% (GAD65ab plus IAA). The latter's 25% predictive value was not improved by requiring concomitant high-risk HLA genotypes. GAD65ab were associated with DQA1*0501/B1*0201 (DQ2; P = 0.007) but not DQA1*0301/B1*0302 (DQ8), and IAA with DQA1*0301/B1*0302 (DQ8; P = 0.03) but not DQA1*0501/B1*0201 (DQ2). GAD65ab were more prevalent in females than males (79 vs. 63%; P < 0.0001) but did not vary with onset age nor season. Combining the three antibody assays yielded sufficient sensitivity for screening. GADab were relatively sensitive/specific for diabetes, but even with HLA marker combinations yielded predictive values insufficient for early immunointervention in the low-prevalence general population.

Authors

W A Hagopian, C B Sanjeevi, I Kockum, M Landin-Olsson, A E Karlsen, G Sundkvist, G Dahlquist, J Palmer, A Lernmark

Glycemic improvement in diabetic db/db mice by overexpression of the human insulin-regulatable glucose transporter (GLUT4).

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The effects of increased GLUT4 (insulin-regulatable muscle/fat glucose transporter) expression on glucose homeostasis in a genetic model of non-insulin-dependent diabetes mellitus were determined by expressing a human GLUT4 transgene (hGLUT4) in diabetic C57BL/KsJ-db/db mice. A genomic hGLUT4 construct was microinjected directly into pronuclear murine embryos of db/+ matings to maintain the inbred background. Four lines of hGLUT4 transgenic mice were bred to homozygosity at the db locus and all showed a marked reduction of both fasted and fed plasma glucose levels (to approximately 50 and 360 mg/dl, respectively) compared with age-matched nontransgenic db/db mice (approximately 215 and 550 mg/dl, respectively), as well as an enhanced disposal of an oral glucose challenge. In situ immunocytochemical localization of GLUT4 protein in muscle from hGLUT4 db/db mice showed elevated plasma membrane-associated GLUT4 protein in the basal state, which markedly increased after an insulin/glucose injection. In contrast, nontransgenic db/db mice had low levels of plasma membrane-associated GLUT4 protein in the basal state with a relatively small increase after an insulin/glucose challenge. Since the intracellular GLUT4 levels in db/db mice were similar to nontransgenic db/+ mice, the glucose transport defect in db/db mice is at the level of glucose transporter translocation. Together, these data demonstrate that GLUT4 upregulation overcomes the glucose transporter translocation defect and alleviates insulin resistance in genetically diabetic mice, thus resulting in markedly improved glycemic control.

Authors

E M Gibbs, J L Stock, S C McCoid, H A Stukenbrok, J E Pessin, R W Stevenson, A J Milici, J D McNeish

Effects of angiotensin II generated by an angiotensin converting enzyme-independent pathway on left ventricular performance in the conscious baboon.

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Human chymase is a serine proteinase that converts angiotensin (Ang) I to Ang II independent of angiotensin converting enzyme (ACE) in vitro. The effects of chymase on systemic hemodynamics and left ventricular function in vivo were studied in nine conscious baboons instrumented with a LV micromanometer and LV minor axis and wall thickness sonomicrometer crystal pairs. Measurements were made at baseline and after [Pro11DAla12] Ang I, a specific substrate for human chymase, was given in consecutive fashion as a 0.1 mg bolus, an hour-long intravenous infusion of 5 mg, a 3 mg bolus, and after 5 mg of an Ang II receptor antagonist. [Pro11DAla12]Ang I significantly increased LV systolic and diastolic pressure, LV end-diastolic and end systolic dimensions and the time constant of LV relaxation and significantly decreased LV fractional shortening and wall thickening. Administration of a specific Ang II receptor antagonist reversed all the hemodynamic changes. In separate studies, similar results were obtained in six of the baboons with ACE blockade (20 mg, intravenous captopril). Post-mortem studies indicated that chymase-like activity was widely distributed in multiple tissues. Thus, in primates, Ang I is converted into Ang II by an enzyme with chymase-like activity. This study provides the first in vivo evidence of an ACE-independent pathway for Ang II production.

Authors

B D Hoit, Y Shao, A Kinoshita, M Gabel, A Husain, R A Walsh

Distinctive anatomical patterns of gene expression for cGMP-inhibited cyclic nucleotide phosphodiesterases.

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Type III cGMP-inhibited phosphodiesterases (PDE3s) play important roles in hormonal regulation of lipolysis, platelet aggregation, myocardial contractility, and smooth muscle relaxation. We have recently characterized two PDE3 subtypes (PDE3A and PDE3B) as products of distinct but related genes. To elucidate their biological roles, in this study we compare cellular patterns of gene expression for these two enzymes during rat embryonic and postnatal development using in situ hybridization. PDE3B [corrected] mRNA is abundant in adipose tissue and is also expressed in hepatocytes throughout development. This mRNA is also highly abundant in embryonic neuroepithelium including the neural retina, but expression is greatly reduced in the mature nervous system. Finally, PDE3B [corrected] mRNA is localized in spermatocytes and renal collecting duct epithelium in adult rats. PDE3B mRNA is highly expressed in the cardiovascular system, including myocardium and arterial and venous smooth muscle, throughout development. It is also abundant in bronchial, genitourinary and gastrointestinal smooth muscle and epithelium, megakaryocytes, and oocytes. PDE3A [corrected] mRNA demonstrates a complex, developmentally regulated pattern of gene expression in the central nervous system. In summary, the two different PDE3s show distinctive tissue-specific patterns of gene expression suggesting that PDE3B [corrected] is involved in hormonal regulation of lipolysis and glycogenolysis, while regulation of myocardial and smooth muscle contractility appears to be a function of PDE3A [corrected]. In addition, the present findings suggest previously unsuspected roles for these enzymes in gametogenesis and neural development.

Authors

R R Reinhardt, E Chin, J Zhou, M Taira, T Murata, V C Manganiello, C A Bondy

The role of complement in experimental bullous pemphigoid.

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Bullous pemphigoid (BP) is a blistering skin disease associated with an IgG autoimmune response directed against the ectodomain of the hemidesmosomal protein, BP180. An animal model of BP has recently been developed by our laboratory based on the passive transfer of rabbit antimurine BP180 antibodies into neonatal BALB/c mice. The experimental animals develop a blistering disease that reproduces all of the key immunopathological features of BP. In the present study we have investigated the role of complement in the pathogenesis of subepidermal blistering in the mouse model of BP. We demonstrate the following. (a) Rabbit anti-murine-BP180 IgG was effective in inducing cutaneous blisters in a C5-sufficient mouse strain, but failed to induce disease in the syngeneic C5-deficient strain; (b) neonatal BALB/c mice, pretreated with cobra venom factor to deplete complement, became resistant to the pathogenic effects of the anti-BP180 IgG; (c) F(ab')2 fragments generated from the anti-BP180 IgG exhibited no pathogenic activity in the mouse model; and (d) histologic evaluation of the skin of mice described in points b and c above showed minimal or no neutrophilic cell infiltration in the upper dermis. Thus, anti-BP180 antibodies trigger subepidermal blistering in this BP model via complement activation. This experimental model of BP should greatly facilitate future studies on the pathophysiology of autoantibody-mediated diseases of the dermal-epidermal junction.

Authors

Z Liu, G J Giudice, S J Swartz, J A Fairley, G O Till, J L Troy, L A Diaz

Identification of four chromosomal loci determining obesity in a multifactorial mouse model.

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We previously described a new mouse model for multigenic obesity, designated BSB. We now report the use of a complete linkage map approach to identify loci contributing to body fat and other traits associated with obesity in this model. Four loci exhibiting linkage with body fat, or with the weights of four different fat depots, residing on mouse chromosomes 6, 7, 12, and 15, were identified and confirmed by analysis of additional BSB mice. Each of the four loci differed with respect to their effects on the percent of body fat, specific fat depots and plasma lipoproteins. The loci exhibited allele-specific, non-additive interactions. A locus for hepatic lipase activity was co-incident with the body fat and total cholesterol loci on chromosome 7, providing a possible mechanism linking plasma lipoproteins and obesity. The chromosome 7 locus affecting body fat, total cholesterol and hepatic lipase activity was isolated in congenic strains whose donor strain regions overlap with the chromosome 7 BSB locus. These results provide candidate genes and candidate loci for the analysis of human obesity.

Authors

C H Warden, J S Fisler, S M Shoemaker, P Z Wen, K L Svenson, M J Pace, A J Lusis

Glanzmann thrombasthenia resulting from a single amino acid substitution between the second and third calcium-binding domains of GPIIb. Role of the GPIIb amino terminus in integrin subunit association.

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To gain insight into region of the platelet GPIIb-IIIa complex involved in receptor biogenesis and function, we examined the biochemical properties of a defective GPIIb-IIIa complex from patient suffering from type II Glanzmann thrombasthenia. Flow cytometric as well as immunoblot analysis of patient platelets showed significantly reduced levels of GPIIb and GPIIIa compared with a normal control. Patient platelets, however, retained the ability to retract a fibrin clot. Sequence analysis of PCR-amplified platelet GPIIb mRNA revealed an Arg327-->His amino acid substitution between the second and third calcium-binding domains of the GPIIb heavy chain, a residue that is highly conserved among integrin alpha-subunits. The recombinant His327 form of GPIIb was found to be fully capable of associating with GPIIIa, therefore the role of the calcium-binding domains in intersubunit association was further examined by constructing amino-terminal segments of GPIIb that ended before the first, second, and third calcium-binding domains. All three fragments were found to associate with GPIIIa, demonstrating that the calcium-binding domains of GPIIb are not necessary for initial complex formation. Regions amino-terminal to the calcium-binding domains of GPIIb may play a heretofore unappreciated role in integrin subunit association.

Authors

D A Wilcox, C M Paddock, S Lyman, J C Gill, P J Newman

Immunodominant minor histocompatibility antigens expressed by mouse leukemic cells can serve as effective targets for T cell immunotherapy.

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Numerous minor histocompatibility antigens (MiHAs) show tissue-specific expression and can induce vigorous T cell responses. They therefore represent attractive targets for leukemia immunotherapy mediated by adoptive transfer of T cells. The main objective of this work was to determine whether MiHAs expressed by normal hematopoietic cells were present on leukemic cells and whether they could trigger lysis by cytotoxic T lymphocytes (CTLs). CTL assays showed that mouse leukemic cells of both lymphoid and myeloid lineages were sensitive to CTLs targeted toward some but not all MiHAs. In four out of four strain combinations in which we primed CTLs against immunodominant MiHAs, effectors killed leukemic blasts, whereas no cytotoxicity was observed when CTLs were targeted toward four immunorecessive MiHAs. Testing of HPLC fractions obtained from normal and leukemic cells provided molecular evidence that leukemic blasts expressed only some of the MiHAs found on normal mouse hematopoietic cells. Decreased density of H-2 class I molecules at the surface of leukemic cells suggests that down-regulation of genes encoding either class I molecules or proteins involved in antigen processing played a role in the aberrant expression of MiHAs. In vivo resistance to the leukemic cells by various strains of mice correlated with in vitro CTL activity. These results show that leukemic cells express only some (immunodominant) MiHAs and suggest that this subset of MiHAs represent prime targets for adoptive immunotherapy.

Authors

S Pion, P Fontaine, C Baron, M Gyger, C Perreault

Identification of a gC1q-binding protein (gC1q-R) on the surface of human neutrophils. Subcellular localization and binding properties in comparison with the cC1q-R.

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Human neutrophils have multiple C1q-binding proteins. Direct ligand-binding studies with the globular domain of C1q and two-dimensional Western blot analysis revealed two gC1q-binding proteins (gC1q-R): a 33,000 M(r) protein (pI 4.5) mainly in the neutrophil plasma membrane and an 80,000-90,000 M(r) protein (pI 4.1-4.2) located mainly in the granules. Direct binding studies showed that C1q bound to this higher molecular weight protein under physiological conditions. In contrast, anti-cC1q-R antibody, which recognizes a protein binding to collagenous tails of C1q, detected only a 68,000 M(r) protein in the plasma membrane. Both the 33,000 and 68,000 M(r) receptors appear early on the surface of differentiating HL-60 cells. On mature neutrophils, surface expression of both C1q receptors was evident, but no upregulation was observed upon stimulation. Phorbol myristate acetate treatment of neutrophils downregulated both the receptors from cell surface, and significant amounts of soluble gC1q-R were in cell media supernatants, suggesting receptor shedding or secretion. gC1q-R, unlike cC1q-R, did not bind to other C1q-like ligands, namely mannose binding protein, surfactant protein-A, surfactant protein-D, or conglutinin under normal ionic conditions, suggesting a greater specificity for C1q than the "collectin" type receptor (cC1q-R). Rather, gC1q-R only bound purified C1q, and the binding was enhanced under low ionic conditions and in the absence of calcium. The role of C1q receptor shedding and its biologic consequence remain to be defined, but may contribute to the diversity of C1q-mediated responses observed in many cell types.

Authors

P Eggleton, B Ghebrehiwet, K N Sastry, J P Coburn, K S Zaner, K B Reid, A I Tauber

Role of organic osmolytes in myelinolysis. A topographic study in rats after rapid correction of hyponatremia.

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Organic osmolytes have been implicated in the pathogenesis of myelinolysis because some of them are accumulated slowly during correction of chronic hyponatremia. I investigated whether there was a topographic correlation between demyelinative lesions and the regional changes of organic osmolytes after rapid correction of chronic hyponatremia. In normal female Sprague-Dawley rats, concentrations of glutamate, glutamine, taurine, and betaine were highest in the cerebral cortex and decreased toward the brain stem. Conversely, glycine level was highest in the brainstem, and decreased toward the cortex. Myoinositol, glycerophosphorylcholine, glycerophosphorylethanolamine, and creatine were distributed more evenly. In chronic hyponatremic rats (plasma Na 110 +/- 4 meq/liter), organic osmolytes decreased globally with the total loss ranging from 13 (medulla) to 24 (cerebellum) mmol/kg H2O. After rapid correction with intraperitoneal injection of hypertonic saline, the recovery of the loss of organic osmolytes was 48% in the cerebral cortex, cerebellum, and medulla oblongata, 44% in pons, but only 17% in midbrain and 36% in striatum. Histopathology of the brain was examined in nine rats 2-7 d after correction of hyponatremia. Large demyelinative lesions were seen persistently in the midbrain and striatum, and smaller lesions in cerebrum, cerebellum, and pons were found less frequently. This is the first report of regional distribution of brain organic osmolytes. After rapid correction of chronic hyponatremia, a topographic correlation between demyelination lesions and delayed accumulation of organic osmolytes exists.

Authors

Y H Lien

Decreased cholesteryl ester transfer protein (CETP) mRNA and protein and increased high density lipoprotein following lipopolysaccharide administration in human CETP transgenic mice.

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Abstract

The plasma cholesteryl ester transfer protein (CETP) mediates the exchange of HDL cholesteryl esters (CE) and VLDL triglycerides leading to catabolism of HDL. There is some evidence that HDL ameliorates the toxicity of LPS, and LPS is known to influence several enzymes affecting HDL metabolism. Therefore, the effects of LPS on CETP and plasma lipoproteins were examined in human CETP transgenic mice. Administration of LPS to mice expressing a CETP transgene linked to its natural flanking sequences (NFR-CETP Tg) resulted in a rapid marked decrease in hepatic CETP mRNA and plasma CETP concentration. Corticosteroid injection produced a similar decrease in hepatic CETP mRNA and adrenalectomy abolished this response to LPS. LPS caused disproportionate reductions in plasma CETP activity compared to mass, and was found to be a potent inhibitor of CETP activity when added directly to plasma. LPS was injected into mice expressing (A) a human apoA-I transgene, (B) apoA-I and NFR-CETP transgenes, or (C) apoA-I and LPS-inducible metallothionein promoter-driven CETP transgenes, producing (A) minimal changes in HDL cholesterol, (B) decreased plasma CETP and increased HDL cholesterol, and (C) increased plasma CETP and decreased HDL cholesterol. Thus, LPS administration produces a profound decrease in hepatic CETP mRNA, primarily as a result of adrenal corticosteroid release. The decrease in plasma CETP activity after LPS administration may reflect both this effect as well as a direct interaction between CETP and LPS. The decrease of CETP in response to LPS has major effects on HDL levels, and may represent an adaptive response to preserve or increase HDL and thereby modify the response to LPS.

Authors

L Masucci-Magoulas, P Moulin, X C Jiang, H Richardson, A Walsh, J L Breslow, A Tall

Secondary alcohol metabolites mediate iron delocalization in cytosolic fractions of myocardial biopsies exposed to anticancer anthracyclines. Novel linkage between anthracycline metabolism and iron-induced cardiotoxicity.

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Abstract

The cardiotoxicity of doxorubicin (DOX) and other quinone-containing antitumor anthracyclines has been tentatively attributed to the formation of drug semiquinones which generate superoxide anion and reduce ferritin-bound Fe(III), favoring the release of Fe(II) and its subsequent involvement in free radical reactions. In the present study NADPH- and DOX-supplemented cytosolic fractions from human myocardial biopsies are shown to support a two-step reaction favoring an alternative mechanism of Fe(II) mobilization. The first step is an enzymatic two-electron reduction of the C-13 carbonyl group in the side chain of DOX, yielding a secondary alcohol metabolite which is called doxorubicinol (3.9 +/- 0.4 nmoles/mg protein per 4 h, mean +/- SEM). The second step is a nonenzymatic and superoxide anion-independent redox coupling of a large fraction of doxorubicinol (3.2 +/- 0.4 nmol/mg protein per 4 h) with Fe(III)-binding proteins distinct from ferritin, regenerating stoichiometric amounts of DOX, and mobilizing a twofold excess of Fe(II) ions (6.1 +/- 0.7 nmol/mg protein per 4 h). The formation of secondary alcohol metabolites decreases significantly (Pi < 0.01) when DOX is replaced by less cardiotoxic anthracyclines such as daunorubicin, 4'-epi DOX, and 4-demethoxy daunorubicin (2.1 +/- 0.1, 1.2 +/- 0.2, and 0.6 +/- 0.2 nmol/mg protein per 4 h, respectively). Therefore, daunorubicin, 4'-epi DOX, and 4-demethoxy daunorubicin are significantly (P < 0.01) less effective than DOX in mobilizing Fe(II) (3.5 +/- 0.1, 1.8 +/- 0.2, and 0.9 +/- 0.3 nmol/mg protein per 4 h, respectively). These results highlight the formation of secondary alcohol metabolites and the availability of nonferritin sources of Fe(III) as novel and critical determinants of Fe(II) delocalization and cardiac damage by structurally distinct anthracyclines, thus providing alternative routes to the design of cardioprotectants for anthracycline-treated patients.

Authors

G Minotti, A F Cavaliere, A Mordente, M Rossi, R Schiavello, R Zamparelli, G Possati

Germline p53 mutations are frequently detected in young children with rhabdomyosarcoma.

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Abstract

We investigated the possibility that a proportion of children with sporadic rhabdomyosarcoma (RMS) carry constitutional mutations of the p53 tumor suppressor gene. 33 patients with sporadic RMS at two large outpatient pediatric oncology clinics submitted blood samples. Genomic DNA was extracted from peripheral blood leukocytes and PCR was used to amplify exons 2-11 of the p53 gene. Amplified genomic DNA was screened for the presence of germline p53 mutations using single-strand conformation polymorphism (SSCP) analysis. The DNA sequence of those samples that showed aberrant migration of bands on SSCP analysis was determined to identify the precise nature of the gene mutations. Patient records were reviewed to assess clinical correlates of the mutant p53 carrier state. Heterozygous constitutional mutations were detected in 3/33 patient samples screened. Two of these missense mutations are located in exon 7 and one in exon 8 of the p53 gene. The presence of mutations was not correlated with tumor histology, stage, or site. However, an association between young age at diagnosis and presence of a constitutional p53 mutation was noted: 3/13 children under the age of 3 yr at diagnosis carried mutations, whereas none of 20 children over 3 yr of age at diagnosis harbored a detectable constitutional mutation. These results in children with RMS corroborates previous findings in other clinical settings suggesting that the mutant p53 carrier state may predispose individuals to malignancy at an early age. Although this study did not assess whether the mutations were preexisting or new germline alterations, assessment of close relatives of RMS patients for cancer risk and predictive genetic testing may be indicated.

Authors

L Diller, E Sexsmith, A Gottlieb, F P Li, D Malkin

An inherited bleeding disorder linked to a defective interaction between ADP and its receptor on platelets. Its influence on glycoprotein IIb-IIIa complex function.

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Abstract

Much discussion has concerned the central role of ADP in platelet aggregation. We now describe a patient (M.L.) with an inherited bleeding disorder whose specific feature is that ADP induces a limited and rapidly reversible platelet aggregation even at high doses. Platelet shape change and other hemostatic parameters were unmodified. A receptor defect was indicated, for, while epinephrine normally lowered cAMP levels of PGE1-treated (M.L.) platelets, ADP was without effect. The binding of [3H]2-methylthio-ADP decreased from 836 +/- 126 molecules/platelet for normals to 30 +/- 17 molecules/platelet for the patient. Flow cytometry confirmed that ADP induced a much lower fibrinogen binding to (M.L.) platelets. Nonetheless, the binding in whole blood of activation-dependent monoclonal antibodies showed that some activation of GP IIb-IIIa complexes by ADP was occurring. Platelets of a patient with type I Glanzmann's thrombasthenia bound [3H]2-methylthio-ADP and responded normally to ADP in the presence of PGE1. Electron microscopy showed that ADP-induced aggregates of (M. L.) platelets were composed of loosely bound shape-changed platelets with few contact points. Thus this receptor defect has a direct influence on the capacity of platelets to bind to each other in response to ADP.

Authors

P Nurden, P Savi, E Heilmann, C Bihour, J M Herbert, J P Maffrand, A Nurden

Vasopressin stimulates Cl- transport in ascending thin limb of Henle's loop in hamster.

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Abstract

The effect of arginine vasopressin (AVP) on NaCl transport was investigated in the isolated microperfused hamster ascending thin limb of Henle's loop by measuring transepithelial voltage (Vt) and transmural 22Na+ and 36Cl- fluxes. In the presence of a transmural NaCl concentration gradient (100 mM higher in the lumen), Vt was 8.4 +/- 0.4 mV. Addition of 1 nM AVP to the basolateral solution increased Vt to 9.6 +/- 0.4 mV, which corresponds to an increase in the Cl- to Na+ permselectivity ratio (PCl/PNa) from 2.8 +/- 0.2 to 3.4 +/- 0.2. AVP at physiological concentrations increased Vt in a dose-dependent manner with an ED50 of 5 pM. AVP increased the Cl- efflux coefficient from 99.6 +/- 6.3 to 131.4 +/- 10.6 x 10(-7) cm2/s without affecting the Na+ efflux coefficient. 5-Nitro-2-(3-phenyl-propylamino)-benzoate (0.2 mM), a Cl- channel inhibitor, in the perfusate decreased the basal Cl- efflux coefficient and inhibited the AVP-induced increase in this parameter. The AVP-induced increase in Vt was not affected by [d(CH2)5(1),O-Me-Tyr2,Arg8] vasopressin, a V1 receptor antagonist, but was abolished by [d(CH2)5,D-Ile2,Ile4,Arg8] vasopressin, a V2 receptor antagonist. The selective V2 agonist dDAVP in 1 nM also increased Vt from 8.6 +/- 0.7 to 9.5 +/- 0.6 mV. Dibutyryl cAMP and forskolin both increased Vt, whereas H89, an inhibitor of cAMP-dependent protein kinase, abolished the AVP-induced increase in Vt. These results demonstrate that AVP stimulates Cl- transport in the ascending thin limb of Henle's loop by activating Cl- channels via a signal transduction cascade comprising V2 receptors, adenylate cyclase, and cAMP-dependent protein kinase. The ascending thin limb of Henle's loop thus participates in the formation of concentrated urine as one of the target renal tubular segments of AVP.

Authors

N Takahashi, Y Kondo, O Ito, Y Igarashi, K Omata, K Abe

Immune complexes inhibit antimicrobial responses through interleukin-10 production. Effects in severe combined immunodeficient mice during Listeria infection.

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Abstract

The presence of soluble antigen-antibody complexes renders mice highly susceptible to infection with the intracellular pathogen Listeria monocytogenes. In this report we show that this inhibition is manifest at the level of the innate immune response and is mediated by IL-10. Like immuno-competent mice, mice with the severe combined immunodeficient mutation (SCID) injected with immune complexes died from a sublethal dose of L. monocytogenes. These mice were protected if pretreated with neutralizing antibodies to IL-10. In vitro, immune complexes stimulated IL-10 production by SCID splenocytes and splenic macrophages. Likewise, immune complexes inhibited TNF and IFN-gamma production by SCID splenocytes cultured with heat-killed-L. monocytogenes. This inhibition was reversed by neutralization of IL-10 but not IL-4 or TGF-beta. Immune complexes and rIL-10 inhibited cytokine production by SCID splenocytes if added before or simultaneously with heat-killed-L. monocytogenes. These data support a model in which immune complexes modulate host defense and the immune response by stimulating the production of IL-10 from macrophages.

Authors

C S Tripp, K P Beckerman, E R Unanue

Genetic polymorphisms of the beta 2-adrenergic receptor in nocturnal and nonnocturnal asthma. Evidence that Gly16 correlates with the nocturnal phenotype.

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Abstract

Nocturnal asthma represents a unique subset of patients with asthma who experience worsening symptoms and airflow obstruction at night. The basis for this phenotype of asthma is not known, but beta 2-adrenergic receptors (beta 2AR) are known to downregulate overnight in nocturnal asthmatics but not normal subjects or nonnocturnal asthmatics. We have recently delineated three polymorphic loci within the coding block of the beta 2AR which alter amino acids at positions 16, 27, and 164 and impart specific biochemical and pharmacologic phenotypes to the receptor. In site-directed mutagenesis/recombinant expression studies we have found that glycine at position 16 (Gly16) imparts an accelerated agonist-promoted downregulation of beta 2AR as compared to arginine at this position (Arg16). We hypothesized that Gly16 might be overrepresented in nocturnal asthmatics and thus determined the beta 2AR genotypes of two well-defined asthmatic cohorts: 23 nocturnal asthmatics with 34 +/- 2% nocturnal depression of peak expiratory flow rates, and 22 nonnocturnal asthmatics with virtually no such depression (2.3 +/- 0.8%). The frequency of the Gly16 allele was 80.4% in the nocturnal group as compared to 52.2% in the nonnocturnal group, while the Arg16 allele was present in 19.6 and 47.8%, respectively. This overrepresentation of the Gly16 allele in nocturnal asthma was significant at P = 0.007 with an odds ratio of having nocturnal asthma and the Gly16 polymorphism being 3.8. Comparisons of the two cohorts as to homozygosity for Gly16, homozygosity for Arg16, or heterozygosity were also consistent with segregation of Gly16 with nocturnal asthma. There was no difference in the frequency of polymorphisms at loci 27 (Gln27 or Glu27) and 164 (Thr164 or Ile164) between the two groups. Thus the Gly16 polymorphism of the beta 2AR, which imparts an enhanced downregulation of receptor number, is overrepresented in nocturnal asthma and appears to be an important genetic factor in the expression of this asthmatic phenotype.

Authors

J Turki, J Pak, S A Green, R J Martin, S B Liggett

Pathways of processing of the gastrin precursor in rat antral mucosa.

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Abstract

The precursor of the acid-stimulating hormone gastrin gives rise to multiple peptides differing markedly in biological activity, but the relevant biosynthetic pathways are poorly understood. We have used antibodies to amidated gastrins, gastrins with COOH-terminal glycine (Gly) gastrins with COOH-terminal hydroxyglycine (GlyOH) and to the COOH terminus of progastrin, to immunoprecipitate peptides labeled with [35S]sulfate or [3H]tyrosine during incubation of rat antral mucosa in vitro. Labeled progastrin was detectable after 30 min of continuous incubation with isotopic precursors, G34 and G34-Gly after 60 min, and G17 and G17-Gly after 120 min. Pulse chase experiments indicated that progastrin is converted to G34-Gly which then follows one of two pathways: (a) hydroxylation of COOH-terminal Gly and conversion to G34 followed by cleavage yielding G17, or (b) cleavage to G17-Gly. The kinetics of G17-Gly and G17 labeling were similar, suggesting that G17-Gly is a product in its own right, and not simply an intermediate in G17 synthesis. Since the two peptides are reported to have distinct biological activities, they appear to be alternative mature products of progastrin processing.

Authors

A Varro, S Voronina, G J Dockray

Cisplatin-associated anemia: an erythropoietin deficiency syndrome.

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Abstract

Cisplatin-based therapy results in a cumulative anemia that is disproportionate to the effects on other blood cells. The severity of this treatment-induced anemia and the resultant transfusion requirement in cancer patients correlate with cisplatin-induced renal tubular dysfunction. Observed/expected serum erythropoietin (EPO) ratios decline with progressive cisplatin therapy and are proportionate to the degree of renal dysfunction. Recovery from anemia and of observed/expected serum EPO ratios in patients occurs after cessation of cisplatin therapy, along with restoration of renal tubular function. Creatinine clearance, however, remains permanently depressed. Cisplatin-treated rats develop progressive renal dysfunction and anemia that persists for many weeks, without effects on white blood cell counts. The anemia is also associated with a lack of expected EPO and reticulocyte response. With EPO administration, cisplatin-treated rats exhibit a greater reticulocyte response and hematocrit increment then non-cisplatin-treated rats given EPO, indicating minimal erythroid precursor cell damage from cisplatin. These results indicate the primary etiology of cisplatin-associated anemia is a transient, but persisting EPO deficiency state resulting from cisplatin-induced renal tubular damage, which can be prevented or treated by hormone (EPO) replacement.

Authors

P A Wood, W J Hrushesky

Characterization of the deoxycytidine kinase promoter in human lymphoblast cell lines.

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Abstract

Deoxycytidine kinase (dCK) phosphorylates 2'-deoxycytidine, as well as the purine deoxyribonucleosides and a number of nucleoside analogues that are important in the chemotherapy of leukemias. The enzyme is highly expressed in the thymus relative to other tissues and may play an important role in the T cell depletion associated with adenosine deaminase and purine nucleoside phosphorylase deficiencies. To characterize the dCK promoter region and to determine whether it mediates higher levels of gene expression in T lymphoblasts, we have analyzed a 700-bp genomic fragment encompassing 548 bp of 5' flanking region for functional activity and for transcription factor binding using T and B lymphoblast cell lines and nuclear extracts. The regions of the promoter that were defined as important to its function include a 5' GC box, and E box, a 3' GC box, and an E2F site. The transcription factor Sp1 binds to both GC boxes, activating at the 5' site but repressing at the 3' site. MLTF/USF activates transcription through the E box, whereas E2F activates through the E2F site, but binds weakly to this site in vitro and does not appear to mediate cell cycle-specific expression of dCK in vivo. No significant differences in promoter activity or transcription factor binding were observed between Jurkat T and Raji B lymphoblasts. The promoter of the dCK gene is thus regulated by a number of ubiquitously expressed transcription factors. DCK expression in cultured lymphoblast cell lines is not solely a function of the T or B lineage derivation.

Authors

E H Chen, E E Johnson 2nd, S M Vetter, B S Mitchell

Involvement of reactive oxygen intermediates in cyclooxygenase-2 expression induced by interleukin-1, tumor necrosis factor-alpha, and lipopolysaccharide.

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Abstract

Reactive oxygen intermediates (ROIs) play an important role in inflammatory processes as mediators of injury and potentially in signal transduction leading to gene expression. Cyclooxygenase (COX) is a rate-limiting enzyme in prostanoid biosynthesis, and its recently cloned inducible form, COX-2, is induced by proinflammatory cytokines. This study linked ROIs to the signaling pathways that induce COX-2 expression. The hydroxyl radical scavengers DMSO (1%), as well as di- and tetramethylthiourea, inhibited IL-1-, TNF alpha-, and LPS-induced COX-2 expression in rat mesangial cells. The suppression of COX-2 mRNA expression correlated with the COX-2 protein level. In comparison with the prolonged induction of the inducible gene encoding protein-tyrosine phosphatase by hydrogen peroxide, the COX-2 gene was only transiently induced. Protein-tyrosine phosphatase is also induced by heat shock and chemical stress, whereas COX-2 is not. Superoxide was a more potent inducer for COX-2 than hydrogen peroxide. In addition, NADPH stimulated COX-2 expression, and an inhibitor of NADPH oxidase blocked COX-2 expression induced by TNF alpha. COX-2 and KC gene expression costimulated by IL-1 were inhibited differentially by the scavengers. These studies demonstrate that oxidant stress is a specific and important inducer of COX-2 gene expression. This induction may contribute to the deleterious amplification of prostanoids in inflammation and compound the direct effects of ROI production.

Authors

L Feng, Y Xia, G E Garcia, D Hwang, C B Wilson

Overexpression of Gs alpha protein in the hearts of transgenic mice.

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Abstract

Alterations in beta-adrenergic receptor-Gs-adenylyl cyclase coupling underlie the reduced catecholamine responsiveness that is a hallmark of human and animal models of heart failure. To study the effect of altered expression of Gs alpha, we overexpressed the short isoform of Gs alpha in the hearts of transgenic mice, using a rat alpha-myosin heavy chain promoter. Gs alpha mRNA levels were increased selectively in the hearts of transgenic mice, with a level 38 times the control. Despite this marked increase in mRNA, Western blotting identified only a 2.8-fold increase in the content of the Gs alpha short isoform, whereas Gs activity was increased by 88%. The discrepancy between Gs alpha mRNA and Gs alpha protein levels suggests that the membrane content of Gs alpha is posttranscriptionally regulated. The steady-state adenylyl cyclase catalytic activity was not altered under either basal or stimulated conditions (GTP + isoproterenol, GTP gamma S, NaF, or forskolin). However, progress curve studies did show a significant decrease in the lag period necessary for GppNHp to stimulate adenylyl cyclase activity. Furthermore, the relative number of beta-adrenergic receptors binding agonist with high affinity was significantly increased. Our data demonstrate that a relatively small increase in the amount of the coupling protein Gs alpha can modify the rate of catalyst activation and the formation of agonist high affinity receptors.

Authors

C Gaudin, Y Ishikawa, D C Wight, V Mahdavi, B Nadal-Ginard, T E Wagner, D E Vatner, C J Homcy

Tumor necrosis factor-alpha eliminates binding of NF-Y and an octamer-binding protein to the lipoprotein lipase promoter in 3T3-L1 adipocytes.

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Abstract

TNF alpha has been shown to reduce lipoprotein lipase (LPL) activity in adipose tissue. Regulation of LPL by TNF alpha occurs at the level of LPL gene transcription and posttranscriptionally. To elucidate further the transcriptional mechanism of TNF alpha inhibition of LPL gene transcription, transfection analysis was used to locate the site(s) of the LPL promoter that imparts the TNF alpha response. Transient transfections using LPL promoter deletions fused to luciferase in differentiated 3T3-L1 cells with and without TNF alpha treatment indicated that a DNA region downstream of -180 bp confers the TNF alpha effect. Electrophoretic mobility shift assays using two 32P-labeled LPL probes spanning the region between -180 and +44 bp revealed the loss of several LPL DNA-protein interactions after TNF alpha treatment, including the binding of NF-Y to the CCAAT box and a protein to the octamer consensus sequence. Protein binding to the OCT-1 consensus sequence is unaffected until after 4 h of TNF alpha treatment. In addition, the amount of mRNA for OCT-1 is not altered with TNF alpha treatment. These results indicate that TNF alpha regulates at least two DNA-binding proteins on the proximal promoter, thereby inhibiting LPL gene transcription.

Authors

C L Morin, I R Schlaepfer, R H Eckel

Phenotypic and functional changes in peripheral blood monocytes during progression of human immunodeficiency virus infection. Effects of soluble immune complexes, cytokines, subcellular particulates from apoptotic cells, and HIV-1-encoded proteins on monocytes phagocytic function, oxidative burst, transendothelial migration, and cell surface phenotype.

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Abstract

We postulated that changes in the cell surface display of molecules that facilitate cell-cell and cell-matrix adhesions may reflect the changing immunosurveillance capacity of blood monocytes during progression of human immunodeficiency virus (HIV) infections. In Centers for Disease Control (CDC) stage A patients, whose monocytes' ability to phagocytose bacteria and generate reactive oxygen intermediates is often increased, the frequency of monocytes expressing CD49d, HLA-DP, HLA-DQ, and an activation epitope of CD11a/CD18 was increased and monocyte transendothelial migration was unimpaired. In CDC stage B/C patients, whose monocytes' ability to phagocytose bacteria and migrate across confluent endothelial monolayers was diminished, surface expression of CD49e and CD62L and the percentage of monocytes expressing CD18, CD11a, CD29, CD49e, CD54, CD58, CD31, and HLA-I were significantly decreased. Incubating normal donor monocytes with immune complexes in vitro reproduced the phenotypic and functional abnormalities seen in stage B/C patients. By contrast, in vitro stimulation with subcellular particulates released by apoptotic lymphocytes reproduced changes seen in stage A patients' monocytes. Although circulating monocytes appear to be activated at all stages, these data suggest that the high levels of circulating immune complexes, found predominantly in the later stages of HIV infection, may be particularly instrumental in reducing the monocyte's capacity to maintain surveillance against infection.

Authors

J Trial, H H Birdsall, J A Hallum, M L Crane, M C Rodriguez-Barradas, A L de Jong, B Krishnan, C E Lacke, C G Figdor, R D Rossen

Molecular study of pyruvate kinase deficient patients with hereditary nonspherocytic hemolytic anemia.

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Abstract

DNA analysis was performed on 30 unrelated patients with hereditary nonspherocytic hemolytic anemia (HNSHA) who had been found to be pyruvate kinase (PK) deficient by enzyme assay. 19 different mutations were identified among 58 of the 60 alleles at risk. 13 of these were missense mutations that caused single amino acid changes. Included were the following nucleotide substitutions: 401A, 464C, 993A, 1022C, 1076A, 1178G, 1179A, 1373A, 1378A, 1456T, 1484T, 1493A, 1529A. The remaining six mutations were as follows: two nonsense mutations, 721T and 808T; a nucleotide deletion, 307C; a nucleotide insertion, 1089GG; a three nucleotide in frame deletion, 391-392-393 and a deletion of 1149 bp from the PKLR gene that resulted in the loss of exon 11. All the patients were studied for two polymorphic sites, nucleotide (nt) 1705 A/C and a microsatellite in intron 11, to better understand the origin of the mutations. The 1529A mutation, which is the most common mutation in the European population, was found in 25 alleles. With a single exception this mutation was in linkage disequilibrium with both of the polymorphic markers, i.e., found with 1705C and 14 repeats in the microsatellite. This finding is consistent with a single origin of this common mutation. Other mutations occurring more than once were of much lower frequency than the 1529A mutation.

Authors

L Baronciani, E Beutler

Direct gene delivery of human tissue kallikrein reduces blood pressure in spontaneously hypertensive rats.

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Abstract

Authors

C Wang, L Chao, J Chao

Expression of an insulin/interleukin-1 receptor antagonist hybrid gene in insulin-producing cell lines (HIT-T15 and NIT-1) confers resistance against interleukin-1-induced nitric oxide production.

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Abstract

A hybrid gene consisting of the insulin gene enhancer/promoter region, the signal sequence, the insulin B- and C-chains, and the human interleukin-1 receptor antagonist (IL-1ra) gene was constructed. This hybrid gene was transfected together with the pSV2-neo construct into the insulin-producing cell lines HIT-T15 and NIT-1. One of the geneticin-selected clones, HITra2, expressed a 1.4-kb mRNA, which hybridized both to insulin and IL-1ra-cDNA in Northern blot analysis. Three proteins, with the mol wt 23, 17, and 14 kD, were immunoprecipitated with anti-IL-1ra antibodies from [35S]methionine-labeled HITra2 cells. Both at a low and at a high glucose concentration, 4-5 ng of IL-1ra/10(6) cells (ELISA) was released from these cells. On the other hand, a high glucose concentration evoked a three-fold increase in the release of insulin, suggesting that IL-1ra was released constitutively. Measured by nitrite production, transfected HIT, and NIT-1 cells exhibited a more than 10-fold decrease in IL-1 beta sensitivity. Since the conditioned culture media from the HITra2 cells exhibited an anti-IL-1 beta activity of only 0.5 U/ml, and mixed culture of HITra2 cells and isolated rat islets prevented IL-1 beta induced inhibition of insulin release, it is likely that IL-1ra acts locally at the cell surface. It is concluded that expression of a hybrid insulin/IL-1ra gene confers resistance to IL-1 and that this technique may be used to elucidate the role of IL-1 in autoimmune disorders such as insulin-dependent diabetes mellitus.

Authors

N Welsh, K Bendtzen, M Welsh

Cytokines from activated T cells induce normal endothelial cells to acquire the phenotypic and functional features of AIDS-Kaposi's sarcoma spindle cells.

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Kaposi's sarcoma (KS) is a proliferative disease of vascular origin particularly frequent in HIV-1-infected homosexual men (AIDS-KS) and characterized by proliferating spindle-shaped cells, angiogenesis, and inflammatory cell infiltration. Previous work has suggested that KS spindle cells are of endothelial cell origin and that chronic immune activation via the release of inflammatory cytokines may cooperate with basic fibroblast growth factor (bFGF) and the HIV-1 Tat protein in the induction and progression of AIDS-KS. Here we show that KS spindle cells have features of activated endothelial cells, and that conditioned media from activated T cells, rich in the same inflammatory cytokines increased in HIV-1-infected individuals, induce normal endothelial cells to acquire the phenotypic and functional features of KS cells. These include (a) acquisition of a similar pattern of cell surface antigen expression; (b) similar proliferative response to bFGF; (c) induction of the responsiveness to the mitogenic effect of extracellular HIV-1 Tat protein that is now able to promote the G1-S transition of endothelial cell cycle; and (d) induction in nude mice of vascular lesions closely resembling early KS as well as the lesions induced by inoculation of KS cells. These results suggest that chronic immune activation, via release of inflammatory cytokines, may play a role in the induction of KS.

Authors

V Fiorelli, R Gendelman, F Samaniego, P D Markham, B Ensoli

Human eosinophil-granule major basic protein and synthetic polycations induce airway hyperresponsiveness in vivo dependent on bradykinin generation.

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In the current series of experiments we investigated the role of bradykinin in airway hyperresponsiveness induced by human eosinophil-granule major basic protein (MBP). Bronchoalveolar lavage was performed after intratracheal instillation of MBP or poly-L-lysine in anesthetized, intubated rats, and levels of immunoreactive kinins and kallikrein-like activity were determined. Both MBP and poly-L-lysine induced a three- and eightfold increase in levels of kallikrein-like activity and i-kinins, respectively. To determine whether kinin production is required for the development of airway hyperresponsiveness induced by cationic proteins, dose-response curves to methacholine were constructed before and 1 h after intratracheal instillation of either MBP or poly-L-lysine (100 micrograms). MBP and poly-L-lysine induced an increase in airway responsiveness, which was inhibited by pretreatment with a selective BK-2 receptor antagonist, NPC 17713 (250 micrograms/ml). Our results demonstrate that MBP and poly-L-lysine activate kallikrein and stimulate the generation of i-kinins in vivo, an effect that may be related to the cationic charge of these proteins. Furthermore, the ability of these proteins to increase airway responsiveness appears to be dependent on the generation of i-kinins.

Authors

A J Coyle, S J Ackerman, R Burch, D Proud, C G Irvin

Immune predispositions for cytomegalovirus retinitis in AIDS. The HNRC Group.

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CMV retinitis develops in approximately 28-35% of all AIDS patients at later stages of disease, often leading to blindness. To determine whether the subset of AIDS patients who developed CMV retinitis (CMV-R) were immunologically predisposed, T cell proliferation responses to CMV were examined prospectively in an HIV infected, HLA typed, longitudinal study population. Individuals who developed CMV-R had significantly lower T cell proliferation responses to CMV, both early and late in disease, compared to CD4 matched controls who have not developed CMV-R. Since HLA proteins influence T-cell recognition, phenotypes of 21 CMV-R patients were examined to determine whether certain HLA alleles were associated with low immune response and predisposed AIDS patients to CMV-R. HLA DR7 and B44 were at increased (nearly twice the expected) frequency in those with CMV-R. The combined association of either B44, 51 or DR7 with CMV-R was highly significant (P = .008, relative risk of CMV-R = 15) with correction for multiple comparisons. Low immune responses were twice as frequent in those with (61%) compared to those without (30%) predisposing alleles. Thus, AIDS patients with immunogenetically related hyporesponsiveness to CMV antigens may be at increased risk of retinitis.

Authors

R D Schrier, W R Freeman, C A Wiley, J A McCutchan

Nitric oxide activity in the human coronary circulation. Impact of risk factors for coronary atherosclerosis.

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Abstract

The bioavailability of nitric oxide (NO) in the human coronary circulation at rest and after acetylcholine (ACH)-induced vasodilation was investigated in 32 patients with angiographically normal coronary arteries. The effects of intracoronary L-NG monomethyl arginine (L-NMMA) were investigated at rest and after ACH, sodium nitroprusside, and adenosine. L-NMMA (64 mumol/min) increased resting coronary vascular resistance by 22% (P < 0.001), reduced distal epicardial coronary artery diameter by 12.6% (P < 0.001), and inhibited ACH-induced coronary epicardial and microvascular vasodilation. These effects were reversed with intracoronary L-arginine. L-NMMA did not inhibit dilation in response to sodium nitroprusside and adenosine. 23 patients were exposed to one or more coronary risk factors. The vasoconstrictor effect of L-NMMA on the epicardial and microvessels was greater in patients free of risk factors: Coronary vascular resistance was 36% higher in patients without risks, compared to 17% higher in patients with risks (P < 0.05). Both epicardial and microvascular dilator effects of ACH were greater in patients without risk factors, and the inhibition of these effects by L-NMMA was also greater in patients without risk factors. Thus: (a) NO contributes importantly to resting epicardial and coronary microvascular tone, (b) coronary vascular dilation in response to ACH is predominantly due to increased production of NO, and (c) despite the absence of angiographic evidence of atherosclerosis, exposure to coronary risk factors is associated with reduced resting and stimulated bioavailability of NO from the human coronary circulation.

Authors

A A Quyyumi, N Dakak, N P Andrews, S Husain, S Arora, D M Gilligan, J A Panza, R O Cannon 3rd

Prevention of in vitro neutrophil-endothelial attachment through shedding of L-selectin by nonsteroidal antiinflammatory drugs.

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Abstract

The activation of the endothelial cells by extravascular stimuli is the key event in the extravasation of circulating leukocytes to target tissues. L-selectin, a member of the selectin family, is constitutively expressed by white cells, and is the molecule involved in the initial binding of leukocytes to activated endothelium. After activation, leukocytes rapidly release L-selectin from the cell surface, suggesting that the functional activity of this molecule is controlled in large part by its appearance and disappearance from cell surface. We have studied in a neutrophil-activated endothelial cell binding assay, the effect of different antiinflammatory drugs (steroidal and nonsteroidal) in the L-selectin-mediated interaction of neutrophils with activated endothelial cells. Some nonsteroidal antiinflammatory drugs (NSAIDs), such as indomethacin, diclofenac, ketoprofen, and aspirin, but not steroids, strongly inhibited the neutrophil-endothelial cell attachment. Furthermore, we also investigated the underlying mechanism of this functional effect. The expression of L-selectin on the neutrophil surface rapidly decreased in the presence of different NSAIDs, in a dose- and time-dependent manner, whereas no changes in the expression of other adhesion molecules such as CD11a, CD11b, CD31, or ICAM-3 (CD50) were observed. Interestingly, studies in vivo on healthy volunteers treated with physiological doses of indomethacin showed a significant decrease of L-selectin neutrophil expression. Only diclofenac induced an upregulation of CD11b expression, suggesting an activating effect on neutrophils. No enzyme release was observed upon treatment of neutrophils with different NSAIDs, indicating a lack of degranulatory activity of NSAIDs, with the exception of diclofenac. The downregulation of L-selectin expression was due to the rapid cleavage and shedding of the membrane L-selectin, as determined by both immunoprecipitation from 125I-labeled neutrophils, and quantitative estimation in cell-free supernatants. These results suggest that NSAIDs exert a specific action on adhesion receptor expression in neutrophils, which might account, at least in part, for the antiinflammatory activities of NSAIDs.

Authors

F Díaz-González, I González-Alvaro, M R Campanero, F Mollinedo, M A del Pozo, C Muñoz, J P Pivel, F Sánchez-Madrid

Population and family studies of three disease-related polymorphic genes in systemic lupus erythematosus.

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Abstract

The contribution to systemic lupus erythematosus (SLE) of three lupus-associated polymorphisms (involving the C4A2 complement component, Humhv3005 and the T cell antigen receptor alpha chain gene) are investigated in 81 individuals from 14 multiplex SLE families, 41 unrelated lupus patients, and 88 unrelated healthy controls. The results show a strong association between C4A deletion and SLE in these families. While the current study confirms the previously reported association between hv3005 deletion and sporadic SLE, the study fails to support this association in familial SLE patients. Moreover, no correlation is detected between the occurrence of hv3005 deletion and C4A null alleles in lupus patients, suggesting that the effects of these genetic polymorphisms on predisposition to lupus are independent. The previously reported lupus-associated T cell receptor (TCR) alpha chain polymorphism is not detected in any of the individuals studied here. The combined data suggest that C4A null alleles predispose strongly to development of lupus, whereas the influence of hv3005 deletion is relatively weak. The results also suggest that contributions of weak susceptibility genes such as hv3005 to disease predisposition may be obscured by the effects of stronger genetic factors and thus need to be examined in patients lacking these factors.

Authors

D F Huang, K A Siminovitch, X Y Liu, T Olee, N J Olsen, C Berry, D A Carson, P P Chen

The carboxy terminus of tissue factor pathway inhibitor is required for interacting with hepatoma cells in vitro and in vivo.

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Abstract

Tissue factor pathway inhibitor (TFPI) is a plasma Kunitz-type serine protease inhibitor that directly inhibits coagulation Factor Xa and also inhibits tissue factor-initiated coagulation. Normal human plasma TFPI exists both as the full-length molecule and as variably carboxy-terminal truncated forms. We reported recently that the low density lipoprotein receptor-related protein mediates the cellular degradation of TFPI after TFPI binding to the hepatoma cell surface. To examine whether the carboxy terminus of TFPI was required for interacting with hepatoma cells, a mutant of TFPI lacking the third Kunitz-type domain and basic carboxy terminus was generated. We found that this mutant, TFPI-160, did not compete with full-length 125I-TFPI-160 for binding to hepatoma cells. We were also unable to demonstrate specific binding of 125I-TFPI-160 to hepatoma cells at 4 degrees C. At 37 degrees C, significantly less 125I-TFPI-160 was internalized and degraded via low density lipoprotein receptor-related protein than full-length 125I-TFPI. Full-length 125I-TFPI binding to hepatoma cells could be inhibited > 90% by heparin and other highly charged molecules. Since TFPI, but not TFPI-160, was capable of effectively binding to cultured hepatoma cells, the fates of TFPI and TFPI-160 in vivo were examined. Both 125I-TFPI and 125I-TFPI-160 disappeared rapidly from the circulation after their intravenous administration into rats. The initial plasma half-life of 125I-TFPI was approximately 30 s whereas the half-life of 125I-TFPI-160 was approximately 4 min. 125I-TFPI was cleared predominantly by the liver. In contrast, 125I-TFPI-160 accumulated in the outer cortex of the kidney. Using microscopic autoradiography, we demonstrate that 125I-TFPI clearance is largely hepatocellular, whereas 125I-TFPI-160 accumulates mainly in the cells of the kidney proximal tubules. Together our findings demonstrate that the carboxy-terminal region(s) distal to amino acid 160 of TFPI mediates TFPI binding to hepatoma cells both in vitro and in vivo.

Authors

I Warshawsky, G Bu, A Mast, J E Saffitz, G J Broze Jr, A L Schwartz

P-selectin/ICAM-1 double mutant mice: acute emigration of neutrophils into the peritoneum is completely absent but is normal into pulmonary alveoli.

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Abstract

Authors

D C Bullard, L Qin, I Lorenzo, W M Quinlin, N A Doyle, R Bosse, D Vestweber, C M Doerschuk, A L Beaudet

Regulation by vascular endothelial growth factor of human colon cancer tumorigenesis in a mouse model of experimental liver metastasis.

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Abstract

To investigate the relationship between angiogenesis and hepatic tumorigenesis, we examined the expression of vascular endothelial growth factor (VEGF) in 8 human colon carcinoma cell lines and in 30 human colorectal cancer liver metastases. Abundant message for VEGF was found in all tumors, localized to the malignant cells within each neoplasm. Two receptors for VEGF, KDR and flt1, were also demonstrated in most of the tumors examined. KDR and flt1 mRNA were limited to tumor endothelial cells and were more strongly expressed in the hepatic metastases than in the sinusoidal endothelium of the surrounding liver parenchyma. VEGF monoclonal antibody administration in tumor-bearing athymic mice led to a dose- and time-dependent inhibition of growth of subcutaneous xenografts and to a marked reduction in the number and size of experimental liver metastases. In hepatic metastases of VEGF antibody-treated mice, neither blood vessels nor expression of the mouse KDR homologue flk-1 could be demonstrated. These data indicate that VEGF is a commonly expressed angiogenic factor in human colorectal cancer metastases, that VEGF receptors are up-regulated as a concomitant of hepatic tumorigenesis, and that modulation of VEGF gene expression or activity may represent a potentially effective antineoplastic therapy in colorectal cancer.

Authors

R S Warren, H Yuan, M R Matli, N A Gillett, N Ferrara

Increased gene expression for VEGF and the VEGF receptors KDR/Flk and Flt in lungs exposed to acute or to chronic hypoxia. Modulation of gene expression by nitric oxide.

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Abstract

Endothelial cells constitute an essential integrator of factors that effect blood vessel remodeling induced by chronic hypoxia. We hypothesized that vascular endothelial growth factor (VEGF) may participate in the lung response to acute and to chronic hypoxia. We found that ex vivo perfusion of isolated lungs under hypoxic conditions (when compared with normoxia) caused an increase in lung tissue mRNA of VEGF and of the VEGF receptors KDR/Flk and Flt. Chronic hypobaric hypoxia also increased lung tissue mRNA levels of VEGF, KDR/Flk, and Flt and the amount of VEGF protein. In situ hybridization studies demonstrated increased VEGF and KDR/flk hybridization signals in lungs from chronically hypoxic rats. Since endotoxin treatment of rats decreased lung VEGF mRNA, we postulated that nitric oxide (NO) or an NO-related metabolite might be involved in lung VEGF gene expression. Indeed, sodium nitroprusside, a NO donor, decreased and L-NAME (N-nitro-L-arginine methyl ester), an inhibitor of NO-synthesis, increased both VEGF and VEGF receptor transcripts. We conclude that VEGF in the isolated perfused lung acts as an early gene in response to hypoxia and that lung VEGF and VEGF receptor mRNA levels are influenced by hypoxia and NO-dependent mechanisms.

Authors

R M Tuder, B E Flook, N F Voelkel

Myoblast transfer of human erythropoietin gene in a mouse model of renal failure.

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Abstract

Anemia is an invariable consequence of end-stage renal failure (ESRF) and recombinant erythropoietin has dramatically improved the quality of life of patients with ESRF. As an alternative approach, we developed a myoblast gene transfer system for the systemic delivery of human erythropoietin (EPO). We recently reported that transplantation of 4 x 10(7) cells of a C2 myoblast cell clone that stably secretes high level of functional human EPO, increased hematocrit from 44.6 +/- 3.0 to 71.2 +/- 7.9(%) in 2 wk, and the increase was sustained for at least 12 wk in nude mice. A renal failure model was created by a two-step nephrectomy in nude mice, and myoblasts were transplanted 3 wk after the second nephrectomy, when mean blood urea nitrogen level had increased from 26.3 +/- 6.1 to 85.4 +/- 24.0 (mg/dl) and the hematocrit had decreased from 45.2 +/- 2.7 to 33.9 +/- 3.7(%). After transplantation, the hematocrit markedly increased to 68.6 +/- 4.2(%) 2 wk, and to 68.5 +/- 4.0(%) 7 wk after the transplantation. Serum human EPO concentration determined by ELISA indicated a persistent steady EPO production from the transplanted muscle cells 8 wk after the transplantation. The fate of transplanted myoblasts in uremic mice was monitored by transplanting the EPO-secreting clone which had also been transduced with BAG retrovirus bearing the beta-galactosidase gene. 8 wk later, X-gal positive myofibers were detected in the entire transplanted area. The results demonstrate that myoblasts can be transplanted in uremic mice, and that myoblast gene transfer can achieve sufficient and sustained delivery of functionally active EPO to correct anemia associated with renal failure in mice.

Authors

Y Hamamori, B Samal, J Tian, L Kedes

Binding, uptake, and intracellular trafficking of phosphorothioate-modified oligodeoxynucleotides.

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Abstract

An enhanced appreciation of uptake mechanisms and intracellular trafficking of phosphorothioate modified oligodeoxynucleotides (P-ODN) might facilitate the use of these compounds for experimental and therapeutic purposes. We addressed these issues by identifying cell surface proteins with which P-ODN specifically interact, studying P-ODN internalization mechanisms, and by tracking internalized P-ODN through the cell using immunochemical and ultrastructural techniques. Chemical cross-linking studies with a biotin-labeled P-ODN (bP-ODN), revealed the existence of five major cell surface P-ODN binding protein groups ranging in size from approximately 20-143 kD. Binding to these proteins was competitively inhibited with unlabeled P-ODN, but not free biotin, suggesting specificity of the interactions. Additional experiments suggested that binding proteins likely exist as single chain structures, and that carbohydrate moieties may play a role in P-ODN binding. Uptake studies with 35S-labeled P-ODN revealed that endocytosis, mediated by a receptor-like mechanism, predominated at P-ODN concentrations < 1 microM, whereas fluid-phase endocytosis prevailed at higher concentrations. Cell fractionation and ultrastructural analysis demonstrated the presence of ODN in clathrin coated pits, and in vesicular structures consistent with endosomes and lysosomes. Labeled ODN were also found in significant amounts in the nucleus, while none was associated with ribosomes, or ribosomes associated with rough endoplasmic reticulum (ER). Since nuclear uptake was not blocked by wheat germ agglutinin or concanavalin A, a nucleoporin independent, perhaps diffusion driven, import process is suggested. These data imply that antisense DNA may exert their effect in the nucleus. They also suggest rational ways to design ODN which might increase their efficiency.

Authors

C Beltinger, H U Saragovi, R M Smith, L LeSauteur, N Shah, L DeDionisio, L Christensen, A Raible, L Jarett, A M Gewirtz

Molecular and cellular aspects of iron-induced hepatic cirrhosis in rodents.

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Abstract

Hepatic fibrosis and cirrhosis are common findings in humans with hemochromatosis. In this study we investigated the molecular pathways of iron-induced hepatic fibrosis and evaluated the anti-fibrogenic effect of vitamin E. Male gerbils were treated with iron-dextran and fed a standard diet or a alpha-tocopherol enriched diet (250 mg/Kg diet). In gerbils on the standard diet at 6 wk after dosing with iron, in situ hybridization analysis documented a dramatic increase of signal for collagen mRNA around iron foci onto liver fat storing cells (FSC), as identified by immunocytochemistry with desmin antibody. After 4 mo, micronodular cirrhosis developed in these animals, with nonparenchymal cells surrounding hepatocyte nodules and expressing high level of TGF beta mRNA. In this group, in vivo labeling with [3H]-thymidine showed a marked proliferation of nonparenchymal cells, including FSC. In iron-dosed gerbils on the vitamin E-enriched diet for 4 mo, in spite of a severe liver iron burden, a normal lobular architecture was found, with a dramatic decrease of collagen mRNA accumulation and collagen deposition. At the molecular level, a total suppression of nonparenchymal cell proliferation was appreciable, although expression of collagen and TGF beta mRNAs was still present into microscopic iron-filled nonparenchymal cell aggregates scattered throughout the hepatic lobule. In conclusion, our study shows that anti-oxidant treatment during experimental hepatic fibrosis arrests fibrogenesis and completely prevents iron induced hepatic cirrhosis mainly through inhibition of nonparenchymal cell proliferation induced by iron.

Authors

A Pietrangelo, R Gualdi, G Casalgrandi, G Montosi, E Ventura

Severe alport phenotype in a woman with two missense mutations in the same COL4A5 gene and preponderant inactivation of the X chromosome carrying the normal allele.

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Abstract

The X-linked form of Alport disease, caused by mutations in the COL4A5 or the COL4A6 gene, usually leads to terminal renal failure in males, while affected females have a more variable and moderate phenotype. We detected in a female patient, with a severe Alport phenotype, two new missense mutations. One mutation (G289V) occurred in exon 15 and converted a glycine in a collagenous domain of COL4A5 to a valine. The second mutation, located in exon 46, substituted a cysteine proximal to the NC1 domain of COL4A5 for an arginine. In white blood cells and kidney both mutations were present on > 90% of the mRNA, while at the genomic level the patient was heterozygous for both mutations. The two mutations therefore occurred in the same COL4A5 allele. No mutation was found in the COL4A5 promoter region by sequencing nor was a major rearrangement of the normal allele detected. A skewed pattern of X inactivation was demonstrated in DNA isolated from the patient's kidney and white blood cells: > 90% of the X chromosomes with the normal COL4A5 allele was inactivated. It is suggested that this skewed inactivation pattern is responsible for the absence of detectable normal COL4A5 mRNA and hence the severe phenotype in this woman.

Authors

C Guo, B Van Damme, Y Vanrenterghem, K Devriendt, J J Cassiman, P Marynen

Lithium-induced downregulation of aquaporin-2 water channel expression in rat kidney medulla.

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Abstract

Lithium, a widely used treatment for bipolar affective disorders, often causes nephrogenic diabetes insipidus. The effect of chronic lithium therapy on the expression of the vasopressin-regulated water channel Aquaporin-2 (AQP2) in rat kidney was examined. Membranes were prepared from inner medulla of one kidney from each rat, while the contralateral one was fixed for immunofluorescence and immunoelectronmicroscopy. Immunoblotting revealed that lithium treatment reduced AQP2 expression dramatically, to 31 +/- 8% after 10 d and to 4 +/- 1% after 25 d, coincident with development of severe polyuria. Immunofluorescence and immunogold quantitation confirmed the lithium-induced decrease in AQP2 expression (from 11.2 +/- 1.0 to 1.1 +/- 0.2 particles/microns 2). The downregulation was only partly reversed by return to lithium-free diet for 1 wk (40 +/- 8% of control). Furthermore, immunoblotting and immunogold quantitation revealed that 2 d of thirsting or 7 d of dDAVP treatment, in the continued presence of lithium, increased AQP2 expression by six- and threefold, respectively, coincident with increased urinary osmolality. Thirsting increased AQP2 immunolabeling mainly of vesicles, whereas dDAVP caused accumulation of AQP2 predominantly in the subapical region and plasma membrane. Thus, lithium causes marked downregulation of AQP2 expression, only partially reversed by cessation of therapy, thirsting or dDAVP treatment, consistent with clinical observations of slow recovery from lithium-induced urinary concentrating defects.

Authors

D Marples, S Christensen, E I Christensen, P D Ottosen, S Nielsen

Skeletal muscle utilization of free fatty acids in women with visceral obesity.

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Abstract

Authors

S R Colberg, J A Simoneau, F L Thaete, D E Kelley

Transgenic mice expressing the human heat shock protein 70 have improved post-ischemic myocardial recovery.

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Abstract

Heat shock treatment induces expression of several heat shock proteins and subsequent post-ischemic myocardial protection. Correlations exist between the degree of stress used to induce the heat shock proteins, the amount of the inducible heat shock protein 70 (HSP70) and the level of myocardial protection. The inducible HSP70 has also been shown to be protective in transfected myogenic cells. Here we examined the role of human inducible HSP70 in transgenic mouse hearts. Overexpression of the human HSP70 does not appear to affect normal protein synthesis or the stress response in transgenic mice compared with nontransgenic mice. After 30 min of ischemia, upon reperfusion, transgenic hearts versus nontransgenic hearts showed significantly improved recovery of contractile force (0.35 +/- 0.08 versus 0.16 +/- 0.05 g, respectively, P < 0.05), rate of contraction, and rate of relaxation. Creatine kinase, an indicator of cellular injury, was released at a high level (67.7 +/- 23.0 U/ml) upon reperfusion from nontransgenic hearts, but not transgenic hearts (1.6 +/- 0.8 U/ml). We conclude that high level constitutive expression of the human inducible HSP70 plays a direct role in the protection of the myocardium from ischemia and reperfusion injury.

Authors

J C Plumier, B M Ross, R W Currie, C E Angelidis, H Kazlaris, G Kollias, G N Pagoulatos

Cultured lung fibroblasts isolated from patients with idiopathic pulmonary fibrosis have a diminished capacity to synthesize prostaglandin E2 and to express cyclooxygenase-2.

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Abstract

Prostaglandin E2 (PGE2) inhibits fibroblast proliferation and collagen synthesis. In this study, we compared lung fibroblasts isolated from patients with idiopathic pulmonary fibrosis (F-IPF) and from patients undergoing resectional surgery for lung cancer (F-nl) with respect to their capacity for PGE2 synthesis and their expression and regulation of cyclooxygenase (COX) proteins. Basal COX activity, assessed by quantitating immunoreactive PGE2 synthesized from arachidonic acid, was twofold less (P < 0.05) in F-IPF than F-nl. In F-nl, incubation with the agonists PMA, LPS, or IL-1 increased COX activity and protein expression of the inducible form of COX, COX-2, and these responses were inhibited by coincubation with dexamethasone. By contrast, F-IPF failed to demonstrate increases in COX-2 protein expression or COX activity in response to these agonists. Under conditions of maximal induction, COX activity in F-IPF was sixfold less than that in F-nl (P < 0.05). Our data indicate that F-IPF have a striking defect in their capacity to synthesize the antiinflammatory and antifibrogenic molecule PGE2, apparently because of a diminished induction of COX-2 protein. This reduction in the endogenous capacity of F-IPF to down-regulate their function via PGE2 may contribute to the inflammatory and fibrogenic response in IPF. Moreover, we believe that this represents the first description of a defect in COX-2 expression in association with a human disease.

Authors

J Wilborn, L J Crofford, M D Burdick, S L Kunkel, R M Strieter, M Peters-Golden

Taxol inhibits neointimal smooth muscle cell accumulation after angioplasty in the rat.

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Abstract

Despite significant improvements in the primary success rate of the medical and surgical treatments for atherosclerotic disease, including angioplasty, bypass grafting, and endarterectomy, secondary failure due to late restenosis continues to occur in 30-50% of individuals. Restenosis and the later stages in atherosclerotic lesions are due to a complex series of fibroproliferative responses to vascular injury involving potent growth-regulatory molecules (such as platelet-derived growth factor and basic fibroblast growth factor) and resulting in vascular smooth muscle cell (VSMC) proliferation, migration, and neointimal accumulation. We show here, based on experiments with both taxol and deuterium oxide, that microtubules are necessary for VSMCs to undergo the multiple transformations contributing to the development of the neointimal fibroproliferative lesion. Taxol was found to interfere both with platelet-derived growth factor-stimulated VSMC migration and with VSMC migration and with VSMC proliferation, at nanomolar levels in vitro. In vivo, taxol prevented medial VSMC proliferation and the neointimal VSMC accumulation in the rat carotid artery after balloon dilatation and endothelial denudation injury. This effect occurred at plasma levels approximately two orders of magnitude lower than that used clinically to treat human malignancy (peak levels achieved in this model were approximately 50-60 nM). Taxol may therefore be of therapeutic value in preventing human restenosis with minimal toxicity.

Authors

S J Sollott, L Cheng, R R Pauly, G M Jenkins, R E Monticone, M Kuzuya, J P Froehlich, M T Crow, E G Lakatta, E K Rowinsky

Molecular basis of subtotal complement C6 deficiency. A carboxy-terminally truncated but functionally active C6.

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Abstract

Individuals with subtotal complement C6 deficiency possess a C6 molecule that is 14% shorter than normal C6 and present in low but detectable concentrations (1-2% of the normal mean). We now show that this dysmorphic C6 is bactericidally active and lacks an epitope that was mapped to the most carboxy-terminal part of C6 using C6 cDNA fragments expressed as fusion proteins in the pUEX expression system. We thus predicted that the abnormal C6 molecule might be carboxy-terminally truncated and sought a mutation in an area approximately 14% from the carboxy-terminal end of the coding sequence. By sequencing PCR-amplified products from this region, we found, in three individuals from two families, a mutation that might plausibly be responsible for the defect. All three have an abnormal 5' splice donor site of intron 15, which would probably prevent splicing. An in-frame stop codon is found 17 codons downstream from the intron boundary, which would lead to a truncated polypeptide 13.5% smaller than normal C6. This result was unexpected, as earlier studies mapped the C5b binding site, or a putative enzymatic region, to this part of C6. Interestingly, all three subjects were probably heterozygous for both subtotal C6 and complete C6 deficiency.

Authors

R Würzner, M J Hobart, B A Fernie, D Mewar, P C Potter, A Orren, P J Lachmann

Splenic B lymphocyte programmed cell death is prevented by nitric oxide release through mechanisms involving sustained Bcl-2 levels.

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Abstract

Incubation of ex vivo cultured mature B cells in the presence of nitric oxide or nitric oxide-donor substances delays programmed cell death as determined by the appearance of DNA laddering in agarose gel electrophoresis or by flow-cytometry analysis of DNA. Nitric oxide also rescues B cells from antigen-induced apoptosis but fails to provide a co-stimulatory signal that converts the signal elicited by the antigen into a proliferative response. The protective effects of nitric oxide against programmed cell death can be reproduced by treatment of the cells with permeant analogues of cyclic GMP. Regarding the mechanisms by which nitric oxide prevents apoptosis in B cells, we have observed that nitric oxide release prevents the drop in the expression of the protooncogene bcl-2, both at the mRNA and protein levels, suggesting the existence of an unknown pathway that links nitric oxide signaling with Bcl-2 expression.

Authors

A M Genaro, S Hortelano, A Alvarez, C Martínez, L Boscá

Detection and expression of a cDNA clone that encodes a polypeptide containing two inhibitory domains of human calpastatin and its recognition by rheumatoid arthritis sera.

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Abstract

RA is the most frequent and most destructive inflammatory arthropathy. Rheumatoid factors, in spite of their lack of disease specificity, are important serological markers for RA and appear important in its immunopathogenesis as well. In search of more disease-specific autoimmune systems, we have screened a human placenta lambda gt11 cDNA expression library using selected sera from patients with classical erosive RA. We have identified one clone (RA-1) that is recognized by three of five screening sera. The 950-bp insert shows a complete nucleotide sequence homology to the cDNA encoding the two COOH-terminal domains of calpastatin. The deduced open reading frame of the RA-1 cDNA predicts a 284-amino acid protein, with a calculated mol wt of 35.9 kD. Calpastatin is the natural inhibitor of calpains, which are members of the cysteine proteinases recently implicated in joint destruction in rheumatic diseases. The two domains encoded by the RA-1 clone each contain the structural features associated with the inhibitory activity of human calpastatin. By Western blotting, 45.5% or 21/44 RA sera specifically recognized both the fusion and the cleaved recombinant protein. This is in contrast to 4.7% (2/43) in nonrheumatoid sera and 0/10 in normal sera. Anticalpastatin autoantibodies could represent a disease-associated marker in chronic erosive arthritis of the rheumatoid type and could hypothetically play a dual pathogenic role, directly via an immune interference and indirectly through an immune complex mechanism.

Authors

N Després, G Talbot, B Plouffe, G Boire, H A Ménard

Apoptosis induced by an anti-epidermal growth factor receptor monoclonal antibody in a human colorectal carcinoma cell line and its delay by insulin.

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Abstract

Both EGF and insulin, or IGF, stimulate the growth of many cell types by activating receptors that contain tyrosine kinase activities. A monoclonal antibody (mAb 225) against the EGF receptor produced in this laboratory has been shown to competitively inhibit EGF binding and block activation of receptor tyrosine kinase. Here we report that a human colorectal carcinoma cell line, DiFi, which expresses high levels of EGF receptors on plasma membranes, can be induced to undergo G1 cell cycle arrest and programmed cell death (apoptosis) when cultured with mAb 225 at concentrations that saturate EGF receptors. Addition of IGF-1 or high concentrations of insulin can delay apoptosis induced by mAb 225, while the G1 arrest cannot be reversed by either IGF-1 or insulin. Insulin/IGF-1 cannot activate EGF receptor tyrosine kinase that has been inhibited by mAb 225. Moreover, an mAb against the IGF-1 receptor, which has little direct effect on DiFi cell growth, can block the capacity of insulin/IGF-1 to delay apoptosis induced by mAb 225, suggesting that the insulin/IGF-1-mediated delay of apoptosis is acting through the IGF-1 receptor. In contrast, insulin/IGF-1 cannot delay the apoptosis caused by the DNA damaging agent, cisplatin. The results indicate that EGF receptor activation is required both for cell cycle progression and for prevention of apoptosis in DiFi cells, and that a signal transduction pathway shared by receptors for insulin/IGF-1 and EGF may be involved in regulating apoptosis triggered by blockade of the EGF receptor.

Authors

X Wu, Z Fan, H Masui, N Rosen, J Mendelsohn

MCF-7 breast cancer cells transfected with protein kinase C-alpha exhibit altered expression of other protein kinase C isoforms and display a more aggressive neoplastic phenotype.

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Increased protein kinase C (PKC) activity in malignant breast tissue and positive correlations between PKC activity and expression of a more aggressive phenotype in breast cancer cell lines suggest a role for this signal transduction pathway in the pathogenesis and/or progression of breast cancer. To examine the role of PKC in the progression of breast cancer, human MCF-7 breast cancer cells were transfected with PKC-alpha, and a group of heterogenous cells stably overexpressing PKC-alpha were isolated (MCF-7-PKC-alpha). MCF-7-PKC-alpha cells expressed fivefold higher levels of PKC-alpha as compared to parental or vector-transfected MCF-7 cells. MCF-7-PKC-alpha cells also displayed a substantial increase in endogenous expression of PKC-beta and decreases in expression of the novel delta- and eta-PKC isoforms. MCF-7-PKC-alpha cells displayed an enhanced proliferative rate, anchorage-independent growth, dramatic morphologic alterations including loss of an epithelioid appearance, and increased tumorigenicity in nude mice. MCF-7-PKC-alpha cells exhibited a significant reduction in estrogen receptor expression and decreases in estrogen-dependent gene expression. These findings suggest that the PKC pathway may modulate progression of breast cancer to a more aggressive neoplastic process.

Authors

D K Ways, C A Kukoly, J deVente, J L Hooker, W O Bryant, K J Posekany, D J Fletcher, P P Cook, P J Parker

Extracellular accumulation of potently microbicidal bactericidal/permeability-increasing protein and p15s in an evolving sterile rabbit peritoneal inflammatory exudate.

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To what extent the host defense role of granule-associated antibacterial proteins and peptides of PMN includes extracellular action has not been established. To address this question, we have analyzed the antibacterial activity of cell-free (ascitic) fluid (AF) obtained from glycogen-induced sterile inflammatory rabbit peritoneal exudates in which > 95% of the accumulating cells are PMN. AF, but not plasma collected in parallel, exhibits potent activity toward serum-resistant Gram-negative and Gram-positive bacteria. Total and specific antibacterial activity of AF increases during the first 12 h after injection of glycogen in parallel with the influx of PMN. At maximum, > 99% of 10(7) encapsulated Escherichia coli and Staphylococcus aureus are killed in 30 min/ml of AF. Neutralizing antibodies against the bactericidal/permeability-increasing protein (BPI) of PMN abolishes activity of AF toward encapsulated E. coli but has no effect on activity vs staphylococci. However, BPI alone (approximately 1 microgram/ml in AF) can only account for < or = 20% of AF activity toward E. coli. AF also contains 15 kD PMN proteins (p15s) that act in synergy with BPI. Purified BPI and p15s, in amounts present in AF, reconstitute the growth-inhibitory activity of AF toward encapsulated E. coli. These findings show for the first time an extracellular function of endogenous BPI, providing, together with the p15s, a potent microbicidal system toward Gram-negative bacteria resistant to plasma-derived proteins and phagocytes in inflammatory exudates.

Authors

Y Weinrauch, A Foreman, C Shu, K Zarember, O Levy, P Elsbach, J Weiss

Severe insulin-resistant diabetes mellitus in patients with congenital muscle fiber type disproportion myopathy.

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Congenital muscle fiber type disproportion myopathy (CFTDM) is a chronic, nonprogressive muscle disorder characterized by universal muscle hypotrophy and growth retardation. Histomorphometric examination of muscle shows a preponderance of smaller than normal type 1 fibers and overall fiber size heterogeneity. Concomitant endocrine dysfunctions have not been described. We report the findings of altered insulin secretion and insulin action in two brothers affected with CFTDM and glucose intolerance as well as in their nonconsanguineous glucose-tolerant parents. Results are compared with those of six normoglycemic control subjects. All study participants underwent an oral glucose tolerance test to estimate insulin secretion. The oldest boy and his parents volunteered for studies of whole-body insulin sensitivity consisting of a 4-h euglycemic hyperinsulinemic clamp in combination with indirect calorimetry. Insulin receptor function and glycogen synthase (GS) activity and expression were examined in biopsies of vastus lateralis muscle. Despite a 45-90-fold increase in both fasting and postprandial serum insulin levels, both CFTDM patients had diabetes mellitus. Clamp studies revealed that the oldest boy had severe insulin resistance of both liver and peripheral tissues. The impaired insulin-stimulated glucose disposal to peripheral tissues was primarily due to reduced nonoxidative glucose metabolism. These changes were paralleled by reduced basal values of muscle GS total activity, allosterical activation of GS by glucose-6-phosphate, GS protein, and GS mRNA. The father expressed a lesser degree of insulin resistance, and studies of muscle insulin receptor function showed a severe impairment of receptor kinase activity. In conclusion, CFTDM is a novel form of severe hyperinsulinemia and insulin resistance. Whether insulin resistance is causally related to the muscle disorder awaits to be clarified.

Authors

H Vestergaard, H H Klein, T Hansen, J Müller, F Skovby, C Bjørbaek, M E Røder, O Pedersen

The diurnal rhythm of bone resorption in the rat. Effect of feeding habits and pharmacological inhibitors.

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Abstract

Prevention of low bone mass is important to reducing the incidence of osteoporotic fractures. This paper shows that, in rats, bone mass can be increased by feeding habits per se. Using six-hourly urinary excretion of [3H]tetracycline from prelabeled rats to monitor bone resorption, we previously found a peak of bone resorption following food administration. We now demonstrate that dividing the solid and liquid intake into portions blunts this peak and leads to a decrease in 24-h bone resorption to the level observed in thyroparathyroidectomized animals. Calcium balance increases and, when such feeding schedules are imposed for 30 d, bone mass increases. Dividing the intake is not effective in thyroparathyroidectomized animals, indicating the importance of PTH and/or calcitonin. Administration of calcitonin inhibits practically only the peak of bone resorption, suggesting that it is osteoclast mediated. In contrast, treatment with a bisphosphonate reduces basal bone resorption without a specific effect on the peak, indicating a fundamentally different mechanism of action. This is also supported by the finding that their combined effects are additive. Whether bone mass in humans is also under the control of dietary habits is not known. If so, an increased meal frequency may be used to prevent osteoporosis.

Authors

R C Mühlbauer, H Fleisch

Amplification of nitric oxide synthase expression by nitric oxide in interleukin 1 beta-stimulated rat mesangial cells.

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Abstract

Nitric oxide (NO) plays an important role in immunological reactions as a host defense mechanism against tumor cells and invasive microorganisms, but it may also damage healthy tissue. The excessive formation of NO in IL-1 beta-stimulated renal mesangial cells not only alters glomerular filtration, but it may also cause tissue injury and thus contribute to the pathogenesis of certain forms of glomerulonephritis. We report here that, although NO alone has no evident effect on NO synthase expression, it potently augments IL-1 beta-stimulated NO synthase expression in mesangial cells. NO donors such as sodium nitroprusside and S-nitroso-N-acetyl-D,L-penicillamine markedly increase IL-1 beta-induced NO synthase mRNA and protein levels as well as enzyme activity. Nuclear run-on experiments suggest that NO acts to increase IL-1 beta-induced NO synthase gene expression at the transcriptional level. Furthermore, inhibition of NO synthesis by different pharmacological approaches reduces IL-1 beta-induced NO synthase expression, thus suggesting that NO functions in a positive feedback loop that speeds up and strengthens its own biosynthesis. We suggest that this potent amplification mechanism forms the basis for the excessive formation of NO in acute and chronic inflammatory diseases.

Authors

H Mühl, J Pfeilschifter

Protection against endotoxic shock by bactericidal/permeability-increasing protein in rats.

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Abstract

Bactericidal/permeability-increasing protein (BPI) is a neutrophil primary granule protein that inhibits effects of LPS in vitro. The current study examined the effects of BPI on hemodynamics, mortality, and circulating endotoxin and cytokines in conscious rats with endotoxic shock. Catheters were implanted into the right femoral artery and vein. 1 d later, human recombinant BPI (10 mg/kg) or vehicle was intravenously injected immediately, 30 min, or 2 h after intravenous injection of LPS (7.5 mg/kg). Mean arterial pressure (MAP) and heart rate were monitored and blood was collected before and after injection. BPI given immediately or 30 min after LPS prevented the LPS-induced reduction in MAP at 4-8 h and markedly reduced mortality. BPI given 2 h after LPS injection had no protective effect. BPI treated immediately after LPS reduced the circulating levels of endotoxin and IL-6 but increased the circulating levels of TNF. We propose that BPI exerts its protective effect through a TNF-independent mechanism, by inhibiting endotoxin-stimulated production of IL-6.

Authors

H Jin, R Yang, S Marsters, A Ashkenazi, S Bunting, M N Marra, R W Scott, J B Baker