Late-onset hereditary anemia: why the delay?

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J P Kushner

Starve a tumor: therapeutic advice for breast cancer?

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Authors

C H Damsky

Absence of the mdr1a P-Glycoprotein in mice affects tissue distribution and pharmacokinetics of dexamethasone, digoxin, and cyclosporin A.

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We have previously shown that absence of the mouse mdr1a (also called mdr3) P-glycoprotein in mdr1a (-/-) "knockout" mice has a profound effect on the tissue distribution and elimination of vinblastine and ivermectin, and hence on the toxicity of these compounds. We show here that the mouse mdr1a and the human MDR1 P-glycoprotein actively transport ivermectin, dexamethasone, digoxin, and cyclosporin A and, to a lesser extent, morphine across a polarized kidney epithelial cell layer in vitro. Injection of these radio-labeled drugs in mdr1a (-/-) and wild-type mice resulted in markedly (20- to 50-fold) higher levels of radioactivity in mdr1a (-/-) brain for digoxin and cyclosporin A, with more moderate effects for dexamethasone (2- to 3-fold) and morphine (1.7-fold). Digoxin and cyclosporin A were also more slowly eliminated from mdr1a (-/-) mice. Our findings show that P-glycoprotein can be a major determinant for the pharmacology of several medically important drugs other than anti-cancer agents, especially in the blood-brain barrier. These results may explain a range of pharmacological interactions observed between various drugs in patients.

Authors

A H Schinkel, E Wagenaar, L van Deemter, C A Mol, P Borst

Lyme borreliosis in transgenic mice tolerant to Borrelia burgdorferi OspA or B.

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The evolution of Lyme borreliosis in transgenic mice tolerant to Borrelia burgdorferi outer surface proteins (Osps) A or B was assessed to investigate the role of immunity to OspA or B in infection and pathogenesis of Lyme disease. Antibodies to OspA or B protect immunocompetent C3H/HeJ or C.B.17 severe combined immunodeficient (scid) mice from challenge with B. burgdorferi. Moreover, arthritis in infected C3H mice resolves with the rise of high titers of B. burgdorferi specific antibodies, including OspA and B, whereas disease persists in scid mice--suggesting that the regression of arthritis may be due to the development of borreliacidal OspA or B antibodies. To evaluate the course of Lyme borreliosis in OspA or B tolerant mice we developed transgenic mice that expressed OspA or B under control of the major histocompatibility complex (MHC) class I promoter. Mice carrying OspA or B transgenes on a C3H/HeJ (C3H, disease-susceptible) or C57BL/6 (B6, disease-resistant) background, immunized with OspA or B, did not mount a humoral or cellular immune response to OspA or B, respectively, but responded normally to other B. burgdorferi antigens. The evolution of Lyme borreliosis, including infection and the development of arthritis and carditis, was similar in transgenic and nontransgenic littermates suggesting that an OspA or B immune response is not singularly involved in either the genesis or regression of Lyme disease in C3H or B6 mice.

Authors

E Fikrig, H Tao, M Chen, S W Barthold, R A Flavell

Recombinant peanut allergen Ara h I expression and IgE binding in patients with peanut hypersensitivity.

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Peanut allergy is a significant health problem because of the frequency, the potential severity, and the chronicity of the allergic sensitivity. Serum IgE from patients with documented peanut hypersensitivity reactions and a peanut cDNA expression library were used to identify clones that encode peanut allergens. One of the major peanut allergens, Ara h I, was selected from these clones using Ara h I specific oligonucleotides and polymerase chain reaction technology. The Ara h I clone identified a 2.3-kb mRNA species on a Northern blot containing peanut poly (A)+ RNA. DNA sequence analysis of the cloned inserts revealed that the Ara h I allergen has significant homology with the vicilin seed storage protein family found in most higher plants. The isolation of the Ara h I clones allowed the synthesis of this protein in E. coli cells and subsequent recognition of this recombinant protein in immunoblot analysis using serum IgE from patients with peanut hypersensitivity. With the production of the recombinant peanut protein it will now be possible to address the pathophysiologic and immunologic mechanisms regarding peanut hypersensitivity reactions specifically and food hypersensitivity in general

Authors

A W Burks, G Cockrell, J S Stanley, R M Helm, G A Bannon

Insulin and insulin-like growth factor-I enhance human skeletal muscle protein anabolism during hyperaminoacidemia by different mechanisms.

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Insulin inhibits proteolysis in human muscle thereby increasing protein anabolism. In contrast, IGF-I promotes muscle protein anabolism principally by stimulating protein synthesis. As increases or decreases of plasma amino acids may affect protein turnover in muscle and also alter the muscle's response to insulin and/or IGF-I, this study was designed to examine the effects of insulin and IGF-I on human muscle protein turnover during hyperaminoacidemia. We measured phenylalanine balance and [3H]-phenylalanine kinetics in both forearms of 22 postabsorptive adults during a continuous [3H] phenylalanine infusion. Measurements were made basally and at 3 and 6 h after beginning a systemic infusion of a balanced amino acid mixture that raised arterial phenylalanine concentration about twofold. Throughout the 6 h, 10 subjects received insulin locally (0.035 mU/min per kg) into one brachial artery while 12 other subjects were given intraaterial IGF-I (100 ng/min per kg) to raise insulin or IGF-I concentrations, respectively, in the infused arm. The contralateral arm in each study served as a simultaneous control for the effects of amino acids (aa) alone. Glucose uptake and lactate release increased in the insulin- and IGF-I-infused forearms (P < 0.01) but did not change in the contralateral (aa alone) forearm in either study. In the aa alone arm in both studies, hyperaminoacidemia reversed the postabsorptive net phenylalanine release by muscle to a net uptake (P < 0.025, for each) due to a stimulation of muscle protein synthesis. In the hormone-infused arms, the addition of either insulin or IGF-I promoted greater positive shifts in phenylalanine balance than the aa alone arm (P < 0.01). With insulin, the enhanced anabolism was due to inhibition of protein degradation (P < 0.02), whereas IGF-I augmented anabolism by a further stimulation of protein synthesis above aa alone (P < 0.02). We conclude that: (a) hyperaminoacidemia specifically stimulates muscle protein synthesis; (b) insulin, even with hyperaminoacidemia, improves muscle protein balance solely by inhibiting proteolysis; and (c) hyperaminoacidemia combined with IGF-I enhances protein synthesis more than either alone.

Authors

D A Fryburg, L A Jahn, S A Hill, D M Oliveras, E J Barrett

Molecular analysis of a major antigenic region of the 240-kD protein of Mi-2 autoantigen.

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Anti-Mi-2 autoantibody is strongly associated with dermatomyositis and found in sera of 20% of patients. Mi-2 antigen contains at least eight components and previous evidence suggested that the 240-kD protein was the antigenic component for at least some sera. In this study, anti-M-2 patient sera were used to screen human thymocyte and HeLa cell lambda gt11 expression libraries, and two clones from each had plaques specifically reactive with anti-Mi-2 sera. Studies with affinity-purified antibody supported the identification of the clones. All of 44 anti-Mi-2 sera reacted with the plaques, but none of 44 control sera reacted significantly. The cDNAs were identical, and full sequencing of one revealed an open reading frame spanning a 1,054-bp insert. Rescreening the library with the cDNA yielded a 1,589-bp cDNA that continued the open reading frame. The Mi-2 cDNA hybridized to a single 7.5-8.0 kb mRNA of HeLa cells, by Northern blot. Rabbit antiserum directed at a portion of the cDNA product reacted with HeLa 240-kD Mi-2 protein. The sequence was notable for four potential zinc-fingers and several charged regions. The protein encoded by the cDNA produced in vitro reacted with only one of five of the Mi-2 sera. These findings indicate that the Mi-2 240 kD is a novel protein that is antigenic for all Mi-2 sera, and strongly suggests that a major common epitope is conformational in nature.

Authors

Q Ge, D S Nilasena, C A O'Brien, M B Frank, I N Targoff

Possible links between glucose-induced changes in the energy state of pancreatic B cells and insulin release. Unmasking by decreasing a stable pool of adenine nucleotides in mouse islets.

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Whether adenine nucleotides in pancreatic B cells serve as second messengers during glucose stimulation of insulin secretion remains disputed. Our hypothesis was that the actual changes in ATP and ADP are obscured by the large pool of adenine nucleotides (ATP/ADP ratio close to 1) in insulin granules. Therefore, mouse islets were degranulated acutely with a cocktail of glucose, KCl, forskolin, and phorbol ester or during overnight culture in RPMI-1640 medium containing 10 mM glucose. When these islets were then incubated in 0 glucose + azide (to minimize cytoplasmic and mitochondrial adenine nucleotides), their content in ATP + ADP + AMP was decreased in proportion to the decrease in insulin stores. After incubation in 10 mM glucose (no azide), the ATP/ADP ratio increased from 2.4 to > 8 in cultured islets, and only from 2 to < 4 in fresh islets. These differences were not explained by changes in glucose oxidation. The glucose dependency (0-30 mM) of the changes in insulin secretion and in the ATP/ADP ratio were then compared in the same islets. In nondegranulated, fresh islets, the ATP/ADP ratio increased between 0 and 10 mM glucose and then stabilized although insulin release kept increasing. In degranulated islets, the ATP/ADP ratio also increased between 0 and 10 mM glucose, but a further increase still occurred between 10 and 20 mM glucose, in parallel with the stimulation of insulin release. In conclusion, decreasing the granular pool of ATP and ADP unmasks large changes in the ATP/ADP ratio and a glucose dependency which persists within the range of stimulatory concentrations. The ATP/ADP ratio might thus serve as a coupling factor between glucose metabolism and insulin release.

Authors

P Detimary, J C Jonas, J C Henquin

Transfer of rheumatoid arthritis into severe combined immunodeficient mice. The pathogenetic implications of T cell populations oligoclonally expanding in the rheumatoid joints.

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To investigate the pathogenicity of T cells infiltrating in the rheumatoid joints, mononuclear cells (MNC), predominantly T cells, isolated from either synovial fluid or synovial tissues of the patients with RA were transferred into severe combined immunodeficient (SCID) mice by intraarticular injections. According to our observations in this experimental system, patients with RA could be classified into at least two groups. In one group of patients, the infiltrating MNC induced synovial hyperplasia in the recipient SCID mice (the positive group). Whereas, in the other group no synovial hyperplasia was observed (the negative group). The induction of synovial hyperplasia observed in the positive group was prevented by an anti-human CD3 antibody (OKT3), indicating T cell mediation. Analysis of T cell receptor (TCR) V beta usage by reverse transcriptase polymerase chain reaction in the infiltrating MNC transferred into SCID mice revealed a marked skew towards the preferential use of certain V beta genes, which was not seen in the peripheral blood MNC, in only the positive group. The patterns of TCR/V beta skew were not uniform among the patients. The analysis of the PCR-amplified genes of such skewed TCR/ V beta by single strand conformational polymorphism showed distinct bands, indicating that the T cell populations expanding in rheumatoid joints of the positive group were oligoclonal. Furthermore, the enrichment of the T cell populations expressing such skewed TCR/V beta by in vitro stimulation of peripheral blood MNC of the patients with the relevant superantigen enabled the induction of synovial hyperplasia in the SCID mice. These results suggest that the pathogenic T cells could be activated locally in rheumatoid joints by certain antigens in some, but not in all patients with RA.

Authors

T Mima, Y Saeki, S Ohshima, N Nishimoto, M Matsushita, M Shimizu, Y Kobayashi, T Nomura, T Kishimoto

Identification and characterization of a gene regulating enzymatic glycosylation which is induced by diabetes and hyperglycemia specifically in rat cardiac tissue.

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Primary cardiac abnormalities have been frequently reported in patients with diabetes probably due to metabolic consequences of the disease. Approximately 2,000 mRNA species from the heart of streptozotocin-induced diabetic and control rats were compared by the mRNA differential display method, two of eight candidate clones thus isolated (DH1 and 13) were confirmed by Northern blot analysis. The expression of clone 13 was increased in the heart by 3.5-fold (P < 0.05) and decreased in the aorta by twofold (P < 0.05) in diabetes as compared to control. Sequence analysis showed that clone 13 is a rat mitochondrial gene. DH1 was predominantly expressed in the heart with an expression level 6.8-fold higher in the diabetic rats than in control (P < 0.001). Insulin treatment significantly (P < 0.001) normalized the expression of DH1 in the hearts of diabetic rats. DH1 expression was observed in cultured rat cardiomyocytes, but not in aortic smooth muscle cells or in cardiac derived fibroblasts. The expression in cardiomyocytes was regulated by insulin and glucose concentration of culture media. The full length cDNA of DH1 had a single open-reading frame with 85 and 92% amino acid identity to human and mouse UDP-GlcNAc:Gal beta 1-3GalNAc alpha R beta 1-6 N-acetylglucosaminyltransferase (core 2 GlcNAc-T), respectively, a key enzyme determining the structure of O-linked glycosylation. Transient transfection of DH1 cDNA into Cos7 cells conferred core 2 GlcNAc-T enzyme activity. In vivo, core 2 GlcNAc-T activity was increased by 82% (P < 0.05) in diabetic hearts vs controls, while the enzymes GlcNAc-TI and GlcNAc-TV responsible for N-linked glycosylation were unchanged. These results suggest that core 2 GlcNAc-T is specifically induced in the heart by diabetes or hyperglycemia. The induction of this enzyme may be responsible for the increase in the deposition of glycoconjugates and the abnormal functions found in the hearts of diabetic rats.

Authors

Y Nishio, C E Warren, J A Buczek-Thomas, J Rulfs, D Koya, L P Aiello, E P Feener, T B Miller Jr, J W Dennis, G L King

Immunohistochemical localization of V2 vasopressin receptor along the nephron and functional role of luminal V2 receptor in terminal inner medullary collecting ducts.

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We investigated immunohistochemical localization of V2 vasopressin receptor along the nephron using a specific polyclonal antibody. Staining was observed in some of thick ascending limbs and all of principal and inner medullary collecting duct (IMCD) cells. Not only basolateral but also luminal membrane was stained in collecting ducts, especially in terminal IMCD (tIMCD). To learn the functional role of luminal V2 receptor in tIMCD, we studied the luminal effects of arginine vasopressin (AVP) on osmotic water permeability (Pf), urea permeability (Pu), and cAMP accumulation using isolated perfused rat tIMCD. In the absence of bath AVP, luminal AVP caused a small increase in cAMP accumulation, Pf and Pu, confirming the presence of V2 receptor in the lumen of tIMCD. In contrast, luminal AVP inhibited Pf and Pu by 30-65% in the presence of bath AVP by decreasing cAMP accumulation via V1a or oxytocin receptors and by an unknown mechanism via V2 receptors in the luminal membrane of tIMCD. These data show that V2 receptors are localized not only in the basolateral membrane but also in the luminal membrane of the distal nephron. Luminal AVP acts as a negative feedback system upon the basolateral action of AVP in tIMCD.

Authors

H Nonoguchi, A Owada, N Kobayashi, M Takayama, Y Terada, J Koike, K Ujiie, F Marumo, T Sakai, K Tomita

Markedly inhibited 7-dehydrocholesterol-delta 7-reductase activity in liver microsomes from Smith-Lemli-Opitz homozygotes.

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We investigated the enzyme defect in late cholesterol biosynthesis in the Smith-Lemli-Opitz syndrome, a recessively inherited developmental disorder characterized by facial dysmorphism, mental retardation, and multiple organ congenital anomalies. Reduced plasma and tissue cholesterol with increased 7-dehydrocholesterol concentrations are biochemical features diagnostic of the inherited enzyme defect. Using isotope incorporation assays, we measured the transformation of the precursors, [3 alpha- 3H]lathosterol and [1,2-3H]7-dehydrocholesterol into cholesterol by liver microsomes from seven controls and four Smith-Lemli-Opitz homozygous subjects. The introduction of the double bond in lathosterol at C-5[6] to form 7-dehydrocholesterol that is catalyzed by lathosterol-5-dehydrogenase was equally rapid in controls and homozygotes liver microsomes (120 +/- 8 vs 100 +/- 7 pmol/mg protein per min, P = NS). In distinction, the reduction of the double bond at C-7 [8] in 7-dehydrocholesterol to yield cholesterol catalyzed by 7-dehydrocholesterol-delta 7-reductase was nine times greater in controls than homozygotes microsomes (365 +/- 23 vs 40 +/- 4 pmol/mg protein per min, P < 0.0001). These results demonstrate that the pathway of lathosterol to cholesterol in human liver includes 7-dehydrocholesterol as a key intermediate. In Smith-Lemli-Opitz homozygotes, the transformation of 7-dehydrocholesterol to cholesterol by hepatic microsomes was blocked although 7-dehydrocholesterol was produced abundantly from lathosterol. Thus, lathosterol 5-dehydrogenase is equally active which indicates that homozygotes liver microsomes are viable. Accordingly, microsomal 7-dehydrocholesterol-delta 7-reductase is inherited abnormally in Smith-Lemli-Opitz homozygotes.

Authors

S Shefer, G Salen, A K Batta, A Honda, G S Tint, M Irons, E R Elias, T C Chen, M F Holick

Parathyroid cell proliferation in normal and chronic renal failure rats. The effects of calcium, phosphate, and vitamin D.

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Secondary hyperparathyroidism is characterized by an increase in parathyroid (PT) cell number, and parathyroid hormone (PTH) synthesis and secretion. It is still unknown as to what stimuli regulate PT cell proliferation and how they do this. We have studied rats with dietary-induced secondary hyper- and hypoparathyroidism, rats given 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and rats after 5/6 nephrectomy for the presence of PT cell proliferation and apoptosis. PT cell proliferation has been measured by staining for proliferating cell nuclear antigen (PCNA) and apoptosis by in situ detection of nuclear DNA fragmentation and correlated with serum biochemistry and PTH mRNA levels. A low calcium diet led to increased levels of PTH mRNA and a 10-fold increase in PT cell proliferation. A low phosphate diet led to decreased levels of PTH mRNA and the complete absence of PT cell proliferation. 1,25 (OH)2D3 (25 pmol/d x 3) led to a decrease in PTH mRNA levels and unlike the hypophosphatemic rats there was no decrease in cell proliferation. There were no cells undergoing apoptosis in any of the experimental conditions. The secondary hyperparathyroidism of 5/6 nephrectomized rats was characterized by an increase in PTH mRNA levels and PT cell proliferation which were both markedly decreased by a low phosphate diet. The number of PCNA positive cells was increased by a high phosphate diet. Therefore hypocalcemia, hyperphosphatemia and uremia lead to PT cell proliferation, and hypophosphatemia completely abolishes this effect. Injected 1,25 (OH)2D3 had no effect. These findings emphasize the importance of a normal phosphate and calcium in the prevention of PT cell hyperplasia.

Authors

T Naveh-Many, R Rahamimov, N Livni, J Silver

Calcium- and CaMKII-dependent chloride secretion induced by the microsomal Ca(2+)-ATPase inhibitor 2,5-di-(tert-butyl)-1,4-hydroquinone in cystic fibrosis pancreatic epithelial cells.

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Microsomal Ca(2+)-ATPase inhibitors such as thapsigargin (THG), cyclopiazonic acid (CPA) and 2,5-di-(tert-butyl)-1,4-hydroquinone (DBHQ) have been shown to inhibit Ca2+ reuptake by the intracellular stores and increase cytosolic free Ca2+ ([Ca2+]i). DBHQ is a commercially available non-toxic synthetic compound chemically unrelated to THG and CPA. In this study, we tested the feasibility of utilizing DBHQ to improve Cl- secretion via the Ca(2+)-dependent pathway, in the cystic fibrosis (CF)-derived pancreatic epithelial cell line CFPAC-1. DBHQ stimulated 125I efflux and mobilized intracellular free Ca2+ in a dose-dependent manner. The maximal effects were seen at concentrations of 25-50 microM. DBHQ (25 microM) caused a short-term rise in [Ca2+]i in the absence of ambient Ca2+, and a sustained elevation of [Ca2+]i in cell monolayers bathed in the efflux solution (1.2 mM Ca2+), which was largely attenuated by Ni2+ (5 mM). Bath-application of DBHQ induced an outwardly-rectifying whole-cell Cl- current, which was abolished by pipette addition of BAPTA (5 mM) or CaMK [273-302] (20 microM), an inhibitory peptide of multifunctional Ca2+/calmodulin-dependent protein kinase (CaMKII). Pretreatment of monolayers of CFPAC-1 cells with DBHQ for 4-5 min significantly increased the Ca(2+)-independent or autonomous activity of CaMKII assayed in the cell homogenates. Thus, DBHQ appears to enhance Cl- channel activity via a Ca(2+)-dependent mechanism involving CaMKII. Pretreatment of CFPAC-1 cells with up to 50 microM DBHQ for 6 h did not cause any detectable change in cell viability and did not significantly affect the cell proliferation rate. These results suggest that appropriate selective microsomal Ca(2+)-ATPase inhibitors may be therapeutically useful in improving Cl- secretion in CF epithelial cells.

Authors

A C Chao, K Kouyama, E K Heist, Y J Dong, P Gardner

Overexpression of glucose transporters in rat mesangial cells cultured in a normal glucose milieu mimics the diabetic phenotype.

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An environment of high glucose concentration stimulates the synthesis of extracellular matrix (ECM) in mesangial cell (MC) cultures. This may result from a similar increase in intracellular glucose concentration. We theorized that increased uptake, rather than glucose concentration per se is the major determinant of exaggerated ECM formation. To test this, we compared the effects of 35 mM glucose on ECM synthesis in normal MCs with those of 8 mM glucose in the same cells overexpressing the glucose transporter GLUT1 (MCGT1). Increasing medium glucose from 8 to 35 mM caused normal MCs to increase total collagen synthesis and catabolism, with a net 81-90% increase in accumulation. MCs transduced with the human GLUT1 gene (MCGT1) grown in 8 mM glucose had a 10-fold greater GLUT1 protein expression and a 1.9, 2.1, and 2.5-fold increase in cell myo-inositol, lactate production, and cell sorbitol content, respectively, as compared to control MCs transduced with bacterial beta-galactosidase (MCLacZ). MCGT1 also demonstrated increased glucose uptake (5-fold) and increased net utilization (43-fold), and greater synthesis of individual ECM components than MCLacZ. In addition, total collagen synthesis and catabolism were also enhanced with a net collagen accumulation 111-118% greater than controls. Thus, glucose transport activity is an important modulator of ECM formation by MCs; the presence of high extracellular glucose concentrations is not necessarily required for the stimulation of matrix synthesis.

Authors

C W Heilig, L A Concepcion, B L Riser, S O Freytag, M Zhu, P Cortes

Antiintegrin alpha v beta 3 blocks human breast cancer growth and angiogenesis in human skin.

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Authors

P C Brooks, S Strömblad, R Klemke, D Visscher, F H Sarkar, D A Cheresh

Angiotensin converting enzyme expression is increased in small pulmonary arteries of rats with hypoxia-induced pulmonary hypertension.

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Previous studies suggest that while lung angiotensin converting enzyme (ACE) activity is reduced during chronic hypoxia, inhibitors of ACE attenuate hypoxic pulmonary hypertension. In an attempt to explain this paradox we investigated the possibility that whole lung ACE activity may not reflect local pulmonary vascular ACE expression. The experimental approach combined in vivo hemodynamic studies in control and chronically hypoxic rats, measurement of whole lung ACE activity, and evaluation of local pulmonary vascular ACE expression by in situ hybridization and immunohistochemistry. Total lung ACE activity was reduced to 50% of control activity by 5 d of hypoxia and remained low for the duration of the study. Immunohistochemistry showed a marked reduction of ACE staining in alveolar capillary endothelium. However, an increase in ACE staining was observed in the walls of small newly muscularized pulmonary arteries at the level of alveolar ducts and walls. In situ hybridization studies showed increased signal for ACE mRNA in the same vessels. Inhibition of ACE by captopril during chronic hypoxia attenuated pulmonary hypertension and markedly reduced distal muscularization of small pulmonary arteries. In addition, we demonstrated marked longitudinal variation in ACE expression along the normal pulmonary vasculature with the highest levels found in small muscular arteries associated with terminal and respiratory bronchioles. We conclude that local ACE expression is increased in the walls of small pulmonary arteries during the development of hypoxic pulmonary hypertension, despite a generalized reduction in alveolar capillary ACE expression, and we speculate that local arteriolar ACE may play a role in the vascular remodeling associated with pulmonary hypertension.

Authors

N W Morrell, E N Atochina, K G Morris, S M Danilov, K R Stenmark

Expression of VAMP-2-like protein in kidney collecting duct intracellular vesicles. Colocalization with Aquaporin-2 water channels.

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Body water balance is controlled by vasopressin, which regulates Aquaporin-2 (AQP2) water channels in kidney collecting duct cells by vesicular trafficking between intracellular vesicles and the plasma membrane. To examine the molecular apparatus involved in vesicle trafficking and vasopressin regulation of AQP2 in collecting duct cells, we tested if targeting proteins expressed in the synaptic vesicles, namely vesicle-associated membrane proteins 1 and 2 (VAMP1 and 2), are expressed in kidney collecting duct. Immunoblotting revealed specific labeling of VAMP2 (18-kD band) but not VAMP1 in membrane fractions prepared from kidney inner medulla. Controls using preadsorbed antibody or preimmune serum were negative. Bands of identical molecular size were detected in immunoblots of brain membrane vesicles and purified synaptic vesicles. VAMP2 in kidney membranes was cleaved by tetanus toxin, revealing a tetanus toxin-sensitive VAMP homologue. Similarly, tetanus toxin cleaved VAMP2 in synaptic vesicles. In kidney inner medulla, VAMP2 was predominantly expressed in the membrane fraction enriched for intracellular vesicles, with little or no VAMP2 in the plasma membrane enriched fraction. This was confirmed by immunocytochemistry using semithin cryosections, which showed mainly vesicular labeling in collecting duct principal cells, with no labeling of intercalated cells. VAMP2 immunolabeling colocalized with AQP2 labeling in intracellular vesicles, as determined by immunoelectron microscopy after double immunolabeling of isolated vesicles. Quantitative analysis of 1,310 vesicles revealed a highly significant association of both AQP2 and VAMP2 in the same vesicles (P < 0.0001). Furthermore, the presence of AQP2 in vesicles immunoisolated with anti-VAMP2 antibodies was confirmed by immunoblotting. In conclusion, VAMP2, a component of the neuronal SNARE complex, is expressed in vesicles carrying AQP2, suggesting a role in vasopressin-regulated vesicle trafficking of AQP2 water channels.

Authors

S Nielsen, D Marples, H Birn, M Mohtashami, N O Dalby, M Trimble, M Knepper

Genetic factors in lipoprotein metabolism. Analysis of a genetic cross between inbred mouse strains NZB/BINJ and SM/J using a complete linkage map approach.

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A genetic cross was constructed from two parental inbred strains of mice, NZB/BINJ and SM/J, which differ markedly in their plasma lipoprotein levels. Plasma lipid and apolipoprotein values were measured in 184 F2 progeny on a normal chow diet and on an atherogenic diet. Genetic markers were typed at 126 loci spanning all chromosomes except the Y. Statistical analysis revealed significant linkage or suggestive linkage of lipoprotein levels with markers on a number of chromosomes. Chromosome 1 markers were linked to levels of total cholesterol (lod 5.9) and high density lipoprotein (HDL) cholesterol (lod 8.1), chromosome 5 markers were linked to levels of total cholesterol (lod 6.7) and HDL cholesterol (lod 5.6), and chromosome 7 markers were linked to levels of total plasma triglycerides (lod 5.1) and free fatty acids (lod 5.6). Plasma apoAII levels were linked to the apoAII gene (lod score 19.6) and were highly correlated with plasma HDL cholesterol levels (r = 0.63, P = 0.0001), indicating that apoAII expression influences HDL cholesterol levels. Molecular studies suggested that structural differences in the apoAII polypeptide of the two strains may contribute to differences in clearance of the protein.

Authors

D A Purcell-Huynh, A Weinreb, L W Castellani, M Mehrabian, M H Doolittle, A J Lusis

Reduced uptake of oxidized low density lipoproteins in monocyte-derived macrophages from CD36-deficient subjects.

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To clarify the physiological roles of CD36 as an oxidized low density lipoprotein (OxLDL) receptor, we analyzed the monocyte-derived macrophages from normal and two CD36-deficient subjects, since we identified the molecular abnormalities (Kashiwagi, H., Y. Tomiyama, Y. Kosugi, M. Shiraga, R. H. Lipsky, Y. Kanayama, Y. Kurata, and Y. Matsuzawa 1994. Blood. 83:3545-3552; and Kashiwagi, H., Y. Tomiyama, S. Honda, S. Kosugi, M. Shiraga, N. Nagao, S. Sekiguchi, Y. Kanayama, Y. Kurata, and Y. Matsuzawa. 1995. J. Clin. Invest. 95:1040-1046). Scatchard analysis of 125I-OxLDL binding showed a linear plot and the maximum binding was lower by approximately 40% in the macrophages from subjects with CD36 deficiency than those from normal controls. Competition studies showed that the uptake of 125I-OxLDL was suppressed by OKM5, an antibody against CD36, by 53% in normal control macrophages, but not in the CD36-deficient macrophages. After incubation with OxLDL for 24 h, cholesteryl ester mass accumulation was reduced by approximately 40% in the macrophages from CD36-deficient subjects than those from normal controls. These results suggest that CD36 is one of the physiological receptors for OxLDL. Since specific binding of OxLDL was only reduced by approximately 40% in spite of the complete deficiency of CD36, several other receptors also may have some role in OxLDL uptake. Further studies will be needed to assess the quantitative role of CD36 in foam cell formation in vivo.

Authors

S Nozaki, H Kashiwagi, S Yamashita, T Nakagawa, B Kostner, Y Tomiyama, A Nakata, M Ishigami, J Miyagawa, K Kameda-Takemura

In vitro cell injury by oxidized low density lipoprotein involves lipid hydroperoxide-induced formation of alkoxyl, lipid, and peroxyl radicals.

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Mounting evidence supports current theories linking lipoprotein oxidation to atherosclerosis. We sought the cellular biochemical mechanism by which oxidized LDL inflicts cell injury. Inhibitors of candidate pathways of cell death were used to treat human fibroblast target cells exposed to oxidized LDL.. Ebselen, which degrades lipid hydroperoxides, inhibited oxidized LDL toxicity, consistent with our recent report that 7 beta-hydroperoxycholesterol (7 beta-OOH chol) is the major cytotoxin of oxidized LDL. Intracellular chelation of metal ions inhibited, while preloading cells with iron enhanced, toxicity, Inhibition of oxidized LDL and 7 beta-OOH chol toxicity by 2-keto-4-thiolmethyl butyric acid, a putative alkoxyl radical scavenger and by vitamin E, probucol and diphenylphenylenediamine, putative scavengers of peroxyl radicals was consistent with the involvement of these radicals in the lethal sequence. Cell death was thus postulated to occur due to lipid peroxidation via a sequence involving lipid hydroperoxide-induced, iron-mediated formation of alkoxyl, lipid, and peroxyl radicals. Pathways involving other reactive oxygen species, new protein synthesis, or altered cholesterol metabolism were considered less likely, since putative inhibitors failed to lessen toxicity. Understanding the mechanism of cell injury by oxidized LDL and its toxic moiety, 7 beta-OOH chol, may indicate specific interventions in the cell injury believed to accompany vascular lesion development.

Authors

M D Coffey, R A Cole, S M Colles, G M Chisolm

Phorbol esters induce death in MCF-7 breast cancer cells with altered expression of protein kinase C isoforms. Role for p53-independent induction of gadd-45 in initiating death.

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Protein kinase C (PKC) modulates growth, differentiation and apoptosis in a cell-specific fashion. Overexpression of PKC-alpha in MCF-7 breast cancer cells (MCF-7-PKC-alpha cell) leads to expression of a more transformed phenotype. The response of MCF-7 and MCF-7-PKC-alpha cells to phorbol esters (TPA) was examined. TPA-treated MCF-7 cells demonstrated a modest cytostatic response associated with a G1 arrest that was accompanied by Cip1 expression and retinoblastoma hypophosphorylation. While p53 was detected in MCF-7 cells, evidence for TPA-induced stimulation of p53 transcriptional activity was not evident. In contrast, TPA treatment induced death of MCF-7-PKC-alpha cells. Bryostatin 1, another PKC activator, exerted modest cytostatic effects on MCF-7 cells while producing a cytotoxic response at low doses in MCF-7-PKC-alpha cells that waned at higher concentrations. TPA-treated MCF-7-PKC-alpha cells accumulated in G2/M, did not express p53, displayed decreased Cip1 expression, and demonstrated a reduction in retinoblastoma hypophosphorylation. TPA-treated MCF-7-PKC-alpha cells expressed gadd-45 which occurred before the onset of apoptosis. Thus, alterations in the PKC pathway can modulate the decision of a breast cancer cell to undergo death or differentiation. In addition, these data show that PKC activation can induce expression of gadd45 in a p53-independent fashion.

Authors

J E de Vente, C A Kukoly, W O Bryant, K J Posekany, J Chen, D J Fletcher, P J Parker, G J Pettit, G Lozano, P P Cook

Neutrophils use both shared and distinct mechanisms to adhere to selectins under static and flow conditions.

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Abstract

Both P-selectin glycoprotein ligand-1 (PSGL-1) and L-selectin are localized on the microvilli of neutrophils and have been implicated in the attachment of neutrophils to P-selectin or E-selectin. We directly compared the attachment and rolling of neutrophils on P-selectin and E-selectin under flow, with emphasis on the functions of PSGL-1 and L-selectin. Flowing neutrophils attached more avidly and rolled at lower velocities on P-selectin than on E-selectin at matched densities. Studies with purified molecules indicated that P-selectin and E-selectin bound to a related site on PSGL-1 that overlapped the epitope for the anti-PSGL-1 mAb PL1. E-selectin bound with lower affinity than P-selectin to this site and also bound to an additional site(s) on PSGL-1.PL1 abolished adhesion of neutrophils to P-selectin under shear or static conditions, whereas DREG-56, a mAb to L-selectin, had no effect on adhesion to P-selectin. PL1 inhibited attachment of neutrophils to E-selectin under flow but not static conditions. DREG-56 also inhibited attachment of flowing neutrophils to E-selectin, and a combination of DREG-56 and PL1 nearly eliminated attachment to E-selectin under flow. These data suggest that PSGL-1 functions cooperatively with L-selectin to mediate optimal attachment of flowing neutrophils to E-selectin but not to P-selectin. Neutrophils attach more efficiently and with greater strength to P-selectin, perhaps because of the higher affinity of P-selectin for the PL1-defined site on PSGL-1.

Authors

K D Patel, K L Moore, M U Nollert, R P McEver

Sympathetic neural mechanisms in obstructive sleep apnea.

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Abstract

Blood pressure, heart rate, sympathetic nerve activity, and polysomnography were recorded during wakefulness and sleep in 10 patients with obstructive sleep apnea. Measurements were also obtained after treatment with continuous positive airway pressure (CPAP) in four patients. Awake sympathetic activity was also measured in 10 age- and sex-matched control subjects and in 5 obese subjects without a history of sleep apnea. Patients with sleep apnea had high levels of nerve activity even when awake (P < 0.001). Blood pressure and sympathetic nerve activity did not fall during any stage of sleep. Mean blood pressure was 92 +/- 4.5 mmHg when awake and reached peak levels of 116 +/- 5 and 127 +/- 7 mmHg during stage II sleep (n = 10) and rapid eye movement (REM) sleep (n = 5), respectively (P < 0.001). Sympathetic activity increased during sleep (P = 0.01) especially during stage II (133 +/- 9% above wakefulness; P = 0.006) and REM (141 +/- 13%; P = 0.007). Peak sympathetic activity (measured over the last 10 s of each apneic event) increased to 299 +/- 96% during stage II sleep and to 246 +/- 36% during REM sleep (both P < 0.001). CPAP decreased sympathetic activity and blood pressure during sleep (P < 0.03). We conclude that patients with obstructive sleep apnea have high sympathetic activity when awake, with further increases in blood pressure and sympathetic activity during sleep. These increases are attenuated by treatment with CPAP.

Authors

V K Somers, M E Dyken, M P Clary, F M Abboud

Intracellular signaling pathways required for rat vascular smooth muscle cell migration. Interactions between basic fibroblast growth factor and platelet-derived growth factor.

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Abstract

Intracellular signaling pathways activated by both PDGF and basic fibroblast growth factor (bFGF) have been implicated in the migration of vascular smooth muscle cells (VSMC), a key step in the pathogenesis of many vascular diseases. We demonstrate here that, while bFGF is a weak chemoattractant for VSMCs, it is required for the PDGF-directed migration of VSMCs and the activation of calcium/calmodulin-dependent protein kinase II (CamKinase II), an intracellular event that we have previously shown to be important in the regulation of VSMC migration. Neutralizing antibodies to bFGF caused a dramatic reduction in the size of the intracellular calcium transient normally seen after PDGF stimulation and inhibited both PDGF-directed VSMC migration and CamKinase II activation. Partially restoring the calcium transient with ionomycin restored migration and CamKinase II activation as did the forced expression of a mutant CamKinase II that had been "locked" in the active state by site-directed mutagenesis. These results suggest that bFGF links PDGF receptor stimulation to changes in intracellular calcium and CamKinase II activation, reinforcing the central role played by CamKinase II in regulating VSMC migration.

Authors

C Bilato, R R Pauly, G Melillo, R Monticone, D Gorelick-Feldman, Y A Gluzband, S J Sollott, B Ziman, E G Lakatta, M T Crow

Myoglobin O2 desaturation during exercise. Evidence of limited O2 transport.

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Abstract

The assumption that cellular oxygen pressure (PO2) is close to zero in maximally exercising muscle is essential for the hypothesis that O2 transport between blood and mitochondria has a finite conductance that determines maximum O2 consumption. The unique combination of isolated human quadriceps exercise, direct measures of arterial, femoral venous PO2, and 1H nuclear magnetic resonance spectroscopy to detect myoglobin desaturation enabled this assumption to be tested in six trained men while breathing room air (normoxic, N) and 12% O2 (hypoxic, H). Within 20 s of exercise onset partial myoglobin desaturation was evident even at 50% of maximum O2 consumption, was significantly greater in H than N, and was then constant at an average of 51 +/- 3% (N) and 60 +/- 3% (H) throughout the incremental exercise protocol to maximum work rate. Assuming a myoglobin PO2 where 50% of myoglobin binding sites are bound with O2 of 3.2 mmHg, myoglobin-associated PO2 averaged 3.1 +/- .3 (N) and 2.1 +/- .2 mmHg (H). At maximal exercise, measurements of arterial PO2 (115 +/- 4 [N] and 46 +/- 1 mmHg [H]) and femoral venous PO2 (22 +/- 1.6 [N] and 17 +/- 1.3 mmHg [H]) resulted in calculated mean capillary PO2 values of 38 +/- 2 (N) and 30 +/- 2 mmHg(H). Thus, for the first time, large differences in PO2 between blood and intracellular tissue have been demonstrated in intact normal human muscle and are found over a wide range of exercise intensities. These data are consistent with an O2 diffusion limitation across the 1-5-microns path-length from red cell to the sarcolemma that plays a role in determining maximal muscle O2 uptake in normal humans.

Authors

R S Richardson, E A Noyszewski, K F Kendrick, J S Leigh, P D Wagner

Influence of glutathione S-transferase B (ligandin) on the intermembrane transfer of bilirubin. Implications for the intracellular transport of nonsubstrate ligands in hepatocytes.

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Abstract

To examine the hypothesis that glutathione S-transferases (GST) play an important role in the hepatocellular transport of hydrophobic organic anions, the kinetics of the spontaneous transfer of unconjugated bilirubin between membrane vesicles and rat liver glutathione S-transferase B (ligandin) was studied, using stopped-flow fluorometry. Bilirubin transfer from glutathione S-transferase B to phosphatidylcholine vesicles was best described by a single exponential function, with a rate constant of 8.0 +/- 0.7 s-1 (+/- SD) at 25 degrees C. The variations in transfer rate with respect to acceptor phospholipid concentration provide strong evidence for aqueous diffusion of free bilirubin. This finding was verified using rhodamine-labeled microsomal membranes as acceptors. Bilirubin transfer from phospholipid vesicles to GST also exhibited diffusional kinetics. Thermodynamic parameters for bilirubin dissociation from GST were similar to those for human serum albumin. The rate of bilirubin transfer from rat liver basolateral plasma membranes to acceptor vesicles in the presence of glutathione S-transferase B declined asymptotically with increasing GST concentration. These data suggest that glutathione S-transferase B does not function as an intracellular bilirubin transporter, although expression of this protein may serve to regulate the delivery of bilirubin, and other nonsubstrate ligands, to sites of metabolism within the cell.

Authors

S D Zucker, W Goessling, B J Ransil, J L Gollan

Identification of a new susceptibility locus for insulin-dependent diabetes mellitus by ancestral haplotype congenic mapping.

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Abstract

The number and exact locations of the major histocompatibility complex (MHC)-linked diabetogenic genes (Idd-1) are unknown because of strong linkage disequilibrium within the MHC. By using a congenic NOD mouse strain that possesses a recombinant MHC from a diabetes-resistant sister strain, we have now shown that Idd-1 consists of at least two components, one in and one outside the class II A and E regions. A new susceptibility gene (Idd-16) was mapped to the < 11-centiMorgan segment of chromosome 17 adjacent to, but distinct from, previously known Idd-1 candidates, class II A, E, and Tap genes. The coding sequences and splicing donor and acceptor sequences of the Tnfa gene, a candidate gene for Idd-16, were identical in the NOD, CTS, and BALB/c alleles, ruling out amino acid changes in the TNF molecule as a determinant of insulin-dependent diabetes mellitus susceptibility. Our results not only map a new MHC-linked diabetogenic gene(s) but also suggest a new way to fine map disease susceptibility genes within a region where strong linkage disequilibrium exists.

Authors

H Ikegami, S Makino, E Yamato, Y Kawaguchi, H Ueda, T Sakamoto, K Takekawa, T Ogihara

Molecular mechanisms of an inborn error of methionine pathway. Methionine adenosyltransferase deficiency.

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Abstract

Methionine adenosyltransferase (MAT) is a key enzyme in transmethylation, transsulfuration, and the biosynthesis of polyamines. Genetic deficiency of alpha/beta-MAT causes isolated persistent hypermethioninemia and, in some cases, unusual breath odor or neural demyelination. However, the molecular mechanism(s) underlying this deficiency has not been clearly defined. In this study, we characterized the human alpha/beta-MAT transcription unit and identified several mutations in the gene of patients with enzymatically confirmed diagnosis of MAT deficiency. Site-directed mutagenesis and transient expression assays demonstrated that these mutations partially inactivate MAT activity. These results establish the molecular basis of this disorder and allow for the development of DNA-based methodologies to investigate and diagnose hypermethioninemic individuals suspected of having abnormalities at this locus.

Authors

T Ubagai, K J Lei, S Huang, S H Mudd, H L Levy, J Y Chou

Comparative distribution of the alpha 1(IV), alpha 5(IV), and alpha 6(IV) collagen chains in normal human adult and fetal tissues and in kidneys from X-linked Alport syndrome patients.

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Abstract

We have shown previously that the 5' ends of the genes for the alpha 5(IV) and alpha 6(IV) collagen chains lie head-to-head on Xq22 and are deleted in patients with Alport syndrome (AS)-associated diffuse leiomyomatosis. In this study, we raised a rabbit anti-human alpha 6(IV)chain antibody, demonstrated its specificity by the analysis of recombinant NC1 domains af all six type IV chains, and studied the distribution of the alpha 6(IV) chain in relation to the alpha 1(IV) and alpha 5(IV) chains in human adult and fetal tissues involved in AS and diffuse leiomyomatosis. The alpha 6(IV) chain colocalizes with the alpha 5(IV) chain in basement membranes (BMs) of many tissues, but not in glomerular BM. These data exclude the alpha 6(IV) chain as a site for AS mutations. The head-to-head genomic pairing of the alpha 5(IV) and alpha 6 (IV) genes implies coordinate transcription of the two genes. Differential localization of the alpha 5(IV) and alpha 6(IV) chains shows that the two chains are not always coordinately regulated. The alpha 6(IV) chain, together with the alpha 3(IV)-alpha 5(IV) chains, was absent from all renal BMs in eight patients with X-linked AS while the alpha 1(IV) and alpha 2(IV) chains were increased. The data support the existence of two independent collagen networks, one for the alpha 3(IV)-alpha 6(IV) chains and one for the alpha 1(IV) and alpha 2(IV) chains.

Authors

B Peissel, L Geng, R Kalluri, C Kashtan, H G Rennke, G R Gallo, K Yoshioka, M J Sun, B G Hudson, E G Neilson

Human suction blister interstitial fluid prevents metal ion-dependent oxidation of low density lipoprotein by macrophages and in cell-free systems.

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Abstract

LDL in the circulation is well protected against oxidation by the highly efficient antioxidant defense mechanisms of human plasma. LDL oxidation contributing to atherosclerosis, therefore, has been hypothesized to take place in the interstitial fluid of the arterial wall. We investigated the antioxidant composition and the capacity to inhibit LDL oxidation of human suction blister interstitial fluid (SBIF), a suitable representative of interstitial fluid. We found that the concentrations in SBIF of the aqueous small-molecule antioxidants ascorbate and urate were, respectively, significantly higher (P < 0.05) and identical to plasma concentrations. In contrast, lipoprotein-associated lipids and lipid-soluble antioxidants (alpha-tocopherol, ubiquinol-10, lycopene, and beta-carotene) were present at only 8-23% of the concentrations in plasma. No lipid hydroperoxides could be detected ( < 5 nM) in either fluid. The capacity of serum and SBIF to protect LDL from oxidation was investigated in three metal ion-dependent systems: copper, iron, and murine macrophages in Ham's F-10 medium. In all three systems, addition of > or = 6% (vol/vol) of either serum or SBIF inhibited LDL oxidation by > 90%. The concentration that inhibited macrophage-mediated LDL oxidation by 50% was as low as 0.3% serum and 0.7% SBIF. The enzymatic or physical removal of ascorbate or urate and other low molecular weight components did not affect the ability of either fluid to prevent LDL oxidation, and the high molecular weight fraction was as protective as whole serum or SBIF. These data demonstrate that both serum and SBIF very effectively protect LDL from metal ion-dependent oxidation, most probably because of a cumulative metal-binding effect of several proteins. Our data suggest that LDL in the interstitial fluid of the arterial wall is very unlikely to get modified by metal ion-mediated oxidation.

Authors

A J Dabbagh, B Frei

Loss of hepatic autoregulation after carbohydrate overfeeding in normal man.

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Abstract

To determine the effect of increased glycogen stores on hepatic carbohydrate metabolism, 15 nondiabetic volunteers were studied before and after 4 d of progressive overfeeding. Glucose production and gluconeogenesis were assessed with [2-3H] glucose and [6-14C] glucose (Study I, n = 6) or [3-3H] glucose and [U-14C]-alanine (Study II, n = 9) and substrate oxidation was determined by indirect calorimetry. Overfeeding was associated with significant (P < 0.01) increases in plasma glucose (4.97 +/- 0.10 to 5.09 +/- 0.11 mmol/liter), insulin (18.8 +/- 1.5 to 46.6 +/- 10.0 pmol/liter) and carbohydrate oxidation (4.7 +/- 1.4 to 18.0 +/- 1.5 mumol.kg-1.min-1) and a decrease in lipid oxidation (1.2 +/- 0.2 to 0.3 +/- 0.1 mumol.kg-1.min-1). Hepatic glucose output (HGO) increased in Study I (10.2 +/- 0.5 to 13.1 +/- 0.9 mumol.kg-1.min-1, P < 0.01) and Study II (11.17 +/- 0.67 to 13.33 +/- 0.83 mumol.kg-1.min-1, P < 0.01), and gluconeogenesis decreased (57.6 +/- 6.4 to 33.4 +/- 4.9 mumol/min, P < 0.01), indicating an increase in glycogenolysis. The increase in glycogenolysis was only partly compensated by an increase in glucose cycle activity (2.2 +/- 0.2 to 3.4 +/- 0.4 mumol.kg-1.min-1, P < 0.01) and the fall in gluconeogenesis, thus resulting in increased HGO. The suppression of gluconeogenesis despite increased lactate and alanine (glycerol was decreased) was associated with decreased free fatty acid (FFA) oxidation and negligible FFA enhanced gluconeogenesis. These studies suggest that increased liver glycogen stores alone can overwhelm normal intrahepatic mechanisms regulating carbohydrate metabolism resulting in increased HGO in nondiabetic man.

Authors

J N Clore, S T Helm, W G Blackard

Mapping of quantitative trait loci for blood pressure and cardiac mass in the rat by genome scanning of recombinant inbred strains.

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Abstract

In the HXB and BXH recombinant inbred strains derived from the spontaneously hypertensive rat and the normotensive Brown Norway rat, we determined the strain distribution patterns of 500 genetic markers to scan the rodent genome for quantitative trait loci regulating cardiac mass and blood pressure. The markers spanned approximately 1,139 cM of the genome and were tested for correlations with left ventricular mass adjusted for body weight, and with systolic, diastolic, and mean arterial pressures. The marker for the dopamine 1A receptor (Drd1a) on chromosome 17 showed the strongest correlation with left ventricular heart weight (P = .00038, r = -0.59) and the relationship to heart weight was independent of blood pressure. The markers showing the strongest correlations with systolic, diastolic, and mean arterial pressure were D19Mit7 on chromosome 19 (P = .0012, r = .55), D2N35 on chromosome 2 (P = .0008, r = .56), and Il6 on chromosome 4 (P = .0018, r = .53), respectively. These studies demonstrate that the HXB and BXH strains can be effectively used for genome scanning studies of complex traits and have revealed several chromosome regions that may be involved in the genetic control of blood pressure and cardiac mass in the rat.

Authors

M Pravenec, D Gauguier, J J Schott, J Buard, V Kren, V Bila, C Szpirer, J Szpirer, J M Wang, H Huang

Adenosine A2b receptors evoke interleukin-8 secretion in human mast cells. An enprofylline-sensitive mechanism with implications for asthma.

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Abstract

Adenosine potentiates mast cell activation, but the receptor type and molecular mechanisms involved have not been defined. We, therefore, investigated the effects of adenosine on the human mast cell line HMC-1. Both the A2a selective agonist CGS21680 and the A2a/A2b nonselective agonist 5'-N-ethylcarboxamidoadenosine (NECA) increased cAMP, but NECA was fourfold more efficacious and had a Hill coefficient of 0.55, suggesting the presence of both A2a and A2b receptors. NECA 10 microM evoked IL-8 release from HMC-1, but CGS21680 10 microM had no effect. In separate studies we found that enprofylline, an antiasthmatic previously thought to lack adenosine antagonistic properties, is as effective as theophylline as an antagonist of A2b receptors at concentrations achieved clinically. Both theophylline and enprofylline 300 micro completely blocked the release of IL-8 by NECA. NECA, but not CGS21680, increases inositol phosphate formation and intracellular calcium mobilization through a cholera and pertussis toxin-insensitive mechanism. In conclusion, both A2a and A2b receptors are present in HMC-1 cells and are coupled to adenylate cyclase. In addition, A2b receptors are coupled to phospholipase C and evoke IL-8 release. This effect is blocked by theophylline and enprofylline, raising the possibility that this mechanism contributes to their antiasthmatic effects.

Authors

I Feoktistov, I Biaggioni

Vitronectin enhances internalization of crocidolite asbestos by rabbit pleural mesothelial cells via the integrin alpha v beta 5.

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Abstract

The mechanism by which pleural mesothelial cells, the likely progenitor cells of asbestos-induced mesothelioma, recognize and internalize crocidolite asbestos is unknown. Because incubation of asbestos fibers with serum increases their association with cells, we asked whether a protein coat on asbestos increased internalization of fibers via specific cellular receptors. Coating crocidolite with citronectin, but not with fibronectin or other proteins, increased fiber internalization by rabbit pleural mesothelial cells, as measured by a new technique using fluorescence confocal microscopy. Receptors for vitronectin, alpha v beta 3 and alpha v beta 5, were identified on mesothelial cells. Inhibiting vitronectin receptors by plating cells on a vitronectin substrate or incubating cells with excess soluble vitronectin reduced internalization of vitronectin-coated crocidolite. Inhibition of alpha v beta 5, but not alpha v beta 3, with blocking antibodies similarly reduced internalization. In addition, alpha v beta 5, but not alpha v beta 3, showed immunocytochemical colocalization with fibers. Of biologic relevance, coating crocidolite with serum also increased internalization via alpha v beta 5, an effect dependent on the vitronectin in serum. We conclude that pleural mesothelial cells recognize and internalize vitronectin- and serum-coated asbestos via the integrin alpha v beta 5. Since integrins initiate some of the same signaling pathways as does asbestos, our findings may provide insights into the mechanisms of asbestos-induced biologic effects.

Authors

A M Boylan, D A Sanan, D Sheppard, V C Broaddus

Functional expression and segmental localization of rat colonic K-adenosine triphosphatase.

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Abstract

A putative cDNA for the colonic K-ATPase has recently been cloned (Crowson, M.S., and G. E. Shull. 1992. J. Biol. Chem. 267:13740-13748). Considerable evidence exists that there are two K-ATPases and active K absorptive processes in the rat distal colon: one that is ouabain sensitive and the other ouabain insensitive. The present study used the baculovirus expression system to express K-ATPase activity in insect Spodoptera frugiperda (Sf 9) cells and a polyclonal antibody (M-1), developed against a fusion protein produced from the 327 nucleotide fragment from 5' coding region of the putative K-ATPase cDNA, to identify the specific localization of the K-ATPase protein. K-ATPase activity (28.7 +/- 1.2 nmol inorganic phosphate/mg protein min) was expressed in plasma membranes isolated from Sf 9 cells infected with baculovirus containing recombinant DNA with the putative K-ATPase cDNA. Km for K for the K-ATPase was 1.2 mM. The expressed K-ATPase activity was not inhibited by ouabain (1 mM); while the Ki for vanadate inhibition was 8.3 microM. Western blot analysis with the M-1 antibody identified a 100-kD protein in apical membranes prepared from distal, but not proximal, rat colon. Immunohistochemical studies with M-1 antibody localized K-ATPase only in the apical membrane of surface cells, while an mAb (c464.6) against Na,K-ATPase localized basolateral membranes of both surface and crypt cells of rat distal colon. In conclusion, the putative K-ATPase cDNA encodes an ouabain-insensitive K-ATPase that is present only in the apical membrane of surface cells of rat distal colon.

Authors

J Lee, V M Rajendran, A S Mann, M Kashgarian, H J Binder

Impairment of selectin-mediated leukocyte adhesion to venular endothelium in spontaneously hypertensive rats.

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Abstract

The present study was designed to elucidate whether molecular mechanisms for leukocyte adhesion to microvascular endothelium may differ between spontaneously hypertensive rats and Wistar Kyoto rats. Leukocyte rolling and adhesion were investigated while monitoring venular wall shear rates in the mesenteric microcirculation stimulated with histamine or tert-butyl hydroperoxide in the two strains. In Wistar Kyoto rats, 10 microM histamine as well as 500 microM tertbutyl hydroperoxide promoted a significant reduction of venular leukocyte rolling velocity and subsequent adhesion. These changes in leukocyte behavior were blocked by monoclonal antibodies against P-selectin (PB 1.3) and against sialyl Lewis X-like carbohydrates (2H5). However, spontaneously hypertensive rats exhibited a blunted response of the stimulus-elicited leukocyte rolling, which was associated with impairment of venular P-selectin expression as well as a decrease in the expression of sialyl Lewis X-like carbohydrates on circulating neutrophils. No significant differences were detected between the two strains not only in the surface CD11b/CD18 expression but also in the CD18-mediated adhesivity of neutrophils to intracellular adhesion molecule-1 transfectants in vitro. These results suggest that impairment of selectin-mediated leukocyte adhesion is an event responsible for disorders of inflammatory responses in spontaneously hypertensive rats.

Authors

M Suematsu, H Suzuki, T Tamatani, Y Iigou, F A DeLano, M Miyasaka, M J Forrest, R Kannagi, B W Zweifach, Y Ishimura

Expression and localization of endothelin-1 and endothelin receptors in human meningiomas. Evidence for a role in tumoral growth.

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In addition to its well-known homoeostatic actions in the cardiovascular system, ET-1 has been shown to constitute a potent growth regulatory peptide in various tissues. We have studied the expression of ET-1 and its receptors (ET-Ar and ET-Br) in human meningiomas (n = 35) as well as their involvement in cellular growth. By PCR of reverse-transcribed RNA we detected ET-1 mRNA in 91% (32 of 35), ET-Ar mRNA in 82% (29 of 35), and ET-Br mRNA in 42% (15 of 35) of human meningiomas examined. The localization of ET-1 mRNA, ET-Ar mRNA, and ET-1 peptide in tumoral cells was observed by in situ hybridization and immunohistochemistry, whereas ET-Br mRNA was expressed at low level only in cells belonging to blood vessels. In addition, we found that ET-1 stimulated [3H] thymidine incorporation in primary cell cultures of 20 meningiomas and that this effect could be blocked by BQ-123, a specific antagonist for ET-Ar. In contrast, RES-701-3, an antagonist of ET-Br, did not block the proliferative effect of ET-1. In conclusion, our data provide evidence that ET-1 constitutes an important growth factor for meningiomas acting via ET-Ar. We can hypothesize that ET-1, acting in concert with other growth factors and cytokines, is involved in the meningioma tumorigenesis.

Authors

U Pagotto, T Arzberger, U Hopfner, J Sauer, U Renner, C J Newton, M Lange, E Uhl, A Weindl, G K Stalla

Intratracheal instillation of keratinocyte growth factor decreases hyperoxia-induced mortality in rats.

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Abstract

Alveolar type II cell proliferation occurs after many forms of lung injury and is thought to play a critical role in alveolar epithelial repair. Keratinocyte growth factor/fibroblast growth factor 7 (KGF) has been shown to promote alveolar type II cell growth in primary culture and alveolar epithelial hyperplasia in vivo. In this study, we used immunohistochemical analysis to determine the intrapulmonary distribution and cellular localization of recombinant human KGF (rhKGF) instilled into the trachea of rats. 6 h after administration, immunoreactive KGF was observed within the lung parenchyma and along alveolar epithelial cell membranes. By 18-24 h, KGF was detected intracellularly in alveolar epithelial cells and intraalveolar macrophages. Immunoreactive KGF was not demonstrable 48 h after delivery or in lung sections from PBS-treated animals. Intratracheal instillation of 5 mg/kg rhKGF stimulated a marked, time-dependent increase in the alveolar type II cell specific labeling index to a maximum level of 33 +/- 3% 48 h after rhKGF administration compared with 1.3 +/- 0.3% after PBS instillation. In addition, this increase in type II cell proliferation in vivo was documented by flow cytometric analysis of isolated type II cells which revealed a nearly fivefold increase in the proportion of cells traversing through the S and G2/M phases of the cell cycle. To test the hypothesis that KGFs effects on type II cells in vivo might affect the response to lung injury, rats were treated with rhKGF and exposed to hyperoxia. Animals that received 1 or 5 mg/kg rhKGF exhibited dramatically reduced mortality (P < 0.001, for both doses). Survival for animals treated with 0.1 mg/kg rhKGF was not significantly different from either untreated rats or animals treated with heat-denatured rhKGF. The lungs of rhKGF-treated animals that survived hyperoxia exposure had minimal hemorrhage and no exudate within the intraalveolar space. These experiments established that intratracheal administration of rhKGF stimulated alveolar type II cell proliferation in vivo and reduced hyperoxia-induced lung injury in rats. Directed delivery of KGF to the lungs may provide a therapeutic strategy to preserve or restore the alveolar epithelium during exposure to hyperoxia or other injurious agents.

Authors

R J Panos, P M Bak, W S Simonet, J S Rubin, L J Smith

Stable fetal cardiomyocyte grafts in the hearts of dystrophic mice and dogs.

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Abstract

This report documents the formation of stable fetal cardiomyocyte grafts in the myocardium of dystrophic dogs. Preliminary experiments established that the dystrophin gene product could be used to follow the fate of engrafted cardiomyocytes in dystrophic mdx mice. Importantly, ultrastructural analyses revealed the presence of intercalated discs consisting of fascia adherens, desmosomes, and gap junctions at the donor-host cardiomyocyte border. To determine if isolated cardiomyocytes could form stable intracardiac grafts in a larger species, preparations of dissociated fetal canine cardiomyocytes were delivered into the hearts of adult CXMD (canine X-linked muscular dystrophy) dogs. CXMD dogs, like Duchenne muscular dystrophy patients and mdx mice, fail to express dystrophin in both cardiac and skeletal muscle. Engrafted fetal cardiomyocytes, identified by virtue of dystrophin immunoreactivity, were observed to be tightly juxtaposed with host cardiomyocytes as long as 10 wk after engraftment, the latest date analyzed. Confocal laser scanning microscopy revealed the presence of connexin43, a major constituent of the gap junction, at the donor-host cardiomyocyte border. The presence of intracardiac grafts was not associated with arrhythmogenesis in the CXMD model. These results indicate that fetal cardiomyocyte grafting can successfully augment cardiomyocyte number in larger animals.

Authors

G Y Koh, M H Soonpaa, M G Klug, H P Pride, B J Cooper, D P Zipes, L J Field

Binding-, intracellular transport-, and biosynthesis-defective mutants of vasopressin type 2 receptor in patients with X-linked nephrogenic diabetes insipidus.

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Abstract

Nephrogenic diabetes insipidus (NDI) is most often an X-linked disorder in which urine is not concentrated due to renal resistance to arginine vasopressin. We recently identified four vasopressin type 2 receptor gene mutations in unrelated X-linked NDI families, including R143P, delta V278, R202C, and 804insG. All these mutations reduced ligand binding activity to < 10% of the normal without affecting mRNA accumulation. To elucidate whether the receptors are expressed on the cell surface, we analyzed biosynthesis and localization of tagged or untagged receptors stably expressed in Chinese hamster ovary (CHO) cells, using two antibodies directed against distinct termini. Whole-cell and surface labeling studies revealed that the R202C clone had both surface-localized (50-55 kD) and intracellular proteins (40 and 75 kD), similar to the wild-type AVPR2 clone, whereas the R143P and delta V278 clones lacked the surface receptors, despite relatively increased intracellular components. The 804insG mutant cell produced no proteins despite an adequate mRNA level. Immunofluorescence staining confirmed that the R202C mutant reaches the cell surface, whereas the R143P and delta V278 mutants are retained within the cytoplasmic compartment. Thus, R202C, R143P/delta V278, and 804insG result in three distinct phenotypes, that is, a simple binding impairment at the cell surface, blocked intracellular transport, and ineffective biosynthesis or/and accelerated degradation of the receptor, respectively, and therefore are responsible for NDI. This phenotypic classification will help understanding of molecular pathophysiology of this disorder.

Authors

H Tsukaguchi, H Matsubara, S Taketani, Y Mori, T Seido, M Inada

A mouse model for the delta F508 allele of cystic fibrosis.

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Abstract

The most common cause of cystic fibrosis is a mutation that deletes phenylalanine 508 in cystic fibrosis transmembrane conductance regulator (CFTR). The delta F508 protein is misprocessed and degraded rather than traveling to the apical membrane. We used a novel strategy to introduce the delta F508 mutation into the mouse CFTR gene. Affected epithelia from homozygous delta F508 mice lacked CFTR in the apical membrane and were Cl-impermeable. These abnormalities are the same as those observed in patients with delta F508 and suggest that these mice have the same cellular defect. 40% of homozygous delta F508 animals survived into adulthood and displayed several abnormalities found in human disease and in CFTR null mice. These animals should provide an excellent model to investigate pathogenesis and to examine therapies directed at correcting the delta F508 defect.

Authors

B G Zeiher, E Eichwald, J Zabner, J J Smith, A P Puga, P B McCray Jr, M R Capecchi, M J Welsh, K R Thomas

Recombinant ob protein reduces feeding and body weight in the ob/ob mouse.

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Abstract

To determine whether the product of the recently cloned ob gene functions as an adipose-related satiety factor, recombinant murine ob protein was administered intraperitoneally to ob/ob mice. Monomeric ob protein given as single morning injections to groups of three animals at seven doses ranging from 5 to 100 micrograms reduced 24-h chow consumption in a dose-dependent manner from values of 81 +/- 6.8% of control (10-micrograms dose, P = 0.04) to 29 +/- 7.7% of control (100-micrograms dose, P < 0.0001). Daily injections of 80 micrograms of ob protein into six ob/ob mice for 2 wk led to an 11 +/- 1.6% decrease in body weight (P = 0.0009) and suppressed feeding to 26 +/- 4.9% of baseline (P < 0.0001), with significant reduction of serum insulin and glucose levels. The effect of recombinant ob protein on feeding was not augmented by cofactors secreted by adipose tissue, nor did exposure of adipose tissue to ob protein affect intracellular ob mRNA levels. Posttranslational modification of ob protein was not required for activity; however, addition of a hexahistidine tag to the amino terminus of the mature ob protein resulted in prolonged suppression of feeding after injection into ob/ob mice. These results demonstrate a direct effect of the ob protein to suppress feeding in the ob/ob mouse and suggest that this molecule plays a critical role in regulating total body fat content.

Authors

D S Weigle, T R Bukowski, D C Foster, S Holderman, J M Kramer, G Lasser, C E Lofton-Day, D E Prunkard, C Raymond, J L Kuijper

Decreased early atherosclerotic lesions in hypertriglyceridemic mice expressing cholesteryl ester transfer protein transgene.

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Abstract

The human cholesteryl ester transfer protein (CETP) facilitates the transfer of cholesteryl ester from HDL to triglyceride-rich lipoproteins. The activity of CETP results in a reduction in HDL cholesterol levels, but CETP may also promote reverse cholesterol transport. Thus, the net impact of CETP expression on atherogenesis is uncertain. The influence of hypertriglyceridemia and CETP on the development of atherosclerotic lesions in the proximal aorta was assessed by feeding transgenic mice a high cholesterol diet for 16 wk. 13 out of 14 (93%) hypertriglyceridemic human apo CIII (HuCIII) transgenic (Tg) mice developed atherosclerotic lesions, compared to 18 out of 29 (62%) controls. In HuCIII/CETPTg, human apo AI/CIIITg and HuAI/CIII/CETPTg mice, 7 of 13 (54%), 5 of 10 (50%), and 5 of 13 (38%), respectively, developed lesions in the proximal aorta (P < .05 compared to HuCIIITg). The average number of aortic lesions per mouse in HuCIIITg and controls was 3.4 +/- 0.8 and 2.7 +/- 0.6, respectively in HuCIII/CETPTg, HuAI/CIIIg, and HuAI/CIII/CETPTg mice the number of lesions was significantly lower than in HuCIIITg and control mice: 0.9 +/- 0.4, 1.5 +/- 0.5, and 0.9 +/- 0.4, respectively. There were parallel reductions in mean lesion area. In a separate study, we found an increased susceptibility to dietary atherosclerosis in nonhypertriglyceridemic CETP transgenic mice compared to controls. We conclude that CETP expression inhibits the development of early atherosclerotic lesions but only in hypertriglyceridemic mice.

Authors

T Hayek, L Masucci-Magoulas, X Jiang, A Walsh, E Rubin, J L Breslow, A R Tall

Beta-carotene inhibits atherosclerosis in hypercholesterolemic rabbits.

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Abstract

Oxidatively damaged LDL may be of central importance in atherogenesis. Epidemiological evidence suggests that high dietary intakes of beta-carotene and vitamin E decreases the risk for atherosclerotic vascular disease, raising the possibility that lipid-soluble antioxidants slow vascular disease by protecting LDL from oxidation. To test this hypothesis, we fed male New Zealand White rabbits a high-cholesterol diet or the same diet supplemented with either 1% probucol, 0.01% vitamin E, 0.01% all-trans beta-carotene, or 0.01% 9-cis beta-carotene; then we assessed both the susceptibility of LDL to oxidation ex vivo and the extent of aortic atherosclerosis. As in earlier studies, probucol protected LDL from oxidation and inhibited lesion formation. In contrast, vitamin E modestly inhibited LDL oxidation but did not prevent atherosclerosis. While beta-carotene had no effect on LDL oxidation ex vivo, the all-trans isomer inhibited lesion formation to the same degree as probucol. Moreover, all-trans beta-carotene was undetectable in LDL isolated from rabbits fed the compound, although tissue levels of retinyl palmitate were increased. The effect of all-trans beta-carotene on atherogenesis can thus be separated from the resistance of LDL to oxidation, indicating that other mechanisms may account for the ability of this compound to prevent vascular disease. Our results suggest that metabolites derived from all-trans beta-carotene inhibit atherosclerosis in hypercholesterolemic rabbits, possibly via stereospecific interactions with retinoic acid receptors in the artery wall.

Authors

A Shaish, A Daugherty, F O'Sullivan, G Schonfeld, J W Heinecke

Sheep lung cytochrome P4501A1 (CYP1A1): cDNA cloning and transcriptional regulation by oxygen tension.

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Abstract

Lung cytochrome P450 activity has been linked to neoplasia and may produce reactive oxidant species and potent arachidonic acid metabolites. In lamb lung, oxygen breathing increases lung P450 activity, and inhibition of lung cytochrome P450 activity reduces oxygen-induced lung injury. The P4501A1 (CYP1A1) isozyme is present in many lung cells, including endothelial cells, and may therefore be involved in the pathogenesis of hyperoxic injury to microvascular endothelium. Therefore, to test the hypothesis that oxygen regulates P4501A1 gene expression in the lung, we cloned the sheep P4501A1 cDNA, and examined its regulation by oxygen breathing significantly increased lung P4501A1 RNA levels and that this increase preceded the increase in isozyme activity. Oxygen exposure also promptly increased P4501A1 RNA levels in cultured lamb lung microvascular endothelial cells but not in endothelial cells isolated from the main pulmonary artery or in lung smooth muscle cells. The oxygen-stimulated increase in P4501A1 RNA levels was not serum dependent, was unaffected by cycloheximide treatment, and could not be mimicked by treatment of the cells with oxygenated medium, conditioned medium, or by chemical oxidants. By nuclear run-on assay in cultured lung endothelial cells, oxygen increased the transcription rate of P4501A1 by almost fourfold after 90 min of oxygen exposure but had no significant effect on P4501A1 RNA stability. We conclude that oxygen tension, but not chemical oxidants, increases P4501A1 gene expression pretranslationally in lung microvascular endothelial cells. We speculate that oxygen induction of P450 activity in these cells may contribute to microvascular injury during oxygen breathing.

Authors

T A Hazinski, E Noisin, I Hamon, A DeMatteo

Late-onset X-linked sideroblastic anemia. Missense mutations in the erythroid delta-aminolevulinate synthase (ALAS2) gene in two pyridoxine-responsive patients initially diagnosed with acquired refractory anemia and ringed sideroblasts.

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Abstract

Authors

P D Cotter, A May, E J Fitzsimons, T Houston, B E Woodcock, A I al-Sabah, L Wong, D F Bishop