The third beta is not the charm.

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Authors

R A Bond, R J Lefkowitz

Mammalian type 2 deiodinase sequences: finally, the end of the beginning.

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Authors

P R Larsen

1H-NMR detectable fatty acyl chain unsaturation in excised leiomyosarcoma correlate with grade and mitotic activity.

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We report on the use of 1H-NMR two-dimensional total correlated spectroscopy (2D TOCSY) at 600 MHz for an ex vivo analysis of fatty acyl chain lipid in normal smooth muscle and a series of primary retroperitoneal leiomyosarcomas. These TOCSY spectra were used to identify and quantitate the methylene protons situated between unsaturated site protons (D) to those bordered by only one unsaturated site proton (C). The D/C cross-peak volume ratios determined for oleic (18:1), linoleic (18:2), linolenic (18:3), and arachidonic (20:4) acids were 0.0, 1.3, 2.7, and 4.0, respectively, suggesting that this ratio can be a measure of the degree of unsaturation for fatty acyl chains of lipids. The D/C cross-peak volume ratio was found to be proportional to the mean mitotic activity (r = 0.94) in nine smooth muscle tissues. These results suggest, that for leiomyosarcoma, the degree of fatty acyl unsaturation may be an important determinant of the metastatic potential of these tumors. Furthermore, application of TOCSY for the ex vivo study of smooth muscle tumors would potentially serve as a pathologist-independent and quantitative method for assessment of leiomyosarcoma grade and mitotic activity thereby rendering a more accurate staging of patients.

Authors

S Singer, M Sivaraja, K Souza, K Millis, J M Corson

The expression of ob gene is not acutely regulated by insulin and fasting in human abdominal subcutaneous adipose tissue.

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The regulation of ob gene expression in abdominal subcutaneous adipose tissue was investigated using a reverse transcription-competitive PCR method to quantify the mRNA level of leptin. Leptin mRNA level was highly correlated with the body mass index of 26 subjects (12 lean, 7 non-insulin-dependent diabetic, and 7 obese patients). The effect of fasting on ob gene expression was investigated in 10 subjects maintained on a hypocaloric diet (1045 KJ/d) for 5 d. While their metabolic parameters significantly changed (decrease in insulinemia, glycemia, and resting metabolic rate and increase in plasma ketone bodies), the caloric restriction did not modify the leptin mRNA level in the adipose tissue. To verify whether insulin regulates ob gene expression, six lean subjects underwent a 3-h euglycemic hyperinsulinemic (846 +/- 138 pmol/liter) clamp. Leptin and Glut 4 mRNA levels were quantified in adipose tissue biopsies taken before and at the end of the clamp. Insulin infusion produced a significant threefold increase in Glut 4 mRNA while leptin mRNA was not affected. It is concluded that ob gene expression is not acutely regulated by insulin or by metabolic factors related to fasting in human abdominal subcutaneous adipose tissue.

Authors

H Vidal, D Auboeuf, P De Vos, B Staels, J P Riou, J Auwerx, M Laville

Association and cosegregation of stroke with impaired endothelium-dependent vasorelaxation in stroke prone, spontaneously hypertensive rats.

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While hypertension is a major risk factor for stroke, it is not its sole determinant. Despite similar blood pressures, spontaneously hypertensive rats (SHR) do not share the predisposition to cerebrovascular disease typical of stroke-prone spontaneously hypertensive rats (SHRSP). We investigated vascular function in male SHR and SHRSP as well as in SHRSP/SHR-F2 hybrid animals. Animals were maintained on the appropriate dietary regimen necessary for the manifestation of stroke. Among the hybrid animals, a group of stroke-prone and a group of stroke-resistant rats were selected. Blood pressure was similar in all groups. Endothelium-independent vascular reactivity tested on isolated rings of thoracic aorta and basilar artery after death showed similar contractile and dilatory responses to serotonin and nitroglycerin, respectively, in all groups. In contrast, endothelium-dependent relaxation, in response to acetylcholine or substance P, was markedly reduced in SHRSP compared with SHR. Similarly, reduced vasodilatory responses were present in aortae of F2 rats that had suffered a stroke when compared with SHR or F2 rats resistant to stroke. The observed association and cosegregation of stroke with significant and specific impairment of endothelium-dependent vasorelaxation among SHRSP and stroke-prone F2 hybrids, respectively, suggest a potential causal role of altered endothelium-dependent vascular relaxation in the pathogenesis of stroke.

Authors

M Volpe, G Iaccarino, C Vecchione, D Rizzoni, R Russo, S Rubattu, G Condorelli, U Ganten, D Ganten, B Trimarco, K Lindpaintner

Suppression of mesangial proliferative glomerulonephritis development in rats by inhibitors of cAMP phosphodiesterase isozymes types III and IV.

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Excessive mesangial cell (MC) proliferation is a hallmark of many glomerulopathies. In our recent study on cultured rat MC (Matousovic, K., J.P. Grande, C.C.S. Chini, E.N. Chini, and T.P. Dousa. 1995. J. Clin. Invest. 96:401-410) we found that inhibition of isozyme cyclic-3',5'-nucleotide phosphodiesterase (PDE) type III (PDE-III) suppressed MC mitogenesis by activating cAMP-dependent protein kinase (PKA) and by decreasing activity of mitogen-activated protein kinase (MAPK). We also found that inhibition of another PDE isozyme, PDE-IV, suppresses superoxide generation in glomeruli (Chini, C.C.S., E.N. Chini, J.M. Williams, K. Matousovic, and T.P. Dousa. 1994. Kidney Int. 46:28-36). We thus explored whether administration in vivo of the selective PDE-III antagonist, lixazinone (LX), together with the specific PDE-IV antagonist, rolipram (RP), can attenuate development of mesangioproliferative glomerulonephritis (MSGN) induced in rats by anti-rat thymocyte serum (ATS). Unlike the vehicle-treated MSGN rats, rats with MSGN treated with LX and RP did not develop proteinuria and maintained normal renal function when examined 5 d after injection of ATS. In PAS-stained kidneys from PDE-antagonists-treated MSGN-rats the morphology of glomeruli showed a reduction in cellularity compared with control rats with ATS. Compared with MSGN rats receiving vehicle, the MSGN rats receiving PDE-antagonists had less glomerular cell proliferation (PCNA delta -65%), a significantly lesser macrophage infiltration (delta -36% ED-1) and a significant reduction of alpha-smooth muscle actin expression by activated MC; in contrast, immunostaining for platelet antigens and laminin were not different. The beneficial effect of PDE inhibitors was not due to a moderate decrease (approximately -20%) in systolic blood pressure (SBP); as a similar decrease in SBP due to administration of hydralazine, a drug devoid of PDE inhibitory effect, did not reduce severity of MSGN in ATS-injected rats. We conclude that antagonists of PDE-III and PDE-IV administered in submicromolar concentrations in vivo to ATS-injected rats can decrease the activation and proliferation of MC, inhibit the macrophage accumulation, and prevent proteinuria in the acute phase of MSGN. We propose that PDE isozyme inhibitors act to block (negative "crosstalk") the mitogen-stimulated intracellular signaling pathway which controls MC proliferation due to activating of the cAMP-PKA pathway. These results suggest that antagonists of PDE-111 and IV may have a suppressive effect in acute phases or relapses of glomerulopathies associated with MC proliferations.

Authors

Y Tsuboi, S J Shankland, J P Grande, H J Walker, R J Johnson, T P Dousa

Therapeutic effect of the anti-Fas antibody on arthritis in HTLV-1 tax transgenic mice.

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We have recently demonstrated Fas-mediated apoptosis in the synovium, of patients with rheumatoid arthritis (RA) and suggested that it may be one factor responsible for the regression of RA. To examine whether the induction of apoptosis caused by anti-Fas mAb may play a potential role as a new therapeutic strategy for RA, we investigated the effect of anti-Fas mAb (RK-8) on synovitis in an animal model of RA, the human T cell leukemia virus type I (HTLV-1) tax transgenic mice. We report here that administration of anti-Fas mAb into mice intra-articularly improved the paw swelling and arthritis within 48 h. Immunohistochemical study and in vitro culture studies showed that 35% of synovial fibroblasts, 75% of mononuclear cells, and some of polymorphonuclear leukocytes infiltrating in synovium underwent apoptosis by anti-Fas mAb. In situ nick end labeling analysis and electron microscope analysis clearly showed that many cells in synovium were induced apoptosis by anti-Fas mAb administration. However, local administration of anti-Fas mAb did not produce systemic side effects. Results demonstrated that administration of anti-Fas mAb in arthritic joints of the HTLV-1 tax transgenic mice produced improvement of arthritis. These findings suggest that local administration of anti-Fas mAb may represent a useful therapeutic strategy for proliferative synovitis such as RA.

Authors

K Fujisawa, H Asahara, K Okamoto, H Aono, T Hasunuma, T Kobata, Y Iwakura, S Yonehara, T Sumida, K Nishioka

Clonal T cell responses in tumor infiltrating lymphocytes from both regressive and progressive regions of primary human malignant melanoma.

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The T cell receptor (TCR) BV variable (V) gene repertoire of tumor infiltrating lymphocytes (TIL) found in progressive and regressive regions of the same primary human melanomas were characterized by reverse transcription coupled polymerase chain reaction (RT-PCR). After surgery, the tumors were divided into different parts which were judged as regressive or progressive regions by visual inspection. Subsequently this diagnosis was confirmed by histology. From a total of four primary melanomas analyzed, 2 were drawn to be HLA-A2+. Only relatively few BV-gene families were expressed at significant levels in each of the samples. Comparison of the BV-expression in regressive versus progressive regions of the same tumor revealed major differences in all cases examined. Direct sequencing of RT-PCR products indicated that highly expressed BV-gene families were of clonal origin in both the regressive and progressive regions. Together, these data strongly suggest the occurrence of clonal T cell responses in both regressive and progressive areas of the same primary tumor. The differences in expression of certain BV-genes may correlate with the functional activity of certain populations of tumor-infiltrating T cells.

Authors

P thor Straten, J C Becker, T Seremet, E B Bröcker, J Zeuthen

Defective cystathionine beta-synthase regulation by S-adenosylmethionine in a partially pyridoxine responsive homocystinuria patient.

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We determined the molecular basis of cystathionine beta-synthase (CBS) deficiency in a partially pyridoxine-responsive homocystinuria patient. Direct sequencing of the entire CBS cDNA revealed the presence of a homozygous G1330A transition. This mutation causes an amino acid change from aspartic acid to asparagine (D444N) in the regulatory domain of the protein and abolishes a TaqI restriction site at DNA level. Despite the homozygous mutation, CBS activities in extracts of cultured fibroblasts of this patient were not in the homozygous but in the heterozygous range. Furthermore, we observed no stimulation of CBS activity by S-adenosylmethionine, contrary to a threefold stimulation in control fibroblast extract. The mutation was introduced in an E. coli expression system and CBS activities were measured after addition of different S-adenosylmethionine concentrations (0-200 microM). Again, we observed a defective stimulation of CBS activity by S-adenosylmethionine in the mutated construct, whereas the normal construct showed a threefold stimulation in activity. These data suggest that this D444N mutation interferes in S-adenosylmethionine regulation of CBS. Furthermore, it indicates the importance of S-adenosylmethionine regulation of the transsulfuration pathway in homocysteine homeostasis in humans.

Authors

L A Kluijtmans, G H Boers, E M Stevens, W O Renier, J P Kraus, F J Trijbels, L P van den Heuvel, H J Blom

IgM-producing chronic lymphocytic leukemia cells undergo immunoglobulin isotype-switching without acquiring somatic mutations.

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The malignant B cells in chronic lymphocytic leukemia (CLL) typically express low-density membrane IgM or IgM/IgD. In vitro experiments have shown that the CLL cells can be induced to differentiate into cells that secrete immunoglobulin (Ig) and can occasionally undergo heavy (H) chain class switching. We now show that the CLL cells also undergo isotype-switching in vivo, since gamma and/or alpha H chain transcripts with identical FW3/CDR3/FW4 regions as the mu CLL transcripts were detected in all of the 13 investigated patients with IgM+ CLL. In most cases switching had occurred to alpha1 and gamma3, but CLL transcripts corresponding to the other gamma chain isotypes were also detected. In one case both the productively and nonproductively rearranged allele were found to undergo H chain class switching. CLL gamma transcripts were also present in surface IgG+ sorted B cells, demonstrating that a small subset of the CLL cells express membrane IgG. In addition, transcripts encoding secretary gamma2 and gamma3 H chains were detected in two cases, which suggests that some serum IgG could be produced by the leukemic clone. Analysis of sorted PBL showed that isotype-switching occurs in CLL cells that express the CD5 antigen. Finally, nucleotide sequence analysis showed that the mu, alpha, and gamma CLL transcripts are identical, demonstrating that the CLL cells do not accumulate somatic mutations in their variable region genes after the H chain class switching. These data provide in vivo evidence that isotype-switching is a frequent phenomenon in CLL, and indicate that a subset of the CLL lymphocytes progress to later stages of B cell differentiation.

Authors

D G Efremov, M Ivanovski, F D Batista, G Pozzato, O R Burrone

Viral infection induces dependence of neuronal M2 muscarinic receptors on cyclooxygenase in guinea pig lung.

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Inhibitory M2 muscarinic receptors on parasympathetic nerve endings in the lungs decrease release of acetylcholine, inhibiting vagally induced bronchoconstriction. Neuronal M2 receptor function can be studied using selective agonists and antagonists such as pilocarpine and gallamine. In pathogen-free guinea pigs indomethacin (1 mg/kg) did not alter the effect of either gallamine or pilocarpine, thus in pathogen free animals neuronal M2 muscarinic receptors function independently of cyclooxygenase products. However, in guinea pigs infected with virus, (which causes temporary loss of M2 receptor function), and then allowed to recover for 8 wk (to allow recovery of M2 receptors), indomethacin prevented both gallamine's potentiation and pilocarpine's inhibition of vagally induced bronchoconstriction. This new effect of indomethacin was not blocked by the addition of a 5-lipoxygenase inhibitor, AA861. However, the selective COX II inhibitor, L-745,337, had the same effect as indomethacin. Since exposure to ozone also caused neuronal M2 receptors to become dependent upon cyclooxygenase the effects of viral infection are likely to be due to inflammation. Thus, despite apparent recovery of normal M2 receptor function after viral infection or ozone, linkage of these receptors is chronically altered such that they become largely dependent on the activity of COX II.

Authors

R M Kahn, O A Okanlami, D B Jacoby, A D Fryer

Interactions between insulin-like growth factor-I (IGF-I) and the renin-angiotensin system in follicular growth and ovulation.

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The interactions between insulin-like growth factor-I (IGF-I) and the renin-angiotensin system (RAS) in follicular growth and ovulation were studied with the use of an isolated perfused rabbit ovary preparation. Ovulation failed to occur in either control ovaries or the experimental ovaries perfused with IGF-I in a concentration of 1, 10, or 100 ng/ml in the absence of gonadotropin. Exposure to IGF-I stimulated the secretion rate of angiotensin II-like immunoreactivity (Ang II-IR) in perfused rabbit ovaries in a dose-dependent manner. The percent increase in follicle diameter in ovaries perfused with IGF-I for 12 h was significantly correlated with the secretion rate of Ang II-IR at 12 h after exposure to IGF-I. The addition of IGFBP-3 to the perfusate did not induce ovulation in the absence of gonadotropin, but exposure to IGFBP-3 inhibited hCG-induced ovulation in a dose-dependent manner. In addition, IGFBP-3 significantly reduced the ovarian secretion rate of Ang II-IR and prostaglandins stimulated by hCG administration. Intrafollicular plasminogen activator (PA) activity significantly increased within 4 h after exposure to 100 ng/ml of IGF-I, compared with that in control ovaries perfused with medium alone. The concomitant addition of IGFBP-3 to the perfusate significantly reduced the IGF-I-stimulated PA activity in the preovulatory follicles at 4, 6, and 8 h after exposure to IGF-I. However, IGFBP-3 alone affected neither the ovarian secretion rate of Ang II-IR nor intrafollicular PA activity. Exposure to streptokinase, an exogenous PA, in vitro stimulated both follicular growth and the intrafollicular Ang II-IR content. In conclusion, IGF-I enhances both ovarian Ang II production and follicular development by stimulating intrafollicular PA activity.

Authors

Y Yoshimura, N Aoki, K Sueoka, T Miyazaki, N Kuji, M Tanaka, T Kobayashi

Adenoviral-mediated transfer of the human endothelial nitric oxide synthase gene reduces acute hypoxic pulmonary vasoconstriction in rats.

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Nitric oxide (NO), a vasodilator involved in the regulation of pulmonary vascular tone, is synthesized by a family of enzymes, nitric oxide synthases (NOS). To investigate whether adenoviral-mediated overexpression of constitutive endothelial NOS (ceNOS) would attenuate hypoxic pulmonary vasoconstriction, we aerosolized 3 X 10(9) plaque forming units of a recombinant adenovirus containing the ceNOS gene (AdCMVceNOS) into rat lungs. Four days after infection, transgene expression was confirmed using immunoblot techniques. Diffuse ceNOS immunostaining was detected in alveoli and medium-sized and small pulmonary vessels of AdCMVceNOS-transduced lungs. AdCMVceNOS-transduction was associated with an 86% increase in [3H]arginine to [3H]citrulline conversion and a rise in pulmonary cGMP levels from 7 +/- 1 to 59 +/- 9 pmol/mg protein in lungs from AdCMVceNOS versus control rats, (P < 0.05). During acute hypoxia (FIO2 = 0.10) for 25 min, mean pulmonary artery pressure (PAP) increased significantly from 17 +/- 1 to 27 +/- 1 mmHg in rats aerosolized with saline (n = 4) and from 18 +/- 1 to 28 +/- 1 mmHg in rats given an adenoviral vector expressing a nuclear-targeted beta-galactosidase gene (AdCMV beta gal, n = 8). In contrast, in AdCMVceNOS-transduced rats (n = 8) the hypoxia-induced increase in PAP was significantly attenuated (18 +/- 1 to 23 +/- 2 mmHg). Systemic blood pressure was not affected by aerosol gene transfer. Thus, adenoviral-mediated ceNOS gene transfer to rat lungs increases ceNOS expression and activity, and reduces acute hypoxic pulmonary vasoconstriction. Aerosolized recombinant adenovirus overexpressing vasodilatory proteins can act as a selective pulmonary vasodilator and may hold promise as a future therapeutic strategy for pulmonary hypertension.

Authors

S P Janssens, K D Bloch, Z Nong, R D Gerard, P Zoldhelyi, D Collen

Renal expression of tissue factor pathway inhibitor and evidence for a role in crescentic glomerulonephritis in rabbits.

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Tissue factor pathway inhibitor (TFPI) was demonstrated in the kidneys of normal rabbits and in a crescentic model of glomerulonephritis (GN), where fibrin is a key mediator of injury. In normal kidneys, TFPI was expressed in glomeruli, in intrarenal arteries and the interstitial capillary network. Evidence for TFPI synthesis in vivo was provided by in situ demonstration of TFPI mRNA in glomeruli and intrarenal vessels and by biosynthetic labeling of TFPI released from glomeruli in vitro. In fibrin-dependent crescentic GN, glomerular TFPI synthesis and expression was initially decreased (TFPI antigen at 24 h, 7.5 +/- 0.7 ng/10(3) glomeruli; normal, 11.1 +/- 0.9 ng/10(3) glomeruli, P < 0.02) and subsequently returned to normal values. Plasma TFPI levels increased progressively throughout the evolution of disease. In vivo inhibition of TFPI using an anti-TFPI antibody during the development of GN significantly increased glomerular fibrin deposition (GFD) and exacerbated renal impairment. Infusion of recombinant human TFPI significantly reduced development of GFD (fibrin scores, TFPI treated 0.82 +/- 0.11, control 1.49 +/- 0.14, P < 0.01), proteinuria and renal impairment. This data indicates that TFPI is synthesized and expressed in normal glomeruli and is down regulated in the early response to glomerular injury. Endogenous glomerular TFPI and treatment with recombinant TFPI reduces GFD and injury in fibrin dependent GN. TFPI has the potential to be of therapeutic benefit in the management of fibrin dependent human GN.

Authors

J H Erlich, J Apostolopoulos, T C Wun, K K Kretzmer, S R Holdsworth, P G Tipping

Inflammatory and hyperproliferative skin disease in mice that express elevated levels of the IL-1 receptor (type I) on epidermal keratinocytes. Evidence that IL-1-inducible secondary cytokines produced by keratinocytes in vivo can cause skin disease.

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Interleukin (IL)-1 induces a cascade of secondary cytokines in a large number of cell types in vitro, including monocytes, fibroblasts, synovial cells, and keratinocytes. Although it has been proposed that autocrine or paracrine activation of such cells by IL- 1 in situ could orchestrate a local inflammatory response, formal proof for such an hypothesis has been lacking. In an attempt to lower the threshold for secondary cytokine production in these cells in response to IL-1, we have generated transgenic mice (designated IR10) which overexpress functional type 1 IL-1 receptor in basal layer of epidermis keratinocytes. As predicted, keratinocytes from these animals were substantially more responsive to exogenous IL-1 than nontransgenic keratinocytes when stimulated in vitro. When challenged with known inducers of keratinocyte IL-1 synthesis and release, skin of IR10 mice exhibited an exaggerated inflammatory response, characterized by epidermal hyperplasia and an acute dermal inflammatory cell infiltrate. In this setting, the secondary epidermal cytokines gro-alpha and GM-CSF were strongly induced in transgenic epidermis but not in control skin. To confirm that these changes were indeed related to IL-1 mediated activation pathways, IR10 mice were crossed to a distinct line of transgenic mice that overexpress 17-kD IL-l alpha in basal keratinocytes. Double transgenic mice derived from this cross breeding experiment developed spontaneous inflammation of the skin, similar in appearance to that induced by PMA, both histologically and macroscopically, and distinct from that seen in either parental strain spontaneously. Furthermore, secondary cytokines were more strongly induced in the double transgenic than in either parental strain. These findings conclusively demonstrate the potential for functional autocrine pathways of keratinocyte activation mediated by IL-1 alpha in vivo, and suggest that level of expression of type 1 IL-1 receptor may function as a significant control point in physiologic IL-1 mediated autocrine pathways.

Authors

R W Groves, T Rauschmayr, K Nakamura, S Sarkar, I R Williams, T S Kupper

Mitochondrial complex I deficiency leads to increased production of superoxide radicals and induction of superoxide dismutase.

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Mitochondria were isolated from skin fibroblast cultures derived from healthy individuals (controls) and from a group patients with complex I (NADH-CoQ reductase) deficiency of the mitochondrial respiratory chain. The complex I deficient patients included those with fatal infantile lactic acidosis (FILA), cardiomyopathy with cataracts (CC), hepatopathy with tubulopathy (HT), Leigh's disease (LD), cataracts and developmental delay (CD), and lactic acidemia in the neonatal period followed by mild symptoms (MS). Production of superoxide radicals, on addition of NADH, were measured using the luminometric probe lucigenin with isolated fibroblast mitochondrial membranes. Superoxide production rates were highest with CD and decreased in the order CD >> MS > LD > control > HT > FILA = CC. The quantity of Mn-superoxide dismutase (MnSOD), as measured by ELISA techniques, however, was highest in CC and FILA and lowest in CD. Plots of MnSOD quantity versus superoxide production showed an inverse relationship for most conditions with complex I deficiency. We hypothesize that oxygen radical production is increased when complex I activity is compromised. However, the observed superoxide production rates are modulated by the variant induction of MnSOD which decreases the rates, sometimes below those seen in control fibroblast mitochondria. In turn, we show that the variant induction of MnSOD is most likely a function of the change in the redox state of the cell experienced rather than a result of the complex I defect per se.

Authors

S Pitkanen, B H Robinson

Mutations in exon 3 of the glycogen debranching enzyme gene are associated with glycogen storage disease type III that is differentially expressed in liver and muscle.

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Glycogen storage disease type HI (GSD-III), an autosomal recessive disease, is caused by deficient glycogen debranching enzyme (GDE) activity. Most GSD-III patients are GDE deficient in both liver and muscle (type IIIa), and some GSD-III patients have GDE absent in liver but retained in muscle (type IIIb). The molecular basis for this enzymatic variability is largely unknown. In the present study, the analysis of the GDE gene in three GSD-IIIb patients by single-strand conformation polymorphism (SSCP), DNA sequencing, restriction analysis, and family studies, revealed each of them as being a compound heterozygote for two different mutations. The first mutant alleles in all three patients involved mutations in exon 3 at amino acid codon 6 of the GDE protein. Two had an AG deletion at nucleotides 17 and 18 of the GDE cDNA (17delAG) which resulted in change of subsequent amino acid sequence and a truncated protein (25X); the other had a C to T transition at nucleotide 16 of the cDNA which changed a Glutamine codon to a stop codon (Q6X). The 17delAG mutation was also found in 8 of the 10 additional GSD-IIIb patients. The Q6X mutation was found in one of the remaining two GSD-IIIb patients. These two mutations were not found in any of the 31 GSD-IIIa patients, 2 GSD-IIId patients, nor 28 unrelated normal controls. The second mutant alleles in each of the three GSD-IIIb patients were R864X, R1228X, and W68OX. The R864X and R1228X were not unique for GSD-IIIb as they were also found in GSD-IIIa patients (frequency of 10.3% and 5.2% in Caucasian patients, respectively). Our data demonstrated that both IIIa and IIIb had mutations in the same GDE gene and established for the first time the molecular basis of GSD-III that differentially expressed in liver and muscle. The striking and specific association of exon 3 mutations with GSD-IIIb may provide insight into mechanisms controlling tissue-specific expression of the GDE gene. The identification of exon 3 mutations has clinical significance as well because it distinguished GSD-IIIb from IIIa hence permitting diagnosis from a blood sample rather than a more invasive muscle biopsy.

Authors

J Shen, Y Bao, H M Liu, P Lee, J V Leonard, Y T Chen

An intronic mutation in a lariat branchpoint sequence is a direct cause of an inherited human disorder (fish-eye disease).

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The first step in the splicing of an intron from nuclear precursors of mRNA results in the formation of a lariat structure. A distinct intronic nucleotide sequence, known as the branchpoint region, plays a central role in this process. We here describe a point mutation in such a sequence. Three sisters were shown to suffer from fish-eye disease (FED), a disorder which is caused by mutations in the gene coding for lecithin:cholesterol acyltransferase (LCAT). Sequencing of the LCAT gene of all three probands revealed compound heterozygosity for a missense mutation in exon 4 which is reported to underlie the FED phenotype, and a point mutation located in intron 4 (IVS4:T-22C). By performing in vitro expression of LCAT minigenes and reverse transcriptase PCR on mRNA isolated from leukocytes of the patient, this gene defect was shown to cause a null allele as the result of complete intron retention. In conclusion, we demonstrated that a point mutation in a lariat branchpoint consensus sequence causes a null allele in a patient with FED. In addition, our finding illustrates the importance of this sequence for normal human mRNA processing. Finally, this report provides a widely applicable strategy which ensures fast and effective screening for intronic defects that underlie differential gene expression.

Authors

J A Kuivenhoven, H Weibusch, P H Pritchard, H Funke, R Benne, G Assmann, J J Kastelein

Liver cirrhosis induces renal and liver phospholipase A2 activity in rats.

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Maintenance of renal function in liver cirrhosis requires increased synthesis of arachidonic acid derived prostaglandin metabolites. Arachidonate metabolites have been reported to be involved in modulation of liver damage. The purpose of the present study was to establish whether the first enzyme of the prostaglandin cascade synthesis, the phospholipase A2(PLA2) is altered in liver cirrhosis induced by bile duct excision. The mRNA of PLA2(group I and II) and annexin-I a presumptive inhibitor of PLA2 enzyme was measured by PCR using glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as an internal standard. The mean mRNA ratio of group II PLA2/GAPDH was increased in liver tissue by 126% (P < 0.001) and in kidney tissue by 263% (P < 0.006) following induction of liver cirrhosis. The increase in group II PLA2 mRNA in cirrhotic animals was reflected by an increase in PLA2 protein and enzyme activity in both liver and kidney tissues. Since the mRNA of group I PLA2 was not detectable and Group IV PLA2 activity measured in liver and kidney tissue samples was very low and not changed following induction of cirrhosis, it is likely that the major PLA2 activity measured in liver and kidney corresponds to group II PLA2 enzyme. The mean mRNA ratio of annexin-I/GAPDH was increased in liver tissue by 115% (P < 0.05) but unchanged in kidney tissue following induction of cirrhosis. The protein content of annexin-I and -V were not affected by bile duct excision in liver and kidney tissue indicating that upregulation of group II PLA2 activity was not due to downregulation of annexin-I or -V. Group II PLA2 activity of glomerular mesangial cells stimulated by interleukin-1 beta was enhanced by bile juice and various bile salts. In conclusion, activity of group II PLA2 is upregulated partly due to enhanced transcription and translation in cirrhosis and is furthermore augmented by elevated levels of bile salts.

Authors

B S Vishwanath, F J Frey, G Escher, J Reichen, B M Frey

Polymorphisms at the 5'-end of the apolipoprotein AI gene and severity of coronary artery disease.

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Elevated HDL-cholesterol (C) and apo AI are associated with decreased coronary artery disease (CAD) risk. We determined distributions of two MspI polymorphisms of the apo AI gene, associated in other studies with increased HDL-C, among 644 patients aged < or = 65 years in relation to circulating lipids and CAD severity assessed angiographically. The rare allele distributions at both sites were in Hardy-Weinberg equilibrium in these patients but the base changes were not associated with HDL-C and apo AI levels. However, patients homozygous for the -75 bp substitution were more likely to have one or more significantly diseased vessels (> 50% luminal obstruction)(OR: 4.75, 95%CI: 1.10- 20.46) as also were patients with the rare +83 bp alleles (OR: 2.56, 95%CI: 1.13-5.81). While there was an additive effect of the two polymorphisms to have severe CAD (OR: 6.33, 95%CI: 1.33-30.02), the polymorphism at +83 bp remained significant in predicting CAD severity after adjusting for other variables in a logistic regression analysis (OR: 2.95, 95%CI: 1.26-6.90), which was also strongly associated with the positive family CAD history (P = 0.009). We conclude that patients with these base changes in this Australian coronary population do not have increased HDL-C and apo AI levels but do have more severe CAD.

Authors

X L Wang, S X Liu, R M McCredie, D E Wilcken

Contributions of gluconeogenesis to glucose production in the fasted state.

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Healthy subjects ingested 2H2O and after 14, 22, and 42 h of fasting the enrichments of deuterium in the hydrogens bound to carbons 2, 5, and 6 of blood glucose and in body water were determined. The hydrogens bound to the carbons were isolated in formaldehyde which was converted to hexamethylenetetramine for assay. Enrichment of the deuterium bound to carbon 5 of glucose to that in water or to carbon 2 directly equals the fraction of glucose formed by gluconeogenesis. The contribution of gluconeogenesis to glucose production was 47 +/- 49% after 14 h, 67 +/- 41% after 22 h, and 93 +/- 2% after 42 h of fasting. Glycerol's conversion to glucose is included in estimates using the enrichment at carbon 5, but not carbon 6. Equilibrations with water of the hydrogens bound to carbon 3 of pyruvate that become those bound to carbon 6 of glucose and of the hydrogen at carbon 2 of glucose produced via glycogenolysis are estimated from the enrichments to be approximately 80% complete. Thus, rates of gluconeogenesis can be determined without corrections required in other tracer methodologies. After an overnight fast gluconeogenesis accounts for approximately 50% and after 42 h of fasting for almost all of glucose production in healthy subjects.

Authors

B R Landau, J Wahren, V Chandramouli, W C Schumann, K Ekberg, S C Kalhan

Vascular incorporation of alpha-tocopherol prevents endothelial dysfunction due to oxidized LDL by inhibiting protein kinase C stimulation.

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Abstract

Excess vascular oxidative stress has been linked to impaired endothelium-dependent arterial relaxation in hypercholesterolemia. alpha-Tocopherol (AT) preserves endothelial function in hypercholesterolemia although the mechanism(s) for this protective effect is (are) not known. We examined the tissue-specific effects of AT on oxidized LDL (ox-LDL)-mediated endothelial dysfunction in male New Zealand White rabbits. Animals consumed chow deficient in (< 10 IU/kg) or supplemented with (1,000 IU/kg) AT for 28 d. Exposure of thoracic aortae from AT-deficient animals to ox-LDL (0-500 microg/ml) for 4 h produced dose-dependent inhibition of acetylcholine-mediated relaxation (P < 0.05) while vessels derived from animals consuming AT were resistant to ox-LDL-mediated endothelial dysfunction. Animals consuming AT demonstrated a 100-fold increase in vascular AT content and this was strongly correlated with vessel resistance to endothelial dysfunction from ox-LDL (R = 0.67; P = 0.0014). These results were not explained by an effect of AT on ox-LDL-mediated cytotoxicity by LDH assay or scanning electron microscopy. Vascular incorporation of AT did produce resistance to endothelial dysfunction from protein kinase C stimulation, an event that has been implicated in the vascular response to ox-LDL. Human aortic endothelial cells loaded with AT also demonstrated resistance to protein kinase C stimulation by both phorbol ester and ox-LDL. Thus, these data indicate that enrichment of vascular tissue with AT protects the vascular endothelium from ox-LDL-mediated dysfunction, at least in part, through the inhibition of protein kinase C stimulation. These findings suggest one potential mechanism for the observed beneficial effect of AT in preventing the clinical expression of coronary artery disease that is distinct from the antioxidant protection of LDL.

Authors

J F Keaney Jr, Y Guo, D Cunningham, G T Shwaery, A Xu, J A Vita

Studies of renal injury. II. Activation of the glucose transporter 1 (GLUT1) gene and glycolysis in LLC-PK1 cells under Ca2+ stress.

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Abstract

Injury to the renal proximal tubule is common and may be followed by either recovery or cell death. The survival of injured cells is supported by a transient change in cellular metabolism that maintains life even when oxygen tension is reduced. This adaptive process involves the activation of the gene encoding the glucose transporter GLUT1, which is essential to maintain the high rates of glucose influx demanded by glycolysis. We hypothesized that after cell injury increases of cell Ca2+ (Ca2+i) initiate the flow of information that culminates with the upregulation of the stress response gene GLUT1. We found that elevations of Ca2+i caused by the calcium ionophore A23187 activated the expression of the GLUT1 gene in LLC-PK1 cells. The stimulatory effect of Ca2+i on GLUT1 gene expression was, at least in part, transcriptional and resulted in higher levels of GLUT1 mRNA, cognate protein, cellular hexose transport activity, glucose consumption, and lactate production. This response was vital to the renal cells, as its interruption severely increased Ca2+-induced cytotoxicity and cell mortality. We propose that increases of Ca2+i initiate stress responses, represented in part by activation of the GLUT1 gene, and that disruption to the flow of information originating from Ca2+-induced stress, or to the coordinated expression of the stress response, prevents cell recovery after injury and may be an important cause of permanent renal cell injury and cell death.

Authors

J H Dominguez, B Song, S Liu-Chen, M Qulali, R Howard, C H Lee, J McAteer

Cloning of the mammalian type II iodothyronine deiodinase. A selenoprotein differentially expressed and regulated in human and rat brain and other tissues.

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Abstract

The deiodination of thyroid hormones in extrathyroidal tissues plays an important role in modulating thyroid hormone action. The type II deiodinase (DII) converts thyroxine to the active hormone 3,5,3'-triiodothyronine, and in the rat is expressed in the brain, pituitary gland, and brown adipose tissue (BAT). Complementary DNAs (cDNAs) for the types I and III deiodinases (DI and DIII, respectively) have been isolated and shown to code for selenoproteins. However, information concerning the structure of the mammalian DII remains limited, and the pattern of its expression in human tissues is undefined. We report herein the identification and characterization of rat and human DII cDNAs. Both code for selenoproteins and exhibit limited regions of homology with the DI and DIII. In the rat pituitary and BAT, DII mRNA levels are altered more than 10-fold by changes in the thyroid hormone status of the animal. Northern analysis of RNA derived from human tissues reveals expression of DII transcripts in heart, skeletal muscle, placenta, fetal brain, and several regions of the adult brain. These studies demonstrate that: (a) the rat and human DII are selenoproteins, (b) DII expression in the rat is regulated, at least in part, at the pretranslational level in some tissues, and (c) DII is likely to be of considerable physiologic importance in thyroid hormone economy in the human fetus and adult.

Authors

W Croteau, J C Davey, V A Galton, D L St Germain

Chronic blockade of AT2-subtype receptors prevents the effect of angiotensin II on the rat vascular structure.

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Abstract

Angiotensin II (Ang II) is both a vasoactive and a potent growth-promoting factor for vascular smooth muscle cells. Little is known about the in vivo contribution of AT1 and AT2 receptor activation to the biological action of Ang II. Therefore, we investigated the effect of AT1 or AT2 subtype receptor chronic blockade by losartan or PD123319 on the vascular hypertrophy in rats with Ang II-induced hypertension. Normotensive rats received for 3 wk subcutaneous infusions of Ang II (120 ng/kg per min), or Ang II + PD 123319 (30 mg/kg per d), or Ang II + losartan (10 mg/kg per d) or PD 123319 alone, and were compared with control animals. In normotensive animals, chronic blockade of AT2 receptors did not affect the plasma level of angiotensin II and the vascular reactivity to angiotensin II mediated by the AT1 receptor. Chronic blockade of AT1I in rats receiving Ang II resulted in normal arterial pressure, but it induced significant aortic hypertrophy and fibrosis. Chronic blockade of AT2 receptors in Ang II-induced hypertensive rats had no effect on arterial pressure, but antagonized the effect of Ang II on arterial hypertrophy and fibrosis, suggesting that in vivo vasotrophic effects of Ang II are at least partially mediated via AT2 subtype receptors.

Authors

B I Levy, J Benessiano, D Henrion, L Caputo, C Heymes, M Duriez, P Poitevin, J L Samuel

Suppression of p53 activity and p21WAF1/CIP1 expression by vascular cell integrin alphaVbeta3 during angiogenesis.

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Abstract

Induction of p53 activity in cells undergoing DNA synthesis represents a molecular conflict that can lead to apoptosis. During angiogenesis, proliferative endothelial cells become apoptotic in response to antagonists of integrin alphavbeta3 and this leads to the regression of angiogenic blood vessels, thereby blocking the growth of various human tumors. Evidence is presented that administration of alphavbeta3 antagonists during angiogenesis in vivo selectively caused activation of endothelial cell p53 and increased expression of the p53-inducible cell cycle inhibitor p21WAF1/CIP1. In vitro studies revealed that the ligation state of human endothelial cell alphavbeta3 directly influenced p53 activity and the bax cell death pathway. Specifically, agonists of endothelial cell alphavbeta3, but not other integrins, suppressed p53 activity, blocked p21WAF1/CIP1 expression, and increased the bcl-2/bax ratio, thereby promoting cell survival. Thus, ligation of vascular cell integrin alphavbeta3 promotes a critical and specific adhesion-dependent cell survival signal during angiogenesis leading to inhibition of p53 activity, decreased expression of p21WAF1/CIP1, and suppression of the bax cell death pathway.

Authors

S Strömblad, J C Becker, M Yebra, P C Brooks, D A Cheresh

The role of vascular injury and hemodynamics in rat pulmonary artery remodeling.

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Abstract

Vascular remodeling in adult human elastic pulmonary arteries is characterized by diffuse neointimal lesions containing smooth muscle cells expressing extracellular matrix genes. Recent studies suggest vascular injury is needed to initiate remodeling and that growth factor mediators participate in the repair response. However, because neointimal formation is only observed in patients with pulmonary artery blood pressures approaching systemic levels, it has been hypothesized that systemic-like hemodynamic conditions are also necessary. To test that hypothesis, subclavian-pulmonary artery anastomoses were created in Sprague-Dawley rats under three different experimental conditions: no accompanying injury, or after monocrotaline or balloon endarterectomy injury. Pulmonary vascular remodeling was not induced by the subclavian-pulmonary artery anastomosis alone. A non-neointimal pattern of remodeling after mild monocrotaline-induced injury was converted into a neointimal pattern in the presence of the anastomosis. Neointima was also observed after severe, balloon endarterectomy-induced injury even in the absence of anastomosis. Tropoelastin, type I procollagen and TGF-beta gene expression, and angiotensin converting enzyme immunoreactivity, was confined to the neointima resembling the pattern of gene expression and immunoreactivity in human hypertensive elastic pulmonary artery neointimal lesions. These observations introduce the concepts that the type of injury and the associated hemodynamic conditions can modify the elastic pulmonary artery response to injury.

Authors

Y Tanaka, D P Schuster, E C Davis, G A Patterson, M D Botney

Sequence-independent inhibition of in vitro vascular smooth muscle cell proliferation, migration, and in vivo neointimal formation by phosphorothioate oligodeoxynucleotides.

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Abstract

Phosphorothioate oligodeoxynucleotides (PS oligos) are antisense (sequence-specific) inhibitors of vascular smooth muscle cell (SMC) proliferation when targeted against different genes. Recently an aptameric G-quartet inhibitory effect of PS oligos has been demonstrated. To determine whether PS oligos manifest non-G-quartet, non-sequence-specific effects on human aortic SMC, we examined the effects of S-dC28, a 28-mer phosphorothioate cytidine homopolymer, on SMC proliferation induced by several SMC mitogens. S-dC28 significantly inhibited SMC proliferation induced by 10% FBS as well as the mitogens PDGF, bFGF, and EGF without cytotoxicity. Moreover, S-dC28 abrogated PDGF-induced in vitro migration in a modified micro-Boyden chamber. Furthermore, S-dC28 manifested in vivo antiproliferative effects in the rat carotid balloon injury model. S-dC28 suppressed neointimal cross-sectional area by 73% and the intima/media area ratio by 59%. Therefore, PS oligos exert potent non-G-quartet, non-sequence-specific effects on in vitro SMC proliferation and migration as well as in vivo neointimal formation.

Authors

W Wang, H J Chen, A Schwartz, P J Cannon, C A Stein, L E Rabbani

The PAX2 tanscription factor is expressed in cystic and hyperproliferative dysplastic epithelia in human kidney malformations.

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Abstract

Human dysplastic kidneys are developmental aberrations which are responsible for many of the very young children with chronic renal failure. They contain poorly differentiated metanephric cells in addition to metaplastic elements. We recently demonstrated that apoptosis was prominent in undifferentiated cells around dysplastic tubules (Winyard, P.J.D., J. Nauta, D.S. Lirenman, P. Hardman, V.R. Sams, R.A. Risdon, and A.S. Woolf. 1996. Kidney Int. 49:135-146), perhaps explaining the tendency of some of these organs to regress. In contrast, apoptosis was rare in dysplastic epithelia which are thought to be ureteric bud malformations. On occasion, these tubules form cysts which distend the abdominal cavity (the multicystic dysplastic kidney) and dysplastic kidneys may rarely become malignant. We now demonstrate that dysplastic tubules maintain a high rate of proliferation postnatally and that PAX2, a potentially oncogenic transcription factor, is expressed in these epithelia. In contrast, both cell proliferation and PAX2 are downregulated during normal maturation of human collecting ducts. We demonstrate that BCL2, a protein which prevents apoptosis in renal mesenchymal to epithelia] conversion, is expressed ectopically in dysplastic kidney epithelia. We propose that dysplastic cyst formation may be understood in terms of aberrant temporal and spatial expression of master genes which are tightly regulated in the normal program of human nephrogenesis.

Authors

P J Winyard, R A Risdon, V R Sams, G R Dressler, A S Woolf

Role of Ca2+ in the action of adrenocorticotropin in cultured human adrenal glomerulosa cells.

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Abstract

The present report details the role of Ca2+ in the early events of ACTH action in human adrenal glomerulosa cells. Threshold stimulations of both aldosterone and cAMP production were obtained with a concentration of 10 pM ACTH, an ED50 of 0.1 nM, and maximal aldosterone stimulation (5.5-fold increase over control) at 10 nM ACTH. ACTH also induced a sustained increase of intracellular calcium ([Ca2+]i) with maximal stimulation of 1.6 +/- 0.1-fold over control values. This increase does not involve mobilization of calcium from intracellular pools since no response was observed in Ca2+-free medium or in the presence of nifedipine, suggesting the involvement of Ca2+ influx by L-type Ca2+ channels. This was confirmed by patch clamp studies that demonstrated that ACTH stimulates L-type Ca2+ channels. Moreover, the Ca2+ ion is not required for ACTH binding to its receptor, but is essential for sustained cAMP production and aldosterone secretion after ACTH stimulation. These results indicate that, in human adrenal glomerulosa cells, a positive feedback loop between adenylyl cyclase-protein kinase A-Ca2+ channels ensures a slow but sustained [Ca2+]i increase that is responsible for sustained cAMP production and aldosterone secretion.

Authors

N Gallo-Payet, E Grazzini, M Côté, L Chouinard, A Chorvátová, L Bilodeau, M D Payet, G Guillon

Regulation of human heart contractility by essential myosin light chain isoforms.

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Abstract

Most of the patients with congenital heart diseases express the atrial myosin light chain 1 (ALC-1) in the right ventricle. We investigated the functional consequences of ALC-1 expression on the myosin cycling kinetics in the intact sarcomeric structure using multicellular demembranated fibers ("skinned fibers") from the right ventricular infundibulum of patients with Tetralogy of Fallot (TOF), double outlet right ventricle (DORV), and infundibular pulmonary stenosis (IPS), Force-velocity relation was analyzed by the constant-load technique at maximal Ca2+ activation (pCa 4.5). Half-time of tension development (t1/2) was investigated by monitoring contraction initiation upon photolytic release of ATP from caged-ATP in rigor. The patients investigated here expressed between 0 and 27% ALC-1. There was a statistically significant correlation between ALC-l and maximal shortening velocity (Vmax) which rose 1.87-fold from 1.2 muscle length per second (ML/s) to 2.25 ML/s in a normal (0% ALC-1) and diseased (19.9% ALC-1) ventricle. Half-time of tension development decreased 1.85-fold with increasing ALC-1 expression (t1/2) was 0.252 s and 0.136 s at 2 and 18.4% ALC-1, respectively). We conclude that the expression of ALC-1 in the human heart modulates cross-bridge cycling kinetics accelerating shortening velocity and isometric tension production.

Authors

M Morano, U Zacharzowski, M Maier, P E Lange, V Alexi-Meskishvili, H Haase, I Morano

Transcriptional activation of RACTK1 K+ channel gene by apical alkalization in renal cortical collecting duct cells.

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Abstract

We have previously demonstrated that RACTK1 cDNA encodes a pH sensitive K+ channel expressed in the apical side of renal collecting tubule cells. To determine whether extracellular pH induces the RACTK1 gene expression in the renal cortical collecting duct (CCD) cells, we measured mRNA of the RACTK1 using cultured rabbit CCD cells. Alkalization of incubation medium activated the transcription of the RACKTK1 gene in a time- and dose-dependent manner after 1 h, and reached a maximal level after 12 h. To examine whether the stimulation of mRNA by alkalization of body fluid occurs also in vivo, mRNA levels were measured in mice loaded with acid or alkali. The RACTK1 mRNA was increased in association with the rise in urinary pH. To examine side face of the effect of pH on stimulation of mRNA, we observed the effect of pH in the apical or the basolateral side in the preparation where CCD cells were cultured on filter membrane supports. Alkalization of the apical side but not of the basolateral side, was shown to be a determinant in inducting the RACTK1 mRNA. These findings suggest that, in addition to rapid direct regulation of RACTK1 K+ channel conductance by intracellular pH, this channel is also regulated by the changes in luminal pH through synthesis of channel protein by transcriptional activation.

Authors

M Ikeda, M Murata, T Miyoshi, K Tamba, S Muto, M Imai, M Suzuki

Vascular endothelial growth factor is produced by peritoneal fluid macrophages in endometriosis and is regulated by ovarian steroids.

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Abstract

Angiogenesis is important in the pathophysiology of endometriosis, a condition characterized by implantation of ectopic endometrium in the peritoneal cavity. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor involved in physiological and pathological angiogenesis, and elevated levels of VEGF are found in peritoneal fluid of patients with endometriosis. Our aim was to investigate the site of expression and regulation of VEGF in endometriosis. VEGF immunoreactivity was found in tissue macrophages present in ectopic endometrium and in activated peritoneal fluid macrophages. Macrophage activation was highest in women with endometriosis, and media conditioned by peritoneal fluid macrophages from these women caused a VEGF-dependent increase in endothelial cell proliferation above that seen from normal women. Peritoneal fluid macrophages secreted VEGF in response to ovarian steroids, and this secretion was enhanced after activation with lipopolysaccharide. Peritoneal fluid macrophages expressed receptors for steroid hormones. VEGF receptors flt and KDR (kinase domain receptor) were also detected, suggesting autocrine regulation. During the menstrual cycle, expression of flt was constant but that of KDR was increased in the luteal phase, at which time the cells migrated in response to VEGF. KDR expression and the migratory response were significantly higher in patients with endometriosis. This study demonstrates that activated macrophages are a major source of VEGF in endometriosis and that this expression is regulated directly by ovarian steroids.

Authors

J McLaren, A Prentice, D S Charnock-Jones, S A Millican, K H Müller, A M Sharkey, S K Smith

Downregulation of vascular endothelial growth factor receptors by tumor necrosis factor-alpha in cultured human vascular endothelial cells.

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Abstract

Vascular endothelial growth factor (VEGF) potently stimulates angiogenesis, whereas TNF-alpha has both pro- and anti-angiogenic activity. By measuring thymidine uptake, we found that TNF-alpha blocked a 2.3-fold increase in DNA synthesis induced by VEGF in human endothelial cells. To explore the possibility that the two interact to regulate endothelial cell proliferation, we examined the effect of TNF-alpha on VEGF receptor expression. In venous and arterial endothelial cells, TNF-alpha potently reduced mRNA transcripts of the two VEGF receptors (KDR/flk-1 and flt-1) in a dose- and time-dependent fashion. TNF-alpha at 1 ng/ml induced maximal inhibition of mRNA expression, which fell by approximately 70% after 24 h. TNF-alpha treatment did not significantly affect the KDR/flk-1 half-life but did decrease its rate of transcription to 40% of control. The decrease in KDR/flk-1 mRNA depended partially on new protein synthesis and was abolished by phorbol ester pretreatment. TNF-alpha decreased the amount of 35S-labeled KDR/flk-1 immunoprecipitated by an antibody specific for KDR/flk-1 to 18% of control. We conclude that TNF-alpha downregulates expression of both VEGF receptors in human endothelial cells and that this effect is transcriptional (at least for KDR/flk-1). These data support the hypothesis that TNF-alpha exerts its antiangiogenic effect in part by modulating the VEGF-specific angiogenic pathway.

Authors

C Patterson, M A Perrella, W O Endege, M Yoshizumi, M E Lee, E Haber

Arylsulfatase B activities and glycosaminoglycan levels in retrovirally transduced mucopolysaccharidosis type VI cells. Prospects for gene therapy.

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Abstract

Mucopolysacchariodosis type VI (MPS VI) is the lysosomal storage disorder caused by the deficient activity of arylsulfatase B (ASB; N-acetylgalactosamine 4-sulfatase) and the subsequent accumulation of the glycosaminoglycan (GAG), dermatan sulfate. In this study, a retroviral vector containing the full-length human ASB cDNA was constructed and used to transduce skin fibroblasts, chondrocytes, and bone marrow cells from human patients, cats, or rats with MPS VI. The ASB vector expressed high levels of enzymatic activity in each of the cell types tested and, in the case of cat and rat cells, enzymatic expression led to complete normalization of 35SO4 incorporation. In contrast, overexpression of ASB in human MPS VI skin fibroblasts did not lead to metabolic correction. High-level ASB expression was detected for up to eight weeks in transduced MPS VI cat and rat bone marrow cultures, and PCR analysis demonstrated retroviral-mediated gene transfer to approximately 30-50% of the CFU GM-derived colonies. Notably, overexpression of ASB in bone marrow cells led to release of the enzyme into the media and uptake by MPS VI cat and rat skin fibroblasts and/or chondrocytes via the mannose-6-phosphate receptor system, leading to metabolic correction. Thus, these studies provide important rationale for the development of gene therapy for this disorder and lay the frame-work for future in vivo studies in the animal model systems.

Authors

C Fillat, C M Simonaro, P L Yeyati, J L Abkowitz, M E Haskins, E H Schuchman

Requirement and role of C5a in acute lung inflammatory injury in rats.

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Abstract

The complement activation product, C5a, may play a key role in the acute inflammatory response. Polyclonal antibody to rat C5a was used to define the requirements for C5a in neutrophil-dependent inflammatory lung injury after systemic activation of complement by cobra venom factor (CVF) or after intrapulmonary deposition of IgG immune complexes. In the CVF model, intravenous infusion (but not intratracheal instillation) of anti-C5a produced a dose-dependent reduction in lung permeability and in lung content of myeloperoxidase. In C6-deficient rats, CVF infusion caused the same level of lung injury (measured by leak of 125I-albumin) as found in C6-sufficient rats. In the IgG immune complex model of lung injury, anti-C5a administered intratracheally (but not intravenously) reduced in a dose-dependent manner both the increase in lung vascular permeability as well as the buildup of lung myeloperoxidase. Treatment with anti-C5a greatly suppressed upregulation of lung vascular intercellular adhesion molecule-1 (ICAM-1). This was correlated with a substantial drop in levels of TNFalpha in bronchoalveolar fluids. These data demonstrate the requirement for C5a in the two models of injury. In the IgG immune complex model, C5a is required for the full production of TNFalpha and the corresponding upregulation of lung vascular ICAM-1.

Authors

M S Mulligan, E Schmid, B Beck-Schimmer, G O Till, H P Friedl, R B Brauer, T E Hugli, M Miyasaka, R L Warner, K J Johnson, P A Ward

Activation of endogenous deltaF508 cystic fibrosis transmembrane conductance regulator by phosphodiesterase inhibition.

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Abstract

Many heterologously expressed mutants of the cystic fibrosis transmembrane conductance regulator (CFTR) exhibit residual chloride channel activity that can be stimulated by agonists of the adenylate cyclase/protein kinase A pathway. Because of clinical implications for cystic fibrosis of activating mutants in vivo, we are investigating whether deltaF508, the most common disease-associated CFTR mutation, can be activated in airway epithelial cells. We have found that, 36Cl- efflux can be stimulated 19-61% above baseline by beta-adrenoreceptor agonists and cGI-phosphodiesterase inhibitors in transformed nasal polyp (CF-T43) cells homozygous for the deltaF508 mutation. The increase in 36Cl- permeability is diminished by protein kinase A inhibitors and is not mediated by an increase in intracellular calcium concentrations. Preincubation of CF-T43 cells with CFTR anti-sense oligonucleotides prevented an increase in 36Cl- efflux in response to beta-agonist and phosphodiesterase inhibitor. Primary cells isolated from CF nasal polyps gave similar results. These data indicate that endogenous levels of deltaF508 protein can be stimulated to increase 36Cl- permeability in airway epithelial cells.

Authors

T J Kelley, L Al-Nakkash, C U Cotton, M L Drumm

Bcr/Abl expression stimulates integrin function in hematopoietic cell lines.

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Abstract

Cell adhesion to the extracellular matrix is largely mediated by adhesion molecules of the integrin family and is often diminished upon oncogenic transformation. However, we show here that the chronic myelogenous leukemia oncogene Bcr/Abl has positive effects on VLA-4 and VLA-5 integrin function. The presence of Bcr/Abl in the GM-CSF- or IL-3-dependent hematopoietic cell lines MO7e, 32D, and BaF/3 enhanced cell binding to both soluble and immobilized fibronectin. The effect was due to enhanced function of the VLA-5 integrin fibronectin receptor and not to increased surface expression. In parallel, Bcr/Abl stimulated cell adhesion to the VLA-4 integrin ligand VCAM-1. Stimulation of VLA-5 function directly correlated with induction of Bcr/Abl tyrosine kinase activity in a temperature-sensitive kinase mutant. Thus, Bcr/Abl stimulates integrin-dependent cell adhesion, by a mechanism involving increased ligand binding, with the tyrosine kinase activity of Bcr/Abl likely playing a key role. Consistent with these results, hematopoietic precursor cells from chronic myelogenous leukemia patients also showed increased adhesion to fibronectin.

Authors

G Bazzoni, N Carlesso, J D Griffin, M E Hemler

Neutrophil infiltration, glial reaction, and neurological disease in transgenic mice expressing the chemokine N51/KC in oligodendrocytes.

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Abstract

Chemokines (pro-inflammatory chemoattractant cytokines) are expressed in pathological conditions of the central nervous system (CNS). Previous studies suggested that the CNS is relatively resistant to leukocyte diapedesis after chemokine injection, leaving their functional role unresolved. The CNS function of N51/KC, a neutrophil-selective chemokine, was addressed by expressing N51/KC under control of the myelin basic protein (MBP) promoter in transgenic (tg) mice (MBP-N51/KC mice). CNS-specific N51/KC expression produced remarkable neutrophil infiltration into perivascular, meningeal, and parenchymal sites, demonstrating that this chemokine exerts the multiple functions in vivo required to recruit leukocytes into the CNS. MBP-N5 1/KC mice represent an incisive model for the molecular dissection of neutrophil entry into the CNS. Unexpectedly, MBP-N51/KC mice developed a neurological syndrome of pronounced postural instability and rigidity at high frequency beginning at 40 days of age, well after peak chemokine expression. 68/182 mice in one tg fine were found dead before one year of age, with prominent neurological symptoms premortem in 26 (38%). Florid microglial activation and blood-brain barrier disruption without dysmyelination were the major neuropathological alterations. Late-onset neurological symptoms in MBP-N51/KC mice may indicate unanticipated consequences of CNS chemokine expression.

Authors

M Tani, M E Fuentes, J W Peterson, B D Trapp, S K Durham, J K Loy, R Bravo, R M Ransohoff, S A Lira

Glucose- and GTP-dependent stimulation of the carboxyl methylation of CDC42 in rodent and human pancreatic islets and pure beta cells. Evidence for an essential role of GTP-binding proteins in nutrient-induced insulin secretion.

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Abstract

Several GTP-binding proteins (G-proteins) undergo post-translational modifications (isoprenylation and carboxyl methylation) in pancreatic beta cells. Herein, two of these were identified as CDC42 and rap 1, using Western blotting and immunoprecipitation. Confocal microscopic data indicated that CDC42 is localized only in islet endocrine cells but not in acinar cells of the pancreas. CDC42 undergoes a guanine nucleotide-specific membrane association and carboxyl methylation in normal rat islets, human islets, and pure beta (HIT or INS-1) cells. GTPgammaS-dependent carboxyl methylation of a 23-kD protein was also demonstrable in secretory granule fractions from normal islets or beta cells. AFC (a specific inhibitor of prenyl-cysteine carboxyl methyl transferases) blocked the carboxyl methylation of CDC42 in five types of insulin-secreting cells, without blocking GTPgammaS-induced translocation, implying that methylation is a consequence (not a cause) of transfer to membrane sites. High glucose (but not a depolarizing concentration of K+) induced the carboxyl methylation of CDC42 in intact cells, as assessed after specific immunoprecipitation. This effect was abrogated by GTP depletion using mycophenolic acid and was restored upon GTP repletion by coprovision of guanosine. In contrast, although rap 1 was also carboxyl methylated, it was not translocated to the particulate fraction by GTPgammaS; furthermore, its methylation was also stimulated by 40 mM K+ (suggesting a role which is not specific to nutrient stimulation). AFC also impeded nutrient-induced (but not K+-induced) insulin secretion from islets and beta cells under static or perifusion conditions, whereas an inactive structural analogue of AFC failed to inhibit insulin release. These effects were reproduced not only by S-adenosylhomocysteine (another methylation inhibitor), but also by GTP depletion. Thus, the glucose- and GTP-dependent carboxyl methylation of G-proteins such as CDC42 is an obligate step in the stimulus-secretion coupling of nutrient-induced insulin secretion, but not in the exocytotic event itself. Furthermore, AFC blocked glucose-activated phosphoinositide turnover, which may provide a partial biochemical explanation for its effect on secretion, and implies that certain G-proteins must be carboxyl methylated for their interaction with signaling effector molecules, a step which can be regulated by intracellular availability of GTP.

Authors

A Kowluru, S E Seavey, G Li, R L Sorenson, A J Weinhaus, R Nesher, M E Rabaglia, J Vadakekalam, S A Metz

Functional beta3-adrenoceptor in the human heart.

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Abstract

Beta3-adrenoceptors are involved in metabolism, gut relaxation, and vascular vasodilation. However, their existence and role in the human heart have not been documented. We investigated the effects of several beta-adrenoceptor agonists and antagonists on the mechanical properties of ventricular endomyocardial biopsies. In the presence of nadolol, a beta1- and beta2-adrenoceptor antagonist, isoprenaline produced consistent negative inotropic effects. Similar negative inotropic effects also resulted from the action of beta3-adrenoceptor agonists with an order of potency: BRL 37344 > SR 58611 approximately CL 316243 > CGP 12177. The dose-response curve to BRL 37344-decreasing myocardial contractility was not modified by pretreatment with nadolol, but was shifted to the right by bupranolol, a nonselective beta-adrenoceptor antagonist. Beta3-adrenoceptor agonists also induced a reduction in the amplitude and an acceleration in the repolarization phase of the human action potential. Beta3-adrenoceptor transcripts were detected in human ventricle by a polymerase chain reaction assay. These results indicate that: (a) beta3-adrenoceptors are present and functional in the human heart; and (b) these receptors are responsible for the unexpected negative inotropic effects of catecholamines and may be involved in pathophysiological mechanisms leading to heart failure.

Authors

C Gauthier, G Tavernier, F Charpentier, D Langin, H Le Marec

Preferential influx and decreased fractional loss of lipoprotein(a) in atherosclerotic compared with nonlesioned rabbit aorta.

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Abstract

The aim was to investigate the atherogenic potential of lipoprotein(a) (Lp(a)) and to further our understanding of the atherogenic process by measuring rates of transfer into the intima-inner media (i.e., intimal clearance) and rates of loss from the intima-inner media (i.e., fractional loss) of Lp(a) and LDL using cholesterol-fed rabbits with nonlesioned (n = 13) or atherosclerotic aortas (n = 12). In each rabbit, 131I-Lp(a) (or 131I-LDL) was injected intravenously 26 h before and 125I-Lp(a) (or 125I-LDL) 3 h before the aorta was removed and divided into six consecutive segments of similar size. The intimal clearance of Lp(a) and LDL was similar and markedly increased in atherosclerotic compared with nonlesioned aortas (ANOVA, effect of atherosclerosis: P < 0.0001). Fractional losses of labeled Lp(a) and labeled LDL in atherosclerotic aorta were on average 25 and 43%, respectively, of that in nonlesioned aortas (ANOVA, effect of atherosclerosis: P < 0.0001). Fractional loss of Lp(a) was 73% of that of LDL (ANOVA, effect of type of lipoprotein: P = 0.07). These data suggest that the development of atherosclerosis is associated with increased influx as well as decreased fractional loss of Lp(a) and LDL from the intima. Accordingly, Lp(a) may share with LDL the potential for causing atherosclerosis.

Authors

L B Nielsen, S Stender, M Jauhiainen, B G Nordestgaard

Infection of human intestinal epithelial cells with invasive bacteria upregulates apical intercellular adhesion molecule-1 (ICAM)-1) expression and neutrophil adhesion.

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Abstract

The acute host response to gastrointestinal infection with invasive bacteria is characterized by an accumulation of neutrophils in the lamina propria, and neutrophil transmigration to the luminal side of the crypts. Intestinal epithelial cells play an important role in the recruitment of inflammatory cells to the site of infection through the secretion of chemokines. However, little is known regarding the expression, by epithelial cells, of molecules that are involved in interactions between the epithelium and neutrophils following bacterial invasion. We report herein that expression of ICAM-1 on human colon epithelial cell lines, and on human enterocytes in an in vivo model system, is upregulated following infection with invasive bacteria. Increased ICAM-1 expression in the early period (4-9 h) after infection appeared to result mainly from a direct interaction between invaded bacteria and host epithelial cells since it co-localized to cells invaded by bacteria, and the release of soluble factors by epithelial cells played only a minor role in mediating increased ICAM-1 expression. Furthermore, ICAM-1 was expressed on the apical side of polarized intestinal epithelial cells, and increased expression was accompanied by increased neutrophil adhesion to these cells. ICAM-1 expression by intestinal epithelial cells following infection with invasive bacteria may function to maintain neutrophils that have transmigrated through the epithelium in close contact with the intestinal epithelium, thereby reducing further invasion of the mucosa by invading pathogens.

Authors

G T Huang, L Eckmann, T C Savidge, M F Kagnoff

Differential sympathetic neural control of oxygenation in resting and exercising human skeletal muscle.

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Abstract

Metabolic products of skeletal muscle contraction activate metaboreceptor muscle afferents that reflexively increase sympathetic nerve activity (SNA) targeted to both resting and exercising skeletal muscle. To determine effects of the increased sympathetic vasoconstrictor drive on muscle oxygenation, we measured changes in tissue oxygen stores and mitochondrial cytochrome a,a3 redox state in rhythmically contracting human forearm muscles with near infrared spectroscopy while simultaneously measuring muscle SNA with microelectrodes. The major new finding is that the ability of reflex-sympathetic activation to decrease muscle oxygenation is abolished when the muscle is exercised at an intensity > 10% of maximal voluntary contraction (MVC). During high intensity handgrip, (45% MVC), contraction-induced decreases in muscle oxygenation remained stable despite progressive metaboreceptor-mediated reflex increases in SNA. During mild to moderate handgrips (20-33% MVC) that do not evoke reflex-sympathetic activation, experimentally induced increases in muscle SNA had no effect on oxygenation in exercising muscles but produced robust decreases in oxygenation in resting muscles. The latter decreases were evident even during maximal metabolic vasodilation accompanying reactive hyperemia. We conclude that in humans sympathetic neural control of skeletal muscle oxygenation is sensitive to modulation by metabolic events in the contracting muscles. These events are different from those involved in either metaboreceptor muscle afferent activation or reactive hyperemia.

Authors

J Hansen, G D Thomas, S A Harris, W J Parsons, R G Victor