Browsing by Author "Sobrevia, L."

Now showing 1 - 9 of 9
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    Adenosine A(2B) receptor mediates an increase on VEGF-A production in rat kidney glomeruli
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2008) Valladares, D.; Quezada, C.; Montecinos, P.; Yanez, Aj.; Sobrevia, L.; Martin, R. San
    Up-regulation of the glomerular expression and the activity of vascular endothelial growth factor-A (VEGF) have been identified as an early pathogenic event for the progression of diabetic nephropathy. Currently, however the mediators are not yet clearly recognized. In this study we identified all four adenosine receptor (AR) subtypes, i.e. A(1), A(2A), A(2B) and A(3) in isolated rat kidney glomeruli. We localized the expression of A(2B)AR in podocytes, the primary VEGF producing cells. The ex vivo treatment of kidney glomeruli with adenosine or a general AR agonist NECA, increases VEGF protein content. In addition, NECA treatment elicits VEGF release. These effects were blocked by the A(2B)AR selective antagonist MRS1754 supplementation. Furthermore, we showed that A(2B)AR activation was necessary to promote a higher expression of VEGF in kidney glomeruli upon exposure to high D-glucose concentration, a pathogenic condition like those observed in diabetic nephropathy. (c) 2007 Elsevier Inc. All rights reserved.
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    Adenosine mediates transforming growth factor-beta 1 release in kidney glomeruli of diabetic rats
    (WILEY, 2009) Roa, H.; Gajardo, C.; Troncoso, E.; Fuentealba, V.; Escudero, C.; Yanez, A.; Sobrevia, L.; Pastor Anglada, M.; Quezada, C.; San Martin, R.
    Up regulation of the transforming growth factor-beta 1 (TGF-beta 1) axis has been recognized as a pathogenic event for progression of glomerulosclerosis in diabetic nephropathy. We demonstrate that glomeruli isolated from diabetic rats accumulate up to sixfold more extracellular adenosine than normal rats. Both decreased nucleoside uptake activity by the equilibrative nucleoside transporter 1 and increased AMP hydrolysis contribute to raise extracellular adenosine. Ex vivo assays indicate that activation of the low affinity adenosine A(2B) receptor subtype (A(2B)AR) mediates TGF-beta 1 release from glomeruli of diabetic rats, a pathogenic event that could support progression of glomerulopathy when the bioavailability of adenosine is increased. (C) 2009 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
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    Differential expression of functional nucleoside transporters in non-differentiated and differentiated human endothelial progenitor cells
    (W B SAUNDERS CO LTD, 2010) Guzman Gutierrez, E.; Sandoval, C.; Nova, E.; Castillo, J. L.; Vera, J. C.; Lamperti, L.; Krause, B.; Salomon, C.; Sepulveda, C.; Aguayo, C.; Sobrevia, L.
    Extracellular adenosine removal is via human equilibrative nucleoside transporters 1 (hENT1) and 2 (hENT2) in the endothelium, thus regulating adenosine-induced revascularization and angiogenesis. Since human endothelial progenitor cells (hEPCs) promote revascularization, we hypothesize differential expression of nucleoside transporters in hEPCs. hEPCs were cultured 3 (hEPC-3d) or 14 (hEPC-14d) days. RT-PCR for prominin 1, CD34, octamer-4, kinase insert domain receptor, oxidized low-density lipoprotein (lectin-like) receptor 1 and tyrosine endothelial kinase was used to evaluate phenotypic differentiation. Flow cytometry was used to estimate CD34(+)/KDR- (non-differentiated), CD34(-)/KDR+ (differentiated) or CD34(+)/KDR+ (mixed) cell populations. Adenosine transport was measured in absence or presence of sodium, S-(4-nitrobenzyl)-6-thio-inosine (NBTI, 1-10 mu M), inosine, hypoxanthine or guanine (0.1-5 mM), hENTs protein abundance by western blot, and hENTs, hCNT1, hCNT2 and hCNT3 mRNA expression by real time RT-PCR. hEPC-3d cells were CD34(+)/KDR- compared with hEPC-14d cells that were CD34(-)/KDR+ hEPC-3d cells exhibit hENT1-like adenosine transport (NBTI-sensitive, Na+-independent), which is absent in hEPC-14d cells. hEPC-14d cells exhibit two transport components: component 1 (NBTI insensitive, Na+-independent) and component 2 (NBTI insensitive, Na+-dependent, Hill coefficient similar to 1.8), the latter resembling CNT3-like transport. hEPC-3d cells express hENT1 protein and mRNA, which is reduced (similar to 90%) in hEPC-14d cells, but instead only hCNT3 mRNA is expressed in this cell type. hENT2, hCNT1 and hCNT2 were undetectable in hEPCs. Thus, hEPCs exhibit a differential expression of hENT1 and hCNT3 functional nucleoside transporters, which could be related with its differentiation stage. (c) 2010 Elsevier Ltd. All rights reserved.
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    ENDOPLASMIC RETICULUM STRESS IN HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS FROM PRE-GESTATIONAL MATERNAL OBESITY
    (W B SAUNDERS CO LTD, 2017) Villalobos Labra, R.; Salsoso, R.; Subiabre, M.; Silva, L.; Farias Jofre, M.; Leiva, A.; Sobrevia, L.
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    HIGH FAT DIET IN MICE INDUCES ENDOPLASMIC RETICULUM STRESS IN LIVERS OF THEIR OFFSPRING
    (W B SAUNDERS CO LTD, 2015) Garces, M.; Chavez, J. L.; Villalobos Labra, R.; Westermeier, F.; Saez, P. J.; Salas Perez, F.; Cautivo, K.; Busso, D.; Varas, J.; Martin, S. San; Sobrevia, L.; Farias Jofre, M.
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    Human equilibrative nucleoside transporters 1 and 2 may be differentially modulated by A(2B) adenosine receptors in placenta microvascular endothelial cells from pre-eclampsia
    (W B SAUNDERS CO LTD, 2008) Escudero, C.; Casanello, P.; Sobrevia, L.
    Pre-eclampsia is associated with elevated maternal blood pressure and proteinuria, altered fetal growth, and increased plasma adenosine concentration in the mother and the fetus. Human equilibrative nucleoside transporters 1 (hENT1) and hENT2 are crucial to maintain physiological plasma levels of adenosine, thus modulating its several biological effects through adenosine receptor activation. However, it is unknown whether hENTs and adenosine receptors are expressed in human placental microvascular endothelium (hPMEC). To assay whether the increased fetal plasma adenosine concentration in pre-eclampsia results from altered hENT-mediated transport, and the potential involvement of adenosine receptors in this phenomenon, we investigated hENTs and A(2A) and A(2B) adenosine receptors expression and function in hPMEC. Cells were isolated and Cultured from normal pregnancies (n = 17) or Pre-eclampsia with adequate-for-gestational age fetuses (n = 7). hENT1, hENT2, A(2A) and A(2B) adenosine receptors were expressed and functional in hPMEC. Extracelhilar adenosine concentration was higher (4-fold) in pre-eclampsia versus normal pregnancies. hPMEC from pre-eclampsia exhibit increased total ;transport (hENT1 + hENT2), and maximal velocity (V-max) for hENT2- (2-fold), but reduced V-max for hENT1-mediated adenosine transport (75%), with no changes in apparent K-m. hENT2 expression was increased (4.5-fold), but hENT1 protein abundance was reduced (80%) in pre-eclampsia. Equally, A2A expression was reduced (50-80%) in pre-eclampsia. CGS-21680 (A(2A) agonist) did not alter hENTs expression or activity, but ZM-241385 (A(2A) antagonist) blocked pre-eclampsia effects and increased hENT1-mechated transport in normal pregnancies. Thus, A(2B) adenosine receptors may differentially modulate hENTs in hPMEC, which could be a mechanism attempting to re-establish physiological extracellular adenosine levels in pre-eclampsia. (C) 2008 Elsevier Ltd. All rights reserved.
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    Hypoxia-reduced nitric oxide synthase activity is partially explained by higher arginase-2 activity and cellular redistribution in human umbilical vein endothelium
    (W B SAUNDERS CO LTD, 2011) Prieto, C. P.; Krause, B. J.; Quezada, C.; San Martin, R.; Sobrevia, L.; Casanello, P.
    Hypoxia relates with altered placental vasodilation, and in isolated endothelial cells, it reduces activity of the endothelial nitric oxide synthase (eNOS) and L-arginine transport. It has been reported that arginase-2 expression, an alternative pathway for L-arginine metabolism, is increased in adult endothelial cells exposed to hypoxia as well as in pre-eclamptic placentae. We studied in human umbilical vein endothelial cells (HUVEC) whether hypoxia-reduced NO synthesis results from increased arginase-mediated L-arginine metabolism and changes in subcellular localization of eNOS and arginase-2. In HUVEC exposed (24 h) to 5% (normoxia) or 2% (hypoxia) oxygen, L-arginine transport kinetics, arginase activity (urea assay), and NO synthase (NOS) activity (L-citrulline assay) were determined. Arginase-1, arginase-2 and eNOS expression were determined by RT-PCR and Western blot. Subcellular localization of arginase-2 and eNOS were studied using confocal microscopy and indirect immunofluorescence. Experiments were done in absence or presence of S-(2-boronoethyl)-L-cysteine-HCl (BEC, arginase inhibitor) or N-G-nitro-L-arginine methyl ester (L-NAME). Hypoxia-induced reduction in eNOS activity was associated with a reduction in eNOS phosphorylation at Serine-1177 and increased phosphorylation at Threonine-495. This was paralleled with an induction in arginase-2 expression and activity, and decreased L-arginine transport. In hypoxia the arginase inhibition, restored NO synthesis and L-arginine transport, without changes in the eNOS post-translational modification status. Hypoxia increased arginase-2/eNOS colocalization, and eNOS redistribution to the cell periphery. Altogether these data reinforce the thought that eNOS cell location, post-translational modification and substrate availability are important mechanisms regulating eNOS activity. If these mechanisms occur in pregnancy diseases where feto-placental oxygen levels are reduced remains to be clarified. (C) 2011 Elsevier Ltd. All rights reserved.
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    MATERNAL OBESITY IMPAIRS MIGRATION OF FETAL ENDOTHELIUM INVOLVING ENDOPLASMIC RETICULUM STRESS
    (W B SAUNDERS CO LTD, 2015) Villalobos Labra, R.; Saez, P. J.; Gonzalez, I.; Westermeier, F.; Sobrevia, L.; Casanello, P.; Owen, G. I.; Farias Jofre, M.
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