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VEGF AND PODOCYTE PROTECTION IN CHRONIC HYPOXIA: EFFECTS OF ENDOTHELIN-A RECEPTOR ANTAGONISM #MMPMID26930122
Harvey TW; Engel JE; Chade AR
Am J Nephrol 2016[]; 43 (2): 74-84 PMID26930122show ga
Background: Podocytes are major components of the filtration barrier and a renal source of vascular endothelial growth factor (VEGF). Chronic renovascular disease (RVD) progressively deteriorates renal function, accompanied by podocyte damage and a progressive reduction in VEGF. We showed that the endothelin (ET) pathway contributes to this pathological process and ET-A (but not ET-B) receptor antagonism protects the kidney in RVD. We hypothesize that ETA-induced renoprotection is largely driven by protection of podocyte integrity and function. Methods: To mimic renal environment of chronic RVD, human podocytes were incubated under chronic hypoxia for 96 hours and divided in untreated or treated with an ET-A or ET-B receptor antagonist. Cells were quantified after 96 hours. Cell homogenates and media were obtained after 1, 24 and 96 hours to quantify production of VEGF, anti-VEGF soluble receptor s-Flt1, and the expression of apoptotic mediators. A separate set of similar experiments was performed after addition of a VEGF-neutralizing antibody (VEGF-NA). Results: Hypoxia decreased podocyte number, which was exacerbated by ET-B but improved after ET-A antagonism. Production of VEGF was preserved by ET-A antagonism whereas s-Flt1 increased in hypoxic cells after ET-B antagonism only, accompanied by a greater expression of pro-apoptotic mediators. On the other hand, treatment with VEGF-NA diminished ET-A-induced protection of podocytes. Conclusion: ET-A antagonism preserves podocyte viability and integrity under chronic hypoxia, whereas ET-B antagonism exacerbates podocyte dysfunction and death. Enhanced bioavailability of VEGF after ET-A antagonism could be a pivotal mechanism of podocyte protection that significantly contributes to ET-A receptor blockade-induced renal recovery in chronic RVD.