Protection of podocytes from hyperhomocysteinemia‐induced injury in the kidneys of mice lacking gp91phox gene

Abstract

NADPH oxidase (NOX) has been reported to contribute to glomerulosclerosis induced by hyperhomocysteinemia (hHcys). In the present study, we used a mouse model lacking gp91phox (gp91−/−), a membrane subunit of NOX, to test whether the pathogenic role of NOX is associated with podocytes injury induced by hHcys. gp91−/− and wild‐type mice (gp91+/+) were fed on folate‐free (FF) or normal chow for 6 weeks. HPLC analysis showed that both strains of mice had higher plasma homocysteine levels on FF diet compared to the mice on normal chow (9.86 ± 1.06 vs. 4.98 ± 0.52 μM in gp91−/− mice and 10.53± 1.27 vs. 5.05 ± 0.68 µM in gp91+/+ mice). ESR analysis showed that hHcys failed to markedly increase NOX‐dependent superoxide production in kidneys from gp91−/− mice compared with gp91+/+ mice. Glomerular sclerosis index was markedly lower in gp91−/− than in gp91+/+ mice on FF diet. RT‐PCR showed that hHcys significantly decreased nephrin mRNA expression in gp91+/+ mice but not in gp91−/− mice. Correspondingly, desmin mRNA expression was less elevated in gp91−/− mice on FF diet. Immunohistochemistry demonstrated decreased nephrin and increased desmin staining in gp91+/+ mice on FF diet, rather than in gp91−/− mice. Our results suggest that knock‐out of gp91phox leads to a substantial reduction of local oxidative stress in glomeruli, which protects podocytes from hHcys‐induced injury (supported by NIH grants DK54927 and HL075316).