Roles of Na+/H+ exchanger type 1 and intracellular pH in angiotensin II-induced reactive oxygen species generation and podocyte apoptosis

A growing body of evidence suggests that podocyte apoptosis is a major cause of decreased podocyte number,which leads to albuminuria and glomerular injury. the aim of this study was to clarify the molecular mechanisms of angiotensin ii (ang ii)-induced apoptosis in cultured mouse podocytes. we examined the effects of ang ii (100 nmol/l) on apoptosis,superoxide anions,and cytosol ph in podocytes. for intracellular ph measurements,image analysis was conducted using confocal laser microscopy after incubation with carboxyseminaphthorhodafluor- 1. superoxide anions and intracellular ph were elevated with ang ii treatment. apoptotic cell numbers,as measured by tunel staining and caspase 3 activity,were also augmented in the ang ii-treated group. pre-treatment with olmesartan (100 nmol/l,an ang ii type 1-receptor blocker),apocynin (50 μmol/l,nadph oxidase inhibitor),or 5-n,n hexamethylene amiloride [30 μmol/l,na+/h+ exchanger type 1 (nhe-1) inhibitor] abolished ang ii-induced podocyte apoptosis,whereas nhe-1 mrna and protein expression was not affected by ang ii treatment. moreover,ang ii increased nhe-1 phosphorylation. these results suggest that superoxide production,nhe-1 activation,and intracellular alkalization were early features prior to apoptosis in ang ii-treated mouse podocytes,and may offer new insights into the mechanisms responsible for ang ii-induced podocyte injury. © 2013 the japanese pharmacological society.