Akt Activation Diminishes Nephrotoxicant‐Induced Mitochondrial Dysfunction and Necrosis in Renal Cells

Abstract

Protein kinase B (Akt) regulates cell growth and survival in different cell types. This study sought to determine if Akt protects against nephrotoxicant-induced injury in renal proximal tubular cells (RPTC). Exposure of RPTC to S-(1, 2 dichlorovinyl)-L-cysteine (DCVC; 0.24 mM), the nephrotoxic metabolite of environmental pollutants, induced mitochondrial dysfunction and cell death by apoptosis (12%) and necrosis (19%). Basal respiration, electron transport rate and oxidative phosphorylation decreased to 74%, 52% and 75% of control, respectively. Reduction in the activities of respiratory complexes I and II (62 and 53% of control, respectively) resulted in decreased state 3 respiration (to 65% of control). Mitochondrial membrane potential and ATP levels decreased to 51% and 57% of control, respectively. Akt was phosphorylated during and after (4 hours) DCVC exposure suggesting Akt activation. Inhibition of Akt activation (by PI3 kinase inhibitor LY294002 or expressing dominant inactive Akt) further reduced complex I (to 32% of controls) but not complex II activity, ATP levels (to 30% of controls) and potentiated RPTC necrosis. In contrast, expressing constitutively active Akt in RPTC maintained ATP levels, decreased necrosis (13%), and stimulated recovery of RPTC number and monolayer DNA content in DCVC-injured RPTC. Akt activation had no effect on DCVC induced apoptosis. We conclude that Akt activation promotes mitochondrial function, prevents ATP decreases, diminishes necrosis, and promotes regeneration in nephrotoxicant-injured RPTC. Supported by NIH/NIDDK R01DK59558 and AHA Predoctoral Fellowship 0510051Z.