Protein kinase B (Akt) activation is well known for its protective effects against apoptosis. However, the role of Akt in regulation of
necrosis is unknown. This study was designed to test whether Akt activation protects against nephrotoxicant-induced injury and death in renal proximal tubular cells (RPTC). Exposure of primary cultures of RPTC to the nephrotoxic
cysteine conjugate, S-(1,2-dichlorovinyl)-l-cysteine (DCVC), resulted in 9% apoptosis and 30%
necrosis at 24 h following the exposure. Akt was activated during 8 h but not at 24 h following toxicant exposure. No RPTC
necrosis was observed during Akt activation. Blocking Akt activation using a
phosphatidylinositol 3-kinase inhibitor,
LY294002 (20 muM), or expressing dominant negative (inactive) Akt increased DCVC-induced RPTC
necrosis to 42%. In contrast, Akt activation by expression of constitutively active Akt diminished
necrosis to 15%. Modulation of Akt activity had no effect on DCVC-induced apoptosis. DCVC-induced RPTC injury was accompanied by decreases in respiration (51% of controls) and
ATP levels (57% of controls). Akt inhibition exacerbated decreases in RPTC respiration and intracellular
ATP content (both to 30% of controls). In contrast, Akt activation reduced DCVC-induced decreases in respiration (80% of controls) and prevented decline in
ATP content. These data show that in RPTC, Akt activation reduces 1) toxicant-induced
mitochondrial dysfunction, 2) decreases in
ATP levels, and 3)
necrosis. We conclude that Akt activation plays a protective role against
necrosis caused by nephrotoxic insult in RPTC. Furthermore, we identified mitochondria as a subcellular target of protective actions of Akt against
necrosis.