Mitochondrial respiratory chain is involved in insulin-stimulated hydrogen peroxide production and plays an integral role in insulin receptor autophosphorylation in neurons

BACKGROUND: Accumulated evidence suggests that hydrogen peroxide (H(2)O(2)) generated in cells during insulin stimulation plays an integral role in insulin receptor signal transduction. The role of insulin-induced H(2)O(2 )in neuronal insulin receptor activation and the origin of insulin-induced H(2)O(2 )in neurons remain unclear. The aim of the present study is to test the following hypotheses (1) whether insulin-induced H(2)O(2 )is required for insulin receptor autophosphorylation in neurons, and (2) whether mitochondrial respiratory chain is involved in insulin-stimulated H(2)O(2 )production, thus playing an integral role in insulin receptor autophosphorylation in neurons. RESULTS: Insulin stimulation elicited rapid insulin receptor autophosphorylation accompanied by an increase in H(2)O(2 )release from cultured cerebellar granule neurons (CGN). N-acetylcysteine (NAC), a H(2)O(2 )scavenger, inhibited both insulin-stimulated H(2)O(2 )release and insulin-stimulated autophosphorylation of insulin receptor. Inhibitors of respiratory chain-mediated H(2)O(2 )production, malonate and carbonyl cyanide-4-(trifluoromethoxy)-phenylhydrazone (FCCP), inhibited both insulin-stimulated H(2)O(2 )release from neurons and insulin-stimulated autophosphorylation of insulin receptor. Dicholine salt of succinic acid, a respiratory substrate, significantly enhanced the effect of suboptimal insulin concentration on the insulin receptor autophosphorylation in CGN. CONCLUSION: Results of the present study suggest that insulin-induced H(2)O(2 )is required for the enhancement of insulin receptor autophosphorylation in neurons. The mitochondrial respiratory chain is involved in insulin-stimulated H(2)O(2 )production, thus playing an integral role in the insulin receptor autophosphorylation in neurons.