Inactivation of mitochondrial respiratory chain complex I leads mitochondrial nitric oxide synthase to become pro-oxidative.

We recently demonstrated that mitochondrial nitric oxide synthase (mtNOS) functionally couples with mitochondrial respiratory chain complex I to produce nitric oxide [M.S. Parihar, R.R. Nazarewicz, E. Kincaid, U. Bringold, P. Ghafourifar, Association of mitochondrial nitric oxide synthase activity with respiratory chain complex I, Biochem. Biophys. Res. Commun. 366 (2008) 23-28]. The present report shows that inactivation of complex I leads mtNOS to become pro-oxidative. Our findings suggest a crucial role for mtNOS in oxidative stress caused by mitochondrial complex I inactivation.