| 18358763 |
Dlaskova A, Hlavata L, Jezek J, Jezek P: Mitochondrial Complex I superoxide production is attenuated by uncoupling. Antioxid Redox Signal. 2005 Sep-Oct;7(9-10):1110-6.
Complex I, i.e. proton-pumping NADH:quinone oxidoreductase, is an essential component of the mitochondrial respiratory chain but produces superoxide as a side-reaction. However, conditions for maximum superoxide production or its attenuation are not well understood. Unlike for Complex III, it has not been clear whether a Complex I-derived superoxide generation at forward electron transport is sensitive to membrane potential or protonmotive force. In order to investigate this, we used Amplex Red for H (2) O (2) monitoring, assessing the total mitochondrial superoxide production in isolated rat liver mitochondria respiring at state 4 as well as at state 3, namely with exclusive Complex I substrates or with Complex I substrates plus succinate. We have shown for the first time, that uncoupling diminishes rotenone-induced H (2) O (2) production also in state 3, while similar attenuation was observed in state 4. Moreover, we have found that 5-(N-ethyl-N-isopropyl) amiloride is a real inhibitor of Complex I H (+) pumping (IC (50) of 27 microM) without affecting respiration. It also partially prevented suppression by FCCP of rotenone-induced H (2) O (2) production with Complex I substrates alone (glutamate and malate), but nearly completely with Complexes I and II substrates. Sole 5-(N-ethyl-N-isopropyl) amiloride alone suppressed 20% and 30% of total H (2) O (2) production, respectively, under these conditions. Our data suggest that Complex I mitochondrial superoxide production can be attenuated by uncoupling, which means by acceleration of Complex I H (+) pumping due to the respiratory control. However, when this acceleration is prevented by 5-(N-ethyl-N-isopropyl) amiloride inhibition, no attenuation of superoxide production takes place. |
85(1,1,1,5) |