Reverse electron flow-mediated ROS generation in ischemia-damaged mitochondria: role of complex I inhibition vs. depolarization of inner mitochondrial membrane.
BACKGROUND
The reverse electron flow-induced ROS generation (RFIR) is decreased in ischemia-damaged mitochondria. Cardiac ischemia leads to decreased complex I activity and depolarized inner mitochondrial membrane potential (ΔΨ) that are two key factors to affect the RFIR in isolated mitochondria. We asked if a partial inhibition of complex I activity without alteration of the ΔΨ is able to decrease the RFIR.


METHODS
Cardiac mitochondria were isolated from mouse heart (C57BL/6) with and without ischemia. The rate of H2O2 production from mitochondria was determined using amplex red coupled with horseradish peroxidase. Mitochondria were isolated from the mitochondrial-targeted STAT3 overexpressing mouse (MLS-STAT3E) to clarify the role of partial complex I inhibition in RFIR production.


RESULTS
The RFIR was decreased in ischemia-damaged mouse heart mitochondria with decreased complex I activity and depolarized ΔΨ. However, the RFIR was not altered in the MLS-STAT3E heart mitochondria with complex I defect but without depolarization of the ΔΨ. A slight depolarization of the ΔΨ in wild type mitochondria completely eliminated the RFIR.


CONCLUSIONS
The mild uncoupling but not the partially decreased complex I activity contributes to the observed decrease in RFIR in ischemia-damaged mitochondria.


GENERAL SIGNIFICANCE
The RFIR is less likely to be a key source of cardiac injury during reperfusion.
['Ross|Thomas|T|', 'Szczepanek|Karol|K|', 'Bowler|Elizabeth|E|', 'Hu|Ying|Y|', 'Larner|Andrew|A|', 'Lesnefsky|Edward J|EJ|', 'Chen|Qun|Q|']
D000818:Animals D004579:Electron Transport D042967:Electron Transport Complex I D006861:Hydrogen Peroxide D051379:Mice D008810:Mice, Inbred C57BL D008929:Mitochondria, Heart D017202:Myocardial Ischemia D017382:Reactive Oxygen Species
Ischemia STAT3 Electron transport chain Reactive oxygen species