Pro-oxidant mitochondrial matrix-targeted ubiquinone MitoQ10 acts as anti-oxidant at retarded electron transport or proton pumping within Complex I.
Oxidative stress of mitochondrial origin, i.e. elevated mitochondrial superoxide production, belongs to major factors determining aging and oxidative-stress-related diseases. Antioxidants, such as the mitochondria-targeted coenzyme Q, MitoQ(10), may prevent or cure these pathological conditions. To elucidate pro- and anti-oxidant action of MitoQ(10), we studied its effects on HepG2 cell respiration, mitochondrial network morphology, and rates of superoxide release (above that neutralized by superoxide dismutase) to the mitochondrial matrix (J(m)). MitoSOX Red fluorescence confocal microscopy monitoring of J(m) rates showed pro-oxidant effects of 3.5-fold increased J(m) with MitoQ(10). MitoQ(10) induced fission of the mitochondrial network which was recovered after 24h. In rotenone-inhibited HepG2 cells (i.e., already under oxidative stress) MitoQ(10) sharply decreased rotenone-induced J(m), but not together with the Complex II inhibitor thenoyltrifluoroacetone. Respiration of HepG2 cells and isolated rat liver mitochondria with MitoQ(10) increased independently of rotenone. The increase was prevented by thenoyltrifluoroacetone. These results suggest that MitoQ(10) accepts electrons prior to the rotenone-bound Q-site, and the Complex II reverse mode oxidizes MitoQ(10)H(2) to regenerate MitoQ(10). Consequently, MitoQ(10) has a pro-oxidant role in intact cells, whereas it serves as an antioxidant when Complex I-derived superoxide generation is already elevated due to electron flow retardation. Moreover, unlike mitochondrial uncoupling, MitoQ(10) exerted its antioxidant role when Complex I proton pumping was retarded by a hydrophobic amiloride, 5-(N-ethyl-N-isopropyl) amiloride. Consequently, MitoQ(10) may be useful in the treatment of diseases originating from impairment of respiratory chain Complex I due to oxidatively damaged mitochondrial DNA, when its targeted delivery to pathogenic tissues is ensured.
Department No 75, Institute of Physiology, Academy of Sciences, Vídenská 1083, Prague, Czech Republic. plecita@biomed.cas.cz
Lydie
L
Plecitá-Hlavatá
Jan
J
Jezek
Petr
P
Jezek
D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D045744:Cell Line, Tumor; D019069:Cell Respiration / Q000187:drug effects; D004579:Electron Transport / Q000187:drug effects; D042967:Electron Transport Complex I / Q000378:metabolism*; D042963:Electron Transport Complex II / Q000378:metabolism; D014450:Electron Transport Complex III / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D017494:Proton Pumps / Q000378:metabolism*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012402:Rotenone / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000378:metabolism
D000975:Antioxidants; D017494:Proton Pumps; D017382:Reactive Oxygen Species; D012402:Rotenone; D013481:Superoxides; D014451:Ubiquinone; D006861:Hydrogen Peroxide; D042963:Electron Transport Complex II; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III; C024989:coenzyme Q10; D005947:Glucose