Antioxidant mechanism of mitochondria-targeted plastoquinone SkQ1 is suppressed in aglycemic HepG2 cells dependent on oxidative phosphorylation

0482786 - FGÚ 2018 RIV NL eng J - Journal Article
Ježek, J. - Engstová, Hana - Ježek, Petr
Antioxidant mechanism of mitochondria-targeted plastoquinone SkQ1 is suppressed in aglycemic HepG2 cells dependent on oxidative phosphorylation.
Biochimica Et Biophysica Acta-Bioenergetics. Roč. 1858, č. 9 (2017), s. 750-762. ISSN 0005-2728. E-ISSN 1879-2650
R&D Projects: GA ČR(CZ) GA17-01813S
Institutional support: RVO:67985823
Keywords : mitochondria-targeted antioxidant SkQ1 * mitochondrial Complex I superoxide formation * mitochondrial Complex III superoxide formation * HepG2 cells * NAD(P)H fluorescence lifetime imaging microscopy
OECD category: Cell biology
Impact factor: 4.280, year: 2017

Previously suggested antioxidant mechanisms for mitochondria-targeted plastoquinone SkQ1 included: i) ion pairing of cationic SkQl(+) with free fatty acid anions resulting in uncoupling, ii) SkQ1H(2) ability to interact with lipoperoxyl radical, interference with electron flow at the inner ubiquinone (Q) binding site of Complex III (Q(i)), involving the reduction of SkQ1 to SkQ1H(2) by ubiquinol. We elucidated SkQl antioxidant properties by confocal fluorescence semi-quantification of mitochondrial superoxide (J(m)) and cytosolic H2O2 (J(c)) release rates in HepG2 cells. Only in glycolytic cells, SkQl prevented the rotenone-induced enhancement of Jm and Jc but not basal releases without rotenone. The effect ceased in glutaminolytic aglycemic cells, in which the redox parameter NAD(P)H/FAD increased after rotenone in contrast to its decrease in glycolytic cells. Autofluorescence decay indicated decreased NADPH/NADH ratios with rotenone in both metabolic modes. SkQl did not increase cell respiration and diminished Jm established high by antimycin or myxothiazol but not by stigmatellin. The revealed SkQ1 antioxidant modes reflect its reduction to SkQ1H(2) at Complex I I-Q or Complex III Q(i) site. Both reductions diminish electron diversions to oxygen thus attenuating superoxide formation. Resulting SkQ1H(2) oxidizes back to SkQ1at the second (flavin) Complex I site, previously indicated for MitoQ(10). Regeneration proceeds only at lower NAD(P)H/FAD in glycolytic cells. In contrast, cyclic SkQ1 reduction/SkQ1H(2) oxidation does not substantiate antioxidant activity in intact cells in the absence of oxidative stress (neither pro-oxidant activity, representing a great advantage). A targeted delivery to oxidative-stressed tissues is suggested for the effective antioxidant therapy based on SkQ1.
Permanent Link: http://hdl.handle.net/11104/0278167