Mitochondrial H2O2 generated from electron transport chain complex I stimulates muscle differentiation

Abstract

Mitochondrial reactive oxygen species (mROS) have been considered detrimental to cells. However, their physiological roles as signaling mediators have not been thoroughly explored. Here, we investigated whether mROS generated from mitochondrial electron transport chain (mETC) complex I stimulated muscle differentiation. Our results showed that the quantity of mROS was increased and that manganese superoxide dismutase (MnSOD) was induced via NF-κB activation during muscle differentiation. Mitochondria-targeted antioxidants (MitoQ and MitoTEMPOL) and mitochondria-targeted catalase decreased mROS quantity and suppressed muscle differentiation without affecting the amount of ATP. Mitochondrial alterations, including the induction of mitochondrial transcription factor A and an increase in the number and size of mitochondria, and functional activations were observed during muscle differentiation. In particular, increased expression levels of mETC complex I subunits and a higher activity of complex I than other complexes were observed. Rotenone, an inhibitor of mETC complex I, decreased the mitochondrial NADH/NAD + ratio and mROS levels during muscle differentiation. The inhibition of complex I using small interfering RNAs and rotenone reduced mROS levels, suppressed muscle differentiation, and depleted ATP levels with a concomitant increase in glycolysis. From these results, we conclude that complex I-derived O 2 · − , produced through reverse electron transport due to enhanced metabolism and a high activity of complex I, was dismutated into H 2 O 2 by MnSOD induced via NF-κB activation and that the dismutated mH 2 O 2 stimulated muscle differentiation as a signaling messenger.

Sites of Superoxide and Hydrogen Peroxide Production by Muscle Mitochondria Assessed ex Vivo under Conditions Mimicking Rest and Exercise

“…The contribution of site I Q in cells and in vivo is unknown. In some cells, the addition of rotenone decreases cellular production of reactive oxygen species (29,(52)(53)(54), which is consistent with a substantial contribution of site I Q . However, if the cells were oxidizing predominantly NADlinked substrates, the addition of rotenone would block reduction of ubiquinone and decrease superoxide/H 2 O 2 production from sites in the QH 2 /Q isopotential group, particularly sites III Qo and II F .…”

“…However, if the cells were oxidizing predominantly NADlinked substrates, the addition of rotenone would block reduction of ubiquinone and decrease superoxide/H 2 O 2 production from sites in the QH 2 /Q isopotential group, particularly sites III Qo and II F . If the cells were running reverse electron transport (29), the addition of rotenone would block reduction of NAD ϩ and decrease superoxide/H 2 O 2 production from sites in the NADH/NAD ϩ isopotential group, particularly sites I F , P F , and O F . These alternative explanations greatly weaken any conclusion from rotenone inhibition experiments that site I Q is active in cells.…”

“…During exercise, the levels of both reactive oxygen species and reactive nitrogen species are increased (26). The production of such species is crucial for the beneficial effects of exercise (27)(28)(29) and for force development (30). However, excess production is detrimental for skeletal muscle performance (30,31).…”

Redox Control of Skeletal Muscle Regeneration

“…MuSC differentiation is accompanied by an increase of mtROS production (200), especially H 2 O 2 (184,353). As a response, an upregulation of antioxidant enzymes, mainly with peroxidase function such as Prx2, is also observed (109,184,353).…”

“…As a response, an upregulation of antioxidant enzymes, mainly with peroxidase function such as Prx2, is also observed (109,184,353). In addition, the treatment of MuSCs with mitochondria-targeted antioxidants such as MitoQ, MitoTEMPOL, or MCAT alters their differentiation (184), as does treatment with nordihydroguaiaretic acid (NDGA) (146).…”