Eccentric contraction increases hydrogen peroxide levels and alters gene expression through Nox2 in skeletal muscle of male mice.

Hydrogen peroxide (HO) is one of the key signaling factors regulating skeletal muscle adaptation to muscle contractions. Eccentric (ECC) and concentric (CONC) contractions drive different muscle adaptations with ECC resulting in greater changes. The present investigation tested the hypothesis that ECC produces higher cytosolic and mitochondrial HO concentrations [HO] and alters gene expression more than CONC. Cytosolic and mitochondrial HO-sensitive fluorescent proteins, HyPer7 and MLS-HyPer7, were expressed in the anterior tibialis muscle of C57BL6J male mice. Before and for 60 min after either CONC or ECC (100 Hz, 50 contractions), [HO] and [HO] were measured by in vivo fluorescence microscopy. RNA sequencing was performed in control (noncontracted), CONC, and ECC muscles to identify genes impacted by the contractions. [HO] immediately after ECC was greater than after CONC (CONC: +6%, ECC: +11% vs. rest, < 0.05) and remained higher for at least 60 min into recovery. In contrast, the elevation of [HO] was independent of the contraction modes (time; < 0.0042, contraction mode; = 0.4965). The impact of ECC on [HO] was abolished by NADPH oxidase 2 (Nox2) inhibition (GSK2795039). Differentially expressed genes were not present after CONC or ECC + GSK but were found after ECC and were enriched for vascular development and apoptosis-related genes, among others. In conclusion, in mouse anterior tibialis, ECC, but not CONC, evokes a pronounced cytosolic HO response, caused by Nox2, that is mechanistically linked to gene expression modifications. This in vivo model successfully characterized the effects of eccentric (ECC) and concentric (CONC) contractions on cytosolic and mitochondrial [HO] in mouse skeletal muscle. Compared with CONC, ECC induced higher and more sustained [HO]-an effect that was abolished by Nox2 inhibition. ECC-induced [HO] elevations were requisite for altered gene expression.