Electrical stimulation prevents doxorubicin-induced atrophy and mitochondrial loss in cultured myotubes.

Muscle contraction may protect against the effects of chemotherapy to cause skeletal muscle atrophy, but the mechanisms underlying these benefits are unclear. To address this question, we utilized modeling of contraction and mechanotransduction in C2C12 myotubes treated with doxorubicin (DOX; 0.2 μM for 3 days). Myotubes expressed contractile proteins and organized these into functional myofilaments, as electrical field stimulation (STIM) induced intracellular calcium (Ca) transients and contractions, both of which were prevented by inhibition of membrane depolarization. DOX treatment reduced myotube myosin content, protein synthesis and Akt (S308) and forkhead box O3a (FoxO3a; S253) phosphorylation, and increased muscle ring fiber 1 (MuRF1) expression. STIM (1 h/d) prevented DOX-induced reductions in myotube myosin content and Akt and FoxO3a phosphorylation, as well as increases in MuRF1 expression, but did not prevent DOX-induced reductions in protein synthesis. Inhibition of myosin-actin interaction during STIM prevented contraction and the anti-atrophic effects of STIM without affecting Cacycling, suggesting the beneficial effect of STIM derives from mechanotransductive pathways. Further supporting this conclusion, mechanical stretch of myotubes recapitulated the effects of STIM to prevent DOX suppression of FoxO3a phosphorylation and upregulation of MuRF1. DOX also increased reactive oxygen species (ROS) production, which led to a decrease in mitochondrial content. While STIM did not alter DOX-induced ROS production, PGC-1α and antioxidant enzyme expression were upregulated and mitochondrial loss prevented. Our results suggest that the activation of mechanotransductive pathways that downregulate proteolysis and preserve mitochondrial content protect against the atrophic effects of chemotherapeutics. Keywords: cachexia, exercise, mechanotransduction.