H2O2 Exposure Affects Myotube Stiffness and Actin Filament Polymerization

Skeletal muscles often experience oxidative stress in anaerobic metabolism and ischemia-reperfusion. This paper reports how oxidative stress affects the stiffness of cultured murine myotubes and their actin filaments polymerization dynamics. H2O2 was applied as an extrinsic oxidant to C2C12 myotubes. Atomic force microscopy results showed that short exposures to H2O2 apparently increased the stiffness of myotubes, but that long exposures made the cells softer. The turning point seemed to take place somewhere between 1 and 2 h of H2O2 exposure. We found that the stiffness change was probably due to actin filaments being favored for depolymerization after prolong H2O2 treatments, especially when the exposure duration exceeded 1 h and the exposure concentration reached 1.0 mM. Such depolymerization effect was associated with the down-regulation of thymosin beta 4, as well as the up-regulation of both cofilin2 and profilin1 after prolong H2O2 treatments.