Heat Shock Protein 70 Regulates Tumor Necrosis Factor-Alpha and Myogenin in Skeletal Muscle Following Chemical-Induced Injury

• Main Author: Baumann, Cory W.
• Format: Others
• Published: ScholarWorks @ Georgia State University 2015
• Subjects: Heat Shock Protein; Injury; Myogenin; Skeletal Muscle; TNF-α
• Online Access: http://scholarworks.gsu.edu/kin_health_diss/12; http://scholarworks.gsu.edu/cgi/viewcontent.cgi?article=1014&context=kin_health_diss

Skeletal muscle injury results in functional deficits that can take several weeks to fully recover. Ultimate recovery of function is dependent on the muscle’s ability to regenerate, a highly coordinated process that involves transient muscle inflammation and the replacement of damaged myofibers. Instrumental in the inflammatory response, is the pro-inflammatory cytokine TNF-α. Expression of TNF-α is thought to be regulated, in part, by the stress sensing 70 kDa heat shock protein (Hsp70). However, it remains unclear how Hsp70 alters TNF-α following injury, and if so, how these changes affect skeletal muscle repair. Therefore, we up-regulated Hsp70 expression using 17-allylamino-17-demethoxygeldanamycin (17-AAG) prior to and following BaCl2-induced injury, and assessed TNF-α and myogenin content. Regenerating fiber cross-sectional area (CSA) and in vivo isometric torque were also analyzed in the weeks following the injury. Treatment of 17-AAG resulted in a ~5 fold increase in Hsp70 of the uninjured muscle, but did not affect any other biochemical, morphological or functional variables compared to controls. In the days following the injury, TNF-α and myogenin were elevated and directly correlated. At these earlier time points (≤7 days), treatment of 17-AAG increased TNF-α above that of the injured controls and resulted in a sustained increase in myogenin. However, no differences were observed in regenerating fiber CSA or in vivo torque production between the groups. Together, these data suggest that Hsp70 induction increases TNF-α and myogenin content following BaCl2-induced injury, but does not appear to alter skeletal muscle regeneration or attenuate functional deficits in otherwise healthy young mice.