Small Heat Shock Proteins (sHSPs), specific markers of exercise-induced muscle damage

Unaccustomed eccentric (ECC) exercise may cause exercise-induced muscle damage (EIMD) whereas repeating submaximal ECC sessions is known to prevent this damage. The present study aimed to better understand the molecular mechanisms underlying EIMD and subsequent adaptation. C57BL adult mice were submitted to different treadmill running protocols: IEE (intense ECC exercise), ET (ECC training), CT (concentric training), LT (level training), ET+IEE, CT+IEE. A 2D-DIGE proteomic analysis on mouse quadriceps muscles revealed that HSP25 and alpha-crystallin B chain were significantly more abundant in IEE, CT+IEE, ET+IEE and ET groups compared to unexercised mice. Interestingly, immunofluorescence analysis highlighted that all damaged fibers also showed positive staining for sHSPs. In contrast, sHSPs+ fibers are not necessarily damaged, suggesting that the sHSPs response precedes increased sarcolemma permeability. Our data demonstrate that ECC exercise specifically increases sHSPs expression which may represent an early marker of damage and/or adaptation of the muscle fibers to ECC contraction