Exercise‐Induced Muscle Damage and Apoptotic Protein Expression in Immune Cells

Abstract

We previously reported (Med Sci Sports Exerc 2006) a higher proportion of apoptotic lymphocytes and neutrophils 24h and 48h after a -10% downhill run (DH1) compared to level running (L) or a second downhill run (DH2). We also found greater muscle damage and lower antioxidant status 24h after DH1. PURPOSE: to determine if the elevation in apoptotic leukocytes was mediated by changes in Bcl-2 and Bax protein expression by further analyzing the blood samples. METHODS: 12 moderately trained subjects (mean±SE age=22.7±0.7yr, VO2max=53.1±1.3ml.kg−1.min−1) performed three 40 min treadmill runs at ~70% VO2max: L followed by DH1 and DH2. Blood samples taken at rest (PRE) and immediately, 2h, 24h, and 48h after each run were further analyzed for Bcl-2 and Bax protein expression (ELISA). Data were analyzed using a 2-way repeated measures ANOVA with post hoc Tukey tests. RESULTS: Bax concentration was higher in DH1 than L and DH2 (P<0.01). Bax at 24h was greater than PRE (P<0.05) following DH1. No significant changes were found for Bcl-2. Bax/Bcl-2 ratio was greater in DH1 than L (P<0.01) and DH2 (P<0.05). At 24h post, Bax/Bcl-2 ratio was higher in DH1 than L and DH2 (P<0.01). In DH1, Bax/Bcl-2 ratio at 24h (P<0.01) and 48h post (P<0.05) was elevated above PRE. CONCLUSIONS: Increased oxidative stress following muscle damaging exercise may alter the Bax/Bcl-2 ratio in white cells towards a pro-apoptotic state.