Interleukin-10 limits intense acute swimming-induced muscle mechanical hyperalgesia in mice

What is the central question of this study? This study investigated the role of the endogenous anti-inflammatory cytokine interleukin-10 in intense acute swimming-induced muscle mechanical hyperalgesia in mice. What is the main finding and its importance? Endogenous interleukin-10 has a key role in limiting exercise-induced muscle pain in a model presenting similarities to delayed-onset muscle soreness in mice. Interleukin-10 reduced muscle pain by diminishing leucocyte recruitment, hyperalgesic cytokine production, oxidative stress and myocyte damage. Interleukin-10 (IL-10) is an antihyperalgesic cytokine. In this study, IL-10-deficient (IL-10(-/-)) mice were used to investigate the role of endogenous IL-10 in intense acute swimming-induced muscle mechanical hyperalgesia, which presents similarities with delayed-onset muscle soreness. An intense acute swimming session of 1 or 2h induced significant muscle mechanical hyperalgesia in a time-dependent manner in wild-type mice compared with the sham group 24h after the session, which was further increased in IL-10(-/-) mice (P?0.05). Intraperitoneal treatment of wild-type mice with IL-10 (1-10ng) reduced muscle mechanical hyperalgesia in a dose-dependent manner and reversed the enhanced muscle hyperalgesia in IL-10(-/-) mice (P?0.05). The 2h swimming session induced increases in tumour necrosis factor-, interleukin-1 and IL-10 production in the soleus muscle. However, tumour necrosis factor- and interleukin-1 production in the soleus muscle were even higher in IL-10(-/-) mice between 2 and 6h after the stimulus (P?0.05). There was no statistical difference in the levels of the antihyperalgesic cytokines interleukin-4, interleukin-5, interleukin-13 and transforming growth factor- between wild-type and IL-10(-/-) mice (P?0.05). Interleukin-10 deficiency also resulted in increased myeloperoxidase activity, greater depletion of reduced glutathione levels, increased superoxide anion production and the maintenance of high plasma concentrations of creatine kinase (until 24h after the swimming session) in soleus muscle (P?0.05). These results demonstrate that endogenous IL-10 controls intense acute swimming-induced muscle mechanical hyperalgesia by limiting oxidative stress and cytokine production.