Exercise-induced alterations in pro-inflammatory cytokines and prostaglandin F2alpha in horses

Using an established standardized exercise test on a high-speed treadmill, thirteen Thoroughbred racehorses were exercised to fatigue (failure); blood samples were obtained before exercise, at failure, and at 2, 6, 24, 48, and 72 h after exercise. The exercise test induced a systemic inflammatory response characterized by a mild transient endotoxemia, leukocytosis, increased leukocyte expression of mRNA for tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, and IL-6, and increased circulating concentrations of TNF-alpha and prostaglandin F2 alpha (PGF 2 alpha), with the most pronounced changes being evident at failure and 2h after exercise. Expression of mRNA for IL-6, TNF-alpha, and IL-1 beta was increased by 120-fold, three-fold, and four-fold, respectively, when compared to pre-exercise values. Plasma concentrations of 6-keto-PGF1alpha and PGE2 did not change in response to the exercise test. Collectively, these findings indicate that brief, strenuous exercise induces endotoxemia and a systemic pro-inflammatory response in horses that persists for at least 2h.