Expression of toll-like receptor 4/nuclear factor-kappa Bp65 signaling pathway in rat myocardium after endurance exercise

BACKGROUND: Acute myocardial ischemia and hypoxia can upregulate the expression of angiotensin II, toll-like receptor 4 (TLR4) and nuclear factor κB (NFκB). In TLR4 deficient mice, cardiac hypertrophy is found to be decreased in the presence of pressure overload, suggesting that TLR4/NFκBp65 is a key signaling pathway in the development and progression of cardiac hypertrophy. OBJECTIVE: To investigate the effect of TLR4/NFκBp65 signaling pathway activation on myocardial adaptation in rats subjected to graded endurance training of different exercise protocols. METHODS: Rats were randomly divided into three groups: a single bout of exercise, 4-and 10-week endurance training, respectively. Treadmill was used for exercise training. All three groups were subdivided into: control group and exercise groups euthanized 0, 3, and 24 hours after last training. RESULTS AND CONCLUSION: The expression level of TLR4 was sustained at high level after a single bout of exercise, but the expression level was increased only immediately after last training in 4 and 10 weeks of endurance in rats. The expression level of NFκBp65 showed a sustained increase in 4-week trained rats, but only transiently increased in 10-week trained rats after last run, and the expression was reduced in the 24-hour exercise group when compared with age-matched control group. The expression level of myosin heavy chain1/2/4/6 appeared to be continuously increased after a single bout of exercise and 4 weeks of endurance training, but was only transiently increased after 10 weeks of endurance training. The exercise-induced activation of TLR4/NFκBp65 signaling pathway may participate in the myocardial adaptation. Subject headings: Myocardium; Sports; Tissue Engineering.