Reversibility of endurance training-induced changes on glucocorticoid sensitivity of monocytes by an acute exercise

Abstract

OBJECTIVE. The aim of this study was to address the effect of endurance training on monocyte glucocorticoid sensitivity in vitro. METHODS. For this purpose, in vitro dexamethasone inhibition of lipopolysaccharide (LPS)- induced interleukin-6 (IL-6) secretion in cultures of peripheral monocytes was compared in 6 untrained subjects (UT) and in 6 endurance-trained (ET) men at 0800 h, 24 h after the end of the last session of exercise (ET men). Moreover, to test the plasticity of these monocytes glucocorticoid sensitivity in ET men, the effect of an acute bout of exercise was further studied 2 h after the end of a 2-h run at 65-75% VO2(max) (1200 h) and compared to the results of UT after 4 h of rest. RESULTS. At 0800 h, monocytes from ET were more sensitive to LPS: lower LPS concentration in ET compared to UT men (0.003 vs. 0.03 μg/ml) induced similar IL-6 concentrations in both ET and UT men (168.4 ± 29.9 pg/ml with 0.003 μg/ml LPS vs. 160.1 ± 34.4 pg/ml with 0.03 μg/ml LPS, ET vs. UT, respectively, P > 0.05 for IL-6). No effect of sampling time was observed in UT subjects (0800 h vs. 1200 h). This was not the case for ET as at 1200 h, compared to pre-exercise values, the LPS-induced IL-6 production was not significantly different from that obtained in UT. Moreover, when sensitivity to dexamethasone (Dex) was studied and expressed as the percent inhibition of stimulated IL-6 production with 0.3 μg/ml LPS, at 0800 h the percent inhibition was lower in ET subjects compared to UT (P < .01 ET vs. UT men) for each Dex concentration used [10-11-10-8 M]. After exercise, the inhibitory effect of Dex on LPS-induced IL-6 production was restored in ET and was no longer significantly different from that obtained in UT. CONCLUSION. We demonstrate in vitro plasticity of monocyte glucocorticoid sensitivity of endurance trained men, with training-induced decreased glucocorticoid sensitivity and acute exercise-induced return to the levels of the control untrained men.