Exercise Induces Apoptosis Of Lymphocytes Subpopulations In Lymphoid Organs

Abstract

Strenuous exercise affects lymphocyte counts in lymphoid and non-lymphoid organs via different mechanisms like mobilization and redistribution as well as proliferation and apoptosis. The role of apoptosis is currently under focus of research since intensive exercise is well known to increase several apoptosis-inducing factors including glucocorticoids, reactive oxygen species, Fas receptor, TNF-α and intracellular calcium. PURPOSE: To investigate the effects of a single bout of intensive exercise on apoptosis of lymphocyte subpopulations in several lymphoid organs and to study the kinetics of these alterations. METHODS: Eight week old male CD1-mice were assigned to an exercise group or a control group. Mice of the exercise group performed an acute treadmill exercise at 80% VO2max until exhaustion, while controls were exposed to treadmill noise without running. Mice were sacrified either immediately, 3h or 24h after exercise. Thymus, spleen, lung, Peyer's patches, ingiunal lymph nodes and bone marrow were excised and blood samples were taken. Lymphocytes were isolated and stained using PE- conjugated monoclonal antibodies against CD3, CD4 and CD8. Detection of apoptotic cells was performed by flow cytometry using FITC-conjugated annexin V. RESULTS: In spleen an increase of apoptotic CD3+ and CD4+− cells was observed immediately and 24h after exercise. Likewise, apoptosis of CD3+, CD4+ and CD8+− lymphocytes in Peyer's patches and thymus increased immediately after exercise and was still enhanced 24h after exercise. In contrast in bone marrow the increase of apoptotic CD3+, CD4+ and CD8+− cells was delayed. Likewise an increased percentage of apoptotic CD3+ and CD4+− cells in lymph nodes was detected only 24h after exercise. CONCLUSION: An acute bout of intensive treadmill running increased lymphocyte apoptosis in several lymphoid organs, but with different kinetics. We speculate that exercise induced apoptosis in different organs might have a regulatory function to remove activated cells mobilized during exercise. It remains to be shown whether different rates of apoptosis in the lymphoid compartments are related to different concentrations of apoptosis-inducing factors.