Changes in Lymphocyte Composition and Functionality After Intensive Training and Exhausting Exercise in Rats

Abstract

Exhausting exercise can have a deleterious effect on the immune system. Nevertheless, the impact of exercise intensity on lymphocyte composition and functionality remains uncertain. The aim of this study was to establish the influence of intensive training on lymphoid tissues (blood, thymus, and spleen) in Wistar rats. Two intensive training programs were performed: a short program, running twice a day for 2 weeks and ending with a final exhaustion test (S-TE group), and a longer program, including two exhaustion tests plus three runs per week for 5 weeks. After this last training program, samples were obtained 24 h after a regular training session (T group), immediately after an additional exhaustion test (TE group) and 24 h later (TE24 group). The composition of lymphocytes in the blood, thymus, and spleen, the function of spleen cells and serum immunoglobulins were determined. In the blood, only the TE group modified lymphocyte proportions. Mature thymocytes' proportions decreased in tissues obtained just after exhaustion. There was a lower percentage of spleen NK and NKT cells after the longer training program. In these rats, the T group showed a reduced lymphoproliferative activity, but it was enhanced immediately after the final exhaustion. Cytokine secretion was modified after the longer training (T group), which decreased IFN-γ and IL-10 secretion but increased that of IL-6. Higher serum IgG concentrations after the longer training program were detected. In conclusion, the intensive training for 5 weeks changed the lymphocyte distribution among primary and secondary lymphoid tissues and modified their function.

Alterations in the mucosal immune system by a chronic exhausting exercise in Wistar rats

“…These findings are in line with previously reported results in serum 23 . We hypothesized that, as previously reported in spleen 23 , MLN could be sensitive to the repetitive stress induced by the intensive training programme, which might upregulate the glucocorticoids and adrenergic receptors 71 and this, in addition to the www.nature.com/scientificreports/ higher cortisol levels observed in similarly exercised animals 23 , may explain the higher in vitro production of IgG by MLN lymphocytes. In summary, intensive training for 5 weeks in female Wistar rats, followed or not by an additional exhaustion test, appears to have caused an overtraining condition which modified both mucosal immunity and the intestinal epithelial barrier integrity.…”

“…In this case, these changes might be explained by a redistribution of lymphocytes within other lymphoid and non-lymphoid organs 25 and the lymphocyte apoptosis 64,65 induced by the release of catecholamines and glucocorticoids due to the intensive exercise stress. In this regard, a previous study in animals with a similar training program showed higher cortisol levels 23,26 .…”

“…Other studies have reported a reduced T cell proportion in mouse submandibular lymph nodes after carrying out an intensive treadmill run test 24 . It could be hypothesized that with exhaustion, MLN Th cells move to the blood thus decreasing (normalizing) their proportion in the MLN; however, we have previously described a reduction in both blood Th and Tc cell proportions due to exhaustion 23 . In this case, these changes might be explained by a redistribution of lymphocytes within other lymphoid and non-lymphoid organs 25 and the lymphocyte apoptosis 64,65 induced by the release of catecholamines and glucocorticoids due to the intensive exercise stress.…”

“…In previous studies, we demonstrated that rats submitted to intensive training and exhausting exercise exhibited www.nature.com/scientificreports/ alterations in both the innate and the acquired immunity 23,26 . The current study aimed to establish the effects of 5 weeks of intensive training on the mucosal immune system in rats and to elucidate the mechanisms underlying these effects.…”

“…On the other hand, exercise also impacts cellular immunity 21 . Most of the studies have assessed changes in blood lymphocytes, whereas only a few have focused on lymphoid compartments such as bone marrow, Peyer’s patches 21 , spleen, thymus 23 and lymph nodes 24 . The changes in the proportion of lymphocyte populations that have been reported in such tissues may reflect a redistribution of cells among lymphoid tissues which must be mainly due to the release of stress hormones such as catecholamines and glucocorticoids 25 .…”