Alterations in the innate immune system due to exhausting exercise in intensively trained rats

Abstract

It is known that intensive physical activity alters the immune system's functionality. However, the influence of the intensity and duration of exercise needs to be studied in more depth. We aimed to establish the changes in the innate immune response induced by two programmes of intensive training in rats compared to sedentary rats. A short training programme included 2 weeks of intensive training, ending with an exhaustion test (short training with exhaustion, S-TE). A second training programme comprised 5-week training including two exhaustion tests and three trainings per week. In this case, immune status was assessed before (T), immediately after (TE) and 24 h after (TE24) an additional final exhaustion test. Biomarkers such as phagocytic activity, macrophage cytokine and reactive oxygen species (ROS) production, and natural killer (NK) cell activity were quantified. S-TE was not enough to induce changes in the assessed innate immunity biomarkers. However, the second training was accompanied by a decrease in the phagocytic activity, changes in the pattern of cytokine secretion and ROS production by macrophages and reduced NK cell proportion but increased NK cytotoxic activity. In conclusion, a 5-week intense training programme, but not a shorter training, induced alterations in the innate immune system functionality. Moderate exercise induces many beneficial effects on human health. In particular, it reduces the risk of developing many chronic disorders, such as cardiovascular disease 1 , metabolic syndrome 2 , type 2 diabetes 3 and even cancer 4,5. Furthermore, moderate exercise has an antioxidant effect 6 and a positive influence on the innate immune system 7,8. On the other hand, intense exercise can induce adverse effects on health, which enhance the risk of upper respiratory tract infections (URTI) 9,10. The observations regarding the amount and intensity of exercise and risk of illnesses have led to the hypothesis that their relationship fits a J-shaped curve 11. This means that very low physical activity or no training is associated with a higher risk of illness compared to moderate activity or training load, whereas very high training loads are related to a higher risk of illness 10. In other words, intensive exercise produces a decrease in the immune system functionality which makes the body more vulnerable to infectious agents. This period is known as an 'open window' to pathogens 12,13. The innate immune system is the first line of organism defence against pathogens. Neutrophils, macrophages and natural killer (NK) cells are the major cellular type of innate immunity susceptible to being altered by exercise. Neutrophils are phagocytic cells able to destroy bacteria by means of the release of enzymes and through the secretion of reactive oxygen species (ROS). Monocytes and macrophages are also phagocytic cells able to secrete a wide range of cytokines, mainly with pro-inflammatory properties 14,15. NK cells are lymphocytes found in small proportions in blood and lymphoid tissues. Nevertheless, due t...

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

“…Exercise performance after the two training programs was assessed by the maximum speed achieved by animals in the performed exhaustion tests. In the short training program, female rats achieved better scores than male rats, as previously reported (Lalanza et al, 2015;Estruel-Amades et al, 2019a). In spite of this difference, the plasma concentrations of cortisol, a hormone released by the adrenal gland in response to stress FIGURE 6 | Changes in the lymphocyte proportion of the main spleen lymphocytes (A), minor spleen lymphocytes (B), and inside TCRγδ+ lymphocytes (C) at the end of the short and the longer intensive training programs compared to the sedentary group (considered as 100%).…”

“…This training allowed the performance of each running rat to be monitored and also the own-regulation of the training (the following days were run according to the maximum speed achieved). The exercise intensity, duration and volume used in this last training have previously been reported to influence the antioxidant status of rats (Estruel-Amades et al, 2019a).…”

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

“…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.…”

Immunoregulation induced by autologous serum collected after acute exercise in obese men: a randomized cross-over trial

“…Here, we found similar changes in redox states in PBMCs after exposure to serum collected after HIIE or exhaustive exercise, as observed by higher ROS production and TBARS content in the cell lysate. Higher levels of lipid peroxidation observed in PBMCs after exercise are related to increased metabolic process and mitochondrial respiration of these cells during the bout 68 – 71 . In contrast, the incubation of zymosan-stimulated phagocytes with post-marathon race plasma leads to decreased ROS production 33 .…”