Impact of Chronic Moderate Exercise on Immune Cells and Cytokine Levels in Rats: Focus on the Endocannabinergic Pathway

Although the modulation of immunity by exercise has been a long-studied paradigm, the molecular pathways connecting the two are still not fully understood. Regular moderate aerobic exercise is associated with improved health and directly impacts the immune system by changing the proportion of cell subpopulations, their function, and interleukin production. The endocannabinoid system has gained importance as an immune modulator, affected by moderate aerobic promoting the production of endocannabinoids, which are ligands of the cannabinoid receptors (CBRs) expressed on the surface of all immune cells. Our group previously reported a reduction of lymphocytic populations in the spleen of chronically exercised rats, accompanied by an increase in CBR expression. Given the complex and compartmentalized nature of the immune system, we decided to study the effects of chronic exercise on the proportion of peripheral blood mononuclear cells, serum interleukins, and the expression of CBRs on these cells. Overall, our results indicate that chronic exercise decreases the proportion of T helper and Tγδ cells but increases the expression of cannabinoids (CBR1) on T helper and natural killer cells, and the production of interleukins, including IL-1β, interferon-gamma, tumor necrosis factor-alpha, IL-10, and IL-4, suggesting higher reactivity and efficiency from the immune system conferred by exercise.