Background: Exercise training induces beneficial effects on neurodegenerative diseases, and specifically on multiple sclerosis (MS) and it’s model experimental autoimmune encephalomyelitis (EAE). However, it is unclear whether exercise training exerts direct protective effects on the central nervous system (CNS), nor are the mechanisms of neuroprotection fully understood. In this study, we investigated the direct neuroprotective effects of high-intensity continuous training (HICT) against the development of autoimmune neuroinflammation and the role of resident microglia.Methods: We used the transfer EAE model to examine the direct effects of training on the CNS. Healthy mice performed HICT by treadmill running, followed by injection of encephalitogenic proteolipid (PLP)-reactive T-cells to induce EAE. EAE severity was assessed clinically and pathologically. Brain microglia from sedentary (SED) and HICT healthy mice, as well as 5-days post EAE induction (before the onset of disease), were analyzed ex vivo for reactive oxygen species (ROS) and nitric oxide (NO) formation, mRNA expression of M1/M2 markers and neurotrophic factors, and secretion of cytokines and chemokines.Results: Transfer of encephalitogenic T-cells into HICT mice resulted in milder EAE, compared to sedentary mice, as indicated by reduced clinical severity, attenuated T-cell, and neurotoxic macrophage/microglial infiltration, and reduced loss of myelin and axons. In healthy mice, HICT reduced the number of resident microglia without affecting their profile. Isolated microglia from HICT mice after transfer of encephalitogenic T-cells exhibited reduced ROS formation and released less IL-6 and monocyte chemoattractant protein (MCP) in response to PLP-stimulation.Conclusions: These findings point to the critical role of training intensity in neuroprotection. HICT protects the CNS against autoimmune neuroinflammation by reducing microglial-derived ROS formation, neurotoxicity, and pro-inflammatory responses involved in the propagation of autoimmune neuroinflammation.

BackgroundStudies have reported beneficial effects of exercise training on autoimmunity, and specifically on multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). However, it is unknown whether different training paradigms affect disease course via shared or separate mechanisms.ObjectiveTo compare the effects and mechanism of immune modulation of high intensity continuous training (HICT) versus high intensity interval training (HIIT) on systemic autoimmunity in EAE.MethodsWe used the proteolipid protein (PLP)‐induced transfer EAE model to examine training effects on the systemic autoimmune response. Healthy mice performed HICT or HIIT by running on a treadmill. Lymph‐node (LN)‐T cells from PLP‐immunized trained‐ versus sedentary donor mice were transferred to naïve recipients and EAE clinical and pathological severity were assessed. LN cells derived from donor trained and sedentary PLP‐immunized mice were analyzed in vitro for T‐cell activation and proliferation, immune cell profiling, and cytokine mRNA levels and cytokine secretion measurements.ResultsBoth HICT and HIIT attenuated the encephalitogenicity of PLP‐reactive T cells, as indicated by reduced EAE clinical severity and inflammation and tissue pathology in the central nervous system, following their transfer into recipient mice. HICT caused a marked inhibition of PLP‐induced T‐cell proliferation without affecting the T‐cell profile. In contrast, HIIT did not alter T‐cell proliferation, but rather inhibited polarization of T cells into T‐helper 1 and T‐helper 17 autoreactive populations.InterpretationHICT and HIIT attenuate systemic autoimmunity and T cell encephalitogenicity by distinct immunomodulatory mechanisms.

Background The mechanisms by which exercise training (ET) elicits beneficial effects on the systemic immune system and the central nervous system (CNS) in autoimmune neuroinflammation are not fully understood. Objectives To investigate (1) the systemic effects of high‐intensity continuous training (HICT) on the migratory potential of autoimmune cells; (2) the direct effects of HICT on blood–brain‐barrier (BBB) properties. Methods Healthy mice were subjected to high‐intensity continuous training (HICT) by treadmill running. The proteolipid protein (PLP) transfer EAE model was utilized to examine the immunomodulatory effects of training, where PLP‐reactive lymph‐node cells (LNCs) from HICT and sedentary donor mice were analyzed in vitro and transferred to naïve recipients that developed EAE. To examine neuroprotection, encephalitogenic LNCs from donor mice were transferred into HICT or sedentary recipient mice and the BBB was analyzed. Results Transfer of PLP‐reactive LNCs obtained from HICT donor mice attenuated EAE severity and inflammation in recipient mice. HICT markedly inhibited very late antigen (VLA)‐4 and lymphocyte function‐associated antigen (LFA)‐1 expression in LNCs. Transfer of encephalitogenic LNCs into HICT recipients resulted in milder EAE and attenuated CNS inflammation. HICT reduced BBB permeability and the expression of intercellular adhesion molecule (ICAM)‐1 and vascular cell adhesion molecule (VCAM)‐1 in CNS blood vessels. Interpretation HICT attenuates EAE development by both immunomodulatory and neuroprotective effects. The reduction in destructive CNS inflammation in EAE is attributed to systemic inhibition of autoreactive cell migratory potential, as well as reduction in BBB permeability, which are associated with reduced VLA‐4/VCAM‐1 and LFA‐1/ICAM‐1 interactions.

Background: Exercise training induces beneficial effects on neurodegenerative diseases, and specifically on multiple sclerosis (MS) and its model experimental autoimmune encephalomyelitis (EAE). However, it is unclear whether exercise training exerts direct protective effects on the central nervous system (CNS), nor are the mechanisms of neuroprotection fully understood. In this study, we investigated the direct neuroprotective effects of high-intensity continuous training (HICT) against the development of autoimmune neuroinflammation and the role of resident microglia.Methods: We used the transfer EAE model to examine the direct effects of training on the CNS. Healthy mice performed HICT by treadmill running, followed by injection of encephalitogenic proteolipid (PLP)- reactive T-cells to induce EAE. EAE severity was assessed clinically and pathologically. Brain microglia from sedentary and HICT healthy mice, as well as 5-days post EAE induction (prior to onset of disease) were analyzed ex vivo for reactive oxygen species (ROS) and nitric oxide (NO) formation, mRNA expression of M1/M2 markers and neurotrophic factors, and secretion of cytokines and chemokines. Results: Transfer of encephalitogenic T-cells into HICT mice resulted in milder EAE, compared to sedentary mice, as indicated by reduced clinical severity, attenuated T-cell and neurotoxic macrophage/microglial infiltration, and reduced loss of myelin and axons. In healthy mice, HICT reduced the number of resident microglia without affecting their profile. Isolated microglia from HICT mice after transfer of encephalitogenic T-cells exhibited reduced ROS formation and released less IL-6 and monocyte chemoattractant protein in response to PLP-stimulation.Conclusions: HICT protects the CNS against autoimmune neuroinflammation by reducing microglial-derived ROS formation, neurotoxicity and pro-inflammatory responses involved in propagation of autoimmune neuroinflammation.