Increased activity of IRE1 improves the clinical presentation of EAE.

Activation of the ER stress sensor IRE1α contributes to neuronal development and is known to induce neuronal remodeling in vitro and in vivo. On the other hand, excessive IRE1 activity is often detrimental and may contribute to neurodegeneration. To determine the consequences of increased activation of IRE1α, we used a mouse model expressing a C148S variant of IRE1α with increased and sustained activation. Surprisingly, the mutation did not affect the differentiation of highly secretory antibody-producing cells, but exhibited a strong protective effect in a mouse model of experimental autoimmune encephalomyelitis (EAE). Significant improvement in motor function was found in IRE1C148S mice with EAE relative to WT mice. Coincident with this improvement, there was reduced microgliosis in the spinal cord of IRE1C148S mice, with reduced expression of pro-inflammatory cytokine genes. This was accompanied by reduced axonal degeneration and enhanced CNPase levels, suggestiing improved myelin integrity. Interestingly, while the IRE1C148S mutation is expressed in all cells, the reduction in proinflammatory cytokines and in the activation of microglial activation marker IBA1, along with preservation of phagocytic gene expression, all point to microglia as the cell type contributing to the clinical improvement in IRE1C148S animals. Our data suggest that sustained increase in IRE1α activity can be protective in vivo, and that this protection is cell type and context dependent. Considering the overwhelming but conflicting evidence for the role of the ER stress in neurological diseases, a better understanding of the function of ER stress sensors in physiological contexts is clearly needed.

Prior regular exercise improves clinical outcome and reduces demyelination and axonal injury in experimental autoimmune encephalomyelitis.

Although previous studies have shown that forced exercise modulates inflammation and is therapeutic acutely for experimental autoimmune encephalomyelitis (EAE), the long-term benefits have not been evaluated. In this study, we investigated the effects of preconditioning exercise on the clinical and pathological progression of EAE. Female C57BL/6 mice were randomly assigned to either an exercised (Ex) or unexercised (UEx) group and all of them were induced for EAE. Mice in the Ex group had an attenuated clinical score relative to UEx mice throughout the study. At 42 dpi, flow cytometry analysis showed a significant reduction in B cells, CD4(+) T cells, and CD8(+) T cells infiltrating into the spinal cord in the Ex group compared to UEx. Ex mice also had a significant reduction in myelin damage with a corresponding increase in proteolipid protein expression. Finally, Ex mice had a significant reduction in axonal damage. Collectively, our study demonstrates for the first time that a prolonged and forced preconditioning protocol of exercise improves clinical outcome and attenuates pathological hallmarks of EAE at chronic disease. In this study, we show that a program of 6 weeks of preconditioning exercise promoted a significant reduction of cells infiltrating into the spinal cord, a significant reduction in myelin damage and a significant reduction in axonal damage in experimental autoimmune encephalomyelitis (EAE) mice at 42 dpi. Collectively, our study demonstrates for the first time that a preconditioning protocol of exercise improves clinical outcome and attenuates pathological hallmarks of EAE at chronic disease.