Metformin inhibits the pathogenic functions of AChR-specific B and Th17 cells by targeting miR-146a

miR-125a-5p regulates Treg function by targeting Foxp3 in experimental autoimmune myasthenia gravis mice

MicroRNAs are a class of endogenous noncoding small RNAs. miR-125a-5p is involved in immunoregulatory mechanisms in autoimmune diseases. Myasthenia gravis (MG) is an autoimmune disease in which regulatory T cells (Tregs) exhibit reduced numbers and functional defects, with decreased expression of the Treg cell-specific transcription factor Foxp3. Our previous study identified an abnormally high expression of miR-125a-5p in thymoma-associated myasthenia gravis, however, the involvement of miR-125a-5p in the pathogenesis of myasthenia gravis in vivo is unclear. In this study, we explored the role of thymic miR-125a-5p abnormalities in the pathogenesis of myasthenia gravis by establishing an experimental autoimmune myasthenia gravis model. Muscle strength score, low-frequency repetitive nerve stimulation, and serum acetylcholine receptor antibody were performed. The relative expression of miR-125a-5p and Foxp3 in the thymus and spleen was quantified, and the percentage of Treg cells, the levels of the inhibitory cytokines IL-10 and TGF-β1, and the proliferative capacity of splenic T lymphocytes were detected. Our findings revealed significant upregulation of miR-125a-5p expression in myasthenia gravis models. Reducing miR-125a-5p levels alleviated muscle weakness symptoms, elevated Foxp3 expression, enhanced the number of Treg cells, elevated the levels of the Treg-associated inhibitory cytokines IL-10 and TGF-β1, and inhibited the proliferative function of splenic T lymphocytes. The opposite result was obtained when miR-125a-5p was overexpressed. These results suggest that miR-125a-5p can inhibit Foxp3 expression, leading to a decrease in the number and abnormal function of Treg cells. Thus, our findings suggest that miR-125a-5p participates in the pathogenesis of myasthenia gravis by targeting Foxp3 to regulate the function of Treg cells, providing new insights to explore the immunoregulatory mechanisms of miR-125a-5p in myasthenia gravis.

Defective autophagy and autophagy activators in myasthenia gravis: a rare entity and unusual scenario

Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ) that results from autoantibodies against nicotinic acetylcholine receptors (nAchRs) at NMJs. These autoantibodies are mainly originated from autoreactive B cells that bind and destroy nAchRs at NMJs preventing nerve impulses from activating the end-plates of skeletal muscle. Indeed, immune dysregulation plays a crucial role in the pathogenesis of MG. Autoreactive B cells are increased in MG due to the defect in the central and peripheral tolerance mechanisms. As well, autoreactive T cells are augmented in MG due to the diversion of regulatory T (Treg) cells or a defect in thymic anergy leading to T cell-mediated autoimmunity. Furthermore, macroautophagy/autophagy, which is a conserved cellular catabolic process, plays a critical role in autoimmune diseases by regulating antigen presentation, survival of immune cells and cytokine-mediated inflammation. Abnormal autophagic flux is associated with different autoimmune disorders. Autophagy regulates the connection between innate and adaptive immune responses by controlling the production of cytokines and survival of Tregs. As autophagy is involved in autoimmune disorders, it may play a major role in the pathogenesis of MG. Therefore, this mini-review demonstrates the potential role of autophagy and autophagy activators in MG.Abbreviations: Ach, acetylcholine; Breg, regulatory B; IgG, immunoglobulin G; MG, myasthenia gravis; NMJ, neuromuscular junction; ROS, reactive oxygen species; Treg, regulatory T; Ubl, ubiquitin-like.