Background: MicroRNAs have emerged as an important class of modulators of gene expression. These molecules\ninfluence protein synthesis through translational repression or degradation of mRNA transcripts. Herein, we investigated\nthe potential role of miR-142a isoforms, miR-142a-3p and miR-142a-5p, in the context of autoimmune neuroinflammation.\nMethods: The expression levels of two mature isoforms of miR-142 were measured in the brains of patients with multiple\nsclerosis (MS) and the CNS tissues from mice with experimental autoimmune encephalomyelitis (EAE), an animal model\nof MS. Expression analyses were also performed in mitogen and antigen-stimulated splenocytes, as well as macrophages\nand astrocytes using real-time RT-PCR. The role of the mature miRNAs was then investigated in T cell differentiation by\ntransfection of CD4+ T cells, followed by flow cytometric analysis of intracellular cytokines. Luciferase assays using vectors\ncontaining the 3�UTR of predicted targets were performed to confirm the interaction of miRNA sequences with transcripts.\nExpression of targets were then analyzed in activated splenocytes and MS/EAE tissues.\nResults: Expression of miR-142-5p was significantly increased in the frontal white matter from MS patients\ncompared with white matter from non-MS controls. Likewise, expression levels of miR-142a-5p and miR-142a-3p showed\nsignificant upregulation in the spinal cords of EAE mice at days 15 and 25 post disease induction. Splenocytes stimulated\nwith myelin oligodendrocyte glycoprotein (MOG) peptide or anti-CD3/anti-CD28 antibodies showed upregulation\nof miR-142a-5p and miR-142a-3p isoforms, whereas stimulated bone marrow-derived macrophages and primary\nastrocytes did not show any significant changes in miRNA expression levels. miR-142a-5p overexpression in activated\nlymphocytes shifted the pattern of T cell differentiation towards Th1 cells. Luciferase assays revealed SOCS1 and\nTGFBR1 as direct targets of miR-142a-5p and miR-142a-3p, respectively, and overexpression of miRNA mimic sequences\nsuppressed the expression of these target transcripts in lymphocytes. SOCS1 levels were also diminished in MS white\nmatter and EAE spinal cords.\nConclusions: Our findings suggest that increased expression of miR-142 isoforms might be involved in the pathogenesis\nof autoimmune neuroinflammation by influencing T cell differentiation, and this effect could be mediated by interaction\nof miR-142 isoforms with SOCS1 and TGFBR-1 transcripts.
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