miR-320 regulates inflammation in EAE through interference with TGF-β signaling pathway

Background: MicroRNAs are small noncoding RNAs that regulate gene expression and involve in many cellular and physiological mechanisems. Recent studies have revealed that dysregulation of microRNAs might contribute to autoimmune disorders such as multiple sclerosis. Based on these findings, we examined the potential role of miR-320 isoforms, miR-320-3p and miR-320-5p, in the context of autoimmune neuroinflammation and pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Methods: The expression levels of miR-320-3p and miR-320-5p, and their predicted target genes,TGFBR2 and Smad2, were quantified in the CNS tissue from mice with experimental autoimmune encephalomyelitis (EAE) using RT-PCR method. Expression were also performed in splenocytes macrophages and astrocytes. To examine the interaction of miR-320-3p and -5p with the 3′-UTR of potential target transcripts, the mimic sequences of both isoforms were transfected into splenocytes which were then examined by RT-PCR. Results: Expression of both isoforms of miR-320 were significantly increased in different phases of EAE and activated lymphocytes whereas the levels of their predicted target genes, Smad2 and TGFBR2, decreased in these cells. Obtained data revealed that miR 320-5p levels were significantly increased in activated macrophages and astrocytes, however, miR­320-3p level did not show statistically changes in these cells after LPS stimulation. The levels of TGFBR2 and Smad2 decreased in transfected splenocytes. Conclusions: Our findings proposed that, upregulation of miR-320 isoforms might be involved in the neuroinflammation and pathogenesis of multiple sclerosis through targeting and suppression of TGFBR2 and Smad2, a protective genes in multiple sclerosis.