MiR-146a Regulates Inflammatory Infiltration by Macrophages in Polymyositis/Dermatomyositis by Targeting TRAF6 and Affecting IL-17/ICAM-1 Pathway.

BACKGROUND/AIMS: The primary objective of this study was to investigate the role of miR-146a in inducing the inflammatory infiltration of macrophages in polymyositis/dermatomyositis (PM/DM) through targeting TNF receptor associated factor 6 (TRAF6), which may further down-regulate the Interleukin-17 (IL-17)/Intercellular Adhesion Molecule 1 (ICAM-1) pathway.

METHODS

Biopsies were collected from PM/DM patients and healthy volunteers. PM/DM model establishment and macrophage isolation were performed on Sprague Dawley (SD) rats. Model rats and macrophages were treated with anti-IL-17, anti-ICAM-1, miR-146a mimics, miR-146a inhibitors, and TRAF6 siRNAs. Serum creatine phosphokinase (S-CK) expression was assessed using double antibody sandwich enzyme-linked immunosorbent assay (ELISA) assay, and immunohistochemistry assay was performed to analyze CD163 expression in muscle samples. Furthermore, we used transwell assay to test cell migration; RT-PCR and western blot were carried out to determine the expression of miR-146a, TRAF6, IL-17, and ICAM-1.

RESULTS

The S-CK, TRAF6, IL-17 and ICAM-1 levels were higher in PM/DM patients compared with healthy controls and were down-regulated after the conventional treatment. Treatment with miR-146a mimics, anti-IL-17 and anti-ICAM-1 decreased the expression of IL-17 and ICAM-1, whereas miR-146a inhibitors exerted the opposite effects. The effects of miR-146a inhibitors were suppressed by treatment with TRAF6 siRNA. In addition, the luciferase reporter assay validated the targeting relationship between miR-146a and TRAF6.

CONCLUSIONS

MiR-146a regulates inflammatory macrophage infiltration in PM/DM by targeting TRAF6 and affecting the IL-17/ICAM-1 pathway.