Tranilast induces MiR-200c expression through blockade of RelA/p65 activity in leiomyoma smooth muscle cells.

Objective: To determine the mechanism by which tranilast induces miR-200c expression in leiomyoma smooth muscle cells (LSMCs).

Design: Experimental study.

Setting: Academic research laboratory.

Patient(s): Women undergoing hysterectomy for leiomyoma.

Intervention(s): Blockade of RelA/p65.

Main Outcome Measure(s): Effects of tranilast and blockade of RelA/p65 on miR-200c expression.

Result(s): Tranilast, an inflammation inhibitor, dose-dependently induced miR-200c in LSMCs and myometrium smooth muscle cells (MSMCs), with a more profound effect in LSMCs than in MSMCs. The treatment of LSMCs with Bay 117082, an inhibitor of IκB phosphorylation, further enhanced miR-200c induction by tranilast. The knockdown of RelA/p65 by small interfering RNA also induced miR-200c expression in LSMCs. Although tranilast had no effect on total RelA/p65 protein levels in LSMCs, it significantly induced RelA/p65 phosphorylation at S536 while reducing its activity as well as its nuclear translocation. ChIP assay indicated that tranilast reduces the binding ability of RelA/p65 to miR-200c promoter, resulting in miR-200c induction. Tranilast also inhibited interleukin-8 (IL8) expression in LSMCs. The induction of miR-200c by tranilast partially mediates the inhibitory effect of tranilast on the expression of IL8 and cyclin-dependent kinase 2 in LSMCs.

Conclusion(s): Induction of miR-200c by tranilast in LSMCs is mediated through a transcriptional mechanism involving inhibition of the nuclear factor κB signaling pathway. These results highlight the significance of inflammation in the pathogenesis of leiomyoma and the potential utility of antiinflammatory drugs for treatment of leiomyomas.