miR-146a-5p acts as a negative regulator of TGF-β signaling in skeletal muscle after acute contusion

Acta Biochim Biophys Sin (Shanghai). 2017 Jul 1;49(7):628-634. doi: 10.1093/abbs/gmx052.

Abstract

Growing evidence suggests the importance of microRNAs (miRNAs) in stress signaling pathways. Transforming growth factor-β (TGF-β) is a potent cytokine that promotes the development of skeletal muscle fibrosis after acute contusion. However, how miRNAs are involved in TGF-β signaling and confer the robustness of TGF-β-induced fibrotic response remains to be fully elucidated. Here, we demonstrated that miR-146a-5p (miR-146) levels were reduced in a fibrotic mouse model after acute muscle contusion. It was also found that TGF-β treatment decreased the expression of miR-146 in vitro in a dose- and time-dependent manner. In addition, overexpression of Smad3 and Samd4, two key players in TGF-β signaling, suppressed the expression of miR-146 in muscle cells. Overexpression of miR-146 inhibited the expressions of fibrosis markers both in vitro and in vivo. Moreover, increase in the expression of miR-146 in muscle cells was able to attenuate the effect of TGF-β on the expressions of fibrosis markers. Mechanistic analysis revealed that Smad4 is a direct target of miR-146 in muscle cells. Furthermore, the anti-fibrotic effect of miR-146 could be blocked by overexpression of Smad4 in vivo. These results suggest that Smad4 is down-regulated by miR-146 in skeletal muscle. Taken together, our results indicate that the anti-fibrotic miR-146 is a component of TGF-β signaling. It is down-regulated by Smad protein, and can inhibit the expression of Smad4. Our study suggests that miR-146 might have a therapeutic potential to reduce skeletal muscle fibrosis after injury.

Keywords: Smad4; fibrosis; microRNA; muscle; transforming growth factor-β.

MeSH terms

  • Acute Disease
  • Animals
  • Cells, Cultured
  • Contusions / metabolism*
  • Fibrosis
  • Male
  • Mice
  • MicroRNAs / physiology*
  • Muscle, Skeletal / metabolism*
  • Muscle, Skeletal / pathology
  • Signal Transduction / physiology*
  • Smad4 Protein / genetics
  • Smad4 Protein / physiology
  • Transforming Growth Factor beta / physiology*

Substances

  • MicroRNAs
  • Mirn146 microRNA, mouse
  • Smad4 Protein
  • Smad4 protein, mouse
  • Transforming Growth Factor beta