microRNA-29b Mediates the Antifibrotic Effect of Tanshinone IIA in Postinfarct Cardiac Remodeling.

BACKGROUND

Tanshinone IIA (TSN) is one of the main components isolated from Danshen, which is widely used for the treatment of cardiovascular diseases. The transforming growth factor beta (TGF-β) signaling pathway and microRNA (miR)-29b play important roles in the progression of cardiac fibrosis and the modulation of cardiac fibroblast (CF) function. Our study investigated the role of miR-29b in the cardioprotective effects of TSN in postinfarct cardiac remodeling.

METHODS AND RESULTS

Echocardiography demonstrated that medium-dose TSN (TSN-M) and high-dose TSN (TSN-H) significantly inhibited postinfarct cardiac fibrosis and improved the impaired left ventricular function in rats subjected to acute myocardial infarction. Moreover, quantitative real-time polymerase chain reaction and Western blot demonstrated that TSN-M and TSN-H downregulated the expression of TGF-β1, Col1a1, Col3a1, and α-SMA but upregulated the expression of miR-29b. CFs treated with TSN showed inhibited TGF-β signaling pathway, downregulated expression of Col1a1, Col3a1, and α-SMA, and upregulated miR-29b expression in vitro. Furthermore, treatment with a miR-29b inhibitor dramatically inhibited these TSN-induced antifibrotic effects, suggesting that miR-29b may be responsible for the antifibrotic effects of TSN. In addition, treatment with Smad3 siRNA significantly inhibited miR-29b expression in CFs, which implies that Smad3 signaling promotes miR-29b expression on CFs.

CONCLUSIONS

TSN exerts antifibrotic effects in postinfarct cardiac fibrosis by upregulating the expression of miR-29b, which is mediated by the TGF-β-Smad3 signaling pathway.