Activation of hepatic stellate cells is suppressed by microRNA-150

Abstract

microRNAs (miRNAs) have recently been reported to be involved in the progression of liver fibrosis. It has previously been shown that miR-150 can inhibit the activation of hepatic stellate cells (HSCs) via the inhibition of C-myb expression. However, the reduced C-myb expression is not responsible for all the effects of miR-150, there may be other molecular mechanisms for the suppression of HSCs by miR-150. In this study, gene array analysis was performed to analyze the miRNAs that were differentially expressed between LX-2 cells induced by transforming growth factor-β1 (TGF-β1) and the control. Our results indicated that the expression of miR-150 was significantly reduced during liver fibrosis. Of note, the reduction of miR-150 induced by TGF-β1 was in a dose- and time-dependent manner. In addition, miR-150 overexpression in LX-2 cells resulted in the inhibition of cell proliferation and the reduction of extracellular matrix proteins and α-smooth muscle actin (α-SMA). However, there was no significant change in the rate of apoptosis in cells transfected with miR-150 mimics compared with the control. Sp1, a mediator of α-1 (I) collagen (Col1A1) expression, and Col4A4 were found to be the targets for miR-150. Also, miR-150 mimics were found to decrease the expression of Sp1 and Col4A4. Smad2 and p-Smad2, the upstream mediators of Sp1, were not affected by miR-150. The same result was also seen in the levels of Smad3 and p-Smad3. Collectively, we conclude that miR-150 can reduce type I and IV collagen by directly binding to Sp1 and Col4A4 without the involvement of upstream of the TGF-α/Smad pathway.