Hes1, an important gene for activation of hepatic stellate cells, is regulated by Notch1 and TGF-β/BMP signaling

AIM: To determine the role of Notch1 and Hes1 in regulating the activation of hepatic stellate cells (HSCs) and whether Hes1 is regulated by transforming growth factor (TGF)/bone morphogenetic protein (BMP) signaling. METHODS: Immunofluorescence staining was used to detect the expression of desmin, glial fibrillary acidic protein and the myofibroblastic marker a-smooth muscle actin (alpha-SMA) after freshly isolated, normal rat HSCs had been activated in culture for different numbers of days (0, 1, 3, 7 and 10 d). The expression of a-SMA, collagen1 alpha 2 (COL1 alpha a2), Notch receptors (Notch1-4), and the Notch target genes Hes1 and Hey1 were analyzed by reverse transcriptase-polymerase chain reaction. Luciferase reporter assays and Western blot were used to study the regulation of alpha-SMA, COL1 alpha 1, COL1 alpha 2 and Hes1 by NICD1, Hes1, CA-ALK3, and CA-ALK5 in HSC-T6 cells. Moreover, the effects of inhibiting Hes1 function in HSC-T6 cells using a Hes1 decoy were also investigated. RESULTS: The expression of Notch1 and Hes1 mRNAs was significantly down-regulated during the culture of freshly isolated HSCs. In HSC-T6 cells, Notch1 inhibited the promoter activities of alpha-SMA, COL1 alpha 1 and COL1 alpha 2. On the other hand, Hes1 enhanced the promoter activities of alpha-SMA and COL1 alpha 2, and this effect could be blocked by inhibiting Hes1 function with a Hes1 decoy. Furthermore, co-transfection of pcDNA3-CA-ALK3 (BMP signaling activin receptor-like kinase 3) and pcDNA3.1-NICD1 further increased the expression of Hes1 compared with transfection of either vector alone in HSC-T6 cells, while pcDNA3-CA-ALK5 (TGF-beta signaling activin receptor-like kinase 5) reduced the effect of NICD1 on Hes1 expression. CONCLUSION: Selective interruption of Hes1 or maintenance of Hes1 at a reasonable level decreases the promoter activities of alpha-SMA and COL1 alpha 2, and these conditions may provide an anti-fibrotic strategy against hepatic fibrosis.