Extent of extracellular signal-regulated kinases phosphorylation determines the sensitivity of hepatic stellate cells to staurosporine-induced apoptosis.

OBJECTIVE:Hepatic stellate cells (HSCs) are the principal cells responsible for the development of hepatic fibrosis and cirrhosis. During the fibrotic process, HSCs undergo proliferation and transdifferentiation from a quiescent to myofibroblast-like phenotype. The fate of myofibroblast like HSCs includes apoptosis or reversion back to a quiescent phenotype. The mechanisms involved in the apoptotic process of HSCs have yet to be determined. The purpose of the present study is to determine the effects of extracellular signal-regulated kinases (ERKs) phosphorylation on the apoptosis of HSCs induced by staurosporine. METHODS:We used Western blot and flow cytometry to detect the expression level of ERK and cell apoptosis status in four rat hepatic stellate cell lines (CFSC-8B, -2G, -3H and-5H). RESULTS:Each hepatic stellate cell line had a distinct morphology consistent with their expression level of α-SMA and that CFSC-8B cells had the highest α-SMA expression. Although all four cell types expressed similar levels of ERK1/2, phosphorylation levels were significantly higher in CFSC- 8B and CFSC-2G than in CFSC-3H and CFSC-5H cells. When CFSC-8B cells (high ERK1/2 phosphorylation) and CFSC-5H cells (low ERK1/2 phosphorylation) were employed to examine staurosporine-induced apoptosis, CFSC-8B cells were significantly more sensitive. Staurosporine further increased ERK1/2 phosphorylation in both cell lines. CONCLUSION:ERK1/2 phosphorylation in HSCs determines the sensitivity of HSCs to staurosporine-induced apoptosis.