BACKGROUND: Proliferation of hepatic stellate cells(HSCs) plays a pivotal role in the progression of liver fibrosis consequent to chronic liver injury. Silibinin, a flavonoid compound,has been shown to possess anti-fibrogenic effects in animal models of liver fibrosis. This was attributed to an inhibition of cell proliferation of activated HSCs. The present study was to gain insight into the molecular pathways involved in silibinin anti-fibrogenic effect. METHODS: The study was conducted on LX-2 human stellate cells treated with three concentrations of silibinin(10, 50 and 100 μmol/L) for 24 and 96 hours. At the end of the treatment cell viability and proliferation were evaluated. Protein expression of p27, p21, p53, Akt and phosphorylated-Akt was evaluated by Western blotting analysis and Ki-67 protein expression was by immunocytochemistry. Sirtuin activity was evaluated by chemiluminescence based assay. RESULTS: Silibinin inhibits LX-2 cell proliferation in doseand time-dependent manner; we showed that silibinin upregulated the protein expressions of p27 and p53. Such regulation was correlated to an inhibition of both downstream Akt and phosphorylated-Akt protein signaling and Ki-67 protein expression. Sirtuin activity also was correlated to silibinininhibited proliferation of LX-2 cells. CONCLUSION: The anti-proliferative effect of silibinin on LX-2 human stellate cells is via the inhibition of the expressions of various cell cycle targets including p27, Akt and sirtuin signaling. BACKGROUND: Proliferation of hepatic stellate cells (HSCs) plays a pivotal role in the progression of liver fibrosis consequent to chronic liver injury. Silibinin, a flavonoid compound, has been shown to possess anti-fibrogenic effects in animal models of liver fibrosis. This was attributed to an inhibition of cell proliferation of activated HSCs. The present study was to gain insight into the molecular pathways involved in silibinin anti-fibrogenic effect. METHODS: The study was conducted on LX-2 human stellate cells treated with three concentrations of silibinin ( Protein expression of p27, p21, p53, Akt and phosphorylated-Akt was evaluated by Western blotting analysis and Ki -67 protein expression was by immunocytochemistry. Sirtuin activity was evaluated by chemiluminescence based assay. RESULTS: Silibinin inhibits LX-2 cell proliferation in dose and time-dependent ma nner; we showed that silibinin upregulated the protein expressions of p27 and p53. This regulation was correlated to an inhibition of both downstream Akt and phosphorylated-Akt protein signaling and Ki-67 protein expression. Sirtuin activity also was associated to silibininhibited proliferation of LX- 2 cells. CONCLUSION: The anti-proliferative effect of silibinin on LX-2 human stellate cells is via the inhibition of the expressions of various cell cycle targets including p27, Akt and sirtuin signaling.