Molecular Pathway of Psoralidin-Induced Apoptosis in HepG2 Cell Line

Objective: To test the role of psoralidin in human liver cancer HepG2 cells in vitro. Methods: Cell viability was assessed by methylthiazolyldiphenyl-tetrazolum bromide assay and apoptotic cells were labeled by annexin V then sorted by flow cytometry. Protein expressions of caspase-3, caspase-8, caspase-9, Bax, Bid, Bcl-2, Bcl-xL and p53 were examined by western blot while activity of caspase-3,-8 and -9 were also determined. Results: Psoralidin reduces cell viability greatly in a time dependent manner(64%, 40%, 21%, 12% at 2, 6, 24 and 48 h treatment with 64 μmol/L psoralidin respectively) and up-regulates activities of caspase-3,-8 and-9 in a concentration dependent manner(between 4 to 64 μmol/L). Psoralidin also increases the expression of pro-apoptosis genes Bax, Bid and p53 while decreases the expression of pro-survival genes Bcl-2 and Bcl-xL, both in a concentration dependent manner between 4 and 64 μmol/L(P<0.05 at 16 and 64 μmol/L). Caspase-3 inhibitor(Ac-DEVD-CHO at concentrations between 10 to 20 μmol/L), p53 inhibitor(pifithrin-α at 5 μmol/L) and cyclosporin A can attenuate the apoptotic effect of psoralidin. Conclusion: The cytotoxic role of psoralidin might work through both intrinsic and extrinsic apoptotic pathway.