Fenretinide stimulates the apoptosis of hepatic stellate cells and ameliorates hepatic fibrosis in mice

Aim: To investigate whether fenretinide, a clinically proved apoptosis-inducing chemopreventive agent in tumor cells, can induce apoptosis in hepatic stellate cells (HSCs) and resolve hepatic fibrosis. Methods: CCl4-induced liver fibrosis in mice and rat activated hepatic stellate cells (HSC-T6) as well as hepatocytes (BRL-3A) were studied. Results: The duplex staining of proliferating cell nuclear antigen and alpha- smooth muscle actin or terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and alpha- smooth muscle actin demonstrated that fenretinide executed its anti-fibrosis effect in liver by inducing apoptosis rather than inhibiting proliferation of HSCs, while it had no apparently apoptotic effect on hepatocytes. Fenretinide could elicit apoptosis of HSC-T6 in vitro at the concentration range from 0.5 to 5 mu M, but at higher concentrations >= 5 mu M was required to induce apoptosis in hepatocytes (BRL-3A). Conclusion: Further studies using malondialdehyde measurement, Western blot, antioxidant, inhibitors for p53, caspase 8 and 9 - as well as anti-Fas neutralizing antibody - have shown that in HSC-T6, fenretinide-induced apoptosis involves a reactive oxygen species (ROS)-generated, P53-independent, mitochondria-associated intrinsic pathway, whereas in hepatocytes (BRL-3A), a ROS-generated, P53-dependent, Fas-related extrinsic pathway is triggered only at high concentration.