Cytoprotective properties of α-tocopherol are related to gene regulation in cultured D-galactosamine-treated human hepatocytes

Vitamin E (alpha-tocopherol) has demonstrated antioxidant activity and gene-regulatory properties. D-Galactosamine (D-GaIN)-induced cell death is mediated by nitric oxide in hepatocytes, and it is associated with hepatic steatosis. The beneficial properties of alpha-tocopherol and their relation to oxidative stress and gene regulation were assessed in D-GaIN-induced cell death. Hepatocytes were isolated from human liver resections by a collagenase perfusion technique. alpha-Tocopherol (50 mu M) was administered at the advanced stages (10 h) of D-GaIN-induced cell death in cultured hepatocytes. Cell death, oxidative stress, alpha-tocopherol metabolism, and NF-kappa B-, pregrane X receptor (PXR)-, and peroxisome proliferator-activated receptor (PPAR-alpha)-associated gene regulation were estimated in the hepatocytes. D-GaIN increased cell death and alpha-tocopherol metabolism. a-Tocopherol exerted a moderate beneficial effect against apoptosis and necrosis induced by D-GaIN. Induction (rifampicin) or inhibition (ketoconazole) of alpha-tocopherol metabolism and overexpression of PXR showed that the increase in PXR-related CYP3A4 expression caused by alpha-tocopherol enhanced cell death in hepatocytes. Nevertheless, the reduction in NF-kappa B activation and inducible nitric oxide synthase expression and the enhancement of PPAR-alpha. and carnitine palmitoyl transferase gene expression by alpha-tocopherol may be relevant for cell survival. In conclusion, the cytoprotective properties of (x-tocopherol are mostly related to gene regulation rather than to antioxidant activity in tox-ininduced cell death in hepatocytes. (C) 2007 Elsevier Inc. All rights reserved.