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

Free Radic Biol Med. 2007 Nov 15;43(10):1439-52. doi: 10.1016/j.freeradbiomed.2007.07.023. Epub 2007 Aug 3.

Abstract

Vitamin E (alpha-tocopherol) has demonstrated antioxidant activity and gene-regulatory properties. d-Galactosamine (D-GalN)-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-GalN-induced cell death. Hepatocytes were isolated from human liver resections by a collagenase perfusion technique. alpha-Tocopherol (50 microM) was administered at the advanced stages (10 h) of D-GalN-induced cell death in cultured hepatocytes. Cell death, oxidative stress, alpha-tocopherol metabolism, and NF-kappaB-, pregnane X receptor (PXR)-, and peroxisome proliferator-activated receptor (PPAR-alpha)-associated gene regulation were estimated in the hepatocytes. D-GalN increased cell death and alpha-tocopherol metabolism. alpha-Tocopherol exerted a moderate beneficial effect against apoptosis and necrosis induced by D-GalN. 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-kappaB 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 alpha-tocopherol are mostly related to gene regulation rather than to antioxidant activity in toxin-induced cell death in hepatocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antioxidants / pharmacology*
  • Apoptosis / drug effects*
  • Apoptosis / genetics
  • Carnitine O-Palmitoyltransferase / genetics
  • Cells, Cultured
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme System / metabolism
  • Cytoprotection*
  • Galactosamine / antagonists & inhibitors
  • Galactosamine / toxicity
  • Gene Expression / drug effects*
  • Gene Expression Regulation
  • Hepatocytes / drug effects*
  • Hepatocytes / metabolism
  • Humans
  • NF-kappa B / antagonists & inhibitors
  • NF-kappa B / metabolism
  • Nitric Oxide Synthase Type II / antagonists & inhibitors
  • Nitric Oxide Synthase Type II / genetics
  • PPAR alpha / metabolism
  • Pregnane X Receptor
  • Reactive Oxygen Species / metabolism
  • Receptors, Steroid / metabolism
  • alpha-Tocopherol / metabolism
  • alpha-Tocopherol / pharmacology*

Substances

  • Antioxidants
  • NF-kappa B
  • PPAR alpha
  • Pregnane X Receptor
  • Reactive Oxygen Species
  • Receptors, Steroid
  • Galactosamine
  • Cytochrome P-450 Enzyme System
  • Nitric Oxide Synthase Type II
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human
  • Carnitine O-Palmitoyltransferase
  • alpha-Tocopherol