Received for publication August 27, 2004.
Revised October 15, 2004.
Accepted for publication October 18, 2004.

Protein Kinase C Signaling as a Survival Pathway Against CYP2E1-Derived Oxidative Stress and Toxicity in HepG2 Cells

Abstract

Hepatic induction of cytochrome P450 2E1 (CYP2E1) is a major pathway involved in oxidative stress and damage caused by chronic ethanol consumption; CYP2E1 also promotes the activation of a variety of hepatotoxins to reactive intermediates. Phorbol esters activate protein kinase C (PKC) thereby blocking cell differentiation and promoting tumor growth. In this study we examined the possible role of PKC signaling as a survival pathway against CYP2E1-mediated toxicity using transfected HepG2 hepatoma cells stably overexpressing CYP2E1 (E47 cells). Cells were exposed to arachidonic acid plus iron (AA+Fe), which has been previously reported to cause a synergistic toxicity in E47 cells by a mechanism dependent on CYP2E1 activity, and involving oxidative stress and lipid peroxidation. Phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), but not the inactive analogue 4--TPA, prevented lipid peroxidation, glutathione depletion, and loss of viability produced by AA+Fe in E47 cells. TPA also protected against the toxicity caused by AA alone, or by iron alone, in the E47 cells. TPA did not lower but instead induced catalytically-active CYP2E1 in these cells. The protective effect of TPA on CYP2E1-dependent AA+Fe toxicity seemed to involve a PKC-related survival mechanism, since PKC inhibitors such as Ro 31-8425 or staurosporine abolished that protection, and activation of PKC by TPA was an early event which occurs prior to the developing toxicity. In conclusion, PKC activation by TPA prevents CYP2E1-derived acute oxidative stress and toxicity in HepG2 cells, and this appears to involve maintenance of the intracellular redox homeostasis via PKC signal transduction.

Key words: CYP2E1, HepG2 cells, lipid peroxidation, oxidative stress, phorbol ester, protein kinase C

This article has been cited by other articles:

				B. Saberi, M. Shinohara, M. D. Ybanez, N. Hanawa, W. A. Gaarde, N. Kaplowitz, and D. Han Regulation of H2O2-induced necrosis by PKC and AMP-activated kinase signaling in primary cultured hepatocytes Am J Physiol Cell Physiol, July 1, 2008; 295(1): C50 - C63. [Abstract] [Full Text] [PDF]

				N. J. Hodges, R. M. Green, J. K. Chipman, and M. Graham Induction of DNA strand breaks and oxidative stress in HeLa cells by ethanol is dependent on CYP2E1 expression Mutagenesis, May 1, 2007; 22(3): 189 - 194. [Abstract] [Full Text] [PDF]

				J. Haorah, B. Knipe, J. Leibhart, A. Ghorpade, and Y. Persidsky Alcohol-induced oxidative stress in brain endothelial cells causes blood-brain barrier dysfunction J. Leukoc. Biol., December 1, 2005; 78(6): 1223 - 1232. [Abstract] [Full Text] [PDF]