Role of p38 MAPK in CYP2E1-dependent Arachidonic Acid Toxicity

Defeng Wu,Arthur I Cederbaum

doi:10.1074/jbc.m207856200

Abstract

Polyunsaturated fatty acids such as arachidonic acid (AA) play an important role in alcohol-induced liver injury. AA promotes toxicity in rat hepatocytes with high levels of cytochrome P4502E1 (CYP2E1) and in HepG2 E47 cells, which express CYP2E1. The possible role of mitogen-activated protein kinase (MAPK) members in this process was evaluated. SB203580, a p38 MAPK inhibitor, and PD98059, an ERK inhibitor, but not wortmannin a phosphatidylinositol 3-kinase (PI3K) inhibitor, prevented AA toxicity in pyrazole hepatocytes and E47 cells. SB203580 prevented the enhancement of AA toxicity by salicylate. SB203580 neither lowered the levels of CYP2E1 nor affected CYP2E1-dependent oxidative stress. The decrease in mitochondrial membrane potential produced by AA was prevented by SB203580. Treating CYP2E1-induced cells with AA activated p38 MAPK but not ERK or AKT. This activation was blocked by antioxidants. AA increased the translocation of NF-kappaB to the nucleus. Salicylate blocked this translocation, which may contribute to the enhancement of AA toxicity by salicylate. SB203580 restored AA-induced NF-kappaB translocation, which may contribute to protection against toxicity. In conclusion, AA toxicity was related to lipid peroxidation and oxidative stress, and to the activation of p38 MAPK, as a consequence of CYP2E1-dependent production of reactive oxygen species. Activation of p38 MAPK by AA coupled to AA-induced oxidative stress may synergize to cause cell toxicity by affecting mitochondrial membrane potential and by modulation of NF-kappaB activation.

Highlights

Polyunsaturated fatty acids (PUFA)1 such as arachidonic acid (AA) or its metabolites play an important role in a variety of biological processes, such as signal transduction, chemo
Arachidonic acid has been shown to induce the phosphorylation of mitogen-activated protein kinase (MAPK) (40 – 42), but whether such activation can be related to AA toxicity and the mechanism through which MAPK plays a role in AA toxicity have not been addressed
Exogenous polyunsaturated fatty acids (PUFAs) such as AA exert a wide range of effects on cells of diverse origin, such as regulation of gap junctions, permeability between adherent cells, neutrophil secretion and migration, NADPH oxidase activities, expression of cell-surface receptors, gene transcription, cytotoxic T cell function, and modulation of the activities of components of intracellular signaling

Summary

Introduction

Polyunsaturated fatty acids (PUFA) such as arachidonic acid (AA) or its metabolites play an important role in a variety of biological processes, such as signal transduction, chemo-. AA induced toxicity in pyrazole-induced rat hepatocytes with high levels of CYP2E1 but not saline control hepatocytes [10] This AA toxicity was prevented by inhibitors of CYP2E1 and by antioxidants [9, 10]. We characterized the possible role of the MAPKs, p38 and ERK, and PI3K on AA or AA plus salicylate-induced toxicity in pyrazole-induced rat hepatocytes, human hepatocyte cultures, and HepG2 E47 cells. Effects of specific kinase inhibitors on cellular toxicity, CYP2E1 levels, lipid peroxidation, mitochondrial membrane potential, and NF-␬B activation and the role of MAPKs in the salicylate enhancement of AA-induced toxicity were evaluated. Results show that AA or AA plus salicylate activated p38 MAPK but not ERK or PI3K, and that p38 MAPK plays a role in AA-induced cytotoxicity in CYP2E1-expressing cells

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Results

Conclusion