HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 278, Issue 36, 33866-33877, September 5, 2003

This Article Full Text Full Text (PDF) All Versions of this Article: 278/36/33866    most recent M300408200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Caro, A. A. Articles by Cederbaum, A. I. Search for Related Content PubMed PubMed Citation Articles by Caro, A. A. Articles by Cederbaum, A. I. Social Bookmarking                      What's this?

Role of Phospholipase A₂ Activation and Calcium in CYP2E1-dependent Toxicity in HepG2 Cells^*

Andres A. Caro and Arthur I. Cederbaum 

From the Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, New York 10029

Previous studies suggested a role for calcium in CYP2E1-dependent toxicity. The possible role of phospholipase A₂ (PLA2) activation in this toxicity was investigated. HepG2 cells that overexpress CYP2E1 (E47 cells) exposed to arachidonic acid (AA) +Fe-NTA showed higher toxicity than control HepG2 cells not expressing CYP2E1 (C34 cells). This toxicity was inhibited by the PLA2 inhibitors aristolochic acid, quinacrine, and PTK. PLA2 activity assessed by release of preloaded [³H]AA after treatment with AA+Fe was higher in the CYP2E1 expressing HepG2 cells. This [³H]AA release was inhibited by PLA2 inhibitors, -tocopherol, and by depleting Ca²⁺ from the cells (intracellular + extracellular sources), but not by removal of extracellular calcium alone. Toxicity was preceded by an increase in intracellular calcium caused by influx from the extracellular space, and this was prevented by PLA2 inhibitors. PLA2 inhibitors also blocked mitochondrial damage in the CYP2E1-expressing HepG2 cells exposed to AA+Fe. Ca²⁺ depletion and removal of extracellular calcium inhibited toxicity at early time periods, although a delayed toxicity was evident at later times in Ca²⁺-free medium. This later toxicity was also inhibited by PLA2 inhibitors. Analogous to PLA2 activity, Ca²⁺ depletion but not removal of extracellular calcium alone prevented the activation of calpain activity by AA+Fe. These results suggest that release of stored calcium by AA+Fe, induced by lipid peroxidation, can initially activate calpain and PLA2 activity, that PLA2 activation is critical for a subsequent increased influx of extracellular Ca²⁺, and that the combination of increased PLA2 and calpain activity, increased calcium and oxidative stress cause mitochondrial damage, that ultimately produces the rapid toxicity of AA+Fe in CYP2E1-expressing HepG2 cells.

Received for publication, January 14, 2003 , and in revised form, June 16, 2003.

^* These studies were supported by United States Public Health Service Grant AA06610 from the National Institutes on Alcohol Abuse and Alcoholism. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

To whom correspondence should be addressed: Dept. of Pharmacology and Biological Chemistry, Box 1603, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029. Tel.: 212-241-7285; Fax: 212-996-7214; E-mail: arthur.cederbaum{at}mssm.edu.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				A. A. Caro and A. I. Cederbaum Role of Phosphatidylinositol 3-Kinase/AKT as a Survival Pathway against CYP2E1-Dependent Toxicity J. Pharmacol. Exp. Ther., July 1, 2006; 318(1): 360 - 372. [Abstract] [Full Text] [PDF]

				Y. Hori, S. J. Spurr-Michaud, C. L. Russo, P. Argueso, and I. K. Gipson Effect of Retinoic Acid on Gene Expression in Human Conjunctival Epithelium: Secretory Phospholipase A2 Mediates Retinoic Acid Induction of MUC16 Invest. Ophthalmol. Vis. Sci., November 1, 2005; 46(11): 4050 - 4061. [Abstract] [Full Text] [PDF]