Assessment of the role of in situ generated (E)-2,4-diene-valproic acid in the toxicity of valproic acid and (E)-2-ene-valproic acid in sandwich-cultured rat hepatocytes.

Abstract

Valproic acid (VPA) undergoes cytochrome P450-mediated desaturation to form 4-ene-VPA, which subsequently yields (E)-2,4-diene-VPA by β-oxidation. Another biotransformation pathway involves β-oxidation of VPA to form (E)-2-ene-VPA, which also generates (E)-2,4-diene-VPA by cytochrome P450-mediated desaturation. Although the synthetic form of (E)-2,4-diene-VPA is more hepatotoxic than VPA as shown in various experimental models, there is no conclusive evidence to implicate the in situ generated (E)-2,4-diene-VPA in VPA hepatotoxicity. The present study investigated the effects of modulating the in situ formation of (E)-2,4-diene-VPA on markers of oxidative stress (formation of 2',7'-dichlorofluorescein; DCF), steatosis (accumulation of BODIPY 558/568 C₁₂), necrosis (release of lactate dehydrogenase; LDH), and on cellular total glutathione (GSH) levels in sandwich-cultured rat hepatocytes treated with VPA or (E)-2-ene-VPA. Treatment with either of these chemicals alone increased each of the toxicity endpoints. In VPA-treated hepatocytes, (E)-2,4-diene-VPA was detected only at trace levels, even after phenobarbital (PB) pretreatment and there was no effect on the toxicity of VPA. Furthermore, pretreatment with a cytochrome P450 enzyme inhibitor, 1-aminobenzotriazole (1-ABT), did not influence the extent of VPA toxicity in both PB-pretreated and vehicle-pretreated hepatocytes. However, in (E)-2-ene-VPA-treated hepatocytes, PB pretreatment greatly enhanced the levels of (E)-2,4-diene-VPA and this was accompanied by a further enhancement of the effects of (E)-2-ene-VPA on DCF formation, BODIPY accumulation, LDH release, and GSH depletion. Pretreatment with 1-ABT reduced the concentrations of (E)-2,4-diene-VPA and the extent of (E)-2-ene-VPA toxicity; however, this occurred in PB-pretreated hepatocytes, but not in control hepatocytes. In conclusion, in situ generated (E)-2,4-diene-VPA is not responsible for the hepatocyte toxicity of VPA, whereas it contributes to the toxicity of (E)-2-ene-VPA in PB-pretreated rat hepatocytes.

• Authors: Jayakumar Surendradoss, Thomas K H Chang, Frank S Abbott
• Journal: Toxicology and applied pharmacology (Toxicol Appl Pharmacol) Vol. 264 Issue 3 Pg. 413-22 (Nov 01 2012) ISSN: 1096-0333 [Electronic] United States
• PMID: 22940460 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2012 Elsevier Inc. All rights reserved.

Chemical References

• Cytochrome P-450 Enzyme Inhibitors
• Triazoles
• 1-aminobenzotriazole
• Valproic Acid
• Cytochrome P-450 Enzyme System
• Phenobarbital

Topics

• Animals
• Cell Culture Techniques
• Cytochrome P-450 Enzyme Inhibitors
• Cytochrome P-450 Enzyme System (genetics, metabolism)
• Enzyme Induction (drug effects)
• Hepatocytes (drug effects, metabolism)
• Male
• Molecular Structure
• Phenobarbital (pharmacology)
• Rats
• Rats, Sprague-Dawley
• Triazoles (pharmacology)
• Valproic Acid (chemistry, metabolism, toxicity)