Inactivation of Hepatic CYP2E1 by an Epoxide of Diallyl Sulfone

• Published in: The Journal of pharmacology and experimental therapeutics 2000-06, Vol.293 (3), p.1112-1120
• Main Authors: Premdas, P D, Bowers, R J, Forkert, P G
• Format: Article
• Language: English
• Subjects: Allyl Compounds - metabolism; Allyl Compounds - pharmacology; Animals; Cytochrome P-450 CYP2E1 - physiology; Cytochrome P-450 CYP2E1 Inhibitors; Female; Glutathione - metabolism; Heme - analysis; Mice; Microsomes, Liver - metabolism; Sulfones - metabolism; Sulfones - pharmacology; Sulfoxides - pharmacology
• ISSN: 0022-3565; 1521-0103

Diallyl sulfone (DASO 2 ) inhibits hepatic CYP2E1. In this investigation, we have tested the hypothesis that an epoxide formed from DASO 2 is responsible for inactivation of hepatic CYP2E1 in mice. An epoxide of DASO 2 (1,2-epoxypropyl-3,3′-sulfonyl-1′-propene; DASO 3 ) was synthesized and conjugated to glutathione (GSH) to produce the conjugates S -(1 R,S -[[ 1-hydroxymethyl-2,3′-sulfonyl]-1′-propenyl]ethyl)glutathione (diastereomers) and S -(1-[[2 R,S -hydroxypropyl]-3,3′-sulfonyl]-1′-propenyl)glutathione (diastereomers). Their identities were confirmed by 1 H NMR analysis, and these were used as analytical standards. HPLC analysis revealed a major peak for the GSH conjugates that eluted at 20.5 min. This peak was detected in liver microsomal incubations performed with DASO 2 in the presence of NADPH. A similar peak also was detected in incubations of CYP2E1-expressed lymphoblastoid microsomes, NADPH and DASO 2 . The generation of the epoxide-derived GSH conjugates in the microsomal incubations was concentration-dependent, and reached saturation at 0.75 to 1.0 mM DASO 2 . Formation of the conjugates was also time-dependent and peaked at 2.0 h after DASO 2 . Levels of DASO 3 formed from DASO 2 , as estimated by production of a 4-( p -nitrobenzyl)pyridine derivative, were maximal at 1 mM DASO 2 at 30 min. CYP2E1-dependent p -nitrophenol hydroxylase activity was decreased in microsomes incubated with DASO 2 , with alterations that were proportional to the concentration of DASO 2 (0.25–1.0 mM) used. Dose-dependent decreases in hydroxylase activity also were found in microsomes from mice treated in vivo with DASO 2 (25–200 mg/kg). These DASO 2 -induced decreases corresponded with reduced amounts of immunodetectable CYP2E1. Levels of spectrally detectable P450 and heme were both diminished by DASO 2 . These results supported the contention that an epoxide formed from DASO 2 mediates the inactivation of hepatic CYP2E1.