Abstract
Diallyl sulfone (DASO2) inhibits hepatic CYP2E1. In this investigation, we have tested the hypothesis that an epoxide formed from DASO2 is responsible for inactivation of hepatic CYP2E1 in mice. An epoxide of DASO2(1,2-epoxypropyl-3,3′-sulfonyl-1′-propene; DASO3) was synthesized and conjugated to glutathione (GSH) to produce the conjugates S-(1R,S-[[ 1-hydroxymethyl-2,3′-sulfonyl]-1′-propenyl]ethyl)glutathione (diastereomers) andS-(1-[[2R,S-hydroxypropyl]-3,3′-sulfonyl]-1′-propenyl)glutathione (diastereomers). Their identities were confirmed by 1H 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 DASO2 in the presence of NADPH. A similar peak also was detected in incubations of CYP2E1-expressed lymphoblastoid microsomes, NADPH and DASO2. 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 DASO2. Formation of the conjugates was also time-dependent and peaked at 2.0 h after DASO2. Levels of DASO3 formed from DASO2, as estimated by production of a 4-(p-nitrobenzyl)pyridine derivative, were maximal at 1 mM DASO2 at 30 min. CYP2E1-dependentp-nitrophenol hydroxylase activity was decreased in microsomes incubated with DASO2, with alterations that were proportional to the concentration of DASO2 (0.25–1.0 mM) used. Dose-dependent decreases in hydroxylase activity also were found in microsomes from mice treated in vivo with DASO2 (25–200 mg/kg). These DASO2-induced decreases corresponded with reduced amounts of immunodetectable CYP2E1. Levels of spectrally detectable P450 and heme were both diminished by DASO2. These results supported the contention that an epoxide formed from DASO2 mediates the inactivation of hepatic CYP2E1.
Footnotes
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Send reprint requests to: Dr. Poh-Gek Forkert, Department of Anatomy and Cell Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6. E-mail: forkertp{at}post.queensu.ca
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↵1 This study was supported by Grant MT-11706 from the Medical Research Council of Canada, Grant 011129 from the National Cancer Institute of Canada, and Grant RO1-CA73220-01 from the U.S. National Cancer Institute (to P.G.F.).
- Abbreviations:
- DAS
- diallyl sulfide
- GSH
- glutathione
- DASO
- diallyl sulfoxide
- DASO2
- diallyl sulfone
- DASO3
- 1,2-epoxypropyl-3,3′-sulfonyl-1′-propene
- NBP
- 4-(p-nitrobenzyl)pyridine
- mAb
- monoclonal antibody
- PNP
- p-nitrophenol
- TFA
- trifluoroacetic acid
- PAGE
- polyacrylamide gel electrophoresis
- ethyl DDC
- 4-ethyl-3,5-diethoxycarbonyl-1,4-dihydro-2,4,6-trimethylpyridine
- Received November 5, 1999.
- Accepted February 9, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
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