Abstract
1,1-Dichloroethylene (DCE) exposure evokes lung toxicity with selective damage to bronchiolar Clara cells. Recent in vitro studies have implicated CYP2E1 and CYP2F2 in the bioactivation of DCE to 2-S-glutathionyl acetate [C], a putative conjugate of DCE epoxide with glutathione. An objective of this study was to test the hypothesis that bioactivation of DCE is catalyzed by both CYP2E1 and CYP2F2 in murine lung. Western blot analysis of lung microsomal proteins from DCE-treated CD-1 mice showed time-dependent loss of immunodetectable CYP2F2 and CYP2E1 protein. Dose-dependent formation of conjugate [C] was observed in the lungs of CD-1 mice treated with DCE (75–225 mg/kg), but it was not detected after pretreatment with 5-phenyl-1-pentyne (5-PIP). Treatment of mice with 5-PIP and also with diallyl sulfone (DASO2) significantly inhibited hydroxylation of p-nitrophenol (PNP) and chlorzoxazone (CHZX). Incubation of recombinant CYP2F3 (a surrogate for CYP2F2) and recombinant CYP2E1 with PNP and CHZX confirmed that they are substrates for both of the recombinant enzymes. Incubation of the recombinant enzymes with DASO2 or 5-PIP significantly inhibited hydroxylation of both PNP and CHZX. Bronchiolar injury was elicited in CD-1 mice treated with DCE (75 mg/kg), but it was abrogated with 5-PIP pretreatment. Bronchiolar toxicity also was manifested in the lungs of CYP2E1-null and wild-type mice treated with DCE (75 mg/kg), but protection ensued after pretreatment with 5-PIP or DASO2. These results showed that bioactivation of DCE in murine lung occurred via the catalytic activities of both CYP2E1 and CYP2F2 and that bioactivation by these enzymes mediated the lung toxicity.
Footnotes
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This study was supported by Grant MOP 11706 from the Canadian Institutes of Health Research and Grant 014061 from the National Cancer Institute of Canada (to P.-G.F.) and United States Public Health Service Grants (HL13645 and HL60143) from the National Heart, Lung, and Blood Institute (to G.S.Y.). A.S. was supported by postdoctoral fellowships from the Cancer Research Society of Canada and Queen's University Principal's Development Fund.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.104.068171.
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ABBREVIATIONS: DCE, 1,1-dichloroethylene; GSH, glutathione; PNP, p-nitrophenol; S-Et-GSH, S-ethyl glutathione; DASO2, diallyl sulfone; 5-PIP, 5-phenyl-1-pentyne; CHZX, chlorzoxazone; LC/MS, liquid chromatography/mass spectrometry; HPLC, high-performance liquid chromatography.
- Received March 14, 2004.
- Accepted April 30, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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