Cyp1a2 protects against reactive oxygen production in mouse liver microsomes.
H(2)O(2) production was evaluated in liver microsomes prepared from Cyp1a1/1a2(+/+) wild-type and Cyp1a1(-/-) and Cyp1a2(-/-) knockout mice pretreated with 5 microg dioxin (TCDD)/kg body wt or vehicle alone. NADPH-dependent H(2)O(2) production in TCDD-induced microsomes from wild-type mice was about one-third of that in noninduced microsomes. In Cyp1a2(-/-) mice, H(2)O(2) production was the same for induced and noninduced microsomes, with levels significantly higher than those in wild-type mice. Cyp1a1(-/-) microsomes displayed markedly lower levels of H(2)O(2) production in both induced and noninduced microsomes, compared with those in wild-type and Cyp1a2(-/-) microsomes. The CYP1A2 inhibitor furafylline in vitro exacerbated microsomal H(2)O(2) production proportional to the degree of CYP1A2 inhibition, and the CYP2E1 inhibitor diethyldithiocarbamate decreased H(2)O(2) production proportional to the degree of CYP2E1 inhibition. Microsomal H(2)O(2) production was strongly correlated to NADPH-stimulated production of thiobarbituric acid-reactive substances, as well as to decreases in microsomal membrane polarization anisotropy, indicative of peroxidation of unsaturated membrane lipids. Our results suggest that possibly acting as an "electron sink," CYP1A2 might decrease CYP2E1-and CYP1A1-mediated H(2)O(2) production and oxidative stress. In this regard, CYP1A2 may be considered an antioxidant enzyme.
Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati Medical Center, Cincinnati, OH 45267, USA. shertzhg@ucmail.uc.edu
Howard G
HG
Shertzer
Corey D
CD
Clay
Mary Beth
MB
Genter
Scott N
SN
Schneider
Daniel W
DW
Nebert
Timothy P
TP
Dalton
D000818:Animals; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism*; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism*; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism*; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004147:Dioxins / Q000633:toxicity; D004050:Ditiocarb / Q000494:pharmacology; D004579:Electron Transport; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D009249:NADP / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013806:Theophylline / Q000031:analogs & derivatives* / Q000494:pharmacology
D065609:Cytochrome P-450 CYP1A2 Inhibitors; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004147:Dioxins; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D009249:NADP; D004050:Ditiocarb; D006861:Hydrogen Peroxide; D013806:Theophylline; C050131:furafylline; D019392:Cytochrome P-450 CYP2E1; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2