Vol. 28, Issue 9, 1112-1120, September 2000

Role of Reactive Oxygen Intermediates in the Decrease of Hepatic Cytochrome P450 Activity by Serum of Humans and Rabbits with an Acute Inflammatory Reaction

Ayman O. S. El-Kadi, Anne-Marie Bleau, Isabelle Dumont, Hélène Maurice, and Patrick du Souich

Département de Pharmacologie, Faculté de Médecine, Université de Montréal Montréal, Québec, Canada

Serum of rabbits with a turpentine-induced acute inflammatory reaction (RS_INFLA) and serum of humans with a viral infection (HS_INF) were previously shown to diminish hepatic cytochrome P450 (P450) content and activity. To document the role of reactive oxygen intermediates in the serum-mediated decrease in P450 content and activity, hepatocytes of rabbits with an acute inflammatory reaction (H_INFLA) were incubated with RS_INFLA and HS_INF for 4 h, and total P450 content (spectrally measurable P450), P450 activity (assessed by estimating the formation of theophylline metabolites), and amount of CYP1A1, CYP1A2, and CYP3A6 proteins were measured. RS_INFLA or HS_INF decreased P450 content and activity without affecting the amount of CYP1A1 and -1A2 H_INFLA. Exposure of H_CONT or H_INFLA to hydrogen peroxide (0.01-1.0 mM) and sodium nitroprusside (0.01-1.0 mM) produced a dose-dependent decrease in P450 content and in the formation of theophylline metabolites without modifying the amount of CYP1A1 and CYP1A2, whereas lipid peroxidation increased. Incubation of L-NAME (0.05-1.0 mM), dimethylthiourea (6.25-50 mM), or N-acetylcysteine (0.01-1.0 mM) with H_INFLA partially prevented the decrease in P450 content and activity and the increased lipid peroxidation induced by RS_INFLA and HS_INF. On the other hand, 3-amino-1,2,4-triazole (10-100 mM) or diethyldithiocarbamate (1.0-10 mM) potentiated RS_INFLA- and HS_INF-mediated decreases in P450 content and activity and the increase in lipid peroxidation, without affecting the amount of CYP1A1 or -1A2; DL-buthionine-(S,R)-sulfoximine (2.5-25 mM) potentiated only the inhibition of 1,3-dimethyluric acid formation. It is concluded that reactive oxygen intermediates are implicated in the decrease of H_INFLA P450 content and activity induced by 4 h of exposure to RS_INFLA or HS_INF.