Role of reactive oxygen intermediates in the decrease of hepatic cytochrome P450 activity by serum of humans and rabbits with an acute inflammatory reaction

Serum of rabbits with a turpentine-induced acute inflammatory reaction (RSINFLA) and serum of humans with a viral infection (HSINF) 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 RSINFLA and HSINF 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. RSINFLA or HSINF 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 RSINFLA and HSINF. On the other hand, 3-amino-1,2,4-triazole (10-100 mM) or diethyldithiocarbamate (1.0-10 mM) potentiated RSINFLA- and HSINF-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 RSINFLA or HSINF.