Role of reactive oxygen intermediates in the decrease of hepatic cytochrome P450 activity by serum of humans and...

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).