title: Inhibition by nitric oxide of cytochrome P450 4A activity contributes to endotoxin-induced hypotension in rats.
abstract: Nitric oxide (NO) production during endotoxemia is associated with decreased total CYP content, CYP 1A1/2, 2B1/2, 2C6, 2C11, 3A1, and 3A2 mRNA, protein expression or activity which is prevented by NO synthase (NOS) inhibitors in rats. This study was conducted to determine if endotoxin-induced hypotension caused by NO production is mediated by inhibition of renal CYP 4A protein expression and activity. In conscious male Sprague-Dawley rats, endotoxin (10 mg/kg, ip) reduced mean arterial pressure (MAP), increased serum and renal nitrite levels, and inducible NOS (iNOS), and decreased renal CYP 4A1/A3 protein and CYP 4A activity. The selective iNOS inhibitor 1,3-PBIT (10 mg/kg, ip; 1h after endotoxin) prevented endotoxin-induced decrease in MAP, renal CYP 4A1/A3 protein level and CYP 4A activity and increase in systemic and renal nitrite production. The selective constitutive NOS (cNOS) inhibitor N(G)-nitro-L-arginine (L-NNA; 20 mg/kg, ip; 1 h after endotoxin) partially attenuated endotoxin-induced decrease in MAP. The selective CYP 4A inhibitor, aminobenzotriazole (50 mg/kg, ip; 1 h after endotoxin) diminished CYP 4A1/A3 protein level and CYP 4A activity. Aminobenzotriazole did not alter the endotoxin-induced decrease in MAP, but it reversed the effect of 1,3-PBIT in preventing endotoxin-induced fall in MAP and CYP 4A activity. These data suggest that the endotoxemia-induced increase in NO production primarily via iNOS suppresses renal CYP 4A expression and activity, and inhibition of iNOS with 1,3-PBIT restores renal CYP 4A protein and activity and MAP presumably due to increased production of arachidonic acid metabolites derived from CYP 4A.
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy, Yenisehir Campus, Mersin University, Turkey. brunctan@yahoo.com
authors.forename: Bahar
authors.initials: B
authors.lastname: Tunctan
authors.forename: Fariborz A
authors.initials: FA
authors.lastname: Yaghini
authors.forename: Anne
authors.initials: A
authors.lastname: Estes
authors.forename: Kafait U
authors.initials: KU
authors.lastname: Malik
mesh_terms: D000818:Animals; D042926:Cytochrome P-450 CYP4A / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004731:Endotoxins / Q000633:toxicity*; D007022:Hypotension / Q000139:chemically induced*; D008297:Male; D009569:Nitric Oxide / Q000494:pharmacology*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014230:Triazoles / Q000494:pharmacology
chemical_list: D004731:Endotoxins; D014230:Triazoles; C033020:1-aminobenzotriazole; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D042926:Cytochrome P-450 CYP4A