title: Hydrogen peroxide inhibits cytochrome p450 epoxygenases: interaction between two endothelium-derived hyperpolarizing factors.
abstract: The cytochrome P450 epoxygenase (CYP)-derived metabolites of arachidonic acid the epoxyeicosatrienoic acids (EETs) and hydrogen peroxide (H2O2) both function as endothelium-derived hyperpolarizing factors (EDHFs) in the human coronary microcirculation. However, the relative importance of and potential interactions between these 2 vasodilators remain unexplored. We identified a novel inhibitory interaction between CYPs and H2O2 in human coronary arterioles, where EDHF-mediated vasodilatory mechanisms are prominent. Bradykinin induced vascular superoxide and H2O2 production in an endothelium-dependent manner and elicited a concentration-dependent dilation that was reduced by catalase but not by 14,15-epoxyeicosa-5(Z)-enoic acid (EEZE), 6-(2-propargyloxyphenyl)hexanoic acid, sulfaphenazole, or iberiotoxin. However, in the presence of catalase, an inhibitory effect of these compounds was unmasked. In a tandem-bioassay preparation, application of bradykinin to endothelium-intact donor vessels elicited dilation of downstream endothelium-denuded detectors that was partially inhibited by donor-applied catalase but not by detector-applied EEZE; however, EEZE significantly inhibited dilation in the presence of catalase. EET production by human recombinant CYP 2C9 and 2J2, 2 major epoxygenase isozymes expressed in human coronary arterioles, was directly inhibited in a concentration-dependent fashion by H2O2 in vitro, as observed by high-performance liquid chromatography (HPLC); however, EETs were not directly sensitive to oxidative modification. H2O2 inhibited dilation to arachidonic acid but not to 11,12-EET. These findings suggest that an inhibitory interaction exists between 2 EDHFs in the human coronary microcirculation. CYP epoxygenases are directly inhibited by H2O2, and this interaction may modulate vascular EET bioavailability.
authors.affiliation: Department of Pharmacology & Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI 53226, USA.
authors.forename: Brandon T
authors.initials: BT
authors.lastname: Larsen
authors.forename: David D
authors.initials: DD
authors.lastname: Gutterman
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sato
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Toyama
authors.forename: William B
authors.initials: WB
authors.lastname: Campbell
authors.forename: Darryl C
authors.initials: DC
authors.lastname: Zeldin
authors.forename: Vijay L
authors.initials: VL
authors.lastname: Manthati
authors.forename: John R
authors.initials: JR
authors.lastname: Falck
authors.forename: Hiroto
authors.initials: H
authors.lastname: Miura
mesh_terms: D001095:Arachidonic Acids / Q000378:metabolism; D001160:Arterioles / Q000378:metabolism*; D001685:Biological Factors / Q000378:metabolism*; D001920:Bradykinin / Q000494:pharmacology; D002374:Catalase / Q000378:metabolism; D003326:Coronary Circulation; D065607:Cytochrome P-450 Enzyme Inhibitors; D004730:Endothelium, Vascular; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D014664:Vasodilation
chemical_list: D001095:Arachidonic Acids; D001685:Biological Factors; D065607:Cytochrome P-450 Enzyme Inhibitors; C067410:endothelium-dependent hyperpolarization factor; D006861:Hydrogen Peroxide; D002374:Catalase; D001920:Bradykinin