title: Cytochrome P450-dependent eicosapentaenoic acid metabolites are novel BK channel activators.
abstract: P450-dependent arachidonic acid (AA) metabolites regulate arterial tone by modulating calcium-activated (BK) potassium channels in vascular smooth muscle cells (VSMC). Because eicosapentaenoic acid (EPA) has been reported to improve vascular function, we tested the hypothesis that P450-dependent epoxygenation of EPA produces alternative vasoactive compounds. We synthesized the 5 regioisomeric epoxyeicosattrienoic acids (EETeTr) and examined them for effects on K(+) currents in rat cerebral artery VSMCs with the patch-clamp technique. 11(R),12(S)-epoxyeicosatrienoic acid (50 nmol/L) was used for comparison and stimulated K(+) currents 6-fold at +60 mV. However, 17(R),18(S)-EETeTr elicited a more than 14-fold increase. 17(S),18(R)-EET and the remaining four regioisomers were inactive. The effect of 17(R),18(S)-EETeTr was blocked by tetraethylammonium but not by 4-aminopyridine. VSMCs expressed P450s 4A1 and 4A3. Recombinant P450 4A1 hydroxylated EPA at C-19 and C-20 and epoxygenated the 17,18-double bond, yielding the R, S- and S, R-enantiomers in a ratio of 64:36. We conclude that 17(R),18(S)-EETeTr represents a novel, potent activator of BK potassium channels. Furthermore, this metabolite can be directly produced in VSMCs. We suggest that 17(R),18(S)-EETeTr may function as an important hyperpolarizing factor, particularly with EPA-rich diets.
authors.affiliation: Max Delbrück Center for Molecular Medicine and Franz Volhard Clinic HELIOS Kliniken-Berlin, Medical Faculty of the Charité, Humboldt University of Berlin, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Lauterbach
authors.forename: Eduardo
authors.initials: E
authors.lastname: Barbosa-Sicard
authors.forename: Mong-Heng
authors.initials: MH
authors.lastname: Wang
authors.forename: Horst
authors.initials: H
authors.lastname: Honeck
authors.forename: Eva
authors.initials: E
authors.lastname: Kärgel
authors.forename: Jürgen
authors.initials: J
authors.lastname: Theuer
authors.forename: Michal L
authors.initials: ML
authors.lastname: Schwartzman
authors.forename: Hermann
authors.initials: H
authors.lastname: Haller
authors.forename: Friedrich C
authors.initials: FC
authors.lastname: Luft
authors.forename: Maik
authors.initials: M
authors.lastname: Gollasch
authors.forename: Wolf-Hagen
authors.initials: WH
authors.lastname: Schunck
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D015118:Eicosapentaenoic Acid / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D010084:Oxidation-Reduction; D018408:Patch-Clamp Techniques; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007527:Isoenzymes; D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D003577:Cytochrome P-450 Enzyme System; D015118:Eicosapentaenoic Acid