title: Stable 5,6-epoxyeicosatrienoic acid analog relaxes coronary arteries through potassium channel activation.
abstract: 5,6-epoxyeicosatrienoic acid (5,6-EET) is a cytochrome P450 epoxygenase metabolite of arachidonic acid that causes vasorelaxation. However, investigations of its role in biological systems have been limited by its chemical instability. We developed a stable agonist of 5,6-EET, 5-(pentadeca-3(Z),6(Z),9(Z)-trienyloxy)pentanoic acid (PTPA), in which the 5,6-epoxide was replaced with a 5-ether. PTPA obviates chemical and enzymatic hydrolysis. In bovine coronary artery rings precontracted with U46619, PTPA (1 nmol/L to 10 micromol/L) induced concentration-dependent relaxations, with maximal relaxation of 86+/-5% and EC50 of 1 micromol/L. The relaxations were inhibited by the cyclooxygenase inhibitor indomethacin (10 micromol/L; max relaxation 43+/-9%); the ATP-sensitive K+ channel inhibitor glybenclamide (10 micromol/L; max relaxation 49+/-6%); and the large conductance calcium-activated K+ channel inhibitor iberiotoxin (100 nmol/L; max relaxation 38+/-6%) and abolished by the combination of iberiotoxin with indomethacin or glybenclamide or increasing extracellular K+ to 20 mmol/L. Whole-cell outward K+ current was increased nearly 6-fold by PTPA (10 micromol/L), which was also blocked by iberiotoxin. Additionally, we synthesized 5-(pentadeca-6(Z),9(Z)-dienyloxy)pentanoic acid and 5-(pentadeca-3(Z),9(Z)-dienyloxy)pentanoic acid (PDPA), PTPA analogs that lack the 8,9 or 11,12 double bonds of arachidonic acid and therefore are not substrates for cyclooxygenase. The PDPAs caused concentration-dependent relaxations (max relaxations 46+/-13% and 52+/-7%, respectively; EC50 1micromol/L), which were not altered by glybenclamide but blocked by iberiotoxin. These studies suggested that PTPA induces relaxation through 2 mechanisms: (1) cyclooxygenase-dependent metabolism to 5-ether-containing prostaglandins that activate ATP-sensitive K+ channels and (2) activation of smooth muscle large conductance calcium-activated K+ channels. PDPAs only activate large conductance calcium-activated K+ channels.
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors.forename: Wenqi
authors.initials: W
authors.lastname: Yang
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Gauthier
authors.forename: L Manmohan
authors.initials: LM
authors.lastname: Reddy
authors.forename: Bhavani
authors.initials: B
authors.lastname: Sangras
authors.forename: Kamalesh K
authors.initials: KK
authors.lastname: Sharma
authors.forename: Kasem
authors.initials: K
authors.lastname: Nithipatikom
authors.forename: John R
authors.initials: JR
authors.lastname: Falck
authors.forename: William B
authors.initials: WB
authors.lastname: Campbell
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000819:agonists / Q000031:analogs & derivatives*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D003331:Coronary Vessels / Q000187:drug effects* / Q000502:physiology*; D004355:Drug Stability; D004553:Electric Conductivity; D005905:Glyburide / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010421:Pentanoic Acids / Q000737:chemistry / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000502:physiology; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
chemical_list: C504896:5-(pentadeca-3,6,9-trienyloxy)pentanoic acid; D010421:Pentanoic Acids; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; C064719:iberiotoxin; C040776:5,6-epoxy-8,11,14-eicosatrienoic acid; D000255:Adenosine Triphosphate; D011451:Prostaglandin-Endoperoxide Synthases; D015126:8,11,14-Eicosatrienoic Acid; D005905:Glyburide; D007213:Indomethacin