title: Vascular hepoxilin and trioxilins mediate vasorelaxation through TP receptor inhibition in mouse arteries.
abstract: 12/15-lipoxygenase (12/15-LO) metabolizes arachidonic acid (AA) into several vasoactive eicosanoids. In mouse arteries, we previously characterized the enzyme's 15-LO metabolites 12(S)-hydroxyeicosatetraenoic acid (HETE), 15-HETE, hydroxyepoxyeicosatrienoic acids (HEETAs) and 11,12,15-trihydroxyeicosatrienoic acids (11,12,15-THETAs) as endothelium-derived relaxing factors. However, the observed 12-LO metabolites remained uncharacterized. The purpose of this study was to determine the structure and biological functions of eicosanoids generated by the enzyme's 12-LO activity.
  
  
  
  Metabolites extracted from aortas of C57BL/6 male mice were separated using a series of reverse and normal phase chromatographic steps and identified as hepoxilin A3, trioxilin A3and trioxilin C3by mass spectrometry. Activities of these natural compounds were tested on isometric tension and intracellular calcium release. The role of thromboxane (TP) receptor was determined in HEK293 cells overexpressing TPα receptor (TPα -HEK).
  
  
  
  All identified vascular 12-LO metabolites were biologically active. In mouse mesenteric arteries, trioxilin A3, C3and hepoxilin A3(3 μm) relaxed arteries constricted with the thromboxane mimetic, U46619-constricted arteries (maximum relaxations of 78.9 ± 3.2, 29.7 ± 4.6, 82.2 ± 5.0 and 88.0 ± 2.4% respectively), but not phenylephrine-constricted arteries. In TPα-HEK cells, trioxilin A3, C3and hepoxilin A3(10 μm) inhibited U46619 (10 nM)-induced increases in intracellular calcium by 53.0 ± 7.2%, 32.8 ± 5.0% and 37.9 ± 13.5% respectively. In contrast, trioxilin B3and hepoxilin B3were not synthesized in arteries and exhibited little biological activity.
  
  
  
  Trioxilin A3and C3and hepoxilin A3are endogenous vascular relaxing factors. They are not endothelium-derived hyperpolarizing factors but mediate vascular relaxation by inhibiting TP agonist-induced increases in intracellular calcium. Thus, they regulate vascular homeostasis by acting as endogenous TP antagonists.
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.|Faculty of Pharmacy, Silpakorn University, Nakorn Pathom, Thailand.
authors.forename: L
authors.initials: L
authors.lastname: Siangjong
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: D H
authors.initials: DH
authors.lastname: Goldman
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: T
authors.initials: T
authors.lastname: Kriska
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Gauthier
authors.affiliation: Department of Pharmacology, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Smyth
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: N
authors.initials: N
authors.lastname: Puli
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: G
authors.initials: G
authors.lastname: Kumar
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Falck
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: W B
authors.initials: WB
authors.lastname: Campbell
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D017482:Receptors, Thromboxane; D014665:Vasodilator Agents; C019121:8,11,12-trihydroxy-5,9,14-eicosatrienoic acid; C038243:8-hydroxy-11,12-epoxyeicosa-5,9,14-trienoic acid; D015126:8,11,14-Eicosatrienoic Acid
keywords: arachidonic acid; endothelium; lipoxygenase; smooth muscle; thromboxane A2 (TP) receptor; trioxilins