title: CYP-epoxygenases contribute to A2A receptor-mediated aortic relaxation via sarcolemmal KATP channels.
abstract: Previously, we have shown that A(2A) adenosine receptor (A(2A)AR) mediates aortic relaxation via cytochrome P-450 (CYP)-epoxygenases. However, the signaling mechanism is not understood properly. We hypothesized that ATP-sensitive K(+) (K(ATP)) channels play an important role in A(2A)AR-mediated relaxation. Organ bath and Western blot experiments were done using isolated aorta from A(2A)KO and corresponding wild-type (WT) mice. Aortic rings from WT and A(2A) knockout (KO) mice were precontracted with submaximal dose of phenylephrine (PE, 10(-6) M), and concentration-response curves for pinacidil, cromakalim (nonselective K(ATP) openers), and diazoxide (mitochondrial K(ATP) opener) were obtained. Diazoxide did not have any relaxation effect on PE-precontracted tissues, whereas relaxation to pinacidil (48.09 ± 5.23% in WT vs. 25.41 ± 2.73% in A(2A)KO; P < 0.05) and cromakalim (51.19 ± 2.05% in WT vs. 38.50 ± 2.26% in A(2A)KO; P < 0.05) was higher in WT than A(2A)KO aorta. This suggested the involvement of sarcolemmal rather than mitochondrial K(ATP) channels. Endothelium removal, treatment with SCH 58651 (A(2A)AR antagonist; 10(-6) M), N(G)-nitro-l-arginine methyl ester (l-NAME, nitric oxide synthase inhibitor) and methylsulfonyl-propargyloxyphenylhexanamide (MS-PPOH, CYP-epoxygenases inhibitor; 10(-5) M) significantly reduced pinacidil-induced relaxation in WT compared with controls, whereas these treatments did not have any effect in A(2A)KO aorta. Glibenclamide (K(ATP) channel inhibitor, 10(-5) M) blocked 2-p-(2-carboxyethyl)phenethylamino-5'N-ethylcarboxamido adenosine hydrochloride (CGS 21680, A(2A)AR agonist)-induced relaxation in WT and changed 5'-N-ethylcarboxamide (NECA) (nonselective adenosine analog)-induced response to higher contraction in WT and A(2A)KO. 5-Hydroxydecanoate (5-HD, mitochondrial K(ATP) channel inhibitor, 10(-4) M) had no effect on CGS 21680-mediated response in WT aorta. Our data suggest that A(2A)AR-mediated vasorelaxation occurs through opening of sarcolemmal K(ATP) channels via CYP-epoxygenases and possibly, nitric oxide, contributing to pinacidil-induced responses.
authors.affiliation: Dept of Physiology and Pharmacology, Center for Cardiovascular and Respiratory Sciences, West Virginia Univ., Morgantown, WV 26506, USA.
authors.forename: Dovenia S
authors.initials: DS
authors.lastname: Ponnoth
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Nayeem
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Tilley
authors.forename: Catherine
authors.initials: C
authors.lastname: Ledent
authors.forename: S
authors.initials: S
authors.lastname: Jamal Mustafa
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000429:Alcohol Oxidoreductases / Q000502:physiology*; D000818:Animals; D019806:Cromakalim; D003652:Decanoic Acids / Q000494:pharmacology; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D006880:Hydroxy Acids / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010627:Phenethylamines / Q000494:pharmacology; D020110:Pinacidil; D043705:Receptor, Adenosine A2A / Q000378:metabolism*; D012508:Sarcolemma / Q000502:physiology*
chemical_list: D003652:Decanoic Acids; D006880:Hydroxy Acids; D010627:Phenethylamines; D043705:Receptor, Adenosine A2A; D019806:Cromakalim; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); C052853:5-hydroxydecanoic acid; D020110:Pinacidil; D010088:Oxidoreductases; D000429:Alcohol Oxidoreductases; C082646:leukotriene B4 12-hydroxydehydrogenase; D000241:Adenosine; D005905:Glyburide