title: Adenosine A1 receptors link to smooth muscle contraction via CYP4a, protein kinase C-α, and ERK1/2.
abstract: Adenosine A1 receptor (A1AR) activation contracts smooth muscle, although signaling mechanisms are not thoroughly understood. Activation of A1AR leads to metabolism of arachidonic acid, including the production of 20-hydroxyeicosatetraenoic acid (20-HETE) by cytochrome P4504a (CYP4a). The 20-HETE can activate protein kinase C-α (PKC-α), which crosstalks with extracellular signal-regulated kinase (ERK1/2) pathway. Both these pathways can regulate smooth muscle contraction, we tested the hypothesis that A1AR contracts smooth muscle through a pathway involving CYP4a, PKC-α, and ERK1/2. Experiments included isometric tension recordings of aortic contraction and Western blots of signaling molecules in wild type (WT) and A1AR knockout (A1KO) mice. Contraction to the A1-selective agonist 2-chloro-N cyclopentyladenosine (CCPA) was absent in A1KO mice aortae, indicating the contractile role of A1AR. Inhibition of CYP4a (HET0016) abolished 2-chloro-N cyclopentyladenosine-induced contraction in WT aortae, indicating a critical role for 20-HETE. Both WT and A1KO mice aortae contracted in response to exogenous 20-HETE. Inhibition of PKC-α (Gö6976) or ERK1/2 (PD98059) attenuated 20-HETE-induced contraction equally, suggesting that ERK1/2 is downstream of PKC-α. Contractions to exogenous 20-HETE were significantly less in A1KO mice; reduced protein levels of PKC-α, p-ERK1/2, and total ERK1/2 supported this observation. Our data indicate that A1AR mediates smooth muscle contraction via CYP4a and a PKC-α-ERK1/2 pathway.
authors.affiliation: Department of Physiology & Pharmacology, West Virginia University School of Medicine, Morgantown, WV 26506-9229, USA.
authors.forename: Swati S
authors.initials: SS
authors.lastname: Kunduri
authors.forename: S Jamal
authors.initials: SJ
authors.lastname: Mustafa
authors.forename: Dovenia S
authors.initials: DS
authors.lastname: Ponnoth
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Dick
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Nayeem
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D058907:Adenosine A1 Receptor Agonists / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002227:Carbazoles / Q000494:pharmacology; D042926:Cytochrome P-450 CYP4A / Q000037:antagonists & inhibitors / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology; D007537:Isometric Contraction / Q000187:drug effects; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D051571:Protein Kinase C-alpha / Q000502:physiology*; D043682:Receptor, Adenosine A1 / Q000187:drug effects / Q000502:physiology*
chemical_list: D058907:Adenosine A1 Receptor Agonists; D002227:Carbazoles; D004791:Enzyme Inhibitors; D005419:Flavonoids; D006893:Hydroxyeicosatetraenoic Acids; D043682:Receptor, Adenosine A1; C081021:Go 6976; C058394:2-chloro-N(6)cyclopentyladenosine; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D042926:Cytochrome P-450 CYP4A; D051571:Protein Kinase C-alpha; D000241:Adenosine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one