title: Vasodilation by the calcium-mobilizing messenger cyclic ADP-ribose.
abstract: In artery smooth muscle, adenylyl cyclase-coupled receptors such as beta-adrenoceptors evoke Ca(2+) signals, which open Ca(2+)-activated potassium (BK(Ca)) channels in the plasma membrane. Thus, blood pressure may be lowered, in part, through vasodilation due to membrane hyperpolarization. The Ca(2+) signal is evoked via ryanodine receptors (RyRs) in sarcoplasmic reticulum proximal to the plasma membrane. We show here that cyclic adenosine diphosphate-ribose (cADPR), by activating RyRs, mediates, in part, hyperpolarization and vasodilation by beta-adrenoceptors. Thus, intracellular dialysis of cADPR increased the cytoplasmic Ca(2+) concentration proximal to the plasma membrane in isolated arterial smooth muscle cells and induced a concomitant membrane hyperpolarization. Smooth muscle hyperpolarization mediated by cADPR, by beta-adrenoceptors, and by cAMP, respectively, was abolished by chelating intracellular Ca(2+) and by blocking RyRs, cADPR, and BK(Ca) channels with ryanodine, 8-amino-cADPR, and iberiotoxin, respectively. The cAMP-dependent protein kinase A antagonist N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide hydrochloride (H89) blocked hyperpolarization by isoprenaline and cAMP, respectively, but not hyperpolarization by cADPR. Thus, cADPR acts as a downstream element in this signaling cascade. Importantly, antagonists of cADPR and BK(Ca) channels, respectively, inhibited beta-adrenoreceptor-induced artery dilation. We conclude, therefore, that relaxation of arterial smooth muscle by adenylyl cyclase-coupled receptors results, in part, from a cAMP-dependent and protein kinase A-dependent increase in cADPR synthesis, and subsequent activation of sarcoplasmic reticulum Ca(2+) release via RyRs, which leads to activation of BK(Ca) channels and membrane hyperpolarization.
authors.affiliation: Division of Biomedical Sciences, School of Biology, Bute Building, University of St Andrews, St Andrews, Fife, KY16 9TS, United Kingdom.
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Boittin
authors.forename: Michelle
authors.initials: M
authors.lastname: Dipp
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Kinnear
authors.forename: Antony
authors.initials: A
authors.lastname: Galione
authors.forename: A Mark
authors.initials: AM
authors.lastname: Evans
mesh_terms: D000818:Animals; D001158:Arteries / Q000166:cytology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D036563:Cyclic ADP-Ribose / Q000031:analogs & derivatives* / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013449:Sulfonamides; D013997:Time Factors; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D007546:Isoquinolines; D010455:Peptides; D015221:Potassium Channels; D019837:Ryanodine Receptor Calcium Release Channel; D013449:Sulfonamides; D014665:Vasodilator Agents; D036563:Cyclic ADP-Ribose; C082175:8-aminoadenosine cyclic 3',5'-(hydrogen phosphate) 5'-ribofuranosyl ester; D012433:Ryanodine; C064719:iberiotoxin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium