title: Purinergic P2Y2 receptors mediate rapid Ca(2+) mobilization, membrane hyperpolarization and nitric oxide production in human vascular endothelial cells.
abstract: In blood vessels, stimulation of the vascular endothelium by the Ca(2+)-mobilizing agonist ATP initiates a number of cellular events that cause relaxation of the adjacent smooth muscle layer. Although vascular endothelial cells are reported to express several subtypes of purinergic P2Y and P2X receptors, the major isoform(s) responsible for the ATP-induced generation of vasorelaxant signals in human endothelium has not been well characterized. To address this issue, ATP-evoked changes in cytosolic Ca(2+), membrane potential and acute nitric oxide production were measured in isolated human umbilical vein endothelial cells (HUVECs) and profiled using established P2X and P2Y receptor probes. Whereas selective P2X agonist (i.e. α,β-methyl ATP) and antagonists (i.e. TNP-ATP and PPADS) could neither mimic nor block the observed ATP-evoked cellular responses, the specific P2Y receptor agonist UTP functionally reproduced all the ATP-stimulated effects. Furthermore, both ATP and UTP induced intracellular Ca(2+) mobilization with comparable EC(50) values (i.e. 1-3μM). Collectively, these functional and pharmacological profiles strongly suggest that ATP acts primarily via a P2Y2 receptor sub-type in human endothelial cells. In support, P2Y2 receptor mRNA and protein were readily detected in isolated HUVECs, and siRNA-mediated knockdown of endogenous P2Y2 receptor protein significantly blunted the cytosolic Ca(2+) elevations in response to ATP and UTP, but did not affect the histamine-evoked response. In summary, these results identify the P2Y2 isoform as the major purinergic receptor in human vascular endothelial cells that mediates the cellular actions of ATP linked to vasorelaxation.
authors.affiliation: Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary and Smooth Muscle Research Group, Libin Cardiovascular Institute, Calgary, Alberta, Canada T2N 4N1.
authors.forename: Abdul
authors.initials: A
authors.lastname: Raqeeb
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Sheng
authors.forename: Ni
authors.initials: N
authors.lastname: Ao
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Braun
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000814:Aniline Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D042783:Endothelial Cells / Q000378:metabolism* / Q000502:physiology; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008564:Membrane Potentials; D009569:Nitric Oxide / Q000378:metabolism*; D058912:Purinergic P2Y Receptor Agonists / Q000737:chemistry / Q000494:pharmacology; D058921:Purinergic P2Y Receptor Antagonists / Q000737:chemistry / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D058473:Receptors, Purinergic P2Y2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014544:Uridine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D014966:Xanthenes / Q000494:pharmacology
chemical_list: D000814:Aniline Compounds; C409648:Fluo 4; D058912:Purinergic P2Y Receptor Agonists; D058921:Purinergic P2Y Receptor Antagonists; D034741:RNA, Small Interfering; D058473:Receptors, Purinergic P2Y2; D014966:Xanthenes; D009569:Nitric Oxide; D000255:Adenosine Triphosphate; D002118:Calcium; D014544:Uridine Triphosphate