title: Diguanosine pentaphosphate: an endogenous activator of Rho-kinase possibly involved in blood pressure regulation.
abstract: OBJECTIVE
  Rho-kinase activity is increased in cardiovascular disease and in the pathophysiology of hypertension. Few endogenous factors are known that activate the Rho-kinase pathway. Stimulation of P2Y receptors activates the Rho-kinase pathway. Recently identified diguanosine pentaphosphate (Gp5G) possibly activates P2Y receptors. In this study, Gp5G was identified and quantified in human plasma. The influence of Gp5G on vascular tone was studied.
  
  
  METHODS
  Gp5G in human plasma was purified to homogeneity by several steps. Gp5G was quantified and identified by matrix-assisted laser desorption/ionization mass spectrometry and enzymatic analysis. The vasoactive effects of Gp5G were studied in the isolated perfused rat kidney and after intra-aortic application. Activation of Rho-kinase was measured using western blot analysis.
  
  
  RESULTS
  The plasma level of Gp5G in healthy donors is 9.47 +/- 4.97 nmol/l. Gp5G increases contractile responses induced by angiotensin II in a dose-dependent way [ED50 (-log mol) angiotensin II: 10.9 +/- 0.1; angiotensin II plus Gp5G (100 nmol/l): 11.5 +/- 0.1]. P2 receptor antagonists inhibited the Gp5G-induced increase in angiotensin II vasoconstriction. MRS2179, a selective P2Y1 receptor antagonist, had no effect on Gp5G-mediated angiotensin II potentiation. Rho-kinase inhibition by Y27632 abolished the Gp5G-induced increase of contractile responses to angiotensin II. Concentrations of 10 nmol/l Gp5G activated the translocation of RhoA from the cytosolic to the membranous fraction indicating the activation of Rho-kinase. The intra-aortic application of 100 pmol Gp5G significantly increased mean arterial blood pressure by 13.5 +/- 4.2 mmHg.
  
  
  CONCLUSIONS
  Gp5G is an endogenous activator of Rho-kinase, which might affect vascular tone control by Rho-kinase at physiological levels. Gp5G activates P2Y4&6 receptors, and might play a role in physiological and pathophysiological vascular tone control.
authors.affiliation: Charite - Campus Benjamin Franklin, Department of Nephrology, Medizinische Klinik IV, Berlin, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Tölle
authors.forename: Günter
authors.initials: G
authors.lastname: Giebing
authors.forename: Uwe Jw
authors.initials: UJ
authors.lastname: Tietge
authors.forename: Joachim
authors.initials: J
authors.lastname: Jankowski
authors.forename: Vera
authors.initials: V
authors.lastname: Jankowski
authors.forename: Lars
authors.initials: L
authors.lastname: Henning
authors.forename: Matthias P
authors.initials: MP
authors.lastname: Hörl
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Weiss
authors.forename: Walter
authors.initials: W
authors.lastname: Zidek
authors.forename: Markus
authors.initials: M
authors.lastname: van der Giet
mesh_terms: D000328:Adult; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D018929:Cell Culture Techniques; D015226:Dinucleoside Phosphates / Q000097:blood* / Q000494:pharmacology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000187:drug effects*; D007668:Kidney / Q000098:blood supply; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects*; D051381:Rats; D011921:Rats, Inbred WKY; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D054460:rho-Associated Kinases
chemical_list: D015226:Dinucleoside Phosphates; D047908:Intracellular Signaling Peptides and Proteins; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; C056829:diguanosine pentaphosphate; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases