Diguanosine pentaphosphate: an endogenous activator of Rho-kinase possibly involved in blood pressure regulation.
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.
Tölle
Markus
M
Charite - Campus Benjamin Franklin, Department of Nephrology, Medizinische Klinik IV, Berlin, Germany.
Giebing
Günter
G
Tietge
Uwe Jw
UJ
Jankowski
Joachim
J
Jankowski
Vera
V
Henning
Lars
L
Hörl
Matthias P
MP
Weiss
Wolfgang
W
Zidek
Walter
W
van der Giet
Markus
M
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
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