title: Adenylic dinucleotides produced by CD38 are negative endogenous modulators of platelet aggregation.
abstract: Diadenosine 5',5'''-P1,P2-diphosphate (Ap2A) is one of the adenylic dinucleotides stored in platelet granules. Along with proaggregant ADP, it is released upon platelet activation and is known to stimulate myocyte proliferation. We have previously demonstrated synthesis of Ap2A and of two isomers thereof, called P18 and P24, from their high pressure liquid chromatography retention time, by the ADP-ribosyl cyclase CD38 in mammalian cells. Here we show that Ap2A and its isomers are present in resting human platelets and are released during thrombin-induced platelet activation. The three adenylic dinucleotides were identified by high pressure liquid chromatography through a comparison with the retention times and the absorption spectra of purified standards. Ap2A, P18, and P24 had no direct effect on platelet aggregation, but they inhibited platelet aggregation induced by physiological agonists (thrombin, ADP, and collagen), with mean IC50 values ranging between 5 and 15 microm. Moreover, the three dinucleotides did not modify the intracellular calcium concentration in resting platelets, whereas they significantly reduced the thrombin-induced intracellular calcium increase. Through binding to the purinergic receptor P2Y11, exogenously applied Ap2A, P18, and P24 increased the intracellular cAMP concentration and stimulated platelet production of nitric oxide, the most important endogenous antiaggregant. The presence of Ap2A, P18, and P24 in resting platelets and their release during thrombin-induced platelet activation at concentrations equal to or higher than the respective IC50 value on platelet aggregation suggest a role of these dinucleotides as endogenous negative modulators of aggregation.
authors.affiliation: Department of Experimental Medicine, Section of Biochemistry and Center of Excellence for Biomedical Research, University of Genova, Viale Benedetto XV, 1 16132 Genova, Italy.
authors.forename: Mirko
authors.initials: M
authors.lastname: Magnone
authors.forename: Giovanna
authors.initials: G
authors.lastname: Basile
authors.forename: Debora
authors.initials: D
authors.lastname: Bruzzese
authors.forename: Lucrezia
authors.initials: L
authors.lastname: Guida
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Signorello
authors.forename: Madhu Parakkottil
authors.initials: MP
authors.lastname: Chothi
authors.forename: Santina
authors.initials: S
authors.lastname: Bruzzone
authors.forename: Enrico
authors.initials: E
authors.lastname: Millo
authors.forename: Ai-Dong
authors.initials: AD
authors.lastname: Qi
authors.forename: Robert A
authors.initials: RA
authors.lastname: Nicholas
authors.forename: Matthias U
authors.initials: MU
authors.lastname: Kassack
authors.forename: Giuliana
authors.initials: G
authors.lastname: Leoncini
authors.forename: Elena
authors.initials: E
authors.lastname: Zocchi
mesh_terms: D051997:ADP-ribosyl Cyclase 1 / Q000235:genetics / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D003094:Collagen / Q000494:pharmacology; D015226:Dinucleoside Phosphates / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D006490:Hemostatics / Q000494:pharmacology; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D032342:Muscle Cells / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D022142:Secretory Vesicles / Q000737:chemistry / Q000378:metabolism; D013237:Stereoisomerism; D013917:Thrombin / Q000494:pharmacology
chemical_list: D015226:Dinucleoside Phosphates; D006490:Hemostatics; D008562:Membrane Glycoproteins; D010975:Platelet Aggregation Inhibitors; C012276:diadenosine pyrophosphate; D000244:Adenosine Diphosphate; D003094:Collagen; C498154:CD38 protein, human; D051997:ADP-ribosyl Cyclase 1; D013917:Thrombin; D002118:Calcium