Prostaglandin E2 differentially modulates human platelet function through the prostanoid EP2 and EP3 receptors.
Activated human platelets synthesize prostaglandin (PG) E(2), although at lower rate than thromboxane A(2). PGE(2) acts through different receptors (EP1-4), but its role in human platelet function remains poorly characterized compared with thromboxane. We studied the effect of PGE(2) and its analogs on in vitro human platelet function and platelet and megakaryocyte EP expression. Platelets preincubated with PGE(2) or its analogs were stimulated with agonists and studied by optical aggregometry. Intraplatelet calcium mobilization was investigated by the stopped flow method; platelet vasodilator-stimulated phosphoprotein (VASP), P-selectin, and microaggregates were investigated by flow cytometry. PGE(2) at nanomolar concentrations dose-dependently increased the slope (velocity) of the secondary phase of ADP-induced platelet aggregation (EC(50), 25.6 ± 6 nM; E(max) of 100 ± 19% increase versus vehicle-treated), without affecting final maximal aggregation. PGE(2) stabilized reversible aggregation induced by low ADP concentrations (EC(50), 37.7 ± 9 nM). The EP3 agonists, 11-deoxy-16,16-dimethyl PGE(2) (11d-16dm PGE(2)) and sulprostone enhanced the secondary wave of ADP-induced aggregation, with EC(50) of 48.6 ± 10 nM (E(max), 252 ± 51%) and 5 ± 2 nM (E(max), 300 ± 35%), respectively. The EP2 agonist butaprost inhibited ADP-induced secondary phase slopes (IC(50), 40 ± 20 nM). EP4 stimulation had minor inhibitory effects. 11d-16dm PGE(2) alone raised intraplatelet Ca(2+) and enhanced ADP-induced Ca(2+) increase. 11d-16dm PGE(2) and 17-phenyltrinor PGE(2) (EP3 > EP1 agonist) at nanomolar concentrations counteracted PGE(1)-induced VASP phosphorylation and induced platelet microaggregates and P-selectin expression. EP1, EP2, EP3, and EP4 were expressed on human platelets and megakaryocytes. PGE(2) through different EPs finely modulates human platelet responsiveness. These findings should inform the rational selection of novel antithrombotic strategies based on EP modulation.
Department of Pharmacology, Catholic University School of Medicine, Largo Francesco Vito 1, 00168 Rome, Italy.
Giovanna
G
Petrucci
Raimondo
R
De Cristofaro
Sergio
S
Rutella
Franco O
FO
Ranelletti
Davide
D
Pocaterra
Stefano
S
Lancellotti
Aida
A
Habib
Carlo
C
Patrono
Bianca
B
Rocca
D000244:Adenosine Diphosphate / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000097:blood; D003094:Collagen / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008840:Microfilament Proteins / Q000097:blood; D019007:P-Selectin / Q000097:blood; D010750:Phosphoproteins / Q000097:blood; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects; D058307:Receptors, Prostaglandin E, EP2 Subtype / Q000502:physiology*; D058308:Receptors, Prostaglandin E, EP3 Subtype / Q000502:physiology*; D000098662:Vasodilator-Stimulated Phosphoprotein
D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D019007:P-Selectin; C545644:PTGER2 protein, human; C545647:PTGER3 protein, human; D010750:Phosphoproteins; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058308:Receptors, Prostaglandin E, EP3 Subtype; D000098662:Vasodilator-Stimulated Phosphoprotein; D000244:Adenosine Diphosphate; D003094:Collagen; D015232:Dinoprostone; D001241:Aspirin; D002118:Calcium