Differential regulation of human platelet responses by cGMP inhibited and stimulated cAMP phosphodiesterases.
Platelets contain two cAMP phosphodiesterases (PDEs) which regulate intracellular cAMP levels, cGMP-inhibited cAMP PDE (PDE3A) and cGMP-stimulated PDE (PDE2A). Using the PDE3 inhibitor, milrinone and the PDE2 inhibitor, erythro-9-(2-hydroxyl-3-nonyl)adenine (EHNA), we have explored the contribution of each PDE to the regulation of platelet function. Inhibition of PDE2 resulted in higher levels of intracellular cAMP than inhibition of PDE3A suggesting this PDE may be the more important regulator of cAMP in human platelets. However, a concentration-dependent inhibition of agonist-induced aggregation was observed with milrinone while little effect was seen with EHNA. In addition, we observed a concentration-dependent inhibition in the increase of intracellular Ca2+ with PDE3 inhibition and significantly less with PDE2 inhibition. PDE3 inhibition also resulted in a concentration-dependent increase in cAMP-mediated phosphorylation of the vasodilator-stimulated phospho-protein (VASP) whereas there was no significant increase with PDE2 inhibition. In each of these experiments, synergism was noted with the combination of milrinone and EHNA. These results suggest that cAMP pools may be localized and the various PDEs regulate specific pools. These data also suggest that inhibitors of PDE3A may be more effective antiplatelet agents.
Manns
J M
JM
Temple University School of Medicine, Sol Sherry Thrombosis Research Center, Philadelphia, PA 19140, USA.
Brenna
K J
KJ
Colman
R W
RW
Sheth
S B
SB
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000502:physiology*; D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000328:Adult; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D002118:Calcium / Q000097:blood; D020013:Calcium Signaling / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology*; D006152:Cyclic GMP / Q000494:pharmacology; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008840:Microfilament Proteins; D020105:Milrinone / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000502:physiology*; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology*; D000098662:Vasodilator-Stimulated Phosphoprotein
D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D008840:Microfilament Proteins; D010750:Phosphoproteins; D010975:Platelet Aggregation Inhibitors; D000098662:Vasodilator-Stimulated Phosphoprotein; C010192:9-(2-hydroxy-3-nonyl)adenine; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; C517275:PDE2A protein, human; C517287:PDE3A protein, human; D006152:Cyclic GMP; D000225:Adenine; D020105:Milrinone; D002118:Calcium