Human platelets bind and degrade 2-arachidonoylglycerol, which activates these cells through a cannabinoid receptor.
The endocannabinoid 2-arachidonoylglycerol (2-Delta(4)Ach-Gro) activates human platelets in platelet-rich plasma at physiological concentrations. The activation was inhibited by selective antagonists of CB(1) and CB(2) cannabinoid receptors, but not by acetylsalicylic acid. Human platelets can metabolize 2-Delta(4)Ach-Gro by internalization through a high affinity transporter (K(m) = 300 +/- 30 nM, V(max) = 10 +/- 1 pmol.min(-1).mg protein(-1)), followed by hydrolysis by a fatty acid amide hydrolase (K(m) = 8 +/- 1 microM, V(max) = 400 +/- 50 pmol.min(-1).mg protein(-1)). The anandamide transport inhibitor AM404, and anandamide itself, were ineffective on 2-Delta(4)Ach-Gro uptake by platelets, whereas anandamide competitively inhibited 2-Delta(4)Ach-Gro hydrolysis (inhibition constant = 10 +/- 1 microM). Platelet activation by 2-Delta(4)Ach-Gro was paralleled by an increase of intracellular calcium and inositol-1,4,5-trisphosphate, and by a decrease of cyclic AMP. Moreover, treatment of preloaded platelet-rich plasma with 2-Delta(4)Ach-Gro induced an approximately threefold increase in [(3)H]2-Delta(4)Ach-Gro release, according to a CB receptor-dependent mechanism. On the other hand, ADP and collagen counteracted the activation of platelets by 2-Delta(4)Ach-Gro, whereas 5-hydroxytryptamine (serotonin) enhanced and extended its effects. Remarkably, ADP and collagen also reduced [(3)H]2-Delta(4)Ach-Gro release from 2-Delta(4)Ach-Gro-activated platelets, whereas 5-hydroxytryptamine further increased it. These findings suggest a so far unnoticed interplay between the peripheral endocannabinoid system and physiological platelet agonists.
MacCarrone
M
M
Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, Italy.
Bari
M
M
Menichelli
A
A
Giuliani
E
E
Del Principe
D
D
Finazzi-Agrò
A
A
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000581:Amidohydrolases / Q000493:pharmacokinetics; D001095:Arachidonic Acids / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D001692:Biological Transport; D001792:Blood Platelets / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D001892:Camphanes / Q000494:pharmacology; D063385:Cannabinoid Receptor Modulators; D003094:Collagen / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D063388:Endocannabinoids; D005989:Glycerides / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007700:Kinetics; D010880:Piperidines / Q000494:pharmacology; D015539:Platelet Activation; D053284:Polyunsaturated Alkamides; D011720:Pyrazoles / Q000494:pharmacology; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000077285:Rimonabant; D012701:Serotonin / Q000494:pharmacology; D013997:Time Factors; D000099252:Fatty Acid Amide Hydrolases
D000244:Adenosine Diphosphate; D000581:Amidohydrolases; D001095:Arachidonic Acids; D001241:Aspirin; D002121:Calcium Channel Blockers; D001892:Camphanes; D063385:Cannabinoid Receptor Modulators; D003094:Collagen; D000242:Cyclic AMP; D063388:Endocannabinoids; D005989:Glycerides; D015544:Inositol 1,4,5-Trisphosphate; D010880:Piperidines; D053284:Polyunsaturated Alkamides; D011720:Pyrazoles; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D000077285:Rimonabant; D012701:Serotonin; D000099252:Fatty Acid Amide Hydrolases; C110630:SR 144528; C094503:glyceryl 2-arachidonate; C078814:anandamide; C107594:N-(4-hydroxyphenyl)arachidonylamide