Baldassarri S, Bertoni A, Bagarotti A, Sarasso C, Zanfa M, Catani MV, Avigliano L, Maccarrone M, Torti M, Sinigaglia F. The endocannabinoid 2-arachidonoylglycerol activates human platelets through non-CB1/CB2 receptors.
J Thromb Haemost 2008;
6:1772-9. [PMID:
18647220 DOI:
10.1111/j.1538-7836.2008.03093.x]
[Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
BACKGROUND
The endocannabinoid 2-arachidonoylglycerol (2-AG) is an endogenous lipid that acts through the activation of G-protein-coupled cannabinoid receptors and plays essential roles in many physiological contexts. In the cardiovascular system 2-AG is generated by both activated endothelial cells and platelets, and participates in the regulation of inflammation and thrombosis. Although human platelets actively metabolize endocannabinoids, 2-AG also binds to platelet surface and leads to cell activation.
OBJECTIVE
To investigate the biological consequence of 2-AG interactions with human platelets and to clarify the role of cannabinoid receptors.
METHODS
Gel-filtered platelets were stimulated with 2-AG in the presence or absence of various inhibitors. Platelet aggregation and secretion were measured in a lumiaggregometer. Calcium ion movements were measured in FURA-2 loaded platelets. Thromboxane A(2) (TxA(2)) generation was evaluated as Thromboxane B(2) accumulation with a commercial EIA assay.
RESULTS
2-AG induced platelet shape change, aggregation and secretion with a dose-dependent mechanism that required engagement of platelet TxA(2) receptors. 2-AG caused also cytosolic calcium increase; however, it was totally dependent on availability of TxA(2). Indeed 2-AG was able to induce a robust generation of TxA(2) through the cyclooxygenase pathway. Treatment of platelets with inhibitors of monoacylglycerol lipase and fatty acid amide hydrolase did not affect the activation induced by 2-AG. Moreover, neither CB(1) and CB(2) proteins nor CB(1)/CB(2) mRNAs were detected in platelets.
CONCLUSIONS
2-AG can be considered a new physiologic platelet agonist able to induce full platelet activation and aggregation with a non-CB(1)/CB(2) receptor-mediated mechanism.
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