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Metabolism of 2-acylglycerol in rabbit and human platelets. Involvement of monoacylglycerol lipase and fatty acid amide hydrolase.
MedLine Citation:
PMID:  19811221     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
The endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide (N-arachidonoylethanolamine, AEA) are produced by neurons and other cells, including platelets, in a stimulus-dependent manner and act as signaling molecules; they are then inactivated through transport into cells followed by enzymatic degradation. A number of studies showed that monoacylglycerol lipase (MAGL) plays an important role in the degradation of 2-AG. In this study we investigated the enzymatic degradation of 2-acylglycerols in rabbit platelets and we characterized the responsible enzyme(s). [(3)H]2-AG and [(3)H]2-oleoylglycerol (2-OG) were both metabolized to [(3)H]glycerol and the respective fatty acid in a time and protein concentration-dependent manner, apparently by the action of MAGL activity. In the presence of the specific fatty acid amide hydrolase (FAAH) inhibitors URB597 and AM374, though, 2-OG hydrolysis was inhibited up to 55% in a concentration-dependent manner (IC(50) = 129.8 nM and 20.9 nM respectively). These results indicate the involvement of both MAGL and FAAH on 2-acylglycerol hydrolysis. MAGL was further characterized in the presence of URB597 and it was found that 2-monoacylglycerols were hydrolyzed in a time, pH and protein concentration-dependent manner and hydrolysis followed Michaelis-Menten kinetics, with an apparent K(M) of 0.11 microM and V(max) of 1.32 nmol/min*mg protein. Subcellular fractionation of platelet homogenate showed that MAGL activity was present in both the cytosolic and membrane fractions. In conclusion, the endocannabinoid 2-AG, as well as other 2-acylglycerols, are substrates of both FAAH and MAGL; the latter was characterized for the first time in platelets. In human platelets, under the same experimental conditions, the hydrolysis of 2-acylglycerols was higher and MAGL activity showed a different sensitivity against the inhibitors mentioned above. Finally, immunoblot analysis revealed the presence of MAGL, both in rabbit and human platelets, with a molecular mass of approximately 33 kDa.
Authors:
Eleni Gkini; Dimitris Anagnostopoulos; Mary Mavri-Vavayianni; Athanasia Siafaka-Kapadai
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Platelets     Volume:  20     ISSN:  1369-1635     ISO Abbreviation:  Platelets     Publication Date:  2009 Sep 
Date Detail:
Created Date:  2009-10-08     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9208117     Medline TA:  Platelets     Country:  England    
Other Details:
Languages:  eng     Pagination:  376-85     Citation Subset:  IM    
Affiliation:
Department of Chemistry, University of Athens, Panepistimioupolis, 15771 Athens, Greece.
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