Human platelets and polymorphonuclear leukocytes synthesize oxygenated derivatives of arachidonylethanolamide (anandamide): Their affinities for cannabinoid receptors and pathways of inactivation

William S. Edgemond, Cecilia J. Hillard, J R Falck, Christopher S. Kearn, William B. Campbell

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Abstract

Arachidonylethanolamide (AEA), the putative endogenous ligand of the cannabinoid receptor, has been shown to be a substrate for lipoxygenase enzymes in vitro. One goal of this study was to determine whether lipoxygenase-rich cells metabolize AEA. [14C]AEA was converted by human polymorphonuclear leukocytes (PMNs) to two major metabolites that comigrated with synthetic 12(S)- and 15(S)-hydroxy-arachidonylethanolamide (HAEA). Human platelets convert [14C]AEA to 12(S)-HAEA. 12(S)-HAEA binds to both CB1 and CB2 receptors with approximately the same affinity as AEA. 12(R)-HAEA, which is not produced by PMNs, has 2-fold lower affinity for the CB1 receptor and 10-fold lower affinity for the CB2 receptor than 12(S)-HAEA. 15-HAEA has a lower affinity than AEA for both receptors, with K(i) values of 738 and >1000 nM for CB1 and CB2 receptors, respectively. The addition of a hydroxyl group at C20 of AEA resulted in a ligand with the same affinity for the CB1 receptor but a 4-fold lower affinity for the CB2 receptor than AEA. 12(S)- HAEA and 15-HAEA are poor substrates for AEA amidohydrolase and do not bind to the AEA uptake carrier. In conclusion the addition of a hydroxyl group at C12 of the arachidonate backbone of AEA does not affect binding to CB receptors but is likely to increase its half-life. The addition of hydroxyl groups at other positions affects ligand affinity for CB receptors; both the position of the hydroxyl group and the configuration of the remaining double bonds are determinants of affinity.

Original languageEnglish (US)
Pages (from-to)180-188
Number of pages9
JournalMolecular Pharmacology
Volume54
Issue number1
DOIs
StatePublished - Jul 1998

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ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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