TY - JOUR T1 - Human Platelets and Polymorphonuclear Leukocytes Synthesize Oxygenated Derivatives of Arachidonylethanolamide (Anandamide): Their Affinities for Cannabinoid Receptors and Pathways of Inactivation JF - Molecular Pharmacology JO - Mol Pharmacol SP - 180 LP - 188 DO - 10.1124/mol.54.1.180 VL - 54 IS - 1 AU - William S. Edgemond AU - Cecilia J. Hillard AU - J. R. Falck AU - Christopher S. Kearn AU - William B. Campbell Y1 - 1998/07/01 UR - http://molpharm.aspetjournals.org/content/54/1/180.abstract N2 - 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. ER -