Human Platelets and Polymorphonuclear Leukocytes Synthesize Oxygenated Derivatives of Arachidonylethanolamide (Anandamide): Their Affinities for Cannabinoid Receptors and Pathways of Inactivation
作者:William S. Edgemond、Cecilia J. Hillard、J. R. Falck、Christopher S. Kearn、William B. Campbell
DOI:10.1124/mol.54.1.180
日期:1998.7.1
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.
花生四烯醇胺(AEA),即大麻素受体的假定内源性配体,已被证明是体外脂氧化酶的底物。本研究的一个目标是确定富含脂氧化酶的细胞是否代谢 AEA。[14C]AEA 被人体多形核白细胞(PMNs)转化为两种主要代谢物,它们与合成的前列腺素 E2(HAEA)共迁移。人血小板将 [14C]AEA 转化为 12(S)-HAEA。12(S)-HAEA 与 AEA 具有大致相同的亲和力,结合 CB1 和 CB2 受体。12(R)-HAEA,PMNs 不产生,对 CB1 受体的亲和力是 12(S)-HAEA 的两倍,对 CB2 受体的亲和力是 10 倍。15-HAEA 对两种受体的亲和力均低于 AEA,其 Ki 值分别为 738 和 >1000 nm,适用于 CB1 和 CB2 受体。在 AEA 的 C20 位添加羟基后,生成的配体对 CB1 受体的亲和力与 AEA 相同,但对 CB2 受体的亲和力降低了 4 倍。12(S)-HAEA 和 15-HAEA 是 AEA 酰胺水解酶的不良底物,并不与 AEA 摄取载体结合。总之,在 AEA 的花生四烯酸主链的 C12 位添加羟基不影响与 CB 受体的结合,但很可能增加其半衰期。在其他位置添加羟基会影响配体对 CB 受体的亲和力;羟基的位置和剩余双键的构型都是亲和力的决定因素。