2-Arachidonoylglycerol, an endogenous cannabinoid receptor ligand, enhances the adhesion of HL-60 cells differentiated into macrophage-like cells and human peripheral blood monocytes

2-Arachidonoylglycerol (2-AG), an endogenous cannabionoid receptor (CB1 and CB2) ligand, enhanced the adhesion of HL-60 cells differentiated into macrophage-like cells to fibronectin and the vascular cell adhesion molecule-1. The CB2 receptor, Gi/Go, intracellular free Ca(2+) and phosphatidylinositol 3-kinase were shown to be involved in 2-AG-induced augmented cell adhesion. 2-AG also enhanced the adhesion of human monocytic leukemia U937 cells and peripheral blood monocytes. These results strongly suggest that 2-AG plays some essential role in inflammatory reactions and immune responses by inducing robust adhesion to extracellular matrix proteins and adhesion molecules in several types of inflammatory cells and immune-competent cells.