EFFECTS OF PUTATIVE CANNABINOID RECEPTOR LIGANDS, ANANDAMIDE AND 2-ARACHIDONYL-GLYCEROL, ON IMMUNE FUNCTION IN B6C3F1 MOUSE SPLENOCYTES

Anandamide (arachidonylethanolamide), isolated from the porcine brain, and 2-arachidonyl-glycerol (2-Ara-Gl), derived from the canine gut, a re two recently identified putative endogenous cannabinoid receptor li gands. Both ligands have been reported to possess binding affinity for cannabinoid receptor subtypes, CB1 and CB2. The objective of the pres ent studies was to investigate the immunomodulatory effects of both of these ligands in B6C3F1 mouse splenocytes. 2-Ara-Gl produced a marked and dose-related inhibition of the mixed lymphocyte response, anti-CD 3 mAb-induced T-cell proliferation and LPS-induced B-cell proliferatio n, whereas having no inhibitory effect on phorbol-12-myristate-13-acet ate/ionomycin-induced cell proliferation. Interestingly, the inhibitor y effects by 2-Ara-Gl on proliferation were at least dependent in part on cell density. At high cell density, 2-Ara-Gl enhanced lymphoprolif eration whereas exhibiting marked inhibitory activity at low cell dens ity. Similarly, in vitro primary immunoglobulin M antibody-forming cel l responses which are dependent on high cell density also were found t o be enhanced by 2-Ara-Gl. Conversely, anand-amide exhibited no inhibi tory effects on cell proliferative responses to stimulation by anti-CD 3 mAb, lipopolysaccharide or phorbol-12-myristate-13-acetate/ionomycin treatment. Anandamide also showed no effect on the in vitro sheep ery throcyte antibody-forming cell response. Although shown previously to markedly inhibit forskolin-stimulated cyclic AMP accumulation, 2-Ara-G l exhibited no effect on basal adenylate cyclase activity in splenocyt es. Additionally, anandamide showed negligible inhibitory effects at e xtremely high concentrations on forskolin-stimulated adenylate cyclase activity and no effect on basal adenylate cyclase activity in splenoc ytes. Taken together, these results demonstrated biological activity i n mouse splenocytes for 2-Ara-Gl, a putative endogenous cannabinoid re ceptor ligand.