FATTY-ACID SULFONYL FLUORIDES INHIBIT ANANDAMIDE METABOLISM AND BIND TO THE CANNABINOID RECEPTOR

Arachidonoyl ethanolamide (anandamide) is an endogenous ligand for can nabinoid receptors (CB1, CB2) and a putative neurotransmitter. Phenylm ethylsulfonyl fluoride (PMSF) is an inhibitor of the enzyme (an amidas e) which hydrolyzes anandamide to arachidonic acid and ethanolamine. W e report here that fatty acid sulfonyl fluorides are potent inhibitors of anandamide metabolism. In order to investigate the SAR of these an andamide amidase inhibitors we tested a series of fatty acid (C12 to C 20) sulfonyl fluorides both as inhibitors of anandamide degradation an d as ligands for the central cannabinoid receptor (CB1). AM374 (palmit ylsulfonyl fluoride, C16) was approximately 20 times more potent than PMSF and 50 times more potent than arachidonyltrifluoromethyl ketone i n preventing the hydrolysis of anandamide in brain homogenates. AM374 was over a thousand-fold more effective than PMSF in inhibiting the am idase in cultured cells. The C12 to C18 sulfonyl fluoride analogs were equipotent as inhibitors of the amidase and the reverse reaction (the synthase) with nanomolar IC50 values. These compounds generally showe d decreasing affinity for the CB1 receptor as the chain length increas ed; thus, C12 sulfonylfluoride had an IC50 of 18 nM and C20 sulfonylfl uoride had an IC50 Of 78 mu M. The C14, C16, and C18 sulfonyl fluoride s showed high selectivity for the amidase over the CB1 receptor and th us are potentially useful selective anandamide amidase inhibitors. (C) 1997 Academic Press.