Vol. 283, Issue 2, 729-734, 1997

Ibuprofen Inhibits Rat Brain Deamidation of Anandamide at Pharmacologically Relevant Concentrations. Mode of Inhibition and Structure-Activity Relationship¹

Christopher J. Fowler, Gunnar Tiger and Anders Stenström

Department of Pharmacology, Umeå University, Umeå, Sweden

The ability of rat brain (minus cerebellum) homogenates to deamidate arachidonyl ethanolamide (anandamide) was determined with a custom-synthesized substrate, arachidonyl ethanolamide-[1-³H] ([³H]anandamide). Conditions whereby initial velocities were measured were established. The homogenates deamidated anandamide with a K_m value of 0.8 µM and a V_max value of 1.73 nmol · (mg protein)¹ · min¹. The deamidation of 2 µM [³H]anandamide was inhibited by phenylmethylsulfonyl fluoride and arachidonyl trifluoromethyl ketone with IC₅₀ values of 3.7 and 0.23 µM, respectively. Ibuprofen inhibited anandamide deamidation in a mixed fashion, with K_i and K_i values of 82 and 1420 µM. At an anandamide concentration of 2 µM, the IC₅₀ values (in µM) of a series of compounds related in structure to ibuprofen were as follows: suprofen, 170; ibuprofen, 270; fenoprofen, 480; naproxen, 550; ketoprofen, 650; diclofenac, ~1000. Sulindac produced 27% inhibition at a concentration of 1000 µM, whereas isobutyric acid, hydrocinnamic acid, acetylsalicylic acid and acetaminophen were essentially inactive at concentrations  1 mM. We conclude that ibuprofen inhibits anandamide deamidation at pharmacologically relevant concentrations and that there is some specificity to the inhibition produced by ibuprofen and suprofen.