Ibuprofen inhibits rat brain deamidation of anandamide at pharmacologically relevant concentrations. Mode of inhibition and structure-activity relationship.

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 Km value of 0.8 microM and a Vmax value of 1.73 nmol . (mg protein)-1 . min-1. The deamidation of 2 microM -3H-anandamide was inhibited by phenylmethylsulfonyl fluoride and arachidonyl trifluoromethyl ketone with IC50 values of 3.7 and 0.23 microM, respectively. Ibuprofen inhibited anandamide deamidation in a mixed fashion, with Ki and K'i values of 82 and 1420 microM. At an anandamide concentration of 2 microM, the IC50 values (in microM) of a series of compounds related in structure to ibuprofen were as follows: suprofen, 170; ibuprofen, 270; fenoprofen, 480; naproxen, 550; ketoprofen, 650; diclofenac, approximately 1000. Sulindac produced 27% inhibition at a concentration of 1000 microM, 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.