n-stearoyl-dopamine and arachidonyl-dopamine

Sulfation of N-acyl dopamines has been shown for the first time in cytosolic fractions of rat liver and nervous system. Sulfation of dopamine amides of docosahexaenoic and oleic acids occurred in all tissues studied, N-arachidonoyl dopamine was sulfated in the liver and spinal cord, and N-stearoyl dopamine was sulfated only in the liver. Depending on the substrate and tissue, the sulfation activity varied from 0.5 to 3.5 nmol/min per mg total protein. Kinetic parameters of N-docosahexaenoyl dopamine sulfation in the brain were determined. The findings characterize the sulfation system as the most productive metabolic pathway of N-acyl dopamines, but the role of this system in the body is unclear because of high K(m) value.

Topics: Animals; Arachidonic Acids; Arylsulfotransferase; Brain; Cytosol; Dopamine; Fatty Acids; Kinetics; Liver; Rats; Rats, Wistar; Spectrometry, Mass, Electrospray Ionization; Spectrophotometry; Spinal Cord; Stearates; Substrate Specificity

Four long-chain, linear fatty acid dopamides (N-acyldopamines) have been identified in nervous bovine and rat tissues. Two unsaturated members of this family of lipids, N-arachidonoyl-dopamine (NADA) and N-oleoyl-dopamine, were shown to potently activate the transient receptor potential channel type V1 (TRPV1), also known as the vanilloid receptor type 1 for capsaicin. However, the other two congeners, N-palmitoyl- and N-stearoyl-dopamine (PALDA and STEARDA), are inactive on TRPV1. We have investigated here the possibility that the two compounds act by enhancing the effect of NADA on TRPV1 ('entourage' effect). When pre-incubated for 5 min with cells, both compounds dose-dependently enhanced NADA's TRPV1-mediated effect on intracellular Ca(2+) in human embryonic kidney cells overexpressing the human TRPV1. In the presence of either PALDA or STEARDA (0.1-10 microm), the EC(50) of NADA was lowered from approximately 90 to approximately 30 nm. The effect on intracellular Ca(2+) by another endovanilloid, N-arachidonoyl-ethanolamine (anandamide, 50 nm), was also enhanced dose-dependently by both PALDA and STEARDA. PALDA and STEARDA also acted in synergy with low pH (6.0-6.7) to enhance intracellular Ca(2+) via TRPV1. When co-injected with NADA (0.5 micrograms) in rat hind paws, STEARDA (5 micrograms) potentiated NADA's TRPV1-mediated nociceptive effect by significantly shortening the withdrawal latencies from a radiant heat source. STEARDA (1 and 10 micrograms) also enhanced the nocifensive behavior induced by carrageenan in a typical test of inflammatory pain. These data indicate that, despite their inactivity per se on TRPV1, PALDA and STEARDA may play a role as 'entourage' compounds on chemicophysical agents that interact with these receptors, with possible implications in inflammatory and neuropathic pain.

Topics: Animals; Arachidonic Acids; Calcium; Carrageenan; Cell Line; Disease Models, Animal; Dopamine; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Drug Synergism; Drug Therapy, Combination; Endocannabinoids; Hindlimb; Humans; Hyperalgesia; Inflammation; Italy; Kidney; Male; Pain Measurement; Palmitates; Polyunsaturated Alkamides; Rats; Rats, Sprague-Dawley; Receptors, Drug; Stearates; TRPV Cation Channels