Arachidonyl serotonin

Interactions of beta-lactoglobulin with serotonin and arachidonyl serotonin.[Pubmed:21732322]

Biopolymers. 2011 Dec;95(12):871-80.

beta-Lactoglobulin (beta-LG) is a lipocalin, which is the major whey protein of cow's milk and the milk of other mammals. However, it is absent from human milk. The biological function of beta-LG is not clear, but its potential role in carrying fatty acids through the digestive tract has been suggested. beta-LG has been found in complexes with lipids such as butyric and oleic acids and has a high affinity for a wide variety of compounds. Serotonin (5-hydroxytryptamine, 5-HT), an important compound found in animals and plants, has various functions, including the regulation of mood, appetite, sleep, muscle contraction, and some cognitive functions such as memory and learning. In this study, the interaction of serotonin and one of its derivatives, Arachidonyl serotonin (AA-5HT), with beta-LG was investigated using circular dichroism (CD) and fluorescence intensity measurements. These two ligands interact with beta-LG forming equimolar complexes. The binding constant for the serotonin/beta-LG interaction is between 10(5) and 10(6) M(-1) , whereas for the AA-5HT/beta-LG complex it is between 10(4) and 10(5) M(-1) as determined by measurements of either protein or ligand fluorescence. The observed binding affinities were higher in hydroethanolic media (25% EtOH). The interactions between serotonin/beta-LG and AA-5HT/beta-LG may compete with self-association (micellization) of both the ligand and the protein. According to far- and near-UV CD results, these ligands have no apparent influence on beta-LG secondary structure, however they partially destabilize its tertiary structure. Their binding by beta-LG may be one of the peripheral mechanisms of the regulation of the content of serotonin and its derivatives in the bowel of milk-fed animals.

Analgesic actions of N-arachidonoyl-serotonin, a fatty acid amide hydrolase inhibitor with antagonistic activity at vanilloid TRPV1 receptors.[Pubmed:17279090]

Br J Pharmacol. 2007 Mar;150(6):766-81.

BACKGROUND AND PURPOSE: N-arachidonoyl-serotonin (AA-5-HT) is an inhibitor of fatty acid amide hydrolase (FAAH)-catalysed hydrolysis of the endocannabinoid/ endovanilloid compound, anandamide (AEA). We investigated if AA-5-HT antagonizes the transient receptor potential vanilloid-1 (TRPV1) channel and, as FAAH and TRPV1 are targets for analgesic compounds, if it exerts analgesia in rodent models of hyperalgesia. EXPERIMENTAL APPROACH: AA-5-HT was tested in vitro, on HEK-293 cells overexpressing the human or the rat recombinant TRPV1 receptor, and in vivo, in rats and mice treated with formalin and in rats with chronic constriction injury of the sciatic nerve. The levels of the endocannabinoids, AEA and 2-arachidonoylglycerol, in supraspinal (periaqueductal grey, rostral ventromedial medulla), spinal or peripheral (skin) tissues were measured. KEY RESULTS: AA-5-HT behaved as an antagonist at both rat and human TRPV1 receptors (IC(50)=37-40 nM against 100 nM capsaicin). It exerted strong analgesic activity in all pain models used here. This activity was partly due to FAAH inhibition, elevation of AEA tissue levels and indirect activation of cannabinoid CB(1) receptors, as it was reversed by AM251, a CB(1) antagonist. AA-5-HT also appeared to act either via activation/desensitization of TRPV1, following elevation of AEA, or as a direct TRPV1 antagonist, as suggested by the fact that its effects were either reversed by capsazepine and 5'-iodo-resiniferatoxin, two TRPV1 antagonists, or mimicked by these compounds administered alone. CONCLUSIONS AND IMPLICATIONS: Possibly due to its dual activity as a FAAH inhibitor and TRPV1 antagonist, AA-5-HT was highly effective against both acute and chronic peripheral pain.

The endocannabinoid system and its therapeutic exploitation.[Pubmed:15340387]

Nat Rev Drug Discov. 2004 Sep;3(9):771-84.

The term 'endocannabinoid' - originally coined in the mid-1990s after the discovery of membrane receptors for the psychoactive principle in Cannabis, Delta9-tetrahydrocannabinol and their endogenous ligands - now indicates a whole signalling system that comprises cannabinoid receptors, endogenous ligands and enzymes for ligand biosynthesis and inactivation. This system seems to be involved in an ever-increasing number of pathological conditions. With novel products already being aimed at the pharmaceutical market little more than a decade since the discovery of cannabinoid receptors, the endocannabinoid system seems to hold even more promise for the future development of therapeutic drugs. We explore the conditions under which the potential of targeting the endocannabinoid system might be realized in the years to come.