am-404 and arvanil

In spite of the rapid advances in our understanding of vanilloid-receptor pharmacology in the PNS, the function of vanilloid receptors in the brain has remained elusive. Recently, the endocannabinoid anandamide has been proposed to function as an endogenous agonist at the vanilloid receptor VR1. This is an exciting hypothesis because the localization of VR1 overlaps with that of anandamide and its preferred cannabinoid receptor CB(1) in various brain areas. The interaction of anandamide and/or related lipid metabolites with these two completely separate receptor systems in the brain clearly places VR1 in a much broader role than pain perception. At a practical level, the overlapping ligand recognition properties of VR1 and CB(1) might be exploited by medicinal chemistry. For example, arvanil, a 'chimeric' ligand that combines structural features of capsaicin and anandamide, promises to be an interesting lead for new drugs that interact at both vanilloid and cannabinoid receptors.

Topics: Animals; Arachidonic Acids; Brain Chemistry; Cannabinoid Receptor Modulators; Capsaicin; Diterpenes; Drug Design; Endocannabinoids; Forecasting; Ganglia, Spinal; Glycerides; Humans; Ligands; Nerve Tissue Proteins; Neurons, Afferent; Polyunsaturated Alkamides; Rats; Receptors, Cannabinoid; Receptors, Drug; Structure-Activity Relationship

The discovery that paracetamol is metabolized to the potent TRPV1 activator N-(4-hydroxyphenyl)-5Z,8Z,11Z,14Z-eicosatetraenamide (AM404) and that this metabolite contributes to paracetamol's antinociceptive effect in rodents via activation of TRPV1 in the central nervous system (CNS) has provided a potential strategy for developing novel analgesics. Here we validated this strategy by examining the metabolism and antinociceptive activity of the de-acetylated paracetamol metabolite 4-aminophenol and 4-hydroxy-3-methoxybenzylamine (HMBA), both of which may undergo a fatty acid amide hydrolase (FAAH)-dependent biotransformation to potent TRPV1 activators in the brain. Systemic administration of 4-aminophenol and HMBA led to a dose-dependent formation of AM404 plus N-(4-hydroxyphenyl)-9Z-octadecenamide (HPODA) and arvanil plus olvanil in the mouse brain, respectively. The order of potency of these lipid metabolites as TRPV1 activators was arvanil = olvanil>>AM404> HPODA. Both 4-aminophenol and HMBA displayed antinociceptive activity in various rodent pain tests. The formation of AM404, arvanil and olvanil, but not HPODA, and the antinociceptive effects of 4-aminophenol and HMBA were substantially reduced or disappeared in FAAH null mice. The activity of 4-aminophenol in the mouse formalin, von Frey and tail immersion tests was also lost in TRPV1 null mice. Intracerebroventricular injection of the TRPV1 blocker capsazepine eliminated the antinociceptive effects of 4-aminophenol and HMBA in the mouse formalin test. In the rat, pharmacological inhibition of FAAH, TRPV1, cannabinoid CB1 receptors and spinal 5-HT3 or 5-HT1A receptors, and chemical deletion of bulbospinal serotonergic pathways prevented the antinociceptive action of 4-aminophenol. Thus, the pharmacological profile of 4-aminophenol was identical to that previously reported for paracetamol, supporting our suggestion that this drug metabolite contributes to paracetamol's analgesic activity via activation of bulbospinal pathways. Our findings demonstrate that it is possible to construct novel antinociceptive drugs based on fatty acid conjugation as a metabolic pathway for the generation of TRPV1 modulators in the CNS.

Topics: Amidohydrolases; Aminophenols; Analgesics; Animals; Arachidonic Acids; Benzylamines; Brain; Capsaicin; Inhibitory Concentration 50; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Motor Activity; Nociception; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB1; TRPV Cation Channels; Vasodilation

Recent studies have addressed the changes in endocannabinoid ligands and receptors that occur in multiple sclerosis, as a way to explain the efficacy of cannabinoid compounds to alleviate spasticity, pain, tremor, and other signs of this autoimmune disease. Using Lewis rats with experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, we recently found a decrease in cannabinoid CB1 receptors mainly circumscribed to the basal ganglia, which could be related to the motor disturbances characteristic of these rats. In the present study, using the same model, we explored the potential changes in several neurotransmitters in the basal ganglia that might be associated with the motor disturbances described in these rats, but we only found a small increase in glutamate contents in the globus pallidus. We also examined whether the motor disturbances and the changes of CB1 receptors found in the basal ganglia of EAE rats disappear after the treatment with rolipram, an inhibitor of type IV phosphodiesterase able to supress EAE in different species. Rolipram attenuated clinical decline, reduced motor inhibition, and normalized CB1 receptor gene expression in the basal ganglia. As a third objective, we examined whether EAE rats also exhibited changes in endocannabinoid levels as shown for CB1 receptors. Anandamide and 2-arachidonoylglycerol levels decreased in motor related regions (striatum, midbrain) but also in other brain regions, although the pattern of changes for each endocannabinoid was different. Finally, we hypothesized that the elevation of the endocannabinoid activity, following inhibition of endocannabinoid uptake, might be beneficial in EAE rats. AM404, arvanil, and OMDM2 were effective to reduce the magnitude of the neurological impairment in EAE rats, whereas VDM11 did not produce any effect. The beneficial effects of AM404 were reversed by blocking TRPV1 receptors with capsazepine, but not by blocking CB1 receptors with SR141716, thus indicating the involvement of endovanilloid mechanisms in these effects. However, a role for CB1 receptors is supported by additional data showing that CP55,940 delayed EAE progression. In summary, our data suggest that reduction of endocannabinoid signaling is associated with the development of EAE in rats. We have also proved that the reduction of CB1 receptors observed in these rats is corrected following treatment with a compound used in EAE such as rolipram. In addition, the direct or i

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Arachidonic Acids; Basal Ganglia; Brain; Cannabinoid Receptor Modulators; Capsaicin; Cyclic Nucleotide Phosphodiesterases, Type 4; Disease Models, Animal; Encephalomyelitis, Autoimmune, Experimental; Endocannabinoids; Gene Expression; Glycerides; Male; Multiple Sclerosis; Phosphodiesterase Inhibitors; Polyunsaturated Alkamides; Rats; Rats, Inbred Lew; Receptor, Cannabinoid, CB1; Receptors, Cannabinoid; Rolipram; TRPV Cation Channels

Some synthetic agonists of the VR1 vanilloid (capsaicin) receptor also inhibit the facilitated transport into cells of the endogenous cannabinoid anandamide (arachidonoylethanolamide, AEA). Here we tested several AEA derivatives containing various derivatized phenyl groups or different alkyl chains as either inhibitors of the AEA membrane transporter (AMT) in intact cells or functional agonists of the VR1 vanilloid receptor in HEK cells transfected with the human VR1. We found that four known AMT inhibitors, AM404, arvanil, olvanil and linvanil, activate VR1 receptors at concentrations 400-10000-fold lower than those necessary to inhibit the AMT. However, we also found three novel AEA derivatives, named VDM11, VDM12 and VDM13, which inhibit the AMT as potently as AM404 but exhibit little or no agonist activity at hVR1. These compounds are weak inhibitors of AEA enzymatic hydrolysis and poor CB(1)/CB(2) receptor ligands. We show for the first time that, despite the overlap between the chemical moieties of AMT inhibitors and VR1 agonists, selective inhibitors of AEA uptake that do not activate VR1 (e.g. VDM11) can be developed.

Topics: Animals; Arachidonic Acids; Binding, Competitive; Biological Transport; Calcium; Capsaicin; Cell Line; Dose-Response Relationship, Drug; Endocannabinoids; Humans; Ligands; Polyunsaturated Alkamides; Rats; Receptors, Cannabinoid; Receptors, Drug; TRPV Cation Channels; Tumor Cells, Cultured