A Structure/Activity Relationship Study on Arvanil, an Endocannabinoid and Vanilloid Hybrid

Abstract

Arvanil, a structural "hybrid" between the endogenous cannabinoid CB 1 receptor ligand anandamide and capsaicin, is a potent agonist for the capsaicin receptor VR 1 (vanilloid receptor type 1), inhibits the anandamide membrane transporter (AMT), and induces cannabimimetic responses in mice. Novel arvanil derivatives prepared by N-methylation, replacement of the amide with urea and thiourea moieties, and manipulation of the vanillyl group were evaluated for their ability to bind/activate CB 1 receptors, activate VR 1 receptors, inhibit the AMT and fatty acid amide hydrolase (FAAH), and produce cannabimimetic effects in mice. The compounds did not stimulate the CB 1 receptor. Methylation of the amide group decreased the activity at VR 1 , AMT, and FAAH. On the aromatic ring, the substitution of the 3-methoxy group with a chlorine atom or the lack of the 4-hydroxy group decreased the activity on VR 1 and AMT, but not the affinity for CB 1 receptors, and increased the capability to inhibit FAAH. The urea or thiourea analogs retained activity at VR 1 and AMT but exhibited little affinity for CB 1 receptors. The urea analog was a potent FAAH inhibitor (IC 50 ϭ 2.0 M). A water-soluble analog of arvanil, O-2142, was as active on VR 1 , much less active on AMT and CB 1 , and more potent on FAAH. All compounds induced a response in the mouse "tetrad", particularly those with EC 50 Ͻ10 nM on VR 1 . However, the most potent compound, N-NЈ-di-(3-chloro-4-hydroxy)benzylarachidonamide (O-2093, ED 50 ϳ0.04 mg/kg), did not activate VR 1 or CB 1 receptors. Our findings suggest that VR 1 and/or as yet uncharacterized receptors produce cannabimimetic responses in mice in vivo.

Evidence against the presence of an anandamide transporter

“…Our results confirmed earlier studies where AM404 was shown to inhibit FAAH with an IC 50 range of 500 nM to 3.6 M (38, 39), and arvanil with an IC 50 of 630 nM (39). These studies are in sharp contrast to those indicating that AM404 (7), arvanil (40), and olvanil (41) had minimal FAAH inhibitory effects and therefore must be inhibiting an anandamide transporter. The enzyme IC 50 values of AM404, arvanil, and olvanil are extremely similar to reported transport IC 50 values (all ranging from 2.2 to 9 M; refs.…”

Development of the First Ultra-Potent “Capsaicinoid” Agonist at Transient Receptor Potential Vanilloid Type 1 (TRPV1) Channels and Its Therapeutic Potential

“…The pharmacological responses of this cell line to vanilloid agonists and antagonists are very similar to those previously described by Witte et al (2002) for the same cell line overex- (Di Marzo et al, 2002b). One day prior to experiments, cells were transferred into six-well dishes coated with poly-L-lysine (Sigma-Aldrich, St. Louis, MO) and grown in the culture medium mentioned above.…”

“…N-Acyl-vanyllamides were reported to interact with proteins of the endocannabinoid system with low to moderate affinity, for cannabinoid CB 1 receptors, or as inhibitors of the activity of the proteins mediating endocannabinoid degradation, the fatty acid amide hydrolase (FAAH), and the putative AMT (Di Marzo et al, 2002b). Therefore, we decided to test the activity of PhAR on recombinant human CB 1 and CB 2 receptors as well as on [ 14 C]anandamide cellular uptake in RBL-2H3 cells and hydrolysis by rat brain membranes.…”

“…The effect of compounds on the uptake of anandamide by RBL-2H3 cells was studied as described previously (Di Marzo et al, 2002b …”

“…For CB 1 and CB 2 receptor binding, Fatty Acid Amide Hydrolase Assays. The effect of compounds on the enzymatic hydrolysis of [ 14 C]anandamide (6 M) was studied by using membranes prepared from rat brain incubated with increasing concentrations of compounds in 50 mM Tris-HCl, pH 9, for 30 min at 37°C (Di Marzo et al, 2002b). […”