N-acyl-dopamines: novel synthetic CB1 cannabinoid-receptor ligands and inhibitors of anandamide inactivation with cannabimimetic activity in vitro and in vivo

Abstract

We reported previously that synthetic amides of polyunsaturated fatty acids with bioactive amines can result in substances that interact with proteins of the endogenous cannabinoid system (ECS). Here we synthesized a series of N-acyl-dopamines (NADAs) and studied their effects on the anandamide membrane transporter, the anandamide amidohydrolase (fatty acid amide hydrolase, FAAH) and the two cannabinoid receptor subtypes, CB1 and CB2. NADAs competitively inhibited FAAH from N18TG2 cells (IC50 = 19–100µM), as well as the binding of the selective CB1 receptor ligand, [3H]SR141716A, to rat brain membranes (Ki = 250–3900nM). The arachidonoyl (20:4 ω6), eicosapentaenoyl (20:5 ω3), docosapentaenoyl (22:5 ω3), α-linolenoyl (18:3 ω3) and pinolenoyl (5c,9c,12c 18:3 ω6) homologues were also found to inhibit the anandamide membrane transporter in RBL-2H3 basophilic leukaemia and C6 glioma cells (IC50 = 17.5–33µM). NADAs did not inhibit the binding of the CB1/CB2 receptor ligand, [3H]WIN55,212-2, to rat spleen membranes (Ki > 10µM). N-arachidonyl-dopamine (AA-DA) exhibited 40-fold selectivity for CB1 (Ki = 250nM) over CB2 receptors, and N-docosapentaenoyl-dopamine exhibited 4-fold selectivity for the anandamide transporter over FAAH. AA-DA (0.1–10µM) did not displace D1 and D2 dopamine-receptor high-affinity ligands from rat brain membranes, thus suggesting that this compound has little affinity for these receptors. AA-DA was more potent and efficacious than anandamide as a CB1 agonist, as assessed by measuring the stimulatory effect on intracellular Ca2+ mobilization in undifferentiated N18TG2 neuroblastoma cells. This effect of AA-DA was counteracted by the CB1 antagonist SR141716A. AA-DA behaved as a CB1 agonist in vivo by inducing hypothermia, hypo-locomotion, catalepsy and analgesia in mice (1–10mg/kg). Finally, AA-DA potently inhibited (IC50 = 0.25µM) the proliferation of human breast MCF-7 cancer cells, thus behaving like other CB1 agonists. Also this effect was counteracted by SR141716A but not by the D2 antagonist haloperidol. We conclude that NADAs, and AA-DA in particular, may be novel and useful probes for the study of the ECS.

N-Arachidonoyl-Dopamine Tunes Synaptic Transmission onto Dopaminergic Neurons by Activating both Cannabinoid and Vanilloid Receptors

“…Remarkably, exogenously applied NADA could facilitate glutamate release via TRPV1 even in the absence of the CB1-R antagonist, when tested at low doses (1 mM). This is in agreement with a reported higher effect of NADA at TRPV1 than at CB1-R (Bisogno et al, 2000;Huang et al, 2002b). It is worth to note that NADA, when applied at a high dose (10 mM) and in the absence of either CB1-R or TRPV1 antagonists, did not significantly modify glutamate transmission to the DA neurons.…”

“…We have previously shown a functional role of TRPV1 in the ventral midbrain (Marinelli et al, 2003(Marinelli et al, , 2005 and other studies have demonstrated a presynaptic modulation of neurotransmission by CB1 in the same area Melis et al, 2004). Compared with AEA, NADA is more potent at TRPV1 and less potent but more efficacious at CB1-R (Bisogno et al, 2000;Bezuglov et al, 2001;Huang et al, 2002b).…”

“…In the hippocampus, NADA enhances paired-pulse depression through an increase of GABAergic transmission (Huang et al, 2002b). Besides these in vitro effects, NADA induces thermal hyperalgesia, stimulates spontaneous and heat-evoked activity in spinal nociceptive neurons (Huang and Walker, 2006), and exerts a contractile action on smooth muscles by acting on TRPV1 (Huang et al, 2002b;Harrison et al, 2003;Price et al, 2004), while it causes analgesia, hypothermia, and catalepsy by activation of CB1-R (Bisogno et al, 2000). Finally, NADA exerts vasorelaxant effects by acting on both CB1-R and TRPV1 in small mesenteric vessels (O'Sullivan et al, 2004).…”

Ultra performance liquid chromatography tandem mass spectrometry method for the measurement of anandamide in human plasma

“…Other endocannabinoids have since been identified including 2-arachidonoylglycerol, noladin ether and N-arachidonoyl dopamine [3][4][5].…”

Cannabinoid as a neuroprotective strategy in perinatal hypoxic-ischemic injury

“…Other recently described endogenous cannabinoids are 2-arachidonyl glyceryl ether (noladin ether) [72] , O-arachidonoyl-ethanolamine (virodhamine) [73] and N-arachidonoylethanolamine [74,75] . [76] and AM251 (CB1 receptorselective antagonists), as well as SR144528 [77] and AM630 (CB2 receptor-selective antagonists).…”