CB1 antagonist 1

Effects of the allosteric antagonist 1-(4-chlorophenyl)-3-[3-(6-pyrrolidin-1-ylpyridin-2-yl)phenyl]urea (PSNCBAM-1) on CB1 receptor modulation in the cerebellum

1-(4-Chlorophenyl)-3-[3-(6-pyrrolidin-1-ylpyridin-2-yl)phenyl] urea (PSNCBAM-1) has recently been described as a cannabinoid CB1 receptor allosteric antagonist associated with hypophagic effects in vivo; however, PSNCBAM-1 effects on CB(1) ligand-mediated modulation of neuronal excitability remain unknown. Here, we investigate PSNCBAM-1 actions on CB(1) receptor-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPγS) binding in cerebellar membranes and on CB(1) ligand modulation of presynaptic CB(1) receptors at inhibitory interneuron-Purkinje cell synapses in the cerebellum using whole-cell electrophysiology. PSNCBAM-1 caused noncompetitive antagonism in [(35)S]GTPγS binding studies, with higher potency against the CB receptor agonist (-)-cis-3-[2-hydroxy-4-(1,1-dimethyl heptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol (CP55940) than for R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]-pyrrolo[1,2,3,-de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone mesylate] [WIN55,212-2 (WIN55)]. In electrophysiological studies, WIN55 and CP55940 reduced miniature inhibitory postsynaptic currents (mIPSCs) frequency but not amplitude. PSNCBAM-1 application alone had no effect on mIPSCs; however, PSNCBAM-1 pretreatment revealed agonist-dependent functional antagonism, abolishing CP55940-induced reductions in mIPSC frequency but having no clear effect on WIN55 actions. The CB(1) antagonist/inverse agonist N-(piperidin-1-yl)-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-1H-multipyrazole-3-carboxamide (AM251) increased mIPSC frequency beyond control; this effect was reversed by PSNCBAM-1. PSNCBAM-1 pretreatment also attenuated AM251 effects. Thus, PSNCBAM-1 reduced CB(1) receptor ligand functional efficacy in the cerebellum. The differential effect of PSNCBAM-1 on CP55940 versus WIN55 actions in [(35)S]GTPγS binding and electrophysiological studies and the attenuation of AM251 effects are consistent with the ligand-dependence associated with allosteric modulation. These data provide the first description of functional PSNCBAM-1 allosteric antagonist effects on neuronal excitability in the mammalian central nervous system (CNS). PSNCBAM-1 allosteric antagonism may provide viable therapeutic alternatives to orthosteric CB(1) antagonists/inverse agonists in the treatment of CNS disease.

Cannabis effects on lipoproteins

Purpose of review: The endocannabinoid system affects several physiological functions. A family of endocannabinoid receptors is susceptible to cannabis constituents. Cannabis is widely used in our society and following its recent legalization in Canada, we focus on how exposure to cannabis and pharmacologic cannabinoid receptor type 1 (CB1) inhibition affect lipoprotein levels.
Recent findings: Several groups have reported that exposure to cannabis does not increase weight despite the marked increase in caloric intake. In observational studies, the effect of smoked cannabis exposure on plasma lipids is variable. Some studies in specific patient populations with longer exposure to cannabis seemed to identify slightly more favorable lipoprotein profiles in the exposed group. Several larger controlled clinical trials using orally administered rimonabant, a CB1 receptor antagonist, have consistently shown relative improvements in weight and plasma levels of triglyceride and high-density lipoprotein cholesterol among patients receiving the treatment.
Summary: The widely variable findings on the relationship of cannabis in various forms with plasma lipids preclude any definitive conclusions. Cannabis has complex effects on the cardiovascular system and its effects on lipid profile must be considered in this overall context. Further properly controlled research is required to better understand this topic.

Hypersensitization of the Orexin 1 receptor by the CB1 receptor: evidence for cross-talk blocked by the specific CB1 antagonist, SR141716

In the present study, we observed evidence of cross-talk between the cannabinoid receptor CB1 and the orexin 1 receptor (OX1R) using a heterologous system. When the two receptors are co-expressed, we observed a major CB1-dependent enhancement of the orexin A potency to activate the mitogen-activated protein kinase pathway; dose-responses curves indicated a 100-fold increase in the potency of orexin-mediated mitogen-activated protein kinase activation. This effect required a functional CB1 receptor as evidenced by the blockade of the orexin response by the specific CB1 antagonist, N-(piperidino-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-pyrazole-3-carboxamide (SR141716), but also by pertussis toxin, suggesting that this potentiation is Gi-mediated. In contrast to OX1R, the potency of direct activation of CB1 was not affected by co-expression with OX1R. In addition, electron microscopy experiments revealed that CB1 and OX1R are closely apposed at the plasma membrane level; they are close enough to form hetero-oligomers. Altogether, for the first time our data provide evidence that CB1 is able to potentiate an orexigenic receptor. Considering the antiobesity effect of SR141716, these results open new avenues to understand the mechanism by which the molecule may prevent weight gain through functional interaction between CB1 and other receptors involved in the control of appetite.

Peripherally acting CB1-receptor antagonist: the relative importance of central and peripheral CB1 receptors in adiposity control

Objective: To investigate whether drugs targeting peripheral cannabinoid-1 (CB1) receptor ameliorate adiposity comparable to central CB1-receptor antagonist or not.
Measurements: Receptor binding assay and functional assay in vitro. Pharmacokinetic parameters in mice, brain uptake clearance of compounds in rats and antagonism on the CB1-agonist-induced hypothermia in mice. Diet consumption, body weight changes, hepatic gene expression of sterol-regulatory element-binding protein-1 (SREBP-1) and plasma/tissue concentrations of compounds in HF diet-induced obese (HF-DIO) mice after acute and chronic treatment.
Results: Compound-1, an SR141716A derivative, is a peripheral CB1-receptor-selective antagonist that is 10 times less potent than SR141716A in in vitro evaluations. Although the plasma concentrations of Compound-1 are five times higher than those of SR141716A, its potency is still 10 times lower than that of SR141716A in reducing the consumption of normal or HF diet by mice. Through evaluations of brain uptake and the effect on CB1-agonist-induced hypothermia, it was verified that the blood-brain barrier (BBB) penetration of Compound-1 is much lower than that of SR141716A. In HF-DIO mice, chronic treatment by Compound-1 showed dose-dependent antiobesity activities, while its brain distribution was very low as compared with that of SR141716A. Compound-1's effective doses for antiobesity activity were just over 30 mg kg(-1). However, Compound-1 completely suppressed the elevated hepatic SREBP-1 expression even at 10 mg kg(-1).
Conclusion: These results suggest that (1) central CB1 receptors mediate anorectic response of CB1-receptor antagonists and (2) peripheral modulations, including SREBP-1 expression, are not major mechanisms in the antiobesity effects of CB1-receptor antagonists.

Synthesis and Biological Studies of a Novel CB1 Antagonist

This paper describes the synthesis, early process development, salt selection strategies and pre clinical evaluation of novel, potent and selective CB1 antagonist, 8-Chloro-1-(2,4-dichloro-phenyl)-4,5-dihydro-1H-6-oxa-1,2-diaza-benzo[e]azulene-3-carboxylic acid piperidin-1-ylamide 1. The CB1 antagonism of compound 1 is also confirmed by reversal of CB1 agonist-induced hypothermia in Swiss albino mice. The process for the preparation of the compound 1 as a crystalline solid is also described. The crystalline form of the compound is found to be low bioavailable, therefore attempts have been made to improve its bioavailability through polymorphic transformation and salt formation. None of the salts prepared were found to be suitable for further development. The amorphous form of the compound 1 is found to be better suited. In vivo efficacy study of the amorphous form of compound 1 in 5% sucrose solution intake model in female Zucker fa/fa rats at single oral dose of 10 mg/kg demonstrates better reduction in the sucrose solution consumption than the corresponding crystalline form. The plasma concentration Cmax at AUC exposure of the amorphous form of the compound 1 is significantly improved and better than the Cmax of the corresponding crystalline form of the compound 1. On the basis of the efficacy, pharmacokinetic and toxicological evaluations, the compound 1 in the amorphous form is selected as a pre-clinical lead candidate.