Novel selective cannabinoid CB1 receptor antagonist MJ08 with potent in vivo bioactivity and inverse agonistic effects
Aim:To characterize the biological profiles of MJ08, a novel selective CB1 receptor antagonist.Methods:Radioligand binding assays were performed using rat brain and spleen membrane preparations. CB1 and CB2 receptor redistribution and intracellular Ca2+ ([Ca2+]i) assays were performed with IN CELL Analyzer. Inverse agonism was studied using intracellular cAMP assays, and in guinea-pig ileum and mouse vas deferens smooth muscle preparations. In vivo pharmacologic profile was assessed in diet-induced obesity (DIO) mice.Results:In radioligand binding assay, MJ08 selectively antagonized CB1 receptor (IC50=99.9 nmol/L). In EGFP-CB1_U2OS cells, its IC50 value against CB1 receptor activation was 30.23 nmol/L (SR141716A: 32.16 nmol/L). WIN 55,212-2 (1 μmol/L) increased [Ca2+]i in the primary cultured hippocampal neuronal cells and decreased cAMP accumulation in CHO-hCB1 cells. MJ08 (10 nmol/L–10 μmol/L) blocked both the WIN 55,212-2-induced effects. Furthermore, MJ08 reversed the inhibition of electrically evoked twitches of mouse vas deferens by WIN 55,212-2 (pA2=10.29±1.05). MJ08 and SR141716A both showed an inverse agonism activity by markedly promoting the contraction force and frequency of guinea pig ileum muscle. MJ08 significantly increased the cAMP level in CHO-hCB1 cells with an EC50 value of 78.6 nmol/L, which was lower than the EC50 value for SR141716A (159.2 nmol/L). Besides the more potent pharmacological effects of cannabinoid CB1 receptor antagonism in DIO mice, such as reducing food intake, decreasing body weight, and ameliorating dyslipidemia, MJ08 (10 mg/kg) unexpectedly raised the fasted blood glucose in vivo.Conclusion:MJ08 is a novel, potent and selective CB1 receptor antagonist/inverse agonist with potent bioactive responses in vitro and in vivo that may be useful for disclosure the versatile nature of CB1 receptors.