We examined the role of SR 144528 (N-[-(1S-endo-1,3,,3-trimethyl-bicycle[2, 2, 1 ] heptan-2-y1]-5-(-4-chloro-3-mothyl-phenyl)-(4-methylbenzyl)-pyrazole-3- carboxamide) in the modulation of certain AC isoforms in transiently transfected COS-7 cells. We found that CB2 in COS cells has a constitutive activity, and thus leading to inhibition of AC-V activity even in the absence of agonist. In addition, this constitutive modulation of AC is reversed by SR144528. It is now well established that several G protein-coupled receptors can signal without agonist stimulation(constitutive receptors). Inverse agonists have been shown to inhibit the activity of such constitutive G protein-coupled receptor signaling. Agonist activation of the Gi/o/-coupled peripheral cannabinoid receptor CB2 normally inhibits adenylyl cyclase type V and stimulates adenylyl cyclase type II. Using transfected COS cells, we show here that application of SR144528, an inverse agonist of CB2, leads to a reverse action (stimulation of adenylyl cyclase V and inhibition of adenylyl cyclase II). This inverse agonism of SR144528 is dependent on the temperature, as well as on the concentration of the cDNA of CB2 transfected. Pertussis toxin blocked the regulation of adenylyl cyclase activity by SR 144528.

The anandamide signaling plays various roles in directing reproductive processes. Mouse embryos are shown to express high levels of CB1 receptor (CB1R). It has recently been shown that an analog of anandamide induces autophagy-mediated cell death through stimulation of ER stress response in glioma cells. Since adverse effects of high levels of anandamide agonists on embryo development and implantation are well known, we hypothesized that anandamide mediates an autophagic response in embryonic cells as in cancer cells via highly abundant CB1R on embryos. We tested this hypothesis by using a stable anandamide agonist, Methanandamide (MET) in three embryonic cell systems, i.e., mouse embryonic fibroblasts (MEF), trophoblast stem (TS) cells, and preimplantation embryos from mice. RT-PCR, immunofluorescence staining, and Western blot analysis were used to examine the effects of anandamide on autophagy in these systems. In MEF cells, the conversion of LCI to LCII was heightened by methanandamide (MET), and AM251, a selective CB1 antagonist partially reversed the effects of MET. Treating MEF cells with a high level of MET induces clustering of GFP-LC3, seen as large puncta throughout the cytoplasm. At 28 nM concentration, MET also weakly increased LC3II in TS cells. When MET was injected to day 4 pregnant mice, autophagy was increased in blastocysts in utero as demonstrated by the increased number of LC3 puncta. Formation of numerous autophagic vacuoles was also confirmed by electron microscopic observation. In conclusion, this work suggests that the anandamide-CB1 signaling pathway may be one inducer of autophagy in embryonic cells.