Activating Cannabinoid Receptor 2 Alleviates Pathogenesis of Experimental Autoimmune Encephalomyelitis Via Activation of Autophagy and Inhibiting NLRP 3 Inflammasome

Summary Aims Activation of cannabinoid receptor 2 ( CB 2R) has been reported to ameliorate the pathogenesis of experimental autoimmune encephalomyelitis ( EAE ). In this study, we examined whether autophagy is involved in the beneficial effect of CB 2R on EAE and explored the mechanism with a focus on inflammasome activation. Methods EAE severity was analyzed with clinical score and histological score stained by hematoxylin and eosin or luxol fast blue in spinal cord. Immunoblot analysis was conducted to detect proteins of NOD ‐like receptor family, pyrin domain containing 3 ( NLRP 3) inflammasome‐related caspase‐1 (Casp‐1) and the maturation of interleukin (IL)‐1β as well as autophagy‐related light chain 3 (LC3), and Beciln 1 both in vivo and in vitro . Reverse transcription and real‐time PCR were used to detect mRNA of NLRP 3, IL‐1β and Casp‐1. Autophagy‐related gene 5 ( ATG 5)‐specific si RNA was transiently transfected in BV 2 microglia, and immunofluorescence staining was carried out to detect the expression of NLRP3, caspase recruitment domain ( ASC ), and pro‐caspase‐1. Results The current data indicated that deleting CB 2R decreased the expression of LC 3‐ II / LC 3‐I ratio, Beclin 1 and increased caspase‐1 activation and IL ‐1β production in the spinal cord of EAE mice, whereas activation of CB 2R with a specific agonist HU ‐308 induced inverse effects. Further study indicated that HU ‐308 could promote autophagy and inhibit expression and activation of NLRP 3 inflammasome in BV 2 microglia. Blocking autophagy by ATG 5‐specific si RNA dismissed the effort of CB 2R in mediating NLRP 3 inflammasome in vitro . Conclusion Collectively, our results demonstrated for the first time that CB 2R plays a protective role in EAE through promoting autophagy and inhibiting NLRP 3 inflammasome activation.