Activation of the Cannabinoid 2 Receptor (CB2) Protects Against Experimental Colitis

Background: Activation of cannabinoid (CB)(1) receptors results in attenuation of experimental colitis. Our aim was to examine the role of CB2 receptors in experimental colitis using agonists (JWH133, AM1241) and an antagonist (AM630) in trinitrobenzene sulfonic acid (TNBS)-induced colitis in wildtype and CB2 receptor-deficient (CB2-/-), mice. Methods: Mice were treated with TNBS to induce colitis and then given intraperitoneal injections of the CB2 receptor agonists JWH133, AM1241, or the CB2 receptor antagonist AM630. Additionally, CB2-/- mice were treated with TNBS and injected with JWH133 or AM1241. Animals were examined 3 days after the induction of colitis. The colons were removed for macroscopic and microscopic evaluation, as well as the determination of myeloperoxidase activity. Quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) for CB2 receptor was also performed in animals with TNBS and dextran sodium Sulfate colitis. Results: Intracolonic installation of TNBS caused severe colitis. CB2, mRNA expression was significantly increased during the course of experimental colitis. Three-day treatment with JWH133 or AM1241 significantly reduced colitis; AM630 exacerbated colitis. The effect of JWH133 was abolished when animals were pretreated with AM630. Neither JWH133 nor AM 1241 had effects in CB2-/- mice. Conclusions: We show that activation of the CB2 receptor protects against experimental colitis in mice. Increased expression of CB2 receptor mRNA and aggravation of colitis by AM630 suggests a role for this receptor in normally limiting the development of colitis. These results Support the idea that the CB2 receptor may be a possible novel therapeutic target in inflammatory bowel disease.