Inverse-agonist (SMM-189) suppresses colitis by inducing endogenous cannabinoids and attenuating Th17, neutrophils, natural killer cells

Abstract

Abstract The cause of inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), are multi-factorial and include activated immune cells, chronic inflammation, genetics, and environmental exposure. It is well known that endocannabinoids mediate protection against intestinal inflammation and other autoimmune diseases. However, the effect of cannabinoid receptors induction by inverse-agonist during experimental colitis has not been investigated. Here, we investigate the activation of the cannabinoid receptor-2 (CB2) by SMM-189, a potent CB2 inverse agonist, on the inhibition of dextran sodium sulfate (DSS) induced colitis. In the present study, we found that SMM-189 effectively attenuated the overall clinical score, reversed colitis-associated pathogenesis, increased body weight and colon length while increasing the expression of CB2 receptors and protein kinase A (PKA) in the colon lamina propria (LPs). We also measured a decrease in the percentage and number of Th17 cells in the spleen, mesenteric lymph nodes (MLNs), and LPs treated with SMM-189 compared to DSS controls. Similarly, the percentage and number of natural killer T (NKT) cells and neutrophils are decreased after SMM-189 treatment. SMM-189 also induces the myeloid-derived suppressor cells (MDSCs) during chronic colitis progression as compared to DSS alone. These findings suggest that SMM-189 ameliorates experimental colitis by inducing CB2 receptors and PKA in the LPs, MDSCs and reduces Th17, NKT cells, and neutrophils from the spleen and LPs. Taken together, these data support the idea that the CB2 inverse agonists, such as SMM-189, may be developed as a novel therapeutic target for IBD. Supported by NIH grant R01 AI140405