Cannabinoid Receptor Activation on Haematopoietic Cells and Enterocytes Protects against Colitis

Background and Aims: Cannabinoid receptor [CB] activation can attenuate inflammatory bowel disease [IBD] in experimental models and human cohorts. However, the roles of the microbiome, metabolome, and the respective contributions of haematopoietic and non-haematopoietic cells in the anti-colitic effects of cannabinoids have yet to be determined. Methods: Female C57BL/6 mice weretreated with either cannabidiol [IBD], Delta(9)-tetrahydrocannabinol [THC], a combination of CBD and THC, or vehicle, in several models of chemically induced colitis. Clinical parameters of colitis were assessed by colonoscopy, histology, flow cytometry, and detection of serum biomarkers; single-cell RNA sequencing and qRT-PCR were used to evaluate the effects of cannabinoids on enterocytes. Immune cell transfer from CB2 knockout mice was used to evaluate the contribution of haematopoietic and non-haematopoietic cells to colitis protection. Results: We found thatTHC prevented colitis and that CBD, at the dose tested, provided little benefit to the amelioration of colitis, nor when added synergistically with THC. THC increased colonic barrier integrity by stimulating mucus and tight junction and antimicrobial peptide production, and these effects were specific to the large intestine. THC increased colonic Gram-negative bacteria, but the anti-colitic effects ofTHC were independent of the microbiome. THC acted both on immune cells via CB2 and on enterocytes, to attenuate colitis. Conclusions: Our findings demonstrate how cannabinoid receptor activation on both immune cells and colonocytes is critical to prevent colonic inflammation. These studies also suggest how cannabinoid receptor activation can be used as a preventive and therapeutic modality against colitis.

Automated summary

The study highlights that THC can prevent colitis while the ameliorative effects of CBD on colitis are limited, even in combination with THC. THC increases colonic barrier integrity by promoting mucus, tight junction, and antimicrobial peptide production, specifically in the large intestine.