D1.409 - Regulation of the intestinal epithelial barrier by the endocannabinoid system

Cannabinoids have been pointed out as potent immunomodulators able to regulate different inflammatory conditions. Previous data showed that the synthetic cannabinoid WIN55212-2 restores both human rhinovirus 16- and IL-13-induced airway epithelial barrier damage. Compelling experimental evidence also suggests that the endocannabinoid system (ECS) may regulate the intestinal epithelial permeability. Nonetheless, the role of cannabinoids in this process are not fully understood yet. Here, we investigate the capacity of cannabinoids to modulate the intestinal epithelial barrier integrity in models of type 1 and type 2 inflammation.

Liquid-liquid interface and monolayer cultures of human colon cancer cells (Caco 2 and HCT116) were used as a model of intestinal epithelial barrier, and the expression of the ECS components analysed by flow cytometry, confocal microscopy, qPCR and transcriptomics. Type 1- and type 2-mediated inflammation was induced with TNF-α or IL-13, respectively, in HCT116 and Caco 2 cell lines. The effects of different cannabinoids (WIN55212-2, HU210, HU308 or cannabidiol (CBD)) on activated Caco 2 and HCT116 cells were analysed by RNAseq, targeted proteomics (OLINK), qPCR, flow cytometry, western blot and transepithelial electrical resistance (TEER) measurement.

Caco 2 cells express the main ECS components at the RNA level as well as cannabinoid receptor 1 (CB1) at the protein level. The synthetic cannabinoids WIN55212-2 and HU210 inhibit TNF-α-induced NF-κB activation in HCT116 cells, diminish IL-13-induced ROS production and preserve the barrier integrity in Caco 2 cells. Mechanistically, WIN55212-2 inhibits IL-13-induced STAT6 phosphorylation thus abolishing downstream IL-13-mediated signalling pathways, encompassing ROS producing enzymes, pro-inflammatory chemokines and barrier disrupting proteins. Additionally, WIN55212-2 promotes Caco 2 phenotypes characterized by enhanced epithelial barrier integrity and mitochondrial fitness.

Cannabinoids restore healthy phenotype in intestinal epithelial cells under both type 1 and type 2 inflammatory conditions by mechanisms depending on NF-κB and phospho-STAT6 inhibition, respectively. The better understanding of the mode of action of cannabinoids in the gut might well pave the way for the future development of alternative therapeutic strategies for different immune-mediated inflammatory diseases.