The effects of cannabinoids on the Caco-2 cell culture model of intestinal permeability

Abdussalam Alhamoruni1, Karen Wright1,2, Mike Larvin1, Saoirse O’Sullivan1. 1University of Nottingham, Nottingham, United Kingdom, 2Lancaster University, Lancaster, United Kingdom.

The endocannabinoid system is expressed in the gastrointestinal system and activation of cannabinoid receptors in the gut decrease emesis, gastric acid secretion and intestinal motility. However, as yet, the effects of cannabinoids on intestinal permeability have not been established. The aim of the present study was to examine the effects of cannabinoids on intestinal permeability using the Caco-2 cell model.

Caco-2 cells were grown until fully confluent on inserts in 12-well plates. Transepithelial electrical resistance (TEER) measurements were made as a measure of permeability. 50 μM EDTA was applied to inserts to cause a fall in TEER (an increase in permeability). The effects of cannabinoids on TEER in combination with EDTA, or alone, were assessed. Potential target sites of action were investigated using the following (all 1 μM); AM251 (CB1 receptor antagonist), AM630 (CB2 receptor antagonist), capsazepine (TRPV1 antagonist), GW9662 (PPARγ antagonist), GW6471 (PPARα antagonist), and O-1918 (proposed endothelial cannabinoid receptor antagonist). Data were analysed by one-way ANOVA and Dunnett’s post hoc test, and are reported as mean ± S.E.M.

50 μM EDTA caused a drop of TEER of about 20% (indicating an increase in cell permeability). Application of phytocannabinoids caused a more rapid recovery of TEER than observed in the control group in a concentration dependent manner (Area under the curve (AUC); vehicle (0.1% ethanol) 3728 ± 234 (n = 3); 10 μM Δ9-tetrahydrocannabinol (THC) 2148 ± 475, P<0.05; 10 μM cannabidiol (CBD) 1201 ± 53, P<0.01). By contrast, application of endocannabinoids caused a further and sustained drop in TEER in addition to the effects of EDTA (AUC; vehicle 3553 ± 211; 10 μM anandamide 4985 ± 409, P <0.05; 10 μM 2-arachidonoylglycerol (2-AG) 5373 ± 271, P <0.05). Only CB1 receptor antagonism inhibited the actions of cannabinoids in Caco-2 cells (THC P <0.001; CBD P <0.001, anandamide P<0.001; 2-AG P <0.05).

These findings suggest that endocannabinoids may play a role in modulating intestinal permeability and that phytocannabinoids may have therapeutic potential in the treatment of abnormally permeable intestinal walls.