Crosstalk between M1 muscarinic acetylcholine receptor and endocannabinoid system promotes attenuation of inflammation in ulcerative colitis.

The crosstalk between the M1 muscarinic acetylcholine receptor and the endocannabinoid system was investigated during acetic acid-induced experimental colitis. In this research, male mice were treated with the agonist M1 receptor McN-A-343 (1.5 mg/kg; intraperitoneal) or dexamethasone (2.0 mg/kg; subcutaneous) 17 h or 17 h 30 min after the induction of acetic acid colitis, respectively. The cannabinoid receptor antagonists, CB1 (AM251, 3.0 mg/kg, intraperitoneal) and CB2 (AM630, 1.0 mg/kg, intraperitoneal), were administered 30 min before McN-A-343 and dimethyl sulfoxide (DMSO, 4 %, intraperitoneal) at the same time as the antagonists. After 18 h of colitis induction, 5 cm of the distal part of the colon was collected for analysis of macroscopic and microscopic lesion scores, intestinal wet weight, biochemical measurements: concentration of myeloperoxidase, tumor necrosis fator alpha (TNF-α), interleukin-1β (IL-1β), malondialdehyde, reduced glutathione, nitrate/nitrite and protein expression of Nf-κB (Nuclear Factor-κBp65), inducible nitric oxide (iNOs) and cyclooxygenases 2 (Cox-2) by Western Blotting. Administration of AM251 or AM630 before treatment with McN-A-343 significantly altered the anti-inflammatory response of the agonist M1 receptor, evidenced by the accentuation of intestinal damage, increased wet weight, myeloperoxidase levels, pro-inflammatory cytokines, oxidative stress markers and protein expression of NF-κB, iNOs and Cox-2. These results suggest that CB1 and CB2 receptors are involved in the anti-inflammatory action of McN-A-343 in experimentally induced colitis. Therefore, the crosstalk between these systems may present promising potential for treatment of intestinal inflammatory conditions.