Combined CB1 antagonist AM6545 and NOP agonist SCH221510 worsen DSS-induced colitis in mice.

Background: Despite the broad range of treatment options available for intestinal inflammation, the development of novel therapeutics remains essential due to the diminishing effectiveness of current therapies over time. Both the endocannabinoid system (ECS) and nociceptin/orphanin FQ peptide (NOP) receptors have been implicated in the pathogenesis of diseases associated with intestinal inflammation, highlighting their potential as therapeutic targets.

Objectives: We hypothesized that an interaction exists between cannabinoid receptors 1 and 2 (CB1 and CB2) and the NOP receptor, which may hold therapeutic relevance for the treatment of colitis.

Material and methods: In this study, we used 3 selective ligands: a CB1 antagonist (AM6545), a CB2 antagonist (AM630) and a NOP agonist (SCH221510) in a mouse model of colitis induced by 3% dextran sulfate sodium (DSS). Quantification of several secondary messengers was conducted using western blot analysis. Real-time quantitative polymerase chain reaction (qPCR) was employed to assess CB1 expression levels in colonic tissue, while liquid chromatography-mass spectrometry (LC-MS) was used to evaluate the concentrations of endocannabinoids and related lipid mediators.

Results: We observed a statistically significant increase in the macroscopic score and a nonsignificant increase in the microscopic score in inflamed mice treated with both AM6545 and SCH221510 compared to those treated with SCH221510 alone. Additionally, the combination-treated group exhibited significantly lower levels of extracellular signal-regulated kinases 1/2 (ERK1/2) and significantly higher levels of phosphorylated protein kinase B (p-AKT) and β-arrestin relative to the SCH221510-only group.

Conclusions: Our study offers novel insights into the interaction between the ECS and the NOP receptor, which may inform the development of new therapeutic strategies for inflammatory conditions such as colitis.