Enhancing Tetrahydrocannabinol's Therapeutic Efficacy in Inflammatory Bowel Disease: The Roles of Cannabidiol and the Cannabinoid 1 Receptor Allosteric Modulator ZCZ011

Abstract

Background/Objectives: Current inflammatory bowel disease (IBD) treatments focus on symptomatic relief, highlighting the need for innovative approaches. Dysregulation of the cannabinoid 1 (CB1) receptor, part of the endocannabinoid system, is linked to colitis. While tetrahydrocannabinol (THC) alleviates colitis via CB1 activation, its psychotropic effects limit clinical use. ZCZ011, a CB1R allosteric modulator, and cannabidiol (CBD), a non-psychoactive cannabinoid, offer alternatives. This study investigated combining sub-therapeutic THC doses with ZCZ011 or CBD in a murine model of dextran sodium sulphate (DSS)-induced colitis. Methods: Acute colitis was induced with 4% DSS for 7 days, followed by 3 days of water. Chronic colitis was modelled over 24 days with alternating DSS concentrations. The combination of 2.5 mg/kg THC with 20 mg/kg ZCZ011 or 10 mg/kg CBD was evaluated. Key markers were assessed to determine efficacy and safety, including disease activity index (DAI), inflammation, cytokine levels, GLP-1, and organ health. Results: DSS-induced colitis resulted in increased DAI scores, cytokines, organ inflammation and dysregulation of GLP-1 and ammonia. THC at 10 mg/kg significantly improved colitis markers but was ineffective at 2.5 and 5 mg/kg. ZCZ011 alone showed transient effects. However, combining 2.5 mg/kg THC with either 20 mg/kg ZCZ011 or 10 mg/kg CBD significantly alleviated colitis markers, restored colon integrity and reestablished GLP-1 homeostasis. This combination also maintained favourable haematological and biochemical profiles, including a notable reduction in colitis-induced elevated ammonia levels. Conclusions: This study demonstrates the synergistic potential of low-dose THC combined with CBD or ZCZ011 as a novel, effective and safer therapeutic strategy for ulcerative colitis.

Keywords: CB1R allosteric modulator; DSS-induced ulcerative colitis; ZCZ011; ammonia; cannabidiol (CBD); cannabinoid 1 receptor (CB1R); glucagon-like peptide 1 (GLP-1); inflammatory bowel disease; tetrahydrocannabinol (THC).

Figure 1

Effects of ZCZ011, THC and their combination on DAI and grimace scores in a DSS-induced acute colitis model. (A) Daily progression of the disease activity index (DAI) score in DSS-challenged mice treated with vehicle, ZCZ011 (20, 30 or 40 mg/kg), THC (2.5, 5 or 10 mg/kg) or a combination of 2.5 mg/kg THC with 20 mg/kg ZCZ011. (B) Statistical significance of daily DAI score. (C) Change in DAI score (final score minus baseline) at the study endpoint (day 11). (D) Daily progression of grimace scores reflecting pain behaviours. (E) Statistical significance of daily grimace score. (F) Change in grimace scores (final score minus baseline) at the study endpoint. Data are presented as mean ± SEM. #### p < 0.0001, ### p < 0.001, ## p < 0.01 vs. healthy control; **** p < 0.0001, *** p < 0.001 ** p < 0.01, * p < 0.05 vs. DSS vehicle group. ns—not statistically significant.

Figure 2

Therapeutic effects of THC combined with ZCZ011 or CBD on DAI scores in chronic colitis. The figure illustrates the progression and modulation of DSS-induced colitis across different treatment groups. (A,B) Disease activity index (DAI) scores. (C,D) Body weight loss. (E,F) Diarrhoea scores. (G,H) Faecal blood scores. Data presented as mean ± SEM, with significant differences denoted as: # p < 0.05, ## p < 0.01, ### p < 0.001, #### p < 0.0001 compared to the healthy control; and * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001 compared to the vehicle group.

Figure 3

Effects of ZCZ011, THC and their combination on colon length, MPO activity and spleen weight in DSS-induced acute colitis. (A) Colon length measured at the study endpoint. (B) Percentage change in colon MPO activity. (C) Representative images of colons from each treatment group. (D) Spleen-to-body weight ratio as an indicator of systemic inflammation. (E) Percentage change in MPO activity in the spleen. Data are presented as mean ± SEM. #### p < 0.0001 vs. healthy controls; **** p < 0.0001, *** p < 0.001, ** p < 0.01, * p < 0.05 vs. DSS vehicle group.

Figure 4

Effects of combination therapies on markers of colitis severity and systemic inflammation. The figure illustrates the modulation of colon and spleen inflammation in chronic colitis across different treatment groups. (A) Colon length. (B) Colonic MPO activity. (C) Representative images of colons. (D) Spleen-to-body weight percentage. (E) Splenic MPO activity. Data expressed as mean ± SEM, with significant differences denoted as ## p < 0.01, #### p < 0.0001 compared to the healthy control; and * p < 0.05, ** p < 0.01, **** p < 0.0001 compared to the vehicle group.

Figure 5

Effects of combination treatments on colonic inflammatory cytokine levels in DSS-induced chronic colitis. The figure presents the levels of pro-inflammatory cytokines and chemokines in colonic tissue across different treatment groups. (A) IFN-γ. (B) IL-1β. (C) IL-6. (D) IL-17. (E) MCP-1. (F) TNF-α. Data are presented as mean ± SEM. Statistical significance: # p < 0.05, ### p < 0.001, #### p < 0.0001 vs. healthy control; * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001 vs. DSS vehicle group.

Figure 6

Effects of THC, ZCZ011 and their combination on plasma GLP-1 levels, body weight, blood glucose and colonic GLP-1 in DSS-induced acute colitis. (A) Plasma GLP-1 (total) levels. (B) Random blood glucose levels. (C) Change in body weight. (D) Colonic GLP-1 levels. Data are presented as mean ± SEM. Statistical significance: # p < 0.05, ## p < 0.01 and ### p < 0.001 compared to healthy controls and * p < 0.05, ** p < 0.01, **** p < 0.0001 compared to DSS vehicle group.

Figure 7

Effects of combination therapies on GLP-1 levels and glucose regulation in DSS-induced chronic colitis. (A) Plasma GLP-1 levels. (B) Random blood glucose levels. (C) Colonic GLP-1 levels (pmol/µg of protein). Data are presented as mean ± SEM with statistical significance # p < 0.05 and ### p < 0.001 compared to health control groups and ** p < 0.01, ****p < 0.0001 compared to the vehicle-treated DSS group.

Figure 8

Effects of ZCZ011 and THC alone or in combination on liver and kidney function parameters. The figure illustrates the effects of treatments in liver and kidney function parameters. (A) Liver-to-body weight ratio (%). (B) Plasma ALT levels (U/L). (C) Plasma AST levels (U/L). (D) Plasma TG levels (mmol/L). (E) Plasma cholesterol levels (mmol/L). (F) Plasma ammonia levels (μmol/L). (G) Kidney-to-body weight ratio (%). (H) Plasma BUN levels (mmol/L). Data are presented as mean ± SEM. Statistical significance was determined using one-way ANOVA followed by Dunnet post hoc test. #### p < 0.0001 versus healthy control; ** p < 0.01, *** p < 0.001, **** p < 0.0001 versus vehicle.

Figure 9

Effects of THC combined with ZCZ011 or CBD on hepatic and renal parameters in DSS-induced chronic colitis. (A) Liver-to-body weight (%). (B) Plasma AST levels (U/L). (C) Plasma ALT levels (U/L). (D) Plasma ammonia levels (µmol/L). (E) Plasma cholesterol levels (mmol/L). (F) Plasma triglyceride levels (mmol/L). (G) Kidney-to-body weight ratio (%) and (H) Plasma blood urea nitrogen (BUN) levels (mmol/L). Data are presented as mean ± SEM. Statistical significance: ## p < 0.01, #### p < 0.0001 vs. healthy control; * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001 vs. vehicle-treated DSS group.

Figure 10

Chemical structure of THC (A), ZCZ011 (B) and cannabidiol (C).