Inflammatory Bowel Disease (IBD) is a term that is mainly used to describe two chronic relapsing inflammatory conditions: Crohn’s Disease (CD) and Ulcerative Colitis (UC). IBD affects millions of people around the world – and its incidence has been consistently on the rise. IBD is characterised by symptoms including abdominal pain, diarrhoea, rectal bleeding, and malabsorption. In recent years there has been a number of advances in developing more aggressive treatments to treat IBD, including strong immunosuppressant. However, despite their development some patients still have symptoms refractory to best medical treatment, whilst others are not able to tolerate their side effects. As such there is a need to develop further novel therapeutics.
A growing body of evidence suggests that alternative therapies derived from the Cannabis Sativa. L plant may be useful in the treatment of symptoms associated with IBD. Anecdotal evidence suggests that IBD patients have experienced relief from symptoms when smoking or otherwise consuming cannabis. Furthermore, in recent years, a number of retrospective observational studies have found that cannabis use is common in patients with IBD and is often associated with symptom relief and improved quality of life. However, randomised controlled trials have failed to demonstrate any effect on bowel inflammation. In a recent study researchers investigated the effects of cannabigerol (CBG) – a non-psychotropic cannabinoid – in an experimental rodent model of colitis.
Design and Methods of the Study
Researchers tested the effects of pure CBG, supplied by GW Pharmaceuticals, in a rodent model of induced colitis. To induce colitis, dinitrobenzene sulphonic acid (DNBS) (150mg/kg) was injected into the colon of male mice. DNBS administration causes a significant increase in colon weight/length ratio, a simple and reliable marker of intestinal inflammation/damage. CBG was administered in various doses both before and after the inflammatory insult to determine the potential preventative and curative effects of the cannabinoid.
There were two arms to this study – a preventative protocol to identify the effects of CBG before DNBS administration (CBG was given once a day for six days starting three days before DNBS administration); and the curative protocol, in which CBG was given for two consecutive days starting 24 hours after DNBS administration.
Histological and immunochemistry evaluations were then performed three days after DNBS administration. These evaluations assessed a segment of 1cm of colon by blinded examiners. Colon was scored considering submucosal infiltration (0, none; 1, mild; 2-3, moderate; 4-5, severe), crypt abscesses (0, none; 1-2, rare; 3-5, diffuse), and mucosal erosion (1, absent; 1, focus; 2-3, extended until the middle of the visible surface; 4-5, extended until the end of the visible surface).
Results of the Study
In their discussion, the researchers explain that CBG (1-30mg/kg) given before (preventative protocol) or after (curative protocol) the inflammatory insult, “significantly reduced the effects of DNBS on colon weight/colon length ratio.” These results imply that CBG was therefore able to provide significant protection, starting from 1mg/kg (preventative) and 5mg/kg (curative) doses. To confirm this effect, the researchers also carried out further investigations: histological analysis, immunohistochemistry and measured intestinal permeability.
Histological examination showed that CBG in doses of 30mg/kg reduced the signs of colon injury; specifically in the glands of CBG-treated animals, the glands were regenerating, the oedema in submucosa was reduced and the infiltration of granulocytes (a type of white blood cell) into the mucosa and submucosa was decreased. CBG was also seen to restore the integrity of intestinal epithelium in mice with DNBS treatment. Neutrophil infiltration, revealed by measuring MPO activity, was also reduced. Furthermore, immunohistochemical analyses demonstrated that CBG limited the colonic diffusion of Ki-67, a useful marker for the evaluation of dysplasia in ulcerative colitis. However, doses of this scale are very high compared to those usually administered from medical cannabis preparations and therefore the translation of these results is uncertain.
CBG Effects on Cytokine Levels
The researchers also measured some cytokines which are known to be involved in IBD: IL-1β (a cytokine which plays an important pro-inflammatory role in the initiation and amplification of the intestinal inflammatory response), IL-10 (a regulatory cytokine which inhibits pro-inflammatory cytokine release, resulting in anti-inflammatory effects within the gut) and interferon-γ (another pro-inflammatory cytokine that plays a crucial function in the initiation of experimental colitis).
It was observed that intracolonic administration of DNBS caused in increase in colonic IL-1β and interferon-γ as well as a decrease in IL-10 levels. CBG was also seen to counteract pro-inflammatory concentrations these cytokines, suggesting the possible involvement of these cytokines in CBG-mediated anti-inflammatory effects in IBD.
CBF Effects on Enzyme Levels
Finally, researchers measured inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression – two key enzymes that mediate several of the most important components of intestinal mucosal defense and play a pivotal role in gut inflammation. Both iNOS and COX-2 expression was seen to increase in the colon of DNBS-treated mice. CBG administration was found to reduce the expression of iNOS, but not COX-2.
Antioxidant Effects of CBG
Having determined that CBG administration could influence inflammation associated with IBD as well as the expression of various cytokines and enzymes associated with the disease, the researchers also explored the possibility that CBG could protect the intestinal mucosa by reducing oxidative stress. To do this, the researchers measured CuZn-superoxide dismutase (SOD) activity, an important antioxidant defense in the gut, and ROS production, a major tissue destructive force which contributed to the pathogenesis of IBD.
They found that CBG restored that decreased SOD activity induced by DNBS administration in colonic tissues and reduced ROS production induced by Fenton’s reagent in mouse intestinal epithelial cells. These results suggest that the curative effects of CBG in IBD could be due, at least in part, to its antioxidant effects.
The results determined by this research demonstrate that CBG administration was associated with a significant improvement in models of IBD – both as a preventative and curative treatment. The researchers conclude that the effect of CBG was “associated to modulation of cytokine levels and down-regulation of iNOS (but not COX-2) expression.” It is also noted that CBG was able to exert antioxidant effects in the inflamed gut as well as in the epithelial cells exposed to oxidative stress.
However, it must be appreciated that these doses might be difficult to replicate in clinical practice, without development of ways to improve bioavailability. Whilst this demonstrates some promise to the utilisation of CBG in IBD there is considerable translational research that must still be undertaken in order for any claims to be made as to the efficacy and safety of CBG in the setting of IBD.