Christopher Broxson
University of Florida
Co-Authors: Ellen M Zimmermann, University of Florida
Background: Inflammatory bowel disease (IBD) is divided into two subcategories known as ulcerative colitis (UC) and Crohn’s disease (CD), of which CD is qualifying medical condition for medical cannabis use. Chronically recuring IBD flares can cause serious medical complications due to a buildup of collagen-rich fibrotic scar tissue in the intestine. In models of skin, liver, and airway fibrosis, the cannabis component cannabidiol (CBD) has antifibrotic therapeutic potential.
Objective: Here, we seek to understand the influence of CBD on human intestinal myofibroblasts (hIMF), the primary cell responsible for fibrotic scarring, to better understand the implications for IBD patients.
Methods: Cultured hIMFs were exposed to 1μM CBD for 4hr before (-4hr), simultaneous to (0hr), or 4hr after (+4hr) fibrotic stimulation using 5ng/ml transforming growth factor beta-1 (TGF) for 20hr to mimic the pro-fibrotic environment of human disease. To interrogate the peroxisome proliferator-activated receptor gamma (PPARG) pathway, 10μM of the PPARG antagonist T0070907 was administered 1hr prior to CBD treatment and TGF-stimulation. Gene expression was measured by qPCR and secreted collagen protein was analyzed by ELISA. Statistical analysis was done using 1 way ANOVA with Sídak’s multiple comparisons correction.
Results: As expected, TGF-stimulation increased pro-fibrotic gene expression compared to vehicle-treated controls (COL1A1 p<0.0001; SERPINH1 p=0.0002; ACTA2 p<0.0001; CCN2 p=0.007). Compared to cells only stimulated with TGF, cells pre-treated with -4h CBD had significantly lower fibrotic gene expression (COL1A1 p0.05). Compared to vehicle-treated cells, cells exposed to only CBD at any time point increased expression of PPARG (-4hr CBD p<0.001; 0hr CBD p=0.003, +4hr CBD p<0.0001). However, compared to TGF-stimulated cells, only the -4hr CBD with TGF increased PPARG mRNA (p=0.001) and decreased COL1A1 protein secretion (p=0.04). Time-course experiments revealed TGF to be a potent, quick-acting, and long-lasting suppressor of PPARG gene expression implicating the PPARG nuclear receptor as a possible CBD effector pathway. Surprisingly, the PPARG blocker failed to block the effects of CBD.
Conclusions: Pretreatment with CBD effectively reduced collagen gene and protein expression and thus had clear anti-fibrotic effects. However, in the presence of TGF, a common mediator of scar formation, the effects of CBD were abrogated. Therefore, the timing of CBD treatment is critical to its actions and may limit its potential efficacy an anti-fibrotic for IBD patients and beyond.