Introduction

Intestinal fibrosis is a common complication of inflammatory bowel diseases (IBD) characterized by increased production of extracellular matrix and crosslinking enzymes by intestinal mesenchymal cells. The advanced process of fibrosis leads to strictures often requiring surgical treatment. Therefore new methods of treatment of intestinal fibrosis are sought with endocannabinoid system (ES) as a potential therapeutic target. Cannabinoid receptors 1 and 2 (CB1 and CB2, respectively) are classic receptors of the ES involved in the regulation of the intestinal mucosa inflammation and permeability. Studies show that the regulation of ES activity can affect the process of fibrosis in various preclinical models of fibrosis.

Aims & Methods

The primary purpose of the study was to evaluate the effect of selective CB1 agonist, WIN 55, 212-2 (WIN) on expression of fibrosis regulatory proteins: alpha smooth muscle Actin 2 (Acta2), Collagen I (ColI), Fibronectin 2 (Fn2) and SMAD family member 3 (Smad3) in a mice model of Dextran sulfate sodium (DSS)-induced intestinal fibrosis. Moreover, the expression of the named proteins in colonic samples of patients with ulcerative colitis (UC) and healthy controls (HC) was compared.
Chronic colitis and fibrosis in mice model were induced by oral administration of 1.5% DSS in rotation with tap water for 3 weeks in three cycles. WIN was administrated starting from day 10th and continued every other day until day 77th, control mice were administered with saline. The mice were sacrificed on day 78th, their colon was excised and samples were taken for molecular analysis. Colonic samples from patients with UC and HC were collected and frozen for further exploration. The expression of genes encoding Acta2, Smad3, Col1, Fn2 in mouse and human material was assessed by Real Time RT-PCR. Statistical analysis was conducted using Student’s t-test to compare means of expressed molecules.

Results

We found lower relative expression of genes encoding assessed fibrosis regulatory proteins in mice treated with WIN than in inflamed mice: 4698±2323 vs. 9656±6032 for ACTA2, 4774±1073 vs 8510±2906 for COL1, 20993±7280 vs. 52148±17877 for FN1 and 373±31 vs. 478±77 for SMAD3. In human samples we noticed higher relative mean expression level of COL1 and SMAD3 in patients with UC compared to 7 HC 37422±6554 vs. 23816±2681 and 2134±261 vs. 1593±255, respectively.

Conclusion

We observed a decrease in relative expression of FN1, ACTA2, COL1, SMAD3 in samples from mice treated with CB1 agonist compared to inflamed mice. Also, a difference in expression of these proteins were found in intestinal samples from UC patients compared to HC, indicating a contribution of these molecules to intestinal fibrosis. Our results show that regulation of ECS activity play role in the inhibition of the intestinal fibrosis in IBD and appears as a potential therapeutic target in patients at high risk of developing strictures.