The Anti-Inflammatory Effect and Intestinal Barrier Protection of HU210 Differentially Depend on TLR4 Signaling in Dextran Sulfate Sodium-Induced Murine Colitis

Background

Ulcerative colitis (UC) is strongly associated with inflammation and intestinal barrier disorder. The nonselective cannabinoid receptor agonist HU210 has been shown to ameliorate inflamed colon in colitis, but its effects on intestinal barrier function and extraintestinal inflammation are unclear.

Aims

To investigate the effects and the underlying mechanism of HU210 action on the UC in relation to a role of TLR4 and MAP kinase signaling.

Methods

Wild-type (WT) and TLR4 knockout (Tlr4 ^?/?) mice were exposed to 4% dextran sulfate sodium (DSS) for 7 days. The effects of HU210 on inflammation and intestinal barrier were explored.

Results

Upon DSS challenge, mice suffered from bloody stool, colon shortening, intestinal mucosa edema, pro-inflammatory cytokine increase and intestinal barrier destruction with goblet cell depletion, increased intestinal microflora accompanied with elevated plasma lipopolysaccharide, reduced mRNA expression of the intestinal tight junction proteins, and abnormal ratio of CD4⁺/CD8⁺ T cells in the intestinal Peyer’s patches. Pro-inflammatory cytokines in the plasma and the lung, as well as pulmonary myeloperoxidase activity, indicators of extraintestinal inflammation were increased. Protein expression of p38α and pp38 was up-regulated in the colon of WT mice. Tlr4 ^?/? mice showed milder colitis. HU210 reversed the intestinal barrier changes in both strains of mice, but alleviated inflammation only in WT mice.

Conclusions

Our study indicates that in experimental colitis, HU210 displays a protective effect on the intestinal barrier function independently of the TLR4 signaling pathway; however, in the extraintestinal tissues, the anti-inflammatory action seems through affecting TLR4-mediated p38 mitogen-activated protein kinase pathway.