Therapeutic Effect of Proteinase-Activated Receptor-1 Antagonist on Colitis-Associated Carcinogenesis

Inflammatory bowel disease is associated with carcinogenesis, which limits the prognosis of the patients. The local expression of proteinases and proteinase-activated receptor 1 (PAR₁) increases in inflammatory bowel disease. The present study investigated the therapeutic effects of PAR₁ antagonism on colitis-associated carcinogenesis.

A colitis-associated carcinogenesis model was prepared in mice by treatment with azoxymethane (AOM) and dextran sulfate sodium (DSS). PAR₁ antagonist E5555 was administered in long- and short-term protocol, starting on the day of AOM injection and 1 week after completing AOM/DSS treatment, respectively. The fecal samples were collected for metagenome analysis of gut microbiota. The intestinal myofibroblasts of the Crohn's disease patients were used to elucidate underlying cellular mechanisms. Caco-2 cells were used to investigate a possible source of PAR₁ agonist proteinases.

AOM/DSS model showed weight loss, diarrhea, tumor development, inflammation, fibrosis, and increased production of inflammatory cytokines. The β-diversity, but not α-diversity, of microbiota significantly differed between AOM/DSS and control mice. E5555 alleviated these pathological changes and altered the microbiota β-diversity in AOM/DSS mice. The thrombin expression was up-regulated in tumor and non-tumor areas, whereas PAR₁ mRNA expression was higher in tumor areas compared with non-tumor areas. E5555 inhibited thrombin-triggered elevation of cytosolic Ca²⁺ concentration and ERK1/2 phosphorylation, as well as IL6-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation in intestinal myofibroblasts. Caco-2 cell-conditioned medium contained immunoreactive thrombin, which cleaved the recombinant protein containing the extracellular domain of PAR₁ at the thrombin cleavage site.

PAR₁ antagonism is proposed to be a novel therapeutic strategy for treatment of inflammatory bowel disease and its associated carcinogenesis.