Recombinant Thrombomodulin Modulates Murine Colitis Possibly via High-Mobility Group Box 1 Protein Inhibition

Background and Aim: Thrombomodulin (TM) is an anticoagulant cofactor protein. We hypothesized that its recombinant soluble TM (rhTM) form, widely used to treat disseminated intravascular coagulation, might have anti-inflammatory action in inflammatory bowel disease (IBD), possibly through its inhibition of high-mobility group box 1 protein (HMGB1). Methods: We investigated inflammatory effects of HMGB1 and anti-inflammatory effect of rhTM in dextran sulfate sodium (DSS)-treated mice, some cell lines and ulcerative colitis (UC) patients, particularly focusing on changes of vascular endothelial adhesion molecules. Results: Treatments with rhTM significantly attenuated DSS-treated mice clinically and histologically. The mRNA levels of proinflammatory cytokines and adhesion molecules were decreased by rhTM. Increased inflammatory cells in the colonic mucosa strongly expressed HMGB1 in the cytoplasm in the DSS-treated mice and UC patients' colonic mucosa, which were significantly decreased by rhTM in mice. In in vitro experiments, rhTM significantly decreased the mRNA levels of tumor necrosis factor-alpha (TNF-α) and adhesion molecules increased by endotoxin exposures in RAW 264.7 (macrophage cell line) and bEND.3 cells (endothelial cell line), suggesting the proinflammatory role of HMGB1 in TNF-α production from macrophages. Conclusions: These findings suggest that rhTM may be useful for the treatment of IBD by attenuating inflammatory cytokine production and adhesion molecule expression, partly because of its inhibition of HMGB1.