Involvement of adaptive immune responses in a model of subacute colitis induced with dextran sulfate sodium in C57BL/6 mice.

Inflammatory bowel disease (IBD) is a non-specific chronic intestinal inflammatory disorder. Pharmacotherapy serves as the main treatment strategy for IBD; however, the current medications have certain limitations, such as inefficacy and a tendency to induce tolerance, thereby requiring the development of innovative drugs to fulfill therapeutic requirements. A model of acute colitis induced with a solution of approx. 3% dextran sulfate sodium (DSS) has been widely used in preclinical drug development. Nevertheless, this model has some drawbacks, including rapid disease progression leading to mortality in some mice and disparities between the inflammatory characteristics of mice and the pathological features of human IBD. The current study found that mice freely consuming a lower concentration of a DSS solution (1-1.5%) for 10-15 days exhibited milder colitis symptoms. Continued consumption of the DSS solution for 15-20 days resulted in chronic inflammation in colon tissue, accompanied by a significant increase in the proportion of Th1 cells, indicating the involvement of adaptive immune responses. Subsequently, mice were treated with mesalazine or Centella triterpenes while concurrently consuming the DSS solution for 10 days. The treated mice had significant improvements in body weight and colon length compared to the control group. The advantages of this subacute model include minimal mortality among experimental mice and the fact that intestinal mucosal inflammation in mice resembles the pathological features of human IBD, enabling the assessment of drug efficacy against IBD.