2.2. Macroscopic Grading and Histological Analysis of Colitis

The macroscopic grading of DSS-induced colitis is based on a standard scoring system called the disease activity index (DAI) [24]. The details are shown in Table 1. The body weight, stool consistency, and rectal bleeding of each mouse were recorded in fact daily. All mice were anesthetized and sacrificed by cervical dislocation 24 h after the last drug treatment. Their colons were excised, and the length was measured promptly. The distal colonic tissues were fixed in 4% paraformaldehyde solution (Servicebio, China), embedded in paraffin (Solarbio, China), sectioned, and then stained with hematoxylin and eosin (HE) (Solarbio, China) for optical microscopic (CKX53, Olympus, Japan) observation. Histopathological scores were determined according to the previous criteria [25] shown in Table 2.

Scoring system for calculating DAI based on weight loss, stool consistency, and the degree of intestinal bleeding.

Scoring system for inflammation-associated histological changes in the colon.