Animal experimental design
Twenty-four 7-to 8-week-old male C57BL/6 mice were purchased from CAVENS LAB ANIMAL Co., (Changzhou, China). After two weeks of adaptive feeding, they were randomly divided into four groups: Normal group (6 mice), DSS group (6 mice), DSS+LE group (6 mice), DSS+HE group (6 mice). Except for the normal group treatment with drinking water, the remaining groups received 3% DSS in drinking water for 8 days. From the first day of adding DSS to the drinking water, EGCG treatment was administered to mice at a dose of 10 and 20 mg/kg per day by gavage for 1 week. During modelling and drug treatment, the stool consistency, rectal bleeding and weight were recorded daily. The disease activity index (DAI), a score used to assess the severity of colitis, was calculated as previously described14. All animal experiments were undertaken according to the institutional guidelines and were approved by the Institutional Animal Care and Use Committee of the Yunnan Agricultural University.
At the end of the experiment, all mice were killed with sodium pentobarbital and received colon tissue,whose length was measured, and then portions of colon ​were stored at -80℃ for the western blot and enzyme-linked immunosorbent assay (ELISA).Portions of colons were fixed in formalin for histopathological and immunohistochemical analysis.