3.1 TBⅡ alleviated DSS-induced colitis and prevented AOM/DSS-induced colon carcinogenesis in mice
The anti-inflammatory effect of TBⅡ was extensively reported (Ji et al., 2019; Liu et al., 2022; Lu, Qiu, Li, Tao, Sun & Chen, 2009). However, the effect of TBⅡ against DSS-induced colitis remain largely unknown thus far. To explore the protective effect of TBⅡ against DSS-induced colon injury, mice were administrated 4% DSS in drinking water for 7 days, and then sacrificed, and their colons were assessed. After consecutive 7 days feeding mice with 4% DSS in drinking water, the mice displayed a prominent decrease of body weight and shortness of colon length (Figure 1A and B; sFigure 1A and B), whereas the DAI score and spleen weight-to-body weight ratios was significantly enhanced (Figure 1C; sFigure 1C), a phenotype resembling the patients with ulcerative colitis that usually experience weight loss, diarrhea and hematochezia. Accordingly, histologic damage of colon was amplified, as seen by an obvious tissue ulcers, involving the submucosa, even complete loss of mucosal epithelium and intestinal glands, and more inflammatory cell infiltration (Figure 1D). However, TBⅡ treatment substantially reversed the DSS-induced the loss of body weight, colon shortening, and bloody diarrhea, and also mitigated DAI score and spleen weight-to-body weight ratios, and subsequently resulting in ameliorating the histologic damage of colon, respectively (Figure 1A-C; sFigure 1 A-C). In addition, DSS-induced colitis model is accompanied by colonic oxidative stress, which is largely involved in the occurrence and aggravation of colitis. Correspondingly, the antioxidant levels (SOD and GSH levels) in the DSS-treated colon tissue homogenate of mice were lower than those of the control-treated colon tissue of mice, while the MDA levels were higher in DSS-treated mice than that of control-treated mice, an effect that was notably reversed after TBⅡ treatment (Figure 1E).
Since TBⅡ alleviated DSS-induced colitis in mice, we next explored whether TBⅡ could have a protective effect against AOM/DSS-induced development of colorectal carcinogenesis (CAC). Mice treated with AOM/DSS demonstrated an evident loss of body weight (Figure 1F), lower survival rate (Figure 1G), colon shortening (Figure 1H and sFigure 1D), increase of the tumors numbers of and tumor size (Figure 1I and J, and sFigure 1E), and more histopathological damage of colon (Figure 1K), those effects that were remarkably inverted by TBⅡ treatment (Figure 1F-K). Taken together, our study firstly revealed that TBⅡ can alleviate DSS-induced colitis and prevent AOM/DSS-induced CRC progression in mice.