Formononetin prevents intestinal injury caused by radiotherapy in colorectal cancer mice via the Keap1-Nrf2 signaling pathway

Radiation-induced intestinal injury (RIII) is a serious complication of radiation therapy. Formononetin (FT) is a methoxy isoflavone with anti-tumor and anti-oxidant properties. This study explored whether FT reduces ROS by activating the Keap1/Nrf2 pathway and thereby protecting against RIII. 30 BABL/C mice were used to construct a colorectal cancer model with CT26 cells and validated the model on day 7. Then, the cancer model mice were divided into 3 groups on day 14 (model control, model, and model + FT) with administration of FT or saline and radiated them on day 21. All samples were collected on day 28. Mechanical intestinal barrier assessed via intestinal absorption function, HE staining, and Claudin-1, Occludin, ZO-1 expression. Apoptosis was measured by TUNEL and cleaved-caspase 3, angiogenesis by CD31, and oxidative stress by NO and ROS levels. Keap1, Nrf2 (cytoplasm) and Nrf2 (nucleus) expression were measured by Western blot. FT treatment enhanced absorption and reduced damage and apoptosis in intestinal tissue. During FT treatment, inhibition of NO and ROS leads to suppression of oxidative stress and promotion of CD31 expression promotes angiogenesis. FT upregulated the expression of nuclear Nrf2 and reduced cytoplasmic Keap1 and Nrf2. FT strengthens mechanical barrier and decreases oxidative stress in intestinal tissue, providing radiation injury protection. Its anti-radiation effect may be through Keap1/Nrf2 pathway activation.