Effect of electroacupuncture at “Zusanli” (ST36) on colonic mucosal injury and expressions of colonic NF-κB and AQP8 in mice with transplanted colorectal cancer after 5-FU chemotherapy

To observe the effect of electroacupuncture (EA) at “Zusanli” (ST36) on colonic mucosa injury, expressions of nuclear factor κB (NF-κB), and Aquaporin 8 (AQP8) in 5-fluorouracil (5-FU)-treated mice with transplanted colorectal cancer (CRC), so as to explore its mechanisms underlying improvement of colonic mucosal injury.

A colorectal cancer cell strain CT26 was subcutaneously injected into BALB/c mice to establish an animal model of transplanted CRC. When the tumor grew to 100—300 mm³, the mice were randomly divided into the tumor-bearing model, chemotherapy, and chemotherapy+EA groups, with 6 mice in each group. Another 6 normal BALB/c mice were used as the normal group. The mice of the chemotherapy group and the chemotherapy+EA group received intraperitoneal injection of 5-FU solution (50 mg/kg, 0.01 mL/g), once daily for 5 d. For mice of the chemotherapy + EA group, EA (2 Hz, 1—2 mA) was applied to bilateral ST36 for 5 min immediately after chemotherapy. During the experiment, the mouse daily Disease Activity Index (DAI) score was determined for assessing the disease severity. The tumor volume was measured once daily. At the end of the experiment, the mice were sacrificed to measure the tumor weight and colonic length. Histopathological changes of the colon tissue were observed after H.E. staining. The serum contents of diamine oxidase (DAO) and D-lactate (D-LA) were detected using ELISA. The immunoactivity of colonic AQP8 was detected using immunohistochemistry, the immunofluorescence intensity of colonic NF-κB was detected using immunofluorescence staining for assessing the nuclear translocation status, and the protein expression levels of colonic NF-κB and AQP8 were detected using Western blot.

Compared with the normal group, the tumor-bearing model group had no significant changes in the DAI score, contents of serum DAO and D-LA, immunoactivity, immunofluorescence intensity and protein expression levels of colonic NF-κB and AQP8. In comparison with the tumor-bearing model group, the DAI score in chemotherapy group, and serum DAO and D-LA contents, nuclear translocation and protein expression levels of NF-κB in the chemotherapy group were considerably increased (P<0.05), while the colonic length, tumor volume, tumor weight, and the immunoactivity level of AQP8 were strikingly decreased (P<0.05). Comparison between the chemotherapy and chemotherapy+EA groups showed that the DAI score, serum DAO and D-LA contents, nuclear translocation and protein expression levels of NF-κB in the chemotherapy+EA group were significantly lower than those in the chemotherapy group (P<0.05), while the immunoactivity level of AQP8 in the chemotherapy+EA group was notably higher than that in the chemotherapy group (P<0.05), and no significant differences were found between the chemotherapy and chemotherapy+EA groups in the levels of colonic length, tumor volume and mass. H. E. staining showed that the colonic tissue structure in the tumor-bearing group had no abnormal changes, and that in the chemotherapy group displayed pathological injury, including shortening and thickening of intestinal villi, destruction of glandular structure, increased shedding of goblet cells, infiltration of inflammatory cells, and enlargement of cell nuclei. Compared with the chemotherapy group, the colonic structure in the chemotherapy+EA group was improved, including increase in the villi length, and reduction in the disordered arrangement of the tissue cells and infiltration of inflammatory cells.

EA of ST36 can mitigate intestinal mucosal damage to maintain intestinal barrier function in 5-FU-treated mice with transplanted CRC, which may be related with its functions in inhibiting the excessive activation of the NF-κB signaling pathway, up-regulating the expression levels of AQP8 protein, and reducing DAO and D-LA release.