Study on the mechanism of electroacupuncture regulating macrophage polarization to improve ulcerative colitis in rats.

Objectives: To investigate the effect of electroacupuncture(EA) at "Changbing Decoction" on alleviating ulcerative colitis (UC) and regulating the polarization of colonic macrophages in rats, so as to explore its mechanisms underlying improvement of UC.

Methods: Twenty-six male SD rats were randomly divided into 4 groups：normal group(6 rats), model group(8 rats), EA group(6 rats), and western medication group(6 rats). The rat model of UC was established by using 5% dextran sulfate sodium (DSS) solution drinking water for 7 days, followed by drinking 1% DSS solution during treatment period. After 7-day model establishment, EA treatment(10 Hz/50 Hz, 20 min) was applied to "Zhongwan"(CV12), bilateral "Tianshu"(ST25) and "Shangjuxu"(ST37) for 3 d, and rats in the western medication group were given mesalazine suspension(200 mg/kg) by gavage for 3 d. The body weight, spleen weight and colon length of rats were measured. The disease activity index (DAI) score was evaluated. The morphological changes and inflammatory cell infiltration of colon were detected after HE staining and pathological scores were eva-luated. The contents of tumor necrosis factor α(TNF-α), interleukin(IL)-1β, IL-2 and IL-10 in serum were detected by ELISA. The protein expressions of M1 and M2 macrophage markers nitric oxide synthase (iNOS) and arginase 1(Arg1) were detected by fluorescence double staining and Western blot, respectively. Quantitative real-time PCR was used to detect iNOS and Arg1 mRNA expressions.

Results: Compared with the normal group, rats in the model group had increased pathological damage degree and inflammatory cell infiltration in the colon tissue, slowed-down body weight gain, decreased colon length, spleen weight, serum anti-inflammatory factors IL-2 and IL-10 contents, colonic Arg1/CD68 fluorescence positive expression, and Arg1 protein and mRNA expressions(P<0.01, P<0.05), as well as increased DAI scores, colon histopathological scores, contents of serum pro-inflammatory factors TNF-α and IL-1β, colonic iNOS/CD68 fluorescence positive expression, iNOS protein and mRNA expressions(P<0.01). Compared with the model group, the above indicators were significantly improved in rats of the EA group and the western medication group(P<0.01, P<0.05).

Conclusions: EA of "Changbing Decoction" can improve UC of rats by regulating the polarization of colonic macrophages, inhibiting the generation of M1 macrophages and promoting the generation of M2 macrophages.