Intervention mechanism of electroacupuncture in rats with ulcerative colitis: an analysis based on the Toll-like receptor 4/myeloid differentiation factor 88/nuclear factor-kappa B signaling pathway

Abstract

To investigate the protective effect of electroacupuncture(EA) on rats with ulcerative colitis (UC) and its effect on the Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor-kappa B (NF-κB) signaling pathway. Sprague-Dawley rats were randomly divided into blank group, model group, salicylazosulfapyridine (SASP) group, low-intensity EA group, and high-intensity EA group, with 8 rats in each group. Enema with 2，4，6-trinitrobenzenesulfonic acid was performed to establish a model of UC. The rats in the two EA groups were given EA at"Tianshu" (ST25), "Guanyuan" (CV4), and "Zusanli"(ST36) for 15 min each time, once a day, with a current intensity of 1 mA for the low-intensity EA group and 5 mA for the high-intensity EA group(among them, "Tianshu" "Zusanli" bilateral alternate acupoints); the rats in the SASP group were given SASP suspension 3 mL every day by gavage. The course of treatment was 15 days for all groups. HE staining was used to observe the pathology of the colon and determine tissue damage index(TDI); ELISA was used to measure the serum levels of interleukin-4 (IL-4), interleukin-10 (IL-10), interleukin-17 (IL-17), and prostaglandin E2 (PGE2); immunohistochemical staining and real-time PCR were used to measure the protein and mRNA expression of TLR4, MyD88, and NF-κB in colonic tissue. Compared with the blank group, the model group had significant reductions in body weight, serum IL-4, and IL-10 (P<0.05) and significant increases in colonic mucosa TID, the serum levels of IL-17 and PGE2 and the protein and mRNA expression of TLR4, MyD88, and NF-κB in colonic tissue (P<0.05). Compared with the model group, the SASP group and the EA groups had significantly higher body weight and serum levels of IL-4 and IL-10 (P<0.05), as well as significantly lower colonic TDI, serum levels of IL-17 and PGE2, and integrated optical density and mRNA expression of TLR4, MyD88, and NF-κB in colonic tissue (P<0.05). Compared with the SASP group, the low-intensity EA group had significantly higher colonic TDI and protein and mRNA expression of TLR4, MyD88, and NF-κB in colonic tissue (P<0.05), and compared with the SASP group, the high-intensity EA group had a significantly higher body weight (P<0.05) and lower colonic TDI and protein and mRNA expression of TLR4, MyD88, and NF-κB in colonic tissue (P<0.05). Compared with the low-intensity EA group, the high-intensity EA group had significantly higher body weight (P<0.05), and lower colonic TDI and protein and mRNA expression of TLR4, MyD88, and NF-kB in colonic tissue (P<0.05). Electroacupuncture exerts a protective effect on the colonic mucosa in rats with UC possibly by inhibiting the TLR4/MyD88/NF-κB signaling pathway and reducing the release of inflammatory cytokines, and high-intensity EA may have a better effect than low-intensity EA.