Acupoint catgut embedding relieves colonic inflammatory injury by down-regulating NLRP3/Caspase-1 signaling pathway in rats with ulcerative colitis

Abstract

To observe the effect of acupoint catgut embedding (CE) on Nod-like receptor protein 3 (NLRP3)/Caspase-1 signaling pathway in "deficiency-stasis" syndrome type ulcerative colitis (UC) rats, so as to explore its mechanisms underlying improvement of UC. A total of 58 male SD rats were randomly divided into control group (10 rats) and model group (48 rats). The "deficiency-stasis" type UC model was established by gavage of adenine and folium sennae solution for 4 weeks, followed by clycter of mixture solution of 5% trinitro-benzene-sulfonic acid and 50% ethanol. A total of 44 UC rats were randomized into model, salicylazosulfapyridine (SASP), non-acupoint CE, and acupoint CE groups (11 rats in each group). The catgut embedment was applied to bilateral "Zusanli"(ST36), "Shenshu"(BL23), "Pishu"(BL20), "Dachangshu"(BL25), "Geshu" (BL17) and "Tianshu"(ST25), or non-acupoints (the fat muscles of the buttocks), separately, once every two weeks, 3 times altogether. Rats of the SASP group received gavage of SASP solution, and those of the other groups received gavage of same amount of normal saline, once daily for 42 days. The rat's general conditions and the colon length were recorded, the disease activity index (DAI, 0 to 4 points) and colonic mucosal damage index (CMDI, 0 to 5 points) were calculated. Histopathological changes of the colonic mucosa tissue were observed after HE staining, and the tissue damage index (TDI, 0 to 6 points) was given. The levels of serum NLRP3, interleukin (IL)-1β and IL-18 were measured by ELISA, and the expression levels of NLRP3, Caspase-1, apoptosis-associated speck-like protein (ASC), IL-1β and IL-18 mRNAs were measured by fluorescence quantitative PCR. The expression levels of NLRP3 and Caspase-1 proteins in the colon tissues were measured by Western blot, and the immunoactivity of colonic ASC was detected by immunohistochemistry. Compared with the control group, the rats' body mass and colonic length were significantly decreased (P<0.01), and DAI score, CMDI score, TDI score, contents of serum NLRP3, IL-1β and IL-18, expression levels of colonic NLRP3, ASC, Caspase-1, IL-1β and IL-18 mRNAs, and NLRP3 and Caspase -1 proteins as well as colonic ASC immunoactivity were significantly up-regulated in the model group (P<0.01). Compared with the model group, both SASP and acupoint CE groups had a significant increase in body mass and colonic length (P<0.01), and a marked decrease in DAI score, CMDI score, TDI score, contents of serum NLRP3, IL-1β and IL-18, expression levels of NLRP3, ASC, Caspase-1, IL-1β and IL-18 mRNAs and NLRP3 and Caspase-1 proteins and ASC immunoactivity (P<0.01). The above indexes were improved in the acupoint CE group in relevant to those of the non-acupoint CE group (P<0.01). HE staining of colonic mucosal tissue showed obvious ulcerative surface, destroyed recess, disordered arrangement of glands, mucosal edema and congestion, infiltration of a large number of inflammatory cells in the model group, which was obviously milder in both SASP and acupoint CE groups. Acupoint embedding can alleviate colonic injury and inhibit inflammatory reaction in rats with "deficiency-stasis" type UC by down-regulating colonic NLRP3/Caspase-1 signaling.