Electroacupuncture of "Shangjuxu"(ST37) and "Tianshu"(ST25) reduces colonic injury by suppressing NF-κB/NLRP3 signaling in rats with ulcerative colitis

Abstract

To observe the effect of electroacupuncture (EA) of "Shangjuxu"(ST37) and "Tianshu"(ST25) on colonic mucosal injury and activities of nuclear factor-κB (NF-κB)/Nod-like receptor family，pyrin domain-containing 3 (NLRP3) inflammasome signaling in the colonic tissue in rats with ulcerative colitis (UC), so as to explore its mechanisms underlying improvement of UC. Male SD rats were randomly divided into blank, model, medication and EA groups, with 12 rats in each group. The UC model was established by enema of 2-4-6 trinitrobenzene sulfonic acid +50% ethanol (2.5 mL). EA (10 Hz/50 Hz) was applied to bilateral ST37 and ST25 for 20 min, once a day, for a total of 10 days. Rats of the medication group received gavage of mesalazine suspension (2 mL：0.2 g/kg+0.9% saline) once a day, for 10 days. The rats' general conditions were recorded for calculating the disease activity index (DAI) score (0-4 points). The colonic tissue was sampled for giving colonic mucosa damage index (CMDI, 0-5 points) score and for observing histopathological changes after hematoxylin-eosin (HE) staining, and for detecting expression levels of NF-κB and NLRP3 by using immunohistochemistry and Western blot, separately. The contents of serum interleukin-1β (IL-1β), NLRP3 and tumor necrosis factor-α (TNF-α) were detected by enzyme-linked immunosorbent assay. Compared with the blank group, the DAI and CMDI scores, contents of serum IL-1β, NLRP3, and TNF-α, as well as the immunoactivity and expression of NF-κB and NLRP3 proteins were significantly increased in the model group (P<0.05). Relevant to the model group, modeling-induced increases of DAI and CMDI scores, serum IL-1β, NLRP3 and TNF-α contents, and NF-κB and NLRP3 expression were reversed in both medication and EA groups (P<0.05), the effect of EA was apparently superior to that of mesalazine in down-regulating CMDI score and serum IL-1β level (P<0.05). No significant diffe-rences were found between the medication and EA groups in down-regulating DAI score, serum TNF-α and NLRP3 contents, and expression of NF-κB and NLRP3 proteins (P>0.05). The rats' general conditions including arch back sloth, anorexia, loss of fur gloss, weight loss, lethargy and loose of stool, and histopathological changes such as necrosis of intestinal mucosa, formation of obvious ulcerative surface, with many neutrophils and pus cells and inflammatory cell infiltration were obvious in the model group, which were relative milder in both medication and EA groups. EA can relieve colonic injury in UC rats, which may be related to its functions in down-regulating serum IL-1β, TNF-α and NLRP3 levels by suppressing colonic NF-κB / NLRP3 inflammasome signaling.