Abstract: BACKGROUND: Acupuncture is an important therapeutic method for ulcerative colitis; however, its mechanism of action remains unclear.
OBJECTIVE: To investigate the mechanism of electroacupuncture in regulating the pathological progression of ulcerative colitis and the imbalance of Th17/Treg immune homeostasis in mice with ulcerative colitis, and to analyze the remodeling effect of electroacupuncture on the dynamic balance of the proinflammatory-anti-inflammatory cell subpopulations and its interaction with the nuclear receptor signaling pathway.
METHODS: Sixty male C57BL/6 mice were randomly divided into five groups (n=12): control, model, sham electroacupuncture, electroacupuncture, and conventional drug treatment. Except for the control group, the other groups were induced with ulcerative colitis by continuous free access to a 3% sodium dextran sulfate solution for 7 days. The mice in the electroacupuncture group received stimulation at the Zusanli (ST36) and Tianshu (ST25) acupoints (20 minutes per day × 7 days). The mice in the sham electroacupuncture group underwent superficial needle insertion at Zusanli and Tianshu to subcutaneous tissue, and the electrode device was left in a non-activated state. Mesalazine solution (33.4 g/kg) was administered by gastric gavage to the mice in the conventional drug treatment group. Following treatment, mouse body mass and colon length were measured. Disease activity and colonic mucosal injury severity were assessed. Colonic histopathology of mice was determined using hematoxylin-eosin staining. Colon-related gene and protein expression were detected by qPCR, western blot, immunohistochemistry, and immunofluorescence. The imbalance in Th17/Treg cell subsets was quantified using flow cytometry.
RESULTS AND CONCLUSION: (1) Mouse body mass was significantly decreased, colon length was significantly shortened, disease activity index scores was significantly elevated, colon mucosal damage index scores and inflammatory cell infiltration density were significantly increased in the model group compared with the normal group (P < 0.01). The expression levels of proinflammatory mediators cyclooxygenase-2, CC chemokine ligand 2, and CXC chemokine ligand 2, hypoxia-inducible factor 1α and its downstream targets matrix metalloproteinase-3, matrix metalloproteinase 9, and nuclear factor κB P65, and blood Th17 cell percentage were significantly increased (P < 0.01), while the expression levels of peroxisome proliferator-activated receptor γ, retinoic acid-related orphan receptor γt (a key factor in Th17 differentiation), and regulatory T cell percentage were significantly decreased in the model group compared with the normal group (P < 0.01). (2) The aforementioned pathological changes were improved in both the electroacupuncture and conventional drug treatment groups compared with the model group (P < 0.01), especially inflammatory cell infiltration was reduced and crypt structural integrity was improved in the colon tissues. Decreased Th17 cell percentage and increased regulatory T cell percentage in the blood were found in the electroacupuncture group compared with the model group (P < 0.01). The findings suggest that electroacupuncture stimulation of Zusanli and Tianshu acupoints may remodel the intestinal immune microenvironment by regulating the bidirectional regulatory network involving the ‌peroxisome proliferator-activated receptor gamma‌/nuclear factor-κB signaling pathway and mediating the immune balance between Th17 and regulatory T cells, thereby offering a novel treatment strategy for ulcerative colitis.

Key words: ulcerative colitis, electroacupuncture, peroxisome proliferator-activated receptor gamma, nuclear factor kappa-B signaling pathway, helper T cell 17, regulatory T cell