Effects of moxibustion on visceral hypersensitivity and colonic inflammatory response in mice with chronic ulcerative colitis.

Objectives: To observe the effects of moxibustion at "Zusanli" (ST36) on the expression levels of tumor necrosis factor (TNF)-α, TNF receptor 1 (TNF-R1), p38 mitogen-activated protein kinase (P38 MAPK), and transient receptor potential vanilloid 1 (TRPV1) in the colon tissue of mice with chronic ulcerative colitis (UC), so as to explore the underlying mechanisms of moxibustion in improving visceral hypersensitivity in chronic UC.

Methods: Male C57BL/6J mice were randomly divided into normal group, normal with moxibustion (NM) group, model group, and model with moxibustion (MM) group, with 10 mice in each group. The chronic UC model was established by drinking 2.5% dextran sodium sulfate for 3 cycles. Mice in the NM and MM groups received moxibustion at ST36 for 20 min, 5 days per week with a 2-day break, for a total of 4 weeks. The disease activity index (DAI) score of each group was evaluated before and after treatment. The minimum volume threshold of abdominal wall retraction reflex (AWR) was measured to observe the intestinal sensitivity of mice. The colon length was measured. The pathological changes of colon tissue were observed by HE staining. The expression of mucin in colon goblet cells was detected by periodate Scheff staining. The intestinal fibrosis was observed by Masson staining. The number of trypsin-positive cells (i.e., mast cell) and the expression level of TNF-α in colon tissue were detected by immunofluorescence staining. The expression levels of TNF-R1, P38 MAPK and TRPV1 in colon tissue were detected by immunohistochemistry.

Results: Compared with the normal group after treatment, the model group showed increased DAI score (P<0.001), decreased AWR minimum volume threshold (P<0.01), shortened colon length (P<0.001), significant inflammatory infiltration in the colon tissue, reduced mucin secretion (P<0.01), increased collagen fiber deposition (P<0.001), and elevated expression levels of TNF-α, TNF-R1, P38 MAPK, and TRPV1 (P<0.001, P<0.01, P<0.05). Compared with the model group, the MM group showed decreased DAI score (P<0.01), increased AWR minimum volume threshold (P<0.001), elongated colon length (P<0.001), reduced inflammatory cell infiltration, improved integrity of mucosal glandular structure, enhanced mucin secretion (P<0.01), decreased collagen fiber deposition (P<0.001), decreased number of mast cells in the colon tissue (P<0.001), and decreased expression levels of TNF-α, TNF-R1, P38 MAPK, and TRPV1 (P<0.001, P<0.01, P<0.05). There were no significant differences in the above index between the NM group and the normal group.

Conclusions: Moxibustion can reduce visceral hypersensitivity, alleviate inflammatory infiltration and fibrotic damage in the colon tissue of mice with chronic UC. These effects may be associated with the down-regulation of TNF-α, TNF-R1, P38 MAPK, and TRPV1 expression in colon.