[Effect of moxibustion on small intestinal mucosal immune barrier in rats with diarrhea-predominant irritable bowel syndrome].

Objective: To observe the effect of moxibustion on small intestinal mucosal immune barrier in rats with diarrhea-predominant irritable bowel syndrome (IBS-D) and explore its underlying mechanisms.

Methods: Of 38 newborn rats from 4 healthy SPF pregnant rats, 12 neonatal rats were randomly selected in a normal group. IBS-D model was prepared by the combined measures for the rest rats, including neonatal maternal separation, acetic acid enema and chronic restraint stress. Twenty-four successfully-modeled rats were randomized into a model group and a moxibustion group, 12 rats in each one. In the moxibustion group, suspending moxibustion was delivered at bilateral "Tianshu" (ST25) and "Shangjuxu" (ST37), 20 min each time, once daily and for 7 consecutive days. Separately, before acetic acid enema (aged 35 days), after modeling (aged 45 days) and after intervention (aged 53 days), the body mass, loose stool rate (LSR) and and the minimum volume threshold when abdominal withdrawal reflex (AWR) scored 3 were observed in the rats of each group. After intervention (aged 53 days), using HE and PAS staining, the morphology of duodenum was observed, the length of villus and the depth of crypt were measured, the ratio of the length of villus to the depth of crypt was calculated; and the numbers of mucosal intraepithelial lymphocytes (IELs) and goblet cells were counted. With ELISA adopted, the contents of γ-interferon (IFN-γ), interleukin-4 (IL-4) and secretory immunoglobulin A (sIgA) in duodenal mucosa of rats were detected. The proportion of T cell subsets in duodenal mucosa was detected using flow cytometry. The microvilli and tight junctions of duodenal mucosal epithelial cells were observed by transmission electron microscopy, and the integrity of duodenal mucosa observed by scanning electron microscopy.

Results: Compared with the normal group, for the rats in the model group, the body mass, the minimum volume threshold when AWR scored 3, the length of duodenal villus and the the ratio of the length of villus to the depth of crypt, as well as the proportion of CD₈⁺ T subset were all reduced (P<0.01, P<0.05), the counts of goblet cells in duodenal mucosa decreased (P<0.01); LRS, the proportion of CD₄⁺ T subset and CD₄⁺/CD₈⁺, as well as the contents of IFN-γ, IL-4 and sIgA in duodenal mucosa and IFN-γ/IL-4 were all elevated (P<0.01); and the numbers of IELs rose (P<0.01). The morphology of duodenal mucosa was irregular, the villi got shorter, sparse and scattered, with uneven density. The morphology of epithelial cells was destroyed and the tight junctions damaged, with larger spaces. When compared with the model group, in the moxibustion group, the body mass, the minimum volume threshold when AWR scored 3, the length of duodenal villus and the ratio of the length of villus to the depth of crypt, as well as the counts of goblet cells in duodenal mucosa increased (P<0.01); LRS, the proportion of CD₄⁺ T subset, and CD₄⁺/CD₈⁺, as well as the contents of IFN-γ, IL-4 and sIgA in duodenal mucosa and IFN-γ/IL-4 were reduced (P<0.01); and the numbers of IELs was dropped (P<0.01). The morphology of duodenal mucosa was more regular, the villi were grew, got longer and arranged regularly, with even density. The morphology of epithelial cells was slightly destroyed, and the tight junctions partially damaged.

Conclusion: Moxibustion at "Tianshu" (ST25) and "Shangjuxu" (ST37) can reduce visceral hypersensitivity in IBS-D rats and relieve abdominal pain, diarrhea and other symptoms. Its effect mechanism may be related to the repair of small intestinal mucosal immune barrier and the improvement in the immune function in IBS-D.