Effect of moxibustion on colonic low-grade inflammatory response in rats with diarrhea-predominant irritable bowel syndrome based on mast cell degranulation.

OBJECTIVES

To observe the effects of moxibustion on colonic mast cell degranulation and inflammatory factor expression in rats with diarrhea-predominant irritable bowel syndrome (IBS-D), and explore the potential mechanism of moxibustion in treating IBS-D.

METHODS

Forty-five rat pups born from 5 healthy SPF-grade pregnant SD rats, with 8 rats were randomly selected as the normal group. The remaining 37 rats were intervened with maternal separation, acetic acid enema, and chronic restraint stress to establish the IBS-D model. The successfully modeled 32 rats were then randomly assigned to a model group, a ketotifen group, a moxibustion group, and a moxibustion-medication group, with 8 rats in each group. The rats in the ketotifen group were intervened with intragastric administration of ketotifen solution (10 mL/kg); the rats in the moxibustion group were intervened with suspended moxibustion on bilateral "Tianshu" (ST 25) and "Shangjuxu" (ST 37); the rats in the moxibustion-medication group were intervened with suspended moxibustion combined with intragastric administration of ketotifen solution. All interventions were administered once daily for 7 consecutive days. The diarrhea rate and minimum volume threshold of abdominal withdrawal reflex (AWR) were calculated before and after modeling, as well as after intervention. After intervention, colonic tissue morphology was observed using HE staining; colonic mucosal ultrastructure was examined by scanning electron microscopy; colonic mast cell ultrastructure was observed using transmission electron microscopy; mast cell degranulation was assessed by toluidine blue staining; serum and colonic levels of histamine, interleukin (IL)-1β, IL-6, IL-1α, trypsin-like enzyme, and protease-activated receptor 2 (PAR-2) were measured by ELISA; the Western blot and real-time quantitative PCR were employed to evaluate the protein and mRNA expression of colonic IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2; the immunofluorescence was used to detect the positive expression of histamine, IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 in the colonic tissue.

RESULTS

Compared to the normal group, the rats in the model group exhibited extensive infiltration of inflammatory cells in colonic tissue, severe damage to the colonic mucosa, disordered arrangement of villi, reduced electron density, and a significant decrease in granule quantity within mast cells. The diarrhea rate and mast cell degranulation rate were increased (<0.01), AWR minimum volume threshold was decreased (<0.01); the serum and colonic levels of histamine, IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 were elevated (<0.01); the positive expression of histamine, as well as protein, mRNA and positive expression of IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 in the colon were all elevated (<0.01). Compared to the model group, the rats in the ketotifen group, the moxibustion group, and the moxibustion-medication group exhibited significantly reduced infiltration of inflammatory cells in colonic tissue, relatively intact colonic mucosa, orderly arranged villi, increased electron density, and an augmented number of mast cell granules; the diarrhea rate and mast cell degranulation rate were decreased (<0.01), and AWR minimum volume threshold was increased (<0.01); the serum and colonic levels of histamine, IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 were reduced (<0.01); the positive expression of histamine, as well as protein, mRNA and positive expression of IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 in the colon were all decreased (<0.01). Compared to the ketotifen group, the moxibustion group showed decreased serum levels of histamine, IL-6, and trypsin-like enzyme (<0.01, <0.05), as well as reduced colonic levels of IL-1β and IL-6 (<0.01, <0.05); the protein expression of colonic IL-1β, IL-1α, and PAR-2 was reduced (<0.05), and the positive expression of colonic IL-1β and trypsin-like enzyme was reduced (<0.01, <0.05). Compared to both the ketotifen group and the moxibustion group, the moxibustion-medication group exhibited decreased diarrhea rate and mast cell degranulation rate (<0.01), an increased AWR minimum volume threshold (<0.01), reduced serum and colonic levels of histamine, IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 (<0.01), decreased protein expression of colonic IL-1β, trypsin-like enzyme, and PAR-2 (<0.01, <0.05), reduced mRNA and positive expression of colonic IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 (<0.01, <0.05), and decreased positive expression of colonic histamine (<0.01).

CONCLUSIONS

Moxibustion on "Tianshu" (ST 25) and "Shangjuxu" (ST 37) might inhibit low-grade inflammatory reactions in the colon of IBS-D model rats. The mechanism may be related to the inhibition of histamine and trypsin-like enzyme secreted by mast cell, thereby reducing the expression of related inflammatory factors.