[Effect of moxibustion on TLR4/MyD88/NF-κB signaling pathway in colon of diarrhea-predo-minant irritable bowel syndrome rats].

Objective: To observe the effect of moxibustion on serum inflammatory factors, Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and nuclear factor Kappa B (NF-κB) in colon tissue of rats with diarrhea-predominant irritable bowel syndrome (IBS-D)，so as to explore the mechanism of moxibustion in the treatment of IBS-D.

Methods: Healthy male SD rats were randomly divided into blank group, model group and moxibustion group, with 8 rats in each group. The IBS-D model was established by chronic restraint combined with gavage of Senna-leaf solution. The rats of the moxibustion group was treated with moxibustion at "Tianshu"(ST25)and "Shangjuxu"(ST37)for 30 min， once a day for 7 d. After the intervention, the rate of loose stools and the minimum threshold volume of abdominal withdrawal reflex (AWR) induced by colorectal distension were observed. The contents of serum inflammatory factors IL-1β, TNF-α and IL-6 were detected by ELISA. The pathological changes of rat colon were observed by H.E. staining. The average optical density of TLR4 and NF-κB (p65) in colon tissue was detected by immunohistochemistry. The relative expressions of TLR4, MyD88 and NF-κB (p65) mRNAs in colon tissues were detected by real-time fluorescence quantitative PCR, and the expression levels of TLR4, MyD88 and NF-κB (p65) proteins in colon tissues were detected by Western blot.

Results: There was a mild degree of inflammation in colon in rats of the model group. Compared with the blank group, the minimum volume threshold of AWR decreased significantly (< 0.01), and the rate of loose stools, the contents of IL-1β, IL-6 and TNF-α in serum as well as the expressions of TLR4, MyD88, NF-κB (p65) mRNAs and protein in colon tissues were significantly increased in the model group (<0.01). Compared with the model group, the inflammation was alleviated in colonic mucosa, the minimum volume threshold of AWR increased significantly (<0.01), and rate of loose stools decreased significantly (<0.01) in the moxibustion group, the contents of IL-1β, TNF-α and IL-6 in serum and the expression levels of TLR4, MyD88, NF-κB (p65) mRNAs and proteins in colon tissue decreased significantly in the moxibustion group (<0.01).

Conclusion: Moxibustion ST25 and ST37 can improve diarrhea symptom and visceral hypersensitivity in IBS-D rats, which may be related with its effects in inhibiting TLR4/MyD88/NF-κB signaling pathway and reducing the expression of inflammatory factors.