The influence of intestinal dysbacteriosis on visceral sensitivity and possible mechanisms

Objective: To detect the changes of visceral sensitivity in rats presenting intestinal dysbacteriosis and the expressions of tight junction protein (ZO-1) and Toll-like receptor 4 (TLR4) so as to explore the effect of intestinal dysbacteriosis on visceral sensitivity and the possible mechanisms. Methods: We randomly divided 30 male SD rats of SPF grade into normal control group (n=12) and dysbacteriosis group (n=18). Rats in dysbacteriosis group were administered with lincomycin hydrochloride (300 mg/mL), 1 mL each time per rat once a day for 7 consecutive days; those in normal control group were fed with the same amount of saline. On the eighth day, six rats were randomly selected from normal control group and dysbacteriosis group respectively to detect whether the model was successful. After the model was successfully constructed, the remaining 12 dysbacteriosis rats were randomly divided into the negative control group and the probiotics intervention group with 6 in each. Rats in the intervention group were given probiotic bifidobacterium triple viable capsules (Bifico) orally, one capsule with 1/3 mL of saline, 1 mL each time per rat once a day for 7 consecutive days; those in the negative control group received the same amount of saline. On the eighth day, fresh feces was cultured for flora to detect visceral sensitivity by abdominal withdrawal reflex (AWR), the mRNA and protein expressions of ZO-1 and TLR4 in the colon, and the expression of serum inflammatory cytokines IL-10 and TNFα. Results: The expression of ZO-1 in the colon was significantly lower in the rats of dysbacteriosis group than those in the control group, and the expression of TLR4 was also significantly increased. Correspondingly, the expression of pro-inflammatory factor TNFα in the serum of the rats in dysbacteriosis group was significantly increased, while that of anti-inflammatory factor IL-10 was significantly lower than in the control group (P<0.05). Furthermore, compared with dysbacteriosis group, the expression of ZO-1 was increased significantly and TLR4 was decreased in probiotics group in varying degrees. Similarly, the expression of TNFα was obviously lower while that of IL-10 in the serum was higher (P<0.05). Conclusion: Inhibiting the expression of ZO-1 and increasing the expression of TLR4, thus leading to chronic low-grade inflammation, may be one mechanism of visceral hypersensitivity caused by intestinal dysbacteriosis. Probiotics may restore the dysbacteriosis and thus improve visceral hypersensitivity.