RESUMO
Objective To evaluate the role of Lactobacillus plantarum (LP) in the treatment of colitis in interleukin (IL)-10 knockout (IL-10-/-) mice and to explore its possible mechanisms.Methods Eight weeks old female wildtype (WT) mice and IL-10-/- mice, twenty mice of each type,were randomly assigned to four groups, WT group, WT+ LP group, IL-10-/- group and IL-I0-/- +LP group. The WT and IL-10-/- mice were gavaged with 0.5 ml saline, WT+Lp and IL-10-/- +Lp groups were gavaged with Lp 0.02 g (0.5 ml) ,took Lp 1 × 109 cfu everyday,continued for 4 weeks and then the experiment finished. The fresh mice faeces was collected once every week before (week 0) and during the experiment. The mice were executed at the end of experiments, the change of mice weight Was recorded, the length and the wet weight of colon were measured, fresh colon tissue specimens were taken for biological slices and proinflammatory cytokines TNF-a and IFN-γ were measured in colon mucosa. The fresh faeces were selectively cultured. The colonization of Lp in normal and colitis mice and its regulation role in intestinal flora were observed. Results Compared with WT mice, IL-10-/- mice demonstrated severe diarrhea, significantly decreased in body weight (P ＜0.05)and serious malnutrition. After Lp treatment, diarrhea relieved in IL-10-/- mice and the body weight increased significantly (P＜0.05). Pathological examination suggested that 100％ of IL-10-/-mice had intestinal inflammation, however after Lp treatment intestinal inflammation improved significantly. Mucosal ulcer, epithelial hyperplasia, the infiltration of neutrophils and lymphocytes in the lamina propria were also significantly reduced.The histopathological score was significantly lowered (P＜0.01). After Lp treatment, colon wet weight and the ratio of wet weight to length of IL-10-/- mice changed significantly (P＜0.01). Colon edema and thickening improved remarkably. The TNF-a and IFN-γ concentration of colon in IL-10-/- mice were 377.4±84.4 μg/g and 602.6±108.1 μg/g,which increased obviously than WT group (139.2 ± 32. 7 μg/g and 173.0± 52.4 μg/g, P＜0.05). After treated with Lp for four weeks, the TNF-α and IFN-γ concentration of colon in IL-10-/-+Lp group mice were 207.2±65.7 μg/g and 442.1 ± 138.4 μg/g, both were lower than that of IL-10-/- group mice (P＜0.05). The intestinal flora was disrupted in IL-10-/- mice. Conclusion Lp can effectively reduce intestinal inflammation in IL-10-/- mice, which take certain part in treatment in colitis. This treatment effect is associated with intestinal flora regulation and the inhibition of proinflammation cytokines expression.