ObjectiveTo investigate the effect of Lactobacillus plantarum (LP) on the intestinal barrier function under inflammation. MethodsInterleukin-10 knockout (IL-10－/－) mice were used as the model of inflammatory bowel disease. IL-10－/－ and wild type (WT) mice received the LP or Ringer solutions for 4 weeks. Colitis was assessed by histological score and clinical manifestation was observed. The gut paracellular permeability was measured by Ussing chamber. The concentrations of tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) were detected by the ELISA method. The expressions and distributions of tight junction proteins were determined by Western blot and immunofluorescence, respectively. ResultsCompared with the WT group, the diarrhea, rectal prolapse, and weight loss were obvious (Plt;0.01), the concentrations of TNF-α and IFN-γ significantly increased (Plt;0.01), the infiltration of numerous inflammatory cells, even transmural ulcers, and crypt abscess were observed, the ultrastructure of tight junction was damaged, the mannitol permeability significantly increased (Plt;0.001) and transepithelial resistance (TER) significantly decreased (Plt;0.001), and the expressions of tight junction proteins (ZO-1, occludin, and claudin-1) significantly decreased (Plt;0.01) in the IL-10－/－ group. Compared with the IL-10－/－ group, the clinical and pathological manifestations of colitis significantly improved (Plt;0.01), the ultrastructural damage of tight junction was prevented, the mannitol permeability significantly decreased (Plt;0.001) and the TER significantly increased (Plt;0.001), the concentrations of TNF-α and IFN-γ significantly decreased (Plt;0.01), and the expressions of tight junction proteins (ZO-1, occludin, and claudin-1) significantly increased (Plt;0.01) in the IL-10－/－+LP group. ConclusionTreatment with LP ameliorates colonic epithelial barrier dysfunction by promoting the expressions of tight junctional proteins in IL-10－/－ mice.