Probiotics are efficacious in the treatment of
inflammatory bowel disease. However, the precise mechanisms remain unknown. To determine whether probiotic Lactobacillus plantarum (LP) ameliorates colonic epithelial barrier dysfunction present in
interleukin-10 knockout (IL-10⁻(/)⁻) mice, IL-10⁻(/)⁻ and wild-type mice received LP or the vehicle for 4 wk.
Colitis was assessed by histological scores and clinical manifestation, and gut paracellular permeability was measured by Ussing chamber.
Oligopeptide transporter 1 (PepT1)-mediated transepithelial transport was evaluated by measuring the plasma
cephalexin concentration. The expression and distribution of apical junctional complex (AJC)
proteins and PepT1 were determined by Western blotting and immunofluorescence and their
mRNA by
reverse transcriptase-PCR. Spontaneous
colitis was observed in all IL-10⁻(/)⁻ mice in which paracellular permeability was increased, in conjunction with decreased expression and redistribution of zonula occludens-1,
occludin,
claudin-1, and β-
catenin. PepT1 expression was increased, accompanied with an enhanced
cephalexin transport. Colonic epithelial barrier dysfunction was further confirmed by increased bacterial translocation and proinflammatory
cytokine production. Treatment with LP decreased colonic paracellular permeability with restoration of expression and distribution of AJC
proteins and partially prevented PepT1 expression and
cephalexin transport in IL-10⁻(/)⁻ mice. Moreover, treatment with LP also prevented bacterial translocation and proinflammatory
cytokine production in IL-10⁻(/)⁻ mice. Results from this study indicated that treatment with LP may ameliorate colonic epithelial barrier dysfunction in IL-10⁻(/)⁻ mice, by modulating the AJC- and PepT1-mediated transepithelial transport.