Fig. 7: BLP blocks Lm from causing disturbance of intestinal epithelial cell–cell junctional integrity.

a, b TEER of Caco-2 cell monolayer treated with LbcWT or BLP strains (MOE; 10, 24 h) before Lm exposure (MOI; 50, 2 h) (a) and on the apical (AP)-to-basolateral (BL) flux of FD4 permeability (b). Data in a and b represent mean ± SEM from n = 3 biologically independent samples. c, d FD4 gut permeability of control (mock-treated) naive uninfected mice or L. casei-treated (10 days, LbcWT or BLP) pre- or post-Lm challenge (48 hpi) in serum (c) and urine (d). Each point represents an individual mouse. Data (c, d) represent mean ± SEM of n = 3 mice for all groups except Lm group, n = 5 mice. e Immunofluorescence micrographs of Caco-2 cells showing increased expression of MLCK and P-MLC (green; arrows) and mislocalization (intracellular puncta) of claudin-1, occludin, and E-cadherin (red; arrows) in cells exposed with Lm (MOI; 50, 2 h) or treated with LbcWT (MOE; 10, 24 h) before Lm exposure but baseline expression of MLCK and P-MLC and intact localization of occludin, claudin-1, and E-cadherin in cells treated to BLP strains before Lm exposure, relative to untreated (control) cells. Nuclei; DAPI, blue. Lm cells are double immunostained in red in the P-MLC panel and green in occludin, claudin-1, and E-cadherin panels. Images are representative of five different fields. Bars, 10 μm. f Immunofluorescence micrographs of the ileal tissues showing increased expression of MLCK and P-MLC (green; arrows) and mislocalization (intracellular puncta) of claudin-1 (green; arrows), occludin and E-cadherin (red; arrows) in naive or LbcWT-treated (10 days) but baseline expression of MLCK and P-MLC and intact localization of occludin, claudin-1, and E-cadherin in BLP-treated mice (10 days) at 48 hpi, relative to uninfected naive mice. Nuclei; DAPI, blue. Images are representative of five different fields from n = 3 mice per treatment. Bars, 10 μm. LP lamina propria. Data in a–e are from three independent experiments. For all analysis, the one-way ANOVA test followed by a Tukey’s multiple comparisons was used; ****P < 0.0001; ***P < 0.001; **P < 0.01; *P < 0.05; ns no significance. Source data are provided as a Source Data file.