Inhibition of Shigella sonnei-induced epithelial barrier disruption by surface- layer associated proteins of lactobacilli from Chinese fermented food

摘要

ABSTRACTSurface-layer associated proteins (SLAP) ofLactobacillus paracaseissp.paracaseiM5-L andLactobacillus caseiQ8-L were examined to identify the functional basis for their protection within intestinal epithelial cells. The results showed that SLAP of M5-L and Q8-L remained active in a trypsin solution and retained a 45-kDa protein band, similar to that observed in controls. In contrast, under conditions of simulated gastric juice, the SLAP were partially degraded. Inhibitory effects of SLAP on adherence ofShigella sonneito HT-29 cells were assessed with use of exclusion, competition, and replacement assays. In response to M5-L at 50 μg/mL SLAP, an inhibition ratio of 33% was obtained, while for Q8-L at 400 μg/mL SLAP, the inhibition ratio was 48%. Hoechst 33258 test results showed that cells infected withS. sonneiand co-incubated with SLAP of M5-L and Q8-L were only partially apoptotic, with apoptosis rates of 37.67 and 43.67%, respectively. These levels of apoptosis were substantially lower than that observed with cells infected withS. sonneialone. In addition, the SLAP of Q8-L and M5-L reduced downstream caspase-1 activity and further modified apoptotic cell damage. Finally, SLAP of M5-L and Q8-L were also able to preventS. sonnei-induced membrane damage by inhibiting delocalization of zonula occludens (ZO)-1 and reducing the amount of occludin produced byS. sonnei.