Interleukin-22 enhanced the mucosal barrier and inhibited the invasion of Salmonella enterica in human-induced pluripotent stem cell-derived small intestinal epithelial cells.

Human-induced pluripotent stem cell-derived small intestinal epithelial cell (hiPSC-SIEC) monolayers are useful in vitro models for evaluating the gut mucosal barrier; however, their reactivity to cytokines, which are closely related to the regulation of mucosal barrier function, remains unclear. Interleukin (IL)-22 is a cytokine that contributes to regulate the mucosal barrier in the intestinal epithelia. Using microarray and gene set enrichment analysis, we found that hiPSC-SIEC monolayers activate the immune response and enhance the mucosal barrier in response to IL-22. Moreover, hiPSC-SIEC monolayers induced the gene expression of antimicrobials, including the regenerating islet-derived protein 3 family. Furthermore, IL-22 stimulation upregulated Mucin 2 secretion and gene expression of an enzyme that modifies sugar chains, suggesting alteration of the state of the mucus layer of hiPSC-SIEC monolayers. To evaluate its physiological significance, we measured the protective activity against Salmonella enterica subsp. enterica infection in hiPSC-SIEC monolayers and found that prestimulation with IL-22 reduced the number of viable intracellular bacteria. Collectively, these results suggest that hiPSC-SIEC monolayers enhance the mucosal barrier and inhibit infection by pathogenic bacteria in response to IL-22, as previously reported. These results can contribute to the further application of hiPSC-SIECs in evaluating mucosal barriers.

Yogurt starter strains ameliorate intestinal barrier dysfunction via activating AMPK in Caco-2 cells.

Lactic acid bacteria (LAB) are commonly used probiotics that improve human health in various aspects. We previously reported that yogurt starter strains, Lactobacillus delbrueckii subsp. bulgaricus 2038 and Streptococcus thermophilus 1131, potentially enhance the intestinal epithelial barrier function by inducing the expression of antimicrobial peptides in the small intestine. However, their effects on physical barrier functions remain unknown. In this study, we found that both strains ameliorated the decreased trans-epithelial resistance and the increased permeability of fluorescein isothiocyanate-dextran induced by tumor necrosis factor (TNF)-α and interferon (IFN)-γ in Caco-2 cells. We also demonstrated that LAB prevented a decrease in the expression and disassembly of tight junctions (TJs) induced by TNF-α and IFN-γ. To assess the repair activity of TJs, a calcium switch assay was performed. Both strains were found to promote the reassembly of TJs, and their activity was canceled by the inhibitor of AMP-activated protein kinase (AMPK). Moreover, these strains showed increased AMPK phosphorylation. These observations suggest that the strains ameliorated physical barrier dysfunction via the activation of AMPK. The activities preventing barrier destruction induced by TNF-α and IFN-γ were strain-dependent. Several strains containing L. bulgaricus 2038 and S. thermophilus 1131 significantly suppressed the barrier impairment, and L. bulgaricus 2038 showed the strongest activity among them. Our findings suggest that the intake of L. bulgaricus 2038 and S. thermophilus 1131 is a potential strategy for the prevention and repair of leaky gut.