Escherichia coli Nissle 1917 Protects Intestinal Barrier Function by Inhibiting NF-κB-Mediated Activation of the MLCK-P-MLC Signaling Pathway.

Shihao Guo,Ju Ma,Pengyuan Wang,Yuanyuan Ma,Yucun Liu,Shanwen Chen,Jing Zhu,Yisheng Pan,Yongchen Ma

doi:10.1155/2019/5796491

Shihao Guo, Ju Ma + Show 7 more

Open Access

https://doi.org/10.1155/2019/5796491

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Journal: Mediators of Inflammation	Publication Date: Jul 3, 2019
Citations: 39	License type: CC BY 4.0

Affiliation: Peking University First Hospital

Abstract

Escherichia coli Nissle 1917 (EcN), a kind of probiotic, has been reported to have a protective effect on the intestinal barrier function and can ameliorate certain gastrointestinal disorders. In this study, the potential protective effect of EcN on the intestinal barrier function in a septic mouse model induced by cecal ligation and puncture (CLP) operation was investigated. FITC-Dextran 4,000 Da (FD-4) flux and the expression levels of tight junction (TJ) proteins were measured to evaluate the protective effect of EcN on the intestinal barrier function. Then, Caco-2 monolayers were utilized to further investigate the protective effect of the EcN supernatant (EcNsup) on the barrier dysfunction induced by TNF-α and IFN-γ in vitro; the plasma level of both the cytokines increased significantly during sepsis. Transepithelial electrical resistance (TEER) and FD-4 transmembrane flux were measured, and the localization of ZO-1 and Occludin was investigated by immunofluorescence. The expression of MLCK and the phosphorylation of MLC were detected by western blot. The activation of NF-κB was explored by immunofluorescence, and CHIP assays were performed to investigate the conjunction of NF-κB with the promoter of MLCK. The results indicated that EcN protected the intestinal barrier function in sepsis by ameliorating the altered expression and localization of TJ proteins and inhibiting the NF-κB-mediated activation of the MLCK-P-MLC signaling pathway which might be one of the mechanisms underlying the effect of EcN.

Highlights

As a life-threatening disorder caused by acute systemic infection, sepsis remains as an important cause of death in critically ill patients [1]
By ChIP assays, we confirmed that the two sites at -136 and -1415 were bound by NF-κB p65 after TNF-α/IFN-γ treatment, but these TNF-α-induced p65 bindings were disrupted in the presence of EcN supernatant (EcNsup) (Figure 6(d)). These results suggested that the blocking of the activation of NF-κB p65 signaling might be one of the mechanisms underlying the protective effect of EcNsup on TNF-α/IFN-γ induced injury of intestinal epithelial barrier function
As the major connection between intestinal epithelial cells, the tight junctions on the surface of intestinal mucosa play an important role in maintaining mechanical integrity and normal functions of the intestinal mucosa [5]

Summary

Introduction

As a life-threatening disorder caused by acute systemic infection, sepsis remains as an important cause of death in critically ill patients [1]. Because sepsis is a heterogeneous disease, people with sepsis always experience multiple organ dysfunction, including the lung, central nervous system, cardiovascular system, liver, kidney, and intestinal injury [2]. The gut, which consists of epithelial cells, immune systems, and microbiota, was assumed to be the promotor of this critical disease. Studies suggested that the intestinal barrier dysfunction propagated the development of multiple organ failure (MOF) in sepsis [3, 4]. ZO-1, a membrane-associated cytosolic protein, can form an anchor for different types of transmembrane proteins, such as Occludin and Claudins, to function as scaffold proteins in the constitution of TJ strands [8].

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