Abstract
BackgroundHuman defensin-5 (HD-5) is a key antimicrobial peptide which plays an important role in host immune defense, while the short half-life greatly limits its clinical application. The purpose of this study was to investigate the effects of an engineering probiotic producing HD-5 on intestinal barrier and explore its underlying mechanismMethodsWe constructed the pN8148-SHD-5 vector, and transfected this plasmid into Lactococcus lactis (L. lactis) to create the recombinant NZ9000SHD-5 strain, which continuously produces mature HD-5. NZ9000SHD-5 was administrated appropriately in a dextran sodium sulfate (DSS)-induced colitis model. Alterations in the wounded intestine were analyzed by hematoxylin–eosin staining. The changes of intestinal permeability were detected by FITC-dextran permeability test, the tight junction (TJ) proteins ZO-1 and occludin and cytokines were analyzed by western blotting or enzyme linked immunosorbent assay. In Caco-2 cell monolayers, the permeability were analyzed by transepithelial electrical resistance, and the TJ proteins were detected by western blotting and immunofluorescence. In addition, NF-κB signaling pathway was investigated to further analyze the molecular mechanism of NZ9000SHD-5 treatment on inducing intestinal protection in vitro.ResultsWe found oral administration with NZ9000SHD-5 significantly reduced colonic glandular structure destruction and inflammatory cell infiltration, downregulated expression of several inflammation-related molecules and preserved epithelial barrier integrity. The same protective effects were observed in in vitro experiments, and pretreatment of macrophages with NZ9000SHD-5 culture supernatants prior to LPS application significantly reduced the expression of phosphorylated nuclear transcription factor-kappa B (NF-κB) p65 and its inhibitor IκBα.ConclusionsThese results indicate the NZ9000SHD-5 can alleviate DSS-induced mucosal damage by suppressing NF-κB signaling pathway, and NZ9000SHD-5 may be a novel therapeutic means for ulcerative colitis.
Highlights
Human defensin-5 (HD-5) is a key antimicrobial peptide which plays an important role in host immune defense, while the short half-life greatly limits its clinical application
NZ9000SHD‐5 ameliorated colon injury and inflammatory symptoms in dextran sodium sulfate (DSS)‐induced Ulcerative colitis (UC) model mice To characterize the effect of NZ9000SHD-5 on inflammation, mice from each treatment group were provided
NZ9000SHD‐5 inhibited the infiltration of pro‐inflammatory cytokines in DSS‐induced colitis mice To assess the protective effect of NZ9000SHD-5 on DSSinduced colitis, we evaluated the protein levels and gene expression of common pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), IL-6, and IL-1β in colon tissue
Summary
Human defensin-5 (HD-5) is a key antimicrobial peptide which plays an important role in host immune defense, while the short half-life greatly limits its clinical application. Intestinal epithelial cells (IECs) are exposed to numerous pro-inflammatory and anti-inflammatory cytokines, which are produced by multiple immune and nonimmune cells as well as by IECs themselves. Pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), alter tight junction activity and contribute to apoptosis of IECs, leading to the loss of barrier function [2]. The apoptosis of IECs is induced; on the other hand, the direct contact with immune cells (such as macrophages, neutrophils, dendritic cells, mastocytes, etc.) in intestinal lamina propria stimulates strong immune response, accompanied by a large number of inflammatory factors and interactions of these factors. If not effectively controlled in a short period of time, inflammatory mediators accumulated constantly, toxic effects on IECs and autoantibodies inspire autoimmune response, leading to the development of gut injury and forming a vicious circle, which is one of the reasons why IBD often breaks out repeatedly
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