Recombinant L. lactis Expressing Defensin-5 Protects Against Mice Colitis via NF-κβ Pathway

Defensin is a key antimicrobial peptide which plays an important role in host immunity and maintaining gut barrier function. In this study, we optimized a defensin mHD-5 clone primarily consisting of the mature human defensin-5 (HD-5) peptide, constructed the pN8148-SHD-5 vector, and transfected this plasmid into Lactococcus lactis to create the recombinant NZ9000SHD-5 strain, which produces HD-5 under nisin-controlled gene expression. We found exposure of mice with colitis induced by dextran sodium sulfate (DSS) to the NZ9000SHD-5 strain attenuated inflammatory cell infiltration and histopathological changes in colonic glands and preserved epithelial barrier integrity. The same protective effects were observed in RAW264.7 cells and Caco-2 cells in in vitro experiments. Moreover, pretreatment of the mouse macrophage cell line RAW264.7 with NZ9000SHD-5 culture supernatants prior to LPS application significantly reduced the expression of phosphorylated nuclear transcription factor-kappa B (NF-κβ) p65 and its inhibitor IκBα. These results indicate the NZ9000SHD-5 strain can alleviate DSS-induced mucosal damage and changes in paracellular permeability, possibly by attenuating colonic inflammation through downregulation of the NF-κβ signaling pathway. Thus, administration of the NZ9000SHD-5 strain may be a possible therapeutic option for colitis. Funding: Supported by the National Natural Science Foundation of China (No. 81570480 and 81770529) and the Special Scientific Research Fund of Public Welfare Profession of National Health and Family Planning Commission (No. 201502026). Declaration of Interest: The author have claimed that there was no competing interest. Ethical Approval: The Southern Medical University Ethics Committee approved the protocols according to the Helsinki Declaration (6th revision, 2008), and all animal procedures were approved by the Institutional Animal Care and Use Committee of Southern Medical University.