Recombinant CRAMP-producing Lactococcus lactis attenuates dextran sulfate sodium-induced colitis by colonic colonization and inhibiting p38/NF-κB signaling

BACKGROUND: Inflammatory bowel diseases (IBDs) are generally characterized by persistent abdominal pain and diarrhea caused by chronic inflammation in the intestine. Cathelicidins are antimicrobial peptides with pleiotropic roles in anti-infection, wound healing, and immune modulation. However, the sensitivity to the acidic environment and short half-life of cathelicidins limit their application in IBD treatment. Recombinant cathelicidin-related antimicrobial peptide (CRAMP)-producing Lactococcus lactis may represent a potential approach for IBD therapy. OBJECTIVE: The aim of this study was to develop recombinant CRAMP-producing L. lactis NZ9000 and explore the role and mechanism of recombinant L. lactis NZ9000 expressing CRAMP in colitis. DESIGN: We constructed two strains of CRAMP-producing L. lactis NZ9000 with different plasmids pMG36e (L.L-pMU45CR) or pNZ8148 (L.L-pNU45CR), which use a Usp45 secretion signal to drive the secretion of CRAMP. Bacterial suspensions were orally supplemented to mice with a syringe for 4 days after dextran sodium sulfate (DSS) treatment. Body weight change, disease active score, colon length, and colonic histology were determined. The expression of tight junction (ZO-1, ZO-2, and Occludin) and cytokines (IL-6, IL-1β, TNF-α, and IL-10) in colon was performed by qPCR. The expression of p-ERK, p-p38, and p-p65 was determined by Western blot analysis. RESULTS: Both CRAMP-producing L. lactis NZ9000 strains protected against colitis, as shown by reduced weight loss and disease activity score, improved colon shortening, and histopathological injury. In addition, CRAMP-producing L. lactis NZ9000 restored gut barrier by upregulating ZO-1, ZO-2, and occludin. Moreover, CRAMP-producing L. lactis NZ9000 regulated the colonic cytokines profile with reduced IL-6, IL-1β, and TNF-α production, and increased IL-10 production. By further analysis, we found that CRAMP-producing L. lactis NZ9000 reduced the expression of p-p38 and p-p65. CONCLUSIONS: Together, our data suggested that CRAMP-secreting L. lactis NZ9000 attenuated dextran sulfate sodium-induced colitis by colonic colonization and inhibiting p38/NF-κB signaling. Orally administered recombinant CRAMP-secreting L. lactis NZ9000 represents a potential strategy for colitis therapy.