Lactobacillus johnsonii L531 Alleviates the Damage Caused by Salmonella Typhimurium via Inhibiting TLR4, NF-κB, and NLRP3 Inflammasome Signaling Pathways

Salmonella Typhimurium (S. Typhimurium) is an aggressive zoonotic pathogen that causes enteritis and diarrhea. Antibiotic therapy is still the primary method at present. However, the increasing emergence of multi-drug resistant bacteria weakens the therapeutic efficacy of antibiotics. Probiotics have been widely studied as an alternative antibiotic therapy. In this study, we established an IPEC-J2 cell model of S. Typhimurium infection, aiming to determine the protective effect of Lactobacillus johnsonii L531 (L. johnsonii L531) on S. Typhimurium infection. As our data showed, S. Typhimurium infection resulted in a robust inflammatory response demonstrated by promoted protein levels of the inflammatory-related pathway (TLR4, MyD88, p-IκBα, and p-p65), increased cytokine levels of IL-6, IL-1β, IL-18, and TNF-α, and activated the NLRP3 inflammasome via promoting its assembly. However, L. johnsonii L531 pre-incubation inhibited the activation of the above inflammatory signaling pathways and reduced the expression levels of pro-inflammatory cytokines. In addition, L. johnsonii L531 alleviated the damage of S. Typhimurium to tight junctions ZO-1, Occludin, and Claudin-1. In summary, our findings suggested that L. johnsonii L531 alleviated S. Typhimurium-induced tight junction injury by inhibiting the TLR4/NF-κB/NLRP3 inflammasome signaling pathway.