Abstract
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.
Highlights
The following antibodies were used as part of this study: TLR4 (WL00196), MyD88 (WL02494), NLRP3 (WL02635), ASC (WL02462) were purchased from Wanleibio (Shenyang, China); p-NF-κB p65 (AP0123) were purchased from Abclonal (Wuhan, China); NF-κB p65 (#6956) was purchased from CST (Danvers, MA, USA); p-IκB-α and IκB-α were purchased from Bioss (Beijing, China); the following primary antibodies were purchased from proteintech (Rosemont, IL, USA): ZO-1 (21773-1-AP), Occludin (272601-AP), Claudin-1 (13050-1-AP), Caspase-1 (22915-1-AP); β-actin (66009-1-Ig), GAPDH
The Western blotting analysis demonstrated that compared with the CN group, and increased proteins expression of TLR4, MyD88, p-IκBα, and p-p65 were observed in the ST group, but the increase in those proteins was less in the LS group (Figure 1A)
Nuclear p65 as an index to reflect the intensity of activation of the NF-κB pathway was measured
Summary
Typhimurium), a Gram-negative bacterium that replicates in cells, is an important zoonotic pathogen that causes intestinal infectious diseases worldwide [1]. As one of the vital pathogens causing diarrhea in weaned piglets, S. Typhimurium can persist in weaners for a prolonged period (even over 28 weeks) and lastingly affect the growth performance of piglets [2]. Antibiotic treatment remains the principal methodology to deal with Salmonella infection [3]. The results of epidemiological investigations indicated that multi-drug resistant Salmonella became more common in swine farms, and the therapeutic efficacy of antibiotics has been undermined [4]
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