Butyrate-mediated autophagy inhibition limits cytosolic Salmonella Infantis replication in the colon of pigs treated with a mixture of Lactobacillus and Bacillus

Bingxin Chu,Yunjing Zou,Jiufeng Wang,Bing Xia,Wei Zhang,Jinhui Su,Yaohong Zhu,Jiawei Nie

doi:10.1186/s13567-020-00823-8

Abstract

Probiotics as an effective and safe strategy for controlling Salmonella infection are much sought after, while autophagy is a central issue in eliminating intracellular pathogens of intestinal epithelial cells. In this study, an animal model of colitis has been developed by infecting weaned pigs orally with a strain of Salmonella Infantis in order to illuminate the potential efficacy of a mixture of Lactobacillus and Bacillus (CBB-MIX) in the resistance to Salmonella infection by regulating butyrate-mediated autophagy. We found that CBB-MIX alleviated S. Infantis-induced colitis and tissue damage. Autophagy markers ATG5, Beclin-1, and the LC3-II/I ratio were significantly enhanced by S. Infantis infection, while treatment with CBB-MIX suppressed S. Infantis-induced autophagy. Additionally, S. Infantis-induced colonic microbial dysbiosis was restored by this treatment, which also preserved the abundance of the butyrate-producing bacteria and the butyrate concentration in the colon. A Caco-2 cell model of S. Infantis infection showed that butyrate had the same effect as the CBB-MIX in restraining S. Infantis-induced autophagy activation. Further, the intracellular S. Infantis load assay indicated that butyrate restricted the replication of cytosolic S. Infantis rather than that in Salmonella-containing vacuoles. Suppression of autophagy by knockdown of ATG5 also attenuated S. Infantis-induced cell injury. Moreover, hyper-replication of cytosolic S. Infantis in Caco-2 cells was significantly decreased when autophagy was inhibited. Our data demonstrated that Salmonella may benefit from autophagy for cytosolic replication and butyrate-mediated autophagy inhibition reduced the intracellular Salmonella load in pigs treated with a probiotic mixture of Lactobacillus and Bacillus.

Highlights

Our data demonstrated that Salmonella may benefit from autophagy for cytosolic replication and butyrate-mediated autophagy inhibition reduced the intracellular Salmonella load in pigs treated with a probiotic mixture of Lactobacillus and Bacillus
The continuous and stable mitochondrial β-oxidation in intestinal epithelial cells can ensure the formation of a physiological anoxic intestinal environment, ensuring a healthy microbiota structure dominated by specialized anaerobic bacteria [41, 42]
It was reported that cyclic dipeptides containing Val-Leu and Val-Ile produced by B. subtilis C-3102 could serve as bifidogenic growth factors to increase the abundance of beneficial microorganisms related to the genus Bifidobacterium in a human colonic microbiota model culture system [46]

Summary

Introduction

Chu et al Vet Res (2020) 51:99 known as hyper-replication (defined as 50 bacteria per cell), a state where Salmonella expresses SPI-1 genes and synthesize flagella in preparation for further invasion [8, 11, 12]. These bacteria pass through infected cells to escape into the interstitium, where they can cause infections in neighboring cells that eventually spread through the enteric cavity [12]. Infantis infection by suppressing activation of intestinal epithelial cell autophagy in pigs [21]. Infantis dissemination and ameliorated enteritis via suppression of autophagy in weaned pigs [22]

Methods

Results

Conclusion