STAT2 dependent Type I Interferon response promotes dysbiosis and luminal expansion of the enteric pathogen Salmonella Typhimurium.

R Paul Wilson,Kevin P Kotredes,Sajan Patel,Nicole J Medeiros,Wenhan Zhu,Shuang Sun,Glenn J Rapsinski,Sebastian E Winter,Ana M Gamero,Laurie Kilpatrick,Çagla Tükel,Long S Le,Elisabetta Liverani,Sarah A Tursi

doi:10.1371/journal.ppat.1007745

R Paul Wilson, Kevin P Kotredes + Show 12 more

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https://doi.org/10.1371/journal.ppat.1007745

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Abstract

The mechanisms by which the gut luminal environment is disturbed by the immune system to foster pathogenic bacterial growth and survival remain incompletely understood. Here, we show that STAT2 dependent type I IFN signaling contributes to the inflammatory environment by disrupting hypoxia enabling the pathogenic S. Typhimurium to outgrow the microbiota. Stat2-/- mice infected with S. Typhimurium exhibited impaired type I IFN induced transcriptional responses in cecal tissue and reduced bacterial burden in the intestinal lumen compared to infected wild-type mice. Although inflammatory pathology was similar between wild-type and Stat2-/- mice, we observed decreased hypoxia in the gut tissue of Stat2-/- mice. Neutrophil numbers were similar in wild-type and Stat2-/- mice, yet Stat2-/- mice showed reduced levels of myeloperoxidase activity. In vitro, the neutrophils from Stat2-/- mice produced lower levels of superoxide anion upon stimulation with the bacterial ligand N-formylmethionyl-leucyl-phenylalanine (fMLP) in the presence of IFNα compared to neutrophils from wild-type mice, indicating that the neutrophils were less functional in Stat2-/- mice. Cytochrome bd-II oxidase-mediated respiration enhances S. Typhimurium fitness in wild-type mice, while in Stat2-/- deficiency, this respiratory pathway did not provide a fitness advantage. Furthermore, luminal expansion of S. Typhimurium in wild-type mice was blunted in Stat2-/- mice. Compared to wild-type mice which exhibited a significant perturbation in Bacteroidetes abundance, Stat2-/- mice exhibited significantly less perturbation and higher levels of Bacteroidetes upon S. Typhimurium infection. Our results highlight STAT2 dependent type I IFN mediated inflammation in the gut as a novel mechanism promoting luminal expansion of S. Typhimurium.

Highlights

A healthy gastrointestinal microbiota is characterized by the dominance of obligate anaerobic members of the phyla Bacteroidetes and Firmicutes
In the absence of STAT2-dependent type I IFN, production of neutrophil reactive oxygen species was impaired, and epithelial metabolism returned to homeostatic hypoxia
Typhimurium utilizes STAT2-dependent type I IFN signaling to generate a niche in the inflamed intestinal tract and outcompete the gut microbiota

Summary

Introduction

A healthy gastrointestinal microbiota is characterized by the dominance of obligate anaerobic members of the phyla Bacteroidetes and Firmicutes. The expansion of facultative anaerobic Enterobacteriaceae (phylum Proteobacteria) is considered a microbial signature for gut inflammation and dysbiosis [1, 2]. This signature is observed in severe human intestinal diseases including inflammatory bowel disease (IBD), [3,4,5] colorectal cancer [6] and necrotizing enterocolitis [7]. Epithelial invasion, recognition of Pathogen-Associated Molecular Patterns (PAMPs) and macrophage survival leads to the production of chemokines and cytokines triggering an inflammatory environment and acute colitis [10,11,12]. Typhimurium outcompetes the healthy microbiota enabling its luminal expansion and eventually facilitating the transmission to subsequent hosts [13,14,15,16]

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