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A Nonpyroptotic IFN-?-Triggered Cell Death Mechanism in Nonphagocytic Cells Promotes Salmonella Clearance In Vivo.

ABSTRACT: The cytokine IFN-? has well-established antibacterial properties against the bacterium Salmonella enterica in phagocytes, but less is known about the effects of IFN-? on Salmonella-infected nonphagocytic cells, such as intestinal epithelial cells (IECs) and fibroblasts. In this article, we show that exposing human and murine IECs and fibroblasts to IFN-? following infection with Salmonella triggers a novel form of cell death that is neither pyroptosis nor any of the major known forms of programmed cell death. Cell death required IFN-?-signaling via STAT1-IRF1-mediated induction of guanylate binding proteins and the presence of live Salmonella in the cytosol. In vivo, ablating IFN-? signaling selectively in murine IECs led to higher bacterial burden in colon contents and increased inflammation in the intestine of infected mice. Together, these results demonstrate that IFN-? signaling triggers release of Salmonella from the Salmonella-containing vacuole into the cytosol of infected nonphagocytic cells, resulting in a form of nonpyroptotic cell death that prevents bacterial spread in the gut.

SUBMITTER: Ingram JP

PROVIDER: S-EPMC6034694 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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A Nonpyroptotic IFN-γ-Triggered Cell Death Mechanism in Nonphagocytic Cells Promotes Salmonella Clearance In Vivo.

Ingram Justin P JP Tursi Sarah S Zhang Ting T Guo Wei W Yin Chaoran C A Wynosky-Dolfi Meghan M van der Heijden Joris J Cai Kathy Q KQ Yamamoto Masahiro M Finlay B Brett BB Brodsky Igor E IE Grivennikov Sergei I SI Tükel Çagla Ç Balachandran Siddharth S

Journal of immunology (Baltimore, Md. : 1950) 20180413 10

The cytokine IFN-γ has well-established antibacterial properties against the bacterium Salmonella enterica in phagocytes, but less is known about the effects of IFN-γ on Salmonella-infected nonphagocytic cells, such as intestinal epithelial cells (IECs) and fibroblasts. In this article, we show that exposing human and murine IECs and fibroblasts to IFN-γ following infection with Salmonella triggers a novel form of cell death that is neither pyroptosis nor any of the major kn ...[more]

PMID: 29654208

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Project description:Salmonella enterica strains are enteropathogenic bacteria that survive and proliferate within vacuolar compartments of epithelial and phagocytic cells. Recently, it has been reported that fibroblast cells are capable of restricting S. enterica serovar Typhimurium intracellular growth. Here, we show that prolonged residence of bacteria in the intracellular environment of fibroblasts results in the appearance of genetically stable small-colony variants (SCV). A total of 103 SCV isolates, obtained from four independent infections, were subjected to phenotypic analysis. The following phenotypes were observed: (i) delta-aminolevulinic acid auxotrophy; (ii) requirement for acetate or succinate for growth in glucose minimal medium; (iii) auxotrophy for aromatic amino acids; and (iv) reduced growth rate under aerobic conditions not linked to nutrient auxotrophy. The exact mutations responsible for the SCV phenotype in three representative isolates were mapped in the lpd, hemL, and aroD genes, which code for dihydrolipoamide dehydrogenase, glutamate-1-semyaldehyde aminotransferase, and 3-dehydroquinate dehydratase, respectively. The lpd, hemL, and aroD mutants had intracellular persistence rates in fibroblasts that were 3 to 4 logs higher than that of the parental strain and decreased susceptibility to aminoglycoside antibiotics. All three of these SCV isolates were attenuated in the BALB/c murine typhoid model. Complementation with lpd(+), hem(+), and aroD(+) genes restored the levels of intracellular persistence and antibiotic susceptibility to levels of the wild-type strain. However, virulence was not exhibited by any of the complemented strains. Altogether, our data demonstrate that similar to what it has been reported for SCV isolates of other pathogens, S. enterica SCV display enhanced intracellular persistence in eucaryotic cells and are impaired in the ability to cause overt disease. In addition, they also suggest that S. enterica SCV may be favored in vivo.

Project description:Edwardsiella piscicida is an important pathogen that infects a wide range of hosts from fish to human. Recent studies demonstrated that E. piscicida can invade and survive within multiple nonphagocytic cells, but the internalization mechanism remains poorly understood. Here, we used HeLa cells as a nonphagocytic cell model to investigate the endocytic strategy used by the pathogenic E. piscicida isolate EIB202. Using a combination of optical and electron microscopy, we observed obvious membrane ruffles and F-actin rearrangements in HeLa cells after EIB202 infection. We also revealed that EIB202 internalization significantly depended on the activity of Na+/H+ exchangers and multiple intracellular signaling events related to macropinocytosis, suggesting that E. piscicida utilizes the host macropinocytosis pathway to enter HeLa cells. Further, using inhibitory drugs and shRNAs to block specific endocytic pathways, we found that a caveolin-dependent but not clathrin-dependent pathway is involved in E. piscicida entry and that its entry requires dynamin and membrane cholesterol. Together, these data suggest that E. piscicida enters nonphagocytic cells via macropinocytosis and caveolin-dependent endocytosis involving cholesterol and dynamin, improving the understanding of how E. piscicida interacts with nonphagocytic cells.IMPORTANCE Bacterial internalization is the first step in breaking through the host cell defense. Therefore, studying the mechanism of bacterial internalization improves the understanding of the pathogenic mechanism of bacteria. In this study, the internalization process on nonphagocytic cells by Edwardsiella piscicida was evaluated. Our results showed that E. piscicida can be internalized into nonphagocytic cells via macropinocytosis and caveolin-mediated endocytosis, and that cholesterol and dynamin are involved in this process. These results reveal a new method for inhibiting E. piscicida infection, providing a foundation for further studies of bacterial pathogenicity.

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Dataset Information

A Nonpyroptotic IFN-?-Triggered Cell Death Mechanism in Nonphagocytic Cells Promotes Salmonella Clearance In Vivo.

Publications

A Nonpyroptotic IFN-γ-Triggered Cell Death Mechanism in Nonphagocytic Cells Promotes <i>Salmonella</i> Clearance In Vivo.

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