Cytosolic replication in epithelial cells fuels intestinal expansion and chronic fecal shedding of Salmonella Typhimurium.
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ABSTRACT:
SUBMITTER: Chong A
PROVIDER: S-EPMC8282707 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The ability of Salmonella typhimurium to enter intestinal epithelial cells constitutes a crucial step in pathogenesis. Salmonella invasion of the intestinal epithelium requires bacterial type three secretion system. Type three secretion system is a transport device that injects virulence proteins, called effectors, to paralyze or reprogram the eukaryotic cells. Avirulence factor for Salmonella (AvrA) is a Salmonella effector that inhibits the host's inflammatory responses. The mechanism by which AvrA modulates host cell signaling is not entirely clear. p53 is situated at the crossroads of a network of signaling pathways that are essential for genotoxic and nongenotoxic stress responses. We hypothesized that Salmonella infection activates the p53 pathway. We demonstrated that Salmonella infection increased p53 acetylation. Cells infected with AvrA-sufficient Salmonella have increased p53 acetylation, whereas cells infected with AvrA-deficient Salmonella have less p53 acetylation. In a cell-free system, AvrA possessed acetyltransferase activity and used p53 as a substrate. AvrA expression increased p53 transcriptional activity and induced cell cycle arrest. HCT116 p53-/- cells had less inflammatory responses. In a mouse model of Salmonella infection, intestinal epithelial p53 acetylation was increased by AvrA expression. Our studies provide novel mechanistic evidence that Salmonella modulates the p53 pathway during intestinal inflammation and infection.
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Project description:Salmonella spp. are estimated to cause 1.2 million cases of human foodborne illness each year in the United States, and pigs can often be asymptomatically colonized with Salmonella spp. (>50% of farms). Recent reports state that 18.3% of Salmonella enterica serovar Typhimurium isolates are resistant to ≥3 antimicrobial classes, and multidrug-resistant (MDR) strains are associated with an increased hospitalization rate and other complications. Chlortetracycline is commonly used in swine production to prevent/treat various diseases; therefore, chlortetracycline treatment of pigs unknowingly colonized with MDR Salmonella may have collateral effects on Salmonella spp. (and other gut bacteria). In this study, we determined the effect of in-feed chlortetracycline (400 g/ton) on shedding and colonization of pigs challenged with the MDR S Typhimurium strain DT104 (n = 11/group). We also assessed the impact on the fecal microbiota over the 12-day experimental period and on the ileum, cecum, and tonsil microbiota at 7 days postinoculation (dpi). In MDR S Typhimurium-inoculated pigs, chlortetracycline administration significantly increased fecal shedding at 2 dpi (+1.4 log10 CFU/g; P < 0.001) and enhanced tonsil colonization (+3.1 log10 CFU/g; P < 0.001). There were few major alterations detected in the gut or tonsillar microbiota of pigs treated with MDR S Typhimurium and/or chlortetracycline. The tonsillar transcriptome was largely unaffected despite increased colonization by MDR S Typhimurium following inoculation of the chlortetracycline-treated pigs. These results highlight the idea that chlortetracycline administration can enhance shedding and colonization of MDR S Typhimurium in pigs, which could increase the risk of environmental dissemination of MDR Salmonella strains.IMPORTANCESalmonella spp. are an important cause of foodborne illness in North America, and pork products are associated with sporadic cases and outbreaks of human salmonellosis. Isolates of Salmonella may be resistant to multiple antibiotics, and infections with multidrug-resistant (MDR) Salmonella spp. are more difficult to treat, leading to increased hospitalization rates. Swine operations commonly use antimicrobials, such as chlortetracycline, to prevent/treat infections, which may have collateral effects on pig microbial populations. Recently, we demonstrated that chlortetracycline induces the expression of genes associated with pathogenesis and invasion in MDR Salmonella enterica serovar Typhimurium in vitro In our current study, we show increased tonsillar colonization and fecal shedding of the MDR S Typhimurium strain DT104 from pigs administered chlortetracycline. Therefore, pigs unknowingly colonized with multidrug-resistant Salmonella spp. and receiving chlortetracycline for an unrelated infection may be at a greater risk for disseminating MDR Salmonella spp. to other pigs and to humans through environmental or pork product contamination.
| S-EPMC6365817 | biostudies-literature
Project description:Tumor necrosis factor (TNF) increases intestinal epithelial cell shedding and apoptosis, potentially challenging the barrier between the gastrointestinal lumen and internal tissues. We investigated the mechanism of tight junction remodeling and barrier maintenance as well as the roles of cytoskeletal regulatory molecules during TNF-induced shedding.We studied wild-type and transgenic mice that express the fluorescent-tagged proteins enhanced green fluorescent protein-occludin or monomeric red fluorescent protein 1-ZO-1. After injection of high doses of TNF (7.5 ?g intraperitoneally), laparotomies were performed and segments of small intestine were opened to visualize the mucosa by video confocal microscopy. Pharmacologic inhibitors and knockout mice were used to determine the roles of caspase activation, actomyosin, and microtubule remodeling and membrane trafficking in epithelial shedding.Changes detected included redistribution of the tight junction proteins ZO-1 and occludin to lateral membranes of shedding cells. These proteins ultimately formed a funnel around the shedding cell that defined the site of barrier preservation. Claudins, E-cadherin, F-actin, myosin II, Rho-associated kinase (ROCK), and myosin light chain kinase (MLCK) were also recruited to lateral membranes. Caspase activity, myosin motor activity, and microtubules were required to initiate shedding, whereas completion of the process required microfilament remodeling and ROCK, MLCK, and dynamin II activities.Maintenance of the epithelial barrier during TNF-induced cell shedding is a complex process that involves integration of microtubules, microfilaments, and membrane traffic to remove apoptotic cells. This process is accompanied by redistribution of apical junctional complex proteins to form intercellular barriers between lateral membranes and maintain mucosal function.
| S-EPMC3066304 | biostudies-literature
Project description:Since the occurrence of swine salmonellosis has increased over time and control strategies other than biosecurity are highly recommended, the present study aimed to evaluate the efficacy of vaccination with Salmonella Choleraesuis and Salmonella Typhimurium bacterins in pigs. Two experimental groups were formed: G1, animals immunized with two doses of a commercial vaccine (n = 20); G2, control group (n = 20). After vaccination, all pigs were orally challenged (D0) with 108 CFU of Salmonella Typhimurium and evaluated for 40 days. Every 10 days after D0, five piglets from each experimental group were euthanized and submitted to the necroscopic examination, when organ samples were collected. Blood samples and rectal swabs were collected before the first dose of the vaccine (D-42), before the second dose (D-21), before the challenge (D0), and thereafter, every three days until D39. Blood count, serum IgG measurement by ELISA, and the excretion of Salmonella Typhimurium in feces were evaluated. While the results from blood count and serum IgG concentration did not differ, the detection and excretion of Salmonella between G1 and G2 differed (p < 0.05). Therefore, it was observed that this vaccine partially protected the animals against experimental infection with Salmonella Typhimurium, reducing the excretion of bacteria in feces.
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Project description:We investigated the role of the inflammasome effector caspases-1 and -11 during Salmonella enterica serovar Typhimurium infection of murine intestinal epithelial cells (IECs). Salmonella burdens were significantly greater in the intestines of caspase-1/11 deficient (Casp1/11-/-), Casp1-/- and Casp11-/- mice, as compared to wildtype mice. To determine if this reflected IEC-intrinsic inflammasomes, enteroid monolayers were derived and infected with Salmonella. Casp11-/- and wildtype monolayers responded similarly, whereas Casp1-/- and Casp1/11-/- monolayers carried significantly increased intracellular burdens, concomitant with marked decreases in IEC shedding and death. Pretreatment with IFN-γ to mimic inflammation increased caspase-11 levels and IEC death, and reduced Salmonella burdens in Casp1-/- monolayers, while high intracellular burdens and limited cell shedding persisted in Casp1/11-/- monolayers. Thus caspase-1 regulates inflammasome responses in IECs at baseline, while proinflammatory activation of IECs reveals a compensatory role for caspase-11. These results demonstrate the importance of IEC-intrinsic canonical and non-canonical inflammasomes in host defense against Salmonella.
| S-EPMC7179941 | biostudies-literature
Project description:Although gut host-pathogen interactions are glycan-mediated processes, few details are known about the participating structures. Here we employ high-resolution mass spectrometric profiling to comprehensively identify and quantitatively measure the exact modifications of native intestinal epithelial cell surface N-glycans induced by S. typhimurium infection. Sixty minutes postinfection, select sialylated structures showed decreases in terms of total number and abundances. To assess the effect of cell surface mannosylation, we selectively rerouted glycan expression on the host using the alpha-mannosidase inhibitor, kifunensine, toward overexpression of high mannose. Under these conditions, internalization of S. typhimurium significantly increased, demonstrating that bacteria show preference for particular structures. Finally, we developed a novel assay to measure membrane glycoprotein turnover rates, which revealed that glycan modifications occur by bacterial enzyme activity rather than by host-derived restructuring strategies. This study is the first to provide precise structural information on how host N-glycans are altered to support S. typhimurium invasion.
| S-EPMC5141278 | biostudies-literature
Project description:Salmonella species infect many vertebrate species, and pigs colonized with Salmonella enterica serovar Typhimurium (ST) are usually asymptomatic, making detection of these Salmonella-carrier pigs difficult. The variable fecal shedding of this gram-negative bacteria in such pigs is an important cause of foodborne illness and zoonotic disease. To investigate gene pathways and biomarkers associated with the variance in Salmonella shedding following experimental inoculation, we have initiated the first analysis of the whole blood transcriptional response induced by Salmonella. A population of pigs (n=40) was inoculated with ST and the peripheral blood and feces were collected between 2 and 20 days post-inoculation. Two groups of pigs with either low shedding (LS) or persistent shedding (PS) phenotypes were identified. The global transcriptional changes in response to ST inoculation were identified by Affymetrix Genechip?analysis of peripheral blood RNA at day 0 and day 2 post-inoculation.
2011-05-28 | GSE27000 | GEO
Project description:Salmonella Typhimurium is a facultative, intracellular pathogen whose products range from self-limited gastroenteritis to systemic diseases. Food ingestion increases biomolecules' concentration in the intestinal lumen, including amino acids such as cysteine, which is toxic in a concentration-dependent manner. When cysteine's intracellular concentration reaches toxic levels, S. Typhimurium expresses a cysteine-inducible enzyme (CdsH), which converts cysteine into pyruvate, sulfide, and ammonia. Despite this evidence, the biological context of cdsH's role is not completely clear, especially in the infective cycle. Since inside epithelial cells both cdsH and its positive regulator, ybaO, are overexpressed, we hypothesized a possible role of cdsH in the intestinal phase of the infection. To test this hypothesis, we used an in vitro model of HT-29 cell infection, adding extra cysteine to the culture medium during the infective process. We observed that, at 6 h post-invasion, the wild type S. Typhimurium proliferated 30% more than the ΔcdsH strain in the presence of extra cysteine. This result shows that cdsH contributes to the bacterial replication in the intracellular environment in increased concentrations of extracellular cysteine, strongly suggesting that cdsH participates by increasing the bacterial fitness in the intestinal phase of the S. Typhimurium infection.
| S-EPMC7767077 | biostudies-literature
Project description:Nontyphoidal serovars of Salmonella enterica are pathogenic bacteria that are common causes of food poisoning. Whereas Salmonella mechanisms of host cell invasion, inflammation, and pathogenesis are mostly well established, a new possible mechanism of immune evasion is being uncovered. Programmed death ligand 1 (PD-L1) is an immunosuppressive membrane protein that binds to activated T cells via their PD-1 receptor and thereby halts their activation. PD-L1 expression plays an essential role in the immunological tolerance of self-antigens but is also exploited for immune evasion by pathogen-infected cells and cancer cells. Here, we show for the first time that Salmonella infection of intestinal epithelial cells causes the induction of PD-L1. The increased expression of PD-L1 through Salmonella infection was seen in both human and rat intestinal epithelial cell lines. We determined that cellular invasion by the bacteria is necessary for PD-L1 induction, potentially indicating that Salmonella strains are delivering mediators from inside the host cell that trigger the increased PD-L1 expression. Using knockout mutants, we determined that this effect largely originates from the Salmonella pathogenicity island 2. We also show for the first time in any cell type that Salmonella combined with gamma interferon (IFN-γ) causes a synergistic induction of PD-L1. Finally, we show that Salmonella plus IFN-γ induction of PD-L1 decreased the cytokine production of activated T cells. Understanding Salmonella immune evasion strategies could generate new therapeutic targets and help to manipulate PD-L1 expression in other diseases.
| S-EPMC5913837 | biostudies-literature
Project description:Within mammalian cells, Salmonella enterica serovar Typhimurium (S. Typhimurium) inhabits a membrane-bound vacuole known as the Salmonella-containing vacuole (SCV). We have recently shown that wild type S. Typhimurium also colonizes the cytosol of epithelial cells. Here we sought to quantify the contribution of cytosolic Salmonella to the total population over a time course of infection in different epithelial cell lines and under conditions of altered vacuolar escape. We found that the lysosomotropic agent, chloroquine, acts on vacuolar, but not cytosolic, Salmonella. After chloroquine treatment, vacuolar bacteria are not transcriptionally active or replicative and appear degraded. Using a chloroquine resistance assay, in addition to digitonin permeabilization, we found that S. Typhimurium lyses its nascent vacuole in numerous epithelial cell lines, albeit with different frequencies, and hyper-replication in the cytosol is also widespread. At later times post-infection, cytosolic bacteria account for half of the total population in some epithelial cell lines, namely HeLa and Caco-2 C2Bbe1. Both techniques accurately measured increased vacuole lysis in epithelial cells upon treatment with wortmannin. By chloroquine resistance assay, we also determined that Salmonella pathogenicity island-1 (SPI-1), but not SPI-2, the virulence plasmid nor the flagellar apparatus, was required for vacuolar escape and cytosolic replication in epithelial cells. Together, digitonin permeabilization and the chloroquine resistance assay will be useful, complementary tools for deciphering the mechanisms of SCV lysis and Salmonella replication in the epithelial cell cytosol.
| S-EPMC3882239 | biostudies-literature