Dataset Information

Genetic and Dietary Iron Overload Differentially Affect the Course of Salmonella Typhimurium Infection.

ABSTRACT: Genetic and dietary forms of iron overload have distinctive clinical and pathophysiological features. HFE-associated hereditary hemochromatosis is characterized by overwhelming intestinal iron absorption, parenchymal iron deposition, and macrophage iron depletion. In contrast, excessive dietary iron intake results in iron deposition in macrophages. However, the functional consequences of genetic and dietary iron overload for the control of microbes are incompletely understood. Using Hfe^+/+ and Hfe^-/- mice in combination with oral iron overload in a model of Salmonella enterica serovar Typhimurium infection, we found animals of either genotype to induce hepcidin antimicrobial peptide expression and hypoferremia following systemic infection in an Hfe-independent manner. As predicted, Hfe^-/- mice, a model of hereditary hemochromatosis, displayed reduced spleen iron content, which translated into improved control of Salmonella replication. Salmonella adapted to the iron-poor microenvironment in the spleens of Hfe^-/- mice by inducing the expression of its siderophore iron-uptake machinery. Dietary iron loading resulted in higher bacterial numbers in both WT and Hfe^-/- mice, although Hfe deficiency still resulted in better pathogen control and improved survival. This suggests that Hfe deficiency may exert protective effects in addition to the control of iron availability for intracellular bacteria. Our data show that a dynamic adaptation of iron metabolism in both immune cells and microbes shapes the host-pathogen interaction in the setting of systemic Salmonella infection. Moreover, Hfe-associated iron overload and dietary iron excess result in different outcomes in infection, indicating that tissue and cellular iron distribution determines the susceptibility to infection with specific pathogens.

SUBMITTER: Nairz M

PROVIDER: S-EPMC5387078 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Genetic and Dietary Iron Overload Differentially Affect the Course of <i>Salmonella</i> Typhimurium Infection.

Nairz Manfred M Schroll Andrea A Haschka David D Dichtl Stefanie S Tymoszuk Piotr P Demetz Egon E Moser Patrizia P Haas Hubertus H Fang Ferric C FC Theurl Igor I Weiss Günter G

Frontiers in cellular and infection microbiology 20170411

Genetic and dietary forms of iron overload have distinctive clinical and pathophysiological features. HFE-associated hereditary hemochromatosis is characterized by overwhelming intestinal iron absorption, parenchymal iron deposition, and macrophage iron depletion. In contrast, excessive dietary iron intake results in iron deposition in macrophages. However, the functional consequences of genetic and dietary iron overload for the control of microbes are incompletely understood. Using <i>Hfe</i><s ...[more]

PMID: 28443246

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Project description:Tissue iron (Fe) overload is a frequent pathologic finding in multiple disease states including non-alcoholic fatty liver disease (NAFLD), neurodegenerative disorders, cardiomyopathy, diabetes, and some forms of cancer. The role of iron, as a cause or consequence of disease progression and observed phenotypic manifestations, remains controversial. In addition, the impact of genetic variation on iron overload related phenotypes is unclear, and the identification of genetic modifiers is incomplete. Here, our aim was to characterize the genetic architecture of dietary iron overload and pathology using the Hybrid Mouse Diversity Panel (HMDP), a panel of over 100 genetically distinct mouse strains optimized for genome-wide association studies and systems genetics. Dietary iron overload was induced by feeding male mice (114 strains, 6-7 mice per strain on average) a high iron diet for six weeks, and then tissues were collected at 10-11 weeks of age. Liver metal levels and gene expression were measured by ICP-MS and RNASeq, and lipids were measured by colorimetric assays. FaST-LMM was used for genetic mapping, and Metascape, WGCNA, and Mergeomics were used for pathway, module, and key driver bioinformatics analyses. Mice on the high Fe diet accumulated Fe in the liver, with a 6.5-fold difference across strain means. The iron loaded diet also led to a spectrum of copper deficiency and anemia, with liver copper levels highly correlated with red blood cell count, hemoglobin, and hematocrit. Hepatic steatosis of various severity was observed histologically, with 52.5-fold variation in triglyceride (TG) levels across the strains. TG and Fe mapped most significantly to an overlapping locus on chromosome 7 that has not been previously associated with either trait. Based on network modeling, significant key drivers for both Fe and TG accumulation are involved in cholesterol biosynthesis and oxidative stress management. To make the full data set accessible and useable by others, we have made our data and analyses available on a resource website.

Project description:BACKGROUND:The molecular mechanisms underlying bacterial cell death due to stresses or bactericidal antibiotics are complex and remain puzzling. Due to the current crisis of antibiotic resistance, development of effective antibiotics is urgently required. Previously, it has been shown that iron is required for effective killing of bacterial cells by numerous bactericidal antibiotics. RESULTS:We investigated the death or growth inhibition of S. Typhimurium under iron-restricted conditions, following disruption of essential genes, by transposon mutagenesis using transposon sequencing (Tn-seq). Our high-resolution Tn-seq analysis revealed that transposon mutants of S. Typhimurium with insertions in essential genes escaped immediate killing or growth inhibition under iron-restricted conditions for approximately one-third of all previously known essential genes. Based on this result, we classified all essential genes into two categories, iron-dependent essential genes, for which the insertion mutants can grow slowly if iron is restricted, and iron-independent essential genes, for which the mutants become nonviable regardless of iron concentration. The iron-dependency of the iron-dependent essential genes was further validated by the fact that the relative abundance of these essential gene mutants increased further with more severe iron restrictions. Our unexpected observation can be explained well by the common killing mechanisms of bactericidal antibiotics via production of reactive oxygen species (ROS). In this model, iron restriction would inhibit production of ROS, leading to reduced killing activity following blocking of essential gene functions. Interestingly, the targets of most antibiotics currently in use clinically are iron-dependent essential genes. CONCLUSIONS:Our result suggests that targeting iron-independent essential genes may be a better strategy for future antibiotic development, because blocking their essential gene functions would lead to immediate cell death regardless of the iron concentration. This work expands our knowledge on the role of iron to a broad range of essential functions and pathways, providing novel insights for development of more effective antibiotics.

Dataset Information

Genetic and Dietary Iron Overload Differentially Affect the Course of Salmonella Typhimurium Infection.

Publications

Genetic and Dietary Iron Overload Differentially Affect the Course of <i>Salmonella</i> Typhimurium Infection.

Similar Datasets

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