Ferritin H deficiency deteriorates cellular iron handling and worsens Salmonella typhimurium infection by triggering hyperinflammation
David Haschka, Piotr Tymoszuk, Verena Petzer, Richard Hilbe, Simon Heeke, Stefanie Dichtl, Sergej Skvortsov, Egon Demetz, Sylvia Berger, Markus Seifert, Anna-Maria Mitterstiller, Patrizia Moser, Dirk Bumann, Manfred Nairz, Igor Theurl, Guenter Weiss
David Haschka, Piotr Tymoszuk, Verena Petzer, Richard Hilbe, Simon Heeke, Stefanie Dichtl, Sergej Skvortsov, Egon Demetz, Sylvia Berger, Markus Seifert, Anna-Maria Mitterstiller, Patrizia Moser, Dirk Bumann, Manfred Nairz, Igor Theurl, Guenter Weiss
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Research Article Immunology Infectious disease

Ferritin H deficiency deteriorates cellular iron handling and worsens Salmonella typhimurium infection by triggering hyperinflammation

Abstract

Iron is an essential nutrient for mammals as well as for pathogens. Inflammation-driven changes in systemic and cellular iron homeostasis are central for host-mediated antimicrobial strategies. Here, we studied the role of the iron storage protein ferritin H (FTH) for the control of infections with the intracellular pathogen Salmonella enterica serovar Typhimurium by macrophages. Mice lacking FTH in the myeloid lineage (LysM-Cre+/+Fthfl/fl mice) displayed impaired iron storage capacities in the tissue leukocyte compartment, increased levels of labile iron in macrophages, and an accelerated macrophage-mediated iron turnover. While under steady-state conditions, LysM-Cre+/+Fth+/+ and LysM-Cre+/+Fthfl/fl animals showed comparable susceptibility to Salmonella infection, i.v. iron supplementation drastically shortened survival of LysM-Cre+/+Fthfl/fl mice. Mechanistically, these animals displayed increased bacterial burden, which contributed to uncontrolled triggering of NF-κB and inflammasome signaling and development of cytokine storm and death. Importantly, pharmacologic inhibition of the inflammasome and IL-1β pathways reduced cytokine levels and mortality and partly restored infection control in iron-treated ferritin-deficient mice. These findings uncover incompletely characterized roles of ferritin and cellular iron turnover in myeloid cells in controlling bacterial spread and for modulating NF-κB and inflammasome-mediated cytokine activation, which may be of vital importance in iron-overloaded individuals suffering from severe infections and sepsis.

Authors

David Haschka, Piotr Tymoszuk, Verena Petzer, Richard Hilbe, Simon Heeke, Stefanie Dichtl, Sergej Skvortsov, Egon Demetz, Sylvia Berger, Markus Seifert, Anna-Maria Mitterstiller, Patrizia Moser, Dirk Bumann, Manfred Nairz, Igor Theurl, Guenter Weiss

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Figure 1

Fth deletion in myeloid cells increases cellular labile iron pool and iron turnover in macrophages.

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Fth deletion in myeloid cells increases cellular labile iron pool and i...
(A–C) Fthfl/fl (Fth+/+) and LysM-Cre Fthfl/fl (FthΔ/Δ) mice were injected i.v. with iron isomaltoside (2 mg elementary Fe/mouse) or left untreated and analyzed 3 days later. (A) Nonheme iron content of the spleen and liver (n = 3 per group). (B) Counts of splenic and hepatic PPB-positive macrophages. Each point denotes mean from at least 3 high-power fields (HPFs) per animal (spleen: Fth+/+ ctrl, Fth+/+ iron, FthΔ/Δ ctrl — n = 4, FthΔ/Δ iron —n = 3; liver: n = 7 per group). (C) Nonheme iron concentrations in serum (n = 7 per group). (D) Iron uptake and release from Fth+/+ and FthΔ/Δ bone marrow–derived macrophages (BMDMs). Iron uptake was measured in cultures stimulated with 5 μM 59Fe3+ (in form of FeCl3) for the indicated time points. Iron release from BMDMs loaded with 5 μM 59Fe3+ into culture supernatant was determined at the indicated time points (uptake and release: n = 6 per group). (E) Surface expression of FPN1 and TFR1 in Fth+/+ and FthΔ/Δ BMDMs cultivated with/without 10 μM Fe3+ (FeCl3) for 12 hours was measured by flow cytometry (n = 5 per group). (F) Calcein-stained Fth+/+ and FthΔ/Δ BMDMs were stimulated with 50 μM Fe3+ (FeCl3) for the indicated time points. Calcein fluorescence expressed as ΔMFI was determined by flow cytometry. Each point denotes single observation (A and C–F) or a mean from at least 3 HPFs per animal (B). Bars with whiskers represent mean ± SEM. Statistical significance was assessed with 2-way ANOVA (A–C and E), Kruskal-Wallis test (E, FPN1), or repeated-measures 2-way ANOVA (E, TFR1 data, and F) with Benjamini-Hochberg-corrected 2-tailed post hoc t tests (A–F) or Mann-Whitney U tests (E, FPN1). In the plots, post-hoc test P values are indicated.