Characterization of the Aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulence

Aspergillus fumigatus is a saprophytic mold that can cause life-threatening infections in immunocompromised patients. In the lung, inhaled conidia are confronted with immune effector cells that attack the fungus by various mechanisms such as phagocytosis, production of antimicrobial proteins or gene...

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Main Authors: Katrin eLapp, Martin eVödisch, Kristin eKroll, Maria eStrassburger, Olaf eKniemeyer, Thorsten eHeinekamp, Axel A Brakhage
Format: Article
Language:English
Published: Frontiers Media S.A. 2014-09-01
Series:Frontiers in Microbiology
Subjects:
Online Access:http://journal.frontiersin.org/Journal/10.3389/fmicb.2014.00469/full
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spelling doaj-f7b4bdf055474537ad38a0015f1f154e2020-11-24T21:06:47ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2014-09-01510.3389/fmicb.2014.00469107500Characterization of the Aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulenceKatrin eLapp0Martin eVödisch1Kristin eKroll2Maria eStrassburger3Olaf eKniemeyer4Olaf eKniemeyer5Olaf eKniemeyer6Thorsten eHeinekamp7Thorsten eHeinekamp8Axel A Brakhage9Axel A Brakhage10Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute (HKI), JenaLeibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute (HKI), JenaLeibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute (HKI), JenaLeibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute (HKI), JenaLeibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute (HKI), JenaFriedrich Schiller University JenaUniversity Hospital JenaLeibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute (HKI), JenaFriedrich Schiller University JenaLeibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute (HKI), JenaFriedrich Schiller University JenaAspergillus fumigatus is a saprophytic mold that can cause life-threatening infections in immunocompromised patients. In the lung, inhaled conidia are confronted with immune effector cells that attack the fungus by various mechanisms such as phagocytosis, production of antimicrobial proteins or generation of reactive oxygen intermediates. Macrophages and neutrophils can also form nitric oxide (NO) and reactive nitrogen intermediates (RNI) that potentially also contribute to killing of the fungus. However, fungi can produce several enzymes involved in RNI detoxification. Based on genome analysis of A. fumigatus, we identified two genes encoding flavohemoglobins, FhpA and FhpB, which have been shown for other fungi to convert NO to nitrate, and a gene encoding S-nitrosoglutathione reductase GnoA reducing S-nitrosoglutathione to ammonium and glutathione disulphide. To elucidate the role of these enzymes in detoxification of RNI, single and double deletion mutants of FhpA, FhpB and GnoA encoding genes were generated. The analysis of mutant strains using the NO donor DETA-NO indicated that FhpA and GnoA play the major role in defense against RNI. By generating fusions with the green fluorescence protein, we showed that both FhpA-eGFP and GnoA-eGFP were located in the cytoplasm of all A. fumigatus morphotypes, from conidia to hyphae, whereas FhpB-eGFP was localized in mitochondria. Because fhpA and gnoA mRNA was also detected in the lungs of infected mice, we investigated the role of these genes in fungal pathogenicity by using a murine infection model for invasive pulmonary aspergillosis. Remarkably, all mutant strains tested displayed wild-type pathogenicity, indicating that the ability to detoxify host-derived RNI is not essential for virulence of A. fumigatus in the applied mouse infection model. Consistently, no significant differences in killing of ΔfhpA, ΔfhpB or ΔgnoA conidia by cells of the macrophage cell line MH-S were observed when compared to the wild type.http://journal.frontiersin.org/Journal/10.3389/fmicb.2014.00469/fullAspergillosisAspergillus fumigatusNitric OxideVirulencereactive nitrogen intermediates
collection DOAJ
language English
format Article
sources DOAJ
author Katrin eLapp
Martin eVödisch
Kristin eKroll
Maria eStrassburger
Olaf eKniemeyer
Olaf eKniemeyer
Olaf eKniemeyer
Thorsten eHeinekamp
Thorsten eHeinekamp
Axel A Brakhage
Axel A Brakhage
spellingShingle Katrin eLapp
Martin eVödisch
Kristin eKroll
Maria eStrassburger
Olaf eKniemeyer
Olaf eKniemeyer
Olaf eKniemeyer
Thorsten eHeinekamp
Thorsten eHeinekamp
Axel A Brakhage
Axel A Brakhage
Characterization of the Aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulence
Frontiers in Microbiology
Aspergillosis
Aspergillus fumigatus
Nitric Oxide
Virulence
reactive nitrogen intermediates
author_facet Katrin eLapp
Martin eVödisch
Kristin eKroll
Maria eStrassburger
Olaf eKniemeyer
Olaf eKniemeyer
Olaf eKniemeyer
Thorsten eHeinekamp
Thorsten eHeinekamp
Axel A Brakhage
Axel A Brakhage
author_sort Katrin eLapp
title Characterization of the Aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulence
title_short Characterization of the Aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulence
title_full Characterization of the Aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulence
title_fullStr Characterization of the Aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulence
title_full_unstemmed Characterization of the Aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulence
title_sort characterization of the aspergillus fumigatus detoxification systems for reactive nitrogen intermediates and their impact on virulence
publisher Frontiers Media S.A.
series Frontiers in Microbiology
issn 1664-302X
publishDate 2014-09-01
description Aspergillus fumigatus is a saprophytic mold that can cause life-threatening infections in immunocompromised patients. In the lung, inhaled conidia are confronted with immune effector cells that attack the fungus by various mechanisms such as phagocytosis, production of antimicrobial proteins or generation of reactive oxygen intermediates. Macrophages and neutrophils can also form nitric oxide (NO) and reactive nitrogen intermediates (RNI) that potentially also contribute to killing of the fungus. However, fungi can produce several enzymes involved in RNI detoxification. Based on genome analysis of A. fumigatus, we identified two genes encoding flavohemoglobins, FhpA and FhpB, which have been shown for other fungi to convert NO to nitrate, and a gene encoding S-nitrosoglutathione reductase GnoA reducing S-nitrosoglutathione to ammonium and glutathione disulphide. To elucidate the role of these enzymes in detoxification of RNI, single and double deletion mutants of FhpA, FhpB and GnoA encoding genes were generated. The analysis of mutant strains using the NO donor DETA-NO indicated that FhpA and GnoA play the major role in defense against RNI. By generating fusions with the green fluorescence protein, we showed that both FhpA-eGFP and GnoA-eGFP were located in the cytoplasm of all A. fumigatus morphotypes, from conidia to hyphae, whereas FhpB-eGFP was localized in mitochondria. Because fhpA and gnoA mRNA was also detected in the lungs of infected mice, we investigated the role of these genes in fungal pathogenicity by using a murine infection model for invasive pulmonary aspergillosis. Remarkably, all mutant strains tested displayed wild-type pathogenicity, indicating that the ability to detoxify host-derived RNI is not essential for virulence of A. fumigatus in the applied mouse infection model. Consistently, no significant differences in killing of ΔfhpA, ΔfhpB or ΔgnoA conidia by cells of the macrophage cell line MH-S were observed when compared to the wild type.
topic Aspergillosis
Aspergillus fumigatus
Nitric Oxide
Virulence
reactive nitrogen intermediates
url http://journal.frontiersin.org/Journal/10.3389/fmicb.2014.00469/full
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