Inhibition of neutrophil function following exposure to the Aspergillus fumigatus toxin fumagillin

The filamentous fungus Aspergillus fumigatus produces a variety of enzymes and toxins that may facilitate fungal colonization of tissue and evasion of the host immune response. One such toxin, fumagillin, was investigated for its ability to inhibit the action of neutrophils, which are a central component of the innate immune response to microbial infection. Neutrophils exposed to 2 μg fumagillin ml−1 for 25 min showed a significantly reduced ability to kill yeast cells (P<0.02), to phagocytose conidia of A. fumigatus (P<0.023) and to consume oxygen (P<0.032). The ability of neutrophils to generate superoxide is dependent upon the action of a functional NADPH oxidase complex which is composed of cytosolic (p40phox, p47phox, p67phox, Rac2) and membrane (gp91phox) proteins. Exposure of neutrophils to fumagillin inhibited the formation of the NADPH oxidase complex by blocking the translocation of p47phox from the cytosolic to the membrane fraction (P=0.02). In addition to the production of superoxide, neutrophils also undergo degranulation, which leads to the release of proteolytic enzymes that contribute to the microbicidal activity of the cell. Fumagillin-treated neutrophils showed reduced degranulation as evidenced by lower myeloperoxidase activity (P<0.019). Fumagillin-treated cells demonstrated reduced levels of F-actin, thus indicating that retarding the formation of F-actin may contribute to the inhibition of the structural rearrangements required in the activated neutrophil. This work indicates that fumagillin may contribute to reducing the local immune response by altering the activity of neutrophils and thus facilitate the continued persistence and growth of A. fumigatus in the host.

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The Aspergillus fumigatus toxin fumagillin suppresses the immune response of Galleria mellonella larvae by inhibiting the action of haemocytes

Microbiology ◽

10.1099/mic.0.043786-0 ◽

2011 ◽

Vol 157 (5) ◽

pp. 1481-1488 ◽

Cited By ~ 44

Author(s):

John P. Fallon ◽

Emer P. Reeves ◽

Kevin Kavanagh

Keyword(s):

Immune Response ◽

Candida Albicans ◽

Aspergillus Fumigatus ◽

Immune Cells ◽

Antimicrobial Agents ◽

Galleria Mellonella ◽

Subsequent Infection ◽

Nadph Oxidase Complex ◽

Cellular Immune

Larvae of Galleria mellonella are widely used to evaluate microbial virulence and to assess the in vivo efficacy of antimicrobial agents. The aim of this work was to examine the ability of an Aspergillus fumigatus toxin, fumagillin, to suppress the immune response of larvae. Administration of fumagillin to larvae increased their susceptibility to subsequent infection with A. fumigatus conidia (P = 0.0052). It was demonstrated that a dose of 2 µg fumagillin ml−1 reduced the ability of insect immune cells (haemocytes) to kill opsonized cells of Candida albicans (P = 0.039) and to phagocytose A. fumigatus conidia (P = 0.016). Fumagillin reduced the oxygen uptake of haemocytes and decreased the translocation of a p47 protein which is homologous to p47phox, a protein essential for the formation of a functional NADPH oxidase complex required for superoxide production. In addition, toxin-treated haemocytes showed reduced levels of degranulation as measured by the release of a protein showing reactivity to an anti-myeloperoxidase antibody (P<0.049) that was subsequently identified by liquid chromatography-MS analysis as prophenoloxidase. This work demonstrates that fumagillin suppresses the immune response of G. mellonella larvae by inhibiting the action of haemocytes and thus renders the larvae susceptible to infection. During growth of the fungus in the larvae, this toxin, along with others, may facilitate growth by suppressing the cellular immune response.

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Myeloperoxidase-Dependent LDL Modifications in Bloodstream Are Mainly Predicted by Angiotensin II, Adiponectin, and Myeloperoxidase Activity: A Cross-Sectional Study in Men

Mediators of Inflammation ◽

10.1155/2013/750742 ◽

2013 ◽

Vol 2013 ◽

pp. 1-4 ◽

Cited By ~ 1

Author(s):

Karim Zouaoui Boudjeltia ◽

Cédric Delporte ◽

Pierre Van Antwerpen ◽

Thierry Franck ◽

Didier Serteyn ◽

...

Keyword(s):

Endothelial Cells ◽

Angiotensin Ii ◽

Nadph Oxidase ◽

Vascular Wall ◽

Cross Sectional Study ◽

Myeloperoxidase Activity ◽

Major Step ◽

Cross Sectional ◽

Subendothelial Space ◽

Nadph Oxidase Complex

The present paradigm of atherogenesis proposes that low density lipoproteins (LDLs) are trapped in subendothelial space of the vascular wall where they are oxidized. Previously, we showed that oxidation is not restricted to the subendothelial location. Myeloperoxidase (MPO), an enzyme secreted by neutrophils and macrophages, can modify LDL (Mox-LDL) at the surface of endothelial cells. In addition we observed that the activation of the endothelial cells by angiotensin II amplifies this process. We suggested that induction of the NADPH oxidase complex was a major step in the oxidative process. Based on these data, we asked whether there was an independent association, in 121 patients, between NADPH oxidase modulators, such as angiotensin II, adiponectin, and levels of circulating Mox-LDL. Our observations suggest that the combination of blood angiotensin II, MPO activity, and adiponectin explains, at least partially, serum Mox-LDL levels.

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Superoxide Production in Galleria mellonella Hemocytes: Identification of Proteins Homologous to the NADPH Oxidase Complex of Human Neutrophils

Infection and Immunity ◽

10.1128/iai.73.7.4161-4170.2005 ◽

2005 ◽

Vol 73 (7) ◽

pp. 4161-4170 ◽

Cited By ~ 146

Author(s):

David Bergin ◽

Emer P. Reeves ◽

Julie Renwick ◽

Frans B. Wientjes ◽

Kevin Kavanagh

Keyword(s):

Immune Response ◽

Nadph Oxidase ◽

Galleria Mellonella ◽

Cell Types ◽

Oxidase Inhibitor ◽

Superoxide Production ◽

Human Neutrophils ◽

Greater Wax Moth ◽

Nadph Oxidase Complex ◽

Insect Hemocytes

ABSTRACT The insect immune response has a number of structural and functional similarities to the innate immune response of mammals. The objective of the work presented here was to establish the mechanism by which insect hemocytes produce superoxide and to ascertain whether the proteins involved in superoxide production are similar to those involved in the NADPH oxidase-induced superoxide production in human neutrophils. Hemocytes of the greater wax moth (Galleria mellonella) were shown to be capable of phagocytosing bacterial and fungal cells. The kinetics of phagocytosis and microbial killing were similar in the insect hemocytes and human neutrophils. Superoxide production and microbial killing by both cell types were inhibited in the presence of the NADPH oxidase inhibitor diphenyleneiodonium chloride. Immunoblotting of G. mellonella hemocytes with antibodies raised against human neutrophil phox proteins revealed the presence of proteins homologous to gp91phox, p67phox, p47phox, and the GTP-binding protein rac 2. A protein equivalent to p40phox was not detected in insect hemocytes. Immunofluorescence analysis localized insect 47-kDa and 67-kDa proteins throughout the cytosol and in the perinuclear region. Hemocyte 67-kDa and 47-kDa proteins were immunoprecipitated and analyzed by matrix-assisted laser desorption ionization—time of flight analysis. The results revealed that the hemocyte 67-kDa and 47-kDa proteins contained peptides matching those of p67phox and p47phox of human neutrophils. The results presented here indicate that insect hemocytes phagocytose and kill bacterial and fungal cells by a mechanism similar to the mechanism used by human neutrophils via the production of superoxide. We identified proteins homologous to a number of proteins essential for superoxide production in human neutrophils and demonstrated that significant regions of the 67-kDa and 47-kDa insect proteins are identical to regions of the p67phox and p47phox proteins of neutrophils.

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NADPH oxidase involved in immune response via regulating the expression of antioxidant genes in Litopenaeus vannamei

Aquaculture Reports ◽

10.1016/j.aqrep.2021.100810 ◽

2021 ◽

Vol 21 ◽

pp. 100810

Author(s):

Zhi Liang ◽

Jinrong Liang ◽

Ling Li ◽

Tianci Chen ◽

Hui Guo

Keyword(s):

Immune Response ◽

Nadph Oxidase ◽

Litopenaeus Vannamei ◽

Antioxidant Genes

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Nod-Like Receptors in Host Defence and Disease at the Epidermal Barrier

International Journal of Molecular Sciences ◽

10.3390/ijms22094677 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4677

Author(s):

Judit Danis ◽

Mark Mellett

Keyword(s):

Immune Response ◽

Tissue Expression ◽

Inflammasome Activation ◽

Nucleotide Binding Domain ◽

Microbial Infection ◽

Epidermal Barrier ◽

The Family ◽

Bona Fide ◽

Activation Antigen

The nucleotide-binding domain and leucine-rich-repeat-containing family (NLRs) (sometimes called the NOD-like receptors, though the family contains few bona fide receptors) are a superfamily of multidomain-containing proteins that detect cellular stress and microbial infection. They constitute a critical arm of the innate immune response, though their functions are not restricted to pathogen recognition and members engage in controlling inflammasome activation, antigen-presentation, transcriptional regulation, cell death and also embryogenesis. NLRs are found from basal metazoans to plants, to zebrafish, mice and humans though functions of individual members can vary from species to species. NLRs also display highly wide-ranging tissue expression. Here, we discuss the importance of NLRs to the immune response at the epidermal barrier and summarise the known role of individual family members in the pathogenesis of skin disease.

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Identification of ferrichrome- and ferrioxamine B-mediated iron uptake by Aspergillus fumigatus

Biochemical Journal ◽

10.1042/bcj20160066 ◽

2016 ◽

Vol 473 (9) ◽

pp. 1203-1213 ◽

Cited By ~ 11

Author(s):

Yong-Sung Park ◽

Ju-Yeon Kim ◽

Cheol-Won Yun

Keyword(s):

Gene Expression ◽

Plasma Membrane ◽

Aspergillus Fumigatus ◽

Virulence Factors ◽

Membrane Transporters ◽

Yeast Cells ◽

Double Deletion ◽

Ferrioxamine B ◽

Uptake Activity ◽

Opportunistic Fungal Pathogen

Aspergillus fumigatus is an opportunistic fungal pathogen for immunocompromised patients, and genes involved in siderophore metabolism have been identified as virulence factors. Recently, we identified the membrane transporters sit1 and sit2, which are putative virulence factors of A. fumigatus; sit1 and sit2 are homologous to yeast Sit1, and sit1 and sit2 gene expression was up-regulated after iron depletion. When expressed heterologously in Saccharomyces cerevisiae, sit1 and sit2 were localized to the plasma membrane; sit1 efficiently complemented ferrichrome (FC) and ferrioxamine B (FOB) uptake in yeast cells, whereas sit2 complemented only FC uptake. Deletion of sit1 resulted in a decrease in FOB and FC uptake, and deletion of sit2 resulted in a decrease in FC uptake in A. fumigatus. It is of interest that a sit1 and sit2 double-deletion mutant resulted in a synergistic decrease in FC uptake activity. Both sit1 and sit2 were localized to the plasma membrane in A. fumigatus. The expression levels of the sit1 and sit2 genes were dependent on hapX under low-but not high-iron conditions. Furthermore, mirB, and sidA gene expression was up-regulated and sreA expression down-regulated when sit1 and sit2 were deleted. Although sit1 and sit2 failed to affect mouse survival rate, these genes affected conidial killing activity. Taken together, our results suggest that sit1 and sit2 are siderophore transporters and putative virulence factors localized to the plasma membrane.

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