| 1. |
- Björnsdottir, Halla, et al.
(författare)
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Phenol-soluble Modulin α Peptide Toxins from aggressive Staphylococcus aureus induce rapid Formation of neutrophil extracellular Traps through a reactive Oxygen species-independent Pathway
- 2017
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Neutrophils have the ability to capture and kill microbes extracellularly through the formation of neutrophil extracellular traps (NETs). These are DNA and protein structures that neutrophils release extracellularly and are believed to function as a defense mechanism against microbes. The classic NET formation process, triggered by, e.g., bacteria, fungi, or by direct stimulation of protein kinase C through phorbol myristate acetate, is an active process that takes several hours and relies on the production of reactive oxygen species (ROS) that are further modified by myeloperoxidase (MPO). We show here that NET-like structures can also be formed by neutrophils after interaction with phenol-soluble modulin alpha (PSM alpha) that are cytotoxic membrane-disturbing peptides, secreted from community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). The PSMa-induced NETs contained the typical protein markers and were able to capture microbes. The PSMa-induced NET structures were disintegrated upon prolonged exposure to DNase-positive S. aureus but not on exposure to DNase-negative Candida albicans. Opposed to classic NETosis, PSMa-triggered NET formation occurred very rapidly, independently of ROS or MPO, and was also manifest at 4 degrees C. These data indicate that rapid NETs release may result from cytotoxic membrane disturbance by PSMa peptides, a process that may be of importance for CA-MRSA virulence.
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| 2. |
- Buck, Alicia, et al.
(författare)
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DPI Selectively Inhibits Intracellular NADPH Oxidase Activity in Human Neutrophils.
- 2019
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Ingår i: ImmunoHorizons. - : The American Association of Immunologists. - 2573-7732. ; 3:10, s. 488-497
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Tidskriftsartikel (refereegranskat)abstract
- Neutrophils are capable of producing significant amounts of reactive oxygen species (ROS) by the phagocyte NADPH oxidase, which consists of membrane-bound and cytoplasmic subunits that assemble during activation. Neutrophils harbor two distinct pools of the membrane-localized oxidase components, one expressed in the plasma membrane and one in the membranes of intracellular granules. Assembly of active oxidase at either type of membrane leads to release of extracellular ROS or to the production of ROS inside intracellular compartments, respectively. The cytoplasmic NADPH oxidase subunit p40phox seems selectively critical for the ability to generate intracellular ROS, and the recent characterization of patients with p40phox deficiency implies that selective loss of intracellular neutrophil ROS leads to disease with pronounced hyperinflammatory features, suggesting that these ROS are critical for regulation of inflammation. This study aimed at characterizing two pharmacological NADPH oxidase inhibitors, the newly described GSK2795039 and the widely used diphenyleneiodonium (DPI), focusing on their abilities to inhibit human neutrophil ROS production extra- and intracellularly. Whereas GSK2795039 blocked extra- and intracellular NADPH oxidase activity equally, DPI was found to selectively interfere with intracellular ROS production. Selectivity for the intracellular NADPH oxidase was evident as a lower IC50 value, faster onset, and irreversibility of inhibition. We found no evidence of direct interactions between DPI and p40phox, but the selectivity of DPI confirms that regulation of NADPH oxidase activity in neutrophils differs depending on the subcellular localization of the enzyme. This information may be used to pharmacologically mimic p40phox deficiency and to further our understanding of how intracellular ROS contribute to health and disease.
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| 3. |
- Christenson, Karin, et al.
(författare)
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In vivo-transmigrated human neutrophils are resistant to antiapoptotic stimulation.
- 2011
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Ingår i: Journal of leukocyte biology. - : Oxford University Press (OUP). - 1938-3673 .- 0741-5400. ; 90:6, s. 1055-63
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Tidskriftsartikel (refereegranskat)abstract
- Neutrophils respond to microbial invasion or injury by transmigration from blood to tissue. Transmigration involves cellular activation and degranulation, resulting in altered levels of surface receptors and changed responsiveness to certain stimuli. Thus, fundamental functional changes are associated with neutrophil transmigration from blood to tissue. Neutrophils isolated from peripheral blood spontaneously enter apoptosis, a process that can be accelerated or delayed by different pro- or antiapoptotic factors. How tissue neutrophils that have transmigrated in vivo regulate cell death is poorly understood. In this study, in vivo-transmigrated neutrophils (tissue neutrophils) were collected using a skin chamber technique and compared with blood neutrophils from the same donors with respect to regulation of cell death. Skin chamber fluid contained a variety of cytokines known to activate neutrophils and regulate their lifespan. Freshly prepared tissue neutrophils had elevated activity of caspase 3/7 but were fully viable; spontaneous cell death after in vitro culture was also similar between blood and tissue neutrophils. Whereas apoptosis of cultured blood neutrophils was delayed by soluble antiapoptotic factors (e.g., TLR ligands), tissue neutrophils were completely resistant to antiapoptotic stimulation, even though receptors were present and functional. In vitro transmigration of blood neutrophils into skin chamber fluid did not fully confer resistance to antiapoptotic stimulation, indicating that a block of antiapoptotic signaling occurs specifically during in vivo transmigration. We describe a novel, functional alteration that takes place during in vivo transmigration and highlights the fact that life and death of neutrophils may be regulated differently in blood and tissue.
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| 4. |
- Sundqvist, Martina, et al.
(författare)
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Elevated Mitochondrial Reactive Oxygen Species and Cellular Redox Imbalance in Human NADPH-Oxidase-Deficient Phagocytes
- 2017
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Chronic granulomatous disease (CGD) is caused by mutations in genes that encode the NADPH-oxidase and result in a failure of phagocytic cells to produce reactive oxygen species (ROS) via this enzyme system. Patients with CGD are highly susceptible to infections and often suffer from inflammatory disorders; the latter occurs in the absence of infection and correlates with the spontaneous production of inflammatory cytokines. This clinical feature suggests that NADPH-oxidase-derived ROS are not required for, or may even suppress, inflammatory processes. Experimental evidence, however, implies that ROS are in fact required for inflammatory cytokine production. By using a myeloid cell line devoid of a functional NADPH-oxidase and primary CGD cells, we analyzed intracellular oxidants, signs of oxidative stress, and inflammatory cytokine production. Herein, we demonstrate that phagocytes lacking a functional NADPH-oxidase, namely primary CGD phagocytes and a gp91phox-deficient cell line, display elevated levels of ROS derived from mitochondria. Accordingly, these cells, despite lacking the major source of cellular ROS, display clear signs of oxidative stress, including an induced expression of antioxidants and altered oxidation of cell surface thiols. These observed changes in redox state were not due to abnormalities in mitochondrial mass or membrane integrity. Finally, we demonstrate that increased mitochondrial ROS enhanced phosphorylation of ERK1/2, and induced production of IL8, findings that correlate with previous observations of increased MAPK activation and inflammatory cytokine production in CGD cells. Our data show that elevated baseline levels of mitochondria-derived oxidants lead to the counter-intuitive observation that CGD phagocytes are under oxidative stress and have enhanced MAPK signaling, which may contribute to the elevated basal production of inflammatory cytokines and the sterile inflammatory manifestations in CGD.
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