Reactive oxygen species-mediated bacterial killing by B lymphocytes

AbstractImmunometabolism and regulation of mitochondrial reactive oxygen species (mROS) control the immune effector phenotype of differentiated macrophages. Mitochondrial function requires dynamic fission and fusion, but whether effector function is coupled to altered dynamics during bacterial responses is unknown. We show that macrophage mitochondria undergo fission after 12 h of progressive ingestion of live Streptococcus pneumoniae (pneumococci), without evidence of Drp-1 phosphorylation at S616. Fission is associated with progressive reduction in oxidative phosphorylation but increased mROS generation. Fission is enhanced by mROS production, PI3Kγ signaling and by cathepsin B, but is independent of inflammasome activation or IL-1β generation. Inhibition of fission reduces bacterial killing. Fission is associated with Parkin recruitment to mitochondria, but not mitophagy. Fission occurs upstream of apoptosis induction and independently of caspase activation. During macrophage innate responses to bacteria mitochondria shift from oxidative phosphorylation and ATP generation to mROS production for microbicidal responses by undergoing fission.Author summaryChanges in metabolism regulate function in immune cells, including macrophages which are key cells in pathogen clearance. Mitochondria are cellular organelles that generate energy during metabolism but also mitochondrial reactive oxygen species (mROS) that contribute to bacterial killing. Mitochondria are dynamic organelles that form complex networks with varying degrees of fragmentation or fusion, but the functional consequences of these processes on macrophage function during bacterial infection are unknown. We show that sustained ingestion of live bacteria triggers mitochondrial fragmentation, reducing metabolism but enhancing mROS generation. Mitochondrial fragmentation is not part of a clearance pathway for damaged mitochondria and is initiated before signs of cell death. Macrophage signalling pathways activated during infection, and mROS generation, enhance mitochondrial fragmentation, and inhibition of pathways promoting fragmentation reduces bacterial killing. Overall, these findings suggest that responses to ingested bacteria trigger mitochondrial fragmentation, allowing mitochondria to switch from energy generation during metabolism to organelles facilitating bacterial killing.

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Modulation of Neutrophil Extracellular Trap and Reactive Oxygen Species Release by Periodontal Bacteria

Infection and Immunity ◽

10.1128/iai.00297-17 ◽

2017 ◽

Vol 85 (12) ◽

Cited By ~ 15

Author(s):

Josefine Hirschfeld ◽

Phillipa C. White ◽

Michael R. Milward ◽

Paul R. Cooper ◽

Iain L. C. Chapple

Keyword(s):

Reactive Oxygen Species ◽

Nadph Oxidase ◽

Reactive Oxygen ◽

Oral Bacteria ◽

Oxygen Species ◽

Antimicrobial Proteins ◽

Bacterial Killing ◽

Content Type ◽

Periodontal Bacteria ◽

Net Release

ABSTRACT Oral bacteria are the main trigger for the development of periodontitis, and some species are known to modulate neutrophil function. This study aimed to explore the release of neutrophil extracellular traps (NETs), associated antimicrobial proteins, and reactive oxygen species (ROS) in response to periodontal bacteria, as well as the underlying pathways. Isolated peripheral blood neutrophils were stimulated with 19 periodontal bacteria. NET and ROS release, as well as the expression of NET-bound antimicrobial proteins, elastase, myeloperoxidase, and cathepsin G, in response to these species was measured using fluorescence-based assays. NET and ROS release was monitored after the addition of NADP (NADPH) oxidase pathway modulators and inhibitors of Toll-like receptors (TLRs). Moreover, bacterial entrapment by NETs was visualized microscopically, and bacterial killing was assessed by bacterial culture. Certain microorganisms, e.g., Veillonella parvula and Streptococcus gordonii, stimulated higher levels of ROS and NET release than others. NETs were found to entrap, but not kill, all periodontal bacteria tested. NADPH oxidase pathway modulators decreased ROS production but not NET production in response to the bacteria. Interestingly, TLR inhibitors did not impact ROS and NET release. These data suggest that the variability in the neutrophil response toward different bacteria may contribute to the pathogenesis of periodontal diseases by mechanisms such as bacterial avoidance of host responses and activation of neutrophils. Moreover, our results indicate that bacterium-stimulated NET release may arise in part via NADPH oxidase-independent mechanisms. The role of TLR signaling in bacterium-induced ROS and NET release needs to be further elucidated.

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Surface-Selective Preferential Production of Reactive Oxygen Species on Piezoelectric Ceramics for Bacterial Killing

ACS Applied Materials & Interfaces ◽

10.1021/acsami.6b07440 ◽

2016 ◽

Vol 8 (37) ◽

pp. 24306-24309 ◽

Cited By ~ 18

Author(s):

Guoxin Tan ◽

Shuangying Wang ◽

Ye Zhu ◽

Lei Zhou ◽

Peng Yu ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Reactive Oxygen ◽

Piezoelectric Ceramics ◽

Oxygen Species ◽

Bacterial Killing

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Neutrophils Kill Reactive Oxygen Species-Resistant Pseudomonas aeruginosa by Sphingosine

Cellular Physiology and Biochemistry ◽

10.1159/000482024 ◽

2017 ◽

Vol 43 (4) ◽

pp. 1603-1616 ◽

Cited By ~ 6

Author(s):

Katrin Anne Becker ◽

Xiang Li ◽

Aaron Seitz ◽

Joerg Steinmann ◽

Anne Koch ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Pseudomonas Aeruginosa ◽

Reactive Oxygen ◽

Early Death ◽

Oxygen Species ◽

New Paradigm ◽

Bacterial Killing ◽

Low Concentrations ◽

Massive Accumulation

Background/Aims: Cystic fibrosis (CF) is dominated by chronic inflammation and infection of the lung resulting in lung destruction and early death of patients. The lungs of CF patients are characterized by a massive accumulation of neutrophils. It requires definition why these massive numbers of neutrophils fail to eliminate typical CF pathogens like Staphylococcus aureus and Pseudomonas aeruginosa (P. aeruginosa) in CF lungs. Methods: We determined ceramide, sphingosine and reactive oxygen species (ROS) in neutrophils from wildtype and CF mice and determined the effect of sphingosine and ROS alone or in combination on killing of different P. aeruginosa strains. Results: We demonstrate that wildtype neutrophils are able to kill non-mucoid and mucoid clinical P. aeruginosa strains, while neutrophils from CF mice are insufficient to kill these P. aeruginosa strains, although both types of neutrophils infected with P. aeruginosa produce comparable levels of superoxide. All three analyzed P. aeruginosa strains are resistant to reactive oxygen species. The inability of CF neutrophils to kill P. aeruginosa is caused by a marked decrease of surface sphingosine levels in CF neutrophils. Wildtype neutrophils contain much higher concentrations of surface sphingosine than CF neutrophils. Further, wildtype neutrophils, but not CF neutrophils, release sphingosine, most likely as microparticles, upon infection. Sphingosine kills P. aeruginosa in vitro at low micromolar concentrations. Reconstitution of sphingosine in CF neutrophils restores their ability to kill these pathogens, demonstrating the significance of sphingosine for bacterial killing. Conclusion: The data provide evidence for a new paradigm explaining how neutrophils kill ROS-resistant P. aeruginosa, i.e. by sphingosine that kills P. aeruginosa at low concentrations. This mechanism is defective in CF neutrophils.

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Novel Regulation of CREB Activation by Reactive Oxygen Species in B Lymphocytes

The FASEB Journal ◽

10.1096/fasebj.25.1_supplement.lb129 ◽

2011 ◽

Vol 25 (S1) ◽

Author(s):

Demetrius Gravis ◽

Adam Stick

Keyword(s):

Reactive Oxygen Species ◽

B Lymphocytes ◽

Reactive Oxygen ◽

Oxygen Species ◽

Creb Activation

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Mesenchymal stem cells enhance NOX2-dependent reactive oxygen species production and bacterial killing in macrophages during sepsis

European Respiratory Journal ◽

10.1183/13993003.02021-2017 ◽

2018 ◽

Vol 51 (4) ◽

pp. 1702021 ◽

Cited By ~ 16

Author(s):

Razieh Rabani ◽

Allen Volchuk ◽

Mirjana Jerkic ◽

Lindsay Ormesher ◽

Linda Garces-Ramirez ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Reactive Oxygen Species Production ◽

Reactive Oxygen ◽

Superoxide Production ◽

Human Macrophage ◽

Prostaglandin E ◽

Oxygen Species ◽

Bacterial Killing ◽

Macrophage Phagocytosis ◽

Species Production

Human mesenchymal stem/stromal cells (MSCs) have been reported to produce an M2-like, alternatively activated phenotype in macrophages. In addition, MSCs mediate effective bacterial clearance in pre-clinical sepsis models. Thus, MSCs have a paradoxical antimicrobial and anti-inflammatory response that is not understood.Here, we studied the phenotypic and functional response of monocyte-derived human macrophages to MSC exposure in vitro.MSCs induced two distinct, coexistent phenotypes: M2-like macrophages (generally elongated morphology, CD163+, acute phagosomal acidification, low NOX2 expression and limited phagosomal superoxide production) and M1-like macrophages characterised by high levels of phagosomal superoxide production. Enhanced phagosomal reactive oxygen species production was also observed in alveolar macrophages from a rodent model of pneumonia-induced sepsis. The production of M1-like macrophages was dependent on prostaglandin E2 and phosphatidylinositol 3-kinase. MSCs enhanced human macrophage phagocytosis of unopsonised bacteria and enhanced bacterial killing compared with untreated macrophages. Bacterial killing was significantly reduced by blockade of NOX2 using diphenyleneiodonium, suggesting that M1-like cells are primarily responsible for this effect. MSCs also enhanced phagocytosis and polarisation of M1-like macrophages derived from patients with severe sepsis.The enhanced antimicrobial capacity (M1-like) and inflammation resolving phenotype (M2-like) may account for the paradoxical effect of these cells in sepsis in vivo.

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Salmonella Rapidly Regulates Membrane Permeability To Survive Oxidative Stress

mBio ◽

10.1128/mbio.01238-16 ◽

2016 ◽

Vol 7 (4) ◽

Cited By ~ 23

Author(s):

Joris van der Heijden ◽

Lisa A. Reynolds ◽

Wanyin Deng ◽

Allan Mills ◽

Roland Scholz ◽

...

Keyword(s):

Oxidative Stress ◽

Reactive Oxygen Species ◽

Hydrogen Peroxide ◽

Membrane Permeability ◽

Outer Membrane ◽

Reactive Oxygen ◽

Gram Negative Bacteria ◽

Oxygen Species ◽

Bacterial Killing ◽

Gram Negative

ABSTRACT The outer membrane (OM) of Gram-negative bacteria provides protection against toxic molecules, including reactive oxygen species (ROS). Decreased OM permeability can promote bacterial survival under harsh circumstances and protects against antibiotics. To better understand the regulation of OM permeability, we studied the real-time influx of hydrogen peroxide in Salmonella bacteria and discovered two novel mechanisms by which they rapidly control OM permeability. We found that pores in two major OM proteins, OmpA and OmpC, could be rapidly opened or closed when oxidative stress is encountered and that the underlying mechanisms rely on the formation of disulfide bonds in the periplasmic domain of OmpA and TrxA, respectively. Additionally, we found that a Salmonella mutant showing increased OM permeability was killed more effectively by treatment with antibiotics. Together, these results demonstrate that Gram-negative bacteria regulate the influx of ROS for defense against oxidative stress and reveal novel targets that can be therapeutically targeted to increase bacterial killing by conventional antibiotics. IMPORTANCE Pathogenic bacteria have evolved ways to circumvent inflammatory immune responses. A decrease in bacterial outer membrane permeability during infection helps protect bacteria from toxic molecules produced by the host immune system and allows for effective colonization of the host. In this report, we reveal molecular mechanisms that rapidly alter outer membrane pores and their permeability in response to hydrogen peroxide and oxidative stress. These mechanisms are the first examples of pores that are rapidly opened or closed in response to reactive oxygen species. Moreover, one of these mechanisms can be targeted to artificially increase membrane permeability and thereby increase bacterial killing by the antibiotic cefotaxime during in vitro experiments and in a mouse model of infection. We envision that a better understanding of the regulation of membrane permeability will lead to new targets and treatment options for multidrug-resistant infections.

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Direct and indirect bacterial killing functions of neutrophil defensins in lung explants

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.2001.281.5.l1240 ◽

2001 ◽

Vol 281 (5) ◽

pp. L1240-L1247 ◽

Cited By ~ 19

Author(s):

Giuliana A. Porro ◽

Jin-Hwa Lee ◽

Joyce de Azavedo ◽

Ian Crandall ◽

Thomas Whitehead ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Antibacterial Activity ◽

Lung Tissue ◽

Reactive Oxygen ◽

Antimicrobial Effect ◽

Mouse Lung ◽

Oxygen Species ◽

Bacterial Killing ◽

Bacterial Counts ◽

Physiological Conditions

Studies of the antimicrobial activity of neutrophil defensins have mostly been carried out in microbiological media, and their effects on the host defense in physiological conditions are unclear. We examined 1) the antibacterial activity of defensins in physiological media with and without lung tissue present, 2) the effect of defensins on hydrogen peroxide (H2O2) production by lung tissue that had been exposed to bacteria, and 3) the effect of diphenyleneiodonium (DPI), an inhibitor of reactive oxygen species formation, on the antibacterial activity of defensins in the presence of lung tissue. Defensins were incubated with Escherichia colior Pseudomonas aeruginosa in the absence or presence of primary cultured mouse lung explants. Defensins reduced bacterial counts by ∼65-fold and ∼25-fold, respectively, at 48 h; bacterial counts were further decreased by ∼600-fold and ∼12,000-fold, respectively, in the presence of lung tissue. Defensins induced H2O2production by lung tissue, and the rate of killing of E. coli by defensins was reduced by ∼2,500-fold in the presence of 10 μM DPI. We conclude that defensins exert a significant antimicrobial effect under physiological conditions and that this effect is enhanced in the presence of lung tissue by a mechanism that involves the production of reactive oxygen species.

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