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Leblanc PO, Bourgoin SG, Poubelle PE, Tessier PA, Pelletier M. Metabolic regulation of neutrophil functions in homeostasis and diseases. J Leukoc Biol 2024; 116:456-468. [PMID: 38452242 DOI: 10.1093/jleuko/qiae025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 01/11/2024] [Accepted: 01/18/2024] [Indexed: 03/09/2024] Open
Abstract
Neutrophils are the most abundant leukocytes in humans and play a role in the innate immune response by being the first cells attracted to the site of infection. While early studies presented neutrophils as almost exclusively glycolytic cells, recent advances show that these cells use several metabolic pathways other than glycolysis, such as the pentose phosphate pathway, oxidative phosphorylation, fatty acid oxidation, and glutaminolysis, which they modulate to perform their functions. Metabolism shifts from fatty acid oxidation-mediated mitochondrial respiration in immature neutrophils to glycolysis in mature neutrophils. Tissue environments largely influence neutrophil metabolism according to nutrient sources, inflammatory mediators, and oxygen availability. Inhibition of metabolic pathways in neutrophils results in impairment of certain effector functions, such as NETosis, chemotaxis, degranulation, and reactive oxygen species generation. Alteration of these neutrophil functions is implicated in certain human diseases, such as antiphospholipid syndrome, coronavirus disease 2019, and bronchiectasis. Metabolic regulators such as AMPK, HIF-1α, mTOR, and Arf6 are linked to neutrophil metabolism and function and could potentially be targeted for the treatment of diseases associated with neutrophil dysfunction. This review details the effects of alterations in neutrophil metabolism on the effector functions of these cells.
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Affiliation(s)
- Pier-Olivier Leblanc
- Infectious and Immune Diseases Axis, CHU de Québec-Université Laval Research Center, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
- ARThrite Research Center, Laval University, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
| | - Sylvain G Bourgoin
- Infectious and Immune Diseases Axis, CHU de Québec-Université Laval Research Center, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
- ARThrite Research Center, Laval University, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
- Department of Microbiology-Infectious Diseases and Immunology, Faculty of Medicine, Laval University, 1050 Av. de la Médecine, Québec City, Québec G1V 0A6, Canada
| | - Patrice E Poubelle
- Infectious and Immune Diseases Axis, CHU de Québec-Université Laval Research Center, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
- Department of Medicine, Faculty of Medicine, Laval University, 1050 Av. de la Médecine, Québec City, Québec G1V 0A6, Canada
| | - Philippe A Tessier
- Infectious and Immune Diseases Axis, CHU de Québec-Université Laval Research Center, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
- ARThrite Research Center, Laval University, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
- Department of Microbiology-Infectious Diseases and Immunology, Faculty of Medicine, Laval University, 1050 Av. de la Médecine, Québec City, Québec G1V 0A6, Canada
| | - Martin Pelletier
- Infectious and Immune Diseases Axis, CHU de Québec-Université Laval Research Center, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
- ARThrite Research Center, Laval University, 2705 Boul. Laurier, Québec City, Québec G1V 4G2, Canada
- Department of Microbiology-Infectious Diseases and Immunology, Faculty of Medicine, Laval University, 1050 Av. de la Médecine, Québec City, Québec G1V 0A6, Canada
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2
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Kopping EJ, Benziger PT, Thanassi DG. TolC and EmrA1 contribute to Francisella novicida multidrug resistance and modulation of host cell death. J Bacteriol 2024:e0024624. [PMID: 39194223 DOI: 10.1128/jb.00246-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Accepted: 07/29/2024] [Indexed: 08/29/2024] Open
Abstract
Francisella spp. are Gram-negative, facultative intracellular pathogens. Francisella tularensis causes the human disease tularemia and is considered a biological threat agent due to its high infectivity and virulence. A central aspect of Francisella virulence is its ability to dampen host immune responses. We previously identified the outer membrane channel (OMC) protein TolC as a critical F. tularensis virulence factor required for suppression of apoptotic and proinflammatory responses during macrophage infection. TolC functions as part of multidrug efflux systems and the type I secretion pathway that exports bacterial effector proteins. In these systems, TolC forms tripartite complexes together with an inner membrane transporter and periplasmic membrane fusion protein (MFP). To advance understanding of TolC function in Francisella, we analyzed OMC and MFP homologs in Francisella novicida, a widely used model species that causes a tularemia-like disease in mice. In agreement with the previous F. tularensis studies, all three OMCs present in F. novicida contributed to multidrug resistance, but only TolC was important for suppressing macrophage cell death. In addition, we identified the EmrA1 MFP as important for resisting antimicrobial compounds and dampening host cell death. In contrast to results obtained with F. tularensis, the cell death triggered during infection with the F. novicida tolC and emrA1 mutants was dominated by pyroptosis rather than apoptosis. These data expand our understanding of TolC function in Francisella and underscore both conserved and differential aspects of F. novicida and F. tularensis. IMPORTANCE Francisella tularensis is a Gram-negative intracellular bacterial pathogen and causative agent of tularemia. We previously identified the outer membrane channel protein TolC as contributing to antimicrobial resistance and subversion of host responses by F. tularensis. To advance understanding of TolC function in Francisella and to identify components that might work together with TolC, we took advantage of a transposon mutant library in F. novicida, a model species that causes a tularemia-like disease in mice. Our findings identify TolC and the membrane fusion protein EmrA1 as important for both antimicrobial resistance and suppression of macrophage cell death. This study also revealed differences in cell death pathways triggered by F. novicida versus F. tularensis infection that may relate to differences in virulence.
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Affiliation(s)
- Erik J Kopping
- Department of Microbiology and Immunology, School of Medicine, Stony Brook University, Stony Brook, New York, USA
- Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA
| | - P Todd Benziger
- Department of Microbiology and Immunology, School of Medicine, Stony Brook University, Stony Brook, New York, USA
- Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA
| | - David G Thanassi
- Department of Microbiology and Immunology, School of Medicine, Stony Brook University, Stony Brook, New York, USA
- Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA
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3
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Murphy DM, Walsh A, Stein L, Petrasca A, Cox DJ, Brown K, Duffin E, Jameson G, Connolly SA, O'Connell F, O'Sullivan J, Basdeo SA, Keane J, Phelan JJ. Human Macrophages Activate Bystander Neutrophils' Metabolism and Effector Functions When Challenged with Mycobacterium tuberculosis. Int J Mol Sci 2024; 25:2898. [PMID: 38474145 DOI: 10.3390/ijms25052898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 02/20/2024] [Accepted: 02/27/2024] [Indexed: 03/14/2024] Open
Abstract
Neutrophils are dynamic cells, playing a critical role in pathogen clearance; however, neutrophil infiltration into the tissue can act as a double-edged sword. They are one of the primary sources of excessive inflammation during infection, which has been observed in many infectious diseases including pneumonia and active tuberculosis (TB). Neutrophil function is influenced by interactions with other immune cells within the inflammatory lung milieu; however, how these interactions affect neutrophil function is unclear. Our study examined the macrophage-neutrophil axis by assessing the effects of conditioned medium (MΦ-CM) from primary human monocyte-derived macrophages (hMDMs) stimulated with LPS or a whole bacterium (Mycobacterium tuberculosis) on neutrophil function. Stimulated hMDM-derived MΦ-CM boosts neutrophil activation, heightening oxidative and glycolytic metabolism, but diminishes migratory potential. These neutrophils exhibit increased ROS production, elevated NET formation, and heightened CXCL8, IL-13, and IL-6 compared to untreated or unstimulated hMDM-treated neutrophils. Collectively, these data show that MΦ-CM from stimulated hMDMs activates neutrophils, bolsters their energetic profile, increase effector and inflammatory functions, and sequester them at sites of infection by decreasing their migratory capacity. These data may aid in the design of novel immunotherapies for severe pneumonia, active tuberculosis and other diseases driven by pathological inflammation mediated by the macrophage-neutrophil axis.
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Affiliation(s)
- Dearbhla M Murphy
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Anastasija Walsh
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Laura Stein
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Andreea Petrasca
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute (TBSI), Trinity College Dublin, The University of Dublin, D02 R590 Dublin, Ireland
| | - Donal J Cox
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Kevin Brown
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Emily Duffin
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Gráinne Jameson
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Sarah A Connolly
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Fiona O'Connell
- Department of Surgery, Trinity St. James's Cancer Institute, Trinity Translational Medicine Institute (TTMI), St. James's Hospital, Dublin 8, D08 W9RT Dublin, Ireland
| | - Jacintha O'Sullivan
- Department of Surgery, Trinity St. James's Cancer Institute, Trinity Translational Medicine Institute (TTMI), St. James's Hospital, Dublin 8, D08 W9RT Dublin, Ireland
| | - Sharee A Basdeo
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - Joseph Keane
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
| | - James J Phelan
- Department of Clinical Medicine, School of Medicine, Trinity Translational Medicine Institute (TTMI), Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, D08 W9RT Dublin, Ireland
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4
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Abstract
Neutrophils or polymorphonuclear neutrophils (PMNs) are an important component of innate host defense. These phagocytic leukocytes are recruited to infected tissues and kill invading microbes. There are several general characteristics of neutrophils that make them highly effective as antimicrobial cells. First, there is tremendous daily production and turnover of granulocytes in healthy adults-typically 1011 per day. The vast majority (~95%) of these cells are neutrophils. In addition, neutrophils are mobilized rapidly in response to chemotactic factors and are among the first leukocytes recruited to infected tissues. Most notably, neutrophils contain and/or produce an abundance of antimicrobial molecules. Many of these antimicrobial molecules are toxic to host cells and can destroy host tissues. Thus, neutrophil activation and turnover are highly regulated processes. To that end, aged neutrophils undergo apoptosis constitutively, a process that contains antimicrobial function and proinflammatory capacity. Importantly, apoptosis facilitates nonphlogistic turnover of neutrophils and removal by macrophages. This homeostatic process is altered by interaction with microbes and their products, as well as host proinflammatory molecules. Microbial pathogens can delay neutrophil apoptosis, accelerate apoptosis following phagocytosis, or cause neutrophil cytolysis. Here, we review these processes and provide perspective on recent studies that have potential to impact this paradigm.
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Affiliation(s)
- Scott D Kobayashi
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Frank R DeLeo
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Mark T Quinn
- Department of Microbiology & Cell Biology, Montana State University, Bozeman, Montana, USA
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5
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Prichard A, Khuu L, Whitmore LC, Irimia D, Allen LAH. Helicobacter pylori-infected human neutrophils exhibit impaired chemotaxis and a uropod retraction defect. Front Immunol 2022; 13:1038349. [PMID: 36341418 PMCID: PMC9630475 DOI: 10.3389/fimmu.2022.1038349] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 10/05/2022] [Indexed: 11/17/2022] Open
Abstract
Helicobacter pylori is a major human pathogen that colonizes the gastric mucosa and plays a causative role in development of peptic ulcers and gastric cancer. Neutrophils are heavily infected with this organism in vivo and play a prominent role in tissue destruction and disease. Recently, we demonstrated that H. pylori exploits neutrophil plasticity as part of its virulence strategy eliciting N1-like subtype differentiation that is notable for profound nuclear hypersegmentation. We undertook this study to test the hypothesis that hypersegmentation may enhance neutrophil migratory capacity. However, EZ-TAXIScan™ video imaging revealed a previously unappreciated and progressive chemotaxis defect that was apparent prior to hypersegmentation onset. Cell speed and directionality were significantly impaired to fMLF as well as C5a and IL-8. Infected cells oriented normally in chemotactic gradients, but speed and direction were impaired because of a uropod retraction defect that led to cell elongation, nuclear lobe trapping in the contracted rear and progressive narrowing of the leading edge. In contrast, chemotactic receptor abundance, adhesion, phagocytosis and other aspects of cell function were unchanged. At the molecular level, H. pylori phenocopied the effects of Blebbistatin as indicated by aberrant accumulation of F-actin and actin spikes at the uropod together with enhanced ROCKII-mediated phosphorylation of myosin IIA regulatory light chains at S19. At the same time, RhoA and ROCKII disappeared from the cell rear and accumulated at the leading edge whereas myosin IIA was enriched at both cell poles. These data suggest that H. pylori inhibits the dynamic changes in myosin IIA contractility and front-to-back polarity that are essential for chemotaxis. Taken together, our data advance understanding of PMN plasticity and H. pylori pathogenesis.
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Affiliation(s)
- Allan Prichard
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, United States
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, United States
| | - Lisa Khuu
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, United States
| | - Laura C. Whitmore
- Department of Medicine, Division of Infectious Diseases, University of Iowa, Iowa City, IA, United States
| | - Daniel Irimia
- Department of Surgery, BioMEMS Resource Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Lee-Ann H. Allen
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, United States
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, United States
- Department of Medicine, Division of Infectious Diseases, University of Iowa, Iowa City, IA, United States
- Iowa City VA Healthcare System, Iowa City, IA, United States
- Harry S. Truman Memorial VA Hospital, Columbia, MO, United States
- *Correspondence: Lee-Ann H. Allen,
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6
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Kinkead LC, Krysa SJ, Allen LAH. Neutrophil Survival Signaling During Francisella tularensis Infection. Front Cell Infect Microbiol 2022; 12:889290. [PMID: 35873156 PMCID: PMC9299441 DOI: 10.3389/fcimb.2022.889290] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 06/07/2022] [Indexed: 12/18/2022] Open
Abstract
Neutrophils are the most abundant and shortest-lived leukocytes in humans and tight regulation of neutrophil turnover via constitutive apoptosis is essential for control of infection and resolution of inflammation. Accordingly, aberrant neutrophil turnover is hallmark of many disease states. We have shown in previous work that the intracellular bacterial pathogen Francisella tularensis markedly prolongs human neutrophil lifespan. This is achieved, in part, by changes in neutrophil gene expression. Still unknown is the contribution of major neutrophil pro-survival signaling cascades to this process. The objective of this study was to interrogate the contributions of ERK and p38 MAP kinase, Class I phosphoinositide 3-kinases (PI3K), AKT, and NF-κB to neutrophil survival in our system. We demonstrate that both ERK2 and p38α were activated in F. tularensis-infected neutrophils, but only p38α MAPK was required for delayed apoptosis and the rate of cell death in the absence of infection was unchanged. Apoptosis of both infected and uninfected neutrophils was markedly accelerated by the pan-PI3K inhibitor LY2094002, but AKT phosphorylation was not induced, and neutrophil death was not enhanced by AKT inhibitors. In addition, isoform specific and selective inhibitors revealed a unique role for PI3Kα in neutrophil survival after infection, whereas only simultaneous inhibition of PI3Kα and PI3kδ accelerated death of the uninfected controls. Finally, we show that inhibition of NF-κB triggered rapid death of neutrophil after infection. Thus, we defined roles for p38α, PI3Kα and NF-κB delayed apoptosis of F. tularensis-infected cells and advanced understanding of Class IA PI3K isoform activity in human neutrophil survival.
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Affiliation(s)
- Lauren C. Kinkead
- Inflammation Program, University of Iowa, Iowa City, IA, United States,Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, United States,Iowa City VA Health Care System, Iowa City, IA, United States
| | - Samantha J. Krysa
- Inflammation Program, University of Iowa, Iowa City, IA, United States,Iowa City VA Health Care System, Iowa City, IA, United States,Molecular Medicine Training Program, University of Iowa, Iowa City, IA, United States
| | - Lee-Ann H. Allen
- Inflammation Program, University of Iowa, Iowa City, IA, United States,Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, United States,Iowa City VA Health Care System, Iowa City, IA, United States,Molecular Medicine Training Program, University of Iowa, Iowa City, IA, United States,Department of Medicine, Division of Infectious Diseases, University of Iowa, Iowa City, IA, United States,Harry S. Truman Memorial VA Hospital, Columbia, MO, United States,Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, United States,*Correspondence: Lee-Ann H. Allen,
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7
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Krysa SJ, Allen LAH. Metabolic Reprogramming Mediates Delayed Apoptosis of Human Neutrophils Infected With Francisella tularensis. Front Immunol 2022; 13:836754. [PMID: 35693822 PMCID: PMC9174434 DOI: 10.3389/fimmu.2022.836754] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 04/28/2022] [Indexed: 01/15/2023] Open
Abstract
Neutrophils (polymorphonuclear leukocytes, PMNs) have a distinctively short lifespan, and tight regulation of cell survival and death is imperative for their normal function. We demonstrated previously that Francisella tularensis extends human neutrophil lifespan, which elicits an impaired immune response characterized by neutrophil dysfunction. Herein, we extended these studies, including our transcriptional profiling data, and employed Seahorse extracellular flux analysis, gas chromatography-mass spectrometry metabolite analysis, flow cytometry and several other biochemical approaches to demonstrate that the delayed apoptosis observed in F. tularensis-infected neutrophils is mediated, in part, by metabolic reprogramming. Specifically, we show that F. tularensis-infected neutrophils exhibited a unique metabolic signature characterized by increased glycolysis, glycolytic flux and glucose uptake, downregulation of the pentose phosphate pathway, and complex glycogen dynamics. Glucose uptake and glycolysis were essential for cell longevity, although glucose-6-phosphate translocation into the endoplasmic reticulum was not, and we identify depletion of glycogen as a potential trigger of apoptosis onset. In keeping with this, we also demonstrate that ablation of apoptosis with the pan-caspase inhibitor Q-VD-OPh was sufficient to profoundly increase glycolysis and glycogen stores in the absence of infection. Taken together, our data significantly advance understanding of neutrophil immunometabolism and its capacity to regulate cell lifespan.
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Affiliation(s)
- Samantha J. Krysa
- Inflammation Program, University of Iowa, Iowa City, IA, United States,Molecular Medicine Program, University of Iowa, Iowa City, IA, United States,Iowa City VA Health Care System, Iowa City, IA, United States
| | - Lee-Ann H. Allen
- Inflammation Program, University of Iowa, Iowa City, IA, United States,Molecular Medicine Program, University of Iowa, Iowa City, IA, United States,Iowa City VA Health Care System, Iowa City, IA, United States,Department of Medicine, Division of Infectious Diseases, University of Iowa, Iowa City, IA, United States,Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, United States,Harry S. Truman Memorial VA Hospital, Columbia, MO, United States,Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, MO, United States,*Correspondence: Lee-Ann H. Allen,
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8
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Miralda I, Vashishta A, Rogers MN, Lamont RJ, Uriarte SM. The emerging oral pathogen, Filifactor alocis, extends the functional lifespan of human neutrophil. Mol Microbiol 2022; 117:1340-1351. [PMID: 35437843 PMCID: PMC9233153 DOI: 10.1111/mmi.14911] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 03/17/2022] [Accepted: 04/10/2022] [Indexed: 12/01/2022]
Abstract
Periodontitis is a chronic inflammatory infectious disease that affects the integrity of tooth‐supporting tissues and has adverse systemic consequences. Advances in sequencing technologies have uncovered organisms that are exclusively found in high numbers in periodontal lesions, such as the gram‐positive anaerobic rod, Filifactor alocis. F. alocis can manipulate neutrophil effector functions, which allows the organism to survive within these granulocytes. Several neutrophil functions have been tested in the context of F. alocis challenge, but the effect of the organism on neutrophil apoptosis is still unknown. RNA sequencing of human neutrophils challenged with F. alocis showed that apoptosis pathways were differentially regulated. Compared to media‐cultured controls, F. alocis‐challenged neutrophils maintain their nuclear morphology, do not stain for Annexin V or 7‐AAD, and have decreased DNA fragmentation. Inhibition of apoptosis by F. alocis involved reduced caspase‐3, −8, and − 9 activation and upregulation of important anti‐apoptotic proteins. Prolonged lifespan was dependent on contact through TLR2/6, and F. alocis‐challenged neutrophils retained their functional capacity to induce inflammation for longer timepoints. This is the first in‐depth characterization of neutrophil apoptotic programs in response to an oral pathogen and provides key information on how bacteria manipulate immune cell mechanisms to maintain a dysregulated inflammatory response.
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Affiliation(s)
- Irina Miralda
- Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of Louisville, Louisville, KY, USA.,Present address: Center for Immunity and Immunotherapies, Seattle Children's Research Institute, Seattle, WA, USA
| | - Aruna Vashishta
- Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of Louisville, Louisville, KY, USA
| | - Max N Rogers
- School of Medicine, University of Louisville, Louisville, KY, USA
| | - Richard J Lamont
- Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of Louisville, Louisville, KY, USA
| | - Silvia M Uriarte
- Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of Louisville, Louisville, KY, USA
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9
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Mohammadi N, Lindgren H, Yamamoto M, Martin A, Henry T, Sjöstedt A. Macrophages Demonstrate Guanylate-Binding Protein-Dependent and Bacterial Strain-Dependent Responses to Francisella tularensis. Front Cell Infect Microbiol 2022; 11:784101. [PMID: 35004352 PMCID: PMC8738097 DOI: 10.3389/fcimb.2021.784101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/09/2021] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis is a facultative intracellular bacterium and the etiological agent of tularemia, a zoonotic disease. Infection of monocytic cells by F. tularensis can be controlled after activation with IFN-γ; however, the molecular mechanisms whereby the control is executed are incompletely understood. Recently, a key role has been attributed to the Guanylate-binding proteins (GBPs), interferon-inducible proteins involved in the cell-specific immunity against various intracellular pathogens. Here, we assessed the responses of bone marrow-derived murine macrophages (BMDM) and GBP-deficient BMDM to F. tularensis strains of variable virulence; the highly virulent SCHU S4 strain, the human live vaccine strain (LVS), or the widely used surrogate for F. tularensis, the low virulent F. novicida. Each of the strains multiplied rapidly in BMDM, but after addition of IFN-γ, significant GBP-dependent control of infection was observed for the LVS and F. novicida strains, whereas there was no control of the SCHU S4 infection. However, no differences in GBP transcription or translation were observed in the infected cell cultures. During co-infection with F. novicida and SCHU S4, significant control of both strains was observed. Patterns of 18 cytokines were very distinct between infected cell cultures and high levels were observed for almost all cytokines in F. novicida-infected cultures and very low levels in SCHU S4-infected cultures, whereas levels in co-infected cultures for a majority of cytokines showed intermediate levels, or levels similar to those of F. novicida-infected cultures. We conclude that the control of BMDM infection with F. tularensis LVS or F. novicida is GBP-dependent, whereas SCHU S4 was only controlled during co-infection. Since expression of GBP was similar regardless of infecting agent, the findings imply that SCHU S4 has an inherent ability to evade the GBP-dependent anti-bacterial mechanisms.
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Affiliation(s)
- Nasibeh Mohammadi
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Helena Lindgren
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Masahiro Yamamoto
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka, Japan
| | - Amandine Martin
- Inserm, U1111, Centre International de Recherche en Infectiologie, Lyon, France
| | - Thomas Henry
- Inserm, U1111, Centre International de Recherche en Infectiologie, Lyon, France
| | - Anders Sjöstedt
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
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10
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Venkataranganayaka Abhilasha K, Kedihithlu Marathe G. Bacterial lipoproteins in sepsis. Immunobiology 2021; 226:152128. [PMID: 34488139 DOI: 10.1016/j.imbio.2021.152128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 07/09/2021] [Accepted: 08/10/2021] [Indexed: 01/05/2023]
Abstract
Bacterial lipoproteins are membrane proteins derived from both gram-negative and gram-positive bacteria. They seem to have diverse functions not only on bacterial growth, but also play an important role in host's virulence. Bacterial lipoproteins exert their action on host immune cells via TLR2/1 or TLR2/6. Therefore, bacterial lipoproteins also need to be considered while addressing bacterial pathogenicity besides classical bacterial endotoxin like LPS and other microbial associated molecular patterns such as LTA, and peptidoglycans. In this mini-review, we provide an overview of general bacterial lipoprotein biosynthesis and the need to understand the lipoprotein-mediated pathogenicity in diseases like sepsis.
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Affiliation(s)
- Kandahalli Venkataranganayaka Abhilasha
- Department of Studies in Biochemistry, University of Mysore, Manasagangothri, Mysuru 570006, Karnataka, India; Cancer and Developmental Biology Laboratory, National Cancer Institute, Frederick, MD 21702, USA
| | - Gopal Kedihithlu Marathe
- Department of Studies in Biochemistry, University of Mysore, Manasagangothri, Mysuru 570006, Karnataka, India; Department of Studies in Molecular Biology, University of Mysore, Manasagangothri, Mysuru 570006, Karnataka, India.
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11
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Abstract
Nearly all animal cells contain proteins evolved to trigger the destruction of the cell in which they reside. The activation of these proteins occurs via sequential programs, and much effort has been expended in delineating the molecular mechanisms underlying the resulting processes of programmed cell death (PCD). These efforts have led to the definition of apoptosis as a form of nonimmunogenic PCD that is required for normal development and tissue homeostasis, and of pyroptosis and necroptosis as forms of PCD initiated by pathogen infection that are associated with inflammation and immune activation. While this paradigm has served the field well, numerous recent studies have highlighted cross talk between these programs, challenging the idea that apoptosis, pyroptosis, and necroptosis are linear pathways with defined immunological outputs. Here, we discuss the emerging idea of cell death as a signaling network, considering connections between cell death pathways both as we observe them now and in their evolutionary origins. We also discuss the engagement and subversion of cell death pathways by pathogens, as well as the key immunological outcomes of these processes.
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Affiliation(s)
- Annelise G Snyder
- NOMIS Center for Immunobiology and Microbial Pathogenesis, Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Andrew Oberst
- Department of Immunology, University of Washington, Seattle, Washington 98109, USA;
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12
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Silva-Del Toro SL, Allen LAH. Microtubules and Dynein Regulate Human Neutrophil Nuclear Volume and Hypersegmentation During H. pylori Infection. Front Immunol 2021; 12:653100. [PMID: 33828562 PMCID: PMC8019731 DOI: 10.3389/fimmu.2021.653100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 02/24/2021] [Indexed: 11/13/2022] Open
Abstract
Neutrophils (also called polymorphonuclear leukocytes, PMNs) are heterogeneous and can exhibit considerable phenotypic and functional plasticity. In keeping with this, we discovered previously that Helicobacter pylori infection induces N1-like subtype differentiation of human PMNs that is notable for profound nuclear hypersegmentation. Herein, we utilized biochemical approaches and confocal and super-resolution microscopy to gain insight into the underlying molecular mechanisms. Sensitivity to inhibition by nocodazole and taxol indicated that microtubule dynamics were required to induce and sustain hypersegmentation, and super-resolution Stimulated Emission Depletion (STED) imaging demonstrated that microtubules were significantly more abundant and longer in hypersegmented cells. Dynein activity was also required, and enrichment of this motor protein at the nuclear periphery was enhanced following H. pylori infection. In contrast, centrosome splitting did not occur, and lamin B receptor abundance and ER morphology were unchanged. Finally, analysis of STED image stacks using Imaris software revealed that nuclear volume increased markedly prior to the onset of hypersegmentation and that nuclear size was differentially modulated by nocodazole and taxol in the presence and absence of infection. Taken together, our data define a new mechanism of hypersegmentation that is mediated by microtubules and dynein and as such advance understanding of processes that regulate nuclear morphology.
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Affiliation(s)
- Stephanie L Silva-Del Toro
- Inflammation Program of the University of Iowa, Iowa City, IA, United States.,Immunology Graduate Program of the University of Iowa, Iowa City, IA, United States
| | - Lee-Ann H Allen
- Inflammation Program of the University of Iowa, Iowa City, IA, United States.,Immunology Graduate Program of the University of Iowa, Iowa City, IA, United States.,Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, United States.,Iowa City VA Healthcare System, Iowa City, IA, United States
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13
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Selvaraj C, Vierra M, Dinesh DC, Abhirami R, Singh SK. Structural insights of macromolecules involved in bacteria-induced apoptosis in the pathogenesis of human diseases. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 126:1-38. [PMID: 34090612 DOI: 10.1016/bs.apcsb.2021.02.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Numbers of pathogenic bacteria can induce apoptosis in human host cells and modulate the cellular pathways responsible for inducing or inhibiting apoptosis. These pathogens are significantly recognized by host proteins and provoke the multitude of several signaling pathways and alter the cellular apoptotic stimuli. This process leads the bacterial entry into the mammalian cells and evokes a variety of responses like phagocytosis, release of mitochondrial cytochrome c, secretion of bacterial effectors, release of both apoptotic and inflammatory cytokines, and the triggering of apoptosis. Several mechanisms are involved in bacteria-induced apoptosis including, initiation of the endogenous death machinery, pore-forming proteins, and secretion of superantigens. Either small molecules or proteins may act as a binding partner responsible for forming the protein complexes and regulate enzymatic activity via protein-protein interactions. The bacteria induce apoptosis, attack the human cell and gain control over various types of cells and tissue. Since these processes are intricate in the defense mechanisms of host organisms against pathogenic bacteria and play an important function in host-pathogen interactions. In this chapter, we focus on the various bacterial-induced apoptosis mechanisms in host cells and discuss the important proteins and bacterial effectors that trigger the host cell apoptosis. The structural characterization of bacterial effector proteins and their interaction with human host cells are also considered.
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Affiliation(s)
- Chandrabose Selvaraj
- Computer Aided Drug Design and Molecular Modeling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India.
| | - Marisol Vierra
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, United States
| | | | - Rajaram Abhirami
- Computer Aided Drug Design and Molecular Modeling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India
| | - Sanjeev Kumar Singh
- Computer Aided Drug Design and Molecular Modeling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India.
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14
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Rungelrath V, DeLeo FR. Staphylococcus aureus, Antibiotic Resistance, and the Interaction with Human Neutrophils. Antioxid Redox Signal 2021; 34:452-470. [PMID: 32460514 PMCID: PMC8020508 DOI: 10.1089/ars.2020.8127] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Significance:Staphylococcus aureus is among the leading causes of bacterial infections worldwide. The high burden of S. aureus among human and animal hosts, which includes asymptomatic carriage and infection, is coupled with a notorious ability of the microbe to become resistant to antibiotics. Notably, S. aureus has the ability to produce molecules that promote evasion of host defense, including the ability to avoid killing by neutrophils. Recent Advances: Significant progress has been made to better understand S. aureus-host interactions. These discoveries include elucidation of the role played by numerous S. aureus virulence molecules during infection. Based on putative functions, a number of these virulence molecules, including S. aureus alpha-hemolysin and protein A, have been identified as therapeutic targets. Although it has not been possible to develop a vaccine that can prevent S. aureus infections, monoclonal antibodies specific for S. aureus virulence molecules have the potential to moderate the severity of disease. Critical Issues: Therapeutic options for treatment of methicillin-resistant S. aureus (MRSA) are limited, and the microbe typically develops resistance to new antibiotics. New prophylactics and/or therapeutics are needed. Future Directions: Research that promotes an enhanced understanding of S. aureus-host interaction is an important step toward developing new therapeutic approaches directed to moderate disease severity and facilitate treatment of infection. This research effort includes studies that enhance our view of the interaction of S. aureus with human neutrophils. Antioxid. Redox Signal. 34, 452-470.
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Affiliation(s)
- Viktoria Rungelrath
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Frank R DeLeo
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
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15
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Mulcahy ME, O'Brien EC, O'Keeffe KM, Vozza EG, Leddy N, McLoughlin RM. Manipulation of Autophagy and Apoptosis Facilitates Intracellular Survival of Staphylococcus aureus in Human Neutrophils. Front Immunol 2020; 11:565545. [PMID: 33262756 PMCID: PMC7686353 DOI: 10.3389/fimmu.2020.565545] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 10/15/2020] [Indexed: 01/13/2023] Open
Abstract
Polymorphonuclear neutrophils (PMN) are critical for first line innate immune defence against Staphylococcus aureus. Mature circulating PMN maintain a short half-life ending in constitutive apoptotic cell death. This makes them unlikely candidates as a bacterial intracellular niche. However, there is significant evidence to suggest that S. aureus can survive intracellularly within PMN and this contributes to persistence and dissemination during infection. The precise mechanism by which S. aureus parasitizes these cells remains to be established. Herein we propose a novel mechanism by which S. aureus subverts both autophagy and apoptosis in PMN in order to maintain an intracellular survival niche during infection. Intracellular survival of S. aureus within primary human PMN was associated with an accumulation of the autophagic flux markers LC3-II and p62, while inhibition of the autophagy pathway led to a significant reduction in intracellular survival of bacteria. This intracellular survival of S. aureus was coupled with a delay in neutrophil apoptosis as well as increased expression of several anti-apoptotic factors. Importantly, blocking autophagy in infected PMN partially restored levels of apoptosis to that of uninfected PMN, suggesting a connection between the autophagic and apoptotic pathways during intracellular survival. These results provide a novel mechanism for S. aureus intracellular survival and suggest that S. aureus may be subverting crosstalk between the autophagic and apoptosis pathways in order to maintain an intracellular niche within human PMN.
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Affiliation(s)
- Michelle E Mulcahy
- Host-Pathogen Interactions Group, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Eóin C O'Brien
- Host-Pathogen Interactions Group, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Kate M O'Keeffe
- Host-Pathogen Interactions Group, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Emilio G Vozza
- Host-Pathogen Interactions Group, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Neal Leddy
- bioTEM, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Rachel M McLoughlin
- Host-Pathogen Interactions Group, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
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16
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Pulavendran S, Prasanthi M, Ramachandran A, Grant R, Snider TA, Chow VTK, Malayer JR, Teluguakula N. Production of Neutrophil Extracellular Traps Contributes to the Pathogenesis of Francisella tularemia. Front Immunol 2020; 11:679. [PMID: 32391009 PMCID: PMC7193117 DOI: 10.3389/fimmu.2020.00679] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 03/26/2020] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis(Ft) is a highly virulent, intracellular Gram-negative bacterial pathogen. Acute Ft infection by aerosol route causes pneumonic tularemia, characterized by nodular hemorrhagic lesions, neutrophil-predominant influx, necrotic debris, fibrin deposition, and severe alveolitis. Ft suppresses activity of neutrophils by impairing their respiratory burst and phagocytic activity. However, the fate of the massive numbers of neutrophils recruited to the infection site is unclear. Here, we show that Ft infection resulted in prominent induction of neutrophil extracellular traps (NETs) within damaged lungs of mice infected with the live attenuated vaccine strain of Ft(Ft-LVS), as well as in the lungs of domestic cats and rabbits naturally infected with Ft. Further, Ft-LVS infection increased lung myeloperoxidase (MPO) activity, which mediates histone protein degradation during NETosis and anchors chromatin scaffolds in NETs. In addition, Ft infection also induced expression of peptidylarginine deiminase 4, an enzyme that causes citrullination of histones during formation of NETs. The released NETs were found largely attached to the alveolar epithelium, and disrupted the thin alveolar epithelial barrier. Furthermore, Ft infection induced a concentration-dependent release of NETs from neutrophils in vitro. Pharmacological blocking of MPO reduced Ft-induced NETs release, whereas addition of H2O2 (a substrate of MPO) significantly augmented NETs release, thus indicating a critical role of MPO in Ft-induced NETs. Although immunofluorescence and electron microscopy revealed that NETs could efficiently trap Ft bacteria, NETs failed to exert bactericidal effects. Taken together, these findings suggest that NETs exacerbate tissue damage in pulmonary Ft infection, and that targeting NETosis may offer novel therapeutic interventions in alleviating Ft-induced tissue damage.
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Affiliation(s)
- Sivasami Pulavendran
- College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, OK, United States
| | - Maram Prasanthi
- College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, OK, United States
| | - Akhilesh Ramachandran
- College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, OK, United States
| | - Rezabek Grant
- College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, OK, United States
| | - Timothy A. Snider
- College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, OK, United States
| | - Vincent T. K. Chow
- Department of Microbiology and Immunology, School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
| | - Jerry R. Malayer
- College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, OK, United States
| | - Narasaraju Teluguakula
- College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, OK, United States
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17
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Characterization of IL-10-producing neutrophils in cattle infected with Ostertagia ostertagi. Sci Rep 2019; 9:20292. [PMID: 31889109 PMCID: PMC6937330 DOI: 10.1038/s41598-019-56824-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 12/17/2019] [Indexed: 02/07/2023] Open
Abstract
IL-10 is a master regulator of immune responses, but its cellular source and function in cattle during the initial phase of immune priming have not been well established. Despite a massive B cell response in the abomasal draining lymph nodes in Ostertagia ostertagi (OO)-infected cattle, protective immunity is slow to develop, and partial protection requires years of repeated exposure. In addressing this problem, our initial hypothesis was that B cells produce IL-10 that downregulates the host protective immune response. However, our results showed that neutrophils made up the majority of IL-10-producing cells in circulation and in secondary lymphoid tissues, particularly the spleen (80%). Conversely, IL-10-producing B cells were rare. In addition, approximately 10% to 20% of the neutrophils in the blood and spleen expressed MHC II and were IL-10 negative, suggesting that neutrophils could also participate in antigen presentation. In vitro investigation of bovine neutrophils revealed that exposure thereof to OO extract increased IL-10 and MHC II expression in these cells in a dose-dependent manner, consistent with IL-10+/MHC II+ neutrophils detected in cattle shortly after experimental OO infection. Co-culture of untreated neutrophils with anti-CD3 antibody (Ab)-stimulated CD4+ T cells led to enhanced T cell activation; also, IL-10 depletion with neutralizing Ab enhanced the stimulatory function of neutrophils. OO extract depressed neutrophil stimulation of CD4+ T cells in the presence of IL-10-neutralizing Ab, suggesting that OO utilizes both IL-10-dependent and independent mechanisms to manipulate the bovine immune response. Finally, contact and viability were required for T cell-stimulatory neutrophil function. This report, to the best of our knowledge, is the first to demonstrate that neutrophil-derived IL-10 is directly involved in T cell regulation in cattle. Our data suggest that neutrophils and neutrophil-derived IL-10 are co-opted by nematode parasites and other pathogens to attenuate host immune responses and facilitate pathogen survival.
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18
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Cytosolic Gram-negative bacteria prevent apoptosis by inhibition of effector caspases through lipopolysaccharide. Nat Microbiol 2019; 5:354-367. [PMID: 31873204 DOI: 10.1038/s41564-019-0620-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 10/24/2019] [Indexed: 02/08/2023]
Abstract
The cytosolic appearance and propagation of bacteria cause overwhelming cellular stress responses that induce apoptosis under normal conditions. Therefore, successful bacterial colonization depends on the ability of intracellular pathogens to block apoptosis and to safeguard bacterial replicative niches. Here, we show that the cytosolic Gram-negative bacterium Shigella flexneri stalls apoptosis by inhibiting effector caspase activity. Our data identified lipopolysaccharide (LPS) as a bona fide effector caspase inhibitor that directly binds caspases by involving its O-antigen (O Ag) moiety. Bacterial strains that lacked the O Ag or failed to replicate within the cytosol were incapable of blocking apoptosis and exhibited reduced virulence in a murine model of bacterial infection. Our findings demonstrate how Shigella inhibits pro-apoptotic caspase activity, effectively delays coordinated host-cell demise and supports its intracellular propagation. Next to the recently discovered pro-inflammatory role of cytosolic LPS, our data reveal a distinct mode of LPS action that, through the disruption of the early coordinated non-lytic cell death response, ultimately supports the inflammatory breakdown of infected cells at later time points.
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19
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Identification of key protein-coding genes and lncRNAs in spontaneous neutrophil apoptosis. Sci Rep 2019; 9:15106. [PMID: 31641174 PMCID: PMC6805912 DOI: 10.1038/s41598-019-51597-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 10/04/2019] [Indexed: 01/17/2023] Open
Abstract
Polymorphonuclear leukocytes (PMNs) are the most abundant cells of the innate immune system in humans, and spontaneous PMN apoptosis plays crucial roles in maintaining neutrophil homeostasis and resolving inflammation. However, the detailed mechanisms of spontaneous PMN apoptosis remain to be elucidated. By analysis of the public microarray dataset GSE37416, we identified a total of 3050 mRNAs and 220 long non-coding RNAs (lncRNAs) specifically expressed during PMN apoptosis in a time-dependent manner. By short time-series expression miner (STEM) analysis, Gene Ontology analysis, and lncRNA-mRNA co-expression network analyses, we identified some key molecules specifically related to PMN apoptosis. STEM analysis identified 12 gene profiles with statistically significance, including 2 associated with apoptosis. Protein-protein interaction (PPI) network analysis of the genes from 2 profiles and lncRNA-mRNA co-expression network analysis identified a 12-gene hub (including NFκB1 and BIRC3) associated with apoptosis, as well as 2 highly correlated lncRNAs (THAP9-AS1, and AL021707.6). We experimentally examined the expression profiles of two mRNA (NFκB1 and BIRC3) and two lncRNAs (THAP9-AS1 andAL021707.6) by quantitative real-time polymerase chain reaction to confirm their time-dependent expressions. These data altogether demonstrated that these genes are involved in the regulation of spontaneous neutrophil apoptosis and the corresponding gene products could also serve as potential key regulatory molecules for PMN apoptosis and/or therapeutic targets for over-reactive inflammatory response caused by the abnormality in PMN apoptosis.
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20
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Soucy AM, Hurteau GJ, Metzger DW. Live Vaccination Generates Both Disease Tolerance and Host Resistance During Chronic Pulmonary Infection With Highly Virulent Francisella tularensis SchuS4. J Infect Dis 2019; 218:1802-1812. [PMID: 29931113 DOI: 10.1093/infdis/jiy379] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 06/18/2018] [Indexed: 11/13/2022] Open
Abstract
Disease tolerance can preserve host homeostasis and limit the negative impact of infections. We report that vaccinated mice survived pulmonary challenge with the extremely virulent SchuS4 strain of Francisella tularensis for at least 100 days, despite the persistence of large numbers (~104) of organisms. Transfer of 100 of these resident bacteria to naive animals caused 100% lethality, demonstrating that virulence was maintained. Tissue damage in the lung was limited over the course of infection and was associated with increased levels of amphiregulin. Mice depleted of CD4+ cells had reduced amphiregulin and succumbed to infection. In addition, neutralization of interferon-γ or depletion of CD8+ cells resulted in increased pathogen loads, bacteremia, and death of the host. Conversely, depletion of Ly6G+ neutrophils had no effect on survival and actually resulted in reduced bacterial levels. Understanding the interplay between host resistance and disease tolerance will provide new insights into the understanding of chronic infectious diseases.
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Affiliation(s)
- Alicia M Soucy
- Department of Immunology and Microbial Disease, Albany Medical College, New York
| | - Gregory J Hurteau
- Department of Immunology and Microbial Disease, Albany Medical College, New York
| | - Dennis W Metzger
- Department of Immunology and Microbial Disease, Albany Medical College, New York
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21
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Rungelrath V, Kobayashi SD, DeLeo FR. Neutrophils in innate immunity and systems biology-level approaches. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2019; 12:e1458. [PMID: 31218817 DOI: 10.1002/wsbm.1458] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 05/22/2019] [Accepted: 05/23/2019] [Indexed: 12/14/2022]
Abstract
The innate immune system is the first line of host defense against invading microorganisms. Polymorphonuclear leukocytes (PMNs or neutrophils) are the most abundant leukocyte in humans and essential to the innate immune response against invading pathogens. Compared to the acquired immune response, which requires time to develop and is dependent on previous interaction with specific microbes, the ability of neutrophils to kill microorganisms is immediate, nonspecific, and not dependent on previous exposure to microorganisms. Historically, studies of PMN-pathogen interaction focused on the events leading to killing of microorganisms, such as recruitment/chemotaxis, transmigration, phagocytosis, and activation, whereas postphagocytosis sequelae were infrequently considered. In addition, it was widely accepted that human neutrophils possessed limited capacity for new gene transcription and thus, relatively little biosynthetic capacity. This notion has changed dramatically within the past 20 years. Further, there is now more effort directed to understand the events occurring in PMNs after killing of microbes. Herein, we give an updated review of the systems biology-level approaches that have been used to gain an enhanced view of the role of neutrophils during host-pathogen interaction and neutrophil-mediated diseases. We anticipate that these and future systems-level studies will continue to provide information important for understanding, treatment, and control of diseases caused by pathogenic microorganisms. This article is categorized under: Physiology > Organismal Responses to Environment Physiology > Mammalian Physiology in Health and Disease Biological Mechanisms > Cell Fates.
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Affiliation(s)
- Viktoria Rungelrath
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana
| | - Scott D Kobayashi
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana
| | - Frank R DeLeo
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana
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22
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Silwedel C, Fehrholz M, Speer CP, Ruf KC, Manig S, Glaser K. Differential modulation of pulmonary caspases: Is this the key to Ureaplasma-driven chronic inflammation? PLoS One 2019; 14:e0216569. [PMID: 31067276 PMCID: PMC6506144 DOI: 10.1371/journal.pone.0216569] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 04/23/2019] [Indexed: 12/26/2022] Open
Abstract
Although accepted agents in chorioamnionitis and preterm birth, the role of Ureaplasma species (spp.) in inflammation-driven morbidities of prematurity, including the development of bronchopulmonary dysplasia, remains controversial. To add to scarce in vitro data addressing the pro-inflammatory capacity of Ureaplasma spp., pulmonary epithelial-like A549 cells and human pulmonary microvascular endothelial cells (HPMEC) were incubated with Ureaplasma (U.) urealyticum, U. parvum, and Escherichia coli lipopolysaccharide (LPS). Ureaplasma isolates down-regulated caspase mRNA levels in A549 cells (caspase 8: p<0.001, 9: p<0.001, vs. broth), while increasing caspase protein expression, enzyme activity, and cell death in HPMEC (active caspase 3: p<0.05, caspase 8: p<0.05, active caspase 9: p<0.05, viability: p<0.05). LPS, contrarily, induced caspase mRNA expression in HPMEC (caspase 3: p<0.01, 4: p<0.001, 5: p<0.001, 8: p<0.001, vs. control), but not in A549 cells, and did not affect enzyme activity or protein levels in either cell line. LPS, but neither Ureaplasma isolate, enhanced mRNA expression of pro-inflammatory interleukin (IL)-6 in both A549 (p<0.05, vs. control) and HPMEC (p<0.001) as well as tumor necrosis factor-α (p<0.01), IL-1β (p<0.001), and IL-8 (p<0.05) in HPMEC. We are therefore the first to demonstrate a differential modulation of pulmonary caspases by Ureaplasma spp. in vitro. Ureaplasma-driven enhanced protein expression and activity of caspases in pulmonary endothelial cells result in cell death and may cause structural damage. Down-regulated caspase mRNA in pulmonary epithelial cells, contrarily, may indicate Ureaplasma-induced inhibition of apoptosis and prevent effective immune responses. Both may ultimately contribute to chronic Ureaplasma colonization and long-term pulmonary inflammation.
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Affiliation(s)
- Christine Silwedel
- University Children´s Hospital, University of Wuerzburg, Wuerzburg, Germany
- * E-mail:
| | - Markus Fehrholz
- University Children´s Hospital, University of Wuerzburg, Wuerzburg, Germany
| | - Christian P. Speer
- University Children´s Hospital, University of Wuerzburg, Wuerzburg, Germany
| | - Katharina C. Ruf
- University Children´s Hospital, University of Wuerzburg, Wuerzburg, Germany
| | - Steffi Manig
- Institute of Hygiene and Microbiology, University of Wuerzburg, Wuerzburg, Germany
| | - Kirsten Glaser
- University Children´s Hospital, University of Wuerzburg, Wuerzburg, Germany
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23
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Solbakken MH, Jentoft S, Reitan T, Mikkelsen H, Gregers TF, Bakke O, Jakobsen KS, Seppola M. Disentangling the immune response and host-pathogen interactions in Francisella noatunensis infected Atlantic cod. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2019; 30:333-346. [PMID: 31054474 DOI: 10.1016/j.cbd.2019.04.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 03/08/2019] [Accepted: 04/12/2019] [Indexed: 12/15/2022]
Abstract
The genetic repertoire underlying teleost immunity has been shown to be highly variable. A rare example is Atlantic cod and its relatives Gadiformes that lacks a hallmark of vertebrate immunity: Major Histocompatibility Complex class II. No immunological studies so far have fully unraveled the functionality of this particular immune system. Through global transcriptomic profiling, we investigate the immune response and host-pathogen interaction of Atlantic cod infected with the facultative intracellular bacterium Francisella noatunensis. We find that Atlantic cod displays an overall classic innate immune response with inflammation, acute-phase proteins and cell recruitment through up-regulation of e.g. IL1B, fibrinogen, cathelicidin, hepcidin and several chemotactic cytokines such as the neutrophil attractants CXCL1 and CXCL8. In terms of adaptive immunity, we observe up-regulation of interferon gamma followed by up-regulation of several MHCI transcripts and genes related to antigen transport and loading. Finally, we find up-regulation of immunoglobulins and down-regulation of T-cell and NK-like cell markers. Our analyses also uncover some contradictory transcriptional findings such as up-regulation of anti-inflammatory IL10 as well as down-regulation of the NADPH oxidase complex and myeloperoxidase. This we interpret as the result of host-pathogen interactions where F. noatunensis modulates the immune response. In summary, our results suggest that Atlantic cod mounts a classic innate immune response as well as a neutrophil-driven response. In terms of adaptive immunity, both endogenous and exogenous antigens are being presented on MHCI and antibody production is likely enabled through direct B-cell stimulation with possible neutrophil help. Collectively, we have obtained novel insight in the orchestration of the Atlantic cod immune system and determined likely targets of F. noatunensis host-pathogen interactions.
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Affiliation(s)
- Monica Hongrø Solbakken
- Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, Oslo, Norway
| | - Sissel Jentoft
- Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, Oslo, Norway.
| | - Trond Reitan
- Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, Oslo, Norway
| | | | - Tone F Gregers
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Oddmund Bakke
- Department of Biosciences, Centre for Immune Regulation, University of Oslo, Oslo, Norway
| | - Kjetill S Jakobsen
- Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, Oslo, Norway
| | - Marit Seppola
- Department of Medical Biology, The Arctic University of Norway, Tromsø, Norway.
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Contributions of TolC Orthologs to Francisella tularensis Schu S4 Multidrug Resistance, Modulation of Host Cell Responses, and Virulence. Infect Immun 2019; 87:IAI.00823-18. [PMID: 30670554 DOI: 10.1128/iai.00823-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 01/14/2019] [Indexed: 02/06/2023] Open
Abstract
Francisella tularensis is a Gram-negative, facultative intracellular pathogen and the causative agent of tularemia. Previous studies with the attenuated live vaccine strain (LVS) identified a role for the outer membrane protein TolC in modulation of host cell responses during infection and virulence in the mouse model of tularemia. TolC is an integral part of efflux pumps that export small molecules and type I secretion systems that export a range of bacterial virulence factors. In this study, we analyzed TolC and its two orthologs, FtlC and SilC, present in the fully virulent F. tularensis Schu S4 strain for their contributions to multidrug efflux, suppression of innate immune responses, and virulence. We found that each TolC ortholog participated in multidrug efflux, with overlapping substrate specificities for TolC and FtlC and a distinct substrate profile for SilC. In contrast to their shared roles in drug efflux, only TolC functioned in the modulation of macrophage apoptotic and proinflammatory responses to Schu S4 infection, consistent with a role in virulence factor delivery to host cells. In agreement with previous results with the LVS, the Schu S4 ΔtolC mutant was highly attenuated for virulence in mice by both the intranasal and intradermal routes of infection. Unexpectedly, FtlC was also critical for Schu S4 virulence, but only by the intradermal route. Our data demonstrate a conserved and critical role for TolC in modulation of host immune responses and Francisella virulence and also highlight strain- and route-dependent differences in the pathogenesis of tularemia.
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25
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Mooney JP, Galloway LJ, Riley EM. Malaria, anemia, and invasive bacterial disease: A neutrophil problem? J Leukoc Biol 2018; 105:645-655. [PMID: 30570786 PMCID: PMC6487965 DOI: 10.1002/jlb.3ri1018-400r] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 11/29/2018] [Accepted: 12/01/2018] [Indexed: 12/16/2022] Open
Abstract
Invasive bacterial disease is well described in immunocompromised hosts, including those with malaria infection. One bacterial infection frequently observed in children with Plasmodium falciparum infection is nontyphoidal salmonella (NTS) infection, in which a typically intestinal infection becomes systemic with serious, often fatal, consequences. In this review, we consider the role of malaria‐induced immunoregulatory responses in tipping the balance from tissue homeostasis during malaria infection to risk of invasive NTS. Also, neutrophils are crucial in the clearance of NTS but their ability to mount an oxidative burst and kill intracellular Salmonella is severely compromised during, and for some time after, an acute malaria infection. Here, we summarize the evidence linking malaria and invasive NTS infections; describe the role of neutrophils in clearing NTS infections; review evidence for neutrophil dysfunction in malaria infections; and explore roles of heme oxygenase‐1, IL‐10, and complement in mediating this dysfunction. Finally, given the epidemiological evidence that low density, subclinical malaria infections pose a risk for invasive NTS infections, we consider whether the high prevalence of such infections might underlie the very high incidence of invasive bacterial disease across much of sub‐Saharan Africa.
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Affiliation(s)
- Jason P Mooney
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, United Kingdom
| | - Lauren J Galloway
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, United Kingdom
| | - Eleanor M Riley
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, United Kingdom
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26
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Kajiume T, Kobayashi M. Human granulocytes undergo cell death via autophagy. Cell Death Discov 2018; 4:111. [PMID: 30534419 PMCID: PMC6281597 DOI: 10.1038/s41420-018-0131-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/18/2018] [Accepted: 11/20/2018] [Indexed: 12/18/2022] Open
Abstract
Mature neutrophils must be quickly removed from inflammatory sites to prevent tissue damage. Neutrophil removal is thought to be accomplished primarily through caspase-dependent apoptosis, which involves several genes of mitochondrial origin. However, mature neutrophils show reduced gene transcription and mitochondrial numbers. We predicted that neutrophils utilize other cell death mechanisms and investigated programmed cell death in human peripheral blood mononuclear cells (MNCs) and polymorphonuclear cells (PMNCs or neutrophil fractions). Unlike MNCs, PMNCs did not undergo DNA fragmentation and were not TUNEL positive, but expressed LC3-II, an autophagy marker. We also found that during differentiation, autophagy inhibitor 3-MA, and not caspase inhibitor zVAD-fmk, prevented segmentation of the nucleus, indicating that these cells undergo autophagy during maturation. Therefore, human neutrophils may undergo spontaneous autophagic cell death rather than apoptosis, during which autophagy may be essential for both maturation and death.
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Affiliation(s)
- Teruyuki Kajiume
- Mukainada Child Clinic, Hiroshima, Japan
- Department of Pediatrics, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan
| | - Masao Kobayashi
- Department of Pediatrics, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan
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27
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Edmisson JS, Tian S, Armstrong CL, Vashishta A, Klaes CK, Miralda I, Jimenez-Flores E, Le J, Wang Q, Lamont RJ, Uriarte SM. Filifactor alocis modulates human neutrophil antimicrobial functional responses. Cell Microbiol 2018; 20:e12829. [PMID: 29377528 PMCID: PMC5980721 DOI: 10.1111/cmi.12829] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 01/19/2018] [Accepted: 01/22/2018] [Indexed: 12/24/2022]
Abstract
Filifactor alocis is a newly appreciated pathogen in periodontal diseases. Neutrophils are the predominant innate immune cell in the gingival crevice. In this study, we examined modulation of human neutrophil antimicrobial functions by F. alocis. Both non-opsonised and serum-opsonised F. alocis were engulfed by neutrophils but were not efficiently eliminated. Challenge of neutrophils with either non-opsonised or serum-opsonised F. alocis induced a minimal intracellular as well as extracellular respiratory burst response compared to opsonised Staphylococcus aureus and fMLF, respectively. However, pretreatment or simultaneous challenge of neutrophils with F. alocis did not affect the subsequent oxidative response to a particulate stimulus, suggesting that the inability to trigger the respiratory response was only localised to F. alocis phagosomes. In addition, although neutrophils engulfed live or heat-killed F. alocis with the same efficiency, heat-killed F. alocis elicited a higher intracellular respiratory burst response compared to viable organisms, along with decreased surface expression of CD35, a marker of secretory vesicles. F. alocis phagosomes remained immature by delayed and reduced recruitment of specific and azurophil granules, respectively. These results suggest that F. alocis withstands neutrophil antimicrobial responses by preventing intracellular ROS production, along with specific and azurophil granule recruitment to the bacterial phagosome.
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Affiliation(s)
- Jacob S. Edmisson
- Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Shifu Tian
- Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Cortney L. Armstrong
- Department of Microbiology & Immunology, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Aruna Vashishta
- Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Christopher K. Klaes
- Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Irina Miralda
- Department of Microbiology & Immunology, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Emeri Jimenez-Flores
- Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, USA
- Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of Louisville, Louisville, KY, USA
| | - Junyi Le
- Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Qian Wang
- Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of Louisville, Louisville, KY, USA
| | - Richard J. Lamont
- Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of Louisville, Louisville, KY, USA
| | - Silvia M. Uriarte
- Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, USA
- Department of Microbiology & Immunology, School of Medicine, University of Louisville, Louisville, KY, USA
- Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of Louisville, Louisville, KY, USA
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28
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Dong W, Lin Y, Cao Y, Liu Y, Xie X, Gu W. Luteolin induces myelodysplastic syndrome‑derived cell apoptosis via the p53‑dependent mitochondrial signaling pathway mediated by reactive oxygen species. Int J Mol Med 2018; 42:1106-1115. [PMID: 29786746 DOI: 10.3892/ijmm.2018.3696] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 05/08/2018] [Indexed: 11/06/2022] Open
Abstract
Luteolin, a common dietary flavonoid, induces the apoptosis of cells in several types of cancer. However, its role in myelodysplastic syndrome (MDS) and the potential underlying mechanisms remain to be elucidated. To evaluate the potential benefit and underlying mechanisms of luteolin in MDS cells, the viability of SKM‑1 cells and primary bone marrow (PBM) mononuclear cells from patients with intermediate‑ or high‑risk MDS were assessed using a Cell Counting Kit‑8 assay. The apoptotic features of cell morphology were assessed using Wright‑Giemsa staining, DNA fragmentation was analyzed by agarose gel electrophoresis, and the extent of apoptosis was quantified by flow cytometry (FCM). Reactive oxygen species (ROS) were measured by FCM with 2,7‑dichlorodihydrofluorescein diacetate staining and mitochondrial membrane potential (ΔΨm) was determined using 5,5',6,6'‑tetrachloro‑1,1',3,3'‑tetraethylbenzimidazolylcarbocyanine iodide staining. Caspase activity was detected using a fluorometric protease assay. Furthermore, the effects of luteolin on the expression of apoptosis‑related proteins were analyzed using western blot analysis. The resulting data revealed that luteolin significantly inhibited the proliferation of SKM‑1 cells in vitro, and its half maximal inhibitory concentration was 139.41 µM at 24 h and 23.95 µM at 72 h. Luteolin also markedly inhibited the proliferation of mononuclear cells from patients with intermediate‑ or high‑risk MDS. Luteolin suppressed cell proliferation, mainly as a result of the induction of apoptosis, as demonstrated by typical apoptotic morphological features, the ladder pattern of genomic DNA fragmentation, and the results of FCM using Annexin V‑FITC/PI double staining. It was also found that short‑term exposure of SKM‑1 cells to luteolin led to a marked increase in the accumulation of ROS. The increased intracellular level of ROS appeared to induce the activation of p53 and elevate the B‑cell lymphoma 2 (Bcl‑2)‑associated X protein/Bcl‑2 ratio, which modulates ΔΨm and triggers the release of cytochrome c, and may increase the activities of apoptotic protease activating factor 1, caspase‑3, ‑8 and ‑9 to further trigger the destruction of structural and specific proteins and thereby cell apoptosis. Notably, the inhibition of ROS generation by the antioxidant N‑acetyl‑L‑cysteine significantly attenuated the luteolin‑induced loss of ΔΨm and activities of caspase‑3, ‑8 and ‑9. These data suggested that luteolin exerts its pro‑apoptotic action partly through the p53‑dependent mitochondrial signaling pathway mediated by intracellular ROS, which provides a promising therapeutic candidate for patients with MDS.
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Affiliation(s)
- Weimin Dong
- Department of Hematology, The Third Affiliated Hospital of Soochow University, The First People's Hospital of Changzhou, Changzhou, Jiangsu 213003, P.R. China
| | - Yan Lin
- Department of Hematology, The Third Affiliated Hospital of Soochow University, The First People's Hospital of Changzhou, Changzhou, Jiangsu 213003, P.R. China
| | - Yang Cao
- Department of Hematology, The Third Affiliated Hospital of Soochow University, The First People's Hospital of Changzhou, Changzhou, Jiangsu 213003, P.R. China
| | - Yue Liu
- Department of Hematology, The Third Affiliated Hospital of Soochow University, The First People's Hospital of Changzhou, Changzhou, Jiangsu 213003, P.R. China
| | - Xiaobao Xie
- Department of Hematology, The Third Affiliated Hospital of Soochow University, The First People's Hospital of Changzhou, Changzhou, Jiangsu 213003, P.R. China
| | - Weiying Gu
- Department of Hematology, The Third Affiliated Hospital of Soochow University, The First People's Hospital of Changzhou, Changzhou, Jiangsu 213003, P.R. China
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29
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Kobayashi SD, Malachowa N, DeLeo FR. Neutrophils and Bacterial Immune Evasion. J Innate Immun 2018; 10:432-441. [PMID: 29642066 DOI: 10.1159/000487756] [Citation(s) in RCA: 120] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 02/14/2018] [Indexed: 12/31/2022] Open
Abstract
Neutrophils are an important component of the innate immune system and provide a front line of defense against bacterial infection. Although most bacteria are killed readily by neutrophils, some bacterial pathogens have the capacity to circumvent destruction by these host leukocytes. The ability of bacterial pathogens to avoid killing by neutrophils often involves multiple attributes or characteristics, including the production of virulence molecules. These molecules are diverse in composition and function, and collectively have the potential to alter or inhibit neutrophil recruitment, phagocytosis, bactericidal activity, and/or apoptosis. Here, we review the ability of bacteria to target these processes.
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30
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Kinkead LC, Whitmore LC, McCracken JM, Fletcher JR, Ketelsen BB, Kaufman JW, Jones BD, Weiss DS, Barker JH, Allen LAH. Bacterial lipoproteins and other factors released by Francisella tularensis modulate human neutrophil lifespan: Effects of a TLR1 SNP on apoptosis inhibition. Cell Microbiol 2017; 20. [PMID: 29063667 PMCID: PMC5764820 DOI: 10.1111/cmi.12795] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/10/2017] [Accepted: 10/15/2017] [Indexed: 12/21/2022]
Abstract
Francisella tularensis infects several cell types including neutrophils, and aberrant neutrophil accumulation contributes to tissue destruction during tularaemia. We demonstrated previously that F. tularensis strains Schu S4 and live vaccine strain markedly delay human neutrophil apoptosis and thereby prolong cell lifespan, but the bacterial factors that mediate this aspect of virulence are undefined. Herein, we demonstrate that bacterial conditioned medium (CM) can delay apoptosis in the absence of direct infection. Biochemical analyses show that CM contained F. tularensis surface factors as well as outer membrane components. Our previous studies excluded roles for lipopolysaccharide and capsule in apoptosis inhibition, and current studies of [14C] acetate‐labelled bacteria argue against a role for other bacterial lipids in this process. At the same time, studies of isogenic mutants indicate that TolC and virulence factors whose expression requires FevR or MglA were also dispensable, demonstrating that apoptosis inhibition does not require Type I or Type VI secretion. Instead, we identified bacterial lipoproteins (BLPs) as active factors in CM. Additional studies of isolated BLPs demonstrated dose‐dependent neutrophil apoptosis inhibition via a TLR2‐dependent mechanism that is significantly influenced by a common polymorphism, rs5743618, in human TLR1. These data provide fundamental new insight into pathogen manipulation of neutrophil lifespan and BLP function.
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Affiliation(s)
- Lauren C Kinkead
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Laura C Whitmore
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Jenna M McCracken
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Joshua R Fletcher
- Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, USA
| | - Brandi B Ketelsen
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Iowa City VA Health Care System, Iowa City, Iowa, USA
| | - Justin W Kaufman
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Bradley D Jones
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA.,Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, USA
| | - David S Weiss
- Emory Vaccine Center, Emory University, Atlanta, Georgia, USA
| | - Jason H Barker
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Lee-Ann H Allen
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA.,Iowa City VA Health Care System, Iowa City, Iowa, USA
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31
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Krocova Z, Macela A, Kubelkova K. Innate Immune Recognition: Implications for the Interaction of Francisella tularensis with the Host Immune System. Front Cell Infect Microbiol 2017; 7:446. [PMID: 29085810 PMCID: PMC5650615 DOI: 10.3389/fcimb.2017.00446] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 09/29/2017] [Indexed: 12/11/2022] Open
Abstract
The intracellular bacterial pathogen Francisella tularensis causes serious infectious disease in humans and animals. Moreover, F. tularensis, a highly infectious pathogen, poses a major concern for the public as a bacterium classified under Category A of bioterrorism agents. Unfortunately, research has so far failed to develop effective vaccines, due in part to the fact that the pathogenesis of intracellular bacteria is not fully understood and in part to gaps in our understanding of innate immune recognition processes leading to the induction of adaptive immune response. Recent evidence supports the concept that immune response to external stimuli in the form of bacteria is guided by the primary interaction of the bacterium with the host cell. Based on data from different Francisella models, we present here the basic paradigms of the emerging innate immune recognition concept. According to this concept, the type of cell and its receptor(s) that initially interact with the target constitute the first signaling window; the signals produced in the course of primary interaction of the target with a reacting cell act in a paracrine manner; and the innate immune recognition process as a whole consists in a series of signaling windows modulating adaptive immune response. Finally, the host, in the strict sense, is the interacting cell.
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Affiliation(s)
- Zuzana Krocova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czechia
| | - Ales Macela
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czechia
| | - Klara Kubelkova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czechia
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32
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Necroptotic debris including damaged mitochondria elicits sepsis-like syndrome during late-phase tularemia. Cell Death Discov 2017; 3:17056. [PMID: 28955505 PMCID: PMC5611684 DOI: 10.1038/cddiscovery.2017.56] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 06/30/2017] [Accepted: 07/18/2017] [Indexed: 12/31/2022] Open
Abstract
Infection with Francisella tularensis ssp. tularensis (Ft) strain SchuS4 causes an often lethal disease known as tularemia in rodents, non-human primates, and humans. Ft subverts host cell death programs to facilitate their exponential replication within macrophages and other cell types during early respiratory infection (⩽72 h). The mechanism(s) by which cell death is triggered remains incompletely defined, as does the impact of Ft on mitochondria, the host cell’s organellar ‘canary in a coal mine’. Herein, we reveal that Ft infection of host cells, particularly macrophages and polymorphonuclear leukocytes, drives necroptosis via a receptor-interacting protein kinase 1/3-mediated mechanism. During necroptosis mitochondria and other organelles become damaged. Ft-induced mitochondrial damage is characterized by: (i) a decrease in membrane potential and consequent mitochondrial oncosis or swelling, (ii) increased generation of superoxide radicals, and (iii) release of intact or damaged mitochondria into the lung parenchyma. Host cell recognition of and response to released mitochondria and other damage-associated molecular patterns engenders a sepsis-like syndrome typified by production of TNF, IL-1β, IL-6, IL-12p70, and IFN-γ during late-phase tularemia (⩾72 h), but are absent early during infection.
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33
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Pocock JM, Storisteanu DML, Reeves MB, Juss JK, Wills MR, Cowburn AS, Chilvers ER. Human Cytomegalovirus Delays Neutrophil Apoptosis and Stimulates the Release of a Prosurvival Secretome. Front Immunol 2017; 8:1185. [PMID: 28993776 PMCID: PMC5622148 DOI: 10.3389/fimmu.2017.01185] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 09/07/2017] [Indexed: 12/24/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a major cause of viral disease in the young and the immune-suppressed. At sites of infection, HCMV recruits the neutrophil, a cell with a key role in orchestrating the initial immune response. Herein, we report a profound survival response in human neutrophils exposed to the clinical HCMV isolate Merlin, but not evident with the attenuated strain AD169, through suppression of apoptosis. The initial survival event, which is independent of viral gene expression and involves activation of the ERK/MAPK and NF-κB pathways, is augmented by HCMV-stimulated release of a secretory cytokine profile that further prolongs neutrophil lifespan. As aberrant neutrophil survival contributes to tissue damage, we predict that this may be relevant to the immune pathology of HCMV, and the presence of this effect in clinical HCMV strains and its absence in attenuated strains implies a beneficial effect to the virus in pathogenesis and/or dissemination. In addition, we show that HCMV-exposed neutrophils release factors that enhance monocyte recruitment and drive monocyte differentiation to a HCMV-permissive phenotype in an IL-6-dependent manner, thus providing an ideal vehicle for viral dissemination. This study increases understanding of HCMV-neutrophil interactions, highlighting the potential role of neutrophil recruitment as a virulence mechanism to promote HCMV pathology in the host and influence the dissemination of HCMV infection. Targeting these mechanisms may lead to new antiviral strategies aimed at limiting host damage and inhibiting viral spread.
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Affiliation(s)
- Joanna M. Pocock
- Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke’s and Papworth Hospitals, Cambridge, United Kingdom
| | - Daniel M. L. Storisteanu
- Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke’s and Papworth Hospitals, Cambridge, United Kingdom
| | - Matthew B. Reeves
- Department of Virology, Institute of Immunity and Transplantation, University College London, London, United Kingdom
| | - Jatinder K. Juss
- Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke’s and Papworth Hospitals, Cambridge, United Kingdom
| | - Mark R. Wills
- Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke’s and Papworth Hospitals, Cambridge, United Kingdom
| | - Andrew S. Cowburn
- Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke’s and Papworth Hospitals, Cambridge, United Kingdom
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Edwin R. Chilvers
- Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke’s and Papworth Hospitals, Cambridge, United Kingdom
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34
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Kinkead LC, Fayram DC, Allen LAH. Francisella novicida inhibits spontaneous apoptosis and extends human neutrophil lifespan. J Leukoc Biol 2017; 102:815-828. [PMID: 28550119 DOI: 10.1189/jlb.4ma0117-014r] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 04/27/2017] [Accepted: 05/02/2017] [Indexed: 01/09/2023] Open
Abstract
Francisella novicida is a Gram-negative bacterium that is closely related to the highly virulent facultative intracellular pathogen, Francisella tularensis Data published by us and others demonstrate that F. tularensis virulence correlates directly with its ability to impair constitutive apoptosis and extend human neutrophil lifespan. In contrast, F. novicida is attenuated in humans, and the mechanisms that account for this are incompletely defined. Our published data demonstrate that F. novicida binds natural IgG that is present in normal human serum, which in turn, elicits NADPH oxidase activation that does not occur in response to F. tularensis As it is established that phagocytosis and oxidant production markedly accelerate neutrophil death, we predicted that F. novicida may influence the neutrophil lifespan in an opsonin-dependent manner. To test this hypothesis, we quantified bacterial uptake, phosphatidylserine (PS) externalization, and changes in nuclear morphology, as well as the kinetics of procaspase-3, -8, and -9 processing and activation. To our surprise, we discovered that F. novicida not only failed to accelerate neutrophil death but also diminished and delayed apoptosis in a dose-dependent, but opsonin-independent, manner. In keeping with this, studies of conditioned media (CM) showed that neutrophil longevity could be uncoupled from phagocytosis and that F. novicida stimulated neutrophil secretion of CXCL8. Taken together, the results of this study reveal shared and unique aspects of the mechanisms used by Francisella species to manipulate neutrophil lifespan and as such, advance understanding of cell death regulation during infection.
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Affiliation(s)
- Lauren C Kinkead
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology, University of Iowa, Iowa City, Iowa, USA.,Iowa City VA Medical Center, Iowa City, Iowa, USA
| | - Drew C Fayram
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology, University of Iowa, Iowa City, Iowa, USA
| | - Lee-Ann H Allen
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA; .,Department of Microbiology, University of Iowa, Iowa City, Iowa, USA.,Iowa City VA Medical Center, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA; and
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35
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Protective Role for Macrophages in Respiratory Francisella tularensis Infection. Infect Immun 2017; 85:IAI.00064-17. [PMID: 28373354 DOI: 10.1128/iai.00064-17] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 03/28/2017] [Indexed: 12/25/2022] Open
Abstract
Francisella tularensis causes lethal pneumonia following infection of the lungs by targeting macrophages for intracellular replication; however, macrophages stimulated with interferon gamma (IFN-γ) can resist infection in vitro We therefore hypothesized that the protective effect of IFN-γ against F. tularensisin vivo requires macrophages receptive to stimulation. We found that the lethality of pulmonary F. tularensis LVS infection was exacerbated under conditions of alveolar macrophage depletion and in mice with a macrophage-specific defect in IFN-γ signaling (termed mice with macrophages insensitive to IFN-γ [MIIG mice]). We previously found that treatment with exogenous interleukin 12 (IL-12) protects against F. tularensis infection; this protection was lost in MIIG mice. MIIG mice also exhibited reduced neutrophil recruitment to the lungs following infection. Systemic neutrophil depletion was found to render wild-type mice highly sensitive to respiratory F. tularensis infection, and depletion beginning at 3 days postinfection led to more pronounced sensitivity than depletion beginning prior to infection. Furthermore, IL-12-mediated protection required NADPH oxidase activity. These results indicate that lung macrophages serve a critical protective role in respiratory F. tularensis LVS infection. Macrophages require IFN-γ signaling to mediate protection, which ultimately results in recruitment of neutrophils to further aid in survival from infection.
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36
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Friedrich A, Pechstein J, Berens C, Lührmann A. Modulation of host cell apoptotic pathways by intracellular pathogens. Curr Opin Microbiol 2017; 35:88-99. [DOI: 10.1016/j.mib.2017.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 12/03/2016] [Accepted: 03/01/2017] [Indexed: 12/13/2022]
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37
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Whitmore LC, Weems MN, Allen LAH. Cutting Edge: Helicobacter pylori Induces Nuclear Hypersegmentation and Subtype Differentiation of Human Neutrophils In Vitro. THE JOURNAL OF IMMUNOLOGY 2017; 198:1793-1797. [PMID: 28148734 DOI: 10.4049/jimmunol.1601292] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 01/07/2017] [Indexed: 12/20/2022]
Abstract
Helicobacter pylori infects the human stomach and causes a spectrum of disease that includes gastritis, peptic ulcers, and gastric adenocarcinoma. A chronic, neutrophil-rich inflammatory response characterizes this infection. It is established that H. pylori stimulates neutrophil chemotaxis and a robust respiratory burst, but other aspects of this interaction are incompletely defined. We demonstrate here that H. pylori induces N1-like subtype differentiation of human neutrophils as indicated by profound nuclear hypersegmentation, a CD62Ldim, CD16bright, CD11bbright, CD66bbright, CD63bright surface phenotype, proinflammatory cytokine secretion, and cytotoxicity. Hypersegmentation requires direct neutrophil-H. pylori contact as well as transcription and both host and bacterial protein synthesis, but not urease, NapA, VacA, CagA, or CagT. The concept of neutrophil plasticity is new and, to our knowledge, these data are the first evidence that neutrophils can undergo subtype differentiation in vitro in response to bacterial pathogen infection. We hypothesize that these changes favor H. pylori persistence and disease.
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Affiliation(s)
- Laura C Whitmore
- Inflammation Program, University of Iowa, Iowa City, IA 52242.,Department of Internal Medicine, University of Iowa, Iowa City, IA 52242
| | - Megan N Weems
- Inflammation Program, University of Iowa, Iowa City, IA 52242.,Department of Internal Medicine, University of Iowa, Iowa City, IA 52242
| | - Lee-Ann H Allen
- Inflammation Program, University of Iowa, Iowa City, IA 52242; .,Department of Internal Medicine, University of Iowa, Iowa City, IA 52242.,Department of Microbiology, University of Iowa, Iowa City, IA 52242; and.,Iowa City VA Health Care System, Iowa City, IA 52246
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Singh A, Rahman T, Bartiss R, Arabshahi A, Prasain J, Barnes S, Musteata FM, Sellati TJ. Lipoxin A4, a 5-lipoxygenase pathway metabolite, modulates immune response during acute respiratory tularemia. J Leukoc Biol 2016; 101:531-542. [PMID: 27630217 DOI: 10.1189/jlb.4a0815-365rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 08/12/2016] [Accepted: 08/16/2016] [Indexed: 12/15/2022] Open
Abstract
Respiratory infection with Francisella tularensis (Ft) is characterized by a muted, acute host response, followed by sepsis-like syndrome that results in death. Infection with Ft establishes a principally anti-inflammatory environment that subverts host-cell death programs to facilitate pathogen replication. Although the role of cytokines has been explored extensively, the role of eicosanoids in tularemia pathogenesis is not fully understood. Given that lipoxin A4 (LXA4) has anti-inflammatory properties, we investigated whether this lipid mediator affects host responses manifested early during infection. The addition of exogenous LXA4 inhibits PGE2 release by Ft-infected murine monocytes in vitro and diminishes apoptotic cell death. Tularemia pathogenesis was characterized in 5‑lipoxygenase-deficient (Alox5-/-) mice that are incapable of generating LXA4 Increased release of proinflammatory cytokines and chemokines, as well as increased apoptosis, was observed in Alox5-/- mice as compared with their wild-type counterparts. Alox5-/- mice also exhibited elevated recruitment of neutrophils during the early phase of infection and increased resistance to lethal challenge. Conversely, administration of exogenous LXA4 to Alox5-/- mice made them more susceptible to infection thus mimicking wild-type animals. Taken together, our results suggest that 5-LO activity is a critical regulator of immunopathology observed during the acute phase of respiratory tularemia, regulating bacterial burden and neutrophil recruitment and production of proinflammatory modulators and increasing morbidity and mortality. These studies identify a detrimental role for the 5-LO-derived lipid mediator LXA4 in Ft-induced immunopathology. Targeting this pathway may have therapeutic benefit as an adjunct to treatment with antibiotics and conventional antimicrobial peptides, which often have limited efficacy against intracellular bacteria.
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Affiliation(s)
- Anju Singh
- Trudeau Institute, Saranac Lake, New York, USA
| | - Tabassum Rahman
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA
| | | | - Alireza Arabshahi
- Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, USA; and
| | - Jeevan Prasain
- Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, USA; and
| | - Stephen Barnes
- Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, USA; and
| | - Florin Marcel Musteata
- Department of Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York, USA
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Affiliation(s)
- William M Nauseef
- Inflammation Program and Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Veterans Administration Medical Center, Iowa City, IA, USA
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Kinkead LC, Allen LAH. Multifaceted effects of Francisella tularensis on human neutrophil function and lifespan. Immunol Rev 2016; 273:266-81. [PMID: 27558340 PMCID: PMC5000853 DOI: 10.1111/imr.12445] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Francisella tularensis in an intracellular bacterial pathogen that causes a potentially lethal disease called tularemia. Studies performed nearly 100 years ago revealed that neutrophil accumulation in infected tissues correlates directly with the extent of necrotic damage during F. tularensis infection. However, the dynamics and details of bacteria-neutrophil interactions have only recently been studied in detail. Herein, we review current understanding regarding the mechanisms that recruit neutrophils to F. tularensis-infected lungs, opsonization and phagocytosis, evasion and inhibition of neutrophil defense mechanisms, as well as the ability of F. tularensis to prolong neutrophil lifespan. In addition, we discuss distinctive features of the bacterium, including its ability to act at a distance to alter overall neutrophil responsiveness to exogenous stimuli, and the evidence which suggests that macrophages and neutrophils play distinct roles in tularemia pathogenesis, such that macrophages are major vehicles for intracellular growth and dissemination, whereas neutrophils drive tissue destruction by dysregulation of the inflammatory response.
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Affiliation(s)
- Lauren C. Kinkead
- Inflammation Program, University of Iowa Iowa City, IA 52242
- Department of Microbiology, University of Iowa Iowa City, IA 52242
| | - Lee-Ann H. Allen
- Inflammation Program, University of Iowa Iowa City, IA 52242
- Department of Microbiology, University of Iowa Iowa City, IA 52242
- Department of Internal Medicine, University of Iowa Iowa City, IA 52242
- VA Medical Center, Iowa City, IA 52242
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41
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Uriarte SM, Edmisson JS, Jimenez-Flores E. Human neutrophils and oral microbiota: a constant tug-of-war between a harmonious and a discordant coexistence. Immunol Rev 2016; 273:282-98. [PMID: 27558341 PMCID: PMC5353849 DOI: 10.1111/imr.12451] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neutrophils are a major component of the innate host response, and the outcome of the interaction between the oral microbiota and neutrophils is a key determinant of oral health status. The composition of the oral microbiome is very complex and different in health and disease. Neutrophils are constantly recruited to the oral cavity, and their protective role is highlighted in cases where their number or functional responses are impeded, resulting in different forms of periodontal disease. Periodontitis, one of the more severe and irreversible forms of periodontal disease, is a microbial-induced chronic inflammatory disease that affects the gingival tissues supporting the tooth. This chronic inflammatory disease is the result of a shift of the oral bacterial symbiotic community to a dysbiotic more complex community. Chronic inflammatory infectious diseases such as periodontitis can occur because the pathogens are able to evade or disable the innate immune system. In this review, we discuss how human neutrophils interact with both the symbiotic and the dysbiotic oral community; an understanding of which is essential to increase our knowledge of the periodontal disease process.
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Affiliation(s)
- Silvia M. Uriarte
- Department of Medicine, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Jacob S. Edmisson
- Department of Biology, School of Arts & Sciences, University of Louisville, Louisville, KY, USA
| | - Emeri Jimenez-Flores
- Department of Oral Immunology and Infectious Diseases, Schoaol of Dentistry, University of Louisville, Louisville, KY, USA
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Deng X, Deng T, Ni Y, Zhan Y, Huang W, Liu J, Liao C. Cytochrome c modulates the mitochondrial signaling pathway and polymorphonuclear neutrophil apoptosis in bile duct-ligated rats. Exp Ther Med 2016; 12:333-342. [PMID: 27347059 DOI: 10.3892/etm.2016.3313] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 02/04/2016] [Indexed: 12/15/2022] Open
Abstract
It has been observed that polymorphonuclear neutrophils (PMN) increase in number and function during obstructive jaundice (OJ). However, the precise mechanisms underlying PMN apoptosis during OJ remain poorly understood. The aim of the present study was to investigate the modulation of cytochrome c (Cytc) on the mitochondrial signaling pathway in bile duct-ligated (BDL) rats and the effect on PMN apoptosis following the intravenous administration of Cytc. Rats were randomly divided into four groups: A control group, a sham group, a BDL group and a BDL + Cytc group (rats with common bile duct ligation as well as Cytc intravenous injection). Blood samples were collected from the inferior vein cava for biochemical analysis and separation of the PMN. PMN apoptosis was evaluated using flow cytometry. The mitochondrial membrane potential (ΔΨm) of PMN was detected by rhodamine-123 staining. The Cytc protein expression levels were examined using western blotting. PMN mitochondria were observed using transmission electron microscopy. The results of the present study revealed that the PMN apoptosis rate in rats decreased gradually from 12 to 72 h following BDL to levels that were significantly lower than those of the control group and the sham group. Compared with the corresponding time point of the BDL group, the BDL + Cytc group showed a significantly increased PMN apoptosis rate. The mean fluorescence intensity (MFI) of ΔΨm decreased from 12 to 72 h following BDL, and was significantly increased compared with the control and sham groups. MFI in the BDL + Cytc group was higher compared with that in the BDL group. Cytc expression levels increased in the mitochondria and decreased in the cytoplasm from the 12 to 72 h in the BDL group, which was significantly different from that in the control and sham groups at the corresponding time points. Compared with the BDL group, Cytc expression levels in the cytoplasm for the BDL + Cytc group tended to gradually and significantly increase. Morphological changes in PMN mitochondria were marginal in BDL rats and marked in the BDL + Cytc group. In the BDL rats, PMN apoptosis was inhibited, a process induced by the mitochondrial apoptotic signaling pathway in which Cytc has an important role. High ΔΨm in the mitochondria and decreased Cytc expression levels in the cytoplasm result in PMN apoptosis inhibition. Intravenous injection of Cytc may help compensate for the lack of Cytc proteins in the cytoplasm, inducing PMN apoptosis following BDL.
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Affiliation(s)
- Xuesong Deng
- Department of Hepatobiliary Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China; Department of Hepatobiliary Surgery, The Second People's Hospital of Shenzhen (The First Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong 518035, P.R. China
| | - Tongming Deng
- Department of General Surgery, Baoan Central Hospital of Shenzhen, Shenzhen, Guangdong 518102, P.R. China
| | - Yong Ni
- Department of Hepatobiliary Surgery, The Second People's Hospital of Shenzhen (The First Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong 518035, P.R. China
| | - Yongqiang Zhan
- Department of Hepatobiliary Surgery, The Second People's Hospital of Shenzhen (The First Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong 518035, P.R. China
| | - Wenlong Huang
- Department of Hepatobiliary Surgery, The Second People's Hospital of Shenzhen (The First Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong 518035, P.R. China
| | - Jianfeng Liu
- Department of Hepatobiliary Surgery, The Second People's Hospital of Shenzhen (The First Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong 518035, P.R. China
| | - Caixian Liao
- Department of Hepatobiliary Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
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Peptidoglycan from the gut microbiota governs the lifespan of circulating phagocytes at homeostasis. Blood 2016; 127:2460-71. [PMID: 26989200 DOI: 10.1182/blood-2015-10-675173] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 03/10/2016] [Indexed: 12/17/2022] Open
Abstract
Maintenance of myeloid cell homeostasis requires continuous turnover of phagocytes from the bloodstream, yet whether environmental signals influence phagocyte longevity in the absence of inflammation remains unknown. Here, we show that the gut microbiota regulates the steady-state cellular lifespan of neutrophils and inflammatory monocytes, the 2 most abundant circulating myeloid cells and key contributors to inflammatory responses. Treatment of mice with broad-spectrum antibiotics, or with the gut-restricted aminoglycoside neomycin alone, accelerated phagocyte turnover and increased the rates of their spontaneous apoptosis. Metagenomic analyses revealed that neomycin altered the abundance of intestinal bacteria bearing γ-d-glutamyl-meso-diaminopimelic acid, a ligand for the intracellular peptidoglycan sensor Nod1. Accordingly, signaling through Nod1 was both necessary and sufficient to mediate the stimulatory influence of the flora on myeloid cell longevity. Stimulation of Nod1 signaling increased the frequency of lymphocytes in the murine intestine producing the proinflammatory cytokine interleukin 17A (IL-17A), and liberation of IL-17A was required for transmission of Nod1-dependent signals to circulating phagocytes. Together, these results define a mechanism through which intestinal microbes govern a central component of myeloid homeostasis and suggest perturbations of commensal communities can influence steady-state regulation of cell fate.
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McCracken JM, Kinkead LC, McCaffrey RL, Allen LAH. Francisella tularensis Modulates a Distinct Subset of Regulatory Factors and Sustains Mitochondrial Integrity to Impair Human Neutrophil Apoptosis. J Innate Immun 2016; 8:299-313. [PMID: 26906922 DOI: 10.1159/000443882] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 01/09/2016] [Indexed: 12/13/2022] Open
Abstract
Tularemia is a disease characterized by profound neutrophil accumulation and tissue destruction. The causative organism, Francisella tularensis, is a facultative intracellular bacterium that replicates in neutrophil cytosol, inhibits caspase activation and profoundly prolongs cell lifespan. Here, we identify unique features of this infection and provide fundamental insight into the mechanisms of apoptosis inhibition. Mitochondria are critical regulators of neutrophil apoptosis. We demonstrate that F. tularensis significantly inhibits Bax translocation and Bid processing during 24-48 h of infection, and in this manner sustains mitochondrial integrity. Downstream of mitochondria, X-linked inhibitor of apoptosis protein (XIAP) and proliferating cell nuclear antigen (PCNA) inhibit caspase-9 and caspase-3 by direct binding. Notably, we find that PCNA disappeared rapidly and selectively from infected cells, thereby demonstrating that it is not essential for neutrophil survival, whereas upregulation of calpastatin correlated with diminished calpain activity and reduced XIAP degradation. In addition, R-roscovitine is a cyclin-dependent kinase inhibitor developed for the treatment of cancer; it also induces neutrophil apoptosis and can promote the resolution of several infectious and inflammatory disorders. We confirm the ability of R-roscovitine to induce neutrophil apoptosis, but also demonstrate that its efficacy is significantly impaired by F. tularensis. Collectively, our findings advance the understanding of neutrophil apoptosis and its capacity to be manipulated by pathogenic bacteria.
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Affiliation(s)
- Jenna M McCracken
- Inflammation Program, University of Iowa and VA Medical Center, Iowa City, Iowa, USA
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Abstract
Upon entry to the systemic circulation, neutrophils exhibit a short mean time to cell death. The viability of most cell types in a steady state is preserved by the interplay of the Bcl-2 family of proteins, wherein the anti-apoptotic members inhibit the action of their pro-apoptotic counterparts. Neutrophils, however, display absent or severely reduced expression of several anti-apoptotic Bcl-2 family proteins. Hence, they rely on the expression of Mcl-1, an anti-apoptotic member of the Bcl-2 family, for survival. This protein is uniquely short-lived relative to related proteins and its loss likely precipitates the induction of apoptosis in neutrophils. This review describes the role of Mcl-1 in the neutrophil in the context of apoptosis and highlights the proteins' importance to the cell. We also address neutrophil apoptosis in the broader context of the cells' response to pathogens, focussing particularly on the strategies used by pathogens to manipulate the apoptotic pathway to their own ends.
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Affiliation(s)
- Mark P Murphy
- Centre for Microbial-Host Interactions, Institute of Technology Tallaght, Old Blessington Road, Tallaght, Dublin 24, Ireland,
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Abstract
During pneumonic plague, the bacterium Yersinia pestis elicits the development of inflammatory lung lesions that continue to expand throughout infection. This lesion development and persistence are poorly understood. Here, we examine spatially distinct regions of lung lesions using laser capture microdissection and transcriptome sequencing (RNA-seq) analysis to identify transcriptional differences between lesion microenvironments. We show that cellular pathways involved in leukocyte migration and apoptosis are downregulated in the center of lung lesions compared to the periphery. Probing for the bacterial factor(s) important for the alteration in neutrophil survival, we show both in vitro and in vivo that Y. pestis increases neutrophil survival in a manner that is dependent on the type III secretion system effector YopM. This research explores the complexity of spatially distinct host-microbe interactions and emphasizes the importance of cell relevance in assays in order to fully understand Y. pestis virulence. Yersinia pestis is a high-priority pathogen and continues to cause outbreaks worldwide. The ability of Y. pestis to be transmitted via respiratory droplets and its history of weaponization has led to its classification as a select agent most likely to be used as a biological weapon. Unrestricted bacterial growth during the initial preinflammatory phase primes patients to be infectious once disease symptoms begin in the proinflammatory phase, and the rapid disease progression can lead to death before Y. pestis infection can be diagnosed and treated. Using in vivo analyses and focusing on relevant cell types during pneumonic plague infection, we can identify host pathways that may be manipulated to extend the treatment window for pneumonic plague patients.
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Simultaneous Host-Pathogen Transcriptome Analysis during Granulibacter bethesdensis Infection of Neutrophils from Healthy Subjects and Patients with Chronic Granulomatous Disease. Infect Immun 2015; 83:4277-92. [PMID: 26283340 DOI: 10.1128/iai.00778-15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 08/11/2015] [Indexed: 11/20/2022] Open
Abstract
Polymorphonuclear leukocytes (PMN) from patients with chronic granulomatous disease (CGD) fail to produce microbicidal concentrations of reactive oxygen species (ROS) due to mutations in NOX2. Patients with CGD suffer from severe, life-threatening infections and inflammatory complications. Granulibacter bethesdensis is an emerging Gram-negative pathogen in CGD that resists killing by PMN of CGD patients (CGD PMN) and inhibits PMN apoptosis through unknown mechanisms. Microarray analysis was used to study mRNA expression in PMN from healthy subjects (normal PMN) and CGD PMN during incubation with G. bethesdensis and, simultaneously, in G. bethesdensis with normal and CGD PMN. We detected upregulation of antiapoptotic genes (e.g., XIAP and GADD45B) and downregulation of proapoptotic genes (e.g., CASP8 and APAF1) in infected PMN. Transcript and protein levels of inflammation- and immunity-related genes were also altered. Upon interaction with PMN, G. bethesdensis altered the expression of ROS resistance genes in the presence of normal but not CGD PMN. Levels of bacterial stress response genes, including the ClpB gene, increased during phagocytosis by both normal and CGD PMN demonstrating responses to oxygen-independent PMN antimicrobial systems. Antisense knockdown demonstrated that ClpB is dispensable for extracellular growth but is essential for bacterial resistance to both normal and CGD PMN. Metabolic adaptation of Granulibacter growth in PMN included the upregulation of pyruvate dehydrogenase. Pharmacological inhibition of pyruvate dehydrogenase by triphenylbismuthdichloride was lethal to Granulibacter. This study expands knowledge of microbial pathogenesis of Granulibacter in cells from permissive (CGD) and nonpermissive (normal) hosts and identifies potentially druggable microbial factors, such as pyruvate dehydrogenase and ClpB, to help combat this antibiotic-resistant pathogen.
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Identifying Francisella tularensis genes required for growth in host cells. Infect Immun 2015; 83:3015-25. [PMID: 25987704 DOI: 10.1128/iai.00004-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 05/06/2015] [Indexed: 12/22/2022] Open
Abstract
Francisella tularensis is a highly virulent Gram-negative intracellular pathogen capable of infecting a vast diversity of hosts, ranging from amoebae to humans. A hallmark of F. tularensis virulence is its ability to quickly grow to high densities within a diverse set of host cells, including, but not limited to, macrophages and epithelial cells. We developed a luminescence reporter system to facilitate a large-scale transposon mutagenesis screen to identify genes required for growth in macrophage and epithelial cell lines. We screened 7,454 individual mutants, 269 of which exhibited reduced intracellular growth. Transposon insertions in the 269 growth-defective strains mapped to 68 different genes. FTT_0924, a gene of unknown function but highly conserved among Francisella species, was identified in this screen to be defective for intracellular growth within both macrophage and epithelial cell lines. FTT_0924 was required for full Schu S4 virulence in a murine pulmonary infection model. The ΔFTT_0924 mutant bacterial membrane is permeable when replicating in hypotonic solution and within macrophages, resulting in strongly reduced viability. The permeability and reduced viability were rescued when the mutant was grown in a hypertonic solution, indicating that FTT_0924 is required for resisting osmotic stress. The ΔFTT_0924 mutant was also significantly more sensitive to β-lactam antibiotics than Schu S4. Taken together, the data strongly suggest that FTT_0924 is required for maintaining peptidoglycan integrity and virulence.
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Pliyev BK, Ivanova AV, Savchenko VG. Extracellular NAD(+) inhibits human neutrophil apoptosis. Apoptosis 2015; 19:581-93. [PMID: 24292505 DOI: 10.1007/s10495-013-0948-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Regulation of neutrophil apoptosis plays a critical role in the inflammatory response. Inflammation has previously been shown to increase levels of extracellular β-nicotinamide adenine dinucleotide (NAD(+)). The present study demonstrates that extracellular NAD(+) at concentrations found in the inflamed tissues profoundly delays spontaneous apoptosis of human neutrophils as was evidenced by inhibition of phosphatidylserine (PS) exposure, DNA fragmentation and caspase-3 activation. The effect was abrogated by NF157, an antagonist of P2Y11 receptor, and was pertussis toxin-insensitive. The NAD(+)-mediated delay of neutrophil apoptosis was reversed by 2',5'-dideoxyadenosine, an inhibitor of adenylyl cyclase, and Rp-8-Br-cAMPS, an inhibitor of type I cAMP-dependent protein kinase A (PKA). Blocking of NAD(+)-induced influx of extracellular Ca(2+) with EGTA did not abolish the pro-survival effect of NAD(+). Extracellular NAD(+) inhibited proteasome-dependent degradation of Mcl-1 upstream of caspase activation and, furthermore, suppressed Bax translocation to the mitochondria and attenuated both dissipation of mitochondrial transmembrane potential (ΔΨm) and cytochrome c release from the mitochondria into the cytosol. Finally, we found that extracellular NAD(+) inhibited spontaneous activation of caspase-9, but not caspase-8, and the pro-survival effect of extracellular NAD(+) was abrogated by the inhibitor of caspase-9, but not by the inhibitor of caspase-8. Together, these results demonstrate that extracellular NAD(+) inhibits neutrophil apoptosis via P2Y11 receptor and cAMP/PKA pathway by regulating Mcl-1 level, Bax targeting to the mitochondria and mitochondrial apoptotic pathway. Thus, extracellular NAD(+) acts as a neutrophil survival factor that can contribute to prolonged neutrophil lifespan in inflammatory response.
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Affiliation(s)
- Boris K Pliyev
- Hematology Research Center, Novy Zykovsky Pr. 4, Moscow, 125167, Russia,
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Dhariwala MO, Anderson DM. Bacterial programming of host responses: coordination between type I interferon and cell death. Front Microbiol 2014; 5:545. [PMID: 25389418 PMCID: PMC4211556 DOI: 10.3389/fmicb.2014.00545] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 09/30/2014] [Indexed: 01/24/2023] Open
Abstract
During mammalian infection, bacteria induce cell death from an extracellular or intracellular niche that can protect or hurt the host. Data is accumulating that associate type I interferon (IFN) signaling activated by intracellular bacteria with programmed death of immune effector cells and enhanced virulence. Multiple pathways leading to IFN-dependent host cell death have been described, and in some cases it is becoming clear how these mechanisms contribute to virulence. Yet common mechanisms of IFN-enhanced bacterial pathogenesis are not obvious and no specific interferon stimulated genes have yet been identified that cause sensitivity to pathogen-induced cell death. In this review, we will summarize some bacterial infections caused by facultative intracellular pathogens and what is known about how type I IFN signaling may promote the replication of extracellular bacteria rather than stimulate protection. Each of these pathogens can survive phagocytosis but their intracellular life cycles are very different, they express distinct virulence factors and trigger different pathways of immune activation and crosstalk. These differences likely lead to widely varying amounts of type I IFN expression and a different inflammatory environment, but these may not be important to the pathologic effects on the host. Instead, each pathogen induces programmed cell death of key immune cells that have been sensitized by the activation of the type I IFN response. We will discuss how IFN-dependent host cell death may increase host susceptibility and try to understand common pathways of pathogenesis that lead to IFN-enhanced bacterial virulence.
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Affiliation(s)
- Miqdad O Dhariwala
- Department of Veterinary Pathobiology, University of Missouri Columbia, MO, USA
| | - Deborah M Anderson
- Department of Veterinary Pathobiology, University of Missouri Columbia, MO, USA
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