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Chen WA, Boskovic DS. Neutrophil Extracellular DNA Traps in Response to Infection or Inflammation, and the Roles of Platelet Interactions. Int J Mol Sci 2024; 25:3025. [PMID: 38474270 DOI: 10.3390/ijms25053025] [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: 11/30/2023] [Revised: 02/29/2024] [Accepted: 03/01/2024] [Indexed: 03/14/2024] Open
Abstract
Neutrophils present the host's first line of defense against bacterial infections. These immune effector cells are mobilized rapidly to destroy invading pathogens by (a) reactive oxygen species (ROS)-mediated oxidative bursts and (b) via phagocytosis. In addition, their antimicrobial service is capped via a distinct cell death mechanism, by the release of their own decondensed nuclear DNA, supplemented with a variety of embedded proteins and enzymes. The extracellular DNA meshwork ensnares the pathogenic bacteria and neutralizes them. Such neutrophil extracellular DNA traps (NETs) have the potential to trigger a hemostatic response to pathogenic infections. The web-like chromatin serves as a prothrombotic scaffold for platelet adhesion and activation. What is less obvious is that platelets can also be involved during the initial release of NETs, forming heterotypic interactions with neutrophils and facilitating their responses to pathogens. Together, the platelet and neutrophil responses can effectively localize an infection until it is cleared. However, not all microbial infections are easily cleared. Certain pathogenic organisms may trigger dysregulated platelet-neutrophil interactions, with a potential to subsequently propagate thromboinflammatory processes. These may also include the release of some NETs. Therefore, in order to make rational intervention easier, further elucidation of platelet, neutrophil, and pathogen interactions is still needed.
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Affiliation(s)
- William A Chen
- Division of Biochemistry, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA
- Department of Pharmaceutical and Administrative Sciences, School of Pharmacy, Loma Linda University, Loma Linda, CA 92350, USA
| | - Danilo S Boskovic
- Division of Biochemistry, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA
- Department of Earth and Biological Sciences, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA
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2
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Tsai Z, Carver KA, Gong HH, Kosai K, Deng JC, Worley MJ. Detailed Mechanisms Underlying Neutrophil Bactericidal Activity against Streptococcus pneumoniae. Biomedicines 2023; 11:2252. [PMID: 37626748 PMCID: PMC10452576 DOI: 10.3390/biomedicines11082252] [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: 07/13/2023] [Revised: 07/28/2023] [Accepted: 08/02/2023] [Indexed: 08/27/2023] Open
Abstract
Neutrophils are an essential cellular component of innate immunity and control bacterial infections through a combination of intracellular and extracellular killing methods. Although the importance of neutrophils has been established, the exact methods used to handle particular bacterial challenges and the efficiency of bacterial killing remain not well understood. In this study, we addressed how neutrophils eliminate Streptococcus pneumoniae (Spn), a leading cause of community acquired and post-influenza bacterial pneumonia. We analyzed killing methods with variable bacterial:neutrophil concentrations and following priming with PAM3CSK4 (P3CSK), an agonist for Toll-like-receptor 2 (TLR2). Our results show that murine neutrophils display surprisingly weak bactericidal activity against Spn, employing a predominantly extracellular mode of killing at lower concentrations of bacteria, whereas challenges with higher bacterial numbers induce both extracellular and intracellular elimination modes but require TLR2 activation. TLR2 activation increased reactive oxygen species (ROS) and neutrophil extracellular trap (NET) formation in response to Spn. Despite this, supernatants from P3CSK-stimulated neutrophils failed to independently alter bacterial replication. Our study reveals that unstimulated neutrophils are capable of eliminating bacteria only at lower concentrations via extracellular killing methods, whereas TLR2 activation primes neutrophil-mediated killing using both intracellular and extracellular methods under higher bacterial burdens.
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Affiliation(s)
- Zachary Tsai
- Division of Pulmonary and Critical Care Medicine, University of Michigan School of Medicine, Ann Arbor, MI 48105, USA (K.A.C.); (K.K.); (M.J.W.)
| | - Kyle A. Carver
- Division of Pulmonary and Critical Care Medicine, University of Michigan School of Medicine, Ann Arbor, MI 48105, USA (K.A.C.); (K.K.); (M.J.W.)
- Research Service and Pulmonary Section, Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA;
| | - Henry H. Gong
- Research Service and Pulmonary Section, Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA;
| | - Kosuke Kosai
- Division of Pulmonary and Critical Care Medicine, University of Michigan School of Medicine, Ann Arbor, MI 48105, USA (K.A.C.); (K.K.); (M.J.W.)
- Department of Laboratory Medicine, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8523, Japan
| | - Jane C. Deng
- Division of Pulmonary and Critical Care Medicine, University of Michigan School of Medicine, Ann Arbor, MI 48105, USA (K.A.C.); (K.K.); (M.J.W.)
- Research Service and Pulmonary Section, Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA;
| | - Matthew J. Worley
- Division of Pulmonary and Critical Care Medicine, University of Michigan School of Medicine, Ann Arbor, MI 48105, USA (K.A.C.); (K.K.); (M.J.W.)
- Research Service and Pulmonary Section, Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA;
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3
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Bomfim CCB, Fisher L, Amaral EP, Mittereder L, McCann K, Correa AAS, Namasivayam S, Swamydas M, Moayeri M, Weiss JM, Chari R, McVicar DW, Costa DL, D’Império Lima MR, Sher A. Mycobacterium tuberculosis Induces Irg1 in Murine Macrophages by a Pathway Involving Both TLR-2 and STING/IFNAR Signaling and Requiring Bacterial Phagocytosis. Front Cell Infect Microbiol 2022; 12:862582. [PMID: 35586249 PMCID: PMC9109611 DOI: 10.3389/fcimb.2022.862582] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 04/01/2022] [Indexed: 11/13/2022] Open
Abstract
Irg1 is an enzyme that generates itaconate, a metabolite that plays a key role in the regulation of inflammatory responses. Previous studies have implicated Irg1 as an important mediator in preventing excessive inflammation and tissue damage in Mycobacterium tuberculosis (Mtb) infection. Here, we investigated the pattern recognition receptors and signaling pathways by which Mtb triggers Irg1 gene expression by comparing the responses of control and genetically deficient BMDMs. Using this approach, we demonstrated partial roles for TLR-2 (but not TLR-4 or -9), MyD88 and NFκB signaling in Irg1 induction by Mtb bacilli. In addition, drug inhibition studies revealed major requirements for phagocytosis and endosomal acidification in Irg1 expression triggered by Mtb but not LPS or PAM3CSK4. Importantly, the Mtb-induced Irg1 response was highly dependent on the presence of the bacterial ESX-1 secretion system, as well as host STING and Type I IFN receptor (IFNAR) signaling with Type II IFN (IFN-γ) signaling playing only a minimal role. Based on these findings we hypothesize that Mtb induces Irg1 expression in macrophages via the combination of two independent triggers both dependent on bacterial phagocytosis: 1) a major signal stimulated by phagocytized Mtb products released by an ESX-1-dependent mechanism into the cytosol where they activate the STING pathway leading to Type I-IFN production, and 2) a secondary TLR-2, MyD88 and NFκB dependent signal that enhances Irg1 production independently of Type I IFN induction.
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Affiliation(s)
- Caio C. B. Bomfim
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
- Laboratory of Parasitic Diseases - National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Logan Fisher
- Laboratory of Parasitic Diseases - National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Eduardo P. Amaral
- Laboratory of Parasitic Diseases - National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Lara Mittereder
- Laboratory of Parasitic Diseases - National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Katelyn McCann
- Laboratory of Clinical Immunology and Microbiology - National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - André A. S. Correa
- Department of Biochemistry and Immunology - Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
- Graduate Program in Basic and Applied Immunology - Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
| | - Sivaranjani Namasivayam
- Laboratory of Parasitic Diseases - National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Muthulekha Swamydas
- Laboratory of Clinical Immunology and Microbiology - National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Mahtab Moayeri
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Jonathan M. Weiss
- Laboratory of Cancer Immunometabolism, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States
| | - Raj Chari
- Laboratory Animal Sciences Program, Frederick National Laboratory for Cancer Research, Frederick, MD, United States
| | - Daniel W. McVicar
- Laboratory of Cancer Immunometabolism, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States
| | - Diego L. Costa
- Department of Biochemistry and Immunology - Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
- Graduate Program in Basic and Applied Immunology - Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
| | - Maria R. D’Império Lima
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Alan Sher
- Laboratory of Parasitic Diseases - National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
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4
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Ricci E, Roselletti E, Gentili M, Sabbatini S, Perito S, Riccardi C, Migliorati G, Monari C, Ronchetti S. Glucocorticoid-Induced Leucine Zipper-Mediated TLR2 Downregulation Accounts for Reduced Neutrophil Activity Following Acute DEX Treatment. Cells 2021; 10:2228. [PMID: 34571877 PMCID: PMC8472062 DOI: 10.3390/cells10092228] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 08/25/2021] [Accepted: 08/25/2021] [Indexed: 12/03/2022] Open
Abstract
Glucocorticoids are the most powerful anti-inflammatory and immunosuppressive pharmacological drugs available, despite their adverse effects. Glucocorticoid-induced leucine zipper (GILZ) is a glucocorticoid-induced gene that shares several anti-inflammatory properties with glucocorticoids. Although immunosuppressive effects of glucocorticoids on neutrophils remain poorly understood, we previously demonstrated that GILZ suppresses neutrophil activation under glucocorticoid treatment. Here, we sought to explore the regulation of Toll-like receptor 2 (TLR2) by the synthetic glucocorticoid dexamethasone (DEX) on neutrophils and the associated GILZ involvement. Peripheral blood neutrophils were isolated from wild type and GILZ-knock-out (KO) mice. TLR2 was found to be downregulated by the in vivo administration of glucocorticoids in wild type but not in GILZ-KO neutrophils, suggesting the involvement of GILZ in TLR2 downregulation. Accordingly, the TLR2-associated anti-fungal activity of neutrophils was reduced by DEX treatment in wild type but not GILZ-KO neutrophils. Furthermore, GILZ did not interact with NF-κB but was found to bind with STAT5, a pivotal factor in the regulation of TLR2 expression. A similar modulation of TLR2 expression, impaired phagocytosis, and killing activity was observed in circulating human neutrophils treated in vitro with DEX. These results demonstrate that glucocorticoids reduce the ability of neutrophils to respond to infections by downregulating TLR2 via GILZ, thereby reducing critical functions.
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Affiliation(s)
- Erika Ricci
- Department of Medicine and Surgery, Pharmacology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (M.G.); (C.R.); (G.M.)
| | - Elena Roselletti
- Department of Medicine and Surgery, Medical Microbiology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (S.S.); (S.P.); (C.M.)
| | - Marco Gentili
- Department of Medicine and Surgery, Pharmacology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (M.G.); (C.R.); (G.M.)
| | - Samuele Sabbatini
- Department of Medicine and Surgery, Medical Microbiology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (S.S.); (S.P.); (C.M.)
| | - Stefano Perito
- Department of Medicine and Surgery, Medical Microbiology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (S.S.); (S.P.); (C.M.)
| | - Carlo Riccardi
- Department of Medicine and Surgery, Pharmacology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (M.G.); (C.R.); (G.M.)
| | - Graziella Migliorati
- Department of Medicine and Surgery, Pharmacology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (M.G.); (C.R.); (G.M.)
| | - Claudia Monari
- Department of Medicine and Surgery, Medical Microbiology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (S.S.); (S.P.); (C.M.)
| | - Simona Ronchetti
- Department of Medicine and Surgery, Pharmacology Division, University of Perugia, 06132 Perugia, Italy; (E.R.); (M.G.); (C.R.); (G.M.)
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5
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Kaushal N, Kumari S, Jhelum H, Sehgal D. In vitro and in vivo characterization of the interaction, proinflammatory, immunomodulatory and antigenic properties of capsular polysaccharide from Streptococcus pneumoniae serotype 1. Int J Biol Macromol 2020; 143:521-532. [PMID: 31816377 DOI: 10.1016/j.ijbiomac.2019.12.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 12/02/2019] [Accepted: 12/03/2019] [Indexed: 11/17/2022]
Abstract
Pneumococcal capsular polysaccharide (PCP) is the major virulence determinant of Streptococcus pneumoniae (pneumococcus). Strains devoid of the capsule are avirulent or highly attenuated. PCP is present in soluble form and on pneumococci in infected individuals. The present study was undertaken to study the interaction of PCP from serotype 1 (PCP1) with immune cells, and its proinflammatory, immunomodulatory and antigenic properties. Binding of PCP1 to the surface of immune cells led to proinflammatory cytokine production which was not cell line or cytokine restricted. HEK293T transfectants expressing TLR1 and TLR2 produced IL-8 upon stimulation with PCP1, untransfected cells did not do so. PCP1 failed to induce TNF-α production from RAW264.7 cells when pre-incubated with a TLR2 blocking antibody. The surface binding of PCP1 was abrogated in the presence of TLR2 blocking antibody. PCP1 failed to bind TLR2 deficient RAW264.7 cells and induce TNF-α production. Unlike PCP1, alkali-treated PCP1 failed to stimulate RAW264.7 cells to produce TNF-α indicating the importance of alkali-sensitive moieties like O-acetyl groups. Alkali-treated PCP1 elicited lower anti-PCP1 antibody response. Mice experiments suggested that alkali-sensitive groups are significant target of protective antibodies in PCP1 immunized mice. Our findings demonstrate that PCP1 is an important modulator of immune response against pneumococci.
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Affiliation(s)
- Nitika Kaushal
- Molecular Immunology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - Sujata Kumari
- Molecular Immunology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - Hina Jhelum
- Molecular Immunology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - Devinder Sehgal
- Molecular Immunology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
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6
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Too LK, Yau B, Baxter AG, McGregor IS, Hunt NH. Double deficiency of toll-like receptors 2 and 4 alters long-term neurological sequelae in mice cured of pneumococcal meningitis. Sci Rep 2019; 9:16189. [PMID: 31700009 PMCID: PMC6838097 DOI: 10.1038/s41598-019-52212-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 10/08/2019] [Indexed: 01/03/2023] Open
Abstract
Toll-like receptor (TLR) 2 and 4 signalling pathways are central to the body’s defence against invading pathogens during pneumococcal meningitis. Whereas several studies support their importance in innate immunity, thereby preventing host mortality, any role in protecting neurological function during meningeal infection is ill-understood. Here we investigated both the acute immunological reaction and the long-term neurobehavioural consequences of experimental pneumococcal meningitis in mice lacking both TLR2 and TLR4. The absence of these TLRs significantly impaired survival in mice inoculated intracerebroventricularly with Streptococcus pneumoniae. During the acute phase of infection, TLR2/4-deficient mice had lower cerebrospinal fluid concentrations of interleukin-1β, and higher interferon-γ, than their wild-type counterparts. After antibiotic cure, TLR2/4 double deficiency was associated with aggravation of behavioural impairment in mice, as shown by diurnal hypolocomotion throughout the adaptation phases in the Intellicage of TLR-deficient mice compared to their wild-type counterparts. While TLR2/4 double deficiency did not affect the cognitive ability of mice in a patrolling task, it aggravated the impairment of cognitive flexibility. We conclude that TLR2 and TLR4 are central to regulating the host inflammatory response in pneumococcal meningitis, which may mediate diverse compensatory mechanisms that protect the host not only against mortality but also long-term neurological complications.
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Affiliation(s)
- Lay Khoon Too
- The University of Sydney, Molecular Immunopathology Unit, Bosch Institute and School of Medical Sciences, University of Sydney, Sydney, New South Wales, 2006, Australia.
| | - Belinda Yau
- The University of Sydney, Molecular Immunopathology Unit, Bosch Institute and School of Medical Sciences, University of Sydney, Sydney, New South Wales, 2006, Australia
| | - Alan G Baxter
- Comparative Genomics Centre, James Cook University, Townsville, Queensland, 4811, Australia
| | - Iain S McGregor
- School of Psychology, University of Sydney, Sydney, New South Wales, 2006, Australia
| | - Nicholas H Hunt
- The University of Sydney, Molecular Immunopathology Unit, Bosch Institute and School of Medical Sciences, University of Sydney, Sydney, New South Wales, 2006, Australia
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7
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Lin Y, Cong H, Liu K, Jiao Y, Yuan Y, Tang G, Chen Y, Zheng Y, Xiao J, Li C, Chen Z, Cao P. Microbicidal Phagocytosis of Nucleus Pulposus Cells Against Staphylococcus aureus via the TLR2/MAPKs Signaling Pathway. Front Immunol 2019; 10:1132. [PMID: 31178866 PMCID: PMC6538773 DOI: 10.3389/fimmu.2019.01132] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 05/07/2019] [Indexed: 11/13/2022] Open
Abstract
Intervertebral disc (IVD) is an immune-privileged organ that lacks immunocytes, such as macrophages or neutrophils; therefore, it is unclear how IVD immunological defense against bacterial infection occurs. Here, we demonstrated that nucleus pulposus cells (NPCs), the vital machinery for maintaining the homeostasis of IVD, exerted microbicidal activity against Staphylococcus aureus via induction of phagolysosome formation. Moreover, we found that the Toll-like receptor 2 (TLR2)/mitogen-activated protein kinases (MAPKs) signaling pathway is critical for bacterial phagocytosis and phagolysosome formation of NPCs. These findings demonstrated for the first time that NPCs could function as non-professional phagocytes against S. aureus infection, thereby enhancing antimicrobial defense against bacterial infections in IVDs.
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Affiliation(s)
- Yazhou Lin
- Department of Orthopedics, Kunshan Hospital of Traditional Chinese Medicine, Kunshan, China.,Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases With Integrated Chinese-Western Medicine, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopedics, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Hui Cong
- Department of Oncology, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Kewei Liu
- Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases With Integrated Chinese-Western Medicine, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopedics, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Yucheng Jiao
- Department of Orthopedics, Kunshan Hospital of Traditional Chinese Medicine, Kunshan, China.,Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases With Integrated Chinese-Western Medicine, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopedics, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Ye Yuan
- Department of Orthopedics, Kunshan Hospital of Traditional Chinese Medicine, Kunshan, China.,Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases With Integrated Chinese-Western Medicine, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopedics, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Guoqing Tang
- Kunshan Hospital of Traditional Chinese Medicine, Kunshan, China
| | - Yong Chen
- Kunshan Hospital of Traditional Chinese Medicine, Kunshan, China
| | - Yuehuan Zheng
- Department of Orthopedics, Ruijin Hospital North, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Jiaqi Xiao
- Department of Medical Microbiology and Parasitology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Changwei Li
- Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases With Integrated Chinese-Western Medicine, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopedics, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Zhe Chen
- Department of Orthopedics, Kunshan Hospital of Traditional Chinese Medicine, Kunshan, China.,Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases With Integrated Chinese-Western Medicine, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopedics, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Peng Cao
- Department of Orthopedics, Kunshan Hospital of Traditional Chinese Medicine, Kunshan, China.,Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases With Integrated Chinese-Western Medicine, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopedics, Shanghai Jiaotong University School of Medicine, Shanghai, China
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8
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Pattabiraman G, Panchal R, Medvedev AE. The R753Q polymorphism in Toll-like receptor 2 (TLR2) attenuates innate immune responses to mycobacteria and impairs MyD88 adapter recruitment to TLR2. J Biol Chem 2017; 292:10685-10695. [PMID: 28442574 DOI: 10.1074/jbc.m117.784470] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 04/15/2017] [Indexed: 12/28/2022] Open
Abstract
Toll-like receptor 2 (TLR2) plays a critical role in host defenses against mycobacterial infections. The R753Q TLR2 polymorphism has been associated with increased incidence of tuberculosis and infections with non-tuberculous mycobacteria in human populations, but the mechanisms by which this polymorphism affects TLR2 signaling are unclear. In this study, we determined the impact of the R753Q TLR2 polymorphism on macrophage sensing of Mycobacterium smegmatis Upon infection with M. smegmatis, macrophages from knock-in mice harboring R753Q TLR2 expressed lower levels of TNF-α, IL-1β, IL-6, and IL-10 compared with cells from WT mice, but both R753Q TLR2- and WT-derived macrophages exhibited comparable bacterial burdens. The decreased cytokine responses in R753Q TLR2-expressing macrophages were accompanied by impaired phosphorylation of IL-1R-associated kinase 1 (IRAK-1), p38, ERK1/2 MAPKs, and p65 NF-κB, suggesting that the R753Q TLR2 polymorphism alters the functions of the myeloid differentiation primary response protein 88 (MyD88)-IRAK-dependent signaling axis. Supporting this notion, HEK293 cells stably transfected with YFP-tagged R753Q TLR2 displayed reduced recruitment of MyD88 to TLR2, decreased NF-κB activation, and impaired IL-8 expression upon exposure to M. smegmatis Collectively, our results indicate that the R753Q polymorphism alters TLR2 signaling competence, leading to impaired MyD88-TLR2 assembly, reduced phosphorylation of IRAK-1, diminished activation of MAPKs and NF-κB, and deficient induction of cytokines in macrophages infected with M. smegmatis.
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Affiliation(s)
- Goutham Pattabiraman
- From the Department of Immunology, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Rahul Panchal
- From the Department of Immunology, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Andrei E Medvedev
- From the Department of Immunology, University of Connecticut Health Center, Farmington, Connecticut 06030
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9
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Sun X, Wang J, Zhou J, Wang H, Wang X, Wu J, He Y, Yin Y, Zhang X, Xu W. Subcutaneous immunization with Streptococcus pneumoniae GAPDH confers effective protection in mice via TLR2 and TLR4. Mol Immunol 2017; 83:1-12. [DOI: 10.1016/j.molimm.2017.01.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Revised: 12/28/2016] [Accepted: 01/01/2017] [Indexed: 01/27/2023]
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10
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Jeraiby M, Sidi Yahya K, Depince-Berger AE, Lambert C. Microbicidal activity measured by flow cytometry: Optimization and standardization for detection of primary and functional deficiencies. J Immunol Methods 2017; 441:8-14. [DOI: 10.1016/j.jim.2016.09.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 08/11/2016] [Accepted: 09/26/2016] [Indexed: 01/26/2023]
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11
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Huang Y, Wang Z, Jin C, Wang L, Zhang X, Xu W, Xiang Y, Wang W, He X, Yin Y, He Y. TLR2 promotes macrophage recruitment and Streptococcus pneumoniae clearance during mouse otitis media. Pediatr Res 2016; 80:886-893. [PMID: 27463737 DOI: 10.1038/pr.2016.154] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 06/10/2016] [Indexed: 12/20/2022]
Abstract
BACKGROUND The natural course of otitis media (OM) in most children is acute and self-limiting; however, approximately 10-20% of children can experience persistent or recurrent OM. Determining the host factors that influence outcome of OM will help us design better therapies. This study focused on the role of Toll-like receptor 2 (TLR2) in a pneumococcal OM mouse model. METHODS The middle ears (MEs) of wild-type (WT) and TLR2-/- mice were inoculated with Streptococcus pneumoniae (Spn) serotype 19F via transbullar injection. ME TLR2 expression in WT mice was determined by qRT-PCR and immunofluorescence. ME pathological manifestations, inflammatory response, and pneumococcal clearance between WT and TLR2-/- mice were compared after Spn inoculation. RESULTS TLR2 expression in ME mucosa was markedly enhanced following infection with Spn in WT mice. In contrast to WT mice, TLR2-/- mice exhibited unaffected early ME inflammatory response. During late stage of ME infection, however, the absence of TLR2 can lead to reduced macrophage recruitment, impaired Spn clearance, and prolonged ME inflammation. CONCLUSION Our results demonstrate that TLR2 signaling is critical for bacterial clearance and timely resolution of inflammation in OM induced by Spn.
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Affiliation(s)
- Yifei Huang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China.,Department of Laboratory Medicine, Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, China
| | - Zimeng Wang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Chunfang Jin
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Lei Wang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Xuemei Zhang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Wenchun Xu
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Yun Xiang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Wei Wang
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Xiujing He
- Department of Laboratory Medicine, Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, China
| | - Yibing Yin
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Yujuan He
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Chongqing Medical University, Chongqing, China
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12
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Thorburn AN, Tseng HY, Donovan C, Hansbro NG, Jarnicki AG, Foster PS, Gibson PG, Hansbro PM. TLR2, TLR4 AND MyD88 Mediate Allergic Airway Disease (AAD) and Streptococcus pneumoniae-Induced Suppression of AAD. PLoS One 2016; 11:e0156402. [PMID: 27309732 PMCID: PMC4911048 DOI: 10.1371/journal.pone.0156402] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 05/15/2016] [Indexed: 12/25/2022] Open
Abstract
Background Exposure to non-pathogenic Streptococcus pneumoniae and vaccination are inversely associated with asthma. Studies in animal models demonstrate that airway administration of S. pneumoniae (live or killed), or its vaccines or components, suppresses the characteristic features of asthma in mouse models of allergic airway disease (AAD). These components could be developed into immunoregulatory therapies. S. pneumoniae components are recognized by Toll-like receptors (TLR) 2 and TLR4, and both induce inflammatory cell responses through the adaptor protein myeloid differentiation primary response gene 88 (MyD88). The involvement of TLR2, TLR4 and MyD88 in the pathogenesis of AAD and asthma is incompletely understood, and has not been studied in S. pneumoniae-mediated suppression of AAD. We investigated the role of TLR2, TLR4 and MyD88 in the development of AAD and S. pneumoniae-mediated suppression of AAD. Methods and Findings OVA-induced AAD and killed S. pneumoniae-mediated suppression of AAD were assessed in wild-type, TLR2-/-, TLR4-/-, TLR2/4-/- and MyD88-/- BALB/c mice. During OVA-induced AAD, TLR2, TLR4 and MyD88 were variously involved in promoting eosinophil accumulation in bronchoalveolar lavage fluid and blood, and T-helper type (Th)2 cytokine release from mediastinal lymph node T cells and splenocytes. However, all were required for the induction of airways hyperresponsiveness (AHR). In S. pneumoniae-mediated suppression of AAD, TLR2, TLR4 and MyD88 were variously involved in the suppression of eosinophilic and splenocyte Th2 responses but all were required for the reduction in AHR. Conclusions These results highlight important but complex roles for TLR2, TLR4 and MyD88 in promoting the development of OVA-induced AAD, but conversely in the S. pneumoniae-mediated suppression of AAD, with consistent and major contributions in both the induction and suppression of AHR. Thus, TLR signaling is likely required for both the development of asthma and the suppression of asthma by S. pneumoniae, and potentially other immunoregulatory therapies.
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Affiliation(s)
- Alison N. Thorburn
- The Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute and The University of Newcastle, Newcastle, New South Wales, Australia
| | - Hsin-Yi Tseng
- The Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute and The University of Newcastle, Newcastle, New South Wales, Australia
| | - Chantal Donovan
- The Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute and The University of Newcastle, Newcastle, New South Wales, Australia
| | - Nicole G. Hansbro
- The Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute and The University of Newcastle, Newcastle, New South Wales, Australia
| | - Andrew G. Jarnicki
- The Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute and The University of Newcastle, Newcastle, New South Wales, Australia
| | - Paul S. Foster
- The Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute and The University of Newcastle, Newcastle, New South Wales, Australia
| | - Peter G. Gibson
- The Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute and The University of Newcastle, Newcastle, New South Wales, Australia
| | - Philip M. Hansbro
- The Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute and The University of Newcastle, Newcastle, New South Wales, Australia
- * E-mail:
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Pulmonary immunostimulation with MALP-2 in influenza virus-infected mice increases survival after pneumococcal superinfection. Infect Immun 2015; 83:4617-29. [PMID: 26371127 DOI: 10.1128/iai.00948-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 09/08/2015] [Indexed: 02/06/2023] Open
Abstract
Pulmonary infection with influenza virus is frequently complicated by bacterial superinfection, with Streptococcus pneumoniae being the most prevalent causal pathogen and hence often associated with high morbidity and mortality rates. Local immunosuppression due to pulmonary influenza virus infection has been identified as a major cause of the pathogenesis of secondary bacterial lung infection. Thus, specific local stimulation of the pulmonary innate immune system in subjects with influenza virus infection might improve the host defense against secondary bacterial pathogens. In the present study, we examined the effect of pulmonary immunostimulation with Toll-like receptor 2 (TLR-2)-stimulating macrophage-activating lipopeptide 2 (MALP-2) in influenza A virus (IAV)-infected mice on the course of subsequent pneumococcal superinfection. Female C57BL/6N mice infected with IAV were treated with MALP-2 on day 5 and challenged with S. pneumoniae on day 6. Intratracheal MALP-2 application increased proinflammatory cytokine and chemokine release and enhanced the recruitment of leukocytes, mainly neutrophils, into the alveolar space of IAV-infected mice, without detectable systemic side effects. Local pulmonary instillation of MALP-2 in IAV-infected mice 24 h before transnasal pneumococcal infection considerably reduced the bacterial number in the lung tissue without inducing exaggerated inflammation. The pulmonary viral load was not altered by MALP-2. Clinically, MALP-2 treatment of IAV-infected mice increased survival rates and reduced hypothermia and body weight loss after pneumococcal superinfection compared to those of untreated coinfected mice. In conclusion, local immunostimulation with MALP-2 in influenza virus-infected mice improved pulmonary bacterial elimination and increased survival after subsequent pneumococcal superinfection.
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14
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Lemire P, Roy D, Fittipaldi N, Okura M, Takamatsu D, Bergman E, Segura M. Implication of TLR- but not of NOD2-signaling pathways in dendritic cell activation by group B Streptococcus serotypes III and V. PLoS One 2014; 9:e113940. [PMID: 25436906 PMCID: PMC4250082 DOI: 10.1371/journal.pone.0113940] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 10/31/2014] [Indexed: 12/31/2022] Open
Abstract
Group B Streptococcus (GBS) is an important agent of life-threatening invasive infection. It has been previously shown that encapsulated type III GBS is easily internalized by dendritic cells (DCs), and that this internalization had an impact on cytokine production. The receptors underlying these processes are poorly characterized. Knowledge on the mechanisms used by type V GBS to activate DCs is minimal. In this work, we investigated the role of Toll-like receptor (TLR)/MyD88 signaling pathway, the particular involvement of TLR2, and that of the intracellular sensing receptor NOD2 in the activation of DCs by types III and V GBS. The role of capsular polysaccharide (CPS, one of the most important GBS virulence factors) in bacterial-DC interactions was evaluated using non-encapsulated mutants. Despite differences in the role of CPS between types III and V GBS in bacterial internalization and intracellular survival, no major differences were observed in their capacity to modulate release of cytokines by DC. For both serotypes, CPS had a minor role in this response. Production of cytokines by DCs was shown to strongly rely on MyD88-dependent signaling pathways, suggesting that DCs recognize GBS and become activated mostly through TLR signaling. Yet, GBS-infected TLR2-/- DCs only showed a partial reduction in the production of IL-6 and CXCL1 compared to control DCs. Surprisingly, CXCL10 release by type III or type V GBS-infected DCs was MyD88-independent. No differences in DC activation were observed between NOD2-/- and control DCs. These results demonstrate the involvement of various receptors and the complexity of the cytokine production pathways activated by GBS upon DC infection.
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Affiliation(s)
- Paul Lemire
- Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, St-Hyacinthe, Quebec, Canada
| | - David Roy
- Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, St-Hyacinthe, Quebec, Canada
| | - Nahuel Fittipaldi
- Public Health Ontario, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Masatoshi Okura
- Bacterial and Parasitic Diseases Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Daisuke Takamatsu
- Bacterial and Parasitic Diseases Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
- The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Eugenia Bergman
- Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, St-Hyacinthe, Quebec, Canada
| | - Mariela Segura
- Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, St-Hyacinthe, Quebec, Canada
- * E-mail:
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15
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Mobilizable Rolling-Circle Replicating Plasmids from Gram-Positive Bacteria: A Low-Cost Conjugative Transfer. Microbiol Spectr 2014; 2:8. [PMID: 25606350 DOI: 10.1128/microbiolspec.plas-0008-2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Conjugation is a key mechanism for horizontal gene transfer in bacteria. Some plasmids are not self-transmissible but can be mobilized by functions encoded in trans provided by other auxiliary conjugative elements. Although the transfer efficiency of mobilizable plasmids is usually lower than that of conjugative elements, mobilizable plasmidsare more frequently found in nature. In this sense, replication and mobilization can be considered as important mechanisms influencing plasmid promiscuity. Here we review the present available information on two families of small mobilizable plasmids from Gram-positive bacteria that replicate via the rolling-circle mechanism. One of these families, represented by the streptococcal plasmid pMV158, is an interesting model since it contains a specific mobilization module (MOBV) that is widely distributed among mobilizable plasmids. We discuss a mechanism in which the promiscuity of the pMV158 replicon is based on the presence of two origins of lagging strand synthesis. The current strategies to assess plasmid transfer efficiency as well as to inhibit conjugative plasmid transfer are presented. Some applications of these plasmids as biotechnological tools are also reviewed.
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16
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Tavares NM, Araújo-Santos T, Afonso L, Nogueira PM, Lopes UG, Soares RP, Bozza PT, Bandeira-Melo C, Borges VM, Brodskyn C. Understanding the mechanisms controlling Leishmania amazonensis infection in vitro: the role of LTB4 derived from human neutrophils. J Infect Dis 2014; 210:656-66. [PMID: 24634497 PMCID: PMC4111911 DOI: 10.1093/infdis/jiu158] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Neutrophils are rapidly recruited to the site of Leishmania infection and play an active role in capturing and killing parasites. They are the main source of leukotriene B4 (LTB4), a potent proinflammatory lipid mediator. However, the role of LTB4 in neutrophil infection by Leishmania amazonensis is not clear. In this study, we show that L. amazonensis or its lipophosphoglycan can induce neutrophil activation, degranulation, and LTB4 production. Using pharmacological inhibitors of leukotriene synthesis, our findings reveal an LTB4-driven autocrine/paracrine regulatory effect. In particular, neutrophil-derived LTB4 controls L. amazonensis killing, degranulation, and reactive oxygen species production. In addition, L. amazonensis infection induces an early increase in Toll-like receptor 2 expression, which facilitates parasite internalization. Nuclear factor kappa B (NFkB) pathway activation represents a required upstream event for L. amazonensis–induced LTB4 synthesis. These leishmanicidal mechanisms mediated by neutrophil-derived LTB4 act through activation of its receptor, B leukotriene receptor 1 (BLT1).
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Affiliation(s)
- Natalia Machado Tavares
- Gonçalo Moniz Research Center, Oswaldo Cruz Foundation-FIOCRUZ Federal University of Bahia-UFBA, Salvador, Brazil
| | - Théo Araújo-Santos
- Gonçalo Moniz Research Center, Oswaldo Cruz Foundation-FIOCRUZ Federal University of Bahia-UFBA, Salvador, Brazil
| | - Lilian Afonso
- Gonçalo Moniz Research Center, Oswaldo Cruz Foundation-FIOCRUZ
| | | | | | - Rodrigo Pedro Soares
- René Rachou Research Center, Oswaldo Cruz Foundation-FIOCRUZ, Belo Horizonte, Brazil
| | - Patrícia Torres Bozza
- Immunopharmacology Laboratory, Oswaldo Cruz Institute-Oswaldo Cruz Foundation-FIOCRUZ, Rio de Janeiro, Brazil
| | | | - Valeria Matos Borges
- Gonçalo Moniz Research Center, Oswaldo Cruz Foundation-FIOCRUZ Federal University of Bahia-UFBA, Salvador, Brazil National Institute of Science and Technology for Immunology Investigation (iii-INCT), Salvador, Bahia, Brazil
| | - Cláudia Brodskyn
- Gonçalo Moniz Research Center, Oswaldo Cruz Foundation-FIOCRUZ Federal University of Bahia-UFBA, Salvador, Brazil National Institute of Science and Technology for Immunology Investigation (iii-INCT), Salvador, Bahia, Brazil
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17
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Fang L, Wu HM, Ding PS, Liu RY. TLR2 mediates phagocytosis and autophagy through JNK signaling pathway in Staphylococcus aureus-stimulated RAW264.7 cells. Cell Signal 2014; 26:806-14. [PMID: 24412754 DOI: 10.1016/j.cellsig.2013.12.016] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 12/29/2013] [Indexed: 01/22/2023]
Abstract
Toll-like receptor 2 (TLR2) is involved in phagocytosis and autophagy to enhance host innate immune response to bacterial infection. TLR2 has been reported to participate in the recognition of Staphylococcus aureus (S. aureus). However, the role of TLR2 in phagocytosis and autophagy in S. aureus-stimulated macrophages and the underlying mechanisms as yet remain unclear. In the present study, stimulation of mouse macrophage cell line RAW264.7 with S. aureus activated multiple signaling pathways including mitogen-activated protein kinases (MAPKs), myeloid differentiation factor 88 (MyD88), phosphatidylinositide 3-kinase (PI3K) and Rac1 and triggered autophagy process. Knockdown of TLR2 by siRNA significantly reduced phagocytosis and autophagy of macrophages upon S. aureus infection. Interestingly, TLR2 siRNA markedly attenuated S. aureus-induced phosphorylation of c-Jun N-terminal kinase (JNK) but not p38 or extracellular regulated protein kinase (ERK) in macrophages. Similarly, SP600125, a JNK inhibitor, also down-regulated phagocytosis and autophagy in S. aureus-stimulated macrophages. Furthermore, TLR2 siRNA and SP600125 simultaneous treatment showed similar phagocytosis and autophagy compared to that in TLR2 siRNA treatment alone. Collectively, our results indicate that TLR2 may be critical for phagocytosis and autophagy through JNK signaling pathway, and provide an underlying mechanistic link between innate immune receptor and induction of phagocytosis and autophagy in S. aureus-stimulated macrophages.
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Affiliation(s)
- Lei Fang
- Department of Pulmonary, Anhui Geriatric Institute, The First Affiliated Hospital of Anhui Medical University, Jixi Road 218, Hefei, Anhui 230022, PR China
| | - Hui-Mei Wu
- Department of Pulmonary, Anhui Geriatric Institute, The First Affiliated Hospital of Anhui Medical University, Jixi Road 218, Hefei, Anhui 230022, PR China
| | - Pei-Shan Ding
- Department of Pulmonary, Anhui Geriatric Institute, The First Affiliated Hospital of Anhui Medical University, Jixi Road 218, Hefei, Anhui 230022, PR China
| | - Rong-Yu Liu
- Department of Pulmonary, Anhui Geriatric Institute, The First Affiliated Hospital of Anhui Medical University, Jixi Road 218, Hefei, Anhui 230022, PR China.
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18
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Impaired innate mucosal immunity in aged mice permits prolonged Streptococcus pneumoniae colonization. Infect Immun 2013; 81:4615-25. [PMID: 24082075 DOI: 10.1128/iai.00618-13] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Streptococcus pneumoniae is a frequent asymptomatic colonizer of the nasopharyngeal niche and only occasionally progresses toward infection. The burden of pneumococcal disease is particularly high in the elderly, and the mechanisms behind this increased susceptibility are poorly understood. Here we used a mouse model of pneumococcal carriage to study immunosenescence in the upper respiratory tract (URT). Nasal mucosa-associated lymphoid tissue (NALT) showed increased expression of Toll-like receptor 1, interleukin-1β, NLRp3 inflammasome, and CCL2 in naive elderly compared to young animals. This suggests an increased proinflammatory expression profile in the NALT of aged mice at baseline. Simultaneously, we observed a more tolerogenic profile in respiratory epithelia of naive elderly compared to young adult mice with upregulation of the NF-κβ pathway inhibitor peroxisome proliferator-activated receptor gamma (PPARγ). After nasal instillation of pneumococci, pneumococcal colonization was prolonged in elderly mice compared to in young adults. The delay in clearance was associated with absent or delayed upregulation of a proinflammatory mediator(s) in the NALT, diminished influx of macrophages into the URT niche, and absent downregulation of PPARγ in respiratory epithelium, accompanied by diminished expression of cathelicidin (CRAMP) at the site of colonization. These findings suggest that unresponsiveness to pneumococcal challenge due to altered mucosal immune regulation is the key to increased susceptibility to disease in the elderly.
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The formins FMNL1 and mDia1 regulate coiling phagocytosis of Borrelia burgdorferi by primary human macrophages. Infect Immun 2013; 81:1683-95. [PMID: 23460512 DOI: 10.1128/iai.01411-12] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Spirochetes of the Borrelia burgdorferi sensu lato complex are the causative agent of Lyme borreliosis, a tick-borne infectious disease primarily affecting the skin, nervous system, and joints. During infection, macrophages and dendritic cells are the first immune cells to encounter invading borreliae. Phagocytosis and intracellular processing of Borrelia by these cells is thus decisive for the eventual outcome of infection. Phagocytic uptake of Borrelia by macrophages proceeds preferentially through coiling phagocytosis, which is characterized by actin-rich unilateral pseudopods that capture and enwrap spirochetes. Actin-dependent growth of these pseudopods necessitates de novo nucleation of actin filaments, which is regulated by actin-nucleating factors such as Arp2/3 complex. Here, we demonstrate that, in addition, also actin-regulatory proteins of the formin family are important for uptake of borreliae by primary human macrophages. Using immunofluorescence, live-cell imaging, and ratiometric analysis, we find specific enrichment of the formins FMNL1 and mDia1 at macrophage pseudopods that are in contact with borreliae. Consistently, small interfering RNA (siRNA)-mediated knockdown of FMNL1 or mDia1 leads to decreased formation of Borrelia-induced pseudopods and to decreased internalization of borreliae by macrophages. Our results suggest that macrophage coiling phagocytosis is a complex process involving several actin nucleation/regulatory factors. They also point specifically to the formins mDia1 and FMNL1 as novel regulators of spirochete uptake by human immune cells.
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Immune receptors involved in Streptococcus suis recognition by dendritic cells. PLoS One 2012; 7:e44746. [PMID: 22984550 PMCID: PMC3440357 DOI: 10.1371/journal.pone.0044746] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 08/06/2012] [Indexed: 12/22/2022] Open
Abstract
Streptococcus suis is an important swine pathogen and an emerging zoonotic agent of septicemia and meningitis. Knowledge on host immune responses towards S. suis, and strategies used by this pathogen for subversion of these responses is scarce. The objective of this study was to identify the immune receptors involved in S. suis recognition by dendritic cells (DCs). Production of cytokines and expression of co-stimulatory molecules by DCs were shown to strongly rely on MyD88-dependent signaling pathways, suggesting that DCs recognize S. suis and become activated mostly through Toll-like receptor (TLR) signaling. Supporting this fact, TLR2−/− DCs were severely impaired in the release of several cytokines and the surface expression of CD86 and MHC-II. The release of IL-12p70 and CXC10, and the expression of CD40 were found to depend on signaling by both TLR2 and TLR9. The release of IL-23 and CXCL1 were partially dependent on NOD2. Finally, despite the fact that MyD88 signaling was crucial for DC activation and maturation, MyD88-dependent pathways were not implicated in S. suis internalization by DCs. This first study on receptors involved in DC activation by S. suis suggests a major involvement of MyD88 signaling pathways, mainly (but not exclusively) through TLR2. A multimodal recognition involving a combination of different receptors seems essential for DC effective response to S. suis.
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Jeon H, Kim JH, Kim JH, Lee WH, Lee MS, Suk K. Plasminogen activator inhibitor type 1 regulates microglial motility and phagocytic activity. J Neuroinflammation 2012; 9:149. [PMID: 22747686 PMCID: PMC3418576 DOI: 10.1186/1742-2094-9-149] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2012] [Accepted: 06/29/2012] [Indexed: 01/05/2023] Open
Abstract
Background Plasminogen activator inhibitor type 1 (PAI-1) is the primary inhibitor of urokinase type plasminogen activators (uPA) and tissue type plasminogen activators (tPA), which mediate fibrinolysis. PAI-1 is also involved in the innate immunity by regulating cell migration and phagocytosis. However, little is known about the role of PAI-1 in the central nervous system. Methods In this study, we identified PAI-1 in the culture medium of mouse mixed glial cells by liquid chromatography and tandem mass spectrometry. Secretion of PAI-1 from glial cultures was detected by ELISA and western blotting analysis. Cell migration was evaluated by in vitro scratch-wound healing assay or Boyden chamber assay and an in vivo stab wound injury model. Phagocytic activity was measured by uptake of zymosan particles. Results The levels of PAI-1 mRNA and protein expression were increased by lipopolysaccharide and interferon-γ stimulation in both microglia and astrocytes. PAI-1 promoted the migration of microglial cells in culture via the low-density lipoprotein receptor-related protein (LRP) 1/Janus kinase (JAK)/signal transducer and activator of transcription (STAT)1 axis. PAI-1 also increased microglial migration in vivo when injected into mouse brain. PAI-1-mediated microglial migration was independent of protease inhibition, because an R346A mutant of PAI-1 with impaired PA inhibitory activity also promoted microglial migration. Moreover, PAI-1 was able to modulate microglial phagocytic activity. PAI-1 inhibited microglial engulfment of zymosan particles in a vitronectin- and Toll-like receptor 2/6-dependent manner. Conclusion Our results indicate that glia-derived PAI-1 may regulate microglial migration and phagocytosis in an autocrine or paracrine manner. This may have important implications in the regulation of brain microglial activities in health and disease.
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Affiliation(s)
- Hyejin Jeon
- Department of Pharmacology, Brain Science & Engineering Institute, CMRI, Kyungpook National University School of Medicine, 101 Dong-In, Daegu, Joong-gu, 700-422, South Korea
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Lammers AJJ, de Porto APNA, de Boer OJ, Florquin S, van der Poll T. The role of TLR2 in the host response to pneumococcal pneumonia in absence of the spleen. BMC Infect Dis 2012; 12:139. [PMID: 22721450 PMCID: PMC3519748 DOI: 10.1186/1471-2334-12-139] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 05/30/2012] [Indexed: 11/18/2022] Open
Abstract
Background Asplenic individuals are susceptible for overwhelming infection with Streptococcus pneumoniae, carrying a high mortality. Although Toll-like receptor (TLR)-2 is considered the major receptor for Gram-positive bacteria in innate immunity, it does not play a major role in host defense against pneumococcal pneumonia. We wanted to investigate if in absence of an intact spleen as a first line of defense, the role of TLR2 during pneumococcal pneumonia becomes more significant, thereby explaining its insignificant role during infections in immune competent hosts. Methods We intranasally infected splenectomized wildtype (WT), TLR2 knock-out (KO) and TLR2/4 double KO mice with either serotype 2 or 3 S. pneumoniae. Results There were no differences between asplenic WT and TLR2KO mice of bacterial loads in lung homogenates and blood, cytokine and chemokine levels in the lungs, and lung pathology scores. TLR2/4 double KO mice were not impaired in bacterial control as well, which indicates that besides the interaction between S. pneumoniae and TLR2, the interaction between pneumolysin and TLR4 does not stimulate antibacterial defense in the asplenic host either. Conclusions These results argue against a significant role of TLR2 in host defense during S. pneumoniae pneumonia in the asplenic state. Therefore, other components can provide sufficient backup mechanisms for TLR2 deficiency in the defense against intrapulmonary infections with S. pneumoniae of the otherwise immune competent host.
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Affiliation(s)
- Adriana J J Lammers
- Center of Infection and Immunity Amsterdam, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
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Beckett EL, Phipps S, Starkey MR, Horvat JC, Beagley KW, Foster PS, Hansbro PM. TLR2, but not TLR4, is required for effective host defence against Chlamydia respiratory tract infection in early life. PLoS One 2012; 7:e39460. [PMID: 22724018 PMCID: PMC3378543 DOI: 10.1371/journal.pone.0039460] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 05/21/2012] [Indexed: 12/14/2022] Open
Abstract
Chlamydia pneumoniae commonly causes respiratory tract infections in children, and epidemiological investigations strongly link infection to the pathogenesis of asthma. The immune system in early life is immature and may not respond appropriately to pathogens. Toll-like receptor (TLR)2 and 4 are regarded as the primary pattern recognition receptors that sense bacteria, however their contribution to innate and adaptive immunity in early life remains poorly defined. We investigated the role of TLR2 and 4 in the induction of immune responses to Chlamydia muridarum respiratory infection, in neonatal wild-type (Wt) or TLR2-deficient (−/−), 4−/− or 2/4−/− BALB/c mice. Wt mice had moderate disease and infection. TLR2−/− mice had more severe disease and more intense and prolonged infection compared to other groups. TLR4−/− mice were asymptomatic. TLR2/4−/− mice had severe early disease and persistent infection, which resolved thereafter consistent with the absence of symptoms in TLR4−/− mice. Wt mice mounted robust innate and adaptive responses with an influx of natural killer (NK) cells, neutrophils, myeloid (mDCs) and plasmacytoid (pDCs) dendritic cells, and activated CD4+ and CD8+ T-cells into the lungs. Wt mice also had effective production of interferon (IFN)γ in the lymph nodes and lung, and proliferation of lymph node T-cells. TLR2−/− mice had more intense and persistent innate (particularly neutrophil) and adaptive cell responses and IL-17 expression in the lung, however IFNγ responses and T-cell proliferation were reduced. TLR2/4−/− mice had reduced innate and adaptive responses. Most importantly, neutrophil phagocytosis was impaired in the absence of TLR2. Thus, TLR2 expression, particularly on neutrophils, is required for effective control of Chlamydia respiratory infection in early life. Loss of control of infection leads to enhanced but ineffective TLR4-mediated inflammatory responses that prolong disease symptoms. This indicates that TLR2 agonists may be beneficial in the treatment of early life Chlamydia infections and associated diseases.
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Affiliation(s)
- Emma L. Beckett
- Centre for Asthma and Respiratory Disease, The University of Newcastle, and Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Simon Phipps
- School of Biomedical Sciences and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - Malcolm R. Starkey
- Centre for Asthma and Respiratory Disease, The University of Newcastle, and Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Jay C. Horvat
- Centre for Asthma and Respiratory Disease, The University of Newcastle, and Hunter Medical Research Institute, Newcastle, New South Wales, Australia
| | - Kenneth W. Beagley
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Paul S. Foster
- Centre for Asthma and Respiratory Disease, The University of Newcastle, and Hunter Medical Research Institute, Newcastle, New South Wales, Australia
- * E-mail: (PMH); (PSF)
| | - Philip M. Hansbro
- Centre for Asthma and Respiratory Disease, The University of Newcastle, and Hunter Medical Research Institute, Newcastle, New South Wales, Australia
- * E-mail: (PMH); (PSF)
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Koppe U, Suttorp N, Opitz B. Recognition of Streptococcus pneumoniae by the innate immune system. Cell Microbiol 2012; 14:460-6. [DOI: 10.1111/j.1462-5822.2011.01746.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Ruiz-Masó JA, López-Aguilar C, Nieto C, Sanz M, Burón P, Espinosa M, del Solar G. Construction of a plasmid vector based on the pMV158 replicon for cloning and inducible gene expression in Streptococcus pneumoniae. Plasmid 2012; 67:53-9. [DOI: 10.1016/j.plasmid.2011.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 09/09/2011] [Accepted: 09/12/2011] [Indexed: 11/17/2022]
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Abstract
Pneumococcal meningitis continues to be associated with high rates of mortality and long-term neurological sequelae. The most common route of infection starts by nasopharyngeal colonization by Streptococcus pneumoniae, which must avoid mucosal entrapment and evade the host immune system after local activation. During invasive disease, pneumococcal epithelial adhesion is followed by bloodstream invasion and activation of the complement and coagulation systems. The release of inflammatory mediators facilitates pneumococcal crossing of the blood-brain barrier into the brain, where the bacteria multiply freely and trigger activation of circulating antigen-presenting cells and resident microglial cells. The resulting massive inflammation leads to further neutrophil recruitment and inflammation, resulting in the well-known features of bacterial meningitis, including cerebrospinal fluid pleocytosis, cochlear damage, cerebral edema, hydrocephalus, and cerebrovascular complications. Experimental animal models continue to further our understanding of the pathophysiology of pneumococcal meningitis and provide the platform for the development of new adjuvant treatments and antimicrobial therapy. This review discusses the most recent views on the pathophysiology of pneumococcal meningitis, as well as potential targets for (adjunctive) therapy.
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Prince LR, Whyte MK, Sabroe I, Parker LC. The role of TLRs in neutrophil activation. Curr Opin Pharmacol 2011; 11:397-403. [PMID: 21741310 DOI: 10.1016/j.coph.2011.06.007] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 06/15/2011] [Accepted: 06/15/2011] [Indexed: 12/20/2022]
Abstract
Neutrophils are key innate immune effector cells that are rapidly recruited to sites of infection and inflammation to provide early defence against invading microorganisms. This function is facilitated by the expression of Toll-like receptor (TLR) family members by neutrophils, allowing the recognition of an extensive repertoire of pathogen-associated molecular patterns (PAMPs) and thus triggering the response to invading pathogens. TLR activation leads to important cellular processes including reactive oxygen species (ROS) generation, cytokine production and increased survival, all of which can contribute to the pathogenesis of chronic inflammation when signalling becomes dysregulated. In turn, inflammation and tissue injury results in the release of endogenous TLR ligands, known as damage-associated molecular patterns (DAMPs), which are a rapidly growing class of potent inflammatory stimuli. DAMPs act in an autocrine manner, alerting the host of damage, but can also amplify inflammation leading to further tissue damage. This review highlights recent literature on neutrophil TLR function and regulation during disease, and provides an overview of the recently emerging area of neutrophil responses to DAMPs.
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Affiliation(s)
- Lynne R Prince
- Department of Infection and Immunity, University of Sheffield, Sheffield, United Kingdom
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Jann NJ, Schmaler M, Ferracin F, Landmann R. TLR2 enhances NADPH oxidase activity and killing of Staphylococcus aureus by PMN. Immunol Lett 2010; 135:17-23. [PMID: 20875459 DOI: 10.1016/j.imlet.2010.09.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 09/06/2010] [Accepted: 09/17/2010] [Indexed: 12/21/2022]
Abstract
Toll-like receptors play an essential role in the detection of invading pathogens. TLR2 is expressed in high concentrations on neutrophils and has been implicated as a critical mediator inducing host antimicrobial defenses against Gram-positive bacteria. Neutrophil responses induced via TLR2 are likely to have important clinical consequences, since Gram-positive organisms, such as Staphylococcus aureus, are an increasingly important source of severe infections. In the present study, we report that TLR2 has a central role in killing of S. aureus by murine PMN via enhancement of NADPH oxidase activity. PMN from TLR2-deficient mice showed a similar inability to kill S. aureus in vitro and under in vivo-like conditions as PMN with a non-functional NADPH oxidase. This defect in killing by TLR2-deficient PMN was not related to phagocytosis but caused by delayed and reduced NADPH oxidase-mediated production of superoxide anion in response to S. aureus and other Gram-positive bacteria. The cause of this was independent of PI3K- and p38 signaling. The TLR2-enhanced induction of superoxide was a defect in proper NADPH oxidase assembly. We hypothesize that early activation of TLR2-signaling may enhance p47(phox) phosphorylation subsequent to phagocytosis-mediated phosphorylation. Summarized, these data demonstrate a novel role of TLR2 in the killing of S. aureus by ensuring a rapid activation of the NADPH oxidase complex.
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Affiliation(s)
- Naja J Jann
- Department of Biomedicine, Division of Infection Biology, University Hospital Basel, Hebelstrasse 20, 4031 Basel, Switzerland
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Toll-like receptor 2- and MyD88-dependent phosphatidylinositol 3-kinase and Rac1 activation facilitates the phagocytosis of Listeria monocytogenes by murine macrophages. Infect Immun 2010; 78:2857-67. [PMID: 20368346 DOI: 10.1128/iai.01138-09] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toll-like receptors (TLRs) play a key role in the innate immune response by sensing bacterial ligands. The mechanisms involved in the TLR-mediated cytokine response are well established; however, the possible contribution of TLR-dependent recognition of bacteria to macrophage phagocytosis remains unclear. Listeria monocytogenes is an intracellular, parasitic, Gram-positive bacterium recognized mainly by TLR2. In this study, we investigated whether TLR2-dependent signaling is involved in the phagocytosis of L. monocytogenes by macrophages. We found no difference in the number of L. monocytogenes cells associating with wild-type (WT) and TLR2(-/-) macrophages 1 h after infection. However, the number of L. monocytogenes cells phagocytosed in TLR2(-/-) and MyD88(-/-) macrophages was significantly lower than that of WT macrophages. In addition, lipopolysaccharide (LPS) treatment restored impaired phagocytic activity of TLR2(-/-) macrophages but did not enhance the activity of MyD88(-/-) macrophages. The efficiency of phagocytosis was suppressed by inhibitors of phosphatidylinositol 3-kinase (PI3K) and the small Rho GTPases but not by cycloheximide. Moreover, functional activation of PI3K and Rac1 was impaired in TLR2(-/-) and MyD88(-/-) macrophages. In an in vivo infection model, we found significantly lower numbers of L. monocytogenes cells phagocytosed in peritoneal macrophages of TLR2(-/-) and MyD88(-/-) mice after intraperitoneal infection. Moreover, a lower number of bacteria were detected in the spleens of TLR2(-/-) mice 1 day after intravenous infection than in WT mice. These results clearly indicated that TLR2-MyD88-dependent signaling enhances the basal level of phagocytosis of L. monocytogenes by macrophages through activation of PI3K and Rac1, not by synthesis of proinflammatory cytokines or expression of phagocytic receptors.
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Schmaler M, Jann NJ, Götz F, Landmann R. Staphylococcal lipoproteins and their role in bacterial survival in mice. Int J Med Microbiol 2010; 300:155-60. [DOI: 10.1016/j.ijmm.2009.08.018] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Toll-like receptor stimulation enhances phagocytosis and intracellular killing of nonencapsulated and encapsulated Streptococcus pneumoniae by murine microglia. Infect Immun 2009; 78:865-71. [PMID: 19933834 DOI: 10.1128/iai.01110-09] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toll-like receptors (TLRs) are crucial pattern recognition receptors in innate immunity that are expressed in microglia, the resident macrophages of the brain. TLR2, -4, and -9 are important in the responses against Streptococcus pneumoniae, the most common agent causing bacterial meningitis beyond the neonatal period. Murine microglial cultures were stimulated with agonists for TLR1/2 (Pam(3)CSK(4)), TLR4 (lipopolysaccharide), and TLR9 (CpG oligodeoxynucleotide) for 24 h and then exposed to either the encapsulated D39 (serotype 2) or the nonencapsulated R6 strain of S. pneumoniae. After stimulation, the levels of interleukin-6 and CCL5 (RANTES [regulated upon activation normal T-cell expressed and secreted]) were increased, confirming microglial activation. The TLR1/2, -4, and -9 agonist-stimulated microglia ingested significantly more bacteria than unstimulated cells (P < 0.05). The presence of cytochalasin D, an inhibitor of actin polymerizaton, blocked >90% of phagocytosis. Along with an increased phagocytic activity, the intracellular bacterial killing was also increased in TLR-stimulated cells compared to unstimulated cells. Together, our data suggest that microglial stimulation by these TLRs may increase the resistance of the brain against pneumococcal infections.
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Role for Toll-like receptor 2 in the immune response to Streptococcus pneumoniae infection in mouse otitis media. Infect Immun 2009; 77:3100-8. [PMID: 19414550 DOI: 10.1128/iai.00204-09] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Streptococcus pneumoniae is the most common pathogen associated with otitis media. To examine the role of Toll-like receptor 2 (TLR2) in host defense against Streptococcus pneumoniae infection in the middle ear, wild-type (WT; C57BL/6) and TLR2-deficient (TLR2(-/-)) mice were inoculated with Streptococcus pneumoniae (1 x 10(6) CFU) through the tympanic membrane. Nineteen of 37 TLR2(-/-) mice showed bacteremia and died within 3 days after the challenge, compared to only 4 of 32 WT mice that died. Of those that survived, more severe hearing loss in the TLR2(-/-) mice than in the WT mice was indicated by an elevation in auditory-evoked brain stem response thresholds at 3 or 7 days postinoculation. The histological pathology was characterized by effusion and tissue damage in the middle ear, and in the TLR2(-/-) mice, the outcome of infection became more severe at 7 days. At both 3 and 7 days postchallenge, the TLR2(-/-) mice had higher blood bacterial titers than the WT mice (P < 0.05), and typical bacteria were identified in the effusion from both ears of both mouse groups by acridine orange staining. Moreover, by 3 days postchallenge, the mRNA accumulation levels of NF-kappaB, tumor necrosis factor alpha, interleukin 1beta, MIP1alpha, Muc5ac, and Muc5b were significantly lower in the ears of TLR2(-/-) mice than in WT mice. In summary, TLR2(-/-) mice may produce relatively low levels of proinflammatory cytokines following pneumococcal challenge, thus hindering the clearance of bacteria from the middle ear and leading to sepsis and a high mortality rate. This study provides evidence that TLR2 is important in the molecular pathogenesis and host response to otitis media.
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Innate immune-induced depletion of bone marrow neutrophils aggravates systemic bacterial infections. Proc Natl Acad Sci U S A 2009; 106:7107-12. [PMID: 19351895 DOI: 10.1073/pnas.0901162106] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Neutrophils are the most abundant leukocytes in circulation and provide a primary innate immune defense function against bacterial pathogens before development of a specific immune response. These specialized phagocytes are short lived (12-24 hours) and continuously replenished from bone marrow. We found that if the host is overwhelmed by a high inoculum of Listeria monocytogenes, neutrophils are depleted despite high granulocyte-colony stimulating factor induction. In contrast to a low-dose innocuous L. monocytogenes infection, high-dose Listeria challenge blocks neutrophil recruitment to infectious abscesses and bacterial proliferation is not controlled, resulting in lethal outcomes. Administering synthetic TLR2-ligand or heat-killed bacteria during the innocuous L. monocytogenes infection reproduced these effects, once again leading to overwhelming bacterial propagation. The same stimuli also severely aggravated Salmonella typhimurium, Staphylococcus aureus, and Streptococcus pyogenes systemic infection. These data implicate systemic innate immune stimulation as a mechanism of bone marrow neutrophil exhaustion which negatively influences the outcome of bacterial infections.
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Reppe K, Tschernig T, Lührmann A, van Laak V, Grote K, Zemlin MV, Gutbier B, Müller HC, Kursar M, Schütte H, Rosseau S, Pabst R, Suttorp N, Witzenrath M. Immunostimulation with Macrophage-Activating Lipopeptide-2 Increased Survival in Murine Pneumonia. Am J Respir Cell Mol Biol 2009; 40:474-81. [DOI: 10.1165/rcmb.2008-0071oc] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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Toll-like receptor 2 deficiency is associated with enhanced severity of group B streptococcal disease. Infect Immun 2009; 77:1524-31. [PMID: 19179417 DOI: 10.1128/iai.00965-08] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Group B streptococcus (GBS) has been recognized as an ever-growing cause of serious invasive infections in nonpregnant adults, in particular, in association with severe underlying diseases. The most common manifestations include primary bacteremia, urinary tract infections, pneumonia, meningitis, peritonitis, and osteoarticular infections. Toll-like receptor-2 (TLR2) mediates host responses to gram-positive bacteria. TLR2 function was investigated in murine GBS-induced sepsis and arthritis in wild-type (wt) and TLR2-deficient (TLR2(-/-)) mice. Mice were infected with different doses of GBS (10(7), 5 x 10(6), or 10(6) CFU per mouse). Mortality, appearance of arthritis, GBS growth in the organs, and local and systemic cytokine and chemokine production were examined. TLR2(-/-) mice showed earlier and higher mortality rates and increased incidence and severity of arthritis than wt mice at all the infecting doses employed. Histopathological analysis of the joints confirmed clinical observations. TLR2(-/-) mice exhibited a higher microbial load in blood, kidneys, and joints than wt animals. In vitro experiments performed with peritoneal polymorphonuclear cells and macrophages showed a significantly lower bactericidal ability of cells from TLR2(-/-) mice. Increased systemic and local levels of interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha, macrophage inflammatory protein-1alpha (MIP-1alpha), and MIP-2 accompanied the more severe development of sepsis and arthritis in TLR2(-/-) mice. In conclusion, the lack of TLR2 was associated with an impaired host resistance to GBS infection, likely due to a diminished bacterial clearing and a consequent enhanced inflammatory response.
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Abstract
Bacterial meningitis is still an important infectious disease with a high morbidity and mortality rate. Bacterial infection of the cerebrospinal fluid (CSF) space causes a powerful inflammatory reaction that is largely responsibly for meningitis-induced tissue damage and adverse outcome of the disease. In a landmark series of experiments in the mid-1980s, cell wall components including lipooligosaccharides and lipoteichoic acid were indicated to be the key bacterial elements that can trigger the host inflammatory response in the CSF. Ten years ago, the discovery of Toll-like receptor proteins (TLRs) that allow the detection of microbial components and initiate the host immune response opened up new horizons in research on the pathophysiology of meningitis. Cell culture approaches provided the first evidence for a crucial role of TLRs in sensing meningeal pathogens including Streptococcus pneumoniae, Neisseria meningitidis, Streptococcus agalactiae, and Listeria monocytogenes. Subsequently, studies in mice with single or combined deficiencies in TLRs demonstrated that TLR activation is a key event in meningeal inflammation and, even more interestingly, a pivotal factor for meningitis-associated tissue damage. A detailed understanding of the mechanisms of host-pathogen interactions in the CSF space may generate new opportunities for specific treatment strategies for bacterial meningitis.
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Wiersinga WJ, de Vos AF, Wieland CW, Leendertse M, Roelofs JJTH, van der Poll T. CD14 impairs host defense against gram-negative sepsis caused by Burkholderia pseudomallei in mice. J Infect Dis 2008; 198:1388-97. [PMID: 18855560 DOI: 10.1086/592220] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND CD14 is a pattern-recognition receptor that can facilitate the presentation of bacterial components to either Toll-like receptor 2 (TLR2) or TLR4. We have recently shown that during melioidosis, a severe infection caused by the gram-negative bacterium Burkholderia pseudomallei, TLR2 but not TLR4 impacts the immune response of the intact host in vivo. METHODS The function of CD14 in melioidosis was analyzed by means of in vitro and in vivo approaches, using wild-type (WT) and CD14 knockout (KO) mice. RESULTS CD14-deficient macrophages and whole blood leukocytes released less tumor necrosis factor (TNF)-alpha on stimulation with B. pseudomallei or B. pseudomallei lipopolysaccharide in vitro, compared with WT cells. Strikingly, CD14 KO mice intranasally inoculated with B. pseudomallei demonstrated reduced lethality and significantly decreased bacterial outgrowth, compared with WT mice. Administration of recombinant soluble CD14 to CD14 KO mice partially reversed their phenotype to that of WT mice. Lastly, CD14 deficiency did not alter the capacity of macrophages or neutrophils to phagocytose or kill B. pseudomallei. CONCLUSION CD14 is crucially involved in the recognition of B. pseudomallei by innate immune cells but plays a remarkable detrimental role in the host response against B. pseudomallei. Inhibition of CD14 may be a novel treatment strategy in melioidosis.
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Affiliation(s)
- W Joost Wiersinga
- Centers for Infection and Immunity Amsterdam, Academic Medical Center, Amsterdam, the Netherlands.
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Hajishengallis G, Wang M, Bagby GJ, Nelson S. Importance of TLR2 in early innate immune response to acute pulmonary infection with Porphyromonas gingivalis in mice. THE JOURNAL OF IMMUNOLOGY 2008; 181:4141-9. [PMID: 18768871 DOI: 10.4049/jimmunol.181.6.4141] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The periodontal pathogen Porphyromonas gingivalis is implicated in certain systemic diseases including atherosclerosis and aspiration pneumonia. This organism induces innate responses predominantly through TLR2, which also mediates its ability to induce experimental periodontitis and accelerate atherosclerosis. Using a validated mouse model of intratracheal challenge, we investigated the role of TLR2 in the control of P. gingivalis acute pulmonary infection. TLR2-deficient mice elicited reduced proinflammatory or antimicrobial responses (KC, MIP-1alpha, TNF-alpha, IL-6, IL-12p70, and NO) in the lung and exhibited impaired clearance of P. gingivalis compared with normal controls. However, the influx of polymorphonuclear leukocytes into the lung and the numbers of resident alveolar macrophages (AM) were comparable between the two groups. TLR2 signaling was important for in vitro killing of P. gingivalis by polymorphonuclear leukocytes or AM and, moreover, the AM bactericidal activity required NO production. Strikingly, AM were more potent than peritoneal or splenic macrophages in P. gingivalis killing, attributed to diminished AM expression of complement receptor-3 (CR3), which is exploited by P. gingivalis to promote its survival. The selective expression of CR3 by tissue macrophages and the requirement of TLR2 inside-out signaling for CR3 exploitation by P. gingivalis suggest that the role of TLR2 in host protection may be contextual. Thus, although TLR2 may mediate destructive effects, as seen in models of experimental periodontitis and atherosclerosis, we have now shown that the same receptor confers protection against P. gingivalis in acute lung infection.
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Affiliation(s)
- George Hajishengallis
- Department of Periodontics/Oral Health & Systemic Disease, University of Louisville Health Sciences Center, Louisville, KY 40292, USA.
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Sellner J, Grandgirard D, Gianinazzi C, Landmann RM, Leib SL. Effects of Toll-like receptor 2 agonist Pam(3)CysSK(4) on inflammation and brain damage in experimental pneumococcal meningitis. J Neuroimmunol 2008; 206:28-31. [PMID: 19012971 DOI: 10.1016/j.jneuroim.2008.10.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Revised: 10/14/2008] [Accepted: 10/14/2008] [Indexed: 11/19/2022]
Abstract
TLR2 signaling participates in the pathogenesis of pneumococcal meningitis. In infant rats, the TLR2 agonist Pam(3)CysSK(4) was applied intracisternally (0.5 microg in 10 microl saline) alone or after induction of pneumococcal meningitis to investigate the effect of TLR2 activation on cerebrospinal fluid (CSF) inflammation and hippocampal apoptosis. A dose effect of Pam(3)CysSK(4) on apoptosis was investigated by intracisternal application of 0.5 microg in 10 microl saline and 40 microg in 20 microl saline. Pam(3)CysSK(4) neither induced apoptosis in sham-operated mice nor aggravated apoptosis in acute infection. However, Pam(3)CysSK(4) induced pleocytosis, TNF-alpha and MMP-9 in CSF in sham-infection but not during acute meningitis. We conclude that TLR2 signaling triggered by Pam(3)CysSK(4) at a dosage capable to induce a neuroinflammatory response does not induce hippocampal apoptosis in the infant rat model of experimental pneumococcal meningitis.
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Affiliation(s)
- Johann Sellner
- Department of Neurology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str.22, D-81675 München, Germany
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Hsu A, Aronoff DM, Phipps J, Goel D, Mancuso P. Leptin improves pulmonary bacterial clearance and survival in ob/ob mice during pneumococcal pneumonia. Clin Exp Immunol 2007; 150:332-9. [PMID: 17822444 PMCID: PMC2219341 DOI: 10.1111/j.1365-2249.2007.03491.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The adipocyte-derived hormone leptin is an important regulator of appetite and energy expenditure and is now appreciated for its ability to control innate and adaptive immune responses. We have reported previously that the leptin-deficient ob/ob mouse exhibited increased susceptibility to the Gram-negative bacterium Klebsiella pneumoniae. In this report we assessed the impact of chronic leptin deficiency, using ob/ob mice, on pneumococcal pneumonia and examined whether restoring circulating leptin to physiological levels in vivo could improve host defences against this pathogen. We observed that ob/ob mice, compared with wild-type (WT) animals, exhibited enhanced lethality and reduced pulmonary bacterial clearance following Streptococcus pneumoniae challenge. These impairments in host defence in ob/ob mice were associated with elevated levels of lung tumour necrosis factor (TNF)-alpha, macrophage inflammatory peptide (MIP)-2 [correction added after online publication 28 September 2007: definition of MIP corrected], prostaglandin E(2) (PGE(2)), lung neutrophil polymorphonuclear leukocyte (PMN) counts, defective alveolar macrophage (AM) phagocytosis and PMN killing of S. pneumoniae in vitro. Exogenous leptin administration to ob/ob mice in vivo improved survival and greatly improved pulmonary bacterial clearance, reduced bacteraemia, reconstituted AM phagocytosis and PMN H(2)O(2) production and killing of S. pneumoniae in vitro. Our results demonstrate, for the first time, that leptin improves pulmonary bacterial clearance and survival in ob/ob mice during pneumococcal pneumonia. Further investigations are warranted to determine whether there is a potential therapeutic role for this adipokine in immunocompromised patients.
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Affiliation(s)
- A Hsu
- Department of Environmental Health Sciences, Ann Arbor, MI, USA
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Nalubamba KS, Gossner AG, Dalziel RG, Hopkins J. Differential expression of pattern recognition receptors in sheep tissues and leukocyte subsets. Vet Immunol Immunopathol 2007; 118:252-62. [PMID: 17604125 DOI: 10.1016/j.vetimm.2007.05.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Revised: 05/30/2007] [Accepted: 05/31/2007] [Indexed: 01/30/2023]
Abstract
The various members of the different pattern recognition receptor families are now recognized as playing a crucial role in the initial interactions between a pathogen and the host. This paper identifies all 10 members of the TLR family in sheep as well as key members of the C-type lectin and NLR families. Our data show that sheep possess the 'human' and not the 'mouse' pattern of TLRs and confirm the high degree of sequence identity between orthologous genes in the different species. In the absence of definitive antibodies, qRT-PCR assays were developed to quantify PRR transcript expression patterns in a range of normal sheep tissues as well as isolated dendritic cell (DC) and leukocyte subsets. These data show that the lymphoid organs (spleen and lymph nodes) express the widest range of PRRs and that organs such as the lung and kidney have distinctive arrays of PRRs that reflect their potential risk of pathogen exposure. In addition we show that the two DC subsets, defined by the differential expression of CD172a/CD45RA and their cytokine expression profiles, have different and characteristic PRR complements again possibly reflecting their distinctive function. These data are important for future studies on the role of PRRs in disease pathogenesis and control.
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Affiliation(s)
- King S Nalubamba
- Centre of Infectious Diseases, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, UK
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Domínguez-Punaro MC, Segura M, Plante MM, Lacouture S, Rivest S, Gottschalk M. Streptococcus suisSerotype 2, an Important Swine and Human Pathogen, Induces Strong Systemic and Cerebral Inflammatory Responses in a Mouse Model of Infection. THE JOURNAL OF IMMUNOLOGY 2007; 179:1842-54. [PMID: 17641051 DOI: 10.4049/jimmunol.179.3.1842] [Citation(s) in RCA: 161] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Streptococcus suis, an important swine and human pathogen, causes septic shock and meningitis. The pathogenesis of both systemic and CNS infections caused by S. suis is poorly understood. A hematogenous model of infection in CD1 mice was developed to study the systemic release of cytokines during the septic shock phase and the proinflammatory events in the CNS associated with this pathogen. Using a liquid array system, high levels of systemic TNF-alpha, IL-6, IL-12, IFN-gamma, CCL2, CXCL1, and CCL5 were observed 24 h after infection and might be responsible for the sudden death of 20% of animals. Infected mice that survived the early sepsis later developed clinical signs of meningitis and exhibited lesions in the meninges and in numerous regions of the brain, such as the cortex, hippocampus, thalamus, hypothalamus, and corpus callosum. Bacterial Ags were found in association with microglia residing only in the affected zones. In situ hybridization combined with immunocytochemistry showed transcriptional activation of TLR2 and TLR3 as well as CD14, NF-kappaB, IL-1beta, CCL2, and TNF-alpha, mainly in myeloid cells located in affected cerebral structures. Early transcriptional activation of TLR2, CD14, and inflammatory cytokines in the choroid plexus and cells lining the brain endothelium suggests that these structures are potential entry sites for the bacteria into the CNS. Our data indicate an important role of the inflammatory response in the pathogenesis of S. suis infection in mice. This experimental model may be useful for studying the mechanisms underlying sepsis and meningitis during bacterial infection.
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Affiliation(s)
- María C Domínguez-Punaro
- Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de médecine vétérinaire, Université de Montréal, St.-Hyacinthe, Québec, Canada
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Lee JY. Toll-like Receptors in Host Defense and Immune Disorders. Toxicol Res 2007. [DOI: 10.5487/tr.2007.23.2.097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Lee KS, Scanga CA, Bachelder EM, Chen Q, Snapper CM. TLR2 synergizes with both TLR4 and TLR9 for induction of the MyD88-dependent splenic cytokine and chemokine response to Streptococcus pneumoniae. Cell Immunol 2007; 245:103-10. [PMID: 17521621 PMCID: PMC2691573 DOI: 10.1016/j.cellimm.2007.04.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Revised: 03/24/2007] [Accepted: 04/16/2007] [Indexed: 12/17/2022]
Abstract
We previously demonstrated that induction of splenic cytokine and chemokine secretion in response to Streptococcus pneumoniae (Pn) is MyD88-, but not critically TLR2-dependent, suggesting a role for additional TLRs. In this study, we investigated the role of TLR2, TLR4, and/or TLR9 in mediating this response. We show that a single deficiency in TLR2, TLR4, or TLR9 has only modest, selective effects on cytokine and chemokine secretion, whereas substantial defects were observed in TLR2(-/-)xTLR9(-/-) and TLR2(-/-)xTLR4(-/-) mice, though not as severe as in MyD88(-/-) mice. Chloroquine, which inhibits the function of intracellular TLRs, including TLR9, completely abrogated detectable cytokine and chemokine release in spleen cells from TLR2(-/-)xTLR4(-/-) mice, similar to what is observed for mice deficient in MyD88. These data demonstrate significant synergy between TLR2 and both TLR4 and TLR9 for induction of the MyD88-dependent splenic cytokine and chemokine response to Pn.
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Affiliation(s)
- Katherine S. Lee
- Department of Pathology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814
| | - Charles A. Scanga
- Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland 20892
| | - Eric M. Bachelder
- Ghost Lab, Laboratory of Cellular and Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Quanyi Chen
- Department of Pathology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814
| | - Clifford M. Snapper
- Department of Pathology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814
- Corresponding Author, Tel: 301-295-4590, FAX: 301-295-1640, E-mail:
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Adjuvant TACE inhibitor treatment improves the outcome of TLR2-/- mice with experimental pneumococcal meningitis. BMC Infect Dis 2007; 7:25. [PMID: 17428319 PMCID: PMC1855056 DOI: 10.1186/1471-2334-7-25] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2006] [Accepted: 04/11/2007] [Indexed: 12/14/2022] Open
Abstract
Background Streptococcus (S.) pneumoniae meningitis has a high lethality despite antibiotic treatment. Inflammation is a major pathogenetic factor, which is unresponsive to antibiotics. Therefore adjunctive therapies with antiinflammatory compounds have been developed. TNF484 is a TNF-alpha converting enzyme (TACE) inhibitor and has been found efficacious in experimental meningitis. Toll-like receptor 2 (TLR2) contributes to host response in pneumococcal meningitis by enhancing bacterial clearing and downmodulating inflammation. In this study, TNF484 was applied in mice, which lacked TLR2 and exhibited a strong meningeal inflammation. Methods 103 CFU S. pneumoniae serotype 3 was inoculated subarachnoidally into C57BL/6 wild type (wt) mice or TLR2-/-, CD14-/- and CD14-/-/TLR2-/- mice. Severity of disease and survival was followed over 9 days. Response to antibiotics (80 mg/kg ceftriaxone i.p. for 5 days) and/or TACE inhibitor treatment (1 mg/kg s.c. twice daily for 4 days) was evaluated. Animals were sacrificed after 12, 24, and 48 h for analysis of bacterial load in cerebrospinal fluid (CSF) and brain and for TNF and leukocyte measurements in CSF. Results TLR2-/- mice were significantly sicker than the other mouse strains 24 h after infection. All knockout mice showed higher disease severity after 48 h and died earlier than wt mice. TNF release into CSF was significantly more elevated in TLR2-/- than in the other strains after 24 h. Brain bacterial numbers were significantly higher in all knockout than wt mice after 24 h. Modulation of outcome by antibiotic and TACE inhibitor treatment was evaluated. With antibiotic therapy all wt, CD14-/- and TLR2-/-/CD14-/- mice, but only 79% of TLR2-/- mice, were rescued. TACE inhibitor treatment alone did not rescue, but prolonged survival in wt mice, and in TLR2-/- and CD14-/- mice to the values observed in untreated wt mice. By combined antibiotic and TACE inhibitor treatment 95% of TLR2-/- mice were rescued. Conclusion During pneumococcal meningitis strong inflammation in TLR2-deficiency was associated with incomplete responsiveness to antibiotics and complete response to combined antibiotic and TACE inhibitor treatment. TACE inhibitor treatment offers a promising adjuvant therapeutic strategy in pneumococcal meningitis.
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