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de Jong MF, Rolán HG, Tsolis RM. Innate immune encounters of the (Type) 4th kind: Brucella. Cell Microbiol 2010; 12:1195-202. [PMID: 20670294 DOI: 10.1111/j.1462-5822.2010.01498.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In humans, pathogenic Brucella species cause a febrile illness known as brucellosis. A key pathogenic trait of this group of organisms is their ability to survive in immune cells and persist in tissues of the reticuloendothelial system, a process that requires the function of a Type IV secretion system. In contrast to other well-studied Gram-negative bacteria, Brucella spp. do not cause inflammation at the site of invasion, but have a latency period of 2-4 weeks before the onset of symptoms. This review discusses several mechanisms that allow Brucella spp. both to evade detection by pattern recognition receptors of the innate immune system and suppress their signalling. In contrast to these stealth features, the VirB Type IV secretion system, which mediates survival within phagocytic cells, stimulates innate immune responses in vivo. The responses stimulated by this virulence factor are sufficient to check bacterial growth, but not to elicit sterilizing immunity. The result is a stand-off between host and pathogen that results in persistent infection.
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Affiliation(s)
- Maarten F de Jong
- Department of Medical Microbiology & Immunology, University of California at Davis, Davis, CA, USA
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Toll-like receptor 2 and class B scavenger receptor type I are required for bacterial uptake by trophoblast giant cells. Mol Immunol 2010; 47:1989-96. [PMID: 20471681 DOI: 10.1016/j.molimm.2010.04.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 04/23/2010] [Accepted: 04/23/2010] [Indexed: 01/06/2023]
Abstract
Trophoblast giant (TG) cells, components cells of the mouse placenta, exhibit phagocytic activity, and participate in the placental defense system by extracellular bacterial antigen uptake via phagocytosis. However, the bacterial uptake mechanisms by TG cells remain to be entirely understood. In an attempt to understand these mechanisms, in this study, we investigated the pattern recognition receptors (PRRs) involved in phagocytosis by TG cells. PRRs such as Toll-like receptors (TLRs) and scavenger receptors play a critical role in the immune response to bacterial pathogens. Among these, we selected TLR2 and class B scavenger receptor type I (SR-BI) and then evaluated their properties in TG cells. TLR2 and SR-BI expression is higher in TG cells than in trophoblast stem (TS) cells. Although interferon-gamma treatment activated bacterial uptake in a concentration-dependent manner, it did not induce TLR2 or SR-BI expression. Depletion of TLR2 and SR-BI by siRNA reduced the bacterial uptake ability of TG cells, which was also affected by treatment with the TLR2 agonist triacylated lipopeptide. These results suggested that the phagocytic activity of TG cells is mediated by both TLR2 and SR-BI.
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53
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Martín-Martín AI, Vizcaíno N, Fernández-Lago L. Cholesterol, ganglioside GM1 and class A scavenger receptor contribute to infection by Brucella ovis and Brucella canis in murine macrophages. Microbes Infect 2010; 12:246-51. [PMID: 20083220 DOI: 10.1016/j.micinf.2009.12.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 12/15/2009] [Accepted: 12/21/2009] [Indexed: 10/20/2022]
Abstract
The establishment of infection by Brucella ovis and Brucella canis in J774.A1 macrophages was found to be dependent upon cholesterol and ganglioside GM(1), two components of lipid rafts. This process also required a class A scavenger receptor of macrophages, and was not inhibited by smooth and rough lipopolysaccharides from Brucella spp. In response to infection, both bacteria induced a weak degree of macrophage activation. These results demonstrate that B. ovis and B. canis use cell surface receptors common to smooth Brucella spp. for macrophage infection, thus limiting macrophage activation and favouring intracellular multiplication and/or the survival of both bacteria.
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Affiliation(s)
- Ana I Martín-Martín
- Departamento de Microbiología y Genética, Edificio Departamental, Universidad de Salamanca, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
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Jiang XC, Yeang C, Li Z, Chakraborty M, Liu J, Zhang H, Fan Y. Sphingomyelin biosynthesis: its impact on lipid metabolism and atherosclerosis. ACTA ACUST UNITED AC 2009. [DOI: 10.2217/clp.09.49] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Glycyrrhizin, the main active compound in liquorice, attenuates pro-inflammatory responses by interfering with membrane-dependent receptor signalling. Biochem J 2009; 421:473-82. [PMID: 19442240 DOI: 10.1042/bj20082416] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The triterpene glycoside glycyrrhizin is the main active compound in liquorice. It is used as a herbal medicine owing to its anticancer, antiviral and anti-inflammatory properties. Its mode of action, however, remains widely unknown. In the present study, we aimed to elucidate the molecular mechanism of glycyrrhizin in attenuating inflammatory responses in macrophages. Using microarray analysis, we found that glycyrrhizin caused a broad block in the induction of pro-inflammatory mediators induced by the TLR (Toll-like receptor) 9 agonist CpG-DNA in RAW 264.7 cells. Furthermore, we found that glycyrrhizin also strongly attenuated inflammatory responses induced by TLR3 and TLR4 ligands. The inhibition was accompanied by decreased activation not only of the NF-kappaB (nuclear factor kappaB) pathway but also of the parallel MAPK (mitogen-activated protein kinase) signalling cascade upon stimulation with TLR9 and TLR4 agonists. Further analysis of upstream events revealed that glycyrrhizin treatment decreased cellular attachment and/or uptake of CpG-DNA and strongly impaired TLR4 internalization. Moreover, we found that the anti-inflammatory effects were specific for membrane-dependent receptor-mediated stimuli, as glycyrrhizin was ineffective in blocking Tnfa (tumour necrosis factor alpha gene) induction upon stimulation with PMA, a receptor- and membrane-independent stimulus. These observations suggest that the broad anti-inflammatory activity of glycyrrhizin is mediated by the interaction with the lipid bilayer, thereby attenuating receptor-mediated signalling.
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McTaggart SJ, Conlon C, Colbourne JK, Blaxter ML, Little TJ. The components of the Daphnia pulex immune system as revealed by complete genome sequencing. BMC Genomics 2009; 10:175. [PMID: 19386092 PMCID: PMC2685406 DOI: 10.1186/1471-2164-10-175] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2008] [Accepted: 04/22/2009] [Indexed: 01/08/2023] Open
Abstract
Background Branchiopod crustaceans in the genus Daphnia are key model organisms for investigating interactions between genes and the environment. One major theme of research on Daphnia species has been the evolution of resistance to pathogens and parasites, but lack of knowledge of the Daphnia immune system has limited the study of immune responses. Here we provide a survey of the immune-related genome of D. pulex, derived from the newly completed genome sequence. Genes likely to be involved in innate immune responses were identified by comparison to homologues from other arthropods. For each candidate, the gene model was refined, and we conducted an analysis of sequence divergence from homologues from other taxa. Results and conclusion We found that some immune pathways, in particular the TOLL pathway, are fairly well conserved between insects and Daphnia, while other elements, in particular antimicrobial peptides, could not be recovered from the genome sequence. We also found considerable variation in gene family copy number when comparing Daphnia to insects and present phylogenetic analyses to shed light on the evolution of a range of conserved immune gene families.
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Affiliation(s)
- Seanna J McTaggart
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
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57
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Watanabe K, Tachibana M, Tanaka S, Furuoka H, Horiuchi M, Suzuki H, Watarai M. Heat shock cognate protein 70 contributes to Brucella invasion into trophoblast giant cells that cause infectious abortion. BMC Microbiol 2008; 8:212. [PMID: 19055850 PMCID: PMC2607286 DOI: 10.1186/1471-2180-8-212] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Accepted: 12/05/2008] [Indexed: 11/21/2022] Open
Abstract
Background The cell tropism of Brucella abortus, a causative agent of brucellosis and facultative intracellular pathogen, in the placenta is thought to be a key event of infectious abortion, although the molecular mechanism for this is largely unknown. There is a higher degree of bacterial colonization in the placenta than in other organs and many bacteria are detected in trophoblast giant (TG) cells in the placenta. In the present study, we investigated mechanism of B. abortus invasion into TG cells. Results We observed internalization and intracellular growth of B. abortus in cultured TG cells. A monoclonal antibody that inhibits bacterial internalization was isolated and this reacted with heat shock cognate protein 70 (Hsc70). Depletion and over expression of Hsc70 in TG cells inhibited and promoted bacterial internalization, respectively. IFN-γ receptor was expressed in TG cells and IFN-γ treatment enhanced the uptake of bacteria by TG cells. Administering the anti-Hsc70 antibody to pregnant mice served to prevent infectious abortion. Conclusion B. abortus infection of TG cells in placenta is mediated by Hsc70, and that such infection leads to infectious abortion.
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Affiliation(s)
- Kenta Watanabe
- Department of Veterinary Public Health, Faculty of Agriculture, Yamaguchi University, Yamaguchi, Japan.
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58
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Alcaraz A, Hammerer P, Tubaro A, Schröder FH, Castro R. Is there evidence of a relationship between benign prostatic hyperplasia and prostate cancer? Findings of a literature review. Eur Urol 2008; 55:864-73. [PMID: 19027219 DOI: 10.1016/j.eururo.2008.11.011] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Accepted: 11/07/2008] [Indexed: 12/22/2022]
Abstract
CONTEXT More than half the male population aged >50 yr have histologic evidence of benign prostatic hyperplasia (BPH), while prostate cancer (PCa) is among the most common male cancers according to recent registry data. Understanding the aetiologies of both conditions is crucial to reduce the resulting burden of mortality and morbidity. OBJECTIVE This review aims to examine the available data on the epidemiology, pathology, risk factors, and genetic markers involved in BPH and PCa; to discuss their clinical implications for management of both conditions; and to discuss their implications for PCa prevention. Our primary objective was to clarify the relationship between BPH and PCa by bringing together evidence from diverse areas of research. EVIDENCE ACQUISITION The primary source of data was PubMed, which was searched using Boolean strategies and by scanning lists of related articles. We also examined secondary sources from reference lists of retrieved articles and data presented at recent congresses. EVIDENCE SYNTHESIS Accumulating evidence suggests that BPH and PCa share important anatomic, pathologic, and genetic links in addition to the well-established epidemiologic association between these conditions. We also found data that suggest interactions between apparently diverse factors, such as dihydrotestosterone levels and inflammation. Recent publications support the hypothesis that both BPH and PCa are part of the metabolic syndrome, while inflammation is emerging as a major contributor to the development of both BPH and PCa. Although many of the findings are preliminary and require further research, they offer new insight into the mechanisms of disease underlying the development of BPH and PCa. CONCLUSIONS Available data suggest that epidemiologic and pathologic links exist between BPH and PCa. Evidence of links between the conditions and contributory factors may offer common preventative strategies for BPH and PCa and common therapeutic approaches to their management.
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Affiliation(s)
- Antonio Alcaraz
- Department of Urology, Hospital Clinic, IDIBAPS, University of Barcelona, Barcelona, Spain.
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59
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Motoyama K, Hashimoto Y, Hirayama F, Uekama K, Arima H. Inhibitory effects of 2,6-di-O-methyl-alpha-cyclodextrin on poly I:C signaling in macrophages. Eur J Pharm Sci 2008; 36:285-91. [PMID: 19013520 DOI: 10.1016/j.ejps.2008.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 09/21/2008] [Accepted: 10/14/2008] [Indexed: 11/26/2022]
Abstract
In the present study, we examined the effects of alpha-cyclodextrin (alpha-CyD), 2-hydroxypropyl-alpha-cyclodextrin (HP-alpha-CyD) and 2,6-di-O-methyl-alpha-cyclodextrin (DM-alpha-CyD) on the nitric oxide (NO) and interferon-beta (IFN-beta) production in murine and human macrophages stimulated with Poly I:C and CpG-DNA, toll-like receptor 3 (TLR3) and TLR9 ligands, respectively. DM-alpha-CyD significantly inhibited NO production in RAW264.7 cells and U937 cells differentiated by phorbol myristate acetate (PMA), murine and human macrophage-like cell lines, respectively, stimulated with Poly I:C without cytotoxicity, but neither alpha-CyD nor HP-alpha-CyD did. Meanwhile, the three alpha-CyDs did not inhibit NO production in RAW264.7 cells stimulated with CpG-DNA. DM-alpha-CyD inhibited inducible NO synthase (iNOS) and IFN-beta expression upon stimulation with Poly I:C. Furthermore, DM-alpha-CyD markedly decreased the cellular uptake of Poly I:C in RAW264.7 cells. Therefore, DM-alpha-CyD may be useful as a potent inhibitor for excess activation of macrophages stimulated with Poly I:C.
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Affiliation(s)
- Keiichi Motoyama
- Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan
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60
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Tamilselvam B, Daefler S. Francisella targets cholesterol-rich host cell membrane domains for entry into macrophages. THE JOURNAL OF IMMUNOLOGY 2008; 180:8262-71. [PMID: 18523292 DOI: 10.4049/jimmunol.180.12.8262] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Francisella tularensis is a pathogen optimally adapted to efficiently invade its respective host cell and to proliferate intracellularly. We investigated the role of host cell membrane microdomains in the entry of F. tularensis subspecies holarctica vaccine strain (F. tularensis live vaccine strain) into murine macrophages. F. tularensis live vaccine strain recruits cholesterol-rich lipid domains ("lipid rafts") with caveolin-1 for successful entry into macrophages. Interference with lipid rafts through the depletion of plasma membrane cholesterol, through induction of raft internalization with choleratoxin, or through removal of raft-associated GPI-anchored proteins by treatment with phosphatidylinositol phospholipase C significantly inhibited entry of Francisella and its intracellular proliferation. Lipid raft-associated components such as cholesterol and caveolin-1 were incorporated into Francisella-containing vesicles during entry and the initial phase of intracellular trafficking inside the host cell. These findings demonstrate that Francisella requires cholesterol-rich membrane domains for entry into and proliferation inside macrophages.
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61
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Genomic island 2 of Brucella melitensis is a major virulence determinant: functional analyses of genomic islands. J Bacteriol 2008; 190:6243-52. [PMID: 18641138 DOI: 10.1128/jb.00520-08] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Brucella genomic islands (GIs) share similarities in their genomic organization to pathogenicity islands from other bacteria and are likely acquired by lateral gene transfer. Here, we report the identification of a GI that is important for the pathogenicity of Brucella melitensis. The deletion of GI-1, GI-5, or GI-6 did not affect bacterial growth in macrophages as well as their virulence in interferon regulatory factor 1-deficient (IRF-1(-/-)) mice, suggesting that these islands do not contribute to Brucella virulence. However, the deletion of GI-2 resulted in the attenuation of bacterial growth in macrophages and virulence in IRF-1(-/-) mice. The GI-2 mutant also displayed a rough lipopolysaccharide (LPS) phenotype indicated by acriflavin agglutination, suggesting that in vitro and in vivo attenuation is a result of LPS alteration. Further, systematic analysis of the entire GI-2 revealed two open reading frames (ORFs), BMEI0997 and I0998, that encode hypothetical sugar transferases and contribute to LPS alteration, as the deletion of either of these ORFs resulted in a rough phenotype similar to that of the GI-2 mutant. Complementation analyses indicated that in addition to I0997 and I0998, I0999 is required to restore the smooth LPS in the GI-2 mutant as well as its full in vitro and in vivo virulence. The I0999 sequence analysis suggested that it might function as a transporter to help facilitate the transport or linking of the O antigen to the LPS. Our study also indicated that the rough LPS resulting from the GI-2 deletion may affect pathogen-associated molecular pattern recognition by Toll-like receptors.
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62
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Pei J, Turse JE, Ficht TA. Evidence of Brucella abortus OPS dictating uptake and restricting NF-kappaB activation in murine macrophages. Microbes Infect 2008; 10:582-90. [PMID: 18457975 PMCID: PMC2752336 DOI: 10.1016/j.micinf.2008.01.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Revised: 12/08/2007] [Accepted: 01/11/2008] [Indexed: 11/16/2022]
Abstract
Smooth Brucella abortus S2308 is virulent while rough derivatives are attenuated. Intracellular killing is often blamed for these differences. In the studies described, uptake kinetics and interaction of S2308 and S2308 manBA::Tn5 (CA180) rough mutants with macrophages were investigated. The results revealed that smooth B. abortus was rapidly internalized, achieving a maximum level in less than 5 min without additional uptake over the next 30 min. In contrast, continued uptake of the rough mutant was observed and only achieves a maximum level after 30 min. The results were confirmed by the differences in F-actin polymerization, lipid raft staining, early endosome colocalization and electron microscopic observations after smooth and rough Brucella infection. We also demonstrated for the first time that uptake of S2308, but not rough mutant CA180 was PI3-kinase and toll-like receptor 4 (TLR4) dependent. Differences in uptake were associated with differences in macrophage activation with regard to NF-kappaB translocation and cytokine production. These results provide evidence that the presence of B. abortus OPS dictates the interactions between Brucella and specific cell surface receptors minimizing macrophage activation and enhancing Brucella survival and/or persistence.
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Affiliation(s)
- Jianwu Pei
- Department of Veterinary Pathobiology, Texas A&M University and Texas Agricultural Experiment Station, College Station, TX 77843-4467, USA
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63
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Yoshizaki F, Nakayama H, Iwahara C, Takamori K, Ogawa H, Iwabuchi K. Role of glycosphingolipid-enriched microdomains in innate immunity: Microdomain-dependent phagocytic cell functions. Biochim Biophys Acta Gen Subj 2008; 1780:383-92. [DOI: 10.1016/j.bbagen.2007.11.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Revised: 11/10/2007] [Accepted: 11/13/2007] [Indexed: 12/16/2022]
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Hollifield M, Bou Ghanem E, de Villiers WJS, Garvy BA. Scavenger receptor A dampens induction of inflammation in response to the fungal pathogen Pneumocystis carinii. Infect Immun 2007; 75:3999-4005. [PMID: 17548480 PMCID: PMC1951997 DOI: 10.1128/iai.00393-07] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alveolar macrophages are the effector cells largely responsible for clearance of Pneumocystis carinii from the lungs. Binding of organisms to beta-glucan and mannose receptors has been shown to stimulate phagocytosis of the organisms. To further define the mechanisms used by alveolar macrophages for clearance of P. carinii, mice deficient in the expression of scavenger receptor A (SRA) were infected with P. carinii, and clearance of organisms was monitored over time. SRA-deficient (SRAKO) mice consistently cleared P. carinii faster than did wild-type control mice. Expedited clearance corresponded to elevated numbers of activated CD4(+) T cells in the alveolar spaces of SRAKO mice compared to wild-type mice. Alveolar macrophages from SRAKO mice had increased expression of CD11b on their surfaces, consistent with an activated phenotype. However, they were not more phagocytic than macrophages expressing SRA, as measured by an in vivo phagocytosis assay. SRAKO alveolar macrophages produced significantly more tumor necrosis factor alpha (TNF-alpha) than wild-type macrophages when stimulated with lipopolysaccharide in vitro but less TNF-alpha in response to P. carinii in vitro. However, upon in vivo stimulation, SRAKO mice produced significantly more TNF-alpha, interleukin 12 (IL-12), and IL-18 in response to P. carinii infection than did wild-type mice. Together, these data indicate that SRA controls inflammatory cytokines produced by alveolar macrophages in the context of P. carinii infection.
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Affiliation(s)
- Melissa Hollifield
- University of Kentucky Chandler Medical Center, 800 Rose Street, Lexington, KY 40536-0298, USA
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65
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Amiel E, Nicholson-Dykstra S, Walters JJ, Higgs H, Berwin B. Scavenger receptor-A functions in phagocytosis of E. coli by bone marrow dendritic cells. Exp Cell Res 2007; 313:1438-48. [PMID: 17362929 PMCID: PMC1905149 DOI: 10.1016/j.yexcr.2007.02.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Revised: 02/08/2007] [Accepted: 02/09/2007] [Indexed: 12/28/2022]
Abstract
Class-A scavenger receptors (SR-A) are cellular pattern recognition receptors that bind and traffic a variety of endogenous and microbial ligands. However, despite an emerging role for SR-A as a contributor to the innate immune system, little is known of the regulation or function of SR-A on dendritic cells (DCs). Here we show that SR-A expression is upregulated during murine DC differentiation and that SR-A expression levels correlate with the expression of the murine DC marker CD11c. Using bone marrow-derived DCs (BMDCs) from SR-A knockout (SR-A(-/-)) mice, we investigated the contribution of SR-A to BMDC particulate phagocytosis. Functional analyses demonstrated that SR-A is a critical phagocytic receptor for BMDC internalization of the gram-negative bacteria E. coli. SR-A(-/-) BMDCs were impaired in their ability to phagocytose bacteria, and this deficit varied with the bacteria:BMDC cell ratio. Microscopic and biochemical analyses revealed that SR-A is broadly distributed on the surface of BMDCs and is not physically associated with lipid rafts. However, cholesterol depletion demonstrated dependence of SR-A-mediated phagocytosis upon lipid rafts. These data demonstrate a functional contribution for SR-A in the BMDC phagocytic pathway.
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Affiliation(s)
- Eyal Amiel
- Department of Microbiology and Immunology, Dartmouth Medical School, Lebanon, NH 03756, USA
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66
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Pierini LM. Uptake of serum-opsonized Francisella tularensis by macrophages can be mediated by class A scavenger receptors. Cell Microbiol 2006; 8:1361-70. [PMID: 16882038 DOI: 10.1111/j.1462-5822.2006.00719.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The bacterium Francisella tularensis is highly infective, and this is one of the chief attributes that has led to its development as a bioweapon. Establishment of infection requires efficient uptake of F. tularensis by host macrophages, which provide a safe in vivo environment for F. tularensis replication. Little is known, however, about the cellular entry mechanisms employed by this organism. This report shows that efficient uptake of F. tularensis live vaccine strain (LVS) by macrophages is dependent on a heat-sensitive serum component and is mediated in part by types I and II class A scavenger receptors (SRA), demonstrating for the first time that SRA can act as a receptor for opsonized pathogens. Specifically, uptake of serum-opsonized LVS was partially blocked by general scavenger receptor inhibitors [fucoidan and poly(I)] and was largely inhibited by a specific function-blocking antibody against SRA. A role for SRA in LVS binding was confirmed by showing that ectopic expression of SRA in human embryonic kidney cells conferred the capacity for robust serum-dependent LVS binding. Finally, SRA-/- macrophages ingested significantly fewer LVS than did macrophages from wild-type mice. These findings support a novel role for SRA in innate immunity and suggest a potential therapeutic approach for modulating F. tularensis infection, namely, blocking SRA as a means of hindering F. tularensis access to its intracellular niche.
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Affiliation(s)
- Lynda M Pierini
- Department of Surgery, Weill Medical College of Cornell University, New York, NY 10021, USA.
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Fulton WB, Reeves RH, Takeya M, De Maio A. A quantitative trait loci analysis to map genes involved in lipopolysaccharide-induced inflammatory response: identification of macrophage scavenger receptor 1 as a candidate gene. THE JOURNAL OF IMMUNOLOGY 2006; 176:3767-73. [PMID: 16517746 DOI: 10.4049/jimmunol.176.6.3767] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Septic shock, which is a major complication observed after trauma and other human diseases, is likely the product of a prolonged and poorly controlled systemic inflammatory response. Symptoms of sepsis can be partially reproduced by injection of bacterial LPS in mice. Differences in mortality between C57BL/6J(high) and A/J(low) mice after LPS injection have been previously observed and correlated with differences in the inflammatory response between these two inbred strains. In the present study, we have mapped four loci responsible for differences in levels of LPS-induced IL-10, named modifier of IL-10, between the two strains. A locus within mouse chromosome 8 was confirmed using chromosome 8 consomic mice. This locus was further reduced in size by haplotype analysis and evaluated by the presence of potential candidate genes. The macrophage scavenger receptor 1 (Msr1) within this locus emerged as a candidate gene based on differences at the expression and structural levels between C57BL/6J and A/J mice. In comparison with wild-type (C57BL/6J) mice, Msr1 knockout mice displayed reduced levels of LPS-induced IL-10, but not of TNF-alpha or IL-6, confirming a specific role for this gene in the regulation of IL-10. These results suggest that Msr1 is involved in the regulation of the anti-inflammatory process, thus offering a new perspective on the molecular mechanisms involved in endotoxemia and sepsis.
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Affiliation(s)
- William B Fulton
- Division of Pediatric Surgery, Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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68
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Celli J. Surviving inside a macrophage: The many ways of Brucella. Res Microbiol 2006; 157:93-8. [PMID: 16364608 DOI: 10.1016/j.resmic.2005.10.002] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 09/24/2005] [Accepted: 10/06/2005] [Indexed: 11/24/2022]
Abstract
Bacteria of the genus Brucella are intracellular pathogens capable of survival and replication within macrophages of mammalian hosts. Recent advances have shed light on virulence factors and host functions involved at various stages of the Brucella intracellular life cycle. This review focuses on how this pathogen uses multiple strategies to circumvent macrophage defense mechanisms and generate an organelle permissive for replication.
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Affiliation(s)
- Jean Celli
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th Street, Hamilton MT 59840, USA.
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69
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Billard E, Cazevieille C, Dornand J, Gross A. High susceptibility of human dendritic cells to invasion by the intracellular pathogens Brucella suis, B. abortus, and B. melitensis. Infect Immun 2006; 73:8418-24. [PMID: 16299342 PMCID: PMC1307067 DOI: 10.1128/iai.73.12.8418-8424.2005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacteria from the Brucella genus are able to survive and proliferate within macrophages. Because they are phylogenetically closely related to macrophages, myeloid dendritic cells (DCs) constitute potential targets for Brucella bacteria. Here we report that DCs display a great susceptibility to Brucella infection. Therefore, DCs might serve as a reservoir and be important for the development of Brucella bacteria within their host.
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Affiliation(s)
- Elisabeth Billard
- INSERM U431, Université Montpellier II, cc100, Place E. Bataillon, 34095 Montpellier, France
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70
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Zaas DW, Duncan M, Rae Wright J, Abraham SN. The role of lipid rafts in the pathogenesis of bacterial infections. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:305-13. [PMID: 16289370 DOI: 10.1016/j.bbamcr.2005.10.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Revised: 10/09/2005] [Accepted: 10/11/2005] [Indexed: 12/22/2022]
Abstract
Numerous pathogens have evolved mechanisms of co-opting normal host endocytic machinery as a means of invading host cells. While numerous pathogens have been known to enter cells via traditional clathrin-coated pit endocytosis, a growing number of viral and bacterial pathogens have been recognized to invade host cells via clustered lipid rafts. This review focuses on several bacterial pathogens that have evolved several different mechanisms of co-opting clustered lipid rafts to invade host cells. Although these bacteria have diverse clinical presentations and many differences in their pathogenesis, they each depend on the integrity of clustered lipid rafts for their intracellular survival. Bacterial invasion via clustered lipid rafts has been recognized as an important virulence factor for a growing number of bacterial pathogens in their battle against host defenses.
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Affiliation(s)
- David W Zaas
- Duke University Medical Center, Box 3221, Jones Building Room 255, Research Drive, Durham, NC 27710, USA.
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71
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Arellano-Reynoso B, Lapaque N, Salcedo S, Briones G, Ciocchini AE, Ugalde R, Moreno E, Moriyón I, Gorvel JP. Cyclic beta-1,2-glucan is a Brucella virulence factor required for intracellular survival. Nat Immunol 2005; 6:618-25. [PMID: 15880113 DOI: 10.1038/ni1202] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Accepted: 03/28/2005] [Indexed: 11/08/2022]
Abstract
Pathogenic brucella bacteria have developed strategies to persist for prolonged periods of time in host cells, avoiding innate immune responses. Here we show that the cyclic beta-1,2-glucans (CbetaG) synthesized by brucella is important for circumventing host cell defenses. CbetaG acted in lipid rafts found on host cell membranes. CbetaG-deficient mutants failed to prevent phagosome-lysosome fusion and could not replicate. However, when treated with purified CbetaG or synthetic methyl-beta-cyclodextrin, the mutants were able to control vacuole maturation by avoiding lysosome fusion, and this allowed intracellular brucella to survive and reach the endoplasmic reticulum. Fusion between the endoplasmic reticulum and the brucella-containing vacuole depended on the brucella virulence type IV secretion system but not on CbetaG. Brucella CbetaG is thus a virulence factor that interacts with lipid rafts and contributes to pathogen survival.
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Affiliation(s)
- Beatriz Arellano-Reynoso
- Centre d'Immunologie, Institut National de la Santé et de la Recherche Médicale-Centre National de la Recherche Scientifique de Marseille-Luminy, Case 906, 13288 Marseille CEDEX 9, France
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72
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Gebbink MFBG, Claessen D, Bouma B, Dijkhuizen L, Wösten HAB. Amyloids--a functional coat for microorganisms. Nat Rev Microbiol 2005; 3:333-41. [PMID: 15806095 DOI: 10.1038/nrmicro1127] [Citation(s) in RCA: 217] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Amyloids are filamentous protein structures approximately 10 nm wide and 0.1-10 mum long that share a structural motif, the cross-beta structure. These fibrils are usually associated with degenerative diseases in mammals. However, recent research has shown that these proteins are also expressed on bacterial and fungal cell surfaces. Microbial amyloids are important in mediating mechanical invasion of abiotic and biotic substrates. In animal hosts, evidence indicates that these protein structures also contribute to colonization by activating host proteases that are involved in haemostasis, inflammation and remodelling of the extracellular matrix. Activation of proteases by amyloids is also implicated in modulating blood coagulation, resulting in potentially life-threatening complications.
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Affiliation(s)
- Martijn F B G Gebbink
- Department of Haematology, Thrombosis and Haemostasis Laboratory, Institute of Biomembranes, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
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73
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Lapaque N, Moriyon I, Moreno E, Gorvel JP. Brucella lipopolysaccharide acts as a virulence factor. Curr Opin Microbiol 2005; 8:60-6. [PMID: 15694858 DOI: 10.1016/j.mib.2004.12.003] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Brucella is a facultative intracellular bacterium responsible for brucellosis. Virulence factors involved in Brucella replication and Brucella's strategies to circumvent the immune response are under investigation. VirB proteins that form the type IV secretion system and that are involved in intracellular replication are considered as one of Brucella's virulence factors. In addition to this secretion system, bacterial outer membrane components have also been described as being implicated in Brucella survival in the host. For example, this bacterium possesses an unconventional non-endotoxic lipopolysaccharide that confers resistance to anti-microbial attacks and modulates the host immune response. These properties make lipopolysaccharide an important virulence factor for Brucella survival and replication in the host.
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Affiliation(s)
- Nicolas Lapaque
- Centre d'Immunologie INSERM-CNRS-Université de la Méditerranée, Parc Scientifique de Luminy, Case 906, 13288 Marseille Cedex 9, France
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74
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Watanabe K, Kim S, Nishiguchi M, Suzuki H, Watarai M. Brucella melitensis infection associated with Guillain-Barré syndrome through molecular mimicry of host structures. ACTA ACUST UNITED AC 2005; 45:121-7. [PMID: 16051063 DOI: 10.1016/j.femsim.2005.03.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Revised: 02/28/2005] [Accepted: 03/02/2005] [Indexed: 10/25/2022]
Abstract
Brucella melitensis is a facultative intracellular bacterium that can survive inside macrophages and the causative agent of brucellosis. In the present study, we found that a lipooligosaccharide of B. melitensis has a GM1 ganglioside-like structure and shows a strong antibody response in mice. The cholera toxin B subunit, which binds to GM1 ganglioside specifically, reacted with the surface of B. melitensis. Immunization with B. melitensis induced the production of anti-GM1 ganglioside antibodies in mice and serum from immunized mice showed a cross-reaction with Guillain-Barré syndrome (GBS)-associated Campylobacter jejuni, but not non-GBS-associated C. jejuni. When B. melitensis was treated with a neuraminidase, antibody responses disappeared. B. melitensis immunization induced the production of anti-GM1 ganglioside antibodies in BALB/c mice but not in C57BL/6 and ddY mice, and for BALB/c mice, immunization with B. melitensis induced much greater production of anti-GM1 ganglioside than GBS-associated C. jejuni. Flaccid limb weakness was observed in B. melitensis immunized mice. These results suggest that B. melitensis is a new etiological agent for GBS and that immunological responses between it and GBS-associated C. jejuni in the mouse model may be different.
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Affiliation(s)
- Kenta Watanabe
- Department of Applied Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
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