751
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Atianand MK, Fitzgerald KA. Molecular basis of DNA recognition in the immune system. THE JOURNAL OF IMMUNOLOGY 2013; 190:1911-8. [PMID: 23417527 DOI: 10.4049/jimmunol.1203162] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Recognition of microbial nucleic acids is one strategy by which mammalian hosts respond to infectious agents. Intracellular DNA that is introduced into cells during infection elicits potent inflammatory responses by triggering the induction of antiviral type I IFNs and the maturation and secretion of inflammatory cytokines, such as TNF-α, IL-1β, and IL-18. In addition, if nucleases, such as DNase II or DNase III (Trex1), fail to clear self-DNA, accumulated DNA gains access to intracellular compartments where it drives inflammatory responses leading to autoimmune disease. In this review, we discuss a rapidly evolving view of how cytosolic DNA-sensing machineries coordinate antimicrobial immunity and, if unchecked, lead to autoimmune disease.
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Affiliation(s)
- Maninjay K Atianand
- Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
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752
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Host-microbe interactions: the difficult yet peaceful coexistence of the microbiota and the intestinal mucosa. Br J Nutr 2013; 109 Suppl 2:S12-20. [PMID: 23360876 DOI: 10.1017/s0007114512004035] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The immune system has evolved to live in a collaborative relationship with the microbiota, while still serving its seminal function to fight off invasive pathogenic bacteria. The mechanisms that rule the interactions between the intestinal microbiota and the intestinal immune system are the focus of intense research. Here, we describe how the innate immunity is, to a great extent, in charge of the control of the microbiota in the intestine and relies on non-specific receptors called pathogen-recognition receptors. While the microbiota has a well-defined effect on the host immune homoeostasis, it has become clear that the opposite is also true, i.e., the mucosal immune system has the capacity to shape the microbial population. The mechanisms that rule the reciprocal regulation between host immunity and commensal bacteria (including specific bacteria) are currently being elucidated and will be described here. A better knowledge of how the host and bacteria interact and how the intestinal microbiota and the immune system are co-regulated will provide the basis for a better understanding of intestinal and systemic immunopathologies and for the development of new therapeutic approaches.
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753
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Amsler L, Malouli D, DeFilippis V. The inflammasome as a target of modulation by DNA viruses. Future Virol 2013; 8:357-370. [PMID: 24955107 DOI: 10.2217/fvl.13.22] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The cellular innate immune response represents the initial reaction of a host against infecting pathogens. Host cells detect incoming microbes by way of a large and expanding array of receptors that react with evolutionarily conserved molecular patterns exhibited by microbial intruders. These receptors are responsible for initiating signaling that leads to both transcriptional activation of immunologically important genes as well as protease-dependent processing of cellular proteins. The inflammasome refers to a protein complex that functions as an activation platform for the cysteine protease caspase-1, which then processes inflammatory molecules such as IL-1β and IL-18 into functional forms. Assembly of this complex is triggered following receptor-mediated detection of pathogen-associated molecules. Receptors have been identified that are essential to inflammasome activation in response to numerous molecular patterns including virus-associated molecules such as DNA. In fact, the importance of cytoplasmic DNA as an immune stimulus is exemplified by the existence of at least nine distinct cellular receptors capable of initiating innate reactivity in response to this molecule. Viruses that employ DNA as genomic material include herpesviruses, poxviruses and adenoviruses. Each has been described as capable of inducing inflammasome-mediated activity. Interestingly, however, the cellular molecules responsible for these responses appear to vary according to host species, cell type and even viral strain. Secretion of IL-1β and IL-18 are important components of antimicrobial immunity and, as a result, pathogens have evolved factors to evade or counteract this response. This includes DNA-based viruses, many of which encode multiple redundant counteractive molecules. However, it is clear that such phenotypes are only beginning to be uncovered. The purpose of this review is to describe what is known regarding the activation of inflammasome-mediated processes in response to infection with well-examined families of DNA viruses and to discuss characterized mechanisms of manipulation and neutralization of inflammasome-dependent activity. This review aims to shed light on the biologically important phenomena regarding this virus-host interaction and to highlight key areas where important information is lacking.
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Affiliation(s)
- Lisi Amsler
- Vaccine & Gene Therapy Institute, Oregon Health & Science University, 505, NW 185th Avenue, Beaverton, OR 97006, USA
| | - Daniel Malouli
- Vaccine & Gene Therapy Institute, Oregon Health & Science University, 505, NW 185th Avenue, Beaverton, OR 97006, USA
| | - Victor DeFilippis
- Vaccine & Gene Therapy Institute, Oregon Health & Science University, 505, NW 185th Avenue, Beaverton, OR 97006, USA
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754
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Abstract
The animal and bacterial kingdoms have coevolved and coadapted in response to environmental selective pressures over hundreds of millions of years. The meta'omics revolution in both sequencing and its analytic pipelines is fostering an explosion of interest in how the gut microbiome impacts physiology and propensity to disease. Gut microbiome studies are inherently interdisciplinary, drawing on approaches and technical skill sets from the biomedical sciences, ecology, and computational biology. Central to unraveling the complex biology of environment, genetics, and microbiome interaction in human health and disease is a deeper understanding of the symbiosis between animals and bacteria. Experimental model systems, including mice, fish, insects, and the Hawaiian bobtail squid, continue to provide critical insight into how host-microbiota homeostasis is constructed and maintained. Here we consider how model systems are influencing current understanding of host-microbiota interactions and explore recent human microbiome studies.
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Affiliation(s)
- Aleksandar D. Kostic
- Harvard School of Public Health, Boston, Massachusetts 02115, USA
- Harvard Medical School, Boston, Massachusetts 02115, USA
- Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
- The Broad Institute of Harvard and Massachusetts Institute of Technology, Boston, Massachusetts 02141, USA
| | - Michael R. Howitt
- Harvard School of Public Health, Boston, Massachusetts 02115, USA
- Harvard Medical School, Boston, Massachusetts 02115, USA
- Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - Wendy S. Garrett
- Harvard School of Public Health, Boston, Massachusetts 02115, USA
- Harvard Medical School, Boston, Massachusetts 02115, USA
- Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
- The Broad Institute of Harvard and Massachusetts Institute of Technology, Boston, Massachusetts 02141, USA
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755
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Aron-Wisnewsky J, Gaborit B, Dutour A, Clement K. Gut microbiota and non-alcoholic fatty liver disease: new insights. Clin Microbiol Infect 2013; 19:338-48. [DOI: 10.1111/1469-0691.12140] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Accepted: 12/21/2012] [Indexed: 12/20/2022]
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756
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Abstract
BACKGROUND Two distinct forms of intestinal epithelial cell (IEC) extrusion are described: 1 with preserved epithelial integrity and 1 that introduced breaches in the epithelial lining. In this study, we sought to determine the mechanism underlying the IEC extrusion that alters the permeability of the gut epithelium. METHODS IEC extrusions in polarized T84 monolayer were induced with nigericin. Epithelial permeability was assessed with transepithelial electrical resistance and movements of latex microspheres and green fluorescent protein-transfected Escherichia coli across the monolayer. In vivo IEC extrusion was modulated in wild-type and a colitic (interleukin-10 knock-out) mouse model with caspase-1 activation and inhibition. Luminal aspirates and mucosal biopsies from control patients and patients with inflammatory bowel disease were analyzed for caspase-1 and caspase-3&7 activation. RESULTS Caspase-1-induced IEC extrusion in T84 monolayers resulted in dose-dependent and time-dependent barrier dysfunction, reversible with caspase-1 inhibition. Moreover, the movements of microspheres and microbes across the treated epithelial monolayers were observed. Increased caspase-1-mediated IEC extrusion in interleukin-10 knock-out mice corresponded to enhanced permeation of dextran, microspheres, and translocation of E. coli compared with wild type. Caspase-1 inhibition in interleukin-10 knock-out mice resulted in a time-dependent reduction in cell extrusion and normalization of permeability to microspheres. Increased IEC extrusion in wild-type mice was induced with caspase-1 activation. In human luminal aspirates, the ratio of positively stained caspase-1 to caspase-3&7 cells were 1:1 and 2:1 in control patients and patients with inflammatory bowel disease, respectively; these observations were confirmed by cytochemical analysis of mucosal biopsies. CONCLUSIONS IEC extrusion mediated by caspase-1 activation contributes to altered intestinal permeability in vitro and in vivo.
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757
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Grumann D, Nübel U, Bröker BM. Staphylococcus aureus toxins--their functions and genetics. INFECTION GENETICS AND EVOLUTION 2013; 21:583-92. [PMID: 23541411 DOI: 10.1016/j.meegid.2013.03.013] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/07/2013] [Accepted: 03/09/2013] [Indexed: 02/07/2023]
Abstract
The outcome of encounters between Staphylococcus (S.) aureus and its human host ranges from life-threatening infection through allergic reactions to symptom-free colonization. The pan-genome of this bacterial species encodes numerous toxins, known or strongly suspected to cause specific diseases or symptoms. Three toxin families are in the focus of this review, namely (i) pore-forming toxins, (ii) exfoliative toxins and (iii) superantigens. The majority of toxin-encoding genes are located on mobile genetic elements (MGEs), resulting in a pronounced heterogeneity in the endowment with toxin genes of individual S. aureus strains. Recent population genomic analysis have provided a framework for an improved understanding of the temporal and spatial scales of the motility of MGEs and their associated toxin genes. The distribution of toxin genes among clonal lineages within the species S. aureus is not random, and phylogenetic (sub-)lineages within clonal complexes feature characteristic toxin signatures. When studying pathogenesis, this lineage association, which is caused by the clonal nature of S. aureus makes it difficult to discriminate effects of specific toxins from contributions of the genetic background and/or other associated genetic factors.
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Affiliation(s)
- Dorothee Grumann
- Institute of Immunology and Transfusion Medicine, University of Greifswald, 17487 Greifswald, Germany
| | | | - Barbara M Bröker
- Institute of Immunology and Transfusion Medicine, University of Greifswald, 17487 Greifswald, Germany.
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758
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Kawai T, Watanabe N, Yokoyama M, Arai K, Oana S, Harayama S, Yasui K, Oh-Ishi T, Onodera M. Thalidomide attenuates excessive inflammation without interrupting lipopolysaccharide-driven inflammatory cytokine production in chronic granulomatous disease. Clin Immunol 2013; 147:122-8. [PMID: 23583898 DOI: 10.1016/j.clim.2013.03.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 02/22/2013] [Accepted: 03/07/2013] [Indexed: 11/26/2022]
Abstract
Chronic granulomatous disease (CGD) is a rare inherited disorder characterized by an inability to produce reactive oxygen species, resulting in recurrent life-threatening infections. Curiously, half of the patients with CGD suffer from aseptic bowel inflammation (CGD colitis) due to dysregulated inflammation induced by TNF-α and IL-1β. Thus, developing therapies that regulate excessive inflammatory responses without interrupting antimicrobial immunity would benefit CGD colitis patients. Here, we show that thalidomide suppressed TNF-α-induced NF-κB activation and ATP-induced IL-1β secretion, but did not interrupt the production of IL-1β, IL-6, IL-8, and TNF-α in response to lipopolysaccharide in CGD monocytes. We report on a CGD colitis patient that showed decreased bowel inflammation characterized by reduced serum levels of inflammatory cytokines without evidence of progression of fungal and bacterial infections present at initiation of thalidomide therapy. Our results suggest that thalidomide could be an efficacious therapeutic option for patients with CGD colitis suffering from serious infections.
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Affiliation(s)
- Toshinao Kawai
- Department of Human Genetics, National Center for Child Health and Development, Tokyo, Japan.
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759
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Epithelial uptake of flagella initiates proinflammatory signaling. PLoS One 2013; 8:e59932. [PMID: 23527288 PMCID: PMC3603936 DOI: 10.1371/journal.pone.0059932] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 02/21/2013] [Indexed: 12/31/2022] Open
Abstract
The airway epithelium serves multiple roles in the defense of the lung. Not only does it act as a physical barrier, it acts as a distal extension of the innate immune system. We investigated the role of the airway epithelium in the interaction with flagella, an important virulence factor of the pathogen Pseudomonas aeruginosa, a cause of ventilator associated pneumonia and significant morbidity and mortality in patients with cystic fibrosis. Flagella were required for transmigration across polarized airway epithelial cells and this was a direct consequence of motility, and not a signaling effect. Purified flagella did not alter the barrier properties of the epithelium but were observed to be rapidly endocytosed inside epithelial cells. Neither flagella nor intact P. aeruginosa stimulated epithelial inflammasome signaling. Flagella-dependent signaling required dynamin-based uptake as well as TLR5 and primarily led to the induction of proinflammatory (Tnf, Il6) as well as neutrophil (Cxcl1, Cxcl2, Ccl3) and macrophage (Ccl20) chemokines. Although flagella are important in invasion across the epithelial barrier their shedding in the airway lumen results in epithelial uptake and signaling that has a major role in the initial recruitment of immune cells in the lung.
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760
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TLR2 and Nod2 mediate resistance or susceptibility to fatal intracellular Ehrlichia infection in murine models of ehrlichiosis. PLoS One 2013; 8:e58514. [PMID: 23526993 PMCID: PMC3602367 DOI: 10.1371/journal.pone.0058514] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 02/05/2013] [Indexed: 01/23/2023] Open
Abstract
Our murine models of human monocytic ehrlichiosis (HME) have shown that severe and fatal ehrlichiosis is due to generation of pathogenic T cell responses causing immunopathology and multi-organ failure. However, the early events in the liver, the main site of infection, are not well understood. In this study, we examined the liver transcriptome during the course of lethal and nonlethal infections caused by Ixodes ovatus Ehrlichia and Ehrlichia muris, respectively. On day 3 post-infection (p.i.), although most host genes were down regulated in the two groups of infected mice compared to naïve counterparts, lethal infection induced significantly higher expression of caspase 1, caspase 4, nucleotide binding oligomerization domain-containing proteins (Nod1), tumor necrosis factor-alpha, interleukin 10, and CCL7 compared to nonlethal infection. On day 7 p.i., lethal infection induced highly significant upregulation of type-1 interferon, several inflammatory cytokines and chemokines, which was associated with increased expression levels of Toll-like receptor-2 (TLR2), Nod2, MyD88, nuclear factor-kappa B (NF-kB), Caspase 4, NLRP1, NLRP12, Pycard, and IL-1β, suggesting enhanced TLR signals and inflammasomes activation. We next evaluated the participation of TLR2 and Nod2 in the host response during lethal Ehrlichia infection. Although lack of TLR2 impaired bacterial elimination and increased tissue necrosis, Nod2 deficiency attenuated pathology and enhanced bacterial clearance, which correlated with increased interferon-γ and interleukin-10 levels and a decreased frequency of pathogenic CD8(+) T cells in response to lethal infection. Thus, these data indicate that Nod2, but not TLR2, contributes to susceptibility to severe Ehrlichia-induced shock. Together, our studies provide, for the first time, insight into the diversity of host factors and novel molecular pathogenic mechanisms that may contribute to severe HME.
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761
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He Y, Franchi L, Núñez G. The protein kinase PKR is critical for LPS-induced iNOS production but dispensable for inflammasome activation in macrophages. Eur J Immunol 2013; 43:1147-52. [PMID: 23401008 DOI: 10.1002/eji.201243187] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2012] [Revised: 01/08/2013] [Accepted: 02/06/2013] [Indexed: 11/06/2022]
Abstract
Inflammasomes are multi-protein platforms that drive the activation of caspase-1 leading to the processing and secretion of biologically active IL-1β and IL-18. Different inflammasomes including NOD-like receptor (NLR) family pyrin domain-containing 3 (NLRP3), NLR caspase-recruitment domain-containing 4 (NLRC4) and absent in melanoma 2 (AIM2) are activated and assembled in response to distinct microbial or endogenous stimuli. However, the mechanisms by which upstream stimuli trigger inflammasome activation remain poorly understood. Double-stranded RNA-activated protein kinase (PKR), a protein kinase activated by viral infection, has been recently shown to be required for the activation of the inflammasomes. Using macrophages from two different mouse strains deficient in PKR, we found that PKR is important for the induction of the inducible nitric oxide synthase (iNOS). However, PKR was dispensable for caspase-1 activation, processing of pro-IL-1β/IL-18 and secretion of IL-1β induced by stimuli that trigger the activation of NLRP3, NLRC4 and AIM2. These results indicate that PKR is not required for inflammasome activation in macrophages.
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Affiliation(s)
- Yuan He
- Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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762
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Regulation of HMGB1 release by inflammasomes. Protein Cell 2013; 4:163-7. [PMID: 23483477 DOI: 10.1007/s13238-012-2118-2] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 12/12/2012] [Indexed: 01/03/2023] Open
Abstract
High mobility group box 1 (HMGB1) is an evolutionarily conserved non-histone chromatin-binding protein. During infection or injury, activated immune cells and damaged cells release HMGB1 into the extracellular space, where HMGB1 functions as a proinflammatory mediator and contributes importantly to the pathogenesis of inflammatory diseases. Recent studies reveal that inflammasomes, intracellular protein complexes, critically regulate HMGB1 release from activated immune cells in response to a variety of exogenous and endogenous danger signals. Double stranded RNA dependent kinase (PKR), an intracellular danger-sensing molecule, physically interacts with inflammasome components and is important for inflammasome activation and HMGB1 release. Together, these studies not only unravel novel mechanisms of HMGB1 release during inflammation, but also provide potential therapeutic targets to treat HMGB1-related inflammatory diseases.
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763
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Yu JW, Farias A, Hwang I, Fernandes-Alnemri T, Alnemri ES. Ribotoxic stress through p38 mitogen-activated protein kinase activates in vitro the human pyrin inflammasome. J Biol Chem 2013; 288:11378-83. [PMID: 23479736 DOI: 10.1074/jbc.m112.448795] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human pyrin with gain-of-function mutations in its B30.2/SPRY domain causes the autoinflammatory disease familial Mediterranean fever by assembling an ASC-dependent inflammasome that activates caspase-1. Wild-type human pyrin can also form an inflammasome complex with ASC after engagement by autoinflammatory PSTPIP1 mutants. How the pyrin inflammasome is activated in the absence of disease-associated mutations is not yet known. We report here that ribotoxic stress triggers the assembly of the human pyrin inflammasome, leading to ASC oligomerization and caspase-1 activation in THP-1 macrophages and in a 293T cell line stably reconstituted with components of the pyrin inflammasome. Knockdown of pyrin and selective inhibition of p38 MAPK greatly attenuated caspase-1 activation by ribotoxic stress, whereas expression of the conditional mutant ΔMEKK3:ER* allowed the activation of caspase-1 without ribotoxic stress. Disruption of microtubules by colchicine also inhibited pyrin inflammasome activation by ribotoxic stress. Together, our results indicate that ribotoxic stress activates the human pyrin inflammasome through a mechanism that requires p38 MAPK signaling and microtubule stability.
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Affiliation(s)
- Je-Wook Yu
- Department of Biochemistry and Molecular Biology and the Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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764
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Abstract
The ASC (apoptosis speck-like protein) is a key component of multimeric protein complexes that mediate inflammation and host defence. Comprising a PYD (Pyrin) domain and a CARD (caspase activation and recruitment domain), ASC functions downstream of NLRs (nucleotide-binding domain, leucine-rich repeat-containing receptors) and AIM2 (absent in melanoma 2) through the formation of supramolecular structures termed inflammasomes. However, the mechanism underlying ASC signalling and its dependency on oligomeric arrangements in inflammasome formation remain poorly understood. When expressed in cells, ASC forms discrete foci (called 'specks') typically with one speck per cell. We employed a BiFC (bimolecular fluorescence complementation) system to investigate and visualize ASC foci formation in living cells. We demonstrated that the CARD of ASC plays a central role in ASC inflammasome assembly, representing the minimal unit capable of forming foci in conjunction with the caspase 1 CARD. Mutational studies point to multiple surfaces on the ASC CARD and two predominant areas on the caspase 1 CARD mediating the formation of ASC/caspase 1 foci. The lack of foci formation for ASC CARD mutants correlates with a loss of IL-1β (interleukin 1β) processing in response to NLRP (NLR family, PYD domain-containing) 3 or AIM2 agonists in RAW264.7 cell reconstitution assays. Analogously, we show that productive formation of the Salmonella typhimurium-induced NLRC4 (NLR family CARD domain-containing protein 4) inflammasome is dependent on ASC-CARD-mediated platform formation. Thus the results of the present study depict a central role of CARDs in the formation of ASC signalling platforms and provide an important tool for investigation of CARD-dependent networks.
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765
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766
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Kasza A. IL-1 and EGF regulate expression of genes important in inflammation and cancer. Cytokine 2013; 62:22-33. [PMID: 23481102 DOI: 10.1016/j.cyto.2013.02.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/09/2013] [Accepted: 02/05/2013] [Indexed: 02/08/2023]
Abstract
This review focuses on the mechanisms by which the expression of specific genes is regulated by two proteins that are important in inflammation and cancer, namely the pro-inflammatory cytokine interleukin (IL)-1β and epidermal growth factor (EGF). In the review the receptors that recognize factors that cause inflammation are described with main focus on the receptors associated with activation of IL-1β. The function of IL-1β and pathways leading to activation of transcription factors, particularly NFκB and Elk-1 are analyzed. Then the mechanisms of EGF action, with particular emphasis of the activation of Elk-1 are illustrated. The link between aberrant signaling of EGF receptor family members and cancer development is explained. The relationship between inflammation and tumorigenesis is discussed.
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Affiliation(s)
- Aneta Kasza
- Department of Cell Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
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767
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Innate immune responses in house dust mite allergy. ISRN ALLERGY 2013; 2013:735031. [PMID: 23724247 PMCID: PMC3658386 DOI: 10.1155/2013/735031] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Accepted: 11/22/2012] [Indexed: 12/20/2022]
Abstract
Sensitizations to house dust mites (HDM) trigger strong exacerbated allergen-induced inflammation of the skin and airways mucosa from atopic subjects resulting in atopic dermatitis as well as allergic rhinitis and asthma. Initially, the Th2-biased HDM allergic response was considered to be mediated only by allergen B- and T-cell epitopes to promote allergen-specific IgE production as well as IL-4, IL-5, and IL-13 to recruit inflammatory cells. But this general molecular model of HDM allergenicity must be revisited as a growing literature suggests that stimulations of innate immune activation pathways by HDM allergens offer new answers to the following question: what makes an HDM allergen an allergen? Indeed, HDM is a carrier not only for allergenic proteins but also microbial adjuvant compounds, both of which are able to stimulate innate signaling pathways leading to allergy. This paper will describe the multiple ways used by HDM allergens together with microbial compounds to control the initiation of the allergic response through engagement of innate immunity.
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768
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Aachoui Y, Leaf IA, Hagar JA, Fontana MF, Campos CG, Zak DE, Tan MH, Cotter PA, Vance RE, Aderem A, Miao EA. Caspase-11 protects against bacteria that escape the vacuole. Science 2013; 339:975-8. [PMID: 23348507 PMCID: PMC3697099 DOI: 10.1126/science.1230751] [Citation(s) in RCA: 415] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Caspases are either apoptotic or inflammatory. Among inflammatory caspases, caspase-1 and -11 trigger pyroptosis, a form of programmed cell death. Whereas both can be detrimental in inflammatory disease, only caspase-1 has an established protective role during infection. Here, we report that caspase-11 is required for innate immunity to cytosolic, but not vacuolar, bacteria. Although Salmonella typhimurium and Legionella pneumophila normally reside in the vacuole, specific mutants (sifA and sdhA, respectively) aberrantly enter the cytosol. These mutants triggered caspase-11, which enhanced clearance of S. typhimurium sifA in vivo. This response did not require NLRP3, NLRC4, or ASC inflammasome pathways. Burkholderia species that naturally invade the cytosol also triggered caspase-11, which protected mice from lethal challenge with B. thailandensis and B. pseudomallei. Thus, caspase-11 is critical for surviving exposure to ubiquitous environmental pathogens.
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Affiliation(s)
- Youssef Aachoui
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Irina A. Leaf
- Seattle Biomedical Research Institute, Seattle, WA 98109, USA
| | - Jon A. Hagar
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Mary F. Fontana
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California at Berkeley, Berkeley, CA, 94720, USA
| | - Cristine G. Campos
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Daniel E. Zak
- Seattle Biomedical Research Institute, Seattle, WA 98109, USA
| | - Michael H. Tan
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California at Berkeley, Berkeley, CA, 94720, USA
| | - Peggy A. Cotter
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Russell E. Vance
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California at Berkeley, Berkeley, CA, 94720, USA
| | - Alan Aderem
- Seattle Biomedical Research Institute, Seattle, WA 98109, USA
| | - Edward A. Miao
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
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769
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Monie TP. NLR activation takes a direct route. Trends Biochem Sci 2013; 38:131-9. [PMID: 23394939 DOI: 10.1016/j.tibs.2013.01.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 12/21/2012] [Accepted: 01/04/2013] [Indexed: 01/01/2023]
Abstract
For the first time there is now clear biochemical and biophysical evidence indicating that members of the nucleotide-binding domain and leucine-rich repeat containing (NLR) family can be activated as a result of direct interaction between the receptor and ligand. NLRX1 leucine-rich repeats bind to RNA; murine NAIP (NLR family, apoptosis inhibitory protein) 5 binds flagellin directly; and NOD (nucleotide-binding oligomerization domain containing) 1 and NOD2 may interact directly with fragments of peptidoglycan. It remains to be seen if NLRP3 has a specific ligand, but progress has been made in addressing its mechanism of activation, with cellular imbalances and mitochondrial dysfunction being important. This review updates our understanding of NLR activation in light of these recent advances and their impact on the NLR research.
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Affiliation(s)
- Tom P Monie
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK.
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770
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Ulett GC, Totsika M, Schaale K, Carey AJ, Sweet MJ, Schembri MA. Uropathogenic Escherichia coli virulence and innate immune responses during urinary tract infection. Curr Opin Microbiol 2013; 16:100-7. [DOI: 10.1016/j.mib.2013.01.005] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 12/19/2012] [Accepted: 01/08/2013] [Indexed: 12/17/2022]
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771
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Higa N, Toma C, Koizumi Y, Nakasone N, Nohara T, Masumoto J, Kodama T, Iida T, Suzuki T. Vibrio parahaemolyticus effector proteins suppress inflammasome activation by interfering with host autophagy signaling. PLoS Pathog 2013; 9:e1003142. [PMID: 23357873 PMCID: PMC3554609 DOI: 10.1371/journal.ppat.1003142] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 12/05/2012] [Indexed: 12/12/2022] Open
Abstract
Bacterial pathogens utilize pore-forming toxins or sophisticated secretion systems to establish infection in hosts. Recognition of these toxins or secretion system by nucleotide-binding oligomerization domain leucine-rich repeat proteins (NLRs) triggers the assembly of inflammasomes, the multiprotein complexes necessary for caspase-1 activation and the maturation of inflammatory cytokines such as IL-1β or IL-18. Here we demonstrate that both the NLRP3 and NLRC4 inflammasomes are activated by thermostable direct hemolysins (TDHs) and type III secretion system 1 (T3SS1) in response to V. parahaemolyticus infection. Furthermore, we identify T3SS1 secreted effector proteins, VopQ and VopS, which induce autophagy and the inactivation of Cdc42, respectively, to prevent mainly NLRC4 inflammasome activation. VopQ and VopS interfere with the assembly of specks in infected macrophages. These data suggest that bacterial effectors interfere with inflammasome activation and contribute to bacterial evasion from the host inflammatory responses. V. parahaemolyticus is Gram-negative pathogen that causes a food poisoning in human. To date, a number of bacterial factors that play a role in V. parahaemolyticus virulence have been characterized, yet little is known about the host factors contributing to the disease process and susceptibility to these pathogens. IL-1β, in addition to TNF-α, is thought to be involved in inflammatory responses and disease development during infection with the pathogen, but the mechanisms of IL-1β production remain poorly defined. In this work we found that both the NLRP3 and NLRC4 inflammasomes are activated by thermostable direct hemolysins (TDHs) and type III secretion system 1 (T3SS1) in response to V. parahaemolyticus infection. The activated inflammasomes then triggers the activation of caspase-1, a cysteine protease that is essential for IL-1β processing and release. Furthermore, we identified T3SS1 secreted effector proteins, VopQ and VopS, which prevent mainly NLRC4 inflammasome activation. VopQ and VopS induce autophagy and the inactivation of Rho GTPases, including Cdc42, respectively, and these cellular events interfere with the assembly of specks, the platform of inflammasome activation. Collectively, T3SS1 effector-based suppression of inflammasome activation may provide important insights into bacterial strategies for evading inflammasome-mediated host immune responses.
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Affiliation(s)
- Naomi Higa
- Department of Molecular Bacteriology and Immunology, Graduate School of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Claudia Toma
- Department of Molecular Bacteriology and Immunology, Graduate School of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Yukiko Koizumi
- Department of Molecular Bacteriology and Immunology, Graduate School of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Noboru Nakasone
- Department of Molecular Bacteriology and Immunology, Graduate School of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Toshitsugu Nohara
- Department of Molecular Bacteriology and Immunology, Graduate School of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Junya Masumoto
- Department of Pathogenomics, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
| | - Toshio Kodama
- International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Tetsuya Iida
- International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Toshihiko Suzuki
- Department of Molecular Bacteriology and Immunology, Graduate School of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
- * E-mail:
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772
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Krishnaswamy JK, Chu T, Eisenbarth SC. Beyond pattern recognition: NOD-like receptors in dendritic cells. Trends Immunol 2013; 34:224-33. [PMID: 23352728 DOI: 10.1016/j.it.2012.12.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 12/12/2012] [Accepted: 12/26/2012] [Indexed: 12/11/2022]
Abstract
Innate instruction of adaptive immunity was proposed more than 20 years ago as a mechanism by which long-lived lymphocyte responses are targeted to appropriate antigens. At the time Charles Janeway proposed this theory, most of the innate immune receptors were unknown, and the pivotal role of the dendritic cell in instructing T cell priming was debated. There is now overwhelming evidence that the innate and adaptive branches of the immune system must interact to generate immunity. Much of this work has focused on families of innate immune receptors called pattern recognition receptors (PRRs) on dendritic cells, which translate these inflammatory triggers into productive T cell responses. Nevertheless, we are only beginning to understand how these defence molecules shape the generation of immunity. We review the varied roles of one class of PRRs, the NOD-like receptors (NLRs), in immune responses and propose a new model in which adaptive immunity requires coordinated PRR activation within the dendritic cell.
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Affiliation(s)
- Jayendra Kumar Krishnaswamy
- Department of Laboratory Medicine, Section of Allergy and Immunology, Yale University School of Medicine, New Haven, CT 06520, USA
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773
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Abstract
Dendritic cells (DCs) are specialized sentinels responsible for coordinating adaptive immunity. This function is dependent upon coupled sensitivity to environmental signs of inflammation and infection to cellular maturation-the programmed alteration of DC phenotype and function to enhance immune cell activation. Although DCs are thus well equipped to respond to pathogens, maturation triggers are not unique to infection. Given that immune cells are exquisitely sensitive to the biological functions of DCs, we now appreciate that multiple layers of suppression are required to restrict the environmental sensitivity, cellular maturation, and even life span of DCs to prevent aberrant immune activation during the steady state. At the same time, steady-state DCs are not quiescent but rather perform key functions that support homeostasis of numerous cell types. Here we review these functions and molecular mechanisms of suppression that control steady-state DC maturation. Corruption of these steady-state operatives has diverse immunological consequences and pinpoints DCs as potent drivers of autoimmune and inflammatory disease.
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Affiliation(s)
- Gianna Elena Hammer
- Department of Medicine, University of California, San Francisco, California 94143
| | - Averil Ma
- Department of Medicine, University of California, San Francisco, California 94143
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774
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Pang IK, Ichinohe T, Iwasaki A. IL-1R signaling in dendritic cells replaces pattern-recognition receptors in promoting CD8⁺ T cell responses to influenza A virus. Nat Immunol 2013; 14:246-53. [PMID: 23314004 PMCID: PMC3577947 DOI: 10.1038/ni.2514] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 12/07/2012] [Indexed: 12/25/2022]
Abstract
Immune responses to vaccines require direct recognition of pathogen-associated molecular patterns (PAMPs) through pattern recognition receptors (PRRs) on dendritic cells (DCs). Unlike vaccines, infection by a live pathogen often impairs DC function and inflicts additional damage to the host. Here, we found that following live influenza A infection, signaling through the interleukin-1 receptor (IL-1R), but not the PRRs, TLR7 and RIG-I, is required for productive CD8+ T cell priming. DCs activated by IL-1 in trans were both required and sufficient for the generation of virus-specific CD8+ T cell immunity. Our data reveal a critical role of a bystander cytokine in CD8+ T cell priming during a live viral infection.
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Affiliation(s)
- Iris K Pang
- Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut, USA
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775
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Vladimer GI, Marty-Roix R, Ghosh S, Weng D, Lien E. Inflammasomes and host defenses against bacterial infections. Curr Opin Microbiol 2013; 16:23-31. [PMID: 23318142 DOI: 10.1016/j.mib.2012.11.008] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 11/14/2012] [Accepted: 11/26/2012] [Indexed: 02/08/2023]
Abstract
The inflammasome has emerged as an important molecular protein complex which initiates proteolytic processing of pro-IL-1β and pro-IL-18 into mature inflammatory cytokines. In addition, inflammasomes initiate pyroptotic cell death that may be independent of those cytokines. Inflammasomes are central to elicit innate immune responses against many pathogens, and are key components in the induction of host defenses following bacterial infection. Here, we review recent discoveries related to NLRP1, NLRP3, NLRC4, NLRP6, NLRP7, NLRP12 and AIM2-mediated recognition of bacteria. Mechanisms for inflammasome activation and regulation are now suggested to involve kinases such as PKR and PKCδ, ligand binding proteins such as the NAIPs, and caspase-11 and caspase-8 in addition to caspase-1. Future research will determine how specific inflammasome components pair up in optimal responses to specific bacteria.
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Affiliation(s)
- Gregory I Vladimer
- Division of Infectious Diseases and Immunology, Department of Medicine, UMass Medical School, Worcester, MA 01605, USA
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776
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Tateya S, Kim F, Tamori Y. Recent advances in obesity-induced inflammation and insulin resistance. Front Endocrinol (Lausanne) 2013; 4:93. [PMID: 23964268 PMCID: PMC3737462 DOI: 10.3389/fendo.2013.00093] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/11/2013] [Indexed: 12/12/2022] Open
Abstract
It has been demonstrated in rodents and humans that chronic inflammation characterized by macrophage infiltration occurs mainly in adipose tissue or liver during obesity, in which activation of immune cells is closely associated with insulin sensitivity. Macrophages can be classified as classically activated (M1) macrophages that support microbicidal activity or alternatively activated (M2) macrophages that support allergic and antiparasitic responses. In the context of insulin action, M2 macrophages sustain insulin sensitivity by secreting IL-4 and IL-10, while M1 macrophages induce insulin resistance through the secretion of proinflammatory cytokines, such as TNFα. Polarization of M1/M2 is controlled by various dynamic functions of other immune cells. It has been demonstrated that, in a lean state, TH2 cells, Treg cells, natural killer T cells, or eosinophils contribute to the M2 activation of macrophages by secreting IL-4 or IL-10. In contrast, obesity causes alteration of the constituent immune cells, in which TH1 cells, B cells, neutrophils, or mast cells induce M1 activation of macrophages by the elevated secretion of TNFα and IFNγ. Increased secretion of TNFα and free fatty acids from hypertrophied adipocytes also contributes to the M1 activation of macrophages. Since obesity-induced insulin resistance is established by macrophage infiltration and the activation of immune cells inside tissues, identification of the factors that regulate accumulation and the intracellular signaling cascades that define polarization of M1/M2 would be indispensable. Regulation of these factors would lead to the pharmacological inhibition of obesity-induced insulin resistance. In this review, we introduce molecular mechanisms relevant to the pathophysiology and review the most recent studies of clinical applications targeting chronic inflammation.
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Affiliation(s)
- Sanshiro Tateya
- Department of Internal Medicine, Division of Diabetes, Metabolism, and Endocrinology, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - Francis Kim
- Department of Medicine, University of Washington, Seattle, WA, USA
- Diabetes and Obesity Center of Excellence, University of Washington, Seattle, WA, USA
| | - Yoshikazu Tamori
- Department of Internal Medicine, Division of Diabetes, Metabolism, and Endocrinology, Graduate School of Medicine, Kobe University, Kobe, Japan
- Department of Internal Medicine, Diabetes Center, Chibune Hospital, Osaka, Japan
- *Correspondence: Yoshikazu Tamori, Department of Internal Medicine, Division of Diabetes, Metabolism, and Endocrinology, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan e-mail:
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777
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Elinav E, Henao-Mejia J, Flavell RA. Integrative inflammasome activity in the regulation of intestinal mucosal immune responses. Mucosal Immunol 2013; 6:4-13. [PMID: 23212196 DOI: 10.1038/mi.2012.115] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The mammalian intestinal tract harbors a vast and diverse ecosystem of microbes that are separated from the sterile host milieu by a single layer of epithelial cells. While this bio-geographical configuration is critical for host biological processes, it imposes a risk for microbial penetration and life-threatening systemic invasion. Inflammasomes are cytosolic multi-protein platforms that sense both microbial and damage-associated molecular patterns and initiate a potent innate immune anti-microbial response. In this review, we will highlight the role of inflammasomes in the orchestration and regulation of the intestinal immune response, focusing on the roles of inflammasomes in maintenance of intestinal homeostasis, enteric infection, auto-inflammation, and tumorigenesis. We highlight the centrality of inflammasome signaling in the complex cross-talk between host mucosal immune arms and the environment, in particular the microflora, with emphasis on the spatial and temporal integration of inflammasome activation with signals from other innate signaling platforms.
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Affiliation(s)
- E Elinav
- Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut, USA
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778
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Zhang Y, Li Y. Regulation of innate receptor pathways by microRNAs. SCIENCE CHINA. LIFE SCIENCES 2013; 56:13-8. [PMID: 23269554 DOI: 10.1007/s11427-012-4428-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 11/26/2012] [Indexed: 01/03/2023]
Abstract
The innate immune response provides the initial defense against infection. This is accomplished by families of pattern recognition receptors (PRRs) that bind to conserved molecules in bacteria, fungi and viruses. PRRs are finely regulated by elaborate mechanisms to ensure a beneficial outcome in response to foreign invaders. MicroRNAs (miRNAs) are a class of small non-coding regulatory RNAs that are emerging as important regulators in immune responses at the post-transcriptional level, through the inhibition of translation, or by inducing mRNA degradation. It has been shown that miRNAs have unique expression profiles in cells of the innate immune systems and play pivotal roles in regulating the signal pathways of innate receptors, including Toll-like receptors, RIG-I-like receptors and Nod-like receptors. We have summarized the recent literature providing new insights into the regulation of innate receptor pathways by miRNAs.
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Affiliation(s)
- Yue Zhang
- Department of General Surgery, East Hospital, Tongji University School of Medicine, Shanghai, 200120, China.
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779
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Kanasaki K, Taduri G, Koya D. Diabetic nephropathy: the role of inflammation in fibroblast activation and kidney fibrosis. Front Endocrinol (Lausanne) 2013; 4:7. [PMID: 23390421 PMCID: PMC3565176 DOI: 10.3389/fendo.2013.00007] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 01/16/2013] [Indexed: 12/13/2022] Open
Abstract
Kidney disease associated with diabetes mellitus is a major health problem worldwide. Although established therapeutic strategies, such as appropriate blood glucose control, blood pressure control with renin-angiotensin system blockade, and lipid lowering with statins, are used to treat diabetes, the contribution of diabetic end-stage kidney disease to the total number of cases requiring hemodialysis has increased tremendously in the past two decades. Once renal function starts declining, it can result in a higher frequency of renal and extra-renal events, including cardiovascular events. Therefore, slowing renal function decline is one of the main areas of focus in diabetic nephropathy research, and novel strategies are urgently needed to prevent diabetic kidney disease progression. Regardless of the type of injury and etiology, kidney fibrosis is the commonly the final outcome of progressive kidney diseases, and it results in significant destruction of normal kidney structure and accompanying functional deterioration. Kidney fibrosis is caused by prolonged injury and dysregulation of the normal wound-healing process in association with excess extracellular matrix deposition. Kidney fibroblasts play an important role in the fibrotic process, but the origin of the fibroblasts remains elusive. In addition to the activation of residential fibroblasts, other important sources of fibroblasts have been proposed, such as pericytes, fibrocytes, and fibroblasts originating from epithelial-to-mesenchymal and endothelial-to-mesenchymal transition. Inflammatory cells and cytokines play a vital role In the process of fibroblast activation. In this review, we will analyze the contribution of inflammation to the process of tissue fibrosis, the type of fibroblast activation and the therapeutic strategies targeting the inflammatory pathways in an effort to slow the progression of diabetic kidney disease.
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Affiliation(s)
- Keizo Kanasaki
- Division of Diabetology and Endocrinology, Kanazawa Medical UniversityKahoku, Japan
- *Correspondence: Keizo Kanasaki and Daisuke Koya, Division of Diabetology and Endocrinology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Kahoku Ishikawa 920-0293, Japan. e-mail: ; ; Gangadhar Taduri, Department of Nephrology, Nizam’s Institute of Medical Sciences, Punjagutta, Hyderabad 500082, Andhra Pradesh, India. e-mail:
| | - Gangadhar Taduri
- Department of Nephrology, Nizam’s Institute of Medical SciencesHyderabad, India
- *Correspondence: Keizo Kanasaki and Daisuke Koya, Division of Diabetology and Endocrinology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Kahoku Ishikawa 920-0293, Japan. e-mail: ; ; Gangadhar Taduri, Department of Nephrology, Nizam’s Institute of Medical Sciences, Punjagutta, Hyderabad 500082, Andhra Pradesh, India. e-mail:
| | - Daisuke Koya
- Division of Diabetology and Endocrinology, Kanazawa Medical UniversityKahoku, Japan
- *Correspondence: Keizo Kanasaki and Daisuke Koya, Division of Diabetology and Endocrinology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Kahoku Ishikawa 920-0293, Japan. e-mail: ; ; Gangadhar Taduri, Department of Nephrology, Nizam’s Institute of Medical Sciences, Punjagutta, Hyderabad 500082, Andhra Pradesh, India. e-mail:
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780
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Elinav E, Thaiss CA, Flavell RA. Analysis of microbiota alterations in inflammasome-deficient mice. Methods Mol Biol 2013; 1040:185-94. [PMID: 23852605 DOI: 10.1007/978-1-62703-523-1_14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Inflammasomes have emerged as central regulators of intestinal infection, immunity, and inflammation. Inflammasome activity mediates intestinal epithelial integrity, antimicrobial responses, and initiates inflammation through generation of the cytokines interleukin (IL-)1 and IL-18. Recent studies have identified an additional layer of inflammasome function in the intestine, namely, the control of intestinal microflora composition. Inflammasome-deficient mice show an aberrant microbial community which is dominantly transmissible to healthy mice. This dysbiosis in inflammasome-deficient mice has a profound impact on their physiology and pathophysiology, both locally in the intestine and systemically. Therefore, it is essential to consider the influence of the composition of microbial communities on experiments performed with inflammasome-deficient and other innate molecule-deficient mice, and to conduct experiments to control for potential dominant effects of the microflora on host responses. In this chapter, we provide experimental procedures to monitor inflammasome-mediated modifications of the intestinal microflora composition in mice and to test the resultant functional consequences of these changes in microbial communities and their transmission to cohoused mice.
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Affiliation(s)
- Eran Elinav
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
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781
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Hwang I, Park S, Hong S, Kim EH, Yu JW. Salmonella Promotes ASC Oligomerization-dependent Caspase-1 Activation. Immune Netw 2012; 12:284-90. [PMID: 23396959 PMCID: PMC3566424 DOI: 10.4110/in.2012.12.6.284] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 11/19/2012] [Accepted: 11/22/2012] [Indexed: 12/27/2022] Open
Abstract
Innate immune cells sense and respond to the cytoplasmic infection of bacterial pathogens through NLRP3, NLRC4 or AIM2 inflammasome depending on the unique molecular pattern of invading pathogens. The infection of flagellin- or type III secretion system (T3SS)-containing Gram-negative bacteria such as Salmonella enterica serovar Typhimurium (S. typhimurium) or Pseudomonas aeruginosa (P. aeruginosa) triggers NLRC4-dependent caspase-1 activation leading to the secretion of proinflammatory cytokines such as interleukin-1-beta (IL-1β) and IL-18. Previous studies have shown that apoptosis-associated speck-like protein containing a CARD (ASC) is also required for Salmonella-induced caspase-1 activation, but it is still unclear how ASC contributes to the activation of NLRC4 inflammasome in response to S. typhimurium infection. In this study, we demonstrate that S. typhimurium triggers the formation of ASC oligomer in a potassium depletion-independent manner as determined by in vitro crosslinking and in situ fluorescence imaging. Remarkably, inhibition of potassium efflux failed to block Salmonella-promoted caspase-1 activation and macrophage cell death. These results collectively suggest that ASC is substantially oligomerized to facilitate the activation of caspase-1 in response to S. typhimurium infection. Contrary to NLRP3 inflammasome, intracellular potassium depletion is not critical for NLRC4 inflammasome signaling by S. typhimurium.
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Affiliation(s)
- Inhwa Hwang
- Department of Microbiology and Immunology, Yonsei University College of Medicine, Seoul 120-752, Korea. ; Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, Korea
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782
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Abstract
The interaction of Candida albicans with macrophages induces the production of interleukin 1β (IL-1β) through inflammasome activation in a process that is required for host survival. C. albicans hypha formation has been linked to IL-1β production, but the question of whether hyphae are sufficient to trigger IL-1β production has not been examined directly. To address this question, a C. albicans library of 165 transcription factor deletion mutants was screened for strains with altered IL-1β production by lipopolysaccharide (LPS)-primed J774 cells, a murine macrophage-like cell line. Eight mutants with decreased and two mutants with increased IL-1β secretion were identified. In addition, 12 mutants with previously identified morphology deficits were found to induce IL-1β secretion to levels similar to those of the wild type. Examination of the morphology of both low and normal IL-1β-inducing mutants in macrophages revealed that two mutants (upc2Δ/upc2Δ and ahr1Δ/Δ mutants) were indistinguishable from the wild type with respect to morphology yet induced low levels of IL-1β; conversely, the ndt80Δ/Δ mutant was deficient for hypha formation but induced levels of IL-1β similar to those of the wild type. Transcription factor mutants deficient for IL-1β secretion also caused markedly lower levels of macrophage lysis. Similarly, the ability of a mutant to cause macrophage lysis was independent of its ability to form hyphae. Taken together, our observations indicate that the physical formation of hyphae is not sufficient to trigger IL-1β secretion or macrophage lysis and suggest that other mechanisms, such as pyroptosis, a caspase-1-dependent response to intracellular pathogens, may play a role in the interaction of macrophages with C. albicans. The ability of Candida albicans to transition from yeast to filamentous cells plays an important and complex role in pathogenesis. Recent results from a number of investigators indicate that the host responds to yeast and hyphal C. albicans differently. For example, a C. albicans mutant unable to form hyphae also fails to induce interleukin 1β (IL-1β) secretion from macrophages. We have identified C. albicans transcription factor mutants that have decreased IL-1β secretion but retain the ability to form hyphae in response to macrophages. In addition, these mutants cause significantly less macrophage lysis. These observations indicate that the physical presence of the hyphal structure in the macrophage is not sufficient to trigger IL-1β secretion nor does it cause physical lysis of the cell. Our data indicate that characteristics of hyphae separate from its physical morphology are responsible for triggering the release of IL-1β release and causing macrophage lysis. Since these observations are inconsistent with some current models, alternative mechanisms for the interaction of C. albicans with macrophages must be considered.
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783
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Cruz-Córdova A, Rocha-Ramírez LM, Ochoa SA, González-Pedrajo B, Gónzalez-Pedrajo B, Espinosa N, Eslava C, Hernández-Chiñas U, Mendoza-Hernández G, Rodríguez-Leviz A, Valencia-Mayoral P, Sadowinski-Pine S, Hernández-Castro R, Estrada-García I, Muñoz-Hernández O, Rosas I, Xicohtencatl-Cortes J. Flagella from five Cronobacter species induce pro-inflammatory cytokines in macrophage derivatives from human monocytes. PLoS One 2012; 7:e52091. [PMID: 23284883 PMCID: PMC3528739 DOI: 10.1371/journal.pone.0052091] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 11/12/2012] [Indexed: 01/26/2023] Open
Abstract
Cronobacter spp. are opportunistic pathogens linked to lie-threatening infections in neonates and contaminated powdered infant formula that has been epidemiologically associated with these cases. Clinical symptoms of Cronobacter include necrotizing enterocolitis, bacteremia, and meningitis. Flagella from C. sakazakii are involved in biofilm formation and its adhesion to epithelial cells. We investigated the role of flagella from C. sakazakii ST1 and ST4, C. malonaticus, C. muytjensii, C. turicensis and C. dublinensis during the activation of cytokines (IL-8, TNF-α, and IL-10) in macrophage derivatives from human monocytes, which has not been extensively studied. The production and identity of flagella from the five Cronobacter species were visualized and recognized with anti-flagella antibodies by immunogold labeling through transmission electron microscopy. Purified flagella were dissociated into monomers in 12% SDS-PAGE Coomassie blue-stained gels showing a band of ∼28 kDa and, in addition, mass spectrometry revealed the presence of several peptides that correspond to flagellin. Flagella (100 ng) induced the release of IL-8 (3314–6025 pg/ml), TNF-α (39–359 pg/ml), and IL-10 (2–96 pg/ml), in macrophage isolates from human monocytes and similar results were obtained when flagella were dissociated into monomers. Inhibition assays using three dilutions of anti-flagella antibodies (1∶10, 1∶100, and 1∶200) suppressed the secretion of IL-8, TNF-α, and IL-10 between 95–100% using 100 ng of protein. A transfection assay using 293-hTLR5 cells showed IL-8 release of 197 pg/ml and suppression in the secretion of IL-8 when anti-hTLR5-IgA antibodies were used at different concentrations. These observations suggest that flagella and flagellin are involved in an inflammatory response dependent on TLR5 recognition, which could contribute to the pathogenesis of the bacteria.
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Affiliation(s)
- Ariadnna Cruz-Córdova
- Laboratorio de Bacteriología Intestinal, Departamento de Infectología, Hospital Infantil de México Federico Gómez, México D.F., México
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784
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Ng TM, Kortmann J, Monack DM. Policing the cytosol--bacterial-sensing inflammasome receptors and pathways. Curr Opin Immunol 2012; 25:34-9. [PMID: 23261344 DOI: 10.1016/j.coi.2012.11.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 11/22/2012] [Accepted: 11/28/2012] [Indexed: 02/06/2023]
Abstract
Pattern recognition receptors recognize signals originating from pathogens and comprise a large part of the arsenal in innate immune responses. The NOD-like receptors (NLRs) are one particular class of these receptors that survey the cytoplasm for signs of pathogen invasion. Upon detection, they trigger the formation of a macromolecular complex called the inflammasome that is required for elimination of the pathogen, as well as amplifying a pro-inflammatory response. Although the core machinery has been defined, recent data emphasize the complexity of how NLR inflammasomes function. Here, we highlight new discoveries that reveal how precisely fine-tuned NLR inflammasome functions are, and how that may be modulated by antagonistic effects of concomitant inflammasome activation as well as novel regulatory factors.
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Affiliation(s)
- Tessie M Ng
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford University, 299 Campus Drive, Mail Code 5124, Stanford, CA 94305, United States
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785
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Kang TB, Yang SH, Toth B, Kovalenko A, Wallach D. Caspase-8 blocks kinase RIPK3-mediated activation of the NLRP3 inflammasome. Immunity 2012; 38:27-40. [PMID: 23260196 DOI: 10.1016/j.immuni.2012.09.015] [Citation(s) in RCA: 419] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 09/20/2012] [Indexed: 11/16/2022]
Abstract
Caspase-8 deficiency in certain cells prompts chronic inflammation. One mechanism suggested to account for this inflammation is enhanced signaling for necrotic cell death, mediated by the protein kinases RIPK1 and RIPK3 that caspase-8 can cleave. We describe an activity of caspase-8 in dendritic cells that controls the initiation of inflammation in another way. Caspase-8 deficiency in these cells facilitated lipopolysaccharide-induced assembly and function of the NLRP3 inflammasome. This effect depended on the functions of RIPK1 and RIPK3, as well as of MLKL and PGAM5, two signaling proteins recently shown to contribute to RIPK3-mediated induction of necrosis. However, although enhancement of inflammasome assembly in the caspase-8-deficient cells shares proximal signaling events with the induction of necrosis, it occurred independently of cell death. These findings provide new insight into potentially pathological inflammatory processes to which RIPK1- and RIPK3-mediated signaling contributes.
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Affiliation(s)
- Tae-Bong Kang
- Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
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786
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He Y, Franchi L, Núñez G. TLR agonists stimulate Nlrp3-dependent IL-1β production independently of the purinergic P2X7 receptor in dendritic cells and in vivo. THE JOURNAL OF IMMUNOLOGY 2012; 190:334-9. [PMID: 23225887 DOI: 10.4049/jimmunol.1202737] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
On the basis of studies in mouse macrophages, activation of the nucleotide-binding oligomerization domain-like receptor (NLR) pyrin domain-containing 3 (Nlrp3) inflammasome is thought to require two signals. The first signal is provided by TLR stimulation and triggers the synthesis of the IL-1β precursor and Nlrp3. The second signal can be mediated by stimulation of the purinergic receptor P2X ligand-gated ion channel 7 (P2X7) by millimolar concentrations of ATP. However, these high concentrations of ATP are not found normally in the in vivo extracellular milieu, raising concern about the physiological relevance of the ATP-P2X7 pathway of inflammasome activation. In this article, we show that unlike macrophages, murine bone marrow-derived and splenic dendritic cells (DCs) can secrete substantial amounts of mature IL-1β upon stimulation with TLR ligands in the absence of ATP stimulation. The differential ability of DCs to release IL-1β and activate caspase-1 was associated with increased expression of Nlrp3 under steady-state conditions and of pro-IL-1β and Nlrp3 after stimulation with TLR agonists. IL-1β secretion from stimulated DCs was largely dependent on the Nlrp3 inflammasome, but independent of P2X7 and unaffected by incubation with apyrase. More importantly, i.p. administration of LPS induced IL-1β production in serum, which was abrogated in Nlrp3-null mice but was unaffected in P2X7-deficient mice. These results demonstrate differential regulation of the Nlrp3 inflammasome in macrophages and DCs. Furthermore, they challenge the idea that the ATP-P2X7 axis is critical for TLR-induced IL-1β production via the Nlrp3 inflammasome in vivo.
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Affiliation(s)
- Yuan He
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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787
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Abstract
Nutrient absorption is the basic function that drives mammalian intestinal biology. To facilitate nutrient uptake, the host's epithelial barrier is composed of a single layer of cells. This constraint is problematic, as a design of this type can be easily disrupted. The solution during the course of evolution was to add numerous host defense mechanisms that can help prevent local and systemic infection. These mechanisms include specialized epithelial cells that produce a physiochemical barrier overlying the cellular barrier, robust and organized adaptive and innate immune cells, and the ability to mount an inflammatory response that is commensurate with a specific threat level. The autophagy pathway is a critical cellular process that strongly influences all these functions. Therefore, a fundamental understanding of the components of this pathway and their influence on inflammation, immunity, and barrier function will facilitate our understanding of homeostasis in the gastrointestinal tract.
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Affiliation(s)
- Khushbu K Patel
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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788
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Rajshankar D, Downey GP, McCulloch CA. IL-1β enhances cell adhesion to degraded fibronectin. FASEB J 2012; 26:4429-44. [PMID: 22829527 PMCID: PMC3475244 DOI: 10.1096/fj.12-207381] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 07/10/2012] [Indexed: 01/01/2023]
Abstract
IL-1β is a prominent proinflammatory cytokine that mediates degradation of extracellular matrix proteins through increased expression of matrix metalloproteinases, which involves a signaling pathway in adherent cells that is restricted by focal adhesions. Currently, the mechanism by which IL-1β affects cell adhesion to matrix proteins is not defined, and it is not known whether degraded matrix proteins affect IL-1β signaling. We examined adhesion-related IL-1β signaling in fibroblasts attaching to native or MMP3-degraded fibronectin. IL-1β increased cell attachment, resistance to shear force and the numbers of focal adhesions containing activated β(1) integrins. IL-1β-enhanced attachment required FAK, kindlins 1/2, and talin. MMP3-degraded fibronectin-inhibited IL-1β-enhanced cell adhesion and promoted spontaneous ERK activation that was independent of IL-1β treatment. We conclude that IL-1β enhances the adhesion of anchorage-dependent cells to MMP3-degraded fibronectin, which, in turn, is associated with deregulated cellular responses to IL-1β. These data point to a novel role of IL-1β as a proadhesive signaling molecule in inflammation that employs kindlins and talin to regulate adhesion.
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Affiliation(s)
| | - Gregory P. Downey
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, National Jewish Health, Denver, Colorado, USA; and
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
- Integrated Department of Immunology, University of Colorado, Aurora, Colorado, USA
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789
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Bueno SM, Riquelme S, Riedel CA, Kalergis AM. Mechanisms used by virulent Salmonella to impair dendritic cell function and evade adaptive immunity. Immunology 2012; 137:28-36. [PMID: 22703384 DOI: 10.1111/j.1365-2567.2012.03614.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Innate and adaptive immunity are inter-related by dendritic cells (DCs), which directly recognize bacteria through the binding of pathogen-associated molecular patterns (PAMPs) to specialized receptors on their surface. After capturing and degrading bacteria, DCs present their antigens as small peptides bound to MHC molecules and prime naive bacteria-specific T cells. In response to PAMP recognition DCs undergo maturation, which is a phenotypic change that increases their immunogenicity and promotes the activation of naive T cells. As a result, a specific immune response that targets bacteria-derived antigens is initiated. Therefore, the characterization of DC-bacteria interactions is important to understand the mechanisms used by virulent bacteria to avoid adaptive immunity. Furthermore, any impairment of DC function might contribute to bacterial survival and dissemination inside the host. An example of a bacterial pathogen capable of interfering with DC function is Salmonella enterica serovar Typhimurium (S. Typhimurium). Virulent strains of this bacterium are able to differentially modulate the entrance to DCs, avoid lysosomal degradation and prevent antigen presentation on MHC molecules. These features of virulent S. Typhimurium are controlled by virulence proteins, which are encoded by pathogenicity islands. Modulation of DC functions by these gene products is supported by several studies showing that pathogenesis might depend on this attribute of virulent S. Typhimurium. Here we discuss some of the recent data reported by the literature showing that several virulence proteins from Salmonella are required to modulate DC function and the activation of host adaptive immunity.
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Affiliation(s)
- Susan M Bueno
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genetica Molecular y Microbiologia, Pontificia Universidad Católica de Chile, Santiago, Chile.
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790
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Gomes MTR, Campos PC, de Almeida LA, Oliveira FS, Costa MMS, Marim FM, Pereira GSM, Oliveira SC. The role of innate immune signals in immunity to Brucella abortus. Front Cell Infect Microbiol 2012; 2:130. [PMID: 23112959 PMCID: PMC3480720 DOI: 10.3389/fcimb.2012.00130] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Accepted: 10/04/2012] [Indexed: 01/18/2023] Open
Abstract
Innate immunity serves as the first line of defense against infectious agents such as intracellular bacteria. The innate immune platform includes Toll-like receptors (TLRs), retinoid acid-inducible gene-I-like receptors and other cytosolic nucleic acid sensors, nucleotide-binding and oligomerization domain-like receptors, adaptors, kinases and other signaling molecules that are required to elicit effective responses against different pathogens. Our research group has been using the Gram-negative bacteria Brucella abortus as a model of pathogen. We have demonstrated that B. abortus triggers MAPK and NF-κB signaling pathways in macrophages in a MyD88 and IRAK-4-dependent manner. Furthermore, we claimed that so far TLR9 is the most important single TLR during Brucella infection. The identification of host receptors that recognize pathogen-derived nucleic acids has revealed an essential role for nucleic acid sensing in the triggering of immunity to intracellular pathogens. Besides TLRs, herein we describe recent advances in NOD1, NOD2, and type I IFN receptors in innate immune pathways during B. abortus infection.
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Affiliation(s)
| | | | | | | | | | | | | | - Sergio C. Oliveira
- Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas GeraisBelo Horizonte, MG, Brazil
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791
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Interactions of Staphylococci with Osteoblasts and Phagocytes in the Pathogenesis of Implant-Associated Osteomyelitis. Int J Artif Organs 2012; 35:713-26. [DOI: 10.5301/ijao.5000158] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/17/2012] [Indexed: 11/20/2022]
Abstract
In spite of great advancements in the field of biomaterials and in surgical techniques, the implant of medical devices is still associated with a high risk of bacterial infection. Implant-associated osteomyelitis is a deep infection of bone around the implant. The continuous inflammatory destruction of bone tissues characterizes this serious bone infectious disease. Staphylococcus aureus and Staphylococcus epidermidis are the most prevalent etiologic agents of implant-associated infections, together with the emerging pathogen Staphylococcus lugdunensis. Various interactions between staphylococci, osteoblasts, and phagocytes occurring in the peri-prosthesis environment play a crucial role in the pathogenesis of implant-associated osteomyelitis. Here we focus on two main events: internalization of staphylococci into osteoblasts, and bacterial interactions with phagocytic cells.
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792
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Novel role of PKR in inflammasome activation and HMGB1 release. Nature 2012; 488:670-4. [PMID: 22801494 PMCID: PMC4163918 DOI: 10.1038/nature11290] [Citation(s) in RCA: 600] [Impact Index Per Article: 50.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 06/08/2012] [Indexed: 02/06/2023]
Abstract
The inflammasome regulates release of caspase activation-dependent cytokines, including IL-1β, IL-18, and high-mobility group box 1 (HMGB1)1-5. During the course of studying HMGB1 release mechanisms, we discovered an important role of double-stranded RNA dependent protein kinase (PKR) in inflammasome activation. Exposure of macrophages to inflammasome agonists induced PKR autophosphorylation. PKR inactivation by genetic deletion or pharmacological inhibition severely impaired inflammasome activation in response to double-stranded RNA, ATP, monosodium urate, adjuvant aluminum, rotenone, live E. coli, anthrax lethal toxin, DNA transfection, and S. Typhimurium infection. PKR deficiency significantly inhibited the secretion of IL-1beta, IL-18 and HMGB1 in E. coli-induced peritonitis. PKR physically interacts with multiple inflammasome components, including NLR family pyrin domain-containing 3 (NLRP3), NLR family pyrin domain-containing 1 (NLRP1), NLR family CARD domain-containing protein 4 (NLRC4), Absent in melanoma 2 (AIM2), and broadly regulates inflammasome activation. PKR autophosphorylation in a cell free system with recombinant NLRP3, ASC and pro-casapse-1 reconstitutes inflammasome activity. These results reveal a critical role of PKR in inflammasome activation, and indicate that it should be possible to pharmacologically target this molecule to treat inflammation.
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793
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Chen G, Severo MS, Sohail M, Sakhon OS, Wikel SK, Kotsyfakis M, Pedra JHF. Ixodes scapularis saliva mitigates inflammatory cytokine secretion during Anaplasma phagocytophilum stimulation of immune cells. Parasit Vectors 2012; 5:229. [PMID: 23050849 PMCID: PMC3503595 DOI: 10.1186/1756-3305-5-229] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Accepted: 10/06/2012] [Indexed: 11/30/2022] Open
Abstract
Background Ixodes scapularis saliva enables the transmission of infectious agents to the mammalian host due to its immunomodulatory, anesthetic and anti-coagulant properties. However, how I. scapularis saliva influences host cytokine secretion in the presence of the obligate intracellular rickettsial pathogen Anaplasma phagocytophilum remains elusive. Methods Bone marrow derived macrophages (BMDMs) were stimulated with pathogen associated molecular patterns (PAMPs) and A. phagocytophilum. Cytokine secretion was measured in the presence and absence of I. scapularis saliva. Human peripheral blood mononuclear cells (PBMCs) were also stimulated with Tumor Necrosis Factor (TNF)-α in the presence and absence of I. scapularis saliva and interleukin (IL)-8 was measured. Results I. scapularis saliva inhibits inflammatory cytokine secretion by macrophages during stimulation of Toll-like (TLR) and Nod-like receptor (NLR) signaling pathways. The effect of I. scapularis saliva on immune cells is not restricted to murine macrophages because decreasing levels of interleukin (IL)-8 were observed after TNF-α stimulation of human peripheral blood mononuclear cells. I. scapularis saliva also mitigates pro-inflammatory cytokine response by murine macrophages during challenge with A. phagocytophilum. Conclusions These findings suggest that I. scapularis may inhibit inflammatory cytokine secretion during rickettsial transmission at the vector-host interface.
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Affiliation(s)
- Gang Chen
- Center for Disease Vector Research and Department of Entomology, University of California-Riverside, Riverside, CA 92521, USA
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794
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Cellular adaptation to anthrax lethal toxin-induced mitochondrial cholesterol enrichment, hyperpolarization, and reactive oxygen species generation through downregulating MLN64 in macrophages. Mol Cell Biol 2012; 32:4846-60. [PMID: 23028046 DOI: 10.1128/mcb.00494-12] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cellular adaptation to different stresses related to survival and function has been demonstrated in several cell types. Anthrax lethal toxin (LeTx) induces rapid cell death, termed "pyroptosis," by activating NLRP1b/caspase-1 in murine macrophages. We and others (S. D. Ha et al., J. Biol. Chem. 282:26275-26283, 2007; I. I. Salles et al., Proc. Natl. Acad. Sci. U. S. A. 100:12426 -12431, 2003) have shown that RAW264.7 cells preexposed to sublethal doses of LeTx become resistant to subsequent high cytolytic doses of LeTx, termed toxin-induced resistance (TIR). To date, the cellular mechanisms of pyroptosis and TIR are largely unknown. We found that LeTx caused NLRP1b/caspase-1-dependent mitochondrial dysfunction, including hyperpolarization and generation of reactive oxygen species, which was distinct from that induced by stimuli such as NLRP3-activating ATP. In TIR cells, these mitochondrial events were not detected, although caspase-1 was activated, in response to LeTx. We identified that downregulation of the late endosomal cholesterol-transferring protein MLN64 in TIR cells was involved in TIR. The downregulation of MLN64 in TIR cells was at least in part due to DNA methyltransferase 1-mediated DNA methylation. In wild-type RAW264.7 cells and primary bone marrow-derived macrophages, LeTx caused NLRP1b/caspase-1-dependent mitochondrial translocation of MLN64, resulting in cholesterol enrichment, membrane hyperpolarization, reactive oxygen species (ROS) generation, and depletion of free glutathione (GSH). This study demonstrates for the first time that MLN64 plays a key role in LeTx/caspase-1-induced mitochondrial dysfunction.
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795
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Janoff EN, Gustafson C, Frank DN. The world within: living with our microbial guests and guides. Transl Res 2012; 160:239-45. [PMID: 22732305 PMCID: PMC6440546 DOI: 10.1016/j.trsl.2012.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 05/17/2012] [Indexed: 01/01/2023]
Affiliation(s)
- Edward N Janoff
- Mucosal and Vaccine Research Colorado, Division of Infectious Diseases, Department of Medicine, University of Colorado Denver School of Medicine, Aurora, CO, USA.
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796
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Affiliation(s)
- Luigi Franchi
- Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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797
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Juliana C, Fernandes-Alnemri T, Kang S, Farias A, Qin F, Alnemri ES. Non-transcriptional priming and deubiquitination regulate NLRP3 inflammasome activation. J Biol Chem 2012; 287:36617-22. [PMID: 22948162 DOI: 10.1074/jbc.m112.407130] [Citation(s) in RCA: 554] [Impact Index Per Article: 46.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The NLRP3 inflammasome is a key component of the innate immune response to pathogenic infection and tissue damage. It is also involved in the pathogenesis of a number of human diseases, including gouty arthritis, silicosis, atherosclerosis, and type 2 diabetes. The assembly of the NLRP3 inflammasome requires a priming signal derived from pattern recognition or cytokine receptors, followed by a second signal derived from extracellular ATP, pore-forming toxins, or crystalline materials. How these two signals activate the NLRP3 inflammasome is not yet clear. Here, we show that in mouse macrophages, signaling by the pattern recognition receptor TLR4 through MyD88 can rapidly and non-transcriptionally prime NLRP3 by stimulating its deubiquitination. This process is dependent on mitochondrial reactive oxygen species production and can be inhibited by antioxidants. We further show that signaling by ATP can also induce deubiquitination of NLRP3 by a mechanism that is not sensitive to antioxidants. Pharmacological inhibition of NLRP3 deubiquitination completely blocked NLRP3 activation in both mouse and human cells, indicating that deubiquitination of NLRP3 is required for its activation. Our findings suggest that NLRP3 is activated by a two-step deubiquitination mechanism initiated by Toll-like receptor signaling and mitochondrial reactive oxygen species and further potentiated by ATP, which could explain how NLRP3 is activated by diverse danger signals.
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Affiliation(s)
- Christine Juliana
- Department of Biochemistry and Molecular Biology and the Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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798
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Dubyak GR. P2X7 receptor regulation of non-classical secretion from immune effector cells. Cell Microbiol 2012; 14:1697-706. [PMID: 22882764 DOI: 10.1111/cmi.12001] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 07/29/2012] [Accepted: 07/30/2012] [Indexed: 12/13/2022]
Abstract
P2X7 receptors (P2X7R) are extracellular ATP-gated ion channels expressed in the immune effector cells that carry out critical protective responses during the early phases of microbial infection or acute tissue trauma. P2X7R-positive cells include monocytes, macrophages, dendritic cells and T cells. Given its presence in all host and pathogen cell types, ATP can be readily released into extracellular compartments at local sites of tissue damage and microbial invasion. Thus, extracellular ATP and its target receptors on host effector cells can be considered as additional elements of the innate immune system. In this regard, stimulation of P2X7R rapidly triggers a key step of the inflammatory response: induction of NLRP3/caspase-1 inflammasome signalling complexes that drive the proteolytic maturation and secretion of the proinflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18). IL-1β (and IL-18) lacks a signal sequence for compartmentation within the Golgi and classical secretory vesicles and the proIL-1β precursor accumulates within the cytosol following translation on free ribosomes. Thus, ATP-induced accumulation of the mature IL-1β cytokine within extracellular compartments requires non-classical mechanisms of export from the cytosolic compartment. Five proposed mechanisms include: (i) exocytosis of secretory lysosomes that accumulate cytosolic IL-1β via undefined protein transporters; (ii) release of membrane-delimited microvesicles derived from plasma membrane blebs formed by evaginationsof the surface membrane that entrap cytosolic IL-β; (iii) release of membrane-delimited exosomes secondary to the exocytosis of multivesicular bodies formed by invaginations of recycling endosomes that entrap cytosolic IL-β; (iv) exocytosis of autophagosomes or autophagolysosomes that accumulate cytosolic IL-1β via entrapment during formation of the initial autophagic isolation membrane or omegasome and (v) direct release of cytosolic IL-1β secondary to regulated cell death by pyroptosis or necroptosis. These mechanisms are not mutually exclusive and may represent engagement of parallel or intersecting membrane trafficking responses to P2X7R activation.
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Affiliation(s)
- George R Dubyak
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
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799
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Abstract
Immunity to pathogens critically requires pattern-recognition receptors (PRRs) to trigger intracellular signaling cascades that initiate and direct innate and adaptive immune responses. For fungal infections, these responses are primarily mediated by members of the C-type lectin receptor family. In this Review, we highlight recent advances in the understanding of the roles and mechanisms of these multifunctional receptors, explore how these PRRs orchestrate antifungal immunity and briefly discuss progress in the use of these receptors as targets for antifungal and other vaccines.
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Affiliation(s)
- Sarah E Hardison
- Aberdeen Fungal Group, Section of Immunology and Infection, University of Aberdeen, Aberdeen, UK
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800
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Broz P, Ruby T, Belhocine K, Bouley DM, Kayagaki N, Dixit VM, Monack DM. Caspase-11 increases susceptibility to Salmonella infection in the absence of caspase-1. Nature 2012; 490:288-91. [PMID: 22895188 PMCID: PMC3470772 DOI: 10.1038/nature11419] [Citation(s) in RCA: 412] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 07/18/2012] [Indexed: 01/07/2023]
Affiliation(s)
- Petr Broz
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford University, California 94305, USA
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