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Abstract
Although the IL-1α molecule has long been recognized, information about its distinct role in various diseases is limited, since most clinical studies have focused on the role of IL-1β. Despite triggering the same IL-1 receptor as does IL-1β, there is, however, a distinct role for IL-1α in some inflammatory diseases. IL-1α is a unique cytokine since it is constitutively present intracellularly in nearly all resting non-hematopoietic cells in health as well as being up-regulated during hypoxia. During cell necrosis, IL-1α functions as an alarm molecule and thus plays a critical role early in inflammation. Following its release from damage tissue cells, IL-1α mediates neutrophil recruitment to the site of injury, inducing IL-1β, other cytokines and chemokines from surrounding resident cells. Another unique attribute of IL-1α is its nuclear localization sequence present in the N-terminal half of the precursor termed the propiece. The IL-1α propiece translocates into the nucleus and participates in the regulation of transcription. Therefore, IL-1α, like IL-1 family members IL-33 and IL-37, is a 'dual-function' cytokine binding to chromatin as well as to its cell surface receptor. Some cancer cells can express membrane IL-1α, which can increase immunogenicity of tumor cells and serve in anti-tumor immune surveillance and tumor regression. However, in the tumor microenvironment, precursor IL-1α released from dying tumor cells is inflammatory and, similar to IL-1β, increases tumor invasiveness and angiogenesis.
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Affiliation(s)
- Peleg Rider
- Faculty of Health Sciences, Department of Clinical Biochemistry and Pharmacology, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
| | - Yaron Carmi
- School of Medicine, Department of Pathology, Stanford University, Palo Alto, CA, USA
| | - Elena Voronov
- The Shraga Segal Department of Microbiology, Immunology and Genetics and The Cancer Research Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Ron N Apte
- The Shraga Segal Department of Microbiology, Immunology and Genetics and The Cancer Research Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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202
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Hirota JA, Hiebert PR, Gold M, Wu D, Graydon C, Smith JA, Ask K, McNagny K, Granville DJ, Knight DA. Granzyme B deficiency exacerbates lung inflammation in mice after acute lung injury. Am J Respir Cell Mol Biol 2013; 49:453-62. [PMID: 23642129 DOI: 10.1165/rcmb.2012-0512oc] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Granzyme B (GzmB) is a serine protease with intracellular and extracellular activities capable of regulating inflammation through cytokine processing and the apoptosis of effector cells. We tested the hypothesis that GzmB expression in T regulatory cells (Tregs) is required for the control of inflammatory responses and pathology during acute lung injury. To substantiate the clinical relevance of GzmB during lung injury, we performed GzmB immunohistochemistry on lung tissue from patients with acute respiratory distress syndrome (ARDS) and healthy control subjects. We also performed in vivo experiments with wild-type (WT) C57BL/6 and GzmB(-/-) mice exposed to a single intranasal instillation of bleomycin to model lung injury. Our results demonstrate that the expression of GzmB was elevated in ARDS lung sections, relative to healthy control samples. Bleomycin-exposed GzmB(-/-) mice exhibited greater morbidity and mortality, which was associated with increased numbers of lung lymphocytes. Bleomycin induced an equal increase in CD4(+)/CD25(+)/FoxP3(+) Treg populations in WT and GzmB(-/-) mice. GzmB expression was not significant in Tregs, with the majority of the expression localized to natural killer (NK)-1.1(+) cells. The expression of GzmB in NK cells of bleomycin-exposed WT mice was associated with greater lymphocyte apoptosis, reduced total lymphocyte numbers, and reduced pathology relative to GzmB(-/-) mice. Our data demonstrate that GzmB deficiency results in the exacerbation of lymphocytic inflammation during bleomycin-induced acute lung injury, which is associated with pathology, morbidity, and mortality.
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Affiliation(s)
- Jeremy A Hirota
- University of British Columbia James Hogg Research Centre, St. Paul's Hospital, 1081 Burrard St., Vancouver, BC, Canada.
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203
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Hiebert PR, Boivin WA, Zhao H, McManus BM, Granville DJ. Perforin and granzyme B have separate and distinct roles during atherosclerotic plaque development in apolipoprotein E knockout mice. PLoS One 2013; 8:e78939. [PMID: 24205352 PMCID: PMC3811993 DOI: 10.1371/journal.pone.0078939] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 09/17/2013] [Indexed: 01/04/2023] Open
Abstract
The granzyme B/perforincytotoxic pathway is a well established mechanism of initiating target cell apoptosis. Previous studies have suggested a role for the granzyme B/perforin cytotoxic pathway in vulnerable atherosclerotic plaque formation. In the present study, granzyme B deficiency resulted in reduced atherosclerotic plaque development in the descending aortas of apolipoprotein E knockout mice fed a high fat diet for 30 weeks while perforindeficiency resulted in greater reduction in plaque development with significantly less plaque area than granzyme Bdeficient mice. In contrast to the descending aorta, no significant change in plaque size was observed in aortic roots from either granzyme Bdeficient or perforindeficient apolipoprotein E knockout mice. However, atherosclerotic plaques in the aortic roots did exhibit significantly more collagen in granzyme B, but not perforin deficient mice. Together these results suggest significant, yet separate roles for granzyme B and perforin in the pathogenesis of atherosclerosis that go beyond the traditional apoptotic pathway with additional implications in plaque development, stability and remodelling of extracellular matrix.
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Affiliation(s)
- Paul R. Hiebert
- UBC James Hogg Research Centre at the Institute for Heart + Lung Health, St. Paul’s Hospital, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Wendy A. Boivin
- UBC James Hogg Research Centre at the Institute for Heart + Lung Health, St. Paul’s Hospital, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Hongyan Zhao
- UBC James Hogg Research Centre at the Institute for Heart + Lung Health, St. Paul’s Hospital, Vancouver, British Columbia, Canada
| | - Bruce M. McManus
- UBC James Hogg Research Centre at the Institute for Heart + Lung Health, St. Paul’s Hospital, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - David J. Granville
- UBC James Hogg Research Centre at the Institute for Heart + Lung Health, St. Paul’s Hospital, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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204
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Lozza L, Farinacci M, Faé K, Bechtle M, Stäber M, Dorhoi A, Bauer M, Ganoza C, Weber S, Kaufmann SHE. Crosstalk between human DC subsets promotes antibacterial activity and CD8+ T-cell stimulation in response to bacille Calmette-Guérin. Eur J Immunol 2013; 44:80-92. [PMID: 24114554 PMCID: PMC3992850 DOI: 10.1002/eji.201343797] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 08/15/2013] [Accepted: 09/17/2013] [Indexed: 12/12/2022]
Abstract
To date, little is known about the unique contributions of specialized human DC subsets to protection against tuberculosis (TB). Here, we focus on the role of human plasmacytoid (p)DCs and myeloid (m)DCs in the immune response to the TB vaccine bacille Calmette-Guérin (BCG). Ex vivo DC subsets from human peripheral blood were purified and infected with BCG expressing GFP to distinguish between infected and noninfected cells. BDCA-1+ myeloid DCs were more susceptible than BDCA-3+ mDCs to BCG infection. Plasmacytoid DCs have poor phagocytic activity but are equipped with endocytic receptors and can be activated by bystander stimulation. Consequently, the mutual interaction of the two DC subsets in response to BCG was analyzed. We found that pDCs were activated by BCG-infected BDCA-1+ mDCs to upregulate maturation markers and to produce granzyme B, but not IFN-α. Reciprocally, the presence of activated pDCs enhanced mycobacterial growth control by infected mDCs and increased IL-1β availability. The synergy between the two DC subsets promoted BCG-specific CD8+ T-cell stimulation and the role of BCG-infected BDCA-1+ mDCs could not be efficiently replaced by infected BDCA-3+ mDCs in the crosstalk with pDCs. We conclude that mDC–pDC crosstalk should be exploited for rational design of next-generation TB vaccines.
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Affiliation(s)
- Laura Lozza
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany
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205
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McCarthy DA, Clark RR, Bartling TR, Trebak M, Melendez JA. Redox control of the senescence regulator interleukin-1α and the secretory phenotype. J Biol Chem 2013; 288:32149-32159. [PMID: 24062309 DOI: 10.1074/jbc.m113.493841] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Senescent cells accumulate in aged tissue and are causally linked to age-associated tissue degeneration. These non-dividing, metabolically active cells are highly secretory and alter tissue homeostasis, creating an environment conducive to metastatic disease progression. IL-1α is a key senescence-associated (SA) proinflammatory cytokine that acts as a critical upstream regulator of the SA secretory phenotype (SASP). We established that SA shifts in steady-state H2O2 and intracellular Ca(2+) levels caused an increase in IL-1α expression and processing. The increase in intracellular Ca(2+) promoted calpain activation and increased the proteolytic cleavage of IL-1α. Antioxidants and low oxygen tension prevented SA IL-1α expression and restricted expression of SASP components IL-6 and IL-8. Ca(2+) chelation or calpain inhibition prevented SA processing of IL-1α and its ability to induce downstream cytokine expression. Conditioned medium from senescent cells treated with antioxidants or Ca(2+) chelators or cultured in low oxygen markedly reduced the invasive capacity of proximal metastatic cancer cells. In this paracrine fashion, senescent cells promoted invasion by inducing an epithelial-mesenchymal transition, actin reorganization, and cellular polarization of neighboring cancer cells. Collectively, these findings demonstrate how SA alterations in the redox state and Ca(2+) homeostasis modulate the inflammatory phenotype through the regulation of the SASP initiator IL-1α, creating a microenvironment permissive to tumor invasion.
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Affiliation(s)
- Donald A McCarthy
- From the College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203
| | - Ryan R Clark
- From the College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203
| | - Toni R Bartling
- From the College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203
| | - Mohamed Trebak
- From the College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203
| | - J Andres Melendez
- From the College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203.
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206
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Edye ME, Lopez-Castejon G, Allan SM, Brough D. Acidosis drives damage-associated molecular pattern (DAMP)-induced interleukin-1 secretion via a caspase-1-independent pathway. J Biol Chem 2013; 288:30485-30494. [PMID: 24022484 PMCID: PMC3798512 DOI: 10.1074/jbc.m113.478941] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The proinflammatory cytokine IL-1β is a key mediator of inflammatory responses that contribute to and exacerbate brain injury. IL-1β is synthesized by microglia in the brain as an inactive precursor (pro-IL-1β). Cleavage of pro-IL-1β to a mature form is stimulated by damage-associated molecular patterns (DAMPs). These DAMPs are sensed by a pattern recognition receptor called NLRP3, which forms an inflammasome, resulting in the activation of caspase-1 and cleavage of pro-IL-1β. To date, regulation of the inflammasome in culture has been studied under normal culture conditions, and it is not known how DAMPs signal under disease relevant conditions such as acidosis. Given the presence of acidosis in pathological states, our objective was to test the hypothesis that acidic conditions modify DAMP-induced IL-1β release from cultured primary mouse glial cells. When LPS-primed glial cells were stimulated with DAMPs under acidic conditions (pH 6.2), the predominant IL-1β form secreted was the 20-kDa rather than the 17-kDa caspase-1-dependent species. Lactic acidosis, induced by the addition of 25 mm lactic acid, also induced the release of 20-kDa IL-1β. This 20-kDa product was produced independently of NLRP3 and caspase-1 but was inhibited by the cathepsin D inhibitor pepstatin A. These data suggest that under disease relevant acidosis, DAMPs and lactic acid induce the secretion of IL-1β independently of the inflammasome. Therapeutic strategies directed to the inhibition of IL-1β processing should therefore consider alternative processing of IL-1β in addition to caspase-1-dependent processing.
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Affiliation(s)
- Michelle E Edye
- From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Gloria Lopez-Castejon
- From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Stuart M Allan
- From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom.
| | - David Brough
- From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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207
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Abstract
Acute cerebrovascular disease can affect people at all stages of life, from neonates to the elderly, with devastating consequences. It is responsible for up to 10% of deaths worldwide, is a major cause of disability, and represents an area of real unmet clinical need. Acute cerebrovascular disease is multifactorial with many mechanisms contributing to a complex pathophysiology. One of the major processes worsening disease severity and outcome is inflammation. Pro-inflammatory cytokines of the interleukin (IL)-1 family are now known to drive damaging inflammatory processes in the brain. The aim of this review is to discuss the recent literature describing the role of IL-1 in acute cerebrovascular disease and to provide an update on our current understanding of the mechanisms of IL-1 production. We also discuss the recent literature where the effects of IL-1 have been targeted in animal models, thus reviewing potential future strategies that may limit the devastating effects of acute cerebrovascular disease.
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Affiliation(s)
- James Galea
- Manchester Academic Health Sciences Center, Brain Injury Research Group, Clinical Sciences Building, Salford Royal Foundation Trust, Salford, UK
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208
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Hiebert PR, Wu D, Granville DJ. Granzyme B degrades extracellular matrix and contributes to delayed wound closure in apolipoprotein E knockout mice. Cell Death Differ 2013; 20:1404-14. [PMID: 23912712 DOI: 10.1038/cdd.2013.96] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2013] [Revised: 05/03/2013] [Accepted: 06/06/2013] [Indexed: 01/09/2023] Open
Abstract
Chronic inflammation and excessive protease activity have a major role in the persistence of non-healing wounds. Granzyme B (GzmB) is a serine protease expressed during chronic inflammation that, in conjunction with perforin, has a well-established role in initiating apoptotic cell death. GzmB is also capable of acting extracellularly, independent of perforin and can degrade several extracellular matrix (ECM) proteins that are critical during wound healing. We used apolipoprotein E (ApoE) knockout (AKO) mice as a novel model of chronic inflammation and impaired wound healing to investigate the role of GzmB in chronic wounds. Wild-type and AKO mice were grown to 7 weeks (young) or 37 weeks (old) of age on a regular chow or high-fat diet (HFD), given a 1-cm diameter full thickness wound on their mid dorsum and allowed to heal for 16 days. Old AKO mice fed a HFD exhibited reduced wound closure, delayed contraction, chronic inflammation and altered ECM remodeling. Conversely, GzmB/ApoE double knockout mice displayed improved wound closure and contraction rates. In addition, murine GzmB was found to degrade both fibronectin and vitronectin derived from healthy mouse granulation tissue. In addition, GzmB-mediated degradation of fibronectin generated a fragment similar in size to that observed in non-healing mouse wounds. These results provide the first direct evidence that GzmB contributes to chronic wound healing in part through degradation of ECM.
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Affiliation(s)
- P R Hiebert
- UBC James Hogg Research Centre, St. Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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209
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Garlanda C, Riva F, Bonavita E, Gentile S, Mantovani A. Decoys and Regulatory "Receptors" of the IL-1/Toll-Like Receptor Superfamily. Front Immunol 2013; 4:180. [PMID: 23847621 PMCID: PMC3705552 DOI: 10.3389/fimmu.2013.00180] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 06/22/2013] [Indexed: 11/24/2022] Open
Abstract
Members of the IL-1 family play a key role in innate and adaptive immunity and in the pathogenesis of diverse diseases. Members of IL-1R like receptor (ILR) family include signaling molecules and negative regulators. The latter include decoy receptors (IL-1RII; IL-18BP) and “receptors” with regulatory function (TIR8/SIGIRR; IL-1RAcPb; DIGIRR). Structural considerations suggest that also TIGIRR-1 and IL-1RAPL may have regulatory function. The presence of multiple pathways of negative regulation of members of the IL-1/IL-1R family emphasizes the need for a tight control of members of this fundamental system.
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Affiliation(s)
- Cecilia Garlanda
- Department of Inflammation and Immunology, Humanitas Clinical and Research Center , Rozzano , Italy
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210
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Voronov E, Dotan S, Krelin Y, Song X, Elkabets M, Carmi Y, Rider P, Idan Cohen, Romzova M, Kaplanov I, Apte RN. Unique Versus Redundant Functions of IL-1α and IL-1β in the Tumor Microenvironment. Front Immunol 2013; 4:177. [PMID: 23847618 PMCID: PMC3703603 DOI: 10.3389/fimmu.2013.00177] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 06/19/2013] [Indexed: 12/13/2022] Open
Abstract
Interleukin-1 (IL-1) is a major “alarm” upstream pro-inflammatory cytokine that also affects immunity and hematopoiesis by inducing cytokine cascades. In the tumor arena, IL-1 is produced by malignant or microenvironmental cells. As a pleiotropic cytokine, IL-1 is involved in tumorigenesis and tumor invasiveness but also in the control of anti-tumor immunity. IL-1α and IL-1β are the major agonists of IL-1, while IL-1Ra is a physiological inhibitor of pre-formed IL-1. In their secreted form, IL-1α and IL-1β bind to the same receptors and induce the same biological functions, but IL-1α and IL-1β differ in their compartmentalization within the producing cell or the microenvironment. IL-1β is only active in its processed, secreted form, and mediates inflammation, which promotes carcinogenesis, tumor invasiveness, and immunosuppression, whereas IL-1α is mainly cell-associated and in the tumor context, when expressed on the cell membrane, it stimulates anti-tumor cell immunity manifested by tumor regression. In the tumor milieu, extracellular levels of IL-1α are usually low and do not stimulate broad inflammation that promotes progression. Immunosuppression induced by IL-1β in the tumor microenvironment, mainly through MDSC induction, usually inhibits or masks anti-tumor cell immunity induced by cell-associated IL-1α. However, in different tumor systems, redundant or unique patterns of IL-1α and IL-1β expression and function have been observed. Recent breakthroughs in inflammasome biology and IL-1β processing/secretion have spurred the development of novel anti-IL-1 agents, which are being used in clinical trials in patients with diverse inflammatory diseases. Better understanding of the integrative role of IL-1α and IL-1β in distinct malignancies will facilitate the application of novel IL-1 modulation approaches at the bedside, in cancer patients with minimal residual disease (MRD), as an adjunct to conventional approaches to reduce the tumor burden.
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Affiliation(s)
- Elena Voronov
- The Shraga Segal Department of Microbiology, Immunology and Genetics, The Faculty of Health Sciences, Ben Gurion University of the Negev , Beer Sheva , Israel
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211
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Fabricius D, Nußbaum B, Busch D, Panitz V, Mandel B, Vollmer A, Westhoff MA, Kaltenmeier C, Lunov O, Tron K, Nienhaus GU, Jahrsdörfer B, Debatin KM. Antiviral Vaccines License T Cell Responses by Suppressing Granzyme B Levels in Human Plasmacytoid Dendritic Cells. THE JOURNAL OF IMMUNOLOGY 2013; 191:1144-53. [DOI: 10.4049/jimmunol.1203479] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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212
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Sollberger G, Strittmatter GE, Garstkiewicz M, Sand J, Beer HD. Caspase-1: the inflammasome and beyond. Innate Immun 2013; 20:115-25. [PMID: 23676582 DOI: 10.1177/1753425913484374] [Citation(s) in RCA: 182] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Caspase-1 plays a fundamental role in innate immunity and in several important inflammatory diseases as the protease activates the pro-inflammatory cytokines proIL-1β and proIL-18. Caspase-1 itself is activated in different inflammasome complexes, which assemble in response to a variety of exogenous and endogenous stressors. More recently, pyroptosis, a caspase-1-dependent type of programmed cell death, has been identified that is able to support secreted IL-1 and IL-18 in triggering an inflammatory response. Whereas these 'canonical' activities are well appreciated, this review also highlights less-known pathways and molecules activated by caspase-1. There is evidence that caspase-1 supports cell survival by activation of NF-κB, induction of membrane repair and regulation of unconventional secretion of certain proteins. The physiologic effects of processing of other downstream targets, such as proteins involved in glycolysis or activation of caspase-7, are less well understood. However, there is increasing evidence that caspase-1 contributes to innate and adaptive immunologic defense mechanisms, repair and pathologic conditions by the regulation of several different and partially opposing pathways.
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Affiliation(s)
- Gabriel Sollberger
- Department of Dermatology, University Hospital Zürich, Zürich, Switzerland
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213
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Lamacchia C, Rodriguez E, Palmer G, Gabay C. Endogenous IL-1α is a chromatin-associated protein in mouse macrophages. Cytokine 2013; 63:135-44. [PMID: 23684408 DOI: 10.1016/j.cyto.2013.04.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 03/19/2013] [Accepted: 04/10/2013] [Indexed: 12/21/2022]
Abstract
The cytokine interleukin-1α (IL-1α) is synthesized as a 31kDa peptide that lacks a leader peptide and is not secreted by the conventional secretory pathway. A distinctive characteristic of pro-IL-1α is the presence of a nuclear localization sequence in its amino-terminal moiety that allows its translocation to the nucleus. However no nuclear function(s) of the endogenous pro-IL-1α has been reported to date. In the present study, we used murine macrophages that produce IL-1α in response to pro-inflammatory stimuli, to gain further insight into the biology of the endogenous IL-1α protein in innate immune cells. We show that endogenous IL-1α is essentially found as a chromatin-associated nuclear protein in LPS-stimulated macrophages. In contrast to IL-1β, IL-1α was not released upon inflammasome activation unless significant cell damage occurred. IL-1β mRNA and protein levels were specifically decreased in IL-1α deficient macrophages after LPS stimulation. However, overexpression of human pro-IL-1α did not rescue this defective IL-1β production, suggesting that this finding might be related to the insertion of the targeting construct into the IL-1 locus, rather than to a specific nuclear function of pro-IL-1α. Finally, by using both genomic and proteomic approaches, we could not identify a nuclear function of IL-1α. Taken together, these observations suggest that in macrophages IL-1α primarily acts as an alarmin that is rapidly released upon cell damage to activate early mechanisms of host defense.
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Affiliation(s)
- Céline Lamacchia
- Division of Rheumatology, Department of Internal Medicine, University Hospital of Geneva, 26 Avenue Beau-Séjour, 1211 Geneva 14, Switzerland.
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214
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McCarthy DA, Ranganathan A, Subbaram S, Flaherty NL, Patel N, Trebak M, Hempel N, Melendez JA. Redox-control of the alarmin, Interleukin-1α. Redox Biol 2013; 1:218-25. [PMID: 24024155 PMCID: PMC3757693 DOI: 10.1016/j.redox.2013.03.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 03/12/2013] [Accepted: 03/26/2013] [Indexed: 12/22/2022] Open
Abstract
The pro-inflammatory cytokine Interleukin-1α (IL-1α) has recently emerged as a susceptibility marker for a wide array of inflammatory diseases associated with oxidative stress including Alzheimer's, arthritis, atherosclerosis, diabetes and cancer. In the present study, we establish that expression and nuclear localization of IL-1α are redox-dependent. Shifts in steady-state H2O2 concentrations (SS-[H2O2]) resulting from enforced expression of manganese superoxide dismutase (SOD2) drive IL-1α mRNA and protein expression. The redox-dependent expression of IL-1α is accompanied by its increased nuclear localization. Both IL-1α expression and its nuclear residency are abrogated by catalase co-expression. Sub-lethal doses of H2O2 also cause IL-1α nuclear localization. Mutagenesis revealed IL-1α nuclear localization does not involve oxidation of cysteines within its N terminal domain. Inhibition of the processing enzyme calpain prevents IL-1α nuclear localization even in the presence of H2O2. H2O2 treatment caused extracellular Ca2+ influx suggesting oxidants may influence calpain activity indirectly through extracellular Ca2+ mobilization. Functionally, as a result of its nuclear activity, IL-1α overexpression promotes NF-kB activity, but also interacts with the histone acetyl transferase (HAT) p300. Together, these findings demonstrate a mechanism by which oxidants impact inflammation through IL-1α and suggest that antioxidant-based therapies may prove useful in limiting inflammatory disease progression. Sod2-dependent increases in steady-state H2O2 promote IL-1α expression. H2O2 causes nuclear localization of IL-1α and extracellular Ca2+ influx. Inhibition of the Ca2+ regulated calpain prevents H2O2 dependent IL-1α nuclear localization. Nuclear IL-1α interacts with p300 and promotes NF-κB activity.
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Affiliation(s)
- Donald A McCarthy
- College of Nanoscale Sciences and Engineering, University at Albany, SUNY, Albany, NY 12203, USA
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215
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Abstract
The molecular mechanisms that regulate functional activation of IL-1α remain elusive. In this issue of Immunity, Zheng et al. (2013) describe a molecular system implicating interleukin-1 receptor-2 (IL-1R2) as a principal cytosolic factor that controls functional IL-1α activation during necrosis.
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Affiliation(s)
- Nelson C Di Paolo
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA 98195-7720, USA
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216
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Abstract
Autophagy is an important intracellular homeostatic mechanism for the targeting of cytosolic constituents, including organelles, for lysosomal degradation. Autophagy plays roles in numerous physiological processes, including immune cell responses to endogenous and exogenous pathogenic stimuli. Moreover, autophagy has a potentially pivotal role to play in the regulation of inflammatory responses. In particular, autophagy regulates endogenous inflammasome activators, as well as inflammasome components and pro-IL-1β. As a result, autophagy acts a key modulator of IL-1β and IL-18, as well as IL-1α, release. This review focuses specifically on the role autophagy plays in regulating the production, processing, and secretion of IL-1 and IL-18 and the consequences of this important function.
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Affiliation(s)
- James Harris
- Faculty of Medicine, Nursing and Health Sciences, Monash Medical Centre, Monash University Clayton, VIC, Australia
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217
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Jiang S, Dupont N, Castillo EF, Deretic V. Secretory versus degradative autophagy: unconventional secretion of inflammatory mediators. J Innate Immun 2013; 5:471-9. [PMID: 23445716 DOI: 10.1159/000346707] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 12/27/2012] [Indexed: 12/29/2022] Open
Abstract
Autophagy (macroautophagy) is often defined as a degradative process and a tributary of the lysosomal pathway. In this context, autophagy carries out cytoplasmic quality control and nutritional functions by removing defunct or disused organelles, particulate targets and invading microbes, and by bulk digestion of the cytoplasm. However, recent studies indicate that autophagy surprisingly affects multiple secretory pathways. Autophagy participates in extracellular delivery of a number of cytosolic proteins that do not enter the conventional secretory pathway via the Golgi apparatus but are instead unconventionally secreted directly from the cytosol. In mammalian cells, a prototypical example of this manifestation of autophagy is the unconventional secretion of a major proinflammatory cytokine, IL-1β. This review examines the concept of secretory autophagy and compares and contrasts the role of autophagy in the secretion of IL-1α and IL-1β. Although IL-1α and IL-1β have closely related extracellular inflammatory functions, they differ in intracellular activation, secretory mechanisms and how they are affected by autophagy. This example indicates that the role of autophagy in secretion is more complex, at least in mammalian cells, than the simplistic view that autophagosomes provide carriers for unconventional secretion of cytosolic proteins.
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Affiliation(s)
- Shanya Jiang
- Department of Molecular Genetics and Microbiology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
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218
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Zheng Y, Humphry M, Maguire JJ, Bennett MR, Clarke MCH. Intracellular interleukin-1 receptor 2 binding prevents cleavage and activity of interleukin-1α, controlling necrosis-induced sterile inflammation. Immunity 2013; 38:285-95. [PMID: 23395675 PMCID: PMC3659285 DOI: 10.1016/j.immuni.2013.01.008] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 01/18/2013] [Indexed: 12/21/2022]
Abstract
Necrosis can induce profound inflammation or be clinically silent. However, the mechanisms underlying such tissue specificity are unknown. Interleukin-1α (IL-1α) is a key danger signal released upon necrosis that exerts effects on both innate and adaptive immunity and is considered to be constitutively active. In contrast, we have shown that necrosis-induced IL-1α activity is tightly controlled in a cell type-specific manner. Most cell types examined expressed a cytosolic IL-1 receptor 2 (IL-1R2) whose binding to pro-IL-1α inhibited its cytokine activity. In cell types exhibiting a silent necrotic phenotype, IL-1R2 remained associated with pro-IL-1α. Cell types possessing inflammatory necrotic phenotypes either lacked IL-1R2 or had activated caspase-1 before necrosis, which degraded and dissociated IL-1R2 from pro-IL-1α. Full IL-1α activity required cleavage by calpain after necrosis, which increased its affinity for IL-1 receptor 1. Thus, we report a cell type-dependent process that fundamentally governs IL-1α activity postnecrosis and the mechanism allowing conditional release of this blockade.
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Affiliation(s)
- Yue Zheng
- Division of Cardiovascular Medicine, Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK
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219
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Mills KHG, Dungan LS, Jones SA, Harris J. The role of inflammasome-derived IL-1 in driving IL-17 responses. J Leukoc Biol 2012; 93:489-97. [PMID: 23271701 DOI: 10.1189/jlb.1012543] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
NLRs are members of the PRR family that sense microbial pathogens and mediate host innate immune responses to infection. Certain NLRs can assemble into a multiprotein complex called the inflammasome, which activates casapse-1 required for the cleavage of immature forms of IL-1β and IL-18 into active, mature cytokines. The inflammasome is activated by conserved, exogenous molecules from microbes and nonmicrobial molecules, such as asbestos, alum, or silica, as well as by endogenous danger signals, such as ATP, amyloid-β, and sodium urate crystals. Activation of the inflammasome is a critical event triggering IL-1-driven inflammation and is central to the pathology of autoinflammatory diseases, such as gout and MWS. Recent studies have also shown IL-1 or IL-18, in synergy with IL-23, can promote IL-17-prduction from Th17 cells and γδ T cells, and this process can be regulated by autophagy. IL-1-driven IL-17 production plays a critical role in host protective immunity to infection with fungi, bacteria, and certain viruses. However, Th17 cells and IL-17-seceting γδ T cells, activated by inflammasome-derived IL-1 or IL-18, have major pathogenic roles in many autoimmune diseases. Consequently, inflammasomes are now major drug targets for many autoimmune and chronic inflammatory diseases, as well as autoinflammatory diseases.
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Affiliation(s)
- Kingston H G Mills
- Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
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220
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Hiebert PR, Granville DJ. Granzyme B in injury, inflammation, and repair. Trends Mol Med 2012; 18:732-41. [DOI: 10.1016/j.molmed.2012.09.009] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 09/14/2012] [Accepted: 09/27/2012] [Indexed: 01/24/2023]
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221
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Peral de Castro C, Jones SA, Ní Cheallaigh C, Hearnden CA, Williams L, Winter J, Lavelle EC, Mills KHG, Harris J. Autophagy regulates IL-23 secretion and innate T cell responses through effects on IL-1 secretion. THE JOURNAL OF IMMUNOLOGY 2012; 189:4144-53. [PMID: 22972933 DOI: 10.4049/jimmunol.1201946] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Autophagy controls IL-1β secretion by regulating inflammasome activation and by targeting pro-IL-1β for degradation. In this article, we show that inhibition of autophagy, either with the PI3K inhibitors 3-methyladenine, wortmannin, and LY294002 or with small interfering RNA against autophagy proteins augmented the secretion of IL-23 by human and mouse macrophages and dendritic cells in response to specific TLR agonists. This process occurred at the transcriptional level and was dependent on reactive oxygen species and IL-1R signaling; it was abrogated with an IL-1R antagonist or with IL-1-neutralizing Abs, whereas treatment with either rIL-1α or IL-1β induced IL-23 secretion. Dendritic cells treated with LPS and 3-methyladenine secreted enhanced levels of both IL-1β and IL-23, and supernatants from these cells stimulated the innate secretion of IL-17, IFN-γ, and IL-22 by γδ T cells. These data demonstrate that autophagy has a potentially pivotal role to play in the induction and regulation of inflammatory responses by innate immune cells, largely driven by IL-1 and its consequential effects on IL-23 secretion.
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Affiliation(s)
- Celia Peral de Castro
- Immune Regulation Research Group, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College, Dublin 2, Ireland
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222
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Abstract
Uric acid is a waste product of purine catabolism. This molecule comes to clinical attention when it nucleates to form crystals of monosodium urate (MSU) in joints or other tissues, and thereby causes the inflammatory disease of gout. Patients with gout frequently suffer from a number of comorbid conditions including hypertension, diabetes mellitus and cardiovascular disease. Why MSU crystals trigger inflammation and are associated with comorbidities of gout has been unclear, but recent studies provide new insights into these issues. Rather than simply being a waste product, uric acid could serve a pathophysiological role as a local alarm signal that alerts the immune system to cell injury and helps to trigger both innate and adaptive immune responses. The inflammatory component of these immune responses is caused when urate crystals trigger both inflammasome-dependent and independent pathways to generate the proinflammatory cytokine IL-1. The resulting bioactive IL-1 stimulates the inflammation of gout and might contribute to the development of other comorbidities. Surprisingly, the same mechanisms underlie the inflammatory response to a number of irritant particles, many of which also cause disease. These new insights help to explain the pathogenesis of gout and point to potential new therapeutic targets for this and other sterile inflammatory diseases.
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223
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Nasti TH, Timares L. Inflammasome activation of IL-1 family mediators in response to cutaneous photodamage. Photochem Photobiol 2012; 88:1111-25. [PMID: 22631445 DOI: 10.1111/j.1751-1097.2012.01182.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Although keratinocytes are relatively resistant to ultraviolet radiation (UVR) induced damage, repeated UVR exposure result in accumulated DNA mutations that can lead to epidermal malignancies. Keratinocytes play a central role in elaborating innate responses that lead to inflammation and influence the generation of adaptive immune responses in skin. Apart from the minor cellular constituents of the epidermis, specifically Langerhans cells and melanocytes, keratinocytes are the major source of cytokines. UVR exposure stimulates keratinocytes to secrete abundant pro-inflammatory IL-1-family proteins, IL-1α, IL-1β, IL-18, and IL-33. Normal skin contains only low levels of inactive precursor forms of IL-1β and IL-18, which require caspase 1-mediated proteolysis for their maturation and secretion. However, caspase-1 activation is not constitutive, but dependents on the UV-induced formation of an active inflammasome complex. IL-1 family cytokines can induce a secondary cascade of mediators and cytokines from keratinocytes and other cells resulting in wide range of innate processes including infiltration of inflammatory leukocytes, induction of immunosuppression, DNA repair or apoptosis. Thus, the ability of keratinocytes to produce a wide repertoire of proinflammatory cytokines can influence the immune response locally as well as systematically, and alter the host response to photodamaged cells. We will highlight differential roles played by each IL-1 family molecule generated by UV-damaged keratinocytes, and reveal their complementary influences in modulating acute inflammatory and immunological events that follow cutaneous UV exposure.
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Affiliation(s)
- Tahseen H Nasti
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL, USA
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224
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Interleukin-1R signaling is essential for induction of proapoptotic CD8 T cells, viral clearance, and pathology during lymphocytic choriomeningitis virus infection in mice. J Virol 2012; 86:8713-9. [PMID: 22674984 DOI: 10.1128/jvi.00682-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The T cell granule exocytosis pathway is essential to control hepatotropic lymphocytic choriomeningitis virus strain WE (LCMV-WE) but also contributes to the observed pathology in mice. Although effective antiviral T cell immunity and development of viral hepatitis are strictly dependent on perforin and granzymes, the molecular basis underlying induction of functionally competent virus-immune T cells, including participation of the innate immune system, is far from being resolved. We demonstrate here that LCMV-immune T cells of interleukin-1 receptor (IL-1R)-deficient mice readily express transcripts for perforin and granzymes but only translate perforin, resulting in the lack of proapoptotic potential in vitro. LCMV is not cleared in IL-1R-deficient mice, and yet the infected mice develop neither splenomegaly nor hepatitis. These results demonstrate that IL-1R signaling is central to the induction of proapoptotic CD8 T cell immunity, including viral clearance and associated tissue injuries in LCMV infection.
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225
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Boivin WA, Shackleford M, Vanden Hoek A, Zhao H, Hackett TL, Knight DA, Granville DJ. Granzyme B cleaves decorin, biglycan and soluble betaglycan, releasing active transforming growth factor-β1. PLoS One 2012; 7:e33163. [PMID: 22479366 PMCID: PMC3316562 DOI: 10.1371/journal.pone.0033163] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 02/10/2012] [Indexed: 11/18/2022] Open
Abstract
Objective Granzyme B (GrB) is a pro-apoptotic serine protease that contributes to immune-mediated target cell apoptosis. However, during inflammation, GrB accumulates in the extracellular space, retains its activity, and is capable of cleaving extracellular matrix (ECM) proteins. Recent studies have implicated a pathogenic extracellular role for GrB in cardiovascular disease, yet the pathophysiological consequences of extracellular GrB activity remain largely unknown. The objective of this study was to identify proteoglycan (PG) substrates of GrB and examine the ability of GrB to release PG-sequestered TGF-β1 into the extracellular milieu. Methods/Results Three extracellular GrB PG substrates were identified; decorin, biglycan and betaglycan. As all of these PGs sequester active TGF-β1, cytokine release assays were conducted to establish if GrB-mediated PG cleavage induced TGF-β1 release. Our data confirmed that GrB liberated TGF-β1 from all three substrates as well as from endogenous ECM and this process was inhibited by the GrB inhibitor 3,4-dichloroisocoumarin. The released TGF-β1 retained its activity as indicated by the induction of SMAD-3 phosphorylation in human coronary artery smooth muscle cells. Conclusion In addition to contributing to ECM degradation and the loss of tissue structural integrity in vivo, increased extracellular GrB activity is also capable of inducing the release of active TGF-β1 from PGs.
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MESH Headings
- Biglycan/metabolism
- Biocatalysis/drug effects
- Blotting, Western
- Cells, Cultured
- Coumarins/pharmacology
- Decorin/metabolism
- Extracellular Matrix/metabolism
- Extracellular Space/metabolism
- Granzymes/antagonists & inhibitors
- Granzymes/metabolism
- Humans
- Isocoumarins
- Kinetics
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Phosphorylation/drug effects
- Proteoglycans/chemistry
- Proteoglycans/metabolism
- Receptors, Transforming Growth Factor beta/chemistry
- Receptors, Transforming Growth Factor beta/metabolism
- Serine Proteinase Inhibitors/pharmacology
- Smad3 Protein/metabolism
- Solubility
- Substrate Specificity
- Transforming Growth Factor beta1/metabolism
- Transforming Growth Factor beta1/pharmacology
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Affiliation(s)
- Wendy A. Boivin
- UBC James Hogg Research Centre, Institute for Heart+Lung Health, St. Paul's Hospital, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Marlo Shackleford
- UBC James Hogg Research Centre, Institute for Heart+Lung Health, St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Amanda Vanden Hoek
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Hongyan Zhao
- UBC James Hogg Research Centre, Institute for Heart+Lung Health, St. Paul's Hospital, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tillie L. Hackett
- UBC James Hogg Research Centre, Institute for Heart+Lung Health, St. Paul's Hospital, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Darryl A. Knight
- UBC James Hogg Research Centre, Institute for Heart+Lung Health, St. Paul's Hospital, Vancouver, British Columbia, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David J. Granville
- UBC James Hogg Research Centre, Institute for Heart+Lung Health, St. Paul's Hospital, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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226
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McElhaney JE, Zhou X, Talbot HK, Soethout E, Bleackley RC, Granville DJ, Pawelec G. The unmet need in the elderly: how immunosenescence, CMV infection, co-morbidities and frailty are a challenge for the development of more effective influenza vaccines. Vaccine 2012; 30:2060-7. [PMID: 22289511 DOI: 10.1016/j.vaccine.2012.01.015] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 12/31/2011] [Accepted: 01/05/2012] [Indexed: 12/22/2022]
Abstract
Influenza remains the single most important cause of excess disability and mortality during the winter months. In spite of widespread influenza vaccination programs leading to demonstrated cost-savings in the over 65 population, hospitalization and death rates for acute respiratory illnesses continue to rise. As a person ages, increased serum levels of inflammatory cytokines are commonly recorded (TNF-α, IL-1, IL-6). Termed "inflammaging", this has been linked to persistent cytomegalovirus (CMV) infection and immune senescence, while increased anti-inflammatory cytokines (IL-10, TGF-β) are possibly associated with more healthy aging. Paradoxically, a shift with aging toward an anti-inflammatory (IL-10) response and decline in the IFN-γ:IL-10 ratio in influenza-challenged peripheral blood mononuclear cells is associated with a decline in the cytolytic capacity of CD8+ T cells responsible for clearing influenza virus from infected lung tissue. Thus, it is seemingly counter intuitive that the immune phenotype of healthy aging predicts a poor cell-mediated immune response and more serious outcomes of influenza. Herein we postulate a mechanistic link between the accumulation of late-stage, potentially terminally differentiated T cells, many or most of which result from CMV infection, and the immunopathogenesis of influenza infection, mediated by granzyme B in older adults. Further, adjuvanted influenza vaccines that stimulate inflammatory cytokines and suppress the IL-10 response to influenza challenge, would be expected to enhance protection in the 65+ population.
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Affiliation(s)
- Janet E McElhaney
- Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, BC, Canada.
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227
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IL-33 is processed into mature bioactive forms by neutrophil elastase and cathepsin G. Proc Natl Acad Sci U S A 2012; 109:1673-8. [PMID: 22307629 DOI: 10.1073/pnas.1115884109] [Citation(s) in RCA: 453] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Interleukin-33 (IL-33) (NF-HEV) is a chromatin-associated nuclear cytokine from the IL-1 family, which has been linked to important diseases, including asthma, rheumatoid arthritis, ulcerative colitis, and cardiovascular diseases. IL-33 signals through the ST2 receptor and drives cytokine production in type 2 innate lymphoid cells (ILCs) (natural helper cells, nuocytes), T-helper (Th)2 lymphocytes, mast cells, basophils, eosinophils, invariant natural killer T (iNKT), and natural killer (NK) cells. We and others recently reported that, unlike IL-1β and IL-18, full-length IL-33 is biologically active independently of caspase-1 cleavage and that processing by caspases results in IL-33 inactivation. We suggested that IL-33, which is released upon cellular damage, may function as an endogenous danger signal or alarmin, similar to IL-1α or high-mobility group box 1 protein (HMGB1). Here, we investigated the possibility that IL-33 activity may be regulated by proteases released during inflammation. Using a combination of in vitro and in vivo approaches, we demonstrate that neutrophil serine proteases cathepsin G and elastase can cleave full-length human IL-33(1-270) and generate mature forms IL-33(95-270), IL-33(99-270), and IL-33(109-270). These forms are produced by activated human neutrophils ex vivo, are biologically active in vivo, and have a ~10-fold higher activity than full-length IL-33 in cellular assays. Murine IL-33 is also cleaved by neutrophil cathepsin G and elastase, and both full-length and cleaved endogenous IL-33 could be detected in the bronchoalveolar lavage fluid in an in vivo model of acute lung injury associated with neutrophil infiltration. We propose that the inflammatory microenvironment may exacerbate disease-associated functions of IL-33 through the generation of highly active mature forms.
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