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Wu J, Sun X, Jiang P. Metabolism-inflammasome crosstalk shapes innate and adaptive immunity. Cell Chem Biol 2024; 31:884-903. [PMID: 38759617 DOI: 10.1016/j.chembiol.2024.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 04/08/2024] [Accepted: 04/16/2024] [Indexed: 05/19/2024]
Abstract
Inflammasomes are a central component of innate immunity and play a vital role in regulating innate immune response. Activation of inflammasomes is also indispensable for adaptive immunity, modulating the development and response of adaptive immunity. Recently, increasing studies have shown that metabolic alterations and adaptations strongly influence and regulate the differentiation and function of the immune system. In this review, we will take a holistic view of how inflammasomes bridge innate and adaptive (especially T cell) immunity and how inflammasomes crosstalk with metabolic signals during the immune responses. And, special attention will be paid to the metabolic control of inflammasome-mediated interactions between innate and adaptive immunity in disease. Understanding the metabolic regulatory functions of inflammasomes would provide new insights into future research directions in this area and may help to identify potential targets for inflammasome-associated diseases and broaden therapeutic avenues.
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Affiliation(s)
- Jun Wu
- School of Pharmaceutical Sciences, Xiamen University, Xiamen 361102, Fujian, China; State Key Laboratory of Molecular Oncology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Center for Life Sciences, Beijing 100084, China
| | - Xuan Sun
- State Key Laboratory of Molecular Oncology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Center for Life Sciences, Beijing 100084, China
| | - Peng Jiang
- State Key Laboratory of Molecular Oncology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Center for Life Sciences, Beijing 100084, China.
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2
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Challagundla N, Saha B, Agrawal-Rajput R. Insights into inflammasome regulation: cellular, molecular, and pathogenic control of inflammasome activation. Immunol Res 2022; 70:578-606. [PMID: 35610534 DOI: 10.1007/s12026-022-09286-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 05/04/2022] [Indexed: 02/07/2023]
Abstract
Maintenance of immune homeostasis is an intricate process wherein inflammasomes play a pivotal role by contributing to innate and adaptive immune responses. Inflammasomes are ensembles of adaptor proteins that can trigger a signal following innate sensing of pathogens or non-pathogens eventuating in the inductions of IL-1β and IL-18. These inflammatory cytokines substantially influence the antigen-presenting cell's costimulatory functions and T helper cell differentiation, contributing to adaptive immunity. As acute and chronic disease conditions may accompany parallel tissue damage, we analyze the critical role of extracellular factors such as cytokines, amyloids, cholesterol crystals, etc., intracellular metabolites, and signaling molecules regulating inflammasome activation/inhibition. We develop an operative framework for inflammasome function and regulation by host cell factors and pathogens. While inflammasomes influence the innate and adaptive immune components' interplay modulating the anti-pathogen adaptive immune response, pathogens may target inflammasome inhibition as a survival strategy. As trapped between health and diseases, inflammasomes serve as promising therapeutic targets and their modus operandi serves as a scientific rationale for devising better therapeutic strategies.
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Affiliation(s)
- Naveen Challagundla
- Immunology lab, Indian Institute of Advanced Research, Gandhinagar, Gujarat, 382007, India
| | - Bhaskar Saha
- National Centre for Cell Science, Lab-5, Ganeshkhind, Pune, Maharashtra, 411007, India
| | - Reena Agrawal-Rajput
- Immunology lab, Indian Institute of Advanced Research, Gandhinagar, Gujarat, 382007, India.
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3
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Praetorius H. The bacteria and the host: a story of purinergic signaling in urinary tract infections. Am J Physiol Cell Physiol 2021; 321:C134-C146. [PMID: 33979212 DOI: 10.1152/ajpcell.00054.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The local environment forces a selection of bacteria that might invade the urinary tract, allowing only the most virulent to access the kidney. Quite similar to the diet in setting the stage for the gut microbiome, renal function determines the conditions for bacteria-host interaction in the urinary tract. In the kidney, the term local environment or microenvironment is completely justified because the environment literally changes within a few micrometers. The precise composition of the urine is a function of the epithelium lining the microdomain, and the microenvironment in the kidney shows more variation in the content of nutrients, ion composition, osmolality, and pH than any other site of bacteria-host interaction. This review will cover some of the aspects of bacterial-host interaction in this unique setting and how uropathogenic bacteria can alter the condition for bacteria-host interaction. There will be a particular focus on the recent findings regarding how bacteria specifically trigger host paracrine signaling, via release of extracellular ATP and activation of P2 purinergic receptors. These finding will be discussed from the perspective of severe urinary tract infections, including pyelonephritis and urosepsis.
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Nilsson J, Hörnberg M, Schmidt-Christensen A, Linde K, Nilsson M, Carlus M, Erttmann SF, Mayans S, Holmberg D. NKT cells promote both type 1 and type 2 inflammatory responses in a mouse model of liver fibrosis. Sci Rep 2020; 10:21778. [PMID: 33311540 PMCID: PMC7732838 DOI: 10.1038/s41598-020-78688-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 11/27/2020] [Indexed: 12/27/2022] Open
Abstract
Sterile liver inflammation and fibrosis are associated with many liver disorders of different etiologies. Both type 1 and type 2 inflammatory responses have been reported to contribute to liver pathology. However, the mechanisms controlling the balance between these responses are largely unknown. Natural killer T (NKT) cells can be activated to rapidly secrete cytokines and chemokines associated with both type 1 and type 2 inflammatory responses. As these proteins have been reported to accumulate in different types of sterile liver inflammation, we hypothesized that these cells may play a role in this pathological process. We have found that a transgenic NKT (tgNKT) cell population produced in the immunodeficient 2,4αβNOD.Rag2−/− mice, but not in 2,4αβNOD.Rag2+/− control mice, promoted a type 1 inflammatory response with engagement of the NOD-, LRR- and pyrin domain-containing protein-3 (NLRP3) inflammasome. The induction of the type 1 inflammatory response was followed by an altered cytokine profile of the tgNKT cell population with a biased production of anti-inflammatory/profibrotic cytokines and development of liver fibrosis. These findings illustrate how the plasticity of NKT cells modulates the inflammatory response, suggesting a key role for the NKT cell population in the control of sterile liver inflammation.
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Affiliation(s)
- Julia Nilsson
- Department of Experimental Medical Sciences, Lund University Diabetes Center, Clinical Research Center, Lund University, Jan Waldenströms gata 35, 214 28, Malmö, Sweden.,InfiCure Bio AB, Tvistevägen 48 C, 907 36, Umeå, Sweden
| | | | - Anja Schmidt-Christensen
- Department of Experimental Medical Sciences, Lund University Diabetes Center, Clinical Research Center, Lund University, Jan Waldenströms gata 35, 214 28, Malmö, Sweden
| | - Kajsa Linde
- InfiCure Bio AB, Tvistevägen 48 C, 907 36, Umeå, Sweden
| | - Maria Nilsson
- Department of Experimental Medical Sciences, Lund University Diabetes Center, Clinical Research Center, Lund University, Jan Waldenströms gata 35, 214 28, Malmö, Sweden
| | - Marine Carlus
- Carlus Pathology Consulting, 2 rue de la Libération, 76630, Bellengreville, France
| | - Saskia F Erttmann
- Department of Molecular Biology, Umeå University, 901 87, Umeå, Sweden
| | - Sofia Mayans
- InfiCure Bio AB, Tvistevägen 48 C, 907 36, Umeå, Sweden
| | - Dan Holmberg
- Department of Experimental Medical Sciences, Lund University Diabetes Center, Clinical Research Center, Lund University, Jan Waldenströms gata 35, 214 28, Malmö, Sweden. .,InfiCure Bio AB, Tvistevägen 48 C, 907 36, Umeå, Sweden.
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5
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Sandall CF, Ziehr BK, MacDonald JA. ATP-Binding and Hydrolysis in Inflammasome Activation. Molecules 2020; 25:molecules25194572. [PMID: 33036374 PMCID: PMC7583971 DOI: 10.3390/molecules25194572] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/02/2020] [Accepted: 10/03/2020] [Indexed: 02/06/2023] Open
Abstract
The prototypical model for NOD-like receptor (NLR) inflammasome assembly includes nucleotide-dependent activation of the NLR downstream of pathogen- or danger-associated molecular pattern (PAMP or DAMP) recognition, followed by nucleation of hetero-oligomeric platforms that lie upstream of inflammatory responses associated with innate immunity. As members of the STAND ATPases, the NLRs are generally thought to share a similar model of ATP-dependent activation and effect. However, recent observations have challenged this paradigm to reveal novel and complex biochemical processes to discern NLRs from other STAND proteins. In this review, we highlight past findings that identify the regulatory importance of conserved ATP-binding and hydrolysis motifs within the nucleotide-binding NACHT domain of NLRs and explore recent breakthroughs that generate connections between NLR protein structure and function. Indeed, newly deposited NLR structures for NLRC4 and NLRP3 have provided unique perspectives on the ATP-dependency of inflammasome activation. Novel molecular dynamic simulations of NLRP3 examined the active site of ADP- and ATP-bound models. The findings support distinctions in nucleotide-binding domain topology with occupancy of ATP or ADP that are in turn disseminated on to the global protein structure. Ultimately, studies continue to reveal how the ATP-binding and hydrolysis properties of NACHT domains in different NLRs integrate with signaling modules and binding partners to control innate immune responses at the molecular level.
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Comparison of mRNA Expression of P2X Receptor Subtypes in Different Arterial Tissues of Rats. Biochem Genet 2020; 58:677-690. [PMID: 32385670 DOI: 10.1007/s10528-020-09968-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 04/24/2020] [Indexed: 10/24/2022]
Abstract
This study aims to compare the expression of P2X receptor subtype mRNA in different arterial tissues of rats. After the rats were sacrificed, the internal carotid, pulmonary, thoracic aorta, mesenteric and caudal arteries were dissected out. Then, the P2X receptor mRNA expression in different blood vessels was detected by reverse transcription-polymerase chain reaction (RT-PCR) and real-time quantitative polymerase chain reaction. The P2X1, P2X4 and P2X7 receptor mRNA amplification products revealed specific bands of the same size as the amplified target fragment in their respective lanes, while the P2X2, P2X3, P2X5 and P2X6 receptor mRNA amplification products did not reveal significant specific bands in their respective lanes by RT-PCR. Based on the P2X1 receptor mRNA expression of the mesenteric artery, there were no significant differences in the internal carotid, pulmonary and thoracic aorta (0.64 ± 0.07, 0.17 ± 0.11 and 1.49 ± 0.65, respectively). However, the P2X1 receptor mRNA expression level in the caudal artery significantly increased (11.06 ± 1.99, P < 0.01). Furthermore, there was no difference in P2X4 receptor mRNA expression among these five blood vessels (P > 0.05). The P2X7 receptor mRNA expression level was significantly different: pulmonary artery < tail artery = thoracic aorta < internal carotid artery < mesenteric artery. The relative P2X1 receptor mRNA expression in the caudal artery was observed to be elevated when compared to that of the internal carotid, pulmonary and thoracic aorta as well as the mesenteric arteries. The P2X7 receptor mRNA expression level is pulmonary artery < caudal artery = thoracic aorta < internal carotid artery < mesenteric artery. P2X4 receptor mRNA expression was not significantly different among these five blood vessels.
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Donado CA, Cao AB, Simmons DP, Croker BA, Brennan PJ, Brenner MB. A Two-Cell Model for IL-1β Release Mediated by Death-Receptor Signaling. Cell Rep 2020; 31:107466. [PMID: 32268091 PMCID: PMC7192215 DOI: 10.1016/j.celrep.2020.03.030] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 12/19/2019] [Accepted: 03/10/2020] [Indexed: 01/22/2023] Open
Abstract
Interleukin-1β (IL-1β) is a key orchestrator of anti-microbial immunity whose secretion is typically dependent on activation of inflammasomes. However, many pathogens have evolved strategies to evade inflammasome activation. Here we describe an alternative, two-cell model for IL-1β release where invariant natural killer T (iNKT) cells use the death receptor pathway to instruct antigen-presenting cells to secrete IL-1β. Following cognate interactions with TLR-primed bone marrow-derived dendritic cells (BMDCs), iNKT cells rapidly translocate intracellular Fas ligand to the surface to engage Fas on BMDCs. Fas ligation activates a caspase-8-dependent signaling cascade in BMDCs that drives IL-1β release largely independent of inflammasomes. The apoptotic program initiated by Fas ligation rapidly transitions into a pyroptosis-like form of cell death mediated by gasdermin D. Together, our findings support a two-cell model for IL-1β secretion that may supersede inflammasome activation when cytosolic triggers fail.
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Affiliation(s)
- Carlos A Donado
- Division of Rheumatology, Inflammation and Immunity, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA; Division of Medical Sciences, Harvard Medical School, Boston, MA 02115, USA
| | - Anh B Cao
- Division of Medical Sciences, Harvard Medical School, Boston, MA 02115, USA
| | - Daimon P Simmons
- Department of Pathology, Brigham and Women's and Harvard Medical School, Boston, MA 02115, USA
| | - Ben A Croker
- Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA; Division of Allergy, Immunology & Rheumatology, Department of Pediatrics, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Patrick J Brennan
- Division of Allergy and Clinical Immunology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
| | - Michael B Brenner
- Division of Rheumatology, Inflammation and Immunity, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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Cortesi F, Delfanti G, Casorati G, Dellabona P. The Pathophysiological Relevance of the iNKT Cell/Mononuclear Phagocyte Crosstalk in Tissues. Front Immunol 2018; 9:2375. [PMID: 30369933 PMCID: PMC6194905 DOI: 10.3389/fimmu.2018.02375] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/24/2018] [Indexed: 12/14/2022] Open
Abstract
CD1d-restricted Natural Killer T (NKT) cells are regarded as sentinels of tissue integrity by sensing local cell stress and damage. This occurs via recognition of CD1d-restricted lipid antigens, generated by stress-related metabolic changes, and stimulation by inflammatory cytokines, such as IL-12 and IL-18. Increasing evidence suggest that this occurs mainly upon NKT cell interaction with CD1d-expressing cells of the Mononuclear Phagocytic System, i.e., monocytes, macrophages and DCs, which patrol parenchymatous organs and mucosae to maintain tissue homeostasis and immune surveillance. In this review, we discuss critical examples of this crosstalk, presenting the known underlying mechanisms and their effects on both cell types and the environment, and suggest that the interaction with CD1d-expressing mononuclear phagocytes in tissues is the fundamental job of NKT cells.
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Affiliation(s)
- Filippo Cortesi
- Experimental Immunology Unit, Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Gloria Delfanti
- Experimental Immunology Unit, Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, Milan, Italy.,Università Vita-Salute San Raffaele, Milan, Italy
| | - Giulia Casorati
- Experimental Immunology Unit, Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Paolo Dellabona
- Experimental Immunology Unit, Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, Milan, Italy
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Bedard M, Salio M, Cerundolo V. Harnessing the Power of Invariant Natural Killer T Cells in Cancer Immunotherapy. Front Immunol 2017; 8:1829. [PMID: 29326711 PMCID: PMC5741693 DOI: 10.3389/fimmu.2017.01829] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 12/04/2017] [Indexed: 12/19/2022] Open
Abstract
Invariant natural killer T (iNKT) cells are a distinct subset of innate-like lymphocytes bearing an invariant T-cell receptor, through which they recognize lipid antigens presented by monomorphic CD1d molecules. Upon activation, iNKT cells are capable of not only having a direct effector function but also transactivating NK cells, maturing dendritic cells, and activating B cells, through secretion of several cytokines and cognate TCR-CD1d interaction. Endowed with the ability to orchestrate an all-encompassing immune response, iNKT cells are critical in shaping immune responses against pathogens and cancer cells. In this review, we examine the critical role of iNKT cells in antitumor responses from two perspectives: (i) how iNKT cells potentiate antitumor immunity and (ii) how CD1d+ tumor cells may modulate their own expression of CD1d molecules. We further explore hypotheses to explain iNKT cell activation in the context of cancer and how the antitumor effects of iNKT cells can be exploited in different forms of cancer immunotherapy, including their role in the development of cancer vaccines.
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Affiliation(s)
- Melissa Bedard
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Mariolina Salio
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Vincenzo Cerundolo
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
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10
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How Inflammasomes Inform Adaptive Immunity. J Mol Biol 2017; 430:217-237. [PMID: 28987733 DOI: 10.1016/j.jmb.2017.09.019] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 09/27/2017] [Accepted: 09/28/2017] [Indexed: 02/07/2023]
Abstract
An immune response consists of a finely orchestrated interplay between initial recognition of potential microbial threats by the innate immune system and subsequent licensed adaptive immune neutralization. The initial recognition integrates environmental cues derived from pathogen-associated molecular patterns and cell-intrinsic damage-associated molecular patterns to contextualize the insult and inform a tailored adaptive response via T and B lymphocytes. While there are much data to support the role of transcriptional responses downstream of pattern recognition receptors in informing the adaptive immune response, markedly less attention has been paid to the role of post-translational responses to pathogen-associated molecular pattern and damage-associated molecular pattern recognition by the innate immune system, and how this may influence adaptive immunity. A well-characterized post-translational consequence of pattern recognition receptor signaling is the assembly of a multimeric signaling platform, termed the inflammasome, by members of the nucleotide-binding oligomerization domain (Nod), leucine-rich repeat-containing receptors (NLRs), and pyrin and HIN domain (PYHIN) families. Inflammasomes assemble in response to cytosolic perturbations, such as mitochondrial dysfunction and aberrant ion fluxes in the case of the canonical NLRP3 inflammasome or the presence of bacterial lipopolysaccharides in the case of the non-canonical inflammasome. Assembly of the inflammasome allows for the cleavage and activation of inflammatory caspases. These activated inflammatory caspases in turn cleave pro-form inflammatory cytokines into their mature bioactive species and lead to unconventional protein secretion and lytic cell death. In this review, we discuss evidence for inflammasome-mediated instruction and contextualization of infectious and sterile agents to the adaptive immune system.
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Greve AS, Skals M, Fagerberg SK, Tonnus W, Ellermann-Eriksen S, Evans RJ, Linkermann A, Praetorius HA. P2X 1, P2X 4, and P2X 7 Receptor Knock Out Mice Expose Differential Outcome of Sepsis Induced by α-Haemolysin Producing Escherichia coli. Front Cell Infect Microbiol 2017; 7:113. [PMID: 28428949 PMCID: PMC5382212 DOI: 10.3389/fcimb.2017.00113] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 03/21/2017] [Indexed: 11/13/2022] Open
Abstract
α-haemolysin (HlyA)-producing Escherichia coli commonly inflict severe urinary tract infections, including pyelonephritis, which comprises substantial risk for sepsis. In vitro, the cytolytic effect of HlyA is mainly mediated by ATP release through the HlyA pore and subsequent P2X1/P2X7 receptor activation. This amplification of the lytic process is not unique to HlyA but is observed by many other pore-forming proteins including complement-induced haemolysis. Since free hemoglobin in the blood is known to be associated with a worse outcome in sepsis one could speculate that inhibition of P2X receptors would ameliorate the course of sepsis. Surprisingly, this study demonstrates that [Formula: see text] and [Formula: see text] mice are exceedingly sensitive to sepsis with uropathogenic E. coli. These mice have markedly lower survival, higher cytokine levels and activated intravascular coagulation. Quite the reverse is seen in [Formula: see text] mice, which had markedly lower cytokine levels and less coagulation activation compared to controls after exposure to uropathogenic E. coli. The high cytokine levels in the [Formula: see text] mouse are unexpected, since P2X7 is implicated in caspase-1-dependent IL-1β production. Here, we demonstrate that IL-1β production during sepsis with uropathogenic E. coli is mediated by caspase-8, since caspase-8 and RIPK3 double knock out mice show substantially lower cytokine during sepsis and increased survival after injection of TNFα. These data support that P2X7 and P2X4 receptor activation has a protective effect during severe E. coli infection.
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Affiliation(s)
| | - Marianne Skals
- Department of Biomedicine, Aarhus UniversityAarhus, Denmark.,Department of Clinical Microbiology, Aarhus University HospitalAarhus, Denmark
| | | | - Wulf Tonnus
- Division of Nephrology, Medical Clinic III, University Hospital Carl Gustav Carus DresdenDresden, Germany
| | | | - Richard J Evans
- Department of Molecular and Cell Biology, University of LeicesterLeicester, UK
| | - Andreas Linkermann
- Division of Nephrology, Medical Clinic III, University Hospital Carl Gustav Carus DresdenDresden, Germany
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Alternative inflammasome activation enables IL-1β release from living cells. Curr Opin Immunol 2016; 44:7-13. [PMID: 27842238 DOI: 10.1016/j.coi.2016.10.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 10/28/2016] [Indexed: 12/11/2022]
Abstract
Classical modes of NLRP3 activation entail a priming step that enables its activation (signal 1) and a potassium efflux-dependent activation signal (signal 2) that triggers pyroptosome formation and pyroptosis, a lytic cell death necessary for IL-1β release. Opposing to that, human monocytes engage an alternative NLRP3 inflammasome pathway in response to LPS that proceeds in the absence of signal 2 activation and enables IL-1β secretion without pyroptosis. This specifically relies on Caspase-8 to propagate signaling to NLRP3, leading to inflammasome activation in absence of pyroptosome formation. Here, we summarize the current knowledge about alternative inflammasome activation, discuss potential extensions of this signaling entity beyond LPS-dependent activation, speculate about its role in tissue homeostasis and sterile inflammation and highlight the implications of pyroptosis-independent IL-1β secretion.
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