RESUMO
Inflammatory caspase sensing of cytosolic lipopolysaccharide (LPS) triggers pyroptosis and the concurrent release of damage-associated molecular patterns (DAMPs). Collectively, DAMPs are key determinants that shape the aftermath of inflammatory cell death. However, the identity and function of the individual DAMPs released are poorly defined. Our proteomics study revealed that cytosolic LPS sensing triggered the release of galectin-1, a ß-galactoside-binding lectin. Galectin-1 release is a common feature of inflammatory cell death, including necroptosis. In vivo studies using galectin-1-deficient mice, recombinant galectin-1 and galectin-1-neutralizing antibody showed that galectin-1 promotes inflammation and plays a detrimental role in LPS-induced lethality. Mechanistically, galectin-1 inhibition of CD45 (Ptprc) underlies its unfavorable role in endotoxin shock. Finally, we found increased galectin-1 in sera from human patients with sepsis. Overall, we uncovered galectin-1 as a bona fide DAMP released as a consequence of cytosolic LPS sensing, identifying a new outcome of inflammatory cell death.
Assuntos
Alarminas/metabolismo , Endotoxemia/imunologia , Galectina 1/metabolismo , Mediadores da Inflamação/metabolismo , Inflamação/imunologia , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Macrófagos/metabolismo , Proteínas de Ligação a Fosfato/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Alarminas/deficiência , Alarminas/genética , Animais , Estudos de Casos e Controles , Modelos Animais de Doenças , Endotoxemia/induzido quimicamente , Endotoxemia/metabolismo , Endotoxemia/patologia , Feminino , Galectina 1/sangue , Galectina 1/deficiência , Galectina 1/genética , Células HeLa , Humanos , Inflamação/induzido quimicamente , Inflamação/metabolismo , Inflamação/patologia , Peptídeos e Proteínas de Sinalização Intracelular/deficiência , Peptídeos e Proteínas de Sinalização Intracelular/genética , Antígenos Comuns de Leucócito/metabolismo , Lipopolissacarídeos , Macrófagos/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pessoa de Meia-Idade , Necroptose , Proteínas de Ligação a Fosfato/deficiência , Proteínas de Ligação a Fosfato/genética , Células RAW 264.7 , Sepse/sangue , Sepse/diagnóstico , Transdução de Sinais , Regulação para CimaRESUMO
An important property of the host innate immune response during microbial infection is its ability to control the expression of antimicrobial effector proteins, but how this occurs post-transcriptionally is not well defined. Here, we describe a critical antibacterial role for the classic antiviral gene 2'-5'-oligoadenylate synthetase 1 (OAS1). Human OAS1 and its mouse ortholog, Oas1b, are induced by interferon-γ and protect against cytosolic bacterial pathogens such as Francisella novicida and Listeria monocytogenes in vitro and in vivo. Proteomic and transcriptomic analysis showed reduced IRF1 protein expression in OAS1-deficient cells. Mechanistically, OAS1 binds and localizes IRF1 mRNA to the rough endoplasmic reticulum (ER)-Golgi endomembranes, licensing effective translation of IRF1 mRNA without affecting its transcription or decay. OAS1-dependent translation of IRF1 leads to the enhanced expression of antibacterial effectors, such as GBPs, which restrict intracellular bacteria. These findings uncover a noncanonical function of OAS1 in antibacterial innate immunity.
Assuntos
2',5'-Oligoadenilato Sintetase , Imunidade Inata , Fator Regulador 1 de Interferon , 2',5'-Oligoadenilato Sintetase/metabolismo , 2',5'-Oligoadenilato Sintetase/genética , Fator Regulador 1 de Interferon/metabolismo , Fator Regulador 1 de Interferon/genética , Animais , Humanos , Camundongos , Biossíntese de Proteínas/imunologia , Listeria monocytogenes/imunologia , Camundongos Knockout , Camundongos Endogâmicos C57BL , Listeriose/imunologia , Interferon gama/metabolismo , Interferon gama/imunologiaRESUMO
IRF8 is a master transcription factor for immune cell development. In this issue, Karki et al. reveal that IRF8 governs the constitutive expression of genes encoding for NAIP proteins that are critical for the innate immune sensing of bacteria.
Assuntos
Inflamassomos , Proteína Inibidora de Apoptose Neuronal/genética , Diferenciação Celular , Regulação da Expressão Gênica , Fatores Reguladores de Interferon/genéticaRESUMO
Monitoring of the cytosolic compartment by the innate immune system for pathogen-encoded products or pathogen activities often enables the activation of a subset of caspases. In most cases, the cytosolic surveillance pathways are coupled to activation of caspase-1 via canonical inflammasome complexes. A related set of caspases, caspase-11 in rodents and caspase-4 and caspase-5 in humans, monitors the cytosol for bacterial lipopolysaccharide (LPS). Direct activation of caspase-11, caspase-4 and caspase-5 by intracellular LPS elicits the lytic cell death called 'pyroptosis', which occurs in multiple cell types. The pyroptosis is executed by the pore-forming protein GSDMD, which is activated by cleavage mediated by caspase-11, caspase-4 or caspase-5. In monocytes, formation of GSDMD pores can induce activation of the NLRP3 inflammasome for maturation of the cytokines IL-1ß and IL-18. Caspase-11-mediated pyroptosis in response to cytosolic LPS is critical for antibacterial defense and septic shock. Here we review the emerging literature on the sensing of cytosolic LPS and its regulation and pathophysiological functions.
Assuntos
Caspases/imunologia , Citosol/imunologia , Imunidade Inata/imunologia , Lipopolissacarídeos/imunologia , Animais , Caspases/metabolismo , Citosol/metabolismo , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Lipopolissacarídeos/metabolismo , Modelos Imunológicos , Proteínas de Neoplasias/imunologia , Proteínas de Neoplasias/metabolismo , Proteínas de Ligação a Fosfato , Piroptose/imunologiaRESUMO
Canonical activation of the inflammasome is critical to promote caspase-1-dependent maturation of the proinflammatory cytokines IL-1ß and IL-18, as well as to induce pyroptotic cell death in response to pathogens and endogenous danger signals. Recent discoveries, however, are beginning to unveil new components of the inflammasome machinery as well as the full spectrum of inflammasome functions, extending their influence beyond canonical functions to regulation of eicosanoid storm, autophagy, and metabolism. In addition, the receptor components of the inflammasome can also regulate diverse biological processes, such as cellular proliferation, gene transcription, and tumorigenesis, all of which are independent of their inflammasome complex-forming capabilities. Here, we review these recent advances that are shaping our understanding of the complex biology of the inflammasome and its constituents.
Assuntos
Inflamassomos/fisiologia , Transdução de Sinais , Animais , Morte Celular , Humanos , Inflamassomos/imunologia , Inflamação/imunologia , Inflamação/metabolismoRESUMO
Sensing of lipopolysaccharide (LPS) in the cytosol triggers caspase-11 activation and is central to host defense against Gram-negative bacterial infections and to the pathogenesis of sepsis. Most Gram-negative bacteria that activate caspase-11, however, are not cytosolic, and the mechanism by which LPS from these bacteria gains access to caspase-11 in the cytosol remains elusive. Here, we identify outer membrane vesicles (OMVs) produced by Gram-negative bacteria as a vehicle that delivers LPS into the cytosol triggering caspase-11-dependent effector responses in vitro and in vivo. OMVs are internalized via endocytosis, and LPS is released into the cytosol from early endosomes. The use of hypovesiculating bacterial mutants, compromised in their ability to generate OMVs, reveals the importance of OMVs in mediating the cytosolic localization of LPS. Collectively, these findings demonstrate a critical role for OMVs in enabling the cytosolic entry of LPS and, consequently, caspase-11 activation during Gram-negative bacterial infections.
Assuntos
Bactérias Gram-Negativas/citologia , Infecções por Bactérias Gram-Negativas/imunologia , Infecções por Bactérias Gram-Negativas/microbiologia , Lipopolissacarídeos/metabolismo , Animais , Proteínas da Membrana Bacteriana Externa/metabolismo , Citosol/metabolismo , Ativação Enzimática , Bactérias Gram-Negativas/química , Imunidade Inata , Inflamação/imunologia , Inflamação/microbiologia , Interleucina-1/imunologia , CamundongosRESUMO
Gasdermins (GSDMs) are pore-forming proteins that play critical roles in host defence through pyroptosis1,2. Among GSDMs, GSDMB is unique owing to its distinct lipid-binding profile and a lack of consensus on its pyroptotic potential3-7. Recently, GSDMB was shown to exhibit direct bactericidal activity through its pore-forming activity4. Shigella, an intracellular, human-adapted enteropathogen, evades this GSDMB-mediated host defence by secreting IpaH7.8, a virulence effector that triggers ubiquitination-dependent proteasomal degradation of GSDMB4. Here, we report the cryogenic electron microscopy structures of human GSDMB in complex with Shigella IpaH7.8 and the GSDMB pore. The structure of the GSDMB-IpaH7.8 complex identifies a motif of three negatively charged residues in GSDMB as the structural determinant recognized by IpaH7.8. Human, but not mouse, GSDMD contains this conserved motif, explaining the species specificity of IpaH7.8. The GSDMB pore structure shows the alternative splicing-regulated interdomain linker in GSDMB as a regulator of GSDMB pore formation. GSDMB isoforms with a canonical interdomain linker exhibit normal pyroptotic activity whereas other isoforms exhibit attenuated or no pyroptotic activity. Overall, this work sheds light on the molecular mechanisms of Shigella IpaH7.8 recognition and targeting of GSDMs and shows a structural determinant in GSDMB critical for its pyroptotic activity.
Assuntos
Proteínas de Bactérias , Gasderminas , Proteínas Citotóxicas Formadoras de Poros , Animais , Humanos , Camundongos , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/ultraestrutura , Sítios de Ligação , Sequência Conservada , Microscopia Crioeletrônica , Proteínas Citotóxicas Formadoras de Poros/química , Proteínas Citotóxicas Formadoras de Poros/metabolismo , Proteínas Citotóxicas Formadoras de Poros/ultraestrutura , Domínios Proteicos , Isoformas de Proteínas/química , Isoformas de Proteínas/metabolismo , Isoformas de Proteínas/ultraestrutura , Piroptose , Shigella , Especificidade da Espécie , Gasderminas/química , Gasderminas/metabolismo , Gasderminas/ultraestruturaRESUMO
Interferon-inducible human oligoadenylate synthetase-like (OASL) and its mouse ortholog, Oasl2, enhance RNA-sensor RIG-I-mediated type I interferon (IFN) induction and inhibit RNA virus replication. Here, we show that OASL and Oasl2 have the opposite effect in the context of DNA virus infection. In Oasl2-/- mice and OASL-deficient human cells, DNA viruses such as vaccinia, herpes simplex, and adenovirus induced increased IFN production, which resulted in reduced virus replication and pathology. Correspondingly, ectopic expression of OASL in human cells inhibited IFN induction through the cGAS-STING DNA-sensing pathway. cGAS was necessary for the reduced DNA virus replication observed in OASL-deficient cells. OASL directly and specifically bound to cGAS independently of double-stranded DNA, resulting in a non-competitive inhibition of the second messenger cyclic GMP-AMP production. Our findings define distinct mechanisms by which OASL differentially regulates host IFN responses during RNA and DNA virus infection and identify OASL as a negative-feedback regulator of cGAS.
Assuntos
2',5'-Oligoadenilato Sintetase/metabolismo , Infecções por Vírus de DNA/imunologia , Vírus de DNA/fisiologia , Infecções por Vírus de RNA/imunologia , Vírus de RNA/imunologia , 2',5'-Oligoadenilato Sintetase/genética , Animais , AMP Cíclico/metabolismo , Humanos , Interferon Tipo I/genética , Interferon Tipo I/metabolismo , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Nucleotidiltransferases/metabolismo , RNA Interferente Pequeno/genética , Transdução de Sinais , Células THP-1 , Replicação ViralRESUMO
Inflammasome-activated caspase-1 cleaves gasdermin D to unmask its pore-forming activity, the predominant consequence of which is pyroptosis. Here, we report an additional biological role for gasdermin D in limiting cytosolic DNA surveillance. Cytosolic DNA is sensed by Aim2 and cyclic GMP-AMP synthase (cGAS) leading to inflammasome and type I interferon responses, respectively. We found that gasdermin D activated by the Aim2 inflammasome suppressed cGAS-driven type I interferon response to cytosolic DNA and Francisella novicida in macrophages. Similarly, interferon-ß (IFN-ß) response to F. novicida infection was elevated in gasdermin D-deficient mice. Gasdermin D-mediated negative regulation of IFN-ß occurred in a pyroptosis-, interleukin-1 (IL-1)-, and IL-18-independent manner. Mechanistically, gasdermin D depleted intracellular potassium (K+) via membrane pores, and this K+ efflux was necessary and sufficient to inhibit cGAS-dependent IFN-ß response. Thus, our findings have uncovered an additional interferon regulatory module involving gasdermin D and K+ efflux.
Assuntos
Proteínas Reguladoras de Apoptose/metabolismo , Francisella/fisiologia , Infecções por Bactérias Gram-Negativas/imunologia , Inflamassomos/metabolismo , Animais , Apoptose , Proteínas Reguladoras de Apoptose/genética , Dano ao DNA , Proteínas de Ligação a DNA/metabolismo , Células HEK293 , Humanos , Interferon Tipo I/metabolismo , Interleucina-1/metabolismo , Interleucina-18/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Camundongos , Camundongos Knockout , Proteínas de Ligação a Fosfato , Potássio/metabolismo , RNA Interferente Pequeno/genéticaRESUMO
Systemic infections with Gram-negative bacteria are characterized by high mortality rates due to the "sepsis syndrome," a widespread and uncontrolled inflammatory response. Though it is well recognized that the immune response during Gram-negative bacterial infection is initiated after the recognition of endotoxin by Toll-like receptor 4, the molecular mechanisms underlying the detrimental inflammatory response during Gram-negative bacteremia remain poorly defined. Here, we identify a TRIF pathway that licenses NLRP3 inflammasome activation by all Gram-negative bacteria. By engaging TRIF, Gram-negative bacteria activate caspase-11. TRIF activates caspase-11 via type I IFN signaling, an event that is both necessary and sufficient for caspase-11 induction and autoactivation. Caspase-11 subsequently synergizes with the assembled NLRP3 inflammasome to regulate caspase-1 activation and leads to caspase-1-independent cell death. These events occur specifically during infection with Gram-negative, but not Gram-positive, bacteria. The identification of TRIF as a regulator of caspase-11 underscores the importance of TLRs as master regulators of inflammasomes during Gram-negative bacterial infection.
Assuntos
Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Caspases/metabolismo , Citrobacter rodentium/metabolismo , Escherichia coli Êntero-Hemorrágica/metabolismo , Inflamassomos/metabolismo , Interferons/metabolismo , Animais , Proteínas de Transporte/metabolismo , Caspases Iniciadoras , Citrobacter rodentium/imunologia , Escherichia coli Êntero-Hemorrágica/imunologia , Bactérias Gram-Negativas/imunologia , Bactérias Gram-Negativas/metabolismo , Bactérias Gram-Positivas/imunologia , Bactérias Gram-Positivas/metabolismo , Camundongos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Transdução de SinaisRESUMO
Pyroptosis is a programmed necrotic cell death executed by gasdermins, a family of pore-forming proteins. The cleavage of gasdermins by specific proteases enables their pore-forming activity. The activation of the prototype member of the gasdermin family, gasdermin D (GSDMD), is linked to innate immune monitoring by inflammasomes. Additional gasdermins such as GSDMA, GSDMB, GSDMC, and GSDME are activated by inflammasome-independent mechanisms. Pyroptosis is emerging as a key host defense strategy against pathogens. However, excessive pyroptosis causes cytokine storm and detrimental inflammation leading to tissue damage and organ dysfunction. Consequently, dysregulated pyroptotic responses contribute to the pathogenesis of various diseases, including sepsis, atherosclerosis, acute respiratory distress syndrome, and neurodegenerative disorders. This review will discuss the inflammatory consequences of pyroptosis and the mechanisms of pyroptosis-induced tissue damage and disease pathogenesis.
Assuntos
Gasderminas , Piroptose , Humanos , Piroptose/fisiologia , Proteínas de Neoplasias/metabolismo , Apoptose , Inflamação , Inflamassomos , Biomarcadores Tumorais , Proteínas Citotóxicas Formadoras de Poros/metabolismoRESUMO
Interleukin 1 (IL-1) is an important mediator of innate immunity but can also promote inflammatory tissue damage. During chronic infections such as tuberculosis, the beneficial antimicrobial role of IL-1 must be balanced with the need to prevent immunopathology. By exogenously controlling the replication of Mycobacterium tuberculosis in vivo, we obviated the requirement for antimicrobial immunity and discovered that both IL-1 production and infection-induced immunopathology were suppressed by lymphocyte-derived interferon-γ (IFN-γ). This effect was mediated by nitric oxide (NO), which we found specifically inhibited assembly of the NLRP3 inflammasome via thiol nitrosylation. Our data indicate that the NO produced as a result of adaptive immunity is indispensable in modulating the destructive innate inflammatory responses elicited during persistent infections.
Assuntos
Proteínas de Transporte/metabolismo , Interleucina-1beta/metabolismo , Mycobacterium tuberculosis/imunologia , Óxido Nítrico/metabolismo , Tuberculose/imunologia , Animais , Proteínas de Transporte/genética , Células Cultivadas , Humanos , Imunidade Inata , Inflamassomos/metabolismo , Interferon gama/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína 3 que Contém Domínio de Pirina da Família NLR , Óxido Nítrico/imunologia , Modificação Traducional de Proteínas/genética , Modificação Traducional de Proteínas/imunologia , Multimerização Proteica/genética , Multimerização Proteica/imunologia , Transdução de Sinais/genética , Transdução de Sinais/imunologiaRESUMO
Phagocytosis is a fundamental cellular process that is pivotal for immunity as it coordinates microbial killing, innate immune activation and antigen presentation. An essential step in this process is phagosome acidification, which regulates many functions of these organelles that allow phagosomes to participate in processes that are essential to both innate and adaptive immunity. Here we report that acidification of phagosomes containing Gram-positive bacteria is regulated by the NLRP3 inflammasome and caspase-1. Active caspase-1 accumulates on phagosomes and acts locally to control the pH by modulating buffering by the NADPH oxidase NOX2. These data provide insight into a mechanism by which innate immune signals can modify cellular defenses and establish a new function for the NLRP3 inflammasome and caspase-1 in host defense.
Assuntos
Proteínas de Transporte/imunologia , Caspase 1/imunologia , Inflamassomos/imunologia , Glicoproteínas de Membrana/imunologia , NADPH Oxidases/imunologia , Fagossomos/imunologia , Animais , Proteínas de Transporte/metabolismo , Caspase 1/metabolismo , Células Cultivadas , Ativação Enzimática/imunologia , Citometria de Fluxo , Células HEK293 , Interações Hospedeiro-Patógeno/imunologia , Humanos , Concentração de Íons de Hidrogênio , Immunoblotting , Inflamassomos/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Macrófagos/microbiologia , Glicoproteínas de Membrana/metabolismo , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Microscopia Confocal , Microscopia Eletrônica , NADPH Oxidase 2 , NADPH Oxidases/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR , Fagocitose/imunologia , Fagossomos/metabolismo , Fagossomos/microbiologia , Fagossomos/ultraestrutura , Espécies Reativas de Oxigênio/imunologia , Espécies Reativas de Oxigênio/metabolismo , Staphylococcus aureus/imunologia , Staphylococcus aureus/fisiologiaRESUMO
Pseudomonas aeruginosa provokes a painful, sight-threatening corneal infection. It progresses rapidly and is difficult to treat. In this study, using a mouse model of P. aeruginosa keratitis, we demonstrate the importance of a carbohydrate-binding protein, galectin-8 (Gal-8), in regulation of the innate immune response. First, using two distinct strains of P. aeruginosa, we established that Gal-8-/- mice are resistant to P. aeruginosa keratitis. In contrast, mice deficient in Gal-1, Gal-3, and Gal-9 were fully susceptible. Second, the addition of exogenous rGal-8 to LPS (TLR4 ligand)-stimulated bone marrow-derived macrophages suppressed 1) the activation of the NF-κB pathway, and 2) formation of the MD-2/TLR4 complex. Additionally, the expression level of reactive oxygen species was substantially higher in infected Gal-8-/- bone marrow neutrophils (BMNs) compared with the Gal-8+/+ BMNs, and the P. aeruginosa killing capacity of Gal-8-/- BMNs was considerably higher compared with that of Gal-8+/+ BMNs. In the bacterial killing assays, the addition of exogenous rGal-8 almost completely rescued the phenotype of Gal-8-/- BMNs. Finally, we demonstrate that a subconjunctival injection of a Gal-8 inhibitor markedly reduces the severity of infection in the mouse model of P. aeruginosa keratitis. These data lead us to conclude that Gal-8 downmodulates the innate immune response by suppressing activation of the TLR4 pathway and clearance of P. aeruginosa by neutrophils. These findings have broad implications for developing novel therapeutic strategies for treatment of conditions resulting from the hyperactive immune response both in ocular as well as nonocular tissues.
Assuntos
Ceratite , Infecções por Pseudomonas , Animais , Camundongos , Pseudomonas aeruginosa , Receptor 4 Toll-Like , Imunidade Inata , Galectinas , Camundongos Endogâmicos C57BLRESUMO
BACKGROUND & AIMS: Gut bacterial translocation contributes to immune dysfunction and spontaneous bacterial peritonitis (SBP) in cirrhosis. We hypothesized that exposure of peritoneal macrophages (PMs) to bacterial DNA results in type-I interferon (IFN) production, shaping subsequent immune responses, inflammasome activation, and the release of damage-associated molecular patterns (DAMPs). METHODS: PMs from patients with cirrhosis were stimulated with E. coli single-stranded DNA (ssDNA), lipopolysaccharide LPS, and IFN or infected with E. coli, S. aureus, and Group B streptococcus in vitro. Cytokine release, inflammasome activation, and DAMP release were quantified by quantitative-PCR, ELISA, western blots, and reporter cells employing primary PMs, monocytes, and caspase-deficient THP-1 macrophages. Serum progranulin concentration was correlated with transplant-free survival in 77 patients with SBP. RESULTS: E. coli ssDNA induced strong type-I IFN activity in PMs and monocytes, priming them for enhanced LPS-mediated tumor necrosis factor production without toll-like receptor 4 tolerance induction. During in vitro macrophage bacterial infection, type-I IFN release aligned with upregulated expression of IFN-regulatory factors (IRF)1/2 and guanylate binding proteins (GBP)2/5. PMs upregulated inflammasome-associated proteins and type-I IFN upon E. coli ssDNA exposure and released interleukin-1ß upon bacterial infection. Proteomic screen in mouse macrophages revealed progranulin as being caspase-11-dependent during E. coli infection. PMs and THP-1 macrophages released significant amounts of progranulin when infected with S. aureus or E. coli via gasdermin-D in a type-I IFN and caspase-5-dependent manner. During SBP, PMs upregulated IRF1, GBP2/5 and caspase-5 and higher serum progranulin concentrations were indicative of lower 90-day transplant-free survival after SBP. CONCLUSIONS: Type-I IFN shapes peritoneal immune responses and regulates caspase-5-mediated progranulin release during SBP. IMPACT AND IMPLICATIONS: Patients with cirrhosis exhibit impaired immune responses and increased susceptibility to bacterial infections. This study reveals that type-I interferon responses, triggered by pathogen-associated molecular patterns, are crucial in regulating macrophage activation and priming them for inflammatory responses. Additionally, we elucidate the mechanisms by which type-I interferons promote the release of progranulin from macrophages during spontaneous bacterial peritonitis. Our findings enhance understanding of how bacterial translocation affects immune responses, identify novel biomarkers for inflammasome activation during infections, and point to potential therapeutic targets.
RESUMO
Innate immune responses have the ability to both combat infectious microbes and drive pathological inflammation. Inflammasome complexes are a central component of these processes through their regulation of interleukin 1ß (IL-1ß), IL-18 and pyroptosis. Inflammasomes recognize microbial products or endogenous molecules released from damaged or dying cells both through direct binding of ligands and indirect mechanisms. The potential of the IL-1 family of cytokines to cause tissue damage and chronic inflammation emphasizes the importance of regulating inflammasomes. Many regulatory mechanisms have been identified that act as checkpoints for attenuating inflammasome signaling at multiple steps. Here we discuss the various regulatory mechanisms that have evolved to keep inflammasome signaling in check to maintain immunological balance.
Assuntos
Imunidade Inata/imunologia , Inflamassomos/imunologia , Transdução de Sinais/imunologia , Animais , Humanos , Inflamassomos/metabolismoRESUMO
Extracellular vesicles (EVs) are membrane-bound structures released by cells and have become significant players in immune system functioning, primarily by facilitating cell-to-cell communication. Immune cells like neutrophils and dendritic cells release EVs containing bioactive molecules that modulate chemotaxis, activate immune cells, and induce inflammation. EVs also contribute to antigen presentation, lymphocyte activation, and immune tolerance. Moreover, EVs play pivotal roles in antimicrobial host defense. They deliver microbial antigens to antigen-presenting cells (APCs), triggering immune responses, or act as decoys to neutralize virulence factors and toxins. This review discusses host and microbial EVs' multifaceted roles in innate and adaptive immunity, highlighting their involvement in immune cell development, antigen presentation, and antimicrobial responses.
Assuntos
Anti-Infecciosos , Exossomos , Vesículas Extracelulares , Células Apresentadoras de Antígenos , Imunidade Adaptativa , Apresentação de AntígenoRESUMO
Cystic fibrosis (CF) is an inherited life-threatening disease accompanied by repeated lung infections and multiorgan inflammation that affects tens of thousands of people worldwide. The causative gene, cystic fibrosis transmembrane conductance regulator (CFTR), is mutated in CF patients. CFTR functions in epithelial cells have traditionally been thought to cause the disease symptoms. Recent work has shown an additional defect: monocytes from CF patients show a deficiency in integrin activation and adhesion. Because monocytes play critical roles in controlling infections, defective monocyte function may contribute to CF progression. In this study, we demonstrate that monocytes from CFTRΔF508 mice (CF mice) show defective adhesion under flow. Transplanting CF mice with wild-type (WT) bone marrow after sublethal irradiation replaced most (60-80%) CF monocytes with WT monocytes, significantly improved survival, and reduced inflammation. WT/CF mixed bone marrow chimeras directly demonstrated defective CF monocyte recruitment to the bronchoalveolar lavage and the intestinal lamina propria in vivo. WT mice reconstituted with CF bone marrow also show lethality, suggesting that the CF defect in monocytes is not only necessary but also sufficient to cause disease. We also show that monocyte-specific knockout of CFTR retards weight gains and exacerbates dextran sulfate sodium-induced colitis. Our findings show that providing WT monocytes by bone marrow transfer rescues mortality in CF mice, suggesting that similar approaches may mitigate disease in CF patients.
Assuntos
Adesão Celular/genética , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Fibrose Cística/terapia , Monócitos/imunologia , Monócitos/transplante , Animais , Transplante de Medula Óssea , Líquido da Lavagem Broncoalveolar/citologia , Colite/patologia , Fibrose Cística/patologia , Integrinas/metabolismo , Mucosa Intestinal/citologia , Mucosa Intestinal/imunologia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Nucleic acid sensing is a critical mechanism by which the immune system monitors for pathogen invasion. A set of germline-encoded innate immune receptors detect microbial DNA in various compartments of the cell, such as endosomes, the cytosol, and the nucleus. Sensing of microbial DNA through these receptors stimulates, in most cases, interferon regulatory factor-dependent type I IFN synthesis followed by JAK/STAT-dependent interferon-stimulated gene expression. In contrast, the detection of DNA in the cytosol by AIM2 assembles a macromolecular complex called the inflammasome, which unleashes the proteolytic activity of a cysteine protease caspase-1. Caspase-1 cleaves and activates the pro-inflammatory cytokines such as IL-1ß and IL-18 and a pore-forming protein, gasdermin D, which triggers pyroptosis, an inflammatory form of cell death. Research over the past decade has revealed that AIM2 plays essential roles not only in host defense against pathogens but also in inflammatory diseases, autoimmunity, and cancer in inflammasome-dependent and inflammasome-independent manners. This review discusses the latest advancements in our understanding of AIM2 biology and its functions in health and disease.
Assuntos
Proteínas de Ligação a DNA , Inflamassomos , Caspase 1 , Interleucina-18 , PiroptoseRESUMO
Autophagy, a cellular process for organelle and protein turnover, regulates innate immune responses. Here we demonstrate that depletion of the autophagic proteins LC3B and beclin 1 enhanced the activation of caspase-1 and secretion of interleukin 1ß (IL-1ß) and IL-18. Depletion of autophagic proteins promoted the accumulation of dysfunctional mitochondria and cytosolic translocation of mitochondrial DNA (mtDNA) in response to lipopolysaccharide (LPS) and ATP in macrophages. Release of mtDNA into the cytosol depended on the NALP3 inflammasome and mitochondrial reactive oxygen species (ROS). Cytosolic mtDNA contributed to the secretion of IL-1ß and IL-18 in response to LPS and ATP. LC3B-deficient mice produced more caspase-1-dependent cytokines in two sepsis models and were susceptible to LPS-induced mortality. Our study suggests that autophagic proteins regulate NALP3-dependent inflammation by preserving mitochondrial integrity.