RESUMO
As an important sensor in the innate immune system, NLRP3 detects exogenous pathogenic invasions and endogenous cellular damage and responds by forming the NLRP3 inflammasome, a supramolecular complex that activates caspase-1. The three major components of the NLRP3 inflammasome are NLRP3, which captures the danger signals and recruits downstream molecules; caspase-1, which elicits maturation of the cytokines IL-1ß and IL-18 and processing of gasdermin D to mediate cytokine release and pyroptosis; and ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain), which functions as a bridge connecting NLRP3 and caspase-1. In this article, we review the structural information that has been obtained on the NLRP3 inflammasome and its components or subcomplexes, with special focus on the inactive NLRP3 cage, the active NLRP3-NEK7 (NIMA-related kinase 7)-ASC inflammasome disk, and the PYD-PYD and CARD-CARD homotypic filamentous scaffolds of the inflammasome. We further implicate structure-derived mechanisms for the assembly and activation of the NLRP3 inflammasome.
Assuntos
Inflamassomos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Humanos , Animais , Inflamassomos/química , Inflamassomos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Apoptose , Citocinas/metabolismo , Caspase 1/metabolismo , Interleucina-1beta/metabolismoRESUMO
ATP, NAD+, and nucleic acids are abundant purines that, in addition to having critical intracellular functions, have evolved extracellular roles as danger signals released in response to cell lysis, apoptosis, degranulation, or membrane pore formation. In general ATP and NAD+ have excitatory and adenosine has anti-inflammatory effects on immune cells. This review focuses on recent advances in our understanding of purine release mechanisms, ectoenzymes that metabolize purines (CD38, CD39, CD73, ENPP1, and ENPP2/autotaxin), and signaling by key P2 purinergic receptors (P2X7, P2Y2, and P2Y12). In addition to metabolizing ATP or NAD+, some purinergic ectoenzymes metabolize other inflammatory modulators, notably lysophosphatidic acid and cyclic GMP-AMP (cGAMP). Also discussed are extracellular signaling effects of NAD+ mediated by ADP-ribosylation, and epigenetic effects of intracellular adenosine mediated by modification of S-adenosylmethionine-dependent DNA methylation.
Assuntos
Inflamação/imunologia , Purinas/metabolismo , Receptores Purinérgicos/metabolismo , ADP-Ribosilação , Trifosfato de Adenosina/metabolismo , Animais , Metilação de DNA , Humanos , Inflamação/genética , Inflamação/metabolismo , Lisofosfolipídeos/metabolismo , Transdução de SinaisRESUMO
NLRs constitute a large, highly conserved family of cytosolic pattern recognition receptors that are central to health and disease, making them key therapeutic targets. NLRC5 is an enigmatic NLR with mutations associated with inflammatory and infectious diseases, but little is known about its function as an innate immune sensor and cell death regulator. Therefore, we screened for NLRC5's role in response to infections, PAMPs, DAMPs, and cytokines. We identified that NLRC5 acts as an innate immune sensor to drive inflammatory cell death, PANoptosis, in response to specific ligands, including PAMP/heme and heme/cytokine combinations. NLRC5 interacted with NLRP12 and PANoptosome components to form a cell death complex, suggesting an NLR network forms similar to those in plants. Mechanistically, TLR signaling and NAD+ levels regulated NLRC5 expression and ROS production to control cell death. Furthermore, NLRC5-deficient mice were protected in hemolytic and inflammatory models, suggesting that NLRC5 could be a potential therapeutic target.
Assuntos
Inflamação , Peptídeos e Proteínas de Sinalização Intracelular , NAD , Animais , Camundongos , Inflamação/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , NAD/metabolismo , Humanos , Imunidade Inata , Camundongos Endogâmicos C57BL , Espécies Reativas de Oxigênio/metabolismo , Camundongos Knockout , Transdução de Sinais , Células HEK293 , Inflamassomos/metabolismo , Proteínas Reguladoras de Apoptose/metabolismo , Proteínas Reguladoras de Apoptose/genética , Receptores Toll-Like/metabolismo , Masculino , Citocinas/metabolismo , Proteínas de Ligação ao CálcioRESUMO
Inflammasomes are critical sentinels of the innate immune system that respond to threats to the host through recognition of distinct molecules, known as pathogen- or damage-associated molecular patterns (PAMPs/DAMPs), or disruptions of cellular homeostasis, referred to as homeostasis-altering molecular processes (HAMPs) or effector-triggered immunity (ETI). Several distinct proteins nucleate inflammasomes, including NLRP1, CARD8, NLRP3, NLRP6, NLRC4/NAIP, AIM2, pyrin, and caspases-4/-5/-11. This diverse array of sensors strengthens the inflammasome response through redundancy and plasticity. Here, we present an overview of these pathways, outlining the mechanisms of inflammasome formation, subcellular regulation, and pyroptosis, and discuss the wide-reaching effects of inflammasomes in human disease.
Assuntos
Inflamassomos , Humanos , Proteínas Reguladoras de Apoptose/metabolismo , Proteínas Adaptadoras de Sinalização CARD/metabolismo , Caspases/metabolismo , Morte Celular , Inflamassomos/metabolismo , Proteínas de Neoplasias/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , PiroptoseRESUMO
The NACHT-, leucine-rich-repeat- (LRR), and pyrin domain-containing protein 3 (NLRP3) is emerging to be a critical intracellular inflammasome sensor of membrane integrity and a highly important clinical target against chronic inflammation. Here, we report that an endogenous, stimulus-responsive form of full-length mouse NLRP3 is a 12- to 16-mer double-ring cage held together by LRR-LRR interactions with the pyrin domains shielded within the assembly to avoid premature activation. Surprisingly, this NLRP3 form is predominantly membrane localized, which is consistent with previously noted localization of NLRP3 at various membrane organelles. Structure-guided mutagenesis reveals that trans-Golgi network dispersion into vesicles, an early event observed for many NLRP3-activating stimuli, requires the double-ring cages of NLRP3. Double-ring-defective NLRP3 mutants abolish inflammasome punctum formation, caspase-1 processing, and cell death. Thus, our data uncover a physiological NLRP3 oligomer on the membrane that is poised to sense diverse signals to induce inflammasome activation.
Assuntos
Inflamassomos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/química , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Sequência de Aminoácidos , Animais , Membrana Celular/metabolismo , Microscopia Crioeletrônica , Células HEK293 , Humanos , Camundongos , Modelos Biológicos , Modelos Moleculares , Mutação/genética , Quinases Relacionadas a NIMA/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/isolamento & purificação , Proteína 3 que Contém Domínio de Pirina da Família NLR/ultraestrutura , Nigericina/farmacologia , Ligação Proteica , Domínios Proteicos , Multimerização Proteica , Rede trans-Golgi/metabolismoRESUMO
Caspases regulate cell death, immune responses, and homeostasis. Caspase-6 is categorized as an executioner caspase but shows key differences from the other executioners. Overall, little is known about the functions of caspase-6 in biological processes apart from apoptosis. Here, we show that caspase-6 mediates innate immunity and inflammasome activation. Furthermore, we demonstrate that caspase-6 promotes the activation of programmed cell death pathways including pyroptosis, apoptosis, and necroptosis (PANoptosis) and plays an essential role in host defense against influenza A virus (IAV) infection. In addition, caspase-6 promoted the differentiation of alternatively activated macrophages (AAMs). Caspase-6 facilitated the RIP homotypic interaction motif (RHIM)-dependent binding of RIPK3 to ZBP1 via its interaction with RIPK3. Altogether, our findings reveal a vital role for caspase-6 in facilitating ZBP1-mediated inflammasome activation, cell death, and host defense during IAV infection, opening additional avenues for treatment of infectious and autoinflammatory diseases and cancer.
Assuntos
Caspase 6/imunologia , Caspase 6/metabolismo , Inflamassomos/imunologia , Animais , Apoptose/imunologia , Morte Celular/imunologia , Imunidade Inata , Inflamassomos/metabolismo , Inflamassomos/fisiologia , Inflamação/imunologia , Inflamação/metabolismo , Inflamação/patologia , Macrófagos/imunologia , Macrófagos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Necroptose/imunologia , Ligação Proteica , Piroptose/imunologia , Proteínas de Ligação a RNA/metabolismo , Proteína Serina-Treonina Quinases de Interação com Receptores/metabolismoRESUMO
Long-term epigenetic reprogramming of innate immune cells in response to microbes, also termed "trained immunity," causes prolonged altered cellular functionality to protect from secondary infections. Here, we investigated whether sterile triggers of inflammation induce trained immunity and thereby influence innate immune responses. Western diet (WD) feeding of Ldlr-/- mice induced systemic inflammation, which was undetectable in serum soon after mice were shifted back to a chow diet (CD). In contrast, myeloid cell responses toward innate stimuli remained broadly augmented. WD-induced transcriptomic and epigenomic reprogramming of myeloid progenitor cells led to increased proliferation and enhanced innate immune responses. Quantitative trait locus (QTL) analysis in human monocytes trained with oxidized low-density lipoprotein (oxLDL) and stimulated with lipopolysaccharide (LPS) suggested inflammasome-mediated trained immunity. Consistently, Nlrp3-/-/Ldlr-/- mice lacked WD-induced systemic inflammation, myeloid progenitor proliferation, and reprogramming. Hence, NLRP3 mediates trained immunity following WD and could thereby mediate the potentially deleterious effects of trained immunity in inflammatory diseases.
Assuntos
Reprogramação Celular , Dieta Ocidental , Epigênese Genética , Imunidade Inata , Memória Imunológica , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Adulto , Idoso , Animais , Células Cultivadas , Feminino , Humanos , Lipoproteínas LDL/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Células Mieloides/imunologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Locos de Características Quantitativas , Receptores de LDL/genéticaRESUMO
NOD-like receptors (NLRs) are pattern recognition receptors for diverse innate immune responses. Self-oligomerization after engagement with a ligand is a generally accepted model for the activation of each NLR. We report here that a catalyzer was required for NLR self-oligomerization. PELO, a well-known surveillance factor in translational quality control and/or ribosome rescue, interacted with all cytosolic NLRs and activated their ATPase activity. In the case of flagellin-initiated NLRC4 inflammasome activation, flagellin-bound NAIP5 recruited the first NLRC4 and then PELO was required for correctly assembling the rest of NLRC4s into the NLRC4 complex, one by one, by activating the NLRC4 ATPase activity. Stoichiometric and functional data revealed that PELO was not a structural constituent of the NLRC4 inflammasome but a powerful catalyzer for its assembly. The catalytic role of PELO in the activation of cytosolic NLRs provides insight into NLR activation and provides a direction for future studies of NLR family members.
Assuntos
Proteínas Reguladoras de Apoptose , Inflamassomos , Adenosina Trifosfatases/metabolismo , Proteínas Reguladoras de Apoptose/metabolismo , Proteínas de Ligação ao Cálcio/química , Proteínas de Ligação ao Cálcio/metabolismo , Flagelina/metabolismo , Inflamassomos/metabolismo , Proteína Inibidora de Apoptose Neuronal/química , Proteína Inibidora de Apoptose Neuronal/metabolismo , Proteínas NLR/metabolismoRESUMO
Intracellular sensing of lipopolysaccharide (LPS) by murine caspase-11 or human caspase-4 initiates a protease cascade, termed the non-canonical inflammasome, that results in gasdermin D (GSDMD) processing and subsequent NLRP3 inflammasome activation. In an effort aimed at identifying additional sensors for intracellular LPS by biochemical screening, we identified the nuclear orphan receptor Nur77 as an LPS-binding protein in macrophage lysates. Nr4a1-/- macrophages exhibited impaired activation of the NLRP3 inflammasome, but not caspase-11, in response to LPS. Biochemical mapping revealed that Nur77 bound LPS directly through a domain in its C terminus. Yeast two-hybrid assays identified NLRP3 as a binding partner for Nur77. The association between Nur77 and NLRP3 required the presence of LPS and dsDNA. The source of dsDNA was the mitochondria, requiring the formation of gasdermin-D pores. In vivo, Nur77 deficiency ameliorated host response to endotoxins. Thus, Nur77 functions as an intracellular LPS sensor, binding mitochondrial DNA and LPS to activate the non-canonical NLRP3 inflammasome.
Assuntos
Inflamassomos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Membro 1 do Grupo A da Subfamília 4 de Receptores Nucleares , Animais , Humanos , Camundongos , Caspase 1/metabolismo , Caspases/metabolismo , Gasderminas , Inflamassomos/metabolismo , Interleucina-1beta/metabolismo , Lipopolissacarídeos/metabolismo , Macrófagos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Membro 1 do Grupo A da Subfamília 4 de Receptores Nucleares/metabolismoRESUMO
Detection of cytosolic DNA constitutes a central event in the context of numerous infectious and sterile inflammatory conditions. Recent studies have uncovered a bipartite mode of cytosolic DNA recognition, in which the cGAS-STING axis triggers antiviral immunity, whereas AIM2 triggers inflammasome activation. Here, we show that AIM2 is dispensable for DNA-mediated inflammasome activation in human myeloid cells. Instead, detection of cytosolic DNA by the cGAS-STING axis induces a cell death program initiating potassium efflux upstream of NLRP3. Forward genetics identified regulators of lysosomal trafficking to modulate this cell death program, and subsequent studies revealed that activated STING traffics to the lysosome, where it triggers membrane permeabilization and thus lysosomal cell death (LCD). Importantly, the cGAS-STING-NLRP3 pathway constitutes the default inflammasome response during viral and bacterial infections in human myeloid cells. We conclude that targeting the cGAS-STING-LCD-NLRP3 pathway will ameliorate pathology in inflammatory conditions that are associated with cytosolic DNA sensing.
Assuntos
Morte Celular , Inflamassomos/metabolismo , Monócitos/citologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , DNA/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Monócitos/metabolismo , Transdução de SinaisRESUMO
Serine metabolism is involved in the fate decisions of immune cells; however, whether and how de novo serine synthesis shapes innate immune cell function remain unknown. Here, we first demonstrated that inflammatory macrophages have high expression of phosphoglycerate dehydrogenase (PHGDH, the rate-limiting enzyme of de novo serine synthesis) via nuclear factor κB signaling. Notably, the pharmacological inhibition or genetic modulation of PHGDH limits macrophage interleukin (IL)-1ß production through NAD+ accumulation and subsequent NAD+-dependent SIRT1 and SIRT3 expression and activity. Mechanistically, PHGDH not only sustains IL-1ß expression through H3K9/27 acetylation-mediated transcriptional activation of Toll-like receptor 4 but also supports IL-1ß maturation via NLRP3-K21/22/24/ASC-K21/22/24 acetylation-mediated activation of the NLRP3 inflammasome. Moreover, mice with myeloid-specific depletion of Phgdh show alleviated inflammatory responses in lipopolysaccharide-induced systemic inflammation. This study reveals a network by which a metabolic enzyme, involved in de novo serine synthesis, mediates post-translational modifications and epigenetic regulation to orchestrate IL-1ß production, providing a potential inflammatory disease target.
Assuntos
NAD , Proteína 3 que Contém Domínio de Pirina da Família NLR , Animais , Camundongos , Acetilação , Epigênese Genética , Inflamassomos/metabolismo , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Macrófagos/metabolismo , NAD/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Processamento de Proteína Pós-Traducional , Serina/metabolismoRESUMO
Mitochondrial DNA (mtDNA) escaping stressed mitochondria provokes inflammation via cGAS-STING pathway activation and, when oxidized (Ox-mtDNA), it binds cytosolic NLRP3, thereby triggering inflammasome activation. However, it is unknown how and in which form Ox-mtDNA exits stressed mitochondria in non-apoptotic macrophages. We found that diverse NLRP3 inflammasome activators rapidly stimulated uniporter-mediated calcium uptake to open mitochondrial permeability transition pores (mPTP) and trigger VDAC oligomerization. This occurred independently of mtDNA or reactive oxygen species, which induce Ox-mtDNA generation. Within mitochondria, Ox-mtDNA was either repaired by DNA glycosylase OGG1 or cleaved by the endonuclease FEN1 to 500-650 bp fragments that exited mitochondria via mPTP- and VDAC-dependent channels to initiate cytosolic NLRP3 inflammasome activation. Ox-mtDNA fragments also activated cGAS-STING signaling and gave rise to pro-inflammatory extracellular DNA. Understanding this process will advance the development of potential treatments for chronic inflammatory diseases, exemplified by FEN1 inhibitors that suppressed interleukin-1ß (IL-1ß) production and mtDNA release in mice.
Assuntos
Inflamassomos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Animais , DNA Mitocondrial/metabolismo , Inflamassomos/metabolismo , Interferons/metabolismo , Camundongos , Mitocôndrias/metabolismo , Poro de Transição de Permeabilidade Mitocondrial , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Nucleotidiltransferases/metabolismoRESUMO
The NLRP3 inflammasome plays a central role in antimicrobial defense as well as in the context of sterile inflammatory conditions. NLRP3 activity is governed by two independent signals: the first signal primes NLRP3, rendering it responsive to the second signal, which then triggers inflammasome formation. Our understanding of how NLRP3 priming contributes to inflammasome activation remains limited. Here, we show that IKKß, a kinase activated during priming, induces recruitment of NLRP3 to phosphatidylinositol-4-phosphate (PI4P), a phospholipid enriched on the trans-Golgi network. NEK7, a mitotic spindle kinase that had previously been thought to be indispensable for NLRP3 activation, was redundant for inflammasome formation when IKKß recruited NLRP3 to PI4P. Studying iPSC-derived human macrophages revealed that the IKKß-mediated NEK7-independent pathway constitutes the predominant NLRP3 priming mechanism in human myeloid cells. Our results suggest that PI4P binding represents a primed state into which NLRP3 is brought by IKKß activity.
Assuntos
Inflamassomos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Humanos , Quinase I-kappa B , Inflamassomos/metabolismo , Camundongos Endogâmicos C57BL , Quinases Relacionadas a NIMA/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Rede trans-Golgi/metabolismoRESUMO
As a key component of the inflammasome, NLRP3 is a critical intracellular danger sensor emerging as an important clinical target in inflammatory diseases. However, little is known about the mechanisms that determine the kinetics of NLRP3 inflammasome stability and activity to ensure effective and controllable inflammatory responses. Here, we show that S-palmitoylation acts as a brake to turn NLRP3 inflammasome off. zDHHC12 is identified as the S-acyltransferase for NLRP3 palmitoylation, which promotes its degradation through the chaperone-mediated autophagy pathway. Zdhhc12 deficiency in mice enhances inflammatory symptoms and lethality following alum-induced peritonitis and LPS-induced endotoxic shock. Notably, several disease-associated mutations in NLRP3 are associated with defective palmitoylation, resulting in overt NLRP3 inflammasome activation. Thus, our findings identify zDHHC12 as a repressor of NLRP3 inflammasome activation and uncover a previously unknown regulatory mechanism by which the inflammasome pathway is tightly controlled by the dynamic palmitoylation of NLRP3.
Assuntos
Autofagia Mediada por Chaperonas , Inflamassomos , Animais , Camundongos , Aciltransferases , Autofagia , Inflamassomos/metabolismo , Inflamação/induzido quimicamente , Inflamação/genética , Lipoilação , Camundongos Endogâmicos C57BL , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismoRESUMO
The nucleotide-binding domain (NBD), leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3) inflammasome is a critical mediator of the innate immune response. How NLRP3 responds to stimuli and initiates the assembly of the NLRP3 inflammasome is not fully understood. Here, we found that a cellular metabolite, palmitate, facilitates NLRP3 activation by enhancing its S-palmitoylation, in synergy with lipopolysaccharide stimulation. NLRP3 is post-translationally palmitoylated by zinc-finger and aspartate-histidine-histidine-cysteine 5 (ZDHHC5) at the LRR domain, which promotes NLRP3 inflammasome assembly and activation. Silencing ZDHHC5 blocks NLRP3 oligomerization, NLRP3-NEK7 interaction, and formation of large intracellular ASC aggregates, leading to abrogation of caspase-1 activation, IL-1ß/18 release, and GSDMD cleavage, both in human cells and in mice. ABHD17A depalmitoylates NLRP3, and one human-heritable disease-associated mutation in NLRP3 was found to be associated with defective ABHD17A binding and hyper-palmitoylation. Furthermore, Zdhhc5-/- mice showed defective NLRP3 inflammasome activation in vivo. Taken together, our data reveal an endogenous mechanism of inflammasome assembly and activation and suggest NLRP3 palmitoylation as a potential target for the treatment of NLRP3 inflammasome-driven diseases.
Assuntos
Aciltransferases , Inflamassomos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Animais , Humanos , Camundongos , Caspase 1/metabolismo , Histidina/metabolismo , Inflamassomos/metabolismo , Interleucina-1beta/metabolismo , Lipoilação , Macrófagos/metabolismo , Quinases Relacionadas a NIMA/genética , Quinases Relacionadas a NIMA/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Aciltransferases/genética , Aciltransferases/metabolismoRESUMO
Epstein-Barr virus (EBV) causes infectious mononucleosis, triggers multiple sclerosis, and is associated with 200,000 cancers/year. EBV colonizes the human B cell compartment and periodically reactivates, inducing expression of 80 viral proteins. However, much remains unknown about how EBV remodels host cells and dismantles key antiviral responses. We therefore created a map of EBV-host and EBV-EBV interactions in B cells undergoing EBV replication, uncovering conserved herpesvirus versus EBV-specific host cell targets. The EBV-encoded G-protein-coupled receptor BILF1 associated with MAVS and the UFM1 E3 ligase UFL1. Although UFMylation of 14-3-3 proteins drives RIG-I/MAVS signaling, BILF1-directed MAVS UFMylation instead triggered MAVS packaging into mitochondrial-derived vesicles and lysosomal proteolysis. In the absence of BILF1, EBV replication activated the NLRP3 inflammasome, which impaired viral replication and triggered pyroptosis. Our results provide a viral protein interaction network resource, reveal a UFM1-dependent pathway for selective degradation of mitochondrial cargo, and highlight BILF1 as a novel therapeutic target.
Assuntos
Infecções por Vírus Epstein-Barr , Herpesvirus Humano 4 , Humanos , Herpesvirus Humano 4/genética , Infecções por Vírus Epstein-Barr/genética , Inflamassomos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Mapas de Interação de ProteínasRESUMO
As substantial constituents of the multiple myeloma (MM) microenvironment, pro-inflammatory macrophages have emerged as key promoters of disease progression, bone destruction, and immune impairment. We identify beta-2-microglobulin (ß2m) as a driver in initiating inflammation in myeloma-associated macrophages (MAMs). Lysosomal accumulation of phagocytosed ß2m promotes ß2m amyloid aggregation in MAMs, resulting in lysosomal rupture and ultimately production of active interleukin-1ß (IL-1ß) and IL-18. This process depends on activation of the NLRP3 inflammasome after ß2m accumulation, as macrophages from NLRP3-deficient mice lack efficient ß2m-induced IL-1ß production. Moreover, depletion or silencing of ß2m in MM cells abrogates inflammasome activation in a murine MM model. Finally, we demonstrate that disruption of NLRP3 or IL-18 diminishes tumor growth and osteolytic bone destruction normally promoted by ß2m-induced inflammasome signaling. Our results provide mechanistic evidence for ß2m's role as an NLRP3 inflammasome activator during MM pathogenesis. Moreover, inhibition of NLRP3 represents a potential therapeutic approach in MM.
Assuntos
Amiloide/metabolismo , Mieloma Múltiplo/patologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Macrófagos Associados a Tumor/metabolismo , Microglobulina beta-2/metabolismo , Animais , Células Cultivadas , Humanos , Inflamação/imunologia , Interleucina-18/metabolismo , Interleucina-1beta/metabolismo , Lisossomos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Fagocitose/imunologia , Transdução de Sinais/imunologia , Microambiente Tumoral/imunologia , Macrófagos Associados a Tumor/imunologia , Microglobulina beta-2/genéticaRESUMO
Acute respiratory distress syndrome (ARDS), an inflammatory condition with high mortality rates, is common in severe COVID-19, whose risk is reduced by metformin rather than other anti-diabetic medications. Detecting of inflammasome assembly in post-mortem COVID-19 lungs, we asked whether and how metformin inhibits inflammasome activation while exerting its anti-inflammatory effect. We show that metformin inhibited NLRP3 inflammasome activation and interleukin (IL)-1ß production in cultured and alveolar macrophages along with inflammasome-independent IL-6 secretion, thus attenuating lipopolysaccharide (LPS)- and SARS-CoV-2-induced ARDS. By targeting electron transport chain complex 1 and independently of AMP-activated protein kinase (AMPK) or NF-κB, metformin blocked LPS-induced and ATP-dependent mitochondrial (mt) DNA synthesis and generation of oxidized mtDNA, an NLRP3 ligand. Myeloid-specific ablation of LPS-induced cytidine monophosphate kinase 2 (CMPK2), which is rate limiting for mtDNA synthesis, reduced ARDS severity without a direct effect on IL-6. Thus, inhibition of ATP and mtDNA synthesis is sufficient for ARDS amelioration.
Assuntos
Trifosfato de Adenosina/metabolismo , DNA Mitocondrial/biossíntese , Inflamassomos/efeitos dos fármacos , Metformina/farmacologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Pneumonia/prevenção & controle , Animais , COVID-19/metabolismo , COVID-19/prevenção & controle , Citocinas/genética , Citocinas/metabolismo , DNA Mitocondrial/metabolismo , Humanos , Inflamassomos/metabolismo , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Lipopolissacarídeos/toxicidade , Metformina/uso terapêutico , Camundongos , Núcleosídeo-Fosfato Quinase/metabolismo , Pneumonia/metabolismo , Síndrome do Desconforto Respiratório/induzido quimicamente , Síndrome do Desconforto Respiratório/prevenção & controle , SARS-CoV-2/patogenicidadeRESUMO
Assembly of inflammasomes after infection or injury leads to the release of interleukin-1ß (IL-1ß) and to pyroptosis. After inflammasome activation, cells either pyroptose or enter a hyperactivated state defined by IL-1ß secretion without cell death, but what controls these different outcomes is unknown. Here, we show that removal of the Toll-IL-1R protein SARM from macrophages uncouples inflammasome-dependent cytokine release and pyroptosis, whereby cells displayed increased IL-1ß production but reduced pyroptosis. Correspondingly, increasing SARM in cells caused less IL-1ß release and more pyroptosis. SARM suppressed IL-1ß by directly restraining the NLRP3 inflammasome and, hence, caspase-1 activation. Consistent with a role for SARM in pyroptosis, Sarm1-/- mice were protected from lipopolysaccharide (LPS)-stimulated sepsis. Pyroptosis-inducing, but not hyperactivating, NLRP3 stimulants caused SARM-dependent mitochondrial depolarization. Thus, SARM-dependent mitochondrial depolarization distinguishes NLRP3 activators that cause pyroptosis from those that do not, and SARM modulation represents a cell-intrinsic mechanism to regulate cell fate after inflammasome activation.
Assuntos
Proteínas do Domínio Armadillo/metabolismo , Citocinas/metabolismo , Proteínas do Citoesqueleto/metabolismo , Inflamassomos/metabolismo , Animais , Proteínas do Domínio Armadillo/genética , Biomarcadores , Sobrevivência Celular , Proteínas do Citoesqueleto/genética , Macrófagos/imunologia , Macrófagos/metabolismo , Camundongos , Camundongos Knockout , Mitocôndrias/genética , Mitocôndrias/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Ligação Proteica , Piroptose , Transdução de SinaisRESUMO
From studies of individual families to global collaborative efforts, the NLRP3 inflammasome is now recognized to be a key regulator of innate immunity. Activated by a panoply of pathogen-associated and endogenous triggers, NLRP3 serves as an intracellular sensor that drives carefully coordinated assembly of the inflammasome, and downstream inflammation mediated by IL-1 and IL-18. Initially discovered as the cause of the autoinflammatory spectrum of cryopyrin-associated periodic syndrome (CAPS), NLRP3 is now also known to play a role in more common diseases including cardiovascular disease, gout, and liver disease. We have seen cohesion in results from clinical studies in CAPS patients, ex vivo studies of human cells and murine cells, and in vivo murine models leading to our understanding of the downstream pathways, cytokine secretion, and cell death pathways that has solidified the role of autoinflammation in the pathogenesis of human disease. Recent advances in our understanding of the structure of the inflammasome have provided ways for us to visualize normal and mutant protein function and pharmacologic inhibition. The subsequent development of targeted therapies successfully used in the treatment of patients with CAPS completes the bench to bedside translational loop which has defined the study of this unique protein.