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Mutant NLRP3 causing Cryopyrin-Associated Periodic Syndromes forms a constitutively active inflammasome and results in alteration in monocyte immunometabolism to limit IL-1β production

ABSTRACT: Cryopyrin-associated periodic syndrome (CAPS) is an autoinflammatory condition resulting from monoallelic NLRP3 variants that exacerbate IL-1 production. Although these are gain-of-function variants, the exact regulatory mechanism of the NLRP3-inflammasome in CAPS is not yet well understood. Despite being considered a hypersensitive inflammasome triggered by cell priming, patients with CAPS and animal models of the disease may present inflammatory flares even in the absence of identifiable external triggers. Herein, we found that CAPS-associated variants result in constitutively active NLRP3-inflammasome, which induce an increased basal cleavage of gasdermin D, IL-18 release and pyroptosis, with a concurrent basal pro-inflammatory gene expression signature, including the induction of nuclear receptors 4A. The constitutively active NLRP3-inflammasome was blocked by MCC950 and was dependent on NLRP3 expression level, further regulated by deubiquitination. Additionally, we determined that the activation of the NF-B pathway with lipopolysaccharide or other endogenous molecules (palmitate, S100A9, IL-6) further modulated the activation of the NLRP3-inflammasome in CAPS, thus expanding the repertoire of molecules secreted from patients’ macrophages involved in disease pathogenesis. NLRP3-inflammasomes with CAPS-associated variants mainly affected the immunometabolism of the myeloid compartment, leading to disruptions in lipids and amino acid pathways and impaired glycolysis, limiting IL-1β production. These findings demonstrate that NLRP3 variants causing CAPS form a constitutively active inflammasome that induces basal pyroptosis and IL-18 release without cell priming, favouring the host's innate defense against pathogens while also tempering the onset of IL-1β–dependent inflammatory episodes through immunometabolism modulation.

ORGANISM(S): Mus musculus

PROVIDER: GSE246713 | GEO | 2023/12/13

REPOSITORIES: GEO

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Project description:BACKGROUND: Cryopyrin-Associated Periodic Syndrome (CAPS) is an autoinflammatory condition consequence of monoallelic variants in the NLRP3 gene that exacerbate IL-1β production. These variants are gain-of-function, but the exact regulatory mechanism of the NLRP3 CAPS-inflammasome is not well yet understood. It is considered as a hypersensitive inflammasome triggered by cell priming, but patients with CAPS and animal disease models present inflammatory flares in the absence of external triggers.OBJECTIVES: To study the regulation and activation of the NLRP3 inflammasome in CAPS.METHODS: CAPS derived blood samples and genetically modified macrophages expressing different NLRP3 CAPS-associated variants were used to assess NLRP3 function dissociated from cell priming and cell metabolism.RESULTS: We found that CAPS-associated variants constitutively result in active NLRP3 inflammasomes, that induce a basal cleavage of gasdermin D, IL-18 release and pyroptosis. The constitutive active NLRP3 inflammasome was blocked by MCC950 and was dependent on NLRP3 expression level, being further regulated by deubiquitination. We also showed that activation of NF-κB with lipopolysaccharide or other endogenous host-derived molecules (palmitate, S100A9 or IL-6) further modulated the activation of the NLRP3 CAPS inflammasome and expanded the repertoire of molecules secreted from CAPS macrophages to IL-1β, IL-1α, HMGB1, cystatin B and the P2X7 receptor, identifying novel proteins involved in CAPS pathogenesis. NLRP3 inflammasomes with CAPS associated variants affected the immunometabolism of the myeloid compartment and impaired glycolysis.CONCLUSIONS: These findings demonstrate that NLRP3 CAPS-associated variants form a constitutive active inflammasome that induce basal pyroptosis and IL-18 release without cell priming, suggesting a priming-independent mechanism for the initiation of CAPS flares characterized with a profound affection in the immunometabolism.

Project description:The cellular stress response plays a vital role in regulating homeostasis by modulating cell survival and death. Stress granules (referred to as SGs) are cytoplasmic compartments that allow cells to survive various stressors. Defects in SG assembly and disassembly have been found to play important roles in neurodegenerative diseases, antiviral responses and cancer1–5. Inflammasomes are multi-protein heteromeric complexes that sense intracellular pathogen- and damage-associated molecular patterns and assemble into cytosolic compartments called ASC specks to facilitate caspase-1 (CASP1) activation. This activation of inflammasomes induces secretion of the leaderless proinflammatory cytokines IL-1β and IL-18 and also drives cell fate towards pyroptosis, a form of programmed inflammatory cell death that plays major role in health and disease6–12. Cellular stress sensing can trigger both SGs and inflammasomes; however, they drive contrasting cell fate decisions during stress conditions. Crosstalk between SGs and inflammasomes to decide cell fate has not been well studied. Here we show that the induction of SGs specifically inhibits NLRP3 inflammasome activation, ASC speck formation and pyroptosis. The SG protein DDX3X interacts with NLRP3 to drive inflammasome activation in the absence of SGs. Assembly of SGs leads to the sequestration of DDX3X to inhibit NLRP3 inflammasome function. SGs and the NLRP3 inflammasome compete for DDX3X molecules to coordinate the activation of innate responses and subsequent cell fate decisions under stress conditions. Induction of SGs or loss of DDX3X in the myeloid compartment leads to decreased production of inflammasome-dependent cytokines in vivo. Our findings suggest that macrophages utilize DDX3X availability to interpret stress signals and choose between pro-survival SGs and pyroptotic ASC specks. Together, our data show the role of DDX3X in driving NLRP3 inflammasome and SG assembly, informing a new rheostat-like mechanistic paradigm for regulating live or die cell fate decisions under stress conditions.

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Mutant NLRP3 causing Cryopyrin-Associated Periodic Syndromes forms a constitutively active inflammasome and results in alteration in monocyte immunometabolism to limit IL-1β production

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