RESUMEN
Upon detecting pathogens or cell stress, several NOD-like receptors (NLRs) form inflammasome complexes with the adapter ASC and caspase-1, inducing gasdermin D (GSDMD)-dependent cell death and maturation and release of IL-1ß and IL-18. The triggers and activation mechanisms of several inflammasome-forming sensors are not well understood. Here we show that mitochondrial damage activates the NLRP10 inflammasome, leading to ASC speck formation and caspase-1-dependent cytokine release. While the AIM2 inflammasome can also sense mitochondrial demise by detecting mitochondrial DNA (mtDNA) in the cytosol, NLRP10 monitors mitochondrial integrity in an mtDNA-independent manner, suggesting the recognition of distinct molecular entities displayed by the damaged organelles. NLRP10 is highly expressed in differentiated human keratinocytes, in which it can also assemble an inflammasome. Our study shows that this inflammasome surveils mitochondrial integrity. These findings might also lead to a better understanding of mitochondria-linked inflammatory diseases.
Asunto(s)
Citocinas , Inflamasomas , Humanos , Inflamasomas/metabolismo , Caspasa 1/metabolismo , Citocinas/metabolismo , Muerte Celular , ADN Mitocondrial/genética , Interleucina-1beta/metabolismo , Proteína con Dominio Pirina 3 de la Familia NLR/genética , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis/metabolismoRESUMEN
Toll-like receptor (TLR) activation induces inflammatory responses in macrophages by activating temporally defined transcriptional cascades. Whether concurrent changes in the cellular metabolism that occur upon TLR activation influence the quality of the transcriptional responses remains unknown. Here, we investigated how macrophages adopt their metabolism early after activation to regulate TLR-inducible gene induction. Shortly after TLR4 activation, macrophages increased glycolysis and tricarboxylic acid (TCA) cycle volume. Metabolic tracing studies revealed that TLR signaling redirected metabolic fluxes to generate acetyl-Coenzyme A (CoA) from glucose resulting in augmented histone acetylation. Signaling through the adaptor proteins MyD88 and TRIF resulted in activation of ATP-citrate lyase, which in turn facilitated the induction of distinct LPS-inducible gene sets. We postulate that metabolic licensing of histone acetylation provides another layer of control that serves to fine-tune transcriptional responses downstream of TLR activation. Our work highlights the potential of targeting the metabolic-epigenetic axis in inflammatory settings.
Asunto(s)
ATP Citrato (pro-S)-Liasa/metabolismo , Acetilcoenzima A/metabolismo , Histonas/metabolismo , Macrófagos/metabolismo , Receptor Toll-Like 4/metabolismo , Acetilación , Proteínas Adaptadoras del Transporte Vesicular/genética , Proteínas Adaptadoras del Transporte Vesicular/metabolismo , Animales , Ciclo del Ácido Cítrico/fisiología , Glucólisis/fisiología , Humanos , Lipopolisacáridos/metabolismo , Macrófagos/inmunología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Factor 88 de Diferenciación Mieloide/genética , Factor 88 de Diferenciación Mieloide/metabolismo , Transducción de Señal , Transcripción Genética/genéticaRESUMEN
The 2'3'-cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulator of IFN genes (STING) pathway can sense infection and cellular stress by detecting cytosolic DNA. Upon ligand binding, cGAS produces the cyclic dinucleotide messenger cGAMP, which triggers its receptor STING. Active STING initiates gene transcription through the transcription factors IFN regulatory factor 3 (IRF3) and NF-κB and induces autophagy, but whether STING can cause changes in the metabolism of macrophages is unknown. In this study, we report that STING signaling activates ATP-citrate lyase (ACLY) by phosphorylation in human macrophages. Using genetic and pharmacologic perturbation, we show that STING targets ACLY via its prime downstream signaling effector TANK (TRAF family member-associated NF-κB activator)-binding kinase 1 (TBK1). We further identify that TBK1 alters cellular metabolism upon cGAMP treatment. Our results suggest that STING-mediated metabolic reprogramming adjusts the cellular response to DNA sensing in addition to transcription factor activation and autophagy induction.
Asunto(s)
FN-kappa B , Proteínas Serina-Treonina Quinasas , Humanos , ATP Citrato (pro-S)-Liasa/metabolismo , ADN , Factor 3 Regulador del Interferón/metabolismo , Macrófagos/metabolismo , Proteínas de la Membrana/metabolismo , FN-kappa B/metabolismo , Nucleotidiltransferasas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismoRESUMEN
Chronic inflammasome activation in mononuclear phagocytes (MNPs) promotes fibrosis in various tissues, including the kidney. The cellular and molecular links between the inflammasome and fibrosis are unclear. To address this question, we fed mice lacking various immunological mediators an adenine-enriched diet, which causes crystal precipitation in renal tubules, crystal-induced inflammasome activation, and renal fibrosis. We found that kidney fibrosis depended on an intrarenal inflammasome-dependent type 3 immune response driven by its signature transcription factor Rorc (retinoic acid receptor-related orphan receptor C gene), which was partially carried out by type 3 innate lymphoid cells (ILC3s). The role of ILCs in the kidney is less well known than in other organs, especially that of ILC3. In this article, we describe that depletion of ILCs or genetic deficiency for Rorc attenuated kidney inflammation and fibrosis. Among the inflammasome-derived cytokines, only IL-1ß expanded ILC3 and promoted fibrosis, whereas IL-18 caused differentiation of NKp46+ ILC3. Deficiency of the type 3 maintenance cytokine, IL-23, was more protective than IL-1ß inhibition, which may be explained by the downregulation of the IL-1R, but not of the IL-23R, by ILC3 early in the disease, allowing persistent sensing of IL-23. Mechanistically, ILC3s colocalized with renal MNPs in vivo as shown by multiepitope-ligand cartography. Cell culture experiments indicated that renal ILC3s caused renal MNPs to increase TGF-ß production that stimulated fibroblasts to produce collagen. We conclude that ILC3s link inflammasome activation with kidney inflammation and fibrosis and are regulated by IL-1ß and IL-23.
RESUMEN
Regulatory T cells (Tregs) maintain self-tolerance and prevent autoimmunity by controlling autoreactive T cells. We recently demonstrated in vivo that Tregs can directly suppress auto-reactive B cells via programmed death ligand 1 (PD-L1) that ligated PD-1 on B cells and caused them to undergo apoptosis. Here, we asked whether this mechanism is utilized by thymus-derived natural Tregs and/or by peripheral lymphoid tissue-induced Tregs. We first demonstrated that antigen-specific PD-L1-expressing Tregs were induced in the draining lymph node of autoantigen-expressing tissue and characterized them by their lack of the transcription factor Helios and of the surface marker Neuropilin-1 (Nrp-1). Next, we established an in vitro co-culture system to study the interaction between B cells and Treg subsets under controlled conditions. We found that Nrp- Treg, but not Nrp+ Treg suppressed autoreactive B cells, whereas both were able to suppress T-helper cells. Such suppression was antigen-specific and was facilitated by PD-L1/PD-1-induced apoptosis. Furthermore, it required physical cell contact and was MHC II-restricted, providing an explanation for the antigen-specificity of peripherally-induced Tregs. These findings identify a role for peripherally induced Helios- Nrp-1- inducible Treg in controlling peripheral B-cell tolerance against tissue auto-antigens.
Asunto(s)
Linfocitos B/inmunología , Antígeno B7-H1/metabolismo , Linfocitos T Reguladores/inmunología , Animales , Apoptosis , Autoantígenos/inmunología , Autoinmunidad , Proteínas de Unión al ADN/metabolismo , Factores de Transcripción Forkhead/metabolismo , Humanos , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Neuropilina-1/metabolismo , Autotolerancia , Factores de Transcripción/metabolismoRESUMEN
Infectious organisms and damage of cells can activate inflammasomes, which mediate tissue inflammation and adaptive immunity. These mechanisms evolved to curb the spread of microbes and to induce repair of the damaged tissue. Chronic activation of inflammasomes, however, contributes to non-resolving inflammatory responses that lead to immuno-pathologies. Inflammasome-activated cells undergo an inflammatory cell death associated with the release of potent pro-inflammatory cytokines and poorly characterized extracellular vesicles (EVs). Since inflammasome-induced EVs could signal inflammasome pathway activation in patients with chronic inflammation and modulate bystander cell activation, we performed a systems analysis of the ribonucleic acid (RNA) content and function of two EV classes. We show that EVs released from inflammasome-activated macrophages carry a specific RNA signature and contain interferon ß (IFNß). EV-associated IFNß induces an interferon signature in bystander cells and results in dampening of NLRP3 inflammasome responses. EVs could, therefore, serve as biomarkers for inflammasome activation and act to prevent systemic hyper-inflammatory states by restricting NLRP3 activation in bystander cells.