Epithelial RIG-I inflammasome activation suppresses antiviral immunity and promotes inflammatory responses in virus-induced asthma exacerbations and COVID-19

Rhinoviruses (RV) and inhaled allergens, such as house dust mite (HDM) are the major agents responsible for asthma onset, its life-threatening exacerbations and progression to severe disease. The role of severe acute respiratory syndrome coronavirus (SARS-CoV-2) in exacerbations of asthma or the influence of preexisting viral or allergic airway inflammation on the development of coronavirus disease 2019 (COVID-19) is largely unknown. To address this, we compared molecular mechanisms of HDM, RV and SARS-CoV-2 interactions in experimental RV infection in patients with asthma and healthy individuals. RV infection was sensed via retinoic acid-inducible gene I (RIG-I) helicase, but not via NLR family pyrin domain containing 3 (NLRP3), which led to subsequent apoptosis-associated speck like protein containing a caspase recruitment domain (ASC) recruitment, oligomerization and RIG-I inflammasome activation. This phenomenon was augmented in bronchial epithelium in patients with asthma, especially upon pre-exposure to HDM, which itself induced a priming step, pro-IL-1β release and early inhibition of RIG-I/TANK binding kinase 1/IκB kinase ϵ/type I/III interferons (RIG-I/TBK1/IKKϵ/IFN-I/III) responses. Excessive activation of RIG-I inflammasomes was partially responsible for the alteration and persistence of type I/III IFN responses, prolonged viral clearance and unresolved inflammation in asthma. RV/HDM-induced sustained IFN I/III responses initially restricted SARS-CoV-2 replication in epithelium of patients with asthma, but even this limited infection with SARS-CoV-2 augmented RIG-I inflammasome activation. Timely inhibition of the epithelial RIG-I inflammasome and reduction of IL-1β signaling may lead to more efficient viral clearance and lower the burden of RV and SARS-CoV-2 infection.

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Targeting NLRP3 Inflammasome Activation in Severe Asthma

Journal of Clinical Medicine ◽

10.3390/jcm8101615 ◽

2019 ◽

Vol 8 (10) ◽

pp. 1615 ◽

Cited By ~ 5

Author(s):

Efthymia Theofani ◽

Maria Semitekolou ◽

Ioannis Morianos ◽

Konstantinos Samitas ◽

Georgina Xanthou

Keyword(s):

Severe Asthma ◽

Nlrp3 Inflammasome ◽

Molecular Mechanisms ◽

Inflammatory Responses ◽

Pulmonary Inflammation ◽

Airflow Obstruction ◽

Inflammasome Activation ◽

Pyrin Domain ◽

Nlrp3 Inflammasome Activation ◽

Reversible Airflow Obstruction

Severe asthma (SA) is a chronic lung disease characterized by recurring symptoms of reversible airflow obstruction, airway hyper-responsiveness (AHR), and inflammation that is resistant to currently employed treatments. The nucleotide-binding oligomerization domain-like Receptor Family Pyrin Domain Containing 3 (NLRP3) inflammasome is an intracellular sensor that detects microbial motifs and endogenous danger signals and represents a key component of innate immune responses in the airways. Assembly of the NLRP3 inflammasome leads to caspase 1-dependent release of the pro-inflammatory cytokines IL-1β and IL-18 as well as pyroptosis. Accumulating evidence proposes that NLRP3 activation is critically involved in asthma pathogenesis. In fact, although NLRP3 facilitates the clearance of pathogens in the airways, persistent NLRP3 activation by inhaled irritants and/or innocuous environmental allergens can lead to overt pulmonary inflammation and exacerbation of asthma manifestations. Notably, administration of NLRP3 inhibitors in asthma models restrains AHR and pulmonary inflammation. Here, we provide an overview of the pathophysiology of SA, present molecular mechanisms underlying aberrant inflammatory responses in the airways, summarize recent studies pertinent to the biology and functions of NLRP3, and discuss the role of NLRP3 in the pathogenesis of asthma. Finally, we contemplate the potential of targeting NLRP3 as a novel therapeutic approach for the management of SA.

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Anti-NLRP3 Inflammasome Natural Compounds: An Update

Biomedicines ◽

10.3390/biomedicines9020136 ◽

2021 ◽

Vol 9 (2) ◽

pp. 136

Author(s):

Baolong Liu ◽

Jiujiu Yu

Keyword(s):

Nlrp3 Inflammasome ◽

Protein Complex ◽

Molecular Mechanisms ◽

Inflammatory Responses ◽

Natural Compounds ◽

Pyrin Domain ◽

Inflammatory Protein ◽

Wide Range ◽

Activation Mechanisms ◽

Stress Signals

The nucleotide-binding domain and leucine-rich repeat related (NLR) family, pyrin domain containing 3 (NLRP3) inflammasome is a multimeric protein complex that recognizes various danger or stress signals from pathogens, the host, and the environment, leading to activation of caspase-1 and inducing inflammatory responses. This pro-inflammatory protein complex plays critical roles in pathogenesis of a wide range of diseases including neurodegenerative diseases, autoinflammatory diseases, and metabolic disorders. Therefore, intensive efforts have been devoted to understanding its activation mechanisms and to searching for its specific inhibitors. Approximately forty natural compounds with anti-NLRP3 inflammasome properties have been identified. Here, we provide an update about new natural compounds that have been identified within the last three years to inhibit the NLRP3 inflammasome and offer an overview of the underlying molecular mechanisms of their anti-NLRP3 inflammasome activities.

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IFN-mediated negative feedback supports bacteria class-specific macrophage inflammatory responses

eLife ◽

10.7554/elife.46836 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 2

Author(s):

Rachel A Gottschalk ◽

Michael G Dorrington ◽

Bhaskar Dutta ◽

Kathleen S Krauss ◽

Andrew J Martins ◽

...

Keyword(s):

Negative Feedback ◽

Molecular Mechanisms ◽

Cytokine Production ◽

Inflammatory Responses ◽

Type I ◽

Gram Negative Bacteria ◽

Gram Positive ◽

Gram Negative

Despite existing evidence for tuning of innate immunity to different classes of bacteria, the molecular mechanisms used by macrophages to tailor inflammatory responses to specific pathogens remain incompletely defined. By stimulating mouse macrophages with a titration matrix of TLR ligand pairs, we identified distinct stimulus requirements for activating and inhibitory events that evoked diverse cytokine production dynamics. These regulatory events were linked to patterns of inflammatory responses that distinguished between Gram-positive and Gram-negative bacteria, both in vitro and after in vivo lung infection. Stimulation beyond a TLR4 threshold and Gram-negative bacteria-induced responses were characterized by a rapid type I IFN-dependent decline in inflammatory cytokine production, independent of IL-10, whereas inflammatory responses to Gram-positive species were more sustained due to the absence of this IFN-dependent regulation. Thus, disparate triggering of a cytokine negative feedback loop promotes tuning of macrophage responses in a bacteria class-specific manner and provides context-dependent regulation of inflammation dynamics.

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NLRP3 inflammasome in endothelial dysfunction

Cell Death and Disease ◽

10.1038/s41419-020-02985-x ◽

2020 ◽

Vol 11 (9) ◽

Cited By ~ 3

Author(s):

Baochen Bai ◽

Yanyan Yang ◽

Qi Wang ◽

Min Li ◽

Chao Tian ◽

...

Keyword(s):

Oxidative Stress ◽

Endothelial Dysfunction ◽

Nlrp3 Inflammasome ◽

Inflammatory Responses ◽

Protein Complexes ◽

Cell Damage ◽

Inflammasome Activation ◽

Pyrin Domain ◽

Nlrp3 Inflammasome Activation ◽

Clinical Drugs

Abstract Inflammasomes are a class of cytosolic protein complexes. They act as cytosolic innate immune signal receptors to sense pathogens and initiate inflammatory responses under physiological and pathological conditions. The NLR-family pyrin domain-containing protein 3 (NLRP3) inflammasome is the most characteristic multimeric protein complex. Its activation triggers the cleavage of pro-interleukin (IL)-1β and pro-IL-18, which are mediated by caspase-1, and secretes mature forms of these mediators from cells to promote the further inflammatory process and oxidative stress. Simultaneously, cells undergo pro-inflammatory programmed cell death, termed pyroptosis. The danger signals for activating NLRP3 inflammasome are very extensive, especially reactive oxygen species (ROS), which act as an intermediate trigger to activate NLRP3 inflammasome, exacerbating subsequent inflammatory cascades and cell damage. Vascular endothelium at the site of inflammation is actively involved in the regulation of inflammation progression with important implications for cardiovascular homeostasis as a dynamically adaptable interface. Endothelial dysfunction is a hallmark and predictor for cardiovascular ailments or adverse cardiovascular events, such as coronary artery disease, diabetes mellitus, hypertension, and hypercholesterolemia. The loss of proper endothelial function may lead to tissue swelling, chronic inflammation, and the formation of thrombi. As such, elimination of endothelial cell inflammation or activation is of clinical relevance. In this review, we provided a comprehensive perspective on the pivotal role of NLRP3 inflammasome activation in aggravating oxidative stress and endothelial dysfunction and the possible underlying mechanisms. Furthermore, we highlighted the contribution of noncoding RNAs to NLRP3 inflammasome activation-associated endothelial dysfunction, and outlined potential clinical drugs targeting NLRP3 inflammasome involved in endothelial dysfunction. Collectively, this summary provides recent developments and perspectives on how NLRP3 inflammasome interferes with endothelial dysfunction and the potential research value of NLRP3 inflammasome as a potential mediator of endothelial dysfunction.

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NLRP3 inflammasome signaling is activated by low-level lysosome disruption but inhibited by extensive lysosome disruption: roles for K+ efflux and Ca2+ influx

AJP Cell Physiology ◽

10.1152/ajpcell.00298.2015 ◽

2016 ◽

Vol 311 (1) ◽

pp. C83-C100 ◽

Cited By ~ 38

Author(s):

Michael A. Katsnelson ◽

Kristen M. Lozada-Soto ◽

Hana M. Russo ◽

Barbara A. Miller ◽

George R. Dubyak

Keyword(s):

Nlrp3 Inflammasome ◽

Inflammatory Responses ◽

Dominant Negative ◽

Cell Physiology ◽

Inflammasome Activation ◽

Negative Effects ◽

Murine Bone Marrow ◽

Caspase 1 ◽

Pyrin Domain ◽

Nlrp3 Inflammasome Activation

Nucleotide-binding domain, leucine-rich-repeat-containing family, pyrin domain-containing 3 (NLRP3) is a cytosolic protein that nucleates assembly of inflammasome signaling platforms, which facilitate caspase-1-mediated IL-1β release and other inflammatory responses in myeloid leukocytes. NLRP3 inflammasomes are assembled in response to multiple pathogen- or environmental stress-induced changes in basic cell physiology, including the destabilization of lysosome integrity and activation of K+-permeable channels/transporters in the plasma membrane (PM). However, the quantitative relationships between lysosome membrane permeabilization (LMP), induction of increased PM K+ permeability, and activation of NLRP3 signaling are incompletely characterized. We used Leu-Leu- O-methyl ester (LLME), a soluble lysosomotropic agent, to quantitatively track the kinetics and extent of LMP in relation to NLRP3 inflammasome signaling responses (ASC oligomerization, caspase-1 activation, IL-1β release) and PM cation fluxes in murine bone marrow-derived dendritic cells (BMDCs). Treatment of BMDCs with submillimolar (≤1 mM) LLME induced slower and partial increases in LMP that correlated with robust NLRP3 inflammasome activation and K+ efflux. In contrast, supramillimolar (≥2 mM) LLME elicited extremely rapid and complete collapse of lysosome integrity that was correlated with suppression of inflammasome signaling. Supramillimolar LLME also induced dominant negative effects on inflammasome activation by the canonical NLRP3 agonist nigericin; this inhibition correlated with an increase in NLRP3 ubiquitination. LMP elicited rapid BMDC death by both inflammasome-dependent pyroptosis and inflammasome-independent necrosis. LMP also triggered Ca2+ influx, which attenuated LLME-stimulated NLRP3 inflammasome signaling but potentiated LLME-induced necrosis. Taken together, these studies reveal a previously unappreciated signaling network that defines the coupling between LMP, changes in PM cation fluxes, cell death, and NLRP3 inflammasome activation.

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Inhibition of the Inflammasome Complex Reduces the Inflammatory Response after Thromboembolic Stroke in Mice

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.2008.143 ◽

2008 ◽

Vol 29 (3) ◽

pp. 534-544 ◽

Cited By ~ 190

Author(s):

Denise P Abulafia ◽

Juan Pablo de Rivero Vaccari ◽

J Diego Lozano ◽

George Lotocki ◽

Robert W Keane ◽

...

Keyword(s):

Inflammatory Responses ◽

Neutralizing Antibody ◽

Immunohistochemical Analysis ◽

Size Exclusion ◽

Macromolecular Complex ◽

Inflammasome Activation ◽

Thromboembolic Stroke ◽

Caspase 1 ◽

Pyrin Domain ◽

Apoptosis Protein

Inflammation is a major contributor to the pathogenesis of cerebral ischemia and stroke. In the peripheral immune response, caspase-1 activation involves the formation of a macromolecular complex termed the inflammasome. We determined whether nucleotide-binding, leucine-rich repeat, pyrin domain containing 1 (NLRP1), molecular platform consisting of capase-1, apoptosis-associated speck-like protein containing a caspase-activating recruitment domain (ASC), and NLRP1, is expressed in the normal and postischemic brain. Mice underwent thromboembolic stroke to investigate the formation of the inflammasome and subsequent activation of downstream inflammatory responses. Western blot analysis showed expression and activation of interleukin (IL) IL-1β and IL-18 at 24 h after stroke. Size-exclusion chromatography and coimmunoprecipitation analysis showed protein association between NLRP1, ASC, caspase-1, and the X-linked inhibitor of apoptosis protein (XIAP). After ischemia, immunohistochemical analysis revealed inflammasome proteins in neurons, astrocytes, and microglia/macrophages. The potential of the inflammasome as an antiinflammatory target was showed by interference of inflammasome activation resulting in reduced cytokine levels in mice treated after ischemia with a neutralizing antibody against NLRP1. These findings show that the inflammasome complex forms after focal brain ischemia and may be a novel therapeutic target for reducing the detrimental consequences of postischemic inflammation.

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Anakinra Activates Superoxide Dismutase 2 to Mitigate Inflammasome Activity

International Journal of Molecular Sciences ◽

10.3390/ijms22126531 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6531

Author(s):

Marilena Pariano ◽

Stefania Pieroni ◽

Antonella De Luca ◽

Rossana G. Iannitti ◽

Monica Borghi ◽

...

Keyword(s):

Superoxide Dismutase ◽

Inflammatory Responses ◽

Interleukin 1 ◽

Inflammasome Activation ◽

Mitochondrial Oxidative Stress ◽

Pyrin Domain ◽

Mitochondrial Ros ◽

Activation Of Transcription ◽

Superoxide Dismutase 2 ◽

Nlrp3 Activity

Inflammasomes are powerful cytosolic sensors of environmental stressors and are critical for triggering interleukin-1 (IL-1)-mediated inflammatory responses. However, dysregulation of inflammasome activation may lead to pathological conditions, and the identification of negative regulators for therapeutic purposes is increasingly being recognized. Anakinra, the recombinant form of the IL-1 receptor antagonist, proved effective by preventing the binding of IL-1 to its receptor, IL-1R1, thus restoring autophagy and dampening NLR family pyrin domain containing 3 (NLRP3) activity. As the generation of mitochondrial reactive oxidative species (ROS) is a critical upstream event in the activation of NLRP3, we investigated whether anakinra would regulate mitochondrial ROS production. By profiling the activation of transcription factors induced in murine alveolar macrophages, we found a mitochondrial antioxidative pathway induced by anakinra involving the manganese-dependent superoxide dismutase (MnSOD) or SOD2. Molecularly, anakinra promotes the binding of SOD2 with the deubiquitinase Ubiquitin Specific Peptidase 36 (USP36) and Constitutive photomorphogenesis 9 (COP9) signalosome, thus increasing SOD2 protein longevity. Functionally, anakinra and SOD2 protects mice from pulmonary oxidative inflammation and infection. On a preclinical level, anakinra upregulates SOD2 in murine models of chronic granulomatous disease (CGD) and cystic fibrosis (CF). These data suggest that protection from mitochondrial oxidative stress may represent an additional mechanism underlying the clinical benefit of anakinra and identifies SOD2 as a potential therapeutic target.

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The Roles of Inflammasomes in Host Defense against Mycobacterium tuberculosis

Pathogens ◽

10.3390/pathogens10020120 ◽

2021 ◽

Vol 10 (2) ◽

pp. 120

Author(s):

Jialu Ma ◽

Shasha Zhao ◽

Xiao Gao ◽

Rui Wang ◽

Juan Liu ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Host Defense ◽

Inflammatory Responses ◽

Inflammasome Activation ◽

Caspase Activation ◽

Nucleotide Binding Domain ◽

Caspase 1 ◽

Pyrin Domain

Mycobacterium tuberculosis (MTB) infection is characterized by granulomatous lung lesions and systemic inflammatory responses during active disease. Inflammasome activation is involved in regulation of inflammation. Inflammasomes are multiprotein complexes serving a platform for activation of caspase-1, which cleaves the proinflammatory cytokines such as interleukin-1β (IL-1β) and IL-18 into their active forms. These cytokines play an essential role in MTB control. MTB infection triggers activation of the nucleotide-binding domain, leucine-rich-repeat containing family, pyrin domain-containing 3 (NLRP3) and absent in melanoma 2 (AIM2) inflammasomes in vitro, but only AIM2 and apoptosis-associated speck-like protein containing a caspase-activation recruitment domain (ASC), rather than NLRP3 or caspase-1, favor host survival and restriction of mycobacterial replication in vivo. Interferons (IFNs) inhibits MTB-induced inflammasome activation and IL-1 signaling. In this review, we focus on activation and regulation of the NLRP3 and AIM2 inflammasomes after exposure to MTB, as well as the effect of inflammasome activation on host defense against the infection.

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Impaired type I interferon activity and exacerbated inflammatory responses in severe Covid-19 patients

10.1101/2020.04.19.20068015 ◽

2020 ◽

Cited By ~ 70

Author(s):

Jérôme Hadjadj ◽

Nader Yatim ◽

Laura Barnabei ◽

Aurélien Corneau ◽

Jeremy Boussier ◽

...

Keyword(s):

Molecular Mechanisms ◽

Inflammatory Responses ◽

High Risk Population ◽

Type I ◽

Interferon Stimulated Genes ◽

Tnf Α ◽

Interferon Activity ◽

Anti Inflammatory ◽

Global Threat ◽

Necrosis Factor

AbstractBackgroundCoronavirus disease 2019 (Covid-19) is a major global threat that has already caused more than 100,000 deaths worldwide. It is characterized by distinct patterns of disease progression implying a diverse host immune response. However, the immunological features and molecular mechanisms involved in Covid-19 severity remain so far poorly known.MethodsWe performed an integrated immune analysis that included in-depth phenotypical profiling of immune cells, whole-blood transcriptomic and cytokine quantification on a cohort of fifty Covid19 patients with a spectrum of disease severity. All patient were tested 8 to 12 days following first symptoms and in absence of anti-inflammatory therapy.ResultsA unique phenotype in severe and critically ill patients was identified. It consists in a profoundly impaired interferon (IFN) type I response characterized by a low interferon production and activity, with consequent downregulation of interferon-stimulated genes. This was associated with a persistent blood virus load and an exacerbated inflammatory response that was partially driven by the transcriptional factor NFĸB. It was also characterized by increased tumor necrosis factor (TNF)-α and interleukin (IL)-6 production and signaling as well as increased innate immune chemokines.ConclusionWe propose that type-I IFN deficiency in the blood is a hallmark of severe Covid-19 and could identify and define a high-risk population. Our study provides a rationale for testing IFN administration combined with adapted anti-inflammatory therapy targeting IL-6 or TNF-α in most severe patients. These data also raise concern for utilization of drugs that interfere with the IFN pathway.

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Mitochondria: powering the innate immune response to Mycobacterium tuberculosis infection

Infection and Immunity ◽

10.1128/iai.00687-20 ◽

2021 ◽

Author(s):

Kristin L. Patrick ◽

Robert O. Watson

Keyword(s):

Mycobacterium Tuberculosis ◽

Immune Responses ◽

Molecular Mechanisms ◽

Bacterial Pathogen ◽

Tuberculosis Patient ◽

Innate Immune ◽

Inflammasome Activation ◽

Type I ◽

Innate Immune Responses ◽

Mycobacterium Tuberculosis Infection

Within the last decade, we have learned that damaged mitochondria activate many of the same innate immune pathways that evolved to sense and respond to intracellular pathogens. These shared responses include cytosolic nucleic acid sensing and type I interferon (IFN) expression, inflammasome activation that leads to pyroptosis, and selective autophagy (called mitophagy when mitochondria are the cargo). Because mitochondria were once bacteria, parallels between how cells respond to mitochondrial and bacterial ligands are not altogether surprising. However, the potential for crosstalk or synergy between bacteria- and mitochondria-driven innate immune responses during infection remains poorly understood. This interplay is particularly striking—and intriguing—in the context of infection with the intracellular bacterial pathogen Mycobacterium tuberculosis (Mtb). Multiple studies point to a role for Mtb infection and/or specific Mtb virulence factors in disrupting the mitochondrial network in macrophages leading to metabolic changes and triggering potent innate immune responses. Research from our labs and others argues that mutations in mitochondrial genes can exacerbate mycobacterial disease severity by hyper-activating innate responses or activating them at the wrong time. Indeed, growing evidence supports a model whereby different mitochondrial defects or mutations alter Mtb infection outcomes in distinct ways. By synthesizing the current literature in this minireview, we hope to gain insight into the molecular mechanisms driving, and consequences of, mitochondrial-dependent immune polarization so that we might better predict tuberculosis patient outcomes and develop host-directed therapeutics designed to correct these imbalances.

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