Inflammasome Platform Research Articles

Endogenous innate sensor NLRP3 is a key component in peritoneal macrophage dynamics required for cestode establishment

The NLRP3 receptor can assemble inflammasome platforms to trigger inflammatory responses; however, accumulating evidence suggests that it can also display anti-inflammatory properties. Here, we explored the role of nucleotide-binding oligomerization domain pyrin-containing protein 3 (NLRP3) in Taenia crassiceps experimental infection, which requires immune polarization into a Th2-type profile and peritoneal influx of suppressive macrophages for successful colonization. NLRP3 deficient mice (NLRP3−/−) were highly resistant against T. crassiceps, relative to wild-type (WT) mice. Resistance in NLRP3−/− mice was associated with a diminished IL-4 output, high levels of IL-15, growth factor for both innate and adaptive lymphocytes, and a dramatic decrease in peritoneum-infiltrating suppressive macrophages. Also, a transcriptional analysis on bone marrow-derived macrophages exposed to Taenia-secreted antigens and IL-4 revealed that NLRP3−/− macrophages express reduced transcripts of relm-α and PD-1 ligands, markers of alternative activation and suppressive ability, respectively. Finally, we found that the resistance displayed by NLRP3−/− mice is transferred through intestinal microbiota exchange, since WT mice co-housed with NLRP3−/− mice were significantly more resistant than WT animals preserving their native microbiota. Altogether, these data demonstrate that NLRP3 is a component of innate immunity required for T. crassiceps to establish, most likely contributing to macrophage recruitment, and controlling lymphocyte-stimulating cytokines such as IL-15.

Pharmacological Analysis of NLRP3 Inflammasome Inhibitor Sodium [(1,2,3,5,6,7-Hexahydro-s-indacen-4-yl)carbamoyl][(1-methyl-1H-pyrazol-4-yl)({[(2S)-oxolan-2-yl]methyl})sulfamoyl]azanide in Cellular and Mouse Models of Inflammation Provides a Translational Framework.

Interleukin (IL)-1β is an apex proinflammatory cytokine produced in response to tissue injury and infection. The output of IL-1β from monocytes and macrophages is regulated not only by transcription and translation but also post-translationally. Release of the active cytokine requires activation of inflammasomes, which couple IL-1β post-translational proteolysis with pyroptosis. Among inflammasome platforms, NOD-like receptor pyrin domain-containing protein 3 (NLRP3) is implicated in the pathogenesis of numerous human disorders in which disease-specific danger-associated molecular patterns (DAMPS) are positioned to drive its activation. As a promising therapeutic target, numerous candidate NLRP3-targeting therapeutics have been described and demonstrated to provide benefits in the context of animal disease models. While showing benefits, published preclinical studies have not explored dose-response relationships within the context of the models. Here, the preclinical pharmacology of a new chemical entity, [(1,2,3,5,6,7-hexahydro-s-indacen-4-yl)carbamoyl][(1-methyl-1H-pyrazol-4-yl)({[(2S)-oxolan-2-yl]methyl})sulfamoyl]azanide (NT-0249), is detailed, establishing its potency and selectivity as an NLRP3 inhibitor. NT-0249 also is evaluated in two acute in vivo mouse challenge models where pharmacodynamic/pharmacokinetic relationships align well with in vitro blood potency assessments. The therapeutic utility of NT-0249 is established in a mouse model of cryopyrin-associated periodic syndrome (CAPS). In this model, mice express a human gain-of-function NLRP3 allele and develop chronic and progressive IL-1β-dependent autoinflammatory disease. NT-0249 dose-dependently reduced multiple inflammatory biomarkers in this model. Significantly, NT-0249 decreased mature IL-1β levels in tissue homogenates, confirming in vivo target engagement. Our findings highlight not only the pharmacological attributes of NT-0249 but also provide insight into the extent of target suppression that will be required to achieve clinical benefit.

The role of inflammasomes as central inflammatory hubs in Mycobacterium tuberculosis infection.

Mycobacterium tuberculosis (Mtb) infection represents a global health problem and is characterized by formation of granuloma with a necrotic center and a systemic inflammatory response. Inflammasomes have a crucial role in the host immune response towards Mtb. These intracellular multi-protein complexes are assembled in response to pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs). Inflammasome platforms activate caspases, leading to the maturation of the proinflammatory cytokines interleukin (IL)-1 and 18 and the cleavage of gasdermin D (GSDMD), a pore-forming protein responsible for cytokine release and pyroptotic cell death. Recent in vitro and in vivo findings have highlighted the importance of inflammasome signaling and subsequent necrotic cell death in Mtb-infected innate immune cells. However, we are just beginning to understand how inflammasomes contribute to disease or to a protective immune response in tuberculosis (TB). A detailed molecular understanding of inflammasome-associated pathomechanisms may foster the development of novel host-directed therapeutics or vaccines with improved activity. In this mini-review, we discuss the regulatory and molecular aspects of inflammasome activation and the associated immunological consequences for Mtb pathogenesis.

Bacillus Calmette-Guérin-Trained Macrophages Elicit a Protective Inflammatory Response against the Pathogenic Bacteria Brucella abortus.

The bacillus Calmette-Guérin (BCG) can elicit enhanced innate immune responses against a wide range of infections, known as trained immunity. Brucella abortus is the causative agent of brucellosis, a debilitating disease that affects humans and animals. In this study, we demonstrate that C57BL/6 mouse bone marrow-derived macrophages under BCG training enhance inflammatory responses against B. abortus. BCG-trained macrophages showed increased MHC class II and CD40 expression on the cell surface and higher IL-6, IL-12, and IL-1β production. The increase in IL-1β secretion was accompanied by enhanced activation of canonical and noncanonical inflammasome platforms. We observed elevated caspase-11 expression and caspase-1 processing in BCG-trained macrophages in response to B. abortus compared with untrained cells. In addition, these BCG-trained cells showed higher NLRP3 expression after B. abortus infection. From a metabolic point of view, signaling through the Akt/mammalian target of rapamycin/S6 kinase pathway was also enhanced. In addition, BCG training resulted in higher inducible NO synthase expression and nitrite production, culminating in an improved macrophage-killing capacity against intracellular B. abortus. In vivo, we monitored a significant reduction in the bacterial burden in organs from BCG-trained C57BL/6 mice when compared with the untrained group. In addition, previous BCG immunization of RAG-1-deficient mice partially protects against Brucella infection, suggesting the important role of the innate immune compartment in this scenario. Furthermore, naive recipient mice that received BM transfer from BCG-trained donors showed greater resistance to B. abortus when compared with their untrained counterparts. These results demonstrate that BCG-induced trained immunity in mice results in better control of intracellular B. abortus invivo and invitro.

Exosomal miRNAs targeting NLRP3 inflammasome platform are associated with radiologic sequelae in survivors of COVID-19-associated acute respiratory distress syndrome

Background: There is limited understanding of the pathophysiology of post-acute pulmonary sequelae in COVID-19-associated acute respiratory distress syndrome (ARDS). We aimed at investigating the association of circulating microRNAs (miRNAs) involved in post-transcriptional regulation of NLRP3-inflammasome pathways and lung radiological features among COVID-19- associated ARDS survivors. Methods: We evaluated COVID-19-associated ARDS survivors at 4±2 months from clinical recovery. Patients were selected based on imaging pattern evolution according to chest high-resolution computerized tomography (HRCT) findings into “fully recovered” (FR), “pulmonary opacities” (PO) and “fibrosis-like lesions” (FL) according to radiological appearance. Plasma miRNA profiling was performed using real time quantitative polymerase chain reaction (RT-qPCR). The exosomal expression of NLRP3 inflammasome related miRNAs (miR-17-5p, miR-223-3p, miR-146a-5p) was evaluated. Results: 31 patients (33% men, mean age 60±6 years, mean BMI 31.1±6.6 Kg/m2) were selected for the present study. No statistically significant differences between FR, PO and FL patterns were observed according to clinical features. NLRP3-inflammasome-related miRNAs such as miR-17-5p, miR-223-3p and miR-146a-5p were significantly up-regulated in patients with PO when compared to patients with FL. miR-146a-5p was also up-regulated in patients with FL than in FR. Conclusions: In patients with long-term pulmonary radiological sequelae following COVID71 19- associated ARDS, a down-regulation of miRNAs inhibiting NLRP3 (miR-17-5p, miR-146a72 3p and miR-223-3p) correlated to fibrosis development in patients showing persistent hyper-reactivity to inflammatory stimulation. NLRP3-Inflammasome-related miRNAs could be a possible therapeutic target to prevent the fibrotic evolution of COVID-19-associated ARDS.

Pyroptosis in neutrophils: Multimodal integration of inflammasome and regulated cell death signaling pathways.

Pyroptosis is a proinflammatory mode of lytic cell death mediated by accumulation of plasma membrane (PM) macropores composed of gasdermin-family (GSDM) proteins. It facilitates two major functions in innate immunity: (i) elimination of intracellular replicative niches for pathogenic bacteria; and (ii) non-classical secretion of IL-1 family cytokines that amplify host-beneficial inflammatory responses to microbial infection or tissue damage. Physiological roles for gasdermin D (GSDMD) in pyroptosis and IL-1β release during inflammasome signaling have been extensively characterized in macrophages. This involves cleavage of GSDMD by caspase-1 to generate GSDMD macropores that mediate IL-1β efflux and progression to pyroptotic lysis. Neutrophils, which rapidly accumulate in large numbers at sites of tissue infection or damage, become the predominant local source of IL-1β in coordination with their potent microbiocidal capacity. Similar to macrophages, neutrophils express GSDMD and utilize the same spectrum of diverse inflammasome platforms for caspase-1-mediated cleavage of GSDMD. Distinct from macrophages, neutrophils possess a remarkable capacity to resist progression to GSDMD-dependent pyroptotic lysis to preserve their viability for efficient microbial killing while maintaining GSDMD-dependent mechanisms for export of bioactive IL-1β. Rather, neutrophils employ cell-specific mechanisms to conditionally engage GSDMD-mediated pyroptosis in response to bacterial pathogens that use neutrophils as replicative niches. GSDMD and pyroptosis have also been mechanistically linked to induction of NETosis, a signature neutrophil pathway that expels decondensed nuclear DNA into extracellular compartments for immobilization and killing of microbial pathogens. This review summarizes a rapidly growing number of recent studies that have produced new insights, unexpected mechanistic nuances, and some controversies regarding the regulation of, and roles for, neutrophil inflammasomes, pyroptosis, and GSDMs in diverse innate immune responses.

The P2X7R-NLRP3 and AIM2 Inflammasome Platforms Mark the Complexity/Severity of Viral or Metabolic Liver Damage

P2X7R-NLRP3 and AIM2 inflammasomes activate caspase-1 and the release of cytokines involved in viral-related liver disease. Little is known about their role in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steato-hepatitis (NASH). We characterized the role of inflammasomes in NAFLD, NASH, and HCV. Gene expression and subcellular localization of P2X7R/P2X4R-NLRP3 and AIM2 inflammasome components were examined in histopathological preparations of 46 patients with biopsy-proven viral and metabolic liver disease using real-time PCR and immunofluorescence. P2X7R, P2X4R, and Caspase-1 are two- to five-fold more expressed in patients with NAFLD/NASH associated with chronic HCV infection than those with metabolic damage only (p ≤ 0.01 for all comparisons). The AIM2 inflammasome is 4.4 times more expressed in patients with chronic HCV infection, regardless of coexistent metabolic abnormalities (p = 0.0006). IL-2, a cytokine playing a pivotal role during chronic HCV infection, showed a similar expression in HCV and NASH patients (p = 0.77) but was virtually absent in NAFLD. The P2X7R-NLRP3 complex prevailed in infiltrating macrophages, while AIM2 was localized in Kupffer cells. Caspase-1 expression correlated with elastography-based liver fibrosis (r = 0.35, p = 0.02), whereas P2X7R, P2X4R, NRLP3, Caspase-1, and IL-2 expression correlated with circulating markers of disease severity. P2X7R and P2X4R play a major role in liver inflammation accompanying chronic HCV infection, especially when combined with metabolic damage, while AIM2 is specifically expressed in chronic viral hepatitis. We describe for the first time the hepatic expression of IL-2 in NASH, so far considered a peculiarity of HCV-related liver damage.

Amniotic fluid stem cell-derived extracellular vesicles are independent metabolic units capable of modulating inflammasome activation in THP-1 cells.

An immunoregulatory role of stem cells, often mediated by their secretome, has been claimed by several studies. Stem cell-derived extracellular vesicles (EVs) are crucial components of the secretome. EVs, a heterogeneous group of membranous vesicles released by many cell types into the extracellular space, are now considered as an additional mechanism for intercellular communication. In this study, we aimed at investigating whether human amniotic stem cell-derived extracellular vesicles (HASC-EVs) were able to interfere with inflammasome activation in the THP-1 cell line. Two subsets of HASC-EVs were collected by sequential centrifugation, namely HASC-P10 and HASC-P100. We demonstrated that HASC-EVs were neither internalized into nor undertake a direct interaction with THP-1 cells. We showed that HASC-P10 and P100 were able to intrinsically produce ATP, which was further converted to adenosine by 5'-nucleotidase (CD73) and ectonucleoside triphosphate diphosphohydrolase-1 (CD39). We found that THP-1 cells conditioned with both types of HASC-EVs failed to activate the NLRP3/caspase-1/inflammasome platform in response to LPS and ATP treatment by a mechanism involving A2a adenosine receptor activation. These results support a role for HASC-EVs as independent metabolic units capable of modifying the cellular functions, leading to anti-inflammatory effects in monocytic cells.

Heme as an inducer of cerebral damage in hemorrhagic stroke: potential therapeutic implications.

Heme as an inducer of cerebral damage in hemorrhagic stroke: potential therapeutic implications.

P2X7 receptor/NLRP3 inflammasome complex and α-synuclein in peripheral blood mononuclear cells: a prospective study in neo-diagnosed, treatment-naïve Parkinson's disease.

Neuroinflammation and probably systemic inflammation, with abnormal α-synuclein deposition, participate in the development of Parkinson's disease (PD). The P2X7 receptor/NLRP3 inflammasome complex is upregulated in the brain of PD patients. By a prospective approach, the degree of systemic activation of such complex, and its regulatory mechanisms, were explored in treatment-naïve PD individuals. The expression and functional activity of the inflammasome were measured in peripheral blood mononuclear cells of 25 newly diagnosed PD patients and 25 controls at baseline and after 12months of pharmacological treatment, exploring the intracellular signalling involved and its epigenetic regulation. De novo PD patients were characterized by a systemic hyper-expression of the P2X7R/NLRP3 inflammasome platform, probably able to modulate lymphomonocyteα-synuclein, whose brain deposits represent the main pathogenetic factor of PD. A reduced c-Jun N-terminal kinase (JNK) phosphorylation might be the intracellular signalling mediating this effect. miR-7 and miR-30, implied in the pathogenesis of PD and in the post-transcriptional control of α-synuclein and NLRP3 expression, were also increased in PD. After 1year of usual anti-Parkinson treatments, such inflammatory platform was significantly reduced. Mononuclear cells of newly diagnosed PD subjects display a hyper-expression of the P2X7R/NLRP3 inflammasome platform that seems to modulate cellular α-synuclein content and is reduced after PD treatment; an impaired JNK phosphorylation might be the intracellular signalling mediating this effect, undergoing an epigenetic regulation by miR-7 and miR-30.

Autoantibodies in severe COVID-19-related acute respiratory distress syndrome: Just innocent bystanders?

Autoantibodies in severe COVID-19-related acute respiratory distress syndrome: Just innocent bystanders?

Sensing soluble uric acid by Naip1-Nlrp3 platform

Uric acid (UA), a product of purine nucleotide degradation able to initiate an immune response, represents a breakpoint in the evolutionary history of humans, when uricase, the enzyme required for UA cleavage, was lost. Despite being inert in human cells, UA in its soluble form (sUA) can increase the level of interleukin-1β (IL-1β) in murine macrophages. We, therefore, hypothesized that the recognition of sUA is achieved by the Naip1-Nlrp3 inflammasome platform. Through structural modelling predictions and transcriptome and functional analyses, we found that murine Naip1 expression in human macrophages induces IL-1β expression, fatty acid production and an inflammation-related response upon sUA stimulation, a process reversed by the pharmacological and genetic inhibition of Nlrp3. Moreover, molecular interaction experiments showed that Naip1 directly recognizes sUA. Accordingly, Naip may be the sUA receptor lost through the human evolutionary process, and a better understanding of its recognition may lead to novel anti-hyperuricaemia therapies.

The gliadin p31-43 peptide: Inducer of multiple proinflammatory effects.

Coeliac disease (CD) is the prototype of an inflammatory chronic disease induced by food. In this context, gliadin p31-43 peptide comes into the spotlight as an important player of the inflammatory/innate immune response to gliadin in CD. The p31-43 peptide is part of the p31-55 peptide from α-gliadins that remains undigested for a long time, and can be present in the small intestine after ingestion of a gluten-containing diet. Different biophysical methods and molecular dynamic simulations have shown that p31-43 spontaneously forms oligomeric nanostructures, whereas experimental approaches using in vitro assays, mouse models, and human duodenal tissues have shown that p31-43 is able to induce different forms of cellular stress by driving multiple inflammatory pathways. Increased proliferative activity of the epithelial cells in the crypts, enterocyte stress, activation of TG2, induction of Ca2+, IL-15, and NFκB signaling, inhibition of CFTR, alteration of vesicular trafficking, and activation of the inflammasome platform are some of the biological effects of p31-43, which, in the presence of appropriate genetic susceptibility and environmental factors, may act together to drive CD.

Parvovirus B19 activates in vitro normal human dermal fibroblasts: a possible implication in skin fibrosis and systemic sclerosis.

ObjectiveFibrosis is the most characteristic pathological hallmark of SSc, a connective tissue disease characterized by vascular and immunological abnormalities, inflammation and enhanced extracellular matrix production, leading to progressive fibrosis of skin and internal organs. We previously demonstrated that parvovirus B19 (B19V) can infect normal human dermal fibroblasts (NHDFs) and that B19V persists in SSc fibroblasts. In this study, we investigated whether parvovirus B19V is able to activate in vitro NHDFs and to induce in these cells some phenotypic features similar to that observed in the SSc fibroblasts.MethodsWe preliminarily analysed the time course of B19V infection in cultured NHDFs, then we investigated the ability of B19V to induce cell migration, invasive phenotype and mRNA expression of some profibrotic and/or proinflammatory genes.ResultsWe confirmed our previous findings that B19V infects NHDFs, but the infection is not productive. After incubation with B19V, NHDFs showed a significant increase of both migration and invasiveness, along with mRNA expression of different profibrotic genes (α-SMA, EDN-1, IL-6, TGF-β1 receptors 1 and 2, Col1α2), some genes associated with inflammasome platform (AIM2, IFI16, IL-1β, CASP-1) and genes for metalloprotease (MMP 2, 9 and 12).ConclusionThese data suggest that B19V can activate dermal fibroblasts and may have a role in the pathogenesis of fibrosis. B19V-induced fibroblast migration and invasiveness could be due to the B19V-associated MMP9 overexpression and activation. Moreover, the up-regulation of MMP12, typical of SSc, could link the B19V infection of fibroblasts to the anti-angiogenic process.

Inflammasomes in the Pathophysiology of Maternal Obesity: Potential Therapeutic Targets to Reduce Long-Term Adverse Health Outcomes in the Mother and Offspring.

Over the past 20 years, the prevalence of obesity has risen dramatically worldwide, with an increase in occurrence among women in their reproductive age. Obesity during pregnancy is associated with significantly increased maternal and fetal morbidity and mortality. In addition to the short-term adverse health outcomes, both mother and the child are prone to develop cardiovascular, metabolic and neurological disorders. Although associations between obesity during pregnancy and adverse maternalfetal health outcomes are clear, the complex molecular mechanisms underlying maternal obesity remain largely unknown. This review describes multimeric self-assembling protein complexes, namely inflammasomes, as potential molecular targets in the pathophysiology of maternal obesity. Inflammasomes are implicated in both normal physiological and in pathophysiological processes that occur in response to an inflammatory milieu throughout gestation. This review highlights the current knowledge of inflammasome expression and its activity in pregnancies affected by maternal obesity. Key discussions in defining pharmacological inhibition of upstream as well as downstream targets of the inflammasome signaling cascade; and the inflammasome platform, as a potential therapeutic strategy in attenuating the pathophysiology underpinning inflammatory component in maternal obesity are presented herein.

Transcriptional analysis of THP-1 cells infected with Leishmania infantum indicates no activation of the inflammasome platform.

Leishmaniasis is caused by intracellular parasites transmitted to vertebrates by sandfly bites. Clinical manifestations include cutaneous, mucosal or visceral involvement depending upon the host immune response and the parasite species. To assure their survival inside macrophages, these parasites developed a plethora of highly successful strategies to manipulate various immune system pathways. Considering that inflammasome activation is critical for the establishment of a protective immune response in many parasite infections, in this study we determined the transcriptome of THP-1 cells after infection with L. infantum, with a particular focus on the inflammasome components. To this end, the human cell line THP-1, previously differentiated into macrophages by PMA treatment, was infected with L. infantum promastigotes. Differentiated THP-1 cells were also stimulated with LPS to be used as a comparative parameter. The gene expression signature was determined 8 hours after by RNA-seq technique. Infected or uninfected THP-1 cells were stimulated with nigericin (NIG) to measure active caspase-1 and TNF-α, IL-6 and IL-1β levels in culture supernatants after 8, 24 and 48 hours. L. infantum triggered a gene expression pattern more similar to non-infected THP-1 cells and very distinct from LPS-stimulated cells. Some of the most up-regulated genes in L. infantum-infected cells were CDC20, CSF1, RPS6KA1, CD36, DUSP2, DUSP5, DUSP7 and TNFAIP3. Some up-regulated GO terms in infected cells included cell coagulation, regulation of MAPK cascade, response to peptide hormone stimulus, negative regulation of transcription from RNA polymerase II promoter and nerve growth factor receptor signaling pathway. Infection was not able to induce the expression of genes associated with the inflammasome signaling pathway. This finding was confirmed by the absence of caspase-1 activation and IL-1β production after 8, 24 and 48 hours of infection. Our results indicate that L. infantum was unable to activate the inflammasomes during the initial interaction with THP-1 cells.

Inflammasomes contributing to inflammation in arthritis.

Inflammasomes are intracellular multiprotein signaling platforms that initiate inflammatory responses in response to pathogens and cellular damage. Active inflammasomes induce the enzymatic activity of caspase-1, resulting in the induction of inflammatory cell death, pyroptosis, and the maturation and secretion of inflammatory cytokines IL-1β and IL-18. Inflammasomes are activated in many inflammatory diseases, including autoinflammatory disorders and arthritis, and inflammasome-specific therapies are under development for the treatment of inflammatory conditions. In this review, we outline the different inflammasome platforms and recent findings contributing to our knowledge about inflammasome biology in health and disease. In particular, we discuss the role of the inflammasome in the pathogenesis of arthritic diseases, including rheumatoid arthritis, gout, ankylosing spondylitis, and juvenile idiopathic arthritis, and the potential of newly developed therapies that specifically target the inflammasome or its products for the treatment of inflammatory diseases.

ASC phosphorylation at Y146 regulates inflammasome activation and pyroptosis

Abstract Rationale Inflammasome assembly and activation is a complex process regulated, in part, by posttranslational modification of inflammasome proteins. ASC is a universal adaptor in virtually all inflammasome platforms and its modification is critical in regulation of inflammasome function. In particular, PTK inhibitor AG126 greatly inhibits inflammasome activation. Methods We generated stable THP-1 cells with either overexpression of ASC (YFP-ASC) or knock down of ASC (siRNA and CRISPR) followed by ASC knock in. To test the role of ASC phosphorylation in inflammasome assembly and activity, we mutated the highly conserved tyrosine 146 to Y146A. Cells were stimulated with LPS or live bacteria and inflammasome activity was measured by fluorescent microscopy, ELISA, and immunoblotting. Results Upon inflammasome activation ASC is released from the cell together with IL-1β, IL-18 and other inflammasome proteins. Inhibition of select tyrosine kinases severely reduces inflammasome activation, pyroptosis and ASC release. Elimination of the potential phosphorylation site Y146 dramatically changes visible ASC complex formation – from a single round speck to a filamentous structure. Cells with the Y146A ASC mutation show significantly abrogated inflammasome activation as compared to a wild type. Screening of a PTK inhibitor library (Selleckchem) linked several tyrosine kinases to regulating ASC phosphorylation and inflammasome activity. Conclusion ASC phosphorylation at Y146 by tyrosine kinases is an important regulator of inflammasome activity and pyroptosis.

Metaflammation: Tissue-Specific Alterations of the NLRP3 Inflammasome Platform in Metabolic Syndrome.

In the last decades, the extension of life expectancy and the increased consumption of foods rich in saturated fats and added sugars have exposed the general population to emerging health problems. The prevalence of metabolic syndrome (MS), composed of a cluster of factors as obesity, dyslipidemia, hyperglycemia, and hypertension, is rapidly increasing in industrialized and developing countries leading to precocious onset of age-related diseases. Indeed, oxidative stress, accumulation of advanced glycation endproducts, and a chronic low-grade inflammation are common features of MS and physiological ageing. In particular, the entire set of MS factors contributes to the development of an inflammatory status named metaflammation, which has been associated with activation of early innate immune response through the assembling of the multiprotein complex inflammasome. The most investigated family of inflammasome platforms is the NOD-like receptor pyridine containing (NLRP) 3, which is activated by several exogenous and endogenous stimuli, leading to the sequential cleavage of caspase-1 and IL-1β, followed by secretion of active IL-1β. We here collect the most recent findings on NLRP3 activation in MS providing evidence of its central role in disease progression and organ dysfunction in target tissues of metaflammation, in particular in cardiovascular, hepatic and renal complications, with a focus on oxidative stress and advanced glycation endproducts. A wide overview of the most promising strategies for the modulation of NLRP3 activation and related metabolic repercussions is also provided, since the finding of specific pharmacological tools is an urgent requirement to reduce the social and economic burden of MS- and elderly-associated diseases.

Aldosterone activates NLRP3/inflammasome in the vasculature of type 2 diabetic mice.

IntroductionAldosterone levels were increased in diabetic patients and animals with type 2 diabetes mellitus (DM2). The excess of aldosterone (aldo) aggravates endothelial dysfunction in diabetes by promoting insulin resistance, fibrosis, oxidative stress and inflammation. The pro‐inflammatory cytokines IL‐1β was release by activation of NOD‐like receptors that comprise a group of pattern recognition receptors involved in a variety of host innate immune responses. Recently, our group demonstrated the involvement of NLRP3 in aldosterone‐induced vascular dysfunction. So, considering that we hypothesized which aldosterone activates the inflammasome platform in the vasculature of DM2 mice.MethodsMesenteric arteries from control (db/+) and diabetic (db/db) mice treated with vehicle or spironolactone (spiro – mineralocorticoid receptor (MR) antagonist, 50 mg/Kg/day) or NLRP3 antagonist (MCC950, 10 mg/Kg/day) were used to determine vascular reactivity and aldosterone‐induced inflammasome activation. The plasma of animals was used to evaluated IL‐1β and aldosterone levels.ResultsDb/db mice exhibited increased IL‐1β levels, increased vascular expression/activation of caspase‐1, as well reduced acetylcholine (ACh) vasodilation, compared to control (Cont) mice. Spironolactone and MCC950 treatment decreased plasma IL‐1β levels [(pg/mL) (Cont: 44.4±9.9 n=7; Cont+Spiro: 27.2±8.3 n=5, db/db: 85.4±21.9 n=7; db/db+Spiro: 11.6±3.2 n=6, p<0.05) and ( Cont: 2.0±2.0 n=6; Cont+MCC950: 0.0±0.0 n=3, db/db: 318.2±97.6 n=5; db/db+MCC950: 37.5±28.8 n=5, p<0.05)]. Spiro treatment but not MCC950 reduced caspase‐1 activity/expression in mesenteric arteries from db/db mice (arbitrary units (a.u.) Cont: 1.0±0.1 n=6; Cont+Spiro: 0.8±0.2 n=5, db/db: 2.4±0.6 n=4; db/db+Spiro: 0.5±0.2 n=6, p<0.05) and ( Cont: 1.0±0.4 n=4; Cont+MCC950: 0.8±0.2 n=4, db/db: 2.0±0.9 n=4; db/db+MCC950: 1.1±0.2 n=5, p>0.05)]. Spiro treatment reduced glucose levels in db/db mice [Glucose (mg/dL), Cont: 156.1±5.7 n=10; Cont+spiro: 150.2±7.3 n=9; db/db: 265.1±17.4 n=12; db/db+spiro: 185.5±21.6 n=8, p<0.05] and improved Ach vasodilation in diabetic mice [Emax (% of relaxation) Cont: 78.5±4.1 n=7; control+spiro: 77.04±3.83 n=3; db/db: 40.5±6.4 n=8; db/db+spiro: 62.83±5.89 n=6, p<0.05]. Despite treatment with MCC950 does not reduce the aldosterone plasma levels [Aldo (pg/mL), Cont: 222.0±29.3 n=6; Cont+MC9950:183.7±81.0 n=3, db/db:552.7±85.4 n=5; db/db+MCC950:434.2±73.8 n=5, p>0.05] and glucose levels in db/db mice [Glucose (mg/dL), Cont: 178.3±9.1 n=6; Cont+MCC950: 166.3±4.8 n=3, db/db: 402.0±36.1 n=4; db/db+MCC950: 317.8±36.5 n=5, p>0.05], MCC950 improve the maximum response (Emax) of ACh [(Emax (% of relaxation) Cont: 78.5±4.1 n=6; Cont+MCC950: 77.0±3.8 n=3; db/db: 40.5±6.4 n=5; db/db+MCC950: 62.8±5.9 n=5, p<0.05].ConclusionThese results suggest that aldosterone activates the inflammasome platform in the vasculature of DM2 mice. The MR and NLRP3 receptors activation plays a crucial role on aldosterone‐induced in diabetes‐associated vascular dysfunction and inflammation.Support or Funding InformationCAPES, CNPq, FAPESPThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.