Canonical Inflammasomes.

The innate immune response represents the first line of host defense, and it is able to detect pathogen- and damage-associated molecular patterns (PAMPs and DAMPs, respectively) through a variety of pattern recognition receptors (PRRs). Among these PRRs, certain cytosolic receptors of the NLRs family (specifically NLRP1, NLRP3, NLRC4, and NAIP) or those containing at least a pyrin domain (PYD) such as pyrin and AIM2, activate the multimeric complex known as inflammasome, and its effector enzyme caspase-1. The caspase-1 induces the proteolytic maturation of the pro-inflammatory cytokines IL-1ß and IL-18, as well as the pore-forming protein gasdermin D (GSDMD). GSDMD is responsible for the release of the two cytokines and the induction of lytic and inflammatory cell death known as pyroptosis. Each inflammasome receptor detects specific stimuli, either directly or indirectly, thereby enhancing the cell's ability to sense infections or homeostatic disturbances. In this chapter, we present the activation mechanism of the so-called "canonical" inflammasomes.

Cervical carcinoma induces NLRP3 inflammasome activation and IL-1ß release in human peripheral blood monocytes affecting patients' overall survival.

PURPOSE: Our group previously demonstrated that genetic variants in inflammasome genes contribute to protection against the establishment of human papilloma virus (HPV)-associated cervical carcinoma (CC). The objective of this study was to better understand the contribution of inflammasome and its cytokines in the CC microenvironment. METHODS: The inflammasome activation was analyzed in CC tumoral cell lines and healthy donors (HD)' monocytes in co-culture. In vitro results were then compared to CC patients' public databases. RESULTS: CC cells did not produce IL-1ß or IL-18 themselves, however, when in co-culture with HD monocytes, induced IL-1ß release in those leucocytes. Inflammasome activation appears to be partially dependent on the NLRP3 receptor. Public data analysis revealed that IL1B expression is increased in the CC compared to normal uterine cervix, and that patients with high IL1B expression had a shorter overall survival. CONCLUSION: CC microenvironment can activate the inflammasome and IL-1ß release in surrounding monocytes, which could be detrimental for CC prognosis.

The Ala134Thr variant in TMEM176B exerts a beneficial role in colorectal cancer prognosis by increasing NLRP3 inflammasome activation.

PURPOSE: TMEM176B was recently described as a negative modulator of Nlrp3 inflammasome activation in mice. In the mouse model, the inhibition of TMEM176B leads to an increased anti-tumoral activity which is dependent on Nlrp3. Since we have recently shown that single nucleotide variants (SNPs) in inflammasome genes, including NLRP3, significantly affect colorectal cancer (CRC) prognosis, we proposed to investigate here the association between genetic variants in TMEM176B and CRC prognosis. METHODS: Considering that, up to now, no genetic study analyzing this gene in humans exists, we selected possible functional SNPs and genotyped them in a cohort of CRC patients submitted to surgery and followed up for more than 10 years. Genotype-guided assays were realized to evaluate the effect of the variant on NLRP3 inflammasome activation. Gene expression from The Cancer Genome Atlas (TCGA) cohort was analyzed to valid possible prognostic and predictive features. RESULTS: We identified the Ala134Thr variant (rs2072443) in TMEM176B as a protective factor for CRC prognosis. This SNP is associated with decreased gene expression and with an increased activation of NLRP3 inflammasome, at least in monocytes and dendritic cells. Furthermore, low TMEM176B expression is associated with higher overall survival. CONCLUSION: Altogether, these findings supported the role of TMEM176B in NLRP3 inflammasome biology and for the first time demonstrated the genetic association between rs2072443 and CRC in humans.

In-vitro NLRP3 functional test assists the diagnosis of cryopyrin-associated periodic syndrome (CAPS) patients: A Brazilian cooperation.

OBJECTIVE: To report our five-years experience on the use of NLRP3 inflammasome functional assays in the differential diagnosis of Brazilian patients with a clinical suspicion of CAPS. PATIENTS AND METHODS: The study included 9 patients belonging to 2 families (I, II) and 7 unrelated patients with a clinical suspicion of AID according to Eurofever/PRINTO classification, recruited between 2017 and 2022. The control group for the NLRP3 functional assay consisted of 10 healthy donors and for the CBA cytokines measurement of 19 healthy controls. Patients underwent clinical evaluation, genetic and functional analysis. RESULTS: All members of the family I received the diagnosis of Muckle-Wells Syndrome (MWS), carried the NLRP3 Thr348Met variant and resulted positive for the functional assay. The 2 patients of the family II resulted negative for the mutational screening but positive for the functional assay compatible with a MWS clinical phenotype. In 2 unrelated patients with NLRP3 mutations, including a novel mutation (Gly309Val, Asp303His), a positive functional test confirmed the clinical diagnosis of NOMID. 3 unrelated MWS and 1 FCAS patients resulted negative to the genetic screening and positive for the functional test. One patient with a FCAS-like phenotype harbored the NLRP12 His304Tyr variant confirming the diagnosis of FCAS2. CONCLUSION: The NLRP3 inflammasome functional assay can assist the clinical diagnosis of CAPS even in patients with unknown genetic defects.

The inflammasomes: crosstalk between innate immunity and hematology.

BACKGROUND: The inflammasome is a cytosolic multi-protein complex responsible for the proteolytic maturation of pro-inflammatory cytokines IL-1ß and IL-18 and of gasdermin-D, which mediates membrane pore formation and the cytokines release, or eventually a lytic cell death known as pyroptosis. Inflammation has long been accepted as a key component of hematologic conditions, either oncological or benign diseases. OBJECTIVES: This study aims to review the current knowledge about the contribution of inflammasome in hematologic diseases. We attempted to depict the participation of specific inflammasome receptors, and the possible cell-specific consequence of complex activation, as well as the use of anti-inflammasome therapies. METHODS: We performed a keyword-based search in public databases (Pubmed.gov, ClinicalTrials.gov.). CONCLUSION: Different blood cells variably express inflammasome components. Considering the immunosuppression associated with both the disease and the treatment of some hematologic diseases, and a microenvironment that allows neoplastic cell proliferation, inflammasomes could be a link between innate immunity and disease progression, as well as an interesting therapeutic target.

Genetic contribution and functional impairment of inflammasome in sickle cell disease.

BACKGROUND: Sickle cell disease (SCD), one of the most common single-gene disorders, is caused by mutations in the hemoglobin ß-chain gene. Clinical presentation is heterogeneous, and inflammation is a common condition. Thereby, we hypothesized that inflammasome and related cytokine IL-1ß could represent significant SCD pathogenesis contributors. MATERIAL AND METHODS: 161 SCD (SS/Sß) patients were enrolled for the study. Seven single nucleotide polymorphisms (SNPs) in 5 inflammasome genes (NLRP1, NLRP3, NLRC4, CARD8, IL1B) were selected based on minor allele frequency. Total peripheral blood mononuclear cells (PBMC) and monocytes were isolated from 10 out of 161 SCD patients (HbSS) and 10 healthy donors (control group, Ctrl) for inflammasome analysis. RESULTS: SCD patients presented a functional impairment of inflammasome, with monocytes and peripheral blood mononuclear cells (PBMC) exhibiting a different NLRP3 inflammasome activation rate. Gain-of-function variants in NLRP1 and IL1B genes resulted associated with a mild SCD clinical presentation. DISCUSSION: Our results can contribute to the understanding of SCD inflammation. SCD patients showed possible exhaustion of monocytes due to chronic inflammation, moreover others cells in PBMC can contribute to the NLRP3 inflammasome activation. NLRP1 gain-of-function was associated with mild clinical presentation, suggesting that other inflammasome receptors can be involved in SCD. This is the first study reporting a significant contribution of inflammasome SNPs in SCD.

Common pathogen-associated molecular patterns induce the hyper-activation of NLRP3 inflammasome in circulating B lymphocytes of HIV-infected individuals.

OBJECTIVE: Despite the antiretroviral treatment, people with HIV (PWH) still experience systemic chronic inflammation and immune-senescence, which represent risk factors for severe comorbidities and inefficient response to pathogens and vaccines. Given the dysregulation of NLRP3 inflammasome in PWH and the recently demonstrated role played by NLRP3 in B lymphocytes, we hypothesized that NLRP3 dysregulation in B cells can contribute to chronic inflammation and humoral dysfunction in PWH. DESIGN: NLRP3 inflammasome activation was evaluated in B lymphocytes and correlated with antibodies production and immunization response in PWH. METHODS: NLRP3 inflammasome activation was compared in B lymphocytes isolated from PWH and healthy donors, in resting and stimulated conditions. Functional polymorphic variants in NLRP3 and IL1B genes were analysed in a cohort of PWH submitted to anti-HBV vaccine to assess the effect of NLRP3 inflammasome on humoral response. RESULTS: The NLRP3 inflammasome activation in response to common PAMPs (LPS, ß-glucan) resulted higher in B lymphocytes of PWH than in HD. CpG-induced IgM secretion was also increased in B cells of PWH. NLRP3, but not IL1B, gain-of-function polymorphism associated to anti-HBs levels. CONCLUSION: These data reveal the dysregulation of NLRP3 inflammasome in B lymphocytes of PWH. Differently from myeloid compartment, which present an exhausted NLRP3 inflammasome, the complex appears to be hyper-activated in B cells of PWH, likely contributing to chronic inflammation and affecting humoral response.

Macrophage inflammatory state in Type 1 diabetes: triggered by NLRP3/iNOS pathway and attenuated by docosahexaenoic acid.

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease characterized by insulin-producing pancreatic ß-cell destruction and hyperglycemia. While monocytes and NOD-like receptor family-pyrin domain containing 3 (NLRP3) are associated with T1D onset and development, the specific receptors and factors involved in NLRP3 inflammasome activation remain unknown. Herein, we evaluated the inflammatory state of resident peritoneal macrophages (PMs) from genetically modified non-obese diabetic (NOD), NLRP3-KO, wild-type (WT) mice and in peripheral blood mononuclear cells (PBMCs) from human T1D patients. We also assessed the effect of docosahexaenoic acid (DHA) on the inflammatory status. Macrophages from STZ-induced T1D mice exhibited increased inflammatory cytokine/chemokine levels, nitric oxide (NO) secretion, NLRP3 and iNOS protein levels, and augmented glycolytic activity compared to control animals. In PMs from NOD and STZ-induced T1D mice, DHA reduced NO production and attenuated the inflammatory state. Furthermore, iNOS and IL-1ß protein expression levels and NO production were lower in the PMs from diabetic NLRP3-KO mice than from WT mice. We also observed increased IL-1ß secretion in PBMCs from T1D patients and immortalized murine macrophages treated with advanced glycation end products and palmitic acid. The present study demonstrated that the resident PMs are in a proinflammatory state characterized by increased NLRP3/iNOS pathway-mediated NO production, up-regulated proinflammatory cytokine/chemokine receptor expression and altered glycolytic activity. Notably, ex vivo treatment with DHA reverted the diabetes-induced changes and attenuated the macrophage inflammatory state. It is plausible that DHA supplementation could be employed as adjuvant therapy for treating individuals with T1D.

Double-edged sword of inflammasome genetics in colorectal cancer prognosis.

Inflammation is a colorectal cancer (CRC) hallmark. Inflammasome-dependent cytokines IL-1ß and IL-18 can play a beneficial or detrimental role in tumorigenesis depending on cancer type. Variants in inflammasome genes were associated with tumor development and/or outcome, and have been proposed as potential biomarkers for population screening. In this study, 215 CRC patients followed-up for 10 years were examined for 9 polymorphisms in selected inflammasome genes. Multivariate association analysis and survival analysis were performed to evaluate the association between the polymorphisms and CRC prognosis. Variants associated with lower levels of IL-18 (rs1834481, rs5744256), or with increased activation of inflammasome receptors NLRP1 (rs12150220) and NLRP3 (rs35829419) resulted detrimental to CRC prognosis and may be used as prognostic markers.

Inflammasome in HIV infection: Lights and shadows.

The importance of inflammasome, and related cytokines IL-1ß and IL-18, in host defense against pathogens is well documented, however, at the same time, dysregulation of inflammasome has been associated to multifactorial diseases characterized by chronic inflammation (i.e.: metabolic disorders, cardiovascular diseases, neurodegenerative diseases, autoimmunity, cancer). Inflammasome activation has been described in response to HIV-1 and possibly contributes to the resistance against virus establishment, however, on the other hand, when viral infection becomes chronic, independently from antiretroviral therapy, the increase constitutive activation of inflammasome has been eventually associated to a worse prognosis, raising the question about the role played by inflammasome and/or some specific receptors in this context. Due to the chance to imply targeted therapies that inhibit inflammasome activation and/or cytokines release, it will be important to define the impact of the complex in the pathogenesis of HIV. The purpose of this review is to depict the double-faced inflammasome role in HIV-1 infection, trying to unveil whether besides its role in first line defense against the virus, it exerts a harmful effect during the chronic phase of infection.

Flagellin/NLRC4 Pathway Rescues NLRP3-Inflammasome Defect in Dendritic Cells From HIV-Infected Patients: Perspective for New Adjuvant in Immunocompromised Individuals.

Introduction: NLRP3 inflammasome plays a key role in dendritic cells (DC) activation in response to vaccine adjuvants, however we previously showed that it is not properly activated in DC from HIV-infected patients (HIV-DC), explaining, at least in part, the poor response to immunization of these patients. Taking in account that several cytoplasmic receptors are able to activate inflammasome, and that bacterial components are considered as a novel and efficient adjuvant, we postulated that bacterial flagellin (FLG), a natural ligand of NAIP/NLRC4 inflammasome, could rescue the activation of the complex in HIV-DC. Objective: Demonstrate that FLG is able to activate monocyte-derived dendritic cells from HIV-infected individuals better than LPS, and to what extent the entity of inflammasome activation differs between DC from HIV-infected patients and healthy donors. Methods: Monocyte-derived dendritic cells from HIV-infected patients (HIV-DC) and healthy donors (HD-DC) were stimulated with FLG, and inflammasome as well as DC activation (phenotypic profile, cytokine production, autologous lymphocytes activation) were compared. Chemical and genetic inhibitors were used to depict the relative contribution of NLRC4 and NLRP3 in HIV/HD-DC response to FLG. Results: FLG properly activates HD-DC and HIV-DC. FLG induces higher inflammasome activation than LPS in HIV-DC. FLG acts through NLRC4 and NLRP3 in HD-DC, but at a lesser extent in HIV-DC due to intrinsic NLRP3 defect. Conclusions: FLG by-passes NLRP3 defect in HIV-DC, through the activation of NAIP/NLRC4 inflammasome, indicating possible future use of the bacterial component as an efficient adjuvant in immunocompromised individuals.

Polymorphisms in inflammasome genes and risk of asthma in Brazilian children.

Considering its role in inflammation and recently described "alternative" roles in epithelial homeostasis and Th1/Th2 balance, we hypothesize that inflammasome genetics could contribute to the development of asthma. Selected functional polymorphisms in inflammasome genes are evaluated in a cohort of asthmatic children and their families. Gain-of-function NLRP1 variants rs11651270, rs12150220 and rs2670660 resulted significantly associated to asthma in trios (TDT) analysis; and rs11651270 and rs2670660 also with asthma severity and total IgE level in asthmatic children. NLRP1 activators in humans are still unknown, however we hypothesized that individuals with gain-of-function SNPs in NLRP1 could be more prone in activating inflammasome in the presence of asthma-related cell stressors (i.e. ER stress or ROS), and this activation contribute to exacerbate inflammatory response and asthma development. Gain-of-function IL1A rs17561 resulted significantly associated with a reduced pulmonary capacity in asthmatic children. IL18 rs5744256 which lead to lower serum level of IL-18 appeared to be associated to a worse response to bronchodilators. Concluding, this work provides evidences about the contribution of inflammasome genetics in the development of paediatric asthma, both considering its inflammatory role in alveolar macrophages (i.e.: NLRP1) or its homeostatic role in lung epithelial cells (i.e.: IL1A, IL18).