Gene expression, synthesis, and secretion of interleukin 18 and interleukin 1beta are differentially regulated in human blood mononuclear cells and mouse spleen cells

Exploring NLRP3-related phenotypic fingerprints in human macrophages using Cell Painting assay

Existing research has proven difficult to understand the interplay between upstream signaling events during NLRP3 inflammasome activation. Additionally, events downstream of inflammasome complex formation such as cytokine release and pyroptosis can exhibit variation, further complicating matters. Cell Painting has emerged as a prominent tool for unbiased evaluation of the effect of perturbations on cell morphological phenotypes. Using this technique, phenotypic fingerprints can be generated that reveal connections between phenotypes and possible modes of action. To the best of our knowledge, this was the first study that utilized Cell Painting on human THP-1 macrophages to generate phenotypic fingerprints in response to different endogenous and exogenous NLRP3 inflammasome triggers and to identify phenotypic features specific to NLRP3 inflammasome complex formation. Our results demonstrated that not only can Cell Painting generate morphological fingerprints that are NLRP3 trigger-specific but it can also identify cellular fingerprints associated with NLRP3 inflammasome activation.

The potential of mesenchymal stem cell coexpressing cytosine deaminase and secretory IL18-FC chimeric cytokine in suppressing glioblastoma recurrence

Glioblastoma multiforme (GBM) patients have a high recurrence rate of 90%, and the 5-year survival rate is only about 5%. Cytosine deaminase (CDA)/5-fluorocytosine (5-FC) gene therapy is a promising glioma treatment as 5-FC can cross the blood-brain barrier (BBB), while 5-fluorouracil (5-FU) cannot. Furthermore, 5-FU can assist reversing the immunological status of cold solid tumors. This study developed mesenchymal stem cells (MSCs) co-expressing yeast CDA and the secretory IL18-FC superkine to prevent recurrent tumor progression by simultaneously exerting cytotoxic effects and enhancing immune responses. IL18 was fused with Igk and IgG2a FC domains to enhance its secretion and serum half-life. The study confirmed the expression and activity of the CDA enzyme, as well as the expression, secretion, and activity of secretory IL18 and IL18-FC superkine, which were expressed by lentiviruses transduced-MSCs. In the transwell tumor-tropism assay, it was observed that the genetically modified MSCs retained their selective tumor-tropism ability following transduction. CDA-expressing MSCs, in the presence of 5-FC (200 µg/ml), induced cell cycle arrest and apoptosis in glioma cells through bystander effects in an indirect transwell co-culture system. They reduced the viability of the direct co-culture system when they constituted only 12.5 % of the cell population. The effectiveness of engineered MSCs in suppressing tumor progression was assessed by intracerebral administration of a lethal dose of GL261 cells combined in a ratio of 1:1 with MSCs expressing CDA, or CDA and sIL18, or CDA and sIL18-FC, into C57BL/6 mice. PET scan showed no conspicuous tumor mass in the MSC-CDA-sIL18-FC group that received 5-FC treatment. The pathological analysis showed that tumor progression suppressed in this group until 20th day after cell inoculation. Cytokine assessment showed that both interferon-gamma (IFN-γ) and interleukin-4 (IL-4) increased in the serum of MSC-CDA-sIL18 and MSC-CDA-sIL18-FC, treated with normal saline (NS) compared to those of the control group. The MSC-CDA-sIL18-FC group that received 5-FC treatment showed reduced serum levels of IL-6 and a considerably improved survival rate compared to the control group. Therefore, MSCs co-expressing yeast CDA and secretory IL18-FC, with tumor tropism capability, may serve as a supplementary approach to standard GBM treatment to effectively inhibit tumor progression and prevent recurrence.

IL-18 signaling is regulated by caspase 6/8 and IL-18BP in turbot (Scophthalmus maximus)

Interleukin (IL)-18 is synthesized as a precursor that requires intracellular processing to become functionally active. In human, IL-18 is processed by caspase 1 (CASP1). In teleost, the maturation and signal transduction mechanisms of IL-18 are unknown. We identified two IL-18 variants, IL-18a and IL-18b, in turbot. IL-18a, but not IL-18b, was processed by CASP6/8 cleavage. Mature IL-18a bound specifically to IL-18 receptor (IL-18R) α-expressing cells and induced IL-18Rα-IL-18Rβ association. Bacterial infection promoted IL-18a maturation in a manner that required CASP6 activation and correlated with gasdermin E activation. The mature IL-18a induced proinflammatory cytokine expression and enhanced bacterial clearance. IL-18a-mediated immune response was suppressed by IL-18 binding protein (IL-18BP), which functioned as a decoy receptor for IL-18a. IL-18BP also functioned as a pathogen pattern recognition receptor and directly inhibited pathogen infection. Our findings revealed unique mechanism of IL-18 maturation and conserved mechanism of IL-18 signaling and regulation in turbot, and provided new insights into the regulation and function of IL-18 related immune signaling.

Inflammatory caspase substrate specificities

Caspases are a family of cysteine proteases that act as molecular scissors to cleave substrates and regulate biological processes such as programmed cell death and inflammation. Extensive efforts have been made to identify caspase substrates and to determine factors that dictate substrate specificity. Thousands of putative substrates have been identified for caspases that regulate an immunologically silent type of cell death known as apoptosis, but less is known about substrates of the inflammatory caspases that regulate an immunostimulatory type of cell death called pyroptosis. Furthermore, much of our understanding of caspase substrate specificities is derived from work done with peptide substrates, which do not often translate to native protein substrates. Our knowledge of inflammatory caspase biology and substrates has recently expanded and here, we discuss the recent advances in our understanding of caspase substrate specificities, with a focus on inflammatory caspases. We highlight new substrates that have been discovered and discuss the factors that engender specificity. Recent evidence suggests that inflammatory caspases likely utilize two binding interfaces to recognize and process substrates, the active site and a conserved exosite.

Mechanistic insights from inflammasome structures

Inflammasomes are supramolecular complexes that form in the cytosol in response to pathogen-associated and damage-associated stimuli, as well as other danger signals that perturb cellular homoeostasis, resulting in host defence responses in the form of cytokine release and programmed cell death (pyroptosis). Inflammasome activity is closely associated with numerous human disorders, including rare genetic syndromes of autoinflammation, cardiovascular diseases, neurodegeneration and cancer. In recent years, a range of inflammasome components and their functions have been discovered, contributing to our knowledge of the overall machinery. Here, we review the latest advances in inflammasome biology from the perspective of structural and mechanistic studies. We focus on the most well-studied components of the canonical inflammasome - NAIP-NLRC4, NLRP3, NLRP1, CARD8 and caspase-1 - as well as caspase-4, caspase-5 and caspase-11 of the noncanonical inflammasome, and the inflammasome effectors GSDMD and NINJ1. These structural studies reveal important insights into how inflammasomes are assembled and regulated, and how they elicit the release of IL-1 family cytokines and induce membrane rupture in pyroptosis.

An antibody to IL-1 receptor 7 protects mice from LPS-induced tissue and systemic inflammation

Introduction

Interleukin-18 (IL-18), a pro-inflammatory cytokine belonging to the IL-1 Family, is a key mediator ofautoinflammatory diseases associated with the development of macrophage activation syndrome (MAS).High levels of IL-18 correlate with MAS and COVID-19 severity and mortality, particularly in COVID-19patients with MAS. As an inflammation inducer, IL-18 binds its receptor IL-1 Receptor 5 (IL-1R5), leadingto the recruitment of the co-receptor, IL-1 Receptor 7 (IL-1R7). This heterotrimeric complex subsequentlyinitiates downstream signaling, resulting in local and systemic inflammation.

Methods

We reported earlier the development of a novel humanized monoclonal anti-human IL-1R7 antibody whichspecifically blocks the activity of human IL-18 and its inflammatory signaling in human cell and wholeblood cultures. In the current study, we further explored the strategy of blocking IL-1R7 inhyperinflammation in vivo using animal models.

Results

We first identified an anti-mouse IL-1R7 antibody that significantly suppressed mouse IL-18 andlipopolysaccharide (LPS)-induced IFNg production in mouse splenocyte and peritoneal cell cultures. Whenapplied in vivo, the antibody reduced Propionibacterium acnes and LPS-induced liver injury and protectedmice from tissue and systemic hyperinflammation. Importantly, anti-IL-1R7 significantly inhibited plasma,liver cell and spleen cell IFNg production. Also, anti-IL-1R7 downregulated plasma TNFa, IL-6, IL-1b,MIP-2 production and the production of the liver enzyme ALT. In parallel, anti-IL-1R7 suppressed LPSinducedinflammatory cell infiltration in lungs and inhibited the subsequent IFNg production andinflammation in mice when assessed using an acute lung injury model.

Discussion

Altogether, our data suggest that blocking IL-1R7 represents a potential therapeutic strategy to specificallymodulate IL-18-mediated hyperinflammation, warranting further investigation of its clinical application intreating IL-18-mediated diseases, including MAS and COVID-19.

Activation of the P2RX7/IL-18 pathway in immune cells attenuates lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is an aggressive interstitial lung disease associated with progressive and irreversible deterioration of respiratory functions that lacks curative therapies. Despite IPF being associated with a dysregulated immune response, current antifibrotics aim only at limiting fibroproliferation. Transcriptomic analyses show that the P2RX7/IL18/IFNG axis is downregulated in IPF patients and that P2RX7 has immunoregulatory functions. Using our positive modulator of P2RX7, we show that activation of the P2RX7/IL-18 axis in immune cells limits lung fibrosis progression in a mouse model by favoring an antifibrotic immune environment, with notably an enhanced IL-18-dependent IFN-γ production by lung T cells leading to a decreased production of IL-17 and TGFβ. Overall, we show the ability of the immune system to limit lung fibrosis progression by targeting the immunomodulator P2RX7. Hence, treatment with a small activator of P2RX7 may represent a promising strategy to help patients with lung fibrosis.

Bioengineering strategies to enhance the interleukin-18 bioactivity in the modern toolbox of cancer immunotherapy

Cytokines are the first modern immunotherapeutic agents used for activation immunotherapy. Interleukin-18 (IL-18) has emerged as a potent anticancer immunostimulatory cytokine over the past three decades. IL-18, structurally is a stable protein with very low toxicity at biological doses. IL-18 promotes the process of antigen presentation and also enhances innate and acquired immune responses. It can induce the production of proinflammatory cytokines and increase tumor infiltration of effector immune cells to revert the immunosuppressive milieu of tumors. Furthermore, IL-18 can reduce tumorigenesis, suppress tumor angiogenesis, and induce tumor cell apoptosis. These characteristics present IL-18 as a promising option for cancer immunotherapy. Although several preclinical studies have reported the immunotherapeutic potential of IL-18, clinical trials using it as a monotherapy agent have reported disappointing results. These results may be due to some biological characteristics of IL-18. Several bioengineering approaches have been successfully used to correct its defects as a bioadjuvant. Currently, the challenge with this anticancer immunotherapeutic agent is mainly how to use its capabilities in a rational combinatorial therapy for clinical applications. The present study discussed the strengths and weaknesses of IL-18 as an immunotherapeutic agent, followed by comprehensive review of various promising bioengineering approaches that have been used to overcome its disadvantages. Finally, this study highlights the promising application of IL-18 in modern combinatorial therapies, such as chemotherapy, immune checkpoint blockade therapy, cell-based immunotherapy and cancer vaccines to guide future studies, circumventing the barriers to administration of IL-18 for clinical applications, and bring it to fruition as a potent immunotherapy agent in cancer treatment.

The tetrapeptide sequence of IL-18 and IL-1β regulates their recruitment and activation by inflammatory caspases

Inflammasomes are multiprotein signaling complexes that activate the innate immune system. Canonical inflammasomes recruit and activate caspase-1, which then cleaves and activates IL-1β and IL-18, as well as gasdermin D (GSDMD) to induce pyroptosis. In contrast, non-canonical inflammasomes, caspases-4/-5 (CASP4/5) in humans and caspase-11 (CASP11) in mice, are known to cleave GSDMD, but their role in direct processing of other substrates besides GSDMD has remained unknown. Here, we show that CASP4/5 but not CASP11 can directly cleave and activate IL-18. However, CASP4/5/11 can all cleave IL-1β to generate a 27-kDa fragment that deactivates IL-1β signaling. Mechanistically, we demonstrate that the sequence identity of the tetrapeptide sequence adjacent to the caspase cleavage site regulates IL-18 and IL-1β recruitment and activation. Altogether, we have identified new substrates of the non-canonical inflammasomes and reveal key mechanistic details regulating inflammation that may aid in developing new therapeutics for immune-related disorders.

SIRT1 regulates hepatocyte programmed cell death via GSDME - IL18 axis in human and mouse liver transplantation

Sirtuin 1 (SIRT1) is a histone/protein deacetylase in the cellular response to inflammatory, metabolic, and oxidative stressors. We previously reported that myeloid SIRT1 regulates the inflamed liver's canonical pyroptosis cell death pathway. However, whether/how hepatocyte SIRT1 is engaged in programmed cell death in the cold-stressed liver remains uncertain. Here, we undertook translational studies in human and mouse orthotopic liver transplantation (OLT) to interrogate the significance of hepatocyte-specific SIRT1 in cold-stored donor livers and liver grafts after reperfusion. In the clinical arm of sixty human OLT patients, hepatic SIRT1 levels in cold-preserved donor livers correlated with the anti-apoptotic Bcl-2 expression. After reperfusion, improved OLT function was accompanied by hepatic SIRT1 levels negatively associated with cleaved caspase-3 expression. In the experimental arm, we compared FLOX-control with hepatocyte-specific SIRT1-KO livers after orthotopic transplantation into WT mouse recipients, parallel with primary murine hepatocyte cultures subjected to cold activation with/without knockdown of SIRT1, GSDME, and IL18Rβ. Indeed, hepatocyte SIRT1 deficiency upregulated apoptosis and GSDME-mediated programmed cell death, deteriorating hepatocellular function and shortening OLT survival. Augmented GSDME processing, accompanied by increased secretion of IL18 by stressed hepatocytes, was prominent in SIRT1-deficient, cold-stored livers. Hepatocyte SIRT1 expression regulated anti-apoptotic Bcl-2/XIAP proteins, suppressed cold stress-triggered apoptosis, and mitigated GSDME licensing to release IL18. Notably, consistent with the ability of IL18 to depress hepatocyte SIRT1 and Bcl-2/XIAP in vitro, IL18 neutralization in vivo prevented hepatocellular damage and restored the anti-apoptotic phenotype in otherwise injury-prone SIRT1-deficient OLTs. In conclusion, this translational study identifies a novel hepatocyte SIRT1-IL18 molecular circuit as a therapeutic target in the mechanism underpinning hepatocyte death pathways in human and mouse liver transplantation.

Increased Levels of Caspase-1 and IL-1β Among Adults With Persistent Immune Activation After 12 Years of Suppressive Antiretroviral Therapy in the Infectious Diseases Institute HIV Treatment Cohort

Background

We sought evidence of activated pyroptosis and the inflammasome pathways among human immunodeficiency virus (HIV)-infected adults after 12 years of suppressive antiretroviral therapy (ART) and persistent immune activation in the Infectious Diseases Institute HIV treatment cohort in Uganda.

Methods

In a cross-sectional study, using peripheral blood mononuclear cells of HIV-infected individuals with high and low immune activation (CD4/CD8+CD38+HLA-DR+ cells) relative to HIV-negative reference group, caspase-1 expression was measured using flow cytometry and plasma interleukin 18 and interleukin 1β (IL-1β) levels using enzyme-linked immunosorbent assay.

Results

There was higher expression of caspase-1 by CD4 T cells of ART-treated individuals with high immune activation relative to those with lower immune activation (P = .04). Similarly, plasma levels of IL-1β were higher among ART-treated individuals with high immune activation levels relative to those with low immune activation levels (P = .009). We observed a low positive correlation between caspase-1 expression by CD4/CD8 T cells and immune activation levels (r= 0.497 and r= 0.329, respectively).

Conclusions

Caspase-1 and IL-1β were high among individuals with high immune activation despite 12 years of suppressive ART. There is a need to further understand the role of persistent abortive infection and the latent HIV reservoir characteristics as drivers of persistent activation and inflammation and to subsequently intervene to prevent the complications of chronic immune activation during long-term ART.

Serum levels of interleukin-18 in diabetic retinopathy patients: A meta-analysis

PURPOSE

To assess the relationship between plasma interleukin-18 (IL-18) levels and the risk of diabetic retinopathy (DR).

MATERIALS AND METHODS

PubMed, Embase, Web of science, and Cochrane were reviewed systemically from inception to August 2022. Searches were performed using a combined term that included all spellings of "diabetic retinopathy," and "interleukin-18". Eligible studies were retrospective studies reporting changes in IL-18 levels between the DR group and the control group. The healthy controls had no identifiable DR disease. Pooled outcomes were reported as standard mean difference (SMD) with 95% confidence intervals (CI) with a random-effects model. Heterogeneity was assessed using the I2 statistics, and it was considered significant if I2 > 75%. Publication bias was evaluated using funnel plots and Begg's and Egger's tests. A meta-analysis was conducted using STATA 12.0 (StataCorp LLC, College Station, TX, USA).

RESULTS

7 studies and four countries incorporated 160 cases, and 119 controls were incorporated in this meta-analysis. When comparing subjects without DR, those with DR tended to have higher serum IL-18 levels (SMD = 3.41, 95% CI = 1.84-4.97). Publication bias indicated that no publication bias existed in the study.

CONCLUSIONS

Elevated circulating IL-18 levels may be one of the significant risk factors positively correlated with the development of DR. Future studies should clarify the mechanism behind this trend.

New Potentiality of Bioactive Substances: Regulating the NLRP3 Inflammasome in Autoimmune Diseases

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is an essential component of the human innate immune system, and is closely associated with adaptive immunity. In most cases, the activation of the NLRP3 inflammasome requires priming and activating, which are influenced by various ion flux signals and regulated by various enzymes. Aberrant functions of intracellular NLRP3 inflammasomes promote the occurrence and development of autoimmune diseases, with the majority of studies currently focused on rheumatoid arthritis, systemic lupus erythematosus and systemic sclerosis. In recent years, a number of bioactive substances have shown new potentiality for regulating the NLRP3 inflammasome in autoimmune diseases. This review provides a concise overview of the composition, functions, and regulation of the NLRP3 inflammasome. Additionally, we focus on the newly discovered bioactive substances for regulating the NLRP3 inflammasome in autoimmune diseases in the past three years.

IL-18 in Autoinflammatory Diseases: Focus on Adult Onset Still Disease and Macrophages Activation Syndrome

Interleukin-18 (IL-18) is a potent pro-inflammatory cytokine that is involved in various innate and adaptive immune processes related to infection, inflammation, and autoimmunity. Therefore, it is described as a key mediator of autoinflammatory diseases associated with the development of macrophage activation syndrome (MAS), including systemic juvenile idiopathic arthritis and adult-onset Still's disease. This review focuses on the role of IL-18 in inflammatory responses, placing emphasis on autoinflammatory diseases associated with chronic excess of serum IL-18, which correlate with clinical and biological signs of the disease. Therefore, it is useful for the diagnosis and monitoring of disease activity. Researchers are currently investigating IL-18's role as a therapeutic target for the treatment of inflammatory diseases. The inhibition of IL-18 signaling through recombinant human IL-18BP (IL-18 binding protein) seems to be an effective therapeutic strategy, though further studies are necessary to clarify its importance as a therapeutic target.

SIRT1 Regulates Hepatocyte Programmed Cell Death via GSDME - IL18 Axis in Human and Mouse Liver Transplantation

Sirtuin 1 (SIRT1) is a histone/protein deacetylase involved in cellular senescence, inflammation, and stress resistance. We previously reported that myeloid SIRT1 signaling regulates the inflamed liver's canonical pyroptosis cell death pathway. However, whether/how hepatocyte SIRT1 is engaged in programmed cell death in the cold-stressed liver remains uncertain. Here, we undertook translational studies in human and mouse orthotopic liver transplantation (OLT) to interrogate the significance of hepatocyte-specific SIRT1 signaling in cold-stored donor livers and liver grafts after reperfusion. In the clinical arm of sixty human OLT patients, hepatic SIRT1 levels in cold-preserved donor livers correlated with anti-apoptotic Bcl-2 expression. After reperfusion, improved OLT function was accompanied by hepatic SIRT1 levels negatively associated with cleaved caspase-3 expression. In the experimental arm, we compared FLOX-control with hepatocyte-specific SIRT1-KO livers after orthotopic transplantation into WT mouse recipients, parallel with primary murine hepatocyte cultures subjected to cold activation with/without knockdown of SIRT1, GSDME, and IL18Rβ signaling. Hepatocyte SIRT1 deficiency upregulated apoptosis and GSDME-mediated programmed cell death, which in turn deteriorated the hepatocellular function and shortened OLT survival. Augmented GSDME processing, accompanied by increased secretion of IL18 by stressed hepatocytes, was prominent in SIRT1-deficient, cold-stored livers. Hepatocyte SIRT1 signaling regulated anti-apoptotic Bcl-2/XIAP proteins, suppressed cold stress-triggered apoptosis, and mitigated GSDME licensing to release IL18. Notably, while crosslinking IL18R depressed SIRT1 and Bcl-2/XIAP signaling in vitro, IL18 neutralization in vivo prevented hepatocellular damage and restored the anti-apoptotic phenotype in otherwise injury-prone SIRT1-deficient OLTs. In conclusion, this translational study identifies a novel hepatocyte SIRT1-IL18 signaling circuit as a therapeutic target in the mechanism underpinning hepatocyte death in human and mouse liver transplantation.

Interleukin-18 signaling promotes activation of hepatic stellate cells in mouse liver fibrosis

BACKGROUND AND AIMS

Nucleotide-binding oligomerization domain-like receptor-family pyrin domain-containing 3 (NLRP3) inflammasome activation has been shown to result in liver fibrosis. Mechanisms and downstream signaling remain incompletely understood. Here, we studied the role of IL-18 in hepatic stellate cells (HSCs), and its impact on liver fibrosis.

APPROACH AND RESULTS

We observed significantly increased serum levels of IL-18 (128.4 pg/ml vs. 74.9 pg/ml) and IL-18 binding protein (BP; 46.50 ng/ml vs. 15.35 ng/ml) in patients with liver cirrhosis compared with healthy controls. Single cell RNA sequencing data showed that an immunoregulatory subset of murine HSCs highly expresses Il18 and Il18r1 . Treatment of cultured primary murine HSC with recombinant mouse IL-18 accelerated their transdifferentiation into myofibroblasts. In vivo , IL-18 receptor-deficient mice had reduced liver fibrosis in a model of fibrosis induced by HSC-specific NLRP3 overactivation. Whole liver RNA sequencing analysis from a murine model of severe NASH-induced fibrosis by feeding a choline-deficient, L-amino acid-defined, high fat diet showed that genes related to IL-18 and its downstream signaling were significantly upregulated, and Il18-/- mice receiving this diet for 10 weeks showed protection from fibrotic changes with decreased number of alpha smooth muscle actin-positive cells and collagen deposition. HSC activation triggered by NLRP3 inflammasome activation was abrogated when IL-18 signaling was blocked by its naturally occurring antagonist IL-18BP. Accordingly, we observed that the severe inflammatory phenotype associated with myeloid cell-specific NLRP3 gain-of-function was rescued by IL-18BP.

CONCLUSIONS

Our study highlights the role of IL-18 in the development of liver fibrosis by its direct effect on HSC activation identifying IL-18 as a target to treat liver fibrosis.

The Role of IL-18 in P2RX7-Mediated Antitumor Immunity

Cancer is the leading cause of death worldwide despite the variety of treatments that are currently used. This is due to an innate or acquired resistance to therapy that encourages the discovery of novel therapeutic strategies to overcome the resistance. This review will focus on the role of the purinergic receptor P2RX7 in the control of tumor growth, through its ability to modulate antitumor immunity by releasing IL-18. In particular, we describe how the ATP-induced receptor activities (cationic exchange, large pore opening and NLRP3 inflammasome activation) modulate immune cell functions. Furthermore, we recapitulate our current knowledge of the production of IL-18 downstream of P2RX7 activation and how IL-18 controls the fate of tumor growth. Finally, the potential of targeting the P2RX7/IL-18 pathway in combination with classical immunotherapies to fight cancer is discussed.

Coronary Artery Plaque Composition and Severity Relate to the Inflammasome in People With Treated Human Immunodeficiency Virus

Background

Inflammasome activation is increased in people with human immunodeficiency virus (PWH), but its relationship with coronary plaque is poorly understood in this setting.

Methods

In a large human immunodeficiency virus cardiovascular prevention cohort, relationships between caspase-1, interleukin (IL)-1β, and IL-18 and coronary plaque indices were assessed by multivariate logistic regression.

Results

Higher IL-18 and IL-1β were associated with Leaman score, an integrative measure of plaque burden and composition.

Conclusions

As Leaman score >5 is associated with cardiovascular events in the general population, future work is needed to determine how the inflammasome relates to events and whether strategies to reduce its activation affect events or plaque progression among PWH.

The tetrapeptide sequence of IL-1β regulates its recruitment and activation by inflammatory caspases

The mammalian innate immune system uses germline-encoded cytosolic pattern-recognition receptors (PRRs) to detect intracellular danger signals. At least six of these PRRs are known to form multiprotein complexes called inflammasomes which activate cysteine proteases known as caspases. Canonical inflammasomes recruit and activate caspase-1 (CASP1), which in turn cleaves and activates inflammatory cytokines such as IL-1β and IL-18, as well as the pore forming protein, gasdermin D (GSDMD), to induce pyroptotic cell death. In contrast, non-canonical inflammasomes, caspases-4/-5 (CASP4/5) in humans and caspase-11 (CASP11) in mice, are activated by intracellular LPS to cleave GSDMD, but their role in direct processing of inflammatory cytokines has not been established. Here we show that active CASP4/5 directly cleave IL-18 to generate the active species. Surprisingly, we also discovered that CASP4/5/11 cleave IL-1β at D27 to generate a 27 kDa fragment that is predicted to be inactive and cannot signal to the IL-1 receptor. Mechanistically, we discovered that the sequence identity of the P4-P1 tetrapeptide sequence adjacent to the caspase cleavage site (D116) regulates the recruitment and processing of IL-1β by inflammatory caspases to generate the bioactive species. Thus, we have identified new substrates of the non-canonical inflammasomes and reveal key mechanistic details regulating inflammation.

p38 MAPK-dependent phosphorylation of TFEB promotes monocyte-to-macrophage differentiation

The transcription factor EB (TFEB) regulates energy homeostasis and cellular response to a wide variety of stress conditions, including nutrient deprivation, oxidative stress, organelle damage, and pathogens. Here we identify S401 as a novel phosphorylation site within the TFEB proline-rich domain. Phosphorylation of S401 increases significantly in response to oxidative stress, UVC light, growth factors, and LPS, whereas this increase is prevented by p38 MAPK inhibition or depletion, revealing a new role for p38 MAPK in TFEB regulation. Mutation of S401 in THP1 cells demonstrates that the p38 MAPK/TFEB pathway plays a particularly relevant role during monocyte differentiation into macrophages. TFEB-S401A monocytes fail to upregulate the expression of multiple immune genes in response to PMA-induced differentiation, including critical cytokines, chemokines, and growth factors. Polarization of M0 macrophages into M1 inflammatory macrophages is also aberrant in TFEB-S401A cells. These results indicate that TFEB-S401 phosphorylation links differentiation signals to the transcriptional control of monocyte differentiation.

Inflammasome activation and formation of ASC specks in patients with juvenile idiopathic arthritis

Objective

The formation of large intracellular protein aggregates of the inflammasome adaptor ASC is a hallmark of inflammasome activation and characteristic of autoinflammation. Inflammasome activated cells release the highly proinflammatory cytokine IL-1β in addition to ASC specks into the extracellular space. Autoinflammatory activity has been demonstrated in systemic JIA, however minimal data exist on the role of inflammasomes in other JIA subtypes. We therefore investigated, if pyroptotic cells are present in the circulation of oligo- and poly-articular JIA.

Methods

Peripheral blood of JIA patients (n = 46) was investigated for ASC speck formation, a key step in inflammasome activation, by flow cytometry and immunofluorescence. Free ASC and proinflammatory cytokine levels were determined by ELISA and multiplex assay.

Results

Oligo-articular JIA patients showed a significantly increased proportion of ASC speck⁺ monocytes compared to poly-articular JIA patients. In serum free ASC alone is not sufficient to assess inflammasome activity and does not correlate with ASC speck⁺ monocytes. Compared to control several cytokines were significantly elevated in samples of JIA patients. JIA serum containing antinuclear antibodies, incubated with ASC specks boosts a secondary inflammation by IL-1β production in macrophages.

Conclusion

For the first time, we detect ex vivo inflammasome activation by ASC speck formation in oligo- and poly-articular JIA patients. Most notably, inflammasome activation was significantly higher in oligo- compared to poly-articular JIA patients. This data suggests that inflammasome derived autoinflammation may have a greater influence in the previously thought autoimmune oligo-articular JIA patients.

The IL-1 Family and Its Role in Atherosclerosis

The IL-1 superfamily of cytokines is a central regulator of immunity and inflammation. The family is composed of 11 cytokines (with agonist, antagonist, and anti-inflammatory properties) and 10 receptors, all tightly regulated through decoy receptor, receptor antagonists, and signaling inhibitors. Inflammation not only is an important physiological response against infection and injury but also plays a central role in atherosclerosis development. Several clinical association studies along with experimental studies have implicated the IL-1 superfamily of cytokines and its receptors in the pathogenesis of cardiovascular disease. Here, we summarize the key features of the IL-1 family, its role in immunity and disease, and how it helps shape the development of atherosclerosis.

Inflammation-related transcripts define "high" and "low" subgroups of individuals with schizophrenia and bipolar disorder in the midbrain

Dopamine dysregulation in schizophrenia may be associated with midbrain inflammation. Previously, we found elevated levels of pro-inflammatory cytokine mRNAs in the post-mortem midbrain of people with schizophrenia (46%) but not from unaffected controls (0%) using a brain cohort from Sydney, Australia. Here, we measured cytokine mRNAs and proteins in the midbrain in the Stanley Medical Research Institute (SMRI) array cohort (N = 105). We tested if the proportions of individuals with schizophrenia and with high inflammation can be replicated, and if individuals with bipolar disorder with elevated midbrain cytokines can be identified. mRNA levels of 7 immune transcripts from post-mortem midbrain tissue were measured via RT-PCR and two-step recursive clustering analysis was performed using 4 immune transcripts to define "high and low" inflammatory subgroups. The clustering predictors used were identical to our earlier midbrain study, and included: IL1B, IL6, TNF, and SERPINA3 mRNA levels. 46% of schizophrenia cases (16/35 SCZ), 6% of controls (2/33 CTRL), and 29% of bipolar disorder cases (10/35 BPD) were identified as belonging to the high inflammation (HI) subgroups [χ² (2) = 13.54, p < 0.001]. When comparing inflammatory subgroups, all four mRNAs were significantly increased in SCZ-HI and BPD-HI compared to low inflammation controls (CTRL-LI) (p < 0.05). Additionally, protein levels of IL-1β, IL-6, and IL-18 were elevated in SCZ-HI and BPD-HI compared to all other low inflammatory subgroups (all p < 0.05). Surprisingly, TNF-α protein levels were unchanged according to subgroups. In conclusion, we determined that almost half of the individuals with schizophrenia were defined as having high inflammation in the midbrain, replicating our previous findings. Further, we detected close to one-third of those with bipolar disorder to be classified as having high inflammation. Elevations in some pro-inflammatory cytokine mRNAs (IL-1β and IL-6) were also found at the protein level, whereas TNF mRNA and protein levels were not concordant.

Pathogenic roles and diagnostic utility of interleukin-18 in autoinflammatory diseases

Interleukin (IL)-18 is a pleiotropic, pro-inflammatory cytokine involved in the regulation of innate and adaptive immune responses. IL-18 has attracted increasing attention as a key mediator in autoinflammatory diseases associated with the development of macrophage activation syndrome (MAS) including systemic juvenile idiopathic arthritis and adult-onset Still’s disease. In these diseases, dysregulation of inflammasome activity and overproduction of IL-18 might be associated with the development of MAS by inducing natural killer cell dysfunction. Serum IL-18 levels are high in patients with these diseases and therefore are useful for the diagnosis and monitoring of disease activity. In contrast, a recent study revealed the overproduction of IL-18 was present in cases of autoinflammation without susceptibility to MAS such as pyogenic sterile arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome. The pathogenic and causative roles of IL-18 remain unclear in these autoinflammatory diseases. Further investigations are necessary to clarify the role of IL-18 and its importance as a therapeutic target in the pathogenesis of autoinflammatory diseases.

Diverse Control Mechanisms of the Interleukin-1 Cytokine Family

The majority of interleukin-1 (IL-1) family cytokines lack amino terminal secretion signals or transmembrane domains for secretion along the conventional biosynthetic pathway. Yet, these factors must be translocated from the cytoplasm across the plasma membrane into the extracellular space in order to regulate inflammation. Recent work has identified an array of mechanisms by which IL-1 family cytokines can be released into the extracellular space, with supramolecular organizing centers known as inflammasomes serving as dominant drivers of this process. In this review, we discuss current knowledge of the mechanisms of IL-1 family cytokine synthesis, processing, and release from cells. Using this knowledge, we propose a model whereby host metabolic state dictates the route of IL-1β secretion, with implications for microbial infection and sterile inflammation.

Investigating the NLRP3 Inflammasome and its Regulator miR-223-3p in Multiple Sclerosis and Experimental Demyelination

Innate immune signalling pathways are essential mediators of inflammation and repair following myelin injury. Inflammasome activation has recently been implicated as a driver of myelin injury in multiple sclerosis (MS) and its animal models, although the regulation and contributions of inflammasome activation in the demyelinated central nervous system (CNS) are not completely understood. Herein, we investigated the NLRP3 (NBD-, LRR- and pyrin domain-containing protein 3) inflammasome and its endogenous regulator microRNA-223-3p within the demyelinated CNS in both MS and an animal model of focal demyelination. We observed that NLRP3 inflammasome components and microRNA-223-3p were upregulated at sites of myelin injury within activated macrophages and microglia. Both microRNA-223-3p and a small-molecule NLRP3 inhibitor, MCC950, supressed inflammasome activation in macrophages and microglia in vitro; compared with microglia, macrophages were more prone to inflammasome activation in vitro. Finally, systemic delivery of MCC950 to mice following lysolecithin-induced demyelination resulted in a significant reduction in axonal injury within demyelinated lesions. In conclusion, we demonstrate that NLRP3 inflammasome activity by macrophages and microglia is a critical component of the inflammatory microenvironment following demyelination and represents a potential therapeutic target for inflammatory-mediated demyelinating diseases, including MS.

Proinflammatory Cytokines (IL-1, -6, -8, -15, -17, -18, -23, TNF-α) Single Nucleotide Polymorphisms in Rheumatoid Arthritis-A Literature Review

Conducted studies highlight that a mixture of genetic and environmental factors is responsible for rheumatoid arthritis (RA) development. This study aimed to analyze the available literature for the relationship between, on the one hand, single-nucleotide polymorphisms (SNPs) in the proinflammatory cytokines genes interleukin-1 (IL-1), -6, -8, -15, -17, -18, and -23, and tumor necrosis factor-alpha (TNF-α), and on the other hand, RA susceptibility, severity, and patients' response to applied treatment. The PubMed database was searched for sources. Preference was given to articles which were published within the past 20 years. Data indicate that the relationship between selected SNPs in proinflammatory cytokines genes and susceptibility to developing RA is inconclusive, and it depends on the ethnicity of the population. Although the allelic and genotypic frequencies of many SNPs in proinflammatory cytokines genes analyzed did not differ between RA patients and healthy controls, deeper analysis showed that these polymorphisms have a relationship with clinicopathological features of RA. SNPs in proinflammatory cytokines genes also "modify patients' response" to applied treatment. Further studies, on larger cohorts of subjects and in different populations, should be conducted to elucidate the role of SNPs in IL-1, -6, -8, -15, -17, -18, and -23, and TNF-α genes in RA patients.

Evaluation of exposure to secondhand smoke and serum level of interleukin 18 in non-smokers

Objective

Smoking is one significant global health care problems, that not only affects the users but also endangers the health of people inhaling the smoke (passive smoking/secondhand smoke). The serum level of IL-18, an important regulator of inherent and acquired immune response, is affected by cigarette smoking. The aim of this study was to evaluate the effect of secondhand smoke (SHS) exposure on IL-18 serum level in non-smoker adults.

Methods

In a case-control study, using easy sampling method, 76 non-smokers who were exposed to cigarette smoke for at least 1 h daily during the past year were considered as exposure group, while 76 of their companions without exposure to cigarette smoke (after matching age) were considered as non-exposure group. Serum IL-18 levels were measured for all participants and finally compared between the two groups using Chi-square test. P value < 0.05 was considered to be statistically significant.

Results

The exposure and non-exposure groups included 58 (76.3%) and 25 (32.9%) males, respectively (P < 0.001). The mean ± SD of age for the exposure and non-exposure groups was 35.42 ± 10.37 and 38.47 ± 12.49 years, respectively (P = 0.102). There was no significant difference between the mean serum levels of IL-18 in the exposure (54.81 ± 57.03 ng/ml) and non-exposure (41.49 ± 42.14 ng/ml) groups (P = 0.104).

Conclusion

The exposure to secondhand smoke has no significant effect on serum level of IL-18 in exposed adult individuals. However, more studies with larger sample sizes on different populations are required to confirm these results.

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Smoking is one significant global health care problems.

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That not only affects the users but also endangers the health of people inhaling the smoke.

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The serum level of IL-18, an important regulator of inherent and acquired immune response.

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The exposure to secondhand smoke has no significant effect on serum level of IL-18.

The Immunological Impact of IL-1 Family Cytokines on the Epidermal Barrier

The skin barrier would not function without IL-1 family members, but their physiological role in the immunological aspects of skin barrier function are often overlooked. This review summarises the role of IL-1 family cytokines (IL-1α, IL-1β, IL-1Ra, IL-18, IL-33, IL-36α, IL-36β, IL-36γ, IL-36Ra, IL-37 and IL-38) in the skin. We focus on novel aspects of their interaction with commensals and pathogens, the important impact of proteases on cytokine activity, on healing responses and inflammation limiting mechanisms. We discuss IL-1 family cytokines in the context of IL-4/IL-13 and IL-23/IL-17 axis-driven diseases and highlight consequences of human loss/gain of function mutations in activating or inhibitory pathway molecules. This review highlights recent findings that emphasize the importance of IL-1 family cytokines in both physiological and pathological cutaneous inflammation and emergent translational therapeutics that are helping further elucidate these cytokines.

Geraniin inhibits whole blood IFN-γ and IL-6 and promotes IL-1β and IL-8, and stimulates calcium-dependent and sucrose-sensitive erythrocyte death

Correlations between circulating cytokine levels and disease states are well established, and pharmacological modulation of the immune response is thus an important aspect of the assessment of investigational new drugs. Moreover, chemotherapy-related anemia is a major obstacle in cancer treatment. Geraniin (GRN), a tannin extracted from Geranium and other plants, possesses promising antitumor potential. However, the effect of GRN on whole blood (WB) cytokine response and RBC physiology remains unexplored. Heparinized blood from consented, healthy adults was challenged with 100 ng/mL of lipopolysaccharide (LPS) with and without pretreatment with 10 μM of GRN for 24 h at 37 °C, and tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), IL-6, IL-8, and IL-10 were assayed by ELISA. Moreover, single-cell RBC suspensions were treated with 5-100 μM of GRN for 24 or 48 h at 37 °C and cytotoxicity and canonical eryptotic markers were examined by flow cytometry. It was revealed that GRN significantly attenuated LPS-induced IFN-γ levels, increased IL-1β, decreased IL-6 only in absence of LPS, and aggravated LPS-induced IL-8 while together with LPS significantly diminished IL-10. Furthermore, GRN induced dose-responsive, Ca²⁺-dependent, and sucrose-sensitive hemolysis, along with phosphatidylserine exposure and Ca²⁺ accumulation with no appreciable cell shrinkage or oxidative damage. GRN was also selectively toxic to platelets, significantly delayed reticulocyte maturation, and significantly disrupted leukocyte proportions. In conclusion, GRN regulates the WB cytokine response and promotes premature hemolysis and eryptosis. This study provides insights into the therapeutic utility of GRN in a highly relevant cellular model system.

IL-18 (Interleukin-18) Produced by Renal Tubular Epithelial Cells Promotes Renal Inflammation and Injury During Deoxycorticosterone/Salt-Induced Hypertension in Mice

IL-18 (interleukin-18) is elevated in hypertensive patients, but its contribution to high blood pressure and end-organ damage is unknown. We examined the role of IL-18 in the development of renal inflammation and injury in a mouse model of low-renin hypertension. Hypertension was induced in male C57BL6/J (WT) and IL-18−/− mice by uninephrectomy, deoxycorticosterone acetate (2.4 mg/d, s.c.) and 0.9% drinking saline (1K/DOCA/salt). Normotensive controls received uninephrectomy and placebo (1K/placebo). Blood pressure was measured via tail cuff or radiotelemetry. After 21 days, kidneys were harvested for (immuno)histochemical, quantitative-PCR and flow cytometric analyses of fibrosis, inflammation, and immune cell infiltration. 1K/DOCA/salt-treated WT mice developed hypertension, renal fibrosis, upregulation of proinflammatory genes, and accumulation of CD3+ T cells in the kidneys. They also displayed increased expression of IL-18 on tubular epithelial cells. IL-18−/− mice were profoundly protected from hypertension, renal fibrosis, and inflammation. Bone marrow transplantation between WT and IL-18−/− mice revealed that IL-18-deficiency in non-bone marrow-derived cells alone afforded equivalent protection against hypertension and renal injury as global IL-18 deficiency. IL-18 receptor subunits—interleukin-18 receptor 1 and IL-18R accessory protein—were upregulated in kidneys of 1K/DOCA/salt-treated WT mice and localized to T cells and tubular epithelial cells. T cells from kidneys of 1K/DOCA/salt-treated mice produced interferon-γ upon ex vivo stimulation with IL-18, whereas those from 1K/placebo mice did not. In conclusion, IL-18 production by tubular epithelial cells contributes to elevated blood pressure, renal inflammation, and fibrosis in 1K/DOCA/salt-treated mice, highlighting it as a promising therapeutic target for hypertension and kidney disease.

Characterization of the turbot (Scophthalmus maximus) interleukin-18: Identification of splicing variants, phylogeny, synteny and expression analysis

Interleukin-18 (IL-18) is a pro-inflammatory cytokine that belongs to the interleukin-1 (IL-1) family of cytokines. As occurs with IL-1β, it is synthetized as an inactive precursor peptide that is mainly processed by the cysteine protease caspase-1 in the inflammasome complex. In mammals, and in collaboration with IL-12, it has been described as an important cytokine controlling the Th1-mediated immune responses through the induction of IFN-γ. Although its function in mammals is well stablished, the activity of this cytokine in teleost remains to be elucidated. This could be due, among other things, to the absence of this gene in the fish model species zebrafish, but also to its complex regulation. As it was observed for rainbow trout and human, il18 splicing variants were also found in turbot, which could represent a regulatory mechanism of its bioactivity. In the case of turbot, three splicing variants were observed (SV1-3), and one of them showed an insertion of 10 amino acids in the middle of the potential caspase-1 cleavage position, reflecting that this is probably a form resistant to the processing by the inflammasome. Phylogenetic and three-dimensional analyses of turbot Il18 revealed that it is relatively well-conserved in vertebrates, although only a partial conservation of the gene synteny was observed between fish and mammals. As it was expected, turbot il18 splicing variants were mainly expressed in immune tissues under healthy conditions, and their expression was induced by a bacterial challenge, although certain inhibitions were observed after viral and parasitic infections. In the case of the viral challenge, il18 downregulations did not seem to be due to the effect of type I IFNs.

Instructions for Flow Cytometric Detection of ASC Specks as a Readout of Inflammasome Activation in Human Blood

Inflammasome activation is linked to the aggregation of the adaptor protein ASC into a multiprotein complex, known as the ASC speck. Redistribution of cytosolic ASC to this complex has been widely used as a readout for inflammasome activation and precedes the downstream proteolytic release of the proinflammatory cytokines, IL-1β and IL-18. Although inflammasomes are important for many diseases such as periodic fever syndromes, COVID-19, gout, sepsis, atherosclerosis and Alzheimer's disease, only a little knowledge exists on the precise and cell type specific occurrence of inflammasome activation in patient samples ex vivo. In this report, we provide detailed information about the optimal conditions to reliably identify inflammasome activated monocytes by ASC speck formation using a modified flow cytometric method introduced by Sester et al. in 2015. Since no protocol for optimal sample processing exists, we tested human blood samples for various conditions including anticoagulant, time and temperature, the effect of one freeze-thaw cycle for PBMC storage, and the fast generation of a positive control. We believe that this flow cytometric protocol will help researchers to perform high quality translational research in multicenter studies, and therefore provide a basis for investigating the role of the inflammasome in the pathogenesis of various diseases.

Inherited Autoinflammatory Syndromes

Autoinflammation describes a collection of diverse diseases caused by indiscriminate activation of the immune system in an antigen-independent manner. The rapid advancement of genetic diagnostics has allowed for the identification of a wide array of monogenic causes of autoinflammation. While the clinical picture of these syndromes is diverse, it is possible to thematically group many of these diseases under broad categories that provide insight into the mechanisms of disease and therapeutic possibilities. This review covers archetypical examples of inherited autoinflammatory diseases in five major categories: inflammasomopathy, interferonopathy, unfolded protein/cellular stress response, relopathy, and uncategorized. This framework can suggest where future work is needed to identify other genetic causes of autoinflammation, what types of diagnostics need to be developed to care for this patient population, and which options might be considered for novel therapeutic targeting. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Pyroptosis in Steatohepatitis and Liver Diseases

Pyroptosis is an inflammatory form of regulated cell death, which functions in the clearance of intracellularly replicating pathogens by cell lysis in order to induce further immune response. Since the discovery of the gasdermin (GSDM) family, pyroptosis has attracted attention in a wide range of inflammatory diseases such as nonalcoholic steatohepatitis and other liver diseases. Due to the cleavage of GSDMs by different caspases, the amino-terminal GSDM fragments form membrane pores essential for pyroptosis that facilitate the release of inflammatory cytokines by loss of ionic gradient and membrane rupture. In this review, we address the key molecular and cellular processes that induce pyroptosis in the liver and its significance in the pathogenesis of common liver diseases in different human and experimental mice studies.

Interleukin-18 accelerates cardiac inflammation and dysfunction during ischemia/reperfusion injury by transcriptional activation of CXCL16

Myocardial ischemia/reperfusion(I/R) injury elicits an inflammatory response that drives tissue damage and cardiac remodeling. The trafficking and recruitment of inflammatory cells are controlled by C-X-C motif chemokine ligands and their receptors. CXCL16, a hallmark of acute coronary syndromes, is responsible for the recruitment of macrophages, monocytes and T lymphocytes. However, its role in cardiac I/R injury remains poorly characterized. Here we reported that CXCL16-mediated cardiac infiltration of CD11b⁺Ly6C⁺ cells played a crucial role in IL-18-induced myocardial inflammation, apoptosis and left ventricular(LV) dysfunction during I/R. Treatment with CXCL16 shRNA attenuated I/R-induced cardiac injury, LV remodeling and cardiac inflammation by reducing the recruitment of inflammatory cells and the release of TNFα, IL-17 and IFN-γ in the heart. We found that I/R-mediated NLRP3/IL-18 signaling pathway triggered CXCL16 transcription in cardiac vascular endothelial cells(VECs). Two binding sites of FOXO3 were found at the promoter region of CXCL16. By luciferase report assay and ChIP analysis, we confirmed that FOXO3 was responsible for endothelial CXCL16 transcription. A pronounced reduction of CXCL16 was observed in FOXO3 siRNA pretreated-VECs. Further experiments revealed that IL-18 activated FOXO3 by promoting the phosphorylation of STAT3 but not STAT4. An interaction between FOXO3 and STAT3 enhanced the transcription of CXCL16 induced by FOXO3. Treatment with Anakinra or Stattic either effectively inhibited IL-18-mediated nuclear import of FOXO3 and CXCL16 transcription. Our findings suggested that IL-18 accelerated I/R-induced cardiac damage and dysfunction through activating CXCL-16 and CXCL16-mediated cardiac infiltration of the CD11b⁺Ly6C⁺ cells. CXCL16 might be a novel therapeutic target for the treatment of I/R-related ischemic heart diseases.

Cystatin C Deficiency Increases LPS-Induced Sepsis and NLRP3 Inflammasome Activation in Mice

Cystatin C is a potent cysteine protease inhibitor that plays an important role in various biological processes including cancer, cardiovascular diseases and neurodegenerative diseases. However, the role of CstC in inflammation is still unclear. In this study we demonstrated that cystatin C-deficient mice were significantly more sensitive to the lethal LPS-induced sepsis. We further showed increased caspase-11 gene expression and enhanced processing of pro-inflammatory cytokines IL-1β and IL-18 in CstC KO bone marrow-derived macrophages (BMDM) upon LPS and ATP stimulation. Pre-treatment of BMDMs with the cysteine cathepsin inhibitor E-64d did not reverse the effect of CstC deficiency on IL-1β processing and secretion, suggesting that the increased cysteine cathepsin activity determined in CstC KO BMDMs is not essential for NLRP3 inflammasome activation. The CstC deficiency had no effect on (mitochondrial) reactive oxygen species (ROS) generation, the MAPK signaling pathway or the secretion of anti-inflammatory cytokine IL-10. However, CstC-deficient BMDMs showed dysfunctional autophagy, as autophagy induction via mTOR and AMPK signaling pathways was suppressed and accumulation of SQSTM1/p62 indicated a reduced autophagic flux. Collectively, our study demonstrates that the excessive inflammatory response to the LPS-induced sepsis in CstC KO mice is dependent on increased caspase-11 expression and impaired autophagy, but is not associated with increased cysteine cathepsin activity.

Analyzing the influence of IL18 in regulation of YAP1 in breast oncogenesis using cBioportal

Background

Yes‐associated protein 1 (YAP1) is responsible for tumor growth, progression and metastasis. The mechanisms controlling the generation and relative ratio of the functional YAP1 and other co‐factors are not well‐understood. Various literature reported that co‐factors like cytokines significantly influence signaling pathways to introduce epithelial immunity and regeneration, which later helps increase cancer‐related phenotypes. Among various cytokines, IL‐18 has emerged as a major player in inflammation and progression of different types of cancers. Till now, much information has not been known about the role of YAP1 in tumor aggressiveness and immune evasion in breast cancer with respect to IL‐18.

Aim

We aimed to explore the effect of YAP1 in tumor aggressiveness and immune evasion in breast invasive carcinoma and metastatic breast cancer in the context of Interleukin‐18 (IL‐18) in silico.

Methods and Results

We used publicly available data generated by The Cancer Genome Atlas (TCGA) Research Network through cBioportal web platform. Kaplan–Meier method was used to determine the overall survival and comparison between curves were made using Log‐Rank test. The p values were determined by Fisher's exact test with the null hypothesis. Correlation plots were analyzed by comparison with gene copy numbers from the GISTIC2.0, available through cBioportal.

Our analyses suggest that IL‐18 influences YAP1 expression in breast oncogenesis via Interferon‐gamma (IFN‐γ) production. Patients having a higher expression of IL‐18 possess a better prognosis and higher YAP1 expression with lower IL18 drives to poor clinical results in breast cancer.

Conclusion

This can provide new approaches to better understand the relation between YAP1 and IL‐18 in breast cancer progression by performing in vitro and in vivo studies. Also, IL‐18 can be considered as a potential target for tumor treatment in YAP1 overexpressed breast carcinoma.

Select hyperactivating NLRP3 ligands enhance the TH1- and TH17-inducing potential of human type 2 conventional dendritic cells

The detection of microorganisms and danger signals by pattern recognition receptors on dendritic cells (DCs) and the consequent formation of inflammasomes are pivotal for initiating protective immune responses. Although the activation of inflammasomes leading to secretion of the cytokine IL-1β is typically accompanied by pyroptosis (an inflammatory form of lytic programmed cell death), some cells can survive and exist in a state of hyperactivation. Here, we found that the conventional type 2 DC (cDC2) subset is the major human DC subset that is transcriptionally and functionally poised for inflammasome formation and response without pyroptosis. When cDC2 were stimulated with ligands that relatively weakly activated the inflammasome, the cells did not enter pyroptosis but instead secreted IL-12 family cytokines and IL-1β. These cytokines induced prominent T helper type 1 (T_H1) and T_H17 responses that were superior to those seen in response to Toll-like receptor (TLR) stimulation alone or to stronger, classical inflammasome ligands. These findings not only define the human cDC2 subpopulation as a prime target for the treatment of inflammasome-dependent inflammatory diseases but may also inform new approaches for adjuvant and vaccine development.

Differential recognition of HIV-stimulated IL-1β and IL-18 secretion through NLR and NAIP signalling in monocyte-derived macrophages

Macrophages are important drivers of pathogenesis and progression to AIDS in HIV infection. The virus in the later phases of the infection is often predominantly macrophage-tropic and this tropism contributes to a chronic inflammatory and immune activation state that is observed in HIV patients. Pattern recognition receptors of the innate immune system are the key molecules that recognise HIV and mount the inflammatory responses in macrophages. The innate immune response against HIV-1 is potent and elicits caspase-1-dependent pro-inflammatory cytokine production of IL-1β and IL-18. Although, NLRP3 has been reported as an inflammasome sensor dictating this response little is known about the pattern recognition receptors that trigger the “priming” signal for inflammasome activation, the NLRs involved or the HIV components that trigger the response. Using a combination of siRNA knockdowns in monocyte derived macrophages (MDMs) of different TLRs and NLRs as well as chemical inhibition, it was demonstrated that HIV Vpu could trigger inflammasome activation via TLR4/NLRP3 leading to IL-1β/IL-18 secretion. The priming signal is triggered via TLR4, whereas the activation signal is triggered by direct effects on Kv1.3 channels, causing K⁺ efflux. In contrast, HIV gp41 could trigger IL-18 production via NAIP/NLRC4, independently of priming, as a one-step inflammasome activation. NAIP binds directly to the cytoplasmic tail of HIV envelope protein gp41 and represents the first non-bacterial ligand for the NAIP/NLRC4 inflammasome. These divergent pathways represent novel targets to resolve specific inflammatory pathologies associated with HIV-1 infection in macrophages.

It has been previously shown that inflammasome activation can be triggered during viral infection to produce the active cytokines IL-1β and IL-18. Our study represents a significant advance, as we now show that in fact there are distinct NLR inflammasome complexes and viral ligands for IL-1β secretion (Vpu) compared to IL-18 secretion (gp41) in response to HIV-1.

Most importantly, we show that the HIV envelope protein gp41 represents the first non-bacterial ligand for the assembly of the NAIP/NLRC4 inflammasome. HIV gp41 is a viroporin, and thus our data demonstrates for the first time that the NAIP/NLRC4 inflammasome assembles for all pore-forming proteins, irrespective of whether they have a viral or bacterial origin. This is critical for the host antiviral response and has broad implications for innate immunity in general.

A novel anti-human IL-1R7 antibody reduces IL-18-mediated inflammatory signaling

Unchecked inflammation can result in severe diseases with high mortality, such as macrophage activation syndrome (MAS). MAS and associated cytokine storms have been observed in COVID-19 patients exhibiting systemic hyperinflammation. Interleukin-18 (IL-18), a proinflammatory cytokine belonging to the IL-1 family, is elevated in both MAS and COVID-19 patients, and its level is known to correlate with the severity of COVID-19 symptoms. IL-18 binds its specific receptor IL-1 receptor 5 (IL-1R5, also known as IL-18 receptor alpha chain), leading to the recruitment of the coreceptor, IL-1 receptor 7 (IL-1R7, also known as IL-18 receptor beta chain). This heterotrimeric complex then initiates downstream signaling, resulting in systemic and local inflammation. Here, we developed a novel humanized monoclonal anti-IL-1R7 antibody to specifically block the activity of IL-18 and its inflammatory signaling. We characterized the function of this antibody in human cell lines, in freshly obtained peripheral blood mononuclear cells (PBMCs) and in human whole blood cultures. We found that the anti-IL-1R7 antibody significantly suppressed IL-18-mediated NFκB activation, reduced IL-18-stimulated IFNγ and IL-6 production in human cell lines, and reduced IL-18-induced IFNγ, IL-6, and TNFα production in PBMCs. Moreover, the anti-IL-1R7 antibody significantly inhibited LPS- and Candida albicans–induced IFNγ production in PBMCs, as well as LPS-induced IFNγ production in whole blood cultures. Our data suggest that blocking IL-1R7 could represent a potential therapeutic strategy to specifically modulate IL-18 signaling and may warrant further investigation into its clinical potential for treating IL-18-mediated diseases, including MAS and COVID-19.

β-Glucan-induced reprogramming of human macrophages inhibits NLRP3 inflammasome activation in cryopyrinopathies

Exposure of mononuclear phagocytes to β-glucan, a naturally occurring polysaccharide, contributes to the induction of innate immune memory, which is associated with long-term epigenetic, metabolic, and functional reprogramming. Although previous studies have shown that innate immune memory induced by β-glucan confers protection against secondary infections, its impact on autoinflammatory diseases, associated with inflammasome activation and IL-1β secretion, remains poorly understood. In particular, whether β-glucan-induced long-term reprogramming affects inflammasome activation in human macrophages in the context of these diseases has not been explored. We found that NLRP3 inflammasome-mediated caspase-1 activation and subsequent IL-1β production were reduced in β-glucan-reprogrammed macrophages. β-Glucan acted upstream of the NLRP3 inflammasome by preventing potassium (K+) efflux, mitochondrial ROS (mtROS) generation, and, ultimately, apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization and speck formation. Importantly, β-glucan-induced memory in macrophages resulted in a remarkable attenuation of IL-1β secretion and caspase-1 activation in patients with an NLRP3-associated autoinflammatory disease, cryopyrin-associated periodic syndromes (CAPS). Our findings demonstrate that β-glucan-induced innate immune memory represses IL-1β-mediated inflammation and support its potential clinical use in NLRP3-driven diseases.

Inflammasome Proteins as Inflammatory Biomarkers of Age-Related Macular Degeneration

Purpose

Age-related macular degeneration (AMD) can result in severe vision loss and blurriness in the older population. The early and intermediate stages of AMD typically start without noticeable symptoms and can only be detected with a comprehensive eye exam. Because of the quiet onset of the disease, it is necessary to identify potential biomarkers to aid in the diagnosis, staging, and association with disease onset. Inflammasome signaling proteins are prominent biomarkers in the central nervous system, and the inflammasome has been shown to play a role in the innate inflammatory response in aging and AMD.

Methods

Serum from healthy controls and AMD patients were analyzed for the protein levels of Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), interleukin (IL)-18 and C-reactive protein (CRP) to determine cutoff points, positive and negative predictive values, and receiver operator characteristic curves, as well as univariate and multivariate linear and logistic regression models.

Results

ASC, IL-18, and CRP were elevated in the serum of AMD patients when compared to healthy controls. The area under the curve (AUC) for ASC was 0.98 with a cutoff point of 365.6 pg/mL, whereas IL-18 had an AUC of 0.73 and a cutoff point of 242.4 pg/mL, and the AUC for CRP was 0.67 with a cutoff point of 8,684,152 pg/mL. Levels of IL-18 had a statistically significant linear correlation with that of ASC with an adjusted R² of 0.1906, indicating that 19% of IL-18 could be explained by ASC protein levels in serum. Moreover, a logistic regression model for the diagnosis of AMD consists of ASC and having a diagnosis of hypertension, indicating that these two factors (elevated levels of ASC and a diagnosis of hypertension [HTN]) are associated with the diagnosis of AMD.

Conclusions

ASC, IL-18, and CRP are elevated in patients with AMD, and the protein levels of IL-18 are partially the result of ASC protein expression. Moreover, elevated protein levels of ASC in serum and a diagnosis of HTN increase the odds of patients having a diagnosis of AMD.

Translational Relevance

Biomarkers of AMD may be used to monitor disease risk, response to treatment and disease progression.

Molecularly Distinct NLRP3 Inducers Mediate Diverse Ratios of Interleukin-1β and Interleukin-18 from Human Monocytes

Inflammasomes cleave and activate interleukin- (IL-) 1β and IL-18 which have both shared and unique biological functions. IL-1β is an important mediator of the acute phase response to infections and tissue damage, whereas IL-18 takes part in activation and tailoring of the adaptive immune response. While IL-1β has served as the prototypic indicator of inflammasome activation, few studies have compared the potential differences in IL-1β and IL-18 production during inflammasome activation. Since these cytokines partake in different immune pathways, the involvement of inflammasome activity in different conditions needs to be described beyond IL-1β production alone. To address a potential heterogeneity in inflammasome functionality, ATP, chitosan, or silica oxide (SiO₂) were used to induce NLRP3 inflammasome activation in THP-1 cells and the subsequent outcomes were quantified. Despite using doses of the inflammasome inducers yielding similar release of IL-1β, SiO₂-stimulated cells showed a lower concentration of released IL-18 compared to ATP and chitosan. Hence, the cells stimulated with SiO₂ responded with a distinctly different IL-18 : IL-1β ratio. The difference in the IL-18 : IL-1β ratio for SiO₂ was constant over different doses. While all downstream responses were strictly dependent on a functional NLRP3 inflammasome, the differences did not depend on the level of gene expression, caspase-1 activity, or pyroptosis. We suggest that the NLRP3 inflammasome response should be considered a dynamic process, which can be described by taking the ratio between IL-1β and IL-18 into account and moving away from an on/off perspective of inflammasome activation.

Current treatment options and safety considerations when treating adult-onset Still's disease

INTRODUCTION

Adult onset Still disease (AOSD) is a rare systemic inflammatory condition. The clinical spectrum of this disease ranges from self-limiting forms with mild symptoms to life-threatening cases. Glucocorticoids and non-steroidal anti-inflammatory drugs (NSAIDs) represent the first line of therapy for AOSD, with add-on therapy with second-line drug reserved to steroid-dependent patients and in life-threatening cases. Currently, early treatment with conventional disease modifying anti-rheumatic drugs (DMARDs) and biologic agents blocking causal cytokines is advocated in patients with severe and recalcitrant clinical manifestations.

AREAS COVERED

This review analyzes the available controlled evidence and observational data regarding the efficacy and safety of conventional and biological pharmacological agents in the treatment of AOSD.

EXPERT OPINION

Non-steroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids are effective in controlling clinical manifestations in the majority of AOSD patients. Conventional DMARDs can be 20 effective in some severe and steroid-dependent cases of AOSD; however, anti-cytokine agents represent an effective and overall more suitable alternative in this specific subset of patients. IL-1 and IL-6 blockade are effective in treating systemic and articular inflammation of AOSD patients. IL-1 blockade also has an excellent safety profile and therefore represent the first choice of biologic treatment in this clinical scenario.

Nlrp3 Inflammasome Inhibitor MCC950 Ameliorates Obliterative Bronchiolitis by Inhibiting Th1/Th17 Response and Promoting Treg Response After Orthotopic Tracheal Transplantation in Mice

BACKGROUND

Obliterative bronchiolitis (OB) remains the major complication limiting long-term survival of patients after lung transplantation. We aimed to explore the effects of the selective NACHT, LRR, and PYD domains-containing protein 3 (Nlrp3) inflammasome inhibitor MCC950 on the pathogenesis of OB.

METHODS

Mouse orthotopic tracheal transplants were performed to mimic OB. MCC950 (50 mg/kg) or saline was intraperitoneally injected daily. The luminal occlusion rate and collagen deposition were evaluated by hematoxylin and eosin and Masson's trichrome staining, respectively. Infiltration of CD4+, CD8+ T cells, and neutrophils was detected with immunohistochemical staining. The frequencies of T helper 1 cell (Th1), T helper 17 cell (Th17), and regulatory T cells (Treg) were measured by flow cytometry. Cytokine levels were measured by ELISA kits.

RESULTS

MCC950 treatment significantly inhibited Nlrp3 inflammasome activation after allogeneic tracheal transplant and markedly decreased the luminal occlusion rate and collagen deposition in the allograft. The numbers of infiltrating CD4+, CD8+ T cells, and neutrophils in the allograft were also significantly reduced by MCC950 treatment. MCC950 dramatically decreased the frequencies of Th1/Th17 cells and the levels of interferon gamma/interleukin (IL)-17A and increased the Treg cell frequencies and IL-10 level; however, these effects were abolished by the addition of IL-1β and IL-18 both in vitro and in vivo. OB was also rescued by the addition of IL-1β and/or IL-18.

CONCLUSIONS

Blocking Nlrp3 inflammasome activation with MCC950 ameliorates OB lesions. The mechanistic analysis showed that MCC950 regulated the balance of Th1/Th17 and Treg cells and that this process is partially mediated by inhibition of IL-1β and IL-18. Therefore, targeting the Nlrp3 inflammasome is a promising strategy for controlling OB after lung transplantation.

PPARγ Cistrome Repression during Activation of Lung Monocyte-Macrophages in Severe COVID-19

The molecular mechanisms of cytokine storm in patients with severe COVID-19 infections are poorly understood. To uncover these events, we performed transcriptome analyses of lung biopsies from patients with COVID-19, revealing a gene enrichment pattern similar to that of PPARγ-knockout macrophages. Single-cell gene expression analysis of bronchoalveolar lavage fluids revealed a characteristic trajectory of PPARγ-related disturbance in the CD14+/CD16+ cells. We identified a correlation with the disease severity and the reduced expression of several members of the PPARγ complex such as EP300, RXRA, RARA, SUMO1, NR3C1, and CCDC88A. ChIP-seq analyses confirmed repression of the PPARγ-RXRA-NR3C1 cistrome in COVID-19 lung samples. Further analysis of protein-protein networks highlighted an interaction between the PPARγ-associated protein SUMO1 and a nucleoprotein of the SARS virus. Overall, these results demonstrate for the first time the involvement of the PPARγ complex in severe COVID-19 lung disease and suggest strongly its role in the major monocyte/macrophage-mediated inflammatory storm.