The NLRP3 inflammasome in pathogenic particle and fibre-associated lung inflammation and diseases

Pulmonary inflammation induced by low-dose particulate matter exposure in mice

Air pollution is a ubiquitous problem and comprises gaseous and particulate matter (PM). Epidemiological studies have clearly shown that exposure to PM is associated with impaired lung function and the development of lung diseases, such as chronic obstructive pulmonary disease and asthma. To understand the mechanisms involved, animal models are often used. However, the majority of such models represent high levels of exposure and are not representative of the exposure levels in less polluted countries, such as Australia. Therefore, in this study, we aimed to determine whether low dose PM₁₀ exposure has any detrimental effect on the lungs. Mice were intranasally exposed to saline or traffic-related PM₁₀ (1μg or 5μg/day) for 3 wk. Bronchoalveolar lavage (BAL) and lung tissue were analyzed. PM₁₀ at 1 μg did not significantly affect inflammatory and mitochondrial markers. At 5 μg, PM₁₀ exposure increased lymphocytes and macrophages in BAL fluid. Increased NACHT, LRR and PYD domains-containing protein 3 (NLRP3) and IL-1β production occurred following PM₁₀ exposure. PM₁₀ (5 μg) exposure reduced mitochondrial antioxidant manganese superoxide (antioxidant defense system) and mitochondrial fusion marker (OPA-1), while it increased fission marker (Drp-1). Autophagy marker light-chain 3 microtubule-associated protein (LC3)-II and phosphorylated-AMPK were reduced, and apoptosis marker (caspase 3) was increased. No significant change of remodeling markers was observed. In conclusion, a subchronic low-level exposure to PM can have an adverse effect on lung health, which should be taken into consideration for the planning of roads and residential buildings.

NLRP inflammasome as a key role player in the pathogenesis of environmental toxicants

Exposure to environmental toxicants (ET) results in specific organ damage and auto-immune diseases, mostly mediated by inflammatory responses. The NLRP3 inflammasome has been found to be the major initiator of the associated pathologic inflammation. It has been found that ETs can trigger all the signals required for an NLRP3-mediated response. The exaggerated activation of the NLRP3 inflammasome and its end product IL-1β, is responsible for the pathogenesis caused by many ETs including pesticides, organic pollutants, heavy metals, and crystalline compounds. Therefore, an extensive study of these chemicals and their mechanisms of inflammasome (INF) activation may provide the scientific evidence for possible targeting of this pathway by proposing possible protective agents that have been previously shown to affect INF compartments and its activation. Melatonin and polyunsaturated fatty acids (PUFA) are among the safest and the most studied of these agents, which affect a wide variety of cellular and physiological processes. These molecules have been shown to suppress the NLRP3 inflammasome mostly through the regulation of cellular redox status and the nuclear factor-κB (NF-κB) pathway, rendering them potential promising compounds to overcome ET-mediated organ damage. In the present review, we have made an effort to extensively review the ETs that exert their pathogenesis via the stimulation of inflammation, their precise mechanisms of action and the possible protective agents that could be potentially used to protect against such toxicants.

In Silico Transcriptomic Analysis of Wound-Healing-Associated Genes in Malignant Pleural Mesothelioma

Background and objectives: Malignant pleural mesothelioma (MPM) is a devastating malignancy with poor prognosis. Reliable biomarkers for MPM diagnosis, monitoring, and prognosis are needed. The aim of this study was to identify genes associated with wound healing processes whose expression could serve as a prognostic factor in MPM patients. Materials and Methods: We used data mining techniques and transcriptomic analysis so as to assess the differential transcriptional expression of wound-healing-associated genes in MPM. Moreover, we investigated the potential prognostic value as well as the functional enrichments of gene ontologies relative to microRNAs (miRNAs) of the significantly differentially expressed wound-healing-related genes in MPM. Results: Out of the 82 wound-healing-associated genes analyzed, 30 were found significantly deregulated in MPM. Kaplan–Meier analysis revealed that low ITGAV gene expression could serve as a prognostic factor favoring survival of MPM patients. Finally, gene ontology annotation enrichment analysis pointed to the members of the hsa-miR-143, hsa-miR-223, and the hsa-miR-29 miRNA family members as important regulators of the deregulated wound healing genes. Conclusions: 30 wound-healing-related genes were significantly deregulated in MPM, which are potential targets of hsa-miR-143, hsa-miR-223, and the hsa-miR-29 miRNA family members. Out of those genes, ITGAV gene expression was a prognostic factor of overall survival in MPM. Our results highlight the role of impaired tissue repair in MPM development and should be further validated experimentally.

The Antioxidant MitoQ Protects Against CSE-Induced Endothelial Barrier Injury and Inflammation by Inhibiting ROS and Autophagy in Human Umbilical Vein Endothelial Cells

Chronic obstructive pulmonary disease (COPD) is a common disease characterized by persistent airflow limitation. Pulmonary vascular endothelial barrier injury and inflammation are increasingly considered to be important pathophysiological processes in cigarette smoke extract (CSE)-induced COPD, but the mechanism remains unclear. To identify the cellular mechanism of endothelial barrier injury and inflammation in CSE-treated human umbilical vein endothelial cells (HUVECs), we investigated the effect of the mitochondrion-targeting antioxidant mitoquinone (MitoQ) on endothelial barrier injury and inflammation. We demonstrated that MitoQ restored endothelial barrier integrity by preventing VE-cadherin disassembly and actin cytoskeleton remodeling, as well as decreased inflammation by the NF-κB and NLRP3 inflammasome pathways in endothelial cells. In addition, MitoQ also maintained mitochondrial function by reducing the production of ROS and excess autophagy. Inhibition of autophagy by 3-MA protected against cytotoxicity that was induced by CSE in HUVECs. Overall, our study indicated that mitochondrial damage is a key promoter in the induction of endothelial barrier dysfunction and inflammation by CSE. The protective effect of MitoQ is related to the inhibition of ROS and excess autophagy in CSE-induced HUVEC injury.

Role of Nephronectin in Pathophysiology of Silicosis

Silicosis is a typical form of pneumoconiosis and is characterized as a type of lung fibrosis. Silica particles are captured and recognized upon by alveolar macrophages via the macrophage receptor with collagenous structure (MARCO) scavenger receptor, and thereafter the inflammasome is activated. Thereafter, various chemokines/cytokines play their roles to eventually form fibrosis. Additionally, silica particles chronically activate T helper cells which sets the background for the formation of silicosis-associated autoimmune disturbances. The occurrence and progression of lung fibrosis, the extracellular matrix-related molecules such as integrins and their ligands including fibronectin, vitronectin, laminin, and collagens, all play important roles. Here, the roles of these molecules in silicosis-related lung fibrosis are reviewed from the literature. Additionally, the measurement of serum nephronectin (Npnt), a new member of the integrin family of ligands, is discussed, together with investigations attempting to delineate the role of Npnt in silica-induced lung fibrosis. Serum Npnt was found to be higher in silicosis patients compared to healthy volunteers and seems to play a role in the progression of fibrosis with other cytokines. Therefore, serum Npnt levels may be employed as a suitable marker to monitor the progression of fibrosis in silicosis patients.

NLRP3 inflammasome activation involved in LPS and coal tar pitch extract-induced malignant transformation of human bronchial epithelial cells

Inflammatory microenvironment has been found as a new characteristic of cancer; however, the mechanisms of inflammation-related lung cancer remain unclear. To explore the role of NLRP3 inflammsome activation in inflammation-related lung carcinogenesis, a cell model was set up. Human bronchial epithelial cells (BEAS-2B) were stimulated with 1 μg/mL lipopolysaccharide (LPS) for 24 hours, and then treated with 2.4 μg/mL coal tar pitch extract (CTPE) for 24 hours, after removal of LPS and CTPE, the cells were numbered passage 1 and were passaged and treated in this way until passage 30, which was called LPS + CTPE group. DMSO and Saline were used as vehicle controls. Malignant transformation of cells in passage 30 was evaluated by morphological change, platelet clone formation assay, and tumor formation in nude mice. The mRNA levels of NLRP3 and IL-1β were detected by real time-PCR. The combination of NLRP3 and caspase-1 were determined using immunofluorescence and confocal. The protein expression of NLRP3, cleaved caspase-1(p10), and cleaved IL-1β was detected using Western blot. It was shown that CTPE, LPS + CTPE-stimulated BEAS-2B cells of passage 30 changed a lot morphologically. The clone formation rates, the rates of positive cells of NLRP3 and caspase-1 combination, the mRNA levels of NLRP3 and IL-1β, the protein expression of NLRP3, cleaved caspase-1(p10) and cleaved IL-1β of cells exposed with CTPE and LPS + CTPE at passage 30 were significantly increased compared to vehicle controls. Furthermore, the ability of tumor formation in nude mice, the rates of clone formation and positive cells, mRNA and protein levels of NLRP3 inflammasome activation-related factors in LPS + CTPE-induced cells were all higher than those in cells stimulated with CTPE alone. In conclusion, the cell model of inflammation-related lung cancer is set up successfully, and NLRP3 inflammasome activation may be involved in the malignant transformation of BEAS-2B cells which induced by CTPE alone or LPS combined with CTPE.

Mesothelium and Malignant Mesothelioma

The mesothelium is an epithelial structure derived from the embryonic mesoderm. It plays an important role in the development of a number of different organs, including the heart, lungs, and intestines. In this publication, we discuss aspects of the development of the mesothelium, where mesothelial structures can be found, and review molecular and cellular characteristics associated with the mesothelium. Furthermore, we discuss the involvement of the mesothelium in a number of disease conditions, in particular in the pathogenesis of mesotheliomas with an emphasis on malignant pleural mesothelioma (MPM)—a primary cancer developing in the pleural cavity.

Risk Analysis Implications of Dose-Response Thresholds for NLRP3 Inflammasome-Mediated Diseases: Respirable Crystalline Silica and Lung Cancer as an Example

Chronic inflammation mediates an extraordinarily wide range of diseases. Recent progress in understanding intracellular inflammasome assembly, priming, activation, cytokine signaling, and interactions with mitochondrial reactive oxygen species, lysosome disruption, cell death, and prion-like polymerization and spread of inflammasomes among cells, has potentially profound implications for dose-response modeling. This article discusses mechanisms of exposure concentration and duration thresholds for NOD-like receptor protein 3 (NLRP3)-mediated inflammatory responses and develops a simple biomathematical model of the onset of exposure-related tissue-level chronic inflammation and resulting disease risks, focusing on respirable crystalline silica (RCS) and lung cancer risk as an example. An inflammation-mediated 2-stage clonal expansion model of RCS-induced lung cancer is proposed that explains why relatively low estimated concentrations of RCS (eg, <1 mg/m³) do not increase lung cancer risk and why even high occupational concentrations increase risk only modestly (typically relative risk <2). The model of chronic inflammation implies a dose-response threshold for excess cancer risk, in contrast to traditional linear-no-threshold assumptions. If this implication is correct, then concentrations of crystalline silica (or amphibole asbestos fibers, or other environmental challenges that act via the NLRP3 inflammasome) below the threshold do not cause chronic inflammation and resulting elevated risks of inflammation-mediated diseases.

Role of Macrophages in Acute Lung Injury and Chronic Fibrosis Induced by Pulmonary Toxicants

A diverse group of toxicants has been identified that cause injury to the lung including gases (eg, ozone, chlorine), particulates/aerosols (eg, diesel exhaust, fly ash, other combustion products, mustards, nanomaterials, silica, asbestos), chemotherapeutics (eg, bleomycin), and radiation. The pathologic response to these toxicants depends on the dose and duration of exposure and their physical/chemical properties. A common response to pulmonary toxicant exposure is an accumulation of proinflammatory/cytotoxic M1 macrophages at sites of tissue injury, followed by the appearance of anti-inflammatory/wound repair M2 macrophages. It is thought that the outcome of the pathogenic responses to toxicants depends on the balance in the activity of these macrophage subpopulations. Overactivation of either M1 or M2 macrophages leads to injury and disease pathogenesis. Thus, the very same macrophage-derived mediators, released in controlled amounts to destroy injurious materials and pathogens (eg, reactive oxygen species, reactive nitrogen species, proteases, tumor necrosis factor α) and initiate wound repair (eg, transforming growth factor β, connective tissue growth factor, vascular endothelial growth factor), can exacerbate acute lung injury and/or induce chronic disease such as fibrosis, chronic obstructive pulmonary disease, and asthma, when released in excess. This review focuses on the role of macrophage subsets in acute lung injury and chronic fibrosis. Understanding how these pathologies develop following exposure to toxicants, and the contribution of resident and inflammatory macrophages to disease pathogenesis may lead to the development of novel approaches for treating lung diseases.

Associations of variants In the hexokinase 1 and interleukin 18 receptor regions with oxyhemoglobin saturation during sleep

Sleep disordered breathing (SDB)-related overnight hypoxemia is associated with cardiometabolic disease and other comorbidities. Understanding the genetic bases for variations in nocturnal hypoxemia may help understand mechanisms influencing oxygenation and SDB-related mortality. We conducted genome-wide association tests across 10 cohorts and 4 populations to identify genetic variants associated with three correlated measures of overnight oxyhemoglobin saturation: average and minimum oxyhemoglobin saturation during sleep and the percent of sleep with oxyhemoglobin saturation under 90%. The discovery sample consisted of 8,326 individuals. Variants with p < 1 × 10(-6) were analyzed in a replication group of 14,410 individuals. We identified 3 significantly associated regions, including 2 regions in multi-ethnic analyses (2q12, 10q22). SNPs in the 2q12 region associated with minimum SpO2 (rs78136548 p = 2.70 × 10(-10)). SNPs at 10q22 were associated with all three traits including average SpO2 (rs72805692 p = 4.58 × 10(-8)). SNPs in both regions were associated in over 20,000 individuals and are supported by prior associations or functional evidence. Four additional significant regions were detected in secondary sex-stratified and combined discovery and replication analyses, including a region overlapping Reelin, a known marker of respiratory complex neurons.These are the first genome-wide significant findings reported for oxyhemoglobin saturation during sleep, a phenotype of high clinical interest. Our replicated associations with HK1 and IL18R1 suggest that variants in inflammatory pathways, such as the biologically-plausible NLRP3 inflammasome, may contribute to nocturnal hypoxemia.

Mapping of Dynamic Transcriptome Changes Associated With Silica-Triggered Autoimmune Pathogenesis in the Lupus-Prone NZBWF1 Mouse

Crystalline silica (cSiO₂) is a widely recognized environmental trigger of autoimmune disease. In the lupus-prone female NZBWF1 mouse, airway exposure to cSiO₂ triggers pulmonary ectopic lymphoid neogenesis, systemic autoantibody elevation, and glomerulonephritis. Here we tested the hypothesis that upregulation of adaptive immune function genes in the lung precedes cSiO₂-triggering of autoimmune disease in this model. The study include three groups of mice, as follows: (1) necropsied 1 d after a single intranasal instillation of 1 mg cSiO₂ or vehicle, (2) necropsied 1 d after four weekly single instillations of 1 mg cSiO₂ or vehicle, or (3) necropsied 1, 5, 9, or 13 weeks after four weekly single instillations of 1 mg cSiO₂ or vehicle. NanoString nCounter analysis revealed modest transcriptional changes associated with innate and adaptive immune response as early as 1 d after a single cSiO₂ instillation. These responses were greatly expanded after four weekly cSiO₂ instillations. Concurrent with ectopic lymphoid neogenesis, dramatic increases in mRNAs associated with chemokine release, cytokine production, sustained interferon activity, complement activation, and adhesion molecules were observed. As disease progressed, expression of these genes persisted and was further amplified. Consistent with autoimmune pathogenesis, the time between 5 and 9 weeks post-instillation reflected an important transition period where considerable immune gene upregulation in the lung was observed. Upon termination of the chronic study (13 weeks), cSiO₂-induced changes in transcriptome signatures were similarly robust in kidney as compared to the lung, but more modest in spleen. Transcriptomic signatures in lung and kidney were indicative of infiltration and/or expansion of neutrophils, macrophages, dendritic cells, B cells, and T cells that corresponded with accelerated autoimmune pathogenesis. Taken together, airway exposure to cSiO₂ elicited aberrant mRNA signatures for both innate and adaptive immunity that were consistent with establishment of the lung as the central autoimmune nexus for launching systemic autoimmunity and ultimately, kidney injury.

Malignant mesothelioma diagnosed at a younger age is associated with heavier asbestos exposure

Asbestos exposure is the main etiology of malignant mesothelioma, but there are conflicting data on whether the intensity of exposure modulates the development of this disease. This study considered 594 patients with malignant mesothelioma for whom count data on asbestos bodies and fibers (per gram of wet lung tissue) were available. The relationships between age at diagnosis (a time-to-event outcome variable) and these two measures of internal asbestos exposure, along with other possible modulating factors (sex, tumor location, histological subtype and childhood exposure), were assessed on multivariable Cox proportional hazard models, stratifying by decade of birth year. For both measures of asbestos in lung tissue, younger age at diagnosis was associated with higher internal measures of exposure to asbestos. Stratified Cox analyses showed that for each doubling in asbestos body count patients were 1.07 times more likely to be diagnosed at a younger age [hazard ratio (HR) = 1.07; 95% confidence interval (CI), 1.04-1.09; P = 2.2 × 10-7] and for each doubling in asbestos fiber count patients were 1.13 times more likely to be diagnosed at a younger age (HR = 1.13; 95% CI, 1.09-1.17; P = 8.6 × 10-11). None of the other variables considered were associated with age at diagnosis. Our finding that tumors become clinically apparent at a younger age in heavily exposed subjects suggests that asbestos is involved not only in the malignant mesothelioma tumor initiation but, somehow, also in the progression of the disease.

The asbestos-carbon nanotube analogy: An update

Nanotechnology is an emerging industry based on commercialization of materials with one or more dimensions of 100 nm or less. Engineered nanomaterials are currently incorporated into thin films, porous materials, liquid suspensions, or filler/matrix nanocomposites with future applications predicted in energy and catalysis, microelectronics, environmental sensing and remediation, and nanomedicine. Carbon nanotubes are one-dimensional fibrous nanomaterials that physically resemble asbestos fibers. Toxicologic studies in rodents demonstrated that some types of carbon nanotubes can induce mesothelioma, and the World Health Organization evaluated long, rigid multiwall carbon nanotubes as possibly carcinogenic for humans in 2014. This review summarizes key physicochemical similarities and differences between asbestos fibers and carbon nanotubes. The "fiber pathogenicity paradigm" has been extended to include carbon nanotubes as well as other high-aspect-ratio fibrous nanomaterials including metallic nanowires. This paradigm identifies width, length, and biopersistence of high-aspect-ratio fibrous nanomaterials as critical determinants of lung disease, including mesothelioma, following inhalation. Based on recent theoretical modeling studies, a fourth factor, mechanical bending stiffness, will be considered as predictive of potential carcinogenicity. Novel three-dimensional lung tissue platforms provide an opportunity for in vitro screening of a wide range of high aspect ratio fibrous nanomaterials for potential lung toxicity prior to commercialization.

The inflammasome NLRP12 is associated with both depression and coronary artery disease in Vietnam veterans

Several studies have established that Major depressive disorder is associated with excess inflammation with an elevation of both pro and anti-inflammatory cytokines in major depressive disorder. In addition, individuals with major depressive disorder are at higher risk of developing coronary artery disease. The role of innate immunity and NFκB-mediated inflammation in depression and its increased association with coronary artery disease is yet to be fully elucidated. Polymorphisms in the Nucleotide-Binding Oligomerization Domain, Leucine Rich Repeat and Pyrin Domain Containing 12 (NLRP12), are associated with depression and coronary artery disease in trauma exposed individuals. In a cohort of Vietnam War veterans (n = 299) NLRP12 polymorphisms were analysed for association with depression and coronary calcium scores. The NLRP12 polymorphism, rs34436714 was associated with a higher DASS21 Score for depression (p = 0.037). NLRP12 polymorphisms rs34971363 and rs6509825 (p = 0.022 and p = 0.020) were associated with raised coronary calcium score. To our knowledge, this is the first time rs34436714 has been investigated in Vietnam veterans identifying AC as a risk genotype for depression in Caucasian cohorts. It is also the first time the rs34971363 (CG) and rs6509825 (CT) genotype have been associated with raised coronary calcium score.

NLRP3 Deficiency Alleviates Severe Acute Pancreatitis and Pancreatitis-Associated Lung Injury in a Mouse Model

The rapid production and release of a large number of inflammatory cytokines can cause excessive local and systemic inflammation in severe acute pancreatitis (SAP) and multiple organ dysfunction syndrome (MODS), especially pancreatitis-associated acute lung injury (P-ALI), which is the main cause of early death in patients with SAP. The NLRP3 inflammasome plays an important role in the maturation of IL-1β and the inflammatory cascade. Here, we established a model of SAP using wild-type (NLRP3^+/+) and NLRP3 knockout (NLRP3^−/−) mice by intraperitoneal injections of caerulein (Cae) and lipopolysaccharide (LPS). Pathological injury to the pancreas and lungs, the inflammatory response, and neutrophil infiltration were significantly mitigated in NLRP3^−/− mice. Furthermore, INF-39, an NLRP3 inflammasome inhibitor, could reduce the severity of SAP and P-ALI in a dose-dependent manner. Our results suggested that SAP and P-ALI were alleviated by NLRP3 deficiency in mice, and thus, reducing NLRP3 expression may mitigate SAP-associated inflammation and P-ALI.

Threshold Rigidity Values for the Asbestos-like Pathogenicity of High-Aspect-Ratio Carbon Nanotubes in a Mouse Pleural Inflammation Model

The qualitative and quantitative evaluation of the physicochemical parameters associated with the pathogenicity of high-aspect-ratio nanomaterials is important for comprehensive regulation efforts and safety-by-design approaches. Here, we report quantitative data on the correlations between the rigidity of these nanomaterials and toxicity endpoints in vitro and in vivo. As measured by new ISO standards published in 2017, rigidity shows a strong positive correlation with inflammogenic potential, as indicated by inflammatory cell counts and IL-1β (a biomarker for frustrated phagocytosis) levels in both the acute and chronic phases. In vitro experiments using differentiated THP-1 cells find that only highly rigid multiwalled carbon nanotubes (MWCNTs) and asbestos fibers lead to piercing and frustrated phagocytosis. Thus, this study suggests a bending ratio of 0.97 and a static bending persistence length of 1.08 as threshold rigidity values for asbestos-like pathogenicity. However, additional research using MWCNTs with rigidity values that lie between those of non-inflammogenic ( D_b = 0.66 and SBPL = 0.87) and inflammogenic fibers ( D_b = 0.97 and SBPL = 1.09) is required to identify more accurate threshold values, which would be useful for comprehensive regulation and safety-by-design approaches based on MWCNTs.

Emerging Role of Immunosuppression in Diseases Induced by Micro- and Nano-Particles: Time to Revisit the Exclusive Inflammatory Scenario

Fibrosis, cancer, and autoimmunity developing upon particle exposure have been exclusively linked with uncontrolled inflammatory processes. The critical role of inflammation is now challenged by several contradictory observations indicating that the emergence of these chronic disorders may result from non-inflammatory events. A growing number of studies reveals that micro- and nano-particles can cause exaggerated and persistent immunosuppression characterized by the release of potent anti-inflammatory cytokines (IL-10 and TGF-β), and the recruitment of major regulatory immune cells (M2 macrophages, T and B regs, and MDSC). This persistent immunosuppressive environment is initially established to limit early inflammation but contributes later to fibrosis, cancer, and infection. Immunosuppression promotes fibroblast proliferation and matrix element synthesis and subverts innate and adaptive immune surveillance against tumor cells and microorganisms. This review details the contribution of immunosuppressive cells and their derived immunoregulatory mediators and delineates the mutual role of inflammatory vs. immunosuppressive mechanisms in the pathogenesis of chronic diseases induced by particles. The consideration of these new results explains how particle-related diseases can develop independently of chronic inflammation, enriches current bioassays predicting particle toxicity and suggests new clinical strategies for treating patients affected by particle-associated diseases.

Role of the NLRP3 inflammasome in cancer

Inflammasomes are large intracellular multi-protein signalling complexes that are formed in the cytosolic compartment as an inflammatory immune response to endogenous danger signals. The formation of the inflammasome enables activation of an inflammatory protease caspase-1, pyroptosis initiation with the subsequent cleaving of the pro-inflammatory cytokines interleukin (IL)-1β and proIL-18 to produce active forms. The inflammasome complex consists of a Nod-like receptor (NLR), the adapter apoptosis-associated speck-like (ASC) protein, and Caspase-1. Dysregulation of NLRP3 inflammasome activation is involved tumor pathogenesis, although its role in cancer development and progression remains controversial due to the inconsistent findings described. In this review, we summarize the current knowledge on the contribution of the NLRP3 inflammasome on potential cancer promotion and therapy.

Curcumin alleviates DSS-induced colitis via inhibiting NLRP3 inflammsome activation and IL-1β production

BACKGROUND

NLRP3 inflammasome mediates IL-1β maturation, therefore plays a vital role in the development of IBD. Curcumin is known for possessing strong anti-inflammatory property.

OBJECTIVE

The present study was to investigate the protective effects of curcumin on dextran sulfate sodium (DSS)-induced colitis through inhibiting NLRP3 inflammasome activation and IL-1β production.

METHODS

LPS-primed macrophages were treated with curcumin prior to DSS triggering NLRP3 inflammasome activation, IL-1β secretion and ASC oligomerization were observed. The mechanisms of curcumin in the inhibition of DSS-induced inflammasome activation were explored. Curcumin or caspase-1/NLRP3 inhibitor was administrated respectively in DSS-induced colitis mouse model. The changes of body weight, disease activity index, colon length were measured. Additionally, mature IL-1β and other inflammatory cytokines, MPO activity and histopathological damage were analyzed for the evaluation of colitis severity.

RESULTS

NLRP3 inflammasome activation was dramatically inhibited by curcumin in DSS-stimulated macrophages, as evidenced by decreased IL-1β secretion, less caspase-1 activation and ASC specks. Mechanistically, curcumin prevented DSS-induced K⁺ efflux, intracellular ROS formation and cathepsin B release, three major cellular events mediating NLRP3 inflammasome activation. In DSS-induced colitis, curcumin administration significantly ameliorated colitis symptoms by reducing weight loss, DAI and colon length shortening. Meanwhile, curcumin significantly decreased the expression of multiple inflammatory cytokines (including mature IL-1β, IL-6, MCP-1), MPO activity, caspase-1 activity as well as histopathological damage. Furthermore, blockage of NLRP3 inflammasome activation in vivo with specific NLRP3 inhibitor abrogated the further inhibitory effect of curcumin on DSS-induced colitis.

CONCLUSION

Curcumin could strongly suppress DSS-induced NLRP3 inflammsome activation and alleviate DSS-induced colitis in mice, thus it may be a promising candidate drug in clinical application for IBD therapy.

4-1BB Signaling Promotes Alveolar Macrophages-Mediated Pro-Fibrotic Responses and Crystalline Silica-Induced Pulmonary Fibrosis in Mice

Silicosis is caused by exposure to crystalline silica (CS). We have previously shown that blocking 4-1BB signaling attenuated CS-induced inflammation and pulmonary fibrosis. However, the cells that express 4-1BB, which plays a vital role in promoting fibrosis, are still unknown. In this study, we demonstrated that the expression of 4-1BB is elevated in alveolar macrophages (AMs) in the lungs of CS-injured mice. CS exposure also markedly enhanced the expression of 4-1BB in macrophage-like, MH-S cells. In these cells, activation of the 4-1BB signaling with an agonist antibody led to upregulated secretion of pro-fibrotic mediators. Consistently, blocking 4-1BB downstream signaling or genetic deletion of 4-1BB alleviated pro-fibrotic responses in vitro, while treatment with a 4-1BB fusion protein promoted pro-fibrotic responses. In vivo experiments showed that blocking 4-1BB signaling decreased the expressions of pro-fibrotic mediators and fibrosis. These data suggest that 4-1BB signaling plays an important role in promoting AMs-mediated pro-fibrotic responses and pulmonary fibrosis. Our findings may provide a potential molecular target to reduce CS-induced fibrotic responses in occupational lung disease.

Biological mechanisms of non-linear dose-response for respirable mineral fibers

Sufficiently high and prolonged inhalation exposures to some respirable elongated mineral particles (REMPs), notably including amphibole asbestos fibers, can increase risk of inflammation-mediated diseases including malignant mesothelioma, pleural diseases, fibrosis, and lung cancer. Chronic inflammation involves ongoing activation of the NLRP3 inflammasome, which enables immune cells to produce potent proinflammatory cytokines IL-1β and IL-18. Reactive oxygen species (ROS) (in particular, mitochondrial ROS) contribute to NRLP3 activation via a well-elucidated mechanism involving oxidation of reduced thioredoxin and association of thioredoxin-interacting protein with NLRP3. Lysosomal destabilization, efflux of cytosolic potassium ions and influx of calcium ions, signals from damaged mitochondria, both translational and post-translational controls, and prion-like polymerization have increasingly clear roles in regulating NLRP3 activation. As the molecular biology of inflammation-mediated responses to REMP exposure becomes clearer, a practical question looms: What do these mechanisms imply for the shape of the dose-response function relating exposure concentrations and durations for EMPs to risk of pathological responses? Dose-response thresholds or threshold-like nonlinearities can arise from (a) Cooperativity in assembly of supramolecular signaling complexes; (b) Positive feedback loops and bistability in regulatory networks; (c) Overwhelming of defensive barriers maintaining homeostasis; and (d) Damage thresholds, as in lysosome destabilization-induced activation of NLRP3. Each of these mechanisms holds for NLRP3 activation in response to stimuli such as REMP exposures. It is therefore timely to consider the implications of these advances in biological understanding for human health risk assessment with dose-response thresholds.

Activation of the Absent in Melanoma 2 Inflammasome in Peripheral Blood Mononuclear Cells From Idiopathic Pulmonary Fibrosis Patients Leads to the Release of Pro-Fibrotic Mediators

Idiopathic pulmonary fibrosis (IPF) is a chronic fibro-proliferative disease characterized by poor prognosis, with a mean survival of ~2–3 years after definite diagnosis. The cause of IPF is still unknown but it is a heterogeneous condition in which the aberrant deposition of extracellular matrix leads to extensive lung remodeling. This remodeling is a consequence of inflammatory responses, but the mechanisms involved are poorly understood. In this study, we first analyzed a bleomycin-induced mouse model, which showed that higher expression of IL-1β, but not IL-18, was correlated to pulmonary cell infiltration and fibrosis. Then, we found that peripheral blood mononuclear cells (PBMCs) from IPF patients released IL-1α and IL-18 in a NLRP3- and calpain-independent manner after LPS ± ATP stimulation. Instead, the activation of the absent in melanoma 2 (AIM2) inflammasome induced the release of IL-1α in a caspase-1-/caspase-8-independent manner; whereas IL-18 release was caspase-1 dependent. These effects correlated with the release of the pro-fibrotic TGF-β, which was induced by AIM2 activation in a caspase-1- and TLR4-independent manner, but dependent on IL-1α. In this context, the activation of AIM2 induced the release of caspase-4 from IPF-derived PBMCs, which correlated with the mRNA levels of this caspase that was higher in IPF than in healthy PBMCs. In conclusion, our findings identify a novel molecular mechanism whereby the activation of AIM2 could lead to the activation of the non-canonical inflammasome (caspase-4 dependent) that induces the release of IL-1α responsible for the release of TGF-β from PBMCs of IPF patients.

Saikosaponin‑d alleviates carbon‑tetrachloride induced acute hepatocellular injury by inhibiting oxidative stress and NLRP3 inflammasome activation in the HL‑7702 cell line

Saikosaponin‑d (SSd) the primary active component of triterpene saponin derived from Bupleurum falcatum L., possesses anti‑inflammatory and antioxidant properties. The present study aimed to examine the potential therapeutic effects of SSd on carbon tetrachloride (CCl4)‑induced acute hepatocellular injury in the HL‑7702 cell line and its underlying mechanisms. HL‑7702 cells were treated with SSd at different doses (0.5, 1 or 2 µmol/l). Cell viability was determined using an MTT assay. Injury was assessed by the levels of serum alanine aminotransferase (ALT) and aspartate transaminase (AST). Oxidative stress was assessed using malondialdehyde (MDA) content and total‑superoxide dismutase (T‑SOD) activity. The expression of nucleotide‑binding domain, leucine‑rich‑containing family, pyrin domain‑containing‑3 (NLRP3), apoptosis‑associated speck‑like protein (ASC), caspase‑1 and high mobility group protein B1 (HMGB1) was assessed by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blot analysis. Interleukin (IL)‑1β and IL‑18 were determined by RT‑qPCR and ELISA. SSd attenuated the inhibition of cell viability and the high AST and ALT levels induced by CCl4 in HL‑7702 cells. Oxidative stress was induced in HL‑7702 cells by CCl4, as demonstrated by the increase of MDA and the decrease of T‑SOD activity. These changes were reversed by SSd. SSd significantly downregulated the mRNA and protein expression of NLRP3, ASC, caspase‑1, IL‑1β, IL‑18 and HMGB1 induced by CCl4. In conclusion SSd alleviated CCl4‑induced acute hepatocellular injury, possibly by inhibiting oxidative stress and NLRP3 inflammasome activation in the HL‑7702 cell line.

Carbon Nanotubes and Other Engineered Nanoparticles Induced Pathophysiology on Mesothelial Cells and Mesothelial Membranes

Nanoparticles have great potential for numerous applications due to their unique physicochemical properties. However, concerns have been raised that they may induce deleterious effects on biological systems. There is accumulating evidence that, like asbestos, inhaled nanomaterials of >5 μm and high aspect ratio (3:1), particularly rod-like carbon nanotubes, may inflict pleural disease including mesothelioma. Additionally, a recent set of case reports suggests that inhalation of polyacrylate/nanosilica could in part be associated with inflammation and fibrosis of the pleura of factory workers. However, the adverse outcomes of nanoparticle exposure to mesothelial tissues are still largely unexplored. In that context, the present review aims to provide an overview of the relevant pathophysiological implications involving toxicological studies describing effects of engineered nanoparticles on mesothelial cells and membranes. In vitro studies primarily emphasize on simulating cellular uptake and toxicity of nanotubes on benign or malignant cell lines. On the other hand, in vivo studies focus on illustrating endpoints of serosal pathology in rodent animal models. From a molecular aspect, some nanoparticle categories are shown to be cytotoxic and genotoxic after acute treatment, whereas chronic incubation may lead to malignant-like transformation. At an organism level, a number of fibrous shaped nanotubes are related with features of chronic inflammation and MWCNT-7 is the only type to consistently inflict mesothelioma.

Short-Term Pulmonary Toxicity Assessment of Pre- and Post-incinerated Organomodified Nanoclay in Mice

Organomodified nanoclays (ONCs) are increasingly used as filler materials to improve nanocomposite strength, wettability, flammability, and durability. However, pulmonary risks associated with exposure along their chemical lifecycle are unknown. This study's objective was to compare pre- and post-incinerated forms of uncoated and organomodified nanoclays for potential pulmonary inflammation, toxicity, and systemic blood response. Mice were exposed via aspiration to low (30 μg) and high (300 μg) doses of preincinerated uncoated montmorillonite nanoclay (CloisNa), ONC (Clois30B), their respective incinerated forms (I-CloisNa and I-Clois30B), and crystalline silica (CS). Lung and blood tissues were collected at days 1, 7, and 28 to compare toxicity and inflammation indices. Well-dispersed CloisNa caused a robust inflammatory response characterized by neutrophils, macrophages, and particle-laden granulomas. Alternatively, Clois30B, I-Clois30B, and CS high-dose exposures elicited a low grade, persistent inflammatory response. High-dose Clois30B exposure exhibited moderate increases in lung damage markers and a delayed macrophage recruitment cytokine signature peaking at day 7 followed by a fibrotic tissue signature at day 28, similar to CloisNa. I-CloisNa exhibited acute, transient inflammation with quick recovery. Conversely, high-dose I-Clois30B caused a weak initial inflammatory signal but showed comparable pro-inflammatory signaling to CS at day 28. The data demonstrate that ONC pulmonary toxicity and inflammatory potential relies on coating presence and incineration status in that coated and incinerated nanoclay exhibited less inflammation and granuloma formation than pristine montmorillonite. High doses of both pre- and post-incinerated ONC, with different surface morphologies, may harbor potential pulmonary health hazards over long-term occupational exposures.

Respiratory hazard of Li-ion battery components: elective toxicity of lithium cobalt oxide (LiCoO2) particles in a mouse bioassay

Rechargeable Li-ion batteries (LIB) are increasingly produced and used worldwide. LIB electrodes are made of micrometric and low solubility particles, consisting of toxicologically relevant elements. The health hazard of these materials is not known. Here, we investigated the respiratory hazard of three leading LIB components (LiFePO₄ or LFP, Li₄Ti₅O₁₂ or LTO, and LiCoO₂ or LCO) and their mechanisms of action. Particles were characterized physico-chemically and elemental bioaccessibility was documented. Lung inflammation and fibrotic responses, as well as particle persistence and ion bioavailability, were assessed in mice after aspiration of LIB particles (0.5 or 2 mg); crystalline silica (2 mg) was used as reference. Acute inflammatory lung responses were recorded with the 3 LIB particles and silica, LCO being the most potent. Inflammation persisted 2 m after LFP, LCO and silica, in association with fibrosis in LCO and silica lungs. LIB particles persisted in the lungs after 2 m. Endogenous iron co-localized with cobalt in LCO lungs, indicating the formation of ferruginous bodies. Fe and Co ions were detected in the broncho-alveolar lavage fluids of LFP and LCO lungs, respectively. Hypoxia-inducible factor (HIF) -1α, a marker of fibrosis and of the biological activity of Co ions, was upregulated in LCO and silica lungs. This study identified, for the first time, the respiratory hazard of LIB particles. LCO was at least as potent as crystalline silica to induce lung inflammation and fibrosis. Iron and cobalt, but not lithium, ions appear to contribute to LFP and LCO toxicity, respectively.

Synthetic Lignan Secoisolariciresinol Diglucoside (LGM2605) Reduces Asbestos-Induced Cytotoxicity in an Nrf2-Dependent and -Independent Manner

Asbestos exposure triggers inflammatory processes associated with oxidative stress and tissue damage linked to malignancy. LGM2605 is the synthetic lignan secoisolariciresinol diglucoside (SDG) with free radical scavenging, antioxidant, and anti-inflammatory properties in diverse inflammatory cell and mouse models, including exposure to asbestos fibers. Nuclear factor-E2 related factor 2 (Nrf2) activation and boosting of endogenous tissue defenses were associated with the protective action of LGM2605 from asbestos-induced cellular damage. To elucidate the role of Nrf2 induction by LGM2605 in protection from asbestos-induced cellular damage, we evaluated LGM2605 in asbestos-exposed macrophages from wild-type (WT) and Nrf2 disrupted (Nrf2⁻/⁻) mice. Cells were pretreated with LGM2605 (50 µM and 100 µM) and exposed to asbestos fibers (20 µg/cm²) and evaluated 8 h and 24 h later for inflammasome activation, secreted cytokine levels (interleukin-1β (IL-1β), interleukin-18 (IL-18), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNFα)), cytotoxicity and cell death, nitrosative stress, and Nrf2-regulated enzyme levels. Asbestos exposure induced robust oxidative and nitrosative stress, cell death and cytotoxicity, which were equally mitigated by LGM2605. Inflammasome activation was significantly attenuated in Nrf2^−/− macrophages compared to WT, and the protective action of LGM2605 was seen only in WT cells. In conclusion, in a cell model of asbestos-induced toxicity, LGM2605 acts via protective mechanisms that may not involve Nrf2 activation.

Volcanic Ash Activates the NLRP3 Inflammasome in Murine and Human Macrophages

Volcanic ash is a heterogeneous mineral dust that is typically composed of a mixture of amorphous (glass) and crystalline (mineral) fragments. It commonly contains an abundance of the crystalline silica (SiO₂) polymorph cristobalite. Inhalation of crystalline silica can induce inflammation by stimulating the NLRP3 inflammasome, a cytosolic receptor complex that plays a critical role in driving inflammatory immune responses. Ingested material results in the assembly of NLRP3, ASC, and caspase-1 with subsequent secretion of the interleukin-1 family cytokine IL-1β. Previous toxicology work suggests that cristobalite-bearing volcanic ash is minimally reactive, calling into question the reactivity of volcanically derived crystalline silica, in general. In this study, we target the NLRP3 inflammasome as a crystalline silica responsive element to clarify volcanic cristobalite reactivity. We expose immortalized bone marrow-derived macrophages of genetically engineered mice and primary human peripheral blood mononuclear cells (PBMCs) to ash from the Soufrière Hills volcano as well as representative, pure-phase samples of its primary componentry (volcanic glass, feldspar, cristobalite) and measure NLRP3 inflammasome activation. We demonstrate that respirable Soufrière Hills volcanic ash induces the activation of caspase-1 with subsequent release of mature IL-1β in a NLRP3 inflammasome-dependent manner. Macrophages deficient in NLRP3 inflammasome components are incapable of secreting IL-1β in response to volcanic ash ingestion. Cellular uptake induces lysosomal destabilization involving cysteine proteases. Furthermore, the response involves activation of mitochondrial stress pathways leading to the generation of reactive oxygen species. Considering ash componentry, cristobalite is the most reactive pure-phase with other components inducing only low-level IL-1β secretion. Inflammasome activation mediated by inhaled ash and its potential relevance in chronic pulmonary disease was further evidenced in PBMC using the NLRP3 small-molecule inhibitor CP-456,773 (CRID3, MCC950). Our data indicate the functional activation of the NLRP3 inflammasome by volcanic ash in murine and human macrophages in vitro. Cristobalite is identified as the apparent driver, thereby contesting previous assertions that chemical and structural imperfections may be sufficient to abrogate the reactivity of volcanically derived cristobalite. This is a novel mechanism for the stimulation of a pro-inflammatory response by volcanic particulate and provides new insight regarding chronic exposure to environmentally occurring particles.

The Antioxidant Procyanidin Reduces Reactive Oxygen Species Signaling in Macrophages and Ameliorates Experimental Colitis in Mice

Management of inflammatory bowel disease (IBD) is a real clinical challenge. Despite intense investigation, the mechanisms of IBD remain substantially unidentified. Some inflammatory conditions, such as matrix metalloproteinases (MMPs) and the nuclear factor-κB (NF-κB) and NOD-like receptor protein 3 (NLRP3) inflammasome signaling pathways, are reported to contribute to the development and maintenance of IBD. Regulation of their common upstream signaling, that is, reactive oxygen species (ROS), may be important to control the progression of IBD. In the present study, we found that procyanidin, a powerful antioxidation flavonoid, has a significant effect on ROS clearance on THP-1 macrophages after lipopolysaccharide (LPS) or LPS-combined adenosine triphosphate stimulation, thus downregulating MMP9 expression, suppressing NF-κB signaling, and interrupting the formation of the NLRP3 inflammasome. Moreover, our in vivo data showed that procyanidin attenuated Dextran sulfate sodium-induced experimental colitis in a dose-dependent fashion by suppressing the expression of MMP9, NF-κB, and NLRP3 inflammasome signaling in colonic tissues in mice. Overall, our results suggested that targeting ROS could be a potential therapeutic choice for colonic inflammation.

The Emerging Role of Inflammasomes as Central Mediators in Inflammatory Bladder Pathology

Irritative voiding symptoms (e.g. increased frequency and urgency) occur in many common pathologic conditions such as urinary tract infections and bladder outlet obstruction, and these conditions are well-established to have underlying inflammation that directly triggers these symptoms. However, it remains unclear as to how such diverse stimuli individually generate a common inflammatory process. Jürg Tschopp provided substantial insight into this conundrum when, working with extracts from THP-1 cells, he reported the existence of the inflammasome. He described it as a structure that senses multiple diverse signals from intracellular/extracellular sources and pathogens and triggers inflammation by the maturation and release of the pro-inflammatory cytokines interleukin-1β and interleukin-18. Recently, many of these sensors were found in the bladder and the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3, has been shown to be a central mediator of inflammation in several urological diseases. In this review, we introduce the nucleotide-binding domain, leucine-rich-containing family, pyrin domaincontaining-3 inflammasome, highlight its emerging role in several common urologic conditions, and speculate on the potential involvement of other inflammasomes in bladder pathology.

Characterization of pulmonary responses in mice to asbestos/asbestiform fibers using gene expression profiles

Humans exposed to asbestos and/or asbestiform fibers are at high risk of developing many lung diseases including asbestosis, lung cancer, and malignant mesothelioma. However, the disease-causing potential and specific metabolic mechanisms and pathways associated with various asbestos/asbestiform fiber exposures triggering different carcinogenic and non-carcinogenic outcomes are still largely unknown. The aim of this this study was to investigate gene expression profiles and inflammatory responses to different asbestos/asbestiform fibers at the acute/sub-acute phase that may be related to delayed pathological outcomes observed at later time points. Mice were exposed to asbestos (crocidolite, tremolite asbestos), asbestiform fibers (erionite), and a low pathogenicity mineral fiber (wollastonite) using oropharyngeal aspiration. Similarities in inflammatory and tissue damage responses, albeit with quantitative differences, were observed at day 1 and 7 post treatment. Exposure to different fibers induced significant changes in regulation and release of a number of inflammatory cytokines/chemokines. Comparative analysis of changes in gene regulation in the lung on day 7 post exposure were interpretable in the context of differential biological responses that were consistent with histopathological findings at days 7 and 56 post treatment. Our results noted differences in the magnitudes of pulmonary responses and gene regulation consistent with pathological alterations induced by exposures to four asbestos/asbestiform fibers examined. Further comparative mechanistic studies linking early responses with the long-term endpoints may be instrumental to understanding triggering mechanisms underlying pulmonary carcinogenesis, that is lung cancer versus mesothelioma.

Mechanistic insight into the impact of nanomaterials on asthma and allergic airway disease

Asthma is a chronic respiratory disease known for its high susceptibility to environmental exposure. Inadvertent inhalation of engineered or incidental nanomaterials is a concern for human health, particularly for those with underlying disease susceptibility. In this review we provide a comprehensive analysis of those studies focussed on safety assessment of different nanomaterials and their unique characteristics on asthma and allergic airway disease. These include in vivo and in vitro approaches as well as human and population studies. The weight of evidence presented supports a modifying role for nanomaterial exposure on established asthma as well as the development of the condition. Due to the variability in modelling approaches, nanomaterial characterisation and endpoints used for assessment in these studies, there is insufficient information for how one may assign relative hazard potential to individual nanoscale properties. New developments including the adoption of standardised models and focussed in vitro and in silico approaches have the potential to more reliably identify properties of concern through comparative analysis across robust and select testing systems. Importantly, key to refinement and choice of the most appropriate testing systems is a more complete understanding of how these materials may influence disease at the cellular and molecular level. Detailed mechanistic insight also brings with it opportunities to build important population and exposure susceptibilities into models. Ultimately, such approaches have the potential to more clearly extrapolate relevant toxicological information, which can be used to improve nanomaterial safety assessment for human disease susceptibility.

In Search of a Converging Cellular Mechanism in Nanotoxicology and Nanomedicine in the Treatment of Cancer

Multiple applications of nanomaterials have raised concern with regard to their toxicity. With increasing research into nanomaterial safety, mechanisms involved in the toxic effects of nanomaterials have begun to emerge. The importance of nanomaterial-induced lysosomal membrane permeabilization through overloading or direct damage of the lysosomal compartment, resulting in the blockade of autophagosome-lysosome fusion and autophagy dysfunction, as well as inflammasome activation were cited as emerging mechanisms of nanomaterial toxicity. It has recently been proposed that these very mechanisms leading to nanomaterial toxicity may be utilized in nanotherapeutics. This review discusses these nanomaterial-induced mechanisms in detail and how it has been exploited in cancer research. This review also addresses certain considerations that need to be kept in mind when using nanomaterials in therapeutics.

Role of the inflammasome in chronic obstructive pulmonary disease (COPD)

Inflammation is central to the development of chronic obstructive pulmonary disease (COPD), a pulmonary disorder characterized by chronic bronchitis, chronic airway obstruction, emphysema, associated to progressive and irreversible decline of lung function. Emerging genetic and pharmacological evidence suggests that IL-1-like cytokines are highly detected in the sputum and broncho-alveolar lavage (BAL) of COPD patients, implying the involvement of the multiprotein complex inflammasome. So far, scientific evidence has focused on nucleotide-binding oligomerization domain-like receptors protein 3 (NLRP3) inflammasome, a specialized inflammatory signaling platform that governs the maturation and secretion of IL-1-like cytokines through the regulation of caspase-1-dependent proteolytic processing. Some studies revealed that it is involved during airway inflammation typical of COPD. Based on the influence of cigarette smoke in various respiratory diseases, including COPD, in this view we report its effects in inflammatory and immune responses in COPD mouse models and in human subjects affected by COPD. In sharp contrast to what reported on experimental and clinical studies, randomized clinical trials show that indirect inflammasome inhibitors did not have any beneficial effect in moderate to severe COPD patients.

Dioscin Exerts Protective Effects Against Crystalline Silica-induced Pulmonary Fibrosis in Mice

Inhalation of crystalline silica particles leads to pulmonary fibrosis, eventually resulting in respiratory failure and death. There are few effective drugs that can delay the progression of this disease; thus, patients with silicosis are usually only offered supportive care. Dioscin, a steroidal saponin, exhibits many biological activities and health benefits including its protective effects against hepatic fibrosis. However, the effect of dioscin on silicosis is unknown.

Methods: We employed experimental mouse mode of silicosis. Different doses of dioscin were gavaged to the animals 1 day after crystalline silica instillation to see the effect of dioscin on crystalline silica induced pulmonary fibrosis. Also, we used RAW264.7 and NIH-3T3 cell lines to explore dioscin effects on macrophages and fibroblasts. Dioscin was also oral treatment but 10 days after crystalline silica instillation to see its effect on established pulmonary fibrosis.

Results: Dioscin treatment reduced pro-inflammation and pro-fibrotic cytokine secretion by modulating innate and adaptive immune responses. It also reduced the recruitment of fibrocytes, protected epithelial cells from crystalline silica injury, inhibited transforming growth factor beta/Smad3 signaling and fibroblast activation. Together, these effects delayed the progression of crystalline silica-induced pulmonary fibrosis. The mechanism by which dioscin treatment alleviated CS-induced inflammation appeared to be via the reduction of macrophage, B lymphocyte, and T lymphocte infiltration into lung. Dioscin inhibits macrophages and fibroblasts from secreting pro-inflammatory cytokines and may also function as a modulator of T helper cells responses, concurrent with attenuated phosphorylation of the apoptosis signal-regulating kinase 1-p38/c-Jun N-terminal kinase pathway. Also, dioscin could block the phosphorylation of Smad3 in fibroblast. Oral treatment of dioscin could also effectively postpone the progression of established silicosis.

Conclusion: Oral treatment dioscin delays crystalline silica-induced pulmonary fibrosis and exerts pulmonary protective effects in mice. Dioscin may be a novel and potent candidate for protection against crystalline silica-induced pulmonary fibrosis.

Length, but Not Reactive Edges, of Cup-stack MWCNT Is Responsible for Toxicity and Acute Lung Inflammation

Multiwalled carbon nanotube (MWCNT) toxicity after inhalation has been associated with size, aspect ratio, rigidity, surface modification, and reactive oxygen species production. In this study, we investigated a series of cup-stacked MWCNT prepared as variants of the Creos 24PS. Mechanical chopping produced a short version (AR10) and graphitization to remove active reaction sites by extreme heat (2,800°C; Creos 24HT) to test the contribution of length and alteration of potential reaction sites to toxicity. The 3 MWCNT variants were tested in vitro in a human macrophage-like cell model and with C57BL/6 alveolar macrophages for dose-dependent toxicity and NLRP3 inflammasome activation. The 24PS and 24HT variants showed significant dose-dependent toxicity and inflammasome activation. In contrast, the AR10 variant showed no toxicity or bioactivity at any concentration tested. The in vivo results reflected those observed in vitro, with the 24PS and 24HT variants resulting in acute inflammation, including elevated polymorphonuclear counts, Interleukin (IL)-18, cathepsin B, and lactate dehydrogenase in isolated lung lavage fluid from mice exposed to 40 µg MWCNT. Taken together, these data indicate that length, but not the absence of proposed reaction sites, on the MWCNT influences particle bioactivity.

The Synthetic Lignan Secoisolariciresinol Diglucoside Prevents Asbestos-Induced NLRP3 Inflammasome Activation in Murine Macrophages

BACKGROUND

The interaction of asbestos with macrophages drives two key processes that are linked to malignancy: (1) the generation of reactive oxygen species (ROS)/reactive nitrogen species (RNS) and (2) the activation of an inflammation cascade that drives acute and chronic inflammation, with the NLRP3 inflammasome playing a key role. Synthetic secoisolariciresinol diglucoside (SDG), LGM2605, is a nontoxic lignan with anti-inflammatory and antioxidant properties and was evaluated for protection from asbestos in murine peritoneal macrophages (MF).

METHODS

MFs were exposed to crocidolite asbestos ± LGM2605 given 4 hours prior to exposure and evaluated at various times for NLRP3 expression, secretion of inflammasome-activated cytokines (IL-1β and IL-18), proinflammatory cytokines (IL-6, TNFα, and HMGB1), NF-κB activation, and levels of total nitrates/nitrites.

RESULTS

Asbestos induces a significant (p < 0.0001) increase in the NLRP3 subunit, release of proinflammatory cytokines, NLRP3-activated cytokines, NF-κB, and levels of nitrates/nitrites. LGM2605 significantly reduced NLRP3 ranging from 40 to 81%, IL-1β by 89-96%, and TNFα by 67-78%, as well as activated NF-κB by 48-49% while decreasing levels of nitrates/nitrites by 85-93%.

CONCLUSIONS

LGM2605 reduced asbestos-induced NLRP3 expression, proinflammatory cytokine release, NF-κB activation, and nitrosative stress in MFs supporting its possible use in preventing the asbestos-induced inflammatory cascade leading to malignancy.

Reactive oxygen species trigger NF-κB-mediated NLRP3 inflammasome activation induced by zinc oxide nanoparticles in A549 cells

Inhaled zinc oxide nanoparticles (ZnO-NPs) induce lung inflammation associated with oxidative stress. The NLRP3 inflammasome plays a pivotal role in the development of lung inflammation. However, the underlying effects of the NLRP3 inflammasome on ZnO-NPs-induced inflammation remain obscure. In the present study, reactive oxygen species (ROS) generation, expression of NLRP3, caspase-1 p10, and cytokines release of interleukin (IL)-1β and IL-18 were determined after A549 cells were exposed to ZnO-NPs. The ROS scavenger N-acetyl-L-cysteine (NAC), nuclear factor kappa B (NF-κB inhibitor BAY11-7082, and NLRP3 inhibitor glibenclamide (GEL) were used to explore the mechanism of NLRP3 inflammasome activation-induced by ZnO-NPs. ZnO-NPs stimulation induced ROS generation and NF-κB p65 phosphorylation. Similarly, the expression of NLRP3 and caspase-1 p10 and the release of IL-1β and IL-18 were significantly increased after ZnO-NPs treatment, which indicated that the NLRP3 inflammasome was activated by ZnO-NPs. Meanwhile, NAC pretreatment inhibited ZnO-NPs-induced activation of NF-κB and NLRP3 inflammasome. The NF-κB inhibitor BAY11-7082 did not affect ROS production but significantly reduced the NLRP3 inflammasome activation induced by ZnO-NPs. Furthermore, the ability of ZnO-NPs to increase the production of IL-1β and IL-18 was significantly inhibited by GEL. The ZnO-NPs induced the activation of the NLRP3 inflammasome in A549 cells, which might be via a ROS-NF-κB-NLRP3 signaling pathway.

IL-10-Producing B Cells Suppress Effector T Cells Activation and Promote Regulatory T Cells in Crystalline Silica-Induced Inflammatory Response In Vitro

Long-term exposure to crystalline silica leads to silicosis, which is characterized by persistent lung inflammation and lung fibrosis. Multiple immune cells have been demonstrated to participate in crystalline silica-induced immune responses. Our previous study indicated that B10 could control lung inflammation through modulating the Th balance in experimental silicosis in mice. However, the regulatory mechanism of B10 on CD4⁺ T cells is still unclear. MACS-sorted CD19⁺ B cells from the three different groups were cultured with CD4⁺ T cells either with or without transwell insert plates to evaluate the effects of B10 on CD4⁺ T cells, including Teff and Treg. B10 was eliminated by anti-CD22 application in vivo. Flow cytometry was used to test the frequencies of CD4⁺ T cells, and the expressions of the related cytokines were detected by real-time PCR and CBA. Insufficient B10 elevated the levels of proinflammatory cytokines and promoted Th responses in a way independent upon cell-cell contact in the Teff and B cell coculture system. B10 could both increase Treg activity and enhance conversion of Teff into Treg. Our findings demonstrated that B10 could affect Th responses by the release of IL-10, enhancing Treg functions and converting Teff into Treg.

Inflammasomes, the cardinal pathology mediators are activated by pathogens, allergens and mutagens: A critical review with focus on NLRP3

Inflammation is a pivotal defense system of body. Unfortunately, when homeostasis falters, the same inflammatory mechanism acts as a double-edged sword, and turns offensive, paving the path for a broad array of pathologies. A multi-protein complex termed as inflammasome perceives the PAMPs (pathogen associated molecular patterns) and DAMPs (danger associated molecular patterns), executing immune responses. This activation predominantly encompasses the elaboration of effector cytokines IL-1β, IL-18, and the cysteine proteases (caspase 1 and 11). Extensive study on an inflammasome NLRP3 has revealed its role in the onset and progression of pathogenic, metabolic, autoimmune, neural, and geriatric diseases. In this regard, this inflammasome's immune activation mechanisms and inhibition strategies have been discussed. Through this rigorous literature analysis, the superficial diversity between pathogens/allergens and mutagens, and NLRP3 activity towards them has been emphasized. Though there is a scope for inhibition of aberrant inflammasomes, including that of NLRP3, given their complexity and unpredictability, prevention of their activation by lifestyle correction has been suggested.

Targeting the epigenome in malignant pleural mesothelioma

Malignant pleural mesotheliomas (MPM) are notoriously refractory to conventional treatment modalities. Recent insights regarding epigenetic alterations in MPM provide the preclinical rationale for the evaluation of novel combinatorial regimens targeting the epigenome in these neoplasms.

Immunomodulatory effects in workers exposed to naturally occurring asbestos fibers

Natural asbestiform fibers are defined 'naturally occurring asbestos' (NOA) and refer to the mineral as a natural component of soils or rocks. The release of NOA fibers into the air from rocks or soils by routine human activities or natural weathering processes represents a risk for human beings. Fluoro-edenite (FE) is a NOA fiber detected in the benmoreitic lava in the area of Biancavilla, South-west slope of Mt. Etna. The aim of the present study was to investigate FE immunotoxicity pathways in a group of 38 occupationally exposed construction workers, in order to find any biological markers of its effect. Subjects underwent respiratory function tests and HRCT total chest scanning. Serum IL-1β, IL-6, IL-8 and TNF-α were measured. The presence of PPs was significantly greater in subjects exposed than in the control (25 vs. 2). In subjects exposed to FE, IL-1β and TNF-α values were significantly higher than the controls. The previously observed increase of IL-1β and IL-18 showed a probable involvement of the proteic complex defined inflammosome by FE fibers.