Autoimmune diseases, autoantibody status and silicosis in a cohort of 1238 workers from the artificial stone benchtop industry.

OBJECTIVES: Autoimmune disorders are multifactorial but occupational exposures have long been implicated, including respirable crystalline silica (RCS). A modern epidemic of silicosis is emerging internationally, associated with dry processing of engineered stone with high (>90%) RCS content. We aimed to investigate the prevalence of clinical autoimmune disease and common autoantibodies in exposed workers. METHODS: Stone benchtop industry workers in Victoria, Australia were offered free screening for silicosis and related disorders. Symptoms or diagnoses of autoimmune disease were evaluated by questionnaire and blood tests taken for rheumatoid factor (RF), antinuclear antibodies (ANAs) and extractable nuclear antigens (ENAs). RESULTS: Among 1238 workers (93.3% male) screened from 2019 to 2021, 0.9% were confirmed with autoimmune disease. Among those without clinical disease, 24.6% had detectable ANAs (93.5% male), 4.6% detectable ENAs and 2.6% were positive for RF. Silicosis was diagnosed in 253 workers (24.3% of those with diagnostic information available). Of those with ANA readings, 54 (6.6%) had ANA titre >1:320. The likelihood of positive autoantibodies increased with age; smoking; higher exposure to RCS and silicosis diagnosis. CONCLUSION: The proportion of workers with detectable ANAs or ENAs was considerably higher than the 5%-9% expected in the general population. Some of the antibodies detected (eg, Scl-70, CENPB) have high sensitivity and specificity for systemic sclerosis. Long-term follow-up will be needed to estimate incidence. Rheumatologists should explore occupational history in new cases of autoimmune disease. Screening for autoimmune disease is indicated in workers exposed to RCS as these individuals need specialised management and may be entitled to compensation.

Differential regulation of lung homeostasis and silicosis by the TAM receptors MerTk and Axl.

Introduction: TAM receptor-mediated efferocytosis plays an important function in immune regulation and may contribute to antigen tolerance in the lungs, a site with continuous cellular turnover and generation of apoptotic cells. Some studies have identified failures in efferocytosis as a common driver of inflammation and tissue destruction in lung diseases. Our study is the first to characterize the in vivo function of the TAM receptors, Axl and MerTk, in the innate immune cell compartment, cytokine and chemokine production, as well as the alveolar macrophage (AM) phenotype in different settings in the airways and lung parenchyma. Methods: We employed MerTk and Axl defective mice to induce acute silicosis by a single exposure to crystalline silica particles (20 mg/50 µL). Although both mRNA levels of Axl and MerTk receptors were constitutively expressed by lung cells and isolated AMs, we found that MerTk was critical for maintaining lung homeostasis, whereas Axl played a role in the regulation of silica-induced inflammation. Our findings imply that MerTk and Axl differently modulated inflammatory tone via AM and neutrophil recruitment, phenotype and function by flow cytometry, and TGF-ß and CXCL1 protein levels, respectively. Finally, Axl expression was upregulated in both MerTk-/- and WT AMs, confirming its importance during inflammation. Conclusion: This study provides strong evidence that MerTk and Axl are specialized to orchestrate apoptotic cell clearance across different circumstances and may have important implications for the understanding of pulmonary inflammatory disorders as well as for the development of new approaches to therapy.

Cuproptosis-associated hub gene identification and immune cell infiltration patterns in silicosis.

Recent research has hinted at a potential connection between silicosis, a fibrotic lung disease caused by exposure to crystalline silica particles, and cuproptosis. The aim of the study was to explore how cuproptosis-related genes (CRGs) may influence the development of silicosis and elucidate the underlying mechanisms. An analysis of genes associated with both silicosis and cuproptosis was conducted. Key gene identification was achieved through the application of two machine learning techniques. Additionally, the correlation between these key genes and immune cell populations was explored and the critical pathways were discerned. To corroborate our findings, the expression of key genes was verified in both a publicly available silica-induced mouse model and our own silicosis mouse model. A total of 12 differentially expressed CRGs associated with silicosis were identified. Further analysis resulted in the identification of 6 CRGs, namely LOX, SPARC, MOXD1, ALB, MT-CO2, and AOC2. Elevated immune cell infiltration of CD8 T cells, regulatory T cells, M0 macrophages, and neutrophils in silicosis patients compared to healthy controls was indicated. Validation in a silica-induced pulmonary fibrosis mouse model supported SPARC and MT-CO2 as potential signature genes for the prediction of silicosis. These findings highlight a strong association between silicosis and cuproptosis. Among CRGs, LOX, SPARC, MOXD1, ALB, MT-CO2, and AOC2 emerged as pivotal players in the context of silicosis by modulating CD8 T cells, regulatory T cells, M0 macrophages, and neutrophils.

Onset of pulmonary Epstein-Barr virus-positive diffuse large B-cell lymphoma in a patient with silicosis.

How Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) occasionally occurs following chronic inflammation remains to be elucidated. The case of a 57-year-old man who developed pulmonary EBV-positive DLBCL from underlying silicosis lesions is presented. Immunohistochemical examination of the resected silicosis lesions showed predominant helper T cells and M1/M2 macrophages, with a lack of B cells, regulatory T cells, and resident memory T cells. Two years later, EBV-positive DLBCL emerged unexpectedly from the silicosis. The imbalance of the immune cells in the microenvironment, at least in part, may help explain how chronic inflammation contributes to EBV-positive DLBCL.

Metabolic Adaptation of Macrophages as Mechanism of Defense against Crystalline Silica.

Silicosis is a lethal pneumoconiosis for which no therapy is available. Silicosis is a global threat, and more than 2.2 million people per year are exposed to silica in the United States. The initial response to silica is mediated by innate immunity. Phagocytosis of silica particles by macrophages is followed by recruitment of mitochondria to phagosomes, generation of mitochondrial reactive oxygen species, and cytokine (IL-1ß, TNF-α, IFN-ß) release. In contrast with LPS, the metabolic remodeling of silica-exposed macrophages is unclear. This study contrasts mitochondrial and metabolic alterations induced by LPS and silica on macrophages and correlates them with macrophage viability and cytokine production, which are central to the pathogenesis of silicosis. Using high-resolution respirometer and liquid chromatography-high-resolution mass spectrometry, we determined the effects of silica and LPS on mitochondrial respiration and determined changes in central carbon metabolism of murine macrophage cell lines RAW 264.7 and IC-21. We show that silica induces metabolic reprogramming of macrophages. Silica, as well as LPS, enhances glucose uptake and increases aerobic glycolysis in macrophages. In contrast with LPS, silica affects mitochondria respiration, reducing complex I and enhancing complex II activity, to sustain cell viability. These mitochondrial alterations are associated in silica, but not in LPS-exposed macrophages, with reductions of tricarboxylic acid cycle intermediates, including succinate, itaconate, glutamate, and glutamine. Furthermore, in contrast with LPS, these silica-induced metabolic adaptations do not correlate with IL-1ß or TNF-α production, but with the suppressed release of IFN-ß. Our data highlight the importance of complex II activity and tricarboxylic acid cycle remodeling to macrophage survival and cytokine-mediated inflammation in silicosis.

Silicon, an important exposure marker in vivo in silicosis research.

PURPOSE: The degree of silicosis exposure is closely related to the progress of silicosis. At present, we use animal and human studies to explore whether silicon can be an important exposure marker in the development of silicosis. METHODS: Rats were randomly divided into 2 groups: (1) controls; and (2) silicosis. Rats in the silicosis group were killed at 4, 8, 12, 16, 24 h, 3, 7, 14, 21, and 28 days. Hematoxylin-eosin (HE) and immunohistochemistry (IHC) were performed to observe the histomorphology of lung tissue. The expression levels of CC16 and SP-D were detected using ELISA kits. In addition, we conducted a population study. Workers who have been selected to work in an iron mine for more than 1 year as research objects. The population was divided into four groups: silicosis exposure group (workers exposed to silica dust for more than 1 year in an iron mine were selected); patients group (silicosis patients); observation group (evidence of disease not meeting formal diagnostic criteria) and control group. Both the levels of trace silicon in the urine and blood of rats and human subjects were measured with ICP-MS. RESULTS: Serum levels of silicon were immediately increased in rats exposed to silicon dust. Similarly, our population study revealed that the silicon level in the silica exposure group and the observing group (exposed but no obvious symptoms) were significantly increased over that of the control group (P < 0.05). In subjects with extended exposure to silica, the serum and urine silicon level in exposed workers appeared to rapidly increase, reaching its peak in 1-5 years, followed by a gradual decline thereafter. Workers exposed to dust for less than 10 years were divided into subgroups by 2-year limit. The levels of serum silicon, urine silicon, TGF-ß1, and TNF-α were significantly higher than that of control group. CONCLUSION: Changes of the serum levels of silicon occurred earlier than the expression of cytokines such as TNF-α, TGF-ß1, CC16, and SP-D. The level of silicon in workers rapidly increased after exposure to silica, and the change occurred before the expression of TGF-ß1 and TNF-α. As a whole, the findings suggest that determining the level of silicon in vivo might be an effective exposure marker in the diagnosis and pathogenesis of silicosis.

[The Function of CD40/CD40L Pathway in Silicosis Fibrosis].

Objective: To investigate the role of CD40/CD40L Pathway in the formation of silicosis fibrosis. Methods: Totally 64 inpatients were recruited and assigned to the silicosis group and the control group, 23 in each group. The alveolar lavage fluid was collected from all patients and isolated. The expression of CD40L protein was detected by Flow Cytometry. The level of IL-8、The IL-6、INF-γ and MCP-1 was detected by ELISA. Two groups of BALF were co-cultured with HFL-1 cells, the expression of Collagen I and α-SMA was detected by Immunohistochemistry. Results: Compared with the control group, CD40L was highly expressed on T lymphocyte cells in silicosis group (P<0.05) , and the contents of IL-8、The IL-6、INF-γand MCP-1 in Silicosis group were significantly higher than those in control group (P<0.05) . After co-culture of BALF and HFL-1 cells, the expression levels of Collagen I and α-SMA in Silicosis group were significantly higher than those in control group (P<0.05) . Conclusion: CD40-CD40L cross-linking system can promote the activation of T cells, release inflammatory factors, promote the synthesis of collagen I and α-SMA by fibroblasts, make the lung fibrous tissue proliferate, and lead to the formation of silicosis fibrosis.

Single Intratracheal Quartz Instillation Induced Chronic Inflammation and Tumourigenesis in Rat Lungs.

Crystalline silica (quartz) is known to induce silicosis and cancer in the lungs. In the present study, we investigated the relationship between quartz-induced chronic inflammation and lung carcinogenesis in rat lungs after a single exposure to quartz. F344 rats were treated with a single intratracheal instillation (i.t.) of quartz (4 mg/rat), and control rats were treated with a single i.t. of saline. After 52 or 96 weeks, the animals were sacrificed, and the lungs and other organs were used for analyses. Quartz particles were observed in the lungs of all quartz-treated rats. According to our scoring system, the lungs of rats treated with quartz had higher scores for infiltration of lymphocytes, macrophages and neutrophils, oedema, fibrosis, and granuloma than the lungs of control rats. After 96 weeks, the quartz-treated rats had higher incidences of adenoma (85.7%) and adenocarcinoma (81.0%) than control rats (20% and 20%, respectively). Quartz-treated and control rats did not show lung neoplastic lesions at 52 weeks after treatment. The number of lung neoplastic lesions per rat positively correlated with the degree of macrophage and lymphocyte infiltration, oedema, fibrosis, and lymph follicle formation around the bronchioles. In conclusion, single i.t. of quartz may induce lung cancer in rat along with chronic inflammation.

Silica particles disorganize the polarization of pulmonary macrophages in mice.

Silicosis is a fatal fibrotic lung disease caused by long-term silica particle exposure, in which pulmonary macrophages play an important role. However, the relationship between macrophage polarization and silicosis remains unclear. We established an experimental silicosis mouse model to investigate macrophage polarization during silicosis development. C57BL/c mice were exposed to silica by intra-tracheal instillation and sacrificed at different time points. Lung tissues and bronchoalveolar lavage fluid were collected for flow cytometry, quantitative reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assays, western blotting, and histology examinations. The polarization of pulmonary macrophages was dysregulated during silicosis development. In the early stage of silicosis, M1 macrophages were induced and played a leading role in eliciting inflammatory; in the late stage, M2 macrophages were induced to promote tissue repair. Levels of several cytokines in lung tissue microenvironment changed with macrophage polarization. Inflammatory cytokines such as tumor necrosis factor-α and interleukin (IL)-1ß and IL-6 were upregulated in the inflammation stage, while the anti-inflammatory cytokine IL-10 was upregulated in the fibrosis stage. Furthermore, we found that STAT (signal transducer and activator of transcription) and IRF (interferon regulatory factor) signaling pathway were involved in the regulation of macrophage polarization in silicosis. In summary, macrophage polarization is closely related to the occurrence and development of silicosis and may be a key point for further elucidating silicosis pathogenesis.

The role of annexin A1 in the modulation of the NLRP3 inflammasome.

Annexins are well-known Ca2+ phospholipid-binding proteins, which have a wide variety of cellular functions. The role of annexin A1 (AnxA1) in the innate immune system has focused mainly on the anti-inflammatory and proresolving properties through its binding to the formyl-peptide receptor 2 (FPR2)/ALX receptor. However, studies suggesting an intracellular role of AnxA1 are emerging. In this study, we aimed to understand the role of AnxA1 for interleukin (IL)-1ß release in response to activators of the nucleotide-binding domain leucine-rich repeat (NLR) and pyrin domain containing receptor 3 (NLRP3) inflammasome. Using AnxA1 knockout mice, we observed that AnxA1 is required for IL-1ß release in vivo and in vitro. These effects were due to reduction of transcriptional levels of IL-1ß, NLRP3 and caspase-1, a step called NLRP3 priming. Moreover, we demonstrate that AnxA1 co-localize and directly bind to NLRP3, suggesting the role of AnxA1 in inflammasome activation is independent of its anti-inflammatory role via FPR2. Therefore, AnxA1 regulates NLRP3 inflammasome priming and activation in a FPR2-independent manner.

MiR-326 Inhibits Inflammation and Promotes Autophagy in Silica-Induced Pulmonary Fibrosis through Targeting TNFSF14 and PTBP1.

Silicosis is a kind of irreversible pulmonary fibrosis induced by the long-term inhalation of silica particles. The therapeutic strategy based on the microRNAs might be an effective way for the treatment of silicosis. Our previous miRNA microarray data indicated that miR-326 was decreased in the mouse lung tissues of silica-induced pulmonary fibrosis. However, the specific functions of miR-326 on silica-induced pulmonary fibrosis remain unclear. The objective was to determine the expression and the biological effects of miR-326 in silica-induced pulmonary fibrosis. Methods included mouse models of silica-induced pulmonary fibrosis and miR-326 intervention that were established separately to explore the effect of miR-326 in vivo. The cell models of SiO2-treated lung epithelial cells (HBE and A549) and TGF-ß1-stimulated lung fibroblast cells (MRC-5 and NIH/3T3) were used to investigate the mechanism of miR-326 in vitro. Hematoxylin and eosin staining was used to evaluate the severity and distribution of fibrosis of mouse lung tissues. Western blot and immunofluorescence assays were performed to measure the downstream molecules of miR-326. Transmission electron microscopy pictures showed the autophagy activity. The results showed miR-326 is down-regulated in the fibrotic lung tissues of silica-treated mice, while increased expression of miR-326 attenuates silica-induced pulmonary fibrosis in vivo. Tumor necrosis factor superfamily-14 (TNFSF14) and polypyrimidine tract-binding protein 1 (PTBP1) are identified as the targets of miR-326. MiR-326 dampens pulmonary inflammation through targeting TNFSF14 and promotes autophagy activity of fibroblasts through targeting PTBP1. LncRNA HOTAIR facilitates inflammation via sponging miR-326. In conclusion, we demonstrate that miR-326 inhibits inflammation and promotes autophagy activity by targeting TNFSF14 and PTBP1 separately to alleviate silica-induced pulmonary fibrosis. Our results might shed new light on the therapeutic strategies for silica-induced pulmonary fibrosis.

Environmental factors and human health: fibrous and particulate substance-induced immunological disorders and construction of a health-promoting living environment.

Among the various scientific fields covered in the area of hygiene such as environmental medicine, epidemiology, public health and preventive medicine, we are investigating the immunological effects of fibrous and particulate substances in the environment and work surroundings, such as asbestos fibers and silica particles. In addition to these studies, we have attempted to construct health-promoting living conditions. Thus, in this review we will summarize our investigations regarding the (1) immunological effects of asbestos fibers, (2) immunological effects of silica particles, and (3) construction of a health-promoting living environment. This review article summarizes the 2014 Japanese Society for Hygiene (JSH) Award Lecture of the 85th Annual Meeting of the JSH entitled "Environmental health effects: immunological effects of fibrous and particulate matter and establishment of health-promoting environments" presented by the first author of this manuscript, Prof. Otsuki, Department of Hygiene, Kawasaki Medical School, Kurashiki, Japan, the recipient of the 2014 JSH award. The results of our experiments can be summarized as follows: (1) asbestos fibers reduce anti-tumor immunity, (2) silica particles chronically activate responder and regulatory T cells causing an unbalance of these two populations of T helper cells, which may contribute to the development of autoimmune disorders frequently complicating silicosis, and (3) living conditions to enhance natural killer cell activity were developed, which may promote the prevention of cancers and diminish symptoms of virus infections.

Annexin A5 promotes macrophage activation and contributes to pulmonary fibrosis induced by silica particles.

OBJECTIVE: To investigate the contributions and underlying molecular mechanisms of annexin A5 toward silica-induced pulmonary fibrosis. METHODS: Male C57BL/6 mice were randomly divided into three groups and instilled intratracheally with silica, saline, or air. Mice were euthanized at 3, 7, 14, or 28 days following treatment. Annexin A5 levels in serum and lung tissues were detected by enzyme-linked immunosorbant assay (ELISA) assays or Western blots. The association of annexin A5 levels with silica-induced lung fibrosis was further investigated in the macrophage cell line, RAW264.7. Following exposure of these cells to silica at a concentration of 200 µg/ml for 6 or 12 h, the expression levels of transforming growth factor ß1 (TGF-ß1), interleukin 1α (IL-1α), Fas ligand (FasL), and their downstream targets were evaluated by Western blots. Furthermore, annexin A5 and FasL were knocked down by small interfering ribonucleic acid (siRNA) and TGF-ß1 secretion into the cell culture medium was measured by ELISA assays or Western blots. RESULTS: Mice treated with silica demonstrated lung fibrosis at 28 days following exposure, whereas, in controls, only mild and transient inflammation was evident at day 3 and day 7 postinstillation and was not present at day 14. Furthermore, silica-exposed mice exhibited significantly (p < 0.05) elevated levels of annexin A5 in serum and lung tissues, relative to control groups. Consistent with these findings, silica exposure of RAW264.7 cells for 6 or 12 h, led to an annexin A5-dependent increase in the expression levels of TGF-ß1, IL-1α, FasL, and their downstream target molecules. These silica-induced changes were reversed by siRNA-mediated knockdown of annexin A5, but downregulation of FasL led to increased annexin A5 expression and reduced levels of TGF-ß1, IL-1α, and FasL downstream target molecules. CONCLUSIONS: These findings define a role of annexin A5 in promoting macrophage activation via Fas/FasL pathways in silica-induced lung fibrosis.

Treatment of silicosis with hepatocyte growth factor-modified autologous bone marrow stromal cells: a non-randomized study with follow-up.

Pulmonary silicosis is an irreversible and untreatable disease that is characterized by interstitial lesions and perpetual fibrosis in the lungs. This study was performed to determine whether mesenchymal stem cells (MSCs) and hepatocyte growth factor (HGF) could exhibit therapeutic effects on human silicosis. This non-randomized uncontrolled trial comprised four patients with pulmonary silicosis who had developed lung fibrosis and received autologous bone marrow MSCs previously transfected by a vector containing human HGF cDNA (MSCs/HGF). MSCs/HGF were intravenously administered weekly for three consecutive weeks at a dose of 2 x 10(6) cells/kg. Pulmonary function, high kilo-voltage chest X-ray radiography, computed tomography (CT) scan, and peripheral blood lymphocyte subset and serum IgG concentrations were evaluated after cell therapy. The treatment was found to be generally safe. Symptoms such as cough and chest distress gradually ameliorated at six months post-therapy, accompanied by the significant improvement of pulmonary function. The ratios of the peripheral CD4- and CD8- positive cell concentrations were increased (P < 0.05). Furthermore, the serum IgG levels in these patients were decreased and reached the normal range (P < 0.05). CT scans showed partial absorption of the nodular and reticulonodular lesions in the lungs during follow-up of at least 12 months. The effectiveness of this novel regimen observed in these patients suggests that a placebo-controlled clinical trial needs to be developed. This study carries trial registration No. NCT01977131 (ClinicalTrials.gov).

Silica-induced inflammasome activation in macrophages: role of ATP and P2X7 receptor.

Silicosis is a fibrotic lung disease caused by the inhalation of silica particles, and is considered an occupational disease, given that these particles are present in the working environment of many mining and civil construction industries. NLRP3 inflammasome activation is an important mechanism during the inflammatory process of silicosis, and it promotes the production of cytokines, such as IL-1ß and IL-18. ATP also plays an important role in silicosis. Specifically, extracellular ATP can activate P2X7 receptor, which then participates in the complete assembly of the NLRP3 inflammasome and its activation. Herein, we analyze the literature to provide a better understanding of the mechanisms underlying inflammasome activation and the role of P2X7 receptors in macrophages during silicosis.

Silica-induced NLRP3 inflammasome activation in vitro and in rat lungs.

RATIONALE: Mineral particles in the lung cause inflammation and silicosis. In myeloid and bronchial epithelial cells the inflammasome plays a role in responses to crystalline silica. Thioredoxin (TRX) and its inhibitory protein TRX-interacting protein link oxidative stress with inflammasome activation. We investigated inflammasome activation by crystalline silica polymorphs and modulation by TRX in vitro, as well as its localization and the importance of silica surface reactivity in rats. METHODS: We exposed bronchial epithelial cells and differentiated macrophages to silica polymorphs quartz and cristobalite and measured caspase-1 activity as well as the release of IL-1ß, bFGF and HMGB1; including after TRX overexpression or treatment with recombinant TRX. Rats were intratracheally instilled with vehicle control, Dörentruper quartz (DQ12) or DQ12 coated with polyvinylpyridine N-oxide. At days 3, 7, 28, 90, 180 and 360 five animals per treatment group were sacrificed. Hallmarks of silicosis were assessed with Haematoxylin-eosin and Sirius Red stainings. Caspase-1 activity in the bronchoalveolar lavage and caspase-1 and IL-1ß localization in lung tissue were determined using Western blot and immunohistochemistry (IHC). RESULTS: Silica polymorphs triggered secretion of IL-1ß, bFGF and HMGB1 in a surface reactivity dependent manner. Inflammasome readouts linked with caspase-1 enzymatic activity were attenuated by TRX overexpression or treatment. At day 3 and 7 increased caspase-1 activity was detected in BALF of the DQ12 group and increased levels of caspase-1 and IL-1ß were observed with IHC in the DQ12 group compared to controls. DQ12 exposure revealed silicotic nodules at 180 and 360 days. Particle surface modification markedly attenuated the grade of inflammation and lymphocyte influx and attenuated the level of inflammasome activation, indicating that the development of silicosis and inflammasome activation is determined by crystalline silica surface reactivity. CONCLUSION: Our novel data indicate the pivotal role of surface reactivity of crystalline silica to activate the inflammasome in cultures of both epithelial cells and macrophages. Inhibitory capacity of the antioxidant TRX to inflammasome activation was evidenced. DQ12 quartz exposure induced acute and chronic functional activation of the inflammasome in the heterogeneous cell populations of the lung in associated with its crystalline surface reactivity.

Silica exposure and altered regulation of autoimmunity.

Silica particles and asbestos fibers, which are known as typical causatives of pneumoconiosis, induce lung fibrosis. Moreover, silicosis patients often complicate with autoimmune diseases, and asbestos-exposed patients suffer from malignant diseases such as pleural mesothelioma and lung cancer. We have been conducting experimental studies to investigate altered regulation of self-tolerance caused by silica exposure, including analyses using specimens such as plasma and immunocompetent cells obtained from silicosis patients, as a means of examining the supposition that silica exposure induces molecular and cellular biological alterations of immune cells. These approaches have resulted in the detection of several specific autoantibodies, alterations of CD95/Fas and its related molecules, and evidence of chronic activation of responder T cells and regulatory T cells following silica exposure. In this review, we present details of our investigations as an introduction to scientific approaches examining the immunological effects of environmental and occupational substances.

Uncoupling between inflammatory and fibrotic responses to silica: evidence from MyD88 knockout mice.

The exact implication of innate immunity in granuloma formation and irreversible lung fibrosis remains to be determined. In this study, we examined the lung inflammatory and fibrotic responses to silica in MyD88-knockout (KO) mice. In comparison to wild-type (WT) mice, we found that MyD88-KO animals developed attenuated lung inflammation, neutrophil accumulation and IL-1ß release in response to silica. Granuloma formation was also less pronounced in MyD88-KO mice after silica. This limited inflammatory response was not accompanied by a concomitant attenuation of lung collagen accumulation after silica. Histological analyses revealed that while pulmonary fibrosis was localized in granulomas in WT animals, it was diffusely distributed throughout the parenchyma in MyD88-KO mice. Robust collagen accumulation was also observed in mice KO for several other components of innate immunity (IL-1R, IL-1, ASC, NALP3, IL-18R, IL-33R, TRIF, and TLR2-3-4,). We additionally show that pulmonary fibrosis in MyD88-KO mice was associated with the accumulation of pro-fibrotic regulatory T lymphocytes (T regs) and pro-fibrotic cytokine expression (TGF-ß, IL-10 and PDGF-B), not with T helper (Th) 17 cell influx. Our findings indicate that the activation of MyD88-related innate immunity is central in the establishment of particle-induced lung inflammatory and granuloma responses. The development of lung fibrosis appears uncoupled from inflammation and may be orchestrated by a T reg-associated pathway.

Silicosis and its progress influenced by genetic variation on TNF-alpha locus- 308, TNF-alpha and IL-10 cytokine on cement factory workers in Indonesia.

This study aimed to assess the association of Tumor Necrosis Factor (TNF-alpha) Locus-308 variant, TNF-alpha and Interleukin (IL-10) Cytokine with the risk of silicosis and its progress in Indonesian cement factory workers, There is an urgent need to explore the determining factors other than exposure since silicosis is chronic progressive and life threatening but remains found, though much industrial hygiene effort has been made. This study population was 6,069 workers registered during 31 December 1990 to 31 December 2003. First, prospective study with Nested Case Control design was conducted on 336 workers in 2003, ten years later the progression of silicosis was assessed in 2013. The result showed proportion of the genetic variation on TNF-alpha on Locus -308 in Indonesia was significantly (p = 0.02) higher on silicosis (13.45%) than nonsilicosis (5.45%) but lower than silicosis in Africa and US miners, since susceptibility loci might vary in different ethnic groups. The sign and symptoms remained as simple silicosis after ten years; The TNF-alpha:IL-10 ratio > 1 was a risk factor in silicosis; the ratio of TNF-alpha:IL-10 > 1 caused a rapid decline of lung function compare to ratio < 1, the decline was chronic progressive during ten years yet not causing significant dyspnea among the cases. Further studies with enlarged sample size are needed. The study concluded, the genetic variation on TNF-alpha gene locus -308 was a risk factor of silicosis in Indonesia cement factory. Its role is indirect, but through mechanism of controlling the blood Cytokine level ratio of TNF-alpha toward IL-10.

Neutralization of interleukin-17A delays progression of silica-induced lung inflammation and fibrosis in C57BL/6 mice.

Silica exposure can cause lung inflammation and fibrosis, known as silicosis. Interleukin-17A (IL-17A) and Th17 cells play a pivotal role in controlling inflammatory diseases. However, the roles of IL-17A and Th17 cells in the progress of silica-induced inflammation and fibrosis are poorly understood. This study explored the effects of IL-17A on silica-induced inflammation and fibrosis. We used an anti-mouse IL-17A antibody to establish an IL-17A-neutralized mice model, and mice were exposed to silica to establish an experimental silicosis model. We showed that IL-17A neutralization delayed neutrophil accumulation and progression of silica-induced lung inflammation and fibrosis. IL-17A neutralization reduced the percentage of Th17 in CD4+ T cells, decreased IL-6 and IL-1ß expression, and increased Tregs at an early phase of silica-induced inflammation. Neutralization of IL-17A delayed silica-induced Th1/Th2 immune and autoimmune responses. These results suggest that IL-17A neutralization alleviates early stage silica-induced lung inflammation and delays progression of silica-induced lung inflammation and fibrosis. Neutralization of IL-17A suppressed Th17 cell development by decreasing IL-6 and/or IL-1ß and increased Tregs at an early phase of silica-induced inflammation. Neutralization of IL-17A also delayed the Th1/Th2 immune response during silica-induced lung inflammation and fibrosis. IL-17A may play a pivotal role in the early phase of silica-induced inflammation and may mediate the Th immune response to influence silica-induced lung inflammation and fibrosis in mice.