Inhibition of the ITGB1 gene attenuates crystalline silica-induced pulmonary fibrosis via epithelial-mesenchymal transformation.

Silicosis is a systemic disease caused by long-term exposure to high concentrations of free silica dust particles in the workplace. It is characterized by a persistent inflammatory response, fibroblast proliferation, and excessive collagen deposition, leading to pulmonary interstitial fibrosis. Epithelial interstitial transformation (EMT) can cause epithelial cells to lose their tight junctions, cell polarity, and epithelial properties, thereby enhancing the properties of interstitial cells, which can lead to the progression of fibrosis and the formation of scar tissue. Integrin 1 (ITGB1) is considered an important factor for promoting EMT and tumor invasion in a variety of tumors and also plays an important role in the progression of fibrotic diseases. Therefore, ITGB1 can be used as a potential target for the treatment of silicosis. In this study, we found that silica exposure induced epithelial-mesenchymal transformation in rats and that the expression of integrin ITGB1 was elevated along with the EMT. We used CRISPR/Cas9 technology to construct integrin ITGB1 knockdown cell lines for in vitro experiments. We compared the expression of the EMT key proteins E-cadherin and vimentin in the ITGB1 knockdown cells and wild-type cells simultaneously stimulated by silica and detected the aggregation point distribution of E-cadherin and vimentin in the cells using laser confocal microscopy. Our results showed that ITGB1 knockout inhibited the ITGB1/ILK/Snail signaling pathway and attenuated the EMT occurrence compared to control cells. These results suggested that ITGB1 is associated with silica-induced EMT and may be a potential target for the treatment of silicosis.

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.

[A rare case: Erasmus syndrome and tuberculosis]. / Un caso poco frecuente: síndrome de Erasmus y tuberculosis.

We present the case of a 35-year-old male patient, sandblaster for eight years, recently diagnosed with pulmonary tuberculosis and systemic sclerosis, who was admitted with dyspnea and poor general condition. Chest X-ray showed a grade I pneumothorax, and on the chest tomography he presented confluent hyperdense masses associated with a pattern of non- specific interstitial pneumonia (NSIP), findings compatible with complicated silicosis. Due to the advanced clinical stage, neither invasive diagnostic test nor pulmonary function test could be performed. Initial treatment included placement of a pleural drainage tube, antituberculosis treatment and chronic home oxygen. The patient was referred to the interstitial disease and rheumatology departments for multidisciplinary management, although the infectious condition contraindicated the possibility of immunosuppressive treatment. The patient eventually died under palliative care. Silica inhalation is the cause of silicosis, but it is also implicated in the development of systemic sclerosis (Erasmus syndrome) and although they share a common risk factor, it is rare to find both diseases coexisting. We present the case of a young patient in whom both diseases presented aggressively, with the aim of highlighting the importance of actively searching for expositional diseases and associated conditions.

Presentamos el caso de un hombre de 35 años, arenador durante ocho años, con diagnóstico reciente de tuberculosis pulmonar y esclerosis sistémica, que ingresó por cuadro de disnea y mal estado general. Se realizó radiografía de tórax donde se evidenció neumotórax grado I, en la tomografía de tórax, también presentó masas hiperdensas confluyentes, asociadas a un patrón de neumonía intersticial no especifica (NSIP), hallazgos compatibles con silicosis pulmonar complicada. Debido al avanzado estadio clínico, no pudieron realizarse estudios diagnósticos invasivos ni estudios de función pulmonar. Como tratamiento inicial se colocó un tubo de avenamiento pleural, se realizó tratamiento antifímico y se indicó oxigenoterapia crónica domiciliaria. Se remitió al paciente a consultorios de enfermedades intersticiales y reumatología para un manejo multidisciplinario, aunque el cuadro infeccioso contraindicó la posibilidad de un tratamiento inmunosupresor. Finalmente, el paciente falleció bajo cuidados paliativos. La inhalación de sílice es la causa de la silicosis, pero también está implicada en el desarrollo de la esclerosis sistémica (síndrome de Erasmus) y aunque comparten un factor de riesgo común, es raro encontrar ambas enfermedades coexistiendo. Presentamos el caso de un paciente joven donde ambas condiciones se presentaron de manera agresiva, con el objetivo de remarcar la importancia de la búsqueda activa de las enfermedades por exposición y sus condiciones asociadas.

Biomarkers related to silicosis and pulmonary function in individuals exposed to silica.

BACKGROUND: The identification of markers that can facilitate the early diagnosis of silicosis has remained challenging. We evaluated the association of inflammatory markers with the presence of silicosis and lung function impairment in individuals exposed to silica. METHODS: Individuals exposed and not exposed to silica were assessed by occupational history, clinical findings, lung function, chest imaging findings, and inflammatory markers. RESULTS: Among 297 men evaluated, 51 were unexposed controls (G1), 149 were exposed to silica without silicosis (G2), and 97 were exposed to silica with silicosis (G3). Inflammatory marker levels were higher in G3 than in G2 and G1. Platelet/lymphocyte ratio (PLR), lactate dehydrogenase (LDH), soluble tumor necrosis factor II (sTNFRII), and macrophage inflammatory protein-4 (MIP-4) were associated with silicosis, and LDH, neutrophil/lymphocyte ratio (NLR), sTNFRII, monocyte chemoattractant protein-1 (MCP-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), and fibrinogen were negatively associated with lung function. CONCLUSION: Blood inflammatory markers are associated with silicosis and impaired lung function.

Silicoproteinosis en paciente minero en Colombia. Reporte de caso / Silicoproteinosis in a mining patient in Colombia. Case report

La silicosis pulmonar es una enfermedad ocupacional que continúa ocasionando morbilidad en el mundo. Debido a que el sílice es el mineral más abundante en la tierra y en las rocas, son numerosas las fuentes de exposición laboral a la inhalación del polvo de sílice en varios sectores industriales. Por su parte, la silicoproteinosis pulmonar es una forma aguda muy rara de silicosis, que puede desarrollarse con un período de latencia más corto en comparación con la silicosis, luego de la primera exposición al sílice, y se caracteriza por un rápido deterioro de la función pulmonar, sin respuesta efectiva a ningún tratamiento. Por su forma de presentación tan atípica, reportamos el caso de un hombre de 58 años, con antecedente laboral de trabajo en mina de extracción de oro en socavón

Pulmonary silicosis is an occupational disease that continues to cause morbidity in the world. Because silica is the most abundant mineral in soil and rock, sources of occupational exposure to inhalation of silica dust are numerous in various industrial sectors. Alternately, pulmonary silicoproteinosis is a very rare acute form of silicosis, which can develop with a shorter latency period compared to silicosis after the first exposure to silica, and is characterized by a rapid deterioration of lung function, without effective response to any treatment. Due to its atypical form of presentation, we report the case of a 58-year-old man, with a history of working in a gold mine

Lung inflammation induced by silica particles triggers hippocampal inflammation, synapse damage and memory impairment in mice.

BACKGROUND: Considerable evidence indicates that a signaling crosstalk between the brain and periphery plays important roles in neurological disorders, and that both acute and chronic peripheral inflammation can produce brain changes leading to cognitive impairments. Recent clinical and epidemiological studies have revealed an increased risk of cognitive impairment and dementia in individuals with impaired pulmonary function. However, the mechanistic underpinnings of this association remain unknown. Exposure to SiO2 (silica) particles triggers lung inflammation, including infiltration by peripheral immune cells and upregulation of pro-inflammatory cytokines. We here utilized a mouse model of lung silicosis to investigate the crosstalk between lung inflammation and memory. METHODS: Silicosis was induced by intratracheal administration of a single dose of 2.5 mg SiO2/kg in mice. Molecular and behavioral measurements were conducted 24 h and 15 days after silica administration. Lung and hippocampal inflammation were investigated by histological analysis and by determination of pro-inflammatory cytokines. Hippocampal synapse damage, amyloid-ß (Aß) peptide content and phosphorylation of Akt, a proxy of hippocampal insulin signaling, were investigated by Western blotting and ELISA. Memory was assessed using the open field and novel object recognition tests. RESULTS: Administration of silica induced alveolar collapse, lung infiltration by polymorphonuclear (PMN) cells, and increased lung pro-inflammatory cytokines. Lung inflammation was followed by upregulation of hippocampal pro-inflammatory cytokines, synapse damage, accumulation of the Aß peptide, and memory impairment in mice. CONCLUSION: The current study identified a crosstalk between lung and brain inflammatory responses leading to hippocampal synapse damage and memory impairment after exposure to a single low dose of silica in mice.

Genetic polymorphisms and their effects on the severity of silicosis in workers exposed to silica in Brazil.

OBJECTIVE: Silicosis is a pneumoconiosis characterized by fibrosis of the lung parenchyma caused by inhalation of silica particles. Genetic factors might play a role in the severity silicosis. We sought to evaluate the influence of polymorphisms in the ACE, FAS, FASLG, NOS2, IL1RN, FAM13A, TGFB1, and TNF genes on the severity of silicosis. METHODS: Nine polymorphisms were genotyped by PCR in a sample of 143 patients with silicosis in the state of Rio de Janeiro, Brazil. RESULTS: Fifty-seven patients (40%) were classified as having simple silicosis and 86 (60%) were classified as having complicated silicosis. The TT genotype of rs1800469 in the TGFB1 gene showed a protective effect for complicated silicosis (OR = 0.35; 95% CI, 0.14-0.92; p = 0.028) when compared with the other two genotypes (CC+CT). The polymorphic T allele of rs763110 in the FASLG gene (OR = 0.56; 95% CI, 0.31-0.99; p = 0.047), as well as a dominant model for the T allele (TT+CT: OR = 0.37; 95% CI, 0.15-0.96; p = 0.037), also showed a protective effect. When patients with simple silicosis despite having been exposed to silica for a longer time (> 44,229 hours) were compared with patients with complicated silicosis despite having been exposed to silica for a shorter time, the T allele of rs763110 in the FASLG gene (OR = 0.20; 95% CI, 0.08-0.48; p < 0.0001), as well as dominant and recessive models (OR = 0.06; 95% CI, 0.00-0.49; p = 0.01 and OR = 0.22; 95% CI, 0.06-0.77; p = 0.014, respectively), showed a protective effect against the severity of silicosis. CONCLUSIONS: It appears that rs1800469 polymorphisms in the TGFB1 gene and rs763110 polymorphisms in the FASLG gene are involved in the severity of silicosis. Given the lack of studies relating genetic polymorphisms to the severity of silicosis, these results should be replicated in other populations.

Non-malignant silica-related diseases in a specialized outpatient clinic.

BACKGROUND: Uncontrolled occupational exposure to silica is still frequent in Brazil, with several recent records in the state of Minas Gerais. However, few national studies have addressed silica-related diseases other than silicosis. AIMS: To describe the occurrence of the main non-malignant silica-related diseases: silicosis, tuberculosis (TB), chronic obstructive pulmonary disease (COPD), and autoimmune diseases in a specialized outpatient clinic. METHODS: Case series study of 1525 patients exposed to silica, seen between 1984 and 2021, with descriptive findings of clinical and occupational data from the first medical evaluation. RESULTS: Medians of age and exposure time were 47 and 15 years, respectively, and 97% of patients were male. The prevalence of silicosis was 44%, of which 27% had large opacities. The main occupational sectors were underground gold mining (28%), precious and semi-precious stone work (20%), and artisanal mining (9%). Spirometries were abnormal in 55%, with obstructive disorder being the most common finding. COPD (25%), active TB or sequelae (12%), and connective tissue diseases (6%) were diagnosed in patients with and without silicosis. CONCLUSIONS: The percentage of silicosis appears to be alarming, even considering the biases of selective referrals. The patients were relatively young and already had a functional impact, caused not only by silicosis but by one or more silica-related diseases. COPD, TB, and connective tissue diseases proved to be frequent, leading to the need for specifics protocols to investigate them in individuals exposed to silica. By adopting strategies to combat silicosis, the prevention of other silica-related diseases is concomitantly promoted.

Volume-based tomography for the diagnosis of incipient silicosis in former gold miners.

OBJECTIVE: To evaluate silicosis diagnosed through CT, with integration of clinical-occupational data, in silica-exposed workers presenting chest X-rays within International Labor Organization (ILO) category 0. METHODS: Cross-sectional study with 339 former gold miners, with comparable exposures and X-rays classified as ILO subcategory 0/0 (n=285) and 0/1 (n=54) were submitted to volume-based CT. The findings were classified according to the International Classification of HRCT CT for Occupational and Environmental Respiratory Diseases. RESULTS: A profusion degree of round opacities (RO)>1 was found in 22.4% (76/339) of the CT exams. After integrating the CT findings with clinical and occupational data, silicosis was diagnosed as follows: 43/285 (15.1%) and 14/54 (25.9%) in workers whose X-rays had been classified as 0/0 and 0/1, respectively. There was an upward trend towards longer exposures, reaching 38.9% when working more than 10 years underground and classified as 0/1 (p=0019). Those with presence of RO whose final diagnosis was not silicosis were mainly cases of tuberculosis or 'indeterminate nodules'. Emphysema was found in 65/339 (19.1%), only 5 being detected in the X-ray. CONCLUSION: Volume-based CT proved to be useful in the investigation of silicosis among individuals with a relevant exposure to silica, capturing diagnoses that had not been identified on X-rays. A response gradient of silicosis was showed by CT even in this population with ILO category 0 radiographs. It can be indicated based on quantitative and/or qualitative criteria of occupational exposure, especially considering the possibilities of low CT dosage.

Occupational exposure to crystalline silica and peripheral biomarkers: An update.

Peripheral biomarkers are important tools for detecting occupational exposures to prevent the onset and/or progression of diseases. Studies that reveal early peripheral biomarkers are highly important to preserve the health of workers and can potentially contribute to diagnosing and/or prognosing occupational pathologies. Exposure to crystalline silica is a problem in several workplaces because it increases the risk of chronic obstructive pulmonary disease (COPD), tuberculosis, cancer, and pulmonary fibrosis, clinically defined as silicosis. Silicosis is diagnosed by chest radiography and/or lung tomography in advanced stages when there is a severe loss of lung function. Peripheral biomarkers can help in diagnosing early changes prior to silicosis and represent a highly important technical-scientific advance that is minimally invasive. This review aimed to investigate the biomarkers studied for evaluating occupational exposure to crystalline silica and to understand the recent advances in this area. Potential oxidative, inflammatory, and immunological biomarkers were reviewed, as well as routine biomarkers such as biochemical parameters. It was found that biomarkers of effect such as serum CC16 and l-selectin levels could represent promising alternatives. Additionally, studies have shown that neopterin levels in urine and serum can be used to monitor worker exposure. However, further studies are needed that include a greater number of participants, different times of exposure to crystalline silica, and a combination of silicosis patients and healthy volunteers. Evaluating the concentration of crystalline silica in occupational environments, its impact on biomarkers of effect, and alterations in lung function could contribute to revealing early health alterations in workers in a more robust manner.

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.

Respiratory health and silicosis in artisanal mine workers in southern Brazil.

BACKGROUND: Artisanal and small-scale mining (ASM) are an important source of employment in southern Brazil. Mining workers are frequently exposed to unhealthy work conditions which increase the risk of occupational diseases. In this study, we assessed the association of sociodemographic factors and the occupational history of artisanal mining workers with the risk of adverse respiratory outcomes. METHODS: The study was conducted with 258 artisanal mining workers in southern Brazil, who were exposed to dust (mainly crystalline silica) in their work. Information on sociodemographic variables and occupational histories was collected between 2017 and 2018. To estimate the worker's exposure to inhalable dust we use the Advanced REACH (Registration, Evaluation, and Authorization of Chemicals) Tool (ART). RESULTS: Study participants were all men, with an average age of 40 years. Median crude dust exposure estimated by ART was 13.2 mg/m³ and median crude crystalline silica exposure was 1.6 mg/m3 . The prevalence ratio (PR) for self-reported silicosis was 3.08 (95% confidence interval, 1.39-7.17) in workers with 20 years or more of mining work. Factors associated with silicosis were age, pack-years of tobacco use, and body mass index. Smokers were over twice as likely to report respiratory symptoms. CONCLUSIONS: Our findings indicate that a high prevalence of silicosis and other associated diseases in mining workers is associated with both unhealthy work environment conditions and the health profile of workers. This study is an important step for understanding health outcomes from work in ASM.

Mortality from silicosis in Brazil: Temporal trends in the period 1980-2017.

BACKGROUND: Silicosis is the most prevalent pneumoconiosis in Brazil. We aimed to estimate mortality rates and temporal trends for silicosis, and to identify areas of highest mortality. METHODS: Records of silicosis as the underlying (1980-2017) or contributory (2000-2017) cause of death in adults aged 20 years and older were retrieved from the Brazilian Mortality Database. Age-standardized mortality rates (ASMR) were calculated. The annual trend in ASMR was analyzed by joinpoint regression. Mortality rates per 100,000 person-years were calculated for each municipality. We analyzed temporal trends in municipalities where similar activities with exposure to silica were performed. RESULTS: There were 3164 death records (96.6% men) distributed over 14% of the municipalities. Mean age of death was 59.2 (SD 15.1) and mean ASMR was 0.085/100,000 (confidence interval 0.080-0.091). Joinpoint regression showed a significant increase in ASMR from 1980 to 2006 and a significant decrease after 2006 driven by a decline in deaths of individuals younger than 70 years. The highest mortality rate was 21.83/100,000 person-years, in a municipality with small mining operations for gems. Gold mining municipalities showed the highest composite death rate, 4.0/100,000 person-years. Tuberculosis was the main cause of death when silicosis was a contributing cause. CONCLUSIONS: In contrast with developed countries, silicosis mortality in Brazil increased to 2006 and subsequently started to drop, mostly from a plateau or decrease in deaths occurring in municipalities which regulated economic activities. However, this decrease did not occur in the older age group nor in the unregulated sector, the latter being the main challenge for exposure control and surveillance.

Predictors of health-related quality of life among semi-precious stone mineworkers exposed to silica dust.

OBJECTIVE: The study aimed to comparatively evaluate HRQOL in miners of semi-precious stones with and without silicosis, and determine the associated factors, as well as the performance of two different questionnaires in measuring HRQOL. METHODS: In a cross-sectional study of 348 male miners (129 with silicosis) who underwent an interview and spirometry, HRQOL was assessed using the World Health Organization Quality of Life (WHOQOL-BREF) questionnaire and the Saint George's Respiratory Questionnaire (SGRQ). RESULTS: Miners with silicosis were older, had less schooling, worked more hours daily, and had longer exposure to silica. They also had worse scores of QoL in both questionnaires. Respiratory symptoms and %FEV1 were contributing factors for the models of total health and all the domains of the SGRQ, and 40% of the variability of the general health domain of WHOQOL-BREF was due to dyspnea, wheezing, %FEV1, and pack-years of cigarette smoking. Respiratory symptoms, lung function, pack-years of cigarette smoking, years of education, and average monthly income were contributing factors for the models of the different domains of the WHOQOL-BREF. CONCLUSIONS: Our study revealed impaired HRQOL in semi-precious stone miners evaluated using both questionnaire tools of SGRQ and WHOQOL-BREF, of which SGRQ had superior performance. Respiratory symptoms, functional impairment, and pack-years of cigarette smoking were the most important determinants of the workers' general HRQOL.

Is individual genetic susceptibility a link between silica exposure and development or severity of silicosis? A systematic review.

BACKGROUND: Silicosis is a lung disease of fibrotic nature resulting from the inhalation and deposition of dust containing crystalline silica. Subjects exposed to the same environmental factors may show distinct radiological manifestations, and since silicosis is known as a multifactorial disease, it is plausible that individual genetic susceptibility may play a role in the pathology. This review of the literature aims to provide an assessment of the present data on the genetic association studies in silicosis and describe the genes that potentially might influence silicosis susceptibility in silica-exposed individuals. METHODS: We accessed the database of PubMed for articles published in English about interindividual genetic susceptibility to silicosis using terms related to the subject matter. RESULTS: Following the evaluation process, 28 studies were included in this systematic review, including 23 original studies and 5 meta-analyses. CONCLUSIONS: Regardless of the advances in the knowledge of the importance of gene variations in silicosis, more studies need to be performed, in particular, special polygenic and genome-wide investigations.

In situ evidence of collagen V and signaling pathway of found inflammatory zone 1 (FIZZ1) is associated with silicotic granuloma in lung mice.

Inhalation of silica particles causes silicosis: an occupational lung disease characterized by persistent inflammation with granuloma formation that leads to tissue remodeling and impairment of lung function. Although silicosis has been studied intensely, little is known about the crucial cellular mechanisms that initiate and drive the process of inflammation and fibrosis. Recently, found in inflammatory zone 1 (FIZZ1) protein, produced by alveolar macrophages and fibroblasts have been shown to induce the proliferation of myofibroblasts and their transdifferentiation, causing tissue fibrosis. Moreover, autoimmunogenic collagen V, produced by alveolar epithelial cells and fibroblasts, is involved in the pathophysiology of interstitial pulmonary fibrosis and bleomycin-induced lung fibrosis. Based on the aforementioned we hypothesized that FIZZ1 and collagen V may be involved in the silicotic granuloma process in mice lungs. Male C57BL/6 mice (N = 20) received intratracheal administration of silica particles (Silica; 20 mg in 50 µL saline) or saline (Control; 50 µL). After 15 days, the lung histology was performed through immunohistochemistry and morphometric analysis. Within silicotic granulomas, collagen V and FIZZ1 increased, while peroxisome proliferator-activated receptor gamma (PPARγ) positive cells decreased. In addition, the expression of proteins Notch-1, alpha smooth muscle actin (α-SMA) and macrophages163 (CD163) were higher in silicotic granulomas than control lungs. A significant positive correlation was found between collagen V and FIZZ1 (r = 0.70; p < 0.05), collagen V and Notch-1 (r = 0.72; p < 0.05), whereas Collagen V was inversely associated with peroxisome proliferator-activated receptor gamma (r=-0.69; p < 0.05). These findings suggested that collagen V association with FIZZ1, Notch-1 and PPARγ might be a key pathogenic mechanism for silicotic granulomas in mice lungs.

Intranasal Flunisolide Suppresses Pathological Alterations Caused by Silica Particles in the Lungs of Mice.

Silicosis is an occupational disease triggered by the inhalation of fine particles of crystalline silica and characterized by inflammation and scarring in the form of nodular lesions in the lungs. In spite of the therapeutic arsenal currently available, there is no specific treatment for the disease. Flunisolide is a potent corticosteroid shown to be effective for controlling chronic lung inflammatory diseases. In this study, the effect of flunisolide on silica-induced lung pathological changes in mice was investigated. Swiss-Webster mice were injected intranasally with silica particles and further treated with flunisolide from day 21 to 27 post-silica challenge. Lung function was assessed by whole body invasive plethysmography. Granuloma formation was evaluated morphometrically, collagen deposition by Picrus sirius staining and quantitated by Sircol. Chemokines and cytokines were evaluated using enzyme-linked immunosorbent assay. The sensitivity of lung fibroblasts was also examined in in vitro assays. Silica challenge led to increased leukocyte numbers (mononuclear cells and neutrophils) as well as production of the chemokine KC/CXCL-1 and the cytokines TNF-α and TGF-ß in the bronchoalveolar lavage. These alterations paralleled to progressive granuloma formation, collagen deposition and impairment of lung function. Therapeutic administration of intranasal flunisolide inhibited granuloma and fibrotic responses, noted 28 days after silica challenge. The upregulation of MIP-1α/CCL-3 and MIP-2/CXCL-2 and the cytokines TNF-α and TGF-ß, as well as deposition of collagen and airway hyper-reactivity to methacholine were shown to be clearly sensitive to flunisolide, as compared to silica-challenge untreated mice. Additionally, flunisolide effectively suppressed the responses of proliferation and MCP-1/CCL-2 production from IL-13 stimulated lung fibroblasts from silica- or saline-challenged mice. In conclusion, we report that intranasal treatment with the corticosteroid flunisolide showed protective properties on pathological features triggered by silica particles in mice, suggesting that the compound may constitute a promising strategy for the treatment of silicosis.