Inflammatory and oxidative stress biomarkers induced by silica exposure in crystal craftsmen

Clinical usefulness of serum angiotensin converting enzyme in silicosis

INTRODUCTION

Silicosis is an irreversible and incurable disease. Preventive measures to eliminate exposure are the only effective way to reduce morbidity and mortality. In such situations, having a biomarker for early diagnosis or to predict evolution would be very useful in order to improve control of the disease. The elevation of serum angiotensin-converting enzyme (sACE) in silicosis has been described in previous studies, although its relationship with severity and prognosis is not clear.

AIMS

To determine the levels of sACE in a cohort of patients with exposure to silica dust with and without silicosis, and to assess their impact on the prognosis of the aforementioned patients.

METHOD

Prospective observational study on patients treated in a silicosis clinic from 2009 to 2018. sACE levels and pulmonary function tests were performed. Radiological progression was assessed in patients who had already had 2 X-rays of the thorax and / or two CT scans with at least a 1-year interval, from the time of inclusion in the study.

RESULTS

A total of 413 cases of silicosis were confirmed, as well as 73 with exposure to silica dust but without silicosis. The mean sACE level for healthy subjects was 27.5±7.3U/L, for exposed patients without silicosis it was 49.6±24.2U/L, for simple silicosis it was 57.8±31,3U/L and for complicated silicosis it was 74.5±38.6U/L. Patients with a higher sACE generally progressed radiologically during follow-up (73.3±38.0 vs. 60.4±33.7; p<.001) and so the category of silicosis changed (73,9±38.1 vs. 62.5±34.6; p<.021).

CONCLUSIONS

sACE was elevated in patients with silicosis, and the greater its severity, the higher it was, which is associated with disease progression measured radiologically or as a category change of silicosis.

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.

Pulmonary Functions and Oxidative Stress Biomarkers Among Silica-Exposed Foundry Workers

OBJECTIVE

To investigate the changes of the ventilatory function tests and the oxidative stress biomarkers among silica-exposed foundry workers.

METHODS

The exposed group included 70 workers in an iron foundry. The nonexposed group included 40 subjects from Kasralainy outpatient clinic. Both groups were subjected to history taking, clinical examination, chest radiograph, spirometry, urinary silica, serum malondialdehyde (MDA), glutathione peroxidase (GPx), and 8-hydroxydeoxyguanosine (8-HdG).

RESULTS

Higher urinary silica, serum MDA and serum 8-HdG, whereas lower serum GPx and ventilatory functions were detected in the exposed group compared with the controls. All parameters correlated with urinary silica. The exposed silicotic subgroup had increased work duration, urinary silica, serum MDA, and serum 8-HdG, and decreased serum GPx and ventilatory functions compared with non-silicotic subgroup.

CONCLUSION

Oxidative stress biomarkers were abnormal with impairment of ventilatory functions among silica-exposed workers.

Evaluation of Oxidative Stress Parameters and Genotoxic Effects in Patients With Work-Related Asthma and Silicosis

OBJECTIVE

To determine the mechanistic roles of oxidative stress, inflammation, and genotoxicity parameters in patients with work-related asthma (WRA) and silicosis.

METHODS

Thirty-eight healthy office workers, 27 employees with a history of exposure and no disease, 24 employees with WRA, and 23 employees with silicosis were included in this study. Superoxide dismutase, catalase, glutathione peroxidase, malondialdehyde, and interleukins (IL) 17, 23, and 27 levels were measured in the serum. Genotoxic damage was evaluated by calculating the frequency of micronuclei in swab samples and 8-hydroxy-2'-deoxyguanosine in serum.

RESULTS

Serum superoxide dismutase, catalase, glutathione peroxidase, malondialdehyde, 8-hydroxy-2'-deoxyguanosine, and IL-17, IL-23, and IL-27 levels were found to be statistically significantly higher in the exposure, WRA, and silicosis groups compared with the control group. The frequency of micronuclei in buccal epithelial cells of the patient group was found to be significantly higher than that of the control group.

CONCLUSION

These results may provide information for molecular mechanisms and early diagnosis of WRA and silicosis and will be a guide for taking precautions in the early period.

Serum metabolic profiling of coal worker's pneumoconiosis using untargeted lipidomics

In this work, untargeted lipidomics was employed to analyze the effects of coal dust exposure on serum metabolite profiles. Furthermore, the potential of differential metabolites as novel biomarkers for diagnosis was investigated by binary logistic classification model. Nineteen differential metabolites were found among the three groups. The compounds were enriched in pathways associated with linoleic acid metabolism and pyrimidine metabolism. Fifty-three differential metabolites were found in coal dust-exposed people and CWP patients, and they were mainly enriched in glycerophospholipid metabolism. Three differential metabolites were correlated with lung function values. The diagnostic model, composed of lysoPI (16:0/0:0), bilirubin, and lysoPC (24:1/0:0), showed strong discrimination ability between dust-exposed people and CWP patients. The sensitivity, specificity, and AUC values of the model were 0.869, 0.600, and 0.750, respectively. The results suggest that coal worker's pneumoconiosis causes abnormal lipid metabolism in the body. A diagnostic model may aid current CWP diagnostic methods, and lysoPI (16:0/0:0), bilirubin, and lysoPC (24:1/0:0) can be used as potential CWP biomarkers. Further study is warranted to validate the findings in larger populations.

Understanding the pathogenesis of occupational coal and silica dust-associated lung disease

Workers in the mining and construction industries are at increased risk of respiratory and other diseases as a result of being exposed to harmful levels of airborne particulate matter (PM) for extended periods of time. While clear links have been established between PM exposure and the development of occupational lung disease, the mechanisms are still poorly understood. A greater understanding of how exposures to different levels and types of PM encountered in mining and construction workplaces affect pathophysiological processes in the airways and lungs and result in different forms of occupational lung disease is urgently required. Such information is needed to inform safe exposure limits and monitoring guidelines for different types of PM and development of biomarkers for earlier disease diagnosis. Suspended particles with a 50% cut-off aerodynamic diameter of 10 µm and 2.5 µm are considered biologically active owing to their ability to bypass the upper respiratory tract's defences and penetrate deep into the lung parenchyma, where they induce potentially irreversible damage, impair lung function and reduce the quality of life. Here we review the current understanding of occupational respiratory diseases, including coal worker pneumoconiosis and silicosis, and how PM exposure may affect pathophysiological responses in the airways and lungs. We also highlight the use of experimental models for better understanding these mechanisms of pathogenesis. We outline the urgency for revised dust control strategies, and the need for evidence-based identification of safe level exposures using clinical and experimental studies to better protect workers' health.

Evaluation of cytokines in exhaled breath condensate in an occupationally exposed population to pneumotoxic pollutants

The quarrying is considered a precarious occupation with high toxicity, is an informal economic activity that employs low technology, limited protection, and poses a risk to workers and their families. In quarrying, silica dust is generated and there is also occupational exposure to significant mixtures of pneumotoxic pollutants, including mineral dust (crystalline silica, carbon or cement, polycyclic aromatic hydrocarbons (PAHs), solvents, and others, which are aggravated by the lack of use of protective equipment, causing irreversible damage to the worker's respiratory health. Thus, the objective of this work focused on the evaluation of the respiratory health of artisan stonemasons in San Luis Potosí, Mexico through the study of exhaled breath condensate (EBC) (pH, pro-inflammatory cytokines) as well as the study of the exposure to pollutants present in the work area (PAHs, toluene, and 2.5 µm particulate matter) through biomarkers of exposure (hippuric acid and hydroxylated metabolites of PAHs). The results show the presence of crystalline SiO₂ in 100% of the samples analyzed; the PM_2.5 concentrations were 5 to 10 times the permitted levels. Regarding exposure to PAHs, all the stonemasons presented urine concentrations of at least 5 of the OH-PAHs evaluated; 9-OH-FLU occurred at higher concentrations of 171.2 (122.7-279.4) µg L^-1; hippuric acid, which was present in 100% of the workers evaluated in concentrations of 283.4 (27.72-1119) mg L^-1, 100% of which were above the values established for occupational scenarios. The pH values obtained for the EBC samples were presented at an average of 7.07 (6.33-7.66). Pro-inflammatory cytokines were present in 86.1% of the study population. The cytokine that was found in higher concentrations was IL-2, with a mean of 178.01 pg mL^-1 and 3124.01 pg mL^-1 for the pH < 7 and pH > 7 groups, respectively. Some correlations between the cytokines and the exposure biomarkers were presented. Stonemasons are highly exposed to pneumotoxic pollutants and markers of inflammation at the pulmonary level; in addition, a high risk of developing silicosis. Quarrying should be addressed as a carcinogenic activity, which would imply the design of monitoring and control strategies for these pollutants that our country currently lacks, particularly in precarious occupations. It is necessary to develop strategies to protect the health of precarious workers.

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.

Serum levels of inflammatory mediators as prognostic biomarker in silica exposed workers

Silicosis is a diffuse interstitial lung disease caused by sustained inhalation of silica and silicates. Several cytokines are activated by their inhalation and can mediate the process of pulmonary fibrosis. The identification of biomarkers could allow an early diagnosis before the development of radiological alterations and help monitor the evolution of patients. The objetive of this study was to determine the clinical significance of specific biomarkers, to estimate their association with the development, severity and/or progression of silicosis, and identify determinants of this evolution. We conducted a prospective observational study in patients attending the pulmonology clinic from 2009 to 2018. Serum levels of the following inflammatory mediators were assessed: interleukin-6 (IL-6), interleukin 2 receptor subunit alpha (IL2R) interleukin 1 beta (IL1B), interleukin-8 (IL-8), tumour necrosis factor-alpha (TNF-α), transforming growth factor-beta1 (TGF-β1), alpha-1 antitrypsin (AAT), C-reactive protein (CRP), lactate dehydrogenase (LDH) and ferritin in subjects exposed to silica, with and without silicosis. Association between those inflammatory mediators with lung function measurements and radiological severity of disease and their impact on prognosis were analysed. 337 exposed to silica (278 with silicosis) and 30 subjects in the control group were included. IL-8, α1AT, ferritin, CRP and LDH levels were higher in silicosis than in those exposed to silica without silicosis. IL-8, LDH and AAT levels were associated with progression of silicosis and IL-6, IL-8, LDH, AAT, ferritin, and CRP with vital status. The results of the ROC analysis indicated the potential of IL-8 as a biomarker in the presence of silicosis and for the prediction of mortality.

Identification of refractory zirconia from catalytic converters in dust: An emerging pollutant in urban environments

Using catalytic converters is one of the most effective methods to control vehicle emissions. A washcoat of cerium oxide-zirconia (CeO₂-ZrO₂) has been used to enhance the performance of the catalytic converter device. To date, the prevalence of this material in the environment has not been assessed. In this study, we present evidence of the existence of inhalable zirconia in urban dust. Samples of the washcoat, exhaust pipe, topsoil, and road dust were analyzed by X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) spectroscopy, and thermally stimulated luminescence (TSL). The results showed a CeO₂-ZrO₂ phase separation after sintering. This causes the emission of ZrO₂, CeO₂, and CeZrO_x particles smaller than 1 μm, which can likely reach the alveolar macrophages in the lungs. The Ce-Zr content in road dust exceeds geogenic levels, and a significant correlation of 0.87 (p < 0.05) reflects a common anthropic source. Chronic exposure to such refractory particles may result in the development of non-occupational respiratory diseases. The inhalable crystalline compounds emitted by vehicles are a significant environmental health hazard, revealing the need for further investigation and assessment of zirconia levels generated by automobiles in urban areas worldwide.

Amorphous nanosilica induced toxicity, inflammation and innate immune responses: A critical review

Nanoparticles are promising bioengineering platforms facilitating various consumer product formulations, including packaged food, electrical, biosensor and biomedical tools. The unique surface and physicochemical properties of amorphous nanosilica supports advanced nano-biomolecular applications for various manufacturing, biotechnology, and healthcare industries including cosmetics, packaging, implants, drug delivery systems and cancer diagnostics. The increased technological and economic benefits of amorphous nanosilica, raises concerns regarding their adverse biological effects on humans. The cellular mechanisms underlying amorphous nanosilica internalization, evasion of biological barriers, inadvertent nano-bio interactions and unexpected long term exposure effects must be taken into consideration from the diverse ecosystems and human safety aspects. Recent research studies reveal cytotoxic, inflammatory and immunomodulatory effects of amorphous nanosilica particles. Our review focuses on studies demonstrating hazardous impact of amorphous nanosilica/bio-systems interface on the cellular and biochemical processes. The review further seeks to evaluate amorphous nanosilica-induced cytotoxicity, innate immune responses, inflammation and immune related dysfunctions, and discuss open research questions related to the use of amorphous nanosilica in biomedicine.