Manganese and extracellular superoxide dismutase polymorphisms and risk for asbestosis

Formalin-Fixed Paraffin-Embedded Proteomics of Malignant Mesothelioma and New Candidate Biomarkers Thioredoxin and Superoxide Dismutase 2 for Immunohistochemistry

The pathogenesis of malignant mesothelioma (MM) has been extensively investigated, focusing on stress derived from reactive oxygen species. We aimed to identify diagnostic biomarkers of MM by analyzing proteins in formalin-fixed paraffin-embedded specimens using liquid chromatography-mass spectrometry. We extracted proteins from formalin-fixed paraffin-embedded sections of MM tissues (n = 7) and compared their profiles with those of benign mesothelial tissues (n = 4) and alveolar tissue (n = 1). Proteomic data were statistically assessed and profiled using principal component analysis. We were successful in the classification of MM and healthy tissue. The levels of superoxide dismutase 2 (SOD2), an enzyme that converts superoxide anion into oxygen and hydrogen peroxide, and thioredoxin (TXN), which plays a crucial role in reducing disulfide bonds in proteins, primarily contributed to the classification. Other redox-related proteins, such as pyruvate dehydrogenase subunit X, and ceruloplasmin also contributed to the classification. Protein-protein interaction analysis demonstrated that these proteins play essential roles in MM pathogenesis. Immunohistochemistry revealed that TXN levels were significantly lower, whereas SOD2 levels were significantly higher in MM and lung cancer tissues than in controls. Proteomic profiling suggested that MM tissues experienced increased exposure to hydrogen peroxide and other reactive oxygen species. Combining immunohistochemistry for TXN and SOD2 allows for differentiation among MM, lung cancer, and control tissues; hence, TXN and SOD2 may be promising MM biomarkers and therapeutic targets.

Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells

Asbestos exposure is a determinate cause of many diseases, such as mesothelioma, fibrosis, and lung cancer, and poses a major human health hazard. At this time, there are no identified biomarkers to demarcate asbestos exposure before the presentation of disease and symptoms, and there is only limited understanding of the underlying biology that governs asbestos-induced disease. In our study, we used exosomes, 30-140 nm extracellular vesicles, to gain insight into these knowledge gaps. As inhaled asbestos is first encountered by lung epithelial cells and macrophages, we hypothesize that asbestos-exposed cells secrete exosomes with signature proteomic cargo that can alter the gene expression of mesothelial cells, contributing to disease outcomes like mesothelioma. In the present study using lung epithelial cells (BEAS2B) and macrophages (THP-1), we first show that asbestos exposure causes changes in abundance of some proteins in the exosomes secreted from these cells. Furthermore, exposure of human mesothelial cells (HPM3) to these exosomes resulted in gene expression changes related to epithelial-to-mesenchymal transition and other cancer-related genes. This is the first report to indicate that asbestos-exposed cells secrete exosomes with differentially abundant proteins and that those exosomes have a gene-altering effect on mesothelial cells.-Munson, P., Lam, Y.-W., Dragon, J. MacPherson, M., Shukla, A. Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells.

The Influence of Genetic Variability on the Risk of Developing Malignant Mesothelioma

Background

Malignant mesothelioma is a rare cancer with poor outcome, associated with asbestos exposure. Reactive oxygen species may play an important role in the mechanism of carcinogenesis; therefore, genetic variability in antioxidative defence may modify an individual’s susceptibility to this cancer. This study investigated the influence of functional polymorphisms of NQO1, CAT, SOD2 and hOGG1 genes, gene-gene interactions and gene-environment interactions on malignant mesothelioma risk.

Patients and methods

In total, 150 cases with malignant mesothelioma and 122 controls with no asbestos-related disease were genotyped for NQO1, CAT, SOD2 and hOGG1 polymorphisms.

Results

The risk of malignant mesothelioma increased with smoking, odds ratio (OR) 9.30 [95% confidence interval (CI): 4.83–17.98] and slightly with age, OR 1.10 (95% CI: 1.08–1.14). Medium and high asbestos exposures represented 7-times higher risk of malignant mesothelioma compared to low exposure, OR 7.05 (95% CI 3.59–13.83). NQO1 rs1800566 was significantly associated with increased malignant mesothelioma risk, OR 1.73 (95% CI 1.02–2.96). Although there was no independent association between either CAT rs1001179 or hOGG1 rs1052133 polymorphism and malignant mesothelioma, interaction between both polymorphisms showed a protective effect, OR_int 0.27 (95% CI 0.10–0.77).

Conclusions

Our findings suggest a role of both genetic variability in antioxidative defence and repair as well as the impact of gene-gene interactions in the development of malignant mesothelioma. The results of this study could add to our understanding of pathogenesis of malignant mesothelioma and contribute to prevention and earlier diagnosis of this aggressive cancer.

Gene-environment interaction from international cohorts: impact on development and evolution of occupational and environmental lung and airway disease

Environmental and occupational pulmonary diseases impose a substantial burden of morbidity and mortality on the global population. However, it has been long observed that only some of those who are exposed to pulmonary toxicants go on to develop disease; increasingly, it is being recognized that genetic differences may underlie some of this person-to-person variability. Studies performed throughout the globe are demonstrating important gene-environment interactions for diseases as diverse as chronic beryllium disease, coal workers' pneumoconiosis, silicosis, asbestosis, byssinosis, occupational asthma, and pollution-associated asthma. These findings have, in many instances, elucidated the pathogenesis of these highly complex diseases. At the same time, however, translation of this research into clinical practice has, for good reasons, proceeded slowly. No genetic test has yet emerged with sufficiently robust operating characteristics to be clearly useful or practicable in an occupational or environmental setting. In addition, occupational genetic testing raises serious ethical and policy concerns. Therefore, the primary objective must remain ensuring that the workplace and the environment are safe for all.

Indications for distinct pathogenic mechanisms of asbestos and silica through gene expression profiling of the response of lung epithelial cells

Occupational and environmental exposures to airborne asbestos and silica are associated with the development of lung fibrosis in the forms of asbestosis and silicosis, respectively. However, both diseases display distinct pathologic presentations, likely associated with differences in gene expression induced by different mineral structures, composition and bio-persistent properties. We hypothesized that effects of mineral exposure in the airway epithelium may dictate deviating molecular events that may explain the different pathologies of asbestosis versus silicosis. Using robust gene expression-profiling in conjunction with in-depth pathway analysis, we assessed early (24 h) alterations in gene expression associated with crocidolite asbestos or cristobalite silica exposures in primary human bronchial epithelial cells (NHBEs). Observations were confirmed in an immortalized line (BEAS-2B) by QRT-PCR and protein assays. Utilization of overall gene expression, unsupervised hierarchical cluster analysis and integrated pathway analysis revealed gene alterations that were common to both minerals or unique to either mineral. Our findings reveal that both minerals had potent effects on genes governing cell adhesion/migration, inflammation, and cellular stress, key features of fibrosis. Asbestos exposure was most specifically associated with aberrant cell proliferation and carcinogenesis, whereas silica exposure was highly associated with additional inflammatory responses, as well as pattern recognition, and fibrogenesis. These findings illustrate the use of gene-profiling as a means to determine early molecular events that may dictate pathological processes induced by exogenous cellular insults. In addition, it is a useful approach for predicting the pathogenicity of potentially harmful materials.

The influence of gene-gene and gene-environment interactions on the risk of asbestosis

This study investigated the influence of gene-gene and gene-environment interactions on the risk of developing asbestosis. The study comprised 262 cases with asbestosis and 265 controls with no asbestos-related disease previously studied for MnSOD, ECSOD, CAT, GSTT1, GSTM1, GSTP1, and iNOS polymorphisms. Data on cumulative asbestos and smoking were available for all subjects. To assess gene-gene and gene-environmental interactions, logistic regression was used. The associations between MnSOD Ala −9Val polymorphism and the risk of asbestosis and between iNOS genotypes and asbestosis were modified by CAT –262 C > T polymorphism (P = 0.038; P = 0.031). A strong interaction was found between GSTM1-null polymorphism and smoking (P = 0.007), iNOS (CCTTT)_n polymorphism and smoking (P = 0.054), and between iNOS (CCTTT)_n polymorphism and cumulative asbestos exposure (P = 0.037). The findings of this study suggest that the interactions between different genotypes, genotypes and smoking, and between genotypes and asbestos exposure have an important influence on the development of asbestosis and should be seriously considered in future research on occupational/environmental asbestos-related diseases.

Inducible nitric oxide synthase genetic polymorphism and risk of asbestosis

Asbestos, a known occupational pollutant, may upregulate the activity of inducible nitric oxide synthase (iNOS) and thus the production of nitric oxide (NO). This study investigated whether iNOS (CCTTT)_n polymorphism is associated with an increased asbestosis risk in exposed workers. The study cohort consisted of 262 cases with asbestosis and 265 controls with no asbestos-related disease. For each subject the cumulative asbestos exposure data were available. The number of CCTTT repeats was determined following PCR amplification of the iNOS promoter region. Logistic regression was performed to estimate asbestosis risk. The OR of asbestosis was 1.20 (95%  CI = 0.85–1.69) for the LL genotype compared to the combined SL and SS genotypes and 1.26 (95% CI = 0.86–1.85) for the LL genotype compared to the SL genotype. The results of this study are borderline significant and suggest a possible role of iNOS (CCTTT)_n polymorphism in the risk of asbestosis; however, further studies are needed.