Inducible nitric oxide synthase genetic polymorphism and risk of asbestosis

The role of nitric oxide in pleural disease

Nitric oxide (NO) regulates various physiological and pathophysiological functions in the lungs. However, there is much less information about the effects of NO in the pleura. The present review aimed to explore the available evidence regarding the role of NO in pleural disease. NO, has a double-edged role in the pleural cavity. It is an essential signaling molecule mediating various physiological cell functions such as lymphatic drainage of the serous cavities, the immune response to intracellular multiplication of pathogens, and downregulation of neutrophil migration, but also induces genocytotoxic and mutagenic effects when present in excess. NO is implicated in the pathogenesis of asbestos-related or exudative pleural disease and mesothelioma. From a clinical point of view, the fraction of exhaled NO has been suggested as a potential non-invasive tool for the diagnosis of benign asbestos-related disorders. Under experimental conditions, NO-mimetics were found to attenuate hypoxia-induced therapy resistance in mesothelioma. Similarly, hybrid agents consisting of an NO donor coupled with a parent anti-inflammatory drug showed an enhancement of the anti-inflammatory activity of anti-inflammatory drugs. However, given the paucity of research work performed over the last years in this area, further research should be undertaken to establish reliable conclusions with respect to the feasibility of determining or targeting the NO signaling pathway for pleural disease diagnosis and therapeutic management.

Extended Exhaled Nitric Oxide Analysis in Interstitial Lung Diseases: A Systematic Review

Fractional exhaled nitric oxide (FeNO) is a well-known and widely accepted biomarker of airways inflammation that can be useful in the therapeutic management, and adherence to inhalation therapy control, in asthmatic patients. However, the multiple-flows assessment of FeNO can provide a reliable measurement of bronchial and alveolar production of NO, supporting its potential value as biomarker also in peripheral lung diseases, such as interstitial lung diseases (ILD). In this review, we first discuss the role of NO in the pathobiology of lung fibrosis and the technique currently approved for the measurement of maximum bronchial flux of NO (J'awNO) and alveolar concentration of NO (CaNO). We systematically report the published evidence regarding extended FeNO analysis in the management of patients with different ILDs, focusing on its potential role in differential diagnosis, prognostic evaluation and severity assessment of disease. The few available data concerning extended FeNO analysis, and the most common comorbidities of ILD, are explored too. In conclusion, multiple-flows FeNO analysis, and CaNO in particular, appears to be a promising tool to be implemented in the diagnostic and prognostic pathways of patients affected with ILDs.

Risk of occupational exposure to asbestos, silicon and arsenic on pulmonary disorders: Understanding the genetic-epigenetic interplay and future prospects

BACKGROUND

Epidemiological studies suggest strong association of lung disorders with occupational exposure to asbestos, silicon and arsenic. The chronic occupational exposure primarily through inhalation results in adverse outcome on the respiratory tract which may also be fatal. Although several mechanisms have attributed towards these diseases; the molecular pathogenesis is still unknown.

OBJECTIVE

In this review, we investigated the plausible molecular mechanism based on current research that may identify the genetic and epigenetic susceptibility of respiratory disorders upon such occupational exposures in humans.

METHODS

We considered genetic variants and epigenetic alterations associated with pulmonary exposure hazards leading to asbestosis, silicosis and arsenicosis. Our review is stringently based on the literatures available through peer-reviewed articles mostly published in the last 10 years. Relevant search were conducted using keywords like "occupational lung disorders" along with "asbestos", "silicon" and "arsenic".

RESULTS

Till September 2015, pubmed search yielded approximately 780 articles relating to asbestos exposure; 240 articles for silicon exposure and 60 articles for arsenic exposure. Extensive screening for genetic and epigenetic factors identified certain genes and related pathways that are important to determine the susceptibility of an individual towards such occupational exposure.

CONCLUSION

The link between genotype and phenotype and its association with disease susceptibility is very complex in nature due to several factors like person's environment, lifestyle and nutritional status. The epigenome is dynamic as well as reversible and can be reshaped further by certain dietary components throughout its life. In the present review, we have addressed the role of molecular pathogenesis of occupational lung diseases based on the genetic variability and epigenetic alterations and also attempted to highlight the promising aspect of dietary interventions to counter toxic outcomes upon occupational exposure to asbestos, silicon or arsenic.

Formation of the nitrative DNA lesion 8-nitroguanine is associated with asbestos contents in human lung tissues: a pilot study

OBJECTIVES

Asbestos causes lung cancer and malignant mesothelioma, and chronic inflammation is considered to participate in carcinogenesis. However, biomarkers to evaluate its carcinogenic risk have not been established. Reactive oxygen/nitrogen species are generated in biological systems under inflammatory conditions and may contribute to carcinogenesis by causing DNA damage. In this study, we examined the relationship between the formation of 8-nitroguanine (8-nitroG), a mutagenic DNA lesion formed during inflammation, and asbestos contents in human lung tissues.

METHODS

We obtained non-tumor lung tissues from patients with (n=15) and without mesothelioma (n=21). The expression of 8-nitroG and related molecules was examined by immunohistochemistry, and their staining intensities were semiquantitatively evaluated. Asbestos contents in lung tissues were analyzed by analytical transmission electron microscopy.

RESULTS

In subjects without mesothelioma, staining intensities of 8-nitroG and apurinic/apyrimidinic endonuclease 1 (APE1) were significantly correlated with total asbestos and amphibole contents (p<0.05), but not with chrysotile content. In mesothelioma patients, their staining intensities were not correlated with asbestos contents. The double immunofluorescence technique revealed that APE1 was expressed in 8-nitroG-positive cells, suggesting that abasic sites were formed possibly due to the removal of 8-nitroG. The staining intensities of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an oxidative DNA lesion, and its repair enzyme 8-oxoguanine DNA-glycosylase were correlated with age (p<0.05), but not with asbestos contents in subjects without mesothelioma.

CONCLUSIONS

This is the first study to demonstrate that 8-nitroG formation is associated with asbestos contents in human lung tissues. This finding raises a possibility that 8-nitroG serves as a biomarker that can be used to evaluate asbestos exposure and carcinogenic risk.

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.