Alterations in DNA methylation corresponding with lung inflammation and as a biomarker for disease development after MWCNT exposure

Abstract

Use of multi-walled carbon nanotubes (MWCNT) is growing which increases occupational exposures to these materials. Their toxic potential makes it important to have an in-depth understanding of the inflammation and disease that develops due to exposure. Epigenetics is one area of interest that has been quickly developing to assess disease processes due to its ability to change gene expression and thus the lung environment after exposure. In this study, promoter methylation of inflammatory genes (IFN-γ and TNF-α) was measured after MWCNT exposure using the pyrosequencing assay and found to correlate with initial cytokine production. In addition, methylation of a gene involved in tissue fibrosis (Thy-1) was also altered in a way that matched collagen deposition. In addition to using epigenetics to better understand disease processes, it has also been used as a biomarker of exposure and disease. In this study, global methylation was determined in the lung to ascertain whether MWCNT alter global methylation at the site of exposure and if those alterations coincide with disease development. Then, global methylation levels were determined in the blood to ascertain whether global methylation could be used as a biomarker of exposure in a more easily accessible tissue. Using the LuUminometric Methylation Assay (LUMA) and 5-Methylcytosine (5-mC) Quantification assay, we found that MWCNT lead to DNA hypomethylation in the lung and blood, which coincided with disease development. This study provides initial data showing that alterations in gene-specific methylation correspond with an inflammatory response to MWCNT exposure. In addition, global DNA methylation in the lung and blood coincides with MWCNT-induced disease development, suggesting its potential as a biomarker of both exposure and disease development.

Perinatal exposure to environmental tobacco smoke is associated with changes in DNA methylation that precede the adult onset of lung disease in a mouse model

“…In our study, Thy-1 was significantly hypermethylated in both 10- to 12- and 20-week old offspring of prenatal and early-life ETS-exposed dams. We previously confirmed that Thy-1 hypermethylation in murine lung tissue corresponds to decreased mRNA expression (Brown et al, 2015). Given that Thy-1 was persistently hypermethylated and preceded the apparent onset of adult lung disease (concluded from collagen deposition and histopathology data), we suggest that prenatal and early-life ETS exposure induces latent fibrotic lung disease and that altered Thy-1 expression via promoter hypermethylation is involved in this adult disease process.…”

“…Using the incorporated iCys Workstation computer software (version 3.4) tools, we randomly hand-selected six interstitial areas and six airways for high-resolution scans. “Phantom” contours were used to divide tissues into very small (8-µm diameter) circles as previously described (Brown et al, 2015; Brown et al, 2016). Briefly, a blue staining contour was considered a collagen-positive event via trichrome stain.…”

“…Methylation levels in the promoter regions of selected genes ( IFN-γ and Thy-1 ) were measured using pyrosequencing assay with primers designed as previously described (Brown et al, 2015). Briefly, genomic DNA was modified via bisulfite conversion of unmethylated cytosine to uracil using Zymo EZ DNA Methylation kits according to the manufacturer’s protocols (Zymo Research, Orange, CA).…”

Nanomedicine and epigenome. Possible health risks

“…Surprisingly, more genes were epigenetically altered with AuNPs than with CNTs, in contrast with the paradigm that exposure to AuNPs does not induce an adverse biological response (Tabish et al, 2017). Alterations in DNA methylation, corresponding with lung inflammation, induced by the exposure to MWCNTs in C57BL/6 mice were shown by another group (Brown et al, 2016). In this study, promoter methylation of inflammatory genes (IFNG and TNF) correlated with initial cytokine production.…”

Claudin 5 Transcripts Following Acrolein Exposure Affected by Epigenetic Enzyme

“…Aging [23], smoking [24,25], and heavy metal exposure [26,27], acrolein [28,29] have all been associated with changes in the DNA methylome, and with changes in DNMT expression, but the mechanisms by which these changes occur are largely unknown. DNA methyltransferases (DNMTs) such as DNMT1, DNMT3A and DNMT3B contribute to various physiologic and pathologic conditions including embryo implantation [30], cytomegalovirus infection [31], radiation [32], cancer, aging, neural cell differentiation [33].…”