Aberrant mitochondrial DNA methylation and declined pulmonary function in a population with polycyclic aromatic hydrocarbon composition in particulate matter

Effects of PM2.5 and high-fat diet on glucose and lipid metabolisms and role of MT-COX3 methylation in male rats

Both fine particulate matter (PM2.5) and high-fat diet (HFD) can cause changes in glucose and lipid metabolisms; however, the mechanism of their combined effects on glucose and lipid metabolisms is still unclear. This study aimed to investigate the effects of PM2.5 and HFD co-exposure on glucose and lipid metabolisms and mitochondrial DNA methylation in Wistar rats. PM2.5 and HFD co-treatment led to an increase in fasting blood glucose levels, an alteration in glucose tolerance, and a decrease in high density lipoprotein cholesterol (HDL-C) levels in Wistar rats. In the homeostasis model assessment (HOMA), HOMA-insulin resistance (HOMA-IR) increased and HOMA-insulin sensitivity (HOMA-IS) and HOMA-β cell function (HOMA-β) decreased in rats co-exposed to PM2.5 and HFD. Additionally, superoxide dismutase (SOD) and malondialdehyde (MDA) levels were increased, and interleukin-6 (IL-6) and interleukin-10 (IL-10) mRNA expressions were upregulated in the brown adipose tissue following PM2.5 and HFD co-exposure. Bisulfite pyrosequencing was used to detect the methylation levels of mitochondrially-encoded genes (MT-COX1, MT-COX2 and MT-COX3), and MT-COX3 was hypermethylated in the PM2.5 and HFD co-exposure group. Moreover, MT-COX3-Pos.2 mediated 36.41 % (95 % CI: -27.42, -0.75) of the total effect of PM2.5 and HFD exposure on HOMA-β. Our study suggests that PM2.5 and HFD co-exposure led to changes in glucose and lipid metabolisms in rats, which may be related to oxidative stress and inflammatory responses, followed by mitochondrial stress leading to MT-COX3 hypermethylation. Moreover, MT-COX3-Pos.2 was found for the first time as a mediator in the impact of co-exposure to PM2.5 and HFD on β-cell function. It could serve as a potential biomarker, offering fresh insights into the prevention and treatment of metabolic diseases.

Unravelling the signaling power of pollutants

Exposure to environmental pollutants contributes to diverse pathologies, including pulmonary disease, lower respiratory infections, cancer, and stroke. Pollutants' entry can occur through inhalation, traversing endothelial and epithelial barriers, and crossing the blood-brain barrier, leading to a wide distribution throughout the human body via systemic circulation. Pollutants cause cellular damage by multiple mechanisms encompassing oxidative stress, mitochondrial dysfunction, (neuro)inflammation, and protein instability/proteotoxicity. Sensing pollutants has added a new dimension to disease progression and drug failure. Understanding the molecular pathways and potential receptor binding/signaling that underpin 'sensing' could contribute to ways to combat the detrimental effects of pollutants. We highlight key points of pollutant signaling, crosstalk with receptors acting as drug targets for chronic diseases, and discuss the potential for future therapeutics.

Toxicomethylomics revisited: A state-of-the-science review about DNA methylation modifications in blood cells from workers exposed to toxic agents

Introduction

Epigenetic marks have been proposed as early changes, at the subcellular level, in disease development. To find more specific biomarkers of effect in occupational exposures to toxicants, DNA methylation studies in peripheral blood cells have been performed. The goal of this review is to summarize and contrast findings about DNA methylation in blood cells from workers exposed to toxicants.

Methods

A literature search was performed using PubMed and Web of Science. After first screening, we discarded all studies performed in vitro and in experimental animals, as well as those performed in other cell types other than peripheral blood cells. Results: 116 original research papers met the established criteria, published from 2007 to 2022. The most frequent investigated exposures/labor group were for benzene (18.9%) polycyclic aromatic hydrocarbons (15.5%), particulate matter (10.3%), lead (8.6%), pesticides (7.7%), radiation (4.3%), volatile organic compound mixtures (4.3%), welding fumes (3.4%) chromium (2.5%), toluene (2.5%), firefighters (2.5%), coal (1.7%), hairdressers (1.7%), nanoparticles (1.7%), vinyl chloride (1.7%), and others. Few longitudinal studies have been performed, as well as few of them have explored mitochondrial DNA methylation. Methylation platforms have evolved from analysis in repetitive elements (global methylation), gene-specific promoter methylation, to epigenome-wide studies. The most reported observations were global hypomethylation as well as promoter hypermethylation in exposed groups compared to controls, while methylation at DNA repair/oncogenes genes were the most studied; studies from genome-wide studies detect differentially methylated regions, which could be either hypo or hypermethylated.

Discussion

Some evidence from longitudinal studies suggest that modifications observed in cross-sectional designs may be transitory; then, we cannot say that DNA methylation changes are predictive of disease development due to those exposures.

Conclusion

Due to the heterogeneity in the genes studied, and scarcity of longitudinal studies, we are far away from considering DNA methylation changes as biomarkers of effect in occupational exposures, and nor can we establish a clear functional or pathological correlate for those epigenetic modifications associated with the studied exposures.

The Effects and Pathogenesis of PM2.5 and Its Components on Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD), a heterogeneous disease, is the leading cause of death worldwide. In recent years, air pollution, especially particulate matter (PM), has been widely studied as a contributing factor to COPD. As an essential component of PM, PM2.5 is associated with COPD prevalence, morbidity, and acute exacerbations. However, the specific pathogenic mechanisms were still unclear and deserve further research. The diversity and complexity of PM2.5 components make it challenging to get its accurate effects and mechanisms for COPD. It has been determined that the most toxic PM2.5 components are metals, polycyclic aromatic hydrocarbons (PAHs), carbonaceous particles (CPs), and other organic compounds. PM2.5-induced cytokine release and oxidative stress are the main mechanisms reported leading to COPD. Nonnegligibly, the microorganism in PM 2.5 may directly cause mononuclear inflammation or break the microorganism balance contributing to the development and exacerbation of COPD. This review focuses on the pathophysiology and consequences of PM2.5 and its components on COPD.