The critical role of epigenetic mechanism in PM2.5-induced cardiovascular diseases

Particulate matter stimulates the NADPH oxidase system via AhR-mediated epigenetic modifications

Stimulation of human keratinocytes with particulate matter 2.5 (PM2.5) elicits complex signaling events, including a rise in the generation of reactive oxygen species (ROS). However, the mechanisms underlying PM2.5-induced ROS production remain unknown. Here, we show that PM2.5-induced ROS production in human keratinocytes is mediated via the NADPH oxidase (NOXs) system and the Ca2+ signaling pathway. PM2.5 treatment increased the expression of NOX1, NOX4, and a calcium-sensitive NOX, dual oxidase 1 (DUOX1), in human epidermal keratinocyte cell line. PM2.5 bound to aryl hydrocarbon receptor (AhR), and this complex bound to promoter regions of NOX1 and DUOX1, suggesting that AhR acted as a transcription factor of NOX1 and DUOX1. PM2.5 increased the transcription of DUOX1 via epigenetic modification. Moreover, a link between DNA demethylase and histone methyltransferase with the promoter regions of DUOX1 led to an elevation in the expression of DUOX1 mRNA. Interestingly, PM2.5 increased NOX4 expression and promoted the interaction of NOX4 and Ca2+ channels within the cytoplasmic membrane or endoplasmic reticulum, leading to Ca2+ release. The increase in intracellular Ca2+ concentration activated DUOX1, responsible for ROS production. Our findings provide evidence for a PM2.5-mediated ROS-generating system network, in which increased NOX1, NOX4, and DUOX1 expression serves as a ROS signal through AhR and Ca2+ activation.

Atmospheric PM2.5 exposure and risk of ischemic heart disease: A systematic review and meta-analysis of observational studies

Fine particulate matter <2.5 μm in diameter (PM2.5) has been validated to associate with cardiovascular diseases (CVD) incidence and mortality. So far, no study has quantitatively evaluated the relationship between the atmospheric PM2.5 exposure and ischemic heart disease (IHD). We conducted a meta-analysis to illustrate the relationship between PM2.5 and IHD. Published articles were systematically searched (until June 2022) from PubMed, EMBASE, Cochrane Library. A random-effect model was performed to summarize the total relative risks (RRs) and 95% confidence intervals (CIs). Meta-analysis was performed using Stata 12.0 software. A total of 28 studies among 23 cohorts (23.38 million individuals and 256256 IHD cases) were included. With PM2.5 increasing 10 μg/m3, the total RRs of IHD incidence and mortality were 1.07 (95% CI: 0.99-1.17), 1.21 (95% CI: 1.15-1.28), respectively. In sub-analyses, our study revealed that the combined RRs of exposure to PM2.5 on IHD mortality in Asian and European population [1.11 (95% CI: 0.93-1.33); 1.06 (95% CI: 1.02-1.11)] were much lower compared with American and Canadian people [1.27 (95% CI: 1.17-1.37); 1.30 (95% CI: 1.24-1.35)]. Furthermore, study duration, size and some adjustments were related with the total RR. Our findings indicated that exposure of an increase in the concentration of atmospheric PM2.5 may increase the risk of IHD incidence and mortality. Further evidence is needed to confirmed the association.

Genome-Wide Profiling of Transcriptome and DNA Methylome in Human Embryonic Stem Cells Exposed to Extractable Organic Matter from PM2.5

Increasing evidence indicates that PM2.5 exposure disrupts early embryonic development, but the mechanisms remain unclear. We hypothesized that PM2.5 cause abnormal embryonic development by interfering with DNA methylation and mRNA expression. In this study, we observed that human embryonic stem cells (hESCs) treated with extractable organic matters (EOM) from PM2.5 concentrations above 100 μg/mL exhibited reduced viability. While EOM within non-cytotoxicity concentrations did not affect the expression levels of pluripotency genes, it did enhance cellular proliferation, as indicated by increased Edu incorporation and the upregulation of cell cycle genes (Cdk2, Mdm2). Additionally, EOM significantly influenced the transcriptome patterns in hESCs. Notably, the differentially expressed genes were found to be significantly enriched in processes such as extracellular matrix organization, cell-cell junction organization, chromatin organization, and DNA methylation. Furthermore, we observed whole genomic-wide DNA methylation changes. Through a cross-analysis of changes in DNA methylation and mRNA expression, we identified an enrichment of terms related to the VEGFR signaling pathway and extracellular matrix. The gene signal transduction networks revealed that crucial hubs were implicated in cell growth and division. In conclusion, our findings demonstrate that PM2.5 induce significant alterations in transcriptome and DNA methylome in hESCs, leading to aberrant cell proliferation. This research provides novel insights into the molecular mechanisms underlying the developmental toxicity of PM2.5.

AHR-mediated m6A RNA methylation contributes to PM2.5-induced cardiac malformations in zebrafish larvae

A growing body of evidence indicates that ambient fine particle matter (PM_2.5) exposure inhibits heart development, but the underlying mechanisms remain elusive. We hypothesized that m⁶A RNA methylation plays an important role in the cardiac developmental toxicity of PM_2.5. In this study, we demonstrated that extractable organic matter (EOM) from PM2.5 significantly decreased global m⁶A RNA methylation levels in the heart of zebrafish larvae, which were restored by the methyl donor, betaine. Betaine also attenuated EOM-induced ROS overgeneration, mitochondrial damage, apoptosis and heart defects. Furthermore, we found that the aryl hydrocarbon receptor (AHR), which was activated by EOM_, directly repressed the transcription of methyltransferases mettl14 and mettl3. EOM also induced genome-wide m⁶A RNA methylation changes, which led us to focus more on the aberrant m⁶A methylation changes that were subsequently alleviated by the AHR inhibitor, CH223191. In addition, we found that the expression levels of traf4a and bbc3, two apoptosis related genes, were upregulated by EOM but restored to control levels by the forced expression of mettl14. Moreover, knockdown of either traf4a or bbc3 attenuated EOM-induced ROS overproduction and apoptosis. In conclusion, our results indicate that PM_2.5 induces m⁶A RNA methylation changes via AHR-mediated mettl14 downregulation, which upregulates traf4a and bbc3, leading to apoptosis and cardiac malformations.

Multi-City Analysis of the Acute Effect of Polish Smog on Cause-Specific Mortality (EP-PARTICLES Study)

Polish smog is a specific type of air pollution present in Eastern Poland, which may cause particularly adverse cardiovascular effects. It is characterized primarily by high concentrations of particulate matter (PM) and different favorable conditions of formation. Our study aimed to assess whether PM and nitrogen dioxide (NO₂) have a short-term impact on mortality due to acute coronary syndrome (ACS) and ischemic stroke (IS). The study covered the years 2016-2020, a total of 6 million person-years from five main cities in Eastern Poland. To evaluate the association between air pollution and cause-specific mortality, a case-crossover study design with conditional logistic regression was used at days with LAG from 0 to 2. We recorded 87,990 all-cause deaths, including 9688 and 3776 deaths due to ACS and IS, respectively. A 10 μg/m³ increase in air pollutants was associated with an increase in mortality due to ACS (PM_2.5 OR = 1.029, 95%CI 1.011-1.047, p = 0.002; PM₁₀ OR = 1.015, 95%CI 1-1.029, p = 0.049) on LAG 0. On LAG 1 we recorded an increase in both IS (PM_2.5 OR = 1.03, 95%CI 1.001-1.058, p = 0.04) and ACS (PM_2.5 OR = 1.028, 95%CI 1.01-1.047, p = 0.003; PM₁₀ OR = 1.026, 95%CI 1.011-1.041, p = 0.001; NO₂ OR = 1.036, 95%CI 1.003-1.07, p = 0.04). There was a strong association between air pollution and cause-specific mortality in women (ACS: PM_2.5 OR = 1.032, 95%CI 1.006-1.058, p = 0.01; PM₁₀ OR = 1.028, 95%CI 1.008-1.05, p = 0.01) and elderly (ACS: PM_2.5 OR = 1.03, 95%CI 1.01-1.05, p = 0.003; PM₁₀ OR = 1.027, 95% CI 1.011-1.043, p < 0.001 and IS: PM_2.5 OR = 1.037, 95%CI 1.007-1.069, p = 0.01; PM₁₀ OR = 1.025, 95%CI 1.001-1.05, p = 0.04). The negative influence of PMs was observed on mortality due to ACS and IS. NO₂ was associated with only ACS-related mortality. The most vulnerable subgroups were women and the elderly.

Unique regulatory roles of ncRNAs changed by PM2.5 in human diseases

PM_2.5 is a type of particulate matter with an aerodynamic diameter smaller than 2.5 µm, and exposure to PM_2.5 can adversely damage human health. PM_2.5 may impair health through oxidative stress, inflammatory reactions, immune function alterations and chromosome or DNA damage. Through increasing in-depth studies, researchers have found that noncoding RNAs (ncRNAs), particularly microRNAs (miRNAs), circular RNAs (circRNAs) as well as long noncoding RNAs (lncRNAs), might play significant roles in PM_2.5-related human diseases via some of the abovementioned mechanisms. Therefore, in this review, we mainly discuss the regulatory function of ncRNAs altered by PM_2.5 in human diseases and summarize the potential molecular mechanisms. The findings reveal that these ncRNAs might induce or promote diseases via inflammation, the oxidative stress response, cell autophagy, apoptosis, cell junction damage, altered cell proliferation, malignant cell transformation, disruption of synaptic function and abnormalities in the differentiation and status of immune cells. Moreover, according to a bioinformatics analysis, the altered expression of potential genes caused by these ncRNAs might be related to the development of some human diseases. Furthermore, some ncRNAs, including lncRNAs, miRNAs and circRNAs, or processes in which they are involved may be used as biomarkers for relevant diseases and potential targets to prevent these diseases. Additionally, we performed a meta-analysis to identify more promising diagnostic ncRNAs as biomarkers for related diseases.

Effects of various environments on epigenetic settings and chromosomal damage

Air pollution is a dominant environmental exposure factor with significant health consequences. Unexpectedly, research in a heavily polluted region of the Czech Republic, with traditional heavy industry, revealed repeatedly the lowest frequency of micronuclei in the season with the highest concentrations of air pollutants including carcinogenic benzo[a]pyrene (B[a]P). Molecular findings have been collected for more than 10 years from various locations of the Czech Republic, with differing quality of ambient air. Preliminary conclusions have suggested adaptation of the population from the polluted locality (Ostrava, Moravian-Silesian Region (MSR)) to chronic air pollution exposure. In this study we utilize the previous findings and, for the first time, investigate micronuclei (MN) frequency by type: (i) centromere positive (CEN+) MN, representing chromosomal losses, and (ii) centromere negative (CEN-) MN representing chromosomal breaks. As previous results indicated differences between populations in the expression of XRCC5, a gene involved in the non-homologous end-joining (NHEJ) repair pathway, possible variations in epigenetic settings in this gene were also investigated. This new research was conducted in two seasons in the groups from two localities with different air quality levels (Ostrava (OS) and Prague (PG)). The obtained new results show significantly lower frequencies of chromosomal breaks in the OS subjects, related to the highest air pollution levels (p < 0.001). In contrast, chromosomal losses were comparable between both groups. In addition, significantly lower DNA methylation was found in 14.3% of the analyzed CpG loci of XRCC5 in the population from OS. In conclusion, the epigenetic adaptation (hypomethylation) in XRCC5 involved in the NHEJ repair pathway in the population from the polluted region, was suggested as a reason for the reduced level of chromosomal breaks. Further research is needed to explore the additional mechanisms, including genetic adaptation.

A Review of the GSTM1 Null Genotype Modifies the Association between Air Pollutant Exposure and Health Problems

Air pollution is one of the significant environmental risks known as the cause of premature deaths. It has deleterious effects on human health, including deteriorating respiratory, cardiovascular, nervous, and endocrine functions. Exposure to air pollution stimulates reactive oxygen species (ROS) production in the body, which can further cause oxidative stress. Antioxidant enzymes, such as glutathione S-transferase mu 1 (GSTM1), are essential to prevent oxidative stress development by neutralizing excess oxidants. When the antioxidant enzyme function is lacking, ROS can accumulate and, thus, cause oxidative stress. Genetic variation studies from different countries show that GSTM1 null genotype dominates the GSTM1 genotype in the population. However, the impact of the GSTM1 null genotype in modifying the association between air pollution and health problem is not yet clear. This study will elaborate on GSTM1's null genotype role in modifying the relationship between air pollution and health problems.

Auto repair workers exposed to PM2.5 particulate matter in Barranquilla, Colombia: telomere length and hematological parameters

Exposure to 2.5 µm particulate matter (PM_2.5) in automotive repair shops is associated with risks to health. We evaluated the effects of occupational exposure to PM_2.5 among auto repair-shop workers. Blood and urine samples were collected from 110 volunteers from Barranquilla, Colombia: 55 active workers and 55 controls. PM_2.5 concentrations were assessed at each of the sampling sites and chemical content was analyzed by SEM-EDS electron microscopy. The biological samples obtained were peripheral blood (hematological profiling, DNA extraction) and urine (malondialdehyde concentration). Telomere length was assessed by qPCR and polymorphisms in the glutathione transferase genes GSTT1 and GSTM1 by PCR-RFLP, with confirmation by allelic exclusion. White blood cell (WBC), lymphocyte (LYM%) and platelet (PLT) counts and the malondialdehyde concentration were higher (4.10 ± 0.93) in the exposed group compared to the control group (1.56 ± 0.96). TL was shorter (5071 ± 891) in the exposed individuals compared to the control group (6271 ± 805). White blood cell (WBC) and platelet counts were positively associated with exposure. Age and TBARS were correlated with TL in exposed individuals. The GSTT1 gene alleles were not in Hardy-Weinberg (H-W) equilibrium. The GSTM1 gene alleles were in H-W equilibrium and allelic exclusion analysis confirmed the presence of heterozygous GSTM1 genotypes. SEM-EDS analysis showed the presence of potentially toxic elements, including Mg, Al, Fe, Mn, Rh, Zn, and Cu. Auto repair shop workers showed effects that may be associated with exposure to mixtures of pollutants present in PM_2.5. The GSTM1 and GSTT1 genes had independent modulatory effects.

Expression levels and network analysis of inflammamiRs in peripheral blood mononuclear cells exposed to DDE "in vitro"

Recent studies have demonstrated that dichlorodiphenyldichloroethylene (DDE) induced a pro-inflammatory condition in peripheral blood mononuclear cells (PBMC). However, the molecular mechanisms implicated in this condition are poorly understood. Therefore, this study aimed to evaluate miR-155, miR-126, and miR-21 expression levels in PBMC exposed "in vitro" to DDE. PBMC were dosed with increasing concentrations of DDE (10-80 µg mL^-1) at different treatment times (0-24 h). The results showed an up-regulation in the expression levels of assessed miRNAs (miR-155, miR-146, and miR-21) after PBMCs were exposed to DDE. Besides, bioinformatic analysis was performed to understand the biological roles of assessed miRNAs. The bioinformatic analysis shows that assessed miRNAs are associated with regulating signaling pathways involved in cancer, apoptosis, cell cycle, inflammation, metabolism, etc. These findings offer new insights into the molecular mechanisms related to the inflammatory processes and their regulation induced by DDE in PBMC exposed "in vitro".

The protective effects of taurine and fish oil supplementation on PM2.5-induced heart dysfunction among aged mice: A random double-blind study

As it is nearly impossible to reduce PM2.5 concentrations in most cities to safe limits in a short period of time, dietary supplementation presents a promising approach for mitigating the adverse effects of PM2.5 exposure. A cross-sectional study showed that the elderly population of Linfen (PM2.5: 102 μg/m3) exhibited significantly lower serum taurine levels, as well as higher oxidative stress levels and cardiovascular health risks, than the corresponding population in Guangzhou (PM2.5: 39 μg/m3). We conducted a random double-blind study on aged mice that employed a "real-world" PM2.5 exposure system to simulate the conditions of Linfen with the aim of investigating the protective effects of taurine and fish oil supplementation on PM2.5-induced heart dysfunction. When compared with the placebo group, supplementation with taurine and fish oil not only maintained normal taurine levels, but also suppressed oxidative stress and inflammation in aged mice subjected to high concentrations of PM2.5. Variations in heart rate, contractile function, cardiac oxidative stress, inflammation and fibrosis among different groups of aged mice were used to clarify the beneficial effects of taurine and fish oil supplementation. Our results not only revealed the protective effects of taurine and fish oil supplementation on heart dysfunction induced by PM2.5 exposure from the aged mice experiments and also provided new means for the elderly to resist PM2.5 pollution at the individual level.

Epigallocatechin Gallate Relieved PM2.5-Induced Lung Fibrosis by Inhibiting Oxidative Damage and Epithelial-Mesenchymal Transition through AKT/mTOR Pathway

Oxidative damage and epithelial-mesenchymal transition (EMT) are main pathological processes leading to the development of PM2.5-induced lung fibrosis. Epigallocatechin gallate (EG), a natural polyphenol extracted from green tea, possesses the ability to combat oxidative stress and inflammation. However, the potential roles of EG in PM2.5-induced lung fibrosis have not been reported yet. In the present study, we investigated whether EG could relieve PM2.5-induced lung injury and fibrosis in vivo and in vitro. To mimic PM2.5-induced lung fibrosis, C57/BL6 mice were intranasally instilled with PM2.5 suspension, and MLE-12 lung epithelial cells were stimulated with PM2.5 (100 μg/mL) in vitro. The results showed that intragastric administration of EG (20 mg/kg/d or 80 mg/kg/d for 8 weeks) significantly prevented lung injury, inflammation, and oxidative stress in PM2.5-induced mice, apart from inhibiting collagen deposition. Additionally, EG treatment also suppressed the activation of AKT/mTOR signaling pathway in lung tissues challenged with PM2.5. In vitro experiments further demonstrated that EG treatment could enhance cell viability in a concentration-dependent manner in PM2.5-treated MLE-12 lung epithelial cells. Also, the overexpression of constitutively active AKT could offset the inhibitory effects of EG on EMT and oxidative stress in PM2.5-treated MLE-12 lung epithelial cells. Finally, AKT overexpression also blocked the inhibitory effect of EG on the phosphorylation of mTOR in PM2.5-treated MLE-12 lung epithelial cells. In conclusion, EG could improve PM2.5-induced lung fibrosis by decreasing oxidative damage and EMT through AKT/mTOR pathway, which might be a potential candidate for the treatment of PM2.5-induced lung fibrosis.