MicroRNAs are associated with blood-pressure effects of exposure to particulate matter: Results from a mediated moderation analysis

Aging, longevity, and the role of environmental stressors: a focus on wildfire smoke and air quality

Aging is a complex biological process involving multiple interacting mechanisms and is being increasingly linked to environmental exposures such as wildfire smoke. In this review, we detail the hallmarks of aging, emphasizing the role of telomere attrition, cellular senescence, epigenetic alterations, proteostasis, genomic instability, and mitochondrial dysfunction, while also exploring integrative hallmarks - altered intercellular communication and stem cell exhaustion. Within each hallmark of aging, our review explores how environmental disasters like wildfires, and their resultant inhaled toxicants, interact with these aging mechanisms. The intersection between aging and environmental exposures, especially high-concentration insults from wildfires, remains under-studied. Preliminary evidence, from our group and others, suggests that inhaled wildfire smoke can accelerate markers of neurological aging and reduce learning capabilities. This is likely mediated by the augmentation of circulatory factors that compromise vascular and blood-brain barrier integrity, induce chronic neuroinflammation, and promote age-associated proteinopathy-related outcomes. Moreover, wildfire smoke may induce a reduced metabolic, senescent cellular phenotype. Future interventions could potentially leverage combined anti-inflammatory and NAD + boosting compounds to counter these effects. This review underscores the critical need to study the intricate interplay between environmental factors and the biological mechanisms of aging to pave the way for effective interventions.

Human milk EV-miRNAs: a novel biomarker for air pollution exposure during pregnancy

Exposure to ambient and near-roadway air pollution during pregnancy has been linked with several adverse health outcomes for pregnant women and their babies. Emerging research indicates that microRNA (miRNA) expression can be altered by exposure to air pollutants in a variety of tissues. Additionally, miRNAs from breast tissue and circulating miRNAs have previously been proposed as a biomarker for breast cancer diagnosis and prognosis. Therefore, this study sought to evaluate the associations between pregnancy exposures to ambient (PM10, PM2.5, NO2, O3) and near-roadway air pollution (total NOx, freeway NOx, non-freeway NOx) with breast milk extracellular vesicle miRNA (EV-miRNA), measured at 1-month postpartum, in a cohort of 108 Latina women living in Southern California. We found that PM10 exposure during pregnancy was positively associated with hsa-miR-200c-3p, hsa-miR-200b-3p, and hsa-let-7c-5p, and was negatively associated with hsa-miR-378d. We also found that pregnancy PM2.5 exposure was positively associated with hsa-miR-200c-3p and hsa-miR-200b-3p. First and second trimester exposure to PM10 and PM2.5 was associated with several EV-miRNAs with putative messenger RNA targets related to cancer. This study provides preliminary evidence that air pollution exposure during pregnancy is associated with human milk EV-miRNA expression.

Effects of Controlled Ozone Exposure on Circulating microRNAs and Vascular and Coagulation Biomarkers: A Mediation Analysis

Exposure to ozone (O3) is associated with adverse respiratory and cardiovascular outcomes. Alterations in circulating microRNAs (miRNAs) may contribute to the adverse vascular effects of O3 exposure through inter-cellular communication resulting in post-transcriptional regulation of messenger RNAs by miRNAs. In this study, we investigated whether O3 exposure induces alterations in circulating miRNAs that can mediate effects on downstream vascular and coagulation biomarkers. Twenty-three healthy male adults were exposed on successive days to filtered air and 300 ppb O3 for 2 h. Circulating miRNA and protein biomarkers were quantified after each exposure session. The data were subjected to mixed-effects model and mediation analyses for the statistical analyses. The results showed that the expression level of multiple circulating miRNAs (e.g., miR-19a-3p, miR-34a-5p) was significantly associated with O3 exposure. Pathway analysis showed that these miRNAs were predictive of changing levels of downstream biomarkers [e.g., D-dimer, C-reactive protein, tumor necrosis factor α (TNFα)]. Mediation analysis showed that miR-19a-3p may be a significant mediator of O3-exposure-induced changes in blood TNFα levels [0.08 (0.01, 0.15), p = 0.02]. In conclusion, this preliminary study showed that O3 exposure of healthy male adults resulted in changes in circulating miRNAs, some of which may mediate vascular effects of O3 exposure.

The potential role of plasma miR-4301 in PM2.5 exposure-associated lung function reduction

The effect of PM_2.5 exposure on lung function reduction has been well-documented, but the underlying mechanism remains unclear. MiR-4301 may be involved in regulating pathways related to lung injury/repairment, and this study aimed to explore the potential role of miR-4301 in PM_2.5 exposure-associated lung function reduction. A total of 167 Wuhan community nonsmokers were included in this study. Lung function was measured and personal PM_2.5 exposure moving averages were evaluated for each participant. Plasma miRNA was determined by real-time polymerase chain reaction. A generalized linear model was conducted to assess the relationships among personal PM_2.5 moving average concentrations, lung function, and plasma miRNA. The mediation effect of miRNA on the association of personal PM_2.5 exposure with lung function reduction was estimated. Finally, we performed pathway enrichment analysis to predict the underlying pathways of miRNA in lung function reduction from PM_2.5 exposure. We found that each 10 μg/m³ increase in the 7-day personal PM_2.5 moving average concentration (Lag0-7) was related to a 46.71 mL, 1.15%, 157.06 mL/s, and 188.13 mL/s reductions in FEV₁, FEV₁/FVC, PEF, and MMF, respectively. PM_2.5 exposure was negatively associated with plasma miR-4301 expression levels in a dose‒response manner. Additionally, each 1% increase in miR-4301 expression level was significantly associated with a 0.36 mL, 0.01%, 1.14 mL/s, and 1.28 mL/s increases in FEV₁, FEV₁/FVC, MMF, and PEF, respectively. Mediation analysis further revealed that decreased miR-4301 mediated 15.6% and 16.8% of PM_2.5 exposure-associated reductions in FEV₁/FVC and MMF, respectively. Pathway enrichment analyses suggested that the wingless related-integration site (Wnt) signaling pathway might be one of the pathways regulated by miR-4301 in the reduction of lung function from PM_2.5 exposure. In brief, personal PM_2.5 exposure was negatively associated with plasma miR-4301 or lung function in a dose‒response manner. Moreover, miR-4301 partially mediated the lung function reduction associated with PM_2.5 exposure.

Air Pollution: Role of Extracellular Vesicles-Derived Non-Coding RNAs in Environmental Stress Response

Air pollution has increased over the years, causing a negative impact on society due to the many health-related problems it can contribute to. Although the type and extent of air pollutants are known, the molecular mechanisms underlying the induction of negative effects on the human body remain unclear. Emerging evidence suggests the crucial involvement of different molecular mediators in inflammation and oxidative stress in air pollution-induced disorders. Among these, non-coding RNAs (ncRNAs) carried by extracellular vesicles (EVs) may play an essential role in gene regulation of the cell stress response in pollutant-induced multiorgan disorders. This review highlights EV-transported ncRNAs' roles in physiological and pathological conditions, such as the development of cancer and respiratory, neurodegenerative, and cardiovascular diseases following exposure to various environmental stressors.

Intermediate and long-term exposure to air pollution and temperature and the extracellular microRNA profile of participants in the normative aging study (NAS)

BACKGROUND

The molecular effects of intermediate and long-term exposure to air pollution and temperature, such as those on extracellular microRNA (ex-miRNA) are not well understood but may have clinical consequences.

OBJECTIVES

To assess the association between exposure to ambient air pollution and temperature and ex-miRNA profiles.

METHODS

Our study population consisted of 734 participants in the Normative Aging Study (NAS) between 1999 and 2015. We used high-resolution models to estimate four-week, eight-week, twelve-week, six-month, and one-year moving averages of PM_2.5, O₃, NO₂, and ambient temperature based on geo-coded residential addresses. The outcome of interest was the extracellular microRNA (ex-miRNA) profile of each participant over time. We used a longitudinal quantile regression approach to estimate the association between the exposures and each ex-miRNA. Results were corrected for multiple comparisons and ex-miRNAs that were still significantly associated with the exposures were further analyzed using KEGG pathway analysis and Ingenuity Pathway Analysis.

RESULTS

We found 151 significant associations between levels of PM_2.5, O₃, NO₂, and ambient temperature and 82 unique ex-miRNAs across multiple quantiles. Most of the significant results were associations with intermediate-term exposure to O₃, long-term exposure to PM_2.5, and both intermediate and long-term exposure to ambient temperature. The exposures were most often associated with the 75th and 90th percentile of the outcomes. Pathway analyses of significant ex-miRNAs revealed their involvement in biological pathways involving cell function and communication as well as clinical diseases such as cardiovascular disease, respiratory disease, and neurological disease.

CONCLUSION

Our results show that intermediate and long-term exposure to all our exposures of interest were associated with changes in the ex-miRNA profile of study participants. Further studies on environmental risk factors and ex-miRNAs are warranted.

The relationship between residential exposure to atmospheric pollution and circulating miRNA in adults living in an urban area in northern France

INTRODUCTION

MicroRNAs are epigenetic regulatory factors capable of silencing the expression of target genes and might mediate the effects of air pollution on health. The objective of the present population-based study was to investigate the association between microRNA expression and long-term, residential exposure to atmospheric PM₁₀ and NO₂.

METHOD

We included 998 non-smoking adult participants from the cross-sectional ELISABET survey (2010-2014) in the Lille urban area of France. The mean residential annual pollution levels were estimated with an atmospheric dispersion modelling system. Ten microRNAs were selected on the basis of the literature data, together with two housekeeping microRNAs (miR-93-5p and miR-191-5p) and were quantified with RT-qPCRs. Multivariate linear regression models were used to study the association between microRNAs and air pollution. The threshold for statistical significance (after correction for the FDR) was set to p < 0.1.

RESULTS

The mean annual exposure between 2011 and the year of inclusion was 26.4 ± 2.0 µg/m³ for PM₁₀ and 24.7 ± 5.1 µg/m³ for NO₂. Each 2 µg/m³ increment in PM₁₀ exposure was associated with an 8.6% increment (95%CI [3.1; 14.3]; p_FDR = 0.019) in miR-451a expression. A 5 µg/m³ increment in NO₂ exposure was associated with a 5.3% increment ([0.7; 10]; p_FDR = 0.056) in miR451a expression, a 3.6% decrement (95%CI [-6.1; -1.1]; p_FDR = 0.052) in miR-223-3p expression, a 3.8% decrement (95%CI[-6.8; -0.7]; p_FDR = 0.079) in miR-28-3p expression, a 4.3% decrement (95%CI [-7.7; -0.8]; p_FDR = 0.055) in miR-146a-5p expression, and a 4.0% decrement (95% CI[-7.4; -0.4]; p_FDR = 0.059) in miR-23a-5p expression. The difference between the two housekeeping microRNAs miR-93-5p and miR-191-5p was also associated with PM₁₀ and NO₂ exposure.

CONCLUSION

Our results suggest that circulating miRNAs are potentially valuable biomarkers of the effects of air pollution.

Prenatal fine particulate matter exposure associated with placental small extracellular vesicle derived microRNA and child neurodevelopmental delays

BACKGROUND AND AIMS

Prenatal fine particulate matter (PM_2.5) exposure has been linked to adverse neurodevelopment. However, epidemiological evidence remains inconclusive and little information about the effects of various PM_2.5 components on child neurodevelopment is currently known. The underlying mechanism was also not elucidated. The study aimed to evaluate the effects of PM_2.5 and components exposure on child neurodevelopmental delays and the role of placental small extracellular vesicles (sEVs)-derived miRNAs in the associations.

METHODS

We included 267 mother-child pairs in this analysis. Prenatal PM_2.5 and components (i.e. elements, water-soluble ions, and PAHs) exposure during three trimesters were monitored through personal PM_2.5 sampling. Child neurodevelopment at 2, 6, and 12 months old were evaluated by Ages and Stages Questionnaire (ASQ). We isolated sEVs from placental tissue to analyze the change of sEVs-derived miRNAs in response to PM_2.5. Associations between the PM_2.5-associated miRNAs and child neurodevelopment were evaluated using multivariate linear regression models.

RESULTS

The PM_2.5 exposure levels in the three trimesters range from 2.51 to 185.21 μg/m³. Prenatal PM_2.5 and the components of Pb, Al, V and Ti exposure in the second and third trimester were related to decreased ASQ scores communication, problem-solving and personal-social domains in children aged 2 or 6 months. RNA sequencing identified fifteen differentially expressed miRNAs. The miR-101-3p and miR-520d-5p were negatively associated with PM_2.5 and Pb component. miR-320a-3p expression was positively associated with PM_2.5 and V component. Meanwhile, the miR-320a-3p was associated with decreased ASQ scores, as reflected by ASQ-T (β: -2.154, 95 % CI: -4.313, -0.516) and problem-solving domain (β: -0.605, 95 % CI: -1.111, -0.099) in children aged 6 months.

CONCLUSION

Prenatal exposure to PM_2.5 and its Pb, Al, V & Ti component were associated with infant neurodevelopmental delays. The placenta sEVs derived miRNAs, especially miR-320a-3p, might contribute to an increased risk of neurodevelopmental delays.

Circulating microRNAs as putative mediators in the association between short-term exposure to ambient air pollution and cardiovascular biomarkers

BACKGROUND

Exposure to ambient air pollution is associated with increased cardiovascular morbidity and mortality. Circulating microRNAs (miRNAs) may mediate cardiovascular effects of exposure to air pollution. This study aims to investigate whether circulating miRNAs mediate the associations between short-term human exposure to ambient air pollution and cardiovascular biomarkers.

METHODS

Twenty-four healthy adults residing in the Research Triangle area of North Carolina, USA were enrolled between December 2016 and July 2019. Circulating miRNAs, protein, and lipid biomarkers were assessed repeatedly for 3 sessions separated by at least 7 days. Linear mixed-effects models were used to assess the associations between air pollutant concentrations obtained from nearby air quality monitoring stations and miRNAs controlling for covariates including omega-3 index, relative humidity, and temperature. miRNAs that were significantly altered were then matched with protein or blood lipid biomarkers using either Ingenuity Pathway Analysis or a literature search. A mediation analysis was performed to test the statistical significance of miRNA's mediating effects between exposure to air pollution and cardiovascular biomarkers.

RESULTS

Short-term exposure to ambient fine particulate matter (PM_2.5), ozone (O₃), and nitrogen dioxide (NO₂) was associated with changes in 11, 9, and 24 circulating miRNAs, respectively. Pathway analysis showed that several miRNAs including miR-125b-5p, miR-144-5p, miR-26a-5p, and miR-34a-5p may mediate the effects of air pollutant exposure on the changes of downstream protein / lipid biomarkers including serum amyloid A (SAA), C-reactive protein (CRP), soluble vascular adhesive molecules 1 (sICAM1), total cholesterol, and high-density lipoproteins (HDL). Mediation analysis showed that only miR-26a-5p significantly mediated air pollutant (PM_2.5 and NO₂)-induced effects on blood CRP and total cholesterol levels. For example, 34.1% of PM_2.5-associated changes in CRP were significantly mediated by miR-26a-5p at lag4 [indirect effects, 0.06 (0.02, 0.10), P = 0.005]. Similarly, the proportions of indirect effects of miR-26a-5p on the association between NO₂ exposure and CRP were 46.8% at lag2 [0.06 (0.02, 0.11), P = 0.003], 61.2% at lag3 [0.05 (0.00, 0.09), P = 0.04], and 30.8% at 5-day moving average [0.06 (0.02, 0.10), P = 0.01]. In addition, omega-3 index may be a significant modifying factor of the mediated effects of miRNAs.

CONCLUSIONS

This study demonstrates that short-term exposure to ambient PM_2.5, O₃, and NO₂ was associated with specific circulating miRNAs, and some of which may mediate their effects on the downstream inflammation and blood lipid markers.

Air pollution and molecular changes in age-related diseases

Assessment of the impact that air contaminants have on health is difficult as this is a complex mixture of substances that varies depending on the time and place. There are many studies on the association between air pollution and increased morbidity and mortality. Before the effect of polluted air is manifested at the level of the organs, an impact can be observed at the molecular level. These include some new biomarkers, like a shortening of the mean telomere length in DNA, dysregulation of gene expression caused by microRNA levels or a variation in the copy number of mitochondrial DNA. These changes may predispose individuals to premature development of age-related diseases and consequently to shortening of life. The common attribute, shared by changes at the molecular level and the development of diseases, is the presence of oxidative stress.

Association between long term exposure to particulate matter and incident hypertension in Spain

Exposure to air particulate matter has been linked with hypertension and blood pressure levels. The metabolic risks of air pollution could vary according to the specific characteristics of each area, and has not been sufficiently evaluated in Spain. We analyzed 1103 individuals, participants in a Spanish nationwide population based cohort study (di@bet.es), who were free of hypertension at baseline (2008-2010) and completed a follow-up exam of the cohort (2016-2017). Cohort participants were assigned air pollution concentrations for particulate matter < 10 μm (PM₁₀) and < 2.5 μm (PM_2.5) during follow-up (2008-2016) obtained through modeling combined with measurements taken at air quality stations (CHIMERE chemistry-transport model). Mean and SD concentrations of PM₁₀ and PM_2.5 were 20.17 ± 3.91 μg/m³ and 10.83 ± 2.08 μg/m³ respectively. During follow-up 282 cases of incident hypertension were recorded. In the fully adjusted model, compared with the lowest quartile of PM_10, the multivariate weighted ORs (95% CIs) for developing hypertension with increasing PM₁₀ exposures were 0.82 (0.59-1.14), 1.28 (0.93-1.78) and 1.45 (1.05-2.01) in quartile 2, 3 and 4 respectively (p for a trend of 0.003). The corresponding weighted ORs according to PM_2.5 exposures were 0.80 (0.57-1.13), 1.11 (0.80-1.53) and 1.48 (1.09-2.00) (p for trend 0.004). For each 5-μg/m³ increment in PM₁₀ and PM_2.5 concentrations, the odds for incident hypertension increased 1.22 (1.06-1.41) p = 0.007 and 1.39 (1.07-1.81) p = 0.02 respectively. In conclusion, our study contributes to assessing the impact of particulate pollution on the incidence of hypertension in Spain, reinforcing the need for improving air quality as much as possible in order to decrease the risk of cardiometabolic disease in the population.

Air pollution-induced epigenetic changes: disease development and a possible link with hypersensitivity pneumonitis

Air pollution is a serious threat to our health and has become one of the major causes of many diseases including cardiovascular disease, respiratory disease, and cancer. The association between air pollution and various diseases has long been a topic of research interest. However, it remains unclear how air pollution actually impacts health by modulating several important cellular functions. Recently, some evidence has emerged about air pollution-induced epigenetic changes, which are linked with the etiology of various human diseases. Among several epigenetic modifications, DNA methylation represents the most prominent epigenetic alteration underlying the air pollution-induced pathogenic mechanism. Several other types of epigenetic changes, such as histone modifications, miRNA, and non-coding RNA expression, have also been found to have been linked with air pollution. Hypersensitivity pneumonitis (HP), one of the most prevalent forms of interstitial lung diseases (ILDs), is triggered by the inhalation of certain organic and inorganic substances. HP is characterized by inflammation in the tissues around the lungs' airways and may lead to irreversible lung scarring over time. This review, in addition to other diseases, attempts to understand whether certain pollutants influence HP development through such epigenetic modifications.

Impact of Nutritional Epigenetics in Essential Hypertension: Targeting microRNAs in the Gut-Liver Axis

PURPOSE OF REVIEW

To review the current knowledge on interactions between dietary factors and microRNAs (miRNAs) in essential hypertension (EH) pathogenesis.

RECENT FINDINGS

There exists an integration of maintenance signals generated by genetic, epigenetic, immune, and environmental (e.g., dietary) factors that work to sustain balance in the gut-liver axis. It is well established that an imbalance in this complex, intertwined system substantially increases the risk for EH. As such, pertinent research has been taken to decipher how each signal operates in isolation and together in EH progression. Recent literature indicates that both macro- and micronutrients interrupt regulatory miRNA expressions and thus, alter multiple cellular processes that contribute to EH and its comorbidities. We highlight how carbohydrates, lipids, proteins, salt, and potassium modify miRNA signatures during EH. The disruption in miRNA expression can negatively impact communication systems such as over activating the renin-angiotensin-aldosterone system, modulating the vascular smooth muscle cell phenotype, and promoting angiogenesis to favor EH. We also delineate the prognostic value of miRNAs in EH and discuss the pros and cons of surgical vs dietary prophylactic approaches in EH prevention. We propose that dietary-dependent perturbation of the miRNA profile is one mechanism within the gut-liver axis that dictates EH development.

The Impact of Air Pollution Exposure on the MicroRNA Machinery and Lung Cancer Development

Small non-coding RNA molecules (miRNAs) play an important role in the epigenetic regulation of gene expression. As these molecules have been repeatedly implicated in human cancers, they have been suggested as biomarkers of the disease. Additionally, miRNA levels have been shown to be affected by environmental pollutants, including airborne contaminants. In this review, we searched the current literature for miRNAs involved in lung cancer, as well as miRNAs deregulated as a result of exposure to air pollutants. We then performed a synthesis of the data and identified those molecules commonly deregulated under both conditions. We detected a total of 25 miRNAs meeting the criteria, among them, miR-222, miR-21, miR-126-3p, miR-155 and miR-425 being the most prominent. We propose these miRNAs as biomarkers of choice for the identification of human populations exposed to air pollution with a significant risk of developing lung cancer.

Environmental Factors Such as Noise and Air Pollution and Vascular Disease

Significance: According to the World Health Organization, noncommunicable diseases are the globally leading cause of mortality. Recent Advances: About 71% of 56 million deaths that occurred worldwide are due to noncommunicable cardiovascular risk factors, including tobacco smoking, unhealthy diets, lack of physical activity, overweight, arterial hypertension, diabetes, and hypercholesterolemia, which can be either avoided or substantially reduced. Critical Issues: Thus, it is estimated that 80% of premature heart disease, stroke, and diabetes can be prevented. More recent evidence indicates that environmental stressors such as noise and air pollution contribute significantly to the global burden of cardiovascular disease. In the present review, we focus primarily on important environmental stressors such as transportation noise and air pollution. We discuss the pathophysiology of vascular damage caused by these environmental stressors, with emphasis on early subclinical damage of the vasculature such as endothelial dysfunction and the role of oxidative stress. Future Directions: Lower legal thresholds and mitigation measures should be implemented and may help to prevent vascular damage.

Role of non-coding-RNAs in response to environmental stressors and consequences on human health

Environmental risk factors, including physicochemical agents, noise and mental stress, have a considerable impact on human health. This environmental exposure may lead to epigenetic reprogramming, including changes in non-coding RNAs (ncRNAs) signatures, which can contribute to the pathophysiology state. Oxidative stress is one of the results of this environmental disturbance by modifying cellular processes such as apoptosis, signal transduction cascades, and DNA repair mechanisms. In this review, we delineate environmental risk factors and their influence on (ncRNAs) in connection to disease. We focus on well-studied miRNAs and analyze the novel roles of long-non-coding-RNAs (lncRNAs). We discuss commonly regulated lncRNAs after exposure to different stressors, such as UV, heavy metals and pesticides among others, and the potential role of these lncRNA as exposure biomarkers, epigenetic regulators and potential therapeutic targets to diminish the deleterious secondary response to environmental agents.

•

Environmental stressors induce epigenetic changes that lead to long-lasting gene expression changes and pathology development.

•

NcRNAs, miRNAs and lncRNAs, are epigenetic modifiers susceptible to changes in expression after environmental insults .

•

LncRNAs influence cell function partnering with other biomolecules such as proteins, DNA, RNA or other ncRNAs.

•

LncRNA dysregulation affects cell development, carcinogenesis, vascular disease and neurodegenerative disorders.

•

ncRNA signatures can be potentially used as biomarkers to identify exposure to specific environmental stressors.

microRNAs expression in relation to particulate matter exposure: A systematic review

MicroRNAs (miRNAs) are a class of small, non-coding RNAs with a post-transcriptional regulatory function on gene expression and cell processes, including proliferation, apoptosis and differentiation. In recent decades, miRNAs have attracted increasing interest to explore the role of epigenetics in response to air pollution. Air pollution, which always contains kinds of particulate matters, are able to reach respiratory tract and blood circulation and then causing epigenetics changes. In addition, extensive studies have illustrated that miRNAs serve as a bridge between particulate matter exposure and health-related effects, like inflammatory cytokines, blood pressure, vascular condition and lung function. The purpose of this review is to summarize the present knowledge about the expression of miRNAs in response to particulate matter exposure. Epidemiological and experimental studies were reviewed in two parts according to the size and source of particles. In this review, we also discussed various functions of the altered miRNAs and predicted potential biological mechanism participated in particulate matter-induced health effects. More rigorous studies are worth conducting to understand contribution of particulate matter on miRNAs alteration and the etiology between environmental exposure and disease development.

Air pollution associated epigenetic modifications: Transgenerational inheritance and underlying molecular mechanisms

Air pollution is one of the leading causes of deaths in Southeast Asian countries including India. Exposure to air pollutants affects vital cellular mechanisms and is intimately linked with the etiology of a number of chronic diseases. Earlier work from our laboratory has shown that airborne particulate matter disturbs the mitochondrial machinery and causes significant damage to the epigenome. Mitochondrial reactive oxygen species possess the ability to trigger redox-sensitive signaling mechanisms and induce irreversible epigenomic changes. The electrophilic nature of reactive metabolites can directly result in deprotonation of cytosine at C-5 position or interfere with the DNA methyltransferases activity to cause alterations in DNA methylation. In addition, it also perturbs level of cellular metabolites critically involved in different epigenetic processes like acetylation and methylation of histone code and DNA hypo or hypermethylation. Interestingly, these modifications may persist through downstream generations and result in the transgenerational epigenomic inheritance. This phenomenon of subsequent transfer of epigenetic modifications is mainly associated with the germ cells and relies on the germline stability of the epigenetic states. Overall, the recent literature supports, and arguably strengthens, the contention that air pollution might contribute to transmission of epimutations from gametes to zygotes by involving mitochondrial DNA, parental allele imprinting, histone withholding and non-coding RNAs. However, larger prospective studies using innovative, integrated epigenome-wide metabolomic strategy are highly warranted to assess the air pollution induced transgenerational epigenetic inheritance and associated human health effects.

The Impact of Air Pollution on Our Epigenome: How Far Is the Evidence? (A Systematic Review)

PURPOSE OF REVIEW

This systematic review evaluated existing evidence linking air pollution exposure in humans to major epigenetic mechanisms: DNA methylation, microRNAs, long noncoding RNAs, and chromatin regulation.

RECENT FINDINGS

Eighty-two manuscripts were eligible, most of which were observational (85%), conducted in adults (66%) and based on DNA methylation (79%). Most observational studies, except panel, demonstrated modest effects of air pollution on the methylome. Panel and experimental studies revealed a relatively large number of significant methylome alterations, though based on smaller sample sizes. Particulate matter levels were positively associated in several studies with global or LINE-1 hypomethylation, a hallmark of several diseases, and with decondensed chromatin structure. Several air pollution species altered the DNA methylation clock, inducing accelerated biological aging. The causal nature of identified associations is not clear, however, especially that most originate from countries with low air pollution levels. Existing evidence, gaps, and perspectives are highlighted herein.

Extracellular vesicle-enriched microRNAs interact in the association between long-term particulate matter and blood pressure in elderly men

BACKGROUND

Several studies have shown that exposure to particulate matter (PM) may lead to increased systemic blood pressure, but the underlying biological mechanisms remain unknown. Emerging evidence shows that extracellular vesicle-enriched miRNAs (evmiRNAs) are associated with PM exposure and cardiovascular risk. In this study, we investigated the role of evmiRNAs in the association between PM and blood pressure, as well as their epigenetic regulation by DNA methylation.

METHODS

Participants (n = 22, men) were randomly selected from the Veterans Affairs Normative Aging Study (NAS). Long-term (1-year and 6-month average) PM_2.5 exposure was estimated at 1 × 1-km resolution using spatio-temporal prediction models and BC was estimated using validated time varying land use regression models. We analyzed 31 evmiRNAs detected in ≥ 90% of all individuals and for statistical analysis, we used mixed effects models with random intercept adjusted for age, body mass index, smoking, C-reactive protein, platelets, and white blood cells.

RESULTS

We found that per each 2-standard deviations increase in 6-month PM_2.5 ambient levels, there was an increase in 0.19 mm Hg (95% Confidence Interval [95%CI]: 0.11, 0.28 mmHg; p < 0.001) in systolic blood pressure (SBP). Per each 2-standard deviations increase in 1-year PM_2.5 levels, there was an increase in 0.11 mm Hg (95% Confidence Interval [95% CI]: 0.03, 0.19 mmHg; p = 0.012) in SBP in older male individuals. We also found that both miR-199a/b (β = 6.13 mmHg; 95% CI: 0.87, 11.39; p_interaction = 0.07) and miR-223-3p (β = 30.17 mmHg; 95% CI: 11.96, 48.39 mmHg; p_interaction = 0.01) modified the association between 1-year PM_2.5 and SBP. When exploring DNA methylation as a potential mechanism that could epigenetically regulate expression of evmiRNAs, we found that PM_2.5 ambient levels were negatively associated with DNA methylation levels at CpG (cg23972892) near the enhancer region of miR-199a/b (β = -13.11; 95% CI: -17.70, -8.52; p_Bonferroni< 0.01), but not miR-223-3p.

CONCLUSIONS

Our findings suggest that expression of evmiRNAs may be regulated by DNA methylation in response to long-term PM_2.5 ambient levels and modify the magnitude of association between PM_2.5 and systolic blood pressure in older individuals.

The Role of MicroRNAs in Environmental Risk Factors, Noise-Induced Hearing Loss, and Mental Stress

SIGNIFICANCE

MicroRNAs (miRNAs) are important regulators of gene expression and define part of the epigenetic signature. Their influence on every realm of biomedicine is established and progressively increasing. The impact of environment on human health is enormous. Among environmental risk factors impinging on quality of life are those of chemical nature (toxic chemicals, heavy metals, pollutants, and pesticides) as well as those related to everyday life such as exposure to noise or mental and psychosocial stress. Recent Advances: This review elaborates on the relationship between miRNAs and these environmental risk factors.

CRITICAL ISSUES

The most relevant facts underlying the role of miRNAs in the response to these environmental stressors, including redox regulatory changes and oxidative stress, are highlighted and discussed. In the cases wherein miRNA mutations are relevant for this response, the pertinent literature is also reviewed.

FUTURE DIRECTIONS

We conclude that, even though in some cases important advances have been made regarding close correlations between specific miRNAs and biological responses to environmental risk factors, a need for prospective large-cohort studies is likely necessary to establish causative roles. Antioxid. Redox Signal. 28, 773-796.

Fine Particulate Air Pollution and the Expression of microRNAs and Circulating Cytokines Relevant to Inflammation, Coagulation, and Vasoconstriction

BACKGROUND

MicroRNAs (miRNAs) are a key factor in epigenetic regulation of gene expression, but miRNA responses to fine particulate matter (PM_2.5) air pollution and their potential contribution to cardiovascular effects of PM_2.5 are unknown.

OBJECTIVE

We explored the potential influence of PM_2.5 on the expression of selected cytokines relevant to systemic inflammation, coagulation, and vasoconstriction, and on miRNAs that may regulate their expression.

METHODS

We designed a double-blind, randomized crossover study in which true and sham air purifiers were used to expose 55 healthy young adult students in Shanghai, China, to reduced or ambient levels of indoor PM_2.5 during two-week periods, and we measured the expression (mRNA and protein) of 10 serum cytokines, and miRNAs that target them, after each intervention period. We used linear mixed-effect models to estimate associations of the intervention, and time-weighted personal PM_2.5 exposures, with the cytokines, mRNA, and miRNAs; we also explored potential mediation by miRNAs.

RESULTS

The findings were generally consistent for associations with the intervention and for associations with an interquartile range increase in time-weighted PM_2.5. Specifically, higher PM_2.5 exposure was positively associated with the expression (mRNA, protein, or both) of interleukin-1 (encoded by IL1), IL6, tumor necrosis factor (encoded by TNF), toll-like receptor 2 (encoded by TLR2), coagulation factor 3 (encoded by F3), and endothelin 1 (encoded by EDN1), and was negatively associated with miRNAs (miR-21-5p, miR-187-3p, miR-146a-5p, miR-1-3p, and miR-199a-5p) predicted to target mRNAs of IL1, TNF, TLR2, and EDN1.

CONCLUSIONS

Our findings require confirmation but suggest that effects of PM_2.5 on cardiovascular diseases may be related to acute effects on cytokine expression, which may be partly mediated through effects of PM_2.5 on miRNAs that regulate cytokine expression. https://doi.org/10.1289/EHP1447.

Association of H3K79 monomethylation (an epigenetic signature) with arsenic-induced skin lesions

Arsenic, a non mutagenic carcinogen, poses a profound health risk upon prolonged exposure. The objective of the study was to analyze the post-translational modifications of the major histone H3 and the associated molecular crosstalk to identify the epigenetic signature of arsenic susceptibility. Herein, we identified significant upregulation of H3K79me1, in individuals with arsenic-induced skin lesion (WSL), and H3K79me1 was found to be regulated by the upstream methyltransferase DOT1L. Moreover, the downstream target molecule 53BP1, a tumor suppressor protein that has a docking preference for H3K79me1 at a site of a double-strand break (DSB), was downregulated, indicating greater DNA damage in the WSL group. Western blot data confirmed higher levels of γH2AX, a known marker of DSBs, in group WSL. In vitro dose-response analysis also confirmed the association of the H3K79me1 signature with arsenic toxicity. Taken together, our findings revealed that H3K79me1 and DOT1L could be a novel epigenetic signature of the arsenic-exposed WSL group.

Future of environmental research in the age of epigenomics and exposomics

Environmental research and public health in the 21st century face serious challenges such as increased air pollution and global warming, widespread use of potentially harmful chemicals including pesticides, plasticizers, and other endocrine disruptors, and radical changes in nutrition and lifestyle typical of modern societies. In particular, exposure to environmental and occupational toxicants may contribute to the occurrence of adverse birth outcomes, neurodevelopmental deficits, and increased risk of cancer and other multifactorial diseases such as diabetes and asthma. Rapidly evolving methodologies of exposure assessment and the conceptual framework of the Exposome, first introduced in 2005, are new frontiers of environmental research. Metabolomics and adductomics provide remarkable opportunities for a better understanding of exposure and prediction of potential adverse health outcomes. Metabolomics, the study of metabolism at whole-body level, involves assessment of the total repertoire of small molecules present in a biological sample, shedding light on interactions between gene expression, protein expression, and the environment. Advances in genomics, transcriptomics, and epigenomics are generating multidimensional structures of biomarkers of effect and susceptibility, increasingly important for the understanding of molecular mechanisms and the emergence of personalized medicine. Epigenetic mechanisms, particularly DNA methylation and miRNA expression, attract increasing attention as potential links between the genetic and environmental determinants of health and disease. Unlike genetics, epigenetic mechanisms could be reversible and an understanding of their role may lead to better protection of susceptible populations and improved public health.

Recent exposure to ultrafine particles in school children alters miR-222 expression in the extracellular fraction of saliva

BACKGROUND

Ultrafine particles (<100 nm) are ubiquitous present in the air and may contribute to adverse cardiovascular effects. Exposure to air pollutants can alter miRNA expression, which can affect downstream signaling pathways. miRNAs are present both in the intracellular and extracellular environment. In adults, miR-222 and miR-146a were identified as associated with particulate matter exposure. However, there is little evidence of molecular effects of ambient air pollution in children. This study examined whether exposure to fine and ultrafine particulate matter (PM) is associated with changes in the extracellular content of miR-222 and miR-146a of children.

METHODS

Saliva was collected from 80 children at two different time points, circa 11 weeks apart and stabilized for RNA preservation. The extracellular fraction of saliva was obtained by means of differential centrifugation and ultracentrifugation. Expression levels of miR-222 and miR-146a were profiled by qPCR. We regressed the extracellular miRNA expression against recent exposure to ultrafine and fine particles measured at the school site using mixed models, while accounting for sex, age, BMI, passive smoking, maternal education, hours of television use, time of the day and day of the week.

RESULTS

Exposure to ultrafine particles (UFP) at the school site was positively associated with miR-222 expression in the extracellular fraction in saliva. For each IQR increase in particles in the class room (+8504 particles/cm(3)) or playground (+28776 particles/cm(3)), miR-222 was, respectively 23.5 % (95 % CI: 3.5 %-41.1 %; p = 0.021) or 29.9 % (95 % CI:10.6 %-49.1 %; p = 0.0027) higher. No associations were found between miR-146a and recent exposure to fine and ultrafine particles.

CONCLUSIONS

Our results suggest a possible epigenetic mechanism via which cells respond rapidly to small particles, as exemplified by miR-222 changes in the extracellular fraction of saliva.