Air pollution and markers of coagulation, inflammation, and endothelial function: associations and epigene-environment interactions in an elderly cohort. Epidemiology. 2012;23:332-340. [PMID: 22237295 DOI: 10.1097/ede.0b013e31824523f0]

DNA methylome profiling of human tissues identifies global and tissue-specific methylation patterns

Background

DNA epigenetic modifications, such as methylation, are important regulators of tissue differentiation, contributing to processes of both development and cancer. Profiling the tissue-specific DNA methylome patterns will provide novel insights into normal and pathogenic mechanisms, as well as help in future epigenetic therapies. In this study, 17 somatic tissues from four autopsied humans were subjected to functional genome analysis using the Illumina Infinium HumanMethylation450 BeadChip, covering 486 428 CpG sites.

Results

Only 2% of the CpGs analyzed are hypermethylated in all 17 tissue specimens; these permanently methylated CpG sites are located predominantly in gene-body regions. In contrast, 15% of the CpGs are hypomethylated in all specimens and are primarily located in regions proximal to transcription start sites. A vast number of tissue-specific differentially methylated regions are identified and considered likely mediators of tissue-specific gene regulatory mechanisms since the hypomethylated regions are closely related to known functions of the corresponding tissue. Finally, a clear inverse correlation is observed between promoter methylation within CpG islands and gene expression data obtained from publicly available databases.

Conclusions

This genome-wide methylation profiling study identified tissue-specific differentially methylated regions in 17 human somatic tissues. Many of the genes corresponding to these differentially methylated regions contribute to tissue-specific functions. Future studies may use these data as a reference to identify markers of perturbed differentiation and disease-related pathogenic mechanisms.

Unraveling the DNA methylome of atherosclerosis

PURPOSE OF REVIEW

Epigenetic mechanisms of transcriptional regulation in atherosclerosis have gained an increasing interest in recent years. We focus on the relevance of DNA methylation, a well characterized epigenetic modification of the genome, as a biomarker and underlying mechanism of atherosclerosis.

RECENT FINDINGS

A growing number of loci have been identified, which are good candidate biomarkers for atherosclerosis and provide novel insights into the molecular changes taking place in the diseased vessel. Understanding the global change in DNA methylation during atherosclerosis remains a challenge. Novel unfolding research avenues include the interplay between genetic variants and DNA methylation patterns, and the role of long noncoding RNAs as epigenetic regulators.

SUMMARY

Epigenetics continues to represent a promising area of research in atherosclerosis. The full exploitation of cutting edge epigenomics will be decisive to define whether epigenetics will contribute to lower the burden of cardiovascular diseases.

Epigenetic epidemiology: promises for public health research

Epigenetic changes underlie developmental and age related biology. Promising epidemiologic research implicates epigenetics in disease risk and progression, and suggests epigenetic status depends on environmental risks as well as genetic predisposition. Epigenetics may represent a mechanistic link between environmental exposures, or genetics, and many common diseases, or may simply provide a quantitative biomarker for exposure or disease for areas of epidemiology currently lacking such measures. This great promise is balanced by issues related to study design, measurement tools, statistical methods, and biological interpretation that must be given careful consideration in an epidemiologic setting. This article describes the promises and challenges for epigenetic epidemiology, and suggests directions to advance this emerging area of molecular epidemiology.

Environmental epigenetics and its implication on disease risk and health outcomes

This review focuses on how environmental factors through epigenetics modify disease risk and health outcomes. Major epigenetic events, such as histone modifications, DNA methylation, and microRNA expression, are described. The function of dose, duration, composition, and window of exposure in remodeling the individual's epigenetic terrain and disease susceptibility are addressed. The ideas of lifelong editing of early-life epigenetic memories, transgenerational effects through germline transmission, and the potential role of hydroxylmethylation of cytosine in developmental reprogramming are discussed. Finally, the epigenetic effects of several major classes of environmental factors are reviewed in the context of pathogenesis of disease. These include endocrine disruptors, tobacco smoke, polycyclic aromatic hydrocarbons, infectious pathogens, particulate matter, diesel exhaust particles, dust mites, fungi, heavy metals, and other indoor and outdoor pollutants. We conclude that the summation of epigenetic modifications induced by multiple environmental exposures, accumulated over time, represented as broad or narrow, acute or chronic, developmental or lifelong, may provide a more precise assessment of risk and consequences. Future investigations may focus on their use as readouts or biomarkers of the totality of past exposure for the prediction of future disease risk and the prescription of effective countermeasures.

Air pollution and gene-specific methylation in the Normative Aging Study: association, effect modification, and mediation analysis

The mechanisms by which air pollution has multiple systemic effects in humans are not fully elucidated, but appear to include inflammation and thrombosis. This study examines whether concentrations of ozone and components of fine particle mass are associated with changes in methylation on tissue factor (F3), interferon gamma (IFN-γ), interleukin 6 (IL-6), toll-like receptor 2 (TLR-2), and intercellular adhesion molecule 1 (ICAM-1). We investigated associations between air pollution exposure and gene-specific methylation in 777 elderly men participating in the Normative Aging Study (1999-2009). We repeatedly measured methylation at multiple CpG sites within each gene's promoter region and calculated the mean of the position-specific measurements. We examined intermediate-term associations between primary and secondary air pollutants and mean methylation and methylation at each position with distributed-lag models. Increase in air pollutants concentrations was significantly associated with F3, ICAM-1, and TLR-2 hypomethylation, and IFN-γ and IL-6 hypermethylation. An interquartile range increase in black carbon concentration averaged over the four weeks prior to assessment was associated with a 12% reduction in F3 methylation (95% CI: -17% to -6%). For some genes, the change in methylation was observed only at specific locations within the promoter region. DNA methylation may reflect biological impact of air pollution. We found some significant mediated effects of black carbon on fibrinogen through a decrease in F3 methylation, and of sulfate and ozone on ICAM-1 protein through a decrease in ICAM-1 methylation.

Built environment and elderly population health: a comprehensive literature review

Global population aging over recent years has been linked to poorer health outcomes and higher healthcare expenditure. Policies focusing on healthy aging are currently being developed but a complete understanding of health determinants is needed to guide these efforts. The built environment and other external factors have been added to the International Classification of Functioning as important determinants of health and disability. Although the relationship between the built environment and health has been widely examined in working age adults, research focusing on elderly people is relatively recent. In this review, we provide a comprehensive synthesis of the evidence on the built environment and health in the elderly.

A curated review of recent literature of biomarkers used for assessing air pollution exposures and effects in humans

This is a cross-sectional review of biomarkers used in air pollution research from January 2009 through December 2012. After an initial keyword search in PubMed retrieving 426 articles, a comprehensive abstract review identified 54 articles of experimental design that used biomarkers of exposure or effect in human studies in the area of air pollution research during this specified time period. A thorough bibliographic search of the included articles retrieved an additional 65 articles meeting the inclusion criteria. This review presents these 119 studies and the 234 biomarkers employed in these air pollution research investigations. Data presented are 70 biomarkers of exposure with 54% relating to polycyclic aromatic hydrocarbons, 36% volatile organic carbons, and 10% classified as other. Of the 164 biomarkers of effect, 91 and 130 were used in investigating effects of short-term and chronic exposure, respectively. Results of biomarkers used in short-term exposure describe different lag times and pollutant components such as primary and secondary pollutants, and particle number associated with corresponding physiological mechanisms including airway inflammation, neuroinflammation, ocular, metabolic, early endothelial dysfunction, coagulation, atherosclerosis, autonomic nervous system, oxidative stress, and DNA damage. The review presents three different exposure scenarios of chronic, occupational, and extreme exposure scenarios (indoor cooking) with associated biomarker findings presented in three broad categories of (1) immune profile, (2) oxidative stress, and (3) DNA damage. This review offers a representation of the scope of data being explored by air pollution researchers through the use of biomarkers and has deliberately been restricted to this particular subject rather than an extensive or in-depth review. This article provides a contextualization of air pollution studies conducted with biomarkers in human subjects in given areas while also integrating this complex body of information to offer a useful review for investigators in this field of study.

Traffic-related exposures and biomarkers of systemic inflammation, endothelial activation and oxidative stress: a panel study in the US trucking industry

BACKGROUND

Experimental evidence suggests that inhaled particles from vehicle exhaust have systemic effects on inflammation, endothelial activation and oxidative stress. In the present study we assess the relationships of short-term exposures with inflammatory endothelial activation and oxidative stress biomarker levels in a population of trucking industry workers.

METHODS

Blood and urine samples were collected pre and post-shift, at the beginning and end of a workweek from 67 male non-smoking US trucking industry workers. Concurrent measurements of microenvironment concentrations of elemental and organic carbon (EC & OC), and fine particulate matter (PM2.5) combined with time activity patterns allowed for calculation of individual exposures. Associations between daily and first and last-day average levels of exposures and repeated measures of intercellular and vascular cell adhesion molecule-1 (ICAM-1 & VCAM-1), interleukin 6 (IL-6) and C-reactive protein (CRP) blood levels and urinary 8-Hydroxy-2'-Deoxyguanosine (8-OHdG) were assessed using linear mixed effects models for repeated measures.

RESULTS

There was a statistically significant association between first and last-day average PM2.5 and 8-OHdG (21% increase, 95% CI: 2, 42%) and first and last-day average OC and IL-6 levels (18% increase 95% CI: 1, 37%) per IQR in exposure. There were no significant findings associated with EC or associations suggesting acute cross-shift effects.

CONCLUSION

Our findings suggest associations between weekly average exposures of PM2.5 on markers of oxidative stress and OC on IL-6 levels.

“Anthropogens” in Lifestyle Medicine

Chronic disease epidemiology currently lacks the mono-causal focus germ theory provides infectious diseases. However, the discovery of a form of low-grade, systemic, and chronic inflammation (“metaflammation) underlying many, if not all, chronic diseases induced by a range of stimulants labeled “anthropogens” may help change this. Anthropogens are “man-made environments, their by-products, and/or lifestyles encouraged by these, some of which are detrimental to human health.” While an exhaustive list of anthropogens associated with chronic disease may be as elusive as a comprehensive list of “germs” with the potential to cause infection, a broad taxonomy provides a focus for the practice of lifestyle medicine. Such a list is considered here under the acronym NASTIE ODOURS.

Ambient air pollution and preeclampsia: a spatiotemporal analysis

BACKGROUND

Available evidence concerning the association between air pollution and preeclampsia is limited, and specific associations with early- and late-onset preeclampsia have not been assessed.

OBJECTIVES

We investigated the association, if any, between preeclampsia (all, early-, and late-onset) and exposure to nitrogen dioxide, nitrogen oxides, particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5; fine particles), ≤ 10 μm, and 2.5-10 μm, and PM2.5 light absorption (a proxy for elemental carbon) during the entire pregnancy and during the first, second, and third trimesters.

METHODS

This study was based on 8,398 pregnancies (including 103 cases of preeclampsia) among women residing in Barcelona, Spain (2000-2005). We applied a spatiotemporal exposure assessment framework using land use regression models to predict ambient pollutant levels during each week of pregnancy at the geocoded residence address of each woman at the time of birth. Logistic and conditional logistic regression models were used to estimate unadjusted and adjusted associations.

RESULTS

We found positive associations for most of our evaluated outcome-exposure pairs, with the strongest associations observed for preeclampsia and late-onset preeclampsia in relation to the third-trimester exposure to fine particulate pollutants, and for early-onset preeclampsia in relation to the first-trimester exposure to fine particulate pollutants. Among our investigated associations, those of first- and third-trimester exposures to PM2.5 and third-trimester exposure to PM2.5 absorbance and all preeclampsia, and third-trimester PM2.5 exposure and late-onset preeclampsia attained statistical significance.

CONCLUSION

We observed increased risk of preeclampsia associated with exposure to fine particulate air pollution. Our findings, in combination with previous evidence suggesting distinct pathogenic mechanisms for early- and late-onset preeclampsia, support additional research on this topic.

Impact of living environment on 2-year mortality in elderly maintenance hemodialysis patients

Background

Studies on risk factors of mortality in elderly patients with hemodialysis usually focus on comorbidities, nutrition, and inflammation. Discussion on the correlation between living environment and mortality of these patients is limited.

Methods

A total of 256 elderly hemodialysis patients participated in this 2-year prospective observational study. The subjects were divided into 2 subgroups based on whether they were living in Taipei Basin (n = 63) or not (n = 193). Demographic, hematological, nutritional, inflammatory, biochemical, and dialysis-related data were obtained for cross-sectional analysis. Causes of death and mortality rates were also analyzed for each subgroup.

Results

Patients in the basin group had a higher incidence of combined protein-energy wasting and inflammation than those in the around basin group. At the end of the 2-year follow-up, 68 patients had died. Univariate binary logistic regression analysis revealed that a very advanced age, basin group, serum albumin levels, serum creatinine levels, non-anuria, and the complications of stroke and CAD were associated with 2-year mortality. Meanwhile, log high-sensitivity C-reactive protein (hs-CRP) levels were not associated with 2-year mortality. Multivariate Cox regression analysis revealed that basin group, serum albumin levels, and the complications of stroke and CAD were significant risk factors for 2-year mortality in these patients.

Conclusion

The results of this study indicate that factors such as living in the Taipei Basin with higher air pollutant levels in elderly hemodialysis patients is associated with protein-energy wasting and inflammation, as well as 2-year mortality. These findings suggest that among this population, living environment is as important as comorbidities and nutrition. Furthermore, air pollution should be getting more attention especially in the overcrowding Basin topography.

Ambient air pollution and hypertensive disorder of pregnancy

BACKGROUND

Ambient air pollution has been implicated in the development of hypertensive disorders of pregnancy (HDP). However, evidence of the association between air pollution and HDP is still limited, and the effects of gaseous air pollutants on HDP and their time windows of exposure have not been well studied.

METHODS

We used the Florida birth registry data to investigate the associations between air pollutants (NO2, SO2, PM(2.5), O3 and CO) and the risks of HDP in 22,041 pregnant women in Jacksonville, Florida, USA from 2004 to 2005. Further, we examined whether air pollution exposure during different time windows defined by trimesters and the entire pregnancy had different effects on HDP.

RESULTS

The single-pollutant logistic regression model showed that exposure to four pollutants during the full pregnancy period was significantly associated with prevalence of HDP after adjusting for covariates: NO2 (OR=1.21, 95% CI 1.09 to 1.35), PM2.5 (OR=1.24, 95% CI 1.08 to 1.43), SO2 (OR=1.13, 95% CI 1.01 to 1.25) and CO (OR=1.12, 95% CI 1.03 to 1.22) per IQR increase. Similar effects were observed when first trimester exposure to NO2, SO2 and CO, and second trimester exposures to PM2.5 were examined. Consistent results were confirmed in multiple-pollutant models.

CONCLUSIONS

This study suggests that exposure to high levels of air pollution during early pregnancy and the full gestational period was associated with increased prevalence of HDP in Florida, USA.

The impacts of short-term exposure to noise and traffic-related air pollution on heart rate variability in young healthy adults

Traffic-related air pollution and noise are associated with cardiovascular diseases, and alternation of heart rate variability (HRV), which reflects cardiac autonomic function, is one of the mechanisms. However, few studies considered the impacts of noise when exploring associations between air pollution and HRV. We explored whether noise modifies associations between short-term exposure to traffic-related air pollution and HRV in young healthy adults. In this randomized, crossover study, 40 young healthy adults stayed for 2 h in a traffic center and, on a separate occasion, in a park. Personal exposure to traffic-related air pollutants and noise were measured and ambulatory electrocardiogram was performed. Effects were estimated using mixed-effects regression models. Traffic-related air pollution and noise were both associated with HRV, and effects of air pollutants were amplified at high noise level (>65.6 A-weighted decibels (dB[A])) compared with low noise level (≤ 65.6 dB[A]). High frequency (HF) decreased by -4.61% (95% confidence interval, -6.75% to-2.42%) per 10 μg/m(3) increment in fine particle (PM2.5) at 5-min moving average, but effects became insignificant at low noise level (P>0.05). Similar effects modification was observed for black carbon (BC) and carbon monoxide (CO). We conclude that noise is an important factor influencing the effects of air pollution on HRV.

The effect of primary organic particles on emergency hospital admissions among the elderly in 3 US cities

BACKGROUND

Fine particle (PM2.5) pollution related to combustion sources has been linked to a variety of adverse health outcomes. Although poorly understood, it is possible that organic carbon (OC) species, particularly those from combustion-related sources, may be partially responsible for the observed toxicity of PM2.5. The toxicity of the OC species may be related to their chemical structures; however, few studies have examined the association of OC species with health impacts.

METHODS

We categorized 58 primary organic compounds by their chemical properties into 5 groups: n-alkanes, hopanes, cyclohexanes, PAHs and isoalkanes. We examined their impacts on the rate of daily emergency hospital admissions among Medicare recipients in Atlanta, GA and Birmingham, AL (2006-2009), and Dallas, TX (2006-2007). We analyzed data in two stages; we applied a case-crossover analysis to simultaneously estimate effects of individual OC species on cause-specific hospital admissions. In the second stage we estimated the OC chemical group-specific effects, using a multivariate weighted regression.

RESULTS

Exposures to cyclohexanes of six days and longer were significantly and consistently associated with increased rate of hospital admissions for CVD (3.40%, 95%CI = (0.64, 6.24%) for 7-d exposure). Similar increases were found for hospitalizations for ischemic heart disease and myocardial infarction. For respiratory related hospital admissions, associations with OC groups were less consistent, although exposure to iso-/anteiso-alkanes was associated with increased respiratory-related hospitalizations.

CONCLUSIONS

Results suggest that week-long exposures to traffic-related, primary organic species are associated with increased rate of total and cause-specific CVD emergency hospital admissions. Associations were significant for cyclohexanes, but not hopanes, suggesting that chemical properties likely play an important role in primary OC toxicity.

Oxidative stress in adolescent passive smokers living in urban and rural environments

Purpose of this study was to study the oxidative stress status through the urinary 15-F(2t)-isoprostane (15-F(2t)-isoP) among a group of 168 adolescents, differently exposed to passive tobacco smoke. Subjects were enrolled, with written informed consent, between two populations of students living and attending school in two areas with different levels of urbanization in Piedmont Region, North-Western Italy. A general linear model (GLM) analysis was performed to evaluate the role of air pollution, dependent from selected degree of urbanization and of passive exposure to tobacco smoke, quantified through cotinine, in the synthesis of 15-F(2t)-isoP, measured with ELISA technique. Formaldehyde (FA) concentration in air was also evaluated as a primary confounding factor in oxidative stress but no significant differences between the two sites were found. Conversely, direct relationship between oxidative stress status and residence of adolescents was found: oxidative stress level was 31% higher for adolescents living in Chivasso (urban site) than for those living in Casalborgone (countryside area). Furthermore, also passive tobacco smoke exposure proved to play another important direct role in the distribution of 15-F(2t)-isoP levels (p<0.0001). Lastly, an inversely proportional relationship was found between the age of adolescents and 15-F(2t)-isoP (p<0.0001). Finally, the detection of such a sensitive biological response as a consequence of limited differences of environmental pollution and exposure to tobacco smoke passively breathed could provide new and useful knowledge for the appraisal of preventive strategies, particularly for young subjects.

A case-control study of medium-term exposure to ambient nitrogen dioxide pollution and hospitalization for stroke

Background

There are several plausible mechanisms whereby either short or long term exposure to pollution can increase the risk of stroke. Over the last decade, several studies have reported associations between short-term (day-to-day) increases in ambient air pollution and stroke. The findings from a smaller number of studies that have looked at long-term exposure to air pollution and stroke have been mixed. Most of these epidemiological studies have assigned exposure to air pollution based on place of residence, but these assignments are typically based on relatively coarse spatial resolutions. To date, few studies have evaluated medium-term exposures (i.e, exposures over the past season or year). To address this research gap, we evaluated associations between highly spatially resolved estimates of ambient nitrogen dioxide (NO₂), a marker of traffic pollution, and emergency department visits for stroke in Edmonton, Canada.

Methods

This was a case-control study with cases defined as those who presented to an Edmonton area hospital emergency department between 2007 and 2009 with an acute ischemic stroke, hemorrhagic stroke, or transient ischemic attack. Controls were patients who presented to the same emergency departments for lacerations, sprains, or strains. A land-use regression model provided estimates of NO₂ that were assigned to the place of residence. Logistic regression methods were used to estimate odds ratios for stroke in relation to an increase in the interquartile range of NO₂ (5 ppb), adjusted for age, sex, meteorological variables, and neighborhood effects.

Results

The study included 4,696 stroke (cases) and 37,723 injury patients (controls). For all strokes combined, there was no association with NO_2. Namely, the odds ratio associated with an interquartile increase in NO₂ was 1.01 (95% confidence interval {CI}: 0.94-1.08). No associations were evident for any of the stroke subtypes examined.

Conclusion

When combined with our earlier work in Edmonton, our findings suggest that day-to-day fluctuations in air pollution increase the risk of ischemic stroke during the summer season, while medium term exposures are unrelated to stroke risk. The findings for medium term exposure should be interpreted cautiously due to limited individual-level risk factor data.

Molecular pathological epidemiology of epigenetics: emerging integrative science to analyze environment, host, and disease

Epigenetics acts as an interface between environmental/exogenous factors, cellular responses, and pathological processes. Aberrant epigenetic signatures are a hallmark of complex multifactorial diseases (including neoplasms and malignancies such as leukemias, lymphomas, sarcomas, and breast, lung, prostate, liver, and colorectal cancers). Epigenetic signatures (DNA methylation, mRNA and microRNA expression, etc) may serve as biomarkers for risk stratification, early detection, and disease classification, as well as targets for therapy and chemoprevention. In particular, DNA methylation assays are widely applied to formalin-fixed, paraffin-embedded archival tissue specimens as clinical pathology tests. To better understand the interplay between etiological factors, cellular molecular characteristics, and disease evolution, the field of 'molecular pathological epidemiology (MPE)' has emerged as an interdisciplinary integration of 'molecular pathology' and 'epidemiology'. In contrast to traditional epidemiological research including genome-wide association studies (GWAS), MPE is founded on the unique disease principle, that is, each disease process results from unique profiles of exposomes, epigenomes, transcriptomes, proteomes, metabolomes, microbiomes, and interactomes in relation to the macroenvironment and tissue microenvironment. MPE may represent a logical evolution of GWAS, termed 'GWAS-MPE approach'. Although epigenome-wide association study attracts increasing attention, currently, it has a fundamental problem in that each cell within one individual has a unique, time-varying epigenome. Having a similar conceptual framework to systems biology, the holistic MPE approach enables us to link potential etiological factors to specific molecular pathology, and gain novel pathogenic insights on causality. The widespread application of epigenome (eg, methylome) analyses will enhance our understanding of disease heterogeneity, epigenotypes (CpG island methylator phenotype, LINE-1 (long interspersed nucleotide element-1; also called long interspersed nuclear element-1; long interspersed element-1; L1) hypomethylation, etc), and host-disease interactions. In this article, we illustrate increasing contribution of modern pathology to broader public health sciences, which attests pivotal roles of pathologists in the new integrated MPE science towards our ultimate goal of personalized medicine and prevention.

Air pollution, genetics, and allergy: an update

PURPOSE OF REVIEW

Air pollution has been increasingly associated with diverse adverse health outcomes, including airway diseases. Data suggest that gene-environment interactions are important in this context. However, evidence regarding causal effects of exposure and development of allergic conditions specifically remains immature. We review the developments of the past 18 months regarding air pollution, genetics and epigenetics, and allergy.

RECENT FINDINGS

Conflicting evidence for air pollution as causative in the development of allergic disease persists. However, recent data support the associations between long-term exposure to traffic-related pollutants and newly developed sensitization in children. Studies from India and China demonstrate the global burden of health-related costs attributed to air pollutants and allergic diseases. The effect of exposure seems to be modified by coexposures of allergens as well as genetic variants, particularly those moderating response to oxidative stress. Potential links between exposures and epigenetic (DNA methylation) changes with consequences for disease development are also reinforced.

SUMMARY

Data over the past 18 months support prior literature that air pollutants cause exacerbation, and possibly onset, of allergic disease. Regarding the onset of asthma specifically, the evidence of causality has grown significantly, but it remains difficult to separate allergic from nonallergic asthma. Effect of modification by genetic variants and epigenetic changes warrants further study.

Chemical constituents of ambient particulate air pollution and biomarkers of inflammation, coagulation and homocysteine in healthy adults: a prospective panel study

Background

Ambient air pollution has been associated with activation of systemic inflammation and hypercoagulability and increased plasma homocysteine, but the chemical constituents behind the association are not well understood. We examined the relations of various chemical constituents of fine particles (PM_2.5) and biomarkers of inflammation, coagulation and homocysteine in the context of traffic-related air pollution.

Methods

A panel of 40 healthy college students underwent biweekly blood collection for 12 times before and after their relocation from a suburban campus to an urban campus with changing air pollution contents in Beijing. Blood samples were measured for circulatory biomarkers of high-sensitivity C reactive protein (hs-CRP), tumor necrosis factor alpha (TNF-α), fibrinogen, plasminogen activator inhibitor type 1 (PAI-1), tissue-type plasminogen activator (t-PA), von Willebrand factor (vWF), soluble platelet selectin (sP-selectin), and total homocysteine (tHcy). Various air pollutants were measured in a central air-monitoring station in each campus and 32 PM_2.5 chemical constituents were determined in the laboratory. We used three different mixed-effects models (single-constituent model, constituent-PM_2.5 joint model and constituent residual model) controlling for potential confounders to estimate the effects of PM_2.5 chemical constituents on circulatory biomarkers.

Results

We found consistent positive associations between the following biomarkers and PM_2.5 chemical constituents across different models: TNF-α with secondary organic carbon, chloride, zinc, molybdenum and stannum; fibrinogen with magnesium, iron, titanium, cobalt and cadmium; PAI-1 with titanium, cobalt and manganese; t-PA with cadmium and selenium; vWF with aluminum. We also found consistent inverse associations of vWF with nitrate, chloride and sodium, and sP-selectin with manganese. Two positive associations of zinc with TNF-α and of cobalt with fibrinogen, and two inverse associations of nitrate with vWF, and of manganese with sP-selectin, were independent of the other constituents in two-constituent models using constituent residual data. We only found weak air pollution effects on hs-CRP and tHcy.

Conclusions

Our results provide clues for the potential roles that PM_2.5 chemical constituents may play in the biological mechanisms through which air pollution may influence the cardiovascular system.

The genetics of obesity in transition

Recent advances in human genetics have revealed a number of genes influencing the susceptibility to obesity and related conditions, but it is likely that their contribution to disease is contingent on numerous environmental factors. As the obesity epidemic has occurred over a relatively short period of recent history, use of gene-by-year of birth analysis may be a useful approach for quantifying, in aggregate, the interaction between genetic susceptibility to obesity and the numerous known and unknown environmental factors that have changed during nutrition and health transitions globally during this recent increase in obesity rates. Evidence from one family-based longitudinal study set in the United States is showcased, which points to significant increases in the effect of common genetic variants on childhood and adulthood BMI over an 80 year period spanning from 1929 to the present. First, common genetic variants previously known to be associated with age at menarche through genome-wide association analysis were examined in aggregate using a genetic risk score approach. The menarche genetic risk score, composed of 42 single-nucleotide polymorphisms (SNPs) was significantly associated with peri-pubertal BMI in both boys and girls, but the magnitude of the association was strongly dependent on year of birth, with greater effect as birth year increased. Second, a similar approach was taken using instead a BMI genetic risk score composed of 32 common variants previously found to be associated with BMI. This score was strongly associated with adulthood BMI, waist circumference, and skinfold thickness, as expected, but the magnitude of the association increased with later year of birth. Such gene-environment interactions call for greater focus on the mechanisms by which environmental factors impact the functional output of the human genome, including how epigenetic mechanisms may be altered during social, technological, nutritional, and ecological transitions.

Vasoactive alteration and inflammation induced by polycyclic aromatic hydrocarbons and trace metals of vehicle exhaust particles

Exposure to particulate matter (PM) increases the incidence of cardiovascular disease, but the underlying mechanisms remain unclear. To characterise ambient PM collected from a coach station in an urban area, particulate polycyclic aromatic hydrocarbons (PAHs) and trace metals were evaluated, and diagnostic ratios were then used to determine the sources based on the PAHs identified in PM. To elucidate the mechanism of PM-induced vascular toxicology, human coronary artery endothelial cells (HCAECs) were exposed to PM, PM-free supernatant and residual PM, and the associations between PAHs and trace metals, nitric oxide (NO), endothelin-1 (ET-1) and interleukin-6 (IL-6) were investigated. Petrogenic-related particulate emissions, such as vehicle exhaust, accounted for 68.75% and 75.00% of mass in the 0.1-1-μm PM (PM(0.1-1)) and <0.1-μm PM (PM(0.1)) size fractions, respectively. Vehicle exhaust particles (VEPs) caused significant NO suppression and increase in ET-1 and IL-6, whereas residual PM caused an increase in NO, ET-1 and IL-6 compared with the effects of the corresponding supernatants. PAHs in PM, particularly those with 4-6 rings, were associated with NO suppression, and ET-1 and IL-6 were positively correlated with the amount of trace metal compounds. These findings suggest that chemical components affect the regulation of vasoactive function and inflammation.

Environmental exposures, epigenetics and cardiovascular disease

PURPOSE OF REVIEW

Epigenetic modifications are heritable alterations of the genome, which can govern gene expression without altering the DNA sequence. The purpose of this review is to render an overview of the possible mechanisms of epigenetic regulation of gene expression in response to environmental pollutants leading to cardiovascular diseases (CVD).

RECENT FINDINGS

An era of cataloging epigenetic marks of the various diseased states has recently commenced, including those within the genes responsible for atherosclerosis, ischemia, hypertension and heart failure. From varied study approaches directed either toward the general understanding of the key pathway regulatory genes, or sampling population cohorts for global and gene-specific changes, it has been possible to identify several epigenetic signatures of environmental exposure relevant to CVD. Signatures of epigenetic dysregulation can be detected in peripheral blood samples, even within a few hours of environmental exposure. However, the field now faces the demand for thorough, systematic, rationalized approaches to establish the relation of exposure-driven epigenetic changes to clinical outcomes, by using sophisticated and reliable research designs and tools.

SUMMARY

An understanding of chromatin remodelling in response to environmental stimuli conducive to CVD is emerging, with the promise of novel diagnostic and therapeutic candidates.

The role of longitudinal cohort studies in epigenetic epidemiology: challenges and opportunities

Longitudinal cohort studies are ideal for investigating how epigenetic patterns change over time and relate to changing exposure patterns and the development of disease. We highlight the challenges and opportunities in this approach.