Use of the Adaptive LASSO Method to Identify PM2.5 Components Associated with Blood Pressure in Elderly Men: The Veterans Affairs Normative Aging Study

Associations between long-term exposure to PM2.5 component species and blood DNA methylation age in the elderly: The VA normative aging study

BACKGROUND

Long-term PM2.5 exposure and aging have been implicated in multiple shared diseases; studying their relationship is a promising strategy to further understand the adverse impact of PM2.5 on human health.

OBJECTIVE

We assessed the relationship of major PM2.5 component species (ammonium, elemental carbon, organic carbon, nitrate, and sulfate) with Horvath and Hannum DNA methylation (DNAm) age, two DNA methylation-based predictors of chronological age.

METHODS

This analysis included 552 participants from the Normative Aging Study with multiple visits between 2000 and 2011 (n=940 visits). We estimated 1-year PM2.5 species levels at participants' addresses using the GEOS-chem transport model. Blood DNAm-age was calculated using CpG sites on the Illumina HumanMethylation450 BeadChip. We fit linear mixed-effects models, controlling for PM2.5 mass and lifestyle/environmental factors as fixed effects, with the adaptive LASSO penalty to identify PM2.5 species associated with DNAm-age.

RESULTS

Sulfate and ammonium were selected by the LASSO in the Horvath DNAm-age models. In a fully-adjusted multiple-species model, interquartile range increases in both 1-year sulfate (95%CI: 0.28, 0.74, P<0.0001) and ammonium (95%CI: 0.02, 0.70, P=0.04) levels were associated with at least a 0.36-year increase in Horvath DNAm-age. No PM2.5 species were selected by the LASSO in the Hannum DNAm-age models. Our findings persisted in sensitivity analyses including only visits with 1-year PM2.5 levels within US EPA national ambient air quality standards.

CONCLUSION

Our results demonstrate that sulfate and ammonium were most associated with Horvath DNAm-age and suggest that DNAm-age measures differ in their sensitivity to ambient particle exposures and potentially disease.

Associations between ambient fine particulate air pollution and hypertension: A nationwide cross-sectional study in China

Limited evidence is available regarding the long-term effects of fine particulate (PM_2.5) air pollution on hypertension in developing countries. This study aimed to explore the associations of long-term exposure to PM_2.5 with hypertension prevalence and blood pressure (BP) in China. We conducted a cross-sectional study based on a nationally representative survey (13,975 participants). We estimated the long-term average exposure to PM_2.5 for all subjects during the study period (June 2011 to March 2012) by a satellite-based model with a spatial resolution of 10×10km. We applied multivariable logistic regression models to evaluate the associations between PM_2.5 and hypertension prevalence and linear regression models for the associations between PM_2.5 and systolic BP and diastolic BP. We also explored potential effect modification by stratification analyses. There were 5715 cases of hypertension, accounting for 40.9% of the study population in this analysis. The annual mean exposure to PM_2.5 for all participants was 72.8μg/m³ on average. An interquartile range increase (IQR, 41.7μg/m³) in PM_2.5 was associated with higher prevalence of hypertension with an odds ratio of 1.11 [95% confidence interval (CI): 1.05, 1.17]. Systolic BP increased by 0.60mmHg (95% CI: 0.05, 1.15) per an IQR increase in PM_2.5. The effects of PM_2.5 on hypertension prevalence were stronger among middle-aged, obese and urban participants. This national study indicated that long-term exposure to PM_2.5 was associated with increased prevalence of hypertension and slightly higher systolic BP in China.

Associations between ambient fine particulate air pollution and hypertension: A nationwide cross-sectional study in China

Limited evidence is available regarding the long-term effects of fine particulate (PM_2.5) air pollution on hypertension in developing countries. This study aimed to explore the associations of long-term exposure to PM_2.5 with hypertension prevalence and blood pressure (BP) in China. We conducted a cross-sectional study based on a nationally representative survey (13,975 participants). We estimated the long-term average exposure to PM_2.5 for all subjects during the study period (June 2011 to March 2012) by a satellite-based model with a spatial resolution of 10×10km. We applied multivariable logistic regression models to evaluate the associations between PM_2.5 and hypertension prevalence and linear regression models for the associations between PM_2.5 and systolic BP and diastolic BP. We also explored potential effect modification by stratification analyses. There were 5715 cases of hypertension, accounting for 40.9% of the study population in this analysis. The annual mean exposure to PM_2.5 for all participants was 72.8μg/m³ on average. An interquartile range increase (IQR, 41.7μg/m³) in PM_2.5 was associated with higher prevalence of hypertension with an odds ratio of 1.11 [95% confidence interval (CI): 1.05, 1.17]. Systolic BP increased by 0.60mmHg (95% CI: 0.05, 1.15) per an IQR increase in PM_2.5. The effects of PM_2.5 on hypertension prevalence were stronger among middle-aged, obese and urban participants. This national study indicated that long-term exposure to PM_2.5 was associated with increased prevalence of hypertension and slightly higher systolic BP in China.

Differential DNA methylation and PM2.5 species in a 450K epigenome-wide association study

Although there is growing evidence that exposure to ambient particulate matter is associated with global DNA methylation and gene-specific methylation, little is known regarding epigenome-wide changes in DNA methylation in relation to particles and, especially, particle components. Using the Illumina Infinium HumanMethylation450 BeadChip, we examined the relationship between one-year moving averages of PM_2.5 species (Al, Ca, Cu, Fe, K, Na, Ni, S, Si, V, and Zn) and DNA methylation at 484,613 CpG probes in a longitudinal cohort that included 646 subjects. Bonferroni correction was applied to adjust for multiple comparisons. Bioinformatics analysis of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment was also performed. We observed 20 Bonferroni significant (P-value < 9.4× 10^-9) CpGs for Fe, 8 for Ni, and 1 for V. Particularly, methylation at Schlafen Family Member 11 (SLFN11) cg10911913 was positively associated with measured levels of all 3 species. The SLFN11 gene codes for an interferon-induced protein that inhibits retroviruses and sensitizes cancer cells to DNA-damaging agents. Bioinformatics analysis suggests that gene targets may be relevant to pathways including cancers, signal transduction, and cell growth and death. Ours is the first study to examine the epigenome-wide association between ambient particles species and DNA methylation. We found that long-term exposures to specific components of ambient particle pollution, especially particles emitted during oil combustion, were associated with methylation changes in genes relevant to immune responses. Our findings provide insight into potential biologic mechanisms on an epigenetic level.

Long-Term Exposure to Particulate Matter and Self-Reported Hypertension: A Prospective Analysis in the Nurses' Health Study

BACKGROUND

Studies have suggested associations between elevated blood pressure and short-term air pollution exposures, but the evidence is mixed regarding long-term exposures on incidence of hypertension.

OBJECTIVES

We examined the association of hypertension incidence with long-term residential exposures to ambient particulate matter (PM) and residential distance to roadway.

METHODS

We estimated 24-month and cumulative average exposures to PM10, PM2.5, and PM2.5-10 and residential distance to road for women participating in the prospective nationwide Nurses' Health Study. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for incident hypertension from 1988 to 2008 using Cox proportional hazards models adjusted for potential confounders. We considered effect modification by age, diet, diabetes, obesity, region, and latitude.

RESULTS

Among 74,880 participants, 36,812 incident cases of hypertension were observed during 960,041 person-years. In multivariable models, 10-μg/m3 increases in 24-month average PM10, PM2.5, and PM2.5-10 were associated with small increases in the incidence of hypertension (HR: 1.02, 95% CI: 1.00, 1.04; HR: 1.04, 95% CI: 1.00, 1.07; and HR: 1.03, 95% CI: 1.00, 1.07, respectively). Associations were stronger among women < 65 years of age (HR: 1.04, 95% CI: 1.01, 1.06; HR: 1.07, 95% CI: 1.02, 1.12; and HR: 1.05, 95% CI: 1.01, 1.09, respectively) and the obese (HR: 1.07, 95% CI: 1.04, 1.12; HR: 1.15, 95% CI: 1.07, 1.23; and HR: 1.13, 95% CI: 1.07, 1.19, respectively), with p-values for interaction < 0.05 for all models except age and PM2.5-10. There was no association with roadway proximity.

CONCLUSIONS

Long-term exposure to particulate matter was associated with small increases in risk of incident hypertension, particularly among younger women and the obese.

CITATION

Zhang Z, Laden F, Forman JP, Hart JE. 2016. Long-term exposure to particulate matter and self-reported hypertension: a prospective analysis in the Nurses' Health Study. Environ Health Perspect 124:1414-1420; http://dx.doi.org/10.1289/EHP163.

Fine particles, genetic pathways, and markers of inflammation and endothelial dysfunction: Analysis on particulate species and sources

Studies have found associations between PM2.5 and cardiovascular events. The role of different components of PM2.5 is not well understood. We used linear mixed-effects models with the adaptive LASSO penalty to select PM2.5 species and source(s), separately, that may be associated with markers of inflammation and endothelial dysfunction, with adjustment for age, obesity, smoking, statin use, diabetes mellitus, temperature, and season as fixed effects in a large longitudinal cohort of elderly men. We also analyzed these associations with source apportionment models and examined genetic pathway-air pollution interactions within three relevant pathways (oxidative stress, metal processing, and endothelial function). We found that independent of PM2.5 mass vanadium (V) was associated with intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). An IQR increase (3.2 ng/m(3)) in 2-day moving average V was associated with a 2.5% (95% CI: 1.2-3.8%) change in ICAM-1 and a 3.9% (95% CI: 2.2-5.7%) change in VCAM-1, respectively. In addition, an oil combustion source rich in V was linked to these adhesion molecules. People with higher allelic risk profiles related to oxidative stress may have greater associations (P-value of interaction=0.11). Our findings suggest that particles derived from oil combustion may be associated with inflammation and endothelial dysfunction, and it is likely that oxidative stress plays a role in the associations.

MicroRNA-1228(*) inhibit apoptosis in A549 cells exposed to fine particulate matter

Studies have reported associations between fine particulate matter (PM2.5) and respiratory disorders; however, the underlying mechanism is not completely clear owing to the complex components of PM2.5. microRNAs (miRNAs) demonstrate tremendous regulation to target genes, which are sensitive to exogenous stimulation, and facilitate the integrative understood of biological responses. Here, significantly modulated miRNA were profiled by miRNA microarray, coupled with bioinformatic analysis; the potential biological function of modulated miRNA were predicted and subsequently validated by cell-based assays. Downregulation of miR-1228-5p (miR-1228(*)) expression in human A549 cells were associated with PM2.5-induced cellular apoptosis through a mitochondria-dependent pathway. Further, overexpression of miR-1228(*) rescued the cellular damages induced by PM2.5. Thus, our results demonstrate that PM2.5-induced A549 apoptosis is initiated by mitochondrial dysfunction and miR-1228(*) could protect A549 cells against apoptosis. The involved pathways and target genes might be used for future mechanistic studies.