Abstract P101: Methylome-wide Association Study Provides Evidence of Particulate Matter Air Pollution-associated Dna Methylation at Cardiovascular Disease-related Genes
Authors: Gondalia Rahul , Baldassari Antoine R , Holliday Katelyn M , Méndez-Giráldez Raúl , Justice Anne E , Stewart James D , Liao Duanping , Yanosky Jeffrey D , Jordhal Kristina M , Bhatti Parveen , Horvath Steve , Assimes Themistocles L , Pankow Jim S , Demerath Ellen W , Guan Weihua , Fornage Myriam , Bressler Jan , North Kari E , Conneely Karen N , Li Yun , Baccarelli Andrea A , Hou Lifang , Whitsel Eric A 
Published: July 2021

Background:
DNA methylation (DNAm), a heritable but dynamic epigenetic modification that can influence gene expression without altering the genome, may underlie the associations between air pollution and cardiovascular disease risk. Therefore, our objective was to evaluate associations between DNAm and ambient concentrations of particulate matter (PM) ≤ 2.5 and ≤ 10 micrometers in diameter (PM
2.5;
PM
10
).

Methods:
We conducted a methylome-wide association study among twelve cohort- and race/ethnicity- stratified subpopulations from the Women’s Health Initiative and the Atherosclerosis Risk in Communities study (discovery n = 6,720; replication n = 1,936; mean age: 61.3 yrs; 83% female; 46% African American; 9% Hispanic/Latino American). We averaged geocoded address-specific estimates of daily and monthly mean PM concentrations over 2, 7, 28, and 365 days and 1 and 12 months before exams at which we measured leukocyte DNAm in whole blood. In each subpopulation, we estimated PM-DNAm associations at approximately 485,000 Cytosine-phosphate-Guanine (CpG) sites in multi-level, linear mixed-effects models adjusting for sociodemographic, behavioral, and meteorological characteristics; estimated leukocyte proportions; and technical covariates. We combined subpopulation-specific PM-DNAm associations in fixed-effects, inverse variance-weighted meta-analyses of the discovery, replication, and overall populations. Then we conducted
in silico
characterization of CpG sites at which PM-DNAm associations exceeded methylome-wide significance and were not heterogeneous (
P
< 1.0 x 10
-7
;

P
Cochran’s Q

> 0.10) to assess their putative function and biological plausibility.

Results:
Discovery analyses identified significant PM
2.5
- and PM
10
-DNAm associations at four CpG sites, but none survived Bonferroni correction. Overall analyses identified significant associations at two CpG sites. On chromosome 20 near
MATN4
, 28-day mean PM
10
was associated with increased DNAm at cg19004594 (

P
all

= 2.8 x 10
-8
;

P
Cochran’s Q

= 0.61).
MATN4
is expressed in heart and lung tissues. It encodes Matrilin 4, a von Willebrand factor A domain-containing protein linked to cardiac remodeling. On chromosome 10 near
ARPP21
, 1-month mean PM
10
was inversely associated with DNAm at cg24102420 (

P
all

= 4.8 x 10
-8
;

P
Cochran’s Q

= 0.51).
ARPP21
is expressed in the brain/spinal cord and neutrophils. It encodes cAMP-regulated phosphoprotein 21, a regulator of calmodulin/calcium signaling.

Conclusions:
Findings from this methylome-wide association study suggest that ambient PM
10
concentrations affect DNA methylation at regions of the genome potentially related to cardiovascular disease among racially, ethnically and environmentally diverse populations of U.S. men and women. Further investigation is warranted to uncover epigenetic mechanisms of PM-associated cardiovascular traits.