Dioxin-like compound exposures and DNA methylation in the Anniston Community Health Survey Phase II
Graphical abstract
Introduction
The major US producer of polychlorinated biphenyls (PCBs) operated in Anniston, Alabama from 1929 until 1971. Due to poor environmental controls at the facility, releases of dioxins, furans, and PCBs over time caused wide-spread environmental contamination in the Anniston community. Because these compounds are highly lipophilic and have long half-lives, they bioaccumulate in the food chain and persist in human tissues. The Anniston Community Health Survey (ACHS-I) was established in 2005 to assess the health effects of PCB exposure in the general population of the community (Birnbaum and Staskal-Wikoff, 2010; Pavuk et al., 2014a) and in 2014, a follow-up study was conducted (ACHS-II) (Birnbaum et al., 2016). Prior ACHS-I research has found links between PCB exposures and hypertension (Goncharov et al., 2010), blood pressure (Goncharov et al., 2011), race (Pavuk et al., 2014b), liver disease (Clair et al., 2018), metabolic syndrome (Rosenbaum et al., 2017), serum lipid levels (Aminov et al., 2014), diabetes (Silverstone et al., 2012), and leukocyte telomere length (Callahan et al., 2017).
A number of studies have found associations between altered DNA methylation and dioxin, furan, and PCB exposures in several populations, including Faroe Islanders (Leung et al., 2018), Dutch (van den Dungen et al., 2017), Taiwanese (Su et al., 2019), Greenlandic Inuits (Rusiecki et al., 2008), Koreans (Kim et al., 2010), and Japanese (Kobayashi et al., 2017). We have recently reported on 28 genome-wide significant associations between serum PCB concentrations in ACHS-I and whole blood DNA methylation (Pittman et al., 2019). We carried out a look-up analysis of the 369 FDR significant ACHS-I associations in the ACHS-II methylation dataset reported in the present project and determined that the most significantly altered ACHS-I CpG, cg00475490 in the PRSS23 gene, was still significantly associated with the group, summed tri/tetra-ortho substituted, nondioxin-like PCBs (p = 1.33E−04) in ACHS-II.
The current ACHS-II study focuses on dioxins and dioxin-like compounds and their toxicities have generally been attributed to sustained aryl hydrocarbon receptor (AHR) activation as measured in model systems, and this property is used in human risk assessment (Theobald and Peterson 1994). Ligand-mediated AHR activation results in upregulation of genes in the AHR pathway, including cytochrome P450s (e.g. CYP1A1 and CYP1B1) and the aryl hydrocarbon receptor repressor (AHRR), a negative regulator of AHR (Hahn et al., 2009). DNA methylation levels at the CpG cg05575921 in AHRR are strongly associated with adult and prenatal tobacco smoke exposure (Joehanes et al., 2016; Joubert et al., 2012; Reynolds et al., 2017; Su et al., 2016; Wan et al., 2018), and this could potentially be related to tobacco smoke polyaromatic hydrocarbons (PAHs), which are also AHR ligands. We recently explored the hypothesis that PCB exposures in ACHS might be associated with whole blood DNA methylation levels in AHRR or other AHR pathway genes, but found no relationship (Pittman et al., 2019). Dioxins are considered stronger ligands for AHR (Theobald and Peterson, 1994), so in this work we also tested if dioxin and dioxin-like exposures might lead to methylation changes in AHRR cg05575921. Because dioxin exposures have been linked with altered immune system effects, we used the Houseman model (Houseman et al., 2012; Houseman et al., 2016) to test if exposure was associated with changes in methylation-based estimated cell-type percentages in whole blood. However, the primary objective was to carry out an epigenome-wide association study (EWAS) assessing if exposures to AHR ligands such as PCDDs, PCDFs, cPCBs, and mPCBs were associated with altered whole blood DNA methylation at CpGs across the genome.
Section snippets
Study population
ACHS-II was conducted in 2014 as a follow-up study to ACHS-I (2005–2007). Both study designs have been previously reported (Birnbaum et al., 2016; Pavuk et al., 2014a). In ACHS-I, two-stage stratified random sampling was used to select households and adults within the household of Anniston, Alabama. We contacted over 1800 households; individuals living in west Anniston (the area closest to the PCB manufacturing facility) were over-sampled (two-thirds of eligible participants). 1100 participants
Demographics
Table 1 provides the demographics for subjects with available DNA methylation and exposure data (n = 292). The cohort was primarily female (74.3%) and had a higher mean BMI (31.6 ± 0.5) relative to that reported (26.0 ± 0.1) in the National Health and Nutrition Examination Survey 2015–2016 (CDC National Center for Health Statistics, 2018). White study participants were older than African-American participants (64.3 vs 60.9 years). African-American participants were more likely to live in west
Look up analysis
We searched the literature for array-based methylation data and associations with dioxins, furans and dioxin-like PCBs. We identified three studies with 450 k methylation array data (Leung et al., 2018; Su et al., 2019; van den Dungen et al., 2017). These studies examined the associations between whole blood DNA methylation and PCBs 105 and 118; 23,478-PeCDF, 123,478-HxCDF, PCBs 153 and 156; and PCBs 28, 52, 105, 118, 138, 153, 156, 170, 180, and 187, respectively (Supplemental File 1 Table
Discussion
In this current study we have examined the associations between dioxin, furan, and dioxin-like PCB exposures and whole blood DNA methylation in the second phase of the Anniston Community Health Study. Among all exposures we identified 10 (Bonferroni p ≤ 6.74E−08) and 116 (FDR p ≤ 5.00E−02) significant associations representing 10 and 113 unique CpGs, respectively. The PCDDs exposure group had the most Bonferroni and FDR significant CpG associations (seven and 107, respectively), and the
Conclusions
This study contributes to the understanding of the effects of dioxin and dioxin-like exposures on whole blood DNA methylation in a human population study. This is the first report to examine dioxin-like exposures and alterations in DNA methylation using the Illumina 850 K methylation array. We identified one highly significant DMR and 10 genome-wide significant CpG/exposure associations with 40% having differential methylation ≥1.00%, based on the methylation difference between the highest and
Author credit statement
GSP: Methodology, Formal data analysis, Visualization, Writing – Original Draft, review and editing.
XW: Formal data analysis.
MRC: Sample preparation, Investigation.
SJC: Sample preparation.
JRO: Resources.
MP: Conceptualization, Resources, Writing- Review and Editing, Project Administration.
LSB: Conceptualization, Resources, Writing – Review and Editing, Funding.
DAB: Conceptualization, Supervision, Resources, Writing- Review and Editing, Project Administration.
Funding details
The baseline study (ACHS-I) was conducted using a grant from ATSDR to Jacksonville State University, #5U50TS473215. The follow up study (ACHS II) was funded by the National Cancer Institute through interagency agreements with the Centers for Disease Control and Prevention (CDC) (IAA#: 11-AT1-001-00; IAA#: 12-AT-12-ANNISTON) and by ATSDR. Data collection was supported via contract from ATSDR to the University of Alabama at Birmingham (UAB) (CDC Contract No. 200-2011-40834). The contents of this
Declaration of competing interest
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
J.R. Olson served as an expert witness for the plaintiffs in legal actions regarding the residents of Anniston, Alabama being exposed to PCBs. The other authors declare that they have no competing interests.
Acknowledgements
The coauthors would like to dedicate this work to the memory of Gary S. Pittman, MSPH, National Institute of Environmental Health Sciences, who died unexpectedly after a short illness just as the final edits on this manuscript were completed. We recognize Dr. Stephen T. Mennemeyer of University of Alabama Birmingham for his study contributions. We express gratitude to the study participants in the ACHS-I and ACHS-II cohorts. We thank Andreas Sjödin and Richard Jones, National Center for
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