Particulate Matter Exposure and Global DNA Methylation in Alaskan Sled Dogs: Sentinels for Human Health

Abstract

Background: Ambient particulate matter (PM) concentrations are known to be associated with increased morbidity and mortality in human populations. During the winter months in Fairbanks, Alaska severe temperature inversions lead to elevated concentrations of ambient PM smaller than 2.5 microns (PM2.5). As there are multiple challenges in studying the impact of PM2.5 on people, sled dogs represent a high concentration easily accessible population that may yield findings relevant to human health risk. Objectives: In this pilot study, we evaluate sled dogs as a surrogate model for human PM exposure and associations with an epigenetic measure of global methylation. Methods: Kennels (n=3) were strategically recruited to provide a wide PM2.5 exposure gradient for the Fairbanks area. Continuous monitoring of ambient PM2.5 was conducted at each kennel during the winter of 2012/13 using a DustTrak 8530. Dogs received a physical evaluation and assessment of standard hematology and clinical chemistries. Global methylation was determined using the LUminometric Methylation Assay (LUMA). Results: Three sled dog kennels (n= ~30 dogs/kennel) were evaluated and sampled. The average PM2.5 concentrations measured for each kennel were 16 µg/m3, 48 µg/m3, 90 µg/m3 (p< 0.0001). The average (standard deviation) global methylation percentage for each kennel was 76.15 (1.80), 76.42 (1.92), and 76.73 (2.26), respectively. There was no statistical difference between the three kennels and their average global methylation percentage (p= 0.61). Conclusions: This is the first use of sled dogs as a surrogate for environmental exposure- related epigenetic effects. Average global methylation among dogs at each kennel had a monotonic relationship with average ambient PM2.5 concentrations, but differences were not statistically significant. Future studies could focus on repetitive elements and specific genes, which have human homologues.