Urinary 1-hydroxypyrene and smoking are determinants of LINE-1 and AhRR promoter methylation in coke oven workers

Coke oven emissions (COE) containing polycyclic aromatic hydrocarbons (PAHs) are predominant toxic constituents of particulate air pollution that have been linked to increased risk of lung cancer. Aberrant DNA methylation is one of the best known epigenetic changes in human cancers and healthy subjects exposed to carcinogens. The purpose of this study is to explore the factors influencing the methylation of long interspersed nuclear element-1 (LINE-1) and aryl-hydrocarbon receptor repressor (AhRR) in coke oven workers. The study population is composed by coke oven workers (348) and water treatment workers (131). And their urinary PAH metabolites were analyzed by high performance liquid chromatography; DNA methylation were measured by pyrosequencing. The urinary PAHs metabolites were significantly elevated in coke oven workers (P < 0.01). The results from multivariate logistic regression analysis showed that a high level of urinary 1-hydroxypyrene was associated with a significantly increased risk of hypomethylation of LINE-1 (OR: 1.80; 95% CI: 1.25, 2.60), and heavy smoking was associated with a significantly increased risk of hypomethylation of AhRR (OR: 1.44; 95% CI: 1.04, 2.00). Our findings demonstrate that urinary 1-hydroxypyrene may be a useful biomarker for evaluating the role of PAHs exposure on hypomethylation of LINE-1 among coke oven workers and that smoking may be an important factor affecting hypomethylation of AhRR.