The global DNA and RNA methylation and their reversal in lung under different concentration exposure of ambient air particulate matter in mice

Particulate matter (PM) in air pollution is a pervasive risk factor in pulmonary diseases that are always associated with gene expression level alterations in many specific-genes. DNA methylation (5-methylcytosine [5mC]) and RNA methylation (N6-methyladenine [6 mA]) influence the gene expression from transcription and post transcription level, and the DNA hydroxymethylation (5-hydroxymethylcytosine [5hmC]) is the oxidized form of 5mC. In the present study, the levels of global 5mC, 5hmC and 6 mA of lungs in experimental mice were investigated. We divided the animals into 3 groups randomly, the group 1 was exposed to heavy PM for 24 h in the unfiltered chamber, the group 2 was exposed to filtered air in the filtered chamber, and the group 3 was 10 of the mice in the group 1 after 24 h exposure and then being moved to the filtered chamber for further 120 h exposure. The morphology of lungs showed that acute PM exposure impaired the structure of pulmonary alveolus. Meanwhile, the global level of DNA methylation was decreased, and DNA hydroxymethylation and RNA methylation levels were increased in lungs after PM exposure for only 24 h. Very notably, after being exposed in purified air for 120 h, the pulmonary morphology, the global levels of DNA methylation, DNA hydroxymethylation and RNA methylation of lungs were all reversed. The present study clearly demonstrated the alteration of DNA and RNA methylation after acute heavy PM exposure and emphasized the reversal of the symptoms caused by PM exposure after the air purification, which provided us a new idea for the intervention of the adverse health effects from air pollution. Capsule: Acute PM exposure resulted in reduced global DNA methylation and increased global DNA hydroxymethylcytosine and RNA methylation, and air purification reversed these alterations.