Abstract Body: Background: Smoking is the strongest modifiable risk factor for abdominal aortic aneurysm (AAA), but the risks of e-cigarette (e-cig) vaping are less well defined. Nicotine can cause heritable epigenetic alterations in animals and humans. We have found that nicotine infusion and e-cig vaping augment murine AAA, and that maternal e-cig vaping augments AAA in their offspring.
Hypothesis: We investigated the effects of maternal e-cig vaping in mice on DNA methylation and accessibility in both parents and offspring, and evaluated effects of nicotine and e-cig condensate (ECC) on germ cells in culture.
Methods: We treated female ApoE-/- and C57BL6J mice (F0) with e-cig nicotine vapor (24 mg/ml, 9 sec/min, 1 hour/day) or room air. Arm 1: mice were treated for 28 days, then mated to untreated controls. Arm 2: mice were mated after 1 week of e-cig exposure, then treated until end of gestation. In parallel mice, aortic tissue and blood were obtained for RRBS-Seq and ATAC-seq analysis to evaluate DNA methylation and accessibility after exposure. Offspring were aged to 10-12 weeks-old, and similarly assayed. We also evaluated abdominal aortic structure in offspring, and treated cultured spermatogonial stem cells and primary oocytes with nicotine or ECC.
Results: Maternal e-cig exposure dramatically altered aortic DNA in both parents and offspring in both Arms, with numerous differentially methylated genes (DMGs). ATAC-seq identified hundreds of differentially accessible genes in their blood (DAGs). Vaping altered offspring DNA patterns in AAA-related genes, with parallel maternal changes noted. DMG/DAG pathway analyses were enriched in transcription factors and inflammation/immune-related genes, as well as numerous chromatin remodeling genes. Many DMG/DAGs overlapped with transcriptionally regulated genes from our array studies of murine AAA tissue. Further, we found that maternal ApoE-/- e-cig treatment alters offspring aortic structure, suggesting developmental dysregulation. Nicotine and ECC promote oocyte spontaneous activation, and alter expression of chromatin remodeling factors in germ cells in culture.
Conclusions: E-cig nicotine led to consistent broad heritable epigenetic changes in aorta and blood, including chromatin-remodeling and key AAA-related genes. These results may provide a partial mechanistic explanation for observed e-cig-induced augmentation of AAA in multiple models across generations, with implications for human health.