Gender-dependent impact on epigenetic modifications caused by nicotine in abdominal aortic aneurysm

腹主动脉瘤(AAA)是一种复杂且高致命性的疾病。由于没有保守的治疗方法，了解发病机制和内在和外在危险因素的影响是至关重要的。然而，吸烟被认为是AAA发生的主要危险因素，可能是因为烟草烟雾的主要成分尼古丁。因此，尼古丁不仅影响加速动脉瘤生长的炎症过程，而且还影响表观遗传调节机制。表观遗传信号包括小的非编码RNA(MicroRNA)的变化，它通过甲基化来调节基因表达和基因区域的化学修饰。这样，基因既可以被激活，也可以被抑制。虽然吸烟/尼古丁暴露被认为是AAA发生的主要风险因素，但女性性行为似乎具有保护性影响。这在一定程度上是由于雌激素信号的性别差异，因为随着绝经后女性AAA发生率的增加，雌激素信号的保护作用在绝经期间消失。雌激素已被证明可以减弱促炎血管过程，从而部分抵消尼古丁对血管系统的依赖作用。此外，雌激素信号被证明调节表观遗传机制，如基因甲基化和microRNA表达。几项基于动物模型的研究进一步支持了雌激素/女性性别对AAA发育的保护作用。来自申请者的宿主实验室的初步数据表明，在尼古丁暴露下，这种情况也是恒定的。该项目旨在回答，这是否可能是由于尼古丁反应的表观遗传调控机制存在性别差异。为了解决这一问题，将对不同性别的小鼠进行恒定水平的尼古丁处理，然后利用两个互补的小鼠AAA模型进行AAA诱导。此外，通过卵巢切除/假手术或补充雌激素，亚组的雌激素水平将发生变化。随后，将探索组织和血液样本中已知受尼古丁影响的基因或被证明受AAA调控的基因的表观遗传调控的变化。此外，还将检查动脉瘤形态、主动脉僵硬和炎症因子变化的差异。为了识别其他性别相关的不同甲基化基因位点对尼古丁的反应，将实施一种表观基因组范围的方法，利用Illumina 450K甲基化珠芯片。

Abdominal aortic aneurysm (AAA) is a complex and and highly lethal disease. Since there are no conservative approaches to therapy, understanding of pathogenesis and influence of intrinsic and extrinsic risk factors is essential. Yet, smoking is considered as the main risk factor in AAA development likely due to nicotine, the main component of tobacco smoke. Thereby nicotine does not only influence inflammatory processes which accelerate aneurysm growth but also affects epigenetic regulatory mechanism. Epigenetic signalling includes changes in small, non-coding RNAs (microRNA), which regulate gene expression and chemical modification of gene-regions by methylation. In this way genes can either be activated or supressed. While smoking/nicotine exposure are considered as major risk factors for AAA development, female sex seems to have protective influence. This partly results from gender-dependent differences in estrogen signalling, since the protective effect is lost during menopause with increasing rate of AAA among post-menopausal women. Estrogen has proven to attenuate pro-inflammatory vascular processes and thereby partly countering nicotine-dependent effects on vasculature. Further, estrogen signalling was shown to regulate epigenetic mechanism like gene-methylation and microRNA expression. The protective effect of estrogen/female sex on AAA development is further supported by several animal model-based studies. Preliminary data from the applicant’s host laboratory suggest this to be constant under nicotine exposure as well. This projects aims to answer, whether this might be due to gender-dependent differences in epigenetic regulatory mechanism in response to nicotine. To address this context, mice of both genders will be treated with constant levels of nicotine followed by AAA induction utilizing two complementary murine AAA models. Additionally, estrogen levels will be altered in subset-groups by ovariectomy/sham operation or estrogen supplementation. Subsequently, tissue and blood samples will be probed for changes in epigenetic regulation of genes known to be affected by nicotine or that were shown to be regulated in AAA. Furthermore, differences in aneurysm morphology, aortic stiffness and changes of inflammatory factors will examined. To identify additional gender-dependent differently methylated gene-sites in response to nicotine, an epigenome-wide approach utilizing the Illumina 450K Methylation BeadChip will be implemented.