DNA damage response and DNA repair triggered by genotoxic phenylpropanoids in the diet

苯丙素类或苯丙烯（PP）是草本植物和香料如罗勒、肉豆蔻、茴香和菖蒲的天然成分。它们是具有不饱和C3侧链的苯的化学衍生物，其含有末端双键（烯丙基PP）或内部双键（1-丙烯基PP）。这些化合物以结构依赖性方式进行代谢活化：1-丙烯基PP通过细胞色素P450酶（CPY），烯丙基PP通过β-内酰胺酶和磺基转移酶（SULT）。主要靶器官为肝脏，已知PP在肝脏中具有遗传毒性和致癌性。然而，它在很大程度上是未知的DNA损伤反应如何赋予对PP诱导的DNA加合物的保护和DNA修复途径参与DNA加合物的去除。本研究的目的是了解PP-DNA加合物引发的DNA损伤反应，揭示PP-DNA加合物参与的DNA修复机制。为此，将研究与食品相关的烯丙基PP甲基丁香酚和1-丙烯基PP β-细辛醚。将使用具有代谢能力的肝细胞系以及在DNA修复中具有特定缺陷的原代肝细胞。由于在我们的初步研究中获得的结果，我们将专注于全球基因组和转录偶联核苷酸切除修复（GG-NER和TC-NER，分别）。这些模型应解决以下问题：1。哪种类型的DNA损伤反应在由烯丙基和1-丙烯基PP形成DNA加合物时在细胞中触发，以及这是如何调节的，2）。GG-NER和TC-NER对于PP诱导的DNA加合物的去除的相关性是什么，并且关于dG-N2-和dA-N6-加合物是否存在差异，以及3.）PP诱导的DNA损伤在细胞毒性和致染色体断裂性方面的生物学后果是什么，GG-NER和TC-NER缺陷分别如何影响这些终点。

Phenylpropanoids or Phenylpropenes (PP) are naturally occurring ingredients of herbs and spices such as basil, nutmeg, anise and calamus. They are chemical derivatives of benzol with an unsaturated C3-side chain, which contains either a terminal double bond (allylic PP) or an internal double bond (1-propenylic PP). These compounds undergo metabolic activation in a structure-dependent manner: 1-propenylic PP via Cytochrome P450 enzymes (CPY) and allylic PP via CYP and Sulfotransferases (SULT). The major target organ represents the liver, where PP are known to act genotoxic and carcinogenic. However, it is largely unknown how the DNA damage response confers protection against PP-induced DNA adducts and which DNA repair pathways are involved in DNA adduct removal. Furthermore, it is unclear how defects in DNA repair will affect cell survival and genome integrity.The objective of this study is to understand the DNA damage response triggered by PP-DNA adducts and to reveal the engaged DNA repair mechanism. To this end, the allylic PP Methyleugenol and the 1-propenylic PP ß-Asaron will be studied, which are both relevant in food. Metabolic competent liver cell lines as well as primary liver cells with specific defects in DNA repair will be used. Due to the results obtained in our preliminary studies, we will focus on global-genomic and transcription-coupled nucleotide excision repair (GG-NER and TC-NER, respectively). The followings issues should be addressed with these models: 1.) Which type of DNA damage response in triggered in cells upon DNA adduct formation by allylic and 1-propenylic PP and how is this regulated, 2.) What is the relevance of GG-NER and TC-NER for the removal of PP-induced DNA adducts and are there differences concerning dG-N2- and dA-N6-adducts, and 3.) What are the biological consequences of PP-induced DNA damage with regard to cytotoxicity and clastogenicity, and how are these endpoints influenced by defects in GG-NER and TC-NER, respectively.