Investigation of DNA repair mechanisms involved in the protection against hepatotoxic pyrrolizidine alkaloids

• Applicant: Professor Dr. Jörg Fahrer
• Subject Area: Toxicology, Laboratory Medicine ; Food Chemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563229752

Pyrrolizidine alkaloids (PAs) are synthesized by 2-3 % of all flowering plants worldwide and serve as protection against herbivores. Humans are exposed to PAs due to the intake of PA-containing herbal medicinal products and dietary supplements as well as the consumption of PA-contaminated food. 1,2-unsaturated PAs are of toxicological concern since they are activated by cytochrome P450 (CYP) to DNA reactive metabolites, causing liver injury and cancer in rodents. Numerous studies demonstrated that the genotoxicity and cytotoxicity of PAs depend on their chemical structure, particularly their degree of esterification. It was shown that PAs cause DNA monoadducts and DNA crosslinks. However, it is still unknown which DNA repair pathway protects against the PA-induced DNA damage and which DNA lesions are of particular importance for the PA triggered cytotoxicity and genome instability. The objective of this study is to identify the DNA repair pathways involved in the removal of PA-induced DNA damage in liver cells. To consider the impact of the chemical structure, a PA monoester (heliotrine), a cyclic PA diester (retrorsine) and an open-chained PA diester (lasiocarpine) will be studied. As those PAs require CYP3A4-catalyzed metabolic activation, both CYP3A4-competent human liver cell models as well as primary murine hepatocytes proficient and deficient in specific DNA repair pathways will be used. In view of the chemical nature of the PA-induced DNA lesions, we will focus on nucleotide excision repair (NER) and interstrand crosslink repair (ICR). The following issues will be addressed using these models: a) to which extent do the structurally diverse PAs cause DNA monoadducts and DNA crosslinks, b) what is the relevance of NER and ICR for the removal of PA-induced DNA damage, and c) which impact do defects in NER or ICR have on PA-triggered cellular effects such as cell death, mutagenicity and clastogenicity.

• DFG Programme: Research Grants