A wide variety of physical and chemical agents may damage the chemical structure of DNA, and in particular nucleic bases. As a consequence, mutations are produced that may trigger the cancerization of the damage cell. Fortunately, all cells have developed a series of enzymatic processes that can repair the damaged portion of DNA and limit the deleterious consequences of the damage. The effect of genotoxic agents results thus from the balance between the formation and the repair of DNA damage.
Monitoring the formation of DNA damage in Human requires collection of tissues, followed by extraction of DNA and analysis. Although internal organs may sometimes be studied when biopsies are taken in patients, samples available in the general population or at the working place are limited to skin biopsies and blood cells. Biopsies is a rather invasive procedure and the nature of the damage in blood cells does not represent the whole body exposure. Some limitations are also encountered in in vitro experiments. There is thus a need for less invasive procedures and more representative data.
In the present PhD project, we want to quantify the damages bases released from DNA by the repair enzymes. In particular, we want to quantify bulky adducts and photoproducts resulting from exposure to solar light. The work will first involve extensive analytical chemistry developments, using mostly solid phase extraction and HPLC associated to mass spectrometry. On-line HPLC preparation of the samples will also be investigated. The method will be then validated on cultured cells. Last, the protocol will be extended to the detection of repair products in biological fluids like urine for in vivo investigations. The technique will be applied to three main topics: the formation of photoproducts induced by solar UV in skin and its prevention by sunscreens (collaboration with the Pierre Fabre Dermo-Cosmétique company), the induction of adducts with pollutants like polycyclic aromatic hydrocarbons, and the formation of adducts between DNA and CEES, an analog of sulfur mustard (collaboration with the Military Biomedical Research Institute).