Early response to ionizing radiation: molecular and cellular effects

Ionizing radiation cause by direct and indirect effects via the free radicals resulting from the radiolysis of water, lesions in cellular structure by alterations of the constitutive molecules of cells (lipids, proteins, nucleic acids). Because of the important role of the DNA molecule, radio-induced DNA lesions are more studied. Many cells are able to respond effectively to the DNA lesions in the minutes, the hours, the days which follow the aggression: early response. This respond can lead, in the case of cells irradiated in mitotic activity, to the stop at critical stages of cell cycle, time to activate the systems of repair of genomic lesions. However, when the badly or not repaired DNA lesions durably persist, this state creates a risk of passage of mutations in the daughter cells. The persistence of these lesions can also engage cells towards processes of cellular death by apoptosis or necrosis. In this lecture will be developed different classes of identified lesions, cellular antioxidant defenses, then the various key molecules involved in the early response after irradiation. (author)