Abstract
Emission of ionizing radiation in the environment is a natural phenomenon which can be enhanced by human activities. Ecosystems are then chronically exposed to ionizing radiations. But environmental risk assessment of chronic exposure suffers from a lack of knowledge. Extrapolation of data from acute to chronic exposure is not always relevant, and can lead to uncertainties as effects could be different between the two irradiation modes, especially regarding reproduction endpoint, which is an ecologically relevant parameter. In the present study, we decided to refine the understanding of the molecular mechanisms involved in response to acute and chronic -irradiation by a global proteome label free LC-MS/MS analysis. C. elegans were exposed to 3 common cumulated radiation doses for acute or chronic exposure condition and global modification of the proteome was studied. This global analysis of protein expression has demonstrated the modulation of proteins involved in regulatory biological processes such as lipid transport, DNA replication, germ cell development, apoptosis, ion transport, cuticle development, and aging at lower doses than those for which individual effects on reproduction have been previously observed. Thus, these proteins could constitute early and sensitive markers of radio-induced reprotoxicity; more specifically HAT-1, RPS-19 in acute and VIT-3 for chronic conditions that are expressed in a dose-dependent manner. Finally, to focus on reproduction process, the proteomic analysis showed either repression or overexpression of 12 common proteins in organisms exposed to acute or chronic irradiation, respectively. These proteins include the vitellogenin cluster notably involved in lipid transport and ovocyte maturation and proteins involved in cuticle development and molting i.e COL-14, GLF-1, NOAH-1, NOAH-2, ACN-1. This results show that protein expression modulation is a sensitive and predictive marker of the effects of acute and chronic exposure regarding reproduction parameter, but also highlight limitation of data extrapolation from acute to chronic exposure.