Abstract
Species are chronically exposed to ionizing radiation, a natural phenomenon which can be enhanced by human activities. The induced toxicity mechanisms still remain unclear and seem depending on the mode of exposure, i.e. acute and chronic. To better understand these phenomena, studies need to be conducted both at the subcellular and individual levels. Proteins, functional molecules in organisms, are the targets of oxidative damage (especially via their carbonylation (PC)) and are likely to be relevant biomarkers. After exposure of Caenorhabditis elegans to either chronic or acute γ rays we showed that hatching success is impacted after acute but not after chronic irradiation. At the molecular level, the carbonylated protein level in relation with dose was slightly different between acute and chronic exposure whereas the proteolytic activity is drastically modified. Indeed, whereas the 20S proteasome activity is inhibited by acute irradiation from 0.5 Gy, it is activated after chronic irradiation from 1 Gy. As expected, the 20S proteasome activity is mainly modified by irradiation whereas the 26S and 30S activity are less changed. This study provides preliminaries clues to understand the role of protein oxidation and proteolytic activity in the radiation-induced molecular mechanisms after chronic versus acute irradiation in C. elegans.
Highlights
To reach the objectives of environmental radiation protection, it seems necessary to use integrated approaches to improve the understanding of the mechanisms involved at different levels of biological organization, to find sensitive markers of exposure and adequately protect the environment[1,2,3,4,5]
Other studies have shown reprotoxicity of chronic gamma irradiation on other organisms than C. elegans. These studies revealed a decrease of progeny number per individual and a decrease of hatching success on Ophryotrocha diadema, Neanthes arenaceodentata, Daphnia magna and Eisenia fetida exposed to 0.19 mGy.h−1, 13.7 mGy.h−1, 31 mGy.h−1 and 43 mGy.h−1 respectively[28,29,30]
Activities of the three forms of proteasome declined at different doses, possibly leading to a defect in the DDR pathway contrary to chronic irradiation, leading to apoptosis possibly explaining the decrease of the hatching success after acute irradiation on C. elegans from 50 Gy
Summary
To reach the objectives of environmental radiation protection, it seems necessary to use integrated approaches to improve the understanding of the mechanisms involved at different levels of biological organization, to find sensitive markers of exposure and adequately protect the environment[1,2,3,4,5]. Proteins are involved in key biological processes, including DNA repair, epigenetic mechanisms, apoptosis and, like DNA, lipids and sugars, are impacted by ionizing radiation. Their oxidation can become critical for the cell. Due to its protein nature, the proteasome itself is a target of ionizing radiation, but studies have only focused on proteasome sensitivity after acute irradiation[21,22]. Regarding sensitivity of proteasome to ionizing radiation, it has been shown that global proteasomal activity is impacted from 2 Gy of acute gamma irradiation in a non-dose-dependent manner[22]
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