Effect of ionizing radiation on the transcription levels of cell stress marker genes in the pacific oyster crassostrea gigas
Résumé
In the North-Cotentin (Normandy, France), the marine environment is chronically exposed to liquid releases from the La Hague nuclear fuel recycling plant (Areva NC), resulting in a small increase in radioactivity compared to natural background. The transcriptional expression levels of stress genes were investigated in oysters exposed to ionizing radiation. Adult oysters were kept for 6 weeks in 60Co-labeled seawater (400 Bq liter-1), resulting in a total dose of 6.2 mGy. Transcriptional expression of target genes was monitored by reverse-transcription quantitative polymerase chain reaction. Nine genes were selected for their sensitivity to ionizing radiation based on the literature and available DNA sequences. They included genes encoding chaperone proteins and genes involved in oxidative stress regulation, cell detoxification and cell cycle regulation. Of the nine genes of interest, metallothionein (MT) and multi-drug resistance (MDR) displayed significant overexpression in response to chronic exposure to an internal low dose. For comparison, oysters were acutely exposed to an external high dose for 100 min, resulting in 20 Gy, and the same target gene expression analysis was carried out. As in the case of chronic exposure to the low dose, MT and MDR displayed significant increases. The results suggest that the transcriptional expression levels of cell stress genes may be used as a biosensor of exposure of oysters to ionizing radiation, with a particular focus on the MT and MDR genes. However, the upregulation of these potential players in the cellular response to radiation-induced stress was not correlated with mortality or apparent morbidity. The possible role of these stress genes in the resistance of oysters to ionizing radiation is discussed. © 2011 by Radiation Research Society.
Mots clés
chaperone
cobalt 60
cytochrome P450
glutathione transferase
heat shock protein 70
heat shock protein 90
messenger RNA
metallothionein
multidrug resistance protein
protein hsc72
superoxide dismutase
unclassified drug
animal experiment
article
biosensor
cell cycle regulation
cell stress
correlation analysis
Crassostrea gigas
detoxification
DNA sequence
gamma radiation
gene expression
ionizing radiation
morbidity
mortality
nonhuman
oxidative stress
oyster
priority journal
quantitative analysis
radiation dose
reverse transcription polymerase chain reaction
sensitivity analysis
thermoluminescence dosimetry
upregulation
Animals
Biological Markers
Cobalt Radioisotopes
Crassostrea
Dose-Response Relationship
Radiation
Gamma Rays
Laboratories
Radiometry
RNA
Messenger
Seawater
Stress
Physiological
Time Factors
Transcription
Genetic
Ostreidae