Seasonal changes in mRNA encoding for cell stress markers in the oyster Crassostrea gigas exposed to radioactive discharges in their natural environment
Résumé
The North Cotentin area (Normandy, France) hosts several nuclear facilities among which the AREVA reprocessing plant of La Hague is responsible for controlled discharges of liquid radioactive wastes into the marine environment. The resulting increase in radioactivity is very small compared to natural radioactivity. However, concerns about environment protection prompted the scientific community to focus on the effects of the chronic exposure to low concentrations of radionuclides in non-human biota. This study contributes to the evaluation of the possible impact of radioactive discharges on the oyster Crassostrea gigas in the field. Real-time polymerase chain reaction was used to quantify the expression levels of genes involved in cell stress in the oyster. They included members of the heat shock protein family (Hsp70, Hsc72, Hsp90), superoxide dismutase (SOD) and metallothionein (MT). Times series measurements were built from periodic samplings in the natural environment in order to characterize the natural variability as well as possible seasonal fluctuations. The genes studied exhibited a general seasonal expression pattern with a peak value in winter. The data inversely correlated with seawater temperature and the nature of the relationship between gene expression and temperature is discussed. In parallel, oysters were collected in four locations on the French shores, exposed or not to radioactive liquid wastes from the nuclear facilities hosted in the North Cotentin. The comparison of data obtained in the reference location on the Atlantic coast (not exposed) and data from oysters of the English Channel (exposed) gave no evidence for any statistical difference. However, because of the complexity of the natural environment, we cannot rule out the possibility that other parameters may have masked the impact of radioactive discharges. This dense set of data is a basis for the use of the expression levels of those genes as biomarkers to address the question of the possible effects of chronic exposure of the oyster to low concentrations of radionuclides in controlled laboratory experimental conditions. © 2006 Elsevier B.V. All rights reserved.
Mots clés
Animal cell culture
Environmental protection
Genes
Marine engineering
Radioactive wastes
RNA
Crassostrea gigas
Heat shock proteins
Metallothionein
mRNA
Radioactive discharges
Seasonal variations
Superoxide dismutase
Climate change
heat shock protein 70
heat shock protein 72
heat shock protein 90
messenger RNA
metallothionein
superoxide dismutase
biomarker
bivalve
discharge
gene expression
marine environment
pollution effect
pollution exposure
radioactive waste
radioactivity
radionuclide
seasonal variation
article
atmospheric radioactivity
biota
cell stress
correlation analysis
evaluation
France
liquid
nonhuman
oyster
priority journal
protein expression
real time polymerase chain reaction
season
Animals
Biological Markers
Crassostrea
Environmental Monitoring
Gene Expression
Gills
Heat-Shock Proteins
Radioactive Waste
Radioisotopes
Messenger
Seasons
Stress
Superoxide Dismutase
Water Pollutants
Radioactive
Basse-Normandie
Cap de la Hague
Cotentin
Eurasia
Europe
Manche
Western Europe
Ostreidae