Hepatic gene expression in flounder chronically exposed to multiply polluted estuarine sediment: Absence of classical exposure ‘biomarker’ signals and induction of inflammatory, innate immune and apoptotic pathways

Abstract

The effects of chronic long term exposure to multiply-polluted environments on fish are not well understood, but environmental surveys suggest that such exposure may cause a variety of pathologies, including cancers. Transcriptomic profiling has recently been used to assess gene expression in European flounder (Platichthys flesus) living in several polluted and clean estuaries. However, the gene expression changes detected were not unequivocally elicited by pollution, most likely due to the confounding effects of natural estuarine ecosystem variables. In this study flounder from an uncontaminated estuary were held on clean or polluted sediments in mesocosms, allowing control of variables such as salinity, temperature, and diet. After 7 months flounder were removed from each mesocosm and hepatocytes prepared from fish exposed to clean or polluted sediments. The hepatocytes were treated with benzo(a)pyrene (BAP), estradiol (E2), copper, a mixture of these three, or with the vehicle DMSO. A flounder cDNA microarray was then used to measure hepatocyte transcript abundance after each treatment. The results show that long term chronic exposure to a multiply-polluted sediment causes increases in the expression of mRNAs coding for proteins of the endogenous apoptotic program, of innate immunity and inflammation. Contrary to expectation, the expression of mRNAs which are commonly used as biomarkers of environmental exposure to particular contaminants were not changed, or were changed contrary to expectation. However, acute treatment of hepatocytes from flounder from both clean and polluted sediments with BAP or E2 caused the expected changes in the expression of these biomarkers. Thus transcriptomic analysis of flounder exposed long-term to chronic pollution causes a different pattern of gene expression than in fish acutely treated with single chemicals, and reveals novel potential biomarkers of environmental contaminant exposure. These novel biomarkers include Diablo, a gene involved in apoptotic pathways and highly differentially regulated by both chronic and acute exposure to multiple pollutants.

Expression profiling of liver in Java medaka fish exposed to 17β-estradiol

“…The installation and running costs of the microarray technique are high, but it is clearly an efficient way to detect on a massive scale the different signals sent by living organisms surrounded by external stressors 13,14 . DNA microarray technology was successfully applied to characterize the gene expression changes that result from E2 exposure in this study and we found that a large number of genes were affected by estrogen in O. javanicus, as has been shown in other studies 15,16 . We identified statistically significantly (P⁄0.05) up-or downregulated expression (an expression ratio of exposed to control ¤2) of 655 genes after E2 exposure for 24 h and 633 genes after E2 exposure for 48 h. The greatest upregulation in response to 100 μg/L E2 was observed in the genes encoding vitellogenins (vitI, vitII), and choriogenins (chgH, chgH minor).…”

Combined effects of temperature changes and metal contamination at different levels of biological organization in yellow perch

“…In contrast, at 28˚C, both metals prevented the failure of the diablo gene observed in control fish, suggesting an enhanced capacity for apoptosis. A stimulation of the diablo gene has been reported in hepatocytes of flounder exposed in mesocosms to sediment contaminated by organic and inorganic contaminants (Leaver et al 2010). The gene therefore appears particularly useful as a biomarker of contaminant exposure, but our study demonstrates that its response to contaminants varies according to acclimation temperature.…”

Effects of pesticide compounds (chlorothalonil and mancozeb) and benzo[a]pyrene mixture on aryl hydrocarbon receptor, p53 and ubiquitin gene expression levels in haemocytes of soft-shell clams (Mya arenaria)

“…Each value is expressed as the mean (n = 4) ± SE (standard error). An asterisk (*) indicates a statistically different values at the level of P B 0.05 Effects of pesticide compounds and BaP mixture 1769 expression of genes involved in disease development in aquatic organisms (David et al 2007;Leaver et al 2010).…”