Molecular Indicators of chemically Mediated Toxicity and Pathology in Marine Organisms
Report No FR/D0026
Tests are required by legislative bodies worldwide to assess the toxicity of new chemicals produced by industry prior to their application being allowed in the community and environment (eg. OECD tests as required by MAFF, UK and CEC). Cellular biomarkers are used to detect the effects of pollutants on organisms and ecosystems and have been applied in a number of field monitoring programmes (eg. North Sea Task Force Biological Effects Programme, Mediterranean Action Plan (MAP-FAO), and the National Status and Trends Programme, USA).
Two projects (toxicity testing and biomarker development) were carried out to address these objectives using laboratory and field studies of mussel and flatfish.
Different chemicals may have different mechanisms of toxicity in different species, making extrapolation of results between different animal groups difficult. The toxicity testing approach was based on the need for small-scale, sublethal, multi-species testing systems. Five tests were developed representative of five major mechanisms of toxicity (reactive oxygen species [ROS] generation, lipid peroxidation, mutagenicity, enzyme inactivation, membrane damage) using model chemicals (petroleum products, PCBs, organochlorine pesticide, plasticiser) and environmental samples (sediment and sea-surface microlayer [SMC]).
Toxicity (ROS production) was observed for harbour sediment and SMC extracts, but not for coastal SMC extracts. Further development of the ROS and inhibition of 7-ethoxyresorufin O-deethylase (EROD) activity tests are recommended.
A cellular dye retention technique based on the lysosomal uptake of neutral red (NRR) has proven to be a very sensitive and robust test for cellular damage induced by a variety of pollutant chemicals (polynuclear aromatic hydrocarbons, PCBs, organochlorine pesticides, mercury and cobalt).
This diagnostic biomarker test is a predictor of developing pathology since there is a well established link between lysosomal damage and disease. Furthermore, the test can be carried out on small samples of cells in blood or body fluids without necessitating any harm to the animals being tested.
Two techniques for pathological markers were identified as useful but require further study. These were molecular recognition tests carried out on sections of fish liver for low-density lipoprotein (LDL) and multi-drug resistance (mdr) protein. The two tests showed elevated LDL and mdr protein in livers of fish from heavily contaminated estuaries in Germany and the UK. The presence of these proteins in the liver cells is abnormal and hence indicative of pathology. Mdr-protein correlated with lysosomal damage and incidence of neoplastic lesions. Mdr protein is also indicative of exposure to a wide range of toxic organic chemicals including many heterocyclic compounds.
Cellular reactions to chemical pollutants are diagnostic of injurious impact and can be prognostic for further more serious pathology. Where this link with pathology is shown, such cellular reactions can be used to assess the probable risk. It is recommended that the cellular dye retention test (NRR) is made available for monitoring purposes and that the multi-drug resistance system should be developed further as a diagnostic biomarker.
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