Within the growing body of proteomics studies, issues addressing problems of ecotoxicology are on the rise. Generally speaking, ecotoxicology uses quantitative expression changes of distinct proteins known to be involved in toxicological responses as biomarkers. Unlike these directed approaches, proteomics examines how multiple expression changes are associated with a contamination that is suspected to be detrimental. Consequently, proteins involved in toxicological responses that have not been described previously may be revealed. Following identification of key proteins indicating exposure or effect, proteomics can potentially be employed in environmental risk assessment. To this end, bioinformatics may unveil protein patterns specific to an environmental stress that would constitute a classifier able to distinguish an exposure from a control state. The combined use of sets of marker proteins associated with a given pollution impact may prove to be more reliable, as they are based not only on a few unique markers which are measured independently, but reflect the complexity of a toxicological response. Such a proteomic pattern might also integrate some of the already established biomarkers of environmental toxicity. Proteomics applications in ecotoxicology may also comprise functional examination of known classes of proteins, such as glutathione transferases or metallothioneins, to elucidate their toxicological responses.
Heat shock proteins (hsps) are potential biomarkers for monitoring environmental pollution. In this study, the use of hsps as biomarkers in field bioassays was evaluated in terrestrial invertebrates exposed to a metal gradient near Avonmouth, UK. We investigated the hsp70 response in resident and transplanted isopods of the species Oniscus asellus and Porcellio scaber and the hsp60 response in transplanted nematodes of the species Plectus acuminatus in six field sites along the metal gradient. Considerable differences were detected in the stress responses between nematodes and isopods (isopods responded in a gradient-specific manner, nematodes did not), the two isopod species and the transplanted and resident specimens of each isopod species: in the sites closest to the smelter, O. asellus residents showed high hsp70 levels while O. asellus transplanted from an unpolluted site displayed comparatively low hsp70 levels. For P. scaber, it was just the opposite. In resident isopod populations of both species, tolerant phenotypes were revealed in the most contaminated field sites. The hsp70 level in both isopod species was a suitable biomarker of effect (but of exposure only in non-tolerant individuals) even in long-term metal-contaminated field sites. The hsp60 response in the nematode alone was not a suitable biomarker for heavily contaminated soils. However, it had indicative value when related to the hsp70 response in the isopods and could be a suitable biomarker for less heavily contaminated soils.
Proteomics provide potential in the discovery of new sensitive biomarkers for environmental pollution. To evaluate this potential, we have utilized ProteinChip technology to analyze the proteomic profile of blue mussels (Mytilus edulis) from polluted marine habitats surrounding the island of Karmøy, Norway. Two different types of contamination, heavy metals and polyaromatic hydrocarbons (PAHs), were compared to a clean reference site. Differentially expressed proteins/peptides were found, which showed a specific induction or a general suppression associated with the field site of origin. By combining sets of protein markers in a tree-building algorithm, we were able to correctly classify samples from these sites with an accuracy of 90%.
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