Research article

'Systems toxicology' approach identifies coordinated metabolic responses to copper in a terrestrial non-model invertebrate, the earthworm Lumbricus rubellus

Jacob G Bundy¹ , Jasmin K Sidhu¹ , Faisal Rana¹ , David J Spurgeon² , Claus Svendsen² , Jodie F Wren^3,4 , Stephen R Stürzenbaum⁵ , A John Morgan³ and Peter Kille³

¹  Department of Biomolecular Medicine, Division of Surgery, Oncology, Reproductive Biology, and Anaesthetics (SORA), Faculty of Medicine, Imperial College London, SW7 2AZ, London, UK

²  Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon PE28 2LS, UK

³  School of Biosciences, University of Cardiff, Main Building, Park Place, Cardiff, CF10 3TL, UK

⁴  School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, UK

⁵  School of Biomedical and Health Sciences, Pharmaceutical Sciences Division, King's College London, Franklin Wilkins Building, Stamford Street, London, SE1 9NH, UK

author email corresponding author email

BMC Biology 2008, 6:25doi:10.1186/1741-7007-6-25

Published:	3 June 2008

Abstract

Background

New methods are needed for research into non-model organisms, to monitor the effects of toxic disruption at both the molecular and functional organism level. We exposed earthworms (Lumbricus rubellus Hoffmeister) to sub-lethal levels of copper (10–480 mg/kg soil) for 70 days as a real-world situation, and monitored both molecular (cDNA transcript microarrays and nuclear magnetic resonance-based metabolic profiling: metabolomics) and ecological/functional endpoints (reproduction rate and weight change, which have direct relevance to population-level impacts).

Results

Both of the molecular endpoints, metabolomics and transcriptomics, were highly sensitive, with clear copper-induced differences even at levels below those that caused a reduction in reproductive parameters. The microarray and metabolomic data provided evidence that the copper exposure led to a disruption of energy metabolism: transcripts of enzymes from oxidative phosphorylation were significantly over-represented, and increases in transcripts of carbohydrate metabolising enzymes (maltase-glucoamylase, mannosidase) had corresponding decreases in small-molecule metabolites (glucose, mannose). Treating both enzymes and metabolites as functional cohorts led to clear inferences about changes in energetic metabolism (carbohydrate use and oxidative phosphorylation), which would not have been possible by taking a 'biomarker' approach to data analysis.

Conclusion

Multiple post-genomic techniques can be combined to provide mechanistic information about the toxic effects of chemical contaminants, even for non-model organisms with few additional mechanistic toxicological data. With 70-day no-observed-effect and lowest-observed-effect concentrations (NOEC and LOEC) of 10 and 40 mg kg^-1 for metabolomic and microarray profiles, copper is shown to interfere with energy metabolism in an important soil organism at an ecologically and functionally relevant level.