Integrated 1H NMR-based metabolomics analysis of earthworm responses to sub-lethal Pb exposure

A H-1 nuclear magnetic resonance (NMR)-based approach to metabolomics combined with atomic absorption spectroscopy, histopathological examination and biochemical assessment was used to determine the toxic effects of lead (Pb) on earthworms (Eisenia fetida). Earthworms were exposed to Pb in a lead nitrate solution at converted concentrations of 1.25, 5.0 and 20 mu g cm(-2) in contact tests for 48 h. Based on histopathological inspection, the epidermis, muscles, chloragogenous tissues and intestinal epithelium were severely impaired. Based on biochemical assessment, a disruption of the antioxidative system and neurotoxic effects in earthworms occurred following exposure to Pb. Orthogonal signal correction-partial least-squares-discriminant analysis of NMR profiles indicated that Pb exposure in earthworms caused widespread metabolic changes, which were associated with oxidative stress, neurotransmitter imbalance, disruption of osmotic equilibrium and interference in energy metabolism and nucleic acid metabolism. The integrated metabolomics approach provided new insights into Pb-induced toxicity in earthworms. Metabolomics is a powerful and highly effective approach and has great promise to determine the ecotoxicological effects and the underlying mechanisms of toxicity of heavy metals.