1H NMR metabolomics of Eisenia fetida responses after sub-lethal exposure to perfluorooctanoic acid and perfluorooctane sulfonate

Abstract

Environmental contextPerfluoroalkyl acids are persistent environmental contaminants that are also found in soils. We use a metabolomics approach based on nuclear magnetic resonance analyses to investigate the responses of earthworms to exposure to sub-lethal levels of two perfluoroalkyl acids. The results indicate that this metabolomics approach is able to delineate the toxic mode of action of contaminants present at sub-lethal levels. AbstractMetabolomics entails the analysis of endogenous metabolites within organisms exposed to an external stressor such as an environmental contaminant. We utilised 1H NMR-based metabolomics to elucidate sub-lethal toxic mechanisms of Eisenia fetida earthworms after exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Earthworms were exposed to a range of concentrations of PFOA (6.25 to 50 μg cm–2) and PFOS (3.125 to 25 μg cm–2) by contact tests for 2 days. Earthworm tissues were extracted using a mixture of chloroform, methanol and water, and the polar fraction was analysed by 1H NMR spectroscopy. NMR-based metabolomic analysis revealed heightened E. fetida toxic responses with higher PFOA and PFOS exposure concentrations. Principal component analysis (PCA) exhibited significant separation between control and exposed earthworms along PC1 for all PFOA and PFOS exposure concentrations. Leucine, arginine, glutamate, maltose and adenosine triphosphate (ATP) are potential indicators of PFOA and PFOS exposure as these metabolite concentrations fluctuated with exposure. Our data also indicate that PFOA and PFOS exposure may increase fatty acid oxidation and interrupt ATP synthesis due to a disruption in the inner mitochondrial membrane structure. NMR-based metabolomics has promise as an insightful tool for elucidating the environmental toxicology of sub-lethal contaminant exposure.

Analysis of Eisenia fetida earthworm responses to sub-lethal C60 nanoparticle exposure using 1H-NMR based metabolomics

“…Difference class 1 H NMR spectra were then obtained by subtracting the buckets of the average controls from that of the average exposure treatments. The buckets representing the peaks of metabolites that weren't statistically significant from the controls were then replaced with a zero resulting in a t-test filtered 1 H NMR difference spectrum (Ekman et al, 2008;Lankadurai et al, 2012;Schock et al, 2013). The buckets were then imported into Origin 7 (version 7.0383, OriginLab Corporation, Northampton, MA) to plot the difference 1 H NMR spectra.…”

“…We also exposed E. fetida to C 60 nanoparticle concentrations of 300 and 3,000 mg/kg with exposure times of 2, 7 and 14 days in soil exposure tests. Our first objective was to determine if NMR-based metabolomics is able to detect significant metabolic changes in response to sub-lethal C 60 nanoparticle exposure via both soil and contact tests as previous studies have noted differences due to the mode of exposure (Lankadurai et al, 2012(Lankadurai et al, , 2013b. In addition, we also identified bioindicators of C 60 nanoparticle exposure and to delineate the MOA.…”

“…Metabolomics involves measuring fluctuations in low molecular weight endogenous metabolites, such as sugars and amino acids, in response to a defined external stressor Viant, 2008). NMR-based earthworm metabolomics has shown promise as a high-throughput and reproducible technique that can elucidate a contaminant's MOA and also identify potential bioindicators of exposure in response to sub-lethal exposure to a range of contaminants such as polycyclic aromatic hydrocarbons, organochlorine pesticides, polychlorinated biphenyls, nanoparticles and heavy metals (Brown et al, 2010;Bundy et al, 2008;Ekman et al, 2009;Jones et al, 2008b;Lankadurai et al, 2012;Viant et al, 2005;Whitfield Åslund et al, 2011Whitfield Åslund et al, , 2012Yuk et al, 2013). As such, NMR-based metabolomics analysis may provide valuable insights into understanding the response of earthworms to C 60 exposure.…”

Metabolomics for Soil Contamination Assessment

“…Baylay et al (2012) specifically relates chlorpyrifos toxicity to increased levels of fumarate, an intermediate of the trycarboxylic acid cycle. Research conducted with the same earthworm (E. fetida) and other families of organic compounds revealed a different metabolic response (Brown et al, 2010;Lankadurai et al, 2012), confirming the capability of metabolomics to discriminate the metabolic pathways involved in the response to a particular toxic compound. Moreover, the results strongly suggest that sets of biomarkers might be soon sufficiently reliable as for their implantation in in toxicity standardized test.…”

Water-mediated NOE: a promising tool for interrogating interfacial clay–xenobiotic interactions

“…Although the acute health effects of these xenobiotics are well documented, the effect of chronic exposure remains an open question [1-3, 5, 6]. The intrinsic interactions between these xenobiotics and soils hold the key to understanding both their environmental accumulation and their bioavailability [7][8][9][10][11]. Therefore, a better understanding as to how xenobiotics are sequestered into complex rock, soil, and sediments is required [12][13][14].…”