Metabolite Changes in an Estuarine Annelid Following Sublethal Exposure to a Mixture of Zinc and Boscalid

Stuck in the mangrove mud: The risk of trace element exposure to shore crabs in restored urban mangroves

The restoration of mangroves in urban environments can increase the risk of contaminant exposure and subsequent health effects to resident biota, yet this risk is rarely considered in mangrove restoration programs. Here we assessed the influence of sediment chemistry on contaminant bioaccumulation in shore crabs from restored and natural mangroves in urban environments compared to a reference site. The concentrations of some trace elements were several-fold higher in the sediment and crab tissues of the urban restored site compared to the natural reference site (Cd = 6×, Co = 7×, Cr = 4×, Mn = 30×, and Ni = 18× greater in sediments, while Cd = 4×, Co = 2×, Cr = 2×, Mn = 6×, and Ni = 3× greater in crab tissues). NMR-based metabolomics on crabs revealed higher abundances of proline and glutamate at urban sites, which may be indicative of physiological stress from trace element contamination. Choice experiments were used to test habitat selectivity by crabs from each population, and showed that crabs avoided sediments from the contaminated urban sites. Our results suggest that restoring mangroves in contaminated environments could create ecological sinks, where animals take residence in the new habitat but are exposed to sediment-based contaminants, with potential implications for organism and population health.

Bioaccumulation and metabolic impact of environmental PFAS residue on wild-caught urban wetland tiger snakes (Notechis scutatus)

PFAS contamination of urban waters is widespread but understanding the biological impact of its accumulation is limited to humans and common ecotoxicological model organisms. Here, we combine PFAS exposure and bioaccumulation patterns with whole organism responses and omics-based ecosurveillance methods to investigate the potential impacts of PFAS on a top predator of wetlands, the tiger snake (Notechis scutatus). Tiger snakes (18 male and 17 female) were collected from four wetlands with varying PFAS chemical profiles and concentrations in Perth, Western Australia. Tiger snake livers were tested for 28 known PFAS compounds, and Σ28PFAS in liver tissues ranged between 322 ± 193 μg/kg at the most contaminated site to 1.31 ± 0.86 μg/kg at the least contaminated site. The dominant PFAS compound detected in liver tissues was PFOS. Lower body condition was associated with higher liver PFAS, and male snakes showed signs of high bioaccumulation whereas females showed signs of maternal offloading. Biochemical profiles of snake muscle, fat (adipose tissue), and gonads were analysed using a combination of liquid chromatography triple quadrupole (QqQ) and quadrupole time-of-flight (QToF) mass spectrometry methodologies. Elevated PFAS was associated with enriched energy production and maintenance pathways in the muscle, and had weak associations with energy-related lipids in the fat tissue, and lipids associated with cellular genesis and spermatogenesis in the gonads. These findings demonstrate the bioavailability of urban wetland PFAS in higher-order reptilian predators and suggest a negative impact on snake health and metabolic processes. This research expands on omics-based ecosurveillance tools for informing mechanistic toxicology and contributes to our understanding of the impact of PFAS residue on wildlife health to improve risk management and regulation.

SDHi fungicides: An example of mitotoxic pesticides targeting the succinate dehydrogenase complex

Succinate dehydrogenase inhibitors (SDHi) are fungicides used to control the proliferation of pathogenic fungi in crops. Their mode of action is based on blocking the activity of succinate dehydrogenase (SDH), a universal enzyme expressed by all species harboring mitochondria. The SDH is involved in two interconnected metabolic processes for energy production: the transfer of electrons in the mitochondrial respiratory chain and the oxidation of succinate to fumarate in the Krebs cycle. In humans, inherited SDH deficiencies may cause major pathologies including encephalopathies and cancers. The cellular and molecular mechanisms related to such genetic inactivation have been well described in neuroendocrine tumors, in which it induces an oxidative stress, a pseudohypoxic phenotype, a metabolic, epigenetic and transcriptomic remodeling, and alterations in the migration and invasion capacities of cancer cells, in connection with the accumulation of succinate, an oncometabolite, substrate of the SDH. We will discuss recent studies reporting toxic effects of SDHi in non-target organisms and their implications for risk assessment of pesticides. Recent data show that the SDH structure is highly conserved during evolution and that SDHi can inhibit SDH activity in mitochondria of non-target species, including humans. These observations suggest that SDHi are not specific inhibitors of fungal SDH. We hypothesize that SDHi could have toxic effects in other species, including humans. Moreover, the analysis of regulatory assessment reports shows that most SDHi induce tumors in animals without evidence of genotoxicity. Thus, these substances could have a non-genotoxic mechanism of carcinogenicity that still needs to be fully characterized and that could be related to SDH inhibition. The use of pesticides targeting mitochondrial enzymes encoded by tumor suppressor genes raises questions on the risk assessment framework of mitotoxic pesticides. The issue of SDHi fungicides is therefore a textbook case that highlights the urgent need for changes in regulatory assessment.

Study on the targeted regulation of Scutellaria baicalensis leaf on glutamine-glutamate metabolism and glutathione synthesis in the liver of d-gal ageing rats

OBJECTIVES

Scutellaria baicalensis leaf (SLE), the above-ground part of the traditional Chinese medicine Scutellaria baicalensis Georgi, is rich in resources and contains a large number of flavonoids with anti-inflammatory, antioxidant and neuroprotective functions. The present study evaluated the ameliorative effects and related mechanisms of SLE on d-gal-induced ageing rats, providing a theoretical basis for the exploitation of SLE.

METHODS

This experiment investigated the mechanism of SLE for anti-ageing by non-targeted metabonomics technology combined with targeted quantitative analysis and molecular biology technology.

KEY FINDINGS

Non-targeted metabonomics analysis showed that 39 different metabolites were screened out. Among them, 38 metabolites were regulated by SLE (0.4 g/kg), and 33 metabolites were regulated by SLE (0.8 g/kg). Through enrichment analysis, glutamine-glutamate metabolic pathway was identified as the key metabolic pathway. Subsequently, the results of targeted quantitative and biochemical analysis displayed that the contents of key metabolites and the activities of enzymes in glutamine-glutamate metabolic pathway and glutathione synthesis could be regulated by SLE. Furthermore, the results of Western blotting indicated that SLE significantly modulated the expression of Nrf2, GCLC, GCLM, HO-1, and NQO1 proteins.

CONCLUSION

To sum up, the anti-ageing mechanism of SLE was related to glutamine-glutamate metabolism pathway and Nrf2 signalling pathway.

Multi-omics eco-surveillance of complex legacy contamination with a locally adapted estuarine invertebrate

Complex legacy contamination from human use is a major issue for estuaries globally. In particular, contamination of water and sediments with bioavailable metals/metalloids, in addition to other industrial contaminants, such as hydrocarbons. Yet, understanding of complex toxicity and local adaptation in field exposed, non-model, invertebrate communities is limited. Herein, we apply multi-omics (metabolomics, lipidomics, proteomics) coupled to traditional sediment quality analyses, to better characterise molecular and cellular responses necessary for application to monitoring, as an eco-surveillance tool. Using these approaches, we characterise functional phenotypes of a sediment associated invertebrate (sipunculid), from an estuary exposed to complex legacy contamination (metals: Zn, Hg, Cd, Pb, Cu, As; and polycyclic aromatic hydrocarbons, PAHs). We sampled individuals at a range of exposure sites, highly (NTB5), moderately (NTB13), and lesser-influenced reference sites. Size differences were observed in sampled individuals between sites, with smaller individuals collected from NTB13. Analysis of environmental variables that correlated with change in the metabolite data revealed that the metabolism of smaller individuals at medium exposure NTB13 was highly differentiated by sediment concentrations of Hg, despite higher concentrations at more exposed NTB5. Functional phenotypes of these smaller individuals were characterised by sulphur and aromatic amino acid metabolism, increases in oxidised intermediates, upregulation of protein responses to oxidative stress, and melanin synthesis, and saturation of membrane and storage of lipids; in addition to the metabolism of naphthalene (PAH). Such widespread change was not observed in the metabolite and lipid profiles of larger individuals at high exposure NTB5, suggesting possible differences in effects between sites may also be associated with size (developmental stage, or age) and/or PAH exposure. This study serves to further understanding of differing modes of toxicity and local adaptation to multiple contaminants, and drivers of functional change in a complex estuary environment.

Is substrate choice an overlooked variable in ecotoxicology experiments?

It is crucial to understand the effects caused by experimental parameters such as temperature, light, and food type on lab and field-based ecotoxicology experiments, as these variables, and combinations thereof, can affect results. The type of substrate used in exposure experiments, however, is generally assumed to have no effect. This may not always be correct. The metabolic changes in the freshwater crustacean, Austrochiltonia subtenuis exposed to copper, using three common substrates, gauze; toilet paper; and cellulose were investigated. Substrate alone did not affect survival, but each substrate elicited a different metabolic response and adult and juvenile amphipods had different substrate preferences. Several classes of metabolites were shown to change in response to different substrates and toxicant. These included disaccharides, monosaccharides, fatty acids, and tricarboxylic acid cycle intermediates. The results illustrate that metabolomic responses can differ in response to experimental factors that were previously thought not to be significant. In fact, our data indicate that substrate should be viewed as an experimental factor as important to control for as more well-known confounders such as temperature or food, thus challenging the current paradigm. Assuming substrate type has no effect on the experiment could potentially lead to errors in contaminant toxicity assessments. We propose that ideal good practise would be that all experimental factors should be evaluated for their potential influence on metabolomic profiles prior to contaminant response experiments being undertaken.

A preliminary study on early postmortem submersion interval (PMSI) estimation and cause-of-death discrimination based on nontargeted metabolomics and machine learning algorithms

Postmortem submersion interval (PMSI) estimation and cause-of-death discrimination of corpses in water have long been challenges in forensic practice. Recently, many studies have linked postmortem metabolic changes with PMI extension, providing a potential strategy for estimating PMSI using the metabolome. Additionally, there is a lack of potential indicators with high sensitivity and specificity for drowning identification. In the present study, we profiled the untargeted metabolome of blood samples from drowning and postmortem submersion rats at different PMSIs within 24 h by liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 601 metabolites were detected. Four different machine learning algorithms, including random forest (RF), partial least squares (PLS), support vector machine (SVM), and neural network (NN), were used to compare the efficiency of the machine learning methods. Nineteen metabolites with obvious temporal regularity were selected as candidate biomarkers according to "IncNodePurity." Robust models were built with these biomarkers, which yielded a mean absolute error of 1.067 h. Additionally, 36 other metabolites were identified to build the classifier model for discriminating drowning and postmortem submersion (AUC = 1, accuracy = 95%). Our results demonstrated the potential application of metabolomics combined with machine learning in PMSI estimation and cause-of-death discrimination.

Metabolomics as a tool for in situ study of chronic metal exposure in estuarine invertebrates

Estuaries are subject to intense human use globally, with impacts from multiple stressors, such as metal contaminants. A key challenge is extending beyond traditional monitoring approaches to understand effects to biota and system function. To explore the metabolic effects of complex metal contaminants to sediment dwelling (benthic) fauna, we apply a multiple-lines-of-evidence approach, coupling environmental monitoring, benthic sampling, total metals analysis and targeted metabolomics. We characterise metabolic signatures of metal exposure in three benthic invertebrate taxa, which differed in distribution across sites and severity of metal exposure: sipunculid (very high), amphipod (high), maldanid polychaete (moderate). We observed sediment and tissue metal loads far exceeding sediment guidelines where toxicity-related adverse effects may be expected, for metals including, As, Cd, Pb, Zn and Hg. Change in site- and taxa-specific metabolite profiles was highly correlated with natural environmental drivers (sediment total organic carbon and water temperature). At the most metal influenced sites, metabolite variation was also correlated with sediment metal loads. Using supervised multivariate regression, taxa-specific metabolic signatures of increased exposure and possibility of toxic effects were characterised against multiple reference sites. Metabolic signatures varied according to each taxon and degree of metal exposure, but primarily indicated altered cysteine and methionine metabolism, metal-binding and elimination (lysosomal) activity, coupled to change in complex biosynthesis pathways, responses to oxidative stress, and cellular damage. This novel multiple-lines-of-evidence approach combining metabolomics with traditional environmental monitoring, enabled detection and characterisation of chronic metal exposure effects in situ in multiple invertebrate taxa. With capacity for application to rapid and effective monitoring of non-model species in complex environments, these approaches are critical for improved assessment and management of systems that are increasingly subject to anthropogenic drivers of change.

An NMR-based metabolomics study on sea anemones Exaiptasia diaphana (Rapp, 1829) with atrazine exposure

Sea anemones have been recommended as critical bioindicators for marine environmental stressors; however, the understanding of the biological effects in response to sublethal pollutant exposure is still limited. In this study, NMR-based metabolomics was performed to investigate the effects of atrazine on Exaiptasia diaphana with concentrations ranging from 3 to 90 ppb. As a result, the metabolic profiling of E. diaphana was significantly affected after 70 ppb treatment while a partial perturbation was observed as early as 3 ppb treatment. Glutamate was significantly changed at low atrazine concentrations with increased upregulation in concentrated atrazine experiments which is a potential biomarker for E. diaphana exposed to atrazine stressors. The TCA intermediates succinate and malate as well as the TCA cycle-related metabolites such as alanine, glycine, and taurine downregulated after atrazine treatment which also indicated the lower energy supply of E. diaphana. In summary, our study demonstrated that significant metabolic level perturbation could be detected at low atrazine concentrations before a physical change could be observed, and glutamate or the nitrogen metabolism may be the initial target for sea anemones by atrazine. The study may provide pioneering results for using E. diaphana to predict the impacts of exposure to atrazine toxin in marine systems.

Toxic mechanism of pyrene to catalase and protective effects of vitamin C: Studies at the molecular and cell levels

Polycyclic aromatic hydrocarbons, distributing extensively in the soil, would potentially threaten the soil organisms (Eisenia fetida) by triggering oxidative stress. As a ubiquitous antioxidant enzyme, catalase can protect organisms from oxidative damage. To reveal the potential impact of polycyclic aromatic hydrocarbon pyrene (Pyr) on catalase (CAT) and the possible protective effect of Ascorbic acid (vitamin C), multi-spectral and molecular docking techniques were used to investigate the influence of structure and function of catalase by pyrene. Fluorescence and circular dichroism analysis showed that pyrene would induce the microenvironmental changes of CAT amino acid residues and increase the α-helix in the secondary structure. Molecular simulation results indicated that the main binding force of pyrene around the active center of CAT is hydrogen bonding force. Furthermore, pyrene inhibited catalase activity to 69.9% compared with the blank group, but the degree of inhibition was significantly weakened after vitamin C added into the research group. Cell level experiments showed that pyrene can increase the level of ROS in the body cavity cell of earthworms, and put the cells under the threat of potential oxidative damage. Antioxidants-vitamin C has a protective effect on catalase and maintains the stability of intracellular ROS levels to a certain extent.

Ecological and toxicological assessments of anthropogenic contaminants based on environmental metabolomics

There has long been a great concern with growing anthropogenic contaminants and their ecological and toxicological effects on living organisms and the surrounding environment for decades. Metabolomics, a functional readout of cellular activity, can capture organismal responses to various contaminant-related stressors, acquiring direct signatures to illustrate the environmental behaviours of anthropogenic contaminants better. This review entails the application of metabolomics to profile metabolic responses of environmental organisms, e.g. animals (rodents, fish, crustacean and earthworms) and microorganisms (bacteria, yeast and microalgae) to different anthropogenic contaminants, including heavy metals, nanomaterials, pesticides, pharmaceutical and personal products, persistent organic pollutants, and assesses their ecotoxicological impacts with regard to literature published in the recent five years. Contaminant-induced metabolism alteration and up/down-regulation of metabolic pathways are revealed in typical organisms. The obtained insights of variations in global metabolism provide a distinct understanding of how anthropogenic contaminants exert influences on specific metabolic pathways on living organisms. Thus with a novel ecotechnique of environmental metabolomics, risk assessments of anthropogenic contaminants are profoundly demonstrated.

What are the effects of PFAS exposure at environmentally relevant concentrations?

The group of synthetic chemicals known as poly and per-fluoroalkyl substances (PFAS) are currently of high concern to environmental regulators and the public due to their widespread occurrence, resistance to degradation and reported toxicity. However, little data exists on the effects of exposure to PFAS at environmentally relevant concentrations and this hampers the effective management of these compounds. This paper reviews current research on the occurrence and ecotoxicology of PFAS at environmentally relevant doses to assess their potential biological impacts. Hazard Quotient (HQ) analysis was undertaken as part of this assessment. Most PFAS detected in the environment were found to have a HQ risk value of <1 meaning their reported concentrations are below their predicted no effect concentration. This indicates many reported toxic effects of PFAS are, theoretically, unlikely to occur outside the laboratory. However, lack of information on new PFAS as well as their precursors and degradation products, coupled with lack of knowledge of their mixture toxicity means our understanding of the risks of PFAS is incomplete, especially in regard to sub-lethal and/or chronic effects. It is proposed that the development of molecular markers for PFAS exposure are needed to aid in the development of environmental PFAS regulations that are effective in fully protecting the environment.

Metabolomics Provide Sensitive Insights into the Impacts of Low Level Environmental Contamination on Fish Health-A Pilot Study

This exploratory study aims to investigate the health of sand flathead (Platycephalus bassensis) sampled from five sites in Port Phillip Bay, Australia using gas chromatography-mass spectrometry (GC-MS) metabolomics approaches. Three of the sites were the recipients of industrial, agricultural, and urban run-off and were considered urban sites, while the remaining two sites were remote from contaminant inputs, and hence classed as rural sites. Morphological parameters as well as polar and free fatty acid metabolites were used to investigate inter-site differences in fish health. Significant differences in liver somatic index (LSI) and metabolite abundance were observed between the urban and rural sites. Differences included higher LSI, an increased abundance of amino acids and energy metabolites, and reduced abundance of free fatty acids at the urban sites compared to the rural sites. These differences might be related to the additional energy requirements needed to cope with low-level contaminant exposure through energy demanding processes such as detoxification and antioxidant responses as well as differences in diet between the sites. In this study, we demonstrate that metabolomics approaches can offer a greater level of sensitivity compared to traditional parameters such as physiological parameters or biochemical markers of fish health, most of which showed no or little inter-site differences in the present study. Moreover, the metabolite responses are more informative than traditional biomarkers in terms of biological significance as disturbances in specific metabolic pathways can be identified.