(1)H NMR-based metabolomics of Daphnia magna responses after sub-lethal exposure to triclosan, carbamazepine and ibuprofen

Metabolomic study on ostracods exposed to environmentally relevant concentrations of five pharmaceuticals selected via a novel approach

Pharmaceuticals (PhACs) are increasingly detected in aquatic ecosystems, yet their effects on biota remain largely unknown. The environmentally relevant concentrations of many PhACs may not result in individual-level responses, like mortality or growth inhibition, traditional toxicity endpoints. However, this doesn't imply the absence of negative effects on biota. Metabolomics offers a more sensitive approach, detecting responses at molecular and cellular levels and providing mechanistic understanding of adverse effects. We evaluated bioaccumulation and metabolic alterations in a benthic ostracod, Heterocypris incongruens, exposed to a mixture of five PhACs (carbamazepine, tiapride, tolperisone, propranolol and amlodipine) at environmentally relevant concentrations for 7 days using liquid chromatography coupled with mass spectrometry. The selection of PhACs was based, among other factors, on risk quotient values determined using toxicological data available in the literature and concentrations of PhACs quantified in our previous research in the sediments of the Odra River estuary. This represents a novel approach to PhACs selection for metabolomic studies that considers strictly quantitative data. Amlodipine and tolperisone exhibited the highest bioaccumulation. Significant impacts were observed in Alanine, aspartate and glutamate metabolism, Starch and sucrose metabolism, Arginine biosynthesis, Histidine metabolism, Tryptophan metabolism, Glycerophospholipid metabolism, and Glutathione metabolism pathways. Most of the below-individual-level responses were likely nonspecific and related to dysregulation in energy metabolism and oxidative stress response. Additionally, some pharmaceutical-specific responses were also observed. Therefore, untargeted metabolomics can be used to detect metabolic changes resulting from environmentally relevant concentrations of PhACs in aquatic ecosystems and to understand their underlying mechanism.

Metabolomic-Based Comparison of Daphnia magna and Japanese Medaka Responses After Exposure to Acetaminophen, Diclofenac, and Ibuprofen

Pharmaceuticals are found in aquatic environments due to their widespread use and environmental persistence. To date, a range of impairments to aquatic organisms has been reported with exposure to pharmaceuticals; however, further comparisons of their impacts across different species on the molecular level are needed. In the present study, the crustacean Daphnia magna and the freshwater fish Japanese medaka, common model organisms in aquatic toxicity, were exposed for 48 h to the common analgesics acetaminophen (ACT), diclofenac (DCF), and ibuprofen (IBU) at sublethal concentrations. A targeted metabolomic-based approach, using liquid chromatography-tandem mass spectrometry to quantify polar metabolites from individual daphnids and fish was used. Multivariate analyses and metabolite changes identified differences in the metabolite profile for D. magna and medaka, with more metabolic perturbations for D. magna. Pathway analyses uncovered disruptions to pathways associated with protein synthesis and amino acid metabolism with D. magna exposure to all three analgesics. In contrast, medaka exposure resulted in disrupted pathways with DCF only and not ACT and IBU. Overall, the observed perturbations in the biochemistry of both organisms were different and consistent with assessments using other endpoints reporting that D. magna is more sensitive to pollutants than medaka in short-term studies. Our findings demonstrate that molecular-level responses to analgesic exposure can reflect observations of other endpoints, such as immobilization and mortality. Thus, environmental metabolomics can be a valuable tool for selecting sentinel species for the biomonitoring of freshwater ecosystems while also uncovering mechanistic information. Environ Toxicol Chem 2024;43:1339-1351. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Mixture effects of pharmaceuticals carbamazepine, diclofenac and venlafaxine on Mytilus galloprovincialis mussel probed by metabolomics and proteogenomics combined approach

Exposure to single molecules under laboratory conditions has led to a better understanding of the mechanisms of action (MeOAs) and effects of pharmaceutical active compounds (PhACs) on non-target organisms. However, not taking the co-occurrence of contaminants in the environment and their possible interactions into account may lead to underestimation of their impacts. In this study, we combined untargeted metabolomics and proteogenomics approaches to assess the mixture effects of diclofenac, carbamazepine and venlafaxine on marine mussels (Mytilus galloprovincialis). Our multi-omics approach and data fusion strategy highlighted how such xenobiotic cocktails induce important cellular changes that can be harmful to marine bivalves. This response is mainly characterized by energy metabolism disruption, fatty acid degradation, protein synthesis and degradation, and the induction of endoplasmic reticulum stress and oxidative stress. The known MeOAs and molecular signatures of PhACs were taken into consideration to gain insight into the mixture effects, thereby revealing a potential additive effect. Multi-omics approaches on mussels as sentinels offer a comprehensive overview of molecular and cellular responses triggered by exposure to contaminant mixtures, even at environmental concentrations.

Toxicity of triclosan, an antimicrobial agent, to a nontarget freshwater zooplankton species, Moina macrocopa

The toxicity of triclosan (TCS) on the freshwater cladoceran Moina macrocopa was investigated by acute and chronic toxicity assessments followed by genotoxicity and oxidative stress response analyses. The 48-h LC50 of TCS for ≤24-h-old M. macrocopa was determined as 539 μg L-1 . Chronic exposure to TCS at concentrations ranging from 5 to 100 μg L-1 showed a stimulatory effect at low concentrations (≤10 μg L-1 ) and an inhibitory effect at high concentrations (≥50 μg L-1 ) on growth, reproduction, and population-growth-related parameters of M. macrocopa. The genotoxicity test results indicated that TCS concentrations ranging from 50 to 100 μg L-1 can alter individuals' DNA. Analysis of the antioxidant enzymes catalase (CAT) and glutathione s-transferase (GST) demonstrated increased levels of these enzymes at high TCS concentrations. Our results indicated that TCS concentrations found in the natural environment have minimal acute toxicity to M. macrocopa. However, TCS at even low concentrations can significantly affect its growth, reproduction, and population-growth-related characteristics. The observed responses suggest a hormetic dose-response pattern and imply a potential endocrine-disrupting effect of TCS. Our molecular and biochemical findings indicated that high concentrations of TCS have the potential to induce oxidative stress that may lead to DNA alterations in M. macrocopa.

Environmental metabolomics uncovers oxidative stress, amino acid dysregulation, and energy impairment in Daphnia magna with exposure to industrial effluents

Anthropogenic activities are regarded as point sources of pollution entering freshwater bodies worldwide. With over 350,000 chemicals used in manufacturing, wastewater treatment and industrial effluents are comprised of complex mixtures of organic and inorganic pollutants of known and unknown origins. Consequently, their combined toxicity and mode of action are not well understood in aquatic organisms such as Daphnia magna. In this study, effluent samples from wastewater treatment and industrial sectors were used to examine molecular-level perturbations to the polar metabolic profile of D. magna. To determine if the industrial sector and/or the effluent chemistries played a role in the observed biochemical responses, Daphnia were acutely (48 h) exposed to undiluted (100%) and diluted (10, 25, and 50%) effluent samples. Endogenous metabolites were extracted from single daphnids and analyzed using targeted mass spectrometry-based metabolomics. The metabolic profile of Daphnia exposed to effluent samples resulted in significant separation compared to the unexposed controls. Linear regression analysis determined that no single pollutant detected in the effluents was significantly correlated with the responses of metabolites. Significant perturbations were uncovered across many classes of metabolites (amino acids, nucleosides, nucleotides, polyamines, and their derivatives) which serve as intermediates in keystone biochemical processes. The combined metabolic responses are consistent with oxidative stress, disruptions to energy metabolism, and protein dysregulation which were identified through biochemical pathway analysis. These results provide insight into the molecular processes driving stress responses in D. magna. Overall, we determined that the metabolic profile of Daphnia could not be predicted by the chemical composition of environmentally relevant mixtures. The findings of this study demonstrate the advantage of metabolomics in conjunction with chemical analyses to assess the interactions of industrial effluents. This work further demonstrates the ability of environmental metabolomics to characterize molecular-level perturbations in aquatic organisms exposed to complex chemical mixtures directly.

The impact of pharmaceutical pollutants on daphnids - A metabolomic approach

Pharmaceuticals have been classified as emerging contaminants in the aquatic ecosystem, mainly due to their increased use and improper disposal. A significant range of pharmaceutical compounds and their metabolites have been globally detected in surface waters and pose detrimental effects to non-target organisms. Monitoring pharmaceutical water pollution relies on the analytical approaches for their detection, however, such approaches are limited by their sensitivity limit and coverage of the wide range pharmaceutical compounds. This lack of realism in risk assessment is bypassed with effect-based methods, which are complemented by chemical screening and impact modelling, and are able to provide mechanistic insight for pollution. Focusing on the freshwater ecosystem, in this study we evaluated the acute effects on daphnids for three distinct groups of pharmaceuticals; antibiotics, estrogens, and a range of commonly encountered environmentally relevant pharmaceutical pollutants. Combining several endpoints such as mortality, biochemical (enzyme activities) and holistic (metabolomics) we discovered distinct patterns in biological responses. In this study, changes in enzymes of metabolism e.g. phosphatases and lipase, as well as the detoxification enzyme, glutathione-S-transferase, were recorded following acute exposure to the selected pharmaceuticals. A targeted analysis of the hydrophilic profile of daphnids revealed mainly the up-regulation of metabolites following metformin, gabapentin, amoxicillin, trimethoprim and β-estradiol. Whereas gemfibrozil, sulfamethoxazole and oestrone exposure resulted in the down-regulation of majority of metabolites.

Freshwater crustacean exposed to active pharmaceutical ingredients: ecotoxicological effects and mechanisms

Concerns over the ecotoxicological effects of active pharmaceutical ingredients (APIs) on aquatic invertebrates have been raised in the last decade. While numerous studies have reported the toxicity of APIs in invertebrates, no attempt has been made to synthesize and interpret this dataset in terms of different exposure scenarios (acute, chronic, multigenerational), multiple crustacean species, and the toxic mechanisms. In this study, a thorough literature review was performed to summarize the ecotoxicological data of APIs tested on a range of invertebrates. Therapeutic classes including antidepressants, anti-infectives, antineoplastic agents, hormonal contraceptives, immunosuppressants, and neuro-active drugs exhibited higher toxicity to crustaceans than other API groups. The species sensitivity towards APIs exposure is compared in D. magna and other crustacean species. In the case of acute and chronic bioassays, ecotoxicological studies mainly focus on the apical endpoints including growth and reproduction, whereas sex ratio and molting frequency are commonly used for evaluating the substances with endocrine-disrupting properties. The multigenerational and "Omics" studies, primarily transcriptomics and metabolomics, were confined to a few API groups including beta-blocking agents, blood lipid-lowing agents, neuroactive agents, anticancer drugs, and synthetic hormones. We emphasize that in-depth studies on the multigenerational effects and the toxic mechanisms of APIs on the endocrine systems of freshwater crustacean are warranted.

Lenz Lenses in a Cryoprobe: Boosting NMR Sensitivity Toward Environmental Monitoring of Mass-Limited Samples

Nuclear magnetic resonance (NMR) spectroscopy is commonly employed in a wide range of metabolomic research. Unfortunately, due to its relatively low sensitivity, smaller samples become challenging to study by NMR. Cryoprobes can be used to increase sensitivity by cooling the coil and preamplifier, offering sensitivity improvements of ∼3 to 4x. Alternatively, microcoils can be used to increase mass sensitivity by improving sample filling and proximity, along with decreased electrical resistance. Unfortunately, combining the two approaches is not just technically challenging, but as the coil decreases, so does its thermal fingerprint, reducing the advantage of cryogenic cooling. Here, an alternative solution is proposed in the form of a Lenz lens inside a cryoprobe. Rather than replacing the detection coil, Lenz lenses allow the B₁ field from a larger coil to be refocused onto a much smaller sample area. In turn, the stronger B₁ field at the sample provides strong coupling to the cryocoil, improving the signal. By combining a 530 I.D. Lenz lens with a cryoprobe, sensitivity was further improved by 2.8x and 3.5x for ¹H and ¹³C, respectively, over the cryoprobe alone for small samples. Additionally, the broadband nature of the Lenz lenses allowed multiple nuclei to be studied and heteronuclear two-dimensional (2D) NMR approaches to be employed. The sensitivity improvements and 2D capabilities are demonstrated on 430 nL of hemolymph and eight eggs (∼350 μm O.D.) from the model organismDaphnia magna. In summary, combining Lenz lenses with cryoprobes offers a relatively simple approach to boost sensitivity for tiny samples while retaining cryoprobe advantages.

Metabolic, cellular and defense responses to single and co-exposure to carbamazepine and methylmercury in Dreissena polymorpha

Carbamazepine (CBZ) and Hg are widespread and persistent micropollutants in aquatic environments. Both pollutants are known to trigger similar toxicity mechanisms, e.g. reactive oxygen species (ROS) production. Here, their effects were assessed in the zebra mussel Dreissena polymorpha, frequently used as a freshwater model in ecotoxicology and biomonitoring. Single and co-exposures to CBZ (3.9 μg L^-1) and MeHg (280 ng L^-1) were performed for 1 and 7 days. Metabolomics analyses evidenced that the co-exposure was the most disturbing after 7 days, reducing the amount of 25 metabolites involved in protein synthesis, energy metabolism, antioxidant response and osmoregulation, and significantly altering cells and organelles' structure supporting a reduction of functions of gills and digestive glands. CBZ alone after 7 days decreased the amount of α-aminobutyric acid and had a moderate effect on the structure of mitochondria in digestive glands. MeHg alone had no effect on mussels' metabolome, but caused a significant alteration of cells and organelles' structure in gills and digestive glands. Single exposures and the co-exposure increased antioxidant responses vs control in gills and digestive glands, without resulting in lipid peroxidation, suggesting an increased ROS production caused by both pollutants. Data globally supported that a higher number of hyperactive cells compensated cellular alterations in the digestive gland of mussels exposed to CBZ or MeHg alone, while CBZ + MeHg co-exposure overwhelmed this compensation after 7 days. Those effects were unpredictable based on cellular responses to CBZ and MeHg alone, highlighting the need to consider molecular toxicity pathways for a better anticipation of effects of pollutants in biota in complex environmental conditions.

Toxicometabolomics and Biotransformation Product Elucidation in Single Zebrafish Embryos Exposed to Carbamazepine from Environmentally-Relevant to Morphologically Altering Doses

Toxicometabolomics and biotransformation product (bioTP) elucidation were carried out in single zebrafish (ZF) embryos exposed to carbamazepine (CBZ). Exposures were conducted in 96-well plates containing six CBZ concentrations ranging from 0.5 μg/L to 50 mg/L (n = 12 embryos per dose). In the 50 mg/L dose group, 33% of embryos developed edema during the exposure (120 hpf), while hatching was significantly delayed in three of the lower-dose groups (0.46, 3.85, and 445 μg/L) compared to the control at 48 hpf. Toxicometabolomic analysis together with random forest modeling revealed a total of 80 significantly affected metabolites (22 identified via targeted lipidomics and 58 via nontarget analysis). The wide range of doses enabled the observation of both monotonic and nonmonotonic dose responses in the metabolome, which ultimately produced a unique and comprehensive biochemical picture that aligns with existing knowledge on the mode of action of CBZ. The combination of high dose exposures and apical endpoint assessment in single embryos also enabled hypothesis generation regarding the target organ for the morphologically altering insult. In addition, two CBZ bioTPs were identified without additional exposure experiments. Overall, this work showcases the potential of toxicometabolomics and bioTP determination in single ZF embryos for rapid and comprehensive chemical hazard assessment.

Long-term exposure to environmental diclofenac concentrations impairs growth and induces molecular changes in Lymnaea stagnalis freshwater snails

As pharmaceutical substances are highly used in human and veterinary medicine and subsequently released in the environment, they represent emerging contaminants in the aquatic compartment. Diclofenac (DCF) is one of the most commonly detected pharmaceuticals in water and little research has been focused on its long-term effects on freshwater invertebrates. In this study, we assessed the chronic impacts of DCF on the freshwater gastropod Lymnaea stagnalis using life history, behavioral and molecular approaches. These organisms were exposed from the embryo to the adult stage to three environmentally relevant DCF concentrations (0.1, 2 and 10 μg/L). The results indicated that DCF impaired shell growth and feeding behavior at the juvenile stage, yet no impacts on hatching, locomotion and response to light stress were noted. The molecular findings (metabolomics and transcriptomic) suggested that DCF may disturb the immune system, energy metabolism, osmoregulation and redox balance. In addition, prostaglandin synthesis could potentially be inhibited by DCF exposure. The molecular findings revealed signs of reproduction impairment but this trend was not confirmed by the physiological tests. Combined omics tools provided complementary information and enabled us to gain further insight into DCF effects in freshwater organisms.

Biomarkers-based assessment of triclosan toxicity in aquatic environment: A mechanistic review

Triclosan (TCS), an emergent pollutant, is raising a global concern due to its toxic effects on organisms and aquatic ecosystems. The non-availability of proven treatment technologies for TCS remediation is the central issue stressing thorough research on understanding the underlying mechanisms of toxicity and assessing vital biomarkers in the aquatic organism for practical monitoring purposes. Given the unprecedented circumstances during COVID 19 pandemic, a several-fold higher discharge of TCS in the aquatic ecosystems cannot be considered a remote possibility. Therefore, identifying potential biomarkers for assessing chronic effects of TCS are prerequisites for addressing the issues related to its ecological impact and its monitoring in the future. It is the first holistic review on highlighting the biomarkers of TCS toxicity based on a comprehensive review of available literature about the biomarkers related to cytotoxicity, genotoxicity, hematological, alterations of gene expression, and metabolic profiling. This review establishes that biomarkers at the subcellular level such as oxidative stress, lipid peroxidation, neurotoxicity, and metabolic enzymes can be used to evaluate the cytotoxic effect of TCS in future investigations. Micronuclei frequency and % DNA damage proved to be reliable biomarkers for genotoxic effects of TCS in fishes and other aquatic organisms. Alteration of gene expression and metabolic profiling in different organs provides a better insight into mechanisms underlying the biocide's toxicity. In the concluding part of the review, the present status of knowledge about mechanisms of antimicrobial resistance of TCS and its relevance in understanding the toxicity is also discussed referring to the relevant reports on microorganisms.

NMR spectroscopy of wastewater: A review, case study, and future potential

NMR spectroscopy is arguably the most powerful tool for the study of molecular structures and interactions, and is increasingly being applied to environmental research, such as the study of wastewater. With over 97% of the planet's water being saltwater, and two thirds of freshwater being frozen in the ice caps and glaciers, there is a significant need to maintain and reuse the remaining 1%, which is a precious resource, critical to the sustainability of most life on Earth. Sanitation and reutilization of wastewater is an important method of water conservation, especially in arid regions, making the understanding of wastewater itself, and of its treatment processes, a highly relevant area of environmental research. Here, the benefits, challenges and subtleties of using NMR spectroscopy for the analysis of wastewater are considered. First, the techniques available to overcome the specific challenges arising from the nature of wastewater (which is a complex and dilute matrix), including an examination of sample preparation and NMR techniques (such as solvent suppression), in both the solid and solution states, are discussed. Then, the arsenal of available NMR techniques for both structure elucidation (e.g., heteronuclear, multidimensional NMR, homonuclear scalar coupling-based experiments) and the study of intermolecular interactions (e.g., diffusion, nuclear Overhauser and saturation transfer-based techniques) in wastewater are examined. Examples of wastewater NMR studies from the literature are reviewed and potential areas for future research are identified. Organized by nucleus, this review includes the common heteronuclei (¹³C, ¹⁵N, ¹⁹F, ³¹P, ²⁹Si) as well as other environmentally relevant nuclei and metals such as ²⁷Al, ⁵¹V, ²⁰⁷Pb and ¹¹³Cd, among others. Further, the potential of additional NMR methods such as comprehensive multiphase NMR, NMR microscopy and hyphenated techniques (for example, LC-SPE-NMR-MS) for advancing the current understanding of wastewater are discussed. In addition, a case study that combines natural abundance (i.e. non-concentrated), targeted and non-targeted NMR to characterize wastewater, along with in vivo based NMR to understand its toxicity, is included. The study demonstrates that, when applied comprehensively, NMR can provide unique insights into not just the structure, but also potential impacts, of wastewater and wastewater treatment processes. Finally, low-field NMR, which holds considerable future potential for on-site wastewater monitoring, is briefly discussed. In summary, NMR spectroscopy is one of the most versatile tools in modern science, with abilities to study all phases (gases, liquids, gels and solids), chemical structures, interactions, interfaces, toxicity and much more. The authors hope this review will inspire more scientists to embrace NMR, given its huge potential for both wastewater analysis in particular and environmental research in general.

Targeted Metabolomic Assessment of the Sub-Lethal Toxicity of Halogenated Acetic Acids (HAAs) to Daphnia magna

Halogenated acetic acids (HAAs) are amongst the most frequently detected disinfection by-products in aquatic environments. Despite this, little is known about their toxicity, especially at the molecular level. The model organism Daphnia magna, which is an indicator species for freshwater ecosystems, was exposed to sub-lethal concentrations of dichloroacetic acid (DCAA), trichloroacetic acid (TCAA) and dibromoacetic acid (DBAA) for 48 h. Polar metabolites extracted from Daphnia were analyzed using liquid chromatography hyphened to a triple quadrupole mass spectrometer (LC-MS/MS). Multivariate analyses identified shifts in the metabolic profile with exposure and pathway analysis was used to identify which metabolites and associated pathways were disrupted. Exposure to all three HAAs led to significant downregulation in the nucleosides: adenosine, guanosine and inosine. Pathway analyses identified perturbations in the citric acid cycle and the purine metabolism pathways. Interestingly, chlorinated and brominated acetic acids demonstrated similar modes of action after sub-lethal acute exposure, suggesting that HAAs cause a contaminant class-based response which is independent of the type or number of halogens. As such, the identified metabolites that responded to acute HAA exposure may serve as suitable bioindicators for freshwater monitoring programs.

Sublethal effects of triclosan and triclocarban at environmental concentrations in silver catfish (Rhamdia quelen) embryos

Although banished in some countries, triclosan (TCS) and triclocarban (TCC) have been detected in surface waters in concentrations ranging from ng L^-1 to μg L^-1 and have shown to affect non-target organisms posing risk to aquatic ecosystems. However, the majority of the studies consider higher levels of these chemicals and single exposure effects to investigate their potential risks, rather than using environmentally relevant concentrations and their binary mixture. In this study, the toxicity of TCS and TCC, and their binary mixture was assessed in catfish embryos (Rhamdia quelen, a south American native species) exposed to environmental concentrations during 96 h. Organisms were evaluated through the endpoints of developmental abnormalities (spine, fin, facial/cranial and thorax), biochemical biomarkers related to oxidative stress responses: catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) activities, protein carbonylation (PCO) and neurotoxicity by acetylcholinesterase activity (AChE). The data showed that TCS caused fin abnormalities, decrease of SOD activity and increase of AChE activity in the catfish embryos of 96hpf. On the other hand, TCC and the binary mixture showed a higher abnormality index for the 96hpf embryos, and an induction of CAT and GST activities for the mixture treatment. The results obtained were able to show potential, but not severe, toxicity of TCS and TCC even in low concentrations and a short period of exposure. The relevance of studies approaching real scenarios of exposure should be reinforced, considering environmental concentrations of chemicals, interactions of contaminants in complex mixtures and the use of a native species such as R. quelen exposed during initial stages of development.

5-Axis CNC Micromilling for Rapid, Cheap, and Background-Free NMR Microcoils

The superior mass sensitivity of microcoil technology in nuclear magnetic resonance (NMR) spectroscopy provides potential for the analysis of extremely small-mass-limited samples such as eggs, cells, and tiny organisms. For optimal performance and efficiency, the size of the microcoil should be tailored to the size of the mass-limited sample of interest, which can be costly as mass-limited samples come in many shapes and sizes. Therefore, rapid and economic microcoil production methods are needed. One method with great potential is 5-axis computer numerical control (CNC) micromilling, commonly used in the jewelry industry. Most CNC milling machines are designed to process larger objects and commonly have a precision of >25 μm (making the machining of common spiral microcoils, for example, impossible). Here, a 5-axis MiRA6 CNC milling machine, specifically designed for the jewelry industry, with a 0.3 μm precision was used to produce working planar microcoils, microstrips, and novel microsensor designs, with some tested on the NMR in less than 24 h after the start of the design process. Sample wells could be built into the microsensor and could be machined at the same time as the sensors themselves, in some cases leaving a sheet of Teflon as thin as 10 μm between the sample and the sensor. This provides the freedom to produce a wide array of designs and demonstrates 5-axis CNC micromilling as a versatile tool for the rapid prototyping of NMR microsensors. This approach allowed the experimental optimization of a prototype microstrip for the analysis of two intact adult Daphnia magna organisms. In addition, a 3D volume slotted-tube resonator was produced that allowed for 2D ¹H-¹³C NMR of D. magna neonates and exhibited ¹H sensitivity (nLOD_ω⁶⁰⁰ = 1.49 nmol s^1/2) close to that of double strip lines, which themselves offer the best compromise between concentration and mass sensitivity published to date.

Aquatic macroinvertebrates under stress: Bioaccumulation of emerging contaminants and metabolomics implications

The current knowledge on bioaccumulation of emerging contaminants (ECs) in aquatic invertebrates exposed to the realistic environmental concentrations is limited. Even less is known about the effects of chemical pollution exposure on the metabolome of aquatic invertebrates. We conducted an in situ translocation experiment with passive filter-feeding caddisfly larvae (Hydropsyche sp.) in an effluent-influenced river in order to i) unravel the bioaccumulation (and recovery) dynamics of ECs in aquatic invertebrates, and ii) test whether exposure to environmentally realistic concentrations of ECs will translate into metabolic profile changes in the insects. The experiment was carried out at two sites, upstream and downstream of the discharge of an urban wastewater treatment plant effluent. The translocated animals were collected at 2-week intervals for 46 days. Both pharmaceuticals and endocrine disrupting compounds (EDCs) were detected in water (62 and 7 compounds, respectively), whereas in Hydropsyche tissues 5 EDCs accumulated. Overall, specimens from the upstream site translocated to the impacted site reached higher ECs concentrations in their tissues, as a reflection of the contaminants' water concentrations. However, bioaccumulation was a temporary process susceptible to change under lower contaminant concentrations. Non-targeted metabolite profiling detected fine metabolic changes in translocated Hydropsyche larvae. Both translocations equally induced stress, but it was higher in animals translocated to the impacted site.

Metabolic profiling of Daphnia magna exposure to a mixture of hydrophobic organic contaminants in the presence of dissolved organic matter

The hydrophobic organic contaminants triclosan, triphenyl phosphate (TPhP) and diazinon sorb to dissolved organic matter (DOM) and this may alter their bioavailability and toxicity. ¹H nuclear magnetic resonance (NMR)-based metabolomics was used to investigate how DOM at 1 and 5 mg organic carbon/L may alter the metabolome of Daphnia magna from exposure to equitoxic mixtures of triclosan, TPhP and diazinon. These contaminants have different modes of action toward D. magna. The contaminant concentrations in each mixture were an equal percentage of their lethal concentration to 50% of the population (LC₅₀) values, which equates to 1250 μg/L TPhP, 330 μg/L triclosan and 0.9 μg/L diazinon. The ternary mixture exposure at 1% LC₅₀ values did not alter the D. magna metabolome. Contaminant mixture exposures at 5%, 10%, and 15% LC₅₀ values decreased glucose, serine and glycine concentrations and increased asparagine and threonine concentrations, suggesting disruptions in energy metabolism. The contaminant mixture had a unique mode of action in D. magna and DOM at 1 and 5 mg organic carbon/L did not change this mode of action. The estimated sorption of triclosan, TPhP or diazinon to DOM at 1 or 5 mg organic carbon/L in this experimental design was calculated to be <50% for each contaminant. This suggests that the mode of action of the contaminant mixture was not altered by DOM because the two environmentally relevant concentrations of DOM may have not substantially altered contaminant bioavailability. Our results indicate that DOM may not inevitably mitigate or alter the sub-lethal toxicity of a mixture of hydrophobic organic contaminants. This indicates the complexity of predicting the molecular-level toxicity of environmental mixtures. For adequate risk assessment of freshwater ecosystems, it is vital to account for the combined sub-lethal toxicity of an environmental mixture of contaminants.

Untargeted metabolomic analysis of the carotenoid-based orange coloration in Haliotis gigantea using GC-TOF-MS

Seafood coloration is typically considered an indicator of quality and nutritional value by consumers. One such seafood is the Xishi abalone (Haliotis gigantea), which displays muscle color polymorphism wherein a small subset of individuals display orange coloration of muscles due to carotenoid enrichment. However, the metabolic basis for carotenoid accumulation has not been thoroughly investigated in marine mollusks. Here, GC-TOF-MS-based untargeted metabolite profiling was used to identify key pathways and metabolites involved in differential carotenoid accumulation in abalones with variable carotenoid contents. Cholesterol was the most statistically significant metabolite that differentiated abalones with orange muscles against those with common white muscles. This observation is likely due to the competitive interactions between cholesterol and carotenoids during cellular absorption. In addition, the accumulation of carotenoids was also related to fatty acid contents. Overall, this study indicates that metabolomics can reflect physiological changes in organisms and provides a useful framework for exploring the mechanisms underlying carotenoid accumulation in abalone types.

Selective Amino Acid-Only in Vivo NMR: A Powerful Tool To Follow Stress Processes

In vivo NMR of small 13C-enriched aquatic organisms is developing as a powerful tool to detect and explain toxic stress at the biochemical level. Amino acids are a very important category of metabolites for stress detection as they are involved in the vast majority of stress response pathways. As such, they are a useful proxy for stress detection in general, which could then be a trigger for more in-depth analysis of the metabolome. 1H-13C heteronuclear single quantum coherence (HSQC) is commonly used to provide additional spectral dispersion in vivo and permit metabolite assignment. While some amino acids can be assigned from HSQC, spectral overlap makes monitoring them in vivo challenging. Here, an experiment typically used to study protein structures is adapted for the selective detection of amino acids inside living Daphnia magna (water fleas). All 20 common amino acids can be selectively detected in both extracts and in vivo. By monitoring bisphenol-A exposure, the in vivo amino acid-only approach identified larger fluxes in a greater number of amino acids when compared to published works using extracts from whole organism homogenates. This suggests that amino acid-only NMR of living organisms may be a very sensitive tool in the detection of stress in vivo and is highly complementary to more traditional metabolomics-based methods. The ability of selective NMR experiments to help researchers to "look inside" living organisms and only detect specific molecules of interest is quite profound and paves the way for the future development of additional targeted experiments for in vivo research and monitoring.

Triclosan: An Update on Biochemical and Molecular Mechanisms

Triclosan (TCS) is a synthetic, chlorinated phenolic antimicrobial agent commonly used in commercial and healthcare products. Items made with TCS include soaps, deodorants, shampoos, cosmetics, textiles, plastics, surgical sutures, and prosthetics. A wealth of information obtained from in vitro and in vivo studies has demonstrated the therapeutic effects of TCS, particularly against inflammatory skin conditions. Nevertheless, extensive investigations on the molecular aspects of TCS action have identified numerous adversaries associated with the disinfectant including oxidative injury and influence of physiological lifespan and longevity. This review presents a summary of the biochemical alterations pertaining to TCS exposure, with special emphasis on the diverse molecular pathways responsive to TCS that have been elucidated during the present decade.

Metabolomic responses to pre-chlorinated and final effluent wastewater with the addition of a sub-lethal persistent contaminant in Daphnia magna

Consumer products such as perfluorooctanesulfonic acid (PFOS) and pharmaceuticals (PCPPs) enter aquatic ecosystems through inefficient removal during wastewater treatment. Often, the sterilization process of wastewater includes the addition of sodium hypochlorite that can react with PCPPs and other organic matter (i.e., dissolve organic matter) to generate disinfection by-products and can cause the final effluent to be more harmful to aquatic organisms. Here, we exposed Daphnia magna to two stages of wastewater, the pre-chlorinated wastewater (PreCl) and the final effluent. In addition, we exposed D. magna, to the final effluent with a concentration gradient of added PFOS, to investigate if this persistent contaminant altered the toxicity of the final effluent. After 48 h of contaminant exposure, we measured the daphnids metabolic responses to the different stages of wastewater treatment, and with the addition of PFOS, utilizing proton nuclear magnetic resonance spectroscopy and liquid chromatography tandem mass spectrometry. We found few significant changes to the metabolic profile of animals exposed to the PreCl wastewater; however, animals exposed to the final effluent displayed increases in many amino acids and decreases in some sugar metabolites. With the addition of PFOS to the final effluent, the metabolic profile shifted from increased amino acids and decreased sugar metabolites and energy molecules especially at the low and high concentrations of PFOS. Overall, our results demonstrate the metabolome is sensitive to changes in the final effluent that are caused by sterilization, and with the addition of a persistent contaminant, the metabolic profile is further altered.

Acute and Chronic Toxicity of Carbamazepine on the Release of Chitobiase, Molting, and Reproduction in Daphnia similis

As one of the most frequently detected pharmaceutical compounds in aquatic environments, carbamazepine (CBZ) has recently been shown to cause acute and chronic toxicity in a variety of non-target aquatic organisms. However, little is known about the ecotoxicological effects it has on the molting and reproduction of crustaceans. The aim of the present work was to evaluate the acute and chronic toxic responses to CBZ in the crustacean Daphnia similis. After acute exposure (4 days), CBZ did not cause lethal toxicity at the tested concentrations. However, CBZ did inhibit the molting and release of chitobiase at concentrations higher than 6.25 μg/L, with 96 h EC₅₀ (median effective concentration) values of 864.38 and 306.17 μg/L, respectively. The results of chronic exposure showed that the mean number of molts, size of the first brood, mean number of offspring per brood, mean number of broods per female, and total offspring per female decreased significantly with increasing CBZ concentrations. Significant effects of CBZ on the molting or fecundity in D. similis were observed even at concentrations as low as 0.03 μg/L. In conclusion, CBZ can cause inhibition of molting, delayed reproduction, and reduced fecundity in D. similis. CBZ toxicity to D. similis depends on the timing and duration of the exposure. Moreover, our results indicated that CBZ would act as an endocrine disrupter in D. similis, as with vertebrates (e.g., fish).

Improvements in lipid suppression for 1 H NMR-based metabolomics: Applications to solution-state and HR-MAS NMR in natural and in vivo samples

Proton nuclear magnetic resonance (NMR) spectra of intact biological samples often show strong contributions from lipids, which overlap with signals of interest from small metabolites. Pioneering work by Diserens et al. demonstrated that the relative differences in diffusivity and relaxation of lipids versus small metabolites could be exploited to suppress lipid signals, in high-resolution magic angle spinning (HR-MAS) NMR spectroscopy. In solution-state NMR, suspended samples can exhibit very broad water signals, which are challenging to suppress. Here, improved water suppression is incorporated into the sequence, and the Carr-Purcell-Meiboom-Gill sequence (CPMG) train is replaced with a low-power adiabatic spinlock that reduces heating and spectral artefacts seen with longer CPMG filters. The result is a robust sequence that works well in both HR-MAS as well as static solution-state samples. Applications are also extended to include in vivo organisms. For solution-state NMR, samples containing significant amount of fats such as milk and hemp hearts seeds are used to demonstrate the technique. For HR-MAS, living earthworms (Eisenia fetida) and freshwater shrimp (Hyalella azteca) are used for in vivo applications. Lipid suppression techniques are essential for non-invasive NMR-based analysis of biological samples with a high-lipid content and adds to the suite of experiments advantageous for in vivo environmental metabolomics.

The Structural Arrangement and Relative Abundance of Aliphatic Units May Effect Long-Wave Absorbance of Natural Organic Matter as Revealed by 1H NMR Spectroscopy

The objective of this study was to shed light on structural features which underlay intensity of long wave absorbance of natural organic matter (NOM) using ¹H NMR spectroscopy. For this purpose, a set of the NOM samples was assembled from arctic and nonarctic sampling sites (the Kolyma river basin and Moscow region, respectively). It was to ensure a substantial difference in the humification degree of the isolated organic matter-the biogeochemical proxy of the long-wave absorbance of NOM. The assembled NOM set was analyzed using solution-state ¹H NMR spectroscopy. The distribution of both backbone and exchangeable protons was determined using acquisition of spectra in three different solvents. The substantially higher contribution of nonfunctionalized aliphatic moieties CHn (e.g., materials derived from linear terpenoids, MDLT) in the arctic NOM samples was revealed as compared to the nonarctic ones. The latter were characterized with the higher content of CHα protons adjacent to electron-withdrawing groups which belong to carboxyl rich alicyclic moieties (CRAMs) or to aromatic constituents of NOM. We have calculated a ratio of CHn to CHα protons as a structural descriptor which showed significant inverse correlation to intensity of long wave absorbance assessed with a use of E₄/ E₆ ratio and the slope of absorption spectrum. The steric hindrance of aromatic chromophoric groups of the NOM ensemble by bulky nonfunctionalized aliphatic moieties (e.g., MDLT) was set as a hypothesis for explanation of this phenomenon. The bulky aliphatics might increase a distance between the interacting groups resulting in inhibition of electronic (e.g., charge-transfer) interactions in the NOM ensemble. The obtained relationships were further explored using Fourier transform mass spectrometry as complementary technique to ¹H NMR spectroscopy. The data obtained on correlation of molecular composition of NOM with ¹H NMR data and optical properties were very supportive of our hypothesis that capabilities of NOM ensemble of charge transfer interactions can be dependent on structural arrangement and relative abundance of nonabsorbing aliphatic moieties.

Sublethal metabolic responses to contaminant mixture toxicity in Daphnia magna

Anthropogenic activity is increasing the presence of contaminants that enter waterways through wastewater effluent and urban and/or agricultural runoff, generally in complex mixtures. Depending on the mode of action of the individual contaminant within the mixture, toxicity can occur due to contaminants having similar or dissimilar modes of action. However, it is unknown how the metabolome responds to sublethal contaminant mixtures in the keystone genus Daphnia. In the present study we examined D. magna metabolic responses to acute sublethal exposure of propranolol, carbamazepine, and perfluorooctanesulfonic acid (PFOS) as well as in binary (propranolol-carbamazepine, propranolol-PFOS, carbamazepine-PFOS) and tertiary mixtures (carbamazepine-propranolol-PFOS), all at 10% of the median lethal concentration of the population (LC50). The metabolome was measured using ¹ H nuclear magnetic resonance (NMR) and characterized using principal component analysis, regression analysis, and fold changes in metabolite relative to the unexposed (control) group. The averaged principal component analysis scores plots revealed that carbamazepine-PFOS and carbamazepine-propranolol-PFOS exposures were significantly different from the control treatment. After normalizing the toxicity of each contaminant, we found that some metabolites responded monotonically, whereas others displayed a nonmonotonic response with increasing toxicity units. The single contaminant exposures and 2 binary mixtures (propranolol-carbamazepine, and propranolol-PFOS) resulted in minimal changes in the identified metabolites, whereas the carbamazepine-PFOS and carbamazepine-propranolol-PFOS displayed increases in several amino acid metabolites and decreases in glucose. Overall, our results highlight the sensitivity of the metabolome to distinguish the composition of the contaminant mixtures, with some mixtures displaying heightened responses versus others. Environ Toxicol Chem 2018;37:2448-2457. © 2018 SETAC.

Metabolomics Discovers Early-Response Metabolic Biomarkers that Can Predict Chronic Reproductive Fitness in Individual Daphnia magna

Chemical risk assessment remains entrenched in chronic toxicity tests that set safety thresholds based on animal pathology or fitness. Chronic tests are resource expensive and lack mechanistic insight. Discovering a chemical's mode-of-action can in principle provide predictive molecular biomarkers for a toxicity endpoint. Furthermore, since molecular perturbations precede pathology, early-response molecular biomarkers may enable shorter, more resource efficient testing that can predict chronic animal fitness. This study applied untargeted metabolomics to attempt to discover early-response metabolic biomarkers that can predict reproductive fitness of Daphnia magna, an internationally-recognized test species. First, we measured the reproductive toxicities of cadmium, 2,4-dinitrophenol and propranolol to individual Daphnia in 21-day OECD toxicity tests, then measured the metabolic profiles of these animals using mass spectrometry. Multivariate regression successfully discovered putative metabolic biomarkers that strongly predict reproductive impairment by each chemical, and for all chemicals combined. The non-chemical-specific metabolic biomarkers were then applied to metabolite data from Daphnia 24-h acute toxicity tests and correctly predicted that significant decreases in reproductive fitness would occur if these animals were exposed to cadmium, 2,4-dinitrophenol or propranolol for 21 days. While the applicability of these findings is limited to three chemicals, they provide proof-of-principle that early-response metabolic biomarkers of chronic animal fitness can be discovered for regulatory toxicity testing.

In-Vivo NMR Spectroscopy: A Powerful and Complimentary Tool for Understanding Environmental Toxicity

Part review, part perspective, this article examines the applications and potential of in-vivo Nuclear Magnetic Resonance (NMR) for understanding environmental toxicity. In-vivo NMR can be applied in high field NMR spectrometers using either magic angle spinning based approaches, or flow systems. Solution-state NMR in combination with a flow system provides a low stress approach to monitor dissolved metabolites, while magic angle spinning NMR allows the detection of all components (solutions, gels and solids), albeit with additional stress caused by the rapid sample spinning. With in-vivo NMR it is possible to use the same organisms for control and exposure studies (controls are the same organisms prior to exposure inside the NMR). As such individual variability can be reduced while continual data collection over time provides the temporal resolution required to discern complex interconnected response pathways. When multidimensional NMR is combined with isotopic labelling, a wide range of metabolites can be identified in-vivo providing a unique window into the living metabolome that is highly complementary to more traditional metabolomics studies employing extracts, tissues, or biofluids.

Investigation of Daphnia magna Sub-Lethal Exposure to Organophosphate Esters in the Presence of Dissolved Organic Matter Using ¹H NMR-Based Metabolomics

Organophosphate esters (OPEs) are frequently detected in aquatic environments. Hydrophobic OPEs with high octanol-water partition coefficients (Log K_OW) will likely sorb to dissolved organic matter (DOM) and consequently alter OPE bioavailability and sub-lethal toxicity. ¹H nuclear magnetic resonance (NMR)-based metabolomics was used to evaluate how DOM (5 mg organic carbon/L) alters the metabolic response of Daphnia magna exposed to sub-lethal concentrations of three individual OPEs with varying hydrophobicity. D. magna exposed to the hydrophilic contaminant (Log K_OW = 1.43) tris(2-chloroethyl) phosphate (TCEP) did not have substantial metabolic changes and DOM did not alter the metabolic response. There were significant increases in amino acids and a decrease in glucose from exposure to the hydrophobic contaminant (Log K_OW = 3.65) tris(2-butoxyethyl) phosphate (TBOEP) which DOM did not mitigate, likely due to the high sub-lethal toxicity of TBOEP. Exposure to DOM and the hydrophobic contaminant (Log K_OW = 4.76) triphenyl phosphate (TPhP) resulted in a unique metabolic response which was unlike TPhP only exposure, perhaps because DOM may be an additional stressor with TPhP exposure. Therefore, Log K_OW values may not always predict how sub-lethal contaminant toxicity will change with DOM and there should be more consideration to incorporate DOM in sub-lethal ecotoxicology testing.

Toxic Effects of Bisphenol A, Propyl Paraben, and Triclosan on Caenorhabditis elegans

Bisphenol A (BPA) is a ubiquitous plasticizer which is absorbed by ingestion and dermal contact; propyl paraben (PPB) inhibits the microbiome and extends the shelf life of many personal care products, whereas triclosan (TCS) is commonly found in antiseptics, disinfectants, or additives. In this work, Caenorhabditis elegans was used as a biological model to assess the toxic effects of BPA, PPB, and TCS. The wild type strain, Bristol N2, was used in bioassays with the endpoints of lethality, growth, and reproduction; green fluorescent protein (GFP) transgenic strains with the hsp-3, hsp-4, hsp-16.2, hsp-70, sod-1, sod-4, cyp-35A4, cyp-29A2, and skn-1 genes were evaluated for their mRNA expression through fluorescence measurement; and quick Oil Red O (q ORO) was utilized to stain lipid deposits. Lethality was concentration-dependent, while TCS and PPB showed more toxicity than BPA. BPA augmented worm length, while PPB reduced it. All toxicants moderately increased the width and the width–length ratio. BPA and PPB promoted reproduction, in contrast to TCS, which diminished it. All toxicants affected the mRNA expression of genes related to cellular stress, control of reactive oxygen species, and nuclear receptor activation. Lipid accumulation occurred in exposed worms. In conclusion, BPA, PPB, and TCS alter the physiology of growth, lipid accumulation, and reproduction in C. elegans, most likely through oxidative stress mechanisms.

Alternatives to Nuclear Overhauser Enhancement Spectroscopy Presat and Carr-Purcell-Meiboom-Gill Presat for NMR-Based Metabolomics

NMR metabolomics are primarily conducted with 1D nuclear Overhauser enhancement spectroscopy (NOESY) presat for water suppression and Carr-Purcell-Meiboom-Gill (CPMG) presat as a T2 filter to remove macromolecule signals. Others pulse sequences exist for these two objectives but are not often used in metabolomics studies, because they are less robust or unknown to the NMR metabolomics community. However, recent improvements on alternative pulse sequences provide attractive alternatives to 1D NOESY presat and CPMG presat. We focus this perspective on PURGE, a water suppression technique, and PROJECT presat, a T2 filter. These two pulse sequences, when optimized, performed at least on par with 1D NOESY presat and CPMG presat, if not better. These pulse sequences were tested on common samples for metabolomics, human plasma, and urine.

Analysis of Sub-Lethal Toxicity of Perfluorooctane Sulfonate (PFOS) to Daphnia magna Using ¹H Nuclear Magnetic Resonance-Based Metabolomics

¹H nuclear magnetic resonance (NMR)-based metabolomics was used to characterize the response of Daphnia magna after sub-lethal exposure to perfluorooctane sulfonate (PFOS), a commonly found environmental pollutant in freshwater ecosystems. Principal component analysis (PCA) scores plots showed significant separation in the exposed samples relative to the controls. Partial least squares (PLS) regression analysis revealed a strong linear correlation between the overall metabolic response and PFOS exposure concentration. More detailed analysis showed that the toxic mode of action is metabolite-specific with some metabolites exhibiting a non-monotonic response with higher PFOS exposure concentrations. Our study indicates that PFOS exposure disrupts various energy metabolism pathways and also enhances protein degradation. Overall, we identified several metabolites that are sensitive to PFOS exposure and may be used as bioindicators of D. magna health. In addition, this study also highlights the important utility of environmental metabolomic methods when attempting to elucidate acute and sub-lethal pollutant stressors on keystone organisms such as D. magna.

Metabolomic responses to sublethal contaminant exposure in neonate and adult Daphnia magna

The use of consumer products and pharmaceuticals that act as contaminants entering waterways through runoff and wastewater effluents alters aquatic ecosystem health. Traditional toxicological endpoints may underestimate the toxicity of contaminants, as lethal concentrations are often orders of magnitude higher than those found within freshwater ecosystems. While newer techniques examine the metabolic responses of sublethal contaminant exposure, there has been no direct comparison with ontogeny in Daphnia. It was hypothesized that Daphnia magna would have distinct metabolic changes after 3 different sublethal contaminant exposures, because of differences in the toxic mode of action and ontogeny. To test this hypothesis, the proton nuclear magnetic resonance metabolomic profiles were measured in D. magna aged day 0 and 18 after exposure to 28% of the lethal concentration of 50% of organisms tested (LC50) of atrazine, propranolol, and perfluorooctanesulfonic acid (PFOS) for 48 h. Principal component analysis revealed significant separation of contaminants from the control daphnids in both neonates and adults exposed to propranolol and PFOS. In contrast, atrazine exposure caused separation from the controls in only the adult D. magna. Minimal ontogenetic changes in the targeted metabolites were seen after exposure to propranolol. For both atrazine and PFOS exposures ontogeny exhibited unique changes in the targeted metabolites. These results indicate that, depending on the contaminant studied, neonates and adults respond uniquely to sublethal contaminant exposure. Environ Toxicol Chem 2017;36:938-946. © 2016 SETAC.

Spotlight on environmental omics and toxicology: a long way in a short time

The applications for high throughput omics technologies in environmental science have increased dramatically in recent years. Transcriptomics, proteomics, and metabolomics have been used to study how chemicals in our environment affect both aquatic and terrestrial organisms, and the characterization of molecular initiating events is a significant goal in toxicology to better predict adverse responses to toxicants. This special journal edition demonstrates the scope of the science that leverages omics-based methods in both laboratory and wild populations within the context of environmental toxicology, ranging from fish to mammals. It is important to recognize that the environment comprises one axis of the One Health concept - the idea that human health is unequivocally intertwined to our environment and to the organisms that inhabit that environment. We have much to learn from a comparative approach, and studies that integrate the transcriptome, proteome, and the metabolome are expected to offer the most detailed mechanism-based adverse outcome pathways that are applicable for use in both environmental monitoring and risk assessment.