7 research outputs found
Metabolomics to Explore Imidacloprid-Induced Toxicity in the Central Nervous System of the Freshwater Snail <i>Lymnaea stagnalis</i>
Modern toxicology is seeking new testing methods to better understand
toxicological effects. One of the most concerning chemicals is the
neonicotinoid pesticide imidacloprid. Although imidacloprid is designed
to target insects, recent studies have shown adverse effects on nontarget
species. Metabolomics was applied to investigate imidacloprid-induced
sublethal toxicity in the central nervous system of the freshwater
snail Lymnaea stagnalis. The snails
(<i>n</i> = 10 snails) were exposed for 10 days to increasing
imidacloprid concentrations (0.1, 1, 10, and 100 μg/L). The
comparison between control and exposure groups highlighted the involvement
and perturbation of many biological pathways. The levels of several
metabolites belonging to different metabolite classes were significantly
changed by imidacloprid exposure. A change in the amino acids and
nucleotide metabolites like tryptophan, proline, phenylalanine, uridine,
and guanosine was found. Many fatty acids were down-regulated, and
the levels of the polyamines, spermidine and putrescine, were found
to be increased which is an indication of neuron cell injury. A turnover
increase between choline and acetylcholine led us to hypothesize an
increase in cholinergic gene expression to overcome imidacloprid binding
to the nicotinic acetylcholine receptors. Metabolomics revealed imidacloprid
induced metabolic changes at low and environmentally relevant concentration
in a nontarget species and generated a novel mechanistic hypothesis
Pesticide Mixture Toxicity in Surface Water Extracts in Snails (<i>Lymnaea stagnalis</i>) by an <i>in Vitro</i> Acetylcholinesterase Inhibition Assay and Metabolomics
Many
chemicals in use end up in the aquatic environment. The toxicity
of water samples can be tested with bioassays, but a metabolomic approach
has the advantage that multiple end points can be measured simultaneously
and the affected metabolic pathways can be revealed. A current challenge
in metabolomics is the study of mixture effects. This study aims at
investigating the toxicity of an environmental extract and its most
abundant chemicals identified by target chemical analysis of >100
organic micropollutants and effect-directed analysis (EDA) using the
acetylcholinesterase (AChE) bioassay and metabolomics. Surface water
from an agricultural area was sampled with a large volume solid phase
extraction (LVSPE) device using three cartridges containing neutral,
anionic, and cationic sorbents able to trap several pollutants classes
like pharmaceuticals, pesticides, PAHs, PCBs, and perfluorinated surfactants.
Targeted chemical analysis and AChE bioassay were performed on the
cartridge extracts. The extract of the neutral sorbent cartridge contained
most of the targeted chemicals, mainly imidacloprid, thiacloprid,
and pirimicarb, and was the most potent AChE inhibitor. Using an EDA
approach, other AChE inhibiting candidates were identified in the
neutral extract, such as carbendazim and esprocarb. Additionally,
a metabolomics experiment on the central nervous system (CNS) of the
freshwater snail <i>Lymnaea stagnalis</i> was conducted.
The snails were exposed to the extract, the three most abundant chemicals
individually, and a mixture of these. The extract disturbed more metabolic
pathways than the three most abundant chemicals individually, indicating
the contribution of other chemicals. Most pathways perturbed by the
extract exposure overlapped with those related to exposure to neonicotinoids,
like the polyamine metabolism involved in CNS injuries. Metabolomics
for the straightforward comparison between a complex mixture and single
compound toxicity is still challenging but, compared to traditional
biotesting, is a promising tool due to its increased sensitivity
High-Throughput Effect-Directed Analysis Using Downscaled in Vitro Reporter Gene Assays To Identify Endocrine Disruptors in Surface Water
Effect-directed analysis (EDA) is
a commonly used approach for
effect-based identification of endocrine disruptive chemicals in complex
(environmental) mixtures. However, for routine toxicity assessment
of, for example, water samples, current EDA approaches are considered
time-consuming and laborious. We achieved faster EDA and identification
by downscaling of sensitive cell-based hormone reporter gene assays
and increasing fractionation resolution to allow testing of smaller
fractions with reduced complexity. The high-resolution EDA approach
is demonstrated by analysis of four environmental passive sampler
extracts. Downscaling of the assays to a 384-well format allowed analysis
of 64 fractions in triplicate (or 192 fractions without technical
replicates) without affecting sensitivity compared to the standard
96-well format. Through a parallel exposure method, agonistic and
antagonistic androgen and estrogen receptor activity could be measured
in a single experiment following a single fractionation. From 16 selected
candidate compounds, identified through nontargeted analysis, 13 could
be confirmed chemically and 10 were found to be biologically active,
of which the most potent nonsteroidal estrogens were identified as
oxybenzone and piperine. The increased fractionation resolution and
the higher throughput that downscaling provides allow for future application
in routine high-resolution screening of large numbers of samples in
order to accelerate identification of (emerging) endocrine disruptors
High-Throughput Effect-Directed Analysis Using Downscaled in Vitro Reporter Gene Assays To Identify Endocrine Disruptors in Surface Water
Effect-directed analysis (EDA) is
a commonly used approach for
effect-based identification of endocrine disruptive chemicals in complex
(environmental) mixtures. However, for routine toxicity assessment
of, for example, water samples, current EDA approaches are considered
time-consuming and laborious. We achieved faster EDA and identification
by downscaling of sensitive cell-based hormone reporter gene assays
and increasing fractionation resolution to allow testing of smaller
fractions with reduced complexity. The high-resolution EDA approach
is demonstrated by analysis of four environmental passive sampler
extracts. Downscaling of the assays to a 384-well format allowed analysis
of 64 fractions in triplicate (or 192 fractions without technical
replicates) without affecting sensitivity compared to the standard
96-well format. Through a parallel exposure method, agonistic and
antagonistic androgen and estrogen receptor activity could be measured
in a single experiment following a single fractionation. From 16 selected
candidate compounds, identified through nontargeted analysis, 13 could
be confirmed chemically and 10 were found to be biologically active,
of which the most potent nonsteroidal estrogens were identified as
oxybenzone and piperine. The increased fractionation resolution and
the higher throughput that downscaling provides allow for future application
in routine high-resolution screening of large numbers of samples in
order to accelerate identification of (emerging) endocrine disruptors
Effect-Directed Analysis To Explore the Polar Bear Exposome: Identification of Thyroid Hormone Disrupting Compounds in Plasma
Compounds
with transthyretin (TTR)-binding potency in the blood
plasma of polar bear cubs were identified with effect-directed analysis
(EDA). This approach contributes to the understanding of the thyroid
disrupting exposome of polar bears. The selection of these samples
for in-depth EDA was based on the difference between the observed
TTR-binding potency on the one hand and the calculated potency (based
on known concentrations of TTR-binding compounds and their relative
potencies) on the other. A library-based identification was applied
to the liquid chromatography–time-of-flight–mass spectrometry
(LC-ToF-MS) data by screening for matches between compound lists and
the LC-ToF-MS data regarding accurate mass and isotope pattern. Then,
isotope cluster analysis (ICA) was applied to the LC-ToF-MS data allowing
specific screening for halogen isotope patterns. The presence of linear
and branched nonylphenol (NP) was observed for the first time in polar
bears. Furthermore, the presence of one di- and two monohydroxylated
octachlorinated biphenyls (octaCBs) was revealed in the extracts.
Linear and branched NP, 4′-OH-CB201 and 4,4′-OH-CB202
could be successfully confirmed with respect to their retention time
in the analytical system. In addition, branched NP, mono- and dihydroxylated-octaCBs
showed TTR-binding potencies and could explain another 32 ± 2%
of the total measured activities in the extracts
High-Resolution Fractionation after Gas Chromatography for Effect-Directed Analysis
This research presents an analytical
technology for highly efficient,
high-resolution, and high-yield fractionation of compounds after gas
chromatography (GC) separations. The technology is straightforward,
does not require sophisticated cold traps or adsorbent traps, and
allows collecting large numbers of fractions during a GC run. The
technology is based on direct infusion of a carrier solvent at the
end of the GC column, where infusion takes place in the GC oven. Pentane
and hexane used as carrier solvent showed good results. Acetonitrile
also showed good results as a more polar carrier solvent. Development
and optimization of the technology is described, followed by demonstration
in a high-throughput effect directed analysis setting toward dioxin
receptor bioactivity. The GC fractionation setup was capable of collecting
fractions in the second range. As a result, fractionated compounds
could be collected into one or two fractions when 6.5 s resolution
fractionation was performed. Subsequently, mixtures containing polycyclic
aromatic hydrocarbons, of which some are bioactive toward the dioxin
receptor, were profiled with a mammalian gene reporter assay. After
fractionation into 96-well plates, we used our new approach for direct
cell seeding onto the fractions prior to assaying which allowed dioxin
receptor bioactivity to be measured directly after fractionation.
The current technology represents a great advance in effect directed
analysis for environmental screening worldwide as it allows combining
the preferred analytical separation technology for often non-polar
environmental pollutants with environmentally relevant bioassays,
in high resolution
Demographic, Reproductive, and Dietary Determinants of Perfluorooctane Sulfonic (PFOS) and Perfluorooctanoic Acid (PFOA) Concentrations in Human Colostrum
To determine demographic, reproductive,
and maternal dietary factors
that predict perfluoroalkyl substance (PFAS) concentrations in breast
milk, we measured perfluorooctane sulfonic (PFOS) and perfluorooctanoic
acid (PFOA) concentrations, using liquid chromatography–mass
spectrometry, in 184 colostrum samples collected from women participating
in a cohort study in Eastern Slovakia between 2002 and 2004. During
their hospital delivery stay, mothers completed a food frequency questionnaire,
and demographic and reproductive data were also collected. PFOS and
PFOA predictors were identified by optimizing multiple linear regression
models using Akaike’s information criterion (AIC). The geometric
mean concentration in colostrum was 35.3 pg/mL for PFOS and 32.8 pg/mL
for PFOA. In multivariable models, parous women had 40% lower PFOS
(95% CI: −56 to −17%) and 40% lower PFOA (95% CI: −54
to −23%) concentrations compared with nulliparous women. Moreover,
fresh/frozen fish consumption, longer birth intervals, and Slovak
ethnicity were associated with higher PFOS and PFOA concentrations
in colostrum. These results will help guide the design of future epidemiologic
studies examining milk PFAS concentrations in relation to health end
points in children