193 research outputs found
Pathway-Based Toxicity: History, Current Approaches and Liver Fibrosis and Steatosis as Prototypes
The Human Toxicology Project Consortium (HTPC) was created to accelerate implementation of the science and policies required to achieve a pathway-based foundation for toxicology as articulated in the 2007 National Research Council report, Toxicity Testing in the 21st Century: a Vision and a Strategy. The HTPC held a workshop, “Building Shared Experience to Advance Practical Application of Pathway-Based Toxicology: Liver Toxicity Mode-of-Action,” in January, 2013, in Baltimore, MD, to further the science of pathway-based approaches to liver toxicity. This review was initiated as a thought-starter for this workshop and has since been updated to include insights from the workshop and other activities occurring in 2013. The report of the workshop has been published elsewhere in this journal (Willett, 2014).JRC.I.5-Systems Toxicolog
Alternative methods for regulatory toxicology – a state-of-the-art review
This state-of-the art review is based on the final report of a project carried out by the European Commission’s Joint Research Centre (JRC) for the European Chemicals Agency (ECHA). The aim of the project was to review the state of the science of non-standard methods that are available for assessing the toxicological and ecotoxicological properties of chemicals. Non-standard methods refer to alternatives to animal experiments, such as in vitro tests and computational models, as well as animal methods that are not covered by current regulatory guidelines.
This report therefore reviews the current scientific status of non-standard methods for a range of human health and ecotoxicological endpoints, and provides a commentary on the mechanistic basis and regulatory applicability of these methods. For completeness, and to provide context, currently accepted (standard) methods are also summarised. In particular, the following human health endpoints are covered: a) skin irritation and corrosion; b) serious eye damage and eye irritation; c) skin sensitisation; d) acute systemic toxicity; e) repeat dose toxicity; f) genotoxicity and mutagenicity; g) carcinogenicity; h) reproductive toxicity (including effects on development and fertility); i) endocrine disruption relevant to human health; and j) toxicokinetics. In relation to ecotoxicological endpoints, the report focuses on non-standard methods for acute and chronic fish toxicity.
While specific reference is made to the information needs of REACH, the Biocidal Products Regulation and the Classification, Labelling and Packaging Regulation, this review is also expected to be informative in relation to the possible use of alternative and non-standard methods in other sectors, such as cosmetics and plant protection products.JRC.I.5-Systems Toxicolog
Advanced in vitro models for studying drug induced toxicity
Bringing safe medicines to the market has remained a major challenge to the pharmaceutical industry. Recent years have seen increased drug attrition rates due to toxicity - even after rigorous testing in both in vitro and in vivo test models. This is partly due to poor prediction of human-specific responses in these models. This thesis aims to address the issue by developing advanced in vitro models and methods that can complement and improve the predictive power of in vitro assays at preclinical level. Liver and kidneys are often susceptible to drug insult due to their respective roles in drug metabolism and reabsorption. We have developed a robust 3D in vitro model for liver toxicity studies, this model shows many hallmarks of in vivo hepatocytes, is applied in a 384-micro-well format and is compatible with standard medium- and high-throughput lab infrastructure for routine drug screening. This thesis also discusses the role of immune mediators in aggravating kidney toxicity and use of sophisticated high-content screening approach to measure apoptosis and necrosis in real time. These models are promising new tools for preclinical drug safety testingNetherlands Toxicogenomics centre (NTC) via Netherlands Genomics InitiativeUBL - phd migration 201
Novel in vitro and mathematical models for the prediction of chemical toxicity
The
focus
of
much
scientific
and
medical
research
is
directed
towards
understanding
the
disease
process
and
defining
therapeutic
intervention
strategies.
Whilst
the
scientific
basis
of
drug
safety
has
received
relatively
little
attention,
despite
the
fact
that
adverse
drug
reactions
(ADRs)
are
a
major
health
concern
and
a
serious
impediment
to
development
of
new
medicines.
Toxicity
issues
account
for
~21%
drug
attrition
during
drug
development
and
safety
testing
strategies
require
considerable
animal
use.
Mechanistic
relationships
between
drug
plasma
levels
and
molecular/cellular
events
that
culminate
in
whole
organ
toxicity
underpins
development
of
novel
safety
assessment
strategies.
Current
in
vitro
test
systems
are
poorly
predictive
of
toxicity
of
chemicals
entering
the
systemic
circulation,
particularly
to
the
liver.
Such
systems
fall
short
because
of
1)
the
physiological
gap
between
cells
currently
used
&
human
hepatocytes
existing
in
their
native
state,
2)
the
lack
of
physiological
integration
with
other
cells/systems
within
organs,
required
to
amplify
the
initial
toxicological
lesion
into
overt
toxicity,
3)
the
inability
to
assess
how
low
level
cell
damage
induced
by
chemicals
may
develop
into
overt
organ
toxicity
in
a
minority
of
patients,
4)
lack
of
consideration
of
systemic
effects.
Reproduction
of
centrilobular
&
periportal
hepatocyte
phenotypes
in
in
vitro
culture
is
crucial
for
sensitive
detection
of
cellular
stress.
Hepatocyte
metabolism/phenotype
is
dependent
on
cell
position
along
the
liver
lobule,
with
corresponding
differences
in
exposure
to
substrate,
oxygen
&
hormone
gradients.
Application
of
bioartificial
liver
(BAL)
technology
can
encompass
in
vitro
predictive
toxicity
testing
with
enhanced
sensitivity
and
improved
mechanistic
understanding.
Combining
this
technology
with
mechanistic
mathematical
models
describing
intracellular
metabolism,
fluid-‐flow,
substrate,
hormone
and
nutrient
distribution
provides
the
opportunity
to
design
the
BAL
specifically
to
mimic
the
in
vivo
scenario.
Such
mathematical
models
enable
theoretical
hypothesis
testing,
will
inform
the
design
of
in
vitro
experiments,
and
will
enable
both
refinement
and
reduction
of
in
vivo
animal
trials.
In
this
way,
development
of
novel
mathematical
modelling
tools
will
help
to
focus
and
direct
in
vitro
and
in
vivo
research,
and
can
be
used
as
a
framework
for
other
areas
of
drug
safety
science
Annotating Adverse Outcome Pathways to Organize Toxicological Information for Risk Assessment
The Adverse Outcome Pathway (AOP) framework connects molecular perturbations with organism and population level endpoints used for regulatory decision-making by providing a conceptual construct of the mechanistic basis for toxicity. Development of an AOP typically begins with the adverse outcome, and intermediate effects connect the outcome with a molecular initiating event amenable to high-throughput toxicity testing (HTT). Publicly available controlled vocabularies were used to provide terminology supporting AOP’s at all levels of biological organization. The resulting data model contains terms from 22 ontologies and controlled vocabularies annotating currently existing AOP’s. The model provides the ability to attach evidence in support of the AOP, supports data aggregation, and promotes the development of AOP networks. Long term, this structured description of the AOP will enable logical reasoning for hazard identification and for dose-response assessment. Case studies showcase how the model informs AOP development in the context of chemical risk assessment.Master of Scienc
Toxicity prediction using multi-disciplinary data integration and novel computational approaches
Current predictive tools used for human health assessment of potential chemical hazards rely primarily on either chemical structural information (i.e., cheminformatics) or bioassay data (i.e., bioinformatics). Emerging data sources such as chemical libraries, high throughput assays and health databases offer new possibilities for evaluating chemical toxicity as an integrated system and overcome the limited predictivity of current fragmented efforts; yet, few studies have combined the new data streams. This dissertation tested the hypothesis that integrative computational toxicology approaches drawing upon diverse data sources would improve the prediction and interpretation of chemically induced diseases. First, chemical structures and toxicogenomics data were used to predict hepatotoxicity. Compared with conventional cheminformatics or toxicogenomics models, interpretation was enriched by the chemical and biological insights even though prediction accuracy did not improve. This motivated the second project that developed a novel integrative method, chemical-biological read-across (CBRA), that led to predictive and interpretable models amenable to visualization. CBRA was consistently among the most accurate models on four chemical-biological data sets. It highlighted chemical and biological features for interpretation and the visualizations aided transparency. Third, we developed an integrative workflow that interfaced cheminformatics prediction with pharmacoepidemiology validation using a case study of Stevens Johnson Syndrome (SJS), an adverse drug reaction (ADR) of major public health concern. Cheminformatics models first predicted potential SJS inducers and non-inducers, prioritizing them for subsequent pharmacoepidemiology evaluation, which then confirmed that predicted non-inducers were statistically associated with fewer SJS occurrences. By combining cheminformatics' ability to predict SJS as soon as drug structures are known, and pharmacoepidemiology's statistical rigor, we have provided a universal scheme for more effective study of SJS and other ADRs. Overall, this work demonstrated that integrative approaches could deliver more predictive and interpretable models. These models can then reliably prioritize high risk chemicals for further testing, allowing optimization of testing resources. A broader implication of this research is the growing role we envision for integrative methods that will take advantage of the various emerging data sources.Doctor of Philosoph
Carcinogenic toxicants and emerging pollutants. A comprehensive case-study on toxicant interactions in vivo and in vitro: from Molecular Toxicology to Environmental Risk Assessment
Noxious chemicals have serious repercussions for wildlife and human health, not just due to
incidental pollution, but also to chronic exposure to mixed pollutants. To the span of legacy toxicants
such as aromatic hydrocarbons we persistently add new, like pharmaceuticals, that become reclassified
as ‘of emerging concern’. Taking diclofenac (DFC), one of the most toxic non-steroid anti-inflammatory
drugs (NSAIDs) to wildlife, and the carcinogenic PAH benzo[a]pyrene (B[a]P) as model compounds, we
disclosed that binary combinations cause interaction effects in vivo and in vitro even at realistically low
concentrations. Comparing both, DFC caused high zebrafish embryo mortality and more acute
morphoanatomical lesions and B[a]P was more cytotoxic for human hepatoma HepG2 cells, however
all this effects seemed to be diminished or delayed by co-exposure. The observed genotoxicity in vivo
and in vitro indicated antagonism in short exposures. Bioinformatics and RNAseq yielded about 300
genes differentially expressed only in co-exposed zebrafish embryos and indicated that pathways
related to cell cycle control may partly explain antagonism. The findings indicate serious chronic effects
even when toxicopathological and genotoxicity-related responses seem to be reduced by co-exposure,
which was confirmed by carryover of effects from parental generations (exposed to toxicants during
embryonic development) to their offspring, even though individual exposures continue to have higher
implications than mixtures. The overall complexity of effects and mechanisms was dependent of dose
and duration of exposure. Altogether, mechanistic aspects and toxicopathology of co-exposure indicate
significant risk of chronic disease along the life cycle of organisms. In vitro assays, in turn, were
paramount to test multiple binary mixtures and enabled refining research towards potential adverse
outcomes and molecular pathways, which is nowadays acknowledged as paramount to quantify risk
under realistic scenarios and associate environment health and human occupational exposure.As substâncias nocivas têm graves repercussões para a vida selvagem e para a saúde
humana, não apenas devido à poluição incidental, mas também à exposição crónica a misturas de
poluentes. À gama de poluentes tradicionais, como os hidrocarbonetos aromáticos, acrescentamos
continuamente novos produtos, como os fármacos, que são reclassificados como “emergentes”. Tendo
o diclofenac (DFC), um dos anti-inflamatórios não esteroides (AINEs) mais tóxicos para a vida
selvagem, e o PAH cancerígeno benzo[a]pireno (B[a]P) como substâncias modelo, revelamos que as
misturas binárias causam efeitos de interação in vivo e in vitro, mesmo em concentrações
realisticamente baixas. Comparando ambos, o DFC causou alta mortalidade embrionária no peixe-
zebra e lesões morfológicas mais agudas e o B[a]P foi mais citotóxico para as células do hepatoma
humano HepG2, no entanto todos estes efeitos pareceram diminuir ou retardar na co-exposição. A
genotoxicidade foi inferior à aditiva, in vivo e in vitro, indicando antagonismo em exposições curtas. A
bioinformática e o RNAseq geraram cerca de 300 genes diferencialmente expressos apenas em
embriões de peixe-zebra co-expostos e indicaram que as vias relacionadas ao controle do ciclo celular
podem parcialmente explicar o antagonismo. As descobertas indicam efeitos crónicos graves, mesmo
quando as respostas toxicopatológicas e relacionadas com a genotoxicidade parecem ser reduzidas
pela co-exposição, o que foi confirmado pela transferência de efeitos das gerações parentais (expostas
aos poluentes durante o desenvolvimento embrionário) para os seus descendentes, embora as
exposições individuais continuem a ter implicações mais elevadas do que as misturas. A complexidade
geral dos efeitos e mecanismos dependeu da dose e da duração da exposição. Em conjunto, os aspetos
mecanicistas e a toxicopatologia nas misturas indicam um risco significativo de doenças crónicas ao
longo do ciclo de vida dos organismos. Os ensaios in vitro, por sua vez, foram fundamentais para testar
múltiplas misturas binárias e permitiram refinar a pesquisa em direção a potenciais resultados adversos
e vias moleculares, o que hoje é reconhecido como fundamental para quantificar o risco em cenários
realistas e associar a saúde ambiental e a exposição ocupacional humana
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