The future trends in toxicology testing

1. Forensic Medicine and
Toxicology,
Assiut University
Professor Eman Ezz Eldawela
Elsharkawy
»

2. Toxicity Testing: New
Approaches
Future trends in toxicology

3. The vision for the future of toxicity
testing
Advances in molecular biology, biotechnology, and other
fields are paving the way for major improvements in how
scientists evaluate the health risks posed by potentially
toxic chemicals found at low levels in the environment.
These advances would make toxicity testing quicker,
less expensive, and more directly relevant to animal or
human exposures.
They could also reduce the need for animal testing by
substituting more laboratory tests based on animal or
human cells.

4. The revolution in biology and biotechnology is
making it increasingly possible to study the
effects of chemicals using cells, cellular
components, and tissues rather than whole
animals.
Systems biology, bioinformatics, and rapid assay
technologies are helping scientists to better
understand how cellular networks or pathways in
the body carry out normal functions that are key
to maintaining health.

5. 5
ToxicityCell
Changes
Molecular
Targets
Tissues
Cellular
Networks
Cellular Systems
Tissue
Dose
Molecular
Pathways
Predicting the level of Toxicity is
the Grand Challenge in Toxicology nowadays


Biochemical
Cell-Based
Complex
Cellular
component
Model
Organism


6. 6
High Technologies
DNA
mRNA
Protein
Metabolites
Transcription
Translation
Metabolism
Molecular Biology

7. Design Criteria:
Toxicity Testing of Environmental Agents
Broadest coverage of
chemicals, end points,
life stages
Lowest cost;
least time
Detailed mode of action and
dose response information for
animal or human health risk
assessment
Fewest animals; least
suffering for those
used
7

8. Components of the Vision
8

9. 1.Toxicity Pathways
The new toxicity-testing system that relies mainly on
understanding “toxicity pathways”—the cellular response
pathways that can result in adverse health effects when
sufficiently perturbed.
Such system would evaluate biologically significant alterations
without relying on studies of whole animals.
Is the focus on “toxicity
pathways” useful or
distracting? 9

10. Nrf2 oxidative
stress
(A redox sensitive
nuclear transcription
factor, plays a pivotal role
in redox homeostasis
during oxidative stress )
Heat-shock proteins
p38 MAPK
(mitogen-activated protein kinase)
PXR (pregnane X ), CAR (Constitutive and rostane ),
PPAR(Peroxisome proliferator-activated and AhR (aryl
hydrocarbon) receptors
Hypo-osmolarity
DNA damage
Endogenous hormones
What are the toxicity pathways?
How many are there?
10

11. 1111
Toxicity Pathways
Receptors / Enzymes / etc.
Direct Molecular Interaction
Pathway Regulation /
Genomics
Cellular Processes
Tissue / Organ / Organism Tox Endpoint

12. 1212
Toxicity Pathways
Receptors / Enzymes / etc.
Direct Molecular Interaction
Pathway Regulation /
Genomics
Cellular Processes
Tissue / Organ / Organism Tox Endpoint
Chemical

13. 1313
Toxicity Pathways
Receptors / Enzymes / etc.
Direct Molecular Interaction
Pathway Regulation /
Genomics
Cellular Processes
Tissue / Organ / Organism Tox Endpoint

14. Biologic
Inputs
Normal
Biologic
Function
Morbidity
and
Mortality
Cell
Injury
Adaptive Stress
Responses
Early Cellular
Changes
Exposure
Tissue Dose
Biologic Interaction
Perturbation
Low Dose
Medium Dose
High Dose
Toxicity Pathways and Dose
Response relationship
How do we distinguish
adaptive versus adverse
(toxic) responses? 14

15. •Assess pathways
•Integrate tissue responses
• Evaluate metabolites
•Detect specific nuclear receptors
2.Targeted Testing – toxicogenomics, etc.
15
we will discuss use of
new technologies in
targeted testing strategies

16. New techniques
A number of emerging fields and techniques are
contributing major new insights for
understanding the biologic responses to
chemicals in different tissues.
For example, new high-throughput
techniques (HTS), computational models and
bioinformatics developed by the
pharmaceutical industry use efficient automated
methods to test certain biologic activities of
thousands of chemicals that used to be studied
in animals.

17. High-throughput screening
HTS is a method for scientific experimentation especially
used in drug discovery and relevant to the fields of
biology, toxicology and chemistry. Using robotics, data
processing and control software, liquid handling devices,
and sensitive detectors.
High-Throughput Screening allows a researcher to
quickly conduct millions of chemical, genetic or
pharmacological tests.
Through this process one can rapidly identify active
compounds, antibodies or genes which modulate a
particular biomolecular pathway.
The results of these experiments provide starting points
for drug design and for understanding the interaction or
role of a particular biochemical process in biology .

18. 1818
Human Relevance/
Cost/Complexity
Throughput/
Simplicity
High-Throughput Screening Assays
10s-100s/yr
10s-100s/day
1000s/day
10,000s-
100,000s/day
LTS HTSMTS uHTS
batch testing of chemicals for pharmacological/toxicological endpoints
using automated liquid handling, detectors, and data acquisition
Gene-expression

19. 1919
Cellular Assays
Biochemical Assays
Toxicology Endpoints
Physical chemical properties
Profile Matching
Variable Toxicity testing by ultra high
throughput screening refers (circa 2008)
Genomic Signatures
In silico Predictions

20. 20
Future of Toxicity Testing
Bioinformatics/
Machine Learning
in silico analysis
"performed on
computer or via
computer
simulation."
Cancer
ReproTox
DevTox
NeuroTox
PulmonaryTox
ImmunoTox
HTS
in vitro testing
$Thousands
www.epa.gov/ncct/toxcast
EPAs Contribution: The ToxCast Research Program

21. In silico analysis
Computer simulation
In silico is an expression used to mean
"performed on computer or via computer
simulation." and refer to experiments done in
living organisms, outside of living organisms,
and where they are found in nature, respectively.
In silico research in medicine is thought to have
the potential to speed the rate of discovery while
reducing the need for expensive lab work and
clinical trials.

22. Tox CastTM
Research program of EPA’s National
Center for Computational Toxicology
“…to integrate modern computing and information technology with
molecular biology to improve Agency prioritization of data
requirements and risk assessment of chemicals”
www.epa.gov/ncct

23. 23
ToxCast Data from
ToxRefDB
Chronic/Cancer
Multigenation
Developmental
Chemicals

24. Conclusion
We can conclude from the previous
presentation the difference between the
nowadays toxicity testing and the future
trends toxicity testing techniques.

25. In new approachNowadays
Toxicity pathways assays, better
reflecting biological targets and
modes of action.
Increased speed and throughput
for chemicals and decreased costs
and animal usage.
Move away from extrapolating
from high dose animal results to
low doses in humans.
Lack of improved methods to
identify or predict the molecular
level of toxicity as test
metabolites- receptors…. ect, in
targeted testing.
Slow development of ‘functional
genomic tools’ to map and model
pathways and use results to
establish safe levels of exposures.
Difficulty in assay design to detect
development in Toxicity Pathways.

26. New extrapolations include in
vitro - in vivo and across levels of
biological organization.
Allow more diverse dose
response models for target and
integrated cellular responses for
ties to possible outcomes.
Creates detailed understanding
of pathway targets, functional
design of toxicity pathway.
Give the chance to train
toxicologists and regulators about
need for new approach.
• Not chemical coverage
• Expensive
• Slow