Adverse Outcome Pathways: A Framework for Organizing ... · Adverse Outcome Pathways: A Framework...
Transcript of Adverse Outcome Pathways: A Framework for Organizing ... · Adverse Outcome Pathways: A Framework...
Adverse Outcome Pathways: A Framework for Organizing Mechanistic Information to
Improve Chemical Assessment
Kristie Sullivan, MPH
Director, Toxicology and Regulatory Testing Issues
OUTLINE
• About Physicians Committee
• Why AOPs?
• OECD AOP Programme
• Case Examples
• Application to Tobacco Chemicals
• How to Get Involved
• Physician-founded in 1985
• Aims to increase scientific and ethical standards for medical
education and research, and improve the public health
• Toxicology: modernize and improve
How are AOPs Used?
• Organize available evidence into context
• Link mechanistic data to adverse outcomes
• Highlight research needs
• Mechanistic support for chemical grouping and read-
across to fill data gaps
• Put in vitro assays into regulatory context
• Create testing strategies/frameworks (IATA)
• Identify assay gaps/needs
9
• Harmonized test guidelines and docs by >30 member countries
• Foundation for chemical characterization & tool support
– QSARs
– Test Guidelines
– Integrated Approaches to Testing and Assessment
• Expert group to develop, guide, and promote: Extended Advisory
Group for Molecular Screening and Toxicogenomics (EAGMST)
10
• AOP-Knowledgebase to collect information and allow
collaboration
• International platform for review and publication
• Guidance Document and User’s Handbook
http://www.oecd.org/chemicalsafety/testing/adverse-
outcome-pathways-molecular-screening-and-
toxicogenomics.htm12
Third party Applications,
plugins
AOP-KBHub
Shared chemical, biological and toxicological ontologies
AOP-KB
Intermediate Effects DBPut
chemical-related AOP components
in a regulatory context
AOP XplorerVisualize attribute networks to
discover & explore AOPs in a broader
context
EffectopediaDetailed development of
structured & computational AOPs
AOP WikiCollaborative development of AOP
descriptions & evidence
Slide: Clemens Whittwher, JRC
AOPKB.orgAOPWIKI.org
AOP Page
Section 1 - Title
Section 4 – Abstract
Section 5a – Summary of the AOP
MIE
KEs
AO
Key Event Relationships
Section 6 – Scientific evidence supporting the linkages in the AOP
Applicability domain(s) of the AOP
Life-stage Taxonomic
Sex
Section 7 – Overall Assessment of the AOP
Modified Bradford Hill Considerations
KE Pages
KER Pages
MIE Page
AO Page
• Description • Measurement/
detection • Taxonomic
applicability
• Description • Measurement/
detection • Taxonomic
applicability • Evidence for
chemical initiation
Chemical initiator(s)
• Description • Measurement/
detection • Taxonomic
applicability • Regulatory relevance
Section 5b – MIE, KE, and AO descriptions Figure 2. Overview of the organization of content pages in the AOP-wiki relative to sections of the AOP template. Sections 1, 4, 5a, and 7 are found on the main page for an individual AOP. Information related to sections 5b and section 6 are entered into separate content pages that can be linked to multiple individual AOP pages.
• Title • Description • Biological plausibility • Empirical support • Inconsistencies and
uncertainties • Quantitative
understanding
Linkage table
AOP Wiki 14
Slide courtesy of Steve Edwards, EPA
How Are AOPs Developed?
Open, stakeholder-inclusive effort
• Expert workshop setting
• By leading experts over time*
• One main team or lab
• “Crowd-sourced”
• Computationally-predicted17
Chemical 1 MIE1 KE KE AO1
Pathway networks
• Vulnerability analysis• Toxicity of mixtures• Alternative test prioritisation
KE
Chemical 2 MIE2 KE AO2
KE
Chemical 3 MIE3
KEX
KE AO3
Chemical 4 MIE4 KEY AO4KE
Chemical 5 MIE5 KE KE AO5KE
Chemical2
Chemical4
Chemical5
concentration Slide: Hristo Aladjov and Joop DeKnecht, OECD
Authors: Malgorzata Nepelska, Sharon Munn, Brigitte Landesmann; Systems Toxicology Unit, Joint Research Centre, European Commission
AOP Wiki
How are AOPs Developed?
• Computationally-predicted
– Automated literature searches
– Data-base mining
– High-content or high-throughput data sets
• Project 1.29: A catalog of putative AOPs that will enhance the
utility of US EPA Toxcast high throughput screening data for
hazard identification
How Are AOPs Developed?
• OECD Guidance:
– Guidance document on developing and assessing adverse
outcome pathways (#184) + Handbook
• Villeneuve et al, Adverse Outcome Pathway (AOP)
Development I: Strategies and Principles, Tox Sci 142(2),
2014, 312–320
• Villeneuve et al, Adverse Outcome Pathway Development
II: Best Practices, Tox Sci, 142(2), 2014, 321–33027
Sensitization of the Respiratory Tract (Project 1.20)
• Occupational Asthma
– Acute and chronic symptoms of upper and lower
airways
– Sensitization and elicitation phase
– Sensitization can occur via dermal exposure
• Focus: LMW organic compounds28
Sensitization of the Respiratory Tract AOP Project
Kent Carlson, CPSC
Stella Cochrane, Unilever
Steve Enoch, LJMU
Janine Ezendam, RIVM
Ian Kimber, U of Manchester
Grace Patlewicz, EPA
Erwin Roggen, Novozymes
Katherina Sewald, Fraun. ITEM
Kristie Sullivan, PCRM
29
Sensitization of the Respiratory Tract AOP Project
• Motivations
– Regulatory need for assays to detect and
distinguish respiratory sensitizers
– Mechanisms not as well understood
– Support development of in silico and in vitro TM
30
Initial Issues
• Sparse literature for LMW RS-chemicals
• Literature available for related, but separate
pathways
– Skin Sensitization
– Metal complexes (e.g., chloroplatinates)
– Proteins
• Defining the Adverse Outcome
• Defining elements cohesively with skin AOP31
Cellular Danger Signals: Activation
of Inflammatory Cytokines and
Chemokines and Cytoprotective
Gene Pathways (Th2)
MIE: Covalent Binding to Lysine Residues on Proteins
T-cell Activation-Proliferation-Polarization (Th2)
LMW Organic Chemical Exposure
AO: Sensitisation of the Respiratory Tract and Allergic Asthma upon Challenge
Dendritic Cell Activation (Th2
Skewed) and Migration
33
Naive dendritic cell
Matured dendritic cell
RecognitionUptake
Processing of Antigen
SIGNAL 1
Naive T-cell
DC-Th2 cellinteraction
SIGNAL 2DANGER SIGNAL
Matured Thcell
SIGNAL 3
T-cell proliferation
B-cell activation
IL-4, IL-5, IL-13
IgE
Mast cells
Protein
LMW agent
EAR
Local antigen presentation to
effector cellsEosinophils
Effector T-cells
LAR
Histamine
Protein
LMW agent
Hapten-carriercomplex MIE
KE 2KE 3a
KE 3b
KE 4
Adverse Outcome
Slide: Katherina Sewald and Janine Ezendam
Evaluating the AOP• Biological Plausibility of KERs: Moderate
• Essentiality of KEs: Moderate
– Some blocking experiments for KEs 2 and 3
• Empirical Support for KERs: Moderate
– Preponderance of evidence supportive
– Mechanistic studies in the literature are confined to one or
a few hallmark sensitizers
– Temporality and quantitative information has been
pursued in only a few studies34
Research Gaps
• Dendritic cell polarization and T-cell effector
response differs from skin sensitization—why?
• There is some indication that binding site and
protein preference sets Th2 response into motion
• Quantitative/Potency considerations
• Individual variation in attainment of AO
35
36
Cellular Danger
Signals
Covalent
Binding to
ProteinsT-cell
Activation-
Proliferation-
Polarization
Chemical
Exposure
AO:
Sensitisation
of the
Respiratory
Tract
Dendritic Cell
Activation and
Migration
QSAR &
structural alerts
Epithelial cells, Tissues
[cytokine release, gene
expression, oxidative stress]
Peptide
Reactivity
[Lys/Cys
depletion ratio]
Dendritic cell-
based assays
[surface
markers,
cytokines,
gene
expression/pr
ofiling]
In vivo assays: T-
cell proliferation,
IgE,
hypersensitivity
response
Cellular
Danger
Signals:
Nrf2-ARE
pathway
vs. Th2
correlation
Covalent
Binding to
Lysine
residues
Th1 T-
cell
Activatio
n
Skin
sensitiz
-ation
Th2-
skewed
DC
activation
Covalent
Binding to
Cysteine
residues
Resp.
sensitiz
-ation
DC
Migra-
tion
DC
activation
Th2 T-
cell
Activatio
n
MIE KE 2 KE 3 KE 4 AO
Skin and Respiratory AOPs
AOPs for Tobacco Assessment• Project 1.25: The Adverse Outcome Pathway from Induction
of Secretion of Inflammatory Cytokines Leading to Lung
Emphysema
• Smoke / Ingredient exposure-outcome (KERs) information
• Complex adverse outcomes amenable to AOP networks
w/shared key events
• Systems toxicology evidence—and sbv process—can
strengthen existing AOPs and connections
• Highlight research needs
– Illuminate species or genetic differences
– Identify potential susceptible populations
– Generate hypotheses
– Prioritize future research based on essential
missing information
39
AOPs for Tobacco Assessment
• Mechanistic support for “alternative”
approaches to assess products
– Read-across with data from structurally similar
constituents
– Rank constituents based on weight of evidence
– Rank products to support modified risk
– Target constituents for replacement
40
AOPs for Tobacco Assessment
AOPs for Tobacco Assessment
• Create testing strategies/frameworks
• Put in vitro assays into regulatory context
Inflammation &
Oxidative stress
Tissue Destruction
& Remodeling
CiliaryDysfunction
&Ion
Transport Irregularity
Goblet Cell Hyperplasi
a &Mucus
Production
“Adversity” vis a visCOPD
Chemical Stressor(s)
41
Non-governmental roles
• Scientific AOP Development
• Tool development AOP KB
• Education, outreach, and training
• Prizes!
Kristie Sullivan, MPH
• YouTube: AOP Learning Channel
• http://www.oecd.org/chemicalsafety/testing/adverse-outcome-
pathways-molecular-screening-and-toxicogenomics.htm
• http://aopwiki.org
• www.ASCCTOX.org
Thank you for your attention!
• Willett et al 2014. Pathway-based toxicity: history, current approaches and liver fibrosis and
steatosis as prototypes. ALTEX. doi: 10.14573/altex.1401283.
• Villeneuve et al 2014a. Adverse Outcome Pathway Development I: Strategies and Principles.
Tox Sci. doi: 10.1093/toxsci/kfu199.
• Villeneuve et al 2014b. Adverse Outcome Pathway Development II: Best Practices. Tox Sci.
doi: 10.1093/toxsci/kfu200.
• Adeleye et al 2014. Implementing Toxicity Testing in the 21st Century (TT21C): Making
safety decisions using toxicity pathways, and progress in a prototype risk assessment.
Toxicology. doi: 10.1016/j.tox.2014.02.007.
• Tollefsen et al 2014. Applying Adverse Outcome Pathways to support Integrated
Approaches to Testing and Assessment. Reg Tox Pharm. doi: 10.1016/j.yrtph.2014.09.009.
• Bal-Price et al. 2015. International STakeholder NETwork (ISTNET): creating a
developmental neurotoxicity (DNT) testing road map for regulatory purposes. Arch
Toxicol. doi: 10.1007/s00204-015-1464-2.
• Patlewicz et al 2015. Proposing a scientific confidence framework to help support the
application of adverse outcome pathways for regulatory purposes. Reg Tox Pharm. doi:
10.1016/j.yrtph.2015.02.011.