AOP

AOP maps in vitro assay results to adverse outcomes in thyroid hormone (TH) signaling to support mechanistic interpretation of effects on brain development and cognitive function in humans and wildlife.

Key Features:

• Central Repository: Part of the OECD-sponsored AOP Knowledgebase (AOP-KB) and hosted in the Collaborative Adverse Outcome Pathway Wiki (AOP-Wiki), integrating AOPs developed under the OECD AOP Development Effort and supported by the Extended Advisory Group on Molecular Screening and Toxicogenomics.
• Integration of In Vitro Assays: Integrates data from in vitro assays that identify chemical interactions with molecular targets in the thyroid system, enabling screening for chemicals that disrupt TH signaling and reducing reliance on vertebrate animal testing.
• Linking Molecular Interactions to Adverse Outcomes: Maps early chemical interactions with thyroid molecular targets to downstream molecular and organismal events, establishing structured linkages between molecular initiating events and adverse outcomes.
• Regulatory and Biological Insights: Provides a framework for characterizing chemicals affecting TH mechanisms and highlights biological knowledge gaps such as TH signaling during fetal brain development.
• Research Facilitation: Identifies research needs to quantify chemical effects on TH signaling to support regulatory decision-making and advance understanding of thyroid-dependent adverse outcomes.

Scientific Applications:

• Chemical Safety Screening: Enables screening and prioritization of large chemical libraries for interactions with thyroid targets using in vitro assay data mapped to AOPs.
• Regulatory Decision-Making: Supports regulatory evaluation of chemical risks by linking molecular interactions to adverse outcomes within OECD AOP frameworks.
• Research Development: Guides research to fill gaps in TH signaling knowledge, particularly regarding developmental neurotoxicity and cognitive outcomes.

Methodology:

Data integration: collecting and synthesizing data from various in vitro assays measuring chemical interactions with thyroid molecular targets; pathway mapping: establishing causal linkages between these molecular interactions and downstream biological events leading to adverse outcomes; knowledge synthesis: utilizing existing research on TH signaling to inform AOP development and identify areas requiring further investigation.