Building a Network of Adverse Outcome Pathways (AOPs) Incorporating the Tau-Driven AOP Toward Memory Loss (AOP429)

Exploring the neurodegenerative potential of per- and polyfluoroalkyl substances through an adverse outcome pathway network

While emerging evidence links per- and polyfluoroalkyl substances (PFAS) to neurotoxicity, their potential role in neurodegeneration remains poorly understood. Moreover, existing neurodegeneration-related adverse outcome pathways (AOPs) available on AOP-Wiki have not yet been integrated into a unified network. To address these gaps, this study aims to develop the first neurodegeneration-related AOP network and utilize it to explore the possible contributions of long-chain legacy PFAS to neurodegeneration, specifically concerning Alzheimer's and Parkinson's diseases. A total of 74 AOPs were screened from AOP-Wiki, of which 13 neurodegeneration-related AOPs met the eligibility criteria and were incorporated into a network. We analyzed the resulting AOP network using topological parameters such as in-degree, out-degree, eccentricity, and betweenness centrality. To elucidate the mechanistic contributions of PFAS exposure to neurodegenerative pathways, we integrated evidence linking PFAS exposure to key events (KEs) within the network. The results highlighted increased intracellular calcium as the network hub with the highest connectivity followed by critical KEs such as neurodegeneration, neuronal apoptosis, oxidative stress, N-methyl-d-aspartate receptor (NMDA-R) overactivation, and mitochondrial dysfunction. Consistent with toxicological evidence, the pathways highlighted by the AOP network indicate that PFAS may adversely affect neurotransmitter systems, particularly through NMDA-R overactivation, leading to excitotoxicity. This may result in calcium dyshomeostasis, mitochondrial dysfunction, inflammatory-oxidative cascades, neuroinflammation, and neuronal cell death. By providing a mechanistic basis for understanding the neurodegenerative potential of PFAS, this study offers a crucial framework for assessing the risks associated with these chemicals which may inform future regulatory measures and public health strategies. Further experimental validation is needed to confirm the mechanistic contributions of PFAS exposure in neurodegeneration, particularly in animal models or human populations.

An integrative data-centric approach to derivation and characterization of an adverse outcome pathway network for cadmium-induced toxicity

Cadmium is a prominent toxic heavy metal that contaminates both terrestrial and aquatic environments. Owing to its high biological half-life and low excretion rates, cadmium causes a variety of adverse biological outcomes. Adverse outcome pathway (AOP) networks were envisioned to systematically capture toxicological information to enable risk assessment and chemical regulation. Here, we leveraged AOP-Wiki and integrated heterogeneous data from four other exposome-relevant resources to build the first AOP network relevant for inorganic cadmium-induced toxicity. From AOP-Wiki, we filtered 309 high confidence AOPs, identified 312 key events (KEs) associated with inorganic cadmium from five exposome-relevant databases using a data-centric approach, and thereafter, curated 30 cadmium relevant AOPs (cadmium-AOPs). By constructing the undirected AOP network, we identified a large connected component of 18 cadmium-AOPs. Further, we analyzed the directed network of 59 KEs and 82 key event relationships (KERs) in the largest component using graph-theoretic approaches. Subsequently, we mined published literature using artificial intelligence-based tools to provide auxiliary evidence of cadmium association for all KEs in the largest component. Finally, we performed case studies to verify the rationality of cadmium-induced toxicity in humans and aquatic species. Overall, cadmium-AOP network constructed in this study will aid ongoing research in systems toxicology and chemical exposome.