Long-Term\nNeurotoxic\nEffects and Alzheimer’s\nDisease Risk of Early EHDPP Exposure in Zebrafish: Insights from Molecular\nMechanisms to Adult Pathology

2-Ethylhexyl diphenyl phosphate (EHDPP),\nubiquitously\nmonitored\nin environmental media, is highly bioaccumulative and may pose long-term\nrisks, even after short-term exposure. In this investigation, larval\nzebrafish were exposed to 0.05, 0.5, and 5.0 μg/L EHDPP from\n4 to 120 h postfertilization (hpf) to examine the long-term neurotoxicity\neffects of early exposure. Exposure to 5.0 μg/L EHDPP yielded\nhyperactive locomotor behavior, which was characterized by increased\nswimming speed, larger turning angles, and heightened sensitivity\nto light-dark stimulation. The predicted targets of EHDPP (top 100\npotential macromolecules) were primarily associated with brain diseases\nlike Alzheimer’s disease (AD). Comparisons of differentially\nexpressed genes (DEGs) from AD patients (GSE48350) and RNA-seq data\nfrom EHDPP-exposed zebrafish confirmed consistently abnormal regulatory\npathways. EHDPP’s interaction with M1 and M5 muscarinic acetylcholine\nreceptors likely disrupted calcium homeostasis, leading to mitochondrial\ndysfunction and neurotransmitter imbalance as well as abnormal locomotor\nbehavior. Especially, 5.0 μg/L EHDPP exposure during early development\n(4–120 hpf) triggered early- and midstage AD-like symptoms\nin adulthood (180 dpf), characterized by cognitive confusion, aggression,\nblood–brain barrier disruption, and mitochondrial damage in\nbrains. These findings provide deep insights into the long-term neurotoxicity\neffects and Alzheimer’s disease risks of early EHDPP exposure\nat extremely low dosages.