Spatial and spectral mapping of traffic-related nanoparticles in hippocampal subregions of an Alzheimer disease model

Chronic exposure to traffic-related air pollution (TRAP) is linked to increased risk of neurodegenerative diseases, including Alzheimer disease (AD). Ultrafine particulate matter (UFPM) is a suspected driver of TRAP neurotoxicity, but its spatial interactions with AD pathology remain poorly defined. We investigated the distribution, composition, and pathological context of TRAP-derived UFPM in the hippocampus of TgF344-AD rats chronically exposed to TRAP or filtered air (FA) for 14 months. Using a multimodal imaging workflow that combines enhanced darkfield hyperspectral imaging (EDF-HSI) with confocal immunofluorescence for microglia (CD68/Iba1) and amyloid beta (Aβ) plaques (Thioflavin S), we mapped the localization and spectral properties of UFPM in situ. UFPM accumulation was elevated in TRAP-exposed females, suggesting sex-specific vulnerability in blood-brain barrier permeability or particle accumulation. Particles near plaques showed red-shifted spectral signatures, suggestive of biochemical transformation. Dimension reduction revealed clustering of particle spectra by TRAP exposure and plaque proximity. However, UFPM was rarely found within plaques or microglia, implying indirect neuroimmune modulation. These findings highlight a novel spatial and spectral imaging approach for characterizing environmental nanoparticle interactions in the brain and suggests chronic TRAP exposure may influence AD-related inflammation and pathology in a sex- and region-dependent manner in this rodent model.