33 Ultrastructural neurovascular alterations in hippocampus induced by environmentally relevant particle exposure revealed by multi-modal imaging

Abstract Airborne particulate matter (PM) is a major environmental risk factor for systemic and neurological disorders. PM has been detected in multiple human tissues, including blood, lung, placenta, breast milk, and brain, raising concerns about its ability to induce inflammation, oxidative stress, and tissue damage. Epidemiological studies link PM2.5 with cognitive decline and dementia, yet the mechanistic pathways underlying neurodegeneration remain poorly understood, particularly regarding neurovascular contribution. To investigate pollutant-induced neurovascular changes, we developed a correlative light and electron microscopy (CLEM) workflow integrating multiphoton microscopy, serial block-face SEM (SBF-SEM), and focused ion beam SEM (FIB-SEM). Volumetric imaging of mouse brain sections enabled multi-scale visualization from whole-brain architecture to nanoscale ultrastructure. Our results reveal that exposure to diesel exhaust particles (DEPs, 0.5 mg/kg, intravenous injection) induces BBB oedema in the hippocampus, endothelial ruffling, basement membrane irregularities, and morphological alterations in pericyte and astrocyte. FIB-SEM revealed disrupted mitochondrial morphology within perivascular cells, including increased ring-shaped (“doughnut”) forms. BBB damage was exacerbated by systemic inflammatory priming (LPS), and putative particle agglomerates were observed within lysosome-like vesicles under certain conditions. “Dark” perivascular macrophages emerged around affected neurovascular regions, suggesting immune cell involvement leading to neuroinflammation and neurotoxicity in the response to PM exposure. Collectively, these results demonstrate that environmentally relevant particulate exposure compromises neurovascular integrity, perturbs cellular and subcellular structures, and disrupts neuro-microvascular homeostasis. This work provides mechanistic insight into how airborne particles contribute to neurological dysfunction and highlights the potential of multi-modal imaging to inform translational strategies for preventing or mitigating pollution-linked neurodegenerative diseases.