29 Understanding the impacts of inhaled particulate matter on the blood-brain barrier

Abstract The blood–brain barrier (BBB) protects the central nervous system by regulating substance passage between blood and brain. Environmental pollutants such as particulate matter (PM) can compromise BBB integrity, potentially contributing to neurodegenerative diseases. PM₂.₅ (less than 2.5 µm in diameter) penetrates deeply into the lungs, raising concerns about its ability to enter the bloodstream and reach the brain. This study investigates the effects of Diesel Exhaust Particulate (DEP) 2,975, a Standard Reference Material from the National Institute of Standards and Technology, on BBB integrity. In vitro models included immortalised human cerebral microvascular endothelial cells (hCMEC/D3) in monoculture, primary endothelial cells with pericytes in co-culture, and triple-culture models containing astrocytes or microglia. Cells were exposed to environmentally relevant concentrations (0.89 to 17.86 μg/cm²). BBB integrity was assessed using transendothelial electrical resistance (TEER). Quantitative PCR measured markers of oxidative stress (SOD1, NOS3), inflammation (IL-1β, IL-6, IL-8, TNFα, COX2), tight junctions (CLDN5, TJP1), integrity (MMP9, LINC00094, LINC00662), transporters (ABCB1, ABCG2, LRP1), and xenobiotic metabolism (CYP1A1, CYP1A2). ZO-1 expression was examined. PM exposure caused a concentration-dependent decline in BBB integrity, with reduced TEER values across all models. qPCR showed significant upregulation of CYP1A1, CYP1A2, and COX2. NOS3 increased, while SOD1 was unchanged. Tight junction genes CLDN5 and TJP1 were downregulated, and fluorescent staining confirmed structural disruption. Cytotoxicity assays showed elevated LDH release at higher PM levels. DEP exposure significantly disrupts BBB integrity, with upregulation of CYP1A1, CYP1A2, and COX2. Increased permeability, inflammation, and cytotoxicity suggest that environmental PM may contribute to neurodegenerative processes.