Acetylcholine mediates nitro-PAHs induced inflammation and ameliorates the abnormalities in blood-brain barrier related proteins

Nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) are important organic components in fine particulate matter (PM_2.5). Recent studies found nitro-PAHs have adverse effects on central nervous system, leading to an increased risk of neurodegenerative diseases (NDDs). Oxidative stress and neuroinflammation can synergistically interfere with multiple signaling pathways regulating blood-brain barrier (BBB) damage, thereby contributing to NDDs. To investigate the roles of nitro-PAHs in mediating PM_2.5-induced nervous system effects and their underlying mechanisms, human glioma cells (U251) were treated with 1-nitropyrene and 9-nitroanthracene, two typical nitro-PAHs in the air. The study demonstrated nitro-PAHs caused extensive neuronal damage, including cellular membrane disruption, mitochondrial membrane potential collapse, and apoptosis. Nitro-PAHs induced neuroinflammation and BBB disruption, as indicated by cytokine release and abnormalities in BBB-related proteins. Inhibitor experiments suggested that cytokines were involved in dysregulation of BBB-related proteins. Furthermore, nitro-PAHs elevated acetylcholinesterase activity and disrupted acetylcholine balance in U251 cells, which modulated neuroinflammation and downstream BBB damage. Finally, inhibitor studies confirmed that oxidative stress played an important regulatory role in acetylcholine balance, as well as in neuroinflammatory responses and the subsequent BBB injuries. This study highlighted the urgent need to identify neurotoxic substances and to establish priority control measures to protect human health.