DNA methylation-mediated alterations in Copper(I/II) redox equilibrium underlie lead-induced neurotoxicity

Lead (Pb), a ubiquitous environmental toxin, poses significant risks to central nervous system health, primarily by disrupting essential metal homeostasis in the brain. While epigenetic regulation and proteomic expression are significantly affected by Pb, its specific molecular impact on copper (Cu) redox states remains poorly understood. This study systematically investigated the molecular mechanisms underlying Pb-induced neurotoxicity in SH-SY5Y cells through integrated epigenomics and proteomics analysis. DNA methylation analysis revealed 141,357 differentially methylated regions (DMRs), primarily in CpG sites, with 62.6 % hypermethylated and 37.4 % hypomethylated. These DMRs were enriched in genes associated with critical processes such as metal ion binding, cell cycle regulation, and nervous system development. Promoter-specific methylation changes were notably pronounced, impacting pathways linked to neurodegenerative diseases, including Alzheimer's disease. Proteomic analysis identified 740 differentially expressed proteins (DEPs), with 366 upregulated and 374 downregulated in Pb-treated cells. Functional annotation revealed significant enrichment of DEPs in mitochondria, where Pb exposure disrupted processes related to oxidative phosphorylation, ion transport, and transmembrane processes. These proteomic changes aligned with the observed epigenetic modifications, reinforcing the role of Pb in impairing neuronal function via its effects on cellular energy metabolism and metal ion dynamics. Notably, Pb exposure disrupted Cu redox transitions between Cu(I) and Cu(II) as well as glutathione (GSH) activity, underscoring its impact on cellular metal homeostasis regulation and oxidative imbalance. In summary, this study provides a comprehensive view of how Pb exposure alters epigenetic and proteomic landscapes, disrupting key biological processes and pathways essential for neuronal health.