12 Multi-omics profiling of protective mechanisms against macrophage senescence induced by brake-derived PM2.5

Abstract Automobile-derived fine particulate matter (PM2.5, <2.5 µm), especially originating from brake wear, is emitted in greater quantities than exhaust particles and has recently emerged as a growing regulatory concern. However, its toxicological mechanisms remain elusive. In this study, we investigated the cellular effects of PM2.5 generated from diesel exhaust and brake wear materials, including non-asbestos organic and low-metallic brake pads, on THP-1 human monocytic cells. Transmission electron microscopy was employed to examine ultrastructural alterations, while transcriptomic and proteomic analyses—using next-generation sequencing and LC-MS/MS—were integrated to delineate molecular pathways and potential pharmacological targets. A 24-hour exposure to either exhaust- or brake-derived PM2.5 (≥50 µg/mL) resulted in approximately a 10% decrease in cell viability and a substantial elevation of intracellular reactive oxygen species. The particles accumulated within lysosomes, causing their swelling, diminished proteolytic activity, and impairment of autophagic flux. Transcriptomic profiling indicated enrichment of pathways associated with lysosomal dysfunction, autophagy suppression, G1 phase arrest, and cellular senescence, findings that were further supported by proteomic evidence. In line with these results, PM2.5-treated cells exhibited increased senescence-associated β-galactosidase activity. Integrated network analysis identified key upstream regulators mediating these senescence-like responses. Collectively, our results demonstrate that both exhaust- and brake wear-derived PM2.5 disrupt lysosomal homeostasis and promote senescence-associated phenotypes in macrophages. The integration of transcriptomic and proteomic datasets provided mechanistic insights into PM2.5-induced cellular toxicity and highlighted molecular drivers that may serve as potential therapeutic or regulatory targets. These findings advance the current understanding of traffic-related PM2.5 toxicity and offer a foundation for developing strategies to mitigate its health impacts.