6PPD-quinone aggravates airway inflammation in neutrophilic asthma: Evidence from network toxicology and in vivo validation.

Abstract

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q), an emerging tire-derived environmental contaminant, is widely detected in airborne particles, raising concerns about its respiratory health effects. However, its role in asthma remains poorly understood. Here, we employed an integrated approach combining network toxicology, bioinformatics analyses, molecular docking, and in vivo validation to investigate the mechanisms of 6PPD-Q in asthma. Network toxicology analysis identified 374 shared targets between 6PPD-Q and asthma that were enriched in inflammatory and immune-related pathways, including chemokine, NF-κB, and IL-17 signaling. Protein-protein interaction analysis further identified 10 hub genes within the target network. Validation using the GSE143303 dataset demonstrated that these hub genes were predominantly associated with neutrophilic asthma, characterized by increased expression of CCL2, CXCL8, and CXCL10. Integration of neutrophilic asthma-related differentially expressed genes with network-derived targets, followed by least absolute shrinkage and selection operator (LASSO) regression, identified seven key genes, with CXCL8, C2, and FGR significantly upregulated. Immune infiltration analysis suggested close associations between these genes and innate immune cell responses. Molecular docking revealed a strong predicted interaction between 6PPD-Q and FGR, with a binding energy of -8.6 kcal/mol. In vivo, 6PPD-Q exposure alone elicited mild pulmonary inflammation in non-asthmatic mice. In mice with neutrophilic asthma, 6PPD-Q further increased airway inflammation and hyperresponsiveness, whereas no significant additional changes were observed in mice with eosinophilic asthma. These effects were accompanied by increased pulmonary FGR expression and activating phosphorylation of Src-family kinases. Collectively, 6PPD-Q exerts intrinsic pro-inflammatory effects but preferentially exacerbates neutrophilic asthma, with FGR representing a candidate mediator warranting functional validation.