Revisiting the NETs-CYBB-p38 MAPK axis in bronchiectasis: The underlying oxidative injury mechanism

Bronchiectasis is a chronic neutrophilic respiratory disease frequently complicated by Pseudomonas aeruginosa (P. aeruginosa) infection. Neutrophil extracellular traps (NETs) exert dual effects in host defense and airway injury, while the roles of CYBB and the p38 MAPK pathway in NETs-mediated epithelial damage in bronchiectasis remain unclear.

Bronchoalveolar lavage fluid (BALF) dsDNA levels were detected to quantify NETs levels, bronchial tissues were subjected to mRNA sequencing, and peripheral blood was used for core gene expression validation via RT-qPCR. We established in vivo P. aeruginosa-induced rat bronchiectasis models, as well as in vitro NETs-exposed bronchial epithelial cell models, CYBB knockdown and p38 MAPK pathway inhibition assays. Primary detection indicators included cell viability, oxidative stress markers (colorimetric detection of malondialdehyde (MDA) content, flow cytometry assessment of reactive oxygen species (ROS) levels), and protein expression of CYBB, p38 and MK2 detected by Western blot assay.

NETs levels were significantly elevated in bronchiectasis patients and positively correlated with disease severity; P. aeruginosa was the predominant pathogen (56.25% detection rate). RNA sequencing combined with machine learning screened CYBB as a key candidate gene, with KEGG enrichment analysis revealing significant enrichment of the MAPK signaling pathway. CYBB expression was markedly upregulated in the bronchiectasis group of clinical samples, the bronchiectasis subgroup of the GSE97298 dataset, and the model group of P. aeruginosa-induced bronchiectasis rats. NETs exposure reduced epithelial cell viability, upregulated CYBB, activated p38 MAPK pathway and increased oxidative stress, which were partially reversed by CYBB knockdown or p38 inhibition.

Our findings support that elevated NETs in P. aeruginosa-associated bronchiectasis may promote airway epithelial oxidative injury via the candidate CYBB-p38 MAPK axis, which may lay a preliminary foundation for future mechanistic and clinical research on bronchiectasis.