CXCL3 deficiency ameliorates COPD by suppressing cigarette smoke-induced NETs formation via MAPK signaling.

Chronic obstructive pulmonary disease (COPD) is a common respiratory disorder characterized by persistent airflow limitation, and its pathogenesis is closely associated with cigarette smoke (CS) exposure. Neutrophil extracellular trap (NET) formation contributes critically to airway inflammation and tissue damage in COPD. However, the upstream regulators of NETosis remain poorly defined. In this study, a CS-induced mouse model of COPD was established, and transcriptomic sequencing of lung tissues was performed to identify differentially expressed genes. CXCL3 was significantly upregulated in COPD mouse lungs, a finding confirmed by qPCR, Western blot, and immunofluorescence, which localized CXCL3 predominantly to airway epithelial cells. Analysis of a public human single-cell RNA-seq dataset further validated CXCL3 enrichment in both immune and epithelial cells in COPD lungs. In vitro, knockdown of CXCL3 in BEAS-2B epithelial cells stimulated with cigarette smoke extract (CSE) reduced the ability of these cells to promote NETosis in neutrophil-like HL-60 cells. In vivo functional knockdown of CXCL3 attenuated NETs formation, pulmonary inflammation, and emphysema in CS-exposed mice. Mechanistically, Gene Set Enrichment Analysis (GSEA) revealed enrichment of the MAPK pathway, and Western blot analysis showed that CXCL3 knockdown suppressed CSE-induced phosphorylation of p38, ERK, and JNK. Pharmacological inhibition of each MAPK component (SB203580, U0126, SP600125) phenocopied the effect of CXCL3 knockdown, confirming that CXCL3 acts upstream of MAPK signaling to promote NETs formation. Collectively, this study identifies CXCL3 as a critical regulator of CS-induced NETosis and COPD progression through activation of the MAPK pathway, and highlights epithelial-derived CXCL3 as a promising therapeutic target for COPD intervention.