Neutrophil extracellular traps are involved in the occurrence of rheumatoid arthritis-associated interstitial lung disease

Background The excessive formation of neutrophil extracellular traps (NETs) has been demonstrated to be a pathogenic mechanism in both rheumatoid arthritis (RA) and interstitial lung disease (ILD). However, whether NETs contribute to RA-associated ILD (RA-ILD) and the underlying mechanisms driving NETs formation remain unclear. This study aimed to assess the involvement of NETs in RA-ILD and elucidate the underlying mechanisms. Methods Single-cell sequencing was used to identify changes in the quantity and function of neutrophils in the lung tissue of a zymosan A (ZYM)-induced interstitial pneumonia arthritis model, along with the detection of NETs components in the lung tissues. Additionally, nuclear receptor 4A3 (NR4A3) expression in HL-60 cells was interfered with to detect the effects on NETs components and the transformation of MRC-5 cells into myofibroblasts. The clinical relevance of plasma myeloperoxidase-DNA (MPO-DNA), citrullinated histone 3 (Cit-H3), and cell-free DNA was evaluated in patients with RA-nonspecific interstitial pneumonia (NSIP) and RA-usual interstitial pneumonia (UIP), RA-organizing pneumonia (OP), RA-other patterns, and healthy cohorts using commercial enzyme-linked immunosorbent assay (ELISA). Results In the ZYM-treated SKG mouse model, which recapitulates key features of RA-ILD, an increased neutrophils population in lung tissue was primarily responsible for NETs formation. Mechanistically, interference with NR4A3 expression was found to promoted NETs formation in HL-60 cells, subsequently enhancing MRC-5 cell differentiation into myofibroblasts. Clinically, plasma levels of MPO-DNA and Cit-H3 were elevated in patients with RA-NSIP and RA-UIP compared to healthy subjects. ROC curve analysis further revealed that plasma MPO-DNA combined with RF and anti-CCP, as well as Cit-H3 combined with RF and anti-CCP, served as superior diagnostic panels for NSIP and UIP in RA-ILD patients, respectively. Conclusions These findings suggest that targeting NETs could provide a novel therapeutic approach for ILD in RA patients.