MGST2hi PMNs mediate NETs and drive pericyte-to-myofibroblast transition in RA-ILD

Neutrophil extracellular trap (NET) formation has been implicated in the pathogenesis of rheumatoid arthritis-associated interstitial lung disease (RA-ILD), yet the specific neutrophil subsets involved and the mechanisms remain incompletely understood. Here, we identified a significantly expanded population of microsomal glutathione S-transferase 2-high NET-releasing polymorphonuclear neutrophils (Mgst2hi PMNs) in the lungs, bronchoalveolar lavage fluid (BALF), and peripheral blood (PB) of zymosan A-induced interstitial pneumonia-arthritis mouse models. Pharmacologic inhibition of Mgst2 with coniferyl ferulate (CF) and genetic knockdown using an adeno-associated virus (AAV9)-delivered shRNA under the Cd11b promoter (AAV9-shRNA-Mgst2) markedly attenuated pulmonary progression by suppressing NET formation. Mechanistically, Mgst2 promoted NET release in neutrophil-differentiated HL-60 cells and primary human peripheral blood neutrophils from healthy donors through a NADPH oxidases 2 (NOX2)-dependent pathway. NETs derived from these cells induced transdifferentiation of primary human pulmonary microvascular pericytes into myofibroblasts by activating transforming growth factor-beta (TGF-β) pathway. Clinically, circulating Mgst2hi NET-releasing PMNs were significantly elevated in the PB of patients with RA-ILD. Of note, more abundant Mgst2hi PMNs were found in RA patients with nonspecific interstitial pneumonia (NSIP) than those with usual interstitial pneumonia (UIP), organizing pneumonia (OP) and other ILD patterns. Moreover, the proportion of circulating Mgst2hi PMNs positively correlated with RA-NSIP severity, as assessed by and mean lung vessel diameter (6 mm), fibrosis score, and vessel score. Collectively, these findings demonstrate a critical pathogenic role for Mgst2hi PMNs in RA-ILD and suggest their utility as a potential therapeutic target through modulation of NET formation.