Sequential nanoparticle therapy targeting neutrophil hyperactivation to prevent neutrophil-induced pulmonary fibrosis.

BACKGROUND: Pulmonary fibrosis, a major complication of severe COVID-19 and post-acute sequelae of SARS-CoV-2 infection (PASC), is driven by excessive neutrophil activation and the formation of neutrophil extracellular trap (NET). RESULTS: This study presents a sequential nanoparticle-based therapy combining DNase-I-loaded polydopamine nanoparticles (DNase-I@PDA NPs) with Sivelestat-encapsulated PLGA nanoparticles (Siv@PLGA NPs) to target both NETs and neutrophil elastase (NE) activity. DNase-I@PDA NPs were aerosolized to the lungs, facilitating NET clearance and reducing the fibrotic microenvironment, followed by intravenous administration of Siv@PLGA NPs to inhibit NE activity and prevent neutrophil hyperactivation. In a murine model of lipopolysaccharide (LPS)-induced pulmonary fibrosis, this dual approach significantly decreased fibrotic lesions, collagen deposition, and myofibroblast activation. Notably, treatment with the nanoparticles led to substantial improvements in pulmonary function. In neutrophils isolated from COVID-19 patients, the combined nanoparticle therapy reduced circulating cell-free DNA, NET, NE, and myeloperoxidase (MPO) levels, while enhancing neutrophil viability and reducing inflammatory responses. CONCLUSIONS: These findings highlight the efficacy of DNase-I@PDA NPs and Siv@PLGA NPs in addressing both acute inflammation and chronic fibrosis by simultaneously targeting NET formation and neutrophil hyperactivation. This dual nanoparticle therapy represents a promising clinical strategy for treating COVID-19-associated pulmonary complications, including PASC, by preventing long-term fibrotic progression and promoting lung recovery.