Nano-sized DNase scavenges cell-free DNA for acute lung injury treatment

Excessive release of cell-free DNA (cf-DNA) from damaged cells activates DNA sensors, triggering robust inflammatory responses and contributing to the pathogenesis of acute lung injury (ALI). To address this, we developed a nano-sized DNase system by conjugating DNase I onto PEGylated bilirubin (BR) nanoparticles (BRn@DNase I) for efficient cf-DNA scavenging and inflammation resolution in ALI. Anchoring DNase I on the nanoparticle surface enhances its stability, pulmonary retention, and DNA-clearing efficiency. Under reactive oxygen species (ROS)-rich conditions typical of inflamed lung tissues, hydrophobic BR undergoes oxidation to hydrophilic biliverdin, inducing disassembly of the nanostructure while preserving the enzymatic activity of the DNase residues. Additionally, the antioxidative property of BR contributes to the protective effects of BRn@DNase I. In vitro, BRn@DNase I significantly inhibited proinflammatory cytokine production in activated macrophages. In an LPS-induced ALI mouse model, the system effectively reduced pulmonary cf-DNA levels, alleviated inflammation, and accelerated tissue recovery. Notably, BRn@DNase I also modulated alveolar macrophage polarization, shifting them from the proinflammatory M1 phenotype to the reparative M2 state. These findings highlight BRn@DNase I as a promising nano-therapeutic strategy for mitigating cf-DNA-mediated inflammation in ALI.