Engineering of glycyrrhizin-loaded chitosan nanogel for pulmonary immunomodulation via regulation of NF-κB signaling and macrophage polarization in lung inflammatory.

Acute lung injury involves excessive inflammation, neutrophil infiltration, and impaired macrophage polarization, underscoring the need for effective immunomodulatory therapies. Here, we developed a glycyrrhizin-loaded chitosan nanogel (GlyU@CS) as a biocompatible macromolecular platform for targeted modulation of pulmonary inflammation. MD simulations verified the structural stability of the nanogel under physiological conditions. Physicochemical analyses confirmed its nanoscale size (57 nm), positive charge (+24.8 ± 1.7 mV), amorphous structure, and efficient GlyU loading. In vitro mucoadhesion assays revealed strong electrostatic interactions with mucin, reflected by increases in hydrodynamic diameter (145.3 → 257 nm) and reduced zeta potential (+24 → +8.7 mV), along with notable rheological synergism, collectively indicating enhanced mucus retention. Cellular studies demonstrated minimal hemolysis (<2%), efficient uptake, and markedly reduced intracellular ROS relative to free GlyU. In LPS-stimulated murine cells, GlyU@CS significantly suppressed pro-inflammatory cytokine expression at both mRNA and protein levels. In an LPS-induced acute lung injury model, the nanogel markedly alleviated inflammation, including a reduction in MPO activity from 2.5 to 1 mU/mg, diminished neutrophil infiltration, and pronounced histopathological improvement. Mechanistically, the nanogel exerted strong anti-inflammatory activity by inhibiting NF-κB signaling, reducing COX-2 and iNOS, and restoring IκB-α. Flow cytometry further confirmed a 7.5-fold shift in macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2 phenotype. Overall, GlyU@CS acts as a potent immunomodulatory system integrating mucoadhesive delivery with molecular regulation of inflammation and macrophage polarization, highlighting the promise of CS-based nanogels for treating acute lung inflammatory disorders.