Dendrimer micelles with glycyrrhizic acid (GA) were developed for anti-inflammatory therapy of acute lung injury (ALI). Cholesterol was conjugated to histidine- and arginine-grafted polyamidoamine (PamHR) for micelle formation. The cholesterol-conjugated PamHR (PamHRchol) was mixed with amphiphilic GA to produce PamHRchol/GA mixed micelles. The GA integrated into the micelles had two functions: it acted as an anti-inflammatory drug and facilitated intracellular gene delivery. The PamHRchol/GA micelles formed stable complexes with plasmid DNA. Integrating GA into the micelles increased their transfection efficiency. Confocal microscopy and flow-cytometry studies confirmed that the PamHRchol/GA micelles improved cellular uptake compared with PamHRchol. A competition assay with free GA suggested that the enhanced transfection efficiency of the micelles might be due to the interaction between GA and its receptor. In addition, GA has a membrane-destabilizing effect, and a chloroquine pretreatment assay confirmed that GA increased endosomal escape. Furthermore, the PamHRchol/GA micelles reduced tumor necrosis factor-α in lipopolysaccharide-activated Raw264.7 cells, suggesting a mechanism for its anti-inflammatory effects. To evaluate the therapeutic potential of the PamHRchol/GA micelles, the heme oxygenase-1 (HO-1) gene was delivered into the lungs of mice with ALI. The PamHRchol/GA micelles had higher gene delivery efficiency into the lungs than polyethylenimine (25 kDa, PEI25k) and the PamHRchol micelles. The combined effects of the HO-1 gene and GA produced effective anti-inflammation response in the lungs of the ALI animals. Therefore, the dual-function PamHRchol/GA micelles, which acted as an anti-inflammatory drug and a gene carrier, could be a useful therapy for inflammatory lung diseases.
Keywords: acute lung injury; gene delivery; glycyrrhizic acid; micelles; polyamidoamine.