Naked Gene Delivery Induces Autophagy for Effective Treatment of Acute Lung Injury in a Mouse Model.

Background: Acute lung injury (ALI) leads to diffuse pulmonary interstitial and alveolar edema, further developing into acute respiratory distress syndrome (ARDS). The present therapeutic approaches showed limited effects with poor clinical efficacy or severe side effects. This study aims to develop novel pharmaceutical agents to reduce lung damage with acceptable side effects for ALI.

Methods: Naked gene delivery system based on epigallocatechin 3-gallate (EGCG) was synthesized to deliver plasmid expressing DNA damage regulated autophagy modulator 1 (DRAM1), designated as EGCG/DRAM1 (ED). ED was characterized by dynamic light scattering analysis and transmission electron microscope. The biodistribution of ED in mice was measured by an in vivo small animal imaging system. The therapeutic potentials of ED were evaluated in MLE12 cells and LPS-induced ALI mice.

Results: Our results showed that ED was nearly spherical with a diameter of ~100 nm and increased the stability of DRAM1 plasmid that encapsulated. The synthesized ED showed negligible toxicity at the selected experimental concentration in MLE12 cells. ED could be taken up by MLE12 cells with high efficiency and escape from the lysosome. In ALI mice, ED facilitated the accumulation and retention of DRAM1 plasmid in lung, and attenuated pulmonary edema and pulmonary vascular permeability. The therapeutic effects of ED on ALI were associated with increased autophagy and reduced oxidative stress in lung.

Conclusion: In summary, ED attenuated pulmonary edema and pulmonary vascular permeability, and improved pulmonary dysfunction in ALI mice. This naked gene delivery system for autophagy enhancement may serve as a potential therapeutic strategy to attenuate ALI.