Protective effect of melatonin entrapped PLGA nanoparticles on radiation-induced lung injury through the miR-21/TGF-β1/Smad3 pathway

[Display omitted] •The preparation procedure of MET/PLGANPS is simplified with a one-step nanoprecipitation-solvent volatilization techniques.•MET/PLGANPS or MET targeted the lungs through the trachea could increase the concentration of the drug and prolong its action time in the lung tissue.•We constructed MET/PLGANPS-Cy5 for fluorescence imaging of various organs and evaluation of the pharmacokinetics.•MET/PLGANPS could better reduce RILI.•T he inhibition of miR-21 could reduce the expression of TGF-β1, miR-21/TGF-β1/Smad3 pathway might be involved MET/PLGANPS to relieve RILI. Radiation-induced lung injury (RILI) is a complication commonly found in victims suffering from nuclear accidents and patients treated with chest tumor radiotherapy, and drugs are limited for effective prevention and treatment. Melatonin (MET) has an anti-radiation effect, but its metabolic period in the body is short. In order to prolong the metabolism period of MET, we prepared MET entrapped poly (lactic-co-glycolic acid) nanoparticles (MET/PLGANPS) for the treatment of RILI. As a result, the release rate of MET/PLGANPS in vitro was lower than MET, with stable physical properties, and it caused no changes in histopathology and biochemical indicators. After 2 weeks and 16 weeks of irradiation with the dose of 15 Gy, MET and MET/PLGANPS could reduce the expression of caspase-3 proteins, inflammatory factors, TGF-β1 and Smad3 to alleviate radiation-induced lung injury. MET/PLGANPS showed better therapeutic effect on RILI than MET. In addition, we also found that high expression of miR-21 could increase the expression levels of TGF-β1, and inhibit the protective effect of MET/PLGANPS. In conclusion, MET/PLGANPS may alleviate RILI by inhibiting the miR-21/TGF-β1/Smad3 pathway, which would provide a new target for the treatment of radiation-induced lung injury.