Glycyrrhetinic acid alleviates radiation-induced lung injury in mice

Radiation-induced lung injury (rili) is a common complication of thoracic radiotherapy,but efficacious therapy for rili is lacking. this study ascertained whether glycyrrhetinic acid (ga; a functional hydrolyzed product of glycyrrhizic acid,which is extracted from herb licorice) can protect against rili and investigated its relationship to the transforming growth factor (tgf)-β1/smads signaling pathway. c57bl/6 mice were divided into four groups: a control group,a ga group and two irradiation (ir) groups. ir groups were exposed to a single fraction of x-rays (12 gy) to the thorax and administered normal saline (ir + ns group) or ga (ir + ga group). two days and 17 days after irradiation,histologic analyses were performed to assess the degree of lung injury,and the expression of tgf-β1,smad2,smad3 and smad7 was recorded. ga administration mitigated the histologic changes of lung injury 2 days and 17 days after irradiation. protein and mrna expression of tgf-β1,smad2 and smad3,and the mrna level of smad7,in lung tissue were significantly elevated after irradiation. ga decreased expression of tgf-β1,smad2 and smad3 in lung tissue,but did not increase smad7 expression. ga can protect against early-stage rili. this protective effect may be associated with inhibition of the tgf-β1/smads signaling pathway. © the author 2016. published by oxford university press on behalf of the japan radiation research society and japanese society for radiation oncology.