The Influence of Radiotherapy on AIM2 Inflammasome in Radiation Pneumonitis

This study aims to investigate the influence of radiotherapy on absent in melanoma 2 (AIM2) inflammasome in radiation pneumonitis (RP). A rat model of RP was established. H&E staining was used to test radiation-induced lung tissue injury. Immunohistochemistry (IHC) was used to detect the expression of AIM2 and IL-1β in rat lung tissues. Milliplex assay was used to test cytokine levels in rat serum. Comet assay was adopted to examine DNA breaks in THP1 cells. RT-PCR was used to detect the messenger RNA (mRNA) expression of AIM2, caspase-1, and IL-1β in THP1 cells. As a result, the rat model indicated that irradiation induced obvious lung injury. A large amount of inflammatory cells infiltrated to the irradiated lung tissues. The structure of lung tissues collapsed. IHC revealed that AIM2 and IL-1β expressions were significantly higher in irradiated lung tissues than in the control. IL-1β level in rat serum significantly elevated on the 7th day post-irradiation, gradually decreased on the 15th day, and became minimal on the 30th day. Irradiation induced dsDNA break in a dose-dependent manner at 24 h after irradiation. Radiotherapy increased the mRNA expression level of AIM2 and IL-1β in a time-dependent manner. In conclusion, radiotherapy triggered some critical components of AIM2 inflammasome in RP. The activation of AIM2 inflammasome by radiotherapy may contribute to the pathogenesis of RP.