Radiation pneumonitis is a common complication of thoracic irradiation for
lung cancer patients. The healthy gut microbiota plays an important role in the local mucosal defense process as well as pulmonary
immunomodulation of the host. However, the effect of the intestinal microbiota on
radiation pneumonitis is not well understood. Here we studied how the intestinal microbiota affected the host response to
radiation pneumonitis. C57BL/6 mice were administered
antibiotics to induce disequilibrium in the gut microbiota, and subsequently irradiated. We found that the intestinal microbiota served as a protective mediator against
radiation pneumonitis, as indicated by decreased
body weight and increased mortality in
antibiotic-treated mice. In mice with gut microbiota disequilibrium, more serious pathological lung damage was observed at two and four weeks postirradiation.
Fecal microbiota transplantation into irradiated mice led to improvement from radiation-induced
inflammation two weeks postirradiation. High-throughput sequencing of murine feces displayed conversion of flora diversity, bacterial composition and community structure in the absence of normal intestinal flora. We filtered the potentially important species among the gut microbiota and considered that the
tissue-type plasminogen activator might be involved in the inflammatory process. This study reveals that the gut microbiota functions as a protective regulator against
radiation pneumonitis. Additionally,
fecal microbiota transplantation was shown to alleviate
lung injury in the irradiated model. The protective role of the healthy gut microbiota and the utilization of the gut-lung axis show potential for innovative therapeutic strategies in radiation-induced
lung injury.