Protective efficacy of inhaled quercetin for radiation pneumonitis.

Radiation pneumonitis is a clinical problem with a high incidence. Once the onset of radiation pneumonitis has occurred, the administration of antioxidants and anti-inflammatory agents is the most commonly used method of clinical treatment. Quercetin (Que) is a common flavonoid, with potent anti-inflammatory and anti-oxidant activities. In the present study, the therapeutic effect of inhaled Que on radiation-induced radiation pneumonitis in rats was investigated. Treatment with Que via inhalation was shown to increase the number of leukocytes and erythrocytes in the blood, and reduce the number of inflammatory cells in bronchoalveolar lavage fluid. Histological examination of lung tissue indicated that inhaled Que reduced hemorrhaging and the infiltration of inflammatory cells, and suppressed the expression of the proinflammatory cytokines transforming growth factor-β1 and interleukin-6. These results indicated that treatment with Que via inhalation ameliorates radiation pneumonitis by reducing the number of inflammatory cells, and attenuating the inflammatory response and pathological changes. This suggests that administration of Que via inhalation has the potential to become a novel treatment for radiation pneumonitis.