Curcumin Mitigates Radiation-induced Lung Pneumonitis and Fibrosis in Rats

Radiation-induced lung injury is one of the most prominent factors that interfere with chest cancer radiotherapy, and poses a great threat to patients exposed to total body irradiation. Upregulation of pro-oxidant enzymes is one of the main mechanisms through which the late effects of ionizing radiation on lung injury can be exerted. Interleukin (IL)-4 and IL-13 are two important cytokines that have been proposed to be involved in this process. Through stimulation of dual oxidase 1 and 2 (DUOX 1 & 2), they induce chronic oxidative stress in irradiated tissues. In this study, we evaluated the effects of curcumin treatment on the regulation of IL-4 and IL-13, DUOX1 & 2 genes as well as the pathological changes developed by this treatment. Twenty male Wistar rats were divided into four groups: radiation only; curcumin only; radiation +curcumin; and control group with neither pharmacotherapy nor radiation. Curcumin was administered for 4 and 6 consecutive days before and after irradiation, respectively. Also, the chest area was irradiated with 15 Gy using a cobalt-60 gamma rays source. All rats were sacrificed 67 days after irradiation, followed by the assessment of the levels of IL-4 and IL-13; the expression of IL- 4 receptor-a1 (IL4Ra1), IL13Ra2, DUOX1 and DUOX2, and finally the histopathological changes were evaluated. Radiation led to the increased level of IL-4, while the level of IL-13 showed no change. QPCR results showed the upregulation of IL4Ra1, DUOX1 and DUOX2 following lung irradiation. Histopathological evaluation also showed a remarkable increase in pneumonitis and fibrosis. Treatment with curcumin downregulated the expression of IL-4, IL4Ra1, DUOX1 & 2. Furthermore, it could mitigate pneumonitis and fibrosis following lung irradiation. The late effects of radiation- induced lung injury may be due to the upregulation of DUOX1 & 2 genes. Curcumin, through modulation of these genes, may contribute to the protection against ionizing radiation.