Mitigation of radiation-induced lung injury by genistein and EUK-207.

PURPOSE: We examined the effects of genistein and/or Eukarion (EUK)-207 on radiation-induced lung damage and investigated whether treatment for 0-14 weeks (wks) post-irradiation (PI) would mitigate late lung injury. MATERIALS AND METHODS: The lungs of female Sprague-Dawley (SD) rats were irradiated with 10 Gy. EUK-207 was delivered by infusion and genistein was delivered as a dietary supplement starting immediately after irradiation (post irradiation [PI]) and continuing until 14 wks PI. Rats were sacrificed at 0, 4, 8, 14 and 28 wks PI. Breathing rate was monitored and lung fibrosis assessed by lung hydroxyproline content at 28 wks. DNA damage was assessed by micronucleus (MN) assay and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels. The expression of the cytokines Interleukin (IL)-1α, IL-1ß, IL-6, Tumor necrosis factor (TNF)-α and Transforming growth factor (TGF)-ß1, and macrophage activation were analyzed by immunohistochemistry. RESULTS: Increases in breathing rate observed in the irradiated rats were significantly reduced by both drug treatments during the pneumonitis phase and the later fibrosis phase. The drug treatments decreased micronuclei (MN) formation from 4-14 wks but by 28 wks the MN levels had increased again. The 8-OHdG levels were lower in the drug treated animals at all time points. Hydroxyproline content and levels of activated macrophages were decreased at 28 wks in all drug treated rats. The treatments had limited effects on the expression of the cytokines. CONCLUSION: Genistein and EUK-207 can provide partial mitigation of radiation-induced lung damage out to at least 28 wks PI even after cessation of treatment at 14 wks PI.

Genistein can mitigate the effect of radiation on rat lung tissue.

We investigated whether genistein could protect the lung from radiation-induced injury. We hypothesized that genistein would reduce the levels of inflammatory cytokines and ROS after irradiation and therefore lead to reduced DNA damage and functional deficits. Whole lungs of Sprague-Dawley rats were irradiated with 18 Gy at approximately 0.5 Gy/min. At 28 weeks a micronucleus assay was used to examine DNA damage and, using immunohistochemical analysis, expression of IL-1alpha, IL-1beta, IL-6, TNF-alpha and TGF-beta, macrophage activation, oxidative stress (8-OHdG) and collagen levels were measured. A TBARS assay was used to measure the level of malondialdehyde. Functional damage was assessed by measuring the breathing rate of the rats over the course of the experiment. The increase in breathing rate after irradiation was damped in rats receiving genistein during the phase of pneumonitis (6-10 weeks), and there was a 50-80-day delay in lethality in this group. Genistein treatment also decreased the levels of the inflammatory cytokines TNF-alpha, IL-1beta and TGF-beta and led to a reduction in collagen content, a reduction in 8-OHdG levels, and complete protection against DNA damage measured in surviving rats at 28 weeks after irradiation. These results demonstrates that genistein treatment can provide partial protection against the early (pneumonitis) effects of lung irradiation and reduce the extent of fibrosis, although not sufficiently to prevent lethality at the radiation dose used in this study.

Partial volume rat lung irradiation: temporal fluctuations of in-field and out-of-field DNA damage and inflammatory cytokines following irradiation.

PURPOSE: The current study investigated the early activation of inflammatory cytokines and macrophages in different regions of the lung following partial volume irradiation. We examined temporal fluctuations in DNA damage, cytokine expression and macrophage activation during 16 weeks post-irradiation. MATERIALS AND METHODS: We irradiated the lower lung of Sprague-Dawley rats with 10 Gy. A micronucleus assay was used to examine DNA damage. Real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was used to analyse the RNA expression of Interleukin-1 alpha (IL-1a), Interleukin-1 beta (IL-1ss), Interleukin-6 (IL-6), Tumour Necrosis Factor alpha (TNF-a) and Transforming Growth Factor beta (TGF-ss) relative to Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH). The activation of macrophages was determined using the antibody ED-1 for immunohistochemical analysis. RESULTS: The expression of DNA damage, the activation of macrophages and the expression of inflammatory cytokines all fluctuated in a cyclic pattern. The initial induction of cytokine expression and the activation of macrophages occurred at very early times (1 h) following irradiation. Waves of cytokine expression and macrophage activation were also seen at later times (up to 16 weeks) following irradiation. DNA damage also occurred in a cyclic pattern though this was less pronounced out-of-field. The levels of cytokines and activated macrophages were elevated to a similar degree both in- and out-of-field, whereas there was a greater micronuclei yield in-field than out-of-field. CONCLUSIONS: An inflammatory response triggered by the partial volume irradiation occurs in the whole rat lung at very early times following irradiation and is maintained in a cyclic pattern to later times when the onset of functional symptoms is expected. We hypothesize that Reactive Oxygen Species (ROS) induced by this response play an important role in the induction of both in-field and out-of-field DNA damage.