Figure 4.

Fractionated irradiation of the lung leads to a reduced gain of body weight and an increased breathing frequency two weeks after irradiation. Lovastatin and EHT1864 treatment have no effect on body weight, but decrease IR-mediated increase in breathing frequency. (a) Selective irradiation of the right mouse lung was achieved using a metal-free device, which is adjustable in x-, y- and z-direction. 6 mm lead shielding prevents irradiation of other tissue. The red arrow marks the radiation field. One hour after single irradiation (4 Gy) of the right lung of anesthesized BALB/c mice, different tissues (lung, heart, liver) were analyzed for the presence of γH2AX foci, which are indicative of DSBs. Nuclei were counterstained with DAPI. Shown are representative photographs. (b) Treatment scheme. As based on previous in vivo studies^{6, 14, 66, 67} male BALB/c mice were treated three times per week with lovastatin (10 mg/kg BW) or the Rac1-specific small molecule inhibitor EHT18641 (5 mg/kg BW) during a total period of six weeks. In the course of the first two weeks the right lung of the animals was irradiated four times with each 4 Gy (4 × 4 Gy), resulting in a cumulative dose of 16 Gy. Control animals were not irradiated (4 × 0 Gy). (c) Body weight was recorded three times per week. Data shown are changes in percent of body weight between the start and end of the experiment. Shown are the mean±S.D. of n=4–6 animals per experimental group. Two-way ANOVA with Bonferroni post hoc test, *P≤0.05. ns, not significant. (d,e) Breathing frequency, which is indicative of radiation pneumonitis,^{24, 25, 68} was determined two weeks (d) and four weeks (e) after the end of the fractionated irradiation. Breathing frequency of control animals was set to 1. Mean±S.D. of n=4–6 animals per experimental group. Two-way ANOVA with Bonferroni post hoc test, *P≤0.05