Edaravone Exerts Protective Effects on Mice Intestinal Injury without Interfering with the Anti-Tumor Effects of Radiation

Abstract

The appropriate dosage of edaravone-a radioprotective agent-and its effect on tumors are unknown. This study evaluated the effects of edaravone on intestinal injuries and tumors in mice induced by whole body X-ray irradiation. Small intestinal mucositis was induced in C3H/HeNSlc mice using a single X-ray dose (15 Gy). Edaravone (15, 30, and 100 mg/kg) was administered 30 min before irradiation to evaluate its protective effect. After 3.5 days, the jejunum was removed and the histological changes were evaluated. Next, C3H/HeNSlc mice with squamous cell carcinoma VII tumors were provided the same single X-ray dose and 100 mg/kg edaravone; further, the tumors were immediately induced after irradiation. The tumor cell viability was detected using an in vivo-in vitro colony formation assay. We found that the intestinal colony-forming ability after irradiation was significantly higher in the 100 mg/kg edaravone group than that in the control group. Moreover, the apoptotic cells in the villi immunohistochemically stained with cleaved caspase-3 were significantly lower in the 100 mg/kg edaravone group than in the control group. We found no radioprotective effects of intraperitoneally inoculated edaravone in both hind legs on squamous cell carcinoma VII tumors. These findings suggest that 100 mg/kg edaravone exerts protective effects on small intestinal injuries without interfering with the antitumor effects of radiation.

Keywords: enteritis; radiation; radioprotector; radiotherapy.

Figure 1

Schematic representation of the experiment. (A) Mice were fed for 1 week as an acclimation period (days 1–7). Next, edaravone or saline was intraperitoneally administered 30 min before administering irradiation. The mice were irradiated on day 8, fed until day 10, and euthanized on day 11. (B) Mice were subcutaneously inoculated with SCC VII cells on day 1. Mice were fed for 2 weeks until the growth of tumor was observed (days 1–14). In addition, edaravone or saline was intraperitoneally administered 30 min before administering irradiation. Mice were irradiated and euthanized on day 15.

Figure 2

Effect of administration of edaravone before irradiation. The intestinal colony-forming ability after irradiation was significantly higher in the 100 mg/kg edaravone group (group 5) (* p < 0.05).

Figure 3

Histopathological evaluation via hematoxylin and eosin staining. (A) Saline and non-irradiated group (group 1); (B) saline and irradiated group (group 2); (C) 15 mg/kg edaravone and irradiated group (group 3); (D) 30 mg/kg edaravone and irradiated group (group 4); (E) 100 mg/kg edaravone and irradiated group (group 5); and (F) 100 mg/kg edaravone and non-irradiated group (group 6).

Figure 4

Percentage of cleaved caspase-3-positive cells. The apoptotic cells in the villi were significantly lower in the 100 mg/kg edaravone group (group 5) (* p < 0.05).

Figure 5

Immunohistochemical evaluation of apoptosis-related cleaved caspase-3. (A) Saline and non-irradiated group (group 1); (B) saline and irradiated group (group 2); (C) 15 mg/kg edaravone and irradiated group (group 3); (D) 30 mg/kg edaravone and irradiated group (group 4); (E) 100 mg/kg edaravone and irradiated group (group 5); and (F) 100 mg/kg edaravone and non-irradiated group (group 6).

Figure 6

Surviving fraction of SCC VII tumor cells after a single dose of 15 Gy to mice treated with normal saline (open circle) or 100 mg/kg edaravone (closed circle). Values represent the means of ≥3 samples in three independent experiments; error bars indicate standard deviations.