Damage of radioprotection and antitumor effects of water-soluble propolis

Abstract

Some natural products are able to inhibit radiation effects and exert an antitumor effect with fewer adverse reactions; however, their antitumor effects are less than those of widely-used synthetic drugs. Propolis is a natural material that has been attracting attention, and we extracted this material with water and investigated the effect of continuous propolis administration on radioactivity-induced reduction of hemocytes, in addition to the antioxidant and antitumor effects of propolis. Following a 1-week adjustment period, water-soluble propolis was administered intraperitoneally to male ICR mice at a dose of 100 mg/kg every other day for 2 weeks. Following administration, 2 Gy whole-body irradiation was performed and the counts of leukocytes, lymphocytes, and granulocytes and monocytes in the peripheral blood were determined 1, 3, 7, 15 and 30 days after irradiation. These cells were considered since they are closely associated with immunity to radioactivity. In a second experiment, water-soluble propolis was similarly administered to the mice for 2 weeks after a 1-week adjustment period, and 2 Gy whole-body irradiation was performed. The antioxidant effects in hemocytes were then investigated using 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH), a radical generator. In a third experiment, <TEX>$1\;{\times}\;10^6$</TEX> Sarcoma-180 cells were inoculated into the right thigh of mice, which were divided into four groups: control, water-soluble propolis-treated, 6 Gy irradiated and water-soluble propolis-treated + 6 Gy irradiated groups, and changes in tumor size were measured for 20 days. Statistical analysis was conducted using ANOVA for multiple groups. In the three experiments, administration of water-soluble propolis inhibited the reduction of hemocytes caused by whole-body irradiation, showed antioxidant effects against radioactivity, and inhibited tumor growth, respectively. In conclusion, our data suggest that the antioxidant effect of watersoluble propolis inhibits hemocyte reduction caused by whole-body irradiation and enhances immunological inhibition of tumor growth.