Study On The Mechanisam Of Free Radical Injury In The Side Effect Of Radiation Therapy

Tumor is one of the most familiar disease which threaten the human health and a major cause for man to death. Because lacking the effective method to cure this disease, many of the patients with tumor get bad results. Radiation therapy is one of the routine methods. The primary mechanism of radiation therapy is its ionizative action, which can kill the tumor cell directly or indirectly by the generation of free radicals and reactive oxygen species, to cure the disease. But at the same time, the radiation cause serious side effects, limiting the therapy going on. Studying on the mechanism of the side effect of radiation therapy maybe can bring us a new way to get rid of the tumor.According to the characters of free radicals and reactive oxygen species and the action of radiation therapy, we hypothesized that the cure effect of radiation therapy is different from its side effect. Making full use of the differences between them maybe a new good method for the tumor therapy. To approve the hypothesis, we designed this experiment to investigate the effect of radiation therapy on the whole body' s peroxide injury and the protection of multiple antioxidants. We also study the gene expressions caused by the local radiation, and the effect of antioxidants on them. The more understanding on the mechanismof radiation therapy , especially if there is part and time differences between the radiation therapy on the tumor and the side effect on the whole body, will help us establish new theory on the tumor radiation therapy.The study began with the selection of effective antioxidants. The transplanting tumor animal model was made to be the object of this experiment. The tumors were radiated by 6癈o (47Gy) in 4 times to simulate the patients with tumor got radiation therapy.The animals were seperated into four groups which are negtive control group, positive control group which also named tumor model group .radiation therapy group and antioxidant protective group.The later two groups were radiated regularly, but the antioxidant protective group were supplied with multiple antioxidants everyday by gavage. We observe the condition of the animals' survival , the oxidative injury of the whole body to analyze the relationship between the local radiation and the whole body oxidative injury and the antioxidant protective effect.We find that the local radiation can increase the contents of MDA, NO and NOS, decrease the activities of T-SOD,Mn-SOD, CAT, GSH and total antioxidative capacity. The antioxidant supplementation can restrain these changes caused by the local radiation. The animals in the antioxidant protective group live longer than that in the radiation therapy group. We also find that the local radiation can cause the more expression of some genes such as p53 and NOS, at the same time reduce the expression of bcl-2 and VEGF. But the antioxidants have the reverse effect.These results demonstrated that the local radiation can cause theoxidative injury on the whole body which was induced by the free radicals and reactive oxygen species. These free radicals and ROS were gengerated by the local radiation.They play a key role in the action of killing tumor cells and also in the side effect on the whole body , but at the different time and parts. The antioxidants have a protective effect against this damage. These all approve the hypothesis to be reasonable.