The Radioprotective Effect And Mechanism Of Emodin And Kaempferol On Gamma Radiation-induced Damage

Objective: Radiotherapy is one of the most important treatment methods for human malignancy.However,radiation is a two-edged sword.Although radiotherapy is effective in tumor treatment,it induces normal tissue toxicity.It has been reported that longtime or megadose ionizing radiation can lead to acute radiation syndrome,involving gastrointestinal tract,the hematopoietic system,immune system and so on.It is reported that radiation can induce oxidative stress,cell apoptosis and inflammation resulting in mortality.It is necessary to develop effective drug to against radiation damage.Emodin,a plant-derived anthraquinone,has been reported to exhibit a variety of biological activities,and anti-inflammatory,antioxidant,anticancer and modulation of immune system,as well as metabolic processes are involved.Sharma has reported that emodin has radioprotective effective in murine splenocytes in vitro by inhibiting DNA damage and scavenging free radicals.However,it remains unknown whether emodin with radioprotective effect in vivo and mechanism.Kaempferol is a dietary flavonol with antioxidant,anti-inflammatory and anti-apoptotic effects.Due to kaempferol is a natural polyphenolic in structure,so it shows obviously scavenging free radicals effect.As we know,generation of free radicals in cellular milieu causes damage in cell after radiation.Hence,this is essential to develop free radical scavengers as radioprotectant to reduce the number of free radicals and attenuate DNA and organelles damage.So far,it still never has reports about kaempferol protecting against gamma radiation injury in vitro or vivo.The aim of this study is to explore the protective effect of emodin and kaempferol on gamma radiation-induced damage.Methods:The C57BL/6 mice were divided into seven groups randomly,including Con group,8.5Gy radiation group,8.5Gy+emodin 30mg/kg group,8.5Gy+kaempferol 15mg/kg group,7Gy radiation group,7Gy+emodin 30mg/kg group,7Gy+ kaempferol 15mg/kg group.Mice were pre-treated with emodin or kaempferol for 5 days via oral gavage before exposed to 8.5Gy or 7Gy total body irradiation(TBI).The survival rate and mice body weight were calculated and recorded after received 8.5Gy TBI.Mice were sacrificed on the seventh day after 7Gy TBI,and body weight,spleen weight,thymus weight were all recorded,meanwhile the level of SOD and MDA in spleen and thymus were tested respectively.The level of EPCs in peripheral blood was measured in fluorescent antibody and Flow cytometry.The jejunum was analyzed via H&E staining,TUNEL staining and Western blot.HUVECs was used in our study and divided into Con group,24 Gy radiation group,24Gy+emodin group,24Gy+ kaempferol group.MTT assay,Flow cytometry,Hoechst 33258 staining,Real-time PCR and Western blot were used to detect cell viability,cell apoptosis and gene expression in m RNA and protein level at 24 h after radiation,except that ROS,NO,SOD and MDA level after radiation were tested at 24 h.Results:1.Emodin and kaempferol can prolong survival rate and attenuate loss of body weight after 8.5Gy TBI.After 8.5Gy TBI con group survival rate was 100% at 30 th day and at 10 th day mean body weight was(20.66±0.93)g,and 8.5Gy radiation group survival rate was 10% at 30 th day and at 10 th day mean body weight was(14.93±2.04)g,however,emodin /kaempferol treatment group showed obviously increased survival rate in 30 th day(50%;40%)and attenuated the loss of body weight in 10 days((17.90±1.47)g;(17.11±1.21))g.2.Emodin and kaempferol can attenuate gamma radiation induced intestinal injury in mice after 7Gy TBI.Emodin and kaempferol alleviated intestinal morphological changes and increased the mean villus height,crypt numbers and reduced villus and crypt apoptosis,as well as inhibited the expression of p53 and recovered the abnormal expression of prx5.3.Emodin and kaempferol increased the spleen index,thymus index and the level of EPCs in peripheral blood after 7Gy TBI.Compared to 7Gy radiation model group,Kaempferol increased the level of SOD and reduced the level of MDA in spleen and thymus respectively.4.Emodin and kaempferol can increase cell viabilities and inhibit cell apoptosis.Emodin decreased the expression of p53,Bax and Caspase 3 in m RNA and protein level after 24 Gy radiation in HUVECs.Kaempferol increased the level of SOD,and decreased the level of NO,ROS and MDA,as well as recovered the abnormal expression of prx5,Cyt-c,Caspase9 and Caspase3 in m RNA and protein level after 24 Gy radiation in HUVECs.Conclusion: 1.Emodin can prolong the survival rate after total body irradiation,and attenuate radiation-induced tissue damage,as well as increase the cell viabilities.Emodin protects against radiation-induce injury via inhibiting the high expression of p53,Bax and Caspase3 in m RNA and protein level after radiation,then decreasing radiation induced intestinal injury and apoptosis.2.Kaempferol can prolong the survival rate after total body irradiation,and attenuate radiation-induced tissue damage,as well as increase the cell viabilities.Kaempferol protects against radiation-induced injury by scavenging free radicals in cell and tissue,recovering the abnormal expression of prx5,Cyt-c,Caspase9 and Caspase3 in m RNA and protein level,then decreasing radiation induced intestinal injury,oxidative stress and apoptosis.