The Protective Effect Of Olive Leaf Extract Against Radiation Damage Of Mice

ObjectiveThis study aimed to investigate the protective effect of olive leaf extracts(OLE)on radiation damage of mice by evaluating peripheral blood cells,oxidative damage,micronucleus of bone marrow cells,expression of apoptosis related proteins Bcl-2 and Bax.The study may provide experimental data and theoretical basis for the further development of health products from OLE against irradiation.MethodsDetermination of polyphenols of the olive leaf extracts:OLE was extracted by using trasonic-assisted water extraction method and its polyphenol content was determined by Folin-ciocalteu colorimetry.Animal experiment:BALB/c male mice(50 days old)were randomized by five groups randomly,6 mice in each group,namely normal control group,radiation control group and low,middle and high dose OLE groups.Mice in low,middle and high dose OLE group were given 150,500 and 1000 mg/kg OLE by gavage,respectively once a day for 30 consecutive days.The mice in normal and radiation control subjects were given the equal volume of saline.On the 31st day,except the normal control group,mice in other 4 groups were radiated by X-ray at the total dose of 1 Gy(5 cGy/s,for 20 s).Within 6～12 hours after irradiation,blood samples were drawn from the eyeballs and serum was separated.Then mice were sacrificed quickly by cervical vertebra dislocation and the femur,spleen,thymus and liver tissues were obtained.Indicator determination:(1)Peripheral blood cell count:The count of peripheral blood cells was measured by three-population hematology analytical instrument.(2)Pathological changes of the liver:The liver was fixed,dehydrated,embedded in paraffin,and sectioned.Hematoxylin Eosin staining(HE)was served to examine the hepatic pathological changes.(3)Oxidative damage:The level of superoxide dismutase(SOD)was measured by xanthine oxidase(hydroxylamine)method,glutathione peroxidase(GSH-Px)activity was determined by enzymatic reaction,and malondialdehyde(MDA)level was evaluated by thiobarbituric acid(TBA)method.(4)Micronucleus rate of bone marrow:The smears with bone marrow cells(BMC)were produced,followed by drying,fixing with methanol and staining with Giemsa.The numbers of micronucleus in BMC were counted by microscope.(5)The expression level of apoptosis regulatory proteins:The expressions of apoptosis regulatory proteins Bcl-2 and Bax of radioactive liver were assessed by Western Blot.Results(1)Olive leaf extracts were rich in polyphenols and the content was as high as(57.55 ± 2.98)mg/g.(2)Effects of OLE on hematopoietic system of irradiated mice:In the mice with middle and high dose of OLE,the numbers of WBC were(1.50±0.43)× 109/L and(2.10± 0.16)× 109/L,and the numbers of PLT were(330.33 ± 10.16)× 109/L and(366.00 ± 10.26)×109/L,both of which were significantly higher than mice of the radiation control group(P<0.05).In the mice with high dose of OLE,the number of red blood cell was(5.43± 0.29)× 1012/L,also dramatically higher than that of the control group(P<0.05).(3)Effect of OLE on liver damage of irradiated mice:Hepatocytes of radiated mice swelled and arranged irregularly and shrunken nuclear and obscure gap junction and cords.The caryolysis could be detected in some cells with obvious inflammatory cell infiltration.The congestion of central vein could be found in partial tissue.However,the pathological changes of hepatocytes of the mice with middle and high dose of OLE were significantly improved with regularly arranged hepatocytes,intact lobule structure,clear hepatocyte cords and alleviated inflammation.Furthermore,the histomorphology of liver tissue in the high dose OLE group was similar to normal mice.(4)Effect of OLE on oxidative damage of irradiated mice:In the mice with middle and high dose of OLE,the serum MDA content were(13.25±0.63)nmol/mL and(10.67 ± 0.40)nmol/mL,which were significantly lower than radiated mice(P<0.05).The activities of SOD were(101.27 ± 12.77)U/mL and(110.42 ± 16.73)U/mL,and GSH-Px were(441.90±27.73)U/mL and(485.71±21.88)U/mL respectively,both of which were significantly higher than those of the radiation control group(P<0.05).Furthermore,the dose-effect relationship could be found between the biomarkers and OLE(P<0.05).(5)Effect of OLE on chromosome damage of irradiated mice:The micronucleus rate of BMC of mice with middle and high dose of OLE were(1.93±0.53)‰ and(1.60 ± 0.46)‰ respectively,which were significantly lower than that of radiated mice(P<0.05).A significantly decrease could be found in the high dose OLE group compared with the low and middle dose(P<0.05).(6)Effect of OLE on the expression of apoptosis related protein in liver of irradiated mice:The expression levels of Bcl-2 protein in mice with middle and high dose of OLE significantly higher than that of the radiation control group.However,the expression levels of Bax protein of mice with middle and high dose of OLE significantly lower than that of the radiation control group(P<0.05).The expression levels of Bcl-2 and Bax protein in the high dose group were both significantly different from those of middle group(P<0.05).ConclusionOlive leaf extracts are rich in polyphenol.It can effectively improve the hematopoietic capacity,reduce the level of lipid peroxidation,alleviate liver inflammation and chromosome damage,positively regulate the expression of Bcl-2 and Bax protein of irradiated mice,and have a good protective effect on radiation injury of mice induced by X-ray irradiation.