Study On DNA Double-strand Breaks In Peripheral Blood Lymphocytes After CT Scan With ?-H2AX Immunofluorescence Microscopy

PART I The Effect of CT Examination on DNA Double Strand Breaks in Peripheral Blood Lymphocytes:An in Vitro and in Vivo StudyPurpose:To evaluate the effect of abdominal contrast-enhanced CT on the levels of DNA double-strand breaks(DSBs)in peripheral blood lymphocytes.Materials and methods:Eight ml venous blood samples were taken from twelve healthy volunteers.The venous blood was divided into Group A,Group B,Group C and Group D,with two ml each group for in vitro study.Group A was set as the control group which did not accept CT radiation exposure.Group B,Group C and Group D received a scan equivalent to one,twice or three times of radiation dose from abdominal contrast-enhanced CT scan,respectively.Thirty patients undergoing abdominal contrast-enhanced CT were selected for the in vivo study.Two ml venous blood were taken before CT examination and 5 min after the examination as baseline Group and radiation Group,respectively.Dose-length product(DLP)and volume CT dose index(CTDIvol)were recorded for each patient.Lymphocytes in blood samples were isolated and stained by immunofluorescence of gamma-H2AX protein to label DSBs.The relationship among DSBs level in group A,B,C and D was compared by repeated measurement of variance analysis for in vitro study.Paired sample t test was used to compare the DSBs level between baseline Group and radiation Group for in vivo study.The relationship between radiation dose and the increase in y-H2AX focus was analyzed using Pearson correlation analysis.Results:In the in vitro study,the DSBs levels in Group B,Group C and Group D were 49.4%,96.6%and 149.4%higher than those in Group A,respectively(all P<0.001).And the radiation dose subgroups had linear trend with the DSBs levels(P<0.001).In the in vivo study,the y-H2AX level before and after CT examination was 0.62±0.35 foci/cell and 0.89±0.42 foci/cell,respectively.The DSBs level in radiation Group was significantly higher(P<0.001)and 43.5%higher than baseline Group.However,the increased DSBs levels after CT examination was not correlated with DLP or CTDIvol.Conclusions:The DSBs level in peripheral blood lymphocytes is significantly increased after abdominal CT enhancement.And studies in vitro have shown that CT radiation dose has linear trand withis significantly related to intracellular DSBs levels.Part ? The Effect of Oral Vitamin C on DNA Double-strand Breaks(DSBs)after Abdominal Contrast-enhanced CTPurpose:To investigate the protective effect of oral Vitamin C on DNA double-strand breaks(DSBs)after abdominal contrast-enhanced CT.Materials and methods:Sixty patients undergoing abdominal multiphase contrast-enhanced CT were divided into control group(n=30)and prevention group(n=30).The control group did not receive any drugs,while the patients in the prevention group got oral 1g Vitamin C 30-120 min before the CT examination who were subdivided into different groups(30 min,n=16;60 min,n=10;120 min,n=4).Two ml blood samples were obtained immediately before and 5 min after CT examination for each subject.Lymphocytes were isolated from all blood samples and performed immunofluorescent staining.The y-H2AX foci representing DSBs in the nucleus were marked by fluorescence.Volume CT dose index(CTDIvol),dose length product(DLP)and y-H2AX foci/cell were compared with t test and u test.The difference in the increase of y-H2AX foci/cell among different time points of oral Vitamin C was compared with ANOVA test.The relationship between radiation dose and the increase in ?-H2AX foci was analyzed with Pearson correlation and Spearman correlation analysis.Results:There was no significant difference for CTDIvol and DLP between the two groups(both P>0.05).The mean increase of y-H2AX was 0.49 foci/cell in the control group and 0.19 foci/cell in the prevention group(P<0.001),with the 61%reduction for y-H2AX increase in the control group.In the prevention group,the increase of y-H2AX foci/cell was significantly correlated with DLP and CTDIvol(r = 0.449 and 0.403,respectively;both P<0.05).No difference was found for increase of y-H2AX foci/cell after CT examination among three oral Vitamin C groups(all P>0.05).Conclusion:Oral Vitamin C can significantly reduce the level of DSBs after abdominal contrast-enhanced CT examination and provide an effective method to decrease DNA damage.