The DNA Damage And Its Repair In Full-Term Neonatal Hyperbilirubinemia After Phototherapy

Background: Neonatal hyperbilirubinemia is a common neonatal disease.Phototherapy can effectively reduce serum unconjugated bilirubin,and has a positive preventive effect on the occurrence of severe hyperbilirubinemia and acute bilirubin encephalopathy.At the same time,it can reduce the frequency of exchange transfusion therapy,and it is a common method of treatment for neonatal hyperbilirubinemia.Phototherapy has long been considered safe and effective,but studies at domestic and foreign have shown that phototherapy can cause DNA damage in newborns,but its effect is still uncertain.Objective: To observe the DNA damage and short-term repair of peripheral blood lymphocytes before and after phototherapy in term neonates with hyperbilirubinemia,and to understand the photoperiodinduced neonatal hyperbilirubinemia lymphocyte DNA Short-term effects of damage.Methods:Twenty-three full-term neonates diagnosed with hyperbilirubinemia with unconjugated bilirubin were selected and treated with light therapy according to the bilirubin hours line chart in the United States Intervention Guidelines for Neonatal Jaundice in 2004.The peripheral blood samples were collected before phototherapy,24 hours after cumulative phototherapy,48 hours after stopping phototherapy,and 1 month after stopping phototherapy.The lymphocytes were isolated by centrifugation and DNA damage in peripheral blood lymphocytes was measured using a neutral comet assay.The comet cells were observed by fluorescence microscopy and photographed.The CASP analysis software was used to measure the tail DNA % and tail distance of the comet cells.In this study,we understood the DNA damage of the peripheral blood lymphocytes before and after phototherapy and their repair status by comparing the tail DNA % and the tail distance before and after phototherapy.Results:Based on total bilirubin values at admission,23 patients who received phototherapy were divided into the common hyperbilirubinemia group(total bilirubin <342?mol/L,n=16)and severe hyperbilirubinemia group(total bilirubin ? 342?mol /L,n=7),There was no statistically significant difference in the tail DNA % and tail distance(18.6 ± 3.6,11.7 ± 4.5,respectively)between the common hyperbilirubinemia group and the severe hyperbilirubinemia group(15.9 ± 3.2,10.1 ± 3.3,respectively)(P>0.05).Compared with pre-phototherapy,24 hours after cumulative phototherapy of tail DNA%(41.3±4.2 vs 17.5±3.5,n=23,P<0.001)and tail distance(67.7±9.5 vs 11.2±4.2,n=23,P<0.001)are increased significantly,and the difference was statistically significant.After stopping phototherapy for 48 hours(DNA tail% and tail distance were 30.3±5.5,40.6±10.2,n=21,respectively),DNA damage in peripheral blood lymphocytes decreased compared with phototherapy for 24 hours,but still increased compared with that before phototherapy.All have significant statistical significance(P<0.001).Conclusion: Phototherapy can lead to DNA damage of peripheral blood lymphocytes in term newborns with hyperbilirubinemia.DNA damage is repaired with time.However,short-term DNA damage is still obvious and repair is not complete.