Study On The Changes Of Human Lymphocyte Mitochondrial Gene Expression Induced By Irradiation

Background and Objective:A number of studies indicated that irradiation can induce mtDNA mutation and changes in mtDNA copy number,which can contribute to the changes of mitochondrial genes expression.However,the relationship between irradiation and mitochondrial genes expression has rarely been studied,and the results of investigations are varied.For these reasons,we explore the alterations in expression level of human lymphoblastoid cell mitochondrial genes and the activities of respiratory chain complexesâ…£induced by ⁶⁰Coγ-rays.Methods:1.Human lymphoblastoid cell lines were irradiated with ⁶⁰Coγ-rays at dose rate of 1Gy/min.The cells were cultured 8h after irradiation of 1～10Gy absorbed dose in order to detect the dose-effect relationship between the dose and expression changes of 13 mitochondrial genes,which encoded peptides.While the expression changes of these genes were analyzed at different post-irradiation time-points between 0.5 and 72h after irradiation of 5Gy in order to explore the time-effect relationship.2.Changes in mitochondrial genes mRNA level were detected by Real-time PCR after the PCR parameters were qualified by RT-PCR.3.Changes in mitochondrial genes COXâ… ,COXâ…¡and COXâ…¢protein expression level were determined by flow cytometry(FCM).4.Spectrophotometric analysis was applied to detect the COX activities.Results:1.The expression level of 13 mitonchondrial genes mRNAs in human lymphocytes were generally up-regulated after 1～10Gy irradiation,and the expression peak of most genes were at 3 or 8Gy exposure.The expression changes of COXâ… , COXâ…¢and ND3 genes showed the dose-effect relationship after 1-3 Gy ⁶⁰Coγ-rays exposure;COXâ…¡,ND2,ND5,Cyt b and ATPase8 gene expression changes showed the dose-effect relationship after 1-8 Gy exposure.Meanwhile the expression levels of mitochondrial genes mRNAs were elevated most significantly by 4h after 5Gy radiation except COXâ… .2.Expression changes of COXâ… and COXâ…¡protein were increased significantly after 3-5Gy exposure,while alterations in COXâ… and COXâ…¡protein expression were elevated significantly 4-8h after 5Gy irradiation.In addition,COXâ…¢protein expression levels were down-regulated generally.3.Activity of COX was found to be decreased significantly after exposure to 3-10Gy.It decreased significantly at 4-72h after exposure to 5Gy irradiation.Conclusions:1.Ionizing radiation might induce significant changes in mitochondrial gene expression.2.The expression levels of human lymphoblastoid cell mitochondrial genes mRNAs are generally up-regulated following ⁶⁰Coγ-rays irradiation and the expression changes of COXâ…¢and ND3 genes show the excellent dose-effect relationship after 1-3 Gy ⁶⁰Coγ-rays exposure.The expression peak changes of the 13 mitochondrial genes are at 4 h after irradiation.3.The expression levels of COXâ… and COXâ…¡protein are increased comprehensively,while COXâ…¢protein expression level is decreased generally after ⁶⁰Coγ-rays exposure.4.Activity of COX was decreased generally after ⁶⁰Coγ-rays exposure.