| BackgroundWith the rapid development of electric power industry,public concerns have been raised about the environmental exposure to extremely low frequency magnetic fields(ELF-MF)and its potential health effects,which are mainly emitted from power lines,and house hold applications.Epidemiological studies have suggested that ELF-MF exposure is associated with increased risk of cancers(e.g.brain tumor),neurodegenerative diseases(e.g.,Alzheimer's disease and amyotrophic lateral sclerosis),infertility,and adverse pregnancy outcomes(e.g.,low birth weight,and congenital malformations).Generally,the epidemiological reports are inconsistent despite of studies for many years.Based on the limited epidemiological evidence,the International Agency for Research on Cancer(IARC)has concluded that ELF-MF is a possibly carcinogen to humans(Group 2B)in 2002.However,laboratory studies have not clarified the carcinogenic or genotoxic effect of ELF-MF exposure.Thus,the mechanisms of ELF-MF exposure induced biological effects remain to be elucidated.MethodsTo systematically investigate the biological effects and possible mechanisms of ELF-MF,our group has evaluated the genotoxic effects of ELF-MF exposure on cell viability in different cell lines and indentified the human choriocarcinoma JAR and JEG-3 cells as ELF-MF sensitive cells.In the present study,we used JAR cells as main research cell model,and examined the effects of 50 Hz MF exposure at 3.0 mT on JAR cell viability using CCK-8 assay.Next,we investigated the co-exposure to 3.0 mT,50 Hz MF and known carcinogen cadmium on cell viability using CCK-8 assay in JAR cells.These experimental evaluations were also conducted in JEG-3 cells,and the differential responses of JAR and JEG-3 cells to MF exposure with or without co-exposure to cadmium were also compared.To further explore the mechanisms of 50 Hz MF influenced cell viability,we also applied proteomic approaches and examined the effects of 50 Hz MF exposure with or without co-exposure to cadmium on proteome profiling in JAR cells.ResultsPart 1:The effects of 50 Hz MF on cell viability in JAR cellsIn JAR cells,the results showed that,comparing to sham exposure group,the cell viability was significantly increased in 3.0 mT of 50 Hz MF exposure group for 6 hours(p<0.05),24 hours(p<0.01)and 48 hours(p<0.01).In JEG-3 cells,we found that,comparing to the sham exposure group,the cell viability was significantly increased in 3.0 mT of 50 Hz MF exposure group for 6 hours(p<0.05)and 24 hours(p<0.01),but the cell viability significantly decreased in 48 hours(p<0.05)exposure group.Part 2:The effects of co-exposure to 50 Hz MF and cadmium on cell viability in JAR cellsFirstly,we investigated the effects of co-exposure to low dose cadmium and chromium on cell viability in JAR cells.Results showed that,comparing to the control group,cell viability was significantly decreased in co-exposure to 0.25?M cadmium and 0.50 ?M chromium group for 6 hours,24 hours or 48 hours(p<0.01).Next,we investigated the effects of 50 Hz MF and low dose cadmium combine exposure on cell viability in JAR cells.Results showed that,comparing to the 0.25 ?M cadmium exposure group,cell viability was significantly increseaed in the co-exposure to 50 Hz MF and cadmium group for 6 hour or 24 hour(p<0.01),but not for 1 hour or 48 hour.Similarly,we found that,in JEG-3 cells,comparing to the 0.25 ?M cadmium exposure group,cell viability was significantly increseaed in the co-exposure to 50 Hz MF and 0.25 ?M cadmium group for 1 hour,6 hour or 24 hour(p<0.01),but not for 48 hours.Part 3:The effects of co-exposure to 50 Hz MF and cadmium on proteome profiling in JAR cellsTo establish the protein expression response to environmental stimuli in JAR cells,we firstly used p53 as a responsive protein,and evaluated the effects of 3.0 mT of 50 Hz MF exposure and/or 2.5?M cadmium on p53 expression.As expected,cadmium exposure up-regulated p53 expression,while 50 Hz MF exposure did not affect the p53 expression.Interestingly,comparing to the cadmium exposure group,p53 expression level was decreased in the co-exposure to 50 Hz MF and cadmium group.Next we used Tandom Mass Tag quantitative proteomic technology to investigatethe JAR cells proteome profiling changes after exposure to 3.0 mT of 50 Hz MF and/or 0.25 ?M cadmium for 6 hours.The results showed that,comparing to the sham exposure group,MF exposure resulted in 16 differentially expressed proteins,including 13 proteins up regulated and 3 proteins down regulated,which were related to signal transduction,protein translation and cytoskeleton associated pathways.Exposure to cadmium resulted in 111 differentially expressed proteins,including 60 proteins up regulated and 51 proteins down regulated,which were mainly related to cytoskeleton associated,signal transduction and stress related pathways.Co-exposure to 50 Hz MF and cadmium resulted in 162 differentially expressed proteins,including 78 proteins up regulated and 84 proteins down regulated,which were related to signal transduction,protein translation and stress related pathways.Interestingly,comparing to cadmium exposure,co-exposure to MF and cadmium resulted in 163 differentially expressed proteins,including 72 proteins up regulated and 91 proteins down regulated,which were related to signal transduction,protein translation and cytoskeleton associated pathways.ConclusionIn conclusions,this study demonstrated that,under current exposure conditions 1)MF exposure enhanced cell viability in time dependent way;2)MF exposure could attenuate cadmium inhibited cell viability in JAR cells;3)exposure to MF or cadmium,or co-exposure to MF and cadmium changed protein expression profile,and the differentially expressed proteins were enriched for signal transduction,protein translation and stress related pathways.Our data suggest that MF exposure enhanced cell viability and attenuated cadmium inhibited cell viability may be through changes of proteome profiling,while the role of differentially expressed proteins responding to MF awaits further investigations. |
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