Study On IL-2,IL-2R Gene Expression Level And IL-2R Gene Polymorphism In Yangjiang High Background Radiation Area

Background:With the wide application of Ionizing radiation,especially low-dose ionizing radiation in our daily life,its immune effects on health have become the research concern in recent years.The Yangjiang area,which locates in Guangdong,China,is one of the several natural high background radiation areas in the world,and the average exposure dose is about 6.4 m Sv/a,which is equivalent to the exposure level of occupational population.The epidemiological results of the health effects with chronic low-dose radiation exposure in this area have contributed evidence on the health effects research of low dose radiation exposure.Previous studies suggested there was a trend of immune enhancement and the expression level of Th1 cytokines increasing in this area with high natural radiation exposure.IL-2 is one of the Th1 cytokines with an important immune function.Our previous results found that the peripheral blood serum level of IL-2 in the HBRA population was slightly higher than that of the CA population,but the difference was not statistically significant.Also,the literature showed that there was no population-based epidemic-biological studies on the association of IL-2 and IL-2R gene expression levels and gene polymorphisms with chronic low dose ionizing radiation exposure.We sought to explore the association of serum level of IL-2,the gene expression level of IL-2R,and the polymorphism of IL-2R genes in the residents in the Yangjiang areas with chronic low dose radiation exposure.Methods:1.Study PopulationWe selected the eligible subjects from Tangkou town(HBRA)of Yangjiang Yangxi county and Hengpo town(CA)of Enping City based on the inclusion and exclusion criteria.2.QuestionnaireQuestionnaire survey was conducted for all subjects.The contents of the survey included general information(age,gender,nationality,etc.),health status,medical behavior,living habits,food and nutrition status,stress life events and other related information.3.Individual dose assessmentThermo luminescent dosimeter(TLD)was used to monitor the cumulative individual external exposure dose for 3 consecutive months.Fg-427A1 TLD reader was used to analyze and read out the specific value,and the annual external exposure dose = 90 days of external exposure dose(quarterly individual external exposure dose)× 4 was calculated.The annual radiation dose is based on the previous research results,annual effective dose = annual external radiation dose + annual radiation dose.4.Experimental methodsThe peripheral blood was collected,and the m RNA levels of IL-2 and IL-2R subunits in peripheral blood leukocytes was measured by RealTime quantitative Polymerase Chain Reaction(RT-q PCR),and compared the expression differences of the above genes in the two groups of residents.DNA was extracted from these blood samples of the two groups.The single nucleotide polymorphisms(SNPs)in the promoter region of IL-2RA,IL-2RB and IL-2RG were detected by sequenom massarray method,and the expression differences of SNPs in the two groups were compared.4.Data ProcessingSPSS 20.0 was used for data statistical analysis,and Excel was used for chart processing.Counting variables: chi-square test,corrected chi-square test,and exact probability method were performed.Measurement data: First,the normality test(Shapiro-Wilk test,K-W test)was performed.If the two groups of data were all subject to normal distribution,or the data could be transformed into normal distribution by taking logarithm,the results were expressed as mean ± standard deviation((?)±s),and the independent sample t test was used to analyze and compare the differences among the groups;If the group of data still does not obey normal distribution after logarithmic transformation,U test(Mann-Whitney U)in non-parametric test should be used for comparative analysis.Spearman rank correlation was used for correlation analysis.The test level was α = 0.05.Results:1.According to the inclusion and exclusion criteria,48 and 51 healthy men aged 45-65 years were selected from Tangkou Town of Yangxi County(HBRA)and Hengpo Town of Enping City,respectively.There was no significant difference in age distribution between the two groups(P > 0.05).The possible confounding factors of the residents in the two areas were analyzed,and the results showed that the residents in the two areas were basically consistent in general conditions,dietary preferences,smoking and alcohol,health status,residential travel history and stress events,which indicated that the two groups of residents were comparable.2.The individual external radiation doses to residents in HBRA and CA were(0.92 ± 0.21)m Sv and(0.32 ± 0.09)m Sv,respectively.The annual effective doses to residents in HBRA were 6.95 m Sv/a and 2.32 m Sv/a,respectively.The annual average effective dose to HBRA residents was about 3 times as much as that to CA residents.3.The relative expression(ΔCt)of interleukin-2 receptor gamma chain(IL-2RG)m RNA in peripheral blood leukocytes of residents in HBRA was significantly higher than that in residents in CA(P < 0.05);There was no significant difference in the relative expression of IL-2m RNA(ΔCt),IL-2RA and IL-2RB between the two regions(P > 0.05).4.The distribution of rs76206423(A/G)genotype on IL-2RB was significantly different between HBRA and CA residents(P < 0.05).The genotype of HBRA was mainly homozygous wild-type AA,while that of CA was mainly heterozygous AG.The distribution of alleles and genotypes of other loci were similar between the two regions(P > 0.05).Compared with the five individual species/population published by Hap Map(https://www.ncbi.nlm.nih.gov/snp/),the distribution frequency of allele G of rs76206423 mutation in HBRA residents was higher than that in African,European,south Asian and American populations,which had a statistically significant difference(P <0.05)from these groups,while the difference was meaningless with that in CA and east Asian populations(P >0.05).Therefore,the HBRA population may have a higher degree of variation at this locus.Comparing the MAF distribution of rs7072793(T>C)in the HBRA population with that in Hap Map,it was found that the MAF distribution was consistent with that in East Asia,South Asia and the Americas(P >0.05),with genetic conservation,and was statistically significant with that in Africa and Europe(P <0.05).In African and European populations,wild-type T was dominant,while variant allele C was dominant in HBRA.At this locus,the degree of variation of HBRA Han men was higher,and the proportion of variant allele C was significantly higher than that of European and American people.The distribution of rs3118470(T>C)in HBRA was consistent with that in East Asia and South Asia for the difference was statistically significant with that in Africa,Europe and America(P <0.05).At this locus,the majority of HBRA and Hap Map population were wild type T,but compared with African,European and American population,HBRA population had higher genetic variability,and the proportion of variant allele C was significantly higher than that of European and American population.Conclusion:1.The expression levels of IL-2,IL-2RA and IL-2RB in HBRA residents are similar to those in CA residents,which might be the performance of maintaining the stability of internal environment;the expression level of IL-2RG gene is higher than that of the control area,which is expected to be a marker of adaptive response to low-dose ionizing radiation.2.The frequencies of rs7072793,rs3118470 and rs76206423 alleles in the promoter region of IL-2R gene in HBRA population are higher than those in most other races/populations,suggesting a higher genetic variability in HBRA population.3.It is speculated that HBRA population may have an immune adaptability under long-term natural high background radiation.