热应激蛋白70与小剂量电离辐射、工频电磁场暴露人群应激适应关联研究
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摘要
随着我国核能事业不断发展,医疗部门X射线诊断治疗、放射性核素诊断治疗广泛应用,电网建设的不断加快,小剂量电离辐射和输变电工程工频电磁场健康危害成为社会关注焦点。目前关于这两种危害的健康效应研究主要集中在细胞和动物实验上,仅有的人群研究尚无明确结论。因此有必要对该领域进行进一步人群流行病学研究。
我国阳江天然放射性高本底地区(high background radiation area,HBRA)是研究小剂量电离辐射健康效应的理想场所,当地居民年有效剂量与现有作业场所的职业照射年有效剂量具有可比性,我国从1972年开始,利用该人群研究小剂量电离辐射与癌症之间的关系,相关的研究结果已发表在国内外杂志。
工频电磁场存在潜在危害,国外流行病学调查显示,工频电磁场可增加白血病、淋巴瘤及乳腺癌的发生率。国内流行病学调查表明长期电磁场暴露与多种非特异性症状有关,其中包括神经衰弱症候群、植物神经功能失调、外周血象、眼晶状体和非特异性免疫功能的轻微改变。
热应激蛋白70(HSP70)是一组高度保守、具有重要生理功能的蛋白质分子,定位于1,5,6,9,11,14号染色体上,可以被高温、氧化应激、重金属、缺血-再灌注、炎症、感染等诱导产生。在各种应激及应激适应状态下,HSP70与其所调节的多种功能蛋白质及其所参与的细胞分子修复机制构成了一种多系统多层次协调的应激损伤修复体系,为应激适应机制的建立提供了可能性和生物学基础。
但目前并无小剂量电离辐射、工频电磁场与HSP70表达的人群流行病学研究。
目的：通过人群流行病学研究初步探讨HSP70与小剂量电离辐射、工频电磁场暴露人群应激适应关联,为研究小剂量电离辐射和工频电磁场暴露人群的健康影响,寻找可实际应用早期效应标记物,为进行早期预防提供基础资料。
方法：
1研究对象采用横断面调查方法,分别选择阳江高本底地区53名50～59岁男性居民作为暴露人群及恩平市横陂镇相匹配的53名男性居民作为对照人群；广东省内500kV263名变电站巡检人员作为暴露人群及抽取252名各变电站行政管理人员作为对照人群。
2问卷调查包括年龄、性别、民族、文化程度和经济状况等一般情况；饮食营养、吸烟及饮酒情况、疾病史、健康状况、医疗照射史、居住史、职业史和生活中发生的重要事件(包括躯体性应激事件如半年内有如手术、烧伤、失血等事件和心理性应激事件如半年内有如亲人去世、离婚、破产等造成心灵创伤的事件)等相关情况。
3实验方法外周血HSP70mRNA的测定：抽取人群外周血5ml,3000r/min离心(离心半径为12.4cm)10min,收集白细胞层,按Trizol试剂盒提取细胞总RNA,M-MLV逆转录试剂盒(美国Promega公司)合成cDNA。PCR引物于琼脂糖凝胶电泳(含0.5μg/ml的溴化乙锭),凝胶成像系统(Vilber Louramt,France)拍照并分析光密度,PCR产物以(积分光密度×面积)表示,β-actin作内对照。
痰样HSP70蛋白的测定：收集3d深部晨痰,加固定液解黏,加蛋白裂解液,13000r/min,4℃离心(离心半径8cm)30min,转移上清至经Bradford法蛋白定量,采用化学发光ECL显色法进行Western blot分析,胶片洗涤干燥后,扫描分析。
外周血HSP70蛋白的测定：抽取外周血5ml,注入装有含有抗凝剂EDTA-Na2负压管,3000r／m离心15min,收集血清,用HSP70 ELISA试剂盒进行测定,于波长450nm的酶标仪上读取OD值,标准品OD值作为对照。
4统计分析用epidata3.02录入数据库,应用SPSS13.0软件进行t检验、χ2检验、协方差分析、Spearman、Dunnet等统计学分析,显著性检验水准取双侧a=0.05。
结果：
1小剂量电离辐射人群
1.1均衡性比较
对照地区和高本底地区调查对象平均年龄分别为(54.3±3.8)岁和(53.4±3.4)岁,经t检验分析两地区调查对象平均年龄无显著性差异(t=1.187,P=0.585)；经,检验分析两组年龄构成比无显著性差异(χ2=2.034,P=0.154)。采用t检验分析两地居民各连续变量影响因素间差异,用χ2检验分析两地居民各计数变量影响因素间差异,对医疗照射、吸烟、喝酒、饮茶、躯体性或心理性应激事件等进行分析,除饮茶有显著性差异外(P<0.05),其余均无显著性差异(P>0.05)。
1.2个体有效剂量比较
对照地区和高本底地区分别发放热释光剂量计各53件,其中对照地区回收40件,回收率为75.5%,高本底地区回收45件,回收率为84.9%。对照地区和高本底地区人群的外照射剂量范围分别为0.72-1.96mSv.a-1,和2.20-4.84mSv.a-1,平均外照射有效剂量分别为1.224mSv.a-1,经方差分析两组间平均外照射剂量有显著性差异(F=274.573,P<0.0001),高本底地区平均外照射剂量是对照地区的2.85倍。
1.3 HSP70mRNA水平、HSP70蛋白水平表达比较
经t检验高本底地区与对照地区居民外周血HSP70mRNA水平无显著性差异(t=0.373,P=0.771),考虑饮茶因素影响,经协方差分析两地区居民外周血HSP70mRNA水平无显著性差异(F=0.465,P=0.498)。经Spearman相关性分析,个人剂量与外周血HSP70mRNA表达不存在负相关关系。
经t检验高本底地区与对照地区居民痰样HSP70蛋白水平无显著性差异(t=1.010,P=0.339),考虑饮茶因素影响,采用协方差分析两地区居民痰样HSP70蛋白水平无显著性差异(F=0.231,P=0.678)。经spearman相关性分析,尚不能认为工龄与痰样HSP70蛋白水平存在正相关关系。
2工频电磁场暴露人群
2.1均衡性比较
本研究分别选取暴露组263人,平均年龄(31.95±6.62)岁,其中男性242人,女性21人；对照组252人,平均年龄(30.88±6.10)岁,其中男性231人,女性21人,经t检验两地区调查对象平均年龄无显著性差异(t=-1.902,P=0.580)；经χ2检验两组年龄构成比无显著性差异(χ2=1.461,P=0.833),两组性别构成比无显著性差异(χ2=0.021,P=0.885)。用t检验分析两地居民各连续变量影响因素间差异,用χ2检验分析两地居民各计数变量影响因素间差异,对医疗照射、吸烟、喝酒、饮茶、膳食摄入、躯体性或心理性应激事件等进行分析,除饮酒、饮茶有显著性差异外(P<0.05),其余均无显著性差异(P>0.05)。
2.2工频电磁场暴露强度检测
500kV变电站工人主要巡检工作场所工频电场强度为0.0009～14.0000kV／m,工频磁场强度为0.62-32.02μT。行政后勤人员办公室的工频电场强度为0.0066～0.1490 kV／m,工频磁场强度为0.03-0.33μT。
2.3 HSP70蛋白表达比较
经t检验变电站巡检工人与对照人群外周血HSP70蛋白表达水平无显著性差异(t=-1.079,P=0.281),考虑混杂因素的影响,采用协方差分析无显著性差异(F=0.624,P=0.430)。按500kV工龄时间进行分组,分为五组,即0年、<5年、5～10年、10～15年、≥15年,分析在不同工龄时间等级的变化趋势,经方差分析五组间HSP70蛋白表达水平无显著性差异(F=0.834,P=0.504),采用ANOVA的Dunnet方法进行组间差异检验,显示各组间比较无显著性差异(P>0.05)。经spearman相关性分析,工龄与外周血HSP70蛋白水平不存在正相关关系。
结论：
1本研究中,对照地区和高本底地区人群的外照射剂量范围分别为0.72～1.96 mSv.a-1和2.20～4.84 mSv.a-1,平均外照射有效剂量分别为1.224mSv.a-1, 3.480mSv.a-1,高本底地区平均外照射剂量是对照地区的2.85倍。阳江高本底地区居民外周血HSP70mRNA、痰样HSP70蛋白表达水平与对照地区相比无显著性差异。
2广东省500kV变电站工人主要巡检工作场所工频电场强度为0.0009-14.0000kV／m,工频磁场强度为0.62-32.02μT,行政后勤人员办公室的工频电场强度为0.0066～0.1490 kV／m,工频磁场强度为0.03-0.33μT。500kV变电站巡检工人外周血HSP70蛋白表达水平与对照组相比无显著性差异。
3从本次研究结果来看,长期接触小剂量电离辐射、工频电磁场没有引起HSP70水平表达的增加,可能与机体在应激源的反复作用下逐步建立的对抗应激适应的一系列复杂生理反应,从而导致机体内环境的相对稳定,提高了机体对外界不良因素的抵抗能力有关。同时,HSP70无特异性,可以受多种因素影响,遗传因素方面,人群中HSP70存在基因多态性,个体HSP70表达水平存在差异；环境因素方面,许多混杂因素如饮食、生活习惯等都可对HSP70表达产生影响,因此HSP70与小剂量电离辐射、工频电磁场暴露人群应激适应确切关系以及可否作为早期生物标志物还有待进一步的研究。
本研究初步探讨了HSP70在小剂量电离辐射、工频电磁场暴露人群应激适应中的变化及相关的生物学效应。应激适应过程中生物功能方面的改变及作用机制仍需深入研究,如进一步运用最新研究方法从基因和蛋白质水平,全面而深入的阐明小剂量电离辐射、工频电磁场应激适应可能的生物学效应及分子机制,从而为其防护或干预提供科学依据。
With the widely application of radiation source and rapidly developing of the electric power in our country, it has created a great deal public concern about health impact induced by low dose radiation and low frequency of electromagnetic fields. Many articles investigated the cumulative effect of exposures to low dose radiation and low frequency of electromagnetic fields in vitro and/or in vivo. A series of epidemiological studies showed controversial results.
Since 1972, epidemiological studies at high background radiation area (HBRA) have been carried on. The conclusion about the relation between low dose radiation and cancer has been published at several articles. And a number of researchers have found increased risk of cancer among children who live close to power lines or among men whose jobs expose them to unusually high levels of EMFs.
HSP70 are highly conserved molecular chaperones with physiological function which located in chromosome 1,5,6,9,11,14. They can be induced by heat stress, oxidative stress, ischemia-reperfusion, inflammation, and infected. HSP70 and the other proteins can built a stress-damage repair system by stress state.
Objective:The present study aims to estimate the associations between the expression levels of heat shock protein 70(HSP70)and stress adaption on the exposed population from chronic low dose radiation and power frequency of electromagnetic fields. To find HSP70 whether is considered as the susceptible biomarker. The expression levels of the HSP70 in the peripheral blood and/or sputum of residents are determined in the exposed population.
Methods:
Fifty-three residents is the range from 50 to 59 years old in the HBRA and the CA were selected as exposed and control group, respectively. The levels on both mRNA and protein of the HSP70 in sera or sputum were determined by RT-PCT or Western blotting assay, respectively. Another study was conducted in the exposed population from 500kV electric substation and the nonexposed population from the executive staff. The number of the exposed population is 263 while the number of the nonexposed population is 252 as a control group.The age of both populations is in the range from 20 to 50 years old. The concentrations of the HSP70 in sera were determined by the ELISA assay.
The contents of the questionnaire including general conditions, physical stress and psychological stress, for example age, education, income, medical exposure, dietary intake, smoke, drink.
HSP70mRNA was detected with RT-PCR. The levels of HSP70 protein were detecte with western blot and ELISA, respectively.
Statistical analysis was performed by SPSS13.0. A statistical level of P<0.05 was considered significant.
Results:
1 low dose radiation exposure population
1.1 The average age of RA and HBRA is 54.3±3.8 and 53.4±3.4 respectively, the difference was not statistically significant (t=1.187,P=0.585) by t test. The difference of age percentage distribution was not statistically significant (χ2=2.034,P=0.154)byχ2 test. The difference of medical exposure, smoking, drinking, tea, mental stress and physical stress was not statistically significant(P>0.05),except for tea (P<0.05).
1.2 The range of external radiation exposure on RA and HBRA population was 0.72-1.96mSv.a-1 and 2.20-4.84mSv.a-1 respectively, the average of effective dose from eternal exposure is 1.224mSv.a-1 and 3.480mSv.a-1,the difference was statistically significant (F=274.573,P=0.000) by analysis of variance.
1.3 There was no statistically significant in concentrations of both HSP70 mRNA and HSP70 protein in the HBRA and RA by t test and covariance analysis.
2 power frequency eletromagnetic field exposure population
2.1 The average age of control group and exposurers is 30.88±6.102 and 31.95±6.62 respectively, the difference was not statistically significant (t=-1.902, P=0.580) by t test. The difference of age percentage distribution was not statistically significant (χ2=1.461,P=0.833)byχ2 test.The difference of sex percentage distribution was not statistically significant (χ2=0.021,P=0.885) by chi-square test. The difference of medical exposure, smoking, mental stress and physical stress was not statistically significant(P>0.05),except for tea and drinking(P<0.05).
2.2 The intensity of electric field at workplace on control area and 500kV electric substation was 0.0066～0.1490 kV/m and 0.0009-14.0000kV/m respectively, the intensity of magnetic field is 0.03-0.33μT and 0.62-32.02μT.
2.3 There was no statistically significant in concentrations of HSP70 protein by t test and covariance analysis.
Conclusion:
The results of the present study showed there was no significantly difference in the concentration of both the HSP70 mRNA and the HSP70 protein between the HBRA and the CA. The previous studies showed that there was no induction of HSP70 for low dose radiation for radiation could be one of the incentives. Some studies showed that the HSP70 was induced by the radiation in myeloid leukemia cell line. The result was opposite with epidemiology research, which indicated the health impact systems was complicated.
In the other research about power frequency eletromagnetic fields, we also found no statistically significance of HSP70 expression on 500kV electric substation exposed workers and the control people. It was accord to christopher A's study that there was no induction of HSP70 by 6.3μELF EMFs in HL60 cells. There were many negative reports about ELF EMFs research.We suggested it was attributed by different experimental condition, and little epidemiology research support.
The expression of HSP70 could be affected by confounding factors. Our research indicated that chronic exposured to low dose radiation or power frequency electromagnetic fields could not lead to induction of HSP70 expression. HSP70 expression could be associated with HSP70 gene polymorphism and confounding factors. More research should be launched to find the biomakers of low dose radiation or power frequency electromagnetic fields exposurers.
Based on the. potential causes for the conflicting data from the reported suggestions and statements about low dose radiation or power frequency electromagnetic fields, more research should be continued to resolve the controversial data.
我国阳江天然放射性高本底地区(high background radiation area,HBRA)是研究小剂量电离辐射健康效应的理想场所,当地居民年有效剂量与现有作业场所的职业照射年有效剂量具有可比性,我国从1972年开始,利用该人群研究小剂量电离辐射与癌症之间的关系,相关的研究结果已发表在国内外杂志。
工频电磁场存在潜在危害,国外流行病学调查显示,工频电磁场可增加白血病、淋巴瘤及乳腺癌的发生率。国内流行病学调查表明长期电磁场暴露与多种非特异性症状有关,其中包括神经衰弱症候群、植物神经功能失调、外周血象、眼晶状体和非特异性免疫功能的轻微改变。
热应激蛋白70(HSP70)是一组高度保守、具有重要生理功能的蛋白质分子,定位于1,5,6,9,11,14号染色体上,可以被高温、氧化应激、重金属、缺血-再灌注、炎症、感染等诱导产生。在各种应激及应激适应状态下,HSP70与其所调节的多种功能蛋白质及其所参与的细胞分子修复机制构成了一种多系统多层次协调的应激损伤修复体系,为应激适应机制的建立提供了可能性和生物学基础。
但目前并无小剂量电离辐射、工频电磁场与HSP70表达的人群流行病学研究。
目的：通过人群流行病学研究初步探讨HSP70与小剂量电离辐射、工频电磁场暴露人群应激适应关联,为研究小剂量电离辐射和工频电磁场暴露人群的健康影响,寻找可实际应用早期效应标记物,为进行早期预防提供基础资料。
方法：
1研究对象采用横断面调查方法,分别选择阳江高本底地区53名50～59岁男性居民作为暴露人群及恩平市横陂镇相匹配的53名男性居民作为对照人群；广东省内500kV263名变电站巡检人员作为暴露人群及抽取252名各变电站行政管理人员作为对照人群。
2问卷调查包括年龄、性别、民族、文化程度和经济状况等一般情况；饮食营养、吸烟及饮酒情况、疾病史、健康状况、医疗照射史、居住史、职业史和生活中发生的重要事件(包括躯体性应激事件如半年内有如手术、烧伤、失血等事件和心理性应激事件如半年内有如亲人去世、离婚、破产等造成心灵创伤的事件)等相关情况。
3实验方法外周血HSP70mRNA的测定：抽取人群外周血5ml,3000r/min离心(离心半径为12.4cm)10min,收集白细胞层,按Trizol试剂盒提取细胞总RNA,M-MLV逆转录试剂盒(美国Promega公司)合成cDNA。PCR引物于琼脂糖凝胶电泳(含0.5μg/ml的溴化乙锭),凝胶成像系统(Vilber Louramt,France)拍照并分析光密度,PCR产物以(积分光密度×面积)表示,β-actin作内对照。
痰样HSP70蛋白的测定：收集3d深部晨痰,加固定液解黏,加蛋白裂解液,13000r/min,4℃离心(离心半径8cm)30min,转移上清至经Bradford法蛋白定量,采用化学发光ECL显色法进行Western blot分析,胶片洗涤干燥后,扫描分析。
外周血HSP70蛋白的测定：抽取外周血5ml,注入装有含有抗凝剂EDTA-Na2负压管,3000r／m离心15min,收集血清,用HSP70 ELISA试剂盒进行测定,于波长450nm的酶标仪上读取OD值,标准品OD值作为对照。
4统计分析用epidata3.02录入数据库,应用SPSS13.0软件进行t检验、χ2检验、协方差分析、Spearman、Dunnet等统计学分析,显著性检验水准取双侧a=0.05。
结果：
1小剂量电离辐射人群
1.1均衡性比较
对照地区和高本底地区调查对象平均年龄分别为(54.3±3.8)岁和(53.4±3.4)岁,经t检验分析两地区调查对象平均年龄无显著性差异(t=1.187,P=0.585)；经,检验分析两组年龄构成比无显著性差异(χ2=2.034,P=0.154)。采用t检验分析两地居民各连续变量影响因素间差异,用χ2检验分析两地居民各计数变量影响因素间差异,对医疗照射、吸烟、喝酒、饮茶、躯体性或心理性应激事件等进行分析,除饮茶有显著性差异外(P<0.05),其余均无显著性差异(P>0.05)。
1.2个体有效剂量比较
对照地区和高本底地区分别发放热释光剂量计各53件,其中对照地区回收40件,回收率为75.5%,高本底地区回收45件,回收率为84.9%。对照地区和高本底地区人群的外照射剂量范围分别为0.72-1.96mSv.a-1,和2.20-4.84mSv.a-1,平均外照射有效剂量分别为1.224mSv.a-1,经方差分析两组间平均外照射剂量有显著性差异(F=274.573,P<0.0001),高本底地区平均外照射剂量是对照地区的2.85倍。
1.3 HSP70mRNA水平、HSP70蛋白水平表达比较
经t检验高本底地区与对照地区居民外周血HSP70mRNA水平无显著性差异(t=0.373,P=0.771),考虑饮茶因素影响,经协方差分析两地区居民外周血HSP70mRNA水平无显著性差异(F=0.465,P=0.498)。经Spearman相关性分析,个人剂量与外周血HSP70mRNA表达不存在负相关关系。
经t检验高本底地区与对照地区居民痰样HSP70蛋白水平无显著性差异(t=1.010,P=0.339),考虑饮茶因素影响,采用协方差分析两地区居民痰样HSP70蛋白水平无显著性差异(F=0.231,P=0.678)。经spearman相关性分析,尚不能认为工龄与痰样HSP70蛋白水平存在正相关关系。
2工频电磁场暴露人群
2.1均衡性比较
本研究分别选取暴露组263人,平均年龄(31.95±6.62)岁,其中男性242人,女性21人；对照组252人,平均年龄(30.88±6.10)岁,其中男性231人,女性21人,经t检验两地区调查对象平均年龄无显著性差异(t=-1.902,P=0.580)；经χ2检验两组年龄构成比无显著性差异(χ2=1.461,P=0.833),两组性别构成比无显著性差异(χ2=0.021,P=0.885)。用t检验分析两地居民各连续变量影响因素间差异,用χ2检验分析两地居民各计数变量影响因素间差异,对医疗照射、吸烟、喝酒、饮茶、膳食摄入、躯体性或心理性应激事件等进行分析,除饮酒、饮茶有显著性差异外(P<0.05),其余均无显著性差异(P>0.05)。
2.2工频电磁场暴露强度检测
500kV变电站工人主要巡检工作场所工频电场强度为0.0009～14.0000kV／m,工频磁场强度为0.62-32.02μT。行政后勤人员办公室的工频电场强度为0.0066～0.1490 kV／m,工频磁场强度为0.03-0.33μT。
2.3 HSP70蛋白表达比较
经t检验变电站巡检工人与对照人群外周血HSP70蛋白表达水平无显著性差异(t=-1.079,P=0.281),考虑混杂因素的影响,采用协方差分析无显著性差异(F=0.624,P=0.430)。按500kV工龄时间进行分组,分为五组,即0年、<5年、5～10年、10～15年、≥15年,分析在不同工龄时间等级的变化趋势,经方差分析五组间HSP70蛋白表达水平无显著性差异(F=0.834,P=0.504),采用ANOVA的Dunnet方法进行组间差异检验,显示各组间比较无显著性差异(P>0.05)。经spearman相关性分析,工龄与外周血HSP70蛋白水平不存在正相关关系。
结论：
1本研究中,对照地区和高本底地区人群的外照射剂量范围分别为0.72～1.96 mSv.a-1和2.20～4.84 mSv.a-1,平均外照射有效剂量分别为1.224mSv.a-1, 3.480mSv.a-1,高本底地区平均外照射剂量是对照地区的2.85倍。阳江高本底地区居民外周血HSP70mRNA、痰样HSP70蛋白表达水平与对照地区相比无显著性差异。
2广东省500kV变电站工人主要巡检工作场所工频电场强度为0.0009-14.0000kV／m,工频磁场强度为0.62-32.02μT,行政后勤人员办公室的工频电场强度为0.0066～0.1490 kV／m,工频磁场强度为0.03-0.33μT。500kV变电站巡检工人外周血HSP70蛋白表达水平与对照组相比无显著性差异。
3从本次研究结果来看,长期接触小剂量电离辐射、工频电磁场没有引起HSP70水平表达的增加,可能与机体在应激源的反复作用下逐步建立的对抗应激适应的一系列复杂生理反应,从而导致机体内环境的相对稳定,提高了机体对外界不良因素的抵抗能力有关。同时,HSP70无特异性,可以受多种因素影响,遗传因素方面,人群中HSP70存在基因多态性,个体HSP70表达水平存在差异；环境因素方面,许多混杂因素如饮食、生活习惯等都可对HSP70表达产生影响,因此HSP70与小剂量电离辐射、工频电磁场暴露人群应激适应确切关系以及可否作为早期生物标志物还有待进一步的研究。
本研究初步探讨了HSP70在小剂量电离辐射、工频电磁场暴露人群应激适应中的变化及相关的生物学效应。应激适应过程中生物功能方面的改变及作用机制仍需深入研究,如进一步运用最新研究方法从基因和蛋白质水平,全面而深入的阐明小剂量电离辐射、工频电磁场应激适应可能的生物学效应及分子机制,从而为其防护或干预提供科学依据。
With the widely application of radiation source and rapidly developing of the electric power in our country, it has created a great deal public concern about health impact induced by low dose radiation and low frequency of electromagnetic fields. Many articles investigated the cumulative effect of exposures to low dose radiation and low frequency of electromagnetic fields in vitro and/or in vivo. A series of epidemiological studies showed controversial results.
Since 1972, epidemiological studies at high background radiation area (HBRA) have been carried on. The conclusion about the relation between low dose radiation and cancer has been published at several articles. And a number of researchers have found increased risk of cancer among children who live close to power lines or among men whose jobs expose them to unusually high levels of EMFs.
HSP70 are highly conserved molecular chaperones with physiological function which located in chromosome 1,5,6,9,11,14. They can be induced by heat stress, oxidative stress, ischemia-reperfusion, inflammation, and infected. HSP70 and the other proteins can built a stress-damage repair system by stress state.
Objective:The present study aims to estimate the associations between the expression levels of heat shock protein 70(HSP70)and stress adaption on the exposed population from chronic low dose radiation and power frequency of electromagnetic fields. To find HSP70 whether is considered as the susceptible biomarker. The expression levels of the HSP70 in the peripheral blood and/or sputum of residents are determined in the exposed population.
Methods:
Fifty-three residents is the range from 50 to 59 years old in the HBRA and the CA were selected as exposed and control group, respectively. The levels on both mRNA and protein of the HSP70 in sera or sputum were determined by RT-PCT or Western blotting assay, respectively. Another study was conducted in the exposed population from 500kV electric substation and the nonexposed population from the executive staff. The number of the exposed population is 263 while the number of the nonexposed population is 252 as a control group.The age of both populations is in the range from 20 to 50 years old. The concentrations of the HSP70 in sera were determined by the ELISA assay.
The contents of the questionnaire including general conditions, physical stress and psychological stress, for example age, education, income, medical exposure, dietary intake, smoke, drink.
HSP70mRNA was detected with RT-PCR. The levels of HSP70 protein were detecte with western blot and ELISA, respectively.
Statistical analysis was performed by SPSS13.0. A statistical level of P<0.05 was considered significant.
Results:
1 low dose radiation exposure population
1.1 The average age of RA and HBRA is 54.3±3.8 and 53.4±3.4 respectively, the difference was not statistically significant (t=1.187,P=0.585) by t test. The difference of age percentage distribution was not statistically significant (χ2=2.034,P=0.154)byχ2 test. The difference of medical exposure, smoking, drinking, tea, mental stress and physical stress was not statistically significant(P>0.05),except for tea (P<0.05).
1.2 The range of external radiation exposure on RA and HBRA population was 0.72-1.96mSv.a-1 and 2.20-4.84mSv.a-1 respectively, the average of effective dose from eternal exposure is 1.224mSv.a-1 and 3.480mSv.a-1,the difference was statistically significant (F=274.573,P=0.000) by analysis of variance.
1.3 There was no statistically significant in concentrations of both HSP70 mRNA and HSP70 protein in the HBRA and RA by t test and covariance analysis.
2 power frequency eletromagnetic field exposure population
2.1 The average age of control group and exposurers is 30.88±6.102 and 31.95±6.62 respectively, the difference was not statistically significant (t=-1.902, P=0.580) by t test. The difference of age percentage distribution was not statistically significant (χ2=1.461,P=0.833)byχ2 test.The difference of sex percentage distribution was not statistically significant (χ2=0.021,P=0.885) by chi-square test. The difference of medical exposure, smoking, mental stress and physical stress was not statistically significant(P>0.05),except for tea and drinking(P<0.05).
2.2 The intensity of electric field at workplace on control area and 500kV electric substation was 0.0066～0.1490 kV/m and 0.0009-14.0000kV/m respectively, the intensity of magnetic field is 0.03-0.33μT and 0.62-32.02μT.
2.3 There was no statistically significant in concentrations of HSP70 protein by t test and covariance analysis.
Conclusion:
The results of the present study showed there was no significantly difference in the concentration of both the HSP70 mRNA and the HSP70 protein between the HBRA and the CA. The previous studies showed that there was no induction of HSP70 for low dose radiation for radiation could be one of the incentives. Some studies showed that the HSP70 was induced by the radiation in myeloid leukemia cell line. The result was opposite with epidemiology research, which indicated the health impact systems was complicated.
In the other research about power frequency eletromagnetic fields, we also found no statistically significance of HSP70 expression on 500kV electric substation exposed workers and the control people. It was accord to christopher A's study that there was no induction of HSP70 by 6.3μELF EMFs in HL60 cells. There were many negative reports about ELF EMFs research.We suggested it was attributed by different experimental condition, and little epidemiology research support.
The expression of HSP70 could be affected by confounding factors. Our research indicated that chronic exposured to low dose radiation or power frequency electromagnetic fields could not lead to induction of HSP70 expression. HSP70 expression could be associated with HSP70 gene polymorphism and confounding factors. More research should be launched to find the biomakers of low dose radiation or power frequency electromagnetic fields exposurers.
Based on the. potential causes for the conflicting data from the reported suggestions and statements about low dose radiation or power frequency electromagnetic fields, more research should be continued to resolve the controversial data.
引文
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[3]陶祖范.受高本底辐照人群流行病学研究的现状[J].国外医学-放射医学核医学分册,1997,21(4)：173-177.
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[5]陶祖范,孙全富,邹剑明,等.中国阳江高本底地区居民恶性肿瘤死亡研究[J].中华放射医学与防护杂志,2004,24(2)：143-148.
[6]Nair RRk, Rajan B, Akiba S, et al.Back ground radiation and cancer incidence in Kerala, India-Karunagappally cohort study[J].Health Physics,2009, 96:55-66.
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