Jain Vinay, Kumar P R Vivek, Koya P K M, Jaikrishan G, Das Birajalaxmi
Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India; Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400 094, India.
Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
Mutat Res. 2016 Jun;788:50-7. doi: 10.1016/j.mrfmmm.2016.03.002. Epub 2016 Mar 25.
The high level natural radiation area (HLNRA) of Kerala is a 55km long and 0.5km wide strip in south west coast of India. The level of background radiation in this area varies from <1.0mGy/year to 45.0mGy/year. It offers unique opportunity to study the effect of chronic low dose/low dose-rate radiation directly on human population. Spontaneous level of DNA double strand breaks (DSBs) was quantified in peripheral blood mononuclear cells of 91 random individuals from HLNRA (N=61, mean age: 36.1±7.43years) and normal level natural radiation area (NLNRA) (N=30, mean age: 35.5±6.35years) using gamma-H2AX as a marker. The mean annual dose received by NLNRA and HLNRA individuals was 1.28±0.086mGy/year and 8.28±4.96mGy/year, respectively. The spontaneous frequency of DSBs in terms of gamma-H2AX foci among NLNRA and HLNRA individuals were 0.095±0.009 and 0.084±0.004 per cell (P=0.22). The individuals from HLNRA were further classified as low dose group (LDG, 1.51-5.0mGy/year, mean dose: 2.63±0.76mGy/year) and high dose group (HDG, >5.0mGy/year, mean dose: 11.04±3.57mGy/year). The spontaneous frequency of gamma-H2AX foci per cell in NLNRA, LDG and HDG was observed to be 0.095±0.009, 0.096±0.008 and 0.078±0.004 respectively. Individuals belonging to HDG of HLNRA showed marginally lower frequency of DSBs as compared to NLNRA and LDG of HLNRA. This could be suggestive of either lower induction or better repair of DSBs in individuals from HDG of HLNRA. The present study indicated that 5.0mGy/year could be a possible threshold dose for DSB induction at chronic low-dose radiation exposure in vivo. However, further studies on DNA damage induction and repair kinetics are required to draw firm conclusions.
喀拉拉邦的高本底天然辐射区（HLNRA）位于印度西南海岸，是一条长55公里、宽0.5公里的地带。该地区的本底辐射水平在<1.0毫戈瑞/年至45.0毫戈瑞/年之间变化。它为直接研究慢性低剂量/低剂量率辐射对人群的影响提供了独特的机会。使用γ-H2AX作为标记物，对来自高本底天然辐射区（N = 61，平均年龄：36.1±7.43岁）和正常本底天然辐射区（NLNRA）（N = 30，平均年龄：35.5±6.35岁）的91名随机个体的外周血单个核细胞中的DNA双链断裂（DSB）自发水平进行了定量。NLNRA和HLNRA个体每年接受的平均剂量分别为1.28±0.086毫戈瑞/年和8.28±4.96毫戈瑞/年。NLNRA和HLNRA个体中以γ-H2AX焦点表示的DSB自发频率分别为每细胞0.095±0.009和0.084±0.004（P = 0.22）。HLNRA的个体进一步分为低剂量组（LDG，1.51 - 5.0毫戈瑞/年，平均剂量：2.63±0.76毫戈瑞/年）和高剂量组（HDG，>5.0毫戈瑞/年，平均剂量：11.04±3.57毫戈瑞/年）。观察到NLNRA、LDG和HDG中每细胞γ-H2AX焦点的自发频率分别为0.095±0.009、0.096±0.008和0.078±0.004。与NLNRA和HLNRA的LDG相比，HLNRA的HDG个体的DSB频率略低。这可能表明HLNRA的HDG个体中DSB的诱导较低或修复较好。本研究表明，在体内慢性低剂量辐射暴露下，5.0毫戈瑞/年可能是DSB诱导的一个可能阈值剂量。然而，需要进一步研究DNA损伤诱导和修复动力学才能得出确凿结论。
