Kumar P R Vivek, Seshadri M, Jaikrishan G, Das Birajalaxmi
Low Level Radiation Research Laboratory, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, IRE Campus, Beach Road, Kollam 691 001, Kerala, 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. 2015 May;775:59-65. doi: 10.1016/j.mrfmmm.2015.03.011. Epub 2015 Mar 28.
This study investigates whether peripheral blood mononuclear cells (PBMCs) from inhabitants of Kerala in southwest India, exposed to chronic low dose natural radiation in vivo (>1 mSv year(-1)), respond with a radioadaptive response to a challenging dose of gamma radiation. Toward this goal, PBMCs isolated from 77 subjects from high-level natural radiation areas (HLNRA) and 37 subjects from a nearby normal level natural radiation area (NLNRA) were challenged with 2 Gy and 4 Gy gamma radiation. Subjects from HLNRA were classified based on the mean annual effective dose received, into low dose group (LDG) and high dose group (HDG) with mean annual effective doses of 2.69 mSv (N=43, range 1.07 mSv year(-1) to 5.55 mSv year(-1)) and 9.62 mSv (N = 34, range 6.07 mSv year(-1) to 17.41 mSv year(-1)), respectively. DNA strand breaks and repair kinetics (at 7 min, 15 min and 30 min after 4 Gy) were evaluated using the alkaline single cell gel electrophoresis (comet) assay. Initial levels of DNA strand breaks observed after either a 2 Gy or a 4 Gy challenging dose were significantly lower in subjects of the HDG from HLNRA compared to subjects of NLNRA (2 Gy, P = 0.01; 4 Gy, P = 0.02) and LDG (2 Gy P = 0.01; 4 Gy, P=0.05). Subjects of HDG from HLNRA showed enhanced rejoining of DNA strand breaks (HDG/NLNRA, P = 0.06) during the early stage of repair (within 7 min). However at later times a similar rate of rejoining of strand breaks was observed across the groups (HDG, LDG and NLNRA). Preliminary results from our study suggest in vivo chronic low-level natural radiation provides an initial exposure that allows an adaptation to a subsequent higher radiation exposure, perhaps through improving DNA repair via an unknown mechanism. Therefore, further investigations would be necessary in this population to understand the biological and health effects of chronic low-level natural radiation exposures.
本研究调查了来自印度西南部喀拉拉邦、体内暴露于慢性低剂量天然辐射（>1 mSv 年(-1)）的居民的外周血单个核细胞（PBMC）是否会对具有挑战性的γ辐射剂量产生辐射适应性反应。为实现这一目标，从77名来自高天然辐射地区（HLNRA）的受试者和37名来自附近正常天然辐射水平地区（NLNRA）的受试者中分离出的PBMC，分别接受2 Gy和4 Gy的γ辐射挑战。HLNRA的受试者根据所接受的年平均有效剂量分为低剂量组（LDG）和高剂量组（HDG），年平均有效剂量分别为2.69 mSv（N = 43，范围为1.07 mSv 年(-1)至5.55 mSv 年(-1)）和9.62 mSv（N = 34，范围为6.07 mSv 年(-1)至17.41 mSv 年(-1)）。使用碱性单细胞凝胶电泳（彗星）试验评估DNA链断裂和修复动力学（4 Gy后7分钟、15分钟和30分钟时）。与NLNRA的受试者（2 Gy，P = 0.01；4 Gy，P = 0.02）和LDG的受试者（2 Gy，P = 0.01；4 Gy，P = 0.05）相比，HLNRA的HDG受试者在接受2 Gy或4 Gy挑战性剂量后观察到的初始DNA链断裂水平显著更低。HLNRA的HDG受试者在修复早期（7分钟内）显示出DNA链断裂的重新连接增强（HDG/NLNRA，P = 0.06）。然而，在后期，各组（HDG、LDG和NLNRA）观察到的链断裂重新连接速率相似。我们研究的初步结果表明，体内慢性低水平天然辐射提供了一种初始暴露，可能通过一种未知机制改善DNA修复，从而使机体适应随后更高的辐射暴露。因此，有必要对该人群进行进一步调查，以了解慢性低水平天然辐射暴露的生物学和健康影响。
