Zhao Weichao, Mao Liang, He Chuqi, Ding Dexin, Hu Nan, Song Xiaohua, Long Dingxin
School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China; Hunan Province Key Laboratory of Typical Evironmental Pollution and Health Hazards, Hengyang Medical School, University of South China, Hengyang 421001, PR China.
Key Discipline Laboratory for National Defence for Biotechnology in Uranium Mining and Hydrometallurgy,University of South China, Hengyang, Hunan 421001, PR China.
Ecotoxicol Environ Saf. 2023 Apr 15;255:114779. doi: 10.1016/j.ecoenv.2023.114779. Epub 2023 Mar 15.
Biological rhythm refers to the internal regulation of various life activities of an organism, which are determined by the specific time structure sequences of each individual. Behavior rhythm is the most intuitive embodiment of biological rhythm. To study the effect of low dose radiation on behavioral rhythm, zebrafish (Danio rerio) was used as a model organism in this study. The early embryos of zebrafish were irradiated at doses of 0.01, 0.1, and 1 Gy to observe the changes in zebrafish development, circadian rhythm, key clock genes, related RNA and protein expression, and melatonin. The results revealed that 0.1 and 1 Gy radiation could lead to different degrees of telencephalic nerve cell apoptosis and the formation of vacuolar structures. 0.1 and 1 Gy radiation could reduce the hatching rate of zebrafish embryos at 72 hpf and delay embryo hatching. The analysis of circadian behavior at 120 hpf demonstrated that 1 Gy dose of radiation altered the circadian rhythm of zebrafish, as well as decreased the distance, amplitude, and phase of movement. RT-PCR analysis of the key clock genes (bmal1b, clock1a, per1b, per2, cry2, and nr1d1) involved in regulating circadian rhythm was performed. The results showed that 1 Gy radiation could interfere with the expression of clock genes in zebrafish embryos and upregulate bmal1b, clock1a, and per1b. Western blot experiments further verified the protein expression of key clock genes, bmal1b and clock. Detection of melatonin secretion at different time points over 24 h showed that radiation doses of 0.1 and 1 Gy could increase melatonin secretion. Based on these findings, it is speculated that a certain dose of radiation may affect melatonin secretion, which impacts the telencephalon structure and ontogeny of zebrafish, delays hatching, and changes the circadian rhythm. This effect is thought to be achieved through upregulating the expression of circadian rhythm genes, clock1a and per1b and related proteins, which may be responsible for the abnormal circadian rhythm caused by radiation.
生物节律是指生物体各种生命活动的内在调节，由每个个体特定的时间结构序列决定。行为节律是生物节律最直观的体现。为研究低剂量辐射对行为节律的影响，本研究以斑马鱼（Danio rerio）作为模式生物。对斑马鱼早期胚胎分别进行0.01、0.1和1 Gy剂量的辐射，观察斑马鱼发育、昼夜节律、关键生物钟基因、相关RNA和蛋白质表达以及褪黑素的变化。结果显示，0.1和1 Gy辐射可导致不同程度的端脑神经细胞凋亡和空泡结构形成。0.1和1 Gy辐射可降低斑马鱼胚胎在72 hpf时的孵化率并延迟胚胎孵化。对120 hpf时的昼夜行为分析表明，1 Gy剂量的辐射改变了斑马鱼的昼夜节律，同时减少了运动距离、振幅和相位。对参与调节昼夜节律的关键生物钟基因（bmal1b、clock1a、per1b、per2、cry2和nr1d1）进行了RT-PCR分析。结果表明，1 Gy辐射可干扰斑马鱼胚胎中生物钟基因的表达并上调bmal1b、clock1a和per1b。蛋白质免疫印迹实验进一步验证了关键生物钟基因bmal1b和clock的蛋白质表达。对24小时内不同时间点褪黑素分泌的检测表明，0.1和1 Gy辐射剂量可增加褪黑素分泌。基于这些发现，推测一定剂量的辐射可能影响褪黑素分泌，进而影响斑马鱼的端脑结构和个体发育，延迟孵化并改变昼夜节律。这种效应被认为是通过上调昼夜节律基因clock1a和per1b以及相关蛋白质的表达来实现的，这可能是辐射导致异常昼夜节律的原因。
