Fisheries Science Institute, Chonnam National University, Yeosu, 59626, South Korea.
Department of Marine Bio-food Science, College of Fisheries and Ocean Sciences, Chonnam National University, 500-749, South Korea.
Aquat Toxicol. 2020 Jul;224:105479. doi: 10.1016/j.aquatox.2020.105479. Epub 2020 May 8.
Lead (Pb) is a toxic environmental pollutant that is frequently present in effluents from urban, mining, and industrial sources. The combinatorial effects of heavy metal exposure and temperature in aquatic organisms have received considerable attention as heat stress occurs simultaneously in conjunction with several contaminants in a natural environment. In this study, we examined the potential effects of Pb exposure in conditions of thermal stress (34 °C) in zebrafish (Danio rerio) embryos. Thermal stress at 34 °C induced a dramatic decrease in the survival rate, although exposure to Pb at 26 °C decreased the survival rate of the embryos. Malformations, such as the curved body shape, were increased in response to exposure to a combination of Pb and heat stress. The combination of Pb and heat stress also caused a decrease in the heart rate. Moreover, Pb and high-temperature exposure induced the upregulation of SOD, CAT, TNF-α, IL-1β, p53, and BAX transcripts, and downregulation of Dnmt1 and Dnmt3b transcripts. Thermal stress enhanced transcriptional responses of eight indicator genes following Pb toxicity. The induction of cell death in response to combined exposures was also confirmed in the body of zebrafish by fluorescence intensity image analysis. These data indicated that thermal stress enhanced the poisonous effects of Pb exposure on antioxidant defense, inflammation, and apoptotic mechanisms. Transcriptional inhibition of DNA methylation-related genes might serve as a crucial factor contributing to the possibility of epigenetic adaptation by altering combined stress. We suggest that a careful evaluation of the potential effects of climate change (especially temperature) should be considered when investigating the toxic levels of metal pollution, such as Pb, in an aquatic environment.
铅（Pb）是一种有毒的环境污染物，经常存在于城市、采矿和工业来源的废水中。重金属暴露和水生生物温度的组合效应已受到广泛关注，因为热应激与自然环境中的几种污染物同时发生。在这项研究中，我们研究了在热应激（34°C）条件下暴露于 Pb 对斑马鱼（Danio rerio）胚胎的潜在影响。34°C 的热应激导致存活率显着下降，尽管 26°C 下暴露于 Pb 会降低胚胎的存活率。畸形，如弯曲的身体形状，在暴露于 Pb 和热应激的组合时增加。Pb 和高温暴露还导致心率下降。此外，Pb 和高温暴露诱导 SOD、CAT、TNF-α、IL-1β、p53 和 BAX 转录物的上调，以及 Dnmt1 和 Dnmt3b 转录物的下调。热应激增强了 Pb 毒性后八个指示基因的转录反应。通过荧光强度图像分析还在斑马鱼体内证实了联合暴露引起的细胞死亡。这些数据表明，热应激增强了 Pb 暴露对抗氧化防御、炎症和细胞凋亡机制的毒性作用。DNA 甲基化相关基因的转录抑制可能是通过改变联合应激改变表观遗传适应的一个关键因素。我们建议，在研究水生环境中金属污染（如 Pb）的毒性水平时，应考虑气候变化（特别是温度）的潜在影响。
