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.
Sci Total Environ. 2020 May 10;716:137130. doi: 10.1016/j.scitotenv.2020.137130. Epub 2020 Feb 4.
Fish are frequently affected by environmental stressors, such as temperature changes and heavy metal exposure, in aquatic ecosystems. In this study, we evaluated the combined effects of cadmium (Cd) toxicity and temperature (rearing temperature of 26 °C and heat stress at 34 °C) on zebrafish (Danio rerio) embryos. The survival and heart rates of zebrafish embryos decreased at relatively high Cd concentrations of 0.07 and 0.1 mg L. Abnormal morphology was induced by exposure to a combination of Cd toxicity and heat stress. The yolk sac edema size was not significantly different between the control- and Cd-treated groups. Cd exposure induced reactive oxygen species (ROS) production and cell death in the live zebrafish. High temperature (34 °C) triggered Cd-induced cell death and intracellular ROS production to a greater extent than the rearing temperature of 26 °C. Transcriptional levels of six genes-CAT, SOD, p53, BAX, Dnmt1, and Dnmt3b-were investigated. The mRNA expression of CAT and SOD, molecular indicators of oxidative stress, was increased significantly at 34 °C after Cd exposure. The mRNA expression of CAT was more sensitive to temperature than that of SOD in Cd-treated zebrafish. p53 and BAX, apoptosis-related genes, were upregulated upon combined exposure to high temperature and Cd. In addition, at 34 °C, the expression of Dnmt1 and Dnmt3b transcripts, markers of DNA methylation, was increased upon exposure of zebrafish to all concentrations of Cd. Overall, these results suggest that high temperature facilitates the potential role of Cd toxicity in the transcriptional regulation of genes involved in the antioxidant system, apoptosis, and DNA methylation.
鱼类经常受到水生生态系统中环境胁迫的影响，如温度变化和重金属暴露。在这项研究中，我们评估了镉（Cd）毒性和温度（26°C 的饲养温度和 34°C 的热应激）对斑马鱼（Danio rerio）胚胎的联合影响。相对较高的 Cd 浓度（0.07 和 0.1 mg/L）会降低斑马鱼胚胎的存活率和心率。暴露于 Cd 毒性和热应激联合作用会导致胚胎形态异常。在对照组和 Cd 处理组之间，卵黄囊水肿大小没有显著差异。Cd 暴露会在活体斑马鱼中诱导活性氧（ROS）的产生和细胞死亡。与 26°C 的饲养温度相比，高温（34°C）更能引发 Cd 诱导的细胞死亡和细胞内 ROS 产生。研究了六个基因（CAT、SOD、p53、BAX、Dnmt1 和 Dnmt3b）的转录水平。CAT 和 SOD 的 mRNA 表达在 Cd 暴露后 34°C 时显著增加，这两个基因是氧化应激的分子指标。在 Cd 处理的斑马鱼中，CAT 的 mRNA 表达比 SOD 对温度更敏感。p53 和 BAX 是与细胞凋亡相关的基因，在高温和 Cd 联合暴露时上调。此外，在 34°C 时，暴露于所有 Cd 浓度会增加 DNA 甲基化标志物 Dnmt1 和 Dnmt3b 转录物的表达。总的来说，这些结果表明，高温促进了 Cd 毒性在抗氧化系统、细胞凋亡和 DNA 甲基化相关基因转录调控中的潜在作用。
