Programa de Pós-graduação Em Ciências Fisiológicas, Universidade Federal Do Rio Grande, Avenida Itália Km 8, Campus Carreiros, 96203-900, Rio Grande, RS, Brazil.
Instituto de Ciências Biológicas, Universidade Federal Do Rio Grande, Avenida Itália Km 8, Campus Carreiros, 96203-900, Rio Grande, RS, Brazil.
Chemosphere. 2019 Jul;227:580-588. doi: 10.1016/j.chemosphere.2019.04.080. Epub 2019 Apr 12.
Copper ions (Cu) are essential to life maintenance, nonetheless, elevated concentrations can be hazardous. Acute and sub-chronic toxic effects of this metal are well known and are usually related to enzymatic inhibition, elevated ROS production and dysfunction of energy metabolism. Despite that, chronic studies are extremely rare. Therefore, the aim of this study was to assess the effects of chronic exposure to 5, 9 and 20 μg/L Cu (28 ad 345 days) on the energy metabolism and survival of the killifish Poecilia vivipara. To accomplish that, we evaluated the activity of enzymes related to aerobic (pyruvate kinase (PK); citrate synthase (CS)) and anaerobic metabolism (lactate dehydrogenase (LDH)) in whole-body (28 days) or in gills, liver and muscle (345 days) of exposed fish. Additionally, whole-body oxygen consumption was evaluated in fish exposed for 28 days and hepatic and muscular expression of genes involved in mitochondrial metabolism (cox I, II and III and atp5a1) was assessed in animals exposed for 345 days. Finally, final survival was evaluated. Following 28 days, Cu did not affect survival neither enzyme activities. However, increased whole-body oxygen consumption was observed in comparison to control condition. After 345 days, 76.8%, 63.9%, 60.9% and 0% survival were observed for control, 5, 9 and 20 μg/L groups, respectively. Animals exposed to 5 and 9 μg/L had a significant reduction in branchial and muscular LDH activity and in hepatic PK activity. Also, exposure to 9 μg/L significantly increased hepatic CS activity. For gene expression, Cu down-regulated muscular cox II (9 μg/L) and III (5 and 9 μg/L), and up-regulated hepatic atp5a1 (9 μg/L). Findings reported in the present study indicate that chronic exposure to Cu induces tissue-specific responses in key aspects of the energetic metabolism. In gills and muscle, Cu leads to reduced energy production through inhibition of anaerobic pathways and mitochondrial respiratory chain. This effect is paralleled by an increased ATP consumption in the liver, characterized by the augmented CS activity and atp5a1 expression. Finally, reduced PK activity indicate that oxidative stress may be involved with the observed outcomes.
铜离子（Cu）对维持生命至关重要，但浓度过高可能会造成危害。这种金属的急性和亚慢性毒性作用已广为人知，通常与酶抑制、ROS 生成增加和能量代谢功能障碍有关。尽管如此，慢性研究却极为罕见。因此，本研究的目的是评估慢性暴露于 5、9 和 20μg/L Cu（28 至 345 天）对食蚊鱼（Poecilia vivipara）能量代谢和生存的影响。为了达到这个目的，我们评估了暴露鱼类的整体（28 天）或鳃、肝脏和肌肉（345 天）中与有氧代谢（丙酮酸激酶（PK）；柠檬酸合酶（CS））和无氧代谢（乳酸脱氢酶（LDH））相关的酶的活性。此外，还评估了暴露 28 天的鱼类的全身耗氧量，并评估了暴露 345 天的动物的肝脏和肌肉中线粒体代谢（cox I、II 和 III 和 atp5a1）相关基因的表达。最后，评估了最终的存活率。暴露 28 天后，Cu 既不影响存活率也不影响酶活性。然而，与对照条件相比，观察到全身耗氧量增加。暴露 345 天后，对照组、5μg/L、9μg/L 和 20μg/L 组的存活率分别为 76.8%、63.9%、60.9%和 0%。暴露于 5μg/L 和 9μg/L 的动物的鳃和肌肉 LDH 活性以及肝脏 PK 活性显著降低。此外，9μg/L 的暴露显著增加了肝脏 CS 活性。对于基因表达，Cu 下调了肌肉 cox II（9μg/L）和 III（5 和 9μg/L），并上调了肝脏 atp5a1（9μg/L）。本研究报告的结果表明，慢性 Cu 暴露会导致能量代谢关键方面的组织特异性反应。在鳃和肌肉中，Cu 通过抑制无氧途径和线粒体呼吸链来减少能量产生。这种效应伴随着肝脏中 CS 活性和 atp5a1 表达增加的 ATP 消耗增加。最后，PK 活性降低表明氧化应激可能与观察到的结果有关。
