de Polo Anna, Margiotta-Casaluci Luigi, Lockyer Anne E, Scrimshaw Mark D
Institute for the Environment, Brunel University, London, United Kingdom.
Institute for the Environment, Brunel University, London, United Kingdom; AstraZeneca, Global Health, Safety and Environment, Freshwater Quarry, Brixham, United Kingdom.
PLoS One. 2014 Oct 1;9(10):e107707. doi: 10.1371/journal.pone.0107707. eCollection 2014.
The majority of ecotoxicological studies are performed under stable and optimal conditions, whereas in reality the complexity of the natural environment faces organisms with multiple stressors of different type and origin, which can activate pathways of response often difficult to interpret. In particular, aquatic organisms living in estuarine zones already impacted by metal contamination can be exposed to more severe salinity variations under a forecasted scenario of global change. In this context, the present study aimed to investigate the effect of copper exposure on the response of fish to osmotic stress by mimicking in laboratory conditions the salinity changes occurring in natural estuaries. We hypothesized that copper-exposed individuals are more sensitive to osmotic stresses, as copper affects their osmoregulatory system by acting on a number of osmotic effector proteins, among which the isoform two of the enzyme carbonic anhydrase (CA2) was identified as a novel factor linking the physiological responses to both copper and osmotic stress. To test this hypothesis, two in vivo studies were performed using the euryhaline fish sheepshead minnow (Cyprinodon variegatus) as test species and applying different rates of salinity transition as a controlled way of dosing osmotic stress. Measured endpoints included plasma ions concentrations and gene expression of CA2 and the α1a-subunit of the enzyme Na+/K+ ATPase. Results showed that plasma ions concentrations changed after the salinity transition, but notably the magnitude of change was greater in the copper-exposed groups, suggesting a sensitizing effect of copper on the responses to osmotic stress. Gene expression results demonstrated that CA2 is affected by copper at the transcriptional level and that this enzyme might play a role in the observed combined effects of copper and osmotic stress on ion homeostasis.
大多数生态毒理学研究是在稳定和最佳条件下进行的，而在现实中，自然环境的复杂性使生物体面临来自不同类型和来源的多种应激源，这可能会激活往往难以解释的反应途径。特别是，生活在已经受到金属污染影响的河口区域的水生生物，在全球变化的预测情景下可能会面临更严重的盐度变化。在此背景下，本研究旨在通过在实验室条件下模拟天然河口发生的盐度变化，研究铜暴露对鱼类渗透应激反应的影响。我们假设，暴露于铜的个体对渗透应激更敏感，因为铜通过作用于多种渗透效应蛋白来影响其渗透调节系统，其中碳酸酐酶（CA2）的同工型2被确定为将生理反应与铜和渗透应激联系起来的新因素。为了验证这一假设，进行了两项体内研究，使用广盐性鱼类红树鳉（Cyprinodon variegatus）作为测试物种，并应用不同的盐度转变速率作为施加渗透应激的可控方式。测量的终点包括血浆离子浓度以及CA2和Na+/K+ ATP酶α1a亚基的基因表达。结果表明，盐度转变后血浆离子浓度发生了变化，但值得注意的是，铜暴露组的变化幅度更大，这表明铜对渗透应激反应有敏感化作用。基因表达结果表明，CA2在转录水平上受到铜的影响，并且该酶可能在观察到的铜和渗透应激对离子稳态的联合作用中发挥作用。
