Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/CIMAR), University of Porto, Rua dos Bragas 289, P 4050-123 Porto, Portugal; ICBAS - Institute of Biomedical Sciences Abel Salazar, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal.
Faculty of Science, Ankara University, Department of Biology, 06100 Tandogan, Ankara, Turkey.
Aquat Toxicol. 2015 Feb;159:225-32. doi: 10.1016/j.aquatox.2014.12.008. Epub 2014 Dec 17.
Cadmium is a priority hazardous substance, persistent in the aquatic environment, with the capacity to interfere with crustacean moulting. Moulting is a vital process dictating crustacean growth, reproduction and metamorphosis. However, for many organisms, moult disruption is difficult to evaluate in the short term, what limits its inclusion in monitoring programmes. N-acetyl-β-D-glucosaminidase (NAGase) is an enzyme acting in the final steps of the endocrine-regulated moulting cascade, allowing for the cast off of the old exoskeleton, with potential interest as a biomarker of moult disruption. This study investigated responses to waterborne cadmium of NAGase activity of Carcinus maenas originating from estuaries with different histories of anthropogenic contamination: a low impacted and a moderately polluted one. Crabs from both sites were individually exposed for seven days to cadmium concentrations ranging from 1.3 to 2000 μg/L. At the end of the assays, NAGase activity was assessed in the epidermis and digestive gland. Detoxification, antioxidant, energy production, and oxidative stress biomarkers implicated in cadmium metabolism and tolerance were also assessed to better understand differential NAGase responses: activity of glutathione S-transferases (GST), glutathione peroxidase (GPx) glutathione reductase (GR), levels of total glutathiones (TG), lipid peroxidation (LPO), lactate dehydrogenase (LDH), and NADP(+)-dependent isocitrate dehydrogenase (IDH). Animals from the moderately polluted estuary had lower NAGase activity both in the epidermis and digestive gland than in the low impacted site. NAGase activity in the epidermis and digestive gland of C. maenas from both estuaries was sensitive to cadmium exposure suggesting its usefulness for inclusion in monitoring programmes. However, in the digestive gland NAGase inhibition was found in crabs from the less impacted site but not in those from the moderately contaminated one. Altered glutathione levels were observed in cadmium-treated crabs from the contaminated site possibly conferring enhanced tolerance to these animals through its chelator action. Investigation of enhanced tolerance should thus be accounted for in monitoring programmes employing NAGase as biomarker to avoid data misinterpretation.
镉是一种优先关注的危险物质，在水生环境中具有持久性，并能干扰甲壳类动物的蜕皮。蜕皮是决定甲壳类动物生长、繁殖和变态的重要过程。然而，对于许多生物来说，蜕皮干扰在短期内很难评估，这限制了它在监测计划中的纳入。N-乙酰-β-D-氨基葡萄糖苷酶（NAGase）是一种在内分泌调节蜕皮级联的最后步骤中起作用的酶，允许旧外骨骼脱落，作为蜕皮干扰的生物标志物具有潜在的兴趣。本研究调查了来自具有不同人为污染历史的河口的贻贝（Carcinus maenas）对水基镉的 NAGase 活性的反应：一个受影响较小和一个中度污染的河口。来自两个地点的螃蟹分别单独暴露于 1.3 至 2000μg/L 的镉浓度下 7 天。在试验结束时，评估了表皮和消化腺中的 NAGase 活性。还评估了与镉代谢和耐受相关的解毒、抗氧化、能量产生和氧化应激生物标志物，以更好地理解不同的 NAGase 反应：谷胱甘肽 S-转移酶（GST）、谷胱甘肽过氧化物酶（GPx）、谷胱甘肽还原酶（GR）的活性、总谷胱甘肽（TG）、脂质过氧化（LPO）、乳酸脱氢酶（LDH）和烟酰胺腺嘌呤二核苷酸（NADP+）-依赖性异柠檬酸脱氢酶（IDH）的水平。来自中度污染河口的动物在表皮和消化腺中的 NAGase 活性均低于低影响点。来自两个河口的贻贝的表皮和消化腺中的 NAGase 活性对镉暴露敏感，表明其对纳入监测计划有用。然而，在消化腺中，在受污染地点的螃蟹中发现了 NAGase 抑制，但在中度污染地点的螃蟹中没有发现。在受污染地点的镉处理螃蟹中观察到了改变的谷胱甘肽水平，这可能通过其螯合作用赋予这些动物更高的耐受性。因此，在使用 NAGase 作为生物标志物进行监测计划时，应考虑到增强的耐受性，以避免数据误判。
