Berlin Institute of Technology-BIT, Department of Ecotoxicological Impact Research and Ecotoxicology, Ernst-Reuter-Platz 1, 10587 Berlin, Germany.
Aquat Toxicol. 2013 Aug 15;138-139:26-34. doi: 10.1016/j.aquatox.2013.04.007. Epub 2013 Apr 26.
Recently, aquatic macrophytes have been considered as promising tools for eco-friendly water management with a low running cost. However, only little information is available thus far regarding the metabolic capacity of macrophytes for coping with cyanobacterial toxins (cyanotoxins) in the aquatic environment. Cyanotoxins have become emerging contaminants of great concern due to the high proliferation of cyanobacteria (cyanobacterial bloom) accelerated by eutrophication and climate change. Anatoxin-a, one of the common and major cyanotoxins, is suggested as a high priority water pollutant for regulatory consideration owing to its notoriously rapid mode of action as a neurotoxin. In this study, the time-course metabolic regulation of the submerged macrophyte Ceratophyllum demersum (C. demersum) was investigated during exposure to anatoxin-a at an environmentally relevant concentration (15 μg/L). Biotransformation and antioxidative systems in C. demersum responded positively to anatoxin-a through the promoted synthesis of most of the involved enzymes within 8h. Maximum enzyme activities were exhibited after 24 or 48 h of exposure to anatoxin-a. However, an apparent decline in enzyme activities was also observed at longer exposure duration (168 and 336 h) in company with high steady-state levels of cell internal H₂O₂, which showed its highest level after 48 h. Meanwhile, irreversible inhibitory influence on chlorophyll content (vitality) was noticed, whereas the ratio of carotenoids to total chlorophyll was increased with the increase in exposure duration. Consequently, the reduction in growth (biomass) of C. demersum was observed in sub-chronic exposure to anatoxin-a (8 weeks). Overall results clearly indicate, on the one hand, that anatoxin-a causes negative allelopathic effects on the macrophyte by inducing oxidative stress. On the other hand, the macrophyte might have interactions with anatoxin-a, based on the prompt reaction of its enzymatic defense systems to the toxin. The result obtained from the present study could contribute to the improvement of basic knowledge about the ecological impact of anatoxin-a and the environmental fate of the toxin in the aquatic environment.
最近，水生植物被认为是具有成本效益的环保型水管理的有前途的工具。然而，迄今为止，关于水生环境中大型植物应对蓝藻毒素（蓝藻毒素）的代谢能力的信息很少。由于富营养化和气候变化加速了蓝藻（蓝藻水华）的大量繁殖，蓝藻毒素已成为人们关注的新兴污染物。由于作为神经毒素的作用方式非常迅速，因此建议将蓝藻毒素之一的anatoxin-a 作为具有高优先级的水污染物进行监管考虑。在这项研究中，在环境相关浓度（15μg/L）下，研究了浸没植物金鱼藻（Ceratophyllum demersum）暴露于anatoxin-a 时的时间过程代谢调节。在 8 小时内，大多数参与的酶的合成促进了生物转化和抗氧化系统对 anatoxin-a 的积极响应。暴露于 anatoxin-a 24 或 48 小时后，表现出最大的酶活性。但是，在较长的暴露时间（168 和 336 小时）下，酶活性也明显下降，同时细胞内部 H₂O₂的稳态水平也很高，48 小时后达到最高水平。同时，发现对叶绿素含量（活力）有不可逆的抑制作用，而类胡萝卜素与总叶绿素的比例随着暴露时间的增加而增加。因此，在亚慢性暴露于 anatoxin-a（8 周）中观察到金鱼藻的生长（生物量）减少。总体结果清楚地表明，一方面，anatoxin-a 通过诱导氧化应激对大型植物产生负的化感作用。另一方面，由于其酶防御系统对毒素的迅速反应，大型植物可能与 anatoxin-a 相互作用。本研究的结果有助于提高关于 anatoxin-a 的生态影响和毒素在水生环境中的环境命运的基本知识。
