Pflugmacher Stephan
Leibniz Institut for Freshwater Ecology and Inland Fisheries, RG Biogeochemical Regulation, Müggelseedamm 301, 12561 Berlin, Germany.
Aquat Toxicol. 2004 Dec 10;70(3):169-78. doi: 10.1016/j.aquatox.2004.06.010.
Cyanobacterial toxins have been shown to have adverse effects on mammals, birds and fish and are therefore being increasingly recognised as a potent stress and health hazard factor in aquatic ecosystems. Microcystins, which are cyclic heptapeptides and a main group of the cyanotoxins, are mainly retained within the producer-cells during cyanobacterial bloom development. However, these toxins are released into the surrounding medium by senescence and lysis of the blooms. The released toxins could then come into contact with a wide range of aquatic organisms including invertebrates, fish and aquatic plants. In many organisms, biotransformation of the toxins will take place via several glutathione-related conjugate. During the biotransformation process in which the toxin and the toxin conjugate are broken down, the formation of reactive oxygen species might occur. These reactive oxygen species activate several antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase and also influence the glutathione-ascorbate cycle. Aim of this study was to investigate formation of the glutathione-conjugate, activation of glutathione S-transferases and the elevation of several antioxidant enzymes giving evidence for the promotion of oxidative stress by microcystins. During exposure of Ceratophyllum demersum to the cyanobacterial toxin microcystin-LR in an concentration of 5.0 microg/L, an elevation of microsomal and cytosolic glutathione S-transferase was measured, showing the beginning formation of the glutathione-toxin conjugate. The superoxide dismutase as well as in parallel the hydrogen peroxide level increased giving evidence for oxidative stress in the aquatic plant. Other reactive oxygen detoxifiying enzymes were also elevated and the glutathione pool, expressed in reduced glutathione and glutathione disulfide concentration was changed accordingly.
蓝藻毒素已被证明对哺乳动物、鸟类和鱼类具有不良影响，因此越来越被视为水生生态系统中一种强大的压力和健康危害因素。微囊藻毒素是一类环状七肽，也是蓝藻毒素的主要类别，在蓝藻水华发展过程中主要保留在产生毒素的细胞内。然而，这些毒素会随着水华的衰老和裂解释放到周围介质中。释放出的毒素随后可能会接触到包括无脊椎动物、鱼类和水生植物在内的多种水生生物。在许多生物体内，毒素会通过几种与谷胱甘肽相关的共轭物进行生物转化。在毒素和毒素共轭物分解的生物转化过程中，可能会产生活性氧物种。这些活性氧物种会激活几种抗氧化酶，如超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶，还会影响谷胱甘肽 - 抗坏血酸循环。本研究的目的是调查谷胱甘肽共轭物的形成、谷胱甘肽 S - 转移酶的激活以及几种抗氧化酶的升高情况，以证明微囊藻毒素会促进氧化应激。在金鱼藻暴露于浓度为5.0微克/升的蓝藻毒素微囊藻毒素 - LR的过程中，检测到微粒体和胞质谷胱甘肽 S - 转移酶升高，这表明开始形成谷胱甘肽 - 毒素共轭物。超氧化物歧化酶以及同时过氧化氢水平升高，这证明了水生植物中存在氧化应激。其他活性氧解毒酶也有所升高，以还原型谷胱甘肽和谷胱甘肽二硫化物浓度表示的谷胱甘肽池也相应发生了变化。
