Aluminium (Al) water pollution is an increasing environmental problem and comprehensive analysis of toxic responses of aquatic primary producer organisms is imperative. We characterized the antioxidant response of Scenedesmus sp. microalga to Al-induced oxidative stress. After 72 h of exposure to Al (0, 10, and 100 μM) in a modified Bold Basal Medium (pH 5.0), we observed cell aggregation and alterations in the subcellular structure, strong lipid peroxidation and oxidative stress induction (detected with the fluorescent probe 2',7'-dichlorodihydrofluorescein diacetate) in parallel with Al accumulation in cells. At the same time, Al toxicity caused depletion of important macronutrients like Ca, which is important for cell-wall structure. Analysis of antioxidant enzymatic activities in Al-treated Scenedesmus cells revealed that catalase, ascorbate peroxidase, as well as different isoforms of superoxide dismutase were inhibited especially at the highest Al dose (100 μM), cells that accumulated the highest concentration of Al. On the other hand, glutathione reductase activity increased at that Al concentration. Immunodetection after Western-blotting confirmed that only ascorbate peroxidase inhibition was apparently due to a decrease in enzyme levels. However, the inhibition of catalase and activation of glutathione reductase activities seemed related with post-translational modifications in protein function as protein expression decreased or increased, respectively under Al stress. Our results may help to understand toxic mechanisms triggered by Al in freshwater microalgae, which in turn could aid to select suitable biomarkers of Al contamination in aquatic ecosystems.

中文翻译：

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铝在微藻栅栏藻中引发氧化应激和抗氧化反应

铝 (Al) 水污染是一个日益严重的环境问题，对水生初级生产者生物的毒性反应进行综合分析势在必行。我们表征了栅藻属的抗氧化反应。微藻对铝诱导的氧化应激。在改良的 Bold 基础培养基（pH 5.0）中暴露于 Al（0、10 和 100 μM）72 小时后，我们观察到细胞聚集和亚细胞结构的改变、强脂质过氧化和氧化应激诱导（用荧光检测探针 2',7'-二氯二氢荧光素二乙酸酯）与细胞中的铝积累平行。同时，铝毒性导致重要的常量营养素如钙的消耗，钙对细胞壁结构很重要。铝处理栅藻细胞中抗氧化酶活性的分析表明，过氧化氢酶、抗坏血酸过氧化物酶以及超氧化物歧化酶的不同亚型受到抑制，尤其是在最高铝剂量 (100 μM) 时，这些细胞积累了最高浓度的铝。另一方面，谷胱甘肽还原酶活性在该铝浓度下增加。蛋白质印迹后的免疫检测证实，只有抗坏血酸过氧化物酶抑制显然是由于酶水平降低所致。然而，过氧化氢酶的抑制和谷胱甘肽还原酶活性的激活似乎与蛋白质功能的翻译后修饰有关，因为蛋白质表达分别在铝胁迫下减少或增加。我们的结果可能有助于了解铝在淡水微藻中引发的毒性机制，进而有助于选择合适的水生生态系统中铝污染的生物标志物。