Discipline of Marine Biotechnology and Ecology, Central Salt and Marine Chemicals Research Institute, Council of Scientific and Industrial Research (CSIR), Gijubhai Badheka Marg, Bhavnagar 364021, India.
Chem Res Toxicol. 2011 Nov 21;24(11):1882-90. doi: 10.1021/tx200228c. Epub 2011 Oct 6.
The green credentials of ionic liquids (ILs) are being increasingly questioned due to the growing evidence of their toxicity to aquatic ecosystems, although the mechanisms of toxicity are unknown. This study provides insights into the mechanism of toxicity and biological effects of 1-alkyl-3-methylimidazolium bromide [C(n)mim]Br (n = 4 to 16) on the marine macroalga Ulva lactuca. The cell viability of this alga during IL exposure was found to be negatively correlated to the chain length of the alkyl group. The IL ([C(12)mim]Br) exposure triggers the generation of reactive oxygen species (ROS viz. O(2)(•-), H(2)O(2), and OH(•)), damage of the membrane and DNA, and inhibition of antioxidant systems in the alga. The enhanced production of ROS and lipid peroxidation in the alga subjected to LC(50) concentration for 4 days was largely attributed to lipoxygenase (LOX) activity coupled with the induction of two LOX isoforms (80 kDa and ~55 kDa). Pretreatment of the algal thallus with enzyme inhibitors such as diphenylene iodonium, sodium azide, cantharidin, and oxadiazoloquinoxalin-1-one, prior to [C(12)mim]Br exposure showed the regulation of ROS by the activation of membrane bound NADPH-oxidase and cytochrome oxidase. The IL exposure resulted in the accumulation of n-3 and n-6 fatty acids at 0.5 LC(50) concentration indicating the induction of desaturase enzymes. Furthermore, antioxidant enzyme activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR) were enhanced by 1.3-2.0-fold, while glutathione peroxidase (GSH-Px) diminished, together with a higher regeneration rate of reduced ascorbate and glutathione. The isoforms of antioxidant enzymes, namely, Mn-SOD (85 kDa), APX (125 and 45 kDa), and GR (135 kDa) regulated differentially to IL exposure. The comet assay performed for the first time for seaweeds revealed the significant induction of DNA damage (>50-70% increase in % tail DNA over control) in alga exposed to ≥ LC(50) concentration.
由于越来越多的证据表明离子液体（ILs）对水生生态系统具有毒性，尽管其毒性机制尚不清楚，但它们的绿色环保资质正受到越来越多的质疑。本研究深入探讨了 1-烷基-3-甲基咪唑溴盐[C(n)mim]Br（n=4 至 16）对海洋大型藻类浒苔的毒性机制和生物效应。研究发现，在 IL 暴露过程中，这种藻类的细胞活力与烷基链的长度呈负相关。IL([C(12)mim]Br)暴露会引发活性氧物种（ROS，如 O(2)(•-), H(2)O(2 和 OH(•))的产生、细胞膜和 DNA 的损伤以及藻类抗氧化系统的抑制。在暴露于 LC(50)浓度 4 天的藻类中，ROS 和脂质过氧化产物的大量产生主要归因于脂氧合酶（LOX）活性与两种 LOX 同工型（80 kDa 和55 kDa）的诱导。在 [C(12)mim]Br 暴露之前，用酶抑制剂如二苯碘鎓、叠氮化钠、斑蝥素和恶二唑并喹喔啉-1-酮对藻体进行预处理，结果表明 ROS 是通过激活膜结合型 NADPH-氧化酶和细胞色素氧化酶来调节的。IL 暴露导致 0.5 LC(50)浓度下 n-3 和 n-6 脂肪酸的积累，表明去饱和酶的诱导。此外，超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APX）和谷胱甘肽还原酶（GR）等抗氧化酶活性增强了 1.3-2.0 倍，而谷胱甘肽过氧化物酶（GSH-Px）减少，同时还原型抗坏血酸和谷胱甘肽的再生率更高。抗氧化酶同工型，即 Mn-SOD（85 kDa）、APX（125 和 45 kDa）和 GR（~135 kDa），对 IL 暴露的调节方式不同。首次对海藻进行的彗星试验显示，暴露于≥LC(50)浓度的藻类中，DNA 损伤显著增加（与对照相比，%尾 DNA 增加超过 50-70%）。
