Department of Biochemistry, Microbiology and Molecular Biology, University of Maine, Orono, Maine 04469, USA.
Environ Toxicol. 2011 Oct;26(5):498-505. doi: 10.1002/tox.20578. Epub 2010 May 18.
Cyanobacteria are prevalent in the freshwater environment, reaching critical mass in harmful algal blooms. These organisms produce a variety of toxins including endotoxins such as lipopolysaccharides (LPS), which have been previously shown to decrease glutathione-S-transferase (GST) activity in zebrafish (Danio rerio) embryos. GST plays a vital role in detoxification response during oxidative stress and provides a first line of defense after toxic heavy metal insult, before increased metallothionein expression. Although some attention has focused on cyanobacterial LPS, little research has focused on effects of concurrent exposures with other toxicants. Because cyanobacterial LPS can alter detoxification enzymes including GST, we hypothesized that cyanobacterial LPS could potentiate metal toxicity. This study investigated the effects of LPS from two cyanobacterial species, Lyngbya spp. and Microcystis aeruginosa, on cadmium toxicity in zebrafish embryos. Forty-eight-hour CdCl(2) LC(50) values showed that coexposure of cadmium and Lyngbya LPS or Microcystis LPS resulted in significantly increased cadmium toxicity in comparison with cadmium alone. However, increased cadmium toxicity was not due to decreased GST activity as initially hypothesized. In concurrent Microcystis LPS-cadmium exposures, GST activity was significantly increased in comparison with control embryos at all time points and cadmium concentrations sampled. Concurrent Lyngbya LPS-cadmium exposures also resulted in increased GST activity at most exposure concentrations. These results indicate that regardless of mechanism, cyanobacterial LPS can potentiate the toxic effects of heavy metals. This represents a significant risk for aquatic organisms exposed to combinations of LPS and metals in the environment.
蓝藻普遍存在于淡水环境中，在有害藻类大量繁殖时达到临界点。这些生物产生多种毒素，包括内毒素如脂多糖（LPS），先前的研究表明 LPS 可降低斑马鱼（Danio rerio）胚胎中的谷胱甘肽-S-转移酶（GST）活性。GST 在氧化应激期间的解毒反应中起着至关重要的作用，并在有毒重金属损伤后提供第一道防线，然后增加金属硫蛋白的表达。尽管一些研究关注蓝藻 LPS 的作用，但很少有研究关注与其他毒物同时暴露的影响。由于蓝藻 LPS 可以改变包括 GST 在内的解毒酶，我们假设蓝藻 LPS 可以增强金属毒性。本研究调查了两种蓝藻，Lyngbya spp. 和微囊藻，的 LPS 对斑马鱼胚胎中镉毒性的影响。48 小时 CdCl 2 LC 50 值表明，与单独镉暴露相比，镉与 Lyngbya LPS 或微囊藻 LPS 共同暴露会导致镉毒性显著增加。然而，如最初假设的那样，增加的镉毒性不是由于 GST 活性降低所致。在同时存在微囊藻 LPS 和镉的暴露中，与对照胚胎相比，在所有时间点和采样的镉浓度下，GST 活性均显著增加。同时存在 Lyngbya LPS 和镉的暴露也导致 GST 活性在大多数暴露浓度下增加。这些结果表明，无论机制如何，蓝藻 LPS 都可以增强重金属的毒性作用。这代表了暴露于环境中 LPS 和金属组合的水生生物的重大风险。
