Bojadzija Savic Gorenka, Colinet Hervé, Bormans Myriam, Edwards Christine, Lawton Linda A, Briand Enora, Wiegand Claudia
UMR ECOBIO, 6553 CNRS, Université de Rennes 1, Campus de Beaulieu, Rennes, France.
School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen, AB10 7GJ, United Kingdom.
Toxicon. 2021 May;195:37-47. doi: 10.1016/j.toxicon.2021.03.009. Epub 2021 Mar 11.
Primary consumers in freshwater ecosystems, such as the zooplankton organism Daphnia magna, are highly affected by cyanobacteria, both as they may use it as a food source but also by cyanobacterial metabolites present in the water. Here, we investigate the impacts of cyanobacterial metabolites focussing on the environmental realistic scenario of the naturally released mixture without crushing cyanobacterial cells or their uptake as food. Therefore, D. magna were exposed to two concentrations of cell free cyanobacterial spent medium from Microcystis aeruginosa PCC 7806 to represent higher and lower ecologically-relevant concentrations of cyanobacterial metabolites. Including microcystin-LR, 11 metabolites have been detected of which 5 were quantified. Hypothesising concentration and time dependent negative impact, survival, gene expression marking digestion and metabolism, oxidative stress response, cell cycle and molting as well as activities of detoxification and antioxidant enzymes were followed for 7 days. D. magna suffered from oxidative stress as both catalase and glutathione S-transferase enzyme activities significantly decreased, suggesting enzyme exhaustibility after 3 and 7 days. Moreover, gene-expressions of the 4 stress markers (glutathione S-transferase, glutathione peroxidase, catalase and thioredoxin) were merely downregulated after 7 days of exposure. Energy allocation (expression of glyceraldehyde-3-phosphate dehydrogenase) was increased after 3 days but decreased as well after 7 days exposure. Cell cycle was impacted time dependently but differently by the two concentrations, along with an increasing downregulation of myosin heavy chain responsible for cell arrangement and muscular movements. Deregulation of nuclear hormone receptor genes indicate that D. magna hormonal steering including molting seemed impaired despite no detection of microviridin J in the extracts. As a consequence of all those responses and presumably of more than investigated molecular and physiological changes, D. magna survival was impaired over time, in a concentration dependent manner. Our results confirm that besides microcystin-LR, other secondary metabolites contribute to negative impact on D. magna survival and stress response.
淡水生态系统中的初级消费者，如浮游动物大型溞，会受到蓝藻的严重影响，这既体现在它们可能将蓝藻作为食物来源，也体现在水中存在的蓝藻代谢产物上。在此，我们聚焦于自然释放的混合物这一环境现实情景，研究蓝藻代谢产物的影响，该情景不涉及破碎蓝藻细胞或其作为食物被摄取。因此，大型溞暴露于两种浓度的来自铜绿微囊藻PCC 7806的无细胞蓝藻用过的培养基中，以代表蓝藻代谢产物在生态上相关的较高和较低浓度。包括微囊藻毒素-LR在内，已检测到11种代谢产物，其中5种被定量。假设存在浓度和时间依赖性的负面影响，对大型溞的生存、标记消化和代谢的基因表达、氧化应激反应、细胞周期和蜕皮以及解毒和抗氧化酶的活性进行了7天的跟踪研究。大型溞遭受氧化应激，因为过氧化氢酶和谷胱甘肽S-转移酶的酶活性均显著降低，这表明在3天和7天后酶已耗尽。此外，在暴露7天后，4种应激标记物（谷胱甘肽S-转移酶、谷胱甘肽过氧化物酶、过氧化氢酶和硫氧还蛋白）的基因表达仅被下调。能量分配（3-磷酸甘油醛脱氢酶的表达）在3天后增加，但在暴露7天后也下降。细胞周期受到时间依赖性影响，但两种浓度的影响不同，同时负责细胞排列和肌肉运动的肌球蛋白重链的下调也在增加。核激素受体基因失调表明，尽管提取物中未检测到微病毒素J，但大型溞的激素调控（包括蜕皮）似乎受到了损害。由于所有这些反应以及可能还有更多未研究的分子和生理变化，大型溞的生存随着时间的推移受到损害，且呈浓度依赖性。我们的结果证实，除了微囊藻毒素-LR外，其他次生代谢产物也会对大型溞的生存和应激反应产生负面影响。
