Cyanobacteria are known for their ability to produce and release mixtures of up to thousands of compounds into the environment. Recently, the production of novel metabolites, retinoids, was reported for some cyanobacterial species along with teratogenic effects of samples containing these compounds. Retinoids are natural endogenous substances derived from vitamin A that play a crucial role in early vertebrate development. Disruption of retinoid signalling- especially during the early development of the nervous system- might lead to major malfunctions and malformations. In this study, the toxicity of cyanobacterial biomass samples from the field containing retinoids was characterized by in vivo and in vitro bioassays with a focus on the potential hazards towards nervous system development and function. Additionally, in order to identify the compounds responsible for the observed in vitro and in vivo effects the complex cyanobacterial extracts were fractionated (C18 column, water-methanol gradient) and the twelve obtained fractions were tested in bioassays. In all bioassays, all-trans retinoic acid (ATRA) was tested along with the environmental samples as a positive control. Retinoid-like activity (mediated via the retinoic acid receptor, RAR) was measured in the transgenic cell line p19/A15. The in vitro assay showed retinoid-like activity by specific interaction with RAR for the biomass samples. Neurotoxic effects of selected samples were studied on zebrafish (Danio rerio) embryos using the light/dark transition test (Viewpoint, ZebraLab system) with 120 hpf larvae. In the behavioural assay, the cyanobacterial extracts caused significant hyperactivity in zebrafish at 120 hpf after acute exposure (3 h prior to the measurement) at concentrations below the teratogenicity LOEC (0.2 g dw L⁻¹). Similar effect was observed after exposure to fractions of the extracts with detected retinoid-like activity and additive effect was observed after combining the fractions. However, the effect on behaviour was not observed after exposure to ATRA only. To provide additional insight into the behavioural effects and describe the underlying mechanism gene expression of selected biomarkers was measured. We evaluated an array of 28 genes related to general toxicity, neurodevelopment, retinoid and thyroid signalling. We detected several affected genes, most notably, the Cyp26 enzymes that control endogenous ATRA concentration, which documents an effect on retinoid signalling.

蓝细菌以其产生和释放多达数千种化合物的混合物到环境中的能力而闻名。最近，据报道某些蓝细菌物种产生了新的代谢产物类维生素A，以及含有这些化合物的样品的致畸作用。类维生素A是衍生自维生素A的天然内源性物质，在脊椎动物的早期发育中起着至关重要的作用。类维生素A信号的破坏-尤其是在神经系统的早期发育期间-可能导致严重的功能失常和畸形。在这项研究中，通过体内和体外表征了含有类维生素A的蓝藻生物质样品的毒性生物测定法，侧重于对神经系统发育和功能的潜在危害。另外，为了鉴定负责观察到的体外和体内作用的化合物，将复杂的蓝细菌提取物进行分级分离（C18色谱柱，水-甲醇梯度洗脱），并在生物测定中测试十二个所得级分。在所有生物测定中，将全反式维甲酸（ATRA）与环境样品一起作为阳性对照进行测试。在转基因细胞系p19 / A15中测量类维生素A活性（通过视黄酸受体RAR介导）。在体外通过与RAR的特异性相互作用，生物质样品显示类维生素A活性。使用具有120 hpf幼虫的明/暗过渡测试（Viewpoint，ZebraLab系统），研究了所选样品对斑马鱼（Danio rerio）胚胎的神经毒性作用。在行为分析中，在低于致畸性LOEC（0.2 g dw L ^-1）的浓度下，急性暴露后（测量前3 h）时120 hpf，蓝细菌提取物在斑马鱼中引起明显的过度活跃。）。暴露于具有检测到的类维生素A活性的提取物级分后，观察到相似的效果，合并这些级分后，观察到加合效果。但是，仅暴露于ATRA后未观察到对行为的影响。为了提供对行为影响的进一步了解并描述潜在机制，对所选生物标志物的基因表达进行了测量。我们评估了28种与一般毒性，神经发育，类维生素A和甲状腺信号转导相关的基因。我们检测到了几种受影响的基因，最著名的是控制内源性ATRA浓度的Cyp26酶，该酶记录了类视黄醇信号传导的影响。