Ecotoxicological profiling of selected cyanobacterial strains using multi-endpoint effect-directed analysis

The main goal of this study was to perform an ecotoxicological profiling of terrestrial and aquatic cyanobacterial strains found in different soils or in toxic cyanobacterial blooms in Vojvodina region, Serbia, using the effect-directed analysis (EDA) approach. The applied procedure was based on a series of in vitro or small-scale bioassays covering multiple endpoints in combination with advanced chemical analytical protocols. Non-selective and non-target preparation techniques were used for the extraction of a broad range of chemical compounds present in three terrestrial (Anabaena Č2, Anabaena Č5, Nostoc S8) and three aquatic (Nostoc Z1, Phormidium Z2, Oscillatoria K3) strains. Ecotoxicological endpoints addressed included evaluation of the fish cytotoxicity in vitro (acute toxicity), algal growth inhibition (chronic toxicity), and interaction with cellular detoxification mechanisms. All cyanobacterial strains tested in the 1^st tier EDA showed significant effects in terms of chronic toxicity and interaction with cellular detoxification. Three major fractions of different polarities were further tested in the 2^nd tier, using bioassays which showed the strongest response: induction of CYP1A1 biotransformation enzyme and inhibition of zebrafish organic anion (Oatp1d1) and cation (Oct1) uptake transporters. Oscillatoria K3 strain was selected for a more detailed 3^rd tier EDA, and the obtained results revealed that positive sub-fractions possess polar anion and cation compounds that are reactive to both uptake transporters, and compounds responsible for the strongest effects have a pronounced lipophilic character. Apart from lipophilic non-polar compounds that represent typical phase I substrates, sub-fractions that contained polar substances are also shown to significantly induce CYP1A1.