Studies on the detection of okadaic acid in mussels: preliminary comparison of bioassays

Okadaic acid meet and greet: an insight into detection methods, response strategies and genotoxic effects in marine invertebrates

Harmful Algal Blooms (HABs) constitute one of the most important sources of contamination in the oceans, producing high concentrations of potentially harmful biotoxins that are accumulated across the food chains. One such biotoxin, Okadaic Acid (OA), is produced by marine dinoflagellates and subsequently accumulated within the tissues of filtering marine organisms feeding on HABs, rapidly spreading to their predators in the food chain and eventually reaching human consumers causing Diarrhetic Shellfish Poisoning (DSP) syndrome. While numerous studies have thoroughly evaluated the effects of OA in mammals, the attention drawn to marine organisms in this regard has been scarce, even though they constitute primary targets for this biotoxin. With this in mind, the present work aimed to provide a timely and comprehensive insight into the current literature on the effect of OA in marine invertebrates, along with the strategies developed by these organisms to respond to its toxic effect together with the most important methods and techniques used for OA detection and evaluation.

The CHROMEVALOA database: a resource for the evaluation of Okadaic Acid contamination in the marine environment based on the chromatin-associated transcriptome of the mussel Mytilus galloprovincialis

Okadaic Acid (OA) constitutes the main active principle in Diarrhetic Shellfish Poisoning (DSP) toxins produced during Harmful Algal Blooms (HABs), representing a serious threat for human consumers of edible shellfish. Furthermore, OA conveys critical deleterious effects for marine organisms due to its genotoxic potential. Many efforts have been dedicated to OA biomonitoring during the last three decades. However, it is only now with the current availability of detailed molecular information on DNA organization and the mechanisms involved in the maintenance of genome integrity, that a new arena starts opening up for the study of OA contamination. In the present work we address the links between OA genotoxicity and chromatin by combining Next Generation Sequencing (NGS) technologies and bioinformatics. To this end, we introduce CHROMEVALOAdb, a public database containing the chromatin-associated transcriptome of the mussel Mytilus galloprovincialis (a sentinel model organism) in response to OA exposure. This resource constitutes a leap forward for the development of chromatin-based biomarkers, paving the road towards the generation of powerful and sensitive tests for the detection and evaluation of the genotoxic effects of OA in coastal areas.

Piezoelectric Immunosensors for Toxins' Detection in Foodstuffs

The procedures of detecting trace concentrations of okadaic acid and staphylococcal enterotoxin A in foodstuffs by the piezoelectric immunosensors have been developed. The conditions for immobilizing antibodies to toxins on the surface of the sensors gold electrode have been facilitated. The calibration curves for the detection of okadaic acid and staphylococcal enterotoxin A are linear in the range of concentrations 5500 ng·ml-1 and 1-80 ng·ml-1, the limits of detection are 1.4 and 0.4 ng·ml-1 correspondingly. The time of analysis does not exceed 30 min. The sensors were tested in detecting okadaic acid in fish products and in detecting staphylococcal enterotoxin A in chicken meat and milk.

Specificity of the test based on modification of cell morphology for detection of lipophilic inhibitors of protein phosphatases

The test based on morphological changes in KB cells was assayed with different toxins. Only lipophilic inhibitors of protein phosphatases, such as okadaic acid or calyculin A, induced visible changes in cell morphology. The activity of contaminated mussel extracts on KB cells was evaluated comparatively by direct interpretation of morphological changes and by a colorimetric method estimating the number of viable cells after staining. The latter technique revealed interferences (not detected by the former) with mussel cytotoxins. These results show that the technique, based on determination of the minimal active concentration of toxic extracts inducing morphological changes, is more specific, faster and preferable to the determination of IC50 for the detection of protein phosphatase inhibitors in shellfish.