NG108-15 cell-based and protein phosphatase inhibition assays as alternative semiquantitative tools for the screening of lipophilic toxins in mussels. Okadaic acid detection

Evaluation of okadaic acid, dinophysistoxin-1 and dinophysistoxin-2 toxicity on Neuro-2a, NG108-15 and MCF-7 cell lines

Marine dinoflagelates from the genus Dynophisis are important producers of Diarrhetic Shellfish Poisoning (DSP) toxins which are responsible for human intoxications. The present work is an approach to study the relative toxicity of DSP toxins effects on Neuro-2a, NG108-15 and MCF-7 cell-lines. Certified standards of okadaic acid (OA), dinophysistoxin-1 (DTX-1) and dinophysistoxin-2 (DTX-2) were used. Our results show that the three toxins exhibit similar cytotoxicity in Neuro-2a and NG108-15 cell lines. Conversely, MCF-7 cells were the least sensitive to these toxins. DTX-1 displayed the most toxic effect in the three tested cell lines.

Dinophysis toxins: causative organisms, distribution and fate in shellfish

Several Dinophysis species produce diarrhoetic toxins (okadaic acid and dinophysistoxins) and pectenotoxins, and cause gastointestinal illness, Diarrhetic Shellfish Poisoning (DSP), even at low cell densities (<103 cells·L⁻¹). They are the main threat, in terms of days of harvesting bans, to aquaculture in Northern Japan, Chile, and Europe. Toxicity and toxin profiles are very variable, more between strains than species. The distribution of DSP events mirrors that of shellfish production areas that have implemented toxin regulations, otherwise misinterpreted as bacterial or viral contamination. Field observations and laboratory experiments have shown that most of the toxins produced by Dinophysis are released into the medium, raising questions about the ecological role of extracelular toxins and their potential uptake by shellfish. Shellfish contamination results from a complex balance between food selection, adsorption, species-specific enzymatic transformations, and allometric processes. Highest risk areas are those combining Dinophysis strains with high cell content of okadaates, aquaculture with predominance of mytilids (good accumulators of toxins), and consumers who frequently include mussels in their diet. Regions including pectenotoxins in their regulated phycotoxins will suffer from much longer harvesting bans and from disloyal competition with production areas where these toxins have been deregulated.

A simple colorimetric enzymatic-assay for okadaic acid detection based on the immobilization of protein phosphatase 2A in sol-gel

Okadaic acid (OA), a lipophilic toxin, is produced by Dinophysis and Prorocentrum, and causes diarrheic shellfish poisoning to humans. The mechanism of OA action is based on the reversible inhibition of protein phosphatase type 2A (PP2A) by the toxin. Therefore, this inhibition could be used to develop assay for OA detection. In this work, a colorimetric test based on the PP2A inhibition was developed for OA detection. PP2A from GTP and Millipore was immobilized on silica sol-gel, and the detection was performed. A limit of detection of 0.29 and 1.14 μg/L was respectively observed for enzyme from GTP and Millipore. The immobilization technique provided a tool to preserve the enzymatic activity, which is very unstable in solution. The PP2A immobilized sol-gel exhibited a storage stability of near 5 months, when microtiter plate with enzyme-immobilized polymer was kept at -18C°. The combination of the simplicity of the colorimetric method, along with long storage stability achieved by sol-gel immobilization, demonstrated the potentiality of this technique to be used for commercial purpose.