Yessotoxins: a toxicological overview.

Yessotoxins (YTXs) are polyciclic ether compounds produced by phytoplanktonic dinoflagellates and accumulated in filter feeding shellfish. These toxins can be ingested by humans through contaminated seafood consumption. Initially, YTXs were classified as Diarrhetic Shellfish (DS) toxins but the biological activity of these compounds, which lack of diarrheogenic effects, differs from that of diarrheic toxins. Thus, YTXs have been recently classified as a separate group of algal toxins. Yessotoxin (YTX), homoyessotoxin and 45-hydroxy-homoyessotoxin are lethal after intraperitoneal injection to mice but not after single or repeated oral administration. The target organ seems to be the cardiac muscle cells, where these toxins induce light and electron microscopy ultrastructural changes not only after intraperitoneal injection, but also after oral exposure. On the other hand, di-desulfo-yessotoxin affects liver and pancreas, where it induces fatty degeneration. The mechanisms at the basis of the cardiac effects of YTX and homoyessotoxins are still not completely understood. No short term and chronic toxicity data are available as well as pharmacokinetic studies are lacking. Nevertheless, YTX is known to exert different in vitro activities, such as changes of intracellular calcium and cyclic AMP levels, alteration of cytoskeletal and adhesion molecules, caspases activation and opening of the permeability transition pore of mitochondria. This review reports the current knowledge on the in vivo toxicity and in vitro effects of these toxins.