Production of Functionally Active Palytoxin-like Compounds by Mediterranean <i>Ostreopsis cf. siamensis</i>

Abstract

Background and purpose: Dinoflagellates from the genus Ostreopsis have been related to the production of palytoxin and analogues. Based on that, this paper describes functional studies of crude extracts from Ostreopsis cf. siamensis collected in the Mediterranean Sea in order to biochemically characterize their toxic compounds. Methods: We compared the effects of 5 crude dinoflagellates extracts with a commercially available palytoxin and a purified Ostreopsis ovata extract on metabolic activity, membrane potential, and cytosolic calcium levels by using fluorescent dyes. Results: All the extracts resulted to be neurotoxic. In addition, all of them induced a membrane depolarization and a calcium increment that were abolished when preincubating with ouabain, an inhibitor of the Na⁺/K⁺ pump. Conclusion: The effects observed were quite close to those induced by palytoxin and the Ostreopsis ovata extract as well, suggesting that Ostreopsis cf. siamensis is actually producing palytoxin-like compounds that are highly toxic and functionally active.

Palytoxin and Analogs: Biological and Ecological Effects

“…Respiratory illness has also occurred when people were exposed to Ostreopsis ovata bloom aerosols during recreational or working activities, in Italy [47]. Symptoms caused by ovatoxin-a from aerosols include fever associated to serious respiratory disturbs, such as bronchoconstriction, mild dyspnea, and wheezes, while conjunctivitis was observed in some cases [11,47,48]. These reports highlight the existence of new routes of exposure to PTX and its analogs while it alerts for the risks experienced by aquarium hobbyists by keeping zoanthid in these artificial ecosystems.…”

Warm Seawater Microalgae: Growth and Toxic Profile of Ostreopsis Spp. from European Coasts

“…It was described that only the Japanese O. siamensis produces ostreocin [34], however other studies demonstrate that also Mediterranean O. siamensis synthesizes this toxin [13,35,36]. In addition PLTX or putative PLTX (depending on the author) have been identified in this specie [4,37,38].…”

“…ovata produces more PLTX-like compounds than O. siamensis. It is known that these two species produce different PLTX analoges, O. ovata produces ovatoxin-a [36,39] while ostreocin-d is synthesized by O. siamensis [34,40]. Probably these two PLTX-like compounds have different affinity for the Na,K-ATPase.…”

Detection of palytoxin-like compounds by a flow cytometry-based immunoassay supported by functional and analytical methods

“…O. cf. siamensis toxicity has been previously reported using different techniques that point to the presence of PLTX-like molecules, however, none of these works found them when using analytical methods [23,49,50], probably due to sensitivity issues or to the lack of standards.…”