Ovatoxin-a, A Palytoxin Analogue Isolated from Ostreopsis cf. ovata Fukuyo: Cytotoxic Activity and ELISA Detection

Abstract

This study provides the first evaluation of the cytotoxic effects of the recently identified palytoxin (PLTX) analog, ovatoxin-a (OVTX-a), the major toxin produced by Ostreopsis cf. ovata in the Mediterranean Sea. Its increasing detection during Ostreopsis blooms and in seafood highlights the need to characterize its toxic effects and to set up appropriate detection methods. OVTX-a is about 100 fold less potent than PLTX in reducing HaCaT cells viability (EC50 = 1.1 × 10(-9) M vs 1.8 × 10(-11) M, MTT test) in agreement with a reduced binding affinity (Kd = 1.2 × 10(-9) vs 2.7 × 10(-11) M, saturation experiments on intact cells). Similarly, OVTX-a hemolytic effect is lower than that of the reference PLTX compound. Ost-D shows the lowest cytotoxicity toward HaCaT keratinocytes, suggesting the lack of a hydroxyl group at C44 as a critical feature for PLTXs cytotoxic effects. A sandwich ELISA developed for PLTX detects also OVTX-a in a sensitive (LOD = 4.2 and LOQ = 5.6 ng/mL) and accurate manner (Bias = 0.3%), also in O. cf. ovata extracts and contaminated mussels. Although in vitro OVTX-a appears less toxic than PLTX, its cytotoxicity at nanomolar concentrations after short exposure time rises some concern for human health. The sandwich ELISA can be a viable screening method for OVTXs detection in monitoring program.

Ostreopsis fattorussoi sp. nov. (Dinophyceae), a new benthic toxic Ostreopsis species from the eastern Mediterranean Sea

“…, Pelin et al. ). Several laboratory studies have shown that Ostreopsis exerts toxicity also on several marine organisms, both invertebrates and vertebrates (Faimali et al.…”

Ostreopsis cf. ovata (Dinophyceae) Molecular Phylogeny, Morphology, and Detection of Ovatoxins in Strains and Field Samples from Brazil

“…The toxicity data of ovatoxins is limited, as only ovatoxin-a has been isolated in a sufficient amount for full structure elucidation (the other OVTXs are minor congeners) and it is possible that different analogues may present different toxin potencies [48]. Considering the biological activity, OVTX-a hemolytic effect was shown to be lower than that of the reference PLTX compound, and a study using HaCaT cells viability indicated that OVTX-a is about 100-fold less potent than PLTX, but it is more toxic than Ostreocin-d (another PLTX analogue) [49].…”

Human Poisoning from Marine Toxins: Unknowns for Optimal Consumer Protection

“…Recent in vivo studies report a lower toxic potency of ostreocin-D by several administration routes, although LD 50 values are not provided [ 244 ]. Only in vitro studies are available for ovatoxin-a, which has shown 100-fold less toxic potency than PLTX in a skin keratinocyte cell line [ 255 ].…”