Prymnesins, produced by the haptophyte Prymnesium parvum, are considered responsible for fish kills when this species blooms. Although their toxic mechanism is not fully understood, membrane disruptive properties have been ascribed to A-type prymnesins. Currently it is suggested that pore-formation is the underlying cause of cell disruption. Here the hypothesis that A-, B-, and C-type prymnesins interact with sterols in order to create pores was tested. Prymnesin mixtures containing various analogs of the same type were applied in hemolysis and cytotoxicity assays using Atlantic salmon Salmo salar erythrocytes or rainbow trout RTgill-W1 cells. The hemolytic potency of the prymnesin types reflected their cytotoxic potential, with approximate concentrations reaching 50 % hemolysis (HC50) of 4 nM (A-type), 54 nM (C-type), and 600 nM (B-type). Variabilities in prymnesin profiles were shown to influence potency. Prymnesin-A (3 Cl) + 2 pentose + hexose was likely responsible for the strong toxicity of A-type samples. Co-incubation with cholesterol and epi-cholesterol pre-hemolysis reduced the potential by about 50 % irrespective of sterol concentration, suggesting interactions with sterols. However, this effect was not observed in RTgill-W1 toxicity. Treatment of RTgill-W1 cells with 10 µM lovastatin or 10 µM methyl-β-cyclodextrin-cholesterol modified cholesterol levels by 20-30 %. Regardless, prymnesin cytotoxicity remained unaltered in the modified cells. SPR data showed that B-type prymnesins likely bound with a single exponential decay while A-types seemed to have a more complex binding. Overall, interaction with cholesterol appeared to play only a partial role in the cytotoxic mechanism of pore-formation. It is suggested that prymnesins initially interact with cholesterol and stabilize pores through a subsequent, still unknown mechanism possibly including other membrane lipids or proteins.

中文翻译：

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甾醇与 prymnesins 的作用方式有多大相关性？


Prymnesins 由触生体 Prymnesium parvum 产生，被认为是该物种开花时鱼类死亡的原因。尽管它们的毒性机制尚不完全清楚，但膜破坏特性已被归因于 A 型 prymnesins。目前认为毛孔形成是细胞破坏的根本原因。这里检验了 A-、B-和 C 型吠吏素与甾醇相互作用以产生孔隙的假设。使用大西洋鲑鱼鲑鱼盐沼红细胞或虹鳟鱼 RTgill-W1 细胞将含有各种相同类型类似物的 Prymnesin 混合物应用于溶血和细胞毒性测定。prymnesin 类型的溶血效力反映了它们的细胞毒潜力，大约 4 nM （A 型）、54 nM （C 型） 和 600 nM （B 型） 的溶血浓度达到 50% 溶血 （HC50）。prymnesin 谱的可变性被证明会影响效力。Prymnesin-A （3 Cl） + 2 戊糖 + 己糖可能是 A 型样品具有强毒性的原因。与胆固醇和表皮胆固醇溶血前的共孵育使溶血前的可能性降低了约 50%，无论甾醇浓度如何，这表明与甾醇存在相互作用。然而，在 RTgill-W1 毒性中未观察到这种影响。用 10 μM 洛伐他汀或 10 μM 甲基-β-环糊精-胆固醇修饰的胆固醇水平处理 RTgill-W1 细胞 20-30 %。无论如何，prymnesin 细胞毒性在修饰的细胞中保持不变。SPR 数据显示，B 型 prymnesins 可能与单个指数衰变结合，而 A 型似乎具有更复杂的结合。总体而言，与胆固醇的相互作用似乎仅在孔形成的细胞毒机制中起部分作用。 研究表明，prymnesins 最初与胆固醇相互作用并通过随后的、仍然未知的机制稳定毛孔，可能包括其他膜脂质或蛋白质。