Cytotoxic and membrane-disruptive properties of Prymnesium parvum extracts

The ichthyotoxic microalga Prymnesium parvum is known to produce a group of complex polyether compounds, called prymnesins. These toxins are known to affect biological membranes, leading to the disruption of membrane integrity in e.g. fish gill tissues. Due to the lack of purified compounds, methanolic extracts of P. parvum (PRM) were applied at varying toxin levels to gain further insights into their cytotoxicity. Molecular studies indicated that PRM can interact with membrane phospholipids and sterols, destabilising the bilayer structure and leading to uncontrolled ion fluxes and cell lysis. To study the underlying features of the cell membrane’s susceptibility to PRM, a set of fluorescence microscopic assays was set up in the rainbow trout-derived gill epithelial cell line, RTgill-W1. Cytotoxicity/loss of membrane integrity was quantified based on the cellular uptake of propidium iodide, Hoechst33342 staining for nuclear morpology and apoptotic cells were detected with AnnexinV staining. Our results demonstrated a concentration-dependent shift in the dominant mode of cell death, where lower toxin levels predominantly triggered apoptosis, characterised by nuclear morphological changes, a decrease in mitochondrial mass, and Annexin V staining. The pH backslide of the lysosomal vesicles might serve as an amplifier of the process. Whereas higher toxin concentrations trigger necrosis, marked by rapid membrane rupture and loss of cellular integrity. These findings highlight the dual nature of toxin-mediated cytotoxicity and underscore the importance of concentrations in determining cellular outcomes. The modifications in membrane integrity and permeability significantly impact both the functional and structural viability of cells, thereby influencing fish survival.

• Mass Spectrometry
• VetImaging