Title

 

Authors

M. Pelin¹, S. Sosa¹, G. Decorti¹, A. Tubaro¹, C. Florio<sup>1

1</sup>Dept. of Life Sciences, University of Trieste, Italy

 

Abstract

Marine algal toxins include different groups of secondary metabolites produced by microscopic dinoflagellates that can pose significant threats to human health mainly through ingestion of contaminated seafood. Palytoxin (PLTX), found in Palythoa zoanthid corals and Ostreopsis dinoflagellates, has been associated to human poisonings after consumption of crabs and fish in tropical and subtropical areas. The most frequent symptoms include general malaise, gastrointestinal symptoms, myalgia, muscle cramps, cardiac dysfunctions, respiratory distress, cyanosis and, in some cases, death. The intestinal tract is one of the first in vivo targets of the toxin before its potential access into the bloodstream. Data on the intestinal absorption of PLTX necessary for the risk assessment associated with oral exposure to the toxin are lacking. Hence, the purpose of this study was to investigate the suitability of the human Caco-2 cells, an in vitro model of the human intestinal barrier, to investigate the oral bioavailability of PLTX. A detailed analysis of PLTX cytotoxic effects revealed a high sensitivity of the Caco-2 cell line. Indeed, 4 h exposure to the toxin concentration-dependently reduced mitochondrial activity (MTT assay, EC₅₀ of 4.5±0.2x10^-12 M), cell mass (SRB assay, EC₅₀ of 1.4±0.8x10^-11 M) and membrane integrity (LDH release, EC₅₀ of 4.5±1.4x10^-9 M; PI uptake, EC₅₀ of 1.0±0.8x10^-8 M). The impairment of mitochondrial activity induced by PLTX was probably caused by a sustained oxidative stress inducedby the toxin, since a concentration-dependent superoxide anion production was found after only 1 h toxin exposure. Exposing the cells to a low PLTX concentration (1.0x10^-11 M) for 1 up to 8 h, followed by a 24 h total recovery time in toxin-free medium, revealed that the loss of cell mass was only partially reversible. On the whole, these results indicate that, due to the high susceptibility to the cytotoxic effects of PLTX, Caco-2 cells do not represent an appropriate and reliable model for investigating the permeation of the intestinal barrier by the toxin.