Effect of yessotoxin on cytosolic calcium levels in human hepatocellular carcinoma cells in vitro

Abstract

Abstract. Yessotoxin (YTX) and its analogs are a type of marine toxins found in marine environments in numerous coastal countries. These toxins tend to accumulate in filter-feeding molluscs and may threaten the shellfish industry and public health. Several previous studies indicated that YTX IntroductionYessotoxin (YTX) and its analogs are a group of lipophilic marine toxins mainly produced by the dinoflagellates Protoceratium reticulatum, Gonyaulax spinifera and Lingulodinium polyedrum. These toxins tend to accumulate in filter-feeding molluscs, have been found in numerous countries worldwide (1-6) and were first detected in shellfish samples collected from Chinese coastal areas in 2009 (7).YTX and its analogs were first isolated from Patinopecten yessoensis in Japan (8) and were long classified as one of the categories of diarrheic shellfish poisoning (DSP) toxins (9). However, as these toxins cannot induce diarrhea, nor inhibit protein phosphatase 2A, like other DSP toxins, they were classified as an independent group by the European Union Commission in 2002 (10).Apoptosis is a programmed form of cell suicide. The process of apoptosis is controlled by genes and is crucial in disease outbreaks, including cancer. Once the signaling pathway of apoptosis is activated, the process cannot be easily undergone, even by tumor cells. Thus, there is an increasing number of studies on tumor cell apoptosis, with the aim to design an effective cancer treatment (11-13). Several studies indicated that YTX may induce apoptosis in different types of cell lines (14-21). However, the exact underlying mechanisms have not been elucidated.As the chemical structure of YTX is similar to that of brevetoxins and ciguatoxins, which were shown to interfere with voltage-gated sodium channels, the effects of YTX on transmembrane ion channels were previously investigated (22,23). The present study mainly investigated the YTX-induced alterations in intracellular Ca 2+ levels in Bel7402 human hepatocellular carcinoma cells and the possible underlying mechanisms. Materials and methodsReagents. Pure YTX was purchased from the National Research Council (NRC; Ottawa, ON, Canada). Fluo-3 acetoxymethyl ester (AM) solution (5 mM) was purchased from Beyotime Institute of Biotechnology (Shanghai, China). Nifedipine was purchased from Sigma (St. Louis, MO, USA) and was dissolved in dimethyl sulfoxide (Merck KGaA, Darmstadt, Germany). All other chemicals were of analytical reagent grade or higher purity.The Hanks' balanced salt solution (HBSS) used for cell washing consisted of 137 mM NaCl, 5.6 mM KCl, 1.26 mM CaCl 2 , 0.81 mM MgSO 4 , 0.38 mM Na 2 HPO 4 , 0.44 mM KH 2 PO 4 and 4.2 mM NaHCO 3 . The pH of the HBSS was adjusted to 7.4 with 0.1 M HCl and NaOH.

Yessotoxin, a Promising Therapeutic Tool

“…However, in the tumor model erythroleukemia K-562 cell line, YTX did not directly modify cytosolic calcium levels, but it increased thapsigargin-independent calcium pools depletion, as well as the influx through store operated calcium channels [ 35 ]. A cytosolic calcium increase in the presence of YTX was also observed in HL7702 human liver cells, Bel7402 human hepatoma cell line and in primary cultures of rat cerebellar neurons [ 36 , 37 , 38 , 39 ]. However, no direct modification in calcium basal levels was observed in rat primary cardiomyocytes after YTX incubation [ 40 ].…”

Marine Heterocyclic Compounds That Modulate Intracellular Calcium Signals: Chemistry and Synthesis Approaches

“…Yessotoxin may modulate L -type Ca 2+ channels and also other types of Ca 2+ channels [ 58 ]. Yessotoxin also induced Ca 2+ influx and apoptosis in human hepatocellular carcinoma (Bel7402) cells, and this effect was blocked by external Ca 2+ chelation and nifedipine, thus suggesting that YTX-induced apoptosis is mediated by activating a Ca 2+ entry pathway and Ca 2+ overload [ 59 ].…”

Mitotic Catastrophe in BC3H1 Cells following Yessotoxin Exposure

“…YTX can induce different cell death modalities through activation of caspase-dependent and caspase-independent signaling pathways (Korsnes and Espenes, 2011 ; Korsnes et al, 2011 ; López et al, 2011 ; Tobío et al, 2012 ; Alonso et al, 2013 ). Cytotoxic effects vary significantly among cells exposed to it, depending on concentration and time of exposure (de la Rosa et al, 2001 ; Leira et al, 2002 ; Malaguti et al, 2002 ; Alfonso et al, 2003 ; Franchini et al, 2004 ; Callegari and Rossini, 2008 ; Ronzitti and Rossini, 2008 ; Orsi et al, 2010 ; Tubaro et al, 2010 ; Martín-López et al, 2012 ; Pang et al, 2014 ; Fernández-Araujo et al, 2015 ; Ferron et al, 2016 ). Anti-allergic and anti-tumoral activities inhibiting melanoma tumor growth and subacute immunotoxicity has been recently reported (Tobío et al, 2016 ; Ferreiro et al, 2017 ).…”