Characterization of distinct apoptotic changes induced by okadaic acid and yessotoxin in the BE(2)-M17 neuroblastoma cell line

Abstract Apoptotic changes induced by okadaic acid and yessotoxin in BE(2)-M17 neuroblastoma cells have been evaluated and quantified by combining classical methods and fast and sensitive fluorimetric microplate assays. The phosphatase inhibitor okadaic acid induced rapid time- and dose-dependent apoptotic changes in this cell line, which were evident after 1 h at concentrations equal or higher than 500 n m . Decreased mitochondrial membrane potential by okadaic acid (IC 50 =350 n m at 1 h) was followed by cell detachment (IC 50 =400 n m at 1 h), changes in total nucleic acids content (50% of controls after 1 h with 1000 n m okadaic acid), caspase-3 activation (3- to 4-fold increase at 6 h) and increased Annexin-V binding (1.5-fold at 6 h). Yessotoxin induced similar changes in BE(2)-M17 cells, although significant differences were found in the time-course and degree of apoptotic events induced by this phycotoxin, indicating a lower potency for yessotoxin when compared with okadaic acid. This is the first report on apoptogenic activity of yessotoxin.