Ether lipid-induced cell damage of neuroblastoma cells is only weakly correlated with increased intracellular Ca2+ levels

The cell-damaging action of the ether lipid ET-18-OCH3 was studied in single NH15-CA2 neuroblastoma x glioma hybrid cells using light microscopy, and correlated with changes of the free intracellular calcium concentration, [Ca2+](i), as measured with the fluorescent Ca2+ indicator Fura-2. Addition of 3-100 mu M ET-18-OCH3 to the cultures caused disintegration of neurites, cell rounding and detachment of the cells from the bottom of the culture dish. The effects occurred within 30-240 min, the faster, the higher the ET-18-OCH3 concentration. Also [Ca2+](i) increased in a concentration-dependent manner, however, within seconds, and stayed high during the recording time of 20 min. The presence of 50 mu M lanthanum or gadolinium ions prevented the ET-18-OCH3-induced increases of [Ca2+](i), but had no effect on neurite destruction and cell rounding. Preincubation with 1 mM diisopropylfluorphosphate or 100 mu M leupeptin, both membrane-permeant inhibitors of intracellular proteases, did not prevent the effects. Nor was neurite destruction prohibited in the presence of 10 mu M of the actin-stabilizing agent phalloidin or 2 mu M taxol, a microtubule-stabilizer. We conclude that [Ca2+](i), although being increased during ET-18-OCH3-induced cell damage, is not the key factor of cell destruction.