Gambogic acid, a xanthone from Garcinia hanburyi, stimulates apoptosis and has thus anticancer potency. Similar to apoptosis of nucleated cells, erythrocytes may undergo apoptosis-like suicidal death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine-exposure at the cell surface. Eryptosis could be triggered by increase of cytosolic Ca2+-activity ([Ca2+]i), ceramide formation, ATP-depletion and caspase activation. The present study explored, whether gambogic acid triggers eryptosis of human erythrocytes. [Ca2+]i was estimated utilizing Fluo-3 fluorescence, cell volume from forward scatter, phosphatidylserine-exposure from annexin-V-binding, hemolysis from hemoglobin release, ceramide abundance utilizing antibodies, and cytosolic ATP with luciferin– luciferase. A 48 h exposure to gambogic acid (500 nM) significantly increased [Ca2+]i, stimulated ceramide formation, decreased forward scatter and increased annexin-V-binding. Gambogic acid exposure was followed by a slight but significant increase of hemolysis. Gambogic acid did not significantly modify cytosolic ATP-concentration. Removal of extracellular Ca2+ slightly, but significantly blunted the effect of gambogic acid (500 nM) on annexin-V-binding. The present observations disclose a novel effect of gambogic acid, i.e. stimulation of suicidal death of human erythrocytes or eryptosis, paralleled by Ca2+-entry, ceramide formation, cell shrinkage and phosphatidylserine-exposure.

Keywords:
Phosphatidylserine, Gambogic acid, Eryptosis, Calcium, Cell volume
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© 2012 S. Karger AG, Basel
2012
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