Beauvericin induced erythrocyte cell membrane scrambling

Beauvericin is a mycotoxin with antiviral, antibacterial, nematicidal, insecticidal, cytotoxic, and apoptotic activity. Similar to nucleated cells erythrocytes may undergo suicidal death or eryptosis, which is characterized by cell shrinkage and phosphatidylserine exposure at the erythrocyte surface. Eryptosis may be triggered by energy depletion leading to increase of cytosolic Ca2+ activity. The present study thus explored whether beauvericin is able to trigger eryptosis and influence eryptosis following energy depletion. Cell membrane scrambling was estimated from binding of annexin V to phosphatidylserine at the erythrocyte surface, cell volume from forward scatter in FACS analysis, cytosolic Ca2+ concentration from Fluo3 fluorescence, cytosolic ATP concentration from a luciferase-assay and ion channel activity with whole cell patch clamp. Exposure to beauvericin (≥5 μM) significantly decreased erythrocyte ATP concentration and increased cytosolic Ca2+ concentration as well as annexin V-binding. The effect of beauvericin on annexin V binding was significantly blunted by removal of extracellular Ca2+. Glucose depletion (48 h) was followed by, increase of Fluo3 fluorescence, decrease of forward scatter and increase of annexin V-binding. Beauvericin (≥1 μM) augmented the effect of glucose withdrawal on Fluo3 fluorescence and annexin V-binding, but significantly blunted the effect of glucose withdrawal on forward scatter, an effect paralleled by inhibition of Ca2+ activated K+ channels. The present observations disclose novel effects of beauvericin, i.e. stimulation of Ca2+ entry with subsequent cell membrane scrambling and inhibition of Ca2+ activated K+ channels with blunting of cell shrinkage.