Decreased cation channel activity and blunted channel-dependent eryptosis in neonatal erythrocytes

Abstract

Eryptosis or apoptosis-like death of erythrocytes is characterized by phosphatidylserine exposure and erythrocyte shrinkage, both typical features of nucleated apoptotic cells. Eryptosis is triggered by activation of nonselective Ca2+-permeable cation channels with subsequent entry of Ca2+and stimulation of Ca2+-sensitive scrambling of the cell membrane. The channels are activated and thus eryptosis is triggered by Cl−removal, osmotic shock, oxidative stress, or glucose deprivation. The present study has been performed to compare cation channel activity and susceptibility to eryptosis in neonatal and adult erythrocytes. Channel activity was determined by patch-clamp analysis, cytosolic Ca2+activity by fluo-3 fluorescence, phosphatidylserine exposure by FITC-labeled annexin V binding, and cell shrinkage by decrease in forward scatter in fluorescence-activated cell sorting analysis. Prostaglandin E2(PGE2) formation, cation channel activity, Ca2+entry, annexin V binding, and decreased forward scatter were triggered by removal of Cl−in both adult and neonatal erythrocytes. The effects were, however, significantly blunted in neonatal erythrocytes. Osmotic shock, PGE2,and platelet-activating factor similarly increased annexin V binding and decreased forward scatter, effects again significantly reduced in neonatal erythrocytes. On the other hand, spontaneous and oxidative (addition of tert-butylperoxide) stress-induced eryptosis was significantly larger in neonatal erythrocytes. In conclusion, cation channel activity, Ca2+leakage, and thus channel-dependent triggering of eryptosis are blunted, whereas spontaneous and oxidative stress-induced eryptosis is more pronounced in neonatal erythrocytes.