Erythrocyte phospholipid scrambling and cell swelling induced by CORM-2.

Human erythrocytes lack nuclei and mitochondria but may undergo suicidal cell death, called eryptosis and characterized by cell shrinkage and phospholipid scrambling of the cell membrane. Eryptosis is triggered by increase of cytosolic Ca2+-activity ([Ca2+]i).Carbon monoxide (CO) intoxication severely interferes with the oxygen transporting function of hemoglobin. Beyond that CO is involved in the regulation of apoptosis. CO could be generated from CO releasing molecules (CORM), such as the tricarbonyl-dichlororuthenium (II) dimer (CORM-2), which is presently considered for the treatment of vascular dysfunction, inflammation, tissue ischaemia and organ rejection. CORM-2 is at least partially effective by modifying gene expression and mitochondrial potential. The present study explored, whether CORM-2 influences eryptosis. To this end, [Ca2+]i was estimated from Fluo3-fluorescence, cell volume from forward scatter, phospholipid scrambling from annexin-V-binding and hemolysis from haemoglobin release. CO binding hemoglobin (COHb) was estimated utilizing a blood gas analyzer. As a result, exposure of erythrocytes for 48 hours to CORM-2 (≥5µM) significantly increased COHb, [Ca2+]i, forward scatter, annexin-V-binding and hemolysis. Annexin-V-binding was significantly blunted by 100% oxygen and was virtually abolished in the nominal absence of Ca2+. In conclusion, CORM-2 stimulates cell membrane scrambling of erythrocytes, an effect largely due to Ca2+ entry and partially reversed by O2.