PGE2-induced apoptotic cell death in k562 human leukaemia cells

Prostaglandin-E-2 (PGE(2)) is known to trigger suicidal death of nucleated cells (apoptosis) and enucleated erythrocytes (eryptosis). In erythrocytes PGE(2) induced suicidal cell death involves activation of nonselective cation channels leading to Ca2+ entry followed by cell shrinkage and triggering of Ca2+ sensitive cell membrane scrambling with phosphatidylserine (PS) exposure at the cell surface. The present study was performed to explore whether PGE(2) induces apoptosis of nucleated cells similarly through cation channel activation and to possibly disclose the molecular identity of the cation channels involved. To this end, Ca2+ activity was estimated from Fluo3 fluorescence, mitochondrial potential from DePsipher fluorescence, phosphatidylserine exposure from annexin binding, caspase activation from caspAce fluorescence, cell volume from FACS forward scatter, and DNA fragmentation utilizing a photometric enzyme immunoassay. Stimulation of K562 human leukaemia cells with PGE(2) (50 mu M) increased cytosolic Ca2+ activity, decreased forward scatter, depolarized the mitochondrial potential, increased annexin binding, led to caspase activation and resulted in DNA fragmentation. Gene silencing of the Ca2+-permeable transient receptor potential cation channel TRPC7 significantly blunted PGE(2)-induced triggering of PS exposure and DNA fragmentation. In conclusion, K562 cells express Ca2+-permeable TRPC7 channels, which are activated by PGE(2) and participate in the triggering of apoptosis. Copyright (c) 2006 S. Karger AG, Basel.