Induction of apoptosis using sphingolipids activates a chloride current in Xenopus laevis oocytes

1 Laboratoire de Pharmacologie, Faculté de Médecine Paris Sud 94275; 2 Service de Cardiologie A, Hôpital Broussais 75014; and 3 Service de Cardiologie, Hôpital Lariboisière, 75475 Paris, France The purpose of this study was to investigate whether the cell shrinkage that occurs during apoptosis could be explained by a change of the activity in ion transport pathways. We tested whether sphingolipids, which are potent pro-apoptotic compounds, can activate ionic currents in Xenopus laevis oocytes. Apoptosis was characterized in our model by a decrease in cell volume, a loss of cell viability, and DNA cleavage. Oocytes were studied using voltage-clamp after injection with N , N -dimethyl- D -erythrosphingosine (DMS) or D -sphingosine (DS). DMS and DS activated a fast-activating, slowly inactivating, outwardly rectifying current, similar to I Cl-swell , a swelling-induced chloride current. Lowering the extracellular chloride dramatically reduced the current, and the channel was more selective for thiocyanate and iodide (thiocyanate > iodide) than for chloride. The current was blocked by 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) and lanthanum but not by niflumic acid. Oocytes injected with a pseudosubstrate inhibitor of protein kinase C (PKC), PKC-(19-31), exhibited the same current. DMS-activated current was abolished by preexposure with phorbol myristate acetate. Our results suggest that induction of apoptosis in X. laevis oocytes, using sphingolipids or PKC inhibitors, activates a current similar to swelling-induced chloride current previously described in oocytes. cell shrinkage; swelling-induced chloride channel; protein kinase C; deoxyribonucleic acid fragmentation