RESUMEN
BACKGROUND AND PURPOSE: In light of recent evidence suggesting that an upregulation of K+ efflux mediated by outward delayed rectifier (I(K)) channels promotes central neuronal apoptosis, we sought to test the possibility that blockers of I(K) channels might be neuroprotective against hypoxia/ischemia-induced neuronal death. METHODS: Membrane currents were recorded with the use of patch clamp recordings in cultured murine cortical neurons. Protective effects of K+ channel blockers were examined in rats subjected to transient middle cerebral artery occlusion followed by 14-day reperfusion. RESULTS: The K+ channel blocker tetraethylammonium (TEA) (5 mmol/L) selectively blocked I(K) without affecting N-methyl-D-aspartate receptor-mediated current or voltage-gated Ca2+ currents. Both TEA and a lipophilic K+ channel blocker, clofilium, attenuated neuronal apoptosis induced by hypoxia in vitro and infarct volume induced by ischemia in vivo. CONCLUSIONS: These data are consistent with the idea that K+ channel-mediated K+ efflux may contribute to ischemia-triggered apoptosis and suggest that preventing excessive K+ efflux through K+ channels may constitute a therapeutic approach for the treatment of stroke.
Asunto(s)
Apoptosis/efectos de los fármacos , Isquemia Encefálica/tratamiento farmacológico , Hipoxia Encefálica/tratamiento farmacológico , Neuronas/efectos de los fármacos , Fármacos Neuroprotectores/uso terapéutico , Bloqueadores de los Canales de Potasio/uso terapéutico , Compuestos de Amonio Cuaternario/farmacología , Tetraetilamonio/farmacología , Animales , Isquemia Encefálica/patología , Calcio/metabolismo , Canales de Calcio/metabolismo , Señalización del Calcio/efectos de los fármacos , Arteria Carótida Común , Hipoxia de la Célula/efectos de los fármacos , Células Cultivadas/efectos de los fármacos , Células Cultivadas/patología , Corteza Cerebral/citología , Medios de Cultivo/farmacología , Evaluación Preclínica de Medicamentos , Glucosa/farmacología , Hipoxia Encefálica/patología , Infarto de la Arteria Cerebral Media/complicaciones , Infarto de la Arteria Cerebral Media/tratamiento farmacológico , Infarto de la Arteria Cerebral Media/patología , Transporte Iónico/efectos de los fármacos , Ligadura , Masculino , Ratones , Arteria Cerebral Media , Neuronas/patología , Fármacos Neuroprotectores/farmacología , Técnicas de Placa-Clamp , Potasio/metabolismo , Bloqueadores de los Canales de Potasio/farmacología , Ratas , Receptores de N-Metil-D-Aspartato/efectos de los fármacos , Receptores de N-Metil-D-Aspartato/fisiologíaRESUMEN
The relationship between intracellular Ca(2+) ([Ca(2+)](i)) regulation and programmed cell death is not well-defined; both increases and decreases in [Ca(2+)](i) have been observed in cells undergoing apoptosis. We determined [Ca(2+)](i) in cultured murine cortical neurons undergoing apoptosis after exposure to staurosporine or following oxygen-glucose deprivation in the presence of glutamate receptor antagonists. Neuronal [Ca(2+)](i) was decreased 1-4 h after exposure to staurosporine (30 nM). A [Ca(2+)](i) decrease was also observed 1 h after the end of the oxygen-glucose deprivation period when MK-801 and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were added to the bathing medium during the deprivation period. A similar decrease in [Ca(2+)](i) produced by reducing extracellular Ca(2+) or chelating intracellular Ca(2+) was sufficient to induce neuronal apoptosis. Raising [Ca(2+)](i) either by activating voltage-sensitive Ca(2+) channels with (-) Bay K8644 or by application of low concentrations of kainate attenuated both staurosporine and oxygen-glucose deprivation-induced apoptosis.