Role Of Ion Channel In The Apoptotic Volume Decrease Of Cultured Hippocampal Neurons

Our previous studies have shown that activation of potassium channel is involved in the apoptosis of hippocampal neurons induced by in vivo ischemia and in vitro hypoxia. Recently, cell shrinkage is proposed as an early prerequisite to apoptotic events leading to cell death. To understand the mechanism underlying ionchannel-mediated neuronal apoptosis, the present study examined the temporal changes in neuronal cell body volume and the involvement of ion channels in the apoptotic volume decrease in a model of staurosporine (STS)-induced apoptosis of cultured hippocampal neurons. STS induced an early cell body volume decrease and this cell shrinkage was completely blocked by high extracellular K+, TEA or DIDS. Raising extracellular K+ concentration or tetraethylammonium (TEA, a nonselective potassium channel blocker) significantly prevented STS-induced neuronal cell death. Similar neuroprotections by treatment with the selective high-conductance calcium-activated potassium channel (BK) blockers iberiotoxin and paxilline was also observed whereas "A" current and SK channel blockers, 4-AP and apamin, showed no neuroprotective effect. Moreover, chloride channel blockers, DIDS and SITS, also significantly prevented STS-induced neuronal cell death. With whole-cell patch-clamp recordings, we found chloride channel currents increased significantly withtime when holding potential at 60mV and 80mV after 5min and 10 min of STS exposure. These results indicate that potassium channel, especially BK channels, and chloride channel contribute to STS-induced neuronal apoptosis and apoptotic volume decrease, which is probably one of the mechanisms underlying mediation of neuronal apoptosis by potassium channel...