Inhibition of the calcium- and voltage-dependent big conductance potassium channel ameliorates cisplatin-induced apoptosis in spiral ligament fibrocytes of the cochlea.
The role of calcium- and voltage-dependent big conductance potassium channels in regulating apoptosis was investigated in cultured type I spiral ligament fibrocytes. Incubation of type I spiral ligament fibrocytes derived from gerbil cochlea with cisplatin induced dose- and time-dependent apoptosis as demonstrated by annexin V conjugated to fluorescein isothiocyanate/prodidium iodide assays. The average voltage activation threshold of whole cell current was sharply shifted to -40 mV in the cisplatin-treated cells as compared with a value of 40 mV in control cells. The average whole-cell current of cisplatin-treated cells induced by a depolarization voltage step from -80 to -10 mV was increased significantly to 1.2+/-0.4 nA as compared with 0.08+/-0.1 nA in control cells. Coincubation with tetraethylammonium and cisplatin retained the whole cell current in the normal range (0.12+/-0.2 nA). The increment of cisplatin-induced whole-cell current was inhibited (97+/-5%) by a specific calcium- and voltage-dependent big conductance potassium channel blocker iberiotoxin. Consistent with this, co-incubation with tetraethylammonium significantly attenuated cisplatin-induced apoptosis in type I spiral ligament fibrocytes by more than 50%. We conclude that the activation of BK channels is an early event associated with cisplatin-induced apoptosis in type I spiral ligament fibrocytes. These findings also point to the calcium- and voltage-dependent big conductance potassium channels as a potential pharmacological target for manipulating cisplatin ototoxicity.
Liang
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Department of Pathology and Laboratory Medicine, 165 Ashley Avenue, Suite 309, PO Box 250908, Charleston, SC 29425, USA.
Schulte
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BA
Qu
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C
Hu
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Shen
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D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D002945:Cisplatin / Q000037:antagonists & inhibitors* / Q000633:toxicity; D003051:Cochlea / Q000166:cytology* / Q000187:drug effects; D004594:Electrophysiology; D005260:Female; D005434:Flow Cytometry; D005849:Gerbillinae; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects*; D008297:Male; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D009412:Nerve Fibers / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects*
D017304:Annexin A5; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D002945:Cisplatin