Effects of SERCA and PMCA inhibitors on the survival of rat cochlear hair cells during ischemia in vitro.
An important mechanism underlying cochlear hair cell (HC) susceptibility to hypoxia/ischemia is the influx of Ca(2+). Two main ATP-dependent mechanisms contribute to maintaining low Ca(2+) levels: uptake of Ca(2+) into intracellular stores via smooth endoplasmic reticulum calcium ATPase (SERCA) and extrusion of Ca(2+) via plasma membrane calcium ATPase (PMCA). The effects of the SERCA inhibitors thapsigargin (10 nM-10 microM) and cyclopiazonic acid (CPA; 10-50 microM) and of the PMCA blockers eosin (1.5-10 microM) and o-vanadate (1-5 mM) on inner and outer hair cells (IHCs/OHCs) were examined in normoxia and ischemia using an in vitro model of the newborn rat cochlea. Exposure of the cultures to ischemia resulted in a significant loss of HCs. Thapsigargin and CPA had no effect. Eosin decreased the numbers of IHCs and OHCs by up to 25 % in normoxia and significantly aggravated the ischemia-induced damage to IHCs at 5 and 10 microM and to OHCs at 10 microM. o-Vanadate had no effect on IHC and OHC counts in normoxia, but aggravated the ischemia-induced HC loss in a dose-dependent manner. The effects of eosin and o-vanadate indicate that PMCA has an important role to play in protecting the HCs from ischemic cell death.
Amarjargal
N
N
Molecular Biological Research Laboratory, Department of Otorhinolaryngology, Charité - University Medicine Berlin, Campus Charité Mitte, Berlin, Germany.
Mazurek
B
B
Haupt
H
H
Andreeva
N
N
Fuchs
J
J
Gross
J
J
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004801:Eosine Yellowish-(YS) / Q000494:pharmacology; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects*; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects*; D066298:In Vitro Techniques; D007511:Ischemia / Q000201:enzymology*; D009925:Organ of Corti / Q000166:cytology / Q000502:physiology; D010498:Perilymph / Q000502:physiology; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D051381:Rats; D017208:Rats, Wistar; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D014638:Vanadates / Q000494:pharmacology
D004791:Enzyme Inhibitors; D014638:Vanadates; D053499:Plasma Membrane Calcium-Transporting ATPases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium; D004801:Eosine Yellowish-(YS)