In vitro effects of hydrogen peroxide on the cochlear neurosensory epithelium of the guinea pig

Reactive oxygen species (ROS) have been postulated to be involved in drug o totoxicity and noise-induced hearing loss. Hydrogen peroxide (H2O2)-induced cell damage in the inner ear was investigated using the neurosensory epith elium of a guinea pig cochlea. Hair cells and supporting cells of the epith elium incubated in Hanks' balanced salt solution were viable up to 6 h. Aft er 2 h of treatment with 0.2 mM H2O2 about 85% of the outer hair cells lost their viability. in contrast inner hair cells slowly began to die after 2 h of H2O2 treatment. The Deiters cells and Hensen cells did not show any si gns of damage in the presence of H2O2. Nifedipine, a calcium channel blocke r, Quin-2 AM, an intracellular calcium chelator, and 2,2'-dipyridyl, a memb rane-permeable iron chelator, all provided partial protection against H2O2- induced outer hair cell death. The combination of both chelators showed an additional protective effect. The antioxidants N-acetylcysteine and glutath ione-monoethyl ester completely protected against H2O2 damage. These result s suggest that calcium, iron, and thiol homeostasis play a crucial role in hair cell death caused by H2O2. (C) 2000 Elsevier Science B.V. All rights r eserved.