DIRECT EFFECTS OF REACTIVE OXYGEN SPECIES ON COCHLEAR OUTER HAIR CELL-SHAPE IN-VITRO

Reactive oxygen species (ROS) have been implicated in the ototoxicity of various agents. This study examines the effects of superoxide anion (O-2(.)), hydroxyl radical (OH.) and hydrogen peroxide (H2O2), on iso lated cochlear outer hair cell (OHC) morphology. OHCs were superfused with artificial perilymph (AP) or AP containing a specific ROS scaveng er, and then with AP, ROS system or scavenger plus ROS system for 90 m in. The generation of ROS as well as the scavenging properties of othe r agents were confirmed by specific biochemical assays. Control cells decreased 4.8% in mean length, and showed no obvious membrane damage. Generation of O-2(.) Or OH. resulted in high rates (85.7 and 42.9%, re spectively) of bleb formation at the synaptic pole, and decreased (O-2 (.), 15.2%; OH.; 17.3%) mean cell length. Length change and bleb forma tion rate were H2O2 concentration-dependent. 20 mM H2O2 led to 33.3% d ecreased mean cell length, and only 20% bleb formation; 0.1 mM H2O2 le d to 83.3% bleb formation, with no length decrease. Superoxide dismuta se, deferoxamine and catalase protected against O-2(.), OH. and H2O2 e ffects, respectively. Bleb formation and diminished cell length likely represent differential lipid peroxidative outcomes at supra- and infr anuclear membranes, and are consistent with effects of certain ototoxi cants.