Cystine protects cochlear outer hair cells against glutamate toxicity.

We previously reported that long-term exposure to glutamate (Glu) induced death of cochlear outer hair cells (OHCs). However, the mechanisms of OHC death induced by Glu were unclear. In the central nervous system, Glu is known to interfere with a cystine-Glu antiporter, leading to a decrease in cystine uptake and reducing the intracellular glutathione level. We therefore investigated the effect of cystine supplementation on degeneration of OHCs caused by long-term exposure to Glu. Supplementation of cystine significantly decreased the number of dying OHCs. These findings suggest that a cystine-Glu interaction may be involved in the mechanism of OHC degeneration caused by Glu.