Minocycline prevents gentamicin-induced ototoxicity by inhibiting p38 MAP kinase phosphorylation and caspase 3 activation.

Aminoglycosides are commonly used antibiotics that often induce ototoxicity leading to permanent hair cell loss and hearing impairment. We hereby examined whether minocycline protects hair cells from gentamicin-induced hair cell damage. Two millimolar gentamicin significantly induced outer hair cell damage and the addition of minocycline to gentamicin-treated explants significantly increased hair cell survival in a dose-dependent manner. Additionally, we demonstrated that gentamicin induced p38 MAPK phosphorylation, cytochrome c release, and caspase 3 activation in these cells and these remarkable changes were blocked by minocycline treatments. Furthermore, we showed that the inhibitor of p38 MAPK or the inhibitor of caspase 3 only partially blocked gentamicin-induced hair cell damage, and the pretreatment of explants with the inhibitor of p38 MAPK and the inhibitor of caspase 3 together exerted a synergic protective effect against gentamicin-induced hair cell damage. Our results suggest that minocycline blocks gentamicin-induced hair cell loss possibly by inhibition of three mechanisms: p38 MAPK phosphorylation, cytochrome c release, and caspase 3 activation. This finding may explain why minocycline has protective activity in a variety of apoptotic models. Therapeutic intervention by using minocycline or related drugs may be a novel means for preventing inner ear injury following the use of aminoglycoside.