Mechanism of gentamicin-induced ototoxicity in the differentiated vestibular cell line(UB/UE-1) : Expression of caveolin-1 and heme oxygenase-1

초록

Objectives : Oxidative stress is an important mechanism of aminoglycoside-induced ototoxicity and recent studies have suggested that free radicals-reactive oxygen species and reactive nitrogen species are the triggers of inner ear hair cell damage. We investigated the expression of caveolin-1, an inhibitory modulator of various signaling pathways, and heme oxygenase-1 (HO-1), a protector to oxidative stress, of differentiated vestibular cell lines (UB/UE-1) during in vitro exposure to gentamicin. PKA inhibitor (H89) was used to investigate the relationship of PKA signaling pathway and caveolin-1 expression, and buthionine sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, and N-acetyl cysteine (NAC), a glutathione precursor, were used to investigate the role GSH redox cycle in protection against the gentamicin toxicity. Study design : UB/UE-1 cells were cultured at 33˚C for 2days and at 39˚C for 24 hours for differentiation. Cells were treated with 1mM of gentamicin, 0.1mM BSO, and 2.5mM NAC, 0.02mM H89, and then incubated for 24hours. Caveolin-1 and HO-1 expressions were examined by western blot. Results : Caveolin-1 was expressed spontaneously in differentiated UB/UE-1 cells and increased after gentamicin treatment. The gentamicin-induced caveolin-1 expression was inhibited by H89 and NAC. HO-1 is induced higher in the group of both gentamicin and H89 treatment than gentamicin or H89 alone, and BSO enhanced expression of HO-1. Conclusions : Our results indicate that gentamicin-induced caveolin-1 expression is mediated by PKA, and HO-1 induction can be increased by inhibition of PKA activity and GSH depletion. We conclude that the caveolin-1 and HO-1 expression through a PKA signaling pathway is the important mechanism of gentamicin ototoxicity. Moreover, the glutathione redox cycle may have a protecting effect against gentamicin-induced oxidative stress.