Adeno-associated virus-mediated Bcl-xL prevents aminoglycoside-induced hearing loss in mice.

Background: Recent studies showed that aminoglycosides destroyed the cochlear cells and induced ototoxicity by producing reactive oxygen species, including free radicals in the mitochondria, damaging the membrane of mitochondria and resulting in apoptotic cell death. Bcl-x(L) is a well characterized anti-apoptotic member of the Bcl-2 family. The aim of this study was to determine the potential cochlear protective effect of Bcl-x(L) as a therapeutic agent in the murine model of aminoglycoside ototoxicity.

Methods: Serotype 2 of adeno-associated virus (AAV2) as a vector encoding the mouse Bcl-x(L) gene was injected into mice cochleae prior to injection of kanamycin. Bcl-x(L) expression in vitro and in vivo was examined with Western blotting and immunohistochemistry separately. Cochlear dissection and auditory steady state responses were checked to evaluate the cochlear structure and function.

Results: The animals in the AAV2-Bcl-x(L)/kanamycin group displayed better auditory steady state responses hearing thresholds and cochlear structure than those in the artificial perilymph/kanamycin or AAV2-enhanced humanized green fluorescent protein/kanamycin control group at all tested frequencies. The auditory steady state responses hearing thresholds and cochlear structure in the inoculated side were better than that in the contralateral side.

Conclusions: AAV2-Bcl-x(L) afforded significant preservation of the cochlear hair cells against ototoxic insults and protected the cochlear function. AAV2-mediated Bcl-x(L) might be an approach with respect to potential therapeutic application in the cochlear degeneration.