Chemical chaperone 4-phenylbutyrate prevents hearing loss and cochlear hair cell death in Cdh23erl/erl mutant mice.

We previously developed Cdh23 mutant mice (erl mice) as a model of hearing loss for otoprotective drug evaluation and showed that the erl mutation leads to hearing loss related to endoplasmic reticulum (ER) stress-induced cochlear hair cell apoptosis. Small molecular chemical chaperones, 4-phenylbutyrate (4PBA), targeting ER stress exert a neuroprotective effect. To evaluate whether 4PBA exerts an otoprotective effect, we intraperitoneally injected erl mice with 4PBA daily from postnatal age day 7 up to 12 weeks. Our results showed that treatment with 4PBA significantly alleviated hearing loss and suppressed hair cell death in erl mice. In addition, ER stress-related proteins were downregulated by 4PBA treatment. Our study showed that 4PBA exerts an otoprotective effect, which provides the potential to repurpose the drug for otoprotection.