Twenty eight million Americans suffer from hearing loss. Hair cell loss induced by ototoxic drugs, such as cisplatin and gentamicin, are among the most common causes of hearing loss, dizziness and tinnitus. Clinically, no drug is available to treat the hair cell loss. Therefore, the long-term goal of our study is to understand the mechanism of hair cell death and develop drugs to prevent and treat hair cell loss. P53 is a key regulator in apoptotic process. We discovered that pifithrin-a (PFT), an inhibitor of p53, blocked cisplatin induced apoptosis and protected hair cells in the cochlear and vestibular cultures. In addition, our data showed PFT also prevented gentamicin-induced hair cell death. Thus, PFT is a potential molecule to treat drugs-induced ototoxicity. Moreover, our data showed that PFT significantly protects the cochlear hair cells but not the vestibular hair cells against low dose gentamicin. Intratympanic injection of low dose gentamicin to damage the vestibular hair cells has been widely used to treat the dizziness of Meniere's disease. However, gentamicin induced hearing loss due to cochlear hair cell damage is the major concern. In this circumstance, PFT has great potential clinical application. In this project, we will study the PFT protective mechanism. In addition, we will delineate p53 upstream and downstream signaling pathways, which will draw a map with specific targets for future protection against cisplatin and gentamicin ototoxicity. We will use organotypic cultures of organ of Corti and utricle of postnatal rats, which are well-established models to study ototoxicity. The outcome of the study will have clinical application toward developing new therapies to protect against drug-induced ototoxicity and will contribute to the understanding of the molecular mechanisms of drug-induced ototoxicity. [unreadable] [unreadable] [unreadable]