Evaluating anti-oxidant and autophagy compounds as potential therapies for mammalian aminoglycoside-induced hair cell loss

• Applicant: Dr. Clara Sophia Draf
• Subject Area: Otolaryngology, Phoniatrics and Audiology
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 392120974

Demographic development outlines an increasing importance for diseases of the elderly, such as sensorineural hearing loss (SNHL) (>65 years up to 50%). Prevention is not currently possible for SNHL induced by most causes such as drugs, genetics or aging. Noise-induced hearing loss can be prevented with ear plugs or protectors, but they are frequently not worn when necessary. SNHL is difficult to treat, since it creates both loss of sensitivity and distortion of perceived sounds. This is partly due to loss of frequency specifity associated with outer hair cell (HC) loss, but also to loss of afferent synapses on the inner HCs, that may not be reflected in loss of hearing sensitivity (Kujawa and Liberman, 2015). Hearing aids increase sensitivity, but typically do not overcome sound distortion (Silverman, 1998). New methods for SNHL prevention and treatment are urgently needed. Prior research using in vitro intervention has characterized a number of pathways that contribute to HC damage and loss (Battaglia, 2003; Brand, 2015) or influence HC regeneration (Masuda, 2006). This knowledge base provides opportunities for pharmacological intervention to protect HCs. The submitted project deals with the evaluation of anti-oxidant and autophagy compounds, which may prevent and protect HCs against aminoglycoside (AG)-induced hair cell loss. Aim:The short-term objective is to determineI) relative potential of antioxidants to protect HCs and hearing from damage in vivo.II) relative potential of autophagy compounds to influence HC damage in vitro.The long term goal of this project is to increase prevention and improve treatment options for different types of SNHL such as AG-induced HC damage and noise- induced SNHL.Methods:Experimental Plan I:For the in vivo test of anti-oxidants, FVB mice will be employed, which do not display age-related hearing loss or increased noise sensitivity. Each mouse will be exposed to octave-band noise (12-24 kHz) at 105 dB SPL (sound pressure level) for 30 minutes. The exposure produces approximately 65 dB of threshold shift measured immediately after noise, and 40 dB of permanent threshold shift measured two weeks later, and loss primarily of outer HCs. The effects of perilymph delivery of three dosages of the top four antioxidant molecules, identified as most effective in a previous in vitro screen, will be compared.Experimental Plan II:For the in vitro autophagy screen, Pou4f3/GFP transgenic mice will be used, in which HCs selectively express green fluorescent protein (GFP). The organs of Corti will be micro-dissected and the apical turns, relatively insensitive to AGs, will be discarded. The basal and middle turns will be divided into short segments, or micro-explants. By means of targeted screening we will assess the Screen-Well Autophagy Library, using an identical assay to that used for the prior in vitro redox screen, to identify compounds with the ability to influence AGS-induced HC damage.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Allen F. Ryan, Ph.D.