Aminoglycosides are a widely used broad spectrum antibiotic. A major side effect of these compounds is oto- (and vestibulo) and nephrotoxicity. Data obtained during an R21 award demonstrates that these compounds enter sensory hair cells of the inner ear via a specialized mechanosensitive ion channel in vitro. Using our unique knowledge of the biophysical properties of the mechanotransduction channel coupled with insights provided by crystallography data that identifies aminoglycoside interacting sites on the bacterial ribosome, we have developed novel compounds that greatly reduced oto- and nephrotoxicity in vivo, though at some cost to the breadth of antimicrobial activity. These proof-of-principal experiments serve as the basis for iteratively designing new compounds. The design component has three phases, first to use our initial screen as a starting point where we will alter the substituted group on sisomicin to try to better separate antimicrobial activity and the toxic side effects. Second we will synthesize and test a novel modification site based on new data arising from experiments on gentamicin derivatives. Finally, we will change the parent compound to better target specific microbes such as Pseudomonas organisms. We have developed the ability to test for purity and specificity of each compound. We can probe activity in terms of antimicrobial function as well as oto- and nephrotoxicity in in vivo and in vitro models. We can also test for sensitivity to the development of resistance and for vestibular pathologies. Together this iterative ability based on a novel hypothesis should yield a new class of nontoxic antibiotics.

Public Health Relevance

Aminoglycosides represent one of the most widely used classes of antibiotics. They are broad spectrum, stable under many environmental conditions, reasonably intolerant to drug resistance, and relatively inexpensive to produce. However, they have the major side effect of causing hearing loss and kidney failure. In studying the biophysical properties of inner ear sensory hair cells, we identified the pathway by which these drugs enter the sensory cells; through a mechanically gated ion channel. The goal of the present work is to design new antibiotics that will not enter this channel and so therefore will not be toxic to hair cells or cause hearing loss. By targeting drug sites not expected to be involved in antimicrobial activity, we can design compounds that selectively lose ototoxic side effects. We have created an iterative process of synthesis and testing of antimicrobial activity, ototoxicity and nephrotoxicity to drive drug design. This approach is novel in drug design as it requires much less synthesis being focused upon specific properties unique to ototoxicity as well as those selective for antimicrobial activity. Given the rampant increases in drug resistance and the paucity of novel antibiotics being developed, it is critical that we take advantage of all avenues when developing new approaches to address this escalating problem.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Auditory System Study Section (AUD)
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Freeman, Nancy
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Stanford University
Schools of Medicine
United States
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O'Sullivan, Mary E; Poitevin, Frédéric; Sierra, Raymond G et al. (2018) Aminoglycoside ribosome interactions reveal novel conformational states at ambient temperature. Nucleic Acids Res 46:9793-9804
O'Sullivan, Mary E; Perez, Adela; Lin, Randy et al. (2017) Towards the Prevention of Aminoglycoside-Related Hearing Loss. Front Cell Neurosci 11:325
Huth, Markus E; Han, Kyu-Hee; Sotoudeh, Kayvon et al. (2015) Designer aminoglycosides prevent cochlear hair cell loss and hearing loss. J Clin Invest 125:583-92