Identification of ion-channel modulators that protect against aminoglycoside-induced hair cell death
Emma J. Kenyon, Nerissa K. Kirkwood, Siân R. Kitcher, Molly O’Reilly, Marco Derudas, Daire M. Cantillon, Richard J. Goodyear, Abigail Secker, Sarah Baxendale, James C. Bull, Simon J. Waddell, Tanya T. Whitfield, Simon E. Ward, Corné J. Kros, Guy P. Richardson
Emma J. Kenyon, Nerissa K. Kirkwood, Siân R. Kitcher, Molly O’Reilly, Marco Derudas, Daire M. Cantillon, Richard J. Goodyear, Abigail Secker, Sarah Baxendale, James C. Bull, Simon J. Waddell, Tanya T. Whitfield, Simon E. Ward, Corné J. Kros, Guy P. Richardson
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Research Article Neuroscience

Identification of ion-channel modulators that protect against aminoglycoside-induced hair cell death

Abstract

Aminoglycoside antibiotics are used to treat life-threatening bacterial infections but can cause deafness due to hair cell death in the inner ear. Compounds have been described that protect zebrafish lateral line hair cells from aminoglycosides, but few are effective in the cochlea. As the aminoglycosides interact with several ion channels, including the mechanoelectrical transducer (MET) channels by which they can enter hair cells, we screened 160 ion-channel modulators, seeking compounds that protect cochlear outer hair cells (OHCs) from aminoglycoside-induced death in vitro. Using zebrafish, 72 compounds were identified that either reduced loading of the MET-channel blocker FM 1-43FX, decreased Texas red–conjugated neomycin labeling, or reduced neomycin-induced hair cell death. After testing these 72 compounds, and 6 structurally similar compounds that failed in zebrafish, 13 were found that protected against gentamicin-induced death of OHCs in mouse cochlear cultures, 6 of which are permeant blockers of the hair cell MET channel. None of these compounds abrogated aminoglycoside antibacterial efficacy. By selecting those without adverse effects at high concentrations, 5 emerged as leads for developing pharmaceutical otoprotectants to alleviate an increasing clinical problem.

Authors

Emma J. Kenyon, Nerissa K. Kirkwood, Siân R. Kitcher, Molly O’Reilly, Marco Derudas, Daire M. Cantillon, Richard J. Goodyear, Abigail Secker, Sarah Baxendale, James C. Bull, Simon J. Waddell, Tanya T. Whitfield, Simon E. Ward, Corné J. Kros, Guy P. Richardson

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Figure 8

Effects of elevated K+ and Na+ and effects of lead otoprotectants on resting membrane potential.

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Effects of elevated K+ and Na+ and effects of lead otoprotectants on res...
(A–F) Cochlear cultures from P2 pups were grown in (A) control medium (n = 5) or (B) medium containing 5 μM gentamicin (n = 3), (C) 18 mM NaCl (n = 4), (D) 18 mM NaCl with 5 μM gentamicin (n = 6), (E) 18 mM KCl (n = 4), and (F) 18 mM KCl with 5 μM gentamicin (n = 6). Cultures were labeled with antibodies to myosin 7a. Scale bar: 50 μm. (G) Box-and-whisker plot showing numbers of OHCs remaining in the mid-basal region. Thick line = median; boxes = interquartile range (IQR). Whiskers extend an additional 1.5× IQR beyond the boxes. Outliers are shown as white circles. (H–M) Representative current clamp recordings of membrane potential in OHCs in cochlear cultures from P2 pups, obtained during and after superfusion with 30 μM of compounds as indicated and 18 mM KCl. The addition of 18 mM KCl to the extracellular solution results in a rapid depolarization of the cell of approximately 15 mV that is reversible upon a return to normal KCl levels (n = 10). Exposing the cells to the otoprotectant compounds 13097 (n = 10), 13142 (n = 5), 13143 (n = 11), 13154 (n = 7), and 13222 (n = 7) has no effect on the resting membrane potential.