Identification of a series of hair-cell MET channel blockers that protect against aminoglycoside-induced ototoxicity
Emma J. Kenyon, Nerissa K. Kirkwood, Siân R. Kitcher, Richard J. Goodyear, Marco Derudas, Daire M. Cantillon, Sarah Baxendale, Antonio de la Vega de León, Virginia N. Mahieu, Richard T. Osgood, Charlotte Donald Wilson, 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, Richard J. Goodyear, Marco Derudas, Daire M. Cantillon, Sarah Baxendale, Antonio de la Vega de León, Virginia N. Mahieu, Richard T. Osgood, Charlotte Donald Wilson, 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 Therapeutics

Identification of a series of hair-cell MET channel blockers that protect against aminoglycoside-induced ototoxicity

Abstract

To identify small molecules that shield mammalian sensory hair cells from the ototoxic side effects of aminoglycoside antibiotics, 10,240 compounds were initially screened in zebrafish larvae, selecting for those that protected lateral-line hair cells against neomycin and gentamicin. When the 64 hits from this screen were retested in mouse cochlear cultures, 8 protected outer hair cells (OHCs) from gentamicin in vitro without causing hair-bundle damage. These 8 hits shared structural features and blocked, to varying degrees, the OHC’s mechano-electrical transducer (MET) channel, a route of aminoglycoside entry into hair cells. Further characterization of one of the strongest MET channel blockers, UoS-7692, revealed it additionally protected against kanamycin and tobramycin and did not abrogate the bactericidal activity of gentamicin. UoS-7692 behaved, like the aminoglycosides, as a permeant blocker of the MET channel; significantly reduced gentamicin–Texas red loading into OHCs; and preserved lateral-line function in neomycin-treated zebrafish. Transtympanic injection of UoS-7692 protected mouse OHCs from furosemide/kanamycin exposure in vivo and partially preserved hearing. The results confirmed the hair-cell MET channel as a viable target for the identification of compounds that protect the cochlea from aminoglycosides and provide a series of hit compounds that will inform the design of future otoprotectants.

Authors

Emma J. Kenyon, Nerissa K. Kirkwood, Siân R. Kitcher, Richard J. Goodyear, Marco Derudas, Daire M. Cantillon, Sarah Baxendale, Antonio de la Vega de León, Virginia N. Mahieu, Richard T. Osgood, Charlotte Donald Wilson, James C. Bull, Simon J. Waddell, Tanya T. Whitfield, Simon E. Ward, Corné J. Kros, Guy P. Richardson

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Figure 11

Transtympanic injection of UoS-7692 protects OHCs from systemic kanamycin treatment.

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Transtympanic injection of UoS-7692 protects OHCs from systemic kanamyci...
(A–L) Assessment of OHC-bundle morphology with phalloidin staining in regions 40% (A, B, G, and H), 60% (C–D, I, and J), and 80% (E, F, K, and L) from the cochlear apex in mice receiving transtympanic injection of UoS-7692 in 1 ear (A, C, E, G, I, and K) and no injection in the opposite ear (B, D, F, H, J, and L), followed by systemic furosemide/kanamycin. Mice were maintained for either 2 (A–F) or 9 (G–L) days. In UoS-7692–treated ears after 2 days, there was minimal or no OHC loss in all regions; in untreated ears, OHC loss was extensive, particularly in the 60% and 80% regions. In UoS-7692–treated ears after 9 days, some OHC loss was observed in the 60% region (I) and total loss seen in the 80% region (K); in untreated ears, there was total loss of OHCs in all regions (H, J, and L). Scale bar: 20 μm. (M) Graphs comparing OHC numbers in cochleae of noninjected (red symbols) and injected (brown and blue symbols) ears of mice 2 days after unilateral transtympanic application of 5% DMSO (brown symbols) or 50 mM UoS-7692 in 5% DMSO (blue symbols), followed by systemic furosemide/kanamycin (groups 1 and 2) or no treatment (group 3). Numbers of mice: group 1 (n = 5), group 2 (n = 9), group 3 (n = 2). OHCs were counted in 140 μm length regions located 40%, 60%, and 80% from the cochlear apex. UoS-7692 provided significant protection in all 3 regions (2-way ANOVA with matched pairs design between cochleae from the same animal, with Šidák’s multiple-comparison test between injected and noninjected ears. ***P < 0.001). Scale bar: 20 μm. Error bars show SDM.