Hair Cell Structure and Function - Ototoxicity

Mission Statement

The mission of this Section is to investigate how the auditory sensory cells are organized on cellular and molecular levels and understand how they function normally and dysfunction in pathologies.

Research Staff

(From left to right): Federico Kalinec, Ph.D., Section Chief; Melissa Mueller, Student Intern; Enrique Navarrete, M.D., Research Associate; Anastasiya Maricle, Research Technician; Gilda M. Kalinec, Ph.D., Senior Research Associate. 

Major Research Focus

At the Section on Cell Structure and Function, we are exploring the function of the inner ear from two perspectives:

• Understanding the structure and function of the outer hair cells (OHC), which play a critical role in hearing as well as a protective role for inner hair cells.

• Investigating how to prevent life-saving drugs and noise from having a noxious effect on the inner ear and killing the outer hair cells.

The first of these objectives seeks a comprehensive understanding of the processes involved in the outer hair cell’s operation.  Its intention is broad-based and will create a foundation for future pursuits in repairing and regenerating these structures. The second pursuit has a more immediate application: the development of intervention strategies to prevent damage to the outer hair cells.

Ongoing Projects

1.  Cytoskeletal regulation of OHC motility.

The human ear is capable of both amplifying faint sounds to increase our hearing range and reducing the energy of loud sounds to protect our ears from damage. It can do that because of the “cochlear amplifier,” an active mechanism that increases the sensitivity and frequency discrimination of the inner ear. The mechanism of cochlear amplification is based in the motile properties of auditory sensory cells known as outer hair cells (OHCs), which elongate and shorten in response to external stimuli.  Damage of the cochlear amplifier by, for example, acoustic trauma, ototoxic drugs or aging, causes sensorineural hearing loss.

 Cell motility implies changes in cell shape. Cell shape changes, in turn, entail loss of equilibrium between internal tensional forces, and its regulation must involve a mechanism able to compensate this imbalance. The crucial role of the cell skeleton (cytoskeleton) for cell motility in non-auditory cell populations, led us to hypothesize that structural and functional changes in this structure are determinant in the generation and regulation of OHC motility. We are addressing this hypothesis at cellular and molecular levels, and our results strongly suggest that small GTPases of the Rho family (RhoA, Rac and Cdc42) are critical components of the mechanism that modulates OHC motility through dynamic changes in the OHC’s cytoskeleton.

Significance: OHC motility is at the core of the cochlear amplifier. To understand how OHC motility - and the gain of the cochlear amplifier - are regulated is an essential step toward the comprehension of the hearing process and may provide critical information for preventing some types of sensorineural hearing loss.

Outer hair cell electromotility. An isolated outer hair cell is being electrically stimulated through a patch-clamp pipette.

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OHCs undergo terminal cell division during embryogenesis, and at the time of birth they are generally unable to resume division and differentiation. Therefore, these cells cannot be replaced when damaged. Since a high percentage of cases of hearing impairment is related to OHC damage, to identify mechanisms of OHC protection against external agents is an essential step to prevent deafness.  Therefore, an additional research aim in our laboratory is to investigate the response of OHCs to ototoxic drugs.

A variety of commonly used drugs have ototoxic properties. The best known are aminoglycoside antibiotics, loop diuretics and antineoplastic agents such as cisplatin. Most ototoxic substances cause hearing loss by damaging the outer hair cells or the stria vascularis, a specialized epithelial organ within the inner ear responsible for the homeostatis of fluids and electrolytes. Since the human cochlea possesses only about 12,000 OHCs, damaging a few of them can lead to substantial hearing loss. Moreover, since ototoxic drugs such as cisplatin and gentamicin are able to pass through the placental barrier, the risk of drug-induced hearing loss in unborn children during the last trimester of gestation is several times higher than in the rest of the population. Therefore, we are investigating how to protect OHCs against ototoxic drugs prioritizing research aimed at helping mothers and babies during and immediately after pregnancy.

Relevant Publications

• He, DZZ, Zheng, J, Kalinec, F, Kakehata, S, and Santos-Sacchi, J. “Tuning in to the amazing outer hair cell: membrane wizardry with a twist and shout”. J.Membrane Biol., In Press.

• Yorgason, JG, Fayad, JN, and Kalinec, F. “Understanding drug ototoxicity: molecular insights for prevention and clinical management”. Expert Opin. Drug Saf., 5(3):383-399, 2006.

• Kalinec, F. “High-throughput Screening of Ototoxic and Otoprotective Pharmacological Drugs”. The Volta Review, 105(3):383-406, 2005.

• Kalinec, G, Fernandez-Zapico, M, Urrutia, R, Esteban-Cruciani, N, Chen, S, and Kalinec, F. “Pivotal role of harakiri in the induction and prevention of gentamicin-induced hearing loss”. Proc.Natl.Acad.Sci. (USA)
  102(44):16019-16024, 2005.

• Matsumoto, N. and Kalinec, F. “Extraction of Prestin-dependent and prestin-independent components from complex motile responses in guinea pig outer hair cells”. Biophys.J. 89:4343-4351, 2005.

• Matsumoto, N. and Kalinec, F. “Prestin-dependent and prestin-independent motility of guinea pig outer hair cells”. Hear. Res. 208:1-13, 2005.

• So H-S, C Park, H-J Kim, J-H Lee, S-Y Park, J-H Lee, Z-W Lee, H-M Kim, F Kalinec, DJ Lim and R Park.  “Protective effect of T-Type calcium Channel blocker flunarizine on cisplatin-induced death of auditory cells”. Hear. Res.  204:127-139, 2005.

• Zhang M, G Kalinec, R Urrutia, DD Billadeau, and F Kalinec.  “ROCK-dependent and ROCK-independent Control of Cochlear Outer Hair Cell Electromotility”.  J.Biol.Chem. 278:35644-35650, 2003.

• Kalinec GM, P Webster, DJ. Lim and F Kalinec.  “A Cochlear Cell Line as an In Vitro System for Drug Ototoxicity Screening”. Audiol.Neurootol.  8(4):177-189, 2003.

• Zhang M, G Kalinec and F Kalinec. “ROCK ‘n’ Rho in Outer Hair Cell Motility” In Biophysics of the Cochlea: From Molecules to Models. Edited by Anthony Gummer. World Scientific, Singapore, 2003. Pp.127-135.

• Devarajan P, M Savoca, M-S Park, MP Castaneda, N Esteban, G Kalinec, and F Kalinec.  “Cisplatin-Induced Apoptosis of Auditory Cells: Role of death receptor and mitochondrial pathways”.  Hear.Res.  174:45-54, 2002.

• Zhang M and Kalinec F  "Structural microdomains in the basolateral plasma membrane of cochlear outer hair cells".  JARO  3:289-301, 2002.

• Bertolaso L, A Martini, D Bindini, I Lanzoni, A Parmeggiani, C Vitali, G Kalinec, F Kalinec, S Capitani and M Previati.  “Apoptosis in the OC-k3 immortalized cell line treated with different agents”.  Audiology  40:327-335, 2001.

• Kakehata S, P Dallos, WE Brownell, KH Iwasa, B Kachar, F Kalinec, K Ikeda K, and T Takasaka.  “Current concept of outer hair cell motility”.   Auris Nasus Larynx. 27(4):349-355, 2000.

• Kalinec F, M Zhang, RA Urrutia and G Kalinec.  “Rho GTPases Mediate the Regulation of Cochlear Outer Hair Cell Motility by Acetylcholine”.  J.Biol.Chem. 275:28000-28005, 2000.

• M Zhang and F Kalinec.  “Outer Hair Cell Force-generator Mechanism Drives Lateral Displacement of Membrane-Soluble Fluorescent Probes”.  In Recent Developments in Auditory Mechanics. Edited by H. Wada, T. Takasaka, K. Ikeda, K. Ohyama & T. Koike. World Scientific, Singapore, 2000. Pp. 330-336.

• Kalinec F, G Kalinec, M Boukhvalova and B Kachar.  “Establishment and Characterization of Conditionally Immortalized Organ of Corti Cell Lines.”  Cell Biol.Int.  23:175-184, 1999.

• Frolenkov, G, M Atzori, F Kalinec, F Mammano and B Kachar.  “The Membrane-Based Mechanism of Cell Motility in Cochlear Outer Hair Cells.”  Mol.Biol.Cell  9:1961-1968, 1998.

• Lim, DJ and F Kalinec.  “Cell and Molecular Basis of Hearing.”  Kidney Int.  53(suppl.65):S104-S113, 1998.

• Kalinec, F, G Kalinec, C Negrini and B Kachar.  “Immunolocalization of Anion Exchanger 2a in Auditory Sensory Hair Cells.”   Hear.Res.  110: 141-146, 1997

• Frolenkov, G, F Kalinec, G Tavarkilazde and B Kachar.  "Cochlear Outer Hair Cell Bending in an External Electric Field."   Biophys.J.  73: 1665-1672, 1997

• Negrini, C, MNC Rivolta, F Kalinec and B. Kachar.  "Cloning of an Organ of Corti AE2 Isoform with a Truncated C-Terminal Domain."  Biochim.Biophys.Acta   1236:207-211, 1995.

• Kalinec, F and B Kachar.  “Structure of the Electromechanical Transduction Mechanism in Mammalian Outer Hair Cells.”   In  Active Hearing. Edited by Å. Flock, D. Ottoson & M. Ulfendhal. Elsevier Science, London, 1995. Pp. 179-191.

• Kalinec, F, RG Jaeger and B Kachar.  “Mechanical Coupling of the Outer Hair Cell Plasma Membrane to the Cortical Cytoskeleton by Anion Exchanger and 4.1 Proteins.”   In  Biophysics of Hair Cell Sensory Systems.  Edited by H. Duifhuis, JW Horst, P van Dijk and SM van Netten. World Scientific, Singapore, 1993. Pp. 175-181.

• Kalinec, F and B Kachar.  “Inhibition of Outer Hair Cell Electromotility by Sulfhydryl Specific Reagents.”   Neurosci.Lett. 157:231-234, 1993. 

• Kalinec, F, MC Holley, KH Iwasa, DJ Lim, and B Kachar.  “A Membrane-Based Force Generation Mechanism in Auditory Sensory Cells.”  Proc.Natl.Acad.Sci. USA   89:8671-8675, 1992.

• Holley, MC, F Kalinec and B Kachar.  “Structure of the Cortical Cytoskeleton in Mammalian Outer Hair Cells.”   J.Cell Sci. 102:569-580, 1992.