80% of affected people live. Given the importance of hearing for communication, enjoyment, and safety, with up to 500 million affected globally at a cost of nearly $800 billion/year, research on new approaches toward prevention and treatment is attracting increased attention. The consequences of noise pollution are largely preventable, but irreversible hearing loss can result from aging, disease, or drug side effects. Once damage occurs, treatment relies on hearing aids and cochlear implants. Preventing, delaying, or reducing some degree of hearing loss may be possible by avoiding excessive noise and addressing major contributory factors such as cardiovascular risk. However, given the magnitude of the problem, these interventions alone are unlikely to be sufficient. Recent advances in understanding principal mechanisms that govern hearing function, together with new drug discovery paradigms designed to identify efficacious therapies, bode well for pharmaceutical intervention. This review surveys various causes of loss of auditory function and discusses potential neurological underpinnings, including mitochondrial dysfunction. Mitochondria mitigate cell protection, survival, and function and may succumb to cumulative degradation of energy production and performance; the end result is cell death. Energy-demanding neurons and vestibulocochlear hair cells are vulnerable to mitochondrial dysfunction, and hearing impairment and deafness are characteristic of neurodegenerative mitochondrial disease phenotypes. Beyond acting as cellular powerhouses, mitochondria regulate immune responses to infections, and studies of this phenomenon have aided in identifying nuclear factor kappa B and nuclear factor erythroid 2-related factor 2/antioxidant response element signaling as targets for discovery of otologic drugs, respectively, suppressing or upregulating these pathways. Treatment with free radical scavenging antioxidants is one therapeutic approach, with lipoic acid and corresponding carnitine esters exhibiting improved biodistribution and other features showing promise. These compounds are also histone deacetylase (HDAC) inhibitors, adding epigenetic modulation to the mechanistic milieu through which they act. These data suggest that new drugs targeting mitochondrial dysfunction and modulating epigenetic pathways via HDAC inhibition or other mechanisms hold great promise." />
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Biores Open Access. 2018 Jul 01;7(1):107-115. doi: 10.1089/biores.2018.0017. eCollection 2018.

A New Approach to Treating Neurodegenerative Otologic Disorders.

BioResearch open access

Walter H Moos, Douglas V Faller, Ioannis P Glavas, David N Harpp, Michael H Irwin, Iphigenia Kanara, Carl A Pinkert, Whitney R Powers, Kosta Steliou, Demetrios G Vavvas, Krishna Kodukula

Affiliations

  1. Department of Pharmaceutical Chemistry, School of Pharmacy, University of California San Francisco, San Francisco, California.
  2. ShangPharma Innovation, Inc., South San Francisco, California.
  3. Department of Medicine, Boston University School of Medicine, Boston, Massachusetts.
  4. Cancer Research Center, Boston University School of Medicine, Boston, Massachusetts.
  5. Department of Ophthalmology, New York University School of Medicine, New York, New York.
  6. Department of Chemistry, Office for Science & Society, McGill University, Montreal, Canada.
  7. Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, Alabama.
  8. Embassy of Greece in Moscow, Moscow, Russia.
  9. Department of Biological Sciences, College of Arts and Sciences, The University of Alabama, Tuscaloosa, Alabama.
  10. Department of Health Sciences, Boston University, Boston, Massachusetts.
  11. Department of Anatomy, Boston University School of Medicine, Boston, Massachusetts.
  12. PhenoMatriX, Inc., Natick, Massachusetts.
  13. Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts.
  14. Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts.
  15. Bridgewater College, Bridgewater, Virginia.

PMID: 30069423 PMCID: PMC6069589 DOI: 10.1089/biores.2018.0017

Abstract

Hearing loss, the most common neurological disorder and the fourth leading cause of years lived with disability, can have profound effects on quality of life. The impact of this "invisible disability," with significant consequences, economic and personal, is most substantial in low- and middle-income countries, where >80% of affected people live. Given the importance of hearing for communication, enjoyment, and safety, with up to 500 million affected globally at a cost of nearly $800 billion/year, research on new approaches toward prevention and treatment is attracting increased attention. The consequences of noise pollution are largely preventable, but irreversible hearing loss can result from aging, disease, or drug side effects. Once damage occurs, treatment relies on hearing aids and cochlear implants. Preventing, delaying, or reducing some degree of hearing loss may be possible by avoiding excessive noise and addressing major contributory factors such as cardiovascular risk. However, given the magnitude of the problem, these interventions alone are unlikely to be sufficient. Recent advances in understanding principal mechanisms that govern hearing function, together with new drug discovery paradigms designed to identify efficacious therapies, bode well for pharmaceutical intervention. This review surveys various causes of loss of auditory function and discusses potential neurological underpinnings, including mitochondrial dysfunction. Mitochondria mitigate cell protection, survival, and function and may succumb to cumulative degradation of energy production and performance; the end result is cell death. Energy-demanding neurons and vestibulocochlear hair cells are vulnerable to mitochondrial dysfunction, and hearing impairment and deafness are characteristic of neurodegenerative mitochondrial disease phenotypes. Beyond acting as cellular powerhouses, mitochondria regulate immune responses to infections, and studies of this phenomenon have aided in identifying nuclear factor kappa B and nuclear factor erythroid 2-related factor 2/antioxidant response element signaling as targets for discovery of otologic drugs, respectively, suppressing or upregulating these pathways. Treatment with free radical scavenging antioxidants is one therapeutic approach, with lipoic acid and corresponding carnitine esters exhibiting improved biodistribution and other features showing promise. These compounds are also histone deacetylase (HDAC) inhibitors, adding epigenetic modulation to the mechanistic milieu through which they act. These data suggest that new drugs targeting mitochondrial dysfunction and modulating epigenetic pathways via HDAC inhibition or other mechanisms hold great promise.

Keywords: carnitine esters; epigenetics; hearing loss; lipoic acid; mitochondrial dysfunction; pharmaceutical

Conflict of interest statement

K.S. owns shares in PhenoMatriX, Inc. K.K. and W.H.M. consult with and/or serve on the boards of various biotechnology and pharmaceutical companies from time to time, where they may receive compensati

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