By the time age-related hearing loss (ARHL) appears – which it does in at least 25-33% of the U.S. population over age 64 – it’s too late to stop it. All that people can do is to treat the symptoms, by wearing hearing aids. What if the changes could be detected before ARHL became apparent?
A new grant from the National Institute on Deafness & Other Communication Disorders (part of the National Institutes of Health) has been awarded to Jeffrey Mellott, Ph.D., a researcher in Northeast Ohio Medical University’s Hearing Research Group.
Dr. Mellott came to NEOMED in 2010 as a postdoctoral fellow and was hired as a faculty member in 2016. Currently he teaches a course in neurobiology for first-year College of Medicine students and a graduate course called Cellular and Molecular Neuroscience.
Regarding his research on hearing changes in aging, Dr. Mellott explains: “As we age, the primary inhibitory neurotransmitter GABA is downregulated in many areas of the brain. This loss of inhibition is often associated with a number of neurodegenerative diseases (e.g., age-related hearing loss; ARHL). In our laboratory we investigate the age-related loss of GABA in the auditory midbrain as it relates to the onset of ARHL.”
The first publication from Dr. Mellott’s lab demonstrated significant GABAergic changes during
middle age. That was an exciting revelation, since it indicated that aspects of GABAergic neurotransmission were dramatically changing before old age, when ARHL is commonly present. Those findings shaped the aims of the recently funded grant. Its primary goal? To establish whether age-related changes to GABA in the auditory midbrain occur before the onset of ARHL.
Going a bit deeper, Dr. Mellott explains, “Specifically, in our grant titled Age-related GABAergic loss in the central auditory circuits, we are examining whether the age-related change of GABA occurs on specific circuits of the auditory midbrain before the onset of AHRL. We are using electron microscopy to investigate where synapses are lost with age on these circuits. Interestingly, in our preliminary data we are finding that GABAergic synapses are lost at different time frames across the auditory midbrain nuclei.
Research Continues Despite Pandemic
Despite the COVID-19 pandemic and subsequent safety changes, Dr. Mellott’s lab continued to be productive during the spring and summer months. “Luckily, much of the work in our lab can be conducted in isolation and analyzed remotely,” he notes.
An incoming first-year College of Medicine student, Vincent Pham, was able to quantify neurons in the auditory midbrain that undergo age-related changes to their plasticity. At the same time, rising second-year College of Medicine students Oren Barat and Matt Russ remotely analyzed electron microscopy images on aging GABAergic synapses. Their data will be included in an upcoming abstract submission to an international conference on hearing research in the winter.
Research assistant Amir Mafi (shown at left in photo, with Dr. Mellott at right) was instrumental in managing and conducting time-sensitive aging experiments to completion throughout the pandemic.
Quality of Life
Many people with ARHL have a substantially diminished quality of life, due to the poor communication that comes with poor hearing. Thus, there is an enormous need to find successful therapies that ameliorate ARHL. While there have been pharmaceutical therapies for the condition, (many, if not most of which, affect the GABAergic synapses), they have been largely ineffective and almost always attempt to treat ARHL after onset.
”A better understanding of when and where GABAergic changes are occurring before ARHL starts to begin may be key in determining when and when therapies are best applied in the central auditory system,” says Dr. Mellott, adding, “These are the questions we hope our data will begin to answer with our new funding.”