A study in mice has shown that hearing loss caused by some life-saving antibiotics is due to the effects of inflammation, the body's reaction to infection. Because of the inflammation, the ion channels in the sensory hair cells of the inner ear become more permeable to antibiotics which then increases the cells' sensitivity to the drugs' toxic effects. These antibiotics are known as aminoglycoside and work on a broad range of bacteria. This makes the drug particularly useful when treating newborns with life-threatening infections, although these newborns have rates of hearing loss at least six times higher than healthy newborns.
Dr. Peter Steyger, PhD, at Creighton University in Nevada and his team tested the effects of gentamicin on mice. They found that one protein involved in ion channels, TRPV1, enabled the drug's entry into the hair cells. The mice that were bred without working TRPV1 were spared from hearing loss caused by the antibiotic.
"Personally, the most surprising aspect was realizing that some loss-of-function mutations in TRPV1 were dominant negative mutations, that protected the cochlea from inflammation-enhanced drug-induced hearing loss," said Dr. Steyger to The Hearing Journal. "This gives us confidence that otoprotective drugs can be developed to prevent this type of hearing loss."
With this discovery in mind, Steyger believes that, if possible, doctors should use antibiotics that don't increase the risk of hearing loss in patients with body-wide infection. However, when aminoglycosides are the only option, healthcare professionals can be aware of those who most likely need post-treatment auditory rehabilitation much earlier.
"This information will help inform patients, or parents of those, with drug-induced hearing loss how this type of hearing loss occurred," said Dr. Steyger. "I recognize this will be of little comfort to those with hospital-prescribed drug-induced hearing loss, however the aminoglycosides are life-saving antibiotics for severe infections. Importantly, we now know that those with severe infections are now likely much more susceptible to aminoglycoside-induced hearing loss."
The primary mission of Creighton's Translational Hearing Center is to find new pharmacotherapeutics that prevent drug-, noise-, and age-related hearing loss. By making these discoveries, Dr. Steyger and his team can now create specific druggable targets to develop otoprotectants and prevent this type of hearing loss.