Listening to music at full volume with headphones can affect your hearing health.
Also do it at a concert or in a nightclub, or display it on stage, where the noise exceeds 100 decibels.
In general, any prolonged exposure to more than 80 decibels is considered harmful to hearing, and in fact the scientific community recommends using earplugs in the noisiest environments to avoid permanent damage.
Because once cells are injured, there is nothing that can be done to regenerate them.
But now a group of researchers from the University of Pittsburgh has discovered the biological mechanism of hearing loss caused by loud noises, which opens the door to finding a way to prevent it.
“Despite the impact that this condition has on society, today treatment strategies that protect and restore hearing are few and insufficient,” acknowledges Thanos Tzounopoulos, director of the Pittsburgh Hearing Research Center and author of the study that It was published this Monday in the journal
PNAS
.
The experiment, done with mice, investigates the correlation between hearing loss and the presence of zinc in the inner ear, a mineral essential for proper cellular function and hearing.
“It is an essential element that we all need to survive.
90% of the zinc we have in the body is bound to proteins and helps them do their job.
It is important for communication between different neurons and cells,” explains Tzounopoulos.
“However, the remaining 10%, which is known as labile zinc, is in a free state, and plays a crucial role in cell signaling.
“Scientific literature tells us that when the zinc signal is deregulated or negatively affected, it can cause cell death, in addition to playing a role in the degeneration of the optic nerves,” he adds.
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To investigate the role of zinc signaling in response to trauma, Tzounopoulos' team exposed unanesthetized mice to a noise of 100 decibels—equivalent, for example, to the noise of a felling mower or a nightclub—for two hours. .
In measurements made after two weeks, it was confirmed that the mice had suffered cochlear damage and a shift in the hearing threshold.
Subsequently, they went on to evaluate the levels and location of zinc in the cochlea of these mice, compared to others that had been exposed to the same level of noise only one day before.
If in the first mice it was observed that labile zinc was found mainly in the outer cells, in the mice that have just been exposed to trauma it was found in the inner part of the cochlea.
"These results demonstrate that exposure to loud sounds causes a massive release of zinc in the intracellular space that interrupts normal communication between cells and causes deterioration," details Brandon Bizup, co-author of the study, who recognizes that although the connection between the two factors It is clear, they still do not know what the factors driving this change are.
After corroborating the biological mechanism behind hearing loss, the team at the University of Pittsburgh has begun working on a device that is capable of preventing it.
Experiments showed that another group of mice, which was treated with a gel that traps excess zinc that is released into the ear canal after exposure to noise, were less prone to hearing loss and were protected from the induced damage.
“The active part of the drug is a chelator, capable of extracting toxic metals from the body.
“We dissolved this chelator in a gel that we surgically applied to the mice directly in the ear canal,” explains Tzounopoulos.
Injections were also made into the abdomen of the mice.
The gel works like a sponge, capable of trapping excess zinc and limiting trauma.
Researcher Thanos Tzounopoulos, in a photo provided by the University of Pittsburgh.Joshua Franzos
Luis Lassaletta, president of the Otology commission of the Spanish Society of Otorhinolaryngology, believes that the conclusions drawn by the authors about the biological mechanism behind noise-induced trauma are solid and novel.
However, he points out some shortcomings of the study.
“Firstly, just as the role of zinc as a cause of hearing loss seems well demonstrated, the possibility of protecting the loss and reversing the effects is not so well demonstrated,” he highlights.
“On the other hand, there are more mechanisms established to explain noise-associated hearing loss, such as inflammation, oxidative stress and cell apoptosis.”
“This is, without a doubt, a discovery that can change the way we relate to this type of ailment,” acknowledges ENT doctor Eduardo Raboso, head of service at the La Princesa Hospital in Madrid, who has not worked in the study.
“Zinc is a mineral that has a marginal but vital function in our body.
And if it is handled poorly and leaves the vesicles where it should be, the damage can be permanent.”
Even so, the expert is skeptical that the experiment with mice will lead to a therapeutic option for humans.
The authors themselves are cautious regarding the following phases of their research.
“Before we can apply the drug to humans, we need to conduct a series of additional experiments to ensure the safety of the drug, including toxicology studies and determination of the precise dosage,” says Bizup.
The scientist recalls that the surgical application of zinc chelators already has precedent, such as the use of steroids for sudden hearing loss.
The long-term goal is to develop two types of medicines.
A preventive one, in the form of a pill, that can be taken before going to a particularly noisy event, such as a concert or a soccer game.
The other reagent, through surgical treatment, in case of involuntary exposure.
For this reason, researchers remember that the best cure remains prevention.
“Awareness about the damage that noise can cause to hearing is crucial, especially in everyday events that easily exceed 100 decibels.
Wearing hearing protectors is essential to protect your ears, regardless of other measures that may come later,” Tzounopoulos insists.
“Hearing loss is the most common sensory disorder, affecting a significant percentage of the population, which underlines the importance of protecting our ears from harmful sound levels in everyday life.”
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