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Treating inflamed brains could ease ringing in the ears

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Ringing in the ears, called tinnitus, and other hearing loss-related disorders could be linked to inflammation in a sound-processing part of the brain, according to researchers studying the condition in mice. In mice with noise-induced hearing loss, the researchers found indicators of neuroinflammation, which they were able to block and prevent tinnitus from developing suggesting a possible method of treating the disorder.

Journal/conference: PLOS Biology

DOI: 10.1371/journal.pbio.3000307

Organisation/s: University of Arizona, USA

Funder: National Institute of Health, Department of Defense, Food and Health Bureau of Hong Kong Special Administrative Region Government.

Media Release

From: PLOS

Reducing brain inflammation could treat tinnitus and other hearing loss-related disorders

Inflammation in a sound-processing region of the brain mediates ringing in the ears in mice that have noise-induced hearing loss, according to a study publishing June 18 in the open-access journal PLOS Biology by Shaowen Bao of the University of Arizona, and colleagues.

Hearing loss is a widespread condition that affects approximately 500 million individuals, and is a major risk factor for tinnitus — the perception of noise or ringing in the ears. Recent studies indicate that hearing loss causes inflammation — the immune system's response to injury and infection — in the auditory pathway. But its contribution to hearing loss-related conditions such as tinnitus is still poorly understood. To address this gap in knowledge, Bao and his colleagues examined neuroinflammation — inflammation that affects the nervous system — in the auditory cortex of the brain following noise-induced hearing loss, and its role in tinnitus, in rodent models.

The results indicate that noise-induced hearing loss is associated with elevated levels of molecules called proinflammatory cytokines and the activation of non-neuronal cells called microglia — two defining features of neuroinflammatory responses—in the primary auditory cortex. Experiments in mice that incur noise-induced hearing loss showed that a cell-signaling molecule called tumor necrosis factor alpha (TNF-α) mediates neuroinflammation, tinnitus, and synaptic imbalance — an altered pattern of signaling between neurons. Moreover, the researchers found that pharmacological blockade of TNF-α or depletion of microglia prevented tinnitus in mice with noise-induced hearing loss. According to the authors, the findings suggest that neuroinflammation may be a therapeutic target for treating tinnitus and other hearing loss-related disorders.

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