Effects of Nitric Oxide Expression on Hearing Loss.

The role of nitric oxide (NO) in the onset and pathogenesis of hearing loss remains a matter of debate. To address this, we conducted a narrative review of the literature on the subject. We performed a literature search of SCOPUS, PubMed, Cochrane Library, EMBASE, and Google Scholar databases on the production and role of NO in hearing loss using the search terms/strategy "nitric oxide" AND "hearing loss" to ensure a comprehensive review of available studies. Results: Of 186 papers initially retrieved, 166 were unrelated to hearing loss and NO and were excluded. Of the 23 papers ultimately reviewed, 58% (12 articles) reported that NO caused or worsened hearing loss, 26% (5 articles) reported a beneficial effect of NO in the treatment of and/or defense against hearing loss, and 16% (3 articles) reached no firm conclusion on whether NO played a positive or negative role. This review highlights the dual role of NO in auditory health, where it is essential for normal cochlear function through regulation of blood flow and neurotransmission. However, excessive or dysregulated NO production, particularly via inducible nitric oxide synthase (iNOS), can lead to oxidative stress and hearing loss. Conversely, NO also exhibits protective effects in certain contexts, such as reducing noise-induced hearing damage through its antioxidant properties. These findings underscore the potential of NO modulation as a therapeutic strategy for hearing loss, emphasizing the need for further research to optimize its application and understand the conditions under which it is beneficial or harmful.