Urolithin A Attenuates Noise-induced Hearing Loss and Is Associated With Increased Cochlear Mitophagy Markers

BACKGROUND/AIM: Noise-induced hearing loss (NIHL) is a prevalent cause of sensorineural hearing impairment, in which mitochondrial dysfunction(definition) plays a key pathogenic role. Mitophagy is essential for maintaining mitochondrial quality control. This study investigated whether urolithin A (UA), a known mitophagy inducer, protects against NIHL. MATERIALS AND METHODS: Eight-week-old CBA/J mice were divided into three groups: control, noise + saline, and noise + UA (10 mg/kg). NIHL was induced by exposure to broadband noise (100 dB SPL, 2 h). UA was administered intraperitoneally before and after noise exposure. Auditory function was evaluated using auditory brainstem response (ABR). Mitophagy-associated markers and mitochondrial function were assessed by Western blotting, quantitative real-time PCR, mitochondrial DNA (mtDNA) integrity analysis, ATP measurements, and immunohistochemistry/immunofluorescence. RESULTS: UA treatment significantly reduced auditory threshold shifts compared with the untreated group. The expression levels of mitophagy-related proteins and genes, including PINK1, Parkin, and BNIP3, were significantly increased in the UA-treated group. In addition, UA restored ATP levels following noise exposure. Immunohistochemical and immunofluorescence analyses demonstrated enhanced formation of mitophagosomes and mitophagolysosomes in the cochlea, including the organ of Corti and the spiral ganglion, in the UA-treated group. CONCLUSION: UA attenuates NIHL by enhancing mitophagy-associated markers and preserving mitochondrial function in the cochlea. These findings suggest that pharmacological activation of mitophagy may represent a promising therapeutic strategy for NIHL.