A Fungal-Derived Bioactive Resource for Cochlear Protection: Sanghuangporus sanghuang Extract Mitigates Acoustic...

Noise-induced hearing loss (NIHL) is a major form of sensorineural hearing impairment driven by oxidative stress-mediated cochlear injury. Sanghuangporus sanghuang (SS), a medicinal fungus extensively studied in microbiology and biotechnology, is known to produce bioactive metabolites with antioxidant properties; however, its functional role in the auditory system has not been established. This study investigated the otoprotective potential of SS extract against oxidative and acoustic stress using complementary in vitro, ex vivo, and in vivo models. In H₂O₂-treated UB-OC1 auditory cells, SS (25-200 μg/mL) dose-dependently restored cell viability and significantly reduced intracellular reactive oxygen species accumulation. Western blot analysis demonstrated that SS suppressed the expression of apoptotic markers, including cleaved caspase-3 and cytochrome C. At the molecular level, SS upregulated Nrf2 and HO-1 expression at both mRNA and protein levels, without a significant change in Keap1 expression, indicating activation of endogenous antioxidant defense via the Nrf2/HO-1 signaling axis. Consequently, downstream antioxidant genes such as SOD1 and NQO1 were significantly upregulated. In ex vivo cochlear explant cultures, SS preserved hair cell integrity against H₂O₂-induced damage, as confirmed by phalloidin staining. In a murine NIHL model, oral administration of SS attenuated ABR threshold shifts, maintained Wave I amplitudes, and preserved the structural organization of outer hair cells across all cochlear turns. Collectively, these findings demonstrate that SS confers otoprotection by modulating the Nrf2/HO-1 antioxidant axis and mitigating oxidative stress-induced sensory cell injury, supporting the potential of SS as a fungal-derived functional bioactive resource for redox-associated cochlear protection.