Astragaloside IV attenuates cisplatin-induced ototoxicity by preserving mitochondrial function and activating the Nrf2 signaling pathway

Background: Cisplatin-induced ototoxicity represents a major dose-limiting adverse effect of chemotherapy, leading to irreversible sensorineural hearing loss. Astragaloside IV (AS-IV), a bioactive saponin derived from Astragalus membranaceus, exhibits potent antioxidant and cytoprotective properties in various pathological settings. This study aimed to elucidate the protective effects and underlying mechanisms of AS-IV in cisplatin-induced cochlear injury.

Methods: In vitro, HEI-OC1 cells, cochlear basilar membrane explants, and spiral ganglion neurons were treated with cisplatin in the presence or absence of AS-IV pretreatment. Cell viability, ATP production, ROS accumulation, mitochondrial membrane potential, and Apoptosis were assessed using CCK-8, EdU incorporation, flow cytometry, immunofluorescence, and TUNEL staining. Mitochondrial DNA (mtDNA) copy number was quantified by qPCR, and exogenous mitochondrial transplantation was performed to confirm functional relevance. The potential involvement of the Nrf2 pathway was predicted by network pharmacology and validated by qPCR, Western blotting, and pharmacological inhibition.

Results: AS-IV markedly improved cell viability without influencing proliferation, and effectively preserved cochlear hair cells and spiral ganglion neurons against cisplatin-induced injury. Mechanistically, AS-IV attenuated mitochondrial dysfunction by reducing ROS overproduction, maintaining mitochondrial membrane potential, and restoring ATP synthesis. Importantly, AS-IV activated the Nrf2/HO-1/NQO1 signaling axis, whereas pharmacological inhibition of Nrf2 abrogated its protective effects.

Conclusion: Our in vitro data demonstrate that AS-IV protects cochlear cells and neurites against cisplatin-induced damage by maintaining mitochondrial integrity and activating the Nrf2-dependent antioxidant pathway. These findings highlight AS-IV as a potential therapeutic candidate for preventing chemotherapy-related hearing loss and provide novel mechanistic insight into mitochondrial preservation as a strategy for otoprotection.