Melatonin attenuates gentamicin-induced cochlear hair cell injury by modulating the cGAS-STING signaling pathway

Melatonin is recognized as a promising otoprotective agent, yet its involvement in aminoglycoside-induced cochlear injury remains unclear. Using HEI-OC1 cells, we established a gentamicin (GM) injury model and evaluated whether melatonin mitigates cellular damage through regulation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway. Melatonin at a non-toxic dose (50 μM) significantly improved cell viability and attenuated GM-triggered activation of the cGAS-STING signaling axis. This suppression was accompanied by reduced levels of downstream inflammatory cytokines, including IFN-β, CXCL10, TNF-α, and HMGB1, as well as IL-1β and IL-18. It also markedly attenuated DNA damage, as evidenced by decreased γ-H2AX levels and ameliorated comet parameters, and lowered apoptosis determined by TUNEL staining. These results indicate that melatonin safeguards cochlear hair cells from GM-triggered cytotoxicity by limiting inflammatory and DNA damage responses through inhibition of cGAS-STING activation. Importantly, pharmacological inhibition of STING mimicked the protective effects of melatonin, and no additive effects were observed upon combined treatment, supporting a STING-dependent mechanism. Together, these findings suggest that melatonin could serve as a therapeutic agent for aminoglycoside-related ototoxicity by targeting the cGAS-STING signaling pathway.