Ethacrynic acid regulates gentamicin ototoxicity via the blood-labyrinth barrier

Gentamicin (GM), a widely used Aminoglycoside antibiotic, has its clinical utility significantly limited by ototoxicity, which may be further exacerbated by co-administered drugs. This study systematically investigated the ototoxic mechanisms of GM combined with ethacrynic acid (EA) and the protective effects of N-acetylcysteine (NAC) using C57BL/6 J mice. Results revealed dose-dependent GM-induced ototoxicity. Intravenous administration caused more severe damage than intraperitoneal injection. Co-administration of EA synergistically potentiated GM toxicity. This exacerbated cochlear hair cell loss, auditory nerve fiber degeneration, and spiral ganglion neuron damage. Additionally, it induced systemic hepatorenal toxicity, manifested by increased macrophage activation and suppressed cell proliferation. EA disrupted inner ear homeostasis via a dual mechanism: impairing blood-labyrinth barrier integrity and triggering compensatory pericyte-mediated repair. NAC intervention significantly attenuated the combined toxicity. The pretreatment group showed the highest hair cell survival rate. Notably, EA facilitated NAC entry into the cochlea, enhancing its protective efficacy. Delayed EA administration (6 h post-GM) reduced hair cell damage by 50%. Furthermore, NAC ameliorated damage to neural fibers and synapses. This study shows that EA modulates GM ototoxicity by disrupting BLB equilibrium. The time-dependent nature of NAC intervention offers a strategy to prevent drug-induced hearing loss. These findings provide critical insights for optimizing clinical regimens involving aminoglycosides and loop diuretics.

Blood-labyrinth barrier; Ethacrynic acid; Gentamicin; N-acetylcysteine; Ototoxicity.