Brimonidine protects IHC ribbon synapses and SGNs from noise-induced hearing loss

Exposure to excessive noise levels can result in hearing impairment. Currently, there are no effective pharmacological interventions available for the prevention of noise-induced hearing loss. This study was designed to investigate the protective effects of brimonidine, an α2-adrenergic receptor agonist, against noise-induced inner ear damage in mice, as well as to explore the underlying mechanisms. Eight-week-old male C57BL/6 mice were randomly assigned to one of three experimental groups: a control group, a noise exposure (NE) group (exposed to broadband noise, 8–16 kHz, at 100 dB SPL for 2 hours), and a brimonidine-treated group (which received intraperitoneal injections of 1 mg/kg brimonidine prior to noise exposure). Our findings demonstrate that brimonidine significantly attenuates noise-induced hearing loss in young adult mice. Furthermore, brimonidine markedly reduces glutamate (Glu) accumulation in the inner ear. RNA sequencing analysis suggests that brimonidine exerts its protective effects, in part, through the downregulation of inflammatory cytokines and immunoglobulin-related pathways. These results indicate that brimonidine is a promising pharmacological agent for the prevention of noise-induced hearing loss.