Furosemide prevents noise-induced hearing loss and enhances the preventive effect of N-acetylcysteine.

Abstract

Disruption of reactive oxygen species (ROS) homeostasis is a key mechanism underlying noise-induced sensory hair cell damage. Antioxidant treatments such as N-acetylcysteine (NAC) have been shown to attenuate noise-induced hearing loss (NIHL), supporting the role of ROS accumulation. However, no FDA-approved pharmaceutical therapy currently exists for the prevention or treatment of NIHL, likely due to the complexity of the damaging mechanisms and the presence of the blood-labyrinth barrier (BLB), which limits drug permeability and prevents therapeutic compounds from reaching effective concentrations via systemic administration. Furosemide (FRS) has demonstrated potential to reduce NIHL and facilitate drug delivery into inner ear by transiently opening the BLB. In this study, we investigated the mechanisms by which FRS pretreatment prevents NIHL. A single dose of 200 mg/kg FRS administered immediately before noise exposure significantly reduced NIHL in FVB/NJ mice. One hour after FRS treatment, the endocochlear potential (EP) was temporarily reduced without altering cochlear sensitivity (ABR thresholds), outer hair cell function (DPOAE amplitudes), or synaptic transmission integrity between hair cells and auditory nerve fibers (suprathreshold ABR wave I amplitudes). Furthermore, this dose of FRS selectively increased stria vascularis permeability to small molecules but not to large protein-bound tracers. Combined treatment with FRS and NAC enhanced NAC's antioxidant effect and additively prevented noise-induced outer hair cell (OHC) loss and NIHL, with OHC loss almost entirely prevented. These findings provide important insight into future strategies for the prevention and treatment of NIHL.