Inhalation of hydrogen gas attenuates ouabain-induced auditory neuropathy in gerbils.

Abstract

Auditory neuropathy (AN) involves dysfunction of the auditory nerve while cochlear hair cells remain structurally intact. A Mongolian gerbil model of AN was established by applying ouabain (1 mmol/L, 20 mL) to the round window membrane. Animals were subsequently exposed to 1%, 2%, or 4% H2 gas for 60 minutes at 1 h and 6 h post-ouabain. Hearing function was assessed via auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) before and 7 days after ouabain administration. Spiral ganglion neuron (SGN) morphology and apoptosis were evaluated using TUNEL and activated caspase-3 immunofluorescence staining. Inhalation of 2% and 4% H2 significantly reduced ABR threshold shifts at 4, 8, and 16 kHz. SGN density loss and apoptotic SGN counts were markedly diminished in H2-treated animals. DPOAE amplitudes and hair cell morphology remained unaffected by either ouabain or H2 exposure. These findings indicate that H2 inhalation confers protection against ouabain-induced SGN damage primarily by suppressing apoptosis.

Mechanism

H2 inhalation suppresses caspase-3 activation and reduces apoptotic cell death in spiral ganglion neurons, thereby limiting ouabain-induced cochlear nerve damage through anti-apoptotic mechanisms.