Glutathione limits noise-induced hearing loss

Area of Science:

• Oto-neurology
• Cellular biology
• Toxicology

Background:

• Reactive oxygen species (ROS) generation is implicated in noise-induced hearing loss (NIHL).
• Glutathione (GSH) is a key endogenous antioxidant that mitigates cellular damage from ROS.
• GSH deficiency may exacerbate NIHL, but its protective role requires further investigation.

Purpose of the Study:

• To evaluate the protective effect of a glutathione supplement against NIHL in GSH-deficient guinea pigs.
• To determine if glutathione monoethyl ester (GSHE) can prevent or reduce NIHL-related auditory threshold shifts and hair cell loss.
• To explore the role of GSH in mitigating oxidative stress during NIHL.

Main Methods:

• Pigmented guinea pigs were fed a low-protein diet to induce GSH deficiency.
• Animals were exposed to loud octave band noise (115 dB SPL) for 5 hours.
• GSHE or a saline control was administered intraperitoneally before and after noise exposure.
• Auditory brainstem response (ABR) and cytocochleograms were used to assess hearing thresholds and hair cell damage.

Main Results:

• GSH-deficient animals (Group 2) exhibited significantly greater threshold shifts and hair cell loss compared to controls (Group 1).
• GSHE administration dose-dependently attenuated threshold shifts and reduced hair cell loss in GSH-deficient animals.
• Higher GSHE doses (Group 4) showed protection comparable to or better than normal-diet animals (Group 1).

Conclusions:

• GSH plays a critical role in protecting the cochlea against noise-induced damage.
• Antioxidant supplementation, specifically with GSH, may serve as an effective prophylactic intervention for NIHL.
• These findings support the hypothesis that ROS generation contributes significantly to NIHL pathogenesis.