Endoplasmic Reticulum Stress and Noise-Induced Hearing Loss

Hearing loss is influenced by many environmental factors, and it greatly affects the quality of life. A specific sensorineural form of hearing loss is noise-induced hearing loss (NIHL). Excessive noise exposure causes damage to sensitive structures within the inner ear resulting in NIHL. The cochlea of the inner ear is extremely vulnerable to stressful conditions. The noise-induced damage is most apparent in the outer hair cells (OHCs) of the cochlea. Noise exposure results in hair cell injury and death, which is most notable in the OHCs due to their crucial role in the amplification of sound for hearing. Noise exposure can induce endoplasmic reticulum stress (ER stress) in cells by oversaturating cells with misfolded and unfolded proteins in the endoplasmic reticulum. Here we identify that elevated noise exposure induces ER stress in the OHCs leading to the onset of the unfolded protein response (UPR), which upregulates certain molecular components that activate apoptosis and inflammatory pathways.