Noise-Induced Hearing Loss / 한양의대학술지

ABSTRACT

Noise-induced hearing loss (NIHL) is the second most common cause of permanent hearing impairment after age-related hearing loss. NIHL is influenced by environmental and genetic factors and the effects of noise can be exacerbated by the administration of ototoxic drugs or exposure to chemicals. The pathophysiology of NIHL is classified as either mechanical injury or metabolic (or biochemical) injury. Exposure of cochleae to intense sounds has been found to disrupt the stereocilia on the hair cells by separating the tip links and to depolymerize actin filaments, resulting in a disturbance in signal transduction. Major mechanisms of metabolic injuries include accumulation of reactive oxygen species enhanced by oxidative stress, cochlear ischemia followed by reperfusion injury, and excitotoxicity to auditory neuron induced by excessive release of the cochlear afferent neurotransmitter, glutamate. Many studies involving therapeutic or preventive trial with antioxidants, JNK inhibitors, and NMDA antagonists have shown partial effectiveness. However, protection from noise before cochlear injury occurs is very important because damaged hair cells and auditory neurons in the mammalian cochleae are unable to regenerate.