Protecting the auditory system with glucocorticoids

Glucocorticoids are hormones released following stress-related events and function to maintain homeostasis. Glucocorticoid receptors localize, among others, to hair cells, spiral ligament and spiral ganglion neurons. Glucocorticoid receptor-induced protection against acoustic trauma is found by i) pretreatment with glucocorticoid agonists; ii) acute restraint stress; and iii) sound conditioning. In contrast, glucocorticoid receptor antagonists exacerbate hearing loss. These findings have important clinical significance since synthetic glucocorticoids are commonly used to treat hearing loss. However, this treatment has limited success since hearing improvement is often not maintained once the treatment has ended, a fact that reduces the overall appeal for this treatment. It must be realized that despite the widespread use of glucocorticoids to treat hearing disorders, the molecular mechanisms underlying this treatment are not well characterized. This review will give insight into some physiological and biochemical mechanisms underlying glucocorticoid treatment for preventing hearing loss.

► Glucocorticoid receptors localize, among others, to hair cells, spiral ligament and spiral ganglion neurons.
► Protection against acoustic trauma is found by pretreatment with i) glucocorticoid agonists; ii) acute restraint stress; or iii) sound conditioning.
► Mineralocorticoid receptors do not influence the effects of acoustic trauma.
► Mechanisms include inhibition of apoptosis, down-regulation of local pro-inflammatory cytokines, and reduced excitotoxicity.