Cochlear Ion Homeostasis Mechanisms Are Suppressed in Autoimmune Inner Ear Disease and Restored by Glucocorticoid Treatment
New way of thinking may help us find more effective treatment with fewer side effects
February 19-23, 2011, Baltimore: National Institutes of Health (NIH)-supported scientists will be presenting their latest research findings at the 2011 Midwinter Meeting of the Association for Research in Otolaryngology (ARO).
People who have an autoimmune disease—such as lupus or rheumatoid arthritis—also frequently experience hearing loss, and the conventional wisdom is that this is due to inflammation in the inner ear. As a result, most doctors will typically prescribe glucocorticoids, a family of steroids that quell the inflammation and improve hearing, but can have serious side effects if taken too long. NIDCD-funded researchers from Oregon Health & Science University see things a different way.
Their research shows that, although glucocorticoids may help improve hearing, they don’t seem to be acting on inflammation, which isn’t present in autoimmune mouse models with hearing loss. Rather, they seem to be correcting an imbalance in ions in the fluid of the inner ear, which is the more likely source of hearing loss.
In this study, the researchers looked at gene expression in autoimmune mice with hearing loss and found that 22 of the 24 genes regulating ion concentration in the inner ear were turned off. Genes that regulate the inflammatory response also were not activated, which is the opposite of what you’d expect to find if inflammation were involved. When the mice received glucocorticoid treatment, the expression of several ion-regulating genes significantly increased, while there was no effect on inflammation.
What’s happening, the researchers suggest, is that glucocorticoid molecules are attaching themselves to receptors for another steroid group, called mineralocorticoids, whose job is to maintain proper ion balances in the inner ear. The researchers propose that developing a treatment that is based on regulating ion concentration instead of controlling inflammation may be more effective and offer fewer side effects for people with autoimmune diseases as well as some other hearing and balance disorders, such as sudden hearing loss and Ménière’s disease.
Source: National Institute on Deafness and Other Communication Disorders (NIDCD)