Autoimmune
inner ear disease (AIED) is a poorly understood disease marked by bilateral, rapidly progressive
hearing loss triggered by unknown stimuli, which is
corticosteroid responsive in 60 % of patients. Although the mechanism of the disease is not precisely understood, a complex interaction of
cytokines is believed to contribute toward the inflammatory disease process and
hearing loss. Previously, we showed the role of TNF-α in
steroid-sensitive and IL-1β in
steroid-resistant immune-mediated
hearing loss.
N-Acetylcysteine (NAC), a broad spectrum
antioxidant, has been effective in other autoimmune disorders. Other studies have shown NAC to have a protective adjunct role in human idiopathic
sudden hearing loss, where the addition of NAC resulted in better hearing recovery than with
steroids alone, although the mechanism of this protection was not elucidated. In the present study, we observed PBMCs from AIED patients exhibited higher baseline TNF-α and MPO levels compared with normal healthy controls. NAC effectively abrogates LPS-mediated TNF-α release from PBMC of both AIED patients and controls. We demonstrated that in AIED patients, the TNF-α downstream signaling pathway appears aberrantly regulated, influencing both MPO and
IL-8 expression. Given that NAC effectively abrogated LPS-mediated TNF-α release and exerted minimal effects on the downstream targets of this pathway, we feel NAC may be a rational adjunct
therapy for this enigmatic disease, worthy of clinical exploration.