title: JNK signaling in neomycin-induced vestibular hair cell death.
abstract: Mechanosensory hair cells are susceptible to apoptotic death in response to exposure to ototoxic drugs, including aminoglycoside antibiotics. The c-Jun n-terminal kinase (JNK) is a stress-activated protein kinase that can promote apoptotic cell death in a variety of systems. Inhibition of the JNK signaling pathway can prevent aminoglycoside-induced death of cochlear and vestibular sensory hair cells. We used an in vitro preparation of utricles from adult mice to examine the role of JNK activation in aminoglycoside-induced hair cell death. CEP-11004 was used as an indirect inhibitor of JNK signaling. Immunohistochemistry showed that both JNK and its downstream target c-Jun are phosphorylated in hair cells of utricles exposed to neomycin. CEP-11004 inhibited neomycin-induced phosphorylation of both JNK and c-Jun. CEP-11004 inhibited hair cell death in utricles exposed to moderate doses of neomycin. However, the results were not uniform across the dose-response function; CEP-11004 did not inhibit hair cell death in utricles exposed to high-dose neomycin. The CEP-11004-induced protective effect was not due to inhibition of PKC or p38, since neither Chelerythrine nor SB203580 could mimic the protective effect of CEP-11004. In addition, inhibition of JNK inhibited the activation of caspase-9 in hair cells. These results indicate that JNK plays an important role in neomycin-induced vestibular hair cell death and caspase-9 activation.
authors.affiliation: Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington, Seattle, WA 98195-7923, USA.
authors.forename: Kazuma
authors.initials: K
authors.lastname: Sugahara
authors.forename: Edwin W
authors.initials: EW
authors.lastname: Rubel
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Cunningham
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002227:Carbazoles / Q000494:pharmacology; D053453:Caspase 9 / Q000378:metabolism; D004789:Enzyme Activation; D006198:Hair Cells, Auditory / Q000187:drug effects* / Q000473:pathology; D007211:Indoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D008808:Mice, Inbred CBA; D009355:Neomycin / Q000633:toxicity*
chemical_list: C469298:CEP-11004; D002227:Carbazoles; D007211:Indoles; D048031:JNK Mitogen-Activated Protein Kinases; D053453:Caspase 9; D009355:Neomycin