title: Anti-apoptotic role of retinoic acid in the inner ear of noise-exposed mice.
abstract: Exposure to loud noise can induce temporary or permanent hearing loss, and acoustic trauma is the major cause of hearing impairment in industrial nations. However, the mechanisms underlying the death of hair cells after acoustic trauma remain unclear. In addition to its involvement in cellular stress and apoptosis, the c-Jun N-terminal kinase (JNK), a member of the mitogen-activated protein kinase family, is involved in cell survival, transformation, embryonic morphogenesis, and differentiation. JNK is primarily activated by various environmental stresses including noise, and the phenotypic result appears be to cell death. All-trans retinoic acid (ATRA) is an active metabolite of vitamin A that regulates a wide range of biological processes, including cell proliferation, differentiation, and morphogenesis. We evaluated the role of ATRA in preserving hearing in mice exposed to noise that can induce permanent hearing loss. Mice fed with ATRA before and during 3 consecutive days of noise exposure had a more preserved hearing threshold than mice fed sesame oil or saline. Histological and TUNEL staining of the cochlea showed significantly enhanced preservation of the organ of Corti, including outer hair cells and relatively low apoptotic nuclei, in mice-fed ATRA than in mice-fed sesame oil or saline. Phospho-JNK immunohistochemistry showed that ATRA inhibited the activation of JNK. These results suggest that ATRA has an anti-apoptotic effect on cochleae exposed to noise.
authors.affiliation: Department of Otolaryngology, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, Republic of Korea.
authors.forename: Joong Ho
authors.initials: JH
authors.lastname: Ahn
authors.forename: Hun Hee
authors.initials: HH
authors.lastname: Kang
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Kim
authors.forename: Jong Woo
authors.initials: JW
authors.lastname: Chung
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D049109:Cell Proliferation; D002470:Cell Survival; D003051:Cochlea / Q000378:metabolism; D007758:Ear, Inner / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D006198:Hair Cells, Auditory / Q000378:metabolism; D034381:Hearing Loss; D006317:Hearing Loss, Noise-Induced; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System; D051379:Mice; D008807:Mice, Inbred BALB C; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009622:Noise; D009925:Organ of Corti / Q000378:metabolism; D013997:Time Factors; D014212:Tretinoin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D014212:Tretinoin; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases