title: AIF and endoG translocation in noise exposure induced hair cell death.
abstract: Activation of caspases is a key element in the apoptotic process. However, mitochondria also play an important role via the release of proapoptotic proteins. This study investigated the roles of mitochondria-related apoptosis inducing factor (AIF) and endonuclease G (endoG), mitochondrion-specific nucleases, as well as caspase-3, an important mediator of apoptosis, in noise exposure induced hair cell death. Guinea pigs were exposed for 4h/day to broadband noise at 122 dB SPL for 2 days. After the noise exposure, the cochleae were examined for the activity of caspase-3 with carboxyfluorescein-labeled fluoromethyl ketone (FMK)-peptide inhibitors. The cochleae were further examined for AIF and endoG translocation from the mitochondria by immunohistochemistry. Noise exposure triggered activation of caspase-3 in apoptotic hair cells. In the normal organ of Corti, AIF and endoG were co-localized to the mitochondria. After noise exposure, AIF translocated into the nuclei of apoptotic and necrotic hair cells. The translocation of endoG from mitochondria into the nucleus was also found in apoptotic OHCs. These findings indicate that mitochondria-released proapoptotic proteins, AIF and endoG, are important factors in a noise-induced hair cell death pathway.
authors.affiliation: Oregon Hearing Research Center, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, NRC04, Portland, OR 972390-3098, USA.
authors.forename: Weiju
authors.initials: W
authors.lastname: Han
authors.forename: Xiaorui
authors.initials: X
authors.lastname: Shi
authors.forename: Alfred L
authors.initials: AL
authors.lastname: Nuttall
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D051033:Apoptosis Inducing Factor / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004789:Enzyme Activation; D005260:Female; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000378:metabolism* / Q000473:pathology*; D006317:Hearing Loss, Noise-Induced / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D008928:Mitochondria / Q000378:metabolism
chemical_list: D051033:Apoptosis Inducing Factor; D004706:Endodeoxyribonucleases; C052391:endonuclease G; D053148:Caspase 3; D020169:Caspases