F-actin cleavage in apoptotic outer hair cells in chinchilla cochleas exposed to intense noise.
Apoptosis is an active cell death pathway involved in a variety of pathological conditions, including noise-induced outer hair cell (OHC) death. During this process, the cytoskeletal proteins have been found to be either damaged and/or enzymatically disassembled in several cell types, leading to formation of apoptotic manifestations. This study was designed to examine the cleavage of filamentous actin (F-actin), an important cytoskeletal protein, in the cochlear OHCs after noise exposure. Chinchillas were exposed to a 4 kHz narrow band noise at 106 dB SPL for 1 h and cochleas were either collected immediately or 3 h after the noise exposure. The organs of Corti were double-stained using FITC-labeled phalloidin for F-actin and propidium iodide for OHC nuclei. The effect of noise on F-actin and nuclei was examined by confocal microscopy. The result showed that the fluorescence associated with F-actin was decreased in the OHCs possessing condensed nuclei, but remained unchanged in the OHCs with swollen nuclei. The change in F-actin labeling occurred coordinately with the changes in nuclear morphology of apoptotic cells and was prevented by administration of caspase-3 inhibitor (Z-DEVD-FMK). The results of this study indicate that F-actin cleavage is an important early cellular event in apoptotic development in OHCs following exposure to traumatic noise.
D000199:Actins / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D061945:Caspase Inhibitors; D002467:Cell Nucleus / Q000473:pathology; D002682:Chinchilla; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D006317:Hearing Loss, Noise-Induced / Q000378:metabolism* / Q000473:pathology*; D018613:Microscopy, Confocal; D009842:Oligopeptides / Q000494:pharmacology
D000199:Actins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; D053148:Caspase 3