[Caspase 3 activation and apoptosis inducing factor translocation in noise exposure induced out hair cells apoptosis].
OBJECTIVE
To investigate the pathway and mechanism of noise exposure induced out hair cells (OHC) apoptosis.


METHODS
The cochleae of control and noise exposure group were dissected. The activity of caspase 3, an important mediator of apoptosis, in OHC, was examined with carboxyfluorescein-labeled fluoromethyl ketone (FMK)-peptide inhibitors. The apoptosis inducing factor (AIF) translocation from mitochondria in OHC were further examined by immunohistology method. The nuclei were labeled with PI and the mitochondrion was labeled with Mito-tracker. Whole mount organ of Corti was prepared. Morphological and fluorescent change was observed use confocal microscope.


RESULTS
In the normal OHC, AIF is distributed where the mitochondria were located and no activated caspase 3 was observed. After the animals exposed to broadband noise at 122 dB in 4 h/day for 2 days, both apoptosis and necrosis were appeared in OHC. AIF translocated from mitochondrion to nuclei in apoptotic and necrotic OHC following noise exposure. The noise exposure triggered activation of caspase 3 in apoptic hair cells. But no caspase 3 activation appeared in necrotic OHC.


CONCLUSIONS
These findings indicated that the caspase-dependent pathway is an important pathway in noise exposure induced apoptosis. And AIF also involves OHC death pathway following noise exposure.
Han
Wei-ju
WJ
Department of Otorhinolaryngology Head and Neck Surgery, Chinese People's Liberation Army General Hospital,100853 Beijing, China. hanweiju@hotmail.com
Shi
Xiao-rui
XR
Nuttall
Alfred
A
D000818:Animals; D017209:Apoptosis; D051033:Apoptosis Inducing Factor / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism*; D005260:Female; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D009622:Noise
D051033:Apoptosis Inducing Factor; D053148:Caspase 3