[Apoptosis and dynamic caspase-3 expression during the immune response of inner ear].
OBJECTIVE
To investigate whether apoptosis is involved in the pathogenesis of the immune response of inner ear, and relation between signal transportation of Caspase-3 and apoptosis.


METHODS
Forty-five healthy, female white guinea pigs were employed in this study. Sensitized systematically with keyhole limpet hemocyanin (KLH), the KLH-immunized animals were inoculated with the same antigen, and the control animals were injected PBS through cochlea basal turn. All animals were sacrificed respectively at 1st, 3rd, 5th, 7th and 14th day after inner ear vaccination. The auditory brainstem response (ABR) was measured before the KLH injection to the inner ear and just before sacrificing the animal. Paraffin sections of cochleas from animals were stained using a TUNEL assay to identify inner ear cells undergoing apoptosis,and immunohistochemistry method was used to detect the expression of Caspase-3 in the inner ears.


RESULTS
After immunization, the ABR thresholds of the KLH-challenged ears were significantly elevated by comparing with the preimmunization (P < 0.05), but after injection, there was no significant difference in the ABR thresholds of the PBS-injected ears compared with preinjection. TUNEL-positive cells were found in the KLH immunized inner ears but no TUNEL-positive cells were observed in the control inner ears except for a few positive cells in the supporting cells, the stria vascularis cells and the spiral ganglion cells. The positive cells are the outer hair cells in Cortis organ, and the marginal cells in the stria vascularis and the neurons in the spiral ganglion. And, under morphological analysis by light microscope, these cells have the features characteristic of apoptosis. Apparent Caspase-3 immunoreactivity expression could be detected in Corti's organ, the lateral wall and the neurons of the spiral ganglion in the KLH-immunized inner ears from 5th day after inner ear vaccination, but no cells staining positive for Caspase-3 were found in the control inner ears.


CONCLUSIONS
Apoptosis is induced by the immune response of inner ear; Caspase-3 cascade has important effect on the course of apoptosis.
Xu
Lijuan
L
Department of Otolaryngology, Affiliated Hospital of Medical College, Wuhan University of Science and Technology, Wuhan, 430064, China. xlj1031@126.com
Gong
Shusheng
S
Wang
Jibao
J
Huang
Xiang
X
D000818:Animals; D017209:Apoptosis; D015551:Autoimmunity; D053148:Caspase 3 / Q000378:metabolism*; D007758:Ear, Inner / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000166:cytology / Q000378:metabolism
D053148:Caspase 3