The Journal of Neuroscience, October 1, 2002, 22(19):8532-8540
Caspase Activation in Hair Cells of the Mouse Utricle
Exposed to Neomycin
Lisa L.
Cunningham,
Alan G.
Cheng, and
Edwin W
Rubel
Virginia Merrill Bloedel Hearing Research Center and Department of
Otolaryngology-Head and Neck Surgery, University of Washington,
Seattle, Washington 98195-7293
Aminoglycoside exposure results in the apoptotic destruction of
auditory and vestibular hair cells. This ototoxic hair cell death is
prevented by broad-spectrum caspase inhibition. We have used in
situ substrate detection, immunohistochemistry, and specific caspase inhibitors to determine which caspases are activated in the
hair cells of the adult mouse utricle in response to neomycin exposure
in vitro. In addition, we have examined the hierarchy of
caspase activation. Our data indicate that both upstream caspase-8 and
upstream caspase-9, as well as downstream caspase-3 are activated in
hair cells exposed to neomycin. The inhibition of caspase-9-like activity provided significant protection of hair cells exposed to
neomycin, whereas the inhibition of caspase-8-like activity was not
effective in preventing neomycin-induced hair cell death. In addition,
caspase-9 inhibition prevented the activation of downstream caspase-3,
whereas the inhibition of caspase-8 did not. These data indicate that
caspase-9 is the primary upstream caspase mediating neomycin-induced
hair cell death in this preparation.
Key words:
hair cell; aminoglycoside; caspase; apoptosis; cell
death; mitochondria; ototoxicity
Copyright © 2002 Society for Neuroscience 0270-6474/02/22198532-09$05.00/0