The Journal of Neuroscience, February 15, 2002, 22(4):1218-1227
Inhibition of Caspases Prevents Ototoxic and Ongoing Hair
Cell Death
Jonathan I.
Matsui1, 2,
Judith M.
Ogilvie1, 3, and
Mark E.
Warchol1, 2, 4, 5
1 Central Institute for the Deaf, Fay and Carl Simons
Center for Biology of Hearing and Deafness, 2 Division of
Biology and Biomedical Sciences, Neuroscience Graduate Program, and
Departments of 3 Ophthalmology and Visual Sciences,
4 Otolaryngology, and 5 Anatomy and
Neurobiology, Washington University School of Medicine, St. Louis,
Missouri 63110
Sensory hair cells die after acoustic trauma or ototoxic insults,
but the signal transduction pathways that mediate hair cell death are
not known. Here we identify several important signaling events that
regulate the death of vestibular hair cells. Chick utricles were
cultured in media supplemented with the ototoxic antibiotic neomycin
and selected pharmacological agents that influence signaling molecules
in cell death pathways. Hair cells that were treated with neomycin
exhibited classically defined apoptotic morphologies such as condensed
nuclei and fragmented DNA. Inhibition of protein synthesis (via
treatment with cycloheximide) increased hair cell survival after
treatment with neomycin, suggesting that hair cell death requires
de novo protein synthesis. Finally, the inhibition of
caspases promoted hair cell survival after neomycin treatment.
Sensory hair cells in avian vestibular organs also undergo continual
cell death and replacement throughout mature life. It is unclear
whether the loss of hair cells stimulates the proliferation of
supporting cells or whether the production of new cells triggers the
death of hair cells. We examined the effects of caspase inhibition on
spontaneous hair cell death in the chick utricle. Caspase inhibitors reduced the amount of ongoing hair cell death and ongoing supporting cell proliferation in a dose-dependent manner. In isolated sensory epithelia, however, caspase inhibitors did not affect supporting cell
proliferation directly. Our data indicate that ongoing hair cell
death stimulates supporting cell proliferation in the mature utricle.
Key words:
auditory; hair cell; vestibular; tissue culture; apop-tosis; proliferation; caspase inhibitors; regeneration
Copyright © 2002 Society for Neuroscience 0270-6474/02/2241218-10$05.00/0