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Naomichi Katai, Takanobu Kikuchi, Hiroto Shibuki, Sachiko Kuroiwa, Jun Arai, Toru Kurokawa, Nagahisa Yoshimura; Caspaselike Proteases Activated in Apoptotic Photoreceptors of Royal College of Surgeons Rats. Invest. Ophthalmol. Vis. Sci. 1999;40(8):1802-1886.
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purpose. To study the role of caspase-like proteases, especially roles of more
extensively characterized caspase-1 and caspase-2, in apoptotic
photoreceptor cell degeneration in Royal College of Surgeons (RCS)
methods. Both RCS and Sprague—Dawley rats were used. Cryosections of the
retinas at various postnatal times were immunostained with antibodies
against caspase-1 (interleukin-1β–converting enzyme, ICE) and
caspase-2 (Nedd2/Ich-1). Double staining with TdT-dUTP terminal
nick–end labeling (TUNEL), propidium iodide, and the antibodies was
also performed. To evaluate the time course of protein expression,
western blot analysis was carried out. The temporal profile of
caspase-like protease activity was studied using a fluorogenic
tetrapeptide substrate, acetyl-tyrosyl-valyl-alanyl-aspartic acid α
(4-methyl-coumaryl-7-amide) (Ac-YVAD-MCA). Intravitreal injection of a
caspase-1 inhibitor, acetyl-tyrosyl-valyl-alanyl-aspartic-aldehyde
(Ac-YVAD-CHO), at postnatal days 21 (P21) and P26 was performed to see
if this caused a decrease in apoptotic cell number at P28.
results. TUNEL-positive photoreceptors of RCS rats stained strongly with
antibodies against caspase-1 and caspase-2. Double staining studies
revealed that caspase-1 and caspase-2 were coexpressed in apoptotic
cells. Western blot analysis showed that active forms of
caspase-1–like and caspase-2–like proteases were upregulated at P28,
concurrent with the peak in TUNEL-positive cells. The enzymatic
activity of caspase-1–like protease was elevated in RCS rat retinas at
P28, and the inhibitor of caspase-1 transiently reduced the number of
the apoptotic photoreceptors.
conclusions. Activation of caspase-like proteases plays an important role in
photoreceptor apoptosis of RCS rats.
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