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Jonathan G. Crowston, Lydia H. Chang, Peter H. Constable, Julie T. Daniels, Arne N. Akbar, Peng T. Khaw; Apoptosis Gene Expression and Death Receptor Signaling in Mitomycin-C–Treated Human Tenon Capsule Fibroblasts. Invest. Ophthalmol. Vis. Sci. 2002;43(3):692-699.
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purpose. To examine the effect of mitomycin-C on the expression of apoptosis
genes in human Tenon capsule fibroblasts and to evaluate whether death
receptor signaling modulates mitomycin-C cytotoxicity.
methods. Bcl-2, Bax, Bcl-x, Fas (CD95) and tumor necrosis factor (TNF) receptor
expression was determined by flow cytometry in control and
mitomycin-C–treated Tenon fibroblasts. Fibroblast death was quantified
using a lactate dehydrogenase release assay. The effect of Fas and
TNF-receptor signaling was evaluated using Fas-specific antibodies and
results. Tenon fibroblasts constitutively express Bcl-2, Bax, and Bcl-x
in culture. Mitomycin-C (0.4 mg/mL) induced a small but consistent
increase in the expression of all three proteins. Tenon fibroblasts
express low levels of Fas but are resistant to the effects of
Fas-receptor ligation. Mitomycin-C (0.01–1.0 mg/mL) led to a
significant increase in Fas expression at all concentrations tested
(P < 0.01). Pretreatment with mitomycin-C (0.4
mg/mL) rendered fibroblasts susceptible to agonistic anti-Fas
monoclonal IgM antibodies (50–500 ng/mL) and led to a further 50%
reduction in viable fibroblasts at 48 hours, compared with mitomycin-C
alone (P < 0.05). Antibodies that block the Fas
receptor did not inhibit mitomycin-C–induced apoptosis.
conclusions. Mitomycin-C alters apoptosis gene expression and primes fibroblasts to
the effects of Fas receptor ligation. Factors other than the level of
Fas receptor expression modulate the response to Fas receptor
signaling. Determining the signals that regulate fibroblast apoptosis
may help to refine therapeutic strategies for switching off the
subconjunctival healing response and maintaining intraocular pressure
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