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Nalini Raghavachari, Kostyantyn Krysan, KuiYi Xing, Marjorie F. Lou; Regulation of Thioltransferase Expression in Human Lens Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2001;42(5):1002-1008.
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© ARVO (1962-2015); The Authors (2016-present)
purpose. To study how the expression of thioltransferase (TTase), a
critical thiol repair and dethiolating enzyme, is regulated in human
lens epithelial cells under oxidative stress. Also to examine whether
depleting the primary cellular antioxidant glutathione (GSH) in these
cells has any influence on TTase expression under the same conditions.
methods. Human lens epithelial cells (B3) were grown to confluence (1.6 million)
and gradually weaned from serum in the medium before exposing to 0.1 mM
H2O2 for 2 hours. Cells were removed at the
time intervals of 0, 5, 10, 15, 30, 60, and 120 minutes for protein
measurements of GSH and TTase activity and for reverse
transcription–polymerase chain reaction (RT-PCR) or Northern
hybridization analysis to quantify TTase mRNA. The effect of GSH
depletion on TTase mRNA expression was examined by treating the cells
with buthionine S,R-sulfoximine (BSO);
1-chloro, 2,4-dinitrobenzene (CDNB); or 1,3-bis
(2-chloroethyl)-1-nitrosourea (BCNU). Lens epithelial cells, depleted
of cellular GSH by treatment with BCNU, were subjected to oxidative
stress to examine the effect on TTase activity and mRNA level.
results. A transient increase was detected in TTase mRNA after 5 minutes of
H2O2 treatment. The upregulation reached a
maximum of 80% above the normal level by 10 minutes and gradually
decreased as the oxidant was detoxified by the cells. Manipulation of
cellular GSH level by treatment with BSO, CDNB, and BCNU resulted in a
minimum change in TTase expression. It is noteworthy that when cells
depleted of GSH were subjected to oxidative stress, TTase expression
was also found to be strongly upregulated.
conclusions. These observations suggest that the upregulation of TTase expression in
the lens epithelial cells could be an adaptive response of the cells to
combat oxidative stress to restore the vital functions of the lens
proteins and enzymes. Such regulation is independent of cellular GSH
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