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J. Exp. Med.,
Volume 187, Number 9, May 4, 1998 1477-1485
By
From the Laboratory of Molecular Biology, Flanders Interuniversity Institute for Biotechnology and
University of Ghent, B-9000 Ghent, Belgium
Murine L929 fibrosarcoma cells treated with tumor necrosis factor (TNF) rapidly die in a necrotic way, due to excessive formation of reactive oxygen intermediates. We investigated the
role of caspases in the necrotic cell death pathway. When the cytokine response modifier A
(CrmA), a serpin-like caspase inhibitor of viral origin, was stably overexpressed in L929 cells,
the latter became 1,000-fold more sensitive to TNF-mediated cell death. In addition, TNF
sensitization was also observed when the cells were pretreated with Ac-YVAD-cmk or
zDEVD-fmk, which inhibits caspase-1- and caspase-3-like proteases, respectively. zVAD-fmk
and zD-fmk, two broad-spectrum inhibitors of caspases, also rendered the cells more sensitive,
since the half-maximal dose for TNF-mediated necrosis decreased by a factor of 1,000. The
presence of zVAD-fmk also resulted in a more rapid increase of TNF-mediated production of oxygen radicals. zVAD-fmk-dependent sensitization of TNF cytotoxicity could be completely
inhibited by the oxygen radical scavenger butylated hydroxyanisole. These results indicate an
involvement of caspases in protection against TNF-induced formation of oxygen radicals and
necrosis.
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