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Infect. Immun., Dec 1997, 5165-5170, Vol 65, No. 12
H Hilbi, Y Chen, K Thirumalai and A Zychlinsky
Shigella, the etiological agent of bacillary dysentery, rapidly kills human
monocyte-derived macrophages in vitro. Wild-type Shigella flexneri, but not
a nonvirulent derivative, induced human macrophage apoptosis as determined
by morphology and terminal deoxynucleotidyltransferase-mediated dUTP-biotin
nick end labeling (TUNEL). Shigella-mediated macrophage cell death was
blocked by the peptide inhibitors of caspases,
acetyl-Tyr-Val-Ala-Asp-aldehyde (acetyl- YVAD-CHO) and
acetyl-Tyr-Val-Ala-Asp-chloromethylketone (acetyl-YVAD- CMK). Protection
from apoptosis by YVAD was observed in monocytes matured in the presence or
absence of colony-stimulating factors (CSF) like macrophage-CSF or
granulocyte-macrophage-CSF. Furthermore, lipopolysaccharide (LPS) or gamma
interferon (IFN-gamma) rendered human macrophages partially resistant to
Shigella cytotoxicity. Macrophages stimulated with either LPS or IFN-gamma
were also protected by YVAD from Shigella-induced cell death. During
Shigella infections of human macrophages, interleukin-1beta (IL-1beta) was
cleaved to the mature form. IL-1beta maturation was severely retarded by
YVAD, indicating that IL-1beta-converting enzyme (ICE; caspase 1) is
activated in Shigella-induced apoptosis. The finding that Shigella induces
apoptosis in human macrophages by activating ICE supports the hypothesis
that the acute inflammation characteristic of shigellosis is initially
triggered by apoptotic macrophages which release mature IL-1beta during
programmed cell death.
Copyright © 1997, American Society for Microbiology
The interleukin 1beta-converting enzyme, caspase 1, is activated during Shigella flexneri-induced apoptosis in human monocyte-derived macrophages
The Skirball Institute, Department of Microbiology, New York University School of Medicine, New York 10016, USA.
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