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Infection and Immunity, May 2001, p. 3181-3189, Vol. 69, No. 5
Department of Bacterial and Blood Products,
National Institute of Infectious Diseases, Tokyo
208-0011,1 and Department of Clinical
Laboratory, Nagoya University Hospital, Nagoya
466-8560,2 Japan
Received 21 November 2000/Returned for modification 15 January
2001/Accepted 19 February 2001
The enhanced gastric epithelial cell apoptosis observed during
infection with Helicobacter pylori has been suggested to be of significance in the etiology of gastritis, peptic ulcers, and neoplasia. To investigate the cell death signaling induced by H. pylori infection, human gastric epithelial cells were incubated with H. pylori for up to 72 h. H. pylori
infection induced the activation of caspase -8, -9, and -3 and the
expression of the proapoptotic Bcl-2 family proteins Bad and Bid. The
peak of the activity of the caspases occurred at 24 h. At this
time, the inhibition of caspase-8 or -9 almost completely suppressed
H. pylori-induced apoptosis. Inhibition of caspase-8
suppressed the expression of Bad and Bid and the subsequent activation
of caspase-9 and -3. These observations indicate that H. pylori induces apoptosis through a pathway involving the
sequential induction of apical caspase-8 activity, the proapoptotic
proteins Bad and Bid, caspase-9 activity, and effector caspase-3
activity. Activation of the pathway was independent of CagA or
vacuolating toxin. A membrane fraction of H. pylori was
sufficient to activate this pathway, and treatment with proteinase K
eliminated the activity. Apoptotic activity of the membrane fraction
was significantly increased by incubating the bacteria under
serum-starved conditions for 24 h. These observations suggest that
environmental conditions in the human stomach could induce H. pylori-mediated pathogenesis, leading to a variety of clinical outcomes.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.5.3181-3189.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Apoptotic Signaling Pathway Activated by
Helicobacter pylori Infection and Increase of
Apoptosis-Inducing Activity under Serum-Starved Conditions
*
Corresponding author. Mailing address: Department of
Bacterial and Blood Products, National Institute of Infectious
Diseases, 4-7-1, Gakuen, Musashimurayama, Tokyo 208-0011, Japan. Phone: 81-42-561-0771. Fax: 81-42-561-7173. E-mail:
keigo{at}nih.go.jp.
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