Significance of the caspase family in Helicobacter pylori induced gastric epithelial apoptosis.
OBJECTIVE
H. pylori infection results in an increased epithelial apoptosis in gastritis and duodenal ulcer patients. We investigated the role and type of activation of caspases in H. pylori-induced apoptosis in gastric epithelial cells.


METHODS
Differentiated human gastric cancer cells (AGS) and human gastric mucous cell primary cultures were incubated with H. pylori for 0.5-24 hours in RPMI 1640 medium, and the effects on cell viability, epithelial apoptosis, and activity of caspases were monitored. Apoptosis was analyzed by detection of DNA-fragments by Hoechst stain(R), DNA-laddering, and Histone-ELISA. Activities of caspases were determined in fluorogenic assays and by Western blotting. Cleavage of BID and release of cytochrome c were analyzed by Western blot. Significance of caspase activation was investigated by preincubation of gastric epithelial cells with cell permeable specific caspase inhibitors.


RESULTS
Incubation of gastric epithelial cells with H. pylori caused a time and concentration dependent induction of DNA fragmentation (3-fold increase), cleavage of BID, release of cytochrome c and a concomittant sequential activation of caspase-9 (4-fold), caspase-8 (2-fold), caspase-6 (2-fold), and caspase-3 (6-fold). No effects on caspase-1 and -7 were observed. Activation of caspases preceded the induction of DNA fragmentation. Apoptosis could be inhibited by prior incubation with the inhibitors of caspase-3, -8, and -9, but not with that of caspase-1.


CONCLUSIONS
Activation of certain caspases and activation of the mitochondrial apoptotic pathway are essential for H. pylori induced apoptosis in gastric epithelial cells.
Potthoff
A
A
Department of Gastroenterology, Hepatology and Endocrinology, Medizinische Hochschule Hannover, Germany.
Ledig
S
S
Martin
J
J
Jandl
O
O
Cornberg
M
M
Obst
B
B
Beil
W
W
Manns
M P
MP
Wagner
S
S
D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000382:microbiology*; D005753:Gastric Mucosa / Q000166:cytology / Q000382:microbiology*; D016480:Helicobacter pylori / Q000472:pathogenicity*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D013274:Stomach Neoplasms; D014407:Tumor Cells, Cultured
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D003574:Cytochrome c Group; D020169:Caspases