Abstract
This study is an investigation into the mechanism of Clostridium difficile toxin A-induced apoptosis in human intestinal epithelial cells. Toxin A induced apoptosis of T84 cells in a dose- and time-dependent fashion. Toxin A-induced apoptosis was completely inhibited by blocking toxin enzymatic activity on Rho GTPases with uridine 5'-diphosphate-2',3'-dialdehyde by a nonspecific caspase inhibitor and was partially inhibited by caspase-1, -3, -6, -8, and -9 inhibitors. Caspases 3, 6, 8, and 9 and Bid activation were detected. Toxin A also induced changes in mitochondrial membrane potential and cytochrome c release at 18-24 h, a time course similar to caspase-9 activation. In conclusion, toxin A induces apoptosis by a mechanism dependent on inactivation of Rho, activation of caspases 3, 6, 8, and 9 and Bid, and mitochondrial damage followed by cytochrome c release. Toxin A proapoptotic activity may contribute to the mucosal disruption seen in toxin A-induced enteritis.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Annexin A5 / pharmacology
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Antibodies / pharmacology
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Apoptosis*
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BH3 Interacting Domain Death Agonist Protein
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Bacterial Toxins / pharmacology*
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Carrier Proteins / metabolism
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Caspase 8
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Caspase 9
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Caspase Inhibitors
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Caspases / metabolism
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Cells, Cultured
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Cytochrome c Group / metabolism
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DNA Fragmentation / drug effects*
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Dose-Response Relationship, Drug
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Drug Interactions
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Enterotoxins / pharmacology*
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Humans
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Membrane Potentials / drug effects
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Mitochondria / drug effects*
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Mitochondria / physiology
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Time Factors
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Tumor Necrosis Factor-alpha / immunology
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Tumor Necrosis Factor-alpha / metabolism
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rho GTP-Binding Proteins / antagonists & inhibitors*
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rho GTP-Binding Proteins / metabolism
Substances
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Annexin A5
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Antibodies
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BH3 Interacting Domain Death Agonist Protein
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BID protein, human
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Bacterial Toxins
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Carrier Proteins
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Caspase Inhibitors
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Cytochrome c Group
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Enterotoxins
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Tumor Necrosis Factor-alpha
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tcdA protein, Clostridium difficile
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CASP8 protein, human
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CASP9 protein, human
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Caspase 8
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Caspase 9
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Caspases
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rho GTP-Binding Proteins