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Nuclear Factor κB Protects against Host Cell Apoptosis during Rickettsia rickettsii Infection by Inhibiting Activation of Apical and Effector Caspases and Maintaining Mitochondrial Integrity
Journal article   Open access   Peer reviewed

Nuclear Factor κB Protects against Host Cell Apoptosis during Rickettsia rickettsii Infection by Inhibiting Activation of Apical and Effector Caspases and Maintaining Mitochondrial Integrity

Suresh G. Joshi, Charles W. Francis, David J. Silverman and Sanjeev K. Sahni
Infection and immunity, v 71(7), pp 4127-4136
01 Jul 2003
PMID: 12819104
url
https://doi.org/10.1128/IAI.71.7.4127-4136.2003View
Published, Version of Record (VoR)Open Access (License Unspecified) Open

Abstract

Cellular Microbiology: Pathogen-Host Cell Molecular Interactions
Apoptotic host cell death is a critical determinant in the progression of microbial infections and outcome of resultant diseases. The potentially fatal human infection caused by Rickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever, involves the vascular endothelium of various organ systems of the host. Earlier studies have shown that survival of endothelial cells (EC) during this infection depends on their ability to activate the transcription factor nuclear factor κB (NF-κB). Here, we investigated the involvement of caspase cascades and associated signaling pathways in regulation of host cell apoptosis by NF-κB. Infection of cultured human EC with R. rickettsii with simultaneous inhibition of NF-κB induced the activation of apical caspases 8 and 9 and also the executioner enzyme, caspase 3, whereas infection alone had no significant effect. Inhibition of either caspase-8 or caspase-9 with specific cell-permeating peptide inhibitors caused a significant decline in the extent of apoptosis, confirming their importance. The peak caspase-3 activity occurred at 12 h postinfection and led to cleavage of poly(ADP-ribose) polymerase, followed by DNA fragmentation and apoptosis. However, the activities of caspases 6 and 7, other important downstream executioners, remained unchanged. Caspase-9 activation was mediated through the mitochondrial pathway of apoptosis, as evidenced by loss of transmembrane potential and cytoplasmic release of cytochrome c. These findings suggest that activation of NF-κB is required for maintenance of mitochondrial integrity of host cells and protection against infection-induced apoptotic death by preventing activation of caspase-9- and caspase-8-mediated pathways. Targeted inhibition of NF-κB may therefore be exploited to enhance the clearance of infections with R. rickettsii and other intracellular pathogens with similar survival strategies.

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Collaboration types
Domestic collaboration
Web of Science research areas
Immunology
Infectious Diseases
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