Modulation of apoptosis during infection with Chlamydia
David M. Ojcius: 0000-0003-1461-4495
Methods in Enzymology
This chapter describes methods used to measure apoptosis or inhibition of apoptosis during infection, particularly techniques that reveal host cell morphological changes, caspase activation, mitochondrial membrane depolarization, cytochrome c release, and DNA fragmentation. Apoptosis is apparently blocked through inhibition of cytochrome c release from mitochondria and subsequent caspase-3 activation, In contrast, induction of host cell apoptosis has also been observed in macrophages and epithelial cells infected by C. psittaci during late stages of the infection, and the apoptosis requires intracellular bacterial replication. C. psittaci-induced apoptosis may require secretion of a bacterial apoptotic factor, potentially via the type III secretion apparatus and/or may be a stress response in the infected cell. Furthermore, the hallmarks of apoptosis are condensation of the nuclear chromatin and cytoplasm, activation of proteases (caspases) and endonucleases, loss of plasma membrane phosphatidylserine (PS) asymmetry, cleavage of the DNA into 200 base-pair oligonucleosomal fragments, and segmentation of the dying cell into membrane-bound apoptotic bodies. Intracellular microbes can also modulate apoptosis of the host cell, either inhibiting or promoting cell death, and it has been proposed that the persistence and pathogenesis of several pathogenic microbes may be related to their ability to dysregulate apoptosis.
Ojcius, D. M.
Modulation of apoptosis during infection with Chlamydia.
Methods in Enzymology, 358, 334–344.