Apoptosis is a process that plays a critical role in the elimination of infected cells. Infectious diseases modulate apoptosis, and this contributes to disease pathogenesis. Apoptosis is initiated by various kinds of stimuli, including infections, radiation, etc. Increased apoptosis may assist the dissemination of intracellular pathogens or induce immunosuppression. However, apoptosis may also help eradicate pathogens from the host in many cases. Consequently, several viruses, bacteria, and parasites have evolved mechanisms to inhibit host cell by apoptosis as a strategy that may support intracellular survival and persistence of the pathogen. Bacteria are recognized by cellular receptors and elicit a multitude of signal transduction events that alter the cell’s response toward apoptotic stimuli. The result of pathogenic bacteria entering into mammalian cells evokes variety of responses, including internalization or phagocytosis of the bacteria, release of cytokines, secretion of defensins, production of oxygen radicals and the triggering of apoptosis. Bacteria can trigger apoptosis through a large variety of mechanisms that include the secretion of protein synthesis inhibitors and pore forming proteins. They can also activate apoptotic proteins such as caspases, inactivate antiapoptotic proteins, or lead to upregulation of the endogenous receptor/ligand system. However, new research has shown that many bacterial pathogens can in fact prevent apoptosis during infection. As in bacteria, many viral genomes encode proteins that repress apoptosis to escape from immune attack by the host or viruses promote apoptotic death of the host cells. Virus-host interactions may determine viral persistence, extent and severity of inflammation, and pathology associated with infectious disease. The elucidation of the signaling pathways, the cellular receptors, and/or the microbial factors involved in the induction or reduction of apoptosis could reveal new therapeutic targets for blocking microbial-induced apoptosis. This chapter will summarize the most recent research on microorganisms’ apoptotic and antiapoptotic strategies and the mechanisms relating to disease.
Part of the book: Cell Death