Caspase-1-induced pyroptotic cell death.

Programmed cell death is a necessary part of development and tissue homeostasis enabling the removal of unwanted cells. In the setting of infectious disease, cells that have been commandeered by microbial pathogens become detrimental to the host. When macrophages and dendritic cells are compromised in this way, they can be lysed by pyroptosis, a cell death mechanism that is distinct from apoptosis and oncosis/necrosis. Pyroptosis is triggered by Caspase-1 after its activation by various inflammasomes and results in lysis of the affected cell. Both pyroptosis and apoptosis are programmed cell death mechanisms but are dependent on different caspases, unlike oncosis. Similar to oncosis and unlike apoptosis, pyroptosis results in cellular lysis and release of the cytosolic contents to the extracellular space. This event is predicted to be inherently inflammatory and coincides with interleukin-1β (IL-1β) and IL-18 secretion. We discuss the role of distinct inflammasomes, including NLRC4, NLRP3, and AIM2, as well as the role of the ASC focus in Caspase-1 signaling. We further review the importance of pyroptosis in vivo as a potent mechanism to clear intracellular pathogens.