Fig. 1: Activation of Pyroptosis
Pyroptosis is initiated by PAMPs binding to pattern-recognition receptors (PRRs) on various defense cells, such as the Toll-like receptors (TLR) shown here. This, in turn, triggers the production of type-1 interferons and inflammatory cytokines such as TNF, IL-12, IL-6, and IL-8. Other PRRs, called nod-like receptors (NLRs) located in the cytosol of these defense cells recognize PAMPs and DAMPs that have entered the host cell’s cytosol. Some NLRs trigger the production of inflammatory cytokines such as IL-1 and IL-18 while others activate caspase 1-dependent pyroptosis of the cell causing the release of its intracellular inflammatory cytokines.
(While not shown here, the binding of PAMPs or DAMPs to their respective NLRs triggers the assembly of multiprotein complexes called inflammasomes in the cytosol of the host cell. It is these inflammasomes that activate caspase 1 and induce inflammation and pyroptosis.)