Understanding the Role of the Inflammasome in Inflammation

The inflammasome is a multiprotein complex expressed in myeloid cells responsible for activation of inflammatory processes as part of the innate immune system. The inflammasome complex contains different proteins depending on the initiating event, but central to the inflammatory process is activation of caspase-1, which in turn activates the cytokines interleukin-1ß and interleukin-18 by proteolytic cleavage of pro-forms of these molecules. Caspase-1 activation also induces pyroptosis, an inflammatory form of cell death. Typically, inflammasome activation is directly monitored with western blotting of processed caspase-1 or indirectly via determination of IL-1b or IL-18 processing or release, using Western blots or ELISAs, respectively. A bioluminescent assay for the rapid detection of caspase-1 activation has been developed that enables direct measurement of an upstream signaling event in the process of inflammation. We will discuss in detail the specificity of this novel assay, monitoring caspase-1 in cells and released into the medium, differences between cell types, and multiplexing with other assays to measure relevant activities, such as cell death and IL-1b release. This new approach enables studies on the kinetics of inflammasome activation and inactivation, allows a more precise assessment of caspase-1 mediated pyroptosis, and provides a means for high throughput screening of inflammasome modulators.