Noncanonical NLRP3 Inflammasome Activation: Standard Protocols

The canonical activation of multimeric inflammasomes usually occurs through caspase-1 activation, and it is characterized by the presence of extracellular IL-1β and IL-18 or measuring danger signal proteins, such as HMGB1 using enzyme-linked immunosorbent assay (ELISA) or Western blots; these assays differentiate non-cleaved and cleaved forms of these two cytokines (the cleaved form is the mature and active form). Similar techniques can be used to assess noncanonical inflammasome activation. Real-time PCR can measure the relative mRNA expression for a specific gene, whereas Western blots or immunocytochemistry can detect the presence of proteins by binding of specific antibodies to their antigens in biological samples. Moreover, noncanonical inflammasome activation can be evaluated through the cleavage of the amino and the carboxy terminals of one important component, gasdermin D (GSDMD), whose cleavage induces its pyroptotic activity. Thus, the analysis of cleaved GSDMD is an ideal pathway to study the noncanonical inflammasome. ELISA and immunoblot can be performed on cell culture supernatants or cell extracts.