A large proportion of the global population is affected by chronic inflammatory disorders, including atherosclerosis, type 2 diabetes and obesity, but the treatment options for these conditions are limited. Virtually, all chronic inflammatory disorders are associated with the excess production of interleukin-1β (IL-1β). IL-1β initiates and enhances inflammatory responses, hence, the production of bioactive IL-1β is normally tightly regulated at multiple levels: IL-1β is initially produced as an inactive precursor molecule that undergoes cleavage to produce bioactive IL-1β. While the bioactive cytokine can be secreted very rapidly, cleavage of IL-1β is the critical and rate-limiting step in driving inflammatory responses. Cleavage of IL-1β is mediated by a caspase-1-activating complex known as the ‘inflammasome’. Several different types of inflammasome have been described, among which the inflammasome that contains NLRP3 represents the most promising therapeutic target for disrupting IL-1β production and restricting subsequent inflammatory pathology. NLRP3 proteins are normally maintained in an auto-suppressive state, but upon activation by diverse stimuli, NLRP3 proteins bind to the ASC adaptor via a homotypic PYD interaction and ASC recruits pro-caspase-1 to initiate IL-1β processing and release. Genetic deletion of NLRP3 abrogates inflammasome signaling and ablates IL-1β release by immune cells.

We designed mimetic peptides that disrupt PYD-PYD interactions between NLRP3 and ASC. The ability of human macrophages to take up FAM-labeled peptides was assessed by flow cytometry. Peptide suppression of the NLRP3/ASC interaction was evaluated as the ability to impair the release of bioactive IL-1β from human macrophages exposed to NLRP3-specific stimuli (monosodium urate crystals, ATP). This proof-of-concept study allowed us to evaluate the therapeutic potential of inhibitory peptides for disrupting immune cell function in inflammatory diseases.