The NLRP3 inflammasome is an intracellular complex containing the proteins ASC, Caspase-1, and NLRP3. Activation of this complex, which leads to secretion of the pro-inflammatory cytokines IL-1? and IL-18, plays an essential role in host defense against various pathogens and danger signals. Gain-of-function mutations in the Nlrp3 gene are responsible for a spectrum of autoinflammatory diseases collectively referred to as cryopyrin-associated periodic syndromes (CAPS). CAPS includes the familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS), and neonatal-onset multisystem inflammatory disease (NOMID). An important role for IL-1? in these diseases has been established. However, little is known about the key cell type(s) that mediate inflammasome activity and produce IL-1? in CAPS. A better knowledge of these cellular events would be beneficial for the design of future therapies for CAPS and other inflammasome- and IL-1? -dependent diseases. The central hypothesis of this proposal is that, by representing an important source of inflammasome activity and IL-1? in CAPS, neutrophils play a key role in the development of these disorders and therefore are potential therapeutic targets in this setting. This hypothesis will be tested using mouse models of CAPS as well as by analyzing blood and skin specimens from CAPS patients.
In Specific Aim 1, we will generate and characterize a new mouse strain allowing selective and inducible depletion of neutrophils or neutrophil-derived products. This new transgenic mouse will be an important tool for this project and, more generally, for investigating diverse neutrophil functions in vivo.
In Specific Aim 2, we will use tis new mouse strain and other transgenic mice to assess the roles of neutrophils and neutrophil-derived IL-1? in mouse models of CAPS. We will also evaluate the clinical relevance of our findings by studying whether neutrophils represent important sources of IL-1? in patients with CAPS by analyzing this cytokine in the patients'skin and blood specimens. We believe that our studies will be the first to investigate the importance of neutrophils in CAPS, and to provide insight into the mechanism by which neutrophils mediate their functions in these diseases, and will advance understanding of both neutrophil and inflammasome biology. This work will be preformed in the laboratory of the sponsor, Stephen Galli. Harold Hoffman will serve as co-mentor, providing scientific expertise as well as blood and skin samples from CAPS patients. An advisory committee with additional expertise in aspects of inflammasome or IL-1? biology will meet regularly to provide scientific feedback and career advice to support Dr. Reber and his project. Stanford University School of Medicine, and the Galli laboratory in particular, offer an environment uniquely suited to completing this project, and to facilitating Dr. Reber's transition to independence.
Patients with a cryopyrin-associated periodic syndrome (CAPS) suffer from one of a group of rare genetic diseases that are due to mutations in the gene Nlrp3, which promotes enhanced production of the pro- inflammatory mediator interleukin-1? (IL-1?), leading to severe inflammation affecting the skin and other organs. This proposal seeks to determine the importance of neutrophils, immune cells normally representing more than 50% of blood leukocytes, as a major source of IL-1? in CAPS patients. This work will provide substantial new insight into the pathogenesis of CAPS and will determine whether neutrophils may be a potential therapeutic target in these disorders.