Specific Inhibition of the NLRP3 Inflammasome as an Antiinflammatory Strategy in Cystic Fibrosis

Abstract

<b>Rationale:</b> Cystic fibrosis (CF) pulmonary disease is characterized by chronic infection with <i>Pseudomonas aeruginosa</i> and sustained neutrophil-dominant inflammation. The lack of effective antiinflammatory therapies for people with CF (PWCF) represents a significant challenge.<b>Objectives:</b> To identify altered immunometabolism in the CF neutrophil and investigate the feasibility of specific inhibition of the NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome as a CF antiinflammatory strategy <i>in vivo</i>.<b>Methods:</b> Key markers of increased aerobic glycolysis, known as a Warburg effect, including cytosolic PKM2 (pyruvate kinase M2), phosphorylated PKM2, succinate, HIF-1α (hypoxia-inducible factor-1α), lactate, and the IL-1β precursor pro-IL-1β, as well as caspase-1 activity and processing of pro-IL-1β to IL-1β by the NLRP3 inflammasome, were measured in neutrophils from blood and airway secretions from healthy control subjects (<i>n</i> = 12), PWCF (<i>n</i> = 16), and PWCF after double-lung transplantation (<i>n</i> = 6). The effects of specific inhibition of NLRP3 on airway inflammation and bacterial clearance in a murine CF model were subsequently assessed <i>in vivo</i>.<b>Measurements and Main Results:</b> CF neutrophils display increased aerobic glycolysis in the systemic circulation. This effect is driven by low-level endotoxemia, unaffected by CFTR (cystic fibrosis transmembrane conductance regulator) modulation, and resolves after transplant. The increased pro-IL-1β produced is processed to its mature active form in the LPS-rich CF lung by the NLRP3 inflammasome via caspase-1. Specific NLRP3 inhibition <i>in vivo</i> with MCC950 inhibited IL-1β in the lungs of CF mice (<i>P</i> < 0.0001), resulting in significantly reduced airway inflammation and improved <i>Pseudomonas</i> clearance (<i>P</i> < 0.0001).<b>Conclusions:</b> CF neutrophil immunometabolism is altered in response to inflammation. NLRP3 inflammasome inhibition may have an antiinflammatory and anti-infective role in CF.