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

Rationale: Cystic fibrosis (CF) pulmonary disease is characterized by chronic infection with Pseudomonas aeruginosa and sustained neutrophil-dominant inflammation. The lack of effective antiinflammatory therapies for people with CF (PWCF) represents a significant challenge. Objectives: 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 in vivo. Methods: Key markers of increased aerobic glycolysis, known as a Warburg effect, including cytosolic PKM2 (pyruvate kinase M2), phosphorylated PKM2, succinate, HIF-1 alpha (hypoxia-inducible factor-1 alpha), lactate, and the IL-1 beta precursor pro-IL-1 beta, as well as caspase-1 activity and processing of pro-IL-1 beta to IL-1 beta by the NLRP3 inflammasome, were measured in neutrophils from blood and airway secretions from healthy control subjects (n = 12), PWCF (n = 16), and PWCF after double-lung transplantation (n = 6). The effects of specific inhibition of NLRP3 on airway inflammation and bacterial clearance in a murine CF model were subsequently assessed in vivo. Measurements and Main Results: 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-1 beta produced is processed to its mature active form in the LPS-rich CF lung by the NLRP3 inflammasome via caspase-1. Specific NLRP3 inhibition in vivo with MCC950 inhibited IL-1 beta in the lungs of CF mice (P < 0.0001), resulting in significantly reduced airway inflammation and improved Pseudomonas clearance (P < 0.0001). Conclusions: CF neutrophil immunometabolism is altered in response to inflammation. NLRP3 inflammasome inhibition may have an antiinflammatory and anti-infective role in CF.