Metabolic Reprogramming of the Cystic Fibrosis Neutrophil

Cystic fibrosis (CF) is the commonest lethal genetic condition affecting Caucasians, arising from a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene on the long arm of chromosome 7. It is a chloride channelopathy, manifesting clinically as a multisystem disorder. The major cause of morbidity and mortality in CF is neutrophilic lung disease, though significant debate exists as to whether the main determinant of this is an intrinsic defect due to defective CFTR within the CF cell, or rather the frequent cycles of infection and sustained inflammation that characterize the condition. Here we show a potential role for metabolic reprogramming in CF airways inflammation, demonstrating the existence of upregulated aerobic glycolysis, known as a Warburg effect, in the CF neutrophil, with implications for intracellular pH regulation and release of the master pro-inflammatory cytokine interleukin (IL)-1β. This shift to a state of increased aerobic glycolysis relies on an intact PKM2/succinate/HIF-1α axis and results in decreased cytosolic pH and increased production of lactate and the IL-1β precursor pro-IL-1β, it’s processing in the lung driven by the NLRP3 inflammasome via caspase-1. We demonstrate that IL-1β levels are significantly increased in the CF lung, and identify IL-1β as an airway biomarker of CF lung disease severity by correlating it with accepted measures of clinical outcome such as FEV1 and the CF-ABLE score, a validated CF-specific clinical prognostic tool developed by this group. We show that this phenomenon is driven by inflammation, rather than an intrinsic CFTR defect, and is abrogated both by inhibition of Warburg metabolism and specific inhibition of NLRP3 by small molecules in vivo, identifying the 4 inflammasome as a therapeutic target in CF. This study also describes the development of Temperature-controlled Two-step Rapid Isolation of Sputum (TETRIS), a specialized method of sputum processing designed to facilitate multicentre studies assessing the effect of therapies targeting IL-1β and other key inflammatory mediators, such as neutrophil elastase (NE), in CF.