The primary defect in cystic fibrosis (CF) is abnormal chloride and bicarbonate transport in the cystic fibrosis transmembrane conductance regulator (CFTR) epithelial ion channel. The apical surface of the respiratory tract is lined by an airway surface liquid layer (ASL) composed of mucin comprising mainly MUC5A and MUC5B glycoproteins. ASL homeostasis depends on sodium bicarbonate secretion into the airways and secretion deficits alter mucus properties leading to airway obstruction, inflammation, and infections. Downstream effects of abnormal ion transport in the lungs include altered intrinsic immune defenses. We observed that neutrophils killed Pseudomonas aeruginosa more efficiently when it had been exposed to sodium bicarbonate, and formation of neutrophil extracellular traps (NETs) by neutrophils was augmented in the presence of increasing bicarbonate concentrations. Physiological levels of bicarbonate sensitized P. aeruginosa to the antimicrobial peptide cathelicidin LL-37, which is present in both lung ASL and in NETs. Sodium bicarbonate has various uses in clinical medicine and in the care of CF patients, and could be further explored as a therapeutic adjunct against Pseudomonas infections.
Abstract Exocrine pancreatic insufficiency (EPI), which leads to malabsorption and poor weight gain, is seen in 85% of patients with cystic fibrosis (CF). EPI is treated with pancreatic enzyme replacement therapy taken with each meal. The highly effective cystic fibrosis transmembrane conductance regulator (CFTR) modulator, ivacaftor, restores CFTR function in patients with responsive mutations. It is a widely held view that EPI in CF is irreversible due to the complete destruction of pancreatic ducts and acinar cells. We describe three pediatric CF patients with EPI who were started on ivacaftor, and subsequently showed evidence of restored exocrine pancreatic function with clinical and biochemical parameters.
The highly polarized architecture of neurons is important for their function. Experimental data based on dominant-negative approaches suggest that the tumor suppressor adenomatous polyposis coli (APC), a regulator of Wnt signaling and the cytoskeleton, regulates polarity of neuroectodermal precursors and neurons, helping specify one neurite as the axon, promoting its outgrowth, and guiding axon pathfinding. However, such dominant-negative approaches might affect processes in which APC is not essential. We completely removed both APCs from Drosophila melanogaster larval neural precursors and neurons, testing whether APCs play universal roles in neuronal polarity. Surprisingly, APCs are not essential for asymmetric cell division or the stereotyped division axis of central brain (CB) neuroblasts, although they do affect cell cycle progression and spindle architecture. Likewise, CB, lobular plug, and mushroom body neurons do not require APCs for polarization, axon outgrowth, or, in the latter two cases, axon targeting. These data suggest that proposed cytoskeletal roles for APCs in mammals should be reassessed using loss of function tools.
fibrosis is a genetic disease characterized by chronic lung infection, often with Pseudomonas aeruginosa, requiring repeated antibiotic treatment for pulmonary exacerbations. In the era of cystic fibrosis transmembrane conductance regulator modulator therapy, we assessed susceptibility to antipseudomonal antibiotics in modulator-eligible and modulator-ineligible children over 3 years and found that P. aeruginosa isolates largely remained susceptible to standard parenteral but not oral antimicrobial agents.
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