Dysregulated Calcium Homeostasis in Cystic Fibrosis Neutrophils Leads to Deficient Antimicrobial Responses

Abstract

Cystic fibrosis (CF), one of the most common human genetic diseases worldwide, is caused by a defect in the CF transmembrane conductance regulator (CFTR). Patients with CF are highly susceptible to infections caused by opportunistic pathogens (including ), which induce excessive lung inflammation and lead to the eventual loss of pulmonary function. Abundant neutrophil recruitment into the lung is a key characteristic of bacterial infections in CF patients. In response to infection, inflammatory neutrophils release reactive oxygen species and toxic proteins, leading to aggravated lung tissue damage in patients with CF. The present study shows a defect in reactive oxygen species production by mouse , human F508del-CFTR, and CF neutrophils; this results in reduced antimicrobial activity against Furthermore, dysregulated Ca homeostasis led to increased intracellular concentrations of Ca that correlated with significantly diminished NADPH oxidase response and impaired secretion of neutrophil extracellular traps in human CF neutrophils. Functionally deficient human CF neutrophils recovered their antimicrobial killing capacity following treatment with pharmacological inhibitors of Ca channels and CFTR channel potentiators. Our findings suggest that regulation of neutrophil Ca homeostasis (via CFTR potentiation or by the regulation of Ca channels) can be used as a new therapeutic approach for reestablishing immune function in patients with CF.

Dysregulated signalling pathways in innate immune cells with cystic fibrosis mutations

“…Although another study was unable to find impaired phagocytosis of P. aeruginosa in neutrophils with CF mutations, they did find that phagocytosis is impaired in monocytes from patients with CF [128]. The treatment of CF patients, carrying at least one copy of the G551D mutation, with Ivacaftor leads to reduced migration and activation of neutrophils [129], as well as improved bacterial clearance in this cohort of patients [127]. Another potential therapeutic target for CF was proposed to be histone deacetylase 6 (HDAC6), as its depletion, in a mouse model, reduced the recruitment of neutrophils to the lungs, followed by an improved response to infection and an increased rate of bacterial clearance and reduced weight loss [130].…”

“…The CFTR has been shown to be expressed on the cellular surface of neutrophils, indicating that their dysregulation is primarily caused by the absence of a functioning CFTR protein, as opposed to just being a secondary effect of mutated CFTR in epithelial cells [123]. Typically, the CFTR is recruited to phagosomes in neutrophils, assisting in the killing of phagocytosed pathogens by moving Cl − ions into the phagolysosome to produce hypochlorous acid (HOCl) [124,125]; however, in neutrophils with CF mutations, the dysfunctional CFTR compromises the ability of neutrophils to kill pathogens due to defective HOCl production in these compartments [124,126,127]. Although another study was unable to find impaired phagocytosis of P. aeruginosa in neutrophils with CF mutations, they did find that phagocytosis is impaired in monocytes from patients with CF [128].…”

Exposure of Pseudomonas aeruginosa to bactericidal hypochlorous acid during neutrophil phagocytosis is compromised in cystic fibrosis

“…In CF, despite excessive infiltration into the infected lung, neutrophils seem incapable of clearing infections, and thus an intrinsically impaired oxidant production has been suggested to exist in these neutrophils (38 -42). So far, evidence for defective HOCl production in particular has come from using nonspecific, indirect, or insensitive markers of oxidant production such as luminol chemiluminescence, R19 fluorescence, and formation of bacterial 3-chlorotyrosine (18,41,43). Because the reactivity of tyrosine and R19S with hypochlorous acid is low (8,22,28), the observed changes in levels of the respective oxidation products, 3-chlorotyrosine and R19, could have been brought about by insubstantial differences in the amount of oxidant produced by healthy and CF neutrophils.…”

Consequences of CRISPR-Cas9-Mediated CFTR Knockout in Human Macrophages

“…While the persistence of pathogens in CF is multi-factorial, recent evidence suggest that alterations in the innate immune system are critically related to both acute and chronic infections in CF. (2,(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). However, the overall relationship between CFTR deficits and immune function remains poorly defined.…”