Letting It All Out: Neutrophils in Early Cystic Fibrosis Airway Inflammation

Dysfunctions of Neutrophils in the Peripheral Blood of Children with Cystic Fibrosis

Dysfunction of neutrophils in patients with cystic fibrosis (CF) is best characterized in bronchoalveolar lavage (BAL), whereas peripheral blood neutrophils are less examined, and the results are contradictory, especially in younger populations. Therefore, this work aimed to study functional and phenotypic changes in circulating neutrophils in children with CF. The study included 19 CF children (5-17 years) and 14 corresponding age-matched healthy children. Isolated neutrophils were cultured either alone or with different stimuli. Several functions were studied: apoptosis, NET-osis, phagocytosis, and production of reactive oxygen species (ROS), neutrophil elastase (NE), and 11 cytokines. In addition, the expression of 20 molecules involved in different functions of neutrophils was evaluated by using flow cytometry. CF neutrophils showed reduced apoptosis and lower production of NE and IL-18 compared to the healthy controls, whereas IL-8 was augmented. All of these functions were further potentiated after neutrophil stimulation, which included higher ROS production and the up-regulation of CD11b and IL-10 expression. NET-osis was higher only when neutrophils from moderate-severe CF were treated with Pseudomonas aeruginosa, and the process correlated with forced expiratory volume in the first second (FEV1). Phagocytosis was not significantly changed. In conclusion, circulating neutrophils from children with CF showed fewer impaired changes in phenotype than in function. Functional abnormalities, which were already present at the baseline levels in neutrophils, depended on the type of stimuli that mimicked different activation states of these cells at the site of infection.

The Effect of CFTR Modulators on Airway Infection in Cystic Fibrosis

The advent of Cystic fibrosis transmembrane receptor (CFTR) modulators in 2012 was a critical event in the history of cystic fibrosis (CF) treatment. Unlike traditional therapies that target downstream effects of CFTR dysfunction, CFTR modulators aim to correct the underlying defect at the protein level. These genotype-specific therapies are now available for an increasing number of CF patients, transforming the way we view the condition from a life-limiting disease to one that can be effectively managed. Several studies have demonstrated the vast improvement CFTR modulators have on normalization of sweat chloride, CFTR function, clinical endpoints, and frequency of pulmonary exacerbation. However, their impact on other aspects of the disease, such as pathogenic burden and airway infection, remain under explored. Frequent airway infections as a result of increased susceptibility and impaired innate immune response are a serious problem within CF, often leading to accelerated decline in lung function and disease progression. Current evidence suggests that CFTR modulators are unable to eradicate pathogenic organisms in those with already established lung disease. However, this may not be the case for those with relatively low levels of disease progression and conserved microbial diversity, such as young patients. Furthermore, it remains unknown whether the restorative effects exerted by CFTR modulators extend to immune cells, such as phagocytes, which have the potential to modulate the response of people with CF (pwCF) to infection. Throughout this review, we look at the potential impact of CFTR modulators on airway infection in CF and their ability to shape impaired pulmonary defences to pathogens.

Aerobic fitness is associated with extracellular DNA levels in the sputum of patients with cystic fibrosis

AIMS

Patients with cystic fibrosis (CF) develop with progressive loss of lung function and aerobic fitness. However, the precise mechanisms of exercise intolerance are still controversial and appear to be influenced by several factors. This study aimed to evaluate the association of aerobic fitness with free DNA levels in the sputum of patients with CF.

METHODS

This cross-sectional study included patients with CF older than 6 years, free from active exacerbations, but who were able to produce spontaneously expectorated sputum. Extracellular DNA in the sputum was quantified. Lung function (spirometry) and aerobic fitness (cardiopulmonary exercise testing [CPET]) were performed. In addition, demographic, anthropometric and clinical data were collected.

RESULTS

Sixteen patients with a mean age of 19.4 ± 6.9 years and mean forced expiratory volume in the first second (FEV₁ ) of 51.8 ± 28.1 (% of predicted) were included. Mean peak oxygen consumption (VO₂ peak) was 32.8 ± 5.2 mL• kg^-1 • min^-1 , oxygen saturation at the end of the test was 90.6% ± 6.3% and mean extracellular DNA levels was 305.3 ± 153.6 μg/mL. Individuals with a VO₂ peak ≤ 30 mL• kg^-1 • min^-1 (P = .03) and a SpO₂ ≤ 90% at the end of the test (P = .03) had a greater amount of extracellular DNA in the sputum. The proportion of patients with reduced VO₂ peak in the group of patients with the lowest concentration of DNA in the sputum (<243 μg/mL) was significantly lower (0% vs 100%; P = .04).

CONCLUSION

There is an association between the presence of free DNA in sputum and aerobic fitness in patients with CF.

Interleukin-13: A pivotal target against influenza-induced exacerbation of chronic lung diseases

Non-communicable, chronic respiratory diseases (CRDs) affect millions of individuals worldwide. The course of these CRDs (asthma, chronic obstructive pulmonary disease, and cystic fibrosis) are often punctuated by microbial infections that may result in hospitalization and are associated with increased risk of morbidity and mortality, as well as reduced quality of life. Interleukin-13 (IL-13) is a key protein that regulates airway inflammation and mucus hypersecretion. There has been much interest in IL-13 from the last two decades. This cytokine is believed to play a decisive role in the exacerbation of inflammation during the course of viral infections, especially, in those with pre-existing CRDs. Here, we discuss the common viral infections in CRDs, as well as the potential role that IL-13 plays in the virus-induced disease pathogenesis of CRDs. We also discuss, in detail, the immune-modulation potential of IL-13 that could be translated to in-depth studies to develop IL-13-based therapeutic entities.

Immunomodulation in Cystic Fibrosis: Why and How?

Cystic fibrosis (CF) lung disease is characterized by unconventional mechanisms of inflammation, implicating a chronic immune response dominated by innate immune cells. Historically, therapeutic development has focused on the mutated cystic fibrosis transmembrane conductance regulator (CFTR), leading to the discovery of small molecules aiming at modulating and potentiating the presence and activity of CFTR at the plasma membrane. However, treatment burden sustained by CF patients, side effects of current medications, and recent advances in other therapeutic areas have highlighted the need to develop novel disease targeting of the inflammatory component driving CF lung damage. Furthermore, current issues with standard treatment emphasize the need for directed lung therapies that could minimize systemic side effects. Here, we summarize current treatment used to target immune cells in the lungs, and highlight potential benefits and caveats of novel therapeutic strategies.