The role of inflammation in cystic fibrosis pulmonary exacerbations

Pulmonary exacerbations in early cystic fibrosis lung disease are marked by strong modulation of CD3 and PD-1 on luminal T cells

Background

In chronic cystic fibrosis (CF) lung disease, neutrophilic inflammation and T-cell inhibition occur concomitantly, partly due to neutrophil-mediated release of the T-cell inhibitory enzyme Arg1. However, the onset of this tonic inhibition of T cells, and the impact of pulmonary exacerbations (PEs) on this process, remain unknown.

Methods

Children with CF aged 0-5 years were enrolled in a longitudinal, single-center cohort study. Blood (n = 35) and bronchoalveolar lavage (BAL) fluid (n = 18) were collected at stable outpatient clinic visits or inpatient PE hospitalizations and analyzed by flow cytometry (for immune cell presence and phenotype) and 20-plex chemiluminescence assay (for immune mediators). Patients were categorized by PE history into (i) no prior PE, (ii) past history of PE prior to stable visit, or (iii) current PE.

Results

PEs were associated with increased concentration of both pro- and anti-inflammatory mediators in BAL, and increased neutrophil frequency and G-CSF in circulation. PE BAL samples showed a trend toward an increased frequency of hyperexocytic "GRIM" neutrophils, which we previously identified in chronic CF. Interestingly, expression levels of the T-cell receptor associated molecule CD3 and of the inhibitory programmed death-1 (PD-1) receptor were respectively decreased and increased on T cells from BAL compared to blood in all patients. When categorized by PE status, CD3 and PD-1 expression on blood T cells did not differ among patients, while CD3 expression was decreased, and PD-1 expression was increased on BAL T cells from patients with current PE.

Conclusions

Our findings suggest that airway T cells are engaged during early-life PEs, prior to the onset of chronic neutrophilic inflammation in CF. In addition, increased blood neutrophil frequency and a trend toward increased BAL frequency of hyperexocytic neutrophils suggest that childhood PEs may progressively shift the balance of CF airway immunity towards neutrophil dominance.

Label-free Raman spectroscopy characterizes signatures of inflammation and fibrosis in the silicosis

Silicosis is an occupational disease that seriously damages the life and health of miners. Herein, we constructed a mouse model of silicosis and used label-free confocal Raman spectroscopy to analyze the biomolecular variations in lung fibrous nodules and inflammatory sites. The mice were exposed to silica particles for 1 month (SIL-1M group), 3 months (SIL-3M group), or no exposure (control tissues, NS). Raman spectra obtained from treated and untreated lung tissue were subjected to chemometric analysis to quantify biochemical composition differences in the silicosis. Simultaneously, immunohistochemistry and collagen staining were used to evaluate inflammation, fibrosis, and apoptosis. As a result, the SIL-1M and SIL-3M groups showed significant differences in cholesterol, lipids, amino acids, nucleic acids, and cytochrome C, and the collagen peaks at 1248 cm^-1 and 1448 cm^-1 were significantly higher than in the NS group. Notably, glycogen and phospholipid may be an inflammatory indicator consistent with NF-κB expression. In addition, significant differences in collagen and cytochrome C content in silicosis lung tissue were found using Raman spectroscopy and were verified by Masson's staining and Bax/Bcl-2 expression ratio. In summary, our findings provide a label-free technique to understand the biochemical changes in lung inflammatory and fibrosis microenvironment after exposure to silica particles and provide a valuable reference for studying the mechanism of silicosis.

Inflammation biomarkers in sputum for clinical trials in cystic fibrosis: current understanding and gaps in knowledge

RATIONALE

Sputum biomarkers hold promise as a direct measure of inflammation within the cystic fibrosis (CF) lung, but variability in study design and sampling methodology have limited their use. A full evaluation of the reliability, validity and clinical relevance of individual biomarkers is required to optimise their use within CF clinical research.

OBJECTIVES

A biomarker Special Interest Working Group was established within the European Cystic Fibrosis Society-Clinical Trials Network Standardisation Committee, to perform a review of the evidence regarding sputum biomarkers in CF.

METHODS

From the 139 included articles, we identified 71 sputum biomarkers to undergo evaluation of their clinimetric properties, responsiveness, discriminant, concurrent and convergent validity.

RESULTS

Current evidence confirms the potential of sputum biomarkers as outcome measures in clinical trials. Inconsistency in responsiveness, concurrent and convergent validity require further research into these markers and processing standardisation before translation into wider use. Of the 71 biomarkers identified, Neutrophil Elastase (NE), IL-8, TNF-α and IL-1β, demonstrated validity and responsiveness to be currently considered for use in clinical trials. Other biomarkers show future promise, including IL-6, calprotectin, HMGB-1 and YKL-40.

CONCLUSION

A concerted international effort across the cystic fibrosis community is needed to promote high quality biomarker trial design, establish large population-based biomarker studies, and work together to create standards for collection, storage and analysis of sputum biomarkers.