Highlights d Neutrophils recruited to cystic fibrosis airways undergo de novo RNA transcription d Neutrophil adaptation to CF airways leads to downregulation of their antimicrobial genes d Transcriptional blockade restores CF airway neutrophil bactericidal capacity

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Cystic fibrosis (CF) lung disease is dominated by the recruitment of myeloid cells (neutrophils and monocytes) from the blood which fail to clear the lung of colonizing microbes. In prior in vitro studies, we showed that blood neutrophils migrated through the well-differentiated lung epithelium into the CF airway fluid supernatant (ASN) mimic the dysfunction of CF airway neutrophils in vivo, including decreased bactericidal activity despite an increased metabolism. Here, we hypothesized that, in a similar manner to neutrophils, blood monocytes undergo significant adaptations upon recruitment to CFASN. To test this hypothesis, primary human blood monocytes were transmigrated in our in vitro model into the ASN from healthy control (HC) or CF subjects to mimic in vivo recruitment to normal or CF airways, respectively. Surface phenotype, metabolic and bacterial killing activities, and transcriptomic profile by RNA sequencing were quantified post-transmigration. Unlike neutrophils, monocytes were not metabolically activated, nor did they show broad differences in activation and scavenger receptor expression upon recruitment to the CFASN compared to HCASN. However, monocytes recruited to CFASN showed decreased bactericidal activity. RNASeq analysis showed strong effects of transmigration on monocyte RNA profile, with differences between CFASN and HCASN conditions, notably in immune signaling, including lower expression in the former of the antimicrobial factor ISG15, defensin-like chemokine CXCL11, and nitric oxide-producing enzyme NOS3. While monocytes undergo qualitatively different adaptations from those seen in neutrophils upon recruitment to the CF airway microenvironment, their bactericidal activity is also dysregulated, which could explain why they also fail to protect CF airways from infection.

Background: In this pilot study, we investigated whether induced sputum (IS) could serve as a viable alternative to bronchoalveolar lavage (BAL) and yield robust inflammatory biomarkers in toddlers with cystic fibrosis (CF) featuring minimal structural lung disease. Methods: We collected IS, BAL (right middle lobe and lingula) and blood, and performed chest computed tomography (CT) scans from 2-year-olds with CF (N=11), all within a single visit. Inflammatory biomarkers included 20 soluble immune mediators and neutrophil elastase (NE), as well as frequency and phenotype of T cells, monocytes / macrophages and neutrophils. Results: At the molecular level, nine mediators showed similar levels in IS and BAL (CXCL1, CXCL8, IL-1, IL-1RA, IL-6, CCL2, CXCL10, M-CSF, VEGF-A), four were higher in IS than in BAL (CXCL5, IL-1, CXCL11, TNFSF10) and two were present in IS but undetectable in BAL (IL-10, IFN-). Meanwhile, soluble NE had lower activity in IS than in BAL. At the cellular level, T-cell frequency was lower in IS than in BAL. Monocytes / macrophages were dominant in IS and BAL with similar frequencies but differing expression of CD16 (lower in IS), CD115 and surface-associated NE (higher in IS). Neutrophil frequency and phenotype did not differ between IS and BAL. Conclusions: IS collected from 2-year-olds with CF yields biomarkers of early airway inflammation with good agreement with BAL notably with regards to molecular and cellular outcomes related to neutrophils and monocytes/macrophages.

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Rationale Neutrophils are often considered the first line of defense against bacterial infections. In cystic fibrosis (CF), massive neutrophil presence is concomitant with phenotypical changes and prolonged bacterial infections. Here, we sought to determine whether this paradox was dependent on transcriptional reprogramming of airway neutrophils. Methods Blood neutrophils were transmigrated in an in vitro model recapitulating the in vivo phenotype of CF airway neutrophils. Blood and airway neutrophils from the in vitro model and from CF patients were analyzed by flow cytometry, microarrays and RNA sequencing, as well as used for bacterial killing assays. Results Airway neutrophils in vivo and in vitro showed increased total RNA content and profound shifts in their transcriptional profile for survival, anabolic, and antimicrobial genes. Furthermore, transcriptional blockade by α-amanitin in airway neutrophils in vitro and ex vivo fully restored their bacterial killing capacity. Conclusions These findings show that some canonical functions in neutrophils, including bacterial clearance, depend on the active repression of RNA transcription, which can be modulated by the local microenvironment at the site of inflammation, challenging the paradigm holding these cells as terminally differentiated.

Juvenile idiopathic arthritis (JIA) is an inflammatory rheumatic disorder. Polymorphonuclear neutrophils (PMNs) are present in JIA synovial fluid (SF), but with variable frequency. SF PMNs in JIA were previously shown to display high exocytic but low phagocytic and immunoregulatory activities. To further assess whether the degree of SF neutrophilia associated with altered immune responses in JIA, we collected SF and blood from 16 adolescent JIA patients. SF and blood leukocytes were analyzed by flow cytometry. SF and plasma were used for immune mediator quantification and metabolomics. Healthy donor blood T cells were cultured in SF to evaluate its immunoregulatory activities. PMN and T cell frequencies were bimodal in JIA SF, delineating PMN high/T cell low (PMNHigh) and PMN low/T cell high (PMNLow) samples. Proinflammatory mediators were increased in SF compared with plasma across patients, and pro- and anti-inflammatory mediators were further elevated in PMNHigh SF. Compared to blood, SF PMNs showed increased exocytosis and programmed death-1/programmed death ligand-1 expression, and SF PMNs and monocytes/macrophages had increased surface-bound arginase-1. SPADE analysis revealed SF monocyte/macrophage subpopulations coexpressing programmed death-1 and programmed death ligand-1, with higher expression in PMNHigh SF. Healthy donor T cells showed reduced coreceptor expression when stimulated in PMNHigh versus PMNLow SF. However, amino acid metabolites related to the arginase-1 and IDO-1 pathways did not differ between the two groups. Hence, PMN predominance in the SF of a subset of JIA patients is associated with elevated immune mediator concentration and may alter SF monocyte/macrophage phenotype and T cell activation, without altering immunoregulatory amino acids.