Systemic levels of anti-PAD4 autoantibodies correlate with airway obstruction in cystic fibrosis

Abstract

Cystic fibrosis (CF) airway disease is characterized by the long-term presence of neutrophil granulocytes. Formation of neutrophil extracellular traps (NETs) and/or autoantibodies directed against extracellular components of NETs are possible contributors to neutrophil-mediated lung damage in CF. The goal of this study was to measure their levels in CF adults compared to healthy controls and subjects with rheumatologic diseases known to develop NET-related autoantibodies and pathologies, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Sera were analyzed from the following number of subjects: 37 CF, 23 healthy controls (HC), 20 RA, and 21 SLE. CF had elevated serum myeloperoxidase (MPO) concentrations (347.5±56.1 ng/ml, mean+/-S.E.M., p = .0132) compared to HC (144.5±14.6 ng/ml) but not of neutrophil elastase (NE) complexed with alpha-1-antitrypsin, cell-free DNA or NE-DNA complexes. The peptidylarginine deiminase 4 (PAD4) enzyme is required for NET formation and associated DNA release in neutrophils. Serum levels of anti-PAD4 antibodies (Ab) were elevated in CF (p = .0147) compared to HC and showed an inverse correlation with a measure of lung function, FEV1% predicted (r = −0.5020, p = .015), as did MPO levels (r = −0.4801, p = .0026). Anti-PAD4 Ab levels in CF sera associated with lung infection by P. aeruginosa, but not that by S. aureus, age, sex, CF-related diabetes or the presence of musculoskeletal pain. Serum levels of anti-citrullinated protein Abs (ACPAs) and anti-nucleosome Abs were not elevated in CF compared to HC (p = .7498, p = .0678). In summary, adult CF subjects develop an autoimmune response against NET components that correlates with worsening lung disease.

SARS-CoV-2–triggered neutrophil extracellular traps mediate COVID-19 pathology

“…The release of NETs has been associated with tissue damage in several immune-mediated diseases, including chronic obstructive pulmonary disease, rheumatoid arthritis, and sepsis (Dicker et al, 2018;Khandpur et al, 2013;Colón et al, 2019). NETs cause tissue damage by extracellular exposure of DNA, granular proteins such as MPO, and histone, inducing apoptosis and fibrosis processes (Thammavongsa et al, 2013;Yadav et al, 2019). COVID-19 is characterized by extensive damage in the alveolar epithelium (Dolhnikoff et al, 2020).…”

Dysregulated signalling pathways in innate immune cells with cystic fibrosis mutations

“…The recent observation of autoantibodies against components of NETs, in patients with CF, has been correlated with declining lung function and provides an insight into the development of autoimmunity in CF [152,153]. Impaired degranulation, due to decreased Rab27a activity and delayed neutrophil apoptosis, leads to an excessive NET formation in the lungs of patients with CF, and these defects are reversed by Ivacaftor therapy in patients with G551D mutations [154,155].…”

Vasculitis in Cystic Fibrosis

“…The long-term presence of neutrophils, and the release of neutrophil extracellular traps (NETs, also see below) and other neutrophil components likely contribute to autoimmune/inflammatory responses (32). Subsequent generation of immune complexes (also see above) containing neutrophil components promotes tissue inflammation and damage (33) (Figure 2). Evidence supporting this comes from several observational studies.…”

“…FIGURE 3 | Proposed model of ANCA involvement in the development of vasculitis and chronic inflammation in CF (13,33). Several hypotheses have been made on what triggers ANCA production in pwCF.…”

“…This is required for NET formation, and associated DNA decondensation and release by neutrophils. Recently, the presence of anti-PAD4 antibodies has been associated with CF (33). Antibody presence correlates with reduced lung function and the presence of P. aeruginosa.…”