Neutrophil-Related Gene Expression and Low-Density Granulocytes Associated With Disease Activity and Response to Treatment in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

Arthritis Rheumatol. 2015 Jul;67(7):1922-32. doi: 10.1002/art.39153.

Abstract

Objective: To discover biomarkers involved in the pathophysiology of antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and to determine whether low-density granulocytes (LDGs) contribute to gene expression signatures in AAV.

Methods: The source of clinical data and linked biologic specimens was a randomized controlled treatment trial in AAV. RNA sequencing of whole blood from patients with AAV was performed during active disease at the baseline visit and during remission 6 months later. Gene expression was compared between patients who met versus those who did not meet the primary trial outcome of clinical remission at 6 months (responders versus nonresponders). Measurement of neutrophil-related gene expression was confirmed in peripheral blood mononuclear cells (PBMCs) to validate the findings in whole blood. A negative-selection strategy isolated LDGs from PBMC fractions.

Results: Differential expression between responders (n = 77) and nonresponders (n = 35) was detected in 2,346 transcripts at the baseline visit (P < 0.05). Unsupervised hierarchical clustering demonstrated a cluster of granulocyte-related genes, including myeloperoxidase (MPO) and proteinase 3 (PR3). A granulocyte multigene composite score was significantly higher in nonresponders than in responders (P < 0.01) and during active disease than during remission (P < 0.01). This signature strongly overlapped an LDG signature identified previously in lupus (false discovery rate by gene set enrichment analysis <0.01). Transcription of PR3 measured in PBMCs was associated with active disease and treatment response (P < 0.01). LDGs isolated from patients with AAV spontaneously formed neutrophil extracellular traps containing PR3 and MPO.

Conclusion: In AAV, increased expression of a granulocyte gene signature is associated with disease activity and decreased response to treatment. The source of this signature is likely LDGs, a potentially pathogenic cell type in AAV.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / drug therapy*
  • Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / metabolism
  • Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / pathology
  • Biomarkers / metabolism
  • Extracellular Traps / metabolism
  • Female
  • Gene Expression Regulation
  • Glucocorticoids / therapeutic use
  • Granulocytes / metabolism
  • Granulocytes / pathology*
  • Humans
  • Leukocyte Elastase / genetics
  • Leukocyte Elastase / metabolism*
  • Leukocytes, Mononuclear / metabolism
  • Leukocytes, Mononuclear / pathology
  • Male
  • Middle Aged
  • Myeloblastin / genetics
  • Myeloblastin / metabolism*
  • Peroxidase / genetics
  • Peroxidase / metabolism*
  • Randomized Controlled Trials as Topic
  • Severity of Illness Index
  • Treatment Outcome

Substances

  • Biomarkers
  • Glucocorticoids
  • Peroxidase
  • Leukocyte Elastase
  • Myeloblastin