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Involvement of X-box binding protein 1 and reactive oxygen species pathways in the pathogenesis of tumour necrosis factor receptor-associated periodic syndrome
  1. Laura J Dickie1,
  2. Azad M Aziz1,
  3. Sinisa Savic2,
  4. Orso M Lucherini3,
  5. Luca Cantarini3,
  6. Janina Geiler1,
  7. Chi H Wong1,
  8. Robert Coughlan4,
  9. Thirusha Lane5,
  10. Helen J Lachmann5,
  11. Philip N Hawkins5,
  12. Philip A Robinson6,
  13. Paul Emery1,
  14. Dennis McGonagle1,
  15. Michael F McDermott1
  1. 1Experimental Rheumatology, National Institute for Health Research–Leeds Musculoskeletal Biomedical Research Unit, Leeds Institute of Molecular Medicine, Leeds, West Yorkshire, UK
  2. 2Department of Clinical Immunology and Allergy, St James's University Hospital, Leeds, West Yorkshire, UK
  3. 3Interdepartmental Research Center of Systemic Autoimmune and Autoinflammatory Diseases, Policlinico Le Scotte, University of Siena, Siena, Italy
  4. 4Department of Rheumatology, Merlin Park Hospital (Galway University Hospital), Renmore, Galway, Ireland
  5. 5National Amyloidosis Centre, Division of Medicine, UCL Medical School, Royal Free Campus, Rowland Hill Street, London, UK
  6. 6Section of Ophthalmology and Neuroscience, Leeds Institute of Molecular Medicine, Leeds, West Yorkshire, UK
  1. Correspondence toProfessor Michael F McDermott, NIHR–Leeds Musculoskeletal Biomedical Research Unit, Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St James's University Hospital, Beckett Street, Leeds, LS9 7TF, UK; M.McDermott{at}leeds.ac.uk

Abstract

Objectives To investigate convergence of endoplasmic reticulum stress pathways and enhanced reactive oxygen species (ROS) production, due to intracellular retention of mutant tumour necrosis factor receptor 1 (TNFR1), as a disease mechanism in TNFR-associated periodic syndrome (TRAPS).

Methods Peripheral blood mononuclear cells from patients with TRAPS (n=16) and healthy controls (HC) (n=22) were studied alongside HEK293T cells expressing wild type-TNFR1 or TRAPS-associated mutations. Unfolded protein response (UPR)-associated proteins (protein kinase-like endoplasmic reticulum kinase, PERK), phosphorylated-PERK (p-PERK), phosphorylated inositol-requiring enzyme 1α (p-IRE1α) and spliced X-box binding protein 1 (sXBP1)) were measured by flow cytometry. XBP1 splicing and UPR-associated transcript expression were assessed by reverse transcription PCR/quantitative real-time PCR. ROS levels were measured using CM-H2DCFDA and MitoSOX Red in patients' monocytes or HEK293T cells by flow cytometry.

Results Mutant TNFR1-expressing HEK293T cells had increased TNFR1 expression associated with intracellular aggregation. TRAPS patients had increased sXBP1 transcripts (p<0.01) compared with HC. Raised p-PERK protein was seen, indicative of an UPR, but other UPR-associated transcripts were normal. Increased ROS levels were observed in TRAPS monocytes compared with HCs (p<0.02); these increased further upon IL-6 stimulation (p<0.01). Lipopolysaccharide-stimulated peripheral blood mononuclear cells of patients with TRAPS, but not HCs, demonstrated increased sXBP1 levels (p<0.01), which were reduced by antioxidant treatment (p<0.05).

Conclusions Patients with TRAPS have evidence of increased sXBP1 and PERK expression but without other signs of classical UPR, and also with high ROS generation that may contribute to the pro-inflammatory state associated with TRAPS. The authors propose a non-traditional XBP1 pathway with enhanced sXBP1 as a novel disease-contributing mechanism in TRAPS.

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Footnotes

  • Funding This work was supported in part by a University of Leeds and Leeds Institute of Molecular Medicine (LIMM) Research Scholarship, an FP7-HEALTH-2007-2.4.4-1 Grant (Number 200923), and the NIHR-Leeds Musculoskeletal Biomedical Research Unit.

  • Competing interests None.

  • Ethics approval Ethics approval was granted by the Leeds (East) Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Correction notice This article has been corrected since it was published Online First.

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