Article Text

PDF
Extended report
SIRT1 overexpression in the rheumatoid arthritis synovium contributes to proinflammatory cytokine production and apoptosis resistance
  1. Fabienne Niederer1,
  2. Caroline Ospelt1,2,
  3. Fabia Brentano1,
  4. Michael O Hottiger3,
  5. Renate E Gay1,4,
  6. Steffen Gay1,4,
  7. Michael Detmar5,
  8. Diego Kyburz1,4
  1. 1Center of Experimental Rheumatology, University Hospital Zurich, Zurich, Switzerland
  2. 2Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
  3. 3Institute of Veterinary Biochemistry and Molecular Biology, University of Zurich, Zurich, Switzerland
  4. 4Zurich Center of Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
  5. 5Swiss Federal Institute of Technology, ETH Zurich, Zurich, Switzerland
  1. Correspondence to Diego Kyburz, Center of Experimental Rheumatology, University Hospital Zurich, Gloriastrasse 25, 8091 Zurich, Switzerland; diego.kyburz{at}usz.ch

Abstract

Objective To analyse the expression of SIRT1 in synovial tissues and cells of patients with rheumatoid arthritis (RA) and to study the function of SIRT1 in inflammation and apoptosis in RA.

Methods Levels of SIRT1 expression were analysed in synovial tissues and cells from patients with RA by real-time PCR and western blotting before and after stimulation with toll-like receptor ligands, tumour necrosis factor α (TNFα) and interleukin 1β (IL-1β). Immunohistochemistry was used to study the localisation of SIRT1. Fluorescence activated cell sorting analysis was performed to investigate the effect of SIRT1 on apoptosis. Peripheral blood monocytes and rheumatoid arthritis synovial fibroblasts (RASFs) were transfected with wild-type or enzymatically inactive SIRT1 expression vectors or with siRNA targeting SIRT1. Cytokine analysis of IL-6, IL-8 and TNFα were performed by ELISA to study the role of SIRT1 on proinflammatory mediators of RA.

Results SIRT1 was found to be constitutively upregulated in synovial tissues and cells from patients with RA compared to osteoarthritis. TNFα stimulation of RASFs and monocytes resulted in further induced expression levels of SIRT1. Silencing of SIRT1 promoted apoptosis in RASFs, whereas SIRT1 overexpression protected cells from apoptosis. Inhibition of SIRT1 enzymatic activity by inhibitors, siRNA and overexpression of an enzymatically inactive form of SIRT1 reduced lipopolysaccharide-induced levels of TNFα in monocytes. Similarly, knockdown of SIRT1 resulted in a reduction of proinflammatory IL-6 and IL-8 in RASFs.

Conclusion The TNFα-induced overexpression of SIRT1 in RA synovial cells contributes to chronic inflammation by promoting proinflammatory cytokine production and inhibiting apoptosis.

Statistics from Altmetric.com

Footnotes

  • Funding This work was supported by the Swiss National Fund grant 32 -120702 (to DK), by FP7 Masterswitch and IAR Epalinges (to CO, REG, SG).

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the ethics committee of the canton of Zurich.

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

Request permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.