PhosphoLipid transfer protein (PLTP) exerts a direct pro-inflammatory effect on rheumatoid arthritis (RA) fibroblasts-like-synoviocytes (FLS) independently of its lipid transfer activity

PLoS One. 2018 Mar 22;13(3):e0193815. doi: 10.1371/journal.pone.0193815. eCollection 2018.

Abstract

Rheumatoid arthritis (RA) is a chronic inflammatory rheumatic disease with modification of lipids profile and an increased risk of cardiovascular events related to inflammation. Plasma phospholipid transfer protein (PLTP) exerts a lipid transfer activity through its active form. PLTP can also bind to receptors such as ATP-binding cassette transporter A1 (ABCA1). In addition to its role in lipoprotein metabolism and atherosclerosis, the latest advances came in support of a complex role of PLTP in the regulation of the inflammatory response, both with pro-inflammatory or anti-inflammatory properties. The aim of the present study was to decipher the role of PLTP in joint inflammation and to assess its relevance in the context of RA. PLTP expression was examined by western-blot and by immunochemistry. ABCA1 expression was analyzed by flow cytometry. Lipid transfer activity of PLTP and pro-inflammatory cytokines were measured in sera and synovial fluid (SF) from RA patients and controls (healthy subjects or osteoarthritis patients [OA]). FLS were treated with both lipid-transfer active form and inactive form of recombinant human PLTP. IL-8, IL-6, VEGF and MMP3 produced by FLS were assessed by ELISA, and proliferation by measuring 3H-Thymidine incorporation. RA synovial tissues showed higher PLTP staining than OA and PLTP protein levels were also significantly higher in RA-FLS. In addition, RA, unlike OA patients, displayed elevated levels of PLTP activity in SF, which correlated with pro-inflammatory cytokines. Both lipid-transfer active and inactive forms of PLTP significantly increased the production of cytokines and proliferation of FLS. ABCA1 was expressed on RAFLS and PLTP activated STAT3 pathway. To conclude, PLTP is highly expressed in the joints of RA patients and may directly trigger inflammation and FLS proliferation, independently of its lipid transfer activity. These results suggest a pro-inflammatory role for PLTP in RA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter 1 / metabolism
  • Arthritis, Rheumatoid / immunology*
  • Arthritis, Rheumatoid / pathology
  • Cell Proliferation / physiology
  • Cells, Cultured
  • Cytokines / metabolism
  • Female
  • Fibroblasts / immunology*
  • Fibroblasts / pathology
  • Gene Expression
  • Humans
  • Inflammation / metabolism
  • Inflammation / pathology
  • Lipid Metabolism / physiology*
  • Male
  • Middle Aged
  • Osteoarthritis / immunology
  • Osteoarthritis / pathology
  • Phospholipid Transfer Proteins / metabolism*
  • Recombinant Proteins / metabolism
  • STAT3 Transcription Factor / metabolism
  • Synovial Fluid / immunology
  • Synoviocytes / immunology*
  • Synoviocytes / pathology

Substances

  • ABCA1 protein, human
  • ATP Binding Cassette Transporter 1
  • Cytokines
  • Phospholipid Transfer Proteins
  • Recombinant Proteins
  • STAT3 Transcription Factor
  • STAT3 protein, human

Grants and funding

This work was supported by PASSERELLE 2013 (Pfizer) grant. This work was also supported by INSERM (Institut National de la Santé et de la Recherche Médicale), the Regional Council of Bourgogne, the European Regional Development Fund, the University of Bourgogne, the Fondation de France, and by a French Government grant managed by the French National Research Agency (ANR) under the program “Investissements d’Avenir” with reference ANR-11-LABX-0021-01-LipSTIC LabEx. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.ration of the manuscript.