title: Increased levels of circulating microparticles in primary Sjögren's syndrome, systemic lupus erythematosus and rheumatoid arthritis and relation with disease activity.
abstract: BACKGROUND
  Cell stimulation leads to the shedding of phosphatidylserine (PS)-rich microparticles (MPs). Because autoimmune diseases (AIDs) are characterized by cell activation, we investigated level of circulating MPs as a possible biomarker in primary Sjögren's syndrome (pSS), systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).
  
  
  METHODS
  We measured plasma levels of total, platelet and leukocyte MPs by prothrombinase capture assay and flow cytometry in 43 patients with pSS, 20 with SLE and 24 with RA and in 44 healthy controls (HCs). Secretory phospholipase A2 (sPLA2) activity was assessed by fluorometry. Soluble CD40 ligand (sCD40L) and soluble P-selectin (sCD62P), reflecting platelet activation, were measured by ELISA.
  
  
  RESULTS
  Patients with pSS showed increased plasma level of total MPs (mean +/- SEM 8.49 +/- 1.14 nM PS equivalent (Eq), P < 0.0001), as did patients with RA (7.23 +/- 1.05 n PS Eq, P = 0.004) and SLE (7.3 +/- 1.25 nM PS Eq, P = 0.0004), as compared with HCs (4.13 +/- 0.2 nM PS Eq). Patients with AIDs all showed increased level of platelet MPs (P < 0.0001), but only those with pSS showed increased level of leukocyte MPs (P < 0.0001). Results by capture assay and flow cytometry were correlated. In patients with high disease activity according to extra-glandular complications (pSS), DAS28 (RA) or SLEDAI (SLE) compared with low-activity patients, the MP level was only slightly increased in comparison with those having a low disease activity. Platelet MP level was inversely correlated with anti-DNA antibody level in SLE (r = -0.65; P = 0.003) and serum beta2 microglobulin level in pSS (r = -0.37; P < 0.03). The levels of total and platelet MPs were inversely correlated with sPLA2 activity (r = -0.37, P = 0.0007; r = -0.36, P = 0.002, respectively). sCD40L and sCD62P concentrations were significantly higher in pSS than in HC (P < or = 0.006).
  
  
  CONCLUSIONS
  Plasma MP level is elevated in pSS, as well as in SLE and RA, and could be used as a biomarker reflecting systemic cell activation. Level of leukocyte-derived MPs is increased in pSS only. The MP level is low in case of more severe AID, probably because of high secretory phospholipase A2 (sPLA2) activity, which leads to consumption of MPs. Increase of platelet-derived MPs, sCD40L and sCD62P, highlights platelet activation in pSS.
authors.affiliation: Rhumatologie, Hôpital Bicêtre, Assistance Publique-Hôpitaux de Paris (AP-HP), INSERM U802, Université Paris-Sud 11, 78 rue du Général Leclerc, 94270, Le Kremlin Bicêtre, France. jeremie.sellam@sat.aphp.fr
authors.forename: Jérémie
authors.initials: J
authors.lastname: Sellam
authors.forename: Valérie
authors.initials: V
authors.lastname: Proulle
authors.forename: Astrid
authors.initials: A
authors.lastname: Jüngel
authors.forename: Marc
authors.initials: M
authors.lastname: Ittah
authors.forename: Corinne
authors.initials: C
authors.lastname: Miceli Richard
authors.forename: Jacques-Eric
authors.initials: JE
authors.lastname: Gottenberg
authors.forename: Florence
authors.initials: F
authors.lastname: Toti
authors.forename: Joelle
authors.initials: J
authors.lastname: Benessiano
authors.forename: Steffen
authors.initials: S
authors.lastname: Gay
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Freyssinet
authors.forename: Xavier
authors.initials: X
authors.lastname: Mariette
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000276:immunology; D015415:Biomarkers / Q000097:blood*; D001792:Blood Platelets / Q000378:metabolism; D002469:Cell Separation; D055252:Cell-Derived Microparticles / Q000276:immunology / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007962:Leukocytes / Q000378:metabolism; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010718:Phosphatidylserines / Q000378:metabolism; D012859:Sjogren's Syndrome / Q000097:blood* / Q000276:immunology; D055815:Young Adult
chemical_list: D015415:Biomarkers; D010718:Phosphatidylserines