Cystatin C binds serum amyloid A, downregulating its cytokine-generating properties
Författare
Summary, in English
Objective. To assess the interaction between cystatin C (CysC) and serum amyloid A protein (SAA). Methods. Levels of CysC and SAA and antibodies against these proteins were assessed in the paired blood and synovial fluid (SF) samples of 90 patients with rheumatoid arthritis (RA). Age and sex matched individuals having normal iohexol clearance (n = 90) and SF following joint trauma (n = 40) were used as controls. In vitro experiments included assessment of interaction between CysC and SAA by ELISA and the influence of CysC on SAA functions. Results. A pilot screening for cystatins C, E, and F in blood and SF of patients with RA found CysC to be by far the predominant extracellular cystatin. Circulating CysC levels were significantly lower in patients with RA compared to the matched controls (0.81 +/- 0.03 vs 1.01 +/- 0.03 mg/l; p = 0.05). These low CysC levels could not be explained by the presence of anti-CysC antibodies in patients with RA. In contrast, concentrations of CysC that accumulated in the inflamed SF were significantly greater in patients with erosive RA (1.66 +/- 0.08 mg/l) compared to nonerosive RA (1.36 +/- 0.06 mg/l; p = 0.003) and controls (1.18 +/- 0.03 mg/l; p = 0.043). In vitro studies showed direct binding of CysC to SAA. CysC/SAA binding impaired proinflammatory effects of SAA, reducing its ability to trigger expression of proinflammatory cytokines. Conclusion. Our study shows a relative deficiency of circulating CysC during systemic inflammation in RA. Physical interaction between CysC and the acute-phase protein SAA (1) provides an explanation for CysC deficiency; and (2) suggests that CysC is regulating inflammatory responses. We hypothesize that decreased systemic CysC levels predispose to accelerated atherosclerosis and development of amyloidosis in patients with RA.
Avdelning/ar
- Avdelningen för klinisk kemi och farmakologi
- Lungmedicin, allergologi och palliativ medicin
- Infektionsmedicin
- Joint and Soft Tissue Unit
Publiceringsår
2007
Språk
Engelska
Sidor
1293-1301
Publikation/Tidskrift/Serie
Journal of Rheumatology
Volym
34
Issue
6
Länkar
Dokumenttyp
Artikel i tidskrift
Förlag
Journal of Rheumatology Publishing Company Limited
Ämne
- Rheumatology and Autoimmunity
Nyckelord
- cytokines
- cystatin C
- serum amyloid A
- rheumatoid arthritis
Status
Published
Forskningsgrupp
- Joint and Soft Tissue Unit
ISBN/ISSN/Övrigt
- ISSN: 0315-162X