Adenosine Deaminase in Synovial Fluid at Rheumatoid Arthritis is Citrullinated

Abstract

AIM: The objective of this article is to compare accumulation and citrullination of small (SADA) and large (LADA) isoforms of adenosine deaminase (ADA) in the synovial fluids (SFs) of patients with rheumatoid arthritis (RA), ankylosing spondylitis, gout, juvenile idiopathic and reactive arthritis.

MATERIALS AND METHODS: The SFs of patients, diagnosed in the Medical Center “Muratsan”, were taken from knee joints. The methods of ion-exchange and gel-chromatography were applied for separation and purification of ADA isoforms from the SFs of above mentioned five arthritis types. The activities and citrullination state of ADA isoforms were studied using appropriate colorimetric assays.

RESULTS: This work revealed accumulation of SADA in RA SFs and of LADA in the SFs of four other arthritis types. The average protein citrullination, measured as A₅₃₀/A₂₈₀ ratio, was of 0.07±0.04 (n=5) in SADA purified from RA SFs with the initial ADA activity between 35-60 U/L. In SADA samples from RA SFs with the initial ADA activity of 70-190 U/L, the average value of protein citrullination was higher by an order (0.83±0.28, n=8). The citrullination of LADA was not registered in any of all five studied arthritis types.

CONCLUSION: In SFs of RA, the citrullinated SADA is accumulated. In four other studied arthritis types, LADA is accumulated. One can suggest: in RA the citrullination of SADA prevents its binding to dipeptidyl peptidase IV and transformation to LADA.

The obtained data permit the assumption of being SADA as a new citrulline containing auto-antigen applicable in RA diagnosis.