Identification of Autoantibodies against Transthyretin for the Screening and Diagnosis of Rheumatoid Arthritis

Abstract

Rheumatoid arthritis (RA) is a chronic, autoimmune, systemic and inflammatory rheumatic disease that leads to inflammation of the joints and surrounding tissues. Identification of novel protein(s) associated with severity of RA is a prerequisite for better understanding of pathogenesis of this disease that may also have potential to serve as novel biomarkers in the diagnosis of RA. Present study was undertaken to compare the amount of autoantigens and autoantibodies in the plasma of RA patients in comparison to healthy controls. Plasma samples were collected from the patients suffering from RA, Osteoarthritis (OA), Systemic lupus erythematosus (SLE) and healthy volunteers. The screening of plasma proteins were carried out using 2-dimensional gel electrophoresis followed by identification of differentially expressed protein by MALDI-TOF MS/MS. Among several differentially expressed proteins, transthyretin (TTR) has been identified as one of the protein that showed significantly up regulated expression in the plasma of RA patients. The results were further validated by Western blot analysis and ELISA. In comparison to OA synovium, an exclusive significantly high expression of TTR in RA has been validated through IHC, Western blotting and IEM studies. Most importantly, the increase in expression of TTR with the progression of severity of RA condition has been observed. The autoantibodies against TTR present in the RA plasma were identified using immunoprecipitation-Western methods. The significant production of autoantibodies was validated by ELISA and Western blot analysis using recombinant pure protein of TTR. Hence, these novel observations on increase in TTR expression with the increase in severity of RA conditions and significant production of autoantibodies against TTR clearly suggest that a systematic studies on the role TTR in the pathogenesis of RA is immediately required and TTR may be used as a serum diagnostic marker together with other biochemical parameters and clinical symptoms for RA screening and diagnosis.

Autoimmune response to transthyretin in juvenile idiopathic arthritis

“…As shown in our study, many JIA patients have significantly increased levels of TTR and anti-TTR antibodies in the SF as well as in the plasma (23, 24, 48). Considering the tendency of TTR to precipitate and aggregate, even a small increase in TTR synthesis or half-life could easily bring the protein out of solution (44–46).…”

“…Prior to any experiment, SFs were digested with hyaluronidase (30 kU/ml) as previously described (24) and depleted of albumins and IgG using Aurum Serum spin columns (Bio-Rad). Total protein concentration from human SF was determined using the Bradford assay (Bio-Rad).…”

Biomarkers of systemic lupus erythematosus identified using mass spectrometry‐based proteomics: a systematic review

“…A pilot study showed that transthyretin levels were upregulated in the sera of paediatric SLE patients compared to healthy controls . Additionally, increased serum levels of transthyretin were associated with the severity of rheumatoid arthritis, suggesting a role in disease pathogenesis . The main biological role of Hp is to bind haemoglobin, prevent iron loss and subsequent kidney damage during haemolysis.…”

Proteomics Analysis for Verification of Rheumatoid Arthritis Biomarker Candidates Using Multiple Reaction Monitoring

“…In addition, autoimmune diseases such as RA are characterized by destruction of the synovium following an autoimmune response. Transthyretin is reported to be one of the targets attacked by autoantibodies . The role of transthyretin has not yet been defined, and research on how transthyretin is associated with the immune response is ongoing.…”