Rheumatoid factor positivity is associated with increased joint destruction and upregulation of matrix metalloproteinase 9 and cathepsin k gene expression in the peripheral blood in rheumatoid arthritic patients treated with methotrexate

Abstract

We evaluated changes in gene expression of mTOR, p21, caspase-3, ULK1, TNF α , matrix metalloproteinase (MMP)-9, and cathepsin K in the whole blood of rheumatoid arthritic (RA) patients treated with methotrexate (MTX) in relation to their rheumatoid factor status, clinical, immunological, and radiological parameters, and therapeutic response after a 24-month follow-up. The study group consisted of 35 control subjects and 33 RA patients without previous history of MTX treatment. Gene expression was measured using real-time RT-PCR. Decreased disease activity in patients at the end of the study was associated with significant downregulation of TNF α expression. Downregulation of mTOR was observed in seronegative patients, while no significant changes in the expression of p21, ULK1, or caspase-3 were noted in any RA patients at the end of the study. The increase in erosion numbers observed in the seropositive patients at the end of the follow-up was accompanied by upregulation of MMP-9 and cathepsin K, while seronegative patients demonstrated an absence of significant changes in MMP-9 and cathepsin K expression and no increase in the erosion score. Our results suggest that increased expression of MMP-9 and cathepsin K genes in the peripheral blood might indicate higher bone tissue destruction activity in RA patients treated with methotrexate. The clinical study registration number is 0120.0810610.

Figure 1

Relative expression of the genes mTOR (a), ULK1 (b), p21 (c), caspase-3 (d), MMP-9 (e), and cathepsin K (f), and TNFα (g) with reference to β-actin determined by real-time PCR analyses in the whole blood of seronegative (RF−) (n = 12) and seropositive (RF+) (n = 21) rheumatoid arthritic patients compared with healthy controls (Control) (n = 35) at baseline (0) and after 24 months of follow-up (24 mo). Control bar is shown as 1.0 as required for relative quantification with the real-time PCR protocol. Asterisks indicate significant differences from the control in pairwise comparisons (Mann-Whitney U test). Number sign (#) shows significant difference from the baseline value (Wilcoxon matched pairs test). & sign indicates significant difference between seronegative and seropositive RA patients (Mann-Whitney U test).