Metabolic aspects of clinical remission prediction from baseline blood gene expression in patients with rheumatoid arthritis treated with methotrexate

Rheumatoid arthritis (RA) is an autoimmune disease of unknown etiology, which is characterized by chronic erosive arthritis (synovitis) and systemic inflammation of the viscera. Methotrexate (MTX) is the drug of choice for RA treatment. However, it is currently impossible to predict the efficacy of MTX in a particular patient; the drug fails to produce the desired effect or causes adverse reactions in a considerable number of patients. The identification of patients who are responsive to MTX could significantly improve the results of therapy. Objective : to investigate the specific features of baseline (pretreatment) expression of genes responsible for major metabolic and energy production pathways in RA patients with different disease activity and to identify the genes, the baseline expression of which could serve as a predictor for remission attainment. Patients and methods . Blood from 40 RA patients (mean age 47.5 years; mean disease duration 7.9 weeks) who had not previously received MTX and 26 healthy donors (mean age 45.1 years). All the patients had used MTX (15 mg/week) for 2 years. Clinical response was evaluated by DAS28 and the serum levels of anti-cyclic citrullinated peptide antibodies, C-reactive protein, and rheumatoid factor. Remission was diagnosed according to ACR/EULAR and DAS28 (DAS28 <2.6). Joint structural changes were radiographically evaluated. Gene expression was determined in peripheral blood cells by real-time reverse transcriptase-polymerase chain reaction. A control group consisted of 26 randomly recruited gender- and sex-matched patients without autoimmune diseases and a family history. Results and discussion . MTX treatment significantly decreased disease activity according to DAS28. At the end of the investigation, the majority of patients had moderate disease activity (3.2≤ DAS28 ≤5.1), 4 had high disease activity, while 12 attained remission (DAS28 <2.6). Gene expression analysis showed that RA patients who had achieved clinical remission after MTX therapy displayed higher baseline expression of the genes associated with glycolysis (Glut1, PKM), inflammation (TNF-α), autophagy (ULK1), apoptosis (caspase 3, p21), and hypoxia (HIF1α), compared with patients who had not attained remission and with healthy individuals. In addition, in patients who had achieved remission, the baseline expression of the CD1 gene was significantly higher than in healthy individuals, while in the remaining patients the expression of this gene was significantly lower than in the controls. While the disease activity remained high, the baseline expression of the p21, caspase 3, TGFβ1, and RUNX2 genes was significantly lower than in healthy individuals and other patients with RA. Conclusion . Remission achievement in RA patients who had not previously received MTX was associated with higher baseline (pretreatment) gene expression associated with glycolytic activity, inflammation, autophagy, apoptosis, and hypoxia compared with patients who failed to attain remission. Elevated baseline expression of the CD1 gene compared with that in healthy individuals may serve as a predictor of sensitivity to MT therapy.