Background Interleukin-20 (IL-20), a recently identified potent pro-inflammatory, angiogenic and chemoattractive cytokine, plays a significant role in the pathogenesis of rheumatoid arthritis (RA). Activated monocytes and dendritic cells are the main source of IL-20, which is significantly up-regulated particularly in synovial fluid and synovial membrane, but to a lesser extent also in plasma, of patients with established RA. However, circulating IL-20 has not yet been studied at early stages of RA.
Objectives Therefore, the aim of the current study was to characterize the role of serum levels of IL-20 in patients with recent-onset RA.
Methods Serum levels of IL-20 were determined in 51 patients with recent-onset RA (symptom duration <6 months) before and 3 months after initiation of treatment with disease-modifying antirheumatic drugs, and cross-sectionally in 36 healthy controls.A majority of RA patients were treated with methotrexate and low dose glucocorticoids. Disease activity (DAS28) was assessed at baseline and at 3, 6 and 12 months. Hand/feet x-rays scored using the Sharp-van der Heijde Score (SHS) were assessed at baseline and month 12.
Results After the initiation of treatment, disease activity had significantly improved (DAS28 decreased from 5.28±1.43 at baseline to 2.75±1.41 at month 3 (n=51), 2.71±1.29 at month 6 (n=49) and 2.50±1.13at month 12 (n=43). Out of 43 patients with available radiographs, 10 (23%) showed an increase in SHS after 12 months (defined as >0 SHS units). Although, there were no differences in the levels of serum IL-20 between patients with recent-onset RA and healthy controls, significant reduction of circulating IL-20 was observed after treatment (from 7.691±39.026 pg/ml at baseline to 0.996±15.502 pg/ml at month 3; p<0.0001). Although serum levels of IL-20 did not correlate with DAS28 at baseline, higher IL-20 levels predicted improvement of disease activity (decrease in DAS28) at 3 months (r= -0.317, p=0.025), but not at later time points. Furthermore, decrease in the levels of IL-20 positively correlated with the change in DAS28 over 3 months (r=0.317; p=0.025). There was no association between baseline levels or changes of IL-20 and achievement of DAS28 remission or radiographic progression.
Conclusions In contrast to its local up-regulation at sites of inflammation, there was no difference in circulating levels of IL-20 in patients with recent-onset RA and healthy controls. However, higher baseline levels of IL-20 were associated with better treatment response at 3 months. We suggest that significant decrease of IL-20 levels and its association with disease activity improvement in patients with RA may reflect local reduction of activated mononuclear infiltrates within the synovial tissue following successful immunosuppressive therapy.
Supported by MH CR-grant project No.10065-4
Disclosure of Interest None Declared
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