Background/Purpose:

We have previously demonstrated that S100A4 is up-regulated in established rheumatoid arthritis (RA) and that S100A4 regulates apoptosis and synthesis of matrix degrading enzymes in synovial fibroblasts. The aim of the present study was to: 1) characterize whether S100A4 reflects disease activity and/or response to treatment in patients with early RA and 2) determine whether S100A4 regulates production of pro-inflammatory cytokines in mononuclear cells.

Methods:

Serum samples were obtained from 59 patients with early RA (symptom duration ≤ 6 months) before and 3 months after treatment with disease modifying anti-rheumatic drugs (DMARDs) and also from 41 healthy individuals. Disease activity score (DAS28-CRP) was assessed at baseline and after 3 and 12 months. S100A4 levels were analyzed by ELISA. Peripheral blood mononuclear cells (PBMCs) and CD3+ T-cells isolated from patients with established RA were stimulated with S100A4, S100A8 and S100A12 proteins (each 1μg/ml). Production of interleukin IL-1β, IL-6 and tumor necrosis factor alpha (TNF-α) was measured by ELISA. Receptor for advanced glycation end products (RAGE) and Toll-like receptor-4 (TLR-4) signalling were examined. For signalling pathway blocking studies, inhibitors of MyD88, NFkB and MAP kinases p38, erk1/2, jnk were used. Activation of MAP kinases was determined by Western blotting.

Results:

S100A4 serum levels were significantly higher in patients with early RA compared with healthy controls (p<0.001) and significantly decreased after 3 months of treatment (p<0.001).

Although S100A4 levels did not correlate with disease activity, in female patients, high S100A4 levels (>1000 ng/ml) at baseline predicted worse response to treatment (DAS28 ≥ 3.2) after 3 and 12 months of therapy (PPV 0.28, OR (95% CI) 2. 846 (1.837, 4.410), p= 0.006 and PPV 0.60, OR (95% CI) 2.700 (0. 992, 7.351), P=0.046). Interestingly, higher S100A4 levels (>1000 ng/ml) at 3 months predicted worse response to treatment (DAS28 ≥ 3.2) in all patients after 12 months (PPV=0.33, OR (95% CI) 2.36 (1.17, 4.74), p=0.04).

Stimulation of PBMCs with S100A4 significantly up-regulated production of IL-1β, IL-6 and TNF-α compared with unstimulated cells (p<0.001). Importantly, production of the cytokines was markedly enhanced in response to S100A4 compared with S100A8 and S100A12 proteins. Extracellular S100A4 induced production of the pro-inflammatory cytokines (p<0.01) also in CD3+ T-cells. Furthermore, enhanced production of pro-inflammatory cytokines in S100A4 stimulated PMBCs was at least partly mediated via TLR-4, but not RAGE, and by the activation of transcription factor NFkB and MAP kinases p38 and erk1/2.

Conclusion:

This is the first study to demonstrate that S100A4 is elevated in patients with early RA and that S100A4 induces inflammatory response mediated by the TLR-4 signalling pathway in mononuclear cells. Taken together, we suggest that high levels of S100A4 may represent a potential biomarker of insufficient treatment response and/or therapeutic target for immune mediated diseases such as RA.

Acknowledgement: This study was supported by Internal Grant Agency of Ministry of Health of the Czech Republic NT/13698-4

---

« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-role-of-s100a4-as-a-biological-marker-of-immune-response-in-early-rheumatoid-arthritis/