Serum Levels of IL-17, IL-6, TNF-α and Disease Activity in Patients with Rheumatoid Arthritis

Abstract

Objective: The aim of this study was to evaluate serum levels of interleukin (IL)-17, IL-6, and tumor necrosis factor alpha (TNF-α) in RA patients and to assess the correlation of these cytokines with clinical and laboratory parameters.

Materials and Methods: 48 patients with RA and 35 healthy volunteers were enrolled in the study. Disease activity was determined by disease activity score (DAS28) in patients with RA. Patients with RA were categorized as mild (DAS28≤3.2), moderate (3.2<DAS28≤5.1), and severe (5.1<DAS28) according to DAS28. The serum levels of IL-17, IL-6 and TNF-α cytokines were measured by enzyme-linked immuno sorbent assay.

Results: The mean serum IL-17 and TNF-α levels did not differ between RA patients and controls (P>0.05). Serum IL-6 levels were significantly elevated in RA patients compared with controls (P<0.001). The increasing trend in mean serum IL-6 levels across group with mild, moderate, and severe disease activity was significant (P<0.001, respectively). In RA patients, serum IL-6 concentrations were significantly correlated with ESR, CRP, DAS28, and VAS (r=0.371, P=0.009; r=0.519, P<0.001; r=0.536, P<0.001; r=0.539, P<0.001, respectively). Also, Serum IL-17 concentrations demonstrated significant correlations with ESR, CRP, but not DAS28 (r=0.349, P=0.015; r=0.299, P=0.039; r=0.274, P=0.060, respectively). Serum TNF-α showed no significant correlation with disease activity indices.

Conclusions: This study showed that patients with RA had significantly increased cytokine level for IL-6, but not IL-17 and TNF-α and high level of serum IL-6 cytokine was associated with disease activity. However, further follow-up studies involving large samples are required to clarify precise role of these cytokines in disease development and progress.

Zusammenfassung

Zielsetzung: Ziel dieser Studie war es, bei RA-Patienten die Serumspiegel von Interleukin (IL)-17, IL-6 und Tumornekrosefaktor-alpha (TNF-α) zu untersuchen und die Korrelation dieser Zytokine mit klinischen und laborchemischen Parametern zu beurteilen.

Material und Methoden: Es wurden 48 Patienten mit RA und 35 gesunde Probanden in die Studie aufgenommen. Bei den Patienten mit RA wurde anhand des Disease Activity Score (DAS28) die Krankheitsaktivität ermittelt. Diese wurde gemäß DAS28 als leicht (DAS28≤3,2), mittelschwer (3,2<DAS28≤5,1) und schwer (5,1<DAS28) eingestuft. Die Serumspiegel der Zytokine IL-17, IL-6 und TNF-α wurden mithilfe eines ELISA [Enzyme-linked Immunosorbent Assay] bestimmt.

Ergebnisse: Bei den mittleren Serumspiegeln von IL-17 und TNF-α fand sich zwischen den RA-Patienten und den Kontrollen kein signifikanter Unterschied (p>0,05). Die Serumspiegel von IL-6 waren bei den RA-Patienten im Vergleich zu den Kontrollen signifikant erhöht (p<0,001). In allen Patientengruppen mit leichter, mittelschwerer und schwerer Krankheitsaktivität fand sich eine signifikante Tendenz zur Zunahme der mittleren Serumspiegel von IL-6 (jeweils p<0,001). Bei den RA-Patienten korrelierten die Serumkonzentrationen von IL-6 signifikant mit ESR, CRP, DAS28 und VAS (r=0,371, p=0,009; r=0,519, p<0,001; r=0,536, p<0,001 bzw. r=0,539, p<0,001). Darüber hinaus zeigten die Serumkonzentrationen von IL-17 eine signifikante Korrelation mit ESR und CRP, nicht aber nicht DAS28 (r=0,349, p=0,015; r=0,299, p=0,039 bzw. r=0,274, p=0,060). Die Serumspiegel von TNF-α zeigten keine signifikante Korrelation mit den Krankheitsaktivitätsindizes.

Schlussfolgerungen: Diese Studie zeigte, dass bei RA-Patienten der Zytokinspiegel von IL-6 signifikant erhöht war, der von IL-17 und TNF-α hingegen nicht. Außerdem ergab die Studie, dass der hohe Serumspiegel des Zytokins IL-6 mit der Krankheitsaktivität assoziiert war. Die genaue Funktion dieser Zytokine bei der Entwicklung und Progression der Erkrankung muss jedoch in weiteren Folgestudien mit großen Stichproben geklärt werden.

Key words

interleukin-17 - interleukin-6 - tumor necrosis factor-α - rheumatoid arthritis - disease activity

Schlüsselwörter

Interleukin-17 - Interleukin- - Tumornekrosefaktor-α - Rheumatoide Arthritis - Krankheitsaktivitat

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