Expression of K2P5.1 potassium channels on CD4+ T lymphocytes correlates with disease activity in rheumatoid arthritis patients

Introduction

CD4⁺ T cells express K_2P5.1 (TWIK-related acid-sensitive potassium channel 2 (TASK2); KCNK5), a member of the two-pore domain potassium channel family, which has been shown to influence T cell effector functions. Recently, it was shown that K_2P5.1 is upregulated upon (autoimmune) T cell stimulation. The aim of this study was to correlate expression levels of K_2P5.1 on T cells from patients with rheumatoid arthritis (RA) to disease activity in these patients.

Methods

Expression levels of K_2P5.1 were measured by RT-PCR in the peripheral blood of 58 patients with RA and correlated with disease activity parameters (C-reactive protein levels, erythrocyte sedimentation rates, disease activity score (DAS28) scores). Twenty patients undergoing therapy change were followed-up for six months. Additionally, synovial fluid and synovial biopsies were investigated for T lymphocytes expressing K_2P5.1.

Results

K_2P5.1 expression levels in CD4⁺ T cells show a strong correlation to DAS28 scores in RA patients. Similar correlations were found for serological inflammatory parameters (erythrocyte sedimentation rate, C-reactive protein). In addition, K_2P5.1 expression levels of synovial fluid-derived T cells are higher compared to peripheral blood T cells. Prospective data in individual patients show a parallel behaviour of K_2P5.1 expression to disease activity parameters during a longitudinal follow-up for six months.

Conclusions

Disease activity in RA patients correlates strongly with K_2P5.1 expression levels in CD4⁺ T lymphocytes in the peripheral blood in cross-sectional as well as in longitudinal observations. Further studies are needed to investigate the exact pathophysiological mechanisms and to evaluate the possible use of K_2P5.1 as a potential biomarker for disease activity and differential diagnosis.