Background: Patients with SLE have an endothelial dysfunction (ED), which is considered the earliest marker of cardiovascular (CV) disease. Endothelial cell activation induced by proinflammatory cytokines is defined by the endothelial expression of cell-surface adhesion molecules, such as vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and E-selectin. The aim of this study was to investigate whether serum endothelial adhesion molecule levels are influenced by blood hydroxychloroquine (HCQ) levels in SLE.

Methods: Consecutive patients with SLE taking a stable dose of HCQ were investigated. At study entry and 6 months later HCQ blood levels were quantified by tandem mass spectrometry. Serum levels of P-selectin, E-selectin, ICAM-1 and VCAM-1 were also measured using a Luminex 200 instrument. Comparison of endothelial soluble adhesion molecules in groups with different HCQ blood levels was performed by t-test.

Results: 83 patients with SLE were enrolled. Correlation were demonstrated between mean blood HCQ concentrations and endothelial soluble adhesion molecules (E-selectin, ICAM-1 and VCAM-1). Moreover, serum levels of ICAM-1 and VCAM-1 were significantly lower in the patients with SLE with HCQ blood levels >500 ng/mL (83.67±52.8 ng/mL vs 158.81±125.1 ng/mL and 8.9±2.2 ng/mL vs 10.4±2.3 ng/mL). Serum levels of E-selectin were nearly significantly lower in the patients with SLE with HCQ blood levels >500 ng/mL (64.7±30.2 ng/mL vs 71.6±42.2 ng/mL, p=0.06). No significant difference in concentration of P-selectin was detected.

Conclusions: In the present study, there was a trend towards higher adhesion molecules levels with lower HCQ blood levels in patients with SLE. Further longitudinal studies will determine whether changes in endothelial biomarkers reflect decreased clinical CV events.