Conclusions
SSc serum induces endothelial cell activation and apoptosis in endothelial cell-neutrophil co-cultures, mediated largely by IL-6 and dependent on the presence of neutrophils. Together with other pathologically relevant effects of IL-6, these data justify further exploration of IL-6 as a therapeutic target in SSc.
Methods
Human dermal microvascular endothelial cells were cultured with healthy control neutrophils in the presence of 25% healthy control or SSc serum for 24 h. Apoptosis was measured by annexin V-FITC binding and endothelial cell activation was measured using an allophycocyanin-conjugated E-selectin antibody. Fluorescence was quantified and localised using confocal microscopy.
Results
SSc serum resulted in significantly increased apoptosis (p=0.006) and E-selectin expression (p=0.00004) in endothelial cells compared with control serum, effects that were critically dependent on the presence of neutrophils. Recombinant interleukin 6 (IL-6) reproduced these findings. Immunodepletion of IL-6 and the use of an IL-6 neutralising antibody decreased the effect of SSc serum on E-selectin expression. Soluble gp130, which specifically blocks IL-6 trans-signalling, negated the effect of SSc serum on both E-selectin expression and apoptosis. Conclusions: SSc serum induces endothelial cell activation and apoptosis in endothelial cell-neutrophil co-cultures, mediated largely by IL-6 and dependent on the presence of neutrophils. Together with other pathologically relevant effects of IL-6, these data justify further exploration of IL-6 as a therapeutic target in SSc.