Effects of sFlt-1 and alpha 2-macroglobulin on vascular endothelial growth factor-induced endothelin-1 upregulation in human microvascular endothelial cells

Introduction Soluble fms-like tyrosine kinase-1 (sFlt-1) is a vascular endothelial growth factor (VEGF) binding protein and potent antagonist of VEGF. Alpha 2 macroglobulin (α₂M) is another major binding protein for circulating VEGF, which is present in human plasma at higher concentration (2-4 mg/mL) than sFlt-1. This study investigated the effects of sFlt-1 and α₂M on VEGF-induced endothelin-1 (ET-1) upregulation in human microvascular endothelial cell-1 (HMEC-1). Methods HMEC-1 was cultured and incubated with varying concentrations of sFlt-1 and α₂M in combination with VEGF. ET-1 mRNA expression in the cells was measured by real time RT-PCR and ET-1 protein by western blot analysis. Results ET-1 expression in HMEC-1 incubated with VEGF significantly increased in time- and dose-dependent manners. Next, HMEC-1 was treated with the sFlt-1 (10-1000 ng/mL) or α₂M (10-10000 ng/mL) in the presence of VEGF (10 ng/mL). We found that sFlt-1 induced a significant decrease of ET-1 expression upregulated by VEGF, while α₂M did not affect the VEGF-induced ET-1 expression. Conclusions sFLT-1 suppressed the VEGF-induced the ET-1 expression of HMEC-1. However, α₂M did not show a significant effect on the ET-1 expression that was induced by VEGF. The results suggest that a certain proportion of the bound form α₂M-VEGF have a biological action involved in the pathophysiology of preeclampsia.