Statins differentially regulate vascular endothelial growth factor synthesis in endothelial and vascular smooth muscle cells

Abstract

Objectives: HMG-CoA reductase inhibitors (statins) can modulate the formation of new blood vessels, but the reports on their contribution to angiogenesis are contradictory. Therefore, we investigated whether the effect of statins is dependent either on the concentration of the drug or on the cell type. Methods and results: Under basal conditions human vascular smooth muscle cells (HVSMC) and microvascular endothelial cells (HMEC-1) constitutively generate and release vascular endothelial growth factor (VEGF). In contrast, primary macrovascular endothelial cells (HUVEC) produce minute amounts of VEGF. Different statins (atorvastatin, simvastatin and lovastatin, 1–10 μmol/l) significantly reduced basal and cytokine-, nitric oxide- or lysophosphatidylcholine (LPC)-induced VEGF synthesis in HMEC-1 and HVSMC. Interestingly, at the same concentrations statins upregulated VEGF generation in HUVEC. Furthermore, statins exerted dual, concentration-dependent influence on angiogenic activities of HUVEC as determined by tube formation assay. At low concentrations (0.03–1 μmol/l) the pro-angiogenic activity of statins is prevalent, whereas at higher concentrations statins inhibit angiogenesis, despite increasing VEGF synthesis. Conclusion: Our data show that statins exert concentration- and cell type-dependent effects on angiogenic activity of endothelial cells and on VEGF synthesis. The data are of relevance for elucidating the differential activity of statins on angiogenesis in cardiovascular diseases and cancer.

Introduction

Statins are potent inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase via blocking the substrate accessibility to the enzyme and thereby effectively subverting cholesterol metabolism. Several large trials have revealed an impressive clinical benefit of statins which has led to a widespread use of these drugs in the primary and secondary prevention of coronary artery disease (for review see [1]). In the last 5 years compelling evidence has accumulated suggesting a beneficial effect of statins beyond their inhibition of cholesterol synthesis (for review see [2], [3], [4]). Indeed, for example, simvastatin and lovastatin have been reported to increase the half-life of the mRNA for eNOS. Atorvastatin, pravastatin and cerivastatin were able to scavenge oxygen derived free radicals and simvastatin and atorvastatin have been shown to decrease the precursor for endothelin-1 [2], [3], [4]. Thus, statins may exert directly vasculoprotective, perhaps cholesterol-independent effects.

Vascular endothelial growth factor (VEGF) has been proven to be an important growth factor critical for blood vessel formation [5]. Recently, it has been suggested that statins may also modulate VEGF synthesis and consequently angiogenesis. Indeed, lovastatin at micromolar concentrations inhibited the production of VEGF in transformed fibroblasts [6] and cytokine-induced VEGF synthesis in rat vascular smooth muscle cells (VSMC) [7], while mevastatin suppressed the VEGF synthesis in rat primary aortic endothelial cells [8]. In contrast, statins at nanomolar concentrations have been recently demonstrated to enhance angiogenesis via activation of Akt kinase in human umbilical vein endothelial cells [9] or endothelial progenitor cells [10], [11]. However, it is not known so far whether the decreasing effect is dependent on the dose of statins or associated to its efficacy on different cell types. Therefore, the aim of this study was to investigate whether the effect of statins on endothelial cell angiogenic activity and on VEGF expression is dependent on the concentration of the drug and/or on the cell type.