Abstract
Matrix metalloproteinase-1 (MMP-1) is a collagenase that is highly active in extracellular matrix and vascular remodeling, angiogenesis, and tumor progression. Vascular endothelial growth factor receptor-2 (VEGFR2), the main receptor for VEGF-A, is expressed on endothelial cells and promotes cell survival, proliferation, and other functions. Although MMP-1 and VEGFR2 co-exist in many normal and pathophysiological conditions, the effect of MMP-1 on cellular VEGFR2 that can promote the above processes is unknown. In this study we test the hypothesis that stimulation of endothelial cells with MMP-1 increases their levels of VEGFR2. The increased VEGFR2 is then available to bind VEGF-A, resulting in increased response. Indeed we found that endothelial cells incubated with active MMP-1 had higher mRNA and protein levels of VEGFR2. Furthermore, VEGF-A-dependent phosphorylation of intracellular signaling molecules and endothelial proliferation were elevated after MMP-1 treatment. MMP-1 caused activation of the nuclear factor-κB (NF-κB) pathway (p65/RelA) in endothelial cells, and this response was dependent upon activation of protease activated receptor-1 (PAR-1). Chromatin immunoprecipitation was used to confirm NF-κB-mediated active transcription of the VEGFR2 (KDR) gene. Elevation in VEGFR2 after MMP-1 stimulation was inhibited by PAR-1 knockdown and NF-κB specific inhibition. We conclude that MMP-1 promotes VEGFR2 expression and proliferation of endothelial cells through stimulation of PAR-1 and activation of NF-κB. These results suggest a mechanism by which MMP-1 may prime or sensitize endothelial cell functions.
Highlights
Matrix metalloproteinases (MMP) and Vascular endothelial growth factor receptor-2 (VEGFR2) often coexist in many settings, but their interactions are unknown
In this study we show that stimulation of endothelial cells with Matrix metalloproteinase-1 (MMP-1) results in elevated VEGFR2 levels
We further demonstrate that MMP-1-mediated VEGFR2 production involves activation of protease activated receptor-1 (PAR-1) and occurs through an nuclear factor-B (NF-B)-dependent mechanism
Summary
Matrix metalloproteinases (MMP) and VEGFR2 often coexist in many settings, but their interactions are unknown. VEGF-A-mediated stimulation of VEGFR2 leads to activation of extracellular signal-related kinase 1/2 (ERK1/2), JNK, MAPK (p38), and others [11, 12] These signaling molecules modulate a variety of endothelial functions, including endothelial survival, permeability, and proliferation [7, 13, 14]. By the use of specific inhibition protocols we found that the mechanism by which VEGFR2 is up-regulated is mediated by PAR-1 and activation of the NF-B pathway These results provide insights regarding the ability of MMP-1 to enhance endothelial functions/activities in conditions associated with increased levels of MMP-1
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