Abstract 4954: A Novel Role of CCN3 in Regulating Endothelial Inflammation
Background: The vascular endothelium plays a fundamental role in the health and disease of the cardiovascular system. However, the molecular mechanisms regulating endothelial homeostasis remain incompletely understood. CCN3, a member of the CCN (Cyr61, Ctgf, Nov) family of cell growth and differentiation regulators, has been shown to play an important role in numerous cell types. While CCN3 expression in endothelial cells has been described, its function in this cell type has yet to be elucidated.
Methods and Results: A detailed immunohistochemical analysis of CCN3 expression in mouse tissues revealed robust immunoreactivity in the endothelium of large arteries, small resistance vessels, as well as veins. Likewise, CCN3 expression is observed in cultured human endothelial cells derived from a variety of vascular beds. CCN3 expression in human umbilical vein endothelial cells (HUVECs) is transcriptionally induced by laminar shear stress (LSS) by ~27-fold. Similarly, treatment of HUVEC with HMG CoA-reductase inhibitors (statins) induced CCN3 expression by ~32-fold. A combination of promoter deletion and mutational analyses coupled with chromatin immuno-precipitation studies identified the Kruppel-like factor 2 as a direct regulator of CCN3 expression. In contrast to LSS, proinflammatory cytokines such as TNFα reduced CCN3 expression. Functionally, adenoviral overexpression of CCN3 in HUVEC markedly inhibited the cytokine-mediated induction of VCAM-1. Consistent with this observation, CCN3 overexpression significantly reduced monocyte adhesion. Conversely, siRNA mediated “knockdown” of CCN3 protein in HUVECs resulted in enhancement of cytokine-induced VCAM-1 expression. Concordant effects were observed on monocyte adhesion. Mechanistically, gain and loss-of-function studies demonstrate that CCN3 negatively regulates NF-κB activity by reducing its translocation into nucleus and DNA binding to VCAM-1 promoter, suggesting that CCN3’s anti-inflammatory effects occur secondary to inhibition of NF-κB nuclear accumulation.
Conclusions: This study identifies CCN3 as a novel regulator of endothelial proinflammatory activation.