Activation of vascular endothelial cells (ECs) plays an important role in atherogenesis and plaque instability. Lipoproteins containing apolipoprotein CIII (apoCIII) predict coronary heart disease (CHD). We recently reported that apoCIII has a proinflammatory effect on human monocytes. In this study, we looked for a direct effect of apoCIII on EC expression of adhesion molecules, leading to monocytic cell adhesion.Methods and Results—
Treatment of ECs with apoCIII or apoCIII-rich VLDL caused human monocytic THP-1 cells to adhere to them under static condition or under laminar sheer stress (1.0 dyne/cm2). ApoCIII increased EC expression of vascular cell adhesion molecule-1 (VCAM-1) protein and intercellular cell adhesion molecule-1 (ICAM-1) protein (4.9±1.5-fold and 1.4±0.5-fold versus control, respectively). Furthermore, apoCIII remarkably increased membrane-bound protein kinase C (PKC) β in ECs, indicating activation. A selective inhibitor of PKCβ prevented the rise in VCAM-1 and THP-1 cell adhesion to ECs. Moreover, exposure of ECs to apoCIII induced nuclear factor-κB (NF-κB) activation. PKCβ inhibition abolished apoCIII-induced NF-κB activation, and NF-κB inhibition reduced expression of VCAM-1, each resulting in reduced THP-1 cell adhesion. ApoCIII-rich VLDL also activated PKCβ and NF-κB in ECs and increased expression of VCAM-1. Pretreatment of ApoCIII-rich VLDL with anti-apoCIII neutralizing antibody abolished its effect on PKCβ activation.Conclusions—
Our findings provide the first evidence that apoCIII increases VCAM-1 and ICAM-1 expression in ECs by activating PKCβ and NF-κB, suggesting a novel mechanism for EC activation induced by dyslipidemia. Therefore, apoCIII-rich VLDL may contribute directly to atherogenesis by activating ECs and recruiting monocytes to them.