CRP promotes monocyte-endothelial cell adhesion via Fcγ receptors in human aortic endothelial cells under static and shear flow conditions

Abstract

Monocyte-endothelial cell adhesion is a key early event in atherogenesis. C-reactive protein (CRP), a cardiovascular risk marker, is known to stimulate ICAM and VCAM in human aortic endothelial cells (HAEC) and induces monocyte-endothelial cell adhesion. In this study, we examined the mechanisms by which native CRP promotes monocyte-endothelial cell adhesion under static conditions and tested the effect of CRP on adhesion under shear flow. Incubation of HAEC with CRP (>25 microg/ml) upregulated NF-kappaB activity, and this resulted in a significant increase in ICAM (54% increase, P<0.001), VCAM (41% increase, P<0.01), and monocyte-endothelial cell adhesion (44% increase, P<0.02) compared with those of control. Preincubation with antibodies to CD32 and CD64 but not CD16 effectively inhibited this activation. Blocking NF-kappaB activity with inhibitors or a dominant negative inhibitory kappaB significantly decreased ICAM, VCAM upregulation, and subsequent monocyte-endothelial cell adhesion. Preincubation with antibodies to CD32 and CD64 or transient transfection with small interference RNA to CD32 attenuated CRP-induced NF-kappaB activity, ICAM, VCAM, and monocyte-endothelial cell adhesion under static conditions. Also, the Syk kinase inhibitor piceatannol and MG-132, a proteasome degradation inhibitor, produced similar attenuation in NF-kappaB activity, ICAM, VCAM, and adhesion. Furthermore, CRP-activated endothelial cells supported monocyte rolling, arrest, and transmigration in shear flow (2 dyn/cm2), and this was also inhibited by preincubation with antibodies to CD32 and CD64. Thus, in HAEC, CRP upregulates monocyte-endothelial adhesion by activation of NF-kappaB through engaging the Fcgamma receptors CD32 and CD64.