Introduction Directory UMM :Data Elmu:jurnal:A:Atherosclerosis:Vol154.Issue1.Jan2001:

Atherosclerosis 154 2001 31 – 38 Inability of plasma high-density lipoproteins to inhibit cell adhesion molecule expression in human coronary artery endothelial cells Anita K. Stannard a , Shabeena Khan c , Annette Graham b , James S. Owen a, , Sean P. Allen c a Department of Medicine, Royal Free and Uni6ersity College Medical School, Uni6ersity College London, Royal Free Campus, London NW 3 2 PF, UK b Department of Biochemistry and Molecular Biology, Royal Free and Uni6ersity College Medical School, Uni6ersity College London, Royal Free Campus, London NW 3 2 PF, UK c Department of Cardiothoracic Surgery, Imperial College of Science, Technology and Medicine, Harefield Hospital, Harefield, Middlesex UB 9 6 JH, UK Received 2 November 1999; received in revised form 21 February 2000; accepted 1 March 2000 Abstract High-density lipoproteins HDL have several antiatherogenic actions, including the ability to sequester cellular cholesterol, to protect low-density lipoproteins from oxidation and to inhibit platelet aggregation. An early event in atherogenesis is the adhesion and recruitment of blood monocytes, a process mediated by cell adhesion molecules CAMs, including vascular cell adhesion molecule-1 VCAM-1 which is rapidly synthesized by endothelial cells in response to cytokines. It has been reported that HDL limits CAM expression in cultured human umbilical vein endothelial cells HUVECs, implying that HDL also protects at an early stage in lesion development. Here, we have studied HDL suppression of CAM induction in human coronary artery endothelial cells HCAECs, a model directly relevant to blood vessels susceptible to atherosclerosis. Arterial endothelial cells were preincubated with increasing amounts of total HDL, or different subfractions, and then activated with the inflammatory cytokine, tumor necrosis factor-alpha TNF-a. Flow cytometric analysis failed to detect any downregulation of VCAM-1 or E-selectin expression by HDL in this model of vascular endothelium. Moreover, we were unable to confirm that HDL could suppress CAM induction in well-characterized, low-passage HUVECs, even though positive controls, 17b-estradiol or a nitric oxide donor, did cause downregulation and factors such as variability in donors and HDL preparation, or culture conditions, were excluded. We tentatively conclude that, as isolated HDL did not downregulate CAM expression in cultured HCAECs or HUVECs, attenuation of CAM induction in arterial endothelium is unlikely to contribute to HDL antiatherogenic actions in vivo. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords : Atherosclerosis; E-Selectin; Human umbilical vein endothelial cells; Inflammatory cytokines; Vascular cell adhesion molecule-1 www.elsevier.comlocateatherosclerosis

1. Introduction

Coronary heart disease CHD is a leading cause of death in industrialized societies and epidemiological studies have established that plasma high-density lipo- protein HDL-cholesterol concentrations are inversely related to the development of the disease [1]. This protective effect of HDL may be associated with several functions, including a central role in reverse cholesterol transport [2,3] and anti-oxidant [4,5] and anti-throm- botic properties [6,7]. Studies in transgenic mice overex- pressing human apolipoprotein A-I apo A-I, the major apolipoprotein in HDL, have confirmed the anti- atherogenic role of HDL; the animals have increased HDL-cholesterol and resist atherosclerosis induced by diet [8], by apo E-deficiency [9] or by the human lipoproteina transgene [10]. A direct protective role of HDL was also shown in cholesterol-fed rabbits when infusions of HDL regressed atherosclerotic lesions [11]. Corresponding author. Tel.: + 44-20-74332853; fax: + 44-20- 74332852. E-mail address : j.owenrfc.ucl.ac.uk J.S. Owen. 0021-915001 - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0021-91500000444-5 Atherosclerotic plaques develop from complex multi- cellular processes in which recruitment of circulating monocytes to focal areas of the arterial sub-endothe- lium is an early event. Localized upregulation of adhe- sive endothelial cell adhesion molecules CAMs, a prerequisite for monocyte adherence and migration [12], is a dynamic process which is sensitive to inflam- matory cytokines, shear stress and oxidative insults. Levels of certain CAMs are elevated in human atherosclerotic tissue with vascular cell adhesion molecule-1 VCAM-1, intercellular adhesion molecule- 1 ICAM-1, E-selectin and P-selectin, in particular, being indicators of inflammation and early atheroscle- rosis [13 – 15]. VCAM-1, a member of the immunoglob- ulin superfamily of CAMs, aids the selective accumulation of monocytes and T-lymphocytes and is a hallmark of early atherogenesis [16 – 18]. It has been reported that levels of cytokine-induced VCAM-1, ICAM-1 and E-selectin were reduced by HDL in human umbilical vein endothelial cells HU- VECs [19], a popular and relatively accessible in vitro model for CAM research [20]. Here, we have investi- gated whether HDL can downregulate CAM expression in primary human coronary artery endothelial cells HCAECs, a model directly relevant to blood vessels susceptible to atherosclerosis. Arterial endothelial cells were preincubated with increasing amounts of total HDL, or different subfractions, and then activated with the inflammatory cytokine, tumor necrosis factor-alpha TNF-a. However, flow cytometric analysis failed to detect any downregulation of VCAM-1 or E-selectin expression by HDL, implying that suppression of CAM induction in arterial endothelium is unlikely to con- tribute to HDL anti-atherogenic effects in vivo.

2. Materials and methods