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

Atherosclerosis 154 2001 113 – 121 Lack of effect of serum amyloid A SAA on the ability of high-density lipoproteins to inhibit endothelial cell adhesion molecule expression Dale Ashby a,b,c , Jenny Gamble c , Mathew Vadas c , Noel Fidge d , Sarah Siggins d , Kerry – Anne Rye a,b,c , Philip J. Barter a,b,c, a Department of Medicine, Royal Adelaide Hospital, Uni6ersity of Adelaide, North Terrace, Adelaide, SA 5000 , Australia b Cardio6ascular In6estigation Unit, Royal Adelaide Hospital. Adelaide, SA, Australia c Hanson Centre for Cancer Research, Department of Human Immunology, IMVS. Adelaide, SA, Australia d Baker Medical Research Institute, Prahran, Vic, Australia Received 27 August 1999; received in revised form 25 January 2000; accepted 18 February 2000 Abstract Studies have been conducted to determine whether the ability of high density lipoproteins HDL to inhibit the cytokine-in- duced expression of vascular cell adhesion molecule-1 VCAM-1 in endothelial cells is altered by the presence in HDL of the acute phase reactant, serum amyloid-A SAA. Preparations of HDL 3 were isolated on two separate occasions from the plasma of each of 19 patients: the first was collected before and the second 3 days after undergoing coronary artery bypass graft surgery. Whereas the preoperative HDL 3 sample contained no SAA, in the postoperative sample SAA accounted for an average of 42 of the HDL 3 protein. The preoperative HDL 3 and postoperative, SAA-enriched HDL 3 were identical in terms of their ability to inhibit the tumour necrosis factor-a TNF-a-induced expression of VCAM-1 in human umbilical vein endothelial cells HUVECs. To assess the effect of having an even greater SAA enrichment of HDL 3 , samples of HDL 3 were incubated with purified SAA, which displaced almost all of the apoAI and about 40 of the apoAII from the HDL 3 . This in vitro SAA-enriched HDL 3 inhibited the TNF-a-induced expression of VCAM-1 in HUVECs in a concentration dependent manner, which was identical to that of the unmodified HDL 3 . The presence of SAA did not alter the cell-surface binding of HDL 3 to endothelial cells. It has been concluded that the presence of SAA in HDL has no effect on the ability of these lipoproteins either to inhibit the expression of VCAM-1 in endothelial cells or to bind to proteins on the endothelial cell surface. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords : Adhesion molecules; Endothelial cells; High density lipoprotiens; Serum amyloid A www.elsevier.comlocateatherosclerosis

1. Introduction

There is a growing consensus that atherosclerosis is a chronic inflammatory condition in which an early event is the recruitment of blood monocytes in a process mediated by the expression of adhesion proteins on the surface of endothelial cells [1]. Our recent observation [2] that human high density lipoproteins HDL inhibit the cytokine-induced expression of the endothelial cell adhesion proteins VCAM-1, ICAM-1 and E-selectin has raised the possibility that anti-inflammatory prop- erties of HDL may contribute to the well documented anti-atherogenic effects of these lipoproteins. We have been systematically investigating how the composition of HDL impacts on their anti-inflamma- tory potential. In studies with both native HDL [3] and reconstituted HDL rHDL [4], we have shown that inhibition of the cytokine-induced expression of VCAM-1 in endothelial cells is unaffected by replacing all of the HDL apolipoprotein apo AI with apoAII. We have also shown that changing the HDL particle size and the cholesteryl ester and triglyceride content of the particles has no effect on inhibitory activity [4]. We now investigate whether the ability of HDL to inhibit Corresponding author. Tel.: + 61-88-2225608; fax: + 61-88- 2225938. E-mail address : pbartermedicine.adelaide.edu.au P.J. Barter. 0021-915001 - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0021-91500000437-8 the cytokine-induced expression of VCAM-1 in en- dothelial cells is altered when the apoAI in HDL is replaced by the acute phase reactant, serum amyloid-A SAA. SAA is synthesised by the liver during times of inflammation. Once released into the circulation, SAA rapidly associates with HDL [5 – 7] in which it may account for up to 87 of HDL protein [8,9]. There have been suggestions that SAA may be pro-athero- genic. For example, HDL enriched with SAA have a reduced reactivity with lecithin:cholesterol acyltrans- ferase LCAT which may compromise their efficiency as promoters of reverse cholesterol transport [10]. SAA- enriched HDL have also been reported to have a decreased ability to protect LDL against oxidation [11]. Furthermore, SAA which is unassociated with HDL has been shown to induce the migration, adhesion and tissue infiltration of monocytes, polymorphonuclear leukocytes and T lymphocytes, and to increase the expression of cellular adhesion molecules [12]. It is not known whether the expression of endothelial cell adhe- sion molecules is also promoted by the SAA, which is associated with HDL. Nor is it known whether the presence of SAA in HDL interferes with the docu- mented ability of HDL to inhibit the cytokine-induced expression of adhesion molecules in endothelial cells. This latter issue is addressed in the studies described in this report.

2. Methods