lesterol transport during the acute phase response but not group IIA secretory phospholipase A 2 . J. Lipid Res . 2010. 51: 743-754. Supplementary key words feces • infl ammation • sepsis • atherosclerosis • miceEpidemiological studies established a strong inverse association between plasma HDL cholesterol levels and the risk of atherosclerotic cardiovascular disease (CVD) ( 1, 2 ). A major anti-atherogenic activity of HDL is regarded to be reverse cholesterol transport (RCT), a process comprising removal of excess cholesterol from peripheral cells, most importantly macrophage foam cells in atherosclerotic lesions, and transport back to the liver for subsequent excretion into bile and feces ( 2, 3 ). Understanding the pathophysiological factors regulating RCT is therefore of prime importance.Infl ammation is strongly linked to atherosclerosis ( 4-6 ). The atherosclerotic plaque itself is increasingly considered a site of chronic infl ammation within the vessel wall ( 5, 7 ). In addition, markers of infl ammation are elevated in plasma of patients with established atherosclerotic CVD, and circulating levels of several acute phase proteins Abstract Atherosclerosis is linked to infl ammation. HDL protects against atherosclerotic cardiovascular disease, mainly by mediating cholesterol effl ux and reverse cholesterol transport (RCT). The present study aimed to test the impact of acute infl ammation as well as selected acute phase proteins on RCT with a macrophage-to-feces in vivo RCT assay using intraperitoneal administration of [ 3 H]cholesterol-labeled macrophage foam cells. In patients with acute sepsis, cholesterol effl ux toward plasma and HDL were signifi cantly decreased ( P < 0.001). In mice, acute infl ammation (75 µg/mouse lipopolysaccharide) decreased [ 3 H] cholesterol appearance in plasma ( P < 0.05) and tracer excretion into feces both within bile acids ( ؊ 84%) and neutral sterols ( ؊ 79%, each P < 0.001). In the absence of systemic infl ammation, overexpression of serum amyloid A (SAA, adenovirus) reduced overall RCT ( P < 0.05), whereas secretory phospholipase A 2 (sPLA 2 , transgenic mice) had no effect. Myeloperoxidase injection reduced tracer appearance in plasma ( P < 0.05) as well as RCT ( ؊ 36%, P < 0.05). Hepatic expression of bile acid synthesis genes ( P < 0.01) and transporters mediating biliary sterol excretion ( P < 0.01) was decreased by infl ammation. In conclusion, our data demonstrate that acute infl ammation impairs cholesterol effl ux in patients and macrophage-to-feces RCT in vivo in mice. Myeloperoxidase and SAA contribute to a certain extent to reduced RCT during infl ammation but not sPLA 2 . However, reduced bile acid formation and decreased biliary sterol excretion might represent major contributing factors to decreased RCT in infl ammation. -Annema, W., N. Nijstad, M. Tölle, J. F. de Boer, R. V. C. Buijs, P. Heeringa, M. van der Giet, and U. J. F. Tietge. Myeloperoxidase and serum amyloid A contribute to impaired in vivo reverse cho-

A major atheroprotective functionality of high-density lipoproteins (HDLs) is to promote ''reverse cholesterol transport'' (RCT). In this process, HDLs mediate the efflux and transport of cholesterol from peripheral cells and its subsequent transport to the liver for further metabolism and biliary excretion. We have previously demonstrated in cultured hepatocytes that P2Y 13 (purinergic receptor P2Y, G protein-coupled, 13) activation is essential for HDL uptake but the potential of P2Y 13 as a target to promote RCT has not been documented. Here, we show that P2Y 13 -deficient mice exhibited a decrease in hepatic HDL cholesterol uptake, hepatic cholesterol content, and biliary cholesterol output, although their plasma HDL and other lipid levels were normal. These changes translated into a substantial decrease in the rate of macrophage-to-feces RCT. Therefore, hallmark features of RCT are impaired in P2Y 13 -deficient mice. Furthermore, cangrelor, a partial agonist of P2Y 13 , stimulated hepatic HDL uptake and biliary lipid secretions in normal mice and in mice with a targeted deletion of scavenger receptor class B type I (SR-BI) in liver (hypomSR-BIknockout liver ) but had no effect in P2Y 13 knockout mice, which indicate that P2Y 13 -mediated HDL uptake pathway is independent of SR-BI-mediated HDL selective cholesteryl ester uptake. Conclusion: These results establish P2Y 13 as an attractive novel target for modulating RCT and support the emerging view that steady-state plasma HDL levels do not necessarily reflect the capacity of HDL to promote RCT.

Scavenger receptor class B type I (SR-BI) mediates selective uptake of cholesterol from highdensity lipoprotein (HDL) particles by the liver and influences biliary cholesterol secretion. However, it is not clear, if this effect is direct or indirect. The aim of this study was to determine the impact of SR-BI on biliary cholesterol secretion, especially in a functional context with ATP-binding cassette transporter g5 (Abcg5)/Abcg8 and Abcb4. SR-BI was overexpressed by means of adenovirus (AdSR-BI) in livers of wild-type, liver X receptor-null (Lxr ؊/؊ ), Abcg5 ؊/؊ , and Abcb4 ؊/؊ mice. Consistent with previous reports, AdSR-BI decreased plasma HDL cholesterol levels in all models (P < 0.001). Hepatic cholesterol content increased (at least P < 0.05), whereas expression of sterol regulatory element binding protein 2 target genes was decreased (at least P < 0.05,) and established Lxr target genes were unaltered. Biliary cholesterol secretion was increased by AdSR-BI in wild-type as well as in Lxr ؊/؊ and Abcg5 ؊/؊ mice, and considerably less in Abcb4 ؊/؊ mice (each P < 0.001), independent of bile acid and phospholipid secretion. T he scavenger receptor class B type I (SR-BI) has been characterized as a receptor that mediates cholesterol transport across membranes. 1,2 In nonpolarized cells, namely macrophages and the hepatoma cell line Fu5AH, SR-BI expression either results in selective uptake of cholesterol, mainly from high-density lipoprotein (HDL), or in cholesterol efflux toward suitable acceptors. [3][4][5][6] In hepatocytes, which is a highly polarized cell type, SR-BI is the main receptor responsible for selective uptake of cholesterol from plasma HDL. 7 Consequently, hepatic overexpression of SR-BI results in decreased plasma HDL cholesterol levels, 8-10 whereas SR-BI knockout mice have increased plasma HDL cholesterol. 11,12 Interestingly, hepatocyte SR-BI appears to accelerate reverse cholesterol transport in vivo in the face of decreased plasma HDL cholesterol levels, 13 which is in line with studies demonstrating that hepatic SR-BI expression protects against atherosclerosis development in mouse models. 14,15 Hepatic SR-BI expression is also linked to biliary cholesterol