Journal of Investigative Medicine:
Disruption of Cholesterol Efflux by Coxib Medications and Inflammatory Processes: Link to Increased Cardiovascular Risk
Reiss, Allison B. MD*; Anwar, Farah MD*; Chan, Edwin S.L. MD†; Anwar, Kamran PhD*
From the *Vascular Biology Institute, Department of Medicine, Winthrop-University Hospital, Mineola, NY, and †Department of Medicine, NYU School of Medicine, New York, NY.
Received December 18, 2008, and in revised form January 29, 2009.
Accepted for publication January 29, 2009.
Reprints: Allison B. Reiss, MD, Vascular Biology Institute, Department of Medicine, Winthrop-University Hospital, Suite 502, 222 Station Plaza N, Mineola, NY 11501. E-mail: AReiss@winthrop.org.
This work was supported by an Innovative Research Grant from the Arthritis Foundation, National Center. This symposium was supported in part by a grant from the National Center for Research Resources (R13 RR023236).
Atherosclerosis is a chronic progressive disease that is a major contributor to cardiac death. It is characterized by inflammation and cholesterol deposition in the arterial wall. Excess cholesterol accumulation occurs as a result of an imbalance between delivery and removal and leads to formation of lipid-laden foam cells. Removal of cholesterol through a process known as reverse cholesterol transport requires the coordinated functioning of a number of genes including the P450 27-hydroxylase and the adenosine triphosphate-binding cassette transporter A1 (ABCA1). Reverse cholesterol transport is a key defense against atheroma formation. This review discusses the role of inflammatory processes in impeding reverse cholesterol transport. Particular emphasis is placed on the disruption of cholesterol outflow observed in the presence of cyclooxygenase inhibitors in cultured monocytes/macrophages. These inhibitors, which are used clinically to relieve pain and inflammation, have been associated with increased risk of cardiovascular disease and myocardial infarction. We explore the relationship between suppression of reverse cholesterol transport and harmful cardiac effects of coxibs.
Nonsteroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase (COX)-2 selective inhibitors (coxibs) are effective in relieving pain and inflammation. However, nonselective NSAIDS are associated with gastrointestinal (GI) complications, such as ulceration, bleeding, perforation, and obstruction.1,2 Coxibs, although safer for the GI tract, increase the risk of cardiovascular events.3 Nonsteroidal anti-inflammatory drugs are also associated with an elevated risk of acute myocardial infarction.4
Given the amount of recent information in the lay press and medical journals, patients are often confused about both the cardiovascular (CV) and GI effects of NSAIDs versus coxibs and may be reluctant to follow physician recommendations. Physicians themselves can also exhibit reluctance to prescribe these types of medications for their patients owing to multiple reasons including the significant length of time it takes to evaluate scientific evidence, contradictory data, and concern about potential legal issues, real or imagined.5-7 Specialty area of the physician may also be a factor.8
It is difficult to unravel the processes that lead from COX inhibition to myocardial infarction. Cyclooxygenase enzymes oxidize arachidonic acid leading to the production of prostaglandins (PGs) and other eicosanoids. The prevailing hypothesis that has been put forward to explain increased incidence of CV events is induction of a prothrombotic state due to loss of the inhibitory effect on platelet aggregation of the endogenous vascular protector endothelial prostacyclin without a balancing concomitant decrease in thromboxane, which promotes platelet aggregation and vasoconstriction.9 Cyclooxygenase-2 inhibitors may decrease production of vascular prostacyclin (PGI2), the primary eicosanoid product of vascular endothelium and smooth muscle cells known for its vasodilatory properties and antiaggregatory effect on platelets.10,11 However, COX-2 inhibitors do not affect production by platelet-derived COX-1 of thromboxane, a potent platelet activator, vasoconstrictor, and mitogen. Thus, loss of PGI2 and its protection against arterial thrombosis destroys the balance between prothrombotic and antithrombotic eicosanoids, leaving thromboxane and its prothrombotic effects unopposed.12
Cardiorenal effects of COX-2 inhibitors include edema and hypertension, which have also been postulated to contribute to their CV risk.13,14 Cyclooxygenase-2 inhibitors have been shown to increase blood pressure in a dose-related fashion.14,15 When sodium intake is high, COX-2 plays a vital role in promoting natriuresis. Cyclooxygenase-2 inhibitors decrease renal blood flow and induce sodium retention.16,17 Cyclooxygenase-2-derived PGs are implicated in physiological and pathological processes in the kidney that impact the renin-angiotensin-aldosterone system. These PGs stimulate renin gene transcription through the cyclic adenosine monophosphate signaling pathway.18 Cyclooxygenase-2 inhibitors suppress plasma rennin.19,20 Elimination of COX-2 expression by gene deletion in murine models prevents increases in renin production and release in response to dietary salt restriction and angiotensin-converting enzyme inhibition.21 The role of the prostanoids PGE2 and PGI2 and their receptors in blood pressure regulation are controversial and contradictory.22 Prostaglandin E2 can cause either vasodilatory or vasoconstrictor responses in the kidney.23 The study of COX effects on blood pressure and renal function is being actively pursued, and new insights are expected in the near future.
The proatherogenic contribution of cholesterol and lipids to COX-associated CV toxicity has received little attention. This paper will provide an overview of cholesterol transport in atherosclerosis and then focus on the disruption of cholesterol homeostasis resulting from COX inhibition as a potential mechanism underlying excess CV risk.
Atherosclerosis: A Multifactorial Process
Atherosclerotic disease is the leading cause of morbidity and mortality in the United States and in many other Westernized countries.24,25 Atherosclerosis can be considered a low-grade chronic inflammatory disease and a lipid disorder.26,27 Dysfunctional lipid homeostasis plays a central role in the initiation and progression of atherosclerotic lesions, which form in large- and medium-sized muscular arteries. An early pathogenic feature of atherosclerosis is injury to the blood vessel endothelium. After the insult, injured endothelium is activated and exhibits increased expression of a variety of cell adhesion molecules and secretes chemoattractants to recruit lymphocytes/monocytes.28 Monocytes infiltrate the intima of the vessel wall and upon lipid loading, form a fatty streak. Ultimately, the fatty streak matures as fibrous tissue and smooth muscle cells overgrow and form a plaque containing a necrotic acellular lipid core. The atherosclerotic plaque narrows the arterial lumen and formation of a thrombus at the site of the plaque initiates arterial occlusion and ischemic coronary events.29,30
Our current view of atherosclerosis as a complex process involving the endothelium as a metabolically active organ and a dynamic participant in the disease is in sharp contrast to an older perspective that looked upon the artery as a passive conduit.31 Healthy endothelium controls vascular integrity and regulates vascular tone.
Cholesterol 27-Hydroxylase, ABCA1, and Reverse Cholesterol Transport
The path toward an understanding of the role of the vessel wall in cholesterol homeostasis has its origins in 1989 with the cloning and sequencing of the gene for cytochrome P450 cholesterol 27-hydroxylase (CYP27A1), a cholesterol metabolizing enzyme, by Dr David Russell's group.32 Shortly thereafter, in 1991, Cali and Russell33 cloned the human 27-hydroxylase complementary DNA. Located in the inner mitochondrial membrane, the 27-hydroxylase catalyzes the first step in the acidic or alternative bile acid biosynthetic pathway in the liver. The enzyme is critical for oxidation of the side chain of cholesterol in connection with bile acid biosynthesis in the liver. Russell detected expression not only in the liver but also in several other organs and tissues, hinting at the possibility that this enzyme might have a role other than in bile acid biosynthesis.
A significant leap forward in our understanding of how the artery itself participates in atherosclerosis was achieved in 1994, when it was reported by our laboratory that the 27-hydroxylase enzyme is expressed in vascular endothelium34 and by Bjorkhem et al.35 that it is found in human monocytes and macrophages. This provided evidence that 2 cell types known to be present in the vessel wall were capable of metabolizing cholesterol. In peripheral cells such as endothelium and monocytes/macrophages, the 27-hydroxylase converts cholesterol into 27-hydroxycholesterol and 3β-hydroxy-5-cholestenoic acid (Fig. 1). These metabolites can then be moved out of the cell and transported to the liver for excretion in the bile, a process known as reverse cholesterol transport.36 Reverse cholesterol transport can remove cholesterol from the artery and from atherosclerotic plaque and is thus protective against atherosclerosis.37,38 Extrahepatic cells, including those in the blood vessel wall, eliminate intracellular cholesterol via reverse cholesterol transport in a lipoprotein-dependent manner using high density lipoprotein (HDL) and also by an alternative reverse cholesterol transport mechanism involving the cholesterol 27-hydroxylase enzyme.35,39 Specifically, in the 27-hydroxylase pathway, introduction of an oxygen moiety to the cholesterol molecule gives it a more hydrophilic character, thus enabling it to cross the plasma membrane and exit the cell more readily.37,40 Unlike neutral sterols, which require extracellular lipoproteins for excretion from extrahepatic cells, cholestenoic acid only requires albumin as an acceptor for cellular export.41
27-Hydroxycholesterol, an important endogenous oxysterol that functions as a signaling molecule, is produced from the action of cholesterol 27-hydroxylase on cholesterol. 27-Hydroxycholesterol is the most abundant oxysterol in plasma, and it exhibits multiple antiatherogenic properties.42 It is a potent suppressor of cholesterol biosynthesis. It inhibits cholesterol synthesis by blocking proteolytic activation of membrane-bound transcription factors known as sterol regulatory element-binding proteins (SREBPs), which are needed for activation of transcription of genes encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase and multiple other enzymes involved in the cholesterol synthesis.43 The 27-hydroxycholesterol down regulates cell surface low density lipoprotein (LDL) receptors resulting in diminished receptor-mediated LDL uptake,44 inhibits macrophage foam cell transformation, and impedes smooth muscle proliferation.45 Mutations in the 27-hydroxylase enzyme lead to a rare, severe genetic disorder called cerebrotendinous xanthomatosis, in which there is progressive neurological impairment and premature coronary artery disease despite normal or low plasma cholesterol concentrations.46
In addition to the 27-hydroxylase, adenosine triphosphate-binding cassette transporter A1 (ABCA1), a macrophage plasma membrane protein, plays a key role in reverse cholesterol transport by mediating the cellular efflux of phospholipid and cholesterol to lipid-poor apolipoprotein (apo) A-I that is further lipidated to form HDL.47 The 27-hydroxycholesterol molecule interconnects the functions of 27-hydroxylase and ABCA1 by binding to and activating liver X receptors (LXRs) that in turn induce transcription of ABCA1.48-50 Adenosine triphosphate-binding cassette transporter A1 in an adenosine triphosphate-dependent process shuttles excess cholesterol and lipids onto an HDL particle. This particle is then taken up by the liver for excretion as bile and other metabolites. Defects in the ABCA1 gene are the underlying cause of Tangier disease, which is characterized by an abnormally low level of HDL and a marked increase risk of coronary artery disease.51
Thus, cholesterol 27-hydroxylase and ABCA1 are vital participants in reverse cholesterol transport, a defensive mechanism against cholesterol overload in the artery wall.52
Exploring Regulation of 27-Hydroxylase and ABCA1
To further characterize and elucidate the mechanisms that control the level of the 27-hydroxylase enzyme expressed in cells of the vessel wall, our laboratory took an innovative approach that applied our knowledge of the immune system as a guide. It is well established that the conditions of individuals diagnosed with autoimmune disorders such as systemic lupus erythematosus (SLE, lupus) and rheumatoid arthritis (RA) have an increased risk of developing atherosclerosis.53,54 Based on this information, we initiated a study of the expression of 27-hydroxylase under conditions mimicking those found in these autoimmune disease states. Our cell culture models were human aortic endothelial cells and THP-1 monocytes/macrophages. THP-1 is a human monocytic cell line that can be easily differentiated into macrophages and that is commonly used as a model system to study the development of atherosclerosis.55-57 Building on the knowledge that individuals with lupus and RA have increased levels of circulating cytokines and a high incidence of atherosclerotic disease,58 we investigated the effect of a number of cytokines on the expression of the 27-hydroxylase. We found that exposure of human aortic endothelial and THP-1 cells to interferon-gamma markedly decreased the 27-hydroxylase message and protein level. This was a significant finding, as this was the first report of an effect on the regulation of this gene in cells outside the liver.59 Immune complexes, which are present in excess in persons with autoimmune disorders, are also capable of inhibiting 27-hydroxylase expression by binding to complement component C1q and acting through the C1q receptor.59
Adenosine triphosphate-binding cassette transporter A1 is involved in reverse cholesterol transport, and as a consequence of impaired ABCA1 function, cholesterol may accumulate in macrophages. We found that immune complexes could decrease ABCA1 as well.59 Panousis et al.60 demonstrated the down-regulation of ABCA1 by interferon-gamma in murine peritoneal macrophages.
Accompanying the interference with reverse cholesterol transport resulting from diminution of 27-hydroxylase and/or ABCA1 is induction of lipid overload and foam cell formation. This physiologic manifestation is observed in THP-1 macrophages using oil red to specifically stain intracellular lipids. THP-1 macrophages treated with interferon-gamma or immune complexes exhibited not only compromised expression of the 27-hydroxylase but also manifested enhanced foam cell formation with the appearance of lipid globule-filled cells.
Cyclooxygenase-2 Inhibition Promotes Atherogenesis
The COX-2 inhibitors are highly effective anti-inflammatory analgesic drugs. This class of drugs works by preventing prostanoid formation and are used to relieve symptoms of osteoarthritis and RA and to treat dysmenorrheal.61 In September of 2004, rofecoxib was withdrawn from the market by its manufacturer because there was an increased incidence of CV events in the Adenomatous Polyp Prevention on Vioxx trial.62 The Adenomatous Polyp Prevention on Vioxx trial was a randomized, placebo-controlled, double-blind study in which rofecoxib was administered to patients to evaluate its effectiveness in preventing the recurrence of polyps in patients with a history of colorectal adenomas so as to decrease the risk of cancer. Celecoxib is now the only COX-2 inhibitor remaining on the market. As was expected, there has been a decreased use of this highly effective class of pain-relieving medications in clinical practice.63
Our laboratory has tackled the problem of explaining the elevated myocardial infarction and stroke incidence attributed to COX-2 inhibitors from the perspective of cholesterol metabolism. We postulated that the mechanisms responsible for increased CV risk likely involved lipids in some integral fashion. Cyclooxygenase-2 is widely expressed in atherosclerotic plaque and the arterial wall.64,65 Cyclooxygenase-2 expression in the artery may play a defensive role against atherosclerosis by stimulating the production of heme oxygenase, an antioxidant, antiapoptotic, and potent anti-inflammatory enzyme that promotes vascular healing, and by limiting cholesterol accumulation.66,67 A proatherogenic consequence of COX-2 inhibition may be compromised cholesterol balance in the artery wall. Cyclooxygenase-2 inhibitors interfere with the natural process of reverse cholesterol transport that requires products of the COX-2 enzyme for normal regulation. To understand this phenomenon, THP-1 human monocyte/macrophage cells were treated with increasing doses of a COX-2 specific inhibitor, NS398. This treatment resulted in a significant decrease in the 27-hydroxylase message. In THP-1 monocytes, exposure to 50 μmol/L of NS398 for 18 hours decreased 27-hydroxylase messenger RNA to 62.4% (2.2) of control (P < 0.001). Western blot analysis revealed a decrease in the expression of 27-hydroxylase protein as well. NS398 exerted similar effects on ABCA1 message and protein. Oil red O staining revealed extensive lipid deposition in macrophages treated with NS398, and the combination of NS398 and interferon-gamma caused massive lipid uptake (Fig. 2). There was not only a change in the expression of these reverse cholesterol transport proteins but also a compromise in the ability to prevent lipid accumulation within the cells.67 Thus, COX-2 inhibition not only promotes a proaggregatory state but also affects the ability of the cell to rid itself of excess cholesterol. Because arterial cholesterol buildup is a process that occurs for months or years, these events are consistent with the reports that COX-2-related myocardial infarction risk becomes apparent only after at least 9 to 12 months of treatment.68
Our study also revealed a concentration-dependent reduction in 27-hydroxylase and ABCA1 messages in THP-1 monocytes exposed to the nonselective COX inhibitor indomethacin.67 Indomethacin is associated with an increased risk of CV events.69
Mason et al.70,71 have found a prooxidant effect of the sulfone COX-2 inhibitor rofecoxib that may contribute to the atherogenicity of that specific drug. They determined that rofecoxib alters the structure of lipid molecules, including human LDL, in a way that increases their susceptibility to oxidative modification, a key event leading to atheroma formation. The effect was blocked by an antioxidant and was not seen with celecoxib or NSAIDs.
Abrogating the Effect of COX-2 Inhibition on Cholesterol Metabolism
Once the effect of COX-2 inhibitors on reverse cholesterol transport had been defined, the next step was to neutralize the effect without losing analgesic or anti-inflammatory potency. The COX-2 pathway leads to the formation of multiple PGs and lipid mediators including PGE1, PGE2, PGD2 and thromboxane A2 (Fig. 3).72 Our simple approach was to expose THP-1 cells to NS398, then reconstitute PGE1, PGE2, PGD2 or thromboxane A2, each individually, then analyze cellular expressions of 27-hydroxylase and ABCA1. Cholesterol transport was restored when cells were treated with either PGE2 or PGD2. It is well documented that PGD2 has anti-inflammatory and proinflammatory effects73; thus, it may be possible to achieve COX-2 inhibition while sparing PGD2 activity and retaining anti-inflammatory properties.
A second approach to counteracting the COX-2 inhibitory effects on cholesterol balance was to evaluate methotrexate (MTX), an anti-inflammatory agent commonly used in RA that is known to reduce CV risk.74 Methotrexate may provide a substantial survival benefit in RA, largely by reducing CV mortality.75 Many of the anti-inflammatory effects of MTX are mediated by the endogenous autocoid adenosine.76,77 Our previous studies have shown that adenosine A2A receptor (A2AR) ligation increases expressions of both 27-hydroxylase and ABCA1.78 Our most recent work has revealed that in THP-1 monocytes, both MTX and CGS-21680 (a specific A2AR ligand), acting through activation of the adenosine A2AR, were able to overcome the reduction in 27-hydroxylase and ABCA1 caused by exposure to the selective COX-2 inhibitor NS398. Methotrexate also ablated the NS398-induced increase in foam cell transformation in THP-1 macrophages that had been cholesterol loaded with acetylated LDL. Although 72.7% (4.9) of THP-1 macrophages became foam cells after NS398 treatment, combined treatment with NS398 and MTX yielded only 36.3% (3.2) foam cells (n = 3, P < 0.001).79 Reversal of inhibitory effects on 27-hydroxylase and ABCA1 in the presence of MTX further support the antiatherogenicity of this drug. Because the phenomenon is mediated via the adenosine A2AR, A2AR ligation may provide a suitable mechanism for the development of a promising treatment paradigm for the in vivo reversal of atherogenic COX-2 effects.
In summary, cellular cholesterol homeostasis is maintained by feedback repression of genes involved in cholesterol synthesis and supply. Macrophage 27-hydroxylase and ABCA1 counteract intracellular cholesterol accumulation by promoting cholesterol efflux from peripheral cells. We demonstrated that COX inhibition (selective or nonselective) reduced these reverse cholesterol transport proteins. We further demonstrated that addition of PGE2 or PGD2 to cells treated with a COX-2 inhibitor restored normal levels of 27-hydroxylase and ABCA1. Adenosine A2AR ligation up regulated both 27-hydroxylase and ABCA1 expressions and prevented COX-2 inhibitor-mediated down-regulation of transcription for both these proteins (Fig. 4).
Cyclooxygenase-2 Effects on Foam Cell Formation Amplified by Lupus Plasma
The population most likely to need coxibs for pain relief on an ongoing basis may ironically consist of those most at risk for CV disease: the elderly, and those with autoimmune inflammatory conditions.61,80 To determine whether the combination of a coxib and plasma derived from patients with SLE would impact foam cell transformation, we exposed THP-1 macrophages to 50% SLE patient plasma with and without the addition of the COX-2 selective inhibitor NS398 (10 μmol/L) then incubated the cells for 48 hours under cholesterol-loading conditions (acetylated LDL, 50 μg/mL). Cyclooxygenase-2 inhibition in the presence of 50% lupus plasma increased foam cell transformation almost 2-fold versus lupus plasma alone (42.8% [5.3] for lupus plasma vs 82.7% [2.8] for lupus plasma combined with NS398, P < 0.001). Enhanced foam cell formation in the presence of SLE plasma and NS398 is reversed by PGD2 or PGE2, but not by PGI2 (unpublished results). The atherogenicity of COX-2 inhibition may result from both blockade of antiaggregatory PG production and concomitant dysregulation of cholesterol efflux mechanisms. This may be further augmented by inflammatory mediators in SLE plasma, posing an exaggerated risk to patients with SLE treated with COX-2 inhibitors. Notably, disrupted cholesterol balance may be corrected by specific PGs, suggesting possible future therapeutic modalities for COX inhibition that would support an antiatherogenic PG state.
Cyclooxygenase-2 inhibition results in perturbation of the healthy equilibrium between the uptake and the efflux of cholesterol, leading to promotion of atheroma formation. Cyclooxygenase-2 inhibition causes a decrease in expression of cholesterol 27-hydroxylase and ABCA1 accompanied by an increase in foam cell formation. The observed elevation in CV risk with COX-2 inhibition may be ascribed at least in part to these effects and is amplified by components in the plasma of patients with lupus. Notably, correction of disrupted cholesterol balance by specific PGs may lead to development of coxibs with less harmful CV consequences that maintain analgesic and anti-inflammatory efficacy. Similarly, MTX and other compounds that activate the adenosine A2AR can restore cholesterol homeostasis in coxib-treated cells. What is needed next is to gain further understanding of the signal transduction pathways involved in the PG- and adenosine-mediated effects on reverse cholesterol transport protein expression.
1. Vonkeman HE, Klok RM, Postma MJ, et al. Direct medical costs of serious gastrointestinal ulcers among users of NSAIDs. Drugs Aging
2. Lanas A, Perez-Aisa MA, Feu F, et al. A nationwide study of mortality associated with hospital admission due to severe gastrointestinal events and those associated with nonsteroidal anti-inflammatory drug use. Am J Gastroenterol
3. Hippisley-Cox J, Coupland C. Risk of myocardial infarction in patients taking cyclo-oxygenase-2 inhibitors or conventional non-steroidal anti-inflammatory drugs: population based nested case-control analysis. Br Med J
4. Fosbøl E, Gislason G, Jacobsen S, et al. Risk of myocardial infarction and death associated with the use of nonsteroidal anti-inflammatory drugs (NSAIDs) among healthy individuals: a nationwide cohort study. Clin Pharmacol Ther
5. Dogne JM, Hanson J, Supuran C, et al. Coxibs and cardiovascular side-effects: from light to shadow. Curr Pharm Des
6. Bannwarth B. Acetaminophen or NSAIDs for the treatment of osteoarthritis. Best Pract Res Clin Rheumatol
7. Solomon DH, Glynn RJ, Rothman KJ, et al. Subgroup analyses to determine cardiovascular risk associated with nonsteroidal antiinflammatory drugs and coxibs in specific patient groups. Arthritis Rheum
8. Chan FK, Abraham NS, Scheiman JM, et al. First International Working Party on Gastrointestinal and Cardiovascular Effects of Nonsteroidal Anti-inflammatory Drugs and Anti-Platelet Agents. Management of patients on nonsteroidal anti-inflammatory drugs: a clinical practice recommendation from the First International Working Party on Gastrointestinal and Cardiovascular Effects of Nonsteroidal Anti-inflammatory Drugs and Anti-platelet Agents. Am J Gastroenterol
9. Solomon DH, Schneeweiss S, Glynn RJ, et al. Relationship between selective cyclooxygenase-2 inhibitors and acute myocardial infarction in older adults. Circulation
10. Graham DJ. COX-2 inhibitors, other NSAIDs, and cardiovascular risk: the seduction of common sense. JAMA
11. McAdam BF, Catella-Lawson F, Mardini IA, et al. Systemic biosynthesis of prostacyclin by cyclooxygenase (COX)-2: the human pharmacology of a selective inhibitor of COX-2. Proc Natl Acad Sci U S A
12. Wright JM. The double-edged sword of COX-2 selective NSAIDs. CMAJ
13. Mamdani M, Juurlink DN, Lee DS, et al. Cyclo-oxygenase-2 inhibitors versus non-selective non-steroidal anti-inflammatory drugs and congestive heart failure outcomes in elderly patients: a population based cohort study. Lancet
14. Aw T-J, Haas SJ, Liew D, et al. Meta-analysis of cyclooxygenase-2 inhibitors and their effects on blood pressure. Arch Intern Med
15. Frishman WH. Effects of non-steroidal anti-inflammation drug therapy on blood pressure and peripheral edema. Am J Cardiol
16. Rodriguez F, Llinas MT, Gonzalez JD, et al. Renal changes induced by a cyclooxygenase-2 inhibitor during normal and low sodium intake. Hypertension
17. Rossat J, Maillard M, Nussberger J, et al. Renal effects of selective cyclooxygenase-2 inhibition in normotensive salt-depleted subjects. Clin Pharmacol Ther
18. Jensen BL, Schmid C, Kurtz A. Prostaglandins stimulate renin secretion and renin mRNA in mouse renal juxtaglomerular cells. Am J Physiol Renal Fluid Electrolyte Physiol
19. Stichtenoth DO, Wagner B, Frolich JC. Effect of selective inhibition of the inducible cyclooxygenase on renin release in healthy volunteers. J Investig Med
20. Harris RC, Breyer MD. Update on cyclo-oxygenase-2 inhibitors. Clin J Am Soc Nephrol
21. Cheng HF, Wang JL, Zhang MZ, et al. Genetic deletion of COX-2 prevents increased renin expression in response to ACE inhibition. Am J Physiol Renal Physiol
22. Francois H, Coffman TM. Prostanoids and blood pressure: which way is up? J Clin Invest
23. Nasrallah R, Clark J, Hébert RL. Prostaglandins in the kidney: developments since Y2K. Clin Sci (Lond)
24. Vinereanu D. Risk factors for atherosclerotic disease: present and future. Herz
. 2006;(suppl 3):5-24.
25. Hobbs R, Hoes A. Effective management of dyslipidaemia among patients with cardiovascular risk: updated recommendations on identification and follow-up. Eur J Gen Pract
26. Ross R. Atherosclerosis-an inflammatory disease. N Engl J Med
27. Steinberg D. Atherogenesis in perspective: hypercholesterolemia and inflammation as partners in crime. Nat Med
28. Tedgui A, Mallat Z. Cytokines in atherosclerosis: pathogenic and regulatory pathways. Physiol Rev
29. Libby P. Changing concepts of atherogenesis. J Intern Med
30. Shah PK. Inflammation and plaque vulnerability. Cardiovasc Drugs Ther
31. Kharbanda R, MacAllister RJ. The atherosclerosis time-line and the role of the endothelium. Curr Med Chem
32. Andersson S, Davis DL, Dahlback H, et al. Cloning, structure and expression of the mitochondrial cytochrome P-450 sterol 26-hydroxylase, a bile acid biosynthetic enzyme. J Biol Chem
33. Cali JJ, Russell DW. Characterization of human sterol 27-hydroxylase. J Biol Chem
34. Reiss AB, Martin KO, Javitt NB, et al. Sterol 27-hydroxylase: high levels of activity in vascular endothelium. J Lipid Res
35. Bjorkhem I, Andersson O, Diczfalusy U, et al. Atherosclerosis and sterol 27-hydroxylase: evidence for a role of this enzyme in elimination of cholesterol from human macrophages. Proc Natl Acad Sci U S A
36. Bjorkhem I, Eggertsen G. Genes involved in initial steps of bile acid synthesis. Curr Opin Lipidol
37. Olkkonen VM, Lehto M. Oxysterols and oxysterol binding proteins: role in lipid metabolism and atherosclerosis. Ann Med
38. Wang X, Rader DJ. Molecular regulation of macrophage reverse cholesterol transport. Curr Opin Cardiol
39. von Eckardstein A, Nofer JR, Assmann G. High density lipoproteins and arteriosclerosis: role of cholesterol efflux and reverse cholesterol transport. Arterioscler Thromb Vasc Biol
40. Meaney S, Bodin K, Diczfalusy U, et al. On the rate of translocation in vitro and kinetics in vivo of the major oxysterols in human circulation: critical importance of the position of the oxygen function. J Lipid Res
41. Babiker A, Diczfalusy U. Transport of side-chain oxidized oxysterols in the human circulation. Biochim Biophys Acta
42. Björkhem I, Diczfalusy U. Oxysterols. Friends, foes or just fellow passengers? Arterioscler Thromb Vasc Biol
43. Lange Y, Ory DS, Ye J, et al. Effectors of rapid homeostatic responses of endoplasmic reticulum cholesterol and 3-hydroxy-3-methylglutaryl-CoA reductase. J Biol Chem
44. Bellosta S, Corsini A, Bernini F, et al. 27-Hydroxycholesterol modulation of low density lipoprotein metabolism in cultured human hepatic and extrahepatic cells. FEBS Lett
45. Corsini A, Verri D, Raiteri M, et al. Effects of 26-aminocholesterol, 27-hydroxycholesterol, and 25-hydroxycholesterol on proliferation and cholesterol homeostasis in arterial myocytes. Arterioscler Thromb Vasc Biol
46. Bjorkhem I, Skrede S. Familial diseases with storage of sterols other than cholesterol: cerebrotendinous xanthomatosis and phytosterolemia. In: Scriver CR, Beaudet AL, Sly WS, eds. The Metabolic Basis of Inherited Disease
. 6th ed. New York, NY: McGraw-Hill; 1989:1283-1302.
47. Lu R, Arakawa R, Ito-Osumi C, et al. ApoA-I facilitates ABCA1 recycle/accumulation to cell surface by inhibiting its intracellular degradation and increases HDL generation. Arterioscler Thromb Vasc Biol
48. Fu X, Menke JG, Chen Y, et al. 27-Hydroxycholesterol is an endogenous ligand for liver X receptor in cholesterol-loaded cells. J Biol Chem
49. Costet P, Luo Y, Wang N, et al. Sterol-dependent trans-activation of the ABC1 promoter by the liver X receptor/retinoid X receptor. J Biol Chem
50. Edwards PA, Kennedy MA, Mak PA. LXRs; oxysterol-activated nuclear receptors that regulate genes controlling lipid homeostasis. Vascul Pharmacol
51. Iatan I, Alrasadi K, Ruel I, et al. Effect of ABCA1 mutations on risk for myocardial infarction. Curr Atheroscler Rep
52. Reiss AB, Glass AD. Atherosclerosis: immune and inflammatory aspects. J. Invest Med
53. Turesson C, Jacobsson LT, Matteson EL. Cardiovascular co-morbidity in rheumatic diseases. Vasc Health Risk Manag
54. Sitia S, Atzeni F, Sarzi-Puttini P, et al. Cardiovascular involvement in systemic autoimmune diseases. Autoimmun Rev
55. Hayden JM, Brachova L, Higgins K, et al. Induction of monocyte differentiation and foam cell formation in vitro by 7-ketocholesterol. J Lipid Res
56. Fach EM, Garulacan LA, Gao J, et al. In vitro biomarker discovery for atherosclerosis by proteomics. Mol Cell Proteomics
57. Reiss AB, Wan DW, Anwar K, et al. Enhanced CD36 scavenger receptor expression in THP-1 human monocytes in the presence of lupus plasma: linking autoimmunity and atherosclerosis. Exp Biol Med (Maywood)
. January 9, 2009; [Epub ahead of print].
58. Zinger H, Sherer Y, Schoenfeld Y. Atherosclerosis in autoimmune rheumatic diseases-mechanisms and clinical findings. Clin Rev Allergy Immunol
. November 8, 2008; [Epub ahead of print].
59. Reiss AB, Awadallah NW, Malhotra S, et al. Immune complexes and interferon-γ decrease cholesterol 27-hydroxylase in human arterial endothelium and macrophages. J Lipid Res
60. Panousis CG, Zuckerman SH. Interferon-gamma induces down regulation of Tangier disease gene (ATP-binding cassette transporter 1) in macrophage-derived foam cells. Arterioscler Thromb Vasc Biol
61. Frampton JE, Keating GM. Celecoxib: a review of its use in the management of arthritis and acute pain. Drugs
62. Bresalier RS, Sandler RS, Quan H, et al. Cardiovascular events associated with rofecoxib in a colorectal adenoma chemoprevention trial. N Engl J Med
63. Kearney PM, Baigent C, Godwin J, et al. Do selective cyclo-oxygenase-2 inhibitors and traditional non-steroidal anti-inflammatory drugs increase the risk of atherothrombosis? Meta-analysis of randomised trials. BMJ
64. Schonbeck U, Sukhova GK, Graber P, et al. Augmented expression of cyclooxygenase-2 in human atherosclerotic lesions. Am J Pathol
65. Baker CS, Hall RJ, Evans TJ, et al. Cyclooxygenase-2 is widely expressed in atherosclerotic lesions affecting native and transplanted human coronary arteries and colocalizes with inducible nitric oxide synthase and nitrotyrosine particularly in macrophages. Arterioscler Thromb Vasc Biol
66. Choi HC, Kim HS, Lee KY, et al. NS-398, a selective COX-2 inhibitor, inhibits proliferation of IL-1beta-stimulated vascular smooth muscle cells by induction of HO-1. Biochem Biophys Res Commun
67. Chan ESL, Zhang H, Fernandez P, et al. Effect of cyclooxygenase inhibition on cholesterol efflux proteins and atheromatous foam cell transformation in THP-1 human macrophages: a possible mechanism for increased cardiovascular risk. Arthritis Res Ther
68. Solomon SD, McMurray JJ, Pfeffer MA, et al. Cardiovascular risk associated with celecoxib in a clinical trial for colorectal adenoma prevention. N Engl J Med
69. McGettigan P, Henry D. Cardiovascular risk and inhibition of cyclooxygenase: a systematic review of the observational studies of selective and nonselective inhibitors of cyclooxygenase 2. JAMA
70. Mason RP, Walter MF, Day CA, et al. A biological rationale for the cardiotoxic effects of rofecoxib: comparative analysis with other COX-2 selective agents and NSAIDs. Subcell Biochem
71. Mason RP, Walter MF, McNulty HP, et al. Rofecoxib increases susceptibility of human LDL and membrane lipids to oxidative damage: a mechanism of cardiotoxicity. J Cardiovasc Pharmacol
. 2006;47(suppl 1):S7-S14.
72. Khanapure SP, Garvey DS, Janero DR, et al. Eicosanoids in inflammation: biosynthesis, pharmacology, and therapeutic frontiers. Curr Top Med Chem
73. Herlong JL, Scott TR. Positioning prostanoids of the D and J series in the immunopathogenic scheme. Immunol Lett
74. van Halm VP, Nurmohamed MT, Twisk JW, et al. Disease-modifying antirheumatic drugs are associated with a reduced risk for cardiovascular disease in patients with rheumatoid arthritis: a case control study. Arthritis Res Ther
75. Choi HK, Hernan MA, Seeger JD, et al. Methotrexate and mortality in patients with rheumatoid arthritis: a prospective study. Lancet
76. Morabito L, Montesinos MC, Schreibman D, et al. Methotrexate and sulfasalazine promote adenosine release by a mechanism that requires ecto-5′-nucleotidase-mediated conversion of adenine nucleotides. J Clin Invest
77. Wessels JA, Kooloos WM, de Jonge R, et al. Relationship between genetic variants in the adenosine pathway and outcome of methotrexate treatment in patients with recent-onset rheumatoid arthritis. Arthritis Rheum
78. Reiss AB, Rahman MM, Chan ESL, et al. Adenosine A2A
receptor occupancy stimulates expression of proteins involved in reverse cholesterol transport and inhibits foam cell formation in macrophages. J Leukoc Biol
79. Reiss AB, Carsons SE, Anwar K, et al. Atheroprotective effects of methotrexate on reverse cholesterol transport proteins and foam cell transformation in THP-1 human monocytes/macrophages. Arthritis Rheum
80. Setakis E, Leufkens HG, van Staa TP. Changes in the characteristics of patients prescribed selective cyclooxygenase 2 inhibitors after the 2004 withdrawal of rofecoxib. Arthritis Rheum
atherosclerosis; cyclooxygenase inhibitor; 27-hydroxylase; ABCA1; foam cell
© 2009 American Federation for Medical Research
Highlight selected keywords in the article text.