Atherosclerotic Area Research Articles

Heterogeneous In Vivo Role of Clotting Factors FVIII and FIX in Atherogenesis

Complications of atherosclerosis are the most common causes of death in Western societies. The knowledge that atherosclerosis is an inflammatory disease and coagulation affects the disease's complications offers new opportunities for prevention and treatment. Population studies demonstrated that the risk for myocardial infarction is reduced by 80% among hemophilia A (HA) men compared to age and gender-matched controls. However, early atherosclerotic lesions were readily identified in small cohorts of adults HA and hemophilia B (HB) by ultrasonography of carotid and femoral arteries in a similar fashion to male controls. Here we sought to determine the role of FVIII and FIX on the development of atherosclerosis in two different mouse models. We compared a group of FVIII (HA) or FIX deficient mice (HB) lacking the low-density lipoprotein receptor (LDLR−/−) or apolipoprotein E (apoE−/−) with hemostatically normal littermate controls lacking either LDLR (LDLR−/−) or apoE (apoE−/−). All mice were on C57Bl/6 background and all groups were matched for gender and age. When mice were 8 weeks old, they were placed on atherogenic diet. Analyzes of whole aortic (Sudan IV staining) or aortic sinus (Oil Red O) revealed that HA/apoE−/− mice exhibit less atherosclerotic lesions in a time-dependent manner. At weeks 22 (n=9) and 37 (n=9), the rate of atherosclerosis was 2-3-fold lower in HA/apoE when compared to age and gender-matched apoE (−/−) control group (p=0.001, and p<0.001, respectively), but not at week 8. In contrast, no differences were noted in the rates of vascular lesions between HA/LDLR(−/−) (n=9) and controls (n=9) at all time points. Overall, HB/LDLR (−/−) developed atherosclerosis lesions at aortic sinus with similar rates as the controls at 8 and 22 weeks. However, at week 37, these mice exhibit more extensive tissue damage than the control (p=0.02). Surprisingly, the analyses of whole aorta revealed that atherosclerotic area was more wide-spread in FIX deficient mice in both models, i.e. HB/apoE(−/−) and HB/LDLR(−/−), compared to matched controls. At week 22, 16% and 11% (p=0.04) of the aorta (HB/LDLR[−/−] vs LDLR[−/−]) was covered by atherosclerosis, whereas the rates were 37% vs 21% (p=0.001) at week 37. Moreover, in the apoE(−/−) model the lack of FIX enhances the vascular lesions (14% vs 7%, p=0.02 at week 22) and (36% vs 22%, p=0.04 at week 37). In another model, we tested whether male transgenic (Tg+) mice for high levels of human FIX (∼ 200% of activity above the normal) would influence the development of atherosclerotic lesions in the apoE(−/−) model. After 20 weeks, the rates of arterial vascular lesions were not different among Tg+FIX mice and controls after weeks 20 or 40 on atherogenic diet. In addition, Tg+FIX mice kept on regular chow diet up to 52 weeks showed no enhanced atherosclerosis but they presented high risk for venous thrombosis, as documented in 3/6 Tg+FIX mice and none of controls (0/6). These data demonstrate that coagulation activation in atherogenesis exhibits a rather heterogenous role in the disease evolution which suggest that clotting factors may have functions other than hemostasis in the development of vascular disease. Further studies in hemophilia B subjects are warranted to define the FIX effect on the onset and progression of occlusive vascular disease which may raises concerns on the onset cardiovascular risks on an aging hemophilia population.

Response to Letter Regarding Article, “Expression of Heat Shock Protein 27 in Human Atherosclerotic Plaques and Increased Plasma Level of Heat Shock Protein 27 in Patients With Acute Coronary Syndrome”

We are grateful to Drs Rose and Dunn for raising interesting questions in response to our article.1 In the atherosclerotic plaque core area, healthy smooth-muscle cells become scarce and are replaced by macrophages and foam cells. As the atherosclerosis progress, cells initially may express proteins involved in the cell survival, but in the later …

Interferon-beta attenuates angiotensin II-accelerated atherosclerosis and vascular remodeling in apolipoprotein E deficient mice

Atherosclerotic vascular disease is an inflammatory disease. Interferon-beta (IFN-β) is an important immune modulator. However, the role of IFN-β in atherosclerotic vascular disease is still not clear. The present study is designed to determine the effects of IFN-β on atherosclerosis, abdominal aortic aneurysm (AAA) formation and proliferative vascular remodeling in apolipoprotein E (apoE) deficient mice. Six-month-old male apoE deficient mice fed a normal chow underwent ligation of the common left carotid artery, and were randomly assigned to receive either vehicle or angiotensin II (Ang II, 1.4 mg/kg daily) via a subcutaneously implanted osmotic infusion pump. The animals were further assigned to groups that were subjected to subcutaneous injection of vehicle or murine IFN-β (10 MIU/kg, daily). Ang II increased atherosclerotic area in the non-ligated carotid artery and aortic arch, induced AAA, and exacerbated ligation-induced adventitial proliferation and neointimal hyperplasia characterized by smooth muscle cell (SMC) proliferation and macrophage infiltration in the ligated carotid artery. Co-treatment with IFN-β, had no effects by itself, significantly attenuated Ang II-accelerated increase in the areas of neointima, adventitia, SMC and macrophage in the ligated carotid artery and suppressed Ang II-exacerbated atherosclerosis, but did not affect Ang II-induced AAA formation. These data indicate that IFN-β can play a prominent anti-atherosclerosis, anti-inflammation, and anti-proliferation role of vasculoprotection.

Leptin deficiency suppresses progression of atherosclerosis in apoE-deficient mice

Both experimental and epidemiological studies suggest that leptin is one of the molecules responsible for accelerated atherosclerosis in obese humans. To confirm the notion, we studied whether leptin accelerates atherosclerosis in apoE−/− mice. Leptin deficient hyperlipidemic mice (ob/ob;apoE−/− mice) developed significantly less atherosclerosis than apoE−/− mice, when fed an atherogenic diet for 16 weeks from 8 weeks of age. Histological analysis revealed that most of the atherosclerotic lesions in ob/ob;apoE−/− mice remained as fatty streaks, while those in apoE−/− mice were mainly fibrous plaques. The decrease in atherosclerosis was not due to changes in the serum levels of cholesterol, TNF-α, or adiponectin. Exogenous leptin significantly increased atherosclerotic areas in apoE−/− mice, even though it decreased food intake and body weight. Our findings support the notion that leptin accelerates atherosclerosis.

Suppression of endothelial or lipoprotein lipase in THP-1 macrophages attenuates proinflammatory cytokine secretion

LPL and endothelial lipase (EL) are associated with macrophages in human atherosclerotic lesions, and overexpression of LPL in mouse macrophages is associated with a greater extent of atherosclerosis. To investigate potential mechanisms by which macrophage-derived lipase expression may mediate proatherogenic effects, we used lentivirus-mediated RNA interference to suppress the expression of either LPL or EL within THP-1 macrophages. After suppression of either LPL or EL, significant decreases in the concentration of interleukin-1beta, interleukin-6, monocyte chemoattractant protein-1, and tumor necrosis factor-alpha were observed. Incubation of THP-1 macrophages with either mildly or extensively oxidized LDL consistently decreased cytokine expression, which was additive to that contributed by lipase suppression. Decreased lipase expression was also associated with an altered lipid composition, with reduced percentages of cholesterol (unesterified and esterified), triglycerides, and lysophosphatidylcholine. Microarray data indicated a decreased expression of proinflammatory genes, growth factors, and antiapoptotic genes. By contrast, there was an increased expression of lipoprotein receptors (scavenger receptor 1, low density lipoprotein receptor, scavenger receptor class B type I, and CD36). Thus, we conclude that the suppression of either LPL or EL decreases proinflammatory cytokine expression and influences the lipid composition of THP-1 macrophages. These results provide further insight into the specific metabolic and potential pathological roles of LPL and EL in human macrophages.

A Diet-Induced Hypercholesterolemic Murine Model to Study Atherogenesis Without Obesity and Metabolic Syndrome

Western-type high-fat/high-cholesterol diets used to induce atherogenesis in low-density lipoprotein (LDL) receptor-deficient mice also lead to obesity with concomitant metabolic complications, eg, hypertriglyceridemia, hyperinsulinemia, and insulin resistance. Our aim was to design a diet inducing atherosclerosis through moderate hypercholesterolemia without associated parameters of the metabolic syndrome. Male LDL receptor-deficient mice were fed regular chow (RC; 0.01% cholesterol/4.4% fat), cholesterol-enriched regular chow (HC; 1% cholesterol/4.4% fat), or Western diet (WD 0.06% cholesterol/21% milk fat) for 28 weeks. HC-feeding led to elevated plasma (approximately 20.7 mmol/L [800 mg/dL]) and LDL cholesterol and accelerated atherosclerosis. Plasma triglycerides were unaffected. Compared with RC-fed controls, HC-fed mice had normal body weight gain and normal fasting levels of glucose, free fatty acids, and insulin. In contrast, WD-fed mice were extremely hypercholesterolemic (>41.4 mmol/L), obese, hypertriglyceridemic, hyperinsulinemic, insulin resistant, and showed adverse health such as skin/fur abnormalities and hepatic steatosis. Although atherosclerotic surface areas in the entire aorta were similar in HC-fed and WD-fed mice, lesions in aortic origin cross sections were significantly larger in WD-fed mice. However, morphology was similar in lesions of equal size. The HC diet induced moderate hypercholesterolemia and extensive atherosclerosis and should be useful to study specific aspects of atherogenesis in the absence of confounding effects of the metabolic syndrome.

Detecting and assessing macrophages in vivo to evaluate atherosclerosis noninvasively using molecular MRI.

We investigated the ability of targeted immunomicelles to detect and assess macrophages in atherosclerotic plaque using MRI in vivo. There is a large clinical need for a noninvasive tool to assess atherosclerosis from a molecular and cellular standpoint. Macrophages play a central role in atherosclerosis and are associated with plaques vulnerable to rupture. Therefore, macrophage scavenger receptor (MSR) was chosen as a target for molecular MRI. MSR-targeted immunomicelles, micelles, and gadolinium-diethyltriaminepentaacetic acid (DTPA) were tested in ApoE-/- and WT mice by using in vivo MRI. Confocal laser-scanning microscopy colocalization, macrophage immunostaining and MRI correlation, competitive inhibition, and various other analyses were performed. In vivo MRI revealed that at 24 h postinjection, immunomicelles provided a 79% increase in signal intensity of atherosclerotic aortas in ApoE-/- mice compared with only 34% using untargeted micelles and no enhancement using gadolinium-DTPA. Confocal laser-scanning microscopy revealed colocalization between fluorescent immunomicelles and macrophages in plaques. There was a strong correlation between macrophage content in atherosclerotic plaques and the matched in vivo MRI results as measured by the percent normalized enhancement ratio. Monoclonal antibodies to MSR were able to significantly hinder immunomicelles from providing contrast enhancement of atherosclerotic vessels in vivo. Immunomicelles provided excellent validated in vivo enhancement of atherosclerotic plaques. The enhancement seen is related to the macrophage content of the atherosclerotic vessel areas imaged. Immunomicelles may aid in the detection of high macrophage content associated with plaques vulnerable to rupture.

Folic acid supplementation delays atherosclerotic lesion development in apoE-deficient mice

Folic acid is a vitamin that when used as a dietary supplementation can improve endothelial function. To assess the effect of folic acid on the development of atherosclerosis, male apolipoprotein E-deficient mice fed a standard chow diet received either water (control group) or an aqueous solution of folic acid that provided a dose of 75 μg/kg/day, for ten weeks. At the time of sacrifice, blood was drawn and the heart removed. The study measured plasma homocysteine, lipids, lipoproteins, low-density lipoprotein (LDL) oxidation, isoprostane, paraoxonase, and apolipoproteins, and aortic atherosclerotic areas. In folic acid-treated animals, total cholesterol, mainly carried in very low-density and low-density lipoproteins, increased significantly, and homocysteine, HDL cholesterol, paraoxonase, and triglyceride levels did not change significantly. Plasma isoprostane and apolipoprotein (apo) B levels decreased. The resistance of LDL to oxidization and plasma apoA-I and apoA-IV levels increased with a concomitant decrease in the area of atherosclerotic lesions. The administration of folic acid decreased atherosclerotic lesions independently of plasma homocysteine and cholesterol levels, but was associated with plasma levels of apolipoproteins A-I, A-IV and B, and decreased oxidative stress.

Hydroxytyrosol Administration Enhances Atherosclerotic Lesion Development in Apo E Deficient Mice

Hydroxytyrosol is a phenol found in olive oil. To verify the effect of hydroxytyrosol on the development of atherosclerosis, two groups of apo E deficient male mice on a standard chow diet were used: the control group receiving only water, and the second group an aqueous solution of hydroxytyrosol in order to provide a dose of 10 mg/kg/day to each mouse. This treatment was maintained for 10 weeks. At the moment of sacrifice, blood was drawn and heart removed. Plasma lipids, apolipoproteins and monocyte Mac-1 expression were assayed as well as aortic atherosclerotic areas in both groups. Data showed no significant changes in HDL cholesterol, paraoxonase, apolipoprotein B or triglyceride levels. However, hydroxytyrosol administration decreased apolipoprotein A-I and increased total cholesterol, atherosclerotic lesion areas and circulating monocytes expressing Mac-1. The latter was highly correlated with lesion areas (r = 0.65, P < 0.01). These results indicate that administration of hydroxytyrosol in low cholesterol diets increases atherosclerotic lesion associated with the degree of monocyte activation and remodelling of plasma lipoproteins. Our data supports the concept that phenolic-enriched products, out of the original matrix, could be not only non useful but also harmful. Our results suggest that the formulation of possible functional foods should approximate as much as possible the natural environment in which active molecules are found.

Enhanced scavenging of lipid substances is a possible effect of corticosteroids in the treatment of cholesterol crystal embolism

Cholesterol crystal embolism (CCE) is a systemic refractory disease especially prevalent amongst elderly patients suffering from atherosclerosis. Treatment of this condition remains controversial due to difficulties in diagnosis. Corticosteroid therapy may be an important treatment option despite its elusive mechanisms. To clarify the role of corticosteroid in CCE therapy, we collected the samples from six autopsied subjects with CCE, three of whom were clinically given various doses of corticosteroid to investigate stable atherosclerosis-related substances, advanced glycation end-products (AGE), and several AGE receptors such as scavenger receptor class B type 1 (SR-B1), receptor for AGE (RAGE), and galectin-3 in the liver tissues and atherosclerotic areas by immunostaining using a tissue macro-array technique. An intense expression of AGE and its receptors was identified in the enlarged Kupffer cells of CCE cases, which were given relatively high doses of corticosteroid. In addition, numerous mononuclear cells in the intimal atheromatous plaque presented strong expressions of AGE and SR-B1. In conclusion, we speculated that corticosteroid treatment for CCE may upregulate the activations, including phagocytic capacity of Kupffer cells mediated by overexpression of RAGE and scavenger receptors, resulting in efficient clearance of the lipid substances from the blood circulation released from atherosclerotic areas.

Severity of Hyperlipidemia Does Not Affect Antiatherosclerotic Effect of an Angiotensin II Receptor Antagonist in Apolipoprotein E-deficient Mice

The purpose of this study was to clarify whether severity of hyperlipidemia affects the antiatherosclerotic effect of angiotensin II receptor blockers (ARBs). The effect of olmesartan medoxomil, an ARB, on atherosclerotic lesion was examined in apolipoprotein E-deficient (ApoEKO) mice fed a normal diet (ND) or a high-fat-supplemented diet (FD) for 25 weeks. ApoEKO mice have high plasma cholesterol levels, which were further increased by feeding of an FD. Both the atherosclerotic lesion area of the aortic luminal surface and the atherosclerotic lesion thickness in the aortic valves were significantly greater in the FD mice than in the ND mice. Olmesartan medoxomil did not affect the plasma cholesterol levels in either the ND or FD ApoEKO mice; however, it reduced effectively both the atherosclerotic lesion surface area and the lesion thickness even in FD ApoEKO mice. It is concluded that the antiatherosclerotic effect of ARBs is not weakened by the high plasma cholesterol level, suggesting the usefulness of ARBs in the treatment of atherosclerosis, even in a situation in which the plasma cholesterol level is not fully controlled.

Zinc supplementation decreases the development of atherosclerosis in rabbits

Developing atherosclerotic plaques in cholesterol-fed rabbits are enriched in iron but depleted in zinc. In order to examine further the role of zinc, New Zealand White rabbits were fed a high-cholesterol 1% (w/w) diet with zinc (1 g/kg) supplementation for 8 weeks. After the 8-week period, the average atherosclerotic lesion cross-sectional areas in the aortas of the animals fed with the zinc supplement were significantly decreased (1.0 mm 2) compared with lesion areas of the animals fed only on the high-cholesterol diet (3.1 mm 2). Using nuclear microscopy, a technique for mapping and measuring trace elements in tissue sections, lesion zinc levels (24 ppm) were observed to be unchanged in the zinc-fed rabbits compared to controls. However, average lesion Fe levels in the zinc-fed group were measured at 32 ppm, whereas in the control group the average Fe levels were significantly higher at 43 ppm ( P = 0.03). Our data support the concept that zinc may have an antiatherogenic effect by decreasing iron levels in the lesion, possibly leading to inhibition of iron-catalyzed free radical reactions.

Eplerenone With Valsartan Effectively Reduces Atherosclerotic Lesion by Attenuation of Oxidative Stress and Inflammation

Angiotensin II contributes to atherogenesis, mainly through oxidative stress and inflammation. Recent data suggest that aldosterone is implicated in some effects of angiotensin II. We hypothesized that aldosterone could directly contribute to oxidative stress and atherosclerotic lesion formation. Male apolipoprotein E-deficient mice 6 weeks of age were placed on a normal diet or 1.25% high-cholesterol diet. After 6 weeks of the high-cholesterol diet, a marked increase in atherosclerotic lesion formation was observed in the aorta, accompanied by significant elevation of plasma cholesterol level. Production of superoxide anion and expression of NAD(P)H oxidase subunit p47phox, tumor necrosis factor-alpha, and monocyte chemoattractant protein-1 in the aorta were increased with the high-cholesterol diet. Eplerenone (1.67 g/kg in high-cholesterol diet) did not affect blood pressure or plasma cholesterol but decreased the atherosclerotic area by nearly 70% (P<0.05), associated with attenuation of oxidative stress and inflammatory response. Valsartan (0.5 mg/kg per day) also decreased the atherosclerotic lesion, whereas coadministration of valsartan and eplerenone further decreased it. Moreover, aldosterone (0.1 micromol/L) enhanced NADPH oxidase activity in cultured vascular smooth muscle cells. These results suggest that aldosterone may play a critical role in atherogenesis subsequent to oxidative stress in part independent of angiotensin II-mediated signaling, and that eplerenone could prevent atherosclerosis by attenuating oxidative stress and inflammation.

A Selective NF&amp;kappa;B Inhibitor, DHMEQ, Reduced Atherosclerosis in ApoE-deficient mice

Atherosclerosis is a chronic inflammatory process, and anti-inflammatory agents potentially inhibit the development of atherosclerosis. We tested whether a novel NFkappaB inhibitor reduces atherosclerosis. Dehydroxymethylepoxyquinomicin (10 mg/kg) or vehicle (chloromethyl cellulose) was injected intraperitoneally into apoE-deficient mice three times a week for 16 weeks. The entire aorta was excised and atherosclerotic area was determined at 4 and 16 weeks. Serum levels of cholesterol, triglyceride, TNF-alpha and adiponectin were also measured. The atherosclerotic area was significantly smaller in mice treated with dehydroxymethyl-epoxyquinomicin both at 4 and 16 weeks. There was no significant difference in body weight or serum levels of cholesterol, triglyceride, and adiponectin. A new NFkappaB inhibitor, dehydroxymethylepoxyquinomicin, reduced atherosclerosis without affecting plasma lipid levels in apoE-deficient mice.

Crocetin Attenuates Atherosclerosis in Hyperlipidemic Rabbits Through Inhibition of LDL Oxidation

Oxidation of low-density lipoprotein plays a crucial role in the pathogenesis of atherosclerosis, raising the possibility of using antioxidants as an inhibitor of atherosclerosis. However, studies with antioxidants have led to contradictory results. In the present study, we investigated the effect of crocetin, a carotenoid with potent antioxidant activity, on experimental atherosclerosis in rabbits. After 8 weeks of feeding on high lipid diet, rabbits developed severe atherosclerotic lesions in thoracic aortas (P < 0.01), together with a significant elevation of plasma lipids level, thiobarbituric acid reactive substances (TBARS), and oxidized low-density lipoprotein (P < 0.01). In contrast, supplementation with crocetin markedly reduced the progression of atherosclerotic lesions (P < 0.01) and plasma levels of Ox-LDL and TBARS, whereas plasma lipids level remained unchanged. Plasma total antioxidant capacity and superoxide dismutase activity were obviously increased in crocetin-treated rabbits. In vitro studies demonstrated that supplementation with crocetin significantly increased the resistance of LDL to cupric ion-induced oxidation. Regression analysis indicated that atherosclerotic areas correlated positively with plasma level of Ox-LDL and the susceptibility of LDL to in vitro oxidation. These findings suggest that suppression of LDL oxidation by crocetin contributes, at least partly, to the attenuation of atherosclerosis.

Effect of combination of calcium antagonist, azelnidipine, and AT1 receptor blocker, olmesartan, on atherosclerosis in apolipoprotein E-deficient mice

Angiotensin II type 1 receptor blockers (ARB) are widely recognized to have a vasculoprotective effect. Accumulating data have revealed that calcium antagonists also retard atherosclerosis. We examined the possibility that combination therapy of ARB and calcium antagonists could more effectively prevent atherosclerosis than monotherapy. We observed a marked increase in the atherosclerotic area, associated with the exaggerated expression of nicotinamide adenine dinucleotide (phosphate), reduced form [NAD(P)H] oxidase subunits (p22 and p47) and superoxide anion production, in the aorta of apolipoprotein E-deficient mice maintained on a 1.25% high-cholesterol diet for 10 weeks. A calcium antagonist, azelnidipine, at a dose of 1 mg/kg a day or an ARB, olmesartan, at a dose of 3 mg/kg a day, significantly inhibited these parameters, with no change in systolic blood pressure and the blood cholesterol level. Moreover, the co-administration of lower doses of azelnidipine (0.1 mg/kg a day) and olmesartan (1 mg/kg a day) significantly inhibited the atherosclerotic area and oxidative stress, whereas azelnidipine or olmesartan alone at these doses did not affect these parameters. Furthermore, we observed similar inhibitory effects of azelnidipine or olmesartan on angiotensin II-induced NADPH oxidase activity and Akt activity in cultured vascular smooth muscle cells. These results suggest that the co-administration of calcium antagonists and ARB synergistically blunts oxidative stress at least partly through the inhibition of Akt activity and enhances the beneficial effects of these drugs on atherosclerosis compared with monotherapy.

Cyclosporine Withdrawal from a Mycophenolate Mofetil–Containing Immunosuppressive Regimen

Maintenance immunosuppression with cyclosporine (CsA) is associated with nephrotoxicity, hyperlipidemia, and hypertension. This long-term study (core study + 4 yr of follow-up) investigated the long-term efficacy and safety of CsA withdrawal from a mycophenolate mofetil (MMF)-based regimen. Seventy-seven patients were maintained on CsA, MMF, and steroids (CsA-MMF group), and 74 were given a CsA-free regimen of MMF and steroids (MMF group). Serum creatinine and creatinine clearance were measured at 6-month intervals. Patient and graft survival, acute rejection episodes, malignancies, BP, and lipid profile were also recorded. At 5 yr, patient and graft survival was 93 and 88%, respectively, for the MMF group and 95 and 92%, respectively, for the CsA-MMF group. During follow-up, seven MMF patients experienced acute rejection episodes compared with one CsA-MMF patient (P = 0.0283). Nine grafts were lost to chronic rejection in the MMF group versus three in the CsA-MMF group. No demographic or immunologic characteristics were associated with acute or chronic rejection in the MMF group, but the doses of both MMF and steroids decreased significantly between 1 and 5 yr. The MMF group showed a trend toward improved creatinine clearance (67.4 versus 61.7 ml/min; P = 0.0500). Withdrawal of CsA from an MMF-containing immunosuppressive regimen resulted in an increased risk for acute rejection episodes and graft loss as a result of rejection throughout the 5-yr study period. The creatinine clearance-confirmed improvement in renal function observed at year 1 was maintained at 5 yr BP and cholesterol levels were well controlled in both groups.

Expression of Human Myeloperoxidase by Macrophages Promotes Atherosclerosis in Mice

Myeloperoxidase (MPO) colocalizes with macrophages in the human artery wall, and its characteristic oxidation products have been detected in atherosclerotic lesions. Thus, oxidants produced by the enzyme might promote atherosclerosis. However, macrophages in mouse atherosclerotic tissue do not express MPO. Therefore, mice are an inappropriate model for testing the role of MPO in vascular disease. To overcome this problem, we generated and studied transgenic (Tg) mice that contained the human MPO gene. We produced human MPO-Tg mice with use of a Visna virus promoter. To confine MPO expression to macrophages, we lethally irradiated LDL receptor-deficient mice and repopulated their bone marrow with cells from wild-type mice or MPO-Tg mice. Despite having similarly high levels of cholesterol after maintenance on a high-fat, high-cholesterol diet, the MPO-Tg animals developed a 2-fold greater atherosclerotic area in the aorta than did mice transplanted with wild-type bone marrow (P=0.00003). Our observations indicate that expression of human MPO in macrophages promotes atherosclerosis in hypercholesterolemic mice, raising the possibility that the enzyme might be a potential therapeutic target for preventing cardiovascular disease in humans.

Atherosclerosis Is Associated with Delirium After Coronary Artery Bypass Graft Surgery

To investigate whether atherosclerosis of the ascending aorta, internal carotid arteries, and coronary arteries is predictive of postoperative delirium in subjects undergoing coronary artery bypass graft (CABG) surgery. Prospective cohort study. Boston Veterans Affairs Healthcare System. Thirty-six male veterans undergoing primary CABG surgery. Subjects underwent Duplex ultrasound to assess stenosis in the internal carotid arteries. Information on the ascending aortic plaque, as assessed by transesophageal echocardiogram, and the number of coronary vessels bypassed was collected. To create an atherosclerosis score, the number of atherosclerotic areas was added. A validated delirium battery was administered to the subjects preoperatively and on postoperative Days 2 and 5. Fifteen subjects (41.7%) developed delirium postoperatively. In bivariate analysis, carotid stenosis of 50% or more (relative risk (RR)=3.5, 95% confidence interval (CI)=1.5-8.1) and moderate-severe ascending aortic plaque (RR=2.9, 95% CI=1.0-8.5) were significantly associated with the development of delirium. There was a trend toward a significant association for three or more vessels bypassed (RR=9.6, 95% CI=0.6-145.3). After controlling for age, baseline cognition, and medical comorbidity, the atherosclerosis score was significantly associated with postoperative delirium (adjusted RR=2.7, 95% CI=1.1-6.8). In this preliminary report, atherosclerosis in the carotid arteries, aorta, and coronary circulation is associated with the development of delirium after CABG surgery. Further investigation into atherosclerosis as a risk factor for delirium is warranted.

Dietary salt restriction accelerates atherosclerosis in apolipoprotein E-deficient mice

Background: Whether a general reduction in salt intake reduces or actually enhances cardiovascular mortality in man remains an issue of controversy. Low sodium diets may lead to adverse side effects by stimulating the renin–angiotensin and sympathetic nervous systems. The present study was designed to investigate the effects of low dietary salt on atherosclerotic lesion progression in apolipoprotein E deficient (apoE −/−) mice. Methods and results: We fed 7-week-old apoE −/− mice on low (0.036% NaCl; n = 28) or regular (0.64% NaCl; n = 26) salt diets for 16 weeks. At the age of 23 weeks, the cross-section surface area of atherosclerotic plaques was measured in aortic root and thoracic aorta. Serum total cholesterol, triglycerides, plasma angiotensin levels and urinary protein/creatinine concentrations were assessed. Exposure to low salt caused significant increases in atherosclerotic lesion surface area in thoracic aorta, but did not alter lesion area in aortic root. Low-salt mice also had higher serum total cholesterol and higher plasma angiotensin II (ANG-II) concentrations. Atherosclerotic lesion area was correlated with ANG-II levels in low-salt but not in regular-salt animals, and with total cholesterol concentration in all mice. Mean arterial pressure was comparable in both groups. Conclusions: Dietary salt restriction accelerated atherosclerotic lesion formation in apoE −/− mice through a mechanism that is probably related to ANG-II formation. Whether these findings are relevant to human cardiovascular disease remains to be evaluated.