Oxidized low-density lipoprotein decreases the expression of endothelial nitric oxide synthase

Lipid lowering reduces oxidative stress and endothelial cell activation in rabbit atheroma

BACKGROUND

Lipid lowering may reduce acute coronary events in patients in part by reducing vascular inflammation. Oxidative stress induces endothelial cell (EC) expression of vascular cell adhesion molecule 1 (VCAM-1) and monocyte chemoattractant protein 1 (MCP-1) and reduces levels of atheroprotective NO, leading to monocyte recruitment and macrophage accumulation. This study tested the hypothesis that lipid lowering decreases oxidative stress and improves EC functions related to inflammatory cell accumulation.

METHODS AND RESULTS

Rabbits consumed an atherogenic diet for 4 months to produce atheroma, followed by a purified chow diet for 16 months. Atherosclerotic aortas from hypercholesterolemic rabbits produced high levels of reactive oxygen species. Oxidized LDL (oxLDL) accumulated in atheroma underlying ECs that overexpress VCAM-1. In contrast, few if any ECs in atheroma stained for endothelial NO synthase (eNOS). Lipid lowering reduced reactive oxygen species production, oxLDL accumulation, and plasma levels of anti-oxLDL IgG. After lipid lowering, VCAM-1 and MCP-1 expression decreased, eNOS expression increased, and ECs exhibited a more normal ultrastructure.

CONCLUSIONS

These results establish that lipid lowering can reduce oxidative stress and EC activation in vivo. These mechanisms may contribute to improvement in endothelial function and plaque stabilization observed clinically.

Atherosclerosis and cancer: common pathways on the vascular endothelium

This article reviews experimental and clinical data on atherosclerosis and cancer showing common pathogenic mechanisms. It is suggested that common pathways follow dysfunction of the vascular endothelium. The activation of the haemostatic system and the overexpression of cytokines and adhesion molecules by the endothelial cells represent important features of this dysfunction. These mechanisms can be responsible for progression of both diseases and explain the higher incidence of thromboembolic events in cancer patients, the occurrence of similar laboratory findings and the effect of many drugs on the course of the two diseases. Our article confirms that atherosclerosis and cancer share common mechanisms, and we hope it will stimulate further clinical trials on the use of drugs active on the haemostatic system in cancer patients.

Obesity, aerobic exercise, and vascular disease: the role of oxidant stress

Oxidant formation in the vasculature contributes to vascular disease and dysfunction associated with obesity. In contrast, exercise-dependent production of oxidants may stimulate adaptive responses that protect against the development of such diseases. In this review, we discuss current concepts in the biology of reactive oxygen and nitrogen species and how their function is modulated in the context of vascular disease, obesity, and aerobic exercise.

Physiological mechanisms regulating the expression of endothelial-type NO synthase

Although endothelial nitric oxide synthase (eNOS) is a constitutively expressed enzyme, its expression is regulated by a number of biophysical, biochemical, and hormonal stimuli, both under physiological conditions and in pathology. This review summarizes the recent findings in this field. Shear stress, growth factors (such as transforming growth factor-beta, fibroblast growth factor, vascular endothelial growth factor, and platelet-derived growth factor), hormones (such as estrogens, insulin, angiotensin II, and endothelin 1), and other compounds (such as lysophosphatidylcholine) upregulate eNOS expression. On the other hand, the cytokine tumor necrosis factor-alpha and bacterial lipopolysaccharide downregulate the expression of this enzyme. The growth status of cells, the actin cytoskeleton, and NO itself are also important regulators of eNOS expression. Both transcriptional and posttranscriptional mechanisms are involved in the expressional regulation of eNOS. Different signaling pathways are involved in the regulation of eNOS promoter activity and eNOS mRNA stability. Changes in eNOS expression and activity under pathophysiological conditions and the pharmacological modulation of eNOS expression are subject of a subsequent brief review (part 2) to be published in the next issue of this journal.

Folic acid and vitamin B(12) supplementation attenuates isoprenaline-induced myocardial infarction in experimental hyperhomocysteinemic rats

Hyperhomocysteinemia (Hhcy) is an independent risk factor for cardiovascular disease. Oxidative stress may contribute to the deleterious effects of homocysteine (Hcy). The aim of the present study is to study the effect of folic acid and Vitamin B(12) supplementation on isoprenaline (ISO)-induced myocardial infarction (MI) in hyperhomocysteinemic rats. Hhcy was induced by daily intake of methionine (1 g kg(-1) body weight) in the drinking water for 4 weeks. MI was then produced by a single subcutaneous injection of ISO (300 mg kg(-1), s.c.). Electrocardiographic parameters, heart rate, ST segment, and blood pressure as well as serum marker enzymes, creatine kinase (CK) and lactate dehydrogenase (LDH) were measured. Lipid peroxidation measured as malondialdehyde (MDA) and reduced glutathione (GSH) concentrations in heart tissue were estimated as indices of oxidative stress. Hhcy resulted in significant blood pressure reduction, ST segment elevation and increase in heart rate and serum CK and LDH levels. Cardiac MDA was significantly increased, while GSH was decreased in Hhcy group compared to the normal control group. All the measured parameters were greatly exaggerated in Hhcy rats treated with ISO in comparison with Hhcy rats alone. Administration of folic acid (10 mg kg(-1), orally via gavage) and Vitamin B(12) (500 microg kg(-1), i.m.) concurrently for 4 weeks during the induction of Hhcy markedly reduced the increase in heart rate, ST segment elevation and blood pressure reduction as well as the increase in serum CK and LDH levels. Cardiac MDA content was decreased while cardiac GSH was elevated in the treated group compared to Hhcy + ISO group. Moreover, the severe cardiac histopathological changes observed in Hhcy + ISO group were attenuated by folic acid and Vitamin B(12). These results suggest that Hhcy aggravates MI via oxidative stress mechanisms and that lowering Hcy level with folic acid and Vitamin B(12) can ameliorate the detrimental effects of Hhcy and may reduce the risk of MI.

A self-fulfilling prophecy: C-reactive protein attenuates nitric oxide production and inhibits angiogenesis

BACKGROUND

Given the central importance of nitric oxide (NO) in the development and clinical course of cardiovascular diseases, we sought to determine whether the powerful predictive value of C-reactive protein (CRP) might be explained through an effect on NO production.

METHODS AND RESULTS

Endothelial cells (ECs) were incubated with recombinant CRP (0 to 100 microg/mL, 24 hours), and NO and cyclic guanosine monophosphate (cGMP) production was assessed. The effects of CRP on endothelial NO synthase (eNOS) protein, mRNA expression, and mRNA stability were also examined. In a separate study, the effects of CRP (25 microg/mL) on EC cell survival, apoptosis, and in vitro angiogenesis were evaluated. Incubation of ECs with CRP resulted in a significant inhibition of basal and stimulated NO release, with concomitant reductions in cGMP production. CRP caused a marked downregulation of eNOS mRNA and protein expression. Actinomycin D studies suggested that eNOS downregulation was related to decreased mRNA stability. In conjunction with a decrease in NO production, CRP inhibited both basal and vascular endothelial growth factor-stimulated angiogenesis as assessed by EC migration and capillary-like tube formation. CRP did not induce EC survival but did, however, promote apoptosis in a NO-dependent fashion.

CONCLUSIONS

CRP, at concentrations known to predict adverse vascular events, directly quenches the production of the NO, in part, through posttranscriptional effect on eNOS mRNA stability. Diminished NO bioactivity, in turn, inhibits angiogenesis, an important compensatory mechanism in chronic ischemia. Through decreasing NO synthesis, CRP may facilitate the development of diverse cardiovascular diseases. Risk reduction strategies designed to lower plasma CRP may be effective by improving NO bioavailability.

The pathophysiology of erectile dysfunction related to endothelial dysfunction and mediators of vascular function

The incidence of erectile dysfunction increases with diabetes, hypertension, hypercholesterolaemia, cardiovascular disease and renal failure. All these conditions are associated with endothelial dysfunction. This review addresses the pathophysiology of erectile dysfunction with a special focus on new insights into nitric oxide (NO)-mediated pathways, oxidative stress and parallels to endothelial dysfunction. NO appears to be the key mediator promoting endothelium-derived vasodilation and penile erection. The possibility is discussed that elevated plasma concentrations of asymmetrical dimethylarginine (ADMA), an endogenous NO synthase inhibitor, may provide an additional pathomechanism for various forms of erectile dysfunction associated with cardiovascular risk factors and disease. Likewise, the role of endothelium-derived factors mediating NO-independent pathways is evaluated.

Effect of glutathione infusion on leg arterial circulation, cutaneous microcirculation, and pain-free walking distance in patients with peripheral obstructive arterial disease: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To assess the effects of glutathione on pain-free walking distance (PFWD) and hemodynamic parameters in patients with peripheral artery disease.

PATIENTS AND METHODS

Forty patients with Fontaine stage II peripheral artery disease who were seen between September 2000 and March 2001 at the vascular laboratory and ward of the Division of Vascular Medicine and Rehabilitation at Verona University were studied in a double-blind, placebo-controlled trial. The patients were randomly assigned (20 per group) to treatment with intravenous glutathione twice a day or saline solution twice a day for 5 days. Treatments were administered in a double-blind manner. The 2 groups of patients underwent measurement of PFWD by strain-gauge plethysmography and laser Doppler flowmetry (with postischemic test) of the symptomatic leg at rest and after treadmill test. All measurements and tests were repeated 12 hours after the last infusion.

RESULTS

Between the 2 groups, hemodynamic tests showed no differences in baseline values and at rest after treatment. At rest, no differences were observed between basal and posttreatment values; findings in the saline group were similar during tests before and after the infusion period. In the glutathione group, we observed increases in PFWD (196+/-15 vs 143+/-11 m; P<.04), macrocirculatory flow after treadmill test with plethysmography at the end of treatment (9.3+/-2 vs 2.8+/-0.5 mL per 100 mL/min; P<.002), and postischemic hyperemia with laser Doppler flowmetry, registered as perfusion units (PU), at the end of infusions (14.4+/-3.2 vs 6.18+/-1.5 PU; P<.005), with a greater area under the curve after treatment (705+/-103 vs 508+/-45 PU/s; P<.001) and reduced time to flow motion (32+/-4 vs 48+/-11 seconds; P<.05).

CONCLUSION

In patients with peripheral artery disease, glutathione prolongs PFWD and shows an improvement of macrocirculatory and microcirculatory parameters.

Statin therapy improves brachial artery endothelial function in nephrotic syndrome

BACKGROUND

Patients with nephrotic syndrome have impaired endothelial function probably related to dyslipidemia. This study evaluated the effects of statin therapy on dyslipidemia and endothelial function in patients with nephrotic syndrome.

METHODS

A sequential, open-label study of the effects of statins on endothelial dysfunction in 10 nephrotic patients treated with an angiotensin-converting enzyme (ACE) inhibitor or angiotensin II (Ang II) receptor antagonist. Endothelial function was assessed at baseline, after 12 weeks of treatment with statins, and after an 8-week washout. Brachial artery endothelial function was measured as post-ischemic flow-mediated dilation (FMD) using ultrasonography. Endothelium-independent, glyceryl trinitrate-mediated vasodilation (GTNMD) also was measured.

RESULTS

Serum lipids were significantly lower following statin: total cholesterol mean 8.2 +/- 0.4 (standard error) mmol/L versus 5.2 +/- 0.3 mmol/L, triglycerides 2.6 +/- 0.4 mmol/L versus 1.6 +/- 0.2 mmol/L, non-HDL-cholesterol 6.7 +/- 0.4 mmol/L versus 3.7 +/- 0.2 mmol/L (all P < 0.001). There was a trend to an increase in serum albumin (31.0 +/- 1.3 g/L vs. 33.8 +/- 1.5 g/L; P = 0.078) and FMD improved significantly following treatment (3.7 +/- 1.1% vs. 7.0 +/- 0.8%, P < 0.01). After washout, FMD deteriorated significantly to 3.5 +/- 1.4% (P < 0.05) versus week 12 FMD. GTNMD was unchanged. In multivariate regression, reduction in non-high-density lipoprotein (HDL)-cholesterol (beta - 0.736, P = 0.027) and increase in serum albumin (beta 0.723, P = 0.028), but not the on-treatment level of non-HDL-cholesterol, were significant independent predictors of improvement in FMD after adjusting for change in resting brachial artery diameter. Changes in serum lipoprotein and albumin concentrations off treatment were not associated with deterioration in FMD.

CONCLUSION

Statin therapy significantly improves dyslipidemia and brachial artery endothelial function in patients with nephrotic syndrome. Improvement in brachial artery endothelial function may be in part related to a non-lipid effect of statins. The findings also suggest a role for dyslipidemia in endothelial dysfunction and the risk for cardiovascular disease in nephrotic syndrome.

Simvastatin restores endothelial NO-mediated vasorelaxation in large arteries after myocardial infarction

Congestive heart failure (CHF) after myocardial infarction is associated with diminished endothelial nitric oxide (NO)-mediated vasorelaxation. The 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors have been shown to modulate vascular tone independent of the effects on lipid lowering. We hypothesized that simvastatin restores NO-dependent vasorelaxation with CHF. We found that incubation of the normal rat aorta with 0.1 mM simvastatin for 24 h enhanced ACh-mediated vasorelaxation (P < 0.05). Moreover, simvastatin increased (P < 0.05) endothelial NO synthase (eNOS) protein content by >200% (82.0 +/- 14.0 vs. 21.6 +/- 7.9% II/microg). In cultured endothelial cells, simvastatin (10 and 20 microM) increased eNOS levels by 114.7 +/- 39.9 and 212.0 +/- 75.0% II/microg protein, respectively (both P < 0.05; n = 8). In the rat coronary artery ligation model, oral gavage with 20 mg. kg(-1). day(-1) simvastatin for 3 wk decreased (P < 0.05) mean arterial pressure (121 +/- 20 vs. 96.5 +/- 10.8 mmHg) and left ventricular change in pressure with time (4,500 +/- 700 vs. 4,091 +/- 1,064 mmHg/s, n = 6). Simvastatin reduced (P < 0.05) basal vasoconstriction and improved ACh-mediated vasorelaxation in CHF arterial rings. Inhibition of NO generation by N(G)-nitro-L-arginine methyl ester (100 microM) abolished the ACh-induced vasorelaxation in all rats. In conclusion, chronic treatment of CHF with simvastatin restores endothelial NO-dependent dysfunction and upregulates eNOS protein content in arterial tissue.

[Interleukin-10 and coronary disease]

Understanding of the pathophysiology of atherosclerosis has changed markedly over the past few decades. It is now widely accepted that inflammation plays a fundamental role in the genesis and development of atherosclerosis. Inflammatory mechanisms also appear to determine clinical presentation and disease outcome. Atherosclerotic lesions have high concentrations of inflammatory cells (T lymphocytes and activated macrophages) as well as an abundance of pro-inflammatory cytokines [interleukin (IL)-1, IL-6, IL-8, interferon-gamma, tumor necrosis factor-alpha, etc.] that modulate local inflammatory responses. These may also alter plaque stability and facilitate the development of acute cardiovascular events. The role of anti-inflammatory cytokines in this context remains to be studied. IL-10 is an anti-inflammatory cytokine synthesised by T-lymphocytes and macrophages and has other anti-inflammatory effects. IL-10 expression within human atherosclerotic plaques has been demonstrated and animal experiments have shown that low levels of IL-10 lead to the development of extensive and unstable atherosclerotic lesions. Currently available evidence suggests a potential protective role for IL-10 in atherosclerosis. This new perspective on coronary disease as a chronic inflammatory process may open new avenues for the management of ischemic heart disease.

Decreased aortic early atherosclerosis in hypercholesterolemic hamsters fed oleic acid-rich TriSun oil compared to linoleic acid-rich sunflower oil

Previous studies have demonstrated that low density lipoprotein (LDL) enriched in polyunsaturated fatty acids (PUFA) are more susceptible to oxidation (ex vivo) than those containing monounsaturated fatty acids (MUFA). To test whether this observation was associated with various parameters considered to be related with the development of early aortic atherosclerosis, hamsters were fed commercial hypercholesterolemic diets (HCD) containing either the PUFA, sunflower oil (SF) or the MUFA, TriSun oil (TS) at 10% with 0.4% cholesterol (wt/wt). LDL isolated from hamsters fed TS had significantly longer lag phase (30%, P < 0.05), a decreased propagation phase (-62%, P < 0.005), and fewer conjugated dienes formed (-37%, P < 0.007) compared to hamsters fed SF. Aortic vasomotor function, measured as degree of aortic relaxation, was significantly greater in the TS vs SF-fed hamsters whether acetylcholine or the calcium ionophore A23187 was used as the endothelium-dependent agonist. As a group, the SF-fed hamsters had significantly more early atherosclerosis than hamsters fed TS (46%, P < 0.006). When animals across the two diets were pair-matched by plasma LDL-C levels, there was an 82% greater mean difference (P < 0.002) in early atherosclerosis in the SF versus the TS-fed hamsters. While there were no significant associations with plasma lipids and lipoprotein cholesterol, early atherosclerosis was significantly correlated with lag phase (r = -0.67, p < 0.02), rate of LDL conjugated diene formation (r = 0.74, p < 0.006) and maximum dienes formed (r = 0.67, p < 0.02). Compared to TS-fed animals, aortic sections from hamsters fed the SF-containing diet revealed that the cytoplasm of numerous foam cells in the subendothelial space reacted positively with the monoclonal anti-bodies MDA-2 and NA59 antibody, epitopes found on oxidized forms of LDL. The present study suggests that compared to TS, hamsters fed the SF-diet demonstrated enhanced LDL oxidative susceptibility, reduced aortic relaxation, greater early aortic atherosclerosis and accumulation of epitopes found on oxidized forms of LDL.

Treatment of hyperhomocysteinemia with folic acid: effects on homocysteine levels, coagulation status, and oxidative stress markers

The aim of the study was to determine whether folic acid treatment in subjects with homocysteinemia would change their coagulation and oxidative status. Thirty-three patients with peripheral vascular disease and 26 elderly subjects with no symptoms of atherosclerosis, all of whom had total homocysteine >20 microM, were treated with folic acid (5 or 10 mg) for 3 months. In the 33 patients with peripheral vascular disease, homocysteine levels decreased from a median of 26.7 microM at baseline to 20.0 microM (p < 0.0001), whereas in the 26 asymptomatic elderly subjects, homocysteine level decreased from 24.4 microM to 18.6 microM (p < 0.0001). Plasma fibrinogen decreased whereas plasminogen and anti-thrombin increased; the differences between pre- and posttreatment values were significant in both patients and healthy subjects. Oxidative status markers showed a shift toward lower oxidative stress. This effect was observed in both study groups. An association of the therapeutic effect with the genetic polymorphism of 5,10-methylenetetrahydrofolate reductase was not detected. Folic acid supplementation to hyperhomocysteinemic subjects resulted in a decrease in total blood homocysteine concentrations; moreover, there was a tendency to reverse the coagulation status and oxidative stress.

Proteinuria is preceded by decreased nitric oxide synthesis and prevented by a NO donor in cholesterol-fed rats

BACKGROUND

Hypercholesterolemia decreases nitric oxide (NO) availability in the circulation and induces podocyte activation and renal injury in rats. It is unknown whether hypercholesterolemia decreases renal NO availability. To dissociate the injury-independent effect of hypercholesterolemia on renal NO availability from secondary effects of proteinuria, increasing concentrations of cholesterol were administered. To determine whether podocyte activation and renal injury were associated with NO deficiency, molsidomine, an exogenous NO donor, was administered to hypercholesterolemic rats.

METHODS

Female rats were fed 0, 0.5, 1, or 2% cholesterol for 24 weeks. Rats fed 2% cholesterol were also studied for two weeks. In addition rats fed 0 or 1% cholesterol received 120 mg molsidomine/L drinking water. Renal NO availability was determined by measuring renal NO synthesis and superoxide activity. Podocyte activation was monitored by desmin staining.

RESULTS

Hypercholesterolemia dose-dependently increased proteinuria. In the absence of proteinuria, hypercholesterolemia decreased renal NO synthesis (4.2 +/- 0.5 in 0.5% cholesterol vs. 6.8 +/- 0.6 pmol/min/mg protein in controls; P < 0.05). With the exception of neuronal nitric oxide synthase (nNOS), renal NOS protein mass remained unaffected. Renal superoxide activity was dose-dependently increased, thus further lowering renal NO availability. Podocyte injury was dose-dependently increased even in the absence of proteinuria (score, 40 +/- 4 in 0.5% cholesterol vs. 9 +/- 4 in controls; P < 0.05). After two weeks, hypercholesterolemia caused no proteinuria, but did cause some podocyte injury. Renal NOS activity was decreased, but glomerular endothelial NOS (eNOS) staining was unchanged. Molsidomine prevented proteinuria, podocyte activation, and all further renal injury.

CONCLUSIONS

Hypercholesterolemia decreases renal NO synthesis, and induces podocyte activation before proteinuria appears. Renal superoxide activity is increased once rats are proteinuric, further lowering renal NO availability. All of these changes can be prevented by a NO donor.

Identification, regulation and function of a novel lectin-like oxidized low-density lipoprotein receptor

Oxidatively modified low-density lipoprotein (ox-LDL) leads to endothelial activation, dysfunction and injury. Recently, a novel lectin-like receptor for ox-LDL (LOX-1) has been identified, primarily in the endothelial cells, and it allows uptake of ox-LDL into endothelial cells. This receptor is transcriptionally upregulated by tumor necrosis factor-alpha, angiotensin II, shear stress and ox-LDL itself. The expression of this receptor activates a variety of intracellular processes that lead to expression of adhesion molecules and endothelial activation. This receptor is highly expressed in the blood vessels of animals and humans with hypertension, diabetes mellitus and atherosclerosis. Expression of this receptor may also be relevant in intra-arterial thrombogenesis and myocardial ischemia-reperfusion injury. Identification and regulation of this receptor and understanding of signal transduction pathways may lead to new therapies of diseases characterized by endothelial dysfunction.

Intensive lipid lowering by statin therapy does not improve vasoreactivity in patients with type 2 diabetes

Cardiovascular disease is the most important cause of morbidity and mortality in patients with type 2 diabetes. Endothelial dysfunction predicts cardiovascular outcome. Type 2 diabetes is characterized by endothelial dysfunction, which may be caused by dyslipidemia. Statin therapy restores endothelial function in hyperlipidemic patients. Therefore, we hypothesize a beneficial effect of atorvastatin on NO-dependent vasodilation in patients with type 2 diabetes and mild dyslipidemia (low density lipoproteins >4.0 mmol/L and/or triglycerides >1.8 mmol/L). We evaluated the effect of intensive lipid lowering (4 weeks of 80 mg atorvastatin once daily) on vasoreactivity in 23 patients with type 2 diabetes by using venous occlusion plethysmography. Twenty-one control subjects were matched for age, sex, body mass index, blood pressure, and smoking habits. The ratio of blood flows in the infused (measurement [M]) and noninfused (control [C]) arm was calculated for each recording (M/C ratio), and M/C% indicates the percentage change from the baseline M/C ratio. Serotonin-induced NO-dependent vasodilation was significantly blunted (52+/-30 versus 102+/-66 M/C%, P<0.005), and nitroprusside-induced endothelium-independent vasodilation was modestly reduced (275+/-146 versus 391+/-203 M/C%, P<0.05) in patients with type 2 diabetes compared with control subjects. Despite significant reduction of total cholesterol, low density lipoproteins, and triglycerides (5.8+/-1.0 to 3.2+/-0.6 [P<0.0001], 4.1+/-1.1 to 1.8+/-0.7 [P<0.0001], and 2.2+/-1.3 to 1.4+/-0.5 [P<0.05] mmol/L, respectively), no effect on NO-dependent (59+/-44 M/C%) and endothelium-independent (292+/-202 M/C%) vasodilation was demonstrated. These data suggest that intensive lipid lowering by atorvastatin has no effect on NO availability in forearm resistance arteries in type 2 diabetic patients. Other factors, such as hyperglycemia, may be a more important contributing factor regarding impaired vasoreactivity in this patient group.

Vasoactive substances: nitric oxide and endothelial dysfunction in atherosclerosis

The endothelium synthesizes and releases nitric oxide (NO) to maintain homeostatic function. Under basal conditions, endothelium-derived NO maintains a nonthrombogenic surface, prohibits leukocyte attachment, and promotes vascular relaxation. In the setting of clinical syndromes associated with the development of atherothrombosis, there is decreased bioavailable NO owing to diminished synthesis and release in addition to increased generation of reactive oxygen species. These biochemical changes perturb significantly vascular homeostatic mechanisms and promote platelet aggregation, inflammatory cell diapedesis, and vasoconstriction. Endothelial dysfunction may be evaluated using invasive and/or noninvasive techniques, including coronary artery reactivity to acetylcholine and brachial artery ultrasonography, respectively. NO replacement therapies may be initiated to restore deficits associated with dysfunctional endothelium. Strategies to replenish bioavailable NO include the administration of organic nitrosovasodilators or NO donor compounds, therapies to improve NO synthase function, and gene therapy.

Impact of body iron status on myocardial perfusion, left ventricular function, and angiographic morphologic features in patients with hypercholesterolemia

BACKGROUND

Previous studies have shown that the effects of iron stores on atherogenesis through promotion of free radical formation and low-density lipoprotein (LDL) oxidation largely depend on the state of hypercholesterolemia (HCL) in animal models. A synergistic association of serum ferritin and LDL cholesterol with the risk of myocardial infarction has also been observed in humans.

METHODS

We sought to assess the relationship of serum iron parameters to myocardial perfusion and wall motion abnormalities and to the extent of angiographic coronary artery disease (CAD) in patients with HCL. Sixty-eight male patients (mean age 58 +/- 9 years) with hypercholesterolemia (LDL cholesterol >130 mg/dL) who had never been treated and 52 normocholesterolemic male subjects of similar age underwent coronary angiography and exercise technetium-99m sestamibi gated single-photon emission computed tomography imaging within 10 days.

RESULTS

Serum ferritin had a significant correlation with the perfusion index (r = 0.70, P <.001), the reversibility index (r = 0.68, P <.01), and the wall motion index (r = 0.54, P <.05), whereas a relatively weak correlation was observed between total iron binding capacity and perfusion index (inversely) (r = -0.59, P <.01) in patients with HCL. Iron parameters were not associated with either perfusion or wall motion indices in the normocholesterolemic group. Stepwise multiple regression analysis confirmed these results. Ferritin was a strong determinant of perfusion in patients with HCL only (beta =.55, P =.002). Iron parameters were not related to the angiographic extent of CAD as defined by angiographic vessel or extent score in either group.

CONCLUSIONS

Our data suggest that increased iron stores are closely associated with a greater extent and severity of perfusion and functional abnormalities but not with the angiographic extent of CAD in patients with HCL. Enhanced iron-mediated oxidative stress and LDL peroxidation may contribute to the hypercholesterolemia-related endothelial dysfunction and cause further impairment of myocardial perfusion and wall motion.

Endothelial dysfunction in cold-induced hypertensive rats

Endothelial dysfunction can be observed in preatherosclerotic conditions. However, its pathogenetic role in hypertension is still controversial. Endothelial-dependent changes of blood pressure (BP) and expression of endothelial nitric oxide synthase (eNOS) were evaluated in cold-induced hypertensive rats. Wistar rats were exposed to cold stress for 8 weeks. Exposure to cold stress significantly increased the systolic BP in rats. The infusion of acetylcholine significantly lowered mean arterial BP in control rats by 48 +/- 2% and by 32 +/- 1% in cold-induced hypertensive rats. The acetylcholine-induced reduction of mean arterial BP was significantly attenuated in cold-induced hypertensive rats (control rats, 45 +/- 2 mm Hg; cold-induced hypertensive rats, 34 +/- 3 mm Hg; P < .05). Administration of N(G)-nitro-L-arginine-methyl ester for 1 week significantly increased BP in control rats, whereas no effect could be observed in cold-induced hypertensive rats. In cold-induced hypertensive rats eNOS in aortic vessels was significantly reduced compared to control rats. In this nongenetic, nonsurgical animal model of cold-induced hypertensive rats an endothelial dysfunction can be observed due to reduced eNOS.

Effects of short-term feeding of a highly palatable diet on vascular reactivity in rats

BACKGROUND

Numerous studies have shown that long-term consumption of high-fat, high-energy diet results in obesity, which in turn, leads to cardiovascular disorders. However, there is little or no data on the acute effects of a highly palatable diet on vascular function.

MATERIAL AND METHODS

In this study we aimed to evaluate the changes in metabolic and vascular reactivity in Wistar rats fed a palatable diet for 2 days.

RESULTS

Two-days feeding of rats with a palatable diet did not effect body weight, fat-pad mass or gastrocnemius muscles weights. Nor there were any changes in plasma glucose, insulin or leptin levels. However, compared with chow-fed rats, palatable diet-fed rats had significantly raised plasma free fatty acids and triglycerides levels (for both, P < 0.01). Compared with chow-fed animals, vasorelaxation responses to carbamylcholine and sodium nitroprusside were significantly attenuated in palatable diet-fed rats (for both, P < 0.01). However, there were no differences in histamine-induced vasorelaxation between chow-fed and palatable diet-fed rats.

CONCLUSION

These data indicates that diet-induced endothelium-dependent and -independent vascular dysfunction occurs long before obesity develops.

Vascular endothelial growth factor synthesis in vascular smooth muscle cells is enhanced by 7-ketocholesterol and lysophosphatidylcholine independently of their effect on nitric oxide generation

Nitric oxide (NO) generated by inducible NO synthase (iNOS) enhances vascular endothelial growth factor (VEGF) synthesis in vascular smooth muscle cells (VSMC) and both NO and modified low density lipoprotein (LDL) augment VEGF production in macrophages. Oxidized LDL (oxLDL) are known inhibitors of NO generation in the cells of vascular wall. As the relationship between VEGF, iNOS and oxLDL has not been well elucidated, we studied the effect of two main components of oxLDL, 7-ketocholesterol (7-Kchol) and lysophosphatidylcholine (LPC), on VEGF and NO synthesis in rat VSMC and on VEGF synthesis in human VSMC. Both LPC and 7-Kchol significantly augmented VEGF production in rat and human VSMC. Increase in VEGF generation was related to the activation of VEGF promoter by both 7-Kchol and LPC and enhancement of VEGF mRNA transcription. In rat, VSMC IL-1beta-induced NO generation and enhanced VEGF synthesis. 7-Kchol decreased rat iNOS promoter activity, iNOS expression and NO generation, but it did not impair IL-1beta-induced VEGF synthesis. LPC did not significantly influence IL-1beta-induced NO production in rat VSMC and VEGF synthesis was significantly enhanced by combined treatment with IL-1beta and LPC in comparison to the effect of either compound alone. The results indicate that VEGF and NO synthesis in VSMC can be modulated by oxLDL. Those interactions might have an effect on the plaque growth and might be of relevance for the physiology of vascular wall cells.

Pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, attenuates renal injury in an experimental model of ischemia-reperfusion

BACKGROUND

Renal dysfunction due to ischemia-reperfusion (IR) injury is a common problem following renovascular surgery or kidney transplantation. There is a lot of emerging evidence that statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors, have anti-inflammatory properties and exert direct beneficial effects on the vascular endothelium. The aim of this study was to determine if pretreatment with pravastatin would attenuate the acute renal dysfunction that occurs following IR injury in an experimental model.

MATERIALS AND METHODS

Male Sprague-Dawley rats were randomized into four groups (n = 7 per group): control, uninephrectomy, IR group, and IR group pretreated with pravastatin (0.4 mg/kg/day for the preceding 5 days). Following a left nephrectomy the IR injury was induced by cross-clamping the right vascular pedicle for 30 min followed by reperfusion for 2 h. In a separate experiment (n = 6 per group) renal function was assessed 12 and 24 h after reperfusion.

RESULTS

IR injury causes significant renal dysfunction characterized by oliguria, 0.11 (0.05) ml/h, decreased glomerular filtration rate (GFR), 0.02 (0.01) ml/min; and marked protein leakage, 7.21 (1.3) g/L, 2 h postreperfusion. This renal dysfunction was also evident 12 and 24 h postreperfusion. This was in contrast to values of 0.61 (0.13) ml/h, 0.23 (0.01) ml/min, and 1.67 (0.12) g/L in the uninephrectomy-only group and values of 2 ml/h, 7.3 ml/min, and 0.72 g/L for uninjured time-matched controls. Pretreatment with pravastatin significantly attenuated IR-induced renal injury, improving urine production to 0.62 (0.2) ml/h and GFR to 0.14 (0.02) ml/min and diminishing protein leakage to 3.76 (0.7) g/L at the 2-h time point. This renoprotective effect was also evident 12 and 24 h postreperfusion. This renal protection was associated with an upregulation of constitutive endothelial nitric oxide synthase in the pravastatin-treated group.

CONCLUSION

These results show that pravastatin may play a role in modulating renal impairment following aortic or transplantation surgery, allowing earlier recovery from an IR injury.

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors upregulate inducible NO synthase expression and activity in vascular smooth muscle cells

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase ameliorate atherosclerosis by both cholesterol-dependent and cholesterol-independent mechanisms. We examined whether HMG-CoA reductase inhibitors affect the expression and activity of inducible NO synthase (iNOS) in cultured rat aortic vascular smooth muscle (VSM) cells. Atorvastatin (34 to 68 micromol/L) markedly increased nitrite production, an increase that was essentially abrogated by the NO synthase inhibitor N(G)-monomethyl-L-arginine (500 micromol/L). Activity of iNOS, determined by the conversion of L-arginine to L-citrulline, increased 9-fold after atorvastatin treatment. Western blot and semiquantitative reverse transcriptase-polymerase chain reaction revealed that atorvastatin (34 to 68 micromol/L) strongly upregulated iNOS protein and mRNA levels, respectively. These concentrations of atorvastatin did not cause cytotoxicity, as judged by the cell survival rate. Similarly, simvastatin and lovastatin (34 micromol/L) caused robust upregulation of the iNOS protein level. Transfection experiments demonstrated that the -1034- to 88-bp human iNOS promoter was strongly induced by atorvastatin (34 micromol/L). Electromobility and supershift assays using a nuclear factor-kappaB (NF-kappaB) consensus oligonucleotide and nuclear extracts from VSM cells as well as transfection studies using an NF-kappaB reporter plasmid suggested that the transcriptional activation of the iNOS gene by atorvastatin is not mediated via the NF-kappaB pathway. We conclude that HMG-CoA reductase inhibitors potently upregulate iNOS expression and activity in VSM cells, at least in part, by transcriptional mechanisms that do not depend on transcription factor NF-kappaB. These effects might have important implications for the impact of HMG-CoA reductase inhibitors on atherosclerosis.

Regulation of endothelial nitric oxide synthase expression in the vascular wall and in mononuclear cells from hypercholesterolemic rabbits

BACKGROUND

We recently obtained evidence demonstrating that cultured bovine endothelial cells contain cytosolic proteins that form complexes with the 3'-untranslated region of endothelial nitric oxide synthase (eNOS) mRNA and are associated with its destabilization. The aim of this study was to determine the presence of such proteins and eNOS expression in hypercholesterolemic rabbits as an in vivo model of endothelial dysfunction.

METHODS AND RESULTS

Endothelium-dependent relaxation to acetylcholine and the calcium ionophore A23187 was reduced in aortic segments from hypercholesterolemic rabbits compared with controls. Treatment of hypercholesterolemic rabbits with cerivastatin (0.1 mg. kg body wt(-1). d(-1)) restored endothelium-dependent relaxation. Aortic eNOS expression was reduced in hypercholesterolemic rabbits and was accompanied by enhanced binding activity of a 60-kDa cytosolic protein and reduced stability of eNOS mRNA. Cerivastatin treatment upregulated eNOS expression and reduced the interaction of the cytosolic protein with the 3'-untranslated region of eNOS mRNA. Mononuclear cells from hypercholesterolemic rabbits also showed a marked reduction of eNOS expression and eNOS mRNA stability and an increase in binding activity of the cytosolic protein, which were also prevented by cerivastatin treatment.

CONCLUSIONS

These results demonstrate the presence of a 60-kDa protein that binds to eNOS mRNA and reductions in eNOS expression in both vascular wall and mononuclear cells that are prevented by cerivastatin.

Reduction of oxidative stress and AT1 receptor expression by the selective oestrogen receptor modulator idoxifene

1. The beneficial vasoprotective effects of oestrogens are hampered by their side effects on secondary sexual organs. Selective oestrogen receptor modulators (SERM) such as idoxifene may exert beneficial vascular effects without influencing cancerogenesis in breast or uterus. 2. In order to investigate vascular effects of selective oestrogen receptor modulators, we examined the impact of idoxifene on production of reactive oxygen species as well as AT1 receptor expression in vascular smooth muscle cells (VSMC). 3. Idoxifene caused a concentration- and time-dependent down-regulation of AT1 receptor mRNA expression, as assessed by Northern analysis. The maximal effect was reached with 10 micromol l(-1) idoxifene after a 4 h incubation period (33+/-7% of control levels). Western blots showed a similar down-regulation of AT1 receptor protein to 36+/-11% of control levels. 4. Confocal laserscanning microscopy using the redox sensitive marker 2',7'-dichlorofluorescein (DCF) and measurement of NAD(P)H oxidase activity in cell homogenates revealed that idoxifene effectively blunted the angiotensin II-induced production of reactive oxygen species. 5. In order to investigate the signal transduction involved in SERM-induced modulation of AT1 receptor expression, VSMC were preincubation with PD98059, genistein, wortmannin, or N(omega)-Nitro-L-arginine. The results suggested that idoxifene caused AT1 receptor down-regulation through nitric oxide-dependent pathways. 6. In conclusion, idoxifene reduces angiotensin II-evoked oxidative stress in VSMC. This could in part be explained by idoxifene-induced down-regulation of AT1 receptor expression. These results demonstrate that the selective oestrogen receptor modulator idoxifene may exert beneficial vascular effects which could be useful for therapeutic regimen in postmenopausal women at risk for cardiovascular diseases.

Oxidative stress contributes to vascular endothelial dysfunction in heart failure

Congestive heart failure (HF) is characterized by inadequate nitric oxide (NO) production in the vasculature. Because NO is degraded by oxygen radicals, we hypothesized that NO is degraded faster in HF from inadequate peripheral arterial antioxidant reserves. HF was induced in male Sprague-Dawley rats by left coronary artery ligation. Vascular endothelial function was evaluated by measuring the NO-mediated vasorelaxation response to acetylcholine (ACh; 10(-9)-10(-4) M) in excised aortas. This was repeated with the free radical generator pyrogallol (20 microM) and again with pyrogallol and superoxide dismutase (SOD; 60 U/ml). Aortic and myocardial SOD activity was also determined. ACh-induced vasorelaxation was reduced in HF (n = 9) compared with normal control rats (n = 11; P < 0.001). Pyrogallol further reduced vasorelaxation in HF: 74 +/- 11% at 10(-4) M ACh versus 58 +/- 10% in normal control rats (P < 0.004). There was a trend (P = 0.06) toward reduced SOD activity in HF aortas. In conclusion, altered NO-dependent vasorelaxation in HF is in part due to excessive degradation of NO and is likely related to reduced vascular SOD activity.

Decreased nitric oxide end-products and its relationship with high density lipoprotein and oxidative stress in people with type 2 diabetes without complications

Diabetes mellitus is associated with hyperglycaemia, hyperlipoproteinaemia, increased oxidative stress and decreased nitric oxide production from endothelial cells. In the present study the aim was to determine the relationships between serum lipids, lipoproteins, erythrocyte malondialdehyde (eMDA), as a marker for oxidative stress, and serum nitrite and nitrate levels, as degradation products of nitric oxide in type 2 diabetic patients without complications. The study group included 30 patients and 30 sex- and age-matched healthy volunteers. Total cholesterol, triacylglycerol, LDL cholesterol, apo B, HbA(1c) and glucose levels in patients were significantly higher than in controls, and HDL cholesterol levels lower. Increased eMDA levels and decreased nitrate and nitrite+nitrate levels (+/-SD) were observed in patients compared to controls (87+/-22 vs 59+/-17 nmol/g-Hb (P<0.01); 11.8+/-8.6 vs 22.8+/-10.8 micromol/l (P<0.01); and 16.8+/-11.0 vs 28.8+/-11.3 micromol/l (P<0.01), respectively). When the patients were divided into two groups according to HDL cholesterol levels (< or =0.91 and >0.91 mmol/l), total plasma nitric oxide end-products were found to be decreased in patients with low HDL levels compared to those patients with high HDL levels [men, 11.7+/-6.4 vs 24.6+/-14.9 micromol/l (P<0.01); women, 12.5+/-6.6 vs 21.4+/-6.6 micromol/l (P<0.01]. Nitrite and nitrate levels were correlated with HDL cholesterol (r=0.50, P<0.05) and eMDA (r=-0.52, P<0.05). It was concluded that the patients with unregulated blood glucose levels have abnormal lipid and lipoprotein metabolism and decreased nitric oxide end-products, with relationships between nitric oxide products and dyslipidaemia, especially between low HDL cholesterol levels and increased oxidative stress.

Oxidized LDL and HDL: antagonists in atherothrombosis

Increased LDL oxidation is associated with coronary artery disease. The predictive value of circulating oxidized LDL is additive to the Global Risk Assessment Score for cardiovascular risk prediction based on age, gender, total and HDL cholesterol, diabetes, hypertension, and smoking. Circulating oxidized LDL does not originate from extensive metal ion-induced oxidation in the blood but from mild oxidation in the arterial wall by cell-associated lipoxygenase and/or myeloperoxidase. Oxidized LDL induces atherosclerosis by stimulating monocyte infiltration and smooth muscle cell migration and proliferation. It contributes to atherothrombosis by inducing endothelial cell apoptosis, and thus plaque erosion, by impairing the anticoagulant balance in endothelium, stimulating tissue factor production by smooth muscle cells, and inducing apoptosis in macrophages. HDL cholesterol levels are inversely related to risk of coronary artery disease. HDL prevents atherosclerosis by reverting the stimulatory effect of oxidized LDL on monocyte infiltration. The HDL-associated enzyme paraoxonase inhibits the oxidation of LDL. PAF-acetyl hydrolase, which circulates in association with HDL and is produced in the arterial wall by macrophages, degrades bioactive oxidized phospholipids. Both enzymes actively protect hypercholesterolemic mice against atherosclerosis. Oxidized LDL inhibits these enzymes. Thus, oxidized LDL and HDL are indeed antagonists in the development of cardiovascular disease.

Renal vascular function in hypercholesterolemia is preserved by chronic antioxidant supplementation

Hypercholesterolemia impairs systemic vascular reactivity in response to endothelium-dependent vasodilators, which may be mediated partly through increased formation of lipid peroxides. However, it is unclear whether these pathophysiological mechanisms play a role in renal vascular impairment in experimental hypercholesterolemia. Hence, pigs were studied after a 3-mo normal (n = 7) or high cholesterol (HC) (n = 7) diet, HC diet supplemented daily with antioxidant vitamins E (100 IU/kg) and C (1000 mg; HC+vitamins, n = 5), or normal diet supplemented with vitamins (N+vitamins, n = 5). Renal blood flow was measured with electron-beam computed tomography before and during infusion of acetylcholine (Ach). Endothelial function, endothelial and inducible nitric oxide synthase (NOS), and nitrotyrosine immunoreactivity were studied in renal arteries ex vivo. Despite similar cholesterol levels, LDL oxidizability (lag time, malondialdehyde, and relative electrophoretic mobility) was increased in pigs that were fed the HC diet but was significantly decreased in pigs that were fed the HC+vitamins diet. Renal blood flow response to Ach was blunted in pigs that were fed the HC diet but was preserved in pigs that were fed the HC+vitamins diet. Maximal relaxation to Ach was attenuated in pigs that were fed the HC diet compared with those that were fed the normal diet (51.5 +/- 6.4% versus 97.0 +/- 2.9%; P < 0.01) but was preserved in pigs that were fed the HC+vitamins diet (103.1 +/- 3.0%; P = 0.39) and N+vitamins diet (87.7 +/- 3.0%; P = 0.1), as were relaxation responses to calcium ionophore A23187. Vascular smooth-muscle relaxation to diethylamine was enhanced in endothelium-denuded HC vessel but was restored in pigs that were on the HC+vitamins regimen. In HC, immuno-reactivity of endothelial NOS was decreased, that of inducible NOS was increased, and both were preserved in pigs that were fed the HC+vitamins and N+vitamins diets, whereas nitrotyrosine was not detected. The present study demonstrates that antioxidant intervention in experimental HC reduces LDL oxidizability and preserves renal vascular responses to endothelium-dependent vasodilators. Therefore, this beneficial effect potentially can protect the kidney from hypercholesterolemia-induced damage.

Oxidized LDL differentially regulates MMP-1 and TIMP-1 expression in vascular endothelial cells

We have reported recently that oxidized low-density lipoprotein (oxLDL) stimulates matrix metalloproteinase-1 (MMP-1) expression in human vascular endothelial cells. The present study was conducted to examine the effect of oxLDL on expression of Tissue inhibitor of metalloproteinase-1 (TIMP-1), an endogenous inhibitor of MMPs, in human vascular endothelial cells. Our enzyme-linked immunosorbent assay and Northern blot analysis showed that oxLDL inhibited TIMP-1 secretion and expression by human umbilical vein endothelial cells. In contrast, PMA stimulated TIMP-1 expression and secretion. Both oxLDL and PMA increased MMP-1 expression and secretion significantly as previously reported. Inhibition by oxLDL of TIMP-1 expression was also observed in human aortic endothelial cells. Collagenase activity as detected by an enzymatic activity assay demonstrated, as expected, an increase in collagenase activity in the culture medium from oxLDL-treated cells as compared with that from untreated cells. The presented data indicates that oxLDL differentially regulates TIMP-1 and MMP-1 expression, whereas PMA coordinately regulates TIMP-1 and MMP-1 in vascular endothelial cells. The lack of coordination in the secretion of MMP-1 and TIMP-1 induced by oxLDL leads to an increased collagen-degrading activity that may contribute to destabilization of atherosclerotic plaques.

3-hydroxy-3-methylglutaryl coenzyme a reductase inhibition prevents endothelial NO synthase downregulation by atherogenic levels of native LDLs: balance between transcriptional and posttranscriptional regulation

Atherogenic levels of native low density lipoproteins (nLDLs) decrease the bioavailability of endothelium-derived NO and downregulate endothelial NO synthase (eNOS) expression in cultured human endothelial cells. Here, we show that simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, within the therapeutic range (0.01 to 1 micromol/L) prevented the downregulation of eNOS mRNA and protein promoted by nLDL (180 mg cholesterol/dL, 48 hours) in human umbilical vein endothelial cells. This effect of simvastatin was completely reversed by mevalonate, the product of the reaction, and to a lesser extent by farnesol and geranyl geraniol. Simvastatin significantly stabilized eNOS mRNA in cells treated with nLDL during 48 hours (eNOS mRNA half-life approximately 11 hours in controls versus >24 hours in nLDL per 0.1 micromol/L simvastatin-treated cells). The downregulation of eNOS by nLDL was abrogated by cycloheximide, an inhibitor of protein synthesis, and by N-acetyl-leucyl-leucyl-norleucinal, a protease inhibitor that reduces the catabolism of sterol regulatory element binding proteins. Sterol deprivation increased the downregulation produced by nLDL on eNOS and sterol regulatory element binding protein-2 expression levels. However, no differential modulation of the retardation bands corresponding to the putative sterol-responsive element present in the eNOS promoter was detected by electrophoretic mobility shift assay. Our results suggest that nLDL promote eNOS downregulation operating at a transcriptional level, whereas simvastatin prevents such an effect through a posttranscriptional mechanism.

Vascular function of the peripheral circulation in patients with nephrosis

BACKGROUND

Nephrotic syndrome is associated with abnormal lipoprotein metabolism and increased risk of coronary heart disease. Endothelial dysfunction, an early phase of atherogenesis that manifests as impaired flow-mediated dilation (FMD) of the peripheral circulation, may link these associations.

METHODS

We examined endothelial function of the brachial artery and forearm resistance arteries in 15 patients with nephrosis (NP), 15 patients with primary hyperlipidemia (HL) alone, and 15 normolipidemic, nonproteinuric subjects (NC) matched for age, sex, and weight. The NP and HL groups had similar serum cholesterol and triglyceride concentrations. Post-ischemic FMD (endothelium-dependent) and glyceryl trinitrate-mediated dilation (GTNMD; endothelium-independent) of the brachial artery were studied using ultrasonography and computerized edge detection software. Postischemic forearm blood flow was also measured using plethysmography.

RESULTS

Postischemic FMD of the brachial artery was significantly lower in the NP and HL groups compared with NC group (mean +/- SE): NP 4.91 +/- 0.8%, HL 4.53 +/- 0.6%, NC 8.45 +/- 0.5% (P < 0.001). There were no significant differences among the groups in baseline diameter and GTNMD of the brachial artery, nor in maximal forearm blood flow and flow debt repayment of the forearm microcirculation. Significant differences in FMD among the groups were principally related to differences in serum low-density lipoprotein cholesterol.

CONCLUSIONS

Patients with NP have abnormal endothelium-dependent but preserved endothelium-independent dilation of the brachial artery following an ischemic stimulus. Postischemic forearm microcirculatory function is unimpaired. Dyslipoproteinemia is probably the principal cause of endothelial dysfunction of conduit arteries in patients with NP and the basis for their increased risk of cardiovascular disease.

Inhibition of oxidized low-density lipoprotein-induced apoptosis in endothelial cells by nitric oxide. Peroxyl radical scavenging as an antiapoptotic mechanism

Proatherogenic oxidized low-density lipoprotein (oxLDL) induces endothelial apoptosis. We investigated the anti-apoptotic effects of intracellular and extracellular nitric oxide (*NO) donors, iron chelators, cell-permeable superoxide dismutase (SOD), glutathione peroxidase mimetics, and nitrone spin traps. Peroxynitrite (ONOO-)-modified oxLDL induced endothelial apoptosis was measured by DNA fragmentation, TUNEL assay, and caspase-3 activation. Results indicated the following: (i) the lipid fraction of oxLDL was primarily responsible for endothelial apoptosis. (ii) Endothelial apoptosis was potently inhibited by *NO donors and lipophilic phenolic antioxidants. OxLDL severely depleted Bcl-2 levels in endothelial cells and *NO donors restored Bcl-2 protein in oxLDL-treated cells. (iii) The pretreatment of a lipid fraction derived from oxLDL with sodium borohydride or potassium iodide completely abrogated apoptosis in endothelial cells, suggesting that lipid hydroperoxides induce apoptosis. (iv) Metalloporphyrins dramatically inhibited oxLDL-induced apoptosis in endothelial cells. Neither S-nitrosation of caspase-3 nor induction of Hsp70 appeared to play a significant role in the antiapoptotic mechanism of *NO in oxLDL-induced endothelial apoptosis. We propose that cellular lipid peroxyl radicals or lipid hydroperoxides induce an apoptotic signaling cascade in endothelial cells exposed to oxLDL, and that *NO inhibits apoptosis by scavenging cellular lipid peroxyl radicals.

Atherogenesis and the arginine hypothesis

In patients who have elevated levels of plasma ADMA, a relative deficiency of L-arginine has been found to contribute to the pathophysiology of athersclerosis, causing vasoconstriction, and accelerating atherogenesis. This finding--that there is a relative deficiency of L-arginine in atherosclerotic disease--is a breakthrough that will open new avenues of therapy.

Hypochlorite-modified low density lipoprotein inhibits nitric oxide synthesis in endothelial cells via an intracellular dislocalization of endothelial nitric-oxide synthase

Hypochlorous acid/hypochlorite, generated by the myeloperoxidase/H(2)O(2)/halide system of activated phagocytes, has been shown to oxidize/modify low density lipoprotein (LDL) in vitro and may be involved in the formation of atherogenic lipoproteins in vivo. Accordingly, hypochlorite-modified (lipo)proteins have been detected in human atherosclerotic lesions where they colocalize with macrophages and endothelial cells. The present study investigates the influence of hypochlorite-modified LDL on endothelial synthesis of nitric oxide (NO) measured as formation of citrulline (coproduct of NO) and cGMP (product of the NO-activated soluble guanylate cyclase) upon cell stimulation with thrombin or ionomycin. Pretreatment of human umbilical vein endothelial cells with hypochlorite-modified LDL led to a time- and concentration-dependent inhibition of agonist-induced citrulline and cGMP synthesis compared with preincubation of cells with native LDL. This inhibition was neither due to a decreased expression of endothelial NO synthase (eNOS) nor to a deficiency of its cofactor tetrahydrobiopterin. Likewise, the uptake of l-arginine, the substrate of eNOS, into the cells was not affected. Hypochlorite-modified LDL caused remarkable changes of intracellular eNOS distribution including translocation from the plasma membrane and disintegration of the Golgi location without altering myristoylation or palmitoylation of the enzyme. In contrast, cyclodextrin known to deplete plasma membrane of cholesterol and to disrupt caveolae induced only a disappearance of eNOS from the plasma membrane that was not associated with decreased agonist-induced citrulline and cGMP formation. The present findings suggest that mislocalization of NOS accounts for the reduced NO formation in human umbilical vein endothelial cells treated with hypochlorite-modified LDL and point to an important role of Golgi-located NOS in these processes. We conclude that inhibition of NO synthesis by hypochlorite-modified LDL may be an important mechanism in the development of endothelial dysfunction and early pathogenesis of atherosclerosis.

A HMG-CoA reductase inhibitor possesses a potent anti-atherosclerotic effect other than serum lipid lowering effects--the relevance of endothelial nitric oxide synthase and superoxide anion scavenging action

We have determined whether the anti-atherosclerotic effect of a 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitor (fluvastatin) is mediated through nitric oxide (NO) as well as affecting plasma lipids. NO related vascular responses, endothelial nitric oxide synthase (eNOS) mRNA and superoxide anion (O(2)(-)) release were examined in vascular walls of oophorectomized female rabbits fed 0.5% cholesterol chow for 12 weeks with or without fluvastatin (2 mg/kg per day). Serum lipid profile was not different between two groups. NO dependent responses stimulated by acetylcholine and calcium ionophore A23187 and tone related basal NO response induced by N(G)-monomethyl-L-arginine acetate (L-NMA); nitric oxide synthase inhibitor were all improved by fluvastatin treatment. Endothelium independent vasorelaxation induced by nitroglycerin was not different between the two groups of rabbits' arteries. Fluvastatin treatment increased cyclic GMP concentration in aorta of rabbits. eNOS mRNA expression and O(2)(-) release were measured in aorta using competitive reverse transcription-polymerase chain reaction (RT-PCR) and with lucigenin analogue, 2-methyl-3,7-dihydroimidazol [1,2-a]pyrazine-3-one (MCLA) chemiluminescence methods. eNOS mRNA in the endothelial cells of aorta was significantly up-regulated and O(2)(-) production was significantly reduced in fluvastatin treated rabbit aorta. Anti-macrophage staining area, but not anti-smooth muscle cell derived actin stained area in the aorta was also reduced by fluvastatin treatment. Conclusion, fluvastatin, a HMG-CoA reductase inhibitor, retards the initiation of atherosclerosis formation through the improvement of NO bioavailability by both up-regulation of eNOS mRNA and decrease of O(2)(-) production in vascular endothelial cells, and this means that part of the anti-atherosclerotic effect of fluvastatin may be due to nonlipid factors.

Pravastatin Attenuates Lower Torso Ischaemia–Reperfusion-induced Lung Injury by Upregulating Constitutive Endothelial Nitric Oxide Synthase

OBJECTIVES

to elicit whether pre-treatment with pravastatin will prevent or ameliorate the acute lung injury that occurs following lower torso ischaemia-reperfusion (IR) in an experimental animal model.

MATERIALS AND METHODS

male Sprague-Dawley rats were randomised into three groups (n=7/group). The control group underwent a sham laparotomy and aortic dissection. The second group underwent infrarenal aortic cross clamping for 30 min followed by reperfusion for 120 min. The third group pre-treated with pravastatin sodium (0.4 mg/kg/day over 5 days) were again subjected to an ischaemia-reperfusion (IR) injury. The parameters used to assess lung injury included: Wet to dry lung weight ratio (W:D), myeloperoxidase activity (MPO), protein concentration (BALprot) and neutrophil count (BAL PMN) of bronchoaveolar lavage fluid. Western blotting was used to determine the expression of constitutive endothelial nitric oxide synthase (ecNOS) within lung tissue.

RESULTS

IR causes an acute lung injury as indicated by statistically significant differences in W:D lung weight ratios, MPO activity, neutrophil count and BALprotein concentration in the IR group over that of controls. Pre-treatment with pravastatin attenuated this neutrophil infiltration and microvascular leakage. The pravastatin group showed a marked increased expression of ecNOS over that of the IR group and controls.

CONCLUSION

this data indicates that pre-treatment with pravastatin protects against ischaemia-reperfusion induced lung injury in an experimental animal model. We believe that its mechanism of action involves an upregulation of ecNOS, which increases basal expression of nitric oxide providing protective effects on the pulmonary circulation against microvascular injury.

Physiological responses to lysophosphatidic acid and related glycero-phospholipids

1-Acyl-2-hydroxy(lyso)-sn-glycero-3-phosphate (lysophosphatidic acid, LPA) has attracted a lot of attention in recent years due to the wide range of its biological effects that span the phylogenetic tree from slime mold to human. LPA can be viewed as a pleiotropic phospholipid growth factor that utilizes the same signal transduction mechanisms as traditional polypeptide growth factors; however, LPA activates these mechanism via specific G protein-coupled receptors. The concentration of LPA in serum is in the high micromolar range, making it the most abundant mitogen/survival factor present in serum, one that is often unknowingly utilized in tissue culture. The present review gives a historical perspective and a critical analysis of the LPA literature with a special emphasis on the physiological implications of its effects.

Cerivastatin prevents tumor necrosis factor-alpha-induced downregulation of endothelial nitric oxide synthase: role of endothelial cytosolic proteins

Cardiovascular disease is accompanied by an impaired endothelium-dependent vasodilatory response. Loss of endothelial nitric oxide synthase (eNOS) expression may contribute to endothelial dysfunction. The aim of the present study was to analyze the effect of cerivastatin, a novel HMG CoA reductase inhibitor, on tumor necrosis factor-alpha (TNF-alpha)-induced downregulation of eNOS protein expression in bovine aortic endothelial cells (BAEC). TNF-alpha (10 ng/ml)- incubated BAEC showed a reduced expression of eNOS protein and decreased eNOS mRNA stabilization. This effect was associated with an increased binding activity of BAEC cytosolic proteins to the 3'-untranslated region (3'UTR) of eNOS mRNA. Cerivastatin prevented TNF-alpha-induced downregulation of eNOS protein expression in a concentration-dependent manner (10(-8) to 10(-5) M). Cerivastatin also prevented the binding of the cytosolic proteins to 3'-UTR of eNOS mRNA and was associated with eNOS mRNA stabilization. The reduced expression of eNOS protein by TNF-alpha was also prevented by coincubation with cycloheximide. In addition cycloheximide inhibited the binding activity of the cytosolic proteins to 3'-UTR of eNOS mRNA, suggesting the inducible character of the mentioned-cytosolic proteins. TNF-alpha stimulated the translocation of nuclear factor-kappaB (NF-kappaB), an effect that was not modified by cerivastatin. Furthermore, an inhibitor of NF-kappaB translocation, pyrrolidine dithiocarbamate failed to modify both the downregulation of eNOS expression and the increased binding activity of the cytosolic proteins to 3'-UTR of eNOS mRNA by TNF-alpha. The effect of cerivastatin on eNOS expression and the binding activity of the cytosolic proteins were reversed by coincubation with L-mevalonate. In conclusion, cerivastatin stabilized eNOS mRNA and upregulated eNOS expression in the endothelium, and this was associated with a decreased binding activity of cytosolic proteins to 3'-UTR of eNOS mRNA. The effect of cerivastatin on the regulation of eNOS expression was independent of NF-kappaB mobilization by TNF-alpha. These findings suggest that cerivastatin may have beneficial effects on the endothelial dysfunction associated with cardiovascular diseases beyond its effect on lowering cholesterol.

Improvement of coronary artery endothelial dysfunction with lipid-lowering therapy: heterogeneity of segmental response and correlation with plasma-oxidized low density lipoprotein

OBJECTIVES

This study assessed coronary artery endothelial function in patients with hypercholesterolemia before and after lipid lowering, using quantitative angiography to examine the acetylcholine (Ach) response along the entire analyzable vessel.

BACKGROUND

Lipid lowering reverses endothelial dysfunction, but whether improvement occurs only in some segments and not others has not been established. Statistical correlation of improvement with specific lipid moieties remains undefined.

METHODS

Quantitative angiography was performed after Ach (10(-6), 10(-5), 10(-4) M) in 29 patients with coronary atherosclerosis before and 18 +/- 5.2 months after lipid-lowering treatment (statins, bile sequestrant resins). Standard lipid moieties and markers of oxidized low density lipoprotein (LDL) (immunoglobulin G and M autoantibody titers to malondialdehyde-LDL, E06 epitope) were measured serially.

RESULTS

Pre-treatment of the vessel diameters at control and with 10(-6)M, 10(-5) M and 10(-4) M Ach were 2.108 +/- 0.085, 2.086 +/- 0.087, 2.069 +/- 0.084 and 1.963 +/- 0.097 mm (M +/- SE), respectively, and increased at follow-up to 2.139 +/- 0.094, 2.119 +/- 0.086, 2.127 +/- 0.084 and 2.080 +/- 0.085 mm (p < 0.0001). Improvement in the most constricted and modest declination in the more dilated segments were observed. Change in the E06 and Apolipoprotein A-1 titers correlated with improved vasomotion (p = 0.027 and 0.005, respectively). The pre- and post-treatment levels of the E06 epitope, as well as the post-treatment IgM autoantibody titer to MDA-low density lipoprotein, also correlated (p < 0.028, < 0.001 and p < 0.004, respectively).

CONCLUSIONS

Drug treatment reverses endothelial dysfunction, but the effect is heterogeneous. Most coronary segments show enhancement, while others show declination of dilation, underscoring the importance of assessing the entire analyzable artery. Improvement in vasomotion correlates most significantly with markers of plasma-oxidized low-density lipoprotein.

Acute exposure to a high cholesterol diet attenuates myocardial ischemia-reperfusion injury in cholesteryl ester transfer protein mice

BACKGROUND

Previous experiments have demonstrated that acute exposure to a high-cholesterol diet (HCD) increases the severity of myocardial infarction in animals. Recent results suggest that the process is modulated by multiple genes and their interactions with circulating cholesterol.

DESIGN

In the present study cholesteryl-ester-transfer-protein (CETP) transgenic mice were generated and fed a normal rodent-chow diet, HCD for 1 week, or a HCD for 6 weeks in order to define the role of CETP in myocardial infarction after acute exposure to a HCD.

METHODS

Cholesterol levels in mice of all groups were measured. Separate groups of mice were exposed to 30 min of in-vivo occlusion of coronary artery and 2 h of reperfusion. We assessed the sizes of the ischemic zone and infarct using Evans blue and 2,3,5-triphenyltetrazolium chloride.

RESULTS

The extent of infarction (percentage infarct/area at risk) was significantly less (P < 0.05) after 1 week of a HCD (18.7 +/- 7.0%) than those for the normal diet group (51.4 +/- 5.5%) and the group fed a HCD for 6 weeks (44.4 +/- 5.2%). Additionally, there was significantly less infiltration of neutrophils into the ischemic-reperfused mouse hearts for mice fed a HCD for 1 week. Levels of reduced and oxidized glutathione in the hearts of CETP mice were measured for separate groups of animals. The reduced:oxidized-glutathione ratio was significantly (P < 0.01) lower for mice fed a HCD for 1 week (1.5 +/- 0.1) than it was for mice fed a normal diet (3.6 +/- 0.3) and a HCD for 6 weeks (3.3 +/- 0.2).

CONCLUSIONS

These data suggest that activity of CETP in hypercholesterolemic mice has an acute effect on size of infarct after 1 week of a HCD. This suggests that CETP induces tolerance of ischemia in the mice fed a HCD via mild oxidative stress.

Cellular regulation of endothelial nitric oxide synthase

Renal function is highly dependent on endothelium-derived nitric oxide (NO). Several renal disorders have been linked to impaired NO bioavailability. The enzyme that is responsible for the synthesis of NO within the renal endothelium is endothelial NO synthase (eNOS). eNOS-mediated NO generation is a highly regulated cellular event, which is induced by calcium-mobilizing agonists and fluid shear stress. eNOS activity is regulated at the transcriptional level but also by a variety of modifications, such as acylation and phosphorylation, by its cellular localization, and by protein-protein interactions. The present review focuses on the complex regulation of eNOS within the endothelial cell.

Induction of endothelial-leukocyte interaction by interferon-gamma requires coactivation of nuclear factor-kappaB

To determine whether nuclear factor (NF)-kappaB is necessary to confer endothelial cell responsiveness to interferon (INF)-gamma in terms of vascular cell adhesion molecule (VCAM)-1 expression and leukocyte adhesion, human endothelial cells were treated with IFN-gamma in the presence of low concentrations (LCs) of interleukin (IL)-1alpha (</=100 pg/mL), which activates NF-kappaB but does not induce VCAM-1 expression. Although IFN-gamma induced major histocompatibility complex class II antigen expression and although a high concentration of IL-1alpha (10 ng/mL) induced leukocyte adhesion and VCAM-1 expression, neither IFN-gamma nor LC IL-1alpha was able to induce VCAM-1 expression or leukocyte adhesion. However, the combination of IFN-gamma and LC IL-1alpha induced VCAM-1 expression and increased leukocyte adhesion (67% and 49% of high-concentration IL-1alpha, respectively). Electrophoretic mobility shift assays and immunoblotting of nuclear extracts showed that IFN-gamma activated signal transducers and activators of transcription (STAT)-1alpha and interferon regulatory factor (IRF)-1 but not NF-kappaB, whereas LC IL-1alpha activated NF-kappaB but not STAT-1alpha or IRF-1. Nuclear run-on studies showed that LC IL-1alpha is necessary but not sufficient for inducing VCAM-1 gene transcription and that the combination of IFN-gamma and LC IL-1alpha is required for full VCAM-1 gene transcription. These findings suggest that factors that activate NF-kappaB can synergize with IFN-gamma in promoting endothelial-leukocyte interaction.

[Cellular and molecular biology of atherosclerotic lesions]

The association of atherosclerosis with the most common risk factors including elevation of low density lipoprotein (LDL) levels, diabetes, hypertension and cigarette smoking, led to the hypothesis of "response to injury" to explain how the lesions develop. According to this hypothesis, one of the earliest events in atherogenesis is the accumulation of LDL in the arterial wall where they undergo oxidation. These LDL impair endothelial function, and thus, all the antiatherogenic properties of the endothelium. In addition, macrophages and smooth muscle cells take up these LDL, through different receptors, and become foam cells. The accumulation of foam cells in the arterial wall contributes to lesion development. Therefore, lesion development involves the activation of endothelial cells, as well as smooth muscle cells and monocytes/macrophages. In this activation different growth factors (PDGF, EGF, etc.), cytokines (IL-1b, TNFa, etc.) and the modified LDL themselves, play an important role. Through several signal transduction pathways these molecules activate transcription factors, such as the nuclear factor kappa B (NF-kB) or protooncogenes such as c-fos, c-myc, that regulate the expression of genes involved in the inflammatory/proliferative response of the lesions.

The effect of polymorphisms of MTHER gene and vitamin B on hyperhomocysteinemia

The relationship between hyperhomocysteinemia and coronary artery disease (CAD) was investigated and the influence of environmental factors (Folate, VitB12) and genetic factors [N5, N10-methylenetetrahydrofolate reductase gene (MTHFR) or MTHFR gene mutation] on plasma homocysteine (Hcy) levels and the risk of CAD observed. Fifty-one CAD patients and 30 CAD-free subjects were recruited in the study. The polymorphisms of MTHFR gene were analyzed by PCR-RFLP and plasma total Hcy levels were measured by high performance liquid chromatography with fluorescence detection. Plasma folate and vitamin B12 concentrations were measured by an automated chemiluminescence method. It was found that mean total plasma Hcy concentrations were significantly higher in CAD patients than in CAD-free subjects (P < 0.01). The differences were also apparent among the three genotypes of MTHFR gene in CAD group (P < 0.05). There was no significant difference in the genotype distributions and allele frequencies between the two groups. A strong inverse correlation was found between folate or vitamin B12 and plasma Hcy levels according to MTHFR genotype (P < 0.01). It was concluded that hyperhomocysteinemia is a new independent risk factor for CAD. However, MTHFR gene mutation alone does not relate significantly to the morbidity of CAD since hyperhomocysteinemia and its influence on the risk of CAD are decided by both environmental and genetic factors. Supplementary treatment with vitamins B can effectively lower the plasma levels of Hcy, thus maybe reducing the risk of CAD.

Nitric oxide and postangioplasty restenosis: pathological correlates and therapeutic potential

Balloon angioplasty revolutionized interventional cardiology as a nonsurgical procedure to clear a diseased artery of atherosclerotic blockage. Despite its procedural reliability, angioplasty's long-term outcome can be compromised by restenosis, the recurrence of arterial blockage in response to balloon-induced vascular trauma. Restenosis constitutes an important unmet medical need whose pathogenesis has yet to be understood fully and remains to be solved therapeutically. The radical biomediator, nitric oxide (NO), is a natural modulator of several processes contributing to postangioplasty restenosis. An arterial NO deficiency has been implicated in the establishment and progression of restenosis. Efforts to address the restenosis problem have included trials evaluating a wide range of NO-based interventions for their potential to inhibit balloon-induced arterial occlusion. All types of NO-based interventions yet investigated benefit at least one aspect of balloon injury to a naive vessel in a laboratory animal without inducing significant side effects. The extent to which this positive, albeit largely descriptive, body of experimental data can be translated into the clinic remains to be determined. Further insight into the pathogenesis of restenosis and the molecular mechanisms by which NO regulates vascular homeostasis would help bridge this gap. At present, NO supplementation represents a unique and potentially powerful approach to help control restenosis, either alone or as a pharmaceutical adjunct to a vascular device.