Hypercholesterolemia impairs myocardial perfusion and permeability: role of oxidative stress and endogenous scavenging activity

Association of High Density Cholesterol With Hyperemic Epicardial Flow and Frame Count Reserve in Patients With Moderate Coronary Lesions and Slow Coronary Flow

Background

Patients with microvascular angina and non-obstructive coronary atherosclerotic disease have an elevated risk of adverse events and all-cause mortality compared with individuals without ischaemic heart disease. The diagnosis coronary microvascular dysfunction in this setting relies on the detection of impaired coronary flow at rest or on calculation of coronary flow reserve. Previous studies demonstrate that the coronary flow reserve assessed by the corrected thrombolysis in myocardial infarction method - the frame count reserve is an objective quantitative alternative to other widely used invasive methods for microvascular status evaluation.

Purpose

We assessed the significance of clinical, hemodynamic, angiographic variables and therapy with reference to FCR in a small group of patients with up to moderate atherosclerotic coronary lesions and slow coronary flow. Materials and methods: Frame count reserve was evaluated in 15 patients without flow-limiting (>50%) coronary stenoses admitted with unstable angina. Frame count reserve was calculated by dividing the baseline corrected thrombolysis in myocardial infarction frame count (cTFC) by the cTFC assessed after intracoronary infusion of 100 µg of the calcium channel blocker - verapamil.

Results

The values of frame count reserve correlate positively with the levels of high density cholesterol (r= 0.900, p=0.001), inversely coronary flow after the application of verapamil - cTFCv (r= - 0.534, p=0.049). cTFCv was positively related with the levels of high density lipoproteins (r = - 0.645; p= 0.044) and was negatively influenced by the presence of atherosclerotic lesions at quantitative angiography (42.8±19.1 (n=8) vs 23±5.4 (n=7), p=0.029).The therapy with β-blocker and long-acting nitrate was associated with insignificantly higher frame count reserves after intracoronary verapamil compared to the continuous intake only of β-blocker or β-blocker and verapamil (2.1±0.78 vs 1.34±0.14 vs 1.70±0.70, p=NS).

Conclusions

Higher high-density lipoproteins relate to higher frame count reserves evaluated using verapamil. The improved blood flow after this microvascular vasodilator is consistently positively related to high-density cholesterol and the lack of atherosclerosis at conventional coronary angiography. The combined intake of micro- and macrovascular vasodilator could be associated with higher frame count reserves compared to therapy with β-blocker and one vasodilating drug.

Downregulation of VEGFR3 signaling alters cardiac lymphatic vessel organization and leads to a higher mortality after acute myocardial infarction

Heart has a wide lymphatic network but the importance of cardiac lymphatic system in heart diseases has remained unclear. Vascular Endothelial Growth Factor Receptor 3 (VEGFR3) is a key molecule in the development and maintenance of cardiac lymphatic vessels. Here we characterized the role of VEGFR3 in healthy hearts and after myocardial infarction (MI) by using sVEGFR3 transgenic mice expressing a soluble decoy VEGFR3 under K14 promoter and Chy mice which have an inactivating mutation in the VEGFR3 gene. Cardiac lymphatic vessels were significantly dilated in the healthy hearts of sVEGFR3 mice when compared to controls. Lymphatic vessels formed large sheet-like structures in Chy mice. Attenuated VEGFR3 signaling led to a more severe MI predisposing to a significantly higher mortality in sVEGFR3 mice than in control mice. sVEGFR3 mice displayed intramyocardial hemorrhages in the infarcted area indicating hyperpermeability of the vasculature. Furthermore, novel MRI methods TRAFF2 and TRAFF4 and histological analysis revealed a modified structure of the fibrotic infarcted area in sVEGFR3 mice. In conclusion, the downregulation of VEGFR3 signaling modifies the structure of cardiac lymphatic network and causes vascular leakiness and increased mortality after MI.

Primary proteasome inhibition results in cardiac dysfunction

AIMS

The proteasome prevents the intracellular accumulation of proteins and its impairment can lead to structural and functional alterations, as noted for the coronary vasculature in a previous study. Utilizing the same model, this study was designed to test the hypothesis that chronic proteasome inhibition (PSI) also leads to structural and functional changes of the heart.

METHODS AND RESULTS

Female domestic pigs were randomized to a normal diet without (N) or with twice-weekly subcutaneous injections of the proteasome inhibitor MLN-273 (0.08 mg/kg, N + PSI, n = 5 each group). In vivo data on cardiac structure and function as well as myocardial perfusion and microvascular permeability response to adenosine and dobutamine were obtained by electron beam computed tomography after 11 weeks. Subsequent ex vivo myocardial analyses included immunoblotting, immunostaining, TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labelling), Masson trichrome, and Congo red staining. Compared with N, an increase in LV mass was observed in N + PSI (106.5 ± 16.4 g vs. 183.1 ± 24.2 g, P < 0.05). The early to late diastolic filling ratio was increased in N + PSI vs. N (3.5 ± 0.6 vs. 1.8 ± 0.1, P < 0.05). The EF tended to be lower (46 ± 12% and 53 ± 9%, respectively) and cardiac output was significantly lower in N + PSI than in N (2.9 ± 1.1 vs. 4.7 ± 1.1 L/min, P < 0.05). Tissue analyses demonstrated an accumulation of proteasome substrates, apoptosis, and fibrosis in the PSI group. Compared with N, the myocardial perfusion response was reduced and microvascular permeability was increased in N + PSI.

CONCLUSION

The current study demonstrates that chronic proeasome inhibition affects the cardiovascular system, leading to functional and structural alteration of the heart consistent with a hypertrophic-restrictive cardiomyopathy phenotype.

Vitamin E slows the progression of hypercholesterolemia-induced oxidative stress in heart, liver and kidney

Vitamin E suppresses the hypercholesterolemia-induced oxidative stress in the heart. The objectives were to investigate if: (a) hypercholesterolemia-induced oxidative stress is similar in heart, liver, and kidney, and is dependent upon duration of hypercholesterolemia; and (b) vitamin E slows the progression of oxidative stress in these organs. The rabbits were assigned to 4 groups: I, regular diet (2 months); II, 0.25 % cholesterol diet (2 months); III, 0.25 % cholesterol diet (4 months); and IV, 0.25 % cholesterol diet (2 months) followed by 0.25 % cholesterol diet plus vitamin E (2 months). Blood samples were collected before and at the end of protocol for the measurement of total cholesterol (TC). Hearts, livers, and kidneys were removed at the end of the protocol under anesthesia for the measurement of oxidative parameters, malondialdehyde (MDA), and chemiluminescence (CL). The basal MDA levels in the heart, liver, and kidney of rabbits in Group I were similar, but increased to 14.65-, 3.18-, and 10.35-fold, respectively, with hypercholesterolemia. The increases in MDA levels were dependent upon the duration of hypercholesterolemia. Vitamin E did not alter the TC levels, but reduced the MDA levels in all organs. Hypercholesterolemia and vitamin E had variable effects on CL activity. In conclusion, (i) hypercholesterolemia induces oxidative stress in heart, liver, and kidney, the heart being the most and the liver the least susceptible to oxidative stress; (ii) oxidative stress is positively associated with duration of hypercholesterolemia; and (iii) vitamin E slows the progression of oxidative stress in these organs.

Angiotensin converting enzyme (ACE) inhibitory, antihypertensive and antihyperlipidaemic activities of protein hydrolysates from Rhopilema esculentum

Angiotensin-converting enzyme (ACE) inhibitory, antihypertensive and antihyperlipidaemic activities of protein hydrolysates (RPH) from the jellyfish Rhopilema esculentum were investigated. R. esculentum was hydrolysed sequentially with pepsin and papain, and then the hydrolysate was ultrafiltered with a 2000 Da cut-off membrane. It was found that RPH contained high levels of Gly, Glu, Pro, Asp and Ala, having potential ACE inhibitory activity in vitro with an IC(50) of 1.28 mg/ml. It was also found that systolic blood pressure was reduced markedly in spontaneously hypertensive rats after single and chronic oral administration of RPH, indicating that RPH had an antihypertensive effect. In addition, oral administration of RPH decreased total serum cholesterol and triglyceride, and increased high-density lipoprotein cholesterol in rats fed with high-fat diet. These results indicate that RPH may prove to be a promising functional food for the prevention and treatment of hypertension and hyperlipidaemia.

Short-term statin administration in hypercholesterolaemic rabbits resistant to postconditioning: effects on infarct size, endothelial nitric oxide synthase, and nitro-oxidative stress

AIMS

The effectiveness of postconditioning (POC) in hypercholesterolaemia is in dispute. We investigated the effects of 3-day lipophilc (simvastatin) or hydrophilic (pravastatin) statin treatment, without or with POC in normocholesterolaemic (Norm) and hypercholesterolaemic (Chol) rabbits.

METHODS AND RESULTS

Norm or Chol rabbits were subjected to 30 min ischaemia and randomized in two series of 12 groups each: control, simvastatin (Sim), pravastatin (Prav), POC, Sim-POC, Prav-POC, Chol, Sim-Chol, Prav-Chol, POC-Chol, Sim-POC-Chol, Prav-POC-Chol. After ischaemia, rabbits of the first series underwent 3 h reperfusion, followed by infarct size, total cholesterol, and low density lipoprotein plasma level evaluation; animals of the second series underwent 10 min reperfusion followed by tissue sampling for nitrotyrosine (NT), malondialdehyde, endothelial nitric oxide synthase (eNOS), and Akt analyses. N-nitro-l-arginine methylester (L-NAME) was given in two additional groups (POC-L-NAME and Prav-Chol-L-NAME) for infarct size assessment. All interventions reduced infarction in Norm (24.3 ± 1.3, 25.9 ± 2.8, 27.9 ± 3.1, 23.3 ± 2.3, and 33.4 ± 2.5%, in POC, Sim, Prav, Sim-POC, and Prav-POC groups, respectively, vs. 49.3 ± 1.9% in control, P < 0.05), but only Prav did so in Chol animals (25.7 ± 3.3 and 25.3 ± 3.9% in Prav-Chol and Prav-POC-Chol vs. 50.9 ± 1.7, 44.8 ± 4.3, 41.5 ± 3.5, and 49.3 ± 5.5% in Chol, Sim-Chol, POC-Chol, and Sim-POC-Chol, respectively, P < 0.05). L-NAME abolished the infarct size-limiting effect of POC and Prav-Chol. Prav induced the greatest reduction in NT, while it was the only intervention that increased myocardial eNOS and Akt in Chol rabbits (P < 0.05 vs. all others).

CONCLUSION

Prav, in contrast to same-dose Sim or POC, reduces infarction in Chol rabbits independently of lipid lowering, potentially through eNOS activation and nitro-oxidative stress attenuation.

Hypercholesterolemia and chronic ischemia alter myocardial responses to selective cyclooxygenase-2 inhibition

OBJECTIVE

Cyclooxygenase-2 inhibitors have been implicated in adverse cardiac events. We hypothesize that hypercholesterolemia and ischemia may alter the myocardial response to the cyclooxygenase-2 inhibitor celecoxib.

METHODS

Yorkshire swine fed normal chow (CX, n = 6) or high-cholesterol diet (HCX, n = 6) underwent placement of an Ameroid constrictor on the left circumflex artery and were started on celecoxib (200 mg/day). After 7 weeks, ischemic and nonischemic myocardium was analyzed for thrombogenic ratio (thromboxane content divided by prostacyclin content), total protein oxidative stress, and expression of prostacyclin synthase, thromboxane synthase, myeloperoxidase, and superoxide dismutase. Cardiac function, tissue perfusion, and vessel density were measured.

RESULTS

HCX animals were significantly hypercholesterolemic compared with CX animals. Thrombogenic ratio was significantly higher in the HCX group than in the CX group, but prostacyclin and thromboxane synthase expression was similar in all tissues. Myocardial perfusion was decreased in the HCX group compared with the CX group. Total oxidative stress, myeloperoxidase, and superoxide dismutase were increased in ischemic tissue compared with nonischemic tissues, but there was no diet-induced difference between groups. There was no difference in capillary or arteriolar density between groups. Left ventricular contractility was greater in the HCX group than in the CX group, but there was no significant difference in heart rate, mean arterial pressure, or left ventricular pressure.

CONCLUSIONS

Hypercholesterolemic patients using celecoxib may be at higher risk for thrombotic events than those with normal cholesterol, but the relationship between dyslipidemia, ischemia, and cyclooxygenase-2 inhibition is likely much more complicated than originally thought.

Relationship between surface area of nonperfused myocardium and extravascular extraction of contrast agent following coronary microembolization

Myocardial microvascular permeability and coronary sinus concentration of muscle metabolites have been shown to increase after myocardial ischemia due to epicardial coronary artery occlusion and reperfusion. However, their association with coronary microembolization is not well defined. This study tested the hypothesis that acute coronary microembolization increases microvascular permeability in the porcine heart. The left anterior descending perfusion territories of 34 anesthetized pigs (32 ± 3 kg) were embolized with equal volumes of microspheres of one of three diameters (10, 30, or 100 μm) and at three different doses for each size. Electron beam computed tomography (EBCT) was used to assess in vivo, microvascular extraction of a nonionic contrast agent (an index of microvascular permeability) before and after microembolization with microspheres at baseline and during adenosine infusion. A high-resolution three-dimensional microcomputed tomography (micro-CT) scanner was subsequently used to obtain ex vivo, the volume and corresponding surface area of the embolized myocardial islands within the perfusion territories of the microembolized coronary artery. EBCT-derived microvascular extraction of contrast agent increased within minutes after coronary microembolization (P < 0.001 vs. baseline and vs. control values). The increase in coronary microvascular permeability was highly correlated to the micro-CT-derived total surface area of the nonperfused myocardium (r = 0.83, P < 0.001). In conclusion, myocardial extravascular accumulation of contrast agent is markedly increased after coronary microembolization and its magnitude is in proportion to the surface area of the interface between the nonperfused and perfused territories.

Combined effects of niacin and chromium treatment on heart of hyperlipidemic rats

The present study was undertaken to investigate the effects of the combination of niacin and chromium(III)-chloride on heart glutathione (GSH), lipid peroxidation (LPO) levels, serum paraoxonase (PON), gamma-glutamyl transferase (GGT) activities and protein carbonyl contents (PCC) of hyperlipidemic rats. In this study, female Swiss albino rats were used. They were divided into four groups. The animals of the first group (group I) were fed with pellet chow. The rats (group II) were fed with a lipogenic diet consisting of 2% cholesterol, 0.5% cholic acid and 20% sunflower oil added to the pellet chow, and given 3% alcoholic water for 60 days. The rats (group III) were fed with the same lipogenic diet and treated by gavage technique with CrCl(3) 6H(2)O to a dose of 250 µg/kg and 100 mg/kg niacin for 45 days, 15 days after experimental animals were done hyperlipidemic. Group IV was fed with pellet chow and treated with 250 µg/kg CrCl(3) 6H(2)O and 100 mg/kg niacin for 45 days. On the 60th day, the heart tissue and blood samples were taken from animals. As a result, heart LPO, serum GGT activity and serum PCC were increased; serum PON activity and heart GSH levels were decreased in hyperlipidemic rats. Treatment with combined niacin and chromium reversed these effects. In conclusion, the combined treatment with niacin and chromium might induce a protective effect on heart tissue.

Early experimental hypertension preserves the myocardial microvasculature but aggravates cardiac injury distal to chronic coronary artery obstruction

Coronary artery disease is a leading cause of death. Hypertension (HT) increases the incidence of cardiac events, but its effect on cardiac adaptation to coexisting coronary artery stenosis (CAS) is unclear. We hypothesized that concurrent HT modulates microvascular function in chronic CAS and aggravates microvascular remodeling and myocardial injury. Four groups of pigs (n=6 each) were studied: normal, CAS, HT, and CAS+HT. CAS and HT were induced by placing local irritant coils in the left circumflex coronary artery and renal artery, respectively. Six weeks later multidetector computerized tomography (CT) was used to assess systolic and diastolic function, microvascular permeability, myocardial perfusion, and responses to adenosine in the "area at risk." Microvascular architecture, inflammation, and fibrosis were then explored in cardiac tissue. Basal myocardial perfusion was similarly decreased in CAS and CAS+HT, but its response to adenosine was significantly more attenuated in CAS. Microvascular permeability in CAS+HT was greater than in CAS and was accompanied by amplified myocardial inflammation, fibrosis, and microvascular remodeling, as well as cardiac systolic and diastolic dysfunction. On the other hand, compared with normal, micro-CT-derived microvascular (20-200 μm) transmural density decreased in CAS but not in HT or CAS+HT. We conclude that the coexistence of early renovascular HT exacerbated myocardial fibrosis and vascular remodeling distal to CAS. These changes were not mediated by loss of myocardial microvessels, which were relatively preserved, but possibly by exacerbated myocardial inflammation and fibrosis. HT modulates cardiac adaptive responses to CAS and bears cardiac functional consequences.

Hyperhomocysteinemia-induced myocardial injury after coronary artery bypass

Hyperhomocysteinemia and other major cardiovascular risk factors are associated with increased vascular oxidative stress. To access the effects preoperative plasma homocysteine levels and other atherosclerotic risk factors on myocardial ischemia-reperfusion injury after conventional coronary artery bypass, 213 patients with normal renal function were enrolled prospectively. Cardiac troponin T was measured postoperatively to determine myocardial injury. There was a significant relationship between hyperhomocysteinemia and postoperative peak troponin T. This was more marked in patients without major atherosclerotic risk factors than in those who had at least one risk factor. Moreover, among current cigarette smokers, those with the highest preoperative plasma homocysteine levels had the lowest postoperative troponin T levels. From multivariate linear regression analysis, the predictors of high postoperative troponin T were hyperhomocysteinemia, hypertension, and aortic crossclamp time, but the presence of major atherosclerotic risk factors paradoxically modified the effects of hyperhomocysteinemia on postoperative myocardial ischemia-reperfusion injury.

Antioxidants improve early survival of cardiomyoblasts after transplantation to the myocardium

PURPOSE

We tested the hypothesis that modulation of the microenvironment (using antioxidants) will increase stem cell survival in hypoxia and after transplantation to the myocardium.

PROCEDURES

Rat cardiomyoblasts were stably transfected with a reporter gene (firefly luciferase) for bioluminescence imaging (BLI). First, we examined the role of oxidative stress in cells under hypoxic conditions. Subsequently, stem cells were transplanted to the myocardium of rats using high-resolution ultrasound, and their survival was monitored daily using BLI.

RESULTS

Under hypoxia, oxidative stress was increased together with decreased cell survival compared to control cells, both of which were preserved by antioxidants. In living subjects, oxidative stress blockade increased early cell survival after transplantation to the myocardium, compared to untreated cells/animals.

CONCLUSION

Modulation of the local microenvironment (with antioxidants) improves stem cell survival. Increased understanding of the interaction between stem cells and their microenvironment will be critical to advance the field of regenerative medicine.

Relations of lipid concentrations to heart failure incidence: the Framingham Heart Study

BACKGROUND

The relations of lipid concentrations to heart failure (HF) risk have not been elucidated comprehensively.

METHODS AND RESULTS

In 6860 Framingham Heart Study participants (mean age, 44 years; 54% women) free of baseline coronary heart disease, we related high-density lipoprotein cholesterol (HDL-C) and non-HDL-C to HF incidence during long-term follow-up, adjusting for clinical covariates and myocardial infarction at baseline and updating these at follow-up examinations. We evaluated dyslipidemia-specific population burden of HF by calculating population attributable risks. During follow-up (mean of 26 years), 680 participants (49% women) developed HF. Unadjusted HF incidence in the low (<160 mg/dL) versus high (> or =190 mg/dL) non-HDL-C groups was 7.9% and 13.8%, respectively, whereas incidence in the high (> or =55 [men], > or =65 [women] mg/dL) versus low (<40 [men], <50 [women] mg/dL) HDL-C groups was 6.1% and 12.8%, respectively. In multivariable models, baseline non-HDL-C and HDL-C, modeled as continuous measures, carried HF hazards (confidence intervals) of 1.19 (1.11 to 1.27) and 0.82 (0.75 to 0.90), respectively, per SD increment. In models updating lipid concentrations every 8 years, the corresponding hazards (confidence intervals) were 1.23 (1.16 to 1.31) and 0.77 (0.70 to 0.85). Participants with high baseline non-HDL-C and those with low HDL-C experienced a 29% and 40% higher HF risk, respectively, compared with those in the desirable categories; the population attributable risks for high non-HDL-C and low HDL-C were 7.5% and 15%, respectively. Hazards associated with non-HDL-C and HDL-C remained statistically significant after additional adjustment for interim myocardial infarction.

CONCLUSIONS

Dyslipidemia carries HF risk independent of its association with myocardial infarction, suggesting that lipid modification may be a means for reducing HF risk.

Role of marginal vitamin C deficiency in atherogenesis: in vivo models and clinical studies

Vitamin C is a pivotal redox modulater in many biological reactions of which several remain poorly understood. Naturally, vitamin C has been the subject of many investigations over the past decades in relation to its possible beneficial effects on cardiovascular disease primarily based on its powerful yet general antioxidant properties. However, growing epidemiological, clinical and experimental evidence now suggests a more specific role of ascorbate in vasomotion and in the prevention of atherosclerosis. For example, in contrast to most other biological antioxidants, administration of vitamin C can apparently induce vasodilation. Millions of people worldwide can be diagnosed with vitamin C deficiency according to accepted definitions. In this perspective, the present review examines the evidence for a specific link between vitamin C deficiency and increased risk of atherosclerosis as well as the possible mechanisms by which vitamin C may exert its protective function.

Monocyte chemoattractant proteins mediate myocardial microvascular dysfunction in swine renovascular hypertension

BACKGROUND

Monocyte chemoattractant proteins (MCPs) play an important role in mediating inflammatory processes. Hypertension (HTN) is associated with inflammation as well as impaired cardiac microcirculatory function and structure, but the contribution of MCPs to these alterations remained unclear. This study tested the hypothesis that MCPs regulate cardiac microvascular function and structure in experimental HTN.

METHODS AND RESULTS

Pigs (n=6 per group) were studied after 10 weeks of normal, renovascular HTN, or renovascular HTN+ bindarit (MCPs inhibitor, 50 mg/kg/d PO). Left ventricular (LV) function, myocardial microvascular permeability, and fractional vascular volume were assessed by fast computed tomography before and after adenosine infusion (400 microg/kg/min). Myocardial fibrosis, inflammation, and microvascular remodeling were determined ex vivo. Hypertension was not altered by bindarit, but LV hypertrophy and diastolic function were improved. In response to adenosine, myocardial microvascular permeability increased in HTN (from 0.0083+/-0.0009 to 0.0103+/-0.0011 AU, P=0.038 versus baseline) and fractional vascular volume decreased, whereas both remained unchanged in normal and HTN+bindarit pigs. HTN upregulated endothelin-1 expression, myocardial inflammation, and microvascular wall thickening, which were inhibited by bindarit.

CONCLUSIONS

MCPs partly mediate myocardial inflammation, fibrosis, vascular remodeling, and impaired vascular integrity induced by hypertension. Inhibition of MCPs could potentially be a therapeutic target in hypertensive cardiomyopathy.

Myocardial microvascular function during acute coronary artery stenosis: effect of hypertension and hypercholesterolaemia

AIMS

Coronary collateral arteries (CCA) reduce cardiovascular events. We tested the hypothesis that new microvessels that proliferate in early atherosclerosis may be associated with myocardial protection during acute subtotal coronary artery obstruction (CAO).

METHODS AND RESULTS

Acute left anterior descending CAO was induced by a balloon catheter in pigs after 12 weeks of high-cholesterol (HC) diet, renovascular hypertension (HTN), or normal control. Cardiac structure, myocardial perfusion, and functional response to iv adenosine and CAO were studied in vivo using electron beam computed tomography (CT). The intra-myocardial microvessels were subsequently evaluated ex vivo using micro-CT, and myocardial expression of growth factors using immunoblotting. Basal myocardial perfusion and microvascular permeability were similar among the groups, whereas their responses to adenosine were attenuated in HC and HTN. A significant decline in myocardial perfusion in normal pigs during acute CAO was attenuated in HC and abolished in HTN. CAO also elicited an increase in normal anterior wall microvascular permeability (+202 +/- 59%, P < 0.05), which was attenuated in HC and HTN (+55 +/- 9 and +31 +/- 8%, respectively, P < 0.05 vs. normal). Microvascular (<200 microm) spatial density was significantly elevated in HC and HTN, accompanied by increased myocardial growth factor expression.

CONCLUSION

This study demonstrates that early exposure to the cardiovascular risk factors HC and HTN protects the heart from decreases in myocardial perfusion during acute subtotal CAO. This protective effect is associated with and potentially mediated by pre-emptive development of intra-myocardial microvessels that might serve as recruitable CCA.

Effect of thrombin fragment (TP508) on myocardial ischemia-reperfusion injury in hypercholesterolemic pigs

Myocardial ischemia-reperfusion (IR) injury occurs frequently in the setting of hypercholesterolemia. We investigated the potential efficacy of a novel thrombin fragment (TP508) on IR injury in a hypercholesterolemic porcine model. Twenty-one hypercholesterolemic male Yucatan pigs underwent 60 min of mid-left anterior descending coronary artery occlusion followed by 120 min of reperfusion. Pigs received either placebo (control, n = 7) or TP508 in two doses (TP508 low dose, n = 7, as bolus of 0.5 mg/kg 50 min into ischemia and an infusion of 1.25 mg.kg(-1).h(-1) during reperfusion period or TP508 high dose, n = 7, a double dose of TP508 low-dose group). Myocardial function was monitored throughout the experiment. The area at risk and myocardial necrosis were determined by Monastryl blue/triphenyl tetrazolium chloride staining. Apoptosis in the ischemic territory was assessed. Coronary microvascular reactivity to endothelium-dependent and -independent factors was measured. Myocardial necrosis was lower in both TP508-treated groups vs. control (P < 0.05). Regional left ventricular function was improved only in the TP508 high-dose group (P < 0.05). Endothelium-dependent coronary microvascular reactivity was greater in both TP508-treated groups (P < 0.05) vs. control. The expression of proteins favoring cell survival, 90-kDa heat shock protein and phospho-Bad (Ser112) was higher in the TP508 high-dose group (P < 0.05). The expression of the cell death signaling proteins, cleaved caspase-3 (P < 0.05), apoptosis-inducing factor (P < 0.05), and poly-ADP ribose polymerase (P = 0.07) was lower in the TP508 low-dose group vs. TP508 high-dose and control. The terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling positive cell count was lower in both TP508 groups compared with the control (P < 0.05). This study demonstrates that, in hypercholesterolemic pigs, TP508 decreases myocardial necrosis and apoptosis after IR. Thus TP508 may offer a novel approach in protecting the myocardium from IR injury.

Resveratrol: a promising agent in promoting cardioprotection against coronary heart diseaseThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 2 of a 2-part Special Issue)

The inverse association between alcohol intake and coronary heart disease has been consistently reported in cross-culture, case–control, and cohort studies. Over the past couple of decades, however, many studies have explained promising health benefits associated with wine consumption. Some studies suggest that red wine is more cardioprotective than white wine, possibly due to the increased content of flavanoid antioxidants found in red wine. Several experimental studies, including ours, support the evidence that these beneficial effects are due to resveratrol, the polyphenolic compound present in red wine. Many studies have provided evidence that resveratrol possesses antioxidant and antiapoptotic effects apart from activation of longevity proteins (such as SIRT-1). We have recently reported the angiogenic, antihypercholesterolemic, and antidiabetic effects of resveratrol and the mechanisms involved in reduced ventricular remodeling and increased cardiac functions. We have also shown different strategic target molecules involved in resveratrol-mediated cardioprotection. Therefore, this review discusses the potential effect of resveratrol and the mechanisms involved in resveratrol-mediated cardioprotection during myocardial infarction, hypercholesterolemia, and diabetes rendering its beneficial effects during health and disease.

Non-invasive Monitoring of Angiogenesis in Cardiology

Angiogenesis plays an important role in the pathophysiology of atherosclerosis and after myocardial infarction. Furthermore, angiogenesis has been the focus of many therapeutic strategies. In view of that, a direct and clear understanding of the role of these pathways in the living subject is needed. Molecular Imaging has emerged as a powerful tool to study biological processes non-invasively. In this review, evidence will be presented and discussed on the feasibility of different molecular imaging strategies to study the involvement of angiogenic pathways in the assessment of the atherosclerotic disease and as a tool to assess angiogenic therapy. Focus will be placed on those imaging modalities with the potential to be translated to clinical use.

Does reversal of oxidative stress and inflammation provide vascular protection?

Chronic inflammation is a pathogenic feature of atherosclerosis and cardiovascular disease mediated by substances including angiotensin II, proinflammatory cytokines, and free fatty acids. This promotes generation of reactive oxygen species in vascular endothelial cells and smooth muscle cells, which mediate injury through several mechanisms. Reciprocal relationships between endothelial dysfunction and insulin resistance as well as cross-talk between hyperlipidaemia and the renin-angiotensin-aldosterone system (RAAS) at multiple levels contribute importantly to a variety of risk factors. Therefore, combination therapy that simultaneously addresses multiple mechanisms for the pathogenesis of atherosclerosis is an attractive emerging concept for slowing progression of atherosclerosis. Combined therapy with statins, peroxisome proliferator-activated receptors, and RAAS blockade demonstrates additive beneficial effects on endothelial dysfunction and insulin resistance when compared with monotherapies in patients with cardiovascular risk factors due to both distinct and interrelated mechanisms. These additive beneficial effects of combined therapies are consistent with laboratory and recent clinical studies. Thus, combination therapy may be an important paradigm for treating and slowing progression of atherosclerosis, coronary heart disease, and co-morbid metabolic disorders characterized by endothelial dysfunction and insulin resistance.

Microcirculation and oxidative stress

The microcirculation is a complex and integrated system, transporting oxygen and nutrients to the cells. The key component of this system is the endothelium, contributing to the local balance between pro and anti-inflammatory mediators, hemostatic balance, as well as vascular permeability and cell proliferation. A constant shear stress maintains vascular endothelium homeostasis while perturbed shear stress leads to changes in secretion of vasodilator and vasoconstrictor agents. Increased oxidative stress is a major pathogenetic mechanism of endothelial dysfunction by decreasing NO bioavailability, promoting inflammation and participating in activation of intracellular signals cascade, so influencing ion channels activation, signal transduction pathways, cytoskeleton remodelling, intercellular communication and ultimately gene expression. Targeting the microvascular inflammation and oxidative stress is a fascinating approach for novel therapies in order to decrease morbidity and mortality of chronic and acute diseases.

Baroreflex sensitivity and oxidative stress in the LDL receptor knockout mice

This study aims at observing the effect of low-density lipoprotein (LDL) receptor deficiency in cholesterol blood levels, baroreflex sensitivity (BRS), nitric oxide (NO) bioavailability, and oxidative stress. The lack of LDL receptors in mice significantly increased the cholesterol blood levels (179+/-35 vs. 109+/-13mg/dL) in the knockout (KO) mice compared to control. There was no difference in basal mean arterial pressure and heart rate between the groups. However, in KO mice the BRS was significantly attenuated and the antioxidant enzyme activities, measured in erythrocytes and heart, were significantly decreased. On the other hand, the oxidative damage measured by chemiluminescence and carbonyls was increased, while total plasma nitrate levels were lower in KO mice, indicating a decrease in NO availability. In conclusion, these results indicate that the lack of LDL receptor increased cholesterol blood levels, induced oxidative stress and decreased BRS.

Effect of gestational hypercholesterolaemia on omental vasoreactivity, placental enzyme activity and transplacental passage of normal and oxidised fatty acids

OBJECTIVE

Maternal hypercholesterolaemia during pregnancy increases lipid peroxidation in mothers and fetuses and programs increased susceptibility to atherosclerosis later in life. The objective of this study was to elucidate the role of the placenta in mediating oxidative stress from mother to offspring.

DESIGN

Comparison between normo- and hypercholesterolaemic mothers (n = 36 each) and their children.

SETTING

Obstetric wards, hospitals of the University of Naples and Regione Campania.

POPULATION

Healthy primiparas delivering by caesarean section.

METHODS

Biochemical measurements of oxidative stress and serum leptin in cord plasma and placenta, immunochemistry of placenta microvessels, and vasoreactivity studies were performed.

MAIN OUTCOME MEASURES

Oxidative status (i.e. lipid composition and content of oxidised fatty acids, activity of pro- and antioxidant enzymes, immunohistochemical presence of oxidation-specific epitopes) in maternal and cord blood and in placental tissue, as well as vascular reactivity in omental arteries.

RESULTS

Hypercholesterolaemia during pregnancy was associated with extensive changes in fatty acid composition of both maternal and cord blood lipids, sufficient to alter vasoreactivity of omental vessels. Results also indicated that the placenta is not only subject to substantial oxidative stress, but that it may further increase fetal oxidative stress through changes of pro- and antioxidant enzyme activities.

CONCLUSIONS

The placenta plays an important role in both transmitting and enhancing pathogenic effects of gestational hypercholesterolaemia.

Antioxidant vitamins induce angiogenesis in the normal pig kidney

The effects of chronic supplementation with antioxidant vitamins on angiogenesis are controversial. The aim of the present study was to evaluate in kidneys of normal pigs the effect of chronic supplementation with vitamins E and C, at doses that are effective in reducing oxidative stress and attenuating angiogenesis under pathological conditions. Domestic pigs were randomized to receive a 12-wk normal diet without ( n = 6) or with antioxidant vitamins supplementation (1g/day vitamin C, 100 IU·kg−1·day−1 vitamin E; n = 6). Electron beam computed tomography (CT) was used to evaluate renal cortical vascular function in vivo, and micro-CT was to assess the spatial density and average diameter of cortical microvessels (diameter <500 μm) ex vivo. Oxidative stress and expressions of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF)-1α were evaluated in renal tissue. The effects of increasing concentrations of the same vitamins on redox status and angiogenesis were also evaluated in human umbilical vascular endothelial cells (HUVEC). Compared with normal pigs, the density of cortical transmural microvessels was significantly greater in vitamin-supplemented pigs (149.0 ± 11.7 vs. 333.8 ± 48.1 vessel/cm2, P < 0.05), whereas the cortical perfusion response to ACh was impaired. This was accompanied by a significant increase in tissue oxidative stress and levels of VEGF and HIF-1α. A low dose of antioxidant decreased, whereas a high dose increased, HUVEC oxidative stress and angiogenesis, which was partly mediated by hydrogen peroxide. Antioxidant vitamin supplementation can increase tissue oxidative redox and microvascular proliferation in the normal kidney, probably due to a biphasic effect that depends on basal redox balance.

Early changes in coronary artery wall structure detected by microcomputed tomography in experimental hypercholesterolemia

Changes in the structure of the artery wall commence shortly after exposure to cardiovascular risk factors, such as hypercholesterolemia (HC), but may be difficult to detect. The ability to study vascular wall structure could be helpful in evaluation of the factors that instigate atherosclerosis and its pathomechanisms. The present study tested the hypothesis that early morphological changes in coronary arteries of hypercholesterolemic (HC) pigs can be detected using the novel X-ray contrast agent OsO(4) and three-dimensional micro-computed tomography (CT). Two groups of pigs were studied after they were fed a normal or an HC (2% cholesterol) diet for 12 wk. Hearts were harvested, coronary arteries were injected with 1% OsO(4) solution, and cardiac samples (6-mum-thick) were scanned by micro-CT. Layers of the epicardial coronary artery wall, early lesions, and perivascular OsO(4) accumulation were determined. Leakage of OsO(4) from myocardial microvessels was used to assess vascular permeability, which was correlated with immunoreactivity of vascular endothelial growth factor in corresponding histological cross sections. OsO(4) enhanced the visualization of coronary artery wall layers and facilitated detection of early lesions in HC in longitudinal tomographic sections of vascular segments. Increased density of perivascular OsO(4) in HC was correlated with increased vascular endothelial growth factor expression and suggested increased microvascular permeability. The use of OsO(4) as a contrast agent in micro-CT allows three-dimensional visualization of coronary artery wall structure, early lesion formation, and changes in vascular permeability. Therefore, this technique can be a useful tool in atherosclerosis research.

Evaluation of porcine myocardial microvascular permeability and fractional vascular volume using 64-slice helical computed tomography (CT)

OBJECTIVES

Myocardial microvascular permeability-surface area product (MPSP) and fractional vascular volume (FVV), indices of endothelial function and microvascular perfusion, can be noninvasively evaluated by electron beam computed tomography (EBCT), but it remains unknown whether comparable assessments can be obtained with 64-slice multidetector CT (CT-64).

METHODS

We studied 12 pigs with both EBCT and CT-64 in randomized order 1 week apart, before and during IV adenosine infusion. Myocardial attenuation changes in the cardiac wall were assessed after a central-venous injection of iopamidol. Time-attenuation curves were analyzed using both indicator-dilution and Patlak models to calculate MPSP and FVV.

RESULTS

CT-64 and EBCT assessments of basal MPSP obtained by the Patlak method were similar (0.37 +/- 0.03 vs. 0.37 +/- 0.04 mL/min/g), as was its response to adenosine, and correlated significantly (r = 0.87). Patlak FVV was also similar between CT-64 and EBCT at baseline (0.08 +/- 0.02 vs. 0.07 +/- 0.02 mL blood/mL) and during adenosine, and correlated well (r = 0.93). MPSP and FVV estimated by the indicator-dilution method were not significantly correlated.

CONCLUSIONS

CT-64 assessments of myocardial MPSP and FVV may not be reliable when using indicator-dilution analysis, likely due to its sensitivity to scan duration. However, CT-64 assessments obtained using the Patlak model are feasible.

Impaired myocardial perfusion reserve in experimental hypercholesterolemia is independent of myocardial neovascularization

Our objective was to investigate the functional role of hypercholesterolemia-associated myocardial neovascularization in early atherosclerosis using the antiangiogenic thalidomide. Experimental atherosclerosis is characterized by myocardial neovascularization, associated with a decrease in myocardial perfusion response to challenge, coronary endothelial dysfunction, and high oxidative stress. However, the functional significance of these neovessels is not known. Three groups of pigs (n = 6 each) were studied after 12 wk of normal or hypercholesterolemic diet without (HC) or with thalidomide (HC + Thal). Myocardial perfusion and permeability were assessed at baseline and in response to cardiac challenge, using electron beam computed tomography, and coronary endothelial function was assessed using organ chambers. Myocardial samples were scanned ex vivo with a three-dimensional microscopic computed tomography scanner, and the spatial density of the myocardial microvessels was quantified. Growth factors and oxidative stress were measured in the myocardial tissue. As a results of these procedures, myocardial perfusion response to adenosine and dobutamine was blunted in both HC and HC + Thal pigs compared with normal pigs (P < 0.05, HC and HC + Thal vs. normal) as was the coronary endothelial function. Myocardial permeability response to adenosine was increased in both HC and HC + Thal pigs compared with normal pigs (P < 0.05, HC and HC + Thal vs. normal, and HC + Thal vs. HC). The microvascular density was increased in HC pigs compared with normal pigs but normalized in HC + Thal pigs (P < 0.001 HC vs. normal and HC + Thal). HC + Thal pigs showed decreased expression of Flk-1 and basic FGF but increased expression of VEGF compared with normal and HC pigs. Oxidative stress was increased in both HC and HC + Thal pigs compared with normal pigs. In conclusion, chronic administration of thalidomide attenuates myocardial neovascularization in experimental HC pigs without affecting myocardial perfusion response to stimulation. This suggests that the myocardial neovascularization may not contribute to the attenuated myocardial perfusion response in hypercholesterolemia.

Assessment of Myocardial Microvascular Function: New Opportunities in Fast Computed Tomography

It has been increasingly recognized that the initial site of cardiac damage in several forms of cardiovascular disease resides in the microcirculation. Noninvasive or minimally invasive evaluation of myocardial microvascular functional attributes, such as myocardial perfusion or microvascular permeability, could be an invaluable tool in the clinical practice. Advances in the field of computed tomography over the past three decades culminated in the advent of fast scanners, which show promise to provide both fine cardiac anatomic detail and quantification of the function of the myocardial microcirculation. This review describes the approach and utility of measurements of myocardial microvascular function obtained with state-of-the-art cardiac computed tomography.

Statin and resveratrol in combination induces cardioprotection against myocardial infarction in hypercholesterolemic rat

Hypercholesterolemia (HC) is a common health problem that significantly increases risk of cardiovascular disease. Both statin (S) and resveratrol (R) demonstrated cardioprotection through nitric oxide-dependent mechanism. Therefore, the present study was undertaken to determine whether combination therapy with statin and resveratrol is more cardioprotective than individual treatment groups in ischemic rat heart model. The rats were fed with 2% high cholesterol diet and after 8 weeks of high cholesterol diet the animals were treated with statin (1 mg/kg bw/day) and resveratrol (20 mg/kg bw/day) for 2 weeks. The rats were assigned to: (1) Control (C), (2) HC, (3) HCR, (4) HCS and (5) HCRS. The hearts, subjected to 30-min global ischemia followed by 120-min reperfusion were used as experimental model. The left ventricular functional recovery (+dp/dt(max)) was found to be significantly better in the HCRS (1926+/-43), HCR (1556+/-65) and HCS (1635+/-40) compared to HC group (1127+/-16). The infarct sizes in the HCRS, HCS and HCR groups were 37+/-3.6, 43+/-3.3 and 44+/-4.2 respectively compared to 53+/-4.6 in HC. The lipid level was found to be decreased in all the treatment groups when compared to HC more significantly in HCS and HCRS groups when compared to HCR. Increased phosphorylation of Akt and eNOS was also observed in all the treatment groups resulting in decreased extent of cardiomyocyte apoptosis but the extent of reduction in apoptosis was more significant in HCRS group compared to all other groups. In vivo rat myocardial infarction (MI) model subjected to 1 week of permanent left descending coronary artery (LAD) occlusion documented increased capillary density in HCR and HCRS treated group when compared to HCS treatment group. We also documented increased beta-catenin translocation and increased VEGF mRNA expression in all treatment groups. Thus, we conclude that the acute as well as chronic protection afforded by combination treatment with statin and resveratrol may be due to pro-angiogenic, anti-hyperlipidemic and anti-apoptotic effects and long-term effects may be caused by increased neo-vascularization of the MI zone leading to less ventricular remodeling.

Redox-sensitive myocardial remodeling and dysfunction in swine diet-induced experimental hypercholesterolemia

OBJECTIVES

The effects of hypercholesterolemia (HC) on the myocardium and the underlying mechanisms are unclear. We tested the hypothesis that diet-induced HC-induced myocardial fibrosis by regulating the transforming growth factor (TGF)-beta pathway and apoptosis through increased oxidative stress, and that these would be functionally consequential.

METHODS

Three groups of pigs (n=6 each) were studied after 12 weeks of normal or 2% HC diet, or HC+antioxidant supplementation. Cardiac function was evaluated by electron beam computed tomography, while fibrogenic mechanisms and apoptosis were evaluated in myocardial tissue.

RESULTS

HC-induced myocardial fibrosis was accompanied by increased ratio of interstitial collagen I/III (1.4+/-0.3 versus 0.5+/-0.1 in normal, p<0.05), expression of TGF-beta1 and its downstream smad mediators, as well as myocyte apoptosis. These alterations were also associated with a decrease in diastolic filling rate compared to normal (134.0+/-10.6 ml/s versus 70.3+/-14.3 ml/s, p<0.05), but were attenuated in HC animals chronically supplemented with antioxidants.

CONCLUSIONS

Myocardial injury elicited by experimental HC includes redox-sensitive increases in TGF-beta1 expression and apoptosis, which are associated with diastolic dysfunction. These observations underscore a role of increased oxidative stress in modulating myocardial tissue remodeling and dysfunction in vivo in HC.

Role of oxidative stress in remodeling of the myocardial microcirculation in hypertension

OBJECTIVE

We tested the hypothesis that in early hypertension (HT), increased oxidative stress leads to myocardial microvascular remodeling.

METHODS AND RESULTS

Pigs were studied after a 12-week observation: normal (n=8), untreated renovascular HT (n=8), or HT+chronic antioxidant supplementation (HT+A, n=6). Left ventricular muscle mass (LVMM) and myocardial blood flow (MBF) reserve were determined using electron beam computer tomography (CT), and the spatial density and tortuousity of myocardial microvessels (<500 microm) was then measured in myocardial samples with micro-CT. Myocardial microvascular morphology, oxidative stress, inflammation, and growth factor expression were determined in vitro. HT and HT+A had similarly increased arterial pressure and LVMM, but only HT showed impaired MBF response to adenosine. Compared with normal, HT had increased spatial density of myocardial microvessels, which was preserved in HT+A (111.8+/-7.8, 166.3+/-15.7, and 106.4+/-6.1 vessels per cm2, respectively). HT also showed microvascular wall thickening, increased systemic and tissue oxidative stress, inflammation, and expression of vascular endothelial growth factor and its receptor Flk-1, most of which were attenuated by antioxidants.

CONCLUSIONS

Myocardial microvascular remodeling in early HT is accompanied by tissue oxidative stress, inflammation, and altered growth factor expression, and attenuated by antioxidant intervention. This study underscores a role of increased oxidative stress in modulating myocardial microvascular architecture in early HT.

Role of lupeol and lupeol linoleate on lipemic–oxidative stress in experimental hypercholesterolemia

Epidemiological studies have shown that there is a positive correlation between the incidence of coronary heart disease (CHD) and the blood cholesterol level. To study the effect of plant derived triterpene, lupeol and its ester lupeol linoleate, on blood lipid status and oxidant stress in heart and hemolysate, male albino Wistar rats were fed high cholesterol diet (normal rat chow supplemented with 4% cholesterol and 1% cholic acid; HCD) for 30 days. A significant increase (p<0.05) in plasma total cholesterol (4.22 fold) and triglycerides (1.7 fold) was observed in HCD fed rats, along with elevated LDL (3.56 fold) and VLDL (1.99 fold) cholesterol and decreased HDL cholesterol (34.14%). Treatment with lupeol and its derivative normalized the lipid profile. The significant increase (p<0.05) in lipid peroxidation (LPO) was paralleled by significantly diminished (p<0.05) activities of antioxidant enzymes (SOD, CAT and GPx) and decreased (p<0.05) concentration of antioxidant molecules (GSH, Vit C and Vit E) in cardiac tissue and hemolysate of HCD fed rats. The oxidative tissue injury in hypercholesterolemic rats was substantiated by the increase in cardiac marker, serum CPK and the drop in its activity in the heart tissue. Lupeol and lupeol linoleate treatment decreased the LPO levels and increased enzymatic and nonenzymatic antioxidants. CPK activity in the treated group was comparable with that of the control. These observations highlight the beneficial effects of the triterpene, lupeol and its linoleate ester derivative, in ameliorating the lipidemic-oxidative abnormalities in the early stage of hypercholesterolemic atherosclerosis.

Chronic antioxidant supplementation impairs coronary endothelial function and myocardial perfusion in normal pigs

Experimental studies have shown the beneficial effects of antioxidant supplementation on endothelial function in the presence of increased endogenous oxidative stress, whereas limited data are available under normal conditions. The present study tested the hypothesis that in normal pigs long-term antioxidants would have deleterious effects on the cardiovascular system. Normal domestic pigs (V, n=6) were studied 12 weeks after dietary supplementation with vitamin E (100 IU/kg per day) and vitamin C (1 g/day) and compared with normal controls (C, n=7). Myocardial perfusion and permeability index were evaluated by electron beam computed tomography after intravenous adenosine and dobutamine. Coronary endothelial function was evaluated in vitro by organ chamber and coronary tissue studied by immunoblotting and staining. Myocardial perfusion response was lower in V than in C after adenosine (10.1+/-4.5 versus 53.4+/-5.2%; P<0.01) and dobutamine (V, 78.4+/-8.1; C, 193.0+/-39.0%; P<0.05). The permeability index increased in V after adenosine (48.8+/-5.1%) and dobutamine (59.9+/-13.6%) and did not change in C. Coronary vasodilation to bradykinin and substance P was lower in V than in C. Moreover, in V, coronary nitrotyrosine and superoxide content was significantly higher than in C. The groups had similar total monomer expression of endothelial nitric oxide synthase, whereas the dimerized form, reflecting coupled enzyme, was lower in V. These findings suggest that long-term experimental antioxidant vitamin supplementation in normal pigs impairs myocardial perfusion and coronary endothelial function via an increased level of oxidative stress in the arterial wall, which may be partly related to the uncoupling of endothelial nitric oxide synthase and/or the direct prooxidant effect of vitamin radicals.

Acute inhibition of the endogenous xanthine oxidase improves renal hemodynamics in hypercholesterolemic pigs

Hypercholesterolemia (HC), a major risk factor for onset and progression of renal disease, is associated with increased oxidative stress, potentially causing endothelial dysfunction. One of the sources of superoxide anion is xanthine oxidase (XO), but its contribution to renal endothelial function in HC remains unclear. We tested the hypothesis that XO modulates renal hemodynamics and endothelial function in HC pigs. Four groups (n = 23) of female domestic pigs were studied 12 wk after either normal (n = 11) or HC diet (n = 12). Oxidative stress was assessed by plasma isoprostanes and oxidized LDL, and the XO system by plasma uric acid, urinary xanthine, and renal XO expression (by immunoblotting and immunohistochemistry). Renal hemodynamics and function were studied with electron beam-computed tomography before and after endothelium-dependent (ACh) and -independent (sodium nitroprusside) challenge, during a concurrent intrarenal infusion of either oxypurinol or saline (n = 5-6 in each group). HC showed elevated oxidative stress, higher plasma uric acid (23.8 +/- 3.8 vs. 6.2 +/- 0.8 microM/mM creatinine, P = 0.001), lower urinary xanthine, and greater renal XO expression compared with normal. Inhibition of XO in HC significantly improved the blunted responses to ACh of cortical perfusion (13.5 +/- 12.1 and 37.2 +/- 10.6%, P = 0.01 and P = not significant vs. baseline, respectively), renal blood flow, and glomerular filtration rate; restored medullary perfusion; and improved the blunted cortical perfusion response to sodium nitroprusside. This study demonstrates that the endogenous XO system is activated in swine HC. Furthermore, it suggests an important role for XO in regulation of renal hemodynamics, function, and endothelial function in experimental HC.

Functional and structural remodeling of the myocardial microvasculature in early experimental hypertension

Advanced hypertension (HT), associated with left ventricular hypertrophy (LVH), impairs myocardial microvascular function and structure and leads to increased myocardial hypoxia and growth factor activation. However, the effect of HT on microvascular architecture and its relation to microvascular function, before the development of LVH (early HT), remains unclear. By way of method, pigs were studied after 12 wk of renovascular HT (n = 7) or control (n = 7) animals. Myocardial microvascular function (blood volume and blood flow at baseline and in response to adenosine) was assessed by using electron beam computed tomography (CT). Microvascular architecture was subsequently studied ex vivo using micro-CT, and microvessels (diameter, <500 microm) were counted in situ in three-dimensional images (40-microm on-a-side cubic voxels). Myocardial expression of vascular endothelial growth factor, basic fibroblast growth factor, and hypoxia-inducible factor-1alpha were also measured. By way of results, left ventricular muscle mass was similar between the groups. The blood volume response to intravenous adenosine was attenuated in HT animals compared with normal animals (+7.4 +/- 17.0 vs. +46.2 +/- 12.3% compared with baseline, P = 0.48 and P = 0.01, respectively). Microvascular spatial density in HT animals was significantly elevated compared with normal animals (246 +/- 26 vs. 125 +/- 20 vessels/cm2, P < 0.05) and correlated inversely with the blood volume response to adenosine. Growth factors expression was increased in HT animals compared with control animals. In conclusion, early HT elicits changes in myocardial microvascular architecture, which are associated with microvascular dysfunction and precede changes in muscle mass. These observations underscore the direct and early effects of HT on the myocardial vasculature.

Myocardial ischemia and coronary microvascular vasomotion: the impact of hypercholesterolemia

Coronary microvascular dilation in response to myocardial ischemia is an important defense mechanism for minimizing heart injury. Since myocardial ischemia is an intense stimulus for a living body, many biologic signals that affect the vascular tone are activated. Recent evidence demonstrated that among them, ischemic myocardium-derived factors play dominant roles as mediators of ischemic vasodilation, and that ischemic myocardium releases vasoconstrictor signals simultaneously. Hypercholesterolemia, a major risk factor for coronary atherosclerosis, is known to produce microvascular dysfunction, although it does not produce atherosclerotic lesions at the microvascular level. A recent bioassay study demonstrated that the vasodilator signal transduction from the myocardium to coronary microvessels is severely impaired in hypercholesterolemia. It is likely that redox-sensitive mechanisms play a major role in the impairment of the defensive responses. The present understanding of the mechanism of ischemic vasodilation and the impact of hypercholesterolemia on coronary microvascular regulation shall be discussed in this review.

Differential effect of experimental hypertension and hypercholesterolemia on adventitial remodeling

OBJECTIVE

Intima-media remodeling, as frequently assessed by changes in the external elastic lamina-to-lumen area (EELLA), is well-described in coronary artery disease in contrast to adventitial remodeling, especially in the early disease stage.

METHOD AND RESULTS

Female domestic pigs were randomized to one of the following 12-week treatment groups: normal diet (N; n=6), high-cholesterol diet (HC; n=6), or renovascular hypertension (HT; n=4). Low-density lipoprotein (LDL) cholesterol serum concentration was higher in HC than in N and HT (395.5+/-106 versus 38.6+/-14 and 37.2+/-6.8 mg/dL; P<0.05 for both). Mean arterial pressure was higher in HT than in N and HC (141.3+/-21 versus 107.4+/-8.9 and 109.4+/-7.8 mm Hg; P<0.05 for both). EELLA ratio, as assessed by morphometry, was similar in N, HC, and HTN (1.03+/-0.32 versus 0.95+/-0.29 and 1.01+/-0.09; P<0.05 for both). Coronary vasa vasorum density, as assessed by 3-dimensional micro-computed tomography, was higher in HC than in N and HT (3.4+/-1.0 versus 1.9+/-0.3 and 2.0+/-1.2; P<0.05 for both). In contrast, immunostaining showed a higher collagen III content and the presence of adventitial myofibroblasts in HT compared with N and HC.

CONCLUSIONS

The current study suggests that adventitial remodeling precedes intima and media remodeling of coronary arteries early after exposure to hypercholesterolemia and hypertension, with distinct qualitative differences between them. Intima-media remodeling is well-described in coronary artery disease in contrast to adventitial remodeling. Results of the current study on coronary arteries of pigs, randomized to 12 weeks of normal diet (N), hypercholesterolemic diet (HC), or renovascular hypertensive (HT), indicate that adventitial remodeling precedes intima-media remodeling early after risk factor exposure with distinct qualitative differences.

Impaired left ventricular diastolic function during isometric exercise in asymptomatic patients with hyperlipidaemia

BACKGROUND

Left ventricular (LV) diastolic dysfunction is an early sign, and may be more sensitive indicator, of ischaemic heart disease (IHD) than systolic dysfunction.

METHODS

LV diastolic function was assessed during isometric exercise (IME) in 37 consecutive normotensive hyperlipidaemics (LIP), without cardiac history or symptoms. Each patient underwent a stress ECG test and 2-D echo and Doppler cardiography. During the latter, transmitral flow at rest and at peak standardised IME using handgrip was studied. From the tracings, the E/A (peak velocity of the early/atrial components), the contribution of atrial systole to LV filling (ACF), the deceleration time (DT) of the E wave and the isovolumic relaxation time (IVRT) were calculated. Results were compared to 37 age-matched normal healthy volunteers (NOR).

RESULTS

Resting E/A was not different between NOR and the LIP. A significant reduction in E/A with IME was observed in LIP but not in NOR. Impaired LV filling (shown by E/A<1) was demonstrated in five patients (13%) at rest and in 20 patients (54%) at peak IME. All NOR had E/A>1 suggesting normal LV filling. Fifteen of the 30 patients with negative stress ECG test demonstrated LV diastolic dysfunction. ACF was higher in LIP than NOR and increased significantly (P<0.005) by 23% during IME. DT and IVRT in LIP were not different from NOR. In neither NOR nor LIP, were the LV diastolic functional parameters related to gender, smoking habit or levels of total cholesterol, LDL- or HDL-cholesterol or triglycerides.

CONCLUSION

The prevalence of LV diastolic dysfunction in asymptomatic patients with hyperlipidaemia despite a negative stress ECG test may be evidence of early underlying pre-clinical myocardial ischaemia.

Salubrious effect of low molecular weight heparin on atherogenic diet-induced cardiac, hepatic and renal lipid peroxidation and collapse of antioxidant defences

The present work showcases the distressing picture of oxidative stress in the cardiac, hepatic and renal tissues, in an experimental model based on early phase atherogenesis. The protection rendered by LMWH intervention forms part of the same study. Male Wistar rats of 140 +/- 10 g were categorized as four groups. One group served as untreated control and another as LMWH drug control group. Two groups were fed a hypercholesterolemic atherogenic diet (rat chow supplemented with 4% cholesterol, 1% cholic acid and 0.5% thiouracil; CCT diet) for 2 weeks; one of these groups received LMWH treatment of 300 microg/day/rat for 7 days. The biochemical index of tissue lipid peroxidation (LPO) was assessed in terms of MDA formation. Heart, liver and kidney tissues of CCT-diet fed rats showed significantly elevated levels of LPO. In the early phase atherosclerotic group, we observed abnormal changes in the activities/levels of tissue enzymic (superoxide dismutase, catalase and glutathione peroxidase) and non-enzymic (reduced glutathione, ascorbate and alpha-tocopherol) antioxidants. We report normalized LPO levels and antioxidant defences in the atherogenic rats treated with LMWH. Thus the present study highlights the hepatic, cardiac and renal oxidative changes induced by experimental atherogenesis, and the protection rendered by LMWH treatment in atherosclerotic cardiovascular conditions.

Role of vasa vasorum in transendothelial solute transport in the coronary vessel wall: a study with cryostatic micro-CT

Using cryostatic microscopic computed tomography (micro-CT), we sought to determine the role of coronary vasa vasorum (VV) in transendothelial solute transport in arteries with normal and increased permeability due to high plasma cholesterol levels. In 6-mo-old pigs on a normal (n=23) and 2% high cholesterol (HC) diet (n=8), 2-cm segments of the proximal left anterior descending coronary arteries were removed in vivo after a selective injection of X-ray contrast solution. Harvesting of the specimens occurred at 0, 15, 25, 35, or 45 s after completion of the contrast injection. Specimens were snap frozen and scanned in our cryostatic micro-CT. The spatial distribution of contrast in the coronary artery wall was quantified using the CT images. Right coronary arteries were infused with Microfil to determine VV density (VV/mm2) and the cumulative lumen surface area (mm2/mm3). Transendothelial diffusion of contrast into the coronary vessel wall is a dynamic process starting at both the subintima and the adventitia. The subintimal opacification moves as a wave toward the adventitia, whereas the adventitial wave resolves. The coronary vessel wall in animals on a HC diet shows higher opacification than in normal coronary arteries without an increase of VV total luminal surface area. The loss of endothelial integrity in hypercholesterolemia significantly alters VV solute washin to, and washout from, the coronary artery wall.

Comparison of acute and chronic antioxidant interventions in experimental renovascular disease

Reactive oxygen species (ROS) can modulate renal hemodynamics and function both directly, by leading to vasoconstriction, and indirectly, by inducing renal inflammation and tissue growth. The involvement of oxidative stress in the pathogenesis of renovascular disease (RVD) is increasingly recognized, but the relative contribution of long-term tissue injury to renal dysfunction remains unclear. We hypothesized that functional and structural alterations elicited by oxidative stress in RVD would be more effectively modulated by chronic than by acute antioxidant intervention. Renal hemodynamics and function were quantified in vivo in pigs using electron-beam computed tomography at baseline and after vasoactive challenge (ACh and sodium nitroprusside); after 12 wk of RVD (simulated by concurrent hypercholesterolemia and renal artery stenosis, n = 7); RVD acutely infused with the SOD-mimetic tempol (RVD+tempol, n = 7); RVD chronically supplemented with antioxidant vitamins C (1 g) and E (100 IU/kg; RVD+vitamins, n = 7); or control (normal, n = 7). Renal tissue was studied ex vivo using immunoblotting and immunohistochemistry. Basal renal blood flow (RBF) and glomerular filtration rate were similarly decreased in all RVD groups. ACh-stimulated RBF remained unchanged in RVD, increased in RVD+tempol, but further increased (similarly to normal) in RVD+vitamins ( P < 0.05 vs. RVD). Furthermore, RVD+vitamins also showed a decreased presence of superoxide anion, decreased NAD(P)H-oxidase and nitrotyrosine expression, increased endothelial nitric oxide synthase expression, and attenuated renal fibrosis. Chronic antioxidant intervention in early RVD improved renal hemodynamic responses more effectively than acute intervention, likely due to increased nitric oxide bioavailability and decreased structural injury. These suggest that chronic tissue changes play an important role in renal compromise mediated by oxidative stress in RVD.