calcimycin and Hypercholesterolemia

N(1)-methylnicotinamide (MNA(+)) has until recently been thought to be a biologically inactive product of nicotinamide metabolism in the pyridine nucleotides pathway. However, the latest observations imply that MNA(+) may exert antithrombotic and anti-inflammatory effects through direct action on the endothelium. We examined both in vivo and in vitro whether the compound might induce vasorelaxation in human blood vessels through the improvement of nitric oxide (NO) bioavailability and a reduction of oxidative stress mediated by endothelial NO synthase (eNOS) function. MNA(+) treatment (100 mg/m(2) orally) in healthy normocholesterolemic and hypercholesterolemic subjects increased the l-arginine (l-NMMA)-inhibitable flow-mediated dilation (FMD) of brachial artery responses that also positively correlated with MNA(+) plasma concentrations (r=0.73 for normocholesterolemics and r=0.78 for hypercholesterolemics; P<0.0001). MNA(+) increased FMD at the same concentration range at which it enhanced NO release from cultured human endothelial cells after stimulation with either the receptor-dependent (acetylcholine) or the receptor-independent endothelial NO synthase agonists (calcium ionophore A23187). MNA(+) restored the endothelial NO synthase agonist-stimulated NO release after the exposure of the cells to oxidized low-density lipoprotein. This effect was also associated with the normalization of the [NO]/[superoxide] balance in the endothelial cells. Taken together, the increased NO bioavailability in the endothelium contributes to the vasorelaxating properties of MNA(+). Targeting eNOS with MNA(+) might be therapeutically relevant for functional disorders of the endothelium, such as hypercholesterolemia and atherosclerosis.

Topics: Acetylcholine; Adult; Brachial Artery; Calcimycin; Cells, Cultured; Dose-Response Relationship, Drug; Double-Blind Method; Endothelium, Vascular; Humans; Hypercholesterolemia; In Vitro Techniques; Niacinamide; Nitric Oxide; Nitric Oxide Synthase Type III; Oxidative Stress; Oxygen; Vasodilation

Inflammation plays a pivotal role in the pathophysiology of cardiovascular disease, (CVD) and leukotrienes may play a role in atherogenesis. Statins reduce mortality from CVD by reducing LDL cholesterol and potentially by other (pleiotropic) mechanisms. The aim of this study was to investigate if atorvastatin exerts an anti-inflammatory effect by reducing leukotriene B₄ (LTB₄) formation from stimulated neutrophils in patients treated with coronary artery bypass grafting. The study was a randomized, placebo-controlled, double-blinded crossover study. Patients (n=80) were allocated to 80 mg atorvastatin or placebo for 6 weeks before crossing over to the opposite treatment for another 6 weeks. There was no significant correlation between baseline LDL cholesterol levels on formation of LTB₄, and atorvastatin had no effect on LTB₄ formation. Hence, this study does not support any effect of atorvastatin on LTB₄ formation as part of the explanation for its beneficial effect on CVD.

Topics: Aged; Anti-Inflammatory Agents, Non-Steroidal; Atorvastatin; Calcimycin; Calcium Ionophores; Cholesterol, LDL; Combined Modality Therapy; Coronary Artery Bypass; Coronary Disease; Cross-Over Studies; Double-Blind Method; Female; Heptanoic Acids; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypercholesterolemia; Leukotriene B4; Male; Middle Aged; Neutrophil Activation; Neutrophils; Pyrroles

Neutrophils can synthesize leukotriene B4 (LTB4) by activating the 5-lipoxygenase (5-LO)signaling pathway. LTB4 is a pro-inflammatory mediator associated with the etiology and progression of atherosclerosis. It can increase function and number of neutrophils in an autocrine manner. Since hypercholesterolemia is associated with an increase in the number and function of neutrophils, we hypothesized that this effect could be mediated through increased production of LTB4 in neutrophils.. Hypercholesterolemia was modeled in Wistar rats by feeding them with a high cholesterol diet. The induction of hypercholesterolemia caused an increase in the plasma levels of LTB4, following lipopolysaccharide stimulation. This effect was recapitulated in vitro, both in the presence and absence of stimulation with the activator of 5-LO, A23187. Neutrophils in hypercholesterolemia rats expressed similar total levels of 5-LO as control rats, but displayed increased nuclear localization of 5-LO, as well as elevated levels of phosphorylated 5-LO and ERK1/2. In vitro, MβCD/cholesterol complexes enriched cholesterol in neutrophils, resulted in similar changes in 5-LO/LTB4. In addition, these alterations could be inhibited with the ERK inhibitor PD98059.. Hypercholesterolemia increases LTB4 production in neutrophils by increasing the nuclear localization of 5-LO, which is the result of its phosphorylation by activated ERK1/2.

Topics: Animals; Arachidonate 5-Lipoxygenase; Calcimycin; Cell Nucleus; Cholesterol; Female; Hypercholesterolemia; Leukotriene B4; MAP Kinase Signaling System; Neutrophils; Rats; Rats, Wistar; Signal Transduction

Dyslipidemia increases the risks for atherosclerosis in part by impairing endothelial integrity; endothelial progenitor cells (EPCs) play a pivotal role in reendothelialization. In this study, we investigated the mechanism whereby oxidized low-density lipoprotein (oxLDL) affects the function of differentiated EPCs (EDCs). In EDCs expanded in vitro from EPCs isolated from human cord blood, we measured EDC responses to both copper-oxidized LDL and L5, an electronegative LDL minimally oxidized in vivo in patients with hypercholesterolemia. OxLDL induced apoptosis of EDCs and impaired their response to nitric oxide. We found that the key to oxLDL-induced apoptosis in both EDCs and endothelial cells is the induction of a conformational change of Bax, leading to Bax activation without altering its expression. The conformationally changed Bax translocated to the mitochondria and stimulated apoptosis, as Bax knockdown prevented oxLDL-induced apoptosis in EDCs. The activation of Bax is mediated by an increase in p53 and knockdown of p53 abolished oxLDL-induced activation of Bax and apoptosis. OxLDL activated p53 through production of mitochondria-derived reactive oxygen species. In EDCs treated with a recombinant adenovirus expressing superoxide dismutase or N-acetyl-cysteine (but not catalase), the p53-Bax pathway activated by oxLDL was blocked, and apoptosis was prevented. Of importance, treatment of EDC with low-concentration L5 stimulated superoxide dismutase expression, which significantly attenuated apoptosis in EDCs exposed to high-concentration L5. These findings suggest that exposure of EDCs and endothelial cells to either experimentally prepared or naturally occurring modified LDL results in an increased transfer of mitochondria-derived superoxide anion to p53, which stimulates a conformational change in Bax favoring its translocation to the mitochondria with resultant apoptosis of these cells.

Topics: AC133 Antigen; Animals; Antigens, CD; Apoptosis; bcl-2-Associated X Protein; Calcimycin; Carotid Arteries; Cell Differentiation; Cells, Cultured; Endothelium, Vascular; Fetal Blood; Glycoproteins; Humans; Hypercholesterolemia; Ionophores; Lipoproteins, LDL; Mitochondria; Peptides; Protein Conformation; Reactive Oxygen Species; RNA, Small Interfering; Sheep; Stem Cells; Tumor Suppressor Protein p53; Vasodilation

Chronic exercise in healthy or hypercholesteremic animals for at least two months improves their vascular functions. This study is to examine whether short-term exercise training protocols can correct early-stage vascular dysfunction induced by high-cholesterol diet feeding. Male New Zealand White rabbits were fed for 2, 4 or 6 weeks with rabbit chow with or without the addition of 2% (w/w) cholesterol. They were further divided into control and exercise groups. Animals in exercise groups ran on a leveled treadmill for the same time periods as diet intervention. At the end of experiments, femoral arteries were dissected, loaded with fura 2-AM, and mounted in a tissue flow chamber. Phenylephrine-precontracted vessel specimens were exposed to acetylcholine. The endothelial intracellular calcium elevation and vasorelaxation were determined simultaneously under an epifluorescence microscope with ratio imaging capability. En face oil red O staining was used to evaluate fatty streak formation. Our results showed that 1) high-cholesterol diet feeding for > or = 4 weeks caused lipid deposition, reduced the acetylcholine-evoked endothelial calcium signaling, and impaired both endothelium-dependent and endothelium-independent vascular responses in a time-dependent manner; 2) vasorelaxation at given levels of endothelial intracellular calcium elevation decreased in hypercholesterolemia; 3) concomitant exercise program had reverse effects. We conclude that high-cholesterol diet intervention for as short as 4 weeks induces vascular structural changes, impairs endothelial intracellular calcium signaling and vasodilatation in rabbit femoral arteries. Short-term exercise training in parallel completely eliminates these adverse effects so long as the diet intervention is no more than 6 weeks.

Topics: Acetylcholine; Animals; Calcimycin; Calcium Signaling; Cholesterol, Dietary; Endothelium, Vascular; Femoral Artery; Hypercholesterolemia; Male; Nitroprusside; Phenylephrine; Physical Conditioning, Animal; Rabbits; Vasodilation

Coronary endothelial dysfunction is associated with an increase in cardiac events. Hypercholesterolemia (HC) and hypertension (HT) are both associated with endothelial dysfunction, and their coexistence is associated with an increased incidence of cardiac events in epidemiological studies. However, pathogenic mechanisms are poorly understood. Here we studied the effects of coexisting HC and HT on coronary endothelial function.. Four groups of pigs were studied after 12 weeks of a normal diet (n=9), a 2% HC diet (n=9), HT (achieved by unilateral renal artery stenosis, n=8), or HC+HT (n=6). Coronary endothelial function was tested, in epicardial arteries and arterioles, by using organ chamber techniques. Oxidative stress was measured in coronary artery tissue. Vasodilatory response to bradykinin and calcium ionophore was significantly impaired in animals with HC+HT compared with each risk factor alone (P<0.05 for both). In animals with coexistent HC and HT, the increase in oxidative stress was more pronounced compared with each risk factor alone (P<0.05). Furthermore, chronic antioxidant supplementation significantly improved coronary artery vasoreactivity.. These results suggest that HC and HT have a synergistic deleterious effect on coronary endothelial function, associated with increased oxidative stress. This interaction may contribute to the increased incidence of coronary heart disease and cardiac events seen when HC and HT coexist.

Topics: Animals; Antioxidants; Ascorbic Acid; Bradykinin; Calcimycin; Coronary Artery Disease; Coronary Vessels; Cyclic GMP; Diet, Atherogenic; Endothelin-1; Endothelium, Vascular; Female; Hemodynamics; Hypercholesterolemia; Hypertension, Renovascular; Lipids; Nitric Oxide; Nitroprusside; Oxidative Stress; Renal Artery Obstruction; Renin; Substance P; Swine; Vasodilator Agents; Vitamin E

This study was to investigate the effects of chronic exercise on vasodilatation and endothelial intracellular calcium (EC [Ca2+]i) signaling in atherosclerotic animals.. For 8 weeks, male New Zealand White rabbits were fed rabbit chow with or without the addition of 2% cholesterol. They were further divided into control and exercise groups. Animals in the exercise groups ran on a leveled treadmill at 0.88 km/h for 10 to 60 minutes gradually for 5 days per week for a total of 8 weeks. At the end of experiments, femoral arteries were dissected, loaded with fura 2-AM, and mounted in a tissue flow chamber. PE-precontracted vessel specimens were exposed to acetylcholine (ACh). The EC [Ca2+]i elevation and vasorelaxation were determined simultaneously under an epifluorescence microscope equipped with a ratio-imaging capability. Our results showed the following: (1) high cholesterol diet feeding caused lipid deposition on vascular surface, reduced the ACh-evoked EC [Ca2+]i elevation, and impaired endothelium-dependent and endothelium-independent vascular responses, but chronic exercise had the opposite effects; (2) ACh-induced vasorelaxation was associated with EC [Ca2+]i elevation in all groups; and (3) vasorelaxation at high levels of EC [Ca2+]i elevation decreased in hypercholesterolemia.. Our data suggest that hypercholesterolemia induces vascular structural changes and impairs EC [Ca2+]i signaling and vasodilatation, whereas chronic exercise partially reverses these adverse effects.

Topics: Acetylcholine; Animals; Arteriosclerosis; Azo Compounds; Calcimycin; Calcium; Calcium Signaling; Citrate (si)-Synthase; Coloring Agents; Endothelium, Vascular; Femoral Artery; Hypercholesterolemia; In Vitro Techniques; Lipid Metabolism; Lipids; Male; Muscle Contraction; Muscle, Skeletal; Nitroprusside; Phenylephrine; Physical Conditioning, Animal; Rabbits; Tunica Intima; Vasodilation; Vasodilator Agents

Hyperlipidemia may increase endothelial damage and promote accelerated atherogenesis in graft coronary vasculopathy. To study the effects of hypercholesterolemia on coronary endothelial dysfunction, intimal hyperplasia, and lipid content, a porcine model of heterotopic heart transplantation, allowing nonacute rejection without immunosuppressive drugs, was used. A high cholesterol diet was fed to donor and recipient swine 1 month before and after transplantation. The endothelial function of coronary arteries of native and transplanted hearts from cholesterol-fed animals was studied in organ chambers 30 days after implantation and compared with endothelial function in arteries from animals fed a normal diet. The total serum cholesterol increased 3-fold in donors and recipients. Endothelium-dependent relaxations to serotonin, to the alpha(2)-adrenergic agonist UK14,304, and to the direct G-protein activator sodium fluoride were decreased significantly in allografted hearts compared with native hearts from both groups. Relaxations to the calcium ionophore A23187 and bradykinin were decreased significantly in allografts from animals fed the high cholesterol diet. The prevalence of intimal hyperplasia was significantly increased in coronary arteries from hypercholesterolemic swine. There was a significant increase in the lipid content of allograft arteries of hypercholesterolemic recipients. Hypercholesterolemia causes a general coronary endothelial dysfunction, increases the prevalence of intimal hyperplasia, and augments the incorporation of lipids in the vascular wall after heart transplantation. Hyperlipidemia accelerates graft coronary atherosclerosis through its effects on the endothelium.

Topics: Adrenergic alpha-Agonists; Animals; Arteriosclerosis; Biological Transport; Brimonidine Tartrate; Calcimycin; Calcium; Cholesterol, HDL; Cholesterol, LDL; Coronary Vessels; Diet, Atherogenic; Dinoprost; Dose-Response Relationship, Drug; Endothelium, Vascular; Erythrocyte Count; Female; Free Radical Scavengers; Heart Transplantation; Hematocrit; Hemoglobins; Hypercholesterolemia; Hyperplasia; Ionophores; Male; Myocardium; Postoperative Period; Potassium Chloride; Quinoxalines; Serotonin; Swine; Transplantation, Homologous; Tunica Intima; Vasodilation

In an experimental model of atherosclerosis we investigated whether rabbits fed an atherogenic diet (0.25% cholesterol, 3% coconut oil) develop endothelial dysfunction accompanied with increased infarct mass compared to normal fed rabbits and, whether hypercholesterolemia would interfere with the beneficial outcome of ischemic preconditioning observed in normal rabbits. After four weeks on either a normal or an atherogenic diet, New Zealand White rabbits (n=7 in each group) were subjected to 30 min of myocardial ischemia by occlusion of a branch of the left anterior descending coronary artery (LAD) followed by 2 hours of reperfusion (infarct studies). For ischemic preconditioning experiments, LAD was additionally occluded twice for 5 min followed by 10 min reperfusion before the long-lasting (30 min) ischemia. Infarct mass was evaluated by triphenyl-tetrazolium staining. Besides the assessment of aortic endothelium-dependent function and NO-release, aortic and cardiac vessels were inspected for atherosclerotic lesions. Total cholesterol serum levels in rabbits on an atherogenic diet were significantly higher (15.3+/-2.7 mmol/L) than those on a standard diet (0.65+/-0.08 mmol/L). The aortas and heart vessels were without any histological evidence of atherosclerosis, whereas endothelial dysfunction and significantly reduced calcium-ionophore stimulated endothelial NO-release were found in isolated aortic rings of hypercholesterolemic animals. Rabbits on a standard diet showed an infarct mass (related to the area at risk) of 41+/-33%, which was reduced to 21+/-2% by ischemic preconditioning (49% decrease, p<0.05). In rabbits on an atherogenic diet, infarct mass was significantly increased to 63+/-3% (52% increase versus standard diet). Interestingly, hypercholesterolemia did not affect the beneficial influence of ischemic preconditioning; infarct mass (21+/-3%, p<0.05 vs hypercholesterolemia) was similar to rabbits on a standard diet with ischemic preconditioning. Our results show that experimental hypercholesterolemia increases infarct mass in nonpreconditioned hearts but it does not interfere with the reduction of infarct mass elicited by preconditioning. This may suggest that NO produced by the endothelium is not a prime factor in the cardioprotective mechanism of preconditioning.

Topics: Animals; Aorta, Thoracic; Arteriosclerosis; Calcimycin; Cholesterol; Diet, Atherogenic; Disease Models, Animal; Endothelium, Vascular; Enzyme Inhibitors; Free Radical Scavengers; Hypercholesterolemia; Ionophores; Ischemic Preconditioning, Myocardial; Male; Myocardial Infarction; NG-Nitroarginine Methyl Ester; Nitric Oxide; Polyethylene Glycols; Potassium Chloride; Rabbits; Superoxide Dismutase; Vasodilation

Hypercholesterolemia is a central pathogenic factor of endothelial dysfunction caused in part by an impairment of endothelial nitric oxide (NO) production through mechanisms that remain poorly characterized. The activity of the endothelial isoform of NO synthase (eNOS) was recently shown to be modulated by its reciprocal interactions with the stimulatory Ca2+-calmodulin complex and the inhibitory protein caveolin. We examined whether hypercholesterolemia may reduce NO production through alteration of this regulatory equilibrium. Bovine aortic endothelial cells were cultured in the presence of serum obtained from normocholesterolemic (NC) or hypercholesterolemic (HC) human volunteers. Exposure of endothelial cells to the HC serum upregulated caveolin abundance without any measurable effect on eNOS protein levels. This effect of HC serum was associated with an impairment of basal NO release paralleled by an increase in inhibitory caveolin-eNOS complex formation. Similar treatment with HC serum significantly attenuated the NO production stimulated by the calcium ionophore A23187. Accordingly, higher calmodulin levels were required to disrupt the enhanced caveolin-eNOS heterocomplex from HC serum-treated cells. Finally, cell exposure to the low-density lipoprotein (LDL) fraction alone dose-dependently reproduced the inhibition of basal and stimulated NO release, as well as the upregulation of caveolin expression and its heterocomplex formation with eNOS, which were unaffected by cotreatment with antioxidants. Together, our data establish a new mechanism for the cholesterol-induced impairment of NO production through the modulation of caveolin abundance in endothelial cells, a mechanism that may participate in the pathogenesis of endothelial dysfunction and the proatherogenic effects of hypercholesterolemia.

Topics: Allosteric Regulation; Animals; Calcimycin; Calcium; Calmodulin; Cattle; Caveolin 1; Caveolins; Cells, Cultured; Endothelium, Vascular; Humans; Hypercholesterolemia; Ion-Selective Electrodes; Lipoproteins, LDL; Membrane Proteins; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Precipitin Tests; Protein Binding

In animal models, a hypercholesterolemic diet induces areas of deendothelialization and impairs endothelium-dependent vasorelaxation. Angiogenic growth factors increase endothelial cell growth in vivo. This study was thus designed to test the hypothesis that chronic administration of basic fibroblast growth factor (bFGF) in hypercholesterolemic rabbits might restore normal physiological responses to endothelium-dependent agonists. After feeding on a 2% cholesterol diet for 6 wk, 14 New Zealand White rabbits received twice-weekly intravenous boluses of either 2.5 microg bFGF (hypercholesterolemic bFGF group, n = 6) or placebo (hypercholesterolemic control group, n = 8) for 3 wk and were killed for assessment of in vitro vasoreactivity and for histological analysis. Six animals fed with standard rabbit diet were used to assess normal responses. Endothelium-dependent responses to acetylcholine and to the calcium ionophore A-23187 were reduced in the hypercholesterolemic control group compared with normal rabbits. Hypercholesterolemic animals treated with bFGF had significantly better endothelium-dependent responses than hypercholesterolemic rabbits not treated with bFGF. Endothelium-independent responses did not differ significantly among the three groups. A similar degree of plaque formation was observed in control- and bFGF-treated hypercholesterolemic rabbits. These results show that, in this model of atherosclerosis, bFGF has a highly beneficial effect on the functional responses of atherosclerotic vessels and does not have a deleterious effect on the degree of plaque formation.

Topics: Acetylcholine; Animals; Aorta, Thoracic; Calcimycin; Endothelium, Vascular; Fibroblast Growth Factor 2; Hypercholesterolemia; Ionophores; Male; Rabbits; Reference Values; Vasodilation

We examined the vascular structure and endothelium-dependent relaxation in two genetic models of hypercholesterolemia: apolipoprotein E (apoE)-knockout mice and combined apoE/LDL receptor-double-knockout mice. Intimal area was increased markedly in proximal segments of thoracic aortas from apoE/LDL receptor-knockout mice [0.13 +/- 0.03 (mean +/- SE) mm2] compared with normal (C57BL/6J) mice (0.002 +/- 0.002 mm2, P < .05). Despite intimal thickening, the vascular lumen was not smaller in the aortas of apoE/LDL receptor-knockout mice (0.52 +/- 0.03 mm2) than in normal mice (0.50 +/- 0.03 mm2). In apoE-deficient mice, intimal thickening was minimal or absent, even though the concentration of plasma cholesterol was only modestly less than that in the double-knockout mouse (14.9 +/- 1.1 vs 18.0 +/- 1.2 mmol/L, respectively, P < .05). Relaxation of the aorta was examined in vitro in vascular rings precontracted with U46619. In normal mice, acetylcholine produced relaxation, which was markedly attenuated by the nitric oxide synthase inhibitor NG-nitro-L-arginine (100 microM). Relaxation to acetylcholine and the calcium ionophore A23187 was normal in apoE-deficient mice (in which lesions were minimal) but greatly impaired in the proximal segments of thoracic aortas of apoE/LDL receptor-deficient mice, which contained atherosclerotic lesions. Vasorelaxation to nitroprusside was similar in normal and apoE-knockout mice, with modest but statistically significant impairment in atherosclerotic segments of apoE/LDL receptor-knockout mice. In distal segments of the thoracic aorta of apoE/LDL receptor-deficient mice, atherosclerotic lesions were minimal or absent, and the endothelium-dependent relaxation to acetylcholine and calcium ionophore was normal. Thus, in apoE/LDL receptor-knockout mice (a genetic model of hyperlipidemia), there is vascular remodeling with preservation of the aortic lumen despite marked intimal thickening, with impairment of endothelium-dependent relaxation to receptor- and nonreceptor-mediated agonists. Atherosclerosis may be accelerated in the apoE/LDL receptor-double-knockout mouse compared with the apoE-knockout strain alone. We speculate that other factors, such as the absence of LDL receptors, may contribute to the differences in the extent of atherosclerosis in these two models of hyperlipidemia.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acetylcholine; Animals; Aorta, Thoracic; Aortic Diseases; Apolipoproteins E; Arteriosclerosis; Calcimycin; Calcium; Disease Models, Animal; Endothelium, Vascular; Enzyme Inhibitors; Female; Hypercholesterolemia; Ionophores; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle Relaxation; Nitric Oxide Synthase; Nitroarginine; Receptors, LDL; Superoxide Dismutase; Vasoconstrictor Agents

We examined the effects of taurine on levels of low-density lipoprotein (LDL) cholesterol and glucose, and an endothelium-dependent relaxation in response to acetylcholine in cholesterol-fed or streptozotocin-induced diabetic mice. The acetylcholine-induced concentration-dependent relaxation was significantly attenuated in aortic rings from cholesterol-fed and streptozotocin-induced diabetic mice. The attenuated vasodilation in both cholesterol-fed and streptozotocin-induced diabetic mice was normalized by the chronic administration of taurine. The endothelium-independent relaxation of aortic rings induced by sodium nitroprusside was not significantly different between control, cholesterol-fed and streptozotocin-induced diabetic mice. The increased serum levels of LDL cholesterol in cholesterol-fed and diabetic mice were returned to normal by the chronic administration of taurine. The chronic administration of taurine had no effects on serum glucose levels. These results suggest that the impaired endothelium-dependent vasodilation seen in both cholesterol-fed and streptozotocin-diabetic mice can be normalized by the chronic administration of taurine and this effect may be, at least in part, due to lowering of serum LDL levels.

Topics: Acetylcholine; Animals; Aorta; Blood Glucose; Calcimycin; Cholesterol, LDL; Diabetes Mellitus, Experimental; Dose-Response Relationship, Drug; Endothelium, Vascular; Hypercholesterolemia; In Vitro Techniques; Ionophores; Male; Mice; Mice, Inbred ICR; Taurine; Vasodilation

The lipoxygenase product 15-hydroxyeicosatetraenoic acid (15-HETE) was shown to be the most important eicosanoid formed in the atherosclerotic rabbit aorta. The aim of the present study was to compare the effects of 15-HETE and its hydroperoxy precursor 15-HpETE with those of other vasoconstrictor and vasodilator agents in arteries from rabbits fed either a control or a cholesterol-rich diet for 16 and 30 weeks. 5-Hydroxytryptamine (5-HT) aggregated platelets and thrombin caused contractions of isolated rabbit aortas. The contractile responses elicited by platelets from control animals were similar to those evoked by platelets from atherosclerotic rabbits. After 16 weeks of hypercholesterolemia, the contractile responses were either augmented (5-HT), unchanged (platelets) or reduced (thrombin). After 30 weeks of hypercholesterolemia, the responses to all contractile agents used had decreased. In both aortas and pulmonary arteries the endothelium-dependent relaxations to the calcium ionophore, A23167, and to acetylcholine were progressively lost and the endothelium-independent relaxations to nitroglycerin were reduced by the progressing hypercholesterolemia. The 15-lipoxygenase metabolites contracted the isolated thoracic aorta and pulmonary artery from control rabbits and to a lesser extent those of the cholesterol-fed rabbits. After raising the tone in these vessels with prostaglandin F2 alpha PGF2 alpha) or noradrenaline, 15-HpETE induced relaxations which were not significantly influenced by the development of fatty streaks. Our data illustrate that the contractions of the blood vessel wall to 15-HETE, like those to other vasoconstrictors, are markedly reduced by developing atherosclerosis. In contrast, the relaxations to 15-HpETE in the rabbit arteries remain unaltered after 16 to 30 weeks of hypercholesterolemia. This is unlike the reactions to other vasodilators, which are markedly reduced.

Topics: Acetylcholine; Animals; Arachidonate 15-Lipoxygenase; Arteriosclerosis; Calcimycin; Dinoprost; Hydroxyeicosatetraenoic Acids; Hypercholesterolemia; In Vitro Techniques; Leukotrienes; Lipid Peroxides; Male; Muscle, Smooth, Vascular; Nitroglycerin; Platelet Aggregation; Rabbits; Thrombin; Vasoconstrictor Agents; Vasodilator Agents

We investigated the effect of hypercholesterolemia on the vascular reactivity of thoracic aortas isolated from hypertensive Dahl salt-sensitive (DS) rats. DS rats were fed on a low-sodium diet (control group), a low-sodium plus high-cholesterol diet (CHOL group), a high-sodium diet (NaCl group) or a high-sodium plus high-cholesterol diet (NaCl + CHOL group) for 8 weeks. Hypercholesterolemia developed in the CHOL and NaCl + CHOL groups, while hypertension developed in the NaCl and NaCl + CHOL groups, with these changes being greatest in the NaCl + CHOL group. Aortic cholesteryl ester accumulation was attenuated in the aortic rings from the NaCl and NaCl + CHOL groups, compared to the control group. The degree of attenuation in the NaCl + CHOL group was significantly greater than that in the NaCl group. Endothelium-dependent relaxations induced by the calcium ionophore A23187 were attenuated only in the NaCl + CHOL group. Endothelium-independent relaxations in response to sodium nitroprusside were slightly but significantly attenuated in the NaCl + CHOL group. The relaxations in the CHOL group were comparable to those in the control group. These findings indicate that cholesterol feeding strikingly enhances the impaired endothelium-dependent relaxations and the slightly impaired endothelium-independent relaxations in the aorta of DS rats with salt-induced hypertension, parallel to the development of hypertension, hypercholesterolemia and cholesterol deposition.

Topics: Acetylcholine; Animals; Antihypertensive Agents; Aorta, Thoracic; Calcimycin; Cholesterol Esters; Cholesterol, Dietary; Endothelium, Vascular; Hypercholesterolemia; Hypertension; Ionophores; Lipid Metabolism; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Nitroprusside; Rats; Rats, Inbred Strains; Sodium, Dietary

1. We investigated the effects of hypercholesterolaemia on relaxation responses in thoracic aortas isolated from two different types of hypertensive rats; spontaneously hypertensive rats (SHR) and Dahl salt-sensitive rats (DSR). 2. All rats fed the high cholesterol diet for 8 weeks showed a significant increase in the serum cholesterol level. The high cholesterol diet did not change the blood pressure of SHR, but increased that of hypertensive DSR fed a high-salt diet. 3. In aortas of SHR, the high-cholesterol diet did not change the endothelium-dependent and -independent relaxation induced by acetylcholine (ACh) and sodium nitroprusside (SNP), respectively. 4. In aortas of hypertensive DSR, the high-cholesterol diet notably reduced the ACh-induced relaxations and slightly reduced SNP-induced relaxation. 5. These results suggest that hypercholesterolaemia causes greater impairment of endothelium-dependent relaxation in rat aorta with salt-induced hypertension than genetic hypertension.

Topics: Acetylcholine; Animals; Antihypertensive Agents; Calcimycin; Cholesterol; Cholesterol, Dietary; Diet; Hypercholesterolemia; Hypertension; Ionophores; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Nitroprusside; Rats; Rats, Inbred SHR; Rats, Inbred WKY

The effect of moderate elevation in serum cholesterol on vascular reactivity to epidermal growth factor (EGF), endothelin (ET-1) and thrombin, vasoactive peptides present at sites of vascular injury, was examined in isolated aortic rings from rabbits fed either a casein-rich or a control diet for 10-12 weeks. In rings from hypercholesterolemic rabbits, development of maximal isometric tension to all peptide agonists was increased 22 +/- 0.6% while the EC50 for contraction was decreased. Vasorelaxant responses to nitroprusside, an endothelium-independent dilator, were largely intact, while those to A231897, an endothelium-dependent agent, were attenuated. These data suggest that elevation in serum cholesterol in the absence of atherosclerotic lesions is sufficient to increase vascular reactivity to peptide vasoactive mediators, an effect which may predispose arteries to vasospasm.

Topics: Animals; Aorta, Abdominal; Calcimycin; Cholesterol; Endothelins; Endothelium, Vascular; Epidermal Growth Factor; Hypercholesterolemia; In Vitro Techniques; Isometric Contraction; Male; Muscle, Smooth, Vascular; Nitroprusside; Peptides; Rabbits; Thrombin

The course of the rabbit aortic wall reactivity changes due to hypercholesterolemia involved, in the first place, the inhibition of the endothelium relaxing influence on the smooth muscle contractile activity and an increase in the muscle sensitivity to neurogenic and humoral tonic influences. Later, a sharp inhibition of the vessel's wall functional activity occurred due to a mechanical factor: the development of connective tissue which prevents active vascular reactions. Nevertheless, endothelial and smooth muscle cells functional activity was high enough. The main cause of the vascular reactivity disturbances involved structural changes in the vessel wall whilst the direct influence of high blood cholesterol was much less obvious.

Topics: Acetylcholine; Animals; Aorta; Calcimycin; Chronic Disease; Diet, Atherogenic; Endothelium, Vascular; Hypercholesterolemia; Muscle Contraction; Muscle, Smooth, Vascular; Nitroglycerin; Norepinephrine; Phenylephrine; Rabbits

We studied the effects of beta-migrating very low density lipoprotein (beta-VLDL) on the vascular responses of isolated thoracic aortic preparations taken from normal and hypercholesterolemic rabbits. The endothelium-dependent relaxation induced by acetylcholine or adenosine triphosphate (ATP) was attenuated in the arteries from hypercholesterolemic rabbits that were fed a cholesterol-rich diet for 12 weeks. In these aortas, the lesional circumference of the atherosclerotic plaques (fatty streaks) was only 12.18 +/- 1.98%. The relaxation induced by the Ca2+ ionophore A23187 or nitroglycerin was not altered. Preincubation with beta-VLDL significantly inhibited the relaxation due to acetylcholine, ATP, or A23187, especially in the aortas of hypercholesterolemic rabbits. However, beta-VLDL did not alter the response to nitroglycerin. Preincubation with high density lipoprotein had no significant effect on vessel relaxation. These results indicated that endothelium-dependent relaxation was already inhibited in the early stages of atherosclerosis, and that the atherogenic lipoprotein, beta-VLDL, further inhibited endothelium-dependent relaxation in atherosclerotic aortas. It may be that beta-VLDL also plays a role in determining the level of vascular tonus in atherosclerosis.

Topics: Acetylcholine; Adenosine Triphosphate; Animals; Aorta, Thoracic; Aortic Diseases; Arteriosclerosis; Calcimycin; Dose-Response Relationship, Drug; Endothelium, Vascular; Hypercholesterolemia; In Vitro Techniques; Lipoproteins, LDL; Male; Muscle Contraction; Muscle Relaxation; Nitric Oxide; Nitroglycerin; Norepinephrine; Rabbits

The influence of hypercholesterolemia on the reactivity of coronary arteries was investigated after feeding a high-cholesterol diet to pigs for 9 weeks. After this duration of hypercholesterolemia, the fatty or intimal proliferative changes of atherosclerosis were not yet evident in the coronary arteries by light or electron microscopy. Changes in isometric tension were compared in isolated ring segments of coronary arteries from normal and hypercholesterolemic animals. The endothelium failed to inhibit contractions caused by 5-hydroxytryptamine in coronary arteries from hypercholesterolemic animals, but it did so in normal vessels. In contracted arteries, endothelium-dependent relaxations caused by 5-hydroxytryptamine and substance P were reduced by hypercholesterolemia. In contrast, endothelium-dependent relaxations mediated by norepinephrine acting at alpha 2-adrenoceptors and those caused by the calcium ionophore A23187 were unaffected. Endothelium-independent beta-adrenergic relaxations caused by norepinephrine, as well as those caused by nitroprusside, and papaverine also were unaffected by hypercholesterolemia. The loss of selective endothelial cell receptor-mediated relaxation suggests that it is not the ability of the coronary artery endothelium to elaborate vasodilators, but the initiation of the coronary artery endothelial cell response to 5-hydroxytryptamine and substance P that is affected by hypercholesterolemia. Thus, during hypercholesterolemia, selective endothelial cell dysfunction giving rise to abnormal coronary artery reactivity precedes the onset of coronary artery atherosclerosis.

Topics: Animals; Calcimycin; Coronary Vessels; Dinoprost; Endothelium, Vascular; Hypercholesterolemia; Nitroprusside; Norepinephrine; Papaverine; Potassium; Serotonin; Substance P; Swine; Vasoconstriction