calcimycin and Coronary-Artery-Disease

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

Endothelial dysfunction is an early event leading to atherosclerosis. It also occurs after orthotopic heart transplantation and can be used to predict the development of intimal hyperplasia in the coronary artery wall. The present study was designed to assess the time course and specific alterations underlying endothelial dysfunction due to rejection after heart transplantation.. A porcine model of heterotopic heart transplantation was used. Preoperative serum typing for the class I antigen of the swine lymphocyte alloantigen was performed to ensure compatibility for this antigen. This permitted survival of the graft with a low grade rejection without immunosuppression. Rings (with or without endothelium) of epicardial coronary arteries of native and transplanted hearts were studied in organ chambers filled with modified Krebs-Ringer bicarbonate solution and compared 1, 30 and 60 days after transplantation.. Myocardial contractility was normal in all grafts studied at 60 days after transplantation and all coronary arteries were patent. Myocardial biopsies showed the progression of rejection from day 1 to day 60 after implantation. All endothelium-dependent relaxations were normal one day after transplantation. Endothelium-dependent relaxations to serotonin and to the alpha 2-adrenergic agonist UK14304 (which both activate receptors coupled to Gi-proteins) and to sodium fluoride (a direct activator of G-proteins) were decreased 30 days after transplantation, while those to the calcium ionophore, A23187, and bradykinin were shifted to the right and those to ADP were normal. At 60 days, endothelium-dependent relaxations mediated by the Gi-protein pathway were decreased further while the concentration-relaxation curves to the other agonists were further shifted to the right. Endothelium-independent relaxations to the nitric oxide donor, Sin-1, were progressively reduced at 30 and 60 days, but maximal relaxations were maintained at 60 days. Histomorphometric studies showed a progressive increase in the percentage of coronary rings with intimal thickening from day 1 to day 60 after transplantation.. The progressive endothelial dysfunction reported in this model of accelerated coronary atherosclerosis after transplantation without immunosuppression involves preferentially the pertussis-toxin-sensitive Gi-protein-mediated pathway. Endothelium-independent relaxations are decreased at 60 days, as are all other endothelium-dependent relaxations. Decreased endothelium-dependent vasodilatation may contribute to the development of coronary graft vasculopathy.

Topics: Adenosine Diphosphate; Analysis of Variance; Animals; Bradykinin; Calcimycin; Coronary Artery Disease; Coronary Vessels; Dose-Response Relationship, Drug; Endothelium, Vascular; Female; Graft Rejection; GTP-Binding Proteins; Heart Transplantation; In Vitro Techniques; Ionophores; Male; Microscopy, Electron; Signal Transduction; Swine; Transplantation, Homologous

Thrombin activation requires assembly of a prothrombinase complex of activated coagulation factors on an anionic phospholipid surface, classically provided by activated platelets. We have previously shown that anionic phosphatidylserine is exposed by rat vascular smooth muscle cells (VSMCs) undergoing apoptosis after serum withdrawal. In this study, using a chromogenic assay, we have shown thrombin generation by apoptotic VSMCs expressing c-myc (VSMC-myc) with an area under the thrombin-generation curve (AUC) of 305 +/- 17 nmol x min/L and a peak thrombin (PT) of 154 +/- 9 nmol/L. The thrombin-generating potential of the apoptotic VSMC-myc cells was greater than that of unactivated platelets (P = .003 for AUC; P = .0002 for PT) and similar to calcium-ionophore activated platelets (AUC of 332 +/- 15 nmol x min/L, P = .3; PT of 172 +/- 8 nmol/L, P = .2). Thrombin activation was also seen with apoptotic human VSMCs (AUC of 211 +/- 8 nmol x min/L; PT of 103 +/- 4 nmol/L) and was inhibited by annexin V (P < .0001 for AUC and PT). VSMC-myc cells maintained in serum generated less thrombin than after serum withdrawal (P = .0002 for AUC and PT). VSMCs derived from human coronary atherosclerotic plaques that apoptose even in serum also generated thrombin (AUC of 260 +/- 2 nmol x min/L; PT of 128 +/- 4 nmol/L). We conclude that apoptotic VSMCs possess a significant thrombin-generating capacity secondary to phosphatidylserine exposure. Apoptotic cells within atherosclerotic plaques may allow local thrombin activation, thereby contributing to disease progression.

Topics: Adenovirus E1A Proteins; Animals; Annexin A5; Aorta, Thoracic; Apoptosis; Arteriosclerosis; Blood Platelets; Calcimycin; Calcium Chloride; Cells, Cultured; Coronary Artery Disease; Culture Media, Serum-Free; DNA, Complementary; Genes, myc; Hirudins; Humans; Ionophores; Muscle, Smooth, Vascular; Platelet Activation; Proto-Oncogene Proteins c-myc; Rats; Rats, Sprague-Dawley; Recombinant Fusion Proteins; Thrombin; Transfection

Oxidized low-density lipoproteins (LDL), which may play an important role in atherogenesis, inhibit endothelium-dependent relaxations of normal arteries in vitro. The effects of probucol, an inhibitor of LDL oxidation, on endothelium-dependent relaxations in thoracic aorta of rabbits that received a cholesterol-rich (0.5%) or standard diet for 10 weeks were determined. In some rabbits in each group, the diet was supplemented with probucol (1%) for the last 6 weeks. The cholesterol-rich diet markedly increased plasma cholesterol and resulted in increased plasma lipid peroxides. Probucol prevented the increase in lipid peroxides, but had no effect on plasma cholesterol. Rings of aorta were mounted in organ chambers for measurement of isometric tension and contracted with phenylephrine. Endothelium-dependent relaxations to acetylcholine and A23187 were significantly impaired in aortic rings from cholesterol-fed rabbits. Aortic rings from rabbits fed cholesterol and treated with probucol relaxed normally to both vasodilators. Relaxations to acetylcholine and A23187 were not significantly changed in rings from rabbits that received probucol-supplemented standard diet. Endothelium-independent relaxations to sodium nitroprusside (SNP) were not influenced by the cholesterol diet or probucol. Thus, probucol preserves endothelium-dependent relaxations of hypercholesterolemic rabbit aorta without reducing plasma cholesterol. As demonstrated by the reduction in plasma lipid peroxides, the effect of probucol may be related to its antioxidant properties and may imply that oxidized lipids have a role in endothelial cell dysfunction of atherosclerotic arteries in vivo.

Topics: Acetylcholine; Animals; Aorta, Thoracic; Body Weight; Calcimycin; Cholesterol; Coronary Artery Disease; Diet, Atherogenic; Endothelium, Vascular; In Vitro Techniques; Lipid Peroxidation; Male; Microscopy, Electron, Scanning; Muscle Relaxation; Muscle, Smooth, Vascular; Nitroprusside; Phenylephrine; Probucol; Rabbits; Thiobarbituric Acid Reactive Substances

This study was undertaken to determine whether atherosclerosis impairs relaxations mediated by endothelium-derived relaxing factor (EDRF) in human coronary arteries. Epicardial coronary arteries were obtained from the hearts of cardiac transplantation patients with or without histologically documented coronary atherosclerosis (atherosclerotic arteries were from patients aged 42-55 years, nonatherosclerotic arteries were from patients aged 14-24 years). Transverse strip preparations were mounted in organ baths for isometric tension recording. Tension was induced with prostaglandins F2 alpha. Indomethacin (10(-5) M) was present to prevent possible interference from endogenously formed prostaglandins. The EDRF-mediated relaxations in response to substance P (10(-10) to 10(-8) M), bradykinin (10(-9) to 10(-7) M), and Ca2+-ionophore A23187 (10(-9) to 10(-7) M) were significantly attenuated in atherosclerotic arteries. In deendothelialized tissues these compounds had no effect. In contrast, endothelium-independent relaxations induced by isoprenaline (10(-7) to 10(-5) M) were not affected by atherosclerosis. Atherosclerotic arteries showed also normal relaxations with high concentrations of glyceryl trinitrate (10(-8) to 10(-7) M), but reduced relaxations with a lower concentration of the compound (10(-9) M). Acetylcholine (10(-7) to 10(-6) M) only produced endothelium-dependent relaxations in 8 of 60 arterial preparations (with or without atherosclerosis). In most of the arteries, it was a direct vasoconstrictor (which may have masked EDRF release in many cases). Omission of indomethacin from the bath solution increased the incidence of moderate acetylcholine-induced relaxations (9 of 16 preparations). It is concluded that atherosclerosis attenuates EDRF-mediated vasospasm and myocardial ischemia.

Topics: Acetylcholine; Adolescent; Adult; Biological Products; Bradykinin; Calcimycin; Coronary Artery Disease; Coronary Vessels; Endothelium, Vascular; Humans; In Vitro Techniques; Indomethacin; Middle Aged; Nitric Oxide; Nitroglycerin; Substance P; Vasodilation