Mario Condorelli

Divergent effects of serotonin on coronary-artery dimensions and blood flow in patients with coronary atherosclerosis and control patients.

BACKGROUND Studies in animals have shown that serotonin constricts coronary arteries if the endothelium is damaged, but in vitro studies have revealed a vasodilating effect on isolated coronary segments with an intact endothelium. To investigate the effect of serotonin in humans, we studied coronary-artery cross-sectional area and blood flow before and after the infusion of serotonin in seven patients with angiographically normal coronary arteries and in seven with coronary artery disease. METHODS We measured the cross-sectional area of the coronary artery by quantitative angiography and coronary blood flow with an intracoronary Doppler catheter. Measurements were obtained at base line and during intracoronary infusions of serotonin (0.1, 1, and 10 micrograms per kilogram of body weight per minute, for two minutes). We repeated the measurements after an infusion of ketanserin, an antagonist of serotonin receptors that is thought to block the effect of serotonin on receptors in the arterial wall but not in the endothelium. RESULTS In patients with normal coronary arteries, the highest dose of serotonin increased cross-sectional area by 52 percent (P less than 0.001) and blood flow by 58 percent (P less than 0.01). The effect was significantly potentiated by administration of ketanserin. In patients with coronary-artery atherosclerosis, serotonin reduced cross-sectional area by 64 percent (P less than 0.001) and blood flow by 59 percent (P less than 0.001). Ketanserin prevented this effect. CONCLUSIONS Serotonin has a vasodilating effect on normal human coronary arteries; when the endothelium is damaged, as in coronary artery disease, serotonin has a direct, unopposed vasoconstricting effect. When considered with other evidence, these data suggest that platelet-derived factors such as serotonin may have a role in certain acute coronary ischemic syndromes.

Deletion of the p66Shc longevity gene reduces systemic and tissue oxidative stress, vascular cell apoptosis, and early atherogenesis in mice fed a high-fat diet

Several experimental and clinical studies have shown that oxidized low-density lipoprotein and oxidation-sensitive mechanisms are central in the pathogenesis of vascular dysfunction and atherogenesis. Here, we have used p66Shc−/− and WT mice to investigate the effects of high-fat diet on both systemic and tissue oxidative stress and the development of early vascular lesions. To date, the p66Shc−/− mouse is the unique genetic model of increased resistance to oxidative stress and prolonged life span in mammals. Computer-assisted image analysis revealed that chronic 21% high-fat treatment increased the aortic cumulative early lesion area by ≈21% in WT mice and only by 3% in p66Shc−/− mice. Early lesions from p66Shc−/− mice had less content of macrophage-derived foam cells and apoptotic vascular cells, in comparison to the WT. Furthermore, in p66Shc−/− mice, but not WT mice, we found a significant reduction of systemic and tissue oxidative stress (assessed by isoprostanes, plasma low-density lipoprotein oxidizability, and the formation of arterial oxidation-specific epitopes). These results support the concept that p66Shc−/− may play a pivotal role in controlling systemic oxidative stress and vascular diseases. Therefore, p66Shc might represent a molecular target for therapies against vascular diseases.

Oxygen radicals generated at reflow induce peroxidation of membrane lipids in reperfused hearts.

To test whether generation of oxygen radicals during postischemic reperfusion might promote peroxidation of cardiac membrane lipids, four groups of Langendorff-perfused rabbit hearts were processed at the end of (a) control perfusion, (b) 30 min of total global ischemia at 37 degrees C without reperfusion, (c) 30 min of ischemia followed by reperfusion with standard perfusate, (d) 30 min of ischemia followed by reperfusion with the oxygen radical scavenger human recombinant superoxide dismutase (h-SOD). The left ventricle was homogenized and tissue content of malonyldialdehyde (MDA), an end product of lipid peroxidation, was measured on the whole homogenate as well as on various subcellular fractions. Reperfusion was accompanied by a significant increase in MDA content of the whole homogenate and of the fraction enriched in mitochondria and lysosomes. This phenomenon was not observed in hearts subjected to ischemia but not reperfused, and was similarly absent in those hearts which received h-SOD at reflow. Reperfused hearts also had significantly greater levels of conjugated dienes (another marker of lipid peroxidation) in the mitochondrial-lysosomal fraction. Again, this phenomenon did not occur in ischemic hearts or in reperfused hearts treated with h-SOD. Unlike the effect on tissue MDA and conjugated dienes, reperfusion did not significantly stimulate release of MDA in the cardiac effluent. Treatment with h-SOD was also associated with significant improvement in the recovery of cardiac function. In conclusion, these data directly demonstrate that postischemic reperfusion results in enhanced lipid peroxidation of cardiac membranes, which can be blocked by h-SOD, and therefore is most likely secondary to oxygen radical generation at reflow.

Blood levels of erythropoietin in congestive heart failure and correlation with clinical, hemodynamic, and hormonal profiles

Plasma levels of erythropoietin (mU/ml) were measured in patients with congestive heart failure (CHF) (n = 108) and in a control group of normal subjects (n = 45). In normal subjects, plasma levels of erythropoietin were 1.9 +/- 0.2. In patients with CHF, plasma levels of erythropoietin increased progressively according to New York Heart Association (NYHA) class (I: 1.4 +/- 0.2, n = 28; II: 5.4 +/- 0.8, n = 27; III: 9.6 +/- 2, n = 32; IV: 34 +/- 8, n = 21; F = 57.7, p < 0.001) and were significantly higher in NYHA classes II, III, and IV than in normal subjects. Plasma erythropoietin significantly decreased (from 43 +/- 14 to 12 +/- 3 mU/ml, p < 0.01) in patients with severe CHF (n = 9) when enalapril (20 mg/day administered orally) was added to long-term treatment for 3 weeks. Finally, in a subgroup of patients with NYHA class IV CHF (n = 9) and high plasma erythropoietin levels (37 +/- 9 mU/ml), packed red blood cell volume, assessed by the iodine-125-albumin dilution method, was higher than that in normal subjects (n = 11) (2,616 +/- 235 vs 2,028 +/- 119 ml, p < 0.05). The present study demonstrates that plasma erythropoietin levels are elevated in a large cohort of patients with CHF of varying etiology, and that this increase is related to the progression of the disease. The increase in circulating erythropoietin is associated with augmented packed red blood cell volume in patients with severe CHF. These results suggest a participation of erythropoietin in the complex neurohormonal response that occurs in CHF.

Local Effect of Serotonin Released during Coronary Angioplasty

BACKGROUND Serotonin is released after the aggregation of platelets, a phenomenon that may occur after coronary angioplasty. We sought to determine whether serotonin is released into the coronary circulation during coronary angioplasty and to assess whether serotonin can affect coronary-artery tone during angioplasty. METHODS Blood samples were drawn from the ascending aorta and the coronary sinus of eight patients scheduled to undergo angioplasty of the left anterior descending or circumflex coronary artery. Samples were obtained before angioplasty and after each balloon dilation. The dimensions of arterial segments distal to the site of dilation were measured angiographically before angioplasty and 5 and 15 minutes after the last dilation in these eight patients and in seven similar patients; the latter group was treated with ketanserin, a serotonin2-receptor antagonist, before angioplasty. RESULTS Before the eight patients underwent angioplasty, their mean (+/- SE) plasma serotonin level in the aorta was 2.5 +/- 0.7 ng per milliliter and that in the coronary sinus was 2.3 +/- 0.6 ng per milliliter (P = 0.34). The serotonin level in plasma from the coronary sinus rose significantly, to 31.5 +/- 13.5, 17.6 +/- 5.3, and 29.1 +/- 8.1 ng per milliliter after the first, second, and third dilations, respectively (P = 0.014 for the comparison with preoperative levels). In contrast, the serotonin level in plasma from the ascending aorta did not change. The cross-sectional area of the coronary artery was significantly reduced 5 and 15 minutes after the last dilation (from a preoperative value of 3.7 +/- 0.5 mm2 to 2.7 +/- 0.4 mm2 15 minutes after the last dilation; P = 0.011). This vasoconstriction was significantly blunted in the seven patients who received ketanserin (from 3.7 +/- 0.5 mm2 before angioplasty to 3.9 +/- 0.4 mm2 after 15 minutes) (P = 0.017 for comparison with the eight patients who did not receive ketanserin). CONCLUSIONS Serotonin is released into the coronary circulation during angioplasty, and this vasoactive substance may contribute to the occurrence of vasoconstriction distal to the dilated site. The vasoconstriction is attenuated by ketanserin, a serotonin2-receptor antagonist.

Smooth Muscle Cell Proliferation Is Proportional to the Degree of Balloon Injury in a Rat Model of Angioplasty

BACKGROUND A variable degree of smooth muscle cell (SMC) proliferation after balloon injury has been reported in previous rat studies. It is unknown whether balloon injury induces c-fos expression and whether it is related to the degree of vascular injury in vivo. Therefore, we tested the hypothesis that proportional increases in neointimal formation and c-fos expression might be present after different degrees of balloon dilation. METHODS AND RESULTS Angioplasty of the carotid artery was performed with a balloon catheter. Vascular injury was evaluated at 0, 0.5, 1.0, 1.5, and 2 atm (n = 6 for all). In 40 additional rats, total RNA dot blots were performed to assess the effect of various degrees of balloon injury on c-fos expression. SMC proliferation proportional to the increases of inflation pressure was found between 0 and 2 atm with neointimal areas of 0.002 +/- 0.002, 0.069 +/- 0.014, 0.128 +/- 0.043, 0.190 +/- 0.010, and 0.255 +/- 0.041 mm2, respectively. When the degree of SMC proliferation (neointima and neointima/media ratio) was plotted against balloon inflation pressure, a linear relation was observed (r = .733, P < .001 and r = .755, P < .001, respectively). An increase in c-fos expression proportional to the degree of injury was found 30 minutes after injury. CONCLUSIONS Neointimal proliferation produced by balloon injury is related to balloon inflation pressure, supporting the concept of an SMC proliferative response proportional to the degree of injury. The increase in SMC proliferation is associated with a proportional increase in the early expression of the c-fos nuclear proto-oncogene.

Oxygen radicals inhibit human plasma acetylhydrolase, the enzyme that catabolizes platelet-activating factor.

Platelet-activating factor (PAF) can exert profound inflammatory effects at very low concentrations. In plasma, PAF is hydrolyzed to lyso-PAF by acetylhydrolase, an enzyme that circulates bound to LDL. Previous studies suggest that oxygen radicals may act synergistically with PAF to potentiate tissue injury. However, mechanisms underlying this interaction have not been elucidated. In this study we investigated whether oxygen radicals may inactivate PAF acetylhydrolase. PAF acetylhydrolase activity was measured in human plasma and purified LDL before and after exposure to radicals (10-20 nmol/min per ml) generated by xanthine/xanthine oxidase. Oxygen radicals induced > 50% loss of PAF acetylhydrolase activity within 60 s and almost complete inactivation by 10 min. This phenomenon was irreversible and independent of oxidative modification of LDL. Inactivation occurred without changes in the affinity constant of the enzyme (Km was 17.9 microM under control conditions and 15.1 microM after exposure to oxygen radicals). Inactivation was prevented by the scavengers superoxide dismutase or dimethylthiourea or by the iron chelator deferoxamine. Thus, superoxide-mediated, iron-catalyzed formation of hydroxyl radicals can rapidly and irreversibly inactivate PAF acetylhydrolase. Since concomitant production of PAF and oxygen radicals can occur in various forms of tissue injury, inactivation of acetylhydrolase might represent one mechanism by which oxygen radicals may potentiate and prolong the proinflammatory effects of PAF.

Effects of converting enzyme inhibition on heart period variability in patients with acute myocardial infarction.

Heart period variability provides useful prognosticinformation on autonomic cardiac control, and a strong association has been demonstrated after myocardial infarction (MI) between cardiac mortality, sudden death, and reduced total power, ultralow-frequency (ULF) power, and very-lowfrequency (VLF) power. Converting enzyme inhibitors are widely used in MI patients, but their influence on heart period variability emains to be defined. Methods and ResultsTime- and frequency-domain measures of heart period variability were calculated from 24-hour Holter monitoring in 40 patients with a first uncomplicated MI. After baseline examination between 48 and 72 hours after symptom onset, patients were randomly assigned to placebo or captopril administration, and on the third day, 24- hour Holter monitoring was repeated. No changes in time and frequency domain were detectable after placebo. After captopril, the SD of all normal RR (NN) intervals (SDNN) increased from 90±29 to 105±30 milliseconds (P < .01); the SD of the average NN intervals for all 5-minute segments (SDANN index) and the mean of the SDs of all NN intervals for all 5-minute segments (SDNN index) also increased from 74±24 to 90±26 milliseconds (P < .01) and from 45±17 to 49±15 milliseconds (P < .05), respectively. The root mean square successive difference (r-MSSD) and the percent of differences between adjacent NN intervals >50 milliseconds (pNN50) remained unchanged. In regard to frequency-domain measures, after captopril, total power (ln unit) increased from 8.28±0.42 to 8.47±0.30 (P < .01); considering the frequency bands, a significant increase was observed in ULF (P < .01), VLF (P < .05), and low-frequency (LF) power (P < .05), whereas high-frequency (HF) power remained unchanged. ConclusionsThis study supports the hypothesis that the renin-angiotensin system modulates the amplitude of ULF and VLF power. Furthermore, it demonstrates that in MI patients, converting enzyme inhibition favorably modifies measures of heart period variability strongly associated with a poor prognosis.

Propionyl-l-carnitine in intermittent claudication: Double-blind, placebo-controlled, dose titration, multicenter study

OBJECTIVES The aim of this double-blind, placebo-controlled, dose titration, multicenter trial was to assess the efficacy and safety of propionyl-carnitine in intermittent claudication. BACKGROUND Human and animal studies indicate that propionyl-L-carnitine increases carnitine content and improves energy metabolism in the ischemic skeletal muscle. METHODS After a 2-week preliminary period to assess maximal walking distance, 245 patients were randomly assigned to receive propionyl-L-carnitine (n = 118) or placebo (n = 127). The initial oral dose of 500 mg twice daily was increased at 2-month intervals to 2 g/day and then to 3 g/day in patients showing improvement in treadmill performance < 30% over baseline. Efficacy analysis was conducted for the 214 patients who completed the 24 weeks of treatment by comparing the effect of placebo and propionyl-L-carnitine on day 180. RESULTS Analysis of variance showed a significant improvement of 73 +/- 9% (mean +/- SE) in maximal walking distance with propionyl-L-carnitine (n = 99) compared with 46 +/- 6% for placebo (n = 115, p = 0.03). For distance walked at onset of claudication, propionyl-L-carnitine showed about double the improvement of placebo; however, the difference was not statistically significant. There were no changes in electrocardiographic and routine biochemical and hematologic tests that would indicate an adverse effect of propionyl-L-carnitine. Adverse events requiring drug discontinuation (11 in the propionyl-L-carnitine group, 3 in the placebo group) were unrelated to study medication. The dose titration design of the study also provided information on the dose-response relation. Slightly less than 67% of patients were expected to improve their maximal walking distance by at least 30%, assuming 2 g/day of propionyl-L-carnitine (95% confidence interval 0.51 to 0.70). The response rate during the entire titration course was significantly in favor of propionyl-L-carnitine compared with placebo. CONCLUSIONS Although the precise mode of therapeutic action requires clarification, propionyl-L-carnitine, at a dose of 1 to 2 g/day, appears to be effective and well tolerated, with minimal adverse effects.

Asymptomatic transient ST changes during ambulatory ECG monitoring in diabetic patients

The reported higher incidence of painless myocardial infarction in diabetic patients suggests that asymptomatic transient myocardial ischemia may also be frequent in diabetes. To explore this possibility 51 subjects with type II diabetes, aged 43 to 71 years (mean +/- SEM 56 +/- 8), 70 nondiabetic patients with coronary artery disease (mean age 55 +/- 5), and 40 nondiabetic patients without overt coronary disease (age 54 +/- 9) were studied. Thirty-eight of the 51 diabetic patients (74%) had evidence of associated coronary disease and 19 (37%) had evidence of previous myocardial infarction. All subjects underwent continuous 24-hour ambulatory ECG monitoring. In 18 of 51 diabetic patients 93 episodes (73% of the total number) of asymptomatic ST segment changes were recorded; the total number of symptomatic episodes was 36, and they were observed in seven patients (27%). Forty-eight (60%) asymptomatic and 32 symptomatic episodes of significant ST changes were found in nondiabetic patients with coronary artery disease. When patients with previous myocardial infarction were examined separately, asymptomatic episodes of significant ST changes were observed in 10 of 19 diabetic patients and in 5 of 25 nondiabetic patients with coronary artery disease (p less than 0.05). In an additional 28 diabetic patients who underwent exercise stress test, 15 exhibited an abnormal ECG response; however, only five of them (33%) were symptomatic. This study suggests that the incidence of transitory myocardial ischemia, as assessed by ambulatory ECG monitoring and exercise stress test, is higher in type II diabetic patients than in nondiabetic control subjects with coronary artery disease.