Activation of nitric oxide synthase in endothelial cells by Akt-dependent phosphorylation

Nitric oxide (NO) produced by the endothelial NO synthase (eNOS) is a fundamental determinant of cardiovascular homesotasis: it regulates systemic blood pressure, vascular remodelling and angiogenesis. Physiologically, the most important stimulus for the continuous formation of NO is the viscous drag (shear stress) generated by the streaming blood on the endothelial layer. Although shear-stress-mediated phosphorylation of eNOS is thought to regulate enzyme activity, the mechanism of activation of eNOS is not yet known. Here we demonstrate that the serine/threonine protein kinase Akt/PKB mediates the activation of eNOS, leading to increased NO production. Inhibition of the phosphatidylinositol-3-OH kinase/Akt pathway or mutation of the Akt site on eNOS protein (at serine 1177) attenuates the serine phosphorylation and prevents the activation of eNOS. Mimicking the phosphorylation of Ser 1177 directly enhances enzyme activity and alters the sensitivity of the enzyme to Ca2+, rendering its activity maximal at sub-physiological concentrations of Ca2+. Thus, phosphorylation of eNOS by Akt represents a novel Ca2+-independent regulatory mechanism for activation of eNOS.

Alirocumab and Cardiovascular Outcomes after Acute Coronary Syndrome

BACKGROUND

Patients who have had an acute coronary syndrome are at high risk for recurrent ischemic cardiovascular events. We sought to determine whether alirocumab, a human monoclonal antibody to proprotein convertase subtilisin-kexin type 9 (PCSK9), would improve cardiovascular outcomes after an acute coronary syndrome in patients receiving high-intensity statin therapy.

METHODS

We conducted a multicenter, randomized, double-blind, placebo-controlled trial involving 18,924 patients who had an acute coronary syndrome 1 to 12 months earlier, had a low-density lipoprotein (LDL) cholesterol level of at least 70 mg per deciliter (1.8 mmol per liter), a non-high-density lipoprotein cholesterol level of at least 100 mg per deciliter (2.6 mmol per liter), or an apolipoprotein B level of at least 80 mg per deciliter, and were receiving statin therapy at a high-intensity dose or at the maximum tolerated dose. Patients were randomly assigned to receive alirocumab subcutaneously at a dose of 75 mg (9462 patients) or matching placebo (9462 patients) every 2 weeks. The dose of alirocumab was adjusted under blinded conditions to target an LDL cholesterol level of 25 to 50 mg per deciliter (0.6 to 1.3 mmol per liter). The primary end point was a composite of death from coronary heart disease, nonfatal myocardial infarction, fatal or nonfatal ischemic stroke, or unstable angina requiring hospitalization.

RESULTS

The median duration of follow-up was 2.8 years. A composite primary end-point event occurred in 903 patients (9.5%) in the alirocumab group and in 1052 patients (11.1%) in the placebo group (hazard ratio, 0.85; 95% confidence interval [CI], 0.78 to 0.93; P<0.001). A total of 334 patients (3.5%) in the alirocumab group and 392 patients (4.1%) in the placebo group died (hazard ratio, 0.85; 95% CI, 0.73 to 0.98). The absolute benefit of alirocumab with respect to the composite primary end point was greater among patients who had a baseline LDL cholesterol level of 100 mg or more per deciliter than among patients who had a lower baseline level. The incidence of adverse events was similar in the two groups, with the exception of local injection-site reactions (3.8% in the alirocumab group vs. 2.1% in the placebo group).

CONCLUSIONS

Among patients who had a previous acute coronary syndrome and who were receiving high-intensity statin therapy, the risk of recurrent ischemic cardiovascular events was lower among those who received alirocumab than among those who received placebo. (Funded by Sanofi and Regeneron Pharmaceuticals; ODYSSEY OUTCOMES ClinicalTrials.gov number, NCT01663402 .).

Effects of atorvastatin on early recurrent ischemic events in acute coronary syndromes: the MIRACL study: a randomized controlled trial

CONTEXT

Patients experience the highest rate of death and recurrent ischemic events during the early period after an acute coronary syndrome, but it is not known whether early initiation of treatment with a statin can reduce the occurrence of these early events.

OBJECTIVE

To determine whether treatment with atorvastatin, 80 mg/d, initiated 24 to 96 hours after an acute coronary syndrome, reduces death and nonfatal ischemic events.

DESIGN AND SETTING

A randomized, double-blind trial conducted from May 1997 to September 1999, with follow-up through 16 weeks at 122 clinical centers in Europe, North America, South Africa, and Australasia.

PATIENTS

A total of 3086 adults aged 18 years or older with unstable angina or non-Q-wave acute myocardial infarction.

INTERVENTIONS

Patients were stratified by center and randomly assigned to receive treatment with atorvastatin (80 mg/d) or matching placebo between 24 and 96 hours after hospital admission.

MAIN OUTCOME MEASURES

Primary end point event defined as death, nonfatal acute myocardial infarction, cardiac arrest with resuscitation, or recurrent symptomatic myocardial ischemia with objective evidence and requiring emergency rehospitalization.

RESULTS

A primary end point event occurred in 228 patients (14.8%) in the atorvastatin group and 269 patients (17.4%) in the placebo group (relative risk [RR], 0.84; 95% confidence interval [CI], 0.70-1.00; P =.048). There were no significant differences in risk of death, nonfatal myocardial infarction, or cardiac arrest between the atorvastatin group and the placebo group, although the atorvastatin group had a lower risk of symptomatic ischemia with objective evidence and requiring emergency rehospitalization (6.2% vs 8.4%; RR, 0.74; 95% CI, 0.57-0.95; P =.02). Likewise, there were no significant differences between the atorvastatin group and the placebo group in the incidence of secondary outcomes of coronary revascularization procedures, worsening heart failure, or worsening angina, although there were fewer strokes in the atorvastatin group than in the placebo group (12 vs 24 events; P =.045). In the atorvastatin group, mean low-density lipoprotein cholesterol level declined from 124 mg/dL (3.2 mmol/L) to 72 mg/dL (1.9 mmol/L). Abnormal liver transaminases (>3 times upper limit of normal) were more common in the atorvastatin group than in the placebo group (2.5% vs 0.6%; P<.001).

CONCLUSION

For patients with acute coronary syndrome, lipid-lowering therapy with atorvastatin, 80 mg/d, reduces recurrent ischemic events in the first 16 weeks, mostly recurrent symptomatic ischemia requiring rehospitalization.

Prognostic impact of coronary vasodilator dysfunction on adverse long-term outcome of coronary heart disease

BACKGROUND

Endothelial vasodilator dysfunction is a characteristic feature of patients at risk for coronary atherosclerosis. Therefore, we prospectively investigated whether coronary endothelial dysfunction predicts disease progression and cardiovascular event rates.

METHODS AND RESULTS

Coronary vasoreactivity was assessed in 147 patients using the endothelium-dependent dilator acetylcholine, sympathetic activation by cold pressor testing, dilator responses to increased blood flow, and dilation in response to nitroglycerin. Cardiovascular events (cardiovascular death, unstable angina, myocardial infarction, percutaneous transluminal coronary angioplasty, coronary bypass grafting, ischemic stroke, or peripheral artery revascularization) served as outcome variables over a median follow-up period of 7.7 years. Patients suffering from cardiovascular events during follow-up (n=16) had significantly increased vasoconstrictor responses to acetylcholine infusion (P=0. 009) and cold pressor testing (P=0.002), as well as significantly blunted vasodilator responses to increased blood flow (P<0.001) and the intracoronary injection of nitroglycerin (P=0.001). Impaired endothelial and endothelium-independent coronary vasoreactivity were associated with a significantly higher incidence of cardiovascular events by Kaplan-Meier analysis. By multivariate analysis, all tests of coronary vasoreactivity were significant, independent predictors of a poor prognosis, even after adjustment for traditional cardiovascular risk factors or the presence of atherosclerosis itself.

CONCLUSIONS

Coronary endothelial vasodilator dysfunction predicts long-term atherosclerotic disease progression and cardiovascular event rates. Thus, the assessment of coronary endothelial vasoreactivity can provide pivotal information as both a diagnostic and prognostic tool in patients at risk for coronary heart disease.

Number and migratory activity of circulating endothelial progenitor cells inversely correlate with risk factors for coronary artery disease

Recent studies provide increasing evidence that postnatal neovascularization involves bone marrow-derived circulating endothelial progenitor cells (EPCs). The regulation of EPCs in patients with coronary artery disease (CAD) is unclear at present. Therefore, we determined the number and functional activity of EPCs in 45 patients with CAD and 15 healthy volunteers. The numbers of isolated EPCs and circulating CD34/kinase insert domain receptor (KDR)-positive precursor cells were significantly reduced in patients with CAD by approximately 40% and 48%, respectively. To determine the influence of atherosclerotic risk factors, a risk factor score including age, sex, hypertension, diabetes, smoking, positive family history of CAD, and LDL cholesterol levels was used. The number of risk factors was significantly correlated with a reduction of EPC levels (R=-0.394, P=0.002) and CD34-/KDR-positive cells (R=-0.537, P<0.001). Analysis of the individual risk factors demonstrated that smokers had significantly reduced levels of EPCs (P<0.001) and CD34-/KDR-positive cells (P=0.003). Moreover, a positive family history of CAD was associated with reduced CD34-/KDR-positive cells (P=0.011). Most importantly, EPCs isolated from patients with CAD also revealed an impaired migratory response, which was inversely correlated with the number of risk factors (R=-0.484, P=0.002). By multivariate analysis, hypertension was identified as a major independent predictor for impaired EPC migration (P=0.043). The present study demonstrates that patients with CAD revealed reduced levels and functional impairment of EPCs, which correlated with risk factors for CAD. Given the important role of EPCs for neovascularization of ischemic tissue, the decrease of EPC numbers and activity may contribute to impaired vascularization in patients with CAD. The full text of this article is available at http://www.circresaha.org.

Transplantation of Progenitor Cells and Regeneration Enhancement in Acute Myocardial Infarction (TOPCARE-AMI)

BACKGROUND

Experimental studies suggest that transplantation of blood-derived or bone marrow-derived progenitor cells beneficially affects postinfarction remodeling. The safety and feasibility of autologous progenitor cell transplantation in patients with ischemic heart disease is unknown.

METHODS AND RESULTS

We randomly allocated 20 patients with reperfused acute myocardial infarction (AMI) to receive intracoronary infusion of either bone marrow-derived (n=9) or circulating blood-derived progenitor cells (n=11) into the infarct artery 4.3+/-1.5 days after AMI. Transplantation of progenitor cells was associated with a significant increase in global left ventricular ejection fraction from 51.6+/-9.6% to 60.1+/-8.6% (P=0.003), improved regional wall motion in the infarct zone (-1.5+/-0.2 to -0.5+/-0.7 SD/chord; P<0.001), and profoundly reduced end-systolic left ventricular volumes (56.1+/-20 mL to 42.2+/-15.1 mL; P=0.01) at 4-month follow-up. In contrast, in a nonrandomized matched reference group, left ventricular ejection fraction only slightly increased from 51+/-10% to 53.5+/-7.9%, and end-systolic volumes remained unchanged. Echocardiography revealed a profound enhancement of regional contractile function (wall motion score index 1.4+/-0.2 at baseline versus 1.19+/-0.2 at follow-up; P<0.001). At 4 months, coronary blood flow reserve was significantly (P<0.001) increased in the infarct artery. Quantitative F-18-fluorodeoxyglucose-positron emission tomography analysis revealed a significant (P<0.01) increase in myocardial viability in the infarct zone. There were no differences for any measured parameter between blood-derived or bone marrow-derived progenitor cells. No signs of an inflammatory response or malignant arrhythmias were observed.

CONCLUSIONS

In patients with AMI, intracoronary infusion of autologous progenitor cells appears to be feasible and safe and may beneficially affect postinfarction remodeling processes.

Outcomes of Cardiovascular Magnetic Resonance Imaging in Patients Recently Recovered From Coronavirus Disease 2019 (COVID-19)

IMPORTANCE

Coronavirus disease 2019 (COVID-19) continues to cause considerable morbidity and mortality worldwide. Case reports of hospitalized patients suggest that COVID-19 prominently affects the cardiovascular system, but the overall impact remains unknown.

OBJECTIVE

To evaluate the presence of myocardial injury in unselected patients recently recovered from COVID-19 illness.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective observational cohort study, 100 patients recently recovered from COVID-19 illness were identified from the University Hospital Frankfurt COVID-19 Registry between April and June 2020.

EXPOSURE

Recent recovery from severe acute respiratory syndrome coronavirus 2 infection, as determined by reverse transcription-polymerase chain reaction on swab test of the upper respiratory tract.

MAIN OUTCOMES AND MEASURES

Demographic characteristics, cardiac blood markers, and cardiovascular magnetic resonance (CMR) imaging were obtained. Comparisons were made with age-matched and sex-matched control groups of healthy volunteers (n = 50) and risk factor-matched patients (n = 57).

RESULTS

Of the 100 included patients, 53 (53%) were male, and the mean (SD) age was 49 (14) years. The median (IQR) time interval between COVID-19 diagnosis and CMR was 71 (64-92) days. Of the 100 patients recently recovered from COVID-19, 67 (67%) recovered at home, while 33 (33%) required hospitalization. At the time of CMR, high-sensitivity troponin T (hsTnT) was detectable (greater than 3 pg/mL) in 71 patients recently recovered from COVID-19 (71%) and significantly elevated (greater than 13.9 pg/mL) in 5 patients (5%). Compared with healthy controls and risk factor-matched controls, patients recently recovered from COVID-19 had lower left ventricular ejection fraction, higher left ventricle volumes, and raised native T1 and T2. A total of 78 patients recently recovered from COVID-19 (78%) had abnormal CMR findings, including raised myocardial native T1 (n = 73), raised myocardial native T2 (n = 60), myocardial late gadolinium enhancement (n = 32), or pericardial enhancement (n = 22). There was a small but significant difference between patients who recovered at home vs in the hospital for native T1 mapping (median [IQR], 1119 [1092-1150] ms vs 1141 [1121-1175] ms; P = .008) and hsTnT (4.2 [3.0-5.9] pg/dL vs 6.3 [3.4-7.9] pg/dL; P = .002) but not for native T2 mapping. None of these measures were correlated with time from COVID-19 diagnosis (native T1: r = 0.07; P = .47; native T2: r = 0.14; P = .15; hsTnT: r = -0.07; P = .50). High-sensitivity troponin T was significantly correlated with native T1 mapping (r = 0.33; P < .001) and native T2 mapping (r = 0.18; P = .01). Endomyocardial biopsy in patients with severe findings revealed active lymphocytic inflammation. Native T1 and T2 were the measures with the best discriminatory ability to detect COVID-19-related myocardial pathology.

CONCLUSIONS AND RELEVANCE

In this study of a cohort of German patients recently recovered from COVID-19 infection, CMR revealed cardiac involvement in 78 patients (78%) and ongoing myocardial inflammation in 60 patients (60%), independent of preexisting conditions, severity and overall course of the acute illness, and time from the original diagnosis. These findings indicate the need for ongoing investigation of the long-term cardiovascular consequences of COVID-19.

Intracoronary bone marrow-derived progenitor cells in acute myocardial infarction

BACKGROUND

Pilot trials suggest that the intracoronary administration of autologous progenitor cells may improve left ventricular function after acute myocardial infarction.

METHODS

In a multicenter trial, we randomly assigned 204 patients with acute myocardial infarction to receive an intracoronary infusion of progenitor cells derived from bone marrow (BMC) or placebo medium into the infarct artery 3 to 7 days after successful reperfusion therapy.

RESULTS

At 4 months, the absolute improvement in the global left ventricular ejection fraction (LVEF) was significantly greater in the BMC group than in the placebo group (mean [+/-SD] increase, 5.5+/-7.3% vs. 3.0+/-6.5%; P=0.01). Patients with a baseline LVEF at or below the median value of 48.9% derived the most benefit (absolute improvement in LVEF, 5.0%; 95% confidence interval, 2.0 to 8.1). At 1 year, intracoronary infusion of BMC was associated with a reduction in the prespecified combined clinical end point of death, recurrence of myocardial infarction, and any revascularization procedure (P=0.01).

CONCLUSIONS

Intracoronary administration of BMC is associated with improved recovery of left ventricular contractile function in patients with acute myocardial infarction. Large-scale studies are warranted to examine the potential effects of progenitor-cell administration on morbidity and mortality.

Essential role of endothelial nitric oxide synthase for mobilization of stem and progenitor cells

Endothelial nitric oxide synthase (eNOS) is essential for neovascularization. Here we show that the impaired neovascularization in mice lacking eNOS is related to a defect in progenitor cell mobilization. Mice deficient in eNOS (Nos3(-/-)) show reduced vascular endothelial growth factor (VEGF)-induced mobilization of endothelial progenitor cells (EPCs) and increased mortality after myelosuppression. Intravenous infusion of wild-type progenitor cells, but not bone marrow transplantation, rescued the defective neovascularization of Nos3(-/-) mice in a model of hind-limb ischemia, suggesting that progenitor mobilization from the bone marrow is impaired in Nos3(-/-) mice. Mechanistically, matrix metalloproteinase-9 (MMP-9), which is required for stem cell mobilization, was reduced in the bone marrow of Nos3(-/-) mice. These findings indicate that eNOS expressed by bone marrow stromal cells influences recruitment of stem and progenitor cells. This may contribute to impaired regeneration processes in ischemic heart disease patients, who are characterized by a reduced systemic NO bioactivity.

MicroRNA-92a controls angiogenesis and functional recovery of ischemic tissues in mice

MicroRNAs (miRs) are small noncoding RNAs that regulate gene expression by binding to target messenger RNAs (mRNAs), leading to translational repression or degradation. Here, we show that the miR-17approximately92 cluster is highly expressed in human endothelial cells and that miR-92a, a component of this cluster, controls the growth of new blood vessels (angiogenesis). Forced overexpression of miR-92a in endothelial cells blocked angiogenesis in vitro and in vivo. In mouse models of limb ischemia and myocardial infarction, systemic administration of an antagomir designed to inhibit miR-92a led to enhanced blood vessel growth and functional recovery of damaged tissue. MiR-92a appears to target mRNAs corresponding to several proangiogenic proteins, including the integrin subunit alpha5. Thus, miR-92a may serve as a valuable therapeutic target in the setting of ischemic disease.

Circulating microRNAs in patients with coronary artery disease

RATIONALE

MicroRNAs are small RNAs that control gene expression. Besides their cell intrinsic function, recent studies reported that microRNAs are released by cultured cells and can be detected in the blood.

OBJECTIVE

To address the regulation of circulating microRNAs in patients with stable coronary artery disease.

METHODS AND RESULTS

To determine the regulation of microRNAs, we performed a microRNA profile using RNA isolated from n=8 healthy volunteers and n=8 patients with stable coronary artery disease that received state-of-the-art pharmacological treatment. Interestingly, most of the highly expressed microRNAs that were lower in the blood of patients with coronary artery disease are known to be expressed in endothelial cells (eg, miR-126 and members of the miR-17 approximately 92 cluster). To prospectively confirm these data, we detected selected microRNAs in plasma of 36 patients with coronary artery disease and 17 healthy volunteers by quantitative PCR. Consistent with the data obtained by the profile, circulating levels of miR-126, miR-17, miR-92a, and the inflammation-associated miR-155 were significantly reduced in patients with coronary artery disease compared with healthy controls. Likewise, the smooth muscle-enriched miR-145 was significantly reduced. In contrast, cardiac muscle-enriched microRNAs (miR-133a, miR-208a) tend to be higher in patients with coronary artery disease. These results were validated in a second cohort of 31 patients with documented coronary artery disease and 14 controls.

CONCLUSIONS

Circulating levels of vascular and inflammation-associated microRNAs are significantly downregulated in patients with coronary artery disease.

Reduced number of circulating endothelial progenitor cells predicts future cardiovascular events: proof of concept for the clinical importance of endogenous vascular repair

BACKGROUND

The maintenance of endothelial integrity plays a critical role in preventing atherosclerotic disease progression. Endothelial progenitor cells (EPCs) were experimentally shown to incorporate into sites of neovascularization and home to sites of endothelial denudation. Circulating EPCs may thus provide an endogenous repair mechanism to counteract ongoing risk factor-induced endothelial injury and to replace dysfunctional endothelium.

METHODS AND RESULTS

In 120 individuals (43 control subjects, 44 patients with stable coronary artery disease, and 33 patients with acute coronary syndromes), circulating EPCs were defined by the surface markers CD34+KDR+ and analyzed by flow cytometry. Cardiovascular events (cardiovascular death, unstable angina, myocardial infarction, PTCA, CABG, or ischemic stroke) served as outcome variables over a median follow-up period of 10 months. Patients suffering from cardiovascular events had significantly lower numbers of EPCs (P<0.05). Reduced numbers of EPCs were associated with a significantly higher incidence of cardiovascular events by Kaplan-Meier analysis (P=0.0009). By multivariate analysis, reduced EPC levels were a significant, independent predictor of poor prognosis, even after adjustment for traditional cardiovascular risk factors and disease activity (hazard ratio, 3.9; P<0.05).

CONCLUSIONS

Reduced levels of circulating EPCs independently predict atherosclerotic disease progression, thus supporting an important role for endogenous vascular repair to modulate the clinical course of coronary artery disease.

Transcoronary transplantation of progenitor cells after myocardial infarction

BACKGROUND

Pilot studies suggest that intracoronary transplantation of progenitor cells derived from bone marrow (BMC) or circulating blood (CPC) may improve left ventricular function after acute myocardial infarction. The effects of cell transplantation in patients with healed myocardial infarction are unknown.

METHODS

After an initial pilot trial involving 17 patients, we randomly assigned, in a controlled crossover study, 75 patients with stable ischemic heart disease who had had a myocardial infarction at least 3 months previously to receive either no cell infusion (23 patients) or infusion of CPC (24 patients) or BMC (28 patients) into the patent coronary artery supplying the most dyskinetic left ventricular area. The patients in the control group were subsequently randomly assigned to receive CPC or BMC, and the patients who initially received BMC or CPC crossed over to receive CPC or BMC, respectively, at 3 months' follow-up.

RESULTS

The absolute change in left ventricular ejection fraction was significantly greater among patients receiving BMC (+2.9 percentage points) than among those receiving CPC (-0.4 percentage point, P=0.003) or no infusion (-1.2 percentage points, P<0.001). The increase in global cardiac function was related to significantly enhanced regional contractility in the area targeted by intracoronary infusion of BMC. The crossover phase of the study revealed that intracoronary infusion of BMC was associated with a significant increase in global and regional left ventricular function, regardless of whether patients crossed over from control to BMC or from CPC to BMC.

CONCLUSIONS

Intracoronary infusion of progenitor cells is safe and feasible in patients with healed myocardial infarction. Transplantation of BMC is associated with moderate but significant improvement in the left ventricular ejection fraction after 3 months.

Myeloperoxidase serum levels predict risk in patients with acute coronary syndromes

BACKGROUND

Polymorphonuclear neutrophils (PMNs) have gained attention as critical mediators of acute coronary syndromes (ACS). Myeloperoxidase (MPO), a hemoprotein abundantly expressed by PMNs and secreted during activation, possesses potent proinflammatory properties and may contribute directly to tissue injury. However, whether MPO also provides prognostic information in patients with ACS remains unknown.

METHODS AND RESULTS

MPO serum levels were assessed in 1090 patients with ACS. We recorded death and myocardial infarctions during 6 months of follow-up. MPO levels did not correlate with troponin T, soluble CD40 ligand, or C-reactive protein levels or with ST-segment changes. However, patients with elevated MPO levels (>350 microg/L; 31.3%) experienced a markedly increased cardiac risk (adjusted hazard ratio [HR] 2.25 [1.32 to 3.82]; P=0.003). In particular, MPO serum levels identified patients at risk who had troponin T levels below 0.01 microg/L (adjusted HR 7.48 [95% CI 1.98 to 28.29]; P=0.001). In a multivariate model that included other biochemical markers, troponin T (HR 1.99; P=0.023), C-reactive protein (1.25; P=0.044), vascular endothelial growth factor (HR 1.87; P=0.041), soluble CD40 ligand (HR 2.78; P<0.001), and MPO (HR 2.11; P=0.008) were all independent predictors of the patient's 6-month outcome.

CONCLUSIONS

In patients with ACS, MPO serum levels powerfully predict an increased risk for subsequent cardiovascular events and extend the prognostic information gained from traditional biochemical markers. Given its proinflammatory properties, MPO may serve as both a marker and mediator of vascular inflammation and further points toward the significance of PMN activation in the pathophysiology of ACS.

Modulation of coronary vasomotor tone in humans. Progressive endothelial dysfunction with different early stages of coronary atherosclerosis

The endothelium plays a critical role in the control of vasomotor tone by the release of vasoactive substances. Because endothelial injury or dysfunction is considered important very early in atherogenesis, we hypothesized that abnormal endothelial function precedes the angiographic detection of coronary atherosclerosis in the human coronary circulation. The coronary vasomotor responses to three different endothelium-mediated stimuli (intracoronary infusion of acetylcholine 10(-8) to 10(-6) M, increase in blood flow to induce flow-dependent dilation, and sympathetic stimulation by cold pressor testing) were assessed by quantitative angiography and subselective intracoronary Doppler flow velocity measurements within the left anterior descending coronary artery in 38 patients. All three stimuli elicited epicardial artery dilation in all 11 patients with smooth coronary arteries and absence of risk factors for coronary artery disease (group 1). All nine patients with smooth coronary arteries but with hypercholesterolemia (group 2) demonstrated a selective impairment in endothelial function with vasoconstriction (35 +/- 12.7% decrease in mean luminal area) in response to acetylcholine but showed a preserved flow-dependent dilation (15.5 +/- 4.4% increase in mean luminal area) and vasodilation in response to cold pressor testing (14.2 +/- 4.6% increase in mean luminal area). In all nine patients with an angiographically defined smooth coronary artery segment but with evidence of atherosclerosis elsewhere in the coronary system (group 3), both acetylcholine and cold pressor testing induced vasoconstriction (26.2 +/- 8.7% and 18.7 +/- 7.9% decrease in mean luminal area, respectively), whereas flow-dependent dilation was preserved (20.4 +/- 8.7% increase in mean luminal area). In the nine patients with angiographic evidence of wall irregularities (group 4), flow-dependent dilation was also abolished and vasoconstriction occurred in response to acetylcholine and cold pressor testing (34.5 +/- 10.7% and 19.9 +/- 6.3% decrease in mean luminal area, respectively). All coronary artery segments dilated in response to nitroglycerin, suggesting preserved function of vascular smooth muscle. Despite similar reductions in coronary vascular resistance in response to the smooth muscle relaxant papaverin, patients with hypercholesterolemia demonstrated a selective impairment of vasodilation of the resistance vasculature in response to acetylcholine (p less than 0.05 versus groups 1, 3, and 4). Thus, there is a progressive impairment of endothelial vasoactive functioning in coronary arteries of patients with different early stages of atherosclerosis, beginning with a selective endothelial dysfunction in angiographically defined normal arteries in patients with hypercholesterolemia and progressively worsening to a complete loss of endothelium-mediated vasodilation in angiographically defined atherosclerotic coronary arteries.(ABSTRACT TRUNCATED AT 400 WORDS)

Increase in circulating endothelial progenitor cells by statin therapy in patients with stable coronary artery disease

BACKGROUND

Therapeutic neovascularization may constitute an important strategy to salvage tissue from critical ischemia. Circulating bone marrow-derived endothelial progenitor cells (EPCs) were shown to augment the neovascularization of ischemic tissue. In addition to lipid-lowering activity, hydroxymethyl glutaryl coenzyme A reductase inhibitors (statins) reportedly promote the neovascularization of ischemic tissue in normocholesterolemic animals. Methods and Results-Fifteen patients with angiographically documented stable coronary artery disease (CAD) were prospectively treated with 40 mg of atorvastatin per day for 4 weeks. Before and weekly after the initiation of statin therapy, EPCs were isolated from peripheral blood and counted. In addition, the number of hematopoietic precursor cells positive for CD34, CD133, and CD34/kinase insert domain receptor was analyzed. Statin treatment of patients with stable CAD was associated with an approximately 1.5-fold increase in the number of circulating EPCs by 1 week after initiation of treatment; this was followed by sustained increased levels to approximately 3-fold throughout the 4-week study period. Moreover, the number of CD34/kinase insert domain receptor-positive hematopoietic progenitor cells was significantly augmented after 4 weeks of therapy. Atorvastatin treatment increased the further functional activity of EPCs, as assessed by their migratory capacity.

CONCLUSION

The results of the present study define a novel mechanism of action of statin treatment in patients with stable CAD: the augmentation of circulating EPCs with enhanced functional activity. Given the well-established role of EPCs of participating in repair after ischemic injury, stimulation of EPCs by statins may contribute to the clinical benefit of statin therapy in patients with CAD.

Transplantation of progenitor cells and regeneration enhancement in acute myocardial infarction

OBJECTIVES

The Transplantation of Progenitor Cells And Regeneration Enhancement in Acute Myocardial Infarction (TOPCARE-AMI) trial investigates both safety, feasibility, and potential effects on parameters of myocardial function of intracoronary infusion of either circulating progenitor cells (CPC) or bone marrow-derived progenitor cells (BMC) in patients with acute myocardial infarction (AMI).

BACKGROUND

In animal experiments, therapy with adult progenitor cells was shown to improve vascularization, left ventricular (LV) remodeling, and contractility after AMI.

METHODS

A total of 59 patients with AMI were randomly assigned to receive either CPC (n = 30) or BMC (n = 29) into the infarct artery at 4.9 +/- 1.5 days after AMI.

RESULTS

Intracoronary progenitor cell application did not incur any measurable ischemic myocardial damage, but one patient experienced distal embolization before cell therapy. During hospital follow-up, one patient in each cell group developed myocardial infarction; one of these patients died of cardiogenic shock. No further cardiovascular events, including ventricular arrhythmias or syncope, occurred during one-year follow-up. By quantitative LV angiography at four months, LV ejection fraction (EF) significantly increased (50 +/- 10% to 58 +/- 10%; p < 0.001), and end-systolic volumes significantly decreased (54 +/- 19 ml to 44 +/- 20 ml; p < 0.001), without differences between the two cell groups. Contrast-enhanced magnetic resonance imaging after one year revealed an increased EF (p < 0.001), reduced infarct size (p < 0.001), and absence of reactive hypertrophy, suggesting functional regeneration of the infarcted ventricles.

CONCLUSIONS

Intracoronary infusion of progenitor cells (either BMC or CPC) is safe and feasible in patients after AMI successfully revascularized by stent implantation. Both the excellent safety profile and the observed favorable effects on LV remodeling, provide the rationale for larger randomized double-blind trials.

Suppression of apoptosis by nitric oxide via inhibition of interleukin-1beta-converting enzyme (ICE)-like and cysteine protease protein (CPP)-32-like proteases

Physiological levels of shear stress alter the genetic program of cultured endothelial cells and are associated with reduced cellular turnover rates and formation of atherosclerotic lesions in vivo. To test the hypothesis that shear stress (15 dynes/cm2) interferes with programmed cell death, apoptosis was induced in human umbilical venous cells (HUVEC) by tumor necrosis factor-alpha (TNF-alpha). Apoptosis was quantified by ELISA specific for histone-associated DNA-fragments and confirmed by demonstrating the specific pattern of internucleosomal DNA-fragmentation. TNF-alpha (300 U/ml) mediated increase of DNA-fragmentation was completely abrogated by shear stress (446 +/- 121% versus 57 +/- 11%, P <0.05). This anti-apoptotic activity of shear stress decreased after pharmacological inhibition of endogenous nitric oxide (NO)-synthase by NG-monomethyl-L-arginine and was completely reproduced by exogenous NO-donors. The activation of interleukin-1beta-converting enzyme (ICE)-like and cysteine protease protein (CPP)-32-like cysteine proteases was required to mediate TNF-alpha-induced apoptosis of HUVEC. Endothelial-derived nitric oxide (NO) as well as exogenous NO donors inhibited TNF-alpha-induced cysteine protease activation. Inhibition of CPP-32 enzyme activity was due to specific S-nitrosylation of Cys 163, a functionally essential amino acid conserved among ICE/CPP-32-like proteases. Thus, we propose that shear stress-mediated NO formation interferes with cell death signal transduction and may contribute to endothelial cell integrity by inhibition of apoptosis.

MicroRNA-34a regulates cardiac ageing and function

Ageing is the predominant risk factor for cardiovascular diseases and contributes to a significantly worse outcome in patients with acute myocardial infarction. MicroRNAs (miRNAs) have emerged as crucial regulators of cardiovascular function and some miRNAs have key roles in ageing. We propose that altered expression of miRNAs in the heart during ageing contributes to the age-dependent decline in cardiac function. Here we show that miR-34a is induced in the ageing heart and that in vivo silencing or genetic deletion of miR-34a reduces age-associated cardiomyocyte cell death. Moreover, miR-34a inhibition reduces cell death and fibrosis following acute myocardial infarction and improves recovery of myocardial function. Mechanistically, we identified PNUTS (also known as PPP1R10) as a novel direct miR-34a target, which reduces telomere shortening, DNA damage responses and cardiomyocyte apoptosis, and improves functional recovery after acute myocardial infarction. Together, these results identify age-induced expression of miR-34a and inhibition of its target PNUTS as a key mechanism that regulates cardiac contractile function during ageing and after acute myocardial infarction, by inducing DNA damage responses and telomere attrition.

Correction of endothelial dysfunction in coronary microcirculation of hypercholesterolaemic patients by L-arginine

Hypercholesterolaemia impairs endothelial function, possibly by interference with the intracellular formation of endothelium-derived relaxing factor from its precursor L-arginine. Whether L-arginine reverses hypercholesterolaemia-induced endothelial dysfunction in the coronary circulation was thus investigated. Epicardial artery cross-sectional area and coronary blood flow velocity were measured in 8 hypercholesterolaemic patients (mean serum cholesterol 7.8 [SE 0.3] mmol/l) and 7 age-matched controls before and after graded intracoronary infusions of the endothelium-dependent agent acetylcholine (0.036, 0.36, 3.6 micrograms/min). The effect of intracoronary infusion of L-arginine (160 mumol/min via the guiding catheter) on these measurements was then examined. In controls, acetylcholine induced a moderate dose-dependent constriction of the epicardial artery segment of the left anterior descending artery and increased coronary blood flow (by 239% [SE 57] at the highest dose). In patients with hypercholesterolaemia, the vasoconstrictive effect of acetylcholine on epicardial segments was similar to that in controls, but the increase in coronary blood flow with acetylcholine was significantly attenuated (highest dose: 61%, p less than 0.02 vs controls). L-arginine restored the acetylcholine-induced increase in blood flow in patients with hypercholesterolaemia (198% [61] vs baseline) but did not affect coronary blood flow in controls. The findings suggest that hypercholesterolaemia impairs endothelium-dependent dilatation of the coronary microcirculation and that this impairment can be restored by short-term administration of L-arginine. The possibility that L-arginine might form the basis of treatment for coronary endothelial abnormalities induced by hypercholesterolaemia could be worth investigating.

Role of Dicer and Drosha for endothelial microRNA expression and angiogenesis

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression by binding to the cellular transcript leading to translational repression or degradation of the target mRNA. Dicer and Drosha are the miRNA processing enzymes that are required for the maturation of miRNAs. Here, we investigated the role of Dicer and Drosha for angiogenesis. Endothelial cells were transfected with siRNA against Dicer and Drosha to inhibit miRNA biogenesis. Genetic silencing of Dicer and Drosha significantly reduced capillary sprouting of endothelial cells and tube forming activity. Migration of endothelial cells was significantly decreased in Dicer siRNA-transfected cells, whereas Drosha siRNA had no effect. Silencing of Dicer but not of Drosha reduced angiogenesis in vivo. Next, we attempted to identify miRNAs expressed in endothelial cells. A screening analysis of 168 human miRNAs using real-time PCR revealed that members of the let-7 family, mir-21, mir-126, mir-221, and mir-222 are highly expressed in endothelial cells. Dicer and Drosha siRNA reduced lef-7f and mir-27b expression. Inhibitors against let-7f and mir-27b also reduced sprout formation indicating that let-7f and mir-27b promote angiogenesis by targeting antiangiogenic genes. In silico analysis of predicted targets for let-7 cluster identified the endogenous angiogenesis inhibitor thrombospondin-1. Indeed, Dicer and Drosha siRNA significantly increased the expression of thrombospondin-1. Taken together, transient reduction of the miRNA-regulating enzyme Dicer impairs angiogenesis in vitro and in vivo, whereas Drosha siRNA induced a minor antiangiogenic effect in vitro and was not effective in vivo. The let-7 family and mir-27b appear to be attractive targets for modulating angiogenesis.