Coronary wave intensity patterns in stable coronary artery disease: influence of stenosis severity and collateral circulation

Objective

Wave intensity analysis is a method that allows separating pulse waves into components generated proximally and in the periphery of arterial trees, as well as characterising them as accelerating or decelerating. The early diastolic suction wave (eaDSW) is one of the most prominent wave events in the coronaries. The aim of this study was to determine whether (1) microvascular dilatation directly influences its energy, (2) stenosis severity can be assessed proximal to stenoses, (3) distal pulse wave entrapment exists in the presence of stenoses and (4) coronary collaterals influence wave entrapment.

Methods

In 43 coronary artery disease patients, Doppler flow velocity and pressure measurements were performed in a proximal coronary segment at rest, in a distal segment at rest, during adenosine-induced hyperaemia and during balloon occlusion. Wave energies were calculated as the area under the wave intensity curves.

Results

The eaDSW energy showed a significant increase during hyperaemia, but did not differ between proximal and distal segments. There was no significant correlation between eaDSW energy and coronary stenosis severity. Pulse wave entrapment could not be observed consistently in the distal segments. Consequently, the effect of coronary collaterals on pulse wave entrapment could not be studied.

Conclusions

Microvascular dilation in the coronary circulation increases distal eaDSW energy. However, it does not show any diagnostically useful variation between measurement sites, various stenosis degrees and amount of collateral flow. The assessment eaDSW and its reflections were not useful for the quantification of coronary stenosis severity or the collateral circulation in clinical practice.

Time-Dependent Myocardial Necrosis in Patients With ST-Segment-Elevation Myocardial Infarction Without Angiographic Collateral Flow Visualized by Cardiac Magnetic Resonance Imaging: Results From the Multicenter STEMI-SCAR Project

Background

Acute complete occlusion of a coronary artery results in progressive ischemia, moving from the endocardium to the epicardium (ie, wavefront). Dependent on time to reperfusion and collateral flow, myocardial infarction (MI) will manifest, with transmural MI portending poor prognosis. Late gadolinium enhancement cardiac magnetic resonance imaging can detect MI with  high diagnostic accuracy. Primary percutaneous coronary intervention is the preferred reperfusion strategy in patients with ST‐segment–elevation MI with <12 hours of symptom onset. We sought to visualize time‐dependent necrosis in a population with ST‐segment–elevation MI by using late gadolinium enhancement cardiac magnetic resonance imaging (STEMI‐SCAR project).

Methods and Results

ST‐segment–elevation MI patients with single‐vessel disease, complete occlusion with TIMI (Thrombolysis in Myocardial Infarction) score 0, absence of collateral flow (Rentrop score 0), and symptom onset <12 hours were consecutively enrolled. Using late gadolinium enhancement cardiac magnetic resonance imaging, the area at risk and infarct size, myocardial salvage index, transmurality index, and transmurality grade (0–50%, 51–75%, 76–100%) were determined. In total, 164 patients (aged 54±11 years, 80% male) were included. A receiver operating characteristic curve (area under the curve: 0.81) indicating transmural necrosis revealed the best diagnostic cutoff for a symptom‐to‐balloon time of 121 minutes: patients with >121 minutes demonstrated increased infarct size, transmurality index, and transmurality grade (all P<0.01) and decreased myocardial salvage index (P<0.001) versus patients with symptom‐to‐balloon times ≤121 minutes.

Conclusions

In MI with no residual antegrade and no collateral flow, immediate reperfusion is vital. A symptom‐to‐balloon time of >121 minutes causes a high grade of transmural necrosis. In this pure ST‐segment–elevation MI population, time to reperfusion to salvage myocardium was less than suggested by current guidelines.

The effect of pegylated granulocyte colony-stimulating factor on collateral function and myocardial ischaemia in chronic coronary artery disease: A randomized controlled trial

OBJECTIVE

To test the effect of long-term pegfilgrastim on collateral function and myocardial ischaemia in patients with chronic stable coronary artery disease (CAD).

METHODS

This was a prospective clinical trial with randomized 2:1 allocation to pegfilgrastim or placebo for 6 months. The primary study endpoint was collateral flow index (CFI) as obtained during a 1-minute ostial coronary artery balloon occlusion. CFI is the ratio of mean coronary occlusive divided by mean aortic pressure both subtracted by central venous pressure (mm Hg/mm Hg). Secondary endpoints were signs of myocardial ischaemia determined during the same coronary occlusion, that is quantitative intracoronary (i.c.) ECG ST-segment shift (mV) and the occurrence of angina pectoris. Endpoints were obtained at baseline before and at follow-up after three subcutaneous study drug injections.

RESULTS

Collateral flow index in the pegfilgrastim group changed from 0.096 ± 0.076 at baseline to 0.126 ± 0.070 at follow-up (P = 0.0039), while in the placebo group CFI changed from 0.157 ± 0.146 to 0.122 ± 0.043, respectively (P = 0.29); the CFI increment at follow-up was +0.030 ± 0.075 in the pegfilgrastim group and -0.034 ± 0.148 in the placebo group (P = 0.0172). In the pegfilgrastim group, i.c. ECG ST-segment shift changed from +1.23 ± 1.01 mV at baseline to +0.93 ± 0.97 mV at follow-up (P = 0.0049), and in the placebo group, it changed from +0.98 ± 1.02 mV to +1.43 ± 1.09 mV, respectively (P = 0.05). At follow-up, the fraction of patients free from angina pectoris during coronary occlusion had increased in the pegfilgrastim but not in the placebo group.

CONCLUSION

Pegfilgrastim given over the course of 6 months improves collateral function in chronic stable CAD, which is reflected by reduced myocardial ischaemia during a controlled coronary occlusion.

Selective Heart Rate Reduction With Ivabradine Increases Central Blood Pressure in Stable Coronary Artery Disease

Abstract—

Heart rate (HR) lowering by β-blockade was shown to be beneficial after myocardial infarction. In contrast, HR lowering with ivabradine was found to confer no benefits in 2 prospective randomized trials in patients with coronary artery disease. We hypothesized that this inefficacy could be in part related to ivabradine’s effect on central (aortic) pressure. Our study included 46 patients with chronic stable coronary artery disease who were randomly allocated to placebo (n=23) or ivabradine (n=23) in a single-blinded fashion for 6 months. Concomitant baseline medication was continued unchanged throughout the study except for β-blockers, which were stopped during the study period. Central blood pressure and stroke volume were measured directly by left heart catheterization at baseline and after 6 months. For the determination of resting HR at baseline and at follow-up, 24-hour ECG monitoring was performed. Patients on ivabradine showed an increase of 11 mm Hg in central systolic pressure from 129±22 mm Hg to 140±26 mm Hg ( P =0.02) and in stroke volume by 86±21.8 to 107.2±30.0 mL ( P =0.002). In the placebo group, central systolic pressure and stroke volume remained unchanged. Estimates of myocardial oxygen consumption (HR×systolic pressure and time-tension index) remained unchanged with ivabradine.The decrease in HR from baseline to follow-up correlated with the concomitant increase in central systolic pressure ( r =−0.41, P =0.009) and in stroke volume ( r =−0.61, P <0.001). In conclusion, the decrease in HR with ivabradine was associated with an increase in central systolic pressure, which may have antagonized possible benefits of HR lowering in coronary artery disease patients.

Clinical Trials—URL:

http://www.clinicaltrials.gov . Unique identifier NCT01039389.

Effects of Thoratec pulsatile ventricular assist device timing on the abdominal aortic wave intensity pattern

Arterial waves are seen as possible independent mediators of cardiovascular risks, and the wave intensity analysis (WIA) has therefore been proposed as a method for patient selection for ventricular assist device (VAD) implantation. Interpreting measured wave intensity (WI) is challenging, and complexity is increased by the implantation of a VAD. The waves generated by the VAD interact with the waves generated by the native heart, and this interaction varies with changing VAD settings. Eight sheep were implanted with a pulsatile VAD (PVAD) through ventriculoaortic cannulation. The start of PVAD ejection was synchronized to the native R wave and delayed between 0 and 90% of the cardiac cycle in 10% steps or phase shifts (PS). Pressure and velocity signals were registered, with the use of a combined Doppler and pressure wire positioned in the abdominal aorta, and used to calculate the WI. Depending on the PS, different wave interference phenomena occurred. Maximum unloading of the left ventricle (LV) coincided with constructive interference and maximum blood flow pulsatility, and maximum loading of the LV coincided with destructive interference and minimum blood flow pulsatility. We believe that noninvasive WIA could potentially be used clinically to assess the mechanical load of the LV and to monitor the peripheral hemodynamics such as blood flow pulsatility and risk of intestinal bleeding.

Direct quantitative assessment of the peripheral artery collateral circulation in patients undergoing angiography

BACKGROUND

Despite the fact that numerous studies have pursued the strategy of improving collateral function in patients with peripheral artery disease, there is currently no method available to quantify collateral arterial function of the lower limb.

METHODS AND RESULTS

Pressure-derived collateral flow index (CFIp, calculated as (occlusive pressure-central venous pressure)/(aortic pressure-central venous pressure); pressure values in mm Hg) of the left superficial femoral artery was obtained in patients undergoing elective coronary angiography using a combined pressure/Doppler wire (n=30). Distal occlusive pressure and toe oxygen saturation (Sao2) were measured for 5 minutes under resting conditions, followed by an exercise protocol (repetitive plantar-flexion movements in supine position; n=28). In all patients, balloon occlusion of the superficial femoral artery over 5 minutes was painless under resting conditions. CFIp increased during the first 3 minutes from 0.451±0.168 to 0.551±0.172 (P=0.0003), whereas Sao2 decreased from 98±2% to 93±7% (P=0.004). Maximal changes of Sao2 were inversely related to maximal CFIp (r(2)=0.33, P=0.003). During exercise, CFIp declined within 1 minute from 0.560±0.178 to 0.393±0.168 (P<0.0001) and reached its minimum after 2 minutes of exercise (0.347±0.176), whereas Sao2 declined to a minimum of 86±6% (P=0.002). Twenty-five patients (89%) experienced pain or cramps/tired muscles, whereas 3 (11%) remained symptom-free for an occlusion time of 10 minutes. CFIp values were positively related to the pain-free time span (r(2)=0.50, P=0.002).

CONCLUSIONS

Quantitatively assessed collateral arterial function at rest determined in the nonstenotic superficial femoral artery is sufficient to prevent ischemic symptoms during a total occlusion of 5 minutes. During exercise, there is a decline in CFIp that indicates a supply-demand mismatch via collaterals or, alternatively, a steal phenomenon. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. UNIQUE IDENTIFIER: NCT01742455.

G-CSF induced arteriogenesis in humans: molecular insights into a randomized controlled trial

AIMS

Recent data have demonstrated the feasibility of therapeutic induction of coronary collateral growth (arteriogenesis); however, mechanisms of action of such therapeutic collateral stimulation in humans are unknown. The aim of this study was to evaluate potential mechanisms, especially the involvement of arteriogenesis-relevant genes.

METHODS AND RESULTS

A total of 52 patients were randomized into two groups: subcutaneous G-CSF (10 μg/kg; n=26) or placebo (n=26). Before and after this 2-week treatment, collateral-flow index (CFI) was determined by simultaneous measurement of mean aortic, distal coronary occlusive and central venous pressure. CD34+ endothelial progenitor cells (EPC) and monocytes were quantified before, during and after treatment; gene-expression analysis of monocytes was performed with real-time polymerase chain reaction (RT-PCR). G-CSF lead to a significant increase of EPC and monocytes (4.8 and 2.6 fold, p < 0.05); for both cell types, the extent of increase correlated with CFI increase (r=0.23 and 0.14, p < 0.05). G-CSF also induced a change in gene expression of pro-and anti-arteriogenic genes in monocytes. Among nine assessed genes, three were found to be differentially regulated (IL8, JAK2, and PNPLa4; p < 0.05).

CONCLUSIONS

The mechanism of induction of collateral growth by G-CSF is related to an increase of EPC and of peripheral monocytes. It also leads to a change toward a pro-arteriogenic gene expression in peripheral monocytes.

Determinants of prognostically relevant intracoronary electrocardiogram ST-segment shift during coronary balloon occlusion

The prognostic relevance of quantitative an intracoronary occlusive electrocardiographic (ECG) ST-segment shift and its determinants have not been investigated in humans. In 765 patients with chronic stable coronary artery disease, the following simultaneous quantitative measurements were obtained during a 1-minute coronary balloon occlusion: intracoronary ECG ST-segment shift (recorded by angioplasty guidewire), mean aortic pressure, mean distal coronary pressure, and mean central venous pressure (CVP). Collateral flow index (CFI) was calculated as follows: (mean distal coronary pressure minus CVP)/(mean aortic pressure minus CVP). During an average follow-up duration of 50 ± 34 months, the cumulative mortality rate from all causes was significantly lower in the group with an ST-segment shift <0.1 mV (n = 89) than in the group with an ST-segment shift ≥0.1 mV (n = 676, p = 0.0211). Factors independently related to intracoronary occlusive ECG ST-segment shift <0.1 mV (r(2) = 0.189, p <0.0001) were high CFI (p <0.0001), intracoronary occlusive RR interval (p = 0.0467), right coronary artery as the ischemic region (p <0.0001), and absence of arterial hypertension (p = 0.0132). "High" CFI according to receiver operating characteristics analysis was ≥0.217 (area under receiver operating characteristics curve 0.647, p <0.0001). In conclusion, absence of ECG ST-segment shift during brief coronary occlusion in patients with chronic coronary artery disease conveys a decreased mortality and is directly influenced by a well-developed collateral supply to the right versus left coronary ischemic region and by the absence of systemic hypertension in a patient's history.

Cause or effect of arteriogenesis: compositional alterations of microparticles from CAD patients undergoing external counterpulsation therapy

Recently, a clinical study on patients with stable coronary artery disease (CAD) showed that external counterpulsation therapy (ECP) at high (300 mmHg) but not at low inflation pressure (80 mmHg) promoted coronary collateral growth, most likely due to shear stress-induced arteriogenesis. The exact molecular mechanisms behind shear stress-induced arteriogenesis are still obscure. We therefore characterized plasma levels of circulating microparticles (MPs) from these CAD patients because of their ambivalent nature as a known cardiovascular risk factor and as a promoter of neovascularization in the case of platelet-derived MPs. MPs positive for Annexin V and CD31CD41 were increased, albeit statistically significant (P<0.05, vs. baseline) only in patients receiving high inflation pressure ECP as determined by flow cytometry. MPs positive for CD62E, CD146, and CD14 were unaffected. In high, but not in low, inflation pressure treatment, change of CD31CD41 was inversely correlated to the change in collateral flow index (CFI), a measure for collateral growth. MPs from the high inflation pressure group had a more sustained pro-angiogenic effect than the ones from the low inflation pressure group, with the exception of one patient showing also an increased CFI after treatment. A total of 1005 proteins were identified by a label-free proteomics approach from MPs of three patients of each group applying stringent acceptance criteria. Based on semi-quantitative protein abundance measurements, MPs after ECP therapy contained more cellular proteins and increased CD31, corroborating the increase in MPs. Furthermore, we show that MP-associated factors of the innate immune system were decreased, many membrane-associated signaling proteins, and the known arteriogenesis stimulating protein transforming growth factor beta-1 were increased after ECP therapy. In conclusion, our data show that ECP therapy increases platelet-derived MPs in patients with CAD and that the change in protein cargo of MPs is likely in favor of a pro angiogenic/arteriogenic property.

Coronary collaterals and risk for restenosis after percutaneous coronary interventions: a meta-analysis

BACKGROUND

The benefit of the coronary collateral circulation (natural bypass network) on survival is well established. However, data derived from smaller studies indicates that coronary collaterals may increase the risk for restenosis after percutaneous coronary interventions. The purpose of this systematic review and meta-analysis of observational studies was to explore the impact of the collateral circulation on the risk for restenosis.

METHODS

We searched the MEDLINE, EMBASE and ISI Web of Science databases (2001 to 15 July 2011). Random effects models were used to calculate summary risk ratios (RR) for restenosis. The primary endpoint was angiographic restenosis > 50%.

RESULTS

A total of 7 studies enrolling 1,425 subjects were integrated in this analysis. On average across studies, the presence of a good collateralization was predictive for restenosis (risk ratio (RR) 1.40 (95% CI 1.09 to 1.80); P = 0.009). This risk ratio was consistent in the subgroup analyses where collateralization was assessed with intracoronary pressure measurements (RR 1.37 (95% CI 1.03 to 1.83); P = 0.038) versus visual assessment (RR 1.41 (95% CI 1.00 to 1.99); P = 0.049). For the subgroup of patients with stable coronary artery disease (CAD), the RR for restenosis with 'good collaterals' was 1.64 (95% CI 1.14 to 2.35) compared to 'poor collaterals' (P = 0.008). For patients with acute myocardial infarction, however, the RR for restenosis with 'good collateralization' was only 1.23 (95% CI 0.89 to 1.69); P = 0.212.

CONCLUSIONS

The risk of restenosis after percutaneous coronary intervention (PCI) is increased in patients with good coronary collateralization. Assessment of the coronary collateral circulation before PCI may be useful for risk stratification and for the choice of antiproliferative measures (drug-eluting stent instead bare-metal stent, cilostazol).

Physical coronary arteriogenesis: a human "model" of collateral growth promotion

In patients with coronary artery disease, the size of myocardial infarction mainly determines the subsequent clinical outcome. Accordingly, it is the primary strategy to decrease cardiovascular mortality by minimizing infarct size. Promotion of collateral artery growth (arteriogenesis) is an appealing option of reducing infarct size. It has been demonstrated in experimental models that tangential fluid shear stress is the major trigger of arterial remodeling and, thus, of collateral growth. Lower-leg, high-pressure external counterpulsation triggered to occur during diastole induces a flow velocity signal and thus tangential endothelial shear stress in addition to the flow signal caused by cardiac stroke volume. We here present two cases of cardiac transplant recipients as human "models" of physical coronary arteriogenesis, providing an example of progressing and regressing clinical arteriogenesis, and review available evidence from clinical studies on other feasible forms of physical arteriogenesis.

Estrogen receptor-α but not -β or GPER inhibits high glucose-induced human VSMC proliferation: potential role of ROS and ERK

CONTEXT

The decreased incidence of cardiovascular disease in premenopausal women has been attributed, at least partially, to protective effects of estrogens. However, premenopausal women with diabetes mellitus are no longer selectively protected. High-glucose (HG) conditions have previously been shown to abolish the antimitogenic effects of 17β-estradiol (E(2)) in vascular smooth muscle cells (VSMCs).

OBJECTIVE

Because E(2) mediates its action via different estrogen receptor (ER) subtypes, we hypothesized that different subtypes may have different, if not opposing, effects on HG-induced VSMC proliferation.

METHODS AND RESULTS

Treatment of human aortic VSMCs isolated from premenopausal women with the selective ERα agonist, 4,4',4'-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol, but not with E(2), the selective ERβ agonist 2,3-bis(4-hydroxyphenyl)-propionitrile, or the selective G protein-coupled ER agonist G-1 completely prevented increased HG-induced VSMC proliferation. Under these conditions, ERα activation selectively prevented increased hydrogen peroxide (H(2)O(2)) and total intracellular reactive oxygen species (ROS) production, caused up-regulation of manganese superoxide dismutase protein and activity, and inhibited prolonged ERK phosphorylation. The latter was mediated by ROS, and ROS inhibition reversed HG-induced ERK-dependent VSMC proliferation. The selective coactivation of ERβ reversed the antimitogenic and antioxidative effects of ERα as well as the up-regulation of manganese superoxide dismutase protein expression.

CONCLUSION

Selective activation of ERα is required for reducing oxidative stress and the consequent hyperproliferation of VSMCs under HG. Our results may further suggest that ERα activation inhibits HG-induced proliferation by down-regulating ROS-mediated ERK activation and may explain why antimitogenic effects of E(2) are abolished under HG. Pharmacological activation of ERα may thus have therapeutic potential for treating cardiovascular dysregulation associated with diabetes.

Safety of diagnostic balloon occlusion in normal coronary arteries

Diagnostic coronary balloon occlusion (CBO) is mandatory for collateral function assessment, during angioscopy and optical coherence imaging, and when using certain coronary protection devices against emboli. Thus far, the safety of diagnostic CBO regarding procedural and long-term complications in normal coronary arteries has not been studied. In 316 patients, diagnostic CBO was performed for collateral function measurement in 426 angiographically normal vessels. The angioplasty balloon was inflated for 60 to 120 seconds using inflation pressures of 1 to 3 atm, followed by control angiography during and after CBO. Patients were divided into groups with entirely normal (n = 133) and partially normal (n = 183) vessels. Primary end points were procedural and long-term complications. De novo stenosis development was assessed by quantitative coronary angiography in 35% of the patients. Secondary end points were cardiac events at 5 years of follow-up. Procedural complications occurred in 1 patient (0.2%). In 150 repeat angiographic procedures in 92 patients (follow-up duration 10 +/- 15 months), quantitative coronary angiography revealed no difference in percentage diameter narrowing between baseline and follow-up (4.1% vs 3.9%, p = 0.69). During follow-up periods of 14 and 72 months, respectively, a new stenotic lesion was detected in 1 patient in each group (1.3%). Major cardiac events and percutaneous coronary intervention for stable angina were less frequent in the group with entirely normal than with partially normal vessels (0.8% vs 5.5%, p = 0.02, and 0.8% vs 18%, p <0.0001). In conclusion, low-inflation pressure diagnostic CBO in angiographically normal coronary arteries bears a minimal risk for procedural and long-term complications and can therefore be regarded as a safe procedure.

Upregulation of vascular ET(B) receptor gene expression after chronic ET(A) receptor blockade in prediabetic NOD mice

In the aorta of prediabetic non-obese diabetic mice, a model of human type 1 diabetes, we investigated gene expression of the endothelin receptors and contractility to big endothelin-1 and endothelin-1 at the ages of 10 and 16 weeks. A subgroup of 10- week-old animals was treated with the endothelin ETA receptor antagonist LU461314 (30 mg/kg per day for 6 weeks). Blood glucose levels were normal in all animals. Real-time polymerase chain reaction analysis revealed that vascular ETB receptor expression was higher in 10-week-old non-obese diabetic (NOD) mice compared with controls. In 16-week-old NOD mice, but not in control mice, ETB receptor mRNA was twofold lower (P < 0.05 vs 10-week-old NOD mice). In all groups ETA receptor expression was unaffected by age or treatment. Contractions to big endothelin-1 and endothelin-1 were lower in 10-week-old NOD mice compared with controls. Treatment with LU461314 increased ETB receptor expression in 16-week-old NOD mice, but had no effect on vascular contractility. These data indicate that dysregulation of ETB receptor expression and a decreased contractile response to big endothelin-1 and endothelin-1 are present in the prediabetic state of a model of human type 1 diabetes. These alterations occur independent of glucose levels. Furthermore, ETA receptor blockade is effective in increasing ETB receptor gene expression, suggesting a potential role for endothelin ETA antagonists in the treatment of type 1 diabetes.

Distinct roles of estrogen receptors alpha and beta mediating acute vasodilation of epicardial coronary arteries

This study investigated the contribution of estrogen receptors (ERs) alpha and beta for epicardial coronary artery function, vascular NO bioactivity, and superoxide (O(2)(-)) formation. Porcine coronary rings were suspended in organ chambers and precontracted with prostaglandin F(2alpha) to determine direct effects of the selective ER agonists 4,4',4''-(4-propyl-[(1)H]pyrazole-1,3,5-triyl)tris-phenol (PPT) or 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) or the nonselective ER agonist 17beta-estradiol. Indirect effects on contractility to U46619 and relaxation to bradykinin were assessed and effects on NO, nitrite, and O(2)(-) formation were measured in cultured cells. Within 5 minutes, selective ERalpha activation by PPT, but not 17beta-estradiol or the ERbeta agonist DPN, caused rapid, NO-dependent, and endothelium-dependent relaxation (49+/-5%; P<0.001 versus ethanol). PPT also caused sustained endothelium- and NO-independent vasodilation similar to 17beta-estradiol after 60 minutes (72+/-3%; P<0.001 versus ethanol). DPN induced endothelium-dependent NO-independent relaxation via endothelium-dependent hyperpolarization (40+/-4%; P<0.01 versus ethanol). 17beta-Estradiol and PPT, but not DPN, attenuated the responses to U46619 and bradykinin. All of the ER agonists increased NO and nitrite formation in vascular endothelial but not smooth muscle cells and attenuated vascular smooth muscle cell O(2)(-) formation (P<0.001). ERalpha activation had the most potent effects on both nitrite formation and inhibiting O(2)(-) (P<0.05). These data demonstrate novel and differential mechanisms by which ERalpha and ERbeta activation control coronary artery vasoreactivity in males and females and regulate vascular NO and O(2)(-) formation. The findings indicate that coronary vascular effects of sex hormones differ with regard to affinity to ERalpha and ERbeta, which will contribute to beneficial and adverse effects of hormone replacement therapy.

Impaired vascular function in normoglycemic mice prone to autoimmune diabetes: Role of nitric oxide

Type 1 diabetes is an immuno-inflammatory condition which increases the risk of cardiovascular disease, particularly in young adults. This study investigated whether vascular function is altered in mice prone to autoimmune diabetes and whether the nitric oxide (NO)-cyclic GMP axis is involved. Aortic rings suspended in organ chambers and precontracted with phenylephrine were exposed to cumulative concentrations of acetylcholine. To investigate the role of NO, some experiments were performed in the presence of either 1400W (N-(3-aminomethyl)benzyl-acetamidine hydrochloride), a selective inhibitor of the iNOS-isoform, L-NAME (N(G)-nitro-L-arginine methyl ester hydrochloride), an inhibitor of all three NOS-isoforms, or ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one), a selective inhibitor of guanylate cyclase. Moreover, contractility to phenylephrine, big endothelin-1, and endothelin-1 was assessed and histological analysis and iNOS immunohistochemistry were performed. Endothelium-dependent relaxation was reduced in prediabetic NOD mice (78+/-4 vs. 88+/-2%, respectively, P<0.05 vs. control) despite normal plasma glucose levels (n.s. vs. control). Preincubation with 1400W further attenuated responses in prediabetic (P<0.05 vs. untreated) but not in diabetic or in control mice. In contrast, basal NO bioactivity remained unaffected until the onset of diabetes in NOD mice. Contractile responses to big endothelin-1 and endothelin-1 were reduced in prediabetic animals (P<0.05 vs. control), whereas in diabetic mice only responses to big endothelin-1 were decreased (P<0.05 vs. control). These data demonstrate that endothelium-dependent and -independent vascular function in NOD mice is abnormal already in prediabetes in the absence of structural injury. Early proinflammatory activation due to iNOS in diabetes-prone NOD mice appears to be one of the mechanisms contributing to impaired vasoreactivity.

Endothelin ETA Receptor Blockade With Darusentan Increases Sodium and Potassium Excretion in Aging Rats

This study investigated whether intrarenal endothelin-1(ET-1) contributes to sodium excretion in aged rats. Metabolic function studies were performed in male Wistar rats (3 and 24 months) treated with placebo or the orally active ET(A) receptor antagonist darusentan (20 mg/kg/d) for 4 weeks. Mean arterial pressure was measured using an intra-arterial catheter. Electrolytes, aldosterone levels, renin activity, and angiotensin converting enzyme activity were determined in plasma, and mRNA expression of epithelial sodium channel (ENaC) and Na(+), K(+)-ATPase subunits was measured in the renal cortex and medulla. Aging was associated with a marked decrease in urinary excretion of sodium, chloride, and potassium (all P < 0.001) as well as renin activity (P < 0.05), but had no significant effect on gene expression of ENaC or Na(+), K(+)-ATPase subunits. In aged rats, darusentan treatment increased ion excretion (P < 0.05), reduced cortical gene expression of alphaENaC and alpha(1)-Na(+), K(+)-ATPase (both P < 0.05), and increased plasma aldosterone levels (P < 0.01). These data demonstrate a decrease of sodium and potassium excretion in aged rats, changes that are partly sensitive to ETA receptor blockade. Treatment with darusentan also reduced cortical expression of alphaENaC and alpha(1)-Na(+), K(+)-ATPase and increased plasma aldosterone levels independently of blood pressure, electrolytes, renin activity, or angiotensin converting enzyme activity. These findings may provide new pathogenetic links between aging and sodium sensitivity.

Endothelin inhibition delays onset of hyperglycemia and associated vascular injury in type I diabetes: evidence for endothelin release by pancreatic islet beta-cells

This study investigated the role of endothelin-1 for hyperglycemia, vascular, and pancreatic injury in early type I diabetes in non-obese-diabetic (NOD) mice. Endothelium dependent relaxation to acetylcholine and vascular gene expression of endothelin converting enzyme (ECE) isoforms 1 and 2 were studied as indicators of vascular injury. Endothelial NO bioactivity in the aorta was reduced in diabetic NOD mice while vascular expression of ECE-1 and ECE-2 mRNA was increased compared with controls (all p<0.05). Vascular histology was normal in all animals. Unexpectedly, treatment of prediabetic NOD mice for 6 weeks with the orally active ET(A) receptor antagonist BSF461314 prevented onset of diabetes without affecting insulitis severity. ET(A) receptor blockade also restored abnormal endothelial NO bioactivity and reduced ECE-1 and ECE-2 gene expression in NOD mice to levels comparable with healthy controls (p<0.05). Moreover, secretion of endothelin-1 in a time-dependent fashion was observed by pancreatic islet beta-cells cultured in vitro. These data suggest a critical role for ET(A) receptor signaling in the development of autoimmune forms of diabetes and the early vascular injury associated with it.

Role of Podocytes for Reversal of Glomerulosclerosis and Proteinuria in the Aging Kidney After Endothelin Inhibition

The cause of focal-segmental glomerulosclerosis as a consequence of physiological aging, which is believed to be inexorable, is unknown. This study investigated whether inhibition of endothelin-1, a growth-promoting peptide contributing to renal injury in hypertension and diabetes, affects established glomerulosclerosis and proteinuria in the aged kidney. We also determined the role of endothelin receptors for podocyte injury in vivo and in vitro. Aged Wistar rats, a model of spontaneous age-dependent glomerulosclerosis, were treated with the orally active endothelin subtype A (ET A ) receptor antagonist darusentan, and evaluation of renal histology, renal function studies, and expression analyses were performed. In vitro experiments using puromycin aminonucleoside to induce podocyte injury investigated the role of ET A receptor signaling for apoptosis, cytoskeletal injury, and DNA synthesis. In aged Wistar rats, established glomerulosclerosis and proteinuria were reduced by >50% after 4 weeks of darusentan treatment, whereas blood pressure, glomerular filtration rate, or tubulo-interstitial renal injury remained unaffected. Improvement of structural injury in glomeruli and podocytes was accompanied by a reduction of the expression of matrix metalloproteinase-9 and p21 Cip1/WAF1 . In vitro experiments blocking ET A receptors using specific antagonists or RNA interference prevented apoptosis and structural damage to podocytes induced by puromycin aminonucleoside. In conclusion, these results support the hypothesis that endogenous endothelin contributes to glomerulosclerosis and proteinuria in the aging kidney. The results further suggest that age-dependent glomerulosclerosis is not merely a “degenerative” but a reversible process locally confined to the glomerulus involving recovery of podocytes from previous injury.

Amiodarone Acutely Inhibits Vascular Activity of Endothelin-Converting Enzymes

Endothelin has been implicated in arrhythmogenesis. Amiodarone, initially developed for the treatment of angina pectoris, is a potent inhibitor of ventricular arrhythmias. We investigated whether amiodarone (34 microg/mL) affects the vascular endothelin system of healthy Wistar-Kyoto rats. Contractility to big endothelin-1 and endothelin-1 was determined in aortic and carotid artery rings suspended in organ chambers. Functional activity of endothelin-converting enzymes was calculated for each concentration, and endothelin-converting enzyme-1 gene expression was analyzed using real-time polymerase chain reaction. Activity of functional endothelin-converting enzymes was sevenfold higher in the carotid artery than in the aorta (P < 0.001). Contractions to big endothelin-1 (0.1 micromol/L) were attenuated by amiodarone in the carotid artery (50 +/- 9% vs 90 +/- 8%, P < 0.01) but not in the aorta. Accordingly, contractility to endothelin-1 (0.1 micromol/L) was decreased by amiodarone in carotid rings only (105 +/- 7% vs 132 +/- 6%, P < 0.01). After acute exposure to amiodarone, functional activity of endothelin-converting enzymes at 0.1 micromol/L was slightly increased in the aorta (17 +/- 2% vs 11 +/- 2%, P < 0.05), but decreased in the carotid artery (40 +/- 9% vs 76 +/- 5%, P < 0.05). Endothelin-converting enzyme-1 mRNA expression in the aorta was not affected by amiodarone treatment. Thus, amiodarone acutely affects the activity of vascular endothelin-converting enzymes depending on the anatomical localization of the artery. Acute effects of amiodarone on endothelin-converting enzymes may contribute to its antiarrhythmic properties.

[Postmenopausal hormone replacement therapy and cardiovascular risk: role of conjugated equine estrogens and medroxyprogesterone acetate]

Atherosclerosis is a chronic systemic inflammatory disease of the vasculature that accounts for the majority of morbidity and mortality in women. The incidence of atherosclerosis is low in premenopausal women and increases after ovariectomy. Experimental studies demonstrate inhibitory effects of natural estrogens on the progression of atherosclerosis. In contrast, results from recent hormone replacement trials using conjugated equine estrogens and medroxyprogesterone acetate in postmenopausal women showed no effects or even an increase in cardiovascular morbidity and mortality such as thrombosis or stroke. Therefore, conjugated equine estrogens alone or in combination with medroxyprogesterone acetate should not be recommended for the prevention or treatment of cardiovascular disease. Optimizing the risk factor profile such as cessation of smoking, normalizing body weight and blood pressure, regular physical activity, and statin treatment of patients with coronary artery disease remain important treatment options.

Obesity-associated activation of angiotensin and endothelin in the cardiovascular system

The renin-angiotensin system (RAS) and the endothelin system have been implicated in the pathogenesis of human cardiovascular and renal diseases, and inhibition of the RAS markedly improves morbidity and survival. Obesity in humans is associated with an increased risk for the development of hypertension, atherosclerosis and focal-segmental glomerulosclerosis, however the exact mechanisms underlying these pathologies in obese individuals are not known. This article discusses the clinical importance of obesity and the current evidence for local activation of the renin-angiotensin system and its interactions with the endothelin system in obesity and the cardiovascular pathologies associated with it.

Endothelial Therapy of Atherosclerosis and its Risk Factors

Atherosclerosis is a chronic systemic disease of the vasculature with an inflammatory component. It accounts for the majority of cardiovascular morbidity and mortality in industrialized countries and its incidence is increasing in developing countries. The impairment of vascular endothelial cell function in atherosclerosis and in conditions associated with increased cardiovascular risk is an important determinant of disease progression. The reduction of endothelium-dependent relaxation in the coronary and systemic circulation in atherosclerosis is in part due to decreased bioavailability of nitric oxide and increased release of oxygen-derived free radicals. Atherosclerosis also increases the formation of vasoconstrictors and growth factors, adhesion of leukocytes, thrombosis, inflammation, cell proliferation, as well as increases in vascular tone. Here we review mechanisms and therapeutic approaches to improve endothelial pathways in atherosclerosis. Restoration of NO bioactivity through pharmacological inhibition of the renin-angiotensin system, statin therapy, or endothelin receptor blockade, ameliorates vascular function in experimental hypercholesterolemia, hypertension and heart failure. These treatments also have therapeutic benefit for patients at risk or with overt atherosclerosis, to reduce vascular and myocardial complications of this disease.

Nephroprotective effects of the endothelin ET(A) receptor antagonist darusentan in salt-sensitive genetic hypertension

We tested the effect of selective endothelin ET(A) receptor blockade on the development renal damage in the Sabra rat model of genetic salt-sensitivity. Animals from the salt-sensitive (SBH/y) and salt-resistant strains (SBN/y) were either salt-loaded with deoxycorticosterone acetate and salt (DOCA) or fed a normal diet. Additional salt-loaded groups were also treated with the selective ET(A) antagonist darusentan (DA). Salt-loading in SBH/y increased systolic blood pressure by 75 mm Hg and urinary albumin excretion 23-fold (P<0.0001). Darusentan attenuated the rise of systolic blood pressure (50%) and urinary albumin excretion (63%, P<0.01, respectively). Salt-loading in SBH/y was associated with significant increased osteopontin mRNA expression as well as glomerulosclerosis and tubulointerstitial damage in the kidney (P<0.05, respectively). This was either significantly reduced or normalized by darusentan (P<0.05, respectively). Thus, darusentan confers a significant renal protection in the Sabra model of salt-sensitive hypertension.

Lovastatin stimulates human vascular smooth muscle cell expression of bone morphogenetic protein-2, a potent inhibitor of low-density lipoprotein-stimulated cell growth

Bone morphogenetic proteins (BMPs) stimulate ectopic bone formation in skeletal muscle. Here we show that human vascular smooth muscle cells (VSMC) abundantly express mRNA encoding for BMP receptor type II, BMP-2, and BMP-7 proteins. Treatment with the 3-hydroxy-3-methylglutaryl coenzyme A inhibitor lovastatin (34 microM) increased BMP-2 gene transcription >14-fold as measured by real-time PCR analysis (P<0.05 vs. solvent control). Moreover, VSMC proliferation stimulated with native low-density lipoprotein (100 microg of protein/mL) was prevented by either human recombinant BMP-2 or BMP-7 at concentrations of 100 ng/mL (P<0.05). Both BMPs also inhibited basal cell proliferation (P<0.05). Induction of BMPs and subsequent inhibition of VSMC growth and/or induction of vascular bone formation could contribute to the mechanisms by which statins increase plaque stability in patients with coronary atherosclerosis.

Obesity increases prostanoid-mediated vasoconstriction and vascular thromboxane receptor gene expression

OBJECTIVES

Vasoconstrictor prostanoids have been implicated in abnormal vasomotion in atherosclerosis and hypertension.

METHOD

Using lean and diet-induced obese mice, we investigated whether obesity affects vascular function or expression of genes involved in prostanoid action.

RESULTS

In lean C57BL/6J mice, at high concentrations acetylcholine caused endothelium-dependent contractions in the carotid artery but not in the aorta. Endothelium-dependent contractions to acetylcholine were blocked by the non-selective cyclooxygenase (COX) inhibitors indomethacin and meclofenamate, or a prostaglandin H2/thromboxane A2 receptor antagonist, but not by inhibitors of COX-2, thromboxane synthase or cytochrome P450 monooxygenase. Obesity increased endothelium-dependent contractions to acetylcholine in the carotid artery, and prostanoid-mediated vasoconstriction was now present in the aorta. Similarly, contractions to endothelin-1 were largely blocked by meclofenamate and were increased in the aorta of obese mice. Real-time quantitative polymerase chain reaction analysis of the thromboxane receptor gene in the carotid artery revealed a robust upregulation in obese animals (18-fold, 0.05); in comparison, obesity had a less pronounced effect on thromboxane synthase (2.1-fold increase, 0.05), or preproendothelin-1 gene expression (4.2-fold increase, 0.05).

CONCLUSIONS

These data demonstrate that obesity augments prostanoid-dependent vasoconstriction and markedly increases vascular thromboxane receptor gene expression. These changes are likely to promote the development of vascular disease, hypertension and thrombosis associated with obesity.

Effects of obesity on endothelium-dependent reactivity during acute nitric oxide synthase inhibition: modulatory role of endothelin

This study investigated vascular reactivity in response to acetylcholine, in the presence of acute inhibition of nitric oxide synthase, in the carotid artery and aorta of obese C57Bl6/J mice fed on a high-fat diet for 30 weeks, and of control mice. A subgroup of obese animals was also treated with the ET(A) receptor antagonist darusentan (50 mg x kg(-1) x day(-1)). In vascular rings from control animals, acetylcholine caused endothelium-dependent contractions in the carotid artery, but not in the aorta. In vascular rings from obese mice, contractility to acetylcholine was also evident in the aorta, and that in the carotid artery was increased compared with control mice. ET(A) receptor blockade by darusentan treatment of the obese mice prevented enhanced vasoconstriction to acetylcholine, resulting in mild vasodilatation. Thus obesity increases endothelium-dependent vasoconstriction in the absence of endothelial nitric oxide. This effect can be completely prevented by chronic ET(A) receptor blockade, suggesting that endothelin modulates increased endothelium-dependent vasoconstriction in obesity.

Oral contraceptives and the risk of thrombosis and atherosclerosis

Oral contraceptives containing synthetic oestrogens have been used successfully as birth control for > 40 years and are currently prescribed to > 100 million women worldwide. Several new progestins have been introduced and the third generation of progestins has now been available for two decades. Oral contraceptives are prescribed over a prolonged period of time and therefore substantially impact on hormonal, metabolic and plasmatic functions. Oral contraceptives increase the risk for venous thrombosis and pulmonary embolism, particularly if associated with confounding factors, such as genetic predisposition, smoking, hypertension or obesity. The risk of developing coronary artery disease is also increased in users with cardiovascular risk factors. This article discusses mechanistic and clinical issues and reviews the need for novel approaches targeting the considerable side effects in order to reduce cardiovascular morbidity in women using oral contraceptives.