Bodo E. Strauer

Plasma nitrite rather than nitrate reflects regional endothelial nitric oxide synthase activity but lacks intrinsic vasodilator action

The plasma level of NOx, i.e., the sum of NO2− and NO3−, is frequently used to assess NO bioavailability in vivo. However, little is known about the kinetics of NO conversion to these metabolites under physiological conditions. Moreover, plasma nitrite recently has been proposed to represent a delivery source for intravascular NO. We therefore sought to investigate in humans whether changes in NOx concentration are a reliable marker for endothelial NO production and whether physiological concentrations of nitrite are vasoactive. NO2− and NO3− concentrations were measured in blood sampled from the antecubital vein and brachial artery of 24 healthy volunteers. No significant arterial-venous gradient was observed for either NO2− or NO3−. Endothelial NO synthase (eNOS) stimulation with acetylcholine (1–10 μg/min) dose-dependently augmented venous NO2− levels by maximally 71%. This effect was paralleled by an almost 4-fold increase in forearm blood flow (FBF), whereas an equieffective dose of papaverine produced no change in venous NO2−. Intraarterial infusion of NO2− had no effect on FBF. NOS inhibition (NG-monomethyl-l-arginine; 4–12 μmol/min) dose-dependently reduced basal NO2− and FBF and blunted acetylcholine-induced vasodilation and NO release by more than 80% and 90%, respectively. In contrast, venous NO3− and total NOx remained unchanged as did systemic arterial NO2− and NO3− levels during all these interventions. FBF and NO release showed a positive association (r = 0.85; P < 0.001). These results contradict the current paradigm that plasma NO3− and/or total NOx are generally useful markers of endogenous NO production and demonstrate that only NO2− reflects acute changes in regional eNOS activity. Our results further demonstrate that physiological levels of nitrite are vasodilator-inactive.

Remodeling and reparation of the cardiovascular system

Growth or altered metabolism of nonmyocyte cells (cardiac fibroblasts, vascular smooth muscle and endothelial cells) alters myocardial and vascular structure (remodeling) and function. However, the precise roles of circulating and locally generated factors such as angiotensin II, aldosterone and endothelin that regulate growth and metabolism of nonmyocyte cells have yet to be fully elucidated. Trials of pharmacologic therapy aimed at preventing structural remodeling and repairing altered myocardial structure to or toward normal in the setting of hypertension, heart failure and diabetes are reviewed. It is proposed that these are therapeutic goals that may reduce cardiovascular morbidity and mortality. Although this hypothesis remains unproved the primary goal of therapy should be to preserve or restore tissue structure and function.

Cytokine removal and cardiovascular hemodynamics in septic patients with continuous venovenous hemofiltration

Objectives: To determine whether continuous venovenous hemofiltration leads to extraction of tumor necrosis factor alpha (TNFα) and cytokines from the circulation of critically ill patients with sepsis and acute renal failure and to quantitate the clearance and the removal rate of these cytokines and their effect on serum cytokine concentrations. Design: Prospective, controlled study in patients with continuous venovenous hemofiltration (24 l/24 h) using a polysulphone membrane in patients with acute renal failure. Patients: 33 ventilated patients with acute renal failure of septic (n = 18) and cardiovascular origin (n = 15) were studied. Interventions: Hemodynamic monitoring and collection of blood and ultrafiltrate samples before and during the first 72 h of continuous hemofiltration. Measurements and main results: Cardiovascular hemodynamics (Swan-Ganz catheter), Acute Physiology and Chronic Health Evaluation II score, creatinine, electrolytes, and blood urea nitrogen were recorded daily. Cytokines (TNFα, TNFα-RII, interleukin (IL) 1β , IL1RA, IL2, IL2R, IL6, IL6R, IL8, IL10) were measured in prefilter blood and in ultrafiltrate immediately preceding and 12, 24, 48, and 72 h after initiating continuous venovenous hemofiltration (CVVH). Septic patients showed elevated cardiovascular values for cardiac output (7.2 ± 2.1 l/min), cardiac index (4.2 ± 1.3 l/min per m2), and stroke volume (67 ± 23 ml) and reduced values for systemic vascular resistance (540 ± 299 dyn · s · cm− 5). All hemodynamic values normalized within the first 24 h after initiating CVVH treatment. TNFα was 1833 ± 1217 pg/ml in septic patients and 42.9 ± 6.3 pg/ml in nonseptic patients (p < 0.05) prior to CVVH. TNFα was detected in ultrafiltrate but did not decrease in blood during treatment with CVVH. There was no difference in IL 1β between septic (3.8 ± 1.9 pg/ml) and nonseptic patients (1.7 ± 0.5 pg/ml). No significant elimination of cytokines was achieved in the present study by CVVH treatment. Conclusions: These findings demonstrate that CVVH can remove TNFα and special cytokines from the circulation of critically ill patients. Cardiovascular hemodynamics seemed to improve in septic patients after induction of hemofiltration treatment, although there was no evidence that extracorporeal removal of cytokines achieved a reduction in blood levels. The study indicates that low volume continuous hemofiltration with polysulphone membranes in patients with acute renal failure is not able to induce significant removal of cytokines.

The BALANCE Study: Clinical Benefit and Long-Term Outcome After Intracoronary Autologous Bone Marrow Cell Transplantation in Patients With Acute Myocardial Infarction

OBJECTIVES The aim of this study was to investigate the quantitative amount of improvement of ventricular hemodynamic status, geometry, and contractility as well as the long-term clinical outcome of cell-treated patients after acute myocardial infarction (AMI). BACKGROUND Animal experiments as well as clinical studies have demonstrated that autologous bone marrow cell (BMC) transplantation might improve ventricular function and prevent remodeling. METHODS Sixty-two patients underwent intracoronary autologous BMC transplantation 7 +/- 2 days after AMI. Cells were infused directly into the infarct-related artery. The control group consisted of 62 patients with comparable left ventricular (LV) ejection fraction (EF) and diagnosis. All patients had several examinations (e.g., coronary angiography, right heart catheterization, biplane left ventriculography, electrocardiogram [ECG] at rest and exercise, echocardiography, late potential [LP], heart rate variability [HRV], and 24-h Holter ECG). The therapeutic follow-up was performed 3, 12, and 60 months after BMC therapy. RESULTS Three months after BMC therapy there was significant improvement of EF and stroke volume index. The infarct size was significantly reduced by 8%. Contraction velocities (lengths/second, volumes/second) increased significantly and the slope of the ventricular function curve (systolic pressure/end-systolic volume) became steeper. There was significant improvement of contractility in the infarct zone, as evidenced by a 31% increase of LV velocity of shortening (VCF), preferably in the border zone of the infarct zone. In contrast, the noninfarcted area showed no difference in VCF before and after BMC therapy. Furthermore, decreases of abnormal HRV, LP, and ectopic beats were documented after BMC therapy. Twelve and 60 months after BMC therapy the parameters of contractility, hemodynamic status, and geometry of the LV were stable. The exercise capacity of treated patients was significantly augmented, and the mortality was significantly reduced in comparison with the control group. CONCLUSIONS BMC therapy leads to significant and longstanding improvements of LV performance as well as quality of life and mortality of patients after AMI. After BMC therapy, no side effects were observed, showing that BMC therapy is safe.

Stem Cell Therapy in Perspective

The concept of regenerative medicine using the body’s own stem cells and growth factors to repair tissues may become a reality as new basic science works and initial clinical experiences have “teamed-up” in an effort to develop alternative therapeutic strategies to treat the diseased myocardium. In particular, revealing the signals that mediate cellular growth and differentiation may provide novel tools designed for myocardial regeneration in patients sustaining ischemic cardiomyopathy syndromes. We attempt herein to provide a critical overview of recent developments of myocardial cell transplantation strategies. Stem cells are a population of immature tissue precursor cells capable of self-renewal and provision of de novo and/or replacement cells for many tissues. Embryonic stem cells can be obtained from the inner cell mass of the embryonal blastocyst. Although it was recently shown that human embryonic stem cells can differentiate into cardiomyocytes,1 because of the immunogenicity and rejection, as well as ethical considerations, these cells may be restricted to experimental in vitro studies and their therapeutical potential remains to be determined. Also, these cells may act as an unanticipated arrhythmogenic source after intramyocardial transplantation.2 Clinical application of these cells is most likely years ahead (Table). View this table: Advantages and Disadvantages of Embryonic Versus Adult Stem Cells In contrast, adult human stem cells (hematopoietic, mesenchymal) are found in mature tissues, eg, the bone marrow. Plasticity of adult stem cells can probably generate lineages of cells different from their original organ of origin. Thus, these cells can be used for organ regeneration and for cellular repair in various species, as well as in humans. Ethical problems for adult autologous stem cells do not exist, and although much experimental work remains to be done, their clinical relevance and therapeutic benefit in heart disease have recently been shown for the first time.3 Except for hematopoietic and …

Repair of Coronary Arterioles After Treatment With Perindopril in Hypertensive Heart Disease

In hypertensive heart disease, no data are available on the repair of coronary resistance vessels in patients after long-term ACE inhibitor treatment. Fourteen patients with essential hypertension were studied with coronary flow reserve and with transvenous endomyocardial biopsy before and after 12 months of antihypertensive treatment with perindopril (4 to 8 mg/d, mean 5.9+/-2.3 mg/d). Left ventricular muscle mass index decreased by 11% (from 145+/-41 to 128+/-36 g/m(2), P=0.04). Maximal coronary blood flow was increased by 54% (from 170+/-46 to 263+/-142 mL. min(-1). 100 g(-1), P=0.001), and minimal coronary vascular resistance was diminished by 33% (from 0.67+/-0.21 to 0.45+/-0.19 mm Hg. min. 100 g. mL(-1), P=0.001); consequently, coronary reserve increased by 67% from 2.1+/-0.6 to 3. 5+/-1.9 (P=0.001). Structural analysis revealed regression of periarteriolar collagen area by 54% (from 558+/-270 to 260+/-173 microm(2), P=0.04) and of total interstitial collagen volume density by 22% (from 5.5+/-3.8 Vv% to 4.3+/-3.2 Vv%, P=0.04), whereas arteriolar wall area was slightly but not significantly reduced. Long-term therapy with the ACE inhibitor perindopril induces structural repair of coronary arterioles that is mainly characterized by the regression of periarteriolar fibrosis and associated with a marked improvement in coronary reserve. These findings indicate the beneficial reparative effects of ACE inhibition on coronary microcirculation in hypertensive heart disease.

Improvement of coronary flow reserve after long-term therapy with enalapril

To date, no clinical study shows an improvement in coronary flow reserve due to long-term antihypertensive therapy. in view of the contribution of the renin-angiotensin system to the process of hypertensive remodeling of the heart and coronary circulation, angiotensin-converting enzyme (ACE) inhibitors might act as cardioreparative drugs in arterial hypertension. Accordingly, our objective in this investigation was to examine under clinical conditions to what extent long-term antihypertensive treatment with an angiotensin-converting enzyme inhibitor improved the diminished coronary flow reserve in hypertensive patients with microvascular angina pectoris. For the purpose of comparison, we also treated a normotensive control group of 6 patients with hypertrophic nonobstructive cardiomyopathy. Fifteen hypertensive individuals (10 men, 5 women; age, 58 +/- 6 years) were treated with enalapril (10 to 20 mg/d; mean, 16.7 +/- 4.9 mg/d) for 11 to 13 months. At the end of the treatment period, systolic pressure decreased from 178 +/- 14 to 137 +/- 12 mm Hg and diastolic pressure from 102 +/- 11 to 86 +/- 4 mm Hg under ambulatory conditions. Left ventricular muscle mass index decreased by 8%, from 149 +/- 32 to 137 +/- 28 g/m2 (P < .05). Maximal coronary blood flow after dipyridamole was increased by 43%, from 181 +/- 69 to 258 +/- 116 mL/min per 100 g (P < .001), and minimal coronary vascular resistance was diminished by 29%, from 0.66 +/- 0.23 to 0.47 +/- 0.24 mm Hg x min x 100g x mL-1 (P < .001) after enalapril treatment. Consequently, the calculated coronary reserve increased from 2.2 +/- 0.6 to 3.3 +/- 1.2 (P < .001). After enalapril therapy, the functional class of angina pectoris according to the Canadian classification system had changed from 2.5 +/- 0.6 to 1.5 +/- 0.6 (P < .01). The maximal working capacity had increased from 23.775 +/- 3.970 to 26.255 +/- 4.598 J (mean +/- SE, P < .05). The maximal ST-segment depression at maximal work-load was reduced from 0.18 +/- 0.02 to 0.06 +/- 0.02 (mean +/- SE, (P < .01). In summary, long-term therapy with the angiotensin-converting enzyme inhibitor enalapril must be considered a cardioreparative treatment with respect to the coronary microcirculation in hypertensive heart disease.

Clinical ResearchClinical TrialThe BALANCE Study: Clinical Benefit and Long-Term Outcome After Intracoronary Autologous Bone Marrow Cell Transplantation in Patients With Acute Myocardial Infarction

OBJECTIVES The aim of this study was to investigate the quantitative amount of improvement of ventricular hemodynamic status, geometry, and contractility as well as the long-term clinical outcome of cell-treated patients after acute myocardial infarction (AMI). BACKGROUND Animal experiments as well as clinical studies have demonstrated that autologous bone marrow cell (BMC) transplantation might improve ventricular function and prevent remodeling. METHODS Sixty-two patients underwent intracoronary autologous BMC transplantation 7 +/- 2 days after AMI. Cells were infused directly into the infarct-related artery. The control group consisted of 62 patients with comparable left ventricular (LV) ejection fraction (EF) and diagnosis. All patients had several examinations (e.g., coronary angiography, right heart catheterization, biplane left ventriculography, electrocardiogram [ECG] at rest and exercise, echocardiography, late potential [LP], heart rate variability [HRV], and 24-h Holter ECG). The therapeutic follow-up was performed 3, 12, and 60 months after BMC therapy. RESULTS Three months after BMC therapy there was significant improvement of EF and stroke volume index. The infarct size was significantly reduced by 8%. Contraction velocities (lengths/second, volumes/second) increased significantly and the slope of the ventricular function curve (systolic pressure/end-systolic volume) became steeper. There was significant improvement of contractility in the infarct zone, as evidenced by a 31% increase of LV velocity of shortening (VCF), preferably in the border zone of the infarct zone. In contrast, the noninfarcted area showed no difference in VCF before and after BMC therapy. Furthermore, decreases of abnormal HRV, LP, and ectopic beats were documented after BMC therapy. Twelve and 60 months after BMC therapy the parameters of contractility, hemodynamic status, and geometry of the LV were stable. The exercise capacity of treated patients was significantly augmented, and the mortality was significantly reduced in comparison with the control group. CONCLUSIONS BMC therapy leads to significant and longstanding improvements of LV performance as well as quality of life and mortality of patients after AMI. After BMC therapy, no side effects were observed, showing that BMC therapy is safe.

Serum nitrite sensitively reflects endothelial NO formation in human forearm vasculature: evidence for biochemical assessment of the endothelial l-arginine–NO pathway

OBJECTIVE A reduced bioactivity of endothelial nitric oxide (NO) has been implicated in the pathogenesis of atherosclerosis. In humans, the endothelial L-arginine-NO pathway has been indirectly assessed via the flow response to endothelium-dependent vasodilators locally administered into the coronary, pulmonary or forearm circulation. However, biochemical quantification of endothelial NO formation in these organ circulations has been hampered so far because of the rapid metabolism of NO. Therefore, we aimed to work out a reliable biochemical index to assess endothelial NO formation in human circulation. METHODS In 33 healthy volunteers, forearm blood flow (FBF) was measured by standard techniques of venous occlusion plethysmography at rest, after local application of the endothelium-dependent vasodilator acetylcholine (ACH), the endothelium-independent vasodilator papaverine (PAP), the stereospecific inhibitor of endothelial NO synthase (eNOS) L-NMMA, and L-arginine (ARG), the natural substrate of eNOS. In parallel, nitrite and nitrate concentrations in blood samples taken from the antecubital vein were measured by HPLC using anion-exchange chromatography in combination with electrochemical and ultraviolet detection following a specific sample preparation method. RESULTS ACH dose-dependently increased resting FBF (from 3.0 +/- 0.3 to 10.4 +/- 0.9 ml/min per 100 ml tissue) and serum nitrite concentration (from 402 +/- 59 to 977 +/- 82 nmol/l, both p < 0.05, n = 12). A significant correlation was observed between the changes in FBF and the serum nitrite concentration (r = 0.61, p < 0.0001). L-NMMA reduced resting FBF and endothelium-dependent vasodilation by 30% and this was paralleled by a significant reduction in serum nitrite concentration at the highest dose of ACH (n = 9, p < 0.001). PAP increased FBF more than fourfold, but did not affect serum nitrite concentration (n = 11), whereas ARG significantly increased both FBF and nitrite. Basal serum nitrate amounted to 25 +/- 4 mumol/l and remained constant during the application of ACH, PAP and L-NMMA. CONCLUSIONS The concentration of serum nitrite sensitively reflects changes in endothelial NO formation in human forearm circulation. This biochemical measure may help to characterize the L-arginine-NO pathway in disease states associated with endothelial dysfunction and to further elucidate its pathophysiological significance for the development of atherosclerosis in humans.

Transplantation of autologous mononuclear bone marrow stem cells in patients with peripheral arterial disease (The TAM-PAD study)

ObjectivesFor patients with severe, chronic limb ischemia in many cases interventional or surgical treatment is not possible anymore. In the past, both intramuscular and intraarterial transplantation of autologous BMCs had been proved therapeutically beneficial. The TAMPAD study is the first one to analyze combined intraarterial and intramuscular BMC transplantation in its acute and long-term effects.Methods13 patients with chronically ischemic limbs due to peripheral arterial disease (Fontaine stage IIb) were recruited and underwent follow-up examinations after 2 and 13 months. Mononuclear cells from bone marrow were injected intramuscular and intraarterial into the ischemic limb.ResultsIn contrast to the control group, after 2 months the pain-free walking distance of the transplanted patients significantly increased (from 147 ± 90 to 500 ± 614 m, p = 0.001). Furthermore the ankle-brachial index was significantly improved (at rest from 0.66±0.18 to 0.80±0.15, p=0.003, after stress from 0.64 ± 0.19 to 0.76 ± 0.16, p = 0.006). Similar improvement was documented in capillary-venous oxygen-saturation (thigh from 59 ± 9 to 66 ± 5, p = 0.005, lower leg from 56 ± 14 to 63 ± 5, p = 0.021) and venous occlusion plethysmography (rest from 2.1 ± 0.7 to 2.5 ± 0.7, p = 0.009, mean reactive hyperemia from 5.3 ± 1.8 to 7.2 ± 1.8, p = 0.003, and peak flow from 7.2 ± 3.2 to 10.8 ± 2.8, p = 0.002). After 13 months these positive effects persisted at their improved level. No side effects or complications were monitored.ConclusionsCombined intraarterial and intramuscular transplantation of autologous mononuclear bone marrow stem cells is a clinically feasible and minimally invasive therapeutic option for patients with severe chronic peripheral occlusive arterial disease.