Stefanie Keymel

Dietary inorganic nitrate mobilizes circulating angiogenic cells.

Nitric oxide (NO) was implicated in the regulation of mobilization and function of circulating angiogenic cells (CACs). The supposedly inert anion nitrate, abundant in vegetables, can be stepwise reduced in vivo to form nitrite, and consecutively NO, representing an alternative to endogenous NO formation by NO synthases. This study investigated whether inorganic dietary nitrate influences mobilization of CACs. In a randomized double-blind fashion, healthy volunteers ingested 150 ml water with 0.15 mmol/kg (12.7 mg/kg) of sodium nitrate, an amount corresponding to 100-300 g of a nitrate-rich vegetable, or water alone as control. Mobilization of CACs was determined by the number of CD34(+)/KDR(+) and CD133(+)/KDR(+) cells using flow cytometry and the mobilization markers stem cell factor (SCF) and stromal cell-derived factor-1a (SDF-1α) were determined in plasma via ELISA. Nitrite and nitrate were measured using high-performance liquid chromatography and reductive gas-phase chemiluminescence, respectively. NOS-dependent vasodilation was measured as flow-mediated vasodilation. Further mechanistic studies were performed in mice after intravenous application of nitrite together with an NO scavenger to identify the role of nitrite and NO in CAC mobilization. Nitrate ingestion led to a rise in plasma nitrite together with an acute increase in CD34(+)/KDR(+) and CD133(+)/KDR(+)-CACs along with increased NOS-dependent vasodilation. This was paralleled by an increase in SCF and SDF-1α and the maximal increase in plasma nitrite correlated with CD133(+)/KDR(+)-CACs (r=0.73, P=0.016). In mice, nitrate given per gavage and direct intravenous injection of nitrite led to CAC mobilization, which was abolished by the NO scavenger cPTIO, suggesting that nitrite mediated its effect via formation of NO. Dietary inorganic nitrate acutely mobilizes CACs via serial reduction to nitrite and NO. The nitrate-nitrite-NO pathway could offer a novel nutritional approach for regulation of vascular regenerative processes.

New functional aspects of the L-arginine-nitric oxide metabolism within the circulating blood

Nitric oxide (NO) is a signaling molecule of major importance modulating not only the function of the vascular wall but also that of blood cells, such as platelets and leukocytes. The synthesis of NO in the circulation has been attributed mainly to the vascular endothelium. Red blood cells (RBC) have been demonstrated to carry a non-functional NOS and--due to their huge haemoglobin content--have been assumed to metabolize large quantities of NO. More recently, however, RBC have been identified to reversibly bind, transport, and release NO within the cardiovascular system. We provide evidence that RBC from humans express an active and functional endothelial type NOS. RBC NOS activity may regulate deformability of RBC, and inhibits activation of platelets. This review aims to discuss the potential role of RBC NOS in the circulation and new concepts of NO research in the microcirculation.

Impaired Red Blood Cell Deformability in Patients with Coronary Artery Disease and Diabetes Mellitus

Patients with diabetes mellitus (DM) have an increased cardiovascular morbidity and mortality. There is increasing evidence that diabetes mellitus is associated with pathological hemorheological alterations, which might contribute to impaired coronary blood flow in coronary artery disease (CAD). We hypothesize that red blood cell (RBC) deformability is impaired in diabetic patients with CAD in comparison to nondiabetic patients with CAD. RBC deformability was measured in 21 patients with CAD and type 2 diabetes mellitus (CAD + DM) and 24 patients with CAD (CAD - DM). RBC deformability was measured by the Laser-assisted optical rotational cell analyzer by determining the elongation index (EI). RBC deformability was reduced in patients with CAD + DM in comparison to patients with CAD - DM (EI @ 1.12 Pa 0.236 ± 0.008 vs. 0.260 ± 0.005, p=0.007). Inverse univariate correlations were found between the EI @ 1.12 Pa and plasma glucose concentration (r= - 0.57; p<0.001) and HbA1c (r= - 0.45; p=0.002). Multivariate linear regression analysis identified plasma glucose concentration as the independent predictor of RBC deformability (β= - 0.58; p=0.007) thereby indicating that increased glucose concentrations determine RBC deformability in diabetic patients with CAD. In patients with CAD, diabetes mellitus leads to an impairment of RBC deformability which might contribute to increased morbidity of diabetic patients with CAD.

Macrovascular and microvascular function after implantation of left ventricular assist devices in end-stage heart failure: Role of microparticles

BACKGROUND The hemodynamic vascular consequences of implanting left ventricular assist devices (LVADs) have not been studied in detail. We investigated the effect of LVAD implantation compared with heart transplant (HTx) on microvascular and macrovascular function in patients with end-stage heart failure and evaluated whether microparticles may play a role in LVAD-related endothelial dysfunction. METHODS Vascular function was assessed in patients with end-stage heart failure awaiting HTx, patients who had undergone implantation of a continuous-flow centrifugal LVAD, and patients who had already received a HTx. Macrovascular function was measured by flow-mediated vasodilation (FMD) using high-resolution ultrasound of the brachial artery. Microvascular function was assessed in the forearm during reactive hyperemia using laser Doppler perfusion imaging and pulsed wave Doppler. Age-matched patients without heart failure and without coronary artery disease (CAD) (healthy control subjects) and patients with stable CAD served as control subjects. Circulating red blood cell (CD253(+)), leukocyte (CD45(+)), platelet (CD31(+)/CD41(+)), and endothelial cell (CD31(+)/CD41(-), CD62e(+), CD144(+)) microparticles were determined by flow cytometry and free hemoglobin by enzyme-linked immunosorbent assay. RESULTS FMD and microvascular function were significantly impaired in patients with end-stage heart failure compared with healthy control subjects and patients with stable CAD. LVAD implantation led to recovery of microvascular function, but not FMD. In parallel, increased free hemoglobin was observed along with red and white cell microparticles and endothelial and platelet microparticles. This finding indicates destruction of blood cells with release of hemoglobin and activation of endothelial cells. HTx and LVAD implantation led to similar improvements in microvascular function. FMD increased and microparticle levels decreased in patients with HTx, whereas shear stress during reactive hyperemia was similar in patients with LVADs and patients with HTx. CONCLUSIONS Our data suggest that LVAD support leads to significant improvements in microvascular perfusion and hemodynamics. However, destruction of blood cells may contribute to residual endothelial dysfunction potentially by increasing nitric oxide scavenging capacity.

Characterization of the Non-Invasive Assessment of the Cutaneous Microcirculation by Laser Doppler Perfusion Scanner

Microcirculation (2010) 17, 358–366. doi: 10.1111/j.1549‐8719.2010.00037.x

Recovery of neutrophil apoptosis by ectoine: a new strategy against lung inflammation

The life span of neutrophilic granulocytes has a determining impact on the intensity and duration of neutrophil driven lung inflammation. Based on the compatible solute ectoine, we aimed to prevent anti-apoptotic reactions in neutrophils triggered by the inflammatory microenvironment in the lung. Neutrophils from chronic obstructive pulmonary disease patients and control individuals were exposed to inflammatory mediators and xenobiotics in the presence or absence of ectoine. The in vivo relevance of this approach was tested in xenobiotic-induced lung inflammation in rats. The reduction of apoptosis rates of ex vivo-exposed neutrophils from all study groups was significantly restored in the presence of ectoine. However, natural apoptosis rates not altered by inflammatory stimuli were not changed by ectoine. Mechanistic analyses demonstrated the preventive effect of ectoine on the induction of anti-apoptotic signalling. Neutrophilic lung inflammation induced by single or multiple expositions of animals to environmental particles was reduced after the therapeutic intervention with ectoine. Analyses of neutrophils from bronchoalveolar lavage indicate that the in vivo effect is due to the restoration of neutrophil apoptosis. Ectoine, a compound of the highly compliant group of compatible solutes, demonstrates a reproducible and robust effect on the resolution of lung inflammation.

Nitric oxide influences red blood cell velocity independently of changes in the vascular tone

Abstract Nitric oxide (NO) plays a key role in regulation of vascular tone and blood flow. In the microcirculation blood flow is strongly dependent on red blood cells (RBC) deformability. In vitro NO increases RBC deformability. This study hypothesized that NO increases RBC velocity in vivo not only by regulating vascular tone, but also by modifying RBC deformability. The effects of NO on RBC velocity were analysed by intra-vital microscopy in the microcirculation of the chorioallantoic membrane (CAM) of the avian embryo at day 7 post-fertilization, when all vessels lack smooth muscle cells and vascular tone is not affected by NO. It was found that inhibition of enzymatic NO synthesis and NO scavenging decreased intracellular NO levels and avian RBC deformability in vitro. Injection of a NO synthase-inhibitor or a NO scavenger into the microcirculation of the CAM decreased capillary RBC velocity and deformation, while the diameter of the vessels remained constant. The results indicate that scavenging of NO and inhibition of NO synthesis decrease RBC velocity not only by regulating vascular tone but also by decreasing RBC deformability.

Prevalence of De Novo Aortic Valve Insufficiency in Patients After Heartware Vad Implantation with an Intermittent Low-speed Algorithm

De novo aortic valve insufficiency (AI) is a frequent occurrence in patients supported with left ventricular assist device (LVAD). The European version of the HeartWare LVAD has intermittent low-speed software (lavare cycle) to facilitate intermittent aortic valve opening. We examined aortic valve opening status and prevalence of AI in patients supported with HeartWare LVAD and activated lavare cycle. HeartWare LVAD patients were prospectively monitored using serial echocardiograms at different time points after the LVAD implantation. Inclusion criteria were patients with no > mild AI and/or no aortic valve surgery at the time of LVAD implantation and at least 60 days of support. Three of 37 patients had aortic valve surgery and were excluded from the analysis. A total of 34 patients with mean age of 57 ± 12 years met the inclusion criteria. After median support duration of 408 days (77–1250 days), eight patients had trace/mild AI (24%) and one patient developed moderate AI (3%). An average pump flow, speed, and mean arterial pressure of 4.4 ± 0.6 L/min, 2,585 ± 147 rpm, and 88 ± 11 mmHg were documented, respectively. Aortic valve opening was persistently seen in 22 patients (65%). Aortic valve opening is frequent, and the development of > mild AI seems to be rare in patients supported with HeartWare LVAD.

Resting microvascular resistance and conduit artery tone: relevance to endothelium-dependent flow-mediated dilation.

Background Conduit arteries respond to increases in flow by dilating, which is mediated by endothelium-derived nitric oxide. The significance of the interaction between microcirculation and macrocirculation in the flow-mediated dilation (FMD) is poorly understood. Hypothesis We hypothesize that baseline conduit artery vasomotor tone (CAVT) and resting microvascular resistance (MVR) predict FMD. Methods We investigated resting diameter and FMD of the brachial artery using high-resolution ultrasound and forearm blood flow with plethysmography in 60 healthy individuals. CAVT was calculated as change of the arterial diameter from baseline to maximal dilation expressed as percentage of the maximum dilation. Resting MVR was determined as quotient of mean arterial blood pressure and forearm blood flow. Results Mean FMD was 10.7 ± 2.0%, indicating normal endothelial function. The extent of brachial artery FMD was not only related to baseline CAVT (r = 0.70, P < 0.01), but inversely to resting MVR (r = –0.69, P < 0.01). Moreover, in a simple regression analysis, baseline CAVT was inversely related to resting MVR (r = −0.82, P < 0.01). In a multivariate linear regression analysis, baseline CAVT and MVR were identified as independent predictors of brachial artery FMD. Conclusion Our data imply a close interaction of resting microvascular resistance and baseline CAVT modulating flow-mediated conduit artery dilation. Eur J Cardiovasc Prev Rehabil 15:677–682

Stenting as a Rescue Treatment of a Pulmonary Artery False Aneurysm Caused by Swan-Ganz Catheterization

Pulmonary vascular injury is a rare but life-threatening complication of Swan-Ganz catheterization. We report an 82-year old patient who underwent right heart catheterization by a balloon-tipped catheter because of suspected pulmonary hypertension. After deflation of the catheter in the wedge position, hemoptoe appeared associated with acute respiratory insufficiency requiring respiratory support by intubation and mechanical ventilation. Pulmonary angiography showed the formation of a false aneurysm of a segment artery of the left lower lobe. Immediate interventional therapy was performed by the implantation of two coated coronary stent grafts into the injured pulmonary artery thereby excluding the false aneurysm. Bleeding was stopped by this interventional approach while antegrade blood flow was maintained. Long term follow-up after 3 months showed an effective treatment with a completely thrombotic false aneurysm. However, despite oral anticoagulation and dual antiplatelet therapy, graft patency could not be achieved after 3 months. In summary, implantation of coated stents is a feasible and safe approach for the acute and long term treatment of potentially life-threatening condition of a pulmonary artery false aneurysm while treatment to achieve long term patency of the affected vessel still remains an issue to be resolved.