Alexander Schmeisser

Monocytes coexpress endothelial and macrophagocytic lineage markers and form cord-like structures in Matrigel® under angiogenic conditions

OBJECTIVESnIt has been shown that circulating human non-adherent CD34+ cells coexpressing vascular endothelial growth factor (VEGF)-R2 and AC133 have the capacity to differentiate into adherent mature endothelial cells. However, prior studies have demonstrated that a much bigger subset of primary adherent mononuclear cells can also form endothelial progenitor cells (EPC). To determine the origin of the latter cell population we tested the hypothesis: do monocytes as a firmly adherent and plastic cell type have the potential to differentiate into an endothelial phenotype.nnnMETHODSnCD34-/CD14+ monocytes were isolated from human peripheral blood by adherence separation and magnetic bead selection (purity >90%) and cultured on fibronectin-coated plastic dishes (medium containing VEGF 10 ng/ml, basic fibroblast growth factor (bFGF) 2 ng/ml, insulin like growth factor (IGF-1) 1 ng/ml, 20% fetal calf serum).nnnRESULTSnAfter 2 weeks of culture, using fluorescence activated cell analysis we observed a new expression of the endothelial markers von Willebrand factor (vWf), VE-cadherin (VE) and ec-NOS in 45.2, 12.4 and 9.8% of the cells, respectively. The proportion of cells expressing these markers further increased after 4 weeks (94.2, 89.7 and 58.8% of these cells, respectively). The proportion of CD45 expressing cells remained unchanged during this period. However, after 14 days the specific macrophage antigen CD68 was newly expressed in 62% of the analysed cells with a further increase to 90% after 28 days of culture. In three-dimensional gel (Matrigel the formation of cord- and tubular-like structures was observed.nnnCONCLUSIONnThe present data indicate that under angiogenic stimulation macrophages develop an endothelial phenotype with expression of specific surface markers and even form cord- and tubular-like structures in vitro suggesting that this cell population may be recruited for vasculogenesis.

Patients with acute coronary syndromes express enhanced CD40 ligand/CD154 on platelets

OBJECTIVE To investigate whether CD40L/CD154 on platelets and soluble CD40L/CD154 may play a role in the inflammatory process of acute coronary syndromes. DESIGN AND SETTING Observational study in a university hospital. PATIENTS 15 patients with acute myocardial infarction, 25 patients with unstable angina, 15 patients with stable angina, and 12 controls. MAIN OUTCOME MEASURES CD40L/CD154 on platelets, P-selectin/CD62P on platelets, soluble CD40L/CD154 serum concentrations. RESULTS Mean (SD) CD40L/CD154 expression on platelets was 6.2 (2.8) MFI (mean fluorescence intensity) in the infarct group, 11 (3.3) MFI in the unstable angina group (pu2009<u20090.001 v infarction), 3.6 (0.9) MFI in the stable angina group (pu2009<u20090.01 vinfarction; pu2009<u20090.001 v unstable angina), and 3.2 (1.0) MFI in the controls (pu2009<u20090.01v infarction; pu2009<u20090.001v unstable angina; NSv stable angina). Soluble CD40L/CD154 concentration was 5.2 (1.1)u2009ng/ml in the infarct group, 4.2 (0.7)u2009ng/ml in the unstable angina group (pu2009<u20090.001v infarction), 2.9 (1.0)u2009ng/ml in stable angina group (pu2009<u20090.001 v infarction and unstable angina), and 3.0 (0.5)u2009ng/ml in the controls (pu2009<u20090.001v infarction and unstable angina; NSv stable angina). At a six months follow up, there was lower expression of CD40L/CD154 on platelets in patients with unstable angina (12.3 (3.6) v 3.8 (1.2) MFI, pu2009<u20090.0001) and acute myocardial infarction (6.2 (2.8)v 3.5 (0.8) MFI, pu2009<u20090.01) compared with their admission values six months earlier. Patients with unstable angina who needed redo coronary angioplasty (PTCA) or who had recurrence of angina were characterised by increased CD40L/CD154 expression on platelets compared with the remainder of the study group (recurrence of angina: 12.7 (3.2) v 9.7 (1.6) MFI, pu2009<u20090.05; re-do PTCA: 14.3 (4.2) v10.3 (2.1) MFI, pu2009<u20090.05). CONCLUSIONS Both CD40L/CD154 on platelets and soluble CD40L/CD154 are raised in patients with unstable angina and myocardial infarction. These findings suggest that CD40–CD40L/CD154 interactions may play a pathogenic role in triggering and propagation of acute coronary syndromes.

Transradial approach for coronary angioplasty in the setting of acute myocardial infarction: A dual-center registry

Although transradial angioplasty has been shown to have no major entry site–related complications, its clinical applicability for balloon angioplasty and stenting in acute myocardial infarction (AMI) is unclear. In order to assess the feasibility, safety, and clinical outcome of transradial access for coronary angioplasty (PTCA) and stenting during AMI, transradial angioplasty for AMI was registered on a prospective database at two European sites (A and B) with experience in the radial approach (RA); 6 Fr catheters with an inner lumen of at least 0.064″ and low‐profile rapid‐exchange balloons were used. Primary success rates and procedural complications of 6 Fr RA were determined and compared to 6 Fr femoral approach (FA) procedures. A total of 1,224 AMI patients entered the registry. Study site A enrolled 185 RA patients (13.6% AMI) and study site B 92 RA patients (63.4%). Patient baseline demographics were similar in both study centers and showed no differences between RA and FA patients, except a more frequent use of abciximab in study site B compared to A. PTCA was successful in > 95% of both RA and FA patients. Total procedural time did not differ between RA and FA patients. Severe access site–related bleeding complications, however, were observed in FA patients only: study site A used closure devices routinely and found 2% severe bleedings; study site B used no closure device for FA patients and observed 7% severe bleedings. In selected patients and in experienced hands, transradial PTCA in AMI has a high success rate, is clinically safe, and could become an attractive alternative access site for patients being at high or even low risk for bleeding complications. Cathet Cardiovasc Intervent 2002;55:206–211.

Enhanced levels of CD154 (CD40 ligand) on platelets in patients with chronic heart failure

Inflammation plays a significant contributory role in the pathogenesis of chronic heart failure (CHF). Previous data have shown enhanced plasma levels of proinflammatory cytokines, i.e. TNF‐α and IL‐6, as well as a persistent immune activation in patients with CHF. Furthermore, the immune modulator CD154 has been receiving increased attention, since it plays a key role in the pathophysiology of multicellular vascular events such as thrombosis, inflammation and atherosclerosis. Since CD154 intitiates and maintains the release of proinflammatory cytokines from endothelial cells, its potential role for the development and progression of CHF is of interest.

ACE Inhibition Lowers Angiotensin-II-Induced Monocyte Adhesion to HUVEC by Reduction of p65 Translocation and AT1 Expression

Angiotensin-converting enzyme (ACE) inhibitors interfere with several key events of vascular inflammation resulting in impressive reductions in coronary vascular events. However, in human arteries ACE inhibitors block the production of angiotensin II (AngII) incompletely because of the involvement of alternative pathways in local AngII formation. Therefore, our study concentrated on the presumed modulation by ACE inhibition of local AngII-mediated inflammatory actions by a mechanism independent of blockage of AngII formation. We analyzed the effect of the ACE inhibitor ramiprilat on AngII-dependent cell adhesion molecule (CAM) expression and adhesion of monocytic THP-1 cells to endothelial cells. AngII induced upregulation of P-selectin, VCAM-1 and ICAM-1 on endothelial cells via activation of AT1, which was correlated with enhanced THP-1 adhesion in flow chamber assays. Both enhanced adhesion and adhesion molecule expression were significantly reduced by pretreatment with ramiprilat. Ramiprilat reduced AT1 expression on endothelial cells and decreased the AngII-induced p65 translocation into the nucleus. Diminished AT1 expression and adhesion molecule expression in response to ramiprilat treatment were partially reversed after incubation with a bradykinin 2 receptor antagonist, suggesting that elevated bradykinin levels under ACE inhibition may be involved in the beneficial effect of ACE inhibitors. Thus, modulation of the local AngII system by ramiprilat may at least in part contribute to the benefits of ACE inhibition in the treatment of atherosclerotic diseases.

Regulation of the Hif-system by micro-RNA 17 and 20a – Role during monocyte-to-macrophage differentiation

MiRNAs are a class of endogenous tiny RNAs that act as inhibitors of translation or promote RNA degradation by duplex-formation within the 3-UTR of target mRNAs. They play an important role during a wide range of cellular processes by fine-tuning of gene expression. The differentiation of monocytes to macrophages plays a pivotal role in physiological as well as pathophysiological processes such as atherosclerosis. Monocytes which can be found in well-oxygenated blood migrate into areas with a high inflammation, such as the atherosclerotic plaque. There, they differentiate into macrophages. Interestingly, macrophages were found mainly at hypoxic sites of the plaque. Key regulators for the adaptation to hypoxia are the hypoxia-inducible factors (Hif). Therefore the aim of the present study was to investigate the regulation of the Hif-system by miRNAs during the process of monocyte differentiation. The present study shows that during the differentiation of monocytes into macrophages a dramatically change in the expression pattern of Hif-1α and Hif-2α took place. This was associated with a downregulation of microRNAs encoded by the miR-17-92 cluster. An in silico analysis of the 3-UTR of Hif-α subunits for binding sites of miRNAs was performed using different miRNA databases in concert with a secondary structure prediction algorithm. This analysis revealed that both 3-UTRs contain binding sites for miRNAs of the miR-17-92 cluster. Transfection of HeLa cells with miR-17 and miR-20a led to an inhibition of Hif-1α and -2α mRNA and protein expression and a lowered Hif DNA binding activity. Using a Luciferase-Reporter assay, it could be shown, that both Hif-α subunits are targeted by miR-17 and miR-20a. Furthermore, miR-overexpression in primary human macrophages demonstrates the important role of this microRNA-mediated regulation of the Hif-system for adaption of macrophages to hypoxia. In conclusion, the present study shows that the Hif-system is activated during monocyte-to-macrophage differentiation. This activation is in part mediated by a miRNA-dependent mechanism, which seems to be crucial for the adaption of macrophages to hypoxia.

Clozapine-induced myocarditis after long-term treatment: case presentation and clinical perspectives

Clozapine is the drug of choice for treatment-resistant schizophrenia. Prompted by a patient who developed reversible clozapine-induced myocarditis after long-term treatment with clozapine for several years for chronic-resistant schizophrenia, we undertook a review of the relevant literature. Concerning the myocarditis, the patient recovered rapidly by withdrawal of clozapine and with supportive management. Psychiatric stabilisation of the patient was at least possible with a combination of quetiapine (600 mg) and amisulpride (800 mg). Well-designed studies with the aim to specifically investigate treatment options after clozapine are limited and clinical possibilities are discussed in this paper. Olanzapine and combinations using non-clozapine atypical neuroleptics have partly shown improvement, whereas evidence for successful augmentation with mood stabilisers, anticonvulsants or electroconvulsive therapy in treatment-resistant schizophrenia is limited.

Right Ventricular Reduction as an Adjunct Procedure in Tricuspid Valve Repair

Functional tricuspid regurgitation secondary to mitral valve disease can not be attributed to the dilatation of the tricuspid annulus alone. Furthermore, geometrical changes of the right ventricle lead to tethering of the tricuspid valve leaflets and thereby to an incomplete leaflet coaptation. With this pathologic entity, conventional isolated tricuspid valve annuloplasty will presumably result in significant residual tricuspid regurgitation. The surgical goal should be the reduction of tricuspid annulus dilatation and annihilation of tethering forces on the tricuspid leaflets. In combination with conventional tricuspid valve annuloplasty, right ventricular reduction surgery, as demonstrated, may be effective in reaching these goals and hereby avoiding residual tricuspid regurgitation in this patient population.