Biomedical subjects

Bodo Levkau

Publications and source records attributed to Bodo Levkau.

32 records · Page 2Linked to original sources

PubMed2004

High-density lipoprotein stimulates myocardial perfusion in vivo.

BACKGROUND: Several clinical studies have demonstrated a close association between plasma HDL cholesterol levels and endothelium-dependent vasodilation in peripheral arteries. In isolated arteries, HDL has been shown to mediate vasodilation via NO release. In vivo, administration of reconstituted HDL restored abnormal endothelial function of the brachial artery in hypercholesterolemic patients. However, no data are currently available on the effect of HDL on myocardial perfusion. METHODS AND RESULTS: In this study, administration of human HDL enhanced incorporation of the perfusion tracer 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) into the murine heart in vivo by approximately 18%. This increase was completely abolished in mice deficient for endothelial NO synthase. Because we have recently identified sphingosine 1-phosphate (S1P) as an important vasoactive component contained in HDL, we measured myocardial perfusion after administration of S1P in vivo. We observed an approximately 25% decrease in myocardial MIBI uptake, which was abolished in mice deficient for the S1P receptor S1P3. In S1P3-/- mice, the stimulatory effect of HDL on myocardial perfusion was preserved. CONCLUSIONS: HDL increased myocardial perfusion under basal conditions in vivo via NO-dependent mechanisms, whereas S1P inhibited myocardial perfusion through the S1P3 receptor. Thus, HDL may reduce coronary risk via direct NO-mediated vasodilatory effects on the coronary circulation.

Animals↗

PubMed2004

Scintigraphic imaging of matrix metalloproteinase activity in the arterial wall in vivo.

BACKGROUND: Matrix metalloproteinases (MMPs) are enzymes involved in the proteolytic degradation of extracellular matrix. They play an important role in several disease processes, such as inflammation, cancer, and atherosclerosis. METHODS AND RESULTS: In this study, we have used the broad-spectrum MMP inhibitor CGS 27023A to develop the radioligand [123I]I-HO-CGS 27023A for in vivo imaging of MMP activity. Using this radioligand, we were able to specifically image MMP activity by scintigraphy in vivo in the MMP-rich vascular lesions that develop after carotid artery ligation and cholesterol-rich diet in apolipoprotein E-deficient mice. These results were confirmed by gamma counting of lesional tissue (counts per minute per milligram). CONCLUSIONS: Imaging of MMP activity in vivo is feasible using radiolabeled MMP inhibitors. Additional studies are needed to test the potential of this approach as a novel noninvasive clinical diagnostic tool for the management of human MMP-related diseases.

Animals↗

PubMed2004

Heat shock protein 72 and apoptosis indicate cardiac decompensation during early multiple organ failure in sheep.

OBJECTIVE: Inducible heat shock protein 72 (HSP 72) preserves myocardial function and prevents apoptosis. We investigated the expression and localization of HSP 72 and apoptosis in our previously described new model of multiple organ failure. DESIGN: Eighteen adult-instrumented sheep and three healthy controls were randomly assigned to one of three groups: (a) norfenefrine-masked hypovolemia plus endotoxemia (NMH+ENDO); (b) norfenefrine-masked hypovolemia without endotoxemia (NMH); (c) recurrent endotoxemia during normovolemia (ENDO); and (d) normovolemia without endotoxemia (CONTROLS). MEASUREMENTS AND RESULTS: Hearts were analyzed by light microscopy, Western blots, immunohistochemistry, and TUNEL staining. HSP 72 expression was approximately threefold increased in NMH+ENDO compared with the other groups ( p<0.05) and was localized mainly in left ventricular cardiomyocytes. HSP 72 was elevated in animals with norfenefrine-refractory shock compared to survivors ( p=0.015). TUNEL-positive cells in the left ventricle were significantly elevated in the NMH+ENDO group ( p=0.05) and correlated with HSP 72 expression (r=0.51, p=0.018). HSP 72 correlated positively with heart rate (r=0.76, p<0.0001), the prefinal hourly dose of norfenefrine (r=0.88, p<0.0001), and negatively with left ventricular stroke work index (r=-0.52, p=0.028). Double staining revealed TUNEL-positive cells with and without HSP 72 expression. Micronecroses were only detectable in NMH and NMH+ENDO without intergroup difference or correlations with hemodynamics. CONCLUSION: HSP 72 overexpression and apoptosis, but not necrosis, indicate cardiovascular decompensation and poor outcome during early multiple organ failure.

Animals↗

PubMed2004

Synthesis and preliminary biological evaluation of new radioiodinated MMP inhibitors for imaging MMP activity in vivo.

Non-invasive measurement of matrix metalloproteinase (MMP) activity in vivo is a clinical challenge in many disease processes such as inflammation, tumor metastasis and atherosclerosis. Therefore, radioiodinated analogues of the non-peptidyl broad-spectrum MMP inhibitor (MMPI) CGS 27023A 1a were synthesized for non-invasive detection of MMP activity in vivo using single photon emission computed tomography (SPECT). The compounds Br-CGS 27023A 1b and HO-CGS 27023A 1d were synthesized from the amino acid D-valine and used as precursors for radioiodinated derivatives of CGS 27023A and their non-radioactive references I-CGS 27023A 1c and HO-I-CGS 27023A 1e. Radioiodination of the precursors with [(123)I]NaI or [(125)I]NaI produced the no-carrier-added MMP inhibitors [(123)I]I-CGS 27023A 1f, [(125)I]I-CGS 27023A 1g, HO-[(123)I]I-CGS27023A 1h, and HO-[(125)I]I-CGS 27023A 1i. In vitro studies showed that the non-radioactive analogues of the MMP inhibitors exhibited affinities against gelatinase A (MMP-2) and gelatinase B (MMP-9) in the nanomolar range, comparable to the parent compound CGS 27023A. In vivo biodistribution using HO-[(125)I]I-CGS 27023A 1i in CL57 Bl6 mice showed rapid blood and plasma clearance and low retention in normal tissues. The preliminary biological evaluation warrant further studies of these radioiodinated MMP inhibitors as potential new radiotracers for imaging MMP activity in vivo.

Animals↗

PubMed2004

Prognostic relevance of activated Akt kinase in node-negative breast cancer: a clinicopathological study of 99 cases.

Patients with lymphnode-negative breast cancer show a 10-year tumor recurrence rate of approximately 30%. Therefore, it is important to identify high-risk patients who would benefit from further adjuvant therapy. For this purpose, we examined the activation state of two kinases important in the regulation of cell proliferation and apoptosis in a series of 99 node-negative breast cancer cases with a mean follow-up of 10 years: Akt and extracellular regulated kinase (ERK1/2). The activation of Akt and ERK1/2 was investigated by immunohistochemistry using phospho-specific antibodies. The results were correlated with HER-2/neu expression, histological grading, receptor status, overall survival (OS) as well as with cell proliferation (Ki67 immunoreactivity, mitotic count) and tumor apoptosis assessed by TUNEL staining. Activation of Akt (pAkt) but not activation of ERK1/2 (pERK1/2) correlated with HER-2/neu overexpression (P<0.05) and was related to reduced tumor apoptosis (P<0.05). No association was found between pAkt or pERK1/2 with cell proliferation assessed by Ki67 and mitotic count (MC). Survival analysis of receptor status, HER2/neu expression, histological grading, MC and pAkt immunoexpression showed a significant correlation with decreased OS, but only pAkt reached statistical significance in the multivariate Cox regression analysis (P=0.015). Activation of Akt in node-negative breast cancer may indicate aggressive tumor behavior and may constitute an independent prognostic factor of OS. The determination of pAkt status may be of value in identifying high-risk patients, who would benefit from adjuvant therapy, and gives a rationale to investigate new therapy strategies by specific inhibition of the Akt signaling pathway in breast cancer.

Apoptosis↗

PubMed2004

HDL induces NO-dependent vasorelaxation via the lysophospholipid receptor S1P3.

HDL is a major atheroprotective factor, but the mechanisms underlying this effect are still obscure. HDL binding to scavenger receptor-BI has been shown to activate eNOS, although the responsible HDL entities and signaling pathways have remained enigmatic. Here we show that HDL stimulates NO release in human endothelial cells and induces vasodilation in isolated aortae via intracellular Ca2+ mobilization and Akt-mediated eNOS phosphorylation. The vasoactive effects of HDL could be mimicked by three lysophospholipids present in HDL: sphingosylphosphorylcholine (SPC), sphingosine-1-phosphate (S1P), and lysosulfatide (LSF). All three elevated intracellular Ca2+ concentration and activated Akt and eNOS, which resulted in NO release and vasodilation. Deficiency of the lysophospholipid receptor S1P3 (also known as LPB3 and EDG3) abolished the vasodilatory effects of SPC, S1P, and LSF and reduced the effect of HDL by approximately 60%. In endothelial cells from S1P3-deficient mice, Akt phosphorylation and Ca2+ increase in response to HDL and lysophospholipids were severely reduced. In vivo, intra-arterial administration of HDL or lysophospholipids lowered mean arterial blood pressure in rats. In conclusion, we identify HDL as a carrier of bioactive lysophospholipids that regulate vascular tone via S1P3-mediated NO release. This mechanism may contribute to the vasoactive effect of HDL and represent a novel aspect of its antiatherogenic function.

Animals↗

PubMed2003

Involvement of Cdc42 signaling in apoA-I-induced cholesterol efflux.

Cholesterol efflux, an important mechanism by which high density lipoproteins (HDL) protect against atherosclerosis, is initiated by docking of apolipoprotein A-I (apoA-I), a major HDL protein, to specific binding sites followed by activation of ATP-binding cassette transporter A1 (ABCA1) and translocation of cholesterol from intracellular compartments to the exofacial monolayer of the plasma membrane where it is accessible to HDL. In this report, we investigated potential signal transduction pathways that may link apoA-I binding to cholesterol translocation to the plasma membrane and cholesterol efflux. By using pull-down assays we found that apoA-I substantially increased the amount of activated Cdc42, Rac1, and Rho in human fibroblasts. Moreover, apoA-I induced actin polymerization, which is known to be controlled by Rho family G proteins. Inhibition of Cdc42 and Rac1 with Clostridium difficile toxin B inhibited apoA-I-induced cholesterol efflux, whereas inhibition of Rho with Clostridium botulinum C3-exoenzyme exerted opposite effects. Adenoviral expression of a Cdc42(T17N) dominant negative mutant substantially reduced apoA-I-induced cholesterol efflux, whereas dominant negative Rac1(T17N) had no effect. We further found that two downstream effectors of Cdc42/Rac1 signaling, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK), are activated by apoA-I. Pharmacological inhibition of JNK but not p38 MAPK decreased apoA-I-induced cholesterol efflux, whereas anisomycin and hydrogen peroxide, two direct JNK activators, could partially substitute for apoA-I in its ability to induce cholesterol efflux. These results for the first time demonstrate activation of Rho family G proteins and stress kinases by apoA-I and implicate the involvement of Cdc42 and JNK in the apoA-I-induced cholesterol efflux.

ADP Ribose Transferases↗

PubMed2003

Dynamic regulation of MEK/Erks and Akt/GSK-3beta in human end-stage heart failure after left ventricular mechanical support: myocardial mechanotransduction-sensitivity as a possible molecular mechanism.

OBJECTIVE: Left ventricular assist devices (LVAD) are used to 'bridge' patients with end-stage heart failure to transplantation. After long-term LVAD support, ventricular function may partially recover, a process called 'reverse remodeling'. As several kinase-mediated signal transduction pathways have been implicated in the development of cardiac hypertrophy and failure, we examined the activities of the Erks, MEKs, Akt, GSK-3 beta, p70S6K, JNKs and p38 under LVAD support as well as during single myocyte strain and whole heart stretch. METHODS: Western blotting and immunohistochemistry were performed using phospho-specific antibodies in matched samples from ten patients with end-stage heart failure before and after LVAD. Cyclic strain was performed in rat neonatal cardiac myocytes, and tensile stretch applied to Langendorff-perfused mouse hearts via a left ventricular balloon. RESULTS: The activity of Erks and Akt in failing hearts dramatically decreased after LVAD support, while that of GSK-3 beta increased. There was an endo/epicardial gradient for Erk activity which persisted after LVAD despite the reduction of total Erk activity. TUNEL-positivity and myocyte size decreased after LVAD, but independently of changes in kinase activity. In cardiomyocytes and Langendorff-perfused mouse hearts both strain/stretch and its relief regulated the activities of Erks, Akt, and GSK-3 beta. CONCLUSION: Erks and Akt/GSK-3 beta are highly responsive to myocyte stretch in vitro and in vivo, and may be sensitive molecular parameters of 'reverse remodeling' under LVAD support.

Adolescent↗

PubMed2002

ADAM15 is an adherens junction molecule whose surface expression can be driven by VE-cadherin.

ADAM15 belongs to the family of proteins containing disintegrin and metalloprotease domains (ADAM) that have been implicated in cell adhesion via integrin binding and shedding of cell surface molecules. Here we provide the first report on the localization of an ADAM in adherens junctions. We show that ADAM15 colocalizes with a cell adhesion molecule, vascular endothelial (VE)-cadherin, which mediates endothelial cell adherens junction formation. In contrast, the distribution of ADAM15 correlates poorly with the localization in cell contacts of one of its proposed ligands, the beta1-integrin. Furthermore, ADAM15 accumulation in cell-cell contacts is preceded by VE-cadherin-mediated adherens junction formation. To investigate the dependence of ADAM15 surface expression on adherens junction formation, we coexpressed VE-cadherin with ADAM15 and an ADAM15 green fluorescence protein (GFP) fusion protein in Chinese hamster ovary cells. VE-cadherin coexpression results in the translocation of ADAM15-GFP to the cell periphery. Analysis of cell surface levels of ADAM15 and ADAM15-GFP, with or without VE-cadherin coexpression, clearly demonstrates that VE-cadherin can drive surface expression of ADAM15. Our data suggest that ADAM15 may be a novel component of adherens junctions and thus could play a role in endothelial functions that are mediated by these cell contacts.

ADAM Proteins↗

PubMed2002

Reduction of hypoxia-inducible heme oxygenase-1 in the myocardium after left ventricular mechanical support.

Left ventricular assist devices (LVAD) may improve cardiac function. The pathogenesis of this phenomenon, called 'reverse remodelling', is not completely elucidated. To examine the hypothesis that LVAD support eliminates tissue stress by reducing local hypoxia, the distribution of heme oxygenase-1 (HO-1), a stress protein inducible by hypoxia, was examined in vivo and in vitro. The immunoreactivity for HO-1 was semi-quantitatively analysed in left ventricular tissue of 23 patients (14 dilated cardiomyopathy (DCM), six ischaemic heart disease (IHD), three myocarditis/congenital heart disease) with end-stage heart failure before and after LVAD support, while two unused donor hearts served as controls. Control hearts stained almost negative for HO-1, while failing hearts showed immunoreactivity mainly in cardiomyocytes, but also in endothelial cells, some smooth muscle cells and fibroblasts. Hearts with IHD showed significantly higher HO-1 immunoreactivity than hearts with DCM or myocarditis/congenital heart disease. After LVAD support, the HO-1 content decreased significantly in the DCM and IHD group and was significantly higher in the subendocardium than in the subepicardium. In vitro, under hypoxic conditions, neonatal rat cardiomyocytes showed an increase of HO-1 protein content up to sixfold above the normal level, which returned to normal values after normoxic cultivation. Mechanical support reduces the HO-1 content of the failing heart and HO-1 is inducible in vitro under hypoxia and is reversible under normoxia. This supports the concept that restoration of cardiac normoxia by mechanical unloading, particularly in the subendocardium, may be in part responsible for the phenomenon of 'reverse remodelling'.

Adult↗

PubMed2002

Molecular mechanisms of inherited ventricular arrhythmias.

BACKGROUND: Inherited ventricular arrhythmias such as the long QT syndrome (LQTS), Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia (CPVT), idiopathic ventricular fibrillation (VF), and arrhythmogenic right ventricular cardiomyopathy (ARVC) account for a relevant proportion of sudden cardiac death cases in young patients cohorts. The detailed pathogenetic mechanisms of inherited ventricular arrhythmias are still poorly understood because systematic investigations are difficult to perform due to low patient numbers and the lack of appropriate experimental models. However, recent advances in research and science have identified a genetic background for many of these diseases. PRESENT KNOWLEDGE: In LQTS, various mutations in different genes encoding for cardiac potassium and sodium channel proteins have been identified ("channelopathy"), and initial progress in genotype-phenotype correlation is made. Mutations in the cardiac sodium channel gene have also been identified in a subset of patients with Brugada syndrome, whereas a genetic background has not yet been demonstrated in idiopathic VF and right ventricular outflow-tract tachycardia (RVO-VT). Very recently, mutations in the cardiac ryanodine receptor gene have been identified in CPVT and in a subgroup of patients with ARVC. Although several chromosomal loci were suggested, no other responsible genes or mutations have been found in autosomal dominant forms of ARVC. However, in Naxos disease, a recessive form of ARVC with coexpression of palmoplantar keratoderma and woolly hair, a mutation in the plakoglobin gene has recently been discovered, thus underscoring the potential role of genetic alterations in cytoskeletal proteins in ARVC. FUTURE PERSPECTIVES: In the next years, significant progress in the genetic diagnosis pathophysiologic understanding of disease mechanisms, genotype-phenotype correlation, and the development of gene- or target-directed treatment strategies can be expected in the field of inherited ventricular arrhythmias. CONCLUSION: This review summarizes the current knowledge of the molecular mechanisms, including aspects of pathoanatomy, autonomic innervation, genetics, and genotype-phenotype correlations with their potential implications for diagnosis and treatment of inherited ventricular arrhythmias.

DNA Mutational Analysis↗

PubMed2002

Reversible activation of nuclear factor-kappaB in human end-stage heart failure after left ventricular mechanical support.

OBJECTIVE: Left ventricular assist devices (LVAD) have been used to 'bridge' patients with end-stage heart failure to transplantation. Although several reports have suggested that the native ventricular function recovers after long-term LVAD support, a process called 'reverse remodeling', the underlying biological mechanisms are still unknown. As the transcription factor nuclear factor-kappaB (NF-kappaB) has been shown to be active in the failing human heart, we examined whether its activity is altered under LVAD support, and may thus contribute to the dynamic process of 'reverse remodeling'. METHODS: The activity of NF-kappaB was studied in 16 patients with end-stage heart failure (eight with dilated cardiomyopathy, six with ischemic heart disease, one with myocarditis, and one with congenital heart disease) before and after LVAD support by immunohistochemistry using an antibody against active NF-kappaB. Gel-shifts for NF-kappaB DNA-binding activity were performed with paired human myocardial tissue from four patients. The mean cardiomyocyte diameter before and after mechanical unloading was measured with an image analyzer system. RESULTS: 15 patients out of 16 showed a significant decrease in the number of NF-kappaB positive cardiomyocyte nuclei after LVAD support in the left ventricular myocardium. The NF-kappaB DNA-binding activity also decreased after LVAD support as measured by gel-shift analysis. While the number of positive cardiomyocytes was significantly higher in the subendocardium than in the subepicardium at the time of LVAD implantation, this difference was no longer present at the time of LVAD explantation. The diameter of cardiomyocytes in the left ventricle decreased significantly as a parameter of structural reverse remodeling. CONCLUSION: LVAD support decreases the extent of NF-kappaB activation in failing human hearts, suggesting that NF-kappaB may be involved in the process of 'reverse remodeling'.

Adult↗

PubMed2002

HDL and arteriosclerosis: beyond reverse cholesterol transport.

The inverse correlation between serum levels of high density lipoprotein (HDL) cholesterol and the risk of coronary heart disease, the protection of susceptible animals from atherosclerosis by transgenic manipulation of HDL metabolism, and several potentially anti-atherogenic in vitro-properties have made HDL metabolism an interesting target for pharmacological intervention in atheroslcerosis. We have previously reviewed the concept of reverse cholesterol transport, which describes both the metabolism and the classic anti-atherogenic function of HDL (Arterioscler. Thromb. Vasc. Biol. 20 2001 13). We here summarize the current understanding of additional biological, potentially anti-atherogenic properties of HDL. HDL inhibits the chemotaxis of monocytes, the adhesion of leukocytes to the endothelium, endothelial dysfunction and apoptosis, LDL oxidation, complement activation, platelet activation and factor X activation but also stimulates the proliferation of endothelial cells and smooth muscle cells, the synthesis of prostacyclin and natriuretic peptide C in endothelial cells, and the activation of proteins C and S. These anti-inflammatory, anti-oxidative, anti-aggregatory, anti-coagulant, and pro-fibrinolytic activities are exerted by different components of HDL, namley apolipoproteins, enzymes, and even specific phospholipids. This complexity further emphasizes that changes in the functionality of HDL rather than changes of plasma HDL-cholesterol levels determine the anti-atherogenicity of therapeutic alterations of HDL metabolism.

Animals↗

PubMed2002

Vascular endothelial growth factor protects cultured rat hippocampal neurons against hypoxic injury via an antiexcitotoxic, caspase-independent mechanism.

The authors investigated the effect of vascular endothelial growth factor (VEGF) on hypoxic injury of cultured rat hippocampal neurons. Treatment with glutamate receptor antagonists prevented hypoxic neuron death. The same magnitude of protection was observed in cultures treated with VEGF, which also reduced excitotoxic neuron death induced directly by an exposure to -methyl-d-aspartate. Vascular endothelial growth factor did not alter the activation of the transcription factor nuclear factor-kappaB during hypoxia and protected cells in a PI-3-kinase-independent manner. Vascular endothelial growth factor failed to protect against staurosporine-induced, caspase-dependent apoptosis. These data suggest that VEGF-induced protection against hypoxic injury primarily involves the inhibition of excitotoxic processes.

Animals↗