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Hermann Haller

Publications and source records attributed to Hermann Haller.

At least 109 records · Page 6Linked to original sources
PubMed2003

Integrin alphavbeta3 binding to human alpha5-laminins facilitates FGF-2- and VEGF-induced proliferation of human ECV304 carcinoma cells.

Human ECV304 cells respond reproducibly by tube formation to complex basement membrane matrices. Laminins are major glycoproteins of basement membranes. We therefore studied the ability of ECV304 cells to attach to defined laminin isoforms and to fibronectin, and identified the involved laminin receptors. The cells bound poorly to fibronectin, to some extent to laminin-1, whereas laminin-2/4 and -10/11 were strong adhesive substrates. Antibody perturbation assays showed that adhesion to laminin-1 was mediated by integrin alpha6beta1, and adhesion to laminin-2/4 by cooperative activity of integrins alpha3beta1 and alpha6beta1. Adhesion of ECV 304 cells to laminin-10/11 was mainly mediated by integrins alpha3beta1, with minor involvement of alpha6beta1/4 and alphavbeta3. Solid-phase binding assays confirmed that integrin alphavbeta3 binds human laminin-10/11 and -10, in an RGD-dependent fashion. Although integrin alphavbeta3 played a very minor role in cell adhesion to laminin-10/11, this interaction facilitated growth factor-induced proliferation of ECV304 cells. In response to FGF-2 or VEGF, the cells proliferated better when attached on laminin-10/11 than on laminin-1, -2/4, or gelatin. The proliferation induced by the joint application of laminin-10/11 and either one of the growth factors could be blocked by antibodies against integrin alphavbeta3. Fragments of several other basement membrane components are known to interact with alphavbeta3. The current data show that that integrin alphavbeta3 can bind intact alpha5-containing laminin trimers. Since the laminin alpha5 chain is broadly expressed in adult basement membranes, this interaction could be physiologically important. Our data suggest that this interaction is involved in the regulation of cellular responses to growth factors known to be involved in epithelial and endothelial development.

Cell Division↗
PubMed2003

Incidence of polyomavirus-nephropathy in renal allografts: influence of modern immunosuppressive drugs.

BACKGROUND: In recent years an increasing number of cases with polyomavirus (PV)-nephropathy after renal transplantation were reported from several transplant centres. New, highly potent immunosuppressive drugs like tacrolimus or mycophenolate mofetil were accused as risk factors for this increase. However, data about the incidence of PV-nephropathy in correlation to different immunosuppressive therapy concepts are lacking. METHODS: All renal transplant biopsies performed at Hannover Medical School between 1999 and 2001 (n=1276) were immunohistochemically screened for the presence of PV-specific proteins. The results were correlated to the different immunosuppressive therapy protocols and patients with PV-nephropathy were compared with a matched control group. RESULTS: PV-nephropathy was found in <1% of all investigated allograft biopsies (11/1276) and in approximately 1% of all patients (7/638), respectively. All patients being immunohistochemically positive for PV-specific proteins also showed the typical morphological changes of PV-nephropathy. Four out of seven patients with PV-nephropathy were under triple immunosuppression comprising tacrolimus and mycophenolate mofetil. Under this immunosuppressive therapy protocol an eight times higher incidence and a 13 times higher risk (multivariate odds ratio 12.7) of PV-nephropathy was observed in our patients compared with the control group. CONCLUSIONS: PV-nephropathy is a rare but serious complication after renal transplantation. A small group of patients under intensive immunosuppression comprising tacrolimus in combination with mycophenolate mofetil has a significantly increased risk of acquiring this deleterious complication.

Adolescent↗
PubMed2003

The right diagnostic work-up: investigating renal and renovascular disorders.

Renovascular disease is present in about 10-40% of patients with end-stage renal disease, and constitutes the fastest-growing group of end-stage renal disease patients. The unselective correction of renal artery stenosis has led to disappointing results. Most studies that have compared conservative treatment with angioplasty have found only modest or no beneficial effects of angioplasty on renal function and blood pressure. It is therefore mandatory to evaluate the functional significance of a stenosis before intervention. Patients most likely to respond favourably to revascularization should be identified. Factors that affect outcome include the severity of renal artery stenosis, type of treatment of renal artery stenosis and, most importantly, underlying renal disease, which prevents a favourable response even after successful correction of renal artery stenosis. Doppler ultrasonography to evaluate the renal resistance index [1 - (end diastolic velocity/maximum systolic velocity) x 100] or captopril scintigraphy are the best methods by which to classify patients as responders or non-responders to intervention. In patients with a renal resistance index > or = 80%, improvement of renal function or blood pressure is highly unlikely, despite successful correction of renal artery stenosis. The value of the renal resistance index can also be extended to patients with non-stenotic renal diseases. Identifying patients at risk for irreversible loss of renal function and who may benefit from intervention is a high research priority.

Humans↗
PubMed2003

Nephrogenesis is induced by partial nephrectomy in the elasmobranch Leucoraja erinacea.

The mammalian kidney responds to partial nephrectomy with glomerular and tubular hypertrophy, but without renal regeneration. In contrast, renal regeneration in lower vertebrates is known to occur. Understanding the underlying mechanisms of renal regeneration is highly important; however, a serviceable animal model has not been developed. A neonephrogenic zone has been identified in the European lesser spotted dogfish, Scyliorhinus caniculus (Hentschel H. Am J Anat 190: 309-333, 1991), as well as in the spiny dogfish Squalus acanthias and the little skate, Leucoraja erinacea. The zone features the production of new nephrons complete with a countercurrent system. To analyze this nephrogenic region of elasmobranch fish further, a renal reduction model was established. The neonephrogenic zone in the adult kidney of the little skate resembles the embryonic metanephric kidney and contains stem cell-like mesenchymal cells, tips of the branching collecting duct system, and outgrowth of the arterial system. Four stages of nephron development were analyzed by serial sections and defined: stage I, aggregated mesenchymal cells; stage II, S-shaped body-like structure with high-prismatic epithelial cells; stage III, segmental nephron segregation; stage IV, functioning nephron. The stages were analyzed after partial nephrectomy. In addition, cell proliferation was assessed by incorporation of bromo-deoxyuridine (BrdU). New nephrons developed in animals undergoing partial nephrectomy. Growth was greatly stimulated in the nephrogenic zone, both in the remnant tissue and in the contralateral kidney within 10 wk. Mesenchymal cell aggregates increased significantly per renal cross-section compared with controls (stage I, 0.64 +/- 0.28 versus 0.27 +/- 0.25; P < 0.005; n = 10 animals per group). The same was the case for S-shaped body-like cysts (stage II, 0.24 +/- 0.19 versus 0.08 +/- 0.09; P < 0.02). Cellular proliferation in the neonephrogenic zone of the contralateral kidney was also greatly enhanced (14.42 +/- 3.26 versus 2.64 +/- 1.08 BrdU-positive cells per cross-section, P < 0.001). It is concluded that the skate possesses a nephrogenic zone containing stem cell-like mesenchymal cells during its entire life. Partial nephrectomy induces renal growth by accelerating nephrogenesis. This unique model may facilitate understanding renal regeneration.

Animals↗
PubMed2003

Participation of the mineralocorticoid receptor in cardiac and vascular remodeling.

The mineralocorticoid receptor mediates the effects of aldosterone. In addition to its influence on fluid and electrolyte, aldosterone plays a role in cardiac hypertrophy, tissue fibrosis, and modulation of vascular reactivity. However, the intracellular signaling mechanisms induced by aldosterone are not fully understood. Aldosterone causes slow transcriptional and rapid non-transcriptional effects. The latter include changes in intracellular calcium, c-Jun N-terminal kinase (JNK) and extracellularly regulated kinase (ERK) phosphorylation. In addition, autocrine loops involving other molecules such as the epidermal growth factor (EGF) receptor are also important in aldosterone-induced cellular mechanisms. This short review covers in vitro and in vivo studies that have investigated the pathophysiological role of aldosterone and the mineralocorticoid receptor in the cardiovascular system.

Aldosterone↗
PubMed2003

Urokinase-induced migration of human vascular smooth muscle cells requires coupling of the small GTPases RhoA and Rac1 to the Tyk2/PI3-K signalling pathway.

Urokinase-type plasminogen activator (uPA) facilitates cell migration by localizing proteolisys on the cell surface and by inducing intracellular signalling pathways. In human vascular smooth muscle cell (VSMC) uPA stimulates migration via the uPA receptor (uPAR) signalling complex containing the Janus kinase Tyk2 and phosphatidylinositol 3-kinase (PI3-K). We report that active GTP-bound forms of small GTPases RhoA and Rac1, but not Cdc42, are directly associated with Tyk2 and PI3-K in an uPA/uPAR-dependent fashion. Endogenous RhoA, but not Rac1 or Cdc42, was significantly activated in response to uPA. RhoA activation was abolished by cell treatment with two unrelated, structurally distinct, specific inhibitors of PI3-K, wortmannin, and LY294002. Downstream of RhoA, phosphorylation of myosin light chain (MLC) was dramatically upregulated by uPA in a Rho kinase- and PI3-K-dependent manner. Thus, selective Rho kinase inhibitor Y27632 and PI3-K inhibitors wortmannin and LY294002 prevented the uPA-induced stimulation of MLC phosphorylation. Rho kinase inhibition also decreased uPA-stimulated VSMC migration as observed in a Boyden chamber. VSMC immunocytochemical staining demonstrated redistribution of RhoA and Rac1 active forms to the newly formed leading edge of migrating cell. VSMC microinjection with antibodies to either Rho or Rac1 decreased uPA-stimulated cell migration, indicating the involvement of both GTPases in the migration process. Our results provide evidence that the small GTPases RhoA and Rac1, together with Rho kinase, are necessary to mediate the uPA/uPAR-directed migration via the Tyk2/PI3-K signalling complex in human VSMC.

Cells, Cultured↗
PubMed2002

A swollen neck.

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Adolescent↗
PubMed2002

Induction of apoptosis by protein kinase C delta is independent of its kinase activity.

Protein kinase C, a multigene family of phospholipid-dependent and diacylglycerol-activated Ser/Thr protein kinases, is a key component in many signal transduction pathways. The kinase activity was thought to be essential for a plethora of biological processes attributed to these enzymes. Here we show that at least one protein kinase C function, the induction of apoptosis by protein kinase C delta, is independent of the kinase activity. Stimulation of green fluorescent protein-protein kinase C delta fusion protein with phorbol ester or diacylglycerol led to its redistribution within seconds after the stimulus. Membrane blebbing, an early hallmark of apoptosis, was visible as early as 20 min after stimulation, and nuclear condensation was visible after 3-5 h. Apoptosis could be inhibited by expression of Bcl-2 but not by specific protein kinase C inhibitors. In addition, a kinase-negative mutant of protein kinase C delta also induced apoptosis to the same extent as the wild type enzyme. Apoptosis was confined to the protein kinase C delta-overexpressing cells. Stimulation of overexpressed protein kinase C epsilon did not result in increased apoptosis. Our results indicate that distinct protein kinase C isozymes induce apoptosis in vascular smooth muscle cells. More importantly, they show that some protein kinase C effector functions are independent of the catalytic activity.

Animals↗
PubMed2002

Protein kinase C induces actin reorganization via a Src- and Rho-dependent pathway.

We have investigated the mechanism of PKC-induced actin reorganization in A7r5 vascular smooth muscle cells. PKC activation by 12-O-tetradecanoylphorbol-13-acetate induces the disassembly of actin stress fibers concomitant with the appearance of membrane ruffles. PKC also induces rapid tyrosine phosphorylation in these cells. As we could show, utilizing the Src-specific inhibitor PP2 and a kinase-deficient c-Src mutant, actin reorganization is dependent on PKC-induced Src activation. Subsequently, the activity of the small G-protein RhoA is decreased, whereas Rac and Cdc42 activities remain unchanged. Disassembly of actin stress fibers could also be observed using the Rho kinase-specific inhibitor Y-27632, indicating that the decrease in RhoA activity on its own is responsible for actin reorganization. In addition, we show that tyrosine phosphorylation of p190RhoGAP is increased upon 12-O-tetradecanoylphorbol-13-acetate stimulation, directly linking Src activation to a decrease in RhoA activity. Our data provide substantial evidence for a model elucidating the molecular mechanisms of PKC-induced actin rearrangements.

Actins↗
PubMed2002

Angiotensin II induced inflammation in the kidney and in the heart of double transgenic rats.

BACKGROUND: We are investigating a double transgenic rat (dTGR) model, in which rats transgenic for the human angiotensinogen and renin genes are crossed. These rats develop moderately severe hypertension but die of end-organ cardiac and renal damage by week 7. The heart shows necrosis and fibrosis, whereas the kidneys resemble the hemolytic-uremic syndrome vasculopathy. Surface adhesion molecules (ICAM-1 and VCAM-1) are expressed early on the endothelium, while the corresponding ligands are found on circulating leukocytes. Leukocyte infiltration in the vascular wall accompanies PAI-1, MCP-1, iNOS and Tissue Factor expression. Furthermore we show evidence that Ang II causes the upregulation of NF-kB in our model. METHODS: We started PDTC-treatment on four weeks old dTGR (200 mg/kg sc) and age-matched SD rats. Blood-pressure- and albuminuria- measurements were monitored during the treatment period (four weeks). The seven weeks old animals were killed, hearts and kidneys were isolated and used for immunohistochemical-and electromobility shift assay analysis. RESULTS: Chronic treatment with the antioxidant PDTC decreased blood pressure (162 plus minus 8 vs. 190 plus minus 7 mm Hg, p = 0.02). Cardiac hypertrophy index was significantly reduced (4.90 plus minus 0.1 vs. 5.77 plus minus 0.1 mg/g, p < 0.001) compared to dTGR. PDTC reduced 24 h albuminuria by 85 % (2.7 plus minus 0.5 vs. 18.0 plus minus 3.4 mg/d, p < 0.001) and prevented death significantly. Vascular injury was ameliorated in small renal and cardiac vessels. PDTC inhibited NF-kappaB binding activity in heart and kidney. Immunohistochemical analysis shows increased expression of the p65 NF-kappaB subunit in the endothelium, smooth muscles cells of damaged small vessels, infiltrated cells, glomeruli, tubuli and collecting ducts of dTGR. PDTC markedly reduced the immunoreactivity of p65. CONCLUSION: Our data show that inhibition of NF-kappaB by PDTC markedly reduces inflammation, iNOS expression in the dTGR most likely leading to decreased cytotoxicity, and cell proliferation. Thus, NF-kappaB activation plays an important role in ANG II-induced end-organ damage.

Angiotensin II↗
PubMed2002

Immunosuppressive treatment protects against angiotensin II-induced renal damage.

Angiotensin (Ang) II promotes renal infiltration by immunocompetent cells in double-transgenic rats (dTGRs) harboring both human renin and angiotensinogen genes. To elucidate disease mechanisms, we investigated whether or not dexamethasone (DEXA) immunosuppression ameliorates renal damage. Untreated dTGRs developed hypertension, renal damage, and 50% mortality at 7 weeks. DEXA reduced albuminuria, renal fibrosis, vascular reactive oxygen stress, and prevented mortality, independent of blood pressure. In dTGR kidneys, p22phox immunostaining co-localized with macrophages and partially with T cells. dTGR dendritic cells expressed major histocompatibility complex II and CD86, indicating maturation. DEXA suppressed major histocompatibility complex II+, CD86+, dendritic, and T-cell infiltration. In additional experiments, we treated dTGRs with mycophenolate mofetil to inhibit T- and B-cell proliferation. Reno-protective actions of mycophenolate mofetil and its effect on dendritic and T cells were similar to those obtained with DEXA. We next investigated whether or not Ang II directly promotes dendritic cell maturation in vitro. Ang II did not alter CD80, CD83, and MHC II expression, but increased CCR7 expression and cell migration. To explore the role of tumor necrosis factor (TNF)-alpha on dendritic cell maturation in vivo, we treated dTGRs with the soluble TNF-alpha receptor etanercept. This treatment had no effect on blood pressure, but decreased albuminuria, nuclear factor-kappaB activation, and infiltration of all immunocompetent cells. These data suggest that immunosuppression prevents dendritic cell maturation and T-cell infiltration in a nonimmune model of Ang II-induced renal damage. Ang II induces dendritic migration directly, whereas in vivo TNF-alpha is involved in dendritic cell infiltration and maturation. Thus, Ang II may initiate events leading to innate and acquired immune response.

Angiotensin II↗
PubMed2002

TNF-alpha--accelerated apoptosis abrogates ANCA-mediated neutrophil respiratory burst by a caspase-dependent mechanism.

BACKGROUND: Tumor necrosis factor (TNF)-alpha rapidly primes neutrophils (PMN) for an anti-neutrophil cytoplasmic antibody (ANCA)-induced respiratory burst and is thus proinflammatory. TNF-alpha also progressively accelerates apoptosis. We investigated the effect of TNF-alpha-mediated apoptosis on ANCA antigen expression and on ANCA-induced superoxide generation in human PMN. METHODS: PMN were brought to apoptosis by 10 ng/mL of TNF-alpha or a combination of TNF-alpha and 2.5 microg/mL cycloheximide, a protein synthesis inhibitor, or cycloheximide alone for three hours. Apoptosis and ANCA antigen expression were assessed by fluorescence-activated cell sorting (FACS) and microscopy. Superoxide was determined with the ferricytochrome C assay. RESULTS: TNF-alpha with cycloheximide for three hours caused apoptosis in 87% PMN compared to 2% in untreated controls (N=18; P < 0.01). Accelerated apoptosis was associated with an increase in ANCA-antigen expression for both proteinase 3 and myeloperoxidase (P < 0.05). Nevertheless, apoptosis was paralleled by a decreased proteinase 3 and myeloperoxidase ANCA-induced respiratory burst (P < 0.05). Furthermore, superoxide release in response to immune complexes, phorbol ester (PMA), and bacterial peptide (FMLP) was significantly decreased. Blocking caspase-3 activity prevented apoptosis in TNF-alpha with cycloheximide-treated cells (83% to 2%) and prevented compromised respiratory burst in response to ANCA. Caspase-3 inhibition abrogated apoptosis-mediated ANCA antigen up-regulation (PR3 141.6 +/- 34.1 MFI to 33.9 +/- 7.8; MPO 48.3 +/- 12.9 MFI to 11.9 +/- 3.2, N=6, P < 0.05). CONCLUSIONS: TNF-alpha-accelerated apoptosis was associated with increased ANCA antigen expression but with down-regulated respiratory burst activity in response to ANCA. Specific inhibition of apoptosis by caspase-3 blockade prevented the increase in ANCA-antigen expression and preserved the capability of generating superoxide, thereby establishing a causative role for apoptosis. We suggest that TNF-alpha exhibits dual actions by both priming and terminating ANCA-mediated activation of human PMN.

Amino Acid Chloromethyl Ketones↗
PubMed2002

Histone H1-mediated transfection: role of calcium in the cellular uptake and intracellular fate of H1-DNA complexes.

Previously, we have shown that the transgene expression in the endothelial cell line ECV 304 strongly depends on the presence of low concentrations of Ca2+. However, it remained unclear, which transfection steps are controlled by Ca2+ ions. In the present study, we constructed transfection complexes of digoxigenin-labelled DNA and FITC-labelled histone H1. We monitored the pathway of these complexes with the use of anti-digoxigenin and anti-cathepsin B antibodies and immunofluorescence microscopy. Double labelling of DNA and cathepsin B permitted the localization of transfection complexes into endosomes/lysosomes which suggests an uptake of transfection complexes via endocytosis. It was also found that the uptake of transfection complexes by the cells was independent of the presence or absence of Ca2+ ions in the transfection medium. On the other hand, the presence of Ca2+ in the transfection medium dramatically changed the composition of the transfection complexes inside the endosome/lysosome compartment, which resulted in a strong reduction of H1 binding to DNA. Presence of Ca2+ in the postincubation medium for 24 h resulted in release of the transfection complexes with reduced H1 content from the endosomes/lysosomes into the cytosol. In the absence of Ca2+ the transfection complexes practically disappeared. These results allow us to come to the following conclusions: Ca2+ ions control the reorganization of the transfection complexes in endosomes/lysosomes and their release into the cytosol, which is an important prerequisite for transgene expression, whereas uptake of transfection complexes by the cells is not dependent on Ca2+.

Animals↗