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A Bierhaus

Publications and source records attributed to A Bierhaus.

At least 19 recordsLinked to original sources
PubMed2001

Diabetes-associated sustained activation of the transcription factor nuclear factor-kappaB.

Activation of the transcription factor nuclear factor-kappaB (NF-kappaB) has been suggested to participate in chronic disorders, such as diabetes and its complications. In contrast to the short and transient activation of NF-kappaB in vitro, we observed a long-lasting sustained activation of NF-kappaB in the absence of decreased IkappaBalpha in mononuclear cells from patients with type 1 diabetes. This was associated with increased transcription of NF-kappaBp65. A comparable increase in NF-kappaBp65 antigen and mRNA was also observed in vascular endothelial cells of diabetic rats. As a mechanism, we propose that binding of ligands such as advanced glycosylation end products (AGEs), members of the S100 family, or amyloid-beta peptide (Abeta) to the transmembrane receptor for AGE (RAGE) results in protein synthesis-dependent sustained activation of NF-kappaB both in vitro and in vivo. Infusion of AGE-albumin into mice bearing a beta-globin reporter transgene under control of NF-kappaB also resulted in prolonged expression of the reporter transgene. In vitro studies showed that RAGE-expressing cells induced sustained translocation of NF-kappaB (p50/p65) from the cytoplasm into the nucleus for >1 week. Sustained NF-kappaB activation by ligands of RAGE was mediated by initial degradation of IkappaB proteins followed by new synthesis of NF-kappaBp65 mRNA and protein in the presence of newly synthesized IkappaBalpha and IkappaBbeta. These data demonstrate that ligands of RAGE can induce sustained activation of NF-kappaB as a result of increased levels of de novo synthesized NF-kappaBp65 overriding endogenous negative feedback mechanisms and thus might contribute to the persistent NF-kappaB activation observed in hyperglycemia and possibly other chronic diseases.

Adult↗
PubMed2001

Tissue factor--a receptor involved in the control of cellular properties, including angiogenesis.

Tissue factor (TF), the major initiator of blood coagulation, serves as a regulator of angiogenesis, tumor growth and metastasis. In several models, TF expression mediates upregulation of the proangiogenic vasular endothelial growth factor (VEGF) that can directly act on endothelial cells to promote vessel formation. This occurs through ligand binding, activation of signaling cascades, signal transduction and alteration of growth factor expression and is mediated by both, coagulation-dependent and -independent pathways. Depending on the cell type and the biological settings, TF seems to affect cellular properties through (i) factor VIIa (FVIIa)-dependent proteolysis of factor Xa (FXa) and thrombin and subsequent activation of proteinase activated receptor (PAR) -1 and PAR-2, (ii) through direct FVIIa signaling and mitogen activated protein (MAP) kinase activation, that is conferred by a not yet identified receptor, (iii) through interaction of FVII(a) proteolytic activity and signaling of the cytoplasmic domain and (iv) through cytoplasmic signaling independent of ligand binding. The role of phosphorylation of the cytoplasmic domain and the pathways controlling phosphorylation of TF remain poorly understood.

Animals↗
PubMed2000

Endothelial dysfunction in diabetes mellitus.

Diabetes mellitus and impaired glucose tolerance are linked to increased cardiovascular morbidity and mortality. Vascular disease is directly associated with plasma glucose levels, and reduction of these levels forestalls to a certain extent the vascular complications of diabetes, such as myocardial infarction, nephropathies, and retinopathies. In addition to hyperglycemia, there are other risk factors that play a prominent role, such as hypertension, hyperlipidemia, and genetic factors. Endothelial dysfunction is one of the major factors in the development of cardiovascular disease. The vascular endothelium regulates the blood flow by tightly controlling the coagulation system, cell-cell interaction, and vascular tone. These functions are disturbed in diabetic patients. In diabetics, endothelin-1 levels are increased, leading to vasoconstriction. Endothelin levels are directly related to plasma glucose levels. In addition, the endothelial cell-NO axis is disturbed. NO release and function are impaired. This seems to be dependent upon hyperglycemia and genetic factors. Impaired NO function also results in vasoconstriction. Furthermore, enhanced vascular permeability is seen in diabetics. This appears to be related to impaired endothelial cell relaxation and reactive oxygen species as well as advanced glycosylated end products (AGEs). The complex changes seen in diabetes and even prediabetes are therefore related to numerous derailments related to endothelial dysfunction, and no single therapeutic approach is likely to solve the problem of vascular complications.

Diabetes Mellitus↗
PubMed2000

LPS and cytokine-activated endothelium.

Endothelial cells coordinate the recruitment of inflammatory cells to sites of vascular injury. Endothelial cells produce and release cytokines and growth factors serving as communication signals to leukocytes as well as with organs and tissues. In addition, endothelial cells respond to inflammatory stimuli such as lipopolysaccharides (endotoxin, LPS), cytokines, or ligation of CD40. Functional changes in response to inflammatory stimuli are mediated by induction of signaling cascades leading to activation of transcription factors and alterations in endothelial gene expression. This article summarizes the current knowledge of molecular events resulting in cytokine-mediated endothelial dysfunction.

Apoptosis↗
PubMed2000

Endothelin 1 transcription is controlled by nuclear factor-kappaB in AGE-stimulated cultured endothelial cells.

Incubation of bovine aortic endothelial cells (BAECs) with erythrocytes from patients with type 2 diabetes induced an increase in endothelin 1 (ET-1) production. The effect of erythrocytes on ET-1 synthesis was dependent on glycemic control. ET-1 levels after incubation with erythrocytes derived from patients with HbA(1c) levels <6% were just half the levels observed after incubation with erythrocytes from patients with HbA(1c) levels >8%. Nepsilon-(carboxymethyl)lysine (CML)-containing protein isolated from patients' erythrocytes induced ET-1, and CML-containing protein-dependent ET-1 induction was blocked by the recombinant decoy peptide soluble receptor for advanced glycation end products (AGEs), which comprises the NH2-terminal Ig domain of the receptor for AGEs. In vitro-generated AGEs induced ET-1 mRNA transcription (nuclear run-on assay and Northern blot) in a time- and dose-dependent manner. Transient transfection of BAECs with a chimeric construct containing the 5' promoter region of the ET-1 gene linked to a reporter gene confirmed that AGE induced ET-1 promoter activity. Electrophoretic mobility shift assay confirmed AGE-inducible binding of members of the nuclear factor-kappab (NF-kappaB) family to a potential binding site at -2,090 bp. Binding was functionally significant because overexpression of the cytoplasmic inhibitor of NF-kappaB or deletion of the NF-kappaB binding site reduced ET-1 induction, whereas overexpression of NF-kappaB p65 induced ET-1 even in the absence of AGEs. Thus, ET-1 transcription is controlled by the AGE-inducible redox-sensitive transcription factor NF-kappaB.

Animals↗
PubMed1999

Regulation of vascular endothelial growth factor production and angiogenesis by the cytoplasmic tail of tissue factor.

Tissue factor (TF), a transmembrane receptor for coagulation factor VII/VIIa, is aberrantly expressed in human cancers. We demonstrated a significant correlation between TF and vascular endothelial growth factor (VEGF) production in 13 human malignant melanoma cell lines (r(2) = 0.869, P < 0.0001). Two of these cell lines, RPMI-7951, a high TF and VEGF producer, and WM-115, a low TF and VEGF producer, were grown s.c. in severe combined immunodeficient mice. The high-producer cell line generated solid tumors characterized by intense vascularity, whereas the low producer generated relatively avascular tumors, as determined by immunohistologic staining of tumor vascular endothelial cells with anti-von Willebrand factor antibody. To investigate the structure-function relationship of TF and VEGF, a low-producer melanoma cell line (HT144) was transfected with a TF cDNA containing the full-length sequence, a cytoplasmic deletion mutant lacking the coding sequence for the distal three serine residues (potential substrates for protein kinase C), or an extracellular domain mutant, which has markedly diminished function for activation of factor X. Cells transfected with the full-length sequence produced increased levels of both TF and VEGF. Transfectants with the full-length sequence and the extracellular domain mutant produced approximately equal levels of VEGF mRNA. However, cells transfected with the cytoplasmic deletion mutant construct produced increased levels of TF, but little or no VEGF. Thus, the cytoplasmic tail of TF plays a role in the regulation of VEGF expression in some tumor cells.

Animals↗
PubMed1999

RAGE mediates a novel proinflammatory axis: a central cell surface receptor for S100/calgranulin polypeptides.

S100/calgranulin polypeptides are present at sites of inflammation, likely released by inflammatory cells targeted to such loci by a range of environmental cues. We report here that receptor for AGE (RAGE) is a central cell surface receptor for EN-RAGE (extracellular newly identified RAGE-binding protein) and related members of the S100/calgranulin superfamily. Interaction of EN-RAGEs with cellular RAGE on endothelium, mononuclear phagocytes, and lymphocytes triggers cellular activation, with generation of key proinflammatory mediators. Blockade of EN-RAGE/RAGE quenches delayed-type hypersensitivity and inflammatory colitis in murine models by arresting activation of central signaling pathways and expression of inflammatory gene mediators. These data highlight a novel paradigm in inflammation and identify roles for EN-RAGEs and RAGE in chronic cellular activation and tissue injury.

Amino Acid Sequence↗
PubMed1999

[Non-enzymatic glycation and oxidative stress in chronic illnesses and diabetes mellitus].

UNLABELLED: New approaches in biochemistry and molecular biology have increased the knowledge on the pathophysiology of chronic diseases as late diabetic complications, Alzheimer's disease, arteriosclerosis and vascular disease by defining the concept of "AGE-formation and oxidative stress." Nonenzymatic glycation, in which reducing sugars are covalently bound to free aminogroups of macromolecules, results in the formation of Advanced Glycation End products (AGEs) which accumulate during aging and at accelerated rate during the course of diabetes. Glycation accompanying oxidation processes support AGE-formation. AGE-formation changes the physicochemical properties of proteins, lipids and nucleic acids. In addition, binding of AGEs to specific surface receptors induces cellular signalling and cell activation. Interaction of AGEs with one of the receptors, RAGE, generates intracellular oxidative stress, which results in activation of the transcription factor NF-kappa B and subsequent gene expression, which might be relevant in late diabetic complications. CONCLUSION: Knowledge of the basis molecular mechanisms allows to understand the interplay of different inducers such as redicals, cytokines, AGE-proteins and amyloid-beta-peptids and to define oxidative stress as a "common endpoint" of cell dysfunction. With respect to therapeutic options it is now possible not only to optimize blood glycemic control, but also to design drugs such as AGE-inhibitors and AGE-"cross-link" breakers. In addition patients with chronic disease associated with increased oxidative stress ay benefit from an antioxidant rich (and AGE protein poor?) nutrition.

Alzheimer Disease↗
PubMed1999

The role of oxidative stress and NF-kappaB activation in late diabetic complications.

A common endpoint of hyperglycemia dependent cellular changes is the generation of reactive oxygen intermediates (ROIs) and the presence of elevated oxidative stress. Therefore, oxidative stress is supposed to play an important role in the development of late diabetic complications. Formation of advanced glycation end products (AGE's) due to elevated nonenzymatic glycation of proteins, lipids and nucleic acids is accompanied by oxidative, radical-generating reactions and thus represents a major source for oxygen free radicals under hyperglycemic conditions. Once formed, AGE's can influence cellular function by binding to several binding sites including the receptor for AGE's, RAGE. Binding of AGE's (and other ligands) to RAGE results in generation of intracellular oxidative stress and subsequent activation of the redox-sensitive transcription factor NF-kappaB in vitro and in vivo. Consistently, activation of NF-kappaB in diabetic patients correlates with the quality of glycemic control and can be reduced by treatment with the antioxidant alpha-lipoic acid. The development of techniques allowing for a tissue culture independent measurement of NF-kappaB activation in patients with diabetes mellitus gives insights into the molecular mechanisms linking diabetes mellitus and hyperglycemia with formation of advanced glycated endproducts and generation of oxidative stress finally resulting in oxidative stress mediated cellular activation.

Animals↗
PubMed1999

Peripheral blood mononuclear cells isolated from patients with diabetic nephropathy show increased activation of the oxidative-stress sensitive transcription factor NF-kappaB.

Increased oxidative stress and subsequent activation of the transcription factor NF-kappaB has been linked to the development of late diabetic complications. To determine whether oxidative stress dependent NF-kappaB activation is evident in patients with diabetic nephropathy we used an Electrophoretic Mobility Shift Assay based semiquantitative detection system which enabled us to determine NF-kappaB activation in ex vivo isolated peripheral blood mononuclear cells. We examined 33 patients with diabetes mellitus (Type I and Type II). Patients with diabetic nephropathy showed higher NF-kappaB binding activity in Electrophoretic Mobility Shift Assays and stronger immunohistological staining for activated NF-kappaBp65 than patients without renal complications. NF-kappaB binding activity correlated with the degree of albuminuria (r = 0.316) and with thrombomodulin plasma concentrations (r = 0.33), indicative for albuminuria associated endothelial dysfunction. In a 3 day intervention study in which 600 mg of the antioxidant thioctic acid (alpha-lipoic acid) per day were given to nine patients with diabetic nephropathy oxidative stress in plasma samples was decreased by 48% and NF-kappaB binding activity in ex vivo isolated peripheral blood mononuclear cells by 38%. In conclusion, activation of the transcription factor NF-kappaB in ex vivo isolated peripheral blood mononuclear cells of patients with diabetes mellitus correlates with the degree of diabetic nephropathy. NF-kappaB activation is at least in part dependent on oxidative stress since thioctic acid (alpha-lipoic acid) reduced NF-kappaB binding activity.

Adult↗
PubMed1999

Cell specific effects of glucocorticoid treatment on the NF-kappaBp65/IkappaBalpha system in patients with Crohn's disease.

UNLABELLED: BACKGROUND/AIMS/PATIENTS: Glucocorticoid treatment is known to reduce nuclear factor-kappa B (NF-kappaB)p65 binding activity and activation in lamina propria cells of patients with Crohn's disease. However, lamina propria cells of glucocorticoid treated patients did not show increased expression of IkappaBalpha, and the hypothesised upregulation of IkappaBalpha by glucocorticoid treatment has not yet been shown in vivo. To investigate whether cells other than lamina propria localised mononuclear cells contribute to increased IkappaBalpha, resection gut specimens from patients matched for Crohn's disease activity index (CDAI) with or without glucocorticoid treatment were studied, and changes in the NF-kappaB/IkappaBalpha system were determined in the lamina propria as well as in underlying submucosal and endothelial cells. METHODS: Changes in the NF-kappaB/IkappaBalpha system were determined by immunohistochemistry, electrophoretic mobility shift assay, and western blot analysis in resected gut specimens from patients matched for CDAI and van Hees index with or without long term glucocorticoid treatment. RESULTS: Resection gut specimens from patients with Crohn's disease under glucocorticoid treatment had significantly lower nuclear NF-kappaBp65 levels in mononuclear, epithelial, and endothelial cells than samples from CDAI and van Hees index matched patients not having glucocorticoid treatment. Nuclear NF-kappaBp65 showed a strong positive correlation with both the CDAI (r = 1 for both groups) and the van Hees index (r = 0.605 for untreated and r = 0.866 for glucocorticoid treated specimens). Lower nuclear translocation of NF-kappaBp65 in the glucocorticoid treated group was paralleled by higher IkappaBalpha levels in vascular endothelial cells, but not in infiltrating mononuclear cells. CONCLUSION: A comparison of resection gut specimens from untreated and treated CDAI matched patients with Crohn's disease showed downregulation of NF-kappaB binding activity and NF-kappaBp65 expression and cell specific induction of endothelial IkappaBkappa expression in the glucocorticoid treated group. As the two groups showed similar disease activity (CDAI, van Hees index), the activation of the NF-kappaBp65/IkappaBalpha system must be only part of the inflammatory cascade leading to the clinical appearance of Crohn's disease.

Adult↗
PubMed1998

Loss of caveolin expression in type I pneumocytes as an indicator of subcellular alterations during lung fibrogenesis.

Caveolin is a major structural protein of caveolae, also known as plasmalemmal vesicles, which are particularly abundant in type I pneumocytes and capillary endothelial cells of lung parenchyma. Here we demonstrate that caveolin expression in the alveolar epithelium of rats and mini pigs is strikingly downregulated after irradiation-induced lung injury. Indirect immunoperoxidase staining with polyclonal anti-caveolin antibodies, confirmed by double fluorescence studies with type I cell-specific monoclonal anti-cytokeratin antibodies or lectins, revealed a dramatic loss of caveolin immunoreactivity in type I pneumocytes. In contrast, caveolin expression increased in endothelial cells. Immunoblotting of lung homogenates from normal and irradiated rats using specific anti-caveolin antibodies confirmed the presence of caveolin in normal tissue and its marked decrease of expression in fibrotic tissue. The loss of caveolin as an important structural protein of caveolae in alveolar epithelial cells may be an early indicator of serious type I cell injury during fibrogenesis. The increase of caveolin immunoreactivity in endothelia of blood vessels may indicate that different types of caveolae and/or different regulatory mechanisms of caveolin expression exist.

Animals↗
PubMed1998

AGEs and their interaction with AGE-receptors in vascular disease and diabetes mellitus. I. The AGE concept.

OBJECTIVE: This is the first part of a bipartite review that summarizes the rising knowledge on the molecular mechanisms underlying the action of advanced glycation endproducts (AGEs) and their contribution to diabetic complications and vascular disease. While the first part presented here focusses on AGE formation, the second part will describe the AGE-protein/receptor interactions and their role in mediating AGE-dependent intracellular signalling. RESULTS: Nonenzymatic glycation, in which reducing sugars are covalently attached to free amino groups and ultimately form AGEs, has been found to occur during normal aging and at accelerated rate in diabetes mellitus. Oxidation, accompanying glycation in vivo, further supports chemical modifications. AGE formation and protein crosslinking are irreversible processes that alter the structural and functional properties of proteins, lipid components and nucleic acids. AGE modifications do not only change the physicochemical properties of the afflicted molecules, but also induce cellular signalling, activation of transcription factors and subsequent gene expression in vitro and in vivo. CONCLUSIONS: AGEs elicit a wide range of cell-mediated responses that might contribute to the pathogenesis of diabetic complications, vascular and renal disease and Alzheimer's disease. Substances that inhibit AGE formation, reduce oxidative stress or destroy already formed crosslinks may limit the progression of disease and may offer new tools for therapeutic interventions in the therapy of AGEs mediated disease.

Diabetes Mellitus↗
PubMed1998

Molecular mechanisms of diabetic angiopathy--clues for innovative therapeutic interventions.

Advanced glycation end products (AGEs), known to accumulate during aging and at accelerated rate during the course of diabetes, have been demonstrated to induce changes in endothelial properties that might contribute to the pathogenesis of micro- and macroangiopathy. Since AGE-formation not only changes the physicochemical properties of proteins, but also induces cellular signalling, activation of transcription factors and subsequent gene expression, AGEs are now regarded as important mediators of diabetic vascular disease. The growing knowledge on the molecular mechanisms underlying the AGE-dependent activation of vascular endothelial cells implicates possible new therapeutic interventions in the therapy of diabetic angiopathy.

Diabetic Angiopathies↗