Biomedical subjects

Bernd Arnold

Publications and source records attributed to Bernd Arnold.

35 records · Page 2Linked to original sources

PubMed2004

Cutting edge: IL-7-dependent homeostatic proliferation of CD8+ T cells in neonatal mice allows the generation of long-lived natural memory T cells.

Healthy, nonimmunized C57BL/6 (B6) mice contain memory phenotype CD8+ T cells, which are assumed to be generated in response to environmental Ags. Since neonatal mice are functionally lymphopenic within the first days after birth, we investigated the alternative possibility that the memory CD8+ T cells of untreated B6 mice are the result of lymphopenia-induced proliferation during neonatal life. We show here that adoptively transferred CD8+ T cells proliferate in neonatal B6 mice, rapidly produce IFN-gamma, and develop into memory cells which are maintained until adulthood. In contrast to CD4+ T cells, neonatal lymphopenia-induced proliferation of CD8+ T cells was IL-7 dependent. Thus, neonatal lymphopenia seems to allow CD8+ thymic emigrants to undergo lymphopenia-induced proliferation during early neonatal life to equip the immune system with a set of preactivated CD8+ T cells before any infection, which might contribute to the rapid initiation of immune responses in the adult.

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PubMed2004

Mini-review: overcoming tumor-intrinsic resistance to immune effector function.

In immunological cancer therapy, the current treatment emphasis is on the generation of effector cells that are specific for tumor antigens. However, there is a distressing lack of correlation between the induction of specific immunity in cancer patients and measurable clinical benefit. By studying mouse models of de novo tumorigenesis we are beginning to understand that the tumor itself, in particular the manifestation of a distinct tumor environment, impairs immune effector function; this concept is yet to be applied in human malignancy.

Animals↗

PubMed2004

Loss of pain perception in diabetes is dependent on a receptor of the immunoglobulin superfamily.

Molecular events that result in loss of pain perception are poorly understood in diabetic neuropathy. Our results show that the receptor for advanced glycation end products (RAGE), a receptor associated with sustained NF-kappaB activation in the diabetic microenvironment, has a central role in sensory neuronal dysfunction. In sural nerve biopsies, ligands of RAGE, the receptor itself, activated NF-kappaBp65, and IL-6 colocalized in the microvasculature of patients with diabetic neuropathy. Activation of NF-kappaB and NF-kappaB-dependent gene expression was upregulated in peripheral nerves of diabetic mice, induced by advanced glycation end products, and prevented by RAGE blockade. NF-kappaB activation was blunted in RAGE-null (RAGE(-/-)) mice compared with robust enhancement in strain-matched controls, even 6 months after diabetes induction. Loss of pain perception, indicative of long-standing diabetic neuropathy, was reversed in WT mice treated with soluble RAGE. Most importantly, loss of pain perception was largely prevented in RAGE(-/-) mice, although they were not protected from diabetes-induced loss of PGP9.5-positive plantar nerve fibers. These data demonstrate, for the first time to our knowledge, that the RAGE-NF-kappaB axis operates in diabetic neuropathy, by mediating functional sensory deficits, and that its inhibition may provide new therapeutic approaches.

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PubMed2004

Receptor for advanced glycation end products (RAGE) regulates sepsis but not the adaptive immune response.

While the initiation of the adaptive and innate immune response is well understood, less is known about cellular mechanisms propagating inflammation. The receptor for advanced glycation end products (RAGE), a transmembrane receptor of the immunoglobulin superfamily, leads to perpetuated cell activation. Using novel animal models with defective or tissue-specific RAGE expression, we show that in these animal models RAGE does not play a role in the adaptive immune response. However, deletion of RAGE provides protection from the lethal effects of septic shock caused by cecal ligation and puncture. Such protection is reversed by reconstitution of RAGE in endothelial and hematopoietic cells. These results indicate that the innate immune response is controlled by pattern-recognition receptors not only at the initiating steps but also at the phase of perpetuation.

Animals↗

PubMed2003

The pattern recognition receptor (RAGE) is a counterreceptor for leukocyte integrins: a novel pathway for inflammatory cell recruitment.

The pattern recognition receptor, RAGE (receptor for advanced glycation endproducts), propagates cellular dysfunction in several inflammatory disorders and diabetes. Here we show that RAGE functions as an endothelial adhesion receptor promoting leukocyte recruitment. In an animal model of thioglycollate-induced acute peritonitis, leukocyte recruitment was significantly impaired in RAGE-deficient mice as opposed to wild-type mice. In diabetic wild-type mice we observed enhanced leukocyte recruitment to the inflamed peritoneum as compared with nondiabetic wild-type mice; this phenomenon was attributed to RAGE as it was abrogated in the presence of soluble RAGE and was absent in diabetic RAGE-deficient mice. In vitro, RAGE-dependent leukocyte adhesion to endothelial cells was mediated by a direct interaction of RAGE with the beta2-integrin Mac-1 and, to a lower extent, with p150,95 but not with LFA-1 or with beta1-integrins. The RAGE-Mac-1 interaction was augmented by the proinflammatory RAGE-ligand, S100-protein. These results were corroborated by analysis of cells transfected with different heterodimeric beta2-integrins, by using RAGE-transfected cells, and by using purified proteins. The RAGE-Mac-1 interaction defines a novel pathway of leukocyte recruitment relevant in inflammatory disorders associated with increased RAGE expression, such as in diabetes, and could provide the basis for the development of novel therapeutic applications.

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PubMed2003

Parenchymal cells in immune and tolerance induction.

There is increasing evidence that dendritic cells are capable of inducing T cell tolerance to tissue-specific antigens by presenting these antigens to CD4 and CD8 T cells in the respective draining lymph nodes. In contrast, parenchymal cells are often seen as immunologically inert. This lecture summarizes studies showing that tissue cells like sinusoidal endothelial cells and hepatocytes in the liver as well as keratinocytes in the skin can induce peripheral T cell tolerance. This tolerance induction is often preceded by T cell activation. Thus, several tolerance mechanisms are operating in parallel. We still have no learn which mechanism is most suitable for therapeutic intervention in autoimmune diseases and organ transplantation.

Animals↗

PubMed2003

RAGE drives the development of glomerulosclerosis and implicates podocyte activation in the pathogenesis of diabetic nephropathy.

Diabetic nephropathy ensues from events involving earliest changes in the glomeruli and podocytes, followed by accumulation of extracellular matrix in the mesangium. Postulated mechanisms include roles for vascular endothelial growth factor (VEGF), produced by podocytes and contributing to enhanced excretion of urinary albumin and recruitment/activation of inflammatory cells, and transforming growth factor-beta (TGF-beta), elicited largely from mesangial cells and driving production of extracellular matrix. RAGE, a receptor for advanced glycation endproducts (AGEs) and S100/calgranulins, displays enhanced expression in podocytes of genetically diabetic db/db mice by age 13 weeks. RAGE-bearing podocytes express high levels of VEGF by this time, in parallel with enhanced recruitment of mononuclear phagocytes to the glomeruli; events prevented by blockade of RAGE. By age 27 weeks, soluble RAGE-treated db/db mice displayed diminished albuminuria and glomerulosclerosis, and improved renal function. Diabetic homozygous RAGE null mice failed to develop significantly increased mesangial matrix expansion or thickening of the glomerular basement membrane. We propose that activation of RAGE contributes to expression of VEGF and enhanced attraction/activation of inflammatory cells in the diabetic glomerulus, thereby setting the stage for mesangial activation and TGF-beta production; processes which converge to cause albuminuria and glomerulosclerosis.

Albuminuria↗

PubMed2003

Neutralizing antibodies in gene-defective hosts.

In a host with a normal immune system and a complete gene defect, the nondefective gene product will be immunogenic. Consequently, neutralizing antibodies against the respective protein can arise either 'spontaneously' or after immunization, as shown in patients and in animal models, such as knockout mice. Accordingly, patients with X-linked or homozygous autosomal gene defects are at risk of developing neutralizing antibodies, in particular after protein substitution or gene therapy. This Review compares and exemplifies the various genetic and immunological contexts that lead to 'neutralizing and generated by gene defect' or 'nagged' antibodies, and outlines implications and solutions for therapeutic strategies.

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PubMed2003

RAGE mediates amyloid-beta peptide transport across the blood-brain barrier and accumulation in brain.

Amyloid-beta peptide (Abeta) interacts with the vasculature to influence Abeta levels in the brain and cerebral blood flow, providing a means of amplifying the Abeta-induced cellular stress underlying neuronal dysfunction and dementia. Systemic Abeta infusion and studies in genetically manipulated mice show that Abeta interaction with receptor for advanced glycation end products (RAGE)-bearing cells in the vessel wall results in transport of Abeta across the blood-brain barrier (BBB) and expression of proinflammatory cytokines and endothelin-1 (ET-1), the latter mediating Abeta-induced vasoconstriction. Inhibition of RAGE-ligand interaction suppresses accumulation of Abeta in brain parenchyma in a mouse transgenic model. These findings suggest that vascular RAGE is a target for inhibiting pathogenic consequences of Abeta-vascular interactions, including development of cerebral amyloidosis.

Aged↗

PubMed2003

Glucose, glycation, and RAGE: implications for amplification of cellular dysfunction in diabetic nephropathy.

Receptor for advanced glycation endproducts (RAGE) is a multi-ligand member of the immunoglobulin superfamily of cell surface molecules. Driven by rapid accumulation and expression of key ligands such as advanced glycation endproducts (AGE) and S100/calgranulins in diabetic tissues, upregulation and activation of RAGE magnifies cellular perturbation in tissues affected by hyperglycemia, such as the large blood vessels and the kidney. In the diabetic glomerulus, RAGE is expressed principally by glomerular visceral epithelial cells (podocytes). Blockade of RAGE in the hyperglycemic db/db mouse suppresses functional and structural alterations in the kidney, in the absence of alterations in blood glucose. Recent studies in homozygous RAGE null mice support a key role for RAGE in glomerular perturbation in diabetes. Importantly, beyond diabetes, studies in other settings of glomerulopathies support a critical RAGE-dependent pathway in podocytes linked to albuminuria, mesangial expansion, and glomerular sclerosis. A new paradigm is proposed in glomerular injury, and it is suggested that blockade of the RAGE axis may provide a novel means to prevent irreparable glomerular injury in diabetes and other sclerosing glomerulopathies.

Animals↗

PubMed2003

Central role of RAGE-dependent neointimal expansion in arterial restenosis.

Cellular proliferation, migration, and expression of extracellular matrix proteins and MMPs contribute to neointimal formation upon vascular injury. Wild-type mice undergoing arterial endothelial denudation displayed striking upregulation of receptor for advanced glycation end products (RAGE) in the injured vessel, particularly in activated smooth muscle cells of the expanding neointima. In parallel, two of RAGE's signal transducing ligands, advanced glycation end products (AGEs) and S100/calgranulins, demonstrated increased deposition/expression in the injured vessel wall. Blockade of RAGE, employing soluble truncated receptor or antibodies, or in homozygous RAGE null mice, resulted in significantly decreased neointimal expansion after arterial injury and decreased smooth muscle cell proliferation, migration, and expression of extracellular matrix proteins. A critical role for smooth muscle cell RAGE signaling was demonstrated in mice bearing a transgene encoding a RAGE cytosolic tail-deletion mutant, specifically in smooth muscle cells, driven by the SM22alpha promoter. Upon arterial injury, neointimal expansion was strikingly suppressed compared with that observed in wild-type littermates. Taken together, these data highlight key roles for RAGE in modulating smooth muscle cell properties after injury and suggest that RAGE is a logical target for suppression of untoward neointimal expansion consequent to arterial injury.

Animals↗

PubMed2002

Combination of T-cell therapy and trigger of inflammation induces remodeling of the vasculature and tumor eradication.

In a transgenic mouse model of multistep carcinogenesis, highly angiogenic insulinomas contain an irregular vascular network and develop an intrinsic resistance to leukocyte infiltration and effector function. Even persistently high levels of activated tumor-specific T lymphocytes fail to eradicate the tumors. In contrast, we show that irradiation before adoptive transfer results in complete macroscopic tumor regression. Thus, effective tumor therapy requires a proinflammatory microenvironment that permits T cells to extravasate and to destroy the tumor. Early after initiation of the irradiation/adoptive transfer therapy, the capillary network reacquires an almost normal appearance, a likely consequence of strong induction of the chemokines monokine induced by IFN-gamma (Mig) and IFN-inducible protein 10 (IP10). This remodeling of the vasculature in a proinflammatory environment may directly affect lymphocyte extravasation and effector function. Therefore, irradiation/adoptive transfer therapy combines antigen-driven tumor cell eradication with anti-angiogenic effects on tumor endothelium, a powerful synergy that has not been previously appreciated.

Animals↗

PubMed2002

Gelatinase B deficiency protects against endotoxin shock.

Gelatinase B or matrix metalloproteinase-9 (MMP-9) is stored in the tertiary granules of polymorphonuclear leukocytes. These cells are key effectors in acute inflammatory diseases such as sepsis. Endotoxin leads to rapid release of gelatinase B from these granules in vitro and in vivo, but the role of this enzyme in bacterial sepsis and endotoxin shock remains unclear. We studied the clinical course of endotoxinemia and its relation with the expression of gelatinase B from the pool of circulating leukocytes in adult as well as in young mice in a model of endotoxin-induced shock and compared wild-type with gelatinase B-deficient mice. The gelatinase B-deficient mice were resistant to endotoxin shock, which implies that specific MMP-9 inhibition constitutes anapproach for the treatment of septic shock syndromes.

Animals↗

PubMed2002

CpG-ODN-induced inflammation is sufficient to cause T-cell-mediated autoaggression against hepatocytes.

Autoimmune diseases are often associated with microbial infections. Molecular mimicry between microbial antigens and self-epitopes has been suggested as a mechanism for breaking self-tolerance and induction of autoimmunity. Since infections also cause inflammatory responses we explored the role of local inflammation in organ-specific autoimmunity. For this purpose, transgenic mice were used expressing the MHC class I molecule Kb exclusively on hepatocytes. These mice exhibit Kb-specific tolerance as exemplified by the acceptance of Kb+ grafts. Inflammatory reactions were induced by injection of immunostimulatory cytosine-phosphorothioate-guanine (CpG)-rich oligodeoxynucleotides (ODN). Application of CpG-ODN is sufficient to break tolerance in vivo, and to cause activation of Kb-specific CD8+ T cells and subsequent autoaggression against hepatocytes. The CpG-ODN-induced inflammation appears to have two major effects. First, it causes infiltration of T cells into the liver parenchyma. Second, adhesion and costimulatory molecules are up-regulated on hepatocytes so that the infiltrating CD8+ T cells encounter Kb on hepatocytes, which display an APC-like phenotype, resulting in activation and tissue damage. Autoimmune hepatitis can be maintained for at least eight weeks by repeated application of CpG-ODN but subsides after termination of the inflammatory stimulus, suggesting the requirement of additional factors for a self-perpetuation of autoimmunity. These observations describe an additional pathway for the induction of autoimmunity, i.e. in the absence of microbial antigens inflammatory reactions alone can lead to infiltration of T cells into organs, resulting in breaking of tolerance and autoaggression. Moreover, the results provide evidence that T cell activation can take place not only in draining lymph nodes but also directly on parenchymal cells.

Animals↗

PubMed2002

Temporal Cre-mediated recombination exclusively in endothelial cells using Tie2 regulatory elements.

SUMMARY: The versatility of the bacteriophage Cre/LoxP system is dependent on the availability of a spectrum of tissue-specific Cre transgenic mice to address a host of biological questions. In this paper, we report on the generation of an inducible Tie2Cre transgenic mouse line that facilitates gene targeting exclusively in endothelial cells. The temporal manner of recombination is feasible through the use of a Cre-estrogen receptor fusion protein ER(T2) and was, in practical terms, achieved by feeding the animals the estrogen antagonist tamoxifen orally for 5 weeks. High efficiency of recombination was found in the vast majority of endothelial cell populations examined, as monitored by an EGFP reporter mouse line. Critically, no EGFP expression was observed in any uninduced mice. This inducible Cre line will be a very beneficial asset to investigating the role of endothelial specific genes in the adult mouse and to induce transgenes in the endothelium in an extremely efficient manner. genesis 33:191-197, 2002.

Animals↗

PubMed2002

Levels of peripheral T cell tolerance.

The immune system is an adaptive defense system capable of specifically recognizing and eliminating an apparently limitless variety of foreign invaders. This highly specific response is provided by T and B lymphocytes. The enormous diversity of the antigen-specific receptors on these cells is generated by random rearrangement of the respective genes. The key challenge of such a defense system is to have as broad a T and B cell repertoire as possible in the absence of autoreactivity. This review summarizes mechanisms of peripheral T cell tolerance induction seen in various animal models. There is increasing evidence that tolerance to tissue-specific antigens can be induced by dendritic cells in the regional lymph nodes as well as by parenchymal cells like keratinocytes and hepatocytes in the respective tissues. Furthermore, tolerance induction should no longer only be viewed as prevention of T cell activation, as in certain systems activation of autoreactive T cells is insufficient to cause tissue damage. Thus, several tolerance mechanisms are operating in parallel under physiological conditions. With increasing knowledge of the molecular basis we will learn which mechanism is most suitable for therapeutic intervention.

Animals↗

PubMed2002

Recombinant mouse granulocyte chemotactic protein-2: production in bacteria, characterization, and systemic effects on leukocytes.

Granulocyte chemotactic protein-2 (GCP-2) is an important neutrophil chemotactic factor in the mouse that belongs to the CXC chemokine family. Although the local tissular effects of chemokines are well known, only recently has the systemic regulation of leukocytes become accepted. To study the pharmacokinetics of mouse GCP-2 and the systemic effects on leukocytes, we expressed a potent natural isoform of mouse GCP-2, GCP-2(9-78), in Escherichia coli and produced electrophoretically pure material. GCP-2(9-78) was 10-fold more potent to chemoattract neutrophils than recombinant GCP-2(5-78). After intravenous (i.v.) injection in mice, GCP-2(9-78) persisted in the circulation with an average half-life of 42 min. When a bolus of 1 mg/kg recombinant mouse GCP-2(9-78) was injected systemically, a significant effect on circulating leukocytes was observed. After a neutropenic phase, at its height at 1 h after injection, neutrophil numbers increased to a maximum at 4 h postinjection, and a concomitant decrease in lymphocyte numbers was observed. In control mice injected with isotonic saline, changes in leukocyte numbers were less pronounced and followed a different kinetic. Whereas tissular neutrophil chemotaxis to GCP-2 is influenced by gelatinase B, the systemic effects on neutrophilia and lymphopenia were not different in gelatinase B-deficient and wild-type mice. These data reinforce the idea that chemokines, including GCP-2, influence the homeostasis of circulating leukocyte numbers.

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