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Biomedical subjects

Johannes Norgauer

Publications and source records attributed to Johannes Norgauer.

At least 37 records · Page 2Linked to original sources
PubMed2004

Interleukin-5, interleukin-3 and granulocyte-macrophage colony-stimulating factor prime actin-polymerization in human eosinophils: a study with hypodense and normodense eosinophils from patients with atopic dermatitis.

Characteristic features of atopic diseases (AD) are immigration and local activation of eosinophils. Reorganization of the cytoskeleton modulates the function of leukocytes and is a prerequisite for the motility response. In this work, the regulation of actin polymerization has been investigated by flow cytometry using NBD-phallacidin and right angle light scatter measurements in purified eosinophils isolated from patients with atopic dermatitis and normal individuals. Stimulation of eosinophils with chemotaxins such as complement fragment C5a (C5a), CC chemokine RANTES/ CCL5 and platelet activating factor (PAF) induced a reversible polymerization of actin. Normodense eosinophils purified from patients with AD showed a decreased chemotaxin-induced actin response as compared to normodense eosinophils from healthy subjects and hypodense eosinophils from patients. Stimulation of eosinophils with Th2-cytokines such as interleukin-3 (IL-3), interleukin-5 (IL-5), granulocyte-macrophage colony-stimulating factor (GM-CSF) did not exert a significant effect on actin polymerization. However, pretreatment with IL-3, IL-5 or GM-CSF potentiated the chemotaxin-induced actin polymerization and graded the differential responsiveness between normodense and hypodense eosinophils. We demonstrate a different actin responsiveness in eosinophils from atopic patients and healthy subjects which could be overcome by modulating effects of Th2-cytokines.

Actins↗
PubMed2003

Stimulation of P2 purinergic receptors induces the release of eosinophil cationic protein and interleukin-8 from human eosinophils.

1. Extracellular nucleotides are the focus of increasing attention for their role as extracellular mediators since they are released into the extracellular environment in a regulated manner and/or as a consequence of cell damage. 2. Here, we show that human eosinophils stimulated with different nucleotides release eosinophil cationic protein (ECP) and the chemokine interleukin 8 (IL-8), and that release of these two proteins has a different nucleotide requirement. 3. Release of ECP was triggered in a dose-dependent manner by ATP, UTP and UDP, but not by 2'-&3'-o-(4-benzoyl-benzoyl)adenosine 5'-triphosphate (BzATP), ADP and alpha,beta-methylene adenosine 5' triphosphate (alpha,beta-meATP). Release of IL-8 was triggered by UDP, ATP, alpha,beta-meATP and BzATP, but not by UTP or ADP. Pretreatment with pertussis toxin abrogated nucleotide-stimulated ECP but not IL-8 release. 4. Release of IL-8 stimulated by BzATP was fully blocked by the P2X(7) blocker KN-62, while release triggered by ATP was only partially inhibited. IL-8 secretion due to UDP was fully insensitive to KN-62 inhibition. 5. Priming of eosinophils with GM-CSF increased IL-8 secretion irrespectively of the nucleotide used as a stimulant. 6. It is concluded that extracellular nucleotides trigger secretion of ECP by stimulating a receptor of the P2Y subfamily (possibly P2Y(2)), while, on the contrary, nucleotide-stimulated secretion of IL-8 can be due to activation of both P2Y (P2Y(6)) and P2X (P2X(1) and P2X(7)) receptors.

Blood Proteins↗
PubMed2003

[Xeroderma pigmentosum: children of the moon].

Xeroderma pigmentosum is based on a genetic defect in the DNA repair system, which is diagnosed in early childhood. Xeroderma pigmentosum is a rare disorder, which is transmitted in an autosomal recessive manner. Children with xeroderma pigmentosum display hypersensitivity to ultraviolet (UV) radiation. These patients experience serious sunburns with minimal exposure and then develop poikiloderma in the sun-exposed areas. Squamous cell carcinomas, basal cell carcinomas and malignant melanomas all appear during childhood. The majority of patients do not reach adult, but die from metastatic cutaneous malignancies. Genetically, xeroderma pigmentosum is differentiated into 7 complementation groups (XP-A to XP-G) and the xeroderma pigmentosum variants (XP-V). The assignment to the specific complementation group is made by fusing of xeroderma pigmentosum fibroblasts. Xeroderma pigmentosum must be distinguished from other so-called DNA repair deficiency syndromes, including Cockayne syndrome and trichothiodystrophy. A topical DNA repair enzyme appears to be helpful. A recombinant liposomal encapsulated T4 endonuclease V repairs UV-induced cyclobutane-pyrimidine dimers. Direct curative treatment of xeroderma pigmentosum could be achieved with gene therapy in future. Transfection of an intact repair gene which specifically codes for the missing repair protein could open new possibilities in the therapy of xeroderma pigmentosum.

Child↗
PubMed2003

Alerting and tuning the immune response by extracellular nucleotides.

The interplay between pro- and anti-inflammatory mechanisms during inflammatory and immune responses is critical for avoiding excessive tissue damage. Extracellular nucleotides (e.g., adenosine 5'-triphosphate) may represent constitutive signals that can alert the immune system of abnormal cell death. Relatively high doses of nucleotides induce rapid release of proinflammatory mediators and favor pathogen killing. However, recent findings on antigen presenting cells, particularly dendritic cells, revealed a more complex role for these molecules. Chronic exposure to low-dose nucleotides can redirect cellular responses to prototypic activation stimuli, leading to suppressed inflammation and immune deviation.

Animals↗
PubMed2003

Prostaglandin E2 synthesis in human monocyte-derived dendritic cells.

Prostaglandin E2 (PGE2), which is generated by the enzymatic activity of cyclooxygenase-1 and -2 (COX-1/2), plays a central role in the maturation process of dendritic cells (DC). Since regulation of COX-1/2 expression in human DC is only partially understood, we addressed the expression and activity of COX-1/2 in these cells. Here we show that lipopolysaccharide (lps) induces COX-2 mRNA and protein synthesis as well as the release of PGE2 in human interleukin-4 and granulocyte/macrophage colony-stimulating factor-differentiated monocyte-derived DC cultivated in the presence of 1% human plasma. Moreover, we found that lps induces p38 stress-activated protein kinase (p38) in these cells and inhibitors of p38 blocked lps-induced COX-2 expression and activity. Our data indicate that during lps-induced maturation p38 regulates COX-2 expression and PGE2 synthesis in DC.

Cell Differentiation↗
PubMed2003

Evidence of involvement of CXC-chemokines in proliferation of cultivated human melanocytes.

The CXC-chemokines 1 and 8 (CXCL1 and CXCL8) are ligands for the G protein-coupled CXC-chemokine receptor 2 (CXCR2). Both chemokines and CXCR2 are components of a potent autocrine growth factor loop in human melanoma cells. Currently, expression and biological function of both chemokines in normal human melanocytes is poorly defined. Here we describe that cocktails of melanocyte growth factors consisting of basic fibroblast growth factor (bFGF), endothelin 1 (ET-1) and alpha-melanocyte-stimulating hormone (alpha-MSH) stimulated release of CXCL1 and CXCL8, but did not influence expression of CXCR2 in human melanocytes. Cell studies revealed that CXCL1 and CXCL8 potentiate the proliferative activity of various combinations of cocktails with growth factor such as bFGF, ET-1 and alpha-MSH. Moreover, ligand blocking anti-CXCR2 antibodies reduced proliferation of melanocytes after stimulation with bFGF, ET-1 and alpha-MSH. This study implicates that CXCL1, CXCL8 and their receptor CXCR2 are components of an autocrine mechanism in proliferating human melanocytes.

Cell Division↗
PubMed2002

Adenosine affects expression of membrane molecules, cytokine and chemokine release, and the T-cell stimulatory capacity of human dendritic cells.

Dendritic cells (DCs) express functional purinergic type 1 receptors, but the effects of adenosine in these antigen-presenting cells have been only marginally investigated. Here, we further characterized the biologic activity of adenosine in immature DCs (iDCs) and lipopolysaccharide (LPS)-matured DCs (mDCs). Chronic stimulation with adenosine enhanced the macropinocytotic activity and the membrane expression of CD80, CD86, major histocompatibility complex (MHC) class I, and HLA-DR molecules on iDCs. Adenosine also increased LPS-induced CD54, CD80, MHC class I, and HLA-DR molecule expression in mDCs. In addition, adenosine dose-dependently inhibited tumor necrosis factor alpha and interleukin-12 (IL-12) release, whereas it enhanced the secretion of IL-10 from mDCs. The use of selective receptor agonists revealed that the modulation of the cytokine and cell-surface marker profile was due to activation of A(2) adenosine receptor. Functionally, adenosine reduced the allostimulatory capacity of iDCs, but not of mDCs. More important, DCs matured in the presence of adenosine had a reduced capacity to induce T helper 1 (Th1) polarization of naive CD4(+) T lymphocytes. Finally, adenosine augmented the release of the chemokine CCL17 and inhibited CXCL10 production by mDCs. In aggregate, the results provide initial evidence that adenosine diminishes the capacity of DCs to initiate and amplify Th1 immune responses.

Adenosine↗
PubMed2002

The influence of lysophosphatidic acid on the functions of human dendritic cells.

Lysophosphatidic acid (LPA) is a bioactive lipid mediator which is generated by secretory phospholipase A(2). In this study, we studied the biological activity of LPA on human dendritic cells (DCs), which are specialized APCs characterized by their ability to migrate into target sites and secondary lymphoid organs to process Ags and activate naive T cells. We show that immature and mature DCs express the mRNA for different LPA receptors such as endothelial differentiation gene (EDG)-2, EDG-4, and EDG-7. In immature DCs, LPA stimulated pertussis toxin-sensitive Ca(2+) increase, actin polymerization, and chemotaxis. During the maturation process, DCs lost their ability to respond toward LPA with Ca(2+) transients, actin polymerization, and chemotaxis. However, LPA inhibited in a pertussis toxin-insensitive manner the secretion of IL-12 and TNFalpha as well as enhanced secretion of IL-10 from mature DCs. Moreover, LPA did not affect the endocytic or phagocytic capacities and the surface phenotype of DCs, although it increased the allostimulatory function of mature DC and inhibited their capacity to induce Th1 differentiation. In summary, our study implicates that LPA might regulate the trafficking, cytokine production, and T cell-activating functions of DCs.

Actins↗
PubMed2002

Nucleotides induce chemotaxis and actin polymerization in immature but not mature human dendritic cells via activation of pertussis toxin-sensitive P2y receptors.

Dendritic cells (DCs) are considered the principal initiators of immune response because of their ability to migrate into peripheral tissues and lymphoid organs, process antigens, and activate naive T cells. There is evidence that extracellular nucleotides regulate certain functions of DCs via G-protein-coupled P2Y receptors (P2YR) and ion-channel-gated P2X receptors (P2XR). Here we investigated the chemotactic activity and analyzed the migration-associated intracellular signaling events such as actin reorganization and Ca(++) transients induced by common P2R agonists such as adenosine 5'-triphosphate (ATP) and 2-methylthioadenosine triphosphate, the P2YR agonists UTP and adenosine 5'-diphosphate (ADP), or the P2XR agonists alphabeta-methylenadenosine-5'-triphosphate and 2',3'-(4-benzoyl)benzoyl-ATP. The common P2R agonists and the selective P2YR agonists turned out to be potent chemotactic stimuli for immature DCs, but not for mature DCs. In contrast, P2XR agonists had only marginal chemotactic activity in both DC types. Chemotaxis was paralleled by a rise in the intracellular Ca(++) concentration and by actin polymerization. Studies with pertussis toxin implicated that intracellular signaling events such as actin polymerization, mobilization of intracellular Ca(++), and migration induced by nucleotides was mediated via G(i/o) protein-coupled P2YR. Moreover, functional studies revealed selective down-regulation of this G(i/o) protein-coupled chemotactic P2YR responsiveness during maturation, although immature and mature DCs expressed similar amounts of mRNA for the P2R subtypes (P2Y(2)R, P2Y(4)R, P2Y(5)R, P2Y(7)R, P2Y(11)R and P2X(1)R, P2X(4)R, P2X(7)R), and no major differences in respect to the mRNA expression of these receptors could be observed by semiquantitative reverse transcription and polymerase chain reaction (RT-PCR). In summary, our data describe a differential chemotactic response of immature and mature DCs to nucleotides, and lend further support to the hypothesis that P2R are a novel class of immunomodulatory plasma membrane receptors suitable for pharmacological intervention.

Actins↗
PubMed2002

Dendritic cells exposed to extracellular adenosine triphosphate acquire the migratory properties of mature cells and show a reduced capacity to attract type 1 T lymphocytes.

We previously reported that chronic stimulation with low, noncytotoxic doses of extracellular adenosine triphosphate (ATP) induced a distorted maturation of dendritic cells (DCs) and impaired their capacity to initiate T-helper (Th) 1 responses in vitro. Here, we examined the effects of ATP on chemokine-receptor expression and chemokine production by DCs. ATP strongly induced expression of CXC chemokine receptor 4 on both immature and lipopolysaccharide (LPS)-stimulated DCs and slightly up-regulated CC chemokine receptor (CCR) 7 on both DC types. In contrast, ATP reduced CCR5 expression on immature DCs. These effects were confirmed at both the messenger RNA and protein levels and were not produced by uridine triphosphate (UTP). Consistent with the changed receptor expression, ATP increased migration and intracellular calcium of immature and mature DCs to stromal-derived factor 1 (CXC ligand [CXCL] 12) and macrophage inflammatory protein [MIP] 3 beta (CC ligand [CCL] 19), whereas responses to MIP-1 beta (CCL4) were reduced. DCs are an important source of chemokines influencing recruitment of distinct T-lymphocyte subsets. ATP, but not UTP, significantly reduced LPS-induced production of interferon-inducible protein 10 (CXCL10) and regulated upon activation, normal T-cell expressed and secreted chemokine (CCL5); increased secretion of macrophage-derived chemokine (CCL22); and did not change production of thymus and activation-regulated chemokine (CCL17). Consistent with these findings, supernatants from ATP-treated mature DCs attracted Th1 and T-cytotoxic 1 cells less efficiently, whereas migration of Th2 and T cytotoxic 2 cells was not affected. Our data suggest that ATP provides a signal for enhanced lymph node localization of DCs but that it may, at the same time, diminish the capacity of DCs to amplify type 1 immune responses.

Adenosine Triphosphate↗
PubMed2002

Expression and function of histamine receptors in human monocyte-derived dendritic cells.

BACKGROUND: Histamine is a well-known mediator eliciting different responses in immune and nonimmune cells, but its role in modulating dendritic cell (DC) functions has been marginally investigated. OBJECTIVE: The purpose of this investigation was to analyze whether human monocyte-derived DCs express functional histamine receptors according to their maturation stage. METHODS: DCs were derived from monocytes and used as immature or LPS-differentiated cells. DCs were tested for histamine receptor expression, chemotaxis, cytokine release, and the capacity to induce T-cell differentiation in response to specific histamine receptor agonists. RESULTS: Immature and mature DCs expressed the mRNA for H1, H2, and H3 histamine receptors. Histamine induced intracellular Ca2+ transients, actin polymerization, and chemotaxis in immature DCs. Maturation of DCs resulted in the loss of these responses. In maturing DCs, however, histamine dose-dependently enhanced intracellular cAMP levels and stimulated IL-10 secretion while inhibiting production of IL-12. As a consequence, histamine might contribute to the impairment of generation of allogeneic type 1 responses via maturing DCs. Specific histamine receptor agonists or antagonists revealed that Ca2+ transients, actin polymerization, and chemotaxis of immature DCs were due to stimulation of H1 and H3 subtypes. Modulation of IL-12 and IL-10 secretion by histamine involved the H2 and H3 receptors exclusively. CONCLUSIONS: Our study suggests that histamine has important biological effects on DC activities, opening the possibility that histamine released during inflammatory or immune responses could regulate DC functions and ultimately favor type 2 lymphocyte-dominated immunity.

Actins↗
PubMed2002

Sphingosine 1-phosphate induces chemotaxis of immature and modulates cytokine-release in mature human dendritic cells for emergence of Th2 immune responses.

Sphingosine 1-phosphate (S1P) is a potent extracellular lysolipid phosphoric acid mediator that is released after IgE-stimulation of mast cells. Here we investigated the biological activity and intracellular signaling of S1P on human dendritic cells (DC), which are specialized antigen presenting cells with the ability to migrate into peripheral tissues and lymph nodes, as well as control the activation of naive T cells. We show that immature and mature DC express the mRNA for different S1P receptors, such as endothelial differentiation gene (EDG)-1, EDG-3, EDG-5, and EDG-6. In immature DC, S1P stimulated pertussis toxin-sensitive Ca2+ increase actin-polymerization and chemotaxis. These responses were lost by DC matured with lipopolysaccharide. In maturing DC, however, S1P inhibited the secretion of tumor necrosis factor alpha and interleukin (IL)-12, whereas it enhanced secretion of IL-10. As a consequence, mature DC exposed to S1P showed a reduced and increased capacity to generate allogeneic Th1 and Th2 responses, respectively. In summary, our study implicates that S1P might regulate the trafficking of DC and ultimately favor Th2 lymphocyte-dominated immunity.

Actins↗
PubMedDate not supplied

Xeroderma pigmentosum.

Xeroderma pigmentosum is a rare disorder transmitted in an autosomal recessive manner. Xeroderma pigmentosum is based on a genetic defect in the DNA repair system. This disease manifests in early childhood. Patients with xeroderma pigmentosum have a marked sensitivity to sunlight and develop serious sunburns with onset of poikilodermia in the light-exposed skin. Squamous cell carcinomas, basal cell carcinomas and malignant melanomas already appear in childhood. The majority of patients die before reaching adulthood because of metastases. Genetically, xeroderma pigmentosum is divided into 7 complementation groups (XP-A to XP-G) and the xeroderma pigmentosum variants (XP-V). Diagnostically, assignment to the specific complementation group is made according to the fusioning of xeroderma pigmentosum fibroblasts. Differential diagnosis must distinguish xeroderma pigmentosum from other so-called DNA-repair-deficiency syndromes like the Cockayne Syndrome and trichothiodystrophy. Currently, there are reports of successful application of a topical DNA Repair Enzyme. This is a recombinant liposomal encapsulated T4 endonuclease V, which repairs UV-induced cyclobutan-pyrimidine dimers. In future, causal therapy could be based on gene therapy. The introduction of an intact repair gene which specifically codes the repair protein, could open new possibilities in the treatment of xeroderma pigmentosum.

Animals↗
PubMedDate not supplied

Tumor necrosis factor alpha induces upregulation of CXC-chemokine receptor type II expression and magnifies the proliferative activity of CXC-chemokines in human melanocytes.

The CXC-chemokines Groalpha and interleukin-8 (IL-8) are ligands for two different G protein-coupled receptors, named CXC-chemokine receptor I & II (CXCRI & II). Both cytokines are potent growth factors for human melanoma cells, with only limited proliferative activity towards normal melanocytes. Here we analysed the influence of various cytokines on the expression of CXCRI & II and the CXC-chemokine-induced proliferation in human melanocytes. Flow cytometric studies revealed no protein expression of CXCRI and low protein expression of CXCRII at the cell surface of normal melanocytes. Tumor necrosis factor alpha (TNFalpha) enhanced the mRNA and protein expression of CXCRII, but did not influence expression of CXCRI. A consequence of TNFalpha-pretreatment of human melanocytes was a significant enhancement of the proliferative activity of IL-8 and Groalpha. This study implicates that TNFalpha magnifies the biological activity of CXC-chemokines in melanocytes by induction of CXCRII expression.

Cell Division↗