Genexpressionsmuster von fibrinolytischen Faktoren des Urokinase-Plasmin-Systems bei Dermatoliposklerose

Die Dermatoliposklerose (DLS) entwickelt sich als Folge einer progredienten primären Varikosis oder eines postthrombotischen Syndroms (PTS). Trotz bestehender Hinweise auf eine veränderte intravasale fibrinolytische Aktivität bei der chronisch-venösen Insuffizienz (CVI), wurden bisher fibrinolytische Faktoren im perivaskulären Gewebe nicht untersucht. Kürzlich zeigten wir, daß bei Dermatoliposklerose Matrix-Metalloproteinasen exprimiert und aktiviert werden. Da spezifische fibrinolytische Faktoren wichtige Haupteffektoren der Matrix-Metalloproteinasenaktivierung sind, untersuchten wir kürzlich die Genexpression der Plasminogenaktivatoren vom Urokinasetyp (uPA) und vom Gewebetyp (tPA), des Urokinase-Rezeptor (uPA-R) sowie der Plasminogenaktivator-Inhibitoren (PAI-1 und PAI-2) in Gewebsbiopsien von Patienten mit Dermatoliposklerose. Zum Nachweis verwandten wir dabei die Technik der reversen Transkription und Polymerase-Kettenreaktion (RT-PCR). Es fand sich in allen Hautproben (n = 21) eine signifikant erhöhte mRNA-Expression von uPA und uPA-R im Vergleich zu gesunder Haut (n = 12). Dagegen konnte kein signifikanter Unterschied für mRNA-Transkripte von tPA, PAI-1 und PAI-2 nachgewiesen werden. Die Dermatoliposklerose zeichnet sich somit durch erhöhte transkriptionelle Expression von uPA und uPA-R aus. Eine gesteigerte De-novo-Synthese von uPA und uPA-R könnte daher bei der Aktivierung von Matrix-Metalloproteinasen und entsprechend in der Pathogenese des Ulcus cruris venosum eine zentrale Rolle spielen.

Iloprost has potent anti-inflammatory properties on human monocyte-derived dendritic cells

BACKGROUND

The stable prostaglandin I2 analogue (iloprost) iloprost has been shown to inhibit allergic airway inflammation in mice by modulating the function of myeloid dendritic cells (DCs).

OBJECTIVE

The aim of the current study was to investigate the biological activity of iloprost on human monocyte-derived DCs.

METHODS

I prostanoid (IP) receptor expression was analysed by RT-PCR. Cytokine secretion by DCs and CD4+ T cells was measured by ELISA. The expression of the transcription factor FoxP3 after co-culture of DCs with CD4+ CD45RA+ T cells was analysed by flow cytometry.

RESULTS

Human monocyte-derived DCs were found to express mRNA specific for the PGI2 receptor IP, and stimulation with iloprost resulted in increased cyclic AMP levels in both immature DCs (iDCs) and mature DCs (mDCs). Moreover, iloprost dose dependently inhibited the secretion of TNF-alpha, IL-6, IL-8 and IL-12p70 in mDCs, while it enhanced IL-10 production. Changes in cytokine secretion were paralleled by an altered T-cell priming capacity of DCs: in co-culture experiments of iloprost-treated mDC and naïve CD45RA+ T cells, an induction of regulatory T cells could be observed, as demonstrated by increased intracellular FoxP3 expression and IL-10 production. Additionally, iloprost inhibited the MIP-3beta-induced migration of mDCs.

CONCLUSION

In summary, our results provide evidence that iloprost profoundly affects the function of human myeloid DCs. Therefore, iloprost might also be a new therapeutical option for the treatment of asthma in humans.

Histamine modulates γδ-T lymphocyte migration and cytotoxicity, via Gi and Gs protein-coupled signalling pathways

BACKGROUND AND PURPOSE

The biogenic amine, histamine plays a pathophysiological regulatory role in cellular processes of a variety of immune cells. This work analyses the actions of histamine on γδ-T lymphocytes, isolated from human peripheral blood, which are critically involved in immunological surveillance of tumours.

EXPERIMENTAL APPROACH

We have analysed effects of histamine on the intracellular calcium, actin reorganization, migratory response and the interaction of human γδ T cells with tumour cells such as the A2058 human melanoma cell line, the human Burkitt's Non-Hodgkin lymphoma cell line Raji, the T-lymphoblastic lymphoma cell line Jurkat and the natural killer cell-sensitive erythroleukaemia cell line, K562.

KEY RESULTS

γδ T lymphocytes express mRNA for different histamine receptor subtypes. In human peripheral blood γδ T cells, histamine stimulated Pertussis toxin-sensitive intracellular calcium increase, actin polymerization and chemotaxis. However, histamine inhibited the spontaneous cytolytic activity of γδ T cells towards several tumour cell lines in a cholera toxin-sensitive manner. A histamine H(4) receptor antagonist abolished the histamine induced γδ T cell migratory response. A histamine H(2) receptor agonist inhibited γδ T cell-mediated cytotoxicity.

CONCLUSIONS AND IMPLICATIONS

Histamine activated signalling pathways typical of chemotaxis (G(i) protein-dependent actin reorganization, increase of intracellular calcium) and induced migratory responses in γδ T lymphocytes, via the H(4) receptor, whereas it down-regulated γδ T cell mediated cytotoxicity through H(2) receptors and G(s) protein-coupled signalling. Our data suggest that histamine activated γδ T cells could modulate immunological surveillance of tumour tissue.

EMMPRIN (CD147) is a novel receptor for platelet GPVI and mediates platelet rolling via GPVI-EMMPRIN interaction

The Extracellular Matrix Metalloproteinase Inducer (EMMPRIN, CD147, basigin) is an immunoglobulin-like receptor expressed in various cell types. During cellular interactions homotypic EMMPRIN-EMMPRIN interactions are known to induce the synthesis of matrix metalloproteinases. Recently, we have identified EMMPRIN as a novel receptor on platelets. To our knowledge EMMPRIN has not been shown to serve as adhesion receptor, yet. Here we characterise platelet glycoprotein VI (GPVI) as a novel adhesion receptor for EMMPRIN. Human platelets were prestimulated with ADP and perfused over immobilised recombinant EMMPRIN-Fc or Fc-fragments under arterial shear conditions. ADP-stimulated platelets showed significantly enhanced rolling (but not enhanced firm adhesion) on immobilised EMMPRIN-Fc compared to Fc. Pretreatment of platelets with blocking mAbs anti-EMMPRIN or anti-GPVI leads to a significant reduction of rolling platelets on immobilised EMMPRIN-Fc, whereas pretreatment with blocking mAbs anti-p-selectin, anti-alpha4-integrin or anti-GPIIb/IIIa complex (20 microg/ml each) had no effect. Consistently, chinese hamster ovary (CHO) cells stably transfected with GPVI showed enhanced rolling (but not adhesion) on immobilised EMMPRIN-Fc in comparison to non-transfected CHO cells. Similarly, CHO cells stably transfected with EMMPRIN showed enhanced rolling on immobilised GPVI-Fc (or EMMPRIN-Fc) compared to non transfected CHO-cells. Finally, specific binding of EMMPRIN to GPVI was demonstrated by a modified ELISA and surface plasmon resonance technology with a dissociation constant of 88 nM. Platelet GPVI is a novel receptor for EMMPRIN and can mediate platelet rolling via GPVI-EMMPRIN interaction.

EMMPRIN and its ligand cyclophilin A regulate MT1-MMP, MMP-9 and M-CSF during foam cell formation

Upon coincubation with platelets, CD34(+) progenitor cells have the potential to differentiate into foam cells, and thereby may promote the progression of atherosclerosis. The exact mechanism of MMP-regulation during the cellular differentiation process to foam cells is still unclear. Thus, we investigated the role of EMMPRIN (CD147) and its ligand cyclophilin A (CyPA) during foam cell formation originating from both monocytes/macrophages and CD34(+) progenitor cells.

METHODS AND RESULTS

Differentiation of CD34(+) progenitor to foam cells was analyzed in a coculture model of progenitor cells and platelets. While CD34(+) cells did not express EMMPRIN or MT1-MMP, mature foam cells strongly expressed EMMPRIN, which was associated with MT1-MMP expression as well as MMP-9. Gene silencing of EMMPRIN by siRNA during the cell differentiation process hindered not only the upregulation of MMPs (MT1-MMP, MMP-9), but also the secretion of the cytokine M-CSF. During the differentiation process CyPA was substantially released into the supernatant. The presence of the CyPA inhibitor NIM811 significantly reduced MMP-9 secretion during the differentiation process. Similar results were obtained using the classical pathway of foam cell formation by coincubating human macrophages with AcLDL. Additionally, the presence of soluble EMMPRIN ligands (CyPA, recombinant EMMPRIN) further enhanced MMP-9 secretion by mature foam cells. Consistently, CyPA and EMMPRIN were found in atherosclerotic plaques of ApoE-deficient mice by immunohistochemistry.

CONCLUSION

EMMPRIN is upregulated during the differentiation process from CD34(+) progenitor cells to foam cells, whereas its ligand, CyPA, is released. The CyPA/EMMPRIN activation pathway may play a relevant role in promoting the vulnerability of atherosclerotic plaques.

5-hydroxytryptamine modulates migration, cytokine and chemokine release and T-cell priming capacity of dendritic cells in vitro and in vivo

Beside its well described role in the central and peripheral nervous system 5-hydroxytryptamine (5-HT), commonly known as serotonin, is also a potent immuno-modulator. Serotoninergic receptors (5-HTR) are expressed by a broad range of inflammatory cell types, including dendritic cells (DCs). In this study, we aimed to further characterize the immuno-biological properties of serotoninergic receptors on human monocyte-derived DCs. 5-HT was able to induce oriented migration in immature but not in LPS-matured DCs via activation of 5-HTR(1) and 5-HTR(2) receptor subtypes. Accordingly, 5-HT also increased migration of pulmonary DCs to draining lymph nodes in vivo. By binding to 5-HTR(3), 5-HTR(4) and 5-HTR(7) receptors, 5-HT up-regulated production of the pro-inflammatory cytokine IL-6. Additionally, 5-HT influenced chemokine release by human monocyte-derived DCs: production of the potent Th1 chemoattractant IP-10/CXCL10 was inhibited in mature DCs, whereas CCL22/MDC secretion was up-regulated in both immature and mature DCs. Furthermore, DCs matured in the presence of 5-HT switched to a high IL-10 and low IL-12p70 secreting phenotype. Consistently, 5-HT favoured the outcome of a Th2 immune response both in vitro and in vivo. In summary, our study shows that 5-HT is a potent regulator of human dendritic cell function, and that targeting serotoninergic receptors might be a promising approach for the treatment of inflammatory disorders.

Tight junctions and compression therapy in chronic venous insufficiency

Tight junctions (TJs) provide a barrier function, inhibiting solute and water flow through the paracellular space. There had been no analysis until now as to how tight junction molecules could be involved in the pathology of patients with chronic venous insufficiency. The aim of the study was to analyse the expression pattern of TJ-molecules occludin (OCLN), claudin-1 (CLDN-1), claudin-3 (CLDN-3) and claudin-5 (CLDN-5) on mRNA and protein level in patients with edema, venous leg ulcers and healthy controls. Biopsy specimens were taken in healthy individuals and in patients before, and four weeks after compression therapy. mRNA-expression was determined by using reverse-transcriptase and polymerase chain reaction (RT-PCR) and the protein-expression was determined by Western blotting from tissue specimens. Quantification performed determining the expression for TJ-molecules displayed diminished expression for CLDN-1 (p<0.01) and CLDN-5 (p<0.01) in patients with chronic venous insufficiency in comparison with healthy controls on mRNA as well as protein level. No statistical differences were detected for OCLN and CLDN-3 between the edema group and healthy controls. There was a significantly elevated expression (p<0.01) on mRNA and protein level between the leg ulcer group and healthy controls for OCLN and CLDN-3. Densitometric evaluation revealed a more significantly elevated expression (p<0.01) for CLDN-1 and CLDN-5 on mRNA and protein level after four weeks of compression therapy in comparison with prior to treatment for the edema as well as the leg ulcer group. Compression therapy tightens the paracellular barrier via elevated expression of specific TJs and prevents thereby the progression of chronic venous insufficiency due to inhibited permeability of fluid into the perivascular tissue.

Characterization of the biological activities of uridine diphosphate in human dendritic cells: Influence on chemotaxis and CXCL8 release

Uridine nucleotides are endogenous nucleotides which are released into the extracellular space from mechanical stressed endothelial and epithelial cells as well as lipopolysaccharide (lps)-stimulated monocytes. Here, we studied the biological activity of the selective purinoreceptor P2Y6 (P2YR6) agonist Uridine 5'diphosphate (UDP) as well as the P2YR2- and P2YR4-activating uridine 5'triphosphate (UTP) on human dendritic cells (DC). These cells in their immature state have the ability to migrate from blood to peripheral target sites where they sense dangerous signals and capture potential antigens. Moreover, mature DC induce innate immune responses and migrate from peripheral tissues to secondary lymphoid organs in order to activate naive T cells and initiate adaptive immunity. Here, we were able to show that uridine nucleotides stimulated Ca(2+) transients, actin polymerization, and chemotaxis in immature DC. Experiments with pertussis toxin, the stable pyrimidine agonist uridine 5'-O-(2-thiodiphosphate) (UDPgammaS) and receptor antagonists, as well as desensitization studies suggested that these uridine nucleotides activities were mediated by different G(i) protein-coupled receptors. During lps-induced maturation, DC lost their ability to respond towards uridine nucleotides with these activities. Instead, UDP, but not UTP, stimulated the release of the CXC-chemokine 8 (CXCL8) from mature DC in a reactive blue sensitive manner. Moreover, our study indicates that UDP stimulates different signaling pathways in immature and mature DC in order to favor the accumulation of immature DC and to augment the capacity to secrete CXCL8 in mature DC.

The serotoninergic receptors of human dendritic cells: identification and coupling to cytokine release

The neurotransmitter 5-hydroxytryptamine (5-HT), commonly known as serotonin, is stored at peripheral sites in mast cells and released from this peripheral source upon IgE cross-linking. In this study, we investigated the expression of serotoninergic receptors (5-HTR), the signaling pathway, and biological activity of 5-HT on human dendritic cells (DC), showing that immature and mature DC expressed mRNA for different serotoninergic receptors. Thereby, the mRNA of 5-HTR(1B), 5-HTR(1E), 5-HTR(2A), 5-HTR(2B), one splicing variant of the 5-HTR(3), 5-HTR(4), and 5-HTR(7) receptors were detected. Immature DC preferentially expressed mRNA for the heptahelical 5-HTR(1B), 5-HTR(1E), and 5-HTR(2B) receptors, while mature DC mostly expressed 5-HTR(4) and 5-HTR(7). The mRNA expression level of the ligand-gated cation channel 5-HTR(3) and the heptahelical 5-HTR(2A) did not significantly change during maturation. Isotype-selective receptor agonists allowed us to show that 5-HT stimulated 5-HTR(3)-dependent Ca(2+) influx in immature and mature DC. Moreover, we revealed that 5-HTR(1) and 5-HTR(2) receptor stimulation induced intracellular Ca(2+) mobilization via G(i/o) proteins in immature, but not mature, DC. Activation of 5-HTR(4) and 5-HTR(7) induced cAMP elevation in mature DC. Functional studies indicated that activation of 5-HTR(4) and 5-HTR(7) enhanced the release of the cytokines IL-1beta and IL-8, while reducing the secretion of IL-12 and TNF-alpha in mature DC. In summary, our study shows that 5-HT stimulated, in a maturation-dependent manner, different signaling pathways in DC. These data point to a role for 5-HT in regulating the immune response at peripheral sites.

Lysophosphatidic acid induces chemotaxis, oxygen radical production, CD11b up-regulation, Ca2+ mobilization, and actin reorganization in human eosinophils via pertussis toxin-sensitive G proteins

Lysophosphatidic acid (LPA) is a bioactive lipid mediator, which is generated by secretory type II phospholipase A(2) and is thought to play a major role in the pathogenesis of atopic diseases. In this study, the biological activity of LPA on human eosinophils was characterized. We showed by reverse transcription and PCR that human eosinophils express the mRNA of the LPA receptors endothelial differentiation gene (EDG)-2 and EDG-7. Experiments revealed that LPA has chemotactic activity toward eosinophils, stimulates the production of reactive oxygen metabolites, and induces up-regulation of the integrin CD11b. Signal pathway measurements indicated Ca(2+)-mobilization from intracellular stores and transient actin polymerization upon stimulation with LPA. Cell responses elicited by LPA were inhibited by pertussis toxin indicating that in eosinophils the LPA receptor(s), presumably EDG-2 and/or EDG-7, are coupled to G(i/o) proteins. Moreover, LPA-induced activation of eosinophils could be completely blocked by the EDG-2/EDG-7 antagonist diacylglycerol pyrophosphate. In addition, at optimal doses the changes induced by LPA were comparable to those obtained by the other well-characterized chemotaxins. These results indicate that LPA is a strong chemotaxin and activator of eosinophils. These findings point to a novel role of LPA in the pathogenesis of diseases with eosinophilic inflammation such as atopic diseases as chemotaxin as well as activator of proinflammatory effector functions.

Wirkung der Kompressionstherapie auf die parazelluläre Barrierefunktion

Tight junctions (TJs) bilden semipermeable interzelluläre Diffusionsbarrieren, die den parazellulären Transport kontrollieren. Als apikale Strukturen des Schlussleistenkomplexes sind TJs selektiv permeabel und somit an der Abdichtung des Interzellularspaltes beteiligt. Ziel: Bestimmung der Expression der TJ-Moleküle Occludin (OCLN), Claudin-1 (CLDN-1), -3 (CLDN-3) und -5 (CLDN-5) auf mRNA- und Proteinebene bei Patienten mit CVI-bedingten Beinödemen und mit venösen Beinulzerationen im Vergleich zu gesunder Haut. Material, Methoden: Gewebeproben von der unteren Extremität aus läsionaler und gesunder Haut wurden mit RT-PCR und Westernblot im Hinblick auf die Expression der genannten TJ-Moleküle untersucht und densitometrisch analysiert. Ergebnisse: CVI-Patienten hatten im Vergleich zu gesunder Haut in allen Proben eine erniedrigte mRNA- und Proteinexpression von CLDN-1 und CLDN-5. Kein statistischer Unterschied wurde für die OCLN- und CLDN-3-Expression festgestellt. Densitometrisch wurde eine signifikant erhöhte Expression von CLDN-1 und CLDN-5 nach einer vierwöchigen Kompressionsstrumpftherapie im Vergleich zum Expressionsmuster vor Therapiebeginn nachgewiesen. Schlussfolgerung: Diese Daten weisen daraufhin, dass spezifische TJ-Moleküle bei Patienten mit CVI in läsionaler Haut vermindert exprimiert werden und dass der antiödematöse Effekt der Kompressionsstrumpftherapie möglicherweise zusätzlich über eine Stärkung der parazellulären Barrierefunktion vermittelt wird.

Inosine stimulates chemotaxis, Ca2+-transients and actin polymerization in immature human dendritic cells via a pertussis toxin-sensitive mechanism independent of adenosine receptors

Inosine is an endogenous purine nucleoside, which is formed by adenosine deaminidase during adenosine breakdown and is released into the extracellular space from the sympathetic nervous system or injured cells. Here, we studied the biological activity of inosine on human dendritic cells (DC), which are specialized antigen presenting cells characterized by their ability to migrate from the blood to peripheral tissues, and then to secondary lymphoid organs where they initiate adaptive immune responses. In immature DC, inosine concentration-dependently stimulated Ca(2+)-transients, actin polymerization, and chemotaxis. Experiments with adenosine receptor antagonists and pertussis toxin (PTX) as well as desensitization studies suggested that the activity of inosine was mediated by a G protein-coupled receptor pathway independent of adenosine receptors. DC, induced to mature by lipopolysaccharide, lost their ability to respond towards inosine with these activities. Moreover, inosine did neither influence membrane expression of CD54, CD80, CD83, CD86, HLA-DR, and MHC class I molecules nor modulated secretion of interleukin (IL)-12, IL-10, and tumor necrosis factor alpha in immature and lipopolysaccharide-matured DC. In aggregate, our study indicates that inosine may be involved in the trafficking control system of immature DC, and mediates its chemotactic activity by a PTX-sensitive mechanism independent of adenosine receptors.

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.

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.

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.

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.

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.

Xeroderma Pigmentosum: Mondscheinkinder. 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.

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.

Elevated expression of extracellular matrix metalloproteinase inducer (CD147) and membrane-type matrix metalloproteinases in venous leg ulcers

BACKGROUND

Matrix metalloproteinases (MMPs) contribute to matrix remodelling in venous leg ulcers. Extracellular MMP inducer (EMMPRIN; CD147) has been reported to increase MMP expression, and membrane type 1 MMP (MT1-MMP) has been implicated in the activation of MMPs.

OBJECTIVES

To examine whether and to what degree EMMPRIN, MMP-2, MT1-MMP and membrane type 2 MMP (MT2-MMP) are expressed in venous leg ulcers as well as the association with MMP activity.

METHODS

EMMPRIN, MMP-2, MT1-MMP and MT2-MMP were analysed by zymography and immunohistochemistry in biopsies from healthy skin and lesional tissue from venous leg ulcers.

RESULTS

Zymography provided direct evidence of increased proteolytic activity of MMP-2 in lesional skin in comparison with healthy controls. Immunostaining showed intense expression of EMMPRIN, MMP-2, MT1-MMP and MT2-MMP in dermal structures of venous leg ulcers, whereas only EMMPRIN and MMP-2 showed elevated expression in perivascular regions. Our findings indicate that venous leg ulcers are characterized by elevated expression of EMMPRIN, MMP-2, MT1-MMP and MT2-MMP. The immunohistological findings of skin alterations reflect the dynamic process of activation of soluble and membrane-bound MMPs, which may be highly induced by EMMPRIN.

CONCLUSIONS

These data suggest for the first time that membrane-bound MMPs may favour enhanced turnover of the extracellular matrix and support unrestrained MMP activity in venous leg ulcers.

Engagement of glycoprotein IIb/IIIa (alpha(IIb)beta3) on platelets upregulates CD40L and triggers CD40L-dependent matrix degradation by endothelial cells

BACKGROUND

CD40L-CD40 interactions induce inflammatory signals in cells of the vascular wall. We evaluated the effects of glycoprotein (GP) IIb/IIIa (alpha(IIb)beta3) engagement that occurs during platelet-endothelium interactions on CD40L surface exposure on platelets and initiation of proteolytic activity in human umbilical vein endothelial cells (HUVECs).

METHODS AND RESULTS

Transient (60-minute) adhesion of thrombin-prestimulated platelets enhanced HUVEC expression of urokinase-type plasminogen activator receptor and membrane type-1 matrix metalloproteinase (MT1-MMP) (reverse transcriptase-polymerase chain reaction, flow cytometry) and secretion of urokinase-type plasminogen activator, tissue-type plasminogen activator, and MMP-1 (ELISA) and induced proteolytic activity via MMP-2 and MMP-9 (gelatin zymography). These effects were abrogated by hindrance of physical platelet-endothelial contacts using transwell systems or inhibited by GRGDSP, mAbs anti-GP IIb/IIIa (7E3), anti-alpha(v)beta3 (LM609), or anti-CD40L (TRAP1). In addition, MMP-2 and MMP-9 were inhibited by specific GP IIb/IIIa antagonists tirofiban, lamifiban, or integrelin. On endothelial cells, induction of proteolytic activity by activated platelets was mimicked by CD40 engagement using soluble CD40L but not affected by antibody clustering of alpha(v)beta3. On platelets, CD40L and CD62P exposure was enhanced on adhesion to HUVECs or immobilized fibrinogen and was abrogated by GRGDSP or LM609. In suspension, cross-linking of GP IIb/IIIa by fibrinogen plus secondary mAb upregulated CD40L surface exposure. Consistently, bivalent mAb 7E3 upregulated CD40L, whereas ligation of GP IIb/IIIa by soluble fibrinogen alone or monovalent Fab-fragment c7E3 had no effect.

CONCLUSIONS

Platelet adhesion via GP IIb/IIIa upregulates CD40L and CD62P surface exposure. Proteolytic activity of HUVEC is induced by the concerted action of beta3-integrin-mediated platelet adhesion and subsequent CD40L-induced signals in HUVECs. Effective anti-GP IIb/IIIa or anti-CD40L strategies might, therefore, contribute to plaque stabilization.

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.

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.

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.

Fractalkine induces chemotaxis and actin polymerization in human dendritic cells

OBJECTIVE AND DESIGN

Dendritic cells (DCs) are considered as the principle initiators of immune responses by virtue of their ability to migrate into target sites, process antigens and activate naive T cells. Here, the chemotactic activity and intracellular signaling of fractalkine was analyzed and compared to well known chemotaxins.

METHODS

The mRNA-expression of G protein-coupled CX3CR1 was analyzed by RT-PCR. Chemotaxis was measured in 48-well Boyden chambers and actin polymerization by flow cytometry.

RESULTS

The mRNA-expression of CX3CR1 in immature and mature DCs was revealed. Fractalkine elicited actin polymerization and chemotaxis in a dose-dependent manner in DCs independent of their state of maturation.

CONCLUSIONS

These results show that immature and mature DCs express mRNA for the CX3CRI and that fractalkine induces chemotaxis and migration associated actin polymerization in immature as well as in mature DCs, contrasting with the action of other chemokines such as RANTES or MIP-3beta which act only on distinct maturation states of DCs.

Expression and function of adenosine receptors in human dendritic cells

Dendritic cells (DCs) are specialized antigen-presenting cells characterized by their ability to migrate into target sites, process antigens, and activate naive T cells. In this study, we analyzed the biological activity and intracellular signaling of adenosine by using reverse transcriptase-polymerase chain reaction assays to investigate mRNA expression of A(1), A(2a) and A(3) adenosine receptors in immature and mature human DCs. Functional experiments on adenosine stimulation showed chemotaxis, intracellular calcium transients, and actin polymerization, but no activation of adenylate cyclase in immature DCs. Experiments with receptor isotype-selective agonists and antagonists as well as pertussis toxin revealed that chemotaxis, calcium transients, and actin polymerization were mediated via G(i-) or G(0-)protein-coupled A(1) and A(3) receptors. Maturation of DCs induced by lipopolysaccharide (LPS) resulted in down-regulation of A(1) and A(3) receptor mRNAs, although A(2a) receptor mRNA was still expressed. However, in LPS-differentiated DCs, adenosine and an A(2a) receptor agonist stimulated adenylate cyclase activity, enhanced intracellular cAMP levels, and inhibited interleukin 12 (IL-12) production. These effects could be completely prevented by pretreatment with A(2) receptor antagonist. These findings strongly suggest that adenosine has important but distinct biological effects in DCs activity as a chemotaxin for immature DCs and as a modulator of IL-12 production in mature DCs. These effects can be explained by differential expression of adenosine receptor subtypes.

Functional characterization of P2Y and P2X receptors in human eosinophils

Activation of purinoceptor by ATP induces in eosinophils various cell responses including calcium transients, actin polymerization, production of reactive oxygen metabolites, CD11b-expression, and chemotaxis. Here, the effect of ion channel-gated P2X and/or G protein-coupled P2Y receptor agonists ATP, ATPgammaS, alpha,beta-meATP, 2-MeSATP, BzATP, ADP, CTP, and UTP on the intracellular Ca(2+)-mobilization, actin polymerization, production of reactive oxygen metabolites, CD11b expression and chemotaxis of human eosinophils were measured and the biological activity was analyzed. Although all tested nucleotides were able to induce all these cell responses, the biological activity of the analyzed nucleotides were distinct. Agonists of the G protein-coupled P2Y receptors such as 2-MeSATP, UTP, and ADP have a higher biological activity for production of reactive oxygen metabolites, actin polymerization and chemotaxis in comparison to the ion channel-gated P2X agonists alphabeta-meATP, BzATP, and CTP. In contrast, P2Y and P2X agonist showed similar potencies in respect to intracellular calcium transient and CD11b up-regulation. This conclusion was further supported by experiments with receptor iso-type antagonist KN62, EGTA or with the G(i) protein-inactivating pertussis toxin. These findings indicate participation of different purinorecptors in the regulation of cell responses in eosinophils.

The role of the urokinase-type plasminogen activator (uPA) and its receptor (CD87) in lipodermatosclerosis

BACKGROUND

Lipodermatosclerosis refers to a sclerosing panniculitis and dermopathy of the lower extremities sometimes seen in association with venous ulceration. Matrix metalloproteinases are implicated in the pathogenesis of venous leg ulcers and the in vitro activation of recombinant MMP-2 is controlled by the plasminogen activation system. To better understand the role of plasminogen activation in the pathogenesis of venous leg ulcers we investigated fibrinolytic factors and their inhibitors in tissue samples of lipodermatolsclerosis.

METHODS

The expression and the functional state of the urokinase-type plasminogen activator (uPA), the tissue-type plasminogen activator (tPA), the urokinase receptor (CD87), the plasminogen activator inhibitors-1 and -2 (PAI-1 and PAI-2) were assayed using reverse transcription polymerase chain reaction, Western blot, fibrin zymography and immunohistochemistry analyses in tissue samples of lipodermatosclerosis.

RESULTS

Our results provide direct evidence of elevated expression of uPA (p<0.01) and CD87 (p<0.01) mRNA and protein level in lipodermatosclerosis in comparison with healthy skin. By immunohistochemistry, elevated expression of uPA and CD87 could be detected. Fibrin zymography showed significantly elevated endogenous uPA activity (p<0.01) in liposclerotic lesions compared to healthy controls.

CONCLUSION

Our findings indicate that elevated plasminogen activation in lipodermatosclerotic tissue may play a crucial role in the pathogenesis of venous leg ulceration.

Inflammation in stasis dermatitis upregulates MMP-1, MMP-2 and MMP-13 expression

Stasis dermatitis is a common disorder, which is a consequence of impaired venous drainage of the legs. It is characterized histologically by proliferation of small blood vessels in the papillary dermis. This neovascularization may lead occasionally to the formation of discrete papules due to inflammatory processes. In order to evaluate the role of matrix metalloproteinases (MMPs) in the acute phase of chronic venous insufficiency, we examined the production of MMP-1, -2, -13 and tissue inhibitors of metalloproteinase (TIMP)-1 and -2 in lesional skin of stasis dermatitis. A total of 19 patients affected by stasis dermatitis were included in this experimental study. Polymerase chain reaction, western blot and immunohistochemical studies on tissue specimen were performed. In lesional skin of stasis dermatitis, there was elevated gene expression and immunoreactivity for MMP-1, -2 and -13 in comparison to healthy controls. In contrast, genexpression and immunoreactivity for TIMP-1 and -2 were diminished in stasis dermatitis in comparison with healthy controls. Overexpression and production of MMP-1, -2 and -13 without inhibitory effects could be the result of cytokine mediated induction. Matrix metalloproteinases (MMPs) may play an important role in the remodeling of lesional skin in stasis dermatitis.

Distinct amplification of the C5a-receptor pathways in normodense and hypodense eosinophils of patients with atopic dermatitis

In patients with atopic dermatitis two different types of blood eosinophils with distinct density can be isolated. The normodense cells represent the huge majority in count, whereas the hypodense eosinophils are characterized by higher effector activity. To understand the altered functional responsiveness of these two cell subtypes, the expression of C5a receptors as well as C5a-induced signal pathways and the production of reactive oxygen metabolites have been analyzed. Chemiluminescence measurements revealed significant higher production of reactive oxygen metabolites in hypodense eosinophils in comparison to normodense cells. However, no difference in the expression level of C5a receptors as well as in the C5a-induced Ca2+-transients between normodense and hypodense eosinophils were found. In contrast, hypodense eosinophils showed a significantly higher actin polymerization response and phosphatidylinositol 4,5 bisphosphate 3-kinase activation after stimulation with C5a than normodense eosinophils. Therefore, normodense and hypodense eosinophils from the blood of patients with atopic dermatitis are characterized by differential amplification of C5a-receptor signal pathways, which might explain the differences in their proinflammatory activity.

Matrix metalloproteinases in skin pathology (Review)

Human tissue is composed in part of cells and in part of amorphous matrix components. Equilibrium exists between the synthesis and degradation of connective tissue under physiological conditions, which serves both the formation and the maintenance of tissue architecture. Synthesis progresses via mesenchymal cells, degradation is controlled by the proteolytic effect of a group of enzymes, which belong to the protein family of matrix metalloproteinases. In biological development, matrix metalloproteinases play an important role in all essential configurative processes in embryo- and histogenesis. As a result of the importance of matrix metalloproteinases in creation of connective tissue, dysregulation with excessive proteolytic activity may result in tissue damage. Histological structural changes are set in relation to the molecular expression pattern of matrix metalloproteinases using matrix relevant diseases of human skin. Discussion includes fibrosing processes, skin inflammations, wound healing, blistering diseases, premature sun-induced skin aging and primary cutaneous malignomas and their metastases.

Downregulation of platelet-activating factor responsiveness during maturation of human dendritic cells

Dendritic cells (DCs) are specialized antigen-presenting cells characterized by their ability to migrate into target sites, process antigens, and activate naive T-cells. Biological activities of platelet-activating factor (PAF) and the cytokine macrophage inflammatory protein-3beta (MIP-3beta) as well as the mRNA expression of their receptors were characterized in human DCs during lipopolysaccharide (LPS)-promoted maturation. Platelet-activating factor induced calcium transients, migration-associated actin polymerization response, and chemotaxis in immature human dendritic cells differentiated in vitro from monocytes with interleukin-4 and granulocyte macrophage colony stimulating factor. In addition, RT-PCR experiments indicated mRNA expression of the PAF receptor in these immature DCs. Cell studies and mRNA analyses further revealed that immature DCs neither respond to MIP-3beta nor express its specific receptor, CCR7. Induction of cell differentiation by LPS led to the loss of the mRNA expression of the PAF receptor, accompanied by decreasing intracellular calcium release, actin polymerization, and migration after stimulation with PAF. In contrast, LPS treatment induced increasing responsiveness toward MIP-3beta and mRNA expression of CCR7. Comparable data regarding mRNA expression of PAF receptor and PAF responsiveness were also obtained with another maturation protocol using TNFalpha instead of LPS. The direct comparison between the two different protocols showed a slower decrease of PAF responsiveness induced by TNFalpha than by LPS. These results show the loss of PAF responsiveness associated with downregulation of PAF receptor mRNA expression during LPS- and TNFalpha-induced maturation in human DCs. Therefore, these findings point to a functional relevance of PAF in recruiting immature DCs, whereas MIP-3beta might regulate the migration of DCs at a later stage of maturation.

Autologous platelet-derived wound healing factor promotes angiogenesis via alphavbeta3-integrin expression in chronic wounds

Healing of venous leg ulcers depends on the adhesive interaction and formation of new vascular cells. Angiogenesis on the surface of angiogenic blood vessels requires the vascular integrin alphavbeta3 also known as the vitronectin receptor. Autologous platelet-derived wound healing factor (autologous PDWHF) has been described to regulate the wound healing process by forming granulation tissue in the early healing phase. Here we analysed the influence of autologous PDWHF on the expression of the alphavbeta3 integrin in tissue specimen of venous leg ulcers in comparison with placebo treated controls by using reverse transcriptase-polymerase chain reaction and immunohistochemistry. Our investigations provide evidence that mRNA and protein expression of alphavbeta3 were significantly increased in healing venous leg ulcers after 96 h treatment (p<0.05), whereas the total amount of alphavbeta3 mRNA and protein was not altered in placebo treated patients. In healing leg ulcers the alphavbeta3 integrin was predominantly localized around capillary vessels preferentially at sites of newly formed granulation tissue. Placebo controlled patients displayed no altered expression of the alphavbeta3 integrin in biopsy specimen. These findings suggest that topical autologous platelet-derived wound healing factor influences the process of angiogenesis/revascularization via alphavbeta3 integrin-expression hereby promoting granulation tissue formation in healing leg ulcers.

Plasminogen activation in venous leg ulcers

BACKGROUND

Venous leg ulceration results from chronic venous insufficiency of the lower extremities. We recently showed that matrix metalloproteinase (MMP) -2 plays a major part in the pathogenesis of venous leg ulcers. In vitro activation of recombinant MMP-2 is controlled by the activity of the urokinase-type plasminogen activator (uPA), which acts as a fibrin-independent plasminogen activator. The activity of MMP-2 is potentiated by binding of uPA to the uPA receptor (uPAR).

OBJECTIVES

We aimed to clarify the role of plasminogen activation in venous leg ulcers.

METHODS

The expression of uPA, uPAR, the tissue-type plasminogen activator, and plasminogen activator inhibitor (PAI) -1 and PAI-2 was investigated using reverse transcription followed by polymerase chain reaction and Western blotting.

RESULTS

These provided direct evidence of elevated expression of uPA and uPAR at the mRNA and protein levels in venous leg ulcers, in comparison with healthy skin. By immunohistochemistry, elevated expression of uPA and uPAR was detected. Fibrin zymography showed significantly elevated endogenous uPA activity in venous leg ulcers in comparison with healthy controls.

CONCLUSIONS

Our findings indicate venous leg ulcers to be characterized by elevated plasminogen activation, suggesting that this enzyme cascade plays a crucial part in maintaining proteolytic activity in venous leg ulcers.

Factor XIII-mediated inhibition of fibrinolysis and venous leg ulcers

Densitometric analysis shows an accelerated healing rate and a significantly diminished lesional fibrinolytic activity in patients with venous leg ulcers treated topically with the fibrin-stabilising factor XIII compared with controls.

Matrix metalloproteinases and venous leg ulceration

Metalloproteinase-mediated proteolysis plays an important role during the phase of venous ulcer formation and wound repair. Venous ulcers manifest as a breakdown of the collagenous stromal tissue and are highly associated to chronic venous insufficiency. A major change in our understanding of the pathogenesis of venous ulcers occurred with the demonstration of extracellular matrix-degrading activity of matrix metalloproteinases to generate a dermal-epidermal skin defect. These proteases were intensely investigated in preceding stages and during wound repair of venous ulcerations. Different studies have revealed their significance in the process of proteolytic remodeling and recognized their potential importance in finding therapeutic rationales to manage late complications of chronic venous ulcers.

Metabolism and function of 3-D-phosphorylated phosphoinositides in C5a-stimulated eosinophils

Eosinophils play a central role in the pathogenesis of parasitic infections, atopic diseases, and bullous dermatoses. To understand the regulative function of phosphatidylinositol 3-kinases in cell responses of eosinophils, phospholipid metabolism and production of reactive oxygen metabolites were followed after stimulation with C5a. Measurements of phosphatidylinositol lipids and analysis of deacylated products of separated lipid extracts showed fast and transient formation of phosphatidylinositol 3,4,5-trisphosphate (PIP(3)). Cell studies in the presence of the tyrosine kinase blocker genistein indicated that C5a-stimulated PIP(3) formation occurred independently of tyrosine kinase activity. To analyze the function of PI4,5P(2)-3-kinase in eosinophils, the influence of wortmannin and LY294002 on production of reactive oxygen metabolites was studied. Both compounds inhibited with similar concentration dependency C5a-induced formation of PIP(3) and production of reactive oxygen metabolites. In summary, these data showed for the first time the involvement of PI4,5P(2)-3-kinase in the production of reactive oxygen metabolites in eosinophils.