[Disseminated osteolytic lesions in a 28-year-old refugee]. / Disseminierte osteolytische Läsionen bei einem 28-jährigen Flüchtling.

A 28-year-old Syrian refugee presented with right-sided knee pain and progressive deterioration of the general condition over the past months. Laboratory diagnostics revealed severe hypercalcemia due to primary hyperparathyroidism, and computed tomography (CT) scanning demonstrated disseminated osteolytic lesions throughout the skeleton. Histologically, these lesions were characterized by multinuclear giant cells (defining these lesions as so-called brown tumors). Finally, surgical removal of a jugular mass allowed the histopathologic diagnosis of a sporadic parathyroid carcinoma. In the patient, this condition was associated with a mutation in the HPRT2 gene locus.

[Constitution of a New Specialised Pediatric Home Care Team - First Year Experience]. / Aufbau eines Palliativteams für Kinder und Jugendliche (SAPV-KJ).

BACKGROUND: Since the amendment of the Social Law V in Germany in 2007 the financial basis for a Specialised Home Palliative Care for Children (SHPC) for children was established. In Hesse 3 different SHPC teams entered into collective negotiations with health insurance companies. In 2014, the team of the University Children's Hospital in Giessen started to treat the first patient with a lead time of two months. METHODS: Thus in this paper the development of a SHPC team is described. After the first year anonymized patients data were retrospectively analyzed. RESULTS: Within 12 months 35 patients, 24 females and 11 males, were treated. All of the 6 patients who died, died at home. Calculated 48 weeks survival was 78%. 45% of the patients suffered from malignancies, 34% of malformations and 34% had metabolic disorders. 51% needed crisis intervention and 51% infusion therapy. Only 26% of parents denied cardiopulmonary resuscitation (CPR). Only 10% of the patients or their families received professional psychological care. CONCLUSION: Formation of a SHPC is feasible within a short time period once a financial basis is established. So, empathic guidance of families to help decision making for emergency situations are considered to be important. Analysis of patient's data after one year could help to improve the quality of care. Our data provides information for developing a palliative care team und could motivate colleagues to start the job.

Neutrophil activation by anti-proteinase 3 antibodies in Wegener's granulomatosis: role of exogenous arachidonic acid and leukotriene B4 generation.

Among the anti-neutrophil cytoplasmic antibodies (ANCA), those targeting proteinase 3 (PR3) have a high specificity for Wegener's granulomatosis (WG). It is known that a preceding priming of neutrophils with cytokines is a prerequisite for membrane surface expression of PR3, which is then accessible to autoantibody binding. Employing a monoclonal antibody directed against human PR3 and ANCA-positive serum from WG patients with specificity for PR3, we now investigated the role of free arachidonic acid (AA) in autoantibody-related human neutrophil activation. Priming of neutrophils with tumor necrosis factor (TNF-alpha) for 15 min or exposure to anti-PR3 antibodies or incubation with free AA (10 microM) as sole events did not provoke superoxide generation, elastase secretion or generation of 5-lipoxygenase products of AA. Similarly, the combination of TNF-alpha-priming and AA incubation was ineffective. When TNF-alpha-primed neutrophils were stimulated by anti-PR3 antibodies, superoxide and elastase secretion was provoked in the absence of lipid mediator generation. However, when free AA was additionally provided, a strong activation of the 5-lipoxygenase pathway was demasked, with the appearance of excessive quantities of leukotriene (LT)B4, LTA4, and 5-hydroxyeicosatetraenoic acid. Moreover, superoxide and elastase secretion were markedly amplified, and studies with 5-lipoxygenase inhibitors and a LTB4-antagonist demonstrated this was due to an LTB4-related autocrine loop of cell activation. In contrast, the increased synthesis of platelet-activating factor in response to TNF-alpha-priming and anti-PR3 stimulation did not contribute to the amplification loop of neutrophil activation under the given conditions. We conclude that anti-PR3 antibodies are potent inductors of the 5-lipoxygenase pathway in primed human neutrophils, and extracellular free AA, as provided at an inflammatory focus, synergizes with the autoantibodies to evoke full-blown lipid mediator generation, granule secretion and respiratory burst. Such events may be enrolled in the pathogenesis of focal necrotizing vascular injury in Wegener's granulomatosis.

Wegener's granulomatosis: anti-proteinase 3 antibodies are potent inductors of human endothelial cell signaling and leakage response.

Anti-neutrophil cytoplasmic antibodies (ANCAs) targeting proteinase 3 (PR3) have a high specifity for Wegener's granulomatosis (WG), and their role in activating leukocytes is well appreciated. In this study, we investigated the influence of PR3-ANCA and murine monoclonal antibodies on human umbilical vascular endothelial cells (HUVECs). Priming of HUVECs with tumor necrosis factor alpha induced endothelial upregulation of PR3 message and surface expression of this antigen, as measured by Cyto-ELISA, with a maximum occurrence after 2 h. Primed cells responded to low concentrations of both antibodies (25 ng-2.5 microg/ml), but not to control immunoglobulins, with pronounced, dose-dependent phosphoinositide hydrolysis, as assessed by accumulation of inositol phosphates. The signaling response peaked after 20 min, in parallel with the appearance of marked prostacyclin and platelet-activating factor synthesis. The F(ab)2 fragment of ANCA was equally potent as ANCA itself. Disrupture of the endothelial F-actin content by botulinum C2 toxin to avoid antigen-antibody internalization did not affect the response. In addition to the metabolic events, anti-PR3 challenge, in the absence of plasma components, provoked delayed, dose-dependent increase in transendothelial protein leakage. We conclude that anti-PR3 antibodies are potent inductors of the preformed phosphoinositide hydrolysis-related signal tranduction pathway in human endothelial cells. Associated metabolic events and the loss of endothelial barrier properties suggest that anti-PR3-induced activation of endothelial cells may contribute to the pathogenetic sequelae of autoimmune vasculitis characterizing WG.

c-ANCA-induced neutrophil-mediated lung injury: a model of acute Wegener's granulomatosis.

Anti-neutrophil cytoplasmic antibodies (c-ANCA) targeting proteinase 3 (PR3) are implicated in the pathogenesis of Wegener's granulomatosis (WG). Fulminant disease can present as acute lung injury (ALI). In this study, a model of ALI in WG was developed using isolated rat lungs. Isolated human polymorphonuclear leukocytes (PMNs) were primed with tumour necrosis factor (TNF) to induce surface expression of PR3. Co-perfusion of TNF-primed neutrophils and monoclonal anti-PR3 antibodies induced a massive weight gain in isolated lungs. This effect was not observed when control immunoglobulin G was co-perfused with TNF-primed PMNs. The c-ANCA-induced oedema formation was paralleled by an increase in the capillary filtration coefficient as a marker of increased pulmonary endothelial permeability. In contrast, pulmonary artery pressure was not affected. In the presence of the oxygen radical scavenger superoxide dismutase and a NADPH oxidase inhibitor, c-ANCA-induced lung oedema could be prevented. Inhibition of neutrophil elastase was equally effective in preventing c-ANCA-induced lung injury. In conclusion, anti-PR3 antibodies induced neutrophil mediated, elastase- and oxygen radical-dependent ALI in the isolated lung. This experimental model supports the hypothesis of a pathogenic role for c-ANCA in WG and offers the possibility of the development of therapeutic strategies for the treatment of lung injury in fulminant WG.

Escherichia coli hemolysin is a potent inductor of phosphoinositide hydrolysis and related metabolic responses in human neutrophils.

Escherichia coli hemolysin (Hly) is a proteinaceous pore-forming exotoxin that probably represents a significant virulence factor in E. coli infections. We investigated its influence on human polymorphonuclear neutrophils (PMN), previously identified as highly susceptible targets. Hly provoked rapid secretion of elastase and myeloperoxidase, generation of superoxide, and synthesis of platelet-activating factor (PAF) and lyso-PAF. Concomitantly, marked phosphatidylinositol (PtdIns) hydrolysis with sequential appearance of the inositol-phosphates, inositol-phosphates, inositol triphosphate, diphosphate, and monophosphate, respectively, and formation of diacylglycerol, occurred. The metabolic responses displayed distinct bell-shaped dose dependencies, with maximum events noted at low toxin concentrations of 0.1-0.5 hemolytic units per milliliter. PtdIns hydrolysis and metabolic responses elicited by Hly exceeded those evoked by optimal concentrations of formylmethionyl-leucyl phenylalanine, PAF, leukotriene B4, A23187, or staphylococcal alpha-toxin. The toxin-induced effects were sensitive toward modulators of PMN stimulus transmission pathways (pertussis toxin, the kinase C inhibitor H7, and phorbol myristate acetate "priming"). We conclude that the marked capacity of low doses of Hly to elicit degranulation, respiratory burst, and lipid mediator generation in human PMN probably envolves signal transduction via PtdIns hydrolysis.

Endotoxin-induced myocardial tumor necrosis factor-alpha synthesis depresses contractility of isolated rat hearts: evidence for a role of sphingosine and cyclooxygenase-2-derived thromboxane production.

BACKGROUND: Although endotoxin (lipopolysaccharides, LPS) is recognized as a mediator of septic cardiodepression, its cardiac effects are still not fully elucidated. METHODS AND RESULTS: Perfusion of isolated rat hearts with LPS for 180 minutes resulted in a decline of left ventricular contractility after 90 minutes, whereas coronary perfusion pressure remained unaffected. This cardiodepression was paralleled by a release of tumor necrosis factor (TNF)-alpha into the perfusate and preceded by myocardial TNF-alpha mRNA upregulation as quantified by real-time polymerase chain reaction. The cardiodepression was abrogated when LPS was perfused with a TNF-alpha antiserum or the ceramidase inhibitor N:-oleoylethanolamine. In contrast, the cardiac release of nitric oxide (NO) was not augmented by LPS. Immunohistochemical studies of LPS-perfused hearts revealed a positive staining for the constitutive (NOSIII) but not for the inducible NO synthase (NOSII). Accordingly, NOSII mRNA levels commenced to increase only at the very end of the LPS perfusion period. Progressive liberation of thromboxane (Tx) A(2) and prostacyclin was induced by LPS together with myocardial cyclooxygenase (Cox)-2 mRNA expression. Both nonselective inhibition of Cox by indomethacin and selective inhibition of the inducible Cox-2 by NS-398 abolished prostanoid release. Interestingly, the generation of TNF-alpha and the associated cardiodepression caused by LPS were reduced by indomethacin, NS-398 and the Tx-receptor antagonist daltroban. CONCLUSIONS: LPS depresses contractility of isolated rat hearts by inducing TNF-alpha synthesis and subsequently activating the sphingomyelinase pathway, whereas no evidence for a role of NOSII- or NOSIII-generated NO was found. Moreover, Cox-2-derived TxA(2) appears to facilitate TNF-alpha synthesis in response to LPS.

Subthreshold concentrations of anti-proteinase 3 antibodies (c-ANCA) specifically prime human neutrophils for fMLP-induced leukotriene synthesis and chemotaxis.

Anti-neutrophil cytoplasmic antibodies (ANCA) targeting proteinase 3 (PR3) possess a high sensitivity and specificity for Wegener's granulomatosis. Due to their capacity of directly activating neutrophils, a pathogenetic role for these autoantibodies has been proposed. We investigated the impact of subthreshold concentrations of monoclonal anti-PR3 antibodies (anti-PR3; 0.1 microg/mL) on neutrophil activation elicited by a secondary agent. Preincubation with anti-PR3 resulted in a massive amplification of N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced leukotriene (LT) generation, with a marked increase in the liberation of LTB4, LTA4, and 5-hydroxyeicosatetraenoic acid (5-HETE). This priming commenced within 2.5 min, with a maximum after 5-7.5 min. Moreover, anti-PR3 pretreatment markedly enhanced PMN movement toward fMLP. The priming effect of anti-PR3 toward fMLP challenge was reproduced by c-ANCA, but not by F(ab)2 fragments of the antibodies and isotype-matched control IgG. Generation of superoxide anion and release of elastase were suppressed in anti-PR3-pretreated neutrophils undergoing fMLP challenge. In contrast, neutrophil activation by platelet-activating factor (PAF) or the calcium ionophore A23187 remained unaffected. We conclude that subthreshold concentrations of anti-PR3 antibodies selectively modify neutrophil responses to fMLP, with enhancement of leukotriene generation and chemotaxis, but suppression of respiratory burst and degranulation. Such priming might contribute to localized neutrophil accumulation together with blunted host defense in Wegener's granulomatosis.

Amplification of LTB4 generation in AM-PMN cocultures: transcellular 5-lipoxygenase metabolism.

The generation of arachidonic acid (AA) metabolites by human polymorphonuclear leukocytes (PMN) and by rabbit alveolar macrophages (AM) was investigated and compared with that produced under conditions of coculture. Incubation of PMN with the calcium ionophore A23187 resulted in rapid generation of leukotriene (LT) B4 and its omega-oxidation products, paralleled by substantial secretion of 5-hydroxyeicosatetraenoic acid (HETE) and intact LTA4. Rapid LTA4 decay to nonenzymatic hydrolysis products in the extracellular space ensued. Exogenous AA, offered simultaneously with the ionophore, markedly increased 5-lipoxygenase product formation. Incubation of AM with A23187 evoked protracted generation of LTB4 in the absence of omega-oxidation, with concomitant liberation of 5-HETE, 15-HETE, free AA, and minor amounts of AA cyclooxygenase products. Exogenously offered LTA4 was avidly taken up and converted into LTB4 by these cells. Costimulation of AM and PMN with the ionophore resulted in an approximately 2.5-fold increase in the generation of LTB4 and its metabolites (compared with the summed amounts of the isolated cell experiments), whereas 5-HETE and nonenzymatic LTA4, hydrolysis product formation were markedly reduced. This change in metabolite profile was dependent on the AM-to-PMN ratio. Acetylsalicylic acid increased 5-lipoxygenase product formation in the coculture studies but not in the isolated cell experiments. AA prelabeling of either PMN or AM resulted in radioactivity detection in all AA lipoxygenase products except for 15-HETE.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression of cytoskeletal rearrangement in activated human neutrophils by botulinum C2 toxin. Impact on cellular signal transduction.

Botulinum C2 toxin, a binary toxin which selectively ADP-ribosylates nonmuscle G-actin, was used to evaluate the role of cytoskeletal rearrangement in ligand-evoked signal transduction and secretory processes in human neutrophils (polymorphonuclear leukocyte). Preincubation with the combined toxin components reduced the basal F-actin content and nearly completely suppressed the actin assembly initiated by the peptide and lipid chemoattractants formyl-methionyl-leucyl-phenylalanine, platelet activating factor, and leukotriene B4. Superoxide production and elastase secretion were increased markedly under these conditions. Concomitantly, ligand-elicited phosphoinositide hydrolysis was augmented with particular increase in inositol monophosphate. This was paralleled by a severalfold amplification of diacylglycerol formation and sustained elevation of cytosolic calcium. The toxin-effected amplification of postreceptor events and secretory responses was most pronounced in response to formyl-methionyl-leucyl-phenylalanine greater than platelet activating factor greater than leukotriene B4. All metabolic and secretory effects in C2 toxin-pretreated cells were sensitive to pertussis toxin inhibition. In conjunction with the recent finding of unchanged formyl-methionyl-leucyl-phenylalanine receptor binding and dissociation dynamics under influence of C2 (Norgauer, J., Just, I., Aktories, K., and Sklar, L. A. (1989) J. Cell Biol. 109, 1133-1140), the present investigation suggests amplification of postreceptor events as a major mechanism underlying C2 toxin-related increase in polymorphonuclear leukocyte secretory responses. Cytoskeletal rearrangement, putatively linked to phosphoinositide turnover and calcium transients, thus appears to be operative in temporal and/or spatial limitation of chemoattractant-evoked cellular signal transduction.

Inhibition of cytoskeletal rearrangement by botulinum C2 toxin amplifies ligand-evoked lipid mediator generation in human neutrophils.

Botulinum C2 toxin, a binary toxin that ADP-ribosylates nonmuscle G-actin, was used as a selective tool to evaluate the role of actin-dependent cytoskeletal rearrangement in ligand-evoked lipid mediator generation. Human neutrophils (PMN) were preincubated with varying concentrations of the toxin for 30 min. Lipoxygenase products of arachidonic acid were measured by chromatographic techniques in the presence of exogenous arachidonic acid to probe PMN 5-lipoxygenase activity. Formation of platelet-activating factor (PAF) was assayed by the bioincorporation of [3H]acetate. Stimulation was performed with the soluble chemotactic ligands formyl-methionyl-leucyl-phenylalanine (FMLP) and PAF, as well as opsonized zymosan. PMN pretreatment with C2 toxin in the range between 200/400 and 800/1600 ng/ml C2I/II caused a dose-dependent suppression of the basal F-actin content and of stimulus-induced actin assembly. Phosphoinositide hydrolysis (measured as liberated inositol phosphates) and PAF generation in response to FMLP and exogenous PAF were markedly increased at these toxin doses. Minor C2 toxin concentrations (range, approximately 25/50 to 200/400 ng/ml C2I/II) were sufficient to amplify stimulus-induced formation of leukotriene B4 and its omega-oxidation products, nonenzymatic hydrolysis products of leukotriene A4, and 5-hydroxyeicosatetraenoic acid (5-HETE). With increasing toxin doses, leukotriene generation declined and 5-HETE became the predominant metabolite. In contrast to the soluble ligands, the zymosan-effected generation of PAF and leukotrienes was dose-dependently inhibited by C2 toxin concentrations of greater than 200/400 ng/ml, paralleled by a loss of motile and phagocytotic functions in these cells. We conclude that selective inhibition of actin assembly amplifies PAF and 5-lipoxygenase product formation in response to soluble chemoattractants with distinct dose dependences. The augmentation of PAF generation may be linked to amplified second messenger levels at higher doses of C2 toxin, whereas the sensitivity of the 5-lipoxygenase metabolism to low concentrations may indicate toxin effect on a small, functionally specified, actin pool. The present data support an important role of cytoskeletal rearrangement in temporal and/or spatial limitation of chemoattractant-evoked PMN activation.

Cell density regulates neutrophil IL-8 synthesis: role of IL-1 receptor antagonist and soluble TNF receptors.

Although cytokine synthesis in polymorphonuclear leukocytes (PMN) was shown to be modulated by soluble mediators, the impact of microenvironmental conditions has not been elucidated. In this study, we investigated the effect of cell density on cytokine release from human neutrophils. PMN were cultured at various cell densities (10 x 10(6) PMN/ml; 60 x 10(6) PMN/ml), and LPS-induced release of cytokines was quantified by ELISA technique. Upon an increase in PMN density, secretion of the CXC chemokine IL-8 was progressively reduced. This effect was paralleled by a decrease in IL-8 mRNA. In contrast, TNF-alpha and IL-1beta rose proportionally with increasing cell density. The inhibition of IL-8 secretion was reproduced by conditioned media of PMN at high cell density, but was not affected by blocking beta(2) integrin-dependent adhesion. When analyzing the supernatant of LPS-challenged neutrophils, large amounts of soluble TNFRs p55 and p75 (sTNFRI, sTNFRII), and IL-1R antagonist (IL-1RA), rising constantly with the cell density, were detected. Interestingly, combined blocking of the bioactivities of these mediators completely restored neutrophil IL-8 secretion at high cell densities, with the anti-IL-1RA Ab being the more potent agent. Moreover, combined application of exogenous IL-1RA and sTNFRs to 10 x 10(6) PMN/ml reproduced the suppression of IL-8 generation. We conclude that neutrophil IL-8 synthesis is autoregulated, being suppressed under conditions of high cell density. IL-1RA and sTNFRs, accumulating under these circumstances, seem to be centrally involved in this regulatory mechanism by interfering with the IL-1beta- and TNF-alpha-dependent IL-8 generation. This feedback mechanism may control further neutrophil recruitment and activation in a neutrophil-rich environment, thereby preventing tissue destruction.

Listeriolysin is a potent inducer of the phosphatidylinositol response and lipid mediator generation in human endothelial cells.

The impact of Listeria monocytogenes listeriolysin O (LLO) secretion on phosphoinositide metabolism and mediator (platelet-activating factor and prostaglandin I2) generation was investigated in human umbilical vein endothelial cells. Wild-type L. monocytogenes, purified LLO, and an L. innocua strain engineered to secrete LLO all elicited a strong response, whereas mutant strains defective in LLO production were ineffective. Thus, human umbilical vein endothelial cell stimulation by listeriae is linked to production of LLO.

Human endothelial cell activation and mediator release in response to the bacterial exotoxins Escherichia coli hemolysin and staphylococcal alpha-toxin.

Escherichia coli hemolysin (HlyA) and Staphylococcus aureus alpha-toxin are membrane-perturbating bacterial exotoxins that have been implicated as significant virulence factors in human diseases. We investigated the capacity of these toxins to cause cell activation and mediator release in human endothelial cells, compared with the efficacies of thrombin and the Ca2+ ionophore A23187. Concentration ranges tested were 1 to 1000 ng/ml (HlyA), 0.01 to 10 micro/ml (alpha-toxin), 0.01 to 10 U/ml (thrombin), and 0.01 to 10 microM (A23187). All stimuli caused dose-dependent generation of platelet-activating factor, nitric oxide, and prostaglandin I2. HlyA and thrombin effected time- and dose-dependent accumulation of large quantities of inositol phosphates, with maximum effects at 100 ng/ml and 1 U/ml, respectively. Corresponding time course and dose dependency were noted for HlyA-elicited diacylglycerol formation. In contrast, only the highest concentrations of alpha-toxin (10 microg/ml) and A23187 (10 microM) effected some moderate inositol phosphate accumulation, and this was suppressed in the presence of the platelet-activating factor antagonist WEB 2086. Metabolic and secretory responses elicited by alpha-toxin were dependent on the presence of extracellular Ca2+. We conclude that both HlyA and alpha-toxin are potent inductors of inflammatory and vasodilatory mediators in human endothelial cells. HlyA-elicited effects may proceed predominantly via activation of the phosphatidylinositol hydrolysis-related signal transduction pathway, whereas transmembrane Ca2+ flux appears to be the major event underlying the release of mediators in response to alpha-toxin. These toxin properties may contribute to vasoregulatory and inflammatory disturbances encountered in states of severe infection and sepsis.

Role of actin depolymerization in the surfactant secretory response of alveolar epithelial type II cells.

Alveolar epithelial type II cells (AET2) respond with exocytosis of surfactant containing lamellar bodies to stimulation with mechanical stretch and secretagogues, a process that is fundamental for maintaining alveolar stability and lung gas exchange. In the present study in cultured rat AET2, we employed botulinum C2 toxin, a binary toxin which ADP ribosylates nonmuscle G-actin, as a specific tool to probe the role of the actin microfilament system in the surfactant secretory process. Incubation of AET2 with C2 toxin caused a dose-dependent decay of the cellular F-actin content to a minimum of 20% of baseline, concomitant with an increase in monomeric actin. In parallel, a significant augmentation of baseline surfactant secretion up to twofold elevated levels above control was noted, as assessed by the release of prelabeled phosphatidylcholine. Pretreatment with phalloidin, which stabilized F-actin and reduced the level of G-actin, prevented the C2 toxin-elicited enhancement of baseline surfactant secretion. Even low C2 toxin concentrations, resulting in a reduction of total cellular F-actin content of approximately 10%, sufficed to augment secretagogue (ATP) and, more impressively, mechanical stress elicited an increase in surfactant secretion; the response to the biophysical challenge more than doubled. When investigated in the absence of toxin, different secretagogues (ATP, phorbol ester, betamimetics) caused a rapid-onset, transient reduction of F-actin in the range between 15 and 25% as a consistent part of their secretory response pattern. These data suggest that the state of actin polymerization is intimately linked to the exocytosis process underlying surfactant secretion in AET2. Microfilament system-related compartmentalization effects and/or or the impact of the state of actin assembly on signaling events may be considered as underlying events.

Neutrophil CD177 (NB1 gp, HNA-2a) expression is increased in severe bacterial infections and polycythaemia vera.

The NB1 glycoprotein (CD177, HNA-2a antigen) is exclusively expressed on human neutrophils. As the clinical significance of CD177 expression is unknown, we investigated its expression in healthy individuals before and after stimulation with granulocyte colony-stimulating factor (G-CSF), in patients with rheumatoid arthritis, viral hepatitis, severe bacterial infections and polycythaemia vera. Expression was quantitatively determined by flow cytometry and by real time polymerase chain reaction. Only G-CSF-stimulated individuals and patients with severe bacterial infections and polycythaemia showed a significantly (P < 0.001) increased CD177 expression compared with healthy individuals, indicating that neutrophil CD177 expression can increase significantly in certain clinical conditions.

The listerial exotoxins listeriolysin and phosphatidylinositol-specific phospholipase C synergize to elicit endothelial cell phosphoinositide metabolism.

Exotoxins such as listeriolysin (LLO) and phosphatidylinositol-specific phospholipase C (PIcA) have been implicated in listerial infection and sepsis. Employing different Listeria strains, mutated in individually known virulence genes, we examined exotoxin-related induction of endothelial cell signaling. Listeria monocytogenes was a potent inductor of phosphatidylinositol (PtdIns) metabolism in HUVEC. This effect was completely absent in a LLO-negative strain. Using a recombinant Listeria innocua strain, engineered to produce high levels of LLO, PtdIns metabolism was restored to approximately 30% of that produced by the parental L. monocytogenes strain. A recombinant L. innocua strain expressing only PIcA did not induce any PtdIns metabolism. Even higher than wild-type levels of PtdIns hydrolysis products were, however, evoked when engineered bacteria secreted both LLO and PIcA. These effects occurred in the absence of bacterial uptake by the endothelial cells. Corresponding results were observed with regard to endothelial diacylglycerol (DAG) generation. The amplification of endothelial cell signaling could be reproduced by engaging purified LLO and PIcA in the absence of bacteria. In these experiments, the unrelated pore-forming agent staphylococcal alpha-toxin, a very weak stimulus for endothelial phosphoinositide metabolism by itself, substituted for LLO to allow marked PtdIns hydrolysis when co-applied with PIcA. We conclude that the listerial exotoxins LLO and PIcA cooperate to provoke potent second messenger synthesis in endothelial cells, in the absence of cell invasion by the bacteria. This is an impressive example of synergism between a pore-forming and an enzymatic bacterial exotoxin in provoking cell signaling and inflammatory events.

Signal transduction pathways of membrane expression of proteinase 3 (PR-3) in human endothelial cells.

At present, the exact mechanism of the pathogenic effect of anti-PR-3 antibodies remains unknown. Interaction of anti-neutrophil cytoplasmic antibodies (ANCAs) with human umbilical vein endothelial cells (HUVECs) may play a key role. Recently we were able to show that ANCAs recognize their target antigen, PR-3, translocated into the membrane of HUVECs. The objective of this study was to investigate regulation, i.e. signal transduction pathways, of PR-3 expression in endothelial cells. HUVECs were isolated according to the method of Jaffe et al. and cultured under standard conditions. A cyto-enzyme-linked immunosorbent assay (ELISA) with unfixed cells was performed. Membrane-expressed PR-3 was detected by affinity-purified and monoclonal anti-PR-3 Ab. Tumour necrosis factor alpha (TNF-alpha)-induced membrane expression of PR-3 could be blocked with the RNA synthesis inhibitor actinomycin D, the protein kinase C (PKC) and proteinase A (PKA) inhibitor staurosporine, the specific PKA inhibitor calphostin C, the c-AMP-dependent PKA inhibitor KT5720 and the tyrosine kinase inhibitor genistein in a dose-dependent manner. The effect of calphostin C was the most significant. In addition, the effect of phorbol 12-myristate 13-acetate (PMA), a mediator of intracellular second messengers, was investigated. In our study, pretreatment of cells with PMA for 48 h led to a down-regulation of PR-3 expression. This effect, however, could be overridden by TNF-alpha stimulation, i.e. TNF-alpha-induced membrane expression of PR-3 was resistant to down-regulation of PKC. In conclusion, our data suggest that translocation of PR-3 in HUVECs is an active process depending on protein synthesis. PR-3 expression by HUVECs may involve a PKC reactive to cytokines such as TNF-alpha which induces PR-3 expression at a transcriptional level.

Prostacyclin enhances stretch-induced surfactant secretion in alveolar epithelial type II cells.

Inhalative vasodilator therapy, employing gaseous nitric oxide (NO) or aerosolized prostaglandin PGI(2), is of interest for regional pulmonary vasodilation in ARDS and pulmonary hypertension. We investigated the impact of the NO donor spermine NONOate as well as PGI(2) and its stable chemical analog iloprost on cultured rat alveolar epithelial type II cell (ATII) surfactant secretion. The NO donor provoked a significant increase in the ATII cGMP content, further enhanced by type V phosphodiesterase (PDE) inhibition, but affected neither baseline nor mechanical stretch-induced surfactant secretion. The prostanoids caused a marked increase in the epithelial cAMP content, further amplified by coadministration of type III/IV PDE inhibitors. Baseline surfactant secretion was not altered by this approach, but mechanical stretch-induced liberation of surfactant was significantly increased, most prominently in the ATII with the highest cAMP levels due to the presence of both iloprost and PDE III/IV inhibitors. In contrast, epithelial phosphoinositide metabolism, well responsive to purinergic stimulation as positive control, was unchanged in prostanoid-exposed cells. We conclude that the PGI(2)-cAMP axis, but not the NO-cGMP axis, forwards a markedly enhanced secretory response to the physiological stimulus of cell surface stretching, which may be relevant for therapeutic use of these agents.

E. coli hemolysin-induced lipid mediator metabolism in alveolar macrophages: impact of eicosapentaenoic acid.

Escherichia coli hemolysin (HlyA) is a prototype of a large family of pore-forming proteinaceous exotoxins that have been implicated in the pathogenetic sequelae of severe infection and sepsis, including development of acute lung injury. In the present study in rabbit alveolar macrophages (AMs), subcytolytic concentrations of purified HlyA evoked rapid synthesis of platelet-activating factor, with quantities approaching those in response to maximum calcium ionophore challenge. In parallel, large quantities of leukotriene (LT) B(4) and 5-, 8-, 9-, 12-, and 15-hydroxyeicosatetraenoic acid (HETE) were liberated from HlyA-exposed AMs depending on exogenous arachidonic acid (AA) supply. Coadministration of eicosapentaenoic acid (EPA) dose dependently suppressed generation of the proinflammatory lipoxygenase products LTB(4) and 5-, 8-, 9-, and 12-HETE in parallel with the appearance of the corresponding EPA-derived metabolites LTB(5) and 5-, 8-, 9-, and 12-hydroxyeicosapentaenoic acid (HEPE). At equimolar concentrations, EPA turned out to be the preferred substrate over AA for these AM lipoxygenase pathways, with the sum of LTB(5) and 5-, 8-, 9-, and 12-HEPE surpassing the sum of LTB(4) and 5-, 8-, 9-, and 12-HETE by >80-fold. In contrast, coadminstration of EPA did not significantly reduce HlyA-elicited generation of the anti-inflammatory AA lipoxygenase product 15-HETE. We conclude that AMs are sensitive target cells for HlyA attack, resulting in marked proinflammatory lipid mediator synthesis. In the presence of EPA, lipoxygenase product formation is shifted from a pro- to an anti-inflammatory profile.