Signalling Effects Induced by Acid Ceramidase in Human Epithelial Or Leukemic Cell Lines

BACKGROUND/AIMS

Recent studies indicated that an inhalation treatment of cystic fibrosis mice with acid ceramidase prevents and eliminates infections with Pseudomonas aeruginosa and Stapyhlococcus aureus. Inhalation of acid ceramidase facilitated the elimination of P. aeruginosa in acutely- or chronically-infected mice with cystic fibrosis. Thus, inhalation of acid ceramidase might be a preventive and/or curative treatment for patients with cystic fibrosis suffering from pneumonia.

METHODS

We treated cultured epithelial cells or leukemic T-lymphocytes (Jurkat cells) with purified acid ceramidase and determined intracellular signalling events, proliferation and cell survival. Specifically, we measured the activity of AKT, p38-kinase and p70S6-kinase using activation-specific phospho-antibodies in western blot studies. Trypan Blue staining served to analyze proliferation and cell survival.

RESULTS

Our studies indicate that treatment of Chang epithelial cells or Jurkat T lymphocytes with purified acid ceramidase results in a dose dependent activation of AKT, p38-kinase and p70S6-kinase, while tyrosine phosphorylation of intracellular proteins remains largely unchanged. Acid ceramidase treatment did not change expression of tight junction proteins such as ZO-1, ZO-2 and occludin. Cellular viability and proliferation were not affected by acid ceramidase treatment.

CONCLUSION

Our data suggest that treatment of epithelial cells and lymphocytes with acid ceramidase results in activation of distinct pathways, in particular AKT- and p38K-dependent pathways, while no global activation or cell death was observed.

Content-based Image Retrieval in Medical Applications

Objectives: To develop a general structure for semantic image analysis that is suitable for content-based image retrieval in medical applications and an architecture for its efficient implementation.

Methods: Stepwise content analysis of medical images results in six layers of information modeling incorporating medical expert knowledge (raw data layer, registered data layer, feature layer, scheme layer, object layer, knowledge layer). A reference database with 10,000 images categorized according to the image modality, orientation, body region, and biological system is used. By means of prototypes in each category, identification of objects and their geometrical or temporal relationships are handled in the object and the knowledge layer, respectively. A distributed system designed with only three core elements is implemented: (i) the central database holds program sources, processing scheme descriptions, images, features, and administrative information about the workstation cluster; (ii) the scheduler balances distributed computing; and (iii) the web server provides graphical user interfaces for data entry and retrieval, which can be easily adapted to a variety of applications for content-based image retrieval in medicine.

Results: Leaving-one-out experiments were distributed by the scheduler and controlled via corresponding job lists offering transparency regarding the viewpoints of a distributed system and the user. The proposed architecture is suitable for content-based image retrieval in medical applications. It improves current picture archiving and communication systems that still rely on alphanumerical descriptions, which are insufficient for image retrieval of high recall and precision.

Staphylococcus aureus Alpha-Toxin Disrupts Endothelial-Cell Tight Junctions via Acid Sphingomyelinase and Ceramide

Staphylococcus aureus (S. aureus) infections are among the most common and severe infections, garnering notoriety in an era of increasing resistance to antibiotics. It is therefore important to define molecular mechanisms by which this pathogen attacks host cells. Here, we demonstrate that alpha-toxin, one of the major toxins of S. aureus, induces activation of acid sphingomyelinase and concomitant release of ceramide in endothelial cells treated with the toxin. Activation of acid sphingomyelinase by alpha-toxin is mediated via ADAM10. Infection experiments employing alpha-toxin-deficient S. aureus and the corresponding wild-type strain reveal that activation of acid sphingomyelinase in endothelial cells requires alpha-toxin expression by the pathogen. Activation of acid sphingomyelinase is linked to degradation of tight junctions in endothelial cells in vitro, which is blocked by pharmacological inhibition of acid sphingomyelinase. Most importantly, alpha-toxin induces severe degradation of tight junctions in the lung and causes lung edema in vivo, which is prevented by genetic deficiency of acid sphingomyelinase. These data indicate a novel and important role of the acid sphingomyelinase/ceramide system for the endothelial response to toxins and provide a molecular link between alpha-toxin and the degradation of tight junctions. The data also suggest that inhibition of acid sphingomyelinase may provide a novel treatment option to prevent lung edema caused by S. aureus alpha-toxin.

Role of Janus-Kinases in Major Depressive Disorder

BACKGROUND/AIMS

Major depressive disorder is a severe, common and often chronic disease with a significant mortality due to suicide. The pathogenesis of major depression is still unknown. It is assumed that a reduction of neurogenesis in the hippocampus plays an important role in the development of major depressive disorder. However, the mechanisms that control proliferation of neuronal stem cells in the hippocampus require definition. Here, we investigated the role of Janus-Kinase 3 (Jak-3) for stress-induced inhibition of neurogenesis and the induction of major depression symptoms in mice.

METHODS

Stress was induced by the application of glucocorticosterone. Brain sections were stained with phospho-specific antibodies and analysed by confocal microscopy to measure phosphorylation of Jak-3 specifically in the hippocampus. Jak-3 inhibitors and the antidepressant amitriptyline were applied to counteract stress. The effects of the inhibitors were determined by a set of behavioural tests and analysis of Jak-3 phosphorylation in brain sections. Acid sphingomyelinase-deficient mice were employed to test whether Jak3 is downstream of ceramide.

RESULTS

The data show that stress reduces neurogenesis, which is restored by simultaneous application of Jak-3 inhibitors. Inhibition of neurogenesis correlated with an anxious-depressive behaviour that was also normalized upon application of a Jak-3-inhibitor. Confocal microscopy data revealed that stress triggers a phosphorylation and thereby activation of Jak-3 in the hippocampus. Amitriptyline, a commonly used antidepressant that blocks the acid sphingomyelinase, or acid sphingomyelinase-deficiency reduced stress-induced phosphorylation of Jak-3.

CONCLUSION

Our data show that Jak-3 is activated by stress at least partially via the acid sphingomyelinase and is involved in the mediation of stress-induced major depression.

Regulation of Neuronal Stem Cell Proliferation in the Hippocampus by Endothelial Ceramide

BACKGROUND/AIMS

Major depressive disorder is one of the most common diseases in western countries. The disease is mainly defined by its psychiatric symptoms. However, the disease has also many symptoms outside the central nervous system, in particular cardiovascular symptoms. Recent studies demonstrated that the acid sphingomyelinase/ceramide system plays an important role in the development of major depressive disorder and functions as a target of antidepressants.

METHODS

Here, we investigated (i) whether ceramide accumulates in endothelial cells in the neurogenetic zone of the hippocampus after glucocorticosterone-mediated stress, (ii) whether ceramide is released into the extracellular space of the hippocampus and (iii) whether extracellular ceramide inhibits neuronal proliferation. Ceramide was determined in endothelial cell culture supernatants or extracellular hippocampus extracts by a kinase assay. Endothelial ceramide in the hippocampus was analyzed by confocal microscopy of brain sections stained with Cy3-labelled anti-ceramide antibodies and FITC-Isolectin B4. Neuronal proliferation was measured by incubation of pheochromocytoma neuronal cells with culture supernatants and extracellular hippocampus extracts.

RESULTS

Treatment of cultured endothelial cells with glucocorticosterone induces a release of ceramide into the supernatant. Likewise, treatment of mice with glucocorticosterone triggers a release of ceramide into the extracellular space of the hippocampus. The release of ceramide is inhibited by concomitant treatment with the antidepressant amitriptyline, which also inhibits the activity of the acid sphingomyelinase. Studies employing confocal microscopy revealed that ceramide is formed and accumulates exclusively in endothelial cells in the hippocampus of stressed mice, a process that was again prevented by co-application of amitriptyline. Ceramide released in the culture supernatant or into the extracellular space of the hippocampus reduced proliferation of neurons in vitro.

CONCLUSION

The data suggest a novel model for the pathogenesis of major depressive disorder, i.e. the release of ceramide-enriched microvesicles from endothelial cells that negatively affect neuronal proliferation in the hippocampus, but may also induce cardiovascular disease and other systemic symptoms of patients with major depressive disorder.

Melatonin Acts as an Antidepressant by Inhibition of the Acid Sphingomyelinase/Ceramide System

BACKGROUND

Melatonin has been shown to have antidepressive effects. We tested whether melatonin inhibits the acid sphingomyelinase/ceramide system and mediates its antidepressive effects via inhibition of the acid sphingomyelinase and a reduction of ceramide in the hippocampus. Antidepressants such as amitriptyline and fluoxetine were previously shown to inhibit the acid sphingomyelinase/ceramide system, which mediates neurogenesis and behavioral changes induced by these drugs.

METHODS

The effect of melatonin on the activity of the acid sphingomyelinase prior to and after treatment with melatonin was determined in cultured neurons and in vivo in the hippocampus of mice by measuring the consumption of [14C] sphingomyelin. Ceramide was measured by DAG kinase assay and fluorescence microscopy of the hippocampus and of cultured neurons. Neurogenesis in the hippocampus was analyzed by in vivo labeling with bromodeoxyuridine. Behavior was assessed in standardized tests.

RESULTS

Melatonin treatment inhibited acid sphingomyelinase in vitro in cultured pheochromocytoma cells and in vivo in the hippocampus, which resulted in a reduction of ceramide in vitro and in vivo. The inhibition of the acid sphingomyelinase/ceramide system translated into increased neurogenesis in glucocorticosterone-stressed mice after treatment with melatonin, an effect that is abrogated in acid sphingomyelinase-deficient mice. Likewise, melatonin improved the depressive behavior of stressed mice, a therapeutic effect that was again absent in acid sphingomyelinase-deficient animals.

CONCLUSION

These data indicate that the antidepressive effects of melatonin as well as the induction of neurogenesis triggered by this drug are mediated by an inhibition of the acid sphingomyelinase/ceramide system. This is the first study to identify melatonin as an inhibitor of the acid sphingomyelinase.

Collisional stability of a three-component degenerate fermi gas

We report on the creation of a degenerate Fermi gas consisting of a balanced mixture of atoms in three different hyperfine states of 6Li. This new system consists of three distinguishable fermions with different and tunable interparticle scattering lengths a_{12}, a_{13}, and a_{23}. We are able to prepare samples containing 5x10;{4} atoms in each state at a temperature of about 215 nK, which corresponds to T/T_{F} approximately 0.37. We investigated the collisional stability of the gas for magnetic fields between 0 and 600 G and found a prominent loss feature at 130 G. From lifetime measurements, we determined three-body loss coefficients, which vary over nearly 3 orders of magnitude.

Content-based image retrieval in medical applications

OBJECTIVES

To develop a general structure for semantic image analysis that is suitable for content-based image retrieval in medical applications and an architecture for its efficient implementation.

METHODS

Stepwise content analysis of medical images results in six layers of information modeling incorporating medical expert knowledge (raw data layer, registered data layer, feature layer, scheme layer, object layer, knowledge layer). A reference database with 10,000 images categorized according to the image modality, orientation, body region, and biological system is used. By means of prototypes in each category, identification of objects and their geometrical or temporal relationships are handled in the object and the knowledge layer, respectively. A distributed system designed with only three core elements is implemented: (i) the central database holds program sources, processing scheme descriptions, images, features, and administrative information about the workstation cluster; (ii) the scheduler balances distributed computing; and (iii) the web server provides graphical user interfaces for data entry and retrieval, which can be easily adapted to a variety of applications for content-based image retrieval in medicine.

RESULTS

Leaving-one-out experiments were distributed by the scheduler and controlled via corresponding job lists offering transparency regarding the viewpoints of a distributed system and the user. The proposed architecture is suitable for content-based image retrieval in medical applications. It improves current picture archiving and communication systems that still rely on alphanumerical descriptions, which are insufficient for image retrieval of high recall and precision.

[Automated image analysis of lateral roentgen images of the spine using anatomic models]

PURPOSE

Development of a software for fully automated image analysis of lateral lumbar spine X-rays.

MATERIAL AND METHOD

Using the concept of active shape models, we developed a software that produces a form model of the lumbar spine from lateral lumbar spine radiographs and runs an automated image segmentation. This model is able to detect lumbar vertebrae automatically after the filtering of digitized X-ray images. The model was trained with 20 lateral lumbar spine radiographs with no pathological findings before we evaluated the software with 30 further X-ray images which were sorted by image quality ranging from one (best) to three (worst). There were 10 images for each quality.

RESULTS

Image recognition strongly depended on image quality. In group one 52 and in group two 51 out of 60 vertebral bodies including the sacrum were recognized, but in group three only 18 vertebral bodies were properly identified.

CONCLUSION

Fully automated and reliable recognition of vertebral bodies from lateral spine radiographs using the concept of active shape models is possible. The precision of this technique is limited by the superposition of different structures. Further improvements are necessary. Therefore standardized image quality and enlargement of the training data set are required.

Allergic cross-reactions between cat and pig serum albumin. Study at the protein and DNA levels

After observing a patient allergic to cat dander and pork but devoid of other allergies, we prospectively screened patients known to be allergic to cat for a second sensitization to pork. After collecting the sera of 10 young patients found to contain specific IgE to cat dander and pork, we undertook this study to detect the possible cross-reactive allergen, define its molecular characteristics, and evaluate its clinical relevance. Through immunoblotting techniques, cat and porcine serum albumin were found to be jointly recognized molecules. These findings were further analyzed by specific anti-albumin IgE titrations and cross-inhibition experiments. Cat serum albumin cDNA was obtained from cat liver, and the corresponding amino acid sequence was deduced and compared to the known porcine and human serum albumin sequences. Inhibition experiments showed that the spectrum of IgE reactivity to cat serum albumin completely contained IgE reactivity to porcine serum albumin, suggesting that sensitization to cat was the primary event. In two cohorts of cat-allergic persons, the frequency of sensitization to cat serum albumin was found to lie between 14% and 23%. Sensitization to porcine albumin was found to lie between 3% and 10%. About 1/3 of these persons are likely to experience allergic symptoms in relation to pork consumption. Sensitization to cat serum albumin should be considered a useful marker of possible cross-sensitization not only to porcine serum albumin but also to other mammalian serum albumins.