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E Gulbins

Publications and source records attributed to E Gulbins.

At least 19 recordsLinked to original sources
PubMed2007

The cold case: are rhinoviruses perfectly adapted pathogens?

Rhinoviruses, which cause common cold, belong to the Picornaviridae family, small non-enveloped viruses (diameter 15-30 nm) containing a single-stranded RNA genome (about 7 kb). Over 100 different rhinoviral serotypes have been identified thus far, establishing rhinoviruses as the most diverse group of Picornaviridae. Based on receptor binding properties, rhinoviruses are divided into two classes: the major group binding to intracellular adhesion molecule-1 and the minor group binding to the very low density lipoprotein receptors. Interactions between virus and the receptor molecules cause a conformational change in the capsid, which is a prerequisite for viral uptake. Rhinoviruses trigger a chemokine response upon infection that may lead to exacerbation of the symptoms of common cold, i.e. asthma and inflammation. The following review aims to summarize the knowledge about rhinoviral infections and discusses therapeutical approaches against this almost perfectly adapted pathogen.

Antiviral Agents↗
PubMed2006

TRAIL activates acid sphingomyelinase via a redox mechanism and releases ceramide to trigger apoptosis.

We have previously shown that activation of the acid sphingomyelinase (ASM), the release of ceramide and the formation of ceramide-enriched membrane domains are central for the induction of apoptosis by CD95. Here, we demonstrate that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and CD95 activate the ASM via a redox mechanism resulting in release of ceramide and formation of ceramide-enriched membrane platforms. Ceramide-enriched membrane platforms serve to cluster DR5 upon stimulation. Antioxidants prevent TRAIL-mediated stimulation of ASM, the release of ceramide, the formation of ceramide-enriched membrane platforms and the induction of apoptosis by TRAIL. Further, ASM-deficient splenocytes fail to cluster DR5 in ceramide-enriched membrane domains upon TRAIL stimulation and resist TRAIL-induced apoptosis, events that were restored by addition of natural C(16)-ceramide. A dose-response analysis indicates that ceramide-enriched membrane platforms greatly sensitized tumor cells to TRAIL-induced apoptosis. Our data indicate that ceramide-enriched membrane platforms are required for the signaling of TRAIL-DR5 complexes under physiological conditions.

Animals↗
PubMed2005

[Molecular biology approach to explain lymphatic metastasis].

The spread of tumor cells of solid tumors to the regional lymph nodes is an important step in the progression of the disease and also an important prognostic factor. While the significance of the prognostic value of the lymphatic progression had been detected long ago, only increased knowledge of the molecular anatomy and mechanisms involved in the lymphatic spread of tumor cells provided a beginning insight into the understanding of lymphatic metastasis. One group of important molecular factors consists of proteins produced by the tumor cells inducing a proliferation of lymphatic vessels into the primary tumor. The vascular endothelial growth factors have been identified as key factors in this process. In addition there are hints for the fact that chemokines, which are cytokine-like proteins taking part in the regulation of processes of inflammation, and their chemokine receptors control cellular key steps of lymphatic metastasis of tumor cells such as migration, proliferation, and invasion. In conclusion new data point to the possible inhibition of lymphatic spread by selective blockade of growth factor receptors or chemokine receptors. The growing insight into cellular understanding of the mechanisms involved in the metastasis of tumor cells into the lymphatics and lymph nodes will hopefully facilitate the development of new diagnostic and therapeutic tools in the treatment of cancer patients.

Animals↗
PubMed2005

Ion channels in cell proliferation and apoptotic cell death.

Cell proliferation and apoptosis are paralleled by altered regulation of ion channels that play an active part in the signaling of those fundamental cellular mechanisms. Cell proliferation must--at some time point--increase cell volume and apoptosis is typically paralleled by cell shrinkage. Cell volume changes require the participation of ion transport across the cell membrane, including appropriate activity of Cl- and K+ channels. Besides regulating cytosolic Cl- activity, osmolyte flux and, thus, cell volume, most Cl- channels allow HCO3- exit and cytosolic acidification, which inhibits cell proliferation and favors apoptosis. K+ exit through K+ channels may decrease intracellular K+ concentration, which in turn favors apoptotic cell death. K+ channel activity further maintains the cell membrane potential, a critical determinant of Ca2+ entry through Ca2+ channels. Cytosolic Ca2+ may trigger mechanisms required for cell proliferation and stimulate enzymes executing apoptosis. The switch between cell proliferation and apoptosis apparently depends on the magnitude and temporal organization of Ca2+ entry and on the functional state of the cell. Due to complex interaction with other signaling pathways, a given ion channel may play a dual role in both cell proliferation and apoptosis. Thus, specific ion channel blockers may abrogate both fundamental cellular mechanisms, depending on cell type, regulatory environment and condition of the cell. Clearly, considerable further experimental effort is required to fully understand the complex interplay between ion channels, cell proliferation and apoptosis.

Animals↗
PubMed2005

High activity of acid sphingomyelinase in major depression.

Acid sphingomyelinase (A-SMase) and its reaction product ceramide may play a role in the pathophysiology of depressive disorders and in the therapeutic action of antidepressive drugs. In a prospective case-control study, A-SMase activity was measured in peripheral blood mononuclear cells of 17 patients with a major depressive episode who were free of antidepressant drug therapy for at least 10 days and 8 healthy volunteers. In the patient group, A-SMase activity was correlated to the score (n=17, r=0.64, P=0.005). The patient group exhibited higher A-SMase activity compared to healthy volunteers (T=2.09, df=21.33, P<0.05). In addition, we demonstrate that the antidepressants imipramine and amitriptyline induce a long-term reduction of the activity of A-SMase in cultured cells.

Adult↗
PubMed2004

Ion channels and membrane rafts in apoptosis.

Ion channels have been demonstrated to be a central element in the induction and the execution of apoptosis. In particular, mitochondrial ion channels, including not only the permeability transition pore but also a mitochondrial, ATP-sensitive (mKATP) channel as well as a mitochondrial calcium-activated potassium channel are involved critically in apoptotic changes in mitochondria. Ion channels in the cell membrane that are altered by induction of apoptosis include potassium, chloride and calcium channels. The Kv1.3 potassium channel belongs to the best-characterized ion channels involved in apoptosis and a genetic model of cells deficient for Kv1.3 has indicated a critical role for Kv1.3, at least in some forms of apoptosis. The mechanisms regulating ion channels during apoptosis are, however, still poorly defined. Recent studies have suggested a function for distinct membrane domains, termed rafts, in the cell membrane for the regulation of ion channels during apoptosis. Small sphingolipid- and cholesterol-enriched membrane domains are modified by many apoptotic stimuli to form large ceramide-enriched membrane platforms. These platforms serve to cluster receptor molecules, to re-organize intracellular signalling molecules including ion channels, to bring ion channels into close contact with their regulators and/or to separate proteins from a specific ion channel. Finally, the lipid composition of the cell membrane might be involved directly in ion channel regulation.

Animals↗
PubMed2003

The LPS receptor (CD14) links innate immunity with Alzheimer's disease.

To rapidly respond to invading microorganisms, humans call on their innate immune system. This occurs by microbe-detecting receptors, such as CD14, that activate immune cells to eliminate the pathogens. Here, we link the lipopolysaccharide receptor CD14 with Alzheimer's disease, a severe neurodegenerative disease resulting in dementia. We demonstrate that this key innate immunity receptor interacts with fibrils of Alzheimer amyloid peptide. Neutralization with antibodies against CD14 and genetic deficiency for this receptor significantly reduced amyloid peptide induced microglial activation and microglial toxicity. The observation of strongly enhanced microglial expression of the LPS receptor in brains of animal models of Alzheimer's disease indicates a clinical relevance of these findings. These data suggest that CD14 may significantly contribute to the overall neuroinflammatory response to amyloid peptide, highlighting the possibility that the enormous progress currently being made in the field of innate immunity could be extended to research on Alzheimer's disease.

Alzheimer Disease↗
PubMed2003

Host defense against Pseudomonas aeruginosa requires ceramide-rich membrane rafts.

Pseudomonas aeruginosa infection is a serious complication in patients with cystic fibrosis and in immunocompromised individuals. Here we show that P. aeruginosa infection triggers activation of the acid sphingomyelinase and the release of ceramide in sphingolipid-rich rafts. Ceramide reorganizes these rafts into larger signaling platforms that are required to internalize P. aeruginosa, induce apoptosis and regulate the cytokine response in infected cells. Failure to generate ceramide-enriched membrane platforms in infected cells results in an unabated inflammatory response, massive release of interleukin (IL)-1 and septic death of mice. Our findings show that ceramide-enriched membrane platforms are central to the host defense against this potentially lethal pathogen.

Animals↗
PubMed2001

CCNU-dependent potentiation of TRAIL/Apo2L-induced apoptosis in human glioma cells is p53-independent but may involve enhanced cytochrome c release.

Death ligands such as CD95 ligand (CD95L) or tumor necrosis factor-related apoptosis-inducing ligand/Apo2 ligand (TRAIL/Apo2L) induce apoptosis in radiochemotherapy-resistant human malignant glioma cell lines. The death-signaling TRAIL receptors 2 (TRAIL-R2/death receptor (DR) 5) and TRAIL-R1/DR4 were expressed more abundantly than the non-death-inducing (decoy) receptors TRAIL-R3/DcR1 and TRAIL-R4/DcR2 in 12 human glioma cell lines. Four of the 12 cell lines were TRAIL/Apo2L-sensitive in the absence of a protein synthesis inhibitor, cycloheximide (CHX). Three of the 12 cell lines were still TRAIL/Apo2L-resistant in the presence of CHX. TRAIL-R2 expression predicted sensitivity to apoptosis. Coexposure to TRAIL/Apo2L and cytotoxic drugs such as topotecan, lomustine (1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, CCNU) or temozolomide resulted in synergistic killing. Synergistic killing was more often observed in cell lines retaining wild-type p53 activity (U87MG, LN-229) than in p53 mutant cell lines (LN-18, T98G, U373MG). Drug exposure resulted in enhanced TRAIL-R2 expression, but decreased TRAIL-R4 expression in U87MG cells. Ectopic expression of dominant-negative p53(V135A) abrogated the drug-induced changes in TRAIL-R2 and TRAIL-R4 expression, but had no effect on synergy. Thus, neither wild-type p53 function nor changes in TRAIL receptor expression were required for synergy. In contrast, synergy resulted possibly from drug-induced cytochrome c release from mitochondria, serving as an amplifier of the TRAIL/Apo2L-mediated cascade of caspase activation. These data provide novel insights into the role of the TRAIL/Apo2L system in malignant gliomas and illustrate that TRAIL/Apo2L-based immunochemotherapy may be an effective therapeutic strategy for these lethal neoplasms.

Antineoplastic Agents, Alkylating↗
PubMed2001

Molecular mechanisms of ceramide-mediated CD95 clustering.

Receptor clustering has been suggested as a crucial mechanism to initiate receptor signaling. Here we show that ceramide in sphingolipid-rich membrane rafts mediates clustering of CD95. Neutralization of surface ceramide or inhibition of its endogenous generation prevented CD95 clustering. Furthermore, application of ceramide at the cell surface triggered clustering of active but not inactive CD95. Apoptosis was inhibited by neutralization of surface ceramide or inhibition of ceramide release in vitro and in vivo. Thus, we conclude that surface ceramide mediates CD95 clustering, which is required for initiation of apoptosis, at least in some cell types.

Antigens, CD↗
PubMed2001

Ceramide enables fas to cap and kill.

Recent studies suggest that trimerization of Fas is insufficient for apoptosis induction and indicate that super-aggregation of trimerized Fas might be prerequisite. For many cell surface receptors, cross-linking by multivalent ligands or antibodies induces their lateral segregation within the plasma membrane and co-localization into "caps" on one pole of the cell. In this study, we show that capping of Fas is essential for optimal function and that capping is ceramide-dependent. In Jurkat T lymphocytes and in primary cultures of hepatocytes, ceramide elevation was detected as early as 15-30 s and peaked at 1 min after CH-11 and Jo2 anti-Fas antibody treatment, respectively. Capping was detected 30 s after Fas ligation, peaked at 2 min, and was maintained at a lower level for as long as 30 min in both cell types. Ceramide generation appeared essential for capping. Acid sphingomyelinase -/- hepatocytes were defective in Jo2-induced ceramide generation, capping, and apoptosis, and nanomolar concentrations of C(16)-ceramide restored these events. To further explore the role of ceramide in capping of Fas, we employed FLAG-tagged soluble Fas ligand (sFasL), which binds trimerized Fas but is unable to induce capping or apoptosis in Jurkat cells. Cross-linking of sFasL with M2 anti-FLAG antibody induced both events. Pretreatment of cells with natural C(16)-ceramide bypassed the necessity for forced antibody cross-linking and enabled sFasL to cap and kill. The presence of intact sphingolipid-enriched membrane domains may be essential for Fas capping since their disruption with cholesterol-depleting agents abrogated capping and prevented apoptosis. These data suggest that capping is a ceramide-dependent event required for optimal Fas signaling in some cells.

Animals↗
PubMed2001

CD95 signaling via ceramide-rich membrane rafts.

Clustering seems to be employed by many receptors for transmembrane signaling. Here, we show that acid sphingomyelinase (ASM)-released ceramide is essential for clustering of CD95. In vitro and in vivo, extracellularly orientated ceramide, released upon CD95-triggered translocation of ASM to the plasma membrane outer surface, enabled clustering of CD95 in sphingolipid-rich membrane rafts and apoptosis induction. Whereas ASM deficiency, destruction of rafts, or neutralization of surface ceramide prevented CD95 clustering and apoptosis, natural ceramide only rescued ASM-deficient cells. The data suggest CD95-mediated clustering by ceramide is prerequisite for signaling and death.

Apoptosis↗
PubMed2001

Mechanisms of Staphylococcus aureus induced apoptosis of human endothelial cells.

Staphylococcus aureus plays an important role in sepsis, pneumonia and wound infections. Here, we demonstrate that infection with several S. aureus strains results in apoptosis of human endothelial cells. S. aureus induced an activation of cellular caspases, the acid sphingomyelinase, a release of cytochrome c and a stimulation of Jun NH2-terminal kinase (JNK). The significance of these findings is indicated by a prevention of S. aureus triggered apoptosis of human cells deficient for ASM or upon genetic or pharmacological inhibition of JNK or caspases, respectively.

Apoptosis↗
PubMed2001

Molecular mechanisms of bacteria induced apoptosis.

Interaction of mammalian cells with pathogenic bacteria results in a whole variety of responses in the infected cells including internalization or phagocytosis of the bacterium, release of cytokines, secretion of defensins or production of oxygen radicals. However, recent studies pointed out that many bacteria are able to trigger apoptosis in the host cell. The induction of apoptosis upon infection results from a complex interaction of bacterial proteins with cellular proteins finally mediating apoptosis. Thus, bacteria are able to activate several pro-apoptotic proteins, e.g. caspases, to inactivate anti-apoptotic proteins, e.g. NF(kappa)B or MAP-kinases, or to upregulate endogenous receptor/ligand systems, that induce apoptosis, on the surface of the infected cell. Host cell apoptosis very often serves the bacteria to attack the host and to gain access to the tissue. However, in some infections, apoptosis of mammalian cells significantly contributes to the host defense against the bacteria further indicating the role of apoptosis in host-pathogen interactions.

Animals↗
PubMed2001

C2-ceramide signaling in glioma cells: synergistic enhancement of CD95-mediated, caspase-dependent apoptosis.

Most human malignant glioma cell lines are susceptible to CD95 ligand (CD95L)-induced apoptosis. Here, we report that glioma cells are also susceptible to the cytotoxic effects of exogenous C2-ceramide. This form of cell death exhibits some morphological features of apoptosis as assessed by electron microscopy, but is unaffected by the broad spectrum caspase inhibitor, zVAD-fmk. Further, CD95L-induced apoptosis is synergistically enhanced by coexposure of the glioma cells to CD95L and C2-ceramide. CD95L-induced caspase 3-like activity, cytochrome c release and cleavage of caspases 3, 8, 9 and poly(ADP-ribose)polymerase (PARP) increase substantially after cotreatment with CD95L and C2-ceramide compared with CD95L treatment alone. None of these events occur in response to cytotoxic concentrations of C2-ceramide alone. C2-ceramide does not alter CD95 expression. Gene transfer-mediated enhancement of CD95 expression results not only in increased susceptibility to CD95L, but also in increased sensitivity to C2-ceramide. We conclude that (i) synergistic induction of apoptosis by C2-ceramide and CD95L depend on a cross-talk between the two signal transduction pathways and that (ii) C2-ceramide, independently of its sensitizing effects on CD95-dependent caspase activation, is also capable of triggering an apoptotic signaling cascade that is unaffected by zVAD-fmk-mediated caspase inhibition, but promoted by high levels of CD95 expression.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Invasion of human epithelial cells by Pseudomonas aeruginosa involves src-like tyrosine kinases p60Src and p59Fyn.

Pseudomonas aeruginosa plays a major role in respiratory tract infections or sepsis in patients with cystic fibrosis or upon suppression of the immune system. Several P. aeruginosa strains have been shown to be internalized by human epithelial cells; however, the molecular mechanisms of the invasion process are poorly characterized. Here, we show that the internalization of P. aeruginosa into human epithelial cells results in and requires activation of the Src-like tyrosine kinases p59Fyn and p60Src and the consequent tyrosine phosphorylation of several eukaryotic proteins. The significance of Src-like tyrosine kinase activation is shown by an almost complete blockade of P. aeruginosa internalization, but not adhesion, upon inhibition of Src-like tyrosine kinases. Likewise, inhibition of P. aeruginosa binding to CFTR, which has been shown to block P. aeruginosa internalization, prevents Src and Fyn activation, supporting a pivotal role of Src-like tyrosine kinases for invasion by P. aeruginosa.

Cells, Cultured↗
PubMed2001

Pseudomonas aeruginosa-induced apoptosis involves mitochondria and stress-activated protein kinases.

Pseudomonas aeruginosa, a gram-negative facultative pathogen, causes severe infections in immunocompromised and cystic fibrosis patients. However, the molecular details of the interaction between P. aeruginosa and mammalian cells are still largely unknown. Here we demonstrate that infection of human conjunctiva epithelial Chang cells with the well-characterized P. aeruginosa strain PAO-I results in rapid induction of apoptosis. Apoptosis was mediated by mitochondrial alterations, in particular mitochondrial depolarization, synthesis of reactive oxygen intermediates, and release of cytochrome c, as well as an activation of Jun N-terminal kinases (JNK). Stimulation of these events was dependent on upregulation of CD95 on infected cells, and a deficiency of CD95 or the CD95 ligand prevented mitochondrial changes, JNK activation, and apoptosis upon infection. Further, efficient apoptosis of Chang epithelial cells required infection with live P. aeruginosa, adhesion but not invasion of the bacteria, and expression of the type III secretion system in PAO-I. The data indicate a type III secretion system-dependent, sequential activation of several signaling pathways by P. aeruginosa PAO-I, resulting in apoptosis of the infected cell.

Animals↗