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H P Deigner

Publications and source records attributed to H P Deigner.

At least 19 recordsLinked to original sources

High-precision fluorescence assay for sphingomyelinase activity of isolated enzymes and cell lysates.

Sphingomyelinases are important enzymes of signal transduction. They catalyze the hydrolysis of sphingomyelin, giving rise to the intracellular formation of biologically active ceramide and phosphatidylcholine. Here we report on a fluorescence method for the fast and accurate determination of this enzyme in biological samples. The assay is based on a fluorescent sphingomyelin analog carrying fluorescent 7-nitro-2-1,3-benzooxadiazolyl amino-dodecanoic acid instead of an aliphatic acyl chain at the nitrogen atom. The fluorescent substrate is hydrolysed by sphingomyelinases to form fluorescent ceramide, which can be separated from the remaining substrate using TLC on silica gel. The fluorescence intensity pattern obtained on the TLC plate can accurately be determined using a CCD camera. Typically, a large number of samples can be analyzed simultaneously. Examples for the quantitative analysis of sphingomyelinases from freshly prepared cellular homogenates as well as from commercial sources are given.

4-Chloro-7-nitrobenzofurazan↗

Ceramide induces aSMase expression: implications for oxLDL-induced apoptosis.

Sphingomyelinase (SMase) stimulation and subsequent ceramide generation are suggested to be involved in signal transduction of stress-induced apoptosis. We now show that apoptosis of human macrophages (MPhi) and fibroblasts initiated by oxidized low density lipoproteins (minimally modified LDL, mmLDL) is associated with an increase in acid SMase (aSMase, E.C. 3.1.4.12) expression and ceramide concentration. Application of a novel, potent, and specific inhibitor of aSMase expression (NB6) diminished the effects of mmLDL and C6-ceramide treatment by inhibiting transcription via Sp1 and AP-2. Moreover, apoptosis was abolished after mmLDL and C6-ceramide treatment of hereditary aSMase-deficient fibroblasts (from Niemann-Pick patients). We suggest that in mmLDL-initiated apoptosis 1) enhanced ceramide generation via aSMase appears to be required as well as 2) a positive feedback control of aSMase expression by the increase in intracellular ceramide concentration.

Apoptosis↗

Procalcitonin and CGRP-1 mrna expression in various human tissues.

Procalcitonin (PCT) is a highly sensitive and specific marker of systemic bacterial infection and sepsis. In contrast to its diagnostic significance, the cellular sources of plasma procalcitonin remain to be clarified. Two forms of PCT mRNAs originate from calcitonin/calcitonin gene-related peptide gene (CALC-I gene) along with mRNA for calcitonin gene-related peptide-I (CGRP-I). Reverse transcription polymerase chain reaction with newly designed primers detecting different PCT mRNAs and CGRP-I mRNA was used to identify tissues that might contribute to PCT production. Our study indicates that a variety of human tissues (13 of the 16 analyzed overall) express PCT-I, PCT-II, and/or CGRP-I mRNAs, with the highest levels detected for liver, testis, lung, prostate, kidney, and small intestine. Various tissues differ in the proportions of PCT-I, PCT-II, and CGRP-I mRNA expression levels. Thus we demonstrate the complexity of tissue-specific regulation of CALC-I gene expression and suppose a variety of tissues as a potential source of CALC-I-encoded peptides.

Calcitonin↗

Antiapoptotic effects of propolis extract and propol on human macrophages exposed to minimally modified low density lipoprotein.

An aqueous extract of propolis and the phenolic component of propolis, propol, were assayed for antioxidative and antiapoptotic properties. Both additions inhibited Cu(2+)-initiated low density lipoprotein (LDL) oxidation as characterized by a reduction of the lag time, reduced the increase of relative electrophoretic mobility during oxidation and markedly diminished apoptosis of human macrophages exposed to minimally modified (mmLDL). Moreover, aqueous propolis extract and propol blocked the mmLDL-induced decrease of glutathione (GSH) and the activation of the transcription factor NF-kappa B in these cells. The potent phenolic antioxidant propol thus expands the capability of cells to neutralize oxidative stress and to prevent apoptosis and is therefore suggested to significantly contribute to the antiinflammatory and antioxidative effects of propolis.

Acrylates↗

Apoptosis modulators in the therapy of neurodegenerative diseases.

Apoptosis is a prerequisite to model the developing nervous system. However, an increased rate of cell death in the adult nervous system underlies neurodegenerative disease and is a hallmark of multiple sclerosis (MS) Alzheimer's- (AD), Parkinson- (PD), or Huntington's disease (HD). Cell surface receptors (e.g., CD95/APO-1/Fas; TNF receptor) and their ligands (CD95-L; TNF) as well as evolutionarily conserved mechanisms involving proteases, mitochondrial factors (e.g. , Bcl-2-related proteins, reactive oxygen species, mitochondrial membrane potential, opening of the permeability transition pore) or p53 participate in the modulation and execution of cell death. Effectors comprise oxidative stress, inflammatory processes, calcium toxicity and survival factor deficiency. Therapeutic agents are being developed to interfere with these events, thus conferring the potential to be neuroprotective. In this context, drugs with anti-oxidative properties, e.g., flupirtine, N-acetylcysteine, idebenone, melatonin, but also novel dopamine agonists (ropinirole and pramipexole) have been shown to protect neuronal cells from apoptosis and thus have been suggested for treating neurodegenerative disorders like AD or PD. Other agents like non-steroidal anti-inflammatory drugs (NSAIDs) partly inhibit cyclooxygenase (COX) expression, as well as having a positive influence on the clinical expression of AD. Distinct cytokines, growth factors and related drug candidates, e.g., nerve growth factor (NGF), or members of the transforming growth factor-beta (TGF-beta ) superfamily, like growth and differentiation factor 5 (GDF-5), are shown to protect tyrosine hydroxylase or dopaminergic neurones from apoptosis. Furthermore, peptidergic cerebrolysin has been found to support the survival of neurones in vitro and in vivo. Treatment with protease inhibitors are suggested as potential targets to prevent DNA fragmentation in dopaminergic neurones of PD patients. Finally, CRIB (cellular replacement by immunoisolatory biocapsule) is an auspicious gene therapeutical approach for human NGF secretion, which has been shown to protect cholinergic neurones from cell death when implanted in the brain. This review summarises and evaluates novel aspects of anti-apoptotic concepts and pharmacological intervention including gene therapeutical approaches currently being proposed or utilised to treat neurodegenerative diseases.

Animals↗

Modulation of the ceramide level, a novel therapeutic concept?

The sphingomyelin (SM) pathway is an ubiquitous and evolutionarily conserved signaling system in which ceramide (CA), generated from SM by the action of various isoforms of sphingomyelinases (SMases) functions as an important second messenger. Recent evidence suggests that branching pathways of sphingolipid metabolism mediate either apoptotic or mitogenic responses depending on cell type and the nature of the stimulus. Events involving SM metabolites and CA in particular include proliferation, differentiation and growth arrest as well as the induction of apoptosis. An improved understanding of SMase-dependent signaling may afford relevant insights into the pathogenesis of diseases and provide novel strategies and selective targets for a therapeutic intervention e.g. in cancer, cardiovascular and neurodegenerative diseases, HIV and septic shock. This article briefly summarizes the role of SMases in signaling pathways, its potential contribution in the development and maintenance of various pathobiological states and analyzes the perspective of a potentially isotype-specifc inhibition of SMases as a novel therapeutic concept.

Animals↗

HepG2 human hepatoma cells express multiple cytokine genes.

Although cytokines are known to be involved in the regulation of a variety of hepatocellular functions, hepatocytes themselves are generally considered only targets but not producers of these important mediators. In order to investigate whether cells of hepatocellular linages are a potential source of various regulatory cytokines we have estimated the multiple cytokine gene expression in the culture of well differentiated human HepG2 hepatoma cells using RT-PCR. Our findings demonstrate that HepG2 cells express mRNAs for interferon gamma (IFN-gamma), tumour necrosis factor alpha (TNF-alpha), transforming growth factor beta (TGF-beta), macrophage colony-stimulating factor (M-CSF), oncostatin-M (OSM), intercellular adhesion molecule (ICAM-1), interleukin 4 (IL-4), IL-5, IL-7, IL-10, IL-11, IL-12 and IL-6 receptor (IL-6R). At the same time the expression of IL-1, IL-2, IL-3, IL-6, CD40 ligand and IL-2R genes was not detected. It was concluded that hepatocytes are potential producers of a variety of cytokines, some of them being able to regulate hepatocellular functions directly, while others are important regulators of leukocyte activity. Thus, on the one hand, hepatocytes may express autoregulatory cytokines and on the other hand, influence the functions of other liver cells like Kupffer, Ito or endothelial cells. Due to their large amount, liver parenchymal cells could be an important source of sytemically acting pro- and anti-inflammatory and other regulatory cytokines.

CD40 Antigens↗

Novel reversible, irreversible and fluorescent inhibitors of platelet-activating factor acetylhydrolase as mechanistic probes.

Phosphatidylcholines (1-O-alcoxy-2-amino-2-desoxy-phosphocholines and 1-pyrene-labeled analogs) were synthesized and used to examine interactions with recombinant human PAF-acetylhydrolase (PAF-AH), an enzyme purified from plasma, and with macrophage-like U937 cells. Novel phosphatidylcholines containing a sn-2-carbamoylester group such as 1-O-hexadecyl-2-desoxy-2-amino-methylcarbamoyl-2-methyl-rac-glycer o-3-phosphocholine 11 were found to act as site-specific irreversible enzyme inhibitors with Ki-values up to 83 (K(irev)) and 177 (Ki(inact)) microm. The compounds exhibit only marginal inhibition of Ca2+-dependent phospholipases. Kinetic data show that phosphocholines carrying a terminal sn-1-pyrene moiety inhibit PAF-AH activity with an effectivity similar to analogs with an aliphatic chain. 1-O-Decyloxy-[10-(4-pyrenyl)-butoxy]-2-desoxy-2-amino-carbamoyl-me thyl-rac(-glycero-3-phosphocholine 13 could be used for enzyme labeling and to demonstrate an inhibitor-enzyme stoichiometry of 0.7:1. At 8 degrees C, the compound accumulated in the membranes of U937 cells, at 37 degrees C it was internalized into intracellular compartments. Structure activity studies in a mixed micelle assay indicated that the inhibition power of reversible and irreversible inhibitors increases along with the (sn)-1-chain length similar to the structure-dependent binding of ether phospholipids to the PAF-receptor. Unlike the situation at the (sn)-1-position, increasing chain length at the sn-2-position, or an alkyl branching of the glycerol backbone significantly reduced the inhibitory potency.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

Characterization of apoptotic macrophages in atheromatous tissue of humans and heritable hyperlipidemic rabbits.

Apoptotic macrophages are regularly found in atherosclerotic plaques indicating programmed cell death as one of their regulatory controls. The objective of this study was to characterize in more detail apoptotic macrophages in atherosclerotic lesions of humans and heritable hyperlipidemic (HHL) rabbits. Macrophages were immunohistochemically analyzed using antibodies directed against alphaMbeta2-integrins (CD11b/CD18), CD44, major histocompatibility complex (MHC) class I and II, inducible nitric oxide synthase (iNOS), manganese superoxide dismutase (MnSOD), tumor necrosis factor alpha (TNFalpha), p53, c-jun/AP-1 and rabbit macrophages (RAM-11) and the TUNEL (TdT-mediated dUTP nick end labeling) technique. Colocalization studies of human atherosclerotic carotid and aortic tissue showed apoptotic plaque macrophages also being MnSOD-, alphaMbeta2-integrin-, CD44-, MHC class I- and II-, iNOS-, TNFalpha- and p53-immunoreactive. Similar results occurred in atherosclerotic aortas of HHL rabbits. Computer-assisted morphometric analyses revealed a positive correlation of the area density of MnSOD-immunoreactive macrophages with those of alphaMbeta2-integrin- and CD44-immunoreactive ones, but not with those of MHC class I- and II- as well as of RAM-11-immunoreactive macrophages. We conclude that apoptotic macrophages located in atherosclerotic vessel wall are activated, antigen-presenting, integrin-expressing and oxidatively stressed cells. Since all these processes have been demonstrated to cause apoptosis of macrophages in vitro, we propose their potency accelerates the susceptibility of the macrophages to programmed cell death in atherosclerotic lesions.

Animals↗

Modulating apoptosis: current applications and prospects for future drug development.

Agents modulating apoptosis are of extraordinary promise for the treatment of several states of disease including cancer, AIDS, neurodegenerative and ischemic diseases. In this review a brief summary of cellular pathways relevant to programmed cell death first is given and potential therapeutic targets therein are emphasized. Current efforts in drug development are discussed from a mechanistic, biochemical point of view and pro- and anti-apoptotic strategies are related to the respective diseases. Therapeutic approaches addressed in this paper include the design and activity of novel low molecular weight agents (e.g. caspase inhibitors) as well as gene therapy (e.g. p53, adenovirus as vector in cancer treatment). In final sections, the latest findings in the field of apoptosis are highlighted and future applications are outlined.

Animals↗

Apoptosis caused by oxidized LDL is manganese superoxide dismutase and p53 dependent.

Oxidized low density lipoprotein (oxLDL) induces apoptosis in human macrophages (Mphi), a significant feature in atherogenesis. We found that induction of apoptosis in Mphi by oxLDL, C2-ceramide, tumor necrosis factor alpha (TNF-alpha), and hydrogen peroxide (H2O2) was associated with enhanced expression of manganese superoxide dismutase (MnSOD) and p53. Treatment of cells with p53 or MnSOD antisense oligonucleotides prior to stimulation with oxLDL, C2-ceramide, TNF-alpha, or H2O2 caused an inhibition of the expression of the respective protein together with a marked reduction of apoptosis. Exposure to N-acetylcysteine before treatment with oxLDL, C2-ceramide, TNF-alpha, or H2O2 reversed a decrease in cellular glutathione concentrations as well as the enhanced production of p53 and MnSOD mRNA and protein. In apoptotic macrophages of human atherosclerotic plaques, colocalization of MnSOD and p53 immunoreactivity was found. These results indicate that in oxLDL-induced apoptosis, a concomitant induction of p53 and MnSOD is critical, and suggest that it is at least in part due to an enhancement of the sphingomyelin/ceramide pathway.

Apoptosis↗

Complement C6 deficiency protects against diet-induced atherosclerosis in rabbits.

Low-density lipoprotein (LDL) can be transformed to an atherogenic moiety by nonoxidative, enzymatic degradation. Enzymatically degraded LDL induces macrophage foam cell formation, provokes release of cytokines, and also activates complement. To determine whether complement activation may contribute to atherogenesis, 6 pairs of homozygous C6-deficient rabbits and their non-C6-deficient heterozygous siblings were fed a cholesterol-rich diet for 14 weeks. Cholesterol levels and plasma lipoprotein profiles of the animals in the C6-competent and C6-deficient groups did not significantly differ, and the high density lipoprotein and LDL cholesterol ratios at the end of the experiment were 0.07+/-0.01 and 0.08+/-0.01 (SEM), respectively. However, differences in atherosclerotic plaque formation were discernible macroscopically, with extensive aortic lesions being visible in all C6-competent animals and absent in all C6-deficient animals. Aortas were sectioned from thorax to abdomen, and 10 sections were stained from each aorta. Quantification of atherosclerotic lesions and lumen stenosis with the use of computer-based morphometry documented a dramatic protective effect of C6 deficiency on the development of diet-induced atherosclerosis. We conclude that the terminal complement sequence is centrally involved in atherosclerotic lesion progression.

Animals↗

Modified low density lipoprotein delivers substrate for ceramide formation and stimulates the sphingomyelin-ceramide pathway in human macrophages.

Exposure of human blood monocytes derived macrophages to modified (oxidized or acetylated) LDL induced a approximately 40% elevation (60 pmol/10(6) cells) of the endogenous level of the sphingolipid ceramide. A rise of both neutral and acidic SMase activity was found after treatment with oxidized LDL (250 and 80%), while addition of acLDL stimulated only the neutral enzyme (280%). Sphingo(phospho)lipids from LDL were transferred to the cell membrane and distributed into intracellular compartments as observed with acLDL containing BODIPY-FL-C5-SM. Quantitation of ceramide after the addition of [3H-N-acetyl]- or BODIPY-FL-C5-SM-labeled modified LDL (27 microg/ml) to the cell culture medium indicated that approximately 210 pmol CA/10(6) cells was generated from exogenous (ox/acLDL) SM. These results demonstrate a stimulation of the sphingomyelin-ceramide pathway by modified LDL utilizing primarily exogenous (LDL-derived) substrate and suggest that the effects of modified LDL are at least partially due to an increased level of the messenger ceramide.

Boron Compounds↗

Effect of alterations of blood cholesterol levels on macrophages in the myocardium of New Zealand White rabbits.

We investigated the effect of alterations of blood cholesterol levels on macrophages (mphi) in the myocardium of New Zealand White (NZW) rabbits. Three groups of NZW rabbits were used: controls, rabbits fed a 0.5% cholesterol-enriched diet (CH-D) for 96 days, and rabbits fed a 0.5% CH-D for 96 days followed by normal chow for 4 months. Immunohistochemical analysis by mAbs directed against mphi (RAM-11) and Mn superoxide dismutase (MnSOD) were quantified by computer-assisted morphometry. Using cultured human and rabbit mphi, a cross-reaction of the human MnSOD mAbs was found as well as the predominant localization of MnSOD-immunoreactivity (IR) in mitochondria. In group 1, only a very few RAM-11-immunoreactive (ir) mphi occurred in the interstitial space of the myocardium. In group II blood cholesterol levels significantly increased in parallel with the numbers of mphi, which often contained lipid droplets (foam cells). Although blood cholesterol concentrations regressed about 10-fold in group III, mphi in the myocardium were found to be reduced only about 20%. Most mphi were also MnSOD-ir. In atherosclerotic coronary arteries RAM-11-IR was located in mphi and also extracellularly, whereas MnSOD-IR was found only in mphi. Drastically induced MnSOD in the mitochondria of mphi is suggested as an indicator of increased oxidative stress caused by in vitro conditions or by phagocytosis of low-density lipoprotein in vivo. Elevation of the cholesterol level leads to a long-term increase and its regression results in a delayed reduction of such mphi, which seem to play a key role in the atherogenesis of the coronary arteries as well.

Animals↗

Oxidized low density lipoprotein stimulates protein kinase C (PKC) activity and expression of PKC-isotypes via prostaglandin-H-synthase in P388D1 cells.

Treatment of P388D1 macrophage-like cells with oxLDL enhanced protein kinase C (PKC) activity in cell extracts. Similar effects were induced by acetylated LDL (acLDL) and maleylated albumin (malBSA). Treatment with oxLDL, acLDL and malBSA was also accompanied by increased production of prostaglandins as well as by an enhanced level of prostaglandin H synthase 2 (cyclooxygenase 2, COX 2). Modified (lipo)proteins differentially affected the levels of individual cytosolic PKC-isoenzymes. Effects of oxLDL on PKC activity/expression were abrogated by indometacin, by pre-exposure to the dual lipoxygenase/cyclooxygenase inhibitor ML 3000 and by treatment with N-(2-cyclohexyloxy-4-nitrophenyl)methane sulfonamide (NS-398). These results suggest a predominantly COX 2-dependent and isotype-specific effect of modified (lipo)proteins on PKC.

Acetates↗

Induction of mitochondrial manganese superoxide dismutase in macrophages by oxidized LDL: its relevance in atherosclerosis of humans and heritable hyperlipidemic rabbits.

The objective of the study was to analyze the intracellular antioxidative response of macrophages (Mphi) exposed to increased levels of low density lipoprotein (LDL). We studied manganese superoxide dismutase (MnSOD) and, in part, GSH in cultured human and rabbit Mphi, and in atheromatous arterial tissue of humans and heritable hyperlipidemic (HHL) rabbits. Incubation of human Mphi with oxidized-LDL (ox-LDL) resulted in an induction of MnSOD mRNA production as shown by RT-PCR. MnSOD immunoreactivity (IR) was found to be located in the mitochondria of Mphi. In HHL rabbits, MnSOD activity and GSH concentration were significantly increased in atherosclerotic intima compared to the media of the aorta, but significantly decreased (P<0.01) in larger plaques compared with smaller ones, resulting in a significant inverse correlation of MnSOD activity (r=-0.67, P<0.001) and GSH concentration (r=-0.57, P<0.01) with plaque size. Immunohistology of the atherosclerotic intima revealed MnSOD-IR in Mac-1 (CD 11b/CD 18)-immunoreactive (ir) Mphi of human arteries and, similarly, in RAM-11-ir Mphi of rabbit ones. The relation of MnSOD-ir Mphi decreased with plaque advancement, which is consistent with biochemical findings. Most MnSOD-ir Mphi in atherosclerotic plaques revealed TUNEL-positive nuclei, indicating DNA strand breaks, and p53-IR. We conclude that mitochondrial antioxidants such as MnSOD are induced in Mphi in vitro and in atherosclerotic arteries as a reply to increased mitochondrial oxidation. As normal consequences of an increased oxidative stress due to the exposure to ox-LDL nuclear DNA strand breaks occur, which are suggested to be a signal to increase p53 protein levels. Reactive oxygen species-mediated mitochondrial-dependent pathways are suggested as major contributing pathomechanisms to nuclear damage, which eventually may result in apoptosis. A common response to increased oxidative stress due to modified LDL is presumed in rabbit and human atherosclerotic plaques.

Animals↗

Stimulation of mitogen activated protein kinase by LDL and oxLDL in human U-937 macrophage-like cells.

Mitogen activated protein kinase in extracts of U-937 macrophage-like cells was stimulated by LDL and oxLDL. A maximum value (161% of the basal phosphotransferase activity) was obtained after 6 min exposure to oxidized LDL (27 microgram/ml) using APRTPGGRR peptide substrate. The activatory effect was more pronounced (LDL 181%, oxLDL 201%) when MAPK of stimulated cells was immunoprecipitated with anti-p42MAPK antibodies and phosphotransferase activity was assayed in immune complexes. Stimulation produced by oxLDL was inhibited by poly I, fucoidan, dextran sulfate and by the MAPKK inhibitor PD 098059 but not by PMA-mediated depletion of PKC or by pre-treatment with chloroquine or with pertussis toxin. These results suggest a direct mitogenic effect of LDL which, in the case of oxLDL, is dependent on scavenger receptor ligation but not on G-protein mediated or PKC-dependent signal transduction.

Amino Acid Sequence↗

Oxidized low-density lipoprotein stimulates protein kinase C (PKC) and induces expression of PKC-isotypes via prostaglandin-H-synthase in P388D1 macrophage-like cells.

Treatment of cells with LPS-free oxLDL significantly enhanced protein kinase C (PKC) activity in cell extracts from P388D1 macrophage-like cells as determined by phosphorylation of histone H1 or Ac-MBP[4-14] substrate peptide. This effect was abolished by the PKC inhibitors H-7 and bisindolylmaleimide I while pertussis toxin failed to block stimulation. The phosphotransferase activity was also increased by acetylated LDL (acLDL) and maleylated albumin (malBSA), the oxLDL effect was inhibited by chloroquine which also blocked oxLDL-induced stimulation of tyrosine kinase activity. Marginal stimulation of PKC activity was observed when lipid extracts from oxLDL were used, indicating that uptake via scavenger receptors (SR) is mandatory. Polyinosinic acid (poly I) exhibited a concentration-dependent inhibition of the oxLDL-induced effect suggesting that SR II/I but not CD36 interactions are critical to PKC activation. Modified (lipo)proteins increased the concentration of diacylglycerol and differentially affected the levels of individual PKC isoenzymes predominantly in the cytosolic fraction. Changes of activity induced by oxLDL could be primarily assigned to alterations of the activities and levels of the isoenzymes beta and delta. Treatment with oxLDL, acLDL, and malBSA was also accompanied by increased production of prostaglandins as well as by an enhanced level of cyclooxygenase 2 (COX 2) as determined by Western blot analysis. Effects (correction) of oxLDL on PKC activity/expression was suppressed by the cyclooxygenase, 2,2-dimethyl-6-(4-chlorophenyl)-7-phenyl-2,2-dihydro-1H-pyrrolizine-5- ylacetic acid (ML 3000), and by treatment with the specific COX 2-inhibitor N-(2-cyclohexyloxy-4-nitrophenyl) methane-sulfonamide (NS-398). These results indicate that oxLDL, acLDL, and malBSA exhibit a COX 2-dependent and isotype specific effect on PKC in P388D1 cells following uptake via SR II/I and subsequent lysosomal degradation.

Animals↗