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S Dimmeler

Publications and source records attributed to S Dimmeler.

At least 73 records · Page 4Linked to original sources
PubMed1998

Apoptosis of endothelial cells. Contribution to the pathophysiology of atherosclerosis?

Endothelial cell injury is a key event in the pathogenesis of atherosclerosis. Importantly, endothelial cells in lesion-prone regions, where atherosclerotic lesions preferentially develop, are characterised by increased endothelial cell turn-over rates suggesting a mechanistic link between endothelial cell turn-over with preceding cell death and the susceptibility to atherosclerotic plaque development. The activation of the cellular suicide pathway leading to apoptosis of the endothelial cell may be an initial step in the development of atherosclerotic lesions. This hypothesis is supported by the finding that proatherosclerotic factors such as angiotensin II, oxidized low density lipoprotein, reactive oxygen species, glucose and inflammatory cytokines have all been shown to induce apoptosis of endothelial cells. In contrast, the known atheroprotective factors, such as oestrogen, nitric oxide or anti-oxidants, prevented endothelial cell apoptosis. Furthermore, laminar flow, which seems to be one of the most potent endogenous anti-atherosclerotic factor as illustrated by the focal nature of atherosclerotic lesion development in areas with turbulent or low blood flow, protects endothelial cell from apoptotic cell death. The present article summarizes the effects of pro and anti-atherosclerotic factors on endothelial cell apoptosis and provides insights into the underlying signalling events.

Animals↗
PubMed1997

Platelet glycoprotein IIIa polymorphisms and risk of coronary stent thrombosis.

BACKGROUND: Coronary stents are an effective treatment for selected coronary stenoses. However, thrombosis of the stented segment is a major adverse complication. Platelet aggregation has a key role in stent thrombosis. We investigated whether a polymorphism of platelet glycoprotein IIIa gene (PIA2) is associated with an increased risk of coronary stent thrombosis. METHODS: 318 consecutive patients were followed up for 30 days after coronary stent insertion. The primary endpoints were death, myocardial infarction, stent-vessel occlusion, and coronary artery bypass surgery. Gel electrophoresis of PCR products was used to identify the PIA1 and PIA2 alleles. The relative risk of stent occlusion was calculated from the odds ratio on logistic regression analysis. FINDINGS: 63 (19.8%) of patients had the PIA2 allele and 255 (80.2%) were homozygous for PIA1. Baseline clinical, angiographic, and procedural features did not differ between the groups with and without the PIA2 allele. Occlusion of the stent vessel occurred in five (1.9%) patients homozygous for PIA1 and six (9.5%) patients with PIA2 allele (odds ratio 5.26 [95% CI 1.55-17.85]). On multivariate regression analysis PIA1/A2 genotype was the only significant independent predictor of stent thrombosis. INTERPRETATION: Patients with the pIA2 allele have an increased risk of coronary stent thrombosis, which may warrant antiplatelet therapy with glycoprotein-IIb/IIIa inhibitors, although bleeding complications may also increase.

Alleles↗
PubMed1997

Oxidized low-density lipoprotein induces apoptosis of human endothelial cells by activation of CPP32-like proteases. A mechanistic clue to the 'response to injury' hypothesis.

BACKGROUND: Oxidized LDL (oxLDL) is believed to play a key role as a triggering molecule that causes injury to the endothelium as an early event in atherogenesis. However, the mechanisms by which oxLDL injures endothelial cells are entirely unknown. We speculate that oxLDL may activate a cellular suicide pathway that leads to apoptosis. METHODS AND RESULTS: Human umbilical venous endothelial cells (HUVEC) were incubated with increasing doses of native or oxLDL for 18 hours. Apoptosis of HUVEC was measured with an ELISA specific for histone-associated DNA fragments and confirmed with DNA laddering. Native LDL had no effect, but incubation with oxLDL dose-dependently induced apoptosis of HUVEC. Induction of apoptosis by oxLDL was associated with increased CPP32-like protease activity, which is the major enzyme that initiates the proteolytical cascade leading to cell death. Specific inhibition of CPP32 activity completely abrogated oxLDL-induced apoptosis. The antioxidants N-acetylcysteine and the combination of vitamins C and E prevented oxLDL-induced apoptosis, abrogated the enhancement of CPP32-like protease activity, and inhibited the proteolytic cleavage of CPP32 into its active subunit p17. CONCLUSIONS: oxLDL activates the suicide pathway leading to apoptosis of endothelial cells by enhancing CPP32-like protease activity. The oxLDL-mediated activation of CPP32 appears to involve the elaboration of reactive oxygen species. Activation of the cell death effector CPP32 by oxLDL may provide a mechanistic clue to the "response-to-injury" hypothesis of atherogenesis.

Acetylcysteine↗
PubMed1997

Suppression of apoptosis by nitric oxide via inhibition of interleukin-1beta-converting enzyme (ICE)-like and cysteine protease protein (CPP)-32-like proteases.

Physiological levels of shear stress alter the genetic program of cultured endothelial cells and are associated with reduced cellular turnover rates and formation of atherosclerotic lesions in vivo. To test the hypothesis that shear stress (15 dynes/cm2) interferes with programmed cell death, apoptosis was induced in human umbilical venous cells (HUVEC) by tumor necrosis factor-alpha (TNF-alpha). Apoptosis was quantified by ELISA specific for histone-associated DNA-fragments and confirmed by demonstrating the specific pattern of internucleosomal DNA-fragmentation. TNF-alpha (300 U/ml) mediated increase of DNA-fragmentation was completely abrogated by shear stress (446 +/- 121% versus 57 +/- 11%, P <0.05). This anti-apoptotic activity of shear stress decreased after pharmacological inhibition of endogenous nitric oxide (NO)-synthase by NG-monomethyl-L-arginine and was completely reproduced by exogenous NO-donors. The activation of interleukin-1beta-converting enzyme (ICE)-like and cysteine protease protein (CPP)-32-like cysteine proteases was required to mediate TNF-alpha-induced apoptosis of HUVEC. Endothelial-derived nitric oxide (NO) as well as exogenous NO donors inhibited TNF-alpha-induced cysteine protease activation. Inhibition of CPP-32 enzyme activity was due to specific S-nitrosylation of Cys 163, a functionally essential amino acid conserved among ICE/CPP-32-like proteases. Thus, we propose that shear stress-mediated NO formation interferes with cell death signal transduction and may contribute to endothelial cell integrity by inhibition of apoptosis.

Apoptosis↗
PubMed1997

Nitric oxide and apoptosis: another paradigm for the double-edged role of nitric oxide.

Apoptosis plays an important role in the development of the organism but also under various pathological conditions. Nitric oxide exhibits contradictory effects in the regulation of apoptosis. Both pro- and antiapoptotic effects have been demonstrated. The proapoptotic effects seem to be linked to pathophysiological conditions, where high amounts of NO are produced by the inducible nitric oxide synthase. In contrast, the continuous release of endothelial NO inhibits apoptosis and may contribute to the antiatherosclerotic function of NO. The present article summarizes these effects and provides insights into the role of NO in apoptotic signal transduction, with special regard to the Bcl-2 homologous proteins, the protease family of caspases and heat shock proteins.

Animals↗
PubMed1997

Effects of redox-related congeners of NO on apoptosis and caspase-3 activity.

Nitric oxide has been shown to inhibit apoptosis of human umbilical venous endothelial cells (HUVEC). Therefore we investigated the effect of different NO donors, PAPA NONOate (NOC-15; NO.) and nitrosodium tetrafluoroborate (NOBF4, NO+), and the reaction product of NO and O2-, peroxynitrite (ONOO- ), on TNF-alpha- or serum depletion-induced apoptosis of HUVEC. TNF-alpha-induced DNA fragmentation, determined by ELISA, was inhibited by NOC-15, NOBF4, and ONOO- in a concentration-dependent manner (maximal effects with 10 microM NO. and ONOO- and 100 microM NO+). The inhibition of apoptosis correlated with a protective effect on cell viability. The caspases, a cysteine protease family, play an important role in apoptotic processes. To determine whether the different NO donors and ONOO- regulate this enzyme, caspase-3-like activity was measured in homogenates of TNF-alpha-treated HUVEC. The TNF-alpha-induced enzyme activity was abrogated by NO., NO+, and ONOO-. Furthermore, caspase-3 activity was determined in vitro by reconstitution of the separately cloned, bacterially expressed, and purified active p17 and p12 subunits. The reconstituted caspase-3 exhibited enzyme activity, which was suppressed by the different NO donors and ONOO- with an IC50 of 50 microM for NOC-15, 1 mM for NOBF4, and 50 microM for ONOO-. The inhibition of caspase-3 activity correlated with a S-nitrosylation of the reactive cysteine residue and was reversed by further addition of dithiothreitol. This study suggests that the cellular regulatory processes of NO to protect cells from apoptosis may be independent of the redox state and that low concentrations of NO and ONOO- inhibit the cellular suicide program in HUVEC via S-nitrosylation of members of the caspase family.

Apoptosis↗
PubMed1997

Shear stress inhibits H2O2-induced apoptosis of human endothelial cells by modulation of the glutathione redox cycle and nitric oxide synthase.

Physiological levels of shear stress reduce endothelial cell turnover and exert a potent antiatherosclerotic effect. Here we demonstrate that oxidative stress-induced apoptosis of human endothelial cells was inhibited by shear stress exposure (15 dynes/cm2). Incubation with H2O2 (200 mumol/L) for 18 hours induced apoptosis of human umbilical venous endothelial cells as demonstrated by an enzyme-linked immunosorbent assay specific for histone-associated DNA fragments and visual analysis of fluorescence-stained nuclei. Shear stress-mediated inhibition of apoptosis was partially prevented by pharmacological inhibition of glutathione (GSH) biosynthesis with buthionine sulfoximine (BSO) or nitric oxide (NO) synthase with NG-monomethyl-L-arginine (LNMA), whereas inhibition of catalase by aminotriazol did not affect the inhibitory action of shear stress. Combined inhibition of NO synthase and GSH biosynthesis completely reversed the protective effect of shear stress, suggesting that both NO synthase and the GSH redox cycle system are involved in the apoptosis-suppressing effect of shear stress. Similar results were obtained when apoptosis was stimulated by tumor necrosis factor alpha (TNF alpha). To gain further insights into the interference of shear stress with apoptosis signal transduction, we measured caspase-3-like activity, a cysteine protease that has been shown to play a predominant role in the cell death effector pathway. Indeed, shear stress prevented the activation of caspase-3-like activity induced by H202 or TNF alpha. The inhibitory effect of shear stress was prevented by LNMA and BSO, suggesting that the reduction of oxidative flux by shear stress prevents the activation of caspase-like proteases and thereby inhibits apoptotic cell death in human endothelial cells.

Apoptosis↗
PubMed1997

Angiotensin II induces apoptosis of human endothelial cells. Protective effect of nitric oxide.

Angiotensin II (Ang II) importantly contributes to the pathobiology of atherosclerosis. Since endothelial injury is a key event early in the pathogenesis of atherosclerosis, we tested the hypothesis that Ang II may injure endothelial cells by activation of cellular suicide pathways leading to apoptosis. Human umbilical venous endothelial cells (HUVECs) were incubated with increasing doses of Ang II for 18 hours. Apoptosis of HUVECs was measured by ELISA specific for histone-associated DNA fragments and confirmed by DNA laddering and nuclear staining. Ang II dose-dependently induced apoptosis of HUVECs. Simultaneous blockade of both the AT1 and AT2 receptor prevented Ang II-induced apoptosis, whereas each individual receptor blocker alone was not effective. Selective agonistic stimulation of the AT2 receptor also dose-dependently induced apoptosis. Ang II-mediated as well as selective AT2 receptor stimulation-mediated apoptosis was associated with the activation of caspase-3, a central downstream effector of the caspase cascade executing the cell death program. Specific inhibition of caspase-3 activity abrogated Ang II-induced apoptosis. In addition, the NO donors sodium nitroprusside and S-nitrosopenicillamine completely inhibited Ang II-induced apoptosis and eliminated caspase-3 activity. Thus, Ang II induces apoptosis of HUVECs via activation of the caspase cascade, the central downstream effector arm executing the cell death program. NO completely abrogated Ang II-induced apoptosis by interfering with the activation of the caspase cascade.

Angiotensin II↗
PubMed1996

Vitamin C and E prevent lipopolysaccharide-induced apoptosis in human endothelial cells by modulation of Bcl-2 and Bax.

Lipopolysaccharide induced apoptosis and necrosis of human umbilical venous endothelial cells in a time-dependent manner. Lipopolysaccharide (1 microgram/ml)-induced apoptosis was maximal after 18 h, whereas necrosis occurred after prolonged incubation for more than 24 h. The increase in apoptosis correlated with a reduction in Bcl-2, a potent cell death inhibitor. Furthermore, lipopolysaccharide treatment upregulated Bax, which heterodimerizes with and thereby inhibits Bcl-2. Both the antioxidant N-acetylcysteine and the combination of vitamin C and E (10 microM) completely inhibited lipopolysaccharide-induced apoptosis, whereas vitamin C or E alone was less effective. The reduction of lipopolysaccharide-induced apoptosis by vitamin C and E was paralleled by an increase in Bcl-2 and a decrease in Bax protein levels. Thus, vitamin C and E seem to interfere with the Bcl-2 family of apoptosis regulators in human umbilical venous endothelial cells.

Acetylcysteine↗
PubMed1996

Shear stress inhibits apoptosis of human endothelial cells.

Physiological levels of shear stress alter the genetic program of cultured endothelial cells and reduce endothelial cell turnover in vivo. To test the hypothesis that shear stress interferes with programmed cell death, apoptosis was induced in human umbilical venous endothelial cells by growth factor withdrawal or incubation with tumor necrosis factor alpha (TNFalpha) for 18 h. Apoptosis was quantified by ELISA specific for histone-associated DNA fragments and confirmed by demonstrating the specific pattern of internucleosomal DNA fragmentation detected by electrophoresis and immunohistochemical staining. The TNFalpha (300 U/ml)-mediated increase in DNA fragmentation was completely abrogated by shear stress. Furthermore, shear stress dose-dependently reduced DNA fragmentation induced by growth factor withdrawal with maximal effect at 45 dyn/cm2. Inhibition of the CPP32-like proteases with Ac-DEVD-CHO (100 microM) revealed similar anti-apoptotic effects. In contrast, CPP32-independent induction of endothelial cell apoptosis by C2-ceramide (50 microM) was not prevented by shear stress. Thus, we propose that shear stress interferes with common cell death signal transduction involving the CPP32-like protease family and may contribute to endothelial cell integrity by inhibition of apoptosis.

Apoptosis↗
PubMed1996

Interleukin-1 alpha (IL-1 alpha) and N-formyl-methionyl-leucyl-phenylalanine (FMLP) as potential inducers of supravital chemotaxis.

The phenomenon of artificially induced local leucocyte reactions during the supravital period could be of practical importance, but has not yet been comprehensively investigated. For a more detailed evaluation, experiments with the chemotactic agents interleukin-1 alpha (IL-1 alpha) and N-formyl-methionyl-leucyl-phenylalanine (FMLP) were performed by subcutaneous injection into various anatomical regions (back, abdomen, limbs) of NMRI-mice (National Medical Research Institute) and pigs 0-5 min after circulatory arrest. Phosphate buffered saline (PBS) without effective components was administered to equivalent areas of the animals as a control. Tissue specimens were collected at 6 h postmortem (mice) and 12-14 h postmortem (pigs), cut into serial sections, stained with H & E and examined under the microscope. A leucocyte reaction did not develop in pigs (n = 10, 30 tissue samples) following injection of FMLP, however, dermal, subcutaneous and perivascular infiltration of leucocytes (in particular mononuclear cells and a few granulocytes) was found in 3 out of 30 tissue specimens in murine experiments. In addition intravascular cell accumulations were detected in 2 out of 30 samples. The injection of IL-1 alpha to mice gave similar results, i.e., aggregations of leucocytes and intravascular cell accumulations in 4 out of 30 and 3 out of 30 tissue samples, respectively. In negative controls no leucocyte reaction was detectable. This shows that potent chemotactic factors such as IL-1 alpha and FMLP administered in the early supravital period can induce moderate local leucocyte reactions in animal models in at least some cases. A clear morphological differentiation between vital and supravital chemotaxis does not seem to be possible. The supravitally stimulated accumulations of leucocytes are interpreted as an aggregation of resident macrophages in combination with a slight migration of blood leucocytes. Presumably, these alterations are restricted to the very early supravital period as long as sufficient energy reserves are available. It must be stated that the observed changes are reactions, not spontaneous actions, so that the general validity of the phenomenon of leucocyte infiltration as a vital parameter is not affected.

Animals↗
PubMed1996

H1-antagonism improves intestinal mucosal pH and heart function in porcine hypodynamic endotoxic shock.

Porcine hypodynamic shock was induced by continuous infusion of 5 micrograms lipopolysaccharide/kg per hour. This resulted in a decrease of cardiac output from baseline values of 3.5 +/- .9 L/min to 1.5 +/- .8 L/min and a reduced left ventricular stroke work index in the endotoxin-group (n = 6 animals). Pretreatment with the H1-antagonist dimethindene (2 mg/kg) in a second group (n = 6) significantly prevented these effects. Furthermore animals pretreated with the H1-antagonist showed a stable mean arterial blood pressure, whereas the control endotoxin-treated group revealed a drastic reduction in mean arterial blood pressure (99 +/- 4.7 mmHg versus 65.8 +/- 10 mmHg after 240 min, respectively). Pulmonary function and systemic vascular resistance were not ameliorated by the H1-antagonist in hypodynamic shock. Gastrointestinal mucosal pH (pHi), which indicates oxygenation of the mucosa, was decreased by endotoxin-infusion (7.45 +/- .32 baseline value to 6.92 +/- .24 after 120 min). This parameter as well as base excess values and lactate levels were significantly improved by dimethindene-pretreatment (p < .05). These results may indicate a beneficial effect of H1-antagonist-pretreatment on endotoxin-induced deterioration of the microcirculation. Furthermore our results clearly demonstrated that only pretreatment before endotoxemia with H1-antagonism is effective, since infusion of H1-antagonist in hypodynamic shock 45 min after addition of endotoxin (n = 6 animals) did not improve the cardiovascular system or the microcirculation.

Animals↗
PubMed1996

Endotoxic shock leads to apoptosis in vivo and reduces Bcl-2.

Endotoxic shock results in multiple organ failure. At present, two different mechanisms of cellular destruction are of interest: necrosis and apoptosis. Therefore, we started to investigate in pigs whether cell death due to apoptosis is involved in this pathophysiological process. DNA fragments were detected by ELISA specific for histone-associated DNA fragments in three different experimental settings, Pigs were laparotomized followed by endotoxin infusion (ETOX group, n = 6), or laparotomized without endotoxin infusion (LAP group; n = 3) and compared with control animals (n = 3). 6 h of continuous endotoxin-infusion (5 micrograms/kg/h) resulted in a significantly enhanced apoptosis in liver as compared with controls animals (295 +/- 11%; p < .01), whereas in the LAP group, only a minor increase of 166 +/- 14% was detectable. In spleen of endotoxin-treated animals, an enhanced apoptosis of 150 +/- 12% compared with controls was shown in the ETOX group (p = .02), whereas kidney remained unaffected. These results were confirmed by agarose DNA gel electrophoresis. A typical DNA ladder was detected in liver and spleen, but not in kidney of endotoxin-treated animals. Furthermore, immunohistochemical detection of DNA strand breaks with terminal deoxynucleotidyl transferase in liver sections revealed a drastic increase of stained cells. The induction of apoptosis correlated with a reduced Bcl-2 content in endotoxin-treated animals. Our study demonstrates that 6 h of endotoxin treatment leads to apoptosis in liver and spleen in vivo, whereas kidney of endotoxin-treated animals remains unaffected. This process may be mediated by reduction of Bcl-2 by endotoxin treatment.

Animals↗
PubMed1995

Endotoxin-induced changes of endothelial cell viability and permeability: protective effect of a 21-aminosteroid.

Endotoxic shock results in endothelial cell dysfunction and oedema formation. Endotoxin decreased in a concentration-dependent fashion endothelial cell viability with maximum effects by adding 10 micrograms/ml lipopolysaccharide for 48 h (47 +/- 15% and 22 +/- 2.6% of control cells in the presence or absence of foetal calf serum, respectively). Furthermore, incubation (10 h) with lower concentrations of lipopolysaccharide (1 microgram/ml) significantly increased endothelial cell permeability to 250% compared to control values. The 21-aminosteroid U-74389G (10 microM) prevented the cytotoxic effect of lipopolysaccharide as well as the lipopolysaccharide-induced increase in endothelial cell permeability. By contrast, the glucocorticoid methylprednisolone was less effective even at higher concentrations (100 microM). The effect of lipopolysaccharide is possibly due to oxidative stress and/or membrane destabilization rather than to the induction of inflammatory mediators, because of the reduced efficacy of the glucocorticoid.

Allopurinol↗
PubMed1995

Effect of H1-antagonism on cardiovascular, pulmonary, and immunological dysfunction in porcine endotoxic shock.

The definite role of histamine in early hyperdynamic septic shock is not yet clear. Therefore a randomized, controlled, blind trial was performed to investigate the effect of the H1-antagonist dimethindene in hyperdynamic porcine shock. Lipopolysaccharide (LPS) infusion (5 micrograms/kg/h) in anesthetized pigs (n = 6) in the control-group induced a hyperdynamic shock state with a decrease in mean arterial blood pressure, and systemic vascular resistance (SVR), and an increase in mean arterial pulmonary pressure and pulmonary vascular resistance (PVR). In the verum group (n = 6) dimethindene (2 mg/kg) administered 15 min before LPS application prevented the decrease in SVR significantly (p < .05) and ameliorated the increase in MPAP and PVR. The impairment in pulmonary function, as measured by the oxygenation ratio (PaO2/FiO2) in LPS-treated animals, was reduced by the H1-antagonist (p = .01). Tissue oxygenation was ameliorated by the H1-antagonist treatment, as demonstrated by plasma lactate levels and base excess values (p < .05, control group versus dimethindene group). The increase in tumor necrosis factor alpha by LPS infusion was not influenced by H1-antagonist pretreatment. The early decrease in SVR did not correlate with an enhanced nitric oxide formation, as measured by nitrate/nitrite plasma levels.

Animals↗
PubMed1995

[Mediator systems and infection].

Sepsis is the systemic response of the body to an infection. Sepsis-like conditions with nearly identical body reactions, however, are also seen without any evidence of bacteremia. Sepsis is a disease of the host response (specific and non-specific immune system). Depending on the time of the disease process, different mediators (released or newly formed) are involved. This review summarizes the current knowledge and interactions of different cells, cascade systems and mediators in the pathogenesis of sepsis and gives an overview of the approaches and results of current "anti-mediator strategies" to control or modulate inadequate mediator responses.

Acute-Phase Reaction↗
PubMed1994

Modulation of glyceraldehyde-3-phosphate dehydrogenase in Salmonella abortus equi lipopolysaccharide-treated mice.

Nitric oxide (NO) is known to inhibit glyceraldehyde-3-phosphate dehydrogenase enzyme activity caused by an NAD(+)-dependent posttranslational protein modification mechanism. In order to study a possible similar protein modification under in vivo conditions, mice were injected with bacterial endotoxin known to endogenously generate NO. In endotoxin-treated mice glyceraldehyde-3-phosphate dehydrogenase enzyme activity was significantly reduced in cytosolic fractions of heart and spleen, compared to 100,000 x g supernatants of untreated control animals. Enzyme activity was unaffected in lung and kidney cytosol of the endotoxin-treated group. Employing the differential NAD(+)-dependent labelling method, glyceraldehyde-3-phosphate dehydrogenase in heart and spleen cytosol of the endotoxin-treated group, versus the control group, had been endogenously modified. These changes were not observed in lung and kidney cytosol of endotoxin-challenged animals. Using Western blot analysis no significant changes in the amount of protein (glyceraldehyde-3-phosphate dehydrogenase) in control versus endotoxin-treated animals was detectable. Since an endogenously NAD(+)-modified glyceraldehyde-3-phosphate dehydrogenase occurred in endotoxin-treated mice, at least in some organs, this NO-stimulated posttranslational protein modification mechanism seems to function under in vivo conditions. A covalent protein modification mechanism, rather than differences in the amount of the protein is likely to cause changes in enzyme activity.

Animals↗