Biomedical subjects

A M Zeiher

Publications and source records attributed to A M Zeiher.

At least 73 records · Page 4Linked to original sources

PubMed2000

Posttranslational modification of Bcl-2 facilitates its proteasome-dependent degradation: molecular characterization of the involved signaling pathway.

The ratio of proapoptotic versus antiapoptotic Bcl-2 members is a critical determinant that plays a significant role in altering susceptibility to apoptosis. Therefore, a reduction of antiapoptotic protein levels in response to proximal signal transduction events may switch on the apoptotic pathway. In endothelial cells, tumor necrosis factor alpha (TNF-alpha) induces dephosphorylation and subsequent ubiquitin-dependent degradation of the antiapoptotic protein Bcl-2. Here, we investigate the role of different putative phosphorylation sites to facilitate Bcl-2 degradation. Mutation of the consensus protein kinase B/Akt site or of potential protein kinase C or cyclic AMP-dependent protein kinase sites does not affect Bcl-2 stability. In contrast, inactivation of the three consensus mitogen-activated protein (MAP) kinase sites leads to a Bcl-2 protein that is ubiquitinated and subsequently degraded by the 26S proteasome. Inactivation of these sites within Bcl-2 revealed that dephosphorylation of Ser87 appears to play a major role. A Ser-to-Ala substitution at this position results in 50% degradation, whereas replacement of Thr74 with Ala leads to 25% degradation, as assessed by pulse-chase studies. We further demonstrated that incubation with TNF-alpha induces dephosphorylation of Ser87 of Bcl-2 in intact cells. Furthermore, MAP kinase triggers phosphorylation of Bcl-2, whereas a reduction in Bcl-2 phosphorylation was observed in the presence of MAP kinase-specific phosphatases or the MAP kinase-specific inhibitor PD98059. Moreover, we show that oxidative stress mediates TNF-alpha-stimulated proteolytic degradation of Bcl-2 by reducing MAP kinase activity. Taken together, these results demonstrate a direct protective role for Bcl-2 phosphorylation by MAP kinase against apoptotic challenges to endothelial cells and other cells.

Apoptosis↗

PubMed2000

Insulin-mediated stimulation of protein kinase Akt: A potent survival signaling cascade for endothelial cells.

Insulin exerts potent antiapoptotic effects in neuronal cells and has been suggested to promote angiogenesis. Therefore, we investigated whether insulin inhibits tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis in human umbilical vein endothelial cells (HUVECs). Because insulin has been shown to stimulate the protein kinase Akt, we investigated whether activation of Akt contributes to the apoptosis-suppressive effect of insulin and characterized the downstream signaling pathway. Incubation with insulin dose-dependently prevented apoptosis induced by TNF-alpha (50 ng/mL). The extent of apoptosis suppression by insulin was similar to the effect of vascular endothelial growth factor. Pharmacological inhibition of Akt activation or overexpression of a dominant-negative Akt mutant prevented the antiapoptotic effect of insulin. Furthermore, we investigated the effect of TNF-alpha on Akt phosphorylation by Western blot analysis with the use of a phosphospecific Akt antibody. Incubation of HUVECs with TNF-alpha induced a marked dephosphorylation of Akt. Insulin counteracted this TNF-alpha-induced dephosphorylation of Akt. Furthermore, we investigated the downstream signaling events. Akt has been shown to mediate its apoptosis-suppressive effects via phosphorylation of Bad or caspase-9. However, incubation with insulin did not lead to enhanced phosphorylation of Bad at Ser 136 or Ser 112. In contrast, insulin inhibited caspase-9 activity and prevented caspase-9-induced apoptosis. Mutation of the Akt site within caspase-9 significantly reduced the apoptosis-suppressive effect of insulin. The present study demonstrates an important role for insulin-mediated Akt activation in the prevention of endothelial cell apoptosis, which may importantly contribute to cell homeostasis and the integrity of the endothelium. In endothelial cells, Akt seems to mediate its antiapoptotic effect, at least in part, via phosphorylation of caspase-9 rather than Bad.

Apoptosis↗

PubMed2000

Endothelial dysfunction in acute coronary syndromes: association with elevated C-reactive protein levels.

Elevated C-reactive protein (CRP) serum level, which is an exquisitely sensitive, objective marker of inflammation, relates to long-term prognosis in patients with stable or unstable coronary artery disease and even in apparently healthy men. CRP is the prototypical, classic acute-phase reactant synthesized in the liver. Several studies have recently shown that elevated CRP levels are associated with a blunted systemic endothelial vasodilator function, indicative of a systemic inflammatory response. Moreover, the identification of elevated CRP levels as a transient independent risk factor for endothelial dysfunction might provide an important clue to link a systemic marker of inflammation to atherosclerotic disease progression. This editorial addresses the role of C-reactive protein in endothelial dysfunction.

Arteriosclerosis↗

PubMed1999

A positive family history of premature coronary artery disease is associated with impaired endothelium-dependent coronary blood flow regulation.

BACKGROUND: The aim of the study was to determine whether a positive family history of coronary artery disease is related to impaired coronary blood flow regulation. METHODS AND RESULTS: In 150 patients with angiographically normal or minimally diseased coronary vessels, risk factors for coronary artery disease, the extent of atherosclerosis and endothelium-dependent vasomotor responses to acetylcholine, and endothelium-independent blood flow regulation by papaverine or adenosine were assessed. Coronary blood flow responses to acetylcholine were reduced in a dose-dependent manner in patients with a positive family history (P=0.030). By multivariate analysis, hypercholesterolemia (P=0.001), age (P=0.002), and a positive family history (P=0.008) remained predictors of coronary blood flow increase to acetylcholine. The extent of atherosclerotic coronary artery disease was, by multivariate analysis, an additional independent predictor of acetylcholine-induced blood flow (P=0.014), but also of endothelium-independent blood flow regulation (P=0.001). A positive family history had additive effects in addition to the other risk factors, such as hypercholesterolemia or increased age. Angiotensin-converting-enzyme genotype polymorphism had no influence either on endothelium-dependent or endothelium-independent coronary blood flow responses. However, in a subset of 28 patients, homocysteine (which is, in part, genetically determined) was inversely related to maximal acetylcholine-induced blood flow regulation (r=-0.47, P=0.012). CONCLUSIONS: The results of this study demonstrate, for the first time, that a positive family history of coronary artery disease is an important predictor of impaired endothelium-dependent coronary blood flow regulation in humans. The influence of a positive family history is independent of other well known risk factors but instead aggravates endothelial vasodilator dysfunction associated with hypercholesterolemia and increased age, suggesting important interacting effects between genetic and environmental risk factors.

Adult↗

PubMed1999

Coronary stent grafts covered by a polytetrafluoroethylene membrane.

In a prospective observational study, 40 patients were treated with coronary stent grafts covered by a polytetrafluoroethylene membrane. These devices may be regarded as therapy of choice for acute coronary rupture; treatment of conventional in-stent restenosis was not associated with a favorable outcome, whereas the promising results in degenerated vein grafts warrant a randomized, controlled trial.

Aged↗

PubMed1999

Activation of nitric oxide synthase in endothelial cells by Akt-dependent phosphorylation.

Nitric oxide (NO) produced by the endothelial NO synthase (eNOS) is a fundamental determinant of cardiovascular homesotasis: it regulates systemic blood pressure, vascular remodelling and angiogenesis. Physiologically, the most important stimulus for the continuous formation of NO is the viscous drag (shear stress) generated by the streaming blood on the endothelial layer. Although shear-stress-mediated phosphorylation of eNOS is thought to regulate enzyme activity, the mechanism of activation of eNOS is not yet known. Here we demonstrate that the serine/threonine protein kinase Akt/PKB mediates the activation of eNOS, leading to increased NO production. Inhibition of the phosphatidylinositol-3-OH kinase/Akt pathway or mutation of the Akt site on eNOS protein (at serine 1177) attenuates the serine phosphorylation and prevents the activation of eNOS. Mimicking the phosphorylation of Ser 1177 directly enhances enzyme activity and alters the sensitivity of the enzyme to Ca2+, rendering its activity maximal at sub-physiological concentrations of Ca2+. Thus, phosphorylation of eNOS by Akt represents a novel Ca2+-independent regulatory mechanism for activation of eNOS.

Androstadienes↗

PubMed1999

Dephosphorylation targets Bcl-2 for ubiquitin-dependent degradation: a link between the apoptosome and the proteasome pathway.

Injury of the endothelial cells by the induction of apoptotic cell death may play an important role in the pathophysiology of atherosclerosis and the progression of inflammatory diseases. Here, we demonstrate an essential role for the ubiquitin-dependent proteasome complex in stimulus-induced degradation of the antiapoptotic protein Bcl-2. Bcl-2 is specifically degraded after stimulation of human endothelial cells with tumor necrosis factor (TNF)-alpha in a process that is inhibited by specific proteasome inhibitors. In addition, the mutation of the potential ubiquitin-acceptor amino acids of Bcl-2 provides protection against TNF-alpha- and staurosporine-induced degradation in vitro and in vivo. Moreover, mimicking phosphorylation of the putative mitogen-activated protein (MAP) kinase sites of the Bcl-2 protein (Thr 56, Thr 74, and Ser 87) abolishes its degradation, suggesting a link between the MAP kinase pathway to the proteasome pathway. Finally, inhibition of Bcl-2 degradation either by suppressing ubiquitin-dependent proteasomal degradation or by mimicking continuous phosphorylation of the putative MAP kinase sites in the Bcl-2 protein confers resistance against induction of apoptosis. Thus, the degradation of Bcl-2 may unleash the inhibitory function of Bcl-2 over the apoptosome and may thereby amplify the activation of the caspase cascade.

Apoptosis↗

PubMed1999

Nitric oxide inhibits caspase-3 by S-nitrosation in vivo.

In cultured human endothelial cells, physiological levels of NO prevent apoptosis and interfere with the activation of the caspase cascade. In vitro data have demonstrated that NO inhibits the activity of caspase-3 by S-nitrosation of the enzyme. Here we present evidence for the in vivo occurrence and functional relevance of this novel antiapoptotic mechanism. To demonstrate that the cysteine residue Cys-163 of caspase-3 is S-nitrosated, cells were transfected with the Myc-tagged p17 subunit of caspase-3. After incubation of the transfected cells with different NO donors, Myc-tagged p17 was immunoprecipitated with anti-Myc antibody. S-Nitrosothiol was detected in the immunoprecipitate by electron spin resonance spectroscopy after liberation and spin trapping of NO by N-methyl-D-glucamine-dithiocarbamate-iron complex. Transfection of cells with a p17 mutant, where the essential Cys-163 was mutated into alanine, completely prevented S-nitrosation of the enzyme. As a functional correlate, in human umbilical vein endothelial cells the NO donors sodium nitroprusside or PAPA NONOate (50 microM) significantly reduced the increase in caspase-3-like activity induced by overexpressing caspase-3 by 75 and 70%, respectively. When human umbilical vein endothelial cells were cotransfected with beta-galactosidase, morphological analysis of stained cells revealed that cell death induction by overexpression of caspase-3 was completely suppressed in the presence of sodium nitroprusside, PAPA NONOate, or S-nitroso-L-cysteine (50 microM). Thus, NO supplied by exogenous NO donors serves in vivo as an antiapoptotic regulator of caspase activity via S-nitrosation of the Cys-163 residue of caspase-3.

Apoptosis↗

PubMed1999

[Endothelial dysfunction in patients with acute coronary syndrome].

Increased vasoconstriction, activation of platelet vessel wall interaction and invasion of monocytes into the subintima as well as vascular smooth muscle cell proliferation play a fundamental role in the pathogenesis of coronary artery disease. Acute coronary syndromes such as myocardial infarction and unstable angina pectoris are characterized by plaque rupture or erosion, activation of platelets and the coagulation system and vasoconstriction. Endothelial dysfunction may be one of the underlying mechanisms linking coronary artery disease and acute coronary syndromes. Both of these are often temporarily limited. Therefore, "non-invasive examination" of endothelial function by venous occlusion plethysmography or high resolution ultrasound might be useful for monitoring high-risk patients.

Animals↗

PubMed1999

[Determinants of treatment costs of unstable angina pectoris].

BACKGROUND AND AIM: Unstable angina, a common serious clinical entity, is associated with a high rate of complications. The aim of our study was to evaluate treatment costs of patients with uncomplicated and complicated follow-up in order to evaluate the economic consequences of new therapeutic strategies, like the introduction of GPIIb/IIIa blockers at our hospital. METHODOLOGY: All 103 patients who were admitted to the medical intensivecare unit of Johann Wolfgang Goethe-University Hospital, Frankfurt am Main between March 2, 1992 and October 31, 1997 for unstable angina of Braunwald class III B were enrolled in the study. Clinical events were the occurrence of refractory ischemia, nontransmural or transmural myocardial infarction or cardiac death. The following were documented: duration of treatment in the ICU and in the general ward, cardiac catheterizations, balloon angioplasties (PTCA), and bypass operations. Treatment costs were calculated on the basis of daily rates, flat rates, and special fees. RESULTS: Following successful primary treatment, a clinical event occurred in 48 of the 103 patients, recurrent refractory ischemia in 34 patients, nontransmural infarction in eight patients, transmural infarction in three patients, and death in four patients. Patients with events were significantly less likely to have had a history of PTCA (38% vs 60%, p < 0.05) and were significantly less likely to be undergoing long-term treatment with aspirin (63% vs 80%, p < 0.05). Other sociodemographic data as well as the initial treatment strategies were comparable. The occurrence of a complication significantly prolonged the duration of treatment in the ICU from 2.6 days (95%-CI [2.1; 3.0]) to 3.6 days (95%-CI [3.1; 4.1]) and the total duration of treatment from 7.0 days (95%-CI [5.7; 8.4]) to 12.8 days (95%-CI [9.6; 16.1]). The total treatment costs rose accordingly from DM 14,360 (95%-CI [12,360; 16,360]) to DM 26,690 (95%-CI [23,150; 30,240]). CONCLUSION: The data show that ischemic complications following successful primary treatment of unstable angina constitute a common problem. Such complications are associated with significantly more intensive treatment and significantly longer hospitalization times, resulting in a near doubling of treatment costs.

Adult↗

PubMed1999

Concordant upregulation of type II-TGF-beta-receptor, the cyclin-dependent kinases inhibitor P27Kip1 and cyclin E in human atherosclerotic tissue: implications for lesion cellularity.

Atherosclerosis is a 'response-to-injury' process associated with chronic inflammation, tissue repair and a considerable cell turnover. These growth-related processes are controlled by the 'cell cycle clock' which is composed of cyclin-dependent kinases (Cdks), their activating subunits, the cyclins, and by inhibitors of Cdks (Ckis). P27 is a Cki which associates with cyclin A-Cdk2, cyclin D-Cdk4 and with cyclin E (CE)-Cdk2 complexes thereby abrogating their catalytic activity leading to potent inhibition of late G1 to S-phase transition. Furthermore, TGF-beta1 mRNA and immunoreactivity are locally increased in atherosclerotic lesions. Since TGF-beta1 growth suppressive function in the late G1 phase may be mediated by p27, blocking the catalytic activity of CE-Cdk2 complexes, via the stimulation of TGF-beta-RI and TGF-beta-RII, we investigated the topographical association between TGF-beta-RI, TGF-beta-RII, P27Kip1 and CE by immunohistochemistry in coronary artery segments without atherosclerosis and carotid atheromatous plaques of 11 patients undergoing carotid endarterectomy. P27-immunoreactivity was present in 11/11 atherosclerotic (92.7 +/- 3.3% of the cells) and 5/5 control (80.9 +/- 3.7% of the cells; P < 0.002 versus control) specimens and localized to nuclei of macrophages (CD68-positive), vascular smooth muscle cells (alpha-actin positive), T-lymphocytes (CD3-positive) as well as to the nuclei of endothelial cells. In the atherosclerotic tissue, TGF-beta-RI and TGF-beta-RII-immunoreactivity was present in 11/11 specimens and localized to inflammatory cells and to cells with VSMC-like-morphology. TGF-beta-RI-immunoreactivity was present in 87.4 +/- 5.3% (controls 75.3 +/- 7.48%; n.s.) and TGF-beta-RII-immunoreactivity was present in 83.7 +/- 6.8% (controls 39.5 +/- 7.3%; P < 0.002) of the cells. Double immunolabeling, and investigation of serial sections revealed co-expression of TGF-beta-RI and TGF-beta-RII in virtually all cells positive for P27. In the atherosclerotic specimens, CE-immunoreactivity was present in all specimens in macrophages (CD68-positive), vascular smooth muscle cells (alpha-actin positive) and in endothelial cells in 12.58 +/- 13.58% of the nuclei whereas in the controls CE staining was restricted to 0.19 +/- 0.43% of the cells (P < 0.001). Importantly, as shown by immunofluorescent double-labeling, we found cells expressing P27 that were simultaneously positive for CE. In summary, the present study provides evidence that TGF-beta1 present in human atherosclerotic tissue may mediate its growth suppressive activity also by p27, blocking the activity of CE-Cdk2 complexes. Quantitative analysis revealed that TGF-beta-RII, p27 and CE are concordantly upregulated in the atherosclerotic tissue with chronic inflammation, supporting the view that TGF-beta1, p27 and CE may play an important role in the processes associated with chronic inflammation and cell turnover in advanced human atherosclerotic plaques. Taken together, these results provide a possible link between the chronic inflammation associated with advanced atherosclerosis, the effects of extracellular growth factors and cell cycle control.

Arteriosclerosis↗

PubMed1999

Nitric oxide and apoptosis.

Apoptosis occurs during normal development of an organism but also plays an important role under pathophysiological conditions. Nitric oxide (NO) exhibits a double-edged role in apoptosis induction. Both pro- and antiapoptotic effects of NO have been demonstrated. The proapoptotic effects appear to be linked to pathophysiological conditions, where high concentrations of NO are produced by the inducible nitric oxide synthase, especially in macrophages. In contrast, NO also prevents apoptosis induction by various stimuli. The antiapoptotic effects thereby were mainly mediated by low amounts of NO or stimulation of the constitutive, endothelial nitric oxide synthase. The present review characterizes the apoptotic cell death program and aims to give a detailed insight into the function of NO in affecting apoptotic processes in biological systems, with special regards to the immune and cardiovascular systems.

Animals↗

PubMed1999

Extracellular matrix structure after heart transplantation.

Following heart transplantation remodeling of the donor heart causes changes in the extracellular myocardial matrix. We investigated 20 right ventricular endomyocardial biopsies taken 17+/-4 days (group I, n=9) and 63+/-13 days (group II, n=11) after heart transplantation from 16 patients transplanted for end-stage cardiomyopathy (15 dilated/1 ischemic). Immunohistochemical staining for collagen I, collagen III, collagen IV, and fibronectin was used. Evaluation was performed at a magnification of 400x using a computer-assisted image analyzing system measuring the relative area stained by the immunoperoxidase method, the number of cells in the given area, and the total area. Collagen I per cell was 13.9+/-5.9 microm2 in group I and increased significantly 66+/-13 days after heart transplantation in the perimysium around the myocardial cells as well as in the endocardium to 49.9+/-15.1 microm2 (P<0.05). No quantitative change in collagen III was noted (75.7+/-12.4 versus 75.5+/-16.0 microm2 n.s.). Collagen IV was found in the perimysial, in the capillary bed and in the vascular network. Significant quantitative change in the amount of collagen IV was not found (64.1+/-12.6 versus 61.0+/-8.9 microm2). Fibronectin was found in the entire perimysial extracellular matrix and in the endocardium in relationship with collagen I and III. An increased amount of fibronectin from 87.09+/-9.9 microm2 (group I) to 140.8+/-17.9 microm2 (group II, P<0.05) was found. The cell area and cell diameters were not significantly different (group I; cell area 772+/-227 microm2, diameter 31.3 microm; group II; cell area 776+/-224 microm2, diameter 31.4 microm). It is concluded that remodeling of the donor heart after transplantation is characterized by a specific increase in collagen I and fibronectin, whereas a change in other collagen subtypes was not observed.

Analysis of Variance↗

PubMed1999

Nitric oxide-an endothelial cell survival factor.

Due to its unique position in the vessel wall, the endothelium acts as a barrier and thereby controls adhesion, aggregation and invasion of immune competent cells. Apoptosis of endothelial cells may critically disturb the integrity of the endothelial monolayer and contribute to the initiation of proinflammatory events. Endothelial cell apoptosis is counteracted by nitric oxide synthesised by the endothelium nitric oxide synthase (eNOS). Thus, nitric oxide inhibits endothelial cell apoptosis induced by proinflammatory cytokines and proatherosclerotic factors including reactive oxygen species and angiotensin II. The apoptosis-suppression may contribute to the profound anti-inflammatory and anti-atherosclerotic effects of endothelial-derived NO. Furthermore, the support of endothelial cell survival by NO may further play a central role for the pro-angiogenic effects of NO.

Animals↗

PubMed1999

Clinical importance of coronary endothelial vasodilator dysfunction and therapeutic options.

The vascular endothelium plays a key role in the control of vasomotor tone, local haemostasis and vascular wall proliferation processes. These responses are mediated by a variety of substances released from the endothelium in response to physiological stimuli, including prostacyclin, endothelin, and most importantly nitric oxide (NO). NO mediates vasodilation and furthermore inhibits platelet aggregation, expression of adhesion molecules for monocytes and adhesion of neutrophils, and it impairs growth of vascular smooth muscle cells. Risk factors for coronary atherosclerosis, such as hypercholesterolaemia, impair NO bioactivity, mainly due to an oxidative stress by superoxide radicals (O2-), which are able of rapidly inactivating endothelium-derived NO. Impaired NO bioactivity leads to unopposed paradoxical vasoconstriction of epicardial conductance vessels in response to physiological stimuli such as sympathetic activation as well as impaired vasodilator function of coronary resistance vessels. Therefore, endothelial dysfunction contributes to ischaemic manifestation of coronary artery disease. In addition, enhanced paradoxical vasoconstriction and a loss of endothelial antithrombotic activities might unfavourably modulate the course of acute coronary syndromes. Thus, the aim of therapeutic interventions is to increase NO bioavailability by either increasing NO production or decreasing O2- production in the endothelium. This goal can be reached, for example by ACE inhibitors, lipid-lowering drugs, increased shear-stress by physical exercise, oestrogens, and L-arginine, which have already been shown to improve endothelial vasodilator function. Nevertheless, it has to be determined whether ameliorated endothelial function will contribute to improved patients prognosis.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1999

Cystic medial degeneration of the aorta is associated with p53 accumulation, Bax upregulation, apoptotic cell death, and cell proliferation.

OBJECTIVE: To address a potential role for p53, Bcl2 associated protein X (Bax), and apoptosis in the processes associated with cell turnover during cystic medial degeneration (CMD) of the aorta. METHODS: Histochemical, immunohistochemical, biochemical, and morphometric methods were used to assess the presence and distribution of p53 immunoreactivity (p53-IR) and Bax immunoreactivity (Bax-IR), as well as the presence of apoptosis and tissue repair processes. RESULTS: Immunohistochemical staining disclosed evidence for p53-IR in all specimens in 26.1 (11.5)% of vascular smooth muscle cells (VSMCs) (controls 0.8 (1.3)%; p < 0. 001). Bax-IR was present in all specimens in 10 (5.4)% of medial cells (controls 0.3 (0.5)%; p < 0.001). Medial VSMCs (alpha-actin positive) with cytoplasmic staining for an apoptosis specific protein (c-jun/ASP) were present in 20/20 specimens (0.7 (0.6)% of VSMCs, controls 0%, p < 0.001), whereas terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) positive VSMCs were present in 17/20 specimens (1 (1.5)% of VSMCs, controls 0%, p < 0.001). The presence of apoptosis was confirmed by electron microscopy and the demonstration of oligonucleosomal DNA fragments after agarose gel electrophoresis. As shown by double labeling and investigation of serial sections, p53-IR, Bax-IR, c-jun/ASP-IR, and positive TUNEL labeling localised to the same compartments of the aortic media, raising a possible role for p53 and Bax in the triggering of apoptosis of VSMC during CMD. MIB1/Ki-67 positive medial VSMCs (alpha-actin positive) and mesenchymal cells (vimentin positive) were present in all specimens (2.5 (2.8)% of medial cells; controls 0.3 (0.9)%, p < 0.001) mainly in the region around the vasa vasorum, indicating that cell regeneration during CMD may originate mainly from the mesenchyme surrounding the vasa vasorum. CONCLUSION: This study shows that the formal pathogenesis of CMD is characterised by p53 accumulation, Bax upregulation, cell death by apoptosis, and cell regeneration. Nevertheless, the precise stimuli of p53 activation and Bax upregulation as well as the role of p53 and apoptosis in the dissection process itself remain elusive.

Adult↗

PubMed1999

Upregulation of superoxide dismutase and nitric oxide synthase mediates the apoptosis-suppressive effects of shear stress on endothelial cells.

Physiological levels of laminar shear stress completely abrogate apoptosis of human endothelial cells in response to a variety of stimuli and might therefore importantly contribute to endothelial integrity. We show here that the apoptosis-suppressive effects of shear stress are mediated by upregulation of Cu/Zn SOD and NO synthase. Shear stress-mediated inhibition of endothelial cell apoptosis in response to exogenous oxygen radicals, oxidized LDL, and tumor necrosis factor-alpha was associated with complete inhibition of caspase-3-like activity, the central effector arm executing the apoptotic cell death program in endothelial cells. Shear stress-dependent upregulation of Cu/Zn SOD and NO synthase blocks activation of the caspase cascade in response to apoptosis-inducing stimuli. These findings establish the upregulation of Cu/Zn SOD and NO synthase by shear stress as a central protective cellular mechanism to preserve the integrity of the endothelium after proapoptotic stimulation.

Antisense Elements (Genetics)↗

PubMed1998

Cyclosporin A inhibits apoptosis of human endothelial cells by preventing release of cytochrome C from mitochondria.

BACKGROUND: Several experimental and clinical studies suggest that cyclosporin A (CSA) treatment reduces transplant atherosclerosis. Because oxidized LDL (oxLDL) is believed to play a key role in the development of atherogenesis, causing injury to the endothelium, and has been shown to induce apoptosis of endothelial cells, we investigated whether CSA inhibits oxLDL-induced apoptosis. METHODS AND RESULTS: Apoptosis was induced in human umbilical venous endothelial cells (HUVECs) by incubation of 10 microg/mL oxLDL for 18 hours. Coincubation with CSA dose dependently decreased oxLDL-induced apoptosis, with a maximal effect at 10 micromol/L. In addition, tumor necrosis factor-alpha- and angiotensin II-induced apoptosis was significantly prevented by CSA treatment, suggesting a general apoptosis-suppressive effect of CSA. CSA has been shown to inhibit disruption of the mitochondrial membrane function, which plays a key role in apoptosis induction. Indeed, oxLDL treatment triggered the release of cytochrome C from the mitochondria into the cytosol, indicating disturbance of the mitochondrial membrane. CSA (10 micromol/L) completely inhibited the oxLDL-induced release of cytochrome C. Moreover, tumor necrosis factor-alpha- and angiotensin II-induced cytochrome C release was prevented by CSA treatment. CONCLUSIONS: OxLDL induces dysfunction of the mitochondrial membrane, leading to cytochrome C release into the cytosol, and thereby stimulates apoptosis of human endothelial cells. Apoptosis suppression by CSA correlates with the prevention of mitochondrial dysfunction and thus indicates the importance of mitochondrial destabilization in oxLDL-induced apoptosis signaling. The inhibition of apoptosis by CSA might preserve the function of the endothelium and may at least in part contribute to the antiatherogenic effects of CSA in transplant atherosclerosis.

Apoptosis↗