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ABSTRACT: Endothelial cells (ECs) play important roles in maintaining vascular homeostasis. Therefore, dysregulation of EC apoptosis may be involved in the mechanism of atherogenesis. Since recent evidence has shown that vascular endothelial growth factor (VEGF), an EC-specific growth factor, is released from vascular smooth muscle cells (VSMCs), we examined whether VSMCs can modulate EC apoptosis using a coculture system. Incubation of ECs with high levels of nitric oxide (NO) released by N-ethyl-2-[1-ethyl-2-hydroxy-2-nitrosohydrazino]-ethanamine, a NO releasing agent, resulted in apoptosis in association with decreased levels of Bcl-2, and increased levels of Bax, an accelerator of aoptosis. Exogenously added VEGF partially inhibited apoptosis and alterations of these bcl-2 family proteins induced by NO. On the other hand, NO-induced apoptosis and down-regulation of Bcl-2 in ECs were almost completely inhibited by coculturing with VSMCs. However, these inhibitory effects by VSMCs were suppressed by a neutralizing antibody against VEGF. In addition, overexpression of Bcl-2 prevented from NO-induced apoptosis in ECs. These findings indicate that VSMCs protect ECs from NO-induced apoptosis through inhibiting down-regulation of Bcl-2. Thus, vascular smooth muscle which releases EC survival factors including VEGF may play important roles in maintaining the levels of Bcl-2 in ECs.
Atherosclerosis 03/2001; 154(2):309-16. · 3.79 Impact Factor
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ABSTRACT: Pneumonia is a major direct cause of death in the elderly. Although aspiration based on a reduced cough reflex is one of the causes of pneumonia in the elderly, there are few studies of angiotensin-I converting enzyme inhibitors (ACE inhibitors), which are antihypertensive drugs that induce cough, as a factor influencing the incidence of pneumonia in institutionalized elderly subjects. To assess the effect of ACE inhibitors and dihydropiridine calcium-channel blockers on the incidence of pneumonia, we conducted a hospital-based case-control study. Cases were 55 pneumonia patients aged > or = 65 years during a 1-year period. The controls were elderly subjects, frequency matched to the cases by age and gender (n = 220). Data were collected on known risk factors and on medication for hypertension, consisting of ACE inhibitors, calcium-channel blockers, and nonantihypertensive medication. The significance of differences in risk factors was analyzed using univariate and multivariate comparisons of cases and controls. After adjustment for potential confounding factors, the relative risk estimates for pneumonia were 0.38 (95% confidence interval [CI], 0.15-0.97) and 1.84 (95% CI, 0.89-3.78) for ACE inhibitors and calcium-channel blockers, respectively, relative to nonantihypertensive medication. The preventive effect of ACE inhibitors on pneumonia was apparent in long-acting ACE inhibitor users (0.24; 95% CI, 0.07-0.88). We conclude that ACE inhibitor use is an independent factor reducing risk of pneumonia among elderly inpatients.
American Journal of Hypertension 08/1999; 12(8 Pt 1):778-83. · 3.18 Impact Factor
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ABSTRACT: Hydrogen peroxide (H2O2), an oxidant generated by inflammatory cells, is an important mediator of injury of endothelial cells (ECs). Here we show that H2O2 induces up-regulation of the expression of Fas, a death signal, in human ECs in culture. Flow cytometric analysis with a mAb against human Fas showed that incubation for 24 h with H2O2 induced a dose-dependent increase in the level of Fas in ECs. Coincubation with catalase, which rapidly degrades H2O2, inhibited H2O2-induced up-regulation of Fas. H2O2 also induced a dose-dependent increase in Fas mRNA level. A significant increase in Fas mRNA levels was observed from 6 h after stimulation with H2O2. Vanadate, a protein phosphatase inhibitor, significantly enhanced Fas mRNA and protein levels in H2O2-treated ECs. On the other hand, genistein, a tyrosine kinase inhibitor, inhibited H2O2-induced Fas mRNA expression. Furthermore, a flow cytometric method with propidium iodide staining and electron microscopic analysis showed that incubation with an agonistic Ab against Fas (anti-Fas IgM) induced apoptosis in H2O2-treated cells. These findings suggest that H2O2 induces up-regulation of Fas in ECs and that activation of protein tyrosine kinase may be involved in the mechanism of H2O2-induced Fas expression. Therefore, Fas-mediated apoptosis may have a pathologic role in H2O2-induced EC injury and thereby provide a new therapeutic target.
The Journal of Immunology 05/1998; 160(8):4042-7. · 5.79 Impact Factor
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ABSTRACT: Increased expression of endothelin-1 (ET-1) immunoreactivity is demonstrated in the active atherosclerotic plaque. Here we show that both ETA and ETB receptors are expressed in rat vascular smooth-muscle cells (VSMCs). ET-1 binding to ETB receptors enhances nitric oxide-induced cell death in VSMCs. These findings suggest that ET-1 may participate in the mechanism of cell death (apoptosis) in the plaque through activation of ETB-mediated pathways and that a selective ETB receptor antagonist could be useful in preventing acute plaque alterations, such as plaque rupture.
Journal of Cardiovascular Pharmacology 02/1998; 31 Suppl 1:S351-3. · 2.29 Impact Factor
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T Nabata,
K Fukuo,
S Morimoto,
S Kitano,
N Momose,
A Hirotani,
T Nakahashi,
A Nishibe, S Hata,
T Niinobu,
T Suhara,
M Shimizu,
H Ohkuma,
S Sakurai,
H Nishimaki,
T Ogihara
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ABSTRACT: Preincubation with interleukin-2 (IL-2), a T cell-derived cytokine, enhanced the increase in intracellular Ca2+ ([Ca2+]i) induced by angiotensin II (AII) in vascular smooth muscle cells (VSMC). IL-2 itself did not affect the basal [Ca2+]i level or the maximal response of [Ca2+]i increase induced by AII. Furthermore, IL-2-induced enhancement was not observed in the absence of extracellular Ca2+, suggesting that IL-2 enhances Ca2+ influx induced by AII. IL-2 also enhanced the stimulation of DNA synthesis induced by AII, although IL-2 alone did not stimulate DNA synthesis. Genistein, an inhibitor of protein tyrosine kinases, significantly inhibited IL-2-induced enhancement of both Ca2+ influx and DNA synthesis induced by AII. A neutralizing antibody against heparin-binding epidermal growth factor-like growth factor (HB-EGF) partially inhibited IL-2-induced enhancement of DNA synthesis induced by AII. These findings suggest that autocrine HB-EGF is partially involved in the mechanism of IL-2-induced enhancement of DNA synthesis. On the other hand IL-2 stimulated both glycosaminoglycan (GAG) and prostacyclin syntheses and enhanced the stimulation of both GAG and prostacyclin syntheses induced by AII. Therefore, IL-2 may play important roles in the pathogenesis of atherosclerosis and vascular disease by modulating the responsiveness to AII in VSMC.
Atherosclerosis 09/1997; 133(1):23-30. · 3.79 Impact Factor
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ABSTRACT: Apoptosis is a programmed cell death that plays a major role during development, homeostasis, and in many diseases. Recent evidence has demonstrated the death of vascular smooth muscle cells (VSMCs) within advanced human atheroma. In the rat balloon-injury model, apoptotic cells were specifically identified in the neointima. The presence of apoptotic cells was demonstrated by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). To clarify the mechanisms that trigger apoptosis in atherosclerotic lesions, we examined whether cytokines released from macrophages can modulate Fas, a death signal, in cultured human VSMCs. Simultaneous treatment with interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) but not with each cytokine alone induced upregulation of Fas in VSMCs. However, coincubation with NG-monomethyl-L-arginine, an inhibitor of nitric oxide (NO) synthesis, inhibited the upregulation of Fas induced by IL-1 and TNF-alpha. Incubation with sodium nitroprusside, a NO donor, also induced upregulation of Fas in VSMCs. Furthermore, fluorescent nuclear staining with Hoechst 33258 revealed that monoclonal antibody to human Fas significantly enhanced NO-induced apoptotis in VSMCs. These findings suggest that macrophage-derived cytokines can induce upregulation of Fas through a NO-dependent mechanism in VSMCs. Thus, Fas-mediated apoptosis may regulate apoptotic death of VSMCs during atherogenesis.
Gerontology 02/1997; 43 Suppl 1:35-42. · 2.78 Impact Factor
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ABSTRACT: Recent evidence has shown that apoptotic cells are present in human atherosclerotic lesions. However, the molecular mechanism of the induction of apoptosis in atherosclerotic lesions is not clear. Since T cells are present in almost all stages of atherosclerosis, we examined whether T cells can modulate the expression of Fas, a death signal, in endothelial cells (ECs), using a coculture system. Human umbilical vein ECs were cultured alone or cocultured with human peripheral T cells activated with phorbol myristate acetate and ionomycin. Flow cytometric (FACscan) analysis showed that Fas antigen was up-regulated in ECs when ECs were cocultured for 24 h with activated T cells. However, Fas antigen was not up-regulated in ECs cocultured with non-activated T cells. The up-regulation of Fas antigen induced by coculturing ECs with activated T cells was partially, but significantly, neutralized by antibody against interferon-gamma (IFN-gamma). Actually, incubation with IFN-gamma induced a dose-dependent increase in the level of Fas antigen in ECs cultured alone. These findings indicate that activated T cells induce up-regulation of Fas antigen in ECs. Thus, the Fas system induced by activated T cells could participate in the mechanism of EC injury in atherosclerotic lesions.
Heart and Vessels 02/1997; Suppl 12:81-3. · 2.05 Impact Factor
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B Jiang,
S Morimoto,
K Fukuo,
A Hirotani,
M Tamatani,
T Nakahashi,
A Nishibe,
T Niinobu, S Hata,
S Chen,
T Ogihara
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ABSTRACT: The effect of human parathyroid hormone-related protein, a powerful vasodilator, on endothelin-1 production in cultured bovine pulmonary arterial endothelial cells was studied. Treatment with parathyroid hormone-related protein(1-34) at concentrations of 10(-9) to 10(-6) mol/L for 24 hours caused dose-dependent suppression of the secretion of endothelin-1, with maximal suppression at 10(-7) mol/L to 74% of the control value. This inhibitory effect was completely abolished by coincubation with 100 ng/mL pertussis toxin, an inhibitor of GTP binding protein. Furthermore, addition of Ng-monomethyl-L-arginine, an inhibitor of nitric oxide synthase, at 10(-3) mol/L significantly blocked the suppressive effect of parathyroid hormone-related protein (1-34) on endothelin-1 secretion, and further addition of 5x10(-3) mol/L L-arginine significantly attenuated the blocking effect of N(G)-monomethyl-L-arginine. Parathyroid hormone-related protein (1-34) at 10(-7) mol/L resulted in an approximately fivefold increase in intracellular cGMP level. Northern blot analysis revealed that parathyroid hormone-related protein (1-34) inhibited both basal and thrombin-induced endothelin-1 gene expression. These findings suggest that the vasodilating property of parathyroid hormone-related protein may be mediated in part through its inhibitory effect on endothelin-1 production, which is probably mediated through nitric oxide and cGMP in endothelial cells. Thus, a feedback regulatory mechanism may exist between parathyroid hormone-related protein and endothelin-1 in the vascular wall.
Hypertension 04/1996; 27(3 Pt 1):360-3. · 6.21 Impact Factor
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ABSTRACT: Interleukin-1 induced a time-dependent release of high levels of nitric oxide from rat vascular smooth muscle cells up to 96 hours. A time-dependent release of lactate dehydrogenase was also induced by Interleukin-1 from 72 to 96 hours after its stimulation. In situ nick end-labeling assay revealed that incubation for 48 hours with interleukin-1 induced a positive staining of fragmented nuclei. However, NG-monomethyl-L-arginine, an inhibitor of nitric oxide synthase, inhibited both lactate dehydrogenase release and DNA fragmentation induced by interleukin-1. Furthermore, sodium nitroprusside, a nitric oxide donor, also induced lactate dehydrogenase release and DNA fragmentation. Fluorescent staining of DNA revealed patches of irregularly dispersed, brightly staining, and condensed chromatin in rat vascular smooth muscle cells treated with sodium nitroprusside. Flow cytometric analysis with monoclonal antibody against human Fas revealed that expression of Fas was upregulated by sodium nitroprusside in human vascular smooth muscle cells. Methylene blue, an inhibitor of soluble guanylate cyclase, did not affect sodium nitroprusside-induced upregulation of Fas. Furthermore, 8-bromo-guanosine 3':5'-cyclic monophosphate, an analogue of cGMP, did not upregulate Fas expression. These findings indicate that nitric oxide released from vascular smooth muscle cells may induce apoptosis in vascular smooth muscle cells themselves and also induced upregulation of Fas via a cGMP-independent mechanism. Thus, nitric oxide could trigger the remodeling of atherosclerotic plaques.
Hypertension 04/1996; 27(3 Pt 2):823-6. · 6.21 Impact Factor
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ABSTRACT: 8-Bromo-guanosine 3':5'-cyclic monophosphate (8-Br-cGMP), an analogue of cyclic guanosine monophosphate (cGMP), induced a time- and dose-dependent enhancement of interleukin-1-induced nitric oxide production in vascular smooth muscle cells. Human atrial natriuretic polypeptide, which stimulates cGMP accumulation in vascular smooth muscle cells, also enhanced interleukin-1-induced nitric oxide release at a concentration of 100 nmol/L. In contrast, coincubation with 10 mumol/L methylene blue, an inhibitor of soluble guanylate cyclase, inhibited interleukin-1-induced nitric oxide release from vascular smooth muscle cells. Furthermore, coincubation with 8-Br-cGMP also enhanced the interleukin-1-induced increase in inducible nitric oxide synthase messenger RNA in vascular smooth muscle cells. However, the enhancement of nitric oxide production induced by 8-Br-cGMP was significantly prevented by coincubation with neutralizing antibody against tumor necrosis factor-alpha. Furthermore, 8-Br-cGMP enhanced the interleukin-1-induced increase in tumor necrosis factor-alpha messenger RNA level in vascular smooth muscle cells. These findings indicate that cGMP may upregulate inducible nitric oxide synthase gene expression through the stimulation of tumor necrosis factor-alpha production in vascular smooth muscle cells. Thus, there may be a positive feedback mechanism between nitric oxide and the cGMP system in vascular smooth muscle cells.
Hypertension 05/1995; 25(4 Pt 2):711-4. · 6.21 Impact Factor
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ABSTRACT: Prolonged incubation with 1 nmol/L interleukin-1 induced high levels of nitric oxide release and cytotoxicity in vascular smooth muscle cells. NG-Monomethyl-L-arginine, an inhibitor of nitric oxide synthesis, inhibited interleukin-1-induced cytotoxicity at a concentration of 3 mmol/L. Furthermore, prolonged incubation with 0.1 mmol/L sodium nitroprusside, a nitric oxide donor, also induced cytotoxicity. On the other hand, endothelin-1 at concentrations from 10(-10) to 10(-7) mol/L induced a concentration-dependent enhancement of cytotoxicity induced by interleukin-1. However, endothelin-1 did not affect interleukin-1-induced nitric oxide production. Coculture study of vascular smooth muscle cells and endothelial cells without direct cell contact revealed that incubation for 72 hours with interleukin-1 induced high levels of nitric oxide release from cocultured vascular smooth muscle cells to the same degree as release from vascular smooth muscle cells alone. However, interleukin-1-induced cytotoxicity was more enhanced in cocultured vascular smooth muscle cells than in vascular smooth muscle cells alone. Furthermore, coincubation with 20 nmol/L BQ-485, an antagonist of one type of endothelin receptor (ETA), prevented the enhancement of interleukin-1-induced cytotoxicity in cocultured vascular smooth muscle cells. These findings suggest that endothelin-1 secreted from endothelial cells may enhance nitric oxide-induced cytotoxicity by means of the ETA receptor in vascular smooth muscle cells.
Hypertension 05/1995; 25(4 Pt 2):744-7. · 6.21 Impact Factor
