Hidetsugu Matsushita

Endothelial Apoptosis Induced by Oxidative Stress Through Activation of NF-κB: Antiapoptotic Effect of Antioxidant Agents on Endothelial Cells

Injury of endothelial cells has been assumed to be an initial trigger of the development of atherosclerosis. In this study, we investigated the molecular mechanisms of endothelial cell death induced by hypoxia, which leads to oxidative stress. To study the relation between hypoxia-induced cell death and activation of nuclear factor-&kgr;B (NF-&kgr;B) in a hypoxic state, we evaluated the effect of 2 antioxidant drugs, probucol and pyrrolidine dithiocarbamate (PDTC), on human endothelial apoptosis. Although hypoxic treatment of human aortic endothelial cells resulted in a significant decrease in cell number and a significant increase in apoptotic cells compared with that of cells under normoxia (P <0.01), treatment with probucol (50 &mgr;mol/L) or PDTC (100 &mgr;mol/L) significantly attenuated the decrease in cell number (P <0.01) and was accompanied by inhibition of NF-&kgr;B activation. Furthermore, downregulation of bcl-2 caused by hypoxia was inhibited by these drugs. We further investigated the translocation of bax protein from the cytoplasm to the mitochondrial heavy fraction membrane, as translocation of bax protein is considered to be a determinant of apoptosis. Interestingly, we found that antioxidant treatment inhibited the translocation of bax protein caused by hypoxia. Moreover, upregulation of p53, a proapoptotic molecule, was observed in hypoxia, whereas treatment with probucol attenuated the expression of p53 accompanied by suppression of NF-&kgr;B activation. These data suggest functional links between p53 and endothelial apoptosis through the activation of NF-&kgr;B. Overall, the current study demonstrated that oxidative stress induced apoptosis in human aortic endothelial cells through the downregulation of bcl-2, translocation of bax, and upregulation of p53, probably through NF-&kgr;B activation. Oxidative stress may play an important role in endothelial apoptosis mediated by hypoxia, through the activation of NF-&kgr;B.

Hypoxia-Induced Endothelial Apoptosis Through Nuclear Factor-κB (NF-κB)–Mediated bcl-2 Suppression: In Vivo Evidence of the Importance of NF-κB in Endothelial Cell Regulation

The transcription factor nuclear factor-kappaB (NF-kappaB) plays a pivotal role in the coordinated transactivation of cytokine and adhesion molecule genes involved in endothelial activation. Although recent reports have documented the contribution of NF-kappaB to apoptosis, it is still controversial. Especially, the role of NF-kappaB in endothelial apoptosis is largely unknown. Hypoxia significantly induced human aortic endothelial cell death and apoptosis in a time-dependent manner (P<0.01), accompanied by NF-kappaB activation. Decrease in total cell number and increase in apoptotic cells induced by hypoxia were significantly attenuated by NF-kappaB decoy, but not by scrambled decoy, oligodeoxynucleotides (ODNs) (P<0.01). Increase in DNA fragmentation induced by hypoxia was also significantly inhibited by NF-kappaB decoy ODNs as compared with scrambled decoy ODNs (P<0.01). Moreover, transfection of NF-kappaB decoy ODNs resulted in a significant decrease in caspase-3-like activity, which is a common pathway for apoptosis, compared with scrambled decoy ODNs. Importantly, transfection of NF-kappaB decoy ODNs significantly increased protein of bcl-2, an inhibitor of apoptosis, and did not alter bax, a promoter of apoptosis, thereby resulting in a significant increase in the ratio of bcl-2 to bax (P<0.01). bcl-2 mRNA was also decreased by hypoxia, whereas transfection of NF-kappaB decoy ODNs significantly attenuated decrease in bcl-2 mRNA. These results demonstrate that activation of NF-kappaB by hypoxia induced endothelial apoptosis in a bcl-2-dependent manner. The importance of NF-kappaB in endothelial apoptosis was confirmed by the observation that pyrrolidine dithiocarbamate, a potent NF-kappaB inhibitor, prevented endothelial apoptosis, caspase 3-like activity, and bcl-2 downregulation induced by hypoxia. To test this hypothesis in vivo, we transfected NF-kappaB decoy ODNs into rat intact carotid artery after reperfusion injury. Reperfusion injury was associated with a significant increase in endothelial apoptosis at 24 hours, whereas NF-kappaB decoy ODN treatment markedly decreased terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL)-positive endothelial cells at 24 hours after reperfusion (P<0.01). Here, using synthetic double-stranded DNA with high affinity for NF-kappaB as a decoy approach, we demonstrated that activation of NF-kappaB by hypoxia caused aortic endothelial cell death and apoptosis through the suppression of bcl-2. NF-kappaB-mediated endothelial apoptosis induced by hypoxia may be involved in the pathogenesis of endothelial dysfunction observed in cardiovascular ischemic diseases.

Cyclic AMP Inhibited Proliferation of Human Aortic Vascular Smooth Muscle Cells, Accompanied by Induction of p53 and p21

Although cAMP is an important second messenger that plays a pivotal role in the regulation of platelet aggregation and dilatation of blood vessels, little is known about the action of cAMP on the growth of vascular smooth muscle cells (VSMCs). Thus, we initially studied the effects of cAMP accumulation by using various cAMP stimulants, including a phosphodiesterase type 3 inhibitor (cilostazol) on human aortic VSMC growth. Accumulation of cAMP inhibited the platelet-derived growth factor (PDGF)-stimulated VSMC growth in a dose-dependent manner (P<0.01), whereas PDGF significantly stimulated the growth of human VSMCs. Thus, we focused on the role of cell cycle regulatory genes, especially on a negative regulator, an anti-oncogene, p53. The protein of p53 was potentiated by cilostazol as well as forskolin and 8-bromo-cAMP, whereas PDGF decreased p53 expression. Upregulation of p53 protein by cAMP was further confirmed by the observation that the decrease in p21, a p53-inducible protein, by PDGF was significantly attenuated by cilostazol in a dose-dependent manner (P<0.01). These results revealed that accumulation of cAMP inhibited VSMC proliferation, which was at least in part due to an increase in p53-p21 expression. Because p53 and p21 have been reported to induce apoptosis, we examined apoptotic cells for cAMP accumulation. Incubation of VSMCs with cilostazol resulted in a significant increase in apoptotic cells in a dose-dependent manner compared with vehicle treatment as assessed by nuclear chromatic morphology (P<0.01); forskolin also stimulated apoptotic cells. Consistent with nuclear staining, DNA fragmentation in VSMCs treated with forskolin as well as 8-bromo-cAMP and cilostazol was significantly increased compared with DNA fragmentation in VSMCs treated with vehicle, whereas PDGF significantly decreased the rate of DNA fragmentation (P<0.01). Overall, these results demonstrated that cAMP inhibited the proliferation of human aortic VSMCs, accompanied by p53-p21-mediated apoptosis. Analogues of cAMP that have direct inhibitory effects on VSMC proliferation can be considered as potential antiproliferative drugs against VSMC growth.

Cyclic strain induces reactive oxygen species production via an endothelial NAD(P)H oxidase

Vascular endothelial cells are constantly subjected to pressure‐induced cyclic strain. Reactive oxygen species (ROS) have been implicated in atherosclerosis and vascular remodeling. Recent evidence indicates that a vascular NAD(P)H oxidase may be an important source of ROS in both physiologic and pathophysiologic situations. The aim of this study was to investigate cyclic strain‐induced NAD(P)H oxidase activity in endothelial cells. ROS production was examined by electron paramagnetic resonance and lucigenin chemiluminescence. Cyclic strain‐induced NAD(P)H oxidase activity was quantified by activity assay while the expression of p22phox was monitored by Northern blotting. Endothelial cells produce basal amounts of ROS that were enhanced by cyclic strain. Moreover subsequent stimulation with TNF‐α resulted in significantly greater ROS production in cells previously exposed to cyclic strain as compared to static conditions. Cyclic strain resulted in a significant increase in message for the p22phox subunit as well as activity of the NAD(P)H oxidase. The induced oxidative stress was accompanied by increased mobilization of the transcription factor NFκB, an effect that was blocked by a pharmacological inhibitor of NAD(P)H. These results demonstrate a pivotal role for NAD(P)H oxidase in cyclic strain‐induced endothelial ROS production and may provide insight into the modulation of vascular disease by biomechanical forces. J. Cell. Biochem. Suppl. 36: 99–106, 2001.

Role of hepatocyte growth factor in endothelial regulation : prevention of high D-glucose-induced endothelial cell death by prostaglandins and phosphodiesterase type 3 inhibitor

Summary Injury of endothelial cells (EC) has been postulated as the initial trigger of the progression of atherosclerosis in patients with diabetes mellitus. We previously reported that decrease in a novel endothelium-specific growth factor, hepatocyte growth factor (HGF), by high d-glucose might be a trigger of endothelial injury. However, the physiological role of the local vascular HGF system has not yet been clarified. To investigate the role of HGF in endothelial injury, we initially examined the effects of HGF on endothelial injury induced by serum deprivation. Decrease in EC number by serum deprivation was significantly attenuated by addition of HGF as well as recombinant basic fibroblast growth factor, whereas vascular endothelial growth factor showed no effect. Apoptotic changes in EC induced by serum deprivation were also significantly attenuated by addition of HGF (p < 0.01). Given the protective action of HGF, we next studied the physiological role of local HGF production in endothelial regulation. We focused on the protective actions of prostaglandin (PG) I2, PGE and a phosphodiesterase type 3 inhibitor (cilostazol) on endothelial injury by high glucose, since these agents are widely used in the treatment of peripheral arterial disease which is frequently observed in diabetic patients. Treatment of human aortic EC with PGE1, PGE2, and a PGI2 analogue (beraprost sodium) as well as cilostazol stimulated EC growth. HGF concentration in conditioned medium from EC treated with PGE1, PGE2 or PGI2 analogue as well as cilostazol was significantly higher than that with vehicle (p < 0.01). Interestingly, treatment with PGI2 analogue or cilostazol attenuated high d-glucose-induced EC death, which was abolished by neutralizing anti-HGF antibody. Moreover, decreased local HGF production by high d-glucose was also significantly attenuated by PGI2 analogue or cilostazol. Finally, we tested the effects of PGE, PGI2 analogue and cilostazol on local HGF production in human aortic vascular smooth muscle cells (VSMC). Although high d-glucose treatment resulted in a significant increase in VSMC number, PGI2 analogue and/or cilostazol treatment had no effects on VSMC growth. However, the decrease in local HGF production by high d-glucose was significantly attenuated by addition of PGI2 analogue or cilostazol.Overall, this study demonstrated that treatment with PGE, PGI2 analogue or cilostazol prevented aortic EC death induced by high d-glucose, probably through the activation of local HGF production. Increased local vascular HGF production by prostaglandins and cilostazol may prevent endothelial injury, potentially resulting in the improvement of peripheral arterial disease. [Diabetologia (1997) 40: 1053–1061]

Contribution of Bcl-2, but Not Bcl-xL and Bax, to Antiapoptotic Actions of Hepatocyte Growth Factor in Hypoxia-Conditioned Human Endothelial Cells

Abstract—Angiogenic growth factors play important roles in angiogenic responses, such as vasculogenesis and angiogenesis in response to hypoxia. A novel angiogenic growth factor, hepatocyte growth factor (HGF), has been reported to inhibit endothelial cell death. However, its molecular mechanisms are largely unknown. Thus, we studied (1) the effects of HGF on hypoxia-induced endothelial apoptosis and (2) the molecular mechanisms of the antiapoptotic actions of HGF in endothelial cells. Severe hypoxia increased the cell death rate in human aortic endothelial cells, whereas HGF significantly attenuated cell death. In addition, hypoxic treatment resulted in a significant increase in apoptotic cells, whereas HGF could attenuate apoptosis, accompanied by attenuation of the increase in caspase-3–like activity (P <0.01). Of importance, HGF significantly increased Bcl-2, an inhibitor of apoptosis, in a dose-dependent manner under normoxic and hypoxic conditions (P <0.01), whereas hypoxic conditions resulted in a significant decrease in Bcl-2. In contrast, HGF failed to affect Bcl-xL, which is also well known as an inhibitor of apoptosis under both normoxic and hypoxic conditions, whereas Bcl-xL was significantly decreased in endothelial cells exposed to hypoxia (P <0.01). No significant change in Bax, a promoter of apoptosis, was also observed in endothelial cells under hypoxia, whereas HGF did not affect Bax. Overall, this study demonstrated that HGF prevented endothelial cell death induced by hypoxia through its antiapoptotic action. The antiapoptotic mechanisms of HGF in hypoxia-induced endothelial cell death largely depend on Bcl-2, but not Bcl-xL and Bax.

Transcription factor decoy for nuclear factor-kappaB inhibits tumor necrosis factor-alpha-induced expression of interleukin-6 and intracellular adhesion molecule-1 in endothelial cells.

Background Several cytokines and adhesion molecules released from endothelium play an important role in inflammation, immune responses, and probably atherogenesis. Objective To determine whether the transcription factor nuclear factor-κB mediated expression of these genes involved in the inflammatory response of endothelial cells to tumor necrosis factor-α, by using transcription factor decoy oligodeoxynucleotides. Design and methods We first transfected fluorescein isothiocyanate (FITC)-labeled double-stranded oligodeoxynucleotides into endothelial cells by a cationic liposome-mediated method of gene transfer. We then confirmed that the decoy oligodeoxynucleotides could block binding of nuclear factor-κB to its specific cis element effectively. In addition, we transfected the reporter gene chloramphenicol acetyltransferase driven by three repeated nuclear factor-κB binding sequences in the promoter and enhancer region. Results FITC-labeled oligodeoxynucleotides were detected in the nuclei of approximately 70% of the total cells. Tumor necrosis factor—stimulated expression of chloramphenicol acetyltransferase was partially inhibited by transfection of nuclear factor-κB decoy oligodeoxynucleotides, but not by transfection of scrambled oligodeoxynucleotides. Also nuclear factor-κB decoy oligodeoxynucleotides but not scrambled oligodeoxynucleotides inhibited tumor necrosis factorinduced expression of interleukin-6 and intracellular adhesion molecule-1 both at the messenger RNA and at protein level (assessed by reverse transcription—polymerase chain reaction and enzyme-linked immunosorbent assay). Conclusion Our results demonstrate that nuclear factor-κB decoy oligodeoxynucleotides transfected by cationic liposome method inhibited tumor necrosis factor —induced expression of interleukin-6 and intracellular adhesion molecule-1 in endothelial cells.

Inhibition of the p53 tumor suppressor gene results in growth of human aortic vascular smooth muscle cells. Potential role of p53 in regulation of vascular smooth muscle cell growth.

Loss of activity of the p53 tumor suppressor gene product has been postulated in the pathogenesis of human restenosis. Although the antioncogenes p53 and retinoblastoma (Rb) susceptibility gene have been reported to play a pivotal role in cell cycle progression in various cells, the role of p53 and Rb in the growth of human vascular smooth muscle cells (VSMC) has not yet been clarified. We used antisense strategy against p53 and Rb genes by the viral envelope-liposomal method. Transfection of antisense p53 oligodeoxynucleotides (ODN) alone resulted in an increase in DNA synthesis compared with control (P<0.01). Similarly, transfection of antisense Rb ODN alone resulted in a higher DNA synthesis rate than control (P<0.01). Moreover, increase in VSMC number was only induced by transfection of antisense p53 ODN alone or cotransfection of p53/Rb ODN (P<0.01), whereas a single transfection of antisense Rb ODN had little effect on cell number. Therefore, we hypothesized that this discrepancy is due to the induction of apoptosis mediated by p53. Interestingly, apoptotic cells were markedly increased in VSMC transfected with antisense Rb ODN alone, accompanied by the induction of p53 protein. The number of apoptotic cells was attenuated by cotransfection of antisense p53 ODN (P<0.01). We finally examined the molecular mechanisms of apoptosis induced by the absence of Rb. In VSMC transfected with antisense Rb ODN, bax, a promoter of apoptosis, was significantly increased in VSMC transfected with antisense Rb ODN (P<0.01), whereas bcl-2 and Fas did not play a pivotal role in the induction of apoptosis. Overall, these data first demonstrated that the antioncogenes p53 and Rb negatively regulated the cell cycle in VSMC, suggesting that the modulation of their activity may mediate VSMC growth such as that in restenosis and atherosclerosis. The presence of p53 plays a pivotal role in the regulation of apoptosis in human VSMC growth, probably through the bax pathway. These results provide evidence that p53 is a functional link between cell growth and apoptosis in VSMC.

Inhibition of intimal hyperplasia after vein grafting by in vivo transfer of human senescent cell-derived inhibitor-1 gene

The senescent cell-derived inhibitor (sdi)-1 (p21) protein has been identified as a downstream mediator of the tumor suppressor p53 in the cell cycle regulation. In this study, we focused on the function of sdi-1 gene in inhibiting vascular smooth muscle cell (VSMC) proliferation after vein grafting in a rabbit model. To test the hypothesis, we transfected human sdi-1 gene by an intra-operative approach. Accompanied by markedly increased sdi-1 protein, the significant increase in PCNA-stained VSMCs in vein grafts was inhibited by transfection of sdi-1 gene. Moreover, at 2 weeks after transfection, transfer of sdi-1 gene resulted in a significant inhibition in neointimal formation, compared with control vector. Of importance, immunohistological studies determining the expression pattern of myosin heavy isoforms, adult type specific SM2 and embryonic specific SMemb/NMHC-B, demonstrated expression of the adult phenotype of VSMCs in the neointima of sdi-1 gene-transfected vein grafts at 2 weeks after the operation, while the neointima was predominantly composed of embryonic phenotype of VSMCs in the control grafts. Overall, these results demonstrate that a single intraluminal incubation of human sdi-1 gene can result in a significant inhibition of neointimal formation after vein grafting, associated with phenotypic change of VSMCs from neonatal to adult type in a rabbit model. Inhibition of hyperplasia in a graft model by transfection of sdi-1 gene may be due to the change in VSMC phenotype from neonatal to adult, in addition to the inhibition of VSMC growth.

Inhibition of Growth of Human Vascular Smooth Muscle Cells by Overexpression of p21 Gene Through Induction of Apoptosis

The senescent cell-derived inhibitor (sdi)-1 protein (p21 product) has been identified as a downstream mediator of the tumor suppressor p53 in the regulation of cell cycle progression through a G1 phase checkpoint. Given the importance of cell cycle inhibition for the treatment of restenosis, in this study we focused on the function of p21 gene in inhibiting proliferation of vascular smooth muscle cells (VSMC). To test the hypothesis, we transfected human p21 gene into human aortic VSMC using hemagglutinating virus of Japan-liposome-mediated transfer. Initially, we examined the successful transfection of human p21 gene into VSMC. p21 protein was increased in VSMC transfected with p21 vector as compared with control vector. Accompanied by increased p21 protein, transfection of p21 vector resulted in a significant decrease in number of VSMC induced by 2% serum (P<.01). Although p21 has been reported to play an important role in the regulation of apoptosis in some cells, apoptosis mediated by p21 is still controversial. Therefore, we hypothesized that overexpression of p21 mediates apoptosis in human VSMC, in addition to the blockade of cell cycle progression. First, we assessed the concordance between morphologic analysis and apoptosis as determined by nuclear staining with Hoechst 33342. Cells transfected with p21 gene exhibited the characteristic features of cell shrinkage, membrane blebbing, and rounding that are typical of apoptotic death. Of greater interest, a significant increase in apoptotic cells was observed in VSMC transfected with p21 vector as compared with control vector (P<.01). These results were confirmed by the measurement of DNA fragmentation. Consistent with nuclear staining, DNA fragmentation in VSMC transfected with human p21 gene was significantly increased as compared with that in VSMC transfected with control vector (P<.05). To study the molecular mechanisms of apoptosis mediated by overexpression of p21 gene, the protein levels of bax, a promoter of apoptosis, and bcl-2, an inhibitor of apoptosis, were also measured by Western blotting. Overexpression of p21 gene significantly increased protein of bax (P<.05), whereas transfection of p21 gene did not alter bcl-2 protein. Importantly, the ratio of bax to bcl-2 was significantly increased in VSMC transfected with human p21 vector as compared with control vector (P<.05). Overall, these results demonstrated that inhibition of VSMC growth by overexpression of human p21 gene was accompanied by induction of apoptosis through an inappropriate increase in bax protein. These results suggest that regulation of cell cycle by p21 may be closely linked to programmed cell death/apoptosis in human VSMC.