Angiotensin II potentiates vascular endothelial growth factor-induced proliferation and network formation of endothelial progenitor cells

Bone marrow-derived endothelial progenitor cells (EPCs) in the peripheral blood of adult animals and adult humans have been shown to play a role in neovascularization into neovascular structures. On the other hand, angiotensin II (Ang II) plays a role in the development of many vascular diseases. To investigate whether Ang II affects human vascular endothelial growth factor (VEGF)-induced EPCs proliferation and network formation. Reverse transcription-polymelase chain reaction analysis demonstrated that Ang II induced a significant increase of VEGF receptor kinase domain-containing receptor (KDR) mRNA in a dose- and time-dependent manner; the maximal increase, which was 3-fold the control value, occurred after a 4-h stimulation. In addition, flow cytometric analysis revealed that Ang II up-regulated KDR protein expression in human EPCs. Both the angiotensin type 1 (AT1) receptor antagonist (valsartan: 200 nmol/l) and the PKC inhibitor, bisindolylmaleimide (GFX: 10 micromol/l) reduced Ang II-induced KDR mRNA expression to almost the control level. The culture assay showed that Ang II dose-dependently enhanced VEGF-induced EPC proliferation by activating AT1 receptors, which was also confirmed by the colorimetric MTS assay with the electron coupling reagent mathosulfate. Finally, in a Matrigel assay, EPCs treated with both Ang II and VEGF were shown to be more likely to integrate into the network formation than those treated with VEGF alone. In conclusion, our data indicate that Ang II potentiates VEGF-induced human EPCs proliferation and network formation through the up-regulation of KDR.

Leptin and membrane fluidity of erythrocytes in essential hypertension. An electron paramagnetic resonance investigation

There has been an indication that leptin, the product of the human obesity gene, actively participates not only in metabolic regulation but also in the control of blood pressure. Recently, it has been proposed that abnormalities in the physical property of cell membranes may underlie the defects that are strongly linked to hypertension, stroke, and other cardiovascular diseases. We have shown previously that leptin significantly increased the membrane fluidity and improved the microviscosity of erythrocytes in humans through the nitric oxide-dependent mechanism. In the present study, we examined the effects of leptin on membrane fluidity of erythrocytes in subjects with essential hypertension by means of an electron paramagnetic resonance (EPR) and spin-labeling method. The values of the order parameter (S) and the peak height ratio (ho/h-1) obtained from the EPR spectra of erythrocytes were significantly greater in patients with essential hypertension (HT) than in age-matched normotensive subjects (NT) (S: HT 0.719 +/- 0.002, n = 16, NT 0.713 +/- 0.001, n = 29, P < .05; ho/h-1: HT 5.17 +/- 0.02, n = 16, NT 5.05 +/- 0.02, n = 29, P < .05). The finding indicated that the erythrocyte membrane fluidity was lower in patients with HT than in NT. Leptin decreased S and ho/h-1 in a dose-dependent manner in both NTs and HTs. The effect of leptin on the membrane fluidity was significantly more pronounced in HTs than in NTs (percent change in S: leptin 10(-8) g/mL, HT -3.4% +/- 0.2%, n = 16, NT -2.3% +/- 0.1%, n = 29, P < .05; leptin 10(-7) g/mL, HT -4.3% +/- 0.3%, n = 16, NT -3.3% +/- 0.1%, n = 29, P < .05). The results of the present study showed that leptin might have a crucial role in the regulation of the rheologic behavior of erythrocytes and the microcirculation in hypertension.

Role of alpha2-adrenergic receptors and cyclic adenosine monophosphate-dependent protein kinase in the regulation of norepinephrine release in the central nervous system of spontaneously hypertensive rats

There has been much evidence showing that the central sympathetic nervous system may be involved in the control of blood pressure. In the present study, we investigated the role of the presynaptic alpha2-adrenergic receptors and the cyclic adenosine monophosphate-dependent protein kinase (protein kinase A) in the regulation of norepinephrine release in the central nervous system in hypertension. The alpha2-adrenergic receptor agonists UK 14, 304 and clonidine inhibited the stimulation-evoked [3H]norepinephrine release in a dose-dependent manner in the medulla oblongata of Sprague-Dawley rats. Pretreatment of pertussis toxin (a potent inhibitor of the Gi-protein) attenuated the suppression of NE release by UK 14, 304. The protein kinase A inhibitor H-8 also reduced the stimulation-evoked [3H]norepinephrine release in rat medulla oblongata. In spontaneously hypertensive rats, the inhibitory effect of UK 14, 304 on the stimulation-evoked norepinephrine release was significantly less than in age-matched normotensive Wistar-Kyoto rats. By contrast, the protein kinase A inhibitor H-8 reduced the stimulation-evoked norepinephrine release to a greater extent in hypertension than in normotensive controls. The results of the present study showed that the alteration in the presynaptic alpha2-receptor-protein kinase A system might actively participate in the regulation of norepinephrine release in the central nervous system in hypertension.

Estrogen Attenuates the Emotional Stress-induced Cardiac Responses in the Animal Model of Tako-Tsubo (Ampulla) Cardiomyopathy

Reduction of estrogen levels may underlie the high incidence of 'Tako-tsubo (Ampulla) cardiomyopathy in postmenopausal females. Ovariectomized (OVX) and estradiol-supplemented ovariectomized female rats (OVX + E) were subjected to immobilization stress, an animal model of Tako-tsubo cardiomyopathy. In order to evaluate cardiac changes, left ventriculography and electrocardiography were performed under anesthesia (control). Next day, the conscious rats were exposed to immobilization stress, and left ventriculography was performed (stress). In OVX rats, percentage contraction in left ventriculography was significantly reduced in response to stress, while it was not significantly changed in OVX + E rats. In both groups, heart rate was significantly increased in response to stress. However, heart rate in stress was significantly higher in OVX than in OVX + E rats. In summary, these data suggest that increase of serum estradiol levels can diminish the pathological changes in the heart induced by emotional stress.

Oxidized low-density lipoprotein inhibits vascular endothelial growth factor-induced endothelial progenitor cell differentiation

1. Bone marrow-derived endothelial progenitor cells (EPC) in the peripheral blood of adult animals and humans have been shown to be incorporated into neovascularization. In contrast, hypercholesterolaemia impairs angiogenesis and collateral vessel formation in response to regional tissue ischaemia. We investigated whether oxidized LDL (oxLDL) affected human EPC differentiation. 2. When isolated human mononuclear cells (MNC) were incubated with vascular endothelial growth factor (VEGF), the number of differentiated, adherent EPC, as assessed by an in vitro culture assay, was increased in a dose-dependent manner (P < 0.01). When MNC were incubated with oxLDL at 1, 5 and 10 microg/mL in the presence of 100 ng/mL VEGF for 24 h, oxLDL dose-dependently reduced the number of differentiated, adherent EPC. 3. Vascular endothelial growth factor-induced EPC differentiation was significantly inhibited by pharmacological phosphatidylinositol 3-kinase blockers (either 10 nmol/L wortmannin or 10 micromol/L LY294002). Interestingly, immunoblotting analysis revealed that oxLDL dose-dependently led to dephosphorylation and, thus, deactivation of Akt in the presence of VEGF. Finally, these inhibitory effects induced by oxLDL were abolished by pretreatment with 1 micromol/L atorvastatin (P < 0.01). 4. Our data indicate that oxLDL inhibits VEGF-induced EPC differentiation through the dephosphorylation of Akt.

Hormone replacement therapy improves membrane fluidity of erythrocytes in postmenopausal women: an electron paramagnetic resonance investigation

BACKGROUND

Many studies have shown that hormone replacement therapy (HRT) might provide protection against the development of hypertension and arteriosclerosis in postmenopausal women. However, the precise mechanism underlying its benefits is unclear. This question was addressed in an electron spin resonance (EPR) study of membrane function of erythrocytes in postmenopausal women. The purpose of this study was to investigate the effects of HRT on membrane fluidity of erythrocytes in postmenopausal women by means of the EPR and spin-labeling method.

METHODS

The healthy postmenopausal women were randomly divided into the HRT group (n = 14) receiving the conjugated estrogen with medroxyprogesterone for 3 months and the non-HRT control group (n = 14). We measured membrane fluidity of erythrocytes in postmenopausal women before and after the trial period.

RESULTS

The HRT group showed a significant decrease in blood pressure (BP) after treatment (systolic BP 145.7 +/- 5.5 v 123.3 +/- 5.1 mm Hg, n = 14, mean +/- SEM, P <.05). The order parameter (S) for 5-nitroxide stearate in the EPR spectra of erythrocyte membranes decreased significantly in the HRT group (S: 0.718 +/- 0.002 v 0.695 +/- 0.002, n = 14, P <.01). The finding indicated that HRT increased the membrane fluidity of erythrocytes and improved the microviscosity of the cell membranes in postmenopausal women.

CONCLUSIONS

These results are consistent with the hypothesis that HRT might have a beneficial effect on the membrane rheologic behavior of erythrocytes and the microcirculation in postmenopausal women.

Effects of mild aerobic physical exercise on membrane fluidity of erythrocytes in essential hypertension

1. The present study was undertaken to investigate the effects of aerobic physical exercise on membrane function in mild essential hypertension. 2. Hypertensive patients were divided into an exercise group (n = 8) and a non-exercise (control) group (n = 8). Physical exercise within the intensity of the anaerobic threshold level was performed twice a week for 6 months. Membrane fluidity of erythrocytes was examined by means of electron paramagnetic resonance (EPR) and spin-labelling methods before and after the trial period in both groups. 3. After physical exercise, blood pressure decreased significantly. 4. Compared with the non-exercise group, in the exercise group both the order parameter (S) and the peak height ratio (ho/h-1) in the EPR spectra of erythrocytes were significantly reduced (S, 0.717 +/- 0.004 vs 0.691 +/- 0.008, respectively (n = 8), P < 0.05; ho/h-1, 5.38 +/- 0.06 vs 4.89 +/- 0.06, respectively (n = 8), P < 0.05). These findings indicated that exercise increased membrane fluidity and improved the membrane microviscosity of erythrocytes. 5. There was no direct correlation between blood pressure reduction and the exercise-induced increase in membrane fluidity of erythrocytes. 6. In the non-exercise (control) group, blood pressure and membrane fluidity were not changed after a 6 month follow-up period. 7. The results show that aerobic physical exercise increased erythrocyte membrane fluidity and improved the rigidity of cell membranes in hypertensive patients. The improvement of rheological properties of erythrocytes may explain, in part, the cellular mechanisms for the beneficial effects of physical exercise in hypertension.

Oxidized low-density lipoprotein sensitizes human vascular smooth muscle cells to FAS (CD95)-mediated apoptosis

1. It was investigated in the present study whether oxidized low-density lipoprotein (oxLDL) was implicated in the susceptibility of human vascular smooth muscle cells (VSMC) to Fas-mediated death. Human fetal aorta smooth muscle cells were treated with agonistic anti-Fas antibody (CH11) and oxLDL and cell death was then determined by viability and DNA fragmentation. 2. The results of the present study show that cross-linking of Fas receptor with anti-Fas antibody in the presence of oxLDL induced death and DNA fragmentation in human VSMC, which were blocked by the caspase inhibitor z-VAD.fmk, followed by the upregulation of cell surface Fas. 3. The data indicate that oxLDL is implicated in death in VSMC and provide evidence that oxLDL is involved in Fas signal transduction. The present study proposes a novel mechanism(s) by which VSMC become susceptible to Fas ligand. 4. One of the mechanisms proposed by which oxLDL upregulates cell surface Fas is by inhibiting the degradation of Fas through the ubiquitin-proteasome pathway.

Nitric oxide is a determinant of membrane fluidity of erythrocytes in postmenopausal women: an electron paramagnetic resonance investigation

In the present study, to determine a possible role of nitric oxide (NO) in the regulation of membrane functions, we examined the relationship between plasma NO level and membrane fluidity of erythrocytes in postmenopausal women. We evaluated the membrane fluidity of erythrocytes obtained from hypertensive and normotensive postmenopausal women by means of an electron paramagnetic resonance (EPR) and spin labeling method. The EPR study revealed that the order parameter (S) for 5-nitroxide stearate in erythrocyte membranes was significantly greater in hypertensive postmenopausal women than in normotensive postmenopausal women. The finding indicated that the membrane fluidity of erythrocytes was decreased in hypertensive postmenopausal women compared with normotensive postmenopausal women. The plasma level of the NO metabolites (nitrite and nitrate) while fasting was significantly lower in hypertensive postmenopausal women than in normotensive postmenopausal women. In addition, the order parameter (S) in the EPR spectra of erythrocyte membranes was inversely correlated with the plasma NO metabolite level, which indicated that the lower membrane fluidity of erythrocytes was associated with the lower plasma NO level in postmenopausal women. These results are consistent with the hypothesis that NO may have a crucial role in the regulation of membrane fluidity of erythrocytes in postmenopausal women.

Inhibition of nuclear translocation of transcription factor nuclear factor-kappa B induces FAS- as well as tumour necrosis factor-alpha-mediated apoptosis through downregulation of a conserved family of inhibitor of apoptosis 1

1. In the present study, we examined whether the nuclear transcription factor (NF)-kappaB activity plays a role in the determination of sensitivity to tumour necrosis factor (TNF)-alpha or agonistic Fas antibody (Ab) in human vascular smooth muscle cells (hVSMC). 2. To inhibit agonist-induced NF-kappaB activation in hVSMC, a cell-permeable peptide (SN50), which carried the nuclear localization sequence of the NF-kappaB p50 subunit, was used. Nuclear factor-kappaB activity was examined by both immunoblot analysis of nuclear extracts and by ELISA. The hVSMC were treated with TNF-alpha or agonistic Fas Ab (CH11) and then apoptosis was determined by cell death ELISA for DNA fragmentation. To investigate the mechanisms for protection against apoptosis in hVSMC, we analysed the expression of a conserved family of inhibitor of apoptosis 1 (c-IAP1) protein using immunoblot analysis. 3. Although both CH11 and TNF-alpha alone failed to induce hVSMC death in the presence of SN50, they markedly increased the apoptotic hVSMC estimated by cell death ELISA. In addition, these effects could be blocked with the pan-caspase inhibitor z-VAD.fmk. Western blotting analysis indicated that TNF-alpha alone increased c-IAP1 protein levels, whereas CH11 alone had no effect. Inhibition of NF-kappaB activation by SN50 suppressed c-IAP1 protein expression and enhanced apoptosis induced by either TNF-alpha or CH11. 4. These findings suggest that c-IAP1 is an important intracellular modulator of Fas as well as TNF-alpha death signalling pathways in hVSMC. The expression of c-IAP1 is regulated by a NF-kappaB-mediated phenomenon.

Molecular mechanism of emotional stress-induced and catecholamine-induced heart attack

Emotional or physical stress triggers 'tako-tsubo' cardiomyopathy or 'transient left ventricular apical ballooning', but the pathogenesis is unclear. In response to the immobilization stress of rats, a useful model of emotional stress, rapid activation of p44/p42 mitogen-activated protein kinase was observed in the heart, followed by a transient upregulation of immediate early genes in the smooth muscle cells of coronary arteries, the endothelial cells and the myocardium. Heat shock protein 70 was induced in the aortic and coronary arterial smooth muscle cells and in the myocardium. Natriuretic peptide genes were also upregulated in the myocardium. Sequential gene expression can be considered as an adaptive response to emotional stress. Blocking of both alpha-adrenoceptors and beta-adrenoceptors eliminated the upregulation of immediate early genes induced by stress, while alpha-agonists and beta-agonists upregulated immediate early genes in the perfused heart. Activation of alpha-adrenoceptors and beta-adrenoceptors is the primary trigger of emotional stress-induced molecular changes in the heart.

Role of protein kinase C in the regulation of acetylcholine release in the central nervous system of spontaneously hypertensive rats

Previous studies have shown that the central cholinergic nervous system may be involved in blood pressure control. In the present study, we investigated the role of protein kinase C in the regulation of cholinergic nervous activity in the central nervous system in hypertension. In superfused slices of the striatum obtained from spontaneously hypertensive rats and age-matched Wistar-Kyoto rats, we examined the effects of the protein kinase C inhibitor H-7 on the release of [3H]-acetylcholine in vitro. The stimulation-evoked [3H]-acetylcholine release was not different between spontaneously hypertensive rats and Wistar-Kyoto rats. The protein kinase C inhibitor H-7 reduced the stimulation-evoked [3H]-acetylcholine release to a greater extent in spontaneously hypertensive rats than in Wistar-Kyoto rats. The results of the present study showed that the enhanced calcium-protein kinase C system might actively participate in the regulation of cholinergic nervous activity in the central nervous system in hypertension.

Oxidized low density lipoprotein potentiation of Fas-induced apoptosis through lectin-like oxidized-low density lipoprotein receptor-1 in human umbilical vascular endothelial cells

Under normal conditions, vascular endothelial cells are resistant to Fas-mediated apoptosis, although they express detectable Fas on their cell surface. Because oxidized Low density lipoprotein (Ox-LDL) is thought to promote atherogenesis, the potential role that Ox-LDL may play in Fas-mediated apoptosis was investigated in human umbilical vascular endothelial cells (HUVECs), focusing particularly on the involvement of the lectin-like Ox-LDL receptor-1 (LOX-1). HUVECs were treated with agonistic anti-Fas antibody (CH11) and Ox-LDL and then the degree of apoptosis was determined by cell death ELISA. Ox-LDL concentration-dependently sensitized Fas-mediated apoptosis. Flow cytometry demonstrated that Ox-LDL dose-dependently up-regulated cell surface Fas expression. On the other hand, treating HUVECs with Ox-LDL did not lead to any significant change in the expression of death mediators, including Fas, Fas ligand (FasL), FADD, and FLICE as assessed by multiplex polymerase chain reaction amplification. More importantly, these effects of Ox-LDL on Fas-mediated apoptosis were significantly blocked by a neutralizing LOX-1 monoclonal antibody, which can block LOX-1-mediated cellular uptake of Ox-LDL. Ox-LDL may be an important factor involved in the regulation of Fas-induced apoptosis via Ox-LDL/LOX-1 interaction in vascular endothelial cells. The results may provide insights into the pathogenesis of accelerated atherosclerosis in patients with hyperlipidemia.

Effect of oestrone on membrane fluidity of erythrocytes is mediated by a nitric oxide-dependent pathway: An electron paramagnetic resonance study

1. It has been recognized that hormone replacement therapy (HRT) may have a beneficial effect on protection against cardiovascular diseases. Oestrone is the major component of conjugated equiline oestrogens, which are commonly used in HRT. The present study was performed in order to investigate the effects of oestrone on the membrane fluidity of erythrocytes by means of an electron paramagnetic resonance (EPR) and spin-labelling method. 2. In an in vitro study, oestrone significantly decreased the order parameter (S) for 5-nitroxide stearate (5-NS) and the peak height ratio (ho/h-1) for 16-nitroxide stearate (16-NS) obtained from EPR spectra of erythrocyte membranes. This finding indicated that oestrone may increase the membrane fluidity and improve the membrane microviscosity of erythrocytes. 3. The effect of oestrone was significantly potentiated by the nitric oxide (NO) donor s-nitroso-N-acetylpenicillamine and the cGMP analogue 8-bromo-cGMP. 4. In contrast, the change in membrane fluidity induced by oestrone was antagonized by the NO synthase inhibitors NG-nitro-l-arginine methyl ester and asymmetric dimethyl-l-arginine. 5. The results of the present study show that oestrone significantly increases membrane fluidity and improves the rigidity of cell membranes, which is partially mediated by a NO- and cGMP-dependent pathway. Furthermore, the data may be consistent with the hypothesis that oestrone could have a beneficial effect on the rheological behaviour of erythrocytes and have a crucial role in the regulation of the microcirculation.

Acute effect of endothelin AB antagonist on sympathetic outflow in conscious rats with heart failure

Although ET-1 antagonists have been beneficial in the treatment of heart failure (HF), their involvement in the effect on the sympathetic nervous system in HF remains unknown. The present study investigated the role of endogenous endothelin (ET) in the sympathetic nervous system in HF by observing the effect of ET AB antagonist (TAK-044) on renal sympathetic nerve activity (RSNA) in conscious rats with HF (n = 7). HF was induced by left coronary artery ligation and 6 weeks later, TAK-044 was intravenously administered in the conscious and freely moving rats. RSNA, mean arterial pressure (MAP) and heart rate were compared with rats with sham operations (sham; n = 7). MAP was significantly decreased in both groups; however, RSNA was significantly decreased only in the HF group at 5 min after administration, and this change continued until 10 min. There was also an effect of TAK-044 on the arterial baroreflex function indicated by the slope of RSNA to the changes in MAP during phenylephrine and nitroprusside injection in both groups. Compared with the sham group, the HF group showed impaired arterial baroreflex control of RSNA during phenylephrine injection, and intravenous administration of TAK-044 normalized this abnormality, whereas the function in the sham group was not changed. These data show that ET AB antagonist suppressed renal sympathetic activity in rats with HF, and improved arterial baroreflex function. The beneficial effect of endothelin antagonist on heart failure may involve improvement of the increased sympathoexcitation and impaired arterial baroreflex function in HF.