Angiotensin II inhibits endothelial cell motility through an AT1-dependent oxidant-sensitive decrement of nitric oxide availability

Lipotoxicity-Related Hematological Disorders in Obesity

Lipotoxicity can mediate endothelial dysfunction in obesity. Altered endothelial cell phenotype during the pathobiological course of the lipotoxicity may lead to hemostatic abnormalities, which is a hallmark of several hematological disorders. Impaired hemostasis could also be directly related to numerous metabolic diseases such as hypertension, diabetes, and atherosclerosis. On the other hand, the local hematopoietic bone marrow (BM) renin-angiotensin system (RAS) contributes to the development of atherosclerosis via acting on the lipotoxicity processes. Local BM RAS, principally an autocrine/paracrine/intracrine hematological system, is located at the crossroads of cellular regulation, molecular interactions, and lipotoxicity-mediated vascular endothelial dysfunction. The positive regulatory role of plasma LDL on AT1 receptor-mediated hematopoietic stem cell (HSC) differentiation and the production of pro-atherogenic monocytes have been described. LDL-regulated HSC function may explain in part hypercholesterolemia-induced inflammation as well as the anti-inflammatory and anti-atherosclerotic effects of AT1 receptor blockers. The role of local adipose tissue RAS is directly related to the pathogenesis of metabolic derangements in obesity. There may be a crosstalk between local BM RAS and local adipose tissue RAS at the genomics and transcriptomics levels. This chapter aims to review hematological alterations propagating the pathological influences of lipotoxicity on the vascular endothelium.

Dysregulated miRNAs network in the critical COVID-19: An important clue for uncontrolled immunothrombosis/thromboinflammation

Known as a pivotal immunohemostatic response, immunothrombosis is activated to restrict the diffusion of pathogens. This beneficial intravascular defensive mechanism represents the close interaction between the immune and coagulation systems. However, its uncontrolled form can be life-threatening to patients with the critical coronavirus disease 2019 (COVID-19). Hyperinflammation and ensuing cytokine storm underlie the activation of the coagulation system, something which results in the provocation of more immune-inflammatory responses by the thrombotic mediators. This vicious cycle causes grave clinical complications and higher risks of mortality. Classified as an evolutionarily conserved family of the small non-coding RNAs, microRNAs (miRNAs) serve as the fine-tuners of genes expression and play a key role in balancing the pro/anticoagulant and pro-/anti-inflammatory factors maintaining homeostasis. Therefore, any deviation from their optimal expression levels or efficient functions can lead to severe complications. Despite their extensive effects on the molecules and processes involved in uncontrolled immunothrombosis, some genetic agents and uncontrolled immunothrombosis-induced interfering factors (e.g., miRNA-single nucleotide polymorphysms (miR-SNPs), the complement system components, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, and reactive oxygen species (ROS)) have apparently disrupted their expressions/functions. This review study aims to give an overview of the role of miRNAs in the context of uncontrolled immunothrombosis/thromboinflammation accompanied by some presumptive interfering factors affecting their expressions/functions in the critical COVID-19. Detecting, monitoring, and resolving these interfering agents mafy facilitate the design and development of the novel miRNAs-based therapeutic approaches to the reduction of complications incidence and mortality in patients with the critical COVID-19.

Transcriptomics of angiotensin II-induced long noncoding and coding RNAs in endothelial cells

OBJECTIVE

Angiotensin II (Ang II)-induced endothelial dysfunction plays an important role in the pathogenesis of cardiovascular diseases such as systemic hypertension, cardiac hypertrophy and atherosclerosis. Recently, long noncoding RNAs (lncRNAs) have been shown to play an essential role in the pathobiology of cardiovascular diseases; however, the effect of Ang II on lncRNAs and coding RNAs expression in endothelial cells has not been evaluated. Accordingly, we sought to evaluate the expression profiles of lncRNAs and coding RNAs in endothelial cells following treatment with Ang II.

METHODS

Human umbilical vein endothelial cells (HUVECs) were cultured and treated with Ang II (10-6 mol/l) for 24 h. The cells were then profiled for the expression of lncRNAs and mRNAs using the Arraystar Human lncRNA Expression Microarray V3.0.

RESULTS

In HUVECs following Ang II treatment, from a total of 30 584 lncRNA targets screened, 25 targets were significantly upregulated, while 69 were downregulated. In the same HUVECs samples, from 26 106 mRNA targets screened, 28 targets were significantly upregulated and 67 were downregulated. Of the differentially expressed lncRNAs, RP11-354P11.2 and RP11-360F5.1 were the most upregulated (11-fold) and downregulated (three-fold) lncRNAs, respectively. Assigning the differentially regulated genes into functional groups using bioinformatics reveals numerous genes involved in the nucleotide excision repair and ECM-receptor interaction.

CONCLUSION

This is the first study to profile the Ang II-induced differentially expressed lncRNAs and mRNAs in human endothelial cells. Our results reveal novel targets and substantially extend the list of potential candidate genes involved in Ang II-induced endothelial dysfunction and cardiovascular diseases.

Alisol A 24-acetate protects oxygen-glucose deprivation-induced brain microvascular endothelial cells against apoptosis through miR-92a-3p inhibition by targeting the B-cell lymphoma-2 gene

CONTEXT

Alisol A 24-acetate has been used to treat vascular diseases. However, the underlying mechanisms still remain unclear.

OBJECTIVE

The present study evaluated the antiapoptotic effect of alisol A 24-acetate on brain microvascular endothelial cells (BMECs) and explored the underlying mechanisms.

MATERIALS AND METHODS

BMECs were injured through oxygen -glucose deprivation (OGD) after alisol A 24-acetate treatment. Cell viability and half-maximal inhibitory concentration (IC₅₀) were measured using CCK-8, whereas inflammatory factors and oxidative stress indicators were measured using enzyme linked immunosorbent assay. Cell invasion and wound healing assays were detected. Cell apoptosis was assessed using flow cytometry. B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X (Bax) expression were analyzed using Western blotting. Dual-luciferase assay was applied to detect target genes of miR-92a-3p.

RESULT

Alisol A 24-acetate had an IC₅₀ of 98.53 mg/L and inhibited cell viability at concentrations over 50mg/L. OGD induced apoptosis and promoted miR-92a-3p overexpression in BMECs. However, alisol A 24-acetate treatment suppressed inflammation, improved migration and invasion abilities, increased Bcl-2 expression, inhibited Bax expression, and repressed apoptosis and miR92a-3p overexpression in OGD-induced BMECs. MiR-92a-3p overexpression promoted cell apoptosis and suppressed Bcl-2 expression, whereas its inhibitor reversed the tendency. Alisol A 24-acetate treatment relieved the effects of miR-92a-3p overexpression. Dual-luciferase assay confirmed that miR-92a-3p negatively regulated the Bcl-2 expression.

CONCLUSIONS

These findings suggest that alisol A 24-acetate exerts antiapoptotic effects on OGD-induced BMECs through miR-92a-3p inhibition by targeting the Bcl-2 gene, indicating its potential for BMECs protection and as a novel therapeutic agent for the treatment of cerebrovascular disease.

Inhibition of Rac1 GTPase Decreases Vascular Oxidative Stress, Improves Endothelial Function, and Attenuates Atherosclerosis Development in Mice

Aims: Oxidative stress and inflammation contribute to atherogenesis. Rac1 GTPase regulates pro-oxidant NADPH oxidase activity, reactive oxygen species (ROS) formation, actin cytoskeleton organization and monocyte adhesion. We investigated the vascular effects of pharmacological inhibition of Rac1 GTPase in mice.

Methods and Results: We treated wild-type and apolipoprotein E-deficient (ApoE^−/−) mice with Clostridium sordellii lethal toxin (LT), a Rac1 inhibitor, and assessed vascular oxidative stress, expression and activity of involved proteins, endothelial function, macrophage infiltration, and atherosclerosis development. LT-treated wild-type mice displayed decreased vascular NADPH oxidase activity and ROS production. Therapeutic LT doses had no impact on behavior, food intake, body weight, heart rate, blood pressure, vascular and myocardial function, differential blood count, and vascular permeability. ApoE^−/− mice were fed a cholesterol-rich diet and were treated with LT or vehicle. LT treatment led to decreased aortic Rac1 GTPase activity, NADPH oxidase activity and ROS production, but had no impact on expression and membrane translocation of NADPH oxidase subunits and RhoA GTPase activity. LT-treated mice showed improved aortic endothelium-dependent vasodilation, attenuated atherosclerotic lesion formation and reduced macrophage infiltration of atherosclerotic plaques. Concomitant treatment of cholesterol-fed ApoE^−/− mice with LT, the specific synthetic Rac1 inhibitor NSC 23766 or simvastatin comparably reduced aortic Rac1 activity, NADPH oxidase activity, oxidative stress, endothelial dysfunction, atherosclerosis development, and macrophage infiltration.

Conclusions: These findings identify an important role of the small GTPase Rac1 in atherogenesis and provide a potential target for anti-atherosclerotic therapy.

Effects of direct high sodium exposure at endothelial cell migration

The present study aimed to test the hypothesis that high sodium affects the migratory phenotype of endothelial cells (EC) and investigates mechanisms involved independently of hemodynamic factors. Cell migration was evaluated by Wound-Healing at conditions: High Sodium (HS; 160 mM) and Control (CT; 140 mM). O₂^- production was evaluated by DHE. NADPH oxidase activity was determined by chemiluminescence assay. Expression of adhesion molecules was analyzed by RT-PCR. Shear Stress was performed using a rhythmic shake. Nitric oxide production was measured by Griess reaction. HS-induced impairment in EC migration while both Candesartan and DPI prevented it. HS increased NADPH oxidase activity, which was blocked by Candesartan. Also, HS increased O₂^- production that was inhibited by Candesartan. HS decreased adhesion molecules expression via ROS (Integrin Alpha 5, Integrin Beta 1, Integrin Beta 3, VE-Cadherin and PECAM) and via AT1R (PECAM). The nitric oxide production induced by shear stress was decreased after EC exposure to HS while both Candesartan and DPI prevented it. Conclusion: This study demonstrated that HS reduced EC migration by AT1R and ROS derived from NADPH Oxidase and mitochondria. The HS reduction in adhesion molecules expression modulated by ROS and AT1R may help to explain the impairment in migration capacity. Also, HS affected EC functionality by reducing their nitric oxide production in response to shear stress.

Inorganic polyphosphate induces accelerated tube formation of HUVEC endothelial cells

In this study, the effect of inorganic polyphosphate (polyP) on the initial phase of angiogenesis and vascularization was investigated, applying the HUVEC cell tube formation assay. PolyP is a physiological and high energy phosphate polymer which has been proposed to act as a metabolic fuel in the extracellular space with only a comparably low ATP content. The experiments revealed that polyP accelerates tube formation of human umbilical vein endothelial cells (HUVEC), seeded onto a solidified basement membrane extract matrix which contains polyP-metabolizing alkaline phosphatase (ALP) activity. This effect is abolished by co-addition of apyrase, which degrades ATP to AMP and inorganic phosphate. The assumption that ATP, derived from polyP, activates HUVEC cells leading to tube formation was corroborated by experiments showing that addition of polyP to the cells causes a strong rise of ATP level in the culture medium. Finally, we show that at a later stage of cultivation of HUVEC cells, after 3 d, polyP causes a strong enhancement of the expression of the genes encoding for the two major matrix metalloproteinases (MMPs) released by endothelial cells during tube formation, MMP-9 and MMP-2. This stimulatory effect is again abrogated by addition of apyrase together with polyP. From these results, we propose that polyP is involved either directly or indirectly in energy supply, via ALP-mediated transfer of energy-rich phosphate under ATP formation. This ATP is utilized for the activation and oriented migration of endothelial cells and for the matrix organization during the initial phases of tube formation.

A Proteomic Approach Identifies Candidate Early Biomarkers to Predict Severe Dengue in Children

BACKGROUND

Severe dengue with severe plasma leakage (SD-SPL) is the most frequent of dengue severe form. Plasma biomarkers for early predictive diagnosis of SD-SPL are required in the primary clinics for the prevention of dengue death.

METHODOLOGY

Among 63 confirmed dengue pediatric patients recruited, hospital based longitudinal study detected six SD-SPL and ten dengue with warning sign (DWS). To identify the specific proteins increased or decreased in the SD-SPL plasma obtained 6-48 hours before the shock compared with the DWS, the isobaric tags for relative and absolute quantification (iTRAQ) technology was performed using four patients each group. Validation was undertaken in 6 SD-SPL and 10 DWS patients.

PRINCIPAL FINDINGS

Nineteen plasma proteins exhibited significantly different relative concentrations (p<0.05), with five over-expressed and fourteen under-expressed in SD-SPL compared with DWS. The individual protein was classified to either blood coagulation, vascular regulation, cellular transport-related processes or immune response. The immunoblot quantification showed angiotensinogen and antithrombin III significantly increased in SD-SPL whole plasma of early stage compared with DWS subjects. Even using this small number of samples, antithrombin III predicted SD-SPL before shock occurrence with accuracy.

CONCLUSION

Proteins identified here may serve as candidate predictive markers to diagnose SD-SPL for timely clinical management. Since the number of subjects are small, so further studies are needed to confirm all these biomarkers.

Angiotensin-converting-enzyme inhibition counteracts angiotensin II-mediated endothelial cell dysfunction by modulating the p38/SirT1 axis

OBJECTIVE

Oxidative stress has been linked to endothelial dysfunction and angiotensin II stimulates the reactive oxygen species production contributing to several cardiovascular diseases. We have studied the chain of events induced by angiotensin-converting-enzyme (ACE) activation in vascular umbilical vein endothelial cells (HUVECs) by using an ACE inhibitor such as zofenoprilat.

METHODS

We used specific assay to measure the superoxide anion production, tetrazolium bromide (MTT) assay for cell viability, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay for cell apoptosis, and western blot for protein analysis in the study.

RESULTS

Zofenoprilat counteracts the superoxide anion production and cell apoptosis induced by angiotensin I treatment by blocking the extrinsic caspase cascade, NF-kB and p38 activation. p38 inhibitor SB203580 reverted the angiotensin II oxidant effects while the p38 constitutively activation, by MKK6 transfection, abrogated the zofenoprilat effects. Characterizing the zofenoprilat downstream effector we found that zofenoprilat reverted the SirT-1 downregulation induced by angiotensin II. p38 activation by angiotensin II was strictly correlated with SirT1 protein downregulation; SB203580 significantly prevented SirT1 downregulation induced by angiotensin II while the p38 constitutive activation abolished SIRT1 protein basal levels. p38 directly bound SirT1 sequestering it in the cytoplasm. SirT1 inhibition by sirtinol annulled zofenoprilat action while SirT1 overexpression reverted the cytotoxic effects of angiotensin II. Finally, zofenoprilat negatively controlled angiotensin I receptor protein expression through SirT1.

CONCLUSION

The p38-SirT1 axis is found markedly relevant in modulating the cardiovascular benefit deriving from ACE-inhibitors and might represent a novel target for innovative drugs in cardiovascular prevention.

Angiotensin-(1-7) treatment ameliorates angiotensin II-induced apoptosis of human umbilical vein endothelial cells

Angiotensin (Ang)-(1-7), a metabolite of AngI and AngII, is a counter-regulatory mediator of AngII. In the present study, we investigated the effects of Ang-(1-7) on AngII-induced apoptosis in human umbilical vein endothelial cells (HUVEC). To this end, HUVEC were pretreated with 10(-9), 10(-8), 10(-7) or 10(-6) mol/L Ang-(1-7) at for 30 min before being stimulated with 10(-6) mol/L Ang-II for another 24 h. Acridine orange/ethidium bromide and propidium iodide staining were used to analyse the effects of Ang-(1-7) on AngII-induced apoptosis. Alone, 10(-6) mol/L Ang-(1-7) had no effect on the apoptosis of HUVEC following exposure of cells for 30 min, whereas AngII (10(-6) mol/L, 24 h) significantly enhanced the number of apoptotic cells (P < 0.01). The AngII-induced apoptosis of HUVEC was suppressed by 10(-9)-10(-6) mol/L Ang-(1-7). The anti-apoptotic effects of Ang-(1-7) were almost completely abolished by A-779 (10(-6) mol/L, 30 min), a specific Mas receptor antagonist. In addition, Ang-(1-7) inhibited AngII-induced accumulation of cleaved caspase 3 and enhanced the expression of the anti-apoptotic factor Bcl-2 at both the mRNA and protein levels. Angiotensin II upregulated the expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), which is involved in endothelial apoptosis, at both the mRNA and protein levels. This effect was blocked by Ang-(1-7) in a concentration-dependent manner, although A-779 almost completely reversed Ang-(1-7)-mediated inhibition of AngII-induced upregulation of LOX-1. Silencing of LOX-1 using short interference RNA enhanced the protective effects of Ang-(1-7) against AngII-induced apoptosis in HUVEC. Together, the results suggest that Ang-(1-7) ameliorates AngII-induced apoptosis of HUVEC at least in part by suppressing LOX-1 expression.

(-)-Epicatechin rich cocoa mediated modulation of oxidative stress regulators in skeletal muscle of heart failure and type 2 diabetes patients

BACKGROUND

Type 2 diabetes (T2D) and heart failure (HF) are associated with high levels of skeletal muscle (SkM) oxidative stress (OS). Health benefits attributed to flavonoids have been ascribed to antioxidation. However, for flavonoids with similar antioxidant potential, end-biological effects vary widely suggesting other mechanistic venues for reducing OS. Decreases in OS may follow the modulation of key regulatory pathways including antioxidant levels (e.g. glutathione) and enzymes such as mitochondrial superoxide dismutase (SOD2) and catalase.

METHODS

We examined OS-related alterations in SkM in T2D/HF patients (as compared vs. healthy controls) and evaluated the effects of three-month treatment with (-)-epicatechin (Epi) rich cocoa (ERC). To evidence Epi as the mediator of the improved OS profile we examined the effects of pure Epi (vs. water) on SkM OS regulatory systems in a mouse model of insulin resistance and contrasted results vs. normal mice.

RESULTS

There were severe alterations in OS regulatory systems in T2D/HF SkM as compared with healthy controls. Treatment with ERC induced recovery in glutathione levels and decreases in the nitrotyrosilation and carbonylation of proteins. With treatment, key transcriptional factors translocate into the nucleus leading to increases in SOD2 and catalase protein expression and activity levels. In insulin resistant mice, there were alterations in muscle OS and pure Epi replicated the beneficial effects of ERC found in humans.

CONCLUSIONS

Major perturbations in SkM OS can be reversed with ERC in T2D/HF patients. Epi likely mediates such effects and may provide an effective means to treat conditions associated with tissue OS.

Angiotensin-II and MARCKS: a hydrogen peroxide- and RAC1-dependent signaling pathway in vascular endothelium

MARCKS is an actin-binding protein that modulates vascular endothelial cell migration and cytoskeleton signaling (Kalwa, H., and Michel, T. (2011) J. Biol. Chem. 286, 2320-2330). Angiotensin-II is a vasoactive peptide implicated in vascular physiology as well as pathophysiology; the pathways connecting angiotensin-II and cytoskeletal remodeling are incompletely understood. Here we show that MARCKS is expressed in intact arterial preparations, with prominent staining of the endothelium. In endothelial cells, angiotensin-II-promoted MARCKS phosphorylation is abrogated by PEG-catalase, implicating endogenous H(2)O(2) in the angiotensin-II response. Studies using the H(2)O(2) biosensor HyPer2 reveal that angiotensin-II promotes increases in intracellular H(2)O(2). We used a Rac1 FRET biosensor to show that angiotensin-II promotes Rac1 activation that is attenuated by PEG-catalase. siRNA-mediated Rac1 knockdown blocks angiotensin-II-stimulated MARCKS phosphorylation. Cell imaging studies using a phosphoinositide 4,5-bisphosphate (PIP(2)) biosensor revealed that angiotensin-II PIP(2) regulation depends on MARCKS and H(2)O(2). siRNA-mediated knockdown of MARCKS or Rac1 attenuates receptor-mediated activation of the tyrosine kinase c-Abl and disrupts actin fiber formation. These studies establish a critical role for H(2)O(2) in angiotensin-II signaling to the endothelial cytoskeleton in a novel pathway that is critically dependent on MARCKS, Rac1, and c-Abl.

HDAC4 mediates development of hypertension via vascular inflammation in spontaneous hypertensive rats

Histone deacetylases (HDACs) are transcriptional corepressors. Our recent study demonstrated that HDAC4 protein specifically increases in mesenteric artery from spontaneous hypertensive rats (SHR) compared with Wistar Kyoto rats (WKY). Vascular inflammation is important for pathogenesis of hypertension. We examined whether HDAC4 affects vascular inflammatory responses and promotes hypertension. In vivo, blood pressure, reactive oxygen species (ROS) production, and VCAM-1 expression in isolated mesenteric artery were elevated in young SHR (7 wk old) compared with age-matched WKY, which were prevented by long-term treatment of SHR with an HDACs inhibitor, trichostatin A (TSA; 500 μg·kg−1·day−1 for 3 wk). In isolated mesenteric artery, the increased angiotensin II-induced contraction in SHR was reversed by TSA. The endothelium-dependent relaxation induced by ACh in SHR was augmented by TSA. In cultured rat mesenteric arterial smooth muscle cells (SMCs), expression of HDAC4 mRNA and protein was increased by TNF-α (10 ng/ml). TSA (10 μM, pretreatment for 30 min) inhibited VCAM-1 expression and NF-κB phosphorylation induced by TNF (10 ng/ml, 24 h or 20 min) in SMCs. HDAC4 small interfering RNA inhibited TNF-induced monocyte adhesion, VCAM-1 expression, transcriptional activity of NF-κB, and ROS production in SMCs. The present results demonstrated that proinflammatory effects of HDACs may mediate the further development of hypertension in SHR. It is also suggested in cultured vascular SMCs that TNF-induced HDAC4 mediates vascular inflammation likely via VCAM-1 induction through ROS-dependent NF-κB activation.

Amlodipine treatment prevents angiotensin II-induced human umbilical vein endothelial cell apoptosis

BACKGROUND AND AIMS

Amlodipine, a long-acting dihydropyridine calcium channel blocker, is able to improve angiotensin II-mediated vascular endothelial dysfunction. However, the underlying mechanism remains not fully understood. In the present study we attempted to determine whether the protective effect of amlodipine against Ang II-induced endothelial impairment was mediated through blockage of endothelial cell apoptosis.

METHODS

We pretreated human umbilical venous endothelial cells with increasing doses of amlodipine (10(-8)-10(-6) M) followed by the addition of Ang II. Cell apoptosis was assessed by acridine orange/ethidium bromide staining and by annexin-V/propidium iodide double-labeled cytometry. The involvement of the apoptosis regulators, Bcl-2, Bax, and lectin-like oxidized low-density lipoprotein receptor-1, was determined.

RESULTS

Pretreatment with amlodipine resulted in a dose-dependent suppression of Ang II-induced HUVEC apoptosis. Moreover, the Bcl-2/Bax ratio was found to be increased in cells pretreated with amlodipine, indicating an enhanced anti-apoptosis potential. Additionally, the induction of LOX-1 by Ang II was remarkably counteracted by the pre-exposure to amlodipine.

CONCLUSIONS

Our data demonstrate that amlodipine ameliorates Ang II-induced endothelial apoptosis, which is likely associated with the elevation of Bcl-2/Bax ratio and reduction of the LOX-1 expression.

Local bone marrow Renin-Angiotensin system and atherosclerosis

Local hematopoietic bone marrow (BM) renin-angiotensin system (RAS) affects the growth, production, proliferation differentiation, and function of hematopoietic cells. Angiotensin II (Ang II), the dominant effector peptide of the RAS, regulates cellular growth in a wide variety of tissues in pathobiological states. RAS, especially Ang II and Ang II type 1 receptor (AT1R), has considerable proinflammatory and proatherogenic effects on the vessel wall, causing progression of atherosclerosis. Recent investigations, by analyzing several BM chimeric mice whose BM cells were positive or negative for AT1R, disclosed that AT1R in BM cells participates in the pathogenesis of atherosclerosis. Therefore, AT1R blocking not only in vascular cells but also in the BM could be an important therapeutic approach to prevent atherosclerosis. The aim of this paper is to review the function of local BM RAS in the pathogenesis of atherosclerosis.

Role of nitric oxide and reactive oxygen species in the pathogenesis of preeclampsia

AIM

Preeclampsia is characterized by a disruption of general vascular dilatation, which is mainly mediated by nitric oxide (NO) and disturbed by reactive oxygen species (ROS). The present study investigated the roles of NO and ROS in the pathogenesis of preeclampsia.

METHODS

Serum samples were obtained prospectively. Serum levels of NO(2)/NO(3) (NOx) and creatol (CTL), the oxidized metabolite of creatine, and flow-mediated dilatation (FMD) of brachial artery were measured in normal pregnant women and preeclamptic patients. To evaluate the effect of circulating factors that control vascular function NO synthase (NOS) and NAD(P)H oxidase mRNA expression was evaluated in cultured human umbilical vein endothelial cells using reverse transcriptase polymerase chain reaction.

RESULTS

Serum NOx concentration was decreased and CTL concentration was increased in preeclamptic patients relative to healthy controls during the first trimester of pregnancy. Further, preeclamptic patients exhibited disrupted FMD, which was regulated in part by NO. Immunohistochemistry demonstrated strong expression of nitrotyrosine in the vasculature of preeclamptic placentas. Treatment with sera derived from preeclamptic patients increased endothelial expression of inducible NOS (iNOS) mRNA, and this increase was inhibited by angiotensin II (Ang II) receptor type 2 (AT2) blocker. Endothelial NAD(P)H oxidase subunit gp91(phox) expression was increased by treatment with sera from preeclamptic patients and this increase was attenuated by Ang II receptor type 1 (AT1) blocker.

CONCLUSION

The present findings suggest that NO and ROS play important roles in the pathogenesis of preeclampsia and that these roles involve Ang II.

Hemorrhagic shock activates lung endothelial reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase via neutrophil NADPH oxidase

The vascular endothelium plays an important role in the regulation of inflammatory responses after trauma and hemorrhage. Interactions of neutrophils with endothelial cells (ECs) contribute to the activation of specific EC responses involved in innate immunity. We have previously reported that oxidants derived from the neutrophil reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is a critical regulator to EC activation. Our objective was to test the role of neutrophil NADPH oxidase-derived oxidants in mediating and enhancing hemorrhagic shock (HS)-induced activation of lung endothelial NADPH oxidase. Mice were subjected to HS and neutrophil depletion. The mice were also replenished with the neutrophil from NADPH oxidase-deficient mice. The resultant activation of lung NADPH oxidase was analyzed. The in vivo studies were also recapitulated with in vitro neutrophil-EC coculture system. HS induces NADPH oxidase activation in neutrophils and lung through high-mobility group box 1/Toll-like receptor 4-dependent signaling. In neutropenic mice, shock-induced NADPH oxidase activation in the lung was reduced significantly, but was restored upon repletion with neutrophils obtained from wild-type mice subjected to shock, but not with neutrophils from shock mice lacking the gp91(phox) subunit of NADPH oxidase. The findings were recapitulated in mouse lung vascular ECs cocultured with neutrophils. The data further demonstrate that neutrophil-derived oxidants are key factors mediating augmented High mobility group box 1 (HMGB1)-induced endothelial NADPH oxidase activation through a Rac1-dependent, but p38 mitogen-activated protein kinase-independent, pathway. Oxidant signaling by neutrophil NADPH oxidase is an important determinant of activation of endothelial NADPH oxidase after HS.

Akt downregulation by flavin oxidase-induced ROS generation mediates dose-dependent endothelial cell damage elicited by natural antioxidants

High intake of natural antioxidants (NA) from plant-derived foods and beverages is thought to provide cardiovascular benefits. The endothelium plays a pivotal role in cardiovascular homeostasis, and for this reason, the molecular events resulting from NA actions on endothelial cells (ECs) are actively investigated. Here, we show the direct impact of two NA, coumaric acid and resveratrol, on intracellular reactive oxygen species levels, protein carbonylation, and cell physiology in human ECs. While at lower doses, both NA promoted antioxidant effects, at moderately high doses, NA elicited a dose-dependent pro-oxidant effect, which was followed by apoptosis, cell damage, and phospho-Akt downregulation. NA-induced pro-oxidant effects were counteracted by N-acetyl cysteine and diphenyleneiodonium (DPI), suggesting a role for flavin oxidases in NA-induced toxicity. DPI also prevented NA-induced phospho-Akt downregulation indicating that Akt can work downstream of flavin oxidases in mediating cellular responses to NA. Stimulation of phospho-Akt by insulin dramatically counteracted NA-induced cell death, an effect abolished by Akt inhibition further suggesting that mechanistically Akt regulates cell survival in response to NA-induced stress. Although further studies are required to better characterize the molecular mechanism of NA-induced cell toxicity, our study is the first to show in a human vascular model that moderately high doses of NA can induce cell damage mediated by flavoproteins and the Akt pathway.

Effects of amlodipine and candesartan on oxidized LDL level in patients with mild to moderate essential hypertension

OBJECTIVE

To compare the effects of amlodipine and candesartan on oxidized low-density lipoprotein (OxLDL), conjugated dienes (CD) and baseline diene conjugation in circulating low-density lipoproteins (LDL-BDC) level during antihypertensive treatment.

METHODS

Forty-nine patients with untreated mild to moderate essential hypertension were recruited in a randomized double-blind study to receive a daily dose either of 8 mg candesartan or 5 mg amlodipine for 16 weeks. Blood pressure, OxLDL, CD, LDL-BDC, triglycerides (TG), total cholesterol and lipoprotein cholesterol were measured at baseline, at week 2 and at week 16.

RESULTS

During treatment, in addition to a significant decrease in systolic and diastolic blood pressure, high level of OxLDL decreased significantly reaching practically upper kit reference values. Both treatment groups were similar with regard to the studied parameters at all time points. At the same time serum TG, lipoprotein and total cholesterol levels as well as LDL-BDC did not change and CD levels did not exceed endemic normal. Decrease in both systolic and diastolic blood pressure was associated with decrease in LDL-BDC/LDL.

CONCLUSIONS

Besides their antihypertensive effects, both candesartan and amlodipine are efficient drugs for reducing OxLDL level, being neutral with regard to serum lipids.

Different effects of angiotensin converting enzyme inhibitors on endothelin-1 and nitric oxide balance in human vascular endothelial cells: evidence of an oxidant-sensitive pathway

Angiotensin converting enzyme inhibitors (ACE-I) are able to reduce the formation of the potent vasoconstrictor endothelin-1 and increase nitric oxide bioavailability in human vascular endothelial cells (HUVECs). We tested the effects of two sulfhydryl-containing ACE-I, zofenoprilat, and captopril, and two nonsulfhydryl containing ACE-I, enalaprilat and lisinopril, on endothelin-1/nitric oxide balance and oxidative stress in HUVECs. All the four tested ACE-I reduced endothelin-1 secretion and increased nitric oxide metabolite production by HUVECs. However, zofenoprilat (−42% after 8 hours of incubation) was more effective (P < .05) than enalaprilat (−25%), lisinopril (−21%), and captopril (−30%) in reducing endothelin-1 secretion. Similarly, zofenoprilat (+110% after 8 hours of incubation) was more effective (P < .05) than enalaprilat (+64%), lisinopril (+63%), and captopril (+65%) in increasing nitric oxide metabolite production. The effect of ACE-I on endothelin-1 and nitric oxide metabolite production is mediated by the activation of bradykinin B₂ receptor being counteracted, at least in part, by a specific antagonist. Zofenoprilat and, to a lesser extent, captopril also reduced oxidative stress in HUVECs. In conclusion, among the four tested ACE-I, zofenoprilat was more effective in improving endothelin-1/nitric oxide balance in HUVECs likely because of its greater antioxidant properties.

Expression of human endothelin-converting enzyme isoforms: role of angiotensin II

A key step in endothelin-1 (ET-1) synthesis is the proteolytic cleavage of big ET-1 by the endothelin-converting enzyme-1 (ECE-1). Four alternatively spliced isoforms, ECE-1a to ECE-1d, have been discovered; however, regulation of the expression of specific ECE-1 isoforms is not well understood. Therefore, we stimulated primary human umbilical vein endothelial cells (HUVECs) with angiotensin II (Ang II). Furthermore, expression of ECE-1 isoforms was determined in internal mammary arteries of patients undergoing coronary artery bypass grafting surgery. Patients had received one of 4 therapies: angiotensin-converting enzyme inhibitors (ACE-I), Ang II type 1 receptor blockers (ARB), HMG-CoA reductase inhibitors (statins), and a control group that had received neither ACE-I, ARB (that is, treatment not interfering in the renin-angiotensin system), nor statins. Under control conditions, ECE-1a is the dominant isoform in HUVECs (4.5+/-2.8 amol/microg RNA), followed by ECE-1c (2.7+/-1.0 amol/microg), ECE-1d (0.49+/-0.17 amol/microg), and ECE-1b (0.17+/-0.04 amol/microg). Stimulation with Ang II did not change the ECE-1 expression pattern or the ET-1 release. We found that ECE-1 mRNA expression was higher in patients treated with statins than in patients treated with ARB therapy (5.8+/-0.76 RU versus 3.0+/-0.4 RU), mainly attributed to ECE-1a. In addition, ECE-1a mRNA expression was higher in patients receiving ACE-I therapy than in patients receiving ARB therapy (1.68+/-0.27 RU versus 0.83+/-0.07 RU). We conclude that ECE-1a is the major ECE-1 isoform in primary human endothelial cells. Its expression in internal mammary arteries can be regulated by statin therapy and differs between patients with ACE-I and ARB therapy.

Tea, flavonoids, and nitric oxide-mediated vascular reactivity

Epidemiological evidence supports the concept that diets rich in fruits and vegetables promote health and attenuate or delay the onset of cardiovascular disease (CVD). Although a variety of factors contribute to the beneficial effects of plant foods, much attention has been addressed to plant polyphenols. In this regard, in the daily Western diet, both black and green teas contribute to a relevant proportion of total phenol intake. The more abundant class of flavonoids that is present in teas is represented by flavanols, i.e., catechin, epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate. Studies using animal models of atherosclerosis indicate that dietary flavonoid consumption delays atherosclerotic plaque development. Accordingly, an inverse association between tea intake and CVD has been demonstrated. Further, flavonoids can reduce endothelial dysfunction, i.e., the key step in the development of atherosclerosis. Concordantly, human data suggest that tea may reduce blood pressure levels. Despite this, although they often show that tea may have cardiovascular protective effects, results from epidemiological studies exploring the association between tea and health are controversial. Conflicting results may be caused by disparate study designs and flavonoid contents in different kinds of tea. Thus, because tea is a popular beverage worldwide, and several studies have shown that it is protective against CVD, further studies are needed to determine the role of tea in primary and secondary cardiovascular prevention.

Nifedipine improves the migratory ability of circulating endothelial progenitor cells depending on manganese superoxide dismutase upregulation

BACKGROUND

Migratory ability of resident endothelial cells and their circulating progenitors, that is endothelial progenitor cells (EPCs), represent a crucial event in vascular repairing processes. Although oxidants are known to counteract the migratory ability of resident endothelial cells, their possible role in modulating EPC motility is unknown. EPCs exhibit stronger resistance to oxidants than mature endothelial cells mainly because of higher expression of manganese (Mn) superoxide dismutase (SOD). As nifedipine is a dihydropyridine calcium antagonist known to enhance MnSOD expression in mature endothelial cells, we investigated the effects of nifedipine on MnSOD expression and motility in EPCs.

METHODS AND RESULTS

EPCs were isolated from peripheral blood of healthy donors and cultured in fibronectin-coated flasks. Nifedipine improved both motility of cultured EPCs (+55% vs. control, P = 0.007) and their adhesion to tumor necrosis factor-alpha-activated mature endothelial cells (+33% vs. control, P = 0.03). Reduction of EPC dichlorofluorescein content (-32% vs. control, P = 0.009) and a parallel increase in nitrite plus nitrate concentration in EPC supernatants (+25% vs. control, P = 0.009) were also observed. The study of SOD showed a nifedipine-dependent upregulation of MnSOD in a time-dependent and dose-dependent manner. MnSOD expression blockade by RNA interference abolished nifedipine effect on EPC motility. Although nifedipine also increased vascular endothelial growth factor (VEGF) release from EPCs, its effect on EPC motility was unaffected by an anti-VEGF antibody.

CONCLUSION

Nifedipine improves EPC motility due to MnSOD upregulation. The capability of this dihydropyridine calcium antagonist to reduce cardiovascular events might also be related to improved EPC function.

Role of combination therapy in the treatment of hypertension: focus on valsartan plus amlodipine

Hypertension control is rare in clinical practice, particularly in high-risk patients. A large factor is therapeutic inertia deriving from poorly prescribed lifestyle changes, excess monotherapy use, and scarce on-treatment modifications. The use of drug combinations significantly improves blood pressure (BP) control; in particular, fixed combinations improve therapy without increasing daily pill intake, thereby favouring patient compliance and therapy continuation. The most widely used fixed combination is based on thiazide diuretics added to either angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs). Several large-scale clinical trials have been conducted showing that these combinations are effective in lowering BP. However, thiazide diuretics can reduce the metabolic benefits derived from renin-angiotensin-aldosterone system (RAAS) inhibitors in high metabolic risk patients. In contrast, ACE inhibitors or ARBs combined with dihydropyridine calcium channel antagonists (DHPCAs) exert a marked antihypertensive effect without decreasing metabolic protection by RAAS blockade. In the recent JIKEI heart study, approximately 60% of patients affected by hypertension, heart failure, coronary heart disease or their combination in the valsartan arm were simultaneously treated with DHPCAs. Of note, a 39% reduction in the primary endpoint of combined morbidity and mortality was reported in the valsartan compared with the non-valsartan arm. Furthermore, in a recent multinational study, 83% of 3161 hypertensive patients treated with valsartan and the DHCPA amlodipine reported a concontrolled BP after 8 weeks of treatment. As expected, amlodipine did not negatively influence the metabolic profile of patients, thereby supporting the role of ARB+DHPCA combinations as effective and promising tools in hypertension treatment. In summary, the combination of ARBs with DHPCAs is an effective strategy in hypertension treatment through synergy between their antihypertensive and vascular protective actions, persistent metabolic benefits deriving from RAAS inhibition, and reduced incidence of side effects.

Taxotere-induced inhibition of human endothelial cell migration is a result of heat shock protein 90 degradation

In addition to effects on tumor cell proliferation and apoptosis, microtubule-binding agents are potent inhibitors of angiogenesis. The cancer chemotherapeutic drug Taxotere (docetaxel) inhibited vascular endothelial growth factor (VEGF)-induced human umbilical vein endothelial cell (HUVEC) migration in vitro at concentrations substantially lower than required to cause cell cycle arrest or apoptosis. Here, we show that Taxotere caused the ubiquitination and subsequent proteasomal degradation of heat shock protein 90 (Hsp90) in HUVEC. This prevented signaling from the focal adhesions and VEGF receptors and inhibited integrin activation. Taxotere prevented the VEGF-induced phosphorylation of focal adhesion kinase, Akt, and endothelial nitric oxide synthase (eNOS), all of which are Hsp90 client proteins. Taxotere completely blocked the VEGF-induced increase in eNOS activity, and the addition of a NO donor reversed the inhibitory effect of Taxotere on VEGF-induced migration. A similar reversal occurred with a proteasomal inhibitor of Hsp90 degradation. Furthermore, overexpression of Hsp90 rescued HUVEC from the inhibition of VEGF-induced migration by Taxotere. Previous studies have suggested that tubulin is also a client protein of Hsp90, and immunocytochemical analysis showed that Taxotere caused the dissociation of Hsp90 from tubulin. We suggest that uncomplexed Hsp90 is more susceptible to ubiquitination and subsequent proteasomal degradation than the bound form. Although inhibitors of Hsp90 are currently under clinical investigation as antitumor agents, this seems to be the first account of a drug that reduces Hsp90 function by enhancing its proteasomal degradation. Further, the loss of Hsp90 and the inactivation of Hsp90 client proteins are previously undescribed actions of Taxotere that may contribute to its antiangiogenic activity.

Angiotensin, bradykinin and the endothelium

Angiotensins and kinins are endogenous peptides with diverse biological actions; as such, they represent current and future targets of therapeutic intervention. The field of angiotensin biology has changed significantly over the last 50 years. Our original understanding of the crucial role of angiotensin II in the regulation of vascular tone and electrolyte homeostasis has been expanded to include the discovery of new angiotensins, their important role in cardiovascular inflammation and the development of clinically useful synthesis inhibitors and receptor antagonists. While less applied progress has been achieved in the kinin field, there are continuous discoveries in bradykinin physiology and in the complexity of kinin interactions with other proteins. The present review focuses on mechanisms and interactions of angiotensins and kinins that deal specifically with vascular endothelium.

Regulation of scavenger receptor class BI gene expression by angiotensin II in vascular endothelial cells

High-density lipoprotein mediates a normal physiological process called reverse cholesterol transport. In this process, a scavenger receptor of the B class (SR-BI)/human homologue of SR-BI, CD36, and LIMPII analogous-1 (hSR-BI/CLA-1) facilitates the cellular uptake of cholesterol from high-density lipoprotein. In endothelial cells, high-density lipoprotein activates endothelial NO synthase via hSR-BI/CLA-1. Angiotensin II (Ang II) is a powerful accelerator of atherosclerosis and modulates the expression of endothelial NO synthase. In the present study, we have examined the role of Ang II on hSR-BI/CLA-1 expression in human umbilical vein endothelial cells. Our results showed that endogenous expression of hSR-BI/CLA-1 was suppressed by exposure to Ang II in human umbilical vein endothelial cells. Administration of the Ang II type-1 receptor blocker olmesartan inhibited Ang II-induced hSR-BI/CLA-1 protein repression. In Ang II-treated cells, high-density lipoprotein had no effect on endothelial NO synthase activation. Ang II decreased transcriptional activity of the hSR-BI/CLA-1 promoter. The inhibitory effect of Ang II on hSR-BI/CLA-1 promoter activity was abrogated by wortmannin and LY294002, specific inhibitors of phosphatidylinositol 3-kinase. Exposure of human umbilical vein endothelial cells to Ang II elicited a rapid phosphorylation of Akt and FoxO1, a known target of Akt signaling. Constitutively active Akt inhibits the activity of the hSR-BI/CLA-1 promoter, and a dominant-negative mutant of Akt or mutagenesis of a FoxO1 response element in the hSR-BI/CLA-1 abolished the ability of Ang II to suppress promoter activity. Together, these results indicate that the phosphatidylinositol 3-kinase/Akt/FoxO1 pathway participates in Ang II suppression of hSR-BI/CLA-1 expression and suggests that the endothelial receptor for hSR-BI/CLA-1 is downregulated by the renin-angiotensin system.

Paracrine and autocrine mechanisms of apelin signaling govern embryonic and tumor angiogenesis

Apelin and its G protein-coupled receptor APJ play important roles in blood pressure regulation, body fluid homeostasis, and possibly the modulation of immune responses. Here, we report that apelin-APJ signaling is essential for embryonic angiogenesis and upregulated during tumor angiogenesis. A detailed expression analysis demonstrates that both paracrine and autocrine mechanisms mark areas of embryonic and tumor angiogenesis. Knockdown studies in Xenopus reveal that apelin-APJ signaling is required for intersomitic vessel angiogenesis. Moreover, ectopic expression of apelin but not vascular endothelial growth factor A (VEGFA) is sufficient to trigger premature angiogenesis. In vitro, apelin is non-mitogenic for primary human endothelial cells but promotes chemotaxis. Epistasis studies in Xenopus embryos suggest that apelin-APJ signaling functions downstream of VEGFA. Finally, we show that apelin and APJ expression is highly upregulated in microvascular proliferations of brain tumors such as malignant gliomas. Thus, our results define apelin and APJ as genes of potential diagnostic value and promising targets for the development of a new generation of anti-tumor angiogenic drugs.

Benefits of candesartan on arterial and renal damage of non-diabetic hypertensive patients treated with calcium channel blockers

BACKGROUND/AIM

Although long-term, intensive blood pressure (BP) control with calcium channel blockers (CCBs) reduced arterial stiffness and renal damage of hypertensive patients, combination therapy with antihypertensive drugs is frequently needed to maintain the intensive BP control. The present study was conducted to examine add-on benefits of candesartan therapy on hypertensive patients treated with CCBs for at least 12 months.

METHODS

Pulse wave velocity (PWV), urinary albumin excretion (UAE), intima-media thickness (IMT) of the carotid arteries, and 24-hour ambulatory BP were determined in 50 non-diabetic hypertensive patients treated with CCBs before and 12 months after the start of therapy with candesartan or placebo.

RESULTS

Candesartan significantly decreased clinic BP and tended to decrease ambulatory BP, but the decreases were similar to those in the placebo group except nocturnal BP decrease, which was significantly enhanced by candesartan. Add-on candesartan significantly decreased PWV and UAE compared to placebo, but IMT was unchanged with candesartan or placebo. The decrease in clinic BP or nocturnal BP decrease did not contribute to the improvement of PWV or UAE.

CONCLUSION

Add-on candesartan functionally improved the stiffened arteries of hypertensive patients treated with CCBs by the end of 12 months of treatment independently of its effects on BPs.

Down-regulation of c-FLIP increases reactive oxygen species, induces phosphorylation of serine/threonine kinase Akt, and impairs motility of cancer cells

The role of c-FLIP in cell motility was investigated using RNA interference. Down-regulation of c-FLIP increased amounts of reactive oxygen species (ROS), while over-expression of c-FLIP produced opposite effect. ROS induced phosphorylation of Akt and impaired cell motility.

Ghrelin inhibits angiotensin II-induced migration of human aortic endothelial cells

Ghrelin, the endogenous ligand for the GH secretagogue receptor, is produced by the oxyntic cells of the stomach and is involved in the regulation of energy balance. However, an increasing number of direct ghrelin cardiovascular effects, and, among them, high ghrelin binding in atherosclerotic coronary arteries, are being reported. We investigated whether ghrelin affects migration of human aorta endothelial cells (HAEC). HAEC bound ghrelin in specific, saturable manner. Ghrelin, as such, did not affect HAEC migration, however it inhibited the angiotensin II-induced migration, and this effect was inhibited by the antagonist (D-Lys(3))-GHRP-6. In HAEC, ghrelin elicited increased intracellular concentration of cAMP that was involved in its effect on AngII-induced HAEC migration, as the AMP cyclase inhibitor SQ22.536 and PKA inhibitor KT5720, respectively, inhibited and blunted it. These findings suggest a role of ghrelin in the control of endothelial cell migration and its possible involvement in vascular changes present in disorders characterized by low plasma ghrelin.

Role of AT1 receptors in permeability of the blood–brain barrier in diabetic hypertensive rats

The precise mechanisms of vascular diseases in patients with diabetic hypertensive are not clearly understood. There are evidences of alteration in permeability of blood-brain barrier (BBB) in diabetic hypertensive rats. This study sought to examine the effect of candesartan on the systolic blood pressure and the brain endothelial barrier function and antioxidant enzymes in rat brain. Five groups of eight male Sprague-Dawley rats include: control group (gpI), diabetic hypertensive group (gpII), diabetic hypertensive group treated with candesartan (gpIII), diabetic hypertensive rats with epinephrine (gpIV) and diabetic hypertensive rats with epinephrine treated with candesartan (gpV). Diabetes was induced by single injection of 55 mg kg(-1) streptozotocin (STZ) i.p. Blood glucose was measured, rats with blood glucose higher than 300 mg/dl were identified as diabetic. After induction of diabetes, rats received L-NAME (0.5 mg/ml in drinking water for 1 week) starting on the day 4 after STZ injection. Systolic blood pressure (SBP) was recorded two times, at day 0 (before starting L-NAME) and at day 7 (after L-NAME treatment). Also, body weight was measured two times, at initial time (before STZ injection) and terminal (at the last day in the experiment). On the day of acute experiment, rats were anesthetized with sodium pentobarbital (35 mg/kg, i.p.). The integrity of the BBB was investigated using Evans blue (EB) dye (4 ml/kg, 2%). Epinephrine was used (40 micro g/kg) to increase the permeability of the brain. After decapitation, first the brain was removed, next homogenized and then the content of EB dye in the brain was measured. Another five groups of rats manipulated with the same manner except EB dye injection. These second group to evaluate antioxidant enzymes, reduced glutathione (GSH), lipid peroxides and superoxide dismutase (SOD) in brain homogenate. This study indicates that, in diabetic hypertensive rats, epinephrine administration leads to increase in microvascular-EB-albumin efflux to brain. However, candesartan treatment significantly attenuates this permeability to brain tissue and significantly increased GSH and SOD activity, while level of lipid peroxides was decreased significantly. The finding supports that the use of candesartan may offer a good alternative in the treatment of diabetic hypertensive subjects because it has an action that might be mediated through an antioxidant effect and beneficial effects on vascular endothelial permeability as well.

Beneficial effects of candesartan, an angiotensin II type 1 receptor blocker, on beta-cell function and morphology in db/db mice

Several epidemiological studies suggested that treatment with angiotensin II type 1 receptor blocker (ARB) provided a risk reduction of developing type 2 diabetes. In this study, we investigated whether and how ARB treatment can improve abnormalities of pancreatic islets in diabetes state. We randomized db/db mice, a model of type 2 diabetes with obesity, at the age of 8 weeks to receive candesartan, an ARB, for 6 weeks. We also studied age-matched db/misty mice as control. Glucose tolerance test revealed that candesartan treatment improved glucose tolerance with the modest increase in serum insulin level in db/db mice. Concurrently, candesartan increased beta-cell mass, increased staining intensity of insulin, and decreased staining intensity of components of NAD(P)H oxidase, p22phox and gp91phox, and those of oxidative stress markers in beta-cells. These changes were accompanied by reduction of mitochondrial volume. Treatment with candesartan also reduced fibrosis in and around the islets and prevented the loss of endothelial cells in islets. Our results showed that candesartan partially prevented deterioration of glucose tolerance by providing protection against progressive beta-cell damage in diabetes.

Vascular but not cardiac remodeling is associated with superoxide production in angiotensin II hypertension

OBJECTIVE

Angiotensin (Ang) II increases reactive oxygen species (ROS), decreases nitric oxide (NO) bioavailability and promotes cardiovascular remodeling. ROS have been identified as critical second messengers of the trophic responses by Ang II. In rats with Ang II-induced hypertension, we investigated the role of ROS in cardiac hypertrophy as well as the remodeling of aortas and mesenteric (resistance) arteries.

METHODS

Sprague-Dawley rats received Ang II (0.7 mg/kg per day by mini-pump, n = 7) or vehicle (n = 7) for 5 days. Endothelium-dependent relaxation to acetylcholine (EDR) in aortas was determined in organ baths and in mesenteric resistance vessels in a pressurized myograph. Superoxide (O2) production was measured by lucigenin chemiluminescence, laser-confocal fluorescence microscopy (LCM) and NADPH oxidase assay.

RESULTS

Ang II-treated rats developed hypertension (183 +/- 3 versus 138 +/- 4 mmHg, P < 0.05), increased aortic O2 (50%), aortic hypertrophy (12%) and impaired EDR. Mesenteric arteries manifested impaired EDR, increased NADPH oxidase activity (356%) and eutrophic inward remodeling (decreased lumen diameter and increased wall/lumen ratio). However, although Ang II-treated rats developed cardiac hypertrophy (13%), this was not accompanied by an increase in cardiac O2, as measured by lucigenin, LCM or NADPH oxidase assay. On the other hand, cardiac calcineurin, a molecule that promotes cardiac hypertrophy linked to Ang II, was increased by 40% (52 +/- 8 versus 33 +/- 5 pmol/min per mg protein, P < 0.05).

CONCLUSION

These studies demonstrate that the role of ROS in Ang II-induced vascular remodeling differ across vascular territories. Although in conduit and resistance vessels, vascular hypertrophy and endothelial dysfunction are linked to increased ROS production, cardiac hypertrophy is not. Instead, cardiac hypertrophy is associated, at least in part, with an increase in calcineurin. These studies unveil novel mechanisms that may play an important role in the pathogenesis of cardiac and vascular injury in hypertension.

Deletion of Angiotensin II Type 2 Receptor Exaggerated Atherosclerosis in Apolipoprotein E–Null Mice

Background— The role of angiotensin II (Ang II) type 2 (AT 2 ) receptor in atherosclerosis was explored with the use of AT 2 receptor/apolipoprotein E (ApoE)–double-knockout (AT 2 /ApoE-DKO) mice, with a focus on oxidative stress.

Methods and Results— After treatment with a high-cholesterol diet (1.25% cholesterol) for 10 weeks, ApoE-knockout (KO) mice developed atherosclerotic lesions in the aorta. In AT 2 /ApoE-DKO mice receiving a high-cholesterol diet, the atherosclerotic changes were further exaggerated, without significant changes in plasma cholesterol level and blood pressure. In the atherosclerotic lesion, an increase in superoxide production, NADPH oxidase activity, and expression of p47 phox was observed. These changes were also greater in AT 2 /ApoE-DKO mice. An Ang II type 1 (AT 1 ) receptor blocker, valsartan, inhibited atherosclerotic lesion formation, superoxide production, NADPH oxidase activity, and p47 phox expression; these inhibitory effects were significantly weaker in AT 2 /ApoE-KO mice. We further examined the signaling mechanism of the AT 2 receptor–mediated antioxidative effect in cultured fetal vascular smooth muscle cells. NADPH oxidase activity and phosphorylation and translocation of p47 phox induced by Ang II were inhibited by valsartan but enhanced by an AT 2 receptor blocker, PD123319.

Conclusions— These results suggest that AT 2 receptor stimulation attenuates atherosclerosis through inhibition of oxidative stress and that the antiatherosclerotic effect of valsartan could be at least partly due to AT 2 receptor stimulation by unbound Ang II.

Angiotensin II induces focal adhesion kinase/paxillin phosphorylation and cell migration in human umbilical vein endothelial cells

In the present study, we demonstrated that Ang II provokes a transitory enhancement of focal adhesion kinase (FAK) and paxillin phosphorylation in human umbilical endothelial cells (HUVEC). Moreover, Ang II induces a time- and dose-dependent augmentation in cell migration, but does not affect HUVEC proliferation. The effect of Ang II on FAK and paxillin phosphorylation was markedly attenuated in cells pretreated with wortmannin and LY294002, indicating that phosphoinositide 3-kinase (PI3K) plays an important role in regulating FAK activation. Similar results were observed when HUVEC were pretreated with genistein, a non-selective tyrosine kinases inhibitor, or with the specific inhibitor PP2 for Src family kinases, demonstrating the involvement of protein tyrosine kinases, and particularly Src family of tyrosine kinases, in the downstream signalling pathway of Ang II receptors. Furthermore, FAK and paxillin phosphorylation was markedly blocked after treatment of HUVEC with AG1478, a selective inhibitor of epidermal growth factor receptor (EGFR) phosphorylation. Pretreatment of cells with inhibitors of PI3K, Src family tyrosine kinases, and EGFR also decreased HUVEC migration. In conclusion, these results suggest that Ang II mediates an increase in FAK and paxillin phosphorylation and induces HUVEC migration through signal transduction pathways dependent on PI3K and Src tyrosine kinase activation and EGFR transactivation.

Nitric oxide, angiotensin II, and reactive oxygen species in hypertension and atherogenesis

A balance among nitric oxide (NO), angiotensin II (Ang II), and reactive oxygen species (ROS) in the endothelium is necessary for maintaining the homeostasis of the vascular wall. Oxidative stress has been shown to play a critical role in the development of hypertension and atherosclerosis. Although there is overwhelming evidence that hypertension promotes atherosclerosis, the relative contribution and/or interaction of hemodynamic and oxidative stress remains undefined. NO is synthesized in the endothelium by NO synthase and antagonizes the vasoconstrictive and proatherosclerotic effects of Ang II. On the other hand, Ang II decreases NO bioavailability by promoting oxidative stress. A better understanding of the pathophysiologic mechanisms involved in the link between hypertension and atherosclerosis may aid in developing therapeutic interventions. We propose that those antihypertensive agents that lower blood pressure and concomitantly restore the homeostatic balance of vasoactive agents in the endothelium would be more effective in preventing or arresting atherosclerosis.

Preprocedural level of soluble CD40L is predictive of enhanced inflammatory response and restenosis after coronary angioplasty

BACKGROUND

Inflammation plays a pathogenic role in the development of restenosis after percutaneous transluminal coronary angioplasty (PTCA). CD40-CD40L interaction is involved in the pathogenesis of atherosclerosis; however, its role in the pathophysiology of restenosis is still unclear. We tested the hypothesis that soluble CD40L (sCD40L) may be involved in the process of restenosis and that it exerts its effect by triggering a complex group of inflammatory reactions on endothelial and mononuclear cells.

METHODS AND RESULTS

We studied 70 patients who underwent PTCA and who had repeated angiograms at 6-month follow-up. Plasma sCD40L was measured before and 1, 5, 15, and 180 days after PTCA, whereas plasma soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, E-selectin, and monocyte chemoattractant protein (MCP)-1 were measured before and 24 hours after PTCA. Furthermore, the release of adhesion molecules and MCP-1 and the ability to repair an injury in endothelial cells, as well as the generation of O2- in monocytes, were analyzed in vitro after stimulation with serum from patients or healthy control subjects. Restenosis occurred in 18 patients (26%). Restenotic patients had preprocedural sCD40L significantly higher than patients with favorable outcomes (2.13+/-0.3 versus 0.87+/-0.12 ng/mL, P<0.0001). Elevated sCD40L at baseline was significantly correlated with adhesion molecules and MCP-1 generation after PTCA and with lumen loss at 6-month follow-up. Furthermore, high sCD40L was directly associated in vitro with adhesion molecules and MCP-1 generation and impaired migration in endothelial cells and with enhanced O2- generation in monocytes.

CONCLUSIONS

We conclude that increased sCD40L is associated with late restenosis after PTCA. This may provide an important biochemical link between restenosis and aspirin-insensitive platelet activation. These results provide a rationale for studies with new antiplatelet treatments in patients who underwent PTCA.