Endothelial dysfunction: a multifaceted disorder (The Wiggers Award Lecture)

Aging-shifted prostaglandin profile in endothelium as a factor in cardiovascular disorders

Age-associated endothelium dysfunction is a major risk factor for the development of cardiovascular diseases. Endothelium-synthesized prostaglandins and thromboxane are local hormones, which mediate vasodilation and vasoconstriction and critically maintain vascular homeostasis. Accumulating evidence indicates that the age-related changes in endothelial eicosanoids contribute to decline in endothelium function and are associated with pathological dysfunction. In this review we summarize currently available information on aging-shifted prostaglandin profiles in endothelium and how these shifts are associated with cardiovascular disorders, providing one molecular mechanism of age-associated endothelium dysfunction and cardiovascular diseases.

Progesterone enhances vascular endothelial cell migration via activation of focal adhesion kinase

The mechanisms of progesterone on endothelial cell motility are poorly investigated. Previously we showed that progesterone stimulated endothelial cell migration via the activation of actin-binding protein moesin, leading to actin cytoskeleton remodelling and the formation of cell membrane structures required for cell movement. In this study, we investigated the effects of progesterone on the formation of focal adhesion complexes, which provide anchoring sites for cell movement. In cultured human umbilical endothelial cells, progesterone enhanced focal adhesion kinase (FAK) phosphorylation at Tyr(397) in a dose- and time-dependent manner. Several signalling inhibitors interfered with progesterone-induced FAK activation, including progesterone receptor (PR) antagonist ORG 31710, specific c-Src kinase inhibitor PP2, phosphatidylinosital-3 kinase (PI3K) inhibitor wortmannin as well as ρ-associated kinase (ROCK-2) inhibitor Y27632. It suggested that PR, c-Src, PI3K and ROCK-2 are implicated in this action. In line with this, we found that progesterone rapidly promoted c-Src/PI3K/Akt activity, which activated the small GTPase RhoA/ρ-associated kinase (ROCK-2) complex, resulting in FAK phosphorylation. In the presence of progesterone, endothelial cells displayed enhanced horizontal migration, which was reversed by small interfering RNAs abrogating FAK expression. In conclusion, progesterone promotes endothelial cell movement via the rapid regulation of FAK. These findings provide new information on the biological actions of progesterone on human endothelial cells that are relevant for vascular function.

Obesity and risk of vascular disease: importance of endothelium-dependent vasoconstriction

Obesity has become a serious global health issue affecting both adults and children. Recent devolopments in world demographics and declining health status of the world's population indicate that the prevalence of obesity will continue to increase in the next decades. As a disease, obesity has deleterious effects on metabolic homeostasis, and affects numerous organ systems including heart, kidney and the vascular system. Thus, obesity is now regarded as an independent risk factor for atherosclerosis-related diseases such as coronary artery disease, myocardial infarction and stroke. In the arterial system, endothelial cells are both the source and target of factors contributing to atherosclerosis. Endothelial vasoactive factors regulate vascular homeostasis under physiological conditions and maintain basal vascular tone. Obesity results in an imbalance between endothelium-derived vasoactive factors favouring vasoconstriction, cell growth and inflammatory activation. Abnormal regulation of these factors due to endothelial cell dysfunction is both a consequence and a cause of vascular disease processes. Finally, because of the similarities of the vascular pathomechanisms activated, obesity can be considered to cause accelerated, 'premature' vascular aging. Here, we will review some of the pathomechanisms involved in obesity-related activation of endothelium-dependent vasoconstriction, the clinical relevance of obesity-associated vascular risk, and therapeutic interventions using 'endothelial therapy' aiming at maintaining or restoring vascular endothelial health.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Serum oxidative stress-induced repression of Nrf2 and GSH depletion: a mechanism potentially involved in endothelial dysfunction of young smokers

Background

Although oxidative stress plays a major role in endothelial dysfunction (ED), the role of glutathione (GSH), of nuclear erythroid-related factor 2 (Nrf2) and of related antioxidant genes (ARE) are yet unknown. In this study we combined an in vivo with an in vitro model to assess whether cigarette smoking affects flow-mediated vasodilation (FMD), GSH concentrations and the Nrf2/ARE pathway in human umbilical vein endothelial cells (HUVECs).

Methods and Results

52 healthy subjects (26 non-smokers and 26 heavy smokers) were enrolled in this study. In smokers we demonstrated increased oxidative stress, i.e., reduced concentrations of GSH and increased concentrations of oxidation products of the phospholipid 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine (oxPAPC) in serum and in peripheral blood mononuclear cells (PBMC), used as in vivo surrogates of endothelial cells. Moreover we showed impairment of FMD in smokers and a positive correlation with the concentration of GSH in PBMC of all subjects. In HUVECs exposed to smokers' serum but not to non-smokers' serum we found that oxidative stress increased, whereas nitric oxide and GSH concentrations decreased; interestingly the expression of Nrf2, of heme oxygenase-1 (HO-1) and of glutamate-cysteine ligase catalytic (GCLC) subunit, the rate-limiting step of synthesis of GSH, was decreased. To test the hypothesis that the increased oxidative stress in smokers may have a causal role in the repression of Nrf2/ARE pathway, we exposed HUVECs to increasing concentrations of oxPAPC and found that at the highest concentration (similar to that found in smokers' serum) the expression of Nrf2/ARE pathway was reduced. The knockdown of Nrf2 was associated to a significant reduction of HO-1 and GCLC expression induced by oxPAPC in ECs.

Conclusions

In young smokers with ED a novel further consequence of increased oxidative stress is a repression of Nrf2/ARE pathway leading to GSH depletion.

Basal and post-ischemic vascular compliance in children/adolescents born small for gestational age

BACKGROUND

Intrauterine growth restriction plays a powerful role in influencing later susceptibility to certain chronic diseases, such as hypertension. Endothelial dysfunction and arterial stiffness are early events in the development of cardiovascular diseases (CVDs). We have studied vascular compliance in small for gestational age (SGA) children/adolescents in comparison with that in appropriate for gestational age (AGA) subjects.

METHODS

We monitored blood pressure, vascular resistance and compliance in 82 children-adolescents (52 SGA, 30 AGA), by means of pulse wave analysis (CR 2000 HDI) at the radial level, before and after 3 min of ischemic stress at the brachial level.

RESULTS

In the children/adolescents born SGA we found a significant increase in systolic and diastolic blood pressure and vascular resistance in the basal condition; the large and small vessels were stiffer. After ischemia we observed an increased vascular response in the SGA children/adolescents: there was a great diminution of systolic and diastolic blood pressure and a larger increase of the elasticity of the conduit and resistance vessels.

CONCLUSIONS

These data show that the SGA group presented some early signs of arterial wall functional disorders. More pediatric data are needed for the evaluation by non-invasive techniques of vascular function in children-adolescents at risk of CVD.

Animal models of erectile dysfunction (ED): potential utility of non-human primates as a model of atherosclerosis-induced vascular ED

Erectile dysfunction (ED) is a prevalent medical condition affecting 18 million men and their sexual partners in the United States alone. In the majority of patients, ED is related to alterations in the flow of blood to or from the penis. Undeniably, significant progress has been made in understanding the multifactorial mechanisms that modulate erectile capacity and predispose one to ED, and this, in turn, has led to the availability of more effective treatment options. Nonetheless, all current therapies have untoward side effects, and moreover, there are still no satisfactory treatments for many patients with ED. Further enhancements in the treatment of ED would logically result from both early intervention and more detailed mechanistic insight into the characteristics of the disease process per se. This fact underscores the importance of improved understanding of the initiation, development and progression of ED. However, to do so requires longitudinal studies on animal models that more closely approximate the corresponding clinical features and time course of human disease. The goal of this report is twofold. First, to provide a brief general overview of the applicability of commonly used animal models for the study of ED. The second and primary goal is to highlight the scientific rationale for using non-human primates to evaluate the impact of atherosclerosis-induced vascular disease on the penile and systemic circulatory systems. This latter goal seems especially relevant in light of the recent literature documenting a link between ED and systemic vascular disease, a finding that has major implications in an aging US male population consuming a high fat diet.

Deletion of G protein-coupled estrogen receptor increases endothelial vasoconstriction

Endogenous estrogens mediate protective effects in the cardiovascular system, affecting both endothelium-dependent and endothelium-independent mechanisms. Previous studies have suggested that nonselective estrogen receptor agonists such as endogenous estrogens inhibit endothelium-dependent vasoconstriction; however, the role of estrogen receptors in this response has not yet been clarified. This study investigated whether the intracellular transmembrane G protein-coupled estrogen receptor (GPER) regulates vascular reactivity in mice. Effects of chronic deficiency (using mice lacking the GPER gene) and acute inhibition (using the GPER-selective antagonist G15) on endothelium-dependent and endothelium-independent vascular reactivity, and the effects of GPER deficiency on vascular gene expression and structure were investigated. We found that chronic GPER deficiency is associated with increased endothelial prostanoid-mediated vasoconstriction but has no effect on endothelial nitric oxide bioactivity, gene expression of endothelial nitric oxide synthase and thromboxane prostanoid (TP) receptor, or vascular structure. GPER deletion also increases TP receptor-mediated contraction. Acute GPER blockade enhances endothelium-dependent contractions and reduces endothelial nitric oxide bioactivity. Contractions in response to TP receptor activation are unaffected by G15. In conclusion, this study identifies GPER as the first estrogen receptor with inhibitory activity on endothelium-dependent contractility. These findings may be important for understanding and treating diseases associated with increased endothelial vasoconstrictor prostanoid activity such as hypertension and obesity.

NF-κB regulates MICA gene transcription in endothelial cell through a genetically inhibitable control site

Endothelial cells form a barrier between blood and the underlying vessel wall, which characteristically demonstrates inflammatory damage in atherosclerotic disease. MICA is a highly polymorphic ligand for the activating immune receptor NKG2D and can be expressed on endothelial cells. We hypothesized that damaged vessel walls, such as those involved in atherosclerosis, might express MICA, which could contribute to the vascular immunopathology. Immune activation resulting from MICA expression could play a significant role in the development of vascular damage. We have demonstrated that TNFα up-regulates MICA on human endothelial cells. The up-regulation is mediated by NF-κB, and we have defined the regulatory control site responsible for this at -130 bp upstream of the MICA transcription start site. This site overlaps with a heat shock response element and integrates input from the two pathways. We have shown that in atherosclerotic lesions there is expression of MICA on endothelial cells. Using lentivirus-mediated gene delivery in primary human endothelial cells, we were able to inhibit the MICA response to TNFα with a truncated HSF1 that lacked a transactivation domain. This highlights the potential for transcription-based therapeutic approaches in atherosclerotic vascular disease to reduce immune-mediated endothelial and vessel wall damage.

Adaptive response of vascular endothelial cells to an acute increase in shear stress magnitude

The adaptation of vascular endothelial cells to shear stress alteration induced by global hemodynamic changes, such as those accompanying exercise or digestion, is an essential component of normal endothelial physiology in vivo. An understanding of the transient regulation of endothelial phenotype during adaptation to changes in mural shear will advance our understanding of endothelial biology and may yield new insights into the mechanism of atherogenesis. In this study, we characterized the adaptive response of arterial endothelial cells to an acute increase in shear stress magnitude in well-defined in vitro settings. Porcine endothelial cells were preconditioned by a basal level shear stress of 15 ± 15 dyn/cm(2) at 1 Hz for 24 h, after which an acute increase in shear stress to 30 ± 15 dyn/cm(2) was applied. Endothelial permeability nearly doubled after 40-min exposure to the elevated shear stress and then decreased gradually. Transcriptomics studies using microarray techniques identified 86 genes that were sensitive to the elevated shear. The acute increase in shear stress promoted the expression of a group of anti-inflammatory and antioxidative genes. The adaptive response of the global gene expression profile is triphasic, consisting of an induction period, an early adaptive response (ca. 45 min) and a late remodeling response. Our results suggest that endothelial cells exhibit a specific phenotype during the adaptive response to changes in shear stress; this phenotype is different than that of fully adapted endothelial cells.

Endothelium-dependent vasoconstriction in isolated vessel grafts: a novel mechanism of vasospasm?

BACKGROUND

YC-1 (3-(5'-hydroxymethyl-2'furyl)-1-benzyl-indazole) is an allosteric activator of soluble guanylyl cyclase (sGC) and a vasodilator. This study describes a paradoxical action of YC-1 in isolated vessels of patients with coronary artery disease (CAD) that appears to trigger an endothelium-dependent vasoconstrictor pathway present in vessels with endothelial dysfunction.

METHODS

Effects of YC-1 on the tensions of isolated vessels were investigated in an organ bath. Vasoconstrictors released from the vessels were quantified through enzyme-linked immunosorbent assay.

RESULTS

YC-1 elicited long-lasting constriction in saphenous veins and radial arteries from patients with CAD, but not in human umbilical veins. The half-maximal effective dose was 1.0 μmol/L. Constriction was attenuated by nifedipine (an L-type Ca(2+)-channel blocker), bosentan (an endothelin [ET](A)/ET(B) inhibitor), BQ-788 (N-[(cis-2,6-Dimethyl-1-piperidinyl)carbonyl]-4-methyl-L-leucyl-1-(methoxycarbonyl)-D-tryptophyl-D-norleucine; an ET(B) inhibitor), and by denuding, but not by ODQ (1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one; an inhibitor of sGC), BQ-123 (cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu); an ET(A) inhibitor), or phosphoramidon (an endothelin converting enzyme inhibitor). Indomethacin (an inhibitor of cyclooxygenase-1 and -2) and SQ29,548 ([1S-[1α,2α(Z),3α,4α]]-7-[3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid; a thromboxane receptor antagonist) suppressed YC-1-induced constriction, whereas DFU (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanone; a cyclooxygenase-2 inhibitor) had no effect. Rings of saphenous vein released significantly more endothelin-1 in the presence than in the absence of YC-1.

CONCLUSIONS

YC-1-induced vasoconstriction demonstrates the existence of an endothelium-dependent vasoconstrictor pathway in the blood vessels of patients with CAD that to date has been described only in animal models of hypertension. Patients with CAD who have elevated plasma levels of endothelin-1 are thus prone to endothelium-dependent vasoconstriction, which may also play a role in vasospasm in vascular grafts.

PPAR-α Agonist Fenofibrate Upregulates Tetrahydrobiopterin Level through Increasing the Expression of Guanosine 5'-Triphosphate Cyclohydrolase-I in Human Umbilical Vein Endothelial Cells

Tetrahydrobiopterin (BH4) is an essential cofactor for endothelial nitric oxide (NO) synthase. Guanosine 5'-triphosphate cyclohydrolase-I (GTPCH-I) is a key limiting enzyme for BH4 synthesis. In the present in vitro study, we investigated whether peroxisome proliferator-activated receptor α (PPAR-α) agonist fenofibrate could recouple eNOS by reversing low-expression of intracellular BH4 in endothelial cells and discussed the potential mechanisms. After human umbilical vein endothelial cells (HUVECs) were treated with lipopolysaccharide (LPS) for 24 hours, the levels of cellular eNOS, BH4 and cell supernatant NO were significantly reduced compared to control group. And the fluorescence intensity of intracellular ROS was significantly increased. But pretreated with fenofibrate (10 umol/L) for 2 hours before cells were induced by LPS, the levels of eNOS, NO, and BH4 were significantly raised compared to LPS treatment alone. ROS production was markedly reduced in fenofibrate group than LPS group. In addition, our results showed that the level of intracellular GTPCH-I detected by western blot was increased in a concentration-dependent manner after being treated with fenofibrate. These results suggested that fenofibrate might help protect endothelial function and against atherosclerosis by increasing level of BH4 and decreasing production of ROS through upregulating the level of intracellular GTPCH-I.

Endothelial dysfunction in the apolipoprotein E-deficient mouse: insights into the influence of diet, gender and aging

Since the early 1990s, several strains of genetically modified mice have been developed as models for experimental atherosclerosis. Among the available models, the apolipoprotein E-deficient (apoE⁻/⁻) mouse is of particular relevance because of its propensity to spontaneously develop hypercholesterolemia and atherosclerotic lesions that are similar to those found in humans, even when the mice are fed a chow diet. The main purpose of this review is to highlight the key achievements that have contributed to elucidating the mechanisms pertaining to vascular dysfunction in the apoE⁻/⁻ mouse. First, we summarize lipoproteins and atherosclerosis phenotypes in the apoE⁻/⁻ mouse, and then we briefly discuss controversial evidence relative to the influence of gender on the development of atherosclerosis in this murine model. Second, we discuss the main mechanisms underlying the endothelial dysfunction of conducting vessels and resistance vessels and examine how this vascular defect can be influenced by diet, aging and gender in the apoE⁻/⁻ mouse.

The role of uridine adenosine tetraphosphate in the vascular system

The endothelium plays a pivotal role in vascular homeostasis, and endothelial dysfunction is a major feature of cardiovascular diseases, such as arterial hypertension, atherosclerosis, and diabetes. Recently, uridine adenosine tetraphosphate (Up(4)A) has been identified as a novel and potent endothelium-derived contracting factor (EDCF). Up(4)A structurally contains both purine and pyrimidine moieties, which activate purinergic receptors. There is an accumulating body of evidence to show that Up(4)A modulates vascular function by actions on endothelial and smooth muscle cells. In this paper, we discuss the effects of Up(4)A on vascular function and a potential role for Up(4)A in cardiovascular diseases.

Lack of modulatory effect of simvastatin on indoxyl sulfate-induced activation of cultured endothelial cells

AIMS

Endothelial dysfunction is a common manifestation of chronic kidney disease (CKD). The protein-bound uremic toxins have emerged as important factors associated with cardiovascular disease and the outcome of CKD. The effect of indoxyl sulfate (IS) on endothelial cells remains unclear.

MAIN METHODS

Human umbilical endothelial cells (HUVEC) were incubated using IS at two concentrations: 100 μM and 1000 μM over two periods of time: 16 and 48 h. HUVEC were also pre-treated with simvastatin to examine its effect. RT-PCR was used to assess changes in the gene expression of intracellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), Monocyte chemotactic protein-1 (MCP-1), E-selectin, and angiotensin receptor type 1 (AT1R). Protein abundance of the investigated molecules was assessed by immunoblotting.

KEY FINDINGS

Treatment with 100 μM IS for 16 h induced a 2-fold increase in the expression of ICAM-1, VCAM-1, and MCP-1. At a concentration of 1000 μM, there was a 2-3-fold increase. An extended treatment period at low concentrations was associated with a 2-3 fold increase and the increase of ICAM-1 and VCAM-1 was more prominent under high concentration. Results of immunoblotting confirmed an increase in the abundance of ICAM-1, VCAM-1 and MCP-1. No significant change was noted in E-selectin and AT1R according to concentration or treatment duration. Pre-treatment with simvastatin did not alter IS-induced changes.

SIGNIFICANCE

IS increased the expression of adhesion molecules of endothelial cells exhibiting a concentration and duration dependent pattern. Simvastatin did not demonstrate any effect on IS-associated endothelial activation.

Causes and consequences of obesity: the contribution of recent twin studies

Obesity is a genetically complex disorder that produces a myriad of health problems. Most of the recognized complications of obesity are not only strongly influenced by lifestyle factors, but also present with independent genetic predispositions that are notoriously difficult to disentangle in humans. Most studies on the causes and consequences of acquired obesity are encumbered by the incomplete ability to control for genetic influences. However, utilizing a unique experiment of nature, namely monozygotic twins (MZ) discordant for obesity as 'clonal controls' of obese and non-obese individuals has enabled the fine characterization of the effects and possible antecedents of acquired obesity while controlling for the genetic background, as well as pointed to novel obesity predisposing candidate genes. This review is a distillation of the findings from more than 10 years of research done in an exceptionally well-characterized collection of MZ and dizygotic (DZ) twins, based on the Finnish Twin Cohorts. Topics covered include the nature of development of obesity from the childhood onwards, the role of exercise in modifying the genetic susceptibility, the resulting inflammatory, prediabetic and preatherosclerotic changes in whole body and adipose tissue physiology, as well as the newest insights provided by the omics revolution.

Betulinic acid ameliorates endothelium-dependent relaxation in L-NAME-induced hypertensive rats by reducing oxidative stress

Zizyphi Spinosi semen (ZSS) is one of the most widely used traditional Chinese herbs with protective effects on the cardiovascular system. It is not clear whether betulinic acid (BA), the key active constituent of ZSS, has beneficial cardiovascular effects on N(ω)-nitro-L-arginine methyl ester hydrochloride (L-NAME)-induced hypertensive rats. The objective of this study was to investigate the effect of BA on endothelium-dependent vasorelaxation in isolated aortic rings from L-NAME-induced hypertensive rats and its underlying mechanisms. Male Sprague-Dawley rats were injected with L-NAME (15 mg/kg/d, i.p.) for 4 weeks to induce hypertension. After treatment with L-NAME for 2 weeks, rats with mean blood pressure >120 mm Hg measured by tail-cuff method were considered hypertensive and then injected with BA (0.8, 4, 20 mg/kg/d, i.p.) for the last 2 weeks. The effect of BA on the tension of rat thoracic aortic rings was measured in an organ bath system. The levels of nitric oxide (NO), reactive oxygen species (ROS), and the activity of superoxide dismutase (SOD) and nitric oxide synthase (NOS) in aortas were assayed. We found that BA (0.1-100 μM) evoked a concentration-dependent vasorelaxation in endothelium-intact normal rat aortic rings, which was significantly attenuated by pretreatment with L-NAME (100 μM) or methylene blue (MB, 10 μM), but not by indomethacin (10 μM). Pretreatment with EC(50) (1.67 μM) concentration of BA enhanced the acetylcholine (ACh)-induced vasorelaxation, which was also markedly reversed by both L-NAME and MB. The blood pressure in hypertensive rats increased to 135.22±5.38 mm Hg (P<0.01 vs. control group), which was markedly attenuated by high dose of BA. The ACh-induced vasorelaxation in hypertensive rat aortic rings was impaired, which was markedly improved by chronic treatment with BA (20 mg/kg/d) for 2 weeks. The increase of ROS level and the decrease of NO level, SOD and eNOS activities in hypertensive rat aortas were all markedly inhibited by BA. These results indicate that BA decreased blood pressure and improved ACh-induced endothelium-dependent vasorelaxation in L-NAME-induced hypertension rats, which may be mediated by reducing oxidative stress and retaining the bioavailability of NO in the cardiovascular system.

Endothelium-derived NO, but not cyclic GMP, is required for hypoxic augmentation in isolated porcine coronary arteries

The present study investigated the mechanism underlying the transient potentiation of vasoconstriction by hypoxia in isolated porcine coronary arteries. Isometric tension was measured in rings with or without endothelium. Hypoxia (Po(2) <30 mmHg) caused a transient further increase in tension (hypoxic augmentation) in contracted (with U46619) preparations. The hypoxic response was endothelium dependent and abolished by inhibitors of nitric oxide synthase [N(ω)-nitro-L-arginine methyl ester (L-NAME)] or soluble guanylyl cyclase (ODQ and NS2028). The addition of DETA NONOate (nitric oxide donor) in the presence of L-NAME restored the hypoxic augmentation, suggesting the involvement of the nitric oxide pathway. However, the same was not observed after incubation with 8-bromo-cyclic GMP, atrial natriuretic peptide, or isoproterenol. Assay of the cyclic GMP content showed no change upon exposure to hypoxia in preparations with and without endothelium. Incubation with protein kinase G and protein kinase A inhibitors did not inhibit the hypoxic augmentation. Thus the hypoxic augmentation is dependent on nitric oxide and soluble guanylyl cyclase but independent of cyclic GMP. The hypoxic augmentation persisted in calcium-free buffer and in the presence of nifedipine, ruling out a role for extracellular calcium influx. Hypoxia did not alter the intracellular calcium concentration, as measured by confocal fluorescence microscopy. This observation and the findings that hypoxic augmentation is enhanced by thapsigargin (sarco/endoplasmic reticulum calcium ATPase inhibitor) and inhibited by HA1077 or Y27632 (Rho kinase inhibitors) demonstrate the involvement of calcium sensitization in the phenomenon.

Effect of hydrogen peroxide and superoxide anions on cytosolic Ca2+: comparison of endothelial cells from large-sized and small-sized arteries

We compared the Ca²⁺ responses to reactive oxygen species (ROS) between mouse endothelial cells derived from large-sized arteries, aortas (aortic ECs), and small-sized arteries, mesenteric arteries (MAECs). Application of hydrogen peroxide (H₂O₂) caused an increase in cytosolic Ca²⁺ levels ([Ca²⁺]_i) in both cell types. The [Ca²⁺]_i rises diminished in the presence of U73122, a phospholipase C inhibitor, or Xestospongin C (XeC), an inhibitor for inositol-1,4,5-trisphosphate (IP₃) receptors. Removal of Ca²⁺ from the bath also decreased the [Ca²⁺]_i rises in response to H₂O₂. In addition, treatment of endothelial cells with H₂O₂ reduced the [Ca²⁺]_i responses to subsequent challenge of ATP. The decreased [Ca²⁺]_i responses to ATP were resulted from a pre-depletion of intracellular Ca²⁺ stores by H₂O₂. Interestingly, we also found that Ca²⁺ store depletion was more sensitive to H₂O₂ treatment in endothelial cells of mesenteric arteries than those of aortas. Hypoxanthine-xanthine oxidase (HX-XO) was also found to induce [Ca²⁺]_i rises in both types of endothelial cells, the effect of which was mediated by superoxide anions and H₂O₂ but not by hydroxyl radical. H₂O₂ contribution in HX-XO-induced [Ca²⁺]_i rises were more significant in endothelial cells from mesenteric arteries than those from aortas. In summary, H₂O₂ could induce store Ca²⁺ release via phospholipase C-IP₃ pathway in endothelial cells. Resultant emptying of intracellular Ca²⁺ stores contributed to the reduced [Ca²⁺]_i responses to subsequent ATP challenge. The [Ca²⁺]_i responses were more sensitive to H₂O₂ in endothelial cells of small-sized arteries than those of large-sized arteries.

Alterations in vasoconstrictor responses to the endothelium-derived contracting factor uridine adenosine tetraphosphate are region specific in DOCA-salt hypertensive rats

Uridine adenosine tetraphosphate (Up(4)A) has been recently identified as a novel and potent endothelium-derived contracting factor and contains both purine and pyrimidine moieties, which activate purinergic P2X and P2Y receptors. The present study was designed to compare contractile responses to Up(4)A and other nucleotides such as ATP (P2X/P2Y agonist), UTP (P2Y(2)/P2Y(4) agonist), UDP (P2Y(6) agonist), and α,β-methylene ATP (P2X(1) agonist) in different vascular regions [thoracic aorta, basilar, small mesenteric, and femoral arteries] from deoxycorticosterone acetate-salt (DOCA-salt) and control rats. In DOCA-salt rats [vs. control uninephrectomized (Uni) rats]: (1) in thoracic aorta, Up(4)A-, ATP-, and UTP-induced contractions were unchanged; (2) in basilar artery, Up(4)A-, ATP-, UTP- and UDP-induced contractions were increased, and expression for P2X(1), but not P2Y(2) or P2Y(6) was decreased; (3) in small mesenteric artery, Up(4)A-induced contraction was decreased and UDP-induced contraction was increased; expression of P2Y(2) and P2X(1) was decreased whereas P2Y(6) expression was increased; (4) in femoral artery, Up(4)A-, UTP-, and UDP-induced contractions were increased, but expression of P2Y(2), P2Y(6) and P2X(1) was unchanged. The α,β-methylene ATP-induced contraction was bell-shaped and the maximal contraction was reached at a lower concentration in basilar and mesenteric arteries from Uni rats, compared to arteries from DOCA-salt rats. These results suggest that Up(4)A-induced contraction is heterogenously affected among various vascular beds in arterial hypertension. P2Y receptor activation may contribute to enhancement of Up(4)A-induced contraction in basilar and femoral arteries. These changes in vascular reactivity to Up(4)A may be adaptive to the vascular alterations produced by hypertension.

Dose-dependent increases in flow-mediated dilation following acute cocoa ingestion in healthy older adults

An inverse relation exists between intake of flavonoid-rich foods, such as cocoa, and cardiovascular-related mortality. Favorable effects of flavonoids on the endothelium may underlie these associations. We performed a randomized, double-blind, placebo-controlled study to test the hypothesis that acute cocoa ingestion dose dependently increases endothelium-dependent vasodilation, as measured by an increase in brachial artery flow-mediated dilation (FMD), in healthy older adults. Measurements were obtained before (preingestion) and after (1- and 2-h postingestion) ingestion of 0 (placebo), 2, 5, 13, and 26 g of cocoa in 23 adults (63 ± 2 yr old, mean ± SE). Changes in brachial artery FMD 1- and 2-h postingestion compared with preingestion were used to determine the effects of cocoa. FMD was unchanged 1 (Δ-0.3 ± 0.2%)- and 2-h (Δ0.1 ± 0.1%) after placebo (0 g cocoa). In contrast, FMD increased both 1-h postingestion (2 g cocoa Δ0.0 ± 0.2%, 5 g cocoa Δ0.8 ± 0.3%, 13 g cocoa Δ1.0 ± 0.3%, and 26 g cocoa Δ1.6 ± 0.3%: P < 0.05 compared with placebo for 5, 13, and 26 g cocoa) and 2-h postingestion (2 g cocoa Δ0.5 ± 0.3%, 5 g cocoa Δ1.0 ± 0.3%, 13 g cocoa Δ1.4 ± 0.2%, and 26 g cocoa Δ2.5 ± 0.4%: P < 0.05 compared with placebo for 5, 13, and 26 g cocoa) on the other study days. A serum marker of cocoa ingestion (total epicatechin) correlated with increased FMD 1- and 2-h postingestion (r = 0.44-0.48; both P < 0.05). Collectively, these results indicate that acute cocoa ingestion dose dependently increases brachial artery FMD in healthy older humans. These responses may help to explain associations between flavonoid intake and cardiovascular-related mortality in humans.

Effect of hypoxia in mice mesenteric arteries surrounded by adipose tissue

AIM

To investigate the influence of hypoxia on the vasoactive effect of peri-vascular white adipose tissue.

METHODS

Isometric tension recordings were performed on mesenteric arteries from Swiss male mice with or without adherent adipose tissue.

RESULTS

Hypoxia (bubbling with 95% N(2), 5% CO(2)) induced a biphasic response, i.e. vasoconstriction followed by vasorelaxation, in pre-contracted (noradrenaline, 10 μm) mesenteric arteries with adipose tissue in the presence of indomethacin (10 μm) and N(ω) -nitro-l-arginine (0.1 mm). Only a small vasorelaxation was observed in arteries without adipose tissue. Pre-contraction with 60 or 120 mm K(+) , incubation with tetraethylammoniumchloride (1 and 3 mm), apamin (1 μm) combined with charybdotoxin (0.1 μm) or 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) (10 μm) significantly impaired the hypoxic vasorelaxation. Removal of the endothelium only reduced the hypoxic vasorelaxation. Apamin (1 μm) and charybdotoxin (0.1 μm) did not influence the vasorelaxation of sodium hydrosulfide hydrate. Zinc protoporphyrin IX (10 μm), miconazole (10 μm), 8-(p-sulfophenyl)theophylline (0.1 mm), 1 H-[1, 2, 4]oxadiazolo[4,3- A]quinoxalin-1-one (10 μm), apocynin (0.3 mm), diphenyliodonium (1 μm), catalase (2500 U mL(-1)) and tempol (0.1 mm) did not influence the hypoxic vasorelaxation. In contrast to losartan (0.1 mm), indomethacin (10 μm) and SQ-29548 (10 μm) significantly reduced the hypoxic vasoconstriction.

CONCLUSIONS

Moderate hypoxia induces a biphasic vasomotor response in mice mesenteric arteries surrounded by adipose tissue. The hypoxic vasoconstriction is endothelium independent, whereas the vasodilation is endothelium dependent, soluble guanylyl cyclase independent and in part mediated by opening K(Ca) channels. Cyclooxygenase metabolites mediate the hypoxic vasoconstriction, while endothelium-derived hyperpolarizing factor plays a small role in the hypoxic vasorelaxation.

Increasing dihydrobiopterin causes dysfunction of endothelial nitric oxide synthase in rats in vivo

An elevation of oxidized forms of tetrahydrobiopterin (BH(4)), especially dihydrobiopterin (BH(2)), has been reported in the setting of oxidative stress, such as arteriosclerotic/atherosclerotic disorders, where endothelial nitric oxide synthase (eNOS) is dysfunctional, but the role of BH(2) in the regulation of eNOS activity in vivo remains to be evaluated. This study was designed to clarify whether increasing BH(2) concentration causes endothelial dysfunction in rats. To increase vascular BH(2) levels, the BH(2) precursor sepiapterin (SEP) was intravenously given after the administration of the specific dihydrofolate reductase inhibitor methotrexate (MTX) to block intracellular conversion of BH(2) to BH(4). MTX/SEP treatment did not significantly affect aortic BH(4) levels compared with control treatment. However, MTX/SEP treatment markedly augmented aortic BH(2) levels (291.1 ± 29.2 vs. 33.4 ± 6.4 pmol/g, P < 0.01) in association with moderate hypertension. Treatment with MTX alone did not significantly alter blood pressure or BH(4) levels but decreased the BH(4)-to-BH(2) ratio. Treatment with MTX/SEP, but not with MTX alone, impaired ACh-induced vasodilator and depressor responses compared with the control treatment (both P < 0.05) and also aggravated ACh-induced endothelium-dependent relaxations (P < 0.05) of isolated aortas without affecting sodium nitroprusside-induced endothelium-independent relaxations. Importantly, MTX/SEP treatment significantly enhanced aortic superoxide production, which was diminished by NOS inhibitor treatment, and the impaired ACh-induced relaxations were reversed with SOD (P < 0.05), suggesting the involvement of eNOS uncoupling. These results indicate, for the first time, that increasing BH(2) causes eNOS dysfunction in vivo even in the absence of BH(4) deficiency, demonstrating a novel insight into the regulation of endothelial function.

Overexpression of CREG attenuates atherosclerotic endothelium apoptosis via VEGF/PI3K/AKT pathway

AIMS

Cellular repressor of E1A-stimulated genes (CREG) is a homeostasis-modulating gene abundantly expressed in adult artery endothelium. Previous studies have demonstrated a protective effect of CREG against atherosclerosis through prevention of vascular smooth muscle cell apoptosis. However, the role of CREG in endothelial cells (ECs) apoptosis and the underlying signaling mechanisms are unknown.

METHOD AND RESULTS

We ascertained that CREG expression was decreased in atherogenesis-prone endothelium in apolipoprotein E-null (apoE(-/-)) mice compared with their wild-type littermates using in situ immunofluorescent staining. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining and caspase-3 activity assays determined that treatment of apoE(-/-) mice arteries with staurosporine (STS) significantly induced endothelial apoptosis associated with a reduction of CREG expression. Gain- and loss-of-function analyses revealed that silencing CREG expression significantly enhanced ECs apoptosis, whereas CREG overexpression abrogated apoptosis stimulated by STS or etoposide (VP-16). Blocking assays using the neutralizing antibody for vascular endothelial growth factor (VEGF) and the specific inhibitor of phosphoinositide 3-kinase (PI3K), such as LY294002 or wortmannin, demonstrated that the protective effect of CREG on ECs apoptosis was mainly mediated by activation of the VEGF/PI3K/AKT signaling pathway.

CONCLUSIONS

These data demonstrate that CREG plays a critical role in protecting the vascular endothelium from apoptosis, and the protective effort of CREG against ECs apoptosis is through the activation of the VEGF/PI3K/AKT signaling pathway.

Vitamin D insufficiency is associated with impaired vascular endothelial and smooth muscle function and hypertension in young rats

Increasing evidence links vitamin D deficiency and cardiovascular dysfunction in human adults. There is a worldwide increase in the prevalence of vitamin D deficiency in women of reproductive age, particularly dark-skinned and/or veiled women and their infants. We used a rat model to determine the functional impact of vitamin D deficiency during intra uterine and early life on resistance artery reactivity and blood pressure in the offspring as young adults. Rat dams were maintained on vitamin D deficient or replete chow before and during pregnancy and lactation. The offspring were maintained on the same chow until studied at 7-8 weeks of age. Conscious blood pressure was measured. Endothelial and smooth muscle function were tested in mesenteric arteries on a pressure myograph. Vitamin D deficient male and female offspring had a 10-fold lower serum 25-hydroxyvitamin D (P < 0.0001) and markedly elevated blood pressures (11-20 mmHg, P < 0.001) and heart rates (21-40 beats min(-1), P < 0.02) than control fed offspring. Serum calcium was unchanged. Mesenteric artery myogenic tone was doubled in vitamin D deficiency. Endothelium-derived nitric oxide-evoked dilation was halved in arteries from vitamin D deficient males and dioestrous females. Dilation attributed to endothelium-derived hyperpolarizing factor was all but abolished in vitamin D deficient oestrous females. Nitroprusside-evoked dilation was unaltered in arteries from males, but was markedly reduced in vessels of vitamin D deplete females. In conclusion, early life vitamin D deficiency is associated with endothelial vasodilator dysfunction, and this is likely to contribute to the accompanying elevation in blood pressure and an increased cardiovascular disease risk.

Novel mechanisms of endothelial dysfunction in diabetes

Diabetes mellitus is a major risk factor for cardiovascular morbidity and mortality. This condition increases the risk of developing coronary, cerebrovascular, and peripheral arterial disease fourfold. Endothelial dysfunction is a major contributor to the pathogenesis of vascular disease in diabetes mellitus patients and has recently received increased attention. In this review article, some recent developments that could improve the knowledge of diabetes-induced endothelial dysfunction are discussed.

Brain iron accumulation in unexplained fetal and infant death victims with smoker mothers--the possible involvement of maternal methemoglobinemia

BACKGROUND

Iron is involved in important vital functions as an essential component of the oxygen-transporting heme mechanism. In this study we aimed to evaluate whether oxidative metabolites from maternal cigarette smoke could affect iron homeostasis in the brain of victims of sudden unexplained fetal and infant death, maybe through the induction of maternal hemoglobin damage, such as in case of methemoglobinemia.

METHODS

Histochemical investigations by Prussian blue reaction were made on brain nonheme ferric iron deposits, gaining detailed data on their localization in the brainstem and cerebellum of victims of sudden death and controls. The Gless and Marsland's modification of Bielschowsky's was used to identify neuronal cell bodies and neurofilaments.

RESULTS

Our approach highlighted accumulations of blue granulations, indicative of iron positive reactions, in the brainstem and cerebellum of 33% of victims of sudden death and in none of the control group. The modified Bielschowsky's method confirmed that the cells with iron accumulations were neuronal cells.

CONCLUSIONS

We propose that the free iron deposition in the brain of sudden fetal and infant death victims could be a catabolic product of maternal methemoglobinemia, a biomarker of oxidative stress likely due to nicotine absorption.

The assessment of vascular function during dietary intervention trials in human subjects

The potential to reduce cardiovascular morbidity through dietary modification remains an area of intense clinical and scientific interest. Any putatively beneficial intervention should be tested within a randomised controlled trial which records appropriate endpoints, ideally incident CVD and death. However, the large sample sizes required for these endpoints and associated high costs mean that the majority of dietary intervention research is conducted over short periods among either healthy volunteers or those at only slightly increased risk, with investigators using a diverse range of surrogate measures to estimate arterial health in these studies. The present review identifies commonly employed techniques, discusses the relative merits of each and highlights emerging approaches.

Pharmacological effects and clinical applications of propionyl-L-carnitine

Propionyl-L-carnitine (PLC) is a naturally occurring derivative of carnitine that plays an important role in the metabolism of both carbohydrates and lipids, leading to an increase of ATP generation. PLC, however, is not only a metabolic drug; it is also a potent antiradical agent and thus may protect tissues from oxidative damage. PLC has been demonstrated to exert a protective effect in different models of both cardiac and endothelial dysfunction, to prevent the progression of atherosclerosis, and, more recently, to improve some of the cardiometabolic alterations that frequently accompany insulin resistance. As a result, most of the clinical trials conducted in humans highlight PLC as a potential treatment option in cardiovascular diseases such as peripheral arterial disease, chronic heart failure, or stable angina, especially when type 2 diabetes mellitus or hyperglycemia (i.e., patients on hemodialysis) are also present. The aim of this review is to summarize the pharmacological effects and possible therapeutic applications of PLC, including the most recent findings to date.

Insufficient nitric oxide bioavailability: a hypothesis to explain adverse effects of red blood cell transfusion

While transfusion of red blood cells (RBCs) is effective at preventing morbidity and mortality in anemic patients, studies have indicated that some RBC components have functional defects ("RBC storage lesions") that may actually cause adverse events when transfused. For example, in some studies patients transfused with RBCs stored more than 14 days have had statistically worse outcomes than those receiving "fresher" RBC units. Recipient-specific factors may also contribute to the occurrence of these adverse events. Unfortunately, these events have been difficult to investigate because up to now they have existed primarily as "statistical occurrences" of increased morbidity and mortality in large data sets. There are currently no clinical or laboratory methods to detect or study them in individual transfusion recipients. We propose a unifying hypothesis, centered on insufficient nitric oxide bioavailability (INOBA), to explain the increased morbidity and mortality observed in some patients after RBC transfusion. In this model, variables associated with RBC units (storage time; 2,3-diphosphoglycerate acid concentration) and transfusion recipients (endothelial dysfunction) collectively lead to changes in nitric oxide (NO) levels in vascular beds. Under certain circumstances, these variables are "aligned" such that NO concentrations are markedly reduced, leading to vasoconstriction, decreased local blood flow, and insufficient O(2) delivery to end organs. Under these circumstances, the likelihood of morbidity and mortality escalates. If the key tenets of the INOBA hypothesis are confirmed, it may lead to improved transfusion methods including altered RBC storage and/or processing conditions, novel transfusion recipient screening methods, and improved RBC-recipient matching.

ROCK inhibition prevents fetal serum-induced alteration in structure and function of organ-cultured mesenteric artery

Chronic treatment with fetal bovine serum (FBS) causes contractility reduction, morphological alteration and DNA synthesis in organ-cultured vascular tissues. Here, we tested the hypothesis that chronic inhibition of ROCK has a protective effect on FBS-induced alterations in small arteries. Rabbit mesenteric arterial rings were cultured in FBS-supplemented culture medium with or without Y-27632, a reversible ROCK inhibitor. Chronic Y-27632 treatment prevented FBS-induced gradual arterial constriction, wall thickening, reduced contractility, and increased ROCK-specific MYPT1 Thr853 phosphorylation. Treatment with Y-27632 also prevented decreased eNOS mRNA expression, and reduced acetylcholine-induced relaxation. Sudden application of Y-27632 to pre-cultured rings reduced MYPT1 phosphorylation and re-widened the constricted rings. Chronic treatment with Y-27632, however, rather augmented than reduced the FBS-induced RhoA over-expression, also increased ROCK1 and MYPT1 expression and averted the FBS-induced reduction of MLC expression, suggesting a compensation of inhibited RhoA/ROCK activity. Sudden removal of Y-27632 caused a rebound in MYPT1 phosphorylation and vasoconstriction in rabbit mesenteric artery. To test which ROCK isoform has greater involvement in FBS-induced contraction, haploinsufficient Rock1+/- and Rock2+/- mouse mesenteric arterial rings were subjected to organ-culture. FBS-induced contraction and RhoA over-expression in either heterozygous animal was not different from wild-type animals. These results suggest that FBS-induced contraction is mediated by up-regulation of RhoA and subsequent activation of ROCK. In conclusion, chronic ROCK inhibition produces some effects that protect against FBS-stimulated vasoconstriction and remodeling. There are also negative effects that a sudden withdrawal of ROCK inhibitor might cause a stronger vasoconstriction than before it was used.

Endothelial Nox4 NADPH Oxidase Enhances Vasodilatation and Reduces Blood Pressure In Vivo

Objective—

Increased reactive oxygen species (ROS) production is involved in the pathophysiology of endothelial dysfunction. NADPH oxidase-4 (Nox4) is a ROS-generating enzyme expressed in the endothelium, levels of which increase in pathological settings. Recent studies indicate that it generates predominantly hydrogen peroxide (H 2 O 2 ), but its role in vivo remains unclear.

Methods and Results—

We generated transgenic mice with endothelium-targeted Nox4 overexpression (Tg) to study the in vivo role of Nox4. Tg demonstrated significantly greater acetylcholine- or histamine-induced vasodilatation than wild-type littermates. This resulted from increased H 2 O 2 production and H 2 O 2 -induced hyperpolarization but not altered nitric oxide bioactivity. Tg had lower systemic blood pressure than wild-type littermates, which was normalized by antioxidants.

Conclusion—

Endothelial Nox4 exerts potentially beneficial effects on vasodilator function and blood pressure that are attributable to H 2 O 2 production. These effects contrast markedly with those reported for Nox1 and Nox2, which involve superoxide-mediated inactivation of nitric oxide. Our results suggest that therapeutic strategies to modulate ROS production in vascular disease may need to separately target individual Nox isoforms.

Augmented skeletal muscle hyperaemia during hypoxic exercise in humans is blunted by combined inhibition of nitric oxide and vasodilating prostaglandins

Exercise hyperaemia in hypoxia is augmented relative to the same level of exercise in normoxia. At moderate exercise intensities, the mechanism(s) underlying this augmented response are currently unclear. We tested the hypothesis that endothelium-derived nitric oxide (NO) and vasodilating prostaglandins (PGs) contribute to the augmented muscle blood flow during hypoxic exercise relative to normoxia. In 10 young healthy adults, we measured forearm blood flow (FBF; Doppler ultrasound) and calculated the vascular conductance (FVC) responses during 5 min of rhythmic handgrip exercise at 20% maximal voluntary contraction in normoxia (NormEx) and isocapnic hypoxia (HypEx; O2 saturation ∼85%) before and after local intra-brachial combined blockade of NO synthase (NOS; via N(G)-monomethyl-L-arginine: L-NMMA) and cyclooxygenase (COX; via ketorolac). All trials were performed during local α- and β-adrenoceptor blockade to eliminate sympathoadrenal influences on vascular tone and thus isolate local vasodilatation. Arterial and deep venous blood gases were measured and oxygen consumption (VO2) was calculated. In control (saline) conditions, FBF after 5 min of exercise in hypoxia was greater than in normoxia (345 ± 21 ml min(−1) vs. 297 ± 18 ml min(−1); P < 0.05). After NO–PG block, the compensatory increase in FBF during hypoxic exercise was blunted ∼50% and thus was reduced compared with control hypoxic exercise (312 ± 19 ml min(−1); P < 0.05), but this was not the case in normoxia (289 ± 15 ml min(−1); P = 0.33). The lower FBF during hypoxic exercise was associated with a compensatory increase in O2 extraction, and thus VO2 was maintained at normal control levels (P = 0.64–0.99). We conclude that under the experimental conditions employed, NO and PGs have little role in normoxic exercise hyperaemia whereas combined NO–PG inhibition reduces hypoxic exercise hyperaemia and abolishes hypoxic vasodilatation at rest. Additionally, VO2 of the tissue was maintained in hypoxic conditions at rest and during exercise, despite attenuated oxygen delivery following NO–PG blockade, due to an increase in O2 extraction at the level of the muscle.

Peripheral vascular dysfunction in chronic kidney disease

There is an increased prevalence of cardiovascular disease- (CVD-) related mortality in patients with chronic kidney disease (CKD). Endothelial dysfunction is a primary event in the development of atherosclerosis and hypertension and likely contributes to the elevated cardiovascular risk in CKD. Endothelial dysfunction has been shown to occur in the peripheral vasculature of patients with both severe and moderate CKD. Mechanisms include oxidative stress, L-arginine deficiency, and elevated plasma levels of ADMA. Interventions designed to restore vascular function in patients with CKD have shown mixed results. Evidence from cell culture studies suggest that the accumulation of uremic toxins inhibits L-arginine transport and reduces nitric oxide production. The results of these studies suggest that endothelial dysfunction may become less reversible with advancing kidney disease. The purpose of this paper is to present the current literature pertaining to potential mechanisms of peripheral vascular dysfunction in chronic kidney disease and to identify possible targets for treatment.

Impaired expression of uncoupling protein 2 causes defective postischemic angiogenesis in mice deficient in AMP-activated protein kinase α subunits

OBJECTIVE

The aim of the present study was to determine whether mitochondrial uncoupling protein (UCP) 2 is required for AMPK-dependent angiogenesis in ischemia in vivo.

METHODS AND RESULTS

Angiogenesis was assayed by monitoring endothelial tube formation (a surrogate for angiogenesis) in human umbilical vein endothelial cells (ECs), isolated mouse aortic endothelial cells (MAECs), and pulmonary microvascular endothelial cells or in ischemic thigh adductor muscles from wild-type (WT) mice or mice deficient in either AMPKα1 or AMPKα2. AMPK inhibition with pharmacological inhibitor (compound C) or genetic means (transfection of AMPKα-specific small interfering RNA) significantly lowered the tube formation in human umbilical vein ECs. Consistently, compared with WT mice, tube formation in MAECs isolated from either AMPKα1(-/-) or AMPKα2(-/-) mice, which exhibited oxidative stress and reduced expression of UCP2, was significantly impaired. In addition, adenoviral overexpression of UCP2, but not adenoviruses encoding green fluorescent protein, normalized tube formation in MAECs from either AMPKα1(-/-) or AMPKα2(-/-) mice. Similarly, supplementation with sodium nitroprusside, a nitric oxide (NO) donor, restored tube formation. Furthermore, ischemia significantly increased angiogenesis, serine 1177 phosphorylation of endothelial NO synthase, and UCP2 in ischemic thigh adductor muscles from WT mice but not in those from either AMPKα1(-/-) or AMPKα2(-/-) mice.

CONCLUSIONS

We conclude that AMPK-dependent UCP2 expression in ECs promotes angiogenesis in vivo.

Endothelial biology in the post-menopausal obese woman

Women generally have a reduced risk of cardiovascular disease (CVD). However, this protection of gender diminishes rapidly after menopause and with advancing age, particularly in obese women. Alterations in vascular function are thought to a key early step in the development of atherosclerosis. In this review, we will describe the features of endothelial dysfunction in the post-menopausal obese female and discuss the interplay of aging, estrogen withdrawal, and obesity. The objectives include (1) a review of endothelial biology and endothelial dysfunction, and (2) a discussion how the endothelial function is altered in the context of aging, hormonal changes and insulin resistance. The clinical consequences of endothelial dysfunction and CVD will also be reviewed.

Aging and vascular endothelial function in humans

Advancing age is the major risk factor for the development of CVD (cardiovascular diseases). This is attributable, in part, to the development of vascular endothelial dysfunction, as indicated by reduced peripheral artery EDD (endothelium-dependent dilation) in response to chemical [typically ACh (acetylcholine)] or mechanical (intravascular shear) stimuli. Reduced bioavailability of the endothelium-synthesized dilating molecule NO (nitric oxide) as a result of oxidative stress is the key mechanism mediating reduced EDD with aging. Vascular oxidative stress increases with age as a consequence of greater production of reactive oxygen species (e.g. superoxide) without a compensatory increase in antioxidant defences. Sources of increased superoxide production include up-regulation of the oxidant enzyme NADPH oxidase, uncoupling of the normally NO-producing enzyme, eNOS (endothelial NO synthase) (due to reduced availability of the cofactor tetrahydrobiopterin) and increased mitochondrial synthesis during oxidative phosphorylation. Increased bioactivity of the potent endothelial-derived constricting factor ET-1 (endothelin-1), reduced endothelial production of/responsiveness to dilatory prostaglandins, the development of vascular inflammation, formation of AGEs (advanced glycation end-products), an increased rate of endothelial apoptosis and reduced expression of oestrogen receptor α (in postmenopausal females) also probably contribute to impaired EDD with aging. Several lifestyle and biological factors modulate vascular endothelial function with aging, including regular aerobic exercise, dietary factors (e.g. processed compared with non-processed foods), body weight/fatness, vitamin D status, menopause/oestrogen deficiency and a number of conventional and non-conventional risk factors for CVD. Given the number of older adults now and in the future, more information is needed on effective strategies for the prevention and treatment of vascular endothelial aging.

Vasorelaxant and hypotensive effects of the extract and the isolated flavonoid rutin obtained from Polygala paniculata L

Objectives

This study aimed to investigate the in-vitro and in-vivo cardiovascular effects of the crude hydroalcoholic extract from Polygala paniculata (HEPP) in rats.

Methods

The procedures were performed on aortic rings and on normotensive anaesthetized rats.

Key findings

When tested in endothelium-intact aorta rings, HEPP (30–1000 µg/ml) produced a significant non-concentration-dependent relaxing effect (∼40%), which was completely prevented by incubation with L-NAME (nitric oxide synthase inhibitor), ODQ (soluble guanylate cyclase inhibitor) and partially inhibited by tetraethylammonium (TEA; a non-selective potassium channel blocker) and charybdotoxin (a large- and intermediate-conductance calcium-activated potassium channel blocker). In contrast, atropine (a muscarinic receptor antagonist) or pyrilamine(a histamine H1 receptor antagonist) had no effect. Furthermore, oral administration of HEPP (30–300 mg/kg) in anaesthetized rats caused a dose-dependent and sustained hypotensive action. This effect was unchanged by atropine or TEA, but was strongly reduced in rats continuously infused with L-NAME or methylene blue. Moreover, rutin (1–3 mg/kg) administered by an intravenous route also caused a dose-dependent hypotensive effect in rats.

Conclusions

Our results demonstrated that the extract obtained from P. paniculata induces potent hypotensive and vasorelaxant effects that are dependent on the nitric oxide/guanylate cyclase pathway. These effects could be related, at least in part, to the rutin contents in this extract.

Chemerin/ChemR23 signaling axis is involved in the endothelial protection by K(ATP) channel opener iptakalim

AIM

To elucidate the modulation of the chemerin/ChemR23 axis by iptakalim-induced opening of K(ATP) channels and to determine the role of the chemerin/ChemR23 axis in the iptakalim-mediated endothelial protection.

METHODS

Cultured rat aortic endothelial cells (RAECs) were used. Chemerin secretion and ChemR23 protein expression were investigated using Western blot analysis. The gene expression level of ChemR23 was examined with RT-PCR. In addition, the release of nitric oxide (NO) was measured with a nitric oxide assay.

RESULTS

Homocysteine, uric acid, high glucose, or oxidized low-density lipoprotein (ox-LDL) down-regulated the chemerin secretion and ChemR23 gene/protein expression in RAECs as a function of concentration and time, which was reversed by pretreatment with iptakalim (1-10 μmol/L). Moreover, these effects of iptakalim were abolished in the presence of the K(ATP) channel antagonist glibenclamide (1 μmol/L). Both iptakalim and recombinant chemerin restored the impaired NO production in RAECs induced by uric acid, and the effects were abolished by anti-ChemR23 antibodies.

CONCLUSION

Iptakalim via opening K(ATP) channels enhanced the endothelial chemerin/ChemR23 axis and NO production, thus improving endothelial function.

Effect of the traditional Chinese medicine tongxinluo on endothelial dysfunction rats studied by using urinary metabonomics based on liquid chromatography-mass spectrometry

A urinary metabonomic method based on ultra-fast liquid chromatography coupled with ion trap-time of flight mass spectrometry (UFLC/MS-IT-TOF) was employed to study the preventive efficacy and the metabolic changes caused by simavastatin and the traditional Chinese medicine tongxinluo in endothelial dysfunction rats. Principal component analysis (PCA) was applied to study metabolic patterns of endothelial dysfunction rats and healthy control rats. 1-Methyladenosine, indoxyl sulfate, hippuric acid, riboflavin, coproporphyrin, and p-cresol glucuronide were identified as potential biomarkers, indicating that pathways of adenine, tryptophan, phenylalanine, riboflavin and porphyrin metabolism were disturbed in endothelial dysfunction rats. Applications of simvastatin and tongxinluo to endothelial dysfunction rats improved endothelial function according to the results of histopathology and measurements of endothelin-1 and nitric oxide. Metabonomic studies suggested that tongxinluo prevents endothelial dysfunction by regulating multiple metabolic pathways to their normal state, whereas simvastatin only altered selected metabolic pathways. This research demonstrated that metabonomics is a powerful and promising tool for disease investigation and the efficacy evaluation of complex traditional Chinese medicines.