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

Entacapone is an Antioxidant More Potent than Vitamin C and Vitamin E for Scavenging of Hypochlorous Acid and Peroxynitrite, and the Inhibition of Oxidative Stress-Induced Cell Death

Background

Entacapone (ENT), a clinical drug for the treatment of Parkinson’s disease, has been shown to have antioxidant effects, but little is known about its antioxidant mechanisms. The objective of the current study was to determine the antioxidant activity of ENT against different species of oxidants and compared it with that of vitamin C and vitamin E. We also determined the effect of ENT on oxidative stress-induced cell death in human umbilical vein endothelial cells (HUVECs).

Material/Methods

The total antioxidant activities of ENT, vitamin C and vitamin E were determined with a standard DPPH-scavenging assay. Specific assays to determine ENT’s scavenging activity on hypochlorous acid (HOCl), peroxynitrite (ONOO⁻), and hydrogen peroxide (H₂O₂), and the chelating effect on Fe(II) were used. H₂O₂-induced cell death in HUVECs was determined with the MTT assay.

Results

ENT (10 and 20 μM) scavenged 60% and 83% of DPPH activity, respectively. These percentages were greater than those resulting from using the same concentrations of vitamin C and vitamin E. ENT’s HOCl-scavenging activity was concentration-dependent and 8 to 20 times stronger than those of vitamin C and vitamin E. ENT’s ONOO⁻-scavenging activity was 8% to 30% stronger than that of vitamin C. However, ENT, vitamin C, and vitamin E were not able to directly scavenge H₂O₂, and did not show any chelating effect on Fe(II). Importantly ENT, but not vitamin C or vitamin E, inhibited H₂O₂-induced cell death in HUVECs.

Conclusions

ENT is an antioxidant that can scavenge toxic HOCl and ONOO⁻ species and inhibit oxidative stress-induced cell death more effectively than vitamin C and vitamin E. ENT may have new clinical applications as an antioxidant in the treatment of ROS-induced diseases including cardiovascular disease, cancer, and neurodegenerative diseases.

Specific cell-derived microvesicles: Linking endothelial function to carotid artery intima-media thickness in low cardiovascular risk menopausal women

BACKGROUND

Decreases in endothelial function measured by reactive hyperemic index (RHI) correlated with increases in carotid intima-media thickness (CIMT) in recently menopausal women with a low risk cardiovascular profile. Factors linking this association are unknown.

OBJECTIVE

Assess, longitudinally, markers of platelet activation and cell-derived, blood-borne microvesicles (MV) in relationship to RHI and CIMT in asymptomatic, low risk menopausal women.

METHODS

RHI by digital pulse tonometry (n = 93), CIMT by ultrasound (n = 113), measures of platelet activation and specific cell-derived, blood-borne MV were evaluated in women throughout the Kronos Early Estrogen Prevention Study (KEEPS) at Mayo Clinic.

RESULTS

CIMT, but not RHI, increased significantly over 4 years. The average change in CIMT correlated significantly with the average follow-up values of MV positive for common leukocyte antigen [CD45; ρ = 0.285 (P = 0.002)] and VCAM-1 [ρ = 0.270 (P = 0.0040)]. Using principal components analysis (PC) on the aggregate set of average follow-up measures, the first derived PC representing numbers of MV positive for markers of vascular endothelium, inflammatory cells (leukocyte and monocytes), pro-coagulant (tissue factor), and cell adhesion molecules (ICAM-1 and VCAM-1) associated with changes in RHI and CIMT. Changes in RHI associated with another PC defined by measures of platelet activation (dense granular ATP secretion, surface expression of P-selectin and fibrinogen receptors).

CONCLUSIONS

MV derived from activated endothelial and inflammatory cells, and those expressing cell adhesion and pro-coagulant molecules may reflect early vascular dysfunction in low risk menopausal women. Assays of MV as non-conventional measures to assess cardiovascular risk in asymptomatic women remain to be developed.

Chronic in vivo or acute in vitro resveratrol attenuates endothelium-dependent cyclooxygenase-mediated contractile signaling in hypertensive rat carotid artery

Exaggerated cyclooxygenase (COX) and thromboxane-prostanoid (TP) receptor-mediated endothelium-dependent contraction can contribute to endothelial dysfunction. This study examined the effect of resveratrol (RSV) on endothelium-dependent contraction and cell signaling in the common carotid artery (CCA) from spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Acetylcholine (Ach)-stimulated endothelium-dependent nitric oxide synthase (NOS)-mediated relaxation in precontracted SHR CCA was impaired (maximum 73 ± 6% vs. 87 ± 5% in WKY) (P < 0.05) by competitive COX-mediated contraction. Chronic (28-day) treatment in vivo (drinking water) with a ∼0.075 mg·kg(-1)·day(-1) RSV dose affected neither endothelium-dependent relaxation nor endothelium-dependent contraction and associated prostaglandin (PG) production evaluated in non-precontracted NOS-blocked CCA. In contrast, a chronic ∼7.5 mg·kg(-1)·day(-1) RSV dose improved endothelium-dependent relaxation (94 ± 6%) and attenuated endothelium-dependent contraction (58 ± 4% vs. 73 ± 5% in No-RSV) and PG production (183 ± 43 vs. 519 ± 93 pg/ml) in SHR CCA, while U46619-stimulated TP receptor-mediated contraction was unaffected. In separate acute in vitro experiments, 20-μM RSV preincubation attenuated endothelium-dependent contraction (6 ± 4% vs. 62 ± 2% in No Drug) and PG production (121 ± 15 vs. 491 ± 93 pg/ml) and attenuated U46619-stimulated contraction (134 ± 5% vs. 171 ± 4%) in non-precontracted NOS-blocked SHR CCA. Compound C, a known AMP-activated protein kinase (AMPK) inhibitor, did not prevent the RSV attenuating effect on Ach- and U46619-stimulated contraction but did prevent the RSV attenuating effect on PG production (414 ± 58 pg/ml). These data demonstrate that RSV can attenuate endothelium-dependent contraction both by suppressing arterial wall PG production, which may be partially mediated by AMPK, and by TP receptor hyporesponsiveness, which does not appear to be mediated by AMPK.

Study of endothelial function response to exercise training in hypertensive individuals (SEFRET): study protocol for a randomized controlled trial

Background

Endothelial dysfunction is a hallmark of diabetes mellitus and systemic arterial hypertension (SAH) and an early maker for atherosclerosis. Aerobic exercise training is known to enhance endothelial function, but little is understood about the effects of resistance or combined exercise training on endothelial function. The aim of this study is to investigate the effect of a 12-week aerobic (AT), resistance (RT), or combined (aerobic and resistance, CT) training program on endothelial function and assess associated effects on blood pressure in individuals with SAH.

Methods/design

Eighty-one subjects with SAH aged 18 to 70 years will be selected and randomly assigned to three types of exercise training: AT, RT or CT. The study will involve the following procedures and tests: anamnesis, anthropometric assessment, echocardiography, blood pressure measurements through ambulatory blood pressure monitoring, flow-mediated dilation, ergospirometry, one repetition maximum test (1-RM), and blood collection (number of circulating endothelial progenitor cells, number of circulating endothelial microparticles, lipid profile, glucose, glycated hemoglobin, and creatinine). The AT intervention will consist of a 40-min exercise session with progressive intensities ranging from 50 to 75 % of heart rate reserve. The RT intervention will consist of a 40-minute session with four sets of six to 12 repetitions with a rest period of 60 to 90 seconds between each set and each type of exercise. Weight loads will be adjusted to 60 to 80 % of 1-RM for six types of exercise. The CT intervention will consist of a 20-min aerobic exercise session, followed by an additional 20-min resistance exercise session; each resistance exercise will have two sets less to match the total training volume.

Discussion

The study results are expected evidence of cardiovascular protective effects of different types of exercise training through the modulation of endothelial function in hypertensive individuals. Knowing the magnitude of improvement of endothelium-dependent vasodilation for the different types of exercise training can provide scientific evidence for the prescription of exercise programs for vascular protection targeting hypertensive individuals.

Trial registration

The Brazilian Clinical Trials Registry (http://www.ensaiosclinicos.gov.br/) under RBR-9ygmdn and dated 1 March 2015.

Effect of vitamin C on endothelial function of children with chronic renal failure: An experimental study

Background:

It is well established that improvement of endothelial dysfunction (ED) could prevent or delay the occurrence of cardiovascular disease (CVD) and its related morbidity and mortality in patients with chronic kidney disease (CKD). In this study we investigated whether administration of vitamin C could be effective by improving brachial artery flow-mediated dilation (FMD) and intima media thickness (IMT), two surrogate markers of ED, in children with CKD or chronic renal failure (CRF).

Materials and Methods:

In this analytic-experimental study children aged 3-18 years with a diagnosis of CRF and a group of healthy children were enrolled. Vitamin C (250 mg/day) administrated for the two studied groups for 1 month. Endothelial function was evaluated by FMD and IMT measurement using vascular Doppler ultrasonography, before and after trial.

Results:

In this study 18 patients with CRF and 19 normal children as the control group were studied. At baseline mean of IMT and FMD was not different in the two studied groups (P > 0.05). After vitamin C administration IMT decreased significantly in the two studied groups (P < 0.05). FMD increased in the two studied groups but the difference was significant in the control group (P < 0.05).

Conclusion:

The findings of this interventional trial have demonstrated that vitamin C could have protective effect on ED of patients with CRF possibly in those with severe form of the disease but for obtaining more conclusive results larger sample size is needed.

Chronic administration of the probiotic kefir improves the endothelial function in spontaneously hypertensive rats

Background

The beverage obtained by fermentation of milk with kefir grains, a complex matrix containing acid bacteria and yeasts, has been shown to have beneficial effects in various diseases. However, its effects on hypertension and endothelial dysfunction are not yet clear. In this study, we evaluated the effects of kefir on endothelial cells and vascular responsiveness in spontaneously hypertensive rats (SHR).

Methods

SHR were treated with kefir (0.3 mL/100 g body weight) for 7, 15, 30 and 60 days and compared with non-treated SHR and with normotensive Wistar-Kyoto rats. Vascular endothelial function was evaluated in aortic rings through the relaxation response to acetylcholine (ACh). The balance between reactive oxygen species (ROS) and nitric oxide (NO) synthase was evaluated through specific blockers in the ACh-induced responses and through flow cytometry in vascular tissue.

Results

Significant effects of kefir were observed only after treatment for 60 days. The high blood pressure and tachycardia exhibited by the SHR were attenuated by approximately 15 % in the SHR-kefir group. The impaired ACh-induced relaxation of the aortic rings observed in the SHR (37 ± 4 %, compared to the Wistar rats: 74 ± 5 %), was significantly attenuated in the SHR group chronically treated with kefir (52 ± 4 %). The difference in the area under the curve between before and after the NADPH oxidase blockade or NO synthase blockade of aortic rings from SHR were of approximately +90 and −60 %, respectively, when compared with Wistar rats. In the aortic rings from the SHR-kefir group, these values were reduced to +50 and −40 %, respectively. Flow cytometric analysis of aortic endothelial cells revealed increased ROS production and decreased NO bioavailability in the SHR, which were significantly attenuated by the treatment with kefir. Scanning electronic microscopy showed vascular endothelial surface injury in SHR, which was partially protected following administration of kefir for 60 days. In addition, the recruitment of endothelial progenitor cells was decreased in the non-treated SHR and partially restored by kefir treatment.

Conclusions

Kefir treatment for 60 days was able to improve the endothelial function in SHR by partially restoring the ROS/NO imbalance and the endothelial architecture due to endothelial progenitor cells recruitment.

The Restorative Effects of Eucommia ulmoides Oliver Leaf Extract on Vascular Function in Spontaneously Hypertensive Rats

Eucommia ulmoides Oliv. leaf is a traditional Chinese antihypertensive and antidiabetic medicine. We examined the effects of chronic Eucommia leaf extract (ELE) administration on artery function and morphology in spontaneously hypertensive rats (SHRs). ELE was orally administered via normal diet ad libitum to six-week-old male SHRs at a concentration of 5% for seven weeks. Acetylcholine (ACh)-induced endothelium-dependent relaxation, sodium nitroprusside (SNP)-induced endothelium-independent relaxation, plasma nitric oxide (NO) levels, and media thickness were assessed. ELE significantly improved ACh-induced aortic endothelium-dependent relaxation but did not affect SNP-induced endothelium-independent relaxation in the SHRs, as compared to the animals receiving normal diet. Plasma NO levels and media thickness were significantly increased and decreased, respectively, in the ELE-treated SHRs. Therefore, long-term ELE administration may effectively improve vascular function by increasing plasma NO levels and bioavailability, and by preventing vascular hypertrophy in the SHR aorta.

Vascular Protective Effect of an Ethanol Extract of Camellia japonica Fruit: Endothelium-Dependent Relaxation of Coronary Artery and Reduction of Smooth Muscle Cell Migration

Camellia japonica is a popular garden plant in Asia and widely used as cosmetic sources and traditional medicine. However, the possibility that C. japonica affects cardiovascular system remains unclear. The aim of the present study was to evaluate vascular effects of an extract of C. japonica. Vascular reactivity was assessed in organ baths using porcine coronary arteries and inhibition of proliferation and migration were assessed using human vascular smooth muscle cells (VSMCs). All four different parts, leaf, stem, flower, and fruits, caused concentration-dependent relaxations and C. japonica fruit (CJF) extract showed the strongest vasorelaxation and its effect was endothelium dependent. Relaxations to CJF were markedly reduced by inhibitor of endothelial nitric oxide synthase (eNOS) and inhibitor of PI3-kinase, but not affected by inhibitor of cyclooxygenase and endothelium-derived hyperpolarizing factor-mediated response. CJF induced activated a time- and concentration-dependent phosphorylation of eNOS in endothelial cells. Altogether, these studies have demonstrated that CJF is a potent endothelium-dependent vasodilator and this effect was involved in, at least in part, PI3K-eNOS-NO pathway. Moreover, CJF attenuated TNF-α induced proliferation and PDGF-BB induced migration of VSMCs. The present findings indicate that CJF could be a valuable candidate of herbal medicine for cardiovascular diseases associated with endothelial dysfunction and atherosclerosis.

Cerium Dioxide Nanoparticle Exposure Improves Microvascular Dysfunction and Reduces Oxidative Stress in Spontaneously Hypertensive Rats

The elevated production of reactive oxygen species (ROS) in the vascular wall is associated with cardiovascular diseases such as hypertension. This increase in oxidative stress contributes to various mechanisms of vascular dysfunction, such as decreased nitric oxide bioavailability. Therefore, anti-oxidants are being researched to decrease the high levels of ROS, which could improve the microvascular dysfunction associated with various cardiovascular diseases. From a therapeutic perspective, cerium dioxide nanoparticles (CeO₂ NP) hold great anti-oxidant potential, but their in vivo activity is unclear. Due to this potential anti-oxidant action, we hypothesize that injected CeO₂ NP would decrease microvascular dysfunction and oxidative stress associated with hypertension. In order to simulate a therapeutic application, spontaneously hypertensive (SH) and Wistar-Kyoto (WKY) rats were intravenously injected with either saline or CeO₂ NP (100 μg suspended in saline). Twenty-four hours post-exposure mesenteric arteriolar reactivity was assessed via intravital microscopy. Endothelium-dependent and –independent function was assessed via acetylcholine and sodium nitroprusside. Microvascular oxidative stress was analyzed using fluorescent staining in isolated mesenteric arterioles. Finally, systemic inflammation was examined using a multiplex analysis and venular leukocyte flux was counted. Endothelium-dependent dilation was significantly decreased in the SH rats (29.68 ± 3.28%, maximal response) and this microvascular dysfunction was significantly improved following CeO₂ NP exposure (43.76 ± 4.33%, maximal response). There was also an increase in oxidative stress in the SH rats, which was abolished following CeO₂ NP treatment. These results provided evidence that CeO₂ NP act as an anti-oxidant in vivo. There were also changes in the inflammatory profile in the WKY and SH rats. In WKY rats, IL-10 and TNF-α were increased following CeO₂ NP treatment. Finally, leukocyte flux was increased in the SH rats (34 ± 4 vs. 17 ± 3 cells/min in the normotensive controls), but this activation was decreased following exposure (15 ± 2 vs. 34 ± 4 cells/min). These results indicated that CeO₂ NP may alter the inflammatory response in both SH and WKY rats. Taken together, these results provide evidence that CeO₂ NP act as an anti-oxidant in vivo and may improve microvascular reactivity in a model of hypertension.

NADPH oxidase 4 protects against development of endothelial dysfunction and atherosclerosis in LDL receptor deficient mice

Aims

Endothelial dysfunction is an early step in the development of atherosclerosis. Increased formation of superoxide anions by NADPH oxidase Nox1, 2, and 5 reduces nitric oxide availability and can promote endothelial dysfunction. In contrast, recent evidence supports a vasoprotective role of H₂O₂ produced by main endothelial isoform Nox4. Therefore, we analysed the impact of genetic deletion of Nox4 on endothelial dysfunction and atherosclerosis in the low-density lipoprotein receptor (Ldlr) knockout model.

Methods and results

Ex vivo analysis of endothelial function by Mulvany myograph showed impaired endothelial function in thoracic aorta of Nox4^−/−/Ldlr^−/− mice. Further progression of endothelial dysfunction due to high-fat diet increased atherosclerotic plaque burden and galectin-3 staining in Nox4^−/−/Ldlr^−/− mice compared with Ldlr^−/− mice. Under physiological conditions, loss of Nox4 does not influence aortic vascular function. In this setting, loss of Nox4-derived H₂O₂ production could be partially compensated for by nNOS upregulation. Using an innovative optical coherence tomography approach, we were able to analyse endothelial function by flow-mediated vasodilation in the murine saphenous artery in vivo. This new approach revealed an altered flow-mediated dilation in Nox4^−/− mice, indicating a role for Nox4 under physiological conditions in peripheral arteries in vivo.

Conclusions

Nox4 plays an important role in maintaining endothelial function under physiological and pathological conditions. Loss of Nox4-derived H₂O₂ could be partially compensated for by nNOS upregulation, but severe endothelial dysfunction is not reversible. This leads to increased atherosclerosis under atherosclerotic prone conditions.

G protein-coupled estrogen receptor inhibits vascular prostanoid production and activity

Complications of atherosclerotic vascular disease, such as myocardial infarction and stroke, are the most common causes of death in postmenopausal women. Endogenous estrogens inhibit vascular inflammation-driven atherogenesis, a process that involves cyclooxygenase (COX)-derived vasoconstrictor prostanoids such as thromboxane A2. Here, we studied whether the G protein-coupled estrogen receptor (GPER) mediates estrogen-dependent inhibitory effects on prostanoid production and activity under pro-inflammatory conditions. Effects of estrogen on production of thromboxane A(2) were determined in human endothelial cells stimulated by the pro-inflammatory cytokine tumour necrosis factor alpha (TNF-α). Moreover, Gper-deficient (Gper(-/-)) and WT mice were fed a pro-inflammatory diet and underwent ovariectomy or sham surgery to unmask the role of endogenous estrogens. Thereafter, contractions to acetylcholine-stimulated endothelial vasoconstrictor prostanoids and the thromboxane-prostanoid receptor agonist U46619 were recorded in isolated carotid arteries. In endothelial cells, TNF-α-stimulated thromboxane A2 production was inhibited by estrogen, an effect blocked by the GPER-selective antagonist G36. In ovary-intact mice, deletion of Gper increased prostanoid-dependent contractions by twofold. Ovariectomy also augmented prostanoid-dependent contractions by twofold in WT mice but had no additional effect in Gper(-/-) mice. These contractions were blocked by the COX inhibitor meclofenamate and unaffected by the nitric oxide synthase inhibitor l-N(G)-nitroarginine methyl ester. Vasoconstrictor responses to U46619 did not differ between groups, indicating intact signaling downstream of thromboxane-prostanoid receptor activation. In summary, under pro-inflammatory conditions, estrogen inhibits vasoconstrictor prostanoid production in endothelial cells and activity in intact arteries through GPER. Selective activation of GPER may therefore be considered as a novel strategy to treat increased prostanoid-dependent vasomotor tone or vascular disease in postmenopausal women.

Effects of Crocetin Esters and Crocetin from Crocus sativus L. on Aortic Contractility in Rat Genetic Hypertension

Background: Endothelial dysfunction, characterized by an enhancement in vasoconstriction, is clearly associated with hypertension. Saffron (Crocus sativus L.) bioactive compounds have been recognized to have hypotensive properties. Recently, we have reported that crocetin exhibits potent vasodilator effects on isolated aortic rings from hypertensive rats. In this work, we have aimed to analyze the anticontractile ability of crocetin or crocetin esters pool (crocins) isolated from saffron. Thus, we have studied the effects of saffron carotenoids on endothelium-dependent and -independent regulation of smooth muscle contractility in genetic hypertension. Methods: We have measured the isometric responses of aortic segments with or without endothelium obtained from spontaneously hypertensive rats. The effects of carotenoids were studied by assessing the endothelial modulation of phenylephrine-induced contractions (10⁻⁹–10⁻⁵ M) in the presence or absence of crocetin or crocins. The role of nitric oxide and prostanoids was analyzed by performing the experiments with L-NAME (NG-nitro-l-arginine methyl ester) or indomethacin (both 10⁻⁵ M), respectively. Results: Crocetin, and to a minor extent crocins, diminished the maximum contractility of phenylephrine in intact rings, while crocins, but not crocetin, increased this contractility in de-endothelizated vessels. In the intact vessels, the effect of crocetin on contractility was unaffected by indomethacin but was abolished by L-NAME. However, crocetin but not crocins, lowered the already increased contractility caused by L-NAME. Conclusions: Saffron compounds, but especially crocetin have endothelium-dependent prorelaxing actions. Crocins have procontractile actions that take place via smooth muscle cell mechanisms. These results suggest that crocetin and crocins activate different mechanisms involved in the vasoconstriction pathway in hypertension.

Endothelial Dysfunction: Clinical Implications in Cardiovascular Disease and Therapeutic Approaches

Atherosclerosis is a chronic progressive vascular disease. It starts early in life, has a long asymptomatic phase, and a progression accelerated by various cardiovascular risk factors. The endothelium is an active inner layer of the blood vessel. It generates many factors that regulate vascular tone, the adhesion of circulating blood cells, smooth muscle proliferation, and inflammation, which are the key mechanisms of atherosclerosis and can contribute to the development of cardiovascular events. There is growing evidence that functional impairment of the endothelium is one of the first recognizable signs of development of atherosclerosis and is present long before the occurrence of atherosclerotic cardiovascular disease. Therefore, understanding the endothelium's central role provides not only insights into pathophysiology, but also a possible clinical opportunity to detect early disease, stratify cardiovascular risk, and assess response to treatments. In the present review, we will discuss the clinical implications of endothelial function as well as the therapeutic issues for endothelial dysfunction in cardiovascular disease as primary and secondary endothelial therapy.

Prenatal lipopolysaccharide exposure causes mesenteric vascular dysfunction through the nitric oxide and cyclic guanosine monophosphate pathway in offspring

Cardiovascular diseases, such as hypertension, could be programmed in fetal life. Prenatal lipopolysaccharide (LPS) exposure in utero results in increased blood pressure in offspring, but the vascular mechanisms involved are unclear. Pregnant Sprague-Dawley rats were intraperitoneally injected with LPS (0.79mg/kg) or saline (0.5ml) on gestation days 8, 10, and 12. The offspring of LPS-treated dams had higher blood pressure and decreased acetylcholine (ACh)-induced relaxation and increased phenylephrine (PE)-induced contraction in endothelium-intact mesenteric arteries. Endothelium removal significantly enhanced the PE-induced contraction in offspring of control but not LPS-treated dams. The arteries pretreated with l-NAME to inhibit nitric oxide synthase (eNOS) in the endothelium or ODQ to inhibit cGMP production in the vascular smooth muscle had attenuated ACh-induced relaxation but augmented PE-induced contraction to a larger extent in arteries from offspring of control than those from LPS-treated dams. In addition, the endothelium-independent relaxation caused by sodium nitroprusside was also decreased in arteries from offspring of LPS-treated dams. The functional results were accompanied by a reduction in the expressions of eNOS and soluble guanylate cyclase (sGC) and production of NO and cGMP in arteries from offspring of LPS-treated dams. Furthermore, LPS-treated dam's offspring arteries had increased oxidative stress and decreased antioxidant capacity. Three-week treatment with TEMPOL, a reactive oxygen species (ROS) scavenger, normalized the alterations in the levels of ROS, eNOS, and sGC, as well as in the production of NO and cGMP and vascular function in the arteries of the offspring of LPS-treated dams. In conclusion, prenatal LPS exposure programs vascular dysfunction of mesenteric arteries through increased oxidative stress and impaired NO-cGMP signaling pathway.

An Investigation of Organic and Inorganic Mercury Exposure and Blood Pressure in a Small-Scale Gold Mining Community in Ghana

There is increasing concern about the cardiovascular effects of mercury (Hg) exposure, and that organic methylmercury and inorganic Hg²⁺ may affect the cardiovascular system and blood pressure differentially. In small-scale gold mining communities where inorganic, elemental Hg exposures are high, little is known about the effects of Hg on blood pressure. In 2011, we assessed the relationship between Hg exposure and blood pressure (BP) in a cross-sectional study of adults from a small-scale gold mining community, Kejetia, and subsistence farming community, Gorogo, in Ghana’s Upper East Region. Participants’ resting heart rate and BP were measured, and hair and urine samples were provided to serve as biomarkers of organic and inorganic Hg exposure, respectively. Participants included 70 miners and 26 non-miners from Kejetia and 75 non-miners from Gorogo. Total specific gravity-adjusted urinary and hair Hg was higher among Kejetia miners than Kejetia non-miners and Gorogo participants (median urinary Hg: 5.17, 1.18, and 0.154 µg/L, respectively; hair Hg: 0.945, 0.419, and 0.181 µg/g, respectively). Hypertension was prevalent in 17.7% of Kejetia and 21.3% of Gorogo participants. Urinary and hair Hg were not significantly associated with systolic or diastolic BP for Kejetia or Gorogo participants while adjusting for sex, age, and smoking status. Although our results follow trends seen in other studies, the associations were not of statistical significance. Given the unique study population and high exposures to inorganic Hg, the work contained here will help increase our understanding of the cardiovascular effects of Hg.

KCa3.1: a new player in progressive kidney disease

PURPOSE OF REVIEW

Hypertension and hyperglycaemia are major risk factors that result in chronic kidney disease (CKD). Achievement of blood pressure goals, optimal control of blood glucose levels and the use of agents to block the renin-angiotensin-aldosterone system slow the progression of CKD. However, not all patients are benefited by these interventions and novel strategies to arrest or reverse the pathological processes inherent in CKD are needed. The therapeutic potential of targeting KCa3.1 in CKD will be discussed in this review.

RECENT FINDINGS

Blockade of KCa3.1 ameliorates activation of renal fibroblasts in diabetic mice by inhibiting the transforming growth factor-β1/small mothers against decapentaplegic pathway. A concomitant reduction in nuclear factor-κB activation in human proximal tubular cells under diabetic conditions has been observed. Advanced glycosylated endproducts induce both protein expression and current density of KCa3.1, which, in turn, mediates migration and proliferation of vascular smooth muscle cells via Ca²⁺-dependent signalling pathways.

SUMMARY

Studies have clearly demonstrated a causal role of chronic hyperglycaemia and hypertension in the development of CKD. However, a large proportion of patients develop end-stage kidney disease despite strict glycaemic control and the attainment of recommended blood pressure goals. Therefore, it is essential to identify and validate novel targets to reduce the development and progression of CKD. Recent findings demonstrate that genetic deletion or pharmacologic inhibition of KCa3.1 significantly reduces the development of diabetic nephropathy in animal models. However, the consequences of blockade of KCa3.1 in preventing and treating established diabetic nephropathy in humans warrants further study.

The Achilles' heel of senescent cells: from transcriptome to senolytic drugs

The healthspan of mice is enhanced by killing senescent cells using a transgenic suicide gene. Achieving the same using small molecules would have a tremendous impact on quality of life and the burden of age-related chronic diseases. Here, we describe the rationale for identification and validation of a new class of drugs termed senolytics, which selectively kill senescent cells. By transcript analysis, we discovered increased expression of pro-survival networks in senescent cells, consistent with their established resistance to apoptosis. Using siRNA to silence expression of key nodes of this network, including ephrins (EFNB1 or 3), PI3Kδ, p21, BCL-xL, or plasminogen-activated inhibitor-2, killed senescent cells, but not proliferating or quiescent, differentiated cells. Drugs targeting these same factors selectively killed senescent cells. Dasatinib eliminated senescent human fat cell progenitors, while quercetin was more effective against senescent human endothelial cells and mouse BM-MSCs. The combination of dasatinib and quercetin was effective in eliminating senescent MEFs. In vivo, this combination reduced senescent cell burden in chronologically aged, radiation-exposed, and progeroid Ercc1^−/Δ mice. In old mice, cardiac function and carotid vascular reactivity were improved 5 days after a single dose. Following irradiation of one limb in mice, a single dose led to improved exercise capacity for at least 7 months following drug treatment. Periodic drug administration extended healthspan in Ercc1^−/Δ mice, delaying age-related symptoms and pathology, osteoporosis, and loss of intervertebral disk proteoglycans. These results demonstrate the feasibility of selectively ablating senescent cells and the efficacy of senolytics for alleviating symptoms of frailty and extending healthspan.

Prostanoid-mediated contractions of the carotid artery become Nox2-independent with aging

Aging is a major risk factor for carotid artery disease that may lead to stroke and dementia. Vascular effects associated with aging include increased vasomotor tone, as well as enhanced contractility to endothelial vasoconstrictor prostanoids and reduced nitric oxide (NO) bioactivity partly due to increased oxidative stress. We hypothesized that vascular NADPH oxidase (Nox)-derived superoxide may be involved in prostanoid- and NO-related functional aging. NO-mediated relaxations and prostanoid-mediated contractions to acetylcholine as well as phenylephrine-dependent contractions were investigated in the carotid artery from young (4 months) and aged mice (24 months). Gene expression of Nox subunits and endothelial NO synthase (eNOS) was determined in the carotid artery and aorta. In young mice, the thromboxane-prostanoid receptor antagonist SQ 29,548 fully blocked acetylcholine-induced contractions while reducing responses to phenylephrine by 75 %. The Nox2-targeted inhibitor Nox2ds-tat and the superoxide scavenger tempol reduced acetylcholine-stimulated, prostanoid-mediated contractions by 85 and 75 %, respectively, and phenylephrine-dependent contractions by 45 %. Unexpectedly, in aged mice, the substantial Nox2-dependent component of acetylcholine- and phenylephrine-induced, prostanoid-mediated contractions was abolished. In addition, endothelium-dependent, NO-mediated relaxations were impaired with aging. The expression of Nox subunits was greater in the aorta compared with the carotid artery, in which Nox1 was undetectable. eNOS gene expression was reduced in the aorta of aged compared to young mice. In conclusion, aging decreases prostanoid-mediated contractility in the carotid artery involving a loss of Nox2 activity and is associated with impaired endothelium-dependent, NO-mediated relaxation. These findings may contribute to a better understanding of the pathophysiology of carotid artery disease and the aging process.

Estimated GFR or albuminuria: which one is really associated with resistant hypertension?

Patients with resistant hypertension belong to a very high cardiovascular risk group and have a high prevalence of target organ damage. Microalbuminuria and low estimated glomerular filtration rate are associated with resistant hypertension, and could be a cause and/or complication of hypertension. In this review, we explore the relationship between these 2 markers of kidney disease and the prevalence of resistant hypertension. We identified different phenotypes of resistant hypertension that associate with microalbuminuria and/or low estimated glomerular filtration rate. These phenotypes suggest that high sympathetic activity associated with fluid overload and endothelial dysfunction may contribute differently to the development of resistant hypertension.

Impairment of IKCa channels contributes to uteroplacental endothelial dysfunction in rat diabetic pregnancy

Diabetes in rat pregnancy is associated with impaired vasodilation of the maternal uteroplacental vasculature. In the present study, we explored the role of endothelial cell (EC) Ca(2+)-activated K(+) channels of small conductance (SKCa channels) and intermediate conductance (IKCa channels) in diabetes-induced uterine vascular dysfunction. Diabetes was induced by injection of streptozotocin to second-day pregnant rats and confirmed by the development of maternal hyperglycemia. Control rats were injected with citrate buffer. Changes in smooth muscle cell intracellular Ca(2+) concentration, membrane potential, and vasodilation induced by SKCa/IKCa channel activators were studied in uteroplacental arteries of control and diabetic rats. The impact of diabetes on SKCa- and IKCa-mediated currents was explored in freshly dissociated ECs. NS309 evoked a potent vasodilation that was effectively inhibited by TRAM-34 but not by apamin. NS309-induced smooth muscle cell intracellular Ca(2+) concentration, membrane potential, and dilator responses were significantly diminished by diabetes; N-cyclohexyl-N-2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-4-pyrimidinamine (CyPPA)-evoked responses were not affected. Ca(2+)-activated ion currents in ECs were insensitive to paxilline, markedly inhibited by charybdotoxin (ChTX), and diminished by apamin. NS309-induced EC currents were generated mostly due to activation of ChTX-sensitive channels. Maternal diabetes resulted in a significant reduction in ChTX-sensitive currents with no effect on apamin-sensitive or CyPPA-induced currents. We concluded that IKCa channels play a prevalent role over SKCa channels in the generation of endothelial K(+) currents and vasodilation of uteroplacental arteries. Impaired function of IKCa channels importantly contributes to diabetes-induced uterine endothelial dysfunction. Therapeutic restoration of IKCa channel function may be a novel strategy for improvement of maternal uteroplacental blood flow in pregnancies complicated by diabetes.

Pathobiology of acute respiratory distress syndrome

The unique characteristics of pulmonary circulation and alveolar-epithelial capillary-endothelial barrier allow for maintenance of the air-filled, fluid-free status of the alveoli essential for facilitating gas exchange, maintaining alveolar stability, and defending the lung against inhaled pathogens. The hallmark of pathophysiology in acute respiratory distress syndrome is the loss of the alveolar capillary permeability barrier and the presence of protein-rich edema fluid in the alveoli. This alteration in permeability and accumulation of fluid in the alveoli accompanies damage to the lung epithelium and vascular endothelium along with dysregulated inflammation and inappropriate activity of leukocytes and platelets. In addition, there is uncontrolled activation of coagulation along with suppression of fibrinolysis and loss of surfactant. These pathophysiological changes result in the clinical manifestations of acute respiratory distress syndrome, which include hypoxemia, radiographic opacities, decreased functional residual capacity, increased physiologic deadspace, and decreased lung compliance. Resolution of acute respiratory distress syndrome involves the migration of cells to the site of injury and re-establishment of the epithelium and endothelium with or without the development of fibrosis. Most of the data related to acute respiratory distress syndrome, however, originate from studies in adults or in mature animals with very few studies performed in children or juvenile animals. The lack of studies in children is particularly problematic because the lungs and immune system are still developing during childhood and consequently the pathophysiology of pediatric acute respiratory distress syndrome may differ in significant ways from that seen in acute respiratory distress syndrome in adults. This article describes what is known of the pathophysiologic processes of pediatric acute respiratory distress syndrome as we know it today while also presenting the much greater body of evidence on these processes as elucidated by adult and animal studies. It is also our expressed intent to generate enthusiasm for larger and more in-depth investigations of the mechanisms of disease and repair specific to children in the years to come.

Reduced activity of SKC a and Na-K ATPase underlies the accelerated impairment of EDH-type relaxations in mesenteric arteries of aging spontaneously hypertensive rats

Aging is accompanied by endothelial dysfunction due to reduced bioavailability of nitric oxide (NO) and/or reduced endothelium-dependent hyperpolarizations (EDH). This study examines the hypothesis that hypertension aggravates the impairment of EDH-type relaxation due to aging. EDH-type relaxations were studied in superior mesenteric arteries isolated from Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats of 12, 36, 60, and 72 weeks of age. EDH-type relaxations in WKY were reduced with aging, and this was associated with an impairment of the function of small-conductance calcium-activated potassium channels (SK_Ca) and sodium-potassium ATPase (Na-K ATPase). EDH-type relaxation in SHR was smaller than that in WKY arteries, and further reduction occurred with aging. Pharmacological experiments suggested a reduced involvement of SK_Ca and Na-K ATPase and activation of adenosine monophosphate-activated protein kinase and silent information regulator T1 (sirtuin-1; SIRT1) in mesenteric arteries of 12-week-old SHR. These pharmacological findings suggest that in superior mesenteric arteries of the rat, the reduction in EDH-type relaxation occurs with aging and that such a reduction is exacerbated in hypertension. The latter exacerbation appears to involve proteins associated with the process of cellular senescence and is related to impaired function of SK_Ca and Na-K ATPase, a phenomenon that is also observed in mesenteric arteries of older normotensive rats.

Enalapril Normalizes Endothelium-Derived Hyperpolarizing Factor-Mediated Relaxation in Mesenteric Artery of Adult Hypertensive Rats Prenatally Exposed to Testosterone

Prenatal exposure to elevated testosterone levels induces adult life hypertension associated with selective impairments in endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation in mesenteric arteries. We tested whether the angiotensin-converting enzyme inhibitor enalapril restores EDHF function through regulating the activities of small (Kcnn3) and intermediate (Kcnn4) conductance calcium-activated potassium channels in mesenteric arteries. Pregnant Sprague-Dawley rats were injected subcutaneously with vehicle or testosterone propionate (0.5 mg/kg/day from Gestation Day 15 to 19), and their 6-mo-old adult male offspring were examined. A subset of rats in these two groups was given enalapril (40 mg/kg/day) for 2 wk through drinking water. Blood pressures were assessed through carotid arterial catheter and endothelium-dependent mesenteric arterial EDHF relaxation, using wire myography. Ace and Kcnn3 and Kcnn4 channel expression levels were also examined. Renal and vascular Ace expression and plasma angiotensin II levels were increased in testosterone offspring. Blood pressure levels were significantly higher in testosterone offspring than in controls, and treatment with enalapril significantly attenuated blood pressure in testosterone offspring. EDHF relaxation in testosterone offspring was reduced compared to that in controls, and it was significantly restored by enalapril treatment. Kcnn4 channel expression and function were similar between control and testosterone rats, but it was not affected by enalapril treatment. Relaxation mediated by Kcnn3 was impaired in testosterone offspring, and it was normalized by enalapril treatment. Furthermore, enalapril treatment restored expression levels of Kcnn3 channels. These findings suggest that enalapril has a positive influence on endothelial function with improvement in EDHF relaxation through normalization of Kcnn3 expression and activity.

Arterial Hypertension Is Characterized by Imbalance of Pro-Angiogenic versus Anti-Angiogenic Factors

OBJECTIVE

Hypertension is the most common cardiovascular disease and the main risk factor for stroke, peripheral arterial disease, arterial aneurysms and kidney disease. It has been reported recently that hypertensive patients and animals are characterized by decreased density of arterioles and capillaries in the tissues, called rarefaction. Rarefaction significantly increases peripheral resistance which results in elevated blood pressure, leads to vessel damage and induction of inflammation. Therefore, we hypothesized that hypertension is associated with decreased serum concentration of physiological pro-angiogenic factors and concomitant increased production of angiogenesis inhibitors.

MATERIALS AND METHODS

82 patients diagnosed with hypertension and 34 healthy volunteers were recruited to the study. Flow cytometry and enzyme-linked immunosorbent assay (ELISA) techniques were used to measure serum levels of the following cytokines: endostatin, vascular endothelial growth factor (VEGF), interleukin 8 (IL-8), angiogenin, and basic fibroblast growth factor (bFGF).

RESULTS

Hypertensive patients were characterized by increased serum concentration of endostatin which is an anti-angiogenic factor. In addition, hypertension was associated with decreased levels of physiological pro-angiogenic mediators such as: angiogenin and bFGF. The hypertensive group was also characterized by elevated levels of CRP, VEGF and IL-8 that are the hallmarks of inflammation.

CONCLUSIONS

Presented results show that hypertension is characterized by imbalance of pro-angiogenic and anti-angiogenic factors in the background of inflammation.

Decreased endothelin-1 plasma levels in multiple sclerosis patients: a possible factor of vascular dysregulation?

BACKGROUND

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system with possible involvement of vascular dysregulation secondary to endothelial dysfunction caused by destruction of the vessel wall. Vascular dysregulation leads to excessive vasoconstriction or insufficient vasodilatation, resulting in vasospasm mediated by endothelin-1 (ET-1), the most potent and long-lasting mediator. Vascular dysregulation can play an important role in the pathogenesis of some eye disorders and it has been hypothesized that it is a vascular risk factor for glaucomatous optic neuropathy. The aim of this study was to estimate endothelin-1 (ET-1) plasma levels in patients with MS.

MATERIAL AND METHODS

The MS group consisted of 39 patients (9 males, 30 females), mean age: 38.8 ± 10.02 years, range: 22-62. The control group consisted of 27 healthy volunteers (3 males and 24 females), mean age: 37.4 ± 10.88 years, range: 20-62; clinically, in a non-active stage of the disease. ET-1 plasma levels were measured using the Endothelin-1 ELISA Kit (Immuno-Biological Laboratories Co., Japan). Statistical analysis was performed with the nonparametric Mann-Whitney U test for independent groups.

RESULTS

Endothelin-1 (ET-1) plasma levels were significantly lower in MS patients compared to healthy controls: mean value 0.55 ± 0.44 pg/ml (146.05 ± 118.27 fmol/ml) vs. 0.95 ± 0.48 pg/ml (252.83 ± 127.16 fmol/ml); P=0.012.

CONCLUSIONS

Significantly decreased ET-1 plasma levels in the MS patients could reflect the non-active disease at the time of ET-1 measurements or the effects of immunomodulatory treatment, but it cannot be excluded that decreased ET-1 plasma levels in these patients might result from vascular dysregulation.

Prevention of atherosclerosis by Yindan Xinnaotong capsule combined with swimming in rats

BACKGROUND

Yindan Xinnaotong capsule has been used for treating cardio-cerebrovascular diseases for several decades in China. Exercise training can protect against the development of atherosclerosis. The aim of the present study is to evaluate the joint effect of YXC and exercise on atherosclerosis in rats.

METHODS

A combined method involving low shear stress and a high-fat diet was used to establish the atherosclerosis model in rats. Partial ligation of the left common carotid artery was performed, and then the rats were divided into 9 treatment groups according to a 3 × 3 factorial design with two factors and three levels for each factor, swimming of 0, 0.5, 1 h daily and YXC administration of 0, 1, 2 g/kg p.o. daily. Next the interventions of swimming and YXC were executed for 8 weeks. After that, blood samples were collected to determine blood viscosity, plasma viscosity, haematocrit (HCT), fibrinogen (FIB), blood lipid profile (including total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), triglyceride (TG) and high-density lipoprotein-cholesterol (HDL-C)), nitric oxide (NO), 6-keto- prostaglandin (PG) F1α, endothelin (ET) and thromboxane (TX) B2. The common carotid arteries of the rats were harvested to examine pathological changes, wall thickness and circumference, and the expression of SM22αwas assayed via immune-histochemistry.

RESULTS

The early pathological changes were observed. The joint effects of YXC and swimming showed significant changes in the examined parameters: (1) decreases in plasma viscosity, blood viscosity and FIB; (2) increases in NO and 6-keto-PGF1α; (3) decreases in ET and TXB2; and (4) decreases in LDL-C and TG. The combination of 2 g/kg YXC and 1 h of swimming led to synergistic decreases in LDL-C and TG. The interactive effect between YXC and swimming was obvious in decreasing wall thickness. Swimming alone was able to up-regulate the expression of SM22α.

CONCLUSIONS

In conclusion, this study indicates that the combination of YXC and swimming may prevent atherosclerosis through a synergistic effect between YXC and swimming in improving blood circulation, hemorheological parameters, blood lipids levels and the vascular endothelium in rats. The vascular remodeling may be contributed to the prevention effects on AS by up-regulating SM22α.

Kaempferol enhances endothelium-dependent relaxation in the porcine coronary artery through activation of large-conductance Ca(2+) -activated K(+) channels

BACKGROUND AND PURPOSE

Kaempferol, a plant flavonoid present in normal human diet, can modulate vasomotor tone. The present study aimed to elucidate the signalling pathway through which this flavonoid enhanced relaxation of vascular smooth muscle.

EXPERIMENTAL APPROACH

The effect of kaempferol on the relaxation of porcine coronary arteries to endothelium-dependent (bradykinin) and -independent (sodium nitroprusside) relaxing agents was studied in an in vitro organ chamber setup. The whole-cell patch-clamp technique was used to determine the effect of kaempferol on potassium channels in porcine coronary artery smooth muscle cells (PCASMCs).

KEY RESULTS

At a concentration without direct effect on vascular tone, kaempferol (3 × 10(-6) M) enhanced relaxations produced by bradykinin and sodium nitroprusside. The potentiation by kaempferol of the bradykinin-induced relaxation was not affected by N(ω)-nitro-L-arginine methyl ester, an inhibitor of NO synthase (10(-4) M) or TRAM-34 plus UCL 1684, inhibitors of intermediate- and small-conductance calcium-activated potassium channels, respectively (10(-6) M each), but was abolished by tetraethylammonium chloride, a non-selective inhibitor of calcium-activated potassium channels (10(-3) M), and iberiotoxin, a selective inhibitor of large-conductance calcium-activated potassium channel (KCa 1.1; 10(-7) M). Iberiotoxin also inhibited the potentiation by kaempferol of sodium nitroprusside-induced relaxations. Kaempferol stimulated an outward-rectifying current in PCASMCs, which was abolished by iberiotoxin.

CONCLUSIONS AND IMPLICATIONS

The present results suggest that, in smooth muscle cells of the porcine coronary artery, kaempferol enhanced relaxations caused by endothelium-derived and exogenous NO as well as those due to endothelium-dependent hyperpolarization. This vascular effect of kaempferol involved the activation of KCa 1.1 channels.

Advanced age protects microvascular endothelium from aberrant Ca(2+) influx and cell death induced by hydrogen peroxide

KEY POINTS

Calcium signalling in endothelial cells of resistance arteries is integral to blood flow regulation. Oxidative stress and endothelial dysfunction can prevail during advanced age and we questioned how calcium signalling may be affected. Intact endothelium was freshly isolated from superior epigastric arteries of Young (∼4 months) and Old (∼24 months) male C57BL/6 mice. Under resting conditions, with no difference in intracellular calcium levels, hydrogen peroxide (H2 O2 ) availability was ∼1/3 greater in endothelium of Old mice while vascular catalase activity was reduced by nearly half. Compared to Old, imposing oxidative stress (200 μm H2 O2 ) for 20 min increased intracellular calcium to 4-fold greater levels in endothelium of Young in conjunction with twice the calcium influx. Prolonged (60 min) exposure to H2 O2 induced 7-fold greater cell death in endothelium of Young. Microvascular adaptation to advanced age may protect endothelial cells during elevated oxidative stress to preserve functional viability of the intima.

ABSTRACT

Endothelial cell Ca(2+) signalling is integral to blood flow control in the resistance vasculature yet little is known of how its regulation may be affected by advancing age. We tested the hypothesis that advanced age protects microvascular endothelium by attenuating aberrant Ca(2+) signalling during oxidative stress. Intact endothelial tubes (width, ∼60 μm; length, ∼1000 μm) were isolated from superior epigastric arteries of Young (3-4 months) and Old (24-26 months) male C57BL/6 mice and loaded with Fura-2 dye to monitor [Ca(2+) ]i . At rest there was no difference in [Ca(2+) ]i between age groups. Compared to Young, the [Ca(2+) ]i response to maximal stimulation with acetylcholine (3 μm, 2 min) was ∼25% greater in Old, confirming signalling integrity with advanced age. Basal H2 O2 availability was ∼33% greater in Old while vascular catalase activity was reduced by half. Transient exposure to elevated H2 O2 (200 μm, 20 min) progressively increased [Ca(2+) ]i to ∼4-fold greater levels in endothelium of Young versus Old. With no difference between age groups at rest, Mn(2+) quench of Fura-2 fluorescence revealed 2-fold greater Ca(2+) influx in Young during elevated H2 O2 ; this effect was attenuated by ∼75% using ruthenium red (5 μm) as a broad-spectrum inhibitor of transient receptor potential channels. Prolonged exposure to H2 O2 (200 μm, 60 min) induced ∼7-fold greater cell death in endothelium of Young versus Old. Thus, microvascular endothelium can adapt to advanced age by reducing Ca(2+) influx during elevated oxidative stress. Protection from cell death during oxidative stress will sustain endothelial integrity during ageing.

Protective role of insulin-like growth factor-1 receptor in endothelial cells against unilateral ureteral obstruction-induced renal fibrosis

Insulin-like growth factor-1 receptor (IGF-1R) can regulate vascular homeostasis and endothelial function. We studied the role of IGF-1R in oxidative stress-induced endothelial dysfunction. Unilateral ureteral obstruction (UUO) was performed in wild-type (WT) mice and mice with endothelial cell (EC)-specific IGF-1R knockout (KO). After UUO in endothelial IGF-1R KO mice, endothelial barrier dysfunction was more severe than in WT mice, as seen by increased inflammatory cell infiltration and vascular endothelial (VE)-cadherin phosphorylation. UUO in endothelial IGF-1R KO mice increased interstitial fibroblast accumulation and enhanced extracellular protein deposition as compared with the WT mice. Endothelial barrier function measured by transendothelial migration in response to hydrogen peroxide (H2O2) was impaired in ECs. Silencing IGF-1R enhanced the influence of H2O2 in disrupting the VE-protein tyrosine phosphatase/VE-cadherin interaction. Overexpression of IGF-1R suppressed H2O2-induced endothelial barrier dysfunction. Furthermore, by using the piggyBac transposon system, we expressed IGF-1R in VE cells in mice. The expression of IGF-1R in ECs also suppressed the inflammatory cell infiltration and renal fibrosis induced by UUO. IGF-1R KO in the VE-cadherin lineage of bone marrow cells had no significant effect on the UUO-induced fibrosis, as compared with control mice. Our results indicate that IGF-1R in the endothelium maintains the endothelial barrier function by stabilization of the VE-protein tyrosine phosphatase/VE-cadherin complex. Decreased expression of IGF-1R impairs endothelial function and increases the fibrosis of kidney disease.

The association of plasma vitamin A and E levels with coronary collateral circulation

OBJECTIVE

To investigate if plasma levels of vitamin A and E have an association with coronary collateral development.

METHODS

A total of 189 patients who underwent coronary angiography and had total occlusion in at least one major epicardial coronary artery were enrolled in the study. To classify coronary collateral circulation (CCC), the Rentrop scoring system was used. Patients were classified as having poor CCC (Rentrop grades 0-1) or good CCC (Rentrop grades 2-3), and all patients were also screened for hypertension, hypercholesterolemia, diabetes, and smoking history.

RESULTS

There were no differences in plasma vitamin A and E levels between the two groups (vitamin A: 2.37 ± 0.65 vs. 2.35 ± 0.78, p = 0.253; vitamin E: 47.1 ± 12.8 vs. 44.6 ± 15.1, p = 0.082), and plasma vitamin A and E levels were not associated with CCC. Serum high-sensitivity C-reactive protein (hs-CRP) levels were significantly higher in patients with poor CCC (4.68 ± 2.52 vs. 3.89 ± 1.78, p = 0.001). The higher frequency of diabetes and higher serum hs-CRP levels were found to be an independent predictor for poor CCC (odds ratio = 2.44, p = 0.006; odds ratio = 1.24, p = 0.007, respectively). And a higher frequency of total occluded RCA was found to be a positive predictor for good CCC (odds ratio = 2.36, p = 0.06) in a multivariate logistic regression analysis.

CONCLUSIONS

We found that serum hs-CRP levels, presence of diabetes, and total occlusion of RCA have an effect on coronary collateral development. We found no correlation between plasma vitamin A and E levels and CCC.

Role of sphingosine-1-phosphate receptor 1 and sphingosine-1-phosphate receptor 2 in hyperglycemia-induced endothelial cell dysfunction

The hyperglycemia-induced production of oxidative stress results in endothelial cell dysfunction. Previous studies have demonstrated that sphingosine-1-phosphate (S1P) regulates an array of biological activities in endothelial cells mediated by sphingosine-1-phosphate receptors (S1PRs). However, the role of S1PR-mediated signaling pathways in hyperglycemia-induced endothelial cell dysfunction is currently unknown. In the present study, we aimed to explore the role of S1PRs in endothelial cell dysfunction. For this purpose, hyperglycemia-induced oxidative stress was examined using human umbilical vein endothelial cells (HUVECs) cultured with either normal (5.6 mM) or high (25 mM) levels of glucose. The levels of reactive oxygen species (ROS) and nitric oxide (NO) were determined by flow cytometric (FCM) analysis and nitrate reductase, respectively. Endothelial morphogenesis assay was performed in three-dimensional Matrigel. The mRNA and protein expression levels of S1PRs in the HUVECs were determined by RT-qPCR and western blot analysis, respectively. In addition, ROS, NO and endothelial morphogenesis assays were conducted using the high glucose-treated endothelial cells transfected with adenoviral vector expressing exogenous S1PR1 gene (pAd-S1PR1) or with adenoviral vector expressing S1PR2-specific shRNA (pAd-shRNA-S1PR2). The expression levels of S1PR1 and S1PR2 in the endothelial cells treated with high levels of glucose decreased and increased, respectively. However, the effects of high levels of glucose on S1PR3 were minimal. In addition, high levels of glucose enhanced ROS generation and markedly reduced NO generation and morphogenetic responses. Nevertheless, all the aforementioned changes were completely reversed by transfection with pAd-S1PR1 or pAd-shRNA-S1PR2, which increased S1PR1 and decreased S1PR2 expression, respectively. It can thus be concluded that S1PR1 and S1PR2 play crucial roles in hyperglycemia-induced endothelial cell dysfunction.

MSCs modified with ACE2 restore endothelial function following LPS challenge by inhibiting the activation of RAS

Angiotensin (Ang) II plays an important role in the process of endothelial dysfunction in acute lung injury (ALI) and is degraded by angiotensin-converting enzyme2 (ACE2). However, treatments that target ACE2 to injured endothelium and promote endothelial repair of ALI are lacking. Mesenchymal stem cells (MSCs) are capable of homing to the injured site and delivering a protective gene. Our study aimed to evaluate the effects of genetically modified MSCs, which overexpress the ACE2 protein in a sustained manner via a lentiviral vector, on Ang II production in endothelium and in vitro repair of lipopolysaccharide (LPS)-induced endothelial injury. We found that the efficiency of lentiviral vector transduction of MSCs was as high as 97.8% and was well maintained over 30 passages. MSCs modified with ACE2 showed a sustained high expression of ACE2 mRNA and protein. The modified MSCs secreted soluble ACE2 protein into the culture medium, which reduced the concentration of Ang II and increased the production of Ang 1-7. MSCs modified with ACE2 were more effective at restoring endothelial function than were unmodified MSCs, as shown by the enhanced survival of endothelial cells; the downregulated production of inflammatory mediators, including ICAM-1, VCAM-1, TNF-α, and IL-6; reduced paracellular permeability; and increased expression of VE-cadherin. These data demonstrate that MSCs modified to overexpress the ACE2 gene can produce biologically active ACE2 protein over a sustained period of time and have an enhanced ability to promote endothelial repair after LPS challenge. These results encourage further testing of the beneficial effects of ACE2-modified MSCs in an ALI animal model.

Inhalation toxicology methods: the generation and characterization of exposure atmospheres and inhalational exposures

In this unit, the need for laboratory-based inhalation toxicology studies, the historical background on adverse health effects of airborne toxicants, and the benefits of advance planning for the building of analytic options into the study design to maximize the scientific gains to be derived from the investments in the study are outlined. The following methods are described: (1) the generation and characterization of exposure atmospheres for inhalation exposures in humans and laboratory animals; (2) the delivery and distribution into and within whole-body exposure chambers, head-only exposure chambers, face-masks, and mouthpieces or nasal catheters; (3) options for on-line functional assays during and between exposures; and (4) options for serial non-invasive assays of response. In doing so, a description beyond exposures to single agents and simple mixtures is presented, and included are methods for evaluating biological responses to complex environmental mixtures. It is also emphasized that great care should be taken in the design and execution of such studies so that the scientific returns can be maximized both initially, and in follow-up utilization of archived samples of the exposure atmospheres, excreta, and tissues collected for histology.

Vascular Dysfunction: A Key Player in Chronic Cardio-renal Syndrome

This review summarizes the current methods for the functional assessment of vascular damage (e.g., assessment of endothelial function, measurement of pulse wave velocity, and pressure wave analysis) and describes the association between vascular dysfunction and chronic cardio-renal syndrome. Vascular dysfunction may contribute to the development and progression of heart failure. Additionally, vascular dysfunction, especially increased arterial stiffness and abnormal pressure wave reflection and central hemodynamics, has been reported to accelerate renal function decline. Furthermore, renal dysfunction worsens vascular pathophysiological abnormalities. Therefore, the functional assessment of vascular damage may be useful in the management of cardio-renal syndrome.

Vascular dysfunctions in the isolated aorta of double-transgenic hypertensive mice developing aortic aneurysm

Angiotensin-II and oxidative stress are involved in the genesis of aortic aneurysms, a phenomenon exacerbated by endothelial nitric oxide synthase (eNOS) deletion or uncoupling. The purpose of this work was to study the endothelial function in wild-type C57BL/6 (BL) and transgenic mice expressing the h-angiotensinogen and h-renin genes (AR) subjected to either a control, or a high-salt diet plus a treatment with a NO-synthase inhibitor, N-ω-nitro-L-arginine-methyl-ester (L-NAME; BLSL and ARSL). BLSL showed a moderate increase in blood pressure, while ARSL became severely hypertensive. Seventy-five percent of ARSL developed aortic aneurysms, characterized by major histo-morphological changes and associated with an increase in NADP(H) oxidase-2 (NOX2) expression. Contractile responses (KCl, norepinephrine, U-46619) were similar in the four groups of mice, and relaxations were not affected in BLSL and AR. However, in ARSL, endothelium-dependent relaxations (acetylcholine, UK-14304) were significantly reduced, and this dysfunction was similar in aortae without or with aneurysms. The endothelial impairment was unaffected by catalase, superoxide-dismutase mimetic, radical scavengers, cyclooxygenase inhibition, or TP-receptor blockade and could not be attributed to sGC oxidation. Thus, ARSL is a severe hypertension model developing aortic aneurysm. A vascular dysfunction, involving both endothelial (reduced role of NO) and smooth muscle cells, precedes aneurysms formation and, paradoxically, does not appear to involve oxidative stress.

Overexpression of mitochondrial antioxidant manganese superoxide dismutase (MnSOD) provides protection against AZT- or 3TC-induced endothelial dysfunction

Nucleoside reverse transcriptase inhibitors (NRTIs) are considered the backbone of current combination therapies for HIV. These therapies have significantly decreased mortality and morbidity in HIV-infected patients, but some are associated with cardiovascular complications, including endothelial dysfunction, an early marker for atherosclerosis. Our prior studies demonstrated that co-treatment of cells with an antioxidant therapy reversed NRTI-induced endothelial injury. Thus, as a proof of concept that mitochondrially-targeted antioxidants may be useful in preventing NRTI toxicity, in the current study, mice overexpressing a mitochondrial antioxidant, manganese superoxide dismutase (MnSOD), were compared with wild-type (WT) mice. Mice were treated chronically with either zidovudine (AZT), lamivudine (3TC), or tenofovir (TDF) to determine whether overexpression of MnSOD protected them from endothelial dysfunction. Endothelial function was assessed using vessel reactivity experiments on thoracic aortas as well as measures of endothelium derived factors nitric oxide (NO), endothelin-1 (ET-1), and prostacyclin. Oxidative stress was evaluated as levels of plasma 8-isoprostane. Alterations in vessel reactivity, NO, and ET-1 in WT mice treated with AZT or 3TC were noted. Overexpression of MnSOD offered protection from decreases in vessel reactivity and increases in ET-1. These findings indicate that mitochondrial oxidative stress induced by AZT or 3TC plays a major role in mediating NRTI-induced endothelial dysfunction, and suggest that the use of targeted antioxidants administered in conjunction with NRTIs may attenuate these effects.

Oxidative status imbalance in patients with metabolic syndrome: role of the myeloperoxidase/hydrogen peroxide axis

The present study evaluated the cardiometabolic and redox balance profiles in patients with Metabolic Syndrome compared to apparently healthy individuals, and the participation of the myeloperoxidase/hydrogen peroxide axis in systemic lipid peroxidation. Twenty-four patients with Metabolic Syndrome and eighteen controls underwent a full clinical assessment. Venous blood samples were collected for general biochemical dosages, as well as for the oxidative stress analyses (superoxide dismutase, catalase, and arginase activities; and lipid peroxidation, myeloperoxidase activity, nitrite, and hydrogen peroxide concentrations in plasma). Arterial stiffness was assessed by radial artery applanation tonometry. Plasma lipid peroxidation, erythrocyte superoxide dismutase activity, myeloperoxidase activity, and hydrogen peroxide concentrations were shown to be increased in Metabolic Syndrome patients, without significant differences for the other enzymes, plasma nitrite concentrations, and arterial stiffness. Linear regression analysis revealed a positive and significant correlation between lipid peroxidation and myeloperoxidase and also between this enzyme and hydrogen peroxide. In contrast, such correlation was not observed between lipid peroxidation and hydrogen peroxide. In summary, Metabolic Syndrome patients exhibited evident systemic redox imbalance compared to controls, with the possible participation of the myeloperoxidase/hydrogen peroxide axis as a contributor in lipid peroxidation.

Asiatic acid reduces blood pressure by enhancing nitric oxide bioavailability with modulation of eNOS and p47phox expression in L-NAME-induced hypertensive rats

We investigated the effect of asiatic acid (AA) on hemodynamic status, vascular function, oxidative stress markers, endothelial nitric oxide synthase (eNOS), and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit expression in Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME)-induced hypertensive rats. Male Sprague-Dawley rats treated with L-NAME (40 mg/kg/day) in drinking water for 5 weeks showed significant increases in mean arterial pressure, heart rate, hindlimb vascular resistance, vascular dysfunction, superoxide anion (O2(•-)) production, and plasma malondialdehyde. Moreover, NO metabolite (NOx) levels were reduced, aortic eNOS expression was downregulated, and NADPH oxidase subunit p47(phox) was upregulated in hypertensive rats (p < 0.05). Hypertensive rats that were administered AA (10 or 20 mg/kg/day) for the last 2 weeks of the study showed significant improvement in hemodynamic status and vascular function. The antihypertensive effects of AA were associated with elevated plasma NOx levels, together with upregulation of eNOS expression. Decreased vascular O2(•-) production, consistent with downregulation of p47(phox) expression, was also observed after AA treatment. Our results are therefore consistent with a model whereby AA reduces blood pressure by enhancing NO bioavailability.

Diminished neurogenic femoral artery vasoconstrictor response in a Zucker obese rat model: differential regulation of NOS and COX derivatives

Objective

Peripheral arterial disease is one of the macrovascular complications of type 2 diabetes mellitus. This study addresses femoral artery regulation in a prediabetic model of obese Zucker rats (OZR) by examining cross-talk between endothelial and neural factors.

Methods and Results

Arterial preparations from lean (LZR) and OZR were subjected to electrical field stimulation (EFS) on basal tone. Nitric oxide synthase (NOS) and cyclooxygenase (COX) isoform expression patterns were determined by immunohistochemical labelling and Western blotting. Results indicate significantly reduced noradrenergic contractions in preparations from OZR compared with those of LZR. Functional inhibition of endothelial NOS (eNOS) indicated a predominant role of this isoform in LZR and its modified activity in OZR. Neural (nNOS) and inducible NOS (iNOS) were activated and their expression was higher in femoral arteries from OZR. Neurotransmission modulated by large-conductance Ca²⁺-activated (BK_Ca) or voltage-dependent (K_V) K⁺ channels did not seem compromised in the obese animals. Endothelial COX-1 and COX-2 were expressed in LZR and an additional adventitial location of COX-2 was also observed in OZR, explaining the higher COX-2 protein levels detected in this group. Prostanoids derived from both isoforms helped maintain vasoconstriction in LZR while in OZR only COX-2 was active. Superoxide anion inhibition reduced contractions in endothelium-intact arteries from OZR.

Conclusions

Endothelial dysfunction led to reduced neurogenic vasoconstriction in femoral arteries from OZR. In a setting of obesity, NO-dependent nNOS and iNOS dilation activity could be an alternative mechanism to offset COX-2- and reactive oxygen species-mediated vasoconstriction, along with impaired endothelial NO relaxation.

Enhanced endothelin receptor type B-mediated vasodilation and underlying [Ca²⁺]i in mesenteric microvessels of pregnant rats

BACKGROUND AND PURPOSE

Normal pregnancy is associated with decreased vascular resistance and increased release of vasodilators. Endothelin-1 (ET-1) causes vasoconstriction via endothelin receptor type A (ET(A)R), but could activate ET(B)R in the endothelium and release vasodilator substances. However, the roles of ET(B)R in the regulation of vascular function during pregnancy and the vascular mediators involved are unclear.

EXPERIMENTAL APPROACH

Pressurized mesenteric microvessels from pregnant and virgin Sprague-Dawley rats were loaded with fura-2/AM for simultaneous measurement of diameter and [Ca²⁺]i.

KEY RESULTS

High KCl (51 mM) and phenylephrine (PHE) caused increases in vasoconstriction and [Ca²⁺]i that were similar in pregnant and virgin rats. ET-1 caused vasoconstriction that was less in pregnant than virgin rats, with small increases in [Ca²⁺]i. Pretreatment with the ET(B)R antagonist BQ-788 caused greater enhancement of ET-1-induced vasoconstriction in pregnant rats. ACh caused endothelium-dependent relaxation and decreased [Ca²⁺]i, and was more potent in pregnant than in virgin rats. ET-1 + ET(A)R antagonist BQ-123, and the ET(B)R agonists sarafotoxin 6c (S6c) and IRL-1620 caused greater vasodilation in pregnant than in virgin rats with no changes in [Ca²⁺]i, suggesting up-regulated ET(B)R-mediated relaxation pathways. ACh-, S6c- and IRL-1620-induced relaxation was reduced by the NO synthase inhibitor Nω-nitro-L-arginine methyl ester, and abolished by tetraethylammonium or endothelium removal. Western blots revealed greater amount of ET(B)R in intact microvessels of pregnant than virgin rats, but reduced levels in endothelium-denuded microvessels, supporting a role of endothelial ET(B)R.

CONCLUSIONS AND IMPLICATIONS

The enhanced ET(B)R-mediated microvascular relaxation may contribute to the decreased vasoconstriction and vascular resistance during pregnancy.

Physical activity on endothelial and erectile dysfunction: a literature review

Physical inactivity, diabetes, hypertension, dyslipidemia, smoking and obesity were associated with imbalance in oxidative stress, leading to endothelial dysfunction. Such dysfunction is present in both cardiovascular disease (CVD) and erectile dysfunction (ED). ED is the persistent inability to achieve or sustain an erection sufficient for satisfactory sexual performance and is one of the first manifestations of endothelial damage in men with CVD risk factors. The purpose of this article is to review the results of studies involving physical activity, CVD, endothelial dysfunction and ED in order to verify its applicability for improving the health and quality of life of men with such disorders. There is consistent evidence that endothelial damage is intimately linked to ED, and this manifestation seems to be associated with the appearance CVDs. On the other hand, physical activity has been pointed out as an important clinical strategy in the prevention and treatment of CVDs and ED mainly associated with improvement of endothelial function. However, further experimental and clinical prospective investigations are needed to test the role of physical exercises in the modulation of endothelial function and their implications on erectile function and the appearance of CVDs.

Cell-autonomous role of endothelial GTP cyclohydrolase 1 and tetrahydrobiopterin in blood pressure regulation

Tetrahydrobiopterin (BH4) is an essential cofactor for endothelial nitric oxide synthase (eNOS) function and NO generation. Augmentation of BH4 levels can prevent eNOS uncoupling and can improve endothelial dysfunction in vascular disease states. However, the physiological requirement for de novo endothelial cell BH4 biosynthesis in eNOS function remains unclear. We generated a novel mouse model with endothelial cell-specific deletion of GCH1, encoding GTP cyclohydrolase 1, an essential enzyme for BH4 biosynthesis, to test the cell-autonomous requirement for endothelial BH4 biosynthesis in vivo. Mice with a floxed GCH1 allele (GCH1(fl/fl)) were crossed with Tie2cre mice to delete GCH1 in endothelial cells. GCH1(fl/fl)Tie2cre mice demonstrated virtually absent endothelial NO bioactivity and significantly greater O2 (•-) production. GCH1(fl/fl)Tie2cre aortas and mesenteric arteries had enhanced vasoconstriction to phenylephrine and impaired endothelium-dependent vasodilatations to acetylcholine and SLIGRL. Endothelium-dependent vasodilatations in GCH1(fl/fl)Tie2cre aortas were, in part, mediated by eNOS-derived hydrogen peroxide (H2O2), which mediated vasodilatation through soluble guanylate cyclase. Ex vivo supplementation of aortic rings with the BH4 analogue sepiapterin restored normal endothelial function and abolished eNOS-derived H2O2 production in GCH1(fl/fl)Tie2cre aortas. GCH1(fl/fl)Tie2cre mice had higher systemic blood pressure than wild-type littermates, which was normalized by NOS inhibitor, NG-nitro-L-arginine methyl ester. Taken together, these studies reveal an endothelial cell-autonomous requirement for GCH1 and BH4 in regulation of vascular tone and blood pressure and identify endothelial cell BH4 as a pivotal regulator of NO versus H2O2 as alternative eNOS-derived endothelial-derived relaxing factors.

Uptake and protective effects of ergothioneine in human endothelial cells

Ergothioneine is a thiourea derivative of histidine found in food, especially mushrooms. Experiments in cell-free systems and chemical assays identified this compound as a powerful antioxidant. Experiments were designed to test the ability of endothelial cells to take up ergothioneine and hence benefit from protection against oxidative stress. Reverse-transcription polymerase chain reaction and Western blotting demonstrated transcription and translation of an ergothioneine transporter in human brain microvascular endothelial cells (HBMECs). Uptake of [(3)H]ergothioneine occurred by the organic cation transporter novel type-1 (OCTN-1), was sodium-dependent, and was reduced when expression of OCTN-1 was silenced by small interfering RNA (siRNA). The effect of ergothioneine on the production of reactive oxygen species (ROS) in HBMECs was measured using dichlorodihydrofluorescein and lucigenin, and the effect on cell viability was studied using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. ROS production and cell death induced by pyrogallol, xanthine oxidase plus xanthine, and high glucose were suppressed by ergothioneine. The antioxidant and cytoprotective effects of ergothioneine were abolished when OCTN-1 was silenced using siRNA. The expression of NADPH oxidase 1 was decreased, and those of glutathione reductase, catalase, and superoxide dismutase enhanced by the compound. In isolated rat basilar arteries, ergothioneine attenuated the reduction in acetylcholine-induced relaxation caused by pyrogallol, xanthine oxidase plus xanthine, or incubation in high glucose. Chronic treatment with the compound improved the response to acetylcholine in arteries of rats with streptozotocin-induced diabetes. In summary, ergothioneine is taken up by endothelial cells via OCTN-1, where the compound then protects against oxidative stress, curtailing endothelial dysfunction.

The effects of hyperuricaemia on flow-mediated and nitroglycerin-mediated dilatation in high-risk patients

BACKGROUND AND AIMS

Uric acid is emerging as one of the newer risk markers to consider in the cardiovascular risk assessment because it is demonstrated to be associated with adverse cardiovascular outcomes, particularly in high cardiovascular risk patients. One of the proposed mechanisms involving hyperuricaemia is the development of vascular damage. The aim of this study is to examine the role of hyperuricaemia on vascular function in patients with high cardiovascular risk.

METHODS AND RESULTS

We examined the clinical significance of hyperuricaemia in relation to vasomotor response of the brachial artery by using high-resolution ultrasound in 304 subjects with coronary artery disease and/or diabetes. Nitroglycerin-mediated dilatation (NMD) was significantly lower in the hyperuricaemic group compared with the normouricaemic group (12.8 ± 6.9% vs. 16.2 ± 7.7%, p < 0.001), but no significant difference was observed in flow-mediated dilatation (FMD) between the two groups [3.78 (95% CR: 1.5-9.9) vs. 3.88 (95% CR: -2.6 to 9.9), p = 0.78]. Multivariate analysis demonstrated that smoking was the strongest predictor of FMD (b = -0.81, p = 0.02); and that smoking (b = -2.62, p = 0.003), SBP (b = -0.11, p = 0.001), hyperuricaemia (b = -2.11, p = 0.02) and use of nitrates (b = -3.30, p = 0.001) were independent predictors of NMD.

CONCLUSION

High cardiovascular risk patients with hyperuricaemia had a lower NMD than those with normouricaemia. Importantly, hyperuricaemia was independently associated with NMD after multivariable adjustments. To further understand the pathophysiological mechanisms involving hyperuricaemia, particularly in the context of impaired NMD, further experimental and clinical studies are needed.

Understanding of chest pain in microvascular disease proved by cardiac magnetic resonance image (UMPIRE): study protocol for a randomized controlled trial

Background

Microvascular angina (MVA) is characterized by anginal chest pain, an abnormal stress test, and normal coronary arteries on coronary angiography. Although the exact pathogenesis remains unclear, endothelial dysfunction is a contributing factor. To date, there exists no specific therapy for this disease. Phosphodiesterase-5 inhibitor improves the endothelial function and subsequently microvascular circulation. The aim of this study is to identify whether udenafil offers benefits in the treatment of MVA in female patients, who have a perfusion defect in their cardiac magnetic resonance image (CMR), but normal coronary arteries.

Methods/Design

The ‘Understanding of Chest Pain in Microvascular Disease Proved by Cardiac Magnetic Resonance Image: (UMPIRE)’ trial is a multicenter, prospective, randomized, placebo controlled trial, designed to evaluate the effect of udenafil on myocardial ischemia and symptoms in female patients with MVA. The myocardial ischemia will be quantified by myocardial stress perfusion defect in CMR. A total of 80 patients with proven perfusion defect in adenosine-stress CMR will be randomly assigned to either the udenafil treatment group (daily dose of 100 mg) or the placebo group for three months. The primary endpoint is >25% improvement in perfusion defect size in adenosine-stress CMR from baseline. The secondary endpoints include <25% improvement in perfusion defect size, chest pain frequency, ST depression in stress test, Duke score in stress test, quality of life (QoL) assessment by SF-36 questionnaire, sexual dysfunction assessment by BISF-W (Brief Index of Sexual Functioning for Women) self-assessment questionnaire, and biomarkers for endothelial function.

Discussion

The UMPIRE trial is the first randomized controlled trial to evaluate the efficacy of udenafil in female MVA patients. If udenafil demonstrates cardioprotective effects, it may provide a novel therapeutic option to reduce myocardial ischemia and improve cardiac function in female MVA patients.

Trial registration

Clinical Trials.gov: NCT01769482 (registered on 20 November 2012).

Lack of angiopoietin-like-2 expression limits the metabolic stress induced by a high-fat diet and maintains endothelial function in mice

Background

Angiopoietin‐like‐2 (angptl2) is produced by several cell types including endothelial cells, adipocytes and macrophages, and contributes to the inflammatory process in cardiovascular diseases. We hypothesized that angptl2 impairs endothelial function, and that lowering angptl2 levels protects the endothelium against high‐fat diet (HFD)‐induced fat accumulation and hypercholesterolemia.

Methods and Results

Acute recombinant angptl2 reduced (P<0.05) acetylcholine‐mediated vasodilation of isolated wild‐type (WT) mouse femoral artery, an effect reversed (P<0.05) by the antioxidant N‐acetylcysteine. Accordingly, in angptl2 knockdown (KD) mice, ACh‐mediated endothelium‐dependent vasodilation was greater (P<0.05) than in WT mice. In arteries from KD mice, prostacyclin contributed to the overall dilation unlike in WT mice. After a 3‐month HFD, overall vasodilation was not altered, but dissecting out the endothelial intrinsic pathways revealed that NO production was reduced in arteries isolated from HFD‐fed WT mice (P<0.05), while NO release was maintained in KD mice. Similarly, endothelium‐derived hyperpolarizing factor (EDHF) was preserved in mesenteric arteries from HFD‐fed KD mice but not in those from WT mice. Finally, the HFD increased (P<0.05) total cholesterol–to–high‐density lipoprotein ratios, low‐density lipoprotein–to–high‐density lipoprotein ratios, and leptin levels in WT mice only, while glycemia remained similar in the 2 strains. KD mice displayed less triglyceride accumulation in the liver (P<0.05 versus WT), and adipocyte diameters in mesenteric and epididymal white adipose tissues were smaller (P<0.05) in KD than in WT fed an HFD, while inflammatory gene expression increased (P<0.05) in the fat of WT mice only.

Conclusions

Lack of angptl2 expression limits the metabolic stress induced by an HFD and maintains endothelial function in mice.