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

KCa 3.1 channels maintain endothelium-dependent vasodilatation in isolated perfused kidneys of spontaneously hypertensive rats after chronic inhibition of NOS

BACKGROUND AND PURPOSE

The purpose of the study was to investigate renal endothelium-dependent vasodilatation in a model of severe hypertension associated with kidney injury.

EXPERIMENTAL APPROACH

Changes in perfusion pressure were measured in isolated, perfused kidneys taken from 18-week-old Wistar-Kyoto rat (WKY), spontaneously hypertensive rats (SHR) and SHR treated for 2 weeks with N(ω) -nitro-L-arginine methyl ester in the drinking water (L-NAME-treated SHR, 6 mg·kg(-1) ·day(-1) ).

KEY RESULTS

Acetylcholine caused similar dose-dependent renal dilatation in the three groups. In vitro administration of indomethacin did not alter the vasodilatation, while the addition of N(w) -nitro-L-arginine (L-NA) produced a differential inhibition of the vasodilatation, (inhibition in WKY > SHR > L-NAME-treated SHR). Further addition of ODQ, an inhibitor of soluble guanylyl cyclase, abolished the responses to sodium nitroprusside but did not affect the vasodilatation to acetylcholine. However, the addition of TRAM-34 (or charybdotoxin) inhibitors of Ca(2+) -activated K(+) channels of intermediate conductance (K(Ca) 3.1), blocked the vasodilatation to acetylcholine, while apamin, an inhibitor of Ca(2+) -activated K(+) channels of small conductance (K(Ca) 2.3), was ineffective. Dilatation induced by an opener of K(Ca) 3.1/K(Ca) 2.3 channels, NS-309, was also blocked by TRAM-34, but not by apamin. The magnitude and duration of NS-309-induced vasodilatation and the renal expression of mRNA for K(Ca) 3.1, but not K(Ca) 2.3, channels followed the same ranking order (WKY < SHR < L-NAME-treated SHR).

CONCLUSIONS AND IMPLICATIONS

In SHR kidneys, an EDHF-mediated response, involving activation of K(Ca) 3.1 channels, contributed to the mechanism of endothelium-dependent vasodilatation. In kidneys from L-NAME-treated SHR, up-regulation of this pathway fully compensated for the decrease in NO availability.

Vasorelaxant prenylated flavonoids from the roots of Sophora flavescens

Bioassay-guided fractionation of the methanol extract from the root of Sophora flavescens led to the isolation of eight known prenylated flavonoids responsible for the vasorelaxation activity in porcine coronary arteries. Among them, kushenol N and 5-methylsophoraflavanone B strongly induced the relaxation of porcine coronary arteries with respective ED(50) values of 8.6 and 12.4 µM. This activity and the results of a high-performance liquid chromatographic analysis suggest that kushenol N and 5-methylsophoraflavanone B could be active markers in the S. flavescens extract for vasorelaxation activity.

Antioxidant effect of captopril and enalapril on reactive oxygen species-induced endothelial dysfunction in the rabbit abdominal aorta

BACKGROUND

Reactive oxygen species (ROS) are known to be related to cardiovascular diseases. Many studies have demonstrated that angiotensin-converting enzyme inhibitors have beneficial effects against ROS. We investigated the antioxidant effect of captopril and enalapril in nitric oxide mediated vascular endothelium-dependent relaxations.

MATERIALS AND METHODS

Isolated rabbit abdominal aorta ring segments were exposed to ROS by electrolysis of the organ bath medium (Krebs-Henseleit solution) after pretreatment with various concentrations (range, 10(-5) to 3×10(-4) M) of captopril and enalapril. Before and after electrolysis, the endothelial function was measured by preconstricting the vessels with norepinephrine (10(-6) M) followed by the cumulative addition of acetylcholine (range, 3×10(-8) to 10(-6) M). The relevance of the superoxide anion and hydrogen peroxide scavenging effect of captopril and enalapril was investigated using additional pretreatments of diethyldithiocarbamate (DETCA, 0.5 mM), an inhibitor of Cu/Zn superoxide dismutase, and 3-amino-1,2,4-triazole (3AT, 50 mM), an inhibitor of catalase.

RESULTS

Both captopril and enalapril preserved vascular endothelium-dependent relaxation after exposure to ROS in a dose-dependent manner (p<0.0001). Pretreatment with DETCA attenuated the antioxidant effect of captopril and enalapril (p<0.0001), but pretreatment with 3AT did not have an effect.

CONCLUSION

Both captopril and enalapril protect endothelium against ROS in a dose-dependent fashion in isolated rabbit abdominal aortas. This protective effect is related to superoxide anion scavenging.

Delayed preconditioning prevents ischemia/reperfusion-induced endothelial injury in rats: role of ROS and eNOS

Ischemic preconditioning (IPC) strongly protects against ischemia/reperfusion (I/R) injury; however, the molecular mechanism involved in delayed preconditioning-induced endothelial protection in peripheral arteries is unknown. Therefore, we examined using functional, morphologic and molecular biologic studies whether delayed IPC decreases formation of reactive oxygen species and upregulates endothelial nitric oxide synthase (eNOS) that in turn contributes to vascular endothelial protection. Adult male Sprague-Dawley rats were subjected to 30-min ischemia induced by mesenteric artery occlusion followed by 60-min reperfusion 24 h after sham surgery or preconditioning (three cycles of 5-min ischemia/5-min reperfusion). Delayed preconditioning prevented the I/R-induced impairment of endothelium-dependent relaxations to acetylcholine (maximal relaxation: sham 91.4±2.2%; I/R 54.0±4.0%; IPC 80.2±6.3%). This protective effect was abolished by NOS inhibitor N(G)-nitro-L-arginine methyl ester and not changed by ascorbic acid. Electron microscopy showed marked endothelial damage after I/R and the ultrastructural changes were prevented by delayed preconditioning. Following I/R, the impairment of eNOS phosphorylation and expression was observed in mesenteric vessels. Furthermore, phosphatidylinositol 3-kinase (PI3K) and Akt phosphorylation were reduced, although total PI3K and Akt remained unchanged. IPC restored I/R-induced impairment of eNOS expression and activity. This was possibly the result of the recovery of PI3K/Akt phosphorylation. Furthermore, I/R increased serum level of malondialdehyde, intravascular superoxide and nitrotyrosine generation, which were abrogated by IPC. These results suggest that delayed preconditioning prevented I/R-induced endothelial injury in peripheral resistance vasculature, both in terms of functional and structural changes. Endothelial protection afforded by delayed IPC is associated with inhibition of oxidative stress and upregulation of PI3K/Akt/eNOS pathway.

Hemoglobin infusion does not alter murine pulmonary vascular tone

Plasma hemoglobin (Hb) scavenges endothelium-derived nitric oxide (NO), producing systemic and pulmonary vasoconstriction in many species. We hypothesized that i.v. administration of murine cell-free Hb would produce pulmonary vasoconstriction and enhance hypoxic pulmonary vasoconstriction (HPV) in mice. To assess the impact of plasma Hb on basal pulmonary vascular tone in anesthetized mice we measured left lung pulmonary vascular resistance (LPVRI) before and after infusion of Hb at thoracotomy. To confirm the findings obtained at thoracotomy, measurements of right ventricular systolic pressure (RVSP) and systemic arterial pressure (SAP) were obtained in closed-chest wild-type mice. To elucidate whether pretreatment with Hb augments HPV we assessed the increase in LPVRI before and during regional lung hypoxia produced by left mainstem bronchial occlusion (LMBO) in wild-type mice pretreated with Hb. Infusion of Hb increased SAP but did not change pulmonary arterial pressure (PAP), left lung pulmonary arterial flow (QLPA) or LPVRI in either wild-type or diabetic mice with endothelial dysfunction. Scavenging of NO by plasma Hb did not alter HPV in wild-type mice. Inhibition of NO synthase with l-NAME did not change the basal LPVRI, but augmented HPV during LMBO. Our data suggest that scavenging of NO by plasma Hb does not alter pulmonary vascular tone in mice. Therefore, generation of NO in the pulmonary circulation is unlikely to be responsible for the low basal pulmonary vascular tone of mice.

Free radical-mediated lipid peroxidation and systemic nitric oxide bioavailability: implications for postexercise hemodynamics

BACKGROUND

The metabolic vasodilator mediating postexercise hypotension (PEH) is poorly understood. Recent evidence suggests an exercise-induced reliance on pro-oxidant-stimulated vasodilation in normotensive young human subjects, but the role in the prehypertensive state is not known.

METHODS

Nine prehypertensives (mean arterial pressure (MAP), 106 ± 5 mm Hg; 50 ± 10 years old) performed 30 minutes of cycle exercise and a nonexercise trial. Arterial distensibility was characterized by simultaneously recording upper- and lower-limb pulse wave velocity (PWV) via oscillometry. Systemic vascular resistance and conductance were determined by MAP/Q and Q/MAP, respectively. Venous blood was assayed for indirect markers of oxidative stress (lipid hydroperoxides (LOOH); spectrophotometry), plasma nitric oxide (NO) and S-nitrosothiols (fluorometry), atrial natriuretic peptide (ANP), and angiotensin II (ANG-II) (radioimmunoassay).

RESULTS

Exercise reduced MAP (6mm Hg) and vascular resistance (15%) at 60 minutes after exercise, whereas conductance was elevated (20%) (P < 0.05). The hypotension resulted in a lower MAP at 60 and 120 minutes after exercise compared with nonexercise (P < 0.05). Upper-limb PWV was also 18% lower after exercise compared with baseline (P < 0.05). Exercise increased LOOH coincident with the nadir in hypotension and vascular resistance but failed to affect plasma NO or S-nitrosothiols. Exercise-induced increases in LOOH were related to ANG-II (r = 0.97; P < 0.01) and complemented by elevated ANP concentrations.

CONCLUSIONS

These data indicate attenuated vascular resistance after exercise with increased oxidative stress and unchanged NO. Whether free radicals are obligatory for PEH requires further investigation, although it seems that oxidative stress occurs during the hyperemia underlying PEH.

The effect of levofloxacin and moxifloxacin on cardiovascular functions of rats with streptozotocin-induced diabetes

Fluoroquinolone antibiotics cause rare, but clinically important, adverse events including hyperglycaemia and hypoglycaemia. The present study focuses on the possible effect of levofloxacin and moxifloxacin on the cardiovascular functions of rats with type I diabetes. Both antibiotics caused bradycardia. Levofloxacin but not moxifloxacin caused hypoglycaemia in diabetic rats and an increase in amplitude of the ST segment revealed by electrocardiogram (ECG) analysis of isolated hearts. In pressurized mesenteric arteries, levofloxacin did not affect the endothelium-derived hyperpolarising factor (EDHF) pathway or its main components, the small-conductance Ca(2+) activated potassium (SK(Ca)) and intermediate-conductance Ca(2+) activated potassium (IK(Ca)) channels. In moxifloxacin-treated rats, an increase in the EDHF response was observed, which was largely attributed to SK(Ca)-activation. In conclusion, levofloxacin and moxifloxacin use appeared to vary but with no evidence of impairment of the cardiovascular function. However, it is still possible that these antibiotics may produce different effects if there are co-morbidities and therefore their use must be with care.

Insulin-like growth factor-1 regulates glutathione peroxidase expression and activity in vascular endothelial cells: Implications for atheroprotective actions of insulin-like growth factor-1

Oxidative stress promotes endothelial cell senescence and endothelial dysfunction, important early steps in atherogenesis. To investigate potential antioxidant effects of IGF-1 we treated human aortic endothelial cells (hAECs) with 0-100ng/mL IGF-1 prior to exposure to native or oxidized low-density lipoprotein (oxLDL). IGF-1 dose- and time- dependently reduced basal- and oxLDL-induced ROS generation. IGF-1 did not alter superoxide dismutase or catalase activity but markedly increased activity of glutathione peroxidase (GPX), a crucial antioxidant enzyme, via a phosphoinositide-3 kinase dependent pathway. IGF-1 did not increase GPX1 mRNA levels but increased GPX1 protein levels by 2.6-fold at 24h, and altered selenocysteine-incorporation complex formation on GPX1 mRNA. Furthermore, IGF-1 blocked hydrogen peroxide induced premature cell senescence in hAECs. In conclusion, IGF-1 upregulates GPX1 expression in hAECs via a translational mechanism, which may play an important role in the ability of IGF-1 to reduce endothelial cell oxidative stress and premature senescence. Our findings have major implications for understanding vasculoprotective effects of IGF-1.

Effect of age and COX-2-derived prostanoids on the progression of adult vascular dysfunction in the offspring of diabetic rats

BACKGROUND AND PURPOSE

The present study was designed to determine how diabetes in pregnancy affects vascular function in their offspring, the influence of age and whether COX activation is involved in this effect.

EXPERIMENTAL APPROACH

Relaxation responses to ACh were analysed in mesenteric resistance arteries from the offspring of control rats (O-CR) and those of diabetic rats (O-DR) at 3, 6 and 12 months of age. TxB₂, PGE₂ and PGF(2α) release were determined by enzyme immunoassay. COX-1 and COX-2 expression were measured by Western blot analysis.

KEY RESULTS

O-DR developed hypertension from 6 months of age compared with O-CR. In O-DR, relaxation responses to ACh were impaired in all ages studied and were restored by COX-2 inhibition. TP receptor blockade (SQ29548) restored ACh relaxation in arteries from 3-month-old O-DR while TP and EP receptor blockade (SQ29548 + AH6809) was required to restore it in 6-month-old O-DR. In 12-month-old O-DR, ACh relaxation was restored when TP, EP and FP receptors were blocked (SQ29548 + AH6809 + AL8810). ACh-stimulated TxB₂ was higher in all O-DR. ACh-stimulated PGE₂ release was increased in arteries from 6- and 12-month-old O-DR, whereas PGF(2α) was increased only in 12-month-old O-DR. COX-2, but not COX-1, expression was higher in O-DR than O-CR.

CONCLUSIONS AND IMPLICATIONS

The results indicate an age-dependent up-regulation of COX-2 coupled to an enhanced formation of vasoconstrictor prostanoids in resistance arteries from O-DR. This effect plays a key role in the pathogenesis of endothelial dysfunction, which in turn could contribute to the progression of vascular dysfunction in these rats.

Overexpression of steroidogenic acute regulatory protein in rat aortic endothelial cells attenuates palmitic acid-induced inflammation and reduction in nitric oxide bioavailability

BACKGROUND

Endothelial dysfunction is a well documented evidence for the onset of atherosclerosis and other cardiovascular diseases. Lipids disorder is among the main risk factors for endothelial dysfunction in these diseases. Steroidogenic acute regulatory protein (StAR), one of the cholesterol transporters, plays an important role in the maintenance of intracellular lipid homeostasis. However, the effect of StAR on endothelial dysfunction is not well understood. Palmitic acid (PA) has been shown to decrease eNOS activity and induce inflammation, both are the causes of endothelial dysfunction, in an endothelial cell culture model.

METHODS

StAR gene was introduced into primary rat aortic endothelial cells by adenovirus infection. Real-time PCR and Western blotting were performed to determine the relative genes and proteins expression level to elucidate the underlying mechanism. The free fatty acid and cholesterol quantification kits were used to detect total cellular free fatty acid and cholesterol. The levels of inflammatory factors and nitric oxide were determined by ELISA and classic Griess reagent methods respectively.

RESULTS

We successfully overexpressed StAR in primary rat aortic endothelial cells. Following StAR overexpression, mRNA levels of IL-1β, TNFα, IL6 and VCAM-1 and protein levels of IL-1β, , TNFα and IL-6 in culture supernatant were significantly decreased, which duing to blocke NFκB nuclear translocation and activation. Moreover, StAR overexpression attenuated the PA-induced reduction of nitric oxide bioavailability by protecting the bioactivity of pAkt/peNOS/NO pathway. Furthermore, the key genes involved in lipid metabolism were greatly reduced following StAR overexpression. In order to investigate the underlying mechanism, cerulenin and lovastatin, the inhibitor of fatty acid and cholesterol synthase, were added prior to PA treatment. The results showed that both cerulenin and lovastatin had a similar effect as StAR overexpression. On the other hand, the role of StAR was inhibited when siRNA was introduced to reduce StAR expression.

CONCLUSIONS

Our results showed that StAR attenuated lipid synthesis and uptake as well as PA-induced inflammation and reduction in NO bioavailability in aortic endothelial cells. StAR can ameliorate endothelial dysfunction induced by PA via reducing the intracellular lipid levels.

Stimulation of non-neuronal muscarinic receptors enhances chemerin/ChemR23 system in dysfunctional endothelial cells

AIMS

Endothelial cells play a pivotal role in vascular intimal inflammation during cardiovascular diseases. The chemerin/ChemR23 system in endothelial cells is one of physiological mechanisms that regulate inflammatory responses. Our previous studies indicated that stimulation of non-neuronal muscarinic receptor (NNMR) improved endothelial dysfunction. However, the relationship between the chemerin/ChemR23 signaling axis and NNMR in endothelial cell is poorly understood. Here, we first investigated whether the modulation of chemerin/ChemR23 signaling axis is involved in NNMR-mediated endothelial protection.

MAIN METHODS

Cultured rat aortic endothelial cells (RAECs) were used. The ChemR23 protein expression and chemerin secretion were measured using Western blot analysis. The gene expression level of ChemR23 was examined with reverse transcriptase PCR (RT-PCR). The production of nitric oxide (NO) was determined by a nitrate reductase assay kit.

KEY FINDINGS

A sharp decline of chemerin secretion and ChemR23 protein/gene expression was observed in RAECs after exposed to homocysteine at concentration of 0.5 mmol/L. Arecoline (10 μmol/L) pretreatment increased ChemR23 protein expression as well as mRNA expression, and enhanced the secretion of chemerin. Arecoline could also reverse the decreased ChemR23 mRNA expression induced by uric acid, high glucose, or oxidized low-density lipoprotein. Furthermore, the modulation of arecoline on chemerin/ChemR23 signaling axis was absolutely abolished in the presence of the nonselective muscarinic receptors antagonist atropine 1 μmol/L. Additionally, arecoline improved endothelial dysfunction by increasing the reduced NO production induced by uric acid, which was blocked by anti-ChemR23 antibody.

SIGNIFICANCE

The chemerin/ChemR23 signaling axis participates in NNMR-mediated protection against endothelial dysfunction in cardiovascular system.

Nitric oxide: orchestrator of endothelium-dependent responses

The present review first summarizes the complex chain of events, in endothelial and vascular smooth muscle cells, that leads to endothelium-dependent relaxations (vasodilatations) due to the generation of nitric oxide (NO) by endothelial nitric oxide synthase (eNOS) and how therapeutic interventions may improve the bioavailability of NO and thus prevent/cure endothelial dysfunction. Then, the role of other endothelium-derived mediators (endothelium-derived hyperpolarizing (EDHF) and contracting (EDCF) factors, endothelin-1) and signals (myoendothelial coupling) is summarized also, with special emphasis on their interaction(s) with the NO pathway, which make the latter not only a major mediator but also a key regulator of endothelium-dependent responses.

Coexistence of macro- and micro-vascular abnormalities in newly diagnosed normal tension glaucoma patients

PURPOSE

To investigate the coexistence of ocular microvascular and systemic macrovascular abnormalities in early stage, newly diagnosed and previously untreated normal tension glaucoma patients (NTG).

METHODS

Retinal vascular reactivity to flickering light was assessed in 19 NTG and 28 age-matched controls by means of dynamic retinal vessel analysis (IMEDOS GmbH, Jena, Germany). Using a newly developed computational model, the entire dynamic vascular response profile to flicker light was imaged and used for analysis. In addition, assessments of carotid intima-media thickness (IMT) and pulse wave analysis (PWA) were conducted on all participants, along with blood pressure (BP) measurements and blood analyses for lipid metabolism markers.

RESULTS

 Patients with NTG demonstrated an increased right and left carotid IMT (p = 0.015, p = 0.045) and an elevated PWA augmentation index (p = 0.017) in comparison with healthy controls, along with an enhanced retinal arterial constriction response (p = 0.028), a steeper retinal arterial constriction slope (p = 0.031) and a reduced retinal venous dilation response (p = 0.026) following flicker light stimulation.

CONCLUSIONS

Early stage, newly diagnosed, NTG patients showed signs of subclinical vascular abnormalities at both macro- and micro-vascular levels, highlighting the need to consider multi-level circulation-related pathologies in the development and progression of this type of glaucoma.

Characterization of endothelium-dependent relaxations in the mesenteric vasculature: a comparative study with potential pathophysiological relevance

BACKGROUND

Endothelium-dependent relaxations in human adult mesenteric microvessels involve 3 different main mechanisms: cyclooxygenase (COX)-derived prostanoids, nitric oxide (NO), and endothelium-derived hyperpolarizing factor (EDHF), which elicits vascular smooth muscle hyperpolarization and relaxation. There are some pathological conditions with an abnormal balance between mesenteric vasoconstriction and vasodilatation inputs leading to endothelial dysfunction and tissue injury.

PURPOSE

The purpose was to characterize the mechanisms mediating endothelium-dependent relaxation and differences in children and adult mesenteric microvessels.

METHODS

Microvessels were dissected from omentum obtained from children (3-6 years old) and adults (25-41 years old) and mounted as ring preparations in a small vessel myograph.

RESULTS

In microvessels precontracted with a thromboxane analogue, the endothelium-dependent relaxations to bradykinin (10 nmol/L to 30 μmol/L) mediated by EDHF, that is, nonsensitive to COX (10 μmol/L indomethacin) and NO synthase blockade (100 μmol/L N-nitro-L-arginine methyl ester), were higher in children than in adults. When EDHF was blunted by a depolarizing precontraction with KCl, the remaining COX- and NO-dependent relaxations were significantly lower in children.

CONCLUSIONS

The EDHF's role in the endothelium-dependent relaxations is higher in children's vasculature. This suggests that endothelial dysfunction in mesenteric microvessels in children is likely more dependent on EDHF-related mechanisms rather than on NO- or COX-derived prostanoids.

TNF-α induces endothelial dysfunction via PKC-ζ-dependent NADPH oxidase activation

Endothelial dysfunction is implicated in a variety of cardiovascular diseases although the detailed mechanisms are not yet completely understood. A relationship has been suggested to exist between inflammation and endothelial dysfunction. TNF-α serves as one of the most important pro-inflammatory cytokines. The main objectives of the present study were to explore the effect of PKC-ζ on TNF-α-impaired endothelial function as well as the underlying mechanisms. Acetylcholine-induced endothelium-dependent vasodilation of mouse thoracic aorta stimulated by TNF-α was initially determined. PKC-ζ deficient mice and the specific inhibitor of NADPH oxidase were respectively applied to elucidate their roles in TNF-α-induced endothelial dysfunction. In vitro superoxide generation in HAECs was detected by DHE staining after administration of TNF-α. Meanwhile, the regulatory p47(phox) subunit of NADPH oxidase was evaluated by Western blotting and RT-PCR. The results showed that TNF-α conspicuously impaired endothelium-dependent vasodilation and the impairment was attenuated by either depleting PKC-ζ or inhibiting NADPH oxidase. In vitro TNF-α increased superoxide production and p47(phox) expression in HAECs, and such increases could be ameliorated by the specific PKC-ζ inhibitor. Our findings suggest that superoxide over-production triggered by PKC-ζ-dependent NADPH oxidase activation contributes to TNF-α-induced endothelial dysfunction.

Studies on the enantiomers of ZJM-289: synthesis and biological evaluation of antiplatelet, antithrombotic and neuroprotective activities

ZJM-289 is a potent racemic agent which inhibits both platelet aggregation and thrombosis superior to a known anti-ischemic stroke drug 3-n-butylphthalide (NBP). Herein, the enantiomers of ZJM-289, (S)-ZJM-289 and (R)-ZJM-289, were synthesized and evaluated for their biological activities. It was observed that the two enantiomers appeared to be almost as effective as ZJM-289 in inhibiting platelet aggregation in vitro and thrombus formation in vivo. Moreover, like ZJM-289, its enantiomers could regulate the ratio of thromboxane B(2) (TXB(2)) and 6-keto-prostaglandin F(1α), and enhanced levels of nitric oxide (NO), cAMP and cGMP, suggesting that the anti-platelet and antithrombotic activities of the enantiomers and ZJM-289 are associated with both the arachidonic acid cascade and cGMP-NO signal pathway. Furthermore, it was found that oral administration of the enantiomers and ZJM-289 for three days significantly reduced the infarct size, brain water content and neurological deficit in rats after cerebral ischemia reperfusion. Importantly, the two enantiomers equally improved blood flow in the ischemic stroke model and modulated endothelial function through releasing moderate levels of NO, which might, at least partially, contribute to their neuroprotection. Collectively, the present study demonstrates that the two enantiomers are as potent as ZJM-289 in inhibition of platelet aggregation and thrombosis and in neuroprotection, and (S)-ZJM-289 shows somewhat better effects than (R)-ZJM-289 and ZJM-289 in a few cases. These findings may provide new insights into the development of therapeutic agents like ZJM-289 for the intervention of thrombosis-related ischemic stroke.

Low tidal volume protects pulmonary vasomotor function from "second-hit" injury in acute lung injury rats

Background

Sepsis could induce indirect acute lung injury(ALI), and pulmonary vasomotor dysfunction. While low tidal volume is advocated for treatment of ALI patients. However, there is no evidence for low tidal volume that it could mitigate pulmonary vasomotor dysfunction in indirect ALI. Our study is to evaluate whether low tidal volume ventilation could protect the pulmonary vascular function in indirect lipopolysaccharide (LPS) induced acute lung injury rats.

Methods

An indirect ALI rat model was induced by intravenous infusion of LPS. Thirty rats (n = 6 in each group) were randomly divided into (1)Control group; (2) ALI group; (3) LV group (tidal volume of 6mL/kg); (4) MV group (tidal volume of 12mL/kg); (5)VLV group (tidal volume of 3mL/kg). Mean arterial pressure and blood gas analysis were monitored every 2 hours throughout the experiment. Lung tissues and pulmonary artery rings were immediately harvested after the rats were bled to be killed to detect the contents of endothelin-1 (ET-1), endothelial nitric oxide synthase (eNOS) and TNF-α. Acetylcholine (Ache)-induced endothelium-dependent and sodium nitroprusside (SNP)-induced endothelium-independent relaxation of isolated pulmonary artery rings were measured by tensiometry.

Results

There was no difference within groups concerning blood pressure, PaCO₂ and SNP-induced endothelium-independent relaxation of pulmonary artery rings. Compared with MV group, LV group significantly reduced LPS-induced expression of ET-1 level (113.79 ± 7.33pg/mL vs. 152.52 ± 12.75pg/mL, P < 0.05) and TNF-α (3305.09 ± 334.29pg/mL vs.4144.07 ± 608.21pg/mL, P < 0.05), increased the expression of eNOS (IOD: 15032.05 ± 5925.07 vs. 11454.32 ± 6035.47, P < 0.05). While Ache (10^-7mol/L-10^-4mol/L)-induced vasodilatation was ameliorated 30% more in LV group than in MV group.

Conclusions

Low tidal volume could protect the pulmonary vasodilative function during indirect ALI by decreasing vasoconstrictor factors, increasing expressions of vasodilator factors in pulmonary endothelial cells, and inhibiting inflammation injuries.

When and how to start prevention of atherosclerosis? Lessons from the Cardiovascular Risk in the Young Finns Study and the Special Turku Coronary Risk Factor Intervention Project

This review provides an up-to-date summary of findings from two ongoing population-based, prospective studies conducted in Finland: The Cardiovascular Risk in Young Finns Study, and the Special Turku Coronary Risk Factor Intervention Project (STRIP), which have contributed significantly to the scientific literature concerning the childhood origin of cardiovascular disease, and whether prevention efforts in adults can be expanded to young people. From the Young Finns Study, we summarize evidence demonstrating childhood risk factors to be associated with both risk factors and preclinical markers of atherosclerosis in adulthood, and from STRIP, we summarize evidence showing that supervised dietary counseling of a low saturated fat diet effectively decreases exposure to cardiovascular risk factors without affecting growth and development of healthy children and adolescents. The evidence available from these studies supports that the ability to prevent or delay the risk of premature atherosclerosis and its clinical sequelae later in life lies in maintaining a low lifetime risk by preventing the development of risk factors in early life.

Betulinic acid inhibits superoxide anion-mediated impairment of endothelium-dependent relaxation in rat aortas

OBJECTIVES

To investigate the protective effect of betulinic acid (BA) on endothelium-dependent relaxation (EDR) in rat aortas exposed to pyrogallol-produced superoxide anion and its underlying mechanism.

MATERIALS AND METHODS

The thoracic aorta of male Sprague-Dawley rats was isolated to mount in the organ bath system and the effect of BA on acetylcholine (ACh)-induced EDR, nitric oxide (NO) level, reactive oxygen species (ROS) level, nitric oxide synthase (NOS) activity, and superoxide dismutase (SOD) activity of aortic rings exposed to pyrogallol (500 μM) for 15 min were measured.

RESULTS

BA evoked a concentration-dependent EDR in aortas, and pretreatment with EC(50) (2.0 μM) concentration of BA markedly enhanced ACh-induced EDR of aortas exposed to pyrogallol-produced superoxide anion (E(max) rose from 23.91 ± 5.41% to 42.45 ± 9.99%), which was markedly reversed by both N(w) -nitro-L-arginine methyl ester hydrochloride (L-NAME) and methylene blue, but not by indomethacin. Moreover, BA significantly inhibited the increase of ROS level, as well as the decrease of NO level, the endothelial NOS (eNOS) activity, and the SOD activity in aortas induced by pyrogallol-derived superoxide anion.

CONCLUSION

These results indicate that BA reduces the impairment of EDR in rat aortas exposed to exogenous superoxide anion, which may closely relate to the reduction of oxidative stress and activation of eNOS-NO pathway.

High resolution imaging of vascular function in zebrafish

Rationale

The role of the endothelium in the pathogenesis of cardiovascular disease is an emerging field of study, necessitating the development of appropriate model systems and methodologies to investigate the multifaceted nature of endothelial dysfunction including disturbed barrier function and impaired vascular reactivity.

Objective

We aimed to develop and test an optimized high-speed imaging platform to obtain quantitative real-time measures of blood flow, vessel diameter and endothelial barrier function in order to assess vascular function in live vertebrate models.

Methods and Results

We used a combination of cutting-edge optical imaging techniques, including high-speed, camera-based imaging (up to 1000 frames/second), and 3D confocal methods to collect real time metrics of vascular performance and assess the dynamic response to the thromboxane A₂ (TXA₂) analogue, U-46619 (1 µM), in transgenic zebrafish larvae. Data obtained in 3 and 5 day post-fertilization larvae show that these methods are capable of imaging blood flow in a large (1 mm) segment of the vessel of interest over many cardiac cycles, with sufficient speed and sensitivity such that the trajectories of individual erythrocytes can be resolved in real time. Further, we are able to map changes in the three dimensional sizes of vessels and assess barrier function by visualizing the continuity of the endothelial layer combined with measurements of extravasation of fluorescent microspheres.

Conclusions

We propose that this system-based microscopic approach can be used to combine measures of physiologic function with molecular behavior in zebrafish models of human vascular disease.

Effect of nisoldipine and olmesartan on endothelium-dependent vasodilation in essential hypertensive patients

AIMS

To investigate whether nisoldipine and olmesartan improve endothelial function, decrease asymmetric dimethylarginine (ADMA) and alleviate the inflammatory and oxidative process.

METHODS

Fifty-five essential hypertensive patients were randomized to receive nisoldipine or olmesartan for 8 weeks according to a parallel-group, active-controlled, single blind study, and 28 matched normotensive subjects served as healthy controls. Flow-mediated dilation (FMD), and plasma levels of nitric oxide (NO), endothelin-1 (ET-1), high-sensitive C-reactive protein (hs-CRP), 8-isoprostane (also named 8-isoPGF2α), and ADMA were determined.

RESULTS

At baseline, the plasma levels of ADMA, ET-1, hs-CRP, and 8-isoPGF2α were markedly higher in patients with essential hypertension than in normotensive subjects (P < 0.05). A significant positive correlation was observed between plasma levels of ET-1 and ADMA in patients with essential hypertension, but not in normotensive subjects. The NO plasma concentrations were significantly lower in patients with essential hypertension than in normotensive subjects. Furthermore, hypertensive subjects demonstrated significantly lower FMD than healthy control (P < 0.05). Nisoldipine and olmesartan significantly and similarly reduced blood pressure in patients with essential hypertension (P < 0.001). At the end of the 8-week treatment, plasma ADMA and ET-1 levels were decreased significantly (P < 0.01). FMD increased significantly in nisoldipine or olmesartan-treated patients (P < 0.05). A significant decrease in plasma hs-CRP contents was observed in patients receiving nisoldipine (P < 0.05).

CONCLUSION

The findings demonstrate that nisoldipine and olmesartan both improve FMD in patients with essential hypertension. This may be associated with decreased circulating levels of CRP, ET-1, and ADMA.

SIRT1 in metabolic syndrome: where to target matters

Sirtuin 1 (SIRT1), the mammalian ortholog of yeast Sir2p, is a highly conserved NAD(+)-dependent protein deacetylase that has emerged as a key cardiometabolic regulator. During the past decade, Sir2p has been the focus of intense investigations and discussion because it regulates longevity in yeast, worms and flies. Although the extrapolation of data obtained from yeast Sir2p to mammalian SIRT1 cannot be automatic, animal studies provide convincing evidence that SIRT1 is a potent protector against aging-associated pathologies, in particular metabolic disorders and cardiovascular diseases. Indeed, many exciting connections exist between the protein deacetylation function of SIRT1 and its role in fundamental biological responses to various nutritional and environmental signals. As a result, pharmaceutical and nutriceutical interventions targeting SIRT1 are promising strategies to combat aging-associated diseases. The present review summarizes the recent progress in SIRT1 research with a particular focus on the specificities of this protein in individual tissues as they relate to cardiometabolic control.

Role of TRPM2 in H(2)O(2)-induced cell apoptosis in endothelial cells

Melastatin-like transient receptor potential channel 2 (TRPM2) is an oxidant-sensitive and cationic non-selective channel that is expressed in mammalian vascular endothelium. Here we investigated the functional role of TRPM2 channels in hydrogen peroxide (H(2)O(2))-induced cytosolic Ca(2+) ([Ca(2+)](i)) elavation, whole-cell current increase, and apoptotic cell death in murine heart microvessel endothelial cell line H5V. A TRPM2 blocking antibody (TM2E3), which targets the E3 region near the ion permeation pore of TRPM2, was developed. Treatment of H5V cells with TM2E3 reduced the [Ca(2+)](i) rise and whole-cell current change in response to H(2)O(2). Suppressing TRPM2 expression using TRPM2-specific short hairpin RNA (shRNA) had similar inhibitory effect. H(2)O(2)-induced apoptotic cell death in H5V cells was examined using MTT assay, DNA ladder formation analysis, and DAPI-based nuclear DNA condensation assay. Based on these assays, TM2E3 and TRPM2-specific shRNA both showed protective effect against H(2)O(2)-induced apoptotic cell death. TM2E3 and TRPM2-specific shRNA also protect the cells from tumor necrosis factor (TNF)-α-induced cell death in MTT assay. In contrast, overexpression of TRPM2 in H5V cells resulted in an increased response in [Ca(2+)](i) and whole-cell currents to H(2)O(2). TRPM2 overexpression also aggravated the H(2)O(2)-induced apoptotic cell death. Downstream pathways following TRPM2 activation was examined. Results showed that TRPM2 activity stimulated caspase-8, caspase-9 and caspase-3. These findings strongly suggest that TRPM2 channel mediates cellular Ca(2+) overload in response to H(2)O(2) and contribute to oxidant-induced apoptotic cell death in vascular endothelial cells. Down-regulating endogenous TRPM2 could be a means to protect the vascular endothelial cells from apoptotic cell death.

The effect of streptozotocin-induced diabetes on the EDHF-type relaxation and cardiac function in rats

The endothelium-derived hyperpolarizing factor (EDHF) response is a critical for the functioning of small blood vessels. We investigated the effect of streptozotocin-induced diabetes on the EDHF response and its possible role in the regulation of cardiac function. The vasorelaxant response to ACh- or NS309- (direct opener endothelial small- (SK_Ca)- and intermediate-conductance (IK_Ca) calcium-activated potassium channels; main components of EDHF response) were measured in pressurized mesenteric arteries (diameter 300–350 μm). The response to 1 μM ACh was reduced in diabetes (84.8 ± 2.8% control vs 22.5 ± 5.8% diabetics; n ⩾ 8; P < 0.001). NS309 (1 μM) relaxations were also decreased in diabetic arteries (78.5 ± 8.7% control vs 32.1 ± 5.8% diabetics; n ⩾ 5; P < 0.001). SK_Ca and IK_Ca-mediated EDHF relaxations in response ACh or NS309 were also significantly reduced by diabetes. Ruthenium red, RuR, a blocker of TRP channels, strongly depress the response to ACh and NS309 in control and diabetic arteries. RuR decreased SK_Ca and IK_Ca-mediated EDHF vasodilatation in response to NS309 but not to ACh. An elevation in systolic blood pressure was observed in diabetic animals. ECG recording of control hearts showed shortening of PR interval. RuR reduced PR interval and R wave amplitude in diabetic hearts. In conclusion, the reduced EDHF-type relaxations in STZ-induced diabetes is due impairment of K_Ca channels function. TRP channels possibly contribute to EDHF vasodilatation via direct opening of endothelial K_Ca. It is possible that EDHF and TRP channels contribute to the regulation of cardiac function and therefore can be considered as therapeutic targets to improve cardiovascular complications of diabetes.

Update on vascular endothelial Ca2+ signalling: A tale of ion channels, pumps and transporters

A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and forms a multifunctional transducing organ that mediates a plethora of cardiovascular processes. The activation of ECs from as state of quiescence is, therefore, regarded among the early events leading to the onset and progression of potentially lethal diseases, such as hypertension, myocardial infarction, brain stroke, and tumor. Intracellular Ca²⁺ signals have long been know to play a central role in the complex network of signaling pathways regulating the endothelial functions. Notably, recent work has outlined how any change in the pattern of expression of endothelial channels, transporters and pumps involved in the modulation of intracellular Ca²⁺ levels may dramatically affect whole body homeostasis. Vascular ECs may react to both mechanical and chemical stimuli by generating a variety of intracellular Ca²⁺ signals, ranging from brief, localized Ca²⁺ pulses to prolonged Ca²⁺ oscillations engulfing the whole cytoplasm. The well-defined spatiotemporal profile of the subcellular Ca²⁺ signals elicited in ECs by specific extracellular inputs depends on the interaction between Ca²⁺ releasing channels, which are located both on the plasma membrane and in a number of intracellular organelles, and Ca²⁺ removing systems. The present article aims to summarize both the past and recent literature in the field to provide a clear-cut picture of our current knowledge on the molecular nature and the role played by the components of the Ca²⁺ machinery in vascular ECs under both physiological and pathological conditions.

Novel diallyldisulfide analogs ameliorate cardiovascular remodeling in rats with L-NAME-induced hypertension

Diallyldisulfide (DADS), an active principle of garlic (Allium sativum) is known for its antihypertensive properties. The present study was designed to evaluate the effect of novel DADS analogs, against L-NAME induced hypertension in Wistar rats. The daily administration of L-NAME (50mg/kg) for six weeks along with DADS analogs (20 mg/kg) significantly decreased the elevated systolic blood pressure (SBP) and the activity of angiotensin converting enzyme (ACE) and also inhibited the decline in nitrite/nitrate (NO(x)) concentrations and cyclic guanosine monophosphate (cGMP) levels. Adverse changes such as lipid peroxidation, protein damage and a decrease in the levels of antioxidant enzymes, were rectified after the administration of DADS analogs. Oral administration of DADS analogs preserved the expression of endothelial nitric oxide synthase (eNOS). The ability of the DADS analogs to inhibit L-NAME induced hypertension was compared with Enalapril (15 mg/kg), which was taken as a standard. The DADS analogs prevented L-NAME-induced cardio toxicity, which was also reflected at the microscopic level indicative of its cardio protective effects. DADS analogs induced vasorelaxation was completely abolished by the removal of the endothelium or by pre-treatment with L-NAME, an inhibitor of nitric oxide synthase. DADS analogs inhibited the calcium influx induced by phenylephrine (0.3 μM) and high K(+) (60mM) and this effect was completely abolished by pretreatment of L-NAME. Taken together, our results show that the DADS analogs induce vasorelaxation and have antihypertensive properties, which may be mediated through activation of eNOS.

AMP-activated protein kinase activator AICAR acutely lowers blood pressure and relaxes isolated resistance arteries of hypertensive rats

OBJECTIVES

AMP-activated protein kinase (AMPK) activity may alter blood pressure by directly influencing vascular tone. The purpose of this study is to examine if these effects occur acutely in a model of hypertension.

METHODS AND RESULTS

Using distinct groups of Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) we compare baseline aortic and mesenteric artery AMPK activation (by immunoblotting), hemodynamic (blood pressure and heart rate via carotid catheter) and biochemical responses to an acute injection of AMPK activator 5-aminoimidazole-4-carboxyamide-1-β-D-ribofuranoside (AICAR) in vivo and vasomotor responses of isolated mesenteric vessels to AICAR exposure in vitro using myography. Mean arterial pressure (MAP) decreased from 196 ± 3 to 122 ± 15 mmHg (P < 0.001) during the 30 min following AICAR injection in SHR (an effect partially prevented by NOS inhibitor L-NAME), but in WKY MAP was unaffected by AICAR. Basal AMPK activation (phosphorylation of AMPK activation site threonine 172) was reduced by approximately 50% in aorta of SHR vs. WKY (0.49 ± 0.1 vs. 1.0 ± 0.1 arbitrary units, P < 0.001), and was improved approximately 1.6-fold in SHR but not in WKY aorta 30 min following AICAR injection. In isolated vessel experiments, dose-dependent vasorelaxation to AICAR was similar in mesenteric arteries of SHR and WKY, although responses were more reliant on nitric oxide in SHR vs. WKY.

CONCLUSIONS

The ability of AICAR to improve vascular AMPK activation, and to generate parallel reductions in blood pressure and relaxation of SHR resistance vasculature, highlights the potential importance of AMPK in the regulation of blood pressure and vascular tone.

Glutathione enhances endothelium-mediated control of coronary vascular resistance via a ROS- and NO intermediate-dependent mechanism

The purpose of this investigation was to determine the effects of acute physiological GSH administration on endothelium-mediated reduction in coronary vascular resistance (CVR) using isolated perfused Sprague-Dawley rat hearts. A dose-response curve to GSH was conducted to determine a threshold concentration of GSH. We demonstrate that 30 μM GSH was sufficient to reduce CVR, and maximal dilation was achieved with 1 mM. In subsequent experiments, GSH was administered at concentrations of 0 [control (CON)], 1 μM, or 10 μM (GSH10), and dose-response curves to the endothelial agonist bradykinin (BK) were constructed. These GSH concentrations were chosen because of the physiological relevance and because the effects of GSH on BK action could be assessed independent of baseline differences in CVR. Sensitivity to BK (EC50) was enhanced in GSH10 vs. CON ( P < 0.05). This enhancement remained in the presence of nitric oxide (NO) synthase inhibition l-ωnitro-l-arginine (lNAME) and/or soluble guanylate cyclase (sGC) inhibition. Treatment with 4-hydroxy (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPOL) enhanced the sensitivity to BK in CON, similar to the effects of GSH10 and GSH10 + TEMPOL. However, the GSH10-dependent enhancement of EC50 observed in the presence of lNAME did not occur in the presence of lNAME + TEMPOL or in the presence of lNAME + sGC inhibition and NO scavenging. Collectively, these results suggest that GSH enhances BK-mediated dilation and reduction in CVR through an antioxidant-dependent mechanism that involves a NO intermediate but is unrelated to acute production of NO and GC-dependent effects of NO. These results suggest a mechanism whereby physiologically relevant levels of GSH modulate the endogenous reactive oxygen species and NO control of endothelium-dependent coronary vascular function.

Gene expression analysis in chronic postradiation proctopathy

PURPOSE

Radiotherapy is one of the important treatment modalities for tumors of pelvic organs. The fixed location of the rectum and its anatomic relationship with other pelvic organs makes it prone to radiation injury resulting in chronic radiation proctopathy in 5% to 20% of patients. Endothelial dysfunction has been associated with a number of pathophysiological processes. Endothelial cells synthesize and release various factors that regulate angiogenesis, inflammatory responses, hemostasis, as well as vascular tone and permeability.

METHODS

Rectum tissue samples from 20 patients with established chronic radiation proctopathy were analysed for the expression of genes related to oxidative stress, tissue hypoxia, angiogenesis, and inflammation [endoglin (ENG), activin receptor-like kinase 1 (ALK1), platelet endothelial cell adhesion molecule 1 (PECAM), vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), hypoxia-inducible factor 1 (HIF-1), and interleukin-1 beta (IL-1β)].

RESULTS

Overexpression of HIF-1, VEGF, FGF2, and IL-1β was detected in affected tissue. For the first time, a significant suppression of activin receptor-like kinase 1 and ENG could be revealed.

CONCLUSION

The data provided here allow further insight into the pathogenesis of radiation-induced rectum injury. Radiation-induced damage is not confined to a single event but involves complex signaling between different pathways, enhancing and maintaining the processes that lead to mucosal damage. The results indicate that postradiation tissue hypoxia is critical for fibrosis, which involves changes in the expression of profibrotic and angiogenic factors in rectal tissue.

Discrepant regulation of QT (QTc) interval duration by calcium channel blockade and angiotensin converting enzyme inhibition in experimental hypertension

Antihypertensive treatment may reduce prolonged QT duration in hypertension. Generally, the reductions of blood pressure and/or of cardiac mass are believed to be the responsible factors. However, drugs are not equivalent in QT modulation despite similar antihypertensive and antihypertrophic action. We investigated the effect of a calcium channel blocker, lacidipine and an angiotensin-converting enzyme inhibitor, enalapril on QT duration in rats. Normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were treated with lacidipine (at the dose of 1.5 mg/kg per day for WKY and 3 mg/kg per day for SHR) or enalapril (5 mg/kg per day for WKY and 10 mg/kg per day for SHR) during 8 weeks. Tail-cuff systolic blood pressure (sBP), left ventricular weight (LVW), vascular function of isolated aorta and mesenteric artery and duration of QT (and QTc) interval on Frank electrocardiograms were evaluated. As expected, untreated SHR showed elevated sBP, impaired vascular reactivity, increased LVW and prolonged QT when compared with WKY (p < 0.05). After treatment, both agents markedly improved vascular reactivity and reduced sBP in SHR (p < 0.05). Additionally, enalapril reduced LVW in both hypertensive (by 17%; p < 0.05) and normotensive rats (by 13%; p < 0.05) and, consequently, corrected QT duration in SHR. Interestingly, lacidipine also reduced LVW in SHR (by 9%; p < 0.05), but without influence on prolonged QT. Moreover, lacidipine had no effect on LVW in WKYs but prolonged their QT interval (by 10%; p < 0.05). In conclusion, lacidipine did not reverse a progressive prolongation of QT in SHR, despite sBP lowering and LVW reduction. Thus, the lowering of blood pressure and/or reduction of LVW are not sufficient per se to normalize ventricular repolarization in hypertensive cardiac disease. More likely, modulation of QT prolongation by antihypertensive drugs is a function of their complex action on blood pressure, vascular function, cardiac mass and on reflex neurohumoral activation.

[Vasoreactivity changes during extracorporeal circulation: effects of halogenated agents]

During cardiopulmonary bypass (CPB), endothelium is exposed to multiple disturbances leading to significant vasomotor tone and vascular systemic resistances (VSR) level modifications. Properties of endothelial function on vascular tone were summarized herein. According bibliographic findings, physiological and clinical impacts of respectively halogenated agents and CPB concerning vasomotor tone were reported. Main effects of halogenated agents administered through oxygenator during CPB were also identified. Usually when administered above one MAC, halogenated agents decreased VSR during hypothermic bypass. Once those mechanisms summarized, increase of halogenated agent's effects on VSR during normothermic CPB was postulated. Assuming that decrease of VSR could be deleterious favoring severe vasoplegia event, clinical experience of administration of isoflurane during CPB among more 4000 patients was retrospectively reported. Incidence of severe vasoplegia was established to 9.5 % in the studied population and this result was similar as others. More over predicting factors of severe vasoplegia were the same as previously reported : severity of preoperative clinical status according Euroscore, hemodynamical instability before induction of anesthesia, surgical procedure complexity and CPB duration. Absence of deleterious effects in SVR decrease when administering isoflurane during normothermic CPB was assumed but prospective comparative studies comparing effects of halogenated agents and other anesthetic agents are needed in order to confirm these findings.

Vascular hyporeactivity to angiotensin II and noradrenaline in a rabbit model of obesity

This study was conducted to explore the vascular reactivity of angiotensin II and noradrenaline and their relationship with endothelial function in rabbits fed a high-fat diet (HFD). The animals were fed either an HFD or regular chow [control diet (CD)]. After 12 weeks, the rabbits fed the HFD showed higher blood pressure, body weight, and insulin levels. Glucose tolerance was impaired and positively related to blood pressure. An endothelium-independent decrease of the sensitivity to angiotensin II [pD2 endothelium-intact aortic rings (E+) in CD: 8.02 ± 0.07 vs. HFD: 7.60 ± 0.01; pD2 endothelium-removed aortic rings (E-) in CD: 8.16 ± 0.11 vs. HFD: 7.83 ± 0.16] and noradrenaline (pD2 E+ in CD: 6.36 ± 0.06 vs. HFD: 5.29 ± 0.06; pD2 E- in CD: 6.11 ± 0.08 vs. HFD: 5.80 ± 0.08) was found. Noradrenaline desensitized the angiotensin II response (pD2 with noradrenaline pretreatment in E+: 7.03 ± 0.16; in E-: 7.10 ± 0.02), but angiotensin II did not change the noradrenaline response. Acetylcholine maximal relaxation and basal nitric oxide (NO) release were comparable in both diet groups. The efficacy of angiotensin II (Rmax CD: 4604 ± 574 mg vs. HFD: 3251 ± 533 mg) and noradrenaline (Rmax CD: 11,675 ± 804 mg vs. HFD: 7975 ± 960 mg) was reduced in E+. L-N-nitroarginine methyl ester (L-NAME) recovered the efficacy of noradrenaline (Rmax L-NAME: 12,015 ± 317 mg). In contrast, L-NAME had no effect on the angiotensin II response. Noradrenaline enhanced NO levels, but angiotensin II did not. Therefore, NO was associated with hyporeactivity to noradrenaline. The resting potential was more negative in E+, and the endothelium diminished the angiotensin II-induced depolarization. These findings demonstrated that the crosstalk and the endothelium may induce hyporeactivity to angiotensin II and noradrenaline as a mechanism to compensate the increase in the blood pressure in HFD-induced obesity.

Progression of renal fibrosis: the underestimated role of endothelial alterations

The vasculature of the kidney is a heterogeneous structure, whose functional integrity is essential for the regulation of renal function. Owing to the importance of the endothelium in vascular biology, chronic endothelial alterations are therefore susceptible to impair multiple aspects of renal physiology and, in turn, to contribute to renal fibrosis. Although systemic endothelial dysfunction is undoubtedly associated with chronic kidney disease, the role of the renal endothelium in the initiation and the progression of renal fibrosis remains largely elusive. In this article, we critically review recent evidence supporting direct and indirect contributions of renal endothelial alterations to fibrosis in the kidney. Specifically, the potential implications of renal endothelial dysfunction and endothelial paucity in parenchymal hypoxia, in the regulation of local inflammation, and in the generation of renal mesenchymal cells are reviewed. We thereafter discuss therapeutic perspectives targeting renal endothelial alterations during the initiation and the progression of renal fibrogenesis.

Physical activity opposes coronary vascular dysfunction induced during high fat feeding in mice

The study's purpose was to investigate if physical activity initiated with the start of high-fat feeding would oppose development of endothelial dysfunction, and if it does, then to determine some potential mechanisms. C57BL/6 female mice were randomly divided into three groups: (1) control low-fat diet (LF-SED; 15% of calories from fat), (2) high-fat diet (HF-SED; 45% of calories from fat), and (3) HF diet given access to a voluntary running wheel (HF-RUN). Our hypothesis was that HF-RUN would differ in multiple markers of endothelial dysfunction from HF-SED after 10 weeks of 45%-fat diet, but would not differ from LF-SED. HF-RUN differed from HF-SED in nine determinations in which HF-SED either had decreases in (1) acetylcholine (ACh)-induced and flow-induced vasodilatations in isolated, pressurized coronary arterioles, (2) heart phosphorylated endothelial nitric oxide synthase (p-eNOS/eNOS) protein, (3) coronary arteriole leptin (ob) receptor protein, (4) phosphorylated signal transducer and activator of transcription 3 (p-STAT3/STAT3) protein, and (5) coronary arteriole superoxide dismutase 1 protein; or had increases in (6) percentage body fat, (7) serum leptin, (8) coronary arteriole suppressor of cytokine signalling 3 (SOCS3) protein, and (9) coronary arteriole gp91(phox) protein. Higher endothelium-dependent vasodilatation by ACh or leptin was abolished with incubation of NOS inhibitor N(G)-nitro-l-arginine-methyl ester (l-NAME) in LF-SED and HF-RUN groups. Further, impaired ACh-induced vasodilatation in HF-SED was normalized by apocynin or TEMPOL to LF-SED and HF-RUN. These findings demonstrate multiple mechanisms (eNOS, leptin and redox balance) by which voluntary running opposes the development of impaired coronary arteriolar vasodilatation during simultaneous high-fat feeding.

The endothelium: influencing vascular smooth muscle in many ways

The endothelium, although only a single layer of cells lining the vascular and lymphatic systems, contributes in multiple ways to vascular homeostasis. Subsequent to the 1980 report by Robert Furchgott and John Zawadzki, there has been a phenomenal increase in our knowledge concerning the signalling molecules and pathways that regulate endothelial - vascular smooth muscle communication. It is now recognised that the endothelium is not only an important source of nitric oxide (NO), but also numerous other signalling molecules, including the putative endothelium-derived hyperpolarizing factor (EDHF), prostacyclin (PGI(2)), and hydrogen peroxide (H(2)O(2)), which have both vasodilator and vasoconstrictor properties. In addition, the endothelium, either via transferred chemical mediators, such as NO and PGI(2), and (or) low-resistance electrical coupling through myoendothelial gap junctions, modulates flow-mediated vasodilatation as well as influencing mitogenic activity, platelet aggregation, and neutrophil adhesion. Disruption of endothelial function is an early indicator of the development of vascular disease, and thus an important area for further research and identification of potentially new therapeutic targets. This review focuses on the signalling pathways that regulate endothelial - vascular smooth muscle communication and the mechanisms that initiate endothelial dysfunction, particularly with respect to diabetic vascular disease.

Differential genomic changes caused by cholesterol- and PUFA-rich diets in regenerated porcine coronary endothelial cells

Endothelial regeneration and dyslipidemia impair endothelium-dependent relaxation, while supplementation with fish oil (FO) prevents it. The genomic impact of different diets was compared in primary cultures derived from native and regenerated endothelial cells. Pigs were fed with high-cholesterol (CHL) or FO-rich diet. Partial in vivo removal of endothelium was performed to induce endothelial regeneration. Native and regenerated cells were harvested, cultured, and prepared for genomic (microarray experiments, real-time PCR) and proteomic (Western blotting) analysis. The analysis identified genomic changes induced by chronic CHL diet in native cultures resembling those induced by in vivo regeneration, as well as those that could be prevented by FO diet. At the protein level, the reduced and increased presences of endothelial nitric oxide synthase and F2, respectively, observed after regeneration combined with CHL diet were alleviated by FO. The comparison of the differential changes induced by regeneration in vivo in endothelial cells from both diet groups revealed a limited number of genes as the most likely contributors to reduction in endothelium-dependent relaxations in porcine coronary arteries lined with regenerated endothelium.

Thymoquinone improves aging-related endothelial dysfunction in the rat mesenteric artery

Aging-related endothelial dysfunction is characterized by blunted nitric oxide (NO)- and endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations in arteries, which may be due, at least in part, to increased oxidative stress. Endothelial dysfunction will promote the initiation and development of major cardiovascular diseases such as atherosclerosis and hypertension. Thymoquinone (TQ) is the most active constituent of the volatile oil of Nigella sativa seeds with well-documented antioxidative properties and vasodilator effects. This study determined whether TQ improves the endothelial function in middle-aged rats. Control young rats (16 weeks) received solvent (ethanol, 3% v/v), and middle-aged rats (46 weeks) either solvent or TQ (10 mg/kg/day) in the drinking water. Mesenteric artery reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine and MitoSOX staining, and expression of target proteins by immunohistochemical staining. Aging-related blunted NO- and EDHF-mediated responses were associated with downregulation of endothelial NO synthase (eNOS) and calcium-activated potassium channels (SK(Ca) and IK(Ca)) expression. Endothelial dysfunction was also associated with oxidative stress and an upregulation of angiotensin II and AT1 receptor expressions. Intake of TQ for 14 days restored NO- and EDHF-mediated relaxations, normalized oxidative stress, the expression level of eNOS, SK(Ca), IK(Ca), and the components of the angiotensin system in the mesenteric artery of middle-aged rats. Thus, TQ improves endothelial function in aging, at least in part, through inhibition of oxidative stress and normalization of the angiotensin system. TQ may represent a novel therapeutic approach for aging-associated vascular diseases.

Pulmonary hypertension in lambs transfused with stored blood is prevented by breathing nitric oxide

BACKGROUND

During extended storage, erythrocytes undergo functional changes. These changes reduce the viability of erythrocytes leading to release of oxyhemoglobin, a potent scavenger of nitric oxide. We hypothesized that transfusion of ovine packed erythrocytes (PRBC) stored for prolonged periods would induce pulmonary vasoconstriction in lambs, and that reduced vascular nitric oxide concentrations would increase this vasoconstrictor effect.

METHODS

We developed a model of autologous stored blood transfusion in lambs (n = 36). Leukoreduced blood was stored for either 2 days (fresh PRBC) or 40 days (stored PRBC). Fresh or stored PRBC were transfused into donors instrumented for awake hemodynamic measurements. Hemodynamic effects of PRBC transfusion were also studied after infusion of N-nitro-L-arginine methyl-ester (25 mg/kg) or during inhalation of nitric oxide (80 ppm).

RESULTS

Cell-free hemoglobin levels were higher in the supernatant of stored PRBC than in supernatant of fresh PRBC (Mean ± SD, 148 ± 20 vs. 41 ± 13 mg/dl, respectively, P < 0.001). Pulmonary artery pressure during transfusion of stored PRBC transiently increased from 13 ± 1 to 18 ± 1 mmHg (P < 0.001) and was associated with increased plasma hemoglobin concentrations. N-nitro-L-arginine methyl-ester potentiated the increase in pulmonary arterial pressure induced by transfusing stored PRBC, whereas inhalation of nitric oxide prevented the vasoconstrictor response.

CONCLUSIONS

Our results suggest that patients with reduced vascular nitric oxide levels because of endothelial dysfunction may be more susceptible to adverse effects of transfusing blood stored for prolonged periods. These patients might benefit from transfusion of fresh PRBC, when available, or inhaled nitric oxide supplementation to prevent the pulmonary hypertension associated with transfusion of stored PRBC.

Effects of glutathione-depleting drug buthionine sulfoximine and aging on activity of endothelium-derived relaxing and contracting factors in carotid artery of Sprague-Dawley rats

The role of the antioxidant glutathione (GSH) in mediating endothelial (dys)function, and how that role may depend on age, is unclear. The main purpose of the current study was to investigate the effect of 10-day treatment with the GSH-depleting drug l-buthionine sulfoximine (BSO) on endothelium-derived relaxing factor and endothelium-derived contracting factor activities in the isolated common carotid artery (CCA) of Adult and Aging animals. CCA blood pressure and flow were unaffected by age or BSO. Endothelium-derived relaxing factor activity, examined in precontracted CCA as relaxation to cumulative acetylcholine (ACh), was largely nitric oxide synthase (NOS) mediated and was not different between Adult and Aging animals at lower ACh; however, at higher ACh, relaxation was blunted in Aging CCA, an effect abolished by cyclooxygenase (COX) inhibition but not by NOS inhibition nor by the reactive oxygen species (ROS) inhibitors 4-hydroxy-TEMPO or Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin,tetratosylate,hydroxide. Specific examination of endothelium-derived contracting factor activity in quiescent NOS-inhibited CCA established that higher ACh elicited a contractile response, ∼3.5-fold greater in Aging versus Adult CCA, which was abolished by COX-1-specific inhibition but unaffected by ROS inhibitors. Aging was unrelated to changes in liver or vascular tissue GSH or ROS content. BSO was effective in significantly decreasing GSH and increasing ROS content in both animal cohorts. However, NOS-mediated endothelium-derived relaxing factor activity was well preserved and age-related COX-mediated endothelium-derived contracting factor activity was unaffected in response to these BSO-induced perturbations, as were exogenous H2O2-stimulated NOS/non-NOS-mediated relaxation and COX-mediated contractile activities. These data suggest that, regardless of age, chronic partial depletion of GSH in vivo does not necessarily cause endothelium-dependent vasomotor dysfunction.

Diet and endothelial function: from individual components to dietary patterns

PURPOSE OF REVIEW

Endothelial dysfunction plays an important role in development and progression of atherosclerosis and may also contribute to the pathogenesis of type 2 diabetes. This review summarizes recent findings on the effects of vitamin D, antioxidant vitamins, polyphenols, polyphenol-rich foods, dietary component combinations and healthy diets on endothelial function.

RECENT FINDINGS

Dietary patterns rich in fruit, vegetables, fish and nuts appear to have beneficial effects on endothelial function. With regard to specific foods, cacao and green tea consumption have been associated with improvement in endothelial function and this seems to be due to their flavan-3-ol (catechins and epigallocatechin gallate) content. The evidence for beneficial effects of other foods such as citrus fruit, apples and red wine is less consistent. Recent studies have also suggested beneficial effects of vitamin D and anthocyanins on endothelial function and have provided more insight into potential mechanisms underlying the effect of diet on endothelial function.

SUMMARY

The currently available evidence supports beneficial effects of various dietary compounds on endothelial function. However, in order to obtain strong evidence for relevant health effects that can be used for specific dietary recommendations, more long-term studies using well characterized diets/supplements in a large number of individuals are needed.

Microvesicles: potential markers and mediators of endothelial dysfunction

PURPOSE OF REVIEW

Microvesicles (also known as microparticles) are small membranous structures that are released from platelets and cells upon activation or during apoptosis. Microvesicles have been found in blood, urine, synovial fluid, extracellular spaces of solid organs, atherosclerotic plaques, tumors, and elsewhere. Here, we focus on new clinical and basic work that implicates microvesicles as markers and mediators of endothelial dysfunction and hence novel contributors to cardiovascular and other diseases.

RECENT FINDINGS

Advances in the detection of microvesicles and the use of cell type-specific markers to determine their origin have allowed studies that associated plasma concentrations of specific microvesicles with major types of endothelial dysfunction - namely, inappropriate or maladaptive vascular tone, leukocyte recruitment, and thrombosis. Recent investigations have highlighted microvesicular transport of key biologically active molecules besides tissue factor, such as ligands for pattern-recognition receptors, elements of the inflammasome, and morphogens. Microvesicles generated from human cells under different pathologic circumstances, for example, during cholesterol loading or exposure to endotoxin, carry different subsets of these molecules and thereby alter endothelial function through several distinct, well characterized molecular pathways.

SUMMARY

Clinical and basic studies indicate that microvesicles may be novel markers and mediators of endothelial dysfunction. This work has advanced our understanding of the development of cardiovascular and other diseases. Opportunities and obstacles to clinical applications are discussed.

Endothelium-mediated control of vascular tone: COX-1 and COX-2 products

Endothelium-dependent contractions contribute to endothelial dysfunction in various animal models of aging, diabetes and cardiovascular diseases. In the spontaneously hypertensive rat, the archetypal model for endothelium-dependent contractions, the production of the endothelium-derived contractile factors (EDCF) involves an increase in endothelial intracellular calcium concentration, the production of reactive oxygen species, the predominant activation of cyclooxygenase-1 (COX-1) and to a lesser extent that of COX-2, the diffusion of EDCF towards the smooth muscle cells and the subsequent stimulation of their thromboxane A2-endoperoxide TP receptors. Endothelium-dependent contractions are also observed in various models of hypertension, aging and diabetes. They generally also involve the generation of COX-1- and/or COX-2-derived products and the activation of smooth muscle TP receptors. Depending on the model, thromboxane A(2), PGH(2), PGF(2α), PGE(2) and paradoxically PGI(2) can all act as EDCFs. In human, the production of COX-derived EDCF is a characteristic of the aging and diseased blood vessels, with essential hypertension causing an earlier onset and an acceleration of this endothelial dysfunction. As it has been observed in animal models, COX-1, COX-2 or both isoforms can contribute to these endothelial dysfunctions. Since in most cases, the activation of TP receptors is the common downstream effector, selective antagonists of this receptor should curtail endothelial dysfunction and be of therapeutic interest in the treatment of cardiovascular disorders.

Effect of cocoa/chocolate ingestion on brachial artery flow-mediated dilation and its relevance to cardiovascular health and disease in humans

Prospective studies indicate that high intake of dietary flavanols, such as those contained in cocoa/chocolate, are associated with reduced rates of cardiovascular-related morbidity and mortality in humans. Numerous mechanisms may underlie these associations such as favorable effects of flavanols on blood pressure, platelet aggregation, thrombosis, inflammation, and the vascular endothelium. The brachial artery flow-mediated dilation (FMD) technique has emerged as a robust method to quantify endothelial function in humans. Collectively, the preponderance of evidence indicates that FMD is a powerful surrogate measure for firm cardiovascular endpoints, such as cardiovascular-related mortality, in humans. Thus, literally thousands of studies have utilized this technique to document group differences in FMD, as well as to assess the effects of various interventions on FMD. In regards to the latter, numerous studies indicate that both acute and chronic ingestion of cocoa/chocolate increases FMD in humans. Increases in FMD after cocoa/chocolate ingestion appear to be dose-dependent such that greater increases in FMD are observed after ingestion of larger quantities. The mechanisms underlying these responses are likely diverse, however most data suggest an effect of increased nitric oxide bioavailability. Thus, positive vascular effects of cocoa/chocolate on the endothelium may underlie (i.e., be linked mechanistically to) reductions in cardiovascular risk in humans.

Grape-derived polyphenols improve aging-related endothelial dysfunction in rat mesenteric artery: role of oxidative stress and the angiotensin system

Aging is characterized by the development of an endothelial dysfunction, which affects both the nitric oxide (NO)- and the endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations, associated with vascular oxidative stress and the activation of the angiotensin system. This study investigated whether red wine polyphenols (RWPs), antioxidants and potent stimulators of NO- and EDHF-mediated relaxations improve aging-related endothelial dysfunction, and, if so, examined the underlying mechanism. Mesenteric artery reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine and MitoSOX staining, and expression of target proteins by immunohistochemical staining. Control young rats (16 weeks) received solvent (ethanol, 3% v/v), and middle-aged rats (46 weeks) either solvent or RWPs (100 mg/kg/day) in the drinking water. The acetylcholine-induced endothelium-dependent NO component was slightly reduced whereas the EDHF component was markedly blunted in rings of middle-aged rats compared to young rats. The endothelial dysfunction was associated with oxidative stress, an upregulation of angiotensin II and AT1 receptors and a down-regulation of SK_Ca, IK_Ca, and angiotensin converting enzyme. Intake of RWPs for either one or two weeks improved the NO and the EDHF components of the relaxation, and normalized oxidative stress, the expression of SK_Ca, IK_Ca and the components of the angiotensin system. The protective effect of the 2-week RWPs treatment persisted for one and two weeks following stopping intake of RWPs. Thus, intake of RWPs caused a persistent improvement of the endothelial function, particularly the EDHF component, in middle-aged rats and this effect seems to involve the normalization of the expression of SK_Ca, IK_Ca and the angiotensin system.

Red wine polyphenols improve an established aging-related endothelial dysfunction in the mesenteric artery of middle-aged rats: role of oxidative stress

Aging is associated with blunted endothelium-dependent relaxations and vascular oxidative stress. Our previous study has indicated that daily intake of red wine polyphenols (RWPs) by young rats retards aging-related endothelial dysfunction in middle-aged rats. The aim of the present study is to determine whether intake of RWPs also improves an established endothelial dysfunction in middle-aged rats and, if so, to determine the underlying mechanism. Middle-aged rats (51 weeks) received either solvent (3% ethanol), RWPs extract (100mg/kg/day) or the antioxidant and NADPH oxidase inhibitor apocynin (100mg/kg/day) in the drinking water for 4 weeks. Vascular reactivity of mesenteric artery rings from control young (12 weeks) and middle-aged rats was assessed in organ chambers. The expression level of endothelial NO synthase (eNOS), arginase I, angiotensin II receptors (AT1R and AT2R), NADPH oxidase subunits and nitrotyrosines was assessed by immunohistochemistry, and the vascular formation of reactive oxygen species (ROS) by dihydroethidine. Aging is associated with blunted endothelium-dependent relaxations, an excessive vascular formation of ROS and peroxynitrites, and an up-regulation of eNOS, arginase I, NADPH oxidase subunits (nox-1, p22phox), and AT1R and AT2R expression. RWPs and apocynin treatments improved endothelial dysfunction, normalized oxidative stress and the expression of the different proteins in the mesenteric artery of middle-aged rats. The present findings indicate that aging is associated with blunted endothelium-dependent relaxations involving an increased oxidative stress, and that these responses are improved by the intake of RWPs or apocynin for 4weeks most likely by normalizing the expression of eNOS, arginase I, NADPH oxidase and angiotensin receptors.