Vascular Relaxation Research Articles

Effects of Grape Supplementation on Age‐Related Vascular Changes in Mice

Chronological aging leads to changes in several physiological process, including vascular function. All blood vessels, including conduit and resistance arteries, develop age‐related impairment in vascular relaxation that is possibly due to endothelium dysfunction and less bioavailability of endothelium‐derived factors such as nitric oxide (NO). We studied vascular responses using aorta from aged female mice that were maintained on four different diets from weaning until 30 months: normal chow (NC), high‐fat diet (HFD), NC + grape supplement (NCG) and HFD + grape supplement (HFDG). Ex‐vivo experiments with aorta using an organ bath showed that HFD had the lowest relaxation when exposed to 10 μM acetylcholine (27.12 ± 7.53%), followed by NC (45.45 ± 5.61%; p = 0.098 NC vs. HFD). The grape supplemented group NCG had higher relaxation than nonsupplement NC (70 ± 24.25%; p >0.05). HFDG also had improved acetylcholine‐mediated relaxation (60 ± 12.8%; p = 0.0642 HFD vs. HFDG). L‐NAME (eNOS inhibitor; 10−4 M) changed the acetylcholine response to contraction in all groups, with the HFD having the highest contraction (80.45 ± 12.23% vs. 35.87 ± 9.43% in HFDG; p <0.05) compared to other groups which had similar contraction. However, indomethacin [prostaglandin (PG) inhibitor] produced the highest contraction in the HFDG group. These data suggest that grape supplementation may preserve PG‐mediated relaxation in vascular tissue in HFDG mice with NO and PG both contributing to relaxation, while in nonsupplemented HFD mice, the vasorelaxation occurred primarily through nitric oxide that was inhibited by the use of L‐NAME. (Supported in part by the California Table Grape Commission)Support or Funding InformationCalifornia Table Grape Commission (JP)

Exercise Training Restores K+ Channel Contributions to Hydrogen Peroxide‐Mediated Dilation Independent of PKG Dimerization in Collateral‐Dependent Coronary Arterioles

In coronary artery disease (CAD), the ability of the coronary circulation to deliver blood to meet oxygen demands of the heart is often impaired. Exercise training has been established to mitigate the negative effects of CAD by preserving reactivity of the coronary microcirculation. We have previously reported that exercise increases the contribution of hydrogen peroxide (H2O2) to enhanced endothelium‐dependent vasodilation in collateral‐dependent coronary arterioles. Others have shown that cGMP‐dependent protein kinase (PKG) can be activated via oxidation by H2O2, inducing dimer formation. The PKG dimer has been shown to act on substrates, such as K+ channels, to contribute to vascular smooth muscle relaxation and vasodilation. In the current study, we tested the hypothesis that exercise training‐enhanced H2O2‐induced vasodilation is mediated through enhanced PKG dimerization and subsequent activation of Kv and BKca channels in coronary arterioles isolated from ischemic myocardium. An ameroid occluder was surgically placed on the proximal left circumflex coronary artery of female Yucatan miniature swine to induce gradual occlusion while the left anterior descending artery was left unoccluded to serve as a control. Eight weeks postoperatively, pigs were assigned to sedentary (n=14) or exercise training (n=13; progressive treadmill training for 13 weeks) regimens. Coronary arterioles (75–150 μm) and small arteries (250–400 um) were isolated from myocardium of the left circumflex and left anterior descending regions. Immunoblot analysis indicated that H2O2 induced PKG dimer formation in both porcine coronary arterioles and small arteries. Chronic coronary artery occlusion appeared to diminish H2O2‐mediated PKG dimer formation in collateral‐dependent arterioles and the reduced dimerization persisted with exercise training. H2O2‐mediated vasodilation tended to be impaired in arterioles isolated from the collateral‐dependent regions of sedentary pigs and was partially restored with exercise training. It also appears that both Kv and BKCa channels contributed to H2O2‐mediated dilation after exercise training. Our data demonstrate that H2O2 stimulates PKG dimer formation in both porcine coronary arterioles and small arteries. Contrary to our hypothesis, H2O2‐induced PKG dimerization is not enhanced by exercise training in either nonoccluded or collateral‐dependent arterioles. However, both Kv and BKCa channels appear to contribute to exercise training‐enhanced H2O2‐mediated dilation in collateral‐dependent coronary arterioles.Support or Funding InformationNational Institutes of Health R01‐HL139903

Postpartum Maternal Vascular Function in a Rat Model of Gestational Obstructive Sleep Apnea

IntroductionDe novo obstructive sleep apnea (OSA) in pregnancy, is associated with adverse gestational outcomes such as preeclampsia, gestational diabetes, and fetoplacental hypoxia. In addition, exposure to chronic intermittent hypoxia (CIH), a model of OSA, induces endothelial dysfunction and enhanced vasoconstriction in pregnant mice. It is currently unknown whether gestational OSA has a long‐term effect on maternal vascular function. We hypothesized that exposure to gestational CIH during late pregnancy will result in postpartum maternal vascular dysfunction.MethodsTimed pregnant female Long‐Evans rats were randomly assigned to two experimental groups: Normoxia (n=6) and CIH (n=6). The CIH group was exposed to five days (gestational days: 15–20) of intermittent hypoxia [6 min cycles of 3 min hypoxia (10% O2) and 3 min normoxia (21% O2)]. Gestational age at delivery was recorded and neonate’s crown‐rump length, abdominal girth, and body weights were measured within 12–16 hours from birth. At weaning (postnatal day 28), dams were euthanized and third‐order mesenteric arteries, and the main uterine artery, and uterine perivascular adipose tissue (PVAT) were excised. To assess endothelium‐dependent relaxation, we performed concentration‐response curves to acetylcholine (ACh: 10−9 – 3×10−5 M) using wire myography. In uterine arteries, we measured responses to ACh in the presence and absence of PVAT (0.1 g) based on our previous findings that uterine PVAT has vasoactive effects on these arteries.ResultsGestational CIH had no effect on the duration of gestation (Normoxia: 22.3 ± 0.21 days vs. CIH: 22.8 ± 1.16 days, p=0.24), litter size (Normoxia: 12.2 ± 1.64 vs. CIH: 10.3 ± 1.40, p=0.34), and neonatal weight at birth (Normoxia: 6.4 ± 0.24 g vs. CIH: 6.7 ± 0.19 g, p=0.16), while it increased neonatal crown‐rump length (Normoxia: 3.98 ± 0.07 cm vs. CIH: 4.19 ± 0.07 cm, p=0.05) and abdominal girth (Normoxia: 4.72 ± 0.10 cm vs. 4.94 ± 0.03 cm, p=0.07). At weaning, dams exposed to gestational CIH were lighter compared to dams exposed to normoxia (Normoxia: 319 ± 6.5 g vs. CIH: 298 ± 8.7 g, p=0.08). Exposure to gestational CIH had no effect on ACh‐induced relaxation in mesenteric resistance arteries (pEC50, Normoxia: 7.80 ± 0.03 vs. CIH: 7.89 ± 0.06, p=0.19). In the absence of PVAT, uterine arteries from dams exposed to gestational CIH had exaggerated responses to ACh compared to dams exposed to normoxia [(−)PVAT/pEC50, Normoxia: 6.77 ± 0.08 vs. CIH: 7.13 ± 0.09, p<0.01], while PVAT normalized this difference [(+)PVAT/pEC50, Normoxia: 6.67 ± 0.08 vs. CIH: 6.70 ± 0.07, p=0.99]. The effects of PVAT were due to its anti‐dilatory influences on uterine arteries from CIH‐treated rats [CIH (−PVAT) vs. CIH (+PVAT), p = 0.003], whereas it had no effect on arteries from control rats [Normoxia (−PVAT) vs. Normoxia (+PVAT), p = 0.77].ConclusionExposure to CIH during gestation resulted in neonatal macrosomia, reduced maternal weight at weaning, and exaggerated postpartum uterine vascular smooth muscle relaxation responses, while it did not affect small resistance artery reactivity. Gestational OSA may impair maternal vascular recovery after birth.Support or Funding InformationUNTHSC Basic Seed Grant

Sex‐Differences in Gastric Smooth Muscle Function: Role of G Protein‐Coupled Estrogen Receptor

The regulation of gastrointestinal (GI) motility by estrogen and its receptors has been a topic of great interest owing to sexual dimorphism that exists in motility disorders. Scientific and clinical evidence establishes the fact of GI motility disturbances during estrous cycle but, there is a gap in the knowledge and understanding of estrogen and its receptors role in GI motility physiology during these cycles. Estrogen activates classical nuclear receptors ERα, ERβ and atypical 7‐transmembrane G protein‐coupled estrogen receptor (GPER or GPR30) to initiate both genomic and non‐genomic effects. GPER is involved in the several rapid cellular signaling events. The pleiotropic effects manifested by GPER action include regulation of body weight, glucose homeostasis, anti‐inflammation, anti‐nociception, and vascular muscle relaxation. Ablation of GPER leads to increase in mean arterial pressure in female mice, whereas treatment with GPER‐specific agonist G‐1 lowers arterial blood pressure in hypertensive and ovariectomized female rats. The role of GPER in mediating estrogen effects on GI smooth muscle is unknown.AimTo understand the role of GPER in gastric smooth muscle function in male and female mice.MethodsMuscle strips and muscle cells were isolated from the stomachs of control and GPER knockout mice. Expression of GPER was analyzed by qRT‐PCR and western blot. cAMP levels in response to estrogen and G‐1 was measured by radioimmunoassay. Relaxation was measured in organ bath studies in muscle strips and by scanning micrometry in isolated muscle cells.ResultsExpression of GPER (mRNA and protein) in the gastric smooth muscle was higher in female mice compared to male mice. 17β‐estradiol and G‐1 caused an increase in cAMP levels and inhibited acetylcholine‐induced muscle contraction (i.e., caused muscle relaxation) in gastric muscle strips and isolated muscle cells from both female and male mice, however, the increase in cAMP levels and the amount of relaxation was significantly greater in gastric muscle from female mice compared to male mice. The effect of 17β‐estradiol and G‐1 on muscle relaxation was concentration‐dependent. Relaxation was blocked by the GPER specific antagonist G15 (10 μM) in gastric muscle from control mice and absent in gastric muscle from GPER knockout mice. Relaxation was higher in proestrus and estrus phases compared to diestrus phase in female mice and this is consistent with higher expression of GPER in proestrus and estrus phases compared to diestrus phase.ConclusionActivation of GPER causes relaxation via cAMP/PKA pathway in gastric smooth muscle from female and male mice. Greater relaxation in gastric smooth muscle from female mice is due to higher expression of GPER in female mice compared to male mice. Pilot studies suggests that higher expression of GPER in the stomach of female mice is due to differential regulation of GPER expression by epigenetic mechanisms.Support or Funding InformationSupported by grants from VETAR (SM); IACUC approval AD10001201

β‐Hydroxybutyrate (βOHB) Activates Gpr109a to Contribute to the Anti‐vascular Aging Effect of Autophagy

The aged phenotype is classically viewed as the accumulation of cellular debris and dysfunctional organelles. Although waste products are an inevitable consequence of normal cellular metabolism, multiple systems are devoted to its repair, clearance, or recycling. Autophagy is the constitutively active catabolic process responsible for cellular degradation. Autophagic activity has also been implicated as a modulator of longevity, as well as inversely related with chronological vascular aging and premature vascular aging associated with hypertension. However, the mechanisms by which autophagy exerts anti‐vascular aging effects are still unknown. Evolutionarily, autophagy functions to mobilize nutrients in times of starvation. Specifically, hepatic autophagy releases free fatty acids from triglycerides, which are oxidized to generate ketone bodies. Therefore, we hypothesized that fasting would increase the systemic expression of ketone body β‐hydroxybutyrate (βOHB) in Dahl salt‐sensitive rats fed a low salt‐diet, and this would be prevented by inhibition of autophagy with chloroquine (CQ). As hypothesized, fasting increased serum βOHB, and treatment with CQ blocked this increase (mmol/L, non‐fasting: 0.38±0.01 vs. fasting: 1.01±0.06* vs. fasting+CQ: 0.45±0.04, *p<0.05) (Figure 1). Next we questioned whether βOHB could potentially contribute to the anti‐vascular aging effect of autophagy. Previously, we have observed that βOHB is a potent vasodilator via endothelial potassium channels. However, it is not known if βOHB acts as an agonist or antagonist to any specific receptor to mediate endothelium‐dependent relaxation. To help answer this question we needed to switch to a genetic knockout model, as pharmacological antagonists for the βOHB receptors, Gpr109a and Gpr41, do not exist. βOHB activates Gpr109a, whereas it is generally recognized as an antagonist of Gpr41. Therefore, we hypothesized that vascular relaxation to βOHB would be significantly attenuated in isolated mesenteric resistance arteries from Gpr109a−/− mice, but not Gpr41−/− mice. As hypothesized, vasodilatory effect of βOHB was significantly blunted in Gpr109a−/− mice, but not Gpr41−/− mice [Emax (%relaxation), WT: 75±2 vs. Gpr109a−/−: 53±3* vs. Gpr41−/−: 73±1, *p<0.05] (Figure 2). Overall, these data reveal that ketone body βOHB is stimulated by autophagy and that activation of Gpr109a by βOHB can cause vasodilation of isolated resistance arteries. Significantly, our data define a novel mechanism that underlies the anti‐vascular aging effect of autophagy.Support or Funding InformationAmerican Heart Association (18POST34060003) and National Institutes of Health (R00GM118885 and R01HL143082).Fasting (24 h) stimulates serum βOHB expression and this is prevented by autophagy inhibition (chloroquine 50 mg/kg i.p.; CQ). n=6–10. One way ANOVA: *p<0.05.Figure 1βOHB mediates vasodilation partially via Gpr109a, and not Gpr41. Concentration response curves to βOHB. n=2–4. Two‐way ANOVA: *p<0.05. vs. wild type (WT).Figure 2

HuangqiGuizhiWuwu Decoction Prevents Vascular Dysfunction in Diabetes via Inhibition of Endothelial Arginase 1.

Hyperglycemia induces vascular endothelial dysfunction, which contributes to the development of vascular complication of diabetes. A classic prescription of traditional medicine, HuangqiGuizhiWuwu Decoction (HGWWD) has been used for the treatment of various cardiovascular and cerebrovascular diseases, which all are related with vascular pathology. The present study investigated the effect of HGWWD treatment in streptozocin (STZ)-induced vascular dysfunction in mouse models. In vivo studies were performed using wild type mice as well as arginase 1 knockout specific in endothelial cells (EC-A1–/–) of control mice, diabetes mice and diabetes mice treated with HGWWD (60 g crude drugs/kg/d) for 2 weeks. For in vitro studies, aortic tissues were treated with mice serum containing HGWWD with or without adenoviral arginase 1 (Ad-A1) transduction in high glucose (HG) medium. We found that HGWWD treatment restored STZ-induced impaired mean velocity and pulsatility index of mouse left femoral arteries, aortic pulse wave velocity and vascular endothelial relaxation accompanied by elevated NO production in the aorta and plasma, as well as reduced endothelial arginase activity and aortic arginase 1 expression. The protective effect of HGWWD is reversed by an inhibitor of nitric oxide synthesis. Meanwhile, the preventive effect of serum containing HGWWD in endothelial vascular dysfunction is completely blocked by Ad-A1 transduction in HG incubated aortas. HGWWD treatment further improved endothelial vascular dysfunction in STZ induced EC-A1–/– mice. This study demonstrates that HGWWD improved STZ-induced vascular dysfunction through arginase 1 – NO signaling, specifically targeting endothelial arginase 1.

Vasculoprotective Effects of Vildagliptin. Focus on Atherogenesis.

Vildagliptin is a representative of Dipeptidyl Peptidase-4 (DPP-4) inhibitors, antihyperglycemic drugs, approved for use as monotherapy and combination therapy in type 2 diabetes mellitus. By inhibiting enzymatic decomposition, DPP-4 inhibitors increase the half-life of incretins such as GLP-1 (Glucagon-like peptide-1) and GIP (Gastric inhibitors polypeptide) and prolong their action. Some studies present results suggesting the anti-sclerotic and vasculoprotective effects of vildagliptin reaching beyond glycemic control. Vildagliptin is able to limit inflammation by suppression of the NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signaling pathway and proinflammatory agents such as TNF-α (tumor necrosis factor α), IL-1β (Interleukin-1β), and IL-8 (Interleukin 8). Moreover, vildagliptin regulates lipid metabolism; attenuates postprandial hypertriglyceridemia; and lowers serum triglycerides, apolipoprotein B, and blood total cholesterol levels. This DPP-4 inhibitor also reduces macrophage foam cell formation, which plays a key role in atheromatous plaque formation and stability. Vildagliptin reduces vascular stiffness via elevation of nitric oxide synthesis, improves vascular relaxation, and results in reduction in both systolic and diastolic blood pressure. Treatment with vildagliptin lowers the level of PAI-1 presenting possible antithrombotic effect. By affecting the endothelium, inflammation, and lipid metabolism, vildagliptin may affect the development of atherosclerosis at its various stages. The article presents a summary of the studies assessing vasculoprotective effects of vildagliptin with special emphasis on atherogenesis.

Rosuvastatin Reverses Hypertension-Induced Changes in the Aorta Structure and Endothelium-Dependent Relaxation in Rats Through Suppression of Apoptosis and Inflammation.

:Vascular remodeling is one of the most critical complications caused by hypertension. Previous studies have demonstrated that rosuvastatin has anti-inflammatory, antioxidant, and antiplatelet effects and therefore can be used to treat cardiovascular disease. In this study, we explored the beneficial effects of rosuvastatin in reversing aortic remodeling in spontaneously hypertensive rats. After treating with different doses of rosuvastatin, its antilipid, antiapoptosis, and anti-inflammatory effects were determined. We also examined whether rosuvastatin can improve the structure and function of the aorta. We found that rosuvastatin treatment of spontaneously hypertensive rats for 2 months at 2 different doses can effectively reduce the media thickness of the aorta compared with the control group. Similarly, rosuvastatin improved the vascular relaxation function of the aortic rings at a high level of acetylcholine in vitro. Mechanistically, it was found that rosuvastatin increased the expression of endothelial nitric oxide synthase and plasma nitrite/nitrate levels. Besides, rosuvastatin suppressed the apoptosis and inflammation and upregulated the expression of gap-junction complex connexin 43 both in media and endothelium. Finally, rosuvastatin inhibited the AT1R/PKCα/HSP70 signaling transduction pathway. In summary, these findings demonstrated that rosuvastatin could improve the vascular structure and function mainly by increasing endothelial nitric oxide synthase expression and preventing apoptosis and inflammation. This study provided evidence that rosuvastatin has beneficial effects in reversing the remodeling of the aorta due to hypertension.

Potential role of angiotensin‐(1–7) in the improvement of vascular insulin sensitivity after a bout of exercise

What is the central question of this study? What is the mechanism by which a bout of exercise increases subsequent insulin-stimulated vasodilatation? What is the main finding and its importance? Angiotensin-(1-7) through the Mas receptor participates in enhanced insulin-induced vasorelaxation after a bout of exercise in healthy rats. This new potential role of angiotensin-(1-7) could help in understanding how physical activity improves vascular insulin sensitivity in normal and insulin-resistant states. Exercise increases insulin-stimulated vasodilatation, but the mechanisms involved are unclear. This study was performed to investigate the possible involvement of angiotensin-(1-7) (Ang-(1-7)), a vasoactive peptide of the renin-angiotensin system (RAS), in enhanced vascular insulin sensitivity after a bout of exercise. Male Wistar rats were subjected to swimming for 2.5 h. After exercise, carbachol- or insulin-induced relaxation in aorta was assessed. Prior exercise improved insulin-stimulated vasorelaxation; however, this insulin-sensitizing effect was prevented by the selective Mas receptor (MasR; an Ang-(1-7) receptor) antagonist A779. Carbachol-mediated vascular relaxation was not modified by exercise. These results suggest that Ang-(1-7) acting through MasR participates in the enhancement of vascular insulin sensitivity after an exercise session. This new potential role of Ang-(1-7) could help in understanding how exercise improves vascular insulin sensitivity in normal and insulin-resistant states.

Helicobacter pylori Infection Impairs Endothelial Function Through an Exosome-Mediated Mechanism.

BackgroundEpidemiological studies have suggested an association between Helicobacter pylori (H pylori) infection and atherosclerosis through undefined mechanisms. Endothelial dysfunction is critical to the development of atherosclerosis and related cardiovascular diseases. The present study was designed to test the hypothesis that H pylori infection impaires endothelial function through exosome‐mediated mechanisms.Methods and ResultsYoung male and female patients (18‐35 years old) with and without H pylori infection were recruited to minimize the chance of potential risk factors for endothelial dysfunction for the study. Endothelium‐dependent flow‐mediated vasodilatation of the brachial artery was evaluated in the patients and control subjects. Mouse infection models with CagA+ H pylori from a gastric ulcer patient were created to determine if H pylori infection‐induced endothelial dysfunction could be reproduced in animal models. H pylori infection significantly decreased endothelium‐dependent flow‐mediated vasodilatation in young patients and significantly attenuated acetylcholine‐induced endothelium‐dependent aortic relaxation without change in nitroglycerin‐induced endothelium‐independent vascular relaxation in mice. H pylori eradication significantly improved endothelium‐dependent vasodilation in both patients and mice with H pylori infection. Exosomes from conditioned media of human gastric epithelial cells cultured with CagA+ H pylori or serum exosomes from patients and mice with H pylori infection significantly decreased endothelial functions with decreased migration, tube formation, and proliferation in vitro. Inhibition of exosome secretion with GW4869 effectively preserved endothelial function in mice with H pylori infection.Conclusions H pylori infection impaired endothelial function in patients and mice through exosome‐medicated mechanisms. The findings indicated that H pylori infection might be a novel risk factor for cardiovascular diseases.

The activity of IKCa and BKCa channels contributes to insulin-mediated NO synthesis and vascular tone regulation in human umbilical vein

Insulin regulates the l-arginine/nitric oxide (NO) pathway in human umbilical vein endothelial cells (HUVECs), increasing the plasma membrane expression of the l-arginine transporter hCAT-1 and inducing vasodilation in umbilical and placental veins. Placental vascular relaxation induced by insulin is dependent of large conductance calcium-activated potassium channels (BKCa), but the role of KCa channels on l-arginine transport and NO synthesis is still unknown. The aim of this study was to determine the contribution of KCa channels in both insulin-induced l-arginine transport and NO synthesis, and its relationship with placental vascular relaxation. HUVECs, human placental vein endothelial cells (HPVECs) and placental veins were freshly isolated from umbilical cords and placenta from normal pregnancies. Cells or tissue were incubated in absence or presence of insulin and/or tetraethylammonium, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole, iberiotoxin or NG-nitro-l-arginine methyl ester. l-Arginine uptake, plasma membrane polarity, NO levels, hCAT-1 expression and placenta vascular reactivity were analyzed. The inhibition of intermediate-conductance KCa (IKCa) and BKCa increases l-arginine uptake, which was related with protein abundance of hCAT-1 in HUVECs. IKCa and BKCa activities contribute to NO-synthesis induced by insulin but are not directly involved in insulin-stimulated l-arginine uptake. Long term incubation (8 h) with insulin increases the plasma membrane hyperpolarization and hCAT-1 expression in HUVECs and HPVECs. Insulin-induced relaxation in placental vasculature was reversed by KCa inhibition. The results show that the activity of IKCa and BKCa channels are relevant for both physiological regulations of NO synthesis and vascular tone regulation in the human placenta, acting as a part of negative feedback mechanism for autoregulation of l-arginine transport in HUVECs.

Sulfur dioxide induces vascular relaxation through PI3K/Akt/eNOS and NO/cGMP signaling pathways in rats.

Sulfur dioxide (SO2) is a common exogenous atmospheric pollutant. Studies have shown that SO2 can cause vasodilation as a gas signaling molecule, but the specific signaling pathways are not well understood. This study aimed to explore the underlying mechanism behind the effects of SO2 on vasodilation of isolated rat aorta. The results showed that when the dose of SO2 was 30 μM, the vasodilation of endothelium-intact rings was partially suppressed by LY294002 and NG-nitro-l-arginine methyl ester, and the protein levels of phosphoinositide 3-kinase (PI3K), p-Akt, and p-endothelial nitric oxide synthase (p-eNOS) were significantly increased. When the dose of SO2 was 300 μM or 1500 μM, the vasodilation of endothelium-denuded rings did not change after application of the inhibitor, but the protein levels of PI3K, p-Akt, and p-eNOS were significantly decreased, and the activity of NOS and the level of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) were significantly increased. We speculate that the mechanism of SO2-induced vasodilatation likely involved the endothelial PI3K/Akt/eNOS and NO/cGMP signal pathways. In addition, at the concentration of 1500 μM, SO2 markedly increased the level of caspase-3 and caspase-9. The results suggest that high concentrations of SO2 may cause damage to blood vessels. This study will help to further inform the etiologies of SO2-related cardiovascular disease.

Blockade of intercellular adhesion molecule-1 prevents angiotensin II-induced hypertension and vascular dysfunction

Monocyte and adhesion infiltration into the arterial subendothelium are initial steps in hypertension development. The endothelial intercellular adhesion molecule-1 (ICAM-1) has been implicated in the recruitment and adhesion of leukocytes in several cardiac diseases. However, the role of ICAM-1 in angiotensin II (Ang II)-induced hypertension development remains unknown. Hypertension was induced by administering an infusion of Ang II (1000 ng/kg/min) to wild-type (WT) mice treated with an IgG control or ICAM-1 neutralizing antibody (1 and 2 mg/mouse/day, respectively). Blood pressure was determined using the tail-cuff system. Vascular remodeling was assessed by performing a histological examination. Inflammation and reactive oxygen species (ROS) levels were determined by using immunostaining. Vascular dysfunction was assessed by aortic ring assay. The expression of fibrotic markers, cytokines and NOX was evaluated by quantitative real-time PCR analysis. Our results demonstrate that Ang II infusion markedly increased the ICAM-1 level in the aorta. Blocking ICAM-1 with a neutralizing antibody significantly attenuated Ang II-induced arterial hypertension, vascular hypertrophy, fibrosis, macrophage infiltration, and ROS production and improved vascular relaxation. In conclusion, ICAM-1-mediated monocyte adhesion and migration play a critical role in Ang II-induced arterial hypertension and vascular dysfunction. ICAM-1 inhibitors may represent a new therapeutic strategy for the treatment of this disease.

Characterization of cytotoxic effects of aristolochic acids on the vascular endothelium

Aristolochic acid nephropathy (AAN) is characterized by interstitial fibrosis, proximal tubular atrophy, and hypoxia. A correlation between a reduced peritubular capillary density and the severity of fibrosis has been demonstrated. As calcium, redox and energetic homeostasis are crucial in maintaining endothelial cell function and survival, we aimed to investigate AA-induced disturbances involved in endothelial cell injury. Our results showed a cytotoxic effect of AA on EAhy926 endothelial cells. Exposure of aortic rings to AA impaired vascular relaxation to Acetylcholine (ACh). Increased levels of intracellular reactive oxygen species (ROS) were observed in cells exposed to AA. Pre-treatment with antioxidant N-acetyl cysteine inhibited AA-induced cell death. Superoxide dismutase resulted in restoring ACh-induced relaxation. An increase in intracellular calcium level ([Ca2+]i) was observed on endothelial cells. Calcium chelators BAPTA-AM or APB, a specific inhibitor of IP3R, improved cell viability. Moreover, AA exposure led to reduced AMP-activated protein kinase (AMPK) expression. AICAR, an activator of AMPK, improved the viability of AA-intoxicated cells and inhibited the rise of cytosolic [Ca2+]i levels.This study provides evidence that AA exposure increases ROS generation, disrupts calcium homeostasis and decreases AMPK activity. It also suggests that significant damage observed in endothelial cells may enhance microcirculation defects, worsening hypoxia and tubulointerstitial lesions.

Decreased expression of neuronal nitric oxide synthase contributes to the endothelial dysfunction associated with cigarette smoking in human

Endothelial nitric oxide synthase (eNOS) malfunctioning has been proposed to contribute to the endothelial damage produced by cigarette. Besides eNOS, neuronal NOS (nNOS) is also expressed in most vascular tissues and plays an important role in the endothelium-dependent vascular relaxation. We hypothesize that nNOS may contribute to the endothelium dysfunction produced by cigarette in smokers. Vascular function was assessed in human resistance mesenteric arteries using a wire myograph, the level of protein expression by Western blot, eNOS and nNOS localization by immunofluorescence. Measurement of NO was assessed by fluorescence microscopy. Arteries of smokers showed impaired endothelium-dependent vascular relaxation in response to acetylcholine. Pharmacological nonselective blockade of NOS with l-NAME and selective nNOS blockade with inhibitor 1 reduced the relaxation of the mesenteric artery of both smokers and nonsmokers. Interestingly, the inhibitory effect of NOS inhibitors was greater in nonsmokers than in smokers. The expression of total nNOS and eNOS and the level of phosphorylation at eNOS-pSer1177 were reduced in arteries of smokers as compared with nonsmokers. No differences between groups were observed in the expression of total COX-1, COX-2, catalase and SOD-1. Immunofluorescence analysis showed the presence of nNOS in the vascular endothelium in both groups. Acetylcholine-induced NO production was impaired in arteries from smokers as compared to nonsmokers. Selective inhibition of nNOS caused a decreased in NO production, which was greater in nonsmokers than in smokers. Our data show that a decrease in nNOS expression contributes to the endothelial dysfunction caused by cigarette smoking in human.

Coronary endothelial dysfunction prevented by small-conductance calcium-activated potassium channel activator in mice and patients with diabetes

ObjectiveTo investigate coronary endothelial protection of a small-conductance calcium-activated potassium (SK) channel activator against a period of cardioplegic-hypoxia and reoxygenation (CP-H/R) injury in mice and patients with diabetes (DM) and those without diabetes (nondiabetic [ND]). MethodsMouse small coronary arteries/heart endothelial cells (MHECs) and human coronary arterial endothelial cells (HCAECs) were dissected from the harvested hearts of mice (n = 16/group) and from discarded right atrial tissue samples of patients with DM and without DM (n = 8/group). The SK current density of MHECs was measured. The in vitro small arteries/arterioles, MHECs, and HCAECs were subjected to 60 minutes of CP hypoxia, followed by 60 minutes of oxygenation. Vessels were treated with or without the selective SK activator NS309 for 5 minutes before and during CP hypoxia. ResultsDM and/or CP-H/R significantly inhibited the total SK currents of MHECs and HCAECs and significantly diminished the mouse coronary relaxation response to NS309. Administration of NS309 immediately before and during CP hypoxia significantly improved the recovery of coronary endothelial function, as demonstrated by increased relaxation responses to adenosine 5′-diphosphate and substance P compared with those seen in controls (P < .05). This protective effect was more pronounced in vessels from ND mice and patients compared with DM mice and patients (P < .05). Cell surface membrane SK3 expression was significantly reduced after hypoxia, whereas cytosolic SK3 expression was greater than that of the sham control group (P < .05). ConclusionsApplication of NS309 immediately before and during CP hypoxia protects mouse and human coronary microvasculature against CP-H/R injury, but this effect is diminished in the diabetic coronary microvasculature. SK inhibition/inactivation and/or internalization/redistribution may contribute to CP-H/R–induced coronary endothelial and vascular relaxation dysfunction.

Aortic dysfunction by chronic cadmium exposure is linked to multiple metabolic risk factors that converge in anion superoxide production

Context The chronic exposure to Cadmium (Cd) constitute an risk to develop hypertension and cardiovascular diseases associated with the increase of oxidative stress. Objective In this study, we investigate the role of metabolic changes produced by exposure to Cd on the endothelial dysfunction via oxidative stress. Methods Male Wistar rats were exposed to Cd (32.5-ppm) for 2-months. The zoometry and blood pressure were evaluated, also glucose and lipids profiles in serum and vascular reactivity evaluated in isolated aorta rings. Results Rats exposed to Cd showed an increase of blood pressure and biochemical parameters similar to metabolic syndrome. Additionally, rats exposed to Cd showed a reduced relaxation in aortic rings, which was reversed after the addition of SOD and apocynin an inhibitor of NADPH. Conclusion The Cd-exposition induced hypertension and endothelial injury by that modifying the vascular relaxation and develop oxidative stress via NADPH oxidase, superoxide and loss nitric oxide bioavailability.

Fast Isolation of Flavonoids from the Endemic Species Nolana ramosissima I.M. Johnst and Its Endothelium-Independent Relaxation Effect in Rat Aorta.

The infusion of the desertic plant Nolana ramosissima I.M. Johnst showed vascular smooth muscle relaxation in rat aorta and the presence of several phenolic compounds, which were detected by high resolution UHPLC-Orbitrap-HESI-MS. In addition, five flavonoids were rapidly isolated from a methanolic extract using high-performance counter-current chromatography (HPCCC). The N. ramosissima extract showed endothelium-independent relaxation effect in rat aorta. Sixty-one compounds were detected in the infusion, mainly glycosylated flavonoids, flavanones and several oxylipins, suggesting that a synergistic effect between the compounds in the extracts could be responsible for the relaxation activity. Vascular activity experiments were done in isolated organ bath. In rat aorta, a nitric oxide inhibitor did not prevent the relaxation effects of the extract; however, a selective guanylyl cyclase inhibitor partially blunted this effect. The compound 5,3′-dihydroxy-4′7-dimethoxyflavone presented higher relaxation effect than 100 μg/mL of N. ramosissima extract. The extract and the isolated metabolites from N. ramosissima can show relaxation effects on rat aorta by a mechanism that is independent of the endothelium.

The influence of Finnish sauna treatments on the concentrations of nitric oxide, 3-nitrotyrosine and selected markers of oxidative status in training and non-training men.

The aim of the study was to evaluate the effects of repeated Finnish sauna baths on the concentrations of nitric oxide metabolites (NOx) and 3-nitrotyrosine in relation to pro-oxidative and antioxidative status in young males with different physical activity levels. The study was performed on healthy males (aged 20-25 years), representing the training (T, N = 10) and non-training groups (NT, N = 10). The protocol included a series of 10 sauna baths during 3 weeks. One bath consisted of three 15-min sessions, with 2 min recovery. Before the first and the 10th treatment, measurements of body composition, blood pressure, rectal temperature, and plasma concentrations of the total pro-oxidative and antioxidative status, 3-nitrotyrosine and NOx were performed. A significant increase in physiological parameters during sauna treatments, as well as a significant decrease in the total antioxidative status before the 10th bath, were observed in both groups. The series of sauna baths caused a significant increase in the total antioxidative status in the T group, and a decrease in the total oxidative status in the NT group. A significant decrease in 3-nitrotyrosine in both groups before the last treatment, and also in the T group after the last treatment, was noted. In both groups, a significant increase in NOx concentrations was observed after the first bath. A series of sauna baths contributes to the improvement in the prooxidative/ antioxidative balance. The increased production of nitric oxide may lead to a better vascular relaxation and blood flow. Int J Occup Med Environ Health. 2020;33(2):173-85.

Quercetin Exerts Age-Dependent Beneficial Effects on Blood Pressure and Vascular Function, But Is Inefficient in Preventing Myocardial Ischemia-Reperfusion Injury in Zucker Diabetic Fatty Rats.

Background: Quercetin (QCT) was shown to exert beneficial cardiovascular effects in young healthy animals. The aim of the present study was to determine cardiovascular benefits of QCT in older, 6-month and 1-year-old Zucker diabetic fatty (ZDF) rats (model of type 2 diabetes). Methods: Lean (fa/+) and obese (fa/fa) ZDF rats of both ages were treated with QCT for 6 weeks (20 mg/kg/day). Isolated hearts were exposed to ischemia-reperfusion (I/R) injury (30 min/2 h). Endothelium-dependent vascular relaxation was measured in isolated aortas. Expression of selected proteins in heart tissue was detected by Western blotting. Results: QCT reduced systolic blood pressure in both lean and obese 6-month-old rats but had no effect in 1-year-old rats. Diabetes worsened vascular relaxation in both ages. QCT improved vascular relaxation in 6-month-old but worsened in 1-year-old obese rats and had no impact in lean controls of both ages. QCT did not exert cardioprotective effects against I/R injury and even worsened post-ischemic recovery in 1-year-old hearts. QCT up-regulated expression of eNOS in younger and PKCε expression in older rats but did not activate whole PI3K/Akt pathway. Conclusions: QCT might be beneficial for vascular function in diabetes type 2; however, increasing age and/or progression of diabetes may confound its vasculoprotective effects. QCT seems to be inefficient in preventing myocardial I/R injury in type 2 diabetes and/or higher age. Impaired activation of PI3K/Akt kinase pathway might be, at least in part, responsible for failing cardioprotection in these subjects.