Endothelium-dependent Vasorelaxation Research Articles

The Vasoactive Role of Perivascular Adipose Tissue and the Sulfide Signaling Pathway in a Nonobese Model of Metabolic Syndrome.

The aim of this study was to evaluate the mutual relationship among perivascular adipose tissue (PVAT) and endogenous and exogenous H2S in vasoactive responses of isolated arteries from adult normotensive (Wistar) rats and hypertriglyceridemic (HTG) rats, which are a nonobese model of metabolic syndrome. In HTG rats, mild hypertension was associated with glucose intolerance, dyslipidemia, increased amount of retroperitoneal fat, increased arterial contractility, and endothelial dysfunction associated with arterial wall injury, which was accompanied by decreased nitric oxide (NO)-synthase activity, increased expression of H2S producing enzyme, and an altered oxidative state. In HTG, endogenous H2S participated in the inhibition of endothelium-dependent vasorelaxation regardless of PVAT presence; on the other hand, aortas with preserved PVAT revealed a stronger anticontractile effect mediated at least partially by H2S. Although we observed a higher vasorelaxation induced by exogenous H2S donor in HTG rats than in Wistar rats, intact PVAT subtilized this effect. We demonstrate that, in HTG rats, endogenous H2S could manifest a dual effect depending on the type of triggered signaling pathway. H2S within the arterial wall contributes to endothelial dysfunction. On the other hand, PVAT of HTG is endowed with compensatory vasoactive mechanisms, which include stronger anti-contractile action of H2S. Nevertheless, the possible negative impact of PVAT during hypertriglyceridemia on the activity of exogenous H2S donors needs to be taken into consideration.

The Cardiovascular Therapeutic Potential of Propolis-A Comprehensive Review.

Simple SummaryPropolis, also described as bee glue, is a natural component made up of a resinous mixture of honeybee compounds from multiple botanical sources. The literature has demonstrated a variety of medicinal properties attributed to propolis due to its chemical complexity. However, the positive effects of propolis on cardiovascular health have gained little coverage. Therefore, we aimed to provide an accurate and up-to-date review of the main cardiovascular health benefits of propolis. In particular, we intend to establish the key varieties of propolis and pharmacological compounds with the therapeutic effects that are most encouraging, as well as the physiological processes by which those advantages are accomplished. The Brazilian green and red varieties reveal the greatest number of beneficial activities among the varieties of propolis studied. While much of the cardiovascular beneficial effects appear to derive from the cumulative actions of several compounds working via multiple signaling mechanisms, some individual compounds that may enhance the existing therapeutic arsenal have also shown significant results. It is also worth exploring the prospect of using propolis as food supplements.Owing to its chemical richness, propolis has a myriad of therapeutic properties. To the authors’ knowledge, this is the first comprehensive review paper on propolis to focus exclusively on its major effects for cardiovascular health. The propolis compound varieties with the most promising therapeutic benefits and their respective physiological mechanisms will be discussed. Propolis displays an anti-atherosclerotic activity, attained through modulation of the plasma lipid profile and through stabilization of the fatty plaque by inhibiting macrophage apoptosis, vascular smooth muscle proliferation and metalloproteinase activity. The antihypertensive effects of propolis probably arise through the combination of several mechanisms, including the suppression of catecholamine synthesis, stimulation of endothelium-dependent vasorelaxation and vascular anti-inflammatory activity. The anti-hemostatic activity of propolis is attributed to the inhibition of platelet plug formation and antifibrinolytic activity. By inhibiting the secretion of proangiogenic factors, propolis suppresses endothelial cell migration and tubulogenesis, exerting antiangiogenic activity. The antioxidant and anti-inflammatory activities are responsible for protection against vascular endothelial and cardiomyocyte dysfunction, mostly by the prevention of oxidative stress. Among the reviewed propolis varieties, the Brazilian green and red varieties show the largest number of beneficial activities. Further research, especially preclinical, should be conducted to assess the cardiovascular benefits of the given varieties with different compositions.

Procaine-The Controversial Geroprotector Candidate: New Insights Regarding Its Molecular and Cellular Effects.

Since its discovery in 1905 and its employment in everyday medical practice as a local anesthetic, to its highly controversial endorsement as an “anti-aging” molecule in the sixties and seventies, procaine is part of the history of medicine and gerontoprophylaxis. Procaine can be considered a “veteran” drug due to its long-time use in clinical practice, but is also a molecule which continues to incite interest, revealing new biological and pharmacological effects within novel experimental approaches. Therefore, this review is aimed at exploring and systematizing recent data on the biochemical, cellular, and molecular mechanisms involved in the antioxidant and potential geroprotective effects of procaine, focusing on the following aspects: (1) the research state-of-the-art, through an objective examination of scientific literature within the last 30 years, describing the positive, as well as the negative reports; (2) the experimental data supporting the beneficial effects of procaine in preventing or alleviating age-related pathology; and (3) the multifactorial pathways procaine impacts oxidative stress, inflammation, atherogenesis, cerebral age-related pathology, DNA damage, and methylation. According to reviewed data, procaine displayed antioxidant and cytoprotective actions in experimental models of myocardial ischemia/reperfusion injury, lipoprotein oxidation, endothelial-dependent vasorelaxation, inflammation, sepsis, intoxication, ionizing irradiation, cancer, and neurodegeneration. This analysis painted a complex pharmacological profile of procaine: a molecule that has not yet fully expressed its therapeutic potential in the treatment and prevention of aging-associated diseases. The numerous recent reports found demonstrate the rising interest in researching the multiple actions of procaine regulating key processes involved in cellular senescence. Its beneficial effects on cell/tissue functions and metabolism could designate procaine as a valuable candidate for the well-established Geroprotectors database.

Hawthorn berry (crataegus songarica) causes endothelium-dependent relaxation of the porcine coronary artery: Role of Estrogen receptors

BACKGROUND: Fruits of Crataegus songarica are commonly used for the treatment of vascular insufficiency and heart problems. OBJECTIVE: Our aim was to determine the effect of C. songarica on vascular tone and to determine the mechanisms underlying the vasorelaxant properties. METHODS: Extracts of C. songarica were tested for vasodilator activity of porcine coronary artery after pre-contraction with the thromboxane mimetic U46619 in the presence or absence of inhibitors of intracellular signaling cascades. Reactive oxygen species were assessed by dihydroethidine staining and the level of eNOS and AKT phosphorylation was measured by immunohistochemical staining. RESULTS: Extracts of C. songarica berries produced endothelium dependent vasorelaxation, with most significant effect induced by aqueous fraction (AS-CS). This vasorelaxant effect of AS-CS was reduced by inhibition of nitric oxide pathways and inhibition of potassium channels. Inhibition of phosphatidylinositol 3- kinase and Src tyrosine kinase, as well as scavenging of reactive oxygen species, produced an attenuation of the relaxation response. Estrogen receptor antagonists (tamoxifen and ICI 182,782) reduced the AS-CS mediated vasorelaxation. AS-CS also stimulated the endothelial formation of ROS and phosphorylation of Akt and eNOS. CONCLUSION: The data indicated that C. songarica produces an endothelium-dependent vasorelaxation, which is partly dependent upon estrogen receptors, and sensitive to inhibition of ROS/Src/PI3K/NO pathways.

Thio-ether functionalized glycolipid amphiphilic compounds reveal a potent activator of SK3 channel with vasorelaxation effect.

The modulation of SK3 ion channels can be efficiently and selectively achieved by using the amphiphilic compound Ohmline (a glyco-glycero-ether-lipid). We report herein a series of Ohmline analogues featuring the replacement of one ether function by a thioether function located at the same position or shifted close to its initial position. The variation of the lipid chain length and the preparation of two analogues featuring either one sulfoxide or one sulfone moiety complete this series. Patch clamp measurements indicate that the presence of the thioether function (compounds 7 and 17a) produces strong activators of SK3 channels, whereas the introduction of a sulfoxide or a sulfone function at the same place produces amphiphiles devoid of an effect on SK3 channels. Compounds 7 and 17a are the first amphiphilic compounds featuring strong activation of SK3 channels (close to 200% activation). The cytosolic calcium concentration determined from fluorescence at 3 different times for compound 7b (13 min, 1 h, 24 h) revealed that the effect is different suggesting that the compound could be metabolized over time. This compound could be used as a strong SK3 activator for a short time. The capacity of 7b to activate SK3 was then used to induce vasorelaxation via an endothelium-derived hyperpolarization (EDH) pathway. For the first time, we report that an amphiphilic compound can affect the endothelium dependent vasorelaxation.

Ginsenoside Rb1 attenuates age-associated vascular impairment by modulating the Gas6 pathway

Context Ginsenoside Rb1 (Rb1) exerts many beneficial effects and protects against cardiovascular disease. Objective To investigate whether Rb1 could attenuate age-related vascular impairment and identify the mechanism. Materials and methods Female C57BL/6J mice aged 2 and 18 months, randomly assigned to Young, Young + 20 mg/kg Rb1, Old + vehicle, Old + 10 mg/kg Rb1 and Old + 20 mg/kg Rb1 groups, were daily intraperitoneal injected with vehicle or Rb1 for 3 months. The thoracic aorta segments were used to inspect the endothelium-dependent vasorelaxation. Left thoracic aorta tissues were collected for histological or molecular expression analyses, including ageing-related proteins, markers relevant to calcification and fibrosis, and expression of Gas6/Axl. Results We found that in Old + vehicle group, the expression of senescence proteins and cellular adhesion molecules were significantly increased, with worse endothelium-dependent thoracic aorta relaxation (58.35% ± 2.50%) than in Young group (88.84% ± 1.20%). However, Rb1 treatment significantly decreased the expression levels of these proteins and preserved endothelium-dependent relaxation in aged mice. Moreover, Rb1 treatment also reduced calcium deposition, collagen deposition, and the protein expression levels of collagen I and collagen III in aged mice. Furthermore, we found that the downregulation of Gas6 protein expression by 41.72% and mRNA expression by 52.73% in aged mice compared with young mice was abrogated by Rb1 treatment. But there was no significant difference on Axl expression among the groups. Conclusions Our study confirms that Rb1 could ameliorate vascular injury, suggesting that Rb1 might be a potential anti-ageing related vascular impairment agent.

Effect of Vitamin D Status on Vascular Function of the Aorta in a Rat Model of PCOS.

Polycystic ovary syndrome (PCOS) is associated with elevated cardiovascular risk. Early vascular dysfunction may lead to the development of cardiovascular disease in PCOS. Vitamin D deficiency (VDD) is a common comorbidity of PCOS that contributes to the pathogenesis of the disease and its complications. Both PCOS and VDD are accompanied by increased oxidative stress that may be involved in the arising vascular dysfunction. We aimed to investigate the role of vitamin D status on aortic function. PCOS was induced by an 8-week-long transdermal testosterone treatment of female rats, and low and adequate vitamin D status was achieved by dietary means. Contraction and relaxation abilities of isolated aortic segments were measured by myograph. Resorcin-fuchsin staining and immunohistochemical labeling of 3-nitrotyrosine were performed. No difference was shown in the norepinephrine-induced contraction of the aortas of different groups, whereas we detected reduced acetylcholine- and insulin-evoked relaxation in VDD groups. A lower level of resorcin-fuchsin staining and elevated 3-nitrotyrosine immunostaining was observed in VDD. In our study, we demonstrated early endothelial dysfunction in VDD PCOS rat model. Vitamin D supplementation could prevent vascular disturbances, while VDD itself damaged endothelium-dependent vasorelaxation and induced nitrative stress.

Hydrogen sulfide as a mediator of endothelium-dependent relaxation evoked by Moringa oleifera leaf extract in mesenteric arterial beds isolated from L-NAME hypertensive rats.

Aqueous extract of Moringa oleifera leaves (MOE) is a potent inducer of endothelium-dependent relaxation of mesenteric resistance arteries of rats induced to be hypertensive using Nω-nitro-L-arginine methyl ester (L-NAME). Hydrogen sulfide (H2S) has been shown to participate in endothelium-dependent relaxation of small resistance arteries. Therefore, this study aimed to investigate whether endothelial H2S-dependent signaling plays a role in the vasorelaxation in response to MOE. Mesenteric arterial beds isolated from L-NAME hypertensive rats were set up in an exvivo perfusion system for measurement of vasoreactivity. All experiments were performed in the presence of the nitric oxide synthase inhibitor, L-NAME (100µM) and the cyclooxygenase inhibitor, indomethacin (10µM) to prevent the formation of nitric oxide and prostanoids, respectively. In the presence of the nitric oxide synthase inhibitor, L-NAME and the cyclooxygenase inhibitor, indomethacin, the endothelium-dependent vasorelaxation induced by MOE (0.001-3mg) was completely inhibited by DL-propargylglycine (100µM), which inhibits the H2Sgenerating enzyme, cystathionine γ-lyase. This H2Sdependent response was reduced by the KATP channel blocker; glibenclamide (10µM), the KCa channel blocker; tetraethylammonium (1µM), and the myo-endothelial gap-junctional uncoupler; 18α-glycyrrhetinic acid (10µM). In contrast, the muscarinic receptor antagonist, atropine (100µM), did not affect the response to MOE. The results may suggest that H2S is the likely mediator of endothelium-dependent relaxation in response to MOE in mesenteric arterial beds of L-NAME-induced hypertensive rats. MOE-induced H2S-dependent vasorelaxation involves activation of KATP and KCa channels and requires myo-endothelial gap-junctional communication.

Ozagrel a thromboxane A2 synthase inhibitor extenuates endothelial dysfunction, oxidative stress and neuroinflammation in rat model of bilateral common carotid artery occlusion induced vascular dementia

The present study investigates the potential of ozagrel, a thromboxane A2 (TXA2) synthase inhibitor, in bilateral common carotid artery occlusion (BCCAo) induced vascular dementia (VaD). Wistar rats were subjected to BCCAo procedure under anesthesia to induce VaD. Morris water maze (MWM) test was employed on 7th day post-surgery to determine learning and memory. Endothelial dysfunction was assessed in isolated aorta by observing endothelial dependent vasorelaxation and levels of serum nitrite. A battery of biochemical and histopathological estimations was performed. Expression analysis of inflammatory cytokines TNF-α and IL-6 was carried out by RT-PCR. BCCAo produced significant impairment in endothelium dependent vasorelaxation and decrease in serum nitrite levels indicating endothelial dysfunction along with poor performance on MWM represents impairment of learning and memory. There was a significant rise in brain oxidative stress level (indicated by increase in brain thiobarbituric acid reactive species and decrease in reduced glutathione levels); increase in brain acetylcholinesterase activity; brain myeloperoxidase activity; brain TNF-α & IL-6 levels, brain TNF-α & IL-6 mRNA expression and brain neutrophil infiltration (as marker of inflammation) were also observed. Treatment of ozagrel (10 & 20 mg/kg, p. o.)/donepezil (0. 5 mg/kg, i.p., serving as standard) ameliorated BCCAo induced endothelial dysfunction; memory deficits; biochemical and histopathological changes in a significant manner. It may be concluded that ozagrel markedly improved endothelial dysfunction; learning and memory; biochemical and histopathological alteration associated with BCCAo induced VaD and that TXA2 can be considered as an important therapeutic target for the treatment of VaD.

Ameliorative effect of ozagrel, a thromboxane A2 synthase inhibitor, in hyperhomocysteinemia-induced experimental vascular cognitive impairment and dementia.

The present study investigates the effect of ozagrel, a selective thromboxane A2 (TXA2) inhibitor, in rat model of hyperhomocysteinemia (HHcy)-induced vascular cognitive impairment and dementia (VCID). Wistar rats were administered L-methionine (1.7g/kg/day; p.o. × 8weeks) to induce VCID. Morris water maze (MWM) test was employed to assess learning and memory. Endothelial dysfunction was assessed in the isolated aorta by observing endothelial-dependent vasorelaxation and levels of serum nitrite. Various biochemical and histopathological estimations were also performed. L-methionine produced significant impairment in endothelium-dependent vasorelaxation and decreases serum nitrite levels indicating endothelial dysfunction. Further, these animals performed poorly on MWM, depicting impairment of learning and memory. Further, a significant rise in brain oxidative stress level (indicated by increase in brain thiobarbituric acid-reactive species and decrease in reduced glutathione levels), brain acetylcholinesterase activity, brain myeloperoxidase activity, brain TNF-α and IL-6 levels, and brain leukocyte (neutrophil) infiltration was also observed. Treatment of ozagrel (10 and 20mg/kg, p. o.)/donepezil (0.5mg/kg, i.p., serving as standard) ameliorated L-methionine-induced endothelial dysfunction, memory deficits, and biochemical and histopathological changes. It may be concluded that ozagrel markedly improved endothelial dysfunction, learning and memory, and biochemical and histopathological alteration associated with L-methionine-induced VCID and that TXA2 can be considered as an important therapeutic target for the management of VCID.

Transglutaminase 2 Inhibitor LDN 27219 Age-Dependently Lowers Blood Pressure and Improves Endothelium-Dependent Vasodilation in Resistance Arteries.

Transglutaminase 2 (TG2) is an enzyme which in the open conformation exerts transamidase activity, leading to protein cross-linking and fibrosis. In the closed conformation, TG2 participates in transmembrane signaling as a G protein. The unspecific transglutaminase inhibitor cystamine causes vasorelaxation in rat resistance arteries. However, the role of TG2 conformation in vascular function is unknown. We investigated the vascular effects of selective TG2 inhibitors by myography in isolated rat mesenteric and human subcutaneous resistance arteries, patch-clamp studies on vascular smooth muscle cells, and blood pressure measurements in rats and mice. LDN 27219 promoted the closed TG2 conformation and inhibited transamidase activity in mesenteric arteries. In contrast to TG2 inhibitors promoting the open conformation (Z-DON, VA5), LDN 27219 concentration-dependently relaxed rat and resistance human arteries by a mechanism dependent on nitric oxide, large-conductance calcium-activated and voltage-gated potassium channels 7, lowering blood pressure. LDN 27219 also potentiated acetylcholine-induced relaxation by opening potassium channels in the smooth muscle; these effects were abolished by membrane-permeable TG2 inhibitors promoting the open conformation. In isolated arteries from 35- to 40-week-old rats, transamidase activity was increased, and LDN 27219 improved acetylcholine-induced relaxation more than in younger rats. Infusion of LDN 27219 decreased blood pressure more effectively in 35- to 40-week than 12- to 14-week-old anesthetized rats. In summary, pharmacological modulation of TG2 to the closed conformation age-dependently lowers blood pressure and, by opening potassium channels, potentiates endothelium-dependent vasorelaxation. Our findings suggest that promoting the closed conformation of TG2 is a potential strategy to treat age-related vascular dysfunction and lowers blood pressure.

Abstract 14853: Acute Inhibition of Mitochondrial Reactive Oxidative Species Improves Endothelial SK Channel Function Following Cardioplegic Hypoxia/Reperfusion and Diabetes

Introduction: Cardioplegic-ischemia/reperfusion (CP-I/R) and diabetes mellitus (DM) are correlated with coronary endothelial dysfunction and inactivated small conductance calcium-activated-potassium (SK) channels. Increased reactive oxidative species (ROS), such as mitochondrial ROS (mROS) may contribute to oxidative injury. Thus, we hypothesized that inhibition of mROS may protect coronary SK channels and endothelial function against CP-I/R-induced injury. Objective: A cardioplegic hypoxia and reoxygenation (CP-H/R) model consisting of coronary endothelial cells and small coronary arteries with or without DM were employed for examining whether MT could protect against coronary endothelial and SK channel dysfunction. Methods: Small coronary arteries (<150μm) and endothelial cells (MHECs) were dissected from the mouse heart with non-diabetes (ND) and DM (n=6/group). The microvessels or MHECs were subjected to hypoxia with cardioplegia and re-oxygenated. The microvessels or MHECs were treated with or without MT (10 -5 M) 5-minutes before and during CP-hypoxia. Microvascular vasodilation function was assessed in vitro by administration of vasoconstrictor, then ADP or NS309,respectively. K + currents of MHECs were measured by whole-cell patch clamp. The levels of endothelial mROS was measured by MitoSox TM . Results: CP-H/R significantly attenuated endothelial SK channels activity and the coronary relaxation responses to ADP and NS309 in the ND and DM groups. Treatment with MT enhanced coronary relaxation responses to ADP or NS309 ( p <0.05, Fig 1. A, B), and similar findings were seen in endothelial SK channel currents in both ND and DM MHECs ( p <0.05, Fig 1. C-F). In addition, treating MHECs with MT reduced CP-H/R-induced mROS in ND and DM groups. Conclusions: Administration of MT improves endothelial SK channels activity which may contribute to its enhancement of endothelium-dependent vasorelaxation following CP-H/R.

Effects of combined exercise training and Chlorella intake on vasorelaxation mediated by nitric oxide in aged mice.

Chronic Chlorella intake and aerobic exercise training reduce arterial stiffness and increase circulating nitric oxide (NO) levels, which has beneficial effects. This study aimed to clarify the combined aortic NO-mediated effects of chronic Chlorella intake and aerobic exercise training on endothelial vasorelaxation in aged mice. In this study, 38-week-old male senescence-accelerated mouse prone 1 (SAMP1) mice were divided into aged sedentary control (Con), aerobic exercise training (AT; voluntary wheel running for 12 weeks), Chlorella intake (CH; 0.5% Chlorella powder in normal diet), and AT and CH combined (AT+CH) groups. Endothelium-dependent vasorelaxation by addition of acetylcholine to the isolated mouse aortic rings was significantly higher in the AT, CH, and AT+CH groups than in the Con group; a significantly greater effect was seen in the AT+CH group than in the AT and CH groups. Similarly, plasma and arterial nitrite/nitrate levels and arterial endothelial NO synthase phosphorylation were significantly higher in the AT, CH, and AT+CH groups than in the Con group; the AT+CH group had higher values than the AT and CH groups. Thus, chronic Chlorella intake combined with aerobic exercise training had pronounced effects on endothelial vasorelaxation in aged mice via an additive increase in arterial NO production. Novelty: Endothelium-dependent vasorelaxation was improved by Chlorella intake and exercise. Chlorella intake and exercise increased arterial Akt/eNOS/NO signaling. This combination approach further improved vasorelaxation via arterial NO production.

The role of matrix metalloproteinase-2 on age-dependent arterial stiffness

Abstract Introduction Arterial stiffness is a well-characterized sign of vascular aging. It strongly predicts the development of several cardiovascular diseases (CVD), such as hypertension, stroke and heart failure. The age-dependent stiffening of elastic arteries is primarily attributed to the loss of interlaminar elastic fibers and the increase of collagen fibers. This process is regulated by matrix metalloproteinases (MMPs), including MMP-2. A strong correlation between MMP-2 levels and arterial stiffness has been previously described. However, the causative link between age-dependent arterial stiffness and MMP-2 remains unclear. Purpose In this study, we aimed to prospectively investigate the effect of MMP-2 gene silencing on the development of age-dependent carotid stiffness in wild type (WT) mice. Methods Pulse Wave Velocity (PWV), as the gold standard technique to assess arterial stiffness, was assessed in the right common carotid artery (RCCA) of C57BL/6 WT mice of various ages ranging between 3 and 25 months. Plasma and vascular levels of MMP-2 on RCCA were also measured and correlate with PWV. Moreover, aged WT male mice (18–21-month-old) were treated for 4 weeks with either MMP-2 siRNA or Scr siRNA via tail vein injection every 4 days and PWV was assessed at baseline, 2 and 4 weeks. Results Mouse carotid PWV increased and was positively correlated with age in our in vivo longitudinal study. Increases of vascular and circulating MMP-2 levels were also observed in this study. MMP-2 knockdown by siRNA treatment reduced vascular MMP-2 level (Fig. 1), which in turn attenuated age-dependent carotid stiffening (data not shown). siMMP-2 treated animals also showed an increase of elastin to collagen ratio. Furthermore, enhanced phosphorylation of the activatory eNOS Ser1177 was observed in the siMMP-2 group without affecting the level of total eNOS and Akt phosphorylation. Interestingly, co-immunoprecipitation experiments demonstrated that MMP-2 directly interacts with eNOS and this interaction is augmented with age. Conclusion The silencing of MMP-2 attenuates age-dependent carotid stiffness by affecting elastin to collagen ratio and interfering with eNOS activation. Thus, MMP-2 may mediate ECM remodeling and endothelial-dependent vasorelaxation in the development of age-dependent vascular stiffness. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Swiss National Science Foundation, Foundation for Cardiovascular Research-Zurich Heart House

L-Arginine Supplementation Improves Vascular Endothelial Dysfunction Induced by High-Fat Diet in Rats Exposed to Hypoxia

Our previous study showed that high-fat diet inhibited the increase in nitric oxide and endothelial nitric oxide synthase expression in the aortic endothelium of rats exposed to hypoxia, and hypoxia plus a high-fat diet led to earlier and more severe vascular endothelial dysfunction (VED) than hypoxia alone. The purpose of the present study was to investigate the effects of L-arginine on high-fat diet-induced VED of rats in hypoxia. Forty male Sprague-Dawley rats were randomly divided into 4 groups and treated with hypoxia (H group), hypoxia plus high-fat diet (H+HFD group), hypoxia plus L-arginine (H+L-Arg group), and hypoxia plus high-fat diet and L-arginine (H+HFD+L-Arg group) for 1 wk. Hypoxia was simulated in a hypobaric chamber with an altitude of 5000 m. Aortic morphology and endothelium-dependent vasorelaxation were used to assess VED. High-fat diet impaired vascular remodeling and reduced endothelium-dependent vasodilator response to acetylcholine in rats exposed to hypoxia, secondary to dysregulation of the nitric oxide pathway. L-arginine supplementation significantly increased plasma nitrates and nitrites and endothelial nitric oxide synthase mRNA levels and improved ultrastructural changes in aortic endothelium and endothelium-dependent vasodilator response. L-arginine prevents aortic ultrastructural changes and reverses VED induced by high-fat diet in rats exposed to hypoxia, which may have implications for VED induced by high-fat diet in high altitude dwellers.

Luteolin-induced vasorelaxation in uterine arteries from normal pregnant rats.

The flavonoid, luteolin, promotes vasorelaxation in various arteries through endothelial-dependent and independent mechanisms. Although there is growing interest in the vasoactive effects of flavonoids on maternal vascular function during pregnancy, it is unknown whether luteolin elicits vasorelaxation in the uterine circulation. We tested the hypothesis that luteolin induces vasorelaxation via endothelial-dependent mechanisms in uterine arteries from normal pregnant rats during late gestation. Uterine arteries and aortas were isolated from Sprague-Dawley rats at gestational day 19 and prepared for wire myography. The potency of luteolin-induced vasorelaxation was examined between uterine arteries and the aortas. By 50µM of luteolin, there was complete relaxation (100.5±5.2%) in uterine arteries as compared to aortas (27.5±10.0%). Even the highest concentration of 100µM luteolin produced less than half relaxation (43.6±8.6%) in aortas compared to uterine arteries. We then explored if luteolin-induced vasorelaxation in uterine arteries from pregnant rats was mediated by endothelial-dependent vasorelaxation pathways, including nitric oxide synthase (NOS), cyclooxygenase (COX), or potassium (K+) channels. Blocking these pathways with N(G)-Nitro-l-arginine methyl ester hydrochloride (L-NAME), indomethacin, or tetraethylammonium (TEA)/high potassium chloride (KCl), respectively, did not alter luteolin responses in uterine arteries from pregnant rats. These findings suggested that endothelial factors may not mediate luteolin-induced vasorelaxation in uterine arteries during pregnancy. Indeed, experiments where the endothelium was removed did not alter luteolin-induced vasorelaxation in uterine arteries during pregnancy. Luteolin directly promotes vasorelaxation in the medial smooth muscle layer of uterine arteries during normal pregnancy.

Modulation of hydrogen sulfide synthesis improves heart function and endothelium-dependent vasorelaxation in diabetes.

Diabetes dramatically increases the risk of cardiovascular complications. The endothelial dysfunction and diastolic heart dysfunction are associated with a decreasing level of hydrogen sulfide (H2S) and inhibition of the activity of endothelial nitric oxide synthase (NOS) in diabetes. The aim of this study is to investigate the effect of modulation of H2S synthesis on heart functions and vasorelaxation in diabetes. The dl-propargylglycine and l-cysteine were administered intraperitoneally. H2S content in the heart tissue, markers of oxidative stress, inducible NOS and constitutive NOS (cNOS) activities, endothelium-dependent vasorelaxation of the aortic rings, and heart function were studied. We demonstrate that our combination increased H2S synthesis 13 times and cNOS activity 5 times in the heart tissue of diabetic rats. Increasing NO and H2S production caused improvement and restoration of endothelium-dependent relaxation of aorta, effective arterial elastance, and diastolic heart function in diabetic rats. The endothelium-dependent relaxation increased 2.4 times; effective arterial elastance decreased by 47%. The end-diastolic myocardial stiffness decreased 2.2 times. Thus, modulation of H2S synthesis leads to increased cNOS activity by up to 5 times in the cardiovascular system. Increasing NO and H2S production restored endothelium-dependent relaxation of aorta and improved heart function in diabetes.

High concentration of uric acid failed to affect endothelial function of small mesenteric arteries, femoral arteries and aortas from aged Wistar-Kyoto rats.

It is known that a high level of uric acid (UA) in plasma, hyperuricemia (HU), is associated with the increased risk of cardiovascular diseases (CVDs). Endothelial damage has been suggested as a potential mechanism involved in HU-induced CVDs, especially in patients with the accumulation of other cardiovascular risk factors. However, the role of UA in the pathogenesis of endothelial dysfunction is still a matter of debate. It is unclear whether UA is a causative risk factor in endothelial dysfunction, an inert marker or an endothelium-protective molecule with respect to its antioxidant properties. Of note, only a few studies have been conducted to investigate the effect of UA on vascular endothelium-dependent relaxation. Therefore, we have studied the acute in vitro effects of high UA concentrations on the endothelial function of arteries isolated from aged rats. Experiments were performed in small mesenteric arteries (SMAs), femoral arteries and thoracic aortas isolated from 68-week-old and 57-week-old male Wistar-Kyoto rats. Vascular reactivity was investigated in isometric conditions using the wire myograph and organ chamber. Acetylcholine (ACh) was used to investigate endothelium-dependent vasorelaxation. Then, UA was added to the myograph or organ chamber at 600 μmol/l (arteries from 68-week-old rats) or 1200 μmol/l (arteries from 57-week-old rats) and incubated for 1 h, and this was followed by determining the ACh concentration-response curve. UA had no significant effect on ACh-induced vasorelaxation and pD2 values in all investigated groups. Likewise, no significant differences in noradrenaline- (SMAs), serotonin- (femoral arteries) and phenylephrine-induced (aortas) vasoconstriction were observed after UA pre-incubation. In conclusion, high concentrations of UA administered acutely failed to affect endothelial function and did not provoke endothelial dysfunction in resistant mesenteric arteries, medium-sized and large arteries from aged rats.

S1677 Topical Cannabidiol (CBD) for the Treatment of Anal Fissures: A Case Series

INTRODUCTION: An anal fissure is defined as a longitudinal tear in the anal canal distal to the dentate line. It is a common benign condition that may be primary, resulting from local trauma, or secondary, stemming from an underlying disorder such as a malignancy, sexually transmitted infection, or inflammatory bowel disease. The primary symptom is anal pain particularly during defecation but may last for several hours. While the pathophysiology remains unclear, a mechanism of internal anal sphincter spasm, reduced perfusion and local ischemia has been proposed. Current first-line therapy involves a combination of a topical vasodilator therapy (nitroglycerin or calcium channel blockers) along with supportive measures such as a high fiber diet, sitz baths, local anesthesia, and stool softeners. Topical vasodilators are effective in 50% of cases but are often limited by side effects. The vasoactive properties of Cannabidiol (CBD) has been described in both human and animal models. CBD induced vasodilation has been shown in renal, mesenteric, opthalmic and cerebral arteries. The vasorelaxant properties of CBD have yet to be exploited in the management of anal fissures. We report five patients with anal fissures that were successfully treated with topical CBD. CASE DESCRIPTION/METHODS: Five consecutive patients who presented or were referred to a single Gastroenterology practice for an anal fissure were prescribed topical cannabidiol (1.4–2 mg/g) twice daily and supplemental fiber. One patient was female. Mean age was 49 (Range 31–63). Duration of symptoms was greater than 6 weeks in all patients. Each patient was asked to complete a modified HEMO-FISS QoL questionnaire to measure symptom improvement after two weeks of therapy. All patients reported a significant improvement in symptoms at follow-up. No side effects were reported. One patient later had a recurrence of symptoms that required treatment with Botulinum toxin injection. DISCUSSION: Cannabidiol has been shown to induce endothelium dependent vasorelaxation in human mesenteric arteries through activation of CB1 receptors. It is likely that the vasoactive properties of CBD reduce local ischemia and promote healing of chronic anal fissures. As far as we are aware, this is the first report showing a potential role for CBD in the management of acute and chronic anal fissures. Given the limited options for topical therapy and significant side effects, CBD provides an attractive alternative to conventional first line treatment. Further studies are warranted.

Endothelial Cell Cystathionine γ-Lyase Expression Level Modulates Exercise Capacity, Vascular Function, and Myocardial Ischemia Reperfusion Injury.

BackgroundHydrogen sulfide (H2S) is an important endogenous physiological signaling molecule and exerts protective properties in the cardiovascular system. Cystathionine γ‐lyase (CSE), 1 of 3 H2S producing enzyme, is predominantly localized in the vascular endothelium. However, the regulation of CSE in vascular endothelium remains incompletely understood.Methods and ResultsWe generated inducible endothelial cell‐specific CSE overexpressed transgenic mice (EC‐CSE Tg) and endothelial cell‐specific CSE knockout mice (EC‐CSE KO), and investigated vascular function in isolated thoracic aorta, treadmill exercise capacity, and myocardial injury following ischemia‐reperfusion in these mice. Overexpression of CSE in endothelial cells resulted in increased circulating and myocardial H2S and NO, augmented endothelial‐dependent vasorelaxation response in thoracic aorta, improved exercise capacity, and reduced myocardial‐reperfusion injury. In contrast, genetic deletion of CSE in endothelial cells led to decreased circulating H2S and cardiac NO production, impaired endothelial dependent vasorelaxation response and reduced exercise capacity. However, myocardial‐reperfusion injury was not affected by genetic deletion of endothelial cell CSE.ConclusionsCSE‐derived H2S production in endothelial cells is critical in maintaining endothelial function, exercise capacity, and protecting against myocardial ischemia/reperfusion injury. Our data suggest that the endothelial NO synthase—NO pathway is likely involved in the beneficial effects of overexpression of CSE in the endothelium.