Endothelium-dependent Relaxation In Response Research Articles

Temporal Changes in Erectile Function and Endothelium-Dependent Relaxing Response of Corpus Cavernosal Smooth Muscle After Ischemia by Ligation of Bilateral Internal Iliac Arteries in the Rabbit

We aimed to elucidate the changes in the relaxation function of corpus cavernosal smooth muscle (CCSM) and erectile function using acute penile ischemic rabbits. Relaxation response to acetylcholine (Ach) was unchanged at 3 days after ischemia. The response to ACh had significantly decreased at 1 week, but had recovered completely at 4 weeks. The reaction to sodium nitroprusside and electrical field stimulation was unchanged by ischemia at all time points. Erectile function was changed in the same manner as the response of ACh. The endothelium-dependent relaxing responses of CCSM and erectile function were found to be initially decreased, but subsequently improved completely.

Extracellular Signal‐Regulated Kinase (ERK) Inhibition Decreases Arginase Activity and Improves Corpora Cavernosal Relaxation in Streptozotocin (STZ)‐Induced Diabetic Mice

Increased arginase activity (AA) has been implicated in hypertension and diabetes-induced endothelial dysfunction by reducing L-arginine availability and nitric oxide production. Higher levels of active extracellular signal-regulated kinase (ERK) have been found in patients with erectile dysfunction (ED) compared to patients without it. Both ERK and arginase have been reported to affect the expression and activity of nitric oxide synthase (NOS) and consequently penile erection. Nevertheless, signaling pathways activated by ERK in the penis are not well known. We hypothesized that inhibition of ERK by ERK inhibitor PD98059 decreases AA and thus improves cavernosal relaxation in streptozotocin (STZ)-diabetic mice. The AA, ERK, eNOS, and arginase I and II expressions were examined through Western blot, and functional response of cavernosal tissue were determined. Control and diabetic cavernosal tissues were pretreated with PD98059 (10(-5) M) and arginase inhibitor ((S)-(2-boronoethyl)-L-cysteine hydrochloride, [BEC]10(-4) M]). Diabetes increased AA significantly (twofold) over control mice and this effect was blocked by acute treatment with PD98059. Cavernosal strips from diabetic mice exhibited decreased relaxation (STZ-diabetic vs. control, respectively) to both the endothelium-dependent agonist acetylcholine (38.0 ± 5% vs. 82.5 ± 7%) and nitrergic stimulation (27 ± 2% vs. 76 ± 6%) by electrical field stimulation (EFS, 1-32 Hz). However, this impairment in cavernosal relaxation from diabetic mice was attenuated by treatment with PD98059 in nitrergic (27 ± 2% vs. 60 ± 4%) and endothelium-dependent relaxation responses (38.0 ± 5% vs. 67.5 ± 6%). Acute treatment with the arginase inhibitor BEC (10(-4) M) also improves EFS-induced relaxation in diabetic mice (31 ± 3% vs. 49 ± 2%). Moreover, vascular expression of activated ERK was increased in diabetic over control mice. These data suggest that ERK inhibition prevents elevation of penile AA and protects against ED caused by diabetes.

Impact of porcine maternal aerobic exercise training during pregnancy on endothelial cell function of offspring at birth.

The purpose of this investigation was to test the hypothesis that maternal exercise training during pregnancy enhances endothelial function in offspring at birth. Six-month-old gilts (n = 8) were artificially inseminated and randomized into exercise-trained (n = 4) and sedentary groups (n = 4). Exercise training consisted of 15 weeks of treadmill exercise. The thoracic aorta of offspring were harvested within 48 h after birth and vascular responsiveness to cumulative doses of endothelium-dependent (bradykinin: 10-11-10-6 M) and independent (sodium nitroprusside: 10-10-10-4 M) vasodilators were assessed using in vitro wire myography. Female offspring from the exercised-trained gilts had a significantly greater endothelium-dependent relaxation response in the thoracic aorta when compared with the male offspring and female offspring from the sedentary gilts. The results of this investigation demonstrate for the first time that maternal exercise during pregnancy produces an enhanced endothelium-dependent vasorelaxation response in the thoracic aortas of female offspring at birth.

Effects of the Novel Polymer Gel LeGoo on Human Internal Thoracic Arteries

Established hemostatic devices can injure vessel wall integrity. LeGoo (Pluromed, Woburn, MA), a novel poloxamer gel with reverse thermosensitive properties, is a new device for temporary occlusion of blood vessels. The present study investigated the effects of LeGoo on vascular function and morphology. The distal end of the human internal thoracic artery was used to assess vascular function of LeGoo-applied segments in organ bath experiments and by scanning electron microscopy. After LeGoo application, both maximal contractile responses to noradrenaline and endothelium-dependent relaxant responses to acetylcholine were significantly reduced. Scanning electron microscopy showed areas of injured endothelium with exposure of subendothelial structures being in line with the functional changes. Data suggested that application of LeGoo induced significant endothelial injury and deterioration of the smooth muscle in human internal thoracic arteries.

The novel ATP-sensitive potassium channel opener iptakalim prevents insulin resistance associated with hypertension via restoring endothelial function.

To investigate the effects of iptakalim on endothelial dysfunction induced by insulin resistance (IR) and to determine whether iptakalim improved IR associated with hypertension in fructose-fed rats (FFRs) and spontaneously hypertensive rats (SHRs). Human umbilical vein endothelial cells (HUVECs) were used for in vitro study. The levels of endothelial vasoactive mediators and eNOS protein expression were determined using radioimmunoassays, ELISAs, colorimetric assays or Western blotting. Sprague-Dawley rats were fed with a high-fructose diet. In both FFRs and SHRs, tail-cuff method was used to measure systolic blood pressure (SBP), and hyperinsulinemic- euglycemic clamp was used to evaluate IR states. (1) Cultured HUVECs incubated with the PI3-kinase inhibitor wortmannin (50 nmol/L) and insulin (100 nmol/L) induced endothelial dysfunction characterized by significantly reduced release of NO and expression of eNOS protein, and significantly increased production of ET-1. Pretreatment with iptakalim (0.1-10 μmol/L) could prevent the endothelial dysfunction. (2) In FFRs, the levels of SBP, fasting plasma glucose and insulin were significantly elevated, whereas the glucose infusion rate (GIR) and insulin sensitive index (ISI) were significantly decreased, and the endothelium-dependent vascular relaxation response to ACh was impaired. These changes could be prevented by oral administration of iptakalim (1, 3, or 9 mg·kg(-1)·d(-1), for 4 weeks). The imbalance between serum NO and ET-1 was also ameliorated by iptakalim. (3) In 2-4 month-old SHRs (IR was established at the age of 4 months), oral administration of iptakalim (1, 3, or 9 mg·kg(-1)·d(-1), for 8 weeks) significantly ameliorated hypertension and increased the GIR to the normal level. These results demonstrate that iptakalim could protect against IR-induced endothelial dysfunction, and ameliorate IR associated with hypertension, possibly via restoring the balance between NO and ET-1 signaling.

Epicatechin lowers blood pressure, restores endothelial function, and decreases oxidative stress and endothelin-1 and NADPH oxidase activity in DOCA-salt hypertension

Flavanol-rich diets have been reported to exert beneficial effects in preventing cardiovascular diseases, such as hypertension. We studied the effects of chronic treatment with epicatechin on blood pressure, endothelial function, and oxidative status in deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Rats were treated for 5weeks with (−)-epicatechin at 2 or 10mg kg−1day−1. The high dose of epicatechin prevented both the increase in systolic blood pressure and the proteinuria induced by DOCA-salt. Plasma endothelin-1 and malondialdehyde levels and urinary iso-prostaglandin F2α excretion were increased in animals of the DOCA-salt group and reduced by the epicatechin 10mg kg−1 treatment. Aortic superoxide levels were enhanced in the DOCA-salt group and abolished by both doses of epicatechin. However, only epicatechin at 10mg kg−1 reduced the rise in aortic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and p47phox and p22phox gene overexpression found in DOCA-salt animals. Epicatechin increased the transcription of nuclear factor-E2-related factor-2 (Nrf2) and Nrf2 target genes in aortas from control rats. Epicatechin also improved the impaired endothelium-dependent relaxation response to acetylcholine and increased the phosphorylation of both Akt and eNOS in aortic rings. In conclusion, epicatechin prevents hypertension, proteinuria, and vascular dysfunction. Epicatechin also induced a reduction in ET-1 release, systemic and vascular oxidative stress, and inhibition of NADPH oxidase activity.

Hydrogen sulfide replacement therapy protects the vascular endothelium in hyperglycemia by preserving mitochondrial function

The goal of the present studies was to investigate the role of changes in hydrogen sulfide (H(2)S) homeostasis in the pathogenesis of hyperglycemic endothelial dysfunction. Exposure of bEnd3 microvascular endothelial cells to elevated extracellular glucose (in vitro "hyperglycemia") induced the mitochondrial formation of reactive oxygen species (ROS), which resulted in an increased consumption of endogenous and exogenous H(2)S. Replacement of H(2)S or overexpression of the H(2)S-producing enzyme cystathionine-γ-lyase (CSE) attenuated the hyperglycemia-induced enhancement of ROS formation, attenuated nuclear DNA injury, reduced the activation of the nuclear enzyme poly(ADP-ribose) polymerase, and improved cellular viability. In vitro hyperglycemia resulted in a switch from oxidative phosphorylation to glycolysis, an effect that was partially corrected by H(2)S supplementation. Exposure of isolated vascular rings to high glucose in vitro induced an impairment of endothelium-dependent relaxations, which was prevented by CSE overexpression or H(2)S supplementation. siRNA silencing of CSE exacerbated ROS production in hyperglycemic endothelial cells. Vascular rings from CSE(-/-) mice exhibited an accelerated impairment of endothelium-dependent relaxations in response to in vitro hyperglycemia, compared with wild-type controls. Streptozotocin-induced diabetes in rats resulted in a decrease in the circulating level of H(2)S; replacement of H(2)S protected from the development of endothelial dysfunction ex vivo. In conclusion, endogenously produced H(2)S protects against the development of hyperglycemia-induced endothelial dysfunction. We hypothesize that, in hyperglycemic endothelial cells, mitochondrial ROS production and increased H(2)S catabolism form a positive feed-forward cycle. H(2)S replacement protects against these alterations, resulting in reduced ROS formation, improved endothelial metabolic state, and maintenance of normal endothelial function.

Mas receptors in modulating relaxation induced by perivascular adipose tissue

Aims Perivascular adipose tissue (PVAT) is known to secrete vascular relaxation factors, and angiotensin 1–7 [Ang-(1–7)] acting on the endothelium is one of the endothelium-dependent relaxation factors. Mas protein is the receptor for Ang-(1–7). Using aorta from Mas-knockout (K/O) and wild type (FVB) mice, we wished to establish the essential role of Mas receptors in mediating the endothelium-dependent relaxation response induced by relaxation factors from PVAT. Main methods Thoracic aortic rings from K/O and FVB mice were prepared with or without PVAT (PVAT+ and PVAT−) and/or intact endothelium (E+) or with the endothelium removed (E−) for functional studies. The contraction and relaxation responses of these vessels to agonist in the presence of different receptor antagonists were studied. Key findings PVAT attenuated the contraction induced by phenylephrine (PHE) in the presence of endothelium only in vessels from FVB mice. Mas receptor antagonists D-Ala-Ang-(1–7) (A779) or D-Pro 7-Ang-(1–7) enhanced the contraction induced by PHE only in vessels from FVB mice. Ang-(1–7) caused a relaxation response only in E + vessels from FVB mice. Transfer of donor solution from PVAT+ vessels to PVAT− recipient vessels caused a relaxation response among FVB vessels and not among vessels from K/O mice. Significance Mas receptors are essential in mediating the endothelium-dependent relaxation response induced by PVAT, therefore highlighting the important role of Ang-(1–7) in the control of vascular functions through PVAT.

The Effect of Supplementation of Grape Seed Proanthocyanidin Extract on Vascular Dysfunction in Experimental Diabetes

Increased oxidative stress and impaired endothelium-dependent relaxation could underlie many of the vascular complications associated with diabetes. We aimed to investigate the effect of supplementation with grape seed proanthocyanidin extract (GSPE), a natural antioxidant, on vascular responses and oxidative stress in streptozotocin-induced diabetic rats. Male Sprague-Dawley rats were divided into three groups: control rats, untreated diabetic rats, and GSPE (100 mg/kg, for 6 weeks)-supplemented diabetic rats. Thoracic aorta rings of the rats were mounted in organ baths, and relaxant responses to acetylcholine (ACh), A23187, and sodium nitroprusside (SNP) were assayed in tissues precontracted with 60 mM KCl. Plasma samples used for the measurement of malondialdehyde (MDA) level and superoxide dismutase (SOD) activity. The endothelium-dependent relaxations in response to ACh and A23187 were impaired, but endothelium-independent relaxation in response to SNP did not change in diabetic rats. Supplementation with GSPE significantly improved the relaxant responses to ACh and A23187. The MDA level was significantly elevated and the plasma SOD activity was decreased in diabetic rats, but supplementation with GSPE attenuated the elevated MDA levels and increased plasma SOD activity. Thus supplementation of GSPE may attenuate oxidative stress through the inhibition of lipid peroxidation and may restore endothelial function and reduce the risk of vascular disease in diabetes.

No Superoxide—No Stress?

NADPH oxidases of the Nox family are enzymes whose only known function is the production of reactive oxygen species (ROS). Since the first report on a vascular NADPH oxidase by Griendling et al in 1994,1 several thousand publications have been devoted to this topic. The general impression is that under physiological conditions, Nox proteins contribute to vascular signaling, whereas the overactivation and induction of NADPH oxidases promote vascular disease.2 See accompanying article on page 1368 In the vascular system, the NADPH oxidases Nox1, Nox2, Nox4, and Nox5 are expressed. Unlike the case with the other vascular Nox homologues, the activity of Nox4 appears to be predominantly controlled by its expression level, and proinflammatory mediators that induce Nox1 or Nox2 instead appear to suppress Nox4 expression.3 Nox4 is also the only vascular homolog that directly produces hydrogen peroxide (H2O2) and thus is incapable of scavenging nitric oxide (NO) or producing peroxynitrite (ONOO−).4 As a consequence of these unique properties, so far little consensus regarding the physiological function of Nox4 has been reached.3 In this issue of Arteriosclerosis, Thrombosis, and Vascular Biology , Ray et al report the generation and characterization of a transgenic mouse with endothelial-specific Nox4 overexpression.5 Vascular segments and endothelial cells of these animals had a significant increase in H2O2 generation that was sufficient to result in a substantial increase in the oxidation of peroxiredoxin 1. Despite these signs of increased protein oxidation, the blood pressure of the animals was lower under basal conditions and after angiotensin II treatment. Furthermore, endothelium-dependent relaxation was enhanced compared with wild-type animals. The latter effects were sensitive to catalase ex vivo and N -acetylcysteine in vivo, suggesting that they were mediated by H2 …

A therapeutic approach to treat cardiovascular dysfunction of diabetes

Diabetes greatly increases risk of cardiovascular dysfunction and interruptions of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) have been shown to reduce the risk by alteration in extracellular matrix. We hypothesized that minocycline induced MMP-2 and MMP-9 inhibition can be enhanced by aspirin (through its COX and tPA inhibitory action) and this combination can reduce cardiovascular dysfunction of diabetes. Four weeks after diabetes induction (streptozotocin, 55 mg/kg, i.p.), rats were treated with minocycline (50 mg/kg, p.o.), aspirin (50 mg/kg, p.o.), or minocycline (50 mg/kg, p.o.) plus aspirin (50 mg/kg, p.o.) for a period of next four weeks. At the end of eighth week arterial pressure, heart rate and left ventricular pressure were recorded. Contractile response to phenylephrine (10(-5) M) and relaxation responses to acetylcholine (10(-9)-10(-4) M) were obtained from aortic rings of diabetic rats. Gel zymography was performed to evaluate MMP-2 and MMP-9 levels. Heart rate, mean arterial pressure, dp/dt(max) and dp/dt(min) were found significantly decreased in STZ diabetic rats when compared with normoglycemic group. Treatment with combination of minocycline and aspirin significantly ameliorate these compared to vehicle treated diabetic group. Endothelium-dependent relaxation responses induced by acetylcholine were decreased in diabetic rats and significantly higher in combination treated group. Collagen, MMP-2 and MMP-9 levels were significantly decreased in combined treated group when compared with diabetic control. Present study revealed that aspirin potentate minocycline induced MMP-2 and MMP-9 inhibition to ameliorate cardiovascular dysfunction of diabetes and this combination can be an approach for the treatment.

Protein Kinase CβII-Mediated Phosphorylation of Endothelial Nitric Oxide Synthase Threonine 495 Mediates the Endothelial Dysfunction Induced by FK506 (Tacrolimus)

FK506 [tacrolimus; hexadecahydro-5,19-dihydroxy-3-[2-(4-hydroxy-3-methoxycyclohexyl)-1-methylethenyl]-14,16-dimethoxy-4,10,12,18-tetramethyl-8-(2-propenyl)-15,19-epoxy-3H-pyrido[2,1-c][1,4]oxa-azacyclotricosine-1,7,20,21(4H,23H)-tetrone] is used clinically to reduce the incidence of allograft rejection; however, chronic administration leads to endothelial dysfunction and hypertension. We have previously shown that FK506 activates Ca(2+)/diacylglycerol-dependent conventional protein kinase C (cPKC), which phosphorylates endothelial nitric oxide synthase (eNOS) at one of its inhibitory sites, Thr495. However, which cPKC isoform is responsible for phosphorylating eNOS Thr495 is unknown. The aim of the current study was to determine the cPKC isoform that is activated by FK506, leading to decreased endothelial function. FK506 reduced endothelium-dependent relaxation responses, yet had no effect on endothelium-independent relaxation responses in aortas from control mice. Of the various cPKC isoforms, only the administration of a PKCβ(II) isoform-specific peptide inhibitor restored aortic relaxation responses to that of controls. In aortic endothelial cells, FK506 significantly increased PKCβ(II) activation compared with vehicle-treated controls, and this was prevented by a PKCβ(II) isoform-specific peptide inhibitor. In addition, a PKCβ(II) isoform-specific peptide inhibitor prevented the increase in eNOS Thr495 phosphorylation induced by FK506. Taken together, our results indicate that β(II) is the cPKC isoform responsible for phosphorylating eNOS at the inhibitory site Thr495 in response to FK506. PKCβ(II) inhibition could prove beneficial in ameliorating the endothelial dysfunction and hypertension in patients treated with FK506.

Transplantation of Endothelial Progenitor Cells Improves Pulmonary Endothelial Function and Gas Exchange in Rabbits with Endotoxin-Induced Acute Lung Injury

Circulating endothelial progenitor cells (EPCs) have been therapeutically applied to aid vascular repair and myocardial regeneration. The number of circulating EPCs also provides invaluable outcome prediction for fatal diseases such as acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). However, evidence for the therapeutic potential of EPCs in subjects with ALI/ADRS is limited. Circulating EPCs were obtained from rabbits using Ficoll centrifugation. One week after culturing EPCs in endothelial growth medium-2, ALI was induced in rabbits by intratracheal instillation of lipopolysaccharide (500 μg/kg). Autologous EPCs or saline were administered IV after induction of ALI and animals were killed 2 days later. Pulmonary artery endothelial function and gas exchange were determined. Degrees of lung injury were assessed by alveolocapillary permeability, lung hemoglobin content, and myeloperoxidase activity. In comparison with controls, Po(2) in arterial blood was significantly elevated and pulmonary artery endothelium-dependent relaxation response was restored in rabbits receiving EPC transplantation. Lung water, Evan's blue, and bronchoalveolar lavage protein contents were significantly reduced in the EPC transplanted group, indicating a better preservation of the alveolocapillary membrane. Transplantation of EPCs decreased the lung hemoglobin level. Furthermore, expressions of CD11b and myeloperoxidase activity were also suppressed after administration of EPCs. Transplantation of EPCs restored pulmonary endothelial function, preserved integrity of the alveolocapillary barrier and suppressed the lung inflammatory response, thereby improving pulmonary gas exchange in rabbits with intratracheal lipopolysaccharide-induced ALI. Transplantation of EPCs can be a novel cell-based, endothelium-targeted therapeutic strategy for prevention and treatment of ALI/ARDS.

Effect of post recruitment maneuver ventilation by different tidal volume on lung vascular endothelial diastole function in rats with acute lung injury.

This study aimed to observe the effect of recruitment maneuver (RM) and post-RM ventilation at different tidal volume on lung vascular diastole endothelial function in rats with acute lung injury (ALI). A ALI rat model was produced by intravenous infusion of lipopolysaccharide (6 mg/ kg). Twenty-five rats were randomly divided into five groups: control group (n=5), ALI group (n=5), low tidal volume group (LV group, VT 6 mL/kg, n=5), sustained inflation (SI) with low tidal volume group (SI+LV group, VT 6 mL/kg, n=5), and SI with moderate tidal volume group (SI+MV group, VT 12 mL/ kg, n=5). RM was performed with SI, airway pressure 30 cmH2O for 30 seconds, and positive end-expiratory pressure (PEEP) was set to 5 cmH2O. Lung tissue was taken after 5 hours of mechanical ventilation. Mean arterial blood pressure (MAP) was monitored during the experiment. Endothelin-1 (ET-1), endothelial nitricoxide synthase (eNOS), Ach-induced endothelium-dependent relaxation response of isolated pulmonary artery rings were determined at 5 hours. LPS increased ET-1 level, decreased the expression of eNOS in lung tissue, impaired the Ach-induced endothelium-dependent relaxation response in the pulmonary artery, without obvious effect on systemic hemodynamics. SI+LV significantly reduced LPS-induced elevation of ET-1 level, increased the expression of eNOS, significantly improved endothelial dysfunction, and improved the dysfunction of endothelium-dependent relaxation in the pulmonary artery. RM with a high or low tidal volume ventilation could improve the lung vascular endothelial function of rats with acute lung injury, and RM with low tidal volume ventilation could lower significantly the injury of lung vascular endothelial diastole function in rats with acute lung injury.

Red wine polyphenols correct vascular function injured by chronic carbon tetrachloride intoxication

The aim of the study was to evaluate the effect of red wine polyphenols extract Provinols™ on the development of cardiovascular injury in the model of carbon tetrachloride (CCl4) intoxication. We followed the thoracic aorta vasoactivity and left ventricle nitric oxide (NO) synthase activity in male Wistar rats. In the preventive experiment lasting for 12 weeks the control group, the group receiving CCl4 (0.5 ml/kg) two times a week subcutaneously, the group receiving Provinols™ (30 mg/kg/day) in drinking water and the group receiving CCl4+Provinols™ was used. In the recovery experiment, the initial 12 weeks of CCl4 treatment were followed by 3 weeks of spontaneous recovery or recovery with Provinols™. CCl4-intoxication resulted in the injury of vasoactivity which was demonstrated by the inhibition of acetylcholine-induced relaxation as well as noradrenaline-induced contraction. In the preventive as well as recovery experiment administration of polyphenols refreshed endothelium-dependent relaxant response and normalized inhibited contraction to adrenergic stimuli. Provinols™ treatment significantly increased NO-synthase activity in all groups. The results revealed beneficial effects of red wine polyphenols on vascular function injured by chronic CCl4 intoxication. The correction of endothelial function seems to be attributed to the activation of NO pathway by polyphenols.

Resveratrol Improves Myocardial Perfusion in a Swine Model of Hypercholesterolemia and Chronic Myocardial Ischemia

Resveratrol may provide protection against coronary artery disease. We hypothesized that supplemental resveratrol will improve cardiac perfusion in the ischemic territory of swine with hypercholesterolemia and chronic myocardial ischemia. Yorkshire swine were fed either a normal diet (control, n=7), a hypercholesterolemic diet (HCC, n=7), or a hypercholesterolemic diet with supplemental resveratrol (100 mg/kg/d orally, HCRV, n=7). Four weeks later, an ameroid constrictor was placed on the left circumflex artery. Animals underwent cardiac MRI and coronary angiography 7 weeks later before euthanasia and tissue harvest. Total cholesterol was lowered about 30% in HCRV animals (P<0.001). Regional wall motion analysis demonstrated a significant decrease in inferolateral function from baseline to 7 weeks in HCC swine (P=0.04). There was no significant change in regional function in HCRV swine from baseline to 7 weeks (P=0.32). Tissue blood flow during stress was 2.8-fold greater in HCRV swine when compared with HCC swine (P=0.04). Endothelium-dependent microvascular relaxation response to Substance P was diminished in HCC swine, which was rescued by resveratrol treatment (P=0.004). Capillary density (PECAM-1 staining) demonstrated fewer capillaries in both HCC and HCRV swine versus control swine (P=0.02). Immunoblot analysis demonstrated significantly greater expression in HCRV versus HCC swine of the following markers of angiogenesis: VEGF (P=0.002), peNOS (ser1177) (P=0.04), NFkB (P=0.004), and pAkt (thr308) (P=0.001). Supplemental resveratrol attenuates regional wall motion abnormalities, improves myocardial perfusion in the collateral dependent region, preserves endothelium-dependent coronary vessel function, and upregulates markers of angiogenesis associated with the VEGF signaling pathway.

Effects of tidal volume with different amount of gas after recruitment maneuver ventilation on lung vascular endothelial diastole function in rats with acute lung injury

Objective To observe the effects of recruitment maneuver (RM) and tidal volume with different amount of gas after RM ventilation on lung diastole function in rats with acute lung injury (ALI). Method ALI rat models were induced by intravenous infusion of lipopolysaccharide (LPS) in dose of 6 mg/kg. Twenty-five rats were randomly(random number) divided into control group ( n = 5), ALI group ( n = 5), low tidal volume group (LV group,VT= 6 mL/kg, n = 5), sustained inflation (SI) with low tidal volume (SI+ LV group, VT=6 mL/kg, n = 5), and SI with moderate tidal volume group (SI+ MV group, VT= 12 mL/kg, n = 5). The RM carried out by using SI with airway pressure 30 cmH-2O for 30 seconds, and the positive end-expiratory pressure (PEEP)was set at 5 cmH2O. Lung tissue was taken after mechanical ventilation for 5 hours. The mean arterial pressure (MAP) was monitored throughout the entire course of experiment. Endothelin-1 ( ET-1 ), endothelial nitricoxide synthase (eNOS), and acetylcholine-(Ach-) induced endothelium-dependent relaxation response of isolated pulmonary artery rings were investigated after mechanical ventilation for 5 hours. Results The LPS increased the ET-1 level in lung tissue, decreased the level of eNOS in lung tissue, and impaired the Ach-induced endothelium-dependent relaxation response in pulmonary vassals, without obvious influence on systemic hemodynamics. SI + LV significantly reduced LPS-induced elevation of ET-1 level, and increased the level of eNOS, and significantly lessened endothelial dysfunction and ameliorated dysfunction od endothelium-dependent relaxation in pulmonary vas sals. Conclusions RM with high tidal volume or lowtidal volume ventilation could improve the lung vascular endothelial function of rats with acute lung injury, and RM with low tidal volume ventilation could lessen more the injury of lung vascular endothelial diastole function in rats with acute lung injury. Key words: Acute lung injury; Recruitment maneuver; Low tidal volume; Lung vascular endothelium; Pulmonary artery diastole

Effect of hydrogen sulfide on rat pulmonary artery reactivity and injury induced by lipopolysaccharide

To explore the effects of hydrogen sulfide (H2S) on abnormal pulmonary artery reactivity and injury induced by lipopolysaccharide (LPS). Seventy-two rats were divided into four groups randomly according to table of random number: control group, LPS group, sodium hydrosulfide (NaHS) as a donor of H2S+LPS group and NaHS+normal saline (NS) group (n=18 in each group). Rats were challenged with 0.8 ml/kg LPS (200 microg/200 microl) by intratracheal instillation. NaHS (28 micromol/kg, 0.5 ml) was injected intraperitoneally 10 minutes before LPS instillation and 2 hours after LPS instillation. Twelve hours later, 6 rats from each group were sacrificed. Blood from carotid artery was collected to detect H2S content in serum. After that, pulmonary artery rings (PARs) were prepared carefully, then the contraction response of PARs to phenylephrine (PE, 10(-6) mol/L) and the endothelium-dependent relaxation response to acetylcholine (ACh, 10(-6) mol/L) were measured using isolated vascular ring tension detecting technique. Six rats from each group were sacrificed for determination of malondialdehyde (MDA) content of pulmonary artery, and the remaining 6 rats from each group were sacrificed for observation of morphological changes in pulmonary artery tissue. Compared with control group, after LPS instillation, the contraction response (g/mg) of PARs to PE increased greatly (0.86+/-0.20 vs. 0.56+/-0.13), the relaxation response to ACh significantly decreased [(65.18+/-7.05)% vs. (84.13+/-8.84)%]. MDA content (mmol/L) in pulmonary artery tissues increased (32.03+/-7.81 vs. 5.82+/-0.92), and H2S (micromol/L) content in serum decreased (175.23+/-27.36 vs. 238.12+/-16.38). Changes of all results were significant (P<0.05 or P<0.01). The pulmonary artery tissue and endothelium were injured. However, these changes were reversed by administration of NaHS intraperitoneally, the contraction response of PARs to PE decreased [(0.61+/-0.17) g/mg], the relaxation response to ACh increased [(82.92+/-9.71)%], MDA content in pulmonary artery tissue decreased [(16.88+/-3.54) mmol/L] and H2S content in serum increased [(242.70+/-38.80) micromol/L]. There was significant difference in all results (P<0.05 or P<0.01). The injury to the tissue induced by LPS were alleviated significantly. There was no statistical difference in above indexes between NaHS+NS group and control group, except for the level of H2S. Exogenous H2S could not only reverse abnormal vascular reactivity of PARs induced by LPS but also alleviate the injury to pulmonary artery tissue induced by LPS.

Endothelium-dependent and -independent coronary relaxation induced by urocortin.

Urocortin, a newly identified polypeptide, possesses cardiac effects. However, the underlying mechanism of its coronary action is still unclear. In the present study we investigated the possible role of endothelial nitric oxide and Ba2+-sensitive K+ channels in the endothelium-dependent relaxant response to urocortin in the isolated rat left anterior descending coronary arteries. Changes of vessel tone were measured in microvessel myographs. Urocortin produced both endothelium-dependent and -independent relaxation with IC50 of 2.52 nM and 16.5 nM, respectively. Denuation of endothelium decreased the relaxing potency of urocortin. In the endothelium-intact rings pretreated with 100 microM N(G)-nitro-L-arginine methyl ester (L-NAME) or 10 microM 1H-[1,2,4]oxadiazolo[4,2-alpha]quinoxalin-1-one (ODQ), the urocortin-induced relaxation was similar to that observed in endothelium-denuded rings. The relaxant response to urocortin was markedly reduced in endothelium-intact rings preconstricted by 35 mM K+. Pretreatment with 100 microM BaCl2 significantly reduced urocortin-induced relaxation without an effect on the maximum relaxation. Combined treatment with BaCl2 plus L-NAME did not produce additive inhibition. In contrast, BaCl2 did not alter urocortin-induced relaxation in the endothelium-denuded rings. In the endothelium-denuded rings, BaCl2 at 100 microM also inhibited nitric oxide donor-induced relaxation. In conclusion, our results suggest that urocortin-induced endothelium-dependent relaxation of rat coronary arteries is primarily mediated by endothelial nitric oxide and subsequent activation of Ba2+-sensitive K+ channels. The urocortin-induced endothelium-dependent relaxation appears to be cyclic GMP-dependent.

Upregulation of Proteinase-Activated Receptor-2 and Increased Response to Trypsin in Endothelial Cells after Exposure to Oxidative Stress in Rat Aortas

Background/Aims: The effects of oxidative stress on the vascular responsiveness to the agonists of proteinase-activated receptors (PARs) were investigated. Methods: Serum-free incubation was utilized to impose oxidative stress to isolated rat aortas. Spontaneously hypertensive rats (SHR) were investigated as a model of in vivo oxidative stress. Results: Thrombin, trypsin, PAR₁-activating peptide (PAR₁-AP), PAR₂-AP and PAR₄-AP induced little or no effect in the aortas of female Wistar-Kyoto rats (WKY). Serum-free incubation induced endothelium-dependent relaxant responses to PAR₂ agonists, but not PAR₁ or PAR₄ agonists, in a manner sensitive to diphenyleneiodonium or ascorbic acid. In male aortas, trypsin and PAR₂-AP induced a transient endothelium-dependent relaxation without serum-free incubation. The acetylcholine-induced endothelium-dependent relaxation and the sodium nitroprusside-induced endothelium-independent relaxation remained unchanged. Immunoblot analyses revealed the upregulation of PAR₂ in endothelial cells, which was abolished by either diphenyleneiodonium or ascorbic acid. Aortas of female SHR expressed a higher level of PAR₂ than WKY and responded to trypsin without serum-free incubation. Treatment with ascorbic acid attenuated the trypsin-induced relaxation and the PAR₂ expression in SHR. Conclusion: This study provides the first evidence that oxidative stress upregulates PAR₂ in endothelial cells, thereby enhancing the endothelium-dependent relaxant response to PAR₂ agonists in rat aortas.