Modulation of cardiac contractility through endothelin-1 release and myocardial mast cell degranulation

The aim of this study was to outline the consequences of a hypertonic saline-dextran-40 (HSD) infusion-induced peripheral flow stimulus on the ventricular function in closed-chest, pentobarbital-anesthetized dogs. We hypothesized that HSD-induced elevation in endothelin-1 (ET-1) and nitric oxide (NO) release can have a role in myocardial contractile responses; and that cardiac mast cells (MC) degranulation may be involved in this process. The consequences of disodium cromoglycate (a MC stabilizer) or ETR-p1/fl peptide (an endothelin-A receptor antagonist) treatment were evaluated. A 4 ml/kg iv HSD40 infusion significantly increased cardiac index and myocardial contractility, and resulted in a decreased peripheral resistance. The postinfusion period was characterized by significant plasma NO and ET-1 elevations, these hemodynamic and biochemical changes being accompanied by a decreased myocardial ET-1 content, NO synthase activity and enhanced myocardial MC degranulation. Disodium cromoglycate treatment inhibited the HSD40-induced elevations in myocardial contractility and MC degranulation, and similar hemodynamic changes were noted after treatment with ETR-p1/fl peptide, together with a normalized myocardial myocardial ET-1 content, NO synthesis and a significant reduction in MC degranulation. These results indicate that peripheral NO and ET-1 release modulates the cardiac contractility through myocardial ET-A receptor activation and MC degranulation.     

Nonspecific inhibition of nitric oxide synthesis evokes endothelin-dependent increases in myocardial contractility

The role of endogenous nitric oxide (NO) in modulating myocardial contractility is still unclear, in part because of unknown, secondary effects of blocking NO release. We hypothesized that the nonspecific inhibition of nitric oxide synthase (NOS) enhances endothelin-1 (ET-1) effects, which can play a role in ET-A receptor-dependent myocardial contractile responses. The myocardial contractility was estimated from the slope of the left ventricular end-systolic pressure–diameter relationship in closed-chest, pentobarbital-anesthetized dogs. Group 1 (n = 7) was the saline-treated control, while in groups 2 (n = 7) and 3 (n = 7) N-nitro-l-arginine (NNA, 4 mg kg^?1), a nonselective NOS blocker, was administered with or without pretreatment with the ET-A receptor antagonist ETR-P1/fl peptide (100 nmol kg^?1 iv). Plasma ET-1, nitrite/nitrate (NO_x) and blood superoxide levels were measured, and myocardial ET-1 content and xanthine oxidoreductase (XOR) activity were determined from myocardial biopsies. The infusion of NNA over 120 min decreased the plasma NO_x, significantly elevated the plasma ET-1 and blood superoxide levels, and in parallel greatly increased the left ventricular contractility as compared with the untreated controls [47.5 vs 30 mm Hg mm^?1]. The myocardial ET-1 content decreased simultaneously, while the XOR activity and blood superoxide level were significantly elevated. These effects, including NNA-induced positive inotropy, were significantly suppressed by pretreatment with ETR-P1/fl peptide. These results demonstrate that a diminished NO synthesis leads to a preponderant ET-1 effect, which increases myocardial contractility through an ET-A receptor-dependent mechanism.     

Role of cardiovascular nitric oxide system in C-type natriuretic peptide effects

The aims were to evaluate the role of cardiovascular nitric oxide (NO)-system in C-type natriuretic peptide (CNP) actions and to investigate receptor types and signaling pathways involved in this interaction. Wistar rats were infused with saline or CNP. Mean arterial pressure (MAP) and nitrites and nitrates (NOx) excretion were determined. NO synthase (NOS) activity and NOS expression (Western blot) were analyzed in atria, ventricle and aorta. CNP decreased MAP and increased NOx excretion. CNP estimulated NOS activity, inducing no changes on cardiac and vascular endothelial NOS expression. NOS activity induced by CNP was abolished by suramin and calmidazoliumand but it is not modified by anantin. CNP would interact with NPR-C receptor coupled via G proteins leading to the activation Ca(2+)-calmodulin dependent endothelial NOS, increasing NO production which would induce the reduction in cardiac myocyte contractility and ANP synthesis and secretion in right atria and the relaxation of vascular smooth muscle.     

The role of asymmetric dimethylarginine in the regulation of nitric oxide level in rats with acute renal injury

Nitric oxide (NO) is synthesized from arginine (ARG) by NO synthase (NOS). Asymmetric dimethylarginine (ADMA), a competitive inhibitor of NOS, participates in the endogenous regulation of NO synthesis. The main amount of ADMA is enzymatically degraded by dimethylarginine dimethylaminohydrolase (DDAH) widely expressed in renal tissue. The aim of our study was to compare the changes in DDAH activity and ARG synthesis in kidneys, ADMA and ARG concentration in plasma and their urinary excretion under physiological conditions and in acute renal injury (ARI) induced by glycerol in rats. Urinary nitrite/nitrate excretion (NOx) was estimated as an indicator of whole-body NO synthesis. DDAH activity was decreased, ADMA excretion was increased and plasma ADMA did not change in ARI. Plasma ARG concentration, renal ARG synthesis and urinary NOx excretion were decreased. In conclusion, the diminished enzymatic hydrolysis of the NOS inhibitor ADMA and the reduced synthesis of the NOS substrate ARG might affect NO production in ARI.     

Relationship between endothelin 1 and nitric oxide system in the corpus luteum regression

The present study was designed to investigate the relationship between the nitric oxide (NO) system and endothelin 1 (ET-1) in the mechanism of corpus luteum (CL) development and consequently regression in rats. We first evaluated basal ET-1 levels in ovarian tissue from rats with different stages of CL development. An increased ovarian ET-1 content was found during CL regression. In a dose-department response, ET-1 decreased progesterone (P4) and increased prostaglandin (PG) PGF2alpha production. By means of a competitive nitric oxide synthase (NOS) inhibitor: L-nitro arginine methyl ester (L-NAME) and a slow NO releasing: diethyl-aminetriamine (DETA-NONOate), we demonstrated that NO system could be the intermediary in the ET-1 diminishing P4 production. The Western blot analysis revealed an increase on iNOS while eNOS protein expression was diminished. We also found a diminution of total NOS activity after ET-1 treatment. These data suggest the existence of a functional relationship between ET-1 and NOS isoforms leading the regulation of CL functionally.     

Intense exercise causes decrease in expression of both endothelial NO synthase and tissue NOx level in hearts

Cardiac myocytes produce nitric oxide (NO). We studied the effects of intense exercise on the expression of NO synthase (NOS) and the tissue level of nitrite (NO(2)(-))/nitrate (NO(3)(-)) (i.e., NOx), which are stable end products of NO in the heart. Rats ran on a treadmill for 45 min. Immediately after this exercise, the heart was quickly removed. Control rats remained at rest during the same 45-min period. The mRNA level of endothelial NOS (eNOS) in the heart was markedly lower in the exercised rats than in the control rats. Western blot analysis confirmed downregulation of eNOS protein in the heart after exercise. Tissue NOx level in the heart was significantly lower in the exercised rats than in the control rats. The present study revealed for the first time that production of NO in the heart is decreased by intense exercise. Because NO attenuates positive inotropic and chronotropic responses to beta(1)-adrenergic stimulation in the heart, the decrease in cardiac production of NO by intense exercise may contribute to the acceleration of increase in myocardial contractility and heart rate during intense exercise.     

一氧化氮在防止心肌肥厚反应中的作用及其机制

本工作从整体和细胞水平探讨一氧化氮（ＮＯ）在防止心肌肥厚反应中的作用及其机制。压力超负荷心肌肥厚大鼠左心室肌ＮＯ含量减少。内源性ＮＯ可能通过非ｃＧＭＰ依赖机制减轻压力超负荷引起的心肌肥厚。在培养的新生大鼠心肌细胞中血管紧张素Ⅱ（ＡⅡ）、内皮素－１（ＥＴ－１）和去甲肾上腺素（ＮＥ）通过各自的受体和偶连的Ｇ蛋白,一方面引起心肌细胞肥大;另一方面抑制一氧化氮合酶（ＮＯＳ）活性和ＮＯ生成。心肌细胞和非心肌     

Impact of NO on ET-1- and AM-induced inotropic responses: potentiation by combined administration

We characterize herein the impact of myocardial nitric oxide (NO) synthesis on the inotropic response to two cardioactive peptides, endothelin-1 (ET-1) and adrenomedullin (AM). In the isolated perfused rat heart preparation, intracoronary infusion of AM (0.03 and 1 nmol/l) and ET-1 (0.08 and 1 nmol/l) for 30 min induced a dose-dependent, gradual increase in developed tension, the maximal responses being equal. Inhibition of myocardial NO synthase (NOS) by N(omega)-nitro-L-arginine methyl ester (L-NAME; 300 micromol/l) enhanced the inotropic response to ET-1 at a concentration of 1 nmol/l; meanwhile, the effect of AM was not augmented significantly. The inotropic response to simultaneous administration of low, equipotent doses of AM (0.03 nmol/l) and ET-1 (0.08 nmol/l) was significantly smaller than that of either peptide alone. This depressed response was more than overcome by concomitant administration of L-NAME. In conclusion, this study reveals that the maximal inotropic response to ET-1 can be augmented by inhibition of myocardial NOS, whereas it has only a minor impact on the effect of AM. The inotropic response to combined administration of low doses of AM and ET-1 is substantially suppressed by endogenous NO, whereas the individual effects of the peptides at these doses are not the subject of secondary modulation by NO.     

Hypertonic sodium resuscitation after hemorrhage improves hemodynamic function by stimulating cardiac, but not renal, sympathetic nerve activity

Small volume hypertonic saline resuscitation can be beneficial for treating hemorrhagic shock, but the mechanism remains poorly defined. We investigated the effects of hemorrhagic resuscitation with hypertonic saline on cardiac (CSNA) and renal sympathetic nerve activity (RSNA) and the resulting cardiovascular consequences. Studies were performed on conscious sheep instrumented with cardiac (n=7) and renal (n=6) sympathetic nerve recording electrodes and a pulmonary artery flow probe. Hemorrhage (20 ml/kg over 20 min) caused hypotension and tachycardia followed by bradycardia, reduced cardiac output, and abolition of CSNA and RSNA. Resuscitation with intravenous hypertonic saline (1.2 mol/l at 2 ml/kg) caused rapid, dramatic increases in mean arterial pressure, heart rate, and CSNA, but had no effect on RSNA. In contrast, isotonic saline resuscitation (12 ml/kg) had a much delayed and smaller effect on CSNA, less effect on mean arterial pressure, no effect on heart rate, but stimulated RSNA, although the plasma volume expansion was similar. Intracarotid infusion of hypertonic saline (1 ml/min bilaterally, n=5) caused similar changes to intravenous administration, indicating a cerebral component to the effects of hypertonic saline. In further experiments, contractility (maximum change in pressure over time), heart rate, and cardiac output increased significantly more with intravenous hypertonic saline (2 ml/kg) than with Gelofusine (6 ml/kg) after hemorrhage; the effects of hypertonic saline were attenuated by the β-receptor antagonist propranolol (n=6). These results demonstrate a novel neural mechanism for the effects of hypertonic saline resuscitation, comprising cerebral stimulation of CSNA by sodium chloride to improve cardiac output by increasing cardiac contractility and rate and inhibition of RSNA.     

EPA effect on NOS gene expression and on NO level in endothelin-1-induced hypertrophied cardiomyocytes

Cardiomyocytes release (or metabolize) several diffusible agents (e.g., nitric oxide [NO], endothelin-1 [ET-1], and angiotensin II) that exert direct effects on myocyte function under various pathologic conditions. Although cardiac hypertrophy is a compensatory mechanism in response to different cardiovascular diseases, there can be a pathologic transition in which the myocardium becomes dysfunctional. Recently, NO has been found to be an important regulator of cardiac remodeling. Specifically, NO has been recognized as a potent antihypertrophic and proapoptotic mediator in cultured cardiomyocytes. We demonstrated that ET-1-induced hypertrophic remodeling in neonatal cardiomyocytes was arrested by pretreatment with eicosapentaenoic acid (EPA), a major component of fish oil. In some recent studies, EPA has demonstrated cardioprotective effects by modulating NO. This study investigated the changes in NO synthase (NOS) in ET-1-induced hypertrophied cardiomyocytes and in total levels of nitrates and nitrites. Ventricular cardiomyocytes were isolated from 2-day-old Sprague-Dawley rats and were cultured in D-MEM/Ham F12 supplemented with 0.1% fatty acid-free bovine serum albumin for 3 days. At Day 4 of culture, the cardiomyocytes were divided into three groups: control group, ET-1 (0.1 nM) group, and ET-1 pretreated with EPA (10 microM) group. NOS gene expression was evaluated 24 hrs after treatment using real-time polymerase chain reaction. Endothelial NOS (eNOS) mRNA expression was decreased in the ET-1 group compared with controls and was unchanged by pretreatment with EPA. mRNA expression of inducible NOS (iNOS) was significantly increased in ET-1-treated cardiomyocytes and was suppressed by EPA pretreatment. Neuronal NOS gene expression and total NO level did not exhibit a statistically significant change in any of the groups. There may be some interaction between ET-1, eNOS, and iNOS in ET-1-induced and EPA-regressed hypertrophied cardiomyocytes that suppress iNOS expression without modulating total NO level or eNOS gene expression.     

Akt activates NOS3 and separately restores barrier integrity in H2O2-stressed human cardiac microvascular endothelium

The integrity of microvascular endothelium is an important regulator of myocardial contractility. Microvascular barrier integrity could be altered by increased reactive oxygen species (ROS) stress seen within minutes after cardiac arrest resuscitation. Akt and its downstream target nitric oxide (NO) synthase (NOS)3 can protect barrier integrity during ROS stress, but little work has studied these oxidant stress responses in human cardiac microvascular endothelial cells (HCMVEC). We, therefore, studied how ROS affects barrier function and NO generation via Akt and its downstream target NOS3 in HCMVEC. HCMVEC exposed to 500 microM H2O2 had increased Akt phosphorylation within 10 min at both Ser-473 and Thr-308 sites, an effect blocked by the phosphatidylinositol 3-kinase inhibitor LY-294002. H2O2 also induced NO generation that was associated with NOS3 Ser-1177 site phosphorylation and Thr-495 dephosphorylation, with Ser-1177 effects attenuated by LY-294002 and an Akt inhibitor, Akt/PKB signaling inhibitor-2 (API-2). H2O2 induced significant barrier disruption in HCMVEC within minutes, but recovery started within 30 min and normalized over hours. The NOS inhibitor Nomega-nitro-L-arginine methyl ester (200 microM) blocked NO generation but had no effect on H2O2-induced barrier permeability or the recovery of barrier integrity. By contrast, the Akt inhibitor API-2 abrogated HCMVEC barrier restoration. These results suggest that oxidant stress in HCMVEC activates NOS3 via Akt. NOS3/NO are not involved in the regulation of H2O2-affected barrier function in HCMVEC. Independent of NOS3 regulation, Akt proves to be critical for the restoration of barrier integrity in HCMVEC.     

蜂花烧烫伤膏对烧伤大鼠血管内皮细胞的保护作用研究

目的:研究蜂花烧烫伤膏对烧伤大鼠血管内皮细胞的保护作用,探讨其治疗烧烫伤的作用机制。方法:热水烧伤法建立大鼠30%TBSA深Ⅱ度烧伤模型。造模成功后随机分为对照组、烧伤延迟复苏组、京万红组与蜂花烧烫伤膏组,分别立即给予相应干预,并比较烫伤后1 h、3 h、6 h、12 h、24 h和48 h的肿瘤坏死因子-α(TNF-α)、内皮素(ET-1)、一氧化氮(NO)与ET-1/NO比值水平。结果:与对照组大鼠比较,烧伤延迟复苏组TNF-α、ET-1与ET-1/NO比值在伤后1 h即明显升高,12 h达高峰后逐渐下降;NO的含量在伤后1h即显著升高,6 h达高峰后逐渐下降;48h后仍与对照组有较大差异。与烧伤延迟复苏组比较,蜂花烧烫伤膏组各时相点的TNF-α、ET-1、NO和ET-1/NO比值均显著降低,但变化趋势基本一致。结论:蜂花烧烫伤膏通过降低TNF-α、ET-1和NO水平,优化ET-1/NO系统,起到保护烧伤大鼠血管内皮细胞的作用。     

Endothelial alterations during inhaled NO in lambs with pulmonary hypertension: implications for rebound hypertension

Clinically significant increases in pulmonary vascular resistance (PVR) have been noted upon acute withdrawal of inhaled nitric oxide (iNO). Previous studies in the normal pulmonary circulation demonstrate that iNO increases endothelin-1 (ET-1) levels and decreases endogenous nitric oxide synthase (NOS) activity, implicating an endothelial etiology for the increase in resistance upon iNO withdrawal. However, the effect of iNO on endogenous endothelial function in the clinically relevant pulmonary hypertensive circulation is unknown. The objective of this study was to determine the effects of iNO on endogenous NO-cGMP and ET-1 signaling in lambs with preexisting pulmonary hypertension secondary to increased pulmonary blood flow. Eight fetal lambs underwent in utero placement of an aortopulmonary vascular graft (shunt lambs). After delivery (4 wk), the shunt lambs were mechanically ventilated with iNO (40 ppm) for 24 h. After 24 h of inhaled NO, plasma ET-1 levels increased by 34.8% independently of changes in protein levels (P < 0.05). Contrary to findings in normal lambs, total NOS activity did not decrease during iNO. In fact, Western blot analysis demonstrated that tissue endothelial NOS protein levels decreased by 43% such that NOS activity relative to protein levels actually increased during iNO (P < 0.05). In addition, the beta-subunit of soluble guanylate cyclase decreased by 70%, whereas phosphodiesterase 5 levels were unchanged (P < 0.05). Withdrawal of iNO was associated with an acute increase in PVR, which exceeded baseline PVR by 45%, and a decrease in cGMP concentrations to levels that were below baseline. These data suggest that the endothelial response to iNO and the potential mechanisms of rebound pulmonary hypertension are dependent upon the underlying pulmonary vasculature.     

Contribution of oxygen radicals to altered NO-dependent pulmonary vasodilation in acute and chronic hypoxia

Chronic hypoxia (CH) increases pulmonary arterial endothelial nitric oxide (NO) synthase (NOS) expression and augments endothelium-derived nitric oxide (EDNO)-dependent vasodilation, whereas vasodilatory responses to exogenous NO are attenuated in CH rat lungs. We hypothesized that reactive oxygen species (ROS) inhibit NO-dependent pulmonary vasodilation following CH. To test this hypothesis, we examined responses to the EDNO-dependent vasodilator endothelin-1 (ET-1) and the NO donor S-nitroso-N-acetyl penicillamine (SNAP) in isolated lungs from control and CH rats in the presence or absence of ROS scavengers under normoxic or hypoxic ventilation. NOS was inhibited in lungs used for SNAP experiments to eliminate influences of endogenously produced NO. Additionally, dichlorofluorescein (DCF) fluorescence was measured as an index of ROS levels in isolated pressurized small pulmonary arteries from each group. We found that acute hypoxia increased DCF fluorescence and attenuated vasodilatory responses to ET-1 in lungs from control rats. The addition of ROS scavengers augmented ET-1-induced vasodilation in lungs from both groups during hypoxic ventilation. In contrast, upon NOS inhibition, DCF fluorescence was elevated and SNAP-induced vasodilation diminished in arteries from CH rats during normoxia, whereas acute hypoxia decreased DCF fluorescence, which correlated with augmented reactivity to SNAP in both groups. ROS scavengers enhanced SNAP-induced vasodilation in normoxia-ventilated lungs from CH rats similar to effects of hypoxic ventilation. We conclude that inhibition of NOS during normoxia leads to greater ROS generation in lungs from both control and CH rats. Furthermore, NOS inhibition reveals an effect of acute hypoxia to diminish ROS levels and augment NO-mediated pulmonary vasodilation.     

Nitric oxide and protein nitration in the cystic fibrosis airway

Cystic fibrosis (CF), characterized by chronic airway infection and inflammation, ultimately leads to respiratory failure. Exhaled nitric oxide (NO), elevated in most inflammatory airway diseases, is decreased in CF, suggesting either decreased production or accelerated metabolism of NO. The present studies performed on two groups of CF patients provide further support for a disordered NO airway metabolism in CF respiratory tract disease. Despite confirmation of subnormal NOS2 in the CF airway epithelium, alternative isoforms NOS1 and NOS3 were present, and inflammatory cells in the CF airway expressed abundant NOS2. Increased immunohistochemical staining for nitrotyrosine was demonstrated in lung tissues from patients with CF as compared to control. To our knowledge, this is the first report localizing nitrotyrosine in diseased CF lung tissue. While the relative NOS2 deficiency in CF respiratory tract epithelium may contribute to the lower expired NO levels, these results suggest that increased metabolism of NO is also present in advanced CF lung disease. The significance of altered NO metabolism and protein nitration in CF remains to be fully elucidated.     

Effects of exercise training of 8 weeks and detraining on plasma levels of endothelium-derived factors, endothelin-1 and nitric oxide, in healthy young humans

Vascular endothelial cells produce nitric oxide (NO), which is a potent vasodilator substance and has been proposed as having antiatherosclerotic property. Vascular endothelial cells also produce endothelin-1 (ET-1), which is a potent vasoconstrictor peptide and has potent proliferating activity on vascular smooth muscle cells. Therefore, ET-1 has been implicated in the progression of atheromatous vascular disease. Because exercise training has been reported to produce an alteration in the function of vascular endothelial cells in animals, we hypothesized that exercise training influences the production of NO and ET-1 in humans. The purpose of the present study was to examine whether chronic exercise could influence the plasma levels of NO (measured as the stable end product of NO, i.e., nitrite/nitrate [NOx]) and ET-1 in humans. Eight healthy young subjects (20.3 +/- 0.5 yr old) participated in the study and exercised by cycling on a leg ergometer (70% VO2max for 1 hour, 3-4 days/week) for 8 weeks. Venous plasma concentrations of NOx and ET-1 were measured before and after (immediately before the end of 8-week exercise training) the exercise training, and also after the 4th and 8th week after the cessation of training. The VO2max significantly increased after exercise training. After the exercise training, the plasma concentration of NOx significantly increased (30.69 +/- 3.20 vs. 48.64 +/- 8.16 micromol/L, p < 0.05), and the plasma concentration of ET-1 significantly decreased (1.65 +/- 0.14 vs. 1.23 +/- 0.12 pg/mL, p < 0.05). The increase in NOx level and the decrease in ET-1 level lasted to the 4th week after the cessation of exercise training and these levels (levels of NOx and ET-1) returned to the basal levels (the levels before the exercise training) in the 8th week after the cessation of exercise training. There was a significant negative correlation between plasma NOx concentration and plasma ET-1 concentration. The present study suggests that chronic exercise causes an increase in production of NO and a decrease in production of ET-1 in humans, which may produce beneficial effects (i.e., vasodilative and antiatherosclerotic) on the cardiovascular system.     

Endothelin receptor antagonist reverses decreased NO system in the kidney in vivo during exercise

Vascular endothelial cells produce endothelin (ET)-1, a potent vasoconstrictor peptide, and nitric oxide (NO), a potent vasodilator substance. There are interactions between ET-1 and NO. Exercise results in a marked decrease in renal blood flow. We previously reported that exercise causes an increase of ET-1 production in the kidney, whereas production of NO in the kidney is decreased. Furthermore, we recently revealed that the magnitude of decrease in blood flow to the kidney during exercise was significantly attenuated by the administration of the endothelin-A (ET(A)) receptor antagonist, strongly suggesting that endogenously increased ET-1 participates in the decrease of blood flow in the kidney during exercise. Because it was demonstrated that ET-1 depresses NO synthase (NOS) activity of cultured cells in vitro, we hypothesized that an increase of ET-1 production in kidney during exercise contributes to a decrease of NO production in kidney in vivo. We studied whether administration of the ET(A) receptor antagonist attenuates the decreases of NOS activity and NO production in the kidney during exercise. Rats performed treadmill running for 30 min after pretreatment with an ET(A) receptor antagonist (TA-0201, 0.5 mg/kg; TA-0201-treated exercise group) or vehicle (vehicle-treated exercise group). Control rats remained at rest (vehicle-treated sedentary group). Blood flow in the kidney was decreased by this exercise, but the magnitude of the decrease after pretreatment with TA-0201 was significantly smaller than that after pretreatment with vehicle. NOS activity in kidney was significantly lower in the vehicle-treated exercise group than in the vehicle-treated sedentary group, whereas that in the TA-0201-treated exercise group was significantly higher than that in the vehicle-treated exercise group. Expressions of endothelial NOS protein and NOx, the stable end product of NO, i.e., nitrite/nitrate, concentration in the kidney were significantly lower in the vehicle-treated exercise group than in the vehicle-treated sedentary group, whereas those in the TA-0201-treated exercise group were significantly higher than those in the vehicle-treated exercise group. The data suggest that increased ET-1 production in the kidney during exercise contributes to the decreases of NOS activity and NO production. Therefore, the present study provides a possibility that the exercise-induced increase in production of ET-1 in the kidney causes a decrease in blood flow in the kidney through two pathways, i.e., vasoconstrictive action and the action of attenuating NO production.     

Cryptotanshinone inhibits endothelin-1 expression and stimulates nitric oxide production in human vascular endothelial cells

The Chinese herb Salvia miltiorrhiza (SM) has been found to have beneficial effects on the circulatory system. In the present study, we investigated the effects of cryptotanshinone (derived from SM) on endothelin-1 (ET-1) expression in human umbilical vein endothelial cells (HUVECs). The effect of cryptotanshinone on nitric oxide (NO) in HUVECs was also examined. We found that cryptotanshinone inhibited basal and tumor necrosis factor-alpha (TNF-alpha) stimulated ET-1 secretion in a concentration-dependent manner. Cryptotanshinone also induced a concentration-dependent decrease in ET-1 mRNA expression. Cryptotanshinone increased basal and TNF-alpha-attenuated NO production in a dose-dependent fashion. Cryptotanshinone induced a concentration-dependent increase in endothelial nitric oxide synthase (eNOS) expression without significantly changing neuronal nitric oxide synthase (nNOS) expression in HUVECs in the presence or absence of TNF-alpha. NOS activities in the HUVECs were also induced by cryptotanshinone. Furthermore, decreased ET-1 expression in response to cryptotanshinone was not antagonized by the NOS inhibitor l-NAME. A gel shift assay further showed that TNF-alpha-induced Nuclear Factor-kappaB (NF-kappaB) activity was significantly reduced by cryptotanshinone. These data suggest that cryptotanshinone inhibits ET-1 production, at least in part, through a mechanism that involves NF-kappaB but not NO production.     

Nitric oxide-cGMP pathway is involved in endotoxin-induced contractile dysfunction in rat hearts.

The mechanisms by which endotoxemia causes cardiac depression have not been fully elucidated. The present study examined the involvement of nitric oxide (NO) in this pathology. Rats were infused with lipopolysaccharide (LPS) or saline, and the plasma and myocardial NO(2)(-) and NO(3)(-) (NOx) concentrations were measured before or 3, 6, and 24 h after treatment. The hearts were then immediately isolated and mounted in a Langendorff apparatus, and left ventricular developed pressure (LVDP) was determined before biochemical analysis of the myocardium. LPS injection effected the expression of inducible NO synthase (iNOS) in the myocardium, a marked increase in plasma and myocardial NOx levels, and a significant decline in LVDP compared with saline controls. The LPS-induced NO production and concomitant cardiac depression were most pronounced 6 h after LPS injection and were accompanied by a significant increase in myocardial cGMP content. Myocardial ATP levels were not significantly altered after LPS injection. Significant negative correlation was observed between LVDP and myocardial cGMP content, as well as between LVDP and plasma NOx levels. Aminoguanidine, an inhibitor of iNOS, significantly attenuated the LPS-induced NOx production and contractile dysfunction. Furthermore, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of soluble guanylate cyclase, significantly decreased myocardial cGMP content and attenuated the contractile depression, although aminoguanidine or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one was not able to completely reverse myocardial dysfunction. Our data suggest that endotoxin-induced contractile dysfunction in rat hearts is associated with NO production by myocardial iNOS and a concomitant increase in myocardial cGMP.