Regulation of endothelial nitric oxide synthase expression in the vascular wall and in mononuclear cells from hypercholesterolemic rabbits

Inducible Nitric Oxide Synthase/Nitric Oxide System as a Biomarker for Stress and Ease Response in Fish: Implication on Na+ Homeostasis During Hypoxia

The cellular and organismal response to stressor-driven stimuli evokes stress response in vertebrates including fishes. Fishes have evolved varied patterns of stress response, including ionosmotic stress response, due to their sensitivity to both intrinsic and extrinsic stimuli. Fishes that experience hypoxia, a detrimental stressor that imposes systemic and cellular stress response, can evoke disturbed ion homeostasis. In addition, like other vertebrates, fishes have also developed mechanisms to recover from the impact of stress by way of shifting stress response into ease response that could reduce the magnitude of stress response with the aid of certain neuroendocrine signals. Nitric oxide (NO) has been identified as a potent molecule that attenuates the impact of ionosmotic stress response in fish, particularly during hypoxia stress. Limited information is, however, available on this important aspect of ion transport physiology that contributes to the mechanistic understanding of survival during environmental challenges. The present review, thus, discusses the role of NO in Na⁺ homeostasis in fish particularly in stressed conditions. Isoforms of nitric oxide synthase (NOS) are essential for the synthesis and availability of NO at the cellular level. The NOS/NO system, thus, appears as a unique molecular drive that performs both regulatory and integrative mechanisms of control within and across varied fish ionocytes. The activation of the inducible NOS (iNOS)/NO system during hypoxia stress and its action on the dynamics of Na⁺/K⁺-ATPase, an active Na⁺ transporter in fish ionocytes, reveal that the iNOS/NO system controls cellular and systemic Na⁺ transport in stressed fish. In addition, the higher sensitivity of iNOS to varied physical stressors in fishes and the ability of NO to lower the magnitude of ionosmotic stress in hypoxemic fish clearly put forth NO as an ease-promoting signal molecule in fishes. This further points to the signature role of the iNOS/NO system as a biomarker for stress and ease response in the cycle of adaptive response in fish.

Widespread Coronary Dysfunction in the Absence of HDL Receptor SR-B1 in an Ischemic Cardiomyopathy Mouse Model

Reduced clearance of lipoproteins by HDL scavenger receptor class B1 (SR-B1) plays an important role in occlusive coronary artery disease. However, it is not clear how much microvascular dysfunction contributes to ischemic cardiomyopathy. Our aim was to determine the distribution of vascular dysfunction in vivo in the coronary circulation of male mice after brief exposure to Paigen high fat diet, and whether this vasomotor dysfunction involved nitric oxide (NO) and or endothelium derived hyperpolarization factors (EDHF). We utilised mice with hypomorphic ApoE lipoprotein that lacked SR-B1 (SR-B1^−/−/ApoER61^h/h, n = 8) or were heterozygous for SR-B1 (SR-B1^+/−/ApoER61^h/h, n = 8) to investigate coronary dilator function with synchrotron microangiography. Partially occlusive stenoses were observed in vivo in SR-B1 deficient mice only. Increases in artery-arteriole calibre to acetylcholine and sodium nitroprusside stimulation were absent in SR-B1 deficient mice. Residual dilation to acetylcholine following L-NAME (50 mg/kg) and sodium meclofenamate (3 mg/kg) blockade was present in both mouse groups, except at occlusions, indicating that EDHF was not impaired. We show that SR-B1 deficiency caused impairment of NO-mediated dilation of conductance and microvessels. Our findings also suggest EDHF and prostanoids are important for global perfusion, but ultimately the loss of NO-mediated vasodilation contributes to atherothrombotic progression in ischemic cardiomyopathy.

Time-course changes of nLDL-induced erectile dysfunction

Hyperlipidemia is an important risk factor for atherosclerosis and is frequently seen in patients with erectile dysfunction (ED). This study was designed to evaluate whether the acute effect of native low-density lipoprotein (nLDL) on intracavernosal pressure (ICP) is reversible and related to plasma asymmetrical dimethylarginine (ADMA), endogenous inhibition of endothelial nitric oxide synthase (eNOS) levels and eNOS expression in cavernous tissues. Hyperlipidemia was induced by a single dose of intravenous 4 mg kg^-1 nLDL. Experiments were performed 72 h (72H), 2 weeks (2W) and 8 weeks (8W) after nLDL injection. Endothelium-dependent relaxations, the ratio of ICP to mean arterial pressure (MAP; ICP/MAP), plasma ADMA levels and eNOS mRNA and protein levels were evaluated. The ICP/MAP ratio decreased in both the 2W and 8W groups. Endothelium-dependent relaxation responses to acetylcholine in the rat thoracic aorta were damaged in the 8W group. Plasma ADMA levels increased in the 8W group. mRNA expression of eNOS decreased in a time-dependent manner, whereas the protein expression increased. These results suggest that acute nLDL injection-induced impairments in erectile functions during an 8-week period are irreversible and might be related to an increase in ADMA levels and changes in the regulation of the eNOS/NO pathway.

Role for Tetrahydrobiopterin in the Fetoplacental Endothelial Dysfunction in Maternal Supraphysiological Hypercholesterolemia

Maternal physiological hypercholesterolemia occurs during pregnancy, ensuring normal fetal development. In some cases, the maternal plasma cholesterol level increases to above this physiological range, leading to maternal supraphysiological hypercholesterolemia (MSPH). This condition results in endothelial dysfunction and atherosclerosis in the fetal and placental vasculature. The fetal and placental endothelial dysfunction is related to alterations in the L-arginine/nitric oxide (NO) pathway and the arginase/urea pathway and results in reduced NO production. The level of tetrahydrobiopterin (BH4), a cofactor for endothelial NO synthase (eNOS), is reduced in nonpregnant women who have hypercholesterolemia, which favors the generation of the superoxide anion rather than NO (from eNOS), causing endothelial dysfunction. However, it is unknown whether MSPH is associated with changes in the level or metabolism of BH4; as a result, eNOS function is not well understood. This review summarizes the available information on the potential link between MSPH and BH4 in causing human fetoplacental vascular endothelial dysfunction, which may be crucial for understanding the deleterious effects of MSPH on fetal growth and development.

Post-Transcriptional Regulation of Endothelial Nitric Oxide Synthase Expression by Polypyrimidine Tract-Binding Protein 1

OBJECTIVE

Endothelial nitric oxide synthase (eNOS) is an important regulator of vascular function and its expression is regulated at post-transcriptional levels through a yet unknown mechanism. The purpose of this study is to elucidate the post-transcriptional factors regulating eNOS expression and function in endothelium.

APPROACHES AND RESULTS

To elucidate the molecular basis of tumor necrosis factor (TNF)-α-mediated eNOS mRNA instability, biotinylated eNOS 3'-untranslational region (UTR) was used to purify its associated proteins by RNA affinity chromatography from cytosolic fractions of TNF-α-stimulated human umbilical vein endothelial cells (HUVECs). We identified 2 cytosolic proteins, with molecular weight of 52 and 57 kDa, which specifically bind to eNOS 3'-UTR in response to TNF-α stimulation. Matrix-assisted laser desorption ionization time-of-flight mass spectrometric analysis identified the 57-kDa protein as polypyrimidine tract-binding protein 1 (PTB1). RNA gel mobility shift and UV cross-linking assays demonstrated that PTB1 binds to a UCUU-rich sequence in eNOS 3'-UTR, and the C-terminal half of PTB1 is critical to this interaction. Importantly, PTB1 overexpression leads to decreased activity of luciferase gene fused with eNOS 3'-UTR as well as reduced eNOS expression and activity in human ECs. In HUVECs, we show that TNF-α markedly increased PTB1 expression, whereas adenovirus-mediated PTB1 overexpression decreased eNOS mRNA stability and reduced protein expression and endothelium-dependent relaxation. Furthermore, knockdown of PTB1 substantially attenuated TNF-α-induced destabilization of eNOS transcript and downregulation of eNOS expression.

CONCLUSIONS

These results indicate that PTB1 is essential for regulating eNOS expression at post-transcriptional levels and suggest a novel therapeutic target for treatment of vascular diseases associated with inflammatory endothelial dysfunction.

Endothelial dysfunction abrogates the efficacy of normobaric hyperoxia in stroke

Hyperoxia has been uniformly efficacious in experimental focal cerebral ischemia. However, pilot clinical trials have showed mixed results slowing its translation in patient care. To explain the discordance between experimental and clinical outcomes, we tested the impact of endothelial dysfunction, exceedingly common in stroke patients but under-represented in experimental studies, on the neuroprotective efficacy of normobaric hyperoxia. We used hyperlipidemic apolipoprotein E knock-out and endothelial nitric oxide synthase knock-out mice as models of endothelial dysfunction, and examined the effects of normobaric hyperoxia on tissue perfusion and oxygenation using high-resolution combined laser speckle and multispectral reflectance imaging during distal middle cerebral artery occlusion. In normal wild-type mice, normobaric hyperoxia rapidly and significantly improved tissue perfusion and oxygenation, suppressed peri-infarct depolarizations, reduced infarct volumes, and improved neurological function. In contrast, normobaric hyperoxia worsened perfusion in ischemic brain and failed to reduce infarct volumes or improve neurological function in mice with endothelial dysfunction. These data suggest that the beneficial effects of hyperoxia on ischemic tissue oxygenation, perfusion, and outcome are critically dependent on endothelial nitric oxide synthase function. Therefore, vascular risk factors associated with endothelial dysfunction may predict normobaric hyperoxia nonresponders in ischemic stroke. These data may have implications for myocardial and systemic circulation as well.

Ceacam1 deletion causes vascular alterations in large vessels

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes hepatic insulin clearance and endothelial survival. However, its role in the morphology of macrovessels remains unknown. Mice lacking Ceacam1 (Cc1-/-) exhibit hyperinsulinemia, which causes insulin resistance and fatty liver. With increasing evidence of an association among hyperinsulinemia, fatty liver disease, and atherosclerosis, we investigated whether Cc1-/- exhibited vascular lesions in atherogenic-prone aortae. Histological analysis revealed impaired endothelial integrity with restricted fat deposition and aortic plaque-like lesions in Cc1-/- aortae, likely owing to their limited lipidemia. Immunohistochemical analysis indicated macrophage deposition, and in vitro studies showed increased leukocyte adhesion to aortic wall, mediated in part by elevation in vascular cell adhesion molecule 1 levels. Basal aortic eNOS protein and NO content were reduced, in parallel with reduced Akt/eNOS and Akt/Foxo1 phosphorylation. Ligand-induced vasorelaxation was compromised in aortic rings. Increased NADPH oxidase activity and plasma 8-isoprostane levels revealed oxidative stress and lipid peroxidation in Cc1-/- aortae. siRNA-mediated CEACAM1 knockdown in bovine aortic endothelial cells adversely affected insulin's stimulation of IRS-1/PI 3-kinase/Akt/eNOS activation by increasing IRS-1 binding to SHP2 phosphatase. This demonstrates that CEACAM1 regulates both endothelial cell autonomous and nonautonomous mechanisms involved in vascular morphology and NO production in aortae. Systemic factors such as hyperinsulinemia could contribute to the pathogenesis of these vascular abnormalities. Cc1-/- mice provide a first in vivo demonstration of distinct CEACAM1-dependent hepatic insulin clearance linking hepatic to macrovascular abnormalities.

Striking crosstalk of ROCK signaling with endothelial function

Rho-associated coiled-coil forming protein kinases (ROCKs), the downstream target proteins of RhoA, are ubiquitously expressed serine-threonine protein kinases. ROCKs have diverse cellular functions, e.g. smooth muscle contraction, actin cytoskeleton organization, cell adhesion, and gene expression. Accumulating evidence has revealed that ROCKs are substantially involved in cardiovascular disorders such as angina, cerebral ischemia, myocardial ischemia, and cardiac hypertrophy. So far, the significant relationship of ROCKs with endothelial function has been reported. ROCKs inhibition by statins or other selective inhibitors leads to the upregulation and activation of endothelial nitric oxide synthase, resulting in the reduction of vascular inflammation and atherosclerosis. Meanwhile, it has been also demonstrated that endogenous nitric oxide could inhibit RhoA/ROCK signaling pathway. Taken together, there might be critical crosstalk of ROCKs with endothelial function. In addition, we further focus on leukocyte ROCK activity as a surrogate marker in patients with atherosclerosis-related diseases. Indeed, leukocyte ROCK activity has been shown to be increased in atherosclerotic patients, indicating the possible usage of leukocyte ROCK activity as a surrogate marker similar to endothelial function evaluated by flow-mediated dilation. Here, we review concerning ROCK signaling pathway, especially focusing on the crosstalk of ROCKs with endothelial function.

Simvastatin modulates remodeling of Kv4.3 expression in rat hypertrophied cardiomyocytes

Objectives: Hypertrophy has been shown to be associated with arrhythmias which can be caused by abnormal remodeling of the Kv4-family of transient potassium channels. Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) have recently been shown to exert pleiotropic protective effects in cardiovascular diseases, including anti-arrhythmias. It is hypothesized that remodeling of Kv4.3 occurs in rat hypertrophied cardiomyocytes and is regulated by simvastatin.

Methods: Male Sprague-Dawley rats and neonatal rat ventricular myocytes (NRVMs) underwent abdominal aortic banding (AAB) for 7 weeks and angiotensin II (AngII) treatment, respectively, to induce cardiac hypertrophy. Kv4.3 expression by NRVMs and myocardium (subepicardial and subendocardial) in the left ventricle was measured. The transient outward potassium current (I_to) of NRVMs was recorded using a whole-cell patch-clamp method.

Results: Expression of the Kv4.3 transcript and protein was significantly reduced in myocardium (subepicardial and subendocardial) in the left ventricle and in NRVMs. Simvastatin partially prevented the reduction of Kv4.3 expression in NRVMs and subepicardial myocardium but not in the subendocardial myocardium. Hypertrophied NRVMs exhibited a significant reduction in the I_to current and this effect was partially reversed by simvastatin.

Conclusions: Simvastatin alleviated the reduction of Kv4.3 expression, I_to currents in hypertrophied NRVMs and alleviated the reduced Kv4.3 expression in subepicardial myocardium from the hypertrophied left ventricle. It can be speculated that among the pleiotropic effects of simvastatin, the anti-arrhythmia effect is partly mediated by its effect on Kv4.3.

Fetoplacental vascular endothelial dysfunction as an early phenomenon in the programming of human adult diseases in subjects born from gestational diabetes mellitus or obesity in pregnancy

Gestational diabetes mellitus (GDM) and obesity in pregnancy (OP) are pathological conditions associated with placenta vascular dysfunction coursing with metabolic changes at the fetoplacental microvascular and macrovascular endothelium. These alterations are seen as abnormal expression and activity of the cationic amino acid transporters and endothelial nitric oxide synthase isoform, that is, the "endothelial L-arginine/nitric oxide signalling pathway." Several studies suggest that the endogenous nucleoside adenosine along with insulin, and potentially arginases, are factors involved in GDM-, but much less information regards their role in OP-associated placental vascular alterations. There is convincing evidence that GDM and OP prone placental endothelium to an "altered metabolic state" leading to fetal programming evidenced at birth, a phenomenon associated with future development of chronic diseases. In this paper it is suggested that this pathological state could be considered as a metabolic marker that could predict occurrence of diseases in adulthood, such as cardiovascular disease, obesity, diabetes mellitus (including gestational diabetes), and metabolic syndrome.

Regulation of smooth muscle contraction by small GTPases

Next to changes in cytosolic [Ca(2+)], members of the Rho subfamily of small GTPases, in particular Rho and its effector Rho kinase, also known as ROK or ROCK, emerged as key regulators of smooth muscle function in health and disease. In this review, we will focus on the regulation of the contractile machinery by Rho/ROK signaling and its interaction with PKC and cyclic nucleotide signaling. We will briefly discuss the emerging evidence that remodeling of cortical actin is necessary for contraction.

Therapeutic interventions and oxidative stress in diabetes

Many therapeutic agents that are used in patients with diabetes mitigate oxidative stress. These agents are of particular interest because oxidative stress is elevated in diabetes and is thought to contribute to vascular dysfunction. Agents that merely quench already formed reactive oxygen species have demonstrated limited success in improving cardiovascular outcomes. Thus, although vitamin E, C, and alpha lipoic acid appeared promising in animal models and initial human studies, subsequent larger trials have failed to demonstrate improvement in cardiovascular outcomes. Drugs that limit the production of oxidative stress are more successful in improving vascular outcomes in patients with diabetes. Thus, although statins, ACE inhibitors, ARBs and thiazolinediones are used for varied clinical purposes, their increased efficacy in improving cardiovascular outcomes is likely related to their success in reducing the production of reactive oxygen species at an earlier part of the cascade, thereby more effectively decreasing the oxidative stress burden. In particular, statins and ACE inhibitors/ ARBs appear the most successful at reducing oxidative stress and vascular disease and have potential for synergistic effects.

Tumor necrosis factor-alpha downregulates endothelial nitric oxide synthase mRNA stability via translation elongation factor 1-alpha 1

Endothelium-derived nitric oxide (NO) is an important regulator of vascular function. NO is produced by endothelial NO synthase (eNOS), whose expression is downregulated by tumor necrosis factor (TNF)-alpha at the posttranscriptional level. To elucidate the molecular basis of TNF-alpha-mediated eNOS mRNA instability, eNOS 3' untranslated region (3'-UTR) binding proteins were purified by RNA affinity chromatography from cytosolic fractions of TNF-alpha-stimulated human umbilical vein endothelial cells (HUVECs). The formation of 3'-UTR ribonucleoprotein complexes, with molecular weight of 52 and 57 kDa, was increased by TNF-alpha. Matrix-assisted laser desorption ionization time-of-flight mass spectrometric analysis of the 52-kDa protein identified 3 peptides that comprise the peptide sequence of translation elongation factor 1-alpha 1 (eEF1A1). In HUVECs, TNF-alpha rapidly increased eEF1A1 expression, which is maximal after 1 hour and persists for up to 48 hours. RNA gel mobility-shift and UV cross-linking assays indicated that recombinant glutathione S-transferase-eEF1A1 fusion protein specifically binds to a UC-rich sequence in the 3'-UTR of eNOS mRNA. In addition, the domain III of eEF1A1 mediates the binding of eNOS 3'-UTR in eEF1A1. Overexpression of eEF1A1 markedly attenuated the expression of eNOS and luciferase gene fused with eNOS 3'-UTR in both COS-7 cells and bovine aortic endothelial cells (BAECs). Furthermore, adenovirus-mediated overexpression of eEF1A1 increased eNOS mRNA instability, whereas knockdown of eEF1A1 substantially attenuated TNF-alpha-induced destabilization of eNOS mRNA and downregulation of eNOS expression in HUVECs. These results indicate that eEF1A1 is a novel eNOS 3'-UTR binding protein that plays a critical role in mediating TNF-alpha-induced decrease in eNOS mRNA stability.

Adverse balance of nitric oxide/peroxynitrite in the dysfunctional endothelium can be reversed by statins

Vascular endothelial dysfunction is a complex phenomenon that might be caused by a deficiency of nitric oxide (NO) and an overproduction of peroxynitrite (ONOO-). This study used a nanotechnological approach to monitor the in vitro effect of statins on the [NO]/[ONOO-] balance in normal and dysfunctional endothelial cells. NO and (ONOO-) were measured by electrochemical nanosensors in a single human umbilical vein endothelial cell (HUVEC) treated with atorvastatin or simvastatin for 24 hours in the presence or absence of 50 microg/mL oxidized-LDL. An imbalance between [NO]/[ONOO-] concentrations was used as an indicator of endothelial dysfunction and correlated with endothelial nitric oxide synthase (eNOS) expression. Ox-LDL induced dysfunction of the endothelium by uncoupling eNOS. NO concentration decreased from 300 +/- 12 to 146 +/- 8 nmol/L and (ONOO-) increased from 200 +/- 9 to 360 +/- 13 nmol/L. The [NO]/[ONOO-] balance decreased from 1.50 +/- 0.04 (control) to 0.40 +/- 0.03 for cells co-incubated with ox-LDL. Treatment with statins reversed eNOS uncoupling, induced by oxidized-LDL and significantly increased the [NO]/[ONOO-] balance to 1.2 +/- 0.1. These results demonstrate that statins can restore endothelial function by increasing eNOS expression, decreasing eNOS uncoupling, reducing the (ONOO-) level (nitroxidative stress), and shifting the [NO]/[ONOO-] balance towards NO.

Relative reduction of endothelial nitric-oxide synthase expression and transcription in atherosclerosis-prone regions of the mouse aorta and in an in vitro model of disturbed flow

Atherosclerosis develops in distinct regions of the arterial tree. Defining patterns and mechanisms of endothelial cell gene expression in different regions of normal arteries is key to understanding the initial molecular events in atherogenesis. In this study, we demonstrated that the expression of endothelial nitric-oxide synthase (eNOS), an atheroprotective gene, and its phosphorylation on Ser(1177), a marker of activity, were lower in regions of the normal mouse aorta that are predisposed to atherosclerosis. The same expression pattern was observed in mouse strains that are both susceptible and resistant to atherosclerosis, and the topography of eNOS expression was inverse to p65, the main nuclear factor-kappaB subunit. Modeling of disturbed and uniform laminar flow in vitro reproduced the expression patterns of eNOS and p65 that were found in vivo. Heterogeneous nuclear RNA expression and RNA polymerase II chromosome immunoprecipitation studies demonstrated that regulation of transcription contributed to increased eNOS expression in response to shear stress. In vivo, the transcription of eNOS was reduced in regions of the mouse aorta predisposed to atherosclerosis, as defined by reporter gene expression in eNOS promoter-beta-galactosidase reporter transgenic mice. These data suggest that disturbed hemodynamic patterns found at arterial branches and curvatures uniquely modulate endothelial cell gene expression by regulating transcription, potentially explaining why these regions preferentially develop atherosclerosis when risk factors such as hypercholesterolemia are introduced.

Alternative polyadenylation sites of human endothelial nitric oxide synthase mRNA

The mRNA 3'-untranslated region (3'-UTR) has been shown to have important roles in the regulation of mRNA function. In this study, we investigated the human endothelial nitric oxide synthase (eNOS) 3'-UTR to evaluate its potential regulatory role. 3'-RACE analysis revealed that the human eNOS mRNA has multiple alternative polyadenylation sites. Apart from the proximal site (418bp downstream of the stop codon), we identified two additional distal sites approximately 770 and 1478bp downstream of the stop codon. In addition, Northern analysis showed that the usage of these sites differed among human tissues. Further, amounts of these eNOS mRNAs were changed during growth of cultured human aortic endothelial cells; mRNAs with long 3'-UTRs decreased more rapidly than total mRNA, as cells approached confluency. Thus, the 3'-UTRs of human eNOS results from alternative polyadenylation sites and differ across tissues and during cell growth.

The nonlipid effects of statins on endothelial function

Hydroxymethylglutaryl-coenzyme A reductase inhibitors or statins constitute one of the wonder drugs of the last 2 decades. Use of this hypolipidemic medication class reduces morbidity and mortality in patients with a wide variety of cholesterol levels. Beneficial effects of the medication are seen in advance of changes in lipids suggesting nonlipid mechanisms may play a role in mediating these benefits of statins. One important nonlipid mechanism by which statins may improve vascular outcomes is restoration of normal endothelial cell function. This review will discuss the nonlipid effects of statins on endothelial cell function to highlight other avenues of benefit conferred by these medications.

Crocetin improves endothelium-dependent relaxation of thoracic aorta in hypercholesterolemic rabbit by increasing eNOS activity

Our previous studies have proven that crocetin (CCT), extracted from Gardenia jasminoides Ellis, possesses the anti-atherosclerotic effect. Because endothelial dysfunction strongly contributes to the initiation and progression of atherosclerosis, the present study aims to investigate whether CCT is capable of improving this dysfunction and to explore the possible mechanisms. Endothelial dysfunction was induced by in vivo feeding high cholesterol diet (HCD) to rabbit and by in vitro treating bovine aortic endothelial cells (BAECs) with oxidized LDL (oxLDL). Endothelium-dependent relaxation (EDR) evoked by acetylcholine (Ach) and endothelium-independent relaxation (RIDR) mediated by sodium nitroprusside (SNP) of thoracic aorta isolated from rabbit were measured. The results indicated that the EDR in HCD alone treated rabbits was seriously impaired and the maximal relaxation induced by Ach (10(-5.5) M) was only 54% that in control rabbit fed with regular diet. Oral complementation with CCT (15, 30 mg/kg) dose-dependently improved this impairment and restored the maximal relaxation to 68% and 80% that in control group, respectively. However, the EIDR maintained comparable in all groups. Complementation with CCT (15, 30 mg/kg) simultaneously increased serum level of nitric oxide (NO), upregulated vessel activity and mRNA expression of endothelial NO synthase (eNOS) as well as vessel cyclic GMP (cGMP) content compared with those in rabbit treated with HCD alone. Inducible NOS (iNOS) activity remained unchangeable in all groups. In BAECs, oxLDL treatment decreased NO production, downregulated both activity and mRNA expression of eNOS. While those decrease or downregulation were inhibited by co-treatment with CCT (0.1, 1, 10 microM) in a dose-dependent manner. These findings suggested that CCT significantly restored the EDR of thoracic aorta in hypercholesterolemic rabbit, which might be explained by its action to increase the vessel eNOS activity, leading to elevation of NO production.

Control of protein expression through mRNA stability in calcium signalling

Specific sequences (cis-acting elements) in the 3'-untranslated region (UTR) of RNA, together with stabilizing and destabilizing proteins (trans-acting factors), determine the mRNA stability, and consequently, the level of expression of several proteins. Such interactions were discovered initially for short-lived mRNAs encoding cytokines and early genes like c-jun and c-myc. However, they may also determine the fate of more stable mRNAs in a tissue and disease-dependent manner. The interactions between the cis-acting elements and the trans-acting factors may also be modulated by Ca(2+) either directly or via a control of the phosphorylation status of the trans-acting factors. We focus initially on the basic concepts in mRNA stability with the trans-acting factors AUF1 (destabilizing) and HuR (stabilizing). Sarco/endoplasmic reticulum Ca(2+) pumps, SERCA2a (cardiac and slow twitch muscles) and SERCA2b (most cells including smooth muscle cells), are pivotal in Ca(2+) mobilization during signal transduction. SERCA2a and SERCA2b proteins are encoded by relatively stable mRNAs that contain cis-acting stability determinants in their 3'-regions. We present several pathways where 3'-UTR mediated mRNA decay is key to Ca(2+) signalling: SERCA2a and beta-adrenergic receptors in heart failure, renin-angiotensin system, and parathyroid hormones. Other examples discussed include cytokines vascular endothelial growth factor, endothelin and endothelial nitric oxide synthase. Roles of Ca(2+) and Ca(2+)-binding proteins in mRNA stability are also discussed. We anticipate that these novel modes of control of protein expression will form an emerging area of research that may explore the central role of Ca(2+) in cell function during development and in disease.

Transcriptional and posttranscriptional regulation of endothelial nitric oxide synthase expression

The ability of the endothelium to produce nitric oxide is essential to maintenance of vascular homeostasis; disturbance of this ability is a major contributor to the pathogenesis of vascular disease. In vivo studies have demonstrated that expression of endothelial nitric oxide synthase (eNOS) is vital to endothelial function and have led to the understanding that eNOS expression is subject to modest but significant degrees of regulation. Subsequently, numerous physiological and pathophysiological stimuli have been identified that modulate eNOS expression via mechanisms that alter steady-state eNOS mRNA levels. These mechanisms involve changes in the rate of eNOS gene transcription (transcriptional regulation) and alteration of eNOS mRNA processing and stability (posttranscriptional regulation). In cultured endothelial cells, shear stress, transforming growth factor-beta1, lysophosphatidylcholine, cell growth, oxidized linoleic acid, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, and hydrogen peroxide have been shown to increase eNOS expression. In contrast, tumor necrosis factor-alpha, hypoxia, lipopolysaccaride, thrombin, and oxidized LDL can decrease eNOS mRNA levels. For many of these stimuli, both transcriptional and posttranscriptional mechanisms contribute to regulation of eNOS expression. Recent studies have begun to further define signaling pathways responsible for changes in eNOS expression and have characterized cis- and trans-acting regulatory elements. In addition, a role has been identified for epigenetic control of eNOS mRNA levels. This review will discuss transcriptional and posttranscriptional regulation of eNOS with emphasis on the molecular mechanisms that have been identified for these processes.

Physiological role of ROCKs in the cardiovascular system

Rho-associated kinases (ROCKs), the immediate downstream targets of RhoA, are ubiquitously expressed serine-threonine protein kinases that are involved in diverse cellular functions, including smooth muscle contraction, actin cytoskeleton organization, cell adhesion and motility, and gene expression. Recent studies have shown that ROCKs may play a pivotal role in cardiovascular diseases such as vasospastic angina, ischemic stroke, and heart failure. Indeed, inhibition of ROCKs by statins or other selective inhibitors leads to the upregulation and activation of endothelial nitric oxide synthase (eNOS) and reduction of vascular inflammation and atherosclerosis. Thus inhibition of ROCKs may contribute to some of the cholesterol-independent beneficial effects of statin therapy. Currently, two ROCK isoforms have been identified, ROCK1 and ROCK2. Because ROCK inhibitors are nonselective with respect to ROCK1 and ROCK2 and also, in some cases, may be nonspecific with respect to other ROCK-related kinases such as myristolated alanine-rich C kinase substrate (MARCKS), protein kinase A, and protein kinase C, the precise role of ROCKs in cardiovascular disease remains unknown. However, with the recent development of ROCK1- and ROCK2-knockout mice, further dissection of ROCK signaling pathways is now possible. Herein we review what is known about the physiological role of ROCKs in the cardiovascular system and speculate about how inhibition of ROCKs could provide cardiovascular benefits.

Physical activity and atherosclerosis: which animal model?

Atherosclerosis is a progressive disease that is the most important single contributor to human cardiovascular morbidity and mortality. Epidemiologic studies show that physical activity, or routine exercise, reduces the risk of developing cardiovascular disease. The mechanisms through which exercise may function in primary or secondary prevention of atherosclerosis remain largely to be established. Most studies in humans are performed after the onset of clinical signs when disease is well advanced and the prescription of exercise is based on empirical evidence of benefit in secondary prevention. Animal models per-mit the study of the initiation and progression of preclinical stages of atherosclerosis. In order to provide information relevant to treatment and prevention, these models should mimic human disease and interactions of physical activity with disease processes as closely as possible. The purpose of this review is to compare animal models of atherosclerosis and to summarize the available data in those models in regard to the effects of exercise.

Molecular mechanisms involved in the regulation of the endothelial nitric oxide synthase

The endothelial nitric oxide synthase (eNOS), the expression of which is regulated by a range of transcriptional and posttranscriptional mechanisms, generates nitric oxide (NO) in response to a number of stimuli. The physiologically most important determinants for the continuous generation of NO and thus the regulation of local blood flow are fluid shear stress and pulsatile stretch. Although eNOS activity is coupled to changes in endothelial cell Ca(2+) levels, an increase in Ca(2+) alone is not sufficient to affect enzyme activity because the binding of calmodulin (CaM) and the flow of electrons from the reductase to the oxygenase domain of the enzyme is dependent on protein phosphorylation and dephosphorylation. Two amino acids seem to be particularly important in regulating eNOS activity and these are a serine residue in the reductase domain (Ser(1177)) and a threonine residue (Thr(495)) located within the CaM-binding domain. Simultaneous alterations in the phosphorylation of Ser(1177) and Thr(495) in response to a variety of stimuli are regulated by a number of kinases and phosphatases that continuously associate with and dissociate from the eNOS signaling complex. eNOS associated proteins, such as caveolin, heat shock protein 90, eNOS interacting protein, and possibly also motor proteins provide the scaffold for the formation of the protein complex as well as its intracellular localization.

Prior aspirin use in unstable angina patients with modified plasma inflammatory markers and endothelial nitric oxide synthase in neutrophils

BACKGROUND

Prior use of aspirin in patients with acute coronary syndrome has been associated with a lower incidence of acute myocardial infarction. The aim of this study was to explore if prior aspirin therapy in unstable angina (UA) patients could modify systemic inflammatory markers such as interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-alpha) and intercellular adhesion molecule-1 (ICAM-1) and the expression of endothelial nitric oxide synthase (eNOS) in neutrophils.

MATERIALS AND METHODS

Unstable angina was defined as transient S-T segment changes without significant increases in CK and CK-MB. We studied 50 consecutive patients admitted to hospital within 24 h after the onset of chest pain. The number of patients with prior aspirin was significantly higher (n = 32) than those not taking aspirin (n = 18) on admission.

RESULTS

Plasma levels of IL-6 and ICAM-1 were significantly increased in the UA patients when compared with the healthy control volunteers (n = 20) used as a reference for normal values. Plasma levels of both IL-6 and ICAM-1 were reduced in patients taking aspirin. There were no differences in the plasma levels of TNF-alpha between the UA patients and the control volunteers. The eNOS protein expression was also higher in neutrophils from the UA patients taking aspirin than in those not taking aspirin.

CONCLUSION

Patients taking aspirin before UA showed a lower systemic inflammatory response and higher eNOS protein expression in their neutrophils

Nitric oxide production by neutrophils obtained from patients during acute coronary syndromes: expression of the nitric oxide synthase isoforms

OBJECTIVES

To analyze the differences in the nitric oxide (NO) forming system between neutrophils obtained from patients during unstable angina (UA) and during acute myocardial infarction (AMI).

BACKGROUND

Neutrophils are involved in the regulation of thrombus formation through the release of active substances such as NO. Acute myocardial infarction is the result of an occlusive thrombus; unstable angina is attributed to intermittent thrombus formation.

METHODS

We studied 49 patients admitted to hospital within 24 h after the onset of chest pain: 31 experienced AMI and 18 experienced UA. Acute myocardial infarction was defined as CK greater than two-fold the upper limit of normal value of biochemical laboratory, with CK-MB >10% total CK. Unstable angina was defined as transient ST segment changes without significant increases in CK and CK-MB.

RESULTS

The amount of NO generated by neutrophils from AMI patients was significantly higher than that generated by neutrophils from UA patients. Neutrophils from UA and AMI patients showed low levels of endothelial-like NO synthase protein expression and a marked expression of the inducible NO synthase (iNOS) isoform. Although neutrophils from patients during acute coronary syndromes generated high amounts of NO, they did not demonstrate an increased ability to stimulate cyclic guanosine monophosphate (cGMP) synthesis in platelets. This lack of activity to release NO by neutrophils from patients during AMI was unrelated to a defect in the platelet cGMP-forming system; sodium nitroprusside, an exogenous NO donor, similarly increased cGMP levels in platelets from AMI patients and healthy donors.

CONCLUSIONS

Neutrophils from patients during AMI and UA showed an increased production of NO and a marked expression of the iNOS isoform. However, NO released from these neutrophils showed a deficient functionality. These findings could have clinical implications because they show differences in thrombus growth in patients with UA versus patients with AMI.