Inducible nitric oxide synthase activation after ischemia/reperfusion contributes to myocardial dysfunction and extent of infarct size in rabbits: evidence for a late phase of nitric oxide-mediated reperfusion injury

Mixture of Doxycycline, ML-7 and L-NAME Restores the Pro- and Antioxidant Balance during Myocardial Infarction-In Vivo Pig Model Study

The restoration of blood flow to the ischemic myocardium inflicts ischemia/reperfusion (I/R) heart injury (IRI). The main contributors to IRI are increased oxidative stress and subsequent excessive production of ROS, increased expression of NOS and peroxinitate, activation of MMPs, and enhanced posttranslational modifications of contractile proteins, which make them more susceptible to proteolytic degradation. Since the pathophysiology of IRI is a complex issue, and thus, various therapeutic strategies are required to prevent or reduce IRI and microvascular dysfunction, in the current study we proposed an innovative multi-drug therapy using low concentrations of drugs applied intracoronary to reach microvessels in order to stabilize the pro- and antioxidant balance during a MI in an in vivo pig model. The ability of a mixture of doxycycline (1 μM), ML-7 (0.5 μM), and L-NAME (2 μM) to modulate the pro- and antioxidative balance was tested in the left ventricle tissue and blood samples. Data showed that infusion of a MIX reduced the total oxidative status (TOS), oxidative stress index (OSI), and malondialdehyde (MDA). It also increased the total antioxidant capacity, confirming its antioxidative properties. MIX administration also reduced the activity of MMP-2 and MMP-9, and then decreased the release of MLC1 and BNP-26 into plasma. This study demonstrated that intracoronary administration of low concentrations of doxycycline in combination with ML-7 and L-NAME is incredibly efficient in regulating pro- and antioxidant balance during MI.

Clinical Applications for Gasotransmitters in the Cardiovascular System: Are We There Yet?

Ischemia is the underlying mechanism in a wide variety of acute and persistent pathologies. As such, understanding the fine intracellular events occurring during (and after) the restriction of blood supply is pivotal to improving the outcomes in clinical settings. Among others, gaseous signaling molecules constitutively produced by mammalian cells (gasotransmitters) have been shown to be of potential interest for clinical treatment of ischemia/reperfusion injury. Nitric oxide (NO and its sibling, HNO), hydrogen sulfide (H2S), and carbon monoxide (CO) have long been proven to be cytoprotective in basic science experiments, and they are now awaiting confirmation with clinical trials. The aim of this work is to review the literature and the clinical trials database to address the state of development of potential therapeutic applications for NO, H2S, and CO and the clinical scenarios where they are more promising.

iNOS expressing macrophages co-localize with nitrotyrosine staining after myocardial infarction in humans

Introduction

Inducible nitric oxide synthase (iNOS) produces micromolar amounts of nitric oxide (NO) upon the right stimuli, whose further reactions can lead to oxidative stress. In murine models of myocardial infarction (MI), iNOS is known to be expressed in infiltrating macrophages, which at early onset enter the infarcted zone and are associated with inflammation. In contrast cardiac tissue resident macrophages are thought to enhance regeneration of tissue injury and re-establish homeostasis. Both detrimental and beneficial effects of iNOS have been described, still the role of iNOS in MI is not fully understood. Our aim was to examine cell expression patterns of iNOS and nitrotyrosine (NT) production in human MI.

Material and Methods

We examined in postmortem human MI hearts the iNOS mRNA expression by means of qPCR. Further we performed immunohistochemical stainings for cell type identification. Afterwards a distance analysis between iNOS and NT was carried out to determine causality between iNOS and NT production.

Results

iNOS mRNA expression was significantly increased in infarcted regions of human MI hearts and iNOS protein expression was detected in resident macrophages in infarcted human hearts as well as in controls hearts, being higher in resident macrophages in MI hearts compared to control. Furthermore in MI and in healthy human hearts cells showing signs of NT production peaked within 10–15 µm proximity of iNOS+ cells.

Discussion

These results indicate that, unexpectedly, resident macrophages are the main source of iNOS expression in postmortem human MI hearts. The peak of NT positive cells within 10–15 µm of iNOS+ cells suggest an iNOS dependent level of NT and therefore iNOS dependent oxidative stress. Our results contribute to understanding the role of iNOS in human MI.

Altered Left Ventricular Rat Gene Expression Induced by the Myosin Activator Omecamtiv Mecarbil

To explore the impact of omecamtiv mecarbil (OM) on the gene expression profile in adult male rats. Fourteen male Wistar rats were randomly assigned to a single OM (1.2 mg/kg/h; n = 6) or placebo (n = 8) 30-min infusion. Echocardiography was performed before and after OM infusion. Seven days after infusion, rats were euthanized, and left ventricular (LV) tissues were removed for real-time quantitative polymerase chain reaction (RTq-PCR) experiments. After OM infusion, pro-apoptotic Bax-to-Bcl2 ratio was decreased, with increased Bcl2 and similar Bax gene expression. The gene expression of molecules regulating oxidative stress, including glutathione disulfide reductase (Gsr) and superoxide dismutases (Sod1/Sod2), remained unchanged, whereas the expression of antioxidant glutathione peroxidase (Gpx) increased. While LV gene expression of key energy sensors, peroxisome proliferator activator (Ppar) α and γ, AMP-activated protein kinase (Ampk), and carnitine palmitoyltransferase 1 (Cpt1) remained unchanged after OM infusion, and the expression of pyruvate dehydrogenase kinase 4 (Pdk4) increased. The LV expression of the major myocardial glucose transporter Glut1 decreased, with no changes in Glut4 expression, whereas the LV expression of oxidized low-density lipoprotein receptor 1 (Olr1) and arachidonate 15-lipoxygenase (Alox15) increased, with no changes in fatty acid transporter Cd36. An increased LV expression of angiotensin II receptors AT1 and AT2 was observed, with no changes in angiotensin I-converting enzyme expression. The Kalikrein-bradykinin system was upregulated with increased LV expression of kallikrein-related peptidases Klk8, Klk1c2, and Klk1c12 and bradykinin receptors B1 and B2 (Bdkrb1 and Bdkrb2), whereas the LV expression of inducible nitric oxide synthase 2 (Nos2) increased. LV expression in major molecular determinants involved in calcium-dependent myocardial contraction remained unchanged, except for an increased LV expression of calcium/calmodulin-dependent protein kinase II delta (Cacna1c) in response to OM. A single intravenous infusion of OM, in adult healthy rats, resulted in significant changes in the LV expression of genes regulating apoptosis, oxidative stress, metabolism, and cardiac contractility.

Carbon monoxide and a change of heart

The relationship between carbon monoxide and the heart has been extensively studied in both clinical and preclinical settings. The Food and Drug Administration (FDA) is keenly focused on the ill effects of carbon monoxide on the heart when presented with proposals for clinical trials to evaluate efficacy of this gasotransmitter in a various disease settings. This review provides an overview of the rationale that examines the actions of the FDA when considering clinical testing of CO, and contrast that with the continued accumulation of data that clearly show not only that CO can be used safely, but is potently cardioprotective in clinically relevant small and large animal models. Data emerging from Phase I and Phase II clinical trials argues against CO being dangerous to the heart and thus it needs to be redefined and evaluated as any other substance being proposed for use in humans. More than twenty years ago, the belief that CO could be used as a salutary molecule was ridiculed by experts in physiology and medicine. Like all agents designed for use in humans, careful pharmacology and safety are paramount, but continuing to hinder progress based on long-standing dogma in the absence of data is improper. Now, CO is being tested in multiple clinical trials using innovative delivery methods and has proven to be safe. The hope, based on compelling preclinical data, is that it will continue to be evaluated and ultimately approved as an effective therapeutic.

Mixture of MMP-2, MLC, and NOS Inhibitors Affects NO Metabolism and Protects Heart from Cardiac I/R Injury

Objectives

Coronary reperfusion procedure leads to ischemia/reperfusion injury of the heart (IRI). IRI arises from increased degradation of myosin light chains and increased activity of matrix metalloproteinase 2 (MMP-2). Increased production of toxic peroxynitrite (ONOO^-) during oxidative stress is a source of increased nitration/nitrosylation of contractile proteins, which enhance their degradation through MMP-2. Hence, an imbalance in nitric oxide (NO) metabolism along with oxidative stress is an important factor contributing to pathophysiology of cardiovascular disorders, including myocardial infarction. The aim of the current study was to provide an important insight into understanding the interaction of iNOS, eNOS, and ADMA during oxidative stress and to propose the beneficial therapy to modulate this interaction. Material and Methods. Pathogen-free Wistar rats were used in this study as a surrogate heart model ex vivo. Rat hearts perfused using the Langendorff method were subjected to global no-flow ischemia with or without administration of DOXY (1 µM), ML-7 (0.5 µM), and L-NAME (2 µM) mixture. Haemodynamic parameters of heart function, markers of I/R injury, tissue expression of iNOS, eNOS, and phospho-eNOS, asymmetric dimethylarginine, and NO production as well as MMP-2 activity were measured.

Results

Mechanical heart function and coronary flow (CF) were decreased in the hearts subjected to I/R. Treatment of the hearts with the tested mixture resulted in a recovery of mechanical function due to decreased activity of MMP-2. An infusion of Doxy, ML-7, and L-NAME mixture into I/R hearts decreased the expression of iNOS, eNOS, and phospho-eNOS and in consequence reduced ADMA expression. Decreased ADMA production led to enhanced NO synthesis and improvement of cardiac function at 85% of aerobic control.

Conclusions

Synergistic effect of the multidrug therapy with the subthreshold doses allows addressing a few pathways of I/R injury simultaneously to achieve protection of cardiac function during I/R.

Evaluation of the cardioprotective effect of Casuarina suberosa extract in rats

The aim of the current study was to examine and compare the cardioprotective activities of the chloroform and petroleum extracts the leaves of Casuarina suberosa in isoproterenol (ISO)-induced cardiac tissue oxidative stress. Rats were categorized into 6 groups as follows: control group, vehicle or Tween 80-treated group, ISO-treated group, chloroform extract + ISO treated group, petroleum ether extract + ISO treated group and Reference drug (Captopril) + ISO treated group. ISO injection significantly (p < 0.05) increased the activities of cardiac marker enzymes (CK-MB, LDH, ALT, and AST), cardiac troponin-I, levels of lipid peroxides (MDA), nitric oxide (NO), and vascular endothelial growth factor (VEGF), serum angiotensin-converting enzyme (ACE) activity and neutrophil infiltration marker; myeloperoxidase (MPO) in the cardiac tissues. Pretreatment with chloroform or petroleum ether extracts significantly (p < 0.05) prevented the ISO-induced alteration; they upregulated VEGF expression. Histopathological findings corroborated biochemical results. These extracts exerted a cardioprotective effect by alleviating oxidative stress.

circDLPAG4/HECTD1 mediates ischaemia/reperfusion injury in endothelial cells via ER stress

Background: Vascular endothelial cell dysfunction, characterized by cell apoptosis and migration, plays a crucial role in ischaemia/reperfusion (I/R) injury, a common aspect of cardiovascular diseases. Recent studies have suggested that non-coding RNAs, such as circular RNAs (circRNA), play a role in cell dysfunction in I/R injury, although the detailed mechanism is unclear.Methods: Human umbilical vein endothelial cells (HUVECs) were used for in vitro I/R model. Protein expression was detected by western blotting (WB) and immunocytochemistry. The CRISPR/Cas9 system, WB, cell viability assays, Hoechst staining and a 3D migration model were used to explore functional changes. RNA expression was evaluated using quantitative real-time PCR and a FISH assay combined with lentivirus transfection regulating circRNAs and miRNAs. A mouse myocardial I/R model using C57 mice was established to confirm the in vitro findings.Results: In HUVECs, I/R induced a significant time-dependent decrease in HECTD1 associated with an approximately 45% decrease in cell viability and increases in cell apoptosis and migration, which were attenuated by HECTD1 overexpression. I/R-induced upregulation of endoplasmic reticulum stress was also attenuated HECTD1 overexpression. Moreover, miR-143 mimics inhibited HECTD1 expression, which was restored by circDLGAP4 overexpression, providing insight as to the molecular mechanism of I/R-induced HECTD1 in endothelial cell dysfunction.Conclusion: Our results suggest a critical role for circDLGAP4 and HECTD1 in endothelial cell dysfunction induced by I/R, providing novel insight into potential therapeutic targets for the treatment of myocardial ischaemia.

The Effect of Hepcidin on Cardiac Ischemia-Reperfusion Injury

Background/aim: Hepcidin is the main hormone in the regulation of iron metabolism which is also released from the heart. The aim of our study was to investigate the effects of hepcidin on the cardiac ischemia-reperfusion injury.Materials and methods: In this study, 12 Wistar albino rats were divided into two groups (n = 6 each): 1) The ischemia-reperfusion group (Group 1); 2) Hepcidin-treated group (Group 2). Rat hearts were perfused on Langendorff system with KH (Krebs-Henseleit) and subjected to 30 min stabilization, 30 min global ischemia, and 30 min reperfusion. Hepcidin (^- M) was applied to group 2 at the onset of ischemia. Malondialdehyde (MDA), glutathione (GSH), and nitric oxide (NOx) levels were measured in heart tissue for NOx levels, viscosity, and ion content of perfusate were collected before ischemia and the 1st, 5th, 10th, 20th, and 30th minutes of reperfusion were determined. Apoptosis in heart was evaluated.Results: NOx and MDA levels significantly decreased in heart tissue in Hepcidin-treated group. NOx and viscosity of perfusate were not significantly different between the groups. Perfusate iron, calcium, magnesium, potassium, and sodium levels in group 2 were more homogeneous. Histologic structures of heart tissue were regularly in group 2. Apoptosis were increased in control group compared to hepcidin treated group.Conclusion: These results suggest that hepcidin may have a protective effect on the heart for the ischemia-reperfusion injury.

The Dual Role of Inducible Nitric Oxide Synthase in Myocardial Ischemia/Reperfusion Injury: Friend or Foe?

Nitric oxide synthases (NOSs) are a family of enzymes that are responsible for the synthesis of nitric oxide (NO) from the amino acid L-arginine in the body. Among the three key NOSs, the expression of inducible NOS (iNOS) can only be induced by inflammatory stimuli and contribute to the large amount of NO production. iNOS-derived NO plays an important role in various physiological and pathophysiological conditions, including the ischemic heart disease. Nowadays, the development of specific iNOS inhibitors and the availability of iNOS knockout mice have provided substantial evidence to support the role of iNOS/NO signaling in the myocardium. Nevertheless, the role of iNOS/NO signaling in the myocardial ischemic reperfusion injury is very complex and highly perplexing; both detrimental and beneficial effects of iNOS have been described. Thus, this review will aim at providing basic insights into the current progress of the role of iNOS in myocardial ischemia reperfusion injury. A better understanding of the dual role of iNOS in details may help facilitate the development of more effective therapies for the management of ischemic heart diseases.

Protective effect of N-acetylcysteine activated carbon release microcapsule on myocardial ischemia-reperfusion injury in rats

With the development of science and technology, and development of artery bypass, methods such as cardiopulmonary cerebral resuscitation have been practiced in recent years. Despite this, some methods fail to promote or recover the function of tissues and organs, and in some cases, may aggravate dysfunction and structural damage to tissues. The latter is typical of ischemia-reperfusion (IR) injury. Lipid peroxidation mediated by free radicals is an important process of myocardial IR injury. Myocardial IR has been demonstrated to induce the formation of large numbers of free radicals in rats, which promotes the peroxidation of lipids within unsaturated fatty acids in the myocardial cell membrane. Markers of lipid peroxidation include malondialdehyde, superoxide dismutase and lactic dehydrogenase. Recent studies have demonstrated that N-acetylcysteine (NAC) is able to dilate blood vessels, prevent oxidative damage, improve immunity, inhibit apoptosis and the inflammatory response and promote glutathione synthesis in cells. NAC also improves the systolic function of myocardial cells and cardiac function, prevents myocardial apoptosis, protects ventricular remodeling and vascular remodeling, reduces opiomelanocortin levels in the serum and increases the content of nitric oxide in the serum, thus improving vascular endothelial function. Therefore, NAC has potent pharmacological activity; however, the relatively fast metabolism of NAC, along with its large clinical dose and low bioavailability, limit its applications. The present study combined NAC with medicinal activated carbons, and prepared N-acetylcysteine activated carbon sustained-release microcapsules (ACNACs) to overcome the limitations of NAC. It was demonstrated that ACNACs exerted greater effective protective effects than NAC alone on myocardial IR injury in rats.

Effects of a novel ascorbate-based protocol on infarct size and ventricle function in acute myocardial infarction patients undergoing percutaneous coronary angioplasty

INTRODUCTION

This study was designed to test the hypothesis that high-dose ascorbate prior to reperfusion followed by low chronic oral doses ameliorate myocardial reperfusion injury (MRI) in acute myocardial infarction patients subjected to primary percutaneous coronary angioplasty (PCA).

MATERIAL AND METHODS

A randomized double-blind placebo-controlled and multicenter clinical trial was performed on acute myocardial infarction (AMI) patients who underwent PCA. Sodium ascorbate (320 mmol/l, n = 53) or placebo (n = 46) was infused 30 min prior to PCA. Blood samples were drawn at enrolment (M1), after balloon deflation (M2), 6-8 h after M2 (M3) and at discharge (M4). Total antioxidant capacity of plasma (ferric reducing ability of plasma - FRAP), erythrocyte reduced glutathione (GSH) and plasma ascorbate levels were determined in blood samples. Cardiac magnetic resonance (CMR) was performed at 7-15 days and 2-3 months following PCA. Ninety-nine patients were enrolled. In 67 patients, the first CMR was performed, and 40 patients completed follow-up.

RESULTS

The ascorbate group showed significantly higher ascorbate and FRAP levels and a decrease in the GSH levels at M2 and M3 (p < 0.05). There were no significant differences in the infarct size, indexed end-systolic volume and ejection fraction at both CMRs. There was a significant amelioration in the decreased ejection fraction between the first and second CMR in the ascorbate group (p < 0.05).

CONCLUSIONS

Ascorbate given prior to reperfusion did not show a significant difference in infarct size or ejection fraction. However, it improved the change in ejection fraction determined between 7-15 days and 2-3 months. This result hints at a possible functional effect of ascorbate to ameliorate MRI.

Four Main Active Ingredients Derived from a Traditional Chinese Medicine Guanxin Shutong Capsule Cause Cardioprotection during Myocardial Ischemia Injury Calcium Overload Suppression

Guanxin Shutong capsule is a traditional Chinese medicine for the treatment of myocardial ischemia (MI). Previous studies have shown that the formula has four main active ingredients (FMAI), protocatechuic acid, cryptotanshinone, borneol, and eugenol. However, the mechanisms of action of these FMAI against MI injury are still not well known. The aim of the present study was to evaluate the protective effects of the FMAI on MI in vitro and in vivo. In vitro, rat neonatal cardiomyocytes were isolated, the cell viability and apoptosis rate were, respectively, measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method and fluorescence activating cell sorter, and the intracellular calcium concentration ([Ca²⁺ ]_i ) and CaM and CaMKII δ mRNA as well as protein levels were determined. Meanwhile, their downstream targets of RyR2 and PLB were also measured by western blot. In vivo, a rat model of coronary artery ligation was used to evaluate the cardioprotective effects. Infarct sizes of heart tissues and levels of serum biochemical indicators, including creatine kinase, lactate dehydrogenase, superoxide dismutase, and glutamate oxaloacetic transaminase, were measured. The in vitro results showed that the FMAI inhibited cell apoptosis, reduced [Ca²⁺ ]_i , decreased the expression of CaM and CaMKII δ, and increased the expression of RyR2 and PLB. In vivo, the FMAI diminished infract size, reduced creatine kinase, lactate dehydrogenase, and aspartate aminotransferase levels, and enhanced superoxide dismutase activity. In conclusion, our data suggest that the FMAI suppressed calcium overload and exerted its protective effect via its antioxidant, antiinflammatory, and anti-apoptosis activities. Copyright © 2017 John Wiley & Sons, Ltd.

Pterostilbene protects against myocardial ischemia/reperfusion injury via suppressing oxidative/nitrative stress and inflammatory response

Recent studies have shown that pterostilbene (Pte) confers protection against myocardial ischemia/reperfusion injury. The oxidative/nitrative stress and inflammation induce injury after myocardial ischemia/reperfusion. The present study was designed to evaluate whether treatment with Pte attenuates oxidative/nitrative stress and inflammation in myocardial ischemia/reperfusion (MI/R). Rats were subjected to 30min of myocardial ischemia and 3h of reperfusion, and the rats were administered with vehicle or Pte. The results showed that Pte (10mg/kg) dramatically improved cardiac function and reduced myocardial infarction and myocardial apoptosis following MI/R. As an indicator of oxidative/nitrative stress, myocardial ONOO^- content was markedly reduced after Pte treatment. And, Pte led to a dramatic decrease in superoxide generation and malondialdehyde (MDA) content and a dramatic increase in superoxide dismutase (SOD) activity. In addition, Pte treatment significantly reduced p38 MAPK activation and the expression of iNOS and gp91^phox and increased phosphorylated eNOS expression. Pte treatment dramatically decreased myocardial TNF-α, and IL-1β levels and myeloperoxidase (MPO) activity. Furthermore, ONOO^- suppression by either Pte or uric acid (UA), an ONOO^- scavenger, reduced myocardial injury. In conclusion, Pte exerts a protective effect against MI/R injury by suppressing oxidative/nitrative stress. These results provide evidence that Pte might be a therapeutic approach for the treatment of MI/R injury.

The Effect of Activated Protein C on Attenuation of Ischemia-Reperfusion Injury in a Rat Muscle Flap Model

Ischemia-reperfusion injury is often the final and irreversible factor causing flap failure in microsurgery. The salvage of a microsurgical flap with an ischemia-reperfusion injury contributes to the success of microsurgical flap transfers. Activated protein C (APC), a serine protease with anticoagulant and anti-inflammatory activities, has been shown to improve ischemic flap survival. To date, APC has yet to be applied to models of free flap with ischemia-reperfusion injury. In this study, we aimed to investigate the effect of APC on gracilis flap ischemia-reperfusion injury induced by gracilis vessels clamping and reopening. Sixty male Sprague-Dawley rats were randomly divided into 2 groups. After 4 hours of clamping for ischemia, flaps were reperfused and recombinant human APC (25 μg/kg) or saline was injected in the flaps through pedicles. At 0, 1, 4, 18, and 24 hours after injection (n = 6 for each time point), the tissue samples were harvested. The muscle viability at 24 hours in saline group was 54.8% (15.1%), whereas the APC-treated group was 90.0% (4.3%) (P < 0.05). The induced nitric oxide synthase (iNOS) mRNA expression increased with the time after reperfusion, which were 0.93 (0.25) to 2.09 (0.22) in saline group, and 0.197 (0.15) to 0.711 (0.15) in the APC-treated group. iNOS mRNA expression in the APC-treated group was significantly higher than the saline group at 1, 18, and 24 hours (P < 0.05). Numerous inflammatory cells were observed infiltrating and invading the muscle fibers in the saline group more than the APC-treated group. Increased number of polymorphonuclear cells was also noted in the saline group compared with the APC-treated group (P < 0.05). In conclusion, APC treatment can significantly attenuate ischemia-reperfusion injury and increase the survival of the free flap through down-regulating iNOS mRNA expression and reducing the inflammatory cells. Further research is still needed to be done on various mechanisms in which APC is protective to prevent tissue damage.

Olive oil-induced reduction of oxidative damage and inflammation promotes wound healing of pressure ulcers in mice

BACKGROUND

The overproduction of reactive oxygen species (ROS) and exacerbated inflammatory response are the main events that impair healing of pressure ulcers. Therefore, olive oil may be a good alternative to improve the healing of these chronic lesions due to its anti-inflammatory and antioxidant properties.

OBJECTIVE

This study investigated the effect of olive oil administration on wound healing of pressure ulcers in mice.

METHODS

Male Swiss mice were daily treated with olive oil or water until euthanasia. One day after the beginning of treatment, two cycles of ischemia-reperfusion by external application of two magnetic plates were performed in skin to induced pressure ulcer formation.

RESULTS

The olive oil administration accelerated ROS and nitric oxide (NO) synthesis and reduced oxidative damage in proteins and lipids when compared to water group. The inflammatory cell infiltration, gene tumor necrosis factor-α (TNF-α) expression and protein neutrophil elastase expression were reduced by olive oil administration when compared to water group. The re-epithelialization and blood vessel number were higher in the olive oil group than in the water group. The olive oil administration accelerated protein expression of TNF-α, active transforming growth factor-β1 and vascular endothelial growth factor-A when compared to water group. The collagen deposition, myofibroblastic differentiation and wound contraction were accelerated by olive oil administration when compared to water group.

CONCLUSION

Olive oil administration improves cutaneous wound healing of pressure ulcers in mice through the acceleration of the ROS and NO synthesis, which reduces oxidative damage and inflammation and promotes dermal reconstruction and wound closure.

Genome-wide association study of new-onset atrial fibrillation after coronary artery bypass grafting surgery

BACKGROUND

Postoperative atrial fibrillation (AF) is a potentially life-threatening complication after coronary artery bypass graft (CABG) surgery. Genetic predisposition may predict risk for developing postoperative AF.

METHODS

Study subjects underwent CABG surgery with cardiopulmonary bypass at Duke University Medical Center. In a discovery cohort of 877 individuals from the Perioperative Genetics and Safety Outcomes Study, we performed a genome-wide association study using a logistic regression model with a covariate adjustment for AF risk index. Single-nucleotide polymorphisms (SNPs) that met a P < 5 × 10(-5) were further tested using a replication dataset of 304 individuals from the CATHeterization GENetics biorepository, followed by meta-analysis. Potential pathways related to postoperative AF were identified through gene enrichment analysis using the top genome-wide association study SNPs (P < 10(-4)).

RESULTS

Nineteen SNPs met the a priori defined discovery threshold for replication, but only 3 met nominal significance (P < .05) in the CATHeterization GENetics group, with only one-rs10504554, in the intronic region in lymphocyte antigen 96 (LY96)-showing the same direction of the effect for postoperative AF (odds ratio [OR] 0.48, 95% CI 0.34-0.68, P = 2.9 × 10(-5) vs OR 0.55, 95% CI 0.31-0.99, P = .046) and strong overall association by meta-analysis (meta-P = 4.0 × 10(-6)). Gene enrichment analysis highlighted the role of LY96 in pathways of biologic relevance to activation and modulation of innate immune responses. Our analysis also showed potential association between LY96 and nuclear factor κ-B interaction and postoperative AF through their relevance to inflammatory signaling pathways.

CONCLUSIONS

In patients undergoing CABG surgery, we found genetic polymorphisms in LY96 associated with decreased risk of postoperative AF.

Effects of apocynin, an NADPH oxidase inhibitor, on levels of ADMA, MPO, iNOS and TLR4 induced by myocardial ischemia reperfusion

PURPOSE

In this study, the effects of apocynin, an NADPH oxidase inhibitor, on the levels of inducible nitric oxide synthase (iNOS) and the toll-like receptor 4 (TLR4), which are inflammatory mediators in myocardial ischemia-reperfusion (MIR) injury, and myeloperoxidase (MPO), which is the indicator of neutrophil infiltration and the endogenous nitric oxide synthase inhibitor asymmetric dimethyl arginine (ADMA) increasing with oxidative stress were investigated.

METHODS

MIR injury was accomplished by the application of occlusion for 30 minutes and reperfusion for 120 minutes in the left anterior descending artery (LAD). In the study, 21 Sprague-Dawley male rats were divided into three groups: a sham group (n = 7); a MIR group (n = 7); and a MIR + apocynin treatment group (n = 7, before the procedure, an intraperitoneal administration of 10 mg/kg of apocynin for 15 days). After reperfusion, iNOS, TLR4, MPO and ADMA levels in myocardial tissue were measured by ELISA.

RESULTS

While myocardial TLR4, MPO and ADMA levels increased in the MIR group, these parameters were found to be decreased significantly in the group treated with apocynin. Although iNOS levels showed an increase in the MIR group compared to the sham group and a reduction in the MIR+apocynin group, there was no statistically significant difference between the groups.

DISCUSSION

In our study, the effect of the treatment of apocynin in MIR on ADMA, MPO, iNOS and TLR4 levels in myocardial tissue was shown for the first time. It is thought that apocynin treatment may show a protective effect in MIR injury by affecting oxidative stress (ADMA) and inflammatory parameters (iNOS, MPO).

Foxp3+ CD4+ T cells improve healing after myocardial infarction by modulating monocyte/macrophage differentiation

RATIONALE

An exaggerated or persistent inflammatory activation after myocardial infarction (MI) leads to maladaptive healing and subsequent remodeling of the left ventricle. Foxp3(+) CD4(+) regulatory T cells (Treg cells) contribute to inflammation resolution. Therefore, Treg cells might influence cardiac healing post-MI.

OBJECTIVE

Our aim was to study the functional role of Treg cells in wound healing post-MI in a mouse model of permanent left coronary artery ligation.

METHODS AND RESULTS

Using a model of genetic Treg-cell ablation (Foxp3(DTR) mice), we depleted the Treg-cell compartment before MI induction, resulting in aggravated cardiac inflammation and deteriorated clinical outcome. Mechanistically, Treg-cell depletion was associated with M1-like macrophage polarization, characterized by decreased expression of inflammation-resolving and healing-promoting factors. The phenotype of exacerbated cardiac inflammation and outcome in Treg-cell-ablated mice could be confirmed in a mouse model of anti-CD25 monoclonal antibody-mediated depletion. In contrast, therapeutic Treg-cell activation by superagonistic anti-CD28 monoclonal antibody administration 2 days after MI led to improved healing and survival. Compared with control animals, CD28-SA-treated mice showed increased collagen de novo expression within the scar, correlating with decreased rates of left ventricular ruptures. Therapeutic Treg-cell activation induced an M2-like macrophage differentiation within the healing myocardium, associated with myofibroblast activation and increased expression of monocyte/macrophage-derived proteins fostering wound healing.

CONCLUSIONS

Our data indicate that Treg cells beneficially influence wound healing after MI by modulating monocyte/macrophage differentiation. Moreover, therapeutic activation of Treg cells constitutes a novel approach to improve healing post-MI.

Nitric oxide synthase regulation of cardiac excitation-contraction coupling in health and disease

Significant advances in our understanding of the ability of nitric oxide synthases (NOS) to modulate cardiac function have provided key insights into the role NOS play in the regulation of excitation-contraction (EC) coupling in health and disease. Through both cGMP-dependent and cGMP-independent (e.g. S-nitrosylation) mechanisms, NOS have the ability to alter intracellular Ca(2+) handling and the myofilament response to Ca(2+), thereby impacting the systolic and diastolic performance of the myocardium. Findings from experiments using nitric oxide (NO) donors and NOS inhibition or gene deletion clearly implicate dysfunctional NOS as a critical contributor to many cardiovascular disease states. However, studies to date have only partially addressed NOS isoform-specific effects and, more importantly, how subcellular localization of NOS influences ion channels involved in myocardial EC coupling and excitability. In this review, we focus on the contribution of each NOS isoform to cardiac dysfunction and on the role of uncoupled NOS activity in common cardiac disease states, including heart failure, diabetic cardiomyopathy, ischemia/reperfusion injury and atrial fibrillation. We also review evidence that clearly indicates the importance of NO in cardioprotection. This article is part of a Special Issue entitled "Redox Signalling in the Cardiovascular System".

Targeting NOS as a therapeutic approach for heart failure

Nitric oxide is a key signaling molecule in the heart and is produced endogenously by three isoforms of nitric oxide synthase, neuronal NOS (NOS1), endothelial NOS (NOS3), and inducible NOS (NOS2). Nitric oxide signals via cGMP-dependent or independent pathways to modulate downstream proteins via specific post translational modifications (i.e. cGMP-dependent protein kinase phosphorylation, S-nitrosylation, etc.). Dysfunction of NOS (i.e. altered expression, location, coupling, activity, etc.) exists in various cardiac disease conditions, such as heart failure, contributing to the contractile dysfunction, adverse remodeling, and hypertrophy. This review will focus on the signaling pathways of each NOS isoform during health and disease, and discuss current and potential therapeutic approaches targeting nitric oxide signaling to treat heart disease.

Preventive effects of Egyptian sweet marjoram (Origanum majorana L.) leaves on haematological changes and cardiotoxicity in isoproterenol-treated albino rats

We made an attempt to evaluate/compare the cardioprotective activity of two different doses (50 and 100 mg/kg body weight, given orally for 30 consecutive days) of Egyptian sweet marjoram leaf powder (MLP) and marjoram leaf aqueous extract (MLE) against isoproterenol (ISO)-induced myocardial infarcted rats (150 mg/kg body weight, twice at an interval of 24 h on days 29 and 30). The present study showed (probably for the first time) that both MLP and MLE (especially the high dose) significantly alleviated (P < 0.05-0.001) erythrocytosis, granulocytosis, thrombocytosis, shortened clotting time, the increase in relative heart weight, myocardial oxidative stress and the leakage of heart enzymes (creatine phosphokinase (CPK), CPK-MB isoenzyme, lactate dehydrogenase and aminotransferase) in ISO-treated rats through reactivating non-enzymic (reduced glutathione) and enzymic (catalase, glutathione peroxidase, glutathione S-transferase, superoxide dismutase) antioxidant defence system and inhibiting the production of nitric oxide and lipid peroxidation in heart tissues. The modulatory effects of marjoram leaves shown in the present study were dose-dependent in most cases and much higher in MLE (4.3-20.3 % for all parameters taken together). In addition, the doses used in the present study were considered safe. In conclusion, this study may have a significant impact on myocardial infarcted patients.

Protective effects of low-frequency magnetic fields on cardiomyocytes from ischemia reperfusion injury via ROS and NO/ONOO-

Background. Cardiac ischemia reperfusion (I/R) injury is associated with overproduction of reactive oxygen species (ROS). Low frequency pulse magnetic fields (LFMFs) have been reported to decrease ROS generation in endothelial cells. Whether LFMFs could assert protective effects on myocardial from I/R injury via ROS regulation remains unclear. Methods. To simulate in vivo cardiac I/R injury, neonatal rat cardiomyocytes were subjected to hypoxia reoxygenation (H/R) with or without exposure to LFMFs. Cell viability, apoptosis index, ROS generation (including O₂⁻ and ONOO⁻), and NO production were measured in control, H/R, and H/R + LFMF groups, respectively. Results. H/R injury resulted in cardiomyocytes apoptosis and decreased cell viability, whereas exposure to LFMFs before or after H/R injury significantly inhibited apoptosis and improved cell viability (P < 0.05). LFMFs treatment could suppress ROS (including O₂⁻ and ONOO⁻) generation induced by H/R injury, combined with decreased NADPH oxidase activity. In addition, LFMFs elevated NO production and enhanced NO/ONOO⁻ balance in cardiomyocytes, and this protective effect was via the phosphorylation of endothelial nitric oxide synthase (eNOS). Conclusion. LFMFs could protect myocardium against I/R injury via regulating ROS generation and NO/ONOO⁻ balance. LFMFs treatment might serve as a promising strategy for cardiac I/R injury.

α-Lipoic acid reduces infarct size and preserves cardiac function in rat myocardial ischemia/reperfusion injury through activation of PI3K/Akt/Nrf2 pathway

Background

The present study investigates the effects and mechanisms of α-Lipoic acid (LA) on myocardial infarct size, cardiac function and cardiomyocyte apoptosis in rat hearts subjected to in vivo myocardial ischemia/reperfusion (MI/R) injury.

Methodology/Principal Findings

Male adult rats underwent 30 minutes of ischemia followed by 3, 24, or 72 h of reperfusion. Animals were pretreated with LA or vehicle before coronary artery ligation. The level of MI/R- induced LDH and CK release, infarct size, cardiomyocyte apoptosis and cardiac functional impairment were examined and compared. Western blot analysis was performed to elucidate the mechanism of LA pretreatment. The level of inflammatory cytokine TNF-α released to serum and accumulated in injured myocardium as well as neutrophil accumulation in injured myocardium were also examined after MI/R injury. Our results reveal that LA administration significantly reduced LDH and CK release, attenuated myocardial infarct size, decreased cardiomyocytes apoptosis, and partially preserved heart function. Western blot analysis showed that LA pretreatment up-regulated Akt phosphorylation and Nrf2 nuclear translocation while producing no impact on p38MAPK activation or nitric oxide (NO) production. LA pretreatment also increased expression of HO-1, a major target of Nrf2. LA treatment inhibited neutrophil accumulation and release of TNF-α. Moreover, PI3K inhibition abolished the beneficial effects of LA.

Conclusions/Significance

This study indicates that LA attenuates cardiac dysfunction by reducing cardiomyoctyes necrosis, apoptosis and inflammation after MI/R. LA exerts its action by activating the PI3K/Akt pathway as well as subsequent Nrf2 nuclear translocation and induction of cytoprotective genes such as HO-1.

Association between plasma cyclic guanosine monophosphate levels and hemodynamic instability during liver transplantation

The activation of cyclic guanosine monophosphate (cGMP) production in patients with end-stage liver disease (ESLD) has been associated with hemodynamic instability during orthotopic liver transplantation (OLT). The aim of this prospective, observational study was to investigate the involvement of cGMP in the mediation of profound hypotension during liver graft reperfusion. An additional objective was to determine whether preoperative cGMP levels are associated with intraoperative hemodynamic instability. Forty-four consecutive patients undergoing OLT were included in the study. Blood samples for cGMP analysis were obtained from (1) the radial artery before the surgical incision; (2) the radial artery, portal vein, and flush blood during the anhepatic phase; and (3) the radial artery 20 minutes after liver graft reperfusion. On the basis of a statistical analysis, the patients were divided into 2 groups: group 1 (preoperative cGMP level ≥ 0.05 μmol/L) and group 2 (preoperative cGMP level < 0.05 μmol/L). We demonstrated a significant correlation between the preoperative levels of cGMP and the amount of catecholamine required to maintain hemodynamic stability during reperfusion (r = 0.52, P < 0.001), the length of the hospital stay (r = 0.38, P = 0.01), and the length of the intensive care unit (ICU) stay (r = 0.44, P = 0.004). We also demonstrated a significantly higher intraoperative catecholamine requirement (P < 0.001) and a prolonged postoperative ICU stay (P = 0.02) in group 1 patients versus group 2 patients. In conclusion, this study demonstrates increased baseline cGMP production in patients with ESLD, which is significantly associated with severe hypotension during OLT. We suggest that preoperative levels of cGMP correlate with hemodynamic instability during liver graft reperfusion.

Diesterified nitrone rescues nitroso-redox levels and increases myocyte contraction via increased SR Ca(2+) handling

Nitric oxide (NO) and superoxide (O₂⁻) are important cardiac signaling molecules that regulate myocyte contraction. For appropriate regulation, NO and O₂^.− must exist at defined levels. Unfortunately, the NO and O₂^.− levels are altered in many cardiomyopathies (heart failure, ischemia, hypertrophy, etc.) leading to contractile dysfunction and adverse remodeling. Hence, rescuing the nitroso-redox levels is a potential therapeutic strategy. Nitrone spin traps have been shown to scavenge O₂^.− while releasing NO as a reaction byproduct; and we synthesized a novel, cell permeable nitrone, 2–2–3,4-dihydro-2H-pyrrole 1-oxide (EMEPO). We hypothesized that EMEPO would improve contractile function in myocytes with altered nitroso-redox levels. Ventricular myocytes were isolated from wildtype (C57Bl/6) and NOS1 knockout (NOS1^−/−) mice, a known model of NO/O₂^.− imbalance, and incubated with EMEPO. EMEPO significantly reduced O₂^.− (lucigenin-enhanced chemiluminescence) and elevated NO (DAF-FM diacetate) levels in NOS1^−/− myocytes. Furthermore, EMEPO increased NOS1^−/− myocyte basal contraction (Ca²⁺ transients, Fluo-4AM; shortening, video-edge detection), the force-frequency response and the contractile response to β-adrenergic stimulation. EMEPO had no effect in wildtype myocytes. EMEPO also increased ryanodine receptor activity (sarcoplasmic reticulum Ca²⁺ leak/load relationship) and phospholamban Serine16 phosphorylation (Western blot). We also repeated our functional experiments in a canine post-myocardial infarction model and observed similar results to those seen in NOS1^−/− myocytes. In conclusion, EMEPO improved contractile function in myocytes experiencing an imbalance of their nitroso-redox levels. The concurrent restoration of NO and O₂^.− levels may have therapeutic potential in the treatment of various cardiomyopathies.

Strategic localization of heart mitochondrial NOS: a review of the evidence

Heart mitochondria play a central role in cell energy provision and in signaling. Nitric oxide (NO) is a free radical with primary regulatory functions in the heart and involved in a broad array of key processes in cardiac metabolism. Specific NO synthase (NOS) isoforms are confined to distinct locations in cardiomyocytes. The present article reviews the chemical reactions through which NO interacts with biomolecules and exerts some of its crucial roles. Specifically, the article discusses the reactions of NO with mitochondrial targets and the subcellular localization of NOS within the myocardium and analyzes the available data about heart mitochondrial NOS activity and identity. The article also describes the regulation of heart mtNOS by the distinctive mitochondrial environment by showing the effects of Ca(2+), O(2), l-arginine, mitochondrial transmembrane potential, and the metabolic states on heart mitochondrial NO production. The article depicts the effects of NO on heart function and highlights the relevance of NO production within mitochondria. Finally, the evidence on the functional implications of heart mitochondrial NOS is delineated with emphasis on chronic hypoxia and ischemia-reperfusion studies.

Protective effect of infliximab on ischemia/reperfusion-induced damage in rat kidney

OBJECTIVE

To investigate the protective effect of infliximab on ischemia-reperfusion (I/R) injury of the rat kidney.

METHODS

Twenty-eight male Wistar albino rats were divided into four groups: sham-operated, I/R, I/R with infliximab administered before ischemia [I/R + infliximab (bi)], and I/R with infliximab administered before reperfusion [I/R + infliximab (br)]. After a right nephrectomy to produce damage, the left renal vessels were occluded for 60 min, followed by 24-h reperfusion in rats. Changes in the rat kidney were observed by measuring the tissue levels of malondialdehyde (MDA), myeloperoxidase (MPO), glutathione (GSH), and superoxide dismutase (SOD) and by evaluating hematoxylin-eosin (H&E)-stained and periodic acid-Schiff (PAS) sections.

RESULTS

The MDA and MPO levels in the I/R group were significantly higher than in the other groups (p < 0.05), and the SOD and GSH levels in the I/R + infliximab (bi) and I/R + infliximab (br) groups were significantly higher than in the I/R group (p < 0.05). However, histological examination revealed that the I/R + infliximab (bi) group and the I/R + infliximab (br) group had significantly fewer tubular changes and interstitial inflammatory cell infiltration than the I/R group.

CONCLUSION

These results show that infliximab may protect against I/R injury in the rat I/R model.

Activation of parenchymal CD47 promotes renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) contributes to decreased allograft function and allograft rejection in transplanted kidneys. Thrombospondin-1 is a stress protein typically secreted in response to hypoxia and the ligand activator for the ubiquitously expressed receptor CD47. The function of activated CD47 in IRI remains completely unknown. Here, we found that both CD47 and its ligand thrombospondin-1 were upregulated after renal IRI in mice. CD47-knockout mice were protected against renal dysfunction and tubular damage, suggesting that the development of IRI requires intact CD47 signaling. Chimeric CD47-knockout mice engrafted with wild-type hematopoietic cells had significantly lower serum creatinine and less tubular damage than wild-type controls after IRI, suggesting that CD47 signaling in parenchymal cells predominantly mediates renal damage. Treatment with a CD47-blocking antibody protected mice from renal dysfunction and tubular damage compared with an isotype control. Taken together, these data imply that CD47 on parenchymal cells promotes injury after renal ischemia and reperfusion. Therefore, CD47 blockade may have therapeutic potential to prevent or suppress ischemia-reperfusion-mediated damage.

Protective effect of ligustrazine against myocardial ischaemia reperfusion in rats: the role of endothelial nitric oxide synthase

1. The aim of the present study was to determine whether ligustrazine (2,3,5,6-tetramethylpyrazine; TMP) exerts a cardioprotective effect during myocardial ischaemia reperfusion (IR), and to investigate the underlying mechanisms and the role of endothelial nitric oxide synthase (eNOS) in cardioprotection. 2. Sprague-Dawley rats were divided into a sham group and five IR groups: IR control, TMP pretreated, TMP + wortmannin (a phosphatidylinositol 3-kinase (PI3K) inhibitor), N(G) -nitro-L-arginine methyl ester (L-NAME; a NOS inhibitor) and TMP + L-NAME. IR was produced by 35 min of regional ischaemia followed by 120 min of reperfusion. Myocardial infarct size, oxidative stress, myocardial apoptosis, nitric oxide (NO) production, and expression of phosphorylated protein kinase B (Akt) and eNOS were measured. 3. TMP markedly decreased infarct size and attenuated myocardial apoptosis, as evidenced by a decrease in the apoptotic index and reduced caspase-3 activity. TMP treatment caused a marked increase in NO production. Cotreatment with wortmannin or L-NAME completely blocked the TMP-induced NO increase. TMP induced phosphorylation of Akt at Ser 473 (1.61 ± 0.18 vs 0.79 ± 0.10 in the IR control group) and phosphorylation of eNOS at Ser1177 (1.87 ± 0.33 vs 0.94 ± 0.22 in the IR control group). Wortmannin abrogated the phosphorylation of Akt and eNOS induced by TMP. 4. These data suggest that ligustrazine has anti-apoptotic and cardioprotective effects against myocardial IR injury and that it acts through the PI3K/Akt pathway. In addition, the phosphorylation of eNOS with subsequent NO production was found to be an important downstream effector that contributes significantly to the cardioprotective effect of TMP.

The protective effect of cilostazol on isolated rabbit femoral arteries under conditions of ischemia and reperfusion: the role of the nitric oxide pathway

OBJECTIVES

The clinical significance of ischemia/reperfusion of the lower extremities demands further investigation to enable the development of more effective therapeutic alternatives. This study investigated the changes in the vascular reactivity of the rabbit femoral artery and nitric oxide metabolites under partial ischemia/ reperfusion conditions following cilostazol administration.

METHODS

Ischemia was induced using infrarenal aortic clamping. The animals were randomly divided into seven groups: Control 90 minutes, Ischemia/Reperfusion 90/60 minutes, Control 120 minutes, Ischemia/Reperfusion 120/90 minutes, Cilostazol, Cilostazol before Ischemia/Reperfusion 120/90 minutes, and Ischemia 120 minutes/Cilostazol/ Reperfusion 90 minutes. Dose-response curves for sodium nitroprusside, acetylcholine, and the calcium ionophore A23187 were obtained in isolated femoral arteries. The levels of nitrites and nitrates in the plasma and skeletal muscle were determined using chemiluminescence.

RESULTS

Acetylcholine-and A23187-induced relaxation was reduced in the Ischemia/Reperfusion 120/90 group, and treatment with cilostazol partially prevented this ischemia/reperfusion-induced endothelium impairment. Only cilostazol treatment increased plasma levels of nitrites and nitrates. An elevation in the levels of nitrites and nitrates was observed in muscle tissues in the Ischemia/Reperfusion 120/90, Cilostazol/Ischemia/Reperfusion, and Ischemia/ Cilostazol/Reperfusion groups.

CONCLUSION

Hind limb ischemia/reperfusion yielded an impaired endothelium-dependent relaxation of the femoral artery. Furthermore, cilostazol administration prior to ischemia exerted a protective effect on endothelium-dependent vascular reactivity under ischemia/reperfusion conditions.

Role of inflammation in the regulation of coronary blood flow in ischemia and reperfusion: mechanisms and therapeutic implications

A multitude of factors, including increased coronary vascular resistance and dysregulated coronary microcirculatory function, contribute to the impairment of coronary blood flow (CBF) regulation and the pathogenesis of myocardial ischemia/reperfusion (I/R) injury. CBF is primarily determined by coronary vascular resistance, which is affected by the balance between various vasodilators and vasoconstrictors. Myocardial I/R causes reduced production of endogenous vasodilators, such as nitric oxide (NO), leaving unopposed vasoconstriction that is caused mainly by continued presence of endothelin-1 (ET-1) and serotonin (5-HT); this imbalance in turn enhances vascular tone, triggers inflammatory response, decreases CBF and exacerbates reperfusion injury. Various inflammatory cytokines participate in the regulation of coronary vasomotor function by affecting the balance between vasodilators and vasoconstrictors. In addition to the enhanced coronary vasoconstriction, coronary microembolization, inflammatory cell infiltration and post-ischemic hyperpermeability contribute to the impairment of coronary microcirculatory function and myocardial perfusion during I/R. Ongoing research examining the role of inflammation in the regulation of CBF and coronary microcirculatory function in myocardial I/R is expected to yield new insights that will lead to therapies for ameliorating the vascular inflammatory response in coronary artery diseases (CADs) in the clinical setting. This article is part of a Special Issue entitled "Coronary Blood Flow".

Protective effects of chinese traditional medicine buyang huanwu decoction on myocardial injury

Many clinical studies have reported that Buyang Huanwu Decoction (BYHWD) has a protective effect on ischemic heart disease (IHD). In the present study, the protective effect of BYHWD on myocardial ischemia was investigated. Different doses of BYHWD and Compound Danshen Dropping Pills (CDDP) were lavaged to rats, respectively, isoproterenol (ISO) was intraperitoneally injected in to all animals to induce myocardial ischemia except the control group. Electrocardiogram (ECG) of each animal was recorded; activities of lactate dehydrogenase (LDH), creatine kinase (CK) and aspartate aminotransferase (AST) in serum were detected. As the results of ECG showed, pre-treatment with BYHWD inhibited ischemic myocardial injury, and the activities of LDH, CK and AST were lower than those in the myocardial ischemia model group, which suggests that BYHWD rescues the myocardium from ischemia status. To research the potential mechanism, the level of nitric oxide (NO), nitric oxide syntheses (NOS) and inducible nitric oxide syntheses (iNOS), the expression of iNOS and ligand of cluster of differentiation 40 (CD40L) were detected. The results revealed that BYHWD significantly decreased the level of NO, NOS and iNOS in serum. Moreover, BYHWD decreased the expression of iNOS and CD40L in myocardial tissues. These results indicate that the protective effect of BYHWD on myocardial ischemia and mechanism are associated with inhibition of iNOS and CD40L expression.

Does inducible NOS have a protective role against hypoxia/reoxygenation injury in rat heart?

PURPOSE

The present study analyzes the role of the nitric oxide (NO) derived from inducible NO synthase (iNOS) under cardiac hypoxia/reoxygenation situations.

METHODS

For this, we have designed a follow-up study of different parameters of cell and tissue damage in the heart of Wistar rats submitted for 30 min to acute hypobaric hypoxia, with or without prior treatment with the selective iNOS inhibitor N-(3-(aminomethyl)benzyl) acetamidine or 1400W (10 mg/kg). The rats were studied at 0 h, 12 h, and 5 days of reoxygenation, analyzing NO production (NOx), lipid peroxidation, apoptosis, and protein nitration expression and location. This is the first time-course study which analyzes the effects of the iNOS inhibition by 1400W during hypoxia/reoxygenation in the adult rat heart.

RESULTS

The results show that when 1400W was administered before the hypoxic episode, NOx levels fell, while both the lipid peroxidation level and the percentage of apoptotic cells rose throughout the reoxygenation period. Levels of nitrated proteins expression fell only at 12 h post-hypoxia.

CONCLUSIONS

The inhibition of iNOS raises the peroxidative and apoptotic level in the hypoxic heart indicating that this isoform may have a protective effect on this organ against hypoxia/reoxygenation injuries, and challenging the conventional wisdom that iNOS is deleterious under these conditions. These findings could help in the design of new treatments based on NO pharmacology against hypoxia/reoxygenation dysfunctions.

Nicotine enhances skin necrosis and expression of inflammatory mediators in a rat pressure ulcer model

BACKGROUND

Many bedridden patients develop pressure ulcers, not only in hospital but also at home. Clinical studies have indicated cigarette smoking to be a risk factor for pressure ulcers. However, the contribution of nicotine to pressure ulcer formation has not been identified.

OBJECTIVES

We aimed to clarify the effect of nicotine on pressure ulcer formation, and its mechanism.

METHODS

Ischaemia-reperfusion (I/R) was performed in rat dorsal skin to induce pressure ulcers. The extent of the resulting necrotic area was determined. To clarify the mechanism of the effect of nicotine, mRNA levels of cyclooxygenase-2 (COX-2), interleukin (IL)-1beta, IL-6 and inducible nitric oxide synthase (iNOS) and protein expression of COX-2 and iNOS in the necrotic area were investigated by real-time reverse transcription-polymerase chain reaction and Western blotting, respectively. Furthermore, the effects of the COX-2 inhibitor NS-398 and the iNOS inhibitor aminoguanidine on necrosis were examined.

RESULTS

Skin necrosis in the I/R-treated area was significantly increased by intraperitoneal administration of nicotine (0.175 mg kg(-1) daily). Repeated nicotine administration had little effect on systolic and diastolic blood pressure. I/R treatment increased mRNA levels of COX-2, IL-1beta, IL-6 and iNOS, which were further augmented by nicotine in a dose-dependent manner. Correspondingly, nicotine (0.35 mg kg(-1) daily) markedly enhanced the protein expression of COX-2 and iNOS. Moreover, NS-398 and aminoguanidine showed a tendency to abrogate the increase of I/R-induced skin necrosis caused by nicotine.

CONCLUSIONS

These results suggest that the increased risk of pressure ulcers due to cigarette smoking is mediated, in part, by nicotine. They also indicated that the effect of nicotine is not mediated by a change in blood pressure, but is elicited via an increase of inflammatory mediators in the I/R-treated skin.

Prenatal hypoxia induces increased cardiac contractility on a background of decreased capillary density

Background

Chronic hypoxia in utero (CHU) is one of the most common insults to fetal development and may be associated with poor cardiac recovery from ischaemia-reperfusion injury, yet the effects on normal cardiac mechanical performance are poorly understood.

Methods

Pregnant female wistar rats were exposed to hypoxia (12% oxygen, balance nitrogen) for days 10–20 of pregnancy. Pups were born into normal room air and weaned normally. At 10 weeks of age, hearts were excised under anaesthesia and underwent retrograde 'Langendorff' perfusion. Mechanical performance was measured at constant filling pressure (100 cm H₂O) with intraventricular balloon. Left ventricular free wall was dissected away and capillary density estimated following alkaline phosphatase staining. Expression of SERCA2a and Nitric Oxide Synthases (NOS) proteins were estimated by immunoblotting.

Results

CHU significantly increased body mass (P < 0.001) compared with age-matched control rats but was without effect on relative cardiac mass. For incremental increases in left ventricular balloon volume, diastolic pressure was preserved. However, systolic pressure was significantly greater following CHU for balloon volume = 50 μl (P < 0.01) and up to 200 μl (P < 0.05). For higher balloon volumes systolic pressure was not significantly different from control. Developed pressures were correspondingly increased relative to controls for balloon volumes up to 250 μl (P < 0.05). Left ventricular free wall capillary density was significantly decreased in both epicardium (18%; P < 0.05) and endocardium (11%; P < 0.05) despite preserved coronary flow. Western blot analysis revealed no change to the expression of SERCA2a or nNOS but immuno-detectable eNOS protein was significantly decreased (P < 0.001) in cardiac tissue following chronic hypoxia in utero.

Conclusion

These data offer potential mechanisms for poor recovery following ischaemia, including decreased coronary flow reserve and impaired angiogenesis with subsequent detrimental effects of post-natal cardiac performance.

Nitric oxide signaling and the regulation of myocardial function

Nitric oxide, which is produced endogenously within cardiac myocytes by three distinct isoforms of nitric oxide synthase, is a key regulator of myocardial function. This review will focus on the regulation of myocardial function by each nitric oxide synthase isoform during health and disease, with a specific emphasis on the proposed end-targets and signaling pathways.

RAGE and modulation of ischemic injury in the diabetic myocardium

OBJECTIVE

Subjects with diabetes experience an increased risk of myocardial infarction and cardiac failure compared with nondiabetic age-matched individuals. The receptor for advanced glycation end products (RAGE) is upregulated in diabetic tissues. In this study, we tested the hypothesis that RAGE affected ischemia/reperfusion (I/R) injury in the diabetic myocardium. In diabetic rat hearts, expression of RAGE and its ligands was enhanced and localized particularly to both endothelial cells and mononuclear phagocytes.

RESEARCH DESIGN AND METHODS

To specifically dissect the impact of RAGE, homozygous RAGE-null mice and transgenic (Tg) mice expressing cytoplasmic domain-deleted RAGE (DN RAGE), in which RAGE-dependent signal transduction was deficient in endothelial cells or mononuclear phagocytes, were rendered diabetic with streptozotocin. Isolated perfused hearts were subjected to I/R.

RESULTS

Diabetic RAGE-null mice were significantly protected from the adverse impact of I/R injury in the heart, as indicated by decreased release of LDH and lower glycoxidation products carboxymethyl-lysine (CML) and pentosidine, improved functional recovery, and increased ATP. In diabetic Tg mice expressing DN RAGE in endothelial cells or mononuclear phagocytes, markers of ischemic injury and CML were significantly reduced, and levels of ATP were increased in heart tissue compared with littermate diabetic controls. Furthermore, key markers of apoptosis, caspase-3 activity and cytochrome c release, were reduced in the hearts of diabetic RAGE-modified mice compared with wild-type diabetic littermates in I/R.

CONCLUSIONS

These findings demonstrate novel and key roles for RAGE in I/R injury in the diabetic heart.

Myocardial cytokine IL-8 and nitric oxide synthase activity during and after resuscitation: preliminary observations in regards to post-resuscitation myocardial dysfunction

AIM

Increases in serum cytokines have been reported after successful resuscitation from prolonged ventricular fibrillation (VF). Pro-inflammatory cytokines can stimulate inducible nitric oxide synthase (iNOS) to produce excessive levels of nitric oxide (NO). High levels of both myocardial inflammatory cytokines and nitric oxide levels can depress myocardial contractile function. We hypothesized that myocardial pro-inflammatory cytokines and iNOS activity would increase following successful resuscitation from prolonged ventricular fibrillation cardiac arrest, and that such increases would parallel the development of post-resuscitation myocardial dysfunction.

METHODS

Ventricular fibrillation cardiac arrest was induced in seven domestic swine (25+/-5 kg). After 10 min of untreated VF, the animals were defibrillated and resuscitated. Left ventricular (LV) systolic and diastolic function measurements, serum samples (arterial and coronary sinus) for IL-8 cytokine quantification, and LV myocardial biopsies were collected before, during, and after resuscitation. Quantification of myocardial endothelial (eNOS) and inducible (iNOS) nitric oxide synthase protein levels were determined using immunoblot analyses and protein localization was examined using immunohistochemistry.

RESULTS

Post-resuscitation LV systolic and diastolic functions were depressed while increases in both coronary sinus IL-8 levels and myocardial iNOS activity were found. Compared to pre-arrest baseline, levels of iNOS protein increased during VF (p < or = 0.05) and continued to increase throughout the post-resuscitation study period of 6 h (p < or = 0.05).

CONCLUSIONS

Myocardial inflammatory cytokines and iNOS activity increase during and after prolonged cardiac arrest and successful resuscitation. These increases correspond to the well described decrease in LV function post-resuscitation.

Nitric oxide synthase isoform inhibition before whole body ischemia reperfusion in pigs: Vital or protective?

BACKGROUND

Nitric oxide (NO) is a critical regulator of vascular tone, and signal transduction. NO is produced via three unique synthases (NOS); endothelial (eNOS), and neuronal (nNOS) are both constitutively expressed and inducible (iNOS) produced primarily after stimulation. NO has been implicated during and after ischemia reperfusion injury as both a detrimental and cardioprotective mediator. Since cardiopulmonary resuscitation (CPR) in ventricular fibrillation (VF) is a model of whole body ischemia reperfusion injury, it provides an opportunity to assess the effects of NO from the three NOS isoforms.

OBJECTIVE

To determine the differential role of nitric oxide synthase isoforms inhibition in ventricular fibrillation CPR and investigate whether inhibition of the NOS isoforms afford any cardioprotection in this model.

METHODS

Thirty-two pigs, weight range 25-35 kg, were assigned to four groups of eight animals each. The animals were randomized to receive (1) N(G)-nitro-L-arginine methyl ester (LNAME), a non-selective endothelial nitric oxide synthase inhibitor, (2) 1-(2-trifluoromethylphenyl) imidazole (TRIM), a selective neuronal NOS inhibitor, (3) aminoguanidine (AMINOG), a selective inducible NOS inhibitor or (4) saline control (Control) in equal volumes, 30 min before induction of ventricular fibrillation (VF). After 3 min VF with no intervention, the animals received standard chest compressions using an automated chest compression device (Thumper) for 15 min. After 18 min of VF, single doses of vasopressin and bicarbonate were given and defibrillation attempted. Hemodynamics, regional blood flows, and echocardiography and were performed, before and after drug infusion, during CPR, and after return of spontaneous circulation (ROSC).

RESULTS

ROSC for 3 h occurred in 5/8 (63%), 1/8 (13%), 0/8 (0%), and 6/8 (75%) in Control, LNAME, TRIM, and AMINOG treated animals, respectively. After infusion of LNAME, there was a significant increase from baseline in blood pressure [127+/-6 mmHg versus 169+/-3 mmHg, p<0.002] and coronary perfusion pressure [119+/-6 mmHg versus 149+/-6 mmHg, p<0.003]. During CPR, there were no differences among groups in hemodynamics or regional blood flow. In surviving animals, AMINOG had significantly better myocardial function (left ventricular ejection fraction, fractional shortening, and wall motion score index) than control or LNAME treated animals, and attenuated the post-resuscitation hyperemic response in heart and brain.

CONCLUSIONS

Intact basal nNOS activity is vital for survival from whole body ischemia reperfusion injury. iNOS inhibition prior to ischemia reperfusion, protects myocardial function after ROSC and decreases myocardial and brain hyperemic response after ROSC.

Cardioprotective effects of nitric oxide-aspirin in myocardial ischemia-reperfused rats

In this study, the cardioprotective effects of nitric oxide (NO)-aspirin, the nitroderivative of aspirin, were compared with those of aspirin in an anesthetized rat model of myocardial ischemia-reperfusion. Rats were given aspirin or NO-aspirin orally for 7 consecutive days preceding 25 min of myocardial ischemia followed by 48 h of reperfusion (MI/R). Treatment groups included vehicle (Tween 80), aspirin (30 mg·kg−1·day−1), and NO-aspirin (56 mg·kg−1·day−1). NO-aspirin, compared with aspirin, displayed remarkable cardioprotection in rats subjected to MI/R as determined by the mortality rate and infarct size. Mortality rates for vehicle ( n = 23), aspirin ( n = 22), and NO-aspirin groups ( n = 22) were 34.8, 27.3, and 18.2%, respectively. Infarct size of the vehicle group was 44.5 ± 2.7% of the left ventricle (LV). In contrast, infarct size of the LV decreased in the aspirin- and NO-aspirin-pretreated groups, 36.7 ± 1.8 and 22.9 ± 4.3%, respectively (both P < 0.05 compared with vehicle group; P < 0.05, NO-aspirin vs. aspirin ). Moreover, NO-aspirin also improved ischemiareperfusion-induced myocardial contractile dysfunction on postischemic LV developed pressure. In addition, NO-aspirin downregulated inducible NO synthase (iNOS; 0.37-fold, P < 0.01) and cyclooxygenase-2 (COX-2; 0.61-fold, P < 0.05) gene expression compared with the vehicle group after 48 h of reperfusion. Treatment with NG-nitro-l-arginine methyl ester (l-NAME; 20 mg/kg), a nonselective NOS inhibitor, aggravated myocardial damage in terms of mortality and infarct size but attenuated effects when coadministered with NO-aspirin. l-NAME administration did not alter the increase in iNOS and COX-2 expression but did reverse the NO-aspirin-induced inhibition of expression of the two genes. The beneficial effects of NO-aspirin appeared to be derived largely from the NO moiety, which attenuated myocardial injury to limit infarct size and better recovery of LV function following ischemia and reperfusion.

Novel rat model of ischemic cardiomyopathy induced by repetitive myocardial ischemia/reperfusion injury while conscious

BACKGROUND

A rodent model of ischemic cardiomyopathy (ICM) induced by repetitive brief ischemia/reperfusion (I/R) injury while conscious has not been previously established.

METHODS AND RESULTS

A newly developed coronary occluder was implanted in male Wistar rats. A repetitive I/R protocol (20 s, 2 min, followed by main 30 min--ischemia, every 48 h, for 4 weeks) was introduced while the animals were conscious. The I/R protocol did not induce transmural scar formation but induced (1) residual myocytes with scattered infiltration of fibrosis (Masson trichrome stain), (2) coronary hypoperfusion ((201)Tl-Cl autoradiogram), (3) reduced coronary microvascular volume fraction (microCT), and (4) gradually progressive left ventricular (LV) dilation (echocardiography). These parameters of ICM showed interindividual variation; however, the percent increase in LV diastolic area on day 3 was significantly correlated with LV dilation (r=0.91, p<0.0001), fibrosis (r=0.77, p=0.0034), and reduction in microvessels (r=0.67, p=0.040) at week 4. The LV dilatory response on day 3 also correlated with inducible nitric oxide synthase expression (immunohistochemistry, day 3) in the LV (r=0.92, p=0.028).

CONCLUSIONS

A novel rat model of ICM induced by repetitive I/R while conscious showed interindividual variation in the severity of ICM in the advanced stage, but this was predictable non-invasively (by LV dilatory response) during the initial stage of repetitive I/R.

Diverse effects of L-arginine on cardiac function of rats subjected to myocardial ischemia and reperfusion in vivo

In vivo administration of L-arginine at different time points during the course of myocardial ischemia and reperfusion (MI/R) has been shown to differentially regulate postischemic apoptosis. Cardiac function is one of the most important indexes used to judge the degree of myocardial injury. The present study attempted to determine whether in vivo administration of L-arginine at different stages of MI/R has a diverse influence on cardiac function of ischemic reperfused hearts and, if so, to investigate the mechanisms involved. Male adult rats were subjected to 30 min myocardial ischemia followed by 5 h reperfusion. An intravenous L-arginine bolus was given either 10 min before and 50 min after reperfusion (early treatment) or 3 h and 4 h after reperfusion (late treatment). Early treatment with L-arginine markedly increased the left ventricular systolic pressure (LVSP) and dP/dt(max), and decreased myocardial nitrotyrosine content. In strict contrast, late treatment with L-arginine resulted in a significant decrease in LVSP and dP/dt(max) from 4 h to 5 h after reperfusion, and increase in toxic peroxynitrite formation as measured by nitrotyrosine. These results suggest that the administration of L-arginine at different time points during the course of MI/R leads to diverse effects on cardiac dysfunction. Early supplementation decreased the nitrative stress and improved left ventricular function. However, late treatment with L-arginine increased the formation of peroxynitrite and aggravated cardiac functional injury.

Improved postischemic function following acute exercise is not mediated by nitric oxide synthase in the rat heart

The mediators of acute exercise-induced preconditioning against ischemia-reperfusion injury are not understood. This study assesses the role of nitric oxide synthase (NOS), a reported mediator of other forms of preconditioning. Male Fischer 344 rats were divided into five groups ( n = 6–7): sedentary (Sed); exercised 2 days on a treadmill at 20 m/min, 6° grade, for 60 min (Run); sedentary, perfused with 100 μM Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME) to inhibit NOS (Sed/L-N); exercised, perfused with l-NAME (Run/L-N); and exercised in a 4°C environment, perfused with l-NAME (CRun/L-N). Twenty-four hours following exercise, isolated, perfused working hearts were subjected to 22.5 min of global ischemia plus 30 min of normoxic reperfusion. Left ventricle contents of several putative preconditioning mediators were determined. Postischemic recovery of cardiac output times systolic pressure was better in Run than Sed (78.4 vs. 50.2% of preischemia, P < 0.05). Inhibition of NOS did not abrogate the improved recovery in the exercise groups or alter recovery in Sed. All exercise groups also displayed improved myocardial efficiency (cardiac output times systolic pressure/oxygen consumption) postischemia and less lactate dehydrogenase release ( P < 0.05). l-NAME appeared to lower lactate dehydrogenase release independent of exercise. The only change in antioxidant enzyme activity was a decrease in manganese superoxide dismutase in CRun/L-N ( P < 0.05). Heat shock protein 72 expression increased only in Run and Run/L-N and endothelial NOS only in CRun/L-N ( P < 0.05). Acute exercise-induced preconditioning of the Fischer 344 rat heart is not mediated by NOS and does not require increases in heat shock protein 72 or antioxidant enzymes.

Repression of anti-apoptotic genes via AP-1 as a mechanism of apoptosis induction in ventricular cardiomyocytes

Nitric oxide (NO) is increased under several pathophysiological, mainly inflammatory processes in the heart and has been characterized as an inducer of apoptosis in cardiomyocytes. The transcription factor activating protein-1 (AP-1) has been identified as a mediator of NO-induced apoptosis. Genes that are regulated by AP-1 under apoptotic conditions have not been identified yet. Therefore, we performed a microarray analysis with subsequent real-time polymerase chain reaction (PCR) to identify genes regulated by AP-1 in NO-induced ventricular cardiomyocytes of rats and tested the functional role of these genes in apoptosis. Cardiomyocytes were transformed with AP-1 decoy oligonucleotides for inhibition of AP-1 activity. These, as well as non-transformed control cells, were stimulated with the NO donor (+/-)-S-nitroso-N-acetylpenicillamine (SNAP, 100 microM) for 2 h. Some of the genes with differential gene expression on microarrays were further analysed by real-time PCR. Genes that are induced by SNAP were not identified. However, four genes, pyridoxal kinase, heat shock protein 10 (Hsp10), antigen identified by monoclonal antibodies 4F2 (4F2) and myosin light chain 2, were downregulated by SNAP in presence of AP-1. Pyridoxal kinase, Hsp10 and 4F2 have anti-apoptotic effects in unstimulated cells because downregulation of their expression by antisense oligos induced apoptosis in cardiomyocytes. An involvement of these genes in NO-induced apoptosis could only be proven for pyridoxal kinase. In conclusion, using microarray technology, we identified three anti-apoptotic genes (Hsp10, 4F2 and pyridoxal kinase) in ventricular cardiomyocytes, which may help the cells to resist some apoptotic stimuli. The downregulation of these genes results in cardiomyocyte apoptosis. Prevention of their downregulation may protect cardiomyocytes against apoptotic stimuli, and this may be of therapeutic benefit.

Endothelial nitric oxide synthase (NOS3) knockout decreases NOS2 induction, limiting hyperoxygenation and conferring protection in the postischemic heart

Although it has been shown that endothelial nitric oxide synthase (eNOS)-derived nitric oxide downregulates mitochondrial oxygen consumption during early reperfusion, its effects on inducible NOS (iNOS) induction and myocardial injury during late reperfusion are unknown. Wild-type (WT) and eNOS(-/-) mice were subjected to 30 min of coronary ligation followed by reperfusion. Expression of iNOS mRNA and protein levels and peroxynitrite production were lower in postischemic myocardium of eNOS(-/-) mice than levels in WT mice 48 h postreperfusion. Significantly improved hemodynamics (+/-dP/dt, left ventricular systolic pressure, mean arterial pressure), increased rate pressure product, and reduced myocardial infarct size (18 +/- 2.5% vs. 31 +/- 4.6%) were found 48 h after reperfusion in eNOS(-/-) mice compared with WT mice. Myocardial infarct size was also significantly decreased in WT mice treated with the specific iNOS inhibitor 1400W (20.5 +/- 3.4%) compared with WT mice treated with PBS (33.9 +/- 5.3%). A marked reperfusion-induced hyperoxygenation state was observed by electron paramagnetic resonance oximetry in postischemic myocardium, but Po(2) values were significantly lower from 1 to 72 h in eNOS(-/-) than in WT mice. Cytochrome c-oxidase activity and NADH dehydrogenase activity were significantly decreased in postischemic myocardium in WT and eNOS(-/-) mice compared with baseline control, respectively, and NADH dehydrogenase activity was significantly higher in eNOS(-/-) than in WT mice. Thus deficiency of eNOS exerted a sustained beneficial effect on postischemic myocardium 48 h after reperfusion with preserved mitochondrial function, which appears to be due to decreased iNOS induction and decreased iNOS-derived peroxynitrite in postischemic myocardium.