Rationale: Coronary artery ligation to induce myocardial infarction (MI) in mice is typically performed by an invasive and time-consuming approach that requires ventilation and chest opening (classic method), often resulting in extensive tissue damage and high mortality. We developed a novel and rapid surgical method to induce MI that does not require ventilation.Objective: The purpose of this study was to develop and comprehensively describe this method and directly compare it to the classic method. Key Words: myocardial ischemia Ⅲ myocardial ischemia/reperfusion injury Ⅲ cardiac injury Ⅲ cardiac dysfunction Ⅲ mouse model C ardiovascular disease represents the leading cause of morbidity and death in developed countries. Coronary heart disease, which is the single largest cause of cardiovascular disease, is the narrowing of arteries over time caused by atherosclerotic plaques or the acute occlusion of the coronary artery by thrombosis, both of which lead to possible myocardial infarction (MI) and the eventual development of heart failure. 1,2 Protection from coronary heart disease-induced damage of the myocardium during myocardial ischemia/ reperfusion (I/R) injury has been a target of investigation for the development of innovative cardioprotective therapies. [3][4][5][6][7] The increase in the availability of various types of genetically manipulated mice has brought about the need for more efficient ways to induce myocardial damage for both molecular mechanistic studies and potentially therapeutic interventions. Two of the most common models used by researchers are permanent left main descending coronary artery (LCA) occlusion to induce a MI and also temporary coronary artery occlusion to induce I/R injury. 8,9 The I/R model is generally used to examine the short-term consequences of ischemic injury, whereas the MI model is usually used to investigate myocardial changes such as remodeling that occur over an extended period of time. Although a variety of surgical manipulations have been used during the past decade to induce the ischemic event, ligation of the LCA is still the most commonly practiced method. 3,9 -11 However, most investigators still use a method requiring ventilation and wide opening the chest (referred to as the classic method), which can cause extensive tissue damage, high surgical-related death and can also be quite time consuming for most surgeons. [12][13][14][15] Over the last few years, we have developed a new MI approach in mice that does not require ventilation. 11,16 -18 Complete characterization and description of this model has Original Methods and Results:

Background-Several clinical studies have demonstrated that levels of adiponectin are significantly reduced in patients with type 2 diabetes and that adiponectin levels are inversely related to the risk of myocardial ischemia. The present study was designed to determine the mechanism by which adiponectin exerts its protective effects against myocardial ischemia/reperfusion. Methods and Results-AdiponectinϪ/Ϫ or wild-type mice were subjected to 30 minutes of myocardial ischemia followed by 3 hours or 24 hours (infarct size and cardiac function) of reperfusion. Myocardial infarct size and apoptosis, production of peroxynitrite, nitric oxide (NO) and superoxide, and inducible NO synthase (iNOS) and gp91 phox protein expression were compared. Myocardial apoptosis and infarct size were markedly enhanced in adiponectin Ϫ/Ϫ mice (PϽ0.01). Formation of NO, superoxide, and their cytotoxic reaction product, peroxynitrite, were all significantly higher in cardiac tissue obtained from adiponectin Ϫ/Ϫ than from wild-type mice (PϽ0.01). Moreover, myocardial ischemia/ reperfusion-induced iNOS and gp91 phox protein expression was further enhanced, but endothelial NOS phosphorylation was reduced in cardiac tissue from adiponectin Ϫ/Ϫ mice. Administration of the globular domain of adiponectin 10 minutes before reperfusion reduced myocardial ischemia/reperfusion-induced iNOS/gp91 phox protein expression, decreased NO/superoxide production, blocked peroxynitrite formation, and reversed proapoptotic and infarctenlargement effects observed in adiponectin Ϫ/Ϫ mice. Conclusion-The present study demonstrates that adiponectin is a natural molecule that protects hearts from ischemia/ reperfusion injury by inhibition of iNOS and nicotinamide adenine dinucleotide phosphate-oxidase protein expression and resultant oxidative/nitrative stress.

Background-Activation of p38 mitogen-activated protein kinase (MAPK) plays an important role in apoptotic cell death.The role of p38 MAPK in myocardial injury caused by ischemia/reperfusion, an extreme stress to the heart, is unknown.

SUMMARY Adiponectin is an abundant plasma protein secreted from adipocytes that elicits protective effects in the vasculature and myocardium. In obesity and insulin-resistant states, adiponectin levels are reduced and loss of its protective effects might contribute to the excess cardiovascular risk observed in these conditions. Adiponectin ameliorates the progression of macrovascular disease in rodent models, consistent with its correlation with improved vascular outcomes in epidemiological studies. The mechanisms of adiponectin signaling are multiple and vary among its cellular sites of action. In endothelial cells, adiponectin enhances production of nitric oxide, suppresses production of reactive oxygen species, and protects cells from inflammation that results from exposure to high glucose levels or tumor necrosis factor, through activation of AMP-activated protein kinase and cyclic AMP-dependent protein kinase (also known as protein kinase A) signaling cascades. In the myocardium, adiponectin-mediated protection from ischemia-reperfusion injury is linked to cyclo-oxygenase-2-mediated suppression of tumor necrosis factor signaling, inhibition of apoptosis by AMP-activated protein kinase, and inhibition of excess peroxynitrite-induced oxidative and nitrative stress. In this Review, we provide an update of studies of the signaling effects of adiponectin in endothelial cells and cardiomyocytes.

Apoptosis contributes to myocardial ischemia/reperfusion (MI/R) injury, and both thioredoxin (Trx) and nitric oxide have been shown to exert antiapoptotic effects in vitro . Recent evidence suggests that this particular action of Trx requires S-nitrosation at Cys-69. The present study sought to investigate whether or not exogenously applied Trx reduces MI/R injury in vivo and to which extent this effect depends on S-nitrosation. Adult mice were subjected to 30 min of MI and treated with either vehicle or human Trx (hTrx, 2 mg/kg, i.p.) 10 min before reperfusion. Native hTrx was incorporated into myocardial tissue as shown by immunostaining, and reduced MI/R injury as evidenced by decreased terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) staining, DNA fragmentation, caspase-3 activity, and infarct size. When hTrx was partially S-nitrosated by preincubation with S -nitrosoglutathione, its cardioprotective effect was markedly enhanced. Treatment with hTrx significantly reduced p38 mitogen-activated protein kinase (MAPK) activity, and this effect was also potentiated by S-nitrosation. To further address the role of S-nitrosation for the overall antiapoptotic effect to Trx, the action of Escherichia coli Trx (eTrx) was investigated in the same model. Whereas eTrx inhibited MI/R-induced apoptosis to a degree similar to hTrx, S-nitrosation of this protein, which lacks Cys-69, failed to further enhance its antiapoptotic action. Collectively, our results demonstrate that systemically applied Trx is taken up by the myocardium to exert potent cardioprotective effects in vivo , offering interesting therapeutic avenues. In the case of hTrx, these effects are further potentiated by S-nitrosation, but this posttranslational modification is not essential for protection.

It is well recognized that insulin resistance found in patients with type 2 diabetes and obesity is a major risk factor for cardiovascular disease. Since its discovery in the 1920s, insulin has been used as an essential therapeutic agent in diabetes for blood glucose management. Recent studies demonstrate that insulin signalling is essential for normal cardiovascular function, and lack of it (i.e. insulin resistance) will result in cardiovascular dysfunction and disease. Moreover, insulin is the key component of glucose-insulin-potassium cocktail and exerts significant cardiovascular protective effect via a phosphatidylinositol 3'-kinase-protein kinase B-endothelial nitric oxide synthase (PI3K-Akt-eNOS)-dependent signalling mechanism in addition to its metabolic modulation, which renders it a potent organ protector in multiple clinical applications. This review focuses on insulin-initiated PI3K-Akt-eNOS survival signalling, with nitric oxide as an 'end effector' delivering cardioprotection in health and disease (especially in ischaemic heart disease), and highlights the impairment of this survival signalling as a key link between insulin resistance and cardiovascular disease.

Recent experimental evidence suggests that reactive nitrogen oxide species can contribute significantly to postischemic myocardial injury. The aim of the present study was to evaluate the role of two reactive nitrogen oxide species, nitroxyl (NO ؊ ) and nitric oxide (NO ⅐ ), in myocardial ischemia and reperfusion injury. Rabbits were subjected to 45 min of regional myocardial ischemia followed by 180 min of reperfusion. Vehicle (0.9% NaCl), 1 mol͞kg Snitrosoglutathione (GSNO) (an NO ⅐ donor), or 3 mol͞kg Angeli's salt (AS) (a source of NO ؊ ) were given i.v. 5 min before reperfusion. Treatment with GSNO markedly attenuated reperfusion injury, as evidenced by improved cardiac function, decreased plasma creatine kinase activity, reduced necrotic size, and decreased myocardial myeloperoxidase activity. In contrast, the administration of AS at a hemodynamically equieffective dose not only failed to attenuate but, rather, aggravated reperfusion injury, indicated by an increased left ventricular end diastolic pressure, myocardial creatine kinase release and necrotic size. Decomposed AS was without effect. Co-administration of AS with ferricyanide, a one-electron oxidant that converts NO ؊ to NO ⅐ , completely blocked the injurious effects of AS and exerted significant cardioprotective effects similar to those of GSNO. These results demonstrate that, although NO ⅐ is protective, NO ؊ increases the tissue damage that occurs during ischemia͞reperfusion and suggest that formation of nitroxyl may contribute to postischemic myocardial injury.free radicals ͉ reperfusion ͉ neutrophils N itric oxide (NO ⅐ ) is produced from L-arginine by a family of isoenzymes, the so-called nitric oxide synthases (NOS). Whereas the physiological production of NO ⅐ from the endothelial isoform (eNOS) plays a critical role in cardiovascular homeostasis, excess production of NO ⅐ by the inducible isoform (iNOS) is involved in host defense mechanisms and has been postulated to not only mediate cytotoxicity but also cause tissue injury in a variety of pathological states (1). Several recent studies have demonstrated that NOS inhibition significantly attenuates postischemic myocardial injury (2-4). It has thus been hypothesized that, in addition to reactive oxygen species (ROS), which have been implicated in ischemia͞reperfusion injury for a number of years (5), reactive nitrogen oxide species (RNOS) generated from NOS may also contribute to postischemic myocardial injury (6).Peroxynitrite anion (ONOO Ϫ ), a RNOS produced from the interaction between NO ⅐ and superoxide (O 2 . ), has received considerable attention in recent years. A number of in vitro biochemical studies have demonstrated that ONOO Ϫ is highly reactive toward a wide variety of compounds and results in an oxidative tissue damage similar to that caused by hydroxyl radicals ( ⅐ OH) (7). Based on these in vitro observations, it has been suggested that ONOO Ϫ may play a significant role in tissue damage mediated by RNOS after ischemia and reperfusion (8). However, recent studies from...

improves endothelial function in hyperlipidemic rats by reducing oxidative/nitrative stress and differential regulation of eNOS/iNOS activity. Am J Physiol Endocrinol Metab 293: E1703-E1708, 2007. First published September 25, 2007 doi:10.1152/ajpendo.00462.2007.-Plasma adiponectin level is significantly reduced in patients with metabolic syndrome, and vascular dysfunction is an important pathological event in these patients. However, whether adiponectin may protect endothelial cells and attenuate endothelial dysfunction caused by metabolic disorders remains largely unknown. Adult rats were fed with a regular or a high-fat diet for 14 wk. The aorta was isolated, and vascular segments were incubated with vehicle or the globular domain of adiponectin (gAd; 2 g/ml) for 4 h. The effect of gAd on endothelial function, nitric oxide (NO) and superoxide production, nitrotyrosine formation, gp91 phox expression, and endothelial nitric oxide synthase (eNOS)/inducible NOS (iNOS) activity/expression was determined. Severe endothelial dysfunction (maximal vasorelaxation in response to ACh: 70.3 Ϯ 3.3 vs. 95.2 Ϯ 2.5% in control, P Ͻ 0.01) was observed in hyperlipidemic aortic segments, and treatment with gAd significantly improved endothelial function (P Ͻ 0.01). Paradoxically, total NO production was significantly increased in hyperlipidemic vessels, and treatment with gAd slightly reduced, rather than increased, total NO production in these vessels. Treatment with gAd reduced (Ϫ78%, P Ͻ 0.01) superoxide production and peroxynitrite formation in hyperlipidemic vascular segments. Moreover, a moderate attenuation (Ϫ30%, P Ͻ 0.05) in gp91 phox and iNOS overexpression in hyperlipidemic vessels was observed after gAd incubation. Treatment with gAd had no effect on eNOS expression but significantly increased eNOS phosphorylation (P Ͻ 0.01). Most noticeably, treatment with gAd significantly enhanced eNOS (ϩ83%) but reduced iNOS (Ϫ70%, P Ͻ 0.01) activity in hyperlipidemic vessels. Collectively, these results demonstrated that adiponectin protects the endothelium against hyperlipidemic injury by multiple mechanisms, including promoting eNOS activity, inhibiting iNOS activity, preserving bioactive NO, and attenuating oxidative/nitrative stress. metabolic syndrome; endothelial dysfunction; cytokine; nitric oxide; endothelial nitric oxide synthase; inducible nitric oxide synthase METABOLIC SYNDROME IS CHARACTERIZED by a group of metabolic and hemostatic abnormalities, including impaired glucose tolerance, hyperinsulinemia, hypertension, dyslipidemia, oxidant stress, and endothelial dysfunction (7). This cluster generates an increased risk of macroangiopathy, which is the leading cause of mortality for patients with metabolic syndrome and type 2 diabetes (3). Therefore, the discovery of therapeutic interventions that block or attenuate metabolic disorder-induced macroangiopathy holds great promise in reducing metabolic syndrome-related death.Endothelial dysfunction is an early pivotal event in the development, progression, and manifestat...