Ischaemia or reperfusion: which is a main trigger for changes in nitric oxide mRNA synthases expression?

Neutrophil Gelatinase-Associated Lipocalin 2 Accelerates Hypoxia-Induced Endothelial Cell Injury via eNOS/NRF2 Signalling

Objective

Neutrophil gelatinase-associated lipocalin (NGAL), a lipocalin, is implicated in many cardiovascular diseases (CVD). The effect of NGAL on endothelial cells (ECs), particularly on ECs injured because of hypoxia, is unclear. In this study, we aim to explore the effect of NGAL in an EC injury in response to hypoxia.

Materials and Methods

In this experimental study, we isolated and cultured mouse heart ECs (MHECs). The EC injury model was established by exposure of the ECs to hypoxia for 24 hours. The ECs were treated with NGAL (30, 60, 120, 250 and 500 ng/ml). Cell inflammation and oxidative stress were detected by corresponding assays. Apoptotic cells were stained by the terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay.

Results

NGAL increased the inflammatory response at the baseline level and further augmented the hypoxia-induced inflammation response. Reactive oxygen species (ROS) levels increased upon NGAL treatment, which caused antioxidase/oxidase imbalance. NGAL also exaggerated hypoxia-induced oxidative stress. The cell apoptosis rate also increased in both the NGAL-treated normoxic and hypoxic conditions. NGAL also reduced endothelial nitric oxide synthase (eNOS)-nitric oxide (NO) signalling, thus decreasing the expression and nuclear translocation of nuclear factor erythroid-2-related factor 2 (NRF2), which was confirmed by overexpression of NRF2.

Conclusion

NGAL exaggerates EC injury in both normoxic and hypoxic conditions by inhibiting the eNOS-NRF2 pathway.

An injectable conductive hydrogel encapsulating plasmid DNA-eNOs and ADSCs for treating myocardial infarction

Myocardial infarction (MI) leads to the mass death of cardiomyocytes accompanying with the unfavorable alternation of microenvironment, a fibrosis scar deprived of electrical communications, and the lack of blood supply in the infarcted myocardium. The three factors are inextricably intertwined and thus result in a conservative MI therapy efficacy in clinic. A holistic approach pertinently targeted to these three key points would be favorable to rebuild the heart functions. Here, an injectable conductive hydrogel was constructed via in situ Michael addition reaction between multi-armed conductive crosslinker tetraaniline-polyethylene glycol diacrylate (TA-PEG) and thiolated hyaluronic acid (HA-SH). The resultant soft conductive hydrogel with equivalent myocardial conductivity and anti-fatigue performance was loaded with plasmid DNA encoding eNOs (endothelial nitric oxide synthase) nanocomplexes and adipose derived stem cells (ADSCs) for treating MI. The TA-PEG/HA-SH/ADSCs/Gene hydrogel-based holistic system was injected into the infarcted myocardium of SD rats. We demonstrated an increased expression of eNOs in myocardial tissue the heightening of nitrite concentration, accompanied with upregulation of proangiogenic growth factors and myocardium related mRNA. The results of electrocardiography, cardiogram, and histological analysis convincingly revealed a distinct increase of ejection fraction (EF), shortened QRS interval, smaller infarction size, less fibrosis area, and higher vessel density, indicating a significant improvement of heart functions. This conception of combination approach by a conductive injectable hydrogel loaded with stem cells and gene-encoding eNOs nanoparticles will become a robust therapeutic strategy for the treatment of MI.

Inducible NO Synthase mRNA Expression and Infiltration of Rats Myocardium with Inflammatory Cells in 2-4 Hours after Modeled Permanent Ischemia or Ischemia/Reperfusion

Expression of inducible NO-synthase mRNA and myocardial infiltration with neutrophils were studied in rats with modeled permanent ischemia and ischemia/reperfusion models. Expression of inducible NO synthase mRNA in the ischemic region increased significantly in 3, 3.5, and 4 h in modeled ischemia/reperfusion and in 3.5 and 4 h in permanent ischemia. Myocardial infiltration with neutrophils was significantly higher than in intact controls throughout the experiment without significant intergroup differences. In non-ischemic myocardium, enhanced expression of inducible NO synthase mRNA and moderate neutrophilic-lymphocytic myocardial infiltration were also observed in 3.5, and 4 h after ischemia.

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".

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.

Strong cardioprotective effect of resveratrol, a red wine polyphenol, on isolated rat hearts after ischemia/reperfusion injury

We have studied some hemodynamic parameters as heart rate (HR) developed pressure (DP) and maximal positive values of the first derivative of pressure (+dP/dt max) in isolated heart from control or resveratrol treated rats. In acute ex vivo experiments, resveratrol (1-100 microM) infusion in Langendorff perfused hearts did not affect contractile function in either normoxic conditions or after ischemia/reperfusion. However when semi-chronically administered by IP injection during 7 days, resveratrol which had no effect on pre-ischemic heart greatly improved post-ischemic indexes of myocardial function. Resveratrol effect is dose-dependent and seemed optimal at a plasma level of 18.5 microM. This concentration is very close to that previously shown to be optimal and non-toxic by others. These beneficial effects of resveratrol are only partly explained by its antioxidant properties as suggested by the lack of any dose-response effect on tissue malondialdehyde (MDA) levels. They are also clearly not mediated by nitric oxide (NO) elevation. When acutely infused resveratrol had no beneficial effect and therefore could not be proposed in acute scenarios of ischemia/reperfusion or stroke. However resveratrol appeared as an efficient and promising molecule in the prevention of heart dysfunction.