Modulating the nitric oxide - cyclic GMP pathway in the pressure-overloaded left ventricle and group II pulmonary hypertension

Contribution of Oxidative Stress (OS) in Calcific Aortic Valve Disease (CAVD): From Pathophysiology to Therapeutic Targets

Calcific aortic valve disease (CAVD) is a major cause of cardiovascular mortality and morbidity, with increased prevalence and incidence. The underlying mechanisms behind CAVD are complex, and are mainly illustrated by inflammation, mechanical stress (which induces prolonged aortic valve endothelial dysfunction), increased oxidative stress (OS) (which trigger fibrosis), and calcification of valve leaflets. To date, besides aortic valve replacement, there are no specific pharmacological treatments for CAVD. In this review, we describe the mechanisms behind aortic valvular disease, the involvement of OS as a fundamental element in disease progression with predilection in AS, and its two most frequent etiologies (calcific aortic valve disease and bicuspid aortic valve); moreover, we highlight the potential of OS as a future therapeutic target.

Cardiovascular bioimaging of nitric oxide: Achievements, challenges, and the future

Nitric oxide (NO) is a ubiquitous, volatile, cellular signaling molecule that operates across a wide physiological concentration range (pM-µM) in different tissues. It is a highly diffusible messenger and intermediate in various metabolic pathways. NO plays a pivotal role in maintaining optimum cardiovascular function, particularly by regulating vascular tone and blood flow. This review highlights the need for accurate, real-time bioimaging of NO in clinical diagnostic, therapeutic, monitoring, and theranostic applications within the cardiovascular system. We summarize electrochemical, optical, and nanoscale sensors that allow measurement and imaging of NO, both directly and indirectly via surrogate measurements. The physical properties of NO render it difficult to accurately measure in tissues using direct methods. There are also significant limitations associated with the NO metabolites used as surrogates to indirectly estimate NO levels. All these factors added to significant variability in the measurement of NO using available methodology have led to a lack of sensors and imaging techniques of clinical applicability in relevant vascular pathologies such as atherosclerosis and ischemic heart disease. Challenges in applying current methods to biomedical and clinical translational research, including the wide physiological range of NO and limitations due to the characteristics and toxicity of the sensors are discussed, as are potential targets and modifications for future studies. The development of biocompatible nanoscale sensors for use in combination with existing clinical imaging modalities provides a feasible opportunity for bioimaging NO within the cardiovascular system.

Attenuating effects of dihydromyricetin on angiotensin II-induced rat cardiomyocyte hypertrophy related to antioxidative activity in a NO-dependent manner

CONTEXT

Dihydromyricetin (DMY) displays a range of biological properties. However, whether DMY attenuates cardiomyocyte hypertrophy is unknown.

OBJECTIVE

To investigate whether DMY had potential therapeutic value to protect against angiotensin II (Ang II)-induced cardiomyocyte hypertrophy.

MATERIALS AND METHODS

Neonatal rat cardiomyocytes were pretreated with DMY (0-320 μM) followed with Ang II (100 nM) stimulation for 24 h, and then degree of hypertrophy was evaluated by cell surface analysis. Levels of reactive oxygen species (ROS) were measured with 2',7'-dichlorfluorescein-diacetate (DCFH-DA) fluorescent staining. Antioxidative activity was evaluated by malondialdehyde (MDA) level, superoxide dismutase (SOD) activity, and total antioxidant capacity (T-AOC). Cyclic guanosine monophosphate (cGMP) was determined with a radioimmunoassay.

RESULTS

Pre-incubation with DMY (20, 40, 80, and 160 μM) for 8 h, 12 h, 24 h, or 48 h decreased cell surface areas. It down-regulated mRNA expression of atrial natriuretic factor (1.95- to 1.24-fold) and β-myosin heavy chains (3.51- to 2.32-fold), reduced levels of MDA as well as increased SOD activity and T-AOC. Expression of SOD and thioredoxin were enhanced by DMY, whereas p22(phox) and phosphorylation of mitogen-activated protein kinases were inhibited. Content of cGMP (0.54- to 0.80-fold) and phosphorylation of endothelial nitric oxide synthase at serine 1177 (0.70- to 1.05-fold) were augmented by DMY. Moreover, attenuating effect of DMY on hypertrophy was abolished when NO production was inhibited by l-NAME.

CONCLUSION

Attenuating effects of DMY on Ang II-induced cardiomyocyte hypertrophy related to antioxidative activity in a NO-dependent manner.

Pulmonary hypertension and right heart failure in heart failure with preserved left ventricular ejection fraction: pathophysiology and natural history

PURPOSE OF REVIEW

Pulmonary hypertension and right heart failure are common findings in patients suffering from heart failure with preserved ejection fraction (HFpEF). In this review, we summarize our current understanding of the pathophysiology of pulmonary hypertension related to heart failure.

RECENT FINDINGS

HFpEF is a clinical syndrome with increasing prevalence and a mortality rate similar to heart failure with reduced ejection fraction. Because the pathophysiology and even the definition of this disease are still controversial, we will first outline the current conceptual framework around heart failure with preserved ejection fraction. Next, we will outline our current knowledge on the pathophysiology of pulmonary hypertension related to left ventricular failure and diastolic dysfunction. Diastolic dysfunction induces pulmonary hypertension through passive transmission of elevated end diastolic pressures, reactive pulmonary vasoconstriction, and vascular remodeling. Eventually, right ventricular failure develops that can further potentiate left ventricular failure because of their close mechanical, cellular, and biochemical integration.

SUMMARY

Exciting new studies have led to an increased understanding of the underlying pathophysiology and indicate that pulmonary hypertension in heart failure may be treatable.

Nitric oxide modulation as a therapeutic strategy in heart failure

Nitric oxide (NO) is recognized as one of the most important cardiovascular signaling molecules, with multiple regulatory effects on myocardial and vascular tissue as well as on other tissues and organ systems. With the growth in understanding of the range and mechanisms of NO effects on the cardiovascular system, it is now possible to consider pharmaceutical interventions that directly target NO or key steps in NO effector pathways. This article reviews aspects of the cardiovascular effects of NO, abnormalities in NO regulation in heart failure, and clinical trials of drugs that target specific aspects of NO signaling pathways.

Inhaled NO and sildenafil combination in cardiac surgery patients with out-of-proportion pulmonary hypertension: acute effects on postoperative gas exchange and hemodynamics

BACKGROUND

The goal of this study was to examine the effects of coadministration of sildenafil and inhaled nitric oxide (iNO) in patients with out-of-proportion pulmonary hypertension who underwent cardiac valve replacement surgery.

METHODS AND RESULTS

Twenty consecutive cardiac surgery patients with out-of-proportion pulmonary hypertension were randomly assigned postoperatively into 2 groups: group A received 10 ppm of iNO followed by sildenafil (100 mg) orally 30 minutes later, and group B initially received sildenafil (100 mg) orally followed by 10 ppm of iNO 60 minutes later. Hemodynamic and gas exchange data were obtained at baseline, after administration of either iNO or sildenafil alone, and at 90 minutes from baseline. In group A, iNO resulted in a significant reduction in mean pulmonary artery pressure (MPAP) and pulmonary vascular resistance index (PVRI) (by 9.6% and 20.8%, respectively). In group B, sildenafil administration also resulted in a significant decrease in mean arterial pressure, MPAP, pulmonary artery occlusive pressure, PVRI, and systemic vascular resistance index but also in the PaO(2)/inspired fraction of oxygen ratio (by 18.7%, 22.0%, 15.7%, 31.6%, 21.3%, and 14%, respectively). In both groups, the coadministration of the 2 drugs resulted in a significant further reduction of mean arterial pressure, MPAP, pulmonary artery occlusive pressure, systemic vascular resistance index, and PVRI, whereas cardiac index and mixed venous oxygen saturation remained unchanged. The hypoxemia after sildenafil administration in group B improved after the coadministration of iNO, and thus PaO(2)/inspired fraction of oxygen returned to values near baseline.

CONCLUSION

In this study, the postoperative coadministration of iNO and oral sildenafil in patients with out-of-proportion pulmonary hypertension undergoing cardiac surgery is safe and results in an additive favorable effect on pulmonary arterial pressure and pulmonary vascular resistance, without systemic hypotension and ventilation/perfusion mismatch.