The role of nitric oxide in heart failure

Facile Synthesis of Conductive Metal-Organic Frameworks Nanotubes for Ultrahigh-Performance Flexible NO Sensors

Cu-benzenehexathiol (Cu-BHT) has attracted significant attention due to its record high electrical conductivity and crystal defects Cu_2c . However, the nonporous structure and small specific surface area of Cu-BHT with two-dimensional kagome lattice invariably limit its practical application in sensing and catalysis. In this work, Cu-BHT nanotubes (Cu-BHT-NTs) are designed and prepared via a facile homogeneous reaction to solve these problems. Compared with the traditional nanorod-like structure, the Cu-BHT-NTs not only have a higher specific surface area but also possess a higher proportion of crystal defects (66.6%). The successfully configured DPPTT/Cu-BHT-NTs heterostructure organic field-effect transistor (OFET)-based sensor exhibits excellent sensitivity as high as 13 610%, a minimum detection limits down to 5 ppb, and exceptional selectivity to nitric oxide (NO) toxic gases. Theoretical analysis systematically shows that Cu_2c sites in the Cu-BHT-NTs increase the number of electrons transferred from the heterostructure to NO molecules, confirming that the high sensitivity and selectivity result from the high binding between Cu-BHT-NTs and NO molecules. Furthermore, a fully flexible device based on the heterojunction OFET sensor is prepared to ensure the convenience of wearing and carrying gas sensors, opening up a new avenue for the next generation of wearable intelligent electronics.

Review of Hemoglobin-Induced Myocardial Lesions

Over 100 preclinical studies in several small and large animal species were performed to evaluate the safety and efficacy of diaspirin cross-linked hemoglobin (DCLHb; Baxter Healthcare Corp.) as an oxygen therapeutic. During the preclinical evaluation of DCLHb, myocardial lesions were observed following the administration of DCLHb to certain species. These lesions were characterized as minimal to moderate, focal-to-multifocal myocardial degeneration and/or necrosis that were scored using a severity scale of minimal to marked in relative severity. The lesions were typically observed 24-48 h after single topload infusions of DCLHb into rhesus monkeys or pigs at doses as low as 200 or 700 mg/kg, respectively. Dogs, sheep, and rats did not develop these lesions after single-dose administrations of DCLHb. The left ventricular myocardium, typically near the base of or including the papillary muscles, was the most severely affected region, followed by the intraventricular septum and the right ventricle. The left and right atria were usually not affected. In a study in rhesus monkeys, morphometric analysis revealed that these lesions comprised less than 3% of the total myocardium. Although increases in serum enzyme activities (AST, CK, LDH) were observed after infusion of DCLHb, myocardial-related isoenzymes did not increase. ECG analysis and echocardiography were not altered by these lesions, and there was no observable adverse effect on myocardial function. Polymerization of DCLHb reduced, but did not eliminate, the incidence and severity of the lesions. However, infusion of hemoglobin solutions with reduced reaction rates with nitric oxide (NO) resulted in a significant decrease in lesion incidence and severity, while administration of L-NAME, an NO synthase inhibitor, resulted in the appearance of lesions that were indistinguishable from those induced by hemoglobin, suggesting that reduction in normal NO levels is an important mechanistic factor. Overall, the presence of myocardial lesions represents a histopathologic finding that must be considered during the preclinical testing and development of new HBOCs.

Nitric oxide signaling in stretch‐induced apoptosis of neonatal rat cardiomyocytes

Pressure overload associated with hypertension is an important pathological factor leading to heart remodeling and ultimately heart failure partially due to cardiomyocyte apoptosis. Here we show that endogenous NO signaling plays a critical role in mechanical stretch-induced cardiomyocyte apoptosis. Mechanical stretch induced elevated expression of both eNOS and inducible NO synthase (iNOS) and increased synthesis of NO. A sustained increase in iNOS expression was also found in hearts of hypertensive rats in vivo. Blockade of NO signaling by inhibitors of NOS (L-NAME and AMT) or downstream guanylyl cyclase (ODQ) strongly inhibited stretch-induced apoptosis, mitochondria depolarization, and cytochrome c release, suggesting that NO is required in stretch-induced cardiomyocyte apoptosis. The expression of iNOS, but not eNOS, was blocked by L-NAME and ODQ, indicating that the iNOS induction is NO dependent. The initial elevation of NO is likely due to Ca(2+)-dependent activation of eNOS because elimination of intracellular calcium by EGTA-AM inhibited both iNOS induction and NO elevation. Other calcium signaling inhibitors (nifedipine, ryanodine, thapsigargin, and ionic gadolinium) also attenuated the initial NO elevation. These data indicate that mechanical signals initiate Ca(2+)-dependent NO synthesis, which is further amplified by activation of NO-induced iNOS expression, to regulate cardiomyocyte apoptosis.

Emerging therapeutic targets in nitric oxide-dependent cardiac disease

Nitric oxide (NO) is a free radical gas that plays paracrine/autocrine and intracrine roles in maintaining physiological cardiovascular performance. In the coronary circulation, NO mediates endothelium-dependent vasodilator responses to shear stress and agonist-induced responses to neurohumoral stimulation. In the heart, NO modulates myocardial relaxation, beta-adrenergic responses, mitochondrial respiration and substrate metabolism and excitation-contraction coupling. Endothelial dysfunction and the resulting decrease in the production, bioavailability and/or second messenger response-coupling has been implicated in coronary artery disease and complications associated with restenosis following coronary angioplasty, stent placement and coronary artery bypass grafting (CABG). However, there are a number of pathophysiological conditions (ischaemia-reperfusion, cardiac transplant rejection, myocarditis, sepsis) in which unregulated overproduction of NO and other reactive oxygen species (ROS) results in deleterious effects on cardiac function. Given the importance of NO in cardiac physiology/pathophysiology it may serve as a potential target for interventions aimed at deterring therapeutic failures of percutaneous or surgical treatments of cardiac disease as well as serving as a primary medical intervention. This review will examine the function of NO in mediating/modulating cardiac function, stressing the concept that, depending on the milieu, NO has the potential to exert either beneficial or deleterious effects on cardiac function. Moreover, this review will summarise studies in laboratory models and human studies in which NO activity, production, availability, or second messenger activation has been enhanced or inhibited in order to provide new insight for future targeting of this system for drug development.