Two Faces of Nitric Oxide

Relationship between abnormal microvolt T-wave alternans and poor glycemic control in type 2 diabetic patients

BACKGROUND

Abnormal microvolt T-wave alternans (TWA) predicts the risk of ventricular arrhythmias and sudden cardiac death. Although type 2 diabetes is associated with an increased risk of these events, there is a dearth of available data on microvolt TWA measurements in type 2 diabetic populations.

METHODS

We studied 59 consecutive type 2 diabetic outpatients without manifest cardiovascular disease (CVD) and 35 non-diabetic controls who were matched for age, sex, and blood pressure values. Microvolt TWA analysis was performed non-invasively using the CH-2000 system during a sub-maximal exercise with the patient sitting on a bicycle ergometer.

RESULTS

The frequency of abnormal TWA was significantly higher in diabetic patients than in controls (25.4 vs 5.7%; P < 0.01). Among diabetic patients, those with abnormal TWA (n = 15) had remarkably higher hemoglobin A1c (HbA1c) (8.1 +/- 0.9 vs 7.1 +/- 0.8%, P < 0.001) and slightly smaller time-domain heart rate variability parameters (i.e., RMSSD, root mean square of difference of successive R-R intervals) than those with normal TWA (n = 44). Gender, age, body mass index, lipids, blood pressure values, cigarette smoking, diabetes duration, microvascular complication status, QTc interval, and current use of medications did not significantly differ between the groups. In multivariate regression logistic analysis, HbA1c (OR 13.6, 95% CI 2.0-89.1; P = 0.0076) predicted abnormal TWA independent of RMSSD values and other potential confounders.

CONCLUSIONS

Our findings suggest that abnormal TWA is a very common condition (approximately 25%) among people with type 2 diabetes without manifest CVD and is closely correlated to glycemic control.

Inhibition of inflammatory nitric oxide production and epidermis damages by Saccharomycopsis Ferment Filtrate

BACKGROUND

Yeast extracts have been shown to perform anti-inflammatory and cytoprotective activities. However, the effects of yeast extracts on lipopolysaccharide (LPS)-induced nitric oxide (NO) production and epidermal damages are still unclear.

OBJECTIVE

To investigate the effect of Saccharomycopsis Ferment Filtrate (SFF) on LPS-induced NO production in RAW264.7 macrophages and epidermal damages.

METHOD

RAW264.7 cells are incubated with LPS (25 ng/mL) and different concentrations of SFF. The amount of NO production is detected by Griess reaction. Additionally, the expression of inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1) are detected by Western blotting. Artificial epidermis is also used to mimic the in vivo condition to investigate the protective effects of SFF on LPS- or ultraviolet radiation (UVR)-induced damages by histology and electron microscopy.

RESULTS

The results show that SFF addition inhibits LPS-induced NO production and iNOS protein expression in a concentration-dependent manner without notable cytotoxicity in RAW264.7 cells, and induction of HO-1 protein expression by SFF was observed. Interestingly, both HO-1 inducers, hemin and CoCl2, significantly attenuated LPS-induced NO production and iNOS protein expression. The addition of CoCl2 potentiated the inhibitory effect of SFF on LPS-induced NO production. It seems that HO-1 protein participates in SFF inhibition of LPS-induced NO production. Furthermore, SFF exhibits significant protective effect on LPS- or UVR-induced damages in the artificial epidermis via histological and electron microscopic observations.

CONCLUSION

This study provided the first evidence to indicate the beneficial effects of SFF in preventing NO production in macrophages and damages in epidermis, respectively. It suggests that SFF possesses potential to be further developed.

Recent advances in the understanding of the role of nitric oxide in cardiovascular homeostasis

Nitric oxide synthases (NOS) are the enzymes responsible for nitric oxide (NO) generation. To date, 3 distinct NOS isoforms have been identified: neuronal NOS (NOS1), inducible NOS (NOS2), and endothelial NOS (NOS3). Biochemically, NOS consists of a flavin-containing reductase domain, a heme-containing oxygenase domain, and regulatory sites. NOS catalyse an overall 5-electron oxidation of one Nomega-atom of the guanidino group of L-arginine to form NO and L-citrulline. NO exerts a plethora of biological effects in the cardiovascular system. The basal formation of NO in mitochondria by a mitochondrial NOS seems to be one of the main regulators of cellular respiration, mitochondrial transmembrane potential, and transmembrane proton gradient. This review focuses on recent advances in the understanding of the role of enzyme and enzyme-independent NO formation, regulation of NO bioactivity, new aspects of NO on cardiac function and morphology, and the clinical impact and perspectives of these recent advances in our knowledge on NO-related pathways.

Enhancement by growth factors of cardiac myocyte differentiation from embryonic stem cells: A promising foundation for cardiac regeneration

Cell transplantation is a promising, still novel, potentially therapeutic approach for the treatment of heart diseases. Clinical applications require generation of large number of donor cells. Embryonic stem (ES) cells are capable of self-renewal apparently in an unlimited fashion, in vitro. Theoretically, they can differentiate into any cell type required for cell transplantation, including cardiac myocytes. Diverse growth factors have been implicated in programming diverse cellular processes, including development of the embryonic heart, ES cell self-renewal, and cardiac myocyte differentiation from ES cells. This review addresses the current understanding of the role of growth factors in the differentiation of cardiac myocytes from ES-embryoid body cell systems in vitro as well as cardiac regeneration in vivo.

THE ACUTE INFLAMMATORY RESPONSE IN DIVERSE SHOCK STATES

A poorly controlled acute inflammatory response can lead to organ dysfunction and death. Severe systemic inflammation can be induced and perpetuated by diverse insults such as the administration of toxic bacterial products (e.g., endotoxin), traumatic injury, and hemorrhage. Here, we probe whether these varied shock states can be explained by a universal inflammatory system that is initiated through different means and, once initiated, follows a course specified by the cellular and molecular mechanisms of the immune and endocrine systems. To examine this question, we developed a mathematical model incorporating major elements of the acute inflammatory response in C57Bl/6 mice, using input from experimental data. We found that a single model with different initiators including the autonomic system could describe the response to various insults. This model was able to predict a dose range of endotoxin at which mice would die despite having been calibrated only in nonlethal inflammatory paradigms. These results show that the complex biology of inflammation can be modeled and supports the hypothesis that shock states induced by a range of physiologic challenges could arise from a universal response that is differently initiated and modulated.

Intercellular communication, NO and the biology of Chinese medicine

New multiple categories of health disciplines have become popular in the west and integration between the medicinal approaches has become essential. The hypothesis presented here suggests a novel integrative view that combines Western biochemistry with the Chinese medicinal concept of qi. The core for this hypothesis is that transmission of qi along the meridians is based on informational molecules that travel via an intercellular communication system. Acupuncture at specific points enhances the flow of the signaling molecules through this communication system. Nitric oxide is suggested as a prime candidate for such a signaling molecule in the meridian system. The biochemistry of nitric oxide can shed light on the biology underlying Chinese medicine while Chinese medicinal data can provide a clue to the sought after framework for nitric oxide.

Apoptosis and oxidants in the heart

Cardiomyocyte (CM) apoptosis has been reported in a variety of cardiovascular diseases, including myocardial infarction, ischemia/reperfusion, end-stage heart failure, arrhythmogenic right ventricular dysplasia, and adriamycin-induced cardiomyopathy. The role of CM apoptosis in the development and progression of cardiac diseases merits further investigation. Cumulative evidence suggests that reactive oxygen species (ROS), which have been implicated in cardiac pathophysiology, can trigger myocyte apoptosis by up-regulating proapoptotic proteins, such as Bax and caspases, and the mitochondria-dependent pathway. These apoptotic proteins and pathways are inhibited by various antioxidants, as well as by overexpression of the antiapoptotic protein Bcl-2 by way of the antioxidant pathway. Detection of CM apoptosis with the terminal transferase-mediated DNA nick-end labeling assay alone has recently been questioned because of technical concerns regarding its sensitivity and specificity. Because CMs are mononuclear or binuclear, if only one nucleus or a certain percentage of fragmented nuclei is stained with TUNEL assay at the early stage of apoptotic cell death, it remains unknown whether this particular early apoptotic CM is still functionally active. The issue of TUNEL specificity further questions reports of high percentages of apoptotic CM nuclei (0.02%-35%) in the heart. Nevertheless, oxidative stress is a major apoptotic stimulus in many cardiovascular diseases and the process can be inhibited by antioxidants both in vitro and in vivo.

Reduction of blood pressure, plasma cholesterol, and atherosclerosis by elevated endothelial nitric oxide

In the vascular system, nitric oxide is generated by endothelial NO synthase (eNOS). NO has pleiotropic effects, most of which are believed to be atheroprotective. Therefore, it has been argued that patients suffering from cardiovascular disease could benefit from an increase in eNOS activity. However, increased NO production can cause oxidative damage, cell toxicity, and apoptosis and hence could be atherogenic rather than beneficial. To study the in vivo effects of increased eNOS activity, we created transgenic mice overexpressing human eNOS. Aortic blood pressure was approximately 20 mm Hg lower in the transgenic mice compared with control mice because of lower systemic vascular resistance. The effects of eNOS overexpression on diet-induced atherosclerosis were studied in apolipoprotein E-deficient mice. Elevation of eNOS activity decreased blood pressure ( approximately 20 mm Hg) and plasma levels of cholesterol ( approximately 17%), resulting in a reduction in atherosclerotic lesions by 40%. We conclude that an increase in eNOS activity is beneficial and provides protection against atherosclerosis.