Regulation of the mammalian heart function by nitric oxide

The mechanism of 25-hydroxycholesterol-mediated suppression of atrial β1-adrenergic responses

25-Hydroxycholesterol (25HC) is a biologically active oxysterol, whose production greatly increases during inflammation by macrophages and dendritic cells. The inflammatory reactions are frequently accompanied by changes in heart regulation, such as blunting of the cardiac β-adrenergic receptor (AR) signaling. Here, the mechanism of 25HC-dependent modulation of responses to β-AR activation was studied in the atria of mice. 25HC at the submicromolar levels decreased the β-AR-mediated positive inotropic effect and enhancement of the Ca2+ transient amplitude, without changing NO production. Positive inotropic responses to β1-AR (but not β2-AR) activation were markedly attenuated by 25HC. The depressant action of 25HC on the β1-AR-mediated responses was prevented by selective β3-AR antagonists as well as inhibitors of Gi protein, Gβγ, G protein-coupled receptor kinase 2/3, or β-arrestin. Simultaneously, blockers of protein kinase D and C as well as a phosphodiesterase inhibitor did not preclude the negative action of 25HC on the inotropic response to β-AR activation. Thus, 25HC can suppress the β1-AR-dependent effects via engaging β3-AR, Gi protein, Gβγ, G protein-coupled receptor kinase, and β-arrestin. This 25HC-dependent mechanism can contribute to the inflammatory-related alterations in the atrial β-adrenergic signaling.

The effect of exenatide (a GLP-1 analogue) and sitagliptin (a DPP-4 inhibitor) on asymmetric dimethylarginine (ADMA) metabolism and selected biomarkers of cardiac fibrosis in rats with fructose-induced metabolic syndrome

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis, is a risk factor for endothelial dysfunction, a common pathophysiological denominator for both atherogenesis and cardiac fibrosis. We aimed to investigate whether the cardioprotective and antifibrotic effects of incretin drugs, exenatide and sitagliptin, may be associated with their ability to affect circulating and cardiac ADMA metabolism. Normal and fructose-fed rats were treated with sitagliptin (5.0/10 mg/kg) or exenatide (5/10 µg/kg) for 4 weeks. The following methods were used: LC-MS/MS, ELISA, Real-Time-PCR, colorimetry, IHC and H&E staining, PCA and OPLS-DA projections. Eight-week fructose feeding resulted in an increase in plasma ADMA and a decrease in NO concentration. Exenatide administration into fructose-fed rats reduced the plasma ADMA level and increased NO level. In the heart of these animals exenatide administration increased NO and PRMT1 level, reduced TGF-ß1, α-SMA levels and COL1A1 expression. In the exenatide treated rats renal DDAH activity positively correlated with plasma NO level and negatively with plasma ADMA level and cardiac α-SMA concentration. Sitagliptin treatment of fructose-fed rats increased plasma NO concentration, reduced circulating SDMA level, increased renal DDAH activity and reduced myocardial DDAH activity. Both drugs attenuated the myocardial immunoexpression of Smad2/3/P and perivascular fibrosis. In the metabolic syndrome condition both sitagliptin and exenatide positively modulated cardiac fibrotic remodeling and circulating level of endogenous NOS inhibitors but had no effects on ADMA levels in the myocardium.

HNO Protects the Myocardium against Reperfusion Injury, Inhibiting the mPTP Opening via PKCε Activation

Donors of nitroxyl (HNO), the one electron-reduction product of nitric oxide (NO^.), positively modulate cardiac contractility/relaxation while limiting ischemia-reperfusion (I/R) injury. The mechanisms underpinning HNO anti-ischemic effects remain poorly understood. Using isolated perfused rat hearts subjected to 30 min global ischemia/1 or 2 h reperfusion, here we tested whether, in analogy to NO^., HNO protection requires PKCε translocation to mitochondria and K_ATP channels activation. To this end, we compared the benefits afforded by ischemic preconditioning (IPC; 3 cycles of I/R) with those eventually granted by the NO^. donor, diethylamine/NO, DEA/NO, and two chemically unrelated HNO donors: Angeli’s salt (AS, a prototypic donor) and isopropylamine/NO (IPA/NO, a new HNO releaser). All donors were given for 19 min before I/R injury. In control I/R hearts (1 h reperfusion), infarct size (IS) measured via tetrazolium salt staining was 66 ± 5.5% of the area at risk. Both AS and IPA/NO were as effective as IPC in reducing IS [30.7 ± 2.2 (AS), 31 ± 2.9 (IPA/NO), and 31 ± 0.8 (IPC), respectively)], whereas DEA/NO was significantly less so (36.2 ± 2.6%, p < 0.001 vs. AS, IPA/NO, or IPC). IPA/NO protection was still present after 120 min of reperfusion, and the co-infusion with the PKCε inhibitor (PKCV1-2500 nM) prevented it (IS = 30 ± 0.5 vs. 61 ± 1.8% with IPA/NO alone, p < 0.01). Irrespective of the donor, HNO anti-ischemic effects were insensitive to the K_ATP channel inhibitor, 5-OH decanoate (5HD, 100 μM), that, in contrast, abrogated DEA/NO protection. Finally, both HNO donors markedly enhanced the mitochondrial permeability transition pore (mPTP) ROS threshold over control levels (≅35–40%), an action again insensitive to 5HD. Our study shows that HNO donors inhibit mPTP opening, thus limiting myocyte loss at reperfusion, a beneficial effect that requires PKCε translocation to the mitochondria but not mitochondrial K⁺ channels activation.

The goldfish Carassius auratus: an emerging animal model for comparative cardiac research

The use of unconventional model organisms is significantly increasing in different fields of research, widely contributing to advance life sciences understanding. Among fishes, the cyprinid Carassius auratus (goldfish) is largely used for studies on comparative and evolutionary endocrinology, neurobiology, adaptive and conservation physiology, as well as for translational research aimed to explore mechanisms that may be useful in an applicative biomedical context. More recently, the research possibilities offered by the goldfish are further expanded to cardiac studies. A growing literature is available to illustrate the complex networks involved in the modulation of the goldfish cardiac performance, also in relation to the influence of environmental signals. However, an overview on the existing current knowledge is not yet available. By discussing the mechanisms that in C. auratus finely regulate the cardiac function under basal conditions and under environmental challenges, this review highlights the remarkable flexibility of the goldfish heart in relation not only to the basic morpho-functional design and complex neuro-humoral traits, but also to its extraordinary biochemical-metabolic plasticity and its adaptive potential. The purpose of this review is also to emphasize the power of the heart of C. auratus as an experimental tool useful to investigate mechanisms that could be difficult to explore using more conventional animal models and complex cardiac designs.

The Hypoxia Tolerance of the Goldfish (Carassius auratus) Heart: The NOS/NO System and Beyond

The extraordinary capacity of the goldfish (Carassius auratus) to increase its cardiac performance under acute hypoxia is crucial in ensuring adequate oxygen supply to tissues and organs. However, the underlying physiological mechanisms are not yet completely elucidated. By employing an ex vivo working heart preparation, we observed that the time-dependent enhancement of contractility, distinctive of the hypoxic goldfish heart, is abolished by the Nitric Oxide Synthase (NOS) antagonist L-NMMA, the Nitric Oxide (NO) scavenger PTIO, as well as by the PI3-kinase (PI3-K) and sarco/endoplasmic reticulum Ca²⁺-ATPase 2a (SERCA2a) pumps’ inhibition by Wortmannin and Thapsigargin, respectively. In goldfish hearts exposed to hypoxia, an ELISA test revealed no changes in cGMP levels, while Western Blotting analysis showed an enhanced expression of the phosphorylated protein kinase B (pAkt) and of the NADPH oxidase catalytic subunit Nox2 (gp91phox). A significant decrease of protein S-nitrosylation was observed by Biotin Switch assay in hypoxic hearts. Results suggest a role for a PI3-K/Akt-mediated activation of the NOS-dependent NO production, and SERCA2a pumps in the mechanisms conferring benefits to the goldfish heart under hypoxia. They also propose protein denitrosylation, and the possibility of nitration, as parallel intracellular events.

Cardioprotection by Metformin: Beneficial Effects Beyond Glucose Reduction

Metformin is a biguanide that is widely used as an insulin-sparing agent to treat diabetes. When compared with the general population, diabetics are twice as likely to die from fatal myocardial infarction and congestive heart failure (CHF). There has been a significant concern regarding the use of metformin in patients with CHF because of their higher tendency to develop lactic acidosis. However, large epidemiological trials have reported better cardiovascular prognosis with metformin compared to other glucose-lowering agents among diabetics. Additionally, metformin has reduced the risk of reinfarction and all-cause mortality in patients with coronary artery disease and CHF, respectively. The protection against cardiovascular diseases appears to be independent of the anti-hyperglycemic effects of metformin. These effects are mediated through an increase in 5' adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and by increased phosphorylation of endothelial nitric oxide synthase (eNOS) in cardiomyocytes with an increased production of nitric oxide (NO). Metformin preconditions the heart against ischemia-reperfusion injury and may improve myocardial remodeling after an ischemic insult. The preponderance of evidence currently suggests that metformin is safe in patients with CHF, prompting the Food and Drug Administration to remove CHF as a contraindication from the package insert of all generic metformin preparations. In this narrative, along with a limited meta-analysis of available studies, we have reviewed the pleiotropic (non-glucose-lowering) effects of metformin that potentially contribute to its cardioprotective properties. Additionally, we have reviewed issues surrounding the safety of metformin in patients with cardiac diseases.

NO, CO and H2 S: What about gasotransmitters in fish and amphibian heart?

The gasotransmitters nitric oxide (NO), carbon monoxide (CO), and hydrogen sulphide (H₂ S), long considered only toxicant, are produced in vivo during the catabolism of common biological molecules and are crucial for a large variety of physiological processes. Mounting evidence is emerging that in poikilotherm vertebrates, as in mammals, they modulate the basal performance of the heart and the response to stress challenges. In this review, we will focus on teleost fish and amphibians to highlight the evolutionary importance in vertebrates of the cardiac control elicited by NO, CO and H₂ S, and the conservation of the intracellular cascades they activate. Although many gaps are still present due to discontinuous information, we will use examples obtained by studies from our and other laboratories to illustrate the complexity of the mechanisms that, by involving gasotransmitters, allow beat-to-beat, short-, medium- and long-term cardiac homoeostasis. By presenting the latest data, we will also provide a framework in which the peculiar morpho-functional arrangement of the teleost and amphibian heart can be considered as a reference tool to decipher cardiac regulatory networks which are difficult to explore using more conventional vertebrates, such as mammals.

Effects of Nitric Oxide on Voltage-Gated K⁺ Currents in Human Cardiac Fibroblasts through the Protein Kinase G and Protein Kinase A Pathways but Not through S-Nitrosylation

This study investigated the expression of voltage-gated K⁺ (K_V) channels in human cardiac fibroblasts (HCFs), and the effect of nitric oxide (NO) on the K_V currents, and the underlying phosphorylation mechanisms. In reverse transcription polymerase chain reaction, two types of K_V channels were detected in HCFs: delayed rectifier K⁺ channel and transient outward K⁺ channel. In whole-cell patch-clamp technique, delayed rectifier K⁺ current (I_K) exhibited fast activation and slow inactivation, while transient outward K⁺ current (I_to) showed fast activation and inactivation kinetics. Both currents were blocked by 4-aminopyridine. An NO donor, S-nitroso-N-acetylpenicillamine (SNAP), increased the amplitude of I_K in a concentration-dependent manner with an EC₅₀ value of 26.4 µM, but did not affect I_to. The stimulating effect of SNAP on I_K was blocked by pretreatment with 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or by KT5823. 8-bromo-cyclic GMP stimulated the I_K. The stimulating effect of SNAP on I_K was also blocked by pretreatment with KT5720 or by SQ22536. Forskolin and 8-bromo-cyclic AMP each stimulated I_K. On the other hand, the stimulating effect of SNAP on I_K was not blocked by pretreatment of N-ethylmaleimide or by DL-dithiothreitol. Our data suggest that NO enhances I_K, but not I_to, among K_V currents of HCFs, and the stimulating effect of NO on I_K is through the PKG and PKA pathways, not through S-nitrosylation.

Effects of nitric oxide on large-conductance Ca2+ -activated K+ currents in human cardiac fibroblasts through PKA and PKG-related pathways

The human cardiac fibroblast (HCF) is the most abundant cell type in the myocardium, and HCFs play critical roles in maintaining normal cardiac function. However, unlike cardiomyocytes, the electrophysiology of HCFs is not well established. In the cardiovascular system, Ca²⁺ -activated K⁺ (KCa) channels have distinct physiological and pathological functions, and nitric oxide (NO) plays a key role. In this study, we investigated the potential effects of NO on KCa channels in HCFs. We recorded strong oscillating, well-maintained outward K⁺ currents without marked inactivation throughout the test pulse period and detected outward rectification in the I-V curve; these are all characteristics that are typical of KCa currents. These currents were blocked with iberiotoxin (IBTX, a BKCa blocker) but not with TRAM-34 (an IKCa blocker). The amplitudes of the currents were increased with SNAP (an NO donor), and these increases were inhibited with IBTX. The SNAP-stimulating effect on the BKCa currents was blocked by pretreatment with KT5823 (a protein kinase G [PKG] inhibitor) or 1 H-[1,-2, -4] oxadiazolo-[4,-3-a] quinoxalin-1-one (ODQ; a soluble guanylate cyclase inhibitor). Additionally, 8-bromo-cyclic guanosine 3',5'-monophosphate (8-Br-cGMP) stimulated the BKCa currents, and pretreatment with KT5720 (a protein kinase A [PKA] inhibitor) and SQ22536 (an adenylyl cyclase inhibitor) blocked the NO-stimulating effect on the BKCa currents. Furthermore, 8-bromo-cyclic adenosine 3',5'-monophosphate (8-Br-cAMP) activated the BKCa currents. These data suggest that BKCa current is the main subtype of the KCa current in HCFs and that NO enhances these currents through the PKG and PKA pathways.

Fructose-rich diet and insulin action in female rat heart: Estradiol friend or foe?

Increased intake of fructose in humans and laboratory animals is demonstrated to be a risk factor for development of metabolic disorders (insulin resistance, metabolic syndrome, type 2 diabetes) and cardiovascular diseases. On the other hand, estradiol is emphasized as a cardioprotective agent. The main goal of this review is to summarize recent findings on damaging cardiac effects of fructose-rich diet in females, mostly experimental animals, and to evaluate protective capacity of estradiol. Published results of our and other research groups indicate mostly detrimental effects of fructose-rich diet on cardiac insulin signaling molecules, glucose and fatty acid metabolism, nitric oxide production and ion transport, as well as renin-angiotensin system and inflammation. Some of these processes are involved in cardiac insulin signal transmission, others are regulated by insulin or have an influence on insulin action. Administration of estradiol to ovariectomized female rats, exposed to increased intake of fructose, was mostly beneficial to the heart, but sometimes it was ineffective or even detrimental, depending on the particular processes. We believe that these data, carefully translated to human population, could be useful for clinicians dealing with postmenopausal women susceptible to metabolic diseases and hormone replacement therapy.

Mechanisms of the cyclic nucleotide cross-talk signaling network in cardiac L-type calcium channel regulation

Regulation of L-type Calcium (Ca2+) Channel (LCC) gating is critical to shaping the cardiac action potential (AP) and triggering the initiation of excitation-contraction (EC) coupling in cardiac myocytes. The cyclic nucleotide (cN) cross-talk signaling network, which encompasses the β-adrenergic and the Nitric Oxide (NO)/cGMP/Protein Kinase G (PKG) pathways and their interaction (cross-talk) through distinctively-regulated phosphodiesterase isoenzymes (PDEs), regulates LCC current via Protein Kinase A- (PKA) and PKG-mediated phosphorylation. Due to the tightly-coupled and intertwined biochemical reactions involved, it remains to be clarified how LCC gating is regulated by the signaling network from receptor to end target. In addition, the large number of EC coupling-related phosphorylation targets of PKA and PKG makes it difficult to quantify and isolate changes in L-type Ca2+ current (ICaL) responses regulated by the signaling network. We have developed a multi-scale, biophysically-detailed computational model of LCC regulation by the cN signaling network that is supported by experimental data. LCCs are modeled with functionally distinct PKA- and PKG-phosphorylation dependent gating modes. The model exhibits experimentally observed single channel characteristics, as well as whole-cell LCC currents upon activation of the cross-talk signaling network. Simulations show 1) redistribution of LCC gating modes explains changes in whole-cell current under various stimulation scenarios of the cN cross-talk network; 2) NO regulation occurs via potentiation of a gating mode characterized by prolonged closed times; and 3) due to compensatory actions of cross-talk and antagonizing functions of PKA- and PKG-mediated phosphorylation of LCCs, the effects of individual inhibitions of PDEs 2, 3, and 4 on ICaL are most pronounced at low levels of β-adrenergic stimulation. Simulations also delineate the contribution of the following two mechanisms to overall LCC regulation, which have otherwise been challenging to distinguish: 1) regulation of PKA and PKG activation via cN cross-talk (Mechanism 1); and 2) LCC interaction with activated PKA and PKG (Mechanism 2). These results provide insights into how cN signals transduced via the cN cross-talk signaling network are integrated via LCC regulation in the heart.

Roles of phosphodiesterases in the regulation of the cardiac cyclic nucleotide cross-talk signaling network

The balanced signaling between the two cyclic nucleotides (cNs) cAMP and cGMP plays a critical role in regulating cardiac contractility. Their degradation is controlled by distinctly regulated phosphodiesterase isoenzymes (PDEs), which in turn are also regulated by these cNs. As a result, PDEs facilitate communication between the β-adrenergic and Nitric Oxide (NO)/cGMP/Protein Kinase G (PKG) signaling pathways, which regulate the synthesis of cAMP and cGMP respectively. The phenomena in which the cAMP and cGMP pathways influence the dynamics of each other are collectively referred to as cN cross-talk. However, the cross-talk response and the individual roles of each PDE isoenzyme in shaping this response remain to be fully characterized. We have developed a computational model of the cN cross-talk network that mechanistically integrates the β-adrenergic and NO/cGMP/PKG pathways via regulation of PDEs by both cNs. The individual model components and the integrated network model replicate experimentally observed activation-response relationships and temporal dynamics. The model predicts that, due to compensatory interactions between PDEs, NO stimulation in the presence of sub-maximal β-adrenergic stimulation results in an increase in cytosolic cAMP accumulation and corresponding increases in PKA-I and PKA-II activation; however, the potentiation is small in magnitude compared to that of NO activation of the NO/cGMP/PKG pathway. In a reciprocal manner, β-adrenergic stimulation in the presence of sub-maximal NO stimulation results in modest cGMP elevation and corresponding increase in PKG activation. In addition, we demonstrate that PDE2 hydrolyzes increasing amounts of cAMP with increasing levels of β-adrenergic stimulation, and hydrolyzes increasing amounts of cGMP with decreasing levels of NO stimulation. Finally, we show that PDE2 compensates for inhibition of PDE5 both in terms of cGMP and cAMP dynamics, leading to cGMP elevation and increased PKG activation, while maintaining whole-cell β-adrenergic responses similar to that prior to PDE5 inhibition. By defining and quantifying reactions comprising cN cross-talk, the model characterizes the cross-talk response and reveals the underlying mechanisms of PDEs in this non-linear, tightly-coupled reaction system.

Low intensity exercise prevents disturbances in rat cardiac insulin signaling and endothelial nitric oxide synthase induced by high fructose diet

Increase in fructose consumption together with decrease in physical activity contributes to the development of metabolic syndrome and consequently cardiovascular diseases. The current study examined the preventive role of exercise on defects in cardiac insulin signaling and function of endothelial nitric oxide synthase (eNOS) in fructose fed rats. Male Wistar rats were divided into control, sedentary fructose (received 10% fructose for 9 weeks) and exercise fructose (additionally exposed to low intensity exercise) groups. Concentration of triglycerides, glucose, insulin and visceral adipose tissue weight were determined to estimate metabolic syndrome development. Expression and/or phosphorylation of cardiac insulin receptor (IR), insulin receptor substrate 1 (IRS1), tyrosine-specific protein phosphatase 1B (PTP1B), Akt, extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and eNOS were evaluated. Fructose overload increased visceral adipose tissue, insulin concentration and homeostasis model assessment index. Exercise managed to decrease visceral adiposity and insulin level and to increase insulin sensitivity. Fructose diet increased level of cardiac PTP1B and pIRS1 (Ser307), while levels of IR and ERK1/2, as well as pIRS1 (Tyr 632), pAkt (Ser473, Thr308) and pERK1/2 were decreased. These disturbances were accompanied by reduced phosphorylation of eNOS at Ser1177. Exercise managed to prevent most of the disturbances in insulin signaling caused by fructose diet (except phosphorylation of IRS1 at Tyr 632 and phosphorylation and protein expression of ERK1/2) and consequently restored function of eNOS. Low intensity exercise could be considered as efficient treatment of cardiac insulin resistance induced by fructose diet.

Quality control systems in cardiac aging

Cardiac aging is an intrinsic process that results in impaired cardiac function, along with cellular and molecular changes. These degenerative changes are intimately associated with quality control mechanisms. This review provides a general overview of the clinical and cellular changes which manifest in cardiac aging, and the quality control mechanisms involved in maintaining homeostasis and retarding aging. These mechanisms include autophagy, ubiquitin-mediated turnover, apoptosis, mitochondrial quality control and cardiac matrix homeostasis. Finally, we discuss aging interventions that have been observed to impact cardiac health outcomes. These include caloric restriction, rapamycin, resveratrol, GDF11, mitochondrial antioxidants and cardiolipin-targeted therapeutics. A greater understanding of the quality control mechanisms that promote cardiac homeostasis will help to understand the benefits of these interventions, and hopefully lead to further improved therapeutic modalities.

The new nitric oxide donor cyclohexane nitrate induces vasorelaxation, hypotension, and antihypertensive effects via NO/cGMP/PKG pathway

We investigated the cardiovascular effects induced by the nitric oxide donor Cyclohexane Nitrate (HEX). Vasodilatation, NO release and the effects of acute or sub-chronic treatment with HEX on cardiovascular parameters were evaluated. HEX induced endothelium-independent vasodilatation (Maximum effect [efficacy, ME] = 100.4 ± 4.1%; potency [pD2] = 5.1 ± 0.1). Relaxation was attenuated by scavenging nitric oxide (ME = 44.9 ± 9.4% vs. 100.4 ± 4.1%) or by inhibiting the soluble guanylyl cyclase (ME = 38.5 ± 9.7% vs. 100.4 ± 4.1%). In addition, pD2 was decreased after non-selective blockade of K⁺ channels (pD2 = 3.6 ± 0.1 vs. 5.1 ± 0.1) or by inhibiting K_ATP channels (pD2 = 4.3 ± 0.1 vs. 5.1 ± 0.1). HEX increased NO levels in mesenteric arteries (33.2 ± 2.3 vs. 10.7 ± 0.2 au, p < 0.0001). Intravenous acute administration of HEX (1–20 mg/kg) induced hypotension and bradycardia in normotensive and hypertensive rats. Furthermore, starting at 6 weeks after the induction of 2K1C hypertension, oral treatment with the HEX (10 mg/Kg/day) for 7 days reduced blood pressure in hypertensive animals (134 ± 6 vs. 170 ± 4 mmHg, respectively). Our data demonstrate that HEX is a NO donor able to produce vasodilatation via NO/cGMP/PKG pathway and activation of the ATP-sensitive K⁺ channels. Furthermore, HEX acutely reduces blood pressure and heart rate as well as produces antihypertensive effect in renovascular hypertensive rats.

The NO stimulator, Catestatin, improves the Frank-Starling response in normotensive and hypertensive rat hearts

The myocardial response to mechanical stretch (Frank-Starling law) is an important physiological cardiac determinant. Modulated by many endogenous substances, it is impaired in the presence of cardiovascular pathologies and during senescence. Catestatin (CST:hCgA352-372), a 21-amino-acid derivate of Chromogranin A (CgA), displays hypotensive/vasodilatory properties and counteracts excessive systemic and/or intra-cardiac excitatory stimuli (e.g., catecholamines and endothelin-1). CST, produced also by the myocardium, affects the heart by modulating inotropy, lusitropy and the coronary tone through a Nitric Oxide (NO)-dependent mechanism. This study evaluated the putative influence elicited by CST on the Frank-Starling response of normotensive Wistar-Kyoto (WKY) and hypertensive (SHR) hearts by using isolated and Langendorff perfused cardiac preparations. Functional changes were evaluated on aged (18-month-old) WKY rats and SHR which mimic human chronic heart failure (HF). Comparison to WKY rats, SHR showed a reduced Frank-Starling response. In both rat strains, CST administration improved myocardial mechanical response to increased end-diastolic pressures. This effect was mediated by EE/IP3K/NOS/NO/cGMP/PKG, as revealed by specific inhibitors. CST-dependent positive Frank-Starling response is paralleled by an increment in protein S-Nitrosylation. Our data suggested CST as a NO-dependent physiological modulator of the stretch-induced intrinsic regulation of the heart. This may be of particular importance in the aged hypertrophic heart, whose function is impaired because of a reduced systolic performance accompanied by delayed relaxation and increased diastolic stiffness.

Nitroxyl (HNO) for treatment of acute heart failure

The loss of contractile function is a hallmark of heart failure. Although increasing intracellular Ca(2+) is a possible strategy for improving contraction, current inotropic agents that achieve this by raising intracellular cAMP levels, such as β-agonists and phosphodiesterase inhibitors, are generally deleterious when administered as long-term therapy due to arrhythmia and myocardial damage. Nitroxyl donors have been shown to improve cardiac function in normal and failing dogs, and in isolated cardiomyocytes they increase fractional shortening and Ca(2+) transients, independently from cAMP/PKA or cGMP/PKG signaling. Instead, nitroxyl targets cysteines in the EC-coupling machinery and myofilament proteins, reversibly modifying them to enhance Ca(2+) handling and myofilament Ca(2+) sensitivity. Phase I-IIa trials with CXL-1020, a novel pure HNO donor, reported declines in left and right heart filling pressures and systemic vascular resistance, and increased cardiac output and stroke volume index. These findings support the concept of nitroxyl donors as attractive agents for the treatment of acute decompensated heart failure.

Sulfur as a signaling nutrient through hydrogen sulfide

Hydrogen sulfide (H₂S) has emerged as an important signaling molecule with beneficial effects on various cellular processes affecting, for example, cardiovascular and neurological functions. The physiological importance of H₂S is motivating efforts to develop strategies for modulating its levels. However, advancement in the field of H₂S-based therapeutics is hampered by fundamental gaps in our knowledge of how H₂S is regulated, its mechanism of action, and its molecular targets. This review provides an overview of sulfur metabolism; describes recent progress that has shed light on the mechanism of H₂S as a signaling molecule; and examines nutritional regulation of sulfur metabolism, which pertains to health and disease.

Arginase induction and activation during ischemia and reperfusion and functional consequences for the heart

Induction and activation of arginase is among the fastest responses of the heart to ischemic events. Induction of arginase expression and enzyme activation under ischemic conditions shifts arginine consumption from nitric oxide formation (NO) to the formation of ornithine and urea. In the heart such a switch in substrate utilization reduces the impact of the NO/cGMP-pathway on cardiac function that requires intact electromechanical coupling but at the same time it induces ornithine-dependent pathways such as the polyamine metabolism. Both effects significantly reduce the recovery of heart function during reperfusion and thereby limits the success of reperfusion strategies. In this context, changes in arginine consumption trigger cardiac remodeling in an unfavorable way and increases the risk of arrhythmia, specifically in the initial post-ischemic period in which arginase activity is dominating. However, during the entire ischemic period arginase activation might be a meaningful adaptation that is specifically relevant for reperfusion following prolonged ischemic periods. Therefore, a precise understanding about the underlying mechanism that leads to arginase induction as well as of it's mechanistic impact on post-ischemic hearts is required for optimizing reperfusion strategies. In this review we will summarize our current understanding of these processes and give an outlook about possible treatment options for the future.

A review of melatonin as a suitable antioxidant against myocardial ischemia-reperfusion injury and clinical heart diseases

Cardiac tissue loss is one of the most important factors leading to the unsatisfactory recovery even after treatment of ischemic heart disease. Melatonin, a circadian molecule with marked antioxidant properties, protects against ischemia-reperfusion (IR) injury. In particular, the myocardial protection of melatonin is substantial. We initially focus on the cardioprotective effects of melatonin in myocardial IR. These studies showed how melatonin preserves the microstructure of the cardiomyocyte and reduces myocardial IR injury. Thereafter, downstream signaling pathways of melatonin were summarized including Janus kinase 2/signal transducers and activators of transcription 3, nitric oxide-synthase, and nuclear factor erythroid 2 related factor 2. Herein, we propose the clinical applications of melatonin in several ischemic heart diseases. Collectively, the information summarized in this review (based on in vitro, animal, and human studies) should serve as a comprehensive reference for the action of melatonin in cardioprotection and hopefully will contribute to the design of future experimental research.

H2S and its role in redox signaling

Hydrogen sulfide (H2S) has emerged as an important gaseous signaling molecule that is produced endogenously by enzymes in the sulfur metabolic network. H2S exerts its effects on multiple physiological processes important under both normal and pathological conditions. These functions include neuromodulation, regulation of blood pressure and cardiac function, inflammation, cellular energetics and apoptosis. Despite the recognition of its biological importance and its beneficial effects, the mechanism of H2S action and the regulation of its tissue levels remain unclear in part owing to its chemical and physical properties that render handling and analysis challenging. Furthermore, the multitude of potential H2S effects has made it difficult to dissect its signaling mechanism and to identify specific targets. In this review, we focus on H2S metabolism and provide an overview of the recent literature that sheds some light on its mechanism of action in cellular redox signaling in health and disease. This article is part of a Special Issue entitled: Thiol-Based Redox Processes.

Vitamin D protects human endothelial cells from oxidative stress through the autophagic and survival pathways

CONTEXT

Recently, vitamin D (VitD) has been recognized as increasingly importance in many cellular functions of several tissues and organs other than bone. In particular, VitD showed important beneficial effects in the cardiovascular system. Although the relationship among VitD, endothelium, and cardiovascular disease is well established, little is known about the antioxidant effect of VitD.

OBJECTIVE

Our objective was to study the intracellular pathways activated by VitD in cultured human umbilical vein endothelial cells undergoing oxidative stress.

DESIGN

Nitric oxide production, cell viability, reactive oxygen species, the mitochondrial permeability transition pore, membrane potential, and caspase-3 activity were measured during oxidative stress induced by administration of 200 μM hydrogen peroxide for 20 minutes. Experiments were repeated in the presence of specific vitamin D receptor ligand ZK191784.

RESULTS

Pretreatment with VitD alone or in combination with ZK191784 is able to reduce the apoptosis-related gene expression, involving both intrinsic and extrinsic pathways. At the same time, it has been shown the activation of pro-autophagic beclin 1 and the phosphorylation of ERK1/2 and Akt, indicating a modulation between apoptosis and autophagy. Moreover, VitD alone or in combination with ZK191784 is able to prevent the loss of mitochondrial potential and the consequent cytochrome C release and caspase activation.

CONCLUSIONS

The present study shows that VitD may prevent endothelial cell death through modulation of the interplay between apoptosis and autophagy. This effect is obtained by inhibiting superoxide anion generation, maintaining mitochondria function and cell viability, activating survival kinases, and inducing NO production.

Effects of NOS1AP rs12742393 polymorphism on repaglinide response in Chinese patients with type 2 diabetes mellitus

STUDY OBJECTIVE

To investigate the associations of NOS1AP rs12742393 polymorphism with the risk of type 2 diabetes mellitus (T2DM) and repaglinide therapeutic efficacy in Chinese patients with T2DM.

DESIGN

Prospective case-control study.

SETTING

Academic medical center.

PATIENTS

A total of 300 patients with T2DM and 200 healthy volunteers were enrolled to identify NOS1AP rs12742393 genotypes using the polymerase chain reaction-restriction fragment length polymorphism assay. Eighty-four patients with various genotypes were randomly selected to receive oral repaglinide as a single-agent therapy (3 mg/day) for 8 weeks.

MEASUREMENTS AND MAIN RESULTS

Anthropometric measurements and fasting plasma glucose (FPG), postprandial plasma glucose, hemoglobin A1c , fasting serum insulin (FINS), postprandial serum insulin, homeostasis model assessment for insulin resistance (HOMA-IR), triglyceride, total cholesterol, low-density lipoprotein-cholesterol, and high-density lipoprotein-cholesterol tests were obtained before and after repaglinide treatment. The risk C allelic frequency of NOS1AP rs12742393 was higher in patients with T2DM than in healthy volunteers (p<0.001). Patients with T2DM and genotypes AA and AC at NOS1AP rs12742393 had a significant reduction in FPG (mmol/l) compared with those with genotype CC (p<0.01). Patients with CC homozygotes and AC heterozygotes had a greater increase in FINS (mU/l) than those with wild-type AA (p<0.05). In addition, the carriers of genotype CC at NOS1AP rs12742393 had higher differential values of HOMA-IR compared with genotypes AC and AA carriers (p<0.001). The effects of repaglinide treatment on FPG (p<0.01), FINS (p<0.05) and HOMA-IR (p<0.001) were reduced in patients with T2DM carrying the NOS1AP rs12742393 risk C allele compared with the AA genotype carriers.

CONCLUSION

The NOS1AP rs12742393 polymorphism is associated with therapeutic efficacy of repaglinide in Chinese T2DM patients.

Evaluation of the Hepa Wash® treatment in pigs with acute liver failure

Background

Mortality of patients with acute liver failure (ALF) is still unacceptably high. Available liver support systems are still of limited success at improving survival. A new type of albumin dialysis, the Hepa Wash^® system, was newly introduced. We evaluated the new liver support system as well as the Molecular Adsorbent Recycling System (MARS) in an ischemic porcine model of ALF.

Methods

In the first study animals were randomly allocated to control (n=5) and Hepa Wash (n=6) groups. In a further pilot study, two animals were treated with the MARS-system. All animals received the same medical and surgical procedures. An intraparenchymal intracranial pressure was inserted. Hemodynamic monitoring and goal-directed fluid therapy using the PiCCO system was done. Animals underwent functional end-to-side portacaval shunt and ligation of hepatic arteries. Treatment with albumin dialysis was started after fall of cerebral perfusion pressure to 45 mmHg and continued for 8 h.

Results

All animals in the Hepa Wash group survived the 13-hour observation period, except for one that died after stopping treatment. Four of the control animals died within this period (p=0.03). Hepa Wash significantly reduced impairment of cerebral perfusion pressure (23±2 vs. 10±3 mmHg, p=0.006) and mean arterial pressure (37±1 vs. 24±2 mmHg, p=0.006) but had no effect on intracranial pressure (14±1 vs. 15±1 mmHg, p=0.72). Hepa Wash also enhanced cardiac index (4.94±0.32 vs. 3.36±0.25 l/min/m2, p=0.006) and renal function (urine production, 1850 ± 570 vs. 420 ± 180 ml, p=0.045) and eliminated water soluble (creatinine, 1.3±0.2 vs. 3.2±0.3 mg/dl, p=0.01; ammonia 562±124 vs. 1382±92 μg/dl, p=0.006) and protein-bound toxins (nitrate/nitrite 5.54±1.57 vs. 49.82±13.27 μmol/l, p=0.01). No adverse events that could be attributed to the Hepa Wash treatment were observed.

Conclusions

Hepa Wash was a safe procedure and improved multiorgan system failure in pigs with ALF. The survival benefit could be the result of ameliorating different organ functions in association with the detoxification capacity of water soluble and protein-bound toxins.

Heart failure entails significant changes in human nucleocytoplasmic transport gene expression

BACKGROUND

Heart failure (HF) induces alterations in nucleocytoplasmic transport, which is essential to the cardiomyocyte biology. The objective of this study was to analyze the changes in gene expression in human HF, particularly focusing on nucleocytoplasmic transport-related genes.

METHODS AND RESULTS

29 RNA heart samples from dilated cardiomyopathy (DCM, n = 12) and ischemic cardiomyopathy (ICM, n = 12) patients undergoing heart transplantation and control donors (CNT, n = 5) were extracted to perform a microarray profiling using Affymetrix Human Gene® 1.0 ST arrays. We focused on the study of 5 nucleocytoplasmic transport-related genes, since this functional category has not previously been studied in HF. XPO1, GABPB2, and RANBP17 were upregulated, while KALRN was downregulated in both DCM and ICM, and XPO5 only in DCM. Validation of the results by RT-qPCR increasing the total heart samples up to 41 showed a high degree of consistency with microarray results. Moreover, we observed a strong relationship between the XPO1 mRNA and robust left ventricular function parameters in ICM: left ventricular end-systolic (r = 0.81, p<0.0001) and end-diastolic diameters (r = 0.80, p<0.0001), and ejection fraction (r = -0.57, p<0.05).

CONCLUSIONS

We show that the expression of nucleocytoplasmic transport-related genes is altered in HF. Furthermore, XPO1 mRNA level is closely related with robust left ventricular function parameters in ICM patients. These changes may help to distinguish DCM and ICM in HF at the level of the transcriptome and provide a base for novel therapeutic approaches.

Individualized therapy for type 2 diabetes: clinical implications of pharmacogenetic data

Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance, abnormally elevated hepatic glucose production, and reduced glucose-stimulated insulin secretion. Treatment with antihyperglycemic agents is initially successful in type 2 diabetes, but it is often associated with a high secondary failure rate, and the addition of insulin is eventually necessary for many patients, in order to restore acceptable glycemic control and to reduce the risk of development and progression of disease complications. Notably, even patients who appear to have similar requirements of antidiabetic regimens show great variability in drug disposition, glycemic response, tolerability, and incidence of adverse effects during treatment. Pharmacogenomics is a promising area of investigation and involves the search for genetic polymorphisms that may explain the interindividual variability in antidiabetic therapy response. The initial positive results portend that genomic efforts will be able to shed important light on variability in pharmacologic traits. In this review, we summarize the current understanding of genetic polymorphisms that may affect the responses of subjects with T2DM to antidiabetic treatment. These genes belong to three major classes: genes involved in drug metabolism and transporters that influence pharmacokinetics (including the cytochrome P450 [CYP] superfamily, the organic anion transporting polypeptide [OATP] family, and the polyspecific organic cation transporter [OCT] family); genes encoding drug targets and receptors (including peroxisome proliferator-activated receptor gamma [PPARG], the adenosine triphosphate [ATP]-sensitive potassium channel [K(ATP)], and incretin receptors); and genes involved in the causal pathway of T2DM that are able to modify the effects of drugs (including adipokines, transcription factor 7-like 2 (T cell specific, HMG-box) [TCF7L2], insulin receptor substrate 1 [IRS1], nitric oxide synthase 1 (neuronal) adaptor protein [NOS1AP], and solute carrier family 30 (zinc transporter), member 8 [SLC30A8]). In addition to these three major classes, we also review the available evidence on novel genes (CDK5 regulatory subunit associated protein 1-like 1 [CDKAL1], insulin-like growth factor 2 mRNA binding protein 2 [IGF2BP2], potassium voltage-gated channel, KQT-like subfamily, member 1 [KCNQ1], paired box 4 [PAX4] and neuronal differentiation 1 [NEUROD1] transcription factors, ataxia telangiectasia mutated [ATM], and serine racemase [SRR]) that have recently been proposed as possible modulators of therapeutic response in subjects with T2DM.

Malvidin, a red wine polyphenol, modulates mammalian myocardial and coronary performance and protects the heart against ischemia/reperfusion injury

A moderate red wine consumption and a colored fruit-rich diet protect the cardiovascular system, thanks to the presence of several polyphenols. Malvidin-3-0-glucoside (malvidin), an anthocyanidine belonging to polyphenols, is highly present in red grape skin and red wine. Its biological activity is poorly characterized, although a role in tumor cell inhibition has been found. To analyze whether and to which extent, like other food-derived polyphenols, malvidin affects the cardiovascular function, in this study, we have performed a quantitative analysis by high-performance liquid chromatography of polyphenolic content of red grape skins extract, showing that it contains a high malvidin amount (63.93 ±12.50 mg/g of fresh grape skin). By using the isolated and Langendorff perfused rat heart, we found that the increasing doses (1-1000 ng/ml) of the extract induced positive inotropic and negative lusitropic effects associated with coronary dilation. On the same cardiac preparations, we observed that malvidin (10(-10)-10(-6) mol/L) elicited negative inotropism and lusitropism and coronary dilation. Analysis of mechanism of action revealed that malvidin-dependent cardiac effects require the activation of the phosphatidylinositol 3-kinase (PI3K)/nitric oxide (NO)/cGMP/PKG pathway and are associated with increased intracellular cGMP and the phosphorylation of endothelial NO synthase (eNOS), PI3K-AKT, ERK1/2, and GSK-3β. AKT and eNOS phosphorylation was confirmed in human umbilical vein endothelial cell. We also found that malvidin act as a postconditioning agent, being able to elicit cardioprotection against ischemia/reperfusion damages. Our results show the cardioactivity of polyphenols-rich red grape extracts and indicate malvidin as a new cardioprotective principle. This is of relevance not only for a better clarification of the beneficial cardiovascular effects of food-derived polyphenols but also for nutraceutical research.

Cardiac heterometric response: the interplay between Catestatin and nitric oxide deciphered by the frog heart

The length-active tension relation or heterometric regulation (Frank-Starling mechanism) is modulated by nitric oxide (NO) which, released in pulsatile fashion from the beating heart, improves myocardial relaxation and diastolic distensibility. The NO signaling is also implicated in the homeometric regulation exerted by extrinsic factors such as autonomic nervous system, endocrine and humoral agents. In the in vitro working frog heart, the Chromogranin A (CGA)-derived peptide, Catestatin (CTS; bovine CGA344-364), exerts a direct cardio-suppressive action through a NOS-NO-cGMP-mediated mechanism which requires the functional integrity of the endocardial endothelium (EE) and its endothelin-1 B type (ETB) receptor. However, functional interplay between NO and CTS and their role in the Frank-Starling response of the frog heart are lacking. Here we show that CTS improves the sensitivity to preload increases similar to that exerted by NO. This effect is abolished by inhibition of NO synthase (L-NAME), guanylate cyclase (ODQ), protein kinase G (KT5823), PI3K (Wortmannin), as well as by the functional damage of EE (Triton X-100) suggesting that CTS operates through an EE-dependent NO release. On the whole, the use of the avascular frog heart revealed the EE as major sensor-transducer interface between the physical (volume load) and chemical (CTS) stimuli, NO functioning as a connector between heterometric and homeometric regulation.

Nitrite is a positive modulator of the Frank-Starling response in the vertebrate heart

Evidence from both mammalian and nonmammalian vertebrates indicates that intracardiac nitric oxide (NO) facilitates myocardial relaxation, ventricular diastolic distensibility, and, consequently, the Frank-Starling response, i.e., the preload-induced increase of cardiac output. Since nitrite ion (NO(2)(-)), the major storage pool of bioactive NO, recently emerged as a cardioprotective endogenous modulator, we explored its influence on the Frank-Starling response in eel, frog, and rat hearts, used as paradigms of fish, amphibians, and mammals, respectively. We demonstrated that, like NO, exogenous nitrite improves the Frank-Starling response in all species, as indicated by an increase of stroke volume and stroke work (eel and frog) and of left ventricular (LV) pressure and LVdP/dt max (rat), used as indexes of inotropism. Unlike in frog and rat, in eel, the positive influence of nitrite appeared to be dependent on NO synthase inhibition. In all species, the effect was sensitive to NO scavengers, independent on nitroxyl anion, and mediated by a cGMP/PKG-dependent pathway. Moreover, the nitrite treatment increased S-nitrosylation of lower-molecular-weight proteins in cytosolic and membrane fractions. These results suggest that nitrite acts as a physiological source of NO, modulating through different species-specific mechanisms, the stretch-induced intrinsic regulation of the vertebrate heart.

Association of IL1B polymorphism with left ventricular systolic dysfunction: a relation with the release of interleukin-1β in stress condition

OBJECTIVE

Proinflammatory cytokines play a major role in the pathomechanisms of heart failure. Besides this, the influence of mental stress on heart failure is poorly documented despite its effects on sympathetic stimulation of interleukin-1β (IL-1β) secretion. We examined whether the polymorphisms of proinflammatory cytokines are predictors of left ventricular systolic dysfunction (LVSD) and if so, whether such associations are related to the secretion of these cytokines, in 572 consecutive patients under mental stress produced by coronary angiography.

METHODS

We examined IL-1RN (VNTR), IL1A-889 C>T, IL1B-511 C>T, IL6-174 G>C and TNFA-308 G>A, according to LVSD (left ventricular ejection fraction, <40%). Saliva IL-1β, serum tumour necrosis factor-α and C-reactive protein were assayed in basal (T0 and T2, before and after coronary angiography) and stress (T1) conditions.

MAIN RESULTS

The 42.1% of patients with LVSD had a 1.5-fold higher frequency of IL1B T allele (P<0.001). IL1B-511TT was associated with LVSD (P=0.008) and with a decrease in IL-1β level in saliva at T1 (P=0.013). IL-1β was the highest at T1 (P<0.001) and was associated with left ventricular ejection fraction (P=0.002). The IL1B TT genotype and the C-reactive protein were the two independent predictors of LVSD in multivariate analysis, with an odds ratio of 2.7 (95% confidence interval: 1.3-5.5; P=0.008) and 1.1 (95% confidence interval: 1.1-1.2; P<0.001), respectively.

CONCLUSION

IL1B was a predictor of LVSD and of the decreased IL-1β response to stress. This suggests that IL1B exerts an influence on LVSD through its effect on IL-1β secretion.

Phosphodiesterase type-2 and NO-dependent S-nitrosylation mediate the cardioinhibition of the antihypertensive catestatin

The chromogranin A (CHGA)-derived peptide catestatin (CST: hCHGA(352-372)) is a noncompetitive catecholamine-release inhibitor that exerts vasodilator, antihypertensive, and cardiosuppressive actions. We have shown that CST directly influences the basal performance of the vertebrate heart where CST dose dependently induced a nitric oxide-cGMP-dependent cardiosuppression and counteracted the effects of adrenergic stimulation through a noncompetitive antagonism. Here, we sought to determine the specific intracardiac signaling activated by CST in the rat heart. Physiological analyses performed on isolated, Langendorff-perfused cardiac preparations revealed that CST-induced negative inotropism and lusitropism involve β(2)/β(3)-adrenergic receptors (β(2)/β(3)-AR), showing a higher affinity for β(2)-AR. Interaction with β(2)-AR activated phosphatidylinositol 3-kinase/endothelial nitric oxide synthase (eNOS), increased cGMP levels, and induced activation of phosphodiesterases type 2 (PDE2), which was found to be involved in the antiadrenergic action of CST as evidenced by the decreased cAMP levels. CST-dependent negative cardiomodulation was abolished by functional denudation of the endothelium with Triton. CST also increased the eNOS expression in cardiac tissue and human umbilical vein endothelial cells. cells, confirming the involvement of the vascular endothelium. In ventricular extracts, CST increased S-nitrosylation of both phospholamban and β-arrestin, suggesting an additional mechanism for intracellular calcium modulation and β-adrenergic responsiveness. We conclude that PDE2 and S-nitrosylation play crucial roles in the CST regulation of cardiac function. Our results are of importance in relation to the putative application of CST as a cardioprotective agent against stress, including excessive sympathochromaffin overactivation.

Ryanodine receptor: a new therapeutic target to control diabetic cardiomyopathy

Diabetes mellitus is a major risk factor for cardiovascular complications. Intracellular Ca(2+) release plays an important role in the regulation of muscle contraction. Sarcoplasmic reticulum Ca(2+) release is controlled by dedicated molecular machinery, composed of a complex of cardiac ryanodine receptors (RyR2s). Acquired and genetic defects in this complex result in a spectrum of abnormal Ca(2+) release phenotypes in heart. Cardiovascular dysfunction is a leading cause for mortality of diabetic individuals due, in part, to a specific cardiomyopathy, and to altered vascular reactivity. Cardiovascular complications result from multiple parameters, including glucotoxicity, lipotoxicity, fibrosis, and mitochondrial uncoupling. In diabetic subjects, oxidative stress arises from an imbalance between production of reactive oxygen and nitrogen species and capability of the system to readily detoxify reactive intermediates. To date, the etiology underlying diabetes-induced reductions in myocyte and cardiac contractility remains incompletely understood. However, numerous studies, including work from our laboratory, suggest that these defects stem in part from perturbation in intracellular Ca(2+) cycling. Since the RyR2s are one of the well-characterized redox-sensitive ion channels in heart, this article summarizes recent findings on redox regulation of cardiac Ca(2+) transport systems and discusses contributions of redox regulation to pathological cardiac function in diabetes.

Effect of genetic polymorphisms on the pharmacokinetics and efficacy of glimepiride in a Korean population

BACKGROUNDS

Glimepiride is a commonly used sulfonylurea hypoglycemic agent. There is considerable interindividual variation in the response to sulfonylurea for patients with type 2 diabetes. The purpose of this study was to investigate whether genetic variations influence the efficacy of glimepiride in healthy Korean subjects.

METHODS

A single 2-mg oral dose of glimepiride was administered to 46 healthy volunteers. Serial blood sampling for 12h after oral dosing was performed for determination of plasma glimepiride, glucose and insulin levels. We tested the association of seven single nucleotide polymorphisms (SNPs) in four candidate genes with the efficacy of glimepiride.

RESULTS

Pharmacodynamic profiles for plasma glucose and insulin showed no statistically significant differences among genotype groups, and parameters were not different from one another. There were no association of the KCNJ11, NOS1AP, TCF7L2 and ABCC8 gene polymorphisms and the efficacy of glimepiride.

CONCLUSIONS

Knowledge of these polymorphisms provides no clinical useful information for the pharmacogenetic therapeutic approach for Korean patients with type 2 diabetes.

Playing with cardiac "redox switches": the "HNO way" to modulate cardiac function

The nitric oxide (NO(•)) sibling, nitroxyl or nitrosyl hydride (HNO), is emerging as a molecule whose pharmacological properties include providing functional support to failing hearts. HNO also preconditions myocardial tissue, protecting it against ischemia-reperfusion injury while exerting vascular antiproliferative actions. In this review, HNO's peculiar cardiovascular assets are discussed in light of its unique chemistry that distinguish HNO from NO(•) as well as from reactive oxygen and nitrogen species such as the hydroxyl radical and peroxynitrite. Included here is a discussion of the possible routes of HNO formation in the myocardium and its chemical targets in the heart. HNO has been shown to have positive inotropic/lusitropic effects under normal and congestive heart failure conditions in animal models. The mechanistic intricacies of the beneficial cardiac effects of HNO are examined in cellular models. In contrast to β-receptor/cyclic adenosine monophosphate/protein kinase A-dependent enhancers of myocardial performance, HNO uses its "thiophylic" nature as a vehicle to interact with redox switches such as cysteines, which are located in key components of the cardiac electromechanical machinery ruling myocardial function. Here, we will briefly review new features of HNO's cardiovascular effects that when combined with its positive inotropic/lusitropic action may render HNO donors an attractive addition to the current therapeutic armamentarium for treating patients with acutely decompensated congestive heart failure.

Nitric oxide averts hypoxia-induced damage during reoxygenation in rat heart

Nitric oxide (NO), synthesized by the hemoproteins NO synthases (NOS), is known to play important roles in physiological and pathological conditions in the heart, including hypoxia/reoxygenation (H/R). This work investigates the role that endogenous NO plays in the cardiac H/R-induced injury. A follow-up study was conducted in Wistar rats subjected to 30 min of hypoxia, with or without prior treatment using the nonselective NOS inhibitor L-NAME (1.5 mM). The rats were studied at 0 h, 12 h, and 5 days of reoxygenation, analysing parameters of cell, and tissue damage (lipid peroxidation, apoptosis, and protein nitration), as well as in situ NOS activity and NO production (NOx). The results showed that after L-NAME administration, in situ NOS activity was almost completely eliminated in all the experimental groups, and consequently, NOx levels fell. Contrarily, the lipid peroxidation level and the percentage of apoptotic cells rose throughout the reoxygenation period. These results reveal that NOS inhibition exacerbates the peroxidative and apoptotic damage observed before the treatment with L-NAME in the hypoxic heart, pointing to a cardioprotective role of NOS-derived NO against H/R-induced injury. These findings could open the possibility of future studies to design new therapies for H/R-dysfunctions based on NO-pharmacology.

Apelin-13 limits infarct size and improves cardiac postischemic mechanical recovery only if given after ischemia

We studied whether apelin-13 is cardioprotective against ischemia/reperfusion injury if given as either a pre- or postconditioning mimetic and whether the improved postischemic mechanical recovery induced by apelin-13 depends only on the reduced infarct size or also on a recovery of function of the viable myocardium. We also studied whether nitric oxide (NO) is involved in apelin-induced protection and whether the reported ischemia-induced overexpression of the apelin receptor (APJ) plays a role in cardioprotection. Langendorff-perfused rat hearts underwent 30 min of global ischemia and 120 min of reperfusion. Left ventricular pressure was recorded. Infarct size and lactate dehydrogenase release were determined to evaluate the severity of myocardial injury. Apelin-13 was infused at 0.5 μM concentration for 20 min either before ischemia or in early reperfusion, without and with NO synthase inhibition by N(G)-nitro-l-arginine (l-NNA). In additional experiments, before ischemia also 1 μM apelin-13 was tested. APJ protein level was measured before and after ischemia. Whereas before ischemia apelin-13 (0.5 and 1.0 μM) was ineffective, after ischemia it reduced infarct size from 54 ± 2% to 26 ± 4% of risk area (P < 0.001) and limited the postischemic myocardial contracture (P < 0.001). l-NNA alone increased postischemic myocardial contracture. This increase was attenuated by apelin-13, which, however, was unable to reduce infarct size. Ischemia increased APJ protein level after 15-min perfusion, i.e., after most of reperfusion injury has occurred. Apelin-13 protects the heart only if given after ischemia. In this protection NO plays an important role. Apelin-13 efficiency as postconditioning mimetic cannot be explained by the increased APJ level.

Nitric oxide pathway in hypertrophied heart: new therapeutic uses of nitric oxide donors

Left ventricular hypertrophy (LVH) is regarded as a complication common to a number of cardiovascular diseases, including hypertension, myocardial infarction and ischaemia associated with coronary artery disease. Initially LVH is a compensatory mechanism, but in the long term cardiac hypertrophy predisposes individuals to heart failure, myocardial infarction and sudden death. Alteration of the nitric oxide (NO) pathway is believed to play an important role in the haemodynamically overloaded heart and pathological cardiac remodelling. Although re-establishment of the physiological NO pathway could be considered an important therapeutic target, the use of conventional nitrates is limited in the clinical setting by the development of tissue resistance and tolerance and by the shortage of large-scale clinical trials unequivocally confirming the beneficial impact of NO donors on cardiovascular morbidity and mortality. The aim of this review is to present current therapeutic options for dealing with changes in the L-arginine-NO pathway. The most promising therapeutic approach is represented by a new neutral sugar organic nitrate, LA-419, the thiol group of which seems to protect NO from degradation, thereby increasing its bioavailability. In a model of aortic stenosis-induced pressure overload, LA-419 has been found to restore the complete NO signalling cascade and reduce left ventricular remodelling, but without restoring the original pressure gradient, indicating a possible direct antiproliferative effect. Future studies are needed to confirm this therapeutic benefit in other animal models of hypertension and in the clinical setting.

Hydrogen sulfide interacts with nitric oxide in the heart: possible involvement of nitroxyl

AIMS

The present study aims to investigate the interaction between nitric oxide (NO) and hydrogen sulfide (H(2)S), the two important gaseous mediators in rat hearts.

METHODS AND RESULTS

Intracellular calcium in isolated cardiomyocytes was measured with a spectrofluorometric method using Fura-2. Myocyte contractility was measured with a video edge system. NaHS (50 µM, an H(2)S donor) had no significant effect on the resting calcium level, electrically induced (EI) calcium transients, and cell contractility in ventricular myocytes. Stimulating endogenous NO production with l-arginine or exogenous application of NO donors [sodium nitroprusside (SNP) and 2-(N,N-diethylamino)-diazenolate-2-oxide] decreased myocyte twitch amplitudes accompanied by slower velocities of both cell contraction and relaxation. Surprisingly, NaHS reversed the negative inotropic and lusitropic effects of the above three NO-increasing agents. In addition, the mixture of SNP + NaHS increased, whereas SNP alone decreased, the resting calcium level and the amplitudes of EI calcium transients. Angeli's salt, a nitroxyl anion (HNO) donor, mimicked the effect of SNP + NaHS on calcium handling and myocyte contractility. Three thiols, N-acetyl-cysteine, l-cysteine, and glutathione, abolished the effects of HNO and SNP + NaHS on myocyte contraction. Neither Rp-cAMP [a protein kinase A (PKA) inhibitor] nor Rp-cGMP [a protein kinase G (PKG) inhibitor] affected the effects of SNP + NaHS, suggesting a cAMP/PKA- or cGMP/PKG-independent mechanism.

CONCLUSION

H(2)S may interact with NO to form a thiol sensitive molecule (probably HNO) which produces positive inotropic and lusitropic effects. Our findings may shed light on the interaction of NO and H(2)S and provide new clues to treat cardiovascular diseases.

Sulfonylurea pharmacogenomics in Type 2 diabetes: the influence of drug target and diabetes risk polymorphisms

The sulfonylureas stimulate insulin release from pancreatic beta cells, and have been a cornerstone of Type 2 diabetes pharmacotherapy for over 50 years. Although sulfonylureas are effective antihyperglycemic agents, interindividual variability exists in drug response (i.e., pharmacodynamics), disposition (i.e., pharmacokinetics) and adverse effects. The field of pharmacogenomics has been applied to sulfonylurea clinical studies in order to elucidate the genetic underpinnings of this response variability. Historically, most studies have sought to determine the influence of polymorphisms in drug-metabolizing enzyme genes on sulfonylurea pharmacokinetics in humans. More recently, polymorphisms in sulfonylurea drug target genes and diabetes risk genes have been implicated as important determinants of sulfonylurea pharmacodynamics in patients with Type 2 diabetes. As such, the purpose of this review is to discuss sulfonylurea pharmacogenomics in the setting of Type 2 diabetes, specifically focusing on polymorphisms in drug target and diabetes risk genes, and their relationship with interindividual variability in sulfonylurea response and adverse effects.

The ups and downs of mitochondrial calcium signalling in the heart

Regulation of intramitochondrial free calcium ([Ca2+]m) is critical in both physiological and pathological functioning of the heart. The full extent and importance of the role of [Ca2+]m is becoming apparent as evidenced by the increasing interest and work in this area over the last two decades. However, controversies remain, such as the existence of beat-to-beat mitochondrial Ca2+ transients; the role of [Ca2+]m in modulating whole-cell Ca2+ signalling; whether or not an increase in [Ca2+]m is essential to couple ATP supply and demand; and the role of [Ca2+]m in cell death by both necrosis and apoptosis, especially in formation of the mitochondrial permeability transition pore. The role of [Ca2+]m in heart failure is an area that has also recently been highlighted. [Ca2+]m can now be measured reasonably specifically in intact cells and hearts thanks to developments in fluorescent indicators and targeted proteins and more sensitive imaging technology. This has revealed interactions of the mitochondrial Ca2+ transporters with those of the sarcolemma and sarcoplasmic reticulum, and has gone a long way to bringing the mitochondrial Ca2+ transporters to the forefront of cardiac research. Mitochondrial Ca2+ uptake occurs via the ruthenium red sensitive Ca2+ uniporter (mCU), and efflux via an Na+/Ca2+ exchanger (mNCX). The purification and cloning of the transporters, and development of more specific inhibitors, would produce a step-change in our understanding of the role of these apparently critical but still elusive proteins. In this article we will summarise the key physiological roles of [Ca2+]m in ATP production and cell Ca2+ signalling in both adult and neonatal hearts, as well as highlighting some of the controversies in these areas. We will also briefly discuss recent ideas on the interactions of nitric oxide with [Ca2+]m.