Nitric oxide inhibits myocardial apoptosis by preventing caspase-3 activity via S-nitrosylation

Inhibition of vascular smooth muscle cell proliferation by Gentiana lutea root extracts

Gentiana lutea belonging to the Gentianaceae family of flowering plants are routinely used in traditional Serbian medicine for their beneficial gastro-intestinal and anti-inflammatory properties. The aim of the study was to determine whether aqueous root extracts of Gentiana lutea consisting of gentiopicroside, gentisin, bellidifolin-8-O-glucoside, demethylbellidifolin-8-O-glucoside, isovitexin, swertiamarin and amarogentin prevents proliferation of aortic smooth muscle cells in response to PDGF-BB. Cell proliferation and cell cycle analysis were performed based on alamar blue assay and propidium iodide labeling respectively. In primary cultures of rat aortic smooth muscle cells (RASMCs), PDGF-BB (20 ng/ml) induced a two-fold increase in cell proliferation which was significantly blocked by the root extract (1 mg/ml). The root extract also prevented the S-phase entry of synchronized cells in response to PDGF. Furthermore, PDGF-BB induced ERK1/2 activation and consequent increase in cellular nitric oxide (NO) levels were also blocked by the extract. These effects of extract were due to blockade of PDGF-BB induced expression of iNOS, cyclin D1 and proliferating cell nuclear antigen (PCNA). Docking analysis of the extract components on MEK1, the upstream ERK1/2 activating kinase using AutoDock4, indicated a likely binding of isovitexin to the inhibitor binding site of MEK1. Experiments performed with purified isovitexin demonstrated that it successfully blocks PDGF-induced ERK1/2 activation and proliferation of RASMCs in cell culture. Thus, Gentiana lutea can provide novel candidates for prevention and treatment of atherosclerosis.

Toll-like receptor signaling pathways in cardiovascular diseases: challenges and opportunities

Toll-like receptors (TLRs), a family of surface molecules, are involved in innate immune responses. Recent studies indicated that TLRs play a critical role in inflammatory responses to exogenous and endogenous triggers. This article focuses on probable effects of TLRs in the morbidity of cardiovascular events, e.g., ischemic reperfusion (I/R) injury and atherosclerosis. TLR2 and TLR4 have been shown to have the most fundamental role in promoting cytokine production and subsequent inflammatory damages in these states. Blockade of these receptors may be beneficial in both preventing the occurrence and decreasing the complications in cardiovascular events. However, controversies exist on the certainty of this beneficial effect; therefore, additional studies are needed.

Reduction of cardiomyocyte S-nitrosylation by S-nitrosoglutathione reductase protects against sepsis-induced myocardial depression

Myocardial depression is an important contributor to morbidity and mortality in septic patients. Nitric oxide (NO) plays an important role in the development of septic cardiomyopathy, but also has protective effects. Recent evidence has indicated that NO exerts many of its downstream effects on the cardiovascular system via protein S-nitrosylation, which is negatively regulated by S-nitrosoglutathione reductase (GSNOR), an enzyme promoting denitrosylation. We tested the hypothesis that reducing cardiomyocyte S-nitrosylation by increasing GSNOR activity can improve myocardial dysfunction during sepsis. Therefore, we generated mice with a cardiomyocyte-specific overexpression of GSNOR (GSNOR-CMTg mice) and subjected them to endotoxic shock. Measurements of cardiac function in vivo and ex vivo showed that GSNOR-CMTg mice had a significantly improved cardiac function after lipopolysaccharide challenge (LPS, 50 mg/kg) compared with wild-type (WT) mice. Cardiomyocytes isolated from septic GSNOR-CMTg mice showed a corresponding improvement in contractility compared with WT cells. However, systolic Ca(2+) release was similarly depressed in both genotypes after LPS, indicating that GSNOR-CMTg cardiomyocytes have increased Ca(2+) sensitivity during sepsis. Parameters of inflammation were equally increased in LPS-treated hearts of both genotypes, and no compensatory changes in NO synthase expression levels were found in GSNOR-overexpressing hearts before or after LPS challenge. GSNOR overexpression however significantly reduced total cardiac protein S-nitrosylation during sepsis. Taken together, our results indicate that increasing the denitrosylation capacity of cardiomyocytes protects against sepsis-induced myocardial depression. Our findings suggest that specifically reducing protein S-nitrosylation during sepsis improves cardiac function by increasing cardiac myofilament sensitivity to Ca(2+).

Age-related loss of nitric oxide synthase in skeletal muscle causes reductions in calpain S-nitrosylation that increase myofibril degradation and sarcopenia

Sarcopenia, the age-related loss of muscle mass, is a highly-debilitating consequence of aging. In this investigation, we show sarcopenia is greatly reduced by muscle-specific overexpression of calpastatin, the endogenous inhibitor of calcium-dependent proteases (calpains). Further, we show that calpain cleavage of specific structural and regulatory proteins in myofibrils is prevented by covalent modification of calpain by nitric oxide (NO) through S-nitrosylation. We find that calpain in adult, non-sarcopenic muscles is S-nitrosylated but that aging leads to loss of S-nitrosylation, suggesting that reduced S-nitrosylation during aging leads to increased calpain-mediated proteolysis of myofibrils. Further, our data show that muscle aging is accompanied by loss of neuronal nitric oxide synthase (nNOS), the primary source of muscle NO, and that expression of a muscle-specific nNOS transgene restores calpain S-nitrosylation in aging muscle and prevents sarcopenia. Together, the findings show that in vivo reduction of calpain S-nitrosylation in muscle may be an important component of sarcopenia, indicating that modulation of NO can provide a therapeutic strategy to slow muscle loss during old age.

A comparison between imidapril and ramipril on attenuation of ventricular remodeling after myocardial infarction

BACKGROUND

Angiotensin converting enzyme inhibitors have been used clinically to prevent myocardial infarction (MI). The angiotensin converting enzyme inhibitors attenuated ventricular remodeling and improved cardiac function by inhibition of matrix metalloproteinases after MI. Although the effect is thought to be a class effect, there are significant differences among the drugs. The aim of this study was to compare the effects of imidapril and ramipril on ventricular remodeling after MI.

METHODS

The middle portion of left anterior descending artery was ligated to induce a moderate size MI in rats (moderate MI group). The proximal portion of the artery was ligated to induce a large size MI (large MI group). The animals were assigned to subgroups in moderate MI group and large MI group: (1) nontreated group, (2) ramipril group (1 mg/kg daily), and (3) imidapril group (1 mg/kg daily). All rats were killed on day 28 after the MI operation.

RESULTS

Although the nontreated MI group showed impaired ventricular contraction and severe fibrosis, imidapril significantly negated ischemia-induced changes. Imidapril had a superior effect for preventing ventricular remodeling characterized by fibrosis and collagen accumulation in left ventricle compared with ramipril in the moderate and large MI groups, even though the dosage used in this study was too small to reduce systemic blood pressure.

CONCLUSIONS

Imidapril can be used as a substitute for ramipril to prevent ventricular remodeling after MI.

Cardioprotection through S-nitros(yl)ation of macrophage migration inhibitory factor

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a structurally unique inflammatory cytokine that controls cellular signaling in human physiology and disease through extra- and intracellular processes. Macrophage migration inhibitory factor has been shown to mediate both disease-exacerbating and beneficial effects, but the underlying mechanism(s) controlling these diverse functions are poorly understood.

METHODS AND RESULTS

Here, we have identified an S-nitros(yl)ation modification of MIF that regulates the protective functional phenotype of MIF in myocardial reperfusion injury. Macrophage migration inhibitory factor contains 3 cysteine (Cys) residues; using recombinant wtMIF and site-specific MIF mutants, we have identified that Cys-81 is modified by S-nitros(yl)ation whereas the CXXC-derived Cys residues of MIF remained unaffected. The selective S-nitrosothiol formation at Cys-81 led to a doubling of the oxidoreductase activity of MIF. Importantly, S-nitrosothiol-MIF formation was measured both in vitro and in vivo and led to a decrease in cardiomyocyte apoptosis in the reperfused heart. This decrease was paralleled by a S-nitrosothiol-MIF- but not Cys81 serine (Ser)-MIF mutant-dependent reduction of infarct size in an in vivo model of myocardial ischemia/reperfusion injury.

CONCLUSIONS

S-nitros(yl)ation of MIF is a pivotal novel regulatory mechanism, providing enhanced activity resulting in increased cytoprotection in myocardial reperfusion injury.

Differential effect of intrauterine hypoxia on caspase 3 and DNA fragmentation in fetal guinea pig hearts and brains

The aim of this study is to quantify the effect of intrauterine hypoxia (HPX) and the role of nitric oxide (NO) on the apoptotic enzyme, caspase 3, and DNA fragmentation in fetal heart and brain. Hypoxia and NO are important regulators of apoptosis, although this has been little studied in the fetal organs. We investigated the effect of intrauterine HPX on apoptosis and the role of NO in both fetal hearts and brains. Pregnant guinea pigs were exposed to room temperature (N = 14) or 10.5% O₂ (N = 12) for 14 days prior to term (term = 65 days) and administered water or L-N6-(1-iminoethyl)-lysine (LNIL), an inducible nitric oxide synthase (iNOS) inhibitor, for 10 days. Fetal hearts and brains were excised from anesthetized near-term fetuses for study. Chronic HPX decreased pro- and active caspase 3, caspase 3 activity, and DNA fragmentation levels in fetal hearts compared with normoxic controls. L-N6-(1-iminoethyl)-lysine prevented the HPX-induced decrease in caspase 3 activity but did not alter DNA fragmentation levels. In contrast, chronic HPX increased both apoptotic indices in fetal brains, which were inhibited by LNIL. Thus, the effect of HPX on apoptosis differs between fetal organs, and NO may play an important role in modulating these effects.

Nitric Oxide-Releasing Hybrid Drugs Target Cellular Processes Through S-Nitrosylation

Nitric oxide (NO)-releasing agents such as JS-K and NO-releasing hybrids such as NO- and NONO-nonsteroidal anti-inflammatory drugs are novel agents with great potential for controlling cancer. Although studied extensively, a key question pertaining to their molecular targets and mechanism of action remains unclear: the role of NO in the overall biological effect of these agents. It has been shown that NO can directly modify sulfhydryl residues of proteins through S-nitrosylation and induce apoptosis. We showed that 3 structurally diverse NO-nonsteroidal anti-inflammatory drugs S-nitrosylated nuclear factor-κB p65 in vitro and in vivo and also showed that these agents S-nitrosylated caspase-3 in vivo. JS-K reduced nuclear β-catenin and cyclin D1 protein levels without affecting cytosolic β-catenin expression. On the basis of a time course study, S-nitrsolyation of nuclear β-catenin was determined to precede its degradation. These data provide a mechanistic role for NO and a rationale for the chemopreventive effects of these novel agents.

Estrogen-responsive nitroso-proteome in uterine artery endothelial cells: role of endothelial nitric oxide synthase and estrogen receptor-β

Covalent adduction of a NO moiety to cysteines (S-nitrosylation or SNO) is a major route for NO to directly regulate protein functions. In uterine artery endothelial cells (UAEC), estradiol-17β (E2) rapidly stimulated protein SNO that maximized within 10-30 min post-E2 exposure. E2-bovine serum albumin stimulated protein SNO similarly. Stimulation of SNO by both was blocked by ICI 182, 780, implicating mechanisms linked to specific estrogen receptors (ERs) localized on the plasma membrane. E2-induced protein SNO was attenuated by selective ERβ, but not ERα, antagonists. A specific ERβ but not ERα agonist was able to induce protein SNO. Overexpression of ERβ, but not ERα, significantly enhanced E2-induced SNO. Overexpression of both ERs increased basal SNO, but did not further enhance E2-stimulated SNO. E2-induced SNO was inhibited by N-nitro-L-arginine-methylester and specific endothelial NO synthase (eNOS) siRNA. Thus, estrogen-induced SNO is mediated by endogenous NO via eNOS and mainly ERβ in UAEC. We further analyzed the nitroso-proteomes by CyDye switch technique combined with two-dimensional (2D) fluorescence difference gel electrophoresis. Numerous nitrosoprotein (spots) were visible on the 2D gel. Sixty spots were chosen and subjected to matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Among the 54 identified, nine were novel SNO-proteins, 32 were increased, eight were decreased, and the rest were unchanged by E2. Tandom MS identified Cys139 as a specific site for SNO in GAPDH. Pathway analysis of basal and estrogen-responsive nitroso-proteomes suggested that SNO regulates diverse protein functions, directly implicating SNO as a novel mechanism for estrogen to regulate uterine endothelial function and thus uterine vasodilatation.

Dramatic increase of nitrite levels in hearts of anoxia-exposed crucian carp supporting a role in cardioprotection

Nitrite (NO(2)(-)) functions as an important nitric oxide (NO) donor under hypoxic conditions. Both nitrite and NO have been found to protect the mammalian heart and other tissues against ischemia (anoxia)-reoxygenation injury by interacting with mitochondrial electron transport complexes and limiting the generation of reactive oxygen species upon reoxygenation. The crucian carp naturally survives extended periods without oxygen in an active state, which has made it a model for studying how evolution has solved the problems of anoxic survival. We investigated the role of nitrite and NO in the anoxia tolerance of this fish by measuring NO metabolites in normoxic, anoxic, and reoxygenated crucian carp. We also cloned and sequenced crucian carp NO synthase variants and quantified their mRNA levels in several tissues in normoxia and anoxia. Despite falling levels of blood plasma nitrite, the crucian carp showed massive increases in nitrite, S-nitrosothiols (SNO), and iron-nitrosyl (FeNO) compounds in anoxic heart tissue. NO(2)(-) levels were maintained in anoxic brain, liver, and gill tissues, whereas SNO and FeNO increased in a tissue-specific manner. Reoxygenation reestablished normoxic values. We conclude that NO(2)(-) is shifted into the tissues where it acts as NO donor during anoxia, inducing cytoprotection under anoxia/reoxygenation. This can be especially important in the crucian carp heart, which maintains output in anoxia. NO(2)(-) is currently tested as a therapeutic drug against reperfusion damage of ischemic hearts, and the present study provides evolutionary precedent for such an approach.

Cysteine 203 of cyclophilin D is critical for cyclophilin D activation of the mitochondrial permeability transition pore

The mitochondrial permeability transition pore (mPTP) opening plays a critical role in mediating cell death during ischemia/reperfusion (I/R) injury. Our previous studies have shown that cysteine 203 of cyclophilin D (CypD), a critical mPTP mediator, undergoes protein S-nitrosylation (SNO). To investigate the role of cysteine 203 in mPTP activation, we mutated cysteine 203 of CypD to a serine residue (C203S) and determined its effect on mPTP opening. Treatment of WT mouse embryonic fibroblasts (MEFs) with H(2)O(2) resulted in an 50% loss of the mitochondrial calcein fluorescence, suggesting substantial activation of the mPTP. Consistent with the reported role of CypD in mPTP activation, CypD null (CypD(-/-)) MEFs exhibited significantly less mPTP opening. Addition of a nitric oxide donor, GSNO, to WT but not CypD(-/-) MEFs prior to H(2)O(2) attenuated mPTP opening. To test whether Cys-203 is required for this protection, we infected CypD(-/-) MEFs with a C203S-CypD vector. Surprisingly, C203S-CypD reconstituted MEFs were resistant to mPTP opening in the presence or absence of GSNO, suggesting a crucial role for Cys-203 in mPTP activation. To determine whether mutation of C203S-CypD would alter mPTP in vivo, we injected a recombinant adenovirus encoding C203S-CypD or WT CypD into CypD(-/-) mice via tail vein. Mitochondria isolated from livers of CypD(-/-) mice or mice expressing C203S-CypD were resistant to Ca(2+)-induced swelling as compared with WT CypD-reconstituted mice. Our results indicate that the Cys-203 residue of CypD is necessary for redox stress-induced activation of mPTP.

S-nitrosylation: a radical way to protect the heart

In this review, the role of S-nitrosylation (SNO) in cardioprotection will be discussed. This review will cover the methodology used to measure SNO levels, and the mechanisms by which SNO serves to modulate cell function and mediate protection. We will also consider whether SNO acts through many targets or whether there are a few key SNO proteins that mediate protection. Issues regarding the percentage of the total protein which is SNO and how this plays a role in the modulation of cell function will also be discussed. The role of nitric oxide synthase uncoupling in cardioprotection will also be addressed. This article is part of a Special Section entitled "Post-translational Modification."

Telmisartan, a unique ARB, improves left ventricular remodeling of infarcted heart by activating PPAR gamma

Unfavorable left ventricular (LV) remodeling after myocardial infarction (MI) leads to cardiac dysfunction. We examined whether Telmisartan, an angiotensin (Ang) II type I receptor blocker (ARB), could improve the recovery of LV function in a rat model of MI. The effect of Telmisartan as a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist was also investigated. After 28 days of MI, a significant improvement of survival was observed in the Telmisartan-treated rat group compared with the vehicle control rat group, non-PPAR-γ agonistic ARB (Losartan)-treated rat group, and Telmisartan plus specific PPAR-γ antagonist (GW9662)-treated rat group. Although no significant differences of blood pressure or infarct size were observed among these four groups, the Telmisartan group had better systolic and diastolic LV function. There was a significant reduction of the plasma brain natriuretic peptide level, cardiac fibrosis area, infiltration of macrophages, size of cardiomyocytes, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive myocytes, activation of matrix metalloproteinases-2 and -9 (MMPs-2/9), and expression of transforming growth factor β-1 (TGF-β1), connective tissue growth factor (CTGF), and osteopontin (OPN), while expression of PPAR-γ and activation of tissue inhibitor of metalloproteinase-1 (TIMP-1) was enhanced, in the noninfarcted myocardium of rats from the Telmisartan group compared with the other three groups. To mimic ischemic conditions in vitro, neonatal rat cardiomyocytes and cardiac fibroblasts were incubated in hypoxic condition for 24 h. Increased transcriptional activation of PPAR-γ and TIMP-1, and inhibition of TGF-β1 expression were observed in cardiomyocytes, while decreased activation of MMPs-2/9 and decrease in CTGF and OPN expression was seen in cardiac fibroblasts cultured with Telmisartan. In conclusion, Telmisartan prevented unfavorable cardiac remodeling through a reduction of cardiac hypertrophy and fibrosis. An anti-inflammatory effect and PPAR-γ activation were suggested to be important in addition to suppression of Ang II activity.

Emergent role of gasotransmitters in ischemia-reperfusion injury

Nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) are lipid-soluble, endogenously produced gaseous messenger molecules collectively known as gasotransmitters. Over the last several decades, gasotransmitters have emerged as potent cytoprotective mediators in various models of tissue and cellular injury. Specifically, when used at physiological levels, the exogenous and endogenous manipulation of these three gases has been shown to modulate ischemia/reperfusion injury by inducing a number of cytoprotective mechanisms including: induction of vasodilatation, inhibition of apoptosis, modulation of mitochondrial respiration, induction of antioxidants, and inhibition of inflammation. However, while the actions are similar, there are some differences in the mechanisms by which these gasotransmitters induce these effects and the regulatory actions of the enzyme systems can vary depending upon the gas being investigated. Furthermore, there does appear to be some crosstalk between the gases, which can provide synergistic effects and additional regulatory effects. This review article will discuss several models and mechanisms of gas-mediated cytoprotection, as well as provide a brief discussion on the complex interactions between the gasotransmitter systems.

Characterization of potential S-nitrosylation sites in the myocardium

S-nitrosylation (SNO) is a reversible protein modification that has the ability to alter the activity of target proteins. However, only a small number of SNO proteins have been found in the myocardium, and even fewer specific sites of SNO have been identified. Therefore, this study aims to characterize potential SNO sites in the myocardium. We utilized a modified version of the SNO-resin-assisted capture technique in tandem with mass spectrometry. In brief, a modified biotin switch was performed using perfused mouse heart homogenates incubated with or without the S-nitrosylating agent S-nitrosoglutathione. Our modified SNO-resin-assisted capture protocol identified 116 unique SNO-modified proteins under basal conditions, and these represent the constitutive SNO proteome. These constitutive SNO proteins are likely to be physiologically relevant targets, since nitric oxide has been shown to play an important role in the regulation of normal cardiovascular physiology. Following S-nitrosoglutathione treatment, we identified 951 unique SNO proteins, many of which contained multiple SNO sites. These proteins show the potential for SNO. This study provides novel information regarding the constitutive SNO proteome of the myocardium, as well as potential myocardial SNO sites, and yields additional information on the SNO sites for many key proteins involved in myocardial contraction, metabolism, and cellular signaling.

Role of nitric oxide in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) occurs upon restoration of hepatic blood flow after a period of ischemia. Decreased endogenous nitric oxide (NO) production resulting in capillary luminal narrowing is central in the pathogenesis of IRI. Exogenous NO has emerged as a potential therapy for IRI based on its role in decreasing oxidative stress, cytokine release, leukocyte endothelial-adhesion and hepatic apoptosis. This review will highlight the influence of endogenous NO on hepatic IRI, role of inhaled NO in ameliorating IRI, modes of delivery, donor drugs and potential side effects of exogenous NO.

Protein tyrosine nitration in cellular signal transduction pathways

How specificity and reversibility in tyrosine nitration are defined biologically in cellular systems is poorly understood. As more investigations identify proteins involved in cell regulatory pathways in which only a small fraction of that protein pool is modified by nitration to affect cell function, the mechanisms of biological specificity and reversal should come into focus. In this review experimental evidence has been summarized to suggest that tyrosine nitration is a highly selective modification and under certain physiological conditions fulfills the criteria of a physiologically relevant signal. It can be specific, reversible, occurs on a physiological time scale, and, depending on a target, can result in either activation or inhibition.

Suppression by Ghrelin of Porphyromonas gingivalis-Induced Constitutive Nitric Oxide Synthase S-Nitrosylation and Apoptosis in Salivary Gland Acinar Cells

Oral mucosal inflammatory responses to periodontopathic bacterium, P. gingivalis, and its key virulence factor, LPS, are characterized by a massive rise in epithelial cell apoptosis and the disturbances in NO signaling pathways. Here, we report that the LPS-induced enhancement in rat sublingual salivary gland acinar cell apoptosis and NO generation was associated with the suppression in constitutive nitric oxide synthase (cNOS) activity and a marked increase in the activity of inducible nitric oxide synthase (iNOS). We demonstrate that the detrimental effect of the LPS on cNOS was manifested by the enzyme protein S-nitrosylation, that was susceptible to inhibition by iNOS inhibitor, 1400 W. Further, we show that a peptide hormone, ghrelin, countered the LPS-induced changes in apoptosis and cNOS activity. This effect of ghrelin was reflected in the decrease in cNOS S-nitrosylation and the increase in phosphorylation. Our findings imply that P. gingivalis-induced disturbances in the acinar cell NO signaling pathways result from upregulation in iNOS-derived NO that causes cNOS S-nitrosylation that interferes with its activation through phosphorylation. We also show that ghrelin protection against P. gingivalis-induced disturbances involves cNOS activation associated with a decrease in its S-nitrosylation and the increase in phosphorylation.

Gene expression, metabolic regulation and stress tolerance during diapause

Diapause entails molecular, physiological and morphological remodeling of living animals, culminating in a dormant state characterized by enhanced stress tolerance. Molecular mechanisms driving diapause resemble those responsible for biochemical processes in proliferating cells and include transcriptional, post-transcriptional and post-translational processes. The results are directed gene expression, differential mRNA and protein accumulation and protein modifications, including those that occur in response to changes in cellular redox potential. Biochemical pathways switch, metabolic products change and energy production is adjusted. Changes to biosynthetic activities result for example in the synthesis of molecular chaperones, late embryogenesis abundant (LEA) proteins and protective coverings, all contributing to stress tolerance. The purpose of this review is to consider regulatory and mechanistic strategies that are potentially key to metabolic control and stress tolerance during diapause, while remembering that organisms undergoing diapause are as diverse as the processes itself. Some of the parameters described have well-established roles in diapause, whereas the evidence for others is cursory.

Ghrelin protection against lipopolysaccharide-induced gastric mucosal cell apoptosis involves constitutive nitric oxide synthase-mediated caspase-3 S-nitrosylation

Ghrelin, a peptide hormone produced mainly in the stomach, has emerged as an important modulator of the inflammatory responses that are of significance to the maintenance of gastric mucosal integrity. Here, we report on the role of ghrelin in controlling the apoptotic processes induced in gastric mucosal cells by H. pylori lipopolysaccharide (LPS). The countering effect of ghrelin on the LPS-induced mucosal cell apoptosis was associated with the increase in constitutive nitric oxide synthase (cNOS) activity, and the reduction in caspase-3 and inducible nitric oxide synthase (NOS-2). The loss in countering effect of ghrelin on the LPS-induced changes in apoptosis and caspase-3 activity was attained with Src kinase inhibitor, PP2, as well as Akt inhibitor, SH-5, and cNOS inhibitor, L-NAME. Moreover, the effect of ghrelin on the LPS-induced changes in cNOS activity was reflected in the increased cNOS phosphorylation that was sensitive to SH-5. Furthermore, the ghrelin-induced up-regulation in cNOS activity was associated with the increase in caspase-3 S-nitrosylation that was susceptible to the blockage by L-NAME. Therefore, ghrelin protection of gastric mucosal cells against H. pylori LPS-induced apoptosis involves Src/Akt-mediated up-regulation in cNOS activation that leads to the apoptotic signal inhibition through the NO-induced caspase-3 S-nitrosylation.

S-nitrosylation in cardiovascular signaling

Well over 2 decades have passed since the endothelium-derived relaxation factor was reported to be the gaseous molecule nitric oxide (NO). Although soluble guanylyl cyclase (which generates cyclic guanosine monophosphate, cGMP) was the first identified receptor for NO, it has become increasingly clear that NO exerts a ubiquitous influence in a cGMP-independent manner. In particular, many, if not most, effects of NO are mediated by S-nitrosylation, the covalent modification of a protein cysteine thiol by an NO group to generate an S-nitrosothiol (SNO). Moreover, within the current framework of NO biology, endothelium-derived relaxation factor activity (ie, G protein-coupled receptor-mediated, or shear-induced endothelium-derived NO bioactivity) is understood to involve a central role for SNOs, acting both as second messengers and signal effectors. Furthermore, essential roles for S-nitrosylation have been implicated in virtually all major functions of NO in the cardiovascular system. Here, we review the basic biochemistry of S-nitrosylation (and denitrosylation), discuss the role of S-nitrosylation in the vascular and cardiac functions of NO, and identify current and potential clinical applications.

Constitutive nitric oxide synthase-mediated caspase-3 S-nitrosylation in ghrelin protection against Porphyromonas gingivalis-induced salivary gland acinar cell apoptosis

Recent advances in identifying the salivary constituents capable of influencing the oral mucosal inflammatory responses have brought to focus the importance of a peptide hormone, ghrelin. Here, we report on the involvement of ghrelin in controlling the apoptotic processes induced in sublingual salivary gland acinar cells by the lipopolysaccharide (LPS) of a periodontopathic bacterium, Porphyromonas gingivalis. We show that the countering effect of ghrelin on the LPS-induced acinar cell apoptosis was associated with the increase in constitutive nitric oxide synthase (cNOS) activity, and the reduction in caspase-3 and inducible nitric oxide synthase (iNOS). The loss in countering effect of ghrelin on the LPS-induced changes in apoptosis and caspase-3 activity was attained with Src kinase inhibitor, PP2, as well as Akt inhibitor, SH-5, and cNOS inhibitor, L-NAME, but not the iNOS inhibitor, 1400W. The effect of ghrelin on the LPS-induced changes in cNOS activity, moreover, was reflected in the increased cNOS phosphorylation that was sensitive to PP2 as well as SH-5. Furthermore, the ghrelin-induced up-regulation in cNOS activity was associated with the increase in caspase-3 S-nitrosylation that was susceptible to the blockage by SH-5 and L-NAME. The findings point to the involvement of ghrelin in Src/Akt kinase-mediated cNOS activation and the apoptogenic signal inhibition through the NO-induced caspase-3 S-nitrosylation.

Nitric oxide inhibits highly selective sodium channels and the Na+/K+-ATPase in H441 cells

Nitric oxide (NO) is an important regulator of Na(+) reabsorption by pulmonary epithelial cells and therefore of alveolar fluid clearance. The mechanisms by which NO affects epithelial ion transport are poorly understood and vary from model to model. In this study, the effects of NO on sodium reabsorption by H441 cell monolayers were studied in an Ussing chamber. Two NO donors, (Z)-1-[N-(3-aminopropyl)-N-(n-propyl)amino]diazen-1-ium-1,2-diolate and diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate, rapidly, reversibly, and dose-dependently reduced amiloride-sensitive, short-circuit currents across H441 cell monolayers. This effect was neutralized by the NO scavenger hemoglobin and was not observed with inactive NO donors. The effects of NO were not blocked by 8-bromoguanosine-3',5'-cyclic monophosphate or by soluble guanylate cyclase inhibitors (methylene blue and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) and were therefore independent of soluble guanylate cyclase signaling. NO targeted apical, highly selective, amiloride-sensitive Na(+) channels in basolaterally permeabilized H441 cell monolayers. NO had no effect on the activity of the human epithelial sodium channel heterologously expressed in Xenopus oocytes. NO decreased Na(+)/K(+)-ATPase activity in apically permeabilized H441 cell monolayers. The inhibition of Na(+)/K(+)-ATPase activity by NO was reversed by mercury and was mimicked by N-ethylmaleimide, which are agents that reverse and mimic, respectively, the reaction of NO with thiol groups. Consistent with these data, S-NO groups were detected on the Na(+)/K(+)-ATPase α subunit in response to NO-donor application, using a biotin-switch approach coupled to a Western blot. These data demonstrate that, in the H441 cell model, NO impairs Na(+) reabsorption by interfering with the activity of highly selective Na(+) channels and the Na(+)/K(+)-ATPase.

Protein S-nitrosylation and cardioprotection

Nitric oxide (NO) plays an important role in the regulation of cardiovascular function. In addition to the classic NO activation of the cGMP-dependent pathway, NO can also regulate cell function through protein S-nitrosylation, a redox dependent, thiol-based, reversible posttranslational protein modification that involves attachment of an NO moiety to a nucleophilic protein sulfhydryl group. There are emerging data suggesting that S-nitrosylation of proteins plays an important role in cardioprotection. Protein S-nitrosylation not only leads to changes in protein structure and function but also prevents these thiol(s) from further irreversible oxidative/nitrosative modification. A better understanding of the mechanism regulating protein S-nitrosylation and its role in cardioprotection will provide us new therapeutic opportunities and targets for interventions in cardiovascular diseases.

Cardioselective nitric oxide synthase 3 gene transfer protects against myocardial reperfusion injury

Nitric oxide modulates the severity of myocardial ischemia-reperfusion (I/R) injury. We investigated whether cardioselective nitric oxide synthase 3 (NOS3) gene transfer could confer myocardial protection against I/R injury in pigs and examined potential molecular mechanisms. I/R injury was induced by balloon occlusion of the left anterior descending artery for 45 min followed by 4 or 72 h reperfusion. Hemodynamic and pathological changes were measured in pigs in the absence (n = 11) or presence of prior intracoronary retroinfusion of human NOS3 (AdNOS3, 5 x 10(10) PFU, n = 13) or control vector (AdRR5, 5 x 10(10) PFU, n = 11). Retrograde NOS3 gene transfer selectively increased NOS3 expression and NO bioavailability in the area at risk (AAR) without changing endogenous NOS isoform expression. At 4 h R, LV systolic (dP/dt(max)) and diastolic (dP/dt(min)) function was better preserved in AdNOS3- than in AdRR5-injected pigs (2,539 +/- 165 vs. 1,829 +/- 156 mmHg/s, and -2,781 +/- 340 vs. -2,062 +/- 292 mmHg/s, respectively, P < 0.05 for both). Myocardial infarct size (% AAR) was significantly smaller in AdNOS3 than in control and AdRR5 and associated with a significantly greater reduction in cardiac myeloperoxidase activity, a marker of neutrophil infiltration. The latter effects were sustained at 72 h R in a subset of pigs (n = 7). In the AAR, intercellular endothelial adhesion molecule-1 expression and cardiomyocyte apoptosis were significantly lower in AdNOS3. In conclusion, single myocardial NOS3 retroinfusion attenuates I/R injury, and causes a sustained reduction in myocardial infarct size and inflammatory cell infiltration. Gene-based strategies to increase NO bioavailability may have therapeutic potential in myocardial I/R.

Myeloperoxidase serves as a redox switch that regulates apoptosis in epithelial ovarian cancer

OBJECTIVES

Resistance to apoptosis is a key feature of cancer cells and is believed to be regulated by nitrosonium ion (NO(+))-induced S-nitrosylation of key enzymes. Nitric oxide (NO), produced by inducible nitric oxide synthase (iNOS), is utilized by MPO to generated NO(+). We sought to investigate the expression of myeloperoxidase (MPO) and iNOS in epithelial ovarian cancer (EOC) and determine their effect on S-nitrosylation of caspase-3 and its activity as well as apoptosis.

METHODS

MPO and iNOS expression were determined using immunofluorescence in SKOV-3 and MDAH-2774 and EOC tissue sections. S-nitrosylation of caspase-3 and its activity, levels of MPO and iNOS, as well as apoptosis, were evaluated in the EOC cells before and after silencing MPO or iNOS genes with specific siRNA probes utilizing real-time RT-PCR, ELISA, and TUNEL assays.

RESULTS

MPO and iNOS are expressed in EOC cell lines and in over 60% of invasive EOC cases with no expression in normal ovarian epithelium. Indeed, silencing of MPO or iNOS gene expression resulted in decreased S-nitrosylation of caspase-3, increased caspase-3 activity, and increased apoptosis but with a more significant effect when silencing MPO.

CONCLUSION

MPO and iNOS are colocalized to the same cells in EOC but not in the normal ovarian epithelium. Silencing of either MPO or iNOS significantly induced apoptosis, highlighting their role as a redox switch that regulates apoptosis in EOC. Understanding the mechanisms by which MPO functions as a redox switch in regulating apoptosis in EOC may lead to future diagnostic tools and therapeutic interventions.

Unraveling the S-nitrosoproteome: tools and strategies

One of the major tasks to be accomplished in the postgenomic era is the characterization of PTMs in proteins. The S-nitrosation of protein thiols is a redox-based PTM that modulating enzymatic activity, subcellular localization, complex formation, and degradation of proteins, largely contributes to the complexity of cellular proteomes. Although the detection of S-nitrosated proteins is problematical due to the lability of S-nitrosothiols, with the improvement of molecular tools an increasing range of proteins has been shown to undergo S-nitrosation. We here review recent proteomic approaches for the systematic assessment of potential targets for protein S-nitrosation. The development of new analytical methods and strategies over the past several years now allows us to investigate the nitrosoproteome on a global scale.

S-nitrosylation of caspase-3 is the mechanism by which adhesion fibroblasts manifest lower apoptosis

We have previously found that adhesion fibroblasts exhibit lower apoptosis and higher protein nitration as compared with normal peritoneal fibroblasts. In this study, we sought to determine whether the decreased apoptosis observed in adhesion fibroblasts is caused by lower caspase-3 activity due to an increase in caspase-3 S-nitrosylation. For this study, we have utilized primary cultures of fibroblasts obtained from normal peritoneum and adhesion tissues of the same patient(s). Cells were treated with increasing concentrations of peroxynitrite and cell lysates were immunoprecipitated with anti-caspase-3 polyclonal antibody. The biotinylated proteins were detected using a nitrosylation detection kit. Caspase-3 activity and apoptosis were measured by colorimetric and TUNEL assays, respectively. Our results showed that caspase-3 S-nitrosylation is significantly higher in adhesion fibroblasts as compared with normal peritoneal fibroblasts. This increase in S-nitrosylation resulted in a 30% decrease in caspase-3 activity in adhesion fibroblasts. Peroxynitrite treatment resulted in a dose response increase in caspase-3 S-nitrosylation, leading to a decrease in caspase-3 activity and apoptosis in normal peritoneal fibroblasts. We conclude that S-nitrosylation of caspase-3 is the reason for its decreased activity and subsequent decrease in apoptosis of adhesion fibroblasts. The mechanism by which caspase-3 S-nitrosylation occurs is not fully understood. However, the role of hypoxia in the formation of peroxynitrite via superoxide production may suggest a possible mechanism.

S-nitrosation of proteins duringd-galactosamine-induced cell death in human hepatocytes

Nitric oxide (NO) participates in the cell death induced by d-Galactosamine (d-GalN) in hepatocytes, and NO-derived reactive oxygen intermediates are critical contributors to protein modification and hepatocellular injury. It is anticipated that S-nitrosation of proteins will participate in the mechanisms leading to cell death in d-GalN-treated human hepatocytes. In the present study, d-GalN-induced cell death was related to augmented levels of NO production and S-nitrosothiol (SNO) content. The biotin switch assay confirmed that d-GalN increased the levels of S-nitrosated proteins in human hepatocytes. S-nitrosocysteine (CSNO) enhanced protein S-nitrosation and altered cell death parameters that were related to S-nitrosation of the executioner caspase-3. Fifteen S-nitrosated proteins participating in metabolism, antioxidative defense and cellular homeostasis were identified in human hepatocytes treated with CSNO. Among them, seven were also identified in d-GalN-treated hepatocytes. The results here reported underline the importance of the alteration of SNO homeostasis during d-GalN-induced cell death in human hepatocytes.

NT-polyplex: a new tool for therapeutic gene delivery to neuroblastoma tumors

Neurotensin (NT)-polyplex is a nonviral system for the targeted gene delivery to cells that express and internalize the high-affinity NT receptor (NTSR1). In hemiparkinsonian rats, we previously demonstrated the morphological and functional recovery from dopaminergic neurodegeneration using the NT-polyplex as a vehicle to transfect a neurotrophic gene. The main objective of this work was to demonstrate the feasibility of NT-polyplex to transfect reporter or therapeutic genes into neuroblastoma tumors through the blood stream or by intratumoral injection. N1E-115 cells known to express NTSR1 were allografted into athymic mice to generate the neuroblastoma tumor model. Both routes of administration allowed the NT-polyplex to reach and transfect tumoral cells. A low transgene expression was also detected in intestinal tract cells only after the injection into the blood stream. The transfection of the thymidine kinase (HSVTK) suicide gene followed by ganciclovir (GCV) treatment decreased the size and weight of neuroblastoma tumors by 30-50% and increased apoptosis compared to controls. This study shows the potential of the NT-polyplex as specific gene-transfer system for NTSR1 cancer cells.

Nebivolol reduces experimentally induced warm renal ischemia reperfusion injury in rats

Ischemia/reperfusion injury, which is commonly seen in the field of renal surgery or transplantation, is a major cause of acute renal failure. The objective of the present study was to examine the role of nebivolol in modulating peroxynitrite species-induced inflammation and apoptosis after renal warm ischemia/reperfusion injury in rats. The present study was designed to investigate the effects of nebivolol on the renal warm ischemia/reperfusion injury in rats treated with the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester. After right nephrectomy, nebivolol was administered for 15 days. On the 16(th) day, ischemia was induced in contra lateral kidney for 45 min, followed by reperfusion for 24 hr. Renal function, inflammation, and apoptosis were estimated at the end of 24 hr reperfusion. Nebivolol improved the renal dysfunction and reduced inflammation and apoptosis after renal ischemia/reperfusion injury. In conclusion, nebivolol shows potent anti-apoptotic and anti-inflammatory properties due to its NO-releasing property. These findings may have major implications in the treatment of human ischemic acute renal failure.

Cardiomyocyte death in doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is one of the most widely used and successful antitumor drugs, but its cumulative and dose-dependent cardiac toxicity has been a major concern of oncologists in cancer therapeutic practice for decades. With the increasing population of cancer survivors, there is a growing need to develop preventive strategies and effective therapies against DOX-induced cardiotoxicity, in particular late-onset cardiomyopathy. Although intensive investigations on DOX-induced cardiotoxicity have continued for decades, the underlying mechanisms responsible for DOX-induced cardiotoxicity have not been completely elucidated. A rapidly expanding body of evidence supports the notion that cardiomyocyte death by apoptosis and necrosis is a primary mechanism of DOX-induced cardiomyopathy and that other types of cell death, such as autophagy and senescence/aging, may participate in this process. This review focuses on the current understanding of the molecular mechanisms underlying DOX-induced cardiomyocyte death, including the major primary mechanism of excess production of reactive oxygen species (ROS) and other recently discovered ROS-independent mechanisms. The different sensitivities to DOX-induced cell death signals between adult and young cardiomyocytes will also be discussed.

Toll-like receptor signaling: a critical modulator of cell survival and ischemic injury in the heart

Toll-like receptors (TLRs) represent the first line of host defense against microbial infection and play a pivotal role in both innate and adaptive immunity. TLRs recognize invading pathogens through molecular pattern recognition, transduce signals via distinct intracellular pathways involving a unique set of adaptor proteins and kinases, and ultimately lead to the activation of transcription factors and inflammatory responses. Among 10 TLRs identified in humans, at least two exist in the heart, i.e., TLR2 and TLR4. In addition to the critical role of these in mediating cardiac dysfunction in septic conditions, emerging evidence suggests that the TLRs can also recognize endogenous ligands and may play an important role in modulating cardiomyocyte survival and in ischemic myocardial injury. In animal models of ischemia-reperfusion injury or in hypoxic cardiomyocytes in vitro, the administration of a sublethal dose of lipopolysaccharide, which signals through TLR4, reduces subsequent myocardial infarction, improves cardiac functions, and attenuates cardiomyocyte apoptosis. By contrast, a systemic deficiency of TLR2, TLR4, or myeloid differentiation primary-response gene 88, an adaptor critical for all TLR signaling, except TLR3, leads to an attenuated myocardial inflammation, a smaller infarction size, a better preserved ventricular function, and a reduced ventricular remodeling after ischemic injury. These loss-of-function studies suggest that both TLRs contribute to myocardial inflammation and ischemic injury in the heart although the exact contribution of cardiac (vs. circulatory cell) TLRs remains to be defined. These recent studies demonstrate an emerging role for TLRs as a critical modulator in both cell survival and tissue injury in the heart.

Effects of rosiglitazone (a peroxysome proliferator-activated receptor gamma agonist) on the blood pressure and aortic structure in metabolically programmed (perinatal low protein) rats

This study investigated the effects of rosiglitazone on nutritionally programmed chronic disease, with a focus on blood pressure (BP) and aortic wall structural remodeling. Wistar pregnant rats were fed one of two diets: a normal protein diet (19% protein; NP rats) or low-protein diet (5% protein; LP rats). Male offspring at 3 months of age were randomly divided into four groups: NP offspring treated with rosiglitazone (NPR); untreated NP offspring (NP); LP offspring treated with rosiglitazone (LPR); untreated LP offspring (LP). Rosiglitazone was administered at a dose of 5 mg/kg/d until 6 months of age. BP was elevated in LP offspring. Rosiglitazone reduced BP beginning in the first week of treatment in the LPR offspring. The insulin sensitivity was increased in LP offspring, and was not altered by rosiglitazone. LP offspring exhibited a 40% reduction in the amount of elastic fibers in the aorta wall compared with NP offspring (p < 0.01), and the quantity of elastic fibers was not altered by rosiglitazone. The smooth muscle cells, elastic lamellae, circumferential wall tension (CWT) and tensile stress (TS) were increased in LP offspring, indicating increased blood flow in the aorta. Rosiglitazone reduced both CWT and TS by 30% compared to the levels in untreated LP offspring (p < 0.01 for both). Rosiglitazone restored the expressions of angiotensin II type 1 receptor and endothelial nitric oxide synthase nearly to the levels in the NP offspring. ANOVA disclosed a significant two-factor interaction between protein content in the diet and rosiglitazone treatment (p < 0.001 for CWT and p < 0.00001 for TS, two-way ANOVA). We conclude that rosiglitazone has beneficial effects in reducing the BP and the aortic tunica media hypertrophy with consequent balance of the wall stress in metabolically programmed offspring.

Role of myofibroblasts in innate chemoresistance of pancreatic carcinoma--epigenetic downregulation of caspases

We recently reported on continuous tumor-stroma interactions essentially contributing to chemoresistance of pancreatic ductal adenocarcinoma (PDAC) cells. As demonstrated here, long-term coculture with pancreatic myofibroblasts representing the main stromal compartment of PDAC resulted in a chemoresistant phenotype in the pancreatic ductal epithelial cell line H6c7 as well as in the chemosensitive PDAC cell line T3M4. This involved a reduced expression of caspases and the caspase inducing transcription factor STAT1, both caused by diminished gene transcription. The DNA-methylation inhibitor 5-azadeoxycytidine enhanced caspase and STAT1 expression in cocultured H6c7 and T3M4 cells along with an increased chemosensitivity, indicating a role for CpG DNA-hypermethylation in the downregulation of these crucial apoptosis mediators. Cocultured H6c7 and T3M4 cells exhibited elevated nuclear levels of DNA-methyltransferase-1 (DNMT1). Silencing of DNMT1 expression by siRNA increased expression of caspases and STAT1 and restored chemosensitivity. In SCID mice, tumors arising from coinoculated T3M4 cells and myofibroblasts (co-tumors) responded less towards chemotherapy than mono-tumors, exhibiting decreased apoptosis, no remission and reduced expression of caspases and STAT1. These data underscore the role of myofibroblasts in chemoresistance of PDAC and point to the importance of caspases as central target structures of epigenetic regulation in this scenario. Furthermore, an activated microenvironment might apparently promote the manifestation of chemoresistance already in premalignant precursor cells at early stages of PDAC tumorigenesis.

Prolonged exposures of cerebellar granule neurons to S-nitroso-N-acetylpenicillamine (SNAP) induce neuronal damage independently of peroxynitrite

Nitric oxide (NO) induces cell proliferation or cell death, depending on the cell type involved, the isoform of nitric oxide synthase activated, and its cellular localisation. In neurons, the damaging effect of NO is usually attributed to the highly toxic peroxynitrite, formed by its reaction with superoxide. Peroxynitrite induces DNA damage and consequently the activation of poly (ADP-ribose) polymerase (PARP). This study set out to examine the contribution of peroxynitrite to the damage induced in cerebellar granule neurons (CGNs) by treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), for short (6 h) or prolonged (24 h) exposures. The Alamar blue assay was used to quantify CGN viability, which was also assessed by morphological examination. SNAP (10 microM-1 mM) induced a concentration- and time-dependent reduction of CGN viability, with associated damage to cell bodies and neurite processes evident following 100 microM SNAP treatments. Damage from 6 h exposures was prevented by the presence of haemoglobin (a NO scavenger), uric acid (a peroxynitrite scavenger), melatonin (a non-specific antioxidant), and by cyclosporin A (a permeability transition pore blocker). It was reduced by the PARP-1 inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinolinone (DPQ), whilst superoxide dismutase (SOD) potentiated the effects. Following 24 h exposure to SNAP, damage was only partially blocked by haemoglobin, melatonin, cyclosporin A and DPQ, but was not affected by uric acid or SOD. The data suggest that short exposure to NO induces neuronal damage through peroxynitrite produced by its interaction with superoxide, whereas a longer exposure to NO can induce damage partly by a mechanism which is independent of peroxynitrite formation.

Post-translational modifications induced by nitric oxide (NO): implication in cancer cells apoptosis

Post-translational modifications of proteins can regulate the balance between survival and cell death signals. It is increasingly recognized that nitric oxide (NO) and reactive oxygen species (ROS)-induced post-translational modifications could play a role in cell death. This review provides an introduction of current knowledge of NO proteins modifications promoting or inhibiting cell death with special attention in cancer cells.

Palmitate-induced NO production has a dual action to reduce cell death through NO and accentuate cell death through peroxynitrite formation

The objective of this study was to determine the role of palmitate-induced stimulation of nitric oxide synthase (NOS) on palmitate-induced cell death, specifically distinguishing the effects of the subtype NOS2 from NOS3, defining the effect of NO on mitochondria death pathways, and determining whether palmitate induces peroxynitrite formation which may impact cardiomyocyte cell survival. Cardiomyocytes from embryonic chick hearts were treated with palmitate 300-500 microM. Cell death was assessed by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. The ability of palmitate to induce NO production and its consequences were tested by using the NOS inhibitor 7-nitroindazole (7-N) and the peroxynitrite scavenger (5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) chloride) (FeTPPS). The effect of palmitate on the mitochondria was assessed by Western blotting for cytochrome c release into the cytosol, and assessment of mitochondrial transmembrane potential (DeltaPsi(m)) by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolyl-carbocyanine iodide staining and immunocytochemistry. The NOS inhibitor 7-N, which is selective for NOS2 and not for NOS3, significantly (p<0.05) increased palmitate-induced cell death. In contrast, 7-N did not alter cell death produced by the combination of potassium cyanide and deoxyglucose, which, respectively, inhibit glycolysis and oxidative phosphorylation. The mitochondrial actions of palmitate, specifically palmitate-induced translocation of mitochondrial cytochrome c to cytosol and loss of mitochondrial transmembrane potential, were not altered by pretreatment with 7-N. FeTPPS, which isomerizes peroxynitrite to nitrate and thereby reduces the toxic effects of peroxynitrite, produced a significant reduction in palmitate-induced cell death. In summary, these data suggest that palmitate stimulates NO production, which has a dual action to protect against cell death or to induce cell death. Palmitate-induced cell death is mediated, in part, through NO generation, which leads to peroxynitrite formation. The protective effect of NO is operative through stimulation of NOS2 but not NOS3. The actions of NO on palmitate-induced cell death are independent of mitochondrial cell death pathways.

Pathophysiology and diagnosis of cancer drug induced cardiomyopathy

The clinical manifestations of anti-cancer drug associated cardiac side effects are diverse and can range from acutely induced cardiac arrhythmias to Q-T interval prolongation, changes in coronary vasomotion with consecutive myocardial ischemia, myocarditis, pericarditis, severe contractile dysfunction, and potentially fatal heart failure. The pathophysiology of these adverse effects is similarly heterogeneous and the identification of potential mechanisms is frequently difficult since the majority of cancer patients is not only treated with a multitude of cancer drugs but might also be exposed to potentially cardiotoxic radiation therapy. Some of the targets inhibited by new anti-cancer drugs also appear to be important for the maintenance of cellular homeostasis of normal tissue, in particular during exposure to cytotoxic chemotherapy. If acute chemotherapy-induced myocardial damage is only moderate, the process of myocardial remodeling can lead to progressive myocardial dysfunction over years and eventually induce myocardial dysfunction and heart failure. The tools for diagnosing anti-cancer drug associated cardiotoxicity and monitoring patients during chemotherapy include invasive and noninvasive techniques as well as laboratory investigations and are mostly only validated for anthracycline-induced cardiotoxicity and more recently for trastuzumab-associated cardiac dysfunction.

Cardiac safety and antitumoral activity of a new nitric oxide derivative of pegylated epirubicin in mice

The use of epirubicin is limited by the risk of a dilatory congestive heart failure that develops as a consequence of induction of a mitochondrial-dependent cardiomyocyte apoptosis. In a previous in-vitro study, we have provided evidence that a new formulation of pegylated epirubicin- bearing moieties that release nitric oxide, named BP-747, exerted a potent antitumoral activity against a colon cancer cell line, which was completely devoid of cytotoxic activity against cardiomyocytes. The aim of this study was to investigate the antitumoral and cardiotoxic profile of BP-747 in Caco-2 and SKOV-2 tumor-bearing mice. Epirubicin-induced cardiomyopathy was detected by clinical (survival, weight loss), anatomical (heart weight loss) and biochemical evaluations (measurement of serum troponin and creatine phosphokinase levels). The antitumoral activity was investigated by the measurement of tumor diameters and weight. In comparison with free epirubicin and pegylated epirubicin, BP-747 showed more potent antineoplastic effects, as demonstrated by the 95% reduction of tumor volume. Moreover, while administration of epirubicin and pegylated epirubicin resulted in the development of a severe anthracycline cardiomyopathy, BP-747-treated mice were virtually devoid of clinical and biochemical signs of cardiotoxicity. The present data provide evidence that addition of a nitric oxide-releasing moiety to pegylated epirubicin confers a new and unique cytotoxic profile to the drug.

Atrial Glutathione Content, Calcium Current, and Contractility

Atrial fibrillation (AF) is characterized by decreased L-type calcium current (I(Ca,L)) in atrial myocytes and decreased atrial contractility. Oxidant stress and redox modulation of calcium channels are implicated in these pathologic changes. We evaluated the relationship between glutathione content (the primary cellular reducing moiety) and I(Ca,L) in atrial specimens from AF patients undergoing cardiac surgery. Left atrial glutathione content was significantly lower in patients with either paroxysmal or persistent AF relative to control patients with no history of AF. Incubation of atrial myocytes from AF patients (but not controls) with the glutathione precursor N-acetylcysteine caused a marked increase in I(Ca,L). To test the hypothesis that glutathione levels were mechanistically linked with the reduction in I(Ca,L), dogs were treated for 48 h with buthionine sulfoximine, an inhibitor of glutathione synthesis. Buthionine sulfoximine treatment resulted in a 24% reduction in canine atrial glutathione content, a reduction in atrial contractility, and an attenuation of I(Ca,L) in the canine atrial myocytes. Incubation of these myocytes with exogenous glutathione also restored I(Ca,L) to normal or greater than normal levels. To probe the mechanism linking decreased glutathione levels to down-regulation of I(Ca), the biotin switch technique was used to evaluate S-nitrosylation of calcium channels. S-Nitrosylation was apparent in left atrial tissues from AF patients; the extent of S-nitrosylation was inversely related to tissue glutathione content. S-Nitrosylation was also detectable in HEK cells expressing recombinant human cardiac calcium channel subunits following exposure to nitrosoglutathione. S-Nitrosylation may contribute to the glutathione-sensitive attenuation of I(Ca,L) observed in AF.

Cyclic GMP and protein kinase-G in myocardial ischaemia-reperfusion: opportunities and obstacles for survival signaling

It is clear that multiple signalling pathways regulate the critical balance between cell death and survival in myocardial ischaemia-reperfusion. Recent attention has focused on the activation of survival or salvage kinases, particularly during reperfusion, as a common mechanism of many cardioprotective interventions. The phosphatidyl inositol 3'-hydroxy kinase/Akt complex (PI3K/Akt) and p42/p44 mitogen-activated protein kinase cascades have been widely promoted in this respect but the cyclic guanosine 3',5'-monophosphate/cGMP-dependent protein kinase (cGMP/PKG) signal transduction cassette has been less systematically investigated as a survival cascade. We propose that activation of the cGMP/PKG signalling pathway, following activation of soluble or particulate guanylate cyclases, may play a pivotal role in survival signalling in ischaemia-reperfusion, especially in the classical preconditioning, delayed preconditioning and postconditioning paradigms. The resurgence of interest in reperfusion injury, largely as a result of postconditioning-related research, has confirmed that the cGMP/PKG pathway is a pivotal salvage mechanism in reperfusion. Numerous studies suggest that the infarct-limiting effects of preconditioning and postconditioning, exogenously donated nitric oxide (NO), natriuretic peptides, phosphodiesterase inhibitors, and other diverse drugs and mediators such as HMG co-A reductase inhibitors (statins), Rho-kinase inhibitors and adrenomedullin, whether given before and during ischaemia, or specifically at the onset of reperfusion, may be mediated by activation or enhancement of the cGMP pathway, either directly or indirectly via endogenous NO generation downstream of PI3K/Akt. Putative mechanisms of protection include PKG regulation of Ca(2+) homeostasis through the modification of sarcoplasmic reticulum Ca(2+) uptake mechanisms, and PKG-induced opening of ATP-sensitive K(+) channels during ischaemia and/or reperfusion. At present, significant technical obstacles in defining the precise roles played by cGMP/PKG signalling include the heavy reliance on pharmacological PKG inhibitors of uncertain selectivity, difficulties in determining PKG activity in intact tissue, and the growing recognition that intracellular compartmentalisation of the cGMP pool may contribute markedly to the nucleotide's biological actions and biochemical determination. Overall, the body of experimental evidence suggests that cGMP/PKG survival signalling ameliorates irreversible injury associated with ischaemia-reperfusion and may be a tractable therapeutic target.