Cytokine-mediated apoptosis in cardiac myocytes: the role of inducible nitric oxide synthase induction and peroxynitrite generation

Dysfunctional and Dysregulated Nitric Oxide Synthases in Cardiovascular Disease: Mechanisms and Therapeutic Potential

Nitric oxide (NO) plays an important and diverse signalling role in the cardiovascular system, contributing to the regulation of vascular tone, endothelial function, myocardial function, haemostasis, and thrombosis, amongst many other roles. NO is synthesised through the nitric oxide synthase (NOS)-dependent L-arginine-NO pathway, as well as the nitrate-nitrite-NO pathway. The three isoforms of NOS, namely neuronal (NOS1), inducible (NOS2), and endothelial (NOS3), have different localisation and functions in the human body, and are consequently thought to have differing pathophysiological roles. Furthermore, as we continue to develop a deepened understanding of the different roles of NOS isoforms in disease, the possibility of therapeutically modulating NOS activity has emerged. Indeed, impaired (or dysfunctional), as well as overactive (or dysregulated) NOS activity are attractive therapeutic targets in cardiovascular disease. This review aims to describe recent advances in elucidating the physiological role of NOS isoforms within the cardiovascular system, as well as mechanisms of dysfunctional and dysregulated NOS in cardiovascular disease. We then discuss the modulation of NO and NOS activity as a target in the development of novel cardiovascular therapeutics.

PDE10A Inactivation Prevents Doxorubicin-Induced Cardiotoxicity and Tumor Growth

BACKGROUND

Cyclic nucleotides play critical roles in cardiovascular biology and disease. PDE10A (phosphodiesterase 10A) is able to hydrolyze both cAMP and cGMP. PDE10A expression is induced in various human tumor cell lines, and PDE10A inhibition suppresses tumor cell growth. Chemotherapy drug such as doxorubicin (DOX) is widely used in chemotherapy. However, cardiotoxicity of DOX remains to be a serious clinical complication. In the current study, we aim to determine the role of PDE10A and the effect of PDE10A inhibition on cancer growth and cardiotoxicity induced by DOX.

METHODS

We used global PDE10A knockout (KO) mice and PDE10A inhibitor TP-10 to block PDE10A function. DOX-induced cardiotoxicity was evaluated in C57Bl/6J mice and nude mice with implanted ovarian cancer xenografts. Isolated adult mouse cardiomyocytes and a human ovarian cancer cell line were used for in vitro functional and mechanistic studies.

RESULTS

We found that PDE10A deficiency or inhibition alleviated DOX-induced myocardial atrophy, apoptosis, and dysfunction in C57Bl/6J mice. RNA sequencing study revealed a number of PDE10A-regulated signaling pathways involved in DOX-induced cardiotoxicity. PDE10A inhibition increased the death, decreased the proliferation, and potentiated the effect of DOX on various human cancer cells. Importantly, in nude mice with implanted ovarian cancer xenografts, PDE10A inhibition attenuated tumor growth while protecting DOX-induced cardiotoxicity. In isolated cardiomyocytes, PDE10A contributed to DOX-induced cardiomyocyte death via increasing Top2β (topoisomerase 2β) expression, mitochondrial dysfunction, and DNA damage by antagonizing cGMP/PKG (protein kinase G) signaling. PDE10A contributed to cardiomyocyte atrophy via potentiating FoxO3 (forkhead box O3) signaling via both cAMP/PKA (protein kinase A)- and cGMP/PKG-dependent signaling.

CONCLUSIONS

Taken together, our study elucidates a novel role for PDE10A in cardiotoxicity induced by DOX and cancer growth. Given that PDE10A has been already proven to be a safe drug target, PDE10A inhibition may represent a novel therapeutic strategy in cancer therapy, with effects preventing DOX-induced cardiotoxicity and simultaneously antagonizing cancer growth.

Significance of Inflammation and Apoptosis in Hepatocellular Death in Rat, Co-treated with Arsenic and Fluoride

Health effects elicited by combined environmental exposures to xenobiotics, in many instances, still remain unresolved. One of these examples is the combined toxicity of arsenic and fluoride. The present study was undertaken to delineate the role of inflammation and apoptosis in hepatocellular death caused by co-exposure to arsenic and fluoride in rat. Sodium arsenate (4 mg/kg body weight) and sodium fluoride (4 mg/kg body weight) were administered to female Wistar rats, individually and in combination, for 90 days. Results on tumor necrotic factor-α (TNF-α), interleukin-12 (IL-12), and comet assay showed increased values in comparison to those obtained in arsenic- or fluoride-treated rats. Results on NO, TBARS, and caspase-9 showed higher values than fluoride-treated rats but lower levels than arsenic-treated rats. It is hypothesized that increased generation of nitric oxide induces the release of cytokines that activates caspase-9. Caspase-9 promotes the synthesis of caspase-3 that executes apoptosis. Histopathological observations on apoptotic bodies and Kupffer cells support these observations.

Cardiac mechanisms of the beneficial effects of SGLT2 inhibitors in heart failure: Evidence for potential off-target effects

Sodium glucose cotransporter 2 inhibitors (SGLT2i) constitute a promising drug treatment for heart failure patients with either preserved or reduced ejection fraction. Whereas SGLT2i were originally developed to target SGLT2 in the kidney to facilitate glucosuria in diabetic patients, it is becoming increasingly clear that these drugs also have important effects outside of the kidney. In this review we summarize the literature on cardiac effects of SGLT2i, focussing on pro-inflammatory and oxidative stress processes, ion transport mechanisms controlling sodium and calcium homeostasis and metabolic/mitochondrial pathways. These mechanisms are particularly important as disturbances in these pathways result in endothelial dysfunction, diastolic dysfunction, cardiac stiffness, and cardiac arrhythmias that together contribute to heart failure. We review the findings that support the concept that SGLT2i directly and beneficially interfere with inflammation, oxidative stress, ionic homeostasis, and metabolism within the cardiac cell. However, given the very low levels of SGLT2 in cardiac cells, the evidence suggests that SGLT2-independent effects of this class of drugs likely occurs via off-target effects in the myocardium. Thus, while there is still much to be understood about the various factors which determine how SGLT2i affect cardiac cells, much of the research clearly demonstrates that direct cardiac effects of these SGLT2i exist, albeit mediated via SGLT2-independent pathways, and these pathways may play a role in explaining the beneficial effects of SGLT2 inhibitors in heart failure.

Participation of nitrogen oxide and its metabolites in the genesis of hyperimmune inflammation in COVID-19

Despite the success in the tactics of treating COVID-19, there are many unexplored issues related to the development and progression of the process in the lungs, brain, and other organs, as well as the role of individual elements, in particular, nitric oxide (NO), and in the pathogenesis of organ damage. Based on the analyzed literature data, we considered a possible pathophysiological mechanism of action of NO and its derivatives in COVID-19. It can be noted that hyperimmune systemic inflammation and "cytokine storm" are enhanced by the production of NO, products of its oxidation ("nitrosative stress"). It is noted in the work that as a result of the oxidation of NO, a large amount of the toxic compound peroxynitrite is formed, which is a powerful proinflammatory agent. Its presence significantly damages the endothelium of the vascular walls and also oxidizes lipids, hemoglobin, myoglobin, and cytochrome, binds SH-groups of proteins, and damages DNA in the target cells. This is confirmed by the picture of the vessels of the lungs on computed tomography and the data of biochemical studies. In case of peroxynitrite overproduction, inhibition of the synthesis of NO and its metabolic products seems to be justified. Another aspect considered in this work is the mechanism of damage by the virus to the central and peripheral nervous system, which remains poorly understood but may be important in understanding the consequences, as well as predicting brain functions in persons who have undergone COVID-19. According to the analyzed literature, it can be concluded that brain damage is possible due to the direct effect of the virus on the peripheral nerves and central structures, and indirectly through the effect on the endothelium of cerebral vessels. Disturbances in the central nervous regulation of immune responses may be associated with the insufficient function of the acetylcholine anti-inflammatory system. It is proposed to further study several approaches to influence various links of NO exchange, which are of interest for theoretical and practical medicine.

Serum cytokine levels associated with myocardial injury in systemic lupus erythematosus

OBJECTIVES

To identify cytokines, markers of endothelial activation [soluble vascular cell adhesion molecule-1 (sVCAM-1)] and myocyte strain [soluble ST2 (sST2)] associated with myocardial injury (MInj) in SLE, classified by cardiac magnetic resonance (CMR) criteria.

METHODS

CMR was performed on patients with SLE, identifying stages of MInj (inflammation and necrosis or fibrosis). Data captured included: clinical assessment, laboratory and serological analyses, cytokine (IL-1β, IL-1Ra, IL-2, IL-6, IL-10, IL-17, IL-18, TNF-alpha), sVCAM-1 and sST2 levels. Cytokines were compared with regard to SLE features and evidence of CMR MInj. Predictors of CMR MInj were determined through regression analyses.

RESULTS

Forty-one patients with high disease activity (SLEDAI-2K: 13; IQR: 3-17) were included. SLE features included: LN (n = 12), neurolupus (n = 6) and clinical lupus myocarditis (LM) (n = 6). Nineteen patients had CMR evidence of MInj. Patients with a SLEDAI-2K ≥ 12 had higher sVCAM-1 (P = 0.010) and sST2 (P = 0.032) levels. Neurolupus was associated with higher IL-1Ra (P = 0.038) and LN with lower IL-1Ra (P = 0.025) and sVCAM-1 (P = 0.036) levels. Higher IL-1Ra (P = 0.012), IL-17 (P = 0.045), IL-18 (P = 0.003), and sVCAM-1 (P = 0.062) levels were observed in patients with CMR MInj compared with those without. On multivariable logistic regression, IL-1Ra predicted CMR inflammation and fibrosis/necrosis (P < 0.005) while anti-Ro/SSA [odds ratio (OR): 1.197; P = 0.035] and the SLE damage index (OR: 4.064; P = 0.011) predicted fibrosis/necrosis.

CONCLUSION

This is a novel description of associations between cytokines and SLE MInj. IL-18 and IL-1Ra were significantly higher in patients with MInj. IL-1Ra independently predicted different stages of CMR MInj. Exploration of the role of these cytokines in the pathogenesis of SLE MInj may promote targeted therapies for LM.

Mechanical Regulation of Apoptosis in the Cardiovascular System

Apoptosis is a highly conserved physiological process of programmed cell death which is critical for proper organism development, tissue maintenance, and overall organism homeostasis. Proper regulation of cell removal is crucial, as both excessive and reduced apoptotic rates can lead to the onset of a variety of diseases. Apoptosis can be induced in cells in response to biochemical, electrical, and mechanical stimuli. Here, we review literature on specific mechanical stimuli that regulate apoptosis and the current understanding of how mechanotransduction plays a role in apoptotic signaling. We focus on how insufficient or excessive mechanical forces may induce apoptosis in the cardiovascular system and thus contribute to cardiovascular disease. Although studies have demonstrated that a broad range of mechanical stimuli initiate and/or potentiate apoptosis, they are predominantly correlative, and no mechanisms have been established. In this review, we attempt to establish a unifying mechanism for how various mechanical stimuli initiate a single cellular response, i.e. apoptosis. We hypothesize that the cytoskeleton plays a central role in this process as it does in determining myriad cell behaviors in response to mechanical inputs. We also describe potential approaches of using mechanomedicines to treat various diseases by altering apoptotic rates in specific cells. The goal of this review is to summarize the current state of the mechanobiology field and suggest potential avenues where future research can explore.

The molecular mechanisms associated with the physiological responses to inflammation and oxidative stress in cardiovascular diseases

The complex physiological signal transduction networks that respond to the dual challenges of inflammatory and oxidative stress are major factors that promote the development of cardiovascular pathologies. These signaling networks contribute to the development of age-related diseases, suggesting crosstalk between the development of aging and cardiovascular disease. Inhibition and/or attenuation of these signaling networks also delays the onset of disease. Therefore, a concept of targeting the signaling networks that are involved in inflammation and oxidative stress may represent a novel treatment paradigm for many types of heart disease. In this review, we discuss the molecular mechanisms associated with the physiological responses to inflammation and oxidative stress especially in heart failure with preserved ejection fraction and emphasize the nature of the crosstalk of these signaling processes as well as possible therapeutic implications for cardiovascular medicine.

The Role of Oxidative Stress in Cardiac Disease: From Physiological Response to Injury Factor

Reactive oxygen species (ROS) are highly reactive chemical species containing oxygen, controlled by both enzymatic and nonenzymatic antioxidant defense systems. In the heart, ROS play an important role in cell homeostasis, by modulating cell proliferation, differentiation, and excitation-contraction coupling. Oxidative stress occurs when ROS production exceeds the buffering capacity of the antioxidant defense systems, leading to cellular and molecular abnormalities, ultimately resulting in cardiac dysfunction. In this review, we will discuss the physiological sources of ROS in the heart, the mechanisms of oxidative stress-related myocardial injury, and the implications of experimental studies and clinical trials with antioxidant therapies in cardiovascular diseases.

Propofol Attenuates the Myocardial Protection Properties of Desflurane by Modulating Mitochondrial Permeability Transition

BACKGROUND

Desflurane and propofol are cardioprotective, but relative efficacy is unclear. The aim was to compare myocardial protection of single, simultaneous, and serial administration of desflurane and propofol.

METHODS

Sixty New Zealand White rabbits and 65 isolated Sprague Dawley rat hearts randomly received desflurane, propofol, simultaneous desflurane and propofol, or sequential desflurane then propofol. Rabbits were subdivided to receive either ischemia-reperfusion with temporary occlusion of the left anterior descending artery or a time-matched, nonischemic perfusion protocol, whereas rat hearts were perfused in a Langendorff model with global ischemia-reperfusion. End points were hemodynamic, functional recovery, and mitochondrial uptake of H-2-deoxy-D-glucose as an indicator of mitochondrial permeability transition.

RESULTS

In rabbits, there were minimal increases in preload-recruitable stroke-work with propofol (P < .001), desflurane (P < .001), and desflurane-and-propofol (P < .001) groups, but no evidence of increases with pentobarbitone (P = .576) and desflurane-then-propofol (P = .374). In terms of end-diastolic pressure-volume relationship, there was no evidence of increase compared to nonischemic controls with desflurane-then-propofol (P = .364), a small but significant increase with desflurane (P < .001), and larger increases with pentobarbitone (P < .001), propofol (P < .001), and desflurane-and-propofol (P < .001).In rat hearts, there was no statistically significant difference in mitochondrial H-activity between propofol and desflurane-and-propofol (165 ± 51 × 10 vs 154 ± 51 × 10 g·mL·min/μmol; P = .998). Desflurane had lower uptake than propofol (65 ± 21 × 10 vs 165 ± 51 × 10 g·mL·min/μmol; P = .039), but there was no statistically significant difference between desflurane and desflurane-then-propofol (65 ± 21 × 10 vs 59 ± 11 × 10 g·mL·min/μmol; P = .999).

CONCLUSIONS

Propofol and desflurane are cardioprotective, but desflurane is more effective than propofol. The added benefit of desflurane is lost when used simultaneously with propofol.

Preconditioning but not postconditioning treatment with resveratrol substantially ameliorates post‑resuscitation myocardial dysfunction through the PI3K/Akt signaling pathway

Post-resuscitation myocardial dysfunction (PRMD) is a severe complication that arises in patients after cardiac arrest (CA). However, there are no safe or effective treatment strategies that are currently available to treat these patients. In the present study, it was investigated whether resveratrol administration could inhibit myocardial nitrative stress to alleviate PRMD. CA was induced in Sprague-Dawley rats by trans-oesophageal alternating electrical stimulation, followed by cardiopulmonary resuscitation. Rats were then randomly divided into a preconditioning or a postconditioning group. Left ventricular function (+dP/dt_max and -dP/dt_min) was recorded for 4 h after the return of spontaneous circulation (ROSC), after which the animals were euthanized. Myocardial nitrative stress was analysed using enzyme-linked immunosorbent assay, western blotting and immunohistochemistry. Wortmannin (a PI3K inhibitor) was used to investigate the involvement of the PI3k/Akt signalling pathway in the cardio-protective activity of resveratrol. After ROSC, resveratrol improved PRMD compared to the vehicle control; however, resveratrol administration significantly improved PRMD in the preconditioning group compared to the postconditioning group. Likewise, resveratrol preconditioning significantly decreased the expression of iNOS and nitrotyrosine in rat hearts but did not significantly ameliorate myocardial nitrative stress. Wortmannin partially inhibited the protective effect of resveratrol preconditioning and resulted in the deterioration of cardiac function and increase in iNOS and nitrotyrosine levels. Resveratrol preconditioning could alleviate PRMD by inhibiting myocardial nitrative stress. The PI3K/Akt signalling pathway may be partially involved in the process.

Dietary l-arginine supplementation influences growth performance and B-cell secretion of immunoglobulin in broiler chickens

Our previous study has shown that high levels of l-arginine (ARG) have reduced serum and mucosal antibody concentrations. In order to provide a better understanding in the application of ARG supplementation in the poultry industry, the study was conducted to investigate the effect of high levels of ARG on performance and B-cell secretion of immunoglobulin M (IgM) and IgG development in broiler chickens. A total of 192 1-day-old male Arbor Acres Plus broilers were randomly allocated into 4 groups (8 replicates per group, 6 birds per replicate) fed diets containing one of four ARG concentrations (analysed): 9.8, 14.7, 19.1 and 23.4 g/kg respectively. Growth performance was measured based on body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR). Increasing ARG quadratically increased (p < 0.05) BWG and FI with reaching plateau at 14.7 g/kg, while linearly decreased (p < 0.05) FCR, indicating that maximal performance required ARG no more than 14.7 g/kg in diets. Serum IgG and IgM concentrations were linearly reduced (p < 0.05) with increasing ARG. Chickens fed 19.1 g/kg or 23.4 g/kg ARG had lower (p < 0.05) serum IgG or IgM than chickens fed 9.8 g/kg ARG. As for the mRNA expression of bursal IgG and IgM, they were significantly downregulated with increasing ARG (p < 0.05). Chickens on ARG (>19.1 g/kg) had a lower (p < 0.05) IgG and IgM mRNA expression than chickens fed 9.8 g/kg. Activator of transcription 3 (STAT3) mRNA expression was linearly reduced with increasing ARG (p < 0.05), the transcriptional repressor B-cell lymphoma 6 (BCL6) mRNA expression was quadratically (p < 0.05) responded, and these cytokines had the lowest expression at 19.1 g/kg. ARG supplementation (>14.7 g/kg) did not significantly improve the growth performance, while it may have a potential negative regulatory effect on B-cell-mediated humoral immunity in chickens associated with suppression of the STAT3 expression associated with the JAK/STAT3 pathway.

Beneficial Effects of Ozone Therapy on Oxidative Stress, Cardiac Functions and Clinical Findings in Patients with Heart Failure Reduced Ejection Fraction

The aim of study was to determine the effects of ozone therapy on the oxidative stress, cardiac functions and clinical findings in patients with heart failure reduced ejection fraction (HFrEF). A total of 40 patients with New York Heart Association 2 and 3 HF with left ventricular ejection fraction (LVEF) <35%, and 40 subjects without HF as control group were included in the study. Patients with HFrEF were given additional ozone therapy of major and minor administrations along with conventional HF treatment for 5 weeks. Before and after ozone therapy, left ventricular end-systolic and end-diastolic volumes (LVESV, LVEDV) and the 6 minute walk distance (6MWD) and blood levels of the superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GSHPx), malondialdehyde (MDA), nitric oxide (NO) and N-terminal pro-brain natriuretic peptide (NT-proBNP) were measured. Ozone therapy significantly reduced the serum levels of NO and MDA (p < 0.001, respectively) and significantly increased the levels of SOD, CAT, GSH and GSHPx (p < 0.001, respectively). LVEDV and LVESV were found to be significantly reduced; however, LVEF was not found to be significantly increased (p = 0.567). As the biochemical improvement marker of HF, NT-proBNP was significantly reduced (p < 0.001). The clinical HF improvement marker of 6 minute walk distance was also modestly increased (p < 0.001). Ozone therapy might be beneficial in terms of activating antioxidant system and merit further therapeutic potential to conventional HF treatment in patients with HFrEF.

Involvement of adipose tissue inflammation and dysfunction in virus-induced type 1 diabetes

The etiopathogenesis of type 1 diabetes (T1D) remains poorly understood. We used the LEW1.WR1 rat model of Kilham rat virus (KRV)-induced T1D to better understand the role of the innate immune system in the mechanism of virus-induced disease. We observed that infection with KRV results in cell influx into visceral adipose tissue soon following infection prior to insulitis and hyperglycemia. In sharp contrast, subcutaneous adipose tissue is free of cellular infiltration, whereas β cell inflammation and diabetes are observed beginning on day 14 post infection. Immunofluorescence studies further demonstrate that KRV triggers CD68⁺ macrophage recruitment and the expression of KRV transcripts and proinflammatory cytokines and chemokines in visceral adipose tissue. Adipocytes from naive rats cultured in the presence of KRV express virus transcripts and upregulate cytokine and chemokine gene expression. KRV induces apoptosis in visceral adipose tissue in vivo, which is reflected by positive TUNEL staining and the expression of cleaved caspase-3. Moreover, KRV leads to an oxidative stress response and downregulates the expression of adipokines and genes associated with mediating insulin signaling. Activation of innate immunity with Poly I:C in the absence of KRV leads to CD68⁺ macrophage recruitment to visceral adipose tissue and a decrease in adipokine expression detected 5 days following Poly (I:C) treatment. Finally, proof-of-principle studies show that brief anti-inflammatory steroid therapy suppresses visceral adipose tissue inflammation and protects from virus-induced disease. Our studies provide evidence raising the hypothesis that visceral adipose tissue inflammation and dysfunction may be involved in early mechanisms triggering β cell autoimmunity.

Downregulation of CUEDC2 prevents doxorubicin‑induced cardiotoxicity in H9c2 cells

Treatment with doxorubicin (DOX), which is an effective anticancer agent, is limited by cardiotoxicity. CUE domain-containing 2 (CUEDC2) serves a role in numerous cellular processes. The present study aimed to elucidate the potential function of CUEDC2 in DOX-induced cardiotoxicity. Cell Counting kit-8 assay demonstrated that DOX induced cytotoxicity of H9c2 cells in a dose-dependent manner. Flow cytometry demonstrated that downregulation of CUEDC2 reduced the levels of DOX-induced reactive oxygen species. Furthermore, compared with in the DOX-treated group, the activity of superoxide dismutase was increased in the DOX + small interfering RNA (si)CUEDC2 group; whereas, the malondialdehyde content was reduced in the DOX + siCUEDC2 group. In addition, flow cytometric analysis indicated that mitochondrial membrane potential was maintained following the depletion of CUEDC2. Furthermore, CUEDC2 downregulation significantly inhibited DOX-induced apoptosis. The expression levels of proapoptotic genes, including B-cell lymphoma 2 (Bcl-2)-associated X protein, cleaved caspase-3 and cytochrome c were inhibited by the depletion of CUEDC2. Conversely, the expression levels of the anti-apoptotic gene Bcl-2 were elevated in the CUEDC2 knockdown group. Downregulation of CUEDC2 also increased phosphorylation of protein kinase B and forkhead box O3a, and decreased the expression of Bcl-2-like protein 11 according to western blot analysis. Taken together, the present study demonstrated that CUEDC2 downregulation prevented DOX-induced cardiotoxicity in H9c2 cells. Therefore, CUEDC2 may be a promising target for the prevention of DOX-induced cardiotoxicity.

Sepsis-Induced Cardiomyopathy: Oxidative Implications in the Initiation and Resolution of the Damage

Cardiac dysfunction may complicate the course of severe sepsis and septic shock with significant implications for patient's survival. The basic pathophysiologic mechanisms leading to septic cardiomyopathy have not been fully clarified until now. Disease-specific treatment is lacking, and care is still based on supportive modalities. Septic state causes destruction of redox balance in many cell types, cardiomyocytes included. The production of reactive oxygen and nitrogen species is increased, and natural antioxidant systems fail to counterbalance the overwhelming generation of free radicals. Reactive species interfere with many basic cell functions, mainly through destruction of protein, lipid, and nucleic acid integrity, compromising enzyme function, mitochondrial structure and performance, and intracellular signaling, all leading to cardiac contractile failure. Takotsubo cardiomyopathy may result from oxidative imbalance. This review will address the multiple aspects of cardiomyocyte bioenergetic failure in sepsis and discuss potential therapeutic interventions.

The Future Challenge of Reactive Oxygen Species (ROS) in Hypertension: From Bench to Bed Side

Reactive oxygen species (ROS) act as signaling molecules that control physiological processes, including cell adaptation to stress. Redox signaling via ROS has quite recently become the focus of much attention in numerous pathological contexts, including neurodegenerative diseases, kidney and cardiovascular disease. Imbalance in ROS formation and degradation has also been implicated in essential hypertension. Essential hypertension is characterized by multiple genetic and environmental factors which do not completely explain its associated risk factors. Thereby, even if advances in therapy have led to a significant reduction in hypertension-associated complications, to interfere with the unbalance of redox signals might represent an additional therapeutic challenge. The decrease of nitric oxide (NO) levels, the antioxidant activity commonly found in preclinical models of hypertension and the ability of antioxidant approaches to reduce ROS levels have spurred clinicians to investigate the contribution of ROS in humans. Indeed, particular effort has recently been devoted to understanding how redox signaling may contribute to vascular pathobiology in human hypertension. However, although biomarkers of oxidative stress have been found to positively correlate with blood pressure in preclinical model of hypertension, human data are less convincing. We herein provide an overview of the most relevant mechanisms via which oxidative stress might contribute to the pathophysiology of essential hypertension. Moreover, alternative approaches, which are directed towards improving antioxidant machinery and/or interfering with ROS production, are also discussed.

Highly pathogenic avian influenza H5N1 virus induces cytokine dysregulation with suppressed maturation of chicken monocyte-derived dendritic cells

One of the major causes of death in highly pathogenic avian influenza virus (HPAIV) infection in chickens is acute induction of pro-inflammatory cytokines (cytokine storm), which leads to severe pathology and acute mortality. DCs and respiratory tract macrophages are the major antigen presenting cells that are exposed to mucosal pathogens. We hypothesized that chicken DCs are a major target for induction of cytokine dysregulation by H5N1 HPAIV. It was found that infection of chicken peripheral blood monocyte-derived dendritic cells (chMoDCs) with H5N1 HPAIV produces high titers of progeny virus with more rounding and cytotoxicity than with H9N2 LPAIV. Expression of maturation markers (CD40, CD80 and CD83) was weaker in both H5N1 and H9N2 groups than in a LPS control group. INF-α, -β and -γ were significantly upregulated in the H5N1 group. Pro-inflammatory cytokines (IL-1β, TNF-α and IL-18) were highly upregulated in early mid (IL-1), and late (IL-6) phases of H5N1 virus infection. IL-8 (CXCLi2) mRNA expression was significantly stronger in the H5N1 group from 6 hr of infection. TLR3, 7, 15 and 21 were upregulated 24 hr after infection by H5N1 virus compared with H9N2 virus, with maximum expression of TLR 3 mRNA. Similarly, greater H5N1 virus-induced apoptotic cell death and cytotoxicity, as measured by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and lactate dehydrogenase assays, respectively, were found. Thus, both H5N1 and H9N2 viruses evade the host immune system by inducing impairment of chMoDCs maturation and enhancing cytokine dysregulation in H5N1 HPAIV-infected cells.

Understanding pacing postconditioning-mediated cardiac protection: a role of oxidative stress and a synergistic effect of adenosine

We and others have demonstrated a protective role for pacing postconditioning (PPC) against ischemia/reperfusion (I/R) injury in the heart; however, the underlying mechanisms behind these protective effects are not completely understood. In this study, we wanted to further characterize PPC-mediated cardiac protection, specifically identify optimal pacing sites; examine the role of oxidative stress; and test the existence of a potential synergistic effect between PPC and adenosine. Isolated rat hearts were subjected to coronary occlusion followed by reperfusion. PPC involved three, 30 s, episodes of alternating left ventricular (LV) and right atrial (RA) pacing. Multiple pacing protocols with different pacing electrode locations were used. To test the involvement of oxidative stress, target-specific agonists or antagonists were infused at the beginning of reperfusion. Hemodynamic data were digitally recorded, and cardiac enzymes, oxidant, and antioxidant status were chemically measured. Pacing at the LV or RV but not at the heart apex or base significantly (P < 0.001) protected against ischemia-reperfusion injury. PPC-mediated protection was completely abrogated in the presence of reactive oxygen species (ROS) scavenger, ebselen; peroxynitrite (ONOO^-) scavenger, uric acid; and nitric oxide synthase inhibitor, L-NAME. Nitric oxide (NO) donor, snap, however significantly (P < 0.05) protected the heart against I/R injury in the absence of PPC. The protective effects of PPC were significantly improved by adenosine. PPC-stimulated protection can be achieved by alternating LV and RA pacing applied at the beginning of reperfusion. NO, ROS, and the product of their interaction ONOO^- play a significant role in PPC-induced cardiac protection. Finally, the protective effects of PPC can be synergized with adenosine.

Ligand activation of cannabinoid receptors attenuates hypertrophy of neonatal rat cardiomyocytes

: Endocannabinoids are bioactive amides, esters, and ethers of long-chain polyunsaturated fatty acids. Evidence suggests that activation of the endocannabinoid pathway offers cardioprotection against myocardial ischemia, arrhythmias, and endothelial dysfunction of coronary arteries. As cardiac hypertrophy is a convergence point of risk factors for heart failure, we determined a role for endocannabinoids in attenuating endothelin-1-induced hypertrophy and probed the signaling pathways involved. The cannabinoid receptor ligand anandamide and its metabolically stable analog, R-methanandamide, suppressed hypertrophic indicators including cardiomyocyte enlargement and fetal gene activation (ie, the brain natriuretic peptide gene) elicited by endothelin-1 in isolated neonatal rat ventricular myocytes. The ability of R-methanandamide to suppress myocyte enlargement and fetal gene activation was mediated by CB2 and CB1 receptors, respectively. Accordingly, a CB2-selective agonist, JWH-133, prevented only myocyte enlargement but not brain natriuretic peptide gene activation. A CB1/CB2 dual agonist with limited brain penetration, CB-13, inhibited both hypertrophic indicators. CB-13 activated AMP-activated protein kinase (AMPK) and, in an AMPK-dependent manner, endothelial nitric oxide synthase (eNOS). Disruption of AMPK signaling, using compound C or short hairpinRNA knockdown, and eNOS inhibition using L-NIO abolished the antihypertrophic actions of CB-13. In conclusion, CB-13 inhibits cardiomyocyte hypertrophy through AMPK-eNOS signaling and may represent a novel therapeutic approach to cardioprotection.

Supplemental dietary L-arginine attenuates intestinal mucosal disruption during a coccidial vaccine challenge in broiler chickens

The present study investigated the effects of dietary arginine (Arg) supplementation on intestinal structure and functionality in broiler chickens subjected to coccidial challenge. The present study was a randomised complete block design employing a 3 × 2 factorial arrangement (n 8) with three dietary concentrations of Arg (11·1, 13·3 and 20·2 g/kg) with or without coccidial vaccine challenge (unchallenged and coccidial challenge). On day 14, birds were orally administered with coccidial vaccine or saline. On day 21, birds were killed to obtain jejunal tissue and mucosal samples for histological, gene expression and mucosal immunity measurements. Within 7 d of the challenge, there was a decrease in body-weight gain and feed intake, and an increase in the feed:gain ratio (P< 0·05). Jejunal inflammation was evidenced by villus damage, crypt dilation and goblet cell depletion. Coccidial challenge increased mucosal secretory IgA concentration and inflammatory gene (iNOS, IL-1β, IL-8 and MyD88) mRNA expression levels (P< 0·05), as well as reduced jejunal Mucin-2, IgA and IL-1RI mRNA expression levels (P< 0·05). Increasing Arg concentration (1) increased jejunal villus height (P< 0·05) and linearly increased jejunal crypt depth (P< 0·05); (2) quadratically increased mucosal maltase activity (P< 0·05) and linearly decreased mucosal secretory IgG concentration (P< 0·05) within the coccidiosis-challenged groups; and (3) linearly decreased jejunal Toll-like receptor 4 (TLR4) mRNA expression level (P< 0·05) within the coccidiosis-challenged groups. The mRNA expression of mechanistic target of rapamycin (mTOR) complex 1 pathway genes (mTOR and RPS6KB1) and the anti-apoptosis gene Bcl-2 quadratically responded to increasing dietary Arg supplementation (P< 0·05). These results indicate that dietary Arg supplementation attenuates intestinal mucosal disruption in coccidiosis-challenged chickens probably through suppressing TLR4 and activating mTOR complex 1 pathways.

Current perspectives on hydralazine and nitrate therapies in heart failure

The origins of the hydralazine/isosorbide dinitrate (H+ISDN) combination therapy are rooted in the first large-scale clinical trial in heart failure: V-HeFT I. Initially utilized for the balanced vasodilatory properties of each drug, we now know there is "more to the story." In fact, the maintenance of the nitroso-redox balance may be the true mechanism of benefit. Since the publication of V-HeFT I 30 years ago, H+ISDN has been the subject of much discussion and debate. Regardless of the many controversies surrounding H+ISDN, one thing is clear: therapy is underutilized and many patients who could benefit never receive the drugs. Ongoing physician and patient education are mandatory to improve the rates of H+ISDN use.

Moxonidine modulates cytokine signalling and effects on cardiac cell viability

Regression of left ventricular hypertrophy and improved cardiac function in SHR by the centrally acting imidazoline I1-receptor agonist, moxonidine, are associated with differential actions on circulating and cardiac cytokines. Herein, we investigated cell-type specific I1-receptor (also known as nischarin) signalling and the mechanisms through which moxonidine may interfere with cytokines to affect cardiac cell viability. Studies were performed on neonatal rat cardiomyocytes and fibroblasts incubated with interleukin (IL)-1β (5 ng/ml), tumor necrosis factor (TNF)-α (10 ng/ml), and moxonidine (10(-7) and 10(-5) M), separately and in combination, for 15 min, and 24 and 48 h for the measurement of MAPKs (ERK1/2, JNK, and p38) and Akt activation and inducible NOS (iNOS) expression, by Western blotting, and cardiac cell viability/proliferation and apoptosis by flow cytometry, MTT assay, and Live/Dead assay. Participation of imidazoline I1-receptors and the signalling proteins in the detected effects was identified using imidazoline I1-receptor antagonist and signalling protein inhibitors. The results show that IL-1β, and to a lower extent, TNF-α, causes cell death and that moxonidine protects against starvation- as well as IL-1β -induced mortality, mainly by maintaining membrane integrity, and in part, by improving mitochondrial activity. The protection involves activation of Akt, ERK1/2, p38, JNK, and iNOS. In contrast, moxonidine stimulates basal and IL-1β-induced fibroblast mortality by mechanisms that include inhibition of JNK and iNOS. Thus, apart from their actions on the central nervous system, imidazoline I1-receptors are directly involved in cardiac cell growth and death, and may play an important role in cardiovascular diseases associated with inflammation.

Therapeutic hypercapnia prevents inhaled nitric oxide-induced right-ventricular systolic dysfunction in juvenile rats

Chronic pulmonary hypertension in the neonate and infant frequently presents with right-ventricular (RV) failure. Current clinical management may include protracted treatment with inhaled nitric oxide (iNO), with the goal of reducing RV afterload. We have previously reported that prolonged exposure to iNO causes RV systolic dysfunction in the chronic hypoxia-exposed juvenile rat, which was prevented by a peroxynitrite decomposition catalyst. Given that inhalation of CO2 (therapeutic hypercapnia) may limit oxidative stress and upregulated cytokine expression in the lung and other organs, we hypothesized that therapeutic hypercapnia would attenuate cytokine-mediated nitric oxide synthase (NOS) upregulation, thus limiting peroxynitrite generation. Sprague-Dawley rat pups were exposed to chronic hypoxia (13% O2) from postnatal day 1 to 21, while receiving iNO (20 ppm) from day 14 to 21, with or without therapeutic hypercapnia (10% CO2). Therapeutic hypercapnia completely normalized RV systolic function, RV hypertrophy, and remodeling of pulmonary resistance arteries in animals exposed to iNO. Inhaled nitric oxide-mediated increases in RV peroxynitrite, apoptosis, and contents of tumor necrosis factor (TNF)-α, interleukin (IL)-1α, and NOS-2 were all attenuated by therapeutic hypercapnia. Inhibition of NOS-2 activity with 1400 W (1 mg/kg/day) prevented iNO-mediated upregulation of peroxynitrite and led to improved RV systolic function. Blockade of IL-1 receptor signaling with anakinra (500 mg/kg/day) decreased NOS-2 content and had similar effects compared to NOS-2 inhibition on iNO-mediated effects, whereas blockade of TNF-α signaling with etanercept (0.4 mg/kg on alternate days) had no effects on these parameters. We conclude that therapeutic hypercapnia prevents the adverse effects of sustained exposure to iNO on RV systolic function by limiting IL-1-mediated NOS-2 upregulation and consequent nitration. Therapeutic hypercapnia also acts synergistically with iNO in normalizing RV hypertrophy, vascular remodeling, and raised pulmonary vascular resistance secondary to chronic hypoxia.

Pulmonary microvascular albumin leak is associated with endothelial cell death in murine sepsis-induced lung injury in vivo

Sepsis is a systemic inflammatory response that targets multiple components of the cardiovascular system including the microvasculature. Microvascular endothelial cells (MVEC) are central to normal microvascular function, including maintenance of the microvascular permeability barrier. Microvascular/MVEC dysfunction during sepsis is associated with barrier dysfunction, resulting in the leak of protein-rich edema fluid into organs, especially the lung. The specific role of MVEC apoptosis in septic microvascular/MVEC dysfunction in vivo remains to be determined. To examine pulmonary MVEC death in vivo under septic conditions, we used a murine cecal ligation/perforation (CLP) model of sepsis and identified non-viable pulmonary cells with propidium iodide (PI) by intravital videomicroscopy (IVVM), and confirmed this by histology. Septic pulmonary microvascular Evans blue (EB)-labeled albumin leak was associated with an increased number of PI-positive cells, which were confirmed to be predominantly MVEC based on specific labeling with three markers, anti-CD31 (PECAM), anti-CD34, and lectin binding. Furthermore, this septic death of pulmonary MVEC was markedly attenuated by cyclophosphamide-mediated depletion of neutrophils (PMN) or use of an anti-CD18 antibody developed for immunohistochemistry but shown to block CD18-dependent signaling. Additionally, septic pulmonary MVEC death was iNOS-dependent as mice lacking iNOS had markedly fewer PI-positive MVEC. Septic PI-positive pulmonary cell death was confirmed to be due to apoptosis by three independent markers: caspase activation by FLIVO, translocation of phosphatidylserine to the cell surface by Annexin V binding, and DNA fragmentation by TUNEL. Collectively, these findings indicate that septic pulmonary MVEC death, putatively apoptosis, is a result of leukocyte activation and iNOS-dependent signaling, and in turn, may contribute to pulmonary microvascular barrier dysfunction and albumin hyper-permeability during sepsis.

Peroxynitrite (ONOO-) is endogenously produced in arabidopsis peroxisomes and is overproduced under cadmium stress

BACKGROUND AND AIMS

Peroxisomes are subcellular compartments involved in multiple cellular metabolic pathways. Peroxynitrite (ONOO(-)) is a nitric oxide-derived molecule which is a nitrating species that causes nitration of proteins. This study used cell biology techniques to explore the potential presence of peroxynitrite in peroxisomes and evaluated its content under stress conditions (excess cadmium).

METHODS

Peroxynitrite, nitric oxide and superoxide anion were studied using cell-permeable specific fluorescent probes by confocal laser scanning microscopy in Arabidopsis thaliana transgenic plants expressing cyan fluorescent protein through the addition of peroxisomal targeting signal 1 (PTS1), which enables peroxisomes to be visualized in vivo. Key Results When no stress was applied, peroxynitrite was clearly localized in the peroxisomes of roots and stomatal guard cells. Under cadmium (150 μm) stress, the generation of peroxynitrite, nitric oxide and the superoxide anion (O2(·-)) increased and was localized in peroxisomes and the cytosol, participating in the generation of nitro-oxidative stress.

CONCLUSIONS

The results show that peroxisomes are an endogenous source of peroxynitrite, which is over-produced under cadmium stress, suggesting that the metabolism of reactive nitrogen species in peroxisomes could participate in the mechanism of the response to this heavy metal.

The NO/ONOO-cycle as the central cause of heart failure

The NO/ONOO-cycle is a primarily local, biochemical vicious cycle mechanism, centered on elevated peroxynitrite and oxidative stress, but also involving 10 additional elements: NF-κB, inflammatory cytokines, iNOS, nitric oxide (NO), superoxide, mitochondrial dysfunction (lowered energy charge, ATP), NMDA activity, intracellular Ca(2+), TRP receptors and tetrahydrobiopterin depletion. All 12 of these elements have causal roles in heart failure (HF) and each is linked through a total of 87 studies to specific correlates of HF. Two apparent causal factors of HF, RhoA and endothelin-1, each act as tissue-limited cycle elements. Nineteen stressors that initiate cases of HF, each act to raise multiple cycle elements, potentially initiating the cycle in this way. Different types of HF, left vs. right ventricular HF, with or without arrhythmia, etc., may differ from one another in the regions of the myocardium most impacted by the cycle. None of the elements of the cycle or the mechanisms linking them are original, but they collectively produce the robust nature of the NO/ONOO-cycle which creates a major challenge for treatment of HF or other proposed NO/ONOO-cycle diseases. Elevated peroxynitrite/NO ratio and consequent oxidative stress are essential to both HF and the NO/ONOO-cycle.

Specificity in S-nitrosylation: a short-range mechanism for NO signaling?

SIGNIFICANCE

Nitric oxide (NO) classical and less classical signaling mechanisms (through interaction with soluble guanylate cyclase and cytochrome c oxidase, respectively) operate through direct binding of NO to protein metal centers, and rely on diffusibility of the NO molecule. S-Nitrosylation, a covalent post-translational modification of protein cysteines, has emerged as a paradigm of nonclassical NO signaling.

RECENT ADVANCES

Several nonenzymatic mechanisms for S-nitrosylation formation and destruction have been described. Enzymatic mechanisms for transnitrosylation and denitrosylation have been also studied as regulators of the modification of specific subsets of proteins. The advancement of modification-specific proteomic methodologies has allowed progress in the study of diverse S-nitrosoproteomes, raising clues and questions about the parameters for determining the protein specificity of the modification.

CRITICAL ISSUES

We propose that S-nitrosylation is mainly a short-range mechanism of NO signaling, exerted in a relatively limited range of action around the NO sources, and tightly related to the very controlled regulation of subcellular localization of nitric oxide synthases. We review the nonenzymatic and enzymatic mechanisms that support this concept, as well as physiological examples of mammalian systems that illustrate well the precise compartmentalization of S-nitrosylation.

FUTURE DIRECTIONS

Individual and proteomic studies of protein S-nitrosylation-based signaling should take into account the subcellular localization in order to gain further insight into the functional role of this modification in (patho)physiological settings.

Does estimated glomerular filtration rate have an effect on left ventricular function after ST-elevation myocardial infarction?

OBJECTIVES

Little is known about whether estimated glomerular filtration rates (eGFR) affect left ventricular (LV) function and gain benefit with antiremodeling treatment in patients with ST-elevation myocardial infarction (STEMI). We investigated the effect of eGFR on LV function using tissue Doppler imaging (TDI) parameters. In addition, we sought to evaluate the antiremodeling effect of standard treatment at follow-up in patients with renal insufficiency (RI) after STEMI.

METHODS AND RESULTS

A retrospective analysis of 579 patients with STEMI was performed. Patients were divided into 3 groups according to eGFR (Group 1: eGFR > 90 mL/min per 1.73 m(2); Group 2: eGFR = 60-89 mL/min per 1.73 m(2); Group 3: eGFR < 60 mL/min per 1.73 m(2)). Conventional echocardiography and TDI were performed within 48-72 hours after STEMI and at 6-month follow-up. The mean left ventricular ejection fraction (LVEF) was significantly lower in Group 3 than in Group 1 (P = 0.021). The mean peak systolic velocity (Sm) was significantly lower in Group 3 than in Group 1 and Group 2 (P = 0.002 and 0.006, respectively). The estimated GFR had a linear association with Sm and LVEF (P = 0.001, r = 0.161; P = 0.005, r = 0.132, respectively). Multivariate analysis showed that an eGFR < 60 mL/min per 1.73 m(2) was an independent predictor of lower Sm and in-hospital mortality. In addition, an antiremodeling effect of standard treatment was seen in all groups at 6-month follow-up.

CONCLUSIONS

Estimated glomerular filtration rate of <60 mL/min per 1.73 m(2) was associated with lower LV function after STEMI, and may gain an antiremodeling effect with standard treatment at follow-up.

Differences in highly pathogenic avian influenza viral pathogenesis and associated early inflammatory response in chickens and ducks

We studied the immunological responses in the lung, brain and spleen of ducks and chickens within the first 7 days after infection with H7N1 highly pathogenic avian influenza (HPAI). Infection with HPAI caused significant morbidity and mortality in chickens, while in ducks the infection was asymptomatic. The HPAI viral mRNA load was higher in all investigated tissues of chickens compared with duck tissues. In the lung, brain and spleen of HPAI-infected chickens, a high, but delayed, pro-inflammatory response of IL-6 and IL-1β mRNA was induced, including up-regulation of IFN-β, IFN-γ, TLR3 and MDA-5 mRNA from 1 day post infection (p.i.). Whereas in ducks already at 8 h p.i., a quicker but lower response was found for IL-6, IL-1β and iNOS mRNA followed by a delayed activation of TLR7, RIG-I, MDA5 and IFN-γ mRNA response. Virus-infected areas in the lung of chickens co-localized with KUL-01⁺ (macrophages, dendritic cells), CD4⁺, and CD8α⁺ cells, during the first day after infection. However, only KUL-01⁺ cells co-localized with the virus after 1 day p.i. In ducks, CVI-ChNL-68.1⁺ (macrophage-like cells), CD4⁺ and CD8α⁺ cells and apoptosis co-localized with the virus within 8 h p.i. Apoptosis was detected in the brain and lung of HPAI-infected chickens after 2 days p.i. and apoptotic cells co-localized with virus-infected areas. In conclusion, excessive delayed cytokine inflammatory responses but inadequate cellular immune responses may contribute to pathogenesis in chickens, while ducks initiate a fast lower cytokine response followed by the activation of major pattern recognition receptors (TLR7, RIG-I, MDA5) and a persistent cellular response.

Modulation of myocardial contraction by peroxynitrite

Peroxynitrite is a potent oxidant that is quickly emerging as a crucial modulator of myocardial function. This review will focus on the regulation of myocardial contraction by peroxynitrite during health and disease, with a specific emphasis on cardiomyocyte Ca²⁺ handling, proposed signaling pathways, and protein end-targets.

Cytosolic Ca2+-induced apoptosis in rat cardiomyocytes via mitochondrial NO-cGMP-protein kinase G pathway

Previously, we showed that in adult rat cardiomyocytes, nitric oxide (NO) donors stimulate mitochondrial cGMP production, followed by cytochrome c release, independently of the mitochondrial permeable transition pore. We investigated whether mitochondrial cGMP-induced cytochrome c release from cardiac mitochondria is Ca(2+)-sensitive. Mitochondria and primary cultured cardiomyocytes were prepared from left ventricles of male Wistar rats. The cytosolic Ca(2+) concentration was adjusted with Ca(2+)-EGTA buffers. Cytochrome c released from mitochondria was measured by Western blotting. Cardiomyocyte apoptosis was assessed by Annexin V staining. Cytochrome c release from cardiac mitochondria was evoked by buffered Ca(2+) (1 μM); this was inhibited by NO-cGMP pathway inhibitors such as N(G)-monomethyl-l-arginine monoacetate (inhibitor of NO synthase), 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NO scavenger), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, NO-sensitive guanylyl cyclase inhibitor) and voltage-dependent anion channel (VDAC) inhibitor, 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene, but not by cyclosporin A (mitochondrial permeable transition pore inhibitor). Furthermore, this release was significantly and dose dependently inhibited by 0.3-3 μM KT5823 (protein kinase G inhibitor). At the cellular level, intracellular perfusion of cardiomyocytes with buffered Ca(2+) (1 μM) also induced apoptosis, which was inhibited in the presence of ODQ. A membrane-permeable cGMP analog, 8-Br-cGMP, but not cGMP itself, mimicked buffered Ca(2+) actions in both cardiac mitochondria and cardiomyocytes. We further confirmed an increase in protein kinase G activity by adding cGMP in mitochondrial protein fraction. Our results suggest that mitochondrial NO-cGMP pathway-induced cytochrome c release from cardiac mitochondria, triggered by increased cytosolic Ca(2+), occurs through VDAC via the stimulation of an undiscovered mitochondrial protein kinase G.

Oleanolic acid: a novel cardioprotective agent that blunts hyperglycemia-induced contractile dysfunction

Diabetes constitutes a major health challenge. Since cardiovascular complications are common in diabetic patients this will further increase the overall burden of disease. Furthermore, stress-induced hyperglycemia in non-diabetic patients with acute myocardial infarction is associated with higher in-hospital mortality. Previous studies implicate oxidative stress, excessive flux through the hexosamine biosynthetic pathway (HBP) and a dysfunctional ubiquitin-proteasome system (UPS) as potential mediators of this process. Since oleanolic acid (OA; a clove extract) possesses antioxidant properties, we hypothesized that it attenuates acute and chronic hyperglycemia-mediated pathophysiologic molecular events (oxidative stress, apoptosis, HBP, UPS) and thereby improves contractile function in response to ischemia-reperfusion. We employed several experimental systems: 1) H9c2 cardiac myoblasts were exposed to 33 mM glucose for 48 hr vs. controls (5 mM glucose); and subsequently treated with two OA doses (20 and 50 µM) for 6 and 24 hr, respectively; 2) Isolated rat hearts were perfused ex vivo with Krebs-Henseleit buffer containing 33 mM glucose vs. controls (11 mM glucose) for 60 min, followed by 20 min global ischemia and 60 min reperfusion ± OA treatment; 3) In vivo coronary ligations were performed on streptozotocin treated rats ± OA administration during reperfusion; and 4) Effects of long-term OA treatment (2 weeks) on heart function was assessed in streptozotocin-treated rats. Our data demonstrate that OA treatment blunted high glucose-induced oxidative stress and apoptosis in heart cells. OA therapy also resulted in cardioprotection, i.e. for ex vivo and in vivo rat hearts exposed to ischemia-reperfusion under hyperglycemic conditions. In parallel, we found decreased oxidative stress, apoptosis, HBP flux and proteasomal activity following ischemia-reperfusion. Long-term OA treatment also improved heart function in streptozotocin-diabetic rats. These findings are promising since it may eventually result in novel therapeutic interventions to treat acute hyperglycemia (in non-diabetic patients) and diabetic patients with associated cardiovascular complications.

l-Tetrahydropalmatine, an active component of Corydalis yanhusuo W.T. Wang, protects against myocardial ischaemia-reperfusion injury in rats

l-Tetrahydropalmatine (l-THP) is an active ingredients of Corydalis yanhusuo W.T. Wang, which protects against acute global cerebral ischaemia-reperfusion injury. In this study, we show that l-THP is cardioprotective in myocardial ischaemia-reperfusion injury and examined the mechanism. Rats were treated with l-THP (0, 10, 20, 40 mg/kg b.w.) for 20 min before occlusion of the left anterior descending coronary artery and subjected to myocardial ischaemia-reperfusion (30 min/6 h). Compared with vehicle-treated animals, the infarct area/risk area (IA/RA) of l-THP (20, 40 mg/kg b.w.) treated rats was reduced, whilst l-THP (10 mg/kg b.w.) had no significant effect. Cardiac function was improved in l-THP-treated rats whilst plasma creatine kinase activity declined. Following treatment with l-THP (20 mg/kg b.w.), subunit of phosphatidylinositol 3-kinase p85, serine⁴⁷³ phosphorylation of Akt and serine¹¹⁷⁷ phosphorylation of endothelial NO synthase (eNOS) increased in myocardium, whilst expression of inducible NO synthase (iNOS) decreased. However, the expression of HIF-1α and VEGF were increased in I_{30 min}R_{6 h}, but decreased to normal level in I_{30 min}R_{24 h}, while treatment with l-THP (20 mg/kg b.w.) enhanced the levels of these two genes in I_{30 min}R_{24 h}. Production of NO in myocardium and plasma, activity of myeloperoxidase (MPO) in plasma and the expression of tumour necrosis factor-α (TNF-α) in myocardium were decreased by l-THP. TUNEL assay revealed that l-THP (20 mg/kg b.w.) reduced apoptosis in myocardium. Thus, we show that l-THP activates the PI3K/Akt/eNOS/NO pathway and increases expression of HIF-1α and VEGF, whilst depressing iNOS-derived NO production in myocardium. This effect may decrease the accumulation of inflammatory factors, including TNF-α and MPO, and lessen the extent of apoptosis, therefore contributing to the cardioprotective effects of l-THP in myocardial ischaemia-reperfusion injury.

Bench-to-bedside review: Neonatal sepsis-redox processes in pathogenesis

The present review is aimed at elucidating the neonatal 'sepsis redox cycle' - the cascade of inflammatory and redox events involved in the pathogenesis of sepsis in neonates. While adult and neonatal sepses share some common features, there are some substantial differences: higher mortality rates occur in adult sepsis and worse long-term effects are evident in neonatal sepsis survivors. Such epidemiological data may be explained by the lower ability of IL6 and IL8 to activate NF-κB-regulated transcription in neonatal sepsis in comparison to TNF-α, which is involved in the mechanisms of adult sepsis. The activation of NF-κB in neonatal sepsis is further promoted by hydrogen peroxide and results in mitochondrial dysfunction and energy failure as septic neonates experience decreased O₂ consumption as well as lower heat production and body temperature in comparison to healthy peers. In neonates, specific organs that are still under development are vulnerable to sepsis-provoked stress, which may lead to brain, lung, and heart injury, as well as vision and hearing impairments. In the light of the processes integrated here, it is clear that therapeutic approaches should also target specific steps in the neonatal 'sepsis redox cycle' in addition to the current therapeutic approach that is mainly focused on pathogen eradication.

Cyclooxygenase-2-derived prostacyclin protective role on endotoxin-induced mouse cardiomyocyte mortality

Cardiovascular dysfunction characterizes septic shock, inducing multiple organ failure and a high mortality rate. In the heart, it has been shown an up-regulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions with subsequent overproduction of nitric oxide (NO) and eicosanoids. This study is focused on the links between these products of inflammation and cell loss of mouse cardiomyocytes during treatment by the Salmonella typhimurium lipopolysaccharide (LPS) in presence or in absence of NOS or COX inhibitors. LPS induced RelA/NF-κB p65 activation, iNOS and COX-2 up-regulations, resulting in NO and prostacyclin releases. These effects were reversed by the NO-synthase inhibitor and increased by the specific COX-2 inhibitor. Immunostainings with FITC-conjugated anti-Annexin-V and propidium iodide and caspase 3/7 activity assay showed that cardiomyocyte necrosis was inhibited by L-NA during LPS treatment challenge, while apoptosis was induced in presence of both LPS and NS-398. No effect on LPS cellular injury was observed using the specific cyclooxygenase-1 (COX-1) inhibitor, SC-560. These findings strongly support the hypothesis of a link between iNOS-dependent NO overproduction and LPS-induced cell loss with a selective protective role allotted to COX-2 and deriving prostacyclins.

Critical illness hyperglycemia in pediatric cardiac surgery

Critical illness hyperglycemia (CIH) is common in pediatric and adult intensive care units (ICUs). Children undergoing surgical repair or palliation of congenital cardiac defects are particularly at risk for CIH and its occurrence has been associated with increased morbidity and mortality in this population. Strict glycemic control through the use of intensive insulin therapy (IIT) has been shown to improve outcomes in some adult and pediatric studies, yet these findings have sparked controversy. The practice of strict glycemic control has been slow in extending to pediatric ICUs because of the documented increase in the incidence of hypoglycemia in patients treated with IIT. Protocol driven approaches with more liberal glycemic targets have been successfully validated in general and cardiac critical care pediatric patients with low rates of hypoglycemia. It is unknown whether a therapeutic benefit is obtained by keeping patients in this more liberal glycemic control target. Definitive randomized controlled trials of IIT utilizing these targets in critically ill children are ongoing.

Ouabain increases iNOS-dependent nitric oxide generation which contributes to the hypertrophic effect of the glycoside: possible role of peroxynitrite formation

In addition to inotropic effects, cardiac glycosides exert deleterious effects on the heart which limit their use for cardiac therapeutics. In this study, we determined the possible contribution of ouabain-induced iNOS stimulation to the resultant hypertrophic as well as cytotoxic effects of the glycoside on cultured adult rat ventricular myocytes. Myocytes were treated with ouabain (50 μM) for up to 24 h. Ouabain significantly increased gene and protein levels of inducible nitric oxide synthase (iNOS) which was associated with significantly increased release of NO from myocytes as well as increased total release of reactive oxygen species (ROS), superoxide anion (O(2) (-)), and increased peroxynitrite formation as assessed by protein tyrosine nitration. Administration of ouabain was also associated with increased levels of myocyte toxicity as determined by myocyte morphology, trypan blue staining and lactate dehydrogenase (LDH) efflux. The nonspecific NOS inhibitor Nω-nitro-L: -arginine methyl ester and the more selective iNOS inhibitor 1400W both abrogated the increase in LDH release but had no significant effect on either morphology or trypan blue staining. Ouabain also significantly increased both myocyte surface area and expression of atrial natriuretic peptide indicating a hypertrophic response with both parameters being completely prevented by NOS inhibition. The effects of iNOS inhibitors were associated with diminished ouabain tyrosine nitration as well as abrogation of ouabain-induced p38 and ERK phosphorylation. Our study shows that ouabain is a potent inducer of NO formation, iNOS upregulation, and increased production of ROS. Inhibition of ouabain-dependent peroxynitrite formation may contribute to the antihypertrophic effect of iNOS inhibition possibly by preventing downstream MAPK activation.

Oxidative stress in heart failure: what are we missing?

Over the past several decades, investigations in humans and animal models of heart failure (HF) have provided substantial evidence that oxidative stress is increased in HF and contributes to disease progression. The high metabolic activity of cardiac myocytes makes these cells active sources of reactive oxygen species. Work in cell and animal models clearly demonstrates that oxidative stress activates processes such as changes in gene expression and cell death that are now accepted components of myocardial remodeling and HF. Antioxidants prevent progressive remodeling and even improve cardiac function in animal models of HF. It is therefore disappointing that to date no antioxidant strategy has translated to a therapeutic in the HF clinic. Possible explanations, including inadequate appreciation of the critical disease-modifying sources of reactive oxygen species, the choice of the wrong antioxidant strategy, or incomplete understanding of individual variability in human antioxidant defenses in this brief review.

β1-Integrin is up-regulated via Rac1-dependent reactive oxygen species as part of the hypertrophic cardiomyocyte response

β(1)-Integrin mediates cardiomyocyte growth and survival and its proper regulation is essential for the structural and functional integrity of the heart. β(1)-Integrin expression is enhanced in hypertrophy, but the mechanism and significance of its up-regulation are unknown. Because reactive oxygen species (ROS) are important mediators of myocardial remodeling we examined their role in regulated β(1)-integrin expression. Hypertrophy was induced in neonatal cardiomyocytes by endothelin-1 (ET-1), which activated the regulatory NADPH oxidase subunit Rac1, evoked ROS, and enhanced fetal gene expression and cardiomyocyte size. ET-1 also enhanced cell adhesion and FAK phosphorylation and inhibited oxidative stress-induced cardiomyocyte apoptosis. Further, ET-1 increased β(1)-integrin mRNA and protein expression via Rac1-ROS-dependent MEK/ERK and EGF receptor-PI3K/Akt activation as shown by adenoviral dominant-negative Rac1 or overexpression of copper/zinc-superoxide dismutase. The relevance of regulated β(1)-integrin expression was examined in cardiomyocytes, in which targeting siRNA impeded the ET-1-induced β(1)-integrin up-regulation. In these cells, ET-1-induced cell adhesion, FAK phosphorylation, and hypertrophic response were significantly blunted, whereas its antiapoptotic effect was predominantly unchanged, suggesting at least partial dissociation of prohypertrophic and prosurvival signaling elicited by ET-1. In conclusion, β(1)-integrin up-regulation in response to ET-1 is mediated via Rac1-ROS-dependent activation of prohypertrophic pathways and is mandatory for ET-1-induced FAK activation, cell adhesion, and hypertrophic response.

Protective effects of chinese traditional medicine buyang huanwu decoction on myocardial injury

Many clinical studies have reported that Buyang Huanwu Decoction (BYHWD) has a protective effect on ischemic heart disease (IHD). In the present study, the protective effect of BYHWD on myocardial ischemia was investigated. Different doses of BYHWD and Compound Danshen Dropping Pills (CDDP) were lavaged to rats, respectively, isoproterenol (ISO) was intraperitoneally injected in to all animals to induce myocardial ischemia except the control group. Electrocardiogram (ECG) of each animal was recorded; activities of lactate dehydrogenase (LDH), creatine kinase (CK) and aspartate aminotransferase (AST) in serum were detected. As the results of ECG showed, pre-treatment with BYHWD inhibited ischemic myocardial injury, and the activities of LDH, CK and AST were lower than those in the myocardial ischemia model group, which suggests that BYHWD rescues the myocardium from ischemia status. To research the potential mechanism, the level of nitric oxide (NO), nitric oxide syntheses (NOS) and inducible nitric oxide syntheses (iNOS), the expression of iNOS and ligand of cluster of differentiation 40 (CD40L) were detected. The results revealed that BYHWD significantly decreased the level of NO, NOS and iNOS in serum. Moreover, BYHWD decreased the expression of iNOS and CD40L in myocardial tissues. These results indicate that the protective effect of BYHWD on myocardial ischemia and mechanism are associated with inhibition of iNOS and CD40L expression.

Cannabinoid/agonist WIN 55,212-2 reduces cardiac ischaemia–reperfusion injury in Zucker diabetic fatty rats: role of CB2 receptors and iNOS/eNOS

BACKGROUND

Diabetes increases cardiac damage after myocardial ischaemia. Cannabinoids can protect against myocardial ischaemia/reperfusion injury. The aim of this study was to examine the cardioprotective effect of the cannabinoid agonist WIN 55,212-2 (WIN) against ischaemia/reperfusion injury in an experimental model of type 2 diabetes. We performed these experiments in the Zucker diabetic fatty rat, and focused on the role of cannabinoid receptors in modulation of cardiac inducible nitric oxide synthase (iNOS)/endothelial-type nitric oxide synthase (eNOS) expression.

METHODS

Male 20-week-old Zucker diabetic fatty rats were treated with vehicle, WIN, the selective CB1 or CB2 receptor antagonists AM251 and AM630, respectively, AM251 + WIN or AM630 + WIN. Hearts were isolated from these rats, and the cardiac functional response to ischaemia/reperfusion injury was evaluated. In addition, cardiac iNOS and eNOS expression were determined by western blot.

RESULTS

WIN significantly improved cardiac recovery after ischaemia/ reperfusion in the hearts from Zucker diabetic fatty rats by restoring coronary perfusion pressure and heart rate to preischaemic levels. Additionally, WIN decreased cardiac iNOS expression and increased eNOS expression after ischaemia/reperfusion in diabetic hearts. WIN-induced cardiac functional recovery was completely blocked by the CB2 antagonist AM630. However, changes in NOS isoenzyme expression were not affected by the CB antagonists.

CONCLUSIONS

This study shows a cardioprotective effect of a cannabinoid agonist on ischaemia/reperfusion injury in an experimental model of a metabolic disorder. The activation mainly of CB2 receptors and the restoration of iNOS/eNOS cardiac equilibrium are mechanisms involved in this protective effect. These initial studies have provided the basis for future research in this field.

Increased inducible nitric oxide synthase expression in organs is associated with a higher severity of H5N1 influenza virus infection

Background

The mechanisms of disease severity caused by H5N1 influenza virus infection remain somewhat unclear. Studies have indicated that a high viral load and an associated hyper inflammatory immune response are influential during the onset of infection. This dysregulated inflammatory response with increased levels of free radicals, such as nitric oxide (NO), appears likely to contribute to disease severity. However, enzymes of the nitric oxide synthase (NOS) family such as the inducible form of NOS (iNOS) generate NO, which serves as a potent anti-viral molecule to combat infection in combination with acute phase proteins and cytokines. Nevertheless, excessive production of iNOS and subsequent high levels of NO during H5N1 infection may have negative effects, acting with other damaging oxidants to promote excessive inflammation or induce apoptosis.

Methodology/Principal Findings

There are dramatic differences in the severity of disease between chickens and ducks following H5N1 influenza infection. Chickens show a high level of mortality and associated pathology, whilst ducks show relatively minor symptoms. It is not clear how this varying pathogenicty comes about, although it has been suggested that an overactive inflammatory immune response to infection in the chicken, compared to the duck response, may be to blame for the disparity in observed pathology. In this study, we identify and investigate iNOS gene expression in ducks and chickens during H5N1 influenza infection. Infected chickens show a marked increase in iNOS expression in a wide range of organs. Contrastingly, infected duck tissues have lower levels of tissue related iNOS expression.

Conclusions/Significance

The differences in iNOS expression levels observed between chickens and ducks during H5N1 avian influenza infection may be important in the inflammatory response that contributes to the pathology. Understanding the regulation of iNOS expression and its role during H5N1 influenza infection may provide insights for the development of new therapeutic strategies in the treatment of avian influenza infection.

Reactive oxygen/nitrogen species and the myocardial cell homeostasis: an ambiguous relationship

The totality of functional cardiomyocytes and an intact cardiac progenitor cell pool are key players in the myocardial cell homeostasis. Perturbation of either one may compromise the structural and functional integrity of the heart and lead to heart failure. Reactive oxygen/nitrogen species (ROS/RNS) are important regulators of cardiomyocyte viability; more recently, the interrelation between ROS and progenitor cell behavior and fate has moved into the spotlight. Increasing evidence suggests not only that ROS participate in the regulation of cardiac progenitor cell survival but also that they likewise affect their functional properties in terms of self-proliferation and differentiation. The apparent dichotomy of ROS/RNS effects with their adaptive and regulatory character on the one hand and their maladaptive and damaging features on the other pose a great challenge in view of the therapeutic exploitation of their role in the regulation of the myocardial cell homeostasis. In this article, mechanisms and potential significance of ROS/RNS action in the regulation of the myocardial cell homeostasis, in particular with respect to the preservation of viable cardiomyocytes and the maintenance of a functional cardiac progenitor cell pool, will be discussed.

Resveratrol improves left ventricular diastolic relaxation in type 2 diabetes by inhibiting oxidative/nitrative stress: in vivo demonstration with magnetic resonance imaging

Resveratrol is a natural phytophenol that exhibits cardioprotective effects. This study was designed to elucidate the mechanisms by which resveratrol protects against diabetes-induced cardiac dysfunction. Normal control (m-Lepr(db)) mice and type 2 diabetic (Lepr(db)) mice were treated with resveratrol orally for 4 wk. In vivo MRI showed that resveratrol improved cardiac function by increasing the left ventricular diastolic peak filling rate in Lepr(db) mice. This protective role is partially explained by resveratrol's effects in improving nitric oxide (NO) production and inhibiting oxidative/nitrative stress in cardiac tissue. Resveratrol increased NO production by enhancing endothelial NO synthase (eNOS) expression and reduced O(2)(·-) production by inhibiting NAD(P)H oxidase activity and gp91(phox) mRNA and protein expression. The increased nitrotyrosine (N-Tyr) protein expression in Lepr(db) mice was prevented by the inducible NO synthase (iNOS) inhibitor 1400W. Resveratrol reduced both N-Tyr and iNOS expression in Lepr(db) mice. Furthermore, TNF-α mRNA and protein expression, as well as NF-κB activation, were reduced in resveratrol-treated Lepr(db) mice. Both Lepr(db) mice null for TNF-α (db(TNF-)/db(TNF-) mice) and Lepr(db) mice treated with the NF-κB inhibitor MG-132 showed decreased NAD(P)H oxidase activity and iNOS expression as well as elevated eNOS expression, whereas m-Lepr(db) mice treated with TNF-α showed the opposite effects. Thus, resveratrol protects against cardiac dysfunction by inhibiting oxidative/nitrative stress and improving NO availability. This improvement is due to the role of resveratrol in inhibiting TNF-α-induced NF-κB activation, therefore subsequently inhibiting the expression and activation of NAD(P)H oxidase and iNOS as well as increasing eNOS expression in type 2 diabetes.

Intragraft gene expression profile associated with the induction of tolerance by allochimeric MHC I in the rat heart transplantation model

The MHC class I allochimeric protein containing donor-type epitopes on recipient-type heavy chains induces indefinite survival of heterotopic cardiac allografts in rats. We analyzed gene expression profile of heart allograft tissue. Mutated peptide [alpha1h1/u]-RT1.Aa that contains donor-type (Wistar Furth, WF; RT1u) immunogenic epitopes displayed on recipient-type (ACI, RT1a) was delivered into ACI recipients of WF hearts at the time of transplantation in addition to a 3 days course of oral cyclosporine. Microarray analysis was performed using Affymetrix Rat 230 2.0 Microarray. Allochimeric molecule treatment caused upregulation of genes involved in structural integrity of heart muscle, downregulation of IL-1beta a key modulator of the immune response, and downregulation of partitioning defective six homolog gamma PAR6, which is involved in T cell polarity, motility, and ability to scan dendritic cells (DC). These indicate that the immunosuppressive function of allochimeric molecule and/or the establishment of allograft tolerance depend on the induction of genes responsible for the heart tissue integrity, the suppression of cytokine pathway(s), and possibly the impairment of T cells mobility and their DC scanning ability. These novel findings may have important clinical implications for inhibition of chronic rejection in transplant recipients.

Does inducible NOS have a protective role against hypoxia/reoxygenation injury in rat heart?

PURPOSE

The present study analyzes the role of the nitric oxide (NO) derived from inducible NO synthase (iNOS) under cardiac hypoxia/reoxygenation situations.

METHODS

For this, we have designed a follow-up study of different parameters of cell and tissue damage in the heart of Wistar rats submitted for 30 min to acute hypobaric hypoxia, with or without prior treatment with the selective iNOS inhibitor N-(3-(aminomethyl)benzyl) acetamidine or 1400W (10 mg/kg). The rats were studied at 0 h, 12 h, and 5 days of reoxygenation, analyzing NO production (NOx), lipid peroxidation, apoptosis, and protein nitration expression and location. This is the first time-course study which analyzes the effects of the iNOS inhibition by 1400W during hypoxia/reoxygenation in the adult rat heart.

RESULTS

The results show that when 1400W was administered before the hypoxic episode, NOx levels fell, while both the lipid peroxidation level and the percentage of apoptotic cells rose throughout the reoxygenation period. Levels of nitrated proteins expression fell only at 12 h post-hypoxia.

CONCLUSIONS

The inhibition of iNOS raises the peroxidative and apoptotic level in the hypoxic heart indicating that this isoform may have a protective effect on this organ against hypoxia/reoxygenation injuries, and challenging the conventional wisdom that iNOS is deleterious under these conditions. These findings could help in the design of new treatments based on NO pharmacology against hypoxia/reoxygenation dysfunctions.