Role of NADPH oxidase in H9c2 cardiac muscle cells exposed to simulated ischaemia-reperfusion

Radical Oxygen Species, Oxidized Low-Density Lipoproteins, and Lectin-like Oxidized Low-Density Lipoprotein Receptor 1: A Vicious Circle in Atherosclerotic Process

Atherosclerosis is a complex condition that involves the accumulation of lipids and subsequent plaque formation in the arterial intima. There are various stimuli, cellular receptors, and pathways involved in this process, but oxidative modifications of low-density lipoprotein (ox-LDL) are particularly important in the onset and progression of atherosclerosis. Ox-LDLs promote foam-cell formation, activate proinflammatory pathways, and induce smooth-muscle-cell migration, apoptosis, and cell death. One of the major receptors for ox-LDL is LOX-1, which is upregulated in several cardiovascular diseases, including atherosclerosis. LOX-1 activation in endothelial cells promotes endothelial dysfunction and induces pro-atherogenic signaling, leading to plaque formation. The binding of ox-LDLs to LOX-1 increases the generation of reactive oxygen species (ROS), which can induce LOX-1 expression and oxidize LDLs, contributing to ox-LDL generation and further upregulating LOX-1 expression. This creates a vicious circle that is amplified in pathological conditions characterized by high plasma levels of LDLs. Although LOX-1 has harmful effects, the clinical significance of inhibiting this protein remains unclear. Further studies both in vitro and in vivo are needed to determine whether LOX-1 inhibition could be a potential therapeutic target to counteract the atherosclerotic process.

Ellagic acid protects against angiotensin II-induced hypertrophic responses through ROS-mediated MAPK pathway in H9c2 cells

The early myocardial response of hypertension is an elevation of angiotensin-II (Ang-II) concentration, leading to heart failure and cardiac hypertrophy. This hypertrophic event of the heart is mediated by the interaction of Ang type 1 receptors (AT-R1), thereby modulating NADPH oxidase activity in cardiomyocytes, which alters redox status in cardiomyocytes. Ellagic acid (EA) has anti-inflammatory and anti-oxidative capacities. Thus, EA has potential preventive effects on cardiovascular diseases and diabetes. In the last decades, because the protective effect of EA on Ang-II-induced hypertrophic responses is unclear, this study aims to investigate the protective effect of EA in cardiomyocytes. H9c2 cells were treated to Ang-II 1 μM for 24 h to induce cellular damage. We found that EA protected against Ang-II-increased cell surface area and pro-hypertrophic gene expression in H9c2. EA reduced Ang-II-caused AT-R1 upregulation, thereby inhibiting oxidative stress NADPH oxidase activation. EA mitigated Ang-II-enhanced p38 and extracellular-signal-regulated kinase (ERK) phosphorylation. Moreover, EA treatment under Ang-II stimulation also reversed NF-κB activity and iNOS expression. This study shows that EA protects against Ang-II-induced myocardial hypertrophy and attenuates oxidative stress through reactive oxygen species-mediated mitogen-activated protein kinase signaling pathways in H9c2 cells. Thus, EA may be an effective compound for preventing Ang-II-induced myocardial hypertrophy.

Do reactive oxygen species damage or protect the heart in ischemia and reperfusion? Analysis on experimental and clinical data

The role of reactive oxygen species (ROS) in ischemic and reperfusion (I/R) injury of the heart has been discussed for more than 40 years. It has been demonstrated that reperfusion triggers a multiple increase in free radical generation in the isolated heart. Antioxidants were found to have the ability to mitigate I/R injury of the heart. However, it is unclear whether their cardioprotective effect truly depends on the decrease of ROS levels in myocardial tissues. Since high doses and high concentrations of antioxidants were experimentally used, it is highly likely that the cardioprotective effect of antioxidants depends on their interaction not only with free radicals but also with other molecules. It has been demonstrated that the antioxidant N-2-mercaptopropionyl glycine or NDPH oxidase knockout abolished the cardioprotective effect of ischemic preconditioning. Consequently, there is evidence that ROS protect the heart against the I/R injury.

Evaluation of fluorene-caused ecotoxicological responses and the mechanism underlying its toxicity in Eisenia fetida: Multi-level analysis of biological organization

Fluorene is an important toxic chemical that exists ubiquitously in the environment, and it has also been suggested to exert potential deleterious effects on soil invertebrates. However, knowledge about the toxic effects of fluorene and its underlying mechanisms of the effects on key soil organism earthworms remains limited. From this view point, this study was undertaken to explore the potential effects of fluorene and its underlying mechanisms in Eisenia fetida at the level of experimental animals, tissue, cell, and molecule. It was concluded that fluorene exerted lethal activity to adult E. fetida on day 14 with the LC₅₀ determined to be 88.61 mg/kg. Fluorene-induced ROS caused oxidative stress in E. fetida, resulting in DNA damage, protein carbonylation, and lipid peroxidation. Moreover, changed antioxidative enzymatic activities, non-enzymatic antioxidative activities, and total antioxidative capacity in E. fetida by fluorene stress are associated with antioxidative and protective effects. High-dose fluorene (> 2.5 mg/kg) exposure significantly caused histopathological lesions including the microstructure of body wall, intestine, and seminal vesicle of earthworms. Also, the reproductive system of E. fetida was clearly disrupted by fluorene stress, leading to poor reproduction ability (decreased cocoon and juvenile production) in earthworms. It is found that E. fetida growth was significantly inhibited when treated with high-dose fluorene, thereby causing normal growth disorders. Additionally, fluorene stress triggered the abnormal mRNA expression related to oxidative stress (e.g., metallothionein and heat shock protein 70), growth (translationally controlled tumour protein), reproduction (annetocin precursor) in E. fetida. Together, both high-dose and long-term exposure elicited more severe poisoning effects on earthworms using the Integrated Biological Response (IBR) index, and E. fetida coelomocyte DNA was the most negatively affected by fluorene stress. This study comprehensively evaluated fluorene-induced toxicity in E. fetida, and its underlying molecular mechanisms mediating the toxic responses have been elucidated. These findings provide valuable data for assessing potential ecological risks posed by fluorene-contaminated soil.

Edaravone Inhibits the Production of Reactive Oxygen Species in Phagocytosis- and PKC-Stimulated Granulocytes from Multiple Sclerosis Patients Edaravone Modulate Oxidative Stress in Multiple Sclerosis

Background

Oxidative stress is associated with the pathogenesis of MS. Edaravone (EDV) has been proposed as a therapeutic resource for central nervous system diseases, and it was effective in reducing oxidative stress. However, the antioxidant mechanisms of EDV are poorly studied.

Objective

This study aimed to evaluate the effects of EDV on resting, phagocytosis, and PKC-activated granulocytes derived from MS patients and a healthy control group.

Methods

The effects of EDV on ROS production in phagocytosis (ROS production in the presence of opsonized particles) and PKC-stimulated granulocytes were evaluated in a luminol-dependent chemiluminescence method. Calphostin C was used in some experiments to compare with those of EDV.

Results

EDV inhibited ROS production in phagocytosis of opsonized particles and PKC-stimulated granulocytes from MS patients and healthy control group. In the presence of calphostin C, the inhibition of ROS production was similar to that observed with EDV.

Conclusion

These findings suggest the involvement of EDV on the ROS-PKC-NOX signaling pathways modulating oxidative stress in MS. EDV represents a promising treatment option to control oxidative innate immune response for MS.

A small molecule inhibitor of Nox2 and Nox4 improves contractile function after ischemia-reperfusion in the mouse heart

The NADPH oxidase enzymes Nox2 and 4, are important generators of Reactive oxygen species (ROS). These enzymes are abundantly expressed in cardiomyocytes and have been implicated in ischemia-reperfusion injury. Previous attempts with full inhibition of their activity using genetically modified animals have shown variable results, suggesting that a selective and graded inhibition could be a more relevant approach. We have, using chemical library screening, identified a new compound (GLX481304) which inhibits Nox 2 and 4 (with IC50 values of 1.25 µM) without general antioxidant effects or inhibitory effects on Nox 1. The compound inhibits ROS production in isolated mouse cardiomyocytes and improves cardiomyocyte contractility and contraction of whole retrogradely (Langendorff) perfused hearts after a global ischemia period. We conclude that a pharmacological and partial inhibition of ROS production by inhibition of Nox 2 and 4 is beneficial for recovery after ischemia reperfusion and might be a promising venue for treatment of ischemic injury to the heart.

Characterization of the Oxidative Stress in Renal Ischemia/Reperfusion-Induced Cardiorenal Syndrome Type 3

In kidney disease (KD), several factors released into the bloodstream can induce a series of changes in the heart, leading to a wide variety of clinical situations called cardiorenal syndrome (CRS). Reactive oxygen species (ROS) play an important role in the signaling and progression of systemic inflammatory conditions, as observed in KD. The aim of the present study was to characterize the redox balance in renal ischemia/reperfusion-induced cardiac remodeling. C57BL/6 male mice were subjected to occlusion of the left renal pedicle, unilateral, for 60 min, followed by reperfusion for 8 and 15 days, respectively. The following redox balance components were evaluated: catalase (CAT), superoxide dismutase (SOD), total antioxidant capacity (FRAP), NADPH oxidase (NOX), nitric oxide synthase (NOS), hydrogen peroxide (H₂O₂), and the tissue bioavailability of nitric oxide (NO) such as S-nitrosothiol (RSNO) and nitrite (NO₂⁻). The results indicated a process of renoprotection in both kidneys, indicated by the reduction of cellular damage and some oxidant agents. We also observed an increase in the activity of antioxidant enzymes, such as SOD, and an increase in NO bioavailability. In the heart, we noticed an increase in the activity of NOX and NOS, together with increased cell damage on day 8, followed by a reduction in protein damage on day 15. The present study concludes that the kidneys and heart undergo distinct processes of damage and repair at the analyzed times, since the heart is a secondary target of ischemic kidney injury. These results are important for a better understanding of the cellular mechanisms involved in CRS.

Molecular insights of NADPH oxidases and its pathological consequences

Reactive oxygen species (ROS), formed by the partial reduction of oxygen, were for a long time considered to be a byproduct of cellular metabolism. Since, increase in cellular levels of ROS results in oxidative stress leading to damage of nucleic acids, proteins, and lipids resulting in numerous pathological conditions; ROS was considered a bane for aerobic species. Hence, the discovery of NADPH oxidases (NOX), an enzyme family that specifically generates ROS as its prime product came as a surprise to redox biologists. NOX family proteins participate in various cellular functions including cell proliferation and differentiation, regulation of genes and protein expression, apoptosis, and host defence immunological response. Balanced expression and activation of NOX with subsequent production of ROS are critically important to regulate various genes and proteins to maintain homeostasis of the cell. However, dysregulation of NOX activation leading to enhanced ROS levels is associated with various pathophysiologies including diabetes, cardiovascular diseases, neurodegenerative diseases, ageing, atherosclerosis, and cancer. Although our current knowledge on NOX signifies its importance in the normal functioning of various cellular pathways; yet the choice of ROS producing enzymes which can tip the scale from homeostasis toward damage, as mediators of biological functions remain an oddity. Though the role of NOX in maintaining normal cellular functions is now deemed essential, yet its dysregulation leading to catastrophic events cannot be denied. Hence, this review focuses on the involvement of NOX enzymes in various pathological conditions imploring them as possible targets for therapies. SIGNIFICANCE OF THE STUDY: The NOXs are multi-subunit enzymes that generate ROS as a prime product. NOX generated ROS are usually regulated by various molecular factors and play a vital role in different physiological processes. The dysregulation of NOX activity is associated with pathological consequences. Recently, the dynamic proximity of NOX enzymes with different molecular signatures of pathologies has been studied extensively. It is essential to identify the precise role of NOX machinery in its niche during the progression of pathology. Although inhibition of NOX could be a promising approach for therapeutic interventions, it is critical to expand the current understanding of NOX's dynamicity and shed light on their molecular partners and regulators.

Protective Effect of a Novel Polysaccharide from Lonicera japonica on Cardiomyocytes of Mice Injured by Hydrogen Peroxide

Lonicera japonica is a traditional Chinese herbal medicine with antioxidation, anti-inflammatory, antibacterial, and immunoregulation functions. A method to isolate polysaccharides from Lonicera japonica (LJP) has been reported previously by our group. We also reported previously that LJP was consisted of 6 types of monosaccharides and had the characteristic absorption of typical polysaccharides. In this study, we investigated the protective effect of LJP on cardiomyocytes of mice injured by hydrogen peroxide (H2O2). The results showed that LJP can increase the cardiomyocyte viability and the activities of the enzyme (SOD, CAT, GSH-Px, AST, CPK, and LDH) in cardiomyocytes of mice injured by hydrogen peroxide. The results of intracellular ROS contents showed that a high dose (40 μg mL-1) of LJP had the best effects on protecting the cardiomyocytes of mice injured by H2O2. In addition, the measurement results of the cardiomyocyte apoptosis and the activity of caspase-3, caspase-8, and caspase-9 in cardiomyocytes confirmed this conclusion from another perspective.

NADPH Oxidase 4 Regulates Inflammation in Ischemic Heart Failure: Role of Soluble Epoxide Hydrolase

Aims: Oxidative stress is implicated in cardiomyocyte cell death and cardiac remodeling in the failing heart. The role of NADPH oxidase 4 (NOX4) in cardiac adaptation to pressure overload is controversial, but its function in myocardial ischemic stress has not been thoroughly elucidated. This study examined the function of NOX4 in the pathogenesis of ischemic heart failure, utilizing mouse models, cell culture, and human heart samples. Results:Nox4^-/- mice showed a protective phenotype in response to permanent left anterior descending coronary artery ligation with smaller infarction area, lower cardiomyocyte cross-sectional area, higher capillary density, and less cell death versus wild-type (WT) mice. Nox4^-/- mice had lower activity of soluble epoxide hydrolase (sEH), a potent regulator of inflammation. Nox4^-/- mice also showed a 50% reduction in the number of infiltrating CD68⁺ macrophages in the peri-infarct zone versus WT mice. Adenoviral overexpression of NOX4 in cardiomyoblast cells increased sEH expression and activity and CCL4 and CCL5 levels; inhibition of sEH activity in NOX4 overexpressing cells attenuated the cytokine levels. Human hearts with ischemic cardiomyopathy showed adverse cardiac remodeling, increased NOX4 and sEH protein expression and CCL4 and CCL5 levels compared with control nonfailing hearts. Innovation and Conclusion: These data from the Nox4^-/- mouse model and human heart tissues show for the first time that oxidative stress from increased NOX4 expression has a functional role in ischemic heart failure. One mechanism by which NOX4 contributes to ischemic heart failure is by increasing inflammatory cytokine production via enhanced sEH activity.

Blockade of Transient Receptor Potential Vanilloid 4 Enhances Antioxidation after Myocardial Ischemia/Reperfusion

Antioxidative stress provides a cardioprotective effect during myocardial ischemia/reperfusion (I/R). Previous research has demonstrated that the blockade of transient receptor potential vanilloid 4 (TRPV4) attenuates myocardial I/R injury. However, the underlying mechanism remains unclear. The current study is aimed at investigating the antioxidative activity of TRPV4 inhibition and elucidating the underlying mechanisms in vitro and ex vivo. We found that the inhibiting TRPV4 by the selective TRPV4 blocker HC-067047 or specific TRPV4-siRNA significantly reduces reactive oxygen species (ROS) and methane dicarboxylic aldehyde (MDA) levels in H9C2 cells exposed to hypoxia/reoxygenation (H/R). Meanwhile, the activity of antioxidative enzymes, particularly superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), is enhanced. Furthermore, after H/R, HC-067047 treatment increases the expression of P-Akt and the translocation of nuclear factor E2-related factor 2 (Nrf2) and related antioxidant response element (ARE) mainly including SOD, GSH-Px, and catalase (CAT). LY294002, an Akt inhibitor, suppresses HC-067047 and specific TRPV4-siRNA-induced Nrf2 expression and its nuclear accumulation. Nrf2 siRNA attenuates HC-067047 and specific TRPV4-siRNA-induced ARE expression. In addition, treatment with LY294002 or Nrf2 siRNA significantly attenuates the antioxidant and anti-injury effects of HC-067047 in vitro. Finally, in experiments on isolated rat hearts, we confirmed the antioxidative stress roles of TRPV4 inhibition during myocardial I/R and the application of exogenous H₂O₂. In conclusion, the inhibition of TRPV4 exerts cardioprotective effects through enhancing antioxidative enzyme activity and expressions via the Akt/Nrf2/ARE pathway.

H2S restores the cardioprotective effects of ischemic post-conditioning by upregulating HB-EGF/EGFR signaling

Hydrogen sulfide (H₂S) reduces ischemia/reperfusion (I/R) injury and apoptosis and restores the cardioprotective effects of ischemic post-conditioning (PC) in aged cardiomyocytes by inhibiting oxidative stress and endoplasmic reticulum stress and increasing autophagy. However, the mechanism is unclear. In the present study, we observed a loss of PC-mediated cardioprotection of aged cardiomyocytes. NaHS (a H₂S donor) exerted significant protective effects against H/R-induced cell damage, apoptosis, production of cleaved caspase-3 and caspase-9, and release of cytochrome c. NaHS also reversed the H/R-induced reduction in cell viability and increased HB-EGF expression, cellular HB-EGF content, and EGFR phosphorylation. Additionally, NaHS increased expression of Bcl-2, c-myc, c-fos and c-jun, and the phosphorylation of ERK1/2, PI3K, Akt and GSK-3β. PC alone did not provide protection to H/R-treated aged cardiomyocytes, but it was significantly restored by supplementation of NaHS. The beneficial effects of NaHS during PC were inhibited by EGFR knockdown, AG1478 (EGFR inhibitor), PD98059 (ERK1/2 inhibitor) or LY294002 (PI3K inhibitor). These results suggest that exogenous H₂S restores PC-mediated cardioprotection by up-regulating HB-EGF/EGFR signaling, which activates the ERK1/2-c-myc (and fos and c-jun) and PI3K-Akt- GSK-3β pathways in the aged cardiomyocytes.

p47phox-Dependent Reactive Oxygen Species Stimulate Nuclear Translocation of the FoxO1 Transcription Factor During Metabolic Inhibition in Cardiomyoblasts

Reactive oxygen species (ROS) control forkhead box O (FOXO) transcription factor activity by influencing their nuclear translocation. However, knowledge of the ROS cellular source(s) involved herein remains scarce. Recently, we have shown p47^phox-dependent activation of ROS-producing NADPH oxidase (NOX) at the nuclear pore in H9c2 rat cardiomyoblasts in response to ischemia. This localizes NOX perfectly to affect protein nuclear translocation, including that of transcription factors. In the current study, involvement of p47^phox-dependent production of ROS in the nuclear translocation of FOXO1 was analyzed in H9c2 cells following 4 h of metabolic inhibition (MI), which mimics the effects of ischemia. Nuclear translocation of FOXO1 was determined by quantitative digital-imaging fluorescence and western blot analysis. Subsequently, the effect of inhibiting p47^phox-dependent ROS production by short hairpin RNA (shRNA) transfection on FOXO1 translocation was analyzed by digital-imaging microscopy. MI induced a significant translocation of FOXO1 into the nucleus. Transfection with p47^phox-shRNA successfully knocked-down p47^phox expression, reduced nuclear nitrotyrosine production, an indirect marker for ROS production, and inhibited the nuclear translocation of FOXO1 following MI. With these results, we show for the first time that nuclear import of FOXO1 induced by MI in H9c2 depends critically on p47^phox-mediated ROS production.

The role of reactive oxygen species in the pathophysiology of cardiovascular diseases and the clinical significance of myocardial redox

Acute and chronic excessive intracellular increase of reactive oxygen species (ROS) is involved in the development and progression of cardiovascular diseases. ROS are by-products of various oxidative physiological and biochemical processes. Sources of ROS are mitochondrial respiration, NADH/NADPH oxidase, xanthine oxidoreductase or the uncoupling of nitric oxide synthase (NOS) in vascular cells. ROS mediate various signaling pathways that underlie cardiovascular pathophysiology. The delicate equilibrium between free-radical generation and antioxidant defense is altered in favor of the former, thus leading to redox imbalance, oxidative stress, and increased cellular injury. An understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of cardiovascular diseases.

NADPH oxidase in brain injury and neurodegenerative disorders

Oxidative stress is a common denominator in the pathology of neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and multiple sclerosis, as well as in ischemic and traumatic brain injury. The brain is highly vulnerable to oxidative damage due to its high metabolic demand. However, therapies attempting to scavenge free radicals have shown little success. By shifting the focus to inhibit the generation of damaging free radicals, recent studies have identified NADPH oxidase as a major contributor to disease pathology. NADPH oxidase has the primary function to generate free radicals. In particular, there is growing evidence that the isoforms NOX1, NOX2, and NOX4 can be upregulated by a variety of neurodegenerative factors. The majority of recent studies have shown that genetic and pharmacological inhibition of NADPH oxidase enzymes are neuroprotective and able to reduce detrimental aspects of pathology following ischemic and traumatic brain injury, as well as in chronic neurodegenerative disorders. This review aims to summarize evidence supporting the role of NADPH oxidase in the pathology of these neurological disorders, explores pharmacological strategies of targeting this major oxidative stress pathway, and outlines obstacles that need to be overcome for successful translation of these therapies to the clinic.

NADPH oxidase activation played a critical role in the oxidative stress process in stable coronary artery disease

OBJECTIVES

The study was designed to investigate the oxidative stress levels of endothelial progenitor cells (EPCs) in stable coronary artery disease (CAD) and to explore the underlying mechanisms of NADPH oxidase activation and subsequent EPCs dysfunction.

METHODS

EPCs were isolated from patients with stable CAD (n=50) and matched healthy volunteers (n=50). NADPH oxidase activation was detected by measuring the expression of each subunit using western blotting and qPCR analyses and the membrane translocation of p47^phox using immunofluorescence. The in vivo angiogenesis capacity was evaluated using immunofluorescence by transplanting EPCs into a rat hind limb ischemia model. The PKC inhibitor GÖ-6983 was used to determine the role of PKC in NADPH oxidase activation.

RESULTS

Oxidative stress level was increased and the in vivo angiogenesis capacity was impaired in EPCs obtained from CAD subjects with the activation of NADPH oxidase. P47^phox membrane translocation increased in CAD group vs controls. These effects were resolved by NADPH oxidase inhibition. Up-regulation of PKCα/β2 was found in EPCs from CAD subjects, PKC inhibition GÖ-6983 could reduce the expression and activity of NADPH oxidation.

CONCLUSIONS

NADPH oxidase activation via p47^phox membrane translocation played a critical role in the initiation and progression of CAD, and the PKCα/β2 signaling pathway might be involved.

Reperfusion injury and reactive oxygen species: The evolution of a concept

Reperfusion injury, the paradoxical tissue response that is manifested by blood flow-deprived and oxygen-starved organs following the restoration of blood flow and tissue oxygenation, has been a focus of basic and clinical research for over 4-decades. While a variety of molecular mechanisms have been proposed to explain this phenomenon, excess production of reactive oxygen species (ROS) continues to receive much attention as a critical factor in the genesis of reperfusion injury. As a consequence, considerable effort has been devoted to identifying the dominant cellular and enzymatic sources of excess ROS production following ischemia-reperfusion (I/R). Of the potential ROS sources described to date, xanthine oxidase, NADPH oxidase (Nox), mitochondria, and uncoupled nitric oxide synthase have gained a status as the most likely contributors to reperfusion-induced oxidative stress and represent priority targets for therapeutic intervention against reperfusion-induced organ dysfunction and tissue damage. Although all four enzymatic sources are present in most tissues and are likely to play some role in reperfusion injury, priority and emphasis has been given to specific ROS sources that are enriched in certain tissues, such as xanthine oxidase in the gastrointestinal tract and mitochondria in the metabolically active heart and brain. The possibility that multiple ROS sources contribute to reperfusion injury in most tissues is supported by evidence demonstrating that redox-signaling enables ROS produced by one enzymatic source (e.g., Nox) to activate and enhance ROS production by a second source (e.g., mitochondria). This review provides a synopsis of the evidence implicating ROS in reperfusion injury, the clinical implications of this phenomenon, and summarizes current understanding of the four most frequently invoked enzymatic sources of ROS production in post-ischemic tissue.

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Reperfusion injury is implicated in a variety of human diseases and disorders.

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Evidence implicating ROS in reperfusion injury continues to grow.

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Several enzymes are candidate sources of ROS in post-ischemic tissue.

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Inter-enzymatic ROS-dependent signaling enhances the oxidative stress caused by I/R.

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Manitoba Lingonberry (Vaccinium vitis-idaea) Bioactivities in Ischemia-Reperfusion Injury

Evidence for the efficacy of dietary interventions in protecting against cardiovascular disease has grown significantly, with flavonoids and anthocyanins receiving special attention. Lingonberry (Vaccinium vitis-idaea L.) is a good source of these compounds, and this study examined the protective effects of wild lingonberry found in Manitoba, Canada, against ischemia-reperfusion (IR) injury. Manitoba lingonberry contained 3793 ± 27 mg gallic acid equiv, 120,501 ± 7651 μmol trolox equiv, and 575 ± 20 mg cyanidin-3-glucoside equiv per 100 g dry weight, which correspond with high total phenolic content, antioxidant activity, and anthocyanin content, respectively. A complete methanolic extract and both anthocyanin-rich and phenolic-rich fractions inhibited apoptosis in H9c2 cells during simulated IR. Lingonberry extract and fractions significantly inhibited several markers of apoptosis induced by IR, including nuclei condensation, caspase-3 activation, and MAP kinase signaling. These results provide the first analysis of Manitoba lingonberry and highlight the mechanistic importance of dietary berry compounds for cardiovascular health.

Diallyl trisulfide protects against high glucose-induced cardiac apoptosis by stimulating the production of cystathionine gamma-lyase-derived hydrogen sulfide

BACKGROUND

Cystathionine-γ-lyase (CSE)-derived hydrogen sulfide (H2S) is a potent cardioprotective agent. We investigated the effects of diallyl trisulfide (DATS) on CSE expression and H2S generation in myocardium and examined whether DATS-mediated H2S generation effectively protects rat heart from diabetes-induced cardiac damage.

METHODS

The correlations between the effects of hyperglycemia and diabetes on CSE expression and the effects of DATS and H2S on hyperglycemia and diabetes were examined in vitro in the cardiomyocyte cell line H9c2 and in vivo in hearts from rats with streptozotocin-induced diabetes mellitus (DM).

RESULTS

Expression of CSE, a catalyst of H2S production, was suppressed in H9c2 cells treated with high glucose (33 mM) and in DM rat hearts. CSE suppression also correlated with a decrease in the activation of the pro-survival protein kinase Akt. Treatment of H9c2 cells with DATS resulted in increased CSE expression and a reduction in apoptosis via a mechanism involving IGF1R/pAkt signaling and by modulating the expression of reactive oxygen species-related enzymes. The role CSE plays in the cardioprotective effects of DATS was further confirmed by CSE inhibition assays including inhibitors and siRNA.

CONCLUSION

DATS produces H2S as efficiently as NaSH and DATS-derived H2S provides effective cardioprotection. Further, our data indicate that H2S plays a major role in the protective effect of DATS against apoptosis of cardiomyocytes.

Necrostatin-1 inhibits Hmgb1-IL-23/IL-17 pathway and attenuates cardiac ischemia reperfusion injury

Ischemia reperfusion (IR) injury is a major issue in cardiac transplantation and inflammatory processes play a major role in myocardial IR injury. Necrostatin-1 (Nec-1) is a small molecule capable of inhibiting RIP1 kinase activity and attenuates inflammation-mediated tissue injury. In our study, hearts of C57Bl/6 mice were flushed and stored in cold Bretschneider solution for 8 h and then transplanted into syngeneic recipients. We found that Nec-1 decreased cardiomyocyte necrosis and recruitment of neutrophils and macrophages. Troponin T (TnT) production on 24 h after myocardial IR injury was reduced by Nec-1 administration. Cardiac output at 60 mmHg of afterload pressure was significantly increased in hearts with Nec-1 administration and the cardiac allograft survival in Nec-1-treated animals was significantly prolonged (MST = 90 days in IR + Nec-1 group, P < 0.05 as compared with IR group, MST = 83.5 days). Nec-1 treatment attenuated ROS generation and increased expression of NOS2 and COX-2. The expression of Hmgb1, IL-23, and IL-17A were also decreased with Nec-1 administration. Furthermore, the decreased TnT expression induced by Nec-1 was abrogated with exogenous Hmgb1 administration. In conclusion, Nec-1 played a protective role in cardiomyocyte IR injury, and this was associated with inhibited Hmgb1-IL-23/IL-17 pathway.

Salidroside improves doxorubicin-induced cardiac dysfunction by suppression of excessive oxidative stress and cardiomyocyte apoptosis

Doxorubicin (DOX) is a potent available antitumor drug; however, its clinical use is limited by the cardiotoxicity. Salidroside (SLD), with strong antioxidative and cytoprotective actions, is of particular interest in the development of antioxidative therapies for oxidative injury in cardiac diseases. Now, the protection and underlying mechanisms of SLD against DOX-induced cardiotoxicity are still unknown. In the present study, we revealed both antioxidative mechanism and Bcl2-dependent survival signaling involved in SLD's protection. We observed that DOX exposure induced mortality elevation, body weight loss, and cardiac dysfunction in mice, increased lactate dehydrogenase leakage and cardiomyocyte apoptosis, but decreased cell viability and size in cardiac tissues and cultured H9c2 cells, respectively, which were effectively antagonized by SLD supplement. We further observed that SLD significantly reduced the intercellular oxidative stress level, partly by inhibiting NOX1 expression and augmenting the expression and activities of the endogenous antioxidative enzymes, catalase, and manganese superoxide dismutase. In addition, SLD treatment upregulated the antiapoptotic Bcl2 and downregulated the proapoptotic Bax and inhibited a downstream pathway of Bcl2/Bax and caspase-3 activity. Our results indicated that SLD effectively protected the cardiomyocytes against DOX-induced cardiotoxicity by suppressing the excessive oxidative stress and activating a Bcl2-mediated survival signaling pathway.

Mild exposure of RIN-5F β-cells to human islet amyloid polypeptide aggregates upregulates antioxidant enzymes via NADPH oxidase-RAGE: an hormetic stimulus

The presence of amyloid aggregates of human islet amyloid polypeptide (hIAPP), a hallmark of type 2 diabetes, contributes to pancreatic β-cell impairment, where oxidative stress plays a key role. A contribution of NADPH oxidase to reactive oxygen species (ROS) generation after cell exposure to micromolar concentrations of hIAPP aggregates has been suggested. However, little is known about β-cells exposure to lower amounts of hIAPP aggregates, similar to those found in human pancreas. Thus, we aimed to investigate the events resulting from RIN-5F cells exposure to nanomolar concentrations of toxic hIAPP aggregates. We found an early and transient rise of NADPH oxidase activity resulting from increased Nox1 expression following the engagement of receptor for advanced glycation end-products (RAGE) by hIAPP aggregates. Unexpectedly, NADPH oxidase activation was not accompanied by a significant ROS increase and the lipoperoxidation level was significantly reduced. Indeed, cell exposure to hIAPP aggregates affected the antioxidant defences, inducing a significant increase of the expression and activity of catalase and glutathione peroxidase. We conclude that exposure of pancreatic β-cells to nanomolar concentrations of hIAPP aggregates for a short time induces an hormetic response via the RAGE-Nox1 axis; the latter stimulates the enzymatic antioxidant defences that preserve the cells against oxidative stress damage.

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Short time exposure of pancreatic β-cells to low hIAPP aggregate amounts is studied.

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NADPH oxidase activity is increased after 3 h treatment with 60 nM hIAPP aggregates.

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RAGE engagement by aggregates increases Nox1 expression.

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Reduced lipoperoxidation and increased antioxidant enzymes were observed.

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A protective hormetic response via RAGE-Nox1 is proposed.

Adiponectin inhibits oxidative/nitrative stress during myocardial ischemia and reperfusion via PKA signaling

The cardioprotective effects of adiponectin (APN) against myocardial ischemia/reperfusion (MI/R) injury are well known. However, comprehension of the mechanisms mediating intracellular APN signaling remains incomplete. We recently demonstrate the antioxidant/antinitrative effects of APN are not dependent on AMPK. Protein kinase A (PKA) has been previously shown to be activated by APN, with uncertain relevance to APN cardiac protection. The current study determined whether the antioxidative/antinitrative effect of APN is mediated by PKA. Administration of APN (2 μg/g) 10 min before reperfusion significantly enhanced cardiac PKA activity, reduced oxidative stress, and decreased infarct size. Knockdown of cardiac PKA expression (PKA-KD) by intramyocardial injection of PKA-siRNAs (>70% suppression) significantly inhibited APN cardioprotection determined by cardiac apoptosis, infarct size, and cardiac function. Moreover, PKA-KD virtually abolished the suppressive effect of APN on MI/R-induced NADPH oxidase overexpression and superoxide overproduction and partially inhibited the effect of APN on nitrative protein modification in MI/R heart. Mechanistically, APN significantly inhibited MI/R-induced IKK/IκB phosphorylation and NF-κB activation, which were blocked in PKA-KD heart. Finally, the PKA-mediated antioxidant/antinitrative and cardioprotective effects of APN are intact in AMPK-deficient mice, suggesting that there is no cross talk between AMPK and PKA signaling in APN cardioprotection. Collectively, we demonstrate for the first time that APN inhibits oxidative/nitrative stress during MI/R via PKA-dependent NF-κB inhibition.

Inhibition of CTRP9, a novel and cardiac-abundantly expressed cell survival molecule, by TNFα-initiated oxidative signaling contributes to exacerbated cardiac injury in diabetic mice

Recently identified as adiponectin (APN) paralogs, C1q/TNF-related proteins (CTRPs) share similar metabolic regulatory functions as APN. The current study determined cardiac expression of CTRPs, their potential cardioprotective function, and investigated whether and how diabetes may regulate cardiac CTRP expression. Several CTRPs are expressed in the heart at levels significantly greater than APN. Most notably, cardiac expression of CTRP9, the closest paralog of APN, exceeds APN by >100-fold. Cardiac CTRP9 expression was significantly reduced in high-fat diet-induced diabetic mice. In H9c2 cells, tumor necrosis factor-alpha (TNF-α) strongly inhibited CTRP9 expression (>60%), and significantly reduced peroxisome proliferator activated receptor-gamma (PPARγ), a known transcription factor promoting adiponectin expression. The inhibitory effect of TNF-α on PPARγ and CTRP9 was reversed by Tiron or rosiglitazone. CTRP9 knockdown significantly enhanced, whereas CTRP9 overexpression significantly attenuated simulated ischemia/reperfusion injury in H9c2 cells. In vivo CTRP9 administration to diabetic mice significantly attenuated NADPH oxidase expression and superoxide generation, reduced infarct size, and improved cardiac function. To the best of our knowledge, this is the first study providing evidence that downregulation of CTRP9, an abundantly expressed and novel cell survival molecule in the heart, by TNF-α-initiated oxidative PPARγ suppression contributes to exacerbated diabetic cardiac injury. Preservation of CTRP9 expression or augmentation of CTRP9-initiated signaling mechanisms may be the potential avenues for ameliorating ischemic diabetic cardiac injury.

Ghrelin protects against cobalt chloride-induced hypoxic injury in cardiac H9c2 cells by inhibiting oxidative stress and inducing autophagy

Ghrelin is a multifunctional peptide that actively protects against cardiovascular ischemic diseases, but the underlying mechanisms are unclear. We used CoCl(2) to mimic hypoxic conditions in cardiac H9c2 cells in order to study the mechanism by which ghrelin protects cardiac myocytes against hypoxic injury by regulating the content of intracellular ROS and autophagy levels. Cell apoptosis and necrosis were evaluated by the flow cytometry assay, Hoechst staining, and LDH activity. Cell viability was detected by the WST-1 assay; ROS levels were assessed using DCFH2-DA; and Nox1, catalase and Mn-SOD were assayed by real-time PCR and activity assays. LC3II was measured by Western blot analysis. We observed that CoCl(2) induced apoptosis and death of H9c2 cells in a dose- and time-dependent manner. This was characterized by an increase in cell apoptosis, LDH activity, ROS content, Nox1 expression, and autophagy levels and a decrease in cell viability, catalase, and Mn-SOD activities. Ghrelin treatment significantly attenuated CoCl(2)-induced hypoxic injury by decreasing cell apoptosis, LDH activity, ROS content, and Nox1 expression and increasing cell viability, autophagy levels, catalase, and Mn-SOD mRNA levels and activities. Further experiments revealed that inhibiting autophagy using 3-MA or AMPK pathway with compound C almost abrogated the induction of ghrelin in autophagy. This was associated with a decrease in cell viability and an increase in LDH activity. Our results indicate that ghrelin protected cardiac myocytes against CoCl(2)-induced hypoxic injury by decreasing Nox1 expression, increasing the expression and activity of endogenous antioxidant enzymes, and inducing protective autophagy in an AMPK-dependent manner.

Paeoniflorin protects myocardial cell from doxorubicin-induced apoptosis through inhibition of NADPH oxidase

Increased intracellular reactive oxygen species (ROS) are involved in doxorubicin (DOX)-induced myocardial cell apoptosis, and paeoniflorin (PEF) has been shown to exert an antioxidant effect. The aim of the present study was to explore the protective effect of PEF on DOX-induced myocardial cell apoptosis and the underlying mechanisms. In cultured H9c2 cells, different concentrations (1, 10, or 100 μmol/L) of PEF was added for 2 h prior to exposure to DOX (5 μmol/L) for 24 h. Cell apoptosis was evaluated by hoechst 33342 staining, and caspase-3 expression and activity. The mRNA and protein expression of NADPH oxidase (NOX) 2 and NOX4 was determined by real-time polymerase chain reaction and Western blot, respectively. Intracellular ROS and NOX activity were measured by assay kit. The results showed that DOX significantly increased myocardial cell apoptosis, increased caspase-3 expression and activity concomitantly with enhanced ROS production, and increased NOX2, NOX4 mRNA and protein expression, and NOX activity. These effects were remarkably inhibited by pretreatment of PEF. Our results suggested that PEF has a protective effect against DOX-induced myocardial cell apoptosis through a mechanism involving a decrease in ROS production by inhibition of NOX2, NOX4 expression, and NOX activity.

Growth hormone secretagogues preserve the electrophysiological properties of mouse cardiomyocytes isolated from in vitro ischemia/reperfusion heart

Ischemic heart diseases often induce cardiac arrhythmia with irregular cardiac action potential (AP). This study aims to demonstrate that GH secretagogues (GHS) ghrelin and its synthetic analog hexarelin can preserve the electrophysiological properties of cardiomyocytes experiencing ischemia/reperfusion (I/R). Isolated hearts from adult male mice underwent 20 min global ischemia followed by 30 min reperfusion using a Langendorff apparatus. Ghrelin (10 nM) or hexarelin (1 nM) was administered in the perfusion solution either 10 min before or after ischemia, termed pre- or posttreatments. Cardiomyocytes isolated from these hearts were used for whole-cell patch clamping to measure AP, voltage-gated L-type calcium current (I(CaL)), transient outward potassium current (I(to)), and sodium current (I(Na)). AP amplitude and duration were significantly decreased by I/R, but GHS treatments maintained their normality. GHS treatments prevented the decrease in I(CaL) and I(Na) after I/R, thereby maintaining AP amplitude. Although the significant increase in I(to) after I/R partially explained the shortened AP duration, the normalization of it by GHS treatments might contribute to the preservation of AP duration. Phosphorylated p38 and c-Jun NH(2)-terminal kinase and the downstream active caspase-9 in the cellular apoptosis pathway were significantly increased after I/R but not when GHS treatments were included, whereas phosphorylation of ERK1/2 associated with cell survival showed increase after I/R and a further increase after GHS treatments by binding to its receptor GHS receptor type 1a. These results suggest GHS can not only preserve the electrophysiological properties of cardiomyocytes after I/R but also inhibit cardiomyocyte apoptosis and promote cell survival by modification of MAPK pathways through activating GHS receptor type 1a.

NADPH oxidases as a source of oxidative stress and molecular target in ischemia/reperfusion injury

Ischemia/reperfusion injury (IRI) is crucial in the pathology of major cardiovascular diseases, such as stroke and myocardial infarction. Paradoxically, both the lack of oxygen during ischemia and the replenishment of oxygen during reperfusion can cause tissue injury. Clinical outcome is also determined by a third, post-reperfusion phase characterized by tissue remodeling and adaptation. Increased levels of reactive oxygen species (ROS) have been suggested to be key players in all three phases. As a second paradox, ROS seem to play a double-edged role in IRI, with both detrimental and beneficial effects. These Janus-faced effects of ROS may be linked to the different sources of ROS or to the different types of ROS that exist and may also depend on the phase of IRI. With respect to therapeutic implications, an untargeted application of antioxidants may not differentiate between detrimental and beneficial ROS, which might explain why this approach is clinically ineffective in lowering cardiovascular mortality. Under some conditions, antioxidants even appear to be harmful. In this review, we discuss recent breakthroughs regarding a more targeted and promising approach to therapeutically modulate ROS in IRI. We will focus on NADPH oxidases and their catalytic subunits, NOX, as they represent the only known enzyme family with the sole function to produce ROS. Similar to ROS, NADPH oxidases may play a dual role as different NOX isoforms may mediate detrimental or protective processes. Unraveling the precise sequence of events, i.e., determining which role the individual NOX isoforms play in the various phases of IRI, may provide the crucial molecular and mechanistic understanding to finally effectively target oxidative stress.

Inhibition of RIP1-dependent necrosis prevents adverse cardiac remodeling after myocardial ischemia-reperfusion in vivo

Accumulating evidence indicates that programmed necrosis plays a critical role in cell death during ischemia-reperfusion. Necrostatin-1 (Nec-1), a small molecule capable of inhibiting a key regulator of programmed necrosis (RIP1), was shown to prevent necrotic cell death in experimental models including cardiac ischemia. However, no functional follow-up was performed and the action of Nec-1 remains unclear. Here, we studied whether Nec-1 inhibits RIP1-dependent necrosis and leads to long-term improvements after ischemia-reperfusion in vivo. Mice underwent 30 min of ischemia and received, 5 min before reperfusion, 3.3 mg/kg Nec-1 or vehicle treatment, followed by reperfusion. Nec-1 administration reduced infarct size to 26.3 ± 1.3% (P = 0.001) compared to 38.6 ± 1.7% in vehicle-treated animals. Furthermore, Nec-1 inhibited RIP1/RIP3 phosphorylation in vivo and significantly reduced necrotic cell death, while apoptotic cell death remained constant. By using MRI, cardiac dimensions and function were assessed before and 28 days after surgery. Nec-1-treated mice displayed less adverse remodeling (end-diastolic volume 63.5 ± 2.8 vs. 74.9 ± 2.8 μl, P = 0.031) and preserved cardiac performance (ejection fraction 45.81 ± 2.05 vs. 36.03 ± 2.37%, P = 0.016). Nec-1 treatment significantly reduced inflammatory influx, tumor necrosis factor-α mRNA levels and oxidative stress levels. Interestingly, this was accompanied by significant changes in the expression signature of oxidative stress genes. Administration of Nec-1 at the onset of reperfusion inhibits RIP1-dependent necrosis in vivo, leading to infarct size reduction and preservation of cardiac function. The cardioprotective effect of Nec-1 highlights the importance of necrotic cell death in the ischemic heart, thereby opening a new direction for therapy in patients with myocardial infarction.

Mesenchymal stem cells secrete multiple cytokines that promote angiogenesis and have contrasting effects on chemotaxis and apoptosis

We have previously shown that mesenchymal stem cells (MSC) improve function upon integration in ischemic myocardium. We examined whether specific cytokines and growth factors produced by MSCs are able to affect angiogenesis, cellular migration and apoptosis. Conditioned media (CM) was prepared by culturing MSC for 48 hours. CM displayed significantly elevated levels of VEGF, Monocyte Chemoattractant Protein-1 (MCP-1), macrophage inflammatory protein-1α (MIP-1α), MIP-1β and monokine induced by IFN-γ (MIG) compared to control media. MSC contained RNA for these factors as detected by RT-PCR. CM was able to induce angiogenesis in canine vascular endothelial cells. MCP-1 and MIP-1α increased cell migration of MSC while VEGF reduced it. H9c2 cells treated with CM under hypoxic conditions for 24 hours displayed a 16% reduction in caspase-3 activity compared to controls. PI 3-kinase γ inhibitor had no effect on controls but reversed the effect of CM on caspase-3 activity. MCP-1 alone mimicked the protective effect of CM while the PI 3-Kγ inhibitor did not reverse the effect of MCP-1. CM reduced phospho-BAD (Ser112) and phospho-Akt (Ser473) while increasing phospho-Akt (Thr308). MCP-1 reduced the level of phospho-Akt (Ser473) while having no effect on the other two; the PI 3-Kγ inhibitor did not alter the MCP-1 effect. ERK 1/2 phosphorylation was reduced in CM treated H9c2 cells, and inhibition of ERK 1/2 reduced the phosphorylation of Akt (Ser473), Akt (Thr308) and Bad (Ser112). In conclusion, MSC synthesize and secrete multiple paracrine factors that are able to affect MSC migration, promote angiogenesis and reduce apoptosis. While both MCP-1 and PI3-kinase are involved in the protective effect, they are independent of each other. It is likely that multiple pro-survival factors in addition to MCP-1 are secreted by MSC which act on divergent intracellular signaling pathways.

Norepinephrine causes epigenetic repression of PKCε gene in rodent hearts by activating Nox1-dependent reactive oxygen species production

Heart disease is the leading cause of death in the United States. Recent studies demonstrate that fetal programming of PKCε gene repression results in ischemia-sensitive phenotype in the heart. The present study tests the hypothesis that increased norepinephrine causes epigenetic repression of PKCε gene in the heart via Nox1-dependent reactive oxygen species (ROS) production. Prolonged norepinephrine treatment increased ROS production in fetal rat hearts and embryonic ventricular myocyte H9c2 cells via a selective increase in Nox1 expression. Norepinephrine-induced ROS resulted in an increase in PKCε promoter methylation at Egr-1 and Sp-1 binding sites, leading to PKCε gene repression. N-acetylcysteine, diphenyleneiodonium, and apocynin blocked norepinephrine-induced ROS production and the promoter methylation, and also restored PKCε mRNA and protein to control levels in vivo in fetal hearts and in vitro in embryonic myocyte cells. Accordingly, norepinephrine-induced ROS production, promoter methylation, and PKCε gene repression were completely abrogated by knockdown of Nox1 in cardiomyocytes. These findings provide evidence of a novel interaction between elevated norepinephrine and epigenetic repression of PKCε gene in the heart mediated by Nox1-dependent oxidative stress and suggest new insights of molecular mechanisms linking the heightened sympathetic activity to aberrant cardioprotection and increased ischemic vulnerability in the heart.

Rutaecarpine prevents hypoxia-reoxygenation-induced myocardial cell apoptosis via inhibition of NADPH oxidases

It is proposed that myocardial cell apoptosis causes ventricular remodeling and heart failure. The aim of the present study was to determine the effects of rutaecarpine (Rut) on hypoxia-reoxygenation (H-R)-induced apoptosis in myocardial cell line H9c2, as well as the underlying mechanisms. Cultured H9c2 cells were exposed to hypoxia for 24 h, followed by 12 h reoxygenation. Rut (in concentrations of 0.1, 1, and 10 µmol/L) was added 1 h prior to H-R. Cell viability and lactate dehydrogenase were measured to evaluate the cell injuries. Apoptosis was evaluated by Hoechst 33258 staining and flow cytometry. NADPH oxidase activity was measured by assay kit; intracellular reactive oxygen species (ROS) generation was detected by 2',7'-dichlorofluorescein diacetate; and Nox2, Nox4, and p47(phox) mRNA and protein expression were analyzed by real-time PCR and Western blotting, respectively. The results showed that H-R significantly decreased cell viability and increased the lactate dehydrogenase release, as well as the apoptotic rate, concomitantly with enhanced NADPH oxidase activity. H-R also upregulated mRNA and protein expressions of Nox2, Nox4, and p47(phox) and increased ROS production. Treatment with Rut markedly reversed these effects introduced by H-R. These results suggest that the protective effects of Rut against H-R-induced myocardial cell injury and apoptosis might, at least partly, be due to the inhibition of the NADPH oxidase - ROS pathway.

NADPH oxidase-dependent oxidative stress in the failing heart: From pathogenic roles to therapeutic approach

Heart failure (HF) occurs when the adaptation mechanisms of the heart fail to compensate for stress factors, such as pressure overload, myocardial infarction, inflammation, diabetes, and cardiotoxic drugs, with subsequent ventricular hypertrophy, fibrosis, myocardial dysfunction, and chamber dilatation. Oxidative stress, defined as an imbalance between reactive oxygen species (ROS) generation and the capacity of antioxidant defense systems, has been authenticated as a pivotal player in the cardiopathogenesis of the various HF subtypes. The family of NADPH oxidases has been investigated as a key enzymatic source of ROS in the pathogenesis of HF. In this review, we discuss the importance of NADPH oxidase-dependent ROS generation in the various subtypes of HF and its implications. A better understanding of the pathogenic roles of NADPH oxidases in the failing heart is likely to provide novel therapeutic strategies for the prevention and treatment of HF.

β-Adrenergic receptors desensitization is not involved in exercise-induced cardiac fatigue: NADPH oxidase-induced oxidative stress as a new trigger

Prolonged strenuous exercise (PSE) induces transient left ventricular (LV) dysfunction. Previous studies suggest that β-adrenergic pathway desensitization could be involved in this phenomenon, but it remains to be confirmed. Moreover, other underlying mechanisms involving oxidative stress have been recently proposed. The present study aimed to evaluate the involvement of both the β-adrenergic pathway and NADPH oxidase (Nox) enzyme-induced oxidative stress in myocardial dysfunction in rats following PSE. Rats were divided into 4 groups: controls (Ctrl), 4-h exercised on treadmill (PSE), and 2 groups in which Nox enzyme was inhibited with apocynin treatment (Ctrl APO and PSE APO, respectively). We evaluated cardiac function in vivo and ex vivo during basal conditions and isoproterenol stress. GSH/GSSG ratio, cardiac troponin I (cTnI) release, and lipid peroxidation (MDA) were evaluated. PSE induced a decrease in LV developed pressure, intrinsic myocardial contractility, and relaxation associated with an increase in plasma cTnI release. Our in vivo and ex vivo results demonstrated no differences in myocardial response to isoproterenol and of effective dose 50 between control and PSE rats. Interestingly, the LV dysfunction was reversed by apocynin treatment. Moreover, apocynin prevented cellular oxidation [GSH/GSSG ratio: PSE APO rats vs. PSE rats in arbitrary units (au): 1.98 ± 0.07 vs. 1.35 ± 0.10; P < 0.001]. However, no differences in MDA were observed between groups. These data suggest that myocardial dysfunction observed after PSE was not due to β-adrenergic receptor desensitization but could be due to a signaling oxidative stress from the Nox enzyme.

Nitric oxide/reactive oxygen species generation and nitroso/redox imbalance in heart failure: from molecular mechanisms to therapeutic implications

Adaptation of the heart to intrinsic and external stress involves complex modifications at the molecular and cellular levels that lead to tissue remodeling, functional and metabolic alterations, and finally to failure depending upon the nature, intensity, and chronicity of the stress. Reactive oxygen species (ROS) have long been considered as merely harmful entities, but their role as second messengers has gradually emerged. At the same time, our comprehension of the multifaceted role of nitric oxide (NO) and the related reactive nitrogen species (RNS) has been upgraded. The tight interlay between ROS and RNS suggests that their imbalance may implicate the impairment in physiological NO/redox-based signaling that contributes to the failing of the cardiovascular system. This review initially provides basic concepts on the role of nitroso/oxidative stress in the pathophysiology of heart failure with a particular focus on sources of ROS/RNS, their downstream targets, and endogenous modulators. Then, the role of NO/redox regulation of cardiomyocyte function, including calcium homeostasis, electrogenesis, and insulin signaling pathways, is described. Finally, an overview of old and emerging therapeutic opportunities in heart failure is presented, focusing on modulation of NO/redox mechanisms and discussing benefits and limitations.

Mouse embryonic fibroblasts from CD38 knockout mice are resistant to oxidative stresses through inhibition of reactive oxygen species production and Ca(2+) overload

CD38 is a multifunctional enzyme that has both ADP-ribosyl cyclase and cADPR hydrolase activities, being capable of cleaving NAD(+) to cyclic ADP ribose (cADPR) and hydrolyzing cADPR to ADPR. It has been reported that there is markedly a reduction of cADPR and elevation of NAD in many tissues from CD38 knockout (CD38(-/-)) mice. Cyclic ADPR is a potent second messenger for intracellular Ca(2+) mobilization, and NAD is a key cellular metabolite for cellular energetic and a crucial regulator for multiple signaling pathways in cells. We hypothesize that CD38 knockout may have a protective effect in oxidative stresses through elevating NAD and decreasing cADPR. In the present study, we observed that the mouse embryonic fibroblasts (MEFs) from CD38(-/-) mice were significantly resistant to oxidative stress such as H(2)O(2) injury and hypoxia/reoxygenation compared with wild type MEFs (WT MEFs). We further found that production of reactive oxygen species (ROS) and concentrations of intracellular Ca(2+) ([Ca(2+)](i)) in CD38(-/-) MEFs were markedly reduced compared with WT MEFs during hypoxia/reoxygenation. Coincidence with these results, a remarkably lower mRNA level of Nox1, one of the enzymes responsible for ROS generation, was observed in CD38(-/-) MEFs. Furthermore, we found that transcription of Nox1 mRNA in WT MEFs could be elevated by calcium ionophore ionomycin in a dose-dependent manner, indicating that the expression of Nox1 mRNA can be regulated by elevation of intracellular [Ca(2+)]. Therefore we concluded that CD38(-/-) MEFs are resistant to oxidative stresses through inhibiting intracellular Ca(2+) overload and ROS production which may be regulated by Ca(2+)-mediated inhibition of Nox1 expression. Our data should provide an insight for elucidating the roles of CD38 in oxidative stresses and a novel perspective of dealing with the ischemia/reperfusion-related diseases.

The role of NOX enzymes in ethanol-induced oxidative stress and apoptosis in mouse embryos

Reactive oxygen species (ROS) play an important role in ethanol-induced apoptosis and teratogenesis. However, the major sources of ROS in ethanol-exposed embryos have remained undefined. This study was conducted to determine the role of NADPH oxidase (NOX) in ethanol-induced oxidative stress and apoptosis in mouse embryos. Analyses of mRNA expression indicated that ethanol treatment resulted in a significant increase in mRNA expression of NOX catalytic subunit Duox-1 in gestational day 9 (GD 9:0) mouse embryos. Ethanol exposure also resulted in significant increases in mRNA expression of NOX regulatory subunits, p22phox, p67phox, NOXA1 and NOXO1. In addition, a significant increase in NOX enzyme activity was found in the ethanol-exposed embryos as compared to controls. Co-treatment with the NOX inhibitor, diphenyleneiodonium (DPI), significantly prevented ethanol-induced increases in NOX enzyme activity, ROS generation and oxidative DNA damage in ethanol-exposed embryos. DPI treatment also resulted in a reduction in caspase-3 activation, decreased caspase-3 activity and diminished prevalence of apoptosis in ethanol-exposed embryos. These results support the hypothesis that NOX is a critical source of ROS in ethanol-exposed embryos and that it plays an important role in ethanol-induced oxidative stress and pathogenesis.

Cardioprotection by metabolic shut-down and gradual wake-up

Mitochondria play a critical role in cardiac function, and are also increasingly recognized as end effectors for various cardioprotective signaling pathways. Mitochondria use oxygen as a substrate, so by default their respiration is inhibited during hypoxia/ischemia. However, at reperfusion a surge of oxygen and metabolic substrates into the cell is thought to lead to rapid reestablishment of respiration, a burst of reactive oxygen species (ROS) generation and mitochondrial Ca(2+) overload. Subsequently these events precipitate opening of the mitochondrial permeability transition (PT) pore, which leads to myocardial cell death and dysfunction. Given that mitochondrial respiration is already inhibited during hypoxia/ischemia, it is somewhat surprising that many respiratory inhibitors can improve recovery from ischemia-reperfusion (IR) injury. In addition ischemic preconditioning (IPC), in which short non-lethal cycles of IR can protect against subsequent prolonged IR injury, is known to lead to endogenous inhibition of several respiratory complexes and glycolysis. This has led to a hypothesis that the wash-out of inhibitors or reversal of endogenous inhibition at reperfusion may afford protection by facilitating a more gradual wake-up of mitochondrial function, thereby avoiding a burst of ROS and Ca(2+) overload. This paper will review the evidence in support of this hypothesis, with a focus on inhibition of each of the mitochondrial respiratory complexes.