Nitric oxide donors protect murine myocardium against infarction via modulation of mitochondrial permeability transition

New advances in the protective mechanisms of acidic pH after ischemia: Participation of NO

BACKGROUND

It has been previously demonstrated that the maintenance of ischemic acidic pH or the delay of intracellular pH recovery at the onset of reperfusion decreases ischemic-induced cardiomyocyte death.

OBJECTIVE

To examine the role played by nitric oxide synthase (NOS)/NO-dependent pathways in the effects of acidic reperfusion in a regional ischemia model.

METHODS

Isolated rat hearts perfused by Langendorff technique were submitted to 40 min of left coronary artery occlusion followed by 60 min of reperfusion (IC). A group of hearts received an acid solution (pH = 6.4) during the first 2 min of reperfusion (AR) in absence or in presence of l-NAME (NOS inhibitor). Infarct size (IS) and myocardial function were determined. In cardiac homogenates, the expression of P-Akt, P-endothelial and inducible isoforms of NOS (P-eNOS and iNOS) and the level of 3-nitrotyrosine were measured. In isolated cardiomyocytes, the intracellular NO production was assessed by confocal microscopy, under control and acidic conditions. Mitochondrial swelling after Ca2+ addition and mitochondrial membrane potential (Δψ) were also determined under control and acidosis.

RESULTS

AR decreased IS, improved postischemic myocardial function recovery, increased P-Akt and P-eNOS, and decreased iNOS and 3-nitrotyrosine. NO production increased while mitochondrial swelling and Δψ decreased in acidic conditions. l-NAME prevented the beneficial effects of AR.

CONCLUSIONS

Our data strongly supports that a brief acidic reperfusion protects the myocardium against the ischemia-reperfusion injury through eNOS/NO-dependent pathways.

Treatment with XMU-MP-1 erases hyperglycaemic memory in hearts of diabetic mice

Hyperglycaemic memory refers to the damages occurred under early hyperglycaemic environment in organs of diabetic patients persisting after intensive glycaemic control. Mammalian sterile 20-like kinase 1 (Mst1) contributes to the development of diabetic cardiomyopathy. Here, we investigated the role of Mst1 in hyperglycaemic memory and test the effect of XMU-MP-1, a Mst1 inhibitor, on hyperglycaemic memory in hearts. Eight weeks after induction of type 1 diabetes by injection with streptozotocin (STZ) in mice, glycaemic control was obtained by means of insulin treatment and maintained for 4 additional weeks. In the diabetic mice, insulin treatment alone did not reduce phosphorylation of Mst1 or improve cardiac function. Treatment with XMU-MP-1 alone immediately after induction of diabetes for 12 weeks did not improve myocardial function in mice. But treatment with XMU-MP-1 for the later 4 weeks relieved myocardial dysfunction when glycaemic control was obtained by insulin treatment simultaneously. Mst1 deficiency and glycaemic control synergistically improved myocardial function and reduced apoptosis in myocardium of diabetic mice. Mechanistically, when Mst1 was deficient or inhibited by XMU-MP-1, AMPK was activated and mitochondrial dysfunction was attenuated. In vitro, treatment with AMPK activator reversed the detrimental effects of Mst1 overexpression in cultured cardiomyocytes. XMU-MP-1 might thus be envisaged as a complement for insulin treatment against diabetic cardiomyopathy.

A review of myocardial ischaemia/reperfusion injury: Pathophysiology, experimental models, biomarkers, genetics and pharmacological treatment

Cardiovascular diseases are known to be the most fatal diseases worldwide. Ischaemia/reperfusion (I/R) injury is at the centre of the pathology of the most common cardiovascular diseases. According to the World Health Organization estimates, ischaemic heart disease is the leading global cause of death, causing more than 9 million deaths in 2016. After cardiovascular events, thrombolysis, percutaneous transluminal coronary angioplasty or coronary bypass surgery are applied as treatment. However, after restoring coronary blood flow, myocardial I/R injury may occur. It is known that this damage occurs due to many pathophysiological mechanisms, especially increasing reactive oxygen types. Besides causing cardiomyocyte death through multiple mechanisms, it may be an important reason for affecting other cell types such as platelets, fibroblasts, endothelial and smooth muscle cells and immune cells. Also, polymorphonuclear leukocytes are associated with myocardial I/R damage during reperfusion. This damage may be insufficient in patients with co-morbidity, as it is demonstrated that it can be prevented by various endogenous antioxidant systems. In this context, the resulting data suggest that optimal cardioprotection may require a combination of additional or synergistic multi-target treatments. In this review, we discussed the pathophysiology, experimental models, biomarkers, treatment and its relationship with genetics in myocardial I/R injury. SIGNIFICANCE OF THE STUDY: This review summarized current information on myocardial ischaemia/reperfusion injury (pathophysiology, experimental models, biomarkers, genetics and pharmacological therapy) for researchers and reveals guiding data for researchers, especially in the field of cardiovascular system and pharmacology.

Exercise training suppresses Mst1 activation and attenuates myocardial dysfunction in mice with type 1 diabetes

Our study was to test the effects of aerobic exercise on myocardial function in mice with type 1 diabetes and investigate the underlying mechanism associated with mammalian sterile 20-like kinase 1 (Mst1). Wild-type mice and Mst1(-/-) mice were injected with streptozotocin to induce diabetes and given moderate-intensity exercise for 12 weeks. Phosphorylation of Mst1 was significantly enhanced in the left ventricles of diabetic mice, which was reversed by exercise training. Exercise training or Mst1 deficiency improved myocardial function and reduced myocardial fibrosis in diabetic mice. Exercise training or Mst1 deficiency reduced TUNEL-positive cells and caspase-3 activity in the myocardium of diabetic mice. Exercise training or Mst1 deficiency abated oxidative stress and reduced mitochondrial reactive oxygen species formation, attenuated mitochondrial swelling, and enhanced mitochondrial adenosine triphosphate formation and mitochondrial membrane potential in the myocardium of diabetic mice. Exercise training or Mst1 deficiency suppressed inflammation in the myocardium of diabetic mice. Furthermore, exercise training did not provide further protection in Mst1 knockout mice in diabetes. In conclusion, chronic exercise training attenuated myocardial dysfunction in mice with type 1 diabetes, at least in part, through suppressing Mst1 activation.

Postconditioning with Nitrates Protects Against Myocardial Reperfusion Injury: A New Use for an Old Pharmacological Agent

Early reperfusion remains the key therapy to salvage viable myocardium and must be applied as soon as possible following an acute myocardial infarction (AMI) to attenuate the ischemic insult. However, reperfusion injury may develop following reintroduction of blood and oxygen to vulnerable myocytes, which results in more severe cell death than in the preceding ischemic episode. Ischemic postconditioning (I-PostC) provides a cardioprotective effect in combination with pharmacological agents. Although nitrates have been tested in many experimental and clinical studies of acute AMI to evaluate the cardioprotective effect, few investigations have been focused on nitrates postconditioning in patients undergoing percutaneous coronary intervention (PCI). This review presents the manifestations of myocardial reperfusion injury (RI) and potential mechanisms underlying it, and provides the mechanisms involved in the cardioprotection of I-PostC. We also present a new therapeutic approach to attenuate RI by use of an ‘old’ agent – nitrates – in AMI patients.

Exercise training protects the heart against ischemia-reperfusion injury: A central role for mitochondria?

Ischemic heart disease is one of the main causes of morbidity and mortality worldwide. Physical exercise is an effective lifestyle intervention to reduce the risk factors for cardiovascular disease and also to improve cardiac function and survival in patients with ischemic heart disease. Among the strategies that contribute to reduce heart damages during ischemia and reperfusion, regular physical exercise is efficient both in rodent experimental models and in humans. However, the cellular and molecular mechanisms of the cardioprotective effects of exercise remain unclear. During ischemia and reperfusion, mitochondria are crucial players in cell death, but also in cell survival. Although exercise training can influence mitochondrial function, the consequences on heart sensitivity to ischemic insults remain elusive. In this review, we describe the effects of physical activity on cardiac mitochondria and their potential key role in exercise-induced cardioprotection against ischemia-reperfusion damage. Based on recent scientific data, we discuss the role of different pathways that might help to explain why mitochondria are a key target of exercise-induced cardioprotection.

Cardioprotection of benzolamide in a regional ischemia model: Role of eNOS/NO

BACKGROUND

Recent studies from our laboratory show the cardioprotective action of benzolamide (BZ, carbonic anhydrase inhibitor) against ischemia-reperfusion injury. However, the mechanisms involved have not been fully elucidated.

OBJECTIVE

To examine the participation of the endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) in the effects of BZ in a model of regional ischemia.

METHODS

Isolated rat hearts perfused by Langendorff technique were submitted to 40 min of coronary artery occlusion followed by 60 min of reperfusion (IC). Other hearts received BZ during the first 10 min of reperfusion in absence or presence of L-NAME, NOS inhibitor. The infarct size (IS) and the post-ischemic recovery of myocardial function were measured. Oxidative/nitrosative damage were assessed by reduced glutathione (GSH) content, thiobarbituric acid reactive substances (TBARS) and 3-nitrotyrosine levels. The expression of phosphorylated forms of Akt, p38MAPK and eNOS, and the concentration of inducible nitric oxide synthase (iNOS) were also determined.

RESULTS

BZ significantly decreased IS (6.2 ± 0.5% vs. 34 ± 4%), improved post-ischemic contractility, preserved GSH levels and diminished TBARS and 3-nitrotyrosine. In IC hearts, P-Akt, P-p38MAPK and P-eNOS decreased and iNOS increased. After BZ addition the levels of P-kinases and P-eNOS increased and iNOS decreased. Except for P-Akt, P-p38MAPK and iNOS, the effects of BZ were abolished by L-NAME.

CONCLUSIONS

Our data demonstrate that the treatment with BZ at the onset of reperfusion was effective to reduce cell death, contractile dysfunction and oxidative/nitrosative damage produced by coronary artery occlusion. These BZ-mediated beneficial actions appear mediated by eNOS/NO-dependent pathways.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.

Roles of Endoplasmic Reticulum Stress in NECA-Induced Cardioprotection against Ischemia/Reperfusion Injury

OBJECTIVE

This study aimed to investigate whether the nonselective A2 adenosine receptor agonist NECA induces cardioprotection against myocardial ischemia/reperfusion (I/R) injury via glycogen synthase kinase 3β (GSK-3β) and the mitochondrial permeability transition pore (mPTP) through inhibition of endoplasmic reticulum stress (ERS).

METHODS AND RESULTS

H9c2 cells were exposed to H2O2 for 20 minutes. NECA significantly prevented H2O2-induced TMRE fluorescence reduction, indicating that NECA inhibited the mPTP opening. NECA blocked H2O2-induced GSK-3β phosphorylation and GRP94 expression. NECA increased GSK-3β phosphorylation and decreased GRP94 expression, which were prevented by both ERS inductor 2-DG and PKG inhibitor KT5823, suggesting that NECA may induce cardioprotection through GSK-3β and cGMP/PKG via ERS. In isolated rat hearts, both NECA and the ERS inhibitor TUDCA decreased myocardial infarction, increased GSK-3β phosphorylation, and reversed GRP94 expression at reperfusion, suggesting that NECA protected the heart by inhibiting GSK-3β and ERS. Transmission electron microscopy showed that NECA and TUDCA reduced mitochondrial swelling and endoplasmic reticulum expansion, further supporting that NECA protected the heart by preventing the mPTP opening and ERS.

CONCLUSION

These data suggest that NECA prevents the mPTP opening through inactivation of GSK-3β via ERS inhibition. The cGMP/PKG signaling pathway is responsible for GSK-3β inactivation by NECA.

Electro-pharmacological profiles of two brain mitoplast anion channels: Inferences from single channel recording

We have characterized the conduction and blocking properties of two different chloride channels from brain mitochondrial inner membranes after incorporation into planar lipid bilayers. Our experiments revealed the existence of channels with a mean conductance of 158 ± 7 and 301 ± 8 pS in asymmetrical 200 mM cis/50 mM trans KCl solutions. We determined that the channels were ten times more permeable for Cl⁻ than for K⁺, calculated from the reversal potential using the Goldman-Hodgkin-Katz equation. The channels were bell-shaped voltage dependent, with maximum open probability 0.9 at ± 20 mV. Two mitochondrial chloride channels were blocked after the addition of 10 µM DIDS. In addition, 158 pS chloride channel was blocked by 300 nM NPPB, acidic pH and 2.5 mM ATP, whereas the 301 pS chloride channel was blocked by 600 µM NPPB but not by acidic pH or ATP. Gating and conducting behaviors of these channels were unaffected by Ca²⁺. These results demonstrate that the 158 pS anion channel present in brain mitochondrial inner membrane, is probably identical to IMAC and 301 pS Cl channel displays different properties than those classically described for mitochondrial anion channels.

Research review on the pharmacological effects of astragaloside IV

Astragalus membranaceus Bunge has been used to treat numerous diseases for thousands of years. As the main active substance of Astragalus membranaceus Bunge, astragaloside IV (AS-IV) also demonstrates the potent protective effect on focal cerebral ischemia/reperfusion, cardiovascular disease, pulmonary disease, liver fibrosis, and diabetic nephropathy. Based on studies published during the past several decades, the current state of AS-IV research and the pharmacological effects are detailed, elucidated, and summarized. This review systematically summarizes the pharmacological effects, metabolism mechanism, and the toxicity of AS-IV. AS-IV has multiple pharmacologic effects, including anti-inflammatory, antifibrotic, antioxidative stress, anti-asthma, antidiabetes, immunoregulation, and cardioprotective effect via numerous signaling pathways. According to the existing studies and clinical practices, AS-IV possesses potential for broad application in many diseases.

Identification of "Multiple Components-Multiple Targets-Multiple Pathways" Associated with Naoxintong Capsule in the Treatment of Heart Diseases Using UPLC/Q-TOF-MS and Network Pharmacology

Naoxintong capsule (NXT) is a commercial medicinal product approved by the China Food and Drug Administration which is used in the treatment of stroke and coronary heart disease. However, the research on the composition and mechanism of NXT is still lacking. Our research aimed to identify the absorbable components, potential targets, and associated pathways of NXT with network pharmacology method. We explored the chemical compositions of NXT based on UPLC/Q-TOF-MS. Then, we used the five principles of drug absorption to identify absorbable ingredients. The databases of PharmMapper, Universal Protein, and the Molecule Annotation System were used to predict the main targets and related pathways. By the five principles of drug absorption as a judgment rule, we identified 63 compositions that could be absorbed in the blood in all 81 chemical compositions. Based on the constructed networks by the significant regulated 123 targets and 77 pathways, the main components that mediated the efficacy of NXT were organic acids, saponins, and tanshinones. Radix Astragali was the critical herbal medicine in NXT, which contained more active components than other herbs and regulated more targets and pathways. Our results showed that NXT had a therapeutic effect on heart diseases through the pattern “multiple components-multiple targets-multiple pathways.”

Preconditioning c-Kit-positive Human Cardiac Stem Cells with a Nitric Oxide Donor Enhances Cell Survival through Activation of Survival Signaling Pathways

Cardiac stem cell therapy has shown very promising potential to repair the infarcted heart but is severely limited by the poor survival of donor cells. Nitric oxide (NO) has demonstrated cytoprotective properties in various cells, but its benefits are unknown specifically for human cardiac stem cells (hCSCs). Therefore, we investigated whether pretreatment of hCSCs with a widely used NO donor, diethylenetriamine nitric oxide adduct (DETA-NO), promotes cell survival. Results from lactate dehydrogenase release assays showed a dose- and time-dependent attenuation of cell death induced by oxidative stress after DETA-NO preconditioning; this cytoprotective effect was abolished by the NO scavenger. Concomitant up-regulation of several cell signaling molecules after DETA-NO preconditioning was observed by Western blotting, including elevated phosphorylation of NRF2, NFκB, STAT3, ERK, and AKT, as well as increased protein expression of HO-1 and COX2. Furthermore, pharmaceutical inhibition of ERK, STAT3, and NFκB activities significantly diminished NO-induced cytoprotection against oxidative stress, whereas inhibition of AKT or knockdown of NRF2 only produced a minor effect. Blocking PI3K activity or knocking down COX2 expression did not alter the protective effect of DETA-NO on cell survival. The crucial roles of STAT3 and NFκB in NO-mediated signaling pathways were further confirmed by stable expression of gene-specific shRNAs in hCSCs. Thus, preconditioning hCSCs with DETA-NO promotes cell survival and resistance to oxidative stress by activating multiple cell survival signaling pathways. These results will potentially provide a simple and effective strategy to enhance survival of hCSCs after transplantation and increase their efficacy in repairing infarcted myocardium.

Ischemic postconditioning altered microRNAs in human valve replacement

BACKGROUND

Although the involvement of microRNAs (miRNAs) has been intensively studied in myocardial infarction, there is no report on the regulation of miRNAs by ischemic postconditioning in patients undergoing cardiac surgery. We aim to explore the regulation of miRNAs by ischemic postconditioning in double valve replacement.

MATERIALS AND METHODS

In this prospective, controlled clinical study, consecutive 30 patients undergoing double valve replacement were enrolled. The patients were randomized into two groups, namely an ischemic postconditioning (IPO) group (n = 15) and a control (CON) group (n = 15). For ethical considerations, samples of right atrial muscle were harvested, respectively, 10 min before cardiopulmonary bypass (pre-CPB) and 5 min after aortic declamping (post-CPB) for analysis of miRNAs, genes and apoptosis.

RESULTS

Compared with the CON group, miR-1 was downregulated, whereas miR-21 was upregulated, and BCL2 messenger RNA (mRNA) was upregulated, whereas BAX mRNA and programmed cell death 4 mRNA remained unchanged in the IPO group. Likewise, a significant increase in BCL2 protein and a striking decrease in BAX protein were observed in the IPO group when compared with those in the CON group. The IPO group showed a significantly smaller increase of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive myocytes after CPB than CON group.

CONCLUSIONS

Ischemic postconditioning could regulate miR-1, miR-21, and downstream effectors and resulted in actual attenuation of apoptosis in patients undergoing valvular heart surgery.

Vasopressin attenuates ischemia-reperfusion injury via reduction of oxidative stress and inhibition of mitochondrial permeability transition pore opening in rat hearts

Aim of this study was to investigate the involvement of the mitochondrial permeability transition pore (MPTP) and oxidative stress in the cardioprotective effect of vasopressin (AVP) on ischemia/reperfusion (I/R) injury. Anesthetized male wistar rats were subjected to regional 30 min ischemia and 120 min reperfusion and randomly divided into nine groups: (1) Control; saline was administered intravenously before ischemia, (2) vasopressin was administrated 10 min prior to ischemia, (3, 4) Atractyloside as MPTP opener, was injected 5 min prior to reperfusion without and with vasopressin, (5, 6) Cyclosporine A as a MPTP closer, was injected 5 min prior to reperfusion without and with vasopressin, (7) mitochondria were isolated from control group and CaCl2 was added as MPTP opener and swelling inducer, (8) isolated mitochondria from Control hearts was incubated with Cyclosporine A before adding the CaCl2 (9) CaCl2 was added to isolated mitochondria from vasopressin group. Infusion of vasopressin decreased infarct size (18.6±1.7% vs. control group 37.6±2.4%), biochemical parameters [LDH (Lactate Dehydrogenase), CK-MB (Creatine Kinase-MB) and MDA (Malondialdehyde) plasma levels, PAB (Prooxidant-antioxidant balance)] compared to control group. Atactyloside suppressed the cardioprotective effect of vasopressin (32.5±1.9% vs. 18.6±1.7%) but administration of the Cyclosporine A without and with vasopressin significantly reduced infarct size to 17.7±4% (P<0.001) and 22.7±3% (P<0.01) respectively, vs. 37.6±2.4% in control group. Also, vasopressin, similar to Cyclosporine A, led to decrease in CaCl2-induced swelling. It seems that vasopressin through antioxidant effect and MPTP inhibition has created a cardioprotection against ischemia/reperfusion injuries.

Mitochondria as key targets of cardioprotection in cardiac ischemic disease: role of thyroid hormone triiodothyronine

Ischemic heart disease is the major cause of mortality and morbidity worldwide. Early reperfusion after acute myocardial ischemia has reduced short-term mortality, but it is also responsible for additional myocardial damage, which in the long run favors adverse cardiac remodeling and heart failure evolution. A growing body of experimental and clinical evidence show that the mitochondrion is an essential end effector of ischemia/reperfusion injury and a major trigger of cell death in the acute ischemic phase (up to 48–72 h after the insult), the subacute phase (from 72 h to 7–10 days) and chronic stage (from 10–14 days to one month after the insult). As such, in recent years scientific efforts have focused on mitochondria as a target for cardioprotective strategies in ischemic heart disease and cardiomyopathy. The present review discusses recent advances in this field, with special emphasis on the emerging role of the biologically active thyroid hormone triiodothyronine (T3).

Isoflurane protects the myocardium against ischemic injury via the preservation of mitochondrial respiration and its supramolecular organization

BACKGROUND

Isoflurane has been demonstrated to limit myocardial ischemic injury. This effect is hypothesized to be mediated in part via effects on mitochondria. We investigated the hypothesis that isoflurane maintains mitochondrial respiratory chain functionality, in turn limiting mitochondrial damage and mitochondrial membrane disintegration during myocardial ischemic injury.

METHODS

Mice (9-12 weeks of age) received isoflurane (1.0 minimum alveolar concentration) 36 hours before a 30-minute coronary artery occlusion that was followed by 24 hours of reperfusion. Cardiac mitochondria were isolated at a time point corresponding to 4 hours of reperfusion. 2,3,5-Triphenyltetrazoliumchloride staining was used to determine myocardial infarct size. Mitochondrial respiratory chain functionality was investigated using blue native polyacrylamide gel electrophoresis, as well as specific biochemical assays. Mitochondrial lipid peroxidation was quantified via the formation of malondialdehyde; mitochondrial membrane integrity was assessed by Ca-induced swelling. Protein identification was achieved via liquid chromatography mass spectrometry/mass spectrometry.

RESULTS

Thirty-one mice were studied. Mice receiving isoflurane displayed a reduced myocardial infarct size (P = 0.0011 versus ischemia/reperfusion [I/R]), accompanied by a preserved activity of respiratory complex III (P = 0.0008 versus I/R). Isoflurane stabilized mitochondrial supercomplexes consisting of oligomers from complex III/IV (P = 0.0086 versus I/R). Alleviation of mitochondrial damage after isoflurane treatment was further demonstrated as decreased malondialdehyde formation (P = 0.0019 versus I/R) as well as a diminished susceptibility to Ca-induced swelling (P = 0.0010 versus I/R).

CONCLUSIONS

Our findings support the hypothesis that isoflurane protects the heart from ischemic injury by maintaining the in vivo functionality of the mitochondrial respiratory chain. These effects may result in part from the preservation of mitochondrial supramolecular organization and minimized oxidative damage, circumventing the loss of mitochondrial membrane integrity.

Mitochondrial dysfunction in uremic cardiomyopathy

Uremic cardiomyopathy (UCM) is characterized by metabolic remodelling, compromised energetics, and loss of insulin-mediated cardioprotection, which result in unsustainable adaptations and heart failure. However, the role of mitochondria and the susceptibility of mitochondrial permeability transition pore (mPTP) formation in ischemia-reperfusion injury (IRI) in UCM are unknown. Using a rat model of chronic uremia, we investigated the oxidative capacity of mitochondria in UCM and their sensitivity to ischemia-reperfusion mimetic oxidant and calcium stressors to assess the susceptibility to mPTP formation. Uremic animals exhibited a 45% reduction in creatinine clearance (P < 0.01), and cardiac mitochondria demonstrated uncoupling with increased state 4 respiration. Following IRI, uremic mitochondria exhibited a 58% increase in state 4 respiration (P < 0.05), with an overall reduction in respiratory control ratio (P < 0.01). Cardiomyocytes from uremic animals displayed a 30% greater vulnerability to oxidant-induced cell death determined by FAD autofluorescence (P < 0.05) and reduced mitochondrial redox state on exposure to 200 μM H2O2 (P < 0.01). The susceptibility to calcium-induced permeability transition showed that maximum rates of depolarization were enhanced in uremia by 79%. These results demonstrate that mitochondrial respiration in the uremic heart is chronically uncoupled. Cardiomyocytes in UCM are characterized by a more oxidized mitochondrial network, with greater susceptibility to oxidant-induced cell death and enhanced vulnerability to calcium-induced mPTP formation. Collectively, these findings indicate that mitochondrial function is compromised in UCM with increased vulnerability to calcium and oxidant-induced stressors, which may underpin the enhanced predisposition to IRI in the uremic heart.

Pharmacological postconditioning with tanshinone IIA attenuates myocardial ischemia-reperfusion injury in rats by activating the phosphatidylinositol 3-kinase pathway

Tanshinone IIA, one of the active ingredients in the Chinese medicine Danshen, is cardioprotective when applied prior to sustained myocardial ischemia. The present study aimed to investigate whether pharmacological postconditioning with tanshinone IIA attenuates myocardial ischemia-reperfusion injury when applied prior to prolonged reperfusion following a sustained ischemia. A total of 88 Sprague-Dawley rats received 30 min myocardial ischemia followed by 5 or 120 min reperfusion. Compared with the ischemia-reperfusion model group, the group that received an intravenous injection of 10 mg/kg tanshinone IIA prior to reperfusion had a reduced myocardial infarct size, higher levels of phospho-Akt and phospho-endothelial nitric oxide synthase and less reduction in the optical density of the mitochondria at 540 nm, indicating that the mitochondrial permeability transition (MPT) was attenuated. The cardioprotective effect conferred by tanshinone IIA was abolished by LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K). These results demonstrate that tanshinone IIA postconditioning protects the myocardium from ischemia-reperfusion injury through the PI3K/Akt pathway, and the MPT may be also involved in this process.

Role of vascular oxidative stress in obesity and metabolic syndrome

Obesity is associated with vascular diseases that are often attributed to vascular oxidative stress. We tested the hypothesis that vascular oxidative stress could induce obesity. We previously developed mice that overexpress p22phox in vascular smooth muscle, tg(sm/p22phox), which have increased vascular ROS production. At baseline, tg(sm/p22phox) mice have a modest increase in body weight. With high-fat feeding, tg(sm/p22phox) mice developed exaggerated obesity and increased fat mass. Body weight increased from 32.16 ± 2.34 g to 43.03 ± 1.44 g in tg(sm/p22phox) mice (vs. 30.81 ± 0.71 g to 37.89 ± 1.16 g in the WT mice). This was associated with development of glucose intolerance, reduced HDL cholesterol, and increased levels of leptin and MCP-1. Tg(sm/p22phox) mice displayed impaired spontaneous activity and increased mitochondrial ROS production and mitochondrial dysfunction in skeletal muscle. In mice with vascular smooth muscle-targeted deletion of p22phox (p22phox(loxp/loxp)/tg(smmhc/cre) mice), high-fat feeding did not induce weight gain or leptin resistance. These mice also had reduced T-cell infiltration of perivascular fat. In conclusion, these data indicate that vascular oxidative stress induces obesity and metabolic syndrome, accompanied by and likely due to exercise intolerance, vascular inflammation, and augmented adipogenesis. These data indicate that vascular ROS may play a causal role in the development of obesity and metabolic syndrome.

Traditional chinese medicine shuang shen ning xin attenuates myocardial ischemia/reperfusion injury by preserving of mitochondrial function

To investigate the potential cardioprotective effects of Shuang Shen Ning Xin on myocardial ischemia/reperfusion injury. Wistar rats were treated with trimetazidine (10 mg/kg/day, ig), Shuang Shen Ning Xin (22.5, 45 mg/kg/day, ig), or saline for 5 consecutive days. Myocardial ischemia/reperfusion injury was induced by ligation of the left anterior descending coronary artery for 40 min and reperfusion for 120 min on the last day of administration. It is found that Shuang Shen Ning Xin pretreatment markedly decreased infarct size and serum LDH levels, and this observed protection was associated with reduced myocardial oxidative stress and cardiomyocyte apoptosis after myocardial ischemia/reperfusion injury. In addition, further studies on mitochondrial function showed that rats treated with Shuang Shen Ning Xin displayed decreased mitochondrial swelling and cytosolic cytochrome c levels, which were accompanied by a preservation of complex I activities and inhibition of mitochondrial permeability transition. In conclusion, the mitochondrial protective effect of Shuang Shen Ning Xin could be a new mechanism, by which Shuang Shen Ning Xin attenuates myocardial ischemia/reperfusion injury.

Aerobic interval training attenuates mitochondrial dysfunction in rats post-myocardial infarction: roles of mitochondrial network dynamics

Aerobic interval training (AIT) can favorably affect cardiovascular diseases. However, the effects of AIT on post-myocardial infarction (MI)—associated mitochondrial dysfunctions remain unclear. In this study, we investigated the protective effects of AIT on myocardial mitochondria in post-MI rats by focusing on mitochondrial dynamics (fusion and fission). Mitochondrial respiratory functions (as measured by the respiratory control ratio (RCR) and the ratio of ADP to oxygen consumption (P/O)); complex activities; dynamic proteins (mitofusin (mfn) 1/2, type 1 optic atrophy (OPA1) and dynamin-related protein1 (DRP1)); nuclear peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α); and the oxidative signaling of extracellular signal-regulated kinase (ERK) 1/2, c-Jun NH₂-terminal protein kinase (JNK) and P53 were observed. Post-MI rats exhibited mitochondrial dysfunction and adverse mitochondrial network dynamics (reduced fusion and increased fission), which was associated with activated ERK1/2-JNK-P53 signaling and decreased nuclear PGC-1α. After AIT, MI-associated mitochondrial dysfunction was improved (elevated RCR and P/O and enhanced complex I, III and IV activities); in addition, increased fusion (mfn2 and OPA1), decreased fission (DRP1), elevated nuclear PGC-1α and inactivation of the ERK1/2-JNK-P53 signaling were observed. These data demonstrate that AIT may restore the post-MI mitochondrial function by inhibiting dynamics pathological remodeling, which may be associated with inactivation of ERK1/2-JNK-P53 signaling and increase in nuclear PGC-1α expression.

Role of β-adrenergic receptors and nitric oxide signaling in exercise-mediated cardioprotection

Exercise promotes cardioprotection in both humans and animals not only by reducing risk factors associated with cardiovascular disease but by reducing myocardial infarction and improving survival following ischemia. This article will define the role that nitric oxide and β-adrenergic receptors play in mediating the cardioprotective effects of exercise in the setting of ischemia-reperfusion injury.

NF-κB-mediated miR-30b regulation in cardiomyocytes cell death by targeting Bcl-2

Angiotensin II(Ang II)-stimulated cardiomyocytes hypertrophy and apoptosis are associated with nuclear factor-κB (NF-κB) activation. NF-κB, a redox-sensitive transcription factor, contributes a critical role in cell death, but, Ang II-stimulated NF-κB-mediated cardiomyocytes apoptosis remains less understood. Recently, microRNAs (miRNAs) have been shown to be critical regulators in various cardiac remodeling processes; however, NF-κB-mediated miRNA's role in cardiomyocytes apoptosis remains undetermined. The miR-30b has been implicated in diverse cardiac remodeling; but, NF-κB-mediated miR-30b modulation in Ang II-induced cardiomyocytes death is currently unknown. In the present study, neonatal cardiomyocytes were pretreated with SN50, a selective cell permeable peptide inhibitor of NF-κB, or transfected with miR-30b mimetic and inhibitors separately, and then challenged with Ang II. The target gene, Bcl-2, and NF-κB transcriptional activity were analyzed. Our results demonstrated that NF-κB positively regulated miR-30b expression in Ang II-induced cardiomyocytes apoptosis, and Bcl-2 was a direct target for miR-30b. NF-κB further regulated the expression of Bcl-2 in the above setting. Furthermore, Ang II-induced cardiomyocytes apoptosis rescued by inhibiting either NF-κB or miR-30b provided an important role in cardiomyocytes cell death. We evaluated a critical role of NF-κB-mediated miR-30b modulation in Ang II-stimulated cardiomyocytes targeting Bcl-2. Our data may provide a new insight of miR-30b's role in myocardial infarction or ischemia.

Regulation of acetylation restores proteolytic function of diseased myocardium in mouse and human

Proteasome complexes play essential roles in maintaining cellular protein homeostasis and serve fundamental roles in cardiac function under normal and pathological conditions. A functional detriment in proteasomal activities has been recognized as a major contributor to the progression of cardiovascular diseases. Therefore, approaches to restore proteolytic function within the setting of the diseased myocardium would be of great clinical significance. In this study, we discovered that the cardiac proteasomal activity could be regulated by acetylation. Histone deacetylase (HDAC) inhibitors (suberoylanilide hydroxamic acid and sodium valproate) enhanced the acetylation of 20S proteasome subunits in the myocardium and led to an elevation of proteolytic capacity. This regulatory paradigm was present in both healthy and acutely ischemia/reperfusion (I/R) injured murine hearts, and HDAC inhibition in vitro restored proteolytic capacities to baseline sham levels in injured hearts. This mechanism of regulation was also viable in failing human myocardium. With 20S proteasomal complexes purified from murine myocardium treated with HDAC inhibitors in vivo, we confirmed that acetylation of 20S subunits directly, at least in part, presents a molecular explanation for the improvement in function. Furthermore, using high-resolution LC-MS/MS, we unraveled the first cardiac 20S acetylome, which identified the acetylation of nine N-termini and seven internal lysine residues. Acetylation on four lysine residues and four N-termini on cardiac proteasomes were novel discoveries of this study. In addition, the acetylation of five lysine residues was inducible via HDAC inhibition, which correlated with the enhancement of 20S proteasomal activity. Taken as a whole, our investigation unveiled a novel mechanism of proteasomal function regulation in vivo and established a new strategy for the potential rescue of compromised proteolytic function in the failing heart using HDAC inhibitors.

Mitochondrial complex I deficiency increases protein acetylation and accelerates heart failure

Mitochondrial respiratory dysfunction is linked to the pathogenesis of multiple diseases, including heart failure, but the specific mechanisms for this link remain largely elusive. We modeled the impairment of mitochondrial respiration by the inactivation of the Ndufs4 gene, a protein critical for complex I assembly, in the mouse heart (cKO). Although complex I-supported respiration decreased by >40%, the cKO mice maintained normal cardiac function in vivo and high-energy phosphate content in isolated perfused hearts. However, the cKO mice developed accelerated heart failure after pressure overload or repeated pregnancy. Decreased NAD(+)/NADH ratio by complex I deficiency inhibited Sirt3 activity, leading to an increase in protein acetylation and sensitization of the permeability transition in mitochondria (mPTP). NAD(+) precursor supplementation to cKO mice partially normalized the NAD(+)/NADH ratio, protein acetylation, and mPTP sensitivity. These findings describe a mechanism connecting mitochondrial dysfunction to the susceptibility to diseases and propose a potential therapeutic target.

Altered mitochondrial functioning induced by preoperative fasting may underlie protection against renal ischemia/reperfusion injury

We reported previously that the robust protection against renal ischemia/reperfusion (I/R) injury in mice by fasting was largely initiated before the induction of renal I/R. In addition, we found that preoperative fasting downregulated the gene expression levels of complexes I, IV, and V of the mitochondrial oxidative phosphorylation (OXPHOS) system, while it did not change those of complexes II and III. Hence, we now investigated the effect of 3 days of fasting on the functioning of renal mitochondria in order to better understand our previous findings. Fasting did not affect mitochondrial density. Surprisingly, fasting significantly increased the protein expression of complex II of the mitochondrial OXPHOS system by 19%. Complex II-driven state 3 respiratory activity was significantly reduced by fasting (46%), which could be partially attributed to the significant decrease in the enzyme activity of complex II (16%). Fasting significantly inhibited Ca(2+) -dependent mitochondrial permeability transition pore opening that is directly linked to protection against renal I/R injury. The inhibition of the mitochondrial permeability transition pore did not involve the expression of the voltage-dependent anion channel by fasting. In conclusion, 3 days of fasting clearly induces the inhibition of complex II-driven mitochondrial respiration state 3 in part by decreasing the amount of functional complex II, and inhibits mitochondrial permeability transition pore opening. This might be a relevant sequence of events that could contribute to the protection of the kidney against I/R injury.

The interactive effects of cytoskeleton disruption and mitochondria dysfunction lead to reproductive toxicity induced by microcystin-LR

The worldwide occurrence of cyanobacterial blooms evokes profound concerns. The presence of microcystins (MCs) in waters and aquatic food increases the risk to human health. Some recent studies have suggested that the gonad is the second most important target organ of MCs, however, the potential toxicity mechanisms are still unclear. For a better understanding of reproductive toxicity of MCs on animals, we conducted the present experimental investigation. Male rats were intraperitoneally injected with MC-LR for 50 d with the doses of 1 and 10 µg/kg body weight per day. After prolonged exposure to MC-LR, the testes index significantly decreased in 10 µg/kg group. Light microscope observation indicated that the space between the seminiferous tubules was increased. Ultrastructural observation showed some histopathological characteristics, including cytoplasmic shrinkage, cell membrane blebbing, swollen mitochondria and deformed nucleus. Using Q-PCR methods, the transcriptional levels of some cytoskeletal and mitochondrial genes were determined. MC-LR exposure affected the homeostasis of the expression of cytoskeletal genes, causing possible dysfunction of cytoskeleton assembly. In MC-LR treatments, all the 8 mitochondrial genes related with oxidative phosphorylation (OXPHOS) significantly increased. The reactive oxygen species (ROS) level significantly increased in 10 µg/kg group. The mitochondria swelling and DNA damage were also determined in 10 µg/kg group. Hormone levels of testis significantly changed. The present study verified that both cytoskeleton disruption possibly due to cytoskeletal reorganization or depolymerization and mitochondria dysfunction interact with each other through inducing of reactive oxygen species and oxidative phosphorylation, and jointly result in testis impairment after exposure to MC-LR.

Strategic localization of heart mitochondrial NOS: a review of the evidence

Heart mitochondria play a central role in cell energy provision and in signaling. Nitric oxide (NO) is a free radical with primary regulatory functions in the heart and involved in a broad array of key processes in cardiac metabolism. Specific NO synthase (NOS) isoforms are confined to distinct locations in cardiomyocytes. The present article reviews the chemical reactions through which NO interacts with biomolecules and exerts some of its crucial roles. Specifically, the article discusses the reactions of NO with mitochondrial targets and the subcellular localization of NOS within the myocardium and analyzes the available data about heart mitochondrial NOS activity and identity. The article also describes the regulation of heart mtNOS by the distinctive mitochondrial environment by showing the effects of Ca(2+), O(2), l-arginine, mitochondrial transmembrane potential, and the metabolic states on heart mitochondrial NO production. The article depicts the effects of NO on heart function and highlights the relevance of NO production within mitochondria. Finally, the evidence on the functional implications of heart mitochondrial NOS is delineated with emphasis on chronic hypoxia and ischemia-reperfusion studies.

Astragaloside IV inhibits oxidative stress-induced mitochondrial permeability transition pore opening by inactivating GSK-3β via nitric oxide in H9c2 cardiac cells

Objective. This study aimed to investigate whether astragaloside IV modulates the mitochondrial permeability transition pore (mPTP) opening through glycogen synthase kinase 3β (GSK-3β) in H9c2 cells. Methods. H9c2 cells were exposed to astragaloside IV for 20 min. GSK-3β (Ser⁹), Akt (Ser⁴⁷³), and VASP (Ser²³⁹) activities were determined with western blot. The mPTP opening was evaluated by measuring mitochondrial membrane potential (ΔΨ_m). Nitric oxide (NO) generation was measured by 4-amino-5-methylamino-2′, 7′-difluorofluorescein (DAF-FM) diacetate. Fluorescence images were obtained with confocal microscopy. Results. Astragaloside IV significantly enhanced GSK-3β phosphorylation and prevented H₂O₂-induced loss of ΔΨ_m. These effects of astragaloside IV were reversed by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, the NO sensitive guanylyl cyclase selective inhibitor ODQ, and the PKG inhibitor KT5823. Astragaloside IV activated Akt and PKG. Astragaloside IV was also shown to increase NO production, an effect that was reversed by L-NAME and LY294002. Astragaloside IV applied at reperfusion reduced cell death caused by simulated ischemia/reperfusion, indicating that astragaloside IV can prevent reperfusion injury. Conclusions. These data suggest that astragaloside IV prevents the mPTP opening and reperfusion injury by inactivating GSK-3β through the NO/cGMP/PKG signaling pathway. NOS is responsible for NO generation and is activated by the PI3K/Akt pathway.

Expression of microRNA-1 and microRNA-21 in different protocols of ischemic conditioning in an isolated rat heart model

BACKGROUND

'Conditioning' [ischemic preconditioning (IPC), ischemic postconditioning (IPO) and remote ischemic preconditioning (RIPC)] the heart to render it more resistant to an episode of acute myocardial ischemia-reperfusion (I/R) injury is an endogenous cardioprotective strategy. There are several mechanisms proposed for 'conditioning', such as endogenous mediators or cytoprotective proteins. In recent reports, microRNAs (miRNAs) were involved in controlling the expression of myocardial ischemia-related genes. Some studies have demonstrated that cardiac miRNA-1 and miRNA-21 were significantly increased by late IPC with an increase in their target proteins [endothelial nitric oxide synthase and heat shock protein 70 (HSP70)], but their expression levels in 'conditioning' strategies are currently unknown.

METHODS

In the current study, Langendorff-perfused Sprague-Dawley rat hearts were randomly assigned to one of four groups [control group (CON group, n = 12), IPC group (n = 12), IPO group (n = 12) and RIPC group (n = 12)]. Cardiac function was digitalized and analyzed. The expression of miRNA-1 and miRNA-21 was detected by real-time reverse transcription polymerase chain reaction. The expression of HSP70, programmed cell death protein 4 (PDCD4), B-cell lymphoma/leukemia-2 (Bcl-2) and Bcl-2-associated X protein (Bax) was detected by Western blot. Cardiac infarct size and myocardial apoptosis were determined using the 2,3,5-triphenyltetrazolium chloride assay and terminal deoxynucleotidyl transferase dUTP nick end labeling assay, respectively.

RESULTS

The results revealed that miRNA-1 (233 ± 45%) and miRNA-21 (356 ± 33%) expression was up-regulated in the IPC group, but the expression of miRNA-1 was down-regulated in the RIPC (61 ± 16%) group and IPO group (61 ± 13%). The expression of PDCD4 [IPC (74 ± 11%), RIPC (81 ± 16%), IPO (83 ± 12%)], HSP70 [IPC (74 ± 5%), RIPC (81 ± 6%), IPO (67 ± 11%)] and Bax [IPC (27 ± 6%), RIPC (21 ± 3%), IPO (27 ± 4%)] was down-regulated in the conditioning groups compared with the CON group [PDCD4 (130 ± 11%), HSP70 (121 ± 11%) and Bax (63 ± 8%)]. In the conditioning hearts, infarct size [IPC (31.7 ± 4.1%), RIPC (29.6 ± 6.19%) and IPO (32.8 ± 4.71%)] and myocardial apoptosis [IPC (15.2 ± 4.21%), RIPC (17.2 ± 1.92%) and IPO (15.6 ± 4.04%)] were significantly decreased compared with the CON group (infarct size: 51.77 ± 4.3%, myocardial apoptosis: 32.8 ± 3.96%).

CONCLUSION

We concluded that miRNA-1 and miRNA-21 expression differed in IPC, RIPC and IPO groups, and their target proteins were not inversely correlated with the miRNAs in all the conditioning groups, which revealed that the miRNAs were regulated but complicated by the different conditioning protocols.

Desflurane-induced post-conditioning against myocardial infarction is mediated by calcium-activated potassium channels: role of the mitochondrial permeability transition pore

BACKGROUND

Desflurane (DES)-induced preconditioning is mediated by large-conductance calcium-activated potassium channels (BK(Ca)). Whether BK(Ca) are involved in anaesthetic-induced post-conditioning is unknown. We tested the hypothesis that DES-induced post-conditioning is mediated by BK(Ca) upstream of the mitochondrial permeability transition pore (mPTP).

METHODS

Pentobarbital-anaesthetized male C57Black/6 mice were subjected to 45 min coronary artery occlusion (CAO) and 3 h reperfusion. Animals received either no intervention or dimethylsulphoxide (DMSO, 10 µl g(-1)). DES (1.0 MAC, 7.5 vol%) was administered for 18 min, starting 3 min before the end of CAO. The following agents were given either alone or in combination with DES: the BK(Ca) activator NS1619 (1 µg g(-1)), the BK(Ca) inhibitor iberiotoxin (IbTx, 0.05 µg g(-1)), the mPTP opener atractyloside (ATRA, 25 µg g(-1)), and the mPTP inhibitor cyclosporine A (CYC A, 10 µg g(-1)). Infarct size (IS) was determined with triphenyltetrazolium chloride and the area at risk with Evans Blue, respectively.

RESULTS

IS in control animals was 48(6)%. Neither DMSO, IbTx nor ATRA affected myocardial IS. DES alone or NS1619 alone or the combination reduced IS (P<0.05), CYC A alone or in combination with IbTx or DES also reduced IS (P<0.05). DES-induced reduction of myocardial IS was completely abolished by IbTx and was partially blocked by ATRA and ATRA partially blocked IS reduction by NS1619.

CONCLUSIONS

These data suggest that DES-induced post-conditioning against myocardial infarction is mediated by BK(Ca) and mPTP. Cardioprotection by BK(Ca) activator NS1619 might occur, at least in part, independently of mPTP.

Catecholamine-induced cardiac mitochondrial dysfunction and mPTP opening: protective effect of curcumin

The present study was designed to characterize the mitochondrial dysfunction induced by catecholamines and to investigate whether curcumin, a natural antioxidant, induces cardioprotective effects against catecholamine-induced cardiotoxicity by preserving mitochondrial function. Because mitochondria play a central role in ischemia and oxidative stress, we hypothesized that mitochondrial dysfunction is involved in catecholamine toxicity and in the potential protective effects of curcumin. Male Wistar rats received subcutaneous injection of 150 mg·kg(-1)·day(-1) isoprenaline (ISO) for two consecutive days with or without pretreatment with 60 mg·kg(-1)·day(-1) curcumin. Twenty four hours after, cardiac tissues were examined for apoptosis and oxidative stress. Expression of proteins involved in mitochondrial biogenesis and function were measured by real-time RT-PCR. Isolated mitochondria and permeabilized cardiac fibers were used for swelling and mitochondrial function experiments, respectively. Mitochondrial morphology and permeability transition pore (mPTP) opening were assessed by fluorescence in isolated cardiomyocytes. ISO treatment induced cell damage, oxidative stress, and apoptosis that were prevented by curcumin. Moreover, mitochondria seem to play an important role in these effects as respiration and mitochondrial swelling were increased following ISO treatment, these effects being again prevented by curcumin. Importantly, curcumin completely prevented the ISO-induced increase in mPTP calcium susceptibility in isolated cardiomyocytes without affecting mitochondrial biogenesis and mitochondrial network dynamic. The results unravel the importance of mitochondrial dysfunction in isoprenaline-induced cardiotoxicity as well as a new cardioprotective effect of curcumin through prevention of mitochondrial damage and mPTP opening.

The cardioprotective efficacy of TVP1022 in a rat model of ischaemia/reperfusion

BACKGROUND AND PURPOSE

Because myocardial infarction is a major cause of morbidity and mortality worldwide, protecting the heart from the ischaemia and reperfusion (I/R) damage is the focus of intense research. Based on our in vitro findings showing that TVP1022 (the S-enantiomer of rasagiline, an anti-Parkinsonian drug) possesses cardioprotective effects, in the present study we investigated the hypothesis that TVP1022 can attenuate myocardial damage in an I/R model in rats.

EXPERIMENTAL APPROACH

The model consisted of 30-min occlusion of the left anterior descending artery followed by 4 or 24 h reperfusion. In addition, we investigated the possible mechanisms of cardioprotection in H9c2 cells and neonatal rat ventricular myocytes (NRVM) exposed to oxidative stress induced by H(2) O(2) .

KEY RESULTS

TVP1022 (20 and 40 mg·kg(-1) ) administered 5 min before reperfusion followed by an additional dose 4 h after reperfusion reduced the infarct size and attenuated the decline in ventricular function. TVP1022 also attenuated I/R-induced deterioration in cardiac mitochondrial integrity evaluated by mitochondrial swelling capacity. In vitro, using H9c2 cells and NRVM, TVP1022 attenuated both serum free- and H(2) O(2) -induced damage, preserved mitochondrial membrane potential and Bcl-2 levels, inhibited mitochondrial cytochrome c release and the increase in cleaved caspase 9 and 3 levels, and enhanced the phosphorylation of protein kinase C and glycogen synthase kinase-3β.

CONCLUSIONS AND IMPLICATIONS

TVP1022 provided cardioprotection in a model of myocardial infarction, and therefore should be considered as a novel adjunctive therapy for attenuating myocardial damage resulting from I/R injuries.

Atractyloside induces low contractile reaction of arteriolar smooth muscle through mitochondrial damage

Atractyloside is the principal naturally occurring active ingredient in ethnomedicines and animal grazing forage. Evidence that atractyloside can induce opening of the mitochondrial permeability transition pore (mPTP) indicates that mitochondrial mechanisms may play an important role in pathophysiological lesions of the heart, liver and kidney after atractyloside poisoning. Therefore, in this study we investigated the association of atractyloside-induced mitochondrial damage in arteriolar smooth muscle cells (ASMCs) with contractile reaction. Atractyloside led to depolarized and swollen or damaged ASMC mitochondria, which might be related to the concentration-dependent induction of mPTP opening. Relative ATP content in ASMCs was significantly reduced by 48%, 63% and 66% of control when cells were treated with 7.5, 10, and 15 µm atractyloside for 10 min, respectively, and ASMCs were hyperpolarized. In addition, the contractile responsiveness of ASMCs was eventually weakened. These results suggest that atractyloside has a toxic effect on vasoreactivity, which is possibly related to mitochondrial damage.

Manganese induces oxidative stress, redox state unbalance and disrupts membrane bound ATPases on murine neuroblastoma cells in vitro: protective role of silymarin

Manganese (Mn) is an essential trace element required for ubiquitous enzymatic reactions. Chronic overexposure to this metal may promote potent neurotoxic effects. The mechanism of Mn toxicity is not well established, but several studies indicate that oxidative stress play major roles in the Mn-induced neurodegenerative processes. Silymarin (SIL) has antioxidant properties and stabilizes intracellular antioxidant defense systems. The aim of this study was to evaluate the toxic effects of MnCl₂ on the mouse neuroblastoma cell lines (Neuro-2A), to characterize the toxic mechanism associated with Mn exposure and to investigate whether SIL could efficiently protect against neurotoxicity induced by Mn. A significant increase in LDH release activity was observed in Neuro-2A cells associated with a significant decrease in cellular viability upon 24 h exposure to MnCl₂ at concentrations of 200 and 800 μM (P < 0.05) when compared with control unexposed cells. In addition, exposure cells to MnCl₂ (200 and 800 μM), increases oxidant biomarkers and alters enzymatic and non enzymatic antioxidant systems. SIL treatment significantly reduced the levels of LDH, nitric oxide, reactive oxygen species and the oxidants/antioxidants balance in Neuro-2A cells as compared to Mn-exposed cells. These results suggested that silymarin is a powerful antioxidant through a mechanism related to its antioxidant activity, able to interfere with radical-mediated cell death. SIL may be useful in diseases known to be aggravated by reactive oxygen species and in the development of novel treatments for neurodegenerative disorders such as Alzheimer or Parkinson diseases.

Emergent role of gasotransmitters in ischemia-reperfusion injury

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

Targeting the mitochondrial permeability transition: cardiac ischemia-reperfusion versus carcinogenesis

Cardiovascular diseases and cancer continue to be major causes of death worldwide, and despite intensive research only modest progress has been reached in reducing the morbidity and mortality of these awful diseases. Mitochondria are broadly accepted as the key organelles that play a crucial role in cell life and death. They provide cells with ATP produced via oxidative phosphorylation under physiological conditions, and initiate cell death through both apoptosis and necrosis in response to severe stress. Oxidative stress accompanied by calcium overload and ATP depletion induces the mitochondrial permeability transition (mPT) with formation of pathological, non-specific mPT pores (mPTP) in the mitochondrial inner membrane. Opening of the mPTP with a high conductance results in matrix swelling ultimately inducing rupture of the mitochondrial outer membrane and releasing pro-apoptotic proteins into the cytoplasm. The ATP level is the determining factor in deciding whether cells die through apoptosis or necrosis. Cardiac cells undergoing ischemia followed by reperfusion (IR) possess exactly the same conditions mentioned above to induce mPTP opening. Due to its critical role in cell death, inhibition of mPTP opening has been accepted as a major therapeutic approach to protect the heart against IR. In contrast to cardiac IR, cancer cells exhibit less sensitivity to pore opening which can be in part explained by increased expression of mPTP compounds/modulators and metabolic remodeling. Since the main goal of chemotherapy is to provoke apoptosis, mPT induction may represent an attractive approach for the development of new cancer therapeutics to induce mitochondria-mediated cell death and prevent cell differentiation in carcinogenesis. This review focuses on the role of the mPTP in cardiac IR and cancer, and pharmacological agents to prevent or initiate mPT-mediated cell death, respectively in these diseases.

A small molecule AMPK activator protects the heart against ischemia-reperfusion injury

AMP-activated protein kinase (AMPK) is a stress signaling enzyme that orchestrates the regulation of energy-generating and -consuming pathways. Intrinsic AMPK activation protects the heart against ischemic injury and apoptosis, but whether pharmacologic AMPK stimulation mitigates ischemia-reperfusion damage is unknown. The aims of this study were to determine whether direct stimulation of AMPK using a small molecule activator, A-769662, attenuates myocardial ischemia-reperfusion injury and to examine its cardioprotective mechanisms. Isolated mouse hearts pre-treated with A-769662 had better recovery of left ventricular contractile function (55% vs. 29% of baseline rate-pressure product; p=0.03) and less myocardial necrosis (56% reduction in infarct size; p<0.01) during post-ischemic reperfusion compared to control hearts. Pre-treatment with A-769662 in vivo attenuated infarct size in C57Bl/6 mice undergoing left coronary artery occlusion and reperfusion compared to vehicle (36% vs. 18%, p=0.025). Mouse hearts with genetically inactivated AMPK were not protected by A-769662, indicating the specificity of this compound. Pre-treatment with A-769662 increased the phosphorylation and inactivation of eukaryotic elongation factor 2 (eEF2), preserved energy charge during ischemia, delayed the development of ischemic contracture, and reduced myocardial apoptosis and necrosis. A-769662 also augmented endothelial nitric oxide synthase (eNOS) activation during ischemia, which partially attenuated myocardial stunning, but did not prevent necrosis. AMPK is a therapeutic target that can be stimulated by a direct-acting small molecule in order to prevent injury during ischemia-reperfusion. The use of AMPK activators may represent a novel strategy to protect the heart and other solid organs against ischemia.

Regulation of mitochondrial processes by protein S-nitrosylation

BACKGROUND

Nitric oxide (NO) exerts powerful physiological effects through guanylate cyclase (GC), a non-mitochondrial enzyme, and through the generation of protein cysteinyl-NO (SNO) adducts-a post-translational modification relevant to mitochondrial biology. A small number of SNO proteins, generated by various mechanisms, are characteristically found in mammalian mitochondria and influence the regulation of oxidative phosphorylation and other aspects of mitochondrial function.

SCOPE OF REVIEW

The principles by which mitochondrial SNO proteins are formed and their actions, independently or collectively with NO binding to heme, iron-sulfur centers, or to glutathione (GSH) are reviewed on a molecular background of SNO-based signal transduction.

MAJOR CONCLUSIONS

Mitochondrial SNO-proteins have been demonstrated to inhibit Complex I of the electron transport chain, to modulate mitochondrial reactive oxygen species (ROS) production, influence calcium-dependent opening of the mitochondrial permeability transition pore (MPTP), promote selective importation of mitochondrial protein, and stimulate mitochondrial fission. The ease of reversibility and the affirmation of regulated S-nitros(yl)ating and denitros(yl)ating enzymatic reactions support hypotheses that SNO regulates the mitochondrion through redox mechanisms. SNO modification of mitochondrial proteins, whether homeostatic or adaptive (physiological), or pathogenic, is an area of active investigation.

GENERAL SIGNIFICANCE

Mitochondrial SNO proteins are associated with mainly protective, bur some pathological effects; the former mainly in inflammatory and ischemia/reperfusion syndromes and the latter in neurodegenerative diseases. Experimentally, mitochondrial SNO delivery is also emerging as a potential new area of therapeutics. This article is part of a Special Issue entitled: Regulation of cellular processes by S-nitrosylation.

Augmented O-GlcNAc signaling attenuates oxidative stress and calcium overload in cardiomyocytes

O-linked β-N-acetylglucosamine (O-GlcNAc) is an inducible, dynamically cycling and reversible post-translational modification of Ser/Thr residues of nucleocytoplasmic and mitochondrial proteins. We recently discovered that O-GlcNAcylation confers cytoprotection in the heart via attenuating the formation of mitochondrial permeability transition pore (mPTP) and the subsequent loss of mitochondrial membrane potential. Because Ca(2+) overload and reactive oxygen species (ROS) generation are prominent features of post-ischemic injury and favor mPTP formation, we ascertained whether O-GlcNAcylation mitigates mPTP formation via its effects on Ca(2+) overload and ROS generation. Subjecting neonatal rat cardiac myocytes (NRCMs, n ≥ 6 per group) to hypoxia, or mice (n ≥ 4 per group) to myocardial ischemia reduced O-GlcNAcylation, which later increased during reoxygenation/reperfusion. NRCMs (n ≥ 4 per group) infected with an adenovirus carrying nothing (control), adenoviral O-GlcNAc transferase (adds O-GlcNAc to proteins, AdOGT), adenoviral O-GlcNAcase (removes O-GlcNAc to proteins, AdOGA), vehicle or PUGNAc (blocks OGA; increases O-GlcNAc levels) were subjected to hypoxia-reoxygenation or H(2)O(2), and changes in Ca(2+) levels (via Fluo-4AM and Rhod-2AM), ROS (via DCF) and mPTP formation (via calcein-MitoTracker Red colocalization) were assessed using time-lapse fluorescence microscopy. Both OGT and OGA overexpression did not significantly (P > 0.05) alter baseline Ca(2+) or ROS levels. However, AdOGT significantly (P < 0.05) attenuated both hypoxia and oxidative stress-induced Ca(2+) overload and ROS generation. Additionally, OGA inhibition mitigated both H(2)O(2)-induced Ca(2+) overload and ROS generation. Although AdOGA exacerbated both hypoxia and H(2)O(2)-induced ROS generation, it had no effect on H(2)O(2)-induced Ca(2+) overload. We conclude that inhibition of Ca(2+) overload and ROS generation (inducers of mPTP) might be one mechanism through which O-GlcNAcylation reduces ischemia/hypoxia-mediated mPTP formation.

Blockade of electron transport during ischemia preserves bcl-2 and inhibits opening of the mitochondrial permeability transition pore

Myocardial ischemia damages the electron transport chain and augments cardiomyocyte death during reperfusion. To understand the relationship between ischemic mitochondrial damage and mitochondrial-driven cell death, the isolated perfused heart underwent global stop-flow ischemia with and without mitochondrial protection by reversible blockade of electron transport. Ischemic damage to electron transport depleted bcl-2 content and favored mitochondrial permeability transition (MPT). Reversible blockade of electron transport preserved bcl-2 content and attenuated calcium-stimulated mitochondrial swelling. Thus, the damaged electron transport chain leads to bcl-2 depletion and MPT opening. Chemical inhibition of bcl-2 with HA14-1 also dramatically increased mitochondrial swelling, augmented by exogenous H(2)O(2) stress, indicating that bcl-2 depleted mitochondria are poised to undergo MPT during the enhanced oxidative stress of reperfusion.

The effects of nitric oxide-oxidase and putative glutathione-peroxidase activities of ceruloplasmin on the viability of cardiomyocytes exposed to hydrogen peroxide

Ceruloplasmin (CP), a ferroxidase (EC 1.16.3.1) and a scavenger of reactive oxygen species, is an important extracellular antioxidant. Bovine CP indeed protects the isolated heart under ischemia-reperfusion conditions. Human CP has been shown to also exhibit, in vitro, glutathione (GSH)-peroxidase and nitric oxide (NO)-oxidase/S-nitrosating activities. This work tested, using bovine CP, the hypothesis that both activities could provide cytoprotection during oxidative stress induced by hydrogen peroxide (H(2)O(2)), the former activity by consuming H(2)O(2) and the latter by shielding thiols from irreversible oxidation. In acellular assays, bovine CP stimulated the generation of the nitrosating NO(+) species from the NO donors propylaminepropylamine-NONOate (PAPA/NO), S-nitroso-N-acetylpenicillamine, and S-nitrosoglutathione. This NO-oxidase activity S-nitrosated GSH as well as CP itself and was not affected by H(2)O(2). In contrast to human CP, bovine CP consumed H(2)O(2) in an additive rather than synergistic manner in the presence of GSH. A nonenzymatic scavenging of H(2)O(2) could have masked the GSH-peroxidase activity. Cytoprotection was evaluated using neonatal rat cardiomyocytes. CP and PAPA/NO were not protective against the H(2)O(2)-induced loss of viability. In contrast, GSH provided a slight protection that increased more than additively in the presence of CP. This increase was canceled by PAPA/NO. CP's putative GSH-peroxidase activity can thus provide cytoprotection but is possibly affected by the S-nitrosation of a catalytically important cysteine residue.

Site-mapping of in vitro S-nitrosation in cardiac mitochondria: implications for cardioprotection

S-nitrosation (SNO) of mitochondrial protein cysteines can be cardioprotective. Several targets have been implicated, yet the scope and identification of specific residues has not been fully assessed. To address this, a comprehensive assessment of mitochondrial SNO-modifiable cysteines was performed to determine nitric oxide (NO) susceptible pathways and identify novel mechanisms of oxidative cardioprotection. The biotin switch assay and mass spectrometry were used on rat cardiac mitochondrial lysates treated with the nitric oxide donor, S-nitrosoglutathione, and controls (n=3) to map 83 SNO-modified cysteine residues on 60 proteins. Of these, three sites have been reported, 30 sites are new to 21 proteins previously known to be S-nitrosated but which lacked site-specific information and 50 sites were found on 39 proteins not previously implicated in SNO pathways. The SNO-modifications occurred in only a subset of available cysteines, indicating a specific targeted effect. Functional annotation and site-specificity analysis revealed a twofold greater nitric oxide-susceptibility for proteins involved in transport; including regulators of mitochondrial permeability transition suggesting SNO-regulation and a possible protective mechanism. Additionally, we identified many novel SNO-modified proteins with cardioprotective potential involved in the electron transport chain, tricarboxylic acid cycle, oxidative stress defense, fatty acid and amino acid metabolism. These findings suggest that SNO-modification may represent a novel mechanism for the regulation of oxidative phosphorylation and/or cell death. S-nitrosation of mitochondrial permeability transition-associated proteins represents an intriguing potential link to cardioprotection.

Cell and molecular mechanisms of insulin-induced angiogenesis

Angiogenesis, the development of new blood vessel from pre-existing vessels, is a key process in the formation of the granulation tissue during wound healing. The appropriate development of new blood vessels, along with their subsequent maturation and differentiation, establishes the foundation for functional wound neovasculature. We performed studies in vivo and used a variety of cellular and molecular approaches in vitro to show that insulin stimulates angiogenesis and to elucidate the signalling mechanisms by which this protein stimulates microvessel development. Mice skin injected with insulin shows longer vessels with more branches, along with increased numbers of associated alpha-smooth muscle actin-expressing cells, suggesting the appropriate differentiation and maturation of the new vessels. We also found that insulin stimulates human microvascular endothelial cell migration and tube formation, and that these effects occur independently of VEGF/VEGFR signalling, but are dependent upon the insulin receptor itself. Downstream signalling pathways involve PI3K, Akt, sterol regulatory element-binding protein 1 (SREBP-1) and Rac1; inhibition of these pathways results in elimination of endothelial cell migration and tube formation and significantly decreases the development of microvessels. Our findings strongly suggest that insulin is a good candidate for the treatment of ischaemic wounds and other conditions in which blood vessel development is impaired.