Oxidative stress reversibly inactivates myocardial enzymes during cardiac arrest

Oral pyruvate prevents high-intensity interval exercise-induced metabolic acidosis in rats by promoting lactate dehydrogenase reaction

Introduction

There is no denying the clinical benefits of exogenous pyruvate in the treatment of pathological metabolic acidosis. However, whether it can prevent exercise physiological metabolic acidosis, delay the occurrence of exercise fatigue, and improve the beneficial effects of exercise and its internal mechanism remain unclear.

Methods

We randomly divided 24 male SD rats into 3 groups: one group was a control without exercise (CC, n = 8), and the other two groups were supplemented with 616 mg/kg/day pyruvate (EP, n = 8) or distilled water of equal volume (EC, n = 8). These groups completed acute high-intensity interval exercise (HIIE) after 7 days of supplementation. The acid metabolism variables were measured immediately after exercise including blood pH (pH_e), base excess (BE), HCO₃ ^-, blood lactic acid and skeletal muscle pH (pH_i). The redox state was determined by measuring the oxidized coenzyme I/reduced coenzyme I (nicotinamide adenine dinucleotide [NAD⁺]/reduced NAD⁺ [NADH]) ratio and lactate/pyruvate (L/P) ratio. In addition, the activities of lactate dehydrogenase A (LDHA), hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) were determined by ELISA.

Results

Pyruvate supplementation significantly reversed the decrease of pHe, BE, HCO₃ ^- and pH_i values after HIIE (p < 0.001), while significantly increased the activities of LDHA (p = 0.048), HK (p = 0.006), and PFK (p = 0.047). Compared with the CC, the NAD+/NADH (p = 0.008) ratio and the activities of LDHA (p = 0.002), HK (p < 0.001), PFK (p < 0.001), and PK (p = 0.006) were significantly improved in EP group.

Discussion

This study provides compelling evidence that oral pyruvate attenuates HIIE-induced intracellular and extracellular acidification, possibly due to increased activity of LDHA, which promotes the absorption of H⁺ in the LDH reaction. The beneficial effects of improving the redox state and glycolysis rate were also shown. Our results suggest that pyruvate can be used as an oral nutritional supplement to buffer HIIE induced metabolic acidosis.

A Global Profile of Reversible and Irreversible Cysteine Redox Post-Translational Modifications During Myocardial Ischemia/Reperfusion Injury and Antioxidant Intervention

Aims: Cysteine (Cys) is a major target for redox post-translational modifications (PTMs) that occur in response to changes in the cellular redox environment. We describe multiplexed, peptide-based enrichment and quantitative mass spectrometry (MS) applied to globally profile reversible redox Cys PTM in rat hearts during ischemia/reperfusion (I/R) in the presence or absence of an aminothiol antioxidant, N-2-mercaptopropionylglycine (MPG). Parallel fractionation also allowed identification of irreversibly oxidized Cys peptides (Cys-SO₂H/SO₃H). Results: We identified 4505 reversibly oxidized Cys peptides of which 1372 were significantly regulated by ischemia and/or I/R. An additional 219 peptides (247 sites) contained Cys-SO₂H/Cys-SO₃H modifications, and these were predominantly identified from hearts subjected to I/R (n = 168 peptides). Parallel reaction monitoring MS (PRM-MS) enabled relative quantitation of 34 irreversibly oxidized Cys peptides. MPG attenuated a large cluster of I/R-associated reversibly oxidized Cys peptides and irreversible Cys oxidation to less than nonischemic controls (n = 24 and 34 peptides, respectively). PRM-MS showed that Cys sites oxidized during ischemia and/or I/R and "protected" by MPG were largely mitochondrial, and were associated with antioxidant functions (peroxiredoxins 5 and 6) and metabolic processes, including glycolysis. Metabolomics revealed I/R induced changes in glycolytic intermediates that were reversed in the presence of MPG, which were consistent with irreversible PTM of triose phosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), altered GAPDH enzyme activity, and reduced I/R glycolytic payoff as evidenced by adenosine triphosphate and NADH levels. Innovation: Novel enrichment and PRM-MS approaches developed here enabled large-scale relative quantitation of Cys redox sites modified by reversible and irreversible PTM during I/R and antioxidant remediation. Conclusions: Cys sites identified here are targets of reactive oxygen species that can contribute to protein dysfunction and the pathogenesis of I/R.

Metabolomics reveals tepotinib-related mitochondrial dysfunction in MET-activating mutations-driven models

Genetic aberrations in the hepatocyte growth factor receptor tyrosine kinase MET induce oncogenic addiction in various types of human cancers, advocating MET as a viable anticancer target. Here, we report that MET signaling plays an important role in conferring a unique metabolic phenotype to cellular models expressing MET-activating mutated variants that are either sensitive or resistant toward MET small molecule inhibitors. MET phosphorylation downregulated by the specific MET inhibitor tepotinib resulted in markedly decreased viability and increased apoptosis in tepotinib-sensitive cells. Moreover, prior to the induction of MET inhibition-dependent cell death, tepotinib also led to an altered metabolic signature, characterized by a prominent reduction of metabolite ions related to amino sugar metabolism, gluconeogenesis, glycine and serine metabolism, and of numerous TCA cycle-related metabolites such as succinate, malate, and citrate. Functionally, a decrease in oxygen consumption rate, a reduced citrate synthase activity, a drop in membrane potential, and an associated misbalanced mitochondrial function were observed exclusively in MET inhibitor-sensitive cells. These data imply that interference with metabolic state can be considered an early indicator of efficient MET inhibition and particular changes reported here could be explored in the future as markers of efficacy of anti-MET therapies.

Cardiopulmonary resuscitation ameliorates myocardial mitochondrial dysfunction in a cardiac arrest rat model

PURPOSE

Previous studies implicate that the mitochondrial injury may play an important role in the development of post-resuscitation myocardial dysfunction, however few of them are available regarding the ultrastructural alterations of myocardial mitochondria, mitochondrial energy producing and utilization ability in the stage of arrest time (no-low) and resuscitation time (low-flow). This study aimed to observe the dynamic changes of myocardial mitochondrial function and metabolic disorders during cardiac arrest (CA) and following cardiopulmonary resuscitation (CPR).

METHODS

A total of 30 healthy male Sprague-Dawley rats were randomized into three groups: 1) VF/CPR: Ventricular fibrillation (VF) was electrically induced, and 5 min of CPR was performed after 10 min of untreated VF; 2) Untreated VF: VF was induced and untreated for 15 min; and 3) Sham: Rats were identically prepared without VF/CPR. Amplitude spectrum area (AMSA) at VF 5, 10 and 15 min were calculated from ECG signals. The rats' hearts were quickly removed at the predetermined time of 15 min after beginning the procedure to gather measurements of myocardial mitochondrial function, high-energy phosphate stores, lactate, mitochondrial ultrastructure, and myocardial glycogen.

RESULTS

The mitochondrial respiratory control ratios significantly decreased after CA compared to sham group. CPR significantly increased respiratory control ratios compared with untreated VF animals. A significant decrease of myocardial glycogen was observed after CA, and a more rapid depletion of myocardial glycogen was observed in CPR animals. CPR significantly reduced the tissue lactate. The mitochondrial ultrastructure abnormalities in CPR animals were less severe than untreated VF animals. AMSA decayed during untreated VF; however, it was significantly greater in CPR group than the untreated VF group. In addition, AMSA was clearly positively correlated with ATP, but negatively correlated with myocardial glycogen.

CONCLUSION

Impairment of myocardial mitochondrial function and the incapability of utilizing glycogen were observed after CA. Furthermore, optimal CPR might, in part, preserved mitochondrial function and enhanced utilization of myocardial glycogen.

Amelioration of neurodegeneration and cognitive impairment by Lemon oil in experimental model of Stressed mice

Citrous lemon (Rutaceae) an Indian folk medicine has been used for the treatment of various pathological diseases viz., diabetes, cardiovascular, inflammation, hepatobiliary dysfunction and neurodegenerative disorder. Can lemon oil altered the memory of unstressed and stressed mice, a basic question for which the present work was put on trial. The present investigation was intended to assess the impact of Lemon oil on memory of unstressed and Stressed Swiss young Albino mice. Lemon oil (50 and 100 mg/kg o.r.) and donepezil (10 mg/kg) were guided for three weeks to different groups of stressed and unstressed mice. The nootropic movement was assessed utilizing elevated plus maze and Hebbs Williams Maze. Cerebrum acetylcholinesterase (AChE), plasmacorticosterone, decreased glutathione, lipid per oxidation alongside superoxide dismutase and catalase was surveyed as marker for disease. Histopathology was performed for estimation of drug effects. Acute immobilized stress was induce, lemon oil (100 mg/kg) and donepezil together indicated memory enhancing movement both in stressed and unstressed mice. Lemon oil significantly (p < 0.001) altered and lowered brain AChE activity both in stressed and unstressed mice. Scopolamine induced amnesia was also significantly altered and reversed both in stressed and unstressed mice by lemon oil at a dose of 50 and 100 mg/kg. Lemon oil (50 and 100 mg/kg) was further able to control the corticosterone level in plasma for stressed mice. Lemon oil significantly (p < 0.001) elevated the level of catalase, superoxide dismutase and reduced glutathione levels both in stressed and unstressed animals with respect to controlled group along with TBARS both in stressed and unstressed compared with control group. Hence it can be concluded that memory enhancing activity might be related to reduction in AChE and TBARS activity and by elevated GSH, SOD and catalase through decrease in raised plasma corticosterone levels.

Pyruvate enhancement of cardiac performance: Cellular mechanisms and clinical application

Cardiac contractile function is adenosine-5'-triphosphate (ATP)-intensive, and the myocardium's high demand for oxygen and energy substrates leaves it acutely vulnerable to interruptions in its blood supply. The myriad cardioprotective properties of the natural intermediary metabolite pyruvate make it a potentially powerful intervention against the complex injury cascade ignited by myocardial ischemia-reperfusion. A readily oxidized metabolic substrate, pyruvate augments myocardial free energy of ATP hydrolysis to a greater extent than the physiological fuels glucose, lactate and fatty acids, particularly when it is provided at supra-physiological plasma concentrations. Pyruvate also exerts antioxidant effects by detoxifying reactive oxygen and nitrogen intermediates, and by increasing nicotinamide adenine dinucleotide phosphate reduced form (NADPH) production to maintain glutathione redox state. These enhancements of free energy and antioxidant defenses combine to augment sarcoplasmic reticular Ca²⁺ release and re-uptake central to cardiac mechanical performance and to restore β-adrenergic signaling of ischemically stunned myocardium. By minimizing Ca²⁺ mismanagement and oxidative stress, pyruvate suppresses inflammation in post-ischemic myocardium. Thus, pyruvate administration stabilized cardiac performance, augmented free energy of ATP hydrolysis and glutathione redox systems, and/or quelled inflammation in a porcine model of cardiopulmonary bypass, a canine model of cardiac arrest-resuscitation, and a caprine model of hypovolemia and hindlimb ischemia-reperfusion. Pyruvate's myriad benefits in preclinical models provide the mechanistic framework for its clinical application as metabolic support for myocardium at risk. Phase one trials have demonstrated pyruvate's safety and efficacy for intravenous resuscitation for septic shock, intracoronary infusion for heart failure and as a component of cardioplegia for cardiopulmonary bypass. The favorable outcomes of these trials, which argue for expanded, phase three investigations of pyruvate therapy, mirror findings in isolated, perfused hearts, underscoring the pivotal role of preclinical research in identifying clinical interventions for cardiovascular diseases. Impact statement This article reviews pyruvate's cardioprotective properties as an energy-yielding metabolic fuel, antioxidant and anti-inflammatory agent in mammalian myocardium. Preclinical research has shown these properties make pyruvate a powerful intervention to curb the complex injury cascade ignited by ischemia and reperfusion. In ischemically stunned isolated hearts and in large mammal models of cardiopulmonary bypass, cardiac arrest-resuscitation and hypovolemia, intracoronary pyruvate supports recovery of myocardial contractile function, intracellular Ca²⁺ homeostasis and free energy of ATP hydrolysis, and its antioxidant actions restore β-adrenergic signaling and suppress inflammation. The first clinical trials of pyruvate for cardiopulmonary bypass, fluid resuscitation and intracoronary intervention for congestive heart failure have been reported. Receiver operating characteristic analyses show remarkable concordance between pyruvate's beneficial functional and metabolic effects in isolated, perfused hearts and in patients recovering from cardiopulmonary bypass in which they received pyruvate- vs. L-lactate-fortified cardioplegia. This research exemplifies the translation of mechanism-oriented preclinical studies to clinical application and outcomes.

The science of reperfusion injury post cardiac arrest--Implications for emergency nurses

Survival following cardiac arrest in the developed world remains below 10%. In those who survive the initial cardiac arrest, prognosis remains poor due to the onset of multi-organ failure with both significant cardiac and neurological dysfunction. Nurses have demonstrated good understanding of cardiac arrest/post arrest guidelines and have good technical skills but deficits remain in their understanding of pathophysiological processes involved in post cardiac arrest syndromes. This article aims to provide an overview of these pathophysiological processes involved in the post cardiac arrest phase, potential treatment options and the nursing interventions that may be required within the emergency department setting. This article will focus emergency nurses to become more involved in patient management at this critical phase of treatment and highlight potential early signs of deterioration. Although return of spontaneous circulation (ROSC) is crucial in the process of recovery from cardiac arrest, it is only the first of many complex stages. Given the complexity of post cardiac arrest syndrome and its impact on the patient, healthcare professionals need to understand the cellular changes associated with reperfusion injuries in order to improve outcomes. It is only through effective nursing care and medical management that improved outcomes will become more common in the future.

Protein "amyloid-like" networks at the phospholipid membrane formed by 4-hydroxy-2-nonenal-modified mitochondrial creatine kinase

4-Hydroxy-2-nonenal (4-HNE) is a reactive aldehyde and a lipid peroxidation product formed in biological tissues under physiological and pathological conditions. Its concentration increases with oxidative stress and induces deleterious modifications of proteins and membranes. Mitochondrial and cytosolic isoforms of creatine kinase were previously shown to be affected by 4-HNE. In the present study, we analyzed the effect of 4-HNE on mitochondrial creatine kinase, an abundant protein from the mitochondrial intermembrane space with a key role in mitochondrial physiology. We show that this effect is double: 4-HNE induces a step-wise loss of creatine kinase activity together with a fast protein aggregation. Protein-membrane interaction is affected and amyloid-like networks formed on the biomimetic membrane. These fibrils may disturb mitochondrial organisation both at the membrane and in the inter membrane space.

1H NMR-metabolomics: can they be a useful tool in our understanding of cardiac arrest?

OBJECTIVE

This review focuses on the presentation of the emerging technology of metabolomics, a promising tool for the detection of identifying the unrevealed biological pathways that lead to cardiac arrest.

DATA SOURCES

The electronic bases of PubMed, Scopus, and EMBASE were searched. Research terms were identified using the MESH database and were combined thereafter. Initial search terms were "cardiac arrest", "cardiopulmonary resuscitation", "post-cardiac arrest syndrome" combined with "metabolomics".

RESULTS

Metabolomics allow the monitoring of hundreds of metabolites from tissues or body fluids and already influence research in the field of cardiac metabolism. This approach has elucidated several pathophysiological mechanisms and identified profiles of metabolic changes that can be used to follow the disease processes occurring in the peri-arrest period. This can be achieved through leveraging the strengths of unbiased metabolome-wide scans, which include thousands of final downstream products of gene transcription, enzyme activity and metabolic products of extraneously administered substances, in order to identify a metabolomic fingerprint associated with an increased risk of cardiac arrest.

CONCLUSION

Although this technology is still under development, metabolomics is a promising tool for elucidating biological pathways and discovering clinical biomarkers, strengthening the efforts for optimizing both the prevention and treatment of cardiac arrest.

Pyruvate-enriched resuscitation: metabolic support of post-ischemic hindlimb muscle in hypovolemic goats

Tourniquet-imposed ischemia-reperfusion of extremities generates reactive oxygen and nitrogen species (RONS), which can disrupt intermediary metabolism and ATP production. This study tested the hypothesis that fluid resuscitation with pyruvate, a natural antioxidant and metabolic fuel, ameliorates the deleterious effects of ischemia-reperfusion on intermediary metabolism in skeletal muscle. Anesthetized male goats (∼25 kg) were bled to a mean arterial pressure of 48 ± 1 mmHg and then subjected to 90 min hindlimb ischemia with a tourniquet and femoral crossclamp, followed by 4-h reperfusion. Lactated Ringers (LR) or pyruvate Ringers (PR) was infused intravenous for 90 min, from 30 min ischemia to 30 min reperfusion, to deliver 0.05 mmol kg(-1) min(-1) lactate or pyruvate. Time controls (TC) underwent neither hemorrhage nor hindlimb ischemia. Lipid peroxidation product 8-isoprostane, RONS-sensitive aconitase and creatine kinase activities, antioxidant superoxide dismutase activity, and phosphocreatine phosphorylation potential ([PCr]/[{Cr}{P(i)}]), an index of tissue energy state, were measured in reperfused gastrocnemius at 90 min resuscitation (n = 6 all groups) and 3.5 h post-resuscitation (n = 8 TC, 9 LR, 10 PR). PR more effectively than LR suppressed 8-isoprostane formation, prevented inactivation of aconitase and creatine kinase, doubled superoxide dismutase activity, and augmented [PCr]/([Cr][P(i)]). Pyruvate-enriched Ringer's is metabolically superior to Ringer's lactate for fluid resuscitation of tourniqueted muscle.

Pyruvate-fortified resuscitation stabilizes cardiac electrical activity and energy metabolism during hypovolemia

AIM: To test the hypothesis that fluid resuscitation with Ringer’s solution enriched with pyruvate (PR), a physiological antioxidant and energy substrate, affords protection of myocardial metabolism and electrophysiological performance superior to lactated Ringer’s (LR) during hypovolemia and hindlimb ischemia-reperfusion.

METHODS: Male domestic goats (25-30 kg) were exsanguinated to a mean arterial pressure of 48 ± 1 mmHg. Right hindlimb ischemia was imposed for 90 min by applying a tourniquet and femoral crossclamp. LR or PR, infused iv, delivered 0.05 mmol/kg per minute L-lactate or pyruvate, respectively, from 30 min hindlimb ischemia until 30 min post-ischemia. Time controls (TC) underwent neither hemorrhage, hindlimb ischemia nor resuscitation. Goats were sacrificed and left ventricular myocardium biopsied at 90 min fluid resuscitation (n = 6 per group) or 3.5 h later (n = 9 LR, 10 PR, 8 TC).

RESULTS: Myocardial 8-isoprostane content, phosphocreatine phosphorylation potential, creatine kinase activity, and heart rate-adjusted QT interval (QTc) variability were evaluated at 90 min resuscitation and 3.5 h post-resuscitation. PR sharply lowered pro-arrhythmic QTc variability vs LR (P < 0.05); this effect persisted 3.5 h post-resuscitation. PR lowered myocardial 8-isoprostane content, a product of oxidative stress, by 39 and 37% during and 3.5 h after resuscitation, respectively, vs LR. Creatine kinase activity fell 42% post-LR vs TC (P < 0.05), but was stable post-PR (P < 0.02 vs post-LR). PR doubled phosphocreatine phosphorylation potential, a measure of ATP free energy state, vs TC and LR (P < 0.05); this energetic enhancement persisted 3.5 h post-resuscitation.

CONCLUSION: By augmenting myocardial energy state and protecting creatine kinase activity, pyruvate-enriched resuscitation stabilized cardiac electrical function during central hypovolemia and hindlimb ischemia-reperfusion.

The preventive effect of Se-methylselenocysteine on γ-radiation-induced oxidative stress in rat lungs

We investigated the preventive effect of Se-methylselenocysteine (MSC) administration on γ-radiation (whole body irradiation, single 10-Gy dose)-induced oxidative damage in rat lungs. Rats were pretreated with MSC (0.75mg/rat/day) for 1 week before γ-irradiation. The MSC pretreatment prevented the irradiation-induced increase in lipid peroxidation and the concomitant decrease in cellular glutathione content. The prevention of irradiation-induced oxidative damage in MSC-pretreated rat lungs appeared to be associated with increased antioxidant capacity, particularly in the glutathione system. The 1-week MSC treatment resulted in an increase in glutathione peroxidase, glutathione reductase, and glucose 6-phosphate dehydrogenase activities, which are involved in glutathione redox cycling. An increase in catalase activity was also observed in the rat lungs. Additionally, a significantly increased level of nuclear factor erythroid 2-related factor 2 (Nrf2) was exhibited in the MSC-treated rat lungs. Heme oxygenase 1, glutathione S-transferase pi, and peroxiredoxin 1, which are known target proteins of Nrf2, were also increased in MSC-treated lungs. These results implicate Nrf2 signaling in the MSC-induced activation of the antioxidant system.

Postresuscitation myocardial dysfunction in a dog

OBJECTIVE

To describe a clinical case of postresuscitation myocardial dysfunction in a dog.

CASE SUMMARY

An 11-month-old, 2.37 kg female spayed Chihuahua was referred for management post CPR after suffering cardiopulmonary arrest. Postresuscitation a gallop rhythm was identified and an echocardiogram revealed severe left ventricular dilation and severely impaired myocardial contractility with a mild eccentric jet of mitral regurgitation on color Doppler interrogation. The primary differentials were idiopathic or nutritional dilated cardiomyopathy, end-stage myocarditis, or postresuscitation myocardial dysfunction. Echocardiogram was repeated 48 hours later and showed normal left ventricular dimensions and contractility assessed as consistent with postresuscitation myocardial dysfunction.

NEW OR UNIQUE INFORMATION PROVIDED

Postresuscitation myocardial dysfunction is a common complication of CPR in human medicine and is associated with a worse outcome. This is the first clinical report of postresuscitation myocardial dysfunction in a dog.

Nitric oxide-mediated protein modification in cardiovascular physiology and pathology

Nitric oxide (NO) is a key regulator of cardiovascular functions including the control of vascular tone, anti-inflammatory properties of the endothelium, cardiac contractility, and thrombocyte activation and aggregation. Numerous experimental data support the view that NO not only acts via cyclic guanosine monophosphate (cGMP)-dependent mechanisms but also modulates protein function by nitrosation, nitrosylation, glutathiolation, and nitration, respectively. To understand how NO regulates all of these diverse biological processes on the molecular level a comprehensive assessment of NO-mediated cGMP-dependent and independent targets is required. Novel proteomic approaches allow the simultaneous identification of large quantities of proteins modified in an NO-dependent manner and thereby will considerably deepen our understanding of the role NO plays in cardiovascular physiology and pathophysiology.

Post-cardiac arrest syndrome: Mechanisms and evaluation of adrenal insufficiency

Cardiac arrest is one of the leading causes of death and represents maximal stress in humans. After restoration of spontaneous circulation, post-cardiac arrest syndrome is the predominant disorder in survivors. Besides the post-arrest brain injury, the post-resuscitation myocardial stunning, and the systemic ischemia/reperfusion response, this syndrome is characterized by adrenal insufficiency, a disorder that often remains undiagnosed. The pathophysiology of adrenal insufficiency has not been elucidated. We performed a comprehensive search of three medical databases in order to describe the major pathophysiological disturbances which are responsible for the occurrence of the disorder. Based on the available evidence, this article will help physicians to better evaluate and understand the hidden yet deadly post-cardiac arrest adrenal insufficiency.

Redox-mediated programed death of myocardial cells after cardiac arrest and cardiopulmonary resuscitation

Besides the fact that prolonged whole-body ischemia causes tissue and organ injury during cardiac arrest, additional damage occurs after the restoration of spontaneous circulation, during which the reperfusion activates a host of intracellular responses. These responses may lead to an increased threshold of oxidant-mediated injury and redox-mediated programed cell death in the stunned myocardium. The aim of this article is to summarize the major intracellular responses occurring from the onset of cardiac arrest until the post-resuscitation period that may lead to redox-mediated programed death of myocardial cells.

Post-cardiac arrest brain injury: pathophysiology and treatment

Cardiac arrest is a leading cause of death that affects more than a million individuals worldwide every year. Despite the recent advancement in the field of cardiac arrest and resuscitation, the management and prognosis of post-cardiac arrest brain injury remain suboptimal. The pathophysiology of post-cardiac arrest brain injury involves a complex cascade of molecular events, most of which remain unknown. Considering that a potentially broad therapeutic window for neuroprotective drug therapy is offered in most successfully resuscitated patient after cardiac arrest, the need for further research is imperative. The aim of this article is to present the major pathophysiological disturbances leading to post-cardiac arrest brain injury, as well as to review the available pharmacological therapies.

Identification and quantification of S-nitrosylation by cysteine reactive tandem mass tag switch assay

Redox-switches are critical cysteine thiols that are modified in response to changes in the cell's environment conferring a functional effect. S-nitrosylation (SNO) is emerging as an important modulator of these regulatory switches; however, much remains unknown about the nature of these specific cysteine residues and how oxidative signals are interpreted. Because of their labile nature, SNO-modifications are routinely detected using the biotin switch assay. Here, a new isotope coded cysteine thiol-reactive multiplex reagent, cysTMT(6), is used in place of biotin, for the specific detection of SNO-modifications and determination of individual protein thiol-reactivity. S-nitrosylation was measured in human pulmonary arterial endothelia cells in vitro and in vivo using the cysTMT(6) quantitative switch assay coupled with mass spectrometry. Cell lysates were treated with S-nitrosoglutathione and used to identify 220 SNO-modified cysteines on 179 proteins. Using this approach it was possible to discriminate potential artifacts including instances of reduced protein disulfide bonds (6) and S-glutathionylation (5) as well as diminished ambiguity in site assignment. Quantitative analysis over a range of NO-donor concentrations (2, 10, 20 μm; GSNO) revealed a continuum of reactivity to SNO-modification. Cysteine response was validated in living cells, demonstrating a greater number of less sensitive cysteine residues are modified with increasing oxidative stimuli. Of note, the majority of available cysteines were found to be unmodified in the current treatment suggesting significant additional capacity for oxidative modifications. These results indicate a possible mechanism for the cell to gauge the magnitude of oxidative stimuli through the progressive and specific accumulation of modified redox-switches.

Antioxidant activity of Citrus limon essential oil in mouse hippocampus

CONTEXT

Citrus limon (L.) Burms (Rutaceae) has been shown in previous studies to have various biological functions (anti-inflammatory, antiallergic, antiviral, antimutagenic, and anticarcinogenic). However, traditional uses in folk medicine suggest that C. limon may have an effect on the central nervous system (CNS).

OBJECTIVE

This study investigated the effects of C. limon essential oil (EO) on lipid peroxidation level, nitrite content, glutathione reduced (GSH) concentration, and antioxidant enzymes [superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx)] activities in mice hippocampus.

MATERIALS AND METHODS

Swiss mice were treated with the suspension of 0.5% Tween 80, in distilled water used as vehicle (i.p., control group) and with EO in three different doses (0.05, 0.1, or 0.15 g/kg, i.p., EO 50, EO 100, and EO 150 groups, respectively). After the treatments, all groups were observed for 24 h. The enzyme activities as well as the lipid peroxidation, nitrite, and GSH concentrations in mice hippocampus were measured using spectrophotometric methods and the results were compared with values obtained from control group.

RESULTS

EO of C. limon treatment significantly reduced the lipid peroxidation level and nitrite content but increased the GSH levels and the SOD, catalase, and GPx activities in mice hippocampus.

DISCUSSION AND CONCLUSION

Our findings strongly support the hypothesis that oxidative stress in hippocampus can occur during neurodegenerative diseases, proving that hippocampal damage induced by the oxidative process plays a crucial role in brain disorders, and also imply that a strong protective effect could be achieved using EO of C. limon as an antioxidant.

Oxidative modification of citrate synthase by peroxyl radicals and protection with novel antioxidants

In mammals, aging is linked to a decline in the activity of citrate synthase (CS; E.C. 2.3.3.1), the first enzyme of the citric acid cycle. We used 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH), a water-soluble generator of peroxyl and alkoxyl radicals, to investigate the susceptibility of CS to oxidative damage. Treatment of isolated mitochondria with AAPH for 8-24 h led to CS inactivation; however, the activity of aconitase, a mitochondrial enzyme routinely used as an oxidative stress marker, was unaffected. In addition to enzyme inactivation, AAPH treatment of purified CS resulted in dityrosine formation, increased protein surface hydrophobicity, and loss of tryptophan fluorescence. Propyl gallate, 1,8-naphthalenediol, 2,3-naphthalenediol, ascorbic acid, glutathione, and oxaloacetate protected CS from AAPH-mediated inactivation, with IC(50) values of 9, 14, 34, 37, 150, and 160 muM, respectively. Surprisingly, the antioxidant epigallocatechin gallate offered no protection against AAPH, but instead caused CS inactivation. Our results suggest that the current practice of using the enzymatic activity of CS as an index of mitochondrial abundance and the use of aconitase activity as an oxidative stress marker may be inappropriate, especially in oxidative stress-related studies, during which alkyl peroxyl and alkoxyl radicals can be generated.

Pyruvate-fortified cardioplegia evokes myocardial erythropoietin signaling in swine undergoing cardiopulmonary bypass

Pyruvate-fortified cardioplegia protects myocardium and hastens postsurgical recovery of patients undergoing cardiopulmonary bypass (CPB). Pyruvate reportedly suppresses degradation of the alpha-subunit of hypoxia-inducible factor-1 (HIF-1), an activator of the gene encoding the cardioprotective cytokine erythropoietin (EPO). This study tested the hypothesis that pyruvate-enriched cardioplegia evoked EPO expression and mobilized EPO signaling mechanisms in myocardium. Hearts of pigs maintained on CPB were arrested for 60 min with 4:1 blood-crystalloid cardioplegia. The crystalloid component contained 188 mM glucose + or - 24 mM pyruvate. After 30-min cardiac reperfusion with cardioplegia-free blood, the pigs were weaned from CPB. Left ventricular myocardium was sampled 4 h after CPB for immunoblot assessment of HIF-1alpha, EPO and its receptor, the signaling kinases Akt and ERK, and endothelial nitric oxide synthase (eNOS), an effector of EPO signaling. Pyruvate-fortified cardioplegia stabilized arterial pressure post-CPB, induced myocardial EPO mRNA expression, and increased HIF-1alpha, EPO, and EPO-R protein contents by 60, 58, and 123%, respectively, vs. control cardioplegia (P < 0.05). Pyruvate cardioplegia also increased ERK phosphorylation by 61 and 118%, respectively, vs. control cardioplegia-treated and non-CPB sham myocardium (P < 0.01), but did not alter Akt phosphorylation. Nitric oxide synthase (NOS) activity and eNOS content fell 32% following control CPB vs. sham, but pyruvate cardioplegia prevented these declines, yielding 49 and 80% greater NOS activity and eNOS content vs. respective control values (P < 0.01). Pyruvate-fortified cardioplegia induced myocardial EPO expression and mobilized the EPO-ERK-eNOS mechanism. By stabilizing HIF-1alpha, pyruvate-fortified cardioplegia may evoke sustained activation of EPO's cardioprotective signaling cascade in myocardium.

Effects of isopulegol on pentylenetetrazol-induced convulsions in mice: possible involvement of GABAergic system and antioxidant activity

The present study investigated the effects of isopulegol, a monoterpene alcohol, in PTZ-induced convulsions and verified possible involved mechanisms. Saline, isopulegol or diazepam were intraperitonealy injected 30 min before PTZ. The latency for development of convulsions and mortality, as well as the mortality protection percentage was recorded. For investigating the involvement of GABAergic system, flumazenil was utilized. The activity of antioxidant enzyme catalase as well as the levels of reduced glutathione and lipid peroxidation were measured in brain hippocampus. Similarly to diazepam, isopulegol significantly prolonged the latency for convulsions and mortality of mice. All animals were protected against mortality at higher dose of isopulegol. Flumazenil pretreatment decreased the prolongation of seizure latency induced by both diazepam and isopulegol, although it was not able to reverse the latency and protection percent for mortality. Isopulegol also significantly prevented PTZ-induced increase in lipid peroxidation, preserved catalase activity in normal levels, and prevented the PTZ-induced loss of GSH in hippocampus of mice. These results suggest that the anticonvulsant and bioprotective effects of isopulegol against PTZ-induced convulsions are possibly related to positive modulation of benzodiazepine-sensitive GABA(A) receptors and to antioxidant properties.

Quantitative analysis of redox-sensitive proteome with DIGE and ICAT

Oxidative modifications of protein thiols are important mechanisms for regulating protein functions. The present study aimed to compare the relative effectiveness of two thiol-specific quantitative proteomic techniques, difference gel electrophoresis (DIGE) and isotope coded affinity tag (ICAT), for the discovery of redox-sensitive proteins in heart tissues. We found that these two methods were largely complementary; each could be used to reveal a set of unique redox-sensitive proteins. Some of these proteins are low-abundant signaling proteins and membrane proteins. From DIGE analysis, we found that both NF-kappaB-repressing protein and epoxide hydrolase were sensitive to H 2O 2 oxidation. In ICAT analysis, we found that specific cysteines within sacroplasmic endoplamic reticulum calcium ATPase 2 and voltage-dependent anion-selective channel protein 1 were sensitive to H 2O 2 oxidation. From these analyses, we conclude that both methods should be employed for proteome-wide studies, to maximize the possibility of identifying proteins containing redox-sensitive cysteinyl thiols in complex biological systems.

Pyruvate enhances neurological recovery following cardiopulmonary arrest and resuscitation

PURPOSE

Cerebral oxidative stress and metabolic dysfunction impede neurological recovery from cardiac arrest-resuscitation. Pyruvate, a potent antioxidant and energy-yielding fuel, has been shown to protect against oxidant- and ischemia-induced neuronal damage. This study tested whether acute pyruvate treatment during cardiopulmonary resuscitation can prevent neurological dysfunction and cerebral injury following cardiac arrest.

METHODS

Anesthetized, open-chest mongrel dogs underwent 5 min cardiac arrest, 5 min open-chest cardiac compression (OCCC), defibrillation and 3-day recovery. Pyruvate (n=9) or NaCl volume control (n=8) were given (0.125 mmol kg(-1) min(-1) i.v.) throughout OCCC and the first 55 min recovery. Sham dogs (n=6) underwent surgery and recovery without cardiac arrest-resuscitation.

RESULTS

Neurological deficit score (NDS), evaluated at 2-day recovery, was sharply increased in NaCl-treated dogs (10.3+/-3.5) versus shams (1.2+/-0.4), but pyruvate treatment mitigated neurological deficit (NDS=3.3+/-1.2; P<0.05 versus NaCl). Brain samples were taken for histological examination and evaluation of inflammation and cell death at 3-day recovery. Loss of pyramidal neurons in the hippocampal CA1 subregion was greater in the NaCl controls than in pyruvate-treated dogs (11.7+/-2.3% versus 4.3+/-1.2%; P<0.05). Cardiac arrest increased caspase-3 activity, matrix metalloproteinase activity, and DNA fragmentation in the CA1 subregion; pyruvate prevented caspase-3 activation and DNA fragmentation, and suppressed matrix metalloproteinase activity.

CONCLUSION

Intravenous pyruvate therapy during cardiopulmonary resuscitation prevents initial oxidative stress and neuronal injury and enhances neurological recovery from cardiac arrest.