3-nitrotyrosine and Arrhythmias--Cardiac

To provide evidence for the protective role of inorganic nitrite against acute ischaemia and reperfusion-induced ventricular arrhythmias in a large animal model.. Dogs, anaesthetized with chloralose and urethane, were administered intravenously with sodium nitrite (0.2 µmol kg(-1) min(-1)) in two protocols. In protocol 1 nitrite was infused 10 min prior to and during a 25 min occlusion of the left anterior descending (LAD) coronary artery (NaNO2-PO; n = 14), whereas in protocol 2 the infusion was started 10 min prior to reperfusion of the occluded vessel (NaNO2-PR; n = 12). Control dogs (n = 15) were infused with saline and subjected to the same period of ischaemia and reperfusion. Severities of ischaemia and ventricular arrhythmias, as well as changes in plasma nitrate/nitrite (NOx) levels in the coronary sinus blood, were assessed throughout the experiment. Myocardial superoxide and nitrotyrosine (NT) levels were determined during reperfusion. Changes in protein S-nitrosylation (SNO) and S-glutathionylation were also examined.. Compared with controls, sodium nitrite administered either pre-occlusion or pre-reperfusion markedly suppressed the number and severity of ventricular arrhythmias during occlusion and increased survival (0% vs. 50 and 92%) upon reperfusion. There were also significant decreases in superoxide and NT levels in the nitrite treated dogs. Compared with controls, increased SNO was found only in NaNO2-PR dogs, whereas S-glutathionylation occurred primarily in NaNO2-PO dogs.. Intravenous infusion of nitrite profoundly reduced the severity of ventricular arrhythmias resulting from acute ischaemia and reperfusion in anaesthetized dogs. This effect, among several others, may result from an NO-mediated reduction in oxidative stress, perhaps through protein SNO and/or S-glutathionylation.

Topics: Administration, Intravenous; Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Disease Models, Animal; Dogs; Hemodynamics; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Nitrates; Nitric Oxide; Nitrites; Protein Processing, Post-Translational; Sodium Nitrite; Superoxides; Tyrosine

Remote ischemic perconditioning (RIPerC) has a promising therapeutic insight to improve the prognosis of acute myocardial infarction. Chronic comorbidities such as diabetes are known to interfere with conditioning interventions by modulating cardioprotective signaling pathways, such as e.g., mTOR pathway and autophagy. However, the effect of acute hyperglycemia on RIPerC has not been studied so far. Therefore, here we investigated the effect of acute hyperglycemia on cardioprotection by RIPerC.. Wistar rats were divided into normoglycemic (NG) and acute hyperglycemic (AHG) groups. Acute hyperglycemia was induced by glucose infusion to maintain a serum glucose concentration of 15-20 mM throughout the experimental protocol. NG rats received mannitol infusion of an equal osmolarity. Both groups were subdivided into an ischemic (Isch) and a RIPerC group. Each group underwent reversible occlusion of the left anterior descending coronary artery (LAD) for 40 min in the presence or absence of acute hyperglycemia. After the 10-min LAD occlusion, RIPerC was induced by 3 cycles of 5-min unilateral femoral artery and vein occlusion and 5-min reperfusion. After 120 min of reperfusion, infarct size was measured by triphenyltetrazolium chloride staining. To study underlying signaling mechanisms, hearts were harvested for immunoblotting after 35 min in both the NG and AHG groups.. Infarct size was significantly reduced by RIPerC in NG, but not in the AHG group (NG + Isch: 46.27 ± 5.31 % vs. NG + RIPerC: 24.65 ± 7.45 %, p < 0.05; AHG + Isch: 54.19 ± 4.07 % vs. 52.76 ± 3.80 %). Acute hyperglycemia per se did not influence infarct size, but significantly increased the incidence and duration of arrhythmias. Acute hyperglycemia activated mechanistic target of rapamycine (mTOR) pathway, as it significantly increased the phosphorylation of mTOR and S6 proteins and the phosphorylation of AKT. In spite of a decreased LC3II/LC3I ratio, other markers of autophagy, such as ATG7, ULK1 phopsphorylation, Beclin 1 and SQSTM1/p62, were not modulated by acute hyperglycemia. Furthermore, acute hyperglycemia significantly elevated nitrative stress in the heart (0.87 ± 0.01 vs. 0.50 ± 0.04 µg 3-nitrotyrosine/mg protein, p < 0.05).. This is the first demonstration that acute hypreglycemia deteriorates cardioprotection by RIPerC. The mechanism of this phenomenon may involve an acute hyperglycemia-induced increase in nitrative stress and activation of the mTOR pathway.

Topics: Animals; Apoptosis Regulatory Proteins; Arrhythmias, Cardiac; Autophagy; Autophagy-Related Protein 7; Autophagy-Related Protein-1 Homolog; Beclin-1; Heat-Shock Proteins; Hyperglycemia; Intracellular Signaling Peptides and Proteins; Ischemic Preconditioning, Myocardial; Myocardial Infarction; Myocardial Reperfusion Injury; Phosphorylation; Proto-Oncogene Proteins c-akt; Rats; Rats, Wistar; Sequestosome-1 Protein; Severity of Illness Index; Signal Transduction; Stress, Physiological; TOR Serine-Threonine Kinases; Tyrosine; Ubiquitin-Activating Enzymes

Superoxide has been shown to play a major role in ventricular remodeling and arrhythmias after myocardial infarction. However, the source of increased myocardial superoxide production and the role of superoxide in sympathetic innervation remain to be further characterized. Male Wistar rats, after coronary artery ligation, were randomized to vehicle, allopurinol, or apocynin for 4weeks. To determine the role of peroxynitrite in sympathetic reinnervation, we also used 3-morpholinosydnonimine (a peroxynitrite generator). The postinfarction period was associated with increased oxidative stress, as measured by myocardial superoxide, nitrotyrosine, xanthine oxidase activity, NADPH oxidase activity, and dihydroethidium fluorescent staining. Measurement of myocardial norepinephrine levels revealed a significant elevation in vehicle-treated infarcted rats compared with sham. Sympathetic hyperinnervation was blunted after administration of allopurinol. Arrhythmic scores in the allopurinol-treated infarcted rats were significantly lower than those in vehicle. For similar levels of ventricular remodeling, apocynin had no beneficial effects on oxidative stress, sympathetic hyperinnervation, or arrhythmia vulnerability. Allopurinol-treated hearts had significantly decreased nerve growth factor expression, which was substantially increased after coadministration of 3-morpholinosydnonimine. These results indicate that xanthine oxidase but not NADPH oxidase largely mediates superoxide production after myocardial infarction. Xanthine oxidase inhibition ameliorates sympathetic innervation and arrhythmias possibly via inhibition of the peroxynitrite-mediated nerve growth factor pathway.

Topics: Acetophenones; Allopurinol; Animals; Arrhythmias, Cardiac; Coronary Vessels; Ethidium; Male; Molsidomine; Myocardial Infarction; Myocardium; NADPH Oxidases; Nerve Growth Factor; Oxidative Stress; Peroxynitrous Acid; Rats; Rats, Wistar; Superoxides; Sympathetic Nervous System; Tyrosine; Xanthine Oxidase

This study has examined whether peroxynitrite (PN), generated during the preconditioning (PC) procedure or administered by brief intracoronary infusions, plays a trigger role in the anti-arrhythmic effects of preconditioning and peroxynitrite in anaesthetized dogs. To achieve this we infused the peroxynitrite scavenger uric acid (UA; 0.2 mg/kg/min, i.v.) over a 30 min period, just prior to a 25 min occlusion of the left anterior descending coronary artery, in preconditioned (UA+PC, n=8), peroxynitrite-treated (UA+PN, n=8) and in control (UAC; n=9) dogs. The effects were compared to those obtained from groups (PC, n=10; PN, n=10; C1, n=14) without uric acid administration. Severities of ischaemia (ST-segment elevation, inhomogeneity of electrical activation) and ventricular arrhythmias (VPBs, VT, VF), plasma nitrate/nitrite levels, as well as myocardial superoxide and nitrotyrosine productions were determined. Both preconditioning and the infusion of peroxynitrite increased nitrotyrosine formation which was abolished by the simultaneous administration of urate. Despite this, the protective effects of preconditioning (i.e. reductions in arrhythmias, superoxide and nitrotyrosine productions, as well as the increase in nitric oxide availability), occurring during the prolonged period of occlusion and reperfusion were still present. In contrast, urate completely abolished the protection resulted from peroxynitrite administration. This effect is most probably due to the fact that urate has already scavenged peroxynitrite during the infusion. Interestingly, urate itself, given prior to ischaemia and reperfusion, was also protective. We conclude that peroxynitrite in nanomolar concentrations can induce an anti-arrhythmic effect but peroxynitrite, generated during the preconditioning stimulus, is not necessary for the preconditioning-induced anti-arrhythmic protection.

Topics: Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Arterial Occlusive Diseases; Coronary Vessels; Dogs; Female; Heart Ventricles; Hemodynamics; Hydrogen-Ion Concentration; Infusions, Intra-Arterial; Ischemic Preconditioning, Myocardial; Male; Myocardial Reperfusion Injury; Nitrates; Nitrites; Peroxynitrous Acid; Superoxides; Time Factors; Tyrosine; Uric Acid

Both ischaemia preconditioning (PC) and the intracoronary infusion of peroxynitrite (PN) suppress ischaemia and reperfusion (I/R)-induced arrhythmias and the generation of nitrotyrosine (NT, a marker of PN). However, it is still unclear whether this latter effect is due to a reduction in nitric oxide (NO) or superoxide (O(2)(-)) production.. Dogs anaesthetized with chloralose and urethane were infused, twice for 5 min, with either saline (control) or 100 nM PN, or subjected to similar periods of occlusion (PC), 5 min prior to a 25 min occlusion and reperfusion of the left anterior descending coronary artery. Severities of ischaemia and ventricular arrhythmias, as well as changes in the coronary sinus nitrate/nitrite (NOx) levels were assessed throughout the experiment. The production of myocardial NOx, O(2)(-) and NT was determined following reperfusion.. Both PC and PN markedly suppressed the I/R-induced ventricular arrhythmias, compared to the controls, and increased NOx levels during coronary artery occlusion. Reperfusion induced almost the same increases in NOx levels in all groups, but superoxide production and, consequently, the generation of NT were significantly less in PC- and PN-treated dogs than in controls.. Since both PC and the administration of PN enhanced NOx levels during I/R, the attenuation of endogenous PN formation in these dogs is primarily due to a reduction in the amount of O(2) produced. Thus, the anti-arrhythmic effect of PC and PN can almost certainly be attributed to the preservation of NO availability during myocardial ischaemia.

Topics: Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Dogs; Female; Infusions, Intra-Arterial; Ischemic Preconditioning, Myocardial; Male; Nitric Oxide; Peroxynitrous Acid; Reactive Nitrogen Species; Superoxides; Tyrosine

Exogenous peroxynitrite from nanomolar to micromolar concentrations exerts cardioprotection. Here, we have assessed its effects on ischaemia- and reperfusion-induced ventricular arrhythmias in vivo and a possible role for mitochondrial K(ATP) channels in these effects, using the channel inhibitor 5-hydroxydecanoate (5-HD).. Chloralose-urethane-anaesthetized dogs were treated twice for 5 min with peroxynitrite (100 nM, by intracoronary infusions) in both the absence and presence of 5-HD (150 microg kg(-1) min(-1)), and then subjected to 25 min occlusion of the left anterior descending coronary artery. The severity of ischaemia and of arrhythmias, as well as the levels of nitrotyrosine were assessed and compared with a group of control dogs, subjected only to a 25 min occlusion and reperfusion insult.. Compared with controls, infusion of peroxynitrite markedly suppressed the number of ventricular premature beats (388+/-88 vs 133+/-44), the incidence of ventricular fibrillation both during occlusion (50% vs 10%) and reperfusion (100% vs 44%), and increased survival (0% vs 50%; all P<0.05). The severity of ischaemia (epicardial ST-segment changes, inhomogeneity of electrical activation) during occlusion and nitrotyrosine levels on reperfusion were significantly less in the peroxynitrite-treated dogs than in the controls. 5-HD did not modify the cardioprotective effects of peroxynitrite.. Exogenous peroxynitrite provided antiarrhythmic protection in vivo, which might have been on account of a reduction in endogenous peroxynitrite formation. This protection seemed not to be mediated through mitoK(ATP) channels.

Topics: Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Coronary Vessels; Decanoic Acids; Dogs; Female; Hydroxy Acids; Male; Myocardial Reperfusion Injury; Peroxynitrous Acid; Potassium Channels; Severity of Illness Index; Survival Rate; Tyrosine; Ventricular Fibrillation

Myocardial ischemia-reperfusion (I/R) injury is associated with contractile dysfunction, arrhythmias, and myocyte death. Intracellular Ca(2+) overload with reduced activity of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) is a critical mechanism of this injury. Although upregulation of SERCA function is well documented to improve postischemic cardiac function, there are conflicting reports where pharmacological inhibition of SERCA improved postischemic function. SERCA2a is the primary cardiac isoform regulating intracellular Ca(2+) homeostasis; however, SERCA1a has been shown to substitute SERCA2a with faster Ca(2+) transport kinetics. Therefore, to further address this issue and to evaluate whether SERCA1a expression could improve postischemic cardiac function and myocardial salvage, in vitro and in vivo myocardial I/R studies were performed on SERCA1a transgenic (SERCA1a(+/+)) and nontransgenic (NTG) mice. Langendorff-perfused hearts were subjected to 30 min of global ischemia followed by reperfusion. Baseline preischemic coronary flow and left ventricular developed pressure were significantly greater in SERCA1a(+/+) mice compared with NTG mice. Independent of reperfusion-induced oxidative stress, SERCA1a(+/+) hearts demonstrated greatly improved postischemic (45 min) contractile recovery with less persistent arrhythmias compared with NTG hearts. Morphometry showed better-preserved myocardial structure with less infarction, and electron microscopy demonstrated better-preserved myofibrillar and mitochondrial ultrastructure in SERCA1a(+/+) hearts. Importantly, intraischemic Ca(2+) levels were significantly lower in SERCA1a(+/+) hearts. The cardioprotective effect of SERCA1a was also observed during in vivo regional I/R with reduced myocardial infarct size after 24 h of reperfusion. Thus SERCA1a(+/+) hearts were markedly protected against I/R injury, suggesting that expression of SERCA 1a isoform reduces postischemic Ca(2+) overload and thus provides potent myocardial protection.

Topics: Animals; Arrhythmias, Cardiac; Calcium; Coronary Circulation; Disease Models, Animal; Electron Spin Resonance Spectroscopy; Fluorescent Dyes; Free Radicals; Heterocyclic Compounds, 3-Ring; Immunohistochemistry; Isoenzymes; Mice; Mice, Transgenic; Mitochondria, Heart; Myocardial Contraction; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Sarcoplasmic Reticulum; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Spectrometry, Fluorescence; Time Factors; Tyrosine; Ventricular Function, Left; Ventricular Pressure