Occlusion Of LAD Coronary Artery Research Articles

DECIPHERING THE NOVEL ROLE OF ERDOSTEINE IN PREVENTION OF MYOCARDIAL ISCHEMIA-REPERFUSION INJURY IN RAT

Objective: Myocardial ischemia-reperfusion injury (MIRI) is caused by thrombotic obstruction of the coronary artery subsequently leading to heart failure. Despite the availability of improved prognosis, MIRI is a foremost cause of morbidity and mortality worldwide. In this study, we investigated the therapeutic potential of Erdosteine (a mucoactive antioxidant molecule, with multifaceted pharmacological properties), to attenuate myocardial infarction in rat model of MIRI. Design and method: This study was conducted in adult male Wistar rats (n=40), randomized into five groups: Sham, IR-C (disease control), Erdosteine (80 mg/kg; s.c.) + IR, Telmisartan (10 mg/kg; orally) +IR and Erdosteine (80 mg/kg) perse groups. Erdosteine and telmisartan were administered for 28 days as a pre-treatment. On the 29th day, animals were subjected to LAD coronary artery occlusion for 1 h followed by reperfusion for 45 minutes. The cardioprotective potential was assessed through measurement of hemodynamic parameters, biochemical markers (MDA, GSH, SOD), cardiac injury markers (CK-MB and LDH), inflammatory markers (IL-6, TNF), histopathological evaluation, TUNEL assay and immunohistochemistry analysis (Bax, caspase 3, Bcl2). Further, the underlying mechanism was evaluated using immune-blotting of MAPK, Nrf-2/HO-1, and Akt/p-Akt. The statistics analysis was performed by one-way ANOVA followed by Turkey-Kramer post hoc tests. Results: Erdosteine and telmisartan pretreatment improves hemodynamic parameters by preserving MAP, ±LVdP/dt, and HR as compared to the IR-C group. Pretreatment markedly restored the levels of antioxidants (GSH and SOD) and decreased peroxidation marker (MDA) compared to the IR-C group. Also, the pretreatment significantly prevented the damage following IR injury as compared to the IR-C group when investigated through cardiac injury markers and histopathological evaluation. Erdosteine profoundly reversed the expressions of Bcl2/BAX ratio, in comparison to the IR-C group indicating its anti-apoptotic effect when reconfirmed through TUNEL assay. Erdosteine pretreatment preserved the levels of NF-kB, TNF, and IL-6 following IR challenge. Erdosteine pretreatment restores FABP, Nrf-2, and Hsp27. Conclusions: Erdosteine protects the myocardial cell membrane from peroxidation and inhibits oxidative burst and inflammation through NF-kB pathway activation. Erdosteine attenuates MIRI injury in rats preserving the MAPK and Nrf-2 signaling cascade.

Abatacept: A Promising Repurposed Solution for Myocardial Infarction-Induced Inflammation in Rat Models.

Myocardial infarction (MI) is irreversible damage to the myocardial tissue caused by prolonged ischemia/hypoxia, subsequently leading to loss of contractile function and myocardial damage. However, after a perilous period, ischemia-reperfusion (IR) itself causes the generation of oxygen free radicals, disturbance in cation homeostasis, depletion of cellular energy stores, and activation of innate and adaptive immune responses. The present study employed Abatacept (ABT), which is an anti-inflammatory drug, originally used as an antirheumatic response agent. To investigate the cardioprotective potential of ABT, primarily, the dose was optimized in a chemically induced model of myocardial necrosis. Thereafter, ABT optimized the dose of 5 mg/kg s.c. OD was investigated for its cardioprotective potential in a surgical model of myocardial IR injury, where animals (n = 30) were randomized into five groups: Sham, IR-C, Telmi10 + IR (Telmisartan, 10 mg/kg oral OD), ABT5 + IR, ABT perse. ABT and telmisartan were administered for 21 days. On the 21st day, animals were subjected to LAD coronary artery occlusion for 60 min, followed by reperfusion for 45 min. Further, the cardioprotective potential was assessed through hemodynamic parameters, oxidant-antioxidant biochemical enzymatic parameters, cardiac injury, inflammatory markers, histopathological analysis, TUNEL assay, and immunohistochemical evaluation, followed by immunoblotting to explore signaling pathways. The statistics were performed by one-way analysis of variance, followed by the Tukey comparison post hoc tests. Noteworthy, 21 days of ABT pretreatment amended the hemodynamic and ventricular functions in the rat models of MI. The cardioprotective potential of ABT is accompanied by inhibiting MAP kinase signaling and modulating Nrf-2/HO-1 proteins downstream signaling cascade. Overall, the present work bolsters the previously known anti-inflammatory role of ABT in MI and contributes a mechanistic insight and application of clinically approved drugs in averting the activation of inflammatory response.

Exogenous GalR2-specific peptide agonist as a tool for treating myocardial ischemia/reperfusion injury.

The aim of this work was to elucidate the role of GalR2 receptor activation in protecting the rat heart in vivo from ischemia/reperfusion (I/R) damage by a pharmacological peptide agonist WTLNSAGYLLGPβAH-OH (G1) and full-length rat galanin GWTLNSAGYLLGPHAIDNHRSFSDKHGLT-NH2 (G2) using M871, a selective inhibitor of GalR2. The peptides were prepared by the automatic solid-phase synthesis using the Fmoc-strategy and purified by high-performance liquid chromatography (HPLC). A 40-min left anterior descending (LAD) coronary artery occlusion followed by a 60-min reperfusion was performed. The criteria for damage/protection of the heart were the infarct size (IS) and plasma activity of creatine kinase-MB (CK-MB) at the end of reperfusion. Intravenous injection of G1 or G2 at an optimal dose of 1mg/kg at the fifth minute of reperfusion significantly reduced the IS (by 35% and 32%, respectively) and activity of CK-MB at the end of reperfusion (by 43% and 38%, respectively) compared with the control. Administration of M871 (8mg/kg) 5min before the onset of reperfusion abolished the effects of G1 on IS and CK-MB activity, returning them to control values. Co-administration of M871 (8mg/kg) with G2 attenuated protective effect of G2 on both IS and plasma СK-MB activity. However, differences in these parameters between the M871+G2 and G2 groups did not reach statistical significance (P = 0.139 and P = 0.121, respectively). Thus, GalR2 is the principal receptor subtype that transduces the protective effects of galanin and ligand G1 in myocardial I/R injury. This suggests that GalR2-specific peptide agonists could be used as drug candidates for treating ischemic heart disease.

JAK2/STAT3 pathway mediates beneficial effects of pterostilbene on cardiac contractile and electrical function in the setting of myocardial reperfusion injury

Contractile dysfunction and fatal arrhythmias are the hallmarks of myocardial ischemia/reperfusion (I/R) injury. Pterostilbene has notable cardioprotective effects, but its main mechanisms are not fully understood. Here, we investigated the effect of PTE on myocardial hemodynamics, arrhythmias, inflammatory/oxidative responses, and the causal role of the JAK2/STAT3 pathway in rats with acute myocardial I/R injury. Sixty male 7-8 months Sprague-Dawley rats (n=10/each group) experienced in vivo model of myocardial I/R injury through 40-min LAD coronary artery occlusion and subsequent 24-h reperfusion. PTE at concentrations of 5 and 25 mg/kg was intraperitoneally administered to rats five min before reperfusion. Cardiac hemodynamics, reperfusion-induced ventricular arrhythmias, infarct size, inflammatory cytokines, oxidative stress markers, the activity of the JAK2/STAT3 pathway were measured as the endpoints. Administration of PTE to I/R-injured rats recovered myocardial contractile function and reduced infarct size and ventricular arrhythmias counts and incidence in a dose-dependent manner. PTE at 25 mg/kg significantly and more potently reduced the levels of inflammatory mediators NF-?B, TNF-?, and IL-1?, suppressed intracellular ROS production, augmented the activity of glutathione, and manganese-superoxide dismutase, and upregulated the JAK2 and STAT3 phosphorylation. Importantly, pretreatment of rats with Ag490 as a JAK2 inhibitor significantly abolished the cardioprotective and signaling effects of PTE in I/R rats. PTE exerts significant protective effects on reducing arrhythmias and myocardial infarction and enhancing cardiac function by stimulating JAK2/STAT3-related suppression of inflammatory and oxidative reactions in the I/R injury setting.

Ischemic Preconditioning Efficacy Following Anabolic Steroid Usage: A Clear Difference Between Sedentary and Exercise-Trained Rat Hearts.

Previous studies show that anabolic steroids impair innate cardioprotective mechanisms. Here, we investigated the effect of supraphysiological doses of nandrolone on ischemic preconditioning (IPC) as a potent cardioprotective tool against ischemia reperfusion (IR) injury in rat hearts. Male Wistar rats in two experimental settings of sedentary and exercise-trained (60min/day swimming, 5days/week, for 8weeks) were either pretreated with intramuscular injections of arachis oil (Arach, n = 16) as vehicle or nandrolone decanoate (ND, n = 8), 10mg/kg/week, for 8weeks. At the end, the hearts were excised and perfused in a Langendorff system. Then, the vehicle-treated hearts subdivided into the IR (30min of LAD coronary artery occlusion and 120min reperfusion, n = 8) and IPC (three cycles of 3-min ischemia and 3-min reperfusion before test ischemia, n = 8) groups and nandrolone-treated hearts served as ND + IPC (nandrolone pretreatment before IR and IPC protocols, n = 8) group. Post-ischemic cardiac function and infarct size were assessed. Reperfusion arrhythmias were analyzed using a standard scoring system. In sedentary hearts, ND slightly increased heart-to-body weight ratio and increased baseline cardiac contractile function. In trained hearts, ND markedly increased heart-to-body weight ratio which was also associated with enhanced baseline cardiac function. ND pretreatment enhanced protective effects of IPC in sedentary group; however, abolished these effects in exercise-trained group. The arrhythmia score was not significantly different between nandrolone-treated groups vs. respective preconditioned groups. Our findings show that ND impairs IPC-induced cardioprotection in exercise-trained rat hearts. Cardiac hypertrophy seems to play a crucial role in this response.

Abstract 429: Intensive Necroptosis Due to Enhanced RIP3-CaMKII Signaling Contributes to Diabetic Myocardial Ischemic Susceptibility

Diabetes increases the vulnerability of the heart to ischemic injury. Recent advances have shown that necroptosis is crucially involved in myocardial ischemia/reperfusion (I/R) injury. Our objectives were thus to extend our knowledge to whether and how necroptosis renders diabetic hearts more vulnerable to I/R injury, which involves activation of Ca 2+ -calmodulin-dependent protein kinase (CaMKII) by receptor-interacting protein 3 (RIP3). In this study, diabetes was induced by streptozotocin (40mg/kg, i.v.) and after 6 weeks, anesthetized open-chest diabetic and age-matched control C57 mice were subjected to 30-min regional ischemia (occlusion of LAD coronary artery) followed by 4-h reperfusion. Diabetic animals manifested significantly greater cardiac injury than their littermate controls. Notably, diabetic hearts were sensitized to I/R-induced myocardial necrosis, as evidenced by rise in lactate dehydrogenase (LDH) release and Evans blue dye (EBD) penetration. Notably, compared with control mice, the activation pattern of CaMKII in diabetic hearts subjected to I/R is altered by earlier advanced (60 min after reperfusion) phosphorylation and enhanced oxidation (21.5% increase). Then we proved that inhibition of CaMKII in early stage of I/R could effectively reduce myocardial necroptosis. Further, RIP3 expression and RIP3-CaMKII interaction are markedly enhanced in diabetic hearts during I/R. Inhibition of RIP3 markedly suppresses CaMKII activation and reduces necroptosis. Collectively, these findings identify enhanced RIP3-CaMKII pathway as a key regulator that increases myocardial necroptosis in diabetic I/R hearts.

Signaling pathways of a structural analogue of apelin-12 involved in myocardial protection against ischemia/reperfusion injury

Exogenously administered chemically modified apelin-12 (MA) has been shown to exhibit protective effects in myocardial ischemia/reperfusion (I/R) injury. They include reduction of ROS formation, cell death and cardiometabolic abnormalities. The aim of the present study was to explore the role of the underlying signaling mechanisms involved in cardioprotection afforded by MA. Isolated perfused working rat hearts subjected to global ischemia and anaesthetized rats in vivo exposed to LAD coronary artery occlusion were used. Myocardial infarct size, cell membrane damage, cardiac dysfunction and metabolic state of the heart were used as indices of I/R injury at the end of reperfusion. Administration of specific inhibitors of MEK1/2, PI3K, NO synthase (NOS) or the mitochondrial ATP-sensitive K+ (mito KATP) channels (UO126, LY294002, L-NAME or 5-hydroxydecanoate, respectively) reduced protective efficacy of MA in both models of I/R injury. This was evidenced by abrogation of infarct size limitation, deterioration of cardiac function recovery, and attenuation of metabolic restoration and sarcolemmal integrity. An enhancement of functional and metabolic recovery in isolated reperfused hearts treated with MA was suppressed by U-73122, chelerythrine, amiloride or KB-R7943 (inhibitors of phospholipase С (PLC), protein kinase C (PKC), Na+/H+ or Na+/Ca2+ exchange, respectively). Additionally, co-infusion of MA with amiloride or L-NAME reduced the integrity of cell membranes at early reperfusion compared with the effect of peptide alone. In conclusion, cardioprotection with MA is mediated by signaling via PLC and survival kinases, PKC, PI3K, and MEK1/2, with activation of downstream targets, NOS and mito KATP channels, and the sarcolemmal Na+/H+ and Na+/Ca2+ exchangers.

Abstract 140: Effect of Transendocardial Autologous Cardiac Stem Cells and Bone Marrow Mesenchymal Stem Cells to Reduce Infarct Size and Restore Cardiac Function in a Heart Failure Swine Model

Background: A cell combination of human mesenchymal stem cells (MSCs) and c-kit+ cardiac stem cells (CSCs) improves left ventricular (LV) performance to a greater degree than MSCs alone in post myocardial infarction swine. To advance the development of cell combination therapy, we administered autologous swine cells, and tested the hypothesis that transendocardial autologous CSCs/MSCs produces greater improvement of performance than MSCs in a rigorous model of heart failure due to post infarct LV remodeling. Methods: Gottingen mini-swine (n=28) underwent LAD coronary artery occlusion followed by reperfusion, and allowed to undergo LV remodeling for 90 days. Autologous MSCs were amplified from bone marrow and CSCs from right ventricular biopsies in each swine, and injections of either CSC/MSC combo (1M/200M, n=7), MSCs (200M, n=7), or placebo (Plasmalyte, n=6) were injected to the infarct-border zone via the NOGA system. Cardiac MRI and pressure volume loops were obtained before and after therapy. Results: Both cell groups had substantially reduced scar size (Combo –37.2.9± 5.4% vs MSCs –38.8±7.5% vs placebo −7.2±6.3, P=0.0001) and increased viable tissue (Combo +30.9±7% vs MSCs +41.8±10.5% vs placebo +7.7±4.5, P<0.0001) relative to placebo. Ejection Fraction (EF) improved only in the Combo group (Combo +7.0±2.8 vs MSCs +3.4±1.3 vs placebo +1.2±1.6 EF units, P=0.04). Accompanying this EF restoration was a substantial improvement in the Combo group in stroke volume (Combo +47.2±11.1% vs MSCs +32.6±12.0% vs placebo +10.8±4.5, P<0.0001), cardiac output (Combo +35.9±7.6% vs MSCs 41.9±26.5% vs placebo −16.4±6.6%, P=0.01) and diastolic strain rate (Combo +18.9±8.6% vs MSCs 14.0±8.8% vs placebo −14.9±9.5%, P=0.03). Conclusions: Combination cell therapy and MSCs alone dramatically reduce scar size in a swine model of chronic ischemic cardiomyopathy. In contrast, combination therapy has much greater impact on functional recovery, increasing EF to [near normal] levels. These findings illustrate that interactions between ckit+ CSCs and MSCs result in substantial enhancement in cardiac performance, establish the safety of autologous cell combination strategies, and support the development of an advanced second generation cell therapeutic product.

Inactivation of the cardiomyocyte glucagon-like peptide-1 receptor (GLP-1R) unmasks cardiomyocyte-independent GLP-1R-mediated cardioprotection.

GLP-1R agonists improve outcomes in ischemic heart disease. Here we studied GLP-1R-dependent adaptive and cardioprotective responses to ventricular injury. Glp1r−/− hearts exhibited chamber-specific differences in gene expression, but normal mortality and left ventricular (LV) remodeling after myocardial infarction (MI) or experimental doxorubicin-induced cardiomyopathy. Selective disruption of the cardiomyocyte GLP-1R in Glp1rCM−/− mice produced no differences in survival or LV remodeling following LAD coronary artery occlusion. Unexpectedly, the GLP-1R agonist liraglutide still produced robust cardioprotection and increased survival in Glp1rCM−/− mice following LAD coronary artery occlusion. Although liraglutide increased heart rate (HR) in Glp1rCM−/− mice, basal HR was significantly lower in Glp1rCM−/− mice. Hence, endogenous cardiomyocyte GLP-1R activity is not required for adaptive responses to ischemic or cardiomyopathic injury, and is dispensable for GLP-1R agonist-induced cardioprotection or enhanced chronotropic activity. However the cardiomyocyte GLP-1R is essential for the control of HR in mice.

Unstable angina due to spontaneous left internal mammary artery dissection seventeen years after coronary artery bypass graft surgery: A case report and literature review

A 64 year-old male was admitted to the emergency department for multiple episodes of chest pain at rest. His cardiac history began seventeen years before when a coronary artery bypass grafting (CABG) was performed. This included left internal mammary artery (LIMA) graft to left anterior descending artery (LAD) and saphenous vein graft (SVG) to the diagonal branch. Since then the patient was subjected to numerous percutaneous coronary angioplasties on LAD, circumflex artery and SVG. The last angiographic control showed LIMA graft patency. The coronary angiography showed LAD, circumflex and right coronary artery occlusion and LIMA graft critical stenosis with evidence of dissection. Then, the lesion was crossed and intravascular ultrasound (IVUS) evaluation was performed to investigate the extent of the dissection. IVUS demonstrated dissection with an intramural hematoma and presence of intimal tear. Therefore, a coronary angioplasty with multiple direct drug eluting stents implantation completed with post-dilatation was performed. Good angiographic and IVUS results were achieved. Spontaneous LIMA graft dissection is a rare condition. We reported the ninth case in literature and the one with the highest latency period between CABG and LIMA graft dissection. This situation may lead to an acute coronary syndrome, an unstable angina in our report, therefore prompt treatment, percutaneous or surgical, is decisive. Spontaneous arterial graft dissection is sometimes seen in women, especially in the post-partum period, it usually occurs during the fifth and sixth decade in patients affected by arterial hypertension, vasculitis, connective tissue disorders or atherosclerotic disease.

Failing Hearts are Preconditioned against Myocardial Infarction and Exhausted their Ischemic Preconditioning Reserve

Background Ischemic preconditioning (IPC) is well documented in naïve animals' hearts; however its clinical efficacy remains questionable. To test whether IPC is clinically applicable, we determined IPC reserve in normal and failing canine hearts. Methods Heart failure was created by chronic rapid pacing (250 bpm for 6 weeks). LV remodeling was confirmed by echocardiography (EF=10–20%, LV dilation). Anesthetized control (n=18) and failing heart (n=27) animals were subjected to 45, 60 or 90 min index ischemia (LAD coronary artery occlusion) and 4 hrs reperfusion. Collateral blood was measured colored microspheres. ATP pool and HSP70 were determined in tissue biopsies. Monastral blue and TTC were used to delineate risk area and infarct size. Results The risk areas were comparable between groups. The infarct sizes (INF) were lower (1.95±1.50*, 8.50±1.38* and 19.70±0.72 *) in the failing hearts than control groups (p<0.05) following 45, 60 and 90 min of ischemia, respectively. After 90 min ischemia, INF size of the naïve hearts were significantly greater (INF%=32.10±2.90) than failing hearts (INF%= 19.70±0.72). IPC limited INF size of the naïve hearts but did not affect the small INF size in failing hearts. Conclusion Failing hearts are chronically preconditioned against an acute MI and exhausted their IPC reserve. Drugs that abolish this tolerance would jeopardize patients' safety.

Off‐Pump Glutamate Pre‐ and Post‐Conditioning against an Acute Myocardial Infarction: Role of ATP‐Sensitive Potassium Channels

Background Metabotropic glutamate receptor 5(mGluR5) is expressed in hearts. We determined whether infusion of glutamate (GLU) pre- (PreC) and post-conditions (Post-C) against acute myocardial infarction (MI) and if mitochondrial (Mito) KATP channel is involved (using 5-Hydroxydecanoate). Methods Anesthetized dogs (n = 46), instrumented to monitor LV contractility using sonomicrometry, subjected to 90 minutes LAD coronary artery occlusion and 4 hrs reperfusion (Rep). Dogs were infused with 50ml of vehicle (control), glutamate (Glu100μmol/L) or 5HD (5 mg/Kg)+GLU before ischemia (PreC) or before Rep (PostC). Coronary blood flow was measured using colored microspheres. LV function (stroke work/end diastolic relationships) was determined. The infarct size and LV and risk areas were measured. Four animals were excluded. Data were analyzed by ANOVA and presented as mean± SEM (n = 6). Results LV function significantly recovered in Glu-treated groups (p=NS vs., baseline, p < 0.05 vs. control, 5HD). Poor LV functional recovery was seen in the control (36.2±5%) and 5HD (46.1±6%)groups (p < 0.05 vs Glu groups). GLU reduced the infarct size (38.2±6% in the control group to11.1±4% and 14.3±3 in GLU PreC and PostC groups. 5-HD abolished Glu-infarct size limitation. Conclusions Infusion of GLU pre- and post-conditions the myocardium against INF. Mito-KATP channels are involved in GLU-mediated cardioprotection.

Thioredoxin 1 enhances neovascularization and reduces ventricular remodeling during chronic myocardial infarction: A study using thioredoxin 1 transgenic mice

Oxidative stress plays a crucial role in disruption of neovascularization by alterations in thioredoxin 1 (Trx1) expression and its interaction with other proteins after myocardial infarction (MI). We previously showed that Trx1 has angiogenic properties, but the possible therapeutic significance of overexpressing Trx1 in chronic MI has not been elucidated. Therefore, we explored the angiogenic and cardioprotective potential of Trx1 in an in vivo MI model using transgenic mice overexpressing Trx1. Wild-type (W) and Trx1 transgenic (Trx1Tg/+) mice were randomized into W sham (WS), Trx1Tg/+ sham (TS), WMI, and TMI. MI was induced by permanent occlusion of LAD coronary artery. Hearts from mice overexpressing Trx1 exhibited reduced fibrosis and oxidative stress and attenuated cardiomyocyte apoptosis along with increased vessel formation compared to WMI. We found significant inhibition of Trx1 regulating proteins, TXNIP and AKAP 12, and increased p-Akt, p-eNOS, p-GSK-3β, HIF-1α, β-catenin, VEGF, Bcl-2, and survivin expression in TMI compared to WMI. Echocardiography performed 30days after MI revealed significant improvement in myocardial functions in TMI compared to WMI. Our study identifies a potential role for Trx1 overexpression and its association with its regulatory proteins TXNIP, AKAP12, and subsequent activation of Akt/GSK-3β/β-catenin/HIF-1α-mediated VEGF and eNOS expression in inducing angiogenesis and reduced ventricular remodeling. Hence, Trx1 and other proteins identified in our study may prove to be potential therapeutic targets in the treatment of ischemic heart disease.

Acute Caloric Restriction is Cardioprotective in Adult Rats

Reduced coronary perfusion in acute coronary syndrome causes myocardial ischemia. Also the effect of reactive oxygen species (ROS) induced ischemia‐reperfusion injury contributes to myocardial lesion. ROS generation in hypoxia is modulated by the redox state. Fasting before exposure to ischemia should increase ketogenesis that consumes reduced coenzymes and consequently reduces free radical damage.We investigated whether the 3‐day fasting affects production of ROS, incidence of ventricular arrhythmias during ischemia/reperfusion and myocardial infarction size.We analyzed production of the lipid peroxidation end products (LFP) in the heart tissue. Open‐chest rats were subjected to 20‐min LAD coronary artery occlusion followed by reperfusion. A single‐lead ECG was recorded and arrhythmias were assessed. The infarction size in excised hearts was determined by triphenyltetrazolium chloride staining and it was normalized to area at risk (IS/AR).Three day fasting reduced LFP production in heart tissue. During early reperfusion the number of premature ventricular complexes was reduced in fasting rats compared to controls, as well as ventricular tachycardia duration. In fasting rats the IS/AR reached 48.5 ± 3.3 % while in controls it was 74.3 ± 2.2 %, p&lt;0.005.Acute caloric restriction limits free radical damage in heart, reperfusion ventricular arrhythmias and myocardial infarction size in rats.Supported by GAUK 60009/2009 and MSMT 1M 0510.

Abstract 5614: In vivo Angiogenic and Anti-Apoptotic Signaling of Trx1 Against Acute Myocardial Infarction: An Insight With Transgenic Mice Overexpressing Trx1

Oxidative stress &amp; alterations in thioredoxin-1 (Trx1) expression/activity &amp; its interactions with several other proteins play a crucial role in cardiovascular complications after acute myocardial infarction (MI). Apart from its antioxidative capacity, Trx1 is known to possess antiapoptotic, growth stimulatory &amp; angiogenic properties by modulating the expression/activity of its protein interacting partners thereby modifying the cell’s response to oxidative stress. However, the exact mechanism of the cardioprotective effect of overexpressing Trx1 has not been elucidated in acute MI. Therefore in the present study we have explored the angiogenic &amp; cardioprotective potential of transgenic overexpression of Trx1 in mice in vivo MI model. The wild type (W) &amp; the Trx1 transgenic (Tg+/+) mice were randomized into 4 groups: Wild type Sham (WS), WMI, Tg+/+ Sham (TS) Tg+/+ MI (TMI). MI was induced by permanent occlusion of LAD coronary artery. Sham groups underwent the same time matched surgical procedure without LAD ligation. We observed significant, reduction in infarct size (49±2vs35±2% infarct size/area at risk) &amp; increase in capillary (2483±112vs3012±178) &amp; arteriolar (15±0.9vs27±1) density (counts/mm2) with a consequent improvement in the myocardial functional parameters such as decreased LVIDs (3±0.2vs2.8±0.2) &amp; increased ejection fraction (40. ±3vs53±3), &amp; fractional shortening (19±2vs27±1) as assessed by echocardiography in the TMI compared to WMI. Immunoblot analysis revealed increased expression of Trx1 (6.2 fold), angiogenic VEGF (1.7 fold), anti-apoptotic survivin (2.4 fold) &amp; Bcl2 (3.2 fold) in the TMI compared to WMI. Our study also identifies the potential of Trx1 overexpression in inducing angiogenesis probably via VEGF, reducing cell death &amp; ventricular remodeling &amp; a possible novel treatment strategy where Trx1 overexpression might alleviate oxidative stress &amp; related human heart failure in several pathological conditions. The results obtained &amp; the proteins identified in our current study may prove to be potential therapeutic targets in the treatment of ischemic heart diseases.

Percutaneous transendocardial VEGF gene therapy: MRI guided delivery and characterization of 3D myocardial strain

Background Patients with myocardial infarcts have unfavorable left ventricular (LV) remodeling and devastating outcomes. This study was performed to determine whether VEGF-gene delivered transendocardially under MR-guidance improves LV three-dimensional (3D) strain (circumferential, longitudinal and radial), reduces infarct transmurality and increases vascular density in a canine model of permanent LAD coronary artery occlusion. Methods Imaging was performed using a 1.5-T MR scanner. Three days after occlusion, a percutaneous catheter was advanced under MR-guidance into the LV chamber for transendocardial delivery of VEGF-gene therapy ( n = 6) or LacZ-gene as control ( n = 6) into infarcted and peri-infarcted myocardium. MRI was performed before (3 days) and after (50 days) the delivery of therapy using cine, tagged and delayed contrast enhancement. Histochemical and pathological stains were used to assess myocardial viability and vascular density, respectively. Results Transendocardial delivery of VEGF-gene therapy and LacZ-gene under MRI guidance was successful in all animals. Significant improvement in 3D strain was observed within 50 days in treated animals. On the other hand, control animals demonstrated deterioration in regional strain over time. Significant reductions in infarct transmurality and increases in capillary and arteriole densities were also observed in VEGF-treated as compared to control animals. Conclusion MR-guided transendocardial delivery of VEGF-gene improved myocardial strain and enhanced transmural infarct resorption. This minimally invasive technique may be useful for delivery of local therapies, designed to promote angiogenesis or myogenesis.

Coronary flow velocity reserve is reduced in mice with atherosclerosis, pressure overload hypertrophy, and coronary occlusion

In man, coronary flow reserve (CFR) is reduced by most forms of heart disease, but it is not known how heart diseases modeled in mice alter CFR. We used Doppler ultrasound to measure left main coronary flow velocity (CFV) noninvasively in: 20 2‐yr old ApoE‐/‐ (atherosclerotic) mice, 10 age‐matched wild‐type (WT) controls, 10 6‐wk old WT mice, and 13 3‐mo old WT mice before and 21 days after transverse aortic banding (TAB) or LAD coronary artery occlusion (OCCL). All mice were C57BL6. We measured CFV and heart rate (HR) at baseline (B) and hyperemia (H) induced by changing the level of isoflurane gas anesthesia from 1 to 2.5%, and estimated CFR as H/B. Baseline HR and CFV in WT mice were 434±20 b/min and 16±3 cm/s (mean±SEM), and CFR was 2.4±0.1 (6‐wk), 3.2±0.3 (3‐mo), and 3.6±0.2 (2‐yr). For the disease models, CFR was: 2.5±0.2 (ApoE‐/‐), 1.1±0.1 (TAB), and 2.0±0.1 (OCCL), all P&lt;0.05 versus control or pre‐intervention. The average change in HR at H versus B was 1.05±0.3. We found that isoflurane gas is a convenient and noninvasive coronary vasodilator with minimal effects on HR in mice, and that CFR increases with age and is reduced significantly in each disease model. Indeed, CFR is nearly abolished 3 wks after TAB. We conclude that the magnitudes of CFV and CFR and the responses to pressure overload hypertrophy and coronary artery disease are similar in mice and man and that global CFR may serve as an index of cardiac function.

Protection against ischemia-induced ventricular arrhythmias and myocardial dysfunction conferred by preconditioning in the rat heart: involvement of mitochondrial KATP channels and reactive oxygen species

Ischemic preconditioning (I-PC) induced by brief episodes of ischemia and reperfusion (I/R) protects the heart against sustained I/R. Although activation of mitochondrial K(ATP) channels (mitoK(ATP)) interacting with reactive oxygen species (ROS) has been proposed as a key event in this process, their role in the antiarrhythmic effect is not clear. This study was designed: 1) to investigate the involvement of mito K(ATP) opening in the effect of I-PC (1 cycle of I/R, 5 min each) on ventricular arrhythmias during test ischemia (TI, 30-min LAD coronary artery occlusion) in Langendorff-perfused rat hearts and subsequent postischemic contractile dysfunction, and 2) to characterize potential mechanisms of protection conferred by I-PC and pharmacological PC induced by mito K(ATP) opener diazoxide (DZX), with particular regards to the modulation of ROS generation. Lipid peroxidation (an indicator of increased ROS production) was determined by measurement of myocardial concentration of conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in non-ischemic controls, non-preconditioned and preconditioned hearts exposed to TI, I-PC alone, as well as after pretreatment with DZX, mito K(ATP) blocker 5-hydroxydecanoate (5-HD) and antioxidant N-acetylcysteine (NAC). Total number of ventricular premature beats (VPB) that occurred in the control hearts (518+/-71) was significantly (P<0.05) reduced by I-PC (195+/-40), NAC (290+/-56) and DZX (168+/-22). I-PC and NAC suppressed an increase in CD and TBARS caused by ischemia indicating lower production of ROS. On the other hand, I-PC and DZX themselves moderately enhanced ROS generation, prior to TI. Bracketing of I-PC with 5-HD suppressed both, ROS production during PC and its cardioprotective effect. In conclusion, potential mechanisms of protection conferred by mito K(ATP) opening in the rat heart might involve a temporal increase in ROS production in the preconditioning phase triggering changes in the pro/antioxidant balance in the myocardium and attenuating ROS production during subsequent prolonged ischemia.

Endothelin-1 Is Not Predictive of Ventricular Ectopy or Ventricular Fibrillation during Acute Myocardial Ischemia

Endothelin(ET)-1 (ET-1) increases after myocardial infarction and may have effects on myocardial function. ET-1 has also been shown to affect the action potential (AP) which may be arrhythmogenic and predispose to ventricular fibrillation (VF). The effects of ET-2 and ET-3 are uncertain. We hypothesized that the ETs increase during acute ischemia and that plasma levels are predictive of ischemically induced VF. Thirty-four domestic swine underwent balloon occlusion of the proximal LAD coronary artery. Occlusion was confirmed angiographically. Venous samples were collected from the right atrium at baseline and at 5 min intervals for 30 min or until VF induction. ET-1, ET-2, and ET-3 were measured using ELISA. Changes in plasma concentrations were assessed using repeated measures ANOVA with Dunnett's. A p < 0.05 was considered statistically significant. All animals had angiographic evidence of successful proximal LAD occlusion. ET-1 levels were significantly increased from a baseline at 20 min and remained elevated during 30 min of occlusion. ET-2 and ET-3 levels did not change from baseline values (figure, mean +/- SE). VF occurred in 60% of animals. Peak ET-1 values were not significantly different between VF and non-VF animals (6.2 +/- 2.2 vs. 4.8 +/- 2.3 pg/mL). No single ET-1 value had a VF predictive value >50%. There is a significant increase in ET-1 level within 20 min of acute myocardial ischemia. Despite known effects of ET-1 on the AP, this increase did not correlate with the occurrence of VF.

Sevoflurane improves myocardial ischaemic tolerance in a closed‐chest porcine model

Volatile anaesthetics prevent experimental myocardial ischaemia-reperfusion injury (I/R) in several species, but this finding is partially inconsistent with clinical evidence. Some experimental models may not accurately represent the complex signal transduction pathways triggered by volatile anaesthetics. We therefore investigated sevoflurane I/R prevention in vivo in a porcine model with greater likeness to human physiology than models previously used and compared it with neutral anaesthetic. Myocardial infarct size [IS/AAR] was compared in three groups of pigs (N=35) randomised to Control anaesthesia (pentobarbital infusion, n=12), sevoflurane inhalation alone (end-tidal concentration 3.2%) (Sevo, n=9), or both Combined (n=14), throughout ischaemia and reperfusion. Anterior/septal myocardial infarcts resulted from distal LAD coronary artery occlusion by balloon catheter for 45 min followed by 120 min of reperfusion. [IS/AAR] was measured in tetrazolium-stained heart slices after standardised image processing with computer-assisted planimetry. Measurements included full invasive monitoring. Control animals developed infarction in 55.0 +/- 3.9% (SEM) of the area at risk, Sevo in 17.5 +/- 4.4% (P=0.0002), and Combined with pentobarbital in 24.3 +/- 3.8% (P=0.0001) of the AAR, sevoflurane reducing infarct size significantly (68% and 60%, respectively). Sevoflurane markedly decreased myocardial infarct size after prolonged coronary occlusion in a porcine model. In addition to novel sevoflurane cardioprotection in the closed-chest model, which is more comparable to normal human hearts than models previously used, sevoflurane cardioprotection is substantiated in the juvenile intact organism. The perspectives underline recommending volatile anaesthetics in risk patients and in cardiac surgery.