Minutes Of Coronary Occlusion Research Articles

Connexin43 overexpression promoted ferroptosis and increased myocardial vulnerability to ischemia-reperfusion injury in type 1 diabetic mice.

Enhancement of Connexin43 (Cx43) and ferroptosis are respectively associated with the exacerbation of myocardial ischemia-reperfusion injury (MIRI) in diabetes. Myocardial vulnerability to ischemic insult has been shown to vary during early and later phases of diabetes in experimental settings. Whether or not Connexin43 (Cx43) and ferroptosis interplay during MIRI in diabetes is unknown. We, thus, aimed to investigate whether or not the content of myocardial Cx43 may be attributable to myocardial vulnerability to MIRI at different stages of diabetes and also to explore the potential interplay between Cx43 and ferroptosis in this pathology. Age-matched control and subgroups of Streptozotocin-induced diabetic mice were subjected to MIRI induced by 30 minutes coronary artery occlusion and 2 hours reperfusion respectively at 1, 2 and 5 weeks of diabetes. Rat cardiac H9C2 cells were exposed to high glucose (HG) for 48h in the absence or presence of Cx43 gene knockdown followed by hypoxia/reoxygenation (HR) respectively for 6 and 12 hours. Post-ischemic myocardial infarct size was reduced in 1 and 2 weeks DM mice concomitant with enhanced GPX4 and reduced cardiac Cx43 and ferroptosis as compared to control. By contrast, cardiac GPX4 was significantly reduced while Cx43 increased at DM 5 weeks (D5w) which was correspondent to significant increases in ferroptosis and myocardial infarction. Post-ischemic cardiac function was improved in 1 and 2 weeks but worsened in 5w DM mice as compared with non-diabetic control. GAP19 (Cx43 inhibitor) significantly attenuated ferroptosis and reduced myocardial infarction in D5w mice. Erastin (ferroptosis activator) reversed the cardioprotective effect of GAP19. In vitro, HR significantly reduced cell viability accompanied with reduced GPX4 but elevated Cx43 expression, MDA production and ferroptosis. Cx43 gene knockdown in H9C2 resulted in a significant increase in GPX4, reduction in MDA and ferroptosis, and subsequently reduced post-hypoxic cell viability. The beneficial effects of Cx43 gene knock-down was minified or eliminated by Erastin. It is concluded that Cx43 overexpression exacerbates MIRI under diabetic conditions via promoting ferroptosis, while its down-regulation at early state of diabetes is attributable to enhanced myocardial tolerance to MIRI.

Abstract 9835: Multi-Modality Imaging Assessment of Microbubbles and Cerebral Emboli in Left Ventricular Pulsed Field Ablation

Introduction: Pulsed field ablation (PFA) may have a superior safety profile compared to other ablation technologies, but the high-voltage electrical fields have the potential to cause gaseous microbubbles (MB), which may be associated with cerebral emboli. In this study, we evaluate the MB burden of a monopolar, biphasic PFA system (CENTAURI, Galaxy Medical), that delivers a waveform designed to limit MB generation. Methods: After anticoagulation with heparin, healthy and chronic MI swine (30 day survival after 90 minute coronary balloon occlusion) underwent PFA in the LV using an open-irrigated focal catheter under intra-cardiac echocardiography (ICE) guidance and monitoring of MBs. Two additional healthy control swine received 0.5 and 1 ml of air MBs through the lumen of the ablation catheter. Swine underwent brain MRI before and after PFA (or control air MB injection) with T1, T2, FLAIR, ADC and susceptibility- and diffusion-weighted imaging (DWI) interpreted by a neuroradiologist blinded to treatment group. Gross pathology and histology of brains with any MRI findings was performed by a neuropathologist. Results: Four healthy swine underwent 50 PFA applications and 5 chronic MI swine underwent 74 applications. No PFA-related MB formation was noted on ICE. Both control swine developed multiple acute emboli in the left thalamus and caudate on DWI, ADC and FLAIR brain MRI sequences in response to air MB injection (Figure). Of the 9 PFA swine, there were no ADC nor FLAIR sequence abnormalities. There was one instance of a hyperintense focus in the left putamen on the DWI trace image, but absence of ADC or FLAIR affirmation suggested it was artifact. Gross pathology and histopathology of this region did not detect any abnormalities (Figure). Conclusion: Catheter air MB injection caused MR-detectable cerebral emboli in swine. Focal monopolar biphasic PFA with CENTAURI does not generate MBs observable on ICE, and did not cause cerebral emboli in healthy or post-infarct LVs.

Abstract 10526: Surface Located Adiponectin On Adipocytes-derived Exosomes Mediates Adipocytes/cardiomyocytes Communication And Contributes To Cardioprotection

Introduction and Hypothesis: Increasing evidence emphasizes the roles of adipocyte-cardiomyocyte (ADp-CM) communication plays in health and diabetes. We recently reported that diabetes switched ADp-derived Exosomes (ADp-Exo) from carrying cardioprotective molecules to delivering cardiotoxic molecules to CM. However, the molecular mechanisms mediating ADp-Exo cardioprotection and its alteration by diabetes remain unknown. Methods and Results: ADp-Exo was isolated from epididymal white adipocytes of WT mice. Western Blot demonstrated high level of adiponectin (APN), a potent cardioprotective adipokine, present in ADp-Exo. More interestingly, APN was detected on the surface of ADp-Exo by flow cytometry using Exo-flow kit (System Biosciences). To determine whether surface-located APN on ADp-Exo protect heart, WT ADp-Exo were intramyocardially injected. Mice were subjected to 90 minutes coronary occlusion, followed by 4 weeks of reperfusion. Cardiac function was evaluated by echocardiograph weekly. WT ADp-Exo significantly reduced MI/R injury in vivo , as evidenced by improved LVEF, radial and longitudinal myocardial Strain and SR (vs vehicle group, p<0.05). Importantly, pre-incubation of ADp-Exo with an APN neutralization antibody blocked ADp-Exo cardioprotection. To determine the role of CM AdipoR1, ex vivo and in vitro experiments were performed. WT ADp-Exo activated AdipoR1 pathway (increased phosphorylation of ACC, ERK and AMPK) in CM and protected against cell injury and death (MTT and LDH assay). However, surface APN blocked WT ADp-Exo or APN -/- ADp-Exo failed to active this signaling and protection. WT ADp-Exo failed to activate cell salvage kinases in AdipoR1 -/- CM. Finally, overexpression of GRK2, a pathogenic molecule that we reported to cause AdipoR1 S205 phosphorylation, blocked WT ADp-Exo cardioprotection. AAV9-mediated overexpression of a phosphorylation resistant AdipoR1 (AdipoR1 S205A ) restored ADp-Exo protective action. Conclusions: We demonstrate for the first time that ADp-Exo surface located APN mediates ADp-CM communication via CM AdipoR1 pathway, promoting cardioprotection. This protective system is blocked by GRK2-induced AdipoR1 phosphorylation in diabetic heart, promoting MI/R injury.

Abstract 13764: Chronic Electronic Cigarette Vapor Exposure Leads to Impaired Cardiac Function in Experimental Rat Myocardial Ischemia/reperfusion Model

Background: We investigated the effects of long-term electronic cigarettes with nicotine (eC) vaping on cardiac function and structure in rats subjected to myocardial infarction (MI). Methods: After 8 weeks of exposure to either pure air (n=20) or eC (n=20), rats were anesthetized, and were subjected to 30 minutes of coronary artery occlusion followed by 3 hours of reperfusion. Cardiac function was assessed by echocardiogram and pressure measurements of the aorta and left ventricle (LV). Cardiac output (CO) was measured using a thermodilution catheter. At 3 hours of reperfusion, ischemic risk zone, no-reflow and infarct areas were determined. Results: Prior to coronary artery occlusion, chronic eC exposure was associated with a lower CO (45 ± 2 ml/min ) compared to air (55 ± 4 ml/min; p<0.05)) and a decrease in +dP/dt (5226 ± 294 mmHg/s versus 6062 ± 271 mmHg/s; p=0.05). After 30 minutes of coronary occlusion and 2.5 hours of reperfusion, CO and LV + dp/dt fell in both groups, but remained significantly lower in eC compared to the pure air group (Table). LV systolic and diastolic dimensions were significantly smaller in the E-Cig group compared to the air group. Systolic and diastolic anterior LV wall thickness were significantly thicker in the eC group after reperfusion. The ischemic risk size was comparable between the 2 groups. MI size was 48.8 ± 4.8% of the ischemic risk zone in the air group and 45.4 ± 4.4 % in the eC group (p=0.603). The area of no reflow was 26.7 ± 4.0% of the ischemic risk zone in the air group and 21.1 ± 3.5% in the E-C group (p=0.298). Chronic eC exposure did not change heart rate and blood pressure, but the significantly increased the systemic arterial resistance. Conclusions: Chronic exposure to eC significantly impaired cardiac function in rats prior to and during ischemia/reperfusion, increased arterial resistance, but did not increase infarct size or no-reflow zone. Increased LV wall thickness of the risk zone suggested that eC may have increased edema.

Tilianin Post-Conditioning Attenuates Myocardial Ischemia/Reperfusion Injury via Mitochondrial Protection and Inhibition of Apoptosis.

BackgroundThe aim of this study was to investigate the role of tilianin in modulating mitochondrial functions and mitochondria-mediated apoptosis during cardio-protection.Material/MethodsMyocardial ischemia/reperfusion (I/R) injury was induced by 30 minutes coronary occlusion followed by two hours reperfusion in Sprague-Dawley rats. To investigate the cardio-protective effects of tilianin, apoptosis was evaluated by TUNEL. Mitochondrial ultrastructure and function were assessed by transmission electron microscopy, dynamics of mitochondrial permeability transition pore (mPTP) opening and ATP production in the myocardium; Ca2+ content and reactive oxygen species (ROS) were measured to evaluated the level of damage factors in the mitochondria. The related apoptotic proteins were analyzed through immunoblot.ResultsPretreatment with tilianin significantly reduced apoptosis after I/R injury in rats (p<0.05). In addition, tilianin could alleviate mitochondrial damage, markedly inhibited mPTP opening and improved ATP production (p<0.05). There was also a significant reduction for content of Ca2+ and ROS in the mitochondria (p<0.01). Apoptosis protein analysis found that treatment with tilianin led to the downregulation of apoptosis-inducing factor (AIF) (p<0.01), and suppressed the leakage of cytochrome c and activation of caspase-3 (p<0.05).ConclusionsThis study showed that tilianin can alleviate apoptosis of cardiomyocytes and protect myocardium, possibly via the protection of mitochondria and repression of mitochondrial apoptotic pathways. Mechanistically, inhibition of Ca2+ overload, mPTP opening, and ROS production in mitochondria may explain the observed tilianin-mediated treatment effects.

Role of Endogenous Opioid System in Ischemic-Induced Late Preconditioning.

BackgroundOpioid receptors (OR) are involved in myocardial late preconditioning (LPC) induced by morphine and δ1-opioid receptor (δ1-OR) agonists. The role of OR in ischemic-induced LPC is unknown. We investigated whether 1) OR are involved in the trigger and/or mediation phase of LPC and 2) a time course effect on the expression of different opioid receptors and their endogenous ligands exists.MethodsMale Wistar rats were randomly allocated to four groups (each group n = 8). Awake animals were ischemic preconditioned by a 5 minutes coronary occlusion. 24 hours later, anesthetized animals underwent 25 minutes coronary occlusion followed by 2 hours of reperfusion. The role of OR was investigated by treatment with intraperitoneal naloxone (Nal) 10 minutes prior to LPC (Nal-LPC; trigger phase) or 10 min prior to sustained ischemia (LPC-Nal; mediation phase).ResultsLPC reduced infarct size from 61±10% in controls to 25±9% (P<0.001). Naloxone during trigger or mediation phase completely abolished LPC-induced cardioprotection (59±9% and 62±9%; P<0.001 vs. LPC). 8, 12 and 24 hours after the ischemic stimulus, expression of δ-OR in the heart was increased, whereas μ-opioid receptor (μ-OR) and κ-opioid receptor (κ-OR) were not. Plasma concentrations of β-endorphin and leu-enkephalin but not dynorphin were increased by LPC.ConclusionIschemic LPC is triggererd and mediated by OR. Expression of δ-OR and plasma levels of endogenous opioid peptides are increased after ischemic LPC.

Rapid Surface Cooling by ThermoSuit System Dramatically Reduces Scar Size, Prevents Post-Infarction Adverse Left Ventricular Remodeling, and Improves Cardiac Function in Rats.

BackgroundThe long-term effects of transient hypothermia by the non-invasive ThermoSuit apparatus on myocardial infarct (MI) scar size, left ventricular (LV) remodeling, and LV function were assessed in rat MI model.Methods and ResultsRats were randomized to normothermic or hypothermic groups (n=14 in each group) and subjected to 30 minutes coronary artery occlusion and 6 weeks of reperfusion. For hypothermia therapy, rats were placed into the ThermoSuit apparatus at 2 minutes after the onset of coronary artery occlusion, were taken out of the apparatus when the core body temperature reached 32°C (in ≈8 minutes), and were then allowed to rewarm. After 6 weeks of recovery, rats treated with hypothermia demonstrated markedly reduced scar size (expressed as % of left ventricular area: hypothermia, 6.5±1.1%; normothermia, 19.4±1.7%; P=1.3×10−6); and thicker anterior LV wall (hypothermia, 1.57±0.09 mm; normothermia, 1.07±0.05 mm; P=3.4×10−5); decreased postmortem left ventricular volume (hypothermia, 0.45±0.04 mL; normothermia, 0.6±0.03 mL; P=0.028); and better LV fractional shortening by echocardiography (hypothermia, 37.2±2.8%; normothermia, 18.9±2.3%; P=0.0002) and LV ejection fraction by LV contrast ventriculography (hypothermia, 66.8±2.3%; normothermia, 56.0±2.0%; P=0.0014).ConclusionsRapid, transient non-invasive surface cooling with the ThermoSuit apparatus in the acute phase of MI decreased scar size by 66.5%, attenuated adverse post-infarct left ventricular dilation and remodeling, and improved cardiac function in the chronic phase of experimental MI.

Hyperpolarized metabolic imaging of myocardial ischemia-reperfusion in a small-animal model at 9.4T

Background Dynamic hyperpolarization (DNP) of Carbon-13 (13C) allows in-vivo assessment of metabolic processes. The aims of the present study were to establish a living rat model of ischemia-reperfusion and to study the metabolic changes in the myocardium following short periods of coronary artery occlusion using intravenous injection of hyperpolarized 1-13C pyruvate. Methods An inflatable balloon was secured around the left coronary artery of Sprague Dawley rats. 5-7 days after surgery rats were placed in a Bruker Biospec 9.4T small animal MR system. To enhance bicarbonate signal, animals received an iv glucose/potassium infusion. The tubing of the occluder was connected to extension tubing to allow occlusion while the animal remained in the bore of the MR system. A custom-built multi-sample DNP polarizer (1) was used to polarize samples (25.4 μ L[ 1- 13 C]-pyruvic acid and 13.5 mM trityl radical doped with 1.5 mM Dotarem). The rats were injected with 1.4 ml DNP solution at 4 time points: baseline, reperfusion directly after 15 minutes of coronary occlusion, after 30 minutes of reperfusion, after 60 minutes of reperfusion. A subgroup of rats underwent repeat imaging 1 week after ischemia. Metabolic data were acquired with a multiband pulse in combination with a multi-echo single-shot EPI readout (2). Hearts were removed and stained to delineate the area at risk (AAR), and for myocardial infarction. Results

Bioengineering silicon quantum dot theranostics using a network analysis of metabolomic and proteomic data in cardiac ischaemia

Metabolomic profiling is ideally suited for the analysis of cardiac metabolism in healthy and diseased states. Here, we show that systematic discovery of biomarkers of ischemic preconditioning using metabolomics can be translated to potential nanotheranostics. Thirty-three patients underwent percutaneous coronary intervention (PCI) after myocardial infarction. Blood was sampled from catheters in the coronary sinus, aorta and femoral vein before coronary occlusion and 20 minutes after one minute of coronary occlusion. Plasma was analysed using GC-MS metabolomics and iTRAQ LC-MS/MS proteomics. Proteins and metabolites were mapped into the Metacore network database (GeneGo, MI, USA) to establish functional relevance. Expression of 13 proteins was significantly different (p<0.05) as a result of PCI. Included amongst these was CD44, a cell surface marker of reperfusion injury. Thirty-eight metabolites were identified using a targeted approach. Using PCA, 42% of their variance was accounted for by 21 metabolites. Multiple metabolic pathways and potential biomarkers of cardiac ischemia, reperfusion and preconditioning were identified. CD44, a marker of reperfusion injury, and myristic acid, a potential preconditioning agent, were incorporated into a nanotheranostic that may be useful for cardiovascular applications. Integrating biomarker discovery techniques into rationally designed nanoconstructs may lead to improvements in disease-specific diagnosis and treatment.

Electrophysiological Effects of Tamoxifen

Reperfusion arrhythmias are currently attributed to ionic imbalance and oxidative stress. Tamoxifen is a potent antioxidant that also modulates some ionic transport pathways. In this work, we tried to correlate the electrophysiological effects of 1, 2, and 5 µM of tamoxifen with the incidence and severity of arrhythmias appearing on reperfusion after 10 minutes of coronary occlusion in isolated hearts from female rats. All tamoxifen concentrations inhibited the action potential shortening observed in the control hearts during late ischemia (6-10 minutes), whereas 2 and 5 µM also reduced the resting membrane potential depolarization. The incidence of sustained ventricular tachycardia and/or ventricular fibrillation on reperfusion decreased from 10 of 12 (control group) to 5 of 10 (1 µM, P = 0.1718), 4 of 12 (2 µM, P = 0.0361), and 2 of 10 (5 µM, P = 0.0083). The possible role of chloride currents activated by cell swelling in these effects was explored in hearts submitted to a 10-minute hypotonic challenge, where tamoxifen (5 µM) blocked the action potential shortening and the late resting membrane potential depolarization produced by hypotonicity, mimicking its action in late ischemia. Tamoxifen produced a similar increase of the total antioxidant capacity of myocardial samples at all the concentration tested. In conclusion, our data strongly suggest that the antiarrhythmic action of this agent is mediated by its electrophysiological effect derived from modulation of chloride currents activated by cell swelling.

228 PACING POSTCONDITIONING PROTECTS THE HEART BY A PATHWAY INVOLVING NITRIC OXIDE AND NATRIURETIC PEPTIDES

<h3>Introduction</h3> Brief periods of ventricular pacing during the early reperfusion phase (pacing-induced postconditioning, (PPC)) have been shown to protect the heart against ischemia reperfusion injury. The aim of this study was to explore the role of natriuretic peptides (atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)), protein kinase G (PKG) and nitric oxide (NO) in the protective effect of PPC. <h3>Methods</h3> Isolated perfused (Langendorff) rat hearts (n=6) were subjected to 30 minutes coronary occlusion and 30 minutes reperfusion. PPC consisted of 3 episodes of 30 seconds ventricular pacing alternated with 30 seconds atrial pacing during early reperfusion. Studied were control with only ischemia and reperfusion, PPC, PPC in combination with selective blockers of the ANP (H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ)), BNP (isatin) and NO (L-nitro-arginine-methylester (L-name)). Another sets of animals were treated with the agonists of ANP (ANP), BNP (Rat BNP-32), NO donor (S-nitroso-N-acetylpenicillamine (SNAP)) and PKG activator 8-(4-chlorophenylthio)-guanosine 39, 59-cyclic monophosphate (CPT) at the beginning of reperfusion. Hemodynamics were computed by a data acquisition program. Infarct size and area at risk were determined using TTC and blue dye. <h3>Results</h3> Ischemia and reperfusion resulted in a poor recovery of heart hemodynamics. PPC significantly (p&lt;0.03) improved cardiac hemodynamics and decreased the infarct size (p&lt;0.05). Isatin and L-name completely abrogated the protective effect of PPC. However, ODQ did affect the protection afforded by PPC. When applied exogenously Rat BNP-32, CPT and SNAP showed a significant (P&lt;0.03) recovery in cardiac hemodynamics and significantly (P&lt;0.05) decreased the infarct size. This protection is comparable to that produced by PPC. <h3>Conclusions</h3> Exogenous and endogenous BNP, NO and PKG protected the heart against ischemia reperfusion injury. However, ANP is not involved in this protection. Interaction between ROS and NO did not block PPC protection to the heart.

Bioengineering Silicon Quantum Dot Theranostics using a Network Analysis of Metabolomic and Proteomic Data in Cardiac Ischemia

Metabolomic profiling is ideally suited for the analysis of cardiac metabolism in healthy and diseased states. Here, we show that systematic discovery of biomarkers of ischemic preconditioning using metabolomics can be translated to potential nanotheranostics. Thirty-three patients underwent percutaneous coronary intervention (PCI) after myocardial infarction. Blood was sampled from catheters in the coronary sinus, aorta and femoral vein before coronary occlusion and 20 minutes after one minute of coronary occlusion. Plasma was analysed using GC-MS metabolomics and iTRAQ LC-MS/MS proteomics. Proteins and metabolites were mapped into the Metacore network database (GeneGo, MI, USA) to establish functional relevance. Expression of 13 proteins was significantly different (p<0.05) as a result of PCI. Included amongst these was CD44, a cell surface marker of reperfusion injury. Thirty-eight metabolites were identified using a targeted approach. Using PCA, 42% of their variance was accounted for by 21 metabolites. Multiple metabolic pathways and potential biomarkers of cardiac ischemia, reperfusion and preconditioning were identified. CD44, a marker of reperfusion injury, and myristic acid, a potential preconditioning agent, were incorporated into a nanotheranostic that may be useful for cardiovascular applications. Integrating biomarker discovery techniques into rationally designed nanoconstructs may lead to improvements in disease-specific diagnosis and treatment.

An Apoptosis Signal-regulating Kinase 1 Inhibitor Reduces Cardiomyocyte Apoptosis and Infarct Size in a Rat Ischemia-reperfusion Model

We determined whether a small molecule inhibitor of apoptosis signal-regulating kinase 1 (ASK1-i) could reduce myocardial infarct size in a rat ischemia/reperfusion model. Sprague-Dawley rats were randomized to 3 groups: ASK1-i infusion (n = 16), vehicle infusion (n = 16), or ischemic preconditioning (IPC; n = 15). Infusion of ASK1-i (10 mg/kg, iv) or vehicle commenced 45 minutes before myocardial ischemia. IPC consisted of 3 cycles of 3 minutes of coronary occlusion followed by 5 minutes of reperfusion immediately before index myocardial ischemia, which consisted of 30-minute left coronary occlusion followed by 180 minutes of reperfusion. Pathologic analysis revealed no significant difference in the ischemic risk size among the 3 groups. ASK1-I and IPC significantly reduced myocardial infarct size (27.7% ± 3.3%, 16.5% ± 3.4%, and 41.5% ± 4.8% in the ASK1-i group, the IPC group, and the vehicle group, respectively; P = 0.0002) and apoptosis (the percentage of apoptotic nuclei averaged 11.6% ± 1.0%, 10.2% ± 1.7%, and 17.7% ± 2.0% in the ASK1-i group, IPC group, and vehicle group, respectively, P = 0.0055). A small molecule inhibitor of ASK1 was shown for the first time to reduce apoptosis and myocardial infarct size in a rat model of ischemia/reperfusion.

Effects of sex and ovarian hormones on the initial renal sympathetic nerve activity response to myocardial infarction

The physiological mechanisms contributing to sex differences following myocardial infarction (MI) are poorly understood. Given the strong relationship between sympathetic nerve activity (SNA) and outcome, we hypothesized there may be a sex difference in SNA responses to MI. In anaesthetized, open-chest male, female and ovariectomized (OVX) female Wistar rats, mean arterial pressure, heart rate and renal SNA were recorded in response to ligation of the left coronary artery. In males, renal SNA increased by 30 ± 6% in the first minute of coronary occlusion (P < 0.05) and remained elevated at 18 ± 7% above baseline (P < 0.05) at 2 h following MI. In response to MI, ovary-intact females displayed no change in renal SNA, whereas OVX females displayed a significant increase, similar to that seen in the males (increases of 43 ± 11% at 1 min and 21 ± 7% at 2 h post-MI, P < 0.05 versus intact females). Arterial baroreflex control of renal SNA had a smaller range in females (ovary intact and OVX) than males; no changes in arterial baroreflex responses were observed 1 h post-MI in males or females. Denervating the arterial baroreceptors abolished the renal SNA response to MI in the males, whereas in ovary-intact females and OVX females the response was unaltered. These findings suggest that ovarian hormones are able to blunt the initial sympathetic activation post-MI in females and that the importance of the arterial baroreflex in mediating initial sympathetic activation post-MI is different between the sexes.

Absence of Actions of Commonly Used Chinese Herbal Medicines and Electroacupuncture on Myocardial Infarct Size

Some studies have suggested that certain Chinese herbal remedies and acupuncture could limit ischemia/reperfusion damage. We sought to determine whether the commonly used single herb Danshen (DS), either alone or in combination with Jiang Xiang (JX), or electroacupuncture (EA) reduces myocardial infarct size. An anesthetized rat model of proximal left coronary artery occlusion (30 minutes) and reperfusion (180 minutes) was used to measure infarct size (triphenyltetrazolium chloride) and ischemic risk zone (blue dye technique). Rats were either untreated (saline) or received an infusion of DS or DS + JX, starting 30 minutes prior to coronary occlusion. In a separate protocol, rats were untreated, received static needle (ND) placement without stimulation or EA at P5-P6 acupuncture points in the rat forearm starting 5 minutes before occlusion and lasting for 40 minutes, or starting 30 minutes before occlusion and lasting for 90 minutes. In the herbal experiments, myocardial infarct size expressed as a fraction of the ischemic risk zone was 0.43 ± 0.06 in controls, 0.39 ± 0.05 in the DS group, and 0.42 ± 0.04 in the Danshen + JX groups (P = not significant [NS]). In the acupuncture study, there was no significant difference in infarct size as a fraction of the risk zone among the control group (0.38 ± 0.04), the ND group (0.47 ± 0.04), or the EA group (0.32 ± 0.05). When EA was started 30 minutes prior to coronary occlusion and continued for 30 minutes into reperfusion, infarct size was 0.41 ± 0.07 in controls and 0.38 ± 0.10 in EA (P = NS). Neither herbs nor EA altered heart rate or blood pressure. In a separate study of 5 minutes of coronary occlusion plus reperfusion, EA failed to reduce ventricular arrhythmias. Our studies do not suggest a cardioprotective effect of DS or DS + JX or EA in an experimental model of myocardial ischemia/reperfusion.

An apoptosis signal‐regulating kinase 1 inhibitor reduces cardiomyocyte apoptosis and infarct size in a rat ischemia‐reperfusion model

Apoptosis Signal‐Regulating Kinase 1 (ASK1) is a critical mediator of oxidative stress‐induced apoptosis. We hypothesized that a small molecule inhibitor of ASK1 (ASK1‐i; Gilead Sciences, Palo Alto, CA) would reduce myocardial infarct size in a rat ischemia/reperfusion model. Forty‐seven SD rats were randomized to 3 groups: ASK1‐i infusion (n=16), vehicle infusion (n=16), or ischemic preconditioning (IPC; n=15). Infusion of ASK1‐i (10 mg/kg) or vehicle commenced 45 minutes prior to myocardial ischemia. IPC consisted of 3 cycles of 3 minutes coronary occlusion and 5 minutes reperfusion immediately prior to index myocardial ischemia. Rats were then subjected to 30 minutes of coronary occlusion followed by 180 minutes of reperfusion. Pathologic analysis revealed no significant difference in the size of the ischemic risk zone between the 3 groups. Infarct size, expressed as a percentage of the risk zone averaged 27.7 +/− 3.3%, 16.5 +/− 3.4%, and 41.5 +/− 4.8% in the ASK1‐i group, the IPC group, and the vehicle group, respectively (p &lt; 0.05 for ASK1‐i and IPC versus vehicle). The percentage of apoptotic nuclei as assessed by TUNEL positivity averaged 12.4 +/− 1.1%, 11.1 +/− 1.9%, and 19.2 +/− 2.2% in the ASK1‐i group, IPC group, and vehicle group respectively (p &lt; 0.05 for ASK1‐i and IPC versus vehicle). Inhibition of the ASK1 was shown to reduce apoptosis and myocardial infarct size in a rat model of ischemia/reperfusion.

Spinal cord stimulation effects on myocardial ischemia, infarct size, ventricular arrhythmia, and noninvasive electrophysiology in a porcine ischemia-reperfusion model

Background Susceptibility to ventricular arrhythmias and sudden cardiac death can be reduced by modulation of autonomic tone. Spinal cord stimulation (SCS) presumably affects autonomic tone and reduces myocardial ischemia. Objective The purpose of this study was to investigate whether SCS could reduce myocardial ischemia, infarct size, and ventricular arrhythmias as well as repolarization alterations in a porcine ischemia–reperfusion model. Methods Anesthetized common Landrace pigs were randomized to SCS (n = 10) or sham treatment (n = 10) before, during, and after 45 minutes of coronary occlusion. Area at risk, infarct size, and spontaneous ventricular arrhythmias were analyzed. Continuous three-dimensional vectorcardiograms was recorded and analyzed with respect to ECG intervals, ST-segment, and T-vector and T-vector–loop morphology. Results SCS was associated with significantly ( P P amplitude and T area suggesting increased repolarization gradients, which were significantly reduced by SCS ( P Conclusion SCS appears to have an antiarrhythmic effect on spontaneous NSVT and SVT during ischemia–reperfusion in association with a reduction of repolarization alterations. Vectorcardiography signs of myocardial ischemia were reduced by SCS, but this intervention was not accompanied by any effect on infarct size.

Magnetic resonance imaging of post-systolic shortening in a closed-chest rat model of coronary occlusion using myocardial tagging

The aim of the study was to evaluate the reliability and sensitivity of tagged cardiac magnetic resonance imaging (cMRI) in assessment of regional cardiac dysfunction induced by short ischemia. For clinical low dose dobutamine tests, quantitative strain analyses derived from tagged cMRI have been shown to be able to detect viable myocardium. However these preliminary data were obtained in patients with high grade coronary stenosis, likely to have a large ischemic territory. So it is not known whether MRI tagging could detect coronary occlusion i) of short duration and ii) in small ischemic areas. A model of closed-chest coronary artery occlusion was developed in Sprague-Dawley rats. 10 rats underwent a 3 minutes coronary occlusion followed by 30 minutes of reperfusion, directly in a 1.5 Tesla clinical MRI scanner. Efficiency and reversibility of the coronary occlusion was assessed by modifications of the ECG recording. Tagged images were acquired every 2.5 minutes using C-SPAMM with segmented cine fast field echo sequence. Strain analysis was performed with the Extrema Temporal Chaining algorithm in six sectors of the short axis slice, classified in 2 groups: anterolateral and inferolateral sectors were considered as ischemic whereas inferior, inferoseptal and anteroseptal sectors were remote. Contraction (maximum strain) and contractility (strain rate) derived from the myocardial strain curves were analysed using a linear model. Eight rats underwent hemodynamic measurements by intraventricular catheterism to evaluate global cardiac function along a similar protocol of ischemia-reperfusion. During the occlusion, contraction was reduced and delayed in the ischemic sectors compared to remote group (p<0.001). The contraction remained delayed during the first minutes of reperfusion (p<0.005) in the ischemic group, demonstrating post-systolic shortening. Contractility was decreased both during the occlusion and the first minutes of reperfusion. Hemodynamic measurements dit not show any abnormality of the systolic or diastolic function after the first minutes of reperfusion. We showed for the first time in a rat model that MRI tagging of a short coronary occlusion is feasible, on a 1.5 Tesla clinical scanner. We demonstrated in the ischemic sectors a transient contractile dysfunction which was not demonstrated by hemodynamic measurements. Besides the interest of such a method for non-invasive study of cardiac function in rodent, our data also suggest that tagged MRI could bring an important improvement in evaluation of the human cardiac function during stress imaging.

Hypoxic Preconditioning Preserves Cardiac Contractility and Reduces Infarct Size In Vivo

Background: Preconditioning is a powerful endogenous mechanism to protect the heart against ischemic dam- age. The second window of preconditioning (SWOP) is therapeutically the most attractive, but is hard to achieve by local cardiac ischemia 24 hrs before the index ischemia in the many mice models for cardiovascular pathology, because of ex- cessive mortality during the two procedures or the period in between. Hypoxic preconditioning is an attractive alternative preconditioning stimulus. To date, the SWOP after hypoxic preconditioning has not been studied in mice concerning in- farct size reduction and preservation of left ventricular contractility in vivo. Aim: To determine whether transient hypoxia can induce a SWOP in vivo in mice. Methods: Hypoxic preconditioning was induced by 5 cycles of 6 minutes of 6% oxygen in 24-week-old wild type mice. Twenty-four hours later, a 30 minutes coronary occlusion was performed. After 1 hour of reperfusion, in vivo cardiac pressure-conductance catheterization was performed with determination of the load-dependent and load-independent pa- rameters. Infarct size was determined by TTC-staining. Sham procedures were used to obtain non-preconditioned con- trols. Results: There was no mortality with the hypoxic preconditioning protocol. The left ventricular contractile parameters ejection fraction, end-systolic elastance and preload recruitable stroke work were significantly better preserved after ischemia in the preconditioned group. Diastolic relaxation (tau) was also significantly better preserved. Infarct size was reduced to half that of the non-preconditioned group. Conclusion: Hypoxic preconditioning is a feasible stimulus to induce in vivo a second window of preconditioning in mice. Infarct size is reduced and cardiac contractility better preserved after 30 min regional ischemia in vivo by hypoxic precon- ditioning 24 hrs earlier.

Effect of dl-praeruptorin A on desmin and vimentin content in rat ischemia/reperfusion myocardiocytes

Intermediate filament (IF) proteins have been thought to play a role in nuclear centration, organelle movement and maintenance of cell shape. dl-praeruptorin A (Pd-Ia), a novel Ca2+-influx blocker and K+-channel opener isolated from Chinese traditional herbal medicine Qian-Hu, has been demonstrated to inhibit expression of apoptosis related proteins and reduce the level of proinflammatory factors in ischemia/reperfusion myocardiocytes. Morphologically, whether Pd-Ia effects myocardiocyte IFs remains unclear. The purpose of this study was, for the first time, to evaluate the in vivo effects of Pd-Ia on IF desmin and vimentin content in order to further explore its cardioprotection against ischemia and elucidate its mechanism of action. Rats underwent a 30 minutes coronary occlusion followed by 120 minutes reperfusion. Assessment of desmin and vimentin content of myocardiocytes was performed by immunohistochemistry, Western blot, Hematoxylin-Eosin staining and densitometry. Pretreatment with i.v. infusion of Pd-Ia prior to ischemia significantly increased desmin and vimentin content and alleviated defects caused by the ischemia/reperfusion insult, e.g. with Pd-Ia at a dose of 0.5 or 1.0 mg/kg, integrated density values of desmin were increased from 61 478 +/- 10 074 to 177 408 +/- 10 395 and 195 784 +/- 20 057, and vimentin from 59 189 +/- 19 853 to 164 781 +/- 19 543 and 185 696 +/- 20 957 (P < 0.01, vs placebo), respectively. The recovery of desmin seemed to be stronger and appeared earlier than that of vimentin. Pd-Ia protectively increased IF desmin and vimentin content in ischemia/reperfusion myocardiocytes, which might be partially responsible for its cardioprotection against ischemia.