Langendorff Model Research Articles

Electrophysiological Profile of Different Antiviral Therapies in a Rabbit Whole-Heart Model

Antiviral therapies for treatment of COVID-19 may be associated with significant proarrhythmic potential. In the present study, the potential cardiotoxic side effects of these therapies were evaluated using a Langendorff model of the isolated rabbit heart. 51 hearts of female rabbits were retrogradely perfused, employing a Langendorff-setup. Eight catheters were placed endo- and epicardially to perform an electrophysiology study, thus obtaining cycle length-dependent action potential duration at 90% of repolarization (APD90), QT intervals and dispersion of repolarization. After generating baseline data, the hearts were assigned to four groups: In group 1 (HXC), hearts were treated with 1 µM hydroxychloroquine. Thereafter, 3 µM hydroxychloroquine were infused additionally. Group 2 (HXC + AZI) was perfused with 3 µM hydroxychloroquine followed by 150 µM azithromycin. In group 3 (LOP) the hearts were perfused with 3 µM lopinavir followed by 5 µM and 10 µM lopinavir. Group 4 (REM) was perfused with 1 µM remdesivir followed by 5 µM and 10 µM remdesivir. Hydroxychloroquine- and azithromycin-based therapies have a significant proarrhythmic potential mediated by action potential prolongation and an increase in dispersion. Lopinavir and remdesivir showed overall significantly less pronounced changes in electrophysiology. In accordance with the reported bradycardic events under remdesivir, it significantly reduced the rate of the ventricular escape rhythm.

Mild therapeutic hypothermia upregulates the O-GlcNAcylation level of COX10 to alleviate mitochondrial damage induced by myocardial ischemia-reperfusion injury.

Mild therapeutic hypothermia (MTH) is an important method for perioperative prevention and treatment of myocardial ischemia-reperfusion injury (MIRI). Modifying mitochondrial proteins after protein translation to regulate mitochondrial function is one of the mechanisms for improving myocardial ischemia-reperfusion injury. This study investigated the relationship between shallow hypothermia treatment improving myocardial ischemia-reperfusion injury and the O-GlcNAcylation level of COX10. We used in vivo Langendorff model and in vitro hypoxia/reoxygenation (H/R) cell model to investigate the effects of MTH on myocardial ischemia-reperfusion injury. Histological changes, myocardial enzymes, oxidative stress, and mitochondrial structure/function were assessed.Mechanistic studies involved various molecular biology methods such as ELISA, immunoprecipitation (IP), WB, and immunofluorescence. Our research results indicate that MTH upregulates the O-GlcNACylation level of COX10, improves mitochondrial function, and inhibits the expression of ROS to improve myocardial ischemia-reperfusion injury. In vivo, MTH effectively alleviates ischemia-reperfusion induced cardiac dysfunction, myocardial injury, mitochondrial damage, and redox imbalance. In vitro, the OGT inhibitor ALX inhibits the OGT mediated O-GlcNA acylation signaling pathway, downregulates the O-Glc acylation level of COX10, promotes ROS release, and counteracts the protective effect of MTH. On the contrary, the OGA inhibitor ThG showed opposite effects to ALX, further confirming that MTH activated the OGT mediated O-GlcNAcylation signaling pathway to exert cardioprotective effects. In summary, MTH activates OGT mediated O-glycosylation modified COX10 to regulate mitochondrial function and improve myocardial ischemia-reperfusion injury, which provides important theoretical basis for the clinical application of MTH.

Novel portable hypothermic machine perfusion preservation device enhances cardiac viability of donated human hearts.

Heart transplant remains the gold standard treatment for patients with advanced heart failure. However, the list of patients waiting for a heart transplant continues to increase. We have developed a portable hypothermic oxygenated machine perfusion device, the VP.S ENCORE®, to extend the allowable preservation time. The purpose of this study was to test the efficacy of the VP.S. ENCORE® using deceased donors derived hearts. Hearts from brain-dead donors not utilized for transplant (n = 11) were offered for research from the Texas Organ Sharing Alliance (TOSA), South and Central Texas' Organ Procurement Organization (OPO) and were preserved in the VP.S ENCORE® for 4 (n = 2), 6 (n = 3), and 8 (n = 3) hours or were kept in static cold storage (SCS) (n = 3). After preservation, the hearts were placed in an isolated heart Langendorff model for reperfusion and evaluated for cardiac function. The mean donor age was 37.82 ± 12.67 with the youngest donor being 19 and the oldest donor being 58 years old. SCS hearts mean weight gain (%) was -1.4 ± 2.77, while perfused at 4 h was 5.6 ± 6.04, perfused at 6 h 2.1 ± 6.04, and 8 h was 7.2 ± 10.76. Venous and arterial lactate concentrations were less than 2.0 mmol/L across all perfused hearts. Left ventricular contractility (+dPdT, mmHg/s) for 4 h (1,214 ± 1,064), 6 (1,565 ± 141.3), and 8 h (1,331 ± 403.6) were within the range of healthy human heart function. Thus, not significant as compared to the SCS group (1,597 ± 342.2). However, the left ventricular relaxation (mmHg/s) was significant in 6-hour perfused heart (p < 0.05) as compared to SCS. Gene expression analysis of inflammation markers (IL-6, IL-1β) showed no significant differences between SCS and perfused hearts, but a 6-hour perfusion led to a downregulated expression of these markers. The results demonstrate that the VP.S ENCORE® device enhances cardiac viability and exhibits comparable cardiac function to a healthy heart. The implications of these findings suggest that the VP.S ENCORE® could introduce a new paradigm in the field of organ preservation, especially for marginal hearts.

Erratum: Advancing the Assessment of Cardiac Injury and Function.

An erratum was issued for:Assessment of Ex Vivo Murine Biventricular Function in a Langendorff Model. The Authors section was updated from: Pierre-Emmanuel Noly1,2 Suyash Naik1 Paul Tang1 Ienglam Lei1 1University of Michigan, Ann Arbor 2University of Montreal to: Pierre-Emmanuel Noly1,2 Wei Huang1 Suyash Naik1 Paul Tang1 Ienglam Lei1 1University of Michigan, Ann Arbor 2University of Montreal.

Discovery of a novel 1,3,4-oxadiazol-2-one-based NLRP3 inhibitor as a pharmacological agent to mitigate cardiac and metabolic complications in an experimental model of diet-induced metaflammation

Inspired by the recent advancements in understanding the binding mode of sulfonylurea-based NLRP3 inhibitors to the NLRP3 sensor protein, we developed new NLRP3 inhibitors by replacing the central sulfonylurea moiety with different heterocycles. Computational studies evidenced that some of the designed compounds were able to maintain important interaction within the NACHT domain of the target protein similarly to the most active sulfonylurea-based NLRP3 inhibitors. Among the studied compounds, the 1,3,4-oxadiazol-2-one derivative 5 (INF200) showed the most promising results being able to prevent NLRP3-dependent pyroptosis triggered by LPS/ATP and LPS/MSU by 66.3 ± 6.6% and 61.6 ± 11.5% and to reduce IL-1β release (35.5 ± 8.8% μM) at 10 μM in human macrophages. The selected compound INF200 (20 mg/kg/day) was then tested in an in vivo rat model of high-fat diet (HFD)-induced metaflammation to evaluate its beneficial cardiometabolic effects. INF200 significantly counteracted HFD-dependent “anthropometric” changes, improved glucose and lipid profiles, and attenuated systemic inflammation and biomarkers of cardiac dysfunction (particularly BNP). Hemodynamic evaluation on Langendorff model indicate that INF200 limited myocardial damage-dependent ischemia/reperfusion injury (IRI) by improving post-ischemic systolic recovery and attenuating cardiac contracture, infarct size, and LDH release, thus reversing the exacerbation of obesity-associated damage. Mechanistically, in post-ischemic hearts, IFN200 reduced IRI-dependent NLRP3 activation, inflammation, and oxidative stress. These results highlight the potential of the novel NLRP3 inhibitor, INF200, and its ability to reverse the unfavorable cardio-metabolic dysfunction associated with obesity.

CARD28: Prolonged Graft Preservation of Biostasis Induced Porcine Hearts using the VP.S ENCORE® Machine Perfusion Device

Purpose: Heart transplantation is the gold standard therapy for patients with end-stage heart failure. However, the supply of donor hearts does not meet the demand, and many patients die on the waitlist. The purpose of this study was to test the efficacy of a novel machine perfusion device, the VP.S ENCORE® cardiac preservation device, in preserving porcine hearts conditioned with a biostasis-inducing compound (WC1) during prolonged 6-8 hour perfusion. Methods: Isolated porcine hearts were recovered under anesthesia. Following cannulation, the hearts were placed in the VP.S ENCORE® cardiac preservation device for oxygenated perfusion at 23-25°C for either 6 (n = 3) or 8 (n = 4) hours. At hour 3, WC1 (n = 2) was administered through the arterial line and the hearts continued to be perfused for additional 5 hours. Hourly flow, pressure, temperature, blood gases, and various metabolites were recorded. After preservation, hearts were placed in a Langendorff model for reperfusion and evaluated for cardiac function. Biopsy samples were taken before and at the end of preservation for histological and gene expression analyses. Results: During perfusion, oxygen consumption was significantly reduced in WC1-treated hearts (p < 0.0001). However, during re-perfusion, WC1-treated hearts had an initial lower oxygen consumption that recovered to normal with time and temperature. Before defibrillating the hearts, oxygen consumption was 1.61 ± 0.59 (vehicle) & 1.05 ± 0.39 (WC1), while after defibrillation the oxygen consumption increased to 3.29 ± 0.63 & 2.66 ± 0.32 ml/min/100g, respectively. The contractility of the WC1-treated hearts was similar to a normal human heart in vivo. Furthermore, gene expression analysis showed a significant reduction (p < 0.0008) of inflammation (IL-6, TNFα), hypoxia (Hif1a), & cell death markers (p53) in WC1 treated hearts when compared to control hearts. Conclusions: Our preliminary results demonstrate that the portable, simple-to-use VP.S ENCORE® cardiac preservation machine perfusion device coupled with the torpor properties of compounds like WC1 may provide a new paradigm to prolonged organ preservation, and may offer many advantages over currently tested machine perfusion technologies. Further, this innovative work is a result of integrating science and engineering to target unmet patients’ needs in the field of organ preservation.Figure 1. Subnormothermic Perfusion of Porcine Hearts using VP.S ENCORE®

Clinical significance of conduction velocity orientation vectors on cardiac mapping surfaces

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): This work was supported by the Lefoulon Delalande Foundation OBJECTIVE Electroanatomical maps using automated conduction velocity (CV) algorithms are now being calculated using 2D mapping tools. The basis of substrate-based functional assessment is to detect slow zones or slow CV of which isochronal late activation mapping (ILAM) is now commonly performed. We studied the accuracy of mapping surface 2D CV, compared to the 3D vectors, and the influence of mapping resolution in non-scarred animal and human heart models. Methods Two models were used: a healthy porcine Langendorff model with transmural needle electrodes and a computer stimulation model of the ventricles built from an MRI-segmented, excised human heart. Local activation times (LAT) within the 3D volume of the mesh were used to calculate true 3D CVs (direction and velocity) for different pixel resolutions ranging between 500 mm – 4 mm (3D CVs). CV was also calculated for endocardial surface-only LATs (2D CV). Results In the experimental model, surface (2D) CV was faster on the epicardium (0.509 m/s) compared to the endocardium (0.262 m/s, Figure 1). In stimulation models, 2D CV significantly exceeded 3D CVs across all mapping resolutions and increased as resolution decreased (Figure 2). 3D and 2D left ventricle CV at 500mm resolution increased from 429.2±189.3 mm/s to 527.7±253.8 mm/s (P&amp;lt;0.01), respectively with modest correlation (R=0.64). Decreasing the resolution to 4mm significantly increased 2D CV and weakened the correlation (R=0.46). The majority of CV vectors were not parallel (&amp;lt;30°) to the mapping surface providing a potential mechanistic explanation for erroneous LAT-based CV over-estimation. Conclusion Ventricular CV is overestimated when using 2D LAT-based CV calculation of the mapping surface and is significantly compounded by mapping resolution. These findings have implications for the current methodology of functional substrate assessment with ILAM and surface CV assessment.

Growth differentiation factor 15 (GDF15) preconditioning but not post-conditioning protects the hearts towards ischemia-reperfusion injury

Growth differentiation factor 15 (GDF15) is a stress-responsive cytokine, which can be produced under certain pathological situations, mainly related to inflammatory stress, aging and disease. While clinical data suggest that GDF15 is a powerful prognosis factor in several high-risk cardiovascular situations, experimental studies rather consider this cytokine as a cardioprotective molecule. We aimed to clarify the direct cardiac effects of GDF15 during ischemia-reperfusion (I-R) injury, at concentrations found in patients with high cardiovascular risk, such as these of patients presenting with acute myocardial infarction or stroke. Wistar male rats (200–400 g) were used for both in vivo and ex vivo ischemia-reperfusion and anesthetized with isoflurane. In vivo rats were injected with either saline (Control groups) or 2.5 μg/kg of GDF15 (GDF15 groups), 20 minutes before ischemia in the preconditioning protocol, or at the end of ischemia in the post-conditioning protocol. Myocardial ischemia was induced by the transient ligation of the left anterior descending artery for 30 min followed by 24 h of reperfusion. In a second set of experiments, rat's hearts were isolated and perfused ex vivo on a Langendorff model with either saline (Control groups) or 2000 ng/L of GDF15 upstream the coronary bed (GDF15 groups) for 10 minutes before ischemia or during reperfusion following 30 minutes of global normothermic total ischemia. GDF15 decreased the infarct size in vivo as well as in ex vivo when administrated before ischemia but not at the end of it. Moreover, in our ex vivo model, only GDF15 preconditioning induced a better recovery of most contractile parameters after ischemia (P < 0.05 for all parameters). These results demonstrate that exogenous GDF15 preconditioning decreased cardiac cell death in vivo but also ex vivo, the latter situation involving that inflammatory, endocrine, and nervous systems are not interfering. Suggesting that GDF15 exerts direct cardioprotective properties towards ischemia-reperfusion injury.

Acute Modulation of Left Ventricular Control by Selective Intracardiac Sympathetic Denervation.

The sympathetic nervous system plays an integral role in cardiac physiology. Nerve fibers innervating the left ventricle are amenable to transvenous catheter stimulation along the coronary sinus (CS). The aim of the present study was to modulate left ventricular control by selective intracardiac sympathetic denervation. First, the impact of epicardial CS ablation on cardiac electrophysiology was studied in a Langendorff model of decentralized murine hearts (n=10 each, ablation and control groups). Second, the impact of transvenous, anatomically driven axotomy by catheter-based radiofrequency ablation via the CS was evaluated in healthy sheep (n=8) before and during stellate ganglion stimulation. CS ablation prolonged epicardial ventricular refractory period without (41.8 ± 8.4ms vs 53.0 ± 13.5ms; P=0.049) and with β1-2-adrenergic receptor blockade (47.8 ± 7.8ms vs 73.1 ± 13.2ms; P<0.001) in mice. Supported by neuromorphological studies illustrating a circumferential CS neural network, intracardiac axotomy by catheter ablation via the CS in healthy sheep diminished the blood pressure increase during stellate ganglion stimulation (Δ systolic bloodpressure 21.9 ± 10.9mmHg vs 10.5 ± 12.0mmHg; P=0.023; Δ diastolic blood pressure 9.0 ± 5.5mmHg vs 3.0± 3.5mmHg; P=0.039). Transvenous, anatomically driven axotomy targeting nerve fibers along the CS enables acute modulation of left ventricular control by selective intracardiac sympathetic denervation.

Glutathione restores the mitochondrial redox status and improves the function of the cardiovascular system in old rats.

Introduction: Aging is accompanied by cardiovascular disorders which is associated with an imbalance of pro- and antioxidant systems, the mitochondrial dysfunction, etc. Glutathione (GSH) plays a critical role in protecting cells from oxidative damage. The aim of the work was to study the effect of exogenous glutathione on the redox status of mitochondria, the content of H2S and the function of the cardiovascular system in old rats. Methods: Experiments were performed on adult (6months) and old (24months) Wistar rats divided into three groups: adult, old and glutathionetreated old rats. Glutathione was injected intraperitoneally at a dose of 52mg/kg. We investigated glutathione redox balance, H2S levels, oxidative stress, the opening of the mitochondrial permeability transition pore (mPTP), the resistance of isolated heart to ischemia/reperfusion in Langendorff model, endothelium-dependent vasorelaxation of isolated aortic rings, and cardiac levels of 3-MST, CSE, and UCP3 mRNA were determined using real-time PCR analysis. Results: Our data shows that in old rats treated with glutathione, the balance of its oxidized and reduced form changes in the direction of a significant increase (by 53.6%) of the reduced form. Glutathione pretreatment significantly increased the H2S levels, mtNOS activity, and UCP3 expression which considered as protective protein, and conversely, significantly decreased oxidative stress markers (the rate of O2•- generation, the levels of H2O2, diene conjugates and malone dialdehyde, in 2.5, 2.3, 2, and 1.6 times, respectively) in heart mitochondria. This was associated with the inhibition mitochondrial permeability transition pore opening and increased resistance of the isolated heart to ischemia/reperfusion in these animals. At the same time, in glutathione-treated old rats, we also observed restoration of endothelium-dependent vasorelaxation responses to acetylcholine, which were almost completely abolished by the NO-synthase inhibitor L-NAME. Conclusion: Thus, the pretreatment of old rats with glutathione restores the mitochondrial redox status and improves the function of the cardiovascular system.

Orientation of conduction velocity vectors on cardiac mapping surfaces.

Electroanatomical maps using automated conduction velocity (CV) algorithms are now being calculated using two-dimensional (2D) mapping tools. We studied the accuracy of mapping surface 2D CV, compared to the three-dimensional (3D) vectors, and the influence of mapping resolution in non-scarred animal and human heart models. Two models were used: a healthy porcine Langendorff model with transmural needle electrodes and a computer stimulation model of the ventricles built from an MRI-segmented, excised human heart. Local activation times (LATs) within the 3D volume of the mesh were used to calculate true 3D CVs (direction and velocity) for different pixel resolutions ranging between 500 μm and 4 mm (3D CVs). CV was also calculated for endocardial surface-only LATs (2D CV). In the experimental model, surface (2D) CV was faster on the epicardium (0.509 m/s) compared to the endocardium (0.262 m/s). In stimulation models, 2D CV significantly exceeded 3D CVs across all mapping resolutions and increased as resolution decreased. Three-dimensional and 2D left ventricle CV at 500 μm resolution increased from 429.2 ± 189.3 to 527.7 ± 253.8 mm/s (P < 0.01), respectively, with modest correlation (R = 0.64). Decreasing the resolution to 4 mm significantly increased 2D CV and weakened the correlation (R = 0.46). The majority of CV vectors were not parallel (<30°) to the mapping surface providing a potential mechanistic explanation for erroneous LAT-based CV over-estimation. Ventricular CV is overestimated when using 2D LAT-based CV calculation of the mapping surface and significantly compounded by mapping resolution. Three-dimensional electric field-based approaches are needed in mapping true CV on mapping surfaces.

Assessment of Ex Vivo Murine Biventricular Function in a Langendorff Model.

Primary graft dysfunction (PGD) remains the leading cause of early death following heart transplantation. Prolonged ischemic time during cold preservation is an important risk factor for PGD, and reliable evaluation of cardiac function is essential to study the functional responses of the donor heart after cold preservation. The accompanying video describes a technique to assess murine right and left ventricular function using ex vivo perfusion based in a Langendorff model after cold preservation for different durations. In brief, the heart is isolated and stored in a cold histidine-tryptophan-ketoglutarate (HTK) solution. Then, the heart is perfused with a Kreb buffer in a Langendorff model for 60 min. A silicone balloon is inserted into the left and right ventricle, and cardiac functional parameters are recorded (dP/dt, pressure-volume relationships). This protocol allows the reliable evaluation of cardiac function after different heart preservation protocols. Importantly, this technique allows the study of cardiac preservation responses specifically in native cardiac cells. The use of very small murine hearts allows access to an enormous array of transgenic mice to investigate the mechanisms of PGD.

Acute cardiac deletion of EMRE protects against ischemia reperfusion injury in an ex vivo Langendorff model

Acute cardiac deletion of EMRE protects against ischemia reperfusion injury in an ex vivo Langendorff model

Abstract 15530: Renal Outer Medullary Potassium (Kir 1.1) is not the Kir Subunit of a Cardioprotective, Diazoxide - Mediated Mitochondrial Adenosine Triphosphate - Sensitive Potassium Channel

Objective: The adenosine triphosphate-sensitive potassium (K ATP ) channel opener diazoxide (DZX) mimics ischemic preconditioning and is cardioprotective. The molecular mechanism of action is unknown, although several mitochondrial candidate protein targets have been proposed. We suggested that cardioprotection occurs at a non-sarcolemmal channel, requires the inhibition of succinate dehydrogenase, and involves K ATP channel subunit SUR1. The renal outer medullary potassium channel (ROMK, or Kir1.1) subunit was proposed as the Kir subunit of a mitochondrial (m)K ATP channel. We tested the hypothesis that genetic deletion of ROMK will result in loss of DZX cardioprotection in a model of prolonged ischemia with cardioplegia. Methods: Mice lacking ROMK in cardiac myocytes (cKO) and wild-type (WT) litter mates were randomly assigned to 90 min. global ischemia in a Langendorff model following hypothermic hyperkalemic cardioplegia (CPG) or CPG + DZX (100 μM/L) (N=6-9 per group). Left ventricular developed pressure (LVDP), end diastolic pressure (EDP), and coronary flow were compared before and after global ischemia. Data acquisition and interpretation were blinded to group. Results: Similar to previous results, prolonged global ischemia was associated with a reduction in LVDP and an increase in EDP with CPG that was prevented by DZX in WT. Unexpectedly, ROMK (cKO) mice were equally responsive to DZX (Figure), indicating that DZX protection is not mediated by ROMK channels. Conclusions: Genetic deletion of ROMK in cardiac myocytes does not negate cardioprotection provided by DZX, indicating ROMK is not a subunit of a cardioprotective mK ATP channel. Alternate proposed DZX-sensitive target channels or mechanisms of action remain to be tested. Identification of the specific subunits of a mK ATP channel would allow for targeted pharmacologic therapy to reduce myocardial stunning following prolonged ischemia, similar to that seen following cardiac surgery.

Impact of various periods of perfusion-pause and reperfusion on the severity of myocardial injury in the langenodorff model.

To explore impact of various periods of ischemia and reperfusion on the severity of myocardial injury. Langendorff model of isolated cardiac perfusion system was established in 56 rat hearts. They were randomly assigned into four groups with four different ischemia (perfusion-pause) time and reperfusion time. The levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and creatine kinase-MB (CK-MB) were measured and the size of myocardial infarction was assessed by 2,3,5-triphenyltetrazolium chloride (TTC) staining. The levels of AST, ALT, LDH, and CK-MB in the heart tissues and perfusate were lowest in the group I (shortest time of perfusion-pause and reperfusion) followed by the groups II, III, and IV (longest time of perfusion-pause and reperfusion) (p < 0.05). The myocardial infarction size was smallest in the group I (6.63 ± 0.47) followed by group II (15.12 ± 1.03), group III (20.32 ± 2.18), and group IV (32.29 ± 5.42) (p < 0.05). Two-way ANOVA analysis revealed that period of perfusion-pause and reperfusion independently and significantly affected the levels of AST and ALT in both heart tissues and perfusate (p < 0.001). The interaction of pausing period and reperfusion significantly affected the level of AST (p = 0.046) and CK-MB (p = 0.001) in the perfusate. In addition, perfusion-pause period significantly affected levels of LDH and CK-MB only in the perfusate (p < 0.001). Neither perfusate nor heart tissue LDH level was significantly affected by the interaction of perfusion-pause and reperfusion period (p > 0.05). The severity of myocardial injury in the Langendorff model was affected by the period of perfusion-pause and reperfusion. The longer period of perfusion-pause followed by the longer the period of reperfusion, the severe myocardial injury was found.

Exogenous ANP Treatment Ameliorates Myocardial Insulin Resistance and Protects against Ischemia-Reperfusion Injury in Diet-Induced Obesity.

Increasing evidence suggests natriuretic peptides (NPs) coordinate interorgan metabolic crosstalk. We recently reported exogenous ANP treatment ameliorated systemic insulin resistance by inducing adipose tissue browning and attenuating hepatic steatosis in diet-induced obesity (DIO). We herein investigated whether ANP treatment also ameliorates myocardial insulin resistance, leading to cardioprotection during ischemia–reperfusion injury (IRI) in DIO. Mice fed a high-fat diet (HFD) or normal-fat diet for 13 weeks were treated with or without ANP infusion subcutaneously for another 3 weeks. Left ventricular BNP expression was substantially reduced in HFD hearts. Intraperitoneal-insulin-administration-induced Akt phosphorylation was impaired in HFD hearts, which was restored by ANP treatment, suggesting that ANP treatment ameliorated myocardial insulin resistance. After ischemia–reperfusion using the Langendorff model, HFD impaired cardiac functional recovery with a corresponding increased infarct size. However, ANP treatment improved functional recovery and reduced injury while restoring impaired IRI-induced Akt phosphorylation in HFD hearts. Myocardial ultrastructural analyses showed increased peri-mitochondrial lipid droplets with concomitantly decreased ATGL and HSL phosphorylation levels in ANP-treated HFD, suggesting that ANP protects mitochondria from lipid overload by trapping lipids. Accordingly, ANP treatment attenuated mitochondria cristae disruption after IRI in HFD hearts. In summary, exogenous ANP treatment ameliorates myocardial insulin resistance and protects against IRI associated with mitochondrial ultrastructure modifications in DIO. Replenishing biologically active NPs substantially affects HFD hearts in which endogenous NP production is impaired.

Short-Term Administration of Lemon Balm Extract Ameliorates Myocardial Ischemia/Reperfusion Injury: Focus on Oxidative Stress.

We aimed to investigate the cardioprotective effects of ethanolic Melissa officinalis L. extract (ME) in the rat model of myocardial ischemia/reperfusion (I/R) injury. Thirty-two Wistar rats were randomly divided into a CTRL non-treated control group with myocardial I/R injury and three experimental groups of rats treated with 50, 100, or 200 mg/kg of ME for 7 days per os. Afterward, hearts were isolated, and cardiodynamic function was assessed via the Langendorff model of global 20 min ischemia and 30 min reperfusion. Oxidative stress parameters were determined spectrophotometrically from the samples of coronary venous effluent (O2−, H2O2, TBARS, and NO2−,) and heart tissue homogenate (TBARS, NO2−, SOD, and CAT). H/E and Picrosirius red staining were used to examine cardiac architecture and cardiac collagen content. ME improved cardiodynamic parameters and achieved to preserve cardiac architecture after I/R injury and to decrease fibrosis, especially in the ME200 group compared to CTRL. ME200 and ME100 markedly decreased prooxidants TBARS, O2−, and H2O2 while increasing NO2−. Hereby, we confirmed the ME`s ability to save the heart from I/R induced damage, even after short-term preconditioning in terms of preserving cardiodynamic alterations, cardiac architecture, fibrosis, and suppressing oxidative stress, especially in dose of 200 mg/kg.

Exogenous growth differentiation factor 15 (GDF15) exerts direct cardioprotective properties towards myocardial ischemia reperfusion injury

Growth differentiation factor 15 (GDF15) is a stress-responsive cytokine which can be produced under certain pathological situations, mainly related to inflammatory stress, aging and disease. While clinical data suggest that GDF15 is a powerful risk factor in several high-risk cardiovascular situations such as myocardial infarction and coronary artery disease, experimental studies rather consider this cytokine as a cardioprotective molecule. We aimed to clarify the direct cardiac effects of GDF15 during ischemia-reperfusion (I-R) injury, at concentrations found in patients with high cardiovascular risk, such as these of patients presenting with acute myocardial infarction or stroke. Wistar male rats (200–400 g) were used for both in vivo and ex vivo ischemia-reperfusion and anesthetized with isoflurane. In vivo rats were intubated before a left thoracotomy was performed between the 3rd and the 4th intercostal space. Rats were injected with either saline (Control groups) or 2.5 μg/kg of GDF15 (GDF15 groups), 20 minutes before the transient ligation of the left anterior descending artery for 30 min followed by 24 h of reperfusion. Ex vivo rat's hearts were isolated and perfused on a Langendorff model with either saline (Control groups) or 2000 ng/L of GDF15 upstream the coronary bed (GDF15 groups) for 10 minutes, then subjected to either 20 or 30 minutes of global normothermic total ischemia, followed by 2 h of reperfusion. GDF15 decreased the infarct size in vivo as well as in ex vivo. Moreover, in our ex vivo model, GDF15 induced a better recovery of most contractile parameters after ischemia ( P < 0.05 for all parameters). These results demonstrate for the first time that exogenous preischemic short-term administration of GDF15 decreased cardiac cell death in vivo but also ex vivo, the latter situation involving that inflammatory, endocrine, and nervous systems are not interfering. These original results suggest that GDF15 exerts direct cardioprotective properties towards ischemia-reperfusion injury.

Selective intracardiac sympathetic denervation acutely modulates left ventricular control

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Centre for Cardiovascular Research (DZHK) Background The sympathetic nervous system plays an integral role in cardiac physiology. Neuromodulation is emerging as a treatment option for ventricular arrhythmias, but selective intracardiac approaches are rare. Sympathetic nerve fibers innervating the left ventricle have been demonstrated to be amenable to transvenous catheter stimulation along the coronary sinus (CS). Purpose The aim of the present study was to modulate left ventricular control by selective sympathetic denervation using epicardial or standard catheter ablation for intracardiac axotomy at the level of the CS. Methods First, the impact of epicardial CS ablation on cardiac electrophysiology was studied in a Langendorff model of murine hearts (n=10 each, ablation and control). Second, the impact of transvenous, anatomically-driven axotomy by catheter-based radiofrequency ablation along the CS was evaluated in a healthy ovine in vivo model (n=8) before and during left stellate ganglion stimulation (LSGS). Results CS ablation for intracardiac sympathetic axotomy prolonged epicardial ventricular refractory period (VRP) without (41.8±8.4 ms vs. 53.0±13.5 ms; P=0.0487) and with beta1-2-adrenergic receptor blockade (47.8±2.8 ms vs. 73.1±5.0 ms; P=0.0009) and enhanced the increasing effect of beta1-2-adrenergic receptor blockade on epicardial VRP (∆VRP 6.3±7.0 ms vs. 20.0±7.5 ms; P=0.0045) in mice (Figure, A). Mean epicardial wave propagation velocity in the left ventricle was faster in ablated hearts than in controls (1.13±0.05 m/s vs. 1.00±0.02 m/s; P=0.0463), but did not differ in the right ventricle (1.15±0.05 m/s vs. 1.20±0.08 m/s; P=0.7938). Transvenous catheter ablation of the CS reduced systolic (SBP, 57.7±5.0 mmHg vs. 46.9±3.6 mmHg; P=0.0428) and diastolic blood pressure (DBP, 35.5±3.0 mmHg vs. 26.7±1.8 mmHg; P=0.0106) and diminished the blood pressure increase during LSGS in sheep (∆SBP 21.9±3.8 mmHg vs. 10.5±4.2 mmHg; P=0.0234; ∆DBP 9.0±1.9 mmHg vs. 3.0±1.2 mmHg; P=0.0391) (Figure, B, C). Cycle length remained unchanged by LSGS, both before (baseline 653.2±20.6 ms vs. LSGS 627.8±27.5 ms; P=0.2309) and after CS ablation (baseline 734.8±24.2 ms vs. LSGS 746.2±37.3 ms; P=0.7145). Conclusions Anatomically-driven axotomy targeting nerve fibers along the CS enables selective intracardiac sympathetic denervation resulting in acute modulation of left ventricular control.

Modification of the Langendorff system of the isolated beating heart for experimental radiotherapy at a synchrotron: 4000 Gy in a heart beat.

Microbeam radiotherapy could help to cure malignant tumours which are currently still considered therapy-resistant. With an irradiation target in the thoracic cavity, the heart would be one of the most important organs at risk. To assess the acute adverse effects of microbeam irradiation in the heart, a powerful ex vivo tool was created by combining the Langendorff model of the isolated beating mammalian heart with X-Tream dosimetry. In a first pilot experiment conducted at the Biomedical and Imaging Beamline of the Australian Synchrotron, the system was tested at a microbeam peak dose approximately ten times higher than the anticipated future microbeam irradiation treatment doses. The entire heart was irradiated with a dose of 4000 Gy at a dose rate of >6000 Gy s-1, using an array of 50 µm-wide microbeams spaced at a centre-to-centre distance of 400 µm. Although temporary arrhythmias were seen, they reverted spontaneously to a stable rhythm and no cardiac arrest occurred. This amazing preservation of cardiac function is promising for future therapeutic approaches.