Increase In Left Ventricular Pressure Research Articles

Enhancing Heart Transplantation: Utilizing Gas-Loaded Nanocarriers to Mitigate Cold/Hypoxia Stress

Gas-loaded nanocarriers (G-LN) show promise in improving heart transplantation (HTx) outcomes. Given their success in reducing cell death during normothermic hypoxia/reoxygenation (H/R) in vitro, we tested their integration into cardioplegic solutions and static cold storage (SCS) during simulated HTx. Wistar rat hearts underwent four hours of SCS with four G-LN variants: O2- or N2-cyclic-nigerosyl-nigerose-nanomonomers (CNN), and O2- or N2-cyclic-nigerosyl-nigerose-nanosponges (CNN-NS). We monitored physiological-hemodynamic parameters and molecular markers during reperfusion to assess cell damage/protection. Hearts treated with nanomonomers (N2-CNN or O2-CNN) showed improvements in left ventricular developed pressure (LVDP) and a trend towards faster recovery of the rate pressure product (RPP) compared to controls. However, nanosponges (N2-CNN-NS or O2-CNN-NS) did not show similar improvements. None of the groups exhibited an increase in diastolic left ventricular pressure (contracture index) during reperfusion. Redox markers and apoptosis/autophagy pathways indicated an increase in Beclin 1 for O2-CNN and in p22phox for N2-CNN, suggesting alterations in autophagy and the redox environment during late reperfusion, which might explain the gradual decline in heart performance. The study highlights the potential of nanomonomers to improve early cardiac performance and mitigate cold/H/R-induced stunning in HTx. These early improvements suggest a promising avenue for increasing HTx success. Nevertheless, further research and optimization are needed before clinical application.

Mechanism of Qili Qiangxin Capsule for Heart Failure Based on miR133a-Endoplasmic Reticulum Stress.

To investigate the pharmacological mechanism of Qili Qiangxin Capsule (QLQX) improvement of heart failure (HF) based on miR133a-endoplasmic reticulum stress (ERS) pathway. A left coronary artery ligation-induced HF after myocardial infarction model was used in this study. Rats were randomly assigned to the sham group, the model group, the QLQX group [0.32 g/(kg·d)], and the captopril group [2.25 mg/(kg·d)], 15 rats per group, followed by 4 weeks of medication. Cardiac function such as left ventricular ejection fraction (EF), fractional shortening (FS), left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), the maximal rate of increase of left ventricular pressure (+dp/dt max), and the maximal rate of decrease of left ventricular pressure (-dp/dt max) were monitored by echocardiography and hemodynamics. Hematoxylin and eosin (HE) and Masson stainings were used to visualize pathological changes in myocardial tissue. The mRNA expression of miR133a, glucose-regulated protein78 (GRP78), inositol-requiring enzyme 1 (IRE1), activating transcription factor 6 (ATF6), X-box binding protein1 (XBP1), C/EBP homologous protein (CHOP) and Caspase 12 were detected by RT-PCR. The protein expression of GRP78, p-IRE1/IRE1 ratio, cleaved-ATF6, XBP1-s (the spliced form of XBP1), CHOP and Caspase 12 were detected by Western blot. TdT-mediated dUTP nick-end labeling (TUNEL) staining was used to detect the rate of apoptosis. QLQX significantly improved cardiac function as evidenced by increased EF, FS, LVSP, +dp/dt max, -dp/dt max, and decreased LVEDP (P<0.05, P<0.01). HE staining showed that QLQX ameliorated cardiac pathologic damage to some extent. Masson staining indicated that QLQX significantly reduced collagen volume fraction in myocardial tissue (P<0.01). Results from RT-PCR and Western blot showed that QLQX significantly increased the expression of miR133a and inhibited the mRNA expressions of GRP78, IRE1, ATF6 and XBP1, as well as decreased the protein expressions of GRP78, cleaved-ATF6 and XBP1-s and decreased p-IRE1/IRE1 ratio (P<0.05, P<0.01). Further studies showed that QLQX significantly reduced the expression of CHOP and Caspase12, resulting in a significant reduction in apoptosis rate (P<0.05, P<0.01). The pharmacological mechanism of QLQX in improving HF is partly attributed to its regulatory effect on the miR133a-IRE1/XBP1 pathway.

Sevoflurane exerts protection against myocardial ischemia–reperfusion injury and pyroptosis through the circular RNA PAN3/microRNA-29b-3p/stromal cell-derived factor 4 axis

ObjectiveSevoflurane is suggested to exert protective functions against myocardial ischemia–reperfusion injury (MIRI). However, the particular mechanism remains elusive. Therefore, this research explored the mechanism of sevoflurane in MIRI-induced damage and pyroptosis. MethodsSubsequent to gain-or loss-of-function assays or/and sevoflurane treatment, the MIRI model was developed in rats. Cardiac function and body and heart weight of rats were evaluated, followed by measurement of apoptosis and creatine kinase MB (CK-MB), lactate dehydrogenase (LDH), and pyroptosis-related protein levels. After loss-of-function assays or/and sevoflurane treatment in human cardiomyocytes (HCMs), the hypoxia/reoxygenation (H/R) model was constructed. In HCMs, cell viability, apoptosis, and pyroptosis-related proteins were detected. Circular RNA PAN3 (circPAN3), microRNA (miR)-29b-3p, and stromal cell-derived factor 4 (SDF4) expression was determined in rat myocardial tissues and HCMs. Mechanistically, interactions among circPAN3, miR-29b-3p, and SDF4 were analyzed. ResultsMIRI modeling increased miR-29b-3p expression and diminished circPAN3 and SDF4 expression in H/R-treated HCMs and MIRI rats, which was nullified by sevoflurane preconditioning. Mechanistically, circPAN3 negatively targeted miR-29b-3p to upregulate SDF4. Moreover, sevoflurane preconditioning reduced heart weight/body weight ratio, LDH, CK-MB, myocardial infarct size, left ventricular end-diastolic pressure, apoptosis, and pyroptosis, while elevating the increase and decrease of left ventricular pressure (±dp/dt max) and left ventricular systolic pressure in MIRI rats. In addition, sevoflurane preconditioning augmented viability while diminishing apoptosis and pyroptosis in H/R-treated HCMs. Moreover, circPAN3 silencing or miR-29b-3p overexpression abrogated alleviatory effects of sevoflurane on myocardial injury and pyroptosis in vitro. ConclusionSevoflurane treatment ameliorated myocardial injury and pyroptosis in MIRI via circPAN3/miR-29b-3p/SDF4 axis.

C34 AN UNUSUAL CASE OF CARDIAC ARREST DUE TO TRAUMA–INDUCED QT PROLONGATION

Abstract Background QT prolongation is a well–known cause of sudden cardiac death due to polymorphic ventricular tachycardia triggered by early afterdepolarizations. Acquired long QT is a common finding in several clinical scenarios and invariably represents a high risk feature. Case Report An 84 years–old woman presented to our emergency department (ED) after experiencing a blunt chest trauma due to a car accident. She reported mild dyspnea and chest pain exacerbated by breathing and movement while denied palpitations and loss of consciousness. Baseline ECG showed atrial fibrillation with normal ventricular rate and a prolonged QT interval (QTc 640, Fig 1A) not present at previous ECGs. She did not assume any QT–prolonging drug and laboratory tests at admittance revealed troponin I values slightly elevated (29,6 ng/ml; n.v.: &amp;lt;11,6 ng/l) and no other significant abnormalities. A CT scan demonstrated a displaced fracture of the sternal body. Due to the QT prolongation, the patient was admitted for ECG monitoring.. During the stay in our ED the patient suffered a cardiac arrest. A torsade des pointes triggered by a late–coupled premature ventricular complex (PVC) was documented (Fig 1B). The arrhythmia was interrupted with external DC shock and magnesium solfate infusion was started. The coronary angiography demonstrated normal coronary arteries. The patient underwent cardiac magnetic resonance (CMR) four days later which showed transmural necrosis of the middle third of the lateral wall of the left ventricle at the insertion of the anterolateral papillary muscle (Fig 2). No further ventricular arrhythmias were observed and the patient was discharged after QTc normalization. Cardiac arrhythmias are a rare complication of cardiac contusion ranging from isolated PVCs to atrial or ventricular fibrillation. However, the role of the ECG in this peculiar subset is unclear. The most common ECG abnormalities are non specific ST–T wave changes, whereas in our case the marked QTc prolongation resulted in a closer monitoring of the patient allowing a prompt recognition of cardiac arrest. On the other hand CMR proved to be an effective method to identify a cardiac injury showing the typical pattern of myocardial damage associated with cardiac contusion (stress–induced lesions at the insertions of papillary muscles due to sudden increase of left ventricular pressure) and, thus, could be adopted as a useful tool to identify patients at higher risk for arrhythmic complications.

Doppler flow velocity profile of the left anterior descending in a patient with hypertrophic cardiomyopathy and markedly elevated left ventricular end-diastolic pressure: a novel observation.

Left anterior descending (LAD) coronary artery blood flow predominantly occurs in diastole and depends on the pressure differential across the myocardium, referred to as the coronary perfusion pressure (CPP). LAD flow can be visualized using two-dimensional/Doppler echocardiography. Restrictive diastolic filling patterns were previously described in the coronary artery Doppler profile as the ‘Doppler square root sign’ [EHJ CVI. 2017; 18(9):1067. doi: 10.1093/ehjci/jex061]. We present a case of a 44-year-old male with hypertrophic cardiomyopathy and no left ventricular outflow tract obstruction. The echocardiogram demonstrated septal wall thickness of 35 mm (Panel A), normal left ventricular ejection fraction (75%), impaired global longitudinal strain (−10%) (Panel B), and grade II diastolic dysfunction with a left atrial volume index of 56 mL/m2, E/A ratio 1.9 (Panel C), and septal e’ velocity 0.05 m/s. Further assessment of diastology revealed a mitral A wave duration of 120 ms (Panel D) and a pulmonary venous A wave duration of 220 ms (Panel E). The difference between the venous and transmitral A wave durations was 100 ms (normal < 30 ms). This degree of difference in the duration of flows is consistent with and indicative of a marked increase in left ventricular end-diastolic pressure (LVEDP). The LAD pulsed wave doppler flow (Panel F) profile (Panel G, see Supplementary data online, Video S1) demonstrated a transient reduction in end-diastolic velocity (‘a’ dip), which correlated with a decrease in CPP secondary to elevated LVEDP from a powerful atrial contraction, indeed a novel observation. Also noted is a small systolic flow reversal.

Oxymatrine ameliorates myocardial injury by inhibiting oxidative stress and apoptosis via the Nrf2/HO-1 and JAK/STAT pathways in type 2 diabetic rats

The necessity of increasing the efficiency of organ preservation has encouraged researchers to explore the mechanisms underlying diabetes-related myocardial injuries. This study intended to evaluate the protective effects of oxymatrine (OMT) in myocardial injury caused by type 2 diabetes mellitus. A model of diabetic rats was established to simulate type 2 diabetes mellitus using an intraperitoneal injection of a single dose of 65 mg/kg streptozotocin with a high-fat and high-cholesterol diet, and diabetic rats were subsequently treated with OMT (60, 120 mg/kg) by gavage for 8 weeks. Thereafter, diabetic rats demonstrated notable decreases in left ventricular systolic pressure (LVSP), ±dp/dtmax, and in the activities of glutathione peroxidase, superoxide dismutase, and catalase. Moreover, we found notable increases in left ventricular end-diastolic pressure, fasting blood glucose, and malondialdehyde, as well as changes in cell apoptosis and decreased expression levels of Nrf2, HO-1, tyrosine protein kinase JAK (JAK), and signal transducer and transcription activator (STAT). Treatment with OMT alleviated all of the measured parameters. Collectively, these findings suggest that activation of the Nrf2/HO-1 and inhibition of the JAK/STAT signaling are involved in mediating the cardioprotective effects of OMT and also highlight the benefits of OMT in ameliorating myocardial injury in diabetic rats.

Remote ischemic preconditioning-induced late cardioprotection: possible role of melatonin-mitoKATP-H2S signaling pathway.

Remote ischemic preconditioning (RIPC) confers cardioprotection against ischemia reperfusion (IR) injury. However, the precise mechanisms involved in RIPC-induced cardioprotection are not fully explored. The present study was aimed to identify the role of melatonin in RIPC-induced late cardioprotective effects in rats and to explore the role of H2S, TNF-α and mitoKATP in melatonin-mediated effects in RIPC. Wistar rats were subjected to RIPC in which hind limb was subjected to four alternate cycles of ischemia and reperfusion of 5 min duration by using a neonatal blood pressure cuff. After 24 h of RIPC or ramelteon-induced pharmacological preconditioning, hearts were isolated and subjected to IR injury on the Langendorff apparatus. RIPC and ramelteon preconditioning protected the hearts from IR injury and it was assessed by a decrease in LDH-1, cTnT and increase in left ventricular developed pressure (LVDP). RIPC increased the melatonin levels (in plasma), H2S (in heart) and decreased TNF-α levels. The effects of RIPC were abolished in the presence of melatonin receptor blocker (luzindole), ganglionic blocker (hexamethonium) and mitochondrial KATP blocker (5-hydroxydecanoic acid). RIPC produce delayed cardioprotection against IR injury through the activation of neuronal pathway, which may increase the plasma melatonin levels to activate the cardioprotective signaling pathway involving the opening of mitochondrial KATP channels, decrease in TNF-α production and increase in H2S levels. Ramelteon-induced pharmacological preconditioning may also activate the cardioprotective signaling pathway involving the opening of mitochondrial KATP channels, decrease in TNF-α production and increase in H2S levels.

Transient Increase in the Terminal Negative Deflection of the P Wave in Lead V1 during Treadmill Testing Identifies Exercise Induced Aggravated Left Ventricular Dysfunction

Terminal negative deflection of the P wave in lead V1 is produced by posteriorly directed depolarization of the left atrium. A value of more than 0.04 mm sec suggests increase in left atrial pressure. Transient new appearance of this finding during treadmill testing suggests transient exercise induced increase in left atrial pressure. Indirectly it suggests transient exercise induced/aggravated increase in left ventricular end diastolic pressure. In presence of clinical and/or electrocardiographic findings of myocardial ischemia, this finding suggest ischemia induced left ventricular dysfunction. Earlier this finding appears during exercise and longer it lasts during recovery, more severe is the left ventricular dysfunction.

Abstract 11494: Electrophysiological Effects of Sympathoexcitation are Mitigated by Blockade of Neuropeptide Y Y2 Receptors on Cardiac Parasympathetic Nerve Terminals

Introduction: Sympathetic activation releases both norepinephrine and co-transmitter neuropeptide Y (NPY). NPY can predispose to ventricular arrhythmias via receptors on cardiomyocytes. Ex vivo studies suggest that NPY may concomitantly reduce vagal tone via activation of NPY Y2 receptors (Y2R) on parasympathetic nerves, reducing acetylcholine release and further augmenting pro-arrhythmic sympathetic effects. We evaluated if parasympathetic Y2R blockade can prevent NPY-induced vagal inhibition, restore autonomic balance and stabilize cardiac electrophysiology. Methods: Yorkshire pigs (n = 12) underwent bilateral stellate ganglia stimulation (BSGS; 10 Hz, 4 ms) for 45 secs, before and after administration of selective Y2R antagonist BIIE0246 (BIIE; 32 nmol/kg bolus + 2 nmol/kg/min infusion). Hemodynamic and electrophysiological recordings were obtained with a left ventricular pressure (LVP) catheter, surface electrogram and a 56-electrode sock placed over the ventricles to measure activation recovery intervals (ARI), a surrogate of local action potential duration, from unipolar electrograms. Heart rate variability parameters, including low to high frequency ratio (LF/HF), were analyzed pre- and post-BIIE. Results: BSGS significantly increased heart rate (HR) and LVP, and shortened ventricular ARIs. BIIE significantly reduced both the rate of change and the maximal changes in HR and ARIs during BSGS. As anticipated, BSGS significantly increased LF/HF ratio, but this effect was abolished after BIIE. BIIE did not affect BSGS related increases in LVP. Conclusions: Cardiac effects of sympathetic activation are mediated, at least in part, by suppression of vagal tone through binding of NPY to parasympathetic Y2Rs. Blockade of this receptor partially counters pro-arrhythmic electrophysiological effects of BSGS and suggests a possible novel adjuvant role for Y2R blockade as a therapy for reducing consequences of sympatho-excitation.

Abstract 12821: Progressive Improvement in Left Ventricular Performance Associated With Progressive Regional Dyssynchrony

Background : We have shown that non-excitatory epicardial stimulation (NES) increases measures of cardiac function mediated by local release of norepinephrine. In this further investigation we determined whether NES is accompanied by improved indices of left ventricular (LV) performance, reflected in PV loops and timing of aortic valve opening and closing. Methods : Anesthetized pigs (n=6) were instrumented with a LV high-fidelity pressure/volume conductance transducer, thoracic aortic pressure transducer, left atrial (LA)/ LV epicardial electrodes, and sonomicrometer segment length (SL) gauges placed proximal (lateral base) and distal (posterior mid LV) to the LV stimulation site. During constant LA pacing, LV pulses (0.8ms, 2-3x threshold volts) were applied during the absolute refractory period for 3 minutes (3x), before and after β-receptor blockade (BB, metoprolol). Data were analyzed at baseline, and at an estimated 30%, 60% and 100% of developed ventricular dyssynchrony (DVD) contraction pattern. Results: Consistent with earlier findings, NES resulted in an early shortening and relaxation pattern of the proximal SL manifest as an 80% decrease in the LVP vs. SL loop area in the absence of change in the remote segment. This was accompanied by an increase in peak systolic pressure and LV dP/dt max. Although NES did not change the area of the LVP vs. LV volume loop (stroke work) or alter the interval from LV electrical activation (R wave) to the onset of LV pressure increase, aortic valve opening occurred up to 14.1 ± 2.8 ms earlier (p &lt;0.01) compared to baseline. The duration of an open aortic valve slightly increased (6.0 ± 3.9 ms) whereas ejection duration from valve opening to peak Pao decreased 18.2 ± 3.0 ms (p &lt; 0.01). Conclusion : These findings demonstrate that NES elicits a local contractile dysynchrony resulting in an enhanced cardiac inotropic state characterized by more rapid global LV contraction with earlier aortic valve opening with no change in stroke work.

Acute afterload leads to increased electrophysiological heterogeneity after myocardial infarction

Abstract Background Myocardial infarction (MI) results in altered mechanical loading and changes in the cardiac electrical properties. The infarct border zone is pro-arrhythmic but the exact role of mechano-electrical coupling remains unclear. Objective We studied spatial electrical heterogeneity in MI animals during acute afterload increase using a novel E-field methodology for high resolution mapping of local activation-repolarization intervals (ARI) in vivo. Methods Anterior-septal MI was induced in five domestic pigs by 120-minute occlusion of the left anterior descending artery followed by reperfusion. This led to an infarct size of 17.7±2.1% of the left ventricle. After 1 month, electro-anatomical mapping was performed before and during an acute afterload challenge induced by partially inflating a balloon in the descending aorta. A non-contact recording of a 64-electrode array was translated to 2048 non-contact electrograms distributed over the left ventricle. The non-contact electrograms were processed to determine the ARIs using a custom-made algorithm, previously validated against monophasic action potential recordings. Based on the contact map we defined border zone (BZ, voltage 0.5 to 1.5 mV) and remote (&amp;gt;1.5mV) regions. Heterogeneity was defined as the interquartile range (IQR) of ARIs in fixed neighborhoods of 1cm radius (figure 1A) and analyzed in 10 segments (5 BZ and 5 remote) of a modified version of the AHA model (49 segments by dividing the 16 non-apical segments). Other segments were discarded due to artefacts mainly caused by the array touching the septal and apical wall. Results Acute afterload challenge resulted in an increase of the systolic left ventricular pressure of 41.7±5.4% and increased left ventricular repolarization heterogeneity (IQR 4.03±1.23ms baseline to 4.85±1.38ms during inflation, p=0.004). There was a significant increase in heterogeneity in both BZ (4.78±1.60ms to 5.64±1.66ms, p=0.020) and remote (2.24±0.17ms to 3.00±0.86ms, p=0.034) regions (figure 1B). The IQR in the infarct BZ was higher compared to the remote zone at rest (4.78±1.60ms vs 2.24±0.17ms, p=0.010) as well as during inflation (5.64±1.66ms vs 3.00±0.86ms, p=0.008) (figure 1B). Both BZ and remote regions responded equally to acute afterload (p for interaction = 0.803). Conclusion Increased afterload leads to increased repolarization heterogeneity. This heterogeneity is higher in the infarct BZ. These alterations could provide a functional substrate for reentry. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): KU Leuven - C1 funding

Microbeam Irradiation of the Beating Rodent Heart: An Ex Vivo Study of Acute and Subacute Effects on Cardiac Function

Microbeam radiation therapy (MRT) has shown several advantages compared with conventional broad-beam radiation therapy in small animal models, including a better preservation of normal tissue function and improved drug delivery based on a rapidly increased vascular permeability in the target region. Normal tissue tolerance is the limiting factor in clinical radiation therapy. Knowledge of the normal tissue tolerance of organs at risk is therefore a prerequisite in evaluating any new radiation therapy approach. With an irradiation target in the thoracic cavity, the heart would be the most important organ at risk. We used the ex vivo beating rodent heart in the Langendorff perfusion system at the synchrotron to administer microbeam irradiation (MBI) with a peak dose of 40 or 400 Gy. By continuously recording the electrocardiogram, the left ventricular pressure, and the aortic pressure before, during and after MBI, we were able to assess acute and subacute effects of MBI on electrophysiological and mechanical cardiac function. In addition, we analyzed histologic and ultrastructural sequelae caused by MBI. There were no significant changes in heart rate, heart rate variability, systolic increase of left ventricular pressure or aortic pressure. Moreover, the changes of heart rate, left ventricular pressure and aortic pressure by adding 10-5 mol/L norepinephrine to the perfusate, were also not significant between MBI and sham experiments. However, the rate-pressure product as a surrogate marker for maximum workload after MBI was significantly lower compared with sham-irradiated controls. On the structural level, no severe membranous, sarcomeric, mitochondrial or nuclear changes caused by MBI were detected by desmin immunohistochemistry and electron microscopy. With respect to acute and subacute toxicity, an MBI peak dose up to 400Gy did not result in severe changes in cardiac electrophysiology or mechanics.

Protective effects of 5(S)-5-carboxystrictosidine on myocardial ischemia-reperfusion injury through activation of mitochondrial KATP channels

5(S)-5-carboxystrictosidine (5-CS) is a compound found in Mappianthus iodoides Hand.-Mazz., root, a traditional Chinese medicine used for the treatment of coronary artery disease. In this study, we investigated whether 5-CS protects heart against I/R injury. Sprague–Dawley rats were treated with 5-CS intraperitoneally for 7 days before the experiment. Hearts were perfused for 20 min global ischemia and 180 min reperfusion. 5-CS significantly inhibited an increase in the post-ischemic left ventricular end-diastolic pressure (LVEDP) and improved the post-ischemic left ventricular developed pressure (LVDP), dP/dt maximum and dP/dt minimum rates of pressure change, and coronary flow as compared with sham group. Pretreatment with 5-hydroxydecanoic acid (5-HD), an inhibitor of mitochondrial KATP channel, for 10 min before ischemia attenuated the improvement of LVEDP, LVDP, dP/dt maximum and dP/dt minimum rates of pressure change, and coronary flow induced by 5-CS. 5-CS markedly decreased the infarct size and attenuated the increased lactate dehydrogenase (LDH) level in effluent during reperfusion. Pretreatment with 5-HD also blocked these protective effects of 5-CS. 5-CS increased Mn-SOD, catalase, and HO-1 levels decreased by I/R injury and pretreatment of 5-HD blocked the 5-CS effects. Increases in Bax, cleaved caspase-3 and cytochrome c levels, caspase-3 and caspase-9 activity, and decrease in Bcl-2 level by I/R injury were attenuated by 5-CS treatment and pretreatment of 5-HD blocked its effects. These results suggest that the protective effects of 5-CS against myocardial I/R injury may be partly related to activating antioxidant enzymes and suppressing apoptosis through opening mitochondrial KATP channels.

Effect and mechanism of leonurine on pressure overload-induced cardiac hypertrophy in rats

To investigate the effects of leonurine(Leo) on abdominal aortic constriction(AAC)-induced cardiac hypertrophy in rats and its mechanism. A rat model of pressure overload-induced cardiac hypertrophy was established by AAC method. After 27-d intervention with high-dose(30 mg·kg~(-1)) and low-dose(15 mg·kg~(-1)) Leo or positive control drug losartan(5 mg·kg~(-1)), the cardiac function was evaluated by hemodynamic method, followed by the recording of left ventricular systolic pressure(LVSP), left ventricular end-diastolic pressure(LVESP), as well as the maximum rate of increase and decrease in left ventricular pressure(±dp/dt_(max)). The degree of left ventricular hypertrophy was assessed based on heart weight index(HWI) and left ventricular mass index(LVWI). Myocardial tissue changes and the myocardial cell diameter(MD) were measured after hematoxylin-eosin(HE) staining. The contents of angiotensin Ⅱ(AngⅡ) and angiotensin Ⅱ type 1 receptor(AT1 R) in myocardial tissue were detected by ELISA. The level of Ca~(2+) in myocardial tissue was determined by colorimetry. The protein expression levels of phospholipase C(PLC), inositol triphosphate(IP3), AngⅡ, and AT1 R were assayed by Western blot. Real-time quantitative PCR(qRT-PCR) was employed to determine the mRNA expression levels of β-myosin heavy chain(β-MHC), atrial natriuretic factor(ANF), AngⅡ, and AT1 R. Compared with the model group, Leo decreased the LVSP, LVEDP, HWI, LVWI and MD values, but increased ±dp/dt_(max) of the left ventricle. Meanwhile, it improved the pathological morphology of myocardial tissue, reduced cardiac hypertrophy, edema, and inflammatory cell infiltration, decreased the protein expression levels of PLC, IP3, AngⅡ, AT1 R, as well as the mRNA expression levels of β-MHC, ANF, AngⅡ, AT1 R, c-fos, and c-Myc in myocardial tissue. Leo inhibited AAC-induced cardiac hypertrophy possibly by influencing the RAS system.

Isosteviol improves cardiac function and promotes angiogenesis after myocardial infarction in rats.

Isosteviol has been indicated as a cardiomyocyte protector. However, the underlying mechanism remains unclear. Thus, we sought to confirm the protective effect of isosteviol after myocardial infarction in a model of permanent coronary artery occlusion and investigate the potential proangiogenic activity in vitro and in vivo. A 4-week permanent coronary artery occlusion rat model was generated, and the protective effect of isosteviol was evaluated by echocardiographic imaging and hemodynamics assays. The coronary capillary density was tested by immunochemistry and micro-computed tomography (μCT) imaging. The effect of isosteviol on endothelial cells was determined in human umbilical vein endothelial cells (HUVECs) in vitro and Tg (kdrl: EGFP) zebrafish in vivo. We also examined the expression of related transcription factors by real-time polymerase chain reaction (RT-qPCR). Isosteviol increased ejection fraction (EF), fractional shortening (FS), cardiac systolic index (CI), maximum rate of increase of left ventricular pressure (Max dp/dt), and left ventricular systolic pressure (LVSP) by 32%, 40%, 25%, 26%, and 10%, respectively, in permanent coronary artery occlusion rats. Interestingly, it also promoted coronary capillary density by 2.5-fold. In addition, isosteviol promoted the proliferation and branching of HUVECs in vitro. It also rescued intersegmental vessel (ISV) development and improved endothelial cell proliferation by approximately fivefold (4-6) in zebrafish embryos in vivo. Isosteviol also upregulated the expression of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor A (VEGFA) in zebrafish by fourfold and 3.5-fold, respectively. Our findings suggest that isosteviol is a proangiogenic agent and that this activity is related to its protective effects against myocardial ischemia. After using the permanent coronary artery occlusion model, we demonstrated that isosteviol promotes angiogenesis directly and increases capillary density in myocardial ischemia rats. Isosteviol promotes angiogenesis in zebrafish in vivo and increases vascular endothelial cell proliferation in HUVECs and zebrafish. The angiogenesis activity of isosteviol may be correlated with VEGFA and HIF-1α signaling.

Chronic GPER activation prevents ischemia/reperfusion injury in ovariectomized rats

During menopause women are exposed to an increase in cardiovascular risk. G protein-coupled estrogen receptor (GPER) is known to mediate several of the protective effects of such hormones. G1 was described as a selective and synthetic agonist for GPER. The aim of the present research is to evaluate the effect of a chronic treatment with G1 in ovariectomized (OVX) rats exposed to ischemia/reperfusion (I/R). Considering the hypothesis that an impaired mitochondrial state could be involved in the alterations produced in OVX rats, other objective of this study was to investigate it in an isolated preparation. Three months old rats were assigned to undergo either bilateral ovariectomy or sham operation. The OVX rats were randomly treated during one month with either G1 or vehicle. Cardiac mitochondria from OVX rats showed a depolarized membrane potential and a decreased calcium retention capacity in comparison with Sham rats, which were prevented by chronic G1 treatment. I/R caused a higher decrease of left ventricular developed pressure and a higher increase of left ventricular end diastolic pressure in OVX compared to Sham hearts. These altered mechanical parameters were prevented by G1. The induced infarct size was significantly higher in OVX, which was reduced by G1 treatment. These results indicate that the mitochondrial state in OVX rats is impaired, accompanied by an altered mechanical response after ischemia and reperfusion injury, which was effectively prevented with chronic treatment with G1. The present study may provide further insights for the potential development of a therapy based on the GPER modulation.

Reduced Cell Excitability of Cardiac Postganglionic Parasympathetic Neurons Correlates With Myocardial Infarction-Induced Fatal Ventricular Arrhythmias in Type 2 Diabetes Mellitus

ObjectiveWithdrawal of cardiac vagal activity is considered as one of the important triggers for acute myocardial infarction (MI)-induced ventricular arrhythmias in type 2 diabetes mellitus (T2DM). Our previous study demonstrated that cell excitability of cardiac parasympathetic postganglionic (CPP) neurons was reduced in T2DM rats. This study investigated whether cell excitability of CPP neurons is associated with cardiac vagal activity and MI-induced ventricular arrhythmias in T2DM rats.MethodsRat T2DM was induced by a high-fat diet plus streptozotocin injection. MI-evoked ventricular arrhythmia was achieved by surgical ligation of the left anterior descending coronary artery. Twenty-four-hour, continuous ECG recording was used to quantify ventricular arrhythmic events and heart rate variability (HRV) in conscious rats. The power spectral analysis of HRV was used to evaluate autonomic function. Cell excitability of CPP neurons was measured by the whole-cell patch-clamp technique.ResultsTwenty-four-hour ECG data demonstrated that MI-evoked fatal ventricular arrhythmias are more severe in T2DM rats than that in sham rats. In addition, the Kaplan-Meier analysis demonstrated that the survival rate over 2 weeks after MI is significantly lower in T2DM rats (15% in T2DM+MI) compared to sham rats (75% in sham+MI). The susceptibility to ventricular tachyarrhythmia elicited by programmed electrical stimulation was higher in anesthetized T2DM+MI rats than that in rats with MI or T2DM alone (7.0 ± 0.58 in T2DM+MI group vs. 3.5 ± 0.76 in sham+MI). Moreover, as an index for vagal control of ventricular function, changes of left ventricular systolic pressure (LVSP) and the maximum rate of increase of left ventricular pressure (LV dP/dtmax) in response to vagal efferent nerve stimulation were blunted in T2DM rats. Furthermore, T2DM increased heterogeneity of ventricular electrical activities and reduced cardiac parasympathetic activity and cell excitability of CPP neurons (current threshold-inducing action potentials being 62 ± 3.3 pA in T2DM rats without MI vs. 27 ± 1.9 pA in sham rats without MI). However, MI did not alter vagal control of the ventricular function and CPP neuronal excitability, although it also induced cardiac autonomic dysfunction and enhanced heterogeneity of ventricular electrical activities.ConclusionThe reduction of CPP neuron excitability is involved in decreased cardiac vagal function, including cardiac parasympathetic activity and vagal control of ventricular function, which is associated with MI-induced high mortality and malignant ventricular arrhythmias in T2DM.

Pleiotropic, non-cell death-associated effects of inhibitors of receptor-interacting protein kinase 1 in the heart.

Inhibition of receptor-interacting protein kinase 1 (RIP1) has been recognized as a compelling tool for limiting necroptosis. Recent findings have indicated that RIP1 inhibitor, necrostatin-1 (Nec-1), is also able to modify heart function under non-cell death conditions. In this study, we investigated its underlying molecular mechanisms and compared with those of novel pharmacologically improved agents (Nec-1s and GSK'772) and its inactive analog (Nec-1i). Heart function was examined in Langendorff-perfused rat hearts. Certain proteins regulating myocardial contraction-relaxation cycle and oxidative stress (OS) were evaluated by immunoblotting and as the extent of lipid peroxidation, protein carbonylation and nitration, respectively. In spite of the increase of left ventricular developed pressure (LVDP) due to treatment by both Nec-1 and Nec-1i, only the former agent increased the phosphorylation of Ca2+/calmodulin-dependent protein kinase II delta (CaMKIIδ) at threonine 287 and cardiac myosin-binding protein-C (cMyBPc) at serine 282. In contrast, Nec-1s did not elicit such changes, while it also increased LVDP. GSK'772 activated CaMKIIδ-phospholamban (PLN) axis. Neither protein kinase A (PKA) nor its selected molecular targets, such as serine 16 phosphorylated PLN and sarco/endoplasmic reticulum Ca2+-ATPase 2a (SERCA2a), were affected by either RIP1 inhibitor. Nec-1, like other necrostatins (Nec-1i, Nec-1s), but not GSK'772, elevated protein tyrosine nitration without affecting other markers of OS. In conclusion, this study indicated for the first time that Nec-1 may affect basal heart function by the modulation of OS and activation of some proteins of contraction-relaxation cycle.

N-myc downstream regulated gene 2 ameliorates myocardial remodeling and cardiac function in heart failure rats.

This study aims to explore the effect of NDRG2 (N-myc downstream regulated gene 2)-mediated Transforming growth factor-beta 1 (TGF-β1)/ Sma- and Mad-related protein (Smad) pathway in heart failure (HF) rats. HF rat models were established and treated with AdEGFP (adenovirus encoding enhanced green fluorescent protein) or AdNDRG2 (adenovirus encoding NDRG2). The echocardiography and hemodynamic parameters were detected, and the infarct size was calculated via 2,3,5-triphenyltetrazolium chloride (TTC) staining. Masson staining was performed to observe the collagen volume fraction (CVF), quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) to detect the expression of Collagen I (Col-I) and Collagen III (Col-III), and Transferase (TdT)-mediated D-UTP-biotin nick end labeling (TUNEL) staining to evaluate the apoptosis. Rats in the Model group presented with the decreases in left ventricular ejection fraction (LVEF), left ventricular shortening fraction (LVFS), left ventricular systolic pressure (LVSP) and maximal/minimum rate of left ventricular pressure (±dp/dt max), and significant increases in left ventricular end-diastolic pressure (LVEDP) and CVF. At the meantime, the expression of Col-I and Col-III as well as the apoptotic rate of myocardial cells was also elevated with increased infarct size in the Model group. The Model rats also had the significant reduction in the expression of NDRG2 and up-regulations of TGF-β1, p-Smad2/Smad2, p-Smad3/Smad3 and tissue inhibitor of metalloproteinases-2 (TIMP-2). However, model rats treated with AdNDRG2 had evident amelioration in aforementioned indicators. In conclusion, NDRG2 reduces the apoptosis of myocardial cells and improves the heart function and myocardial remodeling in HF rats via inhibiting the activity of TGF-β1/Smad.

The effects of acute and chronic Red Bull® consumption on cardiodynamics and oxidative stress in coronary effluent of trained rats

Background/Aim. Energy drinks (EDs) are widely used by athletes as ergogenic agents and Red Bull? is one of the most consumed EDs among them. The aim of this study was to determine the acute and chronic effects of Red Bull? on cardiodynamics and parameters of oxidative stress in physically trained rats. Methods. Rats were subjected to a swimming practice (1h a day, 5 days a week, for 4 weeks). They were divided into 4 groups: rats that did not consume ED either before swimming or prior to sacrificing; rats that did not consume ED before swimming but did consume ED 30 min prior to sacrificing; rats that consumed ED 30 min before every swimming training but did not consume ED prior to sacrificing; rats that consumed ED 30 min before every swimming training and 30 min before sacrificing. After sacrificing, the hearts of the rats were isolated and perfused according to the Langendorff technique. The parameters of cardiac function were recorded, and also the levels of prooxidants were measured in the coronary effluent during coronary autoregulation. Results. Acute administration of the ED had a positive inotropic effect (manifested as a significantly higher level of the maximum and minimum rate of pressure development in the left ventricle), while chronic administration affected the isolated increase in systolic left ventricular pressure. The prooxidative effect of the ED was observed, which was more pronounced in chronic consumption. Conclusion. The main conclusion of our study is that chronic consumption of ED changes the cardiovascular response and redox status in acute consumption ED.