Left Ventricular Developed Pressure Research Articles

Interrelated In Vitro Mechanisms of Sibutramine-Induced Cardiotoxicity.

Consumption of illicit pharmaceutical products containing sibutramine has been reported to cause cardiovascular toxicity problems. This study aimed to demonstrate the toxicity profile of sibutramine, and thereby provide important implications for the development of more effective strategies in both clinical approaches and drug design studies. Action potentials (APs) were determined from freshly isolated ventricular cardiomyocytes with whole-cell configuration of current clamp as online. The maximum amplitude of APs (MAPs), the resting membrane potential (RMP), and AP duration from the repolarization phases were calculated from original records. The voltage-dependent K+-channel currents (IK) were recorded in the presence of external Cd2+ and both inward and outward parts of the current were calculated, while their expression levels were determined with qPCR. The levels of intracellular free Ca2+ and H+ (pHi) as well as reactive oxygen species (ROS) were measured using either a ratiometric micro-spectrofluorometer or confocal microscope. The mechanical activity of isolated hearts was observed with Langendorff-perfusion system. Acute sibutramine applications (10-8-10-5M) induced significant alterations in both MAPs and RMP as well as the repolarization phases of APs and IK in a concentration-dependent manner. Sibutramine (10μM) induced Ca2+-release from the sarcoplasmic reticulum under either electrical or caffeine stimulation, whereas it depressed left ventricular developed pressure with a marked decrease in the end-diastolic pressure. pHi inhibition by sibutramine supports the observed negative alterations in contractility. Changes in mRNA levels of different IK subunits are consistent with the acute inhibition of the repolarizing IK, affecting AP parameters, and provoke the cardiotoxicity.

Resistance training improves cardiac function and cardiovascular autonomic control in doxorubicin-induced cardiotoxicity.

Doxorubicin (DOX) is an anticancer chemotherapy drug that is widely used in clinical practice. It is well documented that DOX impairs baroreflex responsiveness and left ventricular function and enhances sympathetic activity, cardiac sympathetic afferent reflexes and oxidative stress, which contribute to hemodynamic deterioration. Because resistance training (RT)-induced cardioprotection has been observed in other animal models, the objective of this study was to assess the effects of RT during DOX treatment on hemodynamics, arterial baroreflex, cardiac autonomic tone, left ventricular function and oxidative stress in rats with DOX-induced cardiotoxicity. Male Wistar rats were submitted to a RT protocol (3 sets of 10 repetitions, 40% of one-repetition maximum (1RM) of intensity, 3 times per week, for 8weeks). The rats were separated into 3 groups: sedentary control, DOX sedentary (2.5mg/kg of DOX intraperitoneal injection, once a week, for 6weeks) and DOX + RT. After training or time control, the animals were anesthetized and 2 catheters were implanted for hemodynamic, arterial baroreflex and cardiac autonomic tone. Another group of animals was used to evaluate left ventricular function. We found that RT in DOX-treated rats decreased diastolic arterial pressure, heart rate, sympathetic tone and oxidative stress. In addition, RT increased arterial baroreflex sensitivity, vagal tone and left ventricular developed pressure in rats with DOX-induced cardiotoxicity. In summary, RT is a useful non-pharmacological strategy to attenuate DOX-induced cardiotoxicity.

Cardioprotective effects of acute sleep deprivation on ischemia/reperfusion injury

Modulation of sympathetic activity during acute sleep deprivation can produce various effects on body functions. We studied the effects of acute sleep deprivation before ischemia/reperfusion on myocardial injury in isolated rat hearts, and the role of sympathetic nervous system that may mediate these sleep deprivation induced effects.The animals were randomized into four groups (n = 11 per group): Ischemia- Reperfusion group (IR), Acute sleep deprivation group (SD), Control group for sleep deprivation (CON-SD) and Sympathectomy + ASD group (SYM-SD). In SD group, sleep deprivation paradigm was used 24 h prior to induction of ischemia/reperfusion. In SYM-SD group, the animals were chemically sympathectomized using 6-hydroxydopamine, 24 h before sleep deprivation. Then, the hearts of animals were perfused using Langendorff setup and were subjected to 30 min regional ischemia followed by 60 min of reperfusion. Throughout the experiment, the hearts were allowed to beat spontaneously and left ventricular developed pressure (LVDP) and rate pressure product (RPP) were recorded. At the end of study, infarct size and percentage of the area at risk were determined.We found that SD increased LVDP and RPP, while reducing the myocardial infarct size. Moreover, sympathectomy reversed SD induced reduction in infarct size and showed no differences as compared to IR.This study shows cardioprotective effects of acute sleep deprivation, which can be abolished by chemical sympathectomy in isolated hearts of rats.

Liraglutide restores late cardioprotective effects of remote preconditioning in diabetic rats via activation of hydrogen sulfide and nuclear factor erythroid 2-related factor 2 signaling pathway.

ABSTRACTPurposeThe present study explored the influence of liraglutide on remote preconditioning-mediated cardioprotection in diabetes mellitus along with the role of nuclear factor erythroid 2-related factor 2 (Nrf2), hypoxia inducible factor (HIF-1α) and hydrogen sulfide (H2S).MethodsStreptozotocin was given to rats to induce diabetes mellitus and rats were kept for eight weeks. Four cycles of ischemia and reperfusion were given to hind limb to induce remote preconditioning. After 24 h, hearts were isolated and subjected to 30 min of ischemia and 120 min of reperfusion on Langendorff system. Liraglutide was administered along with remote preconditioning. Cardiac injury was assessed by measuring the release of creatine kinase (CK-MB), cardiac troponin (cTnT) and development of left ventricular developed pressure. After ischemia-reperfusion, hearts were homogenized to measure the nuclear cytoplasmic ratio of Nrf2, H2S and HIF-1α levels.ResultsIn diabetic rats, there was more pronounced injury and the cardioprotective effects of remote preconditioning were not observed. Administration of liraglutide restored the cardioprotective effects of remote preconditioning in a dose-dependent manner. Moreover, liraglutide increased the Nrf2, H2S and HIF-1α levels in remote preconditioning-subjected diabetic rats.ConclusionsLiraglutide restores the lost cardioprotective effects of remote preconditioning in diabetes by increasing the expression of Nrf2, H2S and HIF-1α.

Cardioprotective effects of Ginsenoside compound-Mc1 and Dendrobium Nobile Lindl against myocardial infarction in an aged rat model: Involvement of TLR4/NF-κB signaling pathway

Aging is the crucial co-morbidity that prevents the full cardioprotection against myocardial ischemia/reperfusion (I/R) injury. Combination therapy as a promising strategy may overcome this clinical problem. This study aimed to investigate the cardioprotective effects of Ginsenoside compound-Mc1 (GMc1) and Dendrobium Nobile Lindl (DNL) in myocardial I/R injury and explore the involvement of the TLR4/NF-κB signaling pathway in aged rats. In vivo I/R injury and myocardial infarction was established by temporary coronary ligation in 22–24 months’ old Sprague Dawley male rats. GMc1 (10 mg/kg) and DNL (80 mg/kg) were administered intraperitoneally for 4 weeks and orally for 14 days, respectively, before I/R injury. Infarct size was measured through triphenyl-tetrazolium-chloride staining. ELISA assay was conducted to quantify the levels of cardiotroponin, and myocardial content of TNF-α and glutathione. Western blotting was employed to detect the expression of TLR4/MyD88/NF-κB proteins. GMc1 and DNL significantly reduced the infarct size to a similar extent ( p < 0.05) but their combined effect was greater than individual ones ( p < 0.01). Combination therapy significantly restored the left ventricular end-diastolic and developed pressures at the end of reperfusion as compared with the untreated group ( p < 0.01). Although the GMc1 and DNL reduced the levels of inflammatory cytokine TNF-α and increased the contents of antioxidant glutathione significantly, their individual effects on the reduction of protein expression of TLR4/MyD88/NF-κB pathway were not consistent. However, their combination could significantly reduce all parameters of this inflammatory pathway as compared to untreated I/R rats ( p < 0.001). Therefore, the combined treatment with GMc1 and DNL increased the potency of each intervention in protecting the aged hearts against I/R injury. Reduction in the activity of the TLR4/MyD88/NF-κB signaling pathway and subsequent modulation of the activity of inflammatory cytokines and endogenous antioxidants play an important role in this cardioprotection.

The effect of hyperbaric oxygenation on cardiodynamics and oxidative stress in rats with sepsis

Background/Aim. Dysfunctions at the cellular, tissue, and organ level, which can result in death, are caused by metabolic changes and affection on the regulation of gene transcription and micro- and macrocirculation. The aim of the present study was to assess the impact of hyperbaric oxygenation (HBO) on isolated heart as well as on the oxidative status of rats with sepsis. Methods. The investigation included male Wistar albino rats classified into three groups: the first group was a control group (CTRL); the second group included animals exposed only to the induction of sepsis without HBO treatment (the Sepsis group), while the third group included animals treated with HBO after the induction of sepsis (the Sepsis + HBO group). For the induction of sepsis, fecal peritonitis model was used (3 mL/kg of fecal suspension administered intraperitoneally). After the induction of sepsis, the rats were exposed twice a day (on 12 hours) to HBO treatment at 2.8 atmospheres absolute (ATA) for 90 minutes over a period of 3 days. 72 h after the confirmation of sepsis, the animals were sacrificed and the hearts were retrogradely perfused on the Langendorff apparatus at a gradually increased coronary perfusion pressure (CPP = 40?120 cm H2O). The following parameters of heart function were continuously recorded: maximum and minimum rate of left ventricular pressure development (dp/dt max, dp/dt min); systolic and diastolic left ventricular pressure (SLVP and DLVP); heart rate (HR). Coronary flow (CF) was measured flowmetrically. Following oxidative stress markers were measured: nitrites (NO2?), superoxide anion radical (O2?), hydrogen peroxide (H2O2), index of lipid peroxidation (TBARS), activity of superoxide dismutase (SOD) and catalase (CAT) and the level of reduced glutathione (GSH). Results. There were no significant differences in dp/dt max, dp/dt min, SLVP and HR between the groups. CF was statistically significantly higher (p < 0.01) in the sepsis group. The values of all cardiac oxidative markers were lower in the sepsis + HBO group (p < 0.05), while systemic pro-oxidative and antioxidative parameters were unchanged. Conclusion. Our results showed that HBO treatment was not associated with improved cardiac function and coronary perfusion, while expressed promising beneficial effects on cardiac oxidative stress.

Abstract 15316: Paradoxical Reduction in Myocardial Performance When Combining Two Independently Cardioprotective Agents: Mitochondrial-targeted Antioxidant MitoSNO and Adenosine Triphosphate-sensitive Potassium Channel Opener Diazoxide

Introduction: Adenosine triphosphate-sensitive potassium (K ATP ) channel opener diazoxide (DZX) and Antioxidant MitoSNO are both independently cardioprotective in animal models. The cardioprotective mechanism of diazoxide is unknown, and involves a non-sarcolemmal location, requires the inhibition of succinate dehydrogenase, and the K ATP channel subunit SUR1. Mitochondrial - targeted Antioxidant MitoSNO is a S-nitrosylating agent that stalls complex 1, reduces ROS production and succinate accumulation. In an isolated myocyte model of stress due to hyperkalemic cardioplegia (CPG), that the combination of DZX and MitoSNO negated the beneficial effects of each alone. Hypothesis: We hypothesized that the combination of DZX and MitoSNO would negate the beneficial effects of each alone in an isolated heart model of global ischemia. Methods: Isolated mouse hearts underwent assessment of end diastolic pressure (EDP) and left ventricular developed pressure (LVDP) utilizing an LV balloon in a Langendorff model before and after 90 min of global ischemia. Hearts received test solution (CPG (9°C) or CPG±DZX (100μM) at onset of ischemia +/- MitoSNO (1μM/L) at end of ischemia), followed by 30 min reperfusion. LVDP and EDP were compared between groups utilizing a linear mixed model to assess the impact of treatment on the outcome, adjusting for baseline and balloon volume. Results: Similar to previous results, DZX improved LVDP and reduced EDP after ischemia compared to CPG (Figure). Similarly, MitoSNO improved LVDP and reduced EDP compared to CPG (Figure). The addition of MitoSNO with DZX was associated with the loss of cardioprotection observed with MitoSNO or DZX alone. Conclusions: Similar to data in a myocyte model, both MitoSNO and DZX provide cardioprotection that is lost with the combination of both, suggesting mutually exclusive mechanisms of action and that DZX’s mechanism requires a functional complex 1, ROS production, or succinate accumulation.

Autocrine effects of PCSK9 on cardiomyocytes

Proprotein convertase subtilisin kexin type 9 (PCSK9) is in the focus of cardiovascular research due to its role in hepatic low density lipoprotein (LDL) clearance. However, extrahepatic expression of PCSK9 such as in cardiomyocytes and its regulation by oxidized LDL (oxLDL) put notion on extrahepatic effects of PCSK9 as well. This study was aimed to reveal the role of PCSK9 in oxLDL-dependent regulation of cardiomyocyte function. Adult rat and mouse ventricular cardiomyocytes and isolated perfused hearts were used. OxLDL was applied to increase PCSK9 expression in cardiomyocytes. Cell function was analyzed by load-free cell shortening as well as left ventricular developed pressure of isolated hearts. OxLDL decreased shortening in wild-type-derived mouse cardiomyocytes but not in those isolated from PCSK9 knockout mice. Overexpression of human PCSK9 in rat cardiomyocytes reduced shortening in the absence of oxLDL. Addition of recombinant PCSK9 mimicked these effects. In cardiomyocytes, oxLDL induced PCSK9 release into the supernatant. Inhibition of PCSK9 by Pep 2–8 or alirocumab attenuated the oxLDL-induced loss of cardiomyocyte shortening. Cardiomyocytes express surfeit locus protein 4 (SURF-4), a protein required for PCSK9 secretion in human embryonic kidney cells (HEK 293 T), and silencing of SURF-4 reduced the oxLDL effects on cardiomyocytes. In isolated perfused rat hearts PCSK9 inhibition by alirocumab improved the function. In addition, left ventricular function of isolated hearts from PCSK9 knockout mice was increased under basal conditions as well as at 10 min and 120 min of reperfusion following 45 min of ischemia. Collectively, the data show that cardiomyocytes express and release PCSK9 that acts in an autocrine way on cardiomyocytes and impairs their function.

Thiamine treatment preserves cardiac function against ischemia injury via maintaining mitochondrial size and ATP levels.

Thiamine (vitamin B1) is necessary for energy production, especially in the heart. Recent studies have demonstrated that thiamine supplementation for cardiac diseases is beneficial. However, the detailed mechanisms underlying thiamine-preserved cardiac function have not been elucidated. To this end, we conducted a functional analysis, metabolome analysis, and electron microscopic analysis to unveil the mechanisms of preserved cardiac function through supplementation with thiamine for ischemic cardiac disease. Male Sprague-Dawley rats (around 10 wk old) were used. Following pretreatment with or without thiamine pyrophosphate (TPP; 300 µM), hearts were exposed to ischemia (40 min of global ischemia followed by 60 min of reperfusion). We measured the left ventricle developed pressure (LVDP) throughout the protocol. The LVDP during reperfusion in the TPP-treated heart was significantly higher than that in the untreated heart. Metabolome analysis was performed using capillary electrophoresis-time-of-flight mass spectrometry, and it revealed that the TPP-treated heart retained higher adenosine triphosphate (ATP) levels compared with the untreated heart after ischemia. The metabolic pathway showed that there was a significant increase in fumaric acid and malic acid from the tricarboxylic acid cycle following ischemia. Electron microscope analysis revealed that the mitochondria size in the TPP-treated heart was larger than that in the untreated heart. Mitochondrial fission in the TPP-treated heart was also inhibited, which was confirmed by a decrease in the phosphorylation level of DRP1 (fission related protein). TPP treatment for cardiac ischemia preserved ATP levels probably as a result of maintaining larger mitochondria by inhibiting fission, thereby allowing the TPP-treated heart to preserve contractility performance during reperfusion.NEW & NOTEWORTHY We found that treatment with thiamine can have a protective effect on myocardial ischemia. Thiamine likely mediates mitochondrial fission through the inhibition of DRP1 phosphorylation and the preservation of larger-sized mitochondria and ATP concentration, leading to higher cardiac contractility performance during the subsequent reperfusion state.

Fish oil and olive oil-enriched diets alleviate acute ozone-induced cardiovascular effects in rats

Fish oil (FO) and olive oil (OO) supplementations attenuate the cardiovascular responses to inhaled concentrated ambient particles in human volunteers. This study was designed to examine the cardiovascular effects of ozone (O3) exposure and the efficacy of FO and OO-enriched diets in attenuating the cardiovascular effects from O3 exposure in rats. Rats were fed either a normal diet (ND), a diet enriched with 6% FO or OO starting at 4 weeks of age. Eight weeks following the start of these diet, animals were exposed to filtered air (FA) or 0.8 ppm O3, 4 h/day for 2 consecutive days. Immediately after exposure, cardiac function was measured as the indices of left-ventricular developed pressure (LVDP) and contractility (dP/dtmax and dP/dtmin) before ischemia. In addition, selective microRNAs (miRNAs) of inflammation, endothelial function, and cardiac function were assessed in cardiac tissues to examine the molecular alterations of diets and O3 exposure. Pre-ischemic LVDP and dP/dtmax were lower after O3 exposure in rats fed ND but not FO and OO. Cardiac miRNAs expressions were altered by both diet and O3 exposure. Specifically, O3-induced up-regulation of miR-150-5p and miR-208a-5p were attenuated by FO and/or OO. miR-21 was up-regulated by both FO and OO after O3 exposure. This study demonstrated that O3-induced cardiovascular responses appear to be blunted by FO and OO diets. O3-induced alterations in miRNAs linked to inflammation, cardiac function, and endothelial dysfunction support these pathways are involved, and dietary supplementation with FO or OO may alleviate these adverse cardiovascular effects in rats.

Elevated perfusate [Na+] increases contractile dysfunction during ischemia and reperfusion

Recent studies revealed that relatively small changes in perfusate sodium ([Na+]o) composition significantly affect cardiac electrical conduction and stability in contraction arrested ex vivo Langendorff heart preparations before and during simulated ischemia. Additionally, [Na+]o modulates cardiomyocyte contractility via a sodium-calcium exchanger (NCX) mediated pathway. It remains unknown, however, whether modest changes to [Na+]o that promote electrophysiologic stability similarly improve mechanical function during baseline and ischemia–reperfusion conditions. The purpose of this study was to quantify cardiac mechanical function during ischemia–reperfusion with perfusates containing 145 or 155 mM Na+ in Langendorff perfused isolated rat heart preparations. Relative to 145 mM Na+, perfusion with 155 mM [Na+]o decreased the amplitude of left-ventricular developed pressure (LVDP) at baseline and accelerated the onset of ischemic contracture. Inhibiting NCX with SEA0400 abolished LVDP depression caused by increasing [Na+]o at baseline and reduced the time to peak ischemic contracture. Ischemia–reperfusion decreased LVDP in all hearts with return of intrinsic activity, and reperfusion with 155 mM [Na+]o further depressed mechanical function. In summary, elevating [Na+]o by as little as 10 mM can significantly modulate mechanical function under baseline conditions, as well as during ischemia and reperfusion. Importantly, clinical use of Normal Saline, which contains 155 mM [Na+]o, with cardiac ischemia may require further investigation.

Novel in vivo and in vitro mechanisms of positive inotropic effect of atractylodin.

This study was to investigate the inotropic effect of atractylodin and its underlying mechanism. The cardiac pressure-volume loop (P-V loop), Langendroff-perfused isolated rat heart, patch-clamp, Ca2+ transient and western blot techniques were used. The results demonstrated that atractylodin (3mg/kg, ip) remarkably increased the left ventricular stroke work, cardiac output, stroke volume, heart rate, ejection fraction, end-systolic pressure, peak rates of rise and fall of left ventricular pressures (+dP/dtmax , -dP/dtmax ), the slopes of end-systolic pressure-volume relationship (also named as end-systolic elastance, Ees) and reducing end-systolic volume and end-diastolic volume in the in vivo rat study. Also, atractylodin (3mg/kg, ip) significantly decreased diastolic blood pressure and the arterial elastance (Ea) without significant systolic blood pressure change. In addition, atractylodin (0.1, 1, 10µmol/L) also increased the isolated rat heart left ventricular developed pressure which is the difference between the systolic and diastolic pressure in non-pacing and pacing modes. Furthermore, JMV-2959 (1μmol/L), a ghrelin receptor unbiased antagonist, blocked the increased left ventricular developed pressure of atractylodin in isolated rat hearts. Finally, atractylodin (5µmol/L) increased the amplitude of Ca2+ transient by enhancing SERCA2a activity, the sarcoplasmic reticulum Ca2+ content and the phosphorylation of phospholamban at 16-serine. These results demonstrated that atractylodin had a positive inotropic effect by enhancing SERCA2a activity which might be mediated by acting ghrelin receptor in myocardium. In conclusion, atractylodin which had the positive inotropic effect and decreased diastolic blood pressure might serve as an agent for the treatment of heart failure in clinical settings.

Exogenous growth differentiation factor 15 (GDF-15) 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 cardiovascular risks situations such as myocardial infarction and coronary artery disease, experimental studies rather consider this cytokine as a cardioprotective molecule. We therefore 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 (250–400 g) were anesthetized with isoflurane before their hearts were isolated and perfused in a Langendorff model. Hearts were perfused either with 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 induced a better recovery of most contractile parameters after 30 minutes of ischemia (higher left ventricular developed pressure, better heart rate recovery, better recovery in left ventricular contractility and relaxation, P < 0.05 for all parameters). Moreover, after an irreversible 30-minute duration of ischemia, GDF15 decreased infarct size (45.6 ± 3.8% vs. 60.8 ± 3.8%, P < 0.05). These preliminary results demonstrate for the first time in an ex vivo isolated heart model, that exogenous preischemic short-term administration of 2000 ng/L exerts cardioprotective properties towards ischemia reperfusion injury, improving recovery of functional parameters and decreasing cardiac cell death.

Myocardial hypertrophy is prevented by farnesol through oxidative stress and ERK1/2 signaling pathways

Farnesol is a sesquiterpene found in several plants, with multiple pharmacological activities. However, pharmacological actions of farnesol in the treatment of cardiac hypertrophy are not yet reported. This study aimed to investigate the effect and regulatory mechanisms of farnesol against isoproterenol-induced pathological cardiac hypertrophy. Male Wistar rats were treated for 8 days with isoproterenol (4.5 mg/kg; i. p.) and with farnesol (50 μM; i. p.). Hearts were subjected to evaluation of left ventricular developed pressure (LVDP), coronary pressure, electrocardiogram, histopathological analysis, reactive oxygen species (ROS) generation, antioxidant enzyme activity, and pro- and anti-apoptosis protein expression. The results showed that severe impairment of LVDP induced by cardiac hypertrophy was significantly prevented by farnesol treatment. Moreover, farnesol attenuated electrocardiographic changes that are characteristic of cardiac hypertrophy, as well as prevented the increase of fibrosis and migration of inflammatory cells in cardiac tissue. Additionally, farnesol treatment prevented the increase of cardiac ROS generation and restored the activity of endogenous antioxidant enzymes, such as SOD and catalase. It was also evidenced that farnesol decreased the ERK1/2, Bax and Caspase 3 activation, and an increase of AKT and Bcl-2 protein expression, which can be associated with the pathological cardiac remodeling and also with cardioprotection mediated by farnesol, respectively. These results suggest that farnesol is a novel therapeutic agent for amelioration of cardiac hypertrophy in rats.

An acute estrogen receptor agonist enhances protective effects of cardioplegia in hearts from aging male and female mice.

The G-protein coupled estrogen receptor (GPER) mediates rapid responses to estrogen. GPER activation may contribute to cardioprotective effects of estrogen in ischemia and reperfusion, although whether it is beneficial in aging myocardium is unclear. We determined whether a GPER agonist (G1) added to standard cardioplegic solution (used to protect hearts from ischemia-reperfusion injury during cardiac surgery) would improve outcomes in isolated hearts from adult and aged mice of both sexes. Hearts from young adult (6-9 mos) and older (22-28 mos) mice were perfused with Krebs-Henseleit buffer for 15min (37°C) followed by cold (6-7°C) St. Thomas'2 cardioplegia with G1 (0.5μM), G1 (0.5μM) plus G15 (GPER antagonist; 1μM) or vehicle for 6min. Hearts were then subjected to global ischemia (90min; 23-24°C) and reperfusion (30min; 37°C). Infarct size was quantified with triphenyltetrazolium chloride. In adult females, left ventricular developed pressure (LVDP) recovered to only 45.1±11.9% of baseline in control hearts in reperfusion, but recovered to 76.5±3.9% with G1 treatment (p<0.05) and this was blocked by G15. Similar results were obtained in older males and females (LVDP=51.5±10.6% vs. 84.8±8.7% and 51.9±5.5% vs. 90.0±6.1% for older males and females, respectively; p<0.05). By contrast, G1 had no effect on recovery of LVDP in hearts from adult males (26.6±8.9% vs. 46.0±14.2%). The rates of pressure development and decay showed a similar pattern of recovery in reperfusion. Infarcts were significantly smaller in G1-treated hearts from all older mice and in younger females, although G1 had no impact on infarct size in adult males (48.1±7.7% for control vs. 32.6±8.0% for G1). G1 enhances cardioprotective properties of a standard cardioplegic solution in the aging myocardium of both sexes. Supplementation of cardioplegic solutions with GPER agonists is a potential translational intervention that may improve cardiac surgery outcomes in older adults.

Cardiac function and tolerance to ischemia/reperfusion injury in a rat model of polycystic ovary syndrome during the postmenopausal period

AimsThere is much controversy regarding whether cardiovascular events increase in women with polycystic ovary syndrome (PCOS) with aging. Considering the lack of possibility of certain investigations in humans, animal models of PCOS may be suitable resources to obtain the useful data needed. In this study; we aimed to investigate whether cardiac function and tolerance to ischemia/reperfusion (I/R) injury worsen in postmenopausal rats, who had PCOS at younger ages, compared to controls. Main methodsThe hearts of aged rats with a history of PCOS and their controls were isolated and perfused in a Langendorff apparatus. Values of hemodynamic parameters, including left ventricular systolic pressure (LVSP), left ventricular developed pressure (LVDP), rate pressure product (RPP) and peak rates of positive and negative changes in left ventricular pressure (±dp/dt) were recorded using a power lab system. Blood serum levels of total testosterone (TT) and estradiol (E2) were determined by ELISA kits. Generalized Estimating Equation Model and t-student unpaired test results were used to compare the findings documented between two groups. Key findingsNo statistically significant differences were observed in hemodynamic parameters of the heart including, LVSP, LVDP, RPP and ±dp/dt, between the rats of two groups of study, at baseline or before ischemia and after I/R. Nor were any significant differences observed in the levels of two hormones between the two groups (p > 0.05). SignificanceHistory of PCOS during reproductive ages should not be considered an important risk factor for reduction in cardiac contractile function or less tolerance to I/R injury during the postmenopausal period.

Positive inotropic effect of atractylodin in normal rats and its underlying mechanism

Objective: To explore the positive inotropic effect of atractylodin which is major active component of Rhzoma Atractylodis Lanceae and its underlying mechanism. Methods: For in vivo study, six male SD rats were randomly selected for the heart pressure-volume loop (P-V loop) experiment. The effects of atractylodin (3 mg/kg, intraperitoneal injection) on hemodynamic parameters such as LVDP (left ventricular developed pressure), SW (stroke work), HR (heart rate), CO (cardiac output), SBP (systolic blood pressure) and DBP (diastolic blood pressure) were analyzed. For in vitro study, left ventricular developed pressure (LVDP) from the Langendroff-perfused isolated rat heart was analyzed before as the control and after atractylodin perfusion. For in vitro study, the effects of atractylodin and atractylodin with H89 (PKA inhibitor) or KN-93 (CaMKII inhibitor or Calyculin A (PP1, PP2A inhibitor) on LVDP were analyzed. The experiments were separated into four parts with six isolated hearts for each as follows: (1) Control→0.1→1→10 μmol/L atractylodin; (2) Control→200 nmol/L H89 (PKA inhibitor)→200 nmol/L H89+10 μmol/L atractylodin; (3) Control→500 nmol/L KN-93 (CaMKII inhibitor)→500 nmol/L KN-93+10 μmol/L atractylodin; (4) Control→10 nmol/L Calyculin A (PP1, PP2A inhibitor)→10 nmol/L Calyculin A+10 μmol/L atractylodin. For the study of rat left ventricular myocyte Ca2+ transient induced by field stimulation, the experiment design was the same as in vitro study. The six cells from the different rats were used for each part experiment. Results: ① Atractylodin (3 mg/kg) significantly increased the heart rate, cardiac output and stroke work (P＜0.05) and decreased the diastolic blood pressure (P＜0.05). ② Atractylodin (0.1, 1, 10 μmol/L) significantly increased the LVDP in a concentration dependent manner (P＜0.05). The positive inotropic effect of atractylodin could be blocked by PKA inhibitor H89. ③ Atractylodin (10 μmol/L) significantly increased the amplitude of SR Ca2+ transient amplitude mediated by facilitating sarcoplasmic reticulum SERCA2a. The enhanced amplitude of SR Ca2+ transient could be blocked by PKA inhibitor H89. Conclusion: Atractylodin had positive inotropic effect in rat heart both in vivo and in vitro with decreased diastolic blood pressure and its underlying mechanism was mediated by PKA. Based on the fact that the atractylodin exerted its positive inotropic effect was mediated by PKA, the PKA-SERCA2a signaling pathway might be the mechanism of the atractylodin's positive inotropy.

Diazoxide preserves myocardial function in a swine model of hypothermic cardioplegic arrest and prolonged global ischemia

ObjectiveAdenosine triphosphate potassium sensitive channels provide endogenous myocardial protection via coupling of cell membrane potential to myocardial metabolism. Adenosine triphosphate potassium sensitive channel openers, such as diazoxide, mimic ischemic preconditioning, prevent cardiomyocyte swelling, preserve myocyte contractility after stress, and provide diastolic protection. We hypothesize that diazoxide combined with hyperkalemic cardioplegia provides superior myocardial protection compared with cardioplegia alone during prolonged global ischemia in a large animal model. MethodsTwelve pigs were randomized to global ischemia for 2 hours with a single dose of cold blood (4:1) hyperkalemic cardioplegia alone (n = 6) or with diazoxide (500 μmol/L) (n = 6) and reperfused for 1 hour. Cardiac output, myocardial oxygen consumption, left ventricular developed pressure, left ventricular ejection fraction, diastolic function, myocardial troponin, myoglobin, markers of apoptosis, and left ventricular infarct size were compared. ResultsFour pigs in the cardioplegia alone group could not be weaned from cardiopulmonary bypass. There were no differences in myoglobin, troponin, or apoptosis between groups. Diazoxide preserved cardiac output versus control (74.5 vs 18.4 mL/kg/min, P = .01). Linear mixed regression modeling demonstrated that the addition of diazoxide to cardioplegia preserved left ventricular developed pressure by 36% (95% confidence interval, 9.9-61.5; P < .01), dP/dt max by 41% (95% confidence interval, 14.5-67.5; P < .01), and dP/dt min by 33% (95% confidence interval, 8.9-57.5; P = .01). It was also associated with higher (but not significant) myocardial oxygen consumption (3.7 vs 1.4 mL O2/min, P = .12). ConclusionsDiazoxide preserves systolic and diastolic ventricular function in a large animal model of prolonged global myocardial ischemia. Diazoxide as an adjunct to hyperkalemic cardioplegia may allow safer prolonged ischemic times during increasingly complicated cardiac procedures.

Chenodeoxycholic and deoxycholic acids induced positive inotropic and negative chronotropic effects on rat heart.

Bile acids are endogenous amphiphilic steroids from the metabolites of cholesterol. Studies showed that they might contribute to the pathogenesis of cardiopathy in cholestatic liver diseases. Chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA) is associated with colon cancer, gallstones, and gastrointestinal disorders. However, little information is available regarding their cardiac effects. Here, we reported that CDCA (100μM) and DCA (100μM) significantly increased the left ventricular developed pressure of the isolated rat hearts to 122.3 ± 5.6% and 145.1 ± 13.7%, and the maximal rate of the pressure development rising and descending (± dP/dtmax) to 103.4 ± 17.6% and 124.4 ± 37.7% of the basal levels, respectively. They decreased the heart rate and prolonged the RR, QRS, and QT intervals of Langendorff-perfused hearts in a concentration-dependent manner. Moreover, CDCA and DCA increased the developed tension of left ventricular muscle and the cytosolic Ca2+ concentrations in left ventricular myocytes; these functions positively coordinated with their inotropic effects on hearts. Additionally, CDCA (150μM) and DCA (100μM) decreased the sinoatrial node beating rate to 80.6 ± 3.0% and 79.7 ± 0.9% of the basal rate (334.2 ± 10.7bpm), respectively. These results were consistent with their chronotropic effects. In conclusion, CDCA and DCA induced positive inotropic effects by elevating the Ca2+ in left ventricular myocytes. They exerted negative chronotropic effects by lowering the pace of the sinoatrial node in rat heart. These results indicated that the potential role of bile acids in cardiopathy related to cholestasis.

Embryonic cardioprotection by hydrogen sulphide: studies of isolated cardiac function and ischaemia-reperfusion injury in the chicken embryo.

In mammals, pregnancy complications can trigger an embryonic or fetal origin of cardiac dysfunction. However, underlying mechanisms remain uncertain because the partial contributions of the challenge on the mother, placenta or offspring are difficult to disentangle. The avian embryo permits isolation of the direct effects of suboptimal conditions during development on the cardiac function of the offspring, independent of additional effects on the mother and/or the placenta. Therefore, the objectives of this work were to adapt the isolated Langendorff technique using the chicken embryo to study the physiology of the developing heart. Here, we introduce a novel technique and show the utility of the technique for exploring cardioprotective roles of H2 S in the chicken embryo heart. This work lays the foundation for studying the direct effects of H2 S therapy on the embryonic heart independent of effects on the mother and the placenta in adverse development. This study adapted the isolated Langendorff preparation to study the chicken embryo heart in response to ischaemia-reperfusion (IR) injury. The utility of the technique was tested by investigating cardioprotective effects of hydrogen sulphide (H2 S) and underlying mechanisms. Embryonic hearts (19 out of 21 days of incubation) mounted on a Langendorff preparation were exposed to IR (30min ischaemia) after 4 treatments administered randomly, all as a 1mm bolus, into the perfusate: saline vehicle (control); sodium hydrogen sulphide (NaHS); NaHS plus glibenclamide, an antagonist of KATP opening (NaHS Glib), and Glib alone (Glib). Relative to controls, NaHS treatment improved cardiac function after ischaemia (mean±SD for area under the curve, AUC, for left ventricular developed pressure, LVDP: 1767.3±929.5 vs. 492.7±308.1; myocardial contractility, dP/dtmax : 2748.9±1514.9 vs. 763.7±433.1) and decreased infarct size (22.7±8.0 vs.43.9±4.2%) and cardiac damage (% change in creatinine kinase, 49.3±41.3 vs. 214.6±155.1; all P<0.05). Beneficial effects of NaHS were blocked by Glib. Glib alone had no effects. NaHS increased coronary flow rate (CFR) during baseline (mean±SD for AUC: 134.3±91.6 vs. 92.2±35.8) and post IR (1467±529.5 vs. 748.0±222.1; both P<0.05). However, this effect was not prevented by Glib. Therefore, the chicken embryo heart is amenable for study via the Langendorff preparation under basal conditions and during IR. The data show that H2 S confers embryonic cardiac protection via opening of myocardial KATP channels and not via increasing CFR. H2 S may prove a useful therapeutic agent to protect the human fetal heart against IR injury, as may occur in complicated labour.