Ventricular Dysfunction In Rats Research Articles

Increased protein phosphatase 5 expression in inflammation-induced left ventricular dysfunction in rats

Titin phosphorylation contributes to left ventricular (LV) diastolic dysfunction. The independent effects of inflammation on the molecular pathways that regulate titin phosphorylation are unclear. We investigated the effects of collagen-induced inflammation and subsequent tumor necrosis factor-α (TNF-α) inhibition on mRNA expression of genes involved in regulating titin phosphorylation in 70 Sprague-Dawley rats. LV diastolic function was assessed with echocardiography. Circulating inflammatory markers were quantified by enzyme-linked immunosorbent assay and relative LV gene expression was assessed by Taqman® polymerase chain reaction. Differences in normally distributed variables between the groups were determined by two-way analysis of variance (ANOVA), followed by Tukey post-hoc tests. For non-normally distributed variables, group differences were determined by Kruskal-Wallis tests. Collagen inoculation increased LV relative mRNA expression of vascular cell adhesion molecule 1 (VCAM1), pentraxin 3 (PTX3), and inducible nitric oxide synthase (iNOS) compared to controls, indicating local microvascular inflammation. Collagen inoculation decreased soluble guanylate cyclase alpha-2 (sGCα2) and soluble guanylate cyclase beta-2 (sGCβ2) expression, suggesting downregulation of nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate (NO-sGC-cGMP) signaling. Inhibiting TNF-α prevented collagen-induced changes in VCAM1, iNOS, sGCα2 and sGCβ2 expression. Collagen inoculation increased protein phosphatase 5 (PP5) expression. Like LV diastolic dysfunction, increased PP5 expression was not prevented by TNF-α inhibition. Inflammation-induced LV diastolic dysfunction may be mediated by a TNF-α-independent increase in PP5 expression and dephosphorylation of the N2-Bus stretch element of titin, rather than by TNF-α-induced downregulation of NO-sGC-cGMP pathway-dependent titin phosphorylation. The steady rise in number of patients with inflammation-induced diastolic dysfunction, coupled with low success rates of current therapies warrants a better understanding of the systemic signals and molecular pathways responsible for decreased titin phosphorylation in development of LV diastolic dysfunction. The therapeutic potential of inhibiting PP5 upregulation in LV diastolic dysfunction requires investigation.

Myeloid differentiation factor 2 inhibitor and N-acetyl cysteine synergistically reduced left ventricular dysfunction in rats with cardiac ischemia/reperfusion injury

Abstract Background Myeloid differentiation factor 2 inhibitor (MD2i) is a novel anti-inflammatory agent that exerts favorable outcomes in various diseases including cardiac ischemia/reperfusion (I/R) injury. However, whether a potent antioxidant N-acetyl cysteine (NAC) can augment the beneficial effects of MD2i in rats with cardiac I/R injury have never been investigated. Purpose We tested the hypothesis that NAC increases the beneficial effects of MD2i against cardiac I/R injury in rats. Methods Rats were divided into either a sham (n=6) or cardiac I/R group (n=72). Rats in the I/R group received one of the following 6 treatments (n=12 each) at the onset of reperfusion: vehicle, MD2i at 20 and 40 mg/kg, NAC at 75 and 150 mg/kg, and combined MD2i 20 mg/kg with NAC 150 mg/kg. Left ventricular (LV) function, infarct size, arrhythmia score, and cardiac mitochondrial function and dynamics were determined. Results Myocardial infarction, LV dysfunction, and cardiac arrhythmias were observed in rats with cardiac I/R injury, along with mitochondrial dysfunction (Fig. 1). Treatment with MD2i at either 20 or 40 mg/kg effectively reduced LV dysfunction but failed to reduce the infarct size (Fig. 1). NAC at 150 mg/kg, but not at 75 mg/kg, significantly decreased both LV dysfunction and infarct size following cardiac I/R injury (Fig. 1). However, combined treatment exerted even greater efficacy in reducing cardiac I/R injury than monotherapy, through a greater reduction of cardiac mitochondrial dysfunction and mitochondrial fission (Fig. 1). However, no benefit on reducing the arrhythmia score in all groups. Conclusion Combined MD2i and NAC treatment exerted a superior cardioprotective effect against cardiac I/R injury than either monotherapy regimen via an improved cardiac mitochondrial function. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. NSTDA Research Chair Grant from the National Science and Technology Development Agency Thailand2. National Research Council of Thailand

Chronic mitochondrial fusion promotor as a novel pharmacological intervention to alleviate left ventricular dysfunction in rats with chronic myocardial infarction

Abstract Background Decreased cardiac mitochondrial fusion associated with increased mitochondrial dysfunction has been demonstrated in acute myocardial infarction pathology. However, whether this pathophysiologic process is associated with myocardial injury in chronic myocardial infarction (CMI) is still unclear. Recently, a novel pharmacological intervention to promote mitochondrial fusion using mitochondrial fusion promotor-M1 (M1) has been shown to exert cardioprotection against myocardial ischemia and reperfusion injury. However, the roles of M1 in CMI has never been investigated. Purpose We investigated the potential cardioprotective benefits of chronic treatment with mitochondrial fusion promotor-M1 in rats with chronic MI model. Methods Adult male Wistar rats were assigned to the sham group (n=5) and the CMI group (n=15), which was induced by a permanent left anterior descending coronary occlusion. After 1 week of operation, rats in the CMI group were randomly divided into 3 subgroups which was treated with one of the followings: 1) vehicle (3% DMSO/day, ip, CON, n=5), 2) enalapril (10 mg/kg/day, po, ENA, n=5), or 3) mitochondrial fusion promotor-M1 (2 mg/kg/day, ip, M1, n=5) once daily for 4 weeks. In the end, echocardiography for the left ventricular (LV) function was performed, and the heart was removed to determine the mitochondrial function and malondialdehyde (MDA) level for oxidative stress. Results CMI rats that received vehicle showed significantly impaired LV function and cardiac mitochondrial function as evidenced by a 60% reduction in LV ejection fraction (LVEF) along with increased mitochondrial reactive oxygen species (ROS) production, mitochondrial depolarization and mitochondrial swelling, respectively, when compared with the sham rats (Fig. 1A–D). The CMI rats also exhibited a higher cardiac tissue MDA level than those of sham rats, further indicating cardiac oxidative stress (Fig. 1E). Interestingly, chronic treatment with either enalapril or M1 effectively attenuated CMI-induced mitochondrial dysfunction and oxidative stress upregulation, thus increasing LVEF (27% improvement for both ENA and M1), when compared with the vehicle group (Fig. 1A). Conclusion Long-term promotion of mitochondrial fusion mitigated cardiac mitochondrial dysfunction and oxidative stress, eventually culminating in improved LV function in rats with CMI. These findings suggest that chronic modulation of mitochondrial fusion could be a promising pharmacological intervention to improve LV function in CMI. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. The National Science and Technology Development Agency Thailand2. The Thailand Research Fund (RGJ)

Beneficial effects of PEGylated graphene quantum dot on arrhythmias induced by myocardial infarction.

Arrhythmias are one of the leading causes of early death following myocardial infarction (MI) and heart failure. Graphene derivatives have emerged as an therapeutic target that have electrical conductivity. The study aimed to evaluate the impacts of polyethylene glycol-graphene quantum dots (GQDs-PEG) on arrhythmias created by MI in the rat. Animals were randomly assigned to five groups of sham, MI, and MI + GQDs-PEG at doses of 5, 10, and 20 mg/kg. MI was induced by the closure of the left anterior descending artery. The day after MI, animals were administered vehicle (phosphate buffered saline) or GQDs-PEG at different doses every other day for 2 weeks. On day 15, electrocardiogram (ECG), mean arterial pressure (MAP), and heart contractility indices were recorded by the PowerLab data acquisition system. GQDs-PEG 20 mg/kg increased contractility and improved the reduction of MAP in the MI group. The prolonged QT and QTc intervals, inverted T wave, and deviated ST segment were modified by GQDs-PEG 10 and 20 mg/kg in rats with MI. The amplitude of the Q wave was also decreased in a dose-dependent manner in the GQDs-PEG-treated rats. The results demonstrated that 2 weeks of treatment with GQDs-PEG normalized ECG abnormalities and improved left ventricular dysfunction in rats with MI.

Regulation of the Immune Microenvironment by an NLRP3 Inhibitor Contributes to Attenuation of Acute Right Ventricular Failure in Rats with Pulmonary Arterial Hypertension.

BackgroundRight heart failure is the terminal stage of PAH. When PAH patients suffer from pulmonary infection or puerperal infection heart failure often rapidly develops. Low dose of lipopolysaccharide induces rapid right ventricular failure in rats with pulmonary arterial hypertension.PurposeThe objective of this study was to investigate whether the NLRP3 inflammasome mediates disturbance of the ventricular immune microenvironment of PAH rats and promotes right ventricular failure.MethodsIntraperitoneal injection of monocrotaline was used to induce PAH in rats. Right ventricular function was measured via echocardiography before and after the rats were treated with lipopolysaccharide and MCC950. The degree of immune microenvironment disturbance in right ventricular tissue was measured with a rat chemokine and cytokine antibody array, Western blot, flow cytometry and quantitative real-time PCR analysis.ResultsAfter the rats were injected with LPS, they exhibited right ventricular dysfunction and a significant increase in right ventricular tissue inflammation with elevated M1 macrophage proportion. Administration of MCC950 suppressed inflammation and improved right ventricular function. The number of M1 macrophages was decreased after MCC950 treatment. NLRP3 inflammasome inhibition ameliorated LPS-induced changes in the immune microenvironment in the right heart and right ventricular dysfunction in rats with PAH.ConclusionSelective inhibition of NLRP3 pathway interfered the interaction between hypertrophic cardiomyocytes and macrophages in the initial stage of inflammation and maintained the immune microenvironment balance, eventually contributing to attenuation of LPS-induced acute heart failure in PAH rats.

Physical training attenuates right ventricular dysfunction in rats exposed to cigarette smoke

Aim: To evaluate the functional and morphological cardiac variables of rats exposed to chronic cigarette smoke (ECS) and to analyze the influence of exercise training on any cardiac remodeling. Methods: Male Wistar rats were assigned into four groups: control animals (C, n=10); control trained rats (CT, n=10), that underwent swimming physical training; ECS rats (E, n=10), that received the smoke of 40 cigarettes/day; and ECS plus trained rats (TE, n=10), that received the cigarette smoke plus the swimming training protocol, for 15 weeks. At the end of the experiment, the animals underwent hemodynamic measurements of the right ventricle (RV) and morphological examination. Results: There was a decrease in the body weight of E, TE and CT groups (p<0.05). RV pressure (maximum systolic, diastolic initial and end-diastolic) was increased in the E and ET groups (p <0.05), while there was a decrease in RV maximum derivative pressure, RV minimum derivative pressure (+dP/dt and -dP/dt) and systolic duration in the TE group (p <0.05). Heart rate increased in the E group (p<0.05). The lung weight/body weight ratio was higher in the TE group (p=0.008). Fluid retention was increased in the RV, left ventricle (LV) and lung of the E group (p<0.001). Conclusion: ECS caused right ventricular dysfunction, pulmonary hypertension and cardiac remodeling. Physical training attenuated the effects of ECS for heart rate responses and the morphological variables of the RV, LV, and the lung.

Tetrandrine attenuates left ventricular dysfunction in rats with myocardial infarction.

The present study aimed to determine whether tetrandrine could attenuate left ventricular dysfunction and remodeling in rats with myocardial infarction. Sprague-Dawley rats were randomly divided into six groups (n=5/group) as follows: i) Healthy control group; ii) sham operation group; iii) myocardial infarction model group; iv) myocardial infarction + low-dose tetrandrine group (10 mg/kg); v) myocardial infarction + medium-dose tetrandrine group (50 mg/kg); and vi) myocardial infarction + high-dose tetrandrine group (80 mg/kg). Left ventricular end-diastolic diameter (LVIDd), left ventricular end-systolic diameter (LVIDs), ejection fraction (EF%) and left ventricular fractional shortening rate (FS%) were measured using ultrasonography. The pathological changes were observed by hematoxylin and eosin (H&E) staining. Left ventricular tissue section TUNEL staining was also performed. Furthermore, the triglyceride (TG), total cholesterol (TC), high density lipoprotein (HDL) and low-density lipoprotein (LDL) in the arterial blood were examined by biochemical testing. Expression levels of intracellular Ca2+ homeostasis-related proteins including ryanodine receptor calmodulin, CaM-dependent protein kinase IIδ, protein kinase A, FK506 binding protein 12.6 were measured using western blot analysis. Ultrasonography results showed that in the myocardial infarction model rats, the levels of LVIDd and LVIDs were significantly higher; however, the levels of EF% and FS% were lower compared with those in the sham operation group, which was alleviated by tetrandrine. H&E results showed that tetrandrine alleviated the pathological characteristics of myocardial infarction model rats. Furthermore, tetrandrine significantly inhibited myocardial cell apoptosis in rats with myocardial infarction. Tetrandrine significantly inhibited the levels of TG, TC and LDL and increased the levels of HDL in the arterial blood of rats with myocardial infarction. These findings revealed that tetrandrine could attenuate left ventricular dysfunction in rats with myocardial infarction, which might be associated with intracellular Ca2+ homeostasis.

Abstract 14613: Preclinical Animal Model of Doxorubicin-induced Left Ventricular Dysfunction: Echocardiography and Pressure-volume Analysis

Introduction: There is a need to implement a preclinical model in addition to the well established ischemic or volume-overload models that would mimic the clinical course of patients with chemotherapy-induced heart failure. Doxorubicin is an anthracycline chemotherapeutic that is widely used in oncology, although its cardiotoxicity. Hypothesis: Doxorubicin-induced left ventricular dysfunction in rats fulfills echocardiography and hemodynamic characteristics of chemotherapy-induced heart failure. Methods: We randomly assigned Ren-2 transgenic hypertensive (TGR, n = 17) and normotensive rats (HanSD, n = 22), at the age of 8 weeks to doxorubicin (2.5 mg/kg in 0.5 ml of normal saline) or placebo in 6 intraperitoneal doses within two weeks (cumulative doxorubicin dose 15 mg/kg). Two weeks later, we performed echocardiography study, pressure-volume analysis (PV), and we weighed the organs. Results: In doxorubicin groups, there was a decrease in the left ventricle weight (1,22 vs. 0,85 g in TGR), while an increase in wall stress (22036 vs. 29754 μL*mmHg/g in TGR). Echocardiography suggested heart remodeling with a decrease in relative wall thickness - RWT (1.02 vs. 0.65 mm in TGR), and together with PV analysis showed a decrease in systolic parameters - left ventricle ejection fraction - LVEF (71.41 vs. 59.96 % in TGR), end-systolic pressure-volume ratio - ESPVR (0.82 vs. 0.45 mmHg/uL in TGR) and preload recruitable stroke work - PRSW (75.71 vs. 60.98 mmHg in TGR). Ventricular-arterial coupling (VAC = Ea/Ees, a measure of cardiac efficiency) was worsened in the doxorubicin groups (1.69 vs. 2.52 in TGR). For all the above p &lt; 0.05, in HanSD, the results were similar (all p &lt; 0.05). Conclusions: Our results suggest that systolic dysfunction and decrease of cardiac efficiency in this model could be caused by heart atrophy, and such an animal model could potentially be an easily reproducible model of chemotherapy-induced heart failure in preclinical cardio-oncology studies.

Fish oil protects against corn oil-induced cardiac insulin resistance and left ventricular dysfunction in rats via upregulation of PPAR-β/γ and inhibition of diacylglycerol/PCK axis activation

Abstract This study investigated the effects corn oil (CO) and different ratios of corn oil plus fish oil (FO) on insulin signaling in rat's heart. Adult male rats were fed low (LFD) or isocaloric high-fat diets (HFDs) of CO alone or CO + FO (ratios of 9:1 or 4:1). Cultured cardiomyocytes were treated with linoleic acid (LA), DHA + EPA (1:1) or LA + (DHA + EPA) (1:1). CO induced peripheral and cardiac insulin resistance with mitochondria damage, lipotoxicity activation of PKCe. It also upregulated LV levels of PPARα and down regulated PPARβ/δ. FO antagonized corn oil effects at both ratio with more profound effects with the ratio of 4:1. The regulatory roles of CO and FO on PPARs was shown in cultured cardiomyocytes and independent of hyperinsulinemia or free fatty acids. In conclusion, reducing the ratio of n-6/n-3 PUFAs in our diet toward a value of one is cardioprotective.

Is the cardioprotective effect of the ACE2 activator diminazene aceturate more potent than the ACE inhibitor enalapril on acute myocardial infarction in rats?

Myocardial infarction is a major cause of cardiac dysfunction. All components of the cardiac renin-angiotensin system (RAS) are upregulated in myocardial infarction. Angiotensin-converting enzyme (ACE) and ACE2 are key enzymes involved in synthesis of components of RAS and provide a counter-regulatory mechanism within RAS. We compared the cardioprotective effect of the ACE2 activator diminazene aceturate (DIZE) versus the ACE inhibitor enalapril on post acute myocardial infarction (AMI) ventricular dysfunction in rats. Adult male rats received subcutaneous injections of either saline (control) or isoproterenol (85 mg/kg) to induce AMI. Rats with AMI confirmed biochemically and by ECG, were either left untreated (AMI) or administered DIZE (AMI + DIZE) or enalapril (AMI + enalapril) daily for 4 weeks. DIZE caused a significant activation of cardiac ACE2 compared with enalapril. DIZE caused a significantly greater enhancement of cardiac hemodynamics. DIZE also caused greater reductions in heart-type fatty acid binding protein (H-FABP), β-myosin heavy chain (β-MYH), and in heart mass to total body mass ratio. These results indicated that activation of cardiac ACE2 by DIZE enhanced the protective axis of RAS and improved myocardial function following AMI, whereas enalapril was not sufficient to restore all cardiac parameters back to normal.

Protective effect of ghrelin against tilmicosin-induced left ventricular dysfunction in rats.

This study was conducted to investigate the possible protective effects of ghrelin against tilmicosin-induced acute ventricular dysfunction in rats. Forty adult male Sprague Dawley rats were randomly divided into 4 equal groups: control, ghrelin, tilmicosin, and ghrelin + tilmicosin. The left ventricular structural and functional parameters together with cardiac biomarker levels were evaluated. The results showed that tilmicosin treatment alone significantly decreased the left ventricular fractional shortening, left ventricular ejection fraction, left ventricular stroke volume, and cardiac output when compared with control group. In addition, tilmicosin led to a significant increase in left ventricular internal dimension in systole and left ventricular fractional end-systolic volume. At the same time, serum lactate dehydrogenase, creatine kinase, and creatine kinase-myocardial B fraction levels were significantly increased in tilmicosin-treated group when compared with control group. However, ghrelin pretreatment significantly prevented the left ventricular internal dimension in systole, left ventricular fractional end-systolic volume, left ventricular stroke volume, left ventricular ejection fraction, left ventricular fractional shortening, and cardiac output changes caused by tilmicosin. Moreover, ghrelin pretreatment could reduce significantly serum lactate dehydrogenase, creatine kinase, and creatine kinase-myocardial B fraction levels. These data indicated that ghrelin treatment may provide a protective effect against tilmicosin-induced left ventricular systolic dysfunction.

Roles of apoptosis and inflammation in a rat model of acute lung injury induced right ventricular dysfunction.

The effect of intratracheal lipopolysaccharide (LPS) instillation on right ventricular dysfunction in rats was studied with the aim of exploring underlying mechanisms. A single dose of LPS (10 mg/kg) or an equal volume of saline was instilled intratracheally and lung injury evaluated using histopathologic scoring and wet/dry (W/D) weight ratio at 6 or 12 h post-administration. Besides, serum atrial natriuretic peptide (ANP) was detected using an enzyme-linked immunosorbent assay (ELISA) and right ventricle β-myosin heavy chain (β-MHC) presence was examined using reverse transcription polymerase chain reaction (RT-PCR). Echocardiography examined pulmonary artery acceleration time (PAAT), right ventricular free wall thickness (RVFWT), tricuspid annular plane systolic excursion (TAPSE), and right ventricular end-diastolic diameter (RVEDD). In addition, right ventricular TUNEL staining and Western blots of Bax and Bcl-2 were performed. Right ventricle and left ventricle caspases-3, -8, and -9 activity were examined using fluorometric assay. Finally, right ventricle myeloperoxidase (MPO) neutrophil staining, and right ventricle and plasma cytokines TNF-α, IL-1β, IL-6 detection was performed. Histopathologic lung injury and increased W/D weight ratio was seen at 6 h after LPS intratracheal instillation, along with increased ANP, but not β-MHC. Pulmonary hypertension was indicated by decreased PAAT at 6 h post-exposure. Right ventricular systolic dysfunction and dilation were observed at 12 h post-exposure, as indicated by a significant decrease of TAPSE and increase of RVEDD. Of note, the procedure led to an increased right ventricle TUNEL positive cardiomyocytes, an increased Bax/Bcl-2 ratio, and increased right and left ventricle caspases-3, -8, and -9 activity as early as 6 h post-exposure, which was paralleled by increased right ventricle MPO staining and increased expression of right ventricle and serum cytokines TNF-α, IL-1β, and IL-6. As well as acute lung injury, a single dose of LPS intratracheally instilled can induce pulmonary hypertension at 6 h post-exposure, with obvious right ventricular systolic dysfunction and right ventricular dilation present at 12 h post-exposure, possibly via cardiomyocytes apoptosis and inflammation.

Inhibition of TLR9-NF-κB-mediated sterile inflammation improves pressure overload-induced right ventricular dysfunction in rats.

Recent accumulating evidence suggests that sterile inflammation plays a crucial role in the progression of various cardiovascular diseases. However, its contribution to right ventricular (RV) dysfunction remains unknown. The aim of this study was to elucidate whether toll-like receptor 9 (TLR9)-NF-κB-mediated sterile inflammation plays a critical role in the pathogenesis of RV dysfunction. We performed main pulmonary artery banding (PAB) in rats to induce RV pressure overload and dysfunction. On Day 14 after PAB, the pressure overload impaired RV function as indicated by increased RV end-diastolic pressure concomitant with macrophage infiltration and fibrosis, as well as maximal activation of NF-κB and TLR9. Short-term administration (days 14-16 after PAB) of a specific TLR9 inhibitor, E6446, or an NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC) significantly attenuated NF-κB activation. Furthermore, long-term administration of E6446 (treatment: days 14-28) or PDTC (prevention: days -1 to 28; treatment: days 14 to 28) improved RV dysfunction associated with mitigated macrophage infiltration and fibrosis in right ventricle and decreased serum brain natriuretic peptide levels. Inhibition of TLR9-NF-κB pathway-mediated sterile inflammation improved PAB-induced RV dysfunction in rats. This pathway plays a major role in the progression of pressure overload-induced RV dysfunction and is potentially a novel therapeutic target for the disorder.

Effects of acute respiratory distress syndrome induced by endotoxin on the right ventricular function in rats

To explore the effect of acute respiratory distress syndrome (ARDS) induced by endotoxin on the right ventricular function in rats. Sixty male Sprague-Dawley (SD) rats were randomly divided into normal saline (NS) control group and lipopolysaccharide (LPS) model group with 30 rats in each group. The rat model of ARDS was reproduced by intratracheal instillation of LPS 10 mg/kg after tracheotomy, and the rats in NS control group was intratracheally given the same volume of NS instead of LPS. The survival of rats in each group was observed. Right ventricular function was evaluated by echocardiography at 6 hours and 12 hours after instillation of LPS or NS respectively. Then the rats were sacrificed by bloodletting, and the right heart and lung tissue were harvested. The lung wet/dry weight (W/D) ratio was assessed. The pathological changes in cardiopulmonary tissue in rats were observed with hematoxylin and eosin (HE) strain, and the pathological score of lung injury was calculated. There was no animal death in NS control group. In LPS model group, there were 3 rats dead at 6 hours, and 4 dead at 12 hours. The pathological manifestations of lung injury were found at 6 hours after instillation of LPS, and the marked pathological changes of ARDS, such as atelectasis and hyaline membranes were observed at 12 hours. There was no obvious abnormality in the lung tissue of the NS control group. Compared with the NS control group, the 12-hour lung W/D ratio and the lung injury pathological score in the LPS model group were significantly increased (lung W/D ratio: 7.69±1.02 vs. 4.14±0.48, lung injury pathological score: 8.26±2.12 vs. 1.32±0.94, both P < 0.01). Echocardiography showed that the right heart function of rats was significantly abnormal with the prolongation of LPS induction time, which showed that pulmonary arterial diameter (PAD) and right ventricular diastolic diameter (RVDd) were increased, maximum blood flow velocity of pulmonary artery (PAVmax), maximum pulmonary artery pressure gradient (PAmaxPG), pulmonary artery acceleration time (PAAT) and tricuspid annular plane systolic excursion (TAPSE) were decreased, with significant differences at 12 hours as compared with those of NS normal group [PAD (mm): 2.84±0.31 vs. 2.11±0.37, RVDd (mm): 4.18±0.71 vs. 3.17±0.40, PAVmax (mm/s): 704.00±145.13 vs. 809.59±120.48, PAmaxPG (mmHg, 1 mmHg = 0.133 kPa): 2.07±0.88 vs. 2.73±0.76, PAAT (ms): 23.80±4.87 vs. 30.01±3.02, TAPSE (mm): 2.48±0.45 vs. 3.56±0.40, all P < 0.01]. Pathological examination showed that the cardiac tissue in the LPS model group showed disorder of myocardial cells and scattered inflammatory cells at 6 hours, and cardiomyocyte degeneration, structural destruction and inflammatory cells were found at 12 hours. ARDS induced by instillation of LPS at 12 hours causes right ventricular dysfunction in rats.

Contribution of serotonin to cardiac remodeling associated with hypertensive diastolic ventricular dysfunction in rats.

Left-ventricular hypertrophy and interstitial fibrosis are the main pathophysiological factors of heart failure with preserved ejection fraction. Blockade of the serotonin 5-HT2B receptor (5-HT2BR) has been shown to reduce cardiac hypertrophy, oxidative stress, and extracellular cell matrix activation. In this study, we evaluated the effects of the 5-HT2BR blockade, on hemodynamic and cardiac remodeling, in spontaneously hypertensive rats (SHRs) that display a diastolic dysfunction with preserved ejection fraction. Thirty-seven-week-old SHRs were randomized in four groups receiving either saline, the selective 5-HT2BR antagonist RS-127445 (1 mg/kg per day), a calcium channel blocker nicardipine (6 mg/kg per day), or RS-127445 + nicardipine. During the 14 weeks of treatment period, cardiac function and blood pressure were monitored by echocardiography and tail-cuff. Finally, electrocardiograms and invasive hemodynamics were obtained before blood collection. Heart was analyzed for morphology and mRNA expression. A complementary study evaluated the cardiac and vascular effects of serotonin on wild-type and mice knockout for the 5-HT2BR (Htr2B) and/or the 5-HT2AR (Htr2A). Despite the left ventricular 5-HT2BR overexpression, 5-HT2BR blockade by RS-127445 did not affect left ventricular hypertrophy and fibrosis in SHRs. This antagonist did not improve diastolic dysfunction, neither alone nor in combination with nicardipine, although it induced plasma brain natriuretic peptide decrease. Moreover, RS-127445 amplified subendocardial fibrosis and favored left ventricular dilatation. Finally, a subendocardial left ventricular fibrosis was induced by chronic serotonin in wild-type mice, which was increased in Htr2B animals, but prevented in Htr2A and Htr2A/2B mice, and could be explained by a contribution of the endothelial 5-HT2BRs to coronary vasodilatation. This work is the first to identify a cardioprotective function of the 5-HT2BR in an integrated model of diastolic dysfunction with preserved ejection fraction.

Hydrogen sulfide improves left ventricular function in smoking rats via regulation of apoptosis and autophagy

The present study was designed to investigate the protective effects of hydrogen sulfide (H2S) against cigarette smoking-induced left ventricular dysfunction in rats. Left ventricular structure and function were assessed using two-dimensional echocardiography. Cardiomyocyte apoptosis was determined by Annexin V/PI and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. Cardiac autophagy was evaluated by detection of autophagy-related protein expression and observation of autophagosomes. Our results indicated that administration of NaHS (a donor of H2S) could protect against smoking-induced left ventricular systolic dysfunction. H2S was found to exert anti-apoptotic effects in the myocardium of smoking rats by inhibiting JNK and P38 mitogen-activated protein kinases pathways and activating PI3K/Akt signaling. Moreover, H2S could also reduce smoking-induced autophagic cell death via regulation of AMPK/mTOR signaling pathway. In conclusion, our study demonstrates that H2S can improve left ventricular systolic function in smoking rats via regulation of apoptosis and autophagy.

The Heme Oxygenase 1 Inducer (CoPP) Protects Human Cardiac Stem Cells against Apoptosis through Activation of the Extracellular Signal-regulated Kinase (ERK)/NRF2 Signaling Pathway and Cytokine Release

Intracoronary delivery of c-kit-positive human cardiac stem cells (hCSCs) is a promising approach to repair the infarcted heart, but it is severely limited by the poor survival of donor cells. Cobalt protoporphyrin (CoPP), a well known heme oxygenase 1 inducer, has been used to promote endogenous CO generation and protect against ischemia/reperfusion injury. Therefore, we determined whether preconditioning hCSCs with CoPP promotes CSC survival. c-kit-positive, lineage-negative hCSCs were isolated from human heart biopsies. Lactate dehydrogenase release assays demonstrated that preconditioning CSCs with CoPP markedly enhanced cell survival after oxidative stress induced by H(2)O(2), concomitant with up-regulation of heme oxygenase 1, COX-2, and anti-apoptotic proteins (BCL2, BCL2-A1, and MCL-1) and increased phosphorylation of NRF2. Apoptotic cytometric assays showed that pretreatment of CSCs with CoPP enhanced the cells' resistance to apoptosis induced by oxidative stress. Conversely, knocking down HO-1, COX-2, or NRF2 by shRNA gene silencing abrogated the cytoprotective effects of CoPP. Further, preconditioning CSCs with CoPP led to a global increase in release of cytokines, such as EGF, FGFs, colony-stimulating factors, and chemokine ligand. Conditioned medium from cells pretreated with CoPP conferred naive CSCs remarkable resistance to apoptosis, demonstrating that cytokines released by preconditioned cells play a key role in the anti-apoptotic effects of CoPP. Preconditioning CSCs with CoPP also induced an increase in the phosphorylation of Erk1/2, which are known to modulate multiple pro-survival genes. These results potentially provide a simple and effective strategy to enhance survival of CSCs after transplantation and, therefore, their efficacy in repairing infarcted myocardium.

Allopurinol attenuates left ventricular dysfunction in rats with early stages of streptozotocin‐induced diabetes

Xanthine oxidase-derived superoxide production and oxidative stress contribute to the development of diabetic complications including diabetic cardiomyopathy. We hypothesized that xanthine oxidase-inhibitor allopurinol (ALP) may decrease hyperglycemia-induced oxidative stress, ameliorate cardiomyocyte hypertrophy and fibrosis, and attenuate the development of left ventricle (LV) diastolic dysfunction in rats with streptozotocin (STZ)-induced diabetes. Control Sprague Dawley (C) or streptozotocin-induced diabetic (D) rats were either untreated or treated with allopurinol (100 mg/kg/day) for 4 weeks starting at 1 week after streptozotocin injection. Free 15-F2t-isoprostane, a specific indicator of oxidative stress was measured by enzymatic immunoassay. The cardiomyocyte cross-sectional area was assessed by hematoxylin and eosin-stained paraffin-embedded sections of LVs. Myocardial collagens I and III were assessed by immunol histochemistry and Western blotting. Echocardiography was performed to characterize cardiac structure and function. In diabetic rats, both plasma and cardiac tissue levels of free 15-F2t-isoprostane were increased (p < 0.05 vs. control), accompanied with significant increase (p < 0.05 vs. control) in cross-section area and myocardial collagen deposition of LV cardiomyocyte. Echocardiography in diabetic rats showed that LV weight/body weight ratio was significantly higher than in control rats, whereas the levels of LV end-diastolic volume and stroke volume were decreased (all p < 0.05 diabetic vs. control). All these changes were either attenuated or prevented by allopurinol. In addition, LV ejection fraction in diabetic rats treated with allopurinol was higher than that in untreated diabetic rats (p < 0.05). Allopurinol can attenuate hyperglycemia-induced oxidative stress, ameliorate cardiomyocyte hypertrophy and fibrosis and subsequently prevent left ventricular dysfunction in early diabetes.

Dehydroepiandrosterone reverses chronic hypoxia/reoxygenation-induced right ventricular dysfunction in rats

Dehydroepiandrosterone (DHEA) prevents chronic hypoxia-induced pulmonary hypertension and associated right ventricle dysfunction in rats. In this animal model, reoxygenation following hypoxia reverses pulmonary hypertension but not right ventricle dysfunction. We thus studied the effect of DHEA on the right ventricle after reoxygenation, i.e. after a normoxic recovery phase secondary to chronic hypoxia in rats. Right ventricle function was assessed in vivo by Doppler echocardiography and in vitro by the isolated perfused heart technique in three groups of animals: control, recovery (21 days of hypoxia followed by 21 days of normoxia) and recovery DHEA (30 mg · kg(-1) every 2 days during the recovery phase). Right ventricle tissue was assessed by optical and electron microscopy. DHEA abolished right ventricle diastolic dysfunction, as the echographic E wave remained close to that of controls (mean ± SD 76.5 ± 2.4 and 79.7 ± 1.7 cm · s(-1), respectively), whereas it was diminished to 40.3 ± 3.7 in the recovery group. DHEA also abolished right ventricle systolic dysfunction, as shown by the inhibition of the increase in the slope of the pressure-volume curve in isolated heart. The DHEA effect was related to cardiac myocytes proliferation. In conclusion, DHEA prevents right ventricle dysfunction in this animal model by preventing cardiomyocyte alteration.

Prevention of airway hyperresponsiveness induced by left ventricular dysfunction in rats

BackgroundThe effectiveness of strategies for treatment of the altered static lung volume and against the development of bronchial hyperreactivity (BHR) following a left ventricular dysfunction (LVD) induced by myocardial ischaemia was investigated in a rat model of sustained postcapillary pulmonary hypertension.MethodsAirway resistance (Raw) was identified from the respiratory system input impedance (Zrs) in four groups of rats. End-expiratory lung volume (EELV) was determined plethysmographically, and Zrs was measured under baseline conditions and following iv infusions of 2, 6 or 18 μg/kg/min methacholine. Sham surgery was performed in the rats in Group C, while the left interventricular coronary artery was ligated and Zrs and its changes following identical methacholine challenges were reassessed in the same rats 8 weeks later, during which no treatment was applied (Group I), or the animals were treated daily with a combination of an angiotensin enzyme converter inhibitor and a diuretic (enalapril and furosemide, Group IE), or a calcium channel blocker (diltiazem, Group ID). The equivalent dose of methacholine causing a 100% increase in Raw (ED50) was determined in each group. Diastolic pulmonary arterial pressure (PapD) was assessed by introducing a catheter into the pulmonary artery.ResultsThe sustained presence of a LVD increased PapD in all groups of rats, with variable but significant elevations in Groups I (p = 0.004), ID (p = 0.013) and IE (p = 0.006). A LVD for 8 weeks induced no changes in baseline Raw but elevated the EELV independently of the treatments. In Group I, BHR consistently developed following the LVD, with a significant decrease in ED50 from 10.0 ± 2.5 to 6.9 ± 2.5 μg/kg/min (p = 0.006). The BHR was completely abolished in both Groups ID and IE, with no changes in ED50 (9.5 ± 3.6 vs. 10.7 ± 4.7, p = 0.33 and 10.6 ± 2.1 vs. 9.8 ± 3.5 μg/kg/min p = 0.56, respectively).ConclusionsThese findings suggest that a LVD following coronary ischaemia consistently induces BHR. The more consistent efficacy of both treatment strategies in preventing BHR than in treating the adverse pulmonary vascular consequences suggests the benefit of both calcium channel blockade and ACE inhibition to counteract the airway susceptibility following a LVD.