Cardiac Dysfunction In Rats Research Articles

Cardioprotective Effect of Gynostemma pentaphyllum against Streptozotocin Induced Cardiac Toxicity in Rats via Alteration of AMPK/Nrf2/HO-1 Pathway.

Gynostemma pentaphyllum (GP) is a plant commonly used in diabetic therapy in China. GP having potent antioxidant effect against various free radicals. The purpose of the current investigation to identify the cardioprotective effect of GP against streptozotocin (STZ)/ high fat diet (HFD) induced cardiac dysfunction in rats via alteration of AMPK/Nrf2/HO-1 pathway. Wistar rats were used for the current protocol. The rats were received the intraperitoneal injection of STZ and HFD to induce the cardiac remodelling. Blood glucose level, insulin and lipid parameters were estimated. Blood pressure and heart rate were also estimated. Cardiac parameters, antioxidant, cytokines, total protein and inflammatory mediators were analysed. The mRNA expression was detected using the RT-qPCR, respectively. GP significantly (p < 0.001) decreased the BGL and improved the insulin level. GP altered the ratio of heart/BW, liver/BW, and lung/BW. GP treatment significantly (p < 0.001) suppressed the heart rate and blood pressure (diastolic, systolic and mean pressure). GP significantly (p < 0.001) reduced the level of TC, LDL, TG, VLDL and increased the level of HDL. DCM induced rats received the GP administration exhibited reduction in the level of CK and LDH. GP significantly (p < 0.001) reduced the levels of MDA, hydrogen peroxide, peroxynitrite, ROS and increased the level of GSH, SOD, CAT and GPx. GP significantly (p < 0.001) reduced the levels of cytokines (TNF-α, IL-6, IL-1β) and inflammatory parameters (COX-2 and NFκB). GP significantly (p < 0.001) suppressed the NLRP3 and NF-κB expression. GP also boosted mitochondrial biogenesis by boosting the PGC-1α, HO-1 and Nrf2 expression in cardiac tissue. GP treatment showed the cardioprotective effects against STZ induced diabetic cardiac dysfunction via alteration of AMPK/Nrf2/HO-1 pathway.

MicroRNA-499 improved septic myocardial dysfunction by regulating myosin heavy chain gene axis

To investigate the role and mechanism of microRNA-499 (miR-499) regulating α-myosin heavy chain (α-MHC) and β-myosin heavy chain (β-MHC) gene axis in septic myocardial dysfunction (SMD) and its significance. Sixty healthy adult male Sprague-Dawley (SD) rats were divided into phosphate buffered saline (PBS) control group (PBS group), lipopolysaccharide (LPS) induced SMD model group (LPS group), miR-499 agonist pretreatment group (agomir+LPS group), and miR-499 inhibitor pretreatment group (antagomir+LPS group) by random number table, with 15 rats in each group. SMD rat model was reproduced by intraperitoneal injection of LPS 10 mg/kg. The PBS group was intraperitoneally injected with the same amount of PBS. The two pretreatment groups were injected with agomir 30 mg/kg or antagomir 80 mg/kg through the caudal vein for 3 days, once a day. PBS group and LPS group were not pretreated. Echocardiography was detected 5 hours after LPS injection, and relevant indexes were recorded. The expression of miR-499 in plasma and myocardial tissue was detected by real-time quantitative polymerase chain reaction (qPCR). Western blotting was used to detect the protein expressions of α-MHC and β-MHC in myocardial tissue. Plasma N-terminal pro-brain natriuretic peptide (NT-proBNP), a marker of heart failure, was measured by electrochemiluminescence. Compared with the PBS group, the rats in LPS group were depressed. Additionally, LPS down-regulated the level of miR-499 in plasma and myocardial tissue, decreased α-MHC expression in myocardial tissue and up-regulated the expression of β-MHC. Echocardiography showed that left ventricular ejection fraction (LVEF), left ventricle fractional shortening (LVFS), cardiac output (CO), stroke volume (SV) and heart rate (HR) decreased by 49.1%, 59.2%, 48.8%, 39.4% and 15.9%, respectively, and the level of plasma NT-proBNP increased significantly in LPS group, indicating that LPS could induce cardiac dysfunction in rats. Compared with the LPS group, after pretreatment with agomir to overexpress the miR-499, LVEF and LVFS were significantly increased [LVEF: 0.662±0.020 vs. 0.323±0.024, LVFS: (36.16±1.43)% vs. (20.20±1.32)%, both P < 0.01], which suggested that the cardiac function of rats was improved in agomir+LPS group. At the same time, pretreatment with agomir significantly down-regulated the β-MHC protein expression (β-MHC/GAPDH: 0.74±0.04 vs. 2.97±0.34, P < 0.01), significantly up-regulated α-MHC protein expression (α-MHC/GAPDH: 1.59±0.05 vs. 0.74±0.14, P < 0.01), and significantly decreased the plasma NT-proBNP level (ng/L: 114.49±6.85 vs. 334.13±4.36, P < 0.01). After pretreatment with antagomir to inhibit the expression of miR-499, echocardiography showed that LVEF and LVFS were significantly lower than those in the LPS group [LVEF: 0.297±0.021 vs. 0.323±0.024, LVFS: (19.38±1.52)% vs. (21.20±1.32)%, both P < 0.01], which suggested that the cardiac function of rats was significantly inhibited. At the same time, pretreatment with antagomir significantly down-regulated α-MHC protein expression in myocardial tissue (α-MHC/GAPDH: 0.63±0.03 vs. 0.74±0.14, P < 0.01), significantly up-regulated β-MHC protein expression (β-MHC/GAPDH: 3.03±0.47 vs. 2.97±0.34, P < 0.01), and significantly increased the level of plasma NT-proBNP (ng/L: 373.91±4.23 vs. 334.13±4.36, P < 0.05). miR-499 could regulate the expression of α-MHC and β-MHC which improved cardiac dysfunction caused by sepsis. Targeted regulation of miR-499 expression may be an effective way to treat SMD.

Targeting Oxidative Stress, NLRP3 Inflammasome, and Autophagy by Fraxetin to Combat Doxorubicin-Induced Cardiotoxicity.

Doxorubicin belongs to the class of anthracycline antibiotics that is widely used in the treatment protocols of a wide range of malignancies. The major deleterious effect of doxorubicin use is the possible occurrence of cardiotoxicity. This study aimed to delineate the possible effects of targeting oxidative stress, NLRP3 inflammasome, and autophagy by fraxetin on doxorubicin-induced cardiac dysfunction in rats. In a model of doxorubicin-induced cardiotoxicity, the effects of different doses of fraxetin were assessed by determination of biochemical, histopathological, immunohistochemical, and electron microscopic changes. Fraxetin, in a dose-dependent manner, was found to have the ability to mitigate the harmful effects of oxidative stress and inflammation on myocardial muscles with significant decrease in NLRP3 inflammasome, augmentation of autophagy, and amelioration of the apoptotic signaling pathways. In addition, fraxetin, in a dose-dependent manner, had the ability to combat the echocardiographic, histopathological, immunohistochemical, and electron microscopic changes induced by doxorubicin in cardiomyocytes. As a result, fraxetin may be put into consideration as a new adjuvant line of therapy on the way to mitigate doxorubicin-induced cardiotoxicity.

Rice (Oryza sativa L.) bran preserves cardiac function by modulating pro-inflammatory cytokines and redox state in the myocardium from obese rats

PurposeThis study aimed to evaluate the effect of rice bran (RB) supplementation to a high-sugar fat (HSF) diet on cardiac dysfunction in an experimental obesity model.MethodsMale Wistar rats were distributed into three groups: control, high-sugar fat, and high-sugar fat supplemented with 11% RB for 20 weeks.ResultsHSF diet promoted obesity and metabolic complications. Obese rats showed cardiac structural and functional impairment associated with high levels of interleukin-6, tumoral necrosis factor alpha, and malondialdehyde, and decreased activity of superoxide dismutase and catalase in the myocardium. RB supplementation was able to mitigate obesity and its metabolic alterations in HSF diet-fed animals. Moreover, the RB also prevented structural and functional damage, inflammation, and redox imbalance in the heart of these animals.ConclusionThis study suggests that RB supplementation prevents cardiac dysfunction in rats fed on HSF by modulating systemic metabolic complications and inflammation and oxidative stress in the myocardium, representing potential alternative therapy.

A Sodium Oxalate-Rich Diet Induces Chronic Kidney Disease and Cardiac Dysfunction in Rats.

Chronic kidney disease (CKD) is a worldwide public health issue affecting 14% of the general population. However, research focusing on CKD mechanisms/treatment is limited because of a lack of animal models recapitulating the disease physiopathology, including its complications. We analyzed the effects of a three-week diet rich in sodium oxalate (OXA diet) on rats and showed that, compared to controls, rats developed a stable CKD with a 60% reduction in glomerular filtration rate, elevated blood urea levels and proteinuria. Histological analyses revealed massive cortical disorganization, tubular atrophy and fibrosis. Males and females were sensitive to the OXA diet, but decreasing the diet period to one week led to GFR significance but not stable diminution. Rats treated with the OXA diet also displayed classical CKD complications such as elevated blood pressure and reduced hematocrit. Functional cardiac analyses revealed that the OXA diet triggered significant cardiac dysfunction. Altogether, our results showed the feasibility of using a convenient and non-invasive strategy to induce CKD and its classical systemic complications in rats. This model, which avoids kidney mass loss or acute toxicity, has strong potential for research into CKD mechanisms and novel therapies, which could protect and postpone the use of dialysis or transplantation.

Stellaria media tea protects against diabetes-induced cardiac dysfunction in rats without affecting glucose tolerance

Background and aimCommon chickweed (Stellaria media) tea has traditionally been applied for treatment of various metabolic diseases including diabetes in folk medicine; however, experimental evidence to support this practice is lacking. Therefore, we aimed to assess the effect of Stellaria media tea on glucose homeostasis and cardiac performance in a rat model of diabetes. Experimental procedureHot water extract of Stellaria media herb were analyzed and used in this study, where diabetes was induced by fructose-enriched diet supplemented with a single injection of streptozotocin. Half of the animals received Stellaria media tea (100 mg/kg) by oral gavage. At the end of the 20-week experimental period, blood samples were collected and isolated working heart perfusions were performed. Results and conclusionCompared to the animals receiving standard chow, serum fasting glucose level was increased and glucose tolerance was diminished in diabetic rats. Stellaria media tea did not affect significantly fasting hyperglycemia and glucose intolerance; however, it attenuated diabetes-induced deterioration of cardiac output and cardiac work. Analysis of the chemical composition of Stellaria media tea suggested the presence of rutin and various apigenin glycosides which have been reported to alleviate diabetic cardiomyopathy. Moreover, Stellaria media prevented diabetes-induced increase in cardiac STAT3 phosphorylation. We demonstrated for the first time that Stellaria media tea may beneficially affect cardiac dysfunction induced by diabetes without improvement of glucose homeostasis. Rutin and/or apigenin glycosides as well as modulation of STAT3 signaling may be implicated in the protection of Stellaria media tea against diabetic cardiomyopathy.

Upregulation of PCSK9, rho kinase and cardiac troponin by Eucalyptus globulus leaf extract improves fructose-streptozotocin-induced diabetic cardiac dysfunction in rats

Context The effect of Eucalyptus globulus in diabetic cardiac dysfunction and the possible mechanisms involved have not been explored. Objective To evaluate the effect of ethanol leaf extract of E. globulus (NEE) on the cardiac function of fructose/streptozotocin-induced diabetic rats. Materials and methods Type-2 diabetes was induced in rats with 10% fructose feeding for 14 days and an intraperitoneal administration of 40 mg/kg streptozotocin. Diabetic animals were treated with NEE (100–400 mg/kg) or 5 mg/kg glibenclamide orally for 21 days. Biochemical assays, histopathological examination and analyses of PCSK9, Rho kinase and Cardiac troponin expression were performed. Results The untreated diabetic group showed decreased expression of the genes, oxidative stress, dyslipidemia, increased activities of creatine kinase MB and lactate dehydrogenase, reduced nitric oxide level, and depletion of cardiomyocytes, which were reversed in NEE treated groups. Conclusions Eucalyptus globulus ameliorated diabetic cardiac dysfunction through increased PCSK9, Rho kinase and Cardiac troponin expression.

1-Methyl tryptophan, an indoleamine 2,3-dioxygenase inhibitor, attenuates cardiac and hepatic dysfunction in rats with biliary cirrhosis

Kynurenine Pathway (KP) is the dominant metabolic route of tryptophan which is catalyzed by indoleamine-2,3-dioxygenase (IDO). This pathway is upregulated in liver disease where the level of KP metabolites correlates with the severity of disease. Cirrhosis is associated with cardiac dysfunction, which manifests itself during severe physiological challenges such as liver transplantation. Cardiac dysfunction in cirrhosis is linked to systemic inflammation and impaired cardiac beta-adrenergic signaling pathways. The KP pathway is involved in modulation of cardiac signaling and is upregulated by systemic inflammation. Therefore, this study aimed to evaluate the effect of IDO inhibition on development of cardiac dysfunction in an experimental model of cirrhosis. Cirrhosis was induced by bile duct ligation (BDL). Experimental groups were given either 1-methyl tryptophan (1-MT, 1, 3, 9 mg/kg), or saline. 28 days after BDL, cardiac chronotropic response to epinephrine was assessed ex vivo. HPLC was employed to measure hepatic and cardiac levels of tryptophan, kynurenine and kynurenic acid. Cirrhosis in rats was associated with impaired cardiac chronotropic responsiveness to adrenergic stimulation. 1-MT dose-dependently improved cirrhosis-induced chronotropic dysfunction as well as elevated serum levels of CRP and IL-6 in BDL rats. Hepatic and cardiac kynurenine/tryptophan ratio were elevated in cirrhotic rats and were reduced following 1-MT administration. Chronic administration of 1-MT could also reduce hepatic inflammation, fibrosis and ductular proliferation. 1-MT attenuates cardiac dysfunction in rats with biliary cirrhosis. This protective effect is not limited to the cardiac function as liver histopathologic changes were also improved following chronic 1-MT administration.

Pinocembrin alleviates lipopolysaccharide-induced myocardial injury and cardiac dysfunction in rats by inhibiting p38/JNK MAPK pathway

AimRecent studies have shown that, with its excellent anti-inflammatory and antioxidant effects, pinocembrin can reduce the occurrence of arrhythmia in myocardial infarction rats. However, whether it can alleviate lipopolysaccharide (LPS)-induced myocardial injury in rats has not been reported. Therefore, the purpose of this study was to investigate whether pinocembrin could alleviate myocardial injury and arrhythmia in rats with sepsis. Materials and methodsRats were intraperitoneally injected with LPS to simulate animal sepsis, and the caudal vein was injected with pinocembrin or normal saline for intervention. Transthoracic echocardiography, inflammatory factors, electrophysiological recording, histological analysis, and western-blot analysis were performed. Key findingsCompared with the control group, the rats in the LPS group had myocardial injury and cardiac dysfunction, and the incidence of ventricular arrhythmia increased. In addition, LPS resulted in the increase of p-c-Jun N-terminal kinase (JNK), p-p38 proteins in the myocardium, the levels of inflammatory factors in the blood and the apoptosis rate of left ventricular cardiomyocytes. And all these adverse effects were eliminated, thus confirming that pinocembrin has an excellent protective effect on the heart. SignificanceReducing the inflammatory response and cell apoptosis by inhibiting p38/JNK mitogen-activated protein kinase (MAPK) signaling pathway, pinocembrin can alleviate myocardial injury, cardiac dysfunction, and ventricular arrhythmia induced by LPS.

Circ-Zfp644 acts as a pro-hypertrophic mediator in an Ang-II induced in vitro myocardial hypertrophy model.

Cardiac hypertrophy (CH) is a common risk factor for heart failure and even sudden cardiac death. Molecules have emerged as vital regulators in cardiac disorders. LIM domain kinase 1 (Limk1) is reported as a pro-fibrotic mediator in patients with permanent atrial fibrillation and it has also been suggested to aggravate cardiac dysfunction in rats with chronic heart failure. The present study observed that Limk1 was significantly upregulated in the in vitro model of CH induced by angiotensin II (Ang-II). Interestingly, silencing Limk1 led to inhibition ofthe hypertrophic phenotypes in Ang-II-treated cardiomyocytes. Next, through a series of mechanistic assays including RIP assay, RNA pull-down assay, and luciferase reporter assay, miR-93-5p was verified to target Limk1. Furthermore, circ-Zfp644 was validated as the sponge of miR-93-5p. Circ-Zfp644 functioned as a ceRNA to upregulate Limk1 expression via sequestering miR-93-5p in Ang-II-treated cardiomyocytes. Finally, a range of rescue assays revealed that circ-Zfp644 stimulated hypertrophic effects in Ang-II-treated cardiomyocytes via upregulating Limk1 while miR-93-5p exerted the opposite effects via its inhibition on Limk1. On the whole, the present study revealed that circ-Zfp644 aggravated CH through modulating the miR-93-5p/Limk1 axis. The findings observed on the in vitro model of CH provided new potential for developing CH treatment.

Astragaloside IV-targeting miRNA-1 attenuates lipopolysaccharide-induced cardiac dysfunction in rats through inhibition of apoptosis and autophagy

Astragaloside IV (AS-IV), the major active constituent purified from Astragalus membranaceus, was previously reported to have protective effects against cardiac dysfunction. However, the underlying mechanism remains unknown. In the present study, we investigated the protective effect of AS-IV on lipopolysaccharide (LPS)-induced cardiac dysfunction and explored the potential mechanism by focusing on miRNA-1 (miR-1) at the animal and cellular levels. A series of methods were used, including echocardiography, flow cytometry, ELISA, immunofluorescence, transmission electron microscopy, RT-PCR, and western blotting. The results showed that both AS-IV and the miR-1 inhibitor improved cardiac dysfunction, reduced heart injury, inhibited apoptosis and autophagy, and regulated the expression of calcium- and mitochondrial energy metabolism-related proteins in the heart tissue of rats treated with LPS. Importantly, AS-IV downregulated the expression of miR-1 mRNA in heart tissue. All effects of AS-IV were at least partly abolished by miR-1 mimics. In the in vitro study, both AS-IV and the miR-1 inhibitor inhibited apoptosis and autophagy and regulated the expression of calcium- and mitochondrial energy metabolism-related proteins in heart cells treated with LPS. Similarly, AS-IV downregulated the expression of miR-1 mRNA in heart cells. All effects of AS-IV on cells were at least partly abolished by miR-1 mimics. Furthermore, miR-1 mimics exhibited effects similar to LPS both in animal and cellular studies. Taken together, these results suggest that AS-IV protects against LPS-induced cardiac dysfunction by inhibiting calcium-mediated apoptosis and autophagy by targeting miR-1, highlighting a new mechanism for the therapeutic effect of AS-IV on cardiac dysfunction.

Protective effect of Ganoderma lucidum spore extract in trimethylamine-N-oxide-induced cardiac dysfunction in rats.

Previous research has shown that the extracts from the Ganoderma lucidum spore (GS) have potentially cardioprotective effects, but there is still abundant room for development in determining its mechanism. In this study, the rat model of cardiac dysfunction was established by intraperitoneal injection of trimethylamine-N-oxide (TMAO), and the extracts of GS (oil, lipophilic components, and polysaccharides) were given intragastrically at a dose of 50mg/kg/day to screen the pharmacological active components of GS. After 50 days of treatments, we found that the extraction from GS reduced the levels of total cholesterol, triglyceride, and low-density lipoprotein; increased the levels of high-density lipoprotein; and reduced the levels of serum TMAO when compared to the model group (P<0.05); especially the GS polysaccharides (DT) and GS lipophilic components (XF) exhibited decreases in serum TMAO compared to TMAO-induced control. The results of 16S rRNA sequencing showed that GS could change the gut microbiota, increasing the abundance of Firmicutes and Proteobacteria in the DT-treated group and XF-treated group, while reducing the abundance of Actinobacteria and Tenericutes. Quantitative proteomics analysis showed that GS extracts (DT and XF) could regulate the expression of some related proteins, such as Ucp1 (XF-TMAO/M-TMAO ratio is 2.76), Mpz (8.52), Fasn (2.39), Nefl (1.85), Mtnd5 (0.83), Mtnd2 (0.36), S100a8 (0.69), S100a9 (0.70), and Bdh1 (0.72). The results showed that XF can maintain the metabolic balance and function of the heart by regulating the expression of some proteins related to cardiovascular disease, and DT can reduce the risk of cardiovascular diseases by targeting gut microbiota.

Silenced SOX2-OT alleviates ventricular arrhythmia associated with heart failure by inhibiting NLRP3 expression via regulating miR-2355-3p.

BackgroundNucleotide‐binding oligomerization domain‐like receptor family pyrin domain containing 3 (NLRP3) inflammasomes are the most important factors in ventricular arrhythmia associated with heart failure (VA‐HF). However, how the relationship between lncRNA and NLRP3 inflammasomes is regulated in VA‐HF has not been investigated in detail. Thus, we aimed to determine the effects of SOX2‐overlapping transcripts (SOX2‐OT) by targeting NLRP3 in rats with VA‐HF.MethodsWe established rats (SPF, male, weight: 240 ± 10 g) with VA‐HF by aortic coarctation and constant‐current stimulation, then injected them with small interfering SOX2‐OT and anti‐miR‐2355‐3p. Six weeks later, SOX2‐OT and miR‐2355‐3p expression was measured using the quantitative reverse transcriptase‐polymerase chain reaction and NLRP3, ASC, caspase‐1, IL‐1β, and TGF‐β1 expression were measured by Western blot analysis; the ventricular chambers were histopathologically analyzed by staining with hematoxylin and eosin, Masson trichrome, and Picro Sirius Red and reactive oxygen species (ROS) levels were assessed by flow cytometry. The targeting relationship between miR‐2355‐3p and SOX2‐OT or NLRP3 was verified using dual‐luciferase reporter gene assays.ResultsThe expression of SOX2‐OT and levels of NLRP3 inflammasomes gradually increased in normal rats, and in those with heart failure and with VA‐HF. Silencing SOX2‐OT expression inhibited NLRP3, ASC, caspase‐1, IL‐1β, and TGF‐β1 expression and ROS production, reduced the degrees of cardiomyocyte necrosis and fibrosis and alleviated cardiac dysfunction in rats with VA‐HF. MicroR‐2355‐3p can bind the SOX2‐OT and the 3′‐untranslated region of NLRP3. Inhibiting miR‐2355‐3p reversed the effect of SOX2‐OT in rats with VA‐HF.ConclusionsSilencing SOX2‐OT alleviated cardiac dysfunction in rats by reducing the activation of NLRP3 inflammasomes via regulating miR‐2355‐3p.

The Effect of Dipeptidyl Peptidase-4 Inhibitors or Curcumin on Diet Induced Metabolic Syndrome with Cardiac Dysfunction in Rats

ABSTRACT Background: Metabolic syndrome (MS) increases the risk of developing cardiovascular diseases (CVDs) which are the leading cause of death worldwide. Objective: This study is aiming to investigate the curative effects ofdipeptidyl peptidase-4 inhibitorsand the prophylactic effects of curcumin on diet induced metabolic syndrome which is associated with cardiac dysfunction in rats. Methodology: sixty adult male albino rats were divided into six groups: Group I: (control). Group II: (MS induced). Group III: (Vildagliptin only). Group IV: (Curcumin only). Group V (therapeutic):Vildagliptin treated rats after 8 weeks of MS to the end of 12 weeks. Group VI (prophylactic): Curcumin is administered with MS induction concomitantly for 12 weeks. Transthoracic echocardiogram was done while rats were alive. At the end of the experiment, blood was collected and biochemical analysis (blood glucose, serum insulin, lipid profile and cardiac enzymes) was done. Heart tissues were used for oxidative stress parameters (cardiac mitochondrial reactive oxygen species (ROS) and cardiac mitochondrial complex I and complex II) beside histopathological examination. Results: High fat diet (HFD)administration resulted in a significant increase in blood glucose, serum insulin, homeostasis model assessment of IR (HOMA- IR) index with disturbed lipid profile. Significant increase in serum cardiac enzymes and oxidative stress tissue markers were also noticed. Echocardiography revealed structural and functional cardiomyopathy. Histopathological examination showed cellular infiltrations with fat cells and collagen fibers accumulation. DPP- 4 inhibitors and curcuminresulted in a significant decrease in glucose, insulin, and HOMA- IR index, partial amelioration of lipid profile, cardiac enzymes, and cardiac oxidative stress markers. Echocardiography revealed alleviation of cardiomyopathy. Histopathological examination also revealed highly manifested structural improvement. Conclusion: The current study revealed that both DPP- 4 inhibitors and curcumin improve cardiomyopathy resulted from HFD administration with a diversity of mechanisms including anti-inflammatory, anti-apoptotic and anti-oxidative ways.

Abstract 16639: A Novel Approach to Model Heart Failure With Preserved Ejection Fraction in Rats

Introduction: Diastolic dysfunction and cardiac hypertrophic remodeling are hallmark features of heart failure with preserved ejection fraction (HFpEF) in humans. However, an ideal animal model that mimics all these basic clinical features of HFpEF remains to be developed. Methods: Male Sprague-Dawley rats (250-300 g) were subjected to central infusion of either Angiotensin II (Ang II at 20 ng/min, 0.5 μl/h, i.c.v) or isotonic saline (0.5 μl/h, i.c.v) through osmotic mini-pumps for 14 days. Echocardiography was used to measure systolic (ejection fraction) and diastolic functions (E/A and E/E’ ratio) at day 14. Mean arterial pressure (MAP), heart rate (HR), left ventricular pressure (LVP), changes in ±dP/dt, and cardiac responses to isoproterenol (ISO) were also measured in anesthetized rats. Results: Central infusion of Ang II in rats resulted in increased sympathoexcitation and mean arterial pressure. Concomitantly, there was decreased E/A ratio (AngII: 1.2 ± 0.1 vs. Cont: 1.5 ± 0.1) and increased E/E’ ratio (AngII: 14.3 ± 0.8 vs. Cont: 12.9 ± 0.6), indicating diastolic dysfunction. Ejection fractions were comparable between the groups (AngII: 67 ± 2% vs. Cont: 69 ± 5%). Ang II infused rats demonstrated increased heart to body weight ratio (AngII: 4.5 ± 0.5 vs. Cont: 2.9 ± 0.1), cachexia (AngII: 235 ± 18 g vs. Cont: 331 ± 11 g), hypertrophy (AngII: 46 ± 5 μm/unit area vs. Cont: 36 ± 7 μm/unit area), and fibrosis (AngII: 5.2 ± 0.5 intensity/unit area vs. Cont: 2.6 ± 0.4 intensity/unit area). At the same time cardiac contractile responsiveness to ISO (0.5 μg/kg) was significantly lower for negative dP/dt in Ang II rats (AngII: -6998 mmHg/s vs. Cont: -11675 mmHg/s), which is indicative of abnormal diastole or relaxation. However, positive dP/dt response to ISO was similar in the two groups, indicating preserved systolic function in the Ang II group. Conclusions: Central Ang II infusion in rats shows sympathoexcitation, diastolic dysfunction, and pathological cardiac hypertrophy and fibrosis mimicking abnormalities seen in patients with HFpEF. This model of cardiac dysfunction in rats may represent a suitable platform to investigate the underlying mechanisms of HFpEF.

Fangchinoline attenuates cardiac dysfunction in rats with endotoxemia via the inhibition of ERK1/2 and NF-κB p65 phosphorylation.

BackgroundCardiac dysfunction is a complication commonly encountered by patients with endotoxemia. Fangchinoline (Fan) is a natural bisbenzylisoquinoline alkaloid. This study aimed to investigate the cardioprotective effect of Fan against lipopolysaccharide (LPS)-induced acute cardiac dysfunction.MethodsRats were administered with Baicalin (100 mg/kg) and Fan (30 or 60 mg/kg) via intraperitoneal injection (i.p.) for 3 days, followed by LPS treatment (10 mg/kg, i.p.). The rats were randomly grouped (n=10): the control group, the LPS group, the LPS + Baicalin group, the LPS + Fan groups. Echocardiography and hematoxylin and eosin (HE) staining were performed to detect cardiac dysfunction. Cardiac function were also determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), ELISA, and western blot, respectively. The protective mechanisms of Fan were analyzed by western blot and qRT-PCR.ResultsLPS induced the depression of cardiac function, myocardial inflammation, and apoptosis. These changes were associated with decreased GRP78 and GADD34, increased C/EBP-homologous protein (CHOP) and cleaved caspase-12. Fan significantly reduced the release of inflammatory cytokines such as monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-18, and IL-6. Furthermore, Fan treatment increased superoxide dismutase (SOD) and decreased malondialdehyde (MDA. Notably, Fan inhibited myocardial apoptosis following ER stress in the LPS-induced rat model and stimulated phosphorylation activation of ERK1/2 and NF-κB p65 proteins.ConclusionsFan deficiency alleviated LPS-induced endotoxemia in rats. Therefore, Fan may be a new therapeutic approach for the treatment of cardiac dysfunction.

Hydroxysafflor Yellow A Protects Against Myocardial Ischemia/Reperfusion Injury via Suppressing NLRP3 Inflammasome and Activating Autophagy.

Myocardial ischemia/reperfusion (MI/R) injury is a serious threat to human health. Hydroxysafflor yellow A (HSYA), the main water-soluble ingredient extracted from Carthami flos (Carthamus tinctorius L.), has therapeutic potential for treating MI/R injury. However, the mechanisms of HSYA−mediated protection from MI/R injury are incompletely understood. In the present study, we investigated the effects and the underlying mechanisms of HSYA during MI/R. Adult Sprague-Dawley rats were subjected to left anterior descending artery ligation for 30 min followed by 24 h of reperfusion with or without HSYA treatment. The protective effect of HSYA was detected by 2,3,5-triphenyl tetrazolium chloride (TTC) staining, hematoxylin eosin (HE) staining, and myocardial enzymes detections. Serum levels of inflammatory factors such as TNF-α, interleukin (IL)-1β, and IL-18, were detected using ELISA kits. The expression of NLRP3 and other related proteins in the myocardium was detected by western blot and immunohistochemistry. The expression of autophagy-related proteins, including Atg5, BECN1, P62, and LC3B, was detected by western blot to evaluate the effect of HSYA on autophagy. Results showed that HSYA decreased the myocardial infarct size and attenuated the cardiac dysfunction in rats after I/R. In addition, HSYA inhibited myocardial apoptosis compared with the I/R group, decreased the levels of inflammatory cytokines in rat serum, reduced NLRP3 inflammasome expression, and induced autophagy. Mechanistically, our results demonstrated that HSYA can activate AMPK to improve autophagy and inhibit NLRP3 inflammasome by inhibiting the mTOR pathway. This work provides strong data supporting for the clinical applications of HSYA in MI/R injury.

The importance of heart rate in isoprenaline-induced takotsubo-like cardiac dysfunction in rats.

AimsTakotsubo syndrome (TS) is an acute cardiac syndrome characterized by regional myocardial akinesia that cannot be attributed to a culprit lesion in coronary arteries. Cardiac overstimulation by catecholamines in the setting of stress is implicated in the pathogenesis of TS. While catecholamine‐induced alterations in cardiac contractility have been studied as part of the causal pathway in TS, the importance of catecholamine‐mediated tachycardia has not been studied. Our aim was to explore whether the reduction in heart rate, either by pharmacological suppression of the sinoatrial node with ivabradine or by surgical induction of third‐degree atrioventricular block, prevents isoprenaline‐induced TS‐like akinesia in an experimental animal model.Methods and resultsWe used 142 female Sprague–Dawley rats in two separate protocols. The TS‐like phenotype was induced by an intraperitoneal bolus dose of isoprenaline (ISO) 50 mg/kg. In the first protocol, we randomized 54 rats to ivabradine 10 min before ISO (IVAB1), ivabradine 10 min after ISO (IVAB2), or saline 10 min before ISO (CONTROL). In the second protocol, we randomized 88 rats to surgically induced complete heart block (CHB) or sham operation (CTRL) 10 min before the administration of ISO. All drugs were administered intraperitoneally. We recorded heart rate and blood pressure invasively in the right carotid artery. Cardiac morphology and function were evaluated by high‐resolution echocardiography (VisualSonics 770 VEVO, Toronto, Ontario, Canada) 90 min after ISO injection. IVAB1 and IVAB2 rats had significantly lower heart rate and less pronounced TS‐like cardiac dysfunction than CONTROL. CHB rats had a lower (54%) heart rate, and no animal developed left ventricular akinesia. In the first protocol, the CONTROL group had a median degree of akinesia of 10.2 [inter‐quartile range (IQR) 0.0–18.6]. The IVAB1 group showed a median of akinesia of 0% (IQR 0.0–0.0, P < 0.001 vs. CONTROL). In the IVAB2 group, 5% had TS‐like dysfunction (P = 0.001). Ejection fraction was higher in both the IVAB1 (92%, IQR 89–95) and IVAB2 groups (93%, IQR 87–96) than in the CONTROL group (78%, IQR 63–87, P < 0.05). In the second protocol, the median degree of akinesia in the CTRL group was 21.9% (IQR 8.9–24.6). In the CHB group, no rat developed akinesia (median 0%; IQR 0.0–0.0, P < 0.001 vs. CONTROL). Ejection fraction was higher in the CHB group (90%, IQR 87–92) than in the CTRL group (51%, IQR 87–92, P < 0.05).ConclusionsIsoprenaline‐induced TS‐like cardiac dysfunction can be prevented by lowering heart rate. Tachycardia may be an important part of the causal pathway in TS.

Adiponectin in onset and progression of T2DM with cardiac dysfunction in rats.

Cardiovascular disease and type 2 diabetes mellitus (T2DM) patients have low level of adiponectin, however, till now the role of adiponectin in progression of 'T2DM with cardiac dysfunction' in animal model has not been characterized. Therefore, the aim of the present study was to develop and characterize T2DM animal model with cardiac dysfunction and to study the role of cardiac adiponectin expression in cardiac dysfunction. For this, Wistar rats (M/F) were fed a high-fat diet for different time periods: 3, 4 and 5 weeks and given a single, low-dose streptozotocin (25mg/kg), intraperitoneal injection 1 week prior to the experiments. Rats in T2DM group (3 weeks) developed hyperglycaemia, hyperlipidaemia, oxidative stress with normoinsulinaemia and mild cardiac dysfunction suggesting onset of T2DM with cardiac dysfunction. Extended high-fat feeding, that is, 4 and 5 weeks induced insulin resistance accompanied with cardiac hypertrophy, cardiac dysfunction and reduced baroreflex sensitivity indicating development of T2DM with cardiac dysfunction. Cardiac adiponectin expression did not change in rats of T2DM group (3 weeks), however, it significantly decreased in rats of two T2DM groups (4 and 5 weeks) along with increased intracellular adhesion molecule-1 levels. Thus, the present study for the first time indicates that in the present T2DM animal model, as T2DM progresses cardiac adiponectin expression also decreases which might be the precipitating factor for cardiac hypertrophy and decrease in baroreflex sensitivity, which induces cardiac dysfunction.

Simvastatin relieves myocardial ischemia/reperfusion injury in rats through hedgehog signaling pathway.

The aim of this study was to explore the effect of simvastatin (Sim) on myocardial ischemia/reperfusion (I/R) injury in rats and to elucidate the possible underlying mechanism. Our findings might help to provide a certain reference for the clinical prevention and treatment of myocardial I/R injury. A total of 60 male Sprague-Dawley (SD) rats were randomized into three groups using a random number table, including: Sham group (n=20), I/R group (n=20) and I/R + Sim group (n=20). The I/R injury model was successfully established in rats via ligation of the left anterior descending coronary artery (LAD), followed by reperfusion. Before operation, the rats in I/R + Sim group were administered with Sim at 10 mg/kg/d through oral gavage for 7 d. Cardiac ejection fraction (EF) (%) and fractional shortening (FS) (%) of rats in each group were detected using echocardiography. 2,3,5-triphenyltetrazolium chloride (TTC) staining was performed to measure the myocardial infarction (MI) area in each group. Collagen deposition in myocardial tissues of rats in each group was detected by Masson's trichrome staining. The apoptosis level of myocardial cells and fibroblasts in myocardial tissues of rats in each group were evaluated via terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining. The level of reactive oxygen species (ROS) in myocardial tissues of rats in each group was determined using fluorescent probes. Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was conducted to measure the expression levels of pro-inflammatory cytokines interleukin (IL)-1β and monocyte chemoattractant protein-1 (MCP-1) in myocardial tissues of rats in each group. Furthermore, the effects of Sim on the hedgehog signaling pathway-associated proteins were detected using Western blotting. Sim significantly alleviated I/R-induced cardiac dysfunction in rats and increased EF (%) and FS (%) (p<0.05). Meanwhile, it also evidently mitigated the MI caused by I/R and reduced the infarction area (p<0.05). According to the Masson's trichrome staining results, I/R + Sim group exhibited remarkably declined myocardial interstitial collagen deposition compared with I/R group (p<0.05). ROS-sensitive fluorescent staining showed that Sim notably reversed the increase of ROS expression and the decrease of myocardial oxidative stress induced by I/R (p<0.05). Finally, Western blotting results revealed that Sim dramatically restrained the protein expressions of sonic hedgehog (SHH), patched 1 (PTC1) and glioma-associated oncogene homolog 1 (GLI1) (p<0.05). Sim can significantly relieve myocardial I/R injury in rats. The possible underlying mechanism may be related to its inhibition on the hedgehog signaling pathway.