Post-myocardial Infarction Rats Research Articles

Leonurine (SCM-198) attenuates myocardial fibrotic response via inhibition of NADPH oxidase 4

In our previous studies, we have reported that leonurine, a plant phenolic alkaloid in Herba leonuri, exerted cardioprotective properties in a number of preclinical experiments. Herein, we investigated the roles and the possible mechanisms of leonurine for reducing fibrotic responses in angiotensin II (Ang II)-stimulated primary neonatal rat cardiac fibroblasts and post-myocardial infarction (MI) rats. In in vitro experiments performed in neonatal rat cardiac fibroblasts, leonurine (10–20μM) pretreatment attenuated Ang II-induced activation of extracellular signal-regulated kinase 1/2, production of intracellular reactive oxygen species (ROS), expression and activity of matrix metalloproteinase (MMP)-2/9, and expression of α-smooth muscle actin and types I and III collagen. A small interfering RNA-mediated knockdown strategy for NADPH oxidase 4 (Nox4) revealed that Nox4 was required for Ang II-induced activation of cardiac fibroblasts. In vivo studies using a post-MI model in rats indicated that administration of leonurine inhibited myocardial fibrosis while reducing cardiac Nox4 expression, ROS production, NF-κB activation, and plasma MMP-2 activity. In conclusion, our results provide the first evidence that leonurine could prevent cardiac fibrosis and the activation of cardiac fibroblasts partly through modulation of a Nox4–ROS pathway.

Peptidomic profiles of post myocardial infarction rats affinity depleted plasma using matrix‐assisted laser desorption/ionization time of flight (MALDI‐ToF) mass spectrometry

BackgroundDespite major advances in drug development, effective cardiovascular therapies and suitable cardiovascular biomarkers remain limited. The aim of this study was to leverage mass spectrometry (MS) based peptide profiling strategies to identify changes that occur in peptidomic profiles of rat plasma following coronary artery ligation generated myocardial infarction (MI).MethodsOne week after MI, rats were randomized to receive either an ACE inhibitor (ramipril, Ram-1 mg/kg/day), or vehicle (Veh) for 12 weeks. Echocardiography and hemodynamic measurements were made before sacrifice and plasma collection. High abundance proteins were depleted with affinity capture before MS profiling. Differentially expressed peptide ions were identified using proprietary software (ClinProtTools).ResultsMI increased heart/body weight (18%), lung/body weight (56%), and left ventricular (LV) end diastolic pressure (LVEDP, 247%); and significantly reduced percentage fractional shortening (FS, 75%) and rate of pressure rise in the LV (dP/dtmax, 20%). Ram treatment significantly attenuated the changes in LVEDP (61%) and FS (27%). Analysis of MALDI-ToF generated mass spectra demonstrated that peptide ions 1271, 1878, 1955, 2041 and 2254 m/z were consistently decreased by Ram treatment (p < 0.001) and thus may be associated with the agent’s therapeutic effects. Among peptides that were significantly changed, synapsin-2, adenomatous polyposis coli protein and transcription factor jun-D were identified as significantly reduced by Ram treatment.ConclusionsThis approach allows us to screen for potential biomarkers in a window of the blood proteome that previously has been difficult to access. The data obtained from such an approach may potentially useful in prognosis, diagnosis, and monitoring of treatment response.

The plating of rat scar myofibroblasts on matrigel unmasks a novel phenotype; the self assembly of lumen‐like structures

During tissue healing, the primary role of myofibroblasts involves the synthesis and deposition of collagen. However, it has also been reported that selective populations of myofibroblasts can acquire the phenotype and/or differentiate to other cells types. The present study tested the hypothesis that myofibroblasts isolated from the scar of the ischemically damaged rat heart can recapitulate an endothelial cell-like response when plated in a permissive in vitro environment. Scar myofibroblasts, neonatal and adult ventricular fibroblasts express smooth muscle α-actin, collagen α(1) type 1 and a panel of pro-fibrotic and pro-angiogenic peptide growth factor mRNAs. Myofibroblasts plated alone on matrigel led to the self assembly of lumen-like structures whereas neonatal and adult rat ventricular fibroblasts were unresponsive. Myofibroblasts labeled with the fluorescent cell tracker CM-DiI were injected in the viable myocardium of 3-day post-myocardial infarcted Sprague-Dawley rats and sacrificed 7 days later. Injected CM-DiI-labeled myofibroblasts were detected predominantly in the peri-infarct/infarct region, highlighting their migration to the damaged region. However, engrafted myofibroblasts in the peri-infarct/infarct region were unable to adopt an endothelial cell-like phenotype or lead to the de novo formation of CM-DiI-labeled blood vessels. The non-permissive nature of the infarct region may be attributed at least in part to the presence of growth-promoting stimuli as TGF-β and the β-adrenergic agonist isoproterenol inhibited the self assembly of lumen-like structures by myofibroblasts. Thus, when plated in a permissive in vitro environment, scar myofibroblasts can self assemble and form lumen-like structures providing an additional novel phenotype distinguishing this population from normal ventricular fibroblasts.

A Novel Drug Delivery System of Oral Curcumin Markedly Improves Efficacy of Treatment for Heart Failure after Myocardial Infarction in Rats

Curcumin is an inhibitor of p300 histone acetyltransferase activity, which is associated with the deterioration of heart failure. We reported that native curcumin, at a dosage of 50 mg/kg, prevented deterioration of the systolic function in rat models of heart failure. To achieve more efficient oral pharmacological therapy against heart failure by curcumin, we have developed a novel drug delivery system (DDS) which markedly increases plasma curcumin levels. At the dosage of 0.5 mg/kg, DDS curcumin but not native curcumin restored left ventricular fractional shortening in post-myocardial infarction rats. Thus, our DDS strategy will be applicable to the clinical setting in humans.

Effects of exercise of different intensities on the angiogenesis, infarct healing, and function of the left ventricle in postmyocardial infarction rats

Lifestyle interventions, including physical exercise, are feasible options for the prevention and treatment of cardiovascular diseases. In this study, the effects of exercise of different intensities on the infarct region, function, and angiogenesis of the left ventricle (LV) in postmyocardial infarction (MI) rats were investigated and the levels of vascular endothelial growth factor (VEGF) proteins in the LV and plasma were examined. Male Sprague-Dawley rats were randomly assigned to six groups. The exercise-trained rats observed a daily 60-min treadmill routine 5 days/weeks for 6 weeks. Different treadmill speeds were used in the high-intensity exercise (HIE), moderate-intensity exercise (MIE), and low-intensity exercise (LIE) groups, whereas the untrained rats remained sedentary (Sed). At 6 weeks, all rats underwent either an acute MI operation or a sham (Sh) MI operation 24 h after their last treadmill exercise or the corresponding Sed protocol. They were then killed 7 days after recovery. Echocardiographic and hemodynamic measurements were taken at the end of the experimental protocol. The infarct regions were analyzed using Masson's trichrome staining, whereas intramyocardial microvessels were detected using Factor VIII-related antigen staining. The cardiac VEGF protein levels were determined by western blotting analysis, and plasma VEGF concentrations were examined by enzyme-linked immunosorbent assay. Compared with the corresponding parameters in the Sed-Sh group, LV function did not significantly ameliorate and microvessel density did not increase in the MIE-Sh group. Compared with the Sed-MI group, the MIE-MI and HIE-MI groups had significantly reduced LV infarct size, improved hemodynamic parameters, and increased fractional shortening, scar thickness, and microvessel density, these parameters did not significantly change in the LIE-MI group. In addition, the MIE-MI and HIE-MI rats had significant differences in hemodynamic parameters and microvessel density. Compared with those of the Sed-MI group, the heart and plasma of the exercise-trained rats in the MIE-MI and HIE-MI groups displayed higher levels of VEGF protein, but the difference between the MIE-MI and HIE-MI groups was not significant. Moderate-intensity running before acute MI improved LV function, reduced scar size, and increased scar thickness and microvessel density in post-MI rats. Exercise at a higher intensity could have further small effects. LIE may be beneficial, but it would not be sufficient to improve MI. Moderate-intensity and high-intensity running upregulated the expression of VEGF protein and increased microvessels, which may have partly improved cardiac function after MI in this study.

Effect of simvatatin and atorvastatin on Fox03a expression and ventricular remolding in post-myocardial infarction rats

ObjectiveAccumulating evidence suggests non-phosphorylation FoxO3a play a role in cardiovascular diseases. Therefore we examined the expression of non-phosphorylation FoxO3a in Post-myocardial Infarction Rats, to investigate the effect of simvastatin and...

Reproducibility of Serial Left Ventricle Perfusion, Volume, and Ejection Fraction Measurements Using Multiplexed Multipinhole SPECT in Healthy Rats and Rats After Myocardial Infarction

Assessment of small-animal cardiac data acquired using SPECT requires an accurate understanding of the reproducibility and the uncertainties associated with the technique. Furthermore, it is also useful to have a baseline of reference data against which to compare the outcome of a particular study. We scanned both healthy and post-myocardial infarction rats injected with (99m)Tc-tetrofosmin in a multidetector, multipinhole small-animal SPECT scanner. In this paper, we report on the creation of a reference database of the relative myocardial blood perfusion of rats. We also evaluated the reproducibility of perfusion measurements and measurements of left ventricle volume and ejection fraction, defined as the SD of a particular measurement repeated on the same animal or over multiple animals. For the healthy rats, interscan reproducibility of volume measurements was 4%-7% of the total volume, and intersubject reproducibility was 9%-12% of the volume being measured. Interscan reproducibility remained unaffected after infarction (6%-8%), but intersubject reproducibility was much poorer (15%-26%). Ejection fraction in healthy animals was highly reproducible between scans and between rats: 3.1% and 3.3%, respectively. Interscan reproducibility of the postinfarction ejection fraction was 3.6%; intersubject reproducibility after infarction was 8.1%. We have created a reference database for small-animal SPECT perfusion measurements in healthy male Sprague-Dawley rats and quantified the reproducibility of perfusion and functional measurement made with small-animal SPECT in healthy and postinfarction rats.

Exercise improves the dilatation function of mesenteric arteries in postmyocardial infarction rats via a PI3K/Akt/eNOS pathway-mediated mechanism

Myocardial infarction (MI) has been shown to induce endothelial dysfunction in peripheral resistance arteries and thus increase peripheral resistance. This study was designed to investigate the underlying mechanisms of post-MI-related dysfunctional dilatation of peripheral resistance arteries and, furthermore, to examine whether exercise may restore dysfunctional dilatation of peripheral resistance arteries. Adult male Sprague-Dawley rats were divided into three groups: sham-operated, MI, and MI + exercise. Ultrastructure and relaxation function of the mesenteric arteries, as well as phosphatidylinositol-3 kinase (PI3K), Akt kinases (Akt), endothelial nitric oxide synthase (eNOS) activity, and phosphorylation of PI3K, Akt, and eNOS by ACh were determined. Post-MI rats exhibited pronounced ultrastructural changes in mesenteric artery endothelial cells and endothelial dysfunction. In addition, the activities of PI3K, Akt, and eNOS, and their phosphorylation by ACh were significantly attenuated in mesenteric arteries (P < 0.05-0.01). After 8 wk of exercise, not only did endothelial cells appeared more normal in structure, but also ameliorated post-MI-associated mesenteric arterial dysfunction, which were accompanied by elevated activities of PI3K, Akt, and eNOS, and their phosphorylation by ACh (P < 0.05-0.01). Importantly, inhibition of either PI3K or eNOS attenuated exercise-induced restoration of the dilatation function and blocked PI3K, Akt, and eNOS phosphorylation by ACh in the mesenteric arteries. These data demonstrate that MI induces dysfunctional dilation of peripheral resistance arteries by degradation of endothelial structural integrity and attenuating PI3K-Akt-eNOS signaling. Exercise may restore dilatation function of peripheral resistance arteries by protecting endothelial structural integrity and increasing PI3K-Akt-eNOS signaling cascades.

E0197 Effects of prior different intensities exercise on infarct region function and angiogenesis of left ventricle in myocardial infarction rats

ObjectiveLifestyle interventions including exercise training have been shown to be a feasible option for the prevention and treatment of cardiovascular diseases. In this study, we investigated the effects of prior...

Induction of Manganese Superoxide Dismutase by Nuclear Translocation and Activation of SIRT1 Promotes Cell Survival in Chronic Heart Failure

Oxidative stress plays a pivotal role in chronic heart failure. SIRT1, an NAD(+)-dependent histone/protein deacetylase, promotes cell survival under oxidative stress when it is expressed in the nucleus. However, adult cardiomyocytes predominantly express SIRT1 in the cytoplasm, and its function has not been elucidated. The purpose of this study was to investigate the functional role of SIRT1 in the heart and the potential use of SIRT1 in therapy for heart failure. We investigated the subcellular localization of SIRT1 in cardiomyocytes and its impact on cell survival. SIRT1 accumulated in the nucleus of cardiomyocytes in the failing hearts of TO-2 hamsters, postmyocardial infarction rats, and a dilated cardiomyopathy patient but not in control healthy hearts. Nuclear but not cytoplasmic SIRT1-induced manganese superoxide dismutase (Mn-SOD), which was further enhanced by resveratrol, and increased the resistance of C2C12 myoblasts to oxidative stress. Resveratrol's enhancement of Mn-SOD levels depended on the level of nuclear SIRT1, and it suppressed the cell death induced by antimycin A or angiotensin II. The cell-protective effects of nuclear SIRT1 or resveratrol were canceled by the Mn-SOD small interfering RNA or SIRT1 small interfering RNA. The oral administration of resveratrol to TO-2 hamsters increased Mn-SOD levels in cardiomyocytes, suppressed fibrosis, preserved cardiac function, and significantly improved survival. Thus, Mn-SOD induced by resveratrol via nuclear SIRT1 reduced oxidative stress and participated in cardiomyocyte protection. SIRT1 activators such as resveratrol could be novel therapeutic tools for the treatment of chronic heart failure.

Antioxidant Probucol Attenuates Myocardial Oxidative Stress and Collagen Expressions in Post-Myocardial Infarction Rats

This study was designed to evaluate the effects of the antioxidant probucol on myocardial oxidative stress and collagen remodeling by determining type I and III collagen together with relevant collagen mRNA expressions in both the infarcted and noninfarcted myocardium in post-myocardial infarction (MI) rats. Acute myocardial infarction was induced by ligation of the left anterior coronary artery in rats. Rats surviving 24 h after MI were randomly assigned to the group treated with vehicle or probucol. Sham-operated rats served as controls. Cardiac hemodynamics, parameters of oxidative stress in noninfarcted myocardium, collagen content, collagen volume density fraction, collagen type I and III together with the ratio, type I and III collagen mRNA were evaluated after 6 weeks. Probucol decreased oxidative stress as assessed by increased myocardial total antioxidative capacity, superoxide dismutase (SOD) activity, and SOD-to-myocardial malondialdehyde (MDA) ratio accompanied by decreased MDA level, decreased left ventricular end diastolic pressure and LV -dP/dtmax, and decreased collagen content and CVF in the noninfarcted area accompanied by decrease of type I and III mRNA expressions. The increase of collagen type I/III ratio in noninfarcted area was suppressed by probucol accompanied by inhibition of the increase in type I/III collagen mRNA ratio. Probucol did not affect collagen type I/III ratio and the corresponding mRNA ratio in the infarcted area. These results suggest that suppression of oxidative stress by probucol may attenuate collagen synthesis by inhibition of collagen mRNA expressions and improve diastolic function.

Role of γ-glutamyl transpeptidase in redox regulation of K+ channel remodeling in postmyocardial infarction rat hearts

gamma-Glutamyl transpeptidase (gamma-GT) is a key enzyme in GSH metabolism that regulates intracellular GSH levels in response to extracellular GSH (GSH(o)). The objective of this study was to identify the role of gamma-GT in reversing pathogenic K(+) channel remodeling in the diseased heart. Chronic ventricular dysfunction was induced in rats by myocardial infarction (MI), and studies were done after 6-8 wk. Biochemical assays of tissue extracts from post-MI hearts revealed significant increases in gamma-GT activity in left ventricle (47%) and septum (28%) compared with sham hearts, which paralleled increases in protein abundance and mRNA. Voltage-clamp studies of isolated left ventricular myocytes from post-MI hearts showed that downregulation of transient outward K(+) current (I(to)) was reversed after 4-5 h by 10 mmol/l GSH(o) or N-acetylcysteine (NAC(o)), and that the effect of GSH(o) but not NAC(o) was blocked by the gamma-GT inhibitors, acivicin or S-hexyl-GSH. Inhibition of gamma-glutamylcysteine synthetase by buthionine sulfoximine did not prevent upregulation of I(to) by GSH(o), suggesting that intracellular synthesis of GSH was not directly involved. However, pretreatment of post-MI myocytes with an SOD mimetic [manganese (III) tetrapyridylporphyrin] and catalase completely blocked recovery of I(to) by GSH(o). Confocal microscopy using the fluorogenic dye 2',7'-dichlorodihydrofluorescein diacetate confirmed that GSH(o) increased reactive oxygen species (ROS) generation by post-MI myocytes and to a lesser extent in myocytes from sham hearts. Furthermore, GSH(o)-mediated upregulation of I(to) was blocked by inhibitors of tyrosine kinase (genistein, lavendustin A, and AG1024) and thioredoxin reductase (auranofin and 13-cis-retinoic acid). These data suggest that GSH(o) elicits gamma-GT- and ROS-dependent transactivation of tyrosine kinase signaling that upregulates K(+) channel activity or expression via redox-mediated mechanisms. The signaling events stimulated by gamma-GT catalysis of GSH(o) may be a therapeutic target to reverse pathogenic electrical remodeling of the failing heart.

Chronic central versus systemic blockade of AT1 receptors and cardiac dysfunction in rats post-myocardial infarction

In rats, both central and systemic ANG II type 1 (AT(1)) receptor blockade attenuate sympathetic hyperactivity, but central blockade more effectively attenuates left ventricular (LV) dysfunction post-myocardial infarction (MI). In protocol I, we examined whether functional effects on cardiac load may play a role and different cardiac effects disappear after withdrawal of the blockade. Wistar rats were infused for 4 wk post-MI intracerebroventricularly (1 mg.kg(-1).day(-1)) or injected subcutaneously daily (100 mg x kg(-1) x day(-1)) with losartan. LV dimensions and function were assessed at 4 wk and at 6 wk post-MI, i.e., 2 wk after discontinuing treatments. At 4 and 6 wk post-MI, LV dimensions were increased and ejection fraction was decreased. Intracerebroventricular but not subcutaneous losartan significantly improved these parameters. At 6 wk, LV peak systolic pressure (LVPSP) and maximal or minimal first derivative of change in pressure over time (dP/dt(max/min)) were decreased and LV end-diastolic pressure (LVEDP) was increased. All four indexes were improved by previous intracerebroventricular losartan, whereas subcutaneous losartan improved LVEDP only. In protocol II, we evaluated effects of oral instead of subcutaneous administration of losartan for 4 wk post-MI. Losartan ( approximately 200 mg x kg(-1) x day(-1)) either via drinking water or by gavage similarly decreased AT(1) receptor binding densities in brain nuclei and improved LVEDP but further decreased LVPSP and dP/dt(max). These results indicate that effects on cardiac load by peripheral AT(1) receptor blockade or the pharmacokinetic profile of subcutaneous versus oral dosing do not contribute to the different cardiac effects of central versus systemic AT(1) receptor blockade post-MI.

A redox-metabolic-electrical remodeling in the diseased left and right ventricle: direct clinical implications in heart disease and beyond. Focus on “Role of γ-glutamyl transpeptidase in redox regulation of K+ channel remodeling in postmyocardial infarction rat hearts”

“Birth and death are not two different states, but they are different aspects of the same state …” — Mahatma Gandhi both our first and our last breath are associated with inhibition of voltage-gated K+ channels (Kv). Upon our first breath, the transition from the fetal to the adult

Endurance Training On Jak/stat Activation In The Left Ventricle Of Rat

The activation of Janus Kinase(JAK)/ signal transducers and activators of transcription(STAT) pathway has been reported to induce cardiac hypertrophy in genetically hypertensive and experimental post-myocardial infarction rats, as well as in isolated ventricular myocytes subject to mechanical stretch. Our previous study showed that acute exercise induced JAK/STAT pathway activation; however, no reports have documented the activation of JAK/STAT pathway in the myocardium of exercise-induced cardiac hypertrophy. PURPOSE: To evaluate endurance training on JAK/STAT3 pathway and Suppressor of cytokine signaling (SOCS) expression in myocardium in order to understand the mechanism of JAK/STAT3 pathway in exercise induced cardiac hypertrophy. METHODS: Male Sprague-Dawley rats(220±5g) were randomly divided into sedentary and exercise groups, rats in exercise group were submitted to grade treadmill training for 10 weeks, then sacrificed at 0hour and 24 hours after last exercise respectively. phosphorylated (p) - STAT3, STAT3, JAK1, JAK3 and SOCS1, SOCS2,SOCS6 expression in left ventricle determined with either western blot or immunohistochemistry. RESULTS: The heart/body weight ratio of exercised rats significantly higher in comparison with the sedentary rats (p<0.05); the percentage of JAK1 positive cells significantly increased immediately after the last running in exercised rats(p<0.01); however, the percentage of JAK3 positive cells showed no change either immediately or 24 hours after last exercise (p>0.05); p-STAT3/STAT3 ratio increased immediately after last exercise (p<0.05); while the percentage of SOCS1 and SOCS2 positive cells increased remarkably both immediately (p<0.01, p<0.05) and 24 hours (p<0.05) after last exercise, while SOCS6 expression showed no changes in exercised groups compared with the sedentary group(p>0.05). CONCLUSIONS: Exercise training that induced activation of JAK/STAT3 pathway might be related to the exercise-induced cardiac hypertrophy, the different responses of JAK1 and JAK3 might indicate the different functions of JAKs in exercised heart and the expression changes of SOCS1 and SOCS2 might be involved in regulating JAK/STAT3 signal pathway in exercised-induced cardiac hypertrophy.

Up-regulation of myocardial DNA base excision repair activities in experimental heart failure

Base excision repair (BER) is the major pathway to counteract the genotoxic effect of endogenous DNA damaging agents. The present study investigated the enzymatic activities and gene transcription of DNA glycosylases initiating BER in an experimental heart failure (HF) model. Rats were subjected to myocardial infarction or sham-operated. Twenty-eight days after surgical intervention cell-free protein extracts, total RNA and genomic DNA were isolated to analyze DNA glycosylase and AP-endonuclease activities, transcript levels of DNA glycosylases and accumulation of oxidative DNA damage. The capacity to remove major oxidation products (e.g., formamidopyrimidine and 5-hydroxycytosine) was significantly increased in the border zone of infarcted area, while the capacity to remove the highly mutagenic 8-oxoguanine residue was enhanced both in non-infarcted and infarcted areas of left ventricle (LV). DNA glycosylase activities towards 3-methyladenine and uracil were up-regulated in infarcted and non-infarcted areas of LV, indicating that generation of alkylated and deaminated base lesions on DNA increase during HF. Finally, we found no difference in accumulation of oxidative DNA damage in myocardial tissue between rats with post-myocardial infarction and sham-operated rats. This up-regulation of activities, initiating the BER pathway, could play an important role during HF by counteracting the effect of genotoxic stress, structural damage of tissue and myocardial remodeling.

Central infusion of aldosterone synthase inhibitor attenuates left ventricular dysfunction and remodelling in rats after myocardial infarction

Blockade of mineralocorticoid receptors in the central nervous system (CNS) prevents sympathetic hyperactivity and improves left ventricle (LV) function in rats post-myocardial infarction (MI). We examined whether aldosterone produced locally in the brain may contribute to the activation of mineralocorticoid receptors in the CNS. Two days after coronary artery ligation, Wistar rats received an intra-cerebroventricular (icv) infusion via osmotic mini-pumps of the aldosterone synthase inhibitor FAD286 at 100 microg/kg/day or vehicle for 4 weeks. LV function was assessed by echocardiography at 2 and 4 weeks, and by Millar catheter at 4 weeks. At 4 weeks post-MI, aldosterone in the hippocampus was increased by 70% and tended to increase in the hypothalamus by 20%. These increases were prevented by FAD286. Across groups, aldosterone in the hippocampus and hypothalamus showed a high correlation. There were no differences in brain corticosterone levels. Compared to sham rats, at both 2 and 4 weeks post-MI rats treated with vehicle showed increased LV dimensions and decreased LV ejection fraction. Icv infusion of FAD286 attenuated these changes in LV dimensions and ejection fraction by approximately 30%. At 4 weeks post-MI, LV peak systolic pressure (LVPSP) and dP/dt(max/min) were decreased and LV end-diastolic pressure (LVEDP) was increased. In rats treated with icv FAD286, LVPSP and dP/dt(min) remained normal and LVEDP and dP/dt(max) were markedly improved. Post-MI increases in cardiac fibrosis and cardiomyocyte diameter were substantially attenuated by icv FAD286. These data suggest that aldosterone produced locally in the brain acts as the main agonist of mineralocorticoid receptors in the CNS and contributes substantially to the progressive heart failure post MI.

Effects of K-201 on the calcium pump and calcium release channel of rat skeletal muscle

The benzothiazepine derivative K-201 has been suggested as a potential therapeutic agent due to its antiarrhythmogenic action. To understand how the drug alters calcium release from the sarcoplasmic reticulum (SR), we investigated its effects on the SR calcium channel and calcium pump by single channel electrophysiology, whole-cell confocal microscopy, and ATPase activity measurements on control and post-myocardial infarcted (PMI) rat skeletal muscle. In bilayers, K-201 induced two subconductance states corresponding to approximately 24% (S(1)) and approximately 13% (S(2)) of the maximum conductance. Dependence of event frequency and of time spent in S(1) and S(2) on the drug concentration was biphasic both in control and in PMI rats, with a maximum at 50 microM. At this concentration, the channel spends 26 +/- 4% and 24 +/- 4%, respectively, of the total time in these subconductance states at positive potentials, while no subconductances are observed at negative potentials. K-201 altered the frequency of elementary calcium release events: spark frequency decreased from 0.039 +/- 0.001 to 0.023 +/- 0.001 s(-1) sarcomere(-1), while the frequency of embers increased from 0.011 +/- 0.001 to 0.023 +/- 0.001 s(-1) sarcomere(-1). Embers with different amplitude levels were observed after the addition of the drug. K-201 inhibited the Ca(2+) ATPase characterized by IC(50,contr) = 119 +/- 21 muM and n (Hill,contr) = 1.84 +/- 0.48 for control and IC(50,PMI) = 122 +/- 18 microM and n (Hill,PMI) = 1.97 +/- 0.24 for PMI animals. These results suggest that although K-201 would increase the appearance of subconductance states, the overall calcium release is reduced by the drug. In addition, the effect of K-201 is identical on calcium release channels from control and PMI rats.

Changes of CT-1 and JAK/STAT Expression in Myocardium Induced by Acute Exercise

Cardiotrophin-1 (CT-1) has been reported to activate the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway. This activation induces cardiac hypertrophy in genetically hypertensive and experimental post-myocardial infarction rats, as well as in isolated ventricular myocytes subject to mechanical stretch. However, no reports have documented the activation of CT-1 and the JAK/ STAT pathway in the myocardium following exercise. PURPOSE: To investigate the immediate changes of CT-1 and JAK/STAT expressions in the myocardium following a single bout of strenuous treadmill running exercise. METHODS: Adult male Sprague-Dawley rats (220±5g, n=70) were randomly divided into sedentary (S) and exercise groups (E). Rats in exercise groups ran on a treadmill continuously at 8.5 m/min, 0% grade for 15 min, 15m/min, 5%grade for 15min, then followed by 10% grade at 19.5m/min till fatigue. After exercise, rats were sacrificed 0, 1, 3, 5, 12, and 24 hour (hr) s respectively. CT-1, STAT3, phosphorylated (p)-STAT3 and JAK1 expressions in the myocardium were determined with western immunoblots and immunohistochemistry. RESULTS: Expression of CT-1 tended to gradually increase after running, and but did not show significantly higher at any time points in comparison with the control group baroreflex function curve were lower in older subjects at rest. During exercise G (P>0.05), JAK1 expression significantly increased immediately after running, peaking at 1, 3, and 5 hrs(the percentage of JAK-positive cells was 19.0±2.2%, 20.4 ± 19.4%,21.0 ± 5.6%, respectively, all P<0.01), and remained elevated throughout 24 hrs (S: 9.2 ± 5.1%, vs. E:14.8 ± 2.4%, P<0.01).the percentage of STAT3-positive cells was significantly increased 1, 3, and 5,12 hrs(S: 33.8 ± 6.8%, E:64.4 ± 4.8%, 60.9 ±12.2%, 59.3 ±4.5%, 52.5 ± 2.6%, all P<0.01)after running, while p-STAT3 increased only from 1-5 hrs after running (S: 11.9 ± 9.7% vs. E: 30.7± 5.1%, 35.3 ± 5.4%, 47.7 ± 10.5%, P < 0.01). CONCLUSIONS: A single bout of exercise induces a trend to increase in CT-1 expression in the myocardium. This tendency to increase is linked to a clear activation of the JAK/STAT pathway in the myocardium, and is likely an early trigger for cardiac hypertrophy. Increased JAK1 expression remained elevated throughout 24 hrs post-exercise, whereas phosphorylation of STAT3 was transiently increased after acute exercise.

Endurance Training Modulates Lymphocyte Function in Rats with Post-MI CHF

Exercise training restores innate immune system cell function in post-myocardial infarction (post-MI) rats. However, studies of the involvement of lymphocyte (Ly) in the setting of the congestive heart failure (CHF) are few. To address this issue, we investigated the function of Ly obtained from cervical lymph nodes from post-MI CHF rats submitted to treadmill running training. Twenty-five male Wistar rats were randomly assigned to the following groups: rats submitted to ligation of the left coronary artery, which were sedentary (MI-S, N = 7, only limited activity) or trained (MI-T, N = 6, on a treadmill (0% grade at 13-20 m.m) for 60 min.d, 5 d.wk, for 8-10 wk); or sham-operated rats, which were sedentary (sham-S, N = 6) or trained (sham-T, N = 6). The incorporation of [2-C]-thymidine by Ly cultivated in the presence of concanavalin A (Con A) and lipopolysaccharide (LPS), cytokine production by Ly cultivated in the presence of phytohemagglutinin (PHA), and plasma concentration of glutamine were assessed in all groups, 48 h after the last exercise session. Proliferative capacity was increased, following incubation with Con-A in the MI groups, when compared with the sham counterparts. When incubated in the presence of PHA, MI-S produced more IL-4 (96%) than sham-S (P < 0.001). The training protocol induced a 2.2-fold increase in the production of interleukin-2 (P < 0.001) of the cells obtained from the cervical lymph nodes of MI-T, compared with MI-S. The moderate endurance training protocol caused an increase in IL-2 production, and a trend toward the reversion of the Th1/Th2 imbalance associated with IL-4 production increased in the post-MI CHF animal model.