Research progress of ghrelin on cardiovascular disease.

Ghrelin, a 28-aminoacid peptide, was isolated from the human and rat stomach and identified in 1999 as an endogenous ligand for the growth hormone secretagogue-receptor (GHS-R). In addition to stimulating appetite and regulating energy balance, ghrelin and its receptor GHS-R1a have a direct effect on the cardiovascular system. In recent years, it has been shown that ghrelin exerts cardioprotective effects, including the modulation of sympathetic activity and hypertension, enhancement of the vascular activity and angiogenesis, inhibition of arrhythmias, reduction in heart failure and inhibition of cardiac remodeling after myocardial infarction (MI). The cardiovascular protective effect of ghrelin may be associated with anti-inflammation, anti-apoptosis, inhibited sympathetic nerve activation, regulated autophagy, and endothelial dysfunction. However, the molecular mechanisms underlying the effects of ghrelin on the cardiovascular system have not been fully elucidated, and no specific therapeutic agent has been established. It is important to further explore the pharmacological potential of ghrelin pathway modulation for the treatment of cardiovascular diseases.

The new mechanism of Ghrelin/GHSR-1a on autophagy regulation.

Autophagy is associated with several diseases. In recent years, accumulating evidence has suggested that ghrelin pathway exerts a protective effect by regulating autophagy. This review aims to assess the potential role and use of ghrelin as a new treatment for obesity, cardiovascular diseases, nonalcoholic fatty liver disease (NFALD), neurodegenerative diseases, and tissue damage associated with autophagy. Ghrelin reduces the basal expression of autophagy-related genes in obesity-associated type 2 diabetes and ghrelin level changes in obesity, heart failure, and NFALD as well as altered autophagy. Ghrelin and its receptor GHSR-1 activation induce the phosphorylation of ERK1/2 and the induction of PI-3 kinase (PI3 K) and phosphorylation of Akt. In the myocardium and hypothalamic NPY/AgRP neurons, ghrelin increases levels of the intracellular energy sensor AMPK and enhances autophagy, protecting cardiac ischemia and inducing neural stem cells. Nonetheless, ghrelin activates the PI3 K/Akt/Bcl-2 pathway and inhibits the activation of autophagy, such as tissues injured by sepsis or doxorubicin. In conclusion, endogenous ghrelin system could be considered as a new target or treatment for metabolism disorders, cardiac diseases, neurodegenerative diseases, and tissue injuries.

Effects of Traditional Chinese Medicine Shensong Yangxin Capsules on Heart Rhythm and Function in Congestive Heart Failure Patients with Frequent Ventricular Premature Complexes: A Randomized, Double-blind, Multicenter Clinical Trial.

BACKGROUND: Pharmacological therapy for congestive heart failure (CHF) with ventricular arrhythmia is limited. In the study, our aim was to evaluate the effects of Chinese traditional medicine Shensong Yangxin capsules (SSYX) on heart rhythm and function in CHF patients with frequent ventricular premature complexes (VPCs). METHODS: This double-blind, placebo-controlled, multicenter study randomized 465 CHF patients with frequent VPCs to the SSYX (n = 232) and placebo groups (n = 233) for 12 weeks of treatment. The primary endpoint was the VPCs monitored by a 24-h ambulatory electrocardiogram. The secondary endpoints included the left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter, N-terminal pro-brain natriuretic peptide (NT-proBNP), New York Heart Association (NYHA) classification, 6-min walking distance (6MWD), Minnesota Living with Heart Failure Questionnaire (MLHFQ) scores, and composite cardiac events (CCEs). RESULTS: The clinical characteristics were similar at baseline. SSYX caused a significantly greater decline in the total number of VPCs than the placebo did (-2145 ± 2848 vs. -841 ± 3411, P < 0.05). The secondary endpoints of the LVEF, NYHA classification, NT-proBNP, 6MWD, and MLHFQ scores showed a greater improvements in the SSYX group than in the placebo group (ΔLVEF at 12th week: 4.75 ± 7.13 vs. 3.30 ± 6.53; NYHA improvement rate at the 8th and 12th week: 32.6% vs. 21.8%, 40.5% vs. 25.7%; mean level of NT-proBNP in patients with NT-proBNP ≥125 pg/ml at 12th week: -122 [Q1, Q3: -524, 0] vs. -75 [Q1, Q3: -245, 0]; Δ6MWD at 12th week: 35.1 ± 38.6 vs. 17.2 ± 45.6; ΔMLHFQ at the 4th, 8th, and 12th week: -4.24 ± 6.15 vs. -2.31 ± 6.96, -8.19 ± 8.41 vs. -3.25 ± 9.40, -10.60 ± 9.41 vs. -4.83 ± 11.23, all P < 0.05). CCEs were not different between the groups during the study period. CONCLUSIONS: In this 12-week pilot study, SSYX was demonstrated to have the benefits of VPCs suppression and cardiac function improvement with good compliance on a background of standard treatment for CHF. TRIAL REGISTRATION: www.chictr.org.cn, ChiCTR-TRC-12002061 (http://www.chictr.org.cn/showproj.aspx?proj=7487) and Clinicaltrials.gov, NCT01612260 (https://clinicaltrials.gov/ct2/show/NCT01612260).

Advances of the interleukin-21 signaling pathway in immunity and angiogenesis.

Interleukin-21 (IL-21) and its receptor (IL-21R) are broadly expressed on human B cells, activated T cells and other myeloid cells. IL-21 cooperates with IL-6 and transforming growth factor-ß to regulate T-cell differentiation. IL-21-mediated human B cell and dendritic cells differentiation requires signal transducer and activator of transcription 3 (STAT3), and also induces B-cell apoptosis dependents on the Toll-like receptor signal. Recently, in vitro and in vivo experiments showed that IL-21/IL-21R regulate angiogenesis through STAT3. IL-21 signaling pathways are complex due to its cooperation with other transcriptional factors, such as interferon regulatory factor 4 and granulocyte-macrophage colony-stimulating factor. The Janus kinase-STAT pathway has been the most extensively studied. With the increase in the understanding of IL-21 biology in the context of each specific disease or pathological condition, IL-21 could be a new therapeutic target for immune-related disease.

GHSR-1a is a novel pro-angiogenic and anti-remodeling target in rats after myocardial infarction.

Cardiac remodeling and subsequent heart failure is an increasing public health problem after myocardial infarction (MI). The aim of our research is to investigate whether gene therapy of growth hormone secretagogue receptor 1a may regulate cardiac remodeling and function after MI. Adenoviral vector expressing GHSR-1a or empty adeno-null was injected into rat peri-infarct myocardium after left anterior descending coronary artery ligation. GHSR-1a expression was confirmed by western blotting. 14 days after operation, haemodynamic and echocardiographic analysis demonstrated that GHSR-1a treatment significantly improved survive rate, increased scar thickness, preserved LV diameter, restored cardiac function and increased angiogenesis. There was no difference in infarct size between MI+Ad-GHSR-1a group and MI + Ad-null group. Additionally, increased protein expression of Akt phosphorylation and AMP-activated protein kinase phosphorylation in the infarct border myocardium were also observed. Moreover, GHSR-1a overexpression significantly enhanced tube formation in human umbilical endothelial cells (HUVECs) under ischemia condition. Knockdown of GHSR-1a by siRNA markedly decreased vascular endothelial growth factor expression as well as mRNA levels of Akt and AMPK. In conclusion, GHSR-1a gene therapy improves cardiac remodeling and function in rats after myocardial infarction. This may be a new anti-remodeling target to MI.

RETRACTED: Ghrelin protects infarcted myocardium by induction of autophagy and AMP-activated protein kinase pathway.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. It contains LM images in figure 2E, which were originally published in Nat. Comm. 6/2015, p. 1-14 (http://doi:10.1038/ncomms8388). Permission to reproduce this figure was not requested nor granted by the authors of the original article for its re-use. The authors of this article would like to apologize to all affected parties.

Exosomes Mediate the Intercellular Communication after Myocardial Infarction.

The mechanisms of cardiac repair after myocardial infarction (MI) are complicated and not well-understood currently. It is known that exosomes are released from most cells, recognized as new candidates with important roles in intercellular and tissue-level communication. Cells can package proteins and RNA messages into exosome and secret to recipient cells, which regulate gene expression in recipient cells. The research on exosomes in cardiovascular disease is just emerging. It is well-known that exosomes from cardiomyocyte can transfect endothelial cells, stem cells, fibroblasts and smooth muscle cells to induce cellular changes. After myocardial infarction (MI), the exosomes play important roles in local and distant microcommunication. Nowadays, exosomal microRNAs transportation has been found to deliver signals to mediate cardiac repair after MI. However, the exosomes quality and quantities are variable under different pathological conditions. Therefore, we speculate that the monitoring of the quality and quantity of exosomes may serve as diagnosis and prognosis biomarkers of MI, and the study of exosomes will provide insights for the new therapeutics to cardiac remodeling after MI.

Potential new role of the GHSR-1a-mediated signaling pathway in cardiac remodeling after myocardial infarction (Review).

The gastrointestinal hormone ghrelin has important cardiovascular protective effects, however, its specific mechanisms are not yet completely understood. Recent studies have shown that the ghrelin receptor, growth hormone secretagogue receptor type 1a (GHSR-1a), regulates cell proliferation, apoptosis and inflammation-related signaling pathways. In human aortic endothelial cells, ghrelin activates NO production through AMP-activated protein kinase (AMPK) and Akt activation, and these effects can be blocked by knockdown of GHSR-1a. Obese mice have been found to exhibit an increased GHSR-1a content and expression in the heart, associated with an increase in phosphatidylinositol 3-kinase (PI3K) content and an increase AKT content and phosphorylation. Furthermore, GHSR-1a expression was observed to be increased in heart failure after myocardial infarction (MI) in rats. Given such complexity in GHSR-1a signaling and crosstalk with the AMPK and PI3K/Akt signaling pathways, both of which are well-known factors involved in cardiac remodeling after MI, we speculate that GHSR-1a signaling may play a regulatory role in cardiac protection and hope to identify new drugs targets. However, to date, no direct association between GHSR-1a and cardiac remodeling has been found. Therefore, further studies are required.

Expression of ghrelin and its receptor in rats after coronary artery ligation.

Ghrelin is a novel growth hormone-releasing peptide, which has been shown to exert beneficial effects on cardiac function and ventricular remodeling. The present study aimed to investigate the expression of ghrelin and the growth hormone (GH) secretagogue receptor 1a (GHSR-1a), and the association with cardiac remodeling in rats with myocardial infarction (MI). Twenty-four hours after ligation of the anterior descending artery (LAD), adult male Sprague-Dawley rats were randomized to 3 d, 7 d and 28 d group. Sham animals underwent thoracotomy and pericardiotomy, but not LAD ligation. Expression of both ghrelin and GHSR-1a was assessed by means of immunohistochemistry and real-time PCR. Plasma ghrelin levels were measured by ELISA kit. In addition, cardiac remodeling was assessed by echocardiographic and hemodynamic measurements. Plasma and cardiac expression of ghrelin decreased on days 3, 7 and 28 compared with the sham group (P<0.05). In contrast the GHSR-1a mRNA levels increased during the same days (P<0.05). Decreased positive immunoreaction for ghrelin and increased positive GHSR-1a were also observed in the infarcted heart. Interestingly, plasma ghrelin correlated negatively with left ventricular end-diastolic pressure (r=-0.59, P=0.002) and left ventricular end-diastolic dimension (r=-0.73, P<0.01). The ghrelin system may play an important role regulating cardiac remodeling after MI and present as a potential significant target for pharmacological modulation and treating cardiac remodeling.

Myocardial angiogenesis after chronic ghrelin treatment in a rat myocardial infarction model.

Ghrelin has a protective role in a rat model of myocardial infarction (MI), but the underlying mechanism is not clear. Here, we investigated the effects of ghrelin treatment on angiogenesis in an experimental rat MI model. Adult male Sprague-Dawley rats were subjected to MI by ligating the anterior descending coronary artery. The rats were then treated with a subcutaneous injection of ghrelin (100 µg/kg) or saline (control group) for 4 weeks. Sham animals underwent thoracotomy and pericardiotomy, but not LAD ligation. At 28 days after ligation, the ghrelin treatment group showed a higher density of α-SMA positive vessels than the saline treatment MI group in myocardial infarct (6±2.1/mm(2) vs 4±1.8/mm(2), P<0.05) and peri-infarct zones (25±9.5/mm(2) vs 15±5.7/mm(2), P<0.05). RT-PCR and western-blot analyses showed that ghrelin significantly increased vascular endothelial growth factor (VEGF) expression in the peri-infarct zone compared with the control group. Moreover, there was a two-fold increase of Bcl-2 and a 3.5-fold reduction of the Bax protein in the ghrelin-treated MI group compared to the saline treatment MI group. Taken together, ghrelin could induce angiogenesis in rats after MI, the process that may be associated with the enhancement of VEGF and an anti-apoptosis effect.

P75 neurotrophin receptor is a regulatory factor in sudden cardiac death with myocardial infarction.

Sudden cardiac death (SCD) is a major cause of morbidity and mortality in patients with coronary artery diseases and myocardial infarction (MI). Sympathetic stimulation and sympathetic neural remodeling are important in the generation of SCD in diseased heart. The balance of nerve growth factor (NGF) and semaphoring 3A determines the sympathetic innervation patterning. Recently studies showed that P75 neurotrophin receptor (P75 NTR) is the main receptor for NGF mediates sympathetic hyperinnervation in the heart, and also interacts with semaphoring 3A. Sympathetic axons lacking P75 NTR are more sensitive to semaphoring 3A in vitro than control neurons, resulting in decreased sympathetic innervation in the left ventricular subendocardium. P75 NTR(-/-) mice had increased sympathetic heterogeneity and more spontaneous ventricular arrhythmias. Based on current studies, we present a hypothesis that P75 NTR plays an important regulatory role in sudden cardiac after myocardial infarction and hope to find new therapeutic target for SCD.

Effects of ghrelin on Cx43 regulation and electrical remodeling after myocardial infarction in rats.

Ghrelin is a novel growth hormone-releasing peptide, which has been shown to exert beneficial effects on ventricular remodeling. In this study, we investigated whether ghrelin could decrease vulnerability to ventricular arrhythmias in rats with myocardial infarction and the possible mechanism. Twenty-four hours after ligation of the anterior descending artery, adult male Sprague-Dawley rats were randomized to ghrelin (100 µg/kg) and saline (control group) for 4 weeks. Sham animals underwent thoracotomy and pericardiotomy, but not LAD ligation. Myocardial endothelin-1 (ET-1) levels were significantly elevated in saline-treated rats at the border zone compared with sham-operated rats. Myocardial connexin43 (Cx43) expression at the border zone was significantly decreased in saline-treated infarcted rats compared with sham-operated rats. Ghrelin significantly decreased the inducibility of ventricular tachyarrhythmias compared with control group. Arrhythmias sores during programmed stimulation in saline-treated rats were significantly higher than scores in those treated with ghrelin. The electrophysiological improvement of fatal ventricular tachyarrhythmias was accompanied with increased immunofluorescence-stained Cx43, myocardial Cx43 protein and mRNA levels in ghrelin treated rats. We also shown that ghrelin significantly decreased tissue ET-1 levels at the infarcted border zone. Thus, ghrelin showed the protective effect on ventricular arrhythmias after myocardial infarction. Although the precise mechanism by which ghrelin modulates the dephosphorylation of Cx43 remains unknown, it is most likely that the ghrelin increased expression of Cx43 through the inhibition of ET-1.

[Cardioprotective effect and mechanism of post-infarction ventricular remodeling after self-assembling peptide and thermosensitive hydrogel implantation in rat myocardial infarction model].

OBJECTIVE: To compare the cardioprotective effect of self-assembling peptide (RAD16-II) and thermosensitive hydrogel DPHP (Dex-PCL-HEMA/PNIPAAm) and investigate the optimal property of hydrogel for the treatment of myocardial infarction (MI). METHODS: MI model was induced by left anterior descending (LAD) coronary artery ligation in SD rats. The animals were randomized into three groups to receive RAD16-II hydrogel (n = 15), DPHP hydrogel (n = 15) or PBS (phosphate buffered saline; control group n = 15); sham-operated rats (n = 10), a suture was tied loosely around left coronary artery without ligating it. At Day 20 post-MI, left ventricle function was evaluated by echocardiography and cardiac catheter. Masson's trichrome was used for histological examination; anti-alpha-smooth muscle antigen (alpha-SMA) was applied to label the neovasculature formation in infarct area. RESULTS: The rats receiving DPHP hydrogel showed a significantly smaller left ventricle end diastolic diameter (LVEDd) and higher levels of left ventricle fraction shortening (LVFS) and left ventricle end systolic pressure (LVESP) than the rats in RAD16-II group [LVEDd (7.9 +/- 0.9) mm vs (8.9 +/- 0.8) mm]; [LVFS (25.4 +/- 5.1)% vs (21.9 +/- 2.9)%; LVESP (114.0 +/- 7.6) mm Hg vs (99.1 +/- 9.6) mm Hg; P < 0.05]. Histological examination showed uncompleted degraded hydrogel in infarct area of DPHP group but not in RAD16-II group. The animals receiving DPHP hydrogel demonstrated significantly a smaller infarct size, a higher infarct wall thickness and a lower vessel density in infarct than the animals receiving RAD16-II hydrogel (P < 0.05). CONCLUSION: DPHP hydrogel implantation further inhibits the post-MI ventricle remodeling than RAD16-II hydrogel implantation. The mechanism is not correlated with the vascular density in infarct area.

Injectable hydrogel helps bone marrow-derived mononuclear cells restore infarcted myocardium.

BACKGROUNDS: Experimental and clinical studies have suggested that cell implantation could improve cardiac function after myocardial infarction (MI). However, this technique was limited by decreased engraftment and survival of transplanted cells within the ischemic tissue. The present study was performed to investigate whether implantation of bone marrow-derived mononuclear cells (BMMNCs) encapsulated in hydrogel could increase cell engraftment and help to restore cardiac function of MI rabbits. METHODS: MI was induced in rabbits by coronary artery ligation. One week later, cell culture medium, Dex-PCL-HEMA/PNIPAAm hydrogel, BMMNCs in medium or BMMNCs in hydrogel were injected into the infarcted area of the left ventricle (LV). RESULTS: Increased cell engraftment was observed 48 h after injection when cells were encapsulated in hydrogel; 30 days after treatment, echocardiographic studies showed that injection of BMMNCs in hydrogel preserved LV ejection fraction and attenuated LV dilatation compared with other groups. Histological analysis indicated that injection of BMMNCs in hydrogel enhanced neovascular formation and prevented scar expansion compared with the other groups. CONCLUSION: Injection of hydrogel-encapsulated BMMNCs increased cell engraftment and improved LV function; this technique may serve as an effective approach to restore infarcted myocardium.

Ghrelin inhibits post-infarct myocardial remodeling and improves cardiac function through anti-inflammation effect.

Ghrelin is a novel growth hormone-releasing peptide, which has been shown to exert beneficial cardiac effects on chronic heart failure (CHF) recently. In this study, we attempted to investigate the mechanisms for the effect of ghrelin on ventricular remodeling following acute myocardial infarction (MI). Ligation of a coronary artery was used to create an MI in rats. One week after MI, ghrelin (100 microg/kg) or saline was injected subcutaneously twice a day for 4 weeks. When compared to sham groups, ghrelin administration significantly decreased left ventricular (LV) remodeling in post-MI rats, as indicated by increased LV maximum rate of pressure, LV fractional shortening and scar thickness; and decreased LV end-diastolic pressure, LV end-systolic diameter, LV end-diastolic diameter and cardiocytocytes apoptosis. Moreover, ghrelin inhibited the inflammatory response, as shown by decreased mRNA and protein levels of interleukin (IL)-1beta and tumor necrosis factor-alpha (TNF-alpha). Subsequently, the expression of matrix metalloproteinase (MMP)-2 and MMP-9 were also inhibited by ghrelin injection. Ghrelin alleviates LV dysfunction and ventricular remodeling in post-MI rats. This suggests that the beneficial effects of ghrelin on CHF may result from an inhibition of the inflammatory response.

A novel peptide ghrelin inhibits neural remodeling after myocardial infarction in rats.

Ghrelin is a newly discovered peptide as an endogenous ligand for the growth hormone secretagogue receptor, and has been demonstrated to exert beneficial effect in the cardiovascular system. In the present study, we investigated whether ghrelin administration could inhibit cardiac neural remodeling and sympathetic hyperinnervation after myocardial infarction. Sprague-Dawley rats underwent coronary ligation to induce myocardial infarction and receiving ghrelin chronically (100 microg/kg s.c., twice daily) or saline control for 4 weeks after onset of ischemia. Four weeks after treatment, rats were sacrificed. We examined the expression of nerve growth factor and never markers as well as the mRNA expressions of inflammatory mediators in the infarcted border and non-infarcted left ventricular free wall. We also examined the NF-kappaBp65 protein and I-kappaBalpha protein levels by Western blot analysis. Compared to the control group, ghrelin administration significantly decreased the density of nerve fibers with positive immunostaining for GAP43 and TH, and decreased NGF mRNA and protein levels in the infarcted border and the non-infarcted area. Ghrelin also significantly suppressed interleukin-1beta, tumor necrosis factor-alpha, and endothelin-l mRNA expression, and inhibited NF-kappaB activation. In conclusion, treatment with ghrelin inhibited neural remodeling and sympathetic hyperinnervation, the process that may be associated with the inhibition of proinflammatory response and NGF signaling.