Mingya Liu

Repeated remote ischemic postconditioning protects against adverse left ventricular remodeling and improves survival in a rat model of myocardial infarction.

Rationale: Remote ischemic conditioning induced by repeated episodes of transient limb ischemia is a clinically applicable method for protecting the heart against injury at the time of reperfusion. Objective: To assess the effect of chronic, repeated, remote conditioning on infarct size and long-term remodeling after myocardial infarction. Methods and Results: Rats with ischemia/reperfusion injury received different protocols of remote limb conditioning. While a single early episode of remote ischemic conditioning during coronary occlusion (perconditioning) resulted in a decrease in infarct size on both day 4 and day 28, when it was repeated (postconditioning) intermittently (every 3 days) and intensively (every day), it was not associated with a further decrease in infarct size. However, the protection against adverse remodeling offered by a single episode of limb perconditioning was further enhanced by repeated remote postconditioning therapy in a dose-dependent manner. In separate experiments there was a dose-dependent improvement in survival at 84 days by Kaplan–Meier analysis. Conclusions: Whereas a single early episode of remote perconditioning reduces infarct size, repeated remote postconditioning further reduces adverse LV remodeling and improves survival in a dose-dependent fashion. These data may have clinical implications for the treatment of patients with evolving myocardial infarction.

Apelin-13 protects the heart against ischemia-reperfusion injury through inhibition of ER-dependent apoptotic pathways in a time-dependent fashion

Endoplasmic reticulum (ER) stress is activated during and contributes to ischemia-reperfusion (I/R) injury. Attenuation of ER stress-induced apoptosis protects the heart against I/R injury. Using apelin, a ligand used to activate the apelin APJ receptor, which is known to be cardioprotective, this study was designed to investigate 1) the time course of changes in I/R injury after ER stress; 2) whether apelin infusion protects the heart against I/R injury via modulation of ER stress-dependent apoptosis signaling pathways; and 3) how phosphatidylinositol 3-kinase (PI3K)/Akt, endothelial nitric oxide synthase (eNOS), AMP-activated protein kinase (AMPK), and ERK activation are involved in the protection offered by apelin treatment. The results showed that, using an in vivo rat I/R model induced by 30 min of ischemia followed by reperfusion, infarct size (IS) increased from 2 h of reperfusion (34.85 ± 2.14%) to 12 h of reperfusion (48.98 ± 3.35, P < 0.05), which was associated with an abrupt increase in ER stress-dependent apoptosis activation, as evidenced by increased CCAAT/enhancer-binding protein homologous protein (CHOP), caspase-12, and JNK activation (CHOP: 2.49-fold increase, caspase-12: 2.09-fold increase, and JNK: 3.38-fold increase, P < 0.05, respectively). Administration of apelin at 1 μg/kg not only completely abolished the activation of ER stress-induced apoptosis signaling pathways at 2 h of reperfusion but also significantly attenuated time-related changes at 24 h of reperfusion. Using pharmacological inhibition, we also demonstrated that PI3K/Akt, AMPK, and ERK activation were involved in the protection against I/R injury via inhibition of ER stress-dependent apoptosis activation. In contrast, although eNOS activation played a role in decreasing IS at 2 h of reperfusion, it failed to modify either IS or ER stress-induced apoptosis signaling pathways at 24 h after reperfusion.

Resveratrol protects cardiomyocytes from oxidative stress through SIRT1 and mitochondrial biogenesis signaling pathways

Reactive oxygen species (ROS) is generated by oxidative stress and plays an important role in various cardiac pathologies. The SIRT1 signaling pathway and mitochondrial biogenesis play essential roles in mediating the production of ROS. SIRT1 activated by resveratrol protects cardiomyocytes from oxidative stress, but the exact mechanisms by which SIRT1 prevents oxidative stress, and its relationship with mitochondrial biogenesis, remain unclear. In this study, it was observed that after stimulation with 50μMH2O2 for 6h, H9C2 cells produced excessive ROS and downregulated SIRT1. The mitochondrial protein NDUFA13 was also downregulated by ROS mediated by SIRT1. Resveratrol induced the expression of SIRT1 and mitochondrial genes NDUFA1, NDUFA2, NDUFA13 and Mn-SOD. However, the production of these genes was reversed by SIRT1 inhibitor nicotinamide. These results suggest that resveratrol inhibits ROS generation in cardiomyocytes via SIRT1 and mitochondrial biogenesis signaling pathways.

Fasudil Protects the Heart against Ischemia-Reperfusion Injury by Attenuating Endoplasmic Reticulum Stress and Modulating SERCA Activity: The Differential Role for PI3K/Akt and JAK2/STAT3 Signaling Pathways

Disordered calcium homeostasis can lead to endoplasmic reticulum (ER) stress. Our previous data showed that time course activation of ER stress contributes to time-related increase in ischemia-reperfusion (I/R) injury. However, it has not been tested whether PI3K/Akt and JAK2/STAT3 pathways play differential roles in reducing ER stress to protect the heart. In the present study, using fasudil which is a specific inhibitor of ROCK, we aimed to investigate whether improved SERCA expression and activity accounts for reduced ER stress by ROCK inhibition, specifically whether PI3K/Akt and JAK2/STAT3 pathways are differentially involved in modulating SERCA activity to reduce ER stress and hence I/R injury. The results showed that during the reperfusion period following 45 min of coronary ligation the infarct size (IS) increased from 3 h of reperfusion (45.4±5.57%) to 24 h reperfusion (64.21±5.43, P<0.05), which was associated with ER stress dependent apoptosis signaling activation including CHOP, Caspase-12 and JNK (P<0.05, respectively).The dynamic ER stress activation was also related to impaired SERCA activity at 24 h of reperfusion. Administration of fasudil at 10 mg/Kg significantly attenuated ROCK activation during reperfusion and resulted in an improved SERCA activity which was closely associated with decreases in temporal activation of ER stress and IS changes. Interestingly, while both PI3K/Akt and JAK2/STAT3 signaling pathways played equal role in the protection offered by ROCK inhibition at 3 h of reperfusion, the rescued SERCA expression and activity at 24 h of reperfusion by fasudil was mainly due to JAK2/STAT3 activation, in which PI3K/Akt signaling shared much less roles.

Resveratrol suppresses the STAT3 signaling pathway and inhibits proliferation of high glucose-exposed HepG2 cells partly through SIRT1

Hepatocellular carcinoma is the most common type of liver cancer. The risk of hepatocellular carcinoma for type 2 diabetic patients is greater than that for non-diabetic individuals although the mechanism is unclear. The cancer suppressor resveratrol inhibits cancer cell proliferation partly through the STAT3 signaling pathway. However, the effects of resveratrol on STAT3 in high glucose-exposed HepG2 cells and the role of SIRT1 are not clear to date. The aim of the present study was to investigate the effects of resveratrol on STAT3 and SIRT1 regarding the proliferation of high glucose-exposed HepG2 cells. HepG2 cells were cultured in DMEM containing glucose (2.8, 5.5 and 25 mM) and resveratrol (0, 10 and 100 µM). HepG2 cell proliferation and viability were analyzed by MTT assays. The levels of p-STAT3 and SIRT1 were analyzed by western blotting, and RT-PCR methods were used to detect the transcription levels of cyclin B1, cyclin D1, VEGF and MMP-9. SIRT1-specific short-interfering RNA was used to investigate the role of SIRT1 in p-STAT3 signaling. A high glucose concentration (25 mM) induced HepG2 cell proliferation. This effect was suppressed by resveratrol (100 µM), and the effect on the p-STAT3 signaling pathway was found to be SIRT1-dependent. Our findings may provide new insights into the mechanism by which resveratrol suppresses HepG2 cell proliferation under conditions of high glucose. Furthermore, this information may provide the basis for a novel therapeutic strategy for hepatocellular carcinoma patients suffering from either diabetes or hyperglycemia.

Circulating adipocyte fatty acid-binding protein levels are independently associated with heart failure

A-FABP (adipocyte fatty acid-binding protein), one of the most abundant proteins in adipocytes, plays a key role in obesity-related insulin resistance, inflammation and atherosclerosis in animals. In the present study, we sought to investigate the association of A-FABP with HF (heart failure) in Chinese subjects. Serum A-FABP levels were measured in 252 HF patients and 261 age-, gender- and BMI (body mass index)-matched non-HF subjects. Echocardiography was performed on each patient. The severity of HF was determined by the NYHA (New York Heart Association) classification system. After adjustments for age, gender and BMI, serum A-FABP concentrations in patients with HF were significantly higher than in non-HF patients [11.17 (6.63-19.93) ng/ml compared with 5.67 (3.20-8.87) ng/ml; P<0.001] and significantly progressed with the NYHA class (P<0.001). In addition, NT-proBNP (N-terminal pro-brain natriuretic peptide) was independently and positively correlated with A-FABP (standardized β=0.340, P<0.001) after adjusting for confounding factors. Each echocardiographic parameter, especially LVEF (left ventricular ejection fraction), was independently associated with A-FABP (all P<0.05). Multivariate logistic regression analysis demonstrated that A-FABP concentration was an independent risk factor for HF [odds ratio, 6.93 (95% confidence interval, 2.49-19.30); P<0.001]. Our results demonstrate that A-FABP is closely associated with HF, and raise the possibility that increased A-FABP may be causally related to the pathogenesis of heart dysfunction in humans.

Apelin-13 stimulates angiogenesis by promoting cross‑talk between AMP-activated protein kinase and Akt signaling in myocardial microvascular endothelial cells

Currently, there is major interest in the functions of apelin-13, an endogenous ligand for the orphan G-protein coupled receptor APJ, a receptor that closely resembles the angiotensin receptor AT1. In the present study, the role of apelin-13 in angiogenesis and its mechanism as a novel angiogenic factor in myocardial microvascular endothelial cells (MMVECs) was investigated. It was revealed that apelin-13 can promote proliferation, migration and tube formation in MMVECs. In addition, apelin-13 dose dependently stimulated the phosphorylation of AMP-activated protein kinase (AMPK) and endothelial nitric oxide synthase (eNOS) at Thr-172 and Ser-1179, respectively. The treatment with the AMPK (compound C) and protein kinase Akt/protein kinase B (Akt; LY294002) inhibitor significantly suppressed the apelin‑13-induced AMPK, Akt and eNOS phosphorylation. They also inhibited the apelin13‑stimulated endothelial cell migration and tube formation. Therefore, we hypothesize that apelin-13 promotes angiogenesis through the modulation of AMPK and Akt signaling in MMVECs.

Simvastatin attenuates sympathetic hyperinnervation to prevent atrial fibrillation during the postmyocardial infarction remodeling process

Statin, as a 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitor, has been shown to prevent atrial fibrillation (AF) due to its anti-inflammatory and antioxidant effects. However, it is still not known whether statin can improve autonomic remodeling to prevent AF. In the present study, using an in vivo rat myocardial infarction (MI) model, we aimed to test whether simvastatin can attenuate nerve sprouting and sympathetic hyperinnervation to prevent AF during the post-MI remodeling process. Our data demonstrate that simvastatin, delivered 3 days after MI for 4 wk, can result in significant decreases in plasma levels of both TNF-α (239 ± 23 pg/ml) and IL-1β (123 ± 11 pg/ml) compared with MI rats without therapy (TNF-α, 728 ± 57 pg/ml; IL-1β, 213 ± 21 pg/ml; P < 0.05), which, however, were still higher than sham-operated rats (TNF-α, 194 ± 20 pg/ml; IL-1β, 75 ± 8 pg/ml; P < 0.05). The similar pattern of changes in inflammation responses was also observed in TNF-α and IL-1β protein expression in the left atrium free wall. The suppressed inflammation responses were associated with reduced superoxide and malondialdehyde generation in the atrium. These changes account for decreases in neural growth factor expression at levels of both mRNA (1.2 ± 0.09 AU vs. MI group, 1.78 ± 0.16 AU) and protein (1.57 ± 0.17 AU vs. MI group, 2.24 ± 0.19 AU; P < 0.05), thus resulting in reduced nerve sprouting and sympathetic hyperinnervation. Accordingly, the rate adaptation of the atrial effective refractory period also recovered, leading to the decreased inducibility of AF. These data suggest that simvastatin administration after MI can prevent AF through reduced sympathetic hyperinnervation.

Interference of GSM mobile phones with communication between Cardiac Rhythm Management devices and programmers: A combined in vivo and in vitro study

To investigate interference, and how to avoid it, by high-frequency electromagnetic fields (EMFs) of Global System for Mobile Communications (GSM) mobile phone with communication between cardiac rhythm management devices (CRMs) and programmers, a combined in vivo and in vitro testing was conducted. During in vivo testing, GSM mobile phones interfered with CRM-programmer communication in 33 of 65 subjects tested (50.8%). Losing ventricle sensing was representative in this study. In terms of clinical symptoms, only 4 subjects (0.6%) felt dizzy during testing. CRM-programmer communication recovered upon termination of mobile phone communication. During in vitro testing, electromagnetic interference by high-frequency (700-950 MHz) EMFs reproducibly occurred in duplicate testing in 18 of 20 CRMs (90%). During each interference, the pacing pulse signal on the programmer would suddenly disappear while the synchronous signal was normal on the amplifier-oscilloscope. Simulation analysis showed that interference by radiofrequency emitting devices with CRM-programmer communication may be attributed to factors including materials, excitation source distance, and implant depth. Results suggested that patients implanted with CRMs should not be restricted from using GSM mobile phones; however, CRMs should be kept away from high-frequency EMFs of GSM mobile phone during programming.