Quan Yi

Leptin Induces Hypertrophy via Endothelin-1–Reactive Oxygen Species Pathway in Cultured Neonatal Rat Cardiomyocytes

Background—Obesity is a major risk factor for the development of cardiovascular disease. Emerging evidence indicates that leptin, a protein encoded by the obesity gene, is linked with cardiac hypertrophy in obese humans and directly induces cardiomyocyte hypertrophy in vitro. However, the mechanisms by which leptin induces cardiomyocyte hypertrophy are poorly understood. Methods and Results—This study investigated how leptin contributes to cardiomyocyte hypertrophy. Cultured neonatal rat cardiomyocytes were used to evaluate the effects of leptin on hypertrophy. Both endothelin-1 (ET-1) and reactive oxygen species (ROS) levels were elevated in a concentration-dependent manner in cardiomyocytes treated with leptin for 4 hours compared with those cells without leptin treatment. ET-1 stimulated ROS production in a concentration-dependent manner in cardiomyocytes. The augmentation of ROS levels in cardiomyocytes treated with both leptin and ET-1 was reversed by a selective ETA receptor antagonist, ABT-627, and catalase, a hydrogen peroxide–decomposing enzyme. After treatment for 72 hours, leptin or ET-1 concentration-dependently increased total RNA levels, cell surface areas, and protein synthesis in cardiomyocytes, all of which were significantly inhibited by ABT-627 or catalase treatment. ConclusionsThese findings indicate that leptin elevates ET-1 and ROS levels, resulting in hypertrophy of cultured neonatal rat cardiac myocytes. The ET-1–ETA–ROS pathway may be involved in cardiomyocyte hypertrophy induced by leptin. ETA receptor antagonists and antioxidant therapy may provide an effective means of ameliorating cardiac dysfunction in obese humans.

Impaired autophagy contributes to adverse cardiac remodeling in acute myocardial infarction.

Objective Autophagy is activated in ischemic heart diseases, but its dynamics and functional roles remain unclear and controversial. In this study, we investigated the dynamics and role of autophagy and the mechanism(s), if any, during postinfarction cardiac remodeling. Methods and results Acute myocardial infarction (AMI) was induced by ligating left anterior descending (LAD) coronary artery. Autophagy was found to be induced sharply 12–24 hours after surgery by testing LC3 modification and Electron microscopy. P62 degradation in the infarct border zone was increased from day 0.5 to day 3, and however, decreased from day 5 until day 21 after LAD ligation. These results indicated that autophagy was induced in the acute phase of AMI, and however, impaired in the latter phase of AMI. To investigate the significance of the impaired autophagy in the latter phase of AMI, we treated the mice with Rapamycin (an autophagy enhancer, 2.0 mg/kg/day) or 3-methyladenine (3MA, an autophagy inhibitor, 15 mg/kg/day) one day after LAD ligation until the end of experiment. The results showed that Rapamycin attenuated, while 3MA exacerbated, postinfarction cardiac remodeling and dysfunction respectively. In addition, Rapamycin protected the H9C2 cells against oxygen glucose deprivation in vitro. Specifically, we found that Rapamycin attenuated NFκB activation after LAD ligation. And the inflammatory response in the acute stage of AMI was significantly restrained with Rapamycin treatment. In vitro, inhibition of NFκB restored autophagy in a negative reflex. Conclusion Sustained myocardial ischemia impairs cardiomyocyte autophagy, which is an essential mechanism that protects against adverse cardiac remodeling. Augmenting autophagy could be a therapeutic strategy for acute myocardial infarction.

A physiological concentration of glucocorticoid inhibits the pro-inflammatory cytokine-induced proliferation of adult rat cardiac fibroblasts: roles of extracellular signal-regulated kinase 1/2 and nuclear factor-κB.

1. Inflammation‐induced proliferation of cardiac fibroblasts plays an important role in cardiac remodelling. Pharmacological doses of exogenous glucocorticoids (GC) are the most effective therapy for inflammatory diseases. Similarly, physiological concentrations of endogenous GC have recently been shown to have anti‐inflammatory effects. Therefore, the aim of the present study was to determine whether a physiological concentration of GC could inhibit pro‐inflammatory cytokine‐stimulated proliferation of cardiac fibroblasts and to explore the mechanisms involved.

TGF-β Regulates Survivin to Affect Cell Cycle and the Expression of EGFR and MMP9 in Glioblastoma.

Transforming growth factor beta (TGF-β) is suggestive of a molecular target for cancer therapy due to its involvement in cell cycle, differentiation, and morphogenesis. Meanwhile, survivin is identified as an apoptosis inhibitor and involved in tumorgenesis. Here, we aimed to investigate the potential associations between TGF-β and survivin in glioblastoma U87 cell line. Survivin small interfering RNA (siRNA), Western blotting, and cell cycle analysis were introduced to detect relevant proteins in TGF-β pathways. In this study, we observed a concentration- and time-dependent increase of survivin expression after treatment with TGF-β1. However, the kinase inhibitors U0126 and LY294002 inhibited the upregulation of survivin in comparison with DMSO. In addition, survivin siRNA effectively abrogated survivin expression in U87 cells, therefore affected cells’ entry into the S phase of cell cycle, and then repressed the expression of epidermal growth factor receptor (EGFR) and matrix metalloproteinase 9 (MMP9) in comparison with non-transfection. In conclusion, the present study shows that TGF-β upregulates survivin expression via ERK and PI3K/AKT pathway, leading to glioblastoma cell cycle progression. Thus, the blockade of survivin will allow for the treatment of glioblastoma, partially attributing to the inhibition of EGFR and MMP9 expression.

Protection of Long-Term Treatment With Huang-Lian-Jie-Du-Tang on Vascular Endothelium in Rats With Type 2 Diabetes Mellitus

BACKGROUND Huang-Lian-Jie-Du-Tang (HLJDT) is the classical traditional Chinese recipe for heat clearance and detoxification and is used in diabetic patients in the clinical practice of traditional Chinese medicine. OBJECTIVE The aim of this study was to evaluate the protective effects of long-term treatment with HLJDT on vascular endothelial function in rats with type 2 diabetes mellitus (T2DM). METHODS The male T2DM model rats were induced by intraperitoneal injection of low-dose streptozotocin plus a high-fat and high-calorie laboratory diet. The T2DM animals were randomly divided into the T2DM model group, the low-dose HLJDT group (0.42 g/kg/d), and the high-dose HLJDT group (1.25 g/kg/d). RESULTS Administration of HLJDT (0.42 or 1.25 g/kg/d) for 8 weeks decreased the levels of serum fasting blood glucose, malondialdehyde, and vascular tissue interleukin 6 but raised the level of serum superoxide dismutase compared with the T2DM model group in a dose-dependent manner. In addition, HLJDT treatment restored the impaired endothelial-dependent vascular relaxation in aortic preparations from the T2DM model group in a dose-dependent manner. CONCLUSIONS Early and long-term treatments with HLJDT could have anti-inflammatory, antioxidant properties and could protect vascular endothelium from the cardiovascular complications associated with T2DM.

Suppression of Kv1.5 protects against endothelial apoptosis induced by palmitate and in type 2 diabetes mice.

Aims: Palmitate, a common saturated free fatty acid, induces endothelial apoptosis in vitro in culture endothelial cells and in vivo in type 2 diabetes mellitus (T2DM) patients. The present study aimed to investigate whether Kv1.5 regulates palmitate‐induced endothelial apoptosis and endothelial dysfunction in T2DM. Main methods: In vitro experiments were carried out in primary human HUVECs. Apoptosis was analyzed by flow cytometry. Cell viability was determined by Cell Counting Assay Kit‐8. The siRNA transfection was employed to knockdown Kv1.5 protein expression. Intracellular and mitochondrial ROS, and mitochondrial membrane potential were detected using fluorescent probes. Male C57BL/6 mice fed with high‐sucrose/fat diet were injected with streptozotocin (35 mg/kg body weight) to establish T2DM animal model. Key findings: We found that palmitate‐induced endothelial apoptosis was parallel to a significant increase in endogenous Kv1.5 protein expression in endothelial cells. Silencing of Kv1.5 with siRNA reduced palmitate‐induced endothelial apoptosis, intracellular ROS generation, mitochondrial ROS generation and membrane potential (&Dgr;&psgr;m) alteration and cleaved caspase‐3 protein expression; while increased cell viability and ratio of Bcl‐2/Bax. Furthermore, we observed that Kv1.5 protein expression increased in endothelial cells of thoracic aorta of T2DM mice. Silencing of Kv1.5 significantly improved the endothelium‐dependent vasodilation in thoracic aortic rings of T2DM mice. Significance: These results demonstrate that suppression of Kv1.5 protects endothelial cells against palmitate‐induced apoptosis via inhibiting mitochondria‐mediated excessive ROS generation and apoptotic signaling pathway, suggesting that Kv1.5 may serve as a therapeutic target of treatment for endothelial dysfunction induced by palmitate and lipid metabolism in T2DM patients.

Retraction Note to: TGF-β Regulates Survivin to Affect Cell Cycle and the Expression of EGFR and MMP9 in Glioblastoma

Transforming growth factor beta (TGF-β) is suggestive of a molecular target for cancer therapy due to its involvement in cell cycle, differentiation, and morphogenesis. Meanwhile, survivin is identified as an apoptosis inhibitor and involved in tumorgenesis. Here, we aimed to investigate the potential associations between TGF-β and survivin in glioblastoma U87 cell line. Survivin small interfering RNA (siRNA), Western blotting, and cell cycle analysis were introduced to detect relevant proteins in TGF-β pathways. In this study, we observed a concentration- and time-dependent increase of survivin expression after treatment with TGF-β1. However, the kinase inhibitors U0126 and LY294002 inhibited the upregulation of survivin in comparison with DMSO. In addition, survivin siRNA effectively abrogated survivin expression in U87 cells, therefore affected cells’ entry into the S phase of cell cycle, and then repressed the expression of epidermal growth factor receptor (EGFR) and matrix metalloproteinase 9 (MMP9) in comparison with non-transfection. In conclusion, the present study shows that TGF-β upregulates survivin expression via ERK and PI3K/AKT pathway, leading to glioblastoma cell cycle progression. Thus, the blockade of survivin will allow for the treatment of glioblastoma, partially attributing to the inhibition of EGFR and MMP9 expression.

HDAC2 is required by the physiological concentration of glucocorticoid to inhibit inflammation in cardiac fibroblasts

We previously suggested that endogenous glucocorticoids (GCs) may inhibit myocardial inflammation induced by lipopolysaccharide (LPS) in vivo. However, the possible cellular and molecular mechanisms were poorly understood. In this study, we investigated the role of physiological concentration of GCs in inflammation induced by LPS in cardiac fibroblasts and explored the possible mechanisms. The results showed that hydrocortisone at the dose of 127 ng/mL (equivalent to endogenous basal level of GCs) inhibited LPS (100 ng/mL)-induced productions of TNF-α and IL-1β in cardiac fibroblasts. Xanthine oxidase/xanthine (XO/X) system impaired the anti-inflammatory action of GCs through downregulating HDAC2 activity and expression. Knockdown of HDAC2 restrained the anti-inflammatory effects of physiological level of hydrocortisone, and blunted the ability of XO/X system to downregulate the inhibitory action of physiological level of hydrocortisone on cytokines. These results suggested that HDAC2 was required by the physiological concentration of GC to inhibit inflammatory response. The dysfunction of HDAC2 induced by oxidative stress might be account for GC resistance and chronic inflammatory disorders during the cardiac diseases.