[Show abstract][Hide abstract] ABSTRACT: Activation of conventional PKCs (cPKC) is a key signaling that directs the cardiac toxicity of hyperglycemia. AKAP150, a scaffold protein of the A-kinase anchoring proteins (AKAPs) family, is less defined regarding its capability to anchor and regulate cardiac cPKC signaling. This study was designed to investigate the role of AKAP150 in cPKC-mediated cardiac glucotoxicity. In cardiac tissues from streptozotocin induce-diabetic rats and high glucose-treated neonatal rat cardiomyocytes, both mRNA and protein levels of AKAP150 increased significantly, and marked elevations were observed in cPKC activity and both expression and phosphorylation levels of p65NF-κB and p47(phox). AKAP150 knockdown was established via intramyocardial injection in vivo and transfection in vitro of adenovirus carrying AKAP150-targeted shRNA. Downregulation of AKAP150 reversed diabetes-induced diastolic dysfunction as manifested by decreased left ventricular end-diastolic diameter and early/late mitral diastolic wave ratio. AKAP150 inhibition also abrogated high glucose-induced cardiomyocyte apoptosis (TUNEL staining and annexin V/PI flow cytometry) and oxidative stress (ROS production, NADPH oxidase activity and lipid peroxidation). More importantly, reduced AKAP150 expression significantly inhibited high glucose-induced membrane translocation and activation of cPKC, and suppressed the increases in the phosphorylation of p65NF-κB and p47(phox). Immunofluorescent co-expression and immunoprecipitation indicated enhanced anchoring of AKAP150 with cPKC within the plasma membrane under hyperglycemia, and AKAP150 preferentially co-localized and functionally bound with PKC α and β isoforms. These results suggest that cardiac AKAP150 positively responds to hyperglycemia and enhances the efficiency of glucotoxicity signaling through a cPKC/p47phox/ROS pathway that induces myocardial dysfunction, cardiomyocyte apoptosis and oxidative stress.
American journal of physiology. Endocrinology and metabolism. 07/2014;
[Show abstract][Hide abstract] ABSTRACT: Cannabinoid receptor type 2 (CB2) activation is recently reported to promote proliferation of some types of resident stem cells (e.g., hematopoietic stem/progenitor cell or neural progenitor cell). Resident cardiac progenitor cell (CPC) activation and proliferation are crucial for endogenous cardiac regeneration and cardiac repair after myocardial infarction (MI). This study aims to explore the role and possible mechanisms of CB2 receptor activation in enhancing myocardial repair. Our results revealed that CB2 receptor agonist AM1241 can significantly increase CPCs by c-kit and Runx1 staining in ischemic myocardium as well as improve cardiomyocyte proliferation. AM1241 also decreased serum levels of MDA, TNF-α and IL-6 after MI. In addition, AM1241 can ameliorate left ventricular ejection fraction and fractional shortening, and reduce fibrosis. Moreover, AM1241 treatment markedly increased p-Akt and HO-1 expression, and promoted Nrf-2 nuclear translocation. However, PI3K inhibitor wortmannin eliminated these cardioprotective roles of AM1241. In conclusion, AM1241 could induce myocardial regeneration and improve cardiac function, which might be associated with PI3K/Akt/Nrf2 signaling pathway activation. Our findings may provide a promising strategy for cardiac endogenous regeneration after MI.
Science China. Life sciences 01/2014; · 2.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Impaired cardiac microvascular function contributes to cardiovascular complications in diabetes. Glucagon-like peptide-1 (GLP-1) exhibits potential cardioprotective properties in addition to its glucose-lowering effect. This study was designed to evaluate the impact of GLP-1 on cardiac microvascular injury in diabetes and the underlying mechanism involved. Experimental diabetes was induced using streptozotocin in rats. Cohorts of diabetic rats received a 12-week treatment of vildagliptin (DPP-4 inhibitor) or exenatide (GLP-1 analog). Experimental diabetes attenuated cardiac function, glucose uptake, and microvascular barrier function, which were significantly improved by vildagliptin or exenatide treatment. Cardiac microvascular endothelial cells were isolated and cultured in normal or high glucose medium with or without GLP-1. GLP-1 decreased high-glucose-induced reactive oxygen species production and apoptotic index, as well as the levels of NADPH oxidase such as p47(phox) and gp91(phox). Furthermore, cAMP/PKA (cAMP-dependent protein kinase activity) was increased and Rho-expression was decreased in high-glucose-induced cardiac microvascular endothelial cells after GLP-1 treatment. In conclusion, GLP-1 could protect the cardiac microvessels against oxidative stress, apoptosis, and the resultant microvascular barrier dysfunction in diabetes, which may contribute to the improvement of cardiac function and cardiac glucose metabolism in diabetes. The protective effects of GLP-1 are dependent on downstream inhibition of Rho through a cAMP/PKA-mediated pathway.
[Show abstract][Hide abstract] ABSTRACT: Ghrelin is a well-characterized hormone that has protective effects on endothelial cells. Elevated HCY (homocysteine) can be a cardiovascular risk factor, but it is not known whether ghrelin can inhibit HCY-induced dysfunction and inflammatory response in rat CMECs (cardiac microvascular endothelial cells). We found that HCY treatment for 24 h inhibited proliferation and NO (nitric oxide) secretion, but with increased cell apoptosis and secretion of cytokines in CMECs. In contrast, ghrelin pretreatment significantly improved proliferation and NO secretion, and inhibited cell apoptosis and secretion of cytokines in HCY-induced CMECs. In addition, Western blot assay showed that NF-κB (nuclear factor κB) and cleaved-caspase 3 expression were elevated, and PCNA (proliferating cell nuclear antigen) and eNOS (endothelial nitric oxide synthase) expression were decreased after treatment with HCY, which was significantly reversed by pretreatment with ghrelin. The data suggest that ghrelin inhibits HCY-induced CMEC dysfunction and inflammatory response, probably mediated by inhibition of NF-κB activation.
Cell Biology International 02/2012; 36(6):511-7. · 1.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Obesity is a risk factor for the development of certain respiratory diseases, and neonatal overfeeding results in an early onset of obesity in adulthood. However, the influence of neonatal overfeeding on respiratory diseases has rarely been studied. Therefore, this paper is aimed at investigating the effect of neonatal overfeeding on airway responsiveness and inflammation. METHODOLOGY/PRINCIPAL FINDINGS: The neonatal overfeeding was induced by reducing litter size to three pups per litter (small litter, SL) in contrast to the normal litter size with ten pups per litter (NL) on postnatal day 3 (P3) in male ICR mice. On P21, mice were weaned to standard chow diet. Airway responsiveness to methacholine was measured either on P21 or P150. Total and classified inflammatory cells in bronchoalveolar lavage fluid (BALF) were counted, lung inflammatory cells were evaluated through staining with hematoxylin & eosin and F4/80 immunohistochemistry; lung fibrosis was evaluated through staining with Masson and α-SAM immunohistochemistry. Leptin levels in serum were measured by RIA; TNF-α levels in serum and BALF were quantified by ELISA; mRNA levels of TNF-α, CTGF and TGF-β1 in lung tissues were measured using real-time PCR. Mice from SL exhibited accelerated body weight gain, impaired glucose tolerance and hyperleptinemia. Enhanced airway responsiveness to methacholine was observed in SL mice on P150, but not on P21. Pulmonary inflammation was evident in SL mice on P150, as reflected by inflammatory cells especially macrophages around bronchi and interstitium. BALF and serum TNF-α levels and lung TNF-α mRNA expression were significantly increased in SL mice on P150. More collagen accumulated surrounding the bronchi on P150; lung mRNA levels of TGF-β1 and CTGF were also increased on P150. CONCLUSION: In addition to inducing a variety of metabolic defects, neonatal overfeeding enhanced lung inflammation, which may lead to airway remodeling and airway hyperresponsiveness in adulthood.
PLoS ONE 01/2012; 7(10):e47013. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aims: To determine the effects of percutaneous coronary intervention (PCI) on cardiac perfusion, cardiac function, and quality of life in patients with chronic total occlusion (CTO) lesion in left anterior descending (LAD) coronary artery.Methods and Results: Patients (n=99) with CTO lesion in the LAD coronary artery who had successfully undergone PCI were divided into three groups based on the SPECT/CTCA fusion imaging: (a) no severe cardiac perfusion defects (n=9); (b) reversible cardiac perfusion defects (n=40); or (c) fixed cardiac perfusion defects (n=50). No statistical difference of perfusion abnormality was observed at 6 months and 1 year after PCI in group (a). In group (b), SPECT/CTCA fusion imaging demonstrated that cardiac perfusion abnormality was significantly decreased 6 month and 1 year after PCI. Left ventricular ejection fraction (LVEF) increased significantly at 6 months and 1 year follow up. Quality of life improved at 6 months and 1 year after PCI procedure. Moreover, patients in group (c) also benefited from PCI therapy: a decrease in cardiac perfusion abnormality, an increase in LVEF, and an improvement in quality of life. PCI of coronary arteries in addition to LAD did not significantly affect cardiac function and quality of life improvement in each group.Conclusions: PCI exerts functional and clinical benefits in patients with CTO lesion in LAD coronary artery, particularly in patients with reversible cardiac perfusion defects. SPECT/CTCA fusion imaging may serve as a useful tool to evaluate the outcomes of patients with CTO lesion in LAD coronary artery.
[Show abstract][Hide abstract] ABSTRACT: Ghrelin is thought to directly exert a protective effect on the cardiovascular system, specifically by promoting vascular endothelial cell function. Our study demonstrates the ability of ghrelin to promote rat CMEC (cardiac microvascular endothelial cell) proliferation, migration and NO (nitric oxide) secretion. CMECs were isolated from left ventricle of adult male Sprague-Dawley rat by enzyme digestion and maintained in endothelial cell medium. Dil-ac-LDL (1,1'-dioctadecyl-3,3,3',3'- tetramethylindocarbocyanine-labelled acetylated low-density lipoprotein) intake assays were used to identify CMECs. Cells were split into five groups and treated with varying concentrations of ghrelin as follows: one control non-treated group; three ghrelin dosage groups (1×10-9, 1×10-8, 1×10-7 mol/l) and one ghrelin+PI3K inhibitor group (1×10-7 mol/l ghrelin+20 μmol/l LY294002). After 24 h treatment, cell proliferation capability was measured by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay and Western blot for PCNA (proliferating cell nuclear antigen) protein expression. Migration of CMECs was detected by transwell assays, and NO secretion of CMECs was measured via nitrate reduction. Protein expression of AKT and phosphorylated AKT in CMECs was measured by Western blot after exposure to various concentrations of ghrelin and the PI3K inhibitor LY294002. Our results indicate that ghrelin significantly enhanced cell growth at concentrations of 10-8 mol/l (0.271±0.041 compared with 0.199±0.021, P = 0.03) and 10-7 mol/l (0.296±0.039 compared with 0.199±0.021, P<0.01). However, addition of the PI3K/AKT inhibitor LY294002 inhibited the ghrelin-mediated enhancement in cell proliferation (0.227±0.042 compared with 0.199±0.021, P = 0.15). At a concentration between 10-8 and 10-7 mol/l, ghrelin caused a significant increase in the number of migrated cells compared with the control group (126±9 compared with 98±7, P = 0.02; 142±6 compared with 98±7, P<0.01), whereas no such change could be observed in the presence of 20 μmol/l of the PI3K/Akt inhibitor LY294002 (103±7 compared with 98±7, P = 0.32). Ghrelin treatment significantly enhanced NO production in a dose-dependent fashion compared with the untreated control group [(39.93±2.12) μmol/l compared with (30.27±2.71) μmol/l, P = 0.02; (56.80±1.98) μmol/l compared with (30.27±2.71) μmol/l, P<0.01]. However, pretreatment with 20 μmol/l LY294002 inhibited the ghrelin-stimulated increase in NO secretion [(28.97±1.64) μmol/l compared with (30.27±2.71) μmol/l, P = 0.37]. In summary, we have found that ghrelin treatment promotes the proliferation, migration and NO secretion of CMECs through activation of PI3K/AKT signalling pathway.
Cell Biology International 02/2011; 35(2):135-40. · 1.64 Impact Factor