Youngkeun Ahn

Inhibition of Histone Deacetylation Blocks Cardiac Hypertrophy Induced by Angiotensin II Infusion and Aortic Banding

Background— A number of distinct stress signaling pathways in myocardium cause cardiac hypertrophy and heart failure. Class II histone deacetylases (HDACs) antagonize several stress-induced pathways and hypertrophy. However, cardiac hypertrophy induced by transgenic overexpression of the homeodomain only protein, HOP, can be prevented by the nonspecific HDAC inhibitors trichostatin A and valproic acid, suggesting that alternate targets that oppose class II HDAC function might exist in myocardium. We tested the effects of several HDAC inhibitors, including a class I HDAC-selective inhibitor, SK-7041, on cardiac hypertrophy induced by angiotensin II (Ang II) treatment or aortic banding (AB). Methods and Results— Cardiac hypertrophy was induced by chronic infusion of Ang II or by AB in mice or rats and evaluated by determining the ratio of heart weight to body weight or to tibia length, cross-sectional area, or echocardiogram. Cardiac hypertrophy induced by Ang II or AB for 2 weeks was significantly reduced by simultaneous administration of trichostatin A, valproic acid, or SK-7041. Echocardiogram revealed that exaggerated left ventricular systolic dimensions were relieved by HDAC inhibitors. HDAC inhibitors partially reversed preestablished cardiac hypertrophy and improved survival of AB mice. The expressions of atrial natriuretic factor, &agr;-tubulin, &bgr;-myosin heavy chain, and interstitial fibrosis were reduced by HDAC inhibition. Conclusions— These results suggest that the predominant effect of HDAC inhibition, mainly mediated by class I HDACs, is to prevent cardiac hypertrophy in response to a broad range of agonist and stretch stimuli.

Nuclear Targeting of Akt Enhances Kinase Activity and Survival of Cardiomyocytes

Abstract— Heart failure is associated with death of cardiomyocytes leading to loss of contractility. Previous studies using membrane-targeted Akt (myristolated-Akt), an enzyme involved in antiapoptotic signaling, showed inhibition of cell death and prevention of pathogenesis induced by cardiomyopathic stimuli. However, recent studies by our group have found accumulation of activated Akt in the nucleus, suggesting that biologically relevant target(s) of Akt activity may be located there. To test this hypothesis, a targeted Akt construct was created to determine the antiapoptotic action of nuclear Akt accumulation. Nuclear localization of the adenovirally encoded Akt construct was confirmed by confocal microscopy. Cardiomyocytes expressing nuclear-targeted Akt showed no evidence of morphological remodeling such as altered myofibril density or hypertrophy. Nuclear-targeted Akt significantly elevated levels of phospho-Akt and kinase activity and inhibited apoptosis as effectively as myristolated-Akt in hypoxia-induced cell death. Transgenic overexpression of nuclear-targeted Akt did not result in hypertrophic remodeling, altered cardiomyocyte DNA content or nucleation, or enhanced phosphorylation of typical cytoplasmic Akt substrates, yet transgenic hearts were protected from ischemia-reperfusion injury. Gene array analyses demonstrated changes in the transcriptional profile of Akt/nuc hearts compared with nontransgenic controls distinct from prior characterizations of Akt expression in transgenic hearts. Collectively, these experiments show that targeting of Akt to the nucleus mediates inhibition of apoptosis without hypertrophic remodeling, opening new possibilities for therapeutic applications of nuclear-targeted Akt to inhibit cell death associated with heart disease.

Mesenchymal stem cells reciprocally regulate the M1/M2 balance in mouse bone marrow-derived macrophages

Mesenchymal stem cells (MSCs) have been widely studied for their applications in stem cell-based regeneration. During myocardial infarction (MI), infiltrated macrophages have pivotal roles in inflammation, angiogenesis and cardiac remodeling. We hypothesized that MSCs may modulate the immunologic environment to accelerate regeneration. This study was designed to assess the functional relationship between the macrophage phenotype and MSCs. MSCs isolated from bone marrow and bone marrow-derived macrophages (BMDMs) underwent differentiation induced by macrophage colony-stimulating factor. To determine the macrophage phenotype, classical M1 markers and alternative M2 markers were analyzed with or without co-culturing with MSCs in a transwell system. For animal studies, MI was induced by the ligation of the rat coronary artery. MSCs were injected within the infarct myocardium, and we analyzed the phenotype of the infiltrated macrophages by immunostaining. In the MSC-injected myocardium, the macrophages adjacent to the MSCs showed strong expression of arginase-1 (Arg1), an M2 marker. In BMDMs co-cultured with MSCs, the M1 markers such as interleukin-6 (IL-6), IL-1β, monocyte chemoattractant protein-1 and inducible nitric oxide synthase (iNOS) were significantly reduced. In contrast, the M2 markers such as IL-10, IL-4, CD206 and Arg1 were markedly increased by co-culturing with MSCs. Specifically, the ratio of iNOS to Arg1 in BMDMs was notably downregulated by co-culturing with MSCs. These results suggest that the preferential shift of the macrophage phenotype from M1 to M2 may be related to the immune-modulating characteristics of MSCs that contribute to cardiac repair.

Hybrid superparamagnetic iron oxide nanoparticle-branched polyethylenimine magnetoplexes for gene transfection of vascular endothelial cells.

The work demonstrated the development of thermally cross-linked superparamagnetic nanomaterial which possessed polyethylene glycol moiety and covalently linked branched polyethylenimine (BPEI), and exhibited highly efficient magnetofection even under serum conditioned media. The study showed its high anti-biofouling, cell viability and serum stability and thus revealed a potential magnetic nanoparticle-mediated targeted gene delivery system. This superparamagnetic particle mediated rapid and efficient transfection in primary vascular endothelial cells (HUVEC) successfully inhibits expression of PAI-1 which is responsible for various vascular dysfunctions such as vascular inflammation and atherosclerosis and thereby provides a potential strategy to transfect highly sensitive HUVEC. The sequential steps for the enhanced magnetofection had been studied by monitoring cellular uptake with the aid of confocal microscopy.

Curcumin attenuates inflammatory responses of TNF-alpha-stimulated human endothelial cells.

Curcumin, a yellow pigment of turmeric in curry, is reported to interfere with nuclear factor (NF)-κB. This study was designed to investigate the underlying pathway of antiinflammation of curcumin on endothelial cells. Human umbilical vein endothelial cells (HUVECs) were stimulated with 10 ng/mL tumor necrosis factor (TNF)-α. Curcumin blocked the activation of NF-κB by TNF-α. Curcumin also reduced the intracellular reactive oxygen species (ROS), monocyte adhesion, phosphorylation of c-Jun N-terminal kinase (JNK), p38, and signal transducer and activator of transcription (STAT)-3 in TNF-α-stimulated HUVECs. The expression of intracellular cell adhesion molecule (ICAM)-1, monocyte chemoattractant protein (MCP)-1, and interleukin (IL)-8 were attenuated by curcumin at both mRNA and protein level. Curcumin, however, did not affect the expression of TNF receptor I and II in TNF-α-stimulated HUVECs. We suggest that curcumin could contribute to protection against the adverse vascular effect of the proinflammatory response through the modulation of p38 and STAT-3 in addition to NF-κB and JNK in endothelial cells.

Characteristics, Outcomes and Predictors of Long-Term Mortality for Patients Hospitalized for Acute Heart Failure: A Report From the Korean Heart Failure Registry

Background and Objectives Acute heart failure (AHF) is associated with a poor prognosis and it requires repeated hospitalizations. However, there are few studies on the characteristics, treatment and prognostic factors of AHF. The aims of this study were to describe the clinical characteristics, management and outcomes of the patients hospitalized for AHF in Korea. Subjects and Methods We analyzed the clinical data of 3,200 hospitalization episodes that were recorded between June 2004 and April 2009 from the Korean Heart Failure (KorHF) Registry database. The mean age was 67.6±14.3 years and 50% of the patients were female. Results Twenty-nine point six percent (29.6%) of the patients had a history of previous HF and 52.3% of the patients had ischemic heart disease. Left ventricular ejection fraction (LVEF) was reported for 89% of the patients. The mean LVEF was 38.5±15.7% and 26.1% of the patients had preserved systolic function (LVEF ≥50%), which was more prevalent in the females (34.0% vs. 18.4%, respectively, p<0.001). At discharge, 58.6% of the patients received beta-blockers (BB), 53.7% received either angiotensin converting enzyme-inhibitors or angiotensin receptor blockers (ACEi/ARB), and 58.4% received both BB and ACEi/ARB. The 1-, 2-, 3- and 4-year mortality rates were 15%, 21%, 26% and 30%, respectively. Multivariate analysis revealed that advanced age {hazard ratio: 1.023 (95% confidence interval: 1.004-1.042); p=0.020}, a previous history of heart failure {1.735 (1.150-2.618); p=0.009}, anemia {1.973 (1.271-3.063); p=0.002}, hyponatremia {1.861 (1.184-2.926); p=0.007}, a high level of serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) {3.152 (1.450-6.849); p=0.004} and the use of BB at discharge {0.599 (0.360-0.997); p=0.490} were significantly associated with total death. Conclusion We present here the characteristics and prognosis of an unselected population of AHF patients in Korea. The long-term mortality rate was comparable to that reported in other countries. The independent clinical risk factors included age, a previous history of heart failure, anemia, hyponatremia, a high NT-proBNP level and taking BB at discharge.

Value of Early Risk Stratification Using Hemoglobin Level and Neutrophil-to-Lymphocyte Ratio in Patients With ST-Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Complete blood count is the most widely available laboratory datum in the early in-hospital period after ST-elevation myocardial infarction (STEMI). We assessed the clinical utility of the combined use of hemoglobin (Hb) level and neutrophil-to-lymphocyte ratio (N/L) for early risk stratification in patients with STEMI. We analyzed 801 consecutive patients with STEMI treated with primary percutaneous coronary intervention (PCI) within 12 hours of onset of symptoms. Patients with cardiogenic shock or underlying malignancy were excluded, and 739 patients (63 ± 13 years, 74% men) were included in the final analysis. Patients were categorized into 3 groups using the median value of N/L (3.86) and the presence of anemia (Hb <13 mg/dl in men and <12 mg/dl in women); group I had low N/L and no anemia (n = 272), group II had low N/L and anemia, or high N/L and no anemia (n = 331), and group III had high N/L and anemia (n = 136). There were significant differences on clinical outcomes during 6-month follow-up among the 3 groups. Prognostic discriminatory capacity of combined use of Hb level and N/L was also significant in high-risk subgroups such as patients with advanced age, diabetes mellitus, multivessel coronary disease, low ejection fraction, and even in those having higher mortality risk based on Thrombolysis In Myocardial Infarction risk score. In a Cox proportional hazards model, after adjusting for multiple covariates, group III had higher mortality at 6 months (hazard ratio 5.6, 95% confidence interval 1.1 to 27.9, p = 0.036) compared to group I. In conclusion, combined use of Hb level and N/L provides valuable timely information for early risk stratification in patients with STEMI undergoing primary PCI.

Benefit of Early Statin Therapy in Patients With Acute Myocardial Infarction Who Have Extremely Low Low-Density Lipoprotein Cholesterol

OBJECTIVES We investigated whether statin therapy could be beneficial in patients with acute myocardial infarction (AMI) who have baseline low-density lipoprotein cholesterol (LDL-C) levels below 70 mg/dl. BACKGROUND Intensive lipid-lowering therapy with a target LDL-C value <70 mg/dl is recommended in patients with very high cardiovascular risk. However, whether to use statin therapy in patients with baseline LDL-C levels below 70 mg/dl is controversial. METHODS We analyzed 1,054 patients with AMI who had baseline LDL-C levels below 70 mg/dl and survived at discharge from the Korean Acute MI Registry between November 2005 and December 2007. They were divided into 2 groups according to the prescribing of statins at discharge (statin group n = 607; nonstatin group n = 447). The primary endpoint was the composite of 1-year major adverse cardiac events, including death, recurrent MI, target vessel revascularization, and coronary artery bypass grafting. RESULTS Statin therapy significantly reduced the risk of the composite primary endpoint (adjusted hazard ratio [HR]: 0.56; 95% confidence interval [CI]: 0.34 to 0.89; p = 0.015). Statin therapy reduced the risk of cardiac death (HR: 0.47; 95% CI: 0.23 to 0.93; p = 0.031) and coronary revascularization (HR: 0.45, 95% CI: 0.24 to 0.85; p = 0.013). However, there were no differences in the risk of the composite of all-cause death, recurrent MI, and repeated percutaneous coronary intervention rate. CONCLUSIONS Statin therapy in patients with AMI with LDL-C levels below 70 mg/dl was associated with improved clinical outcome.

A20 Is Dynamically Regulated in the Heart and Inhibits the Hypertrophic Response

Background—Nuclear factor (NF)–&kgr;B signaling has been implicated in cardiomyocyte hypertrophy. Here, we determine the cardiac regulation and biological activity of A20, an inhibitor of NF-&kgr;B signaling. Methods and Results—Mice were subjected to aortic banding, and A20 expression was examined. A20 mRNA upregulation (4.3±1.5-fold; P <0.05) was detected 3 hours after banding, coinciding with peak NF-&kgr;B activation. A20 was also upregulated in cultured neonatal cardiomyocytes stimulated with phenylephrine or endothelin-1 (2.8±0.6- and 4±1.1-fold, respectively; P <0.05), again paralleling NF-&kgr;B activation. Infection of cardiomyocytes with an adenoviral vector (Ad) encoding A20 inhibited tumor necrosis factor-&agr;–stimulated NF-&kgr;B signaling with an efficacy comparable to dominant negative inhibitor of &kgr;-B kinase &bgr; (dnIKK&bgr;). Ad.dnIKK&bgr;-infected cardiomyocytes exhibited increased apoptosis when they were serum starved or subjected to hypoxia-reoxygenation, whereas Ad.A20-infected cardiomyocytes did not. Expression of Ad.A20 inhibited the hypertrophic response in cardiomyocytes stimulated with phenylephrine or endothelin-1. Conclusions—A20 is dynamically regulated during acute biomechanical stress in the heart and functions to attenuate cardiac hypertrophy through the inhibition of NF-&kgr;B signaling without sensitizing cardiomyocytes to apoptotic cell death.

Strategic advantages of insulin-like growth factor-I expression for cardioprotection

Insulin‐like growth factor‐I (IGF‐I) peptide has beneficial effects on cardiomyocyte function and survival, many of which are mediated through the serine‐threonine kinase, Akt. However, concerns about systemic effects of IGF‐I peptide limit its clinical application. The present study tested whether local IGF‐I expression could mediate cardioprotection without elevating serum [IGF‐I].