Yi-Gang Li

Micro-RNA-34a Contributes to the Impaired Function of Bone Marrow-Derived Mononuclear Cells From Patients With Cardiovascular Disease

OBJECTIVES This study evaluated the regulation and function of micro-RNAs (miRs) in bone marrow-mononuclear cells (BMCs). BACKGROUND Although cell therapy with BMCs may represent a therapeutic option to treat patients with heart disease, the impaired functionality of patient-derived cells remains a major challenge. Small noncoding miRs post-transcriptionally control gene expression patterns and play crucial roles in modulating cell survival and function. METHODS Micro-RNAs were detected by miR profiling in BMCs isolated from healthy volunteers (n = 6) or from patients with myocardial infarction (n = 6), and the results were confirmed by polymerase chain reaction (PCR) in a larger cohort (n = 37). The function of selected miRs was determined by gain-of-function studies in vitro and by locked nuclear acid (LNA) modified inhibitors in vitro and in vivo. RESULTS We identified several miRs that are up-regulated in BMCs from patients with myocardial infarction compared with BMCs from healthy controls, including the pro-apoptotic and antiproliferative miR-34a and the hypoxia-controlled miR-210. Inhibition of miR-34 by LNA-34a significantly reduced miR-34a expression and blocked hydrogen peroxide-induced cell death of BMC in vitro, whereas overexpression of miR-34a reduced the survival of BMCs in vitro. Pre-treatment of BMCs with LNA-34a ex vivo significantly increased the therapeutic benefit of transplanted BMCs in mice after acute myocardial infarction (AMI). CONCLUSIONS These results demonstrate that cardiovascular disease modulates the miR expression of BMCs in humans. Reducing the expression of the pro-apoptotic miR-34a improves the survival of BMCs in vitro and enhances the therapeutic benefit of cell therapy in mice after AMI.

Digoxin Is Associated With Increased All-cause Mortality in Patients With Atrial Fibrillation Regardless of Concomitant Heart Failure: A Meta-analysis.

Abstract: For decades, digoxin has been widely used to control ventricular rate in atrial fibrillation (AF). However, it remains controversial as to whether digoxin is associated with increased mortality in AF. In this study, we searched relevant studies that were published before December 1, 2014, in PubMed, EMBASE, and the Cochrane central databases. We systematically reviewed the references and performed a meta-analysis of 8 carefully selected studies with 302,738 patients who were included for the final analysis. It was shown that digoxin use was associated with increased risk of all-cause mortality in AF overall [hazard ratio (HR) = 1.375, 95% confidence intervals (CI), 1.201–1.574, P = 0.0001]. Subgroup analysis further revealed that digoxin was associated with increased all-cause mortality in patients with AF, which was complicated by heart failure (HF) (HR = 1.201, CI, 1.074– 1.344, P = 0.001), and in those subjects without HF (HR = 1.172, CI, 1.148–1.198, P = 0.0001). Sensitivity analyses found results to be robust. Our findings indicated that digoxin use was associated with significantly increased all-cause mortality in patients with AF regardless of concomitant HF. We suggest that digoxin should not be preferentially used over other rate control medications in AF.

Resveratrol protects rabbit ventricular myocytes against oxidative stress-induced arrhythmogenic activity and Ca2+ overload.

Aim:To investigate whether resveratrol suppressed oxidative stress-induced arrhythmogenic activity and Ca2+ overload in ventricular myocytes and to explore the underlying mechanisms.Methods:Hydrogen peroxide (H2O2, 200 μmol/L)) was used to induce oxidative stress in rabbit ventricular myocytes. Cell shortening and calcium transients were simultaneously recorded to detect arrhythmogenic activity and to measure intracellular Ca2+ ([Ca2+]i). Ca2+/calmodulin-dependent protein kinases II (CaMKII) activity was measured using a CaMKII kit or Western blotting analysis. Voltage-activated Na+ and Ca2+ currents were examined using whole-cell recording in myocytes.Results:H2O2 markedly prolonged Ca2+ transient duration (CaTD), and induced early afterdepolarization (EAD)-like and delayed afterdepolarization (DAD)-like arrhythmogenic activity in myocytes paced at 0.16 Hz or 0.5 Hz. Application of resveratrol (30 or 50 μmol/L) dose-dependently suppressed H2O2-induced EAD-like arrhythmogenic activity and attenuated CaTD prolongation. Co-treatment with resveratrol (50 μmol/L) effectively prevented both EAD-like and DAD-like arrhythmogenic activity induced by H2O2. In addition, resveratrol markedly blunted H2O2-induced diastolic [Ca2+]i accumulation and prevented the myocytes from developing hypercontracture. In whole-cell recording studies, H2O2 significantly enhanced the late Na+ current (INa,L) and L-type Ca2+ current (ICa,L) in myocytes, which were dramatically suppressed or prevented by resveratrol. Furthermore, H2O2-induced ROS production and CaMKII activation were significantly prevented by resveratrol.Conclusion:Resveratrol protects ventricular myocytes against oxidative stress-induced arrhythmogenic activity and Ca2+ overload through inhibition of INa,L/ICa,L, reduction of ROS generation, and prevention of CaMKII activation.

Rac1b enhances cell survival through activation of the JNK2/c-JUN/Cyclin-D1 and AKT2/MCL1 pathways

Rac1b is a constitutively activated, alternatively spliced form of the small GTPase Rac1. Previous studies showed that Rac1b promotes cell proliferation and inhibits apoptosis. In the present study, we used microarray analysis to detect genes differentially expressed in HEK293T cells and SW480 human colon cancer cells stably overexpressing Rac1b. We found that the pro-proliferation genes JNK2, c-JUN and cyclin-D1 as well as anti-apoptotic AKT2 and MCL1 were all upregulated in both lines. Rac1b promoted cell proliferation and inhibited apoptosis by activating the JNK2/c-JUN/cyclin-D1 and AKT2/MCL1 pathways, respectively. Very low Rac1b levels were detected in the colonic epithelium of wild-type Sprague-Dawley rats. Knockout of the rat Rac1 gene exon-3b or knockdown of endogenous Rac1b in HT29 human colon cancer cells downregulated only the AKT2/MCL1 pathway. Our study revealed that very low levels of endogenous Rac1b inhibit apoptosis, while Rac1b upregulation both promotes cell proliferation and inhibits apoptosis. It is likely the AKT2/MCL1 pathway is more sensitive to Rac1b regulation.

Pharmacogenetics-based warfarin dosing algorithm decreases time to stable anticoagulation and the risk of major hemorrhage: an updated meta-analysis of randomized controlled trials.

Abstract: Warfarin is yet the most widely used oral anticoagulant for thromboembolic diseases, despite the recently emerged novel anticoagulants. However, difficulty in maintaining stable dose within the therapeutic range and subsequent serious adverse effects markedly limited its use in clinical practice. Pharmacogenetics-based warfarin dosing algorithm is a recently emerged strategy to predict the initial and maintaining dose of warfarin. However, whether this algorithm is superior over conventional clinically guided dosing algorithm remains controversial. We made a comparison of pharmacogenetics-based versus clinically guided dosing algorithm by an updated meta-analysis. We searched OVID MEDLINE, EMBASE, and the Cochrane Library for relevant citations. The primary outcome was the percentage of time in therapeutic range. The secondary outcomes were time to stable therapeutic dose and the risks of adverse events including all-cause mortality, thromboembolic events, total bleedings, and major bleedings. Eleven randomized controlled trials with 2639 participants were included. Our pooled estimates indicated that pharmacogenetics-based dosing algorithm did not improve percentage of time in therapeutic range [weighted mean difference, 4.26; 95% confidence interval (CI), −0.50 to 9.01; P = 0.08], but it significantly shortened the time to stable therapeutic dose (weighted mean difference, −8.67; 95% CI, −11.86 to −5.49; P < 0.00001). Additionally, pharmacogenetics-based algorithm significantly reduced the risk of major bleedings (odds ratio, 0.48; 95% CI, 0.23 to 0.98; P = 0.04), but it did not reduce the risks of all-cause mortality, total bleedings, or thromboembolic events. Our results suggest that pharmacogenetics-based warfarin dosing algorithm significantly improves the efficiency of International Normalized Ratio correction and reduces the risk of major hemorrhage.

Prolonged P-wave duration is associated with atrial fibrillation recurrence after radiofrequency catheter ablation: A systematic review and meta-analysis.

BACKGROUND/OBJECTIVES A change in the P-wave duration (PWD) was made in patients with atrial fibrillation recurrence (AFR) after radiofrequency catheter ablation (RFCA). The correlation between the PWD and AFR and the potential utilization of a prolonged PWD in the prediction of AFR after RFCA remains unclear. METHODS Studies of PWD in patients with or without AFR after RFCA, and studies concerned with the predictive effect of prolonged PWD on AFR after RFCA, were included. Outcome measures are reported as absolute risk differences with 95% confidence intervals. A receiver operating characteristic (ROC) curve was used to evaluate the potential cutoff value of PWD for AFR. Summary receiver operating characteristic curve (SROC) analysis was performed to show the overall predictive value of PWD for AFR. RESULTS Nine studies were included. The overall effect test based on 8 studies that contained a total cohort of 1010 patients showed a highly significant association between prolonged PWD and AFR after RFCA (Z=14.20, P<0.000). A summary that included 4 studies with a combined total of 593 patients indicated a higher risk of AFR in patients with prolonged PWD (Z=5.86, P<0.000). ROC curve analysis indicated 149.5ms as the potential cutoff value of PWD for AFR after RFCA. SROC analysis suggested an acceptable predictive efficiency of PWD for AFR (AUC=0.66). CONCLUSIONS The risk of AFR after RFCA is strongly related to a prolonged PWD. PWD is one potential low-cost and feasible predictor of AFR after RFCA.

The crucial role of activin A/ALK4 pathway in the pathogenesis of Ang-II-induced atrial fibrosis and vulnerability to atrial fibrillation

AbstractsAtrial fibrosis, the hallmark of structural remodeling associated with atrial fibrillation (AF), is characterized by abnormal proliferation of atrial fibroblasts and excessive deposition of extracellular matrix. Transforming growth factor-β1 (TGF-β1)/activin receptor-like kinase 5 (ALK5)/Smad2/3/4 pathway has been reported to be involved in the process. Recent studies have implicated both activin A and its specific downstream component activin receptor-like kinase 4 (ALK4) in stimulating fibrosis in non-cardiac organs. We recently reported that ALK4 haplodeficiency attenuated the pressure overload- and myocardial infarction-induced ventricular fibrosis. However, the role of activin A/ALK4 in the pathogenesis of atrial fibrosis and vulnerability to AF remains unknown. Our study provided experimental and clinical evidence for the involvement of activin A and ALK4 in the pathophysiology of atrial fibrosis and AF. Patients with AF had higher activin A and ALK4 expression in atriums as compared to individuals devoid of AF. After angiotensin-II (Ang-II) stimulation which mimicked atrial fibrosis progression, ALK4-deficient mice showed lower expression of ALK4 in atriums, reduced activation of atrial fibroblasts, blunted atrial enlargement and atrial fibrosis, and further reduced AF vulnerability upon right atrial electrophysiological studies as compared to wild-type littermates. Moreover, we found that apart from the well-known TGF-β1/ALK5 pathway, the activation of activin A/ALK4/smad2/3 pathway played an important role in the pathogenesis of Ang-II-mediated atrial fibrosis and inducibility of AF, suggesting that targeting ALK4 might be a potential therapy for atrial fibrosis and AF.

Docosahexaenoic Acid Attenuates Doxorubicin-induced Cytotoxicity and Inflammation by Suppressing NF-κB/iNOS/NO Signaling Pathway Activation in H9C2 Cardiac Cells.

Abstract: Doxorubicin (DOX) is a widely used antineoplastic agent for a variety of carcinomas. However, it is cardiotoxic and leads to cardiomyopathy. Previous studies have indicated that omega-3 polyunsaturated acids (&ohgr;-3 PUFAs) have therapeutic effects on dilated and diabetic cardiomyopathies. However, whether &ohgr;-3 PUFAs exert therapeutic effects on DOX-induced cardiomyopathy remains unclear. In this study, we explored the effect and underlying mechanisms of docosahexaenoic acid (DHA), an important type of &ohgr;-3 PUFA, on DOX-induced cardiotoxicity and inflammation. H9C2 cardiac cells were exposed to DOX (5 &mgr;M) and interfered with by DHA (10 &mgr;M) for 4 hours. The effect of DHA on H9C2 cell viability was measured by Cell Counting Kit-8 assay. The levels of mRNA and protein expression of inflammatory cytokines were determined by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Reactive oxygen species and nitric oxide (NO) levels were determined by corresponding kits. The protein expression of key molecules in the nuclear factor-kappa B/inducible isoform of nitric oxide synthase/nitric oxide (NF-&kgr;B/iNOS/NO) signaling pathway was determined by western blotting. DOX-induced significant cytotoxicity and reactive oxygen species production in H9C2 cardiac cells. It also induced cardiac inflammation as evidenced by significantly increased expressions of inflammatory cytokines, including tumor necrosis factor-&agr;, interleukin-6, interleukin-1&bgr;, monocyte chemoattractant protein-1, and inducible isoform of NO synthase. However, DHA effectively attenuated DOX-induced cytotoxicity and inflammation. A further mechanistic study revealed that DHA suppressed DOX-induced activation of the NF-&kgr;B/iNOS/NO signaling pathway in H9C2 cells. Our results indicate that DHA may protect against DOX-induced cardiotoxicity by inhibiting NF-&kgr;B/iNOS/NO signaling pathway activation.

Crucial Role of ROCK2-Mediated Phosphorylation and Upregulation of FHOD3 in the Pathogenesis of Angiotensin II–Induced Cardiac HypertrophyNovelty and Significance

Cardiac hypertrophy is characterized by increased myofibrillogenesis. Angiotensin II (Ang-II) is an essential mediator of the pressure overload–induced cardiac hypertrophy in part through RhoA/ROCK (small GTPase/Rho-associated coiled-coil containing protein kinase) pathway. FHOD3 (formin homology 2 domain containing 3), a cardiac-restricted member of diaphanous-related formins, is crucial in regulating myofibrillogenesis in cardiomyocytes. FHOD3 maintains inactive through autoinhibition by an intramolecular interaction between its C- and N-terminal domains. Phosphorylation of the 3 highly conserved residues (1406S, 1412S, and 1416T) within the C terminus (CT) of FHOD3 by ROCK1 is sufficient for its activation. However, it is unclear whether ROCK-mediated FHOD3 activation plays a role in the pathogenesis of Ang-II–induced cardiac hypertrophy. In this study, we detected increases in FHOD3 expression and phosphorylation in cardiomyocytes from Ang-II–induced rat cardiac hypertrophy models. Valsartan attenuated such increases. In cultured neonate rat cardiomyocytes, overexpression of phosphor-mimetic mutant FHOD3-DDD, but not wild-type FHOD3, resulted in myofibrillogenesis and cardiomyocyte hypertrophy. Expression of a phosphor-resistant mutant FHOD3-AAA completely abolished myofibrillogenesis and attenuated Ang-II–induced cardiomyocyte hypertrophy. Pretreatment of neonate rat cardiomyocytes with ROCK inhibitor Y27632 reduced Ang-II–induced FHOD3 activation and upregulation, suggesting the involvement of ROCK activities. Silencing of ROCK2, but not ROCK1, in neonate rat cardiomyocytes, significantly lessened Ang-II–induced cardiomyocyte hypertrophy. ROCK2 can directly phosphorylate FHOD3 at both 1412S and 1416T in vitro and is more potent than ROCK1. Both kinases failed to phosphorylate 1406S. Coexpression of FHOD3 with constitutively active ROCK2 induced more stress fiber formation than that with constitutively active ROCK1. Collectively, our results demonstrated the importance of ROCK2 regulated FHOD3 expression and activation in Ang-II–induced myofibrillogenesis, thus provided a novel mechanism for the pathogenesis of Ang-II–induced cardiac hypertrophy.

Superaligned Carbon Nanotubes Guide Oriented Cell Growth and Promote Electrophysiological Homogeneity for Synthetic Cardiac Tissues

Cardiac engineering of patches and tissues is a promising option to restore infarcted hearts, by seeding cardiac cells onto scaffolds and nurturing their growth in vitro. However, current patches fail to fully imitate the hierarchically aligned structure in the natural myocardium, the fast electrotonic propagation, and the subsequent synchronized contractions. Here, superaligned carbon-nanotube sheets (SA-CNTs) are explored to culture cardiomyocytes, mimicking the aligned structure and electrical-impulse transmission behavior of the natural myocardium. The SA-CNTs not only induce an elongated and aligned cell morphology of cultured cardiomyocytes, but also provide efficient extracellular signal-transmission pathways required for regular and synchronous cell contractions. Furthermore, the SA-CNTs can reduce the beat-to-beat and cell-to-cell dispersion in repolarization of cultured cells, which is essential for a normal beating rhythm, and potentially reduce the occurrence of arrhythmias. Finally, SA-CNT-based flexible one-piece electrodes demonstrate a multipoint pacing function. These combined high properties make SA-CNTs promising in applications in cardiac resynchronization therapy in patients with heart failure and following myocardial infarctions.