Multinucleated polyploid cardiomyocytes undergo an enhanced adaptability to hypoxia via mitophagy.

AIMS: There is a large subpopulation of multinucleated polyploid cardiomyocytes (M*Pc CMs) in the adult mammalian heart. However, the pathophysiological significance of increased M*Pc CMs in heart disease is poorly understood. We sought to determine the pathophysiological significance of increased M*Pc CMs during hypoxia adaptation. METHODS AND RESULTS: A model of hypoxia-induced cardiomyocyte (CM) multinucleation and polyploidization was established and found to be associated with less apoptosis and less reactive oxygen species (ROS) production. Compared to mononucleated diploid CMs (1*2c CMs), tetraploid CMs (4c CMs) exhibited better mitochondria quality control via increased mitochondrial autophagy (mitophagy). RNA-seq revealed Prkaa2, the gene for AMPKα2, was the most obviously up-regulated autophagy-related gene. Knockdown of AMPKα2 increased apoptosis and ROS production and suppressed mitophagy in 4c CMs compared to 1*2c CMs. Rapamycin, an autophagy activator, alleviated the adverse effect of AMPKα2 knockdown. Furthermore, silencing PINK1 also increased apoptosis and ROS in 4c CMs and weakened the adaptive superiority of 4c CMs. Finally, AMPKα2-/- mutant mice exhibited exacerbation of apoptosis and ROS production via decreases in AMPKα2-mediated mitophagy in 4c CMs compared to 1*2c CMs during hypoxia. CONCLUSIONS: Compared to 1*2c CMs, hypoxia-induced 4c CMs exhibited enhanced mitochondria quality control and less apoptosis via AMPKα2-mediated mitophagy. These results suggest that multinucleation and polyploidization allow CM to better adapt to stress via enhanced mitophagy. In addition, activation of AMPKα2 may be a promising target for myocardial hypoxia-related diseases.

rs10263935 and rs6045676 identified by genome-wide association study were associated with aortic dissection in a Chinese population.

Aortic dissection (AD) is a disease characterized by a tear in the aortic intimal layer and separation of the arterial wall. Some risk factors, such as hypertension and Marfan syndrome, are well known in AD, but the role of genetic factor is largely unknown. In this study, we investigated the relation between two single nucleotide polymorphisms (SNPs) identified by genome-wide association study and AD. Approximately 177 patients diagnosed with AD through clinical evaluation and imaging techniques and 183 age- and sex-matched control subjects who were suffering from chest pain but without AD were included in the study. Genotyping of rs10263935 and rs6045676 was performed in both patients and control subjects using the TaqMan(®) method [Life Technologies (AB & Invitrogen), Carlsbad, CA]. The frequency of the AA and AG genotype in rs10263935 was significantly higher in the AD patients (0.085 and 0.435, respectively) than in the control subjects (0.033 and 0.355, respectively). The rs10263935 A allele frequency in the AD patients was higher than that in the control subjects [0.302 vs 0.210, odds ratio (OR) = 1.62, 95% confidence interval (CI): 1.26-2.28, P = 0.005]. Similarly, the frequency of the GG genotype in rs6045676 was significantly higher in the AD patients than in the control subjects (0.107 vs 0.038, P = 0.015). The rs6045676 G allele frequency in the AD patients was higher than that in the control subjects (0.282 vs 0.191, OR = 1.67, 95% CI: 1.18-2.50, P = 0.004). After adjustment of the confounding factors, such as smoking, sex, and age, the differences remain significant in several models (rs10263935: GG vs AA: OR = 3.13, 95% CI: 1.15-8.33, P = 0.025; GG vs AG: OR = 1.57, 95% CI: 1.01-2.44, P = 0.045; rs6045676: GG vs CC: OR = 3.30, 95% CI: 1.32-8.25, P = 0.011). rs10263935 on chromosome 7 and rs6045676 on chromosome 20 are associated with AD. Further studies are warranted to elucidate the functional role of these two variants.

Association of gestational diabetes mellitus (GDM) with subclinical atherosclerosis: a systemic review and meta-analysis.

BACKGROUND: Gestational diabetes mellitus (GDM) is associated with an elevated risk of adverse health outcomes such as type 2 diabetes and cardiovascular diseases. Carotid intima-media thickness (cIMT) is increasingly used as a noninvasive marker for subclinical atherosclerosis. Whether there is a direct correlation between GDM and elevated cIMT is still controversial. METHODS: PubMed, Embase and reference lists of relevant papers were reviewed. Studies assessing the relationship between GDM and cIMT were included. Weighted Mean Difference (WMD) of cIMT was calculated using random-effect models. RESULTS: Fifteen studies with a total of 2247 subjects were included in our analysis, giving a pooled WMD of 0.05 (95% confidence interval [CI] 0.03 -0.07). Furthermore, meta regression and subgroup analysis found that the association between GDM and larger cIMT already existed during pregnancy, and this relation was stronger in obese GDM patients. CONCLUSIONS: GDM in and after pregnancy is associated with subclinical atherosclerosis. Weight control may be helpful to prevent cardiovascular diseases for GDM patients.

Serum phosphate concentration and incidence of stroke: a systemic review and meta-analysis.

Elevated serum phosphate is associated with cardiovascular and total mortality in patients with kidney diseases and healthy individuals. But whether serum phosphate is associated with stroke is controversial. We searched PubMed and Embase from January 1, 1970 to May 9, 2014 with keywords such as "serum phosphate", "serum phosphorus", and "stroke". Dose-response meta-analysis was conducted. A restricted cubic spline model was used, and then we estimated pooled RR using generalized least square regression taking into account the correlation among categories of each study. Five studies with a total of 32,608 patients were included. We identified a linear relationship between serum phosphate and risk of stroke (P for non-linearity = 0.5258). The RR of phosphate (1 mg/dL) for stroke was 1.00 (95 % CI 0.97-1.05), similar results were observed in subgroup analysis. A linear relationship between serum phosphate and risk of stroke is identified. There is no association between serum level of phosphate and stroke.

Liver X receptor activation protects against inflammation and enhances autophagy in myocardium of neonatal mouse challenged by lipopolysaccharides.

Liver X receptors (LXRs) has been emerged as negative regulators of cardiomyocytic inflammation. The cellular process of autophagy is believed to play a protective role in myocardium during the inflammatory status. In this study, we investigated the role of LXRs agonist TO901317 (TO) on lipopolysaccharides (LPS)-induced myocardial inflammation and autophagy. The results showed that TO pretreatment significantly reduced the LPS-induced infiltration of inflammatory cells, elevation of NF-κB protein, TNF-α, and IL-6 mRNA levels in the myocardium. Moreover, LPS stimulated autophagy in neonatal mice heart, and this effect was further enhanced by TO pretreatment as evidenced by increased LC3-II/GAPDH ratio increment. Furthermore, TUNEL assay revealed LPS stimulation also increased the number of apoptotic cells in the myocardium, and the increment was inhibited by TO pretreatment. Our findings suggested that attenuation of inflammation and apoptosis, and enhancement of autophagy by TO may contribute to the protection of myocardium under inflammatory condition.

Identification of differently expressed genes and small molecule drugs for Tetralogy of Fallot by bioinformatics strategy.

This study aimed to screen out differentially expressed genes (DEGs) and explore small molecule drugs for Tetralogy of Fallot (TOF). The gene expression profile of TOF GSE26125 was downloaded from the Gene Expression Omnibus database, including 16 idiopathic TOF samples and five healthy controls. The DEGs were identified by the Limma package in R language and underwent functional enrichment analysis via Database for Annotation, Visualization and Integrated Discovery tools. A protein-protein interaction (PPI) network of DEGs was then constructed and the significant clusters were selected for functional analysis. In addition, the DEGs were mapped to the connectivity map (CMap) database to identify potential small-molecule drugs. As a result, a total of 499 DEGs were selected between TOF and healthy controls. Meanwhile, the functional changes of DEGs related to TOF were mainly associated with cellular respiration and energy metabolism. Furthermore, in the PPI network, two clusters were identified via cluster 1 analysis. And only cluster 1 was significantly enriched into gene ontology terms, including respiratory chain, electron transport chain, and oxidation reduction. The hub gene of cluster 1 was NDUFAB1. Additionally, small molecules, such as harmine, solanine, and testosterone, may have the potential to repair the disordered metabolic pathways of TOF.

Silencing suppressor of cytokine signaling 3 induces apoptosis and activates the p-STAT3/NF-κB pathway in hypoxic cultivated H9c2 cells.

Suppressor of cytokine signaling 3 (SOCS3) plays a significant role in the process of myocardial adaptation to chronic hypoxia. SOCS3 finely regulates cell signaling cross-talk that occurs between NF-κB and STAT3 during the compensatory protective response. However, the role and mechanism of SOCS3 in hypoxic cardiomyocytes are not fully understood. In the study, we investigated the effect of SOCS3 on the p65 and STAT3 signaling pathways and further examined the potential molecular mechanism involved in regulating apoptosis. Our data showed that SOCS3 silencing could upregulate Ac-p65, p-p65, and p-STAT3 expression in nuclear extracts of H9c2 cells that received hypoxic treatment for 24, 48, and 72 h. SOCS3 silencing also remarkably increased the DNA-binding activity of the p65 motif in hypoxic cultivated H9c2 cells. We also found that SOCS3 knockdown increased cleaved-caspase-3, Bax, and PUMA expression and decreased cleaved PARP and Bcl-2 in expression in hypoxic H9c2 cells. Silencing of SOCS3 caused an increase in LDH leakage from injured cardiomyocytes and reduced cell viability under conditions of hypoxic stress. Furthermore, SOCS3 silencing enhanced the apoptosis of H9c2 cells at 72 h of hypoxia. These findings suggest that knockdown of SOCS3 leads to excessive activation of the NF-κB pathway, which, in turn, might promote apoptosis under conditions of chronic hypoxia.

Increased expression of connective tissue growth factor and transforming growth factor-beta-1 in atrial myocardium of patients with chronic atrial fibrillation.

OBJECTIVES: This study aimed to investigate the roles of connective tissue growth factor (CTGF) and transforming growth factor-ß1 (TGF-ß1) in atrial fibrosis in patients with chronic atrial fibrillation. METHODS: Up to 40 cases involving simple mitral valve replacement surgery were divided into 2 groups: the chronic atrial fibrillation (cAF) group (n = 28) and the sinus rhythm group (n = 12). Echocardiography was used to measure the cardiac cavity size and analyze the cardiac function. Right atrial specimens were obtained during the operation. The collagen volume fraction in the atrial specimens was examined. The mRNA and protein levels of TGF-ß1, Smad3 and CTGF were also investigated. RESULTS: Compared with the sinus rhythm group, the cAF group had higher collagen content in the right atrial tissues. The mRNA and protein levels of TGF-ß1, Smad3 and CTGF were also significantly elevated in the cAF group (p < 0.05). The mRNA and protein levels of TGF-ß1 and CTGF in the cAF group correlated positively with the collagen volume fraction. The positive correlation between the expression of TGF-ß1 and CTGF was also demonstrated. CONCLUSIONS: CTGF is upregulated via the TGF-ß1/Smad pathway in the atrial myocardium of cAF patients. Furthermore, the TGF-ß1/Smad pathway may play an important role in the structural remodeling during atrial fibrosis.

The application of on-pump beating-heart surgery for partial atrioventricular septal defect: a report of 87 cases.

BACKGROUND: Partial atrioventricular septal defect (P-AVSD) is a common congenital heart disease. Because of the presence of left and right atrioventricular valve deformities and the shift in the atrioventricular node and cardiac conduction bundle, the surgical repair of P-AVSD is difficult. This study was performed to compare the effects on the coronary sinus septum in the left versus the right atrium during surgical treatment for P-AVSD and report our experiences regarding the application of on-pump beating heart surgery under mild hypothermia for patients with P-AVSD. MATERIALS AND METHODS: The effects of on-pump beating heart surgery were analyzed retrospectively in 87 P-AVSD patients. Of the 87 total patients, 84 with anterior mitral leaflet cleft underwent valvuloplasty and 3 underwent mitral valve replacement. Seventy-seven patients underwent tricuspid valve annuloplasty, 2 underwent tricuspid valve replacement, and 1 underwent left superior vena cava ligation, and 3 patients with atrial fibrillation were treated with radiofrequency ablation. Patients with an ostium primum atrial septal defect underwent autologous pericardial modified Kirklin repair. Of these, 46 patients had their coronary sinus septum separated into the left atrium and 41 had their coronary sinus retained in the right atrium. Fingertip oxygen saturation was compared between patients in whom the coronary sinus was separated to the left atrium and those in whom the coronary sinus was retained in the right atrium. RESULTS: There was 1 postoperative early death (1.15%) due to respiratory failure, and 1 patient had a III degree atrioventricular block (1.15%) and underwent implantation of a permanent pacemaker. The fingertip oxygen saturation levels of the left atrium group were 96.81 ± 3.17 preoperatively, 95.37 ± 4.62 at 7 days postoperatively, and 94.53 ± 4.95 at 3 months postoperatively. Those of the right atrium group were 98.53 ± 2.84 preoperatively, 97.19 ± 3.57 at 7 days postoperatively, and 96.89 ± 4.19 at 3 months postoperatively. During the follow-up period, which ranged from 3 months to 7 years, the cardiac function was adequately restored. CONCLUSIONS: On-pump beating heart surgery under mild hypothermia is a safe and feasible method. The retention of the coronary sinus in the right atrium might maintain oxygen saturation.

A rabbit model to study regression of ventricular hypertrophy.

BACKGROUND: The purpose of this study is to develop and characterise a reproducible rabbit model of LVH regression following pressure-induced myocardial hypertrophy. MATERIALS AND METHODS: Without endotracheal intubation and mechanical ventilation, a median sternotomy was performed. The median incision was made exactly along the midline of the sternum. Ascending aortic diameter was reduced 50% above the aortic valve, which lead to an approximate 75% reduction in crosssectional area. The sham-operated rabbits underwent the same procedures without actual ligation of the aorta. The animals of early DB group and late DB group were subjected to the second operation for removing the ligation eight weeks or 16 weeks after the initial banding surgery, respectively. Echocardiography, haemodynamic assessment, histology, and electron microscopy were used to assess functional and structural aspects of myocardial hypertrophy at each time point. RESULTS: The pressure overload resulted in robust LVH assessed by echocardiography, haemodynamic assessment, LV weight/body weight ratios, histology, and electron microscopy. Ascending aortic debanding completely or partially reversed LVH. The degree of LVH regression was association with the duration of pressure overload, proved by the fact that restoration of LV structure and function was complete in animals subjected to eight weeks of aortic banding but incomplete in animals subjected to 16 weeks of aortic banding. The animals did not experience severe mechanical ventilatory impairment. CONCLUSIONS: These results demonstrate an efficient and reproducible method of promoting LVH regression in rabbits without endotracheal intubation and mechanical ventilation.

Endovascular stent graft placement in the treatment of a ruptured tuberculous pseudoaneurysm of the descending thoracic aorta secondary to Pott's disease of the spine.

Ruptured thoracic aortic tuberculous pseudoaneurysms as a complication of mycobacterium tuberculosis infection of the spine are rare. Conventional treatment of a ruptured tuberculous pseudoaneurysm involves surgery with graft interposition or patch repair. We report successful repair of a ruptured tuberculous pseudoaneurysm of the descending thoracic aorta by endovascular stent graft placement and provide a literature review of such entities.

Toll-like receptor 4/nuclear factor-kappa B pathway is involved in myocardial injury in a rat chronic stress model.

Chronic stress is considered to predispose to various cardiovascular events such as coronary artery disease, hypertension, and even heart failure. In this study, rats were exposed to stress for 1 day, 1, 2, 3, and 4 weeks to establish a chronic stress model. A specific toll-like receptor 4 (TLR4) antagonist eritoran was used to block the activity of TLR4. On the second day after the last stress exposure, the animals were killed. The expression of TLR4 mRNA and nuclear factor-kappa B (NF-κB) DNA-binding activity in the myocardium were measured using reverse transcriptase polymerase chain reaction and electrophoretic mobility shift assay. The proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL-6) in myocardium were assayed by enzyme-linked immunosorbent assay. Myocardial injury was evident after chronic stress for 2 weeks. The TLR4 mRNA expression reached a peak after stress for 1 week. It was sustained at a stable level after stress exposure for 3 weeks and was restored to a nearly normal level in the fourth week. NF-κB DNA-binding activity was significantly enhanced after the stress for 1 day and markedly enhanced again after a 2-week stress exposure. It was weakened and reached a normal level after stress exposure for 4 weeks. The levels of TNF-α and IL-6 gradually increased and reached peaks after stress for 4 weeks. Meanwhile, eritoran significantly decreased the TLR4 mRNA expression and NF-κB activity in rats from the 2-week stress group. However, it did not downregulate the levels of TNF-α and IL-6. Importantly, it significantly improved the myocardial injury induced by the chronic stress. In conclusion, TLR4/NF-κB participates in myocardial injury during chronic stress.

Primary fibrosarcoma of the mitral valve.

A case of primary fibrosarcoma of the mitral valve is reported, which was resected and the valve was replaced. Adjuvant chemotherapy was admisinistered, and at one year the patient remains symptom free without evidence of recurrent disease.

A 23-year-old male with Uhl's anomaly.

We report a case of a 23-year-old male with Uhl's anomaly who presented with nonparoxysmal atrioventricular junctional tachycardia with Mobitz I. The patient underwent successful total cavopulmonary conversion.

VKORC1-1639G>A, CYP2C9, EPHX1691A>G genotype, body weight, and age are important predictors for warfarin maintenance doses in patients with mechanical heart valve prostheses in southwest China.

OBJECTIVE: To investigate the contribution of genetic polymorphisms of vitamin K epoxide reductase complex subunit 1 gene VKORC1-1639G>A, cytochrome P450 2C9 gene (CYP2C9), EPHXI, and clinical factors to warfarin sensitivity in southwest Chinese Han patients with mechanical heart valve prostheses. METHODS: A total of 127 patients with mechanical heart valve prostheses who have been followed up at our department during the past 23 years were enrolled in this study and compared to a control group that consisted of 133 randomly selected healthy blood donors. These Chinese patients met stable warfarin dosage requirements and had reached the target international normalized ratio (INR) of 1.5-2.0. PCR and direct sequencing were carried out to identify the polymorphisms of VKORC1-1639G>A (rs9923231), CYP2C9*3 (rs1057910), CYP2C9 IVS3-65G>C (rs9332127), and EPHX1691A>G (rs4653436). In addition, total and free (non-protein-bound) warfarin concentrations were analyzed. RESULTS AND CONCLUSIONS: There were great interindividual differences in warfarin maintenance dosage (ranging from 0.6 to 8.4 mg/day) among the 127 patients with mechanical heart valve prostheses. VKORC1-1639G>A, CYP2C9, EPHX1691A>G polymorphism, body weight, and age were found to affect the dose demands. Multiple linear regression models incorporating genetic polymorphisms of VKORC1, CYP2C9, EPHX1691A>G, and the nongenetic factors of age and body weight were developed, and explained up to 76.8% of the total variation (adjusted R (2) of 0.743) in warfarin maintenance doses in southwest Chinese patients with mechanical heart valve prostheses.

Giant primary leiomyoma of the right ventricle.

Echocardiography detected a giant mass on the lateral wall of the right ventricle in a 13-year-old boy. The mass extended into the cavity of right ventricle without attachment to adjacent structures. We resected the mass under cardiopulmonary bypass. Histology showed it to be a primary leiomyoma of the right ventricle.

Myocardial lipomatous infiltration of the left ventricular wall.

A myocardial mass was found on the left ventricle wall of a four-year-old Chinese girl diagnosed with pulmonary valve stenosis and patent foramen ovale. Surgical valvotomy and partial excision of the myocardial mass were performed, and a biopsy of the myocardial mass revealed myocardial lipomatous infiltration.

Animal model of ascending aortic stenosis in rabbits without endotracheal intubation.

BACKGROUND AND AIM: Experimental animal studies of left ventricular hypertrophy (LVH) usually involve endotracheal intubation, which is associated with a risk of serious tracheal injury and other significant negative sequelae. We developed an animal model of pressure overload hypertrophy caused by constriction of the ascending aorta in rabbits that does not require endotracheal intubation. METHODS: New Zealand White rabbits of either sex (1.94 +/- 0.12 kg) were randomly assigned to the aortic banding (AB) group (n = 9) and the sham-operated group (n = 8). The sternum was carefully incised along the midline to avoid injury to the parietal pleura. Then, the intervention group underwent AB with three to zero Prolene proximal to the innominate artery without endotracheal intubation. To investigate the effects of the surgical procedure on physiological parameters, echocardiography, histology, and electron microscopy were performed to assess functional and structural hypertrophy at various time intervals. RESULTS: Banding of the ascending aorta created the expected increases in both aortic velocity and the pressure gradient between proximal and distal aorta coarctation. The pressure overload resulted in a robust LVH assessed by transthoracic echocardiography and histology. The animals did not experience severe mechanical ventilatory impairment. CONCLUSION: We developed a safe, efficient, and reproducible method of producing LVH in rabbits without the need for endotracheal intubation and mechanical ventilation. Ultimately, this model will facilitate focused study of the mechanisms involved with LVH progression.

AMPKα2 deficiency exacerbates hypoxia-induced pulmonary hypertension by promoting pulmonary arterial smooth muscle cell proliferation.

Increased evidence indicates that adenosine monophosphate-activated protein kinase (AMPK) plays a vital role in vascular homeostasis, especially under hypoxia, and protects against the progression of pulmonary hypertension (PH). However, the role of AMPK in the pathogenesis of PH remains to be clarified. In the present study, we confirmed that a loss of AMPKα2 exacerbated the development of PH by using hypoxia-induced PH model in AMPKα2 -/- mice. After a 4-week period of hypoxic exposure, AMPKα2 -/- mice exhibited more severe pulmonary vascular remodeling and pulmonary vascular smooth muscle cell (SMC) proliferation when compared with wild type (WT) mice. In vitro, AMPKα2 knockdown promoted the proliferation of pulmonary arterial smooth muscle cells (PASMCs) under hypoxia. This phenomenon was accompanied by upregulated Skp2 and downregulated p27kip1 expression and was abolished by rapamycin, an inhibitor of mTOR. These results indicate that AMPKα2 deficiency exacerbates hypoxia-induced PH by promoting PASMC proliferation via the mTOR/Skp2/p27kip1 signaling axis. Therefore, enhanced AMPKα2 activity might underlie a novel therapeutic strategy for the management of PH.

KLF15 is a protective regulatory factor of heart failure induced by pressure overload.

The aim of the present study was to investigate the protective effect of Kruppel­like factor 15 (KLF15) overexpression on heart failure (HF) induced by left ventricular (LV) pressure overload in mice. Wild­type (WT) mice and cardiac­specific KLF15­overexpressed transgenic (TG) mice were selected as research subjects, and an LV pressure overload model was constructed by ascending aortic constriction surgery. Changes in cardiac morphology and function, and ultrastructure and molecular expression were observed via M­mode echocardiography, histological and immunohistochemical staining, ELISA and western blotting at 2 and 6 weeks of LV overload. WT and TG mice subjected to 2 weeks of overload displayed adaptive LV hypertrophy characterized by ventricular thickness, cardiomyocyte size, ejection fraction and fractional shortening of heart­lung weight ratio and KLF15, and increases in vascular endothelial growth factor (VEGF) expression without other pathological changes. WT mice subjected to 6 weeks of overload displayed enlargement of the LV chamber, severe interstitial remodeling, and HW/LW, cardiac capillary and heart function decline, accompanied by downregulated expression of KLF15 and VEGF, and upregulated expression of connective tissue growth factor, phosphorylated p38 (p­p38) and phosphorylated Smad3 (p­Smad3). In contrast, TG mice exhibited improved resistance to 6 weeks of overload and a slighter molecular expression response compared with WT mice. KLF15 was revealed to be a critical factor regulating the expression of CTGF, VEGF, p­p38 and p­Smad3, and could alleviate the progression from adaptive LV hypertrophy to decompensatory cardiac insufficiency.