Exogenous HGF Prevents Cardiomyocytes from Apoptosis after Hypoxia via Up-Regulating Cell Autophagy

Background: Hepatocyte growth factor (HGF) is widely known as a protective factor in ischemic myocardium, however HGF sensitive cellular mechanism remained ill-defined. Autophagy at early stage of hypoxia has been demonstrated to play a role in protecting myocardium both in vivo and vitro. We performed this study to investigate the association between the protective effect of HGF and autophagy. Methods: Ventricular myocytes were isolated from neonatal rat heart (NRVMs). We evaluated cardiomyocytes apoptosis by Hoechst staining and flow cytometry. Autophagy was assessed by transmission electron microscope and mRFP-GFP-LC3 adenovirus infection. Mitochondrial membrane potential was estimated by JC-1 staining. Western blotting and ELISA assay were used to quantify protein concentrations. Results: We found that autophagy in NRVMs increased at early stage after hypoxia and HGF release was consistent with the change of autophagy. Exogenous HGF enhanced autophagy and decreased apoptosis, while neutralizing HGF yielded opposite effects. Besides, inhibition of autophagy increased apoptosis of myocytes. Furthermore, exogenous HGF induced Parkin, the marker of mitochondrial autophagy, indicating increased clearance of injured mitochondria. Conclusions: Our results revealed a potential mechanism in which exogenous HGF prevented NRVMs from apoptosis after hypoxia. Upregulation of Parkin through administration of exogenous HGF may be a potential therapeutic strategy ptotecting myocytes during ischemia

Necroptosis Induced by Ad-HGF Activates Endogenous C-Kit+ Cardiac Stem Cells and Promotes Cardiomyocyte Proliferation and Angiogenesis in the Infarcted Aged Heart

Background/Aims: The discovery of c-kit+ cardiac stem cells (CSCs) provided us with new therapeutic targets to repair the damaged heart. However, the precise mechanisms regulating CSC proliferation and differentiation in the aged heart remained elusive. Necroptosis, a type of regulated cell death, has recently been shown to occur following myocardial infarction (MI); however, its effect on c-kit+ CSCs remains unknown. We investigated the effects of hepatocyte growth factor (HGF) and necroptosis on the proliferation and differentiation of endogenous c-kit+ CSCs in aged rat hearts following MI. Methods: The c-kit+ CSCs and HGF/p-Met expression levels in neonatal, adult and aged rats were compared using immunofluorescence and Western blotting. Immediately after MI, adenovirus carrying the HGF gene (Ad-HGF) was injected into the left ventricular wall surrounding the infarct areas of the aged rat heart. The proliferation and differentiation of the endogenous c-kit+ CSCs were studied using immunofluorescence. The signalling pathways were analysed via Western blotting and ELISA. Results: HGF/p-Met expression levels and c-kit+ CSC abundance gradually decreased with age. Ad-HGF promoted c-kit+ CSC differentiation into precursor cells of cardiomyocyte, endothelial and smooth muscle cell lineages and enhanced cardiomyocyte proliferation and angiogenesis in aged rats; these effects were reversed by the inhibition of necroptosis. Ad-HGF administration induced necroptosis by increasing the expression of receptor interacting protein kinase (RIP) 1 and receptor interacting protein kinase (RIP) 3 proteins in the infarcted heart. Moreover, Ad-HGF-induced necroptosis increased high-mobility group box 1 protein (HMGB1) levels and enhanced the abundance of c-kit+ cells in the bone marrow, which may partly account for the beneficial effect of necroptosis on the c-kit+ CSCs. Conclusion: Ad-HGF-induced necroptosis facilitated aged heart repair after MI by promoting c-kit+ CSC proliferation and differentiation. These findings may lead to the development of new methods for the treatment of ischaemic heart disease in aged populations

Association of admission serum calcium levels and in-hospital mortality in patients with acute ST-elevated myocardial infarction: an eight-year, single-center study in China.

OBJECTIVE: The relationship between admission serum calcium levels and in-hospital mortality in patients with acute ST-segment elevation myocardial infarction (STEMI) has not been well definitively explored. The objective was to assess the predictive value of serum calcium levels on in-hospital mortality in STEMI patients. METHODS: From 2003 to 2010, 1431 consecutive STEMI patients admitted to the First Affiliated Hospital of Nanjing Medical University were enrolled in the present study. Patients were stratified according to quartiles of serum calcium from the blood samples collected in the emergency room after admission. Between the aforementioned groups,the baseline characteristics, in-hospital management, and in-hospital mortality were analyzed. The association of serum calcium level with in-hospital mortality was calculated by a multivariable Cox regression analysis. RESULTS: Among 1431 included patients, 79% were male and the median age was 65 years (range, 55-74). Patients in the lower quartiles of serum calcium, as compared to the upper quartiles of serum calcium, were older, had more cardiovascular risk factors, lower rate of emergency revascularization,and higher in-hospital mortality. According to univariate Cox proportional analysis, patients with lower serum calcium level (hazard ratio 0.267, 95% confidence interval 0.164-0.433, p<0.001) was associated with higher in-hospital mortality. The result of multivariable Cox proportional hazard regression analyses showed that the Killip's class≥3 (HR = 2.192, p = 0.026), aspartate aminotransferase (HR = 1.001, p<0.001), neutrophil count (HR = 1.123, p<0.001), serum calcium level (HR = 0.255, p = 0.001), and emergency revascularization (HR = 0.122, p<0.001) were significantly and independently associated with in-hospital mortality in STEMI patients. CONCLUSIONS: Serum calcium was an independent predictor for in-hospital mortality in patients with STEMI. This widely available serum biochemical index may be incorporated into the current established risk stratification model of STEMI patients. Further studies are required to determine the actual mechanism and whether patients with hypocalcaemia could benefit from calcium supplement

Beneficial effects of schisandrin B on the cardiac function in mice model of myocardial infarction.

The fruit of Schisandra chinensis has been used in the traditional Chinese medicine for thousands of years. Accumulating evidence suggests that Schisandrin B (Sch B) has cardioprotection effect on myocardial ischemia in vitro. However, it is unclear whether Sch B has beneficial effects on continuous myocardial ischemia in vivo. The aim of the present study was to investigate whether Sch B could improve cardiac function and attenuate myocardial remodeling after myocardial infarction (MI) in mice. Mice model of MI was established by permanent ligation of the left anterior descending (LAD) coronary artery. Then the MI mice were randomly treated with Sch B or vehicle alone. After treatment for 3 weeks, Sch B could increase survival rate, improve heart function and decrease infarct size compared with vehicle. Moreover, Sch B could down-regulate some inflammatory cytokines, activate eNOS pathway, inhibit cell apoptosis, and enhance cell proliferation. Further in vitro study on H9c2 cells showed similar effects of Sch B on prevention of hypoxia-induced inflammation and cell apoptosis. Taken together, our results demonstrate that Sch B can reduce inflammation, inhibit apoptosis, and improve cardiac function after ischemic injury. It represents a potential novel therapeutic approach for treatment of ischemic heart disease

Distribution of baseline serum calcium levels at admission in 1,431 STEMI patients.

<p>The admission serum calcium levels were normally distributed with a mean admission calcium level of 2.25±0.21 (mmol/L).</p

In-hospital management and mortality of the STEMI patients according to serum calcium.

<p>Data are expressed as mean ± standard deviation for normally distributed data and percentage (%) for categorical variables. Revascularization  =  percutaneous coronary intervention; ACEI  =  angiotensin-converting enzyme inhibitors; ARB  =  angiotensin receptor blockers.</p

Univariate and multivariable Cox regression analyses of factors associated in-hospital mortality.

<p>^aAdjusted for age, gender, Killip's class≥3, LVEF, neutrophil count, albumin, aspartate aminotransferase, serum calcium and emergency revascularization.</p

Comparisons of the baseline characteristics of the STEMI patients according to serum calcium.

<p>Data are expressed as mean ± standard deviation for normally distributed data, median (inter quartile range) for abnormally distributed data and percentage (%) for categorical variables. CK  =  Creatine kinase; LVEF  =  Left ventricular ejection fraction; LDL  =  Low density lipoprotein; HDL  =  High density lipoprotein; AST  =  Aspartate aminotransferase.</p

Kaplan-Meier curves for in-hospital cumulative mortality according to serum calcium of admission.

<p>Patients were stratified by quartiles of serum calcium. The comparisons among the groups were performed using the log rank test.</p