You Zhou

Induction of Myocardial PDCD4 in Coronary Microembolization-Related Cardiac Dysfunction: Evidence from a Large-Animal Study

Background/Aims: Coronary microembolization (CME) has been linked to myocardial inflammation and apoptosis. This study aims to investigate the role of the apoptotic protein PDCD4 in the myocardium after CME in minipigs. Methods: Seventy Bama minipigs were randomized into four groups: control, CME, CME plus PDCD4-siRNA and CME plus control siRNA. CME was induced by injecting polyethylene microspheres into the left anterior descending artery. Cardiac function was evaluated. HE and HBFP staining were used to observe the degree of infarction. Western blotting and qPCR were used to evaluate the expression of PDCD4, TNF-α and caspase-3. The measurements were performed at 0, 3, 6, 9, 12 and 24 h after CME modeling in the CME and control groups. Results: Cardiac function in the CME group was significantly decreased compared with the control group (P<0.05) and the expression of PDCD4 and TNF-α increased significantly (P<0.05). However, the infarct area did not differ between the CME and control groups at any time point (P>0.05). Furthermore, PDCD4-siRNA improved cardiac function and reduced PDCD4 and TNF-α expression compared with the CME plus control siRNA group at 9 h after modeling (P < 0.05), while the caspase-3 level was not different between the two groups. Conclusion: PDCD4 induction may be involved in CME-related cardiac dysfunction, and PDCD4 inhibition via siRNA may attenuate the cardiac impairment and be used as a treatment strategy for CME.

The involvement of phosphatase and tensin homolog deleted on chromosome ten (PTEN) in the regulation of inflammation following coronary microembolization.

Background/Aims: Growing evidence shows that phosphatase and tensin homolog deleted on chromosome ten (PTEN) is involved in regulating inflammation in different pathological conditions. Therefore, we hypothesized that the upregulation of PTEN correlates with the impairment of cardiac function in swine following coronary microembolization (CME). Methods: To possibly disclose an anti-inflammatory effect of PTEN, we induced swine CME by injecting inertia plastic microspheres (42 μm in diameter) into the left anterior descending coronary artery and analyzed the myocardial tissue by immunochemistry, qRT-PCR and western blot analyses. In addition, we downregulated PTEN using siRNA. Results: Following CME, PTEN mRNA and protein levels were elevated as early as 3 h, peaked at 12 h, and then continuously decreased at 24 h and 48 h but remained elevated. Through linear correlation analysis, the PTEN protein level positively correlated with cTnI and TNF-α but was negatively correlated with LVEF. Furthermore, PTEN siRNA reduced the microinfarct volume, improved cardiac function (LVEF), reduced the release of cTnI, and suppressed PTEN and TNF-α protein expression. Conclusion: This study demonstrated, for the first time, that PTEN is involved in CME-induced inflammatory injury. The data generated from this study provide a rationale for the development of PTEN-based anti-inflammatory strategies.

Atorvastatin Inhibits Myocardial Apoptosis in a Swine Model of Coronary Microembolization by Regulating PTEN/PI3K/Akt Signaling Pathway

Background/Aims: Phosphatase and tensin homolog deleted on chromosome ten (PTEN) has been recognized as a promoter of apoptosis in various tissues, and revealed to be up-regulated in circumstances of coronary microembolization (CME). However, whether this functional protein could be modified by pretreatment of atorvastatin in models of CME has not been disclosed yet. Methods: Swine CME was induced by intra-coronary injection of inertia plastic microspheres (diameter 42 μm) into left anterior descending coronary, with or without pretreatment of atorvastatin or PTEN siRNA. Echocardiologic measurements, pathologic examination, TUNEL staining and western blotting were applied to assess their functional, morphological and molecular effects in CME. Results: PTEN were aberrantly up-regulated in cardiomyocytes following CME, with both the mRNA and protein levels increased after CME modeling. Pretreatment with atorvastatin could attenuate the induction of PTEN. Furthermore, down-regulation of PTEN in vivo via siRNA was associated with an improved cardiac function, attenuated myocardial apoptosis, and concomitantly inhibited expressions of key proapoptotic proteins such as Bax, cleaved-caspase-3. Interestingly, atorvastatin could markedly attenuate PTEN expression and therefore partially reverse cardiac dysfunction and attenuate the apoptosis of the myocardium following CME. Conclusion: Modulation of PTEN was probably as a potential mechanism involved in the beneficial effects of pretreatment of atorvastatin to cardiac function and apoptosis in large animal models of CME.

The PTEN/Akt Signaling Pathway Mediates Myocardial Apoptosis in Swine After Coronary Microembolization

Background/Aims: Phosphatase and the tensin homolog deleted on chromosome ten (PTEN) has been recognized as a promoter of apoptosis in various tissues and has been shown to be upregulated in circumstances of coronary microembolization (CME). We hypothesized that the upregulation of PTEN correlates with CME-induced myocardial apoptosis. Methods: Swine CME was induced by an intracoronary injection of inert plastic microspheres (diameter of 42 μm) into the left anterior descending coronary, with or without pretreatment of the PTEN small-interfering RNA (siRNA). Echocardiological measurements, a pathological examination, Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) staining, and Western blotting, were performed to assess their functional, morphological, and molecular effects in CME. Results: PTEN was aberrantly upregulated in cardiomyocytes following CME. Downregulation of PTEN in vivo via siRNA was associated with improved cardiac function and attenuated myocardial apoptosis; concomitantly inhibited the expression of key proapoptotic proteins, such as phosphorylated Bad (p-Bad); cleaved caspase-3; and enhanced the expression of key antiapoptotic proteins, such as phosphorylated protein kinase B (p-Akt). However, there was no difference in the Akt-regulated downstream protein IκB kinases (IKKα, IKKβ, and IKKγ) among the sham, CME, and control siRNA groups. Conclusion: This study demonstrates, for the first time, that the PTEN/Akt signaling pathway contributes to cardiomyocyte apoptosis. The data generated from this study provide a rationale for the development of PTEN-based therapeutic strategies for CME-induced myocardial injury.

Mechanism of programmed cell death factor 4/nuclear factor-κB signaling pathway in porcine coronary micro-embolization-induced cardiac dysfunction.

The aim of this study was to investigate the role of the programmed cell death factor 4 (PDCD4)/nuclear factor-κB (NF-κB) signaling pathway in coronary micro-embolism (CME)-induced inflammatory responses and cardiac dysfunction in a porcine model. Bama miniature pigs were randomly divided into four groups (n = 5 per group). Micro-embolization balls or saline were infused through a microcatheter in the left anterior descending (LAD) artery in the CME and Sham groups, respectively. PDCD4 siRNA or control siRNA mixed with transfection reagent was infused via the LAD artery 72 h before CME induction in the CME + siRNA-PDCD4 and siRNA-control groups, respectively. Cardiac function was evaluated with ultrasound. Tissue biopsy was stained with hematoxylin–eosin (HE) and hematoxylin basic fuchsin picric acid (HBFP) to measure infarction area. Myocardial PDCD4 and tumor necrosis factor-α (TNF-α) mRNA and protein expression were analyzed by quantitative PCR and Western blotting. NF-κB activity was evaluated in gel electrophoretic mobility shift assay. Echocardiographic parameters showed that compared with the sham group, the CME group had impaired heart function, manifested as systolic dysfunction and left ventricular dilatation (reduced left ventricular ejection fraction [LVEF], left ventricular fractional shortening [FS], and cardiac output [CO] [P < 0.05] and increased left ventricular end-diastolic diameter [LVEDd] [P < 0.05]). Compared with the CME group, the CME + siRNA-PDCD4 group had attenuated CME-induced cardiac function damage (increased LVEF, FS and CO [P < 0.05] and reduced LVEDd [P < 0.05]). Compared with the sham group, the CME group had significantly increased PDCD4 and TNF-α mRNA and protein expression and increased NF-κB activity (P < 0.05). These effects were significantly inhibited in the CME + siRNA-PDCD4 group (P < 0.05). In conclusion, PDCD4/NF-κB signaling pathway activation is an important mechanism for CME-induced cardiac dysfunction, suggesting that inhibition of PDCD4/NF-κB signaling pathway may be a potential target for the prevention and treatment of CME.

Coronary Microembolization Induces Cardiomyocyte Apoptosis in Swine by Activating the LOX-1-Dependent Mitochondrial Pathway and Caspase-8-Dependent Pathway

Background: Cardiomyocyte apoptosis by coronary microembolization (CME) contributes to myocardial dysfunction, in which mitochondrial pathway and death receptor pathway are activated. Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) is a membrane protein involved in apoptosis. The study aimed to explore the role of LOX-1 in the activation of these 2 major apoptotic pathways. Methods: Twenty Bama miniature swine were randomized into 4 groups (n = 5 per group). The groups were Sham, CME, LOX-1 small-interfering RNA (siRNA), and control siRNA. Microspheres were injected into the left anterior descending artery of swine to establish CME model. Twelve hours after operation, cardiac function, serum c-troponin I level, microinfarct, and apoptotic index were examined. The levels of LOX-1, Bcl-2, Bax, cytochrome c as well as cleaved caspase 9, -8, and -3 were detected. Results: Myocardial dysfunction, enhanced serum c-troponin I, microinfarct, and apoptosis were induced following CME. Moreover, CME induced increased expression of LOX-1, Bax, cytochrome c, cleaved caspase 9, -8, and -3 as well as decreased Bcl-2 expression levels. The LOX-1 siRNA reversed these effects by CME except cleaved caspase 8 expression, while the control siRNA had no effect. Conclusion: Coronary microembolization induces cardiomyocyte apoptosis via the LOX-1-dependent mitochondrial pathway and caspase 8-dependent pathway.

Effects of atorvastatin on PDCD4/NF-κB/TNF-α signaling pathway during coronary microembolization of miniature pigs.

OBJECTIVE In this study, we explore the effects of pretreatment with atorvastatin on the cardiac function of piglets after coronary microembolization (CME). METHODS Twenty Bama miniature pigs were randomized to sham surgery group (sham group), CME Group, conventional dose group and intensive-dose group, with 5 miniature pigs in each group. Pigs in the CME group received a total dosage of 100,000 microspheres (42 μm) suspended in 10 ml normal saline within 40 min, while animals in the sham group received the same dosage of normal saline. In the conventional dose group, atorvastatin (1.5mg/kg) was given once daily starting 7d before microembolization. In the intensive-dose group, atorvastatin (1.5mg/kg) was also given once daily 7d before intervention, and an additional 3mg/kg 4h before percutaneous coronary intervention. Cardiac function indices were determined by echocardiography; and infarct size was determined histopathologically. PDCD4 mRNA and TNF-α mRNA and protein expression were evaluated by quantitative fluorescence-polymerase chain reaction and Western blot, respectively. NF-κB activation was evaluated by electrophoretic mobility shift assay. RESULTS (1) Cardiac function was significantly lower (P<0.05) in CME group compared with the sham group. CME reduced myocardial systolic dysfunction and left ventricular dilatation. The conventional and intensive-dose groups showed improved CME-induced cardiac function when compared with the CME Group (P<0.05). (2) Compared with the conventional group, the dose-intensive group showed lower PDCD4 and TNF-α expression and NF-κB activation as well as improved cardiac function (P<0.05). CONCLUSIONS Atorvastatin effectively improved CME-induced cardiac damage with intensive-dose therapy showing better outcome. The protective effects are mediated via suppression of PDCD4/NF-κB/TNF-α signaling in cardiomyocytes.

Effect of metoprolol on myocardial apoptosis after coronary microembolization in rats.

BACKGROUND: Coronary microembolization (CME) is a serious complication following percutaneous coronary intervention (PCI) in patients with acute coronary syndromes. The use of metoprolol before PCI can significantly protect ischemic myocardium from myocardial damage, but the function of metoprolol in the treatment of CME is not entirely clear. This study was to explore the effect and significance of metoprolol on myocardial apoptosis and caspase-3 activation after CME in rats. METHODS: Thirty rats were randomly divided into three groups including sham-operation (control group), CME plus saline (CME group), CME plus metoprolol (metoprolol group), 10 rats for each group. The CME group was induced by injecting 3 000 polyethylene microspheres (42 μm) into the left ventricle during a 10-second occlusion of the ascending aorta; the control group was injected with physiological saline instead of microembolization ball; the metoprolol or saline group was given three intravenous bolus injections before CME. Echocardiography, TUNEL staining, and Western blotting were used to evaluate cardiac function, proportion of apoptotic cells and activation of caspase-3 respectively at 6 hours after operation. RESULTS: Echocardiographic parameters displayed that the metoprolol group improved cardiac function significantly compared with the CME group (P<0.05). The myocardial apoptotic rate of the CME group as well as the contents of activated caspase-3 increased significantly (P<0.05), both of which were ameliorated significantly by metoprolol treatment (P<0.05). CONCLUSIONS: This study demonstrates that metoprolol can protect the myocardium during CME in rats by inhibiting apoptosis and improving cardiac function. These results suggest that the inhibition of apoptosis can be a potential therapeutic strategy for the treatment of CME.

Levosimendan Pretreatment Inhibits Myocardial Apoptosis in Swine after Coronary Microembolization

Background/Aims: In addition to its cardiotonic effect, levosimendan has been thought to have multiple cardiovascular benefits, including anti-inflammatory and anti-apoptotic. Phosphatase and tensin homolog deleted on chromosome ten (PTEN) has been revealed to be up-regulated in circumstances of coronary microembolization (CME), and the PTEN signaling pathway mediates myocardial apoptosis in swine after CME. However, whether this functional protein could be modified by pretreatment of levosimendan in models of CME has not been disclosed yet. Methods: Swine CME was induced by intra-coronary injection of inertia plastic microspheres (diameter 42µm) into left anterior descending coronary, with or without pretreatment of levosimendan or PTEN siRNA. Echocardiologic measurements, Terminal-deoxynucleotidyl Transferase Mediated Nick End Labeling (TUNEL) staining and western blotting were applied to assess their functional, morphological and molecular effects in CME. Results: PTEN mRNA and protein were aberrantly up-regulated in cardiomyocytes following CME. Furthermore, down-regulation of PTEN in vivo via siRNA was associated with an improved cardiac function, attenuated myocardial apoptosis, and concomitantly inhibited expressions of key proapoptotic proteins such as caspase-3. Interestingly, levosimendan could markedly attenuate PTEN expression and inhibit myocardial apoptosis, therefore partially reverse cardiac dysfunction. Conclusion: Modulation of PTEN was probably as a potential mechanism involved in the beneficial effects of pretreatment of levosimendan to cardiac function and apoptosis in animal models of CME.