| Background:CME mainly came from the erosion or rupture of a vulnerableatherosclerotic plague which occurs naturally in the acute coronarysyndrome and iatrogenically during the treatment of percutaneouscoronary interventions (PCI). Animal studies have confirmed thatmyocardial contractile function would get worsen regardless of coronaryblood flow could be restored or not assuming the mismatches betweenmyocardial perfusion and its contractile function. The animal experimenthad found that cardiomyocyte apoptosis were mostly involved in the mechanism of myocardium injury followed CME. Phosphatase and tensinhomolog deleted on chromosome ten(PTEN), which was first identifiedas a tumor suppressor gene, is an essential regulator of cell proliferation,differentiation, adhesion, migration, infiltration, growth and apoptosis.Some studies have showed PTEN is a protein that accelerates apoptosis indifferent types of cells in response to various stimuli and isdown-regulated in many cancer tissues. Then, we came to a hypothesisthat whether PTEN might be involved in the myocardial injury after CME.Up to date, there is none related research in the domestic and overseas.Objective:This study aims to explore the expression and its dynamic change ofPTEN after CME to supply a new treatment target in future.Methods:Forty swine were randomly assigned into receive eithersham-operation (control group) or coronary microembolization (CME)groups. CME was developed by injecting inertia plastic microspheres(diameter42μm) into left anterior descending coronary (LAD) in swinewhile the sham-operation group received the same dose of normal salineinjected into LAD. The swine were sacrificed on hour of3,12,24and48post-operationally and each subgroup consisted of five swine. Thegeneral morphological characteristics were observed in sections with HEstaining, the areas of myocardial infarction was evaluated by percent micronecrotic area in sections with hematoxylin basic fuchsin picric(HBFP) staining, and myocardial apoptosis was determined by TUNELassay.Left ventricular function was measured by echocardiography.Serumtroponin I (cTnI) was detected by electrochemiluminescence (ECL). ThemRNA and protein levels of PTEN were determined by Real-time PCRand western blots, respectively.Results:CME swine exhibited pathological changes evidenced by multi-focalmyocardial necrosis, myocardial apoptosis, inflammatory cell infiltrationwith markedly increased the myocardial microinfarction areas andpersistent reduction of LV functions. The level of serum cTnI, PTENmRNA and PTEN protein were increased by3h, peaked at12h, started todecreases at24h and decreased to a low level higher than the controlgroup by48h. Through the liner correlation analysis, the PTEN proteinwas positively correlated with cTnI and myocardial apoptosis index (AI),however was negatively correlated with LV function (LVEF).Conclusion:PTEN is signally activated in CME swine, and exhibits a dynamicchange consistence with the LV functions (LVEF), serum cTnI andmyocardial apoptosis in time. PTEN might take part in the process ofmyocardial injury after CME, and might be the new treatment target forpreventing the CME. Background：Cumulative research evidences show that myocardial apoptosis wasinvolved in CME-induced myocardial injury pathophysiologicalprocesses. Some studies have showed PTEN is a protein that acceleratesapoptosis in different types of cells in response to various stimuli. Furtherrecent studies found that the pathway of PTEN/PI3K/Akt also had beeninvolved in the development of cardiovascular diseases such ascardiomyocyte survival, cardiomyocyte hypertrophy, myocardialcontractile function, myocardial electrophysiology, cardiomyocytemetabolism and mechanical stress, coronary newborn, heart failure andischemia-reperfusion injury etc. Then, we came to a hypothesis thatwhether PTEN/PI3K/Akt apoptotic signaling pathway is involved in theprocess of CME-induced myocardial injury. Up to date, there is nonerelated research in the domestic and overseas. Objective:The purpose of this experiment is to achieve PTEN silence ofmyocardial cells by interfering RNA technology, and thus the expressionof PTEN was observed downstream of related proteins, cardiac myocyteapoptosis and improves cardiac contractile function.Methods:Twenty swine were randomly assigned to four groups: sham surgery(n=5), CME (n=5), CME＋PTEN siRNA(n=5), CME＋controlsiRNA(n=5). CME was developed by injecting inertia plasticmicrospheres (diameter42μm) into left anterior descending coronary(LAD) in swine while the sham-operation group received the same doseof normal saline injected into LAD. All swine were sacrificed on hour of12h. The general morphological characteristics were observed in sectionswith HE staining, the areas of myocardial infarction was evaluated bypercent micronecrotic area in sections with hematoxylin basic fuchsinpicric (HBFP) staining. Cardiac function was measured byechocardiography. Serum troponin I (cTnI) was detected byelectrochemiluminescence (ECL). The mRNA and protein levels ofPTEN were determined by Real-time PCR and western blots, respectively.The protein levels of Phosphatidyl inositol-3-hydroxy kinase (PI3K),phosphorylation-PI3K, Protein Kinase B (PKB/Akt), phosphorylation-Akt, phosphorylation-Bad, Bad, caspase-3, and cleaved-caspase-3weredetermined by western blots.Results:The results showed that PTEN mRNA and PTEN protein wereaberrantly upregulated in cardiomyocytes following CME. Whereasadministration of PTEN siRNA could reverse the upregulation of PTEN nearly back to the control level. Furthermore, upregulation of PTEN incardiomyocytes in vivo could induce cardiac apoptosis, increased theareas of myocardial infarction, elevated the level of cTnI and deterioratedcardiac function, which could suppress PI3K/Akt. Concomitantly, theexpressions of key proapoptotic proteins such as p-Bad,cleaved-caspase-3were enhanced. However, PTEN siRNA couldmarkedly knockdown PTEN expression and reverse these changesfollowing CME. These results suggest that the contribution of PTENsiRNA to CME may be involved in downregulation of PTEN expression,which suppresses the activity of PI3K/Akt and enhances the activity ofBad, caspase-3in cardiomyocytes following CME.Conclusion:PTEN-mediated apoptosis signaling pathway might be involved inCME-induced myocardial injury in the pathological process, inhibitingthe expression of PTEN could reduce cardiac myocyte apoptosis andimprove cardiac contractile function. |
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