| BackgroundThe incidence rate of coronary heart disease has been ranked the first place indeveloped countries, and it is also the second highest fatal disease in China. The incidenceof acute coronary syndrome also rises, and recently presents a trend of getting youngerover the designated period. Besides thrombolysis and anticoagulation, the technology ofpercutaneous coronary intervention was widely carried out, for the treatment of acutecoronary syndrome.However it also increased the risk of cardiac ischemia/reperfusioninjury, and led to severe cardiovascular events occurred in reperfusion treatment process.Those bring new challenges and dilemmas for this process. Ischemia/reperfusion injurycan lead to a series of pathophysiological changes, such as endothelial dysfunction,inflammatory response and apoptosis and so on, with complex mechanisms. So far, the molecular mechanisms are still unclear.Erythropoietin (EPO), a well-known hematopoietic cytokine, was mainly used for thetreatment of advanced renal anemia in clinical. Many studies showed that it could protectmultiple organs such as heart, kidney, and brain. Recently researches demonstrated thatEPO had tissue-protective properties in a number of experimental models，in vitro and invivo. But the function of erythropoiesis limited its application in clinic which resulted inincreasing the risk of polycythemia, hypertension, thrombosis and the other diseasesrelated with coagulation cascade and platelet thrombosis. HBSP, helix B surface peptide,was a kind of multipeptide derived from EPO and had the similar tissue-protectivefunctions as EPO and other EPO derivant in ischemic heart, renal, nerve tissue, but had oneffect on erythropoiesis. Hence, our study focused on whether HBSP played protectiveeffect on tissues and cells after ischemia/reperfusion injury in cardiac. And exploredprimarily the molecular mechanisms of its cardioprotective effect.Cardiac microvascular was the very important part of the heart tissue, which ismainly constituted by microvascular endothelial cells, and ischemia/reperfusion injury canlead to endothelial dysfunction. The study showed that cardiac microvascular endothelialcells may be implicated firstly when I/R injury occurred. So to explore whether HBSPplay a protective role for cardiac microvascular endothelial cells against I/RI is greatsignificance. In this experiment, we studied whether HBSP has a protective effect，usingthe I/RI model of rat heart. And these may provide new ideas and theoretical basis for theclinical application of HBSP.Aims1. To observe the effects of Helix B surface peptide (HBSP) and EPO in cardiacischemia/reperfusion injury of rat.2. To establish the role of HBSP in cardiac I/RI and the mechanism relative withPI3K-Akt signal pathway.3. To observe the protection of HBSP in CMEC under SI/R injury. Methods1.200to250g male SD rats, ligation of the left anterior descending artery, and to restorecoronary perfusion after ischemia for30min. EPO or HBSP was injected from tailveins5min before reperfusion.2. All rats divided into five groups: Group sham, Group ischemia/reperfusion, GroupEPO (3000U/kg，4ml kg-1), Group HBSP (60μg/kg，4ml kg-1) and GroupHBSP+LY294002(PI3K specific inhibitor, injected from intravenous15min beforereperfusion).3. The hemodynamic values were measured via a cannula inserted into the right commoncarotid artery. The changes of left ventricular systolic pressure (LVSP) and leftventricular pressure differential (±LVdp/dt) were recoed. Small animal ultrasounddetected cardiac function by reperfusion24h and1w in rats.4. Reperfusion3h later，ligated the anterior descending coronary artery again, the area atrisk was assessed by evans blue staining and the infarct size was measured by TTCstaining.5. The expressions of Akt, phospho-Akt were detected by Western bloting. And apoptosisof cardiomyocytes were detected by TUNEL.6. Cardiac microvascular endothelial cells were isolated and cultured by150to200gmale SD rats, the preparation of simulated ischemia/reperfusion model.7. The group of experiment included control group (Con), simulated ischemia/reperfusion(SI/R) group, simulated ischemia/reperfusion+HBSP (SI/R+HBSP) group.8. Reoxygenation after3h, the MTT assay CMECs viability, and the apoptosis was assayby TUNEL.Results1. In this experiment, ST segment elevation as a sign of myocardial ischemia by recordingECG II.2. Compared with Group I/R, Group EPO and Group HBSP improved the hemodynamicvalues of LVSP and dp/dtmax. 3. Compared with I/R group, LVEF%, IVSS and FS%was significantly increased in EPOgroup and HBSP group after reperfusion24hours and1w.4. EPO group and HBSP group the infarct size was reduced compared with the I/Rgroup.5. EPO and HBSP reduced the cardiomyocytes apoptosis compared with the I/R group.The apoptotic index of cardiomyocytes in Group HBSP+LY294002was highercompared with HBSP group, and it partially inhibited cardiomyocytes apoptosis afterblocked the levels of phospho-Akt. There is no statistically significant differencesbetween Group EPO and Group HBSP6. The expressions of phospho-Akt were up-regulated by HBSP after I/RI in heart.7. Compared with the SI/R group, CMECs significantly higher value-added in HBSP+SI/R group.8. Compared with SI/R, apoptosis of CMECs was significantly reduced by HBSP.Conclusion1. HBSP can significantly improve systolic and diastolic function of rat after reperfusion3hours and24hours later, and it is also good at1week later.2. HBSP could obviously decrease the infarct size and myocardial apoptosis induced byischemia/reperfusion injury in vivo rat, and its protective effect may though activationof PI3K-Akt signal pathway. And there are not red blood cells increasing.3. HBSP has a protective effect on cardiac microvascular endothelial cells under imulatedischemic/reperfusion injury. |
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