| 1Background and objectiveAt present, with the continuous improvement of Chinese economic and people’sliving standards, the incidence and consequent mortality of ischemic heart disease isrising.With the development of various means of clinical treatment, which providesfor these diseases more effective ways. But at the same time, the adverse effects ofmyocardial ischemia-reperfusion injury in the recovery of the patients’ condition aregradually highlights. After a period of ischemia, the blood supply regains. However,the process of myocardial reperfusion can itself induce further cardiomyocyte death, aphenomenon known as myocardial reperfusion injury. How to find effectivepreventions of ischemia reperfusion injury in cardiomyocyte damage has became ahot pot in medical research. Related researchs, such as β-blockers, calciumantagonists, renin-angiotensin inhibitors are underging, but the results of theseresearches not very satisfactory. Therefore, to find an effective way or drug toimprove or cure ischemia-reperfusion injury has become a serious problem in clinical.The mechanism of myocardial ischemia-reperfusion injury is very complicated.Apoptosis is considered to be one of the important mechanisms. Apoptosis, known asprogrammed cell death. The expanding of myocardial infarction area after reperfusionthat is believed by apoptosis.The apoptosis during ischemia-reperfusion may becaused by several reasons such as the massive outbreak of oxygen free radicals,intracellular calcium overload, damage of mitochondria.One of these reasons, the massive outbreak of oxygen free radicals is considered to be one of the main reasons.Oxygen free radicals play a crucial role in myocardial ischemia-reperfusion injury.The arrhythmias after reperfusion, expanding of infarct size are all considered byoxygen free radicals. In the process of ischemia/reperfusion, oxygen freeradicals destroy the structure of cells and react with the unsaturated fattyacid, whichcan reduce the ion channels on the cell membrane and the enzyme activity ofmembrane proteins, thus affecting the cell membrane and organelle membranefunction, make its integrity and liquidity destroyed.China is rich in rare earth resources, ceria as a rare earth material is widely used invarious fields. Nano-scale materials for its own reasons, has special physical andchemical properties and the related researches have been done. Ceria nanoparticle as anano-material in recent years is used in industry, the automotive industry and in manyother aspects of daily life. Studies have demonstrated that cerium oxide nanoparticlescan scavenge oxygen free radicals.This study aimed to investigate the ceria nanoparticle on ischemia-reperfusioninjury in myocardial tissue superoxide dismutase, glutathione peroxidase,malondialdehyde and apoptosis. In order to investigate its protective effect onmyocardial ischemia-reperfusion injury, and hope to provide more effective means forischemic-reperfusion injury.2Materials and Methods2.1Preparation of ceria nanoparticles suspension: make ceria nanoparticle ofdifferent particlesizes dissolved in PBS buffer (PH7.4,0.01mM) respectively and mixit thoroughly. Before injection, put it in the ultrasonic cell disrupter2min to makesure the suspension fully mixed again, and after the completion of a filter with a0.2μm filter before use.2.2groups:50healthy male Spragur-Dawley rats, weighing between250~280g,were randomly divided into five groups, sham group, control group,1-10nm particlediameter group,10-25nm particle diameter group,50nm particle diameter group (n=10). After an adaptive feeding week, the rats were anesthetized by10%chloralhydrate (300mg/kg) intraperitoneal injection. The rats were supine position fixed,isolated tracheal intubation, ventilator when connecting thoracotomy.The small animal ventilator was set tidal volume to3ml/100g, respiratory frequency of70times/min, breath2:1. The thoractomy was performed by the4th and5th ribs, torn thepericardium slightly and make heart fully exposed. Threading at about3.0~4.0mmbelow the anterior-inferior edge of left atrium, between the aortic root and thepulmonary cone left atrial appendage. Put a grooved latex tube between the ligatureand the heart surface. Until the heart rhythm regularity, ligature the left anteriordescending coronary artery. The ligature remote myocardium becomes from white tocyanotic, which proveded the ligation was successful.45min after ligation releasedthe ligature, reperfusion120min, site of myocardial ischemia turned back and themodel succeed. Gave the sham group PBS buffer (0.2ml/100g) from caudal vein24hbefore the operation, and ligatured the left anterior descending coronary arterywithout wearing wire. The control group was given PBS buffer (0.2ml/100g) fromcaudal vein24h before the operation too. The left anterior descending coronary arterywas ligatured45min and released120min. The three different nanoparticle groupswere injected CeO2nanoparticle suspension (0.2ml/100g) via the tail vein24h beforethe operation, and the model-making was the same to the control group.2.3The rats were killed120min after reperfusion, removed the heart quickly, rinsethoroughly with cold saline until there was no blood residue. Took the left ventricularmyocardium ischemic area and divided it into two parts. Blot one part dry with filterpaper quickly and transferred it to-80℃stored in the refrigerator. The other partwas fixed in formaldehyde solution, preparing for the observation of histopathologyand detection of apoptosis. Made the-80℃refrigerator stored fresh myocardial tissueprepared for myocardial tissue homogenate in low temperature environment. Theactivity of superoxygen dehydrogenises (SOD) and glutathione peroxidase weredetected with the xanthine oxidase method and colorimetric assay separatedly. Thecontent of malondialdehyde was detected thibatituric acid method. Specific stepsshould in strict accordance with the kit instructions. The fixed part was made intoparaffin sections, preparing for hematoxylin-eosin staining to observe themorphological changes and apoptosis detection to observe the apoptosis cells.2.4Statisticed for each set of data, all data were expressed as mean±standarddeviation. Each set of data were compared with one-way ANOVA and pairwise comparisons used LSD method. The SPSS17.0software was used for statisticalanalysis. The test level α is0.05, P <0.05was considered statistically significant.3Results3.1Compared with the Sham group, the activities of SOD and GSH-Px incontrol group were significantly decreased (P<0.05).The activities of SOD andGSH-Px were increased in the three different particle diameter groups in comparisonwith the control group (P<0.05). The activity of SOD and GSH-Px were increasedin10-25nm particle diameter group than the other two groups (P<0.05). The activityof SOD and GSH-Px were increased in1-10nm particle diameter group than in50nmparticle diameter group (P<0.05).3.2Compared with the Sham group, the content of MDA in control group wassignificantly increased (P<0.05).The content of MDA was decreased in the threedifferent particle diameter groups in comparison with the control group (P<0.05). Thecontent of MDA was decreased in10-25nm particle diameter group than the other twogroups (P<0.05). The content of MDA was decreased in1-10nm particle diametergroup than in50nm particle diameter group (P<0.05).3.3The myocardial histopathology showed that compared with the control group,the integrity of cells in the sham group was much better. The three different particlediameter groups were significantly improved than that in model group. But still not asgood as the sham group, there exist inflammatory cells.3.4The apoptosis detection showed that the apoptosis of myocardial cells in thecontrol group were significantly increased in comparison with the sham group(P<0.05). The apoptosis of myocardial cells were significantly decreased in the threedifferent particle diameter groups in comparison with control group (P<0.05). Theapoptosis of myocardial cells were decreased in10-25nm particle diameter group thanthe other two groups (P<0.05). There was no significant difference (P>0.05) betweenthe two1-10nm and50nm groups.4Conclusion4.1Ceria nanoparticle can significantly improve the activity of SOD〠GSH-Px，and reduce the content of MDA, in ischemia-reperfusion injury myocardial tissue.4.2Ceria nanoparticles significantly reduce the incidence of myocardial apoptosis and improved the morphological changes caused by myocardial reperfusioninjury.4.3Ceria nanoparticle can reduce the oxidative stress in myocardialischemia-reperfusion injury, play a cardioprotection role in a degree. |
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