Injury to primary cultures of rat heart endothelial cells by hypoxia and glucose deprivation

Summary Primary cultures of rat heart endothelial cells were subjected to simulated conditions of ischemia: hypoxia and glucose deprivation for 4 and 24 hr. Cellular injury was evaluated by measuring changes in viability, total protein, cellular morphology, and leakage of cytoplasmic enzymes from the cells into the culture medium. Deprivation of oxygen and glucose for 4 or 24 hr did not lethally injure the cells as noted by no change in cell viability, morphology, and total protein when compared to controls. However, reversible or nonlethal cellular injury was produced as reflected by a significant release of lactate dehydro-genase (LDH) from the cells into the medium after treatment with hypoxia and glucose deprivation for 4 or 24 hr. When the cultures were deprived of glucose, but were oxygenated, cellular injury was not evident after 24 hr. Deprivation of oxygen but not glucose resulted in significant loss of LDH after 4 or 24 hr. When the cultures were allowed to recover after oxygen and glucose deprivation in complete medium containing 1000 mg glucose per l and a normal atmosphere of 20% O₂, they had levels of LDH leakage comparable to those of control cultures. This study was supported by Research Grant HL 18647 from the National Heart, Lung, and Blood Institute and by a National Chicano Council on Higher Education Post-Doctoral Fellowship awarded to D. Acosta from the Ford Foundation. Additional support was provided to D. Acosta by a Faculty Research Assignment Award from the University of Texas Research Institute.     

Reduction of cell injury in hypoxic cultures of rat myocardial cells by methylprednisolone

Summary An in vitro model to study myocardial cell injury was developed with primary monolayer cultures of rat myocardial cells. Two important conditions associated with myocardial ischemia were simulated by depriving the cultures of oxygen and glucose for a specified period of time. Cellular injury caused by hypoxia and glucose deprivation resulted in significant leakage of lactate dehydrogenase (LDH) from the cells into the culture medium. The cells were not lethally injured by treatments as reflected by a lack of change in cell viability and protein content when compared to controls. Pretreatment of cultures with methylprednisolone for 24 hr provided protection to the cells when challenged by hypoxia and glucose deprivation. Methylprednisolone exhibited a dose-response effect in reducing LDH leakage in cultures, which were subsequently deprived of oxygen and glucose for 4 hr. Similar pretreatment with hydrocortisone had no effect in limiting cellular injury in hypoxic and glucose-deprived cultures. The research was supported by Grant HL 18647 from the National Heart, Lung, and Blood Institute and by a National Chicano Council on Higher Education Post-Doctoral Fellowship awarded to D. Acosta from the Ford Foundation. Additional support was provided to D. Acosta by a Faculty Research Assignment Award from the University of Texas Research Institute.     

心肌缺血／再灌注损伤后血清和心肌组织Leptin水平的变能

目的：观察大鼠心肌缺血／再灌注损伤对血清和心肌组织瘦素（Leptin）表达的影响,探讨Leptin在心肌缺血／再灌注损伤中的作用。方法：建立大鼠心肌缺血／再灌注模型,检测血清乳酸脱氢酶（LDH）和Leptin浓度,并用HE染色和免疫组织化学观察心肌组织病理学及Lepfin表达水平。结果：缺血组、再灌注组血清LDH水平显著升高（P〈0．05）,表明该模型制作成功,造成心肌局部一定程度的损伤。缺血组血清Leptin含量（6．34±2．49）ng／ml显著低于对照组（7．50±2．93ng／ml,P〈0．05）;再灌注后Leptin水平缓慢恢复,于再灌注2h时Leptin达到（8．32±1．74）ng／ml,恢复到损伤前水平（8．38±2．56）ng／ml,且随再灌注时间延长有升高趋势。免疫纽化显示与假手术纽心肌Leptin蛋白表达水平相比,其他四组均有显著降低（P〈0．01）,按缺血45min后再灌注1h组、缺血45min后再灌注3h组、单纯缺血45min组、缺血45min后再灌注2h组依次递减。结论：Leptin在心肌缺血／再灌注损伤后早期45min血中有明显减少,心肌组织中也明显表达下降。心肌组织病理损伤与Leptin的改变可能有一定的关系。     

3,6-(二甲氨基)-二苯并碘杂六环葡萄糖酸盐对损伤心肌细胞的保护作用

目的：观察3,6-（二甲氨基）-二苯并碘杂六环葡萄糖酸盐（IHC-93）对培养心肌细胞损伤的影响。方法：在培养的心肌细胞建立低氧／复氧损伤模型和过氧化氢损伤模型,观察心肌细胞存活率、乳酸脱氢酶（LDH活性、超氧化物歧化酶（SOD）活性、丙二醛（MDA含量,以研究IHC-93对培养心肌细胞损伤的影响。结果：10、20、40μmol／LIHC-93呈剂量依赖地提高损伤心肌细胞存活率和SOD的活性,减少LDH的释放,降低MDA含量。结论：IHC-93对损伤心肌细胞具有直接保护作用。     

Ischemic myocardial injury in cultured heart cells: preliminary observations on morphology and beating activity

An in vitro model of myocardial ischemia has been established with primary monolayer cultures of neonatal rat heart cells. Ischemic conditions were simulated in vitro by subjecting the heart cell cultures to various levels of oxygen and glucose deprivation. After the ischemic treatments, cultures of beating muscle (M) cells were evaluated for functional and morphological changes. The experimental protocol consisted of treatment with 20% or 0% O2 and 1000, 500 or 0 mg glucose per 1 of medium for 4, 12 or 24 hr. Control cultures were treated with 20% O2 and 1000 mg glucose. The morphological alterations induced by the deficiency of O2 and glucose in the medium were the formation of pseudopodia and cytoplasmic vacuoles; increased cytoplasmic granulation; and the formation of abnormal cell shapes, such as long, spindly shaped M cells. There was a time-dependent decrease in beating activity as the M cells were exposed to longer durations of ischemic conditions. However, if the cultures were replenished with complete medium (1000 mg glucose) and 20% O2, the cells regained their ability to beat.     

Improved methods for automatic monitoring of contracting heart cells in culture

The present communication describes improved methods for isolating and plating beating heart cells from neonatal rats using collagenase and collagen-coated petri dishes. The amplitude and frequency of contraction are continuously and simultaneously measured under well defined conditions and during prolonged periods of time with a highly sensitive and thermostated instrument. Additions, e.g. drugs and toxic agents, are made through an accessory pump system that involves extensive dilution of the added compound with medium; aliquots of medium can be withdrawn for estimation of metabolites. The system described is reliable and relatively inexpensive and allows a more extensive use of isolated heart cells, especially in studies of heart functions where small changes in amplitude and frequency of beating during prolonged periods of time are important.     

Engineered heart tissue graft derived from somatic cell nuclear transferred embryonic stem cells improve myocardial performance in infarcted rat heart

The concept of regenerating diseased myocardium by implanting engineered heart tissue (EHT) is intriguing. Yet it was limited by immune rejection and difficulties to be generated at a size with contractile properties. Somatic cell nuclear transfer is proposed as a practical strategy for generating autologous histocompatible stem (nuclear transferred embryonic stem [NT‐ES]) cells to treat diseases. Nevertheless, it is controversial as NT‐ES cells may pose risks in their therapeutic application. EHT from NT‐ES cell‐derived cardiomyocytes was generated through a series of improved techniques in a self‐made mould to keep the EHTs from contraction and provide static stretch simultaneously. After 7 days of static and mechanical stretching, respectively, the EHTs were implanted to the infarcted rat heart. Four weeks after transplantation, the suitability of EHT in heart muscle repair after myocardial infarction was evaluated by histological examination, echocardiography and multielectrode array measurement. The results showed that large (thickness/diameter, 2–4 mm/10 mm) spontaneously contracting EHTs was generated successfully. The EHTs, which were derived from NT‐ES cells, inte grated and electrically coupled to host myocardium and exerted beneficial effects on the left ventricular function of infarcted rat heart. No teratoma formation was observed in the rat heart implanted with EHTs for 4 weeks. NT‐ES cells can be used as a source of seeding cells for cardiac tissue engineering. Large contractile EHT grafts can be constructed in vitro with the ability to survive after implantation and improve myocardial performance of infarcted rat hearts.     

缺血预处理对缺血/再灌注离体心脏的保护作用

目的：探讨连续多次短暂缺血预处理对缺血/再灌注损伤心肌的保护作用及机制。方法：采用大鼠离体心脏Lan-gendorff灌流模型,观察缺血预处理对心肌缺血/再灌注后不同时间点冠脉流出液中AST、CPK、UDH及冠脉流量,心肌组织中SOD、LPO以及再灌注性心律失常的影响。结果：缺血预处理可以减少缺血/再灌注损伤的心肌冠脉流出液中AST、CPK、LDH的含量,提高心肌SOD活性,降低LPO水平,并且抑制再灌注性心律失常的发生,提高再灌注期间的冠脉流量。结论：缺血预处理对心肌缺血/再灌注损伤具有一定保护作用。     

Biotransformation of tetrahydroberberine to berberine by enzymes prepared from cultured coptis japonica cells

Crude enzymes were extracted from cultured Coptis japonica cells producing large amounts of berberine. One of the enantiomers of tetrahydroberberine, (S)-(?)-tetrahydroberberine, was dehydrogenated to berberine by the enzyme system.     

Validity of a model of cultured myocardial cells for assessment of cardioplegia

Myocardial protection is usually studied in vitro on perfused heart preparations, but never directly on cultured cardiomyocytes. We evaluated a model of cultured newborn rat cardiomyocytes to study both the cytotoxicity and the protective effect against chemical hypoxia of three cardioplegic solutions (St Thomas' I, Bretschneider, St Thomas' II) under normothermic (37°C) and hypothermic (4°C) conditions. Cytotoxicity was evaluated in 50% and 100% concentrations of the cardioplegic solutions with incubation times from 90 to 360 min. Myocardial protection was studied in 50% cardioplegic solution with metabolic inhibitors. Immediate and late viabilities, after 24 h of recovery in the medium, were evaluated by simultaneous staining with fluorescein diacetate and propidium iodide.At 37°C, the 50% concentration of the three cardioplegic solutions did not modify cell viability. At 37°C, with 360 min of incubation, the 100% concentration of the St Thomas' I and Bretschneider solutions diminished immediate viability (mean ± SD: medium 87% ± 2%; St Thomas' I 58% ± 5%; Bretschneider 37% ± 8%; St Thomas' II 89% ± 3%) as well as late viability (medium 69% ± 2%; St Thomas' I 32% ± 3%; Bretschneider 24% ± 7%; St Thomas' II 65% ± 4%). At 4°C, immediate and late viabilities were unaffected by cardioplegic solutions.At 37°C, after 360 min incubation time, metabolic inhibitors diminished immediate viability to 29% ± 1% and late viability to zero. None of the three cardioplegic solutions used at 50% concentration prevented this effect.At 4°C, immediate viability was not significantly affected by metabolic inhibitors (73% ± 10%), but the use of Bretschneider cardioplegic solution seemed to be detrimental (53% ± 9%). On the other hand, recovery phase after pretreatment with metabolic inhibitors with or without cardioplegic solutions for 360 min significantly diminished late viability (medium 63% ± 7%; metabolic inhibitors 17% ± 8%; St Thomas' I 17% ± 6%; Bretschneider 8% ± 6%; St Thomas' II 15% ± 3%) and again cardioplegia was inefficient. In conclusion, in this in vitro model for the study of cardioplegic solutions, only pure concentrations of the St Thomas' I and Bretschneider solutions under normothermic conditions were cytotoxic. The well-known protective effects of hypothermia against ischemia and reperfusion injury were both reproduced. Therefore, and even though cardioplegia failed to have any protective effect, probably owing to a severe metabolic inhibition, this model may be useful for studying myocardial protection.     

mTOR and Beclin1: Two key autophagy-related molecules and their roles in myocardial ischemia/reperfusion injury

Autophagy is the general term of lysosomal degradation of substances in cells, which is considered the key to maintaining the normal structure and function of the heart. It also has a correlation with several heart diseases, in particular, myocardial ischemia/reperfusion (I/R) injury. At the stage of myocardial ischemia, autophagy degrades nonfunctional cytoplasmic proteins providing the critical nutrients for the critical life activities, thereby suppressing cell apoptosis and necrosis. However, autophagy is likely to affect the heart negatively in the reperfusion stage. Mammalian target of rapamycin (mTOR) and Beclin1 are two vital autophagy-related molecules in myocardial I/R injury playing significant roles in different stages. In the ischemia stage, mTOR plays its roles through AMPK/mTOR and phosphoinositide 3-kinase/Akt/mTOR pathway, whereas Beclin1 plays its roles through its upregulation in the reperfusion stage. A possible interaction between mTOR and Beclin1 has been reported recently, and further studies need to be done to find the underlying interaction between the two molecules in myocardial I/R injury     

The protective role of curcumin in myocardial ischemia–reperfusion injury

Coronary artery disease (CAD) is a well-known pathological condition that is characterized by high morbidity and mortality. The main pathological manifestation of CAD is myocardial injury due to ischemia–reperfusion (I–R). Currently, no efficacious treatment of protecting the heart against myocardial I–R exists. Hence, it is necessary to discover or develop novel strategies to prevent myocardial-reperfusion injury to improve clinical outcomes in patients with CAD. A large body of experimental evidence supports cardioprotective properties of curcumin and the ability of this phytochemical to modify some cardiovascular risk factors. However, the detailed effects of curcumin in myocardial I–R injury are still unclear and there is a lack of evidence concerning which curcumin regimen may be ideal for myocardial I–R injury. This paper presents a brief review of the pathophysiology of myocardial I–R injury and the mechanisms of action of curcumin in reducing myocardial I–R injury.     

KRT1 gene silencing ameliorates myocardial ischemia–reperfusion injury via the activation of the Notch signaling pathway in mouse models

Myocardial ischemia and reperfusion injury (MIRI) includes major drawbacks, such as excessive formation of free radicals and also overload of calcium, which lead to cell death, tissue scarring, and remodeling. The current study aims to explore whether KRT1 silencing may ameliorate MIRI via the Notch signaling pathway in mouse models. Myocardial tissues were used for the determination of the positive rate of KRT1 protein expression, apoptosis of myocardial cells, creatine kinase (CK) and lactate dehydrogenase (LDH) expression, expression of related biomarkers as well as myocardial infarction area. The transfected myocardial cells were treated with KRT1-siRNA, Jagged1, and DAPT (inhibitor of Notch-1 signaling pathway). The expression of KRT1, NICD, Hes1, Bcl-2, and Bax protein was detected. The MTT assay was applied for cell proliferation and flow cytometry was used for cell apoptosis. Mice with MIRI had a higher positive rate of KRT1 protein expression, apoptosis of myocardial cells, CK and LDH expression, myocardial infarction area, increased expression of MDA, NO, SDH, IL-1, IL-6, TNF-α, CRP, KRT1, Bax protein, CK, and LDH, and decreased expression of SOD, NICD, Hes1, and Bcl-2. The downregulation of KRT1 led to decreased expression of KRT1 and Bax protein, increased expression of NICD, Hes1, and Bcl-2, decreased cell apoptosis, and improved cell proliferation. The inhibition of the Notch signaling pathway leads to reduced expression of Bax, increased expression of NICD, Hes1, and Bcl 2, and also decreased cell apoptosis and increased cell proliferation. Our data conclude that KRT1 silencing is able to make MIRI better by activating the Notch signaling pathway in mice.     

心肌缺血预适应循环血中微囊泡对大鼠心肌I/R损伤的作用

目的：研究心肌缺血预适应（IPC）大鼠循环血中微囊泡（MVs）对大鼠在体心肌缺血/再灌注（I/R）损伤的作用及相关机制。方法：反复短暂结扎/松开大鼠冠状动脉左前降支建立大鼠IPC模型,自腹主动脉取血,超速离心法分离循环血中的IPC-MVs,并对其进行流式鉴定。建立在体大鼠心肌I/R模型,股静脉注射IPC-MVs 7 mg/kg。HE染色观察心肌形态学变化,TTC染色检测心肌梗死范围,TUNEL染色检测心肌细胞凋亡率。比色法测定血清乳酸脱氢酶（LDH）活力,分光光度法测定心肌组织caspase 3活力,Western blot法检测心肌组织Bcl-2、Bax蛋白表达水平。结果：流式细胞术检测IPC-MVs浓度为4380±745个/μl。与I/R组比较,IPC-MVs能够减轻I/R大鼠心肌组织损伤,缩小心肌梗死范围（P<0.01）,减少心肌细胞凋亡数量（P<0.01）,明显降低血清LDH活力（P<0.01）,降低心肌组织caspase 3活力（P<0.01）,升高Bcl-2蛋白表达（P<0.01）,降低Bax蛋白表达（P<0.01）,升高Bcl-2/Bax比值（P<0.01）。结论：IPC-MVs显著减轻大鼠在体心肌I/R损伤,通过上调心肌组织中Bcl-2的蛋白表达,下调Bax的蛋白表达,升高Bcl-2/Bax比值,降低caspase 3活力而发挥心肌保护作用。     

骨髓间质干细胞向大鼠损伤心肌组织的迁移

实验旨在动态观察骨髓间充质干细胞（mesenchymal stem cells,MSCs）向不同微环境下心肌组织的迁移特点,明确组织损伤在干细胞迁移中的作用,为提高干细胞治疗的靶向性和高效性奠定初步试验基础。分离纯化雄性Sprague-Dawley（SD）大鼠的骨髓MSCs,输注入雌性SD大鼠。实验分为4组：正常大鼠＋MSCs移植组,假手术＋MSCs移植组,心肌缺血＋MSCs移植组,心肌缺血对照组（心肌缺血＋培养基移植）。结扎冠状动脉前降支制造心肌缺血模型,将相等数量的雄性MSCs经尾静脉注射移植入前3组雌性大鼠体内,对照组注射等体积培养基,分别于移植后1周及8周取心脏组织标本,采用荧光原位杂交方法（fluorescence in situ hybridization,FISH）检测大鼠Y染色体雄性鉴别基因sty片段的表达,用透射电镜观察大鼠心肌组织超微结构改变。结果发现,移植后1周和8周,正常大鼠移植组和对照组大鼠的心肌组织中均未见sry基因的表达,但假手术移植组和心肌缺血移植组的心肌组织中均可见sty基因的表达,心肌缺血移植组的Y染色体sty基因阳性细胞数量在两个时间点均显著高于假手术移植组（P〈0．01）。分别比较心肌缺血移植组和假手术组在移植后1周和8周的Y染色体sry基因阳性细胞的数量,两个时间点无明显差异。心肌组织的超微结构观察发现心肌缺血移植组大鼠的心肌梗死周边区域可见一些细胞,其形态类似于体外培养的MSCs。研究结果提示MSCs具有向损伤心肌组织迁移的特性,迁移的高峰期可能在组织损伤1周左右,组织损伤及其程度在干细胞迁移中起重要作用。     

Relation of several antioxidant enzymes to rapid freezing resistance in suspension cultured cells from alpine Chorispora bungeana

Chorispora bungeana Fisch. & C.A. Mey (Crucifer) is a rare alpine subnival plant surviving sudden snowstorms. In this paper, we have attempted to explore possible roles of autoxidation rate (AR) and the antioxidant enzymes associated with cryoprotective mechanisms in the plant cells. The results showed that when the suspension cultures growing at 25 degrees C were suddenly exposed to -8 degrees C for 15 days, 2,3,5-triphenyltetrazolium chloride reduction was not affected within 9 days and AR remained at a low level in comparison with controls. This indicated that the cells maintained considerable amounts of soluble protein and the integrity of the cell membranes was intact during the whole freezing test. Furthermore, on average, the activity of antioxidant enzymes such as superoxide dismutase, dehydroascorbate reductase, ascorbate peroxidase and glutathione reductase were prominently enhanced in the freezing-stressed cells. Peroxidase activity significantly increased soon after freezing, possibly to make up for the early decrease of catalase activity in the cells. Statistical analysis showed negative correlations between resistance to rapid freezing and antioxidant enzyme activity in the cultured cells after exposure from 25 to -8 degrees C, indicating that the reduction of cell viability with freezing activates a combination of antioxidant enzymes that results in intact cells. All of these findings suggest a synergy between these antioxidant enzymes, leading to a low autoxidation rate that contributes to the protection of the cell membranes and plays an important role in the resistance of suspension cultured cells of C. bungeana to sudden freezing.     

Free radical damage to cultured porcine aortic endothelial cells and lung fibroblasts: Modulation by culture conditions

Summary Culture conditions modulating cell damage from xanthine plus xanthine oxidase-derived partially reduced oxygen species were studied. Porcine thoracic aorta endothelial cells and porcine lung fibroblasts were maintained in monolayer culture. Cells were prelabeled with⁵¹Cr before xanthine plus xanthine oxidase exposure. Endothelial cells showed 30 to 100% more lysis than fibroblasts and thus seemed more sensitive to this oxidant stress. The effect of cell culture age, as indicated by population doubling level (PDL), was examined. Response of low PDL endothelial cells and fibroblasts subjected to oxidant stress was compared with the response of PDL 15 cells. Both low PDL endothelial cells and fibroblasts responded differently to the lytic effect of xanthine oxidase-derived free radicals than did higher PDL cells. Specific activities of the antioxidant enzymes catalase, managanese superoxide dismutase, copper-zinc superoxide dismutase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase were measured in both low and high PDL fibroblasts and endothelial cells. Antioxidant enzyme specific activities could only partially explain the differences in response to oxidant stress between fibroblasts and endothelial cells and between low and high PDL cells. Cell culture medium composition modulated the rate of production, and relative proportions of xanthine plus xanthine oxidase-derived partially reduced species of oxygen, i.e. superoxide, hydrogen peroxide, and hydroxyl radical. Serum content of medium was important in modulating free radical generation; superoxide production rates decreased 32%, H₂O₂ became undetectable, and hydroxyl radical generation decreased 54% in the presence of 10% serum. The medium protein and iron content also modulated free radical generation. The data suggest that cell culture media constituents, cell type, and cell culture age greatly affect in vitro response of cells subjected to oxidant stress. Research supported by American Lung Association Fellowship Training Grant and Research Training Grant, the R. J. Reynolds Corporation, and National Institutes of Health Grants HL29784 and 1 HL 23805.