一氧化氮在乳鼠心肌细胞缺氧—复氧预处理延迟保护效应中的作用

探讨缺氧—复氧损伤对乳鼠心肌细胞一氧化氮释放和一氧化氮合酶活性的影响以及一氧化氮在心肌细胞延迟缺氧预处理中的作用。在培养乳鼠心肌细胞缺氧预处理的模型上，测定缺氧—复氧损伤对乳鼠心肌细胞一氧化氮释放和一氧化氮合酶活性，观察延迟缺氧预处理以及N-硝基-L-精氨酸、L广精氨酸、硝普钠对心肌细胞延迟缺氧预处理的影响。结果发现，缺氧—复氧后乳鼠心肌细胞一氧化氮释放增加，一氧化氮合酶活性升高。延迟缺氧预处理可以减少缺氧一复氧对心肌细胞的损伤。非选择性一氧化氮合酶抑制剂N-硝基-L-广精氨酸可以阻断延迟缺氧预处理的心肌保护作用，L广精氨酸不能模拟延迟缺氧预处理，硝普钠可以模拟延迟缺氧预处理。结果提示，一氧化氮可以诱导心肌细胞的延迟缺氧预处理。     

Near infrared light protects cardiomyocytes from hypoxia and reoxygenation injury by a nitric oxide dependent mechanism

Photobiomodulation with near infrared light (NIR) provides cellular protection in various disease models. Previously, infrared light emitted by a low-energy laser has been shown to significantly improve recovery from ischemic injury of the canine heart. The goal of this investigation was to test the hypothesis that NIR (670 nm) from light emitting diodes produces cellular protection against hypoxia and reoxygenation-induced cardiomyocyte injury. Additionally, nitric oxide (NO) was investigated as a potential cellular mediator of NIR. Our results demonstrate that exposure to NIR at the time of reoxygenation protects neonatal rat cardiomyocytes and HL-1 cells from injury, as assessed by lactate dehydrogenase release and MTT assay. Similarly, indices of apoptosis, including caspase 3 activity, annexin binding and the release of cytochrome c from mitochondria into the cytosol, were decreased after NIR treatment. NIR increased NO in cardiomyocytes, and the protective effect of NIR was completely reversed by the NO scavengers carboxy-PTIO and oxyhemoglobin, but only partially blocked by the NO synthase (NOS) inhibitor L-NMMA. Mitochondrial metabolism, measured by ATP synthase activity, was increased by NIR, and NO-induced inhibition of oxygen consumption with substrates for complex I or complex IV was reversed by exposure to NIR. Taken together these data provide evidence for protection against hypoxia and reoxygenation injury in cardiomyocytes by NIR in a manner that is dependent upon NO derived from NOS and non-NOS sources.     

一氧化氮对缺氧复氧处理的新生大鼠心肌细胞蛋白质酪氨酸磷酸酶-1B活性和表达的影响

目的 验证缺氧复氧诱发的新生大鼠心肌细胞蛋白质酪氨酸磷酸酶-1B(PTP-1B)的表达和活性的增加是否由一氧化氮(NO)介导.方法 分离的新生大鼠心肌细胞,随机分为正常组、缺氧复氧组、非特异性一氧化氮合成酶抑制剂L-NAME组(L-NAME组)、缺氧复氧和L-NAME组(L-NA+H/R组).心肌细胞中PTP-1B的活性和表达分别由405 nm的光谱测量仪和Western blot法检测.同时分析心肌细胞培养基中的NO的浓度和乳酸脱氢酶活性.结果 与正常组比较,缺氧复氧组中心肌细胞PTP-1B的活性和表达较高,(L-NA+H/R)组PTP-1B的活性和表达不高.与缺氧复氧组比较,(L-NA+H/R)组NO和乳酸脱氢酶浓度显著低.缺氧复氧组和L-NA+H/R组中的NO含量分别是正常组(100%)的(368±13)%和(61±7)%(P<0.005);缺氧复氧组、L-NAME+H/R组中的乳酸脱氢酶的活性值分别为41.2±6.7和23.6±4.8(P<0.05).结论 L-NAME预处理阻止了缺氧复氧诱发的大鼠心肌细胞中PTP-1B活性和表达的增加,提示缺氧复氧期间PTP-1B的变化是由NO介导的.     

Cytoprotective mechanism of heat shock protein 70 against hypoxia/reoxygenation injury

The role of heat shock protein 70 (HSP70) in the cytoprotection against hypoxia/reoxygenation injury was examined. Adult rat cardiomyocytes were isolated, subjected to hyperthermia at 42 degrees C for 15 min (heat shock treatment), and then incubated at 37 degrees C for 3 to 24 h (HSP production process). Heat shock treatment increased HSP70 production (80-260% increase); the peak increase was seen after 9 h of HSP production process. Thereafter, the cells were subjected to 120-min hypoxia and 15-min reoxygenation. Heat shock treatment increased the survival of the cells subjected to hypoxia/reoxygenation (1.5-2.5-fold); the maximal cytoprotection was observed after 12 h of HSP production process. Heat shock treatment increased HSP70 content in the nucleus when cells were subjected to 12 h of HSP production process. To examine the role of HSP70 accumulation in the nuclear fraction, the activity of poly(ADP-ribose) synthetase (PARS), which functions in the nucleus and consumes high-energy phosphates excessively in the reoxygenated state, were measured in the cells with heat shock and 12 h of HSP production process. Heat shock treatment attenuated the hypoxia/reoxygenation-induced increase in the PARS activity (50% decrease). Treatment of the cells with 3-aminobenzamide, an inhibitor of PARS, exerted the effects similar to those of heat shock treatment. These results suggest that attenuation of the PARS activity in the nucleus may play an important role in the cytoprotective effect of HSP70 on hypoxia/reoxygenation injury.     

Preconditioning with diazoxide prevents reoxygenation-induced rigor-type hypercontracture

Ischemic preconditioning has a powerful protective potential against a reperfusion-induced injury of the post-ischemic myocardium. Cardiomyocyte hypercontracture, i.e. excessive cell shortening, is an essential mechanism of the reperfusion-induced injury. Rigor contracture, i.e. Ca²⁺-independent contracture, has been shown to be an import component of the reperfusion-induced hypercontracture. Since rigor contracture is dependent on the rapidity of the metabolic recovery during reoxygenation, we hypothesized that preconditioning of the cardiomyocyte mitochondria may improve mitochondrial function to restore the energy balance during the initial phase of reoxygenation and may thus prevent rigor contracture. For this purpose adult rat cardiomyocytes were exposed to anoxia with subsequent reoxygenation. For preconditioning, cells were pre-treated with the mitochondrial ATP-sensitive K⁺ channel opener diazoxide. Pre-treatment with 100 μmol/l diazoxide significantly reduced the reoxygenation-induced hypercontracture of cardiomyocytes due to an attenuation of the Ca²⁺-independent rigor-type contracture, which was accompanied by an acceleration of the phosphocreatine resynthesis during the initial phase of reoxygenation. Treatment with the mitochondrial ATP-sensitive K⁺ channel antagonist 5-hydroxydecanoate (500 μmol/l) during preconditioning phase abolished these protective effects. Similarly, partial suppression of the mitochondrial function with 100 μmol/l NaCN during the reoxygenation phase abolished the diazoxide effects. Finally, in isolated rat hearts, preconditioning with diazoxide prior to global ischemia significantly improved left ventricular function and attenuated hypercontracture during reperfusion. This effect could be abolished by the treatment with 100 μmol/l NaCN during reperfusion. Taken together, pharmacological preconditioning of cardiomyocytes with diazoxide protects against the reoxygenation-induced rigor hypercontracture due to an improvement of the energy recovery at the onset of reoxygenation.     

Long-term treatment with the AT1-receptor antagonist telmisartan inhibits biglycan accumulation in murine atherosclerosis

Accumulation of biglycan, a small leucine-rich proteoglycan, in the neointima precedes the retention of lipids and accumulation of macrophages during early atherosclerosis. Biglycan is therefore considered a pro-atherogenic proteoglycan that might play a key role in atherogenesis. On the other hand biglycan ensures in part establishment of stable collagen networks. Aim of the present study was to determine whether telmisartan affects biglycan accumulation in a murine model of accelerated atherosclerosis and whether collagen matrix is affected. ApoE^−/−-mice on Western diet were chronically (12 weeks) treated either with telmisartan (10 mg/kg) or hydralazine (500 mg/l drinking water) and systolic arterial blood pressure was determined by tail cuff plethysmography. Animals were killed and aortic plaque score, plaque morphology and extracellular matrix as well as cellular plaque composition were analyzed at the aortic root. Furthermore, expression of biglycan and enzymes involved in collagen cross-linking were analyzed in the aorta. Telmisartan and hydralazine lowered systolic arterial blood pressure to the same extent. Biglycan accumulation in the aorta and the aortic root was significantly reduced by telmisartan but not by hydralazine. The amount of collagen and collagen fibril density, macrophages and SMCs was not affected by either treatment as determined by analysis of picrosirius red staining, mac2 and α-SM-actin. Furthermore, telmisartan inhibited aortic plaque score and aortic root plaque size compared to mice receiving hydralazine and untreated controls. The current study shows that telmisartan reduces biglycan accumulation and inhibits atherosclerosis independently of blood pressure lowering and without affecting the collagenous plaque matrix. Thus, biglycan is a pleiotropic target of telmisartan that might contribute to the anti-atherogenic effects of this AT1-antagonist.     

缺氧后处理对缺氧复氧心肌线粒体活性氧及细胞凋亡的影响

目的 观察缺氧后处理对缺氧复氧心肌线粒体活性氧及细胞膜和线粒体Bcl-2和Bax蛋白表达的影响,探讨其调控心肌细胞凋亡的机制.方法 构建大鼠乳鼠心肌细胞缺氧复氧损伤模型,将细胞分为对照组、缺氧/复氧纽(缺氧3h后复氧6h)、缺氧后处理组(缺氧3h后行复氧5min、缺氧5 min,反复3次,再复氧6 h).应用荧光酶标仪测定线粒体活性氧量,流式细胞仪检测心肌细胞凋亡,Western blot检测细胞膜和线粒体Bcl-2和Bax蛋白的表达.结果 缺氧/复氧组和缺氧后处理组心肌细胞线粒体活性氧量较对照组显著升高(P＜0.01).缺氧后处理组心肌细胞线粒体平均荧光强度为30.74±1.88a.u./μg,显著低于缺氧/复氧组(63.17±2.75a.u./μg,P＜0.01),仍高于对照组(14.41±2.15a.u./μg).缺氧/复氧组和缺氧后处理组心肌细胞凋亡率较对照组显著升高(45.86％±3.29％和26.99％±3.35％比5.72％±1.63％,P＜0.01),缺氧后处理组低于缺氧/复氧组(P＜0.01).细胞膜和线粒体Bcl-2蛋白在缺氧后处理组显著上调,在缺氧/复氧组显著下调;Bax蛋白在缺氧后处理组显著下调,在缺氧/复氧组显著上调.结论 缺氧后处理抑制线粒体活性氧爆发,减轻缺氧/复氧诱导的心肌细胞凋亡,其抗凋亡机制可能与线粒体和细胞膜Bcl-2蛋白表达上调及Bax蛋白表达下调有关.     

Biglycan deficiency: Increased aortic aneurysm formation and lack of atheroprotection

Proteoglycans of the arterial wall play a critical role in vascular integrity and the development of atherosclerosis owing to their ability to organize extracellular matrix molecules and to bind and retain atherogenic apolipoprotein (apo)-B containing lipoproteins. Prior studies have suggested a role for biglycan in aneurysms and in atherosclerosis. Angiotensin II (angII) infusions into mice have been shown to induce abdominal aortic aneurysm development, increase vascular biglycan content, increase arterial retention of lipoproteins, and accelerate atherosclerosis. The goal of this study was to determine the role of biglycan in angII-induced vascular diseases. Biglycan-deficient or biglycan wildtype mice crossed to LDL receptor deficient (Ldlr-/-) mice (C57BL/6 background) were infused with angII (500 or 1000 ng/kg/min) or saline for 28 days while fed on normal chow, then pumps were removed, and mice were switched to an atherogenic Western diet for 6 weeks. During angII infusions, biglycan-deficient mice developed abdominal aortic aneurysms, unusual descending thoracic aneurysms, and a striking mortality caused by aortic rupture (76% for males and 48% for females at angII 1000 ng/kg/min). Histological analyses of non-aneurysmal aortic segments from biglycan-deficient mice revealed a deficiency of dense collagen fibers and the aneurysms demonstrated conspicuous elastin breaks. AngII infusion increased subsequent atherosclerotic lesion development in both biglycan-deficient and biglycan wildtype mice. However, the biglycan genotype did not affect the atherosclerotic lesion area induced by the Western diet after treatment with angII. Biglycan-deficient mice exhibited significantly increased vascular perlecan content compared to biglycan wildtype mice. Analyses of the atherosclerotic lesions demonstrated that vascular perlecan co-localized with apoB, suggesting that increased perlecan compensated for biglycan deficiency in terms of lipoprotein retention. Biglycan deficiency increases aortic aneurysm development and is not protective against the development of atherosclerosis. Biglycan deficiency leads to loosely packed aortic collagen fibers, increased susceptibility of aortic elastin fibers to angII-induced stress, and up-regulation of vascular perlecan content.     

Morphological and molecular characterization of adult cardiomyocyte apoptosis during hypoxia and reoxygenation

Apoptosis has been implicated in ischemic heart disease, but its mechanism in cardiomyocytes has not been elucidated. In this study, we investigate the effects of hypoxia and reoxygenation in adult cardiomyocytes and the molecular mechanism involved in cardiomyocyte apoptosis. Morphologically, reoxygenation induced rounding up of the cells, appearance of membrane blebs that were filled with marginated mitochondria, and ultrastructural findings characteristic of apoptosis. Reoxygenation (18 hours of reoxygenation after 6 hours of hypoxia) and prolonged hypoxia (24 hours of hypoxia) resulted in a 59% and 51% decrease in cellular viability, respectively. During reoxygenation, cell death occurred predominantly via apoptosis associated with appearance of cytosolic cytochrome c and activation of caspase-3 and -9. However, nonapoptotic cell death predominated during prolonged hypoxia. Both caspase inhibition and Bcl-2 overexpression during reoxygenation significantly improved cellular viability through inhibition of apoptosis but had minimal effect on hypoxia-induced cell death. Bcl-2 overexpression blocked reoxygenation-induced cytochrome c release and activation of caspase -3 and -9, but caspase inhibition alone did not block cytochrome c release. These results suggest that apoptosis predominates in cardiomyocytes after reoxygenation through a mitochondrion-dependent apoptotic pathway, and Bcl-2 prevents reoxygenation-induced apoptosis by inhibiting cytochrome c release from the mitochondria and prevents activation of caspase-3 and -9.     

Characteristics of death of neonatal rat cardiomyocytes following hypoxia or hypoxia-reoxygenation: the association of apoptosis and cell membrane disintegrity

Irreversibly injured cardiomyocytes are positive for terminal deoxynucleotidyl transferase nick end-labeling (TUNEL), making it controversial as to whether TUNEL-positive cardiomyocytes induced by hypoxia–reoxygenation are apoptotic (secondarily necrotic) or primarily necrotic. We investigated the relationship between plasma membrane integrity and DNA fragmentation in hypoxic-reoxygenated cardiomyocytes. Cardiomyocytes were prepared from neonatal rat heart and exposed to hypoxia. The plasma membrane integrity was assessed by propidium iodide (PI) staining. The mode of DNA fragmentation was assessed by TUNEL and in situ polymerase chain reaction ligation assay. Furthermore, caspase-3 activity was measured in hypoxic-reoxygenated cardiomyocytes. Reoxygenation for 24 h after 3–8 h of hypoxia increased TUNEL positivity. However, the appearance of PI-positivity preceded that of TUNEL at various time points following reoxygenation. In contrast, TUNEL-positive but PI-negative cells were rarely found. In the hypoxic-reoxygenated cells, caspase-3 activity was increased, and PI- and TUNEL-positive cardiomyocytes possessed a sufficient number of double-strand DNA breaks with single-base 3′-OH terminals. In cardiomyocytes subjected to hypoxia–reoxygenation, the appearance of TUNEL positivity was delayed in comparison to membrane disintegrity, but in these cells caspase-3 has been activated and the mode of DNA fragmentation was apoptosis-specific. Thus, hypoxia–reoxygenation induces apoptosis associated with cell membrane disintegrity in cardiomyocytes. Received: December 13, 2001 / Accepted: May 8, 2002 Correspondence to Y. Maruyama     

Pioglitazone limits myocardial infarct size,activates Akt,and upregulates cPLA2 and COX-2 in a PPAR-γ-independent manner

Pioglitazone (PIO), a PPAR-γ agonist, limits myocardial infarct size by activating Akt and upregulating cytosolic phospholipase A₂ (cPLA₂) and cyclooxygenase (COX)-2. However, PIO has several PPAR-γ-independent effects. We assessed whether PIO limits myocardial infarct size in PPAR-γ–knockout mice, attenuates hypoxia-reoxygenation injury and upregulates P-Akt, cPLA₂, and COX-2 expression in PPAR-γ–knockout cardiomyocytes. Cardiac-specific inducible PPAR-γ knockout mice were generated by crossing αMHC-Cre mice to PPAR-γ^loxp/loxp mice. PPAR-γ deletion was achieved after 7 days of intraperitoneal tamoxifen (20 mg/kg/day) administration. Mice received PIO (10 mg/kg/day), or vehicle, for 3 days and underwent coronary occlusion (30 min) followed by reperfusion (4 h). We assessed the area at risk by blue dye and infarct size by TTC. Cultured adult cardiomyocytes of PPAR-γ^{loxp/loxp/cre} mice without or with pretreatment with tamoxifen were incubated with or without PIO and subjected to 2 h hypoxia/2 h reoxygenation. Cardiac-specific PPAR-γ knockout significantly increased infarct size. PIO reduced infarct size by 51% in PPAR-γ knockout mice and by 55% in mice with intact PPAR-γ. Deleting the PPAR-γ gene increased cell death in vitro. PIO reduced cell death in cells with and without intact PPAR-γ. PIO similarly increased myocardial Ser-473 P-Akt, cPLA₂, and COX-2 levels after hypoxia/reoxygenation in cells with and without intact PPAR-γ. PIO limited infarct size in mice in a PPAR-γ-independent manner. PIO activated Akt, increased the expression of cPLA₂ and COX-2, and protected adult cardiomyocytes against the effects of hypoxia/reoxygenation independent of PPAR-γ activation.     

Nitric Oxide Synthase (NOS) Does Not Contribute to Simulated Ischaemic Preconditioning in an Isolated Rat Cardiomyocyte Model

It is widely accepted that nitric oxide (NO) is a trigger and mediator of late ischaemic preconditioning (IP), however its role in classic (protection observed within 2-4 hours after the IP stimulus) IP is less certain. In addition, the contribution of cardiomyocyte nitric oxide synthase (NOS) activation to NO production in ischaemia is unknown. The aim of this study was therefore to investigate the role of NOS, NO, reactive oxygen species (ROS) and cGMP in IP in an isolated cardiomyocyte model. METHODS: Adult rat cardiomyocytes were isolated by collagenase perfusion. Hypoxia was induced by covering pelleted cardiomyocytes with mineral oil. The IP protocol was one 10 min hypoxia/20 min reoxygenation cycle, followed by 2 hr sustained hypoxia. Non-IP cells were subjected to 2 hr sustained hypoxia only. The contribution of NO was investigated by NOS inhibition (L-NAME 50 microM) or by pre-treatment of cells with a NO donor (SNP 100 microM), and that of ROS by inclusion of ROS scavengers (MPG and N-acetyl-cysteine) or pre-treatment with H(2)O(2). End-points were cellular cGMP content and cell viability as assessed by trypan blue exclusion (TBE) and cell morphology. RESULTS: IP significantly improved myocyte viability (54% increase in TBE) at the end of sustained hypoxia. Treatment of cells with L-NAME and ROS scavengers during either the IP protocol or during sustained hypoxia had no effect on cell viability after 2 hr hypoxia, whereas viability of non-IP cells treated with L-NAME during sustained hypoxia improved significantly. cGMP levels were reduced in IP cells. Pre-treatment with SNP and H(2)O(2) did not mimic IP. CONCLUSIONS: IP conferred cardioprotection in isolated cardiomyocytes. Protection in this model was not due to activation of cardiomyocyte NOS or ROS production. However, NOS activation induced by sustained hypoxia, appeared to be harmful to non-IP cells.     

低频脉冲磁场调节NO/ONOO-对缺氧/复氧条件下心肌细胞的保护作用

目的:观察低频脉冲磁场（LF-PMFs）对缺氧/复氧（H/R）条件下乳鼠心肌细胞增殖与凋亡的影响,并探讨一氧化氮/过氧亚硝基阴离子（NO/ONOO-）平衡在LF-PMFs保护心肌细胞的作用。方法: 采用酶消化法分离SD乳鼠心肌细胞,随机分为对照组、H/R组和磁场组。用TUNEL法检测心肌细胞凋亡程度,MTT比色法检测心肌细胞增殖活性,以观察LF-PMFs对损伤心肌细胞的效果,用WST-1 法检测超氧阴离子,Griess法测定NO和ONOO-。结果: LF-PMFs磁场可减少H/R诱导的心肌细胞凋亡,并促进心肌细胞的存活,以15 Hz,4.5 mT LF-PMFs磁场的作用效果最为显著。同时LF-PMFs可减少H/R条件下乳鼠心肌细胞超氧阴离子的生成,促进NO生成,提高NO/ONOO-比值。结论: LF-PMFs可通过抗氧化及调节NO/ONOO-平衡减轻H/R导致的心肌细胞损伤。     

Endothelial-cardiomyocyte crosstalk enhances pharmacological cardioprotection

Endothelial cells (EC) serve a paracrine function to enhance signaling in cardiomyocytes (CM), and conversely, CM secrete factors that impact EC function. Understanding how EC interact with CM may be critically important in the context of ischemia–reperfusion injury, where EC might promote CM survival. We used isoflurane as a pharmacological stimulus to enhance EC protection of CM against hypoxia and reoxygenation injury. Triggering of intracellular signal transduction pathways culminating in the enhanced production of nitric oxide (NO) appears to be a central component of pharmacologically induced cardioprotection. Although the endothelium is well recognized as a regulator for vascular tone, little attention has been given to its potential importance in mediating cardioprotection. In the current investigation, EC–CM in co-culture were used to test the hypothesis that EC contribute to isoflurane-enhanced protection of CM against hypoxia and reoxygenation injury and that this protection depends on hypoxia-inducible factor (HIF1α) and NO. CM were protected against cell injury [lactate dehydrogenase (LDH) release] to a greater extent in the presence vs. absence of isoflurane-stimulated EC (1.7 ± 0.2 vs. 4.58 ± 0.8 fold change LDH release), and this protection was NO-dependent. Isoflurane enhanced release of NO in EC (1103 ± 58 vs. 702 ± 92 pmol/mg protein) and EC–CM in co-culture sustained NO release during reoxygenation. In contrast, lentiviral mediated HIF1α knockdown in EC decreased basal and isoflurane stimulated NO release in an eNOS dependent manner (517 ± 32 vs. 493 ± 38 pmol/mg protein) and prevented the sustained increase in NO during reoxygenation when co-cultured. Opening of mitochondrial permeability transition pore (mPTP), an index of mitochondrial integrity, was delayed in the presence vs. absence of EC (141 ± 2 vs. 128 ± 2.5 arbitrary mPTP opening time). Isoflurane stimulated an increase in HIF1α in EC but not in CM under normal oxygen tension (3.5 ± 0.1 vs. 0.79 ± 0.15 fold change density) and this action was blocked by pretreatment with the Mitogen-activated Protein/Extracellular Signal-regulated Kinase inhibitor U0126. Expression and nuclear translocation of HIF1α were confirmed by Western blot and immunofluorescence. Taken together, these data support the concept that EC are stimulated by isoflurane to produce important cardioprotective factors that may contribute to protection of myocardium during ischemia and reperfusion injury.     

一氧化氮对培养乳鼠心肌细胞低氧复氧损伤的影响

目的 :研究 NO对乳鼠心肌细胞低氧 /复氧 （A/R）损伤的影响。方法 :建立心肌细胞 A/R损伤模型 ,随机分为6组 :A组 ,正常对照组 ;B组 ,单纯低氧 /复氧 （A/R低氧 2 h,复氧 1h） ;C组 ,低氧预处理 ,低氧 2 0 m in后复氧 2 0min,然后 A/R;D、E、F组为 NO预处理组 ,加入 S-亚硝基 -已酰青酶胺 （SNAP）分别使其终浓度为 0 .5、1、2 mm ol/L,预处理 4 0 min后 A/R。于复氧后测定各组培养液中肌酸激酶 （CK）、蛋白漏出量的变化及细胞内丙二醛 （MDA）含量和细胞存活率。结果 :单纯低氧 /复氧组和 2 m mol/L SNAP组 CK、蛋白漏出量、MDA水平显著升高 （P<0 .0 1vs正常组 ） ,细胞存活率显著降低 （P<0 .0 1vs正常组 ）。0 .5和 1mmol/L SNAP预处理组和低氧预处理组上述变化明显减轻 （P<0 .0 1vs低氧复氧组 ）。结论 :NO预处理对乳鼠心肌细胞 A/R损伤具有保护作用 ,并具有浓度依赖性。     

内皮素-1对缺氧/复氧所致心肌细胞凋亡的影响

目的探讨在缺氧/复氧过程中不同时期给予内皮素-1（ET-1）对缺氧/复氧所致心肌损伤与凋亡的影响。方法乳鼠心肌细胞缺氧/复氧模型,流式细胞仪检测心肌细胞凋亡,Hoechst 33258染色计算凋亡率,试剂盒检测乳酸脱氢酶（LDH）的活性。结果ET-1预处理组（EP）细胞生存率较缺氧复氧组（HR）提高,凋亡率下降,LDH活性下降;ET-1缺氧即刻处理组（EH）细胞生存率较HR组降低,凋亡率升高,LDH释放量增加;ET-1复氧处理组（ER）的细胞生存率、凋亡率及LDH活性与HR组均无统计学差异。结论ET-1预处理有心肌细胞保护作用,ET-1缺氧时有促进心肌细胞损伤和凋亡的作用。     

心肌细胞缺氧复氧损伤时Mipu1启动子活性、Mipu1 mRNA表达变化及意义

目的探讨心肌细胞缺氧复氧损伤时心肌缺血预适应表达上调蛋白1(Mipu1)启动子活性的变化及其作用。方法按本课题组的常规方法复制心肌细胞缺氧复氧模型,先予缺氧(95%N2-5%CO2,无血清低糖DMEM)处理6 h,再分别复氧(95%空气-5%CO2,10%FBS-高糖DMEM)6、12、24 h。采用MTT法检测心肌细胞活性,比色法测定心肌细胞LDH活性,双荧光素酶报告基因技术检测启动子PGL3-Mipu1活性,实时定量PCR法检测Mipu1mRNA表达。结果缺氧6 h复氧(6、12、24 h)后心肌细胞活性减低,LDH释放增加,启动子PGL3-Mipu1活性增加,Mipu1 mRNA表达上调,且在缺氧6 h复氧12 h时变化最明显。结论 Mipu1可能参与了心肌细胞的缺氧复氧损伤,其可能通过调控凋亡相关基因发挥作用。     

Nogo-A knockdown inhibits hypoxia/reoxygenation-induced activation of mitochondrial-dependent apoptosis in cardiomyocytes

Programmed cell death of cardiomyocytes following myocardial ischemia increases biomechanical stress on the remaining myocardium, leading to myocardial dysfunction that may result in congestive heart failure or sudden death. Nogo-A is well characterized as a potent inhibitor of axonal regeneration and plasticity in the central nervous system, however, the role of Nogo-A in non-nervous tissues is essentially unknown. In this study, Nogo-A expression was shown to be significantly increased in cardiac tissue from patients with dilated cardiomyopathy and from patients who have experienced an ischemic event. Nogo-A expression was clearly associated with cardiomyocytes in culture and was localized predominantly in the endoplasmic reticulum. In agreement with the findings from human tissue, Nogo-A expression was significantly increased in cultured neonatal rat cardiomyocytes subjected to hypoxia/reoxygenation. Knockdown of Nogo-A in cardiomyocytes markedly attenuated hypoxia/reoxygenation-induced apoptosis, as indicated by the significant reduction of DNA fragmentation, phosphatidylserine translocation, and caspase-3 cleavage, by a mechanism involving the preservation of mitochondrial membrane potential, the inhibition of ROS accumulation, and the improvement of intracellular calcium regulation. Together, these data demonstrate that knockdown of Nogo-A may serve as a novel therapeutic strategy to prevent the loss of cardiomyocytes following ischemic/hypoxic injury.     

Depletion of PHD3 protects heart from ischemia/reperfusion injury by inhibiting cardiomyocyte apoptosis

PHD3, a member of a family of Prolyl-4 Hydroxylase Domain (PHD) proteins, has long been considered a pro-apoptotic protein. Although the pro-apoptotic effect of PHD3 requires its prolyl hydroxylase activity, it may be independent of HIF-1α, the common substrate of PHDs. PHD3 is highly expressed in the heart, however, its role in cardiomyocyte apoptosis remains unclear. This study was undertaken to determine whether inhibition or depletion of PHD3 inhibits cardiomyocyte apoptosis and attenuates myocardial injury induced by ischemia–reperfusion (I/R). PHD3 knockout mice and littermate controls were subjected to left anterior descending (LAD) coronary artery ligation for 40 min followed by reperfusion. Histochemical analysis using Evan's Blue, triphenyl-tetrazolium chloride and TUNEL staining, demonstrated that myocardial injury and cardiomyocyte apoptosis induced I/R injury were significantly attenuated in PHD3 knockout mice. PHD3 knockout mice exhibited no changes in HIF-1α protein level, the expression of some HIF target genes or the myocardium capillary density at physiological condition. However, depletion of PHD3 further enhanced the induction of HIF-1α protein at hypoxic condition and increased expression of HIF-1α inhibited cardiomyocyte apoptosis induced by hypoxia. In addition, it has been demonstrated that PHD3 plays an important role in ATR/Chk1/p53 pathway. Consistently, a prolyl hydroxylase inhibitor or depletion of PHD3 significantly inhibits the activation of Chk1 and p53 in cardiomyocytes and the subsequent apoptosis induced by doxorubicin, hydrogen peroxide or hypoxia/reoxygenation. Taken together, these data suggest that depletion of PHD3 leads to increased stabilization of HIF-1α and inhibition of DNA damage response, both of which may contribute to the cardioprotective effect seen with depletion of PHD3.     

X染色体连锁凋亡抑制蛋白对缺氧-复氧诱导的新生大鼠心肌细胞凋亡的影响

目的:采用X染色体连锁凋亡抑制蛋白(XIAP)对缺氧-复氧诱导心肌细胞凋亡模型进行干预,以探讨脂质体介导XIAP基因转染对缺氧-复氧诱导的新生大鼠心肌细胞凋亡的影响.方法:体外培养新生大鼠心肌细胞,分为4组,①XIAP组:将pDsRed2-XIAP以脂质体转染到心肌细胞48 h后进行缺氧2 h-复氧1 h;②预处理组:先将心肌细胞进行缺氧预处理,然后进行缺氧2 h-复氧1 h;③单纯缺氧-复氧组:将心肌细胞直接进行缺氧2 h-复氧1 h;④常氧组:将心肌细胞在CO2孵箱中培养3 h.各组最后用流式细胞仪Annexin V FITC检测心肌细胞凋亡率结果组间差异.结果:①pDsRed2- XIAP可以通过脂质体转染的方式转染到心肌细胞;②与单纯缺氧-复氧组比较,XIAP组和预处理组心肌细胞凋亡率明显减低,P<0.01;③XIAP组与预处理组比较二者心肌细胞凋亡率相似,P>0.05.结论:以物理性的缺氧2 h-复氧1 h的方式能诱导所培养的心肌细胞发生凋亡;XIAP能明显减少缺氧-复氧诱导新生大鼠心肌细胞的凋亡;XIAP抑制凋亡的效应与缺氧预处理抑制凋亡的效应相似.