低氧预处理对大鼠海马神经元缺氧耐受性和Jun基因表达的影响

目的 :观察低氧预处理对缺氧 复氧后大鼠海马神经元Jun表达的影响。方法 :取培养 12d的两组 (对照组和低氧预处理组 )神经元 ,同时置于缺氧环境 (0 .90L LN2 0 .10L LCO2 )中培养 4h后取出 ,置含 0 .10L LCO2 和空气的培养箱内复氧培养 2 4h和 72h ,于不同时间取出 ,观察神经元存活数 ,并用抗Jun抗血清进行免疫组织化学染色 ,观察Jun表达阳性和阴性神经元数目 ,计算Jun表达神经元所占百分率。结果 :经低氧预处理的海马神经元缺氧 复氧后Jun表达阳性神经元百分率较对照组明显减少 ,神经元存活数明显高于对照组。结论 :低氧预处理可使海马培养神经元对缺氧产生耐受 ,减少缺氧 复氧后神经元Jun的表达。提高神经元存活数     

缺氧对体外培养大鼠海马神经元Bcl—2表达的影响

采用免疫组化方法,观察缺氧对体外培养大鼠海马神经元Bcl-2表达的影响。结果显示,缺氧2h时Bcl-2免疫反应阳性神经元的平均光密度较缺氧前明显增强,但缺氧4h和重新恢复供氧后24—72h时,Bcl-2免疫反应阳性神经元的平均光密度又逐渐减弱。缺氧后Bcl-2免疫反应阳性神经元数和阳性率亦随神经元存活数的下降而逐渐减少。本结果提示,缺氧早期Bcl-2免疫染色阳性神经元的免疫反应增强可能是脑细胞在缺氧条件下的自我保护机制,Bcl-2可能对海马神经元缺氧损伤具有一定调控作用。     

低氧预处理提高离体培养的下丘脑细胞缺氧耐受性及其与线粒体膜电位稳定性的关系

本文用新生大鼠下丘脑培养细胞,研究了低氧预处理对下丘脑细胞缺氧耐受性的影响及其与线粒体膜电位的关系.结果显示：在急性缺氧条件下,低氧预处理可以提高细胞存活率,减少乳酸脱氢酶漏出,此外,低氧预处理可以使线粒体膜电位在缺氧时保持相对高的水平,并诱导B淋巴细胞／白血病－2（B-cell lymphoma/leukemia-2,bcl-2)高表达,结果提示,低氧预处理能提高下丘脑细胞的缺氧耐受性,其机制与线粒体膜电位稳定性增强有关;低氧预处理诱发bcl-2高表达可能是线粒体膜电位稳定性增强的机制之一。     

重组人白细胞介素-6对缺氧-复氧后大鼠海马培养神经元Bcl-2、Bax 表达和神经元凋亡的影响

实验在培养的大鼠海马神经元中观察了重组人白细胞介素-6（recombinant human interleukin-6,rhIL-6）对缺氧-复氧后Bcl-2、Bax表达和神经元凋亡的影响。把培养12d的大鼠海马神经元分为对照组和rhIL-6组,同时于缺氧环境（90% N2 10% CO2）中培养2、4h后,再于常氧培养箱内复氧培养24和72h。于不同时间取出,分别用抗Bcl-2和Bax抗血清进行免疫组织化学染色,观察缺氧-复氧后大鼠海马培养神经元Bcl-2和Bax的表达,并用原位末端标记（TUNEL）法和流式细胞术分别检测缺氧-复氧对体外培养海马神经元凋亡的影响。结果可见,与缺氧前相比,缺氧-复氧后24和72h,海马神经元Bal-2表达明显减弱,Bax表达明显增强,凋亡神经元明显增多。经rhIL-6预处理的海马神经元与对照组相比,缺氧-复氧后24和72h,Bcl-2表达明显增强,Bax神经明显减弱,凋亡神经元明显减少。本实验结果提示,rhIL-6对海马神经元缺氧-复氧损伤具有一定的保护作用。     

二氮嗪预处理上调Bcl-2/Bax蛋白比值减少缺氧复氧所致体外培养的海马神经元凋亡

线粒体内膜ATP敏感钾通道（mitochondrial ATP-sensitive potassium channel,mitoKATP通道）的激活在药物预处理增强神经元对各种损伤的耐受力过程中发挥着重要作用。神经元内含有丰富的mito KATP,通道,二氮嗪（diazoxide,DZ）为选择性的mitoKATP通道开放剂,本实验探讨了DZ预处理能否减少缺氧复氧所致的海马神经元凋亡,以及DZ如何调控Bcl-2蛋白和Bax蛋白的表达。原代培养9～10d的Sprague-Dawley大鼠海马神经元随机分为5组：对照组、DZ0μmol／L、DZ30μmol／L、DZ100μmol／L和DZ100μmol／L＋5-羟癸酸（5-hydroxydecanoate,5-HD）100μmol／L。除对照组外,其他四组神经元白缺氧前3d开始,每天DZ预处理1h,连续3d。体外缺氧4h,于复氧后24h,四唑蓝比色法测定海马神经元存活率,annexin V-FITC流式细胞术测定凋亡率,Western blot法检测Bcl-2和Bax蛋白的表达量。结果显示：与对照组比较,缺氧复氧损伤显著降低海码神经元的存活率,升高凋亡率。与其他浓度比较,100μmol／LDZ预处理使神经元存活率升高约15％,而凋亡率降低约12％：Bcl-2蛋白表达增强约60％,Bax蛋白表达下降近30％。5-HD消除DZ对神经元的保护作用。因此,100μmol／LDZ可通过上调Bcl-2蛋白表达,降低Bax蛋白表达,减少缺氧复氧后海马神经元的凋亡。     

Role of protein phosphatases in hypoxic preconditioning

To find a protein kinase C (PKC)-independent preconditioning mechanism, hypoxic preconditioning (HP; i.e., 10-min anoxia and 10-min reoxygenation) was applied to isolated rat hearts before 60-min global ischemia. HP led to improved recovery of developed pressure and reduced end-diastolic pressure in the left ventricle during reperfusion. Protection was unaffected by the PKC inhibitor bisindolylmaleimide (BIM; 1 micromol/l). It was abolished by the inhibitor of protein phosphatases 1 and 2A cantharidin (20 or 5 micromol/l) and partially enhanced by the inhibitor of protein phosphatase 2A okadaic acid (5 nmol/l). In adult rat cardiomyocytes treated with BIM and exposed to 60-min simulated ischemia (anoxia, extracellular pH 6.4), HP led to attenuation of anoxic Na(+)/Ca(2+) overload and of hypercontracture, which developed on reoxygenation. This protection was prevented by treatment with cantharidin but not with okadaic acid. In conclusion, HP exerts PKC-independent protection on ischemic-reperfused rat hearts and cardiomyocytes. Protein phosphatase 1 seems a mediator of this protective mechanism.     

Modulation of stress proteins and apoptotic regulators in the anoxia tolerant turtle brain

Freshwater turtles survive prolonged anoxia and reoxygenation without overt brain damage by well-described physiological processes, but little work has been done to investigate the molecular changes associated with anoxic survival. We examined stress proteins and apoptotic regulators in the turtle during early (1 h) and long-term anoxia (4, 24 h) and reoxygenation. Western blot analyses showed changes within the first hour of anoxia; multiple stress proteins (Hsp72, Grp94, Hsp60, Hsp27, and HO-1) increased while apoptotic regulators (Bcl-2 and Bax) decreased. Levels of the ER stress protein Grp78 were unchanged. Stress proteins remained elevated in long-term anoxia while the Bcl-2/Bax ratio was unaltered. No changes in cleaved caspase 3 levels were observed during anoxia while apoptosis inducing factor increased significantly. Furthermore, we found no evidence for the anoxic translocation of Bax from the cytosol to mitochondria, nor movement of apoptosis inducing factor between the mitochondria and nucleus. Reoxygenation did not lead to further increases in stress proteins or apoptotic regulators except for HO-1. The apparent protection against cell damage was corroborated with immunohistochemistry, which indicated no overt damage in the turtle brain subjected to anoxia and reoxygenation. The results suggest that molecular adaptations enhance pro-survival mechanisms and suppress apoptotic pathways to confer anoxia tolerance in freshwater turtles.     

缺氧诱导因子-1α在缺氧预处理预防心肌细胞损伤中的作用

本工作旨在研究缺氧预处理(hypoxic preconditioning,HPC)对于心肌细胞外信号调节激酶(extracellular signal-regulated proteinkinases,ERK)活性、缺氧诱导因子-1α(hypoxia-inducible factor-1α,HIF-1α)表达的影响,及其在缺氧复氧诱导心肌细胞损伤中的作用。通过在培养的SD乳鼠心肌细胞缺氧／复氧(H／R)模型上,观察HPC对于24h后H／R诱导心肌细胞损伤的影响,以台盼蓝排斥实验检测心肌细胞存活率、以TUNEL法检测细胞凋亡、并用荧光素染料Hoechst33258测定心肌细胞凋亡率：制备心肌细胞蛋白提取物,以磷酸化的ERK1／2抗体测定ERK1／2活性,以抗HIF-1α抗体检测HIF-1α的表达,并观察ERKs的上游激酶(MEK1／2)抑制剂PD98059对于HPC诱导的ERKs磷酸化、HIF-1α表达以及心肌细胞保护作用的影响,并分析细胞损伤与ERK1／2活性、HIF-1α表达量之间的相互关系。结果 显示缺氧复氧造成心肌细胞损伤,HPC可以增加心肌细胞H／R后存活率,降低凋亡率,并激活ERKll2,诱导HIF-1α表达：细胞凋亡与ERKs活性、HIF-1α表达量之间存在负相关,即ERKs活化、HIF-1α表达与预防细胞损伤有关：而ERKs活性与HIF-1α表达量之间存在正相关,ERKs的上游激酶MEK抑制剂PD98059可以消除HPC诱导的ERKs磷酸化、HIF-1α表达和心肌细胞保护作用。由此得出的结论是HPC可以提高乳鼠心肌细胞对于H／R的耐受性,其机制涉及ERKs介导的HIF-1α表达。     

Development of an in vitro model for study of the efficacy of ischemic preconditioning in human skeletal muscle against ischemia-reperfusion injury.

Ischemia-reperfusion (I/R) injury causes skeletal muscle infarction and ischemic preconditioning (IPC) augments ischemic tolerance in animal models. To date, this has not been demonstrated in human skeletal muscle. This study aimed to develop an in vitro model to investigate the efficacy of simulated IPC in human skeletal muscle. Human skeletal muscle strips were equilibrated in oxygenated Krebs-Henseleit-HEPES buffer (37 degrees C). Aerobic and reperfusion phases were simulated by normoxic incubation and reoxygenation, respectively. Ischemia was simulated by hypoxic incubation. Energy store, cell viability, and cellular injury were assessed using ATP, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), and lactate dehydrogenase (LDH) assays, respectively. Morphological integrity was assessed using electron microscopy. Studies were designed to test stability of the preparation (n = 5-11) under normoxic incubation over 24 h; the effect of 1, 2, 3, 4, or 6 h hypoxia followed by 2 h of reoxygenation; and the protective effect of hypoxic preconditioning (HPC; 5 min of hypoxia/5 min of reoxygenation) before 3 h of hypoxia/2 h of reoxygenation. Over 24 h of normoxic incubation, muscle strips remained physiologically intact as assessed by MTT, ATP, and LDH assays. After 3 h of hypoxia/2 h of reoxygenation, MTT reduction levels declined to 50.1 +/- 5.5% (P < 0.05). MTT reduction levels in HPC (82.3 +/- 10.8%) and normoxic control (81.3 +/- 10.2%) groups were similar and higher (P < 0.05) than the 3 h of hypoxia/2 h of reoxygenation group (45.2 +/- 5.8%). Ultrastructural morphology was preserved in normoxic and HPC groups but not in the hypoxia/reoxygenation group. This is the first study to characterize a stable in vitro model of human skeletal muscle and to demonstrate a protective effect of HPC in human skeletal muscle against hypoxia/reoxygenation-induced injury.     

Hypoxic preconditioning is a phenomenon increasing tolerance of cardiomyocytes to hypoxia-reoxygenation

The work covers the problem of hypoxic preconditioning (HP) carried out in isolated cardiomyocytes. Papers on delayed HP in vivo are comparatively few, and only some single works are devoted to early preconditioning in vivo. It has been established that the HP limits necrosis and apoptosis of cardiomyocytes and improves contractility of the isolated heart after ischemia (hypoxia) and reperfusion (reoxygenation). It was found that adenosine was a trigger of iP in vitro. It was proved that NO* was a trigger of HP both in vitro and in vivo. It was shown that reactive oxygen species also were triggers of hypoxic preconditioning. It was shown that ERK1/2 and p38 kinase played important role in delayed HP in vitro.     

The influence of radiation dose on the magnitude and kinetics of reoxygenation in a C3H mammary carcinoma

The variation in hypoxic fraction as a function of time after various priming doses of radiation has been investigated in a C3H mouse mammary carcinoma in situ. The hypoxic fraction was calculated from data for local tumor control. Untreated tumors were found to contain 4.8% radiobiologically hypoxic cells. Within minutes after a priming dose of 20 Gy given in air, the hypoxic fraction increased to a value not significantly different from 100%. After 4 h, reoxygenation was complete (hypoxic fraction 1.3%), and the hypoxic fraction stabilized at a level significantly below the untreated value. Following a priming dose of 40 Gy the reoxygenation pattern was different: The hypoxic fraction stayed above the pretreatment value for 4 h, and pronounced reoxygenation occurred after 12 h (hypoxic fraction 0.4%). At longer time intervals the hypoxic fraction again increased to--and slightly above--the oxygenation level of untreated tumors. The present findings show that reoxygenation in solid tumors is a function of radiation dose, and the data suggest that mechanisms other than a decrease in tumor cell O2 consumption are involved in tumor reoxygenation.     

低氧预处理提高下丘脑细胞缺氧耐受性与Na+、K+电流的关系

目的 :研究低氧预处理提高下丘脑细胞缺氧耐受性与Na 、K 电流的关系。方法 :采用培养的大鼠下丘脑神经元 ,用膜片钳全细胞记录技术 ,观察低氧预处理对其钠电流 (INa)、钾电流 (IK)的影响。结果 :①低氧预处理未明显改变INa,但增加了IK 幅值 ;②急性缺氧导致对照组细胞INa、IK 明显受抑制 ,而经过低氧预处理的细胞INa、IK 受抑制程度显著低于对照组。结论 :低氧预处理提高下丘脑细胞的耐缺氧能力与低氧预处理后K 通道的大量开放有关     

Desflurane Preconditioning Induces Oscillation of NF-κB in Human Umbilical Vein Endothelial Cells

Background

Nuclear factor kappa B (NF-κB) has been implicated in anesthetic preconditioning (APC) induced protection against anoxia and reoxygenation (A/R) injury. The authors hypothesized that desflurane preconditioning would induce NF-κB oscillation and prevent endothelial cells apoptosis.

Methods

A human umbilical vein endothelial cells (HUVECs) A/R injury model was used. A 30 minute desflurane treatment was initiated before anoxia. NF-κB inhibitor BAY11-7082 was administered in some experiments before desflurane preconditioning. Cells apoptosis was analyzed by flow cytometry using annexin V–fluorescein isothiocyanate staining and cell viability was evaluated by modified tertrozalium salt (MTT) assay. The cellular superoxide dismutases (SOD) activitiy were tested by water-soluble tetrazolium salt (WST-1) assay. NF-κB p65 subunit nuclear translocation was detected by immunofluorescence staining. Expression of inhibitor of NF-κB-α (IκBα), NF-κB p65 and cellular inhibitor of apoptosis 1 (c-IAP1), B-cell leukemia/lymphoma 2 (Bcl-2), cysteine containing aspartate specific protease 3 (caspases-3) and second mitochondrial-derived activator of caspase (SMAC/DIABLO) were determined by western blot.

Results

Desflurane preconditioning caused phosphorylation and nuclear translocation of NF-κB before anoxia, on the contrary, induced the synthesis of IκBα and inhibition of NF-κB after reoxygenation. Desflurane preconditioning up-regulated the expression of c-IAP1 and Bcl-2, blocked the cleavage of caspase-3 and reduced SMAC release, and decreased the cell death of HUVECs after A/R. The protective effect was abolished by BAY11-7082 administered before desflurane.

Conclusions

The results demonstrated that desflurane activated NF-κB during the preconditioning period and inhibited excessive activation of NF-κB in reperfusion. And the oscillation of NF-κB induced by desflurane preconditioning finally up-regulated antiapoptotic proteins expression and protected endothelial cells against A/R.     

Preconditioning improves function and recovery of single muscle fibers during severe hypoxia and reoxygenation

Reperfusion following prolonged ischemia induces cellular damage in whole skeletal muscle models. Ischemic preconditioning attenuates the deleterious effects. We tested whether individual skeletal muscle fibers would be similarly affected by severe hypoxia and reoxygenation (H/R) in the absence of extracellular factors and whether cellular damage could be alleviated by hypoxic preconditioning. Force and free cytosolic Ca2+ ([Ca2+]c) were monitored in Xenopus single muscle fibers (n = 24) contracting tetanically at 0.2 Hz during 5 min of severe hypoxia and 5 min of reoxygenation. Twelve cells were preconditioned by a shorter bout of H/R 1 h before the experimental trial. In preconditioned cells, force relative to initial maximal values (P/P(o)) and relative peak [Ca2+]c fell (P < 0.05) during 5 min of hypoxia and recovered during reoxygenation. In contrast, P/P(o) and relative peak [Ca2+]c fell more during hypoxia (P < 0.05) and recovered less during reoxygenation (P < 0.05) in control cells. The ratio of force to [Ca2+]c was significantly higher in the preconditioned cells during severe hypoxia, suggesting that changes in [Ca2+]c were not solely responsible for the loss in force. We conclude that 1) isolated skeletal muscle fibers contracting in the absence of extracellular factors are susceptible to H/R injury associated with changes in Ca2+ handling; and 2) hypoxic preconditioning improves contractility, Ca2+ handling, and cell recovery during subsequent hypoxic insult.     

七氟醚预处理对大鼠海马脑片缺氧无糖损伤的保护作用:线粒体KATP通道的作用

利用离体海马脑片缺氧无糖(oxygen-glucose deprivation,OGD)损伤模型,探讨七氟醚预处理对神经细胞的保护作用及该作用与线粒体内膜ATP敏感钾通道(mitochondrial ATP-sensitive potassium channels,mitoKATPchannels)的关系,随机将脑片用2%、4%、6%七氟醚,以及6%七氟醚复合mitoKATP通道阻滞剂5-羟基奎酸盐(5-hydroxydecanoic acid,5-HD)预处理30 min,观察OGD损伤14 min复氧1 h期间顺向群峰电位(orthodromic population spike,OPS)的变化,并应用透射电镜观察细胞超微结构的改变.结果表明,与单纯OGD组相比,七氟醚预处理可使海马脑片OPS消失时间明显延长(P＜0.01),使OPS明显恢复,其中4%、6%七氟醚组的恢复率均为71.4%(P＜0.05 vs OGD),相应恢复程度为(61.0±42.3)%和(78.7±21.1)%(P＜0.01),而且6%七氟醚的保护作用可被5-HD取消.OGD组的海马CA1区锥体细胞明显水肿,核膜皱缩、破裂,染色质聚集,线粒体肿胀畸形,嵴断裂或消失,而4%和6%七氟醚组仅见海马CA1区锥体细胞轻度水肿,核膜皱缩不明显,染色质均匀,线粒体轻度肿胀.结果提示,七氟醚预处理对大鼠海马脑片OGD损伤有一定的保护作用,且七氟醚对神经细胞的保护作用与激活mitoKATP通道有关.     

G_(i/o)蛋白介导的信息转导通路在低氧预处理心肌保护中的作用

实验以低氧 3h后复氧期间心肌细胞的生存率和LDH的释放量为指标 ,观察Gi/o蛋白及其下游成分在低氧预处理 (hypoxicpreconditioning ,HP)心肌保护中的作用。与单纯低氧组相比 ,HP组 ( 2 5min低氧 30min复氧作为HP)细胞生存率增高 ,LDH释放减少 (P <0 0 1)。用NEM预处理 ,能完全模拟HP的心肌细胞保护作用 ;而用PTX阻断Gi/o蛋白 ,或Forskolin和 8 Br cAMP预处理后 ,再给予HP及低氧 3h/复氧 1h ,则细胞生存率降低 ,LDH释放增加 (P <0 0 1) ;U 7312 2预处理后 ,细胞生存率和LDH释放量无差异 (P >0 0 5 )。结果提示 :Gi/o蛋白通过抑制AC ,减少第二信使cAMP的生成介导了HP的心肌保护作用。PLC可能不参与HP的心肌保护作用     

EGb 761 protects liver mitochondria against injury induced by in vitro anoxia/reoxygenation.

The present study investigated the protective effects of Ginkgo biloba extract (EGb 761) on rat liver mitochondrial damage induced by in vitro anoxia/reoxygenation. Anoxia/reoxygenation was known to impair respiratory activities and mitochondrial oxidative phosphorylation efficiency. ADP/O (2.57 +/- 0.11) decreased after anoxia/reoxygenation (1.75 +/- 0.09, p < .01), as well as state 3 and uncoupled respiration (-20%, p < .01), but state 4 respiration increased (p < .01). EGb 761 (50-200 microg/ml) had no effect on mitochondrial functions before anoxia, but had a specific dose-dependent protective effect after anoxia/reoxygenation. When mitochondria were incubated with 200 microg/ml EGb 761, they showed an increase in ADP/O (2.09 +/- 0.14, p < .05) and a decrease in state 4 respiration (-22%) after anoxia/reoxygenation. In EPR spin-trapping measurement, EGb 761 decreased the EPR signal of superoxide anion produced during reoxygenation. In conclusion, EGb 761 specially protects mitochondrial ATP synthesis against anoxia/reoxygenation injury by scavenging the superoxide anion generated by mitochondria.