抑制或过表达GRK5 基因对星形胶质细胞凋亡及IL-1β和TNF-α表达的影响

目的:探讨抑制或过表达G 蛋白偶联受体激酶5(GRK5)基因对星形胶质细胞(AS)凋亡及IL-1β和TNF-α 表达的影响。方法:培养原代AS,将干扰GRK5 表达的siRNA(GRK5-siRNA)及GRK5 的过表达质粒(pcDNA3.1-GRK5)分别转染AS,通过Western blot 检测转染24 h 后的细胞中GRK5 蛋白的表达;缺氧处理AS,细胞分为空白组、缺氧组、缺氧+pcDNA3.1-GRK5 组和缺氧+GRK5-siRNA 组,缺氧处理24 h 后通过流式细胞仪检测各组细胞的凋亡率及ROS 含量;RT-PCR检测IL-1β和TNF-α的mRNA 表达;Western blot 检测p53、信号转导与转录因子3(STAT3)和p-STAT3 蛋白表达。结果:与空白组比较,转染GRK5-siRNA 的AS 中GRK5 的表达显著降低,转染pcDNA3.1-GRK5 的细胞GRK5 的表达显著升高(P <0.05);与空白组比较,缺氧组细胞凋亡率、ROS 水平及IL-1β、TNF-α、p53 和p-STAT3 的表达均显著升高(P<0.05);与缺氧组比较,缺氧+pcDNA3.1-GRK5 组细胞凋亡率、ROS 水平及IL-1β、TNF-α、p53 和p-STAT3 的表达均显著降低,缺氧+GRK5-siRNA组细胞凋亡率、ROS 水平及IL-1β、TNF-α、p53 和p-STAT3 的表达均显著升高(P<0.05)。结论:过表达GRK5 可降低AS 凋亡和ROS 水平,下调IL-1β、TNF-α、p53 表达及STAT3 信号通路,抑制GRK5表达反之。     

转化生长因子β2对人晶状体上皮细胞E-钙黏素和α-平滑肌肌动蛋白表达的影响

背景：有研究表明,人晶状体上皮细胞的间质转分化是后发性白内障的主要病理改变,转化生长因子β2可以诱导间质转分化的发生。 目的：体外培养人晶状体上皮细胞,观察转化生长因子β2对人晶状体上皮细胞转分化相关蛋白E-钙黏蛋白和α-平滑肌肌动蛋白表达的影响。 方法：利用组织块法体外培养人晶状体上皮细胞并传代,选择传5代的细胞进行实验,采用100 ng/L转化生长因子β2诱导48 h,反转录-聚合酶链反应方法检测E-钙黏蛋白、α-平滑肌肌动蛋白mRNA的表达,应用蛋白质印迹法Western blot检测其蛋白表达。 结果与结论：转化生长因子β2处理人晶状体上皮细胞48 h后,细胞E-钙黏蛋白表达明显减弱,α-平滑肌肌动蛋白的表达明显增强。提示转化生长因子β2可以成功诱导晶状体上皮细胞间质转分化,转化生长因子β2处理的晶状体上皮细胞可以作为间质转分化的细胞模型。     

肺炎支原体经ROS激活NLRP3炎性体诱导RAW264.7细胞分泌IL-1β

 目的: 观察肺炎支原体(Mycoplasma pneunoniae,Mp)促进NLRP3炎性体的活化及下游促炎性细胞因子白细胞介素-1β(IL-1β)的表达是否与活性氧簇(ROS)有关。方法: 预先用5 mmol/L ROS清除剂N-乙酰半胱氨酸(NAC)预处理RAW264.7细胞30 min,用10 MOI Mp分别感染RAW264.7细胞4、8、16和24 h。流式细胞术检测细胞内ROS水平;real-time PCR法检测细胞NLRP3、ASC和caspase-1 mRNA的表达;Western blot 法检测NLRP3、ASC和caspase-1 p20的蛋白水平;ELISA法检测细胞上清液IL-1β的分泌水平。结果: 与正常组比较,感染后4、8、16和24 h模型组ROS生成显著增加(P< 0.01);感染后8、16和24 h模型组NLRP3、ASC和caspase-1 mRNA的表达显著增加 (P<0.01),感染后16和24 h NLRP3、ASC和caspase-1 p20的蛋白水平上调(P<0.01),感染后24 h 细胞上清液IL-1β含量显著增加(P< 0.01);与模型组比较,NAC组在上述相应时点ROS生成降低,NLRP3、ASC和caspase-1 mRNA的表达下调,蛋白水平下降,细胞上清液IL-1β的含量减少。结论: Mp可能通过刺激RAW264.7细胞生成ROS而激活NLRP3炎性体。     

人参皂苷Rb1对β-淀粉样蛋白25-35诱导神经干细胞分化过程中Tau蛋白过度磷酸化的影响

背景：前期研究发现,人参皂苷Rb1和β-淀粉样蛋白25-35可调节神经干细胞分化过程中Tau蛋白的磷酸化水平。蛋白磷酸酯酶2A与Tau蛋白过度磷酸化密切相关。 目的：观察β-淀粉样蛋白25-35和人参皂苷Rb1对神经干细胞分化过程中Tau蛋白磷酸化水平和蛋白磷酸酯酶2A活性的影响。 方法：分离、培养新生大鼠海马神经干细胞,诱导第3代神经干细胞分化1周后分组：①空白组：不加其他处理因素继续培养36 h。②β-淀粉样蛋白组：培养24 h后,加入β-淀粉样蛋白25-35继续培养12 h。③预处理组：先加入人参皂苷Rb1预处理24 h,再加入β-淀粉样蛋白25-35继续培养12 h。分别采用免疫荧光细胞化学法和western-blot法检测各组细胞Tau[pS396]、Tau[pS262]表达以及蛋白磷酸酯酶2A活性。 结果与结论：正常神经干细胞分化过程中有Tau[pS396]和Tau[pS262]的表达;β-淀粉样蛋白组细胞的Tau[pS396] 和Tau[pS262]表达上调,蛋白磷酸酯酶2A活性无明显变化;预处理组Tau[pS396]和Tau[pS262]表达下调且蛋白磷酸酯酶2A活性显著增强。提示正常神经干细胞分化过程中Tau蛋白表达一定程度的磷酸化水平,人参皂苷Rb1可通过提高蛋白磷酸酯酶2A活性来减轻β-淀粉样蛋白25-35诱导的神经干细胞分化过程中Tau蛋白过度磷酸化。     

Akt/GSK-3β介导高糖上调肾小管上皮细胞Snail1的表达

 目的：观察高糖对原代肾小管上皮细胞Snail1和蛋白激酶B/糖原合成酶激酶3β（Akt/GSK-3β）信号通路的影响,探讨糖尿病肾病时Snail1表达的调节机制。方法：原代培养大鼠肾小管上皮细胞（RTECs）,随机分为正常糖对照组、高渗组和高糖组。Western blotting检测不同处理组 RTECs不同培养时点（30 min、2 h、12 h、24 h、48 h和72 h）Snail1、Akt1、GSK-3β、磷酸化Akt（p-Akt,Ser473）和磷酸化GSK-3β（p-GSK-3β,Ser9）蛋白的水平。RT-PCR检测Snail1、Akt1和GSK3β mRNA的表达。RTECs以磷脂酰肌醇3-激酶（PI3K）抑制剂LY294002（25 μmol/L）预处理50 min,再与高糖共同培养24 h,Western blotting检测上述指标蛋白的表达。结果：与正常糖对照组比较,高糖组RTECs Snail1和Akt1蛋白和mRNA的表达上调,p-Akt及p-GSK-3β蛋白表达增加,但总GSK-3β蛋白和mRNA表达无变化。以LY294002处理后,高糖组RTECs Snail1、p-Akt及p-GSK-3β蛋白表达水平较未处理高糖组明显下降,但LY294002不影响总Akt1和GSK-3β蛋白表达。结论：Akt/GSK-3β可能介导了高糖诱导的RTECs锌指转录因子Snail1的表达上调。     

阿托伐他汀通过下调NLRP1炎性体表达抑制IL-1β和IL-18的释放

 目的:探讨核苷酸结合寡聚化结构域样受体蛋白1(NLRP1)炎性体在阿托伐他汀抑制THP-1巨噬细胞白细胞介素-1β(IL-1β)和白细胞介素-18(IL-18)分泌中的作用。方法:用10 μg/L脂多糖诱导THP-1巨噬细胞分泌IL-1β和IL-18,以不同浓度阿托伐他汀(1、10和20 μmol/L)孵育细胞24 h,或以10 μmol/L阿托伐他汀处理细胞不同时间(12、24和48 h),或转染NLRP1 siRNA以沉默细胞内NLRP1的表达。采用RT-PCR检测细胞内NLRP1炎性体mRNA的表达,Western blot检测细胞内NLRP1炎性体蛋白的表达,ELISA检测细胞上清液中IL-1β和IL-18的含量。结果:阿托伐他汀可抑制THP-1巨噬细胞NLRP1炎性体mRNA和蛋白的表达,且这种效应呈浓度和时间依赖性。转染NLRP1 siRNA后,THP-1巨噬细胞NLRP1的蛋白表达明显下降,且阿托伐他汀对IL-1β和IL-18分泌的抑制作用明显增强。结论:阿托伐他汀通过抑制NLRP1炎性体表达减少巨噬细胞IL-1β和IL-18的释放,发挥抗炎作用,进而延缓动脉粥样硬化进展。     

大肠杆菌感染对大鼠肺组织β-防御素-2基因表达的负相调节作用

目的:探讨细菌对大鼠β-防御素-2(rBD-2)基因的表达调控。方法:将大肠杆菌E.coliML-35p和绿脓杆菌ATCC27853大鼠气管内接种,于24h后提取肺组织RNA,用逆转录-聚合酶链反应(RT-PCR)法和Northernblot检测大鼠β-防御素-2基因的表达变化。结果:气管内接种大肠杆菌24h后使大鼠肺组织β-防御素-2mRNA的表达受到显著抑制,绿脓杆菌对其基因的表达却没有抑制作用。结论:大肠杆菌感染可负相调节大鼠肺组织rBD-2mRNA的表达。     

LPS、TNF-α、IL-1β对人脐静脉内皮细胞COX-2表达的影响

目的:探讨LPS、TNF-α、IL-1β对人脐静脉内皮细胞(HUVEC)环氧合酶2(COX-2)表达及前列腺素(PGs)的影响。方法:在分离培养的HUVEC细胞给予LPS、TNF-α、IL-1β刺激24h后,采用原位杂交、逆转录-聚合酶链反应(RT-PCR)、免疫组化检测HUVECCOX-2mRNA及蛋白的表达并观察了培养液前列腺素(PGs)的变化。结果:静息状态的HUVEC表达极少量的COX-2;受炎性刺激后,HUVEC大量表达COX-2mRNA及蛋白,同时伴有PGs的升高。结论:结果提示,静息状态下HUVEC表达极少量的COX-2,炎性刺激可诱发COX-2高表达和PGs升高,因此内皮细胞可通过COX-2的调节参与炎症反应。     

β-细辛醚对缺糖缺氧再灌注损伤原代大鼠海马神经元的保护作用*

 目的：探讨β-细辛醚对缺糖缺氧再灌注损伤原代海马神经元的保护作用及其机制。方法：利用MTT法检测缺糖缺氧再灌注诱导的原代大鼠海马神经元的细胞活力,用分光光度法检测caspase-3的活性,用Western blotting法检测p-JNK和Bcl-2的蛋白表达,RT-PCR检测Bcl-2和caspase-3 mRNA表达。结果：与正常对照组比较,缺糖缺氧再灌注损伤组细胞活力明显下降,caspase-3活性明显升高,p-JNK蛋白表达和caspases-3 mRNA表达显著升高,Bcl-2蛋白表达显著降低,差异有统计学意义（均P＜0.05）。与缺糖缺氧再灌注损伤组比较,不同剂量β-细辛醚预处理组抑制了这些指标的改变（均P＜0.05）。结论：β-细辛醚通过抑制JNK介导的线粒体通路抑制缺糖缺氧再灌注诱导的原代海马神经元凋亡。     

缺氧和高糖对大鼠肾成纤维细胞ICAM-1mRNA表达的影响

目的:探讨缺氧和高糖对肾成纤维细胞(NRK)细胞间粘附分子-1(ICAM-1)mRNA表达的影响。方法:将大鼠NRK分6组进行体外培养:(1)正常浓度葡萄糖组(常糖组):5.6mmol/L葡萄糖;(2)常糖+缺氧组:5.6mmol/L的葡萄糖+100μmol/L的CoCl2;(3)高糖A组:15mmol/L葡萄糖;(4)高糖+缺氧A组:15mmol/L葡萄糖+100μmol/L的CoCl2;(5)高糖B组:30mmol/L葡萄糖;(6)高糖+缺氧B组:30mmol/L葡萄糖+100μmol/L的CoCl2。分别于24h、48h取各组NRK采用RT-PCR检测ICAM-1mRNA表达水平。结果:与常糖组相比,高糖A组,高糖B组ICAM-1mRNA表达量逐渐升高(P<0.01),常糖+缺氧组、高糖+缺氧A、B组ICAM-1mRNA表达量也升高(P<0.01);高糖+缺氧A、B组ICAM-1mRNA表达量分别比高糖A、B组明显升高(P<0.01);高糖A、B组和常糖+缺氧组、高糖+缺氧A、B组48hICAM-1mRNA表达量均高于24h表达量(P<0.01)。结论:高糖和缺氧均可导致ICAM-1mRNA高表达,缺氧可能进一步增加高糖上调ICAM-1的表达。     

Hypoxia-induced Bax and Bcl-2 protein expression, caspase-9 activation, DNA fragmentation, and lipid peroxidation in mitochondria of the cerebral cortex of newborn piglets: the role of nitric oxide

The present study tests the hypothesis that cerebral hypoxia results in increased ratio of Bax/Bcl-2, activation of caspase-9, lipid peroxidation, and DNA fragmentation in mitochondria of the cerebral cortex of newborn piglets and that the inhibition of nitric oxide synthase by N-nitro-L-arginine during hypoxia will prevent the events leading to mitochondrial DNA fragmentation. To test this hypothesis, six piglets, 3-5 days old, were divided into three groups: normoxic (n=5), hypoxic (n=5), and hypoxic-nitric oxide synthase (n=4). Hypoxic animals were exposed to a FiO2 of 0.6 for 60 min. Nitric oxide synthase (40 mg/kg) was infused over 60 min prior to hypoxia. Tissue hypoxia was confirmed by measuring levels of ATP and phosphocreatine. Cerebral cortical tissue mitochondria were isolated and purified using a discontinuous ficoll gradient. Mitochondrial Bax and Bcl-2 proteins were determined by Western blot. Caspase-9 activity in mitochondria was determined spectro-fluorometrically using fluorogenic substrate for caspase-9. Fluorescent compounds, an index of mitochondrial membrane lipid peroxidation, were determined spectrofluorometrically. Mitochondrial DNA was isolated and separated by electrophoresis on 1% agarose gel and stained with ethidium bromide. ATP levels (micromol/g brain) were 4.52+/-0.34 in normoxic, 1.18+/-0.29 in hypoxic (P<0.05) and 1.00+/-0.26 in hypoxic-nitric oxide synthase animals (P<0.05 vs. normoxic). Phosphocreatine levels (micromol/g brain) were 3.61+/-0.33 in normoxic, 0.70+/-0.20 in hypoxic (P<0.05 vs. normoxic) and 0.57+/-0.14 in hypoxic-nitric oxide synthase animals (P<0.05 vs. normoxic, P=NS vs. hypoxic). Bax density in mitochondrial membranes was 160+/-28 in normoxic and 324+/-65 in hypoxic (P<0.001 vs. normoxic). Bcl-2 density mitochondria was 96+/-18 in normoxic and 98+/-20 in hypoxic (P=NS vs. normoxic). Mitochondrial caspase-9 activity (nmol/mg protein/h) was 1.32+/-0.23 in normoxic and 2.25+/-0.24 in hypoxic (P<0.01 vs. normoxic). Levels of fluorescent compounds (microg of quinine sulfate/g protein) were 12.48+/-4.13 in normoxic and 37.92+/-7.62 in hypoxic (P=0.003 vs. normoxic). Densities (ODxmm2) of low molecular weight DNA fragments were 143+/-38 in normoxic, 365+/-152 in hypoxic, (P<0.05 vs. normoxic) and 163+/-25 in hypoxic-nitric oxide synthase animals (P<0.05 vs. hypoxic, P=NS vs. normoxic). The data demonstrate that hypoxia results in increased mitochondrial proapoptotic protein Bax, increased mitochondrial caspase-9 activity, increased mitochondrial lipid peroxidation, and increased fragmentation of DNA in mitochondria of the cerebral cortex of newborn piglets. The administration of a nitric oxide synthase inhibitor, nitric oxide synthase, prior to hypoxia prevented fragmentation of mitochondrial DNA, indicating that the hypoxia-induced mitochondrial DNA fragmentation is NO-mediated. We propose that NO free radicals generated during hypoxia lead to NO-mediated altered expression of Bax leading to increased ratio of pro-apoptotic/anti-apoptotic protein resulting in modification of mitochondrial membrane, and subsequently Ca2+-influx and fragmentation of mitochondrial DNA.     

RT-PCR法检测神经源性分化因子mRNA在大鼠脑发育过程中的表达

目的 观察大鼠不同发育时期脑内神经源性分化因子（NeuroD）mRNA表达量的变化,探讨其对神经细胞的分化和成熟发挥的作用。方法 提取不同发育阶段大鼠不同脑组织中的mRNA,RT-PCR法反转录扩增NeuroD和β-actin,利用凝胶成像系统检测其相对表达量。 结果 NeuroD在受孕7.5d（E7.5）时出现表达,在E10.5和E21.5时分别达到两次高峰,平均吸光度值为20437.88±598.28和14482.23±1134.49,表达水平显著高于其他各组（P<0.01）,NeuroD/β-actin比值在E12.5、E18.5和E21.5分别为1.59±0.09、1.61±0.07和1.70±0.11,显著高于其他时间段（P<0.01）。 结论 在大鼠脑发育过程中,NeuroD mRNA的表达呈明显时间特异性,在E10.5左右大鼠各原始脑泡的形成过程中,NeuroD-mRNA明显增高;在胚胎发育的晚期,脑组织形态进一步完善和成熟的过程中NeuroD达到第二次表达高峰,与鼠脑的发育过程相符。推测NeuroD对鼠脑的早期神经细胞分化以及晚期细胞的成熟均起一定作用。     

低氧诱导因子1在低氧致肺动脉平滑肌细胞增殖中的作用

目的: 探讨低氧对肺动脉平滑肌细胞(PASMC)增殖和凋亡的影响,以及HIF-1α、P-ERK1/2、iNOS蛋白表达变化在其中的作用与意义。方法: 体外培养大鼠PASMC，设计常氧组、低氧组及ADM、L-NAME、PD98059干预组，用MTT比色法和PCNA的免疫组化法测定细胞增殖反应，用流式细胞仪检测细胞凋亡，用Western blotting法检测HIF-1α、P-ERK1/2、iNOS的蛋白表达。结果: （1）低氧24 h组的A值明显高于常氧组(P<0.01)，而PD98059及ADM干预组明显低于低氧组(P<0.01)， L-NAME干预组明显高于低氧组和常氧组(P<0.01)。（2）免疫组化表明，低氧24 h组呈阳性表达(P<0.01)。PD98059、ADM抑制了PCNA的表达(P<0.01)， L-NAME促进了PCNA的表达(P<0.01)。（3）各组在低氧培养24 h后，凋亡指数差异无显著(均P＞0.05)。（4）Western blotting表明常氧组少量HIF-1α、iNOS、 P-ERK1/2表达，低氧4 h后均表达增高(P<0.01),8 h仍维持在高峰(P<0.01)，而HIF-1α、P-ERK1/2在低氧24 h后表达下调。L-NAME促进了HIF-1α表达(P<0.01),PD98059部分抑制了HIF-1α、iNOS及P-ERK1/2表达(P<0.01)；ADM部分抑制了HIF-1α表达，促进iNOS表达(P<0.01)。结论: 低氧能促进肺动脉平滑肌细胞增殖，对细胞的凋亡无影响；HIF-1在低氧诱导肺动脉平滑肌细胞增殖中起重要作用。     

缺氧对肺动脉平滑肌细胞钾通道Kv1.2、Kv1.6基因表达的影响

目的:研究不同缺氧时间对大鼠肺动脉平滑肌细胞(PASMC)不同亚型钾通道(Kv)mRNA和蛋白质表达的影响。方法:采用半定量RT-PCR和Western-blot方法对常氧和不同缺氧时间后PASMC上Kv1.2、Kv1.6mRNA和蛋白质的表达进行测定。结果:(1)PASMC在常氧和缺氧时均有Kv1.2、Kv1.6mRNA和蛋白质表达;(2)缺氧18h使Kv1.2mRNA和蛋白质表达增强,缺氧48h则使其表达减弱且低于常氧时的表达;(3)缺氧18h、48h对Kv1.6的mRNA和蛋白质表达无影响。结论:Kv1.6不是氧敏感的钾通道;作为氧感受器的Kv1.2,其mRNA和蛋白质表达随缺氧时间而改变。     

低氧条件下成骨细胞的增殖与分化

背景：低氧可通过多种途径作用于成骨细胞影响骨代谢,对骨生成、骨愈合等产生负面影响。 目的：观察低氧对体外培养大鼠成骨细胞增殖、分化的影响,并探讨其分子机制。 方法：分离培养新生Wistar大鼠颅盖骨成骨细胞,取第2代细胞分别在常氧(体积分数20%O₂)与低氧(体积分数3%O₂)条件下培养。 结果与结论：低氧组成骨细胞增殖、碱性磷酸酶活性、骨钙素水平及茜素红结节形成数量均明显低于常氧组(P < 0.05或  P < 0.01),说明缺氧条件对成骨细胞的增殖、分化及功能有抑制作用;低氧组骨形成发生蛋白2及Runx2表达低于常氧组(P < 0.05或P < 0.01),说明低氧条件下大鼠成骨细胞Runx2、骨形成发生蛋白2的表达受抑制。结果表明低氧可通过抑制大鼠成骨细胞的Runx2、骨形成发生蛋白2的表达进一步抑制成骨细胞的增殖与分化。     

间歇低氧小鼠胰腺β细胞凋亡及其机制的实验研究

目的: 探讨间歇低氧对小鼠胰腺β细胞凋亡的影响及其可能机制。方法: 将30只雄性C57BL/6J小鼠随机分为间歇低氧组、持续低氧组和正常对照组,每组10只。实验结束后测定各组小鼠的胰岛素耐量;采用化学比色法测定胰腺组织丙二醛(MDA)含量和超氧化物歧化酶(SOD)活性;用real-time PCR检测小鼠胰腺组织中锰超氧化物歧化酶(MnSOD)和谷胱甘肽过氧化酶(GPx1) mRNA的表达水平;并用TUNEL染色检测胰腺β细胞凋亡。结果: 间歇低氧组小鼠胰岛素抵抗水平及胰腺组织中MDA水平显著高于正常对照组和持续低氧组 (P<0.01);胰腺组织SOD活性显著低于正常对照组和持续低氧组(P<0.01);抗氧化酶MnSOD和GPx1 mRNA的表达水平显著低于正常对照组和持续低氧组 (P<0.01);而胰腺β细胞凋亡率显著高于正常对照组和持续低氧组(P<0.01)。持续低氧组与正常对照组上述各种指标的比较均无显著差异(均P＞0.05)。结论: 间歇低氧可导致胰腺组织氧化应激状态和胰腺β细胞凋亡,这可能是阻塞性睡眠呼吸暂停低通气综合征患者胰岛素抵抗及2型糖尿病的病理生理基础之一。     

Mg2+-dependent modification of the N-methyl-D-aspartate receptor following graded hypoxia in the cerebral cortex of newborn piglets.

The present study tests the hypothesis that Mg2+ modification of N-methyl-D-aspartate receptor ion channel opening is altered during hypoxia and correlates with the progressive decrease in cerebral energy metabolism induced by hypoxia. Studies were performed in five normoxic and nine hypoxic ventilated piglets. In the hypoxic group, varying degrees of cerebral energy metabolism were achieved by administration of different fractions of inspired oxygen (FiO2) (5-9%) for varying durations of time and were documented by cortical tissue phosphocreatine levels. [3H]Dizocilpine maleate binding was performed with increasing concentrations of MgSO4 from 0.01 to 15 mM in cortical P2 membrane fractions. Mg2+ percentage activation and Mg2+ 50% inhibitory concentrations (IC50) were determined. The mean +/- S.D. phosphocreatine value was 3.0 +/- 1.3 micromol/g brain in the normoxic group and 1.4 +/- 1.0 micromol/g brain in the hypoxic group (P < 0.01). Low concentrations of Mg2+ (0.01-1 mM) increased [3H]dizocilpine maleate binding in the normoxic group (to 137 +/- 26% of baseline), significantly greater than in the hypoxic group (109 +/- 13%, P < 0.05). Receptor activation correlated with brain tissue levels of phosphocreatine, with percentage maximal activation decreasing linearly as phosphocreatine levels decreased (r=0.7). Higher levels of Mg2+ (1.5-15 mM) caused inhibition of [3H]dizocilpine maleate binding, with IC50 levels significantly higher in the normoxic group (3.2 +/- 1.1 mM) than in the hypoxic group (1.9 +/- 0.4 mM). Mg2+ IC50 values decreased in a linear fashion as phosphocreatine values decreased (r=0.9). The data demonstrate that, as brain cell energy metabolism decreases during hypoxia, maximal receptor activation by low levels of Mg2+ decreases and receptor inhibition by high levels of Mg2+ increases in a linear fashion. We speculate that, during hypoxia, dephosphorylation of the ion channel of the N-methyl-D-aspartate receptor increases Mg2+ blockade of the receptor by increasing Mg2+ accessibility to its binding site and that receptor modification may be initiated by subtle decreases in cortical oxygenation in the newborn brain.     

Hypoxia-induced expression of vascular endothelial growth factor by retinal glial cells promotes in vitro angiogenesis

To determine whether retinal glial cells (RGCs) participate in the paracrine regulation of retinal neovascularization, we investigated whether cultured RGCs synthesize and release vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) under normoxic or hypoxic conditions. Northern blot analysis demonstrated that cultured RGCs transcribed both VEGF mRNA with two molecular bands approximately 3.9 and 4.3 kilobases (kb), and bFGF mRNA with approximately 3.7 and 6.0 kb. The expression of VEGF mRNA was greatly enhanced by hypoxic cultivation (2% oxygen) when compared with normoxic cultivation (20% oxygen), while the expression of bFGF mRNA by RGCs was not significantly affected by hypoxia. The effects of RGCs-conditioned media (CM) on tritiated-thymidine incorporation and in vitro angiogenesis by retinal capillary endothelial cells (RECs) in producing the formation of capillary-like tubes in type I collagen gels, were evident in the observation that RGCs-CM harvested after hypoxic cultivation significantly enhanced tritiated-thymidine incorporation (1.9 times, P<0.01) and in vitro angiogenesis (2.4 times, P<0.01) compared with the normoxic RGCs-CM. These enhancing effects of RGCs-CM at hypoxia were suppressed by anti-VEGF neutralizing antibody. Furthermore, RECs were shown to express mRNA encoding the VEGF receptor flt-1 by northern blot analysis. These results suggest that VEGF expressed by RGCs under hypoxic conditions plays an integral role in the initiation and progression of retinal neovascularization in a paracrine manner.     

Phosphorylation of caspase-9 in the cytosolic fraction of the cerebral cortex of newborn piglets following hypoxia

We have previously shown that hypoxia leads to increased expression and increased activity of caspase-9 in the cerebral cortex of newborn piglets. Previous studies have demonstrated the importance of caspase-9 in the initiation of the apoptotic cascade, however, the mechanism of caspase-9 activation is not well understood. Experiments were conducted on newborn piglets 2-3 days of age that were anesthetized and mechanically ventilated. Hypoxia was induced by lowering the FiO(2) to 0.05-0.07 x 1h, and was confirmed biochemically by demonstrating decreased levels of ATP and PCr in the hypoxic groups in comparison with the normoxic group. The ATP level was 1.99+/-0.66 in the hypoxic group versus 4.10+/-0.19 in the normoxic group, P<0.05, and the PCr value was 0.68+/-0.14 in the hypoxic group, compared to 2.98+/-0.39 in the normoxic group, P<0.05. The cytosol of the neuronal nuclei from the cerebral cortex was probed with anti-phosphorylated Ser(196) caspase-9 antibody, using Western blot analysis. Protein bands were analyzed using image densitometry. In both the hypoxic and normoxic samples, protein bands were demonstrated just above the 50 kDa marker. Phosphorylated caspase-9 expression in OD x mm(2) was 43.85+/-8.4 in the normoxic group and 67.6+/-9.88 in the hypoxic group, P<0.05. The results of this study demonstrate that caspase-9, a key protein in hypoxia induced apoptosis, is phosphorylated at the Ser(196) site during hypoxia. The results demonstrate that hypoxia results in a post-translational modification of caspase-9 at Ser(196), which may alter the activity of caspase-9 in the hypoxic newborn brain.     

连代低氧培养肺动脉平滑肌及内皮细胞的急性低氧反应中环核苷酸的作用

目的:探讨环核苷酸在慢性低氧动物的低氧性肺血管收缩反应(HPV)弱化机制中的作用。方法:用RIA法测定连代常氧与连代低氧培养猪肺动脉平滑肌细胞(PASMC)和内皮细胞(PAEC)的cAMP和cGMP及其在急性低氧时的变化;用图像分析系统检测常氧与低氧培养PASMC在急性低氧时的收缩程度。结果:低氧组PASMC的cAMP、cGMP和PAEC的cGMP基础值较常氧组低(P＜0.01)。急性低氧状态下,低氧组PASMC的cAMP、cGMP含量升高(P＜0.01);低氧组弱收缩反应PASMC的百分率明显高于常氧组。结论:慢性低氧PASMC和PAEC的cAMP、cGMP基础值下降可能与慢性低氧动物肺动脉基础张力增高有关;慢性低氧PASMC在急性低氧反应时cAMP、cGMP含量升高可能是慢性低氧机体HPV弱化的机制之一。