不同氧体积分数对人胚胎干细胞基因表达谱的影响

背景：低氧培养人胚胎干细胞的相关研究主要集中在干细胞多能性的维持及分化方面,而低氧对人胚胎干细胞基因表达水平的影响研究甚少。 目的：观察不同氧体积分数对人胚胎干细胞基因表达谱的影响。 方法：分别在低氧(体积分数5%O2)和常氧(体积分数21%O2)的条件下持续培养FY-hES-7细胞,收集晚期(第52代)细胞,运用全基因组表达谱芯片技术检测不同氧体积分数组FY-hES-7细胞的基因表达谱,并进行差异基因的功能富集分析及通路分析。 结果与结论：与常氧组相比,低氧组表达上调(>2倍)的基因1 840个,表达下调(>2倍)的基因1 676个。利用基因本体分析发现低氧组表达上调基因与细胞表面受体信号转导、免疫反应、离子转运、生物代谢及细胞活动等功能相关,而表达下调基因则与转录调控,依赖DNA的转录调控、神经分化、细胞形态、胚胎形态、胚胎器官及各系统发育等功能相关。通路分析发现低氧组表达上调的基因与细胞因子受体的相互作用、免疫反应以及造血系统等通路的改变相关,而表达下调的基因则多与胚胎发育及肿瘤通路改变相关。不同氧体积分数下长期培养的人胚胎干细胞基因表达谱存在明显的差异,低氧组出现差异表达基因的功能分析表明低氧有助于人胚胎干细胞的自我更新,防止分化及降低成瘤性。     

Hypoxia-regulated neurotrophin-3 expression by multicopy hypoxia response elements reduces apoptosis in PC12 cells

We have previously reported that 5?copies of the hypoxia response element (HRE) can conditionally regulate brain-derived neurotrophic factor gene expression under hypoxic/ischemic conditions in mice. In the present study, we investigated the controlled expression of neurotrophin-3 (NT-3) by HRE under hypoxic conditions and determined the protective effects of conditionally expressed NT-3 on hypoxia-induced apoptosis in PC12 cells. Five copies of the HRE (5HRE) and the simian virus?40 minimal promoter (SV40mp) were employed to construct a cassette, and transfer of therapeutic gene, NT-3, into PC12 cells was achieved using a retroviral vector. Our results showed that the retroviral vector, pLNC-5HRE-NT3, was successfully constructed and transfected into PC12 cells. Compared with normal conditions, in which NT-3 was expressed at low levels, the expression of NT-3 significantly increased under hypoxic conditions in 5HRE-NT3 transgenic PC12 cells (P<0.05). By contrast, in NT-3 transgenic PC12 cells without HRE, we found no significant difference in NT-3 expression between the normoxic and hypoxic groups. The conditional adjustment of NT-3 expression by 5HRE significantly reduced apoptosis induced by hypoxia in 5HRE-NT3 transgenic PC12 cells (P<0.05) but not in 5HRE-enhanced green fluorescent protein (EGFP) transgenic PC12 cells and PC12 cells without gene transfer. In addition, the hypoxia-induced upregulation of both p38 and caspase-3 activities was suppressed in 5HRE-NT3 transgenic PC12 cells under hypoxic conditions (P<0.05). Taken together, these results demonstrate that 5HRE-SV40mp regulates NT-3 gene expression in response to hypoxia in PC12 cells. The data presented in this study may prove useful in future gene therapy studies for the treatment of ischemic diseases.     

细胞对缺氧的感受和信号转导

缺氧是最常见的病理过程，急性缺氧在数秒或数分钟即可通过改变蛋白质的活性引起细胞的兴奋、抑制、运动、分泌、代谢等变化；数小时或数天的慢性缺氧可通过相关基因转录的变化导致细胞的增殖、分化、凋亡及代谢、机能等变化。     

Role of TRP channels and NCX in mediating hypoxia-induced [Ca(2+)](i) elevation in PC12 cells

Mammalian cells require a constant O2 supply to produce adequate energy, and sustained hypoxia can kill cells. Mammals therefore have evolved sophisticated mechanisms to allow their cells to adapt to hypoxia. In this study, we investigated the role of TRP channels and the Na+-Ca2+ exchanger (NCX) in mediating hypoxia-induced [Ca2+]i elevation in a model of the O2-sensing rat pheochromocytoma (PC12) cell line by using Ca2+ imaging and molecular biological approaches. Non-selective cation channels, such as TRPC1, 3 and 6, were found to be functionally expressed in PC12 cells. They mediated Ca2+ entry when cells were exposed to acute hypoxia (PO2 of 15 mmHg), in addition to Ca2+ entry via VGCCs. Blockage of TRPCs by 2APB and SKF96365 could significantly reduce hypoxia-mediated [Ca2+]i elevation. Suramin and U73122 attenuated the hypoxia-induced [Ca2+]i elevation, implying the involvement of the G-protein and PLC pathways in the hypoxic response. In addition to TRPCs and VGCCs, NCX also contributed to the hypoxia-induced [Ca2+]i elevation, and blockade of NCX by KBR7943 could significantly decrease the hypoxia-induced [Ca2+]i elevation. Our results suggest that the activation of TRP by hypoxia could lead to NCX reversal; furthermore, membrane depolarization and TRPCs may play a primary role in mediating the hypoxic response in PC12 cells.     

牵张应力对人牙周膜细胞MMP-13/TIMP-1表达的影响及其信号转导途径研究

目的研究不同强度机械牵张应力对人牙周膜细胞基质金属蛋白酶-13(MMP-13)及其组织抑制因子-1(TIMP-1)表达的影响,并探讨机械牵张应力作用下人牙周膜细胞MMP-13/TIMP-1表达变化的信号转导途径。方法通过细胞牵张应力加载系统对体外培养的人牙周膜细胞同时施加0%、6%、12%和18%形变率的机械牵张应力,作用24 h后,用RT-PCR方法检测细胞受力后MMP-13/TIMP-1 mRNA表达的变化,用免疫印迹法检测其蛋白表达的变化。另外,通过使用不同信号途径的特异性抑制剂,用RT-PCR方法分别检测不同抑制剂对牵张应力作用下牙周膜细胞MMP-13/TIMP-1 mRNA表达的变化。结果人牙周膜细胞受力后,MMP-13/TIMP-1 mRNA及蛋白表达随牵张应力强度的增大明显增加。PD098059可抑制机械牵张应力作用下牙周膜细胞MMP-13 mRNA表达的增加。放线菌酮可抑制机械牵张应力作用下TIMP-1 mRNA表达的增加。结论不同强度机械牵张应力可以影响人牙周膜细胞MMP-13/TIMP-1的表达,进而影响牙周组织细胞外基质代谢。机械牵张应力作用下MMP-13表达的增加是通过ERK-MAPK途径。机械牵张应力作用下TIMP-1表达的增加是通过新生蛋白途径。     

Glial cell line-derived neurotrophic factor promotes survival and induces differentiation through the phosphatidylinositol 3-kinase and mitogen-activated protein kinase pathway respectively in PC12 cells

PC12-GFRalpha1 cells, a clonal cell line engineered to express glial cell line-derived neurotrophic factor receptor alpha1 were constructed. Given glial cell line-derived neurotrophic factor could induce the differentiation and promote the survival of PC12-GFRalpha1 cells at low concentrations, the cells provide an unlimited source of monoclonal cells for studies on the signal transduction pathway of glial cell line-derived neurotrophic factor. To characterize the involvement of the mitogen-activated protein kinase and phosphatidylinositol 3-kinase pathways in the biological effect of glial cell line-derived neurotrophic factor, we used the mitogen-activated protein kinase kinase inhibitor PD98059 and the phosphatidylinositol 3-kinase inhibitor LY294002. PD98059 blocked glial cell line-derived neurotrophic factor-induced PC12-GFRalpha1 cells neurite formation in a dose-dependent manner, without significantly altering cell viability. LY294002 reversed the survival-promoting effect of glial cell line-derived neurotrophic factor on the PC12-GFRalpha1 cells in serum-deprived medium.The present study demonstrates that phosphatidylinositol 3-kinase pathway seems to mediate the survival-promoting effect of glial cell line-derived neurotrophic factor on PC12-GFRalpha1 cells, while the activation of mitogen-activated protein kinase pathway could be an important step in mediating PC12-GFRalpha1 cells differentiation induced by glial cell line-derived neurotrophic factor. Therefore, it is inferred that similar intracellular signaling components are used by distinct growth factors toward a common biological effect.     

低氧反应元件介导的低氧调控的神经营养因子-3表达上调减少低氧诱导的PC12细胞凋亡

目的 在体外培养的PC12细胞中观察低氧反应元件（HRE）介导的神经营养因子-3（NT-3）对低氧反应性表达上调及其对低氧诱导的PC12细胞凋亡的影响。 方法 用分子生物学方法将5拷贝HRE（5HRE）和NT-3克隆入反转录病毒载体中构建HRE介导的低氧调控表达载体,并转导入PC12细胞,ELISA法检测NT-3的表达和分泌,TUNEL法检测细胞凋亡,Western blotting检测p38丝裂原活化蛋白激酶(p38MAPK）和Caspase-3激活情况。 结果 成功构建重组反转录病毒载体,并将外源基因转导入PC12细胞中（PC12-NT3-EGFP、PC12-5HRE-NT3-EGFP和PC12-5HRE-EGFP）。在正常条件培养下,PC12-5HRE-NT3-EGFP细胞中NT-3表达水平较低,但在低氧处理后,NT-3表达明显升高（n=3,P<0.05）。在低氧处理后,与PC12细胞组相比,PC12-5HRE-NT3-EGFP组中细胞凋亡明显减少（n=3,P<0.05）,且p38 MAPK和Caspase-3磷酸化也明显减少（n=3,P<0.05）。 结论 在PC12细胞中HRE介导的低氧反应性调控NT-3的表达上调可以对PC12细胞产生保护作用。     

两条IL-6信号转导途径在人骨髓瘤细胞系U266中的相互拮抗作用

目的 研究人骨髓瘤细胞系U266中白细胞介素6（IL－6）信号转导途径及彼此之间的相互调控方式。方法 首先采用凝胶阻滞电泳（electrophoretic mobility shift assay,EMSA)方法观察分别参与两条IL－6信号转导途径的转录因子STAT3和NF－IL－6在U266细胞中的诱导激活状态并确定该细胞中的IL－6信号转导通路;继而采用转基因或化学试剂处理方法,特异性上调或下调其中一条IL－6信号途径的化,并同时观察另外一信号途径的激活状态。结果 1、以上两种转录因子分别参与的IL－6信号转导途径－－JAK／STAT和Ras/NF-IL-6,它们都能够在U266细胞中诱导激活;2、在高剂量IL－6（1－100ng/ml）刺激范围之内,一条IL－6信号途径活化水平的升高可同时导致另一条信号途径活化水平的下降。结论 在一定IL－6刺激剂量范围内,U266细胞中两条IL－6信号途径的诱导激活存在着相互拮抗作用。     

Neurite outgrowth of PC12 mutant cells induced by orange oil and d-limonene via the p38 MAPK pathway

We studied the effects of natural essential oil on neurite outgrowth in PC12m3 neuronal cells to elucidate the mechanism underlying the action of the oils used in aromatherapy. Neurite outgrowth can be induced by nerve growth factor (NGF), where ERK and p38 MAPK among MAPK pathways play important roles in activating intracellular signal transduction. In this study, we investigated whether d-limonene, the major component of essential oils from oranges, can promote neurite outgrowth in PC12m3 cells, in which neurite outgrowth can be induced by various physical stimulations. We also examined by which pathways, the ERK, p38 MAPK or JNK pathway, d-limonene acts on PC12m3 cells. Our results showed that neurite outgrowth can be induced when the cells are treated with d-limonene. After treatment with d-limonene, we observed that p38 MAPK is strongly activated in PC12m3 cells, while ERK is weakly activated. In contrast, JNK shows little activity. A study using an inhibitor of p38 MAPK revealed that neurite outgrowth in PC12m3 cells is induced via the activation of p38 MAPK by d-limonene. The results thus indicate that d-limonene may promote neural cell differentiation mainly via activation of the p38 MAPK pathway.