骨桥蛋白反义核苷酸对大鼠血管平滑肌细胞增殖的影响

背景：骨桥蛋白在血管损伤后新生内膜中的表达明显上调,而且能促进血管平滑肌细胞和外膜细胞的增殖、迁移。 目的：探索骨桥蛋白反义核苷酸对大鼠血管平滑肌细胞增殖的影响。 方法：培养大鼠A10主动脉血管平滑肌细胞,通过MTT比色法测定骨桥蛋白反义核苷酸对平滑肌细胞增殖的影响,流式细胞仪测定骨桥蛋白反义核苷酸对平滑肌细胞周期分布的影响;通过RT-PCR方法检测血管平滑肌细胞转染骨桥蛋白反义核苷酸对增殖细胞核抗原表达的影响。 结果与结论：骨桥蛋白反义核苷酸对血管平滑肌细胞的增殖有明显的抑制作用,随时间延长对细胞增殖抑制率下降。骨桥蛋白反义核苷酸主要作用于G1/S限制点,能阻止血管平滑肌细胞由G0/G1期向S期推进,从而将血管平滑肌细胞阻滞于G0/G1期,抑制血管平滑肌细胞的增殖。血管平滑肌细胞转染骨桥蛋白反义核苷酸后,增殖细胞核抗原的表达水平均较对照组降低(P < 0.05)｡因此,得出骨桥蛋白反义核苷酸通过阻止血管平滑肌细胞由G0/G1期向S期推进,从而抑制血管平滑肌细胞的增殖,进而抑制血管内膜增生。     

三七总皂甙通过细胞外信号调节蛋白激酶1/2信号通路促进大鼠

背景：三七总皂甙对骨髓基质细胞向神经样细胞分化的效应及相关信号通路目前尚不明确。 目的：探讨细胞外信号调节蛋白激酶1/2信号通路对三七总皂甙调节大鼠骨髓基质细胞向神经细胞增殖、分化的作用。 设计、时间及地点：细胞学体外观察,于2008-05/10在汕头大学医学院分子生物学实验室完成。 材料：4~6周龄雄性SD大鼠9只,由汕头大学医学院实验动物中心提供。三七总皂甙为广西梧州制药集团股份有限公司产品,细胞外信号调节蛋白激酶的抑制剂PD98059为Cell Signaling Tech 公司产品。 方法：全骨髓法体外分离纯化大鼠骨髓基质细胞,取传至第3代细胞进行诱导分化,设立3组：单纯诱导组向培养液中加入10 μg/L碱性成纤维细胞生长因子,预诱导24 h后全量换为正式诱导液(含10 μg/L碱性成纤维细胞生长因子、2% DMSO、200 μmol/L丁羟回醚的α-MEM培养基),每24 h半量换诱导液1次;三七总皂甙组向预诱导液和正式诱导液内加入终浓度100 mg/L三七总皂甙;PD98059组在三七总皂甙组培养液基础上加入10 μmol/L PD98059。 主要观察指标：细胞形态学观察,MTT法检测细胞增殖情况,免疫组织化学方法鉴定细胞Nestin的表达。 结果：诱导6 h后,少数细胞呈锥形,细胞突起增多伸长,类似神经元,继续诱导培养后细胞突起增多,突起相互连接成网状。与单纯诱导组、PD98059组比较,诱导6,12,24 h三七总皂甙组细胞均明显增殖(P < 0.05),且随诱导时间延长呈递增趋势(P < 0.05);单纯诱导组、PD98059组间比较无明显差异(P > 0.05)。与单纯诱导组比较,诱导24 h后三七总皂甙组Nestin阳性率明显升高(P < 0.05),PD98059组Nestin阳性率明显降低(P < 0.05)。 结论：三七总皂甙可以促进骨髓基质细胞的神经分化和分化后增殖,细胞外信号调节蛋白激酶1/2的特异性抑制剂PD98059能够拮抗三七总皂甙促增殖分化作用,提示细胞外信号调节蛋白激酶1/2信号通路是三七总皂甙促进骨髓基质细胞向神经细胞分化和增殖的重要环节。     

apelin-13下调caveolae可促进血管平滑肌细胞增殖

背景：结合课题组以往研究成果,提出caveolae可能参与apelin-13促血管平滑肌细胞增殖的假设。 目的：实验观察细胞膜特殊凹陷结构caveolae参与G蛋白偶联受体APJ的内源性配体apelin-13促进大鼠血管平滑肌细胞增殖的作用。 方法：采用组织贴块法培养大鼠胸主动脉血管平滑肌细胞,用MTT方法观察血管平滑肌细胞增殖,Western Blotting方法观察信号蛋白表达,免疫共沉淀技术检测信号分子复合物的形成。 结果与结论：①caveolae结构破坏剂β-环糊精(5 mmol/L,25 h)可明显增强apelin-13诱导的血管平滑肌细胞增殖。②apelin-13(0,1,2,4,8 µmol/L)刺激血管平滑肌细胞,caveolin-1的表达下调,在1 µmol/L时下调明显。③β-环糊精 (5 mmol/L)破坏caveolae后,可使apelin-13下调caveolin-1表达的作用增强。④对照组(体积分数为0.1%胎牛血清孵育)及处理组(apelin-13刺激)caveolin-1与PI3K及ERK1/2均有复合物形成,在apelin-13刺激的情况caveolin-1-PI3K复合物减少、caveolin-1-ERK1/2复合物减少,即apelin-13可能促进caveolin-1与PI3K及ERK1/2解离。结果提示细胞膜特殊凹陷结构caveolae参与apelin-13促血管平滑肌细胞增殖作用。     

As2O3对不同p53表型的人胶质瘤细胞系细胞周期蛋白B1、D1表达的影响

目的研究三氧化二砷(As2O3)对两种不同p53表型的人胶质瘤细胞系(U87MG和T98G)细胞周期蛋白B1、D1表达及细胞周期的影响。方法应用激光扫描细胞计数分析仪(LSC),共聚焦显微镜以及Western印迹分析等方法检测As2O3对细胞周期蛋白B1、D1和p53及细胞周期的作用。结果As2O3能使两个胶质瘤细胞系的p53蛋白水平升高,细胞周期蛋白B1表达降低及G2/M期俘获,但仅U87MG细胞的细胞周期蛋白D1表达下降。As2O3还能诱导U87MG细胞凋亡。结论体外低浓度的As2O3能有效地抑制U87MG和T98G细胞增殖,提示As2O3有希望用于神经胶质瘤患者的治疗。     

间歇性高糖对胰岛β细胞生长及细胞周期进程的影响☆

背景：间歇性高糖可阻滞胰岛β细胞生长,增加β细胞的凋亡,但具体作用机制尚不清。 目的：观察间歇性高糖对大鼠胰岛素细胞增殖、凋亡及对细胞周期进程的影响。 方法：实验对大鼠胰岛素细胞进行培养,分为正常糖对照组,恒定性高糖组和间歇性高糖组,分别含葡萄糖5.5,30,30和5.5 mmol/L间歇换液。采用细胞计数试剂盒检测细胞增殖活性,流式细胞仪测定细胞周期,Annexin-V/PI双标流式细胞术检测细胞凋亡,应用Western blot检测细胞周期调控蛋白Cyclin D1的表达水平。 结果与结论：与正常糖对照组相比,恒定性高糖组及间歇性高糖组均明显抑制大鼠胰岛素细胞细胞的生长(P < 0.01),增加大鼠胰岛素细胞的凋亡(P < 0.01),明显抑制细胞周期进程,使大鼠胰岛素细胞的细胞周期更多滞留在G0/G1期(P < 0.01),能显著减弱细胞周期调控蛋白Cyclin D1的表达(P < 0.01)。与恒定性高糖组相比,间歇性高糖以上各指标作用均更显著(P < 0.01)。结果证实,间歇性高糖能够抑制大鼠胰岛素细胞的生长,增殖和诱导凋亡,其机制可能是通过降低Cyclin D1的活性,使细胞阻滞在G0/G1期,抑制细胞周期进程,从而减弱细胞的增殖活性。     

去除蛋白激酶A磷酸化位点的线粒体融合素2基因与血管平滑肌细胞增殖

背景: 线粒体融合素2基因作用于血管平滑肌细胞Ras蛋白,通过胞外信号调节蛋白激酶1/2通路抑制细胞增殖。线粒体融合素2基因氨基酸序列第442位丝氨酸为蛋白激酶A磷酸化位点,与其磷酸化状态密切相关,可能参与其功能调控。 目的：观察大鼠线粒体融合素2基因在去除蛋白激酶A磷酸化位点后对大鼠血管平滑肌细胞增殖的影响及其相关信号通路。 方法：利用已构建的携带绿色荧光蛋白基因、线粒体融合素2基因和去除蛋白激酶A磷酸化位点的线粒体融合素2基因的3种重组腺病毒,感染大鼠主动脉血管平滑肌细胞,将其传代培养3~10代后以抽签法随机分为4组：①不加干预的对照组。②感染携带绿色荧光蛋白的对照组(Adv-GFP组)。③感染携带线粒体融合素2基因的实验组(Adv-Mfn2组)。④感染携带去除蛋白激酶A磷酸化位点的线粒体融合素2基因的实验组(Adv- Mfn2-PKA(△)组)。激光共聚焦显微镜观察完整的和去除蛋白激酶A磷酸化位点的线粒体融合素2基因在细胞中的定位。Western blot检测p-ERK1/2表达水平及完整的和去除蛋白激酶A磷酸化位点的线粒体融合素2基因在血管平滑肌细胞中的表达。MTT法绘制细胞生长曲线。 结果与结论：完整的和去除蛋白激酶A磷酸化位点的线粒体融合素2基因在血管平滑肌细胞中均表达蛋白特异性条带。两种基因表达产物都主要分布于线粒体外膜。与对照组和Adv-GFP组相比,Adv-Mfn2组吸光度值在第3,4,5,6天都显著降低(P < 0.01),Adv-Mfn2-PKA(△)组吸光度值无明显变化。与对照组和Adv-GFP组相比,Adv-Mfn2组p-ERK1/2表达水平显著降低(P < 0.01),Adv-Mfn2-PKA(△)组无明显变化。提示去除蛋白激酶A磷酸化位点的线粒体融合素2基因定位于线粒体外膜,对血管平滑肌细胞的增殖无拮抗作用,对胞外信号调节蛋白激酶1/2通路无抑制作用。     

痹肿消汤干预胶原诱导关节炎模型大鼠关节滑膜组织细胞外信号调节激酶1/2及细胞外信号调节激酶5的表达***

背景：滑膜细胞信号转导异常是类风湿性关节炎的重要发病机制之一。中药复方痹肿消汤治疗类风湿性关节炎具有较好的临床疗效,但在细胞信号转导水平探讨痹肿消汤治疗类风湿性关节炎的作用机制是十分必要的。 目的：观察中药复方痹肿消汤对胶原诱导关节炎模型大鼠滑膜细胞外信号调节激酶1/2,5表达的影响。 方法：SD大鼠45只随机数字表法分为对照组、模型组、痹肿消汤组。胶原诱导关节炎模型大鼠,用痹肿消汤药液3.0~ 3.5 mL灌胃,1次/d,连续14 d。检测造模后第14,21,28天大鼠滑膜细胞外信号调节激酶1/2,5的磷酸化水平。 结果与结论：造模后,大鼠滑膜细胞外信号调节激酶1/2,5的磷酸化表达随时间而增加(P < 0.05)。痹肿消汤治疗后,细胞外信号调节激酶1/2,5磷酸化表达水平则明显下降(P < 0.05)。提示痹肿消汤能抑制细胞外信号调节激酶1/2,5蛋白激酶的激活,从而抑制细胞外信号调节激酶1/2, 5信号转导通路的活化,这可能是其阻抑类风湿性关节炎滑膜异常增殖、关节骨质侵蚀的重要机制之一。     

细胞外信号调节激酶信号通路对癫痫大鼠海马内HIF-1α表达的调控作用

目的 探讨细胞外信号调节激酶(ERK)信号通路是否参与调节癫痫大鼠海马内低氧诱导因子-1α(HIF-1α)的表达. 方法 208只21d龄SD大鼠按随机数字表法分为癫痫持续状态(SE)组(96只)、对照组(96只)和PD98059组(16只),SE组腹腔注射戊四氮(PTZ)溶液制作SE模型,对照组注射等剂量生理盐水,造模后0.5、1、1.5、6、12、24h采用RT-PCR、Western blotting分别检测2组大鼠海马内HIF-1α、ERK1/2 mRNA和蛋白的表达;PD98059组大鼠腹腔注射PD98059,10min后腹腔注射PTZ溶液制作SE模型,造模成功后1h采用RT-PCR检测大鼠海马内HIF-1α、ERK1/2mRNA的表达,造模成功后1.5 h采用Western blotting检测其相应蛋白的表达. 结果 与对照组比较,SE组大鼠海马内HIF-1α、ERK1/2 mRNA及其蛋白的表达明显升高,差异均有统计学意义(P＜0.05);其中ERK1/2 mRNA的表达高峰(1.112±0.126)在SE后1h,蛋白的表达高峰(1.127±0.155)在SE后1.5 h;而HIF-1α mRNA的表达高峰(0.589±0.090)在SE后1.5 h,蛋白的表达高峰(0.230±0.052)在SE后6h.与SE组相比,PD98059组大鼠海马内HIF-1αmRNA、ERK1/2 mRNA和蛋白的表达均降低,差异均有统计学意义(P＜0.05).SE组大鼠中,T-ERK 1/2与HIF-1αmRNA的表达呈正相关(r=0.688,P=0.000). 结论 戊四氮诱导发育期大鼠SE后ERK信号通路被激活,参与了海马内HIF-1α的表达调控.     

电针干预自发性高血压大鼠主动脉丝裂原活化蛋白激酶磷酸酶1及磷酸化细胞外信号调节激酶1/2蛋白的表达

背景：近年来大量临床研究表明针刺风池、太冲、曲池等穴位能有效降低血压,可用于高血压,但对其治疗的分子机制尚未阐明。 目的：观察针刺大鼠风池、太冲、曲池等穴位对丝裂原活化蛋白激酶信号转导调控系统的影响,从而探讨针刺治疗高血压的分子机制。 方法：选取8月龄自发性高血压雄性Wistar大鼠14只,随机分为针刺组和模型组,每组7只;另选取同月龄正常血压雄性Wistar-Kyoto大鼠7只作为对照组。对针刺组大鼠采用电针针刺双侧风池、曲池和三阴交穴,毫针刺太溪和太冲穴。3周后采用RT-PCR方法检测各组大鼠主动脉组织丝裂原活化蛋白激酶磷酸酶1 mRAN的表达,Western blot方法检测丝裂原活化蛋白激酶磷酸酶1、磷酸化细胞外信号调节激酶1/2蛋白表达。 结果与结论：与对照组比较,模型组主动脉组织磷酸化细胞外信号调节激酶1/2蛋白表达水平升高,丝裂原活化蛋白激酶磷酸酶1 mRNA及其蛋白表达水平降低(P < 0.01);与模型组比较,针刺组主动脉组织磷酸化细胞外信号调节激酶1/2蛋白表达水平降低,丝裂原活化蛋白激酶磷酸酶1 mRNA及其蛋白表达水平升高(P < 0.05)。提示针刺治疗自发性高血压大鼠可能是通过调控丝裂原活化蛋白激酶信号转导途径,增强磷酸化细胞外信号调节激酶1/2蛋白表达,降低丝裂原活化蛋白激酶磷酸酶1蛋白表达,从而改善血管重塑,降低血压。     

骨髓间充质干细胞增殖与成骨分化中电磁场激活ERK通路的作用*

背景：研究表明电磁场可调节骨髓间充质干细胞的增殖和分化,但其具体机制尚不清楚。 目的：从ERK信号途径探讨电磁场诱导大鼠骨髓间充质干细胞增殖与分化成骨的作用。 方法：取第3代生长良好的大鼠骨髓间充质干细胞,暴磁组给予15 Hz、1 mT的正弦波电磁场刺激,PD98059+暴磁组在电磁场刺激前给予20 μmol/L ERK阻断剂PD98059,PD98059组仅给PD98059不进行电磁场刺激,对照组正常培养。电磁场刺激后,收集各组细胞,Western blot法检测ERK通路的活性,MTT法检测细胞增殖活性,碱性磷酸酶试剂盒检测细胞碱性磷酸酶活性。 结果与结论：电磁场刺激后,细胞ERK1/2磷酸化水平、细胞的增殖活性、及碱性磷酸酶活性均明显升高(P < 0.01);PD98059可明显抑制ERK1/2磷酸化水平及细胞增殖活性的升高(P < 0.01),而在一定程度上提高细胞的碱性磷酸酶活性(P < 0.01)。说明电磁场刺激可通过激活骨髓间充质干细胞ERK信号通路,并且主要通过该途径促进骨髓间充质干细胞的增殖;而在脉冲电磁场促进骨髓间充质干细胞分化成骨的过程中,激活ERK信号通路所起的作用较小。     

High density lipoproteins induce cell cycle entry in vascular smooth muscle cells via mitogen activated protein kinase-dependent pathway

In this study we found that HDL acts as a potent and specific mitogen in vascular smooth muscle cells (VSMC) by stimulating entry into S-phase and DNA synthesis in a time- and concentration-dependent manner, induction of cyclins D1, E, and A, as well as activation of cyclin D-dependent kinases as inferred from phosphorylation of the retinoblastoma protein (pRb). Moreover, HDL induced activation of the mitogen-activated protein kinase pathway including Raf-, MEK-1, and ERK1/2, as well as the expression of proto-oncogen c-fos, which is controlled by ERK1/2. PD98059, an inhibitor of MEK-1 blocked the mitogenic activity of HDL and cyclin D1 expression. HDL-induced VSMC proliferation, cell cycle progression, cyclin D1 expression, and activation of the Raf-1/MEK-1/ERK1/2 cascade were blocked by preincubation of cells with pertussis toxin indicating involvement of trimeric G-protein. By contrast, none of these responses was inhibited by the protein kinase C inhibitor, GF109203X. The mitogenic effects of native HDL were not mimicked by apo A-I, reconstituted HDL containing apo A-I, or cholesterol-containing liposomes. In conclusion, HDL possesses an intrinsic property to induce G-protein- and MAP-kinase-dependent proliferation and cell cycle progression in VSMC. The strong and specific mitogenic effect of HDL should be taken into account, when therapeutic strategies to elevate the plasma level of these lipoproteins are developed.     

Oxygen-Glucose Deprivation Induces G2/M Cell Cycle Arrest in Brain Pericytes Associated with ERK Inactivation

Growing evidence has revealed that brain pericytes are multifunctional and contribute to the pathogenesis of a number of neurological disorders. However, the role of pericytes in cerebral ischemia, and especially the pathophysiological alterations in pericytes, remains unclear. In the present study, our aim was to determine whether the proliferation of pericytes is affected by cerebral ischemia and, if so, to identify the underlying mechanism(s). Cultured brain pericytes subjected to oxygen-glucose deprivation (OGD) were used as our model of cerebral ischemia; the protein expression levels of cyclin D1, cyclin E, cdk4, and cyclin B1 were determined by Western blot analysis, and cell cycle analysis was assessed by flow cytometry. The OGD treatment reduced the brain pericyte proliferation by causing G2/M phase arrest and downregulating the protein levels of cyclin D1, cyclin E, cdk4, and cyclin B1. Further studies demonstrated a simultaneous decrease in the activity of extracellular regulated protein kinases (ERK), suggesting a critical role of the ERK signaling cascade in the inhibition of OGD-induced pericyte proliferation. We suggest that OGD inhibition of the proliferation of brain pericytes is associated with the inactivation of the ERK signaling pathway, which arrests them in the G2/M phase.     

Antiproliferative action of neomycin is associated with inhibition of cyclin D1 activation in glioma cells

The progression of mammalian cells through G1 phase of the cell cycle is governed by the D-type cyclins (D1, D2, D3). These proteins are induced at the beginning of the G1 phase and associate with serine/threonine cyclin-dependent kinases to form holoenzymes. Overexpression of cyclin D1 in human cancers as well as in several cancer cell lines has been reported. Here, we employed mitotic selection to synchronize the C6 glioma cell cycle at the start of the G1 phase and assessed the effects of neomycin on cyclin D1 protein detection by immunocytochemical analysis. Cyclin D1 activation as well as cell proliferation were already significantly reduced after 3 h of incubation of the cells with neomycin. These findings suggested that the antiproliferative effects of neomycin in gliomas could be mediated by inhibition of the expression of cyclin D1 gene and support further consideration of therapeutic use of neomycin in a Phase I clinical study for patients with recurrent glioblastoma.     

Tissue factor pathway inhibitor-2 is downregulated by ox-LDL and inhibits ox-LDL induced vascular smooth muscle cells proliferation and migration

Introduction

Tissue factor pathway inhibitor-2 (TFPI-2) is a member of the Kunitz-type family of serine protease inhibitors, which inhibits several matrix metalloproteinases activity involved in extracellular matrix degradation. Studies have shown low TFPI-2 expression in the shoulder regions of atherosclerotic plaques. But studies evaluating its role in the progression of atherosclerotic plaque are scarce. Vascular smooth muscle cells (VSMCs) are important components of atherosclerotic plaques and oxidized low density lipoprotein (ox-LDL) is an important detrimental factor of atherosclerosis. The aim of this study is to elucidate the effect of TFPI-2 on smooth muscle cell proliferation and migration induced by ox-LDL.

Methods

Retroviruses expressing human TFPI-2 were constructed. Cell proliferation was determined by CCK-8 assay. Cell apoptosis was analyzed by double staining of FITC-Annexin V and propidium iodide. Cell migration was studied through a Transwell chamber and with a scratch-wound assay. The matrix metalloproteinase-2 and − 9 activities were analyzed by gelatin zymography. Phosphorylation of FAK was analyzed by western blot.

Results

TFPI-2 over-expression of mRNA and protein was confirmed in infected cells. CCK-8 assay showed that TFPI-2 inhibit VSMCs proliferation induced by ox-LDL while without cytotoxicity to VSMCs. Transwell and scratch wound assay confirmed TFPI-2 over-expression can inhibit VSMC migration. Zymography assay showed that TFPI-2 can inhibit MMP-2, 9 activity induced by ox-LDL. Western blot assay showed TFPI-2 can inhibit cyclinD1 expression and FAK phosphorylation.

Conclusion

TFPI-2 over-expression may strongly inhibit the proliferation and migration of VSMCs and suppresses MMP-2, 9 activity induced by ox-LDL, making it a promising candidate for treatment of atherosclerotic process.     

Cyclopamine对神经母细胞瘤细胞系SK-N-SH细胞生长周期的影响及其机制

目的探讨Shh信号途径的抑制剂cyclopamine对人神经母细胞瘤细胞系SK-N-SH细胞生长周期的影响及其分子生物学机制。方法以不同浓度的cyclopamine处理SK-N-SH细胞不同时间,在相差倒置显微镜下观察药物作用后的该细胞形态学变化。用四甲基偶氮唑盐（MTT）分析法检测各组SK-N-SH细胞的增殖情况,流式细胞仪检测不同浓度cyclopamine作用后对细胞周期的影响,Westernblot检测药物作用前后细胞周期蛋白D1、P16和P21蛋白表达的变化。结果cyclopamine各处理组SK-N-SH细胞形态学有所不同。MTT法检测结果显示,cyclopamine对SK-N-SH细胞增殖的抑制是浓度依赖性和时间依赖性的（P〈0.05）。流式细胞仪检测发现随着药物浓度的增加,G0/G1期细胞百分比明显增加（P〈0.05）,而S期细胞百分比明显降低（P〈0.05）。Westernblot检测结果显示,随着药物浓度的增加,SK-N-SH细胞中细胞周期蛋白D1表达逐渐降低,P16和P21表达逐渐增高（P〈0.05）。结论cyclopamine抑制SK-N-SH细胞生长,阻滞细胞从G1期向S期转化,其机制可能与调控细胞周期蛋白表达有关。cyclopamine可能成为未来治疗神经母细胞瘤的药物之一。     

罗格列酮抑制垂体腺瘤GH3细胞及促凋亡作用的研究

目的探讨罗格列酮对GH3细胞增殖的影响及其促细胞凋亡的机制。方法不同浓度罗格列酮作用GH3细胞后,流式细胞仪检测细胞周期和细胞凋亡,Elisa法分析罗格列酮对生长激素合成的影响,Western blot法分析GH3细胞Cyclin D3、bcl-2和bax的变化。结果罗格列酮作用GH3细胞48 h后,以浓度效应关系抑制GH3细胞增殖、并使细胞增殖周期中G0-G1期阻滞,S期和G2-M期百分率降低;Western blot法示罗格列酮作用GH3细胞提高了Cyclin D3和bax的表达,而bcl-2的表达降低。结论罗格列酮促GH3细胞凋亡并抑制GH分泌,可能成为垂体生长激素腺瘤病人新的治疗方法。     

Potassium-induced apoptosis in rat cerebellar granule cells involves cell-cycle blockade at the G1/S transition

The role of regulators controlling the G1/S transition of the cell cycle was analyzed during neuronal apoptosis in post-mitotic cerebellar granule cells in an attempt to identify common mechanisms of control with transformed cells. Cyclin D1 and its associated kinase activity CDK4 (cyclin-dependent kinase 4) are major regulators of the G1/S transition. Whereas cyclin D1 is the regulatory subunit of the complex, CDK4 represents the catalytic domain that, once activated, will phosphorylate downstream targets such as the retinoblastoma protein, allowing cell-cycle progression. Apoptosis was induced in rat cerebellar granule cells by depleting potassium in presence of serum. Western-blot analyses were performed and protein kinase activities were measured. As apoptosis proceeded, loss in cell viability was coincident with a significant increase in cyclin D1 protein levels, whereas CDK4 expression remained essentially constant. Synchronized to cyclin D1 accumulation, cyclin-dependent kinase inhibitor p27Kip1 drastically dropped to 20% normal values. Cyclin D1/CDK4-dependent kinase activity increased early during apoptosis, reaching a maximum at 9-12 h and decreasing to very low levels by 48 h. Cyclin E, a major downstream target of cyclin D1, decreased concomitantly to the reduction in cyclin D1/CDK4-dependent kinase activity. We suggest that neuronal apoptosis takes place through functional alteration of proteins involved in the control of the G1/S transition of the cell cycle. Thus, apoptosis in post-mitotic neurons could result from a failed attempt to re-enter cell cycle in response to extracellular conditions affecting cell viability and it could involve mechanisms similar to those that promote proliferation in transformed cells.     

Beta-amyloid-activated cell cycle in SH-SY5Y neuroblastoma cells: correlation with the MAP kinase pathway

Primary cultures of rat cortical neurons exposed to toxic concentrations of beta-amyloid peptide (betaAP) begin an unscheduled mitotic cell cycle that does not progress beyond the S phase. To analyze possible signal transduction pathways involved in this effect, the action of betaAP has been studied in SH-SY5Y neuroblastoma cells differentiated by a 7-d exposure to 10 microM retinoic acid. Treatment with the betaAP fragment, betaAP(25-35), (25 microM) for 24, 48, or 72 h caused apoptotic cell death, detected by flow cytometry as a prediploid cell population. Cell cycle analysis showed that betaAP(25-35) modified cell cycle profiles by markedly increasing the number of cells in the S phase and reducing the population of the G2/M area. These effects seem to involve activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK1/2). Inhibition of this pathway by the specific inhibitor PD98059 (2 microM) completely prevented changes of cell cycle distribution induced by betaAP and significantly reduced neuronal death. The data suggest that MAPK cascade can mediate the induction of cell cycle induced by betaAP, thus contributing to the toxicity of the peptide.     

Serum and forskolin cooperate to promote G1 progression in Schwann cells by differentially regulating cyclin D1, cyclin E1, and p27Kip expression

Proliferation of Schwann cells in vitro, unlike most mammalian cells, is not induced by serum alone but additionally requires cAMP elevation and mitogenic stimulation. How these agents cooperate to promote progression through the G1 phase of the cell cycle is unclear. We studied the integrative effects of these compounds on receptor-mediated signaling pathways and regulators of G1 progression. We show that serum alone induces strong cyclical expression of cyclin D1 and E1, 6 and 12 h after addition, respectively. Serum also promotes strong but transient erbB2, ERK, and Akt phosphorylation, but Schwann cells remain arrested in G1 due to high levels of the inhibitor, p27(Kip). Forskolin with serum promotes G1 progression in 22% of Schwann cells between 18 and 24 h by inducing a steady decline in p27(Kip) levels that reaches a nadir at 12 h coinciding with peak cyclin E1 expression. Forskolin also delays neuregulin-induced loss of erbB2 receptors allowing strong acute activation of PI3K, sustained erbB2 phosphorylation and G1 progression in 31% of Schwann cells. We find that the ability of forskolin to decrease p27(Kip) is associated with its ability to decrease Krox-20 expression that is induced by serum and further increased by neuregulin. Our results explain why serum is required but insufficient to stimulate proliferation and identify two routes by which forskolin promotes proliferation in the presence of serum and neuregulin. These findings provide insights into how G1 progression and, cell cycle arrest leading to myelination are regulated in Schwann cells.