白细胞介素13诱导足细胞损伤及其作用机制

目的:探讨Th2细胞因子IL-13是否直接介导足细胞损伤,并初步探讨其作用机制. 方法:RT-PCR和免疫组化方法检测温度敏感的小鼠足细胞系(HSMP)上IL-13受体的mRNA和蛋白质表达.使用不同浓度(10 ng/ml,50 ng/ml,100 ng/ml)的IL-13干预足细胞不同时间(8h、12h、24h),免疫荧光法分析足细胞骨架相关蛋白F-actin和细胞间连接蛋白ZO-1的变化情况.并进一步应用Western blot方法检测细胞内信号通路STAT 6的磷酸化水平,探讨IL-13损伤足细胞的作用机制. 结果:HSMP上存在IL-13 Ⅰ型受体mRNA和蛋白质表达.骨架蛋白F-actin和ZO-1的染色结果显示:IL-13可呈剂量和时间依赖性对足细胞造成损伤.50ng/ml IL-13作用24h即可造成足细胞明显损伤.F-actin变细、紊乱,向细胞边缘聚集;ZO-1明显减弱和断裂.进一步的研究还表明,IL-13可诱导足细胞内细胞因子相关的STAT 6信号通路的活化.STAT 6信号通路特异性抑制剂leflunomide可阻断IL-13对足细胞骨架蛋白结构和细胞间连接蛋白的影响. 结论:足细胞表面存在IL-13受体,IL-13可通过与其受体结合损伤足细胞的骨架结构和细胞间连接蛋白.IL-13对足细胞的损伤作用与STAT 6信号通路的活化有关.     

Janus激酶-信号转导子与转录激活子通路介导粒细胞集落刺激因子影响冠状动脉微栓塞后心肌细胞凋亡的实验研究

目的 探讨粒细胞集落刺激因子(G-CSF)对大鼠冠状动脉微栓塞(CME)后心肌细胞凋亡的影响以及Janus激酶-信号转导子与转录激活子(JAK/STAT)通路的介导作用.方法 将92只雄性成年SD大鼠,随机分成CME组(24只)、G-CSF组(24只)、JAK2特异性抑制剂(AG490)组(G-CSF+AG490,24只)和假手术组(20只).CME组、G-CSF组及AG490组升主动脉夹闭后自左室腔内注入自体微血栓,造成CME,假手术组注入等量生理盐水.G-CSF组及AG490组术后2 h起给予皮下注射重组人G-CSF(rhG-CSF)100 μg·kg-1·d-1持续5 d,AG490组同时给予AG490溶液腹腔注射5 mg·kg-1·d-1,其他组给予等量生理盐水.术后3 d、1、2及4周处死动物.各组心肌样品中以实时定量聚合酶链式反应法检测Bcl-2、Bax、Fas及FasL的mRNA表达,并计算Bcl-2/Bax比值;以Western blot法检测Caspase-3、裂解多聚二磷酸腺苷-核糖聚合酶(PARP)、总JAK2(t-JAK2)、磷酸化JAK2(p-JAK2)、t-STAT3以及p-STAT3蛋白的表达;脱氧核糖核苷酸末端转移酶介导的缺口末端标记(TUNEL)法测定凋亡细胞.结果 (1)与假手术组比较,CME组术后Bcl-2、Bax、Fas及FasL的mRNA表达均升高,Bcl-2/Bax比值降低(0.28±0.04比2.98±0.49),Caspase-3(0.762±0.129比0.133±0.027)及PARP蛋白(0.992±0.146比0.386±0.074)表达增强,心肌细胞凋亡指数升高(P＜0.05或P＜0.01);t-JAK2、p-JAK2、t-STAT3以及p-STAT3蛋白表达差异无统计学意义.(2)与CME组比较,G-CSF组术后p-JAK2与p-STAT3蛋白表达明显增强,Bax、Fas及FasL的mRNA表达明显减弱,Bcl-2的mRNA表达增强,Bcl-2/Bax比值升高(2.07±0.29比0.28±0.04),Caspase-3(0.371±0.041比0.762±0.129)及PARP蛋白(0.548±0.093比0.992±0.146)表达减弱;心肌细胞凋亡指数下降(P＜0.05或P＜0.01);t-JAK2及t-STAT3蛋白表达则差异无统计学意义.(3)经AG490干预后,G-CSF引起的基因与蛋白表达的变化均有不同程度减弱(P＜0.05或P＜0.01).结论 G-CSF通过激活JAK2/STAT3细胞内信号通路减轻CME导致的心肌细胞凋亡.     

Drosophila phosphoinositide-dependent kinase-1 regulates apoptosis and growth via the phosphoinositide 3-kinase-dependent signaling pathway

Phosphoinositide-dependent kinase-1 (PDK-1) is a central mediator of the cell signaling between phosphoinositide 3-kinase (PI3K) and various intracellular serine/threonine kinases including Akt/protein kinase B (PKB), p70 S6 kinases, and protein kinase C. Recent studies with cell transfection experiments have implied that PDK-1 may be involved in various cell functions including cell growth and apoptosis. However, despite its pivotal role in cellular signalings, the in vivo functions of PDK-1 in a multicellular system have rarely been investigated. Here, we have isolated Drosophila PDK-1 (dPDK-1) mutants and characterized the in vivo roles of the kinase. Drosophila deficient in the dPDK-1 gene exhibited lethality and an apoptotic phenotype in the embryonic stage. Conversely, overexpression of dPDK-1 increased cell and organ size in a Drosophila PI3K-dependent manner. dPDK-1 not only could activate Drosophila Akt/PKB (Dakt1), but also substitute the in vivo functions of its mammalian ortholog to activate Akt/PKB. This functional interaction between dPDK-1 and Dakt1 was further confirmed through genetic analyses in Drosophila. On the other hand, cAMP-dependent protein kinase, which has been proposed as a possible target of dPDK-1, did not interact with dPDK-1. In conclusion, our findings provide direct evidence that dPDK-1 regulates cell growth and apoptosis during Drosophila development via the PI3K-dependent signaling pathway and demonstrate our Drosophila system to be a powerful tool for elucidating the in vivo functions and targets of PDK-1.     

Autocrine activation of the IL-3/GM-CSF/IL-5 signaling pathway in leukemic cells

The AML14.3D10 human myeloid leukemic cell line expresses receptors for granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-5 (IL-5), but not IL-3. We have found that this cell line produces GM-CSF in amounts up to 113 pg/ml in culture supernatants. Deprivation of endogenous GM-CSF by addition of neutralizing anti-GM-CSF antibody strongly inhibits proliferation of the cells, suggesting a GM-CSF autocrine growth mechanism. To examine whether endogenously produced GM-CSF activates intracellular GM-CSF/IL-3/IL-5-related signal transduction pathways, we performed anti-phosphotyrosine immunoblotting of cell lysates of AML14.3D10 cells before and after deprivation of endogenous GM-CSF. We found constitutive tyrosine-phosphorylation of a number of proteins in AML14.3D10 that could not be detectably increased by the addition of exogenous GM-CSF, IL-3, or IL-5. However, GM-CSF-deprived cells demonstrated a marked increase in phosphorylation of proteins of identical molecular mass following addition of GM-CSF and IL-5, but not IL-3, consistent with the receptor expression of the cells and the known use of the same signaling pathways by the three cytokines. This suggests that AML14.3D10 cells use endogenously produced GM-CSF to activate signal transduction pathways, interfering with activation by exogenous cytokine until the endogenous stimulation is removed. We then assessed the activation of the β-subunit common to the GM-CSF/IL-3/IL-5 receptors (βc), JAK2 and p53/56 lyn, known to be involved in the common signaling pathways of the three cytokines. We found that phosphorylation of βc and JAK2 in response to GM-CSF and IL-5 could be markedly enhanced by depriving cells of endogenous GM-CSF. Constitutive hyperphosphorylation of lyn was found in AML14.3D10 cells, and no further activation of lyn in response to cytokine was demonstrable in GM-CSF-deprived cells, suggesting that lyn is activated in this cell line by a mechanism other than GM-CSF. These studies represent the first demonstration of autocrine activation of intracellular cytokine signaling pathways by malignant hematopoietic cells. Because the addition of anti-GM-CSF to cell cultures improved responsiveness of intracellular signal transducing molecules to exogenous GM-CSF and IL-5, it can be inferred that endogenously produced GM-CSF exerts its effects by secretion and binding to surface GM-CSF receptors, although an intracellular component to signaling cannot be excluded. These observations provide further information regarding an autocrine contribution to leukemic cell growth, and establish a new model for study of these events. Am. J. Hematol. 56:79–85, 1997. © 1997 Wiley-Liss, Inc.     

Platelet-derived growth factor activates porcine thecal cell phosphatidylinositol-3-kinase-Akt/PKB and ras-extracellular signal-regulated kinase-1/2 kinase signaling pathways via the platelet-derived growth factor-beta receptor

Platelet-derived growth factor (PDGF) is a potent mitogenic factor for ovarian thecal cells cultured in vitro. PDGF binds to and induces homo- or heterodimerization of PDGF receptor-a or -beta (PDGF-Ralpha or PDGF-Rbeta). Despite this, little information is available about which PDGF receptors are expressed in the ovary, what signaling cascades are activated by PDGF, and the effects of PDGF on thecal cell steroidogenesis. The present study demonstrates the expression of immunoreactive PDGF-Rbeta, but not PDGF-Ralpha, in the thecal and stromal compartments of intact porcine ovaries as well as in cultured porcine thecal cells. Treatment of porcine thecal cells in vitro with PDGF resulted in rapid and sustained tyrosine phosphorylation of PDGF-Rbeta, activation of Src tyrosine kinase and phosphatidylinositol-3-kinase (PI3-kinase), and serine 473 phosphorylation of Akt/protein kinase B. In addition, PDGF stimulated an increase in GTP-Ras (activated Ras) and extracellular signal-regulated kinase (ERK) phosphorylation. Both forms of PDGF, AB and BB, stimulated thecal cell growth approximately 3- to 4-fold over controls and inhibited LH-stimulated progesterone and androstenedione secretion. Blockade of PI3-kinase activation with wortmannin had no effect on PDGF-stimulated thecal cell growth or PDGF inhibition ofLH-stimulated steroid secretion, indicating that PI3-kinase activation is not necessary for PDGF-stimulated thecal cell growth or inhibition of LH-stimulated steroidogenesis. Conversely, blockade of the MEK-ERK pathway with PD98059 completely blocked PDGF-stimulated cell growth, indicating that activation of the MEK-ERK pathway is required for PDGF-stimulated thecal cell growth. Additionally, the MEK inhibitor PD98059 restored LH-stimulated steroid secretion, demonstrating that activation of the MEK-ERK pathway can lead to inhibition of LH-stimulated steroid secretion. The present study demonstrates that PDGF acts on ovarian thecal cells via activation of the PDGF beta-receptor and stimulates thecal cell growth via activation of a Rasmitogen-activated protein kinase-dependent, PI3-kinase-independent pathway. The strong expression of PDGF-Rbeta and the potent effects of PDGF on thecal cell growth and steroidogenesis suggest an important role for PDGF in thecal cell recruitment and growth during follicular development in vivo.     

JAK-STAT信号转导途径与肺癌的关系

JAK-STAT是细胞因子发挥生物学功能的重要信号转导途径。在正常细胞中激活STATs是一个瞬时的过程,而在癌细胞中,STATs蛋白被持续激活,在肺癌时表达不一。有关STAT信号途径的研究为人类肿瘤的干预治疗提供了新的分子标靶。     

JAK/STAT抑制剂在TNBS诱发大鼠结肠炎中的作用

目的:探讨抑制Janus激酶/信号转导和转录激活子(JAK/STAT)通路在大鼠结肠炎发病机制中的作用.方法:建实验性大鼠结肠炎模型后,给予JAK特异性抑制剂AG490和STAT抑制剂雷帕霉素(RPM),腹腔注射治疗1 wk后处死大鼠,观察结肠炎症改变并进行评分,采用蛋白印迹法(Western blot)检测MMP-1、MMP-2、MMP-3、TIMP-1蛋白表达:用明胶酶谱法检测结肠组织中MMP-2的活性.结果:与对照组相比,AG490治疗组肠道损伤积分降低(5.50±2.16分vs8.53±2.18分,P=0.012);RPM治疗组肠道损伤积分(5.17±1.80分)较对照组低(P<0.05).AG490组和RPM组MMP-1、MMP-2的蛋白质表达量均明显低于对照组(均P<0.05),而两实验组分别与对照组比较其MMP-3、TIMP-1蛋白质表达均无明显差异(均P>0.05).与对照组相比,两实验组MMP-2的活性均显著下降(P<0.05).结论:AG490和RPM通过阻断JAk/STAT信号通路的活化能缓解大鼠结肠炎.这一作用可能是通过抑制MMP-1、MMP-2的表达来实现的.