肿瘤坏死因子-α诱导心肌肥大中CaN信号通路的作用

目的:研究钙调神经磷酸酶(CaN)信号通路在肿瘤坏死因子-α(TNF-α)诱导心肌细胞肥大中的作用。方法:Lowry法测心肌细胞蛋白含量;计算机图象分析系统测心肌细胞体积;[3H]-亮氨酸掺入法测心肌细胞蛋白合成;Till阳离子测定系统观察胞内[Ca2+]i瞬变;Western blot法测定CaN的表达。结果:①CaN特异性抑制剂CsA(0.2μmol/L)明显抑制TNF-α(100μg/L)诱导的心肌细胞蛋白含量、蛋白合成和细胞体积增大,但对正常心肌细胞生长无影响。②CaN特异性抑制剂CsA(0.2μmol/L)明显降低TNF-α诱导的心肌细胞内钙离子浓度([Ca2+]i)瞬变幅度增高。③TNF-α明显增强心肌细胞内CaN的表达。结论:TNF-α可能通过引起心肌细胞[Ca2+]i升高,促进CaN表达诱导心肌细胞肥大。     

肿瘤坏死因子α在中枢神经系统中的作用

概述了肿瘤坏死因子α（TNFα）及其受体在中枢神经系统（CNS）中的作用。TNFα在神经元和胶质细胞中的表达量与神经系统疾病的发病密切相关;TNFα与神经胶质增生、Alzheimer’s病、Parkinson病和多发性硬化症都有关系。然而;当CNS受损伤以后,TNFα能够促进神经营养因子的分泌,增强神经元的粘附和促进轴突的生长;这是它有利的一面。这种双重模式的效应与其受体亚型和激活不同的信号转导途径有关。所以,在CNS的发育中,TNFα可能是一个重要的调节因子。     

PI3K/AKT通路在动物葡萄糖代谢中的研究进展

葡萄糖代谢稳态对维持动物健康水平至关重要.磷脂酰肌醇3-激酶(phosphoinositide 3-kinase,PI3K)是受体酪氨酸激酶(receptor tyrosine kinase,RTK)和G蛋白偶联受体(G protein-coupled receptor,GPCR)共同调控的下游效应因子.它能够磷酸化磷...     

PI3K/AKT途径在大肠埃希菌诱导U937细胞凋亡中的作用

目的探讨PI3K/AKT信号转导通路在大肠埃希菌（Escherichia coli,E.coli）诱导的人巨噬细胞系U937细胞凋亡中的作用。方法利用Western blot分析检测E.coli感染不同时间后磷酸化及非磷酸化AKT的表达;预先用不同浓度的LY294002（PI3K途径抑制剂）处理U937细胞60min,观察E.coli感染30min后U937细胞的凋亡情况。结果随着感染时间的延长,磷酸化AKT的表达逐渐下降。加入PI3K的抑制剂LY294002后,U937细胞的凋亡率逐渐升高。结论PI3K/AKT信号转导通路参与了E. coli诱导的U937细胞凋亡过程。LY294002通过特异性地抑制PI3K/AKT活性增加E.coli诱导的U937细胞凋亡率。     

PGE2抑制肿瘤坏死因子诱导的成骨细胞凋亡

前列腺素E2(PGE2)通过自分泌或旁分泌方式调节成骨细胞的增殖和分化。本文以小鼠原代成骨细胞和成骨样细胞MC3T3-E1为实验材料,研究了PGE2对肿瘤坏死因子α(TNF-α)诱导的成骨细胞凋亡的调节作用。检测发现,振荡型流体剪切力(OFSS)刺激可诱导成骨细胞内环氧合酶2(COX-2)表达升高,进而促进PGE2合成,并抑制TNF-α诱导的成骨细胞凋亡。COX-2选择性活性抑制剂NS-398显著促进TNF-α诱导的成骨细胞内半胱天冬酶3(caspase-3)的激活,且呈时间依赖性。Hoechst 33258/PI染色检测发现,NS-398促使TNF-α诱导的成骨细胞膜通透性进一步增强,核染色质浓缩加剧,而PGE2可显著抑制这一效应。Caspase-3活性检测证实,NS-398显著促进TNF-α诱导的成骨细胞内caspase-3活性增强,外源性PGE2可有效对抗该效应。这些结果表明,内源性和外源性PGE2可抑制TNF-α诱导的成骨细胞凋亡发生。     

蛋白激酶B及其在磷脂酰肌醇3-激酶介导的信号转导中的作用

蛋白激酶Ｂ（ＰＫＢ）是原癌基因ｃ－ａｋｔ的表达产物,它参与由生长因子激活的经磷脂磷肌醇３－激酶（ＰＩ３Ｋ）介导的信号转导过程。与许多蛋白激酶相似,ＰＫＢ分子具有一特殊的ＡＨ／ＰＨ结构域（ＡＨ／ＰＨｄｏｍａｉｎ）,后者能介导信号分子间的相互作用。ＰＫＢ是ＰＩ３Ｋ直接的靶蛋白。ＰＩ３Ｋ产生的脂类第二信使ＰＩ－３,４,Ｐ２和ＰＩ－３,４,５－Ｐ３等均能与ＰＫＢ和磷酸肌醇依赖性蛋白激酶（ＰＤＫ）的ＡＨ／Ｐ     

PI3K/Akt/mTOR信号通路及临床相关肿瘤抑制剂

哺乳动物雷帕霉素靶（mTOR）和蛋白激酶B（Akt/PKB）与肿瘤发生的密切关系已被广泛地认可.mTOR是一种丝/苏氨酸激酶,可以通过影响mRNA转录、代谢、自噬等方式调控细胞的生长.它既是PI3K的效应分子,也可以是PI3K的反馈调控因子.mTORC1 和mTORC2是mTOR的两种不同复合物. 对雷帕霉素敏感的mTORC1受到营养、生长因子、能量和应激4种因素的影响.生长因子通过PI3K/Akt信号通路调控mTORC1是最具特征性调节路径.而mTORC2最为人熟知的是作为Akt473磷酸化位点的上游激酶. 同样,Akt/PKB在细胞增殖分化、迁移生长过程中发挥着重要作用. 随着Thr308和Ser473两个位点激活,Akt/PKB也得以全面活化.因此,mTORC2-Akt-mTORC1的信号通路在肿瘤形成和生长中是可以存在的.目前临床肿瘤治疗中,PI3K/Akt/mTOR是重要的靶向治疗信号通路.然而,仅抑制mTORC1活性,不是所有的肿瘤都能得到预期控制.雷帕霉素虽然能抑制mTORC1,但也能反馈性地增加PI3K信号活跃度,从而影响治疗预后.近来发现的第二代抑制剂可以同时抑制mTORC1/2和PI3K活性,这种抑制剂被认为在肿瘤治疗上颇具前景.本综述着重阐述了PI3K/Akt/mTOR信号通路的传导、各因子之间的相互调控以及相关抑制剂的发展.     

镉负荷大鼠一氧化氮和肿瘤坏死因子-α释放在介导多器官机能活动障碍中的作用

选择健康SD雄性成年大鼠36只,随机分成对照组(C组)、镉负荷中剂量组(M组)、镉负荷高剂量组(H组).将分析纯CdCl2·2.5H2O用生理盐水稀释成含镉0.4mg/ml浓度的注射溶液,高压灭菌.M组和H组大鼠每天分别按含镉0.5和1.0mg/kg体重腹腔注射染毒,C组用同样方法注射与H组同等剂量的生理盐水,进行急性镉负荷实验,连续观察7d.研究急性镉负荷对大鼠血液及几种组织中一氧化氮(NO)自由基、肿瘤坏死因子-α(TNF-a)变化的影响及作用.结果显示在整个实验期内,镉负荷大鼠体重与对照组比较明显下降;睾丸、心脏和肝脏组织中的镉含量极显著上升,并随镉负荷剂量和时间而增加;血浆NO水平M组虽高于对照组,但差异不显著,而H组极显著高于对照组,M和H组血浆TNF-α明显高于对照组;在整个实验期内,镉负荷大鼠睾丸、心脏和肝脏组织匀浆中NO较对照组高或明显高于对照组,睾丸和心脏组织匀浆中TNF-a也均高于或明显高于对照组,但肝脏中的TNF-a三组间没有差异.结果提示,镉负荷诱发NO、TNF-α大量释放在导致大鼠多种器官机能活动障碍发生过程中可能起重要作用.     

中国人群中肿瘤坏死因子α-308 A/G基因多态和α2-巨球蛋白基因缺失多态与晚发性阿尔茨海默病无相关性

晚发性阿尔茨海默病 (LOAD)是老年痴呆中最常见的一种 ,它是一种病因复杂、由遗传因素和环境等其他因素共同作用引起的老年期疾病。服用非甾类抗炎类药物能延缓或防止LOAD的发病说明炎症反应可能参与LOAD病理 ,肿瘤坏死因子 (TNF)是炎症反应中主要的细胞因子 ,并且能增加 β 淀粉样肽 (Aβ)的产生说明其可能是LOAD的易感基因。α2 巨球蛋白 (A2M)是一种血清蛋白酶抑制剂 ,它是低密度脂蛋白受体相关蛋白 (LRP)主要的配体 ,并且能与Aβ结合并介导其降解和清除 ,说明它可能是另一个LOAD的易感基因。在 6 7名晚发性阿尔茨海默病人和 14 2名正常对照中比较了载脂蛋白E基因 (APOE)、TNF启动子区 (- 30 8A G)多态和A2M一 5bp核苷酸缺失 (I D)多态 (A2M 2 )与LOAD发病风险的关系。结果显示 ,APOEε4等位基因在AD病人组中显著高于对照组 (χ2=11 6 6 ,P <0 0 1) ,而TNF(- 30 8A G)多态和A2M缺失多态的基因型和等位基因在LOAD病人组和对照组中都无显著差别 (P >0 1)。按年龄和APOEε4等位基因分组同样无相关性 ,说明TNF 30 8A G位点的多态与A2M缺失不是中国人群的晚发性老年痴呆的风险因子     

PI3-kinase activation by GM-CSF in endothelium is upstream of Jak/Stat pathway: role of alphaGMR

GM-CSF has been identified as a growth factor for endothelial cells. In this study, we investigated the role of PI3-kinase pathway in mediating GM-CSF induced angiogenesis. GM-CSF induced tube formation in human umbilical vein endothelial cells, as examined using Matrigel assay, was inhibited by specific inhibitors of PI3-kinase, wortmannin, and LY294002. The regulatory subunit of PI3-kinase (p85) interacted with alphaGMR via its C-SH2 domain in a GM-CSF-dependent fashion with concomitant phosphorylation of p85 and activation of PI3-kinase pathway. p85 binding site on the alphaGMR was essential to induce GM-CSF receptor-dependent Stat activation. Furthermore, inhibition of PI3-kinase activity also abrogated GM-CSF induced Stat activation. These studies underscore the significance of the GM-CSF mediated PI3-kinase activation and its role in angiogenesis.     

A static pressure sensitive receptor APJ promote H9c2 cardiomyocyte hypertrophy via PI3K-autophagy pathway

This study is designed to investigate whether APJ receptor acts as a sensor in static pressure-induced cardiomyocyte hypertrophy and to investigate the mechanism of PI3K- autophagy pathway. The left ventricular hypertrophy rat model was established by coarctation of abdominal aorta. H9c2 rat cardiomyocytes were cultured in the presence of static pressure which was given by a custom-made pressure in- cubator. The results revealed that the expression of apelin/ APJ system, PI3K, Akt and their phosphorylation were sig- nificantly increased in the operation group. Static pressure up-regulated the APJ expression, PI3K phosphorylation, Akt phosphorylation, LC3-Ⅱ/Ⅰ and beclin-1 expression in cardio- myocytes. APJ shRNA pGPU6/Neo-rat-399, PI3K inhibitor LY294002, Akt inhibitor 1701-1 blocked the up-regulation of APJ, PI3K phosphorylation, Akt phosphorylation, LC3-H/I and beclin-1 expression, respectively. Moreover, static pres- sure increased the diameter, volume, protein content of cells, and these could be reversed when the cells were treated with pGPU6/Neo-rat-399, LY294002, and autop- hagy inhibitor 3-methyladenine, respectively. These results suggested that static pressure up-regulates APJ expression to promote cardiomyocyte hypertrophy by a PI3K-autop- hagy pathway.     

PI3K/Akt信号通路的调控与肿瘤血管生成

肿瘤对人类的生存危害极大,恶性肿瘤的治疗一直是世界性的难题。肿瘤血管生成是肿瘤赖以生长、转移的基础,受多种因子的调节。目前发现有多条信号网络参与调控肿瘤血管生成,PI3K/Akt是其中比较重要的一条信号传导途径,该通路与肿瘤的发生发展密切相关。本文介绍了PI3K/Akt信号通路的结构组成与活性调控,并重点阐述PI3K/Akt信号途径与肿瘤血管生成的关系。     

Importance of PI3-kinase pathway in response/resistance to aromatase inhibitors

Endocrine therapy has been the most effective treatment modality for hormone receptor positive breast cancer. However, its efficacy has been limited by either de novo or acquired resistance. Recent data indicates that activation of the phosphatidylinositol 3-kinase (PI3K) signaling is associated with the poor outcome luminal B subtype of breast cancer and accompanied by the development of endocrine therapy resistance. Importantly, inhibition of PI3K pathway signaling in endocrine resistant breast cancer cell lines reduces cell survival and improves treatment response to endocrine agents. Interestingly, mutations in PIK3CA, the alpha catalytic subunit of the class IA PI3K, which renders cells dependent on PI3K pathway signaling, is the most common genetic abnormality identified in hormone receptor positive breast cancer. The synthetic lethality observed between estrogen deprivation and PI3K pathway inhibition in estrogen receptor positive (ER+) breast cancer cell lines provides further scientific rational to target both estrogen receptor and the PI3K pathway in order to improve the outcome of ER+ breast cancer.     

Recombinant tissue factor pathway inhibitor induces apoptosis in cultured rat mesangial cells via its Kunitz-3 domain and C-terminal through inhibiting PI3-kinase/Akt pathway

Tissue factor pathway inhibitor (TFPI) is an endogenous inhibitor of tissue factor (TF) induced coagulation. In addition to its anticoagulation activity, TFPI has other functions such as antiproliferation and inducing apoptosis. In the present study, we investigated whether or not TFPI induced apoptosis in cultured rat mesangial cells (MsCs) and the possible signal pathway that involved in the apoptotic process. We demonstrated that recombinant TFPI (rTFPI) induced apoptosis in cultured MsCs via its Kunitz-3 domain and C-terminal in a dose- and time-dependent manner by Hoechst 33258 assay, flow cytometry, nucleosomal laddering of DNA, caspase 3 assay. Because the serine/threonine protein kinase Akt has attracted attention as a mediator of survival (anti-apoptotic) signal in MsCs, we investigated the expression of phosphospecific-Akt and its downstream signal phospho-IκB-α and some other signal molecules like Fas and bcl-2. The results indicated that the process of apoptosis triggered by rTFPI is, at least in part, actively conducted by rat MsCs possibly through PI3-Kinase-Akt signal pathway not by binding to tissue factor. Our findings suggest that rTFPI has the potential usefulness in inducing apoptosis of MsCs under inflammatory conditions.     

Insulin utilizes the PI 3-kinase pathway to inhibit SP-A gene expression in lung epithelial cells

Background  

It has been proposed that high insulin levels may cause delayed lung development in the fetuses of diabetic mothers. A key event in lung development is the production of adequate amounts of pulmonary surfactant. Insulin inhibits the expression of surfactant protein A (SP-A), the major surfactant-associated protein, in lung epithelial cells. In the present study, we investigated the signal transduction pathways involved in insulin inhibition of SP-A gene expression.     

Ras regulates neuronal polarity via the PI3-kinase/Akt/GSK-3beta/CRMP-2 pathway

The establishment of a polarized morphology is an essential event in the differentiation of neurons into a single axon and dendrites. We previously showed that glycogen synthase kinase-3beta (GSK-3beta) is critical for specifying axon/dendrite fate by the regulation of the phosphorylation of collapsin response mediator protein-2 (CRMP-2). Here, we found that the overexpression of the small GTPase Ras induced the formation of multiple axons in cultured hippocampal neurons, whereas the ectopic expression of the dominant negative form of Ras inhibited the formation of axons. Inhibition of phosphatidylinositol-3-kinase (PI3-kinase) or extracellular signal-related kinase (ERK) kinase (MEK) suppressed the Ras-induced formation of multiple axons. The expression of the constitutively active form of PI3-kinase or Akt (also called protein kinase B) induced the formation of multiple axons. The overexpression of Ras prevented the phosphorylation of CRMP-2 by GSK-3beta. Taken together, these results suggest that Ras plays critical roles in establishing neuronal polarity upstream of the PI3-kinase/Akt/GSK-3beta/CRMP-2 pathway and mitogen-activated protein kinase cascade.     

Prolactin-stimulated activation of ERK1/2 mitogen-activated protein kinases is controlled by PI3-kinase/Rac/PAK signaling pathway in breast cancer cells

There is strong evidence that deregulation of prolactin (PRL) signaling contributes to pathogenesis and chemoresistance of breast cancer. Therefore, understanding cross-talk between distinct signal transduction pathways triggered by activation of the prolactin receptor (PRL-R), is essential for elucidating the pathogenesis of metastatic breast cancer.In this study, we applied a sequential inhibitory analysis of various signaling intermediates to examine the hierarchy of protein interactions within the PRL signaling network and to evaluate the relative contributions of multiple signaling branches downstream of PRL-R to the activation of the extracellular signal-regulated kinases ERK1 and ERK2 in T47D and MCF-7 human breast cancer cells.Quantitative measurements of the phosphorylation/activation patterns of proteins showed that PRL simultaneously activated Src family kinases (SFKs) and the JAK/STAT, phosphoinositide-3 (PI3)-kinase/Akt and MAPK signaling pathways. The specific blockade or siRNA-mediated suppression of SFK/FAK, JAK2/STAT5, PI3-kinase/PDK1/Akt, Rac/PAK or Ras regulatory circuits revealed that (1) the PI3-kinase/Akt pathway is required for activation of the MAPK/ERK signaling cascade upon PRL stimulation; (2) PI3-kinase-mediated activation of the c-Raf-MEK1/2-ERK1/2 cascade occurs independent of signaling dowstream of STATs, Akt and PKC, but requires JAK2, SFKs and FAK activities; (3) activated PRL-R mainly utilizes the PI3-kinase-dependent Rac/PAK pathway rather than the canonical Shc/Grb2/SOS/Ras route to initiate and sustain ERK1/2 signaling. By interconnecting diverse signaling pathways PLR may enhance proliferation, survival, migration and invasiveness of breast cancer cells.     

Prolactin induced expression of interleukin-1 alpha,tumor necrosis factor-alpha,and transforming growth factor-alpha in cultured astrocytes

Prolactin (PRL) is a potent mitogen in cultured astrocytes. Because one of the major effects of astrocyte proliferation is the expression of inflammatory cytokines, we examined the effect of PRL-induced mitogenesis on the expression of interleukin-1 (IL-1α), tumor necrosis factor-α (TNF-α), and transforming growth factor-α (TGF-α) in cultured astrocytes. Astrocytes were stimulated with PRL or growth hormone (GH), and the expression of cytokines was determined by immunohistochemistry and Western blot analysis. Following incubation of astrocytes with 1 nM PRL for 6 h, strong positive staining of IL-1α and TNF-α, but not TGF-α, was found. No detectable staining for the above cytokines was found in vehicle, or GH treated astrocytes. When astrocytes were incubated in the presence of 1 nM PRL for 18 h, strong positive staining for IL-1α and TGF-α was found. Immunocytochemical analysis of the expression of TNF-α and IL-1α in PRL stimulated astrocytes suggested that the expression of IL-1α preceded the expression of TNF-α. To confirm this observation, Western blot analyses were performed on extracts from astrocytes incubated with 1 nM PRL. In unstimulated astrocytes, IL-1α levels were not detectable. In astrocytes stimulated with 1 nM PRL, expression of IL-1α was clearly detected after 1 h of incubation, and IL-1α levels continued to increase during the course of the experiment (6 h). In contrast, in astrocytes stimulated with 1 nM PRL, an increase in the expression of TNF-α was first apparent after 2 h of incubation. TNF-α levels peaked 3 to 4 h after the addition of PRL, and returned to near control levels after 6 h. Finally, injection of PRL into a wound site in female rats increased the expression of glial fibrillary acid protein (GFAP), an astrocyte specific protein. These data suggest that PRL can stimulate astrogliosis at the wound site in vivo. These data clearly indicate that PRL can stimulate the expression of TNF-α and IL-1α in cultured astrocytes and suggest that PRL may play a role in the regulation of the neuroimmune response in vivo.     

Platelet-activating factor induces matrix metalloproteinase-9 expression through Ca(2+)- or PI3K-dependent signaling pathway in a human vascular endothelial cell line

Platelet-activating factor (PAF) augments angiogenesis by promoting the synthesis of a variety of angiogenic factors, via the nuclear factor (NF)-kappaB activation. Recently, we reported that PAF upregulates MMP-9 expression in a NF-kappaB-dependent manner. In this study, we investigated the signaling pathway involved in PAF-induced MMP-9 expression in ECV304 cells. Our current data indicate that the Ca(2+)- or phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathway is necessary for PAF-induced MMP-9 expression. Furthermore, PAF-induced NF-kappaB activation was blocked by selective inhibitors of Ca(2+), PI3K, or extracellular signal-regulated kinase (ERK). Our results suggest that PAF-induced MMP-9 expression, in a NF-kappaB-dependent manner, is regulated by Ca(2+), PI3K and ERK signaling pathways.