替米沙坦通过磷脂酰肌醇-3-激酶/丝苏氨酸蛋白激酶途径改善内皮祖细胞的功能活性

目的 研究替米沙坦对内皮祖细胞增殖、迁移、黏附等生物学活性的影响并探讨其可能机制.方法 利用密度梯度离心法分离、培养人外周血单个核细胞,经FITC-UEA-I和Dil-acLDL双染色鉴定为正在分化的内皮祖细胞.将分离、培养的内皮祖细胞分为对照组、替米沙坦组(0.1 μmol/L、1μmol/L、10μmol/L)、过氧化体增殖物激活型受体γ抑制剂(GW9662)干预组和磷脂酰肌醇-3-羟基激酶抑制剂(Ly294002)干预组.采用MTT比色法、Transwell小室、细胞计数法观察各组内皮祖细胞增殖、迁移、黏附能力的变化情况.同时采用免疫蛋白印迹法观察替米沙坦处理内皮祖细胞后丝苏氨酸蛋白激酶及磷酸化丝苏氨酸蛋白激酶的表达情况.结果 与对照组相比,替米沙坦组内皮祖细胞增殖、迁移、黏附能力显著提高,且在不同浓度组间呈剂量依赖性增强,而在过氧化体增殖物激活型受体γ抑制剂干预组和磷脂酰肌醇-3-羟基激酶抑制剂干预组,内皮祖细胞功能活性的改善受到明显的抑制.免疫蛋白印迹检测显示,相比于对照组,替米沙坦组磷酸化丝苏氨酸蛋白激酶的表达水平明显增高,而在过氧化体增殖物激活型受体γ抑制剂干预组磷酸化丝苏氨酸蛋白激酶的表达相比于对照组未见明显增高.结论 替米沙坦具有促进内皮祖细胞增殖、迁移、黏附等功能的作用,其主要机制可能与过氧化体增殖物激活型受体γ介导的磷脂酰肌醇-3-激酶/丝苏氨酸蛋白激酶信号通路激活有关.     

血小板活化与磷脂酰肌醇3激酶信号通路

<正> 血小板活化是复杂的过程。多种黏附蛋白和受体及血小板聚集激动剂参与其中,并在血小板活化、聚集反应扩大和血栓形成过程中起着重要作用。磷脂酰肌醇3激酶/蛋白激酶B(PI3K/Akt)信号通路是体内重要的细胞信号通路,在细胞的动员、迁移、分化和抗凋亡中具有重要的作用。近年的研究发现,PI3K/Akt信号通路与血小板活化     

PI3K-Akt/PKB信号通路与胰岛β细胞功能

磷脂酰肌醇3激酶-蛋白激酶B／Akt（P13K-AkL／PKB）介导β细胞的生存通路近来较受关注。P13K-Akt／PKB信号通路是细胞内重要的信号转导通路，与细胞生长、增殖、分化、凋亡等密切相关。P13K-Akt／PKB信号通路激活通过下游效应分子促进β细胞增殖、生长调节、增强β细胞抗凋亡功能，改善β细胞生存。调节该通路P13K、Akt／PKB及其上下游靶位点，可能为2型糖尿病的防治提供广阔前景。     

PI3K-Akt/PKB信号通路与胰岛β细胞功能

磷脂酰肌醇3激酶-蛋白激酶B/Akt(PI3K-Akt/PKB)介导β细胞的生存通路近来较受关注。PI3K-Akt/PKB信号通路是细胞内重要的信号转导通路,与细胞生长、增殖、分化、凋亡等密切相关。PI3K-Akt/PKB信号通路激活通过下游效应分子促进β细胞增殖、生长调节、增强β细胞抗凋亡功能,改善β细胞生存。调节该通路PI3K、Akt/PKB及其上下游靶位点,可能为2型糖尿病的防治提供广阔前景。     

胰岛素样生长因子-1的神经保护作用

胰岛素样生长因子-1(IGF-1)是一种多肽类神经营养因子。在生理条件下，IGF-1及其受体广泛分布于中枢神经系统；在病理条件下，IGF-1表达上调，并通过促分裂原活化蛋白激酶和磷脂酰肌醇3-激酶，丝氨酸一苏氨酸蛋白激酶等信号通路，抑制细胞凋亡、调节离子通道活性、抑制一氧化氮毒性等多种途径发挥神经保护作用。     

Visfatin inhibits pancreatic β-cell line MIN6 apoptosis via PI3K-Akt and MAPK-ERK1/2 signaling pathways

探讨内脂素对胰岛β细胞株MIN6细胞信号通路和棕榈酸诱导细胞凋亡的影响,并探讨其分子机制.人重组内脂素呈剂量和时间依赖性促进MIN6细胞细胞外信号调节激酶(ERK)1/2和蛋白激酶B(Akt)的磷酸化,抑制棕榈酸诱导的MIN6细胞凋亡(P<0.05或P<0.01).激活磷脂酰肌醇3激酶(PBK)-Akt和丝裂原活化蛋白激酶(MAPK)-ERK1/2信号通路是内脂素抑制MIN6细胞凋亡的分子机制之一.     

蛋白激酶在脊髓损伤中作用机制的研究进展

<正>脊髓损伤(SCI)分为原发性脊髓损伤和继发性脊髓损伤〔1〕。炎性因子、活性氧、兴奋性毒性和代谢异常是导致继发性损伤的主要原因。正常或病理条件下,磷酸酶和张力蛋白同源物(PTEN)/磷脂酰肌醇3激酶(PI3K)、丝裂原活化蛋白激酶(MAPK)信号通路在中枢神经系统(CNS)中扮演着不同的角色,两条通路的激活均能够诱导细胞结构和功能的改变。本文就PTEN/PI3K和MAPK信号通路在脊髓损伤中的作用及其分     

胰岛素样生长因子-1的神经保护作用

胰岛素样生长因子- 1(IGF- 1)是一种多肽类神经营养因子。在生理条件下,IGF- 1及其受体广泛分布于中枢神经系统;在病理条件下,IGF -1表达上调,并通过促分裂原活化蛋白激酶和磷脂酰肌醇3 激酶/丝氨酸-苏氨酸蛋白激酶等信号通路,抑制细胞凋亡、调节离子通道活性、抑制一氧化氮毒性等多种途径发挥神经保护作用。     

内脂素激活PI3K-Akt和MAPK-ERK1/2信号通路抑制MIN6细胞凋亡

探讨内脂素对胰岛β细胞株MIN6细胞信号通路和棕榈酸诱导细胞凋亡的影响,并探讨其分子机制.人重组内脂素呈剂量和时间依赖性促进MIN6细胞细胞外信号调节激酶(ERK)1/2和蛋白激酶B(Akt)的磷酸化,抑制棕榈酸诱导的MIN6细胞凋亡(P<0.05或P<0.01).激活磷脂酰肌醇3激酶(PBK)-Akt和丝裂原活化蛋白激酶(MAPK)-ERK1/2信号通路是内脂素抑制MIN6细胞凋亡的分子机制之一.     

PI-3 K/Akt信号转导通路在神经系统疾病中的研究进展

磷脂酰肌醇-3-激酶/蛋白激酶B (PI-3K/Akt)信号转导通路是细胞内重要的信号转导通路,在细胞的凋亡、存活、增殖以及细胞骨架的变化等活动中发挥重要的生物学功能,其中尤为重要的是它对细胞凋亡、存活的调节作用。细胞凋亡参与许多神经系统疾病的发生与发展过程,近年来的研究发现该通路的激活具有一定的神经保护作用,因此针对PI-3K/Akt/GSK3β信号通路内源性神经保护机制的研究,有望为神经系统疾病的治疗提供新的理论依据。     

磷脂酰乙醇胺N-甲基转移酶2过表达抑制磷脂酶Cγ1磷酸化及转位

目的探讨转染磷脂酰乙醇胺N-甲基转移酶2(PEMT2)基因抑制大鼠肝癌CBRH-7919细胞增殖的机制。方法采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和Western blot方法,观察转染PEMT2基因对大鼠肝癌CBRH 7919细胞磷脂酶C γ 1(PLC γ 1)磷酸化及在细胞内转位的影响;同时观察转染PEMT2基因对肝细胞生长因子受体(c- Met)自身磷酸化活化的影响。结果转染PEMT2后,质膜结合的PLC γ下降,为对照组的45％。膜结合的磷酸化PLC γ 1约为对照组细胞的27％,同时c-Met磷酸化程度显著下降,约为对照组细胞的32％。结论转染PEMT2基因可抑制细胞PLC γ 1磷酸化及由胞浆向质膜转位,抑制c-Met自身磷酸化活化,从而下调CBRH-7919细胞c-Met／PLC γ 1信号转导途经。     

Mechanisms of mitogenic and anti-apoptotic signaling by glucose-dependent insulinotropic polypeptide in beta(INS-1)-cells

Glucose-dependent insulinotropic polypeptide (GIP) acts as a glucose-dependent growth factor for beta-cells. Here we show that GIP and glucose also act synergistically as anti-apoptotic factors for beta-cells, using the well-differentiated beta-cell line, INS-1. Mitogenic and anti-apoptotic signaling of GIP were dependent upon pleiotropic activation of protein kinase A (PKA)/cAMP regulatory element binder (CREB), mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3-kinase)/PKB signaling modules. The signaling modules activated by GIP were dependent on glucose metabolism and calcium influx and were tightly linked by multiple activating and inhibiting cross-talk. These interactions included: (i) a central role of tyrosine phosphorylation for stimulation of PKA/CREB, MAPK and PI3-kinase/PKB, (ii) inhibition of PKA/CREB by the MAPK pathway at the level of MAPK kinase-1 or downstream, (iii) activation of MAPK signaling by PI3-kinase and PKA at the level of extracellular-signal regulated kinase 1/2 or upstream, and (iv) activation of PKB by MAPK and PKA signaling at the level of PKB or upstream. Furthermore, we demonstrated inhibition of CREB signaling by Ca(2+)/calmodulin kinase I/IV. These results indicated that GIP acts as a mitogenic and anti-apoptotic factor for beta-cells by pleiotropic activation of tightly linked signaling pathways in beta-cells.     

脂筏介导的内源性大麻素对HepG2细胞的作用及其机制

目的 研究内源性大麻素(AEA)以脂质为基础的信号途径对肝癌细胞株HepG2的作用机制,探讨AEA在肝癌发生和发展中的作用.方法 免疫荧光检测脂肪酸水解酶、大麻素受体(CB)1和CB2在胎肝细胞株L02和肝癌细胞株HepG2中的定位.以不同浓度的AEA及膜胆固醇耗竭剂甲基-β-环糊精(MCD)处理,分为AEA 10 μmol/L组、AEA 20 μmol/L组、AEA40 μmol/L组,MCD 10 mmol/L+AEA 10 μmol/L组、MCD 10 mmol/L+AEA 20 μmol/L组和MCD 10 mmol/L+AEA 40 μmol/L组,分别孵育L02细胞和HepG2细胞,流式细胞术碘化丙啶单染法检测细胞的坏死率.Western Blot检测L02和HepG2细胞中脂肪酸水解酶、CB1和CB2的蛋白表达及其下游信号通路磷酸化P38促分裂原活化蛋白激酶(p-P38MAPK)和磷酸化c-Jun氨基端激酶(P-JNK)的表达变化.组间均数的比较采用独立样本t检验或单因素方差分析.结果 AEA可有效地导致肝癌细胞坏死,以浓度为AEA 40 μmol/L组达到最大效应,F=108.594,P<0.05,差异有统计学意义.MCD 10mmol/L预孵育后的HepG2细胞坏死率在AEA 10 μmol/L组、AEA 20 μmol/L组和AEA 40 μmol/L组分别为7.83%±2.13%,16.30%±0.94%,43.09%±5.10%,MCD处理前AEA 10 μmol/L组、AEA 20 μmol/L组、AEA 40 μmol/L组分别为13.64%±1.69%、20.28%±0.91%,52.71%±4.29%,处理前后比较,t值分别为3.702,5.274和3.503,P值均<0.05,差异均有统计学意义.同时,AEA能激活HepG2细胞中P38 MAPK和JNK,以AEA 40 μmol/L组作用明显,F值分别为11.908和26.054,P值均<0.05,差异均有统计学意义,MCD作用前p-P38 MAPK和p-JNK/β-肌动蛋白灰度值分别为1.63±0.06,1.60±0.31,MCD作用后p-P38 MAPK/β-肌动蛋白、p-JNK灰度值分别为1.14±0.01、1.17±0.29,作用前后相比,t值分别为2.801和12.829,P值均<0.05,差异均有统计学意义.结论 AEA可以有效地导致HepG2细胞坏死而对L02细胞无影响,AEA激活了HepG2细胞p-P38 MAPK和P-JNK相关信号传导途径,且此过程与脂筏有关.     

Wnt/β-catenin signaling regulates MAPK and Akt1 expression and growth of hepatocellular carcinoma cells

In hepatocellular carcinoma (HCC), Wnt/β-catenin, Ras/MAPK and PI3K/AKT signaling pathways form a complex network and play important roles during HCC genesis and development. To study their relationship and the influence on cell growth, the siRNA directed against β-catenin was transfected into HCC HepG2 cells. β-catenin mRNA and protein levels were measured respectively at various times by RT-PCR and Western blot. Furthermore, HCC cell growth was measured by MTT assay. Finally, MAPK family and Akt1 protein levels were also measured by Western blot. After the transfection, β-catenin mRNA levels were markedly inhibited at 24 h and increased gradually at 48, 72 and 96 h; β-catenin protein levels decreased gradually at 24, 48 and 72 h and slightly increased at 96 h. HCC cell growth was inhibited from 24-72 h, but this inhibition decreased at 96 h. ERK1/2 (p42/p44 MAPK), JNK/SAPK, p38 MAPK, and Akt1 protein levels showed no change following transfection, while their phosphorylated protein levels showed changes. Thus, siRNA directed against β-catenin markedly decreased β-catenin gene expression and inhibited cell growth. Wnt/β-catenin signaling pathway might regulate Ras/MAPK and PI3K/Akt signaling pathways through regulation of the phosphorylation state of ERK1/2, JNK/SAPK and Akt1 protein in HCC HepG2 cells. These pathways might compensate for the inhibitory effect of β-catenin, thereby affecting tumor cell growth and others downstream factors.     

Intracellular signaling pathways involved in cell growth inhibition of human umbilical vein endothelial cells by melatonin

Melatonin, an indolamine mainly produced in the pineal gland, has received a great deal of attention in the last decade because of its oncostatic effects, which are due to its immunomodulatory, antiproliferative, antioxidant and its possible antiangiogenesis properties. Herein, we document its antiproliferative action on human umbilical vein endothelial cells (HUVECs). Moreover, the possible cell signaling pathways when melatonin inhibited HUVEC proliferation were explored in this study. Primary HUVECs were isolated, cultured, purified and identified before the studies were performed. HUVECs were found to possess G-protein-coupled membrane receptors for melatonin (MT1 and MT2) and also nuclear melatonin receptors (RORalpha and RORbeta, especially RORbeta). No obvious expression of RORgamma was found. We investigated the membrane receptors and several intracellular signaling pathways including mitogen-activated protein kinases (MAPK)/extracellular signal-related kinases (ERK), phosphoinositol-3-kinase (PI3K)/Akt and protein kinases C (PKC) involved in antiproliferative action of melatonin on HUVECs. The blockade of these pathways using special inhibitors decreased cell growth. Furthermore, the constitutive activation of nuclear factor kappa B (NF-kappaB) contributed to the proliferation of HUVECs. High concentrations of melatonin inhibited both NF-kappaB expression and its binding ability to DNA, possibly through inactivation of ERK/Akt /PKC pathways. Taken together, high concentrations of melatonin markedly reduced HUVEC proliferation; the antiproliferative action of melatonin was closely correlated with following pathway: melatonin receptors/ERK/PI3K/Akt/PKC/ NF-kappaB.     

Effect of cholesterol depletion on mitogenesis and survival: the role of caveolar and noncaveolar domains in insulin-like growth factor-mediated cellular function

The type 1 IGF receptor (IGF-IR) is thought to localize to a subset of lipid rafts, known as caveolae, but the impact on IGF signaling remains controversial. We investigated this potential regulatory mechanism by assessing IGF function in caveolae-positive (3T3L1 and NWTb3) and -negative (HepG2) cells. Coimmunoprecipitation studies demonstrated that IGF-IR and insulin receptor substrate 1 associated with caveolin, a caveolar marker, in 3T3L1 and NWTb3 cells. Subcellular fractionation showed that methyl-cyclodextrin, which disrupts lipid rafts by sequestration of cholesterol, disrupted the colocalization of caveolin and the IGF-IR at the plasma membrane. Methyl-cyclodextrin did not alter IGF-I-induced 3T3L1 or NWTb3 proliferation but significantly impaired the ability of IGF-I to protect these cells from apoptosis. Immunoblotting revealed that methyl-cyclodextrin had no effect on IGF-I-induced activation of the IGF-IR or insulin receptor substrate 1 but increased and decreased the phosphorylation of MAPK and protein kinase B, respectively. In caveolae-negative HepG2 cells, the effect of methyl-cyclodextrin on IGF signaling and cellular function was similar to that observed in caveolae-positive 3T3L1 and NWTb3 cells. Furthermore, transfecting caveolin into HepG2 cells to give morphologically identifiable caveolae made no difference to IGF action, despite a demonstrable interaction between caveolin and the IGF-IR. This suggests that although IGF-IR localizes to caveolin-rich subcellular fractions and coimmunoprecipitates with caveolin, caveolae may not be obligatory for IGF signaling.     

软脂酸诱导HepG2细胞胰岛素抵抗及花生四烯酸防治作用的机制研究

目的 探讨高浓度软脂酸(PA)诱导HepG2细胞胰岛素抵抗(IR)的机制及花生四烯酸(AA)对IR的防治作用。方法 (1)用高浓度软脂酸(PA)或10^-7mol／L高胰岛素(HI)培养HepG2细胞建立具有IR的细胞模型，测定培养液中葡萄糖含量及细胞内糖原含量作为鉴定指标；(2)用Western blot检测胞内糖原合酶(GS)和蛋白激酶B(PKB)蛋白水平；(3)用磷脂酰肌醇3激酶(P13K)抑制剂Wortmannin(WT)探讨其对胰岛素信号通路的影响；(4)观察AA是否对PA引起的IR有防治作用。结果 (1)0．20mmol／L PA或川培养HepG2细胞36h后，培养液中葡萄糖含量极显著增高，细胞内糖原含量极显著减少；(2)高浓度PA使磷酸化的PKB(P-Ser473)蛋白水平显著减少，磷酸化的糖原合酶(P-Ser641 GS)蛋白水平极显著增加；(3)WT使对照组GS活性及胞内糖原含量极显著减少，HI组和PA组胞内糖原含量均无统计学差异，但各实验组PKB活性都极显著减少；(4)PA AA组培养液中葡萄糖含量显著低于PA组，GS和PKB活性及胞内糖原含量显著增加。结论 高浓度PA或HI培养HepG2细胞能够诱导IR，其机制可能是其引起胰岛素信号传递途径中自PKB下游到GS之间的信号通路受阻所致。AA能改善PA引起的IR。     

Assessment of the roles of mitogen-activated protein kinase and phosphatidyl inositol 3-kinase/protein kinase B pathways in the basic fibroblast growth factor regulation of Sertoli cell function

Basic fibroblast growth factor (bFGF) belongs to the large set of intratesticular regulators that provide the fine tuning of cellular processes implicated in the maintenance of spermatogenesis. The aim of the present study was to determine the participation of mitogen-activated protein kinase (MAPK) and phosphatidyl inositol 3-kinase/protein kinase B (PI3K/PKB) pathways in bFGF regulation of Sertoli cell function. Twenty-day-old rat Sertoli cell cultures were used. Stimulation of the cultures with bFGF showed a time-dependent increment in phosphorylated MAPK and PKB levels that reached maximal values in 5-min incubations. MAPK kinase inhibitors U0126 (U) and PD98059 (PD) and a PI3K inhibitor wortmannin (W) were able to block the stimulatory effects of bFGF on phosphorylated MAPK and PKB levels respectively. The participation of MAPK- and PI3K/PKB-signaling pathways in the regulation by bFGF of two well-known Sertoli cell-differentiated functions, lactate and transferrin production, was next explored. As for lactate production, PD and W did not modify the ability of bFGF to stimulate lactate production. However, a combination of PD and W partially impaired the increase in lactate production elicited by bFGF. The participation of MAPK- and PI3K/PKB-signaling pathways in the regulation by bFGF of glucose uptake and lactate dehydrogenase (LDH) activity was also analysed. In this respect, it was observed that W markedly decreased basal and bFGF-stimulated glucose uptake and that U and PD did not modify it. On the other hand, U and PD decreased the stimulation of LDH activity by bFGF whereas W did not modify it. As for transferrin production, while both MAPK kinase inhibitors partially decreased the ability of bFGF to stimulate transferrin secretion, the PI3K inhibitor did not modify it. In summary, the results demonstrated that bFGF stimulates MAPK- and PI3K/PKB-dependent pathways in rat Sertoli cells. Moreover, these results showed that while bFGF utilizes the MAPK pathway to regulate transferrin production and LDH activity, it uses the PI3K/PKB pathway to regulate glucose transport into the cell.     

Modification of PI3K- and MAPK-dependent chemotaxis in aortic vascular smooth muscle cells by protein kinase CbetaII

Hyperglycemia increases expression of platelet-derived growth factor (PDGF)-beta receptor and potentiates chemotaxis to PDGF-BB in human aortic vascular smooth muscle cells (VSMCs) via PI3K and ERK/MAPK signaling pathways. The purpose of this study was to determine whether increased activation of protein kinase C (PKC) isoforms had a modulatory effect on the PI3K and ERK/MAPK pathways, control of cell adhesiveness, and movement. All known PKC isoforms were assessed but only PKCalpha and PKCbetaII levels were increased in 25 mmol/L glucose. However, only PKCbetaII inhibition affected (decreased) PI3K pathway and MAPK pathway activities and inhibited PDGF-beta receptor upregulation in raised glucose, and specific MAPK inhibition was required to completely block the effect of glucose. In raised glucose conditions, activity of the ERK/MAPK pathway, PI3K pathway, and PKCbetaII were all sensitive to aldose reductase inhibition. Chemotaxis to PDGF-BB (360 pmol/L), absent in 5 mmol/L glucose, was present in raised glucose and could be blocked by PKCbetaII inhibition. Formation of lamellipodia was dependent on PI3K activation and filopodia on MAPK activation; both lamellipodia and filopodia were eliminated when PKCbetaII was inhibited. FAK phosphorylation and cell adhesion were reduced by PI3K inhibition, and although MAPK inhibition prevented chemotaxis, it did not affect FAK phosphorylation or cell adhesiveness. In conclusion, chemotaxis to PDGF-BB in 25 mmol/L glucose is PKCbetaII-dependent and requires activation of both the PI3K and MAPK pathways. Changes in cell adhesion and migration speed are mediated mainly through the PI3K pathway.     

Cell signalling of the GLP-1 action in rat liver

GLP-1, incretin with insulin-independent antidiabetic properties, is insulinomimetic upon glucose metabolism in extrapancreatic tissues, acting through specific receptors not associated to adenylate cyclase activation. We investigated the role of enzymes mediating insulin actions, in the GLP-1-induced glycogen synthase a activation in rat hepatocytes. GLP-1, like insulin, activates PI3K/PKB, p70s6k, p44 and p42 MAP-kinase. Wortmannin (PI3K/PKB inhibitor) blocked the stimulatory action of insulin on glycogen synthase a and reduced that of GLP-1; rapamycin (p70s6k inhibitor) was ineffective and PD98059 (MEK/MAPK inhibitor) decreased only the insulin effect; okadaic acid (PP-2A inhibitor) was ineffective, while TNFalpha (PP-1 inhibitor) blocked the action of insulin and reduced that of GLP-1; H-7 or Ro 31-8220 (PKC inhibitors) decreased the GLP-1 effect, while only H-7 reduced that of insulin. The activation of PI3K/PKB, PKC and PP-1, but not PP-2A, seems to mediate the GLP-1 stimulatory action on glycogen synthase a in rat hepatocytes, while MAPKs and p70s6k could participate in other GLP-1 effects.