神经胶质瘤U251细胞氧化损伤中自噬和凋亡过程的时间顺序

目的：探讨过氧化氢（H2O2）诱导神经胶质瘤U251细胞损伤中自噬和凋亡发生的时间顺序。方法：实验分为4组：正常对照组、1mmol／L H2O2作用（6h、12h、24h）组。应用MTF法检测H202对神经胶质瘤U251细胞生存率的影响;MDC染色检测自噬空泡的变化;流式细胞仪检测细胞凋亡率变化。Western blot检测Beclin1和胞浆cyt c蛋白的表达。结果：与对照组相比,1mmol／L H2O2作用下,U251细胞存活率明显降低,并呈时间依赖性。与对照组相比,1mmol／L H2O2作用后,6h时U251细胞自噬空泡明显增加,自噬相关蛋白Beclin1表达明显增加,12h、24h细胞自噬水平逐渐增强;而6h时未见细胞凋亡率明显变化及cyt c由线粒体向胞浆的释放,12h、24h时细胞凋亡率明显增加,胞浆中cyt c蛋白表达明显增强（P〈0．05）。结论：氧化损伤能够诱导神经胶质瘤U251细胞发生自噬和凋亡,并且自噬发生于凋亡之前。     

过表达TNFAIP1促进替莫唑胺对人脑胶质瘤细胞U251迁移和侵袭的抑制作用

为了深入研究人脑胶质瘤治疗时耐药的发生机制,并寻求潜在的治疗手段,以人脑胶质瘤细胞U251为研究对象,研究肿瘤坏死因子α诱导蛋白1(TNFAIP1)对其迁移和侵袭的影响。半定量PCR和蛋白质免疫印迹(Western blot)试验发现,替莫唑胺(TMZ)会上调U251细胞内TNFAIP1的表达。在U251细胞中过表达TNFAIP1后,发现上调TNFAIP1的表达能促进TMZ对U251细胞迁移及侵袭的抑制作用,并且这一作用是通过抑制上皮-间充质转化(EMT)信号通路来实现的。这一发现有助于为人脑胶质瘤的临床治疗提供新的理论依据,为其治疗方法提供新的策略。     

MKL1靶向CAAP1促进胃癌细胞的自噬并抑制凋亡

[目的]探讨MKL1和CAAP1对胃癌细胞凋亡的影响及其分子机制。[方法]蛋白质印迹和实时荧光定量PCR检测MKL1、CAAP1过表达效果;蛋白质印迹、流式细胞术、自噬检测试剂盒检测细胞的自噬和凋亡情况;荧光素酶报告基因活性测定、染色质免疫共沉淀验证MKL1和CAAP1基因启动子的结合。[结果]在MGC80-3细胞中过量表达MKL1后,凋亡抑制蛋白CAAP1的mRNA和蛋白水平与对照组相比均上调(P 0. 05),自噬标记基因LC3BII表达升高(P 0. 05),促凋亡蛋白Caspase3表达降低(P 0. 05)。敲降MKL1,Caspase3蛋白表达升高(P 0. 05)。敲降CAAP1,Caspase3蛋白表达升高(P 0. 05)。过表达CAAP1拮抗敲降MKL1,LC3BII蛋白表达下降,Caspase3蛋白表达升高(P 0. 05)。荧光素酶活性分析以及染色质免疫共沉淀分析结果表明MKL1促进CAAP1基因的转录活性。[结论]MKL1可通过上调CAAP1的表达进而促进胃癌细胞的自噬并抑制细胞凋亡。     

乳酸脱氢酶A通过AMPK信号通路抑制人脑胶质瘤细胞线粒体自噬

该研究旨在探讨乳酸脱氢酶A(lactate dehydrogenase A,LDHA)对人脑胶质瘤细胞线粒体自噬的影响。用质粒sh-EGFP或sh-LDHA转染人脑胶质瘤细胞株U87MG,qRT-PCR和Western blot检测干扰效率,荧光染色技术检测线粒体ROS水平及线粒体膜电位,Western blot检测线粒体自噬相关蛋白及AMPK信号通路相关蛋白表达。结果表明,与sh-EGFP组相比较,sh-LDHA组人脑胶质瘤细胞U87MG中LDHA的mRNA及蛋白质水平均显著降低,线粒体ROS的产生增加,线粒体膜电位明显降低,线粒体自噬相关蛋白PINK1、Parkin及BNIP3、BNIP3L的表达增高,AMPK的磷酸化水平明显升高,而mTOR的磷酸化水平降低。研究结果表明,LDHA能够通过抑制AMPK信号通路,降低线粒体ROS水平,提高线粒体膜电位,抑制线粒体自噬。     

沉默ABCE1对神经胶质瘤细胞U251增殖、迁移和凋亡的影响

ABCE1是ATP结合盒蛋白亚家族成员之一,在病毒感染,细胞增殖,抗凋亡,翻译起始和核糖体生物发生等过程中有重要的作用。为了探讨ABCE1对神经胶质瘤细胞U251增殖、迁移和凋亡的作用,本研究通过实时荧光定量PCR和免疫印迹实验检测ABCE1在神经胶质瘤细胞和正常胶质细胞中的mRNA和蛋白质表达水平,结果发现ABCE1在神经胶质瘤细胞U251中的表达高于在正常胶质细胞中的表达。利用siRNA靶向沉默ABCE1后,神经胶质瘤细胞U251中ABCE1 mRNA和蛋白的表达水平均显著减少,细胞的凋亡率显著提高,细胞增殖和迁移明显受到抑制,而且细胞对化疗药物替莫唑胺的敏感性增强。此外,沉默ABCE1后,Bcl-2的mRNA和蛋白质表达水平显著下调,而Bax的mRNA和蛋白质表达水平显著上调。以上研究结果表明,ABCE1与神经胶质瘤细胞的增殖和迁移密切相关,通过siRNA靶向沉默ABCE1基因可显著降低U251细胞的增殖和迁移能力。     

CRBGP通过抑制FAK-AKT通路和白介素-6的分泌抑制胶质瘤U251细胞的活性

目的 电压门控钠通道(voltage-gated sodium channels,VGSCs)表达于胶质瘤U251细胞,并影响U251细胞的增殖、侵袭和凋亡.富含半胱氨酸的颊腺蛋白(cysteine-rich buccal gland protein,CRBGP)是一种从日本七鳃鳗颊腺中分离出来的VGSCs阻断剂.本文...     

沉默ABCE1对神经胶质瘤细胞U251增殖、迁移和凋亡的影响北大核心CSCD

三磷酸腺苷结合盒蛋白E1(ABCE1)是ATP结合盒蛋白亚家族成员之一,在病毒感染、细胞增殖、抗凋亡、翻译起始和核糖体生物发生等过程中发挥重要作用。为了探讨ABCE1对神经胶质瘤细胞U251增殖、迁移和凋亡的作用,本研究通过实时荧光定量PCR和免疫印迹实验,检测ABCE1在神经胶质瘤细胞和正常胶质细胞中的mRNA和蛋白质表达水平。结果显示,ABCE1在神经胶质瘤细胞U251中的表达高于在正常胶质细胞中的表达。利用siRNA靶向沉默ABCE1后,在神经胶质瘤细胞U251中,ABCE1 mRNA和蛋白质的表达水平均显著减少,细胞的凋亡率显著提高,细胞增殖和迁移明显受到抑制,而且细胞对化疗药物替莫唑胺的敏感性增强。此外,沉默ABCE1后使Bcl-2的mRNA和蛋白质表达水平显著下调,而Bax的mRNA和蛋白质表达水平显著上调。以上结果表明,ABCE1与神经胶质瘤细胞的增殖和迁移密切相关,通过siRNA靶向沉默ABCE1基因,可显著降低U251细胞的增殖和迁移能力。     

紫草素对人脑胶质瘤U251 细胞增殖和凋亡的影响

目的:观察紫草素对体外培养的人脑胶质瘤U251细胞的增殖和凋亡的影响。方法:应用MTT法和Annexin V-FITC/PI双染流式细胞术分别检测2.5、5、10μM/L的紫草素对U251细胞的体外抑杀作用以及凋亡诱导作用,进一步应用Western blot方法检测紫草素对凋亡相关蛋白Bcl-2及Bax表达水平的影响。结果:紫草素对人U251胶质瘤细胞具有明显的增殖抑制作用,且呈一定的剂量依赖性和时间依赖性。紫草素可明显上调U251细胞Bax的表达,下调Bcl-2的表达,与对照组相比存在显著性差异(P0.05)。结论:紫草素对人胶质瘤U251细胞具有明显的抑制增殖和促进凋亡作用。     

人乳腺MCF10A细胞系K~+通道的表达和特性及其与增殖的关系

近年来发现,K+通道与乳腺癌细胞的增殖和转化密切相关,但机制尚不清楚。本研究室前期报道了K+通道阻断剂4-氨基吡啶(4-aminopyridine,4-AP)能够抑制人乳腺上皮细胞的增殖,本文则进一步检测几种电压门控K+通道(voltage-gatedK+channel,Kv)在人乳腺上皮细胞系MCF10A中的表达,运用全细胞膜片钳技术,初步研究了该细胞K+通道的特性,观察K+通道阻断剂对细胞增殖以及信号通路蛋白活性的影响。结果显示,MCF10A细胞均有Kv1.1、Kv1.2、Kv1.3和Kv1.5基因mRNA的表达,其中Kv1.5表达量明显高于乳腺癌细胞MCF7。全细胞膜片钳钳制细胞于-60mV,给予持续时间800ms、范围从-60mV到+60mV的去极化刺激电压,步幅为10mV,然后给予持续150ms的-60mV的刺激,刺激频率为1Hz,可记录到一种跨膜电流,该电流具有电压依赖、外向整流的特性,并且能被Kv通道阻断剂4-AP阻断,证实该细胞膜存在Kv通道。此外,4-AP阻断K+通道10min后,与增殖相关的有丝分裂原活化蛋白激酶(mitogen-activated protein kinases,MAPK)信号通路ERK1/2蛋白活性增强而p38蛋白活性减弱;5mmol/L4-AP处理细胞48h后,MCF10A的生长抑制率为25.29%。以上结果提示,在人乳腺上皮细胞系MCF10A细胞膜上存在不同亚型的Kv通道,该通道可被4-AP阻断,并且4-AP能够抑制MCF10A细胞的增殖,其机制可能与细胞增殖信号通路不同成员的活性调节有关。     

抑制Beclin1促进H2O2诱导的神经胶质瘤U251细胞凋亡

氧化应激能够引起细胞自噬和凋亡同时发生,但其中细胞自噬的作用仍不十分明确,研究表明Beclin 1作为调节前自噬体形成的关键基因,参与了胶质瘤氧化应激的损伤过程.为了探讨自噬在H2O2引起的神经胶质瘤U251细胞损伤中的作用,本文应用真核细胞转染技术将Psilencer3.1-siRNA-Beclin 1重组质粒转入人...     

Involvement of Kv1.5 Protein in Oxidative Vascular Endothelial Cell Injury

Endothelial injury related to oxidative stress is a key event in cardiovascular diseases, such as hypertension and atherosclerosis. The activation of the redox-sensitive Kv1.5 potassium channel mediates mitochondrial reactive oxygen species (ROS)-induced apoptosis in vascular smooth muscle cells and some cancer cells. Kv1.5 channel is therefore taken as a new potential therapeutic target for pulmonary hypertension and cancers. Although Kv1.5 is abundantly expressed in vascular endothelium, there is little knowledge of its role in endothelial injury related to oxidative stress. We found that DPO-1, a specific inhibitor of Kv1.5, attenuated H₂O₂-evoked endothelial cell apoptosis in an in vivo rat carotid arterial model. In human umbilical vein endothelial cells (HUVECs) and human pulmonary arterial endothelial cells (HPAECs), angiotensin II and oxLDL time- or concentration-dependently enhanced Kv1.5 protein expression in parallel with the production of intracellular ROS and endothelial cell injury. Moreover, siRNA-mediated knockdown of Kv1.5 attenuated, whereas adenovirus-mediated Kv1.5 cDNA overexpression enhanced oxLDL–induced cellular damage, NADPH oxidase and mitochondria-derived ROS production and restored the decrease in protein expression of mitochondria uncoupling protein 2 (UCP2). Collectively, these data suggest that Kv1.5 may play an important role in oxidative vascular endothelial injury.     

Reduced expression of proteolipid protein 2 increases ER stress-induced apoptosis and autophagy in glioblastoma

Proteolipid protein 2 (PLP2) is an integral ion channel membrane protein of the endoplasmic reticulum. The protein has been shown to be highly expressed in many cancer types, but its importance in glioma progression is poorly understood. Using publicly available datasets (Rembrandt, TCGA and CGGA), we found that the expression of PLP2 was significantly higher in high-grade gliomas than in low-grade gliomas. We confirmed these results at the protein level through IHC staining of high-grade (n = 56) and low-grade glioma biopsies (n = 16). Kaplan-Meier analysis demonstrated that increased PLP2 expression was associated with poorer patient survival. In functional experiments, siRNA and shRNA PLP2 knockdown induced ER stress and increased apoptosis and autophagy in U87 and U251 glioma cell lines. Inhibition of autophagy with chloroquine augmented apoptotic cell death in U87- and U251-siPLP2 cells. Finally, intracranial xenografts derived from U87- and U251-shPLP2 cells revealed that loss of PLP2 reduced glioma growth in vivo. Our results therefore indicate that increased PLP2 expression promotes GBM growth and that PLP2 represents a potential future therapeutic target.     

RLIP76 Depletion Enhances Autophagic Flux in U251 Cells

Our previous study showed that RalA-binding protein 1 (RLIP76) is overexpressed in gliomas and is associated with higher tumour grade and decreased patient survival. Furthermore, RLIP76 downregulation increases chemosensitivity of glioma cells to temozolomide by inducing apoptosis. However, other mechanisms underlying RLIP76-associated chemoresistance are unknown. In this study, we investigated the effect of RLIP76 depletion on autophagy. RLIP76 was knocked down in U251 glioma cells using shRNA and autophagy-related proteins, and PI3K/Akt signalling components were evaluated. RLIP76 depletion significantly increased cell autophagy as demonstrated by a significant increase in LC3 II, autophagy protein 5 (ATG-5), and Beclin1, and a decrease in p62 expression levels. Furthermore, RLIP76 knockdown increased autophagic flux in U251 cells as autolysosome numbers increased relative to autophagosome numbers. Autophagy induced by RLIP76 knockdown resulted in increased apoptosis that was independent of temozolomide treatment. Moreover, RLIP76 knockdown decreased PI3K and Akt activation. RLIP76 depletion also resulted in decreased levels of the anti-apoptotic protein Bcl2. LY294002, a PI3K/Akt pathway inhibitor, led to increased autophagy and apoptosis in U251 RLIP76-depleted cells. Therefore, RLIP76 knockdown increased autophagic flux and apoptosis in U251 glioma cells, possibly through inhibition of the PI3K/Akt pathway. Thus, this study provides a novel mechanism for the role of RLIP76 in glioma pathogenesis and chemoresistance.     

Suppression of Autophagy Enhanced Growth Inhibition and Apoptosis of Interferon-β in Human Glioma Cells

Interferon-beta (IFN-β) is a cytokine with anti-viral, anti-proliferative, and immunomodulatory effects. In this study, we investigated the effects of IFN-β on the induction of autophagy and the relationships among autophagy, growth inhibition, and apoptosis induced by IFN-β in human glioma cells. We found that IFN-β induced autophagosome formation and conversion of microtubule associated protein 1 light chain 3 (LC3) protein, whereas it inhibited cell growth through caspase-dependent cell apoptosis. The Akt/mTOR signaling pathway was involved in autophagy induced by IFN-β. A dose- and time-dependent increase of p-ERK 1/2 expression was also observed in human glioma cells treated with IFN-β. Autophagy induced by IFN-β was suppressed when p-ERK1/2 was impaired by treatment with U0126. We also demonstrated that suppression of autophagy significantly enhanced growth inhibition and cell apoptosis induced by IFN-β, whereas inhibition of caspase-dependent cell apoptosis impaired autophagy induced by IFN-β. Collectively, these findings indicated that autophagy induced by IFN-β was associated with the Akt/mTOR and ERK 1/2 signaling pathways, and inhibition of autophagy could enhance the growth inhibitory effects of IFN-β and increase apoptosis in human glioma cells. Together, these findings support the possibility that autophagy inhibitors may improve IFN-β therapy for gliomas.     

Inhibition of CLIC4 enhances autophagy and triggers mitochondrial and ER stress-induced apoptosis in human glioma U251 cells under starvation

CLIC4/mtCLIC, a chloride intracellular channel protein, localizes to mitochondria, endoplasmic reticulum (ER), nucleus and cytoplasm, and participates in the apoptotic response to stress. Apoptosis and autophagy, the main types of the programmed cell death, seem interconnected under certain stress conditions. However, the role of CLIC4 in autophagy regulation has yet to be determined. In this study, we demonstrate upregulation and nuclear translocation of the CLIC4 protein following starvation in U251 cells. CLIC4 siRNA transfection enhanced autophagy with increased LC3-II protein and puncta accumulation in U251 cells under starvation conditions. In that condition, the interaction of the 14-3-3 epsilon isoform with CLIC4 was abolished and resulted in Beclin 1 overactivation, which further activated autophagy. Moreover, inhibiting the expression of CLIC4 triggered both mitochondrial apoptosis involved in Bax/Bcl-2 and cytochrome c release under starvation and endoplasmic reticulum stress-induced apoptosis with CHOP and caspase-4 upregulation. These results demonstrate that CLIC4 nuclear translocation is an integral part of the cellular response to starvation. Inhibiting the expression of CLIC4 enhances autophagy and contributes to mitochondrial and ER stress-induced apoptosis under starvation.     

Silencing of Kv4.1 potassium channels inhibits cell proliferation of tumorigenic human mammary epithelial cells

Potassium channel activity has been shown to facilitate cell proliferation in cancer cells. In the present study, the role of Kv4.1 channels in immortal and tumorigenic human mammary epithelial cells was investigated. Kv4.1 protein expression was positively correlated with tumorigenicity. Moreover, transfection with siRNAs targeting Kv4.1 mRNA suppressed proliferation of tumorigenic mammary epithelial cells. Experiments using mRNA isolated from human breast cancer tissues revealed that the level of Kv4.1 mRNA expression varied depending on the stage of the tumor. Kv4.1 protein expression increased during stages T2 and T3 compared to normal tissue. These results demonstrated that Kv4.1 plays a role in proliferation of tumorigenic human mammary epithelial cells. In addition, elevated Kv4.1 expression may be useful as a diagnostic marker for staging mammary tumors and selective blockers of Kv4.1 may serve to suppress tumor cell proliferation.     

Cell cycle-dependent expression of Kv1.5 is involved in myoblast proliferation

Voltage-dependent K(+) channels (Kv) are involved in the proliferation of many types of cells, but the mechanisms by which their activity is related to cell growth remain unclear. Kv antagonists inhibit the proliferation of mammalian cells, which is of physiological relevance in skeletal muscle. Although myofibres are terminally differentiated, some resident myoblasts may re-enter the cell cycle and proliferate. Here we report that the expression of Kv1.5 is cell-cycle dependent during myoblast proliferation. In addition to Kv1.5 other Kv, such as Kv1.3, are also up-regulated. However, pharmacological evidence mainly implicates Kv1.5 in myoblast growth. Thus, the presence of S0100176, a Kv antagonist, but not margatoxin and dendrotoxin, led to cell cycle arrest during the G(1)-phase. The use of selective cell cycle blockers showed that Kv1.5 was transiently accumulated during the early G(1)-phase. Furthermore, while myoblasts treated with S0100176 expressed low levels of cyclin A and D(1), the expression of p21(cip-1) and p27(kip1), two cyclin-dependent kinase inhibitors, increased. Our results indicate that the cell cycle-dependent expression of Kv1.5 is involved in skeletal muscle cell proliferation.     

Tumor cells can evade dependence on autophagy through adaptation

The autophagy-lysosome and the proteasome constitute the two major intracellular degradation systems. Suppression of the proteasome promotes autophagy for compensation and simultaneous inhibition of autophagy can selectively increase apoptosis in transformed cells, but not in untransformed or normal cells. Transformed cells are thus more dependent on autophagy for survival. However, it is unclear whether long-term autophagy inhibition/insufficiency would affect such dependency. To address this question, we transformed wild-type and autophagy-deficient cells lacking a key autophagy-related gene Atg5 with activated Ras. We found that such transformation did not make the autophagy-deficient tumor cells more susceptible to proteasome inhibitors than the wild type tumor cells, although the transformed cells were in general more sensitive to proteasome inhibition. We then compared the effect of acute versus constitutive knock-down of a key autophagy initiating molecule, Beclin 1, in an already transformed cancer cell line. In a wild-type U251 glioblastoma cell line (autophagy intact), increased sensitivity to proteasome inhibition was induced immediately after the knock-down of Beclin 1 expression with a specific siRNA (acute autophagy deficiency). On the other hand, when the tumor cell line was selected over a long period to achieve constitutive knock-down of Beclin 1, its sensitivity to proteasome inhibitors was no higher than that of the wild-type tumor cells. These results suggest that long-term autophagy deficiency either before or after oncogenic transformation can render the tumor cell survival independent of the autophagic activity, and the response to chemotherapy is no longer affected by the manipulation of the autophagy status.