High-efficiency expression of rat protein kinase C-gamma in baculovirus-infected insect cells

Effects of cyclopentenone prostaglandins, Δ¹²-prostaglandin (PG) J₂ and PGA₂ on the expression of N-myc in relation to the effects on cell cycle progression were investigated using human neuroblastoma cell line GOTO. Both PGs suppressed M-myc expression within several hours prior to inducing G₁ arrest. The N-myc suppression with Δ¹²-PGJ₂ was continued but with PGA₂ it was gradually released, followed by the release of G₁ arrest. These results suggest that Δ¹²-PGJ₂ and PGA₂ inhibit cell cycle progression in strong association with N-myc suppression and Δ¹²-PGJ₂ is more potent and has a longer effect than PGA₂.     

α-烯醇化酶基因干扰表达对籽鹅卵泡颗粒细胞增殖及凋亡的影响*

目的: 研究α-烯醇化酶(ENO1)基因干扰表达对籽鹅卵泡颗粒细胞增殖、凋亡和细胞周期的影响。方法: 原代培养籽鹅F1级卵泡颗粒细胞(复合培养),将ENO1基因干扰表达重组质粒转染至籽鹅卵泡颗粒细胞。实验分为四组:ENO1干扰表达组(RNAi)、无关序列干扰组(NC)、培养液组(Control)、转染试剂组(Lip)。流式细胞术检测干扰组和对照各组的凋亡率、细胞周期时相性。结果: ENO1基因干扰表达使籽鹅卵泡颗粒细胞增殖速度变慢,凋亡率增加,G2/M期颗粒细胞比例增高。结论: ENO1基因干扰表达可使籽鹅卵泡颗粒细胞周期发生G2/M期阻滞,诱导细胞发生凋亡,抑制细胞增殖。     

Protein phosphatase magnesium dependent 1A (PPM1A) plays a role in the differentiation and survival processes of nerve cells

The serine/threonine phosphatase type 2C (PPM1A) has a broad range of substrates, and its role in regulating stress response is well established. We have investigated the involvement of PPM1A in the survival and differentiation processes of PC6-3 cells, a subclone of the PC12 cell line. This cell line can differentiate into neuron like cells upon exposure to nerve growth factor (NGF). Overexpression of PPM1A in naive PC6-3 cells caused cell cycle arrest at the G2/M phase followed by apoptosis. Interestingly, PPM1A overexpression did not affect fully differentiated cells. Using PPM1A overexpressing cells and PPM1A knockdown cells, we show that this phosphatase affects NGF signaling in PC6-3 cells and is engaged in neurite outgrowth. In addition, the ablation of PPM1A interferes with NGF-induced growth arrest during differentiation of PC6-3 cells.     

The role of reactive oxygen species (ROS) production on diallyl disulfide (DADS) induced apoptosis and cell cycle arrest in human A549 lung carcinoma cells

Diallyl disulfide (DADS), an oil soluble constituent of garlic (Allium sativum), has been reported to cause antimutagentic and anticarcinogenic effects in vitro and in vivo by modulating phases I and II enzyme activities. In recent years, several studies suggested that the chemopreventive effects of DADS can also be attributed to induction of cell cycle arrest and apoptosis in cancer cells. In the present study, we reported that DADS-induced cell cycle arrest at G2/M and apoptosis in human A549 lung cancer cells in a time- and dose-dependent manner. Additionally, a significant increase of intracellular reactive oxygen species (ROS) was induced in A549 cells less than 0.5 h after DADS treatment, indicating that ROS may be an early event in DADS-modulated apoptosis. Treatment of A549 cells with N-acetyl cysteine (NAC) completely abrogated DADS-induced cell cycle arrest and apoptosis. The result indicated that oxidative stress modulates cell proliferation and cell death induced by DADS.     

Intracellular signaling pathways involved in post-mitotic dopaminergic PC12 cell death induced by 6-hydroxydopamine

Oxidative stress has been shown to mediate neuron damage in Parkinson's disease (PD). In the present report, we intend to clarify the intracellular pathways mediating dopaminergic neuron death after oxidative stress production using post-mitotic PC12 cells treated with the neurotoxin 6-hydroxydopamine (6-OHDA). The use of post-mitotic cells is crucial, because one of the suggested intracellular pathways implicated in neuron death relates to the re-entry of neurons (post-mitotic cells) in the cell cycle. We find that 6-OHDA sequentially increases intracellular oxidants, functional cell damage and caspase-3 activation, leading to cell death after 12 h of incubation. Prevention of cell damage by different antioxidants supports the implication of oxidative stress in the observed neurotoxicity. Oxidative stress-dependent phosphorylation of the MAPK JNK and oxidative stress-independent PKB/Akt dephosphorylation are involved in 6-OHDA neurotoxicity. Decrease in p21(WAF1/CIP1) and cyclin-D1 expression, disappearance of the non-phosphorylated band of retinoblastoma protein (pRb), and expression of proliferating cell nuclear antigen, not present in PC12 post-mitotic cells, suggest a re-entry of differentiated cells into cell cycle. Our results indicate that such a re-entry is mediated by oxidative stress and is involved in 6-OHDA-induced cell death. We conclude that at least three intracellular pathways are involved in 6-OHDA-induced cell death in differentiated PC12 cells: JNK activation, cell cycle progression (both oxidative stress-dependent), and Akt dephosphorylation (not related to the increase of oxidants); the three pathways are necessary for the cells to die, since blocking one of them is sufficient to keep the cells alive.     

Specific checkpoints regulate plant cell cycle progression in response to oxidative stress

The effects of oxidative stress on plant cell cycle progression were studied both in cell suspensions and in planta . Oxidative stress of variable severity was imposed by the addition of different concentrations of the methyl-quinone, menadione, into the growth media. In cell suspensions, flow cytometry analyses demonstrated that low concentrations (20–50 μM) of menadione impaired the G1/S transition, slowed DNA replication, and delayed the entry into mitosis. Furthermore, cells in G1 were more sensitive to menadione-mediated oxidative stress than cells in S phase. Cell cycle arrest was associated with an inhibition of the activity of cyclin-dependent kinases, cell cycle gene expression, and a concomitant activation of stress genes. Menadione-mediated oxidative stress was shown to have very similar effects on tobacco plants, suggesting that a general regulation mechanism takes place in plants. These results define an oxidative stress checkpoint pathway that modulates both the expression of the core cell cycle genes and oxidative defence genes. Redox sensing could be of key importance in controlling cell cycle progression in environmental stress conditions.     

长链非编码RNA Linc00673过表达对胃癌MGC-803细胞增殖与凋亡的影响*

目的: 探讨长链非编码RNA Linc00673过表达对胃癌细胞增殖和凋亡的影响及其机制。方法: 将重组慢病毒表达质粒pLVX-Linc00673和对照空载体质粒pLVX-NC在293T细胞中进行慢病毒包装与扩增,将重组慢病毒转染胃癌细胞MGC-803建立稳定过表达 Linc00673的细胞系,实时荧光定量PCR方法检测Linc00673基因的表达; MTT实验和克隆形成实验观察细胞的生长增殖;流式细胞术检测细胞周期和细胞凋亡;qPCR检测细胞周期相关调控基因表达;免疫印迹法检测PI3K/Akt信号通路关键分子及肿瘤增殖相关蛋白的表达。结果: Linc00673在胃癌细胞系MGC-803、BGC-823和AGS中的表达量显著高于正常胃粘膜细胞GES-1(P＜0.05)。建立了稳定过表达Linc00673的MGC-803细胞系,Linc00673的表达量比对照空载体组高200倍。Linc00673过表达促进MGC-803细胞增殖和克隆形成(P＜0.05),抑制细胞凋亡并影响细胞周期G1→S期进程(P＜0.01);Linc00673过表达可影响MGC-803细胞周期调节基因CCNG2、p19和CDK1的表达;免疫印迹结果显示,Linc00673过表达不仅促进PI3K/Akt信号通路关键分子pAKT及其下游靶点NF-κB和Bcl-2蛋白的表达,而且上调肿瘤相关因子β-catenin和EZH2蛋白的表达。结论: Linc00673过表达可能通过PI3K/Akt信号通路促进MGC-803细胞增殖、抑制凋亡。     

LPS-Stimulating Astrocyte-Conditioned Medium Causes Neuronal Apoptosis Via Increasing CDK11p58 Expression in PC12 Cells Through Downregulating AKT Pathway

Activation of astrocytes in central nervous system inflammation leads to a disturbance of crosstalk between astrocytes and neurons, and that this may contribute to the death of neurons. CDK11^p58 is a member of the large family of p34cdc2-related kinases. It specifically expresses in G2/M phase of the cell cycle and is closely related to cell cycle arrest and apoptosis. Here, we show that astrocyte-conditioned medium stimulated by lipopolysaccharide upregulates CDK11^p58 expression and meanwhile causes neuronal apoptosis. CDK11^p58 knockdown in PC12 cells represses neuronal apoptosis. CDK11^p58 overexpression in PC12 cells promotes neuronal apoptosis. AKT signaling pathway is involved in CDK11^p58-induced neuronal apoptosis process.     

Long noncoding RNA MEG3 silencing protects against hypoxia-induced pheochromocytoma-12 cell injury through inhibition of TIMP2 promoter methylation

Hypoxia is a common pathological process caused by insufficient oxygen. Long noncoding RNAs (lncRNAs) have been proven to participate in this pathology. Hypoxia is reported to significantly reduce the secretion of tissue inhibitor of metalloproteinase 2 (TIMP2) and TIMP2 induces pheochromocytoma-12 (PC12) cell cycle arrest. Thus, our study aimed to explore the mechanism by which lncRNA maternally expressed gene 3 (MEG3) was implicated in hypoxia-induced PC12 cell injury through TIMP2 promoter methylation. To elucidate the potential biological significance of MEG3 and the regulatory mechanism between MEG3 and TIMP2, a hypoxia-induced PC12 cell injury model was generated. The hypoxia-exposed cells were subjected to a series of overexpression plasmids and short hairpin RNAs, followed by the measurement of levels of MEG3, TIMP2, lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), reactive oxygen species (ROS), Bcl-2-associated X protein, B-cell lymphoma-2, and caspase-3, as well as the changes in MMP, cell proliferation, apoptosis, and cell cycle progression. On the basis of the findings, MEG3 was upregulated in hypoxia-injured PC12 cells. MEG3 recruited methylation proteins DNMT3a, DNMT3b, and MBD1 and accelerated TIMP2 promoter methylation, which in turn inhibited its expression. Moreover, PC12 cells following MEG3 silencing and TIMP2 overexpression exhibited significantly decreased levels of LDH, MDA, and ROS along with cell apoptosis, yet increased SOD and MMP levels, as well as cell cycle entry to the S phase and cell proliferation. In conclusion, MEG3 silencing suppresses hypoxia-induced PC12 cell injury by inhibiting TIMP2 promoter methylation. This study may provide novel therapeutic targets for hypoxia-induced injury.     

Schlafen-1 causes a cell cycle arrest by inhibiting induction of cyclin D1

Schlafen-1 (Slfn-1), the prototypic member of the Schlafen family of proteins, was described as an inducer of growth arrest in T-lymphocytes and causes a cell cycle arrest in NIH3T3 fibroblasts prior to the G1/S transition. How Slfn-1 exerts its effects on the cell cycle is not currently known. We report that synchronized murine fibroblasts expressing Slfn-1 do not exit G1 when stimulated with fetal calf serum, platelet-derived growth factor BB (PDGF-BB) or epidermal growth factor (EGF). The induction of cyclin D1 by these stimuli was blocked in the presence of Slfn-1 as were all downstream cell cycle processes. Overexpression of cyclin D1 in growth-arrested, Slfn-1-expressing cells induced an increase in cell growth consistent with this protein being the biological target of Slfn-1. Activation of the mitogen-activated protein kinase pathway by EGF or phorbol 12-myristate 13-acetate was unaffected by Slfn-1 expression. PDGF signaling was, however, almost completely blocked. This was due to a lack of PDGF receptor expression in Slfn-1-expressing cells consistent with Slfn-1 blocking the cell cycle in G1 where PDGF receptor expression is normally down-regulated. Finally, overexpression of Slfn-1 inhibited the activation of the cyclin D1 promoter. Slfn-1 therefore causes a cell cycle arrest during G1 by inhibiting induction of cyclin D1 by mitogens.     

Tyrosine Kinase Activity Is Essential for Interleukin-1β-Stimulated Production of Interleukin-6 in U373 Human Astrocytoma Cells

Abstract: Previous studies have shown that PC12 cells depend on growth factors for their survival. When deprived of growth factors, the cells undergo a dying process termed "apoptosis" (programed cell death). We show here that muscarinic agonists inhibited the apoptotic death of growth factor-deprived PC12M1 cells (PC12 cells stably expressing cloned m1 muscarinic acetylcholine receptors). This protective effect of the muscarinic agonists was observed in both proliferating and neuronal PC12M1 cells, was blocked by the muscarinic antagonist atropine, and was not observed in PC12 cells lacking m1 receptors. Muscarinic receptors therefore mediate inhibition of apoptosis in these cells. In addition to its effect on survival, the muscarinic agonist oxotremorine induced inhibition of DNA synthesis as well as growth arrest of exponentially growing PC12M1 cells at the S and G₂/M phases of the cell cycle. Muscarinic receptors in these cells may therefore mediate inhibition of cell cycle progression.     

外源性H2S恢复缺氧后适应对衰老H9C2细胞的保护作用及机制

目的：探讨外源性硫化氢（H₂S）恢复缺氧后适应对衰老H9C2细胞的保护作用及相关机制。方法：H9C2细胞（心肌细胞系）用30 μmol/L过氧化氢（H₂O₂）处理2 h后再培养3 d,诱导生成衰老细胞。衰老H9C2细胞被随机分5组（n=8）：正常组（Control）、缺氧/复氧组（H/R）、H/R+NaHS组、缺氧后适应（PC）组、PC+NaHS组。缺氧/复氧（H/R）模型：衰老H9C2细胞用缺氧液（无血清、无糖培养基,pH=6.8）培养3 h,然后正常培养6 h;缺氧后适应（PC）模型：方法同H/R模型,缺氧结束复氧前连续进行3次5 min间隔的复氧/再缺氧处理,随后复氧6 h。ELISA试剂盒分别检测大鼠晚期糖基化终末产物（AGEs）含量和caspase-3活性;CCK-8试剂盒检测细胞活力;DCFH-DA染色检测活性氧（ROS）水平;Hoechst 33342染色检测细胞凋亡率;Real-time PCR检测相关基因mRNA水平。结果：30 μmol/L H₂O₂可诱导H9C2细胞衰老但不会导致其凋亡;与Control组比较,H/R和PC均降低细胞活力,增加细胞凋亡率、ROS水平及caspase-3、caspase-9和Bcl-2 mRNA水平（P<0.01）;且PC组与H/R组比较,上述指标变化无明显差异;在H/R和PC组加入NaHS,可显著提高细胞活力,降低细胞凋亡率和氧化应激;PC+NaHS对上述指标的作用明显强于H/R+NaHS。结论：外源性H₂S能够恢复PC对衰老H9C2细胞的保护作用,其机制与抑制氧化应激和细胞凋亡有关。     

Application of confocal laser scanning microscopy to detect oxidative stress in human colon cells

Introduction Excess of intracellular reactive oxygen species in relation to antioxidative systems results in an oxidative environment which may modulate gene expression or damage cellular molecules. These events are expected to greatly contribute to processes of carcinogenesis. Only few studies are available on the oxidative/reductive conditions in the colon, an important tumour target tissue. It was the objective of this work to further develop methods to assess intracellular oxidative stress within human colon cells as a tool to study such associations in nutritional toxicology.

Methods We have measured H₂O₂-induced oxidative stress in different colon cell lines, in freshly isolated human colon crypts, and, for comparative purposes, in NIH3T3 mouse embryo fibroblasts. Detection was performed by loading the cells with the fluorigenic peroxide-sensitive dye 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate (diacetoxymethyl ester), followed by in vitro treatment with H₂O₂ and fluorescence detection with confocal laser scanning microscopy (CLSM). Using the microgel electrophoresis (“Comet”) Assay, we also examined HT29 stem and clone 19A cells and freshly isolated primary colon cells for their relative sensitivity toward H₂O₂-induced DNA damage and for steady-state levels of endogenous oxidative DNA damage.

Results A dose-response relationship was found for the H₂O₂-induced dye decomposition in NIH3T3 cells (7.8-125 μM H₂O₂) whereas no effect occurred in the human colon tumour cell lines HT29 stem and HT29 clone 19A (62-1000 μM H₂O₂). Fluorescence was significantly increased at 62 μM H₂O₂ in the human colon adenocarcinoma cell line Caco-2. In isolated human colon crypts, the lower crypt cells (targets of colon cancer) were more sensitive towards H₂O₂ than the more differentiated upper crypt cells. In contrast to the CLSM results, oxidative DNA damage was detected in both cell lines using the Comet Assay. Endogenous oxidative DNA damage was highest in HT29 clone 19A, followed by the primary colon cells and HT29 stem cells.

Conclusions Oxidative stress in colon cells leads to damage of macromolecules which is sensitively detected in the Comet Assay. The lacking response of the CLSM-approach in colon tumour cells is probably due to intrinsic modes of protective activities of these cells. In general, however, the CLSM method is a sensitive technique to detect very low concentrations of H₂O₂-induced oxidative stress in NIH3T3 cells. Moreover, by using colon crypts it provides the unique possibility of assessing cell specific levels of oxidative stress in explanted human tissues. Our results demonstrate that the actual target cells of colon cancer induction are indeed susceptible to the oxidative activity of H₂O₂.     

三元基序家族蛋白15敲低诱导肝癌细胞周期阻滞

三元基序家族蛋白15 (tripartite motif-containing protein 15,TRIM15)是TRIM家族成员,该家族是一类具有E3泛素连接酶活性的蛋白质.TRIM15在肿瘤中的功能鲜有报导.本研究意在阐释TRIM15在肝细胞癌(hepatocellular carcinoma,HCC)中的作用...     

Up-expression of NapA and other oxidative stress proteins is a compensatory response to loss of major Helicobacter pylori stress resistance factors

Twenty-six Helicobacter pylori targeted mutant strains with deficiencies in oxidative stress combating proteins, including 12 double mutant strains were analyzed via physiological and proteomic approaches to distinguish the major expression changes caused by the mutations. Mutations were introduced into both a Mtz^S and a Mtz^R strain background. Most of the mutations caused increased growth sensitivity of the strains to oxygen, and they all exhibited clear compensatory up-expression of oxidative stress resistance proteins enabling survival of the bacterium. The most frequent up-expressed oxidative stress resistance factor (observed in 16 of the mutants) was the iron-sequestering protein NapA, linking iron sequestration with oxidative stress resistance. The up-expression of individual proteins in mutants ranged from 2 to 10 fold that of the wild type strain, even when incubated in a low O₂ environment. For example, a considerably higher level of catalase expression (4 fold of that in the wild-type strain) was observed in ahpC napA and ahpC sodB double mutants. A Fur mutant up-expressed ferritin (Pfr) protein 20-fold. In some mutant strains the bacterial DNA is protected from oxidative stress damage apparently via overexpression of oxidative stress-combating proteins such as NapA, catalase or MdaB (an NADPH quinone reductase). Our results show that H. pylori has a variety of ways to compensate for loss of major oxidative stress combating factors.     

Propofol Protects Against H<Subscript>2</Subscript>O<Subscript>2</Subscript>-Induced Oxidative Injury in Differentiated PC12 Cells via Inhibition of Ca<Superscript>2+</Superscript>-Dependent NADPH Oxidase

Propofol (2,6-diisopropylphenol) is a widely used general anesthetic with anti-oxidant activities. This study aims to investigate protective capacity of propofol against hydrogen peroxide (H₂O₂)-induced oxidative injury in neural cells and whether the anti-oxidative effects of propofol occur through a mechanism involving the modulation of NADPH oxidase (NOX) in a manner of calcium-dependent. The rat differentiated PC12 cell was subjected to H₂O₂ exposure for 24 h to mimic a neuronal in vitro model of oxidative injury. Our data demonstrated that pretreatment of PC12 cells with propofol significantly reversed the H₂O₂-induced decrease in cell viability, prevented H₂O₂-induced morphological changes, and reduced the ratio of apoptotic cells. We further found that propofol attenuated the accumulation of malondialdehyde (biomarker of oxidative stress), counteracted the overexpression of NOX core subunit gp91^phox (NOX2) as well as the NOX activity following H₂O₂ exposure in PC12 cells. In addition, blocking of L-type Ca²⁺ channels with nimodipine reduced H₂O₂-induced overexpression of NOX2 and caspase-3 activation in PC12 cells. Moreover, NOX inhibitor apocynin alone or plus propofol neither induces a significant downregulation of NOX activity nor increases cell viability compared with propofol alone in the PC12 cells exposed to H₂O₂. These results demonstrate that the protective effects of propofol against oxidative injury in PC12 cells are mediated, at least in part, through inhibition of Ca²⁺-dependent NADPH oxidase.     

新型精胺氧化酶抑制剂SI-4650对人卵巢癌SKVO-3细胞增殖和上皮细胞间质化的影响*

目的: 研究新型精胺氧化酶(SMO)小分子抑制剂SI-4650对人卵巢癌SKVO-3细胞增殖和上皮细胞间质化影响及其分子机制。方法: 体外培养SKVO-3细胞,以未加药作为对照组,30、60 μmol/L SI-4650处理48 h细胞为实验组,每组设3个复孔,检测SI-4650对SKVO-3细胞内SMO的酶活性及多胺含量、酶促反应产物活性氧水平的影响,对细胞增值、周期、线粒体膜电位的作用,以及对细胞凋亡、侵袭和迁移能力的影响,同时检测凋亡相关蛋白Bax、Bcl-2、Caspase3以及上皮细胞间质化(EMT)相关蛋白E-Cad、N-Cad、Vimentin、MMP-2、MMP-9表达。结果: 与对照组相比,实验组SKVO-3细胞中SI-4650浓度增加,明显抑制SKVO-3细胞内SMO酶活性(P＜0.01)、减少SMO酶促反应产物活性氧水平(P＜0.01)、降低细胞内总多胺含量(P＜0.01)。SI-4650高效抑制SKVO-3细胞生长(P＜0.01),实验组细胞生长抑制率分别为32.27%、47.31%;将SKVO-3细胞阻滞在S期(P＜0.01),实验组细胞 Bax表达和Caspase3活化剪切增加,Bcl-2表达减少,线粒体膜电位下降,凋亡细胞比率增加至31.41%、43.51%;同时,实验组E-cad表达显著增加,N-cad、Vimentin表达均明显减少,合成分泌MMP-2、MMP-9减少,干扰了SKVO3细胞EMT进程,降低肿瘤细胞侵袭、迁移能力(P＜0.01)。结论: SI-4650对人卵巢癌SKVO-3 细胞具有杀伤和抑制肿瘤细胞侵袭、迁移的抗肿瘤活性,其机制可能与干扰多胺代谢、诱导细胞S周期阻滞和线粒体途径细胞凋亡以及干扰细胞EMT进程相关。