截短型rhtBIGH3-(RGD)2蛋白通过上调miR-126 表达抑制 人脐静脉内皮细胞的生物活性

目的:探讨miR-126在截短型rhtBIGH3-(RGD)_2蛋白抑制HUVEC细胞生物学活性中的作用。方法:体外培养VEGF孵化的人脐静脉内皮细胞(VEGF-HUVEC),分别加入rhtBIGH3-(RGD)_2蛋白终浓度为0和100μg/mL,作用24、48、72 h条件下,分别检测Caspase-3活性和miR-126表达水平。在rhtBIGH3-(RGD)_2蛋白终浓度为0和100μg/mL时,分别加入miR-126 mimic和miR-126 inhibitor,作用VEGF-HUVEC 48 h后,Real-time PCR检测miR-126表达水平,通过检测Caspase-3活性来检测细胞凋亡情况。结果:在VEGF-HUVEC中,当rhtBIGH3-(RGD)_2蛋白终浓度为100μg/mL条件下,Caspase-3水平升高,miR-126表达水平升高,在48 h下达到最高峰。在VEGF-HUVEC中,当rhtBIGH3-(RGD)_2蛋白终浓度分别为100μg/mL条件下,加入miR-126mimic后,miR-126表达升高,Caspase-3水平升高;加入miR-126 inhibitor后,48 h后检测miR-126表达下降,Caspase-3水平也下降。结论:截短型rhtBIGH3-(RGD)_2蛋白通过上调miR-126表达从而促进细胞凋亡、抑制HUVEC生物活性,从而抑制角膜新生血管的发生     

三氧化二砷对心肌细胞膜延迟整流钾通道蛋白表达的影响研究

目的:观察不同剂量的三氧化二砷(arsenic trioxide,As2O3)对心肌细胞膜上延迟整流钾电流蛋白表达的影响。方法:将豚鼠随机分为4组:正常对照组、As2O3小剂量组(0.4 mg/kg)、中剂量组(0.8 mg/kg)、大剂量组(1.6 mg/kg),给药后不同时间间隔记录心电图,测量QT间期和RR间期,计算QTc的值的变化,同时应用荧光免疫组化技术检测心肌延迟整流钾通道IKr、IKs通道蛋白的表达量。结果:1在不同剂量的As2O3作用下,0.8 mg/kg和1.6 mg/kg As2O3组的豚鼠QTc明显延长,并且这种延长作用与给药剂量和时间密切相关。在2 h的观察时间内,0.8 mg/kg和1.6 mg/kg As2O3分别使QTc从对照组的324±7 ms延长到368±11 ms(P0.01)和388±11 ms(P0.01)。2大剂量组豚鼠心肌缓慢型延迟整流钾通道Kv LQT1和GPERG蛋白表达与对照组相比显著降低(P0.01)。结论:As2O3对豚鼠心肌QT间期有明显延长效果,其机制可能与降低Kv LQT1和GPERG蛋白的表达,影响了钾通道的功能有关。     

Autophagy Is a Critical Mechanism for the Induction of the Antileukemic Effects of Arsenic Trioxide

Arsenic trioxide (As₂O₃) exhibits potent antitumor effects in vitro and in vivo, but the precise mechanisms by which it generates such responses are not well understood. We provide evidence that As₂O₃ is a potent inducer of autophagy in leukemia cells. Such induction of autophagy by As₂O₃ appears to require activation of the MEK/ERK pathway but not the AKT/mammalian target of rapamycin or JNK pathways. In efforts to understand the functional relevance of arsenic-induced autophagy, we found that pharmacological inhibitors of autophagy or molecular targeting of beclin 1 or Atg7 results in reversal of the suppressive effects of As₂O₃ on leukemic cell lines and primary leukemic progenitors from acute myelogenous leukemia patients. Altogether, our data provide direct evidence that autophagic cell death is critical for the generation of the effects of As₂O₃ on acute myelogenous leukemia cells and raise the potential of modulation of elements of the autophagic machinery as an approach to enhance the antitumor properties of As₂O₃ and possibly other heavy metal derivatives.     

Dechlorination of Chloroethenes Is Inhibited by 2-Bromoethanesulfonate in the Absence of Methanogens

2-Bromoethanesulfonate (BES) inhibited the reductive dechlorination of chloroethenes in several sediment-free enrichment cultures in the absence of methanogenic archaea. Archaeon-specific PCR primers confirmed the absence of methanogens in the enrichment cultures. BES should not be used to attribute dechlorination activities to methanogens.     

Arsenic Trioxide (ATO) Influences the Gene Expression of Metallothioneins in Human Glioblastoma Cells

Arsenic trioxide (As₂O₃; ATO, TRISENOX?) is used to treat patients with refractory or relapsed acute promyelocytic leukaemia while its application for treatment of solid cancers like glioblastoma is still under evaluation. In the present study, we investigated the interaction of arsenic trioxide with metallothionein (MT) isoforms as a possible (protective response) resistance of glioblastoma cells to arsenic-induced cytotoxicity. Special attention was focused on MT3, the isoform expressed mainly in the brain. MT3 has low metal inducibility, fast metal binding/releasing properties and outstanding neuronal inhibitory activity. The human astrocytoma (glioblastoma) cell line U87 MG was treated with 0.6, 2 and 6?C7???M arsenic (equivalent to 0.3, 1 and 3?C3.5???M As₂O₃) for 12, 24 or 48?h and gene expression for different MT isoforms, namely MT2A, MT1A, MT1F, MT1X, MT1E and MT3, was measured by real time qPCR using SYBR Green I and Taqman? gene expression assays. TfR, 18S rRNA, GAPDH and AB were tested as reference genes, and the last two evaluated to be appropriate in conditions of low (GAPDH) and high (AB) arsenic exposure. The gene expression of MT3 gene was additionally tested and confirmed by restriction enzyme analysis with PvuII. In the given conditions the mRNAs of six MT isoforms were identified in human glioblastoma cell line U87 MG. Depending on arsenic exposure conditions, an increase or decrease of MT gene expression was observed for each isoform, with the highest increase for isoforms MT1X, MT1F and MT2A mRNA (up to 13-fold) and more persistent decreases for MT1A, MT1E and MT3 mRNA. Despite the common assumption of the noninducibility of MT3, the evident MT3 mRNA increase was observed during high As exposure (up to 4-fold). In conclusion, our results clearly demonstrate the influence of As on MT isoform gene expression. The MT1X, MT1F and MT2A increase could represent brain tumour acquired resistance to As cytotoxicity while the MT3 increase is more enigmatic, with its possible involvement in arsenic-related induction of type II cell death.     

三氧化二砷对胶质瘤U251细胞侵袭迁移和MMP2表达的影响

目的:研究三氧化二砷(As2O3)在体外对胶质瘤U251细胞侵袭迁移及金属基质蛋白酶2(MMP2)表达的影响.方法:采用台盼兰法(MTT法)观察As2O3对U251细胞粘附能力的影响;Transwell侵袭小室测定法检测As2O3对U251细胞侵袭能力的影响;明胶酶谱实验和逆转录-聚合酶链反应(RT-PCR)方法观察As2O3对金属基质蛋白酶2(Matrix metalloproteinase2,MMP2)在U251细胞中表达的影响.结果:As2O3能够降低U251细胞粘附能力,Transwell实验中药物处理组穿膜细胞数明显低于对照组(P＜0.01),As2O3不但降低MMP2前体蛋白的表达,而且影响其mRNA的表达.结论:As2O3能够有效抑制胶质瘤U251细胞的侵袭迁移,其作用机制可能与As2O3下调胶质瘤U251细胞中MMP2的表达有关.     

Upregulation of PEDF expression by PARP inhibition contributes to the decrease in hyperglycemia-induced apoptosis in HUVECs

Poly(ADP-ribose)polymerase (PARP) inhibitors decrease angiogenesis through reducing vascular endothelium growth factor (VEGF) induced proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs). In contrast to VEGF, pigment epithelium-derived factor (PEDF) has been demonstrated to act as a strong endogenous inhibitor of angiogenesis. Here, we show that PARP inhibition with a specific inhibitor PJ-34 or specific PARP antisense oligonucleotide upregulates hyperglycemia-induced PEDF expression in HUVECs in a dose-dependent manner. This results in the retard of activation of p38 MAP kinase and the concomitant decrease in cell apoptosis. These results give the first direct demonstration that PEDF might represent a target for PARP inhibition treatment and the effects of PEDF on endothelial cells growth are context dependent.     

Effects of Arsenic Trioxide on INF-gamma Gene Expression in MRL/lpr Mice and Human Lupus

Arsenic trioxide (As2O3; ATO), a traditional Chinese medicine, is used to treat patients with acute promye-locytic leukemia, while its application for treatment of systemic lupus erythematosus (SLE) is still under evaluation. The high expression of INF-gamma (INF-γ) is a primary pathogenic factor in SLE. It is found that ATO can reduce INF-γ expression levels in lupus-prone mice, whereas it is not clear whether ATO has the same effect on SLE patients. Therefore, this study was to investigate the underlying mechanism of the effects of ATO on the expression of INF-γ in splenocytes of MRL/lpr mice and PBMCs of human lupus. The mRNA and protein expression levels of INF-γ were assessed by real-time RT-PCR and ELISA, respectively. The histone acetylation status of the INF-γ promoter and the binding of RNA polymerase II (RNA Pol II) to the INF-γ promoter were detected using a chromatin immunoprecipitation (ChIP) technique. The mRNA and protein expression levels of INF-γ decreased in both splenocytes of MRL/lpr mice and PBMCs of SLE patients with ATO treatment, which were accompanied by reduced histone H4 and H3 acetylation in INF-γ promoter and decreased combination of RNA Pol II to the INF-γ promoter. Therefore, ATO may reduce the expression level of the INF-γ by altering the levels of INF-γ promoter acetylation and the combination of RNA Pol II to the INF-γ promoter in splenocytes of MRL/lpr mice and PBMCs of SLE patients.     

三氧化二砷对鼻咽癌细胞Cx43表达的影响

目的:探讨三氧化二砷(As2O3)抑制鼻咽癌的作用机制。方法:采用流式细胞仪(FCM)、激光扫描共聚焦显微镜(LSCM)和荧光技术,检测人鼻咽癌细胞株(CNE1)经As2O3诱导后细胞连接蛋白43(Cx43)表达的变化。结果:FCM显示,经过浓度为4μmol L的As2O3处理后,其Cx43阳性细胞计数率明显升高,与未经As2O3处理和经2μmol L的As2O3处理的CNE1比较,其差异具有非常显著性意义(p<0.01);LSCM图像观察到,经4μmol LAs2O3处理后,标记Cx43的绿色荧光显著增强,集中分布于细胞膜。结论:较高剂量浓度的As2O3能提高鼻咽癌细胞Cx43的表达率,升高细胞膜Cx43的含量。As2O3抑制鼻咽癌细胞生长的作用机制之一,是通过恢复细胞间隙连接通讯功能来实现的。     

Expression of the Epidermodysplasia Verruciformis-Associated Genes EVER1 and EVER2 Is Activated by Exogenous DNA and Inhibited by LMP1 Oncoprotein from Epstein-Barr Virus

EVER1 and EVER2 are mutated in epidermodysplasia verruciformis patients, who are susceptible to human betapapillomavirus (HPV) infection. It is unknown whether their products control the infection of other viruses. Here, we show that the expression of both genes in B cells is activated immediately after Epstein-Barr virus (EBV) infection, whereas at later stages, it is strongly repressed via activation of the NF-κB signaling pathway by latent membrane protein 1 (LMP1). Ectopic expression of EVER1 impairs the ability of EBV to infect B cells.     

A Non-Sequence-Specific DNA Binding Mode of RAG1 Is Inhibited by RAG2

RAG1 and RAG2 proteins catalyze site-specific DNA cleavage reactions in V(D)J recombination, a process that assembles antigen receptor genes from component gene segments during lymphocyte development. The first step towards the DNA cleavage reaction is the sequence-specific association of the RAG proteins with the conserved recombination signal sequence (RSS), which flanks each gene segment in the antigen receptor loci. Questions remain as to the contribution of each RAG protein to recognition of the RSS. For example, while RAG1 alone is capable of recognizing the conserved elements of the RSS, it is not clear if or how RAG2 may enhance sequence-specific associations with the RSS. To shed light on this issue, we examined the association of RAG1, with and without RAG2, with consensus RSS versus non-RSS substrates using fluorescence anisotropy and gel mobility shift assays. The results indicate that while RAG1 can recognize the RSS, the sequence-specific interaction under physiological conditions is masked by a high-affinity non-sequence-specific DNA binding mode. Significantly, addition of RAG2 effectively suppressed the association of RAG1 with non-sequence-specific DNA, resulting in a large differential in binding affinity for the RSS versus the non-RSS sites. We conclude that this represents a major means by which RAG2 contributes to the initial recognition of the RSS and that, therefore, association of RAG1 with RAG2 is required for effective interactions with the RSS in developing lymphocytes.     

Arsenic Trioxide Inhibits Hepatitis C Virus RNA Replication through Modulation of the Glutathione Redox System and Oxidative Stress

Arsenic trioxide (ATO), a therapeutic reagent used for the treatment of acute promyelocytic leukemia, has recently been reported to increase human immunodeficiency virus type 1 infectivity. However, in this study, we have demonstrated that replication of genome-length hepatitis C virus (HCV) RNA (O strain of genotype 1b) was notably inhibited by ATO at submicromolar concentrations without cell toxicity. RNA replication of HCV-JFH1 (genotype 2a) and the release of core protein into the culture supernatants were also inhibited by ATO after the HCV infection. To clarify the mechanism of the anti-HCV activity of ATO, we examined whether or not PML is associated with this anti-HCV activity, since PML is known to be a target of ATO. Interestingly, we observed the cytoplasmic translocation of PML after treatment with ATO. However, ATO still inhibited the HCV RNA replication even in the PML knockdown cells, suggesting that PML is dispensable for the anti-HCV activity of ATO. In contrast, we found that N-acetyl-cysteine, an antioxidant and glutathione precursor, completely and partially eliminated the anti-HCV activity of ATO after 24 h and 72 h of treatment, respectively. In this context, it is worth noting that we found an elevation of intracellular superoxide anion radical, but not hydrogen peroxide, and the depletion of intracellular glutathione in the ATO-treated cells. Taken together, these findings suggest that ATO inhibits the HCV RNA replication through modulation of the glutathione redox system and oxidative stress.Hepatitis C virus (HCV) is the causative agent of chronic hepatitis, which progresses to liver cirrhosis and hepatocellular carcinoma. HCV is an enveloped virus with a positive single-stranded 9.6-kb RNA genome, which encodes a large polyprotein precursor of approximately 3,000 amino acid residues. This polyprotein is cleaved by a combination of the host and viral proteases into at least 10 proteins in the following order: core, envelope 1 (E1), E2, p7, nonstructural 2 (NS2), NS3, NS4A, NS4B, NS5A, and NS5B (30).Alpha interferon has been used as an effective anti-HCV reagent in clinical therapy for patients with chronic hepatitis C. The current combination treatment with pegylated alpha interferon and ribavirin, a nucleoside analogue, has been shown to improve the sustained virological response rate to more than 50% (15). However, the adverse effects of the combination therapy and the limited efficacy against genotype 1b warrant the development of new anti-HCV reagents.Arsenic trioxide (ATO) (As₂O₃, arsenite) has been used as a therapeutic reagent in acute promyelocytic leukemia, which bears an oncogenic PML-retinoic acid receptor alpha fusion protein resulting from chromosomal translocation (51, 52, 68, 70). The ATO treatment induces complete remission through degradation of the aberrant PML-retinoic acid receptor α (70). The PML tumor suppressor protein is required for formation of the PML nuclear body (PML-NB), also known as nuclear dot 10 or the PML oncogenic domain, which is often disrupted by infection with DNA viruses, such as herpes simplex virus type 1, human cytomegalovirus, and Epstein-Barr virus (17). The treatment with ATO results in degradation of the PML protein and disruption of the PML-NB (70). Therefore, ATO has been become a useful probe for investigating the functions of the PML-NB, including cell growth, apoptosis, stress response, and viral infection. Indeed, ATO has been shown to increase retroviral infectivity, such as human immunodeficiency virus type 1 (HIV-1) and murine leukemia virus infectivity, but the mechanisms of this change are not well understood (5, 6, 32, 44, 47, 50, 57). In contrast, ATO was recently reported to inhibit the replication of HCV subgenomic replicon RNA (24). However, it also remains unclear how ATO inhibits the HCV RNA replication. In this study, using genome-length HCV RNA replication systems, we investigated the molecular mechanism(s) of the anti-HCV activity of ATO, and we provide evidence that ATO inhibits HCV RNA replication through modulation of the glutathione redox system and oxidative stress.     

Endothelial-specific intron-derived miR-126 is down-regulated in human breast cancer and targets both VEGFA and PIK3R2

Endothelial cells are the key components of vascular intima and play pivotal roles in vasculogenesis, angiogenesis, and tumor growth. Using Northern blot and real-time PCR, we confirmed that miR-126 and its host gene EGF-like domain 7 (EGFL7) were widely expressed in rat tissues but strictly expressed in endothelial cells. In mammals, miR-126 gene is embedded in intron7 of EGFL7. To explore the biogenesis of miR-126, plasmid EGFL7(126)-pEGFPc1 containing segment of exon7-intron7-exon8 of EGFL7 was constructed and expressed in 293T. Expression of spliced exon7-8 and excised mature miR-126 was detected by PCR and Northern blot. Knocking-down of endothelial endogenous miR-126 did not affect EGFL7 expression at mRNA or protein level. To investigate the possible roles of miR-126, PicTar, miRBase, miRanda, Bibiserv, and Targetscan were used to screen the targets. VEGFA and PIK3R2 were confirmed as the targets of miR-126 by luciferase reporter assay and Western blot. Interestingly, Northern blot and western blot showed that miR-126 was down-regulated in breast tumors where the VEGF/PI3K/AKT signaling pathway was activated. Introduction of miR-126 mimics into MCF-7 could effectively decrease VEGF/PI3K/AKT signaling activity. In summary, miR-126 was strictly expressed in endothelial cells and excised from EGFL7 pre-mRNA without affecting splicing and expression of its host gene. In addition, miR-126 could target both VEGFA and PIK3R2, and its expression was decreased in human breast cancer, implying that miR-126 may play a role in tumor genesis and growth by regulating the VEGF/PI3K/AKT signaling pathway.     

LncRNA CCAT2 promotes angiogenesis in glioma through activation of VEGFA signalling by sponging miR-424

Molecular and Cellular Biochemistry - Glioma is characterized by high morbidity, high mortality and poor prognosis. Recent studies exhibited that lncRNA CCAT2 is overexpressed in glioma and...     

趋化因子CCL2对人脐静脉内皮细胞ICAM-1 表达的影响

目的:探讨CC类趋化因子配体2(C-C motif ligand 2,CCL2)对人脐静脉内皮细胞(human umbilical vein endothelial cells,HUVECs)中细胞间粘附分子-1(intercellular adhesion molecule-1,ICAM-1)表达的影响。方法:体外分离培养HUVECs细胞,将HUVECs铺至6孔板中,待细胞融合至80-90%时,将CCL2过表达载体[pc DNA3.1(+)-CCL2]及CCL2小分子干扰RNA(si-RNA)分别转染到HUVECs中,于转染后12 h、24 h和48 h收集细胞进行RNA及蛋白提取。荧光定量PCR方法检测HUVECs中CCL2及ICAM-1基因m RNA表达。Western blotting检测HUVECs中CCL2及ICAM-1蛋白表达。结果:(1)与pc DNA3.1(+)组相比较,pc DNA3.1(+)-CCL2组中CCL2基因m RNA和蛋白水平均显著升高;与si-Control组相比较,si-CCL2组中CCL2基因m RNA和蛋白表达均明显下降。(2)与对照组比较,pc DNA3.1(+)-CCL2组明显增加HUVECs中ICAM-1的m RNA及蛋白表达,而si-CCL2组显著抑制HUVECs中ICAM-1的m RNA及蛋白表达。结论:CCL2能增加HUVECs中ICAM-1基因m RNA和蛋白表达,为深入认识动脉粥样硬化的发病机制提供了理论依据。     

Receptor Activated Ca2+ Release Is Inhibited by Boric Acid in Prostate Cancer Cells

Background

The global disparity in cancer incidence remains a major public health problem. We focused on prostate cancer since microscopic disease in men is common, but the incidence of clinical disease varies more than 100 fold worldwide. Ca²⁺ signaling is a central regulator of cell proliferation, but has received little attention in cancer prevention. We and others have reported a strong dose-dependent reduction in the incidence of prostate and lung cancer within populations exposed to boron (B) in drinking water and food; and in tumor and cell proliferation in animal and cell culture models.

Methods/Principal Findings

We examined the impact of B on Ca²⁺ stores using cancer and non-cancer human prostate cell lines, Ca²⁺ indicators Rhod-2 AM and Indo-1 AM and confocal microscopy. In DU-145 cells, inhibition of Ca²⁺ release was apparent following treatment with Ringers containing RyR agonists cADPR, 4CmC or caffeine and respective levels of BA (50 µM), (1, 10 µM) or (10, 20, 50,150 µM). Less aggressive LNCaP cancer cells required 20 µM BA and the non-tumor cell line PWR1E required 150 µM BA to significantly inhibit caffeine stimulated Ca²⁺ release. BA (10 µM) and the RyR antagonist dantroline (10 µM) were equivalent in their ability to inhibit ER Ca²⁺ loss. Flow cytometry and confocal microscopy analysis showed exposure of DU-145 cells to 50 µM BA for 1 hr decreased stored [Ca²⁺] by 32%.

Conclusion/Significance

We show B causes a dose dependent decrease of Ca²⁺ release from ryanodine receptor sensitive stores. This occurred at BA concentrations present in blood of geographically disparate populations. Our results suggest higher BA blood levels lower the risk of prostate cancer by reducing intracellular Ca²⁺ signals and storage.     

Early Expression of the Calmodulin Gene, Which Precedes Appressorium Formation in Magnaporthe grisea, Is Inhibited by Self-Inhibitors and Requires Surface Attachment

Fungal conidia contain chemicals that inhibit germination and appressorium formation until they are well dispersed in a favorable environment. Recently, such self-inhibitors were found to be present on the conidia of Magnaporthe grisea, and plant surface waxes were found to relieve this self-inhibition. To determine whether the self-inhibitors suppress the expression of early genes involved in the germination and differentiation of conidia, the calmodulin gene was chosen as a representative early gene, because it was found to be expressed early in Colletotrichum gloeosporioides and Colletotrichum trifolii differentiation. After calmodulin cDNA and genomic DNA from M. grisea were cloned, the promoter of the calmodulin gene was fused to a reporter gene, that for green fluorescent protein (GFP), and transformed into the M. grisea genome. Confocal microscopic examination and quantitation of expression of GFP green fluorescence showed (i) that the expression of the calmodulin gene decreased significantly when self-inhibition of M. grisea appressorium formation occurred because of high conidial density or addition of exogenous self-inhibitors and (ii) that the expression level of this gene was restored when self-inhibition was relieved by the addition of plant surface waxes. The increase in fluorescence correlated with the percentage of conidia that formed appressoria. The induction of calmodulin was also confirmed by RNA blotting. Concanavalin A inhibited surface attachment of conidia, GFP expression, and appressorium formation without affecting germination. The high correlation between GFP expression and appressorium formation strongly suggests that calmodulin gene expression and appressorium formation require surface attachment.