信号转导和转录活化因子3通过趋化因子CX3C配体1促进血管内皮细胞增殖迁移

信号转导和转录活化因子3 (STAT3)与趋化因子CX3C配体1 (Fractalkine/CX3CL1)在血管炎症和损伤中起重要作用,为了探讨STAT3是否通过CX3CL1促进血管内皮细胞增殖和迁移,在血管内皮细胞(HUVEC)中过表达或敲降STAT3,通过quantitative real-time PCR、Western blotting实验确定STAT3对CX3CL1表达的影响。构建含有STAT3结合位点及突变STAT3结合位点的CX3CL1启动子荧光素酶报告基因质粒,利用荧光素酶活性分析实验研究STAT3对CX3CL1启动子转录活性的作用。利用MTT实验检测过表达或敲降STAT3或CX3CL1对血管内皮细胞增殖率的影响。利用划痕实验检测过表达或敲降STAT3或CX3CL1对血管内皮细胞迁移率的影响。结果显示,过表达STAT3可以促进CX3CL1表达,敲降STAT3可以使CX3CL1表达下调。STAT3可以直接结合到CX3CL1的启动子促进其转录激活,其促进作用依赖于CX3CL1启动子上的GAS位点。敲降STAT3可以抑制血管内皮细胞的迁移,过表达CX3CL1拮抗该抑制作用。总结得出,STAT3通过结合到CXCL1启动子促进CX3CL1转录与表达进而促进血管内皮的增殖与迁移。     

Shortening of microsatellite deoxy(CA) repeats involved in GL331-induced down-regulation of matrix metalloproteinase-9 gene expression

Matrix metalloproteinase-9 (MMP-9) associates with cancer cell invasion and metastasis. CL1-5 cells, a human lung adenocarcinoma cell line, expressed an elevated level of MMP-9 and exhibited a highly invasive and metastatic ability. By Matrigel assay and gelatinase zymography, the topoisomerase II poison GL331 was found to dose-dependently inhibit the invasiveness and the level of secreted MMP-9 of CL1-5 cells. Northern blot analysis indicated that cellular MMP-9 mRNA level was decreased after GL331 treatment. Furthermore, GL331-induced down-regulation of mmp-9 gene promoter was demonstrated by using a luciferase reporter gene driven by the -216 to -13 region of the mmp-9 gene promoter cloned from CL1-5 cells. By PCR amplification and gel electrophoresis, we found that GL331 caused shortening of the -216 to -13 region of the mmp-9 promoter. Direct sequencing analysis revealed that the number of d(CA) was reduced from 24 to 18 at the microsatellite d(CA) repeat region of the mmp-9 promoter. The CL1-5 cells transfected with the luciferase reporter containing 18 d(CA)s expressed only 53% of those when the reporter contained 24 d(CA)s. The promoter region of mmp-9 gene contains other positive regulatory elements, such as TRE and kappaB. We found that GL331 did not significantly influence the luciferase activity driven by TRE or kappaB. Taken together, these data suggested that GL331 inhibited MMP-9 mRNA expression at least partly through the selective induction of shortening of microsatellite d(CA) repeats. This is the first report that an anti-cancer agent can inhibit mmp-9 gene expression by inducing microsatellite DNA shortening.     

Pitfall of an internal control plasmid: response of Renilla luciferase (pRL-TK) plasmid to dihydrotestosterone and dexamethasone

The thymidine kinase promoter-Renilla luciferase reporter plasmid (pRL-TK) is commonly used as a control for transfection efficiency in the Dual-Luciferase Reporter Assay System. While investigating hormone response elements in the promoters of the androgen-dependent, epididymis-specific EP2 gene, we found that hormone treatment affected the luciferase activity of pRL-TK-transfected cells. In African Green Monkey Kidney (CV-1) cells, cotransfected transiently with a hormone-responsive promoter-firefly luciferase reporter plasmid and with pRL-TK, Renilla luciferase activity increased in response to dihydrotestosterone (DHT) and decreased in response to dexamethasone (DEX). When a thromboxane synthase promoter Renilla luciferase plasmid (pRL-TS) was used in place of pRL-TK, Renilla luciferase activity remained constant in CV-1 cells treated with DHT but decreased in CV-1 cells treated with DEX. In transfection studies, internal control plasmid expression in response to treatment must be carefully monitored to ensure proper interpretation of normalized results.     

Lipopolysaccharide stimulation of ERK1/2 increases TNF-alpha production via Egr-1

Lipopolysaccharide (LPS) is a potent activator of tumor necrosis factor-alpha (TNF-alpha) production by macrophages. LPS stimulates the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and increases TNF-alpha mRNA and protein accumulation in RAW 264.7 murine macrophages. However, the role of ERK1/2 activation in mediating LPS-stimulated TNF-alpha production is not well understood. Inhibition of ERK1/2 activation with PD-98059 or overexpression of dominant negative ERK1/2 decreased LPS-induced TNF-alpha mRNA quantity. LPS rapidly increased early growth response factor (Egr)-1 binding to the TNF-alpha promoter; this response was blunted in cells treated with PD-98059 or transfected with dominant-negative ERK1/2. Using a chloramphenicol acetyltransferase reporter gene linked to the Egr-1 promoter, we show that LPS increased Egr-1 promoter activity via an ERK1/2-dependent mechanism. These results delineate the role of ERK1/2 activation of Egr-1 activity in mediating LPS-induced increases in TNF-alpha mRNA expression in macrophages.     

启动子荧光素酶报告系统检测低浓度过氧化氢激活神经肽PACAP特异受体PAC1-R启动子的作用

垂体腺苷酸环化酶激活多肽（pituitary adenylate cyclase activating polypeptide,PACAP）特异受体PAC1-R (PACAP receptor 1)是神经系统疾病药物开发的重要靶点。为了研究其表达的生物学机制,本研究克隆了PAC1-R基因转录起始位点上游从-2 500到+26的2 526 bp启动子片段,构建PAC1-R启动子驱动的荧光素酶基因报告载体pGL3-PAC1-Rp,并确证PAC1-R启动子荧光素酶报告系统在小鼠脑神经瘤细胞Neuro-2a和人神经母细胞瘤细胞SH-SY5Y中工作正常。运用此PAC1-R启动子荧光素酶报告系统,首次发现低浓度过氧化氢（hydrogen peroxide,H2O2）有效激活PAC1-R启动子,此作用可被转录因子特化蛋白1（specificity protein 1,SP1）抑制剂光神霉素A（mithramycin A）所抑制,提示SP1参与介导H2O2对PAC1-R启动子的激活作用。生物信息学分析显示,PAC1-R启动子含有多个SP1结合位点。PAC1-R启动子的荧光素酶报告系统的构建为深入探索PAC1-R高表达的作用与机制奠定了基础,低浓度H2O2对PAC1-R启动子激活作用的发现有助于深入诠释低浓度活性氧的生理学作用。     

Celecoxib induces apoptosis by inhibiting the expression of survivin in HeLa cells

The effect of celecoxib, a cyclooxygenase-2 selective inhibitor, on a human cervical cancer cell line, HeLa cells, was examined. We found that celecoxib increased DNA ladder formation and the activity of caspase-3, indicating that celecoxib induced apoptosis in HeLa cells. Celecoxib suppressed the expression of an anti-apoptotic protein, survivin, in both protein and mRNA levels. The overexpression of survivin overrode caspase-3 activation induced by celecoxib. Subsequently, we performed luciferase reporter assay with the reporter vector containing human survivin promoter region and electrophoretic mobility shift assay and found that the -75 to -66 bp region relative to the initiating codon played an important role in celecoxib action to suppress survivin promoter activity. Our findings might provide a new insight into the anti-cancer effects of celecoxib.     

MicroRNA-181a regulates the activation of the NLRP3 inflammatory pathway by targeting MEK1 in THP-1 macrophages stimulated by ox-LDL

Atherosclerosis (AS) is a chronic inflammatory disease that is characterized by the deposition of lipids in the vascular wall and the formation of foam cells. Macrophages play a critical role in the development of this chronic inflammation. An increasing amount of research shows that microRNAs affect many steps of inflammation. The goal of our study was to investigate the regulatory effect of miR-181a on the NLRP3 inflammasome pathway and explore its possible mechanism. Compared with the control group, the expression of miR-181a was downregulated in the carotid tissue of AS group mice, while the expression of MEK1 and NLRP3-related proteins was upregulated significantly. In vitro, when THP-1 macrophages were stimulated with oxidized low-density lipoprotein (ox-LDL), the expression of miR-181a was decreased, the MEK/ERK/NF-κB inflammatory pathways were activated and the expression of NLRP3 inflammasome-related proteins was upregulated. Exogenous overexpression of miR-181a downregulated the activation of the MEK/ERK/NF-κB pathway and decreased the expression of NLRP3 inflammasome-related proteins (such as NLRP3, caspase-1, interleukin-18 [IL-18], IL-1β, etc). Exogenous miR-181a knockdown showed the opposite results to those of overexpression group. A luciferase reporter assay proved that miR-181a inhibited the expression of MEK1 by binding to its 3′-untranslated region. When we knocked down miR-181a and then treated cells with U0126 before ox-LDL stimulation, we found that U0126 reversed the increased activation of the MEK/ERK/NF-κB pathway and upregulation of NLRP3 inflammasome-related proteins (NLRP3, caspase-1, IL-18, IL-1β) that resulted from miR-181a knockdown. Our study suggests that miR-181a regulates the activation of the NLRP3 inflammatory pathway by altering the activity of the MEK/ERK/NF-κB pathway via targeting of MEK1.