Pro-caspase-3 overexpression sensitises ovarian cancer cells to proteasome inhibitors

The ubiquitin-proteasome pathway plays a critical role in the degradation of several proteins involved in the cell cycle. Dysregulation of this pathway leads to inhibition of cellular proliferation and the induction of apoptosis. Ubiquitination and its downstream consequences have been investigated intensively as targets for the development of drugs for tumour therapy. Here we have investigated the mechanism of apoptosis induced by the proteasome inhibitors MG-132, lactacystin and calpain inhibitor I (ALLN), in the HEK 293 cell line and the ovarian cancer cell lines SKOV3 and OVCAR3. We have found strong caspase-3-like and caspase-6-like activation upon treatment of HEK 293 cells with MG-132. Using a tricistronic expression vector based on a tetracycline-responsive system we generated stable SKOV3 nd OVCAR3 cell lines with inducible expression of pro-caspase-3. Induction of pro-caspase-3 expression in normally growing cells does not induce apoptosis. However, in the presence of the proteasome inhibitors MG-132, lactacystin or ALLN we found that cells overexpressing pro-caspase-3 are rapidly targeted for apoptosis. Our results demonstrate that pro-caspase-3 can sensitise ovarian cancer cells to proteasome inhibitor-induced apoptosis, and a combination of these approaches might be exploited for therapy of ovarian and other cancers.     

Free radical-mediated transgene inactivation of macrophages by endotoxin

Endotoxin, the lipopolysaccharide component of gram-negative bacteria, is a common contaminant of plasmid DNA preparations. The present study investigated the effect of endotoxin on gene transfection efficiency and the role of reactive oxygen species (ROS) in this process. Gene transfection studies were performed in various cell types with cytomegalovirus-luciferase as a reporter plasmid and cationic liposome as a transfecting agent. The presence of endotoxin in plasmid DNA preparations severely limited transgene expression in macrophages but had little or no effect in other cell types tested. This decreased transfection was dependent on ROS-mediated cellular toxicity induced by endotoxin. Neutralizing the endotoxin by the addition of polymyxin B effectively increased transfection efficiency and reduced toxicity. Electron spin resonance studies confirmed the formation of ROS in endotoxin-treated cells and their inhibition by free radical scavengers. The ROS scavenger N-t-butyl-alpha-phenylnitrone, the H(2)O(2) scavenger catalase, and the.OH scavenger sodium formate effectively inhibited endotoxin-induced effects, whereas the O(2)(-) scavenger superoxide dismutase had lesser effects. These results indicate that multiple oxidative species are involved in the transfection inactivation process and that.OH formed by H(2)O(2)-dependent, metal-catalyzed Fenton reaction play a major role in this process.     

Use of a quaternary ammonium detergent in liposome mediated DNA transfection of mouse L-cells

Sonicated liposomes composed of dioleoylphosphatidylethanolamine (DOPE) and a quaternary ammonium detergent (dodecyl-, tetradecyl-, or cetyl-trimethylammonium bromide) mediates functional transfer of pSV2 CAT plasmid DNA to mouse L929 fibroblasts. Successful transfection was determined by assaying for chloramphenicol acetyltransferase activity in cell lysates collected 40 h after exposure to the lipid-DNA complexes. Liposomes prepared with the quaternary ammonium detergents were less toxic than the free detergents at the same concentrations and were more efficient in their delivery of the plasmid DNA to the cells. Analysis of the three detergents in combination with the lipid showed that cetyltrimethylammonium bromide was least toxic to the cells. This detergent, at a minimal concentration of 20 mol% in DOPE, allowed for stable liposome preparations and efficient transfection. Optimal efficiency of transfection occurred with 30 micrograms of DNA. Further increases in the DNA concentration caused a decrease in the transfection efficiency, perhaps due to charge repulsions between the liposomes now saturated with negatively charged DNA and the negatively charged cell surface. The transfection activity of the liposome was limited by its cytotoxicity at high liposome concentrations. These results are compared with that of the Lipofectin, another positively charged liposome preparation which is commercially available. Although the overall transfection activity of the liposome containing the quaternary ammonium detergent is somewhat lower than that of the Lipofectin, it may serve as an inexpensive and convenient alternative.     

I型单纯疱疹病毒胸苷激酶真核表达载体的构建及其表达鉴定

为构建单纯疱疹病毒I型胸苷激酶(HSV1TK)的真核表达载体pcDNA3.1-EGFP/HSV1TK,鉴定其在真核细胞中的表达和功能.以pORF-HSV1TK为模板,PCR扩增的目的基因HSV1TK片段与pMD18-T载体相连接构建重组克隆pMD18-T/HSV1TK.再双酶切出HSV1TK片段,插入pcDNA3.1-EGFP多克隆位点,构建pcDNA3.1-EGFP/ HSV1TK真核表达载体并进行酶切、测序鉴定[1].分别用荧光显微镜观察和RT-PCR方法检测脂质体介导pcDNA3.1-EGFP/ HSV1TK在卵巢癌细胞SKOV3的表达;分别用MTT法和光镜检测胸苷激酶/丙氧鸟苷(HSV1TK/GCV)系统对SKOV3体外杀伤作用及旁观者效应.结果表明,重组载体酶切鉴定结果与预期结果一致,基因序列与GenBank上报道的HSV1TK基因序列完全一致.荧光显微镜观察转染后的细胞发出绿色荧光;RT-PCR结果表明HSV1TK基因能在SKOV3内有效表达.MTT和光镜结果显示转染HSV1TK基因的SKOV3细胞,加入前体药物丙氧鸟苷(GCV)处理后对其有明显的杀伤作用和旁观者效应.成功构建的真核表达载体pcDNA3.1-EGFP/ HSV1TK能在SKOV3细胞中稳定表达,且HSV1TK对卵巢癌细胞株SKOV3体外有强大的杀伤作用和旁观者效应.     

Cutting edge: repurification of lipopolysaccharide eliminates signaling through both human and murine toll-like receptor 2

Toll-like receptor (TLR) 2 has recently been associated with cellular responses to numerous microbial products, including LPS and bacterial lipoproteins. However, many preparations of LPS contain low concentrations of highly bioactive contaminants described previously as "endotoxin protein," suggesting that these contaminants could be responsible for the TLR2-mediated signaling observed upon LPS stimulation. To test this hypothesis, commercial preparations of LPS were subjected to a modified phenol re-extraction protocol to eliminate endotoxin protein. While it did not influence the ability to stimulate cells from wild-type mice, repurification eliminated the ability of LPS to activate cells from C3H/HeJ (Lpsd) mice. Additionally, only cell lines transfected with human TLR4, but not human or murine TLR2, acquired responsiveness to both re-extracted LPS and to a protein-free, synthetic preparation of lipid A. These results suggest that neither human nor murine TLR2 plays a role in LPS signaling in the absence of contaminating endotoxin protein.     

Transfection property of a new cholesterol-based cationic lipid containing tri-2-hydroxyethylamine as gene delivery vehicle

A novel cholesterol-based cationic lipid containing a tri-2- hydroxyethylamine head group and ether linker (Chol- THEA) was synthesized and examined as a potent gene delivery vehicle. In the preparation of cationic liposome, the addition of DOPE as helper lipid significantly increased the transfection efficiency. To find the optimum transfection efficiency, we screened various weight ratios of DOPE and liposome/DNA (N/P). The best transfection efficiency was found at the Chol-THEA:DOPE weight ratio of 1:1 and N/P weight ratio of 10~15. Most of the plasmid DNA was retarded by this liposome at the optimum N/P weight ratio of 10. The transfection efficiency of Chol-THEA liposome was compared with DOTAP, Lipofectamine, and DMRIE-C using the luciferase assay and GFP expression. Chol-THEA liposome with low toxicity had better or similar potency of gene delivery compared with commercial liposomes in COS-7, Huh-7, and MCF-7 cells. Therefore, Chol-THEA could be a useful non-viral vector for gene delivery.     

Fate and biological activity of exogenous DNA sequences during serial transfections in NIH/3T3 cells

The efficiency and accuracy of serial transfections in NIH/3T3 fibroblasts were investigated with two plasmids carrying a dominant gene. One plasmid carried the activated ras oncogene of human origin inducing morphological alteration and the oncogenic phenotype of NIH/3T3 cells. The second plasmid carried the bacterial neoR gene conferring resistance to the neomycine analogue G 418. We observed no correlation between the presence of biologically active DNAs in primary transfectants and the capacities of these DNAs to transmit the exogenous information in a second cycle of transfection. Cellular DNA of only two of 13 ras and only 1 of 3 neoR transformants could transform NIH/3T3 in a second cycle of transfections. About half of secondary transfectants, derived from those primary transfectants which did transmit the exogenous DNA, contained apparently complete exogenous sequences and transmitted it efficiently and even with the original site of integration in the host DNA in a third cycle of transfection. Exogenous DNA sequences were amplified in the majority of secondary transfectants but did not enhance biological activity in a third cycle of transfer. The exogenous DNA was found to undergo rearrangements in oncogenic transformants propagated in cell culture.     

上调hMLH1基因表达对卵巢癌药物敏感性的影响

构建携带错配修复基因hMLH1编码序列全长的真核表达质粒pCAN—hMLHl,并探讨其对卵巢癌细胞顺铂耐药的逆转作用。应用基因重组技术将pET28-hMLHl中的目的基因hMLHl定向克隆到真核表达载体pCAN,经酶切及测序鉴定：分别将pCAN—hMLHl和空质粒pCAN转染进卵巢癌耐药细胞SKOV3／DDP,同时以对顺铂敏感的sKOV3细胞和未转染的SKOV3／DDP细胞作为对照：应用RT-PCR和Westemblo凇测转染前后细胞内hMLHlmRNA和蛋白的表达变4Jc;四甲基偶氮唑蓝（MTT）比色法检测转染前后sKOv3／DDP细胞对顺铂敏感性的变化;Hoechst染色检测转染前后细胞的凋亡。结果提示：pCAN—hMLHl重组质粒经酶切及测序鉴定,表明真核表达质粒构建正确;采用脂质体法转染sKOv3／DDP细胞后,RT-PCR和Westernblot检测到耐药细胞内hMLHl的表达增强：MTT结果显示转染重组质粒后sKOv3／DDP细胞对顺铂的敏感性显著增加;Hoechst染色观察到转染后耐药细胞的凋亡明显增强。该研究成功构建了pCAN．hMLHl重组质粒,在sKOV3／DDP细胞中进行表达,并能增强耐药细胞对顺铂的敏感性,促进耐药细胞的凋亡。     

Electroporation-mediated transfection of mammalian cells with crude plasmid DNA preparations

We designed a simple and reproducible electroporation-mediated transfection procedure with which to screen mammalian expression vector-constructed cDNA libraries. Using a specific chamber composed of five parallel electrodes, the recipient cells can be electroporated separately with 40 plasmid DNA preparations in a single experiment. Over 300 crude plasmids prepared from E. coli (DH-5) carrying a pcD2neo-vector-derived cDNA library were tested. The efficiency of stable transfection by electroporation with crude plasmid DNA preparations was 10-times higher than with the CsCl-purified plasmid DNA. When the crude plasmids were digested with RNase, the efficiency of stable transfection markedly decreased, indicating that the contaminating bacterial RNA in the crude plasmid preparations has a strong carrier effect during the electroporation. Even when salmon sperm DNA or genomic DNA from the recipient cells was used as the carrier of the purified plasmid, the efficiency was not higher than that using the crude preparations. This procedure is useful not only for screening a number of cDNAs but also for routinely introducing biologically active foreign genes into cultured mammalian cells.     

pH敏脂质体对反义寡核苷酸抗流感病毒活性的影响

为了研究具有临床应用前景的 Ａ Ｓ Ｏ Ｄ Ｎ 脂质体转运系统,以临床药用大豆磷脂为主要原料制备了ｐ Ｈ 敏脂质体,并测定了脂质体体外转染活性、ｐ Ｈ 敏特性、细胞毒性和对 Ａ Ｓ Ｏ Ｄ Ｎ 抗流感病毒活性的影响 结果发现,批号为 ９８０５１９０３,９８０５１１０２ 和 ９８０５１２０２ 的脂质体具有较高转染活性,但只有ｌｉｐｏｆｅｃｔｉｎ 转染活性的 １／５０～１／１００当质粒／脂质体（ Ｗ ／ Ｗ ）为 １∶４～１∶８,转染时间为 ３～５ ｈ,质粒量为 ０５ μｇ,转染后 ２４～４８ ｈ 内检测时转染活性最高 脂质体 ９８０５１２０２ 表现明显 ｐ Ｈ值依赖溶解红细胞膜特性,而脂质体 ９８０５１１０２ 和 ９８０５１９０３ 的 ｐ Ｈ 敏特性不明显 脂质体细胞毒性明显降低,如 ９８０５１９０３、９８０５１１０２ 和 ９８０５１２０２ 的毒性分别是 ｌｉｐｏｆｅｃｔｉｎ 毒性的 １／１６、１／８ 和 １／４ｐ Ｈ 敏脂质体 ９８０５１２０２ 具有促进 Ａ Ｓ Ｏ Ｄ Ｎ 抗流感病毒作用,当 Ａ Ｓ Ｏ Ｄ Ｎ 浓度为 ０２ μｍ ｏｌ／ Ｌ 时,ｐ Ｈ 敏脂质体 ９８０５１２０２ 使其抗病毒活性提高 ５ 倍,但 Ａ Ｓ Ｏ Ｄ Ｎ 浓度较高时ｐ Ｈ 敏脂质体对 Ａ Ｓ Ｏ Ｄ Ｎ抗     

Epigallocatechin-3-gallate delivers hydrogen peroxide to induce death of ovarian cancer cells and enhances their cisplatin susceptibility

The green tea polyphenol epigallocatechin-3-gallate (EGCG) has cancer chemopreventive properties against various types of cancers. The compound is known to attack various targets in transformed cells. In this report, we examined the action of EGCG on ovarian cancer cells. Eight ovarian cancer cell lines were tested (SKOV3, CAOV3, OVCAR3, OVCAR10, A2780, CP70, C30, and C200) and showed IC50s for EGCG at the micromolar range, including ones that are resistant to the chemotherapeutic drug cisplatin. The ovarian cancer cells were sensitive to H2O2 at similar concentrations, and EGCG treatment led to enhanced intracellular H2O2. Neutralization with pyruvate, a scavenger of H2O2, suggests that the toxicity of EGCG may be mediated by oxidative stress from the free radical. Addition of Tempol, a superoxide dismutase mimetic, demonstrates that H2O2 might be generated endogenously from superoxide. The toxicity of cisplatin and the development of cisplatin resistance are major obstacles in treatment of ovarian cancer. We found that addition of EGCG amplified the toxicity of cisplatin. EGCG increased cisplatin potency by three to six-fold in SKOV3, CAOV3, and C200 cells, the latter being a cell line induced to have several hundred fold resistant to cisplatin above the parental line. Our findings suggest that EGCG may accentuate oxidative stress to inhibit growth of ovarian cancer cells and sensitize them to cisplatin.     

Mechanism of taxol-induced apoptosis in human SKOV3 ovarian carcinoma cells

Taxol is extensively used clinically for chemotherapy of patients with ovarian, breast, and lung cancer. Although taxol induces apoptosis of cancer cells, its exact mechanism of action is not yet known. To determine the mechanism of action of taxol in ovarian cancer, we tested the effects of the drug, on the human ovarian carcinoma cell line, SKOV3. We observed that taxol-induced apoptosis of these cells by phosphatidylserine (PS) externalization and DNA fragmentation. While treatment of cells with taxol resulted in bcl-2 phosphorylation and mitochondrial depolarization, cytochrome c was not released and pro-caspase-3 was not activated. Treatment of SKOV3 cells with taxol, however, resulted in the translocation of AIF from the mitochondria to the nucleus via the cytosol. Taken together, these findings suggest that in SKOV3 cells, taxol induces caspase-independent AIF-dependent apoptosis.     

小豆蔻明调控自噬抑制卵巢癌SKOV3细胞增殖的研究

目的：卵巢癌为女性常见病,死亡率高,分子靶向治疗药物较少,研发高效低毒的靶向新药意义重大。细胞自噬（autophagy）维持着细胞内稳态和生长,是抗癌药物作用的关键靶部位。本课题旨在明确小豆蔻明（Cardamonin,CAR）调控自噬对卵巢癌SKOV3细胞增殖的影响。方法：体外培养卵巢癌SKOV3细胞,不同药物分组处理,荧光显微镜下观察单黄酰戊二胺（MDC）染色后细胞自噬囊泡,WesternBlot法检测细胞自噬相关蛋白LC3的表达,四氮唑蓝（MTT）法观察SKOV3细胞增殖情况,流式细胞术检测SKOV3细胞凋亡的变化。结果：自噬抑制剂3-MA显著性降低SKOV3细胞内MDC染色的荧光颗粒数目、LC3II蛋白表达,抑制细胞增殖;而CAR（高、中剂量）、雷帕霉素和AZD8055与3-MA联用后细胞内MDC荧光颗粒数目增多、LC3II蛋白表达增加、细胞增殖抑制率及凋亡率明显升高;且高剂量CAR（10^-6mol·L^-1）的作用比低剂量CAR（10^-6mol·L^-1）明显。结论：CAR能够抑制SKOV3细胞增殖,诱导细胞自噬,促进细胞凋亡。CAR有望成为卵巢癌药物治疗的先导化合物。本研究为进一步研发此类化合物提供了实验依据及一定的理论基础。     

2-(4-Methylphenyl)-1,3-selenazol-4-one induces apoptosis by different mechanisms in SKOV3 and HL 60 cells

We examined the ability of the synthetic selenium compound, 2-(4-methylphenyl)-1,3-selenazol-4-one (hereafter designated 3a), to induce apoptosis in a human ovarian cancer cell line (SKOV3) and a human leukemia cell line (HL-60). Flow cytometry showed that 3a treatment induced apoptosis in both cell lines to degrees comparable to that of the positive control, paclitaxel. Apoptosis was measured by PS externalization, DNA fragmentation and decreased mitochondrial membrane potential (MMP). However, analysis of the mechanism of action revealed differences between the responses of the two cell lines. Treatment with 3a arrested the cell cycle and induced caspase-3 activation in HL-60 cells, but not in SKOV3 cells. In contrast, 3a treatment induced apoptosis through translocation of AIF, a novel pro-apoptotic protein, in SKOV3 cells, but not in HL-60 cells. Collectively, our data demonstrated that 3a induced apoptosis in both cell lines, but via different action mechanisms.     

Gene transfection efficiency of tracheal epithelial cells by DC-chol-DOPE/DNA complexes.

We evaluated the transfection efficiency of five different cationic liposome/plasmid DNA complexes, during the in vitro gene transfer into human epithelial tracheal cell lines. A dramatic correlation between the transfection efficiency and the charge ratio (positive charge of liposome to negative charge of DNA) has been found. DC-Chol-DOPE was found to be the most effective liposome formulation. Therefore, a morphological and structural analysis of DC-Chol-DOPE liposomes and DC-Chol-DOPE/DNA complexes, has been performed by transmission electron microscopy (TEM) and by confocal laser scanning microscopy (CLSM), respectively. The process of interaction between DC-Chol-DOPE/DNA complexes and human epithelial tracheal cells has been studied by CLSM. These results raise some issues for in vivo gene therapy.     

miR-335靶向Rho相关卷曲螺旋形成蛋白激酶1对卵巢癌细胞增殖的影响

目的: 探讨miR-335 靶向Rho相关卷曲螺旋形成蛋白激酶1(rho associated coiled-coil forming protein kinase 1,ROCK1)对卵巢癌细胞系SKOV3增殖的调控作用。方法:(1)选取卵巢癌细胞系SKOV3及人正常卵巢上皮细胞系IOSE80,采用RT-PCR检测各组细胞中miR-335表达;采用Western blot检测各组细胞中ROCK1蛋白表达;(2)选取卵巢癌细胞系SKOV3,分别转染miR-335 mimic及mimic control,采用RT-PCR检测细胞中miR-335表达;(3)选取卵巢癌细胞系SKOV3,将SKOV3荧光素酶报告载体与miR-335 mimic共转染,采用荧光素酶活性实验验证miR-335对SKOV3的靶向作用;(4)选取卵巢癌细胞系SKOV3,分为3组,即SKOV3组(转染mimic control)、miR-335 mimic组(转染miR-335 mimic)及miR-335 mimic+ROCK1组(共转染miR-335 mimic+ROCK1),采用MTT法检测各组细胞增殖活性,采用Western blot检测各组细胞中ROCK1蛋白表达,采用RT-PCR检测细胞中Cyclin D1表达。结果: (1)RT-PCR结果显示,卵巢癌细胞SKOV3中miR-335表达显著低于人正常卵巢上皮细胞IOSE80(P < 0.05);Western blot结果显示,卵巢癌细胞SKOV3中ROCK1蛋白表达显著高于人正常卵巢上皮细胞IOSE80(P < 0.05);(2)RT-PCR结果显示,转染miR-335 mimic可使卵巢癌细胞SKOV3中miR-335表达上调,与转染mimic control相比较差异具有统计学意义(P < 0.05);(3)双荧光素酶活性检测结果显示,miR-335 mimic可显著抑制野生型ROCK1-Wt报告载体的荧光素酶活性,但对突变型ROCK1-Mut报告载体的荧光素酶活性并无显著抑制作用;(4)转染miR-335mimic后,卵巢癌细胞SKOV3增殖活性及Cyclin D1表达较阴性对照组显著降低(P < 0.05);而转染miR-335 mimic+ROCK1后,卵巢癌细胞SKOV3增殖活性及Cyclin D1表达较单纯转染miR-335 mimic组显著提高(P < 0.05),但仍显著低于阴性对照组(P < 0.05)。Western blot检测结果显示,转染miR-335mimic后,卵巢癌细胞SKOV3中ROCK1蛋白表达较阴性对照组显著降低(P < 0.05);而转染miR-335 mimic+ROCK1后,ROCK1蛋白表达较单纯转染miR-335mimic组显著增高(P < 0.05),且显著高于阴性对照组(P < 0.05)。结论: miR-335可通过靶向ROCK1抑制卵巢癌细胞系SKOV3增殖。     

Roflumilast enhances cisplatin‐sensitivity and reverses cisplatin‐resistance of ovarian cancer cells via cAMP/PKA/CREB‐FtMt signalling axis

Objective

We previously demonstrated the roflumilast inhibited cell proliferation and increased cell apoptosis in ovarian cancer. In this study, we aimed to investigate the roles of roflumilast in development of cisplatin (DDP)‐sensitive and ‐resistant ovarian cancer.

Methods

OVCAR3 and SKOV3 were selected and the corresponding DDP‐resistant cells were constructed. Cell viability, proliferation, apoptosis, cycle were performed. Expression cAMP, PKA, CREB, phosphorylation of CREB and FtMt were detected. The roles of roflumilast in development of DDP‐sensitive and ‐resistant ovarian cancer were confirmed by xenograft model.

Results

Roflumilast + DDP inhibited cell proliferation, and induced cell apoptosis and G0/G1 arrest in OVCAR3 and SKOV3 cells, roflumilast induced expression of FtMt, the activity of cAMP and PKA and phosphorylation of CREB in ovarian cancer cells and the above‐effect were inhibited by H89. Downregulation of CREB inhibited the roflumilast‐increased DDP sensitivity of ovarian cancer cells, and the roflumilast‐induced FtMt expression and phosphorylation of CREB. Also, roflumilast reversed cisplatin‐resistance, and induced expression of FtMt and activation of cAMP/PKA/CREB in DDP‐resistant ovarian cancer cells. Similarly, treated with H89 or downregulation of CREB inhibited the changes induced by roflumilast. In vivo, roflumilast inhibited the development of SKOV3 or SKOV3‐DDP‐R xenograft models.

Conclusions

Roflumilast enhanced DDP sensitivity and reversed the DDP resistance of ovarian cancer cells via activation of cAMP/PKA/CREB pathway and upregulation of the downstream FtMt expression, which has great promise in clinical treatment.

     

Induction of neutrophil apoptosis and secondary necrosis during endotoxin-induced pulmonary inflammation in mice

The present study investigated the relationship between apoptotic and necrotic cell death and their role in pulmonary inflammatory response to endotoxin. Pulmonary administration of lipopolysaccharide (LPS) caused a rapid increase in the levels of pro-inflammatory cytokine TNF-alpha and inflammatory cell influx in the bronchoalveolar lavage (BAL) fluids. Control mice showed only resident alveolar macrophages with no apoptosis, whereas LPS-treated mice showed clear apoptosis of BAL cells. Microscopic studies confirmed the presence of apoptotic neutrophils and macrophages ingesting apoptotic bodies. The number of apoptotic neutrophils increased concomitantly with the increase in neutrophil influx which peaked 1 day after the treatment. However, necrosis was not detected at this early time, but increased subsequently and peaked at day 3. The levels of necrosis and apoptosis were both elevated and prolonged at high LPS doses. Treatment of mice with phosphatidylserine (PS)-containing liposome, known to inhibit macrophage phagocytosis of apoptotic cells, increased the level of apoptosis and necrosis caused by LPS, whereas control non-PS liposome or saline treatment had no effects. We conclude that necrosis occurs secondary to apoptosis in LPS-treated lung model and that this development is not the result of direct insult by LPS. Instead, our results and previous studies suggest that inefficient clearance of apoptotic cells by macrophages contributes, at least in part, to the levels of apoptosis and necrosis induced by LPS. Because necrosis is associated with cell damage and release of histotoxic contents, this development is likely to play a role in determining the severity and duration of lung toxicity induced by endotoxin.     

RNA干扰PLCε诱导人膀胱癌BIU-87细胞凋亡的实验研究

目的探讨以RNA干扰沉默人源磷脂酶Ce(phospholipase Cepsilon,PLCε)基因表达后诱导人膀胱癌细胞株BIU-87细胞凋亡的作用和机制。方法脂质体介导重组阳性质粒pGenesil-PLCε(以下简称P)和阴性质粒pGenesil-NP(以下简称NP)转染BIU-87细胞48h后,用RT-PCR和Western blot检测转染前后PLCεmRNA和蛋白表达,流式细胞术检测细胞周期和细胞凋亡率,电镜观察细胞形态改变。结果转染P质粒后可明显抑制PLCεmRNA和蛋白表达水平,抑制率分别为78.7%和76.6%;流式细胞术显示P质粒转染组细胞周期发生改变呈明显G0/G1期阻滞,并出现亚二倍体凋亡峰,细胞凋亡率增加(P0.05);电镜观察P质粒转染组细胞可见凋亡小体。结论:RNA干扰沉默PLCε基因表达可诱导膀胱癌BIU-87细胞凋亡,其作用机制与细胞周期分布的改变有关。     

The role of helper lipids in cationic liposome-mediated gene transfer.

In the procedure for cationic liposome-mediated transfection, the cationic lipid is usually mixed with a "helper lipid" to increase its transfection potency. The importance of helper lipids, including dioleoylphosphatidylcholine (DOPC) and phosphatidylethanolamine (dioleoyl PE), DO was examined. Freeze-fracture electron microscopy of DNA:cationic complexes containing the pSV-beta-GAL plasmid DNA, the cationic lipid dioleoyl trimethylammonium propane, and these helper lipids showed that the most efficient mixtures were aggregates of ensheathed DNA and fused liposomes. PE-containing complexes aggregated rapidly when added to culture media containing polyanions, whereas PC-containing complexes did not. However, more granules of PC-containing complexes were formed on cell surfaces after the complexes were added to Chinese hamster ovary (CHO) cells in transfection media. Pronase treatment inhibited transfection, whereas dilute poly-L-lysine enhanced transfection, indicating that the attachment of DNA:liposome complexes to cell surfaces was mediated by electrostatic interaction. Fluorescence spectroscopy studies confirmed that more PC-containing complexes than PE-containing complexes were associated with CHO cells, and that more PC-containing complexes were located in a low pH environment (likely to be within endosomes) with time. Cytochalasin-B had a stronger inhibitory effect on PC-containing liposome-mediated than on PE-containing liposome-mediated transfection. Confocal microscopic recording of the fluorescently label lipid and DNA uptake process indicated that many granules of DNA:cationic liposome complexes were internalized as a whole, whereas some DNA aggregates were left out on the cell surfaces after liposomes of the complexes fused with the plasma membranes. For CHO cells, endocytosis seems to be the main uptake pathway of DNA:cationic liposome complexes. More PC-containing granules than PE-containing granules were formed on cell surfaces by cytoskeleton-directed membrane motion, after their respective DNA:liposome complexes attached to cell surfaces by electrostatic means. Formation of granules on the cell surface facilitated and/or triggered endocytosis. Fusion between cationic liposomes and the cell membrane played a secondary role in determining transfection efficiency.