Regulation of Vinca alkaloid-induced apoptosis by NF-kappaB/IkappaB pathway in human tumor cells

Antimicrotubule Vinca alkaloids, such as vinblastine and vincristine, interfere with the dynamics of microtubules and have shown significant cell killing activity in a variety of tumor cells through induction of apoptosis. The mechanism by which Vinca alkaloids induce apoptosis is not entirely clear. In this study, we found that glucocorticoids inhibit Vinca alkaloid-induced apoptosis without affecting G(2)-M arrest in human breast cancer BCap37 cells and human epidermoid tumor KB cells, suggesting that Vinca alkaloid-induced apoptosis may occur via a pathway independent of cell cycle arrest. Further analyses indicated that Vinca alkaloids cause significant degradation of IkappaBalpha, which in turn results in nuclear factor-kappaB (NF-kappaB) activation. Transfection of antisense IkappaBalpha in BCap37 cells sensitizes Vinca alkaloid-induced apoptosis. Moreover, in vitro kinase assays show that the activity of IkappaB kinase (IKK) was activated by Vinca alkaloids and was not affected by glucocorticoids. Stable transfection of dominant-negative deletional mutant IkappaBalpha, which is insensitive to IKK-mediated phosphorylation and degradation, resulted in the inhibition of Vinca alkaloid-induced NF-kappaB activation and reduced sensitivity of tumor cells to Vinca alkaloid-induced apoptosis. These findings suggest that the NF-kappaB/IkappaB signaling pathway may contribute to the mediation of Vinca alkaloid-induced apoptosis in human tumor cells.     

Inhibition of apoptosis induced by ischemia-reperfusion prevents inflammation

Ischemia followed by reperfusion leads to severe organ injury and dysfunction. Inflammation is considered to be the most important cause of tissue injury in organs subjected to ischemia. The mechanism that triggers inflammation and organ injury after ischemia remains to be elucidated, although different causes have been postulated. We investigated the role of apoptosis in the induction of inflammation and organ damage after renal ischemia. Using a murine model, we demonstrate a relationship between apoptosis and subsequent inflammation. At the time of reperfusion, administration of the antiapoptotic agents IGF-1 and ZVAD-fmk (a caspase inactivator) prevented the early onset of not only renal apoptosis, but also inflammation and tissue injury. Conversely, when the antiapoptotic agents were administered after onset of apoptosis, these protective effects were completely abrogated. The presence of apoptosis was directly correlated with posttranslational processing of the endothelial monocyte-activating polypeptide II (EMAP-II), which may explain apoptosis-induced influx and sequestration of leukocytes in the reperfused kidney. These results strongly suggest that apoptosis is a crucial event that can initiate reperfusion-induced inflammation and subsequent tissue injury. The newly described pathophysiological insights provide important opportunities to effectively prevent clinical manifestations of reperfusion injury in the kidney, and potentially in other organs.     

Neurotrophin-3 production promotes human neuroblastoma cell survival by inhibiting TrkC-induced apoptosis

Tropomyosin-related kinase receptor C (TrkC) is a neurotrophin receptor with tyrosine kinase activity that was expected to be oncogenic. However, it has several characteristics of a tumor suppressor: its expression in tumors has often been associated with good prognosis; and it was recently demonstrated to be a dependence receptor, transducing different positive signals in the presence of ligand but inducing apoptosis in the absence of ligand. Here we show that the TrkC ligand neurotrophin-3 (NT-3) is upregulated in a large fraction of aggressive human neuroblastomas (NBs) and that it blocks TrkC-induced apoptosis of human NB cell lines, consistent with the idea that TrkC is a dependence receptor. Functionally, both siRNA knockdown of NT-3 expression and incubation with a TrkC-specific blocking antibody triggered apoptosis in human NB cell lines. Importantly, disruption of the NT-3 autocrine loop in malignant human neuroblasts triggered in vitro NB cell death and inhibited tumor growth and metastasis in both a chick and a mouse xenograft model. Thus, we believe that our data suggest that NT-3/TrkC disruption is a putative alternative targeted therapeutic strategy for the treatment of NB.     

NF-kappaB and apoptosis in colorectal tumourigenesis

BACKGROUND: Nuclear factor-kappaB (NF-kappaB) may play an important role in colorectal tumourigenesis, controlling cell cycle and apoptosis gene expression. In addition, imbalances between cell proliferation and cell death are thought to underlie neoplastic development. The aims of this study were to investigate apoptosis and expression of several apoptosis-related proteins, and to determine correlations with colorectal tumour progression. MATERIALS AND METHODS: Apoptosis was evaluated by the TUNEL assay in 48 patient samples, including adenomas, adenocarcinomas and adjacent normal mucosas. Immunohistochemistry was performed for Bcl-2 and NF-kappaB. Expression levels of p53, Bax and IkappaB proteins were determined by immunoblotting. Cultured human colon cancer cells were used to evaluate NF-kappaB expression and nuclear translocation by immunocytochemistry and immunoblotting. RESULTS:Apoptosis and NF-kappaB immunoreactivity were significantly higher in tumour tissue compared with normal mucosa (P < 0.01), increasing in association with histological tumour progression (P < 0.01). Bcl-2 was consistently higher in normal mucosa (P < 0.01) and inversely correlated with the percentage of apoptosis (P < 0.01). Phosphorylated p53 and Bax levels were similar in tumour tissue and normal mucosa; however, the NF-kappaB inhibitor, IkappaB, tended to decrease in tumours. In vitro, nuclear translocation of NF-kappaB was greater in proliferative than in resting phases of colon cancer cells. CONCLUSIONS: NF-kappaB expression and apoptosis are increased from adenoma to poorly differentiated adenocarcinoma tissues. Apoptosis is correlated with suppression of Bcl-2 expression, but appears to proceed through a p53- and Bax-independent pathway. Activation of NF-kappaB may play an important role in colorectal tumour progression.     

Inhibition of platelet aggregation and thromboxane production by low concentrations of aspirin in vitro

1. The aspirin concentrations previously reported to inhibit platelet aggregation in vitro (40-500 mumol/l) are much greater than those required in vivo in man (5 mumol/l). 2. Human platelet-rich plasma was incubated with buffer or various aspirin concentrations at 37 degrees C for up to 4.5 h. Platelet aggregation and thromboxane generation were measured in response to collagen (0.4-6.3 micrograms/ml) and adenosine 5'-pyrophosphate (0.5-4 mumol/l). 3. The concentration of aspirin needed to inhibit platelet aggregation in response to a critical concentration of aggregating agent (lowest concentration to cause greater than 50% aggregation) was lower than that required for higher concentrations of aggregating agent. 4. With more prolonged incubation times with aspirin, lower concentrations of aspirin inhibited platelet aggregation. 5. Inhibition of platelet aggregation and thromboxane formation by 10 mumol/l aspirin was maximal by 90 min. There was progressive inhibition by 3 mumol/l aspirin during incubation for 270 min. By the end of this time there was also significant inhibition by 1 mumol/l aspirin. 6. The apparent discrepancy between inhibitory aspirin concentrations in vivo and those observed in vitro in previous studies appears to have been resolved by extending the incubation time of platelets with low aspirin concentrations, thus mimicking the conditions in vivo.     

黄芪对N-甲基-N-亚硝脲诱导大鼠光感受器细胞凋亡的预防途径

背景：视网膜色素变性是非炎症性、双侧进行性的视网膜变性，其特征是光感受器细胞因发生凋亡而丢失，最终导致失明。中药黄芪在阻止该病的进程上显示出了良好的前景。 目的：观察黄芪对N-甲基-N-亚硝脲致SD大鼠视网膜损伤的保护作用。 设计：随机对照动物实验。 单位：新乡医学院药学院。 材料：实验于2004—03／12在中山大学中山眼科中心药理实验室完成。雌性SD大鼠114只，由中山大学中山医学院动物中心提供，N-甲基-N-亚硝脲为美国Sigma公司产品，黄芪注射液为成都地奥九泓制药厂生产（生产批号：国药准字Z99060535，2mL／支，主要成分为黄芪）。 方法：选用雌性SD大鼠114只，30只用于视网膜层形态学分析；30只用于细胞凋亡检测；54只用于胞核内核因子κBp65活性的检测。采用抽签法随机分组，每组6只。于大鼠生后47d，分别经腹腔注射不同剂量的黄芪（2．5．5和10g／kg），1次／d，除对照组外，其余组的大鼠同时于生后50d腹腔注射N-甲基-N-亚硝脲60mg／kg。在N-甲基-N-亚硝脲处理不同时间后处死动物，取眼球，视网膜形态学分析测量周边视网膜的总厚度，TUNEL试剂盒检测光感受器细胞凋亡，转录因子试剂盒分析核因子κBp65的活性。 主要观察指标：各组视网膜厚度、凋亡指数和胞核内核因子κBp65的活性比较。结果：黄芪可剂量依赖性地显著增加周边视网膜总厚度和降低N-甲基-N-亚硝脲引起的光感受器细胞凋亡指数。黄芪注射液10g／kg还可时间依赖性地上调视网膜细胞胞核内核因子κBp65的活性。但其对N-甲基-N-亚硝脲引起的中心视网膜损伤无明显的保护作用。 结论：黄芪通过上调视网膜细胞胞核内核因子KBp65的活性，抑制光感受器细胞凋亡，从而部分地保护N-甲基-N-亚硝脲引起的视网膜损伤。     

黄芪对N-甲基-N-亚硝脲诱导大鼠光感受器细胞凋亡的预防途径

背景:视网膜色素变性是非炎症性、双侧进行性的视网膜变性,其特征是光感受器细胞因发生凋亡而丢失,最终导致失明。中药黄芪在阻止该病的进程上显示出了良好的前景。目的:观察黄芪对N-甲基-N-亚硝脲致SD大鼠视网膜损伤的保护作用。设计:随机对照动物实验。单位:新乡医学院药学院。材料:实验于2004-03/12在中山大学中山眼科中心药理实验室完成。雌性SD大鼠114只,由中山大学中山医学院动物中心提供,N-甲基-N-亚硝脲为美国Sigma公司产品,黄芪注射液为成都地奥九泓制药厂生产(生产批号:国药准字Z99060535,2mL/支,主要成分为黄芪)。方法:选用雌性SD大鼠114只,30只用于视网膜层形态学分析;30只用于细胞凋亡检测;54只用于胞核内核因子κBp65活性的检测。采用抽签法随机分组,每组6只。于大鼠生后47d,分别经腹腔注射不同剂量的黄芪(2.5,5和10g/kg),1次/d,除对照组外,其余组的大鼠同时于生后50d腹腔注射N-甲基-N-亚硝脲60mg/kg。在N-甲基-N-亚硝脲处理不同时间后处死动物,取眼球,视网膜形态学分析测量周边视网膜的总厚度,TUNEL试剂盒检测光感受器细胞凋亡,转录因子试剂盒分析核因子κBp65的活性。主要观察指标:各组视网膜厚度、凋亡指数和胞核内核因子κBp65的活性比较。结果:黄芪可剂量依赖性地显著增加周边视网膜总厚度和降低N-甲基-N-亚硝脲引起的光感受器细胞凋亡指数。黄芪注射液10g/kg还可时间依赖性地上调视网膜细胞胞核内核因子κBp65的活性。但其对N-甲基-N-亚硝脲引起的中心视网膜损伤无明显的保护作用。结论:黄芪通过上调视网膜细胞胞核内核因子κBp65的活性,抑制光感受器细胞凋亡,从而部分地保护N-甲基-N-亚硝脲引起的视网膜损伤。     

Inhibition of phagocytes by cyclosporin in vitro

Cyclosporin is an immunosuppressant that acts by selectivelyinhibiting the activation of T lymphocytes. Its effects on monocytesand neutrophils are not well explored. We investigated the invitro effects of cyclosporin on these cells, harvested fromvenous blood from nine healthy, non-smoking volunteers. In vitroincubation of monocytes with increasing concentrations of cyclosporin(5, 25 and 625 µg) depressed their phagocytosis by 22%,32% and 49%, respectively, compared to the control values. Theintracellular killing capacity of monocytes decreased by 26%, 31 % and 43% with these doses, and neutrophilphagocytosis was depressed in a similar manner (16%, 30% and40%). Patients receiving cyclosporin are susceptible to infections,and inhibition of these phagocytic cells by cyclosporin maybe partly responsible for this. Neutrophil chemotaxis is reducedin patients with impaired renal function. Treating these patientswith cyclosporin may in addition suppress the phagocytic functionof these cells.     

酸性肽对神经元凋亡的抑制

背景:高浓度的一氧化氮能引起神经细胞的凋亡。因此抑制一氧化氮引起的细胞凋亡就能达到预防和治疗老年痴呆病的目的。目的:观察酸性肽能否抑制一氧化氮引起的神经元凋亡。设计:对照观察细胞和分子实验。材料:实验于2003-05/2005-05在郑州大学生物活性肽研究所第二实验室和郑州大学基础医学院生物化学与分子生物学教研室细胞培养室完成。新生的24h内SD雄性大鼠,由河南省动物中心提供(410117)。方法:对新生的SD大鼠海马神经元进行原代培养。取培养至第11天的神经细胞,用不同剂量的酸性肽预处理6h,再加入终浓度为50μmmol/L的亚硝基铁氰化钠,继续培养24h,收集细胞进行实验。每次实验均分为以下5组:正常对照组、亚硝基铁氰化钠处理组、亚硝基铁氰化钠 0.0375mg/mL酸性肽组、亚硝基铁氰化钠 0.075mg/mL酸性肽组,亚硝基铁氰化钠 0.15mg/mL酸性肽组。用噻唑蓝法测定细胞的存活率,用免疫组织化学法对神经丝蛋白进行染色,再用吖啶橙荧光染色法显示细胞凋亡的形态。用琼脂糖凝胶电泳法分析凋亡细胞的DNA梯带。用WesternBlot和吸光度扫描分析Bcl-2蛋白和Bax蛋白的表达水平。主要观察指标:①噻唑蓝法比色法检测细胞存活率的实验结果。②细胞凋亡的核型观察结果。③细胞凋亡的DNA电泳分析。④Bcl-2和Bax蛋白的WesternBlot分析结果。结果:①亚硝基铁氰化钠处理组的神经元存活率为58.9%,亚硝基铁氰化钠 0.037mg/mL酸性肽处理组为70.0%,亚硝基铁氰化钠 0.075mg/mL酸性肽处理组为72.8%,亚硝基铁氰化钠 0.15mg/mL酸性肽处理组为75.3%。②细胞凋亡的核型观察结果:亚硝基铁氰化钠处理组呈现细胞凋亡的明显特征。不同浓度的酸性肽 亚硝基铁氰化钠共同处理组海马神经元的细胞核接近正常对照组的细胞核形态。③细胞凋亡的DNA电泳分析结果表明,仅亚硝基铁氰化钠处理组的神经元DNA在琼脂糖凝胶电泳上显示出清晰的细胞凋亡的特征性DNA梯带。④Bcl-2和Bax蛋白的Western Blot和吸光度扫描分析结果显示,亚硝基铁氰化钠处理组Bcl-2蛋白表达水平下降,Bax蛋白表达水平升高。而不同浓度的酸性肽 亚硝基铁氰化钠共同处理组的Bcl-2蛋白水平随酸性肽浓度逐渐增加,Bax蛋白的表达水平逐渐下降。结论:酸性肽能够抑制神经元的凋亡,增加神经元Bcl-2蛋白的表达水平,抑制神经元Bax蛋白的表达水平。     

咖啡因通过Caspase通路促进胃癌细胞凋亡的研究

目的探讨咖啡因对于胃癌细胞的抑制效果及作用机制。方法本研究预设了分组和药物处理浓度,采用细胞培养和细胞计数的方法检测了胃癌细胞株的增殖活力,利用流式细胞仪分析胃癌细胞凋亡水平和细胞周期情况,通过目的基因扩增法(PCR)和蛋白免疫印迹法(Western blot)检测凋亡相关的基因和蛋白。结果咖啡因处理后显著抑制了胃癌细胞生长和生存活力,并且通过Caspase-9/-3通路促进胃癌细胞的凋亡。结论咖啡因处理能有效促进胃癌细胞的凋亡。     

American ginseng stimulates insulin production and prevents apoptosis through regulation of uncoupling protein-2 in cultured beta cells

American ginseng root displays the ability to achieve glucose homeostasis both experimentally and clinically but the unknown mechanism used by ginseng to achieve its therapeutic effects on diabetes limits its application. Disruption in the insulin secretion of pancreatic beta cells is considered the major cause of diabetes. A mitochondrial protein, uncoupling protein-2 (UCP-2) has been found to play a critical role in insulin synthesis and beta cell survival. Our preliminary studies found that the extracts of American ginseng inhibit UCP-2 expression which may contribute to the ability of ginseng protecting beta cell death and improving insulin synthesis. Therefore, we hypothesized that ginseng extracts suppress UCP-2 in the mitochondria of pancreatic beta cells, promoting insulin synthesis and anti-apoptosis (a programmed cell-death mechanism). To test the hypothesis, the serum-deprived quiescent beta cells were cultured with or without interleukin-1beta (IL-1beta), (200 pg ml(-1), a cytokine to induce beta cell apoptosis) and water extracts of American ginseng (25 mug per 5 mul administered to wells of 0.5 ml culture) for 24 h. We evaluated effects of ginseng on UCP-2 expression, insulin production, anti-/pro-apoptotic factors Bcl-2/caspase-9 expression and cellular ATP levels. We found that ginseng suppresses UCP-2, down-regulates caspase-9 while increasing ATP and insulin production/secretion and up-regulates Bcl-2, reducing apoptosis. These findings suggest that stimulation of insulin production and prevention of beta cell loss by American ginseng extracts can occur via the inhibition of mitochondrial UCP-2, resulting in increase in the ATP level and the anti-apoptotic factor Bcl-2, while down-regulation of pro-apoptotic factor caspase-9 occurs, lowering the occurrence of apoptosis, which support the hypothesis.     

Inhibition of macrophage activation and phagocytosis by a novel NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin.

Previously, we designed and synthesized a new NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ). In the present research we looked into the effect of DHMEQ on the activation of macrophages, especially on the phagocytotic activity of cells of the mouse macrophage-like cell line RAW264.7. DHMEQ inhibited lipopolysaccharide (LPS)-induced NF-kappaB activation by inhibiting its nuclear translocation from the cytoplasm. It also inhibited the expression of inducible NO synthase (iNOS) and nitric oxide (NO) production induced by LPS and interferon-gamma. Using enzyme-linked immunosorbent assays (ELISAs) we showed DHMEQ to inhibit LPS-induced secretion of IL-6, IL-12, interleukin-1beta (IL-1beta), and TNF-alpha. Furthermore, DHMEQ also inhibited the phagocytosis of fluorescently labeled Escherichia coli by RAW264.7 cells treated with LPS or IL-1beta, thus being the first evidence for the involvement of NF-kappaB in the regulation of phagocytosis by use of this inhibitor. Deletion of p65 by siRNA also inhibited the phagocytosis. DHMEQ inhibited the LPS-induced but not IL-1beta-induced phagocytosis of glass beads, indicating that activation of not only NF-kappaB but also Toll-like receptor 4 (TLR-4) is essential for the phagocytosis of E. coli. Previously we found that DHMEQ inhibited type 2 collagen-induced rheumatoid arthritis and the growth of various human carcinomas in mice. It is thus likely that inhibition of macrophage activation is involved in the mechanism of these anti-inflammatory and antitumor activities of DHMEQ in mice.     

Inhibition of acrolein-induced apoptosis by the antioxidant N-acetylcysteine

Acrolein is a highly electrophilic alpha,beta-unsaturated aldehyde to which humans are exposed in many situations. It is an environmental pollutant that is responsible for multiple respiratory diseases and has been implicated in neurodegenerative diseases such as Alzheimer's disease. The hypothesis of the study is that the antioxidant N-acetylcysteine (NAC), a precursor of glutathione, could protect cells against acrolein-induced apoptosis. Exposure of Chinese hamster ovary cells to a noncytotoxic dose of acrolein (4 fmol/cell) depleted intracellular glutathione to 45% of initial levels. NAC, which increased intracellular glutathione levels by 30%, afforded protection against acrolein-induced cytotoxicity (loss of cell proliferation) and apoptosis. NAC protected against apoptosis by diminishing acrolein-induced activation of the mitochondrial death pathway. NAC inhibited acrolein-induced Bad translocation from the cytosol to the mitochondria, as well as Bcl-2 translocation from mitochondria to the cytosol, as evaluated by Western blot analysis. However, NAC had no effect on acrolein-induced Bax translocation to mitochondria and cytochrome c liberation into the cytosol. Meanwhile, NAC inhibited depolarization of mitochondrial membrane potential, as evaluated by rhodamine fluorescence using flow cytometry. NAC also inhibited procaspase-9 processing, activation of enzymatic activity of caspase-9, -7, and -8, and poly(ADP-ribose) polymerase cleavage induced by acrolein. Inhibition of acrolein-induced apoptosis using NAC was confirmed morphologically by diminished condensation of nuclear chromatin, as evaluated by fluorescence microscopy. These findings suggest that NAC could be potentially useful as a protective agent for people exposed to acrolein.     

17-Acetoxyjolkinolide B irreversibly inhibits IkappaB kinase and induces apoptosis of tumor cells

Nuclear factor-kappaB (NF-kappaB) is critically important for tumor cell survival, growth, angiogenesis, and metastasis. One of the key events in the NF-kappaB signaling is the activation of inhibitor of NF-kappaB kinase (IKK) in response to stimuli of various cytokines. We have identified 17-acetoxyjolkinolide B (17-AJB) from a traditional Chinese medicinal herb Euphorbia fischeriana Steud as a novel small-molecule inhibitor of IKK. 17-AJB effectively inhibited tumor necrosis factor-alpha-induced NF-kappaB activation and induced apoptosis of tumor cells. 17-AJB had no effect on binding of tumor necrosis factor-alpha to its receptor or on binding of NF-kappaB to DNA. It inhibited NF-kappaB nuclear translocation. Detailed analysis revealed that the direct target of 17-AJB was IKK. 17-AJB kept IKK in its phosphorylated form irreversibly. This irreversible modification of IKK inactivated its kinase activity, leading to its failure to activate NF-kappaB. The effect of 17-AJB on IKK was specific. It had no effect on other kinases such as p38, p44/42, and JNK. In addition, 17-AJB induced apoptosis in tumor cells. The effects of 17-AJB on apoptosis correlated with inhibition of expression of the NF-kappaB-regulated genes. Taken together, our data suggest that 17-AJB is a novel type NF-kappaB pathway inhibitor. Its unique interaction mechanism with IKK may render it a strong apoptosis inducer of tumor cells and a novel type anticancer drug candidate.     

Tetrathiomolybdate promotes tumor necrosis and prevents distant metastases by suppressing angiogenesis in head and neck cancer

Angiogenesis is well recognized as an essential process that influences not only the growth of head and neck squamous cell carcinoma (HNSCC) but also promotes its invasive and metastatic behavior. The critical role of copper in multiple facets of angiogenesis makes it an important therapeutic target. Tetrathiomolybdate is a potent copper chelator, which has shown remarkable ability to suppress angiogenesis. Although this may involve multiple mechanisms, the effects on vascular endothelial growth factor (VEGF) are pivotal. In previous work, tetrathiomolybdate suppressed production of several proangiogenic cytokines by HNSCC cell lines. Given these results, we hypothesized that tetrathiomolybdate would impair tumor growth and metastasis by HNSCC. To test this concept, we evaluated the effects of long-term tetrathiomolybdate treatment on the growth and metastatic progression of HNSCC using a xenograft animal model. The results showed that tetrathiomolybdate treatment is able to maintain effective inhibition of angiogenesis. There was a significant reduction in the tumor size and vascularity with evident gross necrosis in the tetrathiomolybdate-treated animals. These effects were highly correlated with suppression of human VEGF expressed in the developing tumors as well as the mouse VEGF levels detected in the plasma. Moreover, tetrathiomolybdate treatment drastically suppressed the development of lung metastases. Taken together, these results show that tetrathiomolybdate can act long-term as a suppressor of vascularity and inhibit the growth of metastasis in this model of HNSCC.