Cellular stress response and apoptosis in cancer therapy.

Anticancer treatment using cytotoxic drugs is considered to mediate cell death by activating key elements of the apoptosis program and the cellular stress response. While proteolytic enzymes (caspases) serve as main effectors of apoptosis, the mechanisms involved in activation of the caspase system are less clear. Two distinct pathways upstream of the caspase cascade have been identified. Death receptors, eg, CD95 (APO-1/Fas), trigger caspase-8, and mitochondria release apoptogenic factors (cytochrome c, Apaf-1, AIF), leading to the activation of caspase-9. The stressed endoplasmic reticulum (ER) contributes to apoptosis by the unfolded protein response pathway, which induces ER chaperones, and by the ER overload response pathway, which produces cytokines via nuclear factor-kappaB. Multiple other stress-inducible molecules, such as p53, JNK, AP-1, NF-kappaB, PKC/MAPK/ERK, and members of the sphingomyelin pathway have a profound influence on apoptosis. Understanding the complex interaction between different cellular programs provides insights into sensitivity or resistance of tumor cells and identifies molecular targets for rational therapeutic intervention strategies.     

玉竹提取物B对人食管癌细胞Eca-109增殖与凋亡的影响

目的观察玉竹提取物B（EB-PAOA）对人食管癌细胞Eca-109增殖与凋亡的影响。方法将体外培养的Eca-109细胞与不同浓度的EB-PAOA共育,采用MTT法检测Eca-109细胞增殖抑制率,采用流式细胞仪检测Eca-109细胞凋亡率。结果随着EB-PAOA浓度增大、作用时间延长,Eca-109细胞的增殖抑制率逐渐升高（P均〈0.05）,呈时间、剂量依赖性;随着EB-PAOA浓度增加,Eca-109细胞凋亡率逐渐增加,呈一定浓度依赖性（P均〈0.05）。结论EB-PAOA能够抑制人食管癌细胞Eca-109的增殖,并诱导其凋亡。     

Nucleostemin基因沉默对食管癌细胞增殖和凋亡的影响

目的探讨RNA干扰沉默Nucleostemin(NS)基因后对食管癌Eca-109细胞株增殖和凋亡的影响。方法用NS基因特异性siRNA表达载体转染食管癌Eca-109细胞株,通过绘制细胞生长曲线和克隆形成实验检测细胞增殖能力;CCK-8法测试细胞增殖抑制率;RT-PCR法检测NS基因表达量的变化,TUNEL法和DNA Ladder检测细胞凋亡情况。结果与对照组相比,S组细胞的增殖速率降低,24、48及72h细胞增殖抑制率分别为60.32%、72.29%和86.00%;NS基因表达量下降;细胞凋亡指数增加(18.28%),可见梯状DNA降解带。结论 NS基因沉默导致食管癌Eca-109细胞株增殖抑制,凋亡增加。     

ALA-PDT对人食管癌Eca-109细胞相关凋亡蛋白表达的影响

目的 探讨5-氨基乙酰丙酸—光动力疗法(ALA-PDT)对人食管癌Eca-109细胞相关凋亡蛋白表达的影响.方法 将人食管癌Eca-109细胞经过培养、处理后分为两组,ALA-PDT组(PDT组)细胞用ALA孵育6h后在光动力治疗系统下进行光照,光照后24h提取细胞总蛋白和胞质蛋白;对照组细胞不进行光动力治疗.采用Western blot法检测两组细胞中的Bcl-2、Cytc蛋白表达.结果 ALA-PDT作用于人食管癌Eca-109细胞后,与对照组比较,PDT组胞质中的Bcl-2蛋白表达量明显降低,Cytc蛋白表达量明显升高(P均＜0.05).结论 线粒体凋亡通路可能是ALA-PDT诱导Eca-109细胞凋亡的主要通路,Bcl-2可能为该凋亡通路的靶基因之一,释放Cytc进而诱导细胞凋亡可能为ALA-PDT诱导人食管癌Eca-109细胞凋亡的线粒体通路终末效应之一.     

Melatonin inhibits apoptosis during early B-cell development in mouse bone marrow

The pineal secretory product, melatonin, exerts a variety of effects on the immune system. Administration of melatonin stimulates cell-mediated immunity, particularly by inhibiting apoptosis among T lymphocytes in the thymus and inducing production of T-cell-derived cytokines. However, its possible effects on the humoral immune system are unclear. In the present study, we have examined whether melatonin may influence the in vivo development of B lymphocytes in mouse bone marrow, a process in which apoptosis is normally a prominent feature. Double immunofluorescence labeling and flow cytometry were used to quantitate phenotypically defined precursor B-cell and mature B-cell populations and their apoptotic rates in bone marrow of mice fed either melatonin-containing or control diet for 16 days from 9 wk of age. In short-term bone marrow cultures, the incidence of apoptosis among large pre-B cells, including cells expressing the lambda5 component of pre-B-cell receptor, was markedly reduced in melatonin-treated mice, associated with an increase in the absolute number of large pre-B cells in bone marrow. In contrast, apoptosis of earlier precursor B cells and mature B lymphocytes did not differ from control values. The results indicate that orally administered melatonin can substantially promote the survival of precursor B cells in mouse bone marrow. Melatonin treatment may thus boost the survival of newly formed B cells mediating humoral immunity.     

Ghrelin inhibits apoptosis in hypothalamic neuronal cells during oxygen-glucose deprivation

Ghrelin is an endogenous ligand for the GH secretagogue receptor, produced and secreted mainly from the stomach. Ghrelin stimulates GH release and induces positive energy balances. Previous studies have reported that ghrelin inhibits apoptosis in several cell types, but its antiapoptotic effect in neuronal cells is unknown. Therefore, we investigated the role of ghrelin in ischemic neuronal injury using primary hypothalamic neurons exposed to oxygen-glucose deprivation (OGD). Here we report that treatment of hypothalamic neurons with ghrelin inhibited OGD-induced cell death and apoptosis. Exposure of neurons to ghrelin caused rapid activation of ERK1/2. Ghrelin-induced activation of ERK1/2 and the antiapoptotic effect of ghrelin were blocked by chemical inhibition of MAPK, phosphatidylinositol 3 kinase, protein kinase C, and protein kinase A. Ghrelin attenuated OGD-induced activation of c-Jun NH2-terminal kinase and p-38 but not ERK1/2. We also investigated ghrelin regulation of apoptosis at the mitochondrial level. Ghrelin protected cells from OGD insult by inhibiting reactive oxygen species generation and stabilizing mitochondrial transmembrane potential. In addition, ghrelin-treated cells showed an increased Bcl-2/Bax ratio, prevention of cytochrome c release, and inhibition of caspase-3 activation. Finally, in vivo administration of ghrelin significantly reduced infarct volume in an animal model of ischemia. Our data indicate that ghrelin may act as a survival factor that preserves mitochondrial integrity and inhibits apoptotic pathways.     

RNA干扰体外抑制人食管鳞癌细胞Eca-109缺氧诱导因子-1α的表达

目的:观察缺氧诱导因子-1α(hypoxia inducible factor-1α,HIF-1α)短发夹状RNA(short hairpin RNA,shRNA)对人食管鳞癌细胞系Eca-109中 HIF-1α基因的沉默效应,筛选有效干扰靶点．方法:设计合成干扰缺氧诱导因子-1α RNA 寡核苷酸片段,经退火、连接等步骤克隆至线性化的PGCsi真核表达载体上,测序鉴定．应用LipofectamineTM2000将该质粒分别转染Eca-109细胞和293T细胞,其中Eca-109抗性细胞又经2-4 wk的G418筛选．荧光显微镜评估转染效率,荧光定量RT-PCR检测HIF-1α mRNA表达情况,western blot检测HIF-1α蛋白表达情况．结果:成功构建了3个靶点的重组质粒pGCsi- H1-shHIF,293T细胞平均转染效率为约85．4％, Eca-109细胞的平均转染效率约73．2％．荧光定量RT-PCR和Western blot显示瞬时转染这3种重组质粒的293T细胞和筛选2 wk的Eca-109 细胞HIF-1 α mRNA和蛋白表达均较对照组有不同程度的下降,其中2号和3号靶点的干扰效应尤为明显．在瞬时转染72 h后的293T 细胞中,其抑制率分别达到了78．5％、86．9％ (P=0．000,P=0．000 vs 72 h空白对照组),筛选2 wk的Eca-109细胞中,3号靶点对HIF-1α mRNA的抑制率也达到了69．7％(P=0．000 vs 2 wk空白对照组)．结论:重组质粒pGCsi-shHIF能有效抑制食管鳞癌细胞Eca-109中HIF-1α基因的表达,经不同细胞中的瞬时和稳定转染筛选出了有效干扰靶位．     

Ascorbate inhibits apoptosis of Kupffer cells during warm ischemia/reperfusion injury

BACKGROUND/AIMS: This study sought to determine whether ascorbate (Asc), a scavenger of reactive oxygen species, inhibits apoptosis of hepatic cells consisting of hepatocytes, Kupffer cells, and sinusoidal endothelial cells (SECs) in the rat liver after warm ischemia/reperfusion (I/R) injury. METHODOLOGY: Hepatic warm ischemia (69% of the total liver) was induced for 30 min, followed by reperfusion for 60 min. In some animals, ascorbate (at 1 or 10 mg/kg) was infused intravenously immediately before the onset of reperfusion. Hepatic cell apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL). Mitochondrial release of cytochrome c into the cytoplasm was assessed by Western blot analysis, and the activation of caspase-3 in liver tissue was determined by colorimetric assays. RESULTS: Assays of cytochrome c release and caspase-3 showed increased levels of these apoptotic related proteins and enzyme activity. While few apoptotic hepatocytes or SECs were detected in the ischemic group by TUNEL staining, the number of TUNEL-positive Kupffer cells was approximately 4.5-fold greater than that seen in the sham-treatment group. Ascorbate treatment reduced this increase in apoptotic Kupffer cells. CONCLUSION: The hepatic cells most vulnerable to oxidative stress in the first hour of reperfusion were Kupffer cells. These may play a key role in hepatic warm I/R injury.     

Arterial wall response to ex vivo exposure to oscillatory shear stress

BACKGROUND: The aim of this study was to analyze the arterial wall response to plaque-prone hemodynamic environments, known to occur mainly in areas of arterial trees such as bifurcations and branching points. In these areas, the vasculature is exposed to cyclically reversing flow that induces an endothelial dysfunction predisposing thus arteries to local development of atherosclerotic plaques. METHODS: We used an ex vivo perfusion system that allows culturing arterial segments under different hemodynamic conditions. Porcine carotid arteries were exposed for 3 days to unidirectional high and low shear stress (6 +/- 3 and 0.3 +/- 0.1 dyn/cm(2)) as well as to oscillatory shear stress (0.3 +/- 3 dyn/cm(2)). This latter condition mimics the hemodynamics present at plaque-prone areas. At the end of the perfusion, the influence of different flow patterns on arterial metabolism was assessed in terms of matrix turnover as well as of smooth muscle cell function, differentiation and migration. RESULTS: Our results show that after 3 days of perfusion none of the applied conditions influence smooth muscle cell phenotype retaining their full contraction capacity. However, an increase in the expression level of matrix metalloproteinase-2 and -9, as well as a decrease in plasminogen activator inhibitor-1 expression were observed in arteries exposed to oscillatory shear stress when compared to arteries exposed to unidirectional shear stress. CONCLUSION: These observations suggest that plaque-prone hemodynamic environment triggers a vascular wall remodelling process and promotes changes in arterial wall metabolism, with important implication in atherogenesis.     

COX-2 inhibits Fas-mediated apoptosis in cholangiocarcinoma cells

Fas expression has been shown to negatively regulate the progression of cholangiocarcinoma cells in xenografts. However, many human cholangiocarcinomas express Fas, suggesting these cancers have developed mechanisms to inhibit Fas-mediated apoptosis. Cyclooxygenase-2 (COX-2), which generates prostanoids, is expressed by many cholangiocarcinomas. Therefore, our aim was to determine whether COX-2 expression inhibits death receptor--mediated apoptosis in KMBC cells, a cholangiocarcinoma cell line. These cells express messenger RNA for the death receptors Fas, tumor necrosis factor receptor 1 (TNF-R1), death receptor 4 (DR4), and DR5. Agonists for these death receptors, CH-11, TNF-alpha, and TRAIL all induced apoptosis. However, COX-2, whether induced by proinflammatory cytokines or transient transfection, only significantly inhibited Fas-mediated apoptosis. The COX-2 inhibitor NS-398 restored Fas-mediated apoptosis in COX-2 transfected cells. Prostaglandin E2 reduced apoptosis and mitochondrial depolarization after treatment with the Fas agonist CH-11. Of a variety of antiapoptotic proteins examined, COX-2/prostaglandin E2 only increased expression of Mcl-1, an antiapoptotic member of the Bcl-2 family. In conclusion, these data suggest that prostanoid generation by COX-2 specifically inhibits Fas-mediated apoptosis, likely by up-regulating Mcl-1 expression. Pharmacologic inhibition of COX-2 may be useful in augmenting Fas-mediated apoptosis of cholangiocarcinoma cells.     

Cellular redox state and its relationship to the inhibition of clonal cell growth and the induction of apoptosis during all-trans retinoic acid exposure in acute myeloblastic leukemia cells

BACKGROUND AND OBJECTIVE: All-trans retinoic acid (ATRA) induces growth arrest and apoptosis in acute myeloblastic leukemia (AML) cells. Since cellular redox state regulates these events, we were interested in studying whether it has any role in the responsiveness of AML cells to ATRA. DESIGN AND METHODS: Two human AML cell lines, the ATRA-sensitive OU-AML-3, and the ATRA-resistant OU-AML-7, were used as models. Clonogenic cell culture assay, annexin V method, and measurement of mitochondrial membrane potential were used for the determination of cell growth and apoptosis. Peroxide formation was analyzed by flow cytometry, glutathione and g-glutamylcysteine synthetase (g-GCS) activity was determined spectrophotometrically, and the expression of manganese superoxide dismutase (MnSOD) by Western blotting. RESULTS: ATRA inhibited clonogenic cell growth and induced apoptosis particularly in OU-AML-3 cells. The OU-AML-7 cells had a higher basal level of glutathione and g-GCS activity than the OU-AML-3 cells. ATRA enhanced the generation of peroxides after 24h exposure, which was more prominent in the sensitive than the resistant cell line and was not preventable by N-acetyl-L-cysteine. ATRA also increased the activity of g-GCS, which was associated with increased intracellular glutathione in the resistant cell line, while the glutathione level was maintained in the sensitive cell line. During ATRA exposure, MnSOD was induced in the sensitive cell line, but not until after 72 h. Buthionine sulfoximine significantly increased the inhibitory effect of ATRA on colony formation in both cell lines, but only marginally enhanced the effect of ATRA on the induction of apoptosis. INTERPRETATION AND CONCLUSIONS: The balance between oxidative and antioxidative actions of ATRA, as well as the basal redox state of the cells seem to have a definite influence on the responsiveness of AML cells to ATRA.     

Cellular immune response to cryptic epitopes during therapeutic gene transfer

The immune response has been implicated as a critical factor in determining the success or failure of clinical gene therapy trials. Generally, such a response is elicited by the desired transgene product or, in some cases, the delivery system. In the current study, we report the previously uncharacterized finding that a therapeutic cassette currently being used for human investigation displays alternative reading frames (ARFs) that generate unwanted protein products to induce a cytotoxic T lymphocyte (CTL) response. In particular, we tested the hypothesis that antigenic epitopes derived from an ARF in coagulation factor IX (F9) cDNA can induce CTL reactivity, subsequently killing F9-expressing hepatocytes. One peptide (p18) of 3 candidates from an ARF of the F9 transgene induced CD8⁺ T cell reactivity in mice expressing the human MHC class I molecule B0702. Subsequently, upon systemic administration of adeno-associated virus (AAV) serotype 2 vectors packaged with the F9 transgene (AAV2/F9), a robust CD8⁺ CTL response was elicited against peptide p18. Of particular importance is that the ARF epitope-specific CTLs eliminated AAV2/F9-transduced hepatocytes but not AAV2/F9 codon-optimized (AAV2/F9-opt)-transduced liver cells in which p18 epitope was deleted. These results demonstrate a previously undiscovered mechanism by which CTL responses can be elicited by cryptic epitopes generated from a therapeutic transgene and have significant implications for all gene therapy modalities. Such unforeseen epitope generation warrants careful analysis of transgene sequences for ARFs to reduce the potential for adverse events arising from immune responses during clinical gene therapy protocols.     

Translational induction of VEGF internal ribosome entry site elements during the early response to ischemic stress

Vascular endothelial growth factor-A (VEGF), a powerful factor involved in vasculogenesis and angiogenesis, is translationally regulated through 2 independent internal ribosome entry sites (IRESs A and B). IRESs enable an mRNA to be translated under conditions in which 5'-cap-dependent translation is inhibited, such as low oxygen stress. In the VEGF mRNA, IRES A influences translation at the canonical AUG codon, whereas the 5' IRES B element regulates initiation at an upstream, in frame CUG. In this study, we have developed transgenic mice expressing reporter genes under the control of these 2 IRESs. We reveal that although these IRESs display low activity in embryos and adult tissues, they permit efficient translation at early time points in ischemic muscle, a stress under which cap-dependent translation is inhibited. These results demonstrate the in vivo efficacy of the VEGF IRESs in response to a local environmental stress such as hypoxia.     

Carbon monoxide inhibits apoptosis in vascular smooth muscle cells

OBJECTIVE: Carbon monoxide (CO) is generated from vascular smooth muscle cells via the degradation of heme by the enzyme heme oxygenase-1. Since smooth muscle cell apoptosis is associated with numerous vascular disorders, we investigated whether CO regulates apoptosis in vascular smooth muscle. METHODS AND RESULTS: Treatment of cultured rat aortic smooth muscle cells with a combination of cytokines (interleukin-1beta, 5 ng/ml; tumor necrosis factor-alpha, 20 ng/ml; interferon-gamma, 200 U/ml) for 48 h stimulated apoptosis, as demonstrated by DNA laddering, annexin V binding, and caspase-3 activation. However, the exogenous administration of CO inhibited cytokine-mediated apoptosis. The antiapoptotic action of CO was partially dependent on the activation of soluble guanylate cyclase and was associated with the inhibition of mitochondrial cytochrome c release and with the suppression of p53 expression. Incubation of smooth muscle cells with the cytokines also resulted in a pronounced increase in heme oxygenase-1 protein after 24 h of stimulation. The addition of the heme oxygenase inhibitor, zinc protoporphyrin-IX, or the CO scavenger, hemoglobin, stimulated apoptosis following 24 h of cytokine exposure. CONCLUSIONS: These results demonstrate that CO, either administered exogenously or endogenously derived from heme oxygenase-1 activity, inhibits vascular smooth muscle cell apoptosis. The ability of CO to block smooth muscle cell apoptosis may play an important role in blocking lesion formation at sites of vascular injury.     

Ghrelin inhibits 5-fluorouracil-induced apoptosis in colonic cancer cells

Background and Aim: The aim of the present study was to investigate if ghrelin inhibits apoptosis in colonic cancer cells. Methods: Cell viability in HT‐29 cells was measured using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. Apoptosis was measured using 4′,6‐diamidino‐2‐phenylindole staining and flow cytometry. The protein expression of Bcl‐2, Bax, and caspase‐3 activation was examined using Western blotting. Results: Ghrelin dose dependently decreased the growth inhibition of HT‐29 cells induced by 5‐fluorouracil (5‐FU). Cells treated with 5‐FU displayed chromatin condensation and nuclear fragmentation, which are typical changes of apoptosis. However, co‐treatment with ghrelin reduced these changes. Flow cytometry after staining with Annexin V and propidium iodide showed that ghrelin decreased the apoptotic rate of HT‐29 cells induced by 5‐FU. Caspase‐3 activation was significantly lower in the co‐treated group than in the group treated with 5‐FU alone. In addition, ghrelin reversed the 5‐FU‐induced Bcl‐2/Bax protein ratio. Conclusion: Ghrelin inhibits 5‐FU‐induced apoptosis in colon cancer cells through the regulation of the Bcl‐2/Bax protein ratio.     

Nedocromil sodium inhibits the early and late asthmatic response to exercise.

A double-blind, crossover study was carried out to investigate the effect of nedocromil sodium on the dual asthmatic response to exercise challenge. Nineteen patients with a late response to bicycle exercise were randomly treated on two study days with 4 mg nedocromil sodium or a matched placebo aerosol, 30 min before commencing exercise. Peak flow was measured before exercise, at intervals up to 60 min after exercise, then hourly for up to 13 h. In 12 of the 19 patients an early reaction to exercise occurred. In 8 of these 12 patients the early reaction could be inhibited by nedocromil sodium (p less than 0.01) although in half of these patients placebo was also shown to be protective. In the case of the late reaction after exercise challenge, 4-13 h after exercise challenge, nine patients were clearly protected by pretreatment with nedocromil sodium (p less than 0.01) when the fall in peak expiratory flow rate was related to the pre-exercise baseline, four patients showed an equal protective effect of placebo and nedocromil sodium, whilst the others were not protected. When the late asthmatic response (fall in peak expiratory flow rate) after exercise challenge was related to control diurnal peak flow values, the number of responses was reduced; the protective effect of nedocromil sodium remained.     

Cellular glutathione and the response of adult rat heart myocytes to oxidant stress

Freshly isolated adult rat heart myocytes contain total glutathione and reduced glutathione (GSH) at levels quite comparable to those in intact rat heart. Total glutathione can be depleted from 11 to 1 nmol/mg protein or less by treatment with cyclohex-2-ene-1-one without effect on either cellular ATP, rod-cell morphology or the integrity of the sarcolemma. Glutathione levels and redox state are not altered significantly when the Ca-tolerant, quiescent cells are subjected to a period of anoxia followed by reoxygenation. This oxygen paradox protocol results in irreversible hypercontracture of the contractile elements into an amorphous mass in the bulk of the cells, but little loss of sarcolemmal integrity. When the myocytes are subjected to an externally applied oxidant stress by the addition of either diamide or t-butylhydroperoxide, GSH is rapidly depleted with accumulation of oxidized glutathione (GSSG. On continued aerobic incubation both of these reagents promote a slower depletion of cellular ATP and a parallel hypercontracture. Cells treated with t-butylhydroperoxide, but not those with diamide, also generate increasing amounts of thiobarbituric acid reactive species as an indication of lipid peroxidation and show a parallel loss of sarcolemmal integrity. It is concluded that respiring myocytes and those subjected to the oxygen paradox do not produce oxygen radicals in sufficient amounts to displace the GSH/GSSG redox poise and depletion of myocyte glutathione per se is not detrimental to the short term survival of the cells. In addition, aerobic myocytes subjected to external oxidant stress can be damaged irreversibly by two pathways, a hypercontracture that correlates with depletion of ATP and a loss of sarcolemmal integrity that correlates with lipid peroxidation.