The end of the (cell) line: methods for the study of apoptosis in vitro

Gamma-radiation induces apoptosis via sarcoplasmatic reticulum in guinea pig ileum smooth muscle cells

We investigated the effects of gamma-radiation on cells isolated from the longitudinal smooth muscle layer of the guinea pig ileum, a relatively radioresistant tissue. Single doses (up to 50 Gy) reduced the amount of sarcoplasmatic reticulum and condensed the myofibrils, as shown by electron microscopy 3 days post-irradiation. After that, contractility of smooth muscle strips was reduced. Ca(2+) handling was altered after irradiation, as shown in fura-2 loaded cells, with elevated basal intracellular Ca(2+), reduced amount of intrareticular Ca(2+), and reduced capacitive Ca(2+) entry. Radiation also induced apoptosis, judged from flow cytometry of cells loaded with proprium iodide. Electron microscopy showed that radiation caused condensation of chromatin in dense masses around the nuclear envelope, the presence of apoptotic bodies, fragmentation of the nucleus, detachment of cells from their neighbors, and reductions in cell volume. Radiation also caused activation of caspase 12. Apoptosis was reduced by the administration of the caspase inhibitor Z-Val-Ala-Asp-fluoromethyl-ketone methyl ester (Z-VAD-FMK) during the 3 day period after irradiation, and by the chelator of intracellular Ca(2+), 1,2-bis(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA), from 1 h before until 2 h after irradiation. BAPTA also reduced the effects of radiation on contractility, basal intracellular Ca(2+), amount of intrareticular Ca(2+), capacitative Ca(2+) entry, and apoptosis. In conclusion, the effects of gamma radiation on contractility, Ca(2+) handling, and apoptosis appear due to a toxic action of intracellular Ca(2+). Ca(2+)-induced damage to the sarcoplasmatic reticulum seems a key event in impaired Ca(2+) handling and apoptosis induced by gamma-radiation.

Cytotoxicity and genotoxicity of ingenamine G isolated from the Brazilian marine sponge Pachychalina alcaloidifera

Marine sponges belonging to the order Haplosclerida are one of the more prolific sources of new natural products possessing various biological activities. The present study examined the cytotoxic and genotoxic potential of ingenamine G, an alkaloid isolated from the Brazilian marine sponge Pachychalina alcaloidifera. Ingenamine G displayed a moderate cytotoxic activity against human proliferating lymphocytes evaluated by the MTT assay (IC(50) 15 microg/mL). The hemolytic assay showed that ingenamine G cytotoxic activity was not related to membrane disruption. The comet assay and chromosome aberration analysis were applied to determine the genotoxic and clastogenic potential of ingenamine G, respectively. Cultured human lymphocytes were treated with 5, 10, 15 and 20 microg/mL of ingenamine G during the G(1), G(1)/S, S (pulses of 1 and 6 h), and G(2) phases of the cell cycle. All tested concentrations were cytotoxic, reduced significantly the mitotic index, and were clastogenic in all phases of the cell cycle, especially in S phase. While an increase in DNA-strand breaks was observed starting with the concentration corresponding to the IC(50). The presence of genotoxicity and polyploidy during interphase and mitosis, respectively, suggests that ingenamine G at high concentrations is clastogenic and indirectly affects the construction of mitotic fuse.

Assessment of apoptosis and necrosis by DNA fragmentation and morphological criteria

Apoptotic cells share a number of common features, such as phosphatidylserine (PS) exposure, cell shrinkage, chromatin cleavage, nuclear condensation, and formation of pyknotic bodies of condensed chromatin. Necrotic cells exhibit nuclear swelling, chromatin flocculation, loss of nuclear basophilia, breakdown of cytoplasmic structure and organelle function, and cytolysis by swelling. This unit describes some of the techniques most commonly used to detect cell death. A number of assays are used for characterizing and distinguishing apoptosis and necrosis. Morphological assays include trypan blue exclusion, differential staining, and Hoechst staining. Methods to detect chromatin cleavage include TUNEL assays for whole cells and paraffin sections, DNA fragmentation assays using whole cells, assays of total genomic DNA, analysis of DNA fragmentation by agarose gel electrophoresis, phenol extraction of DNA for analysis of fragmentation, a quantitative assay for DNA fragmentation, and detection of DNA fragmentation by pulsed-field gel electrophoresis. A protocol is also provided for Cytospin preparations from cell suspensions.

Increased apoptosis in the alveolar microenvironment of the healthy human lung

BACKGROUND

Apoptosis represents a physiological clearance mechanism in human tissues. The role of apoptosis has not been examined in normal lung cell populations, such as alveolar macrophages and polymorphonuclear cells. What is the percentage, as well as the role, of apoptosis in the alveolar microenvironment of the healthy human lung?

PATIENTS AND METHODS

Bronchoalveolar lavage was obtained from 21 volunteers without lung disease. The specimens were analyzed using: Annexin V binding, DNA laddering, light microscopy and immunohistochemistry for bcl-2 expression.

RESULTS

Apoptosis of the total bronchoalveolar lavage cell population was 51.2%. Both alveolar macrophages and polymorphonuclear cells had a high apoptotic rate (62.1% and 48.3%, respectively) as determined by Annexin V binding. These findings were further confirmed using morphological criteria for apoptosis and gel electrophoresis for DNA fragmentation. In the majority of the individuals examined, (8 out of 21), the bcl-2 gene was expressed in the lymphocyte population mainly.

CONCLUSIONS

The percentage of apoptosis in lung cells of healthy humans is high. Apoptosis plays a key role in normal lung cell death. It appears to be the mechanism that opposes cell proliferation by eliminating, aged or damaged cells thus facilitating the process of lung remodeling.

Antiproliferative activity of pristimerin isolated from Maytenus ilicifolia (Celastraceae) in human HL-60 cells

Pristimerin has been shown to be cytotoxic to several cancer cell lines. In the present work, the cytotoxicity of pristimerin was evaluated in human tumor cell lines and in human peripheral blood mononuclear cells (PBMC). This work also examined the effects of pristimerin (0.4; 0.8 and 1.7 microM) in HL-60 cells, after 6, 12 and 24h of exposure. Pristimerin reduced the number of viable cells and increased number of non-viable cells in a concentration-dependent manner by tripan blue test showing morphological changes consistent with apoptosis. Nevertheless, pristimerin was not selective to cancer cells, since it inhibited PBMC proliferation with an IC50 of 0.88 microM. DNA synthesis inhibition assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation in HL-60 cells was 70% and 83% for the concentrations of 0.4 and 0.8 microM, respectively. Pristimerin (10 and 20 microM) was not able to inhibit topoisomerase I. In AO/EB (acridine orange/ethidium bromide) staining, all tested concentrations reduced the number of HL-60 viable cells, with the occurrence of necrosis and apoptosis in a concentration-dependent manner, results in agreement with trypan blue exclusion findings. The analysis of membrane integrity and internucleosomal DNA fragmentation by flow cytometry in the presence of pristimerin indicated that treated cells underwent apoptosis. The present data point to the importance of pristimerin as representative of an emerging class of potential anticancer chemicals, exhibiting an antiproliferative effect by inhibiting DNA synthesis and triggering apoptosis.

The chlorophenoxy herbicide dicamba and its commercial formulation banvel® induce genotoxicity and cytotoxicity in Chinese hamster ovary (CHO) cells

The sister chromatid exchange (SCE) frequency, the cell-cycle progression analysis, and the single cell gel electrophoresis technique (SCGE, comet assay) were employed as genetic end-points to investigate the geno- and citotoxicity exerted by dicamba and one of its commercial formulation banvel (dicamba 57.71%) on Chinese hamster ovary (CHO) cells. Log-phase cells were treated with 1.0-500.0 microg/ml of the herbicides and harvested 24 h later for SCE and cell-cycle progression analyses. All concentrations assessed of both test compounds induced higher SCE frequencies over control values. SCEs increased in a non-dose-dependent manner neither for the pure compound (r=0.48; P>0.05) nor for the commercial formulation (r=0.58, P>0.05). For the 200.0 microg/ml and 500.0 microg/ml dicamba doses and the 500.0 microg/ml banvel dose, a significant delay in the cell-cycle progression was found. A regression test showed that the proliferation rate index decreased as a function of either the concentration of dicamba (r=-0.98, P<0.05) or banvel (r=-0.88, P<0.01) titrated into cultures in the 1.0-500.0 microg/ml dose-range. SCGE performed on CHO cells after a 90 min pulse-treatment of dicamba and banvel within a 50.0-500.0 microg/ml dose-range revealed a clear increase in dicamba-induced DNA damage as an enhancement of the proportion of slightly damaged and damaged cells for all concentrations used (P<0.01); concomitantly, a decrease of undamaged cells was found over control values (P<0.01). In banvel-treated cells, a similar overall result was registered. Dicamba induced a significant increase both in comet length and width over control values (P<0.01) regardless of its concentration whereas banvel induced the same effect only within 100.0-500.0 microg/ml dose range (P<0.01). As detected by three highly sensitive bioassays, the present results clearly showed the capability of dicamba and banvel to induce DNA and cellular damage on CHO cells.

Knockdown of SMN by RNA interference induces apoptosis in differentiated P19 neural stem cells

Spinal muscular atrophy (SMA) is a common neurodegenerative disease that is caused by mutations in the survival of motor neuron gene (SMN), leading to reduced levels of the SMN protein in affected individuals. In SMA, motor neurons selectively degenerate, however, the mechanism of cell death and the precise role of SMN in this process are not completely understood. In this study, we apply RNA interference (RNAi) to knockdown Smn gene expression in the murine embryonal carcinoma stem cell line P19, which can be differentiated into neuronal cells. A direct effect of Smn loss on apoptotic cell death in differentiated P19 neuronal cells, and to a lesser extent in undifferentiated cells was observed. Apoptosis could be partly reversed by expression of an SMN rescue construct, was reversible by the addition of the caspase-inhibitor ZVAD-fmk and involved the cytochrome c pathway. This study shows for the first time that knockdown of SMN results in apoptosis in mammalian neuronal cells and has implications for understanding the cause of motor neuron-specific cell loss in SMA, and for identifying novel therapeutic targets for this disease.

alpha- and epsilon-protein kinase C activity during smooth muscle cell apoptosis in response to gamma-radiation

The use of gamma-radiation in treatment of pelvic cancer is associated with injury of healthy surrounding tissues and disorders of intestinal motility; however, the cellular mechanisms involved are unclear. We tested the hypothesis that exposure of visceral smooth muscle cells (SMCs) to gamma-radiation induces apoptosis via activation of specific protein kinase C (PKC) isoforms. Cultured SMCs and slices from guinea pig ileum smooth muscle longitudinal layer (GPISMLL) were exposed to 10 to 50 Gy. Flow cytometry in gamma-radiated SMCs showed increased percentage of cells in the sub-G(0)/G(1) phase, a hallmark of apoptosis. gamma-Radiation-induced reduction in cell survival was partially but significantly alleviated with the PKC inhibitors. Sections of gamma-irradiated GPISMLL showed DNA fragmentation and apoptotic bodies analyzed by the terminal deoxynucleotidyl transferase dUTP nick-end labeling method, whereas the plasma and nuclear membranes were preserved. Confocal microscopy in gamma-radiated SMCs labeled with annexin V-fluorescein showed an increase in apoptotic cells and phosphatidylserine externalization. Contraction of GPISMLL strips in response to KCl and acetylcholine was reduced in tissues exposed to 30 and 50 Gy. gamma-Radiation of GPISMLL caused an increase in PKC activity in the particulate fraction, a decrease in the cytosolic fraction, and increased particulate/cytosolic PKC activity ratio. Western blot analysis revealed significant amounts of alpha- and epsilon-PKC in the cytosolic fraction of control GPISMLL. gamma-Radiation caused an increase in the amount of alpha- and epsilon-PKC in the particulate fraction and a decrease in the cytosolic fraction. Data suggest that gamma-radiation induces apoptosis, growth arrest, and contractile dysfunction in visceral SMCs of GPISMLL via activation and translocation of alpha- and epsilon-PKC isoforms.

A quantitative study of NF-kappaB activation by H2O2: relevance in inflammation and synergy with TNF-alpha

Although the germicide role of H(2)O(2) released during inflammation is well established, a hypothetical regulatory function, either promoting or inhibiting inflammation, is still controversial. In particular, after 15 years of highly contradictory results it remains uncertain whether H(2)O(2) by itself activates NF-kappaB or if it stimulates or inhibits the activation of NF-kappaB by proinflammatory mediators. We investigated the role of H(2)O(2) in NF-kappaB activation using, for the first time, a calibrated and controlled method of H(2)O(2) delivery--the steady-state titration--in which cells are exposed to constant, low, and known concentrations of H(2)O(2). This technique contrasts with previously applied techniques, which disrupt cellular redox homeostasis and/or introduce uncertainties in the actual H(2)O(2) concentration to which cells are exposed. In both MCF-7 and HeLa cells, H(2)O(2) at extracellular concentrations up to 25 microM did not induce significantly per se NF-kappaB translocation to the nucleus, but it stimulated the translocation induced by TNF-alpha. For higher H(2)O(2) doses this stimulatory role shifts to an inhibition, which may explain published contradictory results. The stimulatory role was confirmed by the observation that 12.5 microM H(2)O(2), a concentration found during inflammation, increased the expression of several proinflammatory NF-kappaB-dependent genes induced by TNF-alpha (e.g., IL-8, MCP-1, TLR2, and TNF-alpha). The same low H(2)O(2) concentration also induced the anti-inflammatory gene coding for heme oxygenase-1 (HO-1) and IL-6. We propose that H(2)O(2) has a fine-tuning regulatory role, comprising both a proinflammatory control loop that increases pathogen removal and an anti-inflammatory control loop, which avoids an exacerbated harmful inflammatory response.

On the cytotoxicity and status of oxidative stress of two novel synthesized tri-aza macrocyclic diamides as studied in the V79 cell lines

Two tri-aza macrocycles as diamide derivatives of macrocyclic compounds possess a hydrophilic cavity surrounded by hydrophobic ring, which enables them to diffuse cell membrane and interfere with different living systems. In this study, we comparatively evaluated cytotoxicity effects of tri-aza dibenzo sulfoxide (TSD) and dibenzo sulfide (TTS) macrocyclic diamides in a range of doses (0.5-8mM) and the role of oxidative stress in V79 cell culture. We assessed the effects of these substances on ROS level, cellular viability, apoptosis events, activity of antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), and on some macromolecules' oxidative damage end-products: malondialdehyde (MDA), dityrosine, and 8-hydroxy-deoxyguanosine (8-OH-dG) that were assessed by spectrometry and HPLC methods. Both compounds revealed cytotoxicity effects on cell culture particularly at doses >1mM after 24-h incubation. They decreased cellular viability and significantly promoted ROS generation, increased enzyme activities, and enhanced oxidative damages in which TSD was more effective. Treatment of cells with each compound alone increased significantly the percent of apoptotic events at 2 and then 4mM. Co-treatment with alpha-tocopherol (alpha-TCP) drastically reduced these events. Cells' exposure with mixture of 30 microM alpha-tocopherol and 8mM of each compound exerted significant decrease in the levels of ROS, enzyme activities, and oxidative damage biomarkers. As conclusion, our study documented the oxidative radical forming ability of the studied compounds and further strengthened the documentation of their cytotoxicity effects through lipids, proteins and DNA oxidation damages.

Control of apoptosis in influenza virus-infected cells by up-regulation of Akt and p53 signaling

PI3k-Akt and p53 pathways are known to play anti- and pro-apoptotic roles in cell death, respectively. Whether these pathways are recruited in influenza virus infection in highly productive monkey (CV-1) and canine (MDCK) kidney cells was studied here. Phosphorylation of Akt (Akt-pho) was found to occur only early after infection (5-9 h.p.i). Nuclear accumulation and phosphorylation of p53 (p53-pho), and expression of its natural target p21/waf showed low constitutive levels at this period, whereas all three parameters were markedly elevated at the late apoptotic stage (17-20 h.p.i.). Up-regulation of Akt-pho and p53-pho was not induced by UV-inactivated virus suggesting that it required virus replication. Also, mRNAs of p53 and its natural antagonist mdm2 were not increased throughout infection indicating that p53-pho was up-regulated by posttranslational mechanisms. However, p53 activation did not seem to play a leading role in influenza-induced cell death: (i) infection of CV1 and MDCK cells with recombinant NS1-deficient virus provoked accelerated apoptotic death characterized by the lack of p53 activation; (ii) mixed apoptosis-necrosis death developed in influenza-infected human bronchial H1299 cells carrying a tetracycline-regulated p53 gene did not depend on p53 gene activation by tetracycline. Virus-induced apoptosis and signaling of Akt and p53 developed in IFN-deficient VERO cells with similar kinetics as in IFN-competent CV1-infected cells indicating that these processes were endocrine IFN-independent. Apoptosis in influenza-infected CV-1 and MDCK cells was Akt-dependent and was accelerated by Ly294002, a specific inhibitor of PI3k-Akt signaling, and down-regulated by the viral protein NS1, an inducer of host Akt. The obtained data suggest that influenza virus (i) initiates anti-apoptotic PI3k-Akt signaling at early and middle phases of infection to protect cells from fast apoptotic death and (ii) provokes both p53-dependent and alternative p53-independent apoptotic and/or necrotic (in some host systems) cell death at the late stage of infection.

Therapy with minocycline aggravates experimental rabies in mice

Minocycline is a tetracycline derivative with antiapoptotic and anti-inflammatory properties, and the drug has been shown to have beneficial effects in a variety of models of neurological disorders. The potentially neuroprotective role of minocycline was assessed in experimental in vitro and in vivo models of rabies virus infection. In this study, 5 nM minocycline did not improve the viability of embryonic mouse cortical and hippocampal neurons infected in vitro with the attenuated SAD-D29 strain of rabies virus, based on assessments using trypan blue exclusion. Two-day-old ICR mice were inoculated in the right hind limb thigh muscle with SAD-D29, and they received daily subcutaneous injections of either 50 mg/kg minocycline or vehicle (phosphate-buffered saline). Infected minocycline-treated mice experienced an earlier onset of neurologic signs and greater mortality (83% versus 50%) than those receiving vehicle (log rank test, P=0.002 and P=0.003, respectively). Immunohistochemical analysis of rabies virus antigen distribution was performed at early time points and in moribund mice. There were greater numbers of infected neurons in the regional brain areas of minocycline-treated mice than in vehicle-treated mice, which was significant in the CA1 region of the hippocampus. There was less apoptosis (P=0.01) and caspase 3 immunostaining (P=0.0008) in the midbrains of mice treated with minocycline than in mice treated with vehicle, consistent with a neuroprotective role of neuronal apoptosis that may have had a mild effect of inhibiting viral spread. Reduced infiltration of CD3+ T cells was observed in the pons/medulla of moribund mice that received minocycline therapy (P=0.008), suggesting that the anti-inflammatory actions of minocycline may intensify the neurologic disease. These findings indicate that minocycline has important detrimental effects in the therapy of experimental rabies. Empirical therapy with minocycline should therefore be approached with caution in cases of human rabies and possibly other viral encephalitides until more experimental data become available.

Piplartine induces inhibition of leukemia cell proliferation triggering both apoptosis and necrosis pathways

Piplartine {5,6-dihydro-1-[1-oxo-3-(3,4,5-trimethoxyphenyl)-2-propenyl]-2(1H)pyridinone} is an alkaloid/amide component of Piper species. The purpose of the present study was to examine the antiproliferative effects of piplartine on human leukemia cell lines HL-60, K562, Jukart, and Molt-4 using the trypan blue exclusion method, as well as the effect of piplartine on DNA synthesis. The viability of all human leukemia cell lines were not affected by piplartine after 6 h, 9 h, and 12 h exposure, whereas a steady decline was seen after an exposure time of 24 h. The antiproliferative activity of piplartine seemed to be related to the inhibition of DNA synthesis, as revealed by the reduction of 5-bromo-2'-deoxyuridine (BrdU) incorporation after 24h of incubation. Piplartine-mediated reduction in cell number was associated with an increasing number of dead cells at a concentration of 10 microg/ml. These findings were corroborated by morphologic analysis. However, at the lowest concentration (2.5 microg/ml), piplartine-treated cells exhibited typical apoptotic morphological changes. The increase in caspase-3 activity was also observed in lysates of piplartine-treated cells (2.5 microg/ml). Our findings suggest that piplartine can suppress leukemia growth and reduce cell survival, triggering both apoptosis and/or necrosis, depending on the concentration used.

Magnolol suppresses NF-kappaB activation and NF-kappaB regulated gene expression through inhibition of IkappaB kinase activation

The mis-regulation of nuclear factor-kappa B (NF-kappaB) signal pathway is involved in a variety of inflammatory diseases that leds to the production of inflammatory mediators. Our studies using human U937 promonocytes cells suggested that magnolol, a low molecular weight lignan isolated from the medicinal plant Magnolia officinalis, differentially down-regulated the pharmacologically induced expression of NF-kappaB-regulated inflammatory gene products MMP-9, IL-8, MCP-1, MIP-1alpha, TNF-alpha. Pre-treatment of magnolol blocked TNF-alpha-induced NF-kappaB activation in different cell types as evidenced by EMSA. Magnolol did not directly affect the binding of p65/p50 heterodimer to DNA. Immunoblot analysis demonstrated that magnolol inhibited the TNF-alpha-stimulated phosphorylation and degradation of the cytosolic NF-kappaB inhibitor IkappaBalpha and the effects were dose-dependent. Mechanistically, a non-radioactive IkappaB kinases (IKK) assay using immunoprecipitated IKKs protein demonstrated that magnolol inhibited both intrinsic and TNF-alpha-stimulated IKK activity, thus suggesting a critical role of magnolol in abrogating the phosphorylation and degradation of IkappaBalpha. The involvement of IKK was further verified in a HeLa cell NF-kappaB-dependent luciferase reporter system. In this system magnolol suppressed luciferase expression stimulated by TNF-alpha and by the transient transfection and expression of NIK (NF-kappaB-inducing kinase), wild type IKKbeta, constitutively active IKKalpha and IKKbeta, or the p65 subunit. Magnolol was also found to inhibit the nuclear translocation and phosphorylation of p65 subunit of NF-kappaB. In line with the observation that NF-kappaB activation may up-regulate anti-apoptotic genes, it was shown in U937 cells that magnolol enhanced TNF-alpha-induced apoptotic cell death. Our results suggest that magnolol or its derivatives may have potential anti-inflammatory actions through IKK inactivation.

Influenza A virus NS1 protein activates the PI3K/Akt pathway to mediate antiapoptotic signaling responses

Recently we have shown that influenza A virus infection leads to activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway and that this cellular reaction is dependent on the expression of the viral nonstructural protein 1 (NS1). These data also suggested that PI3K activation confers a virus-supporting activity at intermediate stages of the infection cycle. So far it is not known which process is regulated by the kinase that supports virus replication. It is well established that upon infection with influenza A virus, the expression of the viral NS1 keeps the induction of beta interferon and the apoptotic response within a tolerable limit. On a molecular basis, this activity of NS1 has been suggested to preclude the activation of cellular double-stranded RNA receptors as well as impaired modulation of mRNA processing. Here we present a novel mode of action of the NS1 protein to suppress apoptosis induction. NS1 binds to and activates PI3K, which results in the activation of the PI3K effector Akt. This leads to a subsequent inhibition of caspase 9 and glycogen synthase-kinase 3beta and limitation of the virus-induced cell death program. Thus, NS1 not only blocks but also activates signaling pathways to ensure efficient virus replication.

c-Jun N-terminal kinase mediates hydrogen peroxide-induced cell death via sustained poly(ADP-ribose) polymerase-1 activation

Reactive oxygen species (ROS) have been closely associated with both apoptotic and non-apoptotic/necrotic cell death. Our previous study has illustrated that c-Jun-N-terminal kinase 1 (JNK1) is the main executor in hydrogen peroxide (H(2)O(2))-induced nonapoptotic cell death. The main objective of this study is to further elucidate the molecular mechanisms downstream of JNK1 in H(2)O(2)-induced cell death. In this study, poly(ADP-ribose) polymerase-1 (PARP-1), a key DNA repair protein, was readily activated by H(2)O(2) and inhibition of PARP-1 activation by either a pharmacological or genetic approach offered significant protection against H(2)O(2)-induced cell death. More importantly, H(2)O(2)-mediated PARP-1 activation is subject to regulation by JNK1. Suppression of JNK1 activation by a chemical inhibitor or genetic deletion markedly suppressed the late-phase PARP-1 activation induced by H(2)O(2), suggesting that JNK1 contributes to the sustained activation of PARP-1. Such findings were supported by the temporal pattern of nuclear translocation of activated JNK and a direct protein-protein interaction between JNK1 and PARP-1 in H(2)O(2)-treated cells. Finally, in vitro kinase assay suggests that PARP-1 may serve as the direct phosphorylation target for JNK1. Taken together, data from our study reveal a novel underlying mechanism in H(2)O(2)-induced nonapoptotic cell death: JNK1 promotes a sustained PARP-1 activation via nuclear translocation, protein-protein interaction and PARP-1 phosphorylation.

Matrix regulation of skeletal cell apoptosis III: Mechanism of ion pair-induced apoptosis

Our previous work has demonstrated that while the Ca(2+) and Pi ions acting in concert function as a potent osteoblast apoptogen, the underlying mechanisms by which it activates cell death is not known. We hypothesize that the ion pair causes release of Ca(2+) from intracellular stores ([Ca(2+)]i); the increase in intracellular calcium prompts the mitochondria to uptake more calcium. This accumulation of calcium eventually results in the loss of mitochondrial membrane potential (MMP) and, subsequently, apoptosis. To test this hypothesis, we evaluated apoptosome formation in MC3T3-E1 osteoblast-like cells treated with the ion pair. Western blot analysis indicated migration of cytochrome-c and Smac/DIABLO from mitochondria to the cytoplasm. Inhibition of either the electron transfer chain (with antimycin a and rotenone), or the activation of a MMP transition (with bongkrekic acid) inhibited apoptosis in a dose-dependent manner. Pre-treating osteoblasts with ruthenium red, a Ca(2+) uniporter inhibitor of both mitochondria and the endoplasmic reticulum (ER), also completely abolished Ca(2+.)Pi-induced apoptosis. Moreover, we showed that an increase in [Ca(2+)]i preceded the increase in MMP over the first 45 min of treatment; a mitochondrial membrane permeability transition was evident at 75 min. To determine the role of ER, Ca(2+) stores in the generation of the apoptotic signal by the ion pair, cells were treated with several inhibitors. Apoptosis was inhibited when cells were treated with dantrolene, an inhibitor of ER ryanodine receptors, and 2-aminodiphenylborate, an IP3 Ca(2+) channel inhibitor, but not cyclopiazonic acid, an ER Ca(2)-ATPase inhibitor. Together, these data demonstrate that Ca(2+) Pi-induced osteoblast apoptosis is characterized by the generation of an apoptosome and that Ca(2+) release from ER stores may promote ion pair-dependent cell death.

Rabies virus infection of primary neuronal cultures and adult mice: failure to demonstrate evidence of excitotoxicity

Cultures derived from the cerebral cortices and hippocampi of 17-day-old mouse fetuses infected with the CVS strain of rabies virus showed loss of trypan blue exclusion, morphological apoptotic features, and activated caspase 3 expression, indicating apoptosis. The NMDA (N-methyl-D-aspartate acid) antagonists ketamine (125 microM) and MK-801 (60 microM) were found to have no significant neuroprotective effect on CVS-infected neurons, while the caspase inhibitor Ac-Asp-Glu-Val aspartic acid aldehyde (25 microM) exerted a marked neuroprotective effect. Glutamate-stimulated increases in levels of intracellular calcium were reduced in CVS-infected hippocampal neurons. Ketamine (120 mg/kg of body weight/day intraperitoneally) given to CVS-infected adult mice produced no beneficial effects. We have found no supportive evidence that excitotoxicity plays an important role in rabies virus infection.

Induction of apoptosis by quercetin: different response of human chronic myeloid (K562) and acute lymphoblastic (HSB-2) leukemia cells

This work shows that 25 microM quercetin caused a marked inhibition of K562 cells growth together with a mild cytotoxicity, while HSB-2 cells were practically unaffected. Moreover, quercetin induced caspase-3 and cytochrome c-dependent apoptosis almost exclusively in the former cell line. Exposure of K562 cells to quercetin caused also a significant increase of cells in G(2)/M phase that reached the maximum peak at 24 h (4-fold with respect to the basal value). The major sensitivity exhibited by K562 cells was only in part imputable to their higher glutathione content, as compared to HSB-2 cells, thus confirming previous reports describing the formation of intracellular quercetin-thiol toxic adducts in cells exposed to the flavonoid. In fact, after induction of intracellular glutathione increase we detected in both cell lines a significant rise of apoptotic cells, again more marked in K562 cells. By contrast, glutathione-depleted cells, failed to show a decrease of apoptosis in both cell lines, thus contradicting our previous findings and literature data. Since the yet unresolved question about the anti-oxidant or the pro-oxidant capacity of quercetin, we investigated which of these two properties worked in our experimental model. Interestingly, not only quercetin did not produce reactive oxygen species but also prevented their formation, as observed in cells exposed to the oxidizing agent ter-butylhydroperoxide, acting as an efficient oxygen radicals scavenger. This result indicates that quercetin exhibited, in these cell lines, anti-oxidant more than pro-oxidant ability.

Cell death, caspase activation, and HMGB1 release of porcine choroid plexus epithelial cells during Streptococcus suis infection in vitro

The choroid plexus epithelium constitutes the structural basis of the blood-cerebrospinal fluid barrier. We previously demonstrated that Streptococcus suis (S. suis), a relevant cause of bacterial meningitis in pigs and humans, affects porcine choroid plexus epithelial cell (PCPEC) barrier function and integrity. We now characterized PCPEC cell death and investigated whether apoptosis or necrosis is responsible for the cytotoxicity after infection with different S. suis isolates. We found S. suis strain-dependent histone associated DNA-fragments quantified by ELISA. This response could partially be inhibited by cylcoheximide, cytochalasin D, dexamethasone, herbimycin A, but most effectively by the pan-caspase inhibitor zVAD-fmk. We further detected caspase-3 and -9 activation after infection with all tested S. suis isolates that could also be blocked by zVAD-fmk. However, we found a significantly stronger caspase activity with the protein kinase inhibitor staurosporine. All tested S. suis isolates induced loss of cell viability in PCPEC as shown with the Live/Dead assay, but strain dependent lactate dehydrogenase-release. Both parameters could not be influenced by zVAD-fmk. Immunostaining showed release of high-mobility group box 1 (HMGB1) protein from the nucleus, indicative of necrosis. Transmission electron microscopy showed cell swelling, cytoplasmic vacuolization, loss of membrane integrity, nuclear fermentation but no nuclear condensation, indices for a primarily necrotic cell morphology. Taken together, our findings indicate that S. suis causes cell death in PCPEC by different mechanisms. Although apoptosis may be involved in the process of PCPEC cell death, necrosis seems to be the predominant mechanism. Through inflammation in the choroid plexus during bacterial meningitis, the blood-cerebrospinal fluid barrier function will be compromised.

A divalent human leukocyte antigen-B7 fusion-protein up-regulates CD25 and CD69 in alloreactive CD8+ T cells bypassing CD28 costimulation

BACKGROUND

T cells recognize major histocompatibility complex (MHC) molecules and their cryptic antigenic peptides on antigen-presenting cells and are generally triggered to proliferate, and when sufficient, co-stimulation is available. In soluble form, monomeric MHC molecules can induce apoptosis, anergy, or decreases of the T-cell receptor (TCR).

METHODS

A dimeric fusion protein of the human leukocyte antigens (HLA)-B7 was molecularly engineered and expressed in a B-cell line to allow secretion. Alloreactive T cells were generated according to the standard protocol.

RESULTS

A dimer of approximately 160 kD was obtained, affinity purified, and used to study T-cell interaction. In immobilized form, this protein efficiently stimulated alloreactive T cells to proliferate and produce interleukin (IL)-2 and interferon (IFN)-gamma in a concentration-dependent manner, up-regulating CD25 and CD69 expression. In contrast, the soluble fusion protein induced T-cell apoptosis.

CONCLUSIONS

The dichotomy in T-cell regulation by a divalent MHC fusion protein warrants the use of MHC multimers as custom-designed immune-regulatory molecules both in transplantation and autoimmune disease.

Effect of dopamine on rat diaphragm apoptosis and muscle performance

The purpose of this study was to determine whether dopamine (DA) decreases diaphragm apoptosis and attenuates the decline in diaphragmatic contractile performance associated with repetitive isometric contraction using an in vitro diaphragm preparation. Strenuous diaphragm contractions produce free radicals and muscle apoptosis. Dopamine is a free radical scavenger and, at higher concentrations, increases muscle contractility by simulating beta2-adrenoreceptors. A total of 47 male Sprague-Dawley rats weighing 330-450 g were used in a prospective, randomized, controlled in vitro study. Following animal anaesthetization, diaphragms were excised, and muscle strips prepared and placed in a temperature-controlled isolated tissue bath containing Krebs-Ringer solution (KR) or KR plus 100 microm DA. The solutions were equilibrated with oxygen (O2) at 10, 21 or 95% and 5% carbon dioxide, with the balance being nitrogen. Diaphragm isometric twitch and subtetanic contractions were measured intermittently over 65 min. The diaphragms were then removed and, using a nuclear differential dye uptake method, the percentages of normal, apoptotic and necrotic nuclei were determined using fluorescent microscopy. There were significantly fewer apoptotic nuclei in the DA group diaphragms than in the KR-only group diaphragms in 10 and 21% O2 following either twitch or subtetanic contractions. Dopamine at 100 microm produced only modest increases in muscle performance in both 10 and 21% O2. The attenuation of apoptosis by DA was markedly greater than the effect of DA on muscle performance. Dopamine decreased diaphragmatic apoptosis, perhaps by preventing the activation of intricate apoptotic pathways, stimulating antiapoptotic mechanisms and/or scavenging free radicals.

Selective cytotoxicity of withaphysalins in myeloid leukemia cell lines versus peripheral blood mononuclear cells

Withaphysalins are C(28)-steroidal lactones structurally based on the ergostane skeleton that possess antiproliferative activity against tumor cell lines. In the present study, the antileukemic actvity of withaphysalin O (1), M (2), and N (3) isolated from Acnistus arborescens, against two leukemic cell lines, HL-60 and K562, was evaluated, and the cytotoxicity compared with the effects on peripheral blood mononuclear cells (PBMC). All tested compounds reduced the number of viable cells of the tumor cell lines after 24 h of exposure, except for compound 2 against the K562 cell line. The reduction was time-and concentration-dependent, and the IC(50) values ranged from 0.7 to 3.5 microM after 72 h of incubation. In addition to the growth inhibitory properties, the drugs decreased DNA synthesis after 24 h of drug exposure evaluated by the 5-bromo-2 -deoxyuridine incorporation method. None of the tested compounds reduced the number of PBMC (IC(50)>20 microM) after 72 h of incubation, in contrast to doxorubicin that decreased viable cells and increased non-viable cells even after 24 h of incubation. Morphological analysis of treated cells using hematoxylin/eosin staining indicated the presence of necrotic cells for all tested compounds in HL-60, confirmed by the use of acridine orange/ethidium bromide staining. In addition to necrotic cells, K562 cells showed morphological alterations consistent with apoptosis.

OspE2 of Shigella sonnei is required for the maintenance of cell architecture of bacterium-infected cells

The OspE2 product of Shigella spp., the expression of which is regulated by the mxiE gene, is secreted through a type III secretion system into host cells. We investigated the function of OspE2 of Shigella sonnei by using cultured epithelial cells. Cells invaded by an ospE2 deletion mutant altered their morphology into the rounding shape, which was not due to cell death, whereas cells invaded by the wild-type strain kept their cell shape intact. The ospE2 mutation did not affect initial cell entry and multiplication in cells, but the mutant formed smaller-than-normal plaques on cell monolayers, indicating a deficiency in cell-to-cell spread by the bacteria. An mxiE deletion mutant also showed changes in cell morphology and deficiency in bacterial spread to adjacent cells. In cells invaded by the ospE2 mutant, disturbance of actin stress fibers was prominent at 3 h after invasion. Analysis of OspE2 localization indicated that the OspE2 protein accumulated on focal contact-like structures in the infected host cells. These results suggest that colocalization of the OspE2 protein in the focal contacts of infected cells may function to maintain an intact cell morphology. The morphological change induced by invasion of the ospE2 mutant may affect secondary bacterial transmission.

Analysis of gene regulation in rabbit corneal epithelial cells induced by ultraviolet radiation

Ultraviolet (UV)-induced cataracts are becoming a major environmental health concern because of the possible decrease in the stratospheric ozone layer. Experiments were designed to isolate gene(s) affected by UV irradiation in rabbit cornea tissues using fluorescent differential display-reverse transcription-polymerase chain reaction (FDDRT-PCR). The epithelial cells were grown in standard medium for 2 or 4 hours post treatment. Cornea epithelial cells were irradiated with UVB for 20 minutes. RNA was extracted and amplified by reverse transcriptase-polymerase chain reaction using poly A+ specific anchoring primers and random arbitrary primers. Polyacrylamide gel electrophoresis revealed several differentially expressed genes in untreated versus UV irradiated cells. Complimentary DNA (cDNA) fragments resulting from fluorescent differentially expressed mRNAs were eluted from the gel and re-amplified. The re-amplified PCR products were cloned directly into the PCR-TRAP cloning system. These data showed that FDDRT-PCR is a useful technique to elucidate UV-regulated gene expressions. Future experiments will involve sequence analysis of cloned inserts. The identification of these genes through sequence analysis could lead to a better understanding of cataract formation via DNA damage and mechanisms of prevention.

Cytoplasmic Ca2+ signals and cellular death by apoptosis in myocardiac H9c2 cells

The incubation of H9c2 cells with 10 microM thapsigargin (TG) was associated with the appearance of a two-component cytoplasmic Ca2+ peak. Experiments performed in a Ca2+-free medium indicated that both components came from intracellular sources. The first component of the signal corresponded to the discharge of the sarco-endoplasmic reticulum (SER) Ca2+ store. The appearance of the second component was prevented by cell preincubation with cyclosporin A (CsA) and gave rise to a clear and permanent depolarization of the mitochondrial inner membrane. These features were indication of a mitochondrial origin. The observed release of mitochondrial Ca2+ was related with opening of the permeability transition pore (PTP). The two-component cytoplasmic Ca2+ peak, i.e., treatment with 10 microM TG, as compared with the first component alone, i.e., treatment with 3 microM TG, was associated with a faster process of cellular death. In both cases, chromatin fragmentation and condensation at the nuclear periphery were observed. Other prominent apoptotic events such as loss of DNA content and cleavage of poly(ADP-ribose) polymerase (PARP) were also dependent on TG concentration and occurred in different time windows. PTP opening induced by 10 microM TG was responsible for the faster apoptotic death.

Dominant role for calpain in thromboxane-induced neuromicrovascular endothelial cytotoxicity

Thromboxane A(2) (TXA(2)) is an important lipid mediator generated during oxidative stress and implicated in ischemic neural injury. This autacoid was recently shown to partake in this injury process by directly inducing endothelial cytotoxicity. We explored the mechanisms for this TXA(2)-evoked neural microvascular endothelial cell death. Stable TXA(2) mimetics 5-heptenoic acid, 7-[6-(3-hydroxy-1-octenyl)-2-oxabicyclo[2.2.1]hept-5-yl]-[1R-[1alpha,4alpha,5beta(Z),6alpha,(1E,3S)]]-9,11-dedioxy-9alpha,11alpha-methanolpoxy (U-46619) [as well as [1S-[1alpha,2alpha(Z),3beta(1E,3S(*)),4alpha]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl]-7-oxabicyclo[2.1.1]-hept-2-yl]-5-heptenoic acid; I-BOP] induced a retinal microvascular degeneration in rat pups in vivo and in porcine retinal explants ex vivo and death of porcine brain endothelial cells (in culture). TXA(2) dependence of these effects was corroborated by antagonism using the selective TXA(2) receptor blocker (-)-6,8-difluoro-9-p-methyl-sulfonyl-benzyl-1,2,3,4-tetrahydrocarbazol-1-yl-acetic acid (L670596). In all cases, neurovascular endothelial cell death was prevented by pan-calpain and specific m-calpain inhibitors but not by caspase-3 or pan-caspase inhibitors. Correspondingly, TXA(2) (mimetics) augmented generation of known active m-calpain (but not mu-calpain) form and increased the activity of m-calpain (cleavage of fluorogenic substrate N-succinyl-Leu-Leu-Val-Tyr-7-amino-4-methylcoumarin; and of alpha-spectrin into specific fragments) but not of pan-caspase or specific caspase-3 (respectively, using sulforhodamine-Val-Arg-Asp-fluoromethyl ketone and detecting its active 17- and 12-kDa fragments). Interestingly, these effects were phospholipase C (PLC)-dependent [associated with increase in inositol triphosphate and inhibited by PLC blocker 1-[6-[[17beta-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U73122)] and required calcium but were not associated with increased intracellular calcium. U-46619-induced calpain activation resulted in translocation of Bax to the mitochondria, loss of polarization of the latter (using potentiometric probe 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide; JC-1) and in turn release of cytochrome c into the cytosol and depletion of cellular ATP; these effects were all blocked by calpain inhibitors. Overall, this work identifies (specifically) m-calpain as a dominant protease in TXA(2)-induced neurovascular endothelial cell death.

Genotoxic and aneugenic properties of an imidazole derivative

To contribute to a more accurate characterization of the mutagenic and aneugenic effects of thiabendazole (TBZ), a widely used antiparasitic and food preservative drug, the induction of sister chromatid exchanges (SCEs) and mitotic spindle anomalies as cytogenetic end-points were investigated. Studies were carried out in Chinese hamster ovary (CHO) cells and human peripheral blood lymphocytes. A significant dose-dependent increase in SCE frequency was observed in CHO cells with S9-Mix (P < 0.01) in the 50-100 microg ml(-1) dose-range, while in the absence of S9-Mix, an enhancement of the SCE frequency was exhibited at the highest dose (P < 0.01). In CHO-K1 cells a significant increase in mitotic spindle anomalies (P < 0.01) was observed with the highest concentration assayed reflecting the specific effect of TBZ formulation at the microtubule level. Cell proliferation kinetics (CPK) were not modified by the addition of this pharmaceutical product. In human lymphocyte cultures, exposure to 100 microg ml(-1) TBZ formulation resulted in a significant decrease of the mitotic index (MI) (P < 0.003) and changes in the replication index (RI) (P < 0.05).

Involvement of glutathione in the cytotoxicity of 9-isothiocyanatoacridine

Isothiocyanates (ITCs) are phytochemicals with promising cancer-preventive potential. To elucidate the mechanism of cytotoxicity of ITCs, their accumulation by cells and the role of intracellular glutathione, fluorescent 9-isothiocyanatoacridine (AcITC) was synthesized. The kinetic parameters for the reactions of AcITC with thiols were estimated and the influence of AcITC on human chronic myeloid leukemia cell line (K562) in regard to intracellular glutathione was studied. Cytotoxicity was evaluated by MTT assay, IC(50)=29.2 +/- 2.5 microM (48 h incubation). This acridine derivative was able to induce apoptosis of cells (morphological changes of cells and DNA fragmentation were observed) at least within certain dose that only decreased the level of intracellular glutathione, excessive doses (completely depleted intracellular pool of glutathione) induced necrosis rather than apoptosis. Our results indicated that apoptosis of leukemia cells induced by ITC is possible only if intracellular glutathione is not entirely depleted.

Honokiol inhibits TNF-α-stimulated NF-κB activation and NF-κB-regulated gene expression through suppression of IKK activation

Honokiol, a small molecular weight lignan originally isolated from Magnolia officinalis, shows anti-angiogenic, anti-invasive and anti-proliferative activities in a variety of cancers. In this study, we investigated whether honokiol affects the transcription factor nuclear factor-kappa B (NF-kappaB) which controls a large number of genes involved in angiogenesis, metastasis and cell survival. We observed that the tumor necrosis factor-alpha (TNF-alpha)-induced NF-kappaB activation was blocked by honokiol in four different cancer cell lines as evidenced by EMSA. Honokiol did not directly affect the NF-kappaB-DNA binding. Immunoblot experiments demonstrated that honokiol inhibited the TNF-alpha-stimulated phosphorylation and degradation of the cytosolic NF-kappaB inhibitor IkappaBalpha. Furthermore, honokiol suppressed the intrinsic and TNF-alpha-stimulated upstream IkappaB kinases (IKKs) activities measured by a non-radioactive kinase assay using immunoprecipitated IKKs, suggesting a critical role of honokiol in abrogating the phosphorylation and degradation of IkappaBalpha. In a HeLa cell NF-kappaB-dependent luciferase reporter system, honokiol suppressed luciferase expression stimulated by TNF-alpha and by the transient transfection and expression of NIK (NF-kappaB-inducing kinase), wild type IKKbeta, constitutively active IKKalpha and IKKbeta, or the p65 subunit. Honokiol was also found to inhibit the nuclear translocation and phosphorylation of p65 subunit of NF-kappaB. RT-PCR results showed that honokiol suppressed NF-kappaB-regulated inflammatory and carcinogenic gene products including MMP-9, TNF-alpha, IL-8, ICAM-1 and MCP-1. In line with the observation that NF-kappaB activation may up-regulate anti-apoptotic genes, it was shown that honokiol enhanced TNF-alpha-induced apoptotic cell death. In summary, our results demonstrate that honokiol suppresses NF-kappaB activation and NF-kappaB-regulated gene expression through the inhibition of IKKs, which provides a possible mechanism for its anti-tumor actions.

ARP2 a novel protein involved in apoptosis of LNCaP cells shares a high degree homology with splicing factor Prp8

The mechanism of apoptosis has been recognized as an important event in processes such as cellular development and homeostasis, as well as degenerative conditions like cancer. Prostate cancer during its advanced stages develops androgen independent cells that ultimately overgrow and promote metastatic events. Our group employing androgen independent LNCaP cells have previously proposed, based on electrophysiological findings, that apoptosis induced cells overexpress a cell death calcium channel-like molecule. Here we report the cloning and expression in Xenopus laevis oocytes of apoptosis regulated protein 2 (ARP2), a protein overexpressed in apoptosis induced LNCaP cells capable to induce calcium inward currents and apoptosis typical morphology changes in oocytes injected with arp2 mRNA. Our results also indicate that clone arp2 cDNA (1.3Kb) shares a 99% homology with a small fragment that corresponds to 18% of the complete sequence of Prp8 cDNA (7.0 Kb), a molecule that codifies for an important protein in the assembly of the spliceosome. We propose that protein ARP2 as a fragment of protein Prp8, corresponds to a molecule with a new function in apoptosis related phenomena.

Peroxynitrite-induced neuronal apoptosis is mediated by intracellular zinc release and 12-lipoxygenase activation

Peroxynitrite toxicity is a major cause of neuronal injury in stroke and neurodegenerative disorders. The mechanisms underlying the neurotoxicity induced by peroxynitrite are still unclear. In this study, we observed that TPEN [N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine], a zinc chelator, protected against neurotoxicity induced by exogenous as well as endogenous (coadministration of NMDA and a nitric oxide donor, diethylenetriamine NONOate) peroxynitrite. Two different approaches to detecting intracellular zinc release demonstrated the liberation of zinc from intracellular stores by peroxynitrite. In addition, we found that peroxynitrite toxicity was blocked by inhibitors of 12-lipoxygenase (12-LOX), p38 mitogen-activated protein kinase (MAPK), and caspase-3 and was associated with mitochondrial membrane depolarization. Inhibition of 12-LOX blocked the activation of p38 MAPK and caspase-3. Zinc itself induced the activation of 12-LOX, generation of reactive oxygen species (ROS), and activation of p38 MAPK and caspase-3. These data suggest a cell death pathway triggered by peroxynitrite in which intracellular zinc release leads to activation of 12-LOX, ROS accumulation, p38 activation, and caspase-3 activation. Therefore, therapies aimed at maintaining intracellular zinc homeostasis or blocking activation of 12-LOX may provide a novel avenue for the treatment of inflammation, stroke, and neurodegenerative diseases in which the formation of peroxynitrite is thought to be one of the important causes of cell death.

Antiproliferative and apoptotic potencies of glucocorticoids: nonconcordance with their antiinflammatory and immunossuppressive properties

Relative antiinflammatory and immunosuppressive potencies of glucocorticoids (GC) were previously well defined. Nonetheless, GC also regulate cell proliferation and programmed death (apoptosis). The aim of this study was to determine the relative potency of different GC on the modulation of cell survival. The GC-sensitive lymphoblast cell line CEM-c7/14 was submitted to 48h-exposure to GC (dose-response curve from 10-8 to 10-5M). Cell survival was analyzed employing the DimethylTiazol-Tetrazolium (MTT) test. For each GC at least 4 experiments were performed in quadruplicate. Responses to different GC at the same molarity were analyzed by ANOVA on Ranks. Cell responses to the same GC in different concentrations were tested by repeated measures ANOVA. The EC50 for each GC was calculated with the GraphPad Prism 3.0 software. The use of low concentrations (10-8 and 10-7M) of hydrocortisone and methylprednisolone determined a similar effects on cell survival, which was less prominent than that observed with betamethasone, budesonide or momethasone. Momethasone was the most potent GC, inducing the most intense dexamethasone reduction on cell survival at the lowest concentration (10-8M). Momethasone and methylprednisolone were the two GC with the strongest impact on cell survival. Our findings suggest that antiproliferative and apoptotic potencies of GC are different from those previously reported antiinflammatory and immunosuppressive actions.

The voltage-dependent anion channel-1 modulates apoptotic cell death

The role of the voltage-dependent anion channel (VDAC) in cell death was investigated using the expression of native and mutated murine VDAC1 in U-937 cells and VDAC inhibitors. Glutamate 72 in VDAC1, shown previously to bind dicyclohexylcarbodiimide (DCCD), which inhibits hexokinase isoform I (HK-I) binding to mitochondria, was mutated to glutamine. Binding of HK-I to mitochondria expressing E72Q-mVDAC1, as compared to native VDAC1, was decreased by approximately 70% and rendered insensitive to DCCD. HK-I and ruthenium red (RuR) reduced the VDAC1 conductance but not that of E72Q-mVDAC1. Overexpression of native or E72Q-mVDAC1 in U-937 cells induced apoptotic cell death (80%). RuR or overexpression of HK-I prevented this apoptosis in cells expressing native but not E72Q-mVDAC1. Thus, a single amino-acid mutation in VDAC prevented HK-I- or RuR-mediated protection against apoptosis, suggesting the direct VDAC regulation of the mitochondria-mediated apoptotic pathway and that the protective effects of RuR and HK-I rely on their binding to VDAC.

Genotoxicity of the herbicide 2,4-dichlorophenoxyacetic and a commercial formulation, 2,4-dichlorophenoxyacetic acid dimethylamine salt. I. Evaluation of DNA damage and cytogenetic endpoints in Chinese Hamster ovary (CHO) cells

Genotoxicity of the 2,4-dichlorophenoxyacetic acid (2,4-D) and a commercially-used derivative, 2,4-D dimethylamine salt (2,4-D DMA), was evaluated in CHO cells using SCE and single cell gel electrophoresis (SCGE) assays. Log-phase cells were treated with 2.0-10.0 microg/ml of herbicides and harvested 24 and 36 h later for SCE analysis. Both agents induced significant dose-dependent increases in SCE, regardless of the harvesting time (2,4-D: r=0.98 and r=0.88, P<0.01, for 24 and 36 h harvesting times; 2,4-D DMA: r=0.97 and r=0.88, P<0.01, for 24 and 36 h harvesting times). Neither test compound altered cell-cycle progression or proliferative replication index (P>0.05), but the higher doses of both compounds reduced the mitotic index of cultures harvested at 24 and 36 h (P<0.05). A 90-min treatment with 2.0-10.0 microg/ml 2,4-D and 2,4-D DMA produced dose-dependent increases in the frequency of DNA-strand breaks detected in the SCGE assay, both in cultures harvested immediately after treatment and in cultures harvested 36 h later. The doses of 2,4-D and 2,4-D DMA were equally genotoxic in all of the assays. The results indicate that 2,4-D induces SCE and DNA damage in mammalian cells, and should be considered as potentially hazardous to humans.

Protective and anti-arthritic effects of deer antler aqua-acupuncture (DAA), inhibiting dihydroorotate dehydrogenase, on phosphate ions-mediated chondrocyte apoptosis and rat collagen-induced arthritis

The effect of water extract of deer antler aqua-acupuncture (DAA; Cervi Pantotrichum Cornu) prepared from the pilose antler of Cervus korean TEMMINCK var. mantchuricus Swinhoe (Nokyong in Korean), a traditional immunosuppressive and immunoactivating Korean herbal acupuncture [Int. Immunopharm. 3 7 (2003) 1001] on rat chondrocyte apoptosis was studied. Terminally differentiated hypertrophic chondrocytes were isolated from rat costochondrial cartilage and cell death was measured in the presence of 3-5 mM phosphate ions (Pi). The effect of 10 microg/ml DAA was compared to that of phosphonoformic acid (PFA), a competitive inhibitor of the Na-Pi co-transport on Pi-induced apoptosis in chondrocytes. A total of 1 mM PFA blocked anion-induced cell death and prevented an increase in the cell Pi content. In a parallel study, we determined that the DAA also protected chondrocytes from death. On the other hand, the effect of DAA was also evaluated as an inhibitor of dihydroorotate dehydrogenase (DHO-DHase) and tested in the rat collagen-induced arthritis (CIA) model. Female 7-week-old Sprague-Dawley rats were used for the evaluation of DAA in the CIA model. Arthritis was evaluated by arthritis score, body weight loss, bone destruction score. DAA was administered by bilateral Shinsu (B23) acupuncture five times per week (10, 20, 30, and 100 microg/kg/day). DAA inhibited rat liver DHO-DHase in vitro with Ki = 843 +/- 43 microg/ml. The anti-proliferative effect of DAA was caused by cell cycle arrest at the S-phase. Treatment with 300 mg/kg/day of DAA completely prevented the development of CIA based on the reduction of the arthritis score. The 50% effective dose (ED50) of DAA on arthritis score was 64 mg/kg. DAA ameliorated body weight loss associated with disease onset. DAA suppressed the development of arthritis, even when it was administered after a booster immunization of collagen. DAA is a novel immunosuppressant which inhibits DHO-DHase and its effects in CIA suggest that it could be useful in the treatment of rheumatoid arthritis.

Differential sensitivity to resveratrol-induced apoptosis of human chronic myeloid (K562) and acute lymphoblastic (HSB-2) leukemia cells

The in vitro effects of resveratrol (RES) on apoptotic pathway in human chronic myeloid (K562) and acute lymphoblastic (HSB-2) leukemia cells were investigated. RES treatment of both cell types significantly and irreversibly inhibited their growth, associated with extensive apoptosis and increase in hypodiploid cells. Cell cycle analysis showed accumulation in G(1) phase in HSB-2 drug exposed cells, while only K562-treated cells exhibited a marked accumulation in S phase with a concomitant decrease in G(1) and G(2)/M at 24 h. Moreover, RES caused internucleosomal DNA fragmentation, even if K562 cells were found less sensitive to the drug, as compared to HSB-2 cells, which also reacted earlier to the treatment. RES-induced apoptosis was associated with an increase of Bax expression and a marked release of cytochrome c from mitochondria. Interestingly, K562 cells exhibited a basal content of glutathione 10-fold that of HSB-2 cells, which increased after 24-48 h RES exposure, together with increment of glutathione reductase and peroxidase activities. However, the major resistance to apoptosis of K562 cells cannot be attributed to their higher pool of reducing power, since neither the inhibition of glutathione synthesis by buthionine sulphoximine nor glutathione depletion by diethylmaleate, sensitized these cells. In addition, glutathione enrichment of HSB-2 cells by N-acetylcysteine did not prevent the apoptotic effects of RES. Our data indicate that RES commitment to apoptosis in both cell lines is independent from the intracellular content of glutathione, while it is associated with either the enhanced expression of Bax and cytochrome c release.

BCR/ABL-mediated downregulation of genes implicated in cell adhesion and motility leads to impaired migration toward CCR7 ligands CCL19 and CCL21 in primary BCR/ABL-positive cells

The mechanism underlying p210(BCR/ABL) oncoprotein-mediated transformation in chronic myelogenous leukemia (CML) is not fully understood. We hypothesized that p210(BCR/ABL) suppresses expression of genes which may explain at least some of the pathogenetic features of CML. A subtractive cDNA library was created between BCR/ABL-enhanced-green-fluorescent-protein (GFP)-transduced umbilical cord blood (UCB) CD34+ cells and GFP-transduced UCB CD34+ cells to identify genes whose expression is downregulated by p210(BCR/ABL). At least 100 genes were identified. We have confirmed for eight of these genes that expression was suppressed by quantitative real-time-RT-PCR (Q-RT-PCR) of additional p210(BCR/ABL)-transduced CD34+ UCB cells as well as primary early chronic phase (CP) bone marrow (BM) CML CD34+ cells. Imatinib mesylate reversed downregulation of some genes, to approximately normal levels. Several of the genes are implicated in cell adhesion and motility, including L-selectin, intercellular adhesion molecule-1 (ICAM-1), and the chemokine receptor, CCR7, consistent with the known defect in adhesion and migration of CML cells. Compared with GFP UCB or normal (NL) BM CD34+ cells, p210 UCB and CML CD34+ cells migrated poorly towards the CCR7 ligands, CCL19 and CCL21, suggesting a possible role for CCR7 in the abnormal migratory behavior of CML CD34+ cells.

Apoptosis and Survival of Osteoblast-like Cells Are Regulated by Surface Attachment

We tested the hypothesis that RGDS peptides regulate osteoblast survival in culture. Osteoblast-like MC3T3-E1 cells were allowed to attach to RGDS peptides that had been tethered to a silicone surface utilizing a previously described grafting technique. The RGDS-modified surface caused up-regulation of alpha(v)beta(3) integrin. We noted that there was an increase in expression of activated focal adhesion kinase and activated Akt. There was no change in the expression level of the anti-apoptotic protein Bcl-2, the pro-apoptotic protein Bad, or the inactivated form of Bad, pBad. Attachment to the RGDS-treated membrane completely abolished apoptosis induced by staurosporine, the Ca(2+).P(i) ion pair, and sodium nitroprusside. However, the surface modification did not interfere with apoptosis mediated by the free RGDS peptide or serum-free medium. When the activity of the phosphatidylinositol 3-kinase pathway was inhibited, RGDS-dependent resistance to apoptosis was eliminated. These results indicated that the binding of cells to RGDS abrogated apoptosis via the mitochondrial pathway and that the suppression of apoptosis was dependent on the activity of phosphatidylinositol 3-kinase.

Caspase-1 and poly (ADP-ribose) polymerase inhibitors may protect against peroxynitrite-induced neurotoxicity independent of their enzyme inhibitor activity

We investigated the mechanism of 3-morpholinosyndnomine (SIN-1) neurotoxicity in nearly pure neuronal cultures. In a simple saline solution, SIN-1 neurotoxicity was found to be mediated by peroxynitrite and independent of glutamate receptor activation [Y. Zhang & P.A. Rosenberg (2002) Eur. J. Neurosci, 16, 1015-1024]. To further study the mechanism of peroxynitrite toxicity to neurons we investigated the role of caspases and poly (ADP-ribose) polymerase (PARP) in this model system. Ac-Tyr-Val-Ala-Asp-chloromethyl ketone (Ac-YVAD-cmk), a specific caspase-1 inhibitor, completely blocked neurotoxicity as well as ATP depletion induced by SIN-1. However, a caspase-3 inhibitor and a pan-caspase inhibitor were both without effect. These results suggested that the protection of Ac-YVAD-cmk might not be due to its inhibition of caspase-1. Indeed, Western blot analysis and assay of caspase activity indicated that caspase activation was not involved in SIN-1 toxicity. Ac-YVAD-cmk also completely blocked in vitro protein nitration induced by SIN-1 or peroxynitrite, suggesting that Ac-YVAD-cmk may interact with peroxynitrite directly. Similarly, although activation of PARP is thought to be a major cause of peroxynitrite-induced ATP depletion, and two PARP inhibitors, 1,5-dihydroxyisoquinoline (DHQ) and 3-aminobenzamide (3-AB), completely prevented ATP depletion and neurotoxicity induced by SIN-1, SIN-1 did not increase poly (ADP-ribosyl)ation and PARP activity. Furthermore, DHQ and 3-AB completely prevented in vitro protein nitration induced by peroxynitrite, indicating that DHQ and 3-AB directly interact with peroxynitrite. Taken together, these results suggest that in the model system used here peroxynitrite neurotoxicity is independent of caspase and PARP activation, and therefore implicate a novel mechanism.

Differentiation of human monocytic cell lines confers susceptibility to Bacillus anthracis lethal toxin

Anthrax lethal toxin (LT) is comprised of protective antigen and lethal factor. Lethal factor enters mammalian cells in a protective antigen-dependent process and cleaves mitogen-activated protein kinase kinases. Although LT has no observable effect on many cell types, it causes necrosis in macrophages derived from certain mouse strains and apoptosis in activated mouse macrophages. In this study, we observed that LT treatment of three different human monocytic cell lines U-937, HL-60 and THP-1 did not induce cell death. Cells did become susceptible to the toxin, however, after differentiation into a macrophage-like state. Treatment with LT resulted in decreased phosphorylation of p38, ERK1/2 and JNK in both undifferentiated and differentiated HL-60 cells, suggesting that the change in susceptibility does not result from differences in toxin delivery or substrate cleavage. Death of differentiated HL-60 cells was accompanied by chromosome condensation and DNA fragmentation, but was not inhibited by the pan-caspase inhibitor Z-VAD-FMK. In addition, we observed that the macrophage differentiation process could be inhibited by LT. Our results indicate that LT-mediated death of mouse and human macrophages may occur through distinct processes and that the differentiation state of human cells can determine susceptibility or resistance to LT.

Oxidative Stress and Apoptosis in Cardiomyocyte Induced by High-Dose Alcohol

Binge drinking of alcohol causes cardiac dysfunction in some people. The mechanism remains unclear. This study was designed to investigate high doses of alcohol-induced oxidative stress and apoptosis in cardiomyocytes and protective effects of antioxidants. Cardiomyocytes isolated from 1- to 2-day-old Sprague-Dawley rats were treated with ethanol at doses of 0 mM, 50 mM, 100 mM, and 200 mM for 24 hours. Vitamin E (1 mM) and vitamin C (0.2 mM) were added to medium 1 hour before addition of ethanol. Results showed typical apoptosis: chromatin condensation, membrane blebbing, shrinkage, and cytoplasm condensation. Apoptosis is concentration-dependent in the range of 0 to 100 mM ethanol (apoptosis rates were respectively 0.68%, 2.03%, and 9.66% at ethanol concentration of 0 mM, 50 mM, and 100 mM). Necrotic cells became greatly increased in the 200 mM ethanol-treated group. Intracellular production of reactive oxygen intermediates increased as mitochondrial membrane potential decreased after ethanol treatment. Cytochrome c was found to be greater in the cytosol of the ethanol-treated groups. Activity of caspase-3 was higher in ethanol-treated groups (P < 0.05). Both vitamin E and vitamin C inhibited oxidative stress and myocyte apoptosis in ethanol-treated groups (P < 0.05). In conclusion, our data indicated that acute high-dose ethanol treatment primarily induces cardiomyocyte apoptosis at concentration up to 100 mM while necrosis is predominate at 200 mM. The underlying mechanism appears to involve mitochondrial damage via an increase in oxidative stress and releasing cytochrome c, which activates caspases that initiate chromatin fragmentation and apoptosis. Antioxidants, to a large extent, inhibit oxidative stress and apoptosis induced by ethanol.

Interleukin-15, as Interferon-gamma, Induces the Killing of Leishmania infantum in Phorbol-Myristate-Acetate-Activated Macrophages Increasing Interleukin-12

The potential leishmanicidal activity of interleukin-15 (IL-15) was examined while priming with the cytokine phorbol-myristate-acetate (PMA)-activated macrophages and infecting them with Leishmania infantum parasites. The activation of macrophage cultures with IL-15 determined a significant anti-leishmanial activity, comparable with that induced by interferon-gamma (IFN-gamma). The killing of Leishmania in macrophages primed with IL-15, as well as with IFN-gamma, was followed by an increase in the IL-12 synthesis. The neutralization of IL-15 or IFN-gamma, by specific monoclonal antibodies (MoAb) caused a significant reduction in leishmanicidal activity. Furthermore, in PMA-activated macrophages, the neutralization of IL-12 production by a specific anti-IL-12 MoAb reduced leishmanicidal activity induced by IL-15 and IFN-gamma. Data indicate that IL-15 could have a role as an activator of leishmanicidal activity, directly or indirectly, by inducing IL-12 production.

Luteolin sensitizes tumor necrosis factor-alpha-induced apoptosis in human tumor cells

Tumor necrosis factor-alpha (TNFalpha) activates both cell death and cell survival pathways, which render most cancer cells resistant to its cytotoxicity. In this study, we found that pretreatment with luteolin, a plant flavonoid, greatly sensitized TNFalpha-induced apoptotic cell death in a number of human cancer cell lines; including colorectal cancer COLO205, HCT116 cells and cervical cancer HeLa cells. In the search of the molecular mechanisms responsible for the sensitization effect of luteolin, we discovered that luteolin inhibited TNFalpha-induced activation of nuclear transcription factor-kappa B (NF-kappaB), the main survival factor in TNFalpha signaling. As a result, luteolin suppressed the expression of NF-kappaB-targeted antiapoptotic genes, including A20 and cellular inhibitor of apoptosis protein-1 (c-IAP1). The role of A20 and c-IAP1 was further confirmed by ectopic expression of these two genes, which significantly protected cell death induced by luteolin followed by TNFalpha. In addition, inhibition of NF-kappaB by luteolin led to augmentation and prolongation of c-Jun N-terminal kinase (JNK) activation induced by TNFalpha. Suppression of JNK activation, either by a synthetic JNK inhibitor (SP600125) or by overexpression of the dominant negative forms of JNK kinase 1 (JNKK1) and JNK kinase 2 (JNKK2), conferred significant protection against apoptotic cell death induced by luteolin and TNFalpha, suggesting that NF-kappaB and JNK are closely associated with the sensitization effect of luteolin. Data from this study reveal a novel function of luteolin and enhance the value of luteolin as an anticancer agent.