Apoptosis detection: an overview

Inflammatory effects of phthalates in neonatal neutrophils

Hospitalized infants are exposed to numerous devices containing the plasticizer di-(2-ethylhexyl) phthalate. Urinary levels of the phthalate metabolite, mono-(2-ethylhexyl) phthalate (MEHP), are markedly elevated in premature infants. Phthalates inactivate peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear transcription factor that mediates the resolution of inflammation, a process impaired in neonates. We speculate that this increases their susceptibility to MEHP, and this was analyzed. MEHP inhibited neutrophil apoptosis; neonatal cells were more sensitive than adult cells. In neonatal, but not in adult neutrophils, MEHP also inhibited chemotaxis, stimulated oxidative metabolism, and up-regulated expression of NADPH oxidase-1. In both adult and neonatal neutrophils, MEHP stimulated IL-1beta and VEGF production, whereas IL-8 production was stimulated only in adult cells. In contrast, MEHP-inhibited production of MIP-1beta by adult cells, and Regulated on Activation Normal T Cell Expressed and Secreted (RANTES) by neonatal neutrophils. The effects of MEHP on apoptosis and oxidative metabolism in neonatal cells were reversed by the PPAR-gamma agonist, troglitazone. Whereas troglitazone had no effect on MEHP-induced alterations in inflammatory protein or chemokine production, constitutive IL-8 and MIP-1beta production was reduced in adult neutrophils, and RANTES and MIP-1beta in neonatal cells. These findings suggest that neonatal neutrophils are more sensitive to phthalate-mediated inhibition of PPAR-gamma, which may be related to decreased anti-inflammatory signaling.

Suprachiasmatic nucleus neurons display endogenous resistance to excitotoxicity

A comprehensive understanding of neuroprotective pathways is essential to progress in the battle against numerous neurodegenerative conditions. The hypothalamic suprachiasmatic nucleus (SCN) is endogenously resistant to glutamate (Glu) excitotoxicity in vivo. This study was designed to determine whether immortalized SCN neurons (SCN2.2 cells) retain this characteristic. We first established that SCN2.2 cells retained the ability to respond to Glu. SCN2.2 cells expressed N-methyl-d-aspartate (NMDA) receptor subtypes NR1 and NR2A/2B, suggesting the presence of functional receptors. mRNA for the NMDA receptor subunits NR2A and NR2B were higher in the SCN2.2 than in the control hypothalamic neurons (GT1-7). Specific NMDA receptor antagonists (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate and d-(-)-2-amino-5-phosphonovaleric acid blocked Glu-induced activation of gene expression. SCN2.2 cells were resistant to Glu excitotoxicity compared with GT1-7 neurons as assessed with a mitochondrial function assay, cell death by trypan blue exclusion and apoptosis by terminal deoxynucleotidyl transferase dUTP nick end labeling. SCN2.2 resistance to Glu excitoxicity was retained in the presence of the broad spectrum Glu transport inhibitor, l-trans-pyrrolidine-2,4 dicarboxylate, excluding glial Glu uptake as a major neuroprotective mechanism. Collectively, these observations demonstrate endogenous neuroprotection in SCN2.2 cells; this cell line is resistant to excitotoxicity under conditions that are toxic to other immortalized cell lines. Thus, the SCN2.2 cell line may provide insights into the molecular mechanisms that confer endogenous neuroprotection in the SCN.

Wavelength-dependent backscattering measurements for quantitative real-time monitoring of apoptosis in living cells

Apoptosis--programmed cell death--is a cellular process exhibiting distinct biochemical and morphological changes. An understanding of the early morphological changes that a cell undergoes during apoptosis can provide the opportunity to monitor apoptosis in tissue, yielding diagnostic and prognostic information. There is avid interest regarding the involvement of apoptosis in cancer. The initial response of a tumor to successful cancer treatment is often massive apoptosis. Current apoptosis detection methods require cell culture disruption. Our aim is to develop a nondisruptive optical method to monitor apoptosis in living cells and tissues. This would allow for real-time evaluation of apoptotic progression of the same cell culture over time without alteration. Elastic scattering spectroscopy (ESS) is used to monitor changes in light-scattering properties of cells in vitro due to apoptotic morphology changes. We develop a simple instrument capable of wavelength-resolved ESS measurements from cell cultures in the backward direction. Using Mie theory, we also develop an algorithm that extracts the size distribution of scatterers in the sample. The instrument and algorithm are validated with microsphere suspensions. For cell studies, Chinese hamster ovary (CHO) cells are cultured to confluence on plates and are rendered apoptotic with staurosporine. Backscattering measurements are performed on pairs of treated and control samples at a sequence of times up to 6-h post-treatment. Initial results indicate that ESS is capable of discriminating between treated and control samples as early as 10- to 15-min post-treatment, much earlier than is sensed by standard assays for apoptosis. Extracted size distributions from treated and control samples show a decrease in Rayleigh and 150-nm scatterers, relative to control samples, with a corresponding increase in 200-nm particles. Work continues to correlate these size distributions with underlying morphology. To our knowledge, this is the first report of the use of backscattering spectral measurements to quantitatively monitor apoptosis in viable cell cultures in vitro.

5-Aza-2'-deoxycytidine restores proapoptotic function of p53 in cancer cells resistant to p53-induced apoptosis

The expression of p53-target genes encoding the proapoptotic factor Noxa, but not PUMA, was not induced by p53 in HCT116 and SW480 cells, which show resistance to apoptosis in response to p53 overexpression. The lack of p53 inducibility of Noxa was restored by treatment with the DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine (5-aza-CdR). Furthermore, p53 induced apoptosis in HCT116 and SW480 cells treated with 5-aza-CdR. Moreover, the inhibition of Noxa expression by RNAi in 5-aza-CdR-treated HCT116 cells resulted in the partial inhibition of p53-induced apoptosis. These results suggest that epigenetic cancer therapy is possible for some cancers in combination with forced p53 activation.

Differential regulation of survivin by p53 contributes to cell cycle dependent apoptosis

Recent studies indicate that cell-cycle checkpoints are tightly correlated with the regulation of apoptosis, in which p53 plays an important role. Our present works show that the expression of E6/E7 oncogenes of human papillomavirus in HeLa cells is inhibited in the presence of anti-tumor reagent tripchlorolide (TC), which results in the up-regulation of p53 in HeLa cells. Interestingly, under the same TC-treatment, the cells at the early S-phase are more susceptible to apoptosis than those at the middle S-phase although p53 protein is stabilized to the same level in both situations. Significant difference is exhibited between the two specified expression profiles. Further analysis demonstrates that anti-apoptotic gene survivin is up-regulated by p53 in the TC-treated middle-S cells, whereas it is down-regulated by p53 in the TC-treated early-S cells. Taken together, the present study indicates that the differential p53-regulated expression of survivin at different stages of the cell cycle results in different cellular outputs under the same apoptosis-inducer.

Morphological and functional alterations in human proximal tubular cell line induced by low level inorganic arsenic: evidence for targeting of mitochondria and initiated apoptosis

The kidney is a known target organ for arsenic and is critical for both arsenic biotransformation and elimination. Previous studies have demonstrated that at high doses (ppm) inorganic arsenic is toxic to mitochondria primarily by affecting cellular respiration. However, the effect of inorganic arsenic on mitochondria after low level exposures is not known, particularly in the kidney. Thus the functional and morphological effects of low level inorganic arsenic were investigated in a human proximal tubular cell line, HK-2. Mitochondrial function was assessed at subcytotoxic concentrations of arsenite (< or = 10 microm) by examining the alteration of the mitochondrial membrane potential using MitoTracker Red, a mitochondrion selective dye. In a subset of cells, subcytotoxic arsenite led to mitochondrial membrane depolarization, which could subsequently lead to permeability transition and apoptosis. Subcytotoxic arsenite also induced translocation of phosphatidylserine, indicative of early-stage apoptosis. To confirm whether subcytotoxic arsenite induces cellular and/or mitochondrial morphological alterations consistent with initiated apoptosis, HK-2 cells were evaluated with transmission electron microscopy. Classic morphology of apoptosis was not observed with subcytotoxic arsenite exposures; however, evidence of necrotic changes in the cytoplasmic structure and mitochondrial morphology were apparent. Therefore, based on depolarization of mitochondria and the externalization of phosphatidylserine, HK-2 cells appear to initiate apoptosis following subcytotoxic arsenite insult, but morphological changes indicate that HK-2 cells fail to complete apoptosis and ultimately undergo necrosis. Therefore, subcytotoxic arsenite can be sufficiently toxic to mitochondria that they lose their ability to keep the cell on course for apoptotic cell death.

Modulation of gamma-ray-induced apoptosis in human peripheral blood leukocytes by famotidine and vitamin C

To study the radioprotective effects of vitamin C and famotidine against radiation-induced apoptosis in human peripheral blood leukocytes, peripheral blood was obtained from six healthy volunteers including three males and three females. Twelve microlitres of blood sample diluted in 1 ml complete RPMI-1640 medium was irradiated with various doses of gamma-rays (4, 8 and 12 Gy) in the presence or absence of various doses of vitamin C and famotidine. After 48 and 72 h incubation in a 37 degrees C CO(2) incubator, neutral comet assay was performed for all samples. At least 1000 cells were analyzed for each sample for presence of apoptosis. Data were statistically evaluated using Mann-Whitney non-parametric and ANOVA tests. Results show a significant increase in apoptosis induction following gamma-irradiation with a dose dependent manner compared to controls (p<0.001). Presence of famotidine at 200 microg/ml produced a significant protective effect against radiation-induced apoptosis for various doses of radiation. Similar effects were observed for vitamin C at much lower doses (10 microg/ml). Dose reduction factor (DRF) calculated for famotidine treatment was about 1.5, and above 2 for vitamin C treatment. These results suggest that both vitamin C and famotidine suppresses radiation-induced apoptosis when used with various doses of gamma-irradiation (4-12 Gy) probably via *OH radical scavenging and an intracellular antioxidation mechanism.

Wolbachia surface protein (WSP) inhibits apoptosis in human neutrophils

Polymorphonuclear cells (PMNs) are essential for the innate immune response against invading bacteria. At the same time, modulation of PMNs' apoptosis or cell death by bacteria has emerged as a mechanism of pathogenesis. Wolbachia bacteria are Gram-negative endosymbionts of filarial nematodes and arthropods, phylogenetically related to the genera Anaplasma, Ehrlichia and Neorickettsia (family Anaplasmataceae). Although several pathogens are known to interfere with apoptosis, there is only limited information on specific proteins that modulate this phenomenon. This is the first evidence for the anti-apoptotic activity of a surface protein of Wolbachia from filarial nematode parasites (the Wolbachia surface protein, WSP). The inhibition of apoptosis was demonstrated on purified human PMNs in vitro by different methods. TUNEL assay showed that the percentage of dead cells was reduced after stimulation with WSP; Annexin V-FITC binding assay confirmed that cell death was due mainly to apoptosis and not to necrosis. Reduced caspase-3 activity in stimulated cells also confirmed an inhibition of the apoptotic process.

Caveolin-1 sensitizes rat pituitary adenoma GH3 cells to bromocriptine induced apoptosis

BACKGROUND

Prolactinoma is the most frequent pituitary tumor in humans. The dopamine D2 receptor agonist bromocriptine has been widely used clinically to treat human breast tumor and prolactinoma through inhibition of hyperprolactinemia and induction of tumor cell apoptosis, respectively, but the molecular mechanism of bromocriptine induction of pituitary tumor apoptosis remains unclear. Caveolin-1 is a membrane-anchored protein enriched on caveolae, inverted flask-shaped invaginations on plasma membranes where signal transduction molecules are concentrated. Currently, caveolin-1 is thought to be a negative regulator of cellular proliferation and an enhancer of apoptosis by blocking signal transduction between cell surface membrane receptors and intracellular signaling protein cascades. Rat pituitary adenoma GH3 cells, which express endogenous caveolin-1, exhibit increased apoptosis and shrinkage after exposure to bromocriptine. Hence, the GH3 cell line is an ideal model for studying the molecular action of bromocriptine on prolactinoma.

RESULTS

The expression of endogenous caveolin-1 in GH3 cells was elevated after bromocriptine treatment. Transiently expressed mouse recombinant caveolin-1 induced apoptosis in GH3 cells by enhancing the activity of caspase 8. Significantly, caveolin-1 induction of GH3 cell apoptosis was sensitized by the administration of bromocriptine. Phosphorylation of caveolin-1 at tyrosine 14 was enhanced after bromocriptine treatment, suggesting that bromocriptine-induced phosphorylation of caveolin-1 may contribute to sensitization of apoptosis in GH3 cells exposed to bromocriptine.

CONCLUSION

Our results reveal that caveolin-1 increases sensitivity for apoptosis induction in pituitary adenoma GH3 cells and may contribute to tumor shrinkage after clinical bromocriptine treatment.

Cumulative genotoxic and apoptotic effects of xenobiotics in a mini organ culture model of human nasal mucosa as detected by the alkaline single cell microgel electrophoresis assay and the annexin V-affinity assay

Three-dimensional mini organ cultures of human inferior nasal turbinate epithelia have proved to be a useful tool in genotoxicology studies. They allow repetitive or chronic exposure of cells to xenobiotics in a well-preserved organ-specific mucosal architecture for an extended period of time. It is the aim of the present study to concurrently monitor cumulative genotoxic and apoptotic effects of sodium dichromate, N-nitrosodiethylamine (NDEA) and N-methyl-N-nitro-N-nitroso-guanidine (MNNG). Mini organs were raised by separating fresh specimens of human inferior nasal turbinates (n=11) into 1 mm3 sized pieces and culturing them on multiwell plates with bronchial epithelial basal medium for 6 days. Aliquots of the mini organs were subsequently exposed to sodium dichromate (1.0 mM, 1h), NDEA (50 mM, 1h) or MNNG (0.07 mM, 1h) on days 7, 9 and 11 versus a single exposure on day 11 only. DNA fragmentation and apoptotic events were assessed on day 11 using the alkaline single cell microgel electrophoresis assay (comet assay) and the annexin V-affinity assay. Significant DNA fragmentation could be demonstrated after a single exposure of the mini organs to sodium dichromate. Following three subsequent incubations, there was a further increase in the genetic damage observed, accompanied by an increase in the rate of apoptotic cells. In contrast, after single and triple incubation with NDEA there was neither an increase in genetic damage nor in the fraction of apoptotic cells detectable. Repetitive exposure to MNNG resulted in an accumulation of DNA damage without an observable increase in apoptosis. The results verify the need to assess apoptosis in genotoxicology research and to investigate cumulative effects of xenobiotics. Three-dimensional mini organ cultures of human upper aerodigestive tract epithelia have shown to be well-suited for improving the ability to distinguish between cumulative genotoxic and apoptotic effects.

Adiponectin modulates the glycogen synthase kinase-3beta/beta-catenin signaling pathway and attenuates mammary tumorigenesis of MDA-MB-231 cells in nude mice

Adiponectin is an adipokine that has pleiotropic beneficial roles in systemic insulin resistance and inflammation. Several recent clinical studies suggest that low serum levels of adiponectin are associated with increased risks of breast cancer. Here, we investigated the direct effects of adiponectin on breast cancer development in vitro and in vivo. Our results showed that adiponectin significantly attenuated the proliferations of two typical human breast cancer cells, MDA-MB-231 and T47D, in a cell type-specific manner. Further analysis revealed that adiponectin could induce apoptosis and arrest the cell cycle progression at G(0)-G(1) phase in MDA-MB-231 cells. Prolonged treatment with adiponectin in this cell line blocked serum-induced phosphorylation of Akt and glycogen synthase kinase-3beta (GSK-3beta), suppressed intracellular accumulation of beta-catenin and its nuclear activities, and consequently reduced expression of cyclin D1. Adiponectin-mediated suppression of cyclin D1 expression and attenuation of cell proliferation was abrogated by the GSK-3beta inhibitor lithium chloride. These results suggest that the inhibitory role of adiponectin on MDA-MB-231 cell growth might be attributed to its suppressive effects on the GSK-3beta/beta-catenin signaling pathway. Furthermore, our in vivo study showed that both supplementation of recombinant adiponectin and adenovirus-mediated overexpression of this adipokine substantially reduced the mammary tumorigenesis of MDA-MB-231 cells in female nude mice. Taken together, these data support the role of adiponectin as a negative regulator of breast cancer development and also suggest that adiponectin might represent a novel therapeutic target for this disease.

Methods for cell sorting of young and senescent cells

Cellular senescence, the ultimate and irreversible loss of replicative capacity of cells in primary culture, has been a popular model for studying the aging process. However, the replicative life span of human fibroblasts is heterogeneous even in clonal populations, with the fraction of senescent cells increasing at each population doubling, rather than all cells entering senescence simultaneously. Thus, the study of individual cells in a mass culture is of extreme importance to the understanding of replicative senescence. Cell sorting is a method that allows physical separation of cells with different characteristics when measured by flow cytometry. Here, we describe various methods by which cells that reach senescence early can be physically sorted out of a bulk of growing cells, and discuss how different methods can affect the posterior analysis of the sorted populations.

Simultaneous detection of a cell surface antigen and apoptosis by microwave-sensitized TUNEL assay on paraffin sections

The TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) technique has been described as a sensitive method for detection of apoptotic nuclei in tissues and preferential staining of apoptotic strand breaks. Short-term microwave pre-treatment, a non-enzymatic pre-treatment technique of antigen retrieval, has been demonstrated to optimize the TUNEL method for in situ detection of apoptotic cells in formalin-fixed paraffin-embedded tissue sections. In the present study, we sensitized internal mammary artery sections by short-term microwave pre-treatment and used a two-step indirect enzymatic method to gain as an end product differentially stained cells, namely TUNEL-positive cells and these positive for the surface marker von Willebrand factor (vWF). This technique enables to clearly distinguish between apoptotic, non-apoptotic and vWF-positive cells that are phenotypic for endothelial cells. Phenotypic identification of cells is simplified by double staining with cell surface markers. This rapid, sensitive and reproducible technique allows simultaneous detection of DNA fragmentation and phenotypic markers in the same paraffin-embedded human tissue section.

Tumour-cell apoptosis after cisplatin treatment is not telomere dependent

Cisplatin is a major chemotherapeutic agent, especially for the treatment of neuroblastoma. Telomeres with their sequence (TTAGGG)n are probable targets for cisplatin intrastrand cross-linking, but the role of telomeres in mediating cisplatin cytotoxicity is not clear. After exposure to cisplatin as single dose or continuous treatment, we found no loss of telomeres in either SHSY5Y neuroblastoma cells (telomere length, approximately 4 kbp), HeLa 229 cells (telomere length, 20 kbp) or in the acute lymphoblastic T cell line 1301 (telomere length, approximately 80 kbp). There was no induction of telomeric single strand breaks, telomeric overhangs were not degraded and telomerase activity was down-regulated only after massive onset of apoptosis. In contrast, cisplatin induced a delayed formation of DNA strand breaks and induced DNA damage foci containing gamma-H2A.X at nontelomeric sites. Interstitial DNA damage appears to be more important than telomere loss or telomeric damage as inducer of the signal pathway towards apoptosis and/or growth arrest in cisplatin-treated tumour cells.

Inhibition of papillomavirus protein function in cervical cancer cells by intrabody targeting

Papillomaviruses (HPVs) are a major cause of human disease, and are responsible for approximately half a million cases of cervical cancer each year. HPVs also cause genital warts, and are the most common sexually transmitted disease in many countries. Despite their importance, there are currently no specific antivirals that are active against HPVs. Papillomavirus protein function is mediated largely by protein-protein interactions, which are difficult to inhibit using conventional approaches. To circumvent these problems, we have prepared an scFv library, and have used this to isolate high-affinity binding molecules that may stearically hinder the association of E6 with p53 and prevent E6-mediated p53 degradation in cervical cancer cells. One of the molecules isolated from the library (GTE6-1), had an affinity for 16E6 of 60nM, and bound within the first zinc finger of the protein. GTE6-1 was able to associate with non-denatured E6 following expression in mammalian cells and could inhibit E6-mediated p53 degradation in in vitro assays. E6-mediated p53 degradation is essential for the continuous growth of cervical cancer cells caused by HPV16. To examine the potential of GTE6-1 as an inhibitor of E6 function in such cells, the molecule was expressed in scFv, diabody and triabody formats in a number of cell lines that are driven to proliferate by the HPV16 oncogenes E6 and E7, including the cervical cancer cell line SiHa. In contrast to small E6-binding peptides containing the ELLG E6-binding motif, GTE6-1 expression lead to changes in nuclear structure, the appearance of apoptosis markers, and an elevation in the levels of p53. No effects were seen with a control scFv molecule, or when GTE6-1 was expressed in cells that are driven to proliferate by simian virus 40 (SV40) T-antigen. Given the accessibility of HPV-associated lesions to topical therapy, our results suggest that large interfering molecules such as intrabodies may be useful inhibitors of viral protein-protein interactions and be particularly appropriate for the treatment of HPV-associated disease.

Apoptosis induced by a new member of saponin family is mediated through caspase-8-dependent cleavage of Bcl-2

OSW-1 is a new member of cholestane saponin family, which is cytotoxic against several types of malignant cells. We reported herein that OSW-1 induced apoptosis of mammalian cells in a concentration- and time-dependent manner. The drug-induced apoptosis was mediated through the mitochondrial pathway, involving the cleavage of Bcl-2. This drug-induced Bcl-2 cleavage in Chinese hamster ovary (CHO) cells could be suppressed either by dominant-negative caspase-8 or by a caspase-8 inhibitor, suggesting that the Bcl-2 cleavage is dependent on caspase-8. In contrast, the Bcl-2 cleavage was independent of caspase-3 activity. The inhibition of caspase-8 activity also resulted in the reduction of apoptotic cells, indicating that Bcl-2 cleavage induced by caspase-8 promotes the progression of apoptosis. The involvement of the caspase-8 activity in the processes of the OSW-1-induced apoptosis was further examined by using caspase-8-deficient Jurkat T cells. It was found that the caspase-8-deficient cells were resistant to OSW-1-induced Bcl-2 cleavage or apoptosis. Furthermore, the small subunit of caspase-8 was found to interact with Bcl-2 as determined by yeast two-hybrid and coimmunoprecipitation assays. Overexpression of caspase-8 small subunit reduced the cleavage of Bcl-2 and inhibited the apoptosis induced by OSW-1. Taken together, these results demonstrate that OSW-1 is capable of inducing apoptosis in mammalian cells, in which the caspase-8-dependent cleavage of Bcl-2 plays an important role.

Activation of focal adhesion kinase enhances the adhesion and invasion of pancreatic cancer cells via extracellular signal-regulated kinase-1/2 signaling pathway activation

BACKGROUND

Interaction with integrin and focal adhesion kinase (FAK) regulates the cancer cell adhesion and invasion into extracellular matrix (ECM). In addition, phosphorylation of FAK correlates with the increase of cell motility and invasion. Adhesion and spreading of cancer cells on a variety of ECM proteins, including collagen type IV (Coll IV), leads to an increase in tyrosine phosphorylation and activation of FAK. In this study, we investigated the mechanism of activation of FAK and its downstream extracellular signal-regulated kinase (ERK)-1/2 signaling following stimulation by interleukin (IL)-1alpha and adhesion to ECM with subsequent enhancement of pancreatic cancer cell adhesion and invasion.

RESULTS

In immunoblotting analysis, all three pancreatic cancer cell lines (AsPC-1, BxPC-3, and Capan-2) expressed the protein of FAK and beta1 integrin. Enhancement of FAK protein association with beta1 integrin when cells were plated on Coll IV was more increased by stimulation with IL-1alpha. Preincubation with anti-beta1 integrin antibody and FAK siRNA transfection inhibited the association of FAK with beta1 integrin of pancreatic cancer cells. FAK phosphorylation was observed by adhesion to Coll IV, furthermore, stronger FAK phosphorylation was observed by stimulation with IL-1alpha of pancreatic cancer cells adhered to Coll IV in time-dependent manner. Genistein, a tyrosine kinase inhibitor, markedly inhibited the FAK phosphorylation. IL-1alpha stimulation and Coll IV adhesion enhanced the activation of Ras, as evidenced by the increased Ras-GTP levels in pancreatic cancer cells. Activation of Ras correlated with the phosphorylation of ERK. While not statistical affecting the apoptosis of pancreatic cancer cells, IL-1alpha-induced adhesion and invasion on Coll IV were inhibited with FAK gene silencing by siRNA, beta1 integrin blocking, and inhibition of FAK phosphorylation. PD98059, a MEK inhibitor, also inhibited IL-1alpha-induced enhancement of adhesion and invasion in pancreatic cancer cells.

CONCLUSION

Our results demonstrated that activation of FAK is involved with the aggressive capability in pancreatic cancer through Ras/ERK signaling pathway. Based on our results, we suggest that the modification of IL-1, FAK, and integrins functions might be a novel therapeutic approach to aggressive spread of pancreatic cancer.

Small interfering RNA targeting survivin sensitizes lung cancer cell with mutant p53 to adriamycin

Survivin is a member of the inhibitor of apoptosis protein (IAP) family that is specifically overexpressed in cancer tissues. p53 is one of the tumor suppressor genes; its induction in response to DNA damage causes apoptosis and correlates with drug sensitivity. To investigate the possible regulation of survivin by p53, we examined the level of survivin expression in lung cancer cell lines in response to adriamycin. Levels of survivin mRNA and protein in cell lines with wild-type p53 decreased dramatically after p53 induction, but no such reduction of survivin was observed in cell lines with mutated or null p53. Inhibition of wild-type p53 in A549 cells by small interfering (si) RNA significantly upregulated the expression of survivin. Survivin inhibition by siRNA in PC9 cells with mutated p53 significantly depressed cell proliferation. To investigate the sensitivity of cancer cells to adriamycin after inhibition of survivin, we depressed survivin expression using siRNA, and then added adriamycin at an IC50 dose. After a further 48 hr incubation with adriamycin, proliferation was significantly depressed in the cells treated with siRNA targeting survivin, in comparison with siRNA targeting scramble. Furthermore, both TUNEL and pro-caspase3 expression assay showed a significant increase in apoptosis after combined treatment with adriamycin and siRNA targeting survivin. Our results demonstrate that survivin is downregulated by p53, and that siRNA targeting of survivin increases cell sensitivity to adriamycin and promotes apoptosis. siRNA targeting of survivin could be potentially useful for increasing sensitivity to anticancer drugs, especially in drug-resistant cells with mutated p53.

Mechanisms mediating the biologic activity of synthetic proline, glycine, and hydroxyproline polypeptides in human neutrophils

The accumulation of neutrophils at sites of tissue injury or infection is mediated by chemotactic factors released as part of the inflammatory process. Some of these factors are generated as a direct consequence of tissue injury or infection, including degradation fragments of connective tissue collagen and bacterial- or viral-derived peptides containing collagen-related structural motifs. In these studies, we examined biochemical mechanisms mediating the biologic activity of synthetic polypeptides consisting of repeated units of proline (Pro), glycine (Gly), and hydroxyproline (Hyp), major amino acids found within mammalian and bacterial collagens. We found that the peptides were chemoattractants for neutrophils. Moreover, their chemotactic potency was directly related to their size and composition. Thus, the pentameric peptides (Pro-Pro-Gly)5 and (Pro-Hyp-Gly)5 were more active in inducing chemotaxis than the corresponding decameric peptides (Pro-Pro-Gly)10 and (Pro-Hyp-Gly)10. In addition, the presence of Hyp in peptides reduced chemotactic activity. The synthetic peptides were also found to reduce neutrophil apoptosis. In contrast to chemotaxis, this activity was independent of peptide size or composition. The effects of the peptides on both chemotaxis and apoptosis were blocked by inhibitors of phosphatidylinositol 3-kinase (PI3-K) and p38 mitogen-activated protein (MAP) kinase. However, only (Pro-Pro-Gly)5 and (Pro-Pro-Gly)10 induced expression of PI3-K and phosphorylation of p38 MAP kinase, suggesting a potential mechanism underlying reduced chemotactic activity of Hyp-containing peptides. Although none of the synthetic peptides tested had any effect on intracellular calcium mobilization, each induced nuclear binding activity of the transcription factor NF-kappa B. These findings indicate that polymeric polypeptides containing Gly-X-Y collagen-related structural motifs promote inflammation by inducing chemotaxis and blocking apoptosis. However, distinct calcium-independent signaling pathways appear to be involved in these activities.

Adalimumab induces apoptosis of human monocytes: a comparative study with infliximab and etanercept

BACKGROUND

Adalimumab, a fully human monoclonal antibody to tumour necrosis factor, was recently introduced for therapy of Crohn's disease.

AIM

Since induction of apoptosis of inflammatory cells is thought to be an important mechanism of action of the antitumour necrosis factor monoclonal antibody infliximab, we studied the induction of apoptosis of activated peripheral blood monocytes by adalimumab.

METHOD

Apoptosis was analysed at the levels of the cell membrane, mitochondria and DNA by flow cytometry.

RESULTS

We found that both adalimumab and infliximab induced apoptosis in cultured monocytes, while etanercept did not. Apoptosis induction was caspase-dependent and detectable already after 2 h. The production of interleukin-10 and interleukin-12 by monocytes was down-regulated significantly by adalimumab and infliximab but not by etanercept, while levels of soluble tumour necrosis factor in monocyte cultures were down-regulated by all three reagents.

CONCLUSIONS

These data show that both adalimumab and infliximab affect monocyte cytokine production and induce apoptosis of activated monocytes. Our findings will have to be further correlated to therapeutic efficacy of these antitumour necrosis factor reagents.

Peripheral benzodiazepine receptor (PBR) ligand cytotoxicity unrelated to PBR expression

Some synthetic ligands of the peripheral-type benzodiazepine receptor (PBR), an 18 kDa protein of the outer mitochondrial membrane, are cytotoxic for several tumor cell lines and arise as promising chemotherapeutic candidates. However, conflicting results were reported regarding the actual effect of these drugs on cellular survival ranging from protection to toxicity. Moreover, the concentrations needed to observe such a toxicity were usually high, far above the affinity range for their receptor, hence questioning its specificity. In the present study, we have shown that micromolar concentrations of FGIN-1-27 and Ro 5-4864, two chemically unrelated PBR ligands are toxic for both PBR-expressing SK-N-BE neuroblastoma cells and PBR-deficient Jurkat lymphoma cells. We have thereby demonstrated that the cytotoxicity of these drugs is unrelated to their PBR-binding activity. Moreover, Ro 5-4864-induced cell death differed strikingly between both cell types, being apoptotic in Jurkat cells while necrotic in SK-N-BE cells. Again, this did not seem to be related to PBR expression since Ro 5-4864-induced death of PBR-transfected Jurkat cells remained apoptotic. Taken together, our results show that PBR is unlikely to mediate all the effects of these PBR ligands. They however confirm that some of these ligands are very effective cytotoxic drugs towards various cancer cells, even for reputed chemoresistant tumors such as neuroblastoma, and, surprisingly, also for PBR-lacking tumor cells.

Mechanisms underlying reduced apoptosis in neonatal neutrophils

Apoptosis, which leads to phagocytosis by mononuclear cells, represents the primary mechanism for removing neutrophils from inflamed tissues and minimizing injury. The present studies show that membrane phosphatidylserine turnover and permeability, as well as DNA fragmentation, were reduced in neutrophils from neonates when compared with adults. The activity of caspase 3 and expression of the proapoptotic proteins Bax, Bad, and Bak were also decreased in neonatal relative to adult neutrophils. These findings are consistent with impaired apoptosis in neonatal cells, which may contribute to prolonged inflammation in infants after oxidative stress or infection. Neutrophil apoptosis is induced by endogenous ligands such as Fas (FasL), which engage death receptors of the tumor necrosis factor/nerve growth factor superfamily, including Fas receptor (FasR). We found that expression of FasR was decreased in neonatal when compared with adult cells. Moreover, neonatal neutrophils did not undergo apoptosis in response to anti-FasR antibody and exhibited impaired chemotaxis to soluble FasL. However, in both adult and neonatal cells, p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase inhibitors blocked Fas-induced activity. These data suggest that prolonged survival of neonatal neutrophils at injured sites is due, in part, to reduced responsiveness to FasL. This may be related to decreased expression of both FasR and Bcl-2-family proteins that mediate neutrophil apoptosis.

P2X7 receptor-mediated apoptosis of human cervical epithelial cells

Normal human ectocervical epithelial (hECE) cells undergo apoptosis in culture. Baseline apoptosis could be increased by shifting cells to serum-free medium and blocked by lowering extracellular calcium. Treatment with the ATPase apyrase attenuated baseline apoptosis, suggesting that extracellular ATP and purinergic mechanisms control the apoptosis. Treatment with ATP and the P2X7 receptor analog 2'-3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (BzATP) increased apoptosis significantly, in a time- and dose-related manner. The threshold of ATP effect was 0.5 microM in hECE cells and approximately 1 microM in CaSki cancer cells. The apoptotic effect of BzATP was additive in part to that of tumor necrosis factor (TNF)-alpha, and it could be attenuated by lowering extracellular calcium and by treatment with the caspase-9 inhibitor Leu-Glu-His-Asp-O-methyl-fluoromethylketone (LEHD-FMK). Treatment with BzATP activated caspase-9, and, in contrast to TNF-alpha, it had only a mild effect on caspase-8. Both BzATP and TNF-alpha activated caspase-3, suggesting that BzATP activates predominantly the mitochondrial apoptotic pathway. Both hECE and CaSki cells secrete ATP into the extracellular fluid, and mean ATP activity in conditioned medium was approximately 0.5 microM, which is in the range of values that suffice to activate the P2X7 receptor. On the basis of these findings we propose a novel autocrine-paracrine mechanism of cervical cell apoptosis that operates by P2X7 receptor control of cytosolic calcium and utilizes the mitochondrial apoptotic pathway.

Apoptosis-detecting radioligands: current state of the art and future perspectives

This review provides a critical and thorough overview of the radiopharmaceutical development and in vivo evaluation of all apoptosis-detecting radioligands that have emerged so far, along with their possible applications in nuclear medicine. The following SPECT and PET radioligands are discussed: all forms of halogenated Annexin V (i.e. (123)I-labelled, (124)I-labelled, (125)I-labelled, (18)F-labelled), (99m)Tc/(94m)Tc-labelled Annexin V derivatives using different chelators and co-ligands (i.e. BTAP, Hynic, iminothiolane, MAG(3), EDDA, EC, tricarbonyl, SDH) or direct (99m)Tc-labelling, (99m)Tc-labelled Annexin V mutants and (99m)Tc/(18)F-radiopeptide constructs (i.e. AFIM molecules), (111)In-DTPA-PEG-Annexin V, (11)C-Annexin V and (64)Cu-, (67)Ga- and (68)Ga-DOTA-Annexin V. In addition, the potential role and clinical relevance of anti-PS monoclonal antibodies and other alternative apoptosis markers are reviewed, including: anti-Annexin V monoclonal antibodies, radiolabelled caspase inhibitors and substrates and mitochondrial membrane permeability targeting radioligands. Nevertheless, major emphasis is placed on the group of Annexin V-based radioligands, in particular (99m)Tc-Hynic-Annexin V, since this molecule is by far the most extensively investigated and best-characterised apoptosis marker at present. Furthermore, the newly emerging imaging modalities for in vivo detection of programmed cell death, such as MRI, MRS, optical, bioluminescent and ultrasound imaging, are briefly described. Finally, some future perspectives are presented with the aim of promoting the development of potential new strategies in pursuit of the ideal cell death-detecting radioligand.

Morphology and ultrastructure of rat hippocampal formation after i.c.v. administration of N-acetyl-L-aspartyl-L-glutamate

N-Acetyl-L-aspartyl-L-glutamate (NAAG) is one of the most abundant neuroactive compounds in the mammalian CNS. Our recent observations have suggested that NAAG administered into rat cerebral ventricles can cause neuronal death by apparently excitotoxic mechanisms that can be antagonized by the N-methyl-D-aspartate-receptor blockers and by ligands of metabotropic glutamate receptor of Group II. Therefore, the principal aim of the present study has been to use quantitative morphology, electron microscopy and terminal deoxynucleotidyl transferase-mediated biotin dUTP nick-end labeling to study a dose- and time-dependence as well as regional distribution of neurodegeneration in hippocampi of rats after the intraventricular infusion of 0.25 micromol NAAG/ventricle and of equimolar doses of L-glutamate (L-GLU) and N-acetyl-L-aspartate (NAA), breakdown products of NAAG. The degenerative changes were observed after the infusion of 0.25 and 1.25 micromol of NAAG/ventricle, but not when a dose of 0.05 micromol of NAAG/ventricle was injected into each lateral cerebral ventricle. With a dose of 0.25 micromol of NAAG/ventricle the number of degenerated neurons reached a maximum on the fourth day after the infusion. The neuronal damage following bilateral administration of 0.25 micromol of NAAG/lateral cerebral ventricle exhibited features of a delayed neuronal degeneration, expressed mainly in the layer of dentate granule neurons. The degeneration was characterized on the basis of ultrastructural appearance and DNA-fragmentation. The morphological changes caused by L-glutamate and NAA were much smaller than those observed after the administration of NAAG and displayed a different pattern of regional distribution. The present findings suggest that NAAG can cause a loss of hippocampal neurons in vivo, apparently resulting from the neurotoxicity of NAAG itself.

c-Myc degradation induced by DNA damage results in apoptosis of CHO cells

Although tripchlorolide (TC), a compound purified from a Chinese herb Tripterygium Wilfordii Hook, has been demonstrated to be a potent antitumor agent, its mechanisms of action are unknown. The present study shows that TC induces apoptosis of Chinese Hamster Ovary (CHO) cells. Most strikingly, TC was particularly potent in inducing apoptosis of the UV41 mutant CHO cells, which are deficient in the ERCC4 gene encoding a nucleotide excision repair protein. TC caused a higher level of DNA damage in UV41 cells than those in the wild-type CHO cells or EM9 cells, which are deficient in single-strand break repair. These results provided a critical link between apoptotic hypersensitivity and DNA damage in defective nucleotide excision repair pathway of UV41 cells by TC treatment. Further analysis showed that degradation of the c-Myc protein in TC-treated UV41 cells was much stronger than those in the wild-type CHOAA8 and the EM9. A proteasome inhibitor, MG132, reduced both the degradation of c-Myc and apoptosis in TC-treated UV41 cells. Expression of exogenous c-Myc also inhibited apoptosis of TC-treated UV41 cells. These results indicate that c-Myc degradation induced by DNA damage in the presence of TC contributes to induction of apoptosis of UV41 cells.

Initial exposed phosphatidylserine levels correlate with cellular response to cytotoxic drugs

Phosphatidylserine's (PS) membranal distribution is associated with an expanding variety of biological processes. We studied the relevance of preliminarily exposed membranal PS levels to cellular effects of cytotoxic agents. PBL of normal controls (n = 18) and patients with doxorubicin-treated breast carcinoma (n = 27) or 5'-fluorouracil-treated colorectal cancer (n = 32) were assayed before and after drug infusion. Membranal expression levels of PS, adhesion molecules (CD18, CD11a-c, CD63) and Fas-R of leukocyte subtypes were assessed by flow cytometer. Statistical analysis was implemented. Our results demonstrate external expression of PS on all leukocyte subpopulations despite non-apoptotic light scatter characteristics. Several distinct features were observed of which the more prominent were: leukocyte subtypes each display characteristic PS levels; cancer patients' PBL display higher preliminary PS levels than normal controls in all cell groups; and existence of negative correlations between initial membranal PS levels and drug-induced changes in its expression. Our findings underscore the complex involvement of PS in PBL apoptosis and possibly drug resistance.

Sulfinosine-induced cell growth inhibition and apoptosis in human lung carcinomas in vitro

In spite of tremendous effort for improved therapy, lung cancer remains the leading cause of cancer-related deaths worldwide. In the present study, we used the novel purine ribunocleoside sulfinosine and evaluated its antiproliferative and apoptotic outcome on the non-small cell lung carcinoma cell line (NSCLC) and the small cell lung carcinoma cell line (SCLC). Using a BrdU incorporation-test sulfinosine inhibited cell growth in a dose dependent-manner. ID50 values were 4.65 +/- 0.17 microM in the case of NSCLC cells, and 3.59 +/- 0.81 microM in the case of SCLC cells. MTT testing revealed that IC50 values were 6.24 +/- 0.77 microM for NSCLC and 5.68 +/- 0.58 microM for SCLC. Inhibitory concentrations (IC50 and ID50) for sulfinosine were nonsignificantly lower in SCLC cells compared to NSCLC cells, indicating similar susceptibility of the cells. Flow-cytometric analysis, TUNEL staining, DNA laddering and cell death ELISA test were used to investigate apoptotic cell death. Our results demonstrated that high concentrations of sulfinosine can cause typical DNA laddering, a hallmark for apoptosis. Evidence of free nucleosomes and enzymatic labeling of fragmented DNA confirmed apoptosis involvement in sulfinosine cytotoxicity. In addition, flow-cytometric analysis showed that 25 microM sulfinosine arrested cell cycle progression at the G2M phase and induction of apoptosis in both cell lines. From these results, we concluded that sulfinosine may act as an anticancer agent and further studies may prove its efficacy in lung cancer cells. Thus the biological effects of sulfinosine may be due to modulation of cell growth, cell death, and cell cycle regulatory molecules.

Apoptosis induced by low-dose and low-dose-rate radiation

BACKGROUND

It has been claimed that external radiation, as a treatment modality for malignant diseases, partly induces apoptosis. It is not known, however, whether therapeutic low-dose and low-dose-rate radiation are able to induce apoptosis.

METHODS

The effect of low-dose radiation on apoptosis induction in HeLa Hep2 cells was studied, and quantitation of the apoptotic cells was performed by immunocytochemistry using TdT-mediated dUtp-x Nick End Labeling (TUNEL) technology and the M30 CytoDEATH antibody method.

RESULTS

When TUNEL staining was used to quantify apoptosis in untreated HeLa Hep2 cells kept in culture, approximately 5 plus minus 3% of the cells showed positive staining without any treatment. In the first experiment, the HeLa Hep2 cells were exposed to gamma radiation (i.e., 0.5, 1, 2, 5, 10, and 15 grays [Gy]) from a cobalt-60 radiation source delivering a dose rate of 0.80 Gy/min. The radiated cells were cultivated for 5, 10, 24, 48, 72 and 168 hours after irradiation. Radiation doses below 2 Gy did not cause any significant apoptosis, but between 5 and 15 Gy significant apoptosis was observed, with peak values at 5 Gy (P < 0.001). Up to 60% of the investigated cells were shown to display apoptosis. Time to this peak value was 168 hours after irradiation. The HeLa Hep2 cells were exposed to doses of 2, 5, and 10 Gy at a 10-fold lower dose rate (0.072 Gy/min). The cells that achieved a dose below 2 Gy did not present increased apoptosis. At doses above 2 Gy, however, the cells again demonstrated significant apoptosis. Up to 24 hours following irradiation, no apoptosis could be documented, whereas beyond 24 and up to 168 hours a highly significant apoptosis induction was observed. Significant cytotoxicity was confirmed by chromium-51 release from the cells at 5 Gy.

CONCLUSIONS

Low-dose and low-dose-rate radiation are able to induce significant apoptosis, and apoptosis may be one of the mechanisms by which low-dose radiation causes growth inhibition.

Hydrogen peroxide-induced DNA damage and DNA repair in lymphocytes from malnourished children

The aim of this study was to assess DNA repair capacity in lymphocytes of children with protein calorie malnutrition using the single-cell gel electrophoresis (comet) assay. Repair capacity was assessed by estimating the relative decrease of DNA migration length 5, 15, 30, and 60 min after hydrogen peroxide treatment, in three groups of children: well-nourished (WN), well-nourished infected (WN-I), and malnourished infected (MN-I). In addition, the DNA migration length was evaluated in all groups before and after peroxide treatment. Comparison of mean migration lengths observed in WN and WN-I children showed significant differences at all times tested; between WN-I and MN-I differences were also observed, except after hydrogen peroxide exposure. This implies that lymphocytes of WN-I and MN-I children were equally sensitive to hydrogen peroxide. Nevertheless, the MN-I group clearly shows the greatest overall percentage of damaged cells at all times tested. In relation to repair capacity, at 5 min it was approximately 30% in both groups of well-nourished children, but only 20% in MN-I; 15 min after exposure, repair capacity increased to 51% in well-nourished children but only to 31% in MN-I; and at 60 min this capacity increased to 82% in well-nourished but only to 55% in MN-I. These data indicate that lymphocytes of malnourished children show a decreased capacity to repair hydrogen peroxide-induced DNA damage compared to that of well-nourished controls. This reflects that only malnutrition is associated with decreased DNA repair capacity. Additionally, the data confirm that severe infection and malnutrition are two factors clearly associated with increased DNA damage.

Flow cytometric analysis of spontaneous and dexamethasone-induced apoptosis in thymocytes from severely malnourished rats

Severe malnutrition is widely distributed throughout the world, showing a high prevalence in developing countries. Experimental animal models have been useful to study the effects of malnutrition at different levels and ages. Apoptosis is a well recognised process of cell death occurring under several physiological and pathological conditions. It represents the principal mechanism involved in cell selection in the thymus. Thymocyte apoptosis induction by dexamethasone is one of the best characterised experimental models of programmed cell death. The aim of the present study was to determine whether severe malnutrition increased spontaneous and/or dexamethasone-induced apoptosis in vivo in thymocytes of experimentally malnourished rats during lactation. Thymocytes were obtained from malnourished rats at weaning (21d of age). Apoptosis frequency was estimated by the terminal transferase-mediated dUTP nick end labelling assay. Spontaneous apoptosis was 1.9 (sd 1.0) % in well nourished rats in contrast to 13.3 (sd 3.8) % in malnourished animals; this is seven times greater (P<0.001). Interestingly, the frequency of dexamethasone-induced apoptosis was similar in both groups of animals (47.9 (sd 10.1) % in well nourished rats and 53.8 (sd 8.0) % in malnourished rats). The results obtained in the present study indicate that malnutrition is associated with a significant increase of spontaneously apoptotic cells. In addition, the data showed that the fraction of thymocytes susceptible to dexamethasone-induced apoptosis was similar in well nourished and malnourished animals. The greater levels of spontaneously apoptotic cells associated with malnutrition could be related to alterations of the microenvironment of the thymus and/or to an obstruction of early thymocyte maturation.

Ribozyme-mediated telomerase inhibition induces immediate cell loss but not telomere shortening in ovarian cancer cells

Telomerase is a promising target for human cancer gene therapy. Its inhibition allows telomere shortening to occur in cancer cells, which in turn is thought to trigger delayed senescence and/or apoptosis. We tested whether telomerase inhibition might have additional, immediate effects on tumor cell growth. Ovarian cancer cell lines with widely differing telomere lengths were efficiently transduced with an adenovirus expressing a ribozyme directed against the T motif of the catalytic subunit of human telomerase, hTERT. Three days after transduction, telomerase activity was significantly reduced and massive cell loss was induced in mass cultures from all four ovarian cancer cell lines tested, whereas transduction of telomerase-negative human fibroblasts did not attenuate their growth. The kinetics of induction of cell death in cancer cells was not significantly dependent on telomere length, and telomeres did not shorten measurably before the onset of apoptosis. The data suggest the existence of a "fast-track" mechanism by which diminution of telomerase can interfere with cancer cell growth and induce cell death, presumably by apoptosis. This phenomenon might be a consequence of the telomere capping function provided by telomerase in tumor cells. Uncapping of telomeres by ribozyme-mediated inhibition of telomerase bears therapeutic potential for ovarian cancer.

Accelerated telomere shortening in Fanconi anemia fibroblasts--a longitudinal study

Fanconi anemia (FA) is a fatal inherited disease displaying chromosomal instability, disturbances in oxygen metabolism and a high burden of intracellular radical oxygen species. Oxygen radicals can damage DNA including telomeric regions. Insufficient repair results in single strand breaks that can induce accelerated telomere shortening. In a longitudinal study we demonstrate that telomeric DNA is continuously lost at a higher rate in FA fibroblasts compared to healthy controls. Furthermore, we show that this loss is caused rather by an increased shortening per cell division in regularly replicating cells than by apoptosis.

Replicative senescence of human endothelial cells in vitro involves G1 arrest, polyploidization and senescence-associated apoptosis

Human ageing is characterized by a progressive loss of physiological functions, increased tissue damage and defects in various tissue renewal systems. Age-related decreases of the cellular replicative capacity can be reproduced by in vitro assays of cellular ageing. When diploid human fibroblasts reach their finite lifespan, they enter an irreversible G1 growth arrest status referred to as replicative senescence. While deregulation of programmed cell death (apoptosis) is a key feature of age-related pathology in several tissues, this is not reflected in the standard in vitro senescence model of human fibroblasts, and the role of apoptosis during cellular ageing remains unclear. We have analyzed replicative senescence of human umbilical vein endothelial cells (HUVEC) in vitro and found that senescent HUVEC also arrest in the G1 phase of the cell cycle but, unlike fibroblasts, accumulate with a 4N DNA content, indicative of polyploidization. In contrast to human fibroblasts, senescent endothelial cells display a considerable increase in spontaneous apoptosis. The data imply that age-dependent apoptosis is a regular feature of human endothelial cells and suggest cell type specific differences in human ageing.

Apoptosis of skeletal muscle cells and the pathogenesis of myositis: a perspective

Apoptosis is a genetically controlled form of cell death that occurs in many biologic processes including embryogenesis, immune cell development, and maintenance of peripheral immune tolerance. Recent studies have yielded evidence suggesting that apoptosis of parenchymal cells may play a role in providing self-antigens to initiate autoimmune reactions. Skeletal muscle cells are fully differentiated and multinucleated. Apoptosis has been described in developing myoblasts and, recently, in mature myotubes. However, the involvement of apoptosis in skeletal muscle pathologies is unclear. This article reviews the available data concerning the occurrence of skeletal muscle cell apoptosis in selected muscle diseases. It also discusses the potential role of muscle cell apoptosis in the development of autoimmune diseases such as idiopathic inflammatory myopathies.

Apoptotic effect of cyanobacterial extract on rat hepatocytes and human lymphocytes

Toxic cyanobacterial blooms are an increasing problem in Poland. The production of cyanobacterial toxins and their presence in drinking and recreational waters represent a growing danger to human and animal health. This is connected with the increase of cyanobacterial biomass caused by excessive eutrophication of the water ecosystem. There is evidence that cyanobacterial hepatotoxins can act as a potent promoter of primary liver cancer. The apoptotic effect of microcystins in Polish cyanobacterial bloom samples on rat hepatocytes and human lymphocytes was observed using light and fluorescence microscopy, flow cytometry, and electrophoretic analysis. The incubation time needed to observe the first morphological apoptotic changes in hepatocytes was approximately 30 min; however, the characteristic biochemical changes in DNA were not observed even after 120 min. In lymphocyte cultures the morphological changes characteristic for apoptosis were observed after 24 h of incubation and a 48-h incubation was found to be optimal for analysis of internucleosomal DNA fragmentation, which is one of the main biochemical hallmarks of programmed cell death. These cells are an easily isolated and inexpensive material for medical diagnostics. Therefore the apoptotic changes, together with the clastogenic effect seen in lymphocyte cultures, are proposed as a future analytical method for these toxins.

New strategies in the treatment of acute myelogenous leukemia (AML): in vitro culture of aml cells--the present use in experimental studies and the possible importance for future therapeutic approaches

In vitro studies of cultured native acute myelogenous leukemia (AML) blasts and cell lines have contributed significantly to our present knowledge about the pathogenesis of AML. In the present article we review different techniques for preparation and in vitro culture of AML blasts. Well-characterized serum-free in vitro conditions can now be used in experimental studies of AML, and this makes comparisons between different studies easier. We also describe assays for characterization of AML progenitor subsets (i.e., suspension cultures, colony assays, long-term in vitro culture, xenotransplantation in immunocompromised mice), and we discuss the possible use of AML cell lines as experimental models in AML. Furthermore, clinical studies suggest that the in vitro growth characteristics of AML blasts assayed by short-term culture of the total native populations can be used as a predictor of prognosis after intensive chemotherapy. These in vitro assays may therefore be used for more accurate identification of prognostic parameters and thereby form a basis for the development of simplified laboratory techniques suitable for routine evaluation of patients undergoing risk-adapted therapy. However, it will be equally important to further evaluate the clinical relevance of assays for primitive AML progenitors, and to develop simplified methods that can be used to characterize these progenitor subsets in the routine clinical evaluation.

Current status of flow cytometry in cell and molecular biology

This review summarizes recent developments in flow cytometry (FC). It gives an overview of techniques currently available, in terms of apparatus and sample handling, a guide to evaluating applications, an overview of dyes and staining methods, an introduction to internet resources, and a broad listing of classic references and reviews in various fields of interest, as well as some recent interesting articles.

Large populations of non-clonogenic early apoptotic CD34-positive cells are present in frozen-thawed peripheral blood stem cell transplants

Apoptosis is the common cell death pathway which is initiated by a variety of different stimuli. The recognition of early apoptotic events would markedly improve reliability and convenience of apoptosis assays. In the present study the vital stain SytoR 16 in combination with the permeability marker 7-amino actinomycin D, (7-AAD) has been used to identify an early stage of apoptosis, not detected with trypan blue or 7-AAD alone or with conventional apoptosis tests and not consistently and only partly detected by the early apoptosis marker annexin V. The method was established using solid tumour cell lines treated with TNF. Subsequently we applied it to determine apoptotic populations in CD34(+) peripheral blood progenitor cells obtained from growth factor and/or chemotherapy mobilised patients and frozen/thawed according to standard stem cell transplantation protocols. In a cell line model as well as CD34(+) progenitor cells, different subpopulations with decreased SytoR 16 fluorescence (SytoR 16int or SytoR 16low, compared with the normal SytoR 16high) appeared which are not, or only partly, apoptotic using conventional techniques including morphology or 7-AAD staining: eg percentages of SytoR 16(int)/7-AAD(-) and SytoR 16(low)/7-AAD(-) may amount to the majority of cells present in a particular CD34(+) sample. Second, upon further incubation these subpopulations become late apoptotic/secondary necrotic much faster than the unmodified SytoR 16high population, as determined with 7-AAD staining and morphology. Third, these cells have strongly or completely reduced clonogenic capacity for committed (CFU-GM) and early (LTC-IC, determined only for CD34(+) cells) progenitors. This technique needs the inclusion of a blocker of P-glycoprotein, which is highly active in CD34(+) progenitor cells. This prevents the interference of the detection of SytoR16(low) apoptotic cells by SytoR 16low cells resulting from P-glycoprotein activity. By comparison with other apoptosis markers we found that early apoptotic subpopulations were detected in the order SytoR 16 > annexin V > 7-AAD. In conclusion, the combination of SytoR 16 and 7-AAD detects apoptotic events earlier than conventional apoptosis techniques or annexin V. Compared to the presently available viability tests, it allows a much better estimation of the number of viable clonogenic CD34(+) cells after freeze/thawing.

Detection of DNA damage in prokaryotes by terminal deoxyribonucleotide transferase-mediated dUTP nick end labeling

Numerous agents can damage the DNA of prokaryotes in the environment (e.g., reactive oxygen species, irradiation, and secondary metabolites such as antibiotics, enzymes, starvation, etc.). The large number of potential DNA-damaging agents, as well as their diverse modes of action, precludes a simple test of DNA damage based on detection of nucleic acid breakdown products. In this study, free 3'-OH DNA ends, produced by either direct damage or excision DNA repair, were used to assess DNA damage. Terminal deoxyribonucleotide transferase (TdT)-mediated dUTP nick end labeling (TUNEL) is a procedure in which 3'-OH DNA ends are enzymatically labeled with dUTP-fluorescein isothiocyanate using TdT. Cells labeled by this method can be detected using fluorescence microscopy or flow cytometry. TUNEL was used to measure hydrogen peroxide-induced DNA damage in the archaeon Haloferax volcanii and the bacterium Escherichia coli. DNA repair systems were implicated in the hydrogen peroxide-dependent generation of 3'-OH DNA ends by the finding that the protein synthesis inhibitors chloramphenicol and diphtheria toxin blocked TUNEL labeling of E. coli and H. volcanii, respectively. DNA damage induced by UV light and bacteriophage infection was also measured using TUNEL. This methodology should be useful in applications where DNA damage and repair are of interest, including mutant screening and monitoring of DNA damage in the environment.

Monoclonal antibodies against oxidized low-density lipoprotein bind to apoptotic cells and inhibit their phagocytosis by elicited macrophages: evidence that oxidation-specific epitopes mediate macrophage recognition

Apoptosis is recognized as important for normal cellular homeostasis in multicellular organisms. Although there have been great advances in our knowledge of the molecular events regulating apoptosis, much less is known about the receptors on phagocytes responsible for apoptotic cell recognition and phagocytosis or the ligands on apoptotic cells mediating such recognition. The observations that apoptotic cells are under increased oxidative stress and that oxidized low-density lipoprotein (OxLDL) competes with apoptotic cells for macrophage binding suggested the hypothesis that both OxLDL and apoptotic cells share oxidatively modified moieties on their surfaces that serve as ligands for macrophage recognition. To test this hypothesis, we used murine monoclonal autoantibodies that bind to oxidation-specific epitopes on OxLDL. In particular, antibodies EO6 and EO3 recognize oxidized phospholipids, including 1-palmitoyl 2-(5-oxovaleroyl) phosphatidylcholine (POVPC), and antibodies EO12 and EO14 recognize malondialdehyde-lysine, as in malondialdehyde-LDL. Using FACS analysis, we demonstrated that each of these EO antibodies bound to apoptotic cells but not to normal cells, whereas control IgM antibodies did not. Confocal microscopy demonstrated cell-surface expression of the oxidation-specific epitopes on apoptotic cells. Furthermore, each of these antibodies inhibited the phagocytosis of apoptotic cells by elicited peritoneal macrophages, as did OxLDL. In addition, an adduct of POVPC with BSA also effectively prevented phagocytosis. These data demonstrate that apoptotic cells express oxidation-specific epitopes-including oxidized phospholipids-on their cell surface, and that these serve as ligands for recognition and phagocytosis by elicited macrophages.