Further characterisation of the in situ terminal deoxynucleotidyl transferase (TdT) assay for the flow cytometric analysis of apoptosis in drug resistant and drug sensitive leukaemic cells

NLRP3 inflammasome activation after ischemic stroke

Cerebral ischemia is a pathological condition resulting from the cessation or reduction of blood supply to the cerebral arteries. Neurological deficits that are clinically relevant can arise as a result of brain damage. The etiology of stroke is multifaceted and intricate, with the inflammatory response being a crucial component that warrants significant attention. Following a cerebrovascular accident, the levels of interleukin-1 beta and interleukin-18 within the central nervous system escalate due to the activation of the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 inflammasome. The inflammation is aggravated by the subsequent occurrence of pyroptosis. The mechanisms that activate the NLRP3 inflammasome pyroptosis signaling pathway axis are described in this article. In addition, we go over how pyroptosis interacts with other processes for regulated cell death. In addition, specific NLRP3 inflammasome pathway inhibitors are identified, which offer new approaches to preventing ischemic brain injury.

The impact of environmental lead exposure on Whooper swan (Cygnus cygnus): Pathological and immunohistochemical studies

This study was carried out to investigate the pathology of environmental lead (Pb) poisoning in Whooper swans (Cygnus cygnus). A number of 12 out 54 swans (22.2%) randomly collected from Honshu, Japan from June 2005 to July 2007 were affected with Pb poisoning. Affected swans showed stained vent with greenish watery diarrhoea and impacted crop. The presence of Pb shots in the gizzard (50%) was confirmed by X-ray, and all cases showed a dark greenish coloured liver. Microscopically, the pathology of Pb poisoning in swans was multisystemic. The severity of the lesions was the highest in the CNS followed by the liver, kidney, spleen, lungs, gizzard, heart, bone marrow respectively and was the least in the peripheral nervous system. CNS lesions were cerebral haemorrhage, malacia, and spongiosis with astrocytic activation and increased neurofilaments accumulations. In addition, there were hepatic and renal hemosiderosis and apoptosis, hepatic granuloma, interstitial pneumonia, gizzard and myocardial necrosis and bone marrow hypoplasia. Chemical analysis of the Pb content in liver and kidneys ranged from 8.18 to 60.6 µg/g, respectively. The extent and severity of lesions varied among individuals and were mostly dose-dependent. Finally, these findings improved the diagnostic procedure of Pb poisoning in free-living Whooper swans.

A Short Duration Transient Ischemia Induces Apoptosis in Retinal Layers: An Experimental Study in Rabbits

Purpose

To investigate retinal cell apoptosis in an experimental transient, short duration ocular ischemia model.

Methods

An experimental ischemia model, which simulates creating temporary high intraocular pressure to control intraocular bleeding during pars plana vitrectomy, was set up. Rabbits were randomly divided into three groups. Group 1 was the control group. In Group 2, intraocular pressure was increased to 97 mmHg for 5 minutes. In Group 3, intraocular pressure was increased to 97 mmHg for 10 minutes. After 24 hours, terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling assay was used to detect retinal apoptosis in rabbit eyes. Only nuclear staining in retinal cells was counted.

Results

Groups with 5 minutes and 10 minutes of ischemia showed significantly higher amount of ganglion cell layer apoptosis when compared with the control group (p<0.05). Light microscopy and standard hematoxylin-eosin did not show any significant damage in the retina cells.

Conclusions

Apoptotic cell death in the retinal cell layers occurs in temporary ischemia-reperfusion as early as 5 and 10 minutes duration.

Antiproliferative and antimetastatic action of quercetin on A549 non-small cell lung cancer cells through its effect on the cytoskeleton

To our knowledge, this study is the first to investigate the effect of the dietary flavonoid quercetin on the main cytoskeletal elements, namely microfilaments, microtubules and vimentin intermediate filaments, as well as cytoskeleton-driven processes in A549 non-small cell lung cancer cells. The methyl-thiazol-diphenyl-tetrazolium assay, annexin V/propidium iodide test, electron microscopic examination, cell cycle analysis based on DNA content, real-time PCR assays, in vitro scratch wound-healing assay, fluorescence staining of F-actin, β-tubulin and vimentin were performed to assess the effects of quercetin on A549 cells. Our results showed that quercetin triggered BCL2/BAX-mediated apoptosis, as well as necrosis and mitotic catastrophe, and inhibited the migratory potential of A549 cells. The disassembling effect of quercetin on microfilaments, microtubules and vimentin filaments along with its inhibitory impact on vimentin and N-cadherin expression might account for the decreased migration of A549 cells in response to quercetin treatment. We also suggest that the possible mechanism underlying quercetin-induced mitotic catastrophe involves the perturbation of mitotic microtubules leading to monopolar spindle formation, and, consequently, to the failure of cytokinesis. We further propose that cytokinesis failure could also be a result of the depletion of actin filaments by quercetin. These findings are important to our further understanding of the detailed mechanism of the antitumor activity of quercetin and render this flavonoid a potentially useful candidate for combination therapy with conventional antimicrotubule drugs, nucleic acid-directed agents or novel cytoskeletal-directed agents.

Upregulation of the MCL-1S protein variant following dihydroartemisinin treatment induces apoptosis in cholangiocarcinoma cells

The aim of the present study was to determine whether dihydroartemisinin (DHA) induces apoptosis in the human cholangiocarcinoma QBC939 cell line through the regulation of myeloid cell leukemia-1 (MCL-1) expression. The inhibitory rates of DHA on QBC939 cell proliferation and the effects of DHA on the cell death rates at various DHA concentrations and following various treatment times were examined. The rate of apoptosis and cell cycle changes following DHA treatment were examined and the changes in the expression of MCL-1 mRNAs and MCL-1 proteins following DHA treatment were also examined. The MTT assay and trypan blue staining demonstrated that DHA significantly inhibited the proliferation (P<0.05) and promoted the death of QBC939 cells (P<0.05). The DNA ladder assay and flow cytometry (FCM) analysis demonstrated that the rate of apoptosis in the experimental group was significantly increased following DHA treatment (P<0.01). FCM analysis also demonstrated that DHA treatment led to a reduction in the percentage of QBC939 cells in the G₀/G₁ and G₂/M phases, and the majority of the DNA-treated cells were arrested in the S phase of the cell cycle (P<0.01). Western blot analysis demonstrated that DHA treatment significantly upregulated the expression of the pro-apoptotic MCL-1S protein. In contrast, no significant difference in the expression of the anti-apoptotic MCL-1L protein was observed following DHA treatment. DHA affected the expression of the apoptosis-associated protein MCL-1 through multiple mechanisms. DHA treatment increased the ratio of MCL-1S/MCL-1L protein, thus inducing apoptosis in cholangiocarcinoma cells.

Detection of end-stage apoptosis by ApopTag® TUNEL technique

DNA fragmentation, the end stage of apoptosis, is the measure of ultimate demise of the cell. A convenient method for examining apoptosis via DNA fragmentation is by the Terminal deoxynucleotidyl transferase (Tdt) dUTP Nick-End Labeling (TUNEL) assay where the DNA strand breaks are detected by enzymatically labeling the free 3'-OH termini with modified nucleotides. ApopTag(®) kits detect single-stranded and double-stranded breaks associated with apoptosis. This technique is also helpful to distinguish between apoptotic and necrotic cell death where the latter is associated with random DNA fragment lengths producing a DNA smear. Apoptotic cells stained positive with ApopTag(®) kits are easier to detect and their identification is more certain, as compared to the examination of simply histochemically stained tissues. In addition, quantitative results can be obtained using flow cytometry and apoptotic cells can be differentiated from necrotic cells with greater than tenfold sensitivity.

Impact of perinatal systemic hypoxic-ischemic injury on the brain of male offspring rats: an improved model of neonatal hypoxic-ischemic encephalopathy in early preterm newborns

In this study, we attempted to design a model using Sprague-Dawley rats to better reproduce perinatal systemic hypoxic-ischemic encephalopathy (HIE) in early preterm newborns. On day 21 of gestation, the uterus of pregnant rats were exposed and the blood supply to the fetuses of neonatal HIE groups were thoroughly abscised by hemostatic clamp for 5, 10 or 15 min. Thereafter, fetuses were moved from the uterus and manually stimulated to initiate breathing in an incubator at 37 °C for 1 hr in air. We showed that survival rates of offspring rats were decreased with longer hypoxic time. TUNEL staining showed that apoptotic cells were significant increased in the brains of offspring rats from the 10 min and 15 min HIE groups as compared to the offspring rats in the control group at postnatal day (PND) 1, but there was no statistical difference between the offspring rats in the 5 min HIE and control groups. The perinatal hypoxic treatment resulted in decreased neurons and increased cleaved caspase-3 protein levels in the offspring rats from all HIE groups at PND 1. Platform crossing times and the percentage of the time spent in the target quadrant of Morris Water Maze test were significantly reduced in the offspring rats of all HIE groups at PND 30, which were associated with decreased brain-derived neurotrophic factor levels and neuronal cells in the hippocampus of offspring rats at PND 35. These data demonstrated that perinatal ischemic injury led to the death of neuronal cells and long-lasting impairment of memory. This model reproduced hypoxic ischemic encephalopathy in early preterm newborns and may be appropriate for investigating therapeutic interventions.

Effects of intermittent high glucose on BeWo choriocarcinoma cells in culture

AIM

The aim of this study was to investigate the cellular effects of intermittent high glucose on the human BeWo placental choriocarcinoma cell line, used as a model of the effects of glucose fluctuation in diabetic pregnancies.

MATERIALS AND METHODS

BeWo cells were subjected to three different glucose conditions for 48 h: 7 mmol/L (control), 42 mmol/L (high glucose), or 7 and 42 mmol/L glucose (intermittent, alternated every 6 h). Cell viability was assessed using cell counts, a cell proliferation assay, and a cell viability assay. Apoptosis was also studied using a terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay and by immunocytochemistry of fractin, the N-terminal fragment of actin, which can distinguish apoptotic from necrotic cells. Furthermore, the expression of the well-known survival factors of trophoblast cells, heparin-binding epidermal growth factor-like growth factor and leptin, was evaluated by real-time polymerase chain reaction and Western blot analyses.

RESULTS

Intermittent high-glucose conditions significantly decreased cell viability and enhanced apoptosis compared with control or continuous high-glucose conditions. Furthermore, the expression of heparin-binding epidermal growth factor-like growth factor, but not that of leptin, was significantly increased under intermittent high-glucose conditions compared to its expression under either control or continuous high-glucose conditions.

CONCLUSIONS

These data indicate that intermittent high glucose is more deleterious to BeWo cells than continuous high-glucose conditions. Although further in vitro and in vivo study is necessary, excess fluctuation of glucose levels in the placental circulation might be involved in the impairment of placental development leading to the placental dysfunction.

A clinically relevant model of perinatal global ischemic brain damage in rats

We have designed a clinically relevant model of perinatal asphyxia providing intrapartum hypoxia in rats. On gestation day 22 SD rats were anesthetized and the uterine horns were exteriorized and placed in a water bath at 37°C for up to 20min. After this, pups were delivered from the uterus and manually stimulated to initiate breathing in an incubator at 37°C for 1 h in air. Brains were harvested and stained with cresyl violet, caspase-3, and TUNEL to detect morphological and apoptotic changes on postnatal days (PND) 1, 3, and 7. Separate cohorts were maintained until PND 50 and tested for learning and memory using Morris water maze (WM). Survival rate was decreased with longer hypoxic time, and 100% mortality was noted when hypoxia time was beyond 18min. Apoptosis was increased with the duration of hypoxia with neuronal loss and cell shrinkage in the CA1 of hippocampus. The time taken for the juveniles to locate the hidden platform during WM was increased in animals subjected to hypoxia. These data demonstrate that perinatal ischemic injury leads to neuronal death in the hippocampus and long-lasting cognitive dysfunction. This model mimics hypoxic ischemic encephalopathy in humans and may be appropriate for investigating therapeutic interventions.

Methods to detect apoptotic-like cell death in filamentous fungi

Fungi are capable of undergoing apoptotic-like cell death, and display many of the characteristic features of apoptosis observed in multicellular organisms. These features include nuclear condensation, DNA fragmentation, translocation of phosphatidylserine from the cytoplasmic to the extracellular side of the plasma membrane, and increased levels of reactive oxygen species (ROS). Several assays can be used to detect apoptotic cells, and here we describe adaptations of assays such as TUNEL, Annexin V, and Evan's Blue for the investigation of apoptotic-like cell death in fungal hyphae. We also present approaches for monitoring nuclear condensation and production of ROS.

Leptin attenuates hypoxia/reoxygenation-induced activation of the intrinsic pathway of apoptosis in rat H9c2 cells

Cardiomyocyte apoptosis is a component of cardiac remodeling that can contribute to heart failure in obesity. A role for leptin in mediating this process has been suggested and the objective of this work was to investigate the effect of leptin on apoptosis and associated mechanisms in H9c2 cells which were subjected to hypoxia/reoxygenation (HR) to mimic myocardial ischemia/reperfusion. Qualitative immunofluorescent and quantitative laser scanning cytometry approaches demonstrated that exposure of cells to HR increased DNA fragmentation (TUNEL staining) which was attenuated by leptin (6 nM, 1 h) pretreatment. We also found increased annexin-V binding and caspase-3 activity in cells exposed to HR, both of which were attenuated by leptin pretreatment. Leptin reduced HR-induced translocation of the pro-apoptotic protein Bax to the mitochondrial membrane, which provides a mechanism to explain its protective effect. Consequently, leptin attenuated the HR-induced decrease in mitochondrial membrane potential and increase in cytochrome c release from mitochondria. Leptin treatment increased the phosphorylation of p38 MAPK and AMPK and respective inhibitors of these kinases, SB203580 and Compound C, prevented the ability of leptin to decrease HR-induced caspase-3 activity. In conclusion, we establish mechanisms via which leptin exerts anti-apoptotic effects that may be of significance in understanding the development of heart failure in obesity.

Biochemical and molecular markers in renal cell carcinoma: an update and future prospects

Cancer is a big problem in the developed world as well as in developing countries. Renal cell carcinoma (RCC) accounts for approximately 3% of adult malignancies and 90-95% of neoplasms arising from the kidney. RCC is more common in men than in women (2:1), and it most often occurs in patients between the ages of 50-70 years. In all cancers the cancerous cells release particular kind of proteins (called tumour markers) and blood tests are used to detect the presence of these markers. These tumour markers nowadays are an area of interest for oncologists who search for a possible solution in the detection and treatment of RCC. Different kinds of biochemical and molecular markers such as ferritin, MN/CA9, apoptotic index, p53, IL-2, gamma-enolase, CD44, CD95, chromosome instability and loss of heterozygosity have been tested in RCC, but so far no marker fulfils one or the other criteria to be considered as an ideal marker for RCC. This review gives basic and updated information about the different kinds of biomarkers studied in RCC and about the role implementation of genomics and proteomics in RCC.

Characterisation of molecular events following cisplatin treatment of two curable ovarian cancer models: contrasting role for p53 induction and apoptosis in vivo

The detailed molecular basis and determinants of in vivo tumour sensitivity to conventional anticancer agents remain unclear. We examined the cellular and molecular consequences of cisplatin treatment using two ovarian tumour xenograft models that had not been previously adapted to culture in vitro. Both xenografts were curable with clinically relevant multiple doses of cisplatin. Following a single dose of cisplatin (6 mg kg⁻¹ i.p.) growth delays of 25 and 75 days were obtained for pxn100 and pxn65, respectively. This difference in response was not due to differences in DNA damage. Pxn100 tumours had a functional p53 response and a wild-type p53 sequence, whereas pxn65 harboured a mutant p53 and lacked a functional p53 response. Microarray analysis revealed the induction of p53-regulated genes and regulators of checkpoint control and apoptosis in pxn100 tumours following cisplatin-treatment. By contrast, there was no p53-dependent response and only limited changes in gene expression were detected in the pxn65 tumours. TUNEL analysis demonstrated high levels of apoptosis in the pxn100 tumours following cisplatin treatment, but there was no detectable apoptosis in the pxn65 tumours. Our observations show that a marked in vivo response to cisplatin can occur via p53-dependent apoptosis or independently of p53 status in human ovarian xenografts.

Increase in colorectal epithelial apoptotic cells in patients with ulcerative colitis ultimately requiring surgery

BACKGROUND AND AIMS

Up to one-third of patients with ulcerative colitis (UC) need to undergo surgery, but the factors that exacerbate inflammation remain unclear. The authors hypothesize that excessive apoptosis reported in active UC may disrupt epithelial defenses and exacerbate the disease. The aim of the present study was to clarify whether apoptotic epithelial cells and histiocytes engulfing them increased in patients with active UC who ultimately require surgery (UC-S) rather than those receiving medication alone (UC-M).

METHODS

The study included 29 patients with UC-S, 35 with UC-M, 18 with infectious colitis, and 16 healthy controls. Apoptotic cells were detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL). Using biopsy specimens taken from the most severely inflamed rectosigmoid mucosa as determined endoscopically, the apoptotic index (apoptotic cells/epithelial cells,%) and density (per mm2) of lamina propria histiocytes positive for CD68 were then evaluated. Statistical differences were tested with the Mann-Whitney U-test.

RESULTS

The apoptotic indices in UC-M patients were significantly higher than those in controls (P < 0.05) but almost equal to those in infectious colitis patients. In the upper and lower halves of the mucosa, both apoptotic indices and histiocyte densities were significantly higher for UC-S than in UC-M (P < 0.01). Ratios of the mean apoptotic index for UC-S to that for UC-M exceeded 3.4, while ratios of the mean histiocyte density were limited to approximately 1.6.

CONCLUSIONS

The results suggest that epithelial apoptosis is a non-specific phenomenon and that an increased number of apoptotic cells exceeding histiocyte phagocytic capacity may play a part in the disruption of epithelial defenses and further accelerate mucosal inflammation.

Nuclear apoptosis detection by flow cytometry: influence of endogenous endonucleases

Nuclear apoptosis is characterized by chromatin condensation and progressive DNA cleavage into high-molecular-weight fragments and oligonucleosomes. These complex phenomena can be mediated by the activation of a multiplicity of enzymes, characterized by specific patterns of cation dependance, pH requirement, and mode of activation. The significance of this multiplicity of enzymes that cleave genomic DNA has been attributed to the need of death effector pathways specific for cell types/tissues, the level of cell differenciation, and the nature of the apoptotic stimuli. The activation of these factors contributes to the development of alterations that can be detected specifically by flow cytometric assays, namely, propidium iodide assays, acridine orange/ethidium bromide double staining, the TUNEL and ISNT techniques, and the assays of DNA sensitivity to denaturation. Although applicable to a wide spectrum of cell types, an increasing body of literature indicates that these techniques cannot be universally applied to all cell lines and apoptotic conditions: The requirement of a particular mediator(s) of nuclear apoptosis or the absence of endonuclease activity can limit the relevance of certain techniques. Finally, endonucleases recruited during primary necrosis can introduce nuclear alterations detected by some assays and raise the problem of their specificity. This review underlines the need for strategies to accurately detect and quantify nuclear apoptosis by flow cytometry when new cell systems and apoptotic conditions are considered.

Using flow cytometry to follow the apoptotic cascade

Flow cytometry has been extensively used to follow the apoptotic cascade and to enumerate apoptotic cells, both in cell cultures and, to a lesser extent, in tissue biopsies. An overview of the apoptotic cascade and how flow cytometric measurements can be used to observe the different elements of this process is presented.

Potent and selective nonpeptide inhibitors of caspases 3 and 7

5-Dialkylaminosulfonylisatins have been identified as potent, nonpeptide inhibitors of caspases 3 and 7. The most active compound within this series (34) inhibited caspases 3 and 7 in the 2-6 nM range and exhibited approximately 1000-fold selectivity for caspases 3 and 7 versus a panel of five other caspases (1, 2, 4, 6, and 8) and was at least 20-fold more selective versus caspase 9. Sequence alignments of the active site residues of the caspases strongly suggest that the basis of this selectivity is due to binding in the S2 subsite comprised of residues Tyr204, Trp206, and Phe256 which are unique to caspases 3 and 7. These compounds inhibit apoptosis in three cell-based models: human Jurkat T cells, human chondrocytes, and mouse bone marrow neutrophils.

Mechanisms of HIV-associated lymphocyte apoptosis

Infection with the human immunodeficiency virus (HIV) is associated with a progressive decrease in CD4 T-cell number and a consequent impairment in host immune defenses. Analysis of T cells from patients infected with HIV, or of T cells infected in vitro with HIV, demonstrates a significant fraction of both infected and uninfected cells dying by apoptosis. The many mechanisms that contribute to HIV-associated lymphocyte apoptosis include chronic immunologic activation; gp120/160 ligation of the CD4 receptor; enhanced production of cytotoxic ligands or viral proteins by monocytes, macrophages, B cells, and CD8 T cells from HIV-infected patients that kill uninfected CD4 T cells; and direct infection of target cells by HIV, resulting in apoptosis. Although HIV infection results in T-cell apoptosis, under some circumstances HIV infection of resting T cells or macrophages does not result in apoptosis; this may be a critical step in the development of viral reservoirs. Recent therapies for HIV effectively reduce lymphoid and peripheral T-cell apoptosis, reduce viral replication, and enhance cellular immune competence; however, they do not alter viral reservoirs. Further understanding the regulation of apoptosis in HIV disease is required to develop novel immune-based therapies aimed at modifying HIV-induced apoptosis to the benefit of patients infected with HIV.

Mechanisms of HIV-associated lymphocyte apoptosis

Infection with the human immunodeficiency virus (HIV) is associated with a progressive decrease in CD4 T-cell number and a consequent impairment in host immune defenses. Analysis of T cells from patients infected with HIV, or of T cells infected in vitro with HIV, demonstrates a significant fraction of both infected and uninfected cells dying by apoptosis. The many mechanisms that contribute to HIV-associated lymphocyte apoptosis include chronic immunologic activation; gp120/160 ligation of the CD4 receptor; enhanced production of cytotoxic ligands or viral proteins by monocytes, macrophages, B cells, and CD8 T cells from HIV-infected patients that kill uninfected CD4 T cells; and direct infection of target cells by HIV, resulting in apoptosis. Although HIV infection results in T-cell apoptosis, under some circumstances HIV infection of resting T cells or macrophages does not result in apoptosis; this may be a critical step in the development of viral reservoirs. Recent therapies for HIV effectively reduce lymphoid and peripheral T-cell apoptosis, reduce viral replication, and enhance cellular immune competence; however, they do not alter viral reservoirs. Further understanding the regulation of apoptosis in HIV disease is required to develop novel immune-based therapies aimed at modifying HIV-induced apoptosis to the benefit of patients infected with HIV.

Analysis of virus-infected cells by flow cytometry

Flow cytometry has been used to study virus-cell interactions for many years. This article critically reviews a number of reports on the use of flow cytometry for the detection of virus-infected cells directly in clinical samples and in virus-infected cultured cells. Examples are presented of the use of flow cytometry to screen antiviral drugs against human immunodeficiency virus (HIV), human cytomegalovirus, and herpes simplex viruses (HSV) and to perform drug susceptibility testing for these viruses. The use of reporter genes such as green fluorescent protein incorporated into HIV or HSV or into cells for the detection of the presence of virus, for drug susceptibility assay, and for viral pathogenesis is also covered. Finally, studies on the use of flow cytometry for studying the effect of virus infection on apoptosis and the cell cycle are summarized. It is hoped that this article will give the reader some understanding of the great potential of this technology for studying virus cell interactions.

Balance between proliferation and apoptosis in leukemic cell lines resistant to cytostatics

Resistance to apoptosis may contribute to tumorigenesis and, in part, explains treatment failures in neoplastic diseases. We evaluated in vitro drug-induced apoptosis in leukemic cells using TdT-dependent labeling of DNA breaks with digoxigenine-dUTP and PI DNA staining in multiparameter flowcytometry. In cell lines developing drug resistance, a significant inhibition of proliferation and increased cell clearance via apoptosis was shown. Moreover, in drug resistant sub-lines and in blasts from AML patients, a variable apoptotic response to in vitro exposure to cytostatics was seen. Half of the studied AML cases were completely resistant to Novantrone-induced apoptosis with no correlation between sensitivity to Novantrone and bcl-2 expression. One case showed intraclonal heterogeneity with two coexisting populations: an immature blast population resistant to Novantrone and a differentiating blast population showing apoptotic response. Another case showed complete resistance to various cytostatics, but incubation with anti-CD95 monoclonal antibody resulted in a considerable apoptotic response. This case demonstrates that a lack of apoptotic response to cytostatics does not preclude sensitivity to other apoptotic stimuli. Our results confirm the role apoptosis plays in selection of drug-resistant clones and suggest different signaling pathways for apoptosis operating in various leukemic blasts.

N-Nitrosodimethylamine-mediated cytotoxicity in a cell line expressing P450 2E1: evidence for apoptotic cell death

N-Nitrosodimethylamine (NDMA) is an acute hepatotoxin and potent carcinogen. The metabolic activation of NDMA to reactive metabolites is a critical step for the expression of its toxic and carcinogenic potential. We have previously demonstrated a strong correlation between methylation of cellular macromolecules and NDMA-mediated cytotoxicity, and we have demonstrated that reactive oxygen species may partially contribute to the toxic effects in P450 2E1-expressing cells. The mode of cell death in NDMA-treated monolayer cultures exhibited the following characteristics: (i) condensation of nuclear chromatin as demonstrated by using Hoechst 33258 staining, (ii) DNA fragmentation as detected by combining pulsed field and conventional agarose gel electrophoresis, and (iii) DNA double strand breaks determined by using the in situ terminal deoxynucleotidyl transferase assay and flow cytometric analysis. These results indicate that reactive metabolites of NDMA trigger activation of the signal pathway for apoptotic cell death in these P450-expressing cells. The NDMA-mediated cell death was partially prevented by the endonuclease inhibitor, aurintricarboxylic acid, as well as the caspase inhibitors, acetyl-Asp-Glu-Val-Asp-CHO and acetyl-Tyr-Val-Ala-Asp-CHO. The cell cycle distribution was altered in NDMA-treated cells resulting in an increase in the G2/M phase and a decrease in the G1 phase. Our results suggest that DNA degradation, the inability to complete DNA repair, the biochemical events associated with G2/M arrest, and the process of apoptotic death all result from P450 2E1-catalyzed metabolism of NDMA.

Cell death by overload of the elastin-laminin receptor on human activated lymphocytes: protection by lactose and melibiose

BACKGROUND

Activated human lymphocytes were shown to express the elastin-laminin receptor in vitro and also in vivo in atherosclerotic plaques. In the presence of the agonist, elastin peptides, this receptor was shown to mediate an increased cell proliferation and an increased synthesis and excretion of an elastase-type serine endopeptidase. In this study, we investigated the variation of the above reaction as a function of agonist concentration.

MATERIALS AND METHODS

Human lymphocytes were obtained by tonsillectomy and cultured in the presence of phytohaemagglutinin and elastin peptides. Cell viability was evaluated by vital dye exclusion. Elastase and cathepsin G activities were determined in culture supernates and cell lysates using synthetic substrates. Apoptotic cells were identified by the TUNEL method and by electron microscopy.

RESULTS

At increasing concentrations of elastin peptides, a dose-dependent increase in cell death was observed. Up to 100 micrograms mL-1 elastin peptides and an increasing fraction of lymphocytes were found permeable to trypan blue, and a large proportion was in apoptosis. Elastin peptide-induced cell death was inhibited by 1 microgram mL-1 lactose and melibiose.

CONCLUSION

We describe here cell death of human activated lymphocytes expressing the elastin-laminin receptor in the presence of increasing concentrations of elastin peptides, agonists of the receptor. The mechanism of cell death appears to be related to the triggering of the release of elastase and free radicals mediated by the elastin-laminin receptor. Antagonists of this receptor, lactose and melibiose, protected the lymphocytes from the receptor-mediated cell death.

Intraclonal heterogeneity in the in vitro daunorubicin-induced apoptosis in acute myeloid leukemia

Leukemic cells from ten patients with acute myeloid leukemia (AML) were sorted on the basis of in vitro daunorubicin (DNR) uptake. The obtained subpopulations with high and low DNR accumulation were compared with regard to induction of apoptosis, expression of bcl-2 and p53. Heterogeneous induction of apoptosis, confined to subpopulations with high DNR uptake, was observed. The size of the DNR-induced apoptotic fraction (4% to 16%) within a given AML blast population was determined by intracellular drug accumulation and was not related to the level of bcl-2 expression. All tested leukemic samples displayed expression of p53 in a growth promoter orientation, i.e. PAb1620-/PAb240+. In two samples, however, subpopulations expressing a growth suppressor orientation of p53, i.e. PAb 1620+/PAb240-, were also present. These subpopulations were confined to high-DNR-uptake fractions and associated with the induction of apoptosis. We conclude that intraclonal heterogeneity in the intracellular drug accumulation and subsequently in DNR-induced apoptosis might allow the selection of inherently drug-resistant AML clones thus contributing to relapse of leukemia.

Cell death induced in lymphocytes expressing the elastin-laminin receptor by excess agonists: necrosis and apoptosis

This manuscript summarizes our experiments carried out during the last years on the expression of the elastin-laminin receptor on human activated lymphocytes and cell death triggered by the activation of this receptor by its agonists, elastin peptides. We could distinguish two types of cell reactions, depending on the elastin peptide concentration added to the cell culture media of lymphocytes. At low concentrations (1-10 micrograms/mL, 1.3-13 x 10(-8) M) of kappa-elastin, there was a stimulation of cell proliferation, elastase biosynthesis and release. As the concentration of kappa-elastin was increased in the culture medium up to 100 micrograms/mL, lymphocyte proliferation and elastase production decreased and the proportion of dead cells increased. Cell death was shown to be due to both apoptotic and non-apoptotic mechanisms. Apoptotic cell death increased with agonist concentration and reached approximately 60% of the lymphocyte population at mg/mL elastin peptide concentrations. This observation was confirmed by the concomitant use of several different methodologies, such as flow cytometry and electron microscopy. The precise nature of the non-apoptotic cell death remains to be established.

Comparison of seven quantitative assays to assess lymphocyte cell death during HIV infection: measurement of induced apoptosis in anti-Fas-treated Jurkat cells and spontaneous apoptosis in peripheral blood mononuclear cells from children infected with HIV

The study of apoptosis in relation to various human disease states, particularly HIV infection, has seen a tremendous increase in activity. In this article, values obtained by seven different assays, designed to quantify apoptosis and applicable to the study of HIV infection, are compared in two cell systems: (1) stimulus-induced apoptosis in Jurkat cells treated with anti-Fas antibody and (2) spontaneous apoptosis in PBMCs isolated from HIV-infected children. The methods used included measurement of cells with subdiploid DNA content, labeling of DNA strand breaks by the TUNEL reaction, annexin V surface labeling for the detection of exposed phosphatidylserine, cytoplasmic antigen labeling with the apoptosis-specific antibody Apo 2.7, detection of changes in flow cytometric light-scattering properties, trypan blue dye exclusion by light microscopy, and detection of changes in cellular chromatin by fluorescence microscopy. These methods produced well-correlated values in the Jurkat system, whereas the same set of methods produced more discrepant values in the PBMC analyses, especially in those patients with low CD4 counts. Specifically, our results showed that the trypan blue test was unacceptable for quantification of apoptosis during HIV infection, whereas TUNEL, of all the methods tested, showed excellent overall correlation in both cell systems, was highly specific, and matched microscopic observation of the cells. Although many of the methods were suited to the study of a homogeneous cell line, caution must be exercised when examining cell death in a heterogeneous cell mixture from an HIV-infected individual.

Measurement of apoptosis

The cell dying by apoptosis undergoes a sequence of morphological, biochemical, and molecular changes which are characteristic, and often unique, to this mode of cell death. Specific features of apoptotic cells resulting from these changes, which serve as markers used to reveal the apoptotic mode of cell death and to quantify the extent of apoptosis in cultures or in tissue, are reviewed. Analysis of these features by flow or image cytometry is the most commonly used approach to detect, quantify, and study various aspects of apoptosis. Flow or laser scanning cytometry also offer all the advantages of rapid, accurate and multiparametric measurements to investigate the biological processes associated with cell death. Numerous methods have been developed to identify apoptotic and necrotic cells, which are widely used in various disciplines, particularly in oncology and immunology. The methods based on changes in cell morphology, plasma membrane molecular structure and transport function, function of cell organelles, DNA stability to denaturation and endonucleolytic DNA degradation are reviewed and their applicability in the research laboratory and in the clinical setting is discussed. The most common pitfalls and improper use of the methodology in analysis of cell death and in data interpretation are also discussed.

Alkylphosphocholines: Effects on human leukemic cell lines and normal bone marrow cells

The anti-leukemic activity of a series of alkylphosphocholines (APCs) was studied against a panel of human leukemic cell lines (HL-60, K-562, Reh, MOLT-4, Jurkat, Ramos and Raji). Cytotoxic efficacy was measured by the MTT cell survival assay. All cell lines were found to be sensitive, except the multipotential CML-derived K-562 cell line. Flow cytometry of HL-60 cells showed a significant decrease of cells in S phase and the formation of a sub-G fraction. DNA fragmentation typical for programmed cell death was detected by DNA gel electrophoresis in these cells but not in any of the other leukemic lines. At concentrations below the cytotoxic range, mitogenic effects were seen in HL-60 cells after 14-hr exposure. Colony formation by K-562 cells revealed an augmented clonogenicity after exposure to APC with a short alkyl chain. In contrast, cells of lymphoid origin did not undergo DNA fragmentation or show mitogenic stimulation after exposure to APC. Normal bone marrow cells were also investigated for mitogenic and genotoxic effects. No decrease was found in the number of hematopoietic progenitors in long-term bone marrow cell cultures after exposure to APC. On the contrary, a significant increase was found after short exposure. Dodecylphosphocholine, hexadecylphosphocholine (HPC) and (octadecyl-[2-(N-methylpiperidino)-ethyl]phosphate exhibited a mild clastogenicity at equimolar high doses on murine bone marrow cells in vivo, which is unusual for the majority of classical DNA-interacting anti-cancer drugs. In conclusion, APCs are agents with a broad spectrum of in vitro anti-leukemic effects, which lack hematological toxicity.

Molecular cloning and characterization of human caspase-activated DNase

Caspase-activated DNase (CAD) cleaves chromosomal DNA during apoptosis. Here, we report isolation of two classes of human CAD cDNAs from a human KT-3 leukemic cell cDNA library. One class of cDNA encoded a protein comprising 338 amino acids, which showed a marked similarity to its murine counterpart. In vitro transcription and translation of this cDNA resulted in a functional CAD protein when the protein was synthesized in the presence of its inhibitor (inhibitor of CAD). The other cDNA class contained many deletions, insertions, and point mutations in the sequence corresponding to the coding region, suggesting that it is derived from a pseudogene. The functional CAD gene was localized to human chromosome 1p36.3 by fluorescent in situ hybridization. The CAD mRNA was expressed in a limited number of human tissues, including pancreas, spleen, prostate, and ovary. The expression of the CAD mRNA in human cell lines correlated with their ability to show DNA fragmentation during apoptosis. Overexpression of CAD potentiated DNA fragmentation by apoptotic stimuli in these cell lines, indicating that CAD is responsible for the apoptotic DNA degradation.

Simultaneous measurement of cell cycle and apoptotic cell death

Understanding the dynamics of cell death in conjunction with those of cell cycle can be illuminating in the investigation of various cellular behaviors. Robust assays for measuring such parameters are invaluable. Many assays of apoptosis and/or cell cycle use flow cytometry. This chapter describes two different assays to measure apoptosis and cell cycle simultaneously using flow cytometry. The first involves the use of terminal transferase (the "TUNEL" assay) together with propidium iodide for identification of cell cycle. The second uses fluorescently labeled annexin V, together with propidium iodide as an indicator of cell membrane integrity; and additionally Hoechst 33342 for determination of cell cycle. Each assay has positive and negative attributes. The terminal transferase assay is performed using fixed cells and is therefore useful in the analysis of samples collected over time. The annexin V assay is performed using unfixed cells, and thus provides information regarding membrane integrity. Other practical aspects of both assays are discussed.

[Significance of apoptotic processes in radiotherapy. I]

According to a considerable amount of publications apoptosis plays an important role for radio- and chemotherapy. The most important results related to this issue will be described in 2 independent articles, covering the following topics: Part I: I. definition, morphology, biochemical processes, II. clinical relevant detection assays, III. signal transduction. Part II: significance of apoptosis for radio- and chemotherapy.

Cytosolic 85-kDa phospholipase A2-mediated release of arachidonic acid is critical for proliferation of vascular smooth muscle cells

Recent evidence suggests that arachidonic acid (AA) may be involved in regulating cellular proliferation. The predominant mechanism of AA release from cellular phospholipids is via phospholipase A2 (PLA2) hydrolysis. The purpose of this study was to examine the roles of the distinct 14-kDa and 85-kDa PLA2 enzymes in human coronary artery vascular smooth muscle cell (hCAVSMC) proliferation. Cultured hCAVSMCs proliferate in the presence of growth medium with a typical doubling time of 30-40 h, grow at a slower proliferative rate upon reaching confluency (day 8), and eventually undergo contact inhibition of growth (day 10). Neither Type II 14-kDa PLA2 activity nor mass changed over a 10-day culture period. In contrast, 85-kDa PLA2 protein activity and mRNA decreased as time in culture progressed. This reduction in 85-kDa PLA2 correlated with reductions in DNA synthesis and suggested a possible association between 85-kDa PLA2 and proliferation. To directly evaluate the role of the 85-kDa PLA2 in proliferation we examined the effects of an 85-kDa PLA2 inhibitor (AACOCF3) and 85-kDa PLA2 antisense oligonucleotides on proliferation. Both reagents dose dependently inhibited proliferation, whereas a 14-kDa PLA2 inhibitor (SB203347), a calcium-independent PLA2 inhibitor (HELSS), an 85-kDa sense oligonucleotide, and a nonrelevant scrambled control oligonucleotide had no effect. The mechanism by which 85-kDa PLA2 influences cellular proliferation remains unclear. Inhibition of 85-kDa PLA2 activity produced neither phase-specific cell cycle arrest nor apoptosis (fluorescence-activated cell sorter analysis). Addition of AA (20 mu M) attenuated the effects of both AACOCF3 and 85-kDa antisense oligonucleotides implicating AA as a key mediator in cellular proliferation. However, although prostaglandin E2 (PGE2) was present in the culture medium, it peaked early (day 3) in culture, and indomethacin had no effect on cellular proliferation indicating that hCAVSMC proliferation was not mediated through PGE2. These data provide the first direct evidence that PLA2 is involved in control of VSMC proliferation and indicate that 85-kDa PLA2-mediated liberation of AA is critical for cellular proliferation.

Induction of differentiation and apoptosis by sodium selenite in human colonic carcinoma cells (HT29)

To explore the mechanism(s) by which selenium (Se) exerts its cancer chemopreventive activity, we studied the effect of selenite (0-100 microM) on cell growth, viability, differentiation, detachment, DNA fragmentation and apoptosis in human colonic carcinoma cells (HT29). Selenite (>5 microM) decreased cell growth, increased cell detachment and decreased intracellular levels of reduced glutathione (GSH), whereas >10 microM selenite induced cell differentiation and apoptosis. The chemopreventive effects of selenite may be related in part to the generation of reactive oxygen species (ROS) resulting from the reaction between selenite and GSH.

Relationship between arachidonate--phospholipid remodeling and apoptosis

Our previous studies reveal that three structurally distinct inhibitors of the enzyme CoA-independent transacylase, including the antiproliferative alkyllysophospholipid ET-18-O-CH3, induce programmed cell death (apoptosis) in the promyelocytic cell line HL-60. The objective of the current study was to better elucidate the mechanism responsible for apoptosis. CoA-IT is an enzyme believed to be responsible for the remodeling of long chain polyunsaturated fatty acids like arachidonate between the phospholipids of mammalian cells. The chronic (24-48 h) treatment of HL-60 cells with all three CoA-IT inhibitors resulted in the inhibition of the remodeling of labeled arachidonate from choline- into ethanolamine-containing phospholipid molecular species. GC-MS analysis of the fatty acids in phospholipids revealed that CoA-IT inhibitor treatment induced a marked loss of arachidonate-containing phosphatidylethanolamine and an increase in arachidonate-containing phosphatidylcholine. This redistribution was specific to arachidonate since the mass distribution of linoleic acid in glycerolipids was not affected. In spite of the dramatic redistribution of arachidonate, the total cellular arachidonate content was not altered nor was the relative distribution of total phospholipid classes. The increase of arachidonate in phosphatidylcholine was specifically due to an increase in 1-acyl-2-arachidonoyl-sn-glycero-3-phosphocholine species, whereas the loss of arachidonate in PE was from both 1-acyl- and 1-alk-1-enyl-2-arachidonoyl-sn-glycero-3-phosphoethanolamine species. The incubation of cells with exogenous arachidonic acid or ethanolamine did not reverse the inhibition of proliferation induced by CoA-IT inhibitor treatment. Incubation with CoA-IT inhibitors also induced the characteristic cytoplasmic and nuclear changes associated with apoptosis as assessed by transmission electron microscopy and DNA fragmentation as determined by flow cytometry. Taken together, these data show that apoptosis in HL-60 cells, induced by blocking arachidonate-phospholipid remodeling, is correlated with a redistribution of arachidonate in membrane phospholipids and suggest that such alterations represent a signal which controls the capacity of cells to proliferate.

Labelling DNA strand breaks with BrdUTP. Detection of apoptosis and cell proliferation

In situ presence of numerous DNA strand breaks is a typical feature of apoptotic cells. Selective DNA strand break induction by photolysis (SBIP) at sites that contain incorporated halogenated DNA precursors has recently been proposed as a method of analysing DNA replication. Detection of DNA strand breaks, thus, enables one to identify apoptotic and/or DNA replicating cells. The current methods for DNA strand break labelling rely on the use of exogenous terminal deoxynucleotidyl transferase which either directly attaches the fluorochrome conjugated triphosphodeoxynucleotides to 3'OH ends in the breaks, or indirectly labels 3'OH ends with digoxygenin or biotin conjugated triphosphodeoxynucleotides. A limitation of these methodologies, especially restricting their routine application in the clinic, is high cost of reagents. In the present study we have tested whether relatively simple compound BrdUTP, which is approximately three orders of magnitude less expensive than dUTP conjugated to digoxygenin, can be used as marker of DNA strand breaks. Apoptosis of HL-60 cells was induced by DNA topoisomerase I inhibitor camptothecin. The incorporated BrdUTP was detected by fluoresceinated anti-BrdUrd MoAb. Cellular fluorescence was measured by flow cytometry as well as by Laser Scanning Cytometer (LSC). The data show that intensity of DNA strand break labelling with BrdUTP was nearly four- and two-fold higher than that obtained with the indirect labelling using biotin- or digoxygenin-conjugated dUTP, respectively, and over eight-fold higher than in the case of direct labelling with the fluorochrome (fluorescein or BODIPY)-conjugated deoxynucleotides. The increased labelling of DNA strand breaks with BrdUTP may reflect more efficient incorporation of this precursor by terminal transferase, compared to the nucleotides with bulky fluorochrome conjugates. DNA strand break labelling with BrdUTP, thus, offers a possibility of more sensitive (and at lower cost) detection of apoptotic or DNA replicating cells, compared to the alternative methods of DNA strand break labelling.