Discrimination of apoptotic thymocytes by forward light scatter

Analysis of Microcystis aeruginosa physiology by spectral flow cytometry: Impact of chemical and light exposure

M. aeruginosa fluorescent changes were observed using a Cytek Aurora spectral flow cytometer that contains 5 lasers and 64 narrow band detectors located between 365 and 829 nm. Cyanobacteria were treated with different concentrations of H2O2 and then monitored after exposure between 1 and 8 days. The red fluorescence emission derived from the excitation of cyanobacteria with a yellow green laser (550 nm) was measured in the 652-669 nm detector while green fluorescence from excitation with a violet laser (405 nm) was measured in the 532-550 nm detector. The changes in these parameters were measured after the addition of H2O2. There was an initial increase in red fluorescence intensity at 24 hours. This was followed by a daily decrease in red fluorescence intensity. In contrast, green fluorescence increased at 24 hours and remained higher than the control for the duration of the 8-day study. A similar fluorescence intensity effect as H2O2 on M. aeruginosa fluorescence emissions was observed after exposure to acetylacetone, diuron (DCMU), peracetic acid, and tryptoline. Minimal growth was also observed in H2O2 treated cyanobacteria during exposure of H2O2 for 24 days. In another experiment, H2O2-treated cyanobacteria were exposed to high-intensity blue (14 mW) and UV (1 mW) lights to assess the effects of light stress on fluorescence emissions. The combination of blue and UV light with H2O2 had a synergistic effect on M. aeruginosa that induced greater fluorescent differences between control and treated samples than exposure to either stimulus individually. These experiments suggest that the early increase in red and green fluorescence may be due to an inhibition in the ability of photosynthesis to process photons. Further research into the mechanisms driving these increases in fluorescence is necessary.

A comparative study of U937 cell size changes during apoptosis initiation by flow cytometry, light scattering, water assay and electronic sizing

A decrease in flow cytometric forward light scatter (FSC) is commonly interpreted as a sign of apoptotic cell volume decrease (AVD). However, the intensity of light scattering depends not only on the cell size but also on its other characteristics, such as hydration, which may affect the scattering in the opposite way. That makes estimation of AVD by FSC problematic. Here, we aimed to clarify the relationship between light scattering, cell hydration (assayed by buoyant density) and cell size by the Coulter technique. We used human lymphoid cells U937 exposed to staurosporine, etoposide or hypertonic stress as an apoptotic model. An initial increase in FSC was found to occur in apoptotic cells treated with staurosporine and hypertonic solutions; it is accompanied by cell dehydration and is absent in apoptosis caused by etoposide that is consistent with the lack of dehydration in this case. Thus, the effect of dehydration on the scattering signal outweighs the effect of reduction in cell size. The subsequent FSC decrease, which occurred in parallel to accumulation of annexin-positive cells, was similar in apoptosis caused by all three types of inducers. We conclude that an increase, but not a decrease in light scattering, indicates the initial cell volume decrease associated with apoptotic cell dehydration.

Methods for cell volume measurement

Volume is an essential characteristic of a cell, and this review describes the main methods of its measurement that have been used in the past several decades. The discussed methods include various implementations of light scattering, estimates based on one or two cell dimensions, surface scanning, fluorescence confocal and transmission slice-by-slice imaging, intracellular volume markers, displacement of extracellular solution, quantitative phase imaging, radioactive methods, and some others. Suitability of these methods to some typical samples and applications is discussed. © 2017 International Society for Advancement of Cytometry.

High-frequency ultrasound detection of cell death: Spectral differentiation of different forms of cell death in vitro

High frequency quantitative ultrasound techniques were investigated to characterize different forms of cell death in vitro. Suspension-grown acute myeloid leukemia cells were treated to cause apoptosis, oncosis, mitotic arrest, and heat-induced death. Samples were scanned with 20 and 40 MHz ultrasound and assessed histologically in terms of cellular structure. Frequency-domain analysis of 20 MHz ultrasound data demonstrated midband fit changes of 6.0 ± 0.7 dBr, 6.2 ± 1.8 dBr, 4.0 ± 1.0 dBr and −4.6 ± 1.7 dBr after 48-hour cisplatinum-induced apoptosis, 48-hour oncotic decay, 36-hour colchicine-induced mitotic arrest, and heat treatment compared to control, respectively. Trends from 40 MHz ultrasound were similar. Spectral slope changes obtained from 40 MHz ultrasound data were reflective of alterations in cell and nucleus size. Chromatin pyknosis or lysis trends suggested that the density of nuclear material may be responsible for observed changes in ultrasound backscatter. Flow cytometry analysis confirmed the modes of cell death and supported midband fit trends in ultrasound data. Scatterer-size and concentration estimates obtained from a fluid-filled sphere form factor model further corresponded with spectral analysis and histology. Results indicate quantitative ultrasound spectral analysis may be used for probing anti-cancer response and distinguishing various modes of cell death in vitro.

Original Research: Label-free detection for radiation-induced apoptosis in glioblastoma cells

Current flow cytometry (FCM) requires fluorescent dyes labeling cells which make the procedure costly and time consuming. This manuscript reports a feasibility study of detecting the cell apoptosis with a label-free method in glioblastoma cells. A human glioma cell line M059K was exposed to 8 Gy dose of radiation, which enables the cells to undergo radiation-induced apoptosis. The rates of apoptosis were studied at different time points post-irradiation with two different methods: FCM in combination with Annexin V-FITC/PI staining and a newly developed technique named polarization diffraction imaging flow cytometry. Totally 1000 diffraction images were acquired for each sample and the gray level co-occurrence matrix (GLCM) algorithm was used in morphological characterization of the apoptotic cells. Among the feature parameters extracted from each image pair, we found that the two GLCM parameters of angular second moment (ASM) and sum entropy (SumEnt) exhibit high sensitivities and consistencies as the apoptotic rates (Pa) measured with FCM method. In addition, no significant difference exists between Pa and ASM_S, Pa and SumEnt_S, respectively (P > 0.05). These results demonstrated that the new label-free method can detect cell apoptosis effectively. Cells can be directly used in the subsequent biochemical experiments as the structure and function of cells and biomolecules are well-preserved with this new method.

Improved detection of diffuse large B-cell lymphoma by flow cytometric immunophenotyping-Effect of tissue disaggregation method

BACKGROUND

Flow cytometric immunophenotyping (FCI) is recognized as a rapid, sensitive, and accurate method for diagnosis of B-cell lymphomas. We observed that FCI failed to identify the clonal B-cell population in several cases of large B-cell lymphoma (DLBCL) when tissue samples were prepared by a commercially available mechanical tissue disaggregation method. We tested a manual tissue disaggregation method and compared it with the mechanical method.

METHODS

FCI findings from 51 cases of DLBCL processed with the mechanical tissue disaggregation method, 27 cases processed using the manual method, and 15 cases processed using a combination of both methods were compared. The histological and immunohistochemical findings in each case were reviewed.

RESULTS

FCI detected a clonal B-cell population in 88.9% of cases processed by the manual tissue disaggregation method, 66.7% of cases processed by a combination of the manual and mechanical disaggregation methods, and in 62.7% of cases processed solely by the mechanical tissue disaggregation method (P < 0.01 Fisher exact). Manual processing yielded positive FCI results in 81.8% of the nodal tissue samples and 93.8% of the extra-nodal tissue samples, whereas mechanical disaggregation was particularly inefficient in preserving large lymphoma cells from extra-nodal tissue: 71.4% of the nodal and 56.8% of the extra-nodal tissue samples processed by the mechanical method showed clonal B-cells by flow cytometry (P < 0.006, Fisher exact).

CONCLUSIONS

The diagnostic yield of FCI in DLBCL can be significantly improved by utilizing a manual disaggregation method, particularly in extra-nodal tissue samples. © 2015 International Clinical Cytometry Society.

A quantitative method for measurement of HL-60 cell apoptosis based on diffraction imaging flow cytometry technique

A quantitative method for measurement of apoptosis in HL-60 cells based on polarization diffraction imaging flow cytometry technique is presented in this paper. Through comparative study with existing methods and the analysis of diffraction images by a gray level co-occurrence matrix algorithm (GLCM), we found 4 GLCM parameters of contrast (CON), cluster shade (CLS), correlation (COR) and dissimilarity (DIS) exhibit high sensitivities as the apoptotic rates. It was further demonstrated that the CLS parameter correlates significantly (R(2) = 0.899) with the degree of nuclear fragmentation and other three parameters showed a very good correlations (R(2) ranges from 0.69 to 0.90). These results demonstrated that the new method has the capability for rapid and accurate extraction of morphological features to quantify cellular apoptosis without the need for cell staining.

In search of antiaging modalities: evaluation of mTOR- and ROS/DNA damage-signaling by cytometry

This review presents the evidence in support of the IGF-1/mTOR/S6K1 signaling as the primary factor contributing to aging and cellular senescence. Reviewed are also specific interactions between mTOR/S6K1 and ROS-DNA damage signaling pathways. Outlined are critical sites along these pathways, including autophagy, as targets for potential antiaging (gero-suppressive) and/or chemopreventive agents. Presented are applications of flow- and laser scanning- cytometry utilizing phospho-specific Abs, to monitor activation along these pathways in response to the reported antiaging drugs rapamycin, metformin, berberine, resveratrol, vitamin D3, 2-deoxyglucose, and acetylsalicylic acid. Specifically, effectiveness of these agents to attenuate the level of constitutive mTOR signaling was tested by cytometry and confirmed by Western blotting through measuring phosphorylation of the mTOR-downstream targets including ribosomal protein S6. The ratiometric analysis of phosphorylated to total protein along the mTOR pathway offers a useful parameter reporting the effects of gero-suppressive agents. In parallel, their ability to suppress the level of constitutive DNA damage signaling induced by endogenous ROS was measured. While the primary target of each of these agents may be different the data obtained on several human cancer cell lines, WI-38 fibroblasts and normal lymphocytes suggest common downstream mechanism in which the decline in mTOR/S6K1 signaling and translation rate is coupled with a reduction of oxidative phosphorylation and ROS that leads to decreased oxidative DNA damage. The combined assessment of constitutive γH2AX expression, mitochondrial activity (ROS, ΔΨm), and mTOR signaling provides an adequate gamut of cell responses to test effectiveness of gero-suppressive agents. Described is also an in vitro model of induction of cellular senescence by persistent replication stress, its quantitative analysis by laser scanning cytometry, and application to detect the property of the studied agents to attenuate the induction of senescence. Discussed is cytometric analysis of cell size and heterogeneity of size as a potential biomarker used to asses gero-suppressive agents and longevity.

Acoustophoretic sorting of viable mammalian cells in a microfluidic device

We report the first use of ultrasonic acoustophoresis for the label-free separation of viable and nonviable mammalian cells within a microfluidic device. Cells that have undergone apoptosis are physically smaller than viable cells, and our device exploits this fact to achieve efficient sorting based on the strong size dependence of acoustic radiation forces within a microchannel. As a model, we have selectively enriched viable MCF-7 breast tumor cells from heterogeneous mixtures of viable and nonviable cells. We found that this mode of separation is gentle and enables efficient, label-free isolation of viable cells from mixed samples containing 10(6) cells/mL at flow rates of up to 12 mL/h. We have extensively characterized the device, and we report the effects of piezoelectric voltage and sample flow rate on device performance and describe how these parameters can be tuned to optimize recovery, purity, or throughput.

Technologies supporting analytical cytology: clinical, research and drug discovery applications

The tools and techniques developed for analytical cytology have become invaluable in expanding the development of cancer screening programs and biomarker discovery for personalized medicine. Detecting cellular, molecular, and functional changes of diseased tissue as defined by quantitative analytical methodologies has enhanced the field of medical diagnostics and prognostics. The focus of this review is to outline applications and recent technical advances in flow cytometry, laser scanning cytometry, image cytometry, and quantitative image analysis, as they pertain to clinical, research, and drug discovery applications.

Apoptosis and beyond: cytometry in studies of programmed cell death

A cell undergoing apoptosis demonstrates multitude of characteristic morphological and biochemical features, which vary depending on the inducer of apoptosis, cell type and the "time window" at which the process of apoptosis is observed. Because the gross majority of apoptotic hallmarks can be revealed by flow and image cytometry, the cytometric methods become a technology of choice in diverse studies of cellular demise. Variety of cytometric methods designed to identify apoptotic cells, detect particular events of apoptosis and probe mechanisms associated with this mode of cell death have been developed during the past two decades. In the present review, we outline commonly used methods that are based on the assessment of mitochondrial transmembrane potential, activation of caspases, DNA fragmentation, and plasma membrane alterations. We also present novel developments in the field such as the use of cyanine SYTO and TO-PRO family of probes. Strategies of selecting the optimal multiparameter approaches, as well as potential difficulties in the experimental procedures, are thoroughly summarized.

Effect of mitoxantrone on proliferation dynamics and cell-cycle progression

MTX (mitoxantrone), an anti-tumour antibiotic, is known to cause cell death by intercalating the DNA bases. But how it interferes with the cellular proliferation is not well known. Hence, in the present study, we have tried to evaluate the interaction of this drug using proliferation dynamics to gain a better understanding of MTX's antineoplastic action. Inhibition of proliferation by these drugs was detected by evaluating its effect on cell proliferation and growth curve of the cells. MTX was also found to affect the cell viability and, thereby, cell physiology. Typical apoptotic morphologies such as condensation of nuclei and membrane permeabilization were observed through CLSM (confocal laser scanning microscopy) and fluorescence spectroscopy, which implicates commitment to cell death. Cell-cycle distribution was measured by flow cytometric measurements. The analysis demonstrated significant cell-cycle arrest on MTX treatment. Inhibition of lacZ gene expression was also observed on drug treatment, which implicates its interaction with gene expression.

Assessment of cellular uptake and cytotoxicity of carbon nanotubes using flow cytometry

The field of carbon nanotube (CNT) functionalization is increasingly growing for the purpose of enhancing the biocompatibility of CNT for medical and biological applications. Properties of CNT such as the type of functionalization, charge density, and the dispersibility profile are expected to modulate CNT cellular uptake and toxicity profile in vitro. The assay described here allows for rapid screening of CNT cellular uptake in vitro and assessing the acute cytotoxicity simultaneously. CNT cellular uptake is measured qualitatively by light scattering analysis without differentiating between cell binding and internalisation of the CNT by the cells. In addition, flow cytometry is used to combine light scattering analysis with flow cytometry-based Annexin V/propidium iodide assay to measure the cytotoxicity. This assay is rapid, reliable, and allows for comparative analysis between various types of CNT studied.

Evaluation of cell surface expression of phosphatidylserine in ovarian carcinoma effusions using the annexin-V/7-AAD assay: clinical relevance and comparison with other apoptosis parameters

Phosphatidylserine cell surface exposure during apoptosis can be detected by its binding to the protein annexin-V. We investigated annexin-V expression in 76 ovarian carcinoma effusions using flow cytometry. Results were analyzed for association with clinicopathologic parameters and survival. Annexin-V expression was additionally compared with the previously studied apoptotic markers cleaved caspase-3, cleaved caspase-8, and deoxyuridine triphosphate (dUTP) incorporation into DNA fragments. Annexin-V was expressed in all specimens and was more frequently detected compared with cleaved caspases and dUTP incorporation (P < .001). Annexin-V expression was higher in grade 3 vs grades 1 and 2 tumors (P = .014). A higher percentage of annexin-V-expressing cells in postchemotherapy specimens was associated with poor overall (P = .005) and progression-free (P = .013) survival. We present the first evidence of annexin-V expression in ovarian carcinoma effusions. The higher annexin-V expression compared with other apoptosis parameters and its association with high-grade disease and poor survival in postchemotherapy patients suggest a role in cell survival rather than apoptosis in effusions.

The anti-apoptotic role for p53 following exposure to ultraviolet light does not involve DDB2

The p53 tumour suppressor is a transcription factor that can either activate or repress the expression of specific genes in response to cellular stresses such as exposure to ultraviolet light. The p53 protein can exert both pro- and anti-apoptotic effects depending on cellular context. In primary human fibroblasts, p53 protects cells from UV-induced apoptosis at moderate doses but this is greatly affected by the nucleotide excision repair (NER) capacity of the cells. The damage-specific DNA binding protein 2 (DDB2) is involved in NER and is associated with xeroderma pigmentosum subgroup E (XP-E). Importantly, DDB2 is also positively regulated by the p53 protein. To study the potential interplay between DDB2 and p53 in determining the apoptotic response of primary fibroblasts exposed to UV light, the expression of these proteins was manipulated in primary normal and XP-E fibroblast strains using human papillomavirus E6 protein (HPV-E6), RNA interference and recombinant adenoviruses expressing either p53 or DDB2. Normal and XP-E fibroblast strains were equally sensitive to UV-induced apoptosis over a broad range of doses and disruption of p53 in these strains using HPV-E6 or RNA interference led to a similar increase in apoptosis following exposure to UV light. In contrast, forced expression of p53 or DDB2 did not affect UV-induced apoptosis greatly in these normal or XP-E fibroblast strains. Collectively, these results indicate that p53 is primarily protective against UV-induced apoptosis in primary human fibroblasts and this activity of p53 does not require DDB2.

Methods for simultaneous measurement of apoptosis and cell surface phenotype of epithelial cells in effusions by flow cytometry

We describe here a protocol for the detection of epithelial cells in effusions combined with quantification of apoptosis by flow cytometry (FCM). The procedure described consists of the following stages: culturing and induction of apoptosis by staurosporine in control ovarian carcinoma cell lines (SKOV-3 and OVCAR-8); preparation of effusion specimens and cell lines for staining; staining of cancer cells in effusions and cell lines for cell surface markers (Ber-EP4, EpCAM and CD45) and intracellular/nuclear markers of apoptosis (cleaved caspase-3 and caspase-8, and incorporated deoxyuridine triphosphates); and FCM analysis of stained cell lines and effusions. This protocol identifies a specific cell population in cytologically heterogeneous clinical specimens and applies two methods to measure different aspects of apoptosis in the cell population of interest. The cleaved caspase and deoxyuridine triphosphate incorporation FCM assays are run in parallel and require (including sample preparation, staining, instrument adjustment and data acquisition) 8 h. The culturing of cell lines requires 2-3 days and induction of apoptosis requires 16 h.

Morphological, biochemical, and flow cytometric assays of apoptosis

As programmed cell death (PCD), or apoptosis, has emerged as an important regulator of development and homeostasis in multicellular organisms, methods to quantify apoptosis and to distinguish it from necrosis have been developed. Necrosis refers to the morphology usually associated with accidental cell death, while apoptosis is seen when cell death is programmed or physiologically regulated. This unit presents a set of assays for these purposes, many of which are technically very simple. Featured in this unit is the TUNEL method of detecting cells that exhibit DNA fragmentation, which can also be performed on tissue sections to locate apoptotic cells in situ.

Small-conductance Cl- channels contribute to volume regulation and phagocytosis in microglia

The shape and volume of microglia (brain immune cells) change when they activate during brain inflammation and become migratory and phagocytic. Swollen rat microglia express a large Cl(-) current (I(Clswell)), whose biophysical properties and functional roles are poorly understood and whose molecular identity is unknown. We constructed a fingerprint of useful biophysical properties for comparison with I(Clswell) in other cell types and with cloned Cl(-) channels. The microglial I(Clswell) was rapidly activated by cell swelling but not by voltage, and showed no time-dependence during voltage-clamp steps. Like I(Clswell) in many cell types, the halide selectivity sequence was I(-) > Br(-) > Cl(-) > F(-). However, it differed in lacking inactivation, even at +100 mV with high extracellular Mg(2+), and in having a much lower single-channel conductance: 1-3 pS. Based on these fundamental differences, the microglia channel is apparently a different gene product than the more common intermediate-conductance I(Clswell). Microglia express several candidate genes, with relative mRNA expression levels of: CLIC1 > ClC3 > I(Cln) > or = ClC2 > Best2 > Best1 > or = Best3 > Best4. Using a pharmacological toolbox, we show that all drugs that reduced the microglia current (NPPB, IAA-94, flufenamic acid and DIOA) increased the resting cell volume in isotonic solution and inhibited the regulatory volume decrease that followed cell swelling in hypotonic solution. Both channel blockers tested (NPPB and flufenamic acid) dose-dependently inhibited microglia phagocytosis of E. coli bacteria. Because I(Clswell) is involved in microglia functions that involve shape and volume changes, it is potentially important for controlling their ability to migrate to damage sites and phagocytose dead cells and debris.

Regulatory T Cells Are Resistant to Apoptosis via TCR but Not P2X7

Regulatory T cells (Tregs) are relatively autoreactive yet, paradoxically, have been found to display normal sensitivity to thymic deletion. The relationship between self-avidity, apoptosis, and the selection of Tregs therefore remains unclear. We show that thymic Tregs develop efficiently, even at low self-avidity, and are moderately resistant to apoptosis in comparison to conventional thymocytes. Consistent with this, although conventional self-reactive T cell populations undergo chronic peripheral deletion, self-reactive Tregs are largely spared removal. Similarly, the distribution of Tregs among peripheral CD4(+) cells exhibits a linear inverse relationship with CD45RB expression, indicating relative apoptosis resistance of Tregs in chronic responses to environmental Ags. We also show that appropriate controls for CD45RB levels are important for comparisons of Treg and conventional T cell activity. When thus controlled, and contrary to previous reports, Tregs exhibit normal sensitivity to cell death through TCR-independent stimuli, such as the purinergic receptor, P2X(7). Finally, although absence of CD45 in gene-targeted mice results in profound T cell hyporesponsiveness, there is little or no effect on thymic Treg frequency. In summary, the data support a model in which signal strength plays little part in Treg lineage specification, though moderate resistance of self-reactive Tregs to apoptosis may result in progressive biasing of peripheral Treg TCRs toward autoreactivity in comparison to those of conventional T cells.

Phosphatidylserine exposure in B lymphocytes: a role for lipid packing

Plasma membrane lipids are usually distributed asymmetrically, with phosphatidylserine (PS) confined to the inner leaflet. PS exposure at the outer leaflet occurs early in apoptosis, but it is also constitutive on some nonapoptotic cell populations where it plays a role in cell signaling. How PS is transported (“flopped”) to the cell surface is unknown. Contrary to previous reports that normal murine B lymphocytes lack lipid asymmetry, we show that PS is normally restricted to the inner leaflet of these cells. PS exposure on normal B cells did, however, occur spontaneously ex vivo. Consistent with the hypothesis that loss of PS asymmetry is regulated by CD45, PS is constitutively exposed on viable, CD45-deficient B cells. We show that calcium-stimulated PS exposure in B cells is strain variable, ABCA1 independent, and both preceded by and dependent on a decrease in lipid packing. This decrease in lipid packing is concomitant with cell shrinkage and consequent membrane distortion, both of which are potently inhibited by blockers of volume-regulatory K+ and Cl- ion channels. Thus, changes in plasma membrane organization precede PS translocation. The data suggest a model in which PS redistribution may occur by a translocase-independent mechanism at energetically favorable sites of membrane perturbation where lipid packing is decreased.

Malondialdehyde-acetaldehyde haptenated protein binds macrophage scavenger receptor(s) and induces lysosomal damage

There is evidence that the chemical modification of proteins (haptens) with malondialdehyde-acetaldehyde (MAA) and the immune response to these haptenated proteins is associated with the initiation and/or progression of alcohol liver disease. Experimentally, proteins modified with MAA induce antibody and T cell responses, which are mediated by scavenger receptor(s). Moreover, macrophages have been shown to play an important role in processing and presenting MAA-haptenated proteins in vitro. In vitro, MAA-modified proteins have been shown to induce both apoptosis and necrosis in a dose- and cell-type-dependent manner. Natural ligands modified by oxidative stress, such as oxidized LDL, similarly initiate not only antibody responses, but also cause cell death by disrupting lysosomes after binding to scavenger receptors and internalization. We therefore investigated the binding, internalization, and lysosomal integrity in a macrophage cell line to a MAA-haptenated protein. We demonstrate for the first time that MAA-haptenated proteins are preferentially bound by scavenger receptors on macrophages, which internalize the ligands and shuttle them to lysosomes. Moreover, MAA-haptenated proteins are demonstrated to be associated with a rapid dose-dependent disruption in lysosomal integrity, resulting in leakage and caspase activation. Similarly, as hen egg lysozyme (HEL)-MAA concentrations increased (>31.3 microg/ml), increased levels of apoptosis and a G1/S cell cycle checkpoint inhibition were identified. This study identifies mechanisms by which MAA-haptenated proteins are taken up by a representative antigen-presenting cell and may delineate steps by which MAA-haptenated proteins induce cell death and induce their immunogenicity to the carrier protein.

The alteration of protein profile of Walker 256 carinosarcoma cells during the apoptotic process induced by ultrasound

The objective of this study was to investigate the alteration of the protein profile in cells after sonication and to identify the key proteins involved in the process of cell apoptosis. Walker 256 carinosarcoma cells were exposed to focused ultrasound (US) at the intensity of 2.0, 7.0, 10.2, 14.2 and 17.0 W/cm2 (I(spta)) for 10 min in vitro and the morphologic and functional changes of the cells were detected by hematoxylin & eosin staining and flow cytometry, with double staining of fluorescein isothiocyanate (FITC)-labeled Annexin V/propidium iodide (PI). The protein compositions in the cells after sonication were detected by 2-D SDS polyacrylamide gel electrophoresis. Our results showed that apoptosis of Walker 256 carinosarcoma cells could be induced by US. The percentage of early apoptosis and secondary necrosis increased with increasing intensity of US irradiation. Comparing with the protein patterns of cells before sonication, it was found that around 420 new protein spots were present in the gel after sonication. Among them, Hsp60 and Bcl-2 like protein 13 were found to be involved in the process of cell apoptosis and US-induced apoptosis of the cells was probably performed through the pathway of promoting the activation of caspase-3.

Cell volume regulation and swelling-activated chloride channels

Maintenance of a constant volume is essential for normal cell function. Following cell swelling, as a consequence of reduction of extracellular osmolarity or increase of intracellular content of osmolytes, animal cells are able to restore their original volume by activation of potassium and chloride conductances. The loss of these ions, followed passively by water, is responsible for the homeostatic response called regulatory volume decrease (RVD). Activation of a chloride conductance upon cell swelling is a key step in RVD. Several proteins have been proposed as candidates for this chloride conductance. The status of the field is reviewed, with particular emphasis on ClC-3, a member of the ClC family which has been recently proposed as the chloride channel involved in cell volume regulation.

Flow cytometry of apoptosis

Application of flow cytometry to the study of cell death has three goals: identification and quantification of dead and dying cells; discrimination between apoptotic and necrotic modes of cell death; and elucidation of mechanisms involved in cell death. This massively detailed unit by a pioneer in the field brings together the most common flow cytometric methods for the study of apoptosis, covering a wide variety of apoptotic indices, from loss of membrane potential, caspase activation, and phosphatidyl exposure to DNA fragmentation and tissue transglutaminase activation. The authors also present their recently developed protocol, analogous to the FLICA approach for caspases, for the detection of serine proteases ('serpases'). The protocols are accompanied by extensive commentary discussion of applicability, strategic planning, problems, and pitfalls, plus a comprehensive list of references.

Apoptosis in glioma cells: review and analysis of techniques used for study with focus on the laser scanning cytometer

Traditional approaches to the treatment of brain tumors are based on the hypothesis that tumors arise and grow because of the disordered regulation of cell proliferation. More recently, it has become apparent that tumor growth depends not only on the rate of cell proliferation but also on the rate of apoptosis (programmed cell death). Genomic alterations that occur in malignancy may limit the cell's ability to undergo apoptosis. Many new treatment strategies for gliomas stem from the use of techniques aimed at manipulating apoptosis. Being able to assess the efficacy of experimental treatments with refined techniques and being able to use instruments that can provide accurate measurements of the apoptotic markers will open the door for discovering novel strategies with the potential to induce effective and selective cytotoxicity. We discuss here in detail the major traditional techniques of assessing apoptosis. We provide an overview of cytometric techniques, including flow cytometry (FC), and will compare it with the laser scanning cytometer (LSC). This is a powerful new tool with potential for obtaining a fast and objective analysis of apoptosis through multiple mechanisms, as well as for assessing proliferation and DNA ploidy in solid malignant tumors.

IKCa1 activity is required for cell shrinkage, phosphatidylserine translocation and death in T lymphocyte apoptosis

Apoptotic cell volume decrease (AVD) and exposure of phosphatidylserine (PtdSer) at the cell surface are early events in apoptosis. However, the ion channels responsible for AVD, and their relationship to PtdSer translocation and cell death are poorly understood. Real-time analysis of calcium-induced apoptosis in lymphocytes and thymocytes showed that AVD occurs rapidly, and precedes PtdSer translocation. Blockers of the K(+) channel IKCa1 completely inhibited AVD. Blockade of IKCa1, and hence AVD, also completely prevented PtdSer translocation and cell death. Thus, IKCa1-mediated AVD is the earliest-defined essential step in calcium-induced apoptosis, required for both PtdSer translocation and cell death.

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.

Malondialdehyde-acetaldehyde-haptenated protein induces cell death by induction of necrosis and apoptosis in immune cells

Recent studies have demonstrated that circulating antibodies against malondialdehyde-acetaldehyde (MAA)-haptenated proteins are significantly increased in patients with alcohol-induced cirrhosis and hepatitis and correlate with the severity of liver damage. Additionally, when proteins are haptenated with MAA, they become highly immunogenic in vivo in the absence of adjuvants. However, the mechanism(s) of this immunogenicity are currently unknown. Initial in vitro studies on the effects of MAA-modified proteins on cells demonstrated an increase in cell death at concentrations that were cell type specific and time-dependent. Since immunogenicity due to cell death has been described, we investigated the mechanism(s) by which cell death was occurring. Assessment of cell death in splenocytes after 1 h found significant levels of apoptosis as compared to controls. After 5 h, a significant and dose-dependent necrosis occurred in which cells were exposed to >62.5 microg/ml (43.1 mM) MAA-haptenated protein. After 24 h, exposure to >31.3 microg/ml (21.6 mM) MAA-haptenated protein resulted in significant levels of necrosis, although DNA laddering studies found apoptosis was occurring as well. Morphological changes in the cells were observed by light microscopy that correlated with a "low" forward scatter population by flow cytometry. Since necrosis has been implicated in enhancing both primary and secondary immune responses, and necrosis was predominantly occurring in response to MAA-haptenated proteins, a possible mechanism by which the immunogenicity of MAA modification of proteins in vivo may occur is suggested. Specifically, MAA modification of self proteins may result in the death of various cell types, most likely those in the liver. These necrotic materials may induce anti-MAA antibodies and other auto antibodies, whose levels may then correlate with the severity of ALD.

Analysis of laser scattering pattern as an early measure of apoptosis

Light scattering pattern analysis (LSPA) was applied in the current study for accurate and sensitive detection of subtle changes in cell size, which occur in mouse thymocytes undergoing apoptosis. The decrease in cell diameter as measured by LSPA was found to be an early signal of apoptosis preceding the externalization of phosphatidylserine on the outer membrane. When apoptosis was induced by dexamethasone, the change in cell size was dose and time dependent, and could be blocked by pretreatment of the thymocytes with N-acetylcysteine (NAC). This implies that the scattering pattern, when combined with fluorescent markers such as annexine-V, may be a powerful tool for early detection of apoptosis. Another advantage gained by the use of this method is the ability to repeatedly trace the same cells and to monitor the kinetics of their size changes.

Immunophenotyping large B-cell lymphomas. Flow cytometric pitfalls and pathologic correlation

Large cell lymphomas often challenge the diagnostic flow cytometrist. The purposes of this study were to improve our protocols for diagnosing large cell lymphomas and to correlate flow cytometric (FC) data with demographic and histologic features. We identified 63 cases of large B-cell lymphoma between January 1, 1995, and July 30, 1999, and reviewed the diagnostic slides and FC light scatter and staining patterns. The 51 lymphomas with adequate material for systemic review fell into 2 light scatter patterns: "clear cut," with large abnormal cells (high forward scatter relative to normal lymphocytes), 17 cases (33%); and "complex," 34 cases (67%). Clear-cut cases were more mitotically active (average of 42 vs 25 per 10 high-power fields), with higher cellularity. Apoptosis, geographic necrosis, and sclerosis were present histologically in many cases, regardless of FC findings. We conclude that morphologic features of large cell lymphomas do not predict which cases will be difficult to diagnose by FC. Gating strategies can be critical to improve the diagnostic yield.

Flow cytometry in analysis of cell cycle and apoptosis

The capacity for multiparametric measurement of large cell populations rapidly and accurately offered by cytometry has made this methodology indispensable in studies of cell proliferation and cell death. The reviewed cell cycle applications include (1) the univariate analysis of cellular DNA content for identification of G(0/1) versus S versus G(2)/M cells; (2) discrimination between noncycling (G(0); quiescent) and proliferating cells, based on the presence of proliferation-associated proteins; (3) identification of mitotic cells by histone H3 phosphorylation; (4) bivariate analysis of expression of cyclins D, E, A, or B1 versus DNA content; and (5) detection of DNA replicating cells and analysis of cell kinetics from the bivariate distributions of 5-bromo-2'-deoxyuridine (BrdU) incorporation versus DNA content. For the identification of apoptotic cells and discrimination between apoptosis and necrosis, flow cytometry techniques are applied to evaluate for changes in cell morphology, the presence of phosphatidylserine on cell surface, collapse of mitochondrial transmembrane potential, DNA fragmentation, and evidence of caspase activation. Semin Hematol 38:179-193.

Analysis of apoptotic cells by flow and laser scanning cytometry

A large number of flow cytometric methods to identify apoptotic cells and analyze morphological, biochemical, and molecular changes that occur during apoptosis have been developed. These methods are also applicable to the laser scanning cytometer (LSC), a microscope-based cytofluorometer that combines advantages of flow and image cytometry and that, by offering a possibility of assessment of cell morphology, is of particular utility in analysis of apoptosis. Apoptosis-related changes in cell morphology associated with cell shrinkage and condensation of cytoplasm and chromatin are detected by measurements of the intensity of light scatter of the laser beam in the forward and 90 degrees angle directions. Changes in plasma membrane composition and function are analyzed by its altered permeability to certain dyes and by the appearance of phosphatidylserine, which reacts with annexin V-fluorochrome conjugates on the external surface of the membrane. Decrease in mitochondrial transmembrane potential is measured with several fluorochromes of the rhodamine or carbocyanine family. DNA fragmentation is detected either by measurement of cellular DNA content after elution of the degraded DNA from the cell before or during the staining procedure or by in situ labeling DNA strand breaks. Apoptotic cells are then recognized either on the basis of their reduced DNA-associated fluorescence as the cells with fractional DNA content ("sub-G1 cells"), or as the cells with an extensive number of DNA breaks, respectively. Advantages and limitations of the preceding methods are discussed and their adaptation to LSC is presented.

Flow cytometry of apoptotic cell death

The term apoptosis or programmed cell death defines a genetically encoded cell death program, which is morphologically and biochemically distinct from necrosis or accidental cell death. The characteristic morphological signs of apoptosis (cellular shrinkage, membrane blebbing, nuclear condensation and fragmentation) are the final results of a complex biochemical cascade of events which is an integral part of physiological homeostasis. Techniques designed to identify, quantitate and characterize apoptosis are numerous, but flow cytometry (FCM) remains the methodology of choice to study the apoptotic cascade in relation to cell type, trigger and time. This review outlines the main stages of the apoptotic cascade together with current FCM methods. All FCM apoptosis assays described have a solid experimental basis and have been used successfully in basic research on molecular and biochemical mechanisms of apoptosis. In various clinical settings the ability to follow the apoptotic process in patient samples may offer the rationale for optimal treatment schedules.

Developmental shift in the relative percentages of lung fibroblast subsets: role of apoptosis postseptation

We have used the lipophilic, fluorescent dye Nile red and flow cytometry to identify and isolate two rat lung fibroblast subsets, lipid-containing interstitial cells (LICs) and non-LICs (NLICs) and to quantitate developmental changes in the relative percentages of these subsets. A significant decrease was observed in the percentage of LICs (from 79.0 +/- 3.8% on postnatal day 4 to 28.6 +/- 4.2% on day 30; P < 0.0001). To determine whether one or both subsets undergo apoptosis postseptation, fibroblasts from 16- to 18-day rats were treated with BODIPY-conjugated dUTP to label DNA strand breaks, which were then quantitated by flow cytometry. Apoptotic cells were judged to be predominantly LICs based on flow cytometric estimates of cell size and granularity and on light-microscopic colocalization of intracellular lipid and Hoechst-positive apoptotic bodies. Cell proliferation was compared in LICs and NLICs with both an in vitro [(3)H]thymidine incorporation assay and cell cycle analysis of propidium iodide-stained cells. Results of both assays indicated that on days 4-5, LICs proliferated more rapidly than NLICs. Tropoelastin and fibronectin mRNA expression, evaluated by RT-PCR, indicated that although tropoelastin mRNA levels did not differ, fibronectin mRNA levels were approximately ninefold greater in LICs. These results demonstrate the feasibility of a flow cytometric assay for the analysis of size, granularity, and intracellular lipid content of neonatal rat lung fibroblast subsets. Subsets differed substantially with respect to proliferative capacity, fibronectin mRNA expression, and incidence of apoptosis postseptation. Together with the observed changes in relative percentages of fibroblast subsets with age, these data suggest that the ratio of LICs to NLICs could be a critical determinant of fibroblast function during lung development.

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.