Comparative Studies of Steroidogenesis Inhibitors (Econazole, Ketoconazole) on Human Breast Cancer MCF-7 Cell Proliferation by Growth Experiments, Thymidine Incorporation and Flow Cytometric DNA Analysis

The effects of aminoglutethimide, econazole and ketoconazole on human breast cancer cells in culture were compared with those of tamoxifen using four methods (growth experiments, thymidine incorporation, monoparameter and bivariate DNA content flow cytometry analysis). Aminoglutethimide (1 nM-10 microM) had no effect on cell proliferation after 8 days of treatment and did not decrease thymidine tritiated incorporation during logarithmic phase. Even at 20 microM, similar results were obtained with flow cytometry. Econazole and ketoconazole (1 nM-1 microM) decreased MCF-7 cell proliferation in a time- and dose-dependent fashion. They also decreased tritiated thymidine incorporation. By using flow cytometry and a monoclonal antibody against bromodeoxyuridine, we showed an accumulation of MCF-7 cells treated by imidazoles derivatives in G0-G1 phase of the cell cycle.

Activation of Bad trafficking is involved in the BCR-mediated apoptosis of immature B cells

The activity of Bad, a pro-apoptotic protein, is regulated by reversible phosphorylation. Moreover, sequestration of Bad within subcellular compartments may be a new mechanism of apoptosis regulation. In this study, we report that Bad interacts with 14-3-3 protein in WEHI-231 immature B cells. This association is disrupted following BCR stimulation in correlation with Bad translocation to mitochondria and apoptosis. Confocal microscopy was further used to examine the co-localization of Bad with lipid rafts in WEHI-231 and murineex vivoB cells. Bad was found colocalized to lipid rafts in freshly isolated mature B lymphocytes, in contrast to immature cells. Finally, co-immunoprecipitation experiments performed on WEHI-231 B cells revealed that PP1alpha interacts with Bcl-2 and Bad, and dissociation of the complex was found correlated with appearance of apoptosis. Bcl-2 seemed to be required to assemble the complex which may regulate Bad phosphorylation status and consequently cell survival. Collectively, present data outline the role of Bad trafficking in the BCR-mediated apoptosis and suggest that differences in intracellular Bad trafficking may be involved in the differential outcome of BCR signaling.

Changes in Bad phosphorylation are correlated with BCR-induced apoptosis of WEHI-231 immature B cells

Signaling through the B cell antigen receptor (BCR) is a key determinant in the regulation of B cell physiology. Depending on additional factors, such as microenvironment and developmental stage, ligation of the BCR can trigger B lymphocyte activation, proliferation, or apoptosis. The regulatory mechanisms determining B cell apoptosis and survival are not completely known. Using the murine B lymphoma cell line WEHI-231 as a model system, we investigated the role of Bad phosphorylation, a pro-apoptotic member of the Bcl-2 family, in anti-IgM mediated apoptosis. For apoptotic analysis we focused in particular on the mitochondrial potential (deltapsi(m)) collapse which has been reported as a rate-limiting step in the BCR-induced cell death of immature B lymphocytes. Bad phosphorylation at serine 112, 136 and 155 was found in WEHI-231 cell control cultures and its hypophosphorylation on the three sites correlated with the appearance of apoptosis when cross-linking surface IgM. Furthermore, treatment of cells with specific PK inhibitors known to be involved in serine phosphorylation of Bad (LY294002 for PI3K and H-89 for PKA) mimiced or enhanced BCR-induced cell death. These results strongly suggest that regulation of Bad phosphorylation plays an active role in mediating anti-IgM-induced apoptosis of immature B cells.

Alterations in the expression of cytochrome c oxidase subunits in doxorubicin-resistant leukemia K562 cells

Doxorubicin (DOX), a widely used antitumoral drug, induces numerous modifications in sensitive cells, interacting with nuclear and mitochondrial DNA. In previous studies achieved in two K562 DOX-resistant sublines (K562/0.2R and K562/0.5R), we have shown stable mitochondrial damage comparatively with sensitive parental cells, such as decrease of cytochrome c oxidase activity (COX; EC 1.9.3.1) and cytochrome aa3 content. In order to explain these data, we have studied several COX genes and their expression, in relationship with altered COX activity and multidrug resistance (MDR) phenotype. We have observed a lower expression of the catalytic subunits COX I and II in MDR sublines, which was neither related to mutations in the corresponding mitochondrial genes, nor to a reduced transcription rate. In contrast, we have noticed an increase in both MDR K562 variants, in the mRNA expression of the catalytic subunit COX III, related to an increase in the half-life of these transcripts. Moreover, the doxorubicin resistance phenotype in K562 cells was accompanied by modifications of the expression and steady-state mRNA levels of several nuclear-encoded regulatory COX subunits. Thus, doxorubicin-resistant K562 cells represent an interesting model to study stable modifications concomitant to MDR phenotype. Our results seem to indicate compensatory mechanisms which highlight the complexity of regulatory systems of COX enzyme, involving coordinate regulation of both nuclear and mitochondrial subunit expression.

Characterization of the murine gene for subunit VIIaL of cytochrome c oxidase

Mammalian cytochrome c oxidase consists of thirteen subunits, ten encoded by the nuclear genome and three by the mitochondrial DNA. In several species, two isoforms have been isolated for nuclear-encoded subunits VIa, VIIa and VIII: an ubiquitous L (liver) form and a heart- and skeletal-muscle specific H form. The gene for murine cytochrome c oxidase subunit VIIa-L (Cox7aL) and its promoter region were isolated, sequenced and analysed. The coding region is split in four exons spanning 4.1 kbp and the promoter carries potential binding sites for Sp1, NRF1 and NRF2 transcription factors. Transcriptional activity of the promoter in reporter assays suggested an ubiquitous expression in mouse tissues.

Sequential gene expression of P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP) and lung resistance protein: functional activity of P-gp and MRP present in the doxorubicin-resistant human K562 cell lines

Previous studies have reported that P-glycoprotein (P-gp), a transmembrane efflux pump involved in multidrug resistance (MDR), was overexpressed in the doxorubicin (Dox)-resistant human erythroleukemia cell line K562. Nevertheless, several results suggested that P-gp was not the only mechanism involved in these resistant cells. Sequential co-expression of other MDR-associated proteins was sometimes reported, as MDR-associated protein (MRP) and lung resistance protein (LRP), in different MDR cell lines. Thus, mRNA expression and stability of P-gp, MRP and LRP were analyzed, while their corresponding protein levels were quantified in correlation with functional assay, in the K562 cell line and two Dox-resistant variants (K562/R). Their P-gp content was in accordance with their degree of resistance, but not as much in the level of mRNA expression, suggesting a post-transcriptional regulation. On the other hand, MRP could play a minor role in MDR because of an unchanged expression in K562/R sublines. A surprising progressive disappearance of LRP in both resistant cells suggested that the original mechanism of drug redistribution may be operative, involving a negative role for LRP.

Optimization of cell permeabilization for multiparametric flow cytometric analysis with lectin staining

BACKGROUND

This study was undertaken in mice to develop a reproducible procedure of cell permeabilization, allowing intracellular protein staining by immunofluorescence (i.e., Bcl-2) without losing surface labeling especially for lectins (i.e., B220 and peanut agglutinin [PNA]). This article reports results obtained with different permeabilization protocols.

METHODS

Lymphoid cells were extracted and prepared from Peyer's patches and spleen. After surface labeling using anti-B220-Cy-chrome and PNA-biotin/streptavidin-phycoerythrin, we comparatively tested three permeabilization protocols: saponin 0.3%, methanol 70%, and the commercial kit Dako Intrastain. Final Bcl-2 staining was performed and cells were analyzed by flow cytometry.

RESULTS

With 0.3% saponin as the permeabilization reagent, a significant loss of lectin labeling was observed when comparing mono PNA and triple (i.e. , B220-PNA-Bcl-2) staining (74.8% and 22.5% positive cells, respectively). Quality of PNA staining was conserved with Intrastain when comparing multiparametric versus monoparametric stainings (82. 4% of positive cells versus 78.3%, respectively). Intrastain preserved scatter characteristics (69.9% of total cells in the lymphocyte gate with Intrastain versus 13.7% with saponin 0.3% and 20.9% with methanol 70%). This protocol has been used for a preliminary multiparametric analysis in order to quantify Bcl-2 expression in PNA/B220-positive cells.

CONCLUSION

This protocol may be useful to assess simultaneously lectin cell surface labeling and intracellular target staining.

Age-associated changes in mitochondrial parameters on peripheral human lymphocytes

Among theories of aging, mitochondria are believed to be involved in senescence. Alterations of respiratory chain function and accumulation of various mitochondrial DNA mutations have been reported in mammalian postmitotic tissues. Because mitochondria have a central role in apoptosis and in adenosine triphosphate production, alteration of mitochondria function could contribute to immune senescence. We searched for alterations of mitochondrial parameters in peripheral lymphocytes with aging. Comparisons of respiratory chain activities of complex II+III, III, and IV were carried out in two populations of healthy volunteers with average ages of 35.3 +/- 6.7 years and 80.8 +/- 8.7 years. No difference was observed in complex IV activity between each group, whereas a significant decrease of complex II+III and a nonsignificant decrease of complex III activity were observed with aging. Alterations in mitochondrial functions can result from mutations in mitochondrial DNA (mtDNA), the most common being the 4977-bp deletion (mtDNA(-4977)). In either group we observed many deletions of mtDNA on peripheral blood lymphocytes by large-fragment polymerase chain reaction. This result suggests that alterations of respiratory chain activities observed with aging in lymphocytes could be the result of nuclear DNA dysfunction, with consequences on immune function (reduced responsiveness to antigen). Its possible implication on the recent observation of increased apoptosis of CD45RA+ RO- T cells with aging is discussed.

Modifications of oxido-reductase activities in adriamycin-resistant leukaemia K562 cells

Adriamycin (ADR), a well-known antitumoral drug, interacts with DNA (nuclear and mitochondrial) and cardiolipin. Moreover, ADR induces numerous mitochondrial modifications in sensitive cells. However, no results have yet been obtained as to the repercussions of drug effects on oxido-reductase activities in ADR-resistant cells. To analyze mitochondrial damage induced by ADR treatment, we investigated lactate content, oxygen consumption, respiratory chain activities, and cytochrome content in ADR-sensitive K562 cells and two ADR-resistant variants (K562/R0.2 and K562/R0.5 cells). Biochemical investigations in ADR-resistant cells showed several mitochondrial modifications (in comparison to the parental cell line) according to the variant line and the physiologic state. More particularly, in K562/R0.5 cells cytochrome c (cyt c) oxidase (COX; EC 1.9.3.1) activity and cytochrome aa3 content dramatically decreased since cells enter into the stationary phase. Regardless of the number of multidrug-resistant cell subcultures in ADR-free medium, the cytochrome c oxidase activity in the stationary phase remained unchanged, indicating an irreversible effect of the drug. These alterations could correspond to several modifications of the nuclear and/or mitochondrial genome(s) following acquisition of the ADR resistance phenotype by K562 cells.

Expression of Bcl-2 and Bax in cultured normal human keratinocytes and melanocytes: relationship to differentiation and melanogenesis

Keratinocyte differentiation and melanogenesis are two major cellular processes by which the epidermal compartment of the skin acquires its protective properties. Bcl-2; an oncoprotein involved in the regulation of apoptosis, has been shown to be expressed by keratinocytes and melanocytes. To determine whether Bcl-2 and Bax, a protein which heterodimerizes with Bcl-2, may control these epidermal functions, we investigated the expression of these two oncogenes in cultivated human keratinocytes and melanocytes from the same donors, respectively induced to differentiate and to produce melanin. As determined by cytometry, we observed that these two cell types constitutively express the two proto-oncogenes. Quantification of Bcl-2 antigen sites per cell showed that Bcl-2 expression is higher in keratinocytes than in melanocytes. An increase in transglutaminase activity, a marker of keratinocyte terminal differentiation initiating cornified envelope formation, was accompanied by a decrease in Bcl-2 levels without significant modification of Bax expression. In melanocyte cultures, stimulation of the dopa-oxidase pool, a key enzyme in melanin synthesis, paralleled Bcl-2 down-regulation and Bax up-regulation. This led us to conclude that the expression of these two oncogenes and their cellular ratio are closely involved in keratinocyte differentiation and melanogenesis.

Nucleic acid specificity of an acridine derivative permits its use for flow cytometric analysis of the cell cycle

3-amino-6-methoxy-9-(2-hydroxyethylamine) acridine (AMHA) is an acridine derivative, which is easily excited in near ultraviolet and which emits a bright green fluorescence. The dye was preferentially incorporated into nucleic structures as attested by microscopic and cytometric analyses after RNase and DNase treatments. The affinity for RNA seemed low and similar to that observed for propidium iodide. AMHA was quickly accumulated in fixed cells, and in appropriate concentrations (10-50 microM) was a DNA- and RNA-specific dye. AMHA probably exhibits an adenine-thymine specificity, as suggested by its quenching after bromodeoxyuridine uptake: the fluorescence quenching was similar to that obtained for Hoechst 33258. After cell treatment by RNase and in the presence of MgCl2, AMHA staining allowed flow cytometric analysis of the cell-cycle distribution. The resulting histograms were similar to those obtained with propidium iodide (CV near 3.5%, and similar cell cycle distribution). Thus, AMHA is a suitable fluorescent dye for efficient analysis of the cell cycle by flow cytometry.

Methimazole inhibits peripheral lymphocyte proliferation by inducing S-quiescent phase arrest

The influence of methimazole (MTI) on the mitogenic proliferation of human blood lymphocytes was studied in vitro to evaluate the potential immunomodulatory activity of this antithyroid drug. The effects of the drug on the lymphocyte cell cycle were assessed by multiparametric flow cytometry. Although MTI induced an increase in the number of lymphocytes in the synthesis and G2M compartments, it failed to stimulate proliferation as the cells tended to accumulate in the quiescent S compartment. The effect was dose-dependent over a range from 0.1 to 100 mM. These in vitro results indicate that MTI possesses immunosuppressive activity.

Mouse testis cell sorting according to DNA and mitochondrial changes during spermatogenesis

Flow cytometry can measure variations in DNA content and chromatin structure as well as dramatic changes in the mitochondria of germ cells during maturation from spermatogonia to elongated spermatids. Using 10-N nonyl acridine orange (NAO), an inner mitochondrial membrane dye, it is easy to follow mitochondria rearrangements. Mouse testis cells stained with the DNA fluorescent probe propidium iodide (PI) and analyzed by flow cytometry can be discriminated on the basis of their ploidy levels into five main regions corresponding to elongated spermatids, round spermatids, diploid, S-phase, and tetraploid cells. The simultaneous use of PI and NAO demonstrated the presence of cells having low and high mitochondrial content in the haploid, diploid, and tetraploid compartments. Eleven sorting windows were selected from the bivariate analysis (PI/NAO) and the corresponding cells were identified by microscopic observation. Cells were also discriminated by two parameter analysis of DNA content vs. cell diameter. The definition of seven different regions allowed us to determine NAO or rhodamine 123 (Rh 123) uptakes in each compartment. We observed that the ratio (Rh 123/NAO) dramatically changed according to the progression of cell differentiation which occurs during spermatogenesis.

Flow cytometric analysis of human epidermal cell ageing using two fluorescent mitochondrial probes

Cardiolipin, mitochondrial transmembrane potential, cell refringence and cell diameter were examined in epidermal cells obtained from 42 women between 9- to 75-year-old. The study was carried out in situ by flow cytometry on cells having incorporated either Nonyl Acridine Orange or Rhodamine 123, 2 mitochondria-specific dyes. Cardiolipin levels, determined by the binding of the cardiolipin-specific probe Nonyl Acridine Orange, decreased significantly with age, especially in young individuals. This suggests 2 stages in the age-dependent transformation of mitochondria (organelle number and/or size): one during childhood development and to adulthood (9 to 27 years) in which cardiolipin levels decrease dramatically (slope: -3.742; p = 0.0243) and the other corresponding to senescence (35 to 75 years) in which this decrease is less pronounced (slope: -0.618; p = 0.0467). These changes have no effect on mitochondrial potential, measured by Rhodamine 123 incorporation, which remained constant with age. This function, controlling calcium partitioning within the cell, might allow keratinocytes to differentiate and maintain the skin barrier function of the epidermis. Like cardiolipin, intrinsic parameters such as cell size and refringence also significantly decreased in epidermal cells from elderly subjects. The methodology can be used to determine physiological ageing in various cell types and to analyse human ageing and related parameters.

Rhodamine 123: is it an appropriate dye to study P-glycoprotein activity in adriamycin-resistant K562 cells?

The ability of the P-glycoprotein to efflux rhodamine 123 and adriamycin was evaluated using adriamycin-sensitive and -resistant human leukemia K562 cells. We observed that low temperature or verapamil (a P-glycoprotein blocker) inhibited adriamycin efflux in multidrug resistant cells. In the same conditions, resistant K562 cells did not significantly retain rhodamine 123. This dye was located in the cytoplasm of resistant cells and did not display spectral properties characteristic of stacked rhodamine 123 molecules in mitochondria of sensitive K562 cells. Thus, in adriamycin-resistant K562 cells, the rhodamine efflux may be due to P-glycoprotein activity and also to a nonspecific targeting of dye in resistant K562 cells.

Human epidermal cells progressively lose their cardiolipins during ageing without change in mitochondrial transmembrane potential

Mitochondria dysfunction is considered to be a major cause of the modifications that occur during cell ageing. For this reason, cardiolipin, a suitable marker of the chondriome, as well as the mitochondrial transmembrane potential were examined in keratinocytes obtained from 9- to 75-year-old women. The study was carried out by flow cytometry using two fluorescent mitochondria probes: nonyl acridine orange, which binds specifically to cardiolipin, and rhodamine 123, which is incorporated mainly in response to transmembrane potential. Cardiolipin levels in cells from elderly donors (75 years old) would be 57% lower (r = 0.540; P = 0.0002) than those in children (9 years old), while the inner transmembrane potential remained unchanged (r = 0.0394; P = 0.8017). The stability of the membrane potential may be explained by either or both of the following hypotheses: (i) the same pool of organelles able to maintain membrane potential is conserved even when cardiolipin levels decrease (ii) mitochondria membrane potential does indeed decrease with age but is compensated by glycolysis energy production. Finally, it may be stated that the fluorescent probes nonyl acridine orange and rhodamine 123 might be of interest in testing the phenotype of senescent cells and would be useful in screening the role of certain specific genes in cell ageing.

Direct analysis and significance of cardiolipin transverse distribution in mitochondrial inner membranes

The distribution of cardiolipin across the inner mitochondrial membrane was directly determined by using the ability of the fluorescent dye 10-N-nonyl-3,6-bis(dimethylamino)acridine (10-N-nonyl acridine orange) to form dimers when it interacts with the diacidic phospholipid. Two independent methods were employed: (a) a spectrophotometric measurement of 10-N-nonyl acridine orange binding to isolated rat liver mitochondria, mitoplasts and inside-out submitochondrial particles, and (b) a flow-cytometric analysis of specific red fluorescence, emitted when two dye molecules are bound to one membrane cardiolipin; the stoichiometry of 10-N-nonyl acridine orange binding to phosphatidylserine and phosphatidylinositol, 1 mol dye/mol phospholipid, prevented dye dimerisation and subsequent red-fluorescence appearance. 57% total cardiolipin was present in the outer leaflets of inner membranes of isolated organelles, a distribution confirmed by saturation measurements for mitoplasts and inside-out submitochondrial particles. The same asymmetry was directly observed in situ with mitochondrial membranes of quiescent L1210 cells, and with mitochondrial membranes of respiring yeasts. Nevertheless, alterations in ATP synthesis and inhibition of mitochondrial protein synthesis revealed that cardiolipin distribution was apparently tightly correlated with mitochondrial membrane assembly and activity.

Use of a biotinyl-estradiol derivative to demonstrate estradiol-membrane binding sites on adherent human breast cancer MCF-7 cells

A biotinyl-derivative of 17 beta-estradiol has been used to demonstrate a site of recognition and binding of estradiol located on the plasma membrane of human breast cancer MCF-7 cells by using the biotin/avidin-FITC system. The specificity of this binding has been shown by a displacement of the fluorescent label by 17 beta-estradiol. No displacement was observed when testosterone was added. Quantification of this phenomenon has been shown by laser scanning cytometry while preserving the cells adhesiveness to their growth support as well as their membrane integrity. An analysis by confocal laser scanning microscopy suggested that the fluorescence distribution on MCF-7 cells treated with estradiol-biotin was on the cell periphery. The results obtained are in favour of the recognition and binding site of 17 beta-estradiol located on the plasma membrane of MCF-7 cells and they would indicate that the biological activity of estradiol, among others, could be initiated by an interaction with the membrane.

Membrane permeabilization of Listeria monocytogenes and mitochondria by the bacteriocin mesentericin Y105

Mesentericin Y105, a bacteriocin produced by a Leuconostoc mesenteroides strain, dissipates the plasma membrane potential of Listeria monocytogenes and inhibits the transport of leucine and glutamic acid. It also induces an efflux of preaccumulated amino acids from cells. In addition, the bacteriocin uncouples mitochondria by increasing state 4 respiration and decreasing state 3 respiration. The bacteriocin inhibits ATP synthase and adenine nucleotide translocase of the organelle while the affinity of ADP for its carrier is not modified. The results suggest that mesentericin Y105 acts by inducing, directly or indirectly, pore formation in the energy-transducing membranes, especially those of its natural target.

Cell cycle analysis by flow cytometry: principles and applications

Numerous flow cytometric analyses are based on DNA content studies. We have considered firstly monoparametric cell cycle analyses, which only take DNA content into account, but are sometimes of limited interest. Then, we have presented multiparametric analyses, which can be used to improve cycle phase identification by taking simultaneously into account DNA and other cellular components, or by considering some events occurring during cell cycle. Finally, we have discussed monoparametric and multiparametric cell cycle analysis interest in various application fields, particularly in pharmacology, toxicology, tumoral pathology and higher plant system studies.

Flow cytometry's contribution to the measurement of cell functions

Flow cytometry has important advantages over conventional techniques. It is rapid, highly sensitive and allows multi-parametric analysis and cell sorting. Potential exists for the measurement of many cell functions by flow cytometry. The technique can be used to determine cell viability, intracellular calcium and pH, membrane potential, enzyme activities, membrane fluidity and endocytosis. Numerous examples are given on the applications of flow cytometry for cell functions measurements in the fundamental and biomedical fields.

Assessment of fluorochromes for cellular structure and function studies by flow cytometry

Because flow cytometry permits the analysis of individual whole cells, one of the key requirements in selecting a probe is its ability to target the site of interest into cells. In addition, dyes must possess ideal properties (ie extinction coefficient, Stoke's shift) rendering them appropriate for this methodology. Other characteristics, such as fluorescence quenching and energy transfer, inherent to the staining, provide numerous applications in flow cytometry. The available fluorophores used in flow cytometry are classified according to their cellular incorporation and binding. Thus, probes are presented and discussed as follows: 1) dyes of cellular components (DNA, RNA, proteins, lipids); 2) probes of membrane potential; 3) fluorophores that are sensitive to their microenvironment (pH, calcium, etc); and 4) those used for measurement of enzymatic activities into cells.

Recent advances of flow cytometry in fundamental and applied microbiology

This review focuses on the recent applications of flow cytometry (FCM) in microbiological research (1987-mid 1992). It tries to give a scope of the important breakthroughs which occurred in this field during this period. The technical difficulties of microorganism analysis by flow cytometry is briefly appraised. The significance and the limits of the different microbial cell parameters attainable by flow analyses are systematically evaluated: light scatter for cell size and structure, fluorescence measurements for quantification of cellular components, microbial antigen detection and cell physiological activity estimation. Emphasis is given on the new technological advances which appeared in the last two years. The second part of the review is devoted to the analysis of the usefulness of flow cytometric approach in the different fields of microbiology: fundamental studies in microbial physiology, differentiation, microbial ecology and aquatic sciences, medical microbiology, parasitology, microbial pharmacology and biotechnology.

On-line visualization of the competitive behavior of antagonistic bacteria

To study the interaction between cocultured Listeria monocytogenes and an antagonistic Leuconostoc strain producing an anti-Listeria bacteriocin, flow cytometry, a technique allowing on-line and real-time analysis, was used along with classical microbiological methods. Culture methods and flow cytometric measurements of the mixed culture over time point to a bactericidal action of the lactic acid-producing bacterial strain against L. monocytogenes cells.

10N-nonyl acridine orange interacts with cardiolipin and allows the quantification of this phospholipid in isolated mitochondria

The acridine orange derivative, 10N-nonyl acridine orange, is an appropriate marker of the inner mitochondrial membrane in whole cells. We use membrane model systems to demonstrate that 10N-nonyl acridine orange binds to negatively charged phospholipids (cardiolipin, phosphatidylinositol and phosphatidylserine). The stoichiometry has been found to be 2 mol 10N-nonyl acridine orange/mol cardiolipin and 1 mol dye/mol phosphatidylserine or phosphatidylinositol, while, with zwitterionic phospholipids, significant binding could not be detected. The affinity constants were 2 x 10(6) M-1 for cardiolipin-10N-nonyl-acridine-orange association and only 7 x 10(4) M-1 for that of phosphatidylserine and phosphatidylinositol association. The high affinity of the dye for cardiolipin may be explained by two essential interactions; firstly an electrostatic interaction between the quaternary ammonium of nonyl acridine orange and the ionized phosphate residues of cardiolipin and secondly, hydrophobic interactions between adjacent chromophores. A linear relationship was demonstrated between the cardiolipin content of model membranes and the incorporated dye. Consequently, a convenient and rapid method for cardiolipin quantification in membranes was established and applied to the cardiolipin-containing organelle, the mitochondrion.

NADH-dependent dehydrogenase activity estimation by flow cytometric analysis of 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction

MTT reduction is usually analysed by colorimetric assay to study mitochondrial dehydrogenase activity as a test of cytotoxicity. This enzymatic reaction produces dark-blue granules of formazan, which increase cell refringency. In this work, we define the conditions for MTT use in quantitative flow cytometric analysis. MTT reduction provides a non-fluorescent dye usable by this technique to study an intracellular NADH-dependent dehydrogenase activity in vital cells. We observe that formazan production increases asymptotically with cell concentration and that this temperature-dependent Michaelis enzymatic reduction is produced essentially by mitochondrial dehydrogenases. In isolated mitochondria from rat hepatocytes and in whole L1210 murine leukemia cells, the Michaelis constants (KM) observed in the presence of respiratory substrates were, respectively, 10 microM and 500 microM. The inhibition of mitochondrial protein synthesis by chloramphenicol, which induces a rise of MTT reduction due to the correlative stimulation of glycolysis (Pasteur effect), is a limit of the MTT assay as a cytotoxicity test.

Evaluation of 2-methoxyacetic acid toxicity on mouse germ cells by flow cytometry

Flow cytometric (FCM) DNA content measurements were carried out on testicular monocellular suspensions obtained from mice exposed per os to a single dose of 50, 100, 300, 600, and 900 mg/kg body weight (b.w.) of 2-methoxyacetic acid (MAA) in order to investigate its cytotoxic action on germ cells. The effects of MAA were evaluated 2, 7, 14, 28, and 45 d after treatment in terms of altered cell type ratios in FCM fluorescence distribution histograms. Testis weight and histological tissue sections were also analyzed. MAA induced marked changes in the relative percentages of tetraploid and haploid cells, indicating the occurrence of cytotoxic damage on primary spermatocytes. Multiparameter FCM analysis showed that, besides its action on nucleic acid synthesis, MAA can also affect the cellular energy metabolism reflected in an altered mitochondrial mass distribution on round spermatids surviving the MAA treatment. This study demonstrates that rapid and unique FCM procedures can be usefully applied in reproductive toxicology.

3-Amino-6-methoxy-9-(2-hydroxyethylamino) acridine: a new fluorescent dye to detect Mycoplasma contamination in cell cultures

A new fluorescent acridine orange derivative, 3-amino-6-methoxy-9-(2-hydroxyethylamino) acridine (AMHA), has been applied to Hela cells in order to set up appropriate conditions for the detection of mycoplasma contaminations. Since AMHA staining reveals intensely fluorescent nuclei and slight fluorescent cytoplasm, we can visualize and localize mycoplasma contamination on each cell. In combination with a shortened Chen's staining method (1977), AMHA should allow a better detection of mycoplasma in animal cell cultures than the well established Hoechst dye.

Comparative flow cytometric analysis of bleomycin toxicity on normal and tumour sheep cell kinetics in vitro

The cytotoxic effects of bleomycin on cell proliferation, morphology and cycle progression were compared in a sheep tumour cell line and in normal sheep sinus cells. They were concentration and time dependent, irreversible, and were accompanied by increased cell diameter and cytosolic synthetic activity. Cell accumulation in the G2M phase, without much change in the cell cycle progression through the S phase, was observed using flow cytometry. Although the tumour cells showed a greater sensitivity to low bleomycin concentrations compared to the normal cells, both cell types exhibited equal sensitivity to higher drug concentrations. Provided that tumour cells are also preferentially affected by bleomycin in vivo, these findings raise the possibility that bleomycin cytotoxicity can be reduced or avoided in normal tissue.

A new method for testing cell ageing using two mitochondria specific fluorescent probes

Cell culture techniques have considerably improved our understanding of the numerous changes related to aging. For instance, murine lymphocytes obtained from animals older than 6 months progressively lose their, in vitro, proliferative capacity. Numerous studies have shown that this loss is due to changes in the mitochondrial compartment such as reduction in the transmembrane potential and/or membrane mass. Using two mitochondria specific probes with a potential-dependent (Rhodamine 123) or independent (Nonyl Acridine Orange) uptake, we found that the decline in the respiratory activity in the mouse occurred approximately 6 months prior to the decrease in mitochondrial membrane mass. The analysis of the Rh 123/NAO fluorescence ratio measured in splenocytes obtained from mice aged more than 6 months, showed that there was a linear loss of respiratory efficiency per unit of mitochondrial membrane mass. Moreover, cells with a ratio of less than 0.85 were incapable of proliferating and remained quiescent. The time separating the infection points of the two dye uptake curves might provide informations about the regulation and coordination of nuclear and/or mitochondrial genomes. Moreover, the ratio between the two fluorescent probes, in particular during the linear phase, may also have a predictive value.

Use of nonyl acridine orange and rhodamine 123 to follow biosynthesis and functional assembly of mitochondrial membrane during L1210 cell cycle

Specific mitochondrial incorporation of 10 N-nonyl acridine orange (NAO) is demonstrated by subcellular fractionation of rat hepatocytes. Moreover, comparative studies with NAO and rhodamine 123 (Rh 123) prove that acridine orange-derivative uptake is independent of transmembrane mitochondrial potential, a property allowing its utilization for the assessment of mitochondrial membrane mass modifications under various physiological states. Using NAO and Rh 123, we have respectively followed the biosynthesis of mitochondrial membrane and its assembly under a functional state during the L1210 cell cycle. Their evolution occurs in two stages according to a well-defined sequential order. Mitochondrial biogenesis, as revealed by NAO incorporation, occurs essentially in the G1 phase (probably mitochondrion enlargement) but also starts in late S phase (probably mitochondrion division). The increased amount of functional mitochondrial membrane, monitored by Rh 123 uptake, is emphasized in late G1 (prerequisite to DNA synthesis) and during G2M phases (prerequisite to mitosis). This alternative succession of phases displays the existence of a time-lag between the biosynthesis of mitochondrial membrane and its functional organization. Such an analysis confirms the potential of the NAO probe to evaluate mitochondrial membrane mass changes in various biological fields.

10-N nonyl-acridine orange: a fluorescent probe which stains mitochondria independently of their energetic state

The specificity of binding of 10-N Nonyl Acridine Orange to mitochondria, and more precisely to inner membranes, is demonstrated by subcellular fractionation of hepatocytes. Unlike Rhodamine 123, which is a preferential marker of the transmembrane potential, Nonyl Acridine Orange binding is essentially independent of the mitochondria energization state although a low uptake of this dye, in response to the potential, may be measured. So 10-N Nonyl acridine orange is an appropriate marker of the mitochondial membrane surface per unit of cell mass.

In situ flow cytometric analysis of nonyl acridine orange-stained mitochondria from splenocytes

Due to its spectral characteristics, the fluorochrome nonyl acridine orange (NAO) (lambda abs:489 nm, lambda em:525 nm), which is spontaneously incorporated by mitochondria with a high relative specificity, provides a new probe for the in situ study of these organelles by flow cytometry. In 15 min at 20 degrees C, the dye at 4.75 X 10(-6) M saturates the mitochondrial binding sites present in 1.5 X 10(6) cells. Unlike Rh 123, the fixation of the probe is not affected by the action of uncouplers and ionophores. Unlike acridine orange, its binding is not sensitive to nucleases. By studying the mitochondrial incorporation of the fluorochrome during the cell cycle of murine splenocytes, it was possible to show that the biogenesis of NAO-stained mitochondrial constituents mainly occurs during the G1 phase.

Alterations in the human immune response to the hepatitis B vaccine among the elderly

The specific binding of hepatitis B (HBs) antigen by lymphocytes from old people immunized with hepatitis B vaccine was explored. For that purpose HBs antigen was combined with fluorescent microspheres, and labeled antigen was allowed to react with lymphocytes from HBs vaccine-responsive or unresponsive people. Lymphocytes from 10 responders and 14 nonresponders were tested for their antigen-binding ability. For controls, lymphocytes were incubated with microspheres bearing human albumin. Lymphocytes from 8 out of 10 responders were able to recognize HBs antigen; for the nonresponders the ratio was 9 out of 14. HBs-binding lymphocytes were B cells but not T lymphocytes. B and T cells from responders and nonresponders were combined and cultivated for 8 days in the presence of HBs antigen, and antibody-producing cells were counted. Neither B cells alone nor B cells plus T cells from nonresponders were able to produce antibody. On the other hand B cells from unresponsive old people produced antibodies when they were cultivated in the presence of HBs antigen and T cells from responsive old people. These data suggest that some elderly individuals who do not produce antibody after in vivo immunization by HBs vaccine do have antibody-producing cells. Instead of a gap in their immune repertoire, these people are suffering from immune dysfunction.

Flow cytometry: technical description and some applications in France

After reviewing basic technical considerations, we discuss some applications of flow cytometry in French laboratories. This methodology is used in several areas: oncology, cellular pharmacotoxicology, molecular biology and genetics, immunology, as well as cellular biology and physiology. We also examine the evolution of this technique in two directions: on the one hand, the appearance of increasingly sophisticated instruments; on the other, the development of less expensive and less complicated apparatuses principally directed at clinical applications.

Variation of cellular mitochondrial activity in culture: analysis by flow cytometry

Cytometric analysis of various cultured cells using fluorescent probes to stain mitochondria, in combination with other methods, has shown that mitochondrial activity is an essential part of cell cycle completion. Among the existing fluorochromes, Rhodamine 123 is most often used for analyses of growth and cellular differentiation, and the action of various compounds. These studies permit a better understanding of the role of the mitochondria in situ and especially of the interactions that occur between the cytoplasm and the nucleus. However, the development of this type of study is limited by the small number of specific fluorochromes available.

Immunosuppression induced in vivo by 15 hydroxyeicosatetraenoic acid (15 HETE)

We have investigated the in vivo effects of 15 HETE on C57Bl/6 (H-2b) mice injected IP daily with this product. After that the 15 HETE treated animals and the controls were challenged in vivo by DBA/2 (H-2d) cells. Splenocytes from 15 HETE injected animals were either stimulated in vitro by lectins or cocultivated with DBA/2 irradiated splenocytes. It was observed that the response of splenocytes from in vivo treated animals is weaker than the control's response. The data suggest that 15 HETE induce the generation of suppressor cells.

Dimeric glutamyl-tRNA synthetases from wheat. Kinetic properties and functional structures

The Michaelis constants in the tRNA aminoacylation reaction have been studied for the three dimeric glutamyl-tRNA synthetases C, P and E. The values were found to be: for tRNA, 0.20 microM, and 0.44 microM; for glutamic acid, 10 microM, 83 microM and 83 microM; for MgATP, 0.46 mM, 0.38 mM and 0.26 mM. MgATP concentrations higher than 2 mM induce pronounced inhibition. The presence of the cognate tRNA is required for [32P]PPi-ATP isotopic exchange. In the absence of tRNA no hyperbolic saturation of the enzymes by glutamic acid occurs in our experimental conditions. Analysis of the enzymic activity as a function of enzyme concentration leads to the conclusion that the active forms are dimers which are in equilibrium with inactive monomers. The values of the dissociation constants Kd were found to be 43 nM, 53 nM and 87 nM for glutamyl-tRNA synthetases C, P and E respectively.

Glutamyl-tRNA synthetases from wheat. Isolation and characterization of three dimeric enzymes

Three dimeric glutamyl-tRNA synthetases (GluRS) were isolated from extracts of quiescent wheat germ and wheat chloroplasts. The chloroplast enzyme (Mr = 110 000), called GluRS C, exhibits a prokaryotic (Escherichia coli) tRNA specificity. Two enzymes were found in the quiescent germ and were separated on phosphocellulose P11: one called GluRS P, probably the mitochondrial enzyme, has the same tRNA specificity as GluRS C; the other, called GluRS E, has eukaryotic (wheat germ) tRNA specificity. Both enzymes exhibit a molecular weight close to 160 000. Each of these enzymes co-eluate on hydroxyapatite and phosphocellulose chromatographies with an unstable active monomer whose molecular weight is approximately half that of the corresponding dimer. Two assumptions are discussed about these monomers.