Dexamethasone modifies the functional responses of the granulocytic differentiating HL-60 cells

Discrimination of cell-differentiation using a cell-binding assay based on the conversion of cell-patterns with dielectrophoresis

We developed a simple, rapid, and label-free method to obtain the ratio of cells with a specific surface protein from heterogeneous cell populations, and applied it to estimate the cell differentiation states. The repulsive force of negative dielectrophoresis was used to form the first pattern of HL60 cells on a substrate immobilized with anti-CD13 or anti-CD11b antibody. Next, the patterned cells were converted to form the second pattern by switching the pattern of the electric field. The cells exhibiting a specific protein remained in the original position due to the immunorecognition event, while the unwanted cells that were not bound to the antibody on the substrates could be simply removed. The cell-binding efficiencies of substrates modified with anti-CD13 and anti-CD11b decreased and increased, respectively, with increasing duration of cell culture in medium containing differentiation-inducing agents, including all-trans retinoic acid. This is explained by the downregulation of CD13 and upregulation of CD11b throughout the differentiation process of HL60 cells. Furthermore, the assay was applied to investigate the effects of various differentiation-inducing agents. The total assay time required for discriminating the proteins expressed on the cell surface in each differentiation state was as short as 120 s. No fluorescence label is required for the proposed assay. The method could be useful to estimate the cell differentiation and factors that influence the differentiation trajectory for numerous cell types.

Genome-wide miRNA profiling and pivotal roles of miRs 125a-5p and 17-92 cluster in human neutrophil maturation and differentiation of acute myeloid leukemia cells

MicroRNAs (miRNAs, miRs) are short non-coding post-transcriptional regulators of gene expression in normal physiology and disease. Acute myeloid leukemia is characterized by accumulation of malignantly transformed immature myeloid precursors, and differentiation therapy, used to overcome this differentiation blockage, has become a successful therapeutic option. The human HL-60 acute leukemia cell line serves as a cell culture model for granulocytic maturation, and dimethyl sulfoxide (DMSO) incubation leads to its differentiation towards neutrophil-like cells, as assessed by biochemical, functional and morphological parameters. DMSO-induced HL-60 cell differentiation constitutes an excellent model to examine molecular processes that turn a proliferating immortal leukemic cell line into mature non-proliferating and apoptosis-prone neutrophil-like end cells. By performing genome-wide miRNA profiling and functional assays, we have identified a signature of 86 differentially expressed canonical miRNAs (51 upregulated; 35 downregulated) during DMSO-induced granulocytic differentiation of HL-60 cells. Quantitative real-time PCR was used to validate miRNA expression. Among these differentially expressed canonical miRNAs, we found miR-125a-5p upregulation and miR-17-92 cluster downregulation acted as major regulators of granulocytic differentiation in HL-60 cells. Enforced expression of miR-125a-5p promoted granulocytic differentiation in HL-60 cells, whereas miR-17-92 ectopic expression inhibited DMSO-induced HL-60 granulocytic differentiation. Ectopic expression of miR-125a-5p also promoted granulocytic differentiation in human acute promyelocytic leukemia NB4 cells, as well as in naïve human primary CD34⁺-hematopoietic progenitor/stem cells. These findings provide novel molecular insights into the identification of miRNAs regulating granulocytic differentiation of human leukemia cells and normal CD34⁺-hematopoietic progenitor/stem cells, and may assist in the development of novel miRNA-targeted therapies for leukemia.

Isoliquiritigenin induces monocytic differentiation of HL-60 cells

It has been proven that isoliquiritigenin could inhibit the proliferation of some kinds of cancer cell lines and has a strong antioxidative activity. The purpose of this study is to investigate whether the antioxidant isoliquiritigenin affects the proliferation and redifferentiation in HL-60 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) colorimetric method and trypan blue staining were used to measure cell proliferentiation and survival. The morphological changes, nitroblue tetrazolium chloride (NBT) reductive activity, and the CD11b and CD14 surface antigens were used as the biomarkers of redifferentiation of HL-60 cells. The intracellular reactive oxygen species (iROS) level was detected by a fluorescent probe, 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA). Isoliquiritigenin (ISL) inhibited the cell proliferation and decreased the iROS levels in a dose-dependent manner, while the treatment did not increase the lethality rate. After 72 h treatment with 10 microg/ml ISL, a typical differentiated morphology was observed in HL-60 cells, including the decrease of karyoplasmic ratio and the increase of kidney-shape nuclear cells. The positive rate (%) of CD11b (26.4+/-3.90 vs 7.70+/-1.04, P<0.01) and CD14 (20.4+/-2.30 vs 2.63+/-0.133, P<0.01) cells increased significantly. The NBT reductive activity increased 2.3-fold as compared to that of the control group. As an antioxidant, ISL decreased the iROS formation in a dose-dependent manner. All the results indicate that the antioxidant ISL is able to induce the monocytic differentiation in leukemia cells. ISL has the potential as a drug to cure leukemia with fewer side effects.

1Alpha,25-dihydroxyvitamin D3-mediated stimulation of steroid sulphatase activity in myeloid leukaemic cell lines requires VDRnuc-mediated activation of the RAS/RAF/ERK-MAP kinase signalling pathway

1Alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) stimulates the activity of steroid sulphatase (STS) in myeloid cells [Hughes et al., 2001, 2005]. This was attenuated by inhibitors of phospholipase D (PLD) (n-butanol, 2,3-diphosphoglyceric acid, C(2)-ceramide) and phosphatidate phosphohydrolase (PAP) (propranolol and chlorpromazine), but was unaffected by inhibitors of phospholipase C. The 1alpha,25(OH)(2)D(3)-induced STS activity was also attenuated by inhibitors of protein kinase Calpha and protein kinase Cdelta (Go 6976, HBDDE and rottlerin), but not by an inhibitor of protein kinase Cbeta (LY379196). Additionally, 1alpha,25(OH)(2)D(3)-induced STS activity was attenuated by inhibitors of RAS (manumycin A), RAF (GW5074), MEK (PD098059 and U1026) and JNK (SP600125), but not p38 (PD169316). 1alpha,25(OH)(2)D(3) produced a rapid and long lasting stimulation of the ERK-MAP kinase signalling cascade in HL60 myeloid leukaemic cells. This 'non-genomic' effect of 1alpha,25(OH)(2)D(3) blocked by pharmacological antagonists of nuclear vitamin D receptors (VDR(nuc)) and does not appear to require hetero-dimerisation with the retinoid-X receptor (RXR). Inhibitors of the Src tyrosine kinase (PP1), RAS (manumycin A), RAS-RAF interactions (sulindac sulphide and RAS inhibitory peptide), RAF (GW5074 or chloroquine), and protein kinase Calpha (HBDDE) abrogated the 1alpha,25(OH)(2)D(3)-stimulated increase in ERK-MAP kinase activity. Taken together, these results show that 1alpha,25(OH)(2)D(3)/VDR(nuc) activation of the RAS/RAF/ERK-MAP kinase signalling pathway plays an important role in augmenting STS activity in human myeloid leukaemic cell lines.

Subtractive screening reveals up-regulation of NADPH oxidase expression in Crohn's disease intestinal macrophages

Macrophages play a central role during the pathogenesis of inflammation. In normal intestinal mucosa surface expression of typical macrophage markers such as CD14, CD16, CD11b or T-cell co-stimulatory molecules such as CD80 or CD86 is low indicating anergy and low pro-inflammatory activity of these cells. During inflammatory bowel disease (IBD) the mucosa is invaded by a population of macrophages displaying these markers, secreting higher cytokine levels and representing an activated cell population. CD33(+) cells (macrophages) were isolated from normal and Crohn's disease mucosa and mRNA was isolated by polyT magnetic beads. A subtractive screening was performed subtracting mRNA from normal macrophages from those of Crohn's disease macrophages. Oxidative burst activity was determined by flow cytometry. Seventy clones were obtained by the subtractive mRNA screening. Sequencing showed > 99% homology to mRNA of monocyte chemoattractant protein-1 (MCP-1) for three clones. Five clones obtained by subtraction revealed > 99% homology to mRNA of cytochrome b (subunit gp91). Differential expression of the cytochrome b subunit gp91 and the cytosolic NADPH oxidase subunit p67 was confirmed by RT-PCR and 'virtual' Northern blots. The fluorescence ratio of stimulated versus unstimulated cells was 0.9 +/- 0.16 in control macrophages indicating a lack of oxidative burst activity. In Crohn's disease this ratio was significantly increased to 1.80 +/- 0.8 (P = 0.004) confirming the molecular data. In conclusion NADPH oxidase mRNA is down-regulated or absent in macrophages from normal mucosa correlating with a lack of oxidative burst activity. In IBD macrophage-oxidative burst activity is increased and NADPH oxidase mRNA induced. Inhibition of NADPH oxidase could be a new therapeutical target in IBD and reduce mucosal tissue damage in active IBD.

An investigation into the suitability of silica beads for cell separations based on density perturbation

This study has investigated possible alternative types of beads for fractionating cells on the basis of density perturbation. It is well known that uniform magnetic beads can be extremely important tools for separating cells by both magnetic separation techniques and density perturbation. However, because of the inherent expense associated with the use of magnetic beads, it was decided to study the possible use of inexpensive silica beads for density perturbation in terms of their attachment and modification of density of cells and to compare them with uniform Dynabeads. Silica beads were analyzed to determine their size and effect on the density of cells. Differentiated HL60 cells were used as a model system. As differentiation occurs, different levels of antigens are expressed on the cell surface and this results in different numbers of beads binding to cells. DMSO-differentiated HL60 cells were mixed with anti-CD11b-coated beads at a ratio of 20:1 (beads/cell), and gentle mixing was carried out at 20 degrees C on the end-over-end mixer. The binding of antibody-coated silica beads and Dynabeads to partially differentiated HL60 cells were compared. The conclusions reached on the basis of these experiments are that antibody-coated silica beads (Ab-coated silica) can be used as alternative beads for some cell fractionations. However, compared with Dynabeads, there are more beads that are only transiently associated with cells, possibly indicating that higher levels of detachment of beads from cells occur when silica beads are used. In addition, silica beads are usually heterogeneous in size and this would make it difficult to use these beads for the isolation of purified subpopulations of differentiated cells.

Fractionation of differentiating cells using density perturbation

This paper describes the development of a new method for the fractionation of purified subpopulations of partially differentiated cells on continuous isopycnic gradients, using a density perturbation method based on the ability of cells to bind dense antibody-coated beads. Until now none of the available fractionation techniques, such as magnetic cell fractionation has been efficient for separating subpopulations of partially differentiated cells. The fractionation experiments described in this report used promyelocytic HL-60 and DMSO-induced granulocytic HL-60 cells as a model system. Populations of cells, modified by the binding of dense beads were fractionated on isotonic, isopycnic Optiprep gradients by centrifugation at 220xg for 90 min at 20 degrees C. Examination of the different gradient fractions showed that, as cells bind increasing numbers of beads, they are found in the denser regions of the isopycnic gradients. Indirect immunofluorescence was combined with flow cytometric techniques to characterise the fractionation of partially differentiated cells. Flow cytometric results confirmed that as antigenic determinants appear on the surface at higher levels of expression, the number of beads binding to each cell increased. Furthermore, after fractionation, when the bead-bound and non-bead-bound cells were cultured in the presence of DMSO, those cells that had bound more beads targeted to differentiated cells were found to achieve terminal differentiation faster than those cells that had not been associated with any beads.

Effect of dexamethasone on leukotriene synthesis in DMSO-stimulated HL-60 cells

Human leukemia (HL) 60 cells were differentiated by dimethylsulfoxide (DMSO) treatment to granulocyte-like cells, leukotriene (LT) synthesizing activity of which was increased in response to the differentiation of the cells. Four synthesizing enzymes, cytosolic phospholipase A2 (cPLA2), 5-lipoxygenase (5-LO), LTA4 hydrolase and LTC4 synthase, and an enzyme associated protein, 5-lipoxygenase activating protein (FLAP) are involved in the generation of LTC4 and LTB4. We examined the expression of messenger RNA (mRNA) for these LT synthesizing enzymes and an associated protein in DMSO differentiated HL-60 cells by reverse transcriptase polymerase chain reaction (RT-PCR). The production of LTC4 and LTB4, measured by radioimmunoassay (RIA), was increased after the incubation with DMSO for more than 3 days. Messenger RNA abundance for 5-LO, LTC4 synthase and LTA4 hydrolase was increased, that for FLAP was stable, but that for cPLA2 was decreased. These results indicate that DMSO induced increase of LT synthesis is associated with the increase of mRNA expression of 5-LO, LTC4 synthase and LTA4 hydrolase, although the precise regulatory mechanisms of the increased mRNA expression are not determined. We also investigated an action of dexamethasone (DEX) on DMSO-induced enhancement of LT synthesis. DEX suppressed DMSO induced increase of LTC4 synthesis, but rather enhanced DMSO induced LTB4 production. The DEX attenuated the DMSO-induced increase of mRNA expression for LTC4 synthase, but showed no effect on that for LTA4 hydrolase. The inhibition of LTC4 synthesis is associated with the suppression of mRNA expression for LTC4 synthase. However, increased LTB4 synthesis by DEX is regulated by the mechanisms which are independent from mRNA level of LTA4 hydrolase.

Dexamethasone But Not Indomethacin Inhibits Human Phagocyte Nicotinamide Adenine Dinucleotide Phosphate Oxidase Activity by Down-Regulating Expression of Genes Encoding Oxidase Components

We investigated the effects of dexamethasone or indomethacin on the NADPH oxidase activity, cytochrome b558 content, and expression of genes encoding the components gp91-phox and p47-phox of the NADPH oxidase system in the human monocytic THP-1 cell line, differentiated with IFN-γ and TNF-α, alone or in combination, for up to 7 days. IFN-γ and TNF-α, alone or in combination, caused a significant up-regulation of the NADPH oxidase system as reflected by an enhancement of the PMA-stimulated superoxide release, cytochrome b558 content, and expression of gp91-phox and p47-phox genes on both days 2 and 7 of cell culture. Noteworthy was the tremendous synergism between IFN-γ and TNF-α for all studied parameters. Dexamethasone down-regulated the NADPH oxidase system of cytokine-differentiated THP-1 cells as assessed by an inhibition on the PMA-stimulated superoxide release, cytochrome b558 content, and expression of the gp91-phox and p47-phox genes. The nuclear run-on assays indicated that dexamethasone down-regulated the NADPH oxidase system at least in part by inhibiting the transcription of gp91-phox and p47-phox genes. Indomethacin inhibited only the PMA-stimulated superoxide release of THP-1 cells differentiated with IFN-γ and TNF-α during 7 days. None of the other parameters was affected by indomethacin. We conclude that dexamethasone down-regulates the NADPH oxidase system at least in part by inhibiting the expression of genes encoding the gp91-phox and p47-phox components of the NADPH oxidase system.