Changes in antigen expression on differentiating HL60 cells treated with dimethylsulphoxide, all-trans retinoic acid, alpha1,25-dihydroxyvitamin D3 or 12-O-tetradecanoyl phorbol-13-acetate

Intracellular Accumulation and Secretion of YKL-40 (CHI3L1) in the Course of DMSO-Induced HL-60 Cell Differentiation

YKL-40 (CHI3L1) is a matrix glycoprotein stored in human neutrophil-specific granules and released upon activation. While it is implicated in inflammation, cancer progression, and cell differentiation, its exact physiological role remains unclear. This study investigated the intracellular expression and secretion of YKL-40 by untreated and DMSO-treated HL-60 cells in association with surface expression of CD11b and CD66b throughout the differentiation process (up to 120 h). Secreted YKL-40 protein and mRNA levels of YKL-40, CD66b, and CD11b were measured by ELISA and quantitative RT-PCR, respectively. The intracellular YKL-40 and surface CD11b and CD66b expression were assessed by flow cytometry. A significant increase in CD11b expression confirmed DMSO-induced differentiation of HL-60 cells. Upon DMSO stimulation, YKL-40 mRNA expression increased in a time-dependent manner, unlike CD66b. The lack of CD66b (a granulocyte maturation and activation marker) on the surface of HL-60 cells might suggest that DMSO treatment did not induce full maturation or activation. The intracellular YKL-40 protein expression was increasing up to 96 h of DMSO treatment and then declined. YKL-40 secretion into the culture medium was detectable only at later time points (96 and 120 h), which was correlated with a decreased proliferation of DMSO-treated HL-60 cells. These findings suggest sequential changes in YKL-40 production and secretion during DMSO-induced differentiation of HL-60 cells and might contribute to a better understanding of YKL-40's involvement in both physiological processes and disease development, including multiple sclerosis.

Decreasing effects of protein kinase inhibitors on the expression of NOS2 and inflammatory cytokines and on phagocytosis in rat peritoneal macrophages is partly related to repolarization

The JAK/STAT (Janus Kinase/Signal Transducer and Activator of Transcription) pathway plays a pivotal role in macrophage polarization, but other signaling routes may also be involved. The aim of this study was to reveal the relationship of activation between rat peritoneal macrophages and their polarization, to detect the signaling routes involved, and find selective protein kinase inhibitors decreasing the production of inflammatory proteins in activated peritoneal macrophages. Rat macrophages were elicited with i.p. casein injection. CD80 and CD206 markers, NOS2 (Nitric oxide synthase 2), arginase, cytokines and phagocytosis were investigated by ELISA (Enzyme Linked Immunosorbent Assay), Western Blot, fluorescent microscopic and flow cytometry. Statistical methods were ANOVA (Analysis Of Variance) and Student t-tests. Resident and elicited cells expressed both CD80 and CD206 polarization markers. The involvement of MAPK (mitogen-activated protein kinases) and JAK/STAT pathways in the polarization was evidenced by a phosphorylation array, supported by Western blotting, by cytokine markers and by the inhibitory effects of kinase inhibitors. The expression of NOS2 and inflammatory cytokines was higher in elicited cells suggesting their M1 polarization. This effect was reduced by the inhibitors of MAPK and JAK/STAT pathways. Phagocytosis was also higher in elicited macrophages and decreased by these inhibitors. Nevertheless, they cannot change macrophage polarization unambiguously, as levels of CD80 and CD206 markers were not changed. For comparison, human blood macrophages were also studied. Similar effects and several differences were observed between the two types of macrophages, suggesting the role of the previous differentiation in defining their characteristics. Selected anti-cancer protein kinase inhibitors of p38, MAPK and JAK/STAT pathways are possible candidates for the therapy of inflammatory diseases.

Application and Utility of Liposomal Neuroprotective Agents and Biomimetic Nanoparticles for the Treatment of Ischemic Stroke

Ischemic stroke is still one of the leading causes of high mortality and severe disability worldwide. Therapeutic options for ischemic stroke and subsequent cerebral ischemia/reperfusion injury remain limited due to challenges associated with drug permeability through the blood-brain barrier (BBB). Neuroprotectant delivery with nanoparticles, including liposomes, offers a promising solution to address this problem, as BBB disruption following ischemic stroke allows nanoparticles to pass through the intercellular gaps between endothelial cells. To ameliorate ischemic brain damage, a number of nanotherapeutics encapsulating neuroprotective agents, as well as surface-modified nanoparticles with specific ligands targeting the injured brain regions, have been developed. Combination therapy with nanoparticles encapsulating neuroprotectants and tissue plasminogen activator (t-PA), a globally approved thrombolytic agent, has been demonstrated to extend the narrow therapeutic time window of t-PA. In addition, the design of biomimetic drug delivery systems (DDS) employing circulating cells (e.g., leukocytes, platelets) with unique properties has recently been investigated to overcome the injured BBB, utilizing these cells’ inherent capability to penetrate the ischemic brain. Herein, we review recent findings on the application and utility of nanoparticle DDS, particularly liposomes, and various approaches to developing biomimetic DDS functionalized with cellular membranes/membrane proteins for the treatment of ischemic stroke.

Characterization of Campylobacter jejuni-Neutrophil Interactions

Campylobacter jejuni is the leading cause of bacterial-derived gastroenteritis worldwide, infecting 96 million individuals annually. During infection, inflammation and tissue pathology occur in the lower gastrointestinal tract, including the recruitment of leukocytes. Neutrophils are the most abundant leukocyte in humans, and recruitment is associated with bacterial infections and the development of various inflammatory disorders, including inflammatory bowel disease. Neutrophils possess three main antibacterial functions: phagocytosis and degradation of microbes, degranulation to release antimicrobial proteins, and extrusion of neutrophil extracellular traps (NETs). Because neutrophils are recruited to the site of C. jejuni infection and they are associated with damaging inflammation in other diseases, it is imperative to understand the immunopathology that occurs during C. jejuni infection and thoroughly study the neutrophil response to the pathogen. Detailed protocols for human and ferret neutrophil isolations, neutrophil gentamicin protection assay, neutrophil activation flow cytometry assay, NET induction and quantification, and neutrophil western blot analysis are included in this article. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Isolation of human and ferret neutrophils Basic Protocol 2: Neutrophil gentamicin protection assay Basic Protocol 3: Neutrophil activation flow cytometry analyses Basic Protocol 4: Neutrophil extracellular trap induction and quantification Basic Protocol 5: Western blot detection of neutrophil-derived antimicrobial proteins.

Mitofusin-2 regulates leukocyte adhesion and β2 integrin activation

Neutrophils are critical for inflammation and innate immunity, and their adhesion to vascular endothelium is a crucial step in neutrophil recruitment. Mitofusin-2 (MFN2) is required for neutrophil adhesion, but molecular details are unclear. Here, we demonstrated that β₂ -integrin-mediated slow-rolling and arrest, but not PSGL-1-mediated cell rolling, are defective in MFN2-deficient neutrophil-like HL60 cells. This adhesion defect is associated with reduced expression of fMLP (N-formylmethionyl-leucyl-phenylalanine) receptor FPR1 as well as the inhibited β₂ integrin activation, as assessed by conformation-specific monoclonal antibodies. MFN2 deficiency also leads to decreased actin polymerization, which is important for β2 integrin activation. Mn²⁺ -induced cell spreading is also inhibited after MFN2 knockdown. MFN2 deficiency limited the maturation of β2 integrin activation during the neutrophil-directed differentiation of HL60 cells, which is indicated by CD35 and CD87 markers. MFN2 knockdown in β2-integrin activation-matured cells (CD87^high population) also inhibits integrin activation, indicating that MFN2 directly affects β2 integrin activation. Our study illustrates the function of MFN2 in leukocyte adhesion and may provide new insights into the development and treatment of MFN2 deficiency-related diseases.

Immunomodulation: Immunoglobulin Preparations Suppress Hyperinflammation in a COVID-19 Model via FcγRIIA and FcαRI

The rapid spread of SARS-CoV-2 has induced a global pandemic. Severe forms of COVID-19 are characterized by dysregulated immune response and "cytokine storm". The role of IgG and IgM antibodies in COVID-19 pathology is reasonably well studied, whereas IgA is neglected. To improve clinical outcome of patients, immune modulatory drugs appear to be beneficial. Such drugs include intravenous immunoglobulin preparations, which were successfully tested in severe COVID-19 patients. Here we established a versatile in vitro model to study inflammatory as well as anti-inflammatory processes by therapeutic human immunoglobulins. We dissect the inflammatory activation on neutrophil-like HL60 cells, using an immune complex consisting of latex beads coated with spike protein of SARS-CoV-2 and opsonized with specific immunoglobulins from convalescent plasma. Our data clarifies the role of Fc-receptor-dependent phagocytosis via IgA-FcαRI and IgG-FcγR for COVID-19 disease followed by cytokine release. We show that COVID-19 associated inflammation could be reduced by addition of human immunoglobulin preparations (IVIG and trimodulin), while trimodulin elicits stronger immune modulation by more powerful ITAMi signaling. Besides IgG, the IgA component of trimodulin in particular, is of functional relevance for immune modulation in this assay setup, highlighting the need to study IgA mediated immune response.

Induced Pluripotent Stem Cell-Derived Conditioned Medium Promotes Endogenous Leukemia Inhibitory Factor to Attenuate Endotoxin-Induced Acute Lung Injury

The conditioned medium of induced pluripotent stem cells (iPSC-CM) can attenuate neutrophil recruitment and endothelial leakage of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Therefore, we investigated the mechanisms by which iPSC-CM regulate the interaction between neutrophils and the endothelium in ALI. Murine iPSCs (miPSCs) were delivered intravenously to male C57BL/6 mice (8–12 weeks old) 4 h after intratracheal LPS injection. A miPSC-derived conditioned medium (miPSC-CM) was delivered intravenously to mice after intratracheal LPS injection. DMSO-induced HL-60 cells (D-HL-60, neutrophil-like cells) and human umbilical vein endothelial cells (HUVECs) were used as in vitro models to assess the interaction of neutrophils and endothelial cells. miPSC-CM diminished the histopathological changes in the lungs and the neutrophil count in bronchoalveolar lavage fluids of ALI mice. miPSC-CM attenuated the expression of adhesion molecules in the lungs of ALI mice. Human iPSC conditioned medium (hiPSC-CM) reduced the expression of adhesion molecules in a HUVEC and D-HL-60 co-culture after LPS stimulation, which decreased the transendothelial migration (TEM) of D-HL-60. A human angiogenesis factors protein array revealed that leukemia inhibitory factor (LIF) was not detected in the absence of D-HL-60 and hiPSC-CM groups. hiPSC-CM significantly promoted the production of endogenous LIF in in vitro models. Administration of an anti-LIF antibody not only reversed the effect of iPSC-CM in ALI mice, but also blocked the effect of iPSC-CM on neutrophils TEM in in vitro models. However, a controlled IgG had no such effect. Our study demonstrated that iPSC-CM promoted endogenous LIF to inhibit neutrophils TEM and attenuate the severity of sepsis-induced ALI.

Native Human Antibody to Shr Promotes Mice Survival After Intraperitoneal Challenge With Invasive Group A Streptococcus

BACKGROUND

A vaccine against group A Streptococcus (GAS) has been actively pursued for decades. The surface receptor Shr is vital in GAS heme uptake and provides an effective target for active and passive immunization. Here, we isolated human monoclonal antibodies (mAbs) against Shr and evaluated their efficacy and mechanism.

METHODS

We used a single B-lymphocyte screen to discover the mAbs TRL186 and TRL96. Interactions of the mAbs with whole cells, proteins, and peptides were investigated. Growth assays and cultured phagocytes were used to study the mAbs' impact on heme uptake and bacterial killing. Efficacy was tested in prophylactic and therapeutic vaccination using intraperitoneal mAb administration and GAS challenge.

RESULTS

Both TRL186 and TRL96 interact with whole GAS cells, recognizing the NTR and NEAT1 domains of Shr, respectively. Both mAbs promoted killing by phagocytes in vitro, but prophylactic administration of only TRL186 increased mice survival. TRL186 improved survival also in a therapeutic mode. TRL186 but not TRL96 also impeded Shr binding to hemoglobin and GAS growth on hemoglobin iron.

CONCLUSIONS

Interference with iron acquisition is central for TRL186 efficacy against GAS. This study supports the concept of antibody-based immunotherapy targeting the heme uptake proteins to combat streptococcal infections.

Extracellular vesicles from dHL-60 cells as delivery vehicles for diverse therapeutics

Extracellular vesicles (EVs) are membrane-derived heterogeneous vesicles that mediate intercellular communications. They have recently been considered as ideal vehicles for drug-delivery systems, and immune cells are suggested as a potential source for drug-loaded EVs. In this study, we investigated the possibility of neutrophils as a source for drug-loaded EVs. Neutrophil-like differentiated human promyelocytic leukemia cells (dHL-60) produced massive amounts of EVs within 1 h. The dHL-60 cells are also easily loaded with various cargoes such as antibiotics (penicillin), anticancer drug (paclitaxel), chemoattractant (MCP-1), miRNA, and Cas9. The EVs derived from the dHL-60 cells showed efficient incorporation of these cargoes and significant effector functions, such as bactericidal activity, monocyte chemotaxis, and macrophage polarization. Our results suggest that neutrophils or neutrophil-like promyelocytic cells could be an attractive source for drug-delivery EVs.

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.

Novel self-nanoemulsifying drug-delivery system enhances antileukemic properties of all-trans retinoic acid

Aim: All- trans retinoic acid (ATRA) shows erratic oral bioavailability when administered orally against leukemia, which can be solved through its incorporation in self-nanoemulsifying drug-delivery systems (SEDDS). The SEDDS developed contained a hydrophobic ion pair between benzathine (BZT) and ATRA and was enriched with tocotrienols by the input of a palm oil tocotrienol rich fraction (TRF) in its composition. Results: SEDDS-TRF-ATRA-BZT allowed the formation of emulsions with nanometric size that retained ATRA within their core after dispersion. Pharmacokinetic parameters after oral administration of SEDDS-TRF-ATRA-BZT in mice were improved compared with what was seen for an ATRA solution. Moreover, SEDDS-TRF-ATRA-BZT had improved activity against HL-60 cells compared with SEDDS without TRF. Conclusion: SEDDS-TRF-ATRA-BZT is a promising therapeutic choice over ATRA conventional medicine.

RAF Kinase Inhibitor Protein in Myeloid Leukemogenesis

RAF kinase inhibitor protein (RKIP) is an essential regulator of intracellular signaling. A somatic loss of RKIP expression is a frequent event in solid human cancers, and a role of RKIP as metastasis-suppressor is widely accepted nowadays. Recently, RKIP loss has been described in acute myeloid leukemia (AML) and a series of other myeloid neoplasias (MNs). Functional in vitro and in vivo experiments revealed that RKIP is an essential player within the development of these liquid tumors; however, the respective role of RKIP seems to be complex and multi-faceted. In this review, we will summarize the current knowledge about RKIP in myeloid leukemogenesis. We will initially describe its involvement in physiologic hematopoiesis, and will then proceed to discuss its role in the development of AML and other MNs. Finally, we will discuss potential therapeutic implications arising thereof.

Ubiquitin-specific peptidase 3 induces TPA-mediated leukemia cell differentiation via regulating H2AK119ub

Acute myeloid leukemia (AML) is the most common type of leukemia in adults. Owing to the chemotherapy associated side effects and toxicity, it is necessary to find a new mechanism, which can identify new potential therapeutic targets at the molecular level. Here, we identified new target genes that are induced during the TPA-induced HL-60 cell differentiation by ChIP-seq and microarray data analysis. Using q-PCR and ChIP assay, we confirmed that the target genes including USP3, USP35, TCF4, and SGK1 are upregulated during TPA-mediated HL-60 cell differentiation. Levels of USP3, one of the deubiquitinating enzymes (DUBs), increased by TPA treatment, resulting in the reduction of H2AK119ub levels. In addition, we revealed that depletion of USP3 inhibits TPA-mediated leukemia cell differentiation q-PCR and FACS analysis. Taken together, our data indicate that USP3 promotes TPA-mediated leukemia cell differentiation via regulating H2AK119ub levels.

Neutrophilic Dermatoses Associated with Myeloid Malignancies

Neutrophilic dermatoses (ND) are a group of conditions characterized by an aseptic accumulation of polymorphonuclear leukocytes in the skin. Occurrence of ND in association with myeloid malignancies, mainly myelodysplastic syndrome and myelogenous acute leukemia, is not rare and is often associated with a poor prognosis. Recent findings have improved understanding of the pathophysiology of myeloid malignancy-associated ND. We review the clinical spectrum of myeloid malignancy-associated ND with an emphasis on recently identified mechanisms. Myeloid leukemia cells retain the potential for terminal differentiation into polymorphonuclear leukocytes in the skin. Many studies suggest a clonal link between myeloid malignancies and ND. Activation of autoinflammatory pathways (NOD-like receptor family pyrin domain-containing-3, Familial Mediterranean Fever Gene) in the clonal cells of myeloid disorders may also be involved in this setting.

Detection of sepsis in patient blood samples using CD64 expression in a microfluidic cell separation device

A microfluidic affinity separation device was developed for the detection of sepsis in critical care patients.

High-throughput downstream process development for cell-based products using aqueous two-phase systems

As the clinical development of cell-based therapeutics has evolved immensely within the past years, downstream processing strategies become more relevant than ever. Aqueous two-phase systems (ATPS) enable the label-free, scalable, and cost-effective separation of cells, making them a promising tool for downstream processing of cell-based therapeutics. Here, we report the development of an automated robotic screening that enables high-throughput cell partitioning analysis in ATPS. We demonstrate that this setup enables fast and systematic investigation of factors influencing cell partitioning. Moreover, we examined and optimized separation conditions for the differentiable promyelocytic cell line HL-60 and used a counter-current distribution-model to investigate optimal separation conditions for a multi-stage purification process. Finally, we show that the separation of CD11b-positive and CD11b-negative HL-60 cells is possible after partial DMSO-mediated differentiation towards the granulocytic lineage. The modeling data indicate that complete peak separation is possible with 30 transfers, and >93% of CD11b-positive HL-60 cells can be recovered with >99% purity. The here described screening platform facilitates faster, cheaper, and more directed downstream process development for cell-based therapeutics and presents a powerful tool for translational research.

Adrenomedullin in the growth modulation and differentiation of acute myeloid leukemia cells

Adrenomedullin (ADM) is a regulatory peptide endowed with multiple biological effects, including the regulation of blood pressure, cell growth and innate host defence. In the present study, we demonstrated that ADM signaling could be involved in the impaired cellular differentiation of myeloid leukemia cells to mature granulocytes or monocytes by modulating RAMPs/CRLR expression, PI3K/Akt cascade and the ERK/MAPK signaling pathway. When exogenously administered to in vitro cultures of HL60 promyelocytic leukemia cells, ADM was shown to exert a strong proliferative effect with minimal upregulation in the expression level of monocyte antigen CD14. Notably, the experimental inhibition of ADM signaling with inhibitor ADM22-52 promoted a differentiative stimulation towards monocytic and granulocytic lineages. Moreover, based on the expression of CD31 relative to CD38, we hypothesized that an excess of ADM in bone marrow (BM) niche could increase the transendothelial migration of leukemia cells while any inhibitory event of ADM activity could raise cell retention in hyaluronate matrix by upregulating CD38. Taken into consideration the above evidence, we concluded that ADM and ADM22-52 could differently affect the growth of leukemia cells by autocrine/paracrine mechanisms and may have clinical relevance as biological targets for the intervention of tumor progression.

Ascorbic acid inhibits TPA-induced HL-60 cell differentiation by decreasing cellular H₂O₂ and ERK phosphorylation

Retinoic acid (RA), vitamin D and 12-O‑tetradecanoyl phorbol-13-acetate (TPA) can induce HL-60 cells to differentiate into granulocytes, monocytes and macrophages, respectively. Similar to RA and vitamin D, ascorbic acid also belongs to the vitamin family. High‑dose ascorbic acid (>100 µM) induces HL‑60 cell apoptosis and induces a small fraction of HL‑60 cells to express the granulocyte marker, CD66b. In addition, ascorbic acid exerts an anti‑oxidative stress function. Oxidative stress is required for HL‑60 cell differentiation following treatment with TPA, however, the effect of ascorbic acid on HL‑60 cell differentiation in combination with TPA treatment remains to be fully elucidated. The aim of the present study was to investigate the cellular effects of ascorbic acid treatment on TPA-differentiated HL-60 cells. TPA-differentiated HL-60 cells were used for this investigation, this study and the levels of cellular hydrogen peroxide (H2O2), caspase activity and ERK phosphorylation were determined following combined treatment with TPA and ascorbic acid. The results demonstrated that low‑dose ascorbic acid (5 µM) reduced the cellular levels of H2O2 and inhibited the differentiation of HL‑60 cells into macrophages following treatment with TPA. In addition, the results of the present study further demonstrated that low‑dose ascorbic acid inactivates the ERK phosphorylation pathway, which inhibited HL‑60 cell differentiation following treatment with TPA.

Phenotypic and functional analysis of HL-60 cells used in opsonophagocytic-killing assay for Streptococcus pneumoniae

Differentiated HL-60 is an effector cell widely used for the opsonophagocytic-killing assay (OPKA) to measure efficacy of pneumococcal vaccines. We investigated the correlation between phenotypic expression of immunoreceptors and phagocytic ability of HL-60 cells differentiated with N,N-dimethylformamide (DMF), all-trans retinoic acid (ATRA), or 1α, 25-dihydroxyvitamin D3 (VitD3) for 5 days. Phenotypic change was examined by flow cytometry with specific antibodies to CD11c, CD14, CD18, CD32, and CD64. Apoptosis was determined by flow cytometry using 7-aminoactinomycin D. Function was evaluated by a standard OPKA against serotype 19F and chemiluminescence-based respiratory burst assay. The expression of CD11c and CD14 gradually increased upon exposure to all three agents, while CD14 expression increased abruptly after VitD3. The expression of CD18, CD32, and CD64 increased during differentiation with all three agents. Apoptosis remained less than 10% until day 3 but increased after differentiation by DMF or ATRA. Differentiation with ATRA or VitD3 increased the respiratory burst after day 4. DMF differentiation showed a high OPKA titer at day 1 which sustained thereafter while ATRA or VitD3-differentiated cells gradually increased. Pearson analysis between the phenotypic changes and OPKA titers suggests that CD11c might be a useful differentiation marker for HL-60 cells for use in pneumococcal OPKA.

GATA2 germline mutations impair GATA2 transcription, causing haploinsufficiency: functional analysis of the p.Arg396Gln mutation

Germline GATA2 mutations have been identified as the cause of familial syndromes with immunodeficiency and predisposition to myeloid malignancies. GATA2 mutations appear to cause loss of function of the mutated allele leading to haploinsufficiency; however, this postulate has not been experimentally validated as the basis of these syndromes. We hypothesized that mutations that are translated into abnormal proteins could affect the transcription of GATA2, triggering GATA2 deficiency. Chromatin immunoprecipitation and luciferase assays showed that the human GATA2 protein activates its own transcription through a specific region located at -2.4 kb, whereas the p.Thr354Met, p.Thr355del, and p.Arg396Gln germline mutations impair GATA2 promoter activation. Accordingly, GATA2 expression was decreased to ∼58% in a patient with p.Arg396Gln, compared with controls. p.Arg396Gln is the second most common mutation in these syndromes, and no previous functional analyses have been performed. We therefore analyzed p.Arg396Gln. Our data show that p.Arg396Gln is a loss-of-function mutation affecting DNA-binding ability and, as a consequence, it fails to maintain the immature characteristics of hematopoietic stem and progenitor cells, which could result in defects in this cell compartment. In conclusion, we show that human GATA2 binds to its own promoter, activating its transcription, and that the aforementioned mutations impair the transcription of GATA2. Our results indicate that they can affect other GATA2 target genes, which could partially explain the variability of symptoms in these diseases. Moreover, we show that p.Arg396Gln is a loss-of-function mutation, which is unable to retain the progenitor phenotype in cells where it is expressed.

Microfluidic device capable of medium recirculation for non-adherent cell culture

We present a microfluidic device designed for maintenance and culture of non-adherent mammalian cells, which enables both recirculation and refreshing of medium, as well as easy harvesting of cells from the device. We demonstrate fabrication of a novel microfluidic device utilizing Braille perfusion for peristaltic fluid flow to enable switching between recirculation and refresh flow modes. Utilizing fluid flow simulations and the human promyelocytic leukemia cell line, HL-60, non-adherent cells, we demonstrate the utility of this RECIR-REFRESH device. With computer simulations, we profiled fluid flow and concentration gradients of autocrine factors and found that the geometry of the cell culture well plays a key role in cell entrapping and retaining autocrine and soluble factors. We subjected HL-60 cells, in the device, to a treatment regimen of 1.25% dimethylsulfoxide, every other day, to provoke differentiation and measured subsequent expression of CD11b on day 2 and day 4 and tumor necrosis factor-alpha (TNF-α) on day 4. Our findings display perfusion sensitive CD11b expression, but not TNF-α build-up, by day 4 of culture, with a 1:1 ratio of recirculation to refresh flow yielding the greatest increase in CD11b levels. RECIR-REFRESH facilitates programmable levels of cell differentiation in a HL-60 non-adherent cell population and can be expanded to other types of non-adherent cells such as hematopoietic stem cells.

A review of molecular mechanisms of the anti-leukemic effects of phenolic compounds in honey

Hematologic malignancies constitute about 9% of all new cases of cancers as reported via the GLOBOCAN series by International Agency for Research on Cancer (IARC) in 2008. So far, the conventional therapeutic and surgical approaches to cancer therapy have not been able to curtail the rising incidence of cancers, including hematological malignancies, worldwide. The last decade has witnessed great research interest in biological activities of phenolic compounds that include anticancer, anti-oxidation and anti-inflammation, among other things. A large number of anticancer agents combat cancer through cell cycle arrest, induction of apoptosis and differentiation, as well as through inhibition of cell growth and proliferation, or a combination of two or more of these mechanisms. Various phenolic compounds from different sources have been reported to be promising anticancer agents by acting through one of these mechanisms. Honey, which has a long history of human consumption both for medicinal and nutritional uses, contains a variety of phenolic compounds such as flavonoids, phenolic acids, coumarins and tannins. This paper presents a review on the molecular mechanisms of the anti-leukemic activity of various phenolic compounds on cell cycle, cell growth and proliferation and apoptosis, and it advocates that more studies should be conducted to determine the potential role of honey in both chemoprevention and chemotherapy in leukemia.

Hyperforin inhibits Akt1 kinase activity and promotes caspase-mediated apoptosis involving Bad and Noxa activation in human myeloid tumor cells

BACKGROUND

The natural phloroglucinol hyperforin HF displays anti-inflammatory and anti-tumoral properties of potential pharmacological interest. Acute myeloid leukemia (AML) cells abnormally proliferate and escape apoptosis. Herein, the effects and mechanisms of purified HF on AML cell dysfunction were investigated in AML cell lines defining distinct AML subfamilies and primary AML cells cultured ex vivo.

METHODOLOGY AND RESULTS

HF inhibited in a time- and concentration-dependent manner the growth of AML cell lines (U937, OCI-AML3, NB4, HL-60) by inducing apoptosis as evidenced by accumulation of sub-G1 population, phosphatidylserine externalization and DNA fragmentation. HF also induced apoptosis in primary AML blasts, whereas normal blood cells were not affected. The apoptotic process in U937 cells was accompanied by downregulation of anti-apoptotic Bcl-2, upregulation of pro-apoptotic Noxa, mitochondrial membrane depolarization, activation of procaspases and cleavage of the caspase substrate PARP-1. The general caspase inhibitor Z-VAD-fmk and the caspase-9- and -3-specific inhibitors, but not caspase-8 inhibitor, significantly attenuated apoptosis. HF-mediated apoptosis was associated with dephosphorylation of active Akt1 (at Ser(473)) and Akt1 substrate Bad (at Ser(136)) which activates Bad pro-apoptotic function. HF supppressed the kinase activity of Akt1, and combined treatment with the allosteric Akt1 inhibitor Akt-I-VIII significantly enhanced apoptosis of U937 cells.

SIGNIFICANCE

Our data provide new evidence that HF's pro-apoptotic effect in AML cells involved inhibition of Akt1 signaling, mitochondria and Bcl-2 members dysfunctions, and activation of procaspases -9/-3. Combined interruption of mitochondrial and Akt1 pathways by HF may have implications for AML treatment.

Allium compounds, dipropyl and dimethyl thiosulfinates as antiproliferative and differentiating agents of human acute myeloid leukemia cell lines

Epidemiologic studies support the premise that Allium vegetables may lower the risk of cancers. The beneficial effects appear related to the organosulfur products generated upon processing of Allium. Leukemia cells from patients with acute myeloid leukemia (AML) display high proliferative capacity and have a reduced capacity of undergoing apoptosis and maturation. Whether the sulfur-containing molecules thiosulfinates (TS), diallyl TS (All(2)TS), dipropyl TS (Pr(2)TS) and dimethyl TS (Me(2)TS), are able to exert chemopreventative activity against AML is presently unknown. The present study was an evaluation of proliferation, cytotoxicity, differentiation and secretion of AML cell lines (U937, NB4, HL-60, MonoMac-6) in response to treatment with these TS and their related sulfides (diallylsulfide, diallyl disulfide, dipropyl disulfide, dimethyl disulfide). As assessed by flow cytometry, ELISA, gelatin zymogaphy and RT-PCR, we showed that Pr(2)TS and Me(2)TS, but not All(2)TS and sulfides, 1) inhibited cell proliferation in dose- and time-dependent manner and this process was neither due to cytotoxicity nor apoptosis, 2) induced macrophage maturation, and 3) inhibited the levels of secreted MMP-9 (protein and activity) and TNF-alpha protein, without altering mRNA levels. By establishing for the first time that Pr(2)TS and Me(2)TS affect proliferation, differentiation and secretion of leukemic cell lines, this study provides the opportunity to explore the potential efficiency of these molecules in AML.

The potassium channel Ether à go-go is a novel prognostic factor with functional relevance in acute myeloid leukemia

Background

The voltage-gated potassium channel hEag1 (K_V10.1) has been related to cancer biology. The physiological expression of the human channel is restricted to the brain but it is frequently and abundantly expressed in many solid tumors, thereby making it a promising target for a specific diagnosis and therapy. Because chronic lymphatic leukemia has been described not to express hEag1, it has been assumed that the channel is not expressed in hematopoietic neoplasms in general.

Results

Here we show that this assumption is not correct, because the channel is up-regulated in myelodysplastic syndromes, chronic myeloid leukemia and almost half of the tested acute myeloid leukemias in a subtype-dependent fashion. Most interestingly, channel expression strongly correlated with increasing age, higher relapse rates and a significantly shorter overall survival. Multivariate Cox regression analysis revealed hEag1 expression levels in AML as an independent predictive factor for reduced disease-free and overall survival; such an association had not been reported before. As a functional correlate, specific hEag1 blockade inhibited the proliferation and migration of several AML cell lines and primary cultured AML cells in vitro.

Conclusion

Our observations implicate hEag1 as novel target for diagnostic, prognostic and/or therapeutic approaches in AML.

Nuclear translocation of beta-actin is involved in transcriptional regulation during macrophage differentiation of HL-60 cells

The functional significance of nuclear translocation of β-actin remains unclear. Here, we demonstrate that PMA induces β-actin accumulation in the nucleus and binding to various target genes with different functions. We also find that accumulated nuclear β-actin is involved in recruitment of RNA polymerase II and in transcription regulation.

Studies have shown that nuclear translocation of actin occurs under certain conditions of cellular stress; however, the functional significance of actin import remains unclear. Here, we demonstrate that during the phorbol 12-myristate 13-acetate (PMA)-induced differentiation of HL-60 cells toward macrophages, β-actin translocates from the cytoplasm to the nucleus and that this process is dramatically inhibited by pretreatment with p38 mitogen-activated protein kinase inhibitors. Using chromatin immunoprecipitation-on-chip assays, the genome-wide maps of β-actin binding to gene promoters in response to PMA treatment is analyzed in HL-60 cells. A gene ontology-based analysis shows that the identified genes belong to a broad spectrum of functional categories such as cell growth and differentiation, signal transduction, response to external stimulus, ion channel activity, and immune response. We also demonstrate a correlation between β-actin occupancy and the recruitment of RNA polymerase II at six selected target genes, and β-actin knockdown decreases the mRNA expression levels of these target genes induced by PMA. We further show that nuclear β-actin is required for PMA-induced transactivation of one target gene, solute carrier family 11 member 1, which is important for macrophage activation. Our data provide novel evidence that nuclear accumulation of β-actin is involved in transcriptional regulation during macrophage-like differentiation of HL-60 cells.

Phagocytosis of Streptococcus pyogenes by all-trans retinoic acid-differentiated HL-60 cells: roles of azurophilic granules and NADPH oxidase

BACKGROUND

New experimental approaches to the study of the neutrophil phagosome and bacterial killing prompted a reassessment of the usefulness of all-trans retinoic acid (ATRA)-differentiated HL-60 cells as a neutrophil model. HL-60 cells are special in that they possess azurophilic granules while lacking the specific granules with their associated oxidase components. The resulting inability to mount an effective intracellular respiratory burst makes these cells more dependent on other mechanisms when killing internalized bacteria.

METHODOLOGY/PRINCIPAL FINDINGS

In this work phagocytosis and phagosome-related responses of ATRA-differentiated HL-60 cells were compared to those earlier described in human neutrophils. We show that intracellular survival of wild-type S. pyogenes bacteria in HL-60 cells is accompanied by inhibition of azurophilic granule-phagosome fusion. A mutant S. pyogenes bacterium, deficient in M-protein expression, is, on the other hand, rapidly killed in phagosomes that avidly fuse with azurophilic granules.

CONCLUSIONS/SIGNIFICANCE

The current data extend our previous findings by showing that a system lacking in oxidase involvement also indicates a link between inhibition of azurophilic granule fusion and the intraphagosomal fate of S. pyogenes bacteria. We propose that differentiated HL-60 cells can be a useful tool to study certain aspects of neutrophil phagosome maturation, such as azurophilic granule fusion.

Gene expression analysis of human promyelocytic leukemia HL-60 cell differentiation and cytotoxicity induced by natural and synthetic retinoids

AIMS

This study analyzed gene expression profiles of human promyelocytic leukemia HL-60 cells treated with natural and synthetic retinoids (ATRA, RII and R9158), in an attempt to investigate the structure-function relationship of the retinoids in inducing cell differentiation and cytotoxicity.

MAIN METHODS

Flow cytometry was used to determine cell cycle changes in HL-60 cells following treatment (1.0 muM) with natural and synthetic retinoids (ATRA, RII and R9158), and cDNA microarrays were used to monitor the gene expression profiles of HL-60 cells treated with the various retinoids.

KEY FINDINGS

Consistent with retinoid-induced cell differentiation, treatment with these three retinoids correlated with an increase in the percentage of cells arrested in the G1/G0 phase of the cell cycle. Microarray analysis showed upregulation of known differentiation genes, adhesion molecules, and the oxidase activation pathway following retinoid treatment. Differential expression of several genes was observed in HL-60 cells treated with the three retinoids. For example, tissue remodeling protein genes, ubiquitin genes, and signal transduction genes were highly expressed in ATRA- and R9158-treated HL-60 cells, but remained unchanged in HL-60 cells treated with RII.

SIGNIFICANCE

The above findings suggest that the differentiation of HL-60 cells induced by the three retinoids occurs through similar pathways, and that there exists a structure-function relationship regarding retinoids and the induction of cell differentiation and cytotoxicity.

Granulocytic differentiation of HL-60 promyelocytic leukemia cells is associated with increased expression of Cul5

The human HL-60 promyelocytic leukemia cell line has been widely used as a model for studying granulocytic differentiation. All-trans retinoic acid (ATRA) treatment of HL-60 cells promotes granulocytic differentiation and is effective as differentiation therapy for patients with acute promyelocytic leukemia. The identification of genes that are transcriptionally regulated by ATRA has provided insight into granulocytic differentiation and differentiation therapy. The Asb-2 (ankyrin repeat SOCS box 2) gene has previously been identified as a transcriptional target in ATRA-treated HL-60 cells. The ASB-2 protein forms an E3 ubiquitin ligase complex with the proteins, Cul5, regulator of cullin 2 (ROC2), and elongin B and C. The purpose of this study was to determine if there is increased expression of Cul5 during granulocytic differentiation of HL-60 cells. To induce granulocytic differentiation, HL-60 cells were treated for 5 d with ATRA and differentiation was confirmed by examining superoxide anion production, nuclear morphology, and changes in the expression of CD11b, CD13, and CD15. Quantitative real-time RT-PCR was used to measure Cul5 mRNA expression and also the expression of other components of the E3 ubiquitin ligase (ASB-2, ROC2, elongin B and C). Granulocytic differentiation of HL-60 cells was associated with a 1.6-, 1.7-, and 23-fold statistically significant (P <or= 0.05) increase in mRNA expression for Cul5, ROC2, and ASB-2, respectively. No significant change was found in elongin B and C mRNA expression. Using Western blot analysis, the expression of Cul5 protein was increased 6.5-fold with granulocytic differentiation of the HL-60 cells. Increased expression of multiple components of the Cul5-containing E3 ubiquitin ligase complex with ATRA treatment of HL-60 cells indicates that this complex may play an important role in granulocytic differentiation.

Identification and role of the homodimerization interface of the glycosylphosphatidylinositol-anchored membrane type 6 matrix metalloproteinase (MMP25)

The membrane type (MT) 6 matrix metalloproteinase (MMP) (MMP25) is a glycosylphosphatidylinositol-anchored matrix metalloproteinase (MMP) that is highly expressed in leukocytes and in some cancer tissues. We previously showed that natural MT6-MMP is expressed on the cell surface as a major reduction-sensitive form of M(r) 120, likely representing enzyme homodimers held by disulfide bridges. Among the membrane type-MMPs, the stem region of MT6-MMP contains three cysteine residues at positions 530, 532, and 534 which may contribute to dimerization. A systematic site-directed mutagenesis study of the Cys residues in the stem region shows that Cys(532) is involved in MT6-MMP dimerization by forming an intermolecular disulfide bond. The mutagenesis data also suggest that Cys(530) and Cys(534) form an intramolecular disulfide bond. The experimental observations on cysteines were also investigated by computational studies of the stem peptide, which validate these proposals. Dimerization is not essential for transport of MT6-MMP to the cell surface, partitioning into lipid rafts or cleavage of alpha-1-proteinase inhibitor. However, monomeric forms of MT6-MMP exhibited enhanced autolysis and metalloprotease-dependent degradation. Collectively, these studies establish the stem region of MT6-MMP as the dimerization interface, an event whose outcome imparts protease stability to the protein.

Smooth muscle type isoform of 20 kDa myosin light chain is expressed in monocyte/macrophage cell lineage

Myosin light chain genes of human hematopoietic cells have not been fully characterized. We previously reported the cloning of the full-length cDNAs of 20 kDa regulatory myosin light chain (MLC-2), named as MLC-2A, from Meg-01, a human megakaryoblastic leukemia cell line (J. Smooth Muscle Res. 37: 25-38, 2001). We now cloned another MLC-2 isoforms from human platelets and U937, a human monocytic leukemia cell line, named as MLC-2B and MLC-2C, respectively. Both MLC-2A and MLC-2B consisted of three exons, which were situated on gene loci 18p1.3. Analysis of the gene structure indicated that MLC-2A and MLC-2B utilized different exons. MLC-2C also consisted of three exons, which was situated on gene loci 20p12. Amino acid sequence of MLC-2C was, of interest, apparently almost the same as that of MLC-2 from chicken gizzard smooth muscle LC20-A (one amino acid's difference) and human vascular smooth muscle LC-20 (two amino acids' difference). All three protein kinase C phosphorylation residues (Ser-1, Ser-2, Thr-9) and both myosin light chain kinase phosporylation residues (Thr-18, Ser-19) are conserved in these three isoforms. The MLC-2A and MLC-2B mRNA were expressed constitutively in all of the human hematopoietic cell lines examined and their expression levels were almost the same. On the other hand, MLC-2C mRNA was expressed in untreated monocytic cell lines (U937 and A-THP-1) and HL-60 differentiated into monocyte/macrophage cell lineage by TPA treatment. These results indicate that smooth muscle type isoform, MLC-2C is the inducible isoform, and might play a crucial role in monocyte/macrophage cell lineage.

Dendritic cells and myeloid leukaemias: plasticity and commitment in cell differentiation

Dendritic cells (DCs) are key antigen-presenting cells (APCs), which link innate and adaptive immunity, ultimately activating antigen-specific T cells. This review examines the relationship between the acute and chronic myeloid leukaemias and cells with DC properties. DCs are non-dividing terminally differentiated cells, and ex vivo leukaemic cells or cell lines show little similarity to DCs. However, many leukaemias differentiate further in response to defined stimuli, and retain a degree of lineage plasticity. Therefore, several studies have explored the response of leukaemic cells to the in vitro regimens used to differentiate ex vivo primary DCs. Recent data suggest that the most 'dendritic-like' cells can be derived from more undifferentiated myeloid leukaemias, such as the myelomonocytic Mutz-3 cell line. These findings have important implications for understanding the developmental origins of DCs, for harnessing the APC properties of this class of tumour to stimulate the therapeutic anti-tumour immunity, and for developing useful models for the study of human DC physiology and pathology. There is a strong rationale for further exploration of this class of tumour and its relationship to the normal DC.

Combination of automated high throughput platforms, flow cytometry, and hierarchical clustering to detect cell state

BACKGROUND

This study examined whether hierarchical clustering could be used to detect cell states induced by treatment combinations that were generated through automation and high-throughput (HT) technology. Data-mining techniques were used to analyze the large experimental data sets to determine whether nonlinear, non-obvious responses could be extracted from the data.

METHODS

Unary, binary, and ternary combinations of pharmacological factors (examples of stimuli) were used to induce differentiation of HL-60 cells using a HT automated approach. Cell profiles were analyzed by incorporating hierarchical clustering methods on data collected by flow cytometry. Data-mining techniques were used to explore the combinatorial space for nonlinear, unexpected events. Additional small-scale, follow-up experiments were performed on cellular profiles of interest.

RESULTS

Multiple, distinct cellular profiles were detected using hierarchical clustering of expressed cell-surface antigens. Data-mining of this large, complex data set retrieved cases of both factor dominance and cooperativity, as well as atypical cellular profiles. Follow-up experiments found that treatment combinations producing "atypical cell types" made those cells more susceptible to apoptosis. CONCLUSIONS Hierarchical clustering and other data-mining techniques were applied to analyze large data sets from HT flow cytometry. From each sample, the data set was filtered and used to define discrete, usable states that were then related back to their original formulations. Analysis of resultant cell populations induced by a multitude of treatments identified unexpected phenotypes and nonlinear response profiles.

Granulocyte differentiation inducer, hexapeptide HLDF-6, decreases cytotoxic effect of tumor necrosis factor on HL-60 cell line

The effect of hexapeptide HLDF-6, the granulocytic differentiation inducer, on the tumor necrosis factor alpha (TNF-alpha)-induced differentiation and apoptosis of human promyelocytic leukemia HL-60 cells has been investigated. Costimulation of HL-60 cells with HLDF-6 and TNF-alpha enhanced granulocyte differentiation, whereas the level of monocyte differentiation remained unchanged; however, the cytotoxic action of TNF-alpha on these cells decreased. The protective effect of HLDF-6 peptide did not depend on activation of NF-kappaB (nuclear transcription factor). Since HLDF-6 peptide decreases the number of cells entering apoptosis caused by C(2)-ceramide, a mediator of TNF-induced apoptosis, and also reduces TNF-alpha-mediated activation of caspase-3, we have proposed the hypothesis that HLDF-6 increases resistance of HL-60 cells to the TNF-alpha cytotoxic effect due to inhibition of some stages of mitochondria-dependent apoptotic signaling.

Synthesis and Cancer Chemopreventive Activity of Zapotin, a Natural Product fromCasimiroaedulis

An efficient method has been developed to synthesize zapotin (5,6,2',6'-tetramethoxyflavone), a component of the edible fruit Casimiroa edulis, on a multigram scale. The synthesis utilizes a regioselective C-acylation of a dilithium dianion derived from a substituted o-hydroxyactophenone to afford a beta-diketone intermediate that can be cyclized to zapotin in good overall yield, thus avoiding the inefficient Baker-Venkataraman rearrangement pathway. Zapotin was found to induce both cell differentiation and apoptosis with cultured human promyelocytic leukemia cells (HL-60 cells). In addition, the compound inhibits 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity with human bladder carcinoma cells (T24 cells), and TPA-induced nuclear factor-kappa B (NF-kappaB) activity with human hepatocellular liver carcinoma cells (HepG2 cells). These data suggest that zapotin merits further investigation as a potential cancer chemopreventive agent.

C/EBPalpha inactivation in FAK-overexpressed HL-60 cells impairs cell differentiation

We previously demonstrated that focal adhesion kinase (FAK)-overexpressed (HL-60/FAK) cells have marked resistance against various apoptotic stimuli such as oxidative stress, ionizing radiation and TNF-receptor-induced ligand (TRAIL) compared with vector-transfected (HL-60/Vect) cells. Here, we show that HL-60/FAK cells are highly resistant to all-trans retinoic acid (ATRA)-induced differentiation, whereas original HL-60 or HL-60/Vect cells are sensitive. Treatment with ATRA at 1 muM for 5 days markedly inhibited the proliferation and increased the expression of differentiation markers (CD38, CD11b) in HL-60/Vect cells, but showed no such effect in HL-60/FAK cells. Electrophoretic mobility shift assay (EMSA) using an oligonucleotide for the c/EBP consensus binding sequence showed that c/EBPalpha was activated in ATRA-treated HL-60/Vect cells but not in HL-60/FAK cells, indicating that c/EBPalpha activation by ATRA was impaired in HL-60/FAK cells. In addition, the association of retinoblastoma protein (pRb) and c/EBPalpha after treatment with ATRA was seen in HL-60/Vect cells but not in HL-60/FAK cells. Further, hyperphosphorylation of pRb was observed in HL-60/FAK cells. Finally, the introduction of FAK siRNA into HL-60/FAK cells resulted in the recovery of sensitivity to ATRA-induced differentiation, confirming that the inhibition of HL-60/FAK differentiation resulted from both the induction of pRb hyperphosphorylation and the inhibition of association of pRb and c/EBPalpha.

Multistable and multistep dynamics in neutrophil differentiation

Background

Cell differentiation has long been theorized to represent a switch in a bistable system, and recent experimental work in micro-organisms has revealed bistable dynamics in small gene regulatory circuits. However, the dynamics of mammalian cell differentiation has not been analyzed with respect to bistability.

Results

Here we studied how HL60 promyelocytic precursor cells transition to the neutrophil cell lineage after stimulation with the differentiation inducer, dimethyl sulfoxide (DMSO). Single cell analysis of the expression kinetics of the differentiation marker CD11b (Mac-1) revealed all-or-none switch-like behavior, in contrast to the seemingly graduated change of expression when measured as a population average. Progression from the precursor to the differentiated state was detected as a discrete transition between low (CD11b^Low) and high (CD11b^High) expressor subpopulations distinguishable in a bimodal distribution. Hysteresis in the dependence of CD11b expression on DMSO dose suggests that this bimodality may reflect a bistable dynamic. But when an "unswitched" (CD11b^Low) subpopulation of cells in the bistable/bimodal regime was isolated and cultured, these cells were found to differ from undifferentiated precursor cells in that they were "primed" to differentiate.

Conclusion

These findings indicate that differentiation of human HL60 cells into neutrophils does not result from a simple state transition of a bistable switch as traditionally modeled. Instead, mammalian differentiation appears to be a multi-step process in a high-dimensional system, a result which is consistent with the high connectivity of the cells' complex underlying gene regulatory network.

Utilization of the human cell line HL-60 for chemiluminescence based detection of microorganisms and related substances

In this paper we describe a new pyrogen assay using the human leukemia cell line HL-60. The cell line is differentiated using all-trans retinoic acid (ATRA) to generate a cell population that resembles mature granulocytes. The differentiated HL-60 cell is capable of generating reactive oxygen species (ROS) when challenged with pyrogenic substances. In a luminol enhanced chemilumimetric assay the responsiveness of differentiated HL-60 cells is tested towards Salmonella typhimurium, Bacillus subtilis, Saccharomyces cerevisiae, Candida albicans, lipopolysaccharide (LPS) and lipoteichoic acid (LTA). The results show a poor sensitivity to S. typhimurium but displays good sensitivity towards B. subtilis, LTA and LPS. Furthermore, the sensitivity towards the yeasts C. albicans and S. cerevisiae is considerably better than obtained in other in vitro cell systems. Overall these results indicate that the HL-60 cell assay possibly could be evolved to a supplementary assay for the known pyrogenic detection assays. Furthermore, the utilization of the assay for pyrogenic examination of recombinant drugs derived from yeast expression systems would be relevant to examine.

Influence of galangin on HL-60 cell proliferation and survival

The effect of galangin, a flavonol component of India root spice and the 'herbal' medicine propolis, on HL-60 human leukaemia cell survival is characterised. Galangin (1-100 microM) exerted an antiproliferative effect that, with dose and exposure longevity, was progressively associated with an elevated hypodiploid DNA content and expression of the active form of caspase-3, principally prior to membrane damage. At >or=50 microM, plasmamembrane phosphatidylserine exposure was observed. There was no evidence for intracellular oxidative stress as an orchestrator of cytotoxicity and significant phagocyte-like differentiation was not detected. We discuss whether such cytotoxicity will be therapeutically exploitable or contribute to cancer prevention within a pharmacological or dietary context.

PDE1B2 regulates cGMP and a subset of the phenotypic characteristics acquired upon macrophage differentiation from a monocyte

Monocyte-to-macrophage differentiation with the cytokine granulocyte-macrophage colony-stimulating factor induces expression of the cyclic nucleotide phosphodiesterase PDE1B2. However, what role PDE1B2 plays in macrophage biology has not been elucidated. We have addressed this question by inhibiting PDE1B2 induction by using RNA interference. Using a retrovirus-based system, we created HL-60 stable cell lines that express a short-hairpin RNA targeting PDE1B2. HL-60 cells treated with phorbol-12-myristate-13-acetate differentiate to a macrophage-like phenotype and up-regulate PDE1B2. However, expression of PDE1B2 short hairpin RNA effectively suppresses PDE1B2 mRNA, protein, and activity up-regulation. Using the HL-60 PDE1B2 knockdown cells and agonists for either adenylyl or guanylyl cyclase, it was found that PDE1B2 predominantly regulates cGMP and plays a lesser role in cAMP regulation in response to cyclase agonists. Furthermore, in intact HL-60 cells, PDE1B2 activity can be regulated by changes in Ca+2 levels. Inhibiting PDE1B2 up-regulation does not prevent HL-60 cell differentiation, because several markers of macrophage differentiation are unaffected. However, suppression of PDE1B2 expression alters some aspects of the macrophage-like phenotype, because cell spreading, phagocytic ability, and CD11b expression are augmented. The cAMP analog 8-Bromo-cAMP reverses the changes caused by PDE1B2 knockdown. Also, PDE1B2 knockdown cells have lower basal levels of cAMP and alterations in the phosphorylation state of several probable PKA substrate proteins. Thus, the effects of PDE1B2 on differentiation may ultimately be mediated through decreased cAMP. In conclusion, PDE1B2 regulates a subset of phenotypic changes that occur upon phorbol-12-myristate-13-acetate-induced differentiation and likely also plays a role in differentiated macrophages by regulating agonist-stimulated cGMP levels.

Cooperative action of 1α,25-dihydroxyvitamin D3 and retinoic acid in NB4 acute promyelocytic leukemia cell differentiation is transcriptionally controlled

All-trans-retinoic acid (RA) and 1alpha,25-dihydroxyvitamin D3 (1,25D3) are involved in the control of hematopoiesis and have been suggested to play a role in cellular differentiation and are as such potent inducers of differentiation of myeloid leukemia cells. In this study, we show that, in promyelocytic NB4 cells, addition of 1,25D3 enhances terminal granulocytic RA-dependent differentiation concomitant with the enhanced activation of the RA transcriptional activity through an RARbeta promoter. By EMSA and ChIP assays, we further demonstrate that, while both VDR and RAR are bound to the RARbeta promoter in NB4 cells, addition of 1,25D3 increases VDR binding to this promoter, while that of RA induces the release of VDR and increases the binding of RAR. Thus, contrary to normal myeloid cells, 1,25D3 does not act as a transrepressor of RA transcriptional activity in leukemic cells, suggesting that transcriptional regulation of RA-target genes may be modified in malignant cells. In promyelocytic leukemic cells, the combination of 1,25D3 and RA results in both enhanced transactivation and differentiation.

Mitochondrial gene knockout HL60rho0 cells show preferential differentiation into monocytes/macrophages

This study compares the differentiation potential of mitochondrial gene knockout (rho0) and parental HL60 cells in response to 1.25% dimethylsulfoxide (DMSO) and 10nM phorbol myristate acetate (PMA). Compared to HL60 cells, undifferentiated HL60rho0 cells showed partial monocyte/macrophage differentiation, with increased CD11c and CD14 expression, decreased CD71 expression, and weak non-specific esterase staining. Differentiation along the monocyte/macrophage pathway (PMA) was more pronounced in HL60rho0 than parental HL60 cells with increased CD11c and CD14 expression and stronger non-specific esterase staining. DMSO-exposure resulted in a poorly differentiated nuclear morphology, small respiratory burst and marginal up-regulation of CD15 expression in HL60rho0 cells.

Immunophenotypic changes induced on human HL60 leukaemia cells by 1alpha,25-dihydroxyvitamin D3 and 12-O-tetradecanoyl phorbol-13-acetate

1alpha,25-Dihydroxyvitamin D3 (1,25D3) induces HL60 cells to acquire a monocyte-like phenotype, while cells treated with 12-O-tetradecanoyl phorbol-13-acetate (TPA) resemble macrophages. Using a microarray of 82 CD antibodies, 24 cluster of differentiation (CD) antigens were detected on HL60 cells. 1,25D3 induced the following antigens in decreasing order of the change: CD14, CD11c, CD11b, CD54, CD86, CD38 and CD66c, with repression of CD117, CD71, CD95, CD45 and CD64. TPA induced the following antigens in decreasing order of the change: CD11c, CD9, CD11b, CD54, CD38, CD45RO and CD66c, with repression of CD4, CD117, CD95, CD71 and CD64. The results presented provide a basis for monitoring differentiation therapy of myeloid leukaemias in patients.

In vivo and in vitro roles of IL-21 in inflammation

IL-21 is a cytokine known to mediate its biological action via the IL-21R, composed of a specific chain, IL-21Ralpha, and the common gamma-chain (CD132). Recent data suggest that IL-21 possesses proinflammatory properties. However, there is no clear evidence that IL-21 induces inflammation in vivo and, curiously, the interaction between IL-21 and neutrophils has never been investigated, despite the fact that these cells express CD132 and respond to other CD132-dependent cytokines involved in inflammatory disorders. Using the murine air pouch model, we found that IL-21 induced inflammation in vivo, based on recruitment of neutrophil and monocyte populations. In contrast to LPS, administration of IL-21 into the air pouch did not significantly increase the concentration of IL-6, CCL5, CCL3, and CXCL2. We demonstrated that HL-60 cells expressed IL-21Ralpha, which is down-regulated during their differentiation toward neutrophils, and that IL-21Ralpha is not detected in neutrophils. Concomitant with this, IL-21 induced Erk-1/2 phosphorylation in HL-60 cells, but not in neutrophils. To eliminate the possibility that IL-21 could activate neutrophils even in the absence of IL-21Ralpha, we demonstrated that IL-21 did not modulate several neutrophil functions. IL-21-induced Erk-1/2 phosphorylation was not associated with proliferation or differentiation of HL-60 toward neutrophils, monocytes, or macrophages. IL-21Ralpha was detected in human monocytes and monocyte-derived macrophages, but IL-21 increased CXCL8 production only in monocyte-derived macrophages. We conclude that IL-21 is a proinflammatory cytokine, but not a neutrophil agonist. We propose that IL-21 attracts neutrophils indirectly in vivo via a mechanism independent of IL-6, CCL3, CCL5, and CXCL2 production.