Promyelocytic Leukemia HL-60 Cells Research Articles

Essential oil from Ocimum viride exerts caspase-3 interceded apoptosis in human leukemia HL-60 cells

The present study discusses the apoptotic potential of essential oil from whole plant of Ocimum viride (EOV) against human promyelocytic leukemia HL-60 cells. IC50 value of EOV on HL-60 cells was 0.087, 0.0503, and 0.034 µl/ml respectively at 6, 12, and 24 h. Several parameters were used to access the role of EOV in inducing apoptosis in human HL-60 cancer cells, including nuclear binding fluoroprobes, electron micrographs, DNA laddering, and annexin V-FITC/PI affinity assay. Quantification of BrdU incorporation was done to determine the degree of DNA damage. It was further determined that EOV has an effect on the DNA cell cycle and mitochondria, which was observed in the form of a prominent subdivision of G0 peaks in the analysis of the DNA cell cycle, as well as a reduction in the mitochondrial membrane potential. A higher level of cytosolic cytochrome-c was associated with these events. Bcl-2 depletion and increase in ROS were also analysed. Both initiator caspases namely caspase-9 and -8 activated caspase-3 which eventually leads to apoptosis. These effects revealed that EOV has apoptosis inducing potential towards HL-60 cells and can be a promising candidate for further anticancer studies.

Biochemical characterization of the human ubiquitous glucose-6-phosphatase in neutrophil granulocytes.

Glucose-6-phosphatase-β (G6PC3) is a ubiquitous phosphatase present in the endoplasmic reticulum, which, unlike G6PC1, is not responsible for maintaining blood glucose level under starvation. Recently, G6PC3 has been shown to play an important role in neutrophil granulocytes, eliminating the toxic metabolite 1,5-anhydroglucitol-6-phosphate. The present study aimed to look for alternative substrates for the enzyme and outline the expression changes in the parts of this multicomponent system during neutrophil granulocyte differentiation. We determined the kinetic characteristics of recombinant human G6PC3 towards different sugar phosphates, and the transport of these compounds was also measured in rat liver microsomes. We found that all investigated sugar phosphates are substrates for G6PC3, although their microsomal transport is much slower than that of glucose-6-phosphate. Using the HL-60 promyelocytic leukemia cell line as an in vitro model system for myeloid differentiation, we found no significant differences in enzyme expression and phosphatase activity latency between undifferentiated and differentiated cells. Our results provide novel insights into the possible role of G6PC3 in the dephosphorylation of alternative sugar phosphates or their metabolites synthesized in the endoplasmic reticulum and confirm the potential feature of the enzyme in the promyelocytic stage as well. These findings contribute to our knowledge of intracellular carbohydrate metabolism of neutrophil granulocytes, which facilitates further research directions to better understand the underlying mechanisms of neutropenias.

Potential of NRF2 Inhibitors-Retinoic Acid, K67, and ML-385-In Overcoming Doxorubicin Resistance in Promyelocytic Leukemia Cells.

Drug resistance is one of the major obstacles to the clinical use of doxorubicin, an extensively used chemotherapeutic drug to treat various cancers, including leukemia. Inhibition of the nuclear factor erythroid 2-related factor 2 (NRF2) seems a promising strategy to reverse chemoresistance in cancer cells. NRF2 is a transcription factor that regulates both antioxidant defense and drug detoxification mechanisms. In this study, we investigated the potential of three inhibitors of NRF2-K67, retinoic acid and ML-385-to overcome doxorubicin resistance in promyelocytic leukemia HL-60 cells. For this purpose, low-dose doxorubicin was used to establish doxorubicin-resistant HL-60/DR cells. The expression of NRF2 and its main repressor, Kelch-like ECH-associated protein 1 (KEAP1), at mRNA and protein levels was examined. HL-60/DR cells overexpressed NRF2 at mRNA and protein levels and down-regulated KEAP1 protein compared to drug-sensitive HL-60 cells. The effects of NRF2 inhibitors on doxorubicin-resistant HL-60/DR cell viability, apoptosis, and intracellular reactive oxygen species (ROS) levels were analyzed. We observed that NRF2 inhibitors significantly sensitized doxorubicin-resistant HL-60/DR cells to doxorubicin, which was associated with increased intracellular ROS levels and the expression of CAS-9, suggesting the participation of the mitochondrial-dependent apoptosis pathway. Furthermore, ML-385 inhibitor was used to study the expression of NRF2-KEAP1 pathway genes. NRF2 gene and protein expression remained unchanged; however, we noted the down-regulation of KEAP1 protein upon ML-385 treatment. Additionally, the expression of NRF2-regulated antioxidant and detoxification genes including SOD2, HMOX2, and GSS was maintained upon ML-385 treatment. In conclusion, our results demonstrated that all the studied inhibitors, namely K67, retinoic acid, and ML-385, increased the efficacy of doxorubicin in doxorubicin-resistant HL-60/DR cells, and suggested a potential strategy of combination therapy using NRF2 inhibitors and doxorubicin in overcoming doxorubicin resistance in leukemia.

Monitoring Apoptosis and Myeloid Differentiation of Acridine Orange-Mediated Sonodynamic Therapy-Induced Human Promyelocytic Leukemia HL60 Cells.

In the treatment of acute myeloid leukemia (AML), conventional therapies can lead to severe side effects and drug resistance. There is a need for alternative treatments that do not cause treatment resistance and have minimal or no side effects. Sonodynamic therapy (SDT), due to its noninvasive, multiple repeatability, localized treatment feature and do not cause treatment resistance, emerges as an alternative treatment option. However, it has not received sufficient attention in the treatment of AML especially acute promyelocytic leukemia (APL). The aim of the study was to investigate the potential differentiation and antileukemic effects of acridine orange (AO)-mediated SDT on HL60 cells. Cell viability was determined by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT)method in the control, ultrasound, AO concentrations, and ultrasound-exposed AO concentrations groups. Transmission electron microscopy (TEM) was used to determine morphology, and flow cytometry was used to determine apoptosis, DNA cycle, cell volume, mitochondria membrane potential (Δψm), reactive oxygen species (ROS) production, and differentiation markers (CD11b and CD15) expressions. Additionally, toluidine blue staining for semithin sections was used to determine differentiation. The cytotoxicity of AO-mediated SDT on HL60 cells was significantly higher than other groups, and TEM images showed that it caused various morphological changes typical for apoptosis. Flow cytometry results showed the presence of early apoptosis, subG1 arrest, loss of Δψm, increase of intracellular ROS production, decreased cell volume, and increased expression of CD11b (1.3-fold) antigen and CD15 (1.2-fold) antigen. Data showed that AO-mediated SDT significantly induced apoptosis in HL60 cells. Increased expression of CD11b and CD15 antigens and morphological findings demonstrated that AO-mediated SDT contributes to granulocytic differentiation in HL60 cells. AO-mediated SDT has potential as an alternative treatment of APL.

MitoBADY-based Raman sensing of neutrophil-like cells

The aim was to evaluate the potential of MitoBADY as a Raman sensor in monitoring the drug-induced differentiation of promyelocytic cells into neutrophils. Neutrophils are important immune system components, and their metabolic disorders lead to serious diseases. Primary neutrophils found in the bloodstream are short-lived cells, terminally differentiated, and unable to proliferate. Thus, the characteristics of induced differentiation of promyelocytic cells are valuable for better chemotherapy design, as it is difficult to conduct such studies in vivo or ex vivo in bone marrow environments. Alternatively, a stable in vitro model can be used to analyze the differentiation process, e.g., the HL-60 promyelocytic leukemia cell line. The standard method to confirm the promyelocytic differentiation is immunophenotyping, which is complex and laborious. Here, we propose a simple spectroscopic-based alternative that uses the Raman signal of the MitoBADY sensor to identify neutrophil-like cells. We found that the ratio of the intensity of three bands, i.e., A= (I750+I2220)/I750, B=(I2850+I2220)/I2850, and A/B, of the Raman spectra of cells incubated with the MitoBADY is a specific marker indicating the induction of neutrophil differentiation of HL-60 cells. Flow cytometry, measuring the level of the expression of the CD11b surface protein, was used as a reference method. Raman measurements allowed the classification of neutrophil-like cells with a sensitivity of 79.8 % and a specificity of 79.5 %. These values demonstrate the great potential of the proposed methodology as a rapid and reliable technique for the evaluation of the differentiation of promyelocytic cells into neutrophils.

Vallaris solanacea induces mitochondrial mediated apoptosis in HL-60 human promyelocytic leukemia cells

In the present study, the apoptosis-inducing potential of a chloroform fraction from an alcoholic extract of Vallaris solanacea aerial parts (VS) was examined using human promyelocytic leukemia HL-60 cells. We discovered a concentration and time-dependent decrease in cell growth using MTT assay. Scanning electron micrographs and fluorescence microscopy were used to observe several well-documented morphological and nuclear alterations, such as reduction in cell size, chromatin condensation, fragmentation, and the creation of cell surface blebs. A considerable rise in the Sub-G0 population was revealed by cell cycle analysis. Additionally, a dose-dependent rise in cells positive for Annexin V was observed. DCFH-DA test on VS-treated HL-60 cells showed an increase in endogenous ROS generation of up to 4.3 fold. Additionally, suppression in Bcl-2 levels and increased mitochondrial membrane depolarization in treated cells were also associated with a rise in cytosolic cytochrome-c levels that was consequently followed by the activation of the caspase cascade. Further, the DNA fragmentation assay exhibited a typical ladder formation at 25 μg/ml, which became prominent in a concentration-dependent manner. Our study revealed that VS has apoptosis-inducing potential towards HL-60 cells in vitro and is an effective candidate for further anti-cancer studies.

Synthesis of New Chiral β-Carbonyl Selenides with Antioxidant and Anticancer Activity Evaluation-Part I.

A series of unsymmetrical phenyl β-carbonyl selenides with o-amido function substituted on the nitrogen atom with chiral alkyl groups was obtained. The compounds form a series of enantiomeric and diastereomeric pairs and present the first examples of this type of chiral Se derivatives. All obtained selenides were further evaluated as antioxidants and anticancer agents to define the influence of the particular stereochemistry of the attached functional groups on the bioactivity of the molecules. The highest H2O2 reduction potential was observed for N-(cis-2-hydroxy-1-indanyl)-2-((2-oxopropyl)selanyl)benzamide, and the best radical scavenging properties for N-(-1-hydroxy-2-butanyl)-2-((2-oxopropyl)selanyl)benzamide. Also, both enantiomers of the N-(1-hydroxy-2-butanyl) selenide expressed the highest cytotoxic potential towards human promyelocytic leukemia HL-60 cell line with similar IC50 values 14.4 ± 0.5 and 16.2 ± 1.1 µM, respectively. On the other hand, breast cancer cell line MCF-7 was most sensitive to N-((R)-(-)-1-hydroxy-2-butanyl)- 2-((2-oxopropyl)selanyl)benzamide (IC50 of 35.7 ± 0.6 µM). The structure-activity dependence of the obtained Se derivatives was discussed, and the most potent compounds were selected.

A novel aminopeptidase N/CD13 inhibitor selectively targets an endothelial form of CD13 after coupling to proteins

Aminopeptidase N/CD13, a membrane-bound enzyme upregulated in tumor vasculature and involved in angiogenesis, can be used as a receptor for the targeted delivery of drugs to tumors through ligand-directed targeting approaches. We describe a novel peptide ligand (VGCARRYCS, called “G4”) that recognizes CD13 with high affinity and selectivity. Enzymological and computational studies showed that G4 is a competitive inhibitor that binds to the catalytic pocket of CD13 through its N-terminal region. Fusing the peptide C-terminus to tumor necrosis factor-alpha (TNF) or coupling it to a biotin/avidin complex causes loss of binding and inhibitory activity against different forms of CD13, including natural or recombinant ectoenzyme and a membrane form expressed by HL60 promyelocytic leukemia cells (likely due to steric hindrance), but not binding to a membrane form of CD13 expressed by endothelial cells (ECs). Furthermore, G4-TNF systemically administered to tumor-bearing mice exerted anticancer effects through a CD13-targeting mechanism, indicating the presence of a CD13 form in tumor vessels with an accessible binding site. Biochemical studies showed that most CD13 molecules expressed on the surface of ECs are catalytically inactive. Other functional assays showed that these molecules can promote endothelial cell adhesion to plates coated with G4-avidin complexes, suggesting that the endothelial form of CD13 can exert catalytically independent biological functions. In conclusion, ECs express a catalytically inactive form of CD13 characterized by an accessible conformation that can be selectively targeted by G4-protein conjugates. This form of CD13 may represent a specific target receptor for ligand-directed targeted delivery of therapeutics to tumors.

Dimeric 3,5-Bis(benzylidene)-4-piperidones: Tumor-Selective Cytotoxicity and Structure-Activity Relationships.

Background: The objective of this study is to find novel antineoplastic agents that display greater toxicity to malignant cells than to neoplasms. In addition, the mechanisms of action of representative compounds are sought. This report describes the cytotoxicity of a number of dimers of 3,5-bis(benzylidene)-4-piperidones against human malignant cells (promyelocytic leukemia HL-60 and squamous cell carcinoma HSC-2, HSC-3, and HSC-4). Methods: Tumor specificity was evaluated by the selectivity index (SI), that is the ratio of the mean CC50 for human non-malignant oral cells (gingival fibroblasts, pulp cells, periodontal ligament fibroblasts) to that for malignant cells. Results: The compounds were highly toxic to human malignant cells. On the other hand, these molecules were less toxic to human non-malignant cells. In particular, a potent lead molecule, 3b, was identified. A QSAR study revealed that the placement of electron-releasing and hydrophilic substituents into the aryl rings led to increases in cytotoxic potencies. The modes of action of a lead compound discovered in this study designated 3b were the activation of caspases-3 and -7, as well as causing PARP1 cleavage and G2 arrest, followed by sub-G1 accumulation in the cell cycle. This compound also depolarized the mitochondrial membrane and generated reactive oxygen species in human colon carcinoma HCT116 cells. In conclusion, this study has revealed that, in general, the compounds described in this report are tumor-selective cytotoxins.

Neutrophil-Derived MicroRNA-1290 Promotes Keratinocyte Proliferation in Psoriasis

The pathological hallmark of psoriasis is the infiltration of neutrophils into the skin. Some neutrophil-derived microRNAs (miRNAs) serve as biomarkers for various diseases, but none have been reported for psoriasis. In this study, we investigated the involvement of miRNAs released from neutrophils in psoriasis pathogenesis. We compared the expression of miRNAs in the sera of patients with psoriasis with that in healthy individuals and found that the expression of 2 miRNAs-miR-223 and miR-1290-was significantly upregulated in the sera of patients with psoriasis. The serum levels of these miRNAs positively correlated with the PASI and CRP levels. We used all-trans retinoic acid to induce the differentiation of human promyelocytic leukemia HL-60 cells into neutrophil-like cells and found that the release of both miRNAs increased during differentiation. Furthermore, the release of miR-1290 was increased by TNF-α in neutrophil-like cells and human neutrophils. Treatment with the miR-1290 precursor promoted the proliferation of human keratinocytes, increased the proportion of S-phase cells, and upregulated the phosphorylation of extracellular signal-regulated kinase 1/2. These results suggest that miR-1290 plays a vital role in regulating neutrophil differentiation and keratinocyte proliferation and could be a serum marker of psoriasis severity.

A microRNA sponge, LINC02193, promotes neutrophil activation by upregulating ICAM1 and is correlated with ANCA-associated vasculitis.

To investigate the pathogenic role and underlying mechanisms of long noncoding RNAs (lncRNAs) in ANCA-associated vasculitis (AAV). RNA-sequencing (RNA-seq) was applied to screen the expression profile of lncRNAs in peripheral leukocytes from five AAV patients and five healthy controls (HC). Candidate lncRNAs were preliminarily verified in peripheral leukocytes from 46 AAV patients and 35 HC by qRT-PCR. Then, the identified LINC02193 was further validated in peripheral neutrophils from 67 AAV patients, 45 HC and 64 disease controls. Correlation between LINC02193 levels and disease activity was analysed. Then, a loss-of-function study was conducted to investigate the role of LINC02193 in neutrophils activation. Furthermore, bioinformatics analysis, dual luciferase reporter and RNA immunoprecipitation assays were performed to explore the mechanism of LINC02193 regulating neutrophils activation. A total of 467 upregulated and 412 downregulated lncRNAs were identified in AAV patients. From the top five upregulated lncRNAs, an elevation of LINC02193 was validated in a larger sample of AAV patients, and positively correlated with disease activity. Knockdown of LINC02193 inhibited reactive oxygen species and nitric oxide production, neutrophil extracellular traps release and adhesion to endothelial cells of differentiated human promyelocytic leukaemia HL-60 cells, whereas overexpression of ICAM1 counteracted these effects. Mechanistic analysis demonstrated that LINC02193 acted as an miR-485-5p sponge to relieve the repressive effect of miR-485-5p on ICAM1, thus promoting ICAM1 expression. LINC02193, a novel lncRNA identified in AAV, could function as competing endogenous RNAs for miR-485-5p to promote ICAM1 expression and neutrophils activation, suggesting its potential as a therapeutic target of AAV.

Unripe Rubus occidentalis, Ellagic Acid, and Urolithin A Attenuate Inflammatory Responses in IL-1β-Stimulated A549 Cells and PMA-Stimulated Differentiated HL-60 Cells.

Unripe Rubus occidentalis (uRO) contains various natural polyphenols with beneficial physiological activities and is particularly rich in ellagic acid (EA). EA has ameliorated type 2 inflammation and airway hyperresponsiveness in animal models of eosinophilic asthma. EA is metabolized by the gut microbiota to urolithin A (UA), which exhibits anti-inflammatory properties. However, it remains unclear whether uRO, EA, and UA reduce inflammatory responses and oxidative stress in respiratory epithelial cells and neutrophils. In this study, inflammation was induced in A549 (human lung epithelial cells) and dHL-60 cells (neutrophil-like cells differentiated from human promyelocytic leukemia HL-60 cells) and treated with various concentrations of water extract of uRO (uRO-w), EA, and UA. EA, uRO-w and UA suppressed the inflammatory cytokine and chemokine levels and reduced the expression of matrix metalloproteinase-9 in A549 cells stimulated with IL-1β. As a result of analyzing the mechanism by which these inflammatory molecules are expressed, it was found that EA, uRO-w, and UA regulated corticosteroid-sensitive mitogen activated protein kinase, nuclear factor κB, and corticosteroid-insensitive AKT. In addition, uRO-w, EA, and UA significantly reduced reactive oxygen species levels in phorbol 12-myristate 13-acetate-stimulated dHL-60 cells and inhibited neutrophil extracellular trap formation. Therefore, our results suggest that uRO-w, EA, and UA are potential therapeutic agents for preventing and treating inflammatory respiratory diseases.

Synthesis and Cytotoxicity Evaluation of Tyrosine-5 Fluorinated Analogues of RA-VII, An Antitumor Bicyclic Hexapeptide

AbstractRA-VII analogues fluorinated at each ε-position of Tyr-5 were designed. The synthesis of these peptide analogues commenced with the preparation of atropisomeric fluorocycloisodityrosines from protected 3-fluoro-L-tyrosyl-3-boronyl-L-tyrosine mediated by copper(II) acetate and 4-(dimethylamino)pyridine. After N-methylation, the tetrapeptide segment was coupled with the N-terminus of each fluorocycloisodityrosine to afford a hexapeptide. After removal of the C- and N-terminal protecting groups, each peptide was subjected to macrocyclization to produce an analogue. The analogue with a β-oriented fluorine atom was equipotent to RA-VII with regard to cytotoxicity toward human mammary carcinoma MCF-7 cells, and showed 2.1-fold and 1.4-fold lower cytotoxicities than RA-VII toward human promyelocytic leukemia HL-60 and human colorectal cancer HCT-116 cells, respectively, whereas the analogue with an α-oriented fluorine atom showed 7.7-fold, 6.0-fold, and 14-fold lower cytotoxicities than RA-VII toward those cells, respectively.

Cytotoxicity and Induction of G1 Phase Cell Cycle Arrest in human acute promyelocytic leukemia HL60 cells by indole alkaloids isolated from Dialium corbisieri seeds.

The phytochemical investigation of Dialium corbisieri seeds led to the isolation of five monoterpenoid indole alkaloids along with a phytoserotonin, 1-6 and among the known compounds, the spectroscopic data of (5S)-methoxy-akuammiline (1) was reported for the first time. The structures were elucidated based on NMR spectroscopic techniques such as UV, IR, HRESITOFMS, and ECD spectrum calculations. The isolated compounds were evaluated for their cytotoxicity and cell progression in the human acute promyelocytic leukemia HL60 cell line.

Comparison of Proanthocyanidin Content in Rabbiteye Blueberry (Vaccinium virgatum Aiton) Leaves and the Promotion of Apoptosis against HL-60 Promyelocytic Leukemia Cells Using ‘Kunisato 35 Gou’ Leaf Extract

Polyphenol-rich rabbiteye blueberry (Vaccinium virgatum Aiton) leaves have attracted attention as a food material. In this study, we compared the total polyphenols, total proanthocyanidin content, and antioxidant activity of the leaves of 18 blueberry varieties and investigated the seasonal variation in polyphenols. We also evaluated the anti-cancer cell proliferation properties of the rabbiteye blueberry leaf specific cultivar 'Kunisato 35 Gou'. Rabbiteye blueberry leaves had significantly higher total polyphenol and total proanthocyanidin values than northern highbush blueberry and southern highbush blueberry leaves. The antioxidant activity of blueberry leaves was highly positively correlated with both the total polyphenol and total proanthocyanidin content. Variations were observed in the total polyphenol and total proanthocyanidin content of rabbiteye blueberry leaves harvested at different points in the growing season; leaves collected in fall to winter contained more epicatechin in addition to proanthocyanidins. In the evaluation of anti-cancer cell proliferation properties against HL-60 promyelocytic leukemia cells, the September-harvested extracts of rabbiteye blueberry 'Kunisato 35 Gou' showed strong properties, and the use of an FITC Annexin V apoptosis detection kit with propidium iodide confirmed that this HL-60 cell death occurred via apoptosis. Limiting the harvest time would make rabbiteye blueberry leaves a more functional food ingredient.

Synthesis of 1-O-acyl- and 1-oxo-kamebanin analogues and their cytotoxic activity

A series of 1-O-acyl- and 1-oxo-kamebanin analogues were prepared from kamebanin, isolated from Rabdosia excisa and their cytotoxicity was assayed on HL60 promyelocytic leukemia cells and HCT116 human colon cancer cells. The structure–activity relationship study showed that the presence of 1-O-acyl groups of a C3–C5 carbon chain increased the cytotoxic activity.

Bridged Peptide Analogue of RA-VII, an Antitumor Bicyclic Hexapeptide

AbstractA bridged peptide analogue of RA-VII was designed, in which the α carbons of residues 1 and 4 were linked by a tetramethylene chain to restrict the conformational freedom of the backbone of the 18-membered cyclopeptide. This peptide analogue was synthesized by a ring-closing metathesis reaction of [l-2-allylglycine-1, l-2-allylglycine-4]RA-VII and a subsequent hydrogenation of the resulting olefinic compound. Compared with RA-VII, the analogue showed much weaker cytotoxic activity toward human promyelocytic leukemia HL-60 cells and human colon carcinoma HCT-116 cells, which may be accounted for by the difference in the orientation of the Tyr-6 phenyl ring plane between the analogue and RA-VII.

CDDO Induces Differentiation through PTEN Expression in HL-60 Cells

Acute promyelocytic leukemia (APL) represents a group of haematological malignancies characterized by blocked differentiation. Cell differentiation has been as a strong target of treatment of APL. Peroxisome proliferator-activated receptors gamma (PPAR-γ) play an important role in the differentiation of APL cell lines. Previous study has shown that PPAR-γ ligands induce neutrophil/ monocytic differentiation in human acute promyelocytic leukemia HL-60 cells. It has recently been shown that the novel synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) induces differentiation in leukemia HL-60 cells. In this study we established a CDDO-induced differentiation model for the treatment of APL. We evaluated for the surface antigen expression associated with myeloid maturation, CD11b and CD14 by flow cytometric analysis and RT-PCR. We demonstrated that CD11b and CD14 increased as CDDO -induced differentiation. In addition, CDDO induced a HL-60 differentiation through the regulation of PTEN expression. PTEN also has various cellular function such as cell differentiation. PPAR-γ could synergistically up-regulate PTEN in human leukemia cells and consequently stimulate the differentiation of these cells We confirmed that suppression of PTEN with the inhibitor (SF1760) caused reduction of differentiated HL-60 cells. Our results suggest PPAR-γ an important role in controlling the differentiation of leukemia cells via the regulation of PTEN. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Low NETosis Induced in Anaplasma phagocytophilum-Infected Cells

Anaplasma phagocytophilum are obligatory intracellular bacteria that preferentially replicate inside leukocytes by utilizing biological compounds and processes of these primary host defensive cells. In this study, bioinformatics analysis was conducted to further characterize A. phagocytophilum–host interactions using the neutrophil-like model of human Caucasian promyelocytic leukemia HL60 cells. We detected a hierarchy of molecules involved in A. phagocytophilum-HL60 interactions with overrepresentation in infected human cells of proteins involved in the reactive oxygen species (ROS) pathway and cell surface monocyte markers. As A. phagocytophilum phagocytosis by neutrophils is inhibited, the results suggested a possible explanation for our bioinformatics data: radical oxygen compounds could induce the killing of bacteria activating NETosis, a unique form of defense mechanism resulting in cell death that is characterized by the release of decondensed chromatin and granular contents to the extracellular space, forming neutrophil extracellular traps (NETs) to eliminate invading microorganisms. Thus, we confirmed the existence of a low NETosis induced in A. phagocytophilum-infected cells by immunofluorescence (IF) experiments. These results provide new insights into the complex mechanisms that govern immune response during A. phagocytophilum host interactions.

EGCG Prevents the Transcriptional Reprogramming of an Inflammatory and Immune-Suppressive Molecular Signature in Macrophage-like Differentiated Human HL60 Promyelocytic Leukemia Cells.

Simple SummaryScientists are increasingly harnessing the power of the immune system to prevent cancer. While macrophages are a major component of the tumor microenvironment where they orchestrate various aspects of immunity, dysregulated immune and inflammatory responses will play a key role in cancer initiation and progression. Depending on their activation status, macrophages can have a dual impact on tumorigenesis by either antagonising cytotoxic immune cells or enhancing antitumor responses. Increased infiltration of tumor-associated macrophages has long been associated with poor patient prognosis in most solid cancers, highlighting their value as potential diagnostic and prognostic biomarkers in cancer. A variety of macrophage-centered approaches to cancer therapy have been investigated, including strategies to prevent tumor-promoting activities. In this study, we highlight the chemopreventive properties of EGCG derived from green tea that underpin its ability to re-program macrophage molecular signature and function.Background: The promyelocytic leukemia cell differentiation process enables recapitulation of the polarized M1 or M2 macrophage-like phenotype with inflammatory and immune-suppressive properties. While evidence supports the anti-inflammatory effect of dietary-derived epigallocatechin-3-gallate (EGCG), its impact on the onset of immune phenotype molecular signature remains unclear. Methods: Human HL60 promyelocytic cells grown in suspension were differentiated into CD11bHigh/CD14Low adherent macrophages with phorbol 12-myristate 13-acetate (PMA). Gelatin zymography was used to assess the levels of matrix metalloproteinase (MMP)-9, and total RNA was isolated for RNAseq and RT-qPCR assessment of differentially expressed gene levels involved in inflammation and immunity. Protein lysates were used to assess the phosphorylation status of signaling intermediates involved in macrophage-like cell differentiation. Results: Cell adhesion and induction of MMP-9 were indicative of HL60 cell differentiation into a macrophage-like phenotype. The extracellular signal-regulated kinase (ERK), glycogen synthase kinase (GSK)-3, p90 ribosomal S6 kinases (RSK), and cAMP-response-element-binding protein (CREB) were all phosphorylated, and EGCG reduced such phosphorylation status. Increases in inflammation and immunity genes included, among others, CCL22, CSF1, CSF2, IL1B, and TNF, which inductions were prevented by EGCG. This was corroborated by unbiased transcriptomic analysis which further highlighted the capacity of EGCG to downregulate the hematopoietic stem cell regulator CBFA2T3. Conclusion: EGCG inhibits inflammatory signaling crosstalk and prevents the onset of an immune phenotype in macrophage-like differentiated cells.