Human Leukemia Cell Line HL-60 Research Articles

Myeloid differentiation and retinoblastoma phosphorylation changes in HL-60 cells induced by retinoic acid receptor- and retinoid X receptor- selective retinoic acid analogs

The ability of subtypes of retinoic acid receptors (RARs) and retinoid X receptors (RXRs) singly and in combination to elicit myeloid differentiation, G1/0-specific growth arrest, and retinoblastoma (RB) tumor suppressor protein dephosphorylation was determined in the human myeloblastic leukemia cell line HL-60 using subtype-selective retinoic acid (RA) analogs. RA analogs that selectively bind only to RARs (Am580 and/or TTNPB) or to RXRs (Ro 25-6603, SR11237, and/or SR11234) did not elicit the above-mentioned three cellular responses. In contrast, simultaneous treatment with both an RAR-selective ligand (Am580 or TTNPB) and an RXR-selective ligand (Ro 25-6603, SR11237, or SR11234) induced all three cellular processes. An RAR alpha-selective ligand used with an RXR-selective ligand generated the same responses as did all-trans RA or 9-cis RA, which affect both families of receptors, suggesting an important role for RAR alpha among RAR subtypes in eliciting cellular response. Consistent with this finding, the RAR alpha antagonist, Ro 41-5253, reduced the level of the cellular responses elicited by treatment with an RAR alpha-selective ligand plus RXR-selective ligand. The coupling of the shift of RB to its hypophosphorylated form with G1/0 arrest and differentiation in response to ligands is consistent with a possible role of RB as a downstream target or effector of RAR alpha and RXR in combination.

Withanolide-Type Steroids from Withania aristata as Potential Anti-Leukemic Agents.

Leukemia is a blood or bone marrow cancer with increasing incidence in developed regions of the world. Currently, there is an ongoing need for novel and safe anti-leukemic agents, as no fully effective chemotherapy is available to treat this life-threatening disease. Herein, are reported the isolation, structural elucidation, and anti-leukemic evaluation of twenty-nine withanolide-type steroids (1–29) from Withania aristata. Among them, the new isolated withanolides, withaperoxidins A–D (1–4) have an unusual six-membered cyclic peroxide moiety on the withasteroid skeleton as a structural novelty. Their structures have been elucidated by means of spectroscopic analyses, including 2D NMR experiments. In addition, extensive structure–activity relationships and in silico ADME studies were employed to understand the pharmacophore and pharmacokinetic properties of this series of withasteroids. Compounds 15, 16, and 22 together with withaferin A (14) were identified as having improved antiproliferative effect (IC50 ranging from 0.2 to 0.7 μM) on human leukemia HL-60 cell lines compared with the reference drug, etoposide. This cytotoxic potency was also coupled with good selectivity index (SI 33.0–9.2) on non-tumoral Vero cell line and in silico drug likeness. These findings revealed that these natural withasteroids are potential candidates as chemotherapeutic agents in the treatment of leukemia.

Effects and Mechanism of PARP Inhibitor Olaparib on the Expression of NKG2D Ligands in HL-60 Cells

To investigate the regulatory effects of Olaparib on natural killer cell activating receptor (NKG2D) ligands expression on human acute myeloid leukemia (AML) cell line HL-60, and to explore the molecular mechanism of Olaparib on HL-60 cells. After HL-60 cells in logarithmic growth phase were treated with Olaparib at different concentrations for different times (24, 48 h), the expression of NKG2D ligand on the surface of HL-60 cells was detected by flow cytometry. Western blot was used to dectect the expression of ERK expression in HL-60 cells. The killing effect of NK cells to HL-60 cells was detected by CFSE/PI method. 10 μmol/L Olaparib could upregulate the expression of NKG2D ligand on the surface of HL-60 cell at 24 and 48 hours, while 5 μmol/L Olaparib could induce up-regulation of the expression of ULBP-2 and ULBP-3 at 48 hours. Western blot analysis showed that ERK phosphorylation of HL-60 cells was enhanced after treating with Olaparib. The killing effect of NK cells to HL-60 cells could be enhanced by Olaparib, however, ERK inhibitor could suppress the killing effect of NK cells to HL-60 cells. Olaparib can upregulate NKG2D ligands expression on the surface of HL-60 cells and enhance the cytotoxicity of NK cell to HL-60 cells. The mechanism may be related to Olaparib promoting ERK phosphorylation expression.

Azodyrecins A-C: Azoxides from a Soil-Derived Streptomyces Species.

Azoxy compounds belong to a small group of natural products sharing a common functional group with the general structure RN = N+(O-)R. Three new azoxides, azodyrecins A-C (1-3), were isolated from a soil-derived Streptomyces sp. strain P8-A2. The cis-alkenyl unit in 1-3 was found to readily isomerize to the trans-congeners (4-6). The structures of the new compounds were determined by detailed spectroscopic (1D/2D NMR) and HRMS data analysis. Azodyrecins belong to a new class of natural azoxy compounds and are proposed to derive from l-alanine and alkylamines. The absolute configurations of 1-6 were defined by comparison of ECD spectra. While no antimicrobial effects were observed for 1 against Staphylococcus aureus, Vibrio anguillarum, or Candida albicans, azodyrecin B (2) exhibited cytotoxicity against the human leukemia cell line HL-60 with an IC50 value of 2.2 μM.

First identification of Anaplasma phagocytophilum in both a biting tick Ixodes nipponensis and a patient in Korea: a case report

BackgroundHuman granulocytic anaplasmosis (HGA) is a tick-borne infectious disease caused by Anaplasma phagocytophilum. To date, there have been no reported cases of A. phagocytophilum infection found in both the biting tick and the patient following a tick bite.Case presentationAn 81-year-old woman presented with fever following a tick bite, with the tick still intact on her body. The patient was diagnosed with HGA. The tick was identified as Ixodes nipponensis by morphological and molecular biological detection methods targeting the 16S rRNA gene. The patient’s blood was cultured after inoculation into the human promyelocytic leukemia cell line HL-60. A. phagocytophilum growth was confirmed via culture and isolation. A. phagocytophilum was identified in both the tick and the patient’s blood by Anaplasma-specific groEL- and ankA-based nested polymerase chain reaction followed by sequencing. Moreover, a four-fold elevation in antibodies was observed in the patient’s blood.ConclusionWe report a case of a patient diagnosed with HGA following admission for fever due to a tick bite. A. phagocytophilum was identified in both the tick and the patient, and A. phagocytophilum was successfully cultured. The present study suggests the need to investigate the possible incrimination of I. nipponensis as a vector for HGA in Korea.

Potentiation of Differentiation and Apoptosis in a Human Promyelocytic Leukemia Cell Line by Garlic Essential Oil and Its Organosulfur Compounds.

The clinical course of acute leukemia is complicated, and it is often necessary to combine or change treatment methods due to the rapid increase and spread of malignant cells. In this study, the potential anti-leukemia activities of prepared garlic essential oil (GEO) and some organosulfur compounds contained therein were examined. Garlic essential oil component identification by gas chromatography-mass spectrometry (GC-MS). MTT assay evaluated cytotoxicity of tested samples. Leukemia cell differentiation was determined by NBT assay. Apoptosis and related mechanisms were investigated by western blotting. GC-MS analysis confirmed that the two most abundant constituents, diallyl disulfide (DADS) and diallyl trisulfide (DATriS), constituted 80% of the composition. GEO and DADS exhibited the best effects in terms of significant production of intracellular reactive oxygen species (ROS), induction apoptosis and potentiation differentiation of human promyelocytic leukemia cell line HL-60 cells. The GEO-mediated apoptosis was alleviated by the free radical scavenger N-acetyl-L-cysteine (NAC). The anti-leukemia activity of GEO and organosulfur compound DADS through the action of ROS elevation was herein confirmed.

An Evaluation of the Activity of Histidine-Rich Glycoprotein on Differentiated Neutrophil-Like Cells from Human Cell Lines.

Histidine-rich glycoprotein (HRG) treatment ameliorated the survival rate of septic mice by suppressing excess immunothrombus formation. Although such findings suggested that HRG may be one of the most useful drugs for sepsis, obtaining a stable experimental system to standardize the HRG drug product is difficult to achieve using neutrophils isolated from volunteers. This is due to the short survival time and individual differences of human neutrophils. In the present study, we determined whether the differentiated neutrophil-like cell lines exhibited similar responses to HRG compared with human purified neutrophils. All-trans retinoic acid (ATRA) was employed to induce the differentiation of the human myeloid leukemia cell lines HL-60 and NB-4. Thereafter, the cells were treated with Hank's balanced salt solution, human serum albumin, or HRG. The effects of HRG on these cells were evaluated according to cell shape, microcapillary passage, reactive oxygen species (ROS) production, neutrophil extracellular traps (NETs) formation, the expression of activated CD11b, and cell viability. HRG maintained the round shape of differentiated neutrophil-like cells, decreased the time required by cells to pass through the microcapillaries, and inhibited ROS production, NETs formation, and the expression of activated CD11b on the cell surface. Moreover, the cells could survive longer in the presence of HRG than the control. The ATRA-induced differentiated cell lines could be used as alternatives to neutrophils to investigate the effects of HRG on neutrophils. This method can thus be used as an essential standardization test in pharmaceutical development. SIGNIFICANCE STATEMENT: Human neutrophils exhibit varying responses to histidine-rich glycoprotein (HRG); however, all-trans retinoic acid-induced differentiated neutrophil-like cell lines can be used as reliably proxies to investigate the effects of HRG on neutrophils. Additionally, these cell lines can be employed in the development of therapies for the treatment of sepsis.

Synthesis and structure of a new thiazoline-based palladium(II) complex that promotes cytotoxicity and apoptosis of human promyelocytic leukemia HL-60 cells

Cisplatin is one of the most widely used chemotherapeutic agents in the treatment of different tumors but has high toxicity and side effects. Therefore, the synthesis of new chemotherapeutic agents is necessary, so that they are effective in the treatment of cancer while avoiding such toxicity. In this study, we have synthesized and characterized a palladium(II) complex, [PdCl2(µ-PyTT)2]Cl2·4H2O (PdPyTT), with 2-(2-pyridyl)imine-N-(2-thiazolin-2-yl)thiazolidine (PyTT) as a ligand; besides, its cytotoxicity and pro-apoptotic capacity was tested in human promyelocytic leukemia HL-60 cell line. Similar to cisplatin, PdPyTT produced a time- and dose-dependent decrease in cell viability. Additionally, the palladium complex increased both the proportion of cells with apoptotic morphology and the activation of caspase-3 and -9. PdPyTT, like cisplatin, also increased intracellular ROS production and DNA oxidative damage. Therefore, our findings demonstrated the promising application of palladium(II) complexes as novel anti-leukemic agents.

Axolotl Ambystoma mexicanum extract induces cell cycle arrest and differentiation in human acute myeloid leukemia HL-60 cells.

Acute myeloid leukemia is the most common form of acute leukemia in adults, constituting about 80% of cases. Although remarkable progress has been made in the therapeutic scenario for patients with acute myeloid leukemia, research and development of new and effective anticancer agents to improve patient outcome and minimize toxicity is needed. In this study, the antitumor activity of axolotl (AXO) Ambystoma mexicanum crude extract was assessed in vitro on the human acute myeloid leukemia HL-60 cell line. The anticancer activity was evaluated in terms of ability to influence proliferative activity, cell viability, cell cycle arrest, and differentiation. Moreover, gene expression analysis was performed to evaluate the genes involved in the regulation of these processes. The AXO crude extract exhibited antiproliferative but not cytotoxic activities on HL-60 cells, with cell cycle arrest in the G0/G1 phase. Furthermore, the AXO-treated HL-60 cells showed an increase in both the percentage of nitroblue tetrazolium positive cells and the expression of CD11b, whereas the proportion of CD14-positive cells did not change, suggesting that extract is able to induce differentiation toward the granulocytic lineage. Finally, the treatment with AXO extract caused upregulation of CEBPA, CEBPB, CEBPE, SPI1, CDKN1A, and CDKN2C, and downregulation of c-MYC. Our data clearly show the potential anticancer activity of Ambystoma mexicanum on HL-60 cells and suggest that it could help develop promising therapeutic agents for the treatment of acute myeloid leukemia.

Cytotoxicity of the Sesquiterpene Lactone Spiciformin and Its Acetyl Derivative against the Human Leukemia Cell Lines U-937 and HL-60.

Spiciformin (1) is a sesquiterpene lactone with a germacrane skeleton that is found in two Tanacetum species endemic to the Canary Islands. In this study, the cytotoxicities of 1 and its acetyl derivative (2) were evaluated against human tumor cells. These sesquiterpene lactones were cytotoxic against human acute myeloid leukemia (U-937 and HL-60) cells, even in cells over-expressing the pro-survival protein Bcl-2, but melanoma (SK-MEL-1) and human mononuclear cells isolated from blood of healthy donors were more resistant. Both compounds are apoptotic inducers in human leukemia U-937 cells. Cell death was mediated by the processing and activation of initiator and effector caspases and the cleavage of poly(ADP-ribose) polymerase, and it was blocked by a broad-spectrum caspase inhibitor and (in the case of sesquiterpene lactone 2) by the selective caspase-3/7, -8, and -9 inhibitors. In addition, certainly in the case of compound 2, this was found to be associated with a decrease in mitochondrial membrane potential, downregulation of the anti-apoptotic protein Bcl-2, activation of the mitogen-activated protein kinases signaling pathway, and generation of reactive oxygen species. It will, therefore, be relevant to continue characterization of this class of compounds.

A New Hybrid δ-Lactone Induces Apoptosis and Potentiates Anticancer Activity of Taxol in HL-60 Human Leukemia Cells.

In the search for new drug candidates, researchers turn to natural substances isolated from plants which may be either used directly or may serve as a source for chemical modifications. An interesting strategy in the design of novel anticancer agents is based on the conjugation of two or more biologically active structural motifs into one hybrid compound. In this study, we investigated the anticancer potential of 4-benzyl-5,7-dimethoxy-4-methyl-3-methylidene-3,4-dihydro-2H-chroman-2-one (DL-247), a new hybrid molecule combining a chroman-2-one skeleton with an exo-methylidene bond conjugated with a carbonyl group, in human myeloid leukemia HL-60 cell line. The cytotoxicity of the new compound was tested using MTT assay. The effect of DL-247 on cell proliferation and apoptosis induction were studied by flow cytometry, fluorometric assay and ELISA analysis. DL-247 displayed high cytotoxic activity (IC50 = 1.15 µM, after 24 h incubation), significantly inhibited cell proliferation and induced apoptosis by both, the intrinsic and extrinsic pathways. A combination of DL-247 with taxol exhibited a strong synergistic effect on DNA damage generation, apoptosis induction and inhibition of cell growth.

Triterpenes from Poria cocos are revealed as potential retinoid X receptor selective agonists based on cell and in silico evidence.

Poria cocos is an edible and medicinal fungus that is widely used in Traditional Chinese Medicines as well as in modern applications. Retinoid X receptor (RXR) occupies a central place in nuclear receptor signaling, and a pharmacological RXR-dependent pathway is involved in myeloid cell function. Here, structural information for 82 triterpenes from P.cocos and 17 known RXR agonists was collected in a compound library and retrieved for a molecular docking study. Three triterpenes, 16α-hydroxytrametenolic acid (HTA), pachymic acid (PA), and polyporenic acid C (PPAC), were identified as novel RXR-specific agonists based on luciferase reporter assays and in silico evidence. Treatment with HTA, PA, and PPAC significantly induced differentiation of the human promyelocytic leukemia cell line HL-60 with EC50 values of 21.0±0.52, 6.7±0.37, and 9.4±0.65μM, respectively. These effects were partly blocked by the RXR antagonist UVI3003, suggesting that an RXR-dependent pathway may play an important role in their anti-acute promyelocytic leukemia (APL) effects. Taken together, triterpenes from P.cocos are revealed as naturally occurring RXR selective agonists with the potential for anti-cancer activity. These results suggest a novel approach to the treatment or prevention of APL.

The Contribution of IgG Glycosylation to Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) and Complement-Dependent Cytotoxicity (CDC) in Hashimoto's Thyroiditis: An in Vitro Model of Thyroid Autoimmunity.

Antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) are involved in destruction of thyroid tissue in Hashimoto’s thyroiditis (HT). N-glycosylation of the Fc fragment affects the effector functions of IgG by enhancing or suppressing the cytotoxicity effect. The aim of the present study was to assess the impact of HT-specific IgG glycosylation in ADCC and CDC, using in vitro models. The normal thyroid Nthy-ori 3-1 cell line and thyroid carcinoma FTC-133 cells were used as the target cells. Peripheral blood mononuclear cells (PBMCs) from healthy donors and the HL-60 human promyelotic leukemia cell line served as the effector cells. IgG was isolated from sera of HT and healthy donors and then treated with α2-3,6,8-neuraminidase to cut off sialic acids (SA) from N-glycans. We observed more intensive cytotoxicity in the presence of IgG from HT patients than in the presence of IgG from healthy donors. Removal of SA from IgG N-glycans increased ADCC intensity and reduced CDC. We conclude that the enhanced thyrocyte lysis resulted from the higher anti-TPO content in the whole IgG pool of HT donors and from altered IgG glycosylation in HT autoimmunity.

Whole-genome fingerprint of the DNA methylome during chemically induced differentiation of the human AML cell line HL-60/S4.

ABSTRACTEpigenomic regulation plays a vital role in cell differentiation. The leukemic HL-60/S4 [human myeloid leukemic cell line HL-60/S4 (ATCC CRL-3306)] promyelocytic cell can be easily differentiated from its undifferentiated promyelocyte state into neutrophil- and macrophage-like cell states. In this study, we present the underlying genome and epigenome architecture of HL-60/S4 through its differentiation. We performed whole-genome bisulphite sequencing of HL-60/S4 cells and their differentiated counterparts. With the support of karyotyping, we show that HL-60/S4 maintains a stable genome throughout differentiation. Analysis of differential Cytosine-phosphate-Guanine dinucleotide methylation reveals that most methylation changes occur in the macrophage-like state. Differential methylation of promoters was associated with immune-related terms. Key immune genes, CEBPA, GFI1, MAFB and GATA1 showed differential expression and methylation. However, we observed the strongest enrichment of methylation changes in enhancers and CTCF binding sites, implying that methylation plays a major role in large-scale transcriptional reprogramming and chromatin reorganisation during differentiation. Correlation of differential expression and distal methylation with support from chromatin capture experiments allowed us to identify putative proximal and long-range enhancers for a number of immune cell differentiation genes, including CEBPA and CCNF. Integrating expression data, we present a model of HL-60/S4 differentiation in relation to the wider scope of myeloid differentiation.

Toxicity and Antitumor Activity of a Thiophene-Acridine Hybrid.

The antitumor effects of thiophene and acridine compounds have been described; however, the clinical usefulness of these compounds is limited due to the risk of high toxicity and drug resistance. The strategy of molecular hybridization presents the opportunity to develop new drugs which may display better target affinity and less serious side effects. Herein, 2-((6-Chloro-2-methoxy-acridin-9-yl)amino)-5,6,7,8-tetrahydro-4H-cyclohepta[b]-thiophene-3-carbonitrile (ACS03), a hybrid thiophene–acridine compound with antileishmanial activity, was tested for toxicity and antitumor activity. The toxicity was evaluated in vitro (on HaCat and peripheral blood mononuclear cells) and in vivo (zebrafish embryos and acute toxicity in mice). Antitumor activity was also assessed in vitro in HCT-116 (human colon carcinoma cell line), K562 (chronic myeloid leukemic cell line), HL-60 (human promyelocytic leukemia cell line), HeLa (human cervical cancer cell line), and MCF-7 (breast cancer cell line) and in vivo (Ehrlich ascites carcinoma model). ACS03 exhibited selectivity toward HCT-116 cells (Half maximal inhibitory concentration, IC50 = 23.11 ± 1.03 µM). In zebrafish embryos, ACS03 induced an increase in lactate dehydrogenase, glutathione S-transferase, and acetylcholinesterase activities. The LD50 (lethal dose 50%) value in mice was estimated to be higher than 5000 mg/kg (intraperitoneally). In vivo, ACS03 (12.5 mg/kg) induced a significant reduction in tumor volume and cell viability. In vivo antitumor activity was associated with the nitric oxide cytotoxic effect. In conclusion, significant antitumor activity and weak toxicity were recorded for this hybrid compound, characterizing it as a potential anticancer compound.

New uracil analogs as downregulators of ABC transporters in 5-fluorouracil-resistant human leukemia HL-60 cell line

Overexpression of ATP-binding cassette (ABC) transporters causing multidrug resistance (MDR) in cancer cells is one of the major obstacles in cancer chemotherapy. The 5-FU resistant subclone (HL-60/5FU) of the human HL-60 promyelocytic leukemia cell line was selected by the conventional method of continuous exposure of the cells to the drug up to 0.08 mmol/L concentration. HL-60/5FU cells exhibited six-fold enhanced resistance to 5-FU than HL-60 cells. RT-PCR and ELISA assay showed significant overexpression of MDR-related ABC transporters, ABCB1, ABCG2 but especially ABCC1 in the HL-60/5FU as compared with the parental cell line. Three novel synthetic 5-methylidenedihydrouracil analogs, U-236, U-332 and U-359, selected as highly cytotoxic for HL-60 cells in MTT test, showed similar cytotoxicity in the resistant cell line. When co-incubated with 5-FU, these analogs were found to down-regulate the expression of all three transporters. However, the most pronounced effect was caused by U-332 which almost completely abolished ABCC1 expression in the resistant HL-60/5FU cells. Additionally, U-332 inhibited the activity of ATPase, an enzyme which catalyzes hydrolysis of ATP, providing energy to efflux drugs from the cells through the cellular membranes. Taken together, the obtained data suggest that acquired 5-FU resistance in HL-60/5FU cells results from overexpression of ABCC1 and that targeting ABCC1 expression could be a potential approach to re-sensitize resistant leukemia cells to 5-FU. The synthetic uracil analog U-332, which can potently down-regulate ABC transporter expression and therefore disturb drug efflux, can be considered an efficient ABCC1 regulator in cancer cells.

Cytotoxicity against HL60 Cells of Ficifolidione Derivatives with Methyl, n-Pentyl, and n-Heptyl Groups.

Ficifolidione, a natural insecticidal compound isolated from the essential oils of Myetaceae species, is a spiro phloroglucinol with an isobutyl group at the C-4 position. We found that ficifolidione showed cytotoxicity against cancer cells via apoptosis. Replacement of the isobutyl group by n-propyl group did not influence the potency, but the effect of the replacement of this group by a shorter or longer alkyl group on the biological activity remains unknown. In this study, ficifolidione derivatives with alkyl groups such as methyl, n-pentyl, and n-heptyl group—instead of the isobutyl group at the C-4 position—were synthesized to evaluate their cytotoxicity against the human promyelocytic leukaemia cell line HL60 and their insecticidal activity against mosquito larvae. The biological activities of their corresponding 4-epimers were also evaluated. As a result, the conversion of the isobutyl group to another alkyl group did not significantly influence the cytotoxicity or insecticidal activity. In HL60 cells treated with the n-heptyl-ficifolidione derivative, the activation of caspase 3/7 and the early stages of apoptosis were detected by using immunofluorescence and flow cytometric techniques, respectively, suggesting that the cytotoxicity should be induced by apoptosis even though the alkyl group was changed.

Bioselectivity Induced by Chirality of New Terpenyl Organoselenium Compounds.

A series of new chiral benzisoselenazol-3(2H)-ones substituted on the nitrogen atom with three monoterpene moieties—p-menthane, pinane and carane—was synthesized. The compounds were obtained by the reaction of 2-(chloroseleno)benzoyl chloride with an appropriate terpene amine, first synthesized by a multistep methodology starting from the corresponding alcohol (p-menthane system) or alkene (pinene and carene systems). Compounds were tested as antioxidants and anticancer agents. The N-isopinocampheyl-1,2-benzisoselenazol-3(2H)-one was the best peroxide scavenger and antiproliferative agent on the human promyelocytic leukemia cell line HL-60. The N-menthyl-1,2-benzisoselenazol-3(2H)-one revealed the highest anticancer potential towards breast cancer line MCF-7. The influence of structure and chirality on the bio-activity of the obtained organoselenium compounds was thoroughly evaluated.

Tris-heteroleptic ruthenium(II) polypyridyl complexes: Synthesis, structural characterization, photophysical, electrochemistry and biological properties

Three water-soluble tris-heteroleptic ruthenium(II) polypyridyl complexes [Ru(bpy)(phen)(bpg)]2+ (1), [Ru(bpy)(dppz)(bpg)]2+ (2), and [Ru(phen)(dppz)(bpg)]2+ (3) (where bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, dppz = dipyrido[3,2-a:2′,3′-c] phenazine, bpg = 4b,5,7,7a-tetrahydro-4b,7a-epiminomethanoimino-6H-imidazo[4,5-f] [1,10] phenanthroline-6,13-dione) have been synthesized and characterized. Molecular structures of complexes 1 and 3 are confirmed by single crystal X-ray structure determination. Interaction of complexes 1–3 with DNA is explored by various spectroscopic techniques. The complexes 1–3 show solvent dependent photophysical properties. Complexes 2 and 3 show extensive “molecular light switch” effect for DNA. The complexes 1–3 are low toxic towards HeLa (human cervical cancer) and HL-60 (human promyelocytic leukemia) cell lines. Further, the cellular uptake of complexes 2 and 3 by cells shows that complexes mainly localised on the nucleus of the cells.

An acute lytic cell death induced by xanthohumol obstructed ROS detecting in HL-60 cells

Serum is an important component in cell culture medium. It also possesses potent antioxidant properties. Therefore, the conventional protocols for detecting reactive oxygen species (ROS) in cultured cells with fluorescent probes include washing and suspending cells with serum-free buffers, such as PBS. This transient serum deprivation is essential for the ROS detecting. Unfortunately, it may also cause unexpected results, which push us to choose more optimal experiment conditions. In the present study, we found an acute lytic cell death induced by xanthohumol (XN), which obstructed ROS detecting in human leukemia cell line HL-60 cells. XN induced ROS burst, caused cell swelling, membrane permeability increase, LDH release, and ultimately an acute lytic cell death and cell rupture. These effects could be alleviated by the antioxidant N-Acetyl-L-cysteine (NAC). Apoptosis, pyroptosis or necroptosis were not observed in this process. Results also indicated that 2% serum addition had already completely scavenged ROS induced by 10 μM XN. Taken together, it is strongly suggested to detecting ROS in a serum-free medium when studying where and how ROS generated in cells. The concentration at the ROS maximum point (10 μM XN in this study) can be selected as the optimal concentration.