Characterization of a fluorescent 1,8-naphthalimide-functionalized PAMAM dendrimer and its Cu(ii) complexes as cytotoxic drugs: EPR and biological studies in myeloid tumor cells

The activity and interacting ability of a polyamidoamine (PAMAM) dendrimer modified with 4-N-methylpiperazine-1,8-naphthalimide units (termed D) and complexed by Cu(ii) ions, towards healthy and cancer cells were studied. Comparative electron paramagnetic resonance (EPR) studies of the Cu(ii)-D complex are presented: coordination mode, chemical structure, flexibility and stability of these complexes, in the absence and presence of myeloid cancer cells and peripheral blood mononuclear cells (PBMC). The interactions of Cu(ii) ions in the biological media at different equilibrium times were studied, highlighting different stability and interacting conditions with the cells. Furthermore, flow cytometry and confocal analysis, trace the peculiar properties of the dendrimers in PBMC and U937 cells. Indeed, a new probe (Fly) was used as a potential fluorescent tool for biological imaging of Cu(ii). The study highlights that dendrimer and, mainly, the Cu(ii) metallodendrimer are cytotoxic agents for the cells, specifically for U937 tumor cells, inducing mitochondrial dysfunction, ROS increase and lysosome involvement. The metallodendrimer shows antitumor selectivity, fewer affecting healthy PBMC, inducing a massive apoptotic cell death on U937 cells, in line with the high stability of this complex, as verified by EPR studies. The results underline the potentiality of this metallodendrimer to be used as anticancer drug.

N-acetylcysteine Can Induce Massive Oxidative Stress, Resulting in Cell Death with Apoptotic Features in Human Leukemia Cells

N-acetylcysteine (NAC), often used as an antioxidant-scavenging reactive oxygen species (ROS) in vitro, was recently shown to increase the cytotoxicity of other compounds through ROS-dependent and ROS-independent mechanisms. In this study, NAC itself was found to induce extensive ROS production in human leukemia HL-60 and U937 cells. The cytotoxicity depends on ROS-modulating enzyme expression. In HL-60 cells, NAC activated NOX2 to produce superoxide (O2•−). Its subsequent conversion into H2O2 by superoxide dismutase 1 and 3 (SOD1, SOD3) and production of ClO− from H2O2 by myeloperoxidase (MPO) was necessary for cell death induction. While the addition of extracellular SOD potentiated NAC-induced cell death, extracellular catalase (CAT) prevented cell death in HL-60 cells. The MPO inhibitor partially reduced the number of dying HL-60 cells. In U937 cells, the weak cytotoxicity of NAC is probably caused by lower expression of NOX2, SOD1, SOD3, and by the absence of MOP expression. However, even here, the addition of extracellular SOD induced cell death in U937 cells, and this effect could be reversed by extracellular CAT. NAC-induced cell death exhibited predominantly apoptotic features in both cell lines. Conclusions: NAC itself can induce extensive production of O2•− in HL-60 and U937 cell lines. The fate of the cells then depends on the expression of enzymes that control the formation and conversion of ROS: NOX, SOD, and MPO. The mode of cell death in response to NAC treatment bears apoptotic and apoptotic-like features in both cell lines.

Role of cation-chloride cotransporters, Na/K-pump, and channels in cell water/ionic balance regulation under hyperosmolar conditions: in silico and experimental studies of opposite RVI and AVD responses of U937 cells to hyperosmolar media

The work provides a modern mathematical description of animal cell electrochemical system under a balanced state and during the transition caused by an increase in external osmolarity, considering all the main ionic pathways in the cell membrane: the sodium pump, K+, Na+, Cl- electroconductive channels and cotransporters NC, KC, and NKCC. The description is applied to experimental data obtained on U937 cells cultured in suspension, which allows the required assays to be performed, including determination of cell water content using buoyant density, cell ion content using flame photometry, and optical methods using flow cytometry. The study of these cells can serve as a useful model for understanding the general mechanisms of regulation of cellular water and ionic balance, which cannot be properly analyzed in many important practical cases, such as ischemic disturbance of cellular ionic and water balance, when cells cannot be isolated. An essential part of the results is the developed software supplied with an executable file, which allows researchers with no programming experience to calculate unidirectional fluxes of monovalent ions through separate pathways and ion-electrochemical gradients that move ions through them, which is important for studying the functional expression of channels and transporters. It is shown how the developed approach is used to reveal changes in channels and transporters underlying the RVI and AVD responses to the hyperosmolar medium in the studied living U937 cells.

Establishing the Role of EPS15, DVL2 and Cortactin in CALM-AF10 Leukemogenesis

Background: Leukemia is the most common type of childhood cancer. Although the prognosis for many pediatric leukemias has improved, leukemias associated with the t(10;11) CALM-AF10 translocation remain difficult to treat. CALM-AF10 leukemias account for ~5-10% of childhood T-cell acute lymphoblastic leukemia (T-ALL)as well as a subset of acute myeloid leukemia (AML). CALM-AF10 leukemias exhibit increased expression of proleukemic HOXA genes, but relatively little is known about the cellular mechanisms that drive CALM-AF10 leukemogenesis. Our laboratory has demonstrated that the CALM protein contains a nuclear export signal (NES) that is critical for CALM-AF10-dependent leukemogenesis. The NES interacts with the CRM1/XPO1 nuclear export receptor, which shuttles proteins from the nucleus to the cytoplasm through the nuclear pore complex. We have shown that transcriptional activation of HOXA genes by CALM-AF10 is dependent on its interaction with CRM1. Importantly, CRM1 does not contain a recognized DNA binding domain, and it is not currently understood how the CALM-AF10/CRM1 complex interacts with regulatory regions of HOXA genes. To identify proteins that mediate the interaction between the CALM-AF10/CRM1 complex and DNA, we took advantage of a proximity-based labeling approach using BioID2, a second-generation biotin ligase. When fused to a protein of interest and in the presence of biotin, BioID2 biotinylates proteins in close proximity to the ligase. These biotinylated proteins can then be identified by mass spectrometry (MS). Methods: We prepared an expression plasmid in which BioID2 was cloned in-frame with CALM-AF10. Human Embryonic Kidney 293 (HEK293) cells were transiently transfected with BioID2-CALM-AF10 and grown in the presence or absence of biotin. MS was performed to identify candidate interacting proteins. We validated direct interactions of candidate proteins with CALM-AF10 using co-immunoprecipitation experiments in HEK293 cells transfected with a CALM-AF10 plasmid. We confirmed that candidate proteins are present in murine CALM-AF10 leukemia cells via Western blotting. In order to efficiently knockout (KO) candidate proteins, we have generated a human U937 cell line (which harbors a t(10;11) CALM-AF10 translocation) with a stable incorporated Cas9. To assess whether KO of EPS15, DVL2 or CTTN affects HOXA5 expression, we performed RT-qPCR in U937-Cas9 cells lines with confirmed KO. Results: We carried out three independent transfections/MS experiments, which identified 71, 95 and 61 proteins, respectively. Of the proteins identified, 12 candidates were common to all three experiments . Importantly, we identified Disruptor Of Telomeric silencing 1-Like (DOT1L), a protein known to interact with AF10, and Nuclear pore complex protein 214 (NUP214), a protein that interacts with CRM1 and that is involved in leukemogenic translocations. We chose EPS15, DVL2 and CTTN for further study, as each of these proteins plays a role in leukemogenesis. We performed initial validation of direct interactions via co-immunoprecipitation and found that all three proteins co-precipitate with CALM-AF10. Western blotting showed that all three proteins are expressed in a murine CALM-AF10 leukemia cell line. We effectively knocked out EPS15 protein expression in U937 cells, and showed that HOXA5 expression is reduced in the setting of EPS15 knockout. Conclusion: We used biotin ligase-dependent proximity-based labeling to identify candidate proteins that potentially interact with the CALM-AF10 fusion protein. Our identification of DOT1L validates the approach, since DOT1L is known to interact with CALM-AF10. We have started to investigate three candidate proteins - EPS15, DVL2 and CTTN - all of which are involved in leukemogenic transformation. We have shown that EPS15, DVL2 and CTTN are expressed in murine CALM-AF10 leukemia cells and directly interact with the CALM-AF10 fusion protein. Knockout of EPS15 in U937 cells results in decreased HOXA5 expression, suggesting the importance of EPS15 in CALM-AF10 leukemogenesis. Evaluation of the roles of these proteins in leukemogenesis may lead to identification of novel pathways involved in CALM-AF10 leukemogenesis. Disclosures No relevant conflicts of interest to declare.

Nodal/SMAD2 and Bone Morphogenic Protein 4 RNA Expression in Microgravity. Implications for Spacial Orientation Signaling in Hematopoesis and the Implications for the Hematosuppressive Effects of Space Flight

Introduction: Nodal proteins are members of the TGF alpha family which direct right left orientation in the developing embryo. Nodal/SMAD2 signaling controls BMP4 expression and with canonical Wnt signaling, regulates the posteriorization of the primitive streak, development of the mesoderm, development of early hematopoetic stem cells, and the property of self renewal in adult hematopoiesis. This study investigated the extent that microgravity alters expression of these spatially orienting proteins of BMP4, Nodal, Wnt, and SMAD2 thus influencing the anemia, thrombocytopenia, and immune alteration associated with space flight. Method: The Gene Expression Omnibus Database (GEO) of the National Institutes of Health was accessed to define RNA expression of Nodal, SMAD2, Wnt and BMP4 in hematopoetic cells in microgravity. Initial queries for "Low Gravity" studies resulted in 565 investigations within the GEO Omnibus. Of the 565 studies, the GSE136939, GSE101102, and the GSE101309 datasets were explored which assessed the lymphoid and macrophage cell lines TK6, U937, and Jurkat. RNA expression with normal and microgravity environments were compared. In the U937 cells hypergravity environments were also studied. Nodal, Lefty, Wnt, BMP4, as well as the NODAL signaling cascade proteins of SMAD 1/5, SMAD2, SMAD3, and the inhibitory SMAD 7. Affymetrix Expression Arrays were utilized for the TK^ and Jurkat cells assays. The U937 cell lines were assayed with NimbleGen Human Gene Assay Arrays. Results: Significant decreases in BMP4 expression were seen in microgravity environments (P value, <0.005) where SMAD2 expression was significantly elevated (P value <0.05) in microgravity. Conversely, hypergravity effects on U937 cells resulted in a reverse expression pattern. (BMP4 expression increased while SMAD2 decreased (P value <0.01) ). Comparisons of 14, 12, and 4 expression assays were made in U937, Jurkat, and TK6 cells respectively. LEFTY, NODAL, Wnt, SMA1/5/3/7 expression assays all showed changes in expression, but the small sample numbers resulted in poor statistical power and insignificant P values to detect differences in the RNA expression assessed. Comparisons of the gravitational pressures and time spent in these environments for the cellular cultures resulted in insignificant statistical differences. Conclusions: Microgravity induces decreases in BMP4 RNA expression and increases in SMAD2 RNA expression in TK6, U937, and Jurkat cell as defined by the GSE101309, GSE101102 and GSE136939 datasets. BMP4 is required for stem cell posteriorization, HSC number, and adult hematopoetic self renewal. This diminishment in BMP4 expression in microgravity may result in diminished HSC number and self renewal capacity. This qualitative change in gene expression in microgravity and may be a significant component of the anemia, thrombocytopenia, and immune alterations of space flight. Moreover such changes in RNA expression in microgravity implicates the importance of hematopoetic spacial orientation signals in normal hematopoiesis. Therapeutic targeting of the BMP/SMAD2 pathway in refractory multilineage hematopoetic diseases may prove to be fruitful. Statistical interpretation of the data is hindered by the small number of samples, the cell type, hematopoetic maturation stage of the samples, and microenvironmental differences in the studies utilized in these datasets. If this result is confirmed in future and larger studies, it would have significant biologic and therapeutic implications for long term space flight and the developing concept of spacial hematopoiesis. Disclosures No relevant conflicts of interest to declare.

New Diterpenoids from Mesona procumbens with Antiproliferative Activities Modulate Cell Cycle Arrest and Apoptosis in Human Leukemia Cancer Cells

Mesona procumbens is a popular material used in foods and herbal medicines in Asia for clearing heat and resolving toxins. However, phytochemical research on this plant is very rare. In this study, eleven new diterpenoids, mesonols A-K (1–11), comprising seven ent-kauranes, three ent-atisanes, and one sarcopetalane, were isolated from its methanolic extract. Structural elucidation of compounds 1–11 was performed by spectroscopic methods, especially 2D NMR, HRESIMS, and X-ray crystallographic analysis. All isolates were assessed for their antiproliferative activity, and compounds 1-4 showed potential antiproliferative activities against A549, Hep-3B, PC-3, HT29, and U937 cancer cells, with IC50 values ranging from 1.97 to 19.86 µM. The most active compounds, 1 and 2, were selected for further investigation of their effects on cell cycle progression, apoptosis, and ROS generation in U937 human leukemia cancer cells. Interestingly, it was found that compounds 1 and 2 induced antiproliferative effects in U937 cells through different mechanisms. Compound 1 caused cell cycle arrest at the G2/M phase and subsequent cell death in a dose- and time-dependent manner. However, 2-mediated antiproliferation of U937 cells triggered ROS-mediated mitochondrial-dependent apoptosis. These results provide insight into the molecular mechanism involved in the antiproliferative activities of compounds 1 and 2 in U937 cells. Altogether, the study showed that new diterpenoid compounds 1 and 2 from M. procumbens are potent and promising anticancer agents.

Indole alkaloids inhibit zika and chikungunya virus infection in different cell lines

Background In recent years, an increase in the occurrence of illnesses caused by two clinically- important arboviruses has been reported: Zika virus (ZIKV) and Chikungunya virus (CHIKV). There is no licensed antiviral treatment for either of the two abovementioned viruses. Bearing in mind that the antiviral effect of indole alkaloids has been reported for other arboviral models, the present study proposed to evaluate the antiviral in vitro and in silico effects of four indole alkaloids on infections by these two viruses in different cell lines. Methods The antiviral effects of voacangine (VOAC), voacangine-7-hydroxyindolenine (VOAC-OH), rupicoline and 3-oxo voacangine (OXO-VOAC) were evaluated in Vero, U937 and A549 cells using different experimental strategies (Pre, Trans, Post and combined treatment). Viral infection was quantified by different methodologies, including infectious viral particles by plating, viral genome by RT-qPCR, and viral protein by cell ELISA. Moreover, molecular docking was used to evaluate the possible interactions between structural and nonstructural viral proteins and the compounds. The results obtained from the antiviral strategies for each experimental condition were compared in all cases with the untreated controls. Statistically significant differences were identified using a parametric Student’s t-test. In all cases, p values below 0.05 (p < 0.05) were considered statistically significant. Results In the pre-treatment strategy in Vero cells, VOAC and VOAC-OH inhibited both viral models and OXO-VOAC inhibited only ZIKV; in U937 cells infected with CHIKV/Col, only VOAC-OH inhibited infection, but none of the compounds had activity in A549 cells; in U937 cells and A549 cells infected with ZIKV/Col, the three compounds that were effective in Vero cells also had antiviral activity. In the trans-treatment strategy, only VOAC-OH was virucidal against ZIKV/Col. In the post-treatment strategy, only rupicoline was effective in the CHIKV/Col model in Vero and A549 cells, whereas VOAC and VOAC-OH inhibited ZIKV infection in all three cell lines. In the combined strategy, VOAC, VOAC-OH and rupicoline inhibited CHIKV/Col and ZIKV/Col, but only rupicoline improved the antiviral effect of ZIKV/Col-infected cultures with respect to the individual strategies. Molecular docking showed that all the compounds had favorable binding energies with the structural proteins E2 and NSP2 (CHIKV) and E and NS5 (ZIKV). Conclusions The present study demonstrates that indole alkaloids are promising antiviral drugs in the process of ZIKV and CHIKV infection; however, the mechanisms of action evaluated in this study would indicate that the effect is different in each viral model and, in turn, dependent on the cell line.

Naja atra Cardiotoxin 1 Induces the FasL/Fas Death Pathway in Human Leukemia Cells

This study aimed to investigate the mechanistic pathway of Naja atra (Taiwan cobra) cardiotoxin 1 (CTX1)–induced death of leukemia cell lines U937 and HL-60. CTX1 increased cytoplasmic Ca2+ and reactive oxygen species (ROS) production, leading to the death of U937 cells. It was found that Ca2+-induced NOX4 upregulation promoted ROS-mediated p38 MAPK phosphorylation, which consequently induced c-Jun and ATF-2 phosphorylation. Using siRNA knockdown, activated c-Jun and ATF-2 were demonstrated to regulate the expression of Fas and FasL, respectively. Suppression of Ca2+-mediated NOX4 expression or ROS-mediated p38 MAPK activation increased the survival of U937 cells exposed to CTX1. FADD depletion abolished CTX1-induced cell death, caspase-8 activation, and t-Bid production, supporting the correlation between the Fas death pathway and CTX1-mediated cytotoxicity. Among the tested N. atra CTX isotoxins, only CTX1 induced Fas and FasL expression. Chemical modification studies revealed that intact Met residues were essential for the activity of CTX1 to upregulate Fas and FasL expression. Taken together, the data in this study indicate that CTX1 induces c-Jun-mediated Fas and ATF-2-mediated FasL transcription by the Ca2+/NOX4/ROS/p38 MAPK axis, thereby activating the Fas death pathway in U937 cells. Furthermore, CTX1 activates Fas/FasL death signaling in the leukemia cell line HL-60.

Human macrophages utilize a wide range of pathogen recognition receptors to recognize Legionella pneumophila, including Toll-Like Receptor 4 engaging Legionella lipopolysaccharide and the Toll-like Receptor 3 nucleic-acid sensor

Cytokines made by macrophages play a critical role in determining the course of Legionella pneumophila infection. Prior murine-based modeling indicated that this cytokine response is initiated upon recognition of L. pneumophila by a subset of Toll-like receptors, namely TLR2, TLR5, and TLR9. Through the use of shRNA/siRNA knockdowns and subsequently CRISPR/Cas9 knockouts (KO), we determined that TRIF, an adaptor downstream of endosomal TLR3 and TLR4, is required for full cytokine secretion by human primary and cell-line macrophages. By characterizing a further set of TLR KO’s in human U937 cells, we discerned that, contrary to the viewpoint garnered from murine-based studies, TLR3 and TLR4 (along with TLR2 and TLR5) are in fact vital to the macrophage response in the early stages of L. pneumophila infection. This conclusion was bolstered by showing that i) chemical inhibitors of TLR3 and TLR4 dampen the cytokine output of primary human macrophages and ii) transfection of TLR3 and TLR4 into HEK cells conferred an ability to sense L. pneumophila. TLR3- and TLR4-dependent cytokines promoted migration of human HL-60 neutrophils across an epithelial layer, pointing to the biological importance for the newfound signaling pathway. The response of U937 cells to L. pneumophila LPS was dependent upon TLR4, a further contradiction to murine-based studies, which had concluded that TLR2 is the receptor for Legionella LPS. Given the role of TLR3 in sensing nucleic acid (i.e., dsRNA), we utilized newly-made KO U937 cells to document that DNA-sensing by cGAS-STING and DNA-PK are also needed for the response of human macrophages to L. pneumophila. Given the lack of attention given them in the bacterial field, C-type lectin receptors were similarly examined; but, they were not required. Overall, this study arguably represents the most extensive, single-characterization of Legionella-recognition receptors within human macrophages.