THP-1 Apoptosis Research Articles

At Clinically Achievable Concentrations Obatoclax (GX15-070) Potentiates The Cytotoxic Effect Of Cytarabine On Acute Myeloid Leukemia Cells By Enhancing DNA Damage

AML accounts for one-fourth of acute leukemias in children, but is responsible for more than half of the pediatric acute leukemia deaths. Most adult AML patients treated with chemotherapeutic regimens relapse and die of their disease or associated complications. One major cause of treatment failure in this disease is resistance to anthracycline [e.g. daunorubicin (DNR)] and cytarabine (ara-C)-based chemotherapy. Therefore more effective therapies are urgently needed. One common cancer-causing defect arises from the overexpression of the anti-apoptotic Bcl-2 family members, including Bcl-2, Bcl-xL, and Mcl-1, which inactivate the intrinsic apoptotic pathway in many types of cancer cells. Overexpression of Bcl-2, Bcl-xL, and/or Mcl-1 has been associated with chemoresistance in leukemia cell lines and with a poor clinical outcome in studies of adult patients with leukemia, including AML. Therefore, small molecules that inhibit the anti-apoptotic Bcl-2 family proteins could be novel therapeutic agents for the treatment of leukemia.In this study, we investigated the effects of clinically achievable doses (175 nM and lower) of obatoclax (a hydrophobic small molecule pan-Bcl-2 inhibitor that binds to the BH3-binding site of Bcl-2, Bcl-xL and Mcl-1) on cytarabine sensitivity in AML cell lines (n=5) and diagnostic AML blasts (n=6). The majority of the AML cell lines and diagnostic AML blast samples expressed Bcl-2, Bcl-xL, and/or Mcl-1 proteins as determined by Western blots, though the levels were variable and did not correlate with sensitivities to cytarabine or obatoclax. Simultaneous combination of obatoclax and cytarabine resulted in synergistic inhibition of proliferation of 4 AML cell lines and 4 diagnostic AML blast samples. Cytarabine IC50s were reduced by 3.4-26.6 fold in the presence of 175 nM obatoclax. The two drugs also synergistically induced apoptosis in THP-1 and OCI-AML3 cells (combination index values ranged from 0.23 to 0.55). Bax activation was detected in the combined drug treatments but not in the individual drug treatments. This was accompanied by significantly increased loss of mitochondrial membrane potential (MMP). Interestingly, co-treatment of THP-1 and OCI-AML3 cells with cytarabine and obatoclax resulted in decreased levels of Mcl-1 and increased nuclear accumulation of Bcl-2 and Bcl-xL that can occur as early as 24h after combined treatment with cytarabine and obatoclax. Apoptosis and MMP loss induced by the combination of cytarabine and obatoclax could be completely attenuated by ectopic overexpression of Bcl-xL. Emerging evidence suggests that Bcl-2, Bcl-xL, and Mcl-1 also possess nuclear functions and can influence the repair of DNA double-strand breaks (DSBs) and/or the regulation of cell cycle checkpoints. It is conceivable that obatoclax may target the nuclear functions of these anti-apoptotic Bcl-2 family proteins to enhance ara-C-induced apoptosis in AML cells. Interestingly, combined drug treatment showed an increase in DNA DSBs, as indicated by increased levels of phosphorylated H2AX (γH2AX) and comet assay, in both THP-1 and OCI-AML3 cells. Further, γH2AX foci coincided with increased nuclear localization of Bcl-2 and Bcl-xL. Furthermore, a time course experiment revealed that γH2AX levels in AML cells treated with combined cytarabine and obatoclax positively correlated with cleavage of caspase-3 and PARP and inversely correlated with Mcl-1 levels. Additional experiments suggest that induction of a decrease of Mcl-1 and nuclear accumulation of Bcl-2 and Bcl-xL may represent a common mechanism underlying apoptosis induced by DNA DSBs.Our study provides convincing evidence that obatoclax enhances cytarabine-induced DNA DSBs which may trigger a decrease of Mcl-1 and nuclear accumulation of Bcl-2 and Bcl-xL, tipping the balance toward apoptosis. Our new findings strongly support the clinical use of obatoclax in combination with DNA damaging agents for treating AML and possibly a broader range of malignancies. Disclosures:No relevant conflicts of interest to declare.

Inhibition Of CXCR2 As a Therapeutic Strategy In AML and MDS

Acute Myeloid Leukemia (AML) and Myelodysplastic syndrome (MDS) arise from accumulation of multiple stepwise genetic and epigenetic changes in hematopoietic stem cells (HSC) and/or committed progenitors. A series of transforming events can initially give rise to pre-leukemia stem cells (pre-LSC) as well as fully transformed leukemia stem cells (LSC), both of which need to be targeted in strategies aimed at curing these diseases. We conducted parallel transcriptional analysis of multiple, highly fractionated stem and progenitor populations in individual patients of MDS and AML (N=16) and identified candidate genes that are consistently dysregulated at multiple immature stem and progenitor cell stages. Interleukin 8 (IL8), was one of the most consistently overexpressed genes in MDS/AML Hematolpoetic Stem Cells (HSCs) and progenitors when compared to healthy control HSCs and progenitors. IL8 is a pro-inflammatory chemokine, which is able to activate multiple intracellular signaling pathways after binding to its surface receptor CXCR2. Even though increased IL8-CXCR2 signaling has been shown to promote angiogenesis, metastasis and chemotherapy resistance in many solid tumors, its role in AML and MDS is not well elucidated. We further analyzed gene expression profiles of CD34+ cells from 183 MDS patients and found significant increased expression of CXCR2 in MDS when compared to healthy controls (FDR<0.1). Most importantly, analysis of The Cancer Genome Atlas (TCGA) AML (n=200) dataset showed that CXCR2 expression was predictive of significantly adverse prognosis (log rank P value=0.0182; median survival of 245 days in cxcr2 high vs 607 days in cxcr2 low) in patients, further pointing to a critical role of IL8-CXCR2 signaling in AML/MDS.Next, we studied the functional role of IL8 and CXCR2 in AML. A panel of leukemic cell lines (THP-1, U937, KG-1, MOLM13, HL-60, K532) were screened for CXCR2 expression and revealed significantly higher expression when compared to healthy CD34+ control cells. SB-332235, a specific inhibitor of CXCR2 was used for functional studies. CXCR2 inhibition led to significant, (p<0.05) reduction in proliferation in all 6 cell lines tested and an effect was seen as early as 24 hrs of exposure. CXCR2 inhibition was found to lead to G0/G1 cell cycle arrest and trigged apoptosis in THP-1 and U937 cells (p-value 0.004 and 0.02 respectively). Incubation of primary AML/MDS bone marrow samples with SB-332235 similarly lead to significantly reduced proliferation at 24hrs, when compared to healthy CD34+ cells. Selective, and highly significant inhibition of leukemic cell growth was also seen in colony assays from primary MDS/AML samples (mean leukemic colonies in AML/MDS= 73 vs 313 in controls, P < 0.001). Interestingly, inhibition of CXCR2 in primary AML marrow samples led to induction of apoptosis in immature CD34+/CD38- cells when compared to healthy controls. Lastly, xenografting studies with THP-1 leukemic cells revealed that CXCR2 inhibitor treatment led to decreased leukemic burden and organ infiltration when compared to placebo controls in vivo.In summary we have found significantly increased expression of IL8 and its receptor CXCR2 in sorted HSCs and progenitors from AML and MDS patients. High CXCR2 expression was a marker of adverse prognosis in a large cohort of AML patients. Most importantly, in vitro and in vivo functional studies showed that CXCR2 is a potential therapeutic target in AML/MDS and is able to selectively target immature, LSC-enriched cell fractions in AML. Disclosures:No relevant conflicts of interest to declare.

Mycobacterium avium Biofilm Attenuates Mononuclear Phagocyte Function by Triggering Hyperstimulation and Apoptosis during Early Infection

Mycobacterium avium subsp. hominissuis is an opportunistic human pathogen that has been shown to form biofilm in vitro and in vivo. Biofilm formation in vivo appears to be associated with infections in the respiratory tract of the host. The reasoning behind how M. avium subsp. hominissuis biofilm is allowed to establish and persist without being cleared by the innate immune system is currently unknown. To identify the mechanism responsible for this, we developed an in vitro model using THP-1 human mononuclear phagocytes cocultured with established M. avium subsp. hominissuis biofilm and surveyed various aspects of the interaction, including phagocyte stimulation and response, bacterial killing, and apoptosis. M. avium subsp. hominissuis biofilm triggered robust tumor necrosis factor alpha (TNF-α) release from THP-1 cells as well as superoxide and nitric oxide production. Surprisingly, the hyperstimulated phagocytes did not effectively eliminate the cells of the biofilm, even when prestimulated with gamma interferon (IFN-γ) or TNF-α or cocultured with natural killer cells (which have been shown to induce anti-M. avium subsp. hominissuis activity when added to THP-1 cells infected with planktonic M. avium subsp. hominissuis). Time-lapse microscopy and the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) assay determined that contact with the M. avium subsp. hominissuis biofilm led to early, widespread onset of apoptosis, which is not seen until much later in planktonic M. avium subsp. hominissuis infection. Blocking TNF-α or TNF-R1 during interaction with the biofilm significantly reduced THP-1 apoptosis but did not lead to elimination of M. avium subsp. hominissuis. Our data collectively indicate that M. avium subsp. hominissuis biofilm induces TNF-α-driven hyperstimulation and apoptosis of surveilling phagocytes, which prevents clearance of the biofilm by cells of the innate immune system and allows the biofilm-associated infection to persist.

Preclinical characterization of a potent and selective inhibitor of the histone demethylase KDM1A for MLL leukemia.

e13543 Background: The lysine-specific demethylase KDM1A catalyzes the removal of methyl groups from mono and dimethylated H3K4/K9, changes that have inductive or inhibitory effects on gene expression. KDM1A is a key regulator of leukemia stem cell (LSC) potential and is required for MLL-AF9 oncogenic transformation. Inhibition of KDM1A expression or activity overcomes the differentiation block in AML. Mixed lineage leukemia (MLL) is a form of AML that is especially sensitive to inhibition of KDM1A. Methods: Gene expression was analyzed using microarrays, cell differentiation was assessed by FACS, viability and apoptosis were assessed by MTT assay and PI staining, me2H3K4 levels were quantified by qPCR and ChIPseq. Results: We used computational models based on reported X-ray structures fine-tuned with the SAR of a first series of molecules to design and synthesize &gt;800 KDM1A inhibitors. ORY-1001 is an enantiomerically pure KDM1A inhibitor (IC50 &lt;20nM) with high selectivity against related FAD dependent aminoxidases (MAO-A/B, IL4I1, KDM1B &gt;100uM, SMOX 7uM). ORY-1001 does not inhibit non-related histone modifiers, and is clean in a CEREP diversity panel. Treatment of THP-1 (MLL-AF9) cells with ORY-1001, results in a time/dose dependent me2H3K4 accumulation at KDM1A target genes and concomitant induction of differentiation markers (EC50 me2H3K4 and FACS CD11b &lt;1nM). Microarray analysis of treated THP-1 cells reveals differentiation towards a monocyte-like phenotype. ORY-1001 induces apoptosis in THP-1 and inhibits proliferation and colony formation of MV(4;11) (MLL-AF4) cells (EC50 &lt;1nM). Daily oral administration of doses &lt;0.020mg/kg leads to significantly reduced tumor growth in rodent MV(4;11) xenografts. In vivo and in vitro IND/IMPD enabling studies have shown that ORY-1001 presents excellent oral bioavailability, target exposure and activity in vivo. The compound is stable in hepatocytes (Clint&lt;0.6 mL/min/g liver, @1uM) and does not exhibit CYP (IC50&gt;100uM) or hERG (%inhib.&lt;2%, @10uM) inhibition. No off-target activity has been detected in 28d rat toxicology studies. Conclusions: A potent and selective KDM1A inhibitor is described with in vitro and vivo anti-leukemic efficacy.

Peptidoglycans Promotes Human Leukemic THP-1 Cell Apoptosis and Differentiation

The innate immune system coordinates the inflammatory response to pathogens. To do so, its cells must discriminate self from non-self utilizing receptors that identify molecules synthesized exclusively by microbes. Toll- like receptors have a crucial role in the detection of microbial infection in mammals and insects. In mammals, they have evolved to recognize conserved products unique to microbial metabolism. These include lipopolysaccharide (LPS), lipotechoic acids, and peptidoglycans (PGN). We show here that TLRs, including TLR2, are expressed on the THP-1 human leukemia cell line. Activation of TLR2 signaling in THP-1 by PGN induces the synthesis of various soluble factors and proteins including interleukin-1β, interleukin-8 and TNF-α and apoptosis of THP-1 with PGN dose and time dependence. Moreover , in this study we show that PGN induces apoptosis of THP-1 cells in a TNF-α-dependent manner. These findings indicate that TLR2 signaling results in a cascade leading to tumor apoptosis and differentiation, which may suggest new clinical prospects using TLR2 agonists as cytotoxic agents in certain cancers.

Sonic hedgehog antagonists induce cell death in acute myeloid leukemia cells with the presence of lipopolysaccharides, tumor necrosis factor-α, or interferons

Due to the development of drug resistance, the outcome for the majority of patients with acute myeloid leukemia (acute myelogenous leukemia; AML) remains poor. To prevent drug resistance and increase the therapeutic efficacy of treating AML, the development of new combinatory drug therapies is necessary. Sonic hedgehog (Shh) is expressed in AML biopsies and is essential for the drug resistance of cancer stem cells of AML. AML patients are frequently infected by bacteria and exposed to lipopolysaccharide (LPS). LPS itself, its derivatives, and its downstream effectors, such as tumor necrosis factor-α (TNF-α) and interferons (IFNs), have been shown to provoke anti-tumor effects. The application of a Shh inhibitor against AML cells in the presence of LPS/TNF-α/IFNs has not been investigated. We found that the Shh inhibitor cyclopamine in combination with LPS treatment synergistically induced massive cell apoptosis in THP-1 and U937 cells. The cytotoxic effects of this combined drug treatment were confirmed in 5 additional AML cell lines, in primary AML cells, and in an AML mouse model. Replacing cyclopamine with another Shh inhibitor, Sant-1, had the same effect. LPS could be substituted by TNF-α or IFNs to induce AML cell death in combination with cyclopamine. Our results suggest a potential strategy for the development of new therapies employing Shh antagonists in the presence of LPS/TNF-α/IFNs for the treatment of AML patients.

Deferasirox Inhibit Doxorubicin-Induced Reactive Oxygen Species Generation in Both Acute Myeloid Leukemia and Normal Heart Cell While Maintain the Cytotoxicity of Doxorubicin Only on Acute Myeloid Leukemia

AbstractAbstract 3620 Background:Deferasirox (DFX) was recently found to have anti-leukemia effect both in vitro and in vivo. DFX can also potently inhibit the generation of intracellular reactive oxygen species (ROS). On the other hand, the generation of ROS by Doxorubicin (DOX) is critical for the cytotoxicity on both leukemia and normal heart cells. It is not known whether combining DFX and DOX will have synergistic or antagonizing effect on leukemic cells. Similarly, it is also unknown whether adding DFX to DOX will have protective effect on normal heart cell. Method:Cells of human acute myeloid leukemia (AML) cell line THP1, mice AML cell line WEHI3, and rat normal heart cell line H9C2 were treated with Doxorubicin 5microM for various duration in the presence of absence of DFX pretreatment (100microM for 10 minutes). Intracellular ROS generation was measured by the detection of 2,7-dichlorodihydrofluorescein (DCF) fluorescence intensity using flow cytometry. Apoptosis was determined by Annexin V-Propidium Iodide staining using flow cytometry. Cytotoxicity was determined by Trypan blue exclusion assay. Results:Although intracellular ROS was reduced, DFX alone induced apoptosis of THP1 (from 3% to 18%) and WEHI3 (from 31% to 49%) AML cells. DOX-induced ROS production was also significantly reduced when THP1, WEHI3, and H9C2 cells were pretreated with DFX (Figure 1a, 1b, 1c respectively). However, the DOX-induced apoptosis of THP1 and WEHI3 AML cells were not antagonized by DFX (Figure 2a). 24 hours after exposure to this physiological dose DOX, all the WEHI3 cells died in both DFX treated or untreated group (figure 2b). More importantly, DFX-pretreated H9C2 heart cells had fewer cell death (3.7%) after exposure to DOX (5microM for 24 hours) compared to non-DFX pretreated cells (8.5%). Conclusions:DFX alone induced apoptosis in two different AML cell lines. DFX also markedly reduced the ROS generation due to DOX treatment. However, DFX did not negatively influence the pro-apoptotic and cytotoxic effect of DOX on these AML cell lines. Interestingly, DFX also markedly reduced the DOX-induced ROS generation and DOX-induced cell death in normal rat heart cell, which might have protective effect on DOX-related cardiomyopathy. We are now using Balb/c-WEHI3 AML mice model to test whether DFX can protect cardiomyocytes from DOX-related damage while maintain the cytotoxic effect of DOX on AML cells. [Display omitted] [Display omitted] Disclosures:No relevant conflicts of interest to declare.

The role of calcium in the rVvhA induced THP-1 cells apoptosis

Objective To study the role of Vibrio vulnificus cytolysin(rVvhA) induced THP-1 apoptosis and calcium influx.Methods CCK-8 cell proliferation kit,Fluo3/AM staining and AnnexinV/PI staining were performed to identify the apoptosis and calcium influx induced by rVvhA in THP-1 cells.Results rVvhA could induce THP-1 apoptosis and up-regulate the cellular calcium concentration.BAPTAAM could enhance the calcium influx induced by rVvhA in THP-1.Conclusion rVvhA had cytotoxic to THP-1 cells by inducing apoptosis and triggering extracellular calcium influx. Key words: Vibrio vulnificus; Cytolysin; Calcium; THP-1

Involvement of Toll-like receptor 2 in apoptosis of Aggregatibacter actinomycetemcomitans-infected THP-1 cells

Aggregatibacter (Actinobacillus) actinomycetemcomitans is a gram-negative bacterium that has been associated with aggressive periodontitis. A actinomycetemcomitans infection induces apoptosis in the human monocytic cell line THP-1, and p38 mitogen-activated protein kinase (p38) activity and tumor necrosis factor-α (TNF-α) production are enhanced by A actinomycetemcomitans infection. However, mechanisms governing the recognition of A actinomycetemcomitans by monocytes during apoptosis have not been elucidated. A actinomycetemcomitans cell wall components stimulate Toll-like receptor (TLR)2 and/or TLR4. The authors examined whether TLR2 and/or TLR4 were involved in the apoptosis of A actinomycetemcomitans-infected THP-1 cells. A actinomycetemcomitans-infected THP-1 cells were transferred to six-well culture plates and incubated for 0 to 6 hours. In some experiments, THP-1 cells were incubated with anti-TLR2, anti-TLR4, or isotype control antibody (10μg/mL) for 30 minutes prior to A actinomycetemcomitans infection. Expression of messenger RNA (mRNA) was examined by reverse transcription-polymerase chain reaction. Intracellular bacteria recovered from A actinomycetemcomitans-infected cells and apoptotic cells were detected by APOPercentage dye (Biocolor Ltd, Northern Ireland, UK) staining. Cellular p38 activity and TNF-α production were assessed with enzyme-linked immunosorbent assay. The expression of TLR2 mRNA was increased by A actinomycetemcomitans infection. Phagocytosis and apoptosis in A actinomycetemcomitans-infected THP-1 cells were inhibited by the addition of anti-TLR2 antibody. Also, anti-TLR2 antibody suppressed the activation of p38 and production of TNF-α in A actinomycetemcomitans-infected THP-1 cells. These results suggest that A actinomycetemcomitans induces increased expression of TLR2, leading to phagocytosis and apoptosis of THP-1 cells via p38 activation and TNF-α production.

Experimental research on the inhibition of SALL4 expression in acute myeloid leukemia THP-1 cells by RNA interference

Objective To inhibit the expression level of SALI4 in AML cell line THP-1 and investigate its potential effects on pathogenesis of leukemia. Methods AML cell line THP-1 was transfected with plasmids that expressed small interfering RNA targeting SALL4. The samples were divided into 4 groups:(1) blank group: samples with not any treatments; (2) control group: cells with empty pRS vector alone;(3) test1 group:cells with SALL4-shRNA-pRS-1 plasmid transfection complex; (4) test2 group:cells with SALL4-shRNA-pRS-2 plasmid transfection complex. The expression levels of SALL4 mRNA and protein were measured by real time fluorescence quantitative PCR and WB. C-myc, Cyclin D1 and β-catenin were important components of Wnt/β-catenin signaling pathway and their expression levels in SALL4 knockdown THP-1 cells were detected by real-time fluorescence PCR. Furthermore, THP-1 apoptosis was analyzed by flow cytometry after Annexin V-PI staining. Results Real time fluorescent quantitative PCR illustrated that the expression of SALL4 in testl group, test2 group, control group and blank group were ( 36. 0 ± 4. 3 ) %,(32. 0 ± 2. 4) %, ( 102. 0 ± 6.5 ) % and ( 100. 0 ± 2. 6 ) % respectively. There was statistical significance ( F = 226. 3, P < 0. 05 ). The expression of SALL4 in testl and test2 group respectively were significant lower than that in blank group (t = 19.7,19. 1, P<0. 05). The expression of SALL4 had no significant difference between blank group and control group (t = 1.1, P ＞0. 05). Western blot analysis revealed SALL4 protein in testl and test2 group were significantly decreased compared with those of control and blank group. All above data indicated the high efficiency of RNA interference targeting SALL4. Comparing with the blank group, the relative expression of C-myc, Cyclin D1 and β-catenin mRNA in test1, test2 and control group were(44.0 ±6.2)%,(44.0 ±5.1)% and (107.0±13.6)%;(22.0±4.5)%,(25.0±3.5)% and (48.0 ± 7. 6 ) %; ( 42.0 ± 3.5 ) %, ( 59. 0 ± 3.7 ) % and ( 79. 0 ± 5.6 ) %. The expression of C-myc,β-catenin and Cyclin D1 mRNA in testl and test2 group were significant lower than that in blank group (t = 10. 1,9. 5, 23. 3, 22. 9; 17.4, 12. 4; P < 0. 05). The percentage of apoptotic cells in group of test1,test2,control, blank were (57.2 ±9.1)%, (34.4 ±8.6)%, (14.4 ±3.6)% and (14.8 ±4.8)%respectively. There was statistical significance ( F = 42. 5, P < 0. 05 ). After the inhibition of SALL4, the percentages of apoptotic cell in testl and test2 group were significantly increased( t =9. 7, 4. 5 ;P <0. 05).Conclusion The inhibition of SALL4 in leukemia cell line THP-1 downregulates the expression of cell proliferation related genes such as C-myc, Cyclin D1,β-catenin and promoted apoptosis. Key words: Leukemia; Cell line, tumor; Transcription factors; RNA interference; Apoptosis

Systematic evaluation of biocompatibility of magnetic Fe3O4 nanoparticles with six different mammalian cell lines

This article systematically evaluated the biocompatibility of multiple mammalian cell lines to 11-nm DMSA-coated Fe3O4 magnetic nanoparticles (MNPs). Cells including RAW264.7, THP-1, Hepa1-6, HepG2, HL-7702, and HeLa were incubated with six different concentrations (0, 20, 30, 40, 50, and 100 μg/mL) of MNPs for 48 h, and then the cell labeling, iron loading, cell viability, apoptosis, cycle, and oxidative stress were all quantitatively evaluated. The results revealed that all the cells were effectively labeled by the nanoparticles; however, the iron loading of RAW264.7 was significantly higher than that of other cells at any dose. The proliferations of all the cells were not significantly suppressed by MNPs at the studied dose except HepG2 that was exposed to 100 μg/mL MNPs. The investigation of oxidative stress demonstrated that the levels of total superoxide dismutase and xanthine oxidase had no significant changes in all the cells treated by all the doses of MNPs, while the levels of malonyldialdehyde activity of MNP-treated cells significantly increased. The nanoparticles did not produce any significant effect on cell cycles at any of the doses, but resulted in significant apoptosis of THP-1 and HepG2 cells at the highest concentration of 100 μg/mL. At a concentration of 30 μg/mL which was used in human studies with an intravascular nanoparticle imaging agent (Combidex), the nanoparticles efficiently labeled all the cells studied, but did not produce any significant influence on their viability, oxidative stress, and apoptosis and cycle. Therefore, the nanoparticles were concluded with better biocompatibility, which provided some useful information for its clinical applications.

Lipids-induced Apoptosis Is Aggravated by Acyl-coenzyme A: Cholesterol Acyltransferase Inhibitor

To investigate the role of acyl-coenzyme A: cholesterol acyltransferase inhibitor (ACATI) in apoptosis induced by lipids and whether lipids-induced apoptosis is accompanied by increase of free cholesterol in endoplasmic reticulum (ER), in order to further understand the mechanism of lipids-induced apoptosis in advanced atherosclerosis. Human vascular smooth muscle cells (VSMCs) and phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 macrophages were used. Tritiated thymidine incorporation was applied to detect cell proliferation. Cytotoxicity was assessed by lactate dehydrogenase (LDH) release. 4',6-diamidino-2-phenylindole (DAPI) staining, caspase-3, -7 assay, and Annexin-V/propidium iodide (PI) staining were used to detect apoptosis. High performance liquid chromatography was used in intracellular free cholesterol and cholesterol ester assay. ER free cholesterol was quantified. Different lipids had different effects on proliferation and cytotoxicity of VSMCs. 25-hydroxycholesterol (25OHC) had biphasic effects on the proliferation of VSMCs. At low concentration, it stimulated cell proliferation, but turned to proliferation inhibition as concentration reached 15 mug/mL. 25OHC and acetylated low density lipoprotein (AcLDL) could respectively induce apoptosis in human VSMCs and PMA differentiated THP-1 macrophages, which was aggravated by ACATI, accompanied by increase of intracellular free cholesterol content. There was also an increase of cholesterol content in ER with AcLDL-induced apoptosis in THP-1 macrophages. Lipids could induce apoptosis, accompanied by increase of intracellular free cholesterol content, which could be augmented by ACATI, suggesting that insults resulting in ER free cholesterol rise might be the initiator of apoptosis.

Role of microRNA-214-targeting PTEN in advanced glycation endproducts-induced apoptosis delay of monocytes (89.35)

Abstract Advanced glycation endproduct(AGE) delays spontaneous apoptosis of human monocytes and contributes to the development of a local inflammatory response. The mechanism by which AGEs effect monocyte apoptosis, however, is unclear. Here we report that AGE-modified BSA and β2-microglobulin(β2m) can increase miR-214 expression in monocytes, which in turn, enhances cell survival by reducing the expression of phosphatase and tensin homolog(PTEN). Employing miRNA microarray, we obtains a genome-wide miRNA expression profiling of THP-1 cells treated with/without AGEs. Among 470 miRNAs screened, 6 miRNAs including miR-214 are upregulated while 5 miRNAs were down-regulated (fold-change&amp;gt;2) in AGE-treated cells. AGE-induced miRNA differential expression is validated by miRNA qRT-PCR. Significant upregulation of miR-214 is confirmed in normal human monocytes treated with AGEs and monocytes isolated from patients with chronic renal failure. Both AGE-treated monocytes and patient monocytes have a delayed apoptosis. Luciferase reporter assay shows that miR-214 targets PTEN mRNA 3’-untranslated region. Furthermore, PTEN expression is inversely correlated with miR-214 expression in monocytes and the forced expression of miR-214 leads to a delayed apoptosis of THP-1. In contrast, decrease of miR-214 expression via anti-miR-214 largely abolishes AGE-induced cell survival. In summary, our findings define a new regulation role of miR-214 on AGE-induced monocyte survival by impeding PTEN expression.

DcR3 protects THP-1 macrophages from apoptosis by increasing integrin α4

In order to analyze the function of DcR3 for the regulation of cell adhesion and apoptosis in macrophages, we investigated the expression of decoy receptor 3 (DcR3) in THP-1 monocytes/macrophages. DcR3 was expressed in THP-1 and increased by phorbol 12-myristate 13-acetate (PMA). The formation of macrophage aggregates was observed when THP-1 cells were differentiated by PMA or stimulated with DcR3-Fc. Undifferentiated THP-1 cells were also induced to form aggregates by DcR3-Fc. The expression of integrin α4 was significantly increased by DcR3-Fc. CHX-induced apoptosis in THP-1 was inhibited by DcR3-Fc, of which inhibition against CHX-induced apoptosis and aggregate formation were ameliorated by anti-VLA4 antibody. DcR3 may play a significant role in macrophages not only by a decoy receptor but also by increasing α4 integrin.

9-cis-canthaxanthin exhibits higher pro-apoptotic activity than all-trans-canthaxanthin isomer in THP-1 macrophage cells

All-trans-canthaxanthin (4, 4′-diketo β-carotene) but not 9-cis-canthaxanthin has been shown to induce apoptosis in some cell lines. In this study apoptotic activity of 9-cis-canthaxanthin on THP-1 macrophage is reported. Comparison of apoptotic activities of the two canthaxanthin isomers on this cell line by annexin V-cy3 and TUNEL assays indicated the higher pro-apoptotic activity of 9-cis-isomer than the all-trans-isomer. Canthaxanthin-induced apoptosis in this cell line was found to be accompanied by increased caspase-3 and caspase-8 activities, indicating its progression via caspase cascade. Induction of both caspase activities was higher by 9-cis-canthaxanthin than that by trans-canthaxanthin. All these results suggest that canthaxanthin stereoisomers differentially induce apoptosis of THP-1 monocyte/macrophage.

Phospholipid Transfer Protein Augments Apoptosis in THP-1–Derived Macrophages Induced by Lipolyzed Hypertriglyceridemic Plasma

Lipolysis of triglyceride-rich lipoproteins (TGRLPs) generates phospholipid-rich surface remnants and induces cytotoxic effects in adjacent vascular cells. We hypothesized that by integrating surface remnants into HDL, phospholipid transfer protein (PLTP) alleviates cytotoxicity. To test this hypothesis and gain insight into cytotoxicity during the postprandial phase in vivo, we injected normo-TG and hyper-TG human volunteers after a standardized fat meal (postprandial sample) with heparin, thereby stimulating lipolysis (postprandial heparinized sample). Incubation of (primary) human macrophages and primary human endothelial cells with postprandial heparinized hyper-TG plasma induced pronounced cytotoxic effects that were dose dependent on the TG content of the sample. No such effects were seen with normo-TG and postprandial hyper-TG plasma. In vitro lipolysis of VLDL and chylomicrons indicated that both lipoprotein fractions can cause cytotoxicity. Interestingly, in experiments with THP-1-derived macrophages stably transfected with PLTP, PLTP substantially augmented both net phospholipid uptake and apoptotic cell death due to postprandial heparinized hyper-TG plasma. We observed that activation of caspase-3/7, poly-ADP-ribose polymerase, and enhanced bioactivity of acid sphingomyelinase may all contribute to this augmented apoptosis. Our data show that lipolysis of TGRLPs and their remodelling by PLTP interact to disturb cellular phospholipid flux and intracellular signaling processes, ultimately leading to apoptosis in human macrophages and endothelial cells.

Anti-apoptotic Effects of Probucol are Associated with Downregulation of Daxx Expression in THP-1 Macrophage

To study the relationship between Daxx expression and the antiapoptotic effects of probucol in THP-1 macrophage. Apoptosis of THP-1 derived macrophages was induced by exposure to oxidized low density lipoprotein (oxLDL). The development of apoptosis was determined by flow cytometry analysis and nucleic acid-binding dye acridin orange. Reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting and indirect immunofluorescence were used to evaluate the expression of Daxx and caspase-3 at both mRNA and protein level. As expected, THP-1 macrophages exposed to 100 mg/l oxLDL for 48 h exhibited typical morphologic changes of apoptosis, including condensed chromatin and shrunken nucleus. oxLDL treatment markedly increased Daxx expression in a time- and dose-dependent manner, and facilitated Daxx translocation from cytoplasm to nucleus. The percentage of cells with Daxx in nuclei was significantly increased from 8 to 59%. Treatment with probucol (50 micromol/l) for 4 h prior to exposure to oxLDL significantly inhibited Daxx expression and THP-1 macrophage apoptosis by 61.3%. Furthermore, oxLDL enhanced caspase-3 expression with increased mRNA and protein levels, but without obvious change in translocation of caspase-3 (the cells with nuclear Daxx: 14 vs 8%). In contrast, probucol attenuated oxLDL-stimulated caspase-3 expression in THP-1 macrophages. OxLDL-induced apoptosis of THP-1 macrophage is associated with Daxx up-regulation; while inhibition of apoptosis by probucol is related to decreased Daxx expression and nuclear translocation.

Moxifloxacin enhances antiproliferative and apoptotic effects of etoposide but inhibits its proinflammatory effects in THP-1 and Jurkat cells

Etoposide (VP-16) is a topoisomerase II (topo II) inhibitor chemotherapeutic agent. Studies indicate that VP-16 enhances proinflammatory cytokines secretion from tumour cells, including IL-8, a chemokine associated with proangiogenic effects. Fluoroquinolones inhibit topo II activity in eukaryotic cells by a mechanism different from that of VP-16. The fluoroquinolone moxifloxacin (MXF) has pronounced anti-inflammatory effects in vitro and in vivo. We studied the effects of MXF and VP-16 on purified human topo II activity and further analysed their combined activity on proliferation, apoptosis and caspase-3 activity in THP-1 and Jurkat cells. Moxifloxacin alone slightly inhibited the activity of human topo II; however, in combination with VP-16 it led to a 73% reduction in enzyme activity. VP-16 inhibited cell proliferation in a time and dose-dependent manner. The addition of moxifloxacin for 72 h to low-dose VP-16 doubled its cytotoxic effect in THP-1 and Jurkat cells (1.8- and 2.6-fold decrease in cell proliferation, respectively) (P<0.004). Moxifloxacin given alone did not induce apoptosis but enhanced VP-16-induced apoptosis in THP-1 and Jurkat cells (1.8- and two-fold increase in annexin V positive cells and caspase-3 activity, respectively) (P<0.04). VP-16 induced the release of IL-8 in a time and dose-dependent manner from THP-1 cells. Moxifloxacin completely blocked the enhanced release of IL-8 induced by 0.5 and 1 μg ml−1 VP-16, and decreased IL-8 release from cells incubated for 72 h with 3 μg ml−1 VP-16 (P<0.001). VP-16 enhanced the release of IL-1β and TNF-α from THP-1 cells, whereas the addition of MXF prevented the enhanced cytokine secretion (P<0.001). We conclude that MXF significantly enhances VP-16 cytotoxicity in tumour-derived cells while preventing VP-16-induced proinflammatory cytokine release. This unique combination may have clinical benefits and cytotoxic drug ‘sparing effect’ and should be further studied in vivo.

Campylobacter jejuni infection of differentiated THP-1 macrophages results in interleukin 1 beta release and caspase-1-independent apoptosis.

Apoptosis induction of host macrophages has emerged as a common virulence mechanism among bacterial pathogens. Infection with Campylobacter jejuni is a leading cause of gastroenteritis worldwide and is characterized by an acute inflammatory response in the small intestine. The authors used the human monocytic cell line THP-1 to examine apoptosis induction and pro-inflammatory cytokine production during C. jejuni infection. Flow cytometric analysis revealed that 48 h after inoculation, a C. jejuni wild-type isolate induced apoptosis in 63 % of THP-1 cells while only 34 % of cells inoculated with a ciaB mutant, which does not secrete the Cia (Campylobacter invasion antigens) proteins, underwent apoptosis. Complementation of the ciaB mutant resulted in levels of apoptosis similar to those induced by the C. jejuni wild-type isolate, suggesting that the Cia proteins have a role in apoptosis induction. It was shown that a proteinase K- and heat-stable component of C. jejuni also stimulated THP-1 apoptosis. Inoculation with a C. jejuni gmhD mutant indicated that lipooligosaccharide was not the stimulatory molecule. Immunoblot and ELISA analyses revealed that C. jejuni infection stimulated the synthesis, processing and secretion of interleukin 1 beta (IL-1 beta). Inhibition of caspase 1 activity eliminated IL-1 beta processing and secretion, but did not affect apoptosis induction. In addition, treatment of cells with a caspase-9-specific inhibitor did not affect apoptosis induction, arguing against activation of an apoptotic pathway dependent on either caspase 1 or 9 activation. Collectively, these data suggest that the inoculation of macrophages with C. jejuni results in the processing of IL-1 beta and apoptosis through different regulatory pathways. Furthermore, these data argue that C. jejuni may use a mechanism distinct from Salmonella typhimurium and Shigella flexneri to initiate macrophage apoptosis and release of IL-1 beta.

Estrogen and progesterone modulate monocyte cell cycle progression and apoptosis.

Pregnancy is characterized by dramatic immunologic changes most commonly characterized as suppression of cell-mediated immunity. Mechanisms of this immunosuppression are obscure but may be caused by increases in pregnancy-associated sex steroids such as 17-beta-estradiol or progesterone. Using five myelomonocytic cell lines in various stages of differentiation, the effects of 17-beta-estradiol and progesterone on cell cycling, apoptosis, and bcl-2 expression in randomly cycling cells before and after lipopolysaccharide (LPS) activation were examined. Lipopolysaccharide alone inhibited cell cycle progression in THP-1 monocyte-like cells and U-937 histiocyte-like cells. Estrogen alone produced cell cycle arrest in all myelomonocytic cells except HL-60 pro-myelocyte-like cells. Progesterone had effects predominantly on pro-myelocytic-like HL-60 cells, inducing apoptosis. Estrogen and progesterone both decreased levels of bcl-2 in KG-1alpha, HL-60, and THP-1 cells. LPS partially antagonized both estrogen-induced THP-1 apoptosis and its suppression of bcl-2 protein. Sex steroid-induced effects on cell cycle transition and apoptosis are potential mechanisms by which pregnancy-induced cell-mediated immune suppression may occur. Further investigation should provide a better understanding of pregnancy-induced immune changes and, perhaps, sex-based differences in monocyte function and immunologic responses.