The effects of Phorbol 12-myristate 13-acetate concentration on the expression of miR-155 and miR-125b and their macrophage function-related genes in the U937 cell line

The phorbol 12-myristate 13-acetate (PMA)-induced U937 cell line has been widely used as an in vitro model for studying the functions of human macrophages. However, there are several concentrations of PMA commonly used to drive the differentiation of monocytic cell line to macrophage. Also, the expression of microRNA-155 (miR-155) and miR-125b in PMA-treated human monocytic cell line has not yet been reported. The five usual concentrations of PMA for stimulating macrophage differentiation are 10, 25, 50, 100, and 200 nM. In this study we compared the expression levels of miR-155, miR-125b and their related genes involved in macrophage functions in U937-derived cells after treatment with those five concentrations. The morphological study results showed that the five concentrations of PMA could induce macrophage differentiation in a similar manner. Moreover, cell proliferation and viability were not significantly different among these five conditions excepted the lower cell viability at 200 nM of PMA treatment. The five concentrations of PMA could upregulate the expression of miR-155 and miR-125b and increase the phagocytic activity of U937-derived cells in dose-reversal manner. The upregulation of miR-155 was correlated with increased expression levels of TNFα and decreased expression levels of BACH1 and CEBPβ, while the reduction of IRF4 was correlated with increased expression levels of miR-125b. Our study found that PMA could stimulate macrophage differentiation in a broad range of concentrations, however, the lower concentration could upregulate the higher expression of both miR-155 and miR-125b, and that correlated with the phagocytic functional activity of U937-derived macrophages.

Anti-Tumor Effects of Vitamin B2, B6 and B9 in Promonocytic Lymphoma Cells

Chronic inflammation can lead to tumour initiation and progression. Vitamin B complex has the ability to regulate the immune response and, therefore, inflammation but many of the mechanistic and molecular processes involved in this regulation are still not fully understood. This study sought to determine some of these processes by studying the effects of vitamin B2 (riboflavin) B6 (pyridoxine) and B9 (folic acid) on un-differentiated pro-monocytic lymphoma cells in regard to their ability to alter the proliferation, migration, apoptosis, cytokines and expression levels of programmed death ligand 1. We show that vitamin B2, B6 and B9, on pro-monocytic lymphoma cells exerted an anti-tumorigenic effect. This data could form the basis for future studies in using vitamin B supplementation to reduce cancer cell growth in vivo.

Effect of certain non-steroidal anti-inflammatory drugs on the paraoxonase 2 (PON2) in human monocytic cell line U937

The paraoxonase gene family in humans consists of three members as PON1, PON2 and PON3. PON2 can be expressed in several tissues; however, it is not released from the cells in those tissues. PON2 is also expressed in macrophages. Firstly, the commonly used NSAIDs diclofenac sodium and tenoxicam were applied on U937 cell line, the in vitro human monocyte cell line. Than PON2 specific Lactonase activity and paraoxonase family specific arylesterase were determined. Use of Diclofenac sodium in 0.845 mM dose during 6-12 h of incubation and Tenoxicam in 0.74 mM dose during 6 h of incubation resulted in a significant decline in the lactonase activity. Diclofenac sodium didn't make any change in the arylesterase activity. On the other hand, tenoxicam decreased arylesterase activity during the use of 12 h, in 0.74 mM and 1.48 mM dose.

Synergism between phorbol-12-myristate-13-acetate and vitamin D3 in the differentiation of U937 cells to monocytes and macrophages

Phorbol-12-myristate-13-acetate (PMA) and 1,25-dihydroxyvitamin D3 (VD3) are stimuli commonly used to induce macrophage differentiation in monocytic cell lines, but the extent of differentiation in comparison to primary tissue macrophages is unclear. Here, we examine the morphological/phenotypic markers associated with differentiation of U937 cells into monocytes/macrophages, in response to PMA or VD3 treatment. PMA stimulus but not with VD3, induced changes in cell morphology indicative of differentiation, but did not show differentiation comparable to monocyte-derive macrophage (MDM). The cells treated with PMA+VD3 for 2 days (d) acquired morphological/phenotypic features similar to those acquired by monocytes. In contrast, U937 cells treated for 2d with PMA and VD3 followed by 6d of resting in culture without PMA but in the presence of VD3 acquired morphological and phenotypic markers similar to those of MDM; i.e. reduced nucleus/cytoplasmic ratio, high auto-fluorescence and cytoplasmic complexity. Furthermore, low expression of CD14/TLR2 and high expression of CD68/CD86 were observed. In conclusion, our results indicate a synergistic effect between PMA and VD3 in U937 cells differentiation into both monocytes or macrophages and we propose a modified PMA differentiation protocol to enhance monocyte/macrophage differentiation of U937 cells.

The transcription factor C/EBP α controls the role of cystatin F during the differentiation of monocytes to macrophages

Cystatin F is an inhibitor of cysteine peptidases expressed solely in immune cells. It is the only type II cystatin able to enter endosomal/lysosomal vesicles and to regulate directly the activity of intracellular cysteine cathepsins. Its expression in promonocytic U937 and promyeloblastic HL-60 cells is highly upregulated but, after differentiation with phorbol 12-myristate 13-acetate - PMA, its levels drop significantly. In contrast, the activities of intracellular cysteine cathepsins C, L and S are higher in differentiated cells than in non-differentiated ones due, presumably, to the lower inhibitory capacity of cystatin F. Using immunofluorescence confocal microscopy, proximity ligation assay and co-immunoprecipitation, cathepsins C, L and S were confirmed to be the main interacting partners of cystatin F in U937 and HL-60 cells. The promoter region of the cystatin F gene, CST7, contains a unique binding site for transcription factor C/EBP α, one of the main myeloid differentiation instructors. Using the chromatin immunoprecipitation assay, C/EBP α was shown to bind to CST7 gene in U937 cells. Following cell differentiation with PMA, the binding of C/EBP α was decreased significantly. The protein level of C/EBP α was also significantly lower in differentiated than in non-differentiated cells. It was shown that, during monocyte to macrophage differentiation, the endosomal/lysosomal proteolytic activity can be regulated by cystatin F whose expression is under the control of transcriptional factor C/EBP α.

The Effects of Hypoxia on U937 Cell Line in Mesenchymal Stem Cells Co-Culture System

Purpose: Mesenchymal Stem Cells (MSCs) are the most important members of Bone Marrow (BM) milieu. MSCs affect different kinds of cells, particularly malignant cells of hematologic malignancies, but the effects of MSCs are unclear exactly. Here we analyzed the effects of derived Umbilical Cord Blood-MSCs on proliferation, cell death and some surface markers of U937 cell line in a Co-culture system with MSCs. Methods: Here we designed Co-culture systems as a model of BM milieu. We cultured U937 cells on UCB-MSCs and MSCs Conditioned Medium (C.M) driven and then treated U937 cells with optimum concentration of chloride cobalt (CoCl₂) as a hypoxia-mimetic agent. In addition, we applied suitable concentrations of H₂O₂ to induce cell death. Proliferation rate, cell death rate and some surface markers of hypoxic U937 cells were analyzed by MTT assay, flow cytometry and Real Time-PCR were flown respectively. Results: UCB-MSCs showed supportive effects on U937 proliferation rate in normoxia and hypoxia. Lethal effect of H₂O₂ suppressed in the presence of UCB-MSCs in hypoxia and normoxia. Among CD11a, CD14, CD49d, CD54 and CD116 markers, CD49d was down regulated in presence of UCB-MSCs and CD116 was up regulated in hypoxia. Other markers didn't show any significant changes. Conclusion: This work provides evidences that MSCs play critical roles in U937 cells biology. These observations shed new light on MSCs roles and demonstrated that MSCs should be regarded as an important member of BM milieu in several clinical applications such as BM transplantation prognosis and treatment of hematologic malignancies.

Macrophages Exhibit a Large Repertoire of Activation States via Multiple Mechanisms of Macrophage-activating Factors

BACKGROUND/AIM

Macrophages are important components of human defense systems and consequently key to antitumor immunity. Human-serum macrophage activation factor (serum MAF) can activate macrophages, making it a promising reagent for anticancer therapy.

MATERIALS AND METHODS

We established four different macrophage subtypes through introduction of different culture conditions to THP-1- and U937-derived macrophages. We assessed phagocytic activity to understand subtype responses to typical macrophage activation factors (MAFs) and the activation mechanisms of serum MAF.

RESULTS

All four macrophage subtypes differed in their response to all MAFs. Moreover, serum MAF had two different activation mechanisms: N-acetylgalactosamine (GalNAc)-dependent and GalNAc-independent.

CONCLUSION

Macrophage activation states and mechanisms are heterogeneous.

Establishment of a Macrophage-activating Factor Assay System Using the Human Monocytic Cell Line THP-1

BACKGROUND

As the mechanism of macrophage activation is not well-understood, standardization of an assay system for measuring phagocytic activities of macrophages will be useful for research on macrophages. Previously, we established a novel standardized macrophage-activating factor (MAF) assay system using U937.

MATERIALS AND METHODS

Using the human monocytic cell line THP-1, another standardized MAF assay system was established. Characteristic gene expression of U937- and THP-1-derived macrophages was compared by gene expression microarray analysis.

RESULTS

Both U937- and THP-1-derived macrophages showed obvious phagocytic activities with unique characteristics and, therefore, could not be assigned to a single sub-type.

CONCLUSION

Activation of macrophages is an intricate cellular process. Comparison of our two novel assay systems provides new insights into macrophage activation mechanisms.

Macrophage Activation Mechanisms in Human Monocytic Cell Line-derived Macrophages

BACKGROUND

Although the mechanisms of macrophage activation are important for cancer immunotherapy, they are poorly understood. Recently, easy and robust assay systems for assessing the macrophage-activating factor (MAF) using monocytic cell line-derived macrophages were established.

MATERIALS AND METHODS

Gene-expression profiles of U937- and THP-1-derived macrophages were compared using gene expression microarray analysis and their responses against several MAFs were examined by in vitro experiments.

RESULTS

Activated states of these macrophages could not be assigned to a specific sub-type but showed, however, different unique characteristics.

CONCLUSION

The unique of monocytic cell line-derived macrophages could provide clues to understand the activation mechanism of macrophages and, therefore, help to develop effective cancer immunotherapy with MAFs.

A novel assay system for macrophage-activating factor activity using a human U937 cell line

BACKGROUND

Macrophages play important roles in antitumor immunity, and immunotherapy with the group-specific component protein-derived macrophage-activating factor (GcMAF) has been reported to be effective in patients with various types of cancers. However, in macrophage research, it is important to properly evaluate macrophage activity.

MATERIALS AND METHODS

U937 macrophages were induced by 12-O-tetradecanoyl-13-phorbolacetate (TPA). The phagocytic activity of macrophages was evaluated as the internalized beads ratio. The MAF activity was assessed at 30 min after MAF addition as the activation ratio.

RESULTS

We established a novel assay for phagocytic activities using differentiated U937 macrophages.

CONCLUSION

The novel protocol was simple and rapid and was sensitive for GcMAF. This protocol should be useful not only for basic studies, such as those on molecular mechanisms underlying macrophage activation, but also for clinical studies, such as assessment of GcMAF activity prior to clinical use.