Expression of cell kinetics and death during monocyte-macrophage differentiation: effects of Actinomycin D and Vinblastine treatments

THP-1 cell line model for tuberculosis: A platform for in vitro macrophage manipulation

Macrophages are large mononuclear phagocytic cells that play a vital role in the immune response. They are present in all body tissues with extremely heterogeneous and plastic phenotypes that adapt to the organs and tissues in which they live and respond in the first-line against invading microorganisms. Tuberculosis (TB) is caused by the pathogenic bacteria Mycobacterium tuberculosis (Mtb), which is among the top 10 global infectious agents and the leading cause of mortality, ranking above human immunodeficiency virus (HIV), as a single infectious agent. Macrophages, upon Mtb infection, not only phagocytose the bacteria and present the antigens to T-cells, but also react rapidly by developing antimycobacterial immune response depending highly on the production of cytokines. However, Mtb is also capable of intracellular survival in instances of sub-optimal activation of macrophages. Hence, several systems have been established to evaluate the Mtb-macrophage interaction, where the THP-1 monocytes have been developed as an attractive model for in vitro polarized monocyte-derived macrophages. This model is extensively used for Mtb as well as other intracellular bacterial studies. Herein, we have summarized the updated implications of the THP-1 model for TB-related studies and discussed the pros and cons compared to other cell models of TB.

The choice of phorbol 12-myristate 13-acetate differentiation protocol influences the response of THP-1 macrophages to a pro-inflammatory stimulus

The human monocytic cell line, THP-1, is the most widely used model for primary human monocytes/macrophages. This is because, following differentiation using phorbol 12-myristate 13-acetate (PMA), THP-1 cells acquire a macrophage-like phenotype, which mimics, in many respects, primary human macrophages. Despite the widespread use of THP-1 cells in studies elucidating macrophage responses to inflammatory stimuli, as well as the development and screening of potential therapeutics, there is currently no standardised protocol for the reliable differentiation of THP-1 monocytes to a macrophage phenotype using PMA. Consequently, reports using THP-1 cells have demonstrated significant phenotypic and functional differences between resultant THP-1 macrophage populations, which are largely attributable to the varying PMA differentiation methods used. Thus, to guarantee consistency and reproducibility between studies, and to ensure the relevance of THP-1 cells as an appropriate model for primary human macrophages, it is crucial to develop a standardised protocol for the differentiation of THP-1 macrophages. Accordingly, we compared the function and phenotype of THP-1 macrophages generated using the range of published PMA differentiation protocols, specifically in response to the pro-inflammatory stimulus, lipopolysaccharide (LPS). Our results demonstrated that the function of the resultant THP-1 macrophage populations, as determined by tumour necrosis factor (TNF) secretion in response to LPS stimulation, varied significantly, and was dependent upon the concentration of PMA used to stimulate the differentiation of monocytes, and the period of rest following PMA exposure. These data indicate that exposure of monocytic THP-1 cells to 25 nM PMA over 48 h, followed by a recovery period of 24h in culture in the absence of PMA, was the optimal protocol for the differentiation of THP-1 cells.

Modulation of Human Macrophage Responses to Mycobacterium tuberculosis by Silver Nanoparticles of Different Size and Surface Modification

Exposure to silver nanoparticles (AgNP) used in consumer products carries potential health risks including increased susceptibility to infectious pathogens. Systematic assessments of antimicrobial macrophage immune responses in the context of AgNP exposure are important because uptake of AgNP by macrophages may lead to alterations of innate immune cell functions. In this study we examined the effects of exposure to AgNP with different particle sizes (20 and 110 nm diameters) and surface chemistry (citrate or polyvinlypyrrolidone capping) on cellular toxicity and innate immune responses against Mycobacterium tuberculosis (M.tb) by human monocyte-derived macrophages (MDM). Exposures of MDM to AgNP significantly reduced cellular viability, increased IL8 and decreased IL10 mRNA expression. Exposure of M.tb-infected MDM to AgNP suppressed M.tb-induced expression of IL1B, IL10, and TNFA mRNA. Furthermore, M.tb-induced IL-1β, a cytokine critical for host resistance to M.tb, was inhibited by AgNP but not by carbon black particles indicating that the observed immunosuppressive effects of AgNP are particle specific. Suppressive effects of AgNP on the M.tb-induced host immune responses were in part due to AgNP-mediated interferences with the TLR signaling pathways that culminate in the activation of the transcription factor NF-κB. AgNP exposure suppressed M.tb-induced expression of a subset of NF-κB mediated genes (CSF2, CSF3, IFNG, IL1A, IL1B, IL6, IL10, TNFA, NFKB1A). In addition, AgNP exposure increased the expression of HSPA1A mRNA and the corresponding stress-induced Hsp72 protein. Up-regulation of Hsp72 by AgNP can suppress M.tb-induced NF-κB activation and host immune responses. The observed ability of AgNP to modulate infectious pathogen-induced immune responses has important public health implications.

Curdlan-Conjugated PLGA Nanoparticles Possess Macrophage Stimulant Activity and Drug Delivery Capabilities

PURPOSE

There is significant interest in the application of nanoparticles to deliver immunostimulatory signals to cells. We hypothesized that curdlan (immune stimulating polymer) could be conjugated to PLGA and nanoparticles from this copolymer would possess immunostimulatory activity, be non-cytotoxic and function as an effective sustained drug release system.

METHODS

Carbodiimide chemistry was employed to conjugate curdlan to PLGA. The conjugate (C-PLGA) was characterized using (1)H and (13)C NMR, FTIR, DSC and TGA. Nanoparticles were synthesized using an emulsion-solvent evaporation technique. Immunostimulatory activity was characterized in THP-1 derived macrophages. MTT assay and real-time impedance measurements were used to characterize polymer and nanoparticle toxicity and uptake in macrophages. Drug delivery capability was assessed across Caco-2 cells using rifampicin as a model drug.

RESULTS

Spectral characterization confirmed successful synthesis of C-PLGA. C-PLGA nanoparticles enhanced phosphorylated ERK production in macrophages indicating cell stimulation. Nanoparticles provided slow release of rifampicin across Caco-2 cells. Polymers but not nanoparticles altered the adhesion profiles of the macrophages. Impedance measurements suggested Ca(2+) dependent uptake of nanoparticles by the macrophages.

CONCLUSIONS

PLGA nanoparticles with macrophage stimulating and sustained drug delivery capabilities have been prepared. These nanoparticles can be used to stimulate macrophages and concurrently deliver drug in infectious disease therapy.

Biological effects of the aqueous extract of Bridelia grandis stem bark on normal and neoplastic human cells: an in vitro preliminary evaluation

The aim of the work is to investigate the effects of Bridelia grandis (Pierre ex Hutch) stem bark water extract on human HeLa cancer cells and normal monocytes treated in vitro, evaluating the morphological modifications with light and electron microscopy. The phytocomplex obtained from B. grandis caused a significant decrease in the mitotic index of both HeLa cancer cells and normal monocytes. In addition, a reduction of the typical aneuploid-polyploid pattern has been observed in HeLa cells after treatment. Various alterations at fine structural level, both in neoplastic (HeLa cells) and normal (monocytes) cells have been observed. In particular, electron-dense cells containing condensed mitochondria, autophagic vacuoles and dense spherical cytoplasmic inclusions have been observed. The results show that B. grandis water extracts have an antiproliferative effect on human cells, with a different effect on neoplastic and normal cells. The antiproliferative effect is accompanied by the appearance of various subcellular alterations. The morphological alterations observed are likely to represent the condition of 'dark cell' as a possible preliminary phase towards the autophagic and/or apoptotic cell death.

PMA withdrawal in PMA-treated monocytic THP-1 cells and subsequent retinoic acid stimulation, modulate induction of apoptosis and appearance of dendritic cells

OBJECTIVES

To analyse proliferation, differentiation and apoptosis in THP-1 cells after stimulation with phorbol 12-myristate 13-acetate (PMA) and retinoic acid (RA).

MATERIALS AND METHODS

PMA and RA were used in a three-step-procedure: (i) treatment with 6, 30, 60 nm PMA, that induced initial, intermediate and advanced levels of monocyte-macrophage transition, respectively; (ii) recovery in PMA-free medium; (iii) incubation with 4 μm RA. Cultures were characterized cytokinetically (flow cytometry/bromodeoxyuridine uptake) and immunocytochemically (static cytometry) for expression of CD14, CD11b (monocyte-macrophage) and DC-SIGN (dendritic cell: DCs) markers.

RESULTS

Some treatments determined appearance of monocyte/macrophage, dendritic and apoptotic phenotypes, percentages of which were related to PMA dose used in step 1, and dependent on presence/absence of PMA and RA. PMA withdrawal induced dedifferentiation and partial restoration of proliferative activity, specially in 6 and 30 nm PMA-derived cells. Recovery in the presence of serum (fundamental to DC appearance) indicated that depending on differentiation level, cell proliferation and apoptosis were inversely correlated. Treatment with 30 nm PMA induced intermediate levels of monocytic-macrophagic differentiation, with expression of alternative means of differentiation and acquisition of DCs without using cytokines, after PMA withdrawal and RA stimulation.

CONCLUSIONS

Our experimental conditions favoured differentiation, dedifferentiation and transdifferentiational pathways, in monocytic THP-1 cells, the balance of which could be related to both cell proliferation and cell death.

The podosome marker protein Tks5 regulates macrophage invasive behavior

Tks5 is a Src substrate and adaptor protein previously recognized for its regulation of cancer cell invasion through modulation of specialized adhesion structures called podosomes/invadopodia. Here we show for the first time that Tks5 localizes to the podosomes of primary macrophages, and that Tks5 protein levels increase concurrently with podosome deposition during the differentiation of monocytes into macrophages. Similar results are reported for model THP-1 cells, which differentiate into macrophages and form proteolytically active podosomes in response to a PKC signaling agonist (PMA) and with sensitivity to a PKC inhibitor (bisindolylmaleimide). Genetic manipulation of Tks5 expression (silencing and overexpression) in stable THP-1 cell lines does not independently alter this macrophage differentiation process. Nor do these cells lose the ability to focalize F-actin and its accessory proteins into podosome-like structures following PMA treatment. However, Tks5 directly controls podosome-associated gelatin degradation and invasion through collective changes in adhesion, chemotaxis, and the expression/proteolytic activity of MMP9. The Src family kinase-dependent phosphorylation of Tks5 is also implicated in the regulation of THP-1 macrophage invasive behavior. These results therefore define a previously unappreciated function of Tks5 signaling specific to the functional attributes of the macrophage podosome in adhesion, motility, and extracellular matrix-remodeling.

A Cell Profiling Framework for Modeling Drug Responses from HCS Imaging

The authors present an unsupervised, scalable, and interpretable cell profiling framework that is compatible with data gathered from high-content screening. They demonstrate the effectiveness of their framework by modeling drug differential effects of IC-21 macrophages treated with microtubule and actin disrupting drugs. They identify significant features of cell phenotypes for unsupervised learning based on maximum relevancy and minimum redundancy criteria. A 2-stage clustering approach annotates, clusters cells, and then merges them together to form super-clusters. An interpretable cell profile consisting of super-cluster proportions profiled at each drug treatment, concentration, or duration is obtained. Differential changes in super-cluster profiles are the basis for understanding the drug’s differential effect and biology. The authors’ method is validated by significant chi-squared statistics obtained from similar drug-treated super-cluster profiles from a 5-fold cross-validation. In addition, drug profiles of 2 microtubule drugs with equivalent mechanisms of action are statistically similar. Several distinct trends are identified for the 5 cytoskeletal drugs profiled under different conditions.

State-of-the-art technologies, current opinions and developments, and novel findings: news from the field of histochemistry and cell biology

Investigations of cell and tissue structure and function using innovative methods and approaches have again yielded numerous exciting findings in recent months and have added important data to current knowledge, inspiring new ideas and hypotheses in various fields of modern life sciences. Topics and contents of comprehensive expert reviews covering different aspects in methodological advances, cell biology, tissue function and morphology, and novel findings reported in original papers are summarized in the present review.

Recent progress in histochemistry

The progress in discerning the structure and function of cells and tissues in health and disease has been achieved to a large extent by the continued development of new reagents for histochemistry, the improvement of existing techniques and new imaging techniques. This review will highlight some advancements made in these fields.

The histochemistry and cell biology vade mecum: a review of 2005–2006

The procurement of new knowledge and understanding in the ever expanding discipline of cell biology continues to advance at a breakneck pace. The progress in discerning the physiology of cells and tissues in health and disease has been driven to a large extent by the continued development of new probes and imaging techniques. The recent introduction of semi-conductor quantum dots as stable, specific markers for both fluorescence light microscopy and electron microscopy, as well as a virtual treasure-trove of new fluorescent proteins, has in conjunction with newly introduced spectral imaging systems, opened vistas into the seemingly unlimited possibilities for experimental design. Although it oftentimes proves difficult to predict what the future will hold with respect to advances in disciplines such as cell biology and histochemistry, it is facile to look back on what has already occurred. In this spirit, this review will highlight some advancements made in these areas in the past 2 years.