Monocyte macrophage differentiation in vitro: Fibronectin-dependent upregulation of certain macrophage-specific activities

Comparison of human macrophages derived from peripheral blood and bone marrow

Macrophage differentiation, phenotype, and function have been assessed extensively in vitro by predominantly deriving human macrophages from peripheral blood. It is accepted that there are differences between macrophages isolated from different human tissues; however, the importance of anatomical source for in vitro differentiation and characterization is less clear. Here, phenotype and function were evaluated between human macrophages derived from bone marrow or peripheral blood. Macrophages were differentiated by adherence of heterogenous cell populations or CD14 isolation and polarized with IFNγ and LPS or IL-4 and IL-13 for 48 hours before evaluation of phenotype and phagocytic capacity. The presence of stromal cells in bone marrow heterogenous cultures resulted in a reduction in macrophage purity compared to peripheral blood, which was negated after CD14 isolation. Phenotypically, monocyte-derived macrophages (MDMs) derived from peripheral blood and bone marrow resulted in similar expression of classical and polarized macrophages markers, including CD14, HLA-DR, CD38, and CD40 (increased after IFNγ/LPS), and CD11b and CD206 (elevated after IL-4/IL-13). Functionally, these cells also showed similar levels of Fc-independent and Fc-dependent phagocytosis, although there was a nonsignificant reduction of Fc-dependent phagocytosis in the bone marrow derived macrophages after IFNγ/LPS stimulation. In summary, we have identified that human MDMs differentiated from peripheral blood and bone marrow showed similar characteristics and functionality, suggesting that isolating cells from different anatomical niches does not affect macrophage differentiation after CD14 isolation. Consequently, due to high yield and ready availability peripheral blood derived macrophages are still the most suitable source.

MXRA7 is involved in monocyte-to-macrophage differentiation

Macrophages are critical in mediating immune and inflammatory responses, while monocyte-to-macrophage differentiation is one of the main macrophage resources that involves various matrix proteins. Matrix remodeling associated 7 (MXRA7) was recently discovered to affect a variety of physiological and pathological processes related to matrix biology. In the present study, we investigated the role of MXRA7 in monocyte-to-macrophage differentiation in vitro. We found that knockdown of MXRA7 inhibited the proliferation of THP-1 human monocytic cells. Knockdown of MXRA7 increased the adhesion ability of THP-1 cells through upregulation the expression of adhesion molecules VCAM-1 and ICAM1. Knockdown of MXRA7 alone could promoted the differentiation of THP-1 cells to macrophages. Furthermore, the MXRA7-knockdown THP-1 cells produced a more significant upregulation pattern with M1-type cytokines (TNF-α, IL-1β and IL-6) than with those M2-type molecules (TGF-β1 and IL-1RA) upon PMA stimulation, indicating that knockdown of MXRA7 facilitated THP-1 cells differentiation toward M1 macrophages. RNA sequencing analysis revealed the potential biological roles of MXRA7 in cell adhesion, macrophage and monocyte differentiation. Moreover, MXRA7 knockdown promoted the expression of NF-κB p52/p100, while PMA stimulation could increase the expression of NF-κB p52/p100 and activating MAPK signaling pathways in MXRA7 knockdown cells. In conclusion, MXRA7 affected the differentiation of THP-1 cells toward macrophages possibly through NF-κB signaling pathways.

SVEP1 influences monocyte to macrophage differentiation via integrin α4β1/α9β1 and Rho/Rac signalling

BACKGROUND

The large extracellular matrix protein SVEP1 mediates cell adhesion via integrin α9β1. Recent studies have identified an association between a missense variant in SVEP1 and increased risk of coronary artery disease (CAD) in humans and in mice Svep1 deficiency alters the development of atherosclerotic plaques. However how SVEP1 functionally contributes to CAD pathogenesis is not fully understood. Monocyte recruitment and differentiation to macrophages is a key step in the development of atherosclerosis. Here, we investigated the requirement for SVEP1 in this process.

METHODS

SVEP1 expression was measured during monocyte-macrophage differentiation in primary monocytes and THP-1 human monocytic cells. SVEP1 knockout THP-1 cell lines and the dual integrin α4β1/α9β1 inhibitor, BOP, were utilised to investigate the effect of these proteins in THP-1 cell adhesion, migration and cell spreading assays. Subsequent activation of downstream integrin signalling intermediaries was quantified by western blotting.

RESULTS

SVEP1 gene expression increases in monocyte to macrophage differentiation in human primary monocytes and THP-1 cells. Using two SVEP1 knockout THP-1 cells we observed reduction in monocyte adhesion, migration, and cell spreading compared to control cells. Similar results were found with integrin α4β1/α9β1 inhibition. We demonstrate reduced activity of Rho and Rac1 in SVEP1 knockout THP-1 cells.

CONCLUSIONS

SVEP1 regulates monocyte recruitment and differentiation phenotypes through an integrin α4β1/α9β1 dependent mechanism.

GENERAL SIGNIFICANCE

These results describe a novel role for SVEP1 in monocyte behaviour relevant to CAD pathophysiology.

A positive feedback loop driven by fibronectin and IL-1β sustains the inflammatory microenvironment in breast cancer

Inflammatory alterations of the extracellular matrix shape the tumor microenvironment and promote all stages of carcinogenesis. This study aims to determine the impact of cellular fibronectin on inflammatory facets of tumor-associated macrophages (TAMs) in breast cancer. Cellular fibronectin (FN) harboring the alternatively spliced extra domain A (FN-EDA) was determined to be a matrix component produced by the triple-negative breast cancer (TNBC) cells. High levels of FN-EDA correlated with poor survival in breast cancer patients. The proinflammatory cytokine IL-1β enhanced the expression of cellular fibronectin including FN-EDA. TAMs were frequently observed in the tumor areas rich in FN-EDA. Conditioned media from TNBC cells induced the differentiation of CD206⁺CD163⁺ macrophages and stimulated the STAT3 pathway, ex vivo. In the macrophages, the STAT3 pathway enhanced FN-EDA-induced IL-1β secretion and NF-κB signaling. In conclusion, our data indicate a self-reinforcing mechanism sustained by FN-EDA and IL-1β through NF-κB and STAT3 signaling in TAMs which fosters an inflammatory environment in TNBC.

Expression of O-glycosylated oncofetal fibronectin in alternatively activated human macrophages

Macrophage (Mϕ) polarization is an essential phenomenon for the maintenance of homeostasis and tissue repair, and represents the event by which Mϕ reach divergent functional phenotypes as a result to specific stimuli and/or microenvironmental signals. Mϕ can be polarized into two main phenotypes, M1 or classically activated and M2 or alternatively activated. These two categories diverge in many aspects, such as secreted cytokines, markers of cell surface, and biological functions. Over the last 10 years, many potential markers have been proposed for both M1 and M2 human Mϕ. However, there is scarce information regarding the glycophenotype adopted by these cells. Here, we show that M2- but not M1-polarized Mϕ expresses high levels of an unusual glycoform of fibronectin (FN), named O-glycosylated oncofetal FN (onf-FN), found in fetal/cancer cells, but not in healthy tissues. The onf-FN expression was confirmed in vitro by Western blot and real-time RT-qPCR in primary and cell line monocyte-derived Mϕ. onf-FN was induced by IL-4 and IL-13, but not by pro-inflammatory stimuli (LPS and INF-γ). RNA and protein analysis clearly demonstrated that it is specifically associated with the M2 polarization. In conclusion, we show by the first time that O-glycosylated onf-FN is expressed by M2-polarized Mϕ.

Submolecular Ligand Size and Spacing for Cell Adhesion

Cell adhesion occurs when integrin recognizes and binds to Arg-Gly-Asp (RGD) ligands present in fibronectin. In this work, submolecular ligand size and spacing are tuned via template-mediated in situ growth of nanoparticles for dynamic macrophage modulation. To tune liganded gold nanoparticle (GNP) size and spacing from 3 to 20 nm, in situ localized assemblies of GNP arrays on nanomagnetite templates are engineered. 3 nm-spaced ligands stimulate the binding of integrin, which mediates macrophage-adhesion-assisted pro-regenerative polarization as compared to 20 nm-spaced ligands, which can be dynamically anchored to the substrate for stabilizing integrin binding and facilitating dynamic macrophage adhesion. Increasing the ligand size from 7 to 20 nm only slightly promotes macrophage adhesion, not observed with 13 nm-sized ligands. Increasing the ligand spacing from 3 to 17 nm significantly hinders macrophage adhesion that induces inflammatory polarization. Submolecular tuning of ligand spacing can dominantly modulate host macrophages.

Elevated Fibronectin Levels in Profibrotic CD14+ Monocytes and CD14+ Macrophages in Systemic Sclerosis

Background

Systemic sclerosis (SSc) is an autoimmune disease characterized by overproduction of extracellular matrix (ECM) and multiorgan fibrosis. Animal studies pointed to bone marrow-derived cells as a potential source of pathological ECM-producing cells in immunofibrotic disorders. So far, involvement of monocytes and macrophages in the fibrogenesis of SSc remains poorly understood.

Methods and Results

Immunohistochemistry analysis showed accumulation of CD14⁺ monocytes in the collagen-rich areas, as well as increased amount of alpha smooth muscle actin (αSMA)-positive fibroblasts, CD68⁺ and mannose-R⁺ macrophages in the heart and lungs of SSc patients. The full genome transcriptomics analyses of CD14⁺ blood monocytes revealed dysregulation in cytoskeleton rearrangement, ECM remodeling, including elevated FN1 (gene encoding fibronectin) expression and TGF-β signalling pathway in SSc patients. In addition, single cell RNA sequencing analysis of tissue-resident CD14⁺ pulmonary macrophages demonstrated activated profibrotic signature with the elevated FN1 expression in SSc patients with interstitial lung disease. Peripheral blood CD14⁺ monocytes obtained from either healthy subjects or SSc patients exposed to profibrotic treatment with profibrotic cytokines TGF-β, IL-4, IL-10, and IL-13 increased production of type I collagen, fibronectin, and αSMA. In addition, CD14⁺ monocytes co-cultured with dermal fibroblasts obtained from SSc patients or healthy individuals acquired a spindle shape and further enhanced production of profibrotic markers. Pharmacological blockade of the TGF-β signalling pathway with SD208 (TGF-β receptor type I inhibitor), SIS3 (Smad3 inhibitor) or (5Z)-7-oxozeaenol (TGF-β-activated kinase 1 inhibitor) ameliorated fibronectin levels and type I collagen secretion.

Conclusions

Our findings identified activated profibrotic signature with elevated production of profibrotic fibronectin in CD14⁺ monocytes and CD14⁺ pulmonary macrophages in SSc and highlighted the capability of CD14⁺ monocytes to acquire a profibrotic phenotype. Taking together, tissue-infiltrating CD14⁺ monocytes/macrophages can be considered as ECM producers in SSc pathogenesis.

Phenotypical modifications of immune cells are enhanced by extracellular matrix

Immune cells not only constitute tumour microenvironment but they may even affect disease prognosis as a result of dual functional roles that they may play in tumour tissues. Two frequently used established immune cell lines (lymphocytic Jurkat and monocytic THP-1) were used to test whether microenvironmental factors, especially molecular components of extracellular matrix, can shape the phenotype of immune cells. Proliferation, morphological and phenotypical analyses were applied to compare behaviour of the immune cells, typically cultured as suspensions in culture medium, with their behaviour in collagen type I-based and Matrigel-based 3D cultures. Density of both immune cell types in routine suspension cultures affected their subsequent proliferation in extracellular matrices. THP-1 cells appeared to be more sensitive to their surrounding microenvironment as judged from extracellular matrix type-dependent changes in their cell doubling times and from slight increase in their diameters in both extracellular matrix-containing cell cultures. Moreover, even chemically uninduced monocytic THP-1 cells were present in a minor fraction as CD68 positive cell population in collagen type I matrix indicating their partial differentiation to macrophages. Observed modifications of immune cells by microenvironmental factors may have profound implications for their roles in healthy and pathological tissues.

Targeting Fibrosis: The Bridge That Connects Pancreatitis and Pancreatic Cancer

Pancreatic fibrosis is caused by the excessive deposits of extracellular matrix (ECM) and collagen fibers during repeated necrosis to repair damaged pancreatic tissue. Pancreatic fibrosis is frequently present in chronic pancreatitis (CP) and pancreatic cancer (PC). Clinically, pancreatic fibrosis is a pathological feature of pancreatitis and pancreatic cancer. However, many new studies have found that pancreatic fibrosis is involved in the transformation from pancreatitis to pancreatic cancer. Thus, the role of fibrosis in the crosstalk between pancreatitis and pancreatic cancer is critical and still elusive; therefore, it deserves more attention. Here, we review the development of pancreatic fibrosis in inflammation and cancer, and we discuss the therapeutic strategies for alleviating pancreatic fibrosis. We further propose that cellular stress response might be a key driver that links fibrosis to cancer initiation and progression. Therefore, targeting stress proteins, such as nuclear protein 1 (NUPR1), could be an interesting strategy for pancreatic fibrosis and PC treatment.

Biomechanical Contributions to Macrophage Activation in the Tumor Microenvironment

Alterations in extracellular matrix composition and organization are known to promote tumor growth and metastatic progression in breast cancer through interactions with tumor cells as well as stromal cell populations. Macrophages display a spectrum of behaviors from tumor-suppressive to tumor-promoting, and their function is spatially and temporally dependent upon integrated signals from the tumor microenvironment including, but not limited to, cytokines, metabolites, and hypoxia. Through years of investigation, the specific biochemical cues that recruit and activate tumor-promoting macrophage functions within the tumor microenvironment are becoming clear. In contrast, the impact of biomechanical stimuli on macrophage activation has been largely underappreciated, however there is a growing body of evidence that physical cues from the extracellular matrix can influence macrophage migration and behavior. While the complex, heterogeneous nature of the extracellular matrix and the transient nature of macrophage activation make studying macrophages in their native tumor microenvironment challenging, this review highlights the importance of investigating how the extracellular matrix directly and indirectly impacts tumor-associated macrophage activation. Additionally, recent advances in investigating macrophages in the tumor microenvironment and future directions regarding mechano-immunomodulation in cancer will also be discussed.

Coating of cobalt chrome substrates with thin films of polar/hydrophobic/ionic polyurethanes: Characterization and interaction with human immunoglobulin G and fibronectin

Biomaterial implants often lead to specific tissue reactions that could compromise their bio-integration and/or optimal cellular interactions. Polyurethanes (PU) are of particular interest as coatings to mask CoCr's bioactivity, since they are generally more biocompatible than metal substrates, present a broad range of chemistry, and have highly tunable-mechanical properties. In the current work, complex polyvinyl-urethanes (referred to as D-PHI materials) are studied for their surface phase structures: specifically, an original D-PHI polymer (O-D-PHI) and a differential formulation with relatively higher hydrophobic and ionic content (HHHI) are of interest. The PUs are diluted in tetrahydrofuran (THF) to generate thin films which differentially influence the physical and chemical properties of the D-PHI coatings. AFM images over time show the gradual appearance of domains exhibiting crystalline organisation, and whose shape and size were dependent on D-PHI thickness (thin films vs non-solvent cast resin materials). After three weeks, a complete stabilization of the crystal state is observed. The thin coatings are stable in an aqueous and 37 °C environment. The adsorption of two human plasmatic proteins Immunoglobulin G (IgG) and Fibronectin (Fn), involved in inflammation and coagulation, was studied. The exposure of specific protein sequences (IgG-Fab, Fn-Cell Binding Domain and Fn-N-terminal domain) were dramatically reduced on both D-PHI materials when compared to bare metal CoCr. The implications of these findings would be relevant to defining coating strategies used to improve the blood clotting and immune cell reactivity to CoCr implant materials.

Mono vs multilayer fibronectin coatings on polar/hydrophobic/ionic polyurethanes: Altering surface interactions with human monocytes

Monocyte interactions with materials that are biofunctionalized with fibronectin (Fn) are of interest because of the documented literature which associates this protein with white blood cell function at implant sites. A degradable-polar hydrophobic ionic polyurethane (D-PHI), has been reported to promote an anti-inflammatory response from human monocytes. The aim of the current work was to study the influence of intrinsic D-PHI material chemistry on Fn adsorption (mono and multi-layer structures), and to investigate the influence of such chemistry on the structural state of the Fn, as well as the latter's influence on the activity of human monocytes on the protein coated substrates. Significant differences in Fn adsorption, surface hydrophobicity and the availability of defined peptide sequences (N terminal, C terminal or Cell Binding Domain) for the Fn in mono vs multilayer structures were observed as a function of the changes in intrinsic material chemistry. A D-PHI-formulated polyurethane substrate with subtle changes in anionic and hydrophobic domain content relative to the polar non-ionic urethane/carbonate groups within the polymer matrix promoted the lowest activation of monocytes, in the presence of multi-layer Fn constructs. These results highlight the importance of chemical heterogeneity as a design parameter for biomaterial surfaces, and establishes a desired strategy for controlling human monocyte activity at the surface of devices, when these are coated with multi-layer Fn structures. The latter is an important step towards functionalizing the materials with multi-layer protein drug carriers as interventional therapeutic agents.

STATEMENT OF SIGNIFICANCE

The control of the behavior of monocytes, especially migration and activation, is of crucial interest to modulate the inflammatory response at the site of implanted biomaterial. Several studies report the influence of adsorbed serum proteins on the behavior of monocytes on biomaterials. However, few studies show the influence of surface chemical group distribution on the controlled adsorption and the subsequent induced conformation- of mono versus multi-layer assembled structures generated from specific proteins implicated in wound repair. The current research considered the role of Fn adsorption and conformation in thin films while interacting with the intrinsic chemistry of segmented block polyurethanes; and the influence of the former on modulation and activation of human monocytes.

Fibronectin adsorption on surface-modified polyetherurethanes and their differentiated effect on specific blood elements related to inflammatory and clotting processes

After the introduction of a medical device into the body, adhesive proteins such as fibronectin (Fn) will adsorb to the surface of the biomaterial. Monocytes (MCs) will interact with these adsorbed proteins, and adopt either a proinflammatory and/or prowound healing phenotype, thereby influencing many blood interaction events including thrombogenesis. In this work, Fn adsorption as well as subsequent MC response and thrombus formation were investigated on two surfaces-modified polyetherurethanes (PEUs) using different surface modifiers: an anionic/dihydroxyl oligomeric (ADO) additive, known to enable cell adhesion, and a fluorinated polypropylene oxide oligomer (PPO), known to reduce platelet adhesion. Results indicated that at 24 h of MC culture, PEU-ADO and PEU-PPO promoted an anti-inflammatory character relative to the base PEU. Longer clotting times, based on a free hemoglobin assay, were also found on the two surface-modified PEUs relative to the native one, suggesting their potential for the reduction of thrombus formation. In presence of a Fn monolayer, the surface-modified PEUs conserved a lower thrombogenic character than the base PEU, and was however significantly decreased when compared to prior protein adsorption. Furthermore, Fn coatings increased the MC production levels of tumor necrosis factor-α and interleukin-10 at 24 h, while not affecting the anti-inflammatory effect of the modifications relative to the base PEU. This finding was most prominent on PEU-PPO, suggesting that the interaction of the adsorbed Fn with blood cells was different for the two additives. Hence, the results highlighted differentiating effects of Fn adsorption on specific blood activating processes related to inflammatory and thrombotic responses.

A responsive human triple-culture model of the air-blood barrier: incorporation of different macrophage phenotypes

Current pulmonary research underlines the relevance of the alveolar macrophage (AM) integrated in multicellular co-culture-systems of the respiratory tract to unravel, for example, the mechanisms of tissue regeneration. AMs demonstrate a specific functionality, as they inhabit a unique microenvironment with high oxygen levels and exposure to external hazards. Healthy AMs display an anti-inflammatory phenotype, prevent hypersensitivity to normally innocuous contaminants and maintain tissue homeostasis in the alveolus. To mirror the actual physiological function of the AM, we developed three different polarized [classically activated (M1) and alternatively activated (M2_wh , wound-healing; M2_reg , regulatory)] macrophage models using a mixture of differentiation mediators, as described in the current literature. To test their immunological impact, these distinct macrophage phenotypes were seeded on to the epithelial layer of an established in vitro air-blood barrier co-culture, consisting of alveolar epithelial cells A549 or H441 and microvascular endothelial cells ISO-HAS-1 on the opposite side of a Transwell filter-membrane. IL-8 and sICAM release were measured as functionality parameters after LPS challenge. The M1 model itself already provoked a severe inflammatory-like response of the air-blood barrier co-culture, thus demonstrating its potential as a useful in vitro model for inflammatory lung diseases. The two M2 models represent a 'non-inflammatory' phenotype but still showed the ability to trigger inflammation following LPS challenge. Hence, the latter could be used to establish a quiescent, physiological in vitro air-blood model. Thus, the more complex differentiation protocol developed in the present study provides a responsive in vitro triple-culture model of the air-blood-barrier that mimics AM features as they occur in vivo. © 2015 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons, Ltd.

Integrin-driven monocyte to dendritic cell conversion in modified extracorporeal photochemotherapy

Due to clinical efficacy and safety profile, extracorporeal photochemotherapy (ECP) is a commonly used cell treatment for patients with cutaneous T cell lymphoma (CTCL) and graft-versus-host disease (GVHD). The capacity of ECP to induce dendritic antigen-presenting cell (DC)-mediated selective immunization or immunosuppression suggests a novel mechanism involving pivotal cell signalling processes that have yet to be clearly identified as related to this procedure. In this study we employ two model systems of ECP to dissect the role of integrin signalling and adsorbed plasma proteins in monocyte-to-DC differentiation. We demonstrate that monocytes that were passed through protein-modified ECP plates adhered transiently to plasma proteins, including fibronectin, adsorbed to the plastic ECP plate and activated signalling pathways that initiate monocyte-to-DC conversion. Plasma protein adsorption facilitated 54·2 ± 4·7% differentiation, while fibronectin supported 29·8 ± 7·2% differentiation, as detected by DC phenotypic expression of membrane CD80 and CD86, as well as CD36, human leucocyte antigen D-related (HLA-DR) and cytoplasmic CD83. Further, we demonstrate the ability of fibronectin and other plasma proteins to act through cell adhesion via the ubiquitous arginine-glycine-aspartic (RGD) motif to drive monocyte-to-DC differentiation, with high-density RGD substrates supporting 54·1 ± 5·8% differentiation via αVβ3 and α5β1integrin signalling. Our results demonstrate that plasma protein binding integrins and plasma proteins operate through specific binding domains to induce monocyte-to-DC differentiation in ECP, providing a mechanism that can be harnessed to enhance ECP efficacy.

Monocyte/macrophage cytokine activity regulates vascular smooth muscle cell function within a degradable polyurethane scaffold

Tissue engineering strategies rely on the ability to promote cell proliferation and migration into porous biomaterial constructs, as well as to support specific phenotypic states of the cells in vitro. The present study investigated the use of released factors from monocytes and their derived macrophages (MDM) and the mechanism by which they regulate vascular smooth muscle cell (VSMC) response in a VSMC-monocyte co-culture system within a porous degradable polyurethane (D-PHI) scaffold. VSMCs cultured in monocyte/MDM-conditioned medium (MCM), generated from the culture of monocytes/MDM on D-PHI scaffolds for up to 28 days, similarly affected VSMC contractile marker expression, growth and three-dimensional migration when compared to direct VSMC-monocyte co-culture. Monocyte chemotactic protein-1 (MCP-1) and interleukin-6 (IL-6) were identified as two cytokines present in MCM, at concentrations that have previously been shown to influence VSMC phenotype. VSMCs cultured alone on D-PHI scaffolds and exposed to MCP-1 (5 ng ml(-1)) or IL-6 (1 ng ml(-1)) for 7 days experienced a suppression in contractile marker expression (with MCP-1 or IL-6) and increased growth (with MCP-1) compared to no cytokine medium supplementation. These effects were also observed in VSMC-monocyte co-culture on D-PHI. Neutralization of IL-6, but not MCP-1, was subsequently shown to decrease VSMC growth and enhance calponin expression for VSMC-monocyte co-cultures on D-PHI scaffolds for 7 days, implying that IL-6 mediates VSMC response in monocyte-VSMC co-cultures. This study highlights the use of monocytes and their derived macrophages in conjunction with immunomodulatory biomaterials, such as D-PHI, as agents for regulating VSMC response, and demonstrates the importance of monocyte/MDM-released factors, such as IL-6 in particular, in this process.

Monocyte Migration Driven by Galectin-3 Occurs through Distinct Mechanisms Involving Selective Interactions with the Extracellular Matrix

Monocyte migration into tissues, an important event in inflammation, requires an intricate interplay between determinants on cell surfaces and extracellular matrix (ECM). Galectin-3 is able to modulate cell-ECM interactions and is an important mediator of inflammation. In this study, we sought to investigate whether interactions established between galectin-3 and ECM glycoproteins are involved in monocyte migration, given that the mechanisms by which monocytes move across the endothelium and through the extravascular tissue are poorly understood. Using the in vitro transwell system, we demonstrated that monocyte migration was potentiated in the presence of galectin-3 plus laminin or fibronectin, but not vitronectin, and was dependent on the carbohydrate recognition domain of the lectin. Only galectin-3-fibronectin combinations potentiated the migration of monocyte-derived macrophages. In binding assays, galectin-3 did not bind to fibronectin, whereas both the full-length and the truncated forms of the lectin, which retains carbohydrate binding ability, were able to bind to laminin. Our results show that monocytes migrate through distinct mechanisms and selective interactions with the extracellular matrix driven by galectin-3. We suggest that the lectin may bridge monocytes to laminin and may also activate these cells, resulting in the positive regulation of other adhesion molecules and cell adhesion to fibronectin.

NaCl potentiates human fibrocyte differentiation

Excessive NaCl intake is associated with a variety of fibrosing diseases such as renal and cardiac fibrosis. This association has been attributed to increased blood pressure as the result of high NaCl intake. However, studies in patients with high NaCl intake and fibrosis reveal a connection between NaCl intake and fibrosis that is independent of blood pressure. We find that increasing the extracellular concentration of NaCl to levels that may occur in human blood after high-salt intake can potentiate, in serum-free culture conditions, the differentiation of freshly-isolated human monocytes into fibroblast-like cells called fibrocytes. NaCl affects the monocytes directly during their adhesion. Potassium chloride and sodium nitrate also potentiate fibrocyte differentiation. The plasma protein Serum Amyloid P (SAP) inhibits fibrocyte differentiation. High levels of extracellular NaCl change the SAP Hill coefficient from 1.7 to 0.8, and cause a four-fold increase in the concentration of SAP needed to inhibit fibrocyte differentiation by 95%. Together, our data suggest that NaCl potentiates fibrocyte differentiation. NaCl-increased fibrocyte differentiation may thus contribute to NaCl-increased renal and cardiac fibrosis.

Fibronectin inhibits cytokine production induced by CpG DNA in macrophages without direct binding to DNA

Fibronectin (FN) is known to have four DNA-binding domains although their physiological significance is unknown. Primary murine peritoneal macrophages have been shown to exhibit markedly lower responsiveness to CpG motif-replete plasmid DNA (pDNA), Toll-like receptor-9 (TLR9) ligand, compared with murine macrophage-like cell lines. The present study was conducted to examine whether FN having DNA-binding domains is involved in this phenomenon. The expression of FN was significantly higher in primary macrophages than in a macrophage-like cell line, RAW264.7, suggesting that abundant FN might suppress the responsiveness in the primary macrophages. However, electrophoretic analysis revealed that FN did not bind to pDNA in the presence of a physiological concentration of divalent cations. Surprisingly, marked tumor necrosis factor - (TNF-)α production from murine macrophages upon CpG DNA stimulation was significantly reduced by exogenously added FN in a concentration-dependent manner but not by BSA, laminin or collagen. FN did not affect apparent pDNA uptake by the cells. Moreover, FN reduced TNF-α production induced by polyI:C (TLR3 ligand), and imiquimod (TLR7 ligand), but not by LPS (TLR4 ligand), or a non-CpG pDNA/cationic liposome complex. The confocal microscopic study showed that pDNA was co-localized with FN in the same intracellular compartment in RAW264.7, suggesting that FN inhibits cytokine signal transduction in the endosomal/lysosomal compartment. Taken together, the results of the present study has revealed, for the first time, a novel effect of FN whereby the glycoprotein modulates cytokine signal transduction via CpG-DNA/TLR9 interaction in macrophages without direct binding to DNA through its putative DNA-binding domains.

Retargeted clostridial neurotoxins as novel agents for treating chronic diseases

Botulinum neurotoxin (BoNT) A and B are used to treat neuropathic disorders; if retargeted, these agents could be used to treat medical conditions that involve secretion from nonneuronal cells. Here, we report novel strategies for successfully retargeting BoNTs, and also tetanus neurotoxin (TeNT), to primary human blood monocyte-derived macrophages where BoNT/B inhibited the release of tumor necrosis factor-α, a cytokine that plays a key role in inflammation. Furthermore, mice treated with retargeted BoNT/B exhibited a significant reduction in macrophage (MΦ) recruitment, indicating that these toxins can be used to treat chronic inflammation.

Evaluation of cytokine expression by blood monocytes of lactating Holstein cows with or without postpartum uterine disease

Whereas neutrophils are the main phagocytic leukocytes, monocytes and macrophages are actively involved in immunomodulation after infection. Recent studies have demonstrated that neutrophil function is impaired by the state of negative energy balance around parturition, and that cows that develop uterine disease have a greater degree of negative energy balance than healthy cows. The objectives of this study were to compare monocyte gene expression and protein secretion of selected cytokines from calving to 42 d after calving in Holstein cows that did or did not develop uterine disease. Real time quantitative RT-PCR (Tumor necrosis factor-α (TNFα), Interleukin (IL)-1β, IL-6, IL-8 and IL-10) and ELISA (TNFα, IL-1β and IL-8) were used to evaluate cytokine response following in vitro stimulation of blood-derived monocytes with irradiated E. coli. Relative to unstimulated cells, E. coli-stimulated monocytes from cows with metritis had lower gene expression of key pro-inflammatory cytokines than healthy cows from calving to 14 d after calving (TNFα at 0, 7, and 14 d after calving, IL-1β and IL-6 at 7 and 14 d after calving; P < 0.05). There were no significant differences between groups for expression of IL-8 or the anti-inflammatory cytokine IL-10. This was due, in part, to higher gene expression in unstimulated monocytes (TNFα, IL-1β, IL-6 and IL-10) in early lactation from cows with metritis. Expression of mRNA in stimulated cells (relative to housekeeping genes) was lower for TNFα (7 and 14 d postpartum) and for IL-10 (7 and 14 d postpartum) in cows with metritis. Concentration of TNFα was lower in the culture medium of E. coli-stimulated monocytes from cows with metritis than healthy cows at calving and 7 and 21 d after calving (P < 0.05). Circulating cytokine concentrations were not different between groups for IL-8 and were below the limits of detection for TNFα and IL-1β. Cytokine gene expression and production were similar between healthy cows and cows that developed endometritis, diagnosed cytologically at 42 d after calving. We concluded that altered levels of expression and production of pro-inflammatory cytokines postpartum could contribute to impaired inflammatory response and predispose cows to development of metritis.

ATRA-induced HL-60 myeloid leukemia cell differentiation depends on the CD38 cytosolic tail needed for membrane localization, but CD38 enzymatic activity is unnecessary

Leukocyte antigen CD38 expression is an early marker of all-trans retinoic acid (ATRA) stimulated differentiation in the leukemic cell line HL-60. It promotes induced myeloid maturation when overexpressed, whereas knocking it down is inhibitory. It is a type II membrane protein with an extracellular C-terminal enzymatic domain with NADase/NADPase and ADPR cyclase activity and a short cytoplasmic N-terminal tail. Here we determined whether CD38 enzymatic activity or the cytoplasmic tail is required for ATRA-induced differentiation. Neither a specific CD38 ectoenzyme inhibitor nor a point mutation that cripples enzymatic activity (CD38 E226Q) diminishes ATRA-induced differentiation or G1/0 arrest. In contrast a cytosolic deletion mutation (CD38 Δ11-20) prevents membrane expression and inhibits differentiation and G1/0 arrest. These results may be consistent with disrupting the function of critical molecules necessary for membrane-expressed CD38 signal transduction. One candidate molecule is the Src family kinase Fgr, which failed to undergo ATRA-induced upregulation in CD38 Δ11-20 expressing cells. Another is Vav1, which also showed only basal expression after ATRA treatment in CD38 Δ11-20 expressing cells. Therefore, the ability of CD38 to propel ATRA-induced myeloid differentiation and G1/0 arrest is unimpaired by loss of its ectoenzyme activity. However a cytosolic tail deletion mutation disrupted membrane localization and inhibited differentiation. ATRA-induced differentiation thus does not require the CD38 ectoenzyme function, but is dependent on a membrane receptor function.

Adhesion of monocytes to type I collagen stimulates an APP-dependent proinflammatory signaling response and release of Abeta1-40

BACKGROUND

Amyloid precursor protein (APP) is a ubiquitously expressed cell surface protein reported to be involved in mediating cell-cell or cell-matrix interactions. Prior work has demonstrated that APP co-localizes with beta1 integrin in different cell types.

METHODS

In an effort to determine the function of APP on monocytic lineage cells, in particular, the human monocyte cell line, THP-1, was used to assess the role of APP during adhesion to the extracelluar matrix component type I collagen.

RESULTS

Pull-down assays demonstrated that THP-1 adhesion to collagen stimulated a tyrosine kinase-associated signaling response which included subsequent phosphorylation of p38 MAP kinase and increased association of APP with alpha2beta1 integrin, specifically. In addition, cell adhesion was dependent upon APP expression since APP siRNA knockdown attenuated THP-1 adhesion to collagen compared to mock transfected controls. One consequence of the tyrosine kinase-dependent signaling response was increased secretion of interleukin-1beta (IL-1beta) and Abeta1-40 but not the Abeta1-42 fragment of APP. Increased secretion of IL-1beta was dependent upon p38 MAP kinase activity while Abeta1-40 secretion required Src family kinase activity since the specific p38 inhibitor, SB202190, and the Src family kinase inhibitor, PP2, attenuated IL-1beta and Abeta1-40 secretion, respectively.

CONCLUSIONS

These data demonstrate that APP is involved in classic integrin-dependent tyrosine kinase-associated adhesion and activation of peripheral monocytic cells. Moreover, divergent APP-dependent signaling is required for increased secretion of both IL-1beta and Abeta1-40 as a component of the adhesion-dependent change in phenotype. This suggests that APP may have a broad role in not only mediating cell-matrix adhesion but also in the function of peripheral immune cells.

Arhgef1 regulates alpha5beta1 integrin-mediated matrix metalloproteinase expression and is required for homeostatic lung immunity

Pulmonary immunity depends on the ability of leukocytes to neutralize potentially harmful and frequent insults to the lung, and appropriate regulation of leukocyte migration and adhesion is integral to this process. Arhgef1 is a hematopoietic-restricted signaling molecule that regulates leukocyte migration and integrin-mediated adhesion. To explore a possible regulatory role for Arhgef1 in pulmonary immunity we examined the lung and its leukocytes in wild-type and Arhgef1-deficient animals. Here we report that the lungs of Arhgef1-/- mice harbored significantly more leukocytes, increased expression and activity of matrix metalloproteinases (MMPs), airspace enlargement, and decreased lung elastance compared with wild-type lungs. Transfer of Arhgef1-/- lung leukocytes to wild-type mice led to airspace enlargement and impaired lung function, indicating that loss of Arhgef1 in leukocytes was sufficient to induce pulmonary pathology. Furthermore, we showed that Arhgef1-deficient peritoneal macrophages when either injected into the lungs of wild-type mice or cultured on fibronectin significantly increased expression and activity of MMPs relative to control macrophages, and the in vitro fibronectin induction was dependent on the alpha5beta1 integrin pair. Together these data demonstrate that Arhgef1 regulates alpha5beta1-mediated MMP expression by macrophages and that loss of Arhgef1 by leukocytes leads to pulmonary pathology.

The effects of dexamethasone on cigarette smoke induced gene expression changes in COPD macrophages

Chronic obstructive pulmonary disease (COPD) is a smoking related inflammatory airway disease in which macrophages play a key role. Previously we have shown that cigarette smoke extract (CSE) causes suppression of macrophage inflammatory mediators, with the exception of IL-8. We now investigate the effects of dexamethasone on these gene expression changes. Monocyte derived macrophages (MDMs) were cultured with CSE and dexamethasone. Microarray analysis was used to assess inflammatory mediator regulation, with qPCR and ELISA also performed for selected cytokines. The major effect of CSE was down-regulation of inflammatory genes (11 probe sets). For CSE regulated genes (n=13), the median fold change with CSE alone was -2.84 and with dexamethasone alone was -2.97. Both treatments combined caused the greatest suppression of gene expression; -4.47. qPCR also showed that IL-1beta, GM-CSF and IL-6 mRNA levels were significantly reduced by CSE and further suppressed by dexamethasone. qPCR and ELISA showed that IL-8 levels were increased by CSE, with suppression by dexamethasone. We show that CSE suppressed the expression of some inflammatory genes whilst up-regulating IL-8. Dexamethasone further suppressed gene expression when combined with CSE. The combined effect of GC and CSE causes suppression of the macrophage innate immune response.

Exercise training decreases the size and alters the composition of the neointima in a porcine model of percutaneous transluminal coronary angioplasty (PTCA)

Exercise training (EX) following percutaneous transluminal coronary angiography (PTCA) reduces progression to restenosis and increases event-free survival rates. Our aim was to determine whether EX inhibits lesion development and/or alters the extracellular matrix (ECM) composition of the neointima (NI) in a porcine PTCA model. Miniature Yucatan swine were assigned to cage confinement (SED) or EX for 20 wk. After 16 wk, all animals underwent a PTCA procedure of the left anterior descending artery (LAD) and left circumflex artery (LCX), with subsequent placement of an externalized jugular catheter. Animals recovered for 2 days and then resumed the previous protocol of SED or EX. Twelve days following PTCA, all animals received an intravenous bromodeoxyuridine (BrdU) injection to label proliferating cells. At 28 days following PTCA, the animals were euthanized, the LAD and LCX excised, and underwent standard histological processing for total collagen, type I collagen, fibronectin, BrdU, and Verhoeff-van Gieson stain. Our results demonstrate that EX significantly decreased lesion size and NI proliferation (-48%) in the LAD (P < 0.05) but not the LCX. Furthermore, EX attenuated type I collagen expression only in LAD, whereas total collagen was increased (5.9%) and fibronectin was decreased (-7.9%) in the NI of both vessels (P < 0.05). In conclusion, EX following PTCA may increase event-free survival rates following PTCA by decreasing lesion size and altering ECM composition.

Macrophages in breast cancer: do involution macrophages account for the poor prognosis of pregnancy-associated breast cancer?

Macrophage influx is associated with negative outcomes for women with breast cancer and has been demonstrated to be required for metastasis of mammary tumors in mouse models. Pregnancy-associated breast cancer is characterized by particularly poor outcomes, however the reasons remain obscure. Recently, post-pregnancy mammary involution has been characterized as having a wound healing signature. We have proposed the involution-hypothesis, which states that the wound healing microenvironment of the involuting gland is tumor promotional. Macrophage influx is one of the prominent features of the involuting gland, identifying the macrophage a potential instigator of tumor progression and a novel target for breast cancer treatment and prevention.

Inhibiting the platelet derived growth factor receptor increases signs of retinoic acid syndrome in myeloid differentiated HL-60 cells

PDGFR inhibitors are successfully used in a number of cancer treatments. The standard treatment for acute promyelocytic leukemia (APL) involves differentiation therapy with retinoic acid (RA). However, the relapse rates are significant. In the present work we evaluated the effects of RA therapy in the presence of PDGFR inhibitor, AG1296. Adding AG1296 with RA increased secretion of TNF-alpha, IL-8, and MMP-9 expression. This treatment induced higher levels of ICAM-1 endothelial cell expression, and increased cellular mobility. Inhibiting PDGFR enhanced RA-induced expression of integrin. Integrin ligand increased differentiation markers CD11b, inducible oxidative metabolism and PDGFR-beta phosphorylation. While the neutrophil-endothelial cell interactions are strengthened by the combined treatment, the endothelium-substratum interactions are weakened, a situation common in RAS.

Influence of oxidatively modified LDL on monocyte-macrophage differentiation

Transendothelial migration of peripheral blood mononuclear cells (PBMCs) and their subsequent interaction with the subendothelial matrix lead to their differentiation to macrophages (mphis). To study whether preexposure of monocytes in circulation to modified proteins influences their differentiation to mphis, an in vitro model system using isolated PBMC in culture was used. The effect of modified proteins such as oxidatively modified LDL (ox-LDL), acetylated and non-enzymatically glycated-BSA (NEG-BSA) on the differentiation process was studied by monitoring the upregulation of mphi specific functions such as endocytosis, production of matrix metalloproteinases (MMPs), expression of surface antigen, activity of beta-glucuronidase and down regulation of monocyte specific myeloperoxidase activity. Rate of endocytosis, production of MMPs and beta-glucuronidase activity were significantly greater in cells treated with modified proteins irrespective of the nature of modification. Both CuSO4 ox-LDL and HOCl ox-LDL increased the rate of expression of the mphi specific functions. FACS analysis showed that the rate of upregulation of mphi specific CD71 and down regulation of monocyte specific CD14 were high in cells supplemented with modified proteins. Studies using PPARgamma antagonist and agonist suggest its involvement in CuSO4 ox-LDL induced monocyte-macrophage (mo-mphi) differentiation whereas the expression of macrophage specific functions in cells exposed to other modified proteins was independent of PPARgamma. PBMC isolated from hypercholesterolemic rabbits in culture expressed mphi specific functions at a faster rate compared to normal controls indicating that these observations are relevant in vivo. These results indicate that preexposure of monocytes to modified proteins promote their differentiation to mphis and may serve as a feed forward type control for clearing modified proteins.