CD11c integrin gene promoter activity during myeloid differentiation

Macrophage-mediated heart repair and remodeling: A promising therapeutic target for post-myocardial infarction heart failure

Heart failure (HF) remains prevalent in patients who survived myocardial infarction (MI). Despite the accessibility of the primary percutaneous coronary intervention and medications that alleviate ventricular remodeling with functional improvement, there is an urgent need for clinicians and basic scientists to further reveal the mechanisms behind post-MI HF as well as investigate earlier and more efficient treatment after MI. Growing numbers of studies have highlighted the crucial role of macrophages in cardiac repair and remodeling following MI, and timely intervention targeting the immune response via macrophages may represent a promising therapeutic avenue. Recently, technology such as single-cell sequencing has provided us with an updated and in-depth understanding of the role of macrophages in MI. Meanwhile, the development of biomaterials has made it possible for macrophage-targeted therapy. Thus, an overall and thorough understanding of the role of macrophages in post-MI HF and the current development status of macrophage-based therapy will assist in the further study and development of macrophage-targeted treatment for post-infarction cardiac remodeling. This review synthesizes the spatiotemporal dynamics, function, mechanism and signaling of macrophages in the process of HF after MI, as well as discusses the emerging bio-materials and possible therapeutic agents targeting macrophages for post-MI HF.

Heat Shock Protein 27 Affects Myeloid Cell Activation and Interaction with Prostate Cancer Cells

Heat shock proteins are cytoprotective molecules induced by environmental stresses. The small heat shock protein 27 (Hsp27) is highly expressed under oxidative stress conditions, mediating anti-oxidative effects and blocking apoptosis. Since medical gas plasma treatment subjects cancer cells to a multitude of reactive oxygen species (ROS), inducing apoptosis and immunomodulation, probable effects of Hsp27 should be investigated. To this end, we quantified the extracellular Hsp27 in two prostate cancer cell lines (LNCaP, PC-3) after gas plasma-induced oxidative stress, showing a significantly enhanced release. To investigate immunomodulatory effects, two myeloid cell lines (THP-1 and HL-60) were also exposed to Hsp27. Only negligible effects on viability, intracellular oxidative milieu, and secretion profiles of the myeloid cells were found when cultured alone. Interestingly, prostate cancer-myeloid cell co-cultures showed altered secretion profiles with a significant decrease in vascular endothelial growth factor (VEGF) release. Furthermore, the myeloid surface marker profiles were changed, indicating an enhanced differentiation in co-culture upon Hsp27 treatment. Finally, we investigated morphological changes, proliferation, and interaction with prostate cancer cells, and found significant alterations in the myeloid cells, supporting the tendency to differentiate. Collectively, our results suggest an ambiguous effect of Hsp27 on myeloid cells in the presence of prostate cancer cells which needs to be further investigated.

Celiac Disease Defined by Over-Sensitivity to Gliadin Activation and Superior Antigen Presentation of Dendritic Cells

The autoimmune condition, Celiac Disease (CeD), displays broad clinical symptoms due to gluten exposure. Its genetic association with DQ variants in the human leukocyte antigen (HLA) system has been recognised. Monocyte-derived mature dendritic cells (MoDCs) present gluten peptides through HLA-DQ and co-stimulatory molecules to T lymphocytes, eliciting a cytokine-rich microenvironment. Having access to CeD associated families prevalent in the Czech Republic, this study utilised an in vitro model to investigate their differential monocyte profile. The higher monocyte yields isolated from PBMCs of CeD patients versus control individuals also reflected the greater proportion of dendritic cells derived from these sources following lipopolysaccharide (LPS)/ peptic-tryptic-gliadin (PTG) fragment stimulation. Cell surface markers of CeD monocytes and MoDCs were subsequently profiled. This foremost study identified a novel bio-profile characterised by elevated CD64 and reduced CD33 levels, unique to CD14++ monocytes of CeD patients. Normalisation to LPS stimulation revealed the increased sensitivity of CeD-MoDCs to PTG, as shown by CD86 and HLA-DQ flow cytometric readouts. Enhanced CD86 and HLA-DQ expression in CeD-MoDCs were revealed by confocal microscopy. Analysis highlighted their dominance at the CeD-MoDC membrane in comparison to controls, reflective of superior antigen presentation ability. In conclusion, this investigative study deciphered the monocytes and MoDCs of CeD patients with the identification of a novel bio-profile marker of potential diagnostic value for clinical interpretation. Herein, the characterisation of CD86 and HLA-DQ as activators to stimulants, along with robust membrane assembly reflective of efficient antigen presentation, offers CeD targeted therapeutic avenues worth further exploration.

Limitations of cell-lineage-specific non-dynamic gene recombination in CD11c.Cre+ITGA4fl/fl mice

BACKGROUND

The Cre-lox system is a non-dynamic method of gene modification and characterization. Promoters thought to be relatively cell-specific are utilized for generation of cell-lineage-specific gene modifications.

METHODS

CD11c.Cre⁺ITGA4^fl/fl mice were generated to abolish the expression of ITGA (α4-integrin) in CD11c⁺ cells. Ex vivo flow cytometry studies were used to assess the expression of cellular surface markers in different lymphoid compartments and leukocytes subsets after Cre-mediated recombination.

RESULTS

A significant reduction of α4-integrin expression among CD11c^+- cells was achieved in CD11c.Cre⁺ITGA4^fl/fl mice in primary and secondary lymphoid tissues. A similar reduction in the expression of α4-integrin was also observed in CD11c^- cells.

CONCLUSION

Cre-lox-mediated cell lineage-specific gene deletion is limited by the transient expression of recombination regulating sequences in hematopoietic cell lines. These methodological issues indicate the need to consider when to employ non-dynamic DNA recombination models in animal models of CNS autoimmunity. An experimental algorithm to address the biological complexities of non-dynamic gene recombination is provided.

C-kit-derived CD11b+ cells are critical for cardiac allograft prolongation by autologous C-kit+ progenitor cells

Autologous C-kit⁺ cells robustly prolong cardiac allografts. As C-kit⁺ cells can transdifferentiate to hematopoietic cells as well as non-hematopoietic cells, we aimed to clarify the class(es) of C-kit-derived cell(s) required for cardiac allograft prolongation. Autologous C-kit⁺ cells were administered post-cardiac transplantation and allografts were evaluated for C-kit⁺ inoculum-derived cells. Results suggested that alloimmunity was a major signal for trafficking of C-kit-derived cells to the allograft and demonstrated that C-kit⁺ inoculum-derived cells expressed CD11b early after transfer. Allograft survival studies with CD11b-DTR C-kit⁺ cells demonstrated a requirement for C-kit⁺-derived CD11b⁺ cells. Co-therapy studies demonstrated near complete abrogation of acute rejection with concomitant CTLA4-Ig therapy and no loss of prolongation in combination with Cyclosporine A. These results strongly implicate a C-kit-derived myeloid population as critical for allograft preservation and demonstrate the potential therapeutic application of autologous C-kit⁺ progenitor cells as calcineurin inhibitor-sparing agents and possibly as co-therapeutics for durable graft survival.

Quantitative Visualization of Leukocyte Infiltrate in a Murine Model of Fulminant Myocarditis by Light Sheet Microscopy

Light-sheet fluorescence microscopy (LSFM), in combination with chemical clearing protocols, has become the gold standard for analyzing fluorescently labelled structures in large biological specimens, and is down to cellular resolution. Meanwhile, the constant refinement of underlying protocols and the enhanced availability of specialized commercial systems enable us to investigate the microstructure of whole mouse organs and even allow for the characterization of cellular behavior in various live-cell imaging approaches. Here, we describe a protocol for the spatial whole-mount visualization and quantification of the CD45⁺ leukocyte population in inflamed mouse hearts. The method employs a transgenic mouse strain (CD11c.DTR)that has recently been shown to serve as a robust, inducible model for the study of the development of fulminant fatal myocarditis, characterized by lethal cardiac arrhythmias. This protocol includes myocarditis induction, intravital antibody-mediated cell staining, organ preparation, and LSFM with subsequent computer-assisted image post-processing. Although presented as a highly-adapted method for our particular scientific question, the protocol represents the blueprint of an easily adjustable system that can also target completely different fluorescent structures in other organs and even in other species.

Characterization of the immune cell repertoire in the normal fallopian tube

Recent studies implicating the fallopian tube as the site of putative precursors of ovarian serous carcinoma, and the hypothesis that injury, inflammation, and repair of the ovarian surface epithelium at the time of ovulation, may be contributing factors to ovarian carcinogenesis, prompted us to undertake a comprehensive analysis of the immune cells in the normal fallopian tube. Accordingly, the aim of this study was to provide a baseline for future studies exploring the relationship of inflammation with the early events of ovarian carcinogenesis by characterizing the immune cell repertoire in 13 normal human fallopian tubes, combining digital microscopy of immunostained slides and flow cytometry of fresh single-cell suspensions, with a panel of markers that identify the most important adaptive and innate immune cells. We found that CD45(+) leukocytes are regularly observed in the fallopian tube and are mainly composed of CD163(+) macrophages, CD11c dendritic cells, and CD8(+) T cells. In addition, there are minor populations of CD56(+) NK cells, CD4(+) T cells, CD20(+) B cells, TCRγδ(+) T cells, and, among dendritic cells, CD207(Langerin)(+) Langerhans cells. The cellular mapping that we performed indicates that the local immune system in the human fallopian tube is composed of a mixture of innate and adaptive immune cells, many of which are recognized as playing a role in cancer immune surveillance. This local immune system could provide a first line of defense against early precancerous lesions and could potentially be exploited for immune-based therapies.

hnRNP K in PU.1-containing complexes recruited at the CD11b promoter: a distinct role in modulating granulocytic and monocytic differentiation of AML-derived cells

PU.1 is essential for the differentiation of haemopoietic precursors and is strongly implicated in leukaemogenesis, yet the protein interactions that regulate its activity in different myeloid lineages are still largely unknown. In the present study, by combining fluorescent EMSA (electrophoretic mobility-shift assay) with MS, we reveal the presence of hnRNP K (heterogeneous nuclear ribonucleoprotein K) in molecular complexes that PU.1 forms on the CD11b promoter during the agonist-induced maturation of AML (acute myeloid leukaemia)-derived cells along both the granulocytic and the monocytic lineages. Although hnRNP K and PU.1 act synergistically during granulocytic differentiation, hnRNP K seems to have a negative effect on PU.1 activity during monocytic maturation. Since hnRNP K acts as a docking platform, integrating signal transduction pathways to nucleic acid-directed processes, it may assist PU.1 in activating or repressing transcription by recruiting lineage-specific components of the transcription machinery. It is therefore possible that hnRNP K plays a key role in the mechanisms underlying the specific targeting of protein-protein interactions identified as mediators of transcriptional activation or repression and may be responsible for the block of haemopoietic differentiation.

Directing traffic: IL-17 and IL-22 coordinate pulmonary immune defense

Respiratory infections and diseases are among the leading causes of death worldwide, and effective treatments probably require manipulating the inflammatory response to pathogenic microbes or allergens. Here, we review mechanisms controlling the production and functions of interleukin-17 (IL-17) and IL-22, cytokines that direct several aspects of lung immunity. Innate lymphocytes (γδ T cells, natural killer cells, innate lymphoid cells) are the major source of IL-17 and IL-22 during acute infections, while CD4(+) T-helper 17 (Th17) cells contribute to vaccine-induced immunity. The characterization of dendritic cell (DC) subsets has revealed their central roles in T-cell activation. CD11b(+) DCs stimulated with bacteria or fungi secrete IL-1β and IL-23, potent inducers of IL-17 and IL-22. On the other hand, recognition of viruses by plasmacytoid DCs inhibits IL-1β and IL-23 release, increasing susceptibility to bacterial superinfections. IL-17 and IL-22 primarily act on the lung epithelium, inducing antimicrobial proteins and neutrophil chemoattractants. Recent studies found that stimulation of macrophages and DCs with IL-17 also contributes to antibacterial immunity, while IL-22 promotes epithelial proliferation and repair following injury. Chronic diseases such as asthma and chronic obstructive pulmonary disease have been associated with IL-17 and IL-22 responses directed against innocuous antigens. Future studies will evaluate the therapeutic efficacy of targeting the IL-17/IL-22 pathway in pulmonary inflammation.

Deficient IFN signaling by myeloid cells leads to MAVS-dependent virus-induced sepsis

The type I interferon (IFN) signaling response limits infection of many RNA and DNA viruses. To define key cell types that require type I IFN signaling to orchestrate immunity against West Nile virus (WNV), we infected mice with conditional deletions of the type I IFN receptor (IFNAR) gene. Deletion of the Ifnar gene in subsets of myeloid cells resulted in uncontrolled WNV replication, vasoactive cytokine production, sepsis, organ damage, and death that were remarkably similar to infection of Ifnar^−/− mice completely lacking type I IFN signaling. In Mavs^−/−×Ifnar^−/− myeloid cells and mice lacking both Ifnar and the RIG-I-like receptor adaptor gene Mavs, cytokine production was muted despite high levels of WNV infection. Thus, in myeloid cells, viral infection triggers signaling through MAVS to induce proinflammatory cytokines that can result in sepsis and organ damage. Viral pathogenesis was caused in part by massive complement activation, as liver damage was minimized in animals lacking complement components C3 or factor B or treated with neutralizing anti-C5 antibodies. Disease in Ifnar^−/− and CD11c Cre⁺Ifnar^f/f mice also was facilitated by the proinflammatory cytokine TNF-α, as blocking antibodies diminished complement activation and prolonged survival without altering viral burden. Collectively, our findings establish the dominant role of type I IFN signaling in myeloid cells in restricting virus infection and controlling pathological inflammation and tissue injury.

Although it is well established that the interferon (IFN) signaling pathway restricts infection by many viruses, the key cell types in vivo that contribute to this process remain poorly characterized. To address this question in the context of West Nile virus (WNV) pathogenesis, we infected mice that specifically delete the type I IFN receptor gene (Ifnar) in subsets of myeloid cells, including dendritic cells and macrophages. Remarkably, mice lacking Ifnar expression only in myeloid cell subsets rapidly developed a sepsis-like syndrome that was characterized by enhanced WNV infection and visceral organ injury and caused by massive proinflammatory cytokine production and complement activation. By using additional gene targeted deletion mice, we show that WNV infection triggered signaling through the RIG-I like receptor adaptor protein MAVS to cause complement activation, sepsis, and tissue damage. Indeed, liver damage was minimized in animals lacking specific complement components, or treated with neutralizing anti-complement or anti-TNF-α antibodies. Our results establish how type I IFN signaling in dendritic cells and macrophages restricts infection, controls inflammatory cascades, and prevents pathogenesis in vivo.

Comparative promoter analysis in vivo: identification of a dendritic cell-specific promoter module

Dendritic cells (DCs) are important immune cells. This study focused on transcriptional networks active in murine DCs, but DCs are difficult to study using conventional molecular techniques. Therefore, comparative promoter analysis was used to identify evolutionarily conserved features between the murine CD11c and DC-STAMP promoters. A promoter framework consisting of 4 transcription factor binding sites was identified that included signal transducer and activator of transcription, homeodomain transcription factors, and 2 members of the Brn POU domain factors family. This promoter module was functionally verified by in vivo promoter analysis and site-directed mutagenesis. Hematopoietic stem cells were engineered by lentiviral vectors and expression of green fluorescent protein reporter was monitored in primary hematopoietic cell types that develop without further manipulation in irradiated recipient mice. The verified promoter module was then modeled and used in a bioinformatics-based search for other potential coregulated genes in murine DCs. A promoter database search identified 2 additional genes, Ppef2 and Pftk1, which have a similar promoter organization and are preferentially expressed in murine DCs. The results define a regulatory network linked to development of murine DCs.

Disruption of PTH receptor 1 in T cells protects against PTH-induced bone loss

Background

Hyperparathyroidism in humans and continuous parathyroid hormone (cPTH) treatment in mice cause bone loss by regulating the production of RANKL and OPG by stromal cells (SCs) and osteoblasts (OBs). Recently, it has been reported that T cells are required for cPTH to induce bone loss as the binding of the T cell costimulatory molecule CD40L to SC receptor CD40 augments SC sensitivity to cPTH. However it is unknown whether direct PTH stimulation of T cells is required for cPTH to induce bone loss, and whether T cells contribute to the bone catabolic activity of PTH with mechanisms other than induction of CD40 signaling in SCs.

Methodology/Principal Findings

Here we show that silencing of PTH receptor 1 (PPR) in T cells blocks the bone loss and the osteoclastic expansion induced by cPTH, thus demonstrating that PPR signaling in T cells is central for PTH-induced reduction of bone mass. Mechanistic studies revealed that PTH activation of the T cell PPR stimulates T cell production of the osteoclastogenic cytokine tumor necrosis factor α (TNF). Attesting to the relevance of this effect, disruption of T cell TNF production prevents PTH-induced bone loss. We also show that a novel mechanism by which TNF mediates PTH induced osteoclast formation is upregulation of CD40 expression in SCs, which increases their RANKL/OPG production ratio.

Conclusions/Significance

These findings demonstrate that PPR signaling in T cells plays an essential role in PTH induced bone loss by promoting T cell production of TNF. A previously unknown effect of TNF is to increase SC expression of CD40, which in turn increases SC osteoclastogenic activity by upregulating their RANKL/OPG production ratio. PPR-dependent stimulation of TNF production by T cells and the resulting TNF regulation of CD40 signaling in SCs are potential new therapeutic targets for the bone loss of hyperparathyroidism.

BNP directly immunoregulates the innate immune system of cardiac transplant recipients in vitro

BACKGROUND

The innate immune system plays an important role in cardiac allograft rejection. BNP has frequently been reported to elevate during acute cardiac rejection, yet the explanation behind this phenomenon is unclear. We hypothesized that BNP might interact with the innate immune system in cardiac transplant recipients and devised a series of in vitro culture experiments to explore this phenomena.

METHODS

PBMCs were isolated from whole blood of (total n = 40) cardiac transplant recipients. Short (24h, n = 20) and long term (72h, n = 20) co-cultures of innate cells in the presence or absence of BNP were performed. BNP was added at two specific concentrations and compared to placebo control. Innate cells were immunophenotyped using flow cytometry.

RESULTS

BNP dose dependently reduced the total number of monocytes, B cells and NK cells. Furthermore, BNP co-culture impaired NK cell cytotoxicity and adhesion of non-classical monocytes (via down-regulation of CD11c).

DISCUSSION

BNP has an additional physiological role of moderating components of the innate immune system. Although speculative, this could be beneficial to cardiac transplant recipients as the innate immune system is involved in allograft rejection. Further investigation is required to elucidate the mechanism behind how BNP affects immune cells and whether the same effects are consistent with the adaptive immune system.

T cells potentiate PTH-induced cortical bone loss through CD40L signaling

Parathyroid hormone (PTH) promotes bone catabolism by targeting bone marrow (BM) stromal cells (SCs) and their osteoblastic progeny. Here we show that a continuous infusion of PTH that mimics hyperparathyroidism fails to induce osteoclast formation, bone resorption, and cortical bone loss in mice lacking T cells. T cells provide proliferative and survival cues to SCs and sensitize SCs to PTH through CD40 ligand (CD40L), a surface molecule of activated T cells that induces CD40 signaling in SCs. As a result, deletion of T cells or T cell-expressed CD40L blunts the bone catabolic activity of PTH by decreasing bone marrow SC number, the receptor activator of nuclear factor-kappaB ligand (RANKL)/OSTEOPROTEGERN (OPG) ratio, and osteoclastogenic activity. Therefore, T cells play an essential permissive role in hyperparathyroidism as they influence SC proliferation, life span, and function through CD40L. T cell-SC crosstalk pathways may thus provide pharmacological targets for PTH-induced bone disease.

Surfactant protein D regulates the cell surface expression of alveolar macrophage β2-integrins

The β2-integrin receptors (CD11a/CD18, CD11b/CD18, and CD11c/CD18) are expressed on the surface of alveolar macrophages and are important for the phagocytic clearance of pathogens. In the present study, we demonstrate that surfactant protein D (SP-D) modulates surface expression of CD11b and CD11c, but not CD11a or CD18, on alveolar macrophages. While cell surface receptors were reduced, CD11b and CD11c mRNAs were increased by SP-D deficiency. CCSP-rtTA+/(tetO)7-rSPD+/SP-D−/−mice, which conditionally express SP-D in the lung, were used to study the kinetics and reversibility of β2-integrin receptors in response to changes in alveolar SP-D. Surface CD11b and CD11c were reduced on the alveolar macrophages within 3 days of SP-D deficiency and were restored with 3 days for CD11b and 7 days for CD11c of repletion of SP-D. SP-D deficiency caused a loss of cellular CD11b and CD11c content, indicating that the decrease in total cell content of the receptors was related to degradation rather than to redistribution of the receptor within the macrophage. CD11b and CD11c staining colocalized with Lamp-1 during SP-D deficiency, supporting the concept that reduced macrophage receptor levels resulted from increased lysosomal trafficking. Hydroxychloroquine, a lysomotropic agent, prevented the reduction of cellular and surface CD11b and CD11c. SP-D regulates surface CD11b and CD11c levels on the alveolar macrophage by modulating receptor trafficking, providing a mechanism by which SP-D mediates phagocytic activity in the alveolar macrophage.

Se-methylselenocysteine enhances PMA-mediated CD11c expression via phospholipase D1 activation in U937 cells

CD11c/CD18 is expressed primarily on myeloid cells, where its expression is regulated both during differentiation and during monocyte maturation into tissue macrophages, and is also a receptor for fibrinogen and lipopolysaccharide (LPS). We focused on the molecular mechanisms leading to the activation of CD11c expression in differentiating U937 cells. During phorbol myristate acetate (PMA)-induced differentiation of U937 cells, we found that the mRNA expression of CD11c was increased. Se-methylselenocysteine (Se-MSC) potentiated up-regulation of CD11c expression and its promoter activity and increased PLD1 activity without affecting the level of PLD1 protein in PMA-treated cells. To examine the regulation mechanism of PMA and Se-MSC on CD11c gene expression through the activation of PLD1, we analyzed changes in the CD11c mRNA level and the promoter activity following treatment of a selective PLD inhibitor n-butanol. The combinatory effect of PMA and Se-MSC on CD11c gene expression was abolished by n-butanol in a dose-dependent manner. Further, introduction of PLD1 gene into U937 cells increased CD11c mRNA expression and activated CD11c promoter activity in a dose-dependent manner. These results showed that Se-MSC increased PMA-induced CD11c expression through the activation of PLD1 signaling pathway. To our knowledge, this is the first report that expression of the CD11c gene is regulated by PLD1 and is enhanced by Se-MSC during PMA-induced U937 differentiation.

Lipopolysaccharide heterogeneity: innate host responses to bacterial modification of lipid a structure

The innate host response system is composed of various mechanisms designed to detect and facilitate host responses to microbial components, such as lipopolysaccharides (LPS). To enable this to occur, innate systems contain multiple pattern recognition receptors (i.e., LBP, CD14, and TLRs), which identify certain features within bacterial LPS that are foreign to the host, as well as essential and uniquely specific for bacteria. Innate host identification of unique bacterial components or patterns, therefore, relies on the inability of bacteria to alter these essential or critical components dramatically. Historically, LPS have been viewed as essential outer-membrane molecules containing both a highly variable outer region (O-segment) as well as a relatively conserved inner region (lipid A). However, over the last decade, new evidence has emerged, revealing that increased natural diversity or heterogeneity within specific components of LPS, such as lipid A-resulting in minor to moderate changes in lipid A structure-can produce dramatic host responses. Therefore, examples of natural lipid A heterogeneity, and the mechanisms that control it, represent a novel approach in which bacteria modulate host responses and may thereby confer specific advantages to certain bacterial species under changing environmental host conditions.

Identification of cell surface targets for HIV-1 therapeutics using genetic screens

Human immunodeficiency virus (HIV) drugs designed to interfere with obligatory utilization of certain host cell factors by virus are less likely to encounter development of resistant strains than drugs directed against viral components. Several cellular genes required for productive infection by HIV were identified by the use of genetic suppressor element (GSE) technology as potential targets for anti-HIV drug development. Fragmented cDNA libraries from various pools of human peripheral blood mononuclear cells (PBMC) were expressed in vitro in human immunodeficiency virus type 1 (HIV-1)-susceptible cell lines and subjected to genetic screens to identify GSEs that interfered with viral replication. After three rounds of selection, more than 15000 GSEs were sequenced, and the cognate genes were identified. The GSEs that inhibited the virus were derived from a diverse set of genes including cell surface receptors, cytokines, signaling proteins, transcription factors, as well as genes with unknown function. Approximately 2.5% of the identified genes were previously shown to play a role in the HIV-1 life cycle; this finding supports the biological relevance of the assay. GSEs were derived from the following 12 cell surface proteins: CXCR4, CCR4, CCR7, CD11C, CD44, CD47, CD68, CD69, CD74, CSF3R, GABBR1, and TNFR2. Requirement of some of these genes for viral infection was also investigated by using RNA interference (RNAi) technology; accordingly, 10 genes were implicated in early events of the viral life cycle, before viral DNA synthesis. Thus, these cell surface proteins represent novel targets for the development of therapeutics against HIV-1 infection and AIDS.

CD11c gene expression in hairy cell leukemia is dependent upon activation of the proto-oncogenes ras and junD

Hairy cell leukemia (HCL) is a chronic lymphoproliferative disease, the cause of which is unknown. Diagnostic of HCL is abnormal expression of the gene that encodes the beta2 integrin CD11c. In order to determine the cause of CD11c gene expression in HCL the CD11c gene promoter was characterized. Transfection of the CD11c promoter linked to a luciferase reporter gene indicated that it is sufficient to direct expression in hairy cells. Mutation analysis demonstrated that of predominant importance to the activity of the CD11c promoter is its interaction with the activator protein-1 (AP-1) family of transcription factors. Comparison of nuclear extracts prepared from hairy cells with those prepared from other cell types indicated that hairy cells exhibit abnormal constitutive expression of an AP-1 complex containing JunD. Functional inhibition of AP-1 expressed by hairy cells reduced CD11c promoter activity by 80%. Inhibition of Ras, which represents an upstream activator of AP-1, also significantly inhibited the CD11c promoter. Furthermore, in the hairy cell line EH, inhibition of Ras signaling through mitogen-activated protein kinase/extracellular signal-regulated kinase kinases 1 and 2 (MEK1/2) reduced not only CD11c promoter activity but also reduced both CD11c surface expression and proliferation. Expression in nonhairy cells of a dominant-positive Ras mutant activated the CD11c promoter to levels equivalent to those in hairy cells. Together, these data indicate that the abnormal expression of the CD11c gene characteristic of HCL is dependent upon activation of the proto-oncogenes ras and junD.

Two histone deacetylase inhibitors, trichostatin A and sodium butyrate, suppress differentiation into osteoclasts but not into macrophages

Histone deacetylase (HDAC) inhibitors are emerging as a new class of anticancer therapeutic agents and have been demonstrated to induce differentiation in some myeloid leukemia cell lines. In this study, we show that HDAC inhibitors have a novel action on osteoclast differentiation. The effect of 2 HDAC inhibitors, trichostatin A (TSA) and sodium butyrate (NaB), on osteoclastogenesis was investigated using rat and mouse bone marrow cultures and a murine macrophage cell line RAW264. Both TSA and NaB inhibited the formation of preosteoclast-like cells (POCs) and multinucleated osteoclast-like cells (MNCs) in rat bone marrow culture. By reverse transcription-polymerase chain reaction analysis, TSA reduced osteoclast-specific mRNA expression of cathepsin K and calcitonin receptor (CTR). In contrast, TSA and NaB did not affect the formation of bone marrow macrophages (BMMs) induced by macrophage colony-stimulating factor as examined by nonspecific esterase staining. Fluorescence-activated cell sorting analysis showed that TSA did not affect the surface expression of macrophage markers for CD11b and F4/80 of BMMs. TSA and NaB also inhibited osteoclast formation and osteoclast-specific mRNA expression in RAW264 cells stimulated with receptor activator of nuclear factor-kappa B (NF-kappa B) ligand (RANKL). Transient transfection assay revealed that TSA and NaB dose dependently reduced the sRANKL-stimulated or tumor necrosis factor alpha (TNF-alpha)-stimulated transactivation of NF-kappa B-dependent reporter genes. The treatment of RAW264 cells with TSA and NaB inhibited TNF-alpha-induced nuclear translocation of NF-kappa B and sRANKL-induced activation of p38 mitogen-activated protein kinase (MAPK) signals. These data suggest that both TSA and NaB exert their inhibitory effects by modulating osteoclast-specific signals and that HDAC activity regulates the process of osteoclastogenesis.

Endocytic internalization of adenovirus, nonspecific phagocytosis, and cytoskeletal organization are coordinately regulated in alveolar macrophages by GM-CSF and PU.1

GM-CSF gene-targeted (GM(-/-)) mice have impaired pulmonary clearance of bacterial and fungal pathogens by alveolar macrophages (AMs). Because AMs also clear adenovirus from the lung, the role of GM-CSF in endocytic internalization of adenovirus by AMs was evaluated. Pulmonary clearance of adenovirus was severely impaired in GM(-/-) mice compared to wild-type (GM(+/+)) mice as determined by Southern analysis of viral DNA. Internalization of adenovirus by AMs was deficient in GM(-/-) mice in vivo and in vitro as determined by uptake of fluorescently labeled adenovirus or by PCR quantification of adenoviral DNA internalized within AMs. An AM cell line previously established from GM(-/-) mice (mAM) had impaired internalization of adenovirus and transferrin-coated 100-nm latex beads compared to MH-S, a GM(+/+) AM cell line. Phagocytosis of 4- micro m latex beads was also impaired in mAM cells as determined by confocal and fluorescence microscopy. Retroviral vector-mediated reconstitution of PU.1 expression in cultured GM(-/-) AMs restored phagocytosis of 4- micro m beads, endocytosis of adenovirus, and transferrin-coated 100-nm beads (independent of integrin alpha(V) and transferrin receptors, respectively), and restored normal cytoskeletal organization, filamentous actin distribution, and stimulated formation of filopodia. Interestingly, mRNA for the phosphoinositide 3 kinase p110gamma isoform, important in macrophage phagocytic function, was absent in GM(-/-) AMs and was restored by PU.1 expression. These data show that GM-CSF, via PU.1, regulates endocytosis of small ( approximately 100 nm) pathogens/inert particles and phagocytosis of very large inert particles and suggests regulation of cytoskeletal organization by GM-CSF/PU.1 as the molecular basis of this control.

Activation of the gamma-glutamyltransferase promoter 2 in the rat colon carcinoma cell line CC531 by histone deacetylase inhibitors is mediated through the Sp1 binding motif

The single-copy gene for rat gamma-glutamyltransferase (GGT) encodes at least seven distinct mRNAs that differ in their 5'-untranslated regions only. Tissue- and developmental-specific expression of GGT is partly achieved by the presence of many transcription factor-binding sites in the promoters of this gene. In an earlier study we found that GGT mRNAs II and IV levels were increased upon butyrate-induced differentiation of the rat colon carcinoma cell line CC531. The mechanism for this butyrate-induced upregulation remains unknown, but may result from altered promoter activity as butyrate is a known histone deacetylase inhibitor. In the present study, we show by transient transfection studies that butyrate enhanced the expression of the luciferase reporter gene driven by the rat GGT promoter 2 (P2). Trichostatine A (TSA), another histone deacetylase inhibitor, also enhanced transcription from this promoter. The role of the transcription factor site Sp1 in butyrate- or TSA-induced activation of the GGT P2 was examined as Sp1 has been previously shown to play a central role in the transcriptional activation of other genes during butyrate and TSA stimulation. A triple sequence-motif of this isolated Sp1 site linked to a minimal promoter was able to mediate butyrate- and TSA-induced expression of the luciferase reporter gene, while no effect was measured using the minimal promoter alone. Deleting the Sp1 site in the context of the rat GGT P2 strongly reduced the basal transcription activity and abrogated butyrate- and TSA-induced activation of the mutated promoter. These results suggest that butyrate- or TSA-induced activation of the rat GGT P2 can be mediated by a Sp1 binding motif.

During differentiation of the monocytic cell line U937, Pur alpha mediates induction of the CD11c beta 2 integrin gene promoter

CD11c is a member of the beta(2) integrin family of adhesion molecules that, together with CD18, forms a heterodimeric receptor on the surface of myeloid, NK, dendritic, and certain leukemic, lymphoma, and activated lymphoid cells. Monocytic differentiation is associated with an induction of both CD11c and CD18 gene expression. The resulting CD11c/CD18 receptor mediates firm adhesion to the vascular endothelium, transendothelial migration, chemotaxis, and phagocytosis. Monocytic differentiation can be mimicked in vitro by treatment of the promonocytic cell line U937 with PMA. Recently, we reported that in U937 cells, expression of the CD11c gene is controlled by an unidentified transcription factor that binds ssDNA. This finding suggested that DNA secondary structure plays an important role in controlling the CD11c gene and prompted us to search for additional ssDNA-binding activities with which this gene interacts. In this study, we report that in U937 cells, expression of the CD11c gene is mediated by the ssDNA-binding protein Puralpha. During PMA-induced differentiation, the ability of Puralpha to activate the CD11c promoter in U937 cells increases, as does that of Sp1. Together, these increases in the functional activity of both Puralpha and Sp1 combine to induce CD11c expression.

During U937 monocytic differentiation repression of the CD43 gene promoter is mediated by the single-stranded DNA binding protein Pur alpha

Human CD43 is an abundant, heavily glycosylated molecule expressed exclusively on the surface of leucocytes. When leucocytes are at rest, CD43 acts to prevent intercellular interaction but during leucocyte differentiation such cell-cell interaction is facilitated by CD43. This change in the function of CD43 is mediated in part by a reduction in its level of expression. Previous studies have implicated proteolytic cleavage events at the cell surface in causing such reduction. Here, we report that, in an in vitro model of leucocyte differentiation, CD43 mRNA levels were also subject to reduction. Specifically, we demonstrated that within 48 h of the cell line U937 being induced to differentiate along the monocytic pathway, CD43 mRNA levels were reduced by 69%. This decline coincided with a decrease in the activity of the CD43 gene promoter mediated by the single-stranded DNA binding protein Pur alpha. Previously, we have demonstrated that Pur alpha mediates induction of the CD11c beta 2 integrin promoter during U937 differentiation. Consequently, Pur alpha represents a potential means by which the induction of pro-adhesive molecules and the repression of anti-adhesive molecules is co-ordinated during leucocyte differentiation.

Studies on transcriptional regulation of the mucosal T-cell integrin alphaEbeta7 (CD103)

Integrin alphaEbeta7 is expressed almost exclusively by mucosal T cells and mucosal dendritic antigen-presenting cells (APCs) and is thought to be induced locally by transforming growth factor-beta (TGF-beta). In mice, mRNA for the alphaE subunit was found to be abundant in mucosal T cells but absent from other tissues. Exposure of a T-cell line to TGF-beta strongly up-regulated alphaE mRNA levels within 30 min, and nuclear run-on experiments established that regulation occurred at the level of transcription. The organization of the human alphaE gene and a very closely linked novel gene, ELG, was determined. The alphaE promoter was tested in T cells and fibroblasts and functioned equally well in both cell types and did not confer TGF-beta responsiveness. Regions of the promoter providing enhancer activity and phorbol 12-myristate 13-acetate (PMA) responsiveness were identified by deletion studies. DNAse 1 hypersensitivity analysis of 36 kb of the alphaE gene revealed one hypersensitive site, found only in alphaE+ cells, located near the transcription start points. These results show that, unlike the situation with other integrins, lineage specificity and cytokine responsiveness of alphaE transcription are not conferred by the proximal promoter. Specificity may depend on distant control elements that have not yet been identified.

Immunophenotypic analysis of the inflammatory infiltrates in herniated intervertebral discs

STUDY DESIGN

The herniated portion of the lumbar disc was analyzed immunohistochemically for inflammatory infiltrates to determine their immunophenotype.

OBJECTIVE

To investigate the pathomechanism behind spontaneous regression of herniated discs.

SUMMARY OF BACKGROUND DATA

Spontaneous regression of herniated intervertebral discs has been increasingly reported. The inflammatory response of the host has been suggested as a factor in this phenomenon. However, whether the inflammation is induced from direct chemical irritation of the nucleus pulposus material or whether it is secondary to an autoimmune response to the nucleus pulposus remains controversial.

METHODS

The herniated portion of the disc was collected from 38 patients who underwent surgery for lumbar disc herniation. Thin cryostat sections were made, and the extent to which inflammatory cells had infiltrated the disc specimen was defined. Then the immunophenotype of cellular infiltrates in the herniated disc specimens was assessed by immunostaining using a series of antibodies for lymphocyte, monocyte, macrophage, and dendritic cell markers.

RESULTS

The inflammatory infiltrates in 14 of the 38 herniated discs were subjected to immunohistochemical analysis. None of them expressed the immunophenotypic markers of the lymphocyte (CD20, CD45RO, CD4, CD8, TCRgammadelta), mature monocyte (CD33), or dendritic cell (CD1a, CD80, CD86, S100). Abundant infiltration of CD68-positive cells that lacked CD33 but had a variable amount of CD11b, CD11c, and CD40 likely represents a process of differentiation from monocytes to macrophages.

CONCLUSIONS

These findings are consistent with an immunophenotype of inflammatory responses to tissue injury or chemical irritation rather than antigen-specific immune responses. Therefore, understanding the mechanism of tissue repair is fundamentally important in the management of patients with disc herniations.

Expression and transcriptional regulation of the human alpha1, 3-fucosyltransferase 4 (FUT4) gene in myeloid and colon adenocarcinoma cell lines

In fucosyltransferase genes, mRNA expression is regulated in a cell-type-specific manner. The expression level of human fucosyltransferase 4 (FUT4) mRNA is high in both colon adenocarcinoma and myeloid cell lines. We will demonstrate here cell-specific expression and transcriptional regulation of the FUT4 gene. FUT4 has two different transcription initiation sites that respectively produce long- and short-form mRNAs. To determine the major FUT4 transcript in colon adenocarcinoma and myeloid cell lines, we analyzed the transcriptional starting sites of the FUT4 gene in myeloid and colon adenocarcinoma cell lines, using 5'-RACE, RT-PCR, and luciferase analysis. The results suggested that the expression level of short-form mRNA is higher than the long-form transcript in the colon adenocarcinoma cell lines and that the expression level of long-form mRNA is higher than the short-form transcript in the myeloid cell lines. Using a luciferase assay, we identified a functional DNA portion within FUT4 genomic DNA that confers a colon adenocarcinoma cell line-specific enhancer, located in nucleotide number (nt) -256 to -44, and a myeloid cell line-specific enhancer, located in nt -686 to -582. The present results suggest that these elements play a critical role in the colon adenocarcinoma and leukemia cell-specific transcriptional regulation of the FUT4 gene.

CD43 gene expression is mediated by a nuclear factor which binds pyrimidine-rich single-stranded DNA

CD43 is a leukocyte-specific surface molecule which plays an important role both in adhesion and signal transduction. We have identified a site spanning nucleotides +18 to +39 within the human CD43 gene promoter which in vitro is hypersensitive to cleavage by nuclease S1. Repeats of this region are sufficient to activate expression of a heterologous promoter in CD43-positive cell lines. Two nuclear factors, PyRo1 and PyRo2, interact with the hypersensitive site. PyRo1 is a single-stranded DNA-binding protein which binds the pyrimidine-rich sense strand. Mutation analysis demonstrates that the motif TCCCCT is critical for PyRo1 interaction. Replacement of this motif with the sequence CATATA abolishes PyRo1 binding and reduces expression of the CD43 promoter by 35% in Jurkat T lymphocytic cells and by 52% in the pre-erythroid/pre-megakaryocytic cell line K562. However, this same replacement failed to affect expression in U937 monocytic cells or in CEM T lymphocytic cells. PyRo1, therefore, exhibits cell-specific differences in its functional activity. Further analysis demonstrated that PyRo1 not only interacts with the CD43 gene promoter but also motifs present within the promoters of the CD11a, CD11b, CD11c and CD11d genes. These genes encode the alpha subunits of the beta2 integrin family of leukocyte adhesion receptors. Deletion of the PyRo1 binding site within the CD11c gene reduced promoter activity in T lymphocytic cells by 47%. However, consistent with our analysis of the CD43 gene, the effect of this same deletion within U937 monocytic cells was less severe. That PyRo1 binds preferentially to single-stranded DNA and sequences within the CD43 and CD11 gene promoters suggests that expression of these genes is influenced by DNA secondary structure.

Transcriptional regulation of human beta-galactoside alpha2, 6-sialyltransferase (hST6Gal I) gene during differentiation of the HL-60 cell line

We have previously shown that the expression of beta-galactoside alpha2,6-sialyltransferase (hST6Gal I) mRNA decreases during HL-60 differentiation induced with dimethyl sulfoxide (DMSO) and that transcriptional regulation depends on the P3 promoter that exists 5'-upstream of exon Y (A. Taniguchi et al., FEBS Lett.,441, 191-194, 1998). The regulation of hST6Gal I may be important for the expression of sialyl-Le(x)in HL-60 cells. In the present report, we studied the transcriptional regulation of hST6Gal I gene during DMSO-induced differentiation of HL-60 cells. To elucidate the molecular basis of hST6Gal I gene expression, the genomic region containing the P3 promoter of hST6Gal I was isolated and functionally characterized. Using a luciferase assay, we identified a functional DNA portion that confers an enhancer, located at nucleotide number (nt) -317 to -174 within the P3 promoter of hST6Gal I genomic DNA. This element contains two sequences similar to Sp1 (GC-box) and one sequence similar to Oct-1 recognition motifs (octamer sequence). Site-directed mutagenesis of Sp1 and Oct-1 sites showed that two Sp1 motifs and one Oct-1 motif are essential for transcriptional activity in HL-60 cells. Enhancer activity is suppressed during HL-60 cell differentiation induced with DMSO. These results suggest that GC-box and octamer sequence may play a critical role in the transcriptional regulation of the hST6Gal I gene during HL-60 cell differentiation.

Down-regulation of human Galbeta1,3GalNAc/Galbeta1,4GlcNAc alpha2,3-sialyltransferase (hST3Gal IV) gene during differentiation of the HL-60 cell line

We studied the regulation of the human Galbeta1, 3GalNAc/Galbeta1,4GlcNAc alpha2,3-sialyltransferase (hST3Gal IV) gene during HL-60 cell differentiation induced by dimethyl sulfoxide (DMSO), all trans-retinoic acid (ATRA), and phorbol myristate acetate (PMA). During differentiation, levels of hST3Gal IV mRNA dramatically decreased after 1 day of stimulation. Reverse-transcription PCR identified two mRNA isoforms, types B1 and BX, in HL-60 cells. The results of luciferase assays showed that the level of B3 promoter activity is high, whereas A1/2 and B2 promoter activities are low in HL-60 cells, suggesting that type B1, BX, and B3 mRNA isoforms are expressed in HL-60 cells. A luciferase assay identified a functional DNA portion within the proximal region of the B3 promoter that confers negative transcriptional regulation on the hST3Gal IV B3 promoter during HL-60 differentiation. These results suggest that this element plays a critical role in down-regulating the B3 promoter activity during HL-60 cell differentiation.

CCAAT-enhancer-binding proteins (C/EBP) regulate the tissue specific activity of the CD11c integrin gene promoter through functional interactions with Sp1 proteins

The CD11c/CD18 integrin binds lipopolysaccharide, fibrinogen, and heparin, and mediates leukocyte adhesion, spreading, and migration. CD11c/CD18 is primarily found on myeloid cells and its expression is regulated during myeloid differentiation by transcriptional mechanisms acting on the CD11c gene promoter. We now describe that CCAAT/enhancer-binding proteins (C/EBP) contribute to the basal, tissue-specific and developmentally regulated activity of the CD11c promoter. A C/EBP-binding site within the CD11c promoter (CEBP-80) is bound by CEBPalpha in undifferentiated U937 cells and by C/EBPalpha- and C/EBPbeta-containing dimers in phorbol 12-myristate 13-acetate-differentiating cells, and its disruption decreased the CD11c promoter activity in a cell type-dependent manner. C/EBPalpha transactivated the CD11c promoter through the CEBP-80 element, and C/EBPalpha transactivation was also dependent on the Sp1-70- and Sp1-120 Sp1-binding sites. The -90/-50 fragment from the CD11c promoter, containing the adjacent CEBP-80, Sp1-70, and AP1-60 sites, differentially enhanced the activity of the minimal prolactin promoter in hematopoietic and epithelial cells. Altogether, these results demonstrate that C/EBP factors participate in the tissue-restricted and regulated expression of the CD11c/CD18 integrin through functional interactions with Sp1, suggest that Sp1-related factors modulate C/EBPalpha transcriptional activity on the CD11c promoter, and demonstrate the existence of a composite regulatory element recognized by C/EBP, Sp1, and AP-1 factors and whose enhancing effects are cell-type dependent.