Identification of CCR2, flotillin, and gp49B genes as new G-CSF targets during neutrophilic differentiation

Human Beta-Defensin 2 and 3 Inhibit HIV-1 Replication in Macrophages

Human beta-defensins (hBDs) are broad-spectrum antimicrobial peptides, secreted by epithelial cells of the skin and mucosae, and astrocytes, which we and others have shown to inhibit HIV-1 in primary CD4⁺ T cells. Although loss of CD4⁺ T cells contributes to mucosal immune dysfunction, macrophages are a major source of persistence and spread of HIV and also contribute to the development of various HIV-associated complications. We hypothesized that, besides T cells, hBDs could protect macrophages from HIV. Our data in primary human monocyte-derived macrophages (MDM) in vitro show that hBD2 and hBD3 inhibit HIV replication in a dose-dependent manner. We determined that hBD2 neither alters surface expression of HIV receptors nor induces expression of anti-HIV cytokines or beta-chemokines in MDM. Studies using a G-protein signaling antagonist in a single-cycle reporter virus system showed that hBD2 suppresses HIV at an early post-entry stage via G-protein coupled receptor (GPCR)-mediated signaling. We find that MDM express the shared chemokine-hBD receptors CCR2 and CCR6, albeit at variable levels among donors. However, cell surface expression analyses show that neither of these receptors is necessary for hBD2-mediated HIV inhibition, suggesting that hBD2 can signal via additional receptor(s). Our data also illustrate that hBD2 treatment was associated with increased expression of APOBEC3A and 3G antiretroviral restriction factors in MDM. These findings suggest that hBD2 inhibits HIV in MDM via more than one CCR thus adding to the potential of using β-defensins in preventive and therapeutic approaches.

Engineering an anti-granulocyte colony stimulating factor receptor nanobody for improved affinity

AIMS

Granulocyte colony-stimulating factor (G-CSF) is a cytokine that induces proliferation and differentiation of hematopoietic precursor cells and activation of mature neutrophils. G-CSF is overexpressed in several malignant tumors and blocking its binding to the receptor can lead to significant decrease in tumor growth, vascularization and metastasis. Furthermore, targeting G-CSF receptor has shown therapeutic benefit in other diseases such as rheumatoid arthritis, progressive neurodegenerative disorder and uveitis. Camelid single-chain antibodies (nanobodies) have exceptional properties making them appropriate for tumor imaging and therapeutic application. In this study we aim to use the rational design approach to engineer a previously described G-CSF-R targeting nanobody (VHH1), to improve its affinity toward G-CSF-R.

MAIN METHODS

We redesigned the complementary determining region 3 (CDR3) domain of the VHH1 nanobody to mimic G-CSF interaction to its receptor and developed five new engineered nanobodies. Binding affinity of the engineered nanobodies was evaluated by ELISA (Enzyme-linked immunosorbent assay) on NFS60 cells.

KEY FINDINGS

Enzyme-linked immunosorbent assay (ELISA) confirmed the specificity of the engineered nanobodies and ELISA-based determination of affinity revealed that two of the engineered nanobodies (1c and 5a) bind to G-CSF-R on the surface of NFS60 cells in a dose-dependent manner and with a higher potency compared to the parental nanobody.

SIGNIFICANCE

Additional studies are required to better characterize these nanobodies and assess their interaction with G-CSF-R in vitro and in vivo. These newly developed nanobodies could be beneficial in tumor imaging and therapy and make a basis for development of additional engineered nanobodies.

Expression of recombinant G-CSF receptor domains and their inhibitory role on G-CSF function

Background and purpose:

Granulocyte colony-stimulating factor (G-CSF) is routinely used in combination with chemotherapy to battle neutropenia. However, studies suggest that this chemokine may increase the risk of metastasis and malignancy in many cancers. To counteract the adverse effects of G-CSF in cancer, antibodies have been used to block its action. However, antibodies are large and complex molecules which makes their production expensive. Thus in this study, we aim to construct different structure variants of the G-CSF receptor containing different domains and select the best variant that prevents the adverse actions of this chemokine. These novel structures are smaller than antibodies and easier to produce.

Experimental approach:

Different domains of the G-CSF receptor were designed and cloned into the pET28a expression vector. These recombinant receptor subunits were then expressed in Escherichia coli and purified using standard affinity chromatography techniques. Interaction of recombinant receptor subunits with G-CSF was assessed using enzyme-linked immunosorbent assay and NFS60 cells.

Findings / Results:

Two recombinant receptor subunits containing D1 + D2 + D3 domains and D2 domain showed the strongest inhibitory activity to G-CSF.

Conclusion and implications:

These novel recombinant receptor variants could be candidates for further studies in the development of novel therapeutics.

Regulation of hematopoiesis by the chemokine system

Although chemokines are best known for their role in directing cell migration, accumulating evidence indicate their involvement in many other processes. This review focus on the role of chemokines in hematopoiesis with an emphasis on myelopoiesis. Indeed, many chemokine family members are an important component of the cytokine network present in the bone marrow that controls proliferation, retention, and mobilization of hematopoietic progenitors.

Neutrophils in innate immunity and systems biology-level approaches

The innate immune system is the first line of host defense against invading microorganisms. Polymorphonuclear leukocytes (PMNs or neutrophils) are the most abundant leukocyte in humans and essential to the innate immune response against invading pathogens. Compared to the acquired immune response, which requires time to develop and is dependent on previous interaction with specific microbes, the ability of neutrophils to kill microorganisms is immediate, nonspecific, and not dependent on previous exposure to microorganisms. Historically, studies of PMN-pathogen interaction focused on the events leading to killing of microorganisms, such as recruitment/chemotaxis, transmigration, phagocytosis, and activation, whereas postphagocytosis sequelae were infrequently considered. In addition, it was widely accepted that human neutrophils possessed limited capacity for new gene transcription and thus, relatively little biosynthetic capacity. This notion has changed dramatically within the past 20 years. Further, there is now more effort directed to understand the events occurring in PMNs after killing of microbes. Herein, we give an updated review of the systems biology-level approaches that have been used to gain an enhanced view of the role of neutrophils during host-pathogen interaction and neutrophil-mediated diseases. We anticipate that these and future systems-level studies will continue to provide information important for understanding, treatment, and control of diseases caused by pathogenic microorganisms. This article is categorized under: Physiology > Organismal Responses to Environment Physiology > Mammalian Physiology in Health and Disease Biological Mechanisms > Cell Fates.

Human β-defensin 2 is involved in CCR2-mediated Nod2 signal transduction, leading to activation of the innate immune response in macrophages

Beta-defensins contribute to host innate defense against various pathogens, including viruses, although the details of their roles in innate immune cells are unclear. We previously reported that human β-defensin 2 (HBD 2) activates primary innate immunity against viral infection and suggested that it plays a role in the induction of the adaptive immune response. We analyzed the mechanisms by which HBD 2 primes innate antiviral immunity and polarized activation of macrophage-like THP-1 cells using the receptor-binding domain (RBD) of Middle East respiratory syndrome coronavirus (MERS-CoV) spike protein (S RBD) as a model antigen. The expression of nucleotide-binding oligomerization domain containing 2 (Nod2), type I interferons, (IFNs), and proinflammatory mediators was enhanced in S RBD-HBD 2-treated THP-1 cells. S RBD-HBD 2 treatment also enhanced phosphorylation and activation of receptor-interacting serine/threonine-protein kinase 2 and IFN regulatory factor 3 compared to S RBD alone. Finally, HBD 2-conjugated S RBD interacted with C-C chemokine receptor 2 (CCR2), and Nod2 was involved in HBD 2-mediated CCR2 signaling, which was associated with the activation and M1 polarization of THP-1 cells. Therefore, HBD 2 promotes CCR2-mediated Nod2 signaling, which induces production of type I IFNs and an inflammatory response, and enhances primary innate immunity leading to an effective adaptive immune response to HBD 2-conjugated antigen.

Systems Biology Analysis of the Effect and Mechanism of Qi-Jing-Sheng-Bai Granule on Leucopenia in Mice

Qi-Jing-Sheng-Bai granule (QJSB) is a newly developed traditional Chinese medicine (TCM) formula. Clinically, it has been used for the treatment of leucopenia. However, its pharmacological mechanism needs more investigation. In this study, we firstly tested the effects of QJSB on leucopenia using mice induced by cyclophosphamide. Our results suggested that QJSB significantly raised the number of peripheral white blood cells, platelets and nucleated bone marrow cells. Additionally, it markedly enhanced the cell viability and promoted the colony formation of bone marrow mononuclear cells. Furthermore, it reversed the serum cytokines IL-6 and G-CSF disorders. Then, using transcriptomics datasets and metabonomic datasets, we integrated transcriptomics-based network pharmacology and metabolomics technologies to investigate the mechanism of action of QJSB. We found that QJSB regulated a series of biological processes such as hematopoietic cell lineage, homeostasis of number of cells, lymphocyte differentiation, metabolic processes (including lipid, amino acid, and nucleotide metabolism), B cell receptor signaling pathway, T cell activation and NOD-like receptor signaling pathway. In a summary, QJSB has protective effects to leucopenia in mice probably through accelerating cell proliferation and differentiation, regulating metabolism response pathways and modulating immunologic function at a system level.

A novel CC chemokine ligand 2 like gene from ayu Plecoglossus altivelis is involved in the innate immune response against to Vibrio anguillarum

Chemokine (CC motif) ligand 2 (CCL2), also known as monocyte chemoattractant protein 1 (MCP-1), is one of the key chemokines that regulate migration and infiltration of monocytes/macrophages (MO/MФ) in mammals. However, the functional repertoire of fish CCL2 remains unclear. Here, we identified a cDNA sequence encoding a novel CCL2-like protein (PaCCL2L) in ayu, Plecoglossus altivelis. Sequence analysis revealed that PaCCL2L grouped with CCL2 homologs, and is most closely related to Mexican tetra (Astyanax mexicanus) and zebrafish (Danio rerio) homologs. PaCCL2 transcripts were expressed in all tested tissues from healthy ayu, with the highest level in the spleen. Upon Vibrio anguillarum infection, PaCCL2L transcripts increased significantly in tested tissues, including the liver, spleen, and head kidney. We then produced the recombinant PaCCL2L mature peptide (rPaCCL2L) by prokaryotic expression and generated the corresponding antibodies (anti-PaCCL2L). A significant increase in PaCCL2L protein and mRNA expression was observed in ayu MO/MФ following V. anguillarum challenge. Intraperitoneal injection of rPaCCL2L resulted in significantly improved survival and reduced tissue bacterial load in V. anguillarum-infected ayu. rPaCCL2L had a positive effect on the chemotaxis of MO/MΦ and neutrophils both in vitro and in vivo. Meanwhile, rPaCCL2L exhibited a positive effect on the chemotaxis of LPS-stimulated MO/MΦ (M1 type) in vitro, whereas it exhibited no chemotaxis effect on cAMP-stimulated MO/MΦ (M2 type). In addition, rPaCCL2L treatment exhibited an enhanced effect on MO/MΦ phagocytosis, bacterial killing, respiratory burst, and mRNA expression of proinflammatory cytokines, whereas anti-PaCCL2L treatment had an inhibitory effect. Our study demonstrates that PaCCL2L might play a role in the immune response of ayu against V. anguillarum infection through chemotactic recruitment and activation of MO/MΦ.

Plasma Monocyte Chemoattractant Protein-1 Level as a Predictor of the Severity of Community-Acquired Pneumonia

Monocyte chemoattractant protein (MCP)-1 increases in the serum of immunocompetent patients with community-acquired pneumonia (CAP). However, the correlation between the circulating level of MCP-1 and severity of CAP remains unclear. This study investigated differential changes in the plasma MCP-1 levels of patients with CAP before and after an antibiotic treatment and further analyzes the association between the CAP severity and MCP-1 levels. We measured the plasma MCP-1 levels of 137 patients with CAP and 74 healthy controls by using a commercial enzyme-linked immunosorbent assay. Upon initial hospitalization, Acute Physiology and Chronic Health Evaluation II (APACHE II); confusion, urea level, respiratory rate, blood pressure, and age of >64 years (CURB-65); and pneumonia severity index (PSI) scores were determined for assessing the CAP severity in these patients. The antibiotic treatment reduced the number of white blood cells (WBCs) and neutrophils as well as the level of C-reactive protein (CRP) and MCP-1. The plasma MCP-1 level, but not the CRP level or WBC count, correlated with the CAP severity according to the PSI (r = 0.509, p < 0.001), CURB-65 (r = 0.468, p < 0.001), and APACHE II (r = 0.360, p < 0.001) scores. We concluded that MCP-1 levels act in the development of CAP and are involved in the severity of CAP.

CCR2 inhibition sequesters multiple subsets of leukocytes in the bone marrow

Chemokine receptor CCR2 mediates monocyte mobilization from the bone marrow (BM) and subsequent migration into target tissues. The degree to which CCR2 is differentially expressed in leukocyte subsets, and the contribution of CCR2 to these leukocyte mobilization from the BM are poorly understood. Using red fluorescence protein CCR2 reporter mice, we found heterogeneity in CCR2 expression among leukocyte subsets in varying tissues. CCR2 was highly expressed by inflammatory monocytes, dendritic cells, plasmacytoid dendritic cells and NK cells in all tissues. Unexpectedly, more than 60% of neutrophils expressed CCR2, albeit at low levels. CCR2 expression in T cells, B cells and NK T cells was greatest in the BM compared to other tissues. Genetic CCR2 deficiency markedly sequestered all leukocyte subsets in the BM, with reciprocal reduction noted in the peripheral blood and spleen. CCR2 inhibition via treatment with CCR2 signaling inhibitor propagermanium produced similar effects. Propagermanium also mitigated lipopolysaccharide-induced BM leukocyte egress. Consistent with its functional significance, CCR2 antibody staining revealed surface CCR2 expression within a subset of BM neutrophils. These results demonstrate the central role CCR2 plays in mediating leukocyte mobilization from the BM, and suggest a role for CCR2 inhibition in managing monocytes/macrophages-mediated chronic inflammatory conditions.

Intrapulmonary G-CSF rescues neutrophil recruitment to the lung and neutrophil release to blood in Gram-negative bacterial infection in MCP-1-/- mice

We previously demonstrated that MCP-1 is important for E. coli-induced neutrophil migration to the lungs. However, E. coli neither disseminates nor induces death in mice. Furthermore, the cell types and the host defense mechanisms that contribute to MCP-1-dependent neutrophil trafficking have not been defined. In this study, we sought to explore the cell types and the mechanisms associated with Klebsiella pneumoniae-mediated MCP-1-dependent neutrophil influx. MCP-1(-/-) mice are more susceptible to pulmonary K. pneumoniae infection and show higher bacterial burden in the lungs and dissemination. MCP-1(-/-) mice also display attenuated neutrophil influx, cytokine/chemokine production, and activation of NF-κB and MAPKs following intratracheal K. pneumoniae infection. rMCP-1 treatment in MCP-1(-/-) mice following K. pneumoniae infection rescued impairment in survival, bacterial clearance, and neutrophil accumulation in the lung. Neutrophil numbers in the blood of MCP-1(-/-) mice were associated with G-CSF concentrations in bronchoalveolar lavage fluid and blood. Bone marrow or resident cell-derived MCP-1 contributed to bacterial clearance, neutrophil accumulation, and cytokine/chemokine production in the lungs following infection. Furthermore, exogenous MCP-1 dose dependently increased neutrophil counts and G-CSF concentrations in the blood. Intriguingly, administration of intratracheal rG-CSF to MCP-1(-/-) mice after K. pneumoniae infection rescued survival, bacterial clearance and dissemination, and neutrophil influx in MCP-1(-/-) mice. Collectively, these novel findings unveil an unrecognized role of MCP-1 in neutrophil-mediated host immunity during K. pneumoniae pneumonia and illustrate that G-CSF could be used to rescue impairment in host immunity in individuals with absent or malfunctional MCP-1.

Glutaminyl cyclases as novel targets for the treatment of septic arthritis

BACKGROUND

Septic arthritis is a severe and rapidly debilitating disease mainly caused by Staphylococcus aureus. Here, we assess the antiarthritic efficiency of glutaminyl cyclase (QC) inhibitors.

METHODS

Mice were inoculated with an arthritogenic amount of S. aureus intravenously or by local administration into the knee joint. Animals were treated with QC inhibitors (PBD155 and PQ529) via chow during the experiment. QC and isoQC knockout mice were also analyzed for arthritis symptoms after local administration of bacteria.

RESULTS

Both QC inhibitors significantly delayed the onset of clinical signs of arthritis, and inhibitors significantly decreased weight loss in treated animals. Following intraarticular injection of S. aureus, PBD155-treated mice had lower levels of synovitis and bone erosion, as well as less myeloperoxidase in synovial tissue. Fluorescence-activated cell sorter analysis revealed that PBD155 treatment affected the expression pattern of adhesion molecules, preventing the upregulation of cells expressing CD11b/CD18.

CONCLUSION

The compounds investigated here represent a novel class of small molecular antiarthritic inhibitors. In our studies, they exerted strong antiinflammatory actions, and therefore they might be suited for disease-modifying treatment of infectious arthritis.

Transcriptional regulation of flotillins by the extracellularly regulated kinases and retinoid X receptor complexes

Flotillin-1 and flotillin-2 are important regulators of signal transduction pathways such as growth factor signaling. Flotillin expression is increased under pathological conditions such as neurodegenerative disorders and cancer. Despite their importance for signal transduction, very little is known about the transcriptional regulation of flotillins. Here, we analyzed the expression of flotillins at transcriptional level and identified flotillins as downstream targets of the mitogen activated kinases ERK1/2. The promoter activity of flotillins was increased upon growth factor stimulation in a MAPK dependent manner. Overexpression of serum response factor or early growth response gene 1 resulted in increased flotillin mRNA and protein expression. Furthermore, both promoter activity and expression of endogenous flotillins were increased upon treatment with retinoic acid or by overexpression of the retinoid X receptor and its binding partners RARα and PPARγ. Our data indicate that the expression of flotillins, which can be detected in all cultured cells, is fine-tuned in response to various external stimuli. This regulation may be critical for the outcome of signaling cascades in which flotillins are known to be involved.

C-C motif chemokine CCL3 and canonical neutrophil attractants promote neutrophil extravasation through common and distinct mechanisms

Initial observations suggested that C-C motif chemokines exclusively mediate chemotaxis of mononuclear cells. In addition, recent studies also implicated these chemotactic cytokines in the recruitment of neutrophils. The underlying mechanisms remained largely unknown. Using in vivo microscopy on the mouse cremaster muscle, intravascular adherence and subsequent paracellular transmigration of neutrophils elicited by the chemokine (C-C motif) ligand 3 (CCL3, synonym MIP-1α) were significantly diminished in mice with a deficiency of the chemokine (C-C motif) receptor 1 (Ccr1(-/-)) or 5 (Ccr5(-/-)). Using cell-transfer techniques, neutrophil responses required leukocyte CCR1 and nonleukocyte CCR5. Furthermore, neutrophil extravasation elicited by CCL3 was almost completely abolished on inhibition of G protein-receptor coupling and PI3Kγ-dependent signaling, while neutrophil recruitment induced by the canonical neutrophil attractants chemokine (C-X-C motif) ligand 1 (CXCL1, synonym KC) or the lipid mediator platetelet-activating factor (PAF) was only partially reduced. Moreover, Ab blockade of β(2) integrins, of α(4) integrins, or of their putative counter receptors ICAM-1 and VCAM-1 significantly attenuated CCL3-, CXCL1-, or PAF-elicited intravascular adherence and paracellular transmigration of neutrophils. These data indicate that the C-C motif chemokine CCL3 and canonical neutrophil attractants exhibit both common and distinct mechanisms for the regulation of intravascular adherence and transmigration of neutrophils.

Tyrosine kinase chromosomal translocations mediate distinct and overlapping gene regulation events

Background

Leukemia is a heterogeneous disease commonly associated with recurrent chromosomal translocations that involve tyrosine kinases including BCR-ABL, TEL-PDGFRB and TEL-JAK2. Most studies on the activated tyrosine kinases have focused on proximal signaling events, but little is known about gene transcription regulated by these fusions.

Methods

Oligonucleotide microarray was performed to compare mRNA changes attributable to BCR-ABL, TEL-PDGFRB and TEL-JAK2 after 1 week of activation of each fusion in Ba/F3 cell lines. Imatinib was used to control the activation of BCR-ABL and TEL-PDGFRB, and TEL-JAK2-mediated gene expression was examined 1 week after Ba/F3-TEL-JAK2 cells were switched to factor-independent conditions.

Results

Microarray analysis revealed between 800 to 2000 genes induced or suppressed by two-fold or greater by each tyrosine kinase, with a subset of these genes commonly induced or suppressed among the three fusions. Validation by Quantitative PCR confirmed that eight genes (Dok2, Mrvi1, Isg20, Id1, gp49b, Cxcl10, Scinderin, and collagen Vα1(Col5a1)) displayed an overlapping regulation among the three tested fusion proteins. Stat1 and Gbp1 were induced uniquely by TEL-PDGFRB.

Conclusions

Our results suggest that BCR-ABL, TEL-PDGFRB and TEL-JAK2 regulate distinct and overlapping gene transcription profiles. Many of the genes identified are known to be involved in processes associated with leukemogenesis, including cell migration, proliferation and differentiation. This study offers the basis for further work that could lead to an understanding of the specificity of diseases caused by these three chromosomal translocations.

Monocyte chemoattractant protein 1 regulates pulmonary host defense via neutrophil recruitment during Escherichia coli infection

Neutrophil accumulation is a critical event to clear bacteria. Since uncontrolled neutrophil recruitment can cause severe lung damage, understanding neutrophil trafficking mechanisms is important to attenuate neutrophil-mediated damage. While monocyte chemoattractant protein 1 (MCP-1) is known to be a monocyte chemoattractant, its role in pulmonary neutrophil-mediated host defense against Gram-negative bacterial infection is not understood. We hypothesized that MCP-1/chemokine (C-C motif) ligand 2 is important for neutrophil-mediated host defense. Reduced bacterial clearance in the lungs was observed in MCP-1(-/-) mice following Escherichia coli infection. Neutrophil influx, along with cytokines/chemokines, leukotriene B(4) (LTB(4)), and vascular cell adhesion molecule 1 levels in the lungs, was reduced in MCP-1(-/-) mice after infection. E. coli-induced activation of NF-κB and mitogen-activated protein kinases in the lung was also reduced in MCP-1(-/-) mice. Administration of intratracheal recombinant MCP-1 (rMCP-1) to MCP-1(-/-) mice induced pulmonary neutrophil influx and cytokine/chemokine responses in the presence or absence of E. coli infection. Our in vitro migration experiment demonstrates MCP-1-mediated neutrophil chemotaxis. Notably, chemokine receptor 2 is expressed on lung and blood neutrophils, which are increased upon E. coli infection. Furthermore, our findings show that neutrophil depletion impairs E. coli clearance and that exogenous rMCP-1 after infection improves bacterial clearance in the lungs. Overall, these new findings demonstrate that E. coli-induced MCP-1 causes neutrophil recruitment directly via chemotaxis as well as indirectly via modulation of keratinocyte cell-derived chemokine, macrophage inflammatory protein 2, and LTB(4).

Distinct CCR2(+) Gr1(+) cells control growth of the Yersinia pestis ΔyopM mutant in liver and spleen during systemic plague

We are using a systemic plague model to identify the cells and pathways that are undermined by the virulence protein YopM of the plague bacterium Yersinia pestis. In this study, we pursued previous findings that Gr1(+) cells are required to selectively limit growth of ΔyopM Y. pestis and that CD11b(+) cells other than polymorphonuclear leukocytes (PMNs) are selectively lost in spleens infected with parent Y. pestis. When PMNs were ablated from mice, ΔyopM Y. pestis grew as well as the parent strain in liver but not in spleen, showing that these cells are critical for controlling growth of the mutant in liver but not spleen. In mice lacking expression of the chemokine receptor CCR2, wild-type growth was restored to ΔyopM Y. pestis in both organs. In spleen, the Gr1(+) cells differentially recruited by parent and ΔyopM Y. pestis infections were CCR2(+) Gr1(+) CD11b(+) CD11c(Lo-Int) MAC3(+) iNOS(+) (inducible nitric oxide synthase-positive) inflammatory dendritic cells (iDCs), and their recruitment to spleen from blood was blocked when YopM was present in the infecting strain. Consistent with influx of iDCs being affected by YopM in spleen, the growth defect of the ΔyopM mutant was relieved by the parent Y. pestis strain in a coinfection assay in which the parent strain could affect the fate of the mutant in trans. In a mouse model of bubonic plague, CCR2 also was shown to be required for ΔyopM Y. pestis to show wild-type growth in skin. The data imply that YopM's pathogenic effect indirectly undermines signaling through CCR2. We propose a model for how YopM exerts its different effects in liver and spleen.

Essential role of p400/mDomino chromatin-remodeling ATPase in bone marrow hematopoiesis and cell-cycle progression

p400/mDomino is an ATP-dependent chromatin-remodeling protein that catalyzes the deposition of histone variant H2A.Z into nucleosomes to regulate gene expression. We previously showed that p400/mDomino is essential for embryonic development and primitive hematopoiesis. Here we generated a conditional knock-out mouse for the p400/mDomino gene and investigated the role of p400/mDomino in adult bone marrow hematopoiesis and in the cell-cycle progression of embryonic fibroblasts. The Mx1-Cre- mediated deletion of p400/mDomino resulted in an acute loss of nucleated cells in the bone marrow, including committed myeloid and erythroid cells as well as hematopoietic progenitor and stem cells. A hematopoietic colony assay revealed a drastic reduction in colony-forming activity after the deletion of p400/mDomino. Moreover, the loss of p400/mDomino in mouse embryonic fibroblasts (MEFs) resulted in strong growth inhibition. Cell-cycle analysis revealed that the mDomino-deficient MEFs exhibited a pleiotropic cell-cycle defect at the S and G(2)/M phases, and polyploid and multi-nucleated cells with micronuclei emerged. DNA microarray analysis revealed that the p400/mDomino deletion from MEFs caused the impaired expression of many cell-cycle-regulatory genes, including G(2)/M-specific genes targeted by the transcription factors FoxM1 and c-Myc. These results indicate that p400/mDomino plays a key role in cellular proliferation by controlling the expression of cell-cycle-regulatory genes.

Human beta-defensin 2 and 3 and their mouse orthologs induce chemotaxis through interaction with CCR2

Beta-defensins play a dual role during immune response. Their direct antimicrobial properties contribute to the local innate immune response by combating microbial invasions. Furthermore, previous studies revealed the capacity of certain beta-defensin family members to chemoattract immature dendritic cells and CD45RO+ CD4+ T cells through chemokine receptor CCR6. However, because beta-defensins also chemoattract macrophages and monocytes, which do not express CCR6, efforts have been made to identify other receptors for these polypeptides. In this study, we demonstrate the capacity of human beta-defensin (hBD)2 and 3 and their mouse orthologs, beta-defensin 4 and 14, to interact with CCR2, a chemokine receptor expressed on monocytes, macrophages, and neutrophils. These beta-defensins, fused to the Fc region of human IgG1, showed binding to CCR2-transfected HEK293 cells, as revealed by flow cytometry. The beta-defensin fusion proteins also induced CCR2-specific chemotaxis of transfected HEK293 cells, human peripheral blood monocytes, and mouse peritoneal exudate cells in a dose-dependent manner. Preincubation of human monocytes with CCL2/MCP-1, the chemokine ligand for CCR2, abolished migration induced by beta-defensins. Conversely, preincubation with hBD2:Ig or hBD3:Ig inhibited MCP-1 induced migration. Peritoneal exudate cells from CCR2-deficient mice failed to migrate toward these fusion proteins. In conclusion, the beta-defensins used in this study contribute to the innate and adaptive immune response in their role as chemoattractants. Our data indicate that hBD2 and hBD3, together with their mouse orthologs (beta-defensin 4 and 14), are chemotactic for a broad spectrum of leukocytes in a CCR6- and CCR2-dependent manner.

Flotillins are involved in the polarization of primitive and mature hematopoietic cells

Background

Migration of mature and immature leukocytes in response to chemokines is not only essential during inflammation and host defense, but also during development of the hematopoietic system. Many molecules implicated in migratory polarity show uniform cellular distribution under non-activated conditions, but acquire a polarized localization upon exposure to migratory cues.

Methodology/Principal Findings

Here, we present evidence that raft-associated endocytic proteins (flotillins) are pre-assembled in lymphoid, myeloid and primitive hematopoietic cells and accumulate in the uropod during migration. Furthermore, flotillins display a polarized distribution during immunological synapse formation. Employing the membrane lipid-order sensitive probe Laurdan, we show that flotillin accumulation in the immunological synapse is concomittant with membrane ordering in these regions.

Conclusions

Together with the observation that flotillin polarization does not occur in other polarized cell types such as polarized epithelial cells, our results suggest a specific role for flotillins in hematopoietic cell polarization. Based on our results, we propose that in hematopoietic cells, flotillins provide intrinsic cues that govern segregation of certain microdomain-associated molecules during immune cell polarization.

Role of neutrophils in innate immunity: a systems biology-level approach

The innate immune system is the first line of host defense against invading microorganisms. Polymorphonuclear leukocytes (PMNs or neutrophils) are the most abundant leukocyte in humans and essential to the innate immune response against invading pathogens. Compared with the acquired immune response, which requires time to develop and is dependent on previous interaction with specific microbes, the ability of neutrophils to kill microorganisms is immediate, non-specific, and not dependent on previous exposure to microorganisms. Historically, studies on PMN-pathogen interaction focused on the events leading to killing of microorganisms, such as recruitment/chemotaxis, transmigration, phagocytosis, and activation, whereas post-phagocytosis sequelae were infrequently considered. In addition, it was widely accepted that human neutrophils possessed limited capacity for new gene transcription and thus, relatively little biosynthetic capacity. This notion has changed dramatically within the past decade. Further, there is now more effort directed to understand the events occurring in PMNs after killing of microbes. Herein we review the systems biology-level approaches that have been used to gain an enhanced view of the role of neutrophils during host-pathogen interaction. We anticipate that these and future systems-level studies will ultimately provide information critical to our understanding, treatment, and control of diseases caused by pathogenic microorganisms.

Role of Toll-like receptor 5 in the innate immune response to acute P. aeruginosa pneumonia

Pseudomonas aeruginosa is a leading cause of hospital-acquired pneumonia and an important pathogen in patients with chronic lung disease, such as cystic fibrosis and bronchiectasis. The contribution of Toll-like receptor 5 (TLR5) to the innate immune response to this organism is incompletely understood. We exposed wild-type and TLR5-deficient (Tlr5(-/-)) mice to aerosolized P. aeruginosa at low and high inocula and assessed bacterial clearance, lung inflammation, and cytokine production 4 and 24 h after infection. Bacterial clearance was impaired in Tlr5(-/-) mice after low-inoculum, but not high-inoculum, infection. Early bronchoalveolar accumulation of neutrophils was reduced in Tlr5(-/-) mice after low- and high-dose infection. Cytokine responses, including markedly impaired monocyte chemoattractant protein-1 production 4 h after low- and high-inoculum challenge, were selectively altered in Tlr5(-/-) mice. In contrast, there was no impairment of bacterial clearance, neutrophil recruitment, or monocyte chemoattractant protein-1 production in Tlr5(-/-) mice after infection with a nonflagellated isotypic strain of P. aeruginosa. Thus TLR5-mediated recognition of flagellin is involved in activating pulmonary defenses against P. aeruginosa and contributes to antibacterial resistance in a manner that is partially inoculum dependent. These data are the first to demonstrate a unique role for TLR5 in the innate immune response to P. aeruginosa lung infection.

Role of IL-23 in mobilization of immunoregulatory nitric oxide- or superoxide-producing Gr-1+ cells from bone marrow

Spleens of mice injected with heat-killed Mycobacterium tuberculosis increase their Gr-1+ cell content and develop a system of interactive Ly-6G+ and Ly-6G-Gr-1+ populations or "Greg" subsets, which, upon stimulation by activated T cells, produce immunoregulatory superoxide (O2(-)) and nitric oxide (NO), respectively. The balance between immunosuppressive NO and its antagonist O2(-) regulates T cell expansion, similar to regulation of vasodilation. Reduction of NO levels by O2(-) is required for efficient T cell expansion and development of autoimmunity. We studied the source of Gr-1+ cells in bone marrow (BM), where their levels were higher than in spleen, with both Greg subsets expressing strong activity. In the spleens of primed IL-23-/- mice, Ly-6G+ cells remained at naïve levels and produced no O2(-). The complementary Ly-6G(-)Gr-1+ splenocytes and their suppressive activity were partially reduced. Surprisingly, Gr-1+ cell levels in BM of IL-23-/- mice were increased, as were their O2(-) and NO production. Transfer of primed BM cells partially restored regulatory function in the spleen of IL-23-/- recipients. The results suggest that IL-23 is involved in mobilization of O2(-)- and NO-producing Gr-1+ cells from BM, which may contribute to its widely studied role in (auto)immunity.

Essential role of C/EBPalpha in G-CSF-induced transcriptional activation and chromatin modification of myeloid-specific genes

Granulocyte colony-stimulating factor (G-CSF) regulates the proliferation and differentiation of neutrophilic progenitor cells. Here, we investigated the roles of CCAAT/enhancer-binding protein (C/EBP)alpha in the G-CSF-induced transcriptional activation and chromatin modification of the CCR2 and myeloperoxidase (MPO) genes in IL-3-dependent myeloid FDN1.1 cells. Chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assays revealed that G-CSF activates C/EBPalpha to bind target promoters. ChIP mapping experiments across the CCR2 and MPO genes showed that G-CSF induces histone H3 modifications: the acetylation of Lys9, trimethylation of Lys4 and trimethylation of Lys9. The distribution profile of the trimethylated Lys9 was distinct from that of the two other modifications. All the G-CSF-induced C/EBPalpha recruitment, transcriptional activation and histone modifications were reversed by re-stimulation with IL-3, and were abolished by short hairpin RNA (shRNA)-mediated knockdown of C/EBPalpha. These results indicate that C/EBPalpha is activated by G-CSF to bind target promoters, and plays critical roles in the transcriptional activation and dynamic chromatin modification of target genes during neutrophil differentiation.

Recombinant human granulocyte colony-stimulating factor enhanced the resolution of venous thrombi

BACKGROUND

Bone marrow-derived cells are recruited into the thrombus during resolution. This study explored whether mobilization of bone marrow cells with recombinant human granulocyte colony-stimulating factor (rhG-CSF) could enhance the resolution of venous thrombi and the accumulation of macrophages in thrombi and explored the effect of rhG-CSF on cysteine-cysteine chemokine receptor 2 (CCR2) expression.

METHODS

The Sprague-Dawley adult rats were randomly divided into four groups: control, sham-operated, thrombus, and treatment groups. Thrombi were induced in the thrombus and treatment group, which received a subcutaneous injection of rhG-CSF once daily for 6 days postoperatively. The thrombus, sham-operated, and control groups received equal volumes of 0.9% saline. The mononuclear cells in peripheral blood were analyzed by an automated hematology analyzer and counted under microscope. The cell marker CD68 was used to determine the number of macrophages in thrombi tissue sections. Levels of monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1alpha (MIP1alpha) in the peripheral blood were detected by enzyme-linked immunosorbent assay. Real-time reverse transcriptase-polymerase chain reaction and Western blot were used to analyze, respectively, the expression of CCR2 messenger RNA in the peripheral blood and CCR2 protein of THP-1 monocyte.

RESULTS

At postoperative days 3 (P < .05) and 7 (P < .01), mononuclear cells significantly increased in treatment group (2.1 +/- 0.3, 4.4 +/- 0.3 x 10(6)/L) vs the thrombus group (1.7 +/- 0.2, 1.3 +/- 0.4 x 10(6)/L). The organization and recanalization of thrombi in treatment group progressed more quickly compared with the thrombus group (P < .01). The macrophage number of the thrombus in the treatment group (338 +/- 26 cells/15 high-power fields) increased significantly vs the thrombus group (125 +/- 11 cells/15 high-power fields, P < .01). No statistical difference was observed between the thrombus and treatment group in the MCP-1 and MIP-1alpha level in peripheral blood. Expressions of the CCR2 gene in the peripheral blood of the treatment group significantly increased compared with the thrombus group (P < .05). Recombinant human G-CSF induced higher expression of CCR2 protein of human monocytic cell line THP-1.

CONCLUSIONS

Bone marrow mobilization enhanced the resolution and recanalization of venous thrombi. This process was associated with increased macrophage accumulation in thrombi, which might be the result of higher CCR2 expression of monocytes.

CLINICAL RELEVANCE

The classic treatment of venous thrombi is anticoagulation. Anticoagulant therapy and thrombolysis both have limited effects on existing thrombi and have a small but significant risk of severe hemorrhage. In clinical practice, we lack specific treatment for patients with venous thrombosis combined with brain hemorrhage or a gastrointestinal activated ulcer, which are contraindicated for anticoagulation and thrombolytic therapy. Enhancing the resolution of venous thrombi would contribute to its therapy. Bone marrow-derived cells are recruited into the thrombus during resolution. Many of these cells express a macrophage phenotype and may represent a population of plastic stem cells that orchestrate thrombus recanalization. Recombinant human granulocyte colony stimulating factor (rhG-CSF) can mobilize monocytic lineage cells into peripheral blood and may contribute to this cell in the thrombi. If rhG-CSF enhances the resolution of venous thrombi and recanalization, it might be used to treat patients with venous thrombi, especially those who have contraindication for anticoagulation and thrombolytic therapy.

Critical role of the p400/mDomino chromatin-remodeling ATPase in embryonic hematopoiesis

The SWI2/SNF2 family ATPase, p400/mDomino, is a core subunit of a large chromatin-remodeling complex, and is currently suggested to play a unique function in histone variant exchange, a process by which chromatin structure is altered. Here, we investigated the role of p400/mDomino in mammalian development by generating mutant mice with a targeted deletion of the N-terminal domain of p400/mDomino (referred to as mDom(DeltaN/DeltaN)). The mDom(DeltaN/DeltaN) mice died on embryonic day 11.5 (E11.5), and displayed an anemic appearance and slight deformity of the neural tube. DNA microarray and quantitative RT-PCR analyses revealed that all of the embryonic globin genes and a globin chaperone gene were poorly expressed in the mDom(DeltaN/DeltaN) embryo and yolk sac on E8.5, indicating that primitive erythropoiesis was impaired. A hematopoietic colony assay indicated that the hematopoietic activity of the yolk sac was significantly blocked in the mutant mice. We also found that the expression of a limited set of Hox genes, including Hoxa7, Hoxa9 and Hoxb9, was drastically enhanced in the mDom(DeltaN/DeltaN) yolk sacs. These results suggest that p400/mDomino plays a critical role in embryonic hematopoiesis by regulating the expression of developmentally essential genes such as those in the Hox gene cluster.

The lipid raft proteins flotillins/reggies interact with Galphaq and are involved in Gq-mediated p38 mitogen-activated protein kinase activation through tyrosine kinase

The heterotrimeric G protein alpha q subunit (Galphaq) mediates a variety of cell functions by activating the effector molecule phospholipase Cbeta. Galphaq activity is regulated by G protein betagamma subunits, G protein-coupled receptors, RGS proteins, and Ric-8. In this study, we identified the lipid raft resident proteins, flotillin-1/reggie-2 and flotillin-2/reggie-1, as Galphaq-binding proteins. The interactions of Galphaq and flotillins were independent of the nucleotide-binding state of Galphaq, and the N-terminal portion of flotillins was critical for the interaction. A short interfering RNA-mediated knockdown of flotillins, particularly flotillin-2, attenuated the UTP-induced activation of p38 mitogen-activated protein kinase (MAPK) but not that of ERK1/2. The activation of p38 MAPK was inhibited by the Src family tyrosine kinase inhibitor PP2 and the cholesterol-depleting agent methyl-beta-cyclodextrin, which is generally used for the disruption of lipid rafts. In contrast, the activation of ERK1/2 was not inhibited by these compounds. These lines of evidence suggested that a Gq-coupled receptor activates specifically p38 MAPK through lipid rafts and Src kinase activation, in which flotillins positively modulate the Gq signaling.

p120 nucleolar-proliferating antigen is a direct target of G-CSF signaling during myeloid differentiation

Granulocyte-colony stimulating factor (G-CSF) is an essential cytokine, which contributes to proliferation and differentiation of granulocyte precursor cells in the bone marrow. Despite recent progress in understanding G-CSF signaling events, the mechanisms that underlie the distinct spectrum of biological functions attributed to G-CSF-mediated gene expression remain unclear. Previous studies have identified a number of genes, which are up-regulated in G-CSF-stimulated myeloid precursor cells. In this study, we sought to identify additional target genes of G-CSF-mediated proliferation and/or differentiation. cDNA representational difference analysis was used with the 32Dcl3 cell line as a model system to isolate genes, which are up-regulated in an immediate-early manner upon G-CSF stimualtion. We isolated p120 nucleolar-proliferation antigen (NOL1), a highly conserved, nucleolar-specific, RNA-binding protein of unknown function, and confirmed its expression by Northern blot analysis in 4-h, G-CSF-induced 32Dcl3 cells. Isolation of a mouse p120 genomic clone revealed the presence of a signal tranducer and activator of transcription (STAT)-binding site in the first intron of the gene. We demonstrate the importance of STAT3 and STAT5 in mediating the G-CSF response with respect to p120 expression by transient transfection analysis, oligonucleotide pull-down assays, and the loss of p120 expression in the bone marrow of mice lacking normal STAT3 signaling. In addition, overexpression of p120 in G-CSF-induced 32D cells revealed normal, morphologic maturation and growth characteristics but loss of lactoferrin expression, a marker of normal neutrophil maturation, suggesting that inappropriate expression of the p120 gene can result in aberrant neutrophil maturation.

Chemokine receptors Ccr1, Ccr2, and Ccr5 mediate neutrophil migration to postischemic tissue

Leukocyte infiltration of reperfused tissue is a key event in the pathogenesis of ischemia-reperfusion. However, the role of chemokine receptors Ccr1, Ccr2, and Ccr5 for each single step of the postischemic recruitment process of leukocytes has not yet been characterized. Leukocyte rolling, firm adherence, transendothelial, and extravascular migration were analyzed in the cremaster muscle of anaesthetized C57BL/6 mice using near-infrared reflected light oblique transillumination microscopy. Prior to 30 min of ischemia as well as at 5, 30, 60, 90, and 120 min after onset of reperfusion, migration parameters were determined in wild-type, Ccr1-/-, Ccr2-/-, and Ccr5-/- mice. Sham-operated wild-type mice without ischemia were used as controls. No differences were detected in numbers of rolling leukocytes among groups. In contrast, the number of firmly adherent leukocytes was increased significantly in wild-type mice as compared with sham-operated mice throughout the entire reperfusion phase. Already after 5 min of reperfusion, this increase was reduced significantly in Ccr1-/- and Ccr5-/- mice, whereas only in Ccr2-/- mice, was adherence attenuated significantly at 120 min after onset of reperfusion. Furthermore, after 120 min of reperfusion, the number of transmigrated leukocytes (>80% Ly-6G+ neutrophils) was elevated in wild-type mice as compared with sham-operated animals. This elevation was significantly lower in Ccr1-/-, Ccr2-/-, and Ccr5-/- mice. Leukocyte extravascular migration distances were comparable among groups. In conclusion, these in vivo data demonstrate that Ccr1, Ccr2, and Ccr5 mediate the postischemic recruitment of neutrophils through effects on intravascular adherence and subsequent transmigration.