The vitronectin receptor and its associated CD47 molecule mediates proinflammatory cytokine synthesis in human monocytes by interaction with soluble CD23

The zebrafish heart harbors a thermogenic beige fat depot analog of human epicardial adipose tissue

Epicardial adipose tissue (eAT) is a metabolically active fat depot that has been associated with a wide array of cardiac homeostatic functions and cardiometabolic diseases. A full understanding of its diverse physiological and pathological roles is hindered by the dearth of animal models. Here, we show, in the heart of an ectothermic teleost, the zebrafish, the existence of a fat depot localized underneath the epicardium, originating from the epicardium and exhibiting the molecular signature of beige adipocytes. Moreover, a subset of adipocytes within this cardiac fat tissue exhibits primitive thermogenic potential. Transcriptomic profiling and cross-species analysis revealed elevated glycolytic and cardiac homeostatic gene expression with downregulated obesity and inflammatory hallmarks in the teleost eAT compared to that of lean aged humans. Our findings unveil epicardium-derived beige fat in the heart of an ectotherm considered to possess solely white adipocytes for energy storage and identify pathways that may underlie age-driven remodeling of human eAT.

CD47: The Next Frontier in Immune Checkpoint Blockade for Non-Small Cell Lung Cancer

The success of PD-1/PD-L1-targeted therapy in lung cancer has resulted in great enthusiasm for additional immunotherapies in development to elicit similar survival benefits, particularly in patients who do not respond to or are ineligible for PD-1 blockade. CD47 is an immunosuppressive molecule that binds SIRPα on antigen-presenting cells to regulate an innate immune checkpoint that blocks phagocytosis and subsequent activation of adaptive tumor immunity. In lung cancer, CD47 expression is associated with poor survival and tumors with EGFR mutations, which do not typically respond to PD-1 blockade. Given its prognostic relevance, its role in facilitating immune escape, and the number of agents currently in clinical development, CD47 blockade represents a promising next-generation immunotherapy for lung cancer. In this review, we briefly summarize how tumors disrupt the cancer immunity cycle to facilitate immune evasion and their exploitation of immune checkpoints like the CD47-SIRPα axis. We also discuss approved immune checkpoint inhibitors and strategies for targeting CD47 that are currently being investigated. Finally, we review the literature supporting CD47 as a promising immunotherapeutic target in lung cancer and offer our perspective on key obstacles that must be overcome to establish CD47 blockade as the next standard of care for lung cancer therapy.

Versatile Applications of Cyanobacteria in Biotechnology

Cyanobacteria are blue-green Gram-negative and photosynthetic bacteria which are seen as one of the most morphologically numerous groups of prokaryotes. Because of their ability to fix gaseous nitrogen and carbon dioxide to organic materials, they are known to play important roles in the universal nutrient cycle. Cyanobacteria has emerged as one of the promising resources to combat the issues of global warming, disease outbreaks, nutrition insecurity, energy crises as well as persistent daily human population increases. Cyanobacteria possess significant levels of macro and micronutrient substances which facilitate the versatile popularity to be utilized as human food and protein supplements in many countries such as Asia. Cyanobacteria has been employed as a complementary dietary constituent of feed for poultry and as vitamin and protein supplement in aquatic lives. They are effectively used to deal with numerous tasks in various fields of biotechnology, such as agricultural (including aquaculture), industrial (food and dairy products), environmental (pollution control), biofuel (bioenergy) and pharmaceutical biotechnology (such as antimicrobial, anti-inflammatory, immunosuppressant, anticoagulant and antitumor); recently, the growing interest of applying them as biocatalysts has been observed as well. Cyanobacteria are known to generate a numerous variety of bioactive compounds. However, the versatile potential applications of cyanobacteria in biotechnology could be their significant growth rate and survival in severe environmental conditions due to their distinct and unique metabolic pathways as well as active defensive mechanisms. In this review, we elaborated on the versatile cyanobacteria applications in different areas of biotechnology. We also emphasized the factors that could impede the implementation to cyanobacteria applications in biotechnology and the execution of strategies to enhance their effective applications.

Dual Role of Thrombospondin-1 in Flow-Induced Remodeling

(1) Background: Chronic increases in blood flow, as in cardiovascular diseases, induce outward arterial remodeling. Thrombospondin-1 (TSP-1) is known to interact with matrix proteins and immune cell-surface receptors, but its contribution to flow-mediated remodeling in the microcirculation remains unknown. (2) Methods: Mesenteric arteries were ligated in vivo to generate high- (HF) and normal-flow (NF) arteries in wild-type (WT) and TSP-1-deleted mice (TSP-1-/-). After 7 days, arteries were isolated and studied ex vivo. (3) Results: Chronic increases in blood flow induced outward remodeling in WT mice (increasing diameter from 221 ± 10 to 280 ± 10 µm with 75 mmHg intraluminal pressure) without significant effect in TSP-1-/- (296 ± 18 to 303 ± 14 µm), neutropenic or adoptive bone marrow transfer mice. Four days after ligature, pro inflammatory gene expression levels (CD68, Cox2, Gp91phox, p47phox and p22phox) increased in WT HF arteries but not in TSP-1-/- mice. Perivascular neutrophil accumulation at day 4 was significantly lower in TSP-1-/- than in WT mice. (4) Conclusions: TSP-1 origin is important; indeed, circulating TSP-1 participates in vasodilation, whereas both circulating and tissue TSP-1 are involved in arterial wall thickness and diameter expansion.

Extracellular Matrix Proteins Confer Cell Adhesion-Mediated Drug Resistance Through Integrin α v in Glioblastoma Cells

Chemotherapy resistance to glioblastoma (GBM) remains an obstacle that is difficult to overcome, leading to poor prognosis of GBM patients. Many previous studies have focused on resistance mechanisms intrinsic to cancer cells; the microenvironment surrounding tumor cells has been found more recently to have significant impacts on the response to chemotherapeutic agents. Extracellular matrix (ECM) proteins may confer cell adhesion-mediated drug resistance (CAMDR). Here, expression of the ECM proteins laminin, vitronectin, and fibronectin was assessed in clinical GBM tumors using immunohistochemistry. Then, patient-derived GBM cells grown in monolayers on precoated laminin, vitronectin, or fibronectin substrates were treated with cilengitide, an integrin inhibitor, and/or carmustine, an alkylating chemotherapy. Cell adhesion and viability were quantified. Transcription factor (TF) activities were assessed over time using a bioluminescent assay in which GBM cells were transduced with lentiviruses containing consensus binding sites for specific TFs linked to expression a firefly luciferase reporter. Apoptosis, mediated by p53, was analyzed by Western blotting and immunocytofluorescence. Integrin α_v activation of the FAK/paxillin/AKT signaling pathway and effects on expression of the proliferative marker Ki67 were investigated. To assess effects of integrin α_v activation of AKT and ERK pathways, which are typically deregulated in GBM, and expression of epidermal growth factor receptor (EGFR), which is amplified and/or mutated in many GBM tumors, shRNA knockdown was used. Laminin, vitronectin, and fibronectin were abundant in clinical GBM tumors and promoted CAMDR in GBM cells cultured on precoated substrates. Cilengitide treatment induced cell detachment, which was most pronounced for cells cultured on vitronectin. Cilengitide treatment increased cytotoxicity of carmustine, reversing CAMDR. ECM adhesion increased activity of NFκB and decreased that of p53, leading to suppression of p53-mediated apoptosis and upregulation of multidrug resistance gene 1 (MDR1; also known as ABCB1 or P-glycoprotein). Expression of Ki67 was correlative with activation of the integrin α_v-mediated FAK/paxillin/AKT signaling pathway. EGFR expression increased with integrin α_v knockdown GBM cells and may represent a compensatory survival mechanism. These results indicate that ECM proteins confer CAMDR through integrin α_v in GBM cells.

The Integrin Inhibitor Cilengitide and Bleomycin-Induced Pulmonary Fibrosis : Cilengitide and Bleomycin-Induced Pulmonary Fibrosis

PURPOSE

Fibroproliferation and excess deposition of extracellular matrix (ECM) are the pathologic hallmarks of idiopathic pulmonary fibrosis (IPF), a chronic progressive disorder with high mortality and suboptimal treatment options. Although the etiologic mechanisms responsible for the development and progression of IPF remain unclear, cell-ECM interactions and growth factors are considered important. Cilengitide is a cyclic RGD pentapeptide with anti-angiogenic activity that targets αvβ3, αvβ5 and α5β1, integrins known to mediate cell-ECM interactions and activate the pro-fibrotic growth factor Transforming Growth Factor beta (TGF-β).

METHODS

Cilengitide was studied in vitro with the use of NIH/3T3 cells and primary lung fibroblasts, and in vivo in the well-characterized bleomycin-induced lung injury model. The extent of ECM deposition was determined by RT-PCR, Western blot, histologic analysis and hydroxyproline assay of lung tissue. Bronchoalveolar lavage analysis was used to determine cell counts.

RESULTS

Cilengitide treatment of cultured fibroblasts showed decreased adhesion to vitronectin and fibronectin, both integrin-dependent events. Cilengitide also inhibited TGF-β-induced fibronectin gene expression and reduced the accumulation of mRNAs and protein for fibronectin and collagen type I. Both preventive and treatment effects of daily injections of cilengitide (20 mg/kg) failed to inhibit the development of pulmonary fibrosis as determined by histological analysis (Ashcroft scoring), bronchoalveolar lavage (BAL) fluid cell counts, and hydroxyproline content.

CONCLUSIONS

Overall, our data suggest that, despite its in vitro activity in fibroblasts, daily injections of cilengitide (20 mg/kg) did not inhibit the development of or ameliorate bleomycin-induced pulmonary fibrosis in mice.

CD23 is a glycan-binding receptor in some mammalian species

CD23, the low-affinity IgE receptor found on B lymphocytes and other cells, contains a C-terminal lectin-like domain that resembles C-type carbohydrate-recognition domains (CRDs) found in many glycan-binding receptors. In most mammalian species, the CD23 residues required to form a sugar-binding site are present, although binding of CD23 to IgE does not involve sugars. Solid-phase binding competition assays, glycoprotein blotting experiments, and glycan array analysis employing the lectin-like domains of cow and mouse CD23 demonstrate that they bind to mannose, GlcNAc, glucose, and fucose and to glycoproteins that bear these sugars in nonreducing terminal positions. Crystal structures of the cow CRD in the presence of α-methyl mannoside and GlcNAcβ1-2Man reveal that a range of oligosaccharide ligands can be accommodated in an open binding site in which most interactions are with a single terminal sugar residue. Although mouse CD23 shows a pattern of monosaccharide and glycoprotein binding similar to cow CD23, the binding is weaker. In contrast, no sugar binding was observed in similar experiments with human CD23. The absence of sugar-binding activity correlates with accumulation of mutations in the gene for CD23 in the primate lineage leading to humans, resulting in loss of key sugar-binding residues. These results are consistent with a role for CD23 in many species as a receptor for potentially pathogenic microorganisms as well as IgE. However, the ability of CD23 to bind several different ligands varies between species, suggesting that it has distinct functions in different organisms.

Nanoparticle Optimization for Enhanced Targeted Anticancer Drug Delivery

Nanoparticle (NP)-based drug delivery is a promising method to increase the therapeutic index of anticancer agents with low median toxic dose. The delivery efficiency, corresponding to the fraction of the injected NPs that adhere to the tumor site, depends on NP size a and aspect ratio AR. Values for these variables are currently chosen empirically, which may not result in optimal targeted drug delivery. This study applies rigorous optimization to the design of NPs. A preliminary investigation revealed that delivery efficiency increases monotonically with a and AR. However, maximizing a and AR results in nonuniform drug distribution, which impairs tumor regression. Therefore, a multiobjective optimization (MO) problem is formulated to quantify the trade-off between NPs accumulation and distribution. The MO is solved using the derivative-free mesh adaptive direct search algorithm. Theoretically, the Pareto-optimal set consists of an infinite number of mathematically equivalent solutions to the MO problem. However, interesting design solutions can be identified subjectively, e.g., the ellipsoid with a major axis of 720 nm and an aspect ratio of 7.45, as the solution closest to the utopia point. The MO problem formulation is then extended to optimize NP biochemical properties: ligand-receptor binding affinity and ligand density. Optimizing physical and chemical properties simultaneously results in optimal designs with reduced NP sizes and thus enhanced cellular uptake. The presented study provides an insight into NP structures that have potential for producing desirable drug delivery.

Design Optimization of Tumor Vasculature-Bound Nanoparticles

Nanotherapy may constitute a promising approach to target tumors with anticancer drugs while minimizing systemic toxicity. Computational modeling can enable rapid evaluation of nanoparticle (NP) designs and numerical optimization. Here, an optimization study was performed using an existing tumor model to find NP size and ligand density that maximize tumoral NP accumulation while minimizing tumor size. Optimal NP avidity lies at lower bound of feasible values, suggesting reduced ligand density to prolong NP circulation. For the given set of tumor parameters, optimal NP diameters were 288 nm to maximize NP accumulation and 334 nm to minimize tumor diameter, leading to uniform NP distribution and adequate drug load. Results further show higher dependence of NP biodistribution on the NP design than on tumor morphological parameters. A parametric study with respect to drug potency was performed. The lower the potency of the drug, the bigger the difference is between the maximizer of NP accumulation and the minimizer of tumor size, indicating the existence of a specific drug potency that minimizes the differential between the two optimal solutions. This study shows the feasibility of applying optimization to NP designs to achieve efficacious cancer nanotherapy, and offers a first step towards a quantitative tool to support clinical decision making.

The effects of intra-hippocampal L-thyroxine infusion on long-term potentiation and long-term depression: A possible role for the αvβ3 integrin receptor

Although the effects of long-term experimental dysthyroidism on long-term potentiation (LTP) and long-term depression (LTD) have been documented, the relationship between LTP/LTD and acute administration of L-thyroxine (T4) has not been described. Here, we investigated the effects of intra-hippocampal administration of T4 on synaptic plasticity in the dentate gyrus of the hippocampal formation. After a 15-minute baseline recording, LTP and LTD were induced by application of high- and low-frequency stimulation protocols, respectively. Infusions of saline or T4 and tetraiodothyroacetic acid (tetrac), a T4 analog that inhibits binding of iodothyronines to the integrin αvβ3 receptor, either alone or together, were made during the stimulation protocols. The averages of the excitatory postsynaptic potential (EPSP) slopes and population spike (PS) amplitudes, between 55 to 60 minutes, were used as a measure of the LTP/LTD magnitude and were analyzed by two-way univariate ANOVA with T4 and tetrac as between-subjects factors. The input-output curves of the infusion groups were comparable to each other, as shown by the non significant interaction observed between stimulus intensity and infused drug. The magnitude of the LTP in T4-infused rats was significantly lower as compared to saline-infused rats. Both the PS amplitude and the EPSP slope were depressed more markedly with T4 infusion than with saline, tetrac, and T4 + tetrac infusion. Data of this study provide in vivo evidence that T4 can promote LTD over LTP via the integrin αvβ3 receptor, and that the effect of endogenous T4 on this receptor can be suppressed by tetrac in the hippocampus. © 2016 Wiley Periodicals, Inc.

Disrupted Endothelial Cell Layer and Exposed Extracellular Matrix Proteins Promote Capture of Late Outgrowth Endothelial Progenitor Cells

Late outgrowth endothelial progenitor cells (LO-EPC) possess a high proliferative potential, differentiate into vascular endothelial cells (EC), and form networks, suggesting they play a role in vascular repair. However, due to their scarcity in the circulation there is a requirement for ex vivo expansion before they could provide a practical cell therapy and it is currently unclear if they would home and engraft to an injury site. Using an in vitro flow system we studied LO-EPC under simulated injury conditions including EC activation, ischaemia, disrupted EC integrity, and exposed basement membrane. Perfused LO-EPC adhered to discontinuous EC paracellularly at junctional regions between adjacent cells under shear stress 0.7 dyn/cm(2). The interaction was not adhesion molecule-dependent and not enhanced by EC activation. LO-EPC expressed high levels of the VE-Cadherin which may explain these findings. Ischaemia reperfusion injury decreased the interaction with LO-EPC due to cell retraction. LO-EPC interacted with exposed extracellular matrix (ECM) proteins, fibronectin and vitronectin. The interaction was mediated by integrins α5β3, αvβ1, and αvβ3. This study has demonstrated that an injured local environment presents sufficient adhesive signals to capture flow perfused LO-EPC in vitro and that LO-EPC have properties consistent with their potential role in vascular repair.

Activation of the P2X7 receptor induces the rapid shedding of CD23 from human and murine B cells

Activation of the P2X7 receptor by the extracellular damage-associated molecular pattern, adenosine 5'-triphosphate (ATP), induces the shedding of cell surface molecules including the low-affinity IgE receptor, CD23, from human leukocytes. A disintegrin and metalloprotease (ADAM) 10 mediates P2X7-induced shedding of CD23 from multiple myeloma RPMI 8226 B cells; however, whether this process occurs in primary B cells is unknown. The aim of the current study was to determine whether P2X7 activation induces the rapid shedding of CD23 from primary human and murine B cells. Flow cytometric and ELISA measurements showed that ATP treatment of human and murine B cells induced the rapid shedding of CD23. Treatment of cells with the specific P2X7 antagonist, AZ10606120, near-completely impaired ATP-induced CD23 shedding from both human and murine B cells. ATP-induced CD23 shedding was also impaired in B cells from P2X7 knockout mice. The absence of full-length, functional P2X7 in the P2X7 knockout mice was confirmed by immunoblotting of splenic cells, and by flow cytometric measurements of ATP-induced YO-PRO-1(2+) uptake into splenic B and T cells. The broad-spectrum metalloprotease antagonist, BB-94, and the ADAM10 antagonist, GI254023X, impaired P2X7-induced CD23 shedding from both human and murine B cells. These data indicate that P2X7 activation induces the rapid shedding of CD23 from primary human and murine B cells and that this process may be mediated by ADAM10.

Activated γδ T cells inhibit osteoclast differentiation and resorptive activity in vitro

Extensive evidence suggests that the immune system exerts powerful effects on bone cells, particularly in chronic disease pathologies such as rheumatoid arthritis (RA). The chronic inflammatory state in RA, particularly the excessive production of T cell-derived proinflammatory cytokines such as tumour necrosis factor (TNF)-α and interleukin (IL)-17, triggers bone erosions through the increased stimulation of osteoclast formation and activity. While evidence supports a role for IL-17 and TNF-α secreted by conventional CD4⁺ T cells in RA, recent evidence in animal models of RA have implicated γδ T cells as a major producer of pathogenic IL-17. However, the capacity of γδ T cells to influence osteoclast formation and activity in humans has not yet been investigated widely. To address this issue we investigated the effects of γδ T cells on osteoclast differentiation and resorptive activity. We have demonstrated that anti-CD3/CD28-stimulated γδ T cells or CD4⁺ T cells inhibit human osteoclast formation and resorptive activity in vitro. Furthermore, we assessed cytokine production by CD3/CD28-stimulated γδ T cells and observed a lack of IL-17 production, with activated γδ T cells producing abundant interferon (IFN)-γ. The neutralization of IFN-γ markedly restored the formation of osteoclasts from precursor cells and the resorptive activity of mature osteoclasts, suggesting that IFN-γ is the major factor responsible for the inhibitory role of activated γδ T cells on osteoclastogenesis and resorptive activity of mature osteoclasts. Our work therefore provides new insights on the interactions between γδ T cells and osteoclasts in humans.

Glatiramer acetate treatment effects on gene expression in monocytes of multiple sclerosis patients

Background

Glatiramer acetate (GA) is a mixture of synthetic peptides used in the treatment of patients with relapsing-remitting multiple sclerosis (RRMS). The aim of this study was to investigate the effects of GA therapy on the gene expression of monocytes.

Methods

Monocytes were isolated from the peripheral blood of eight RRMS patients. The blood was obtained longitudinally before the start of GA therapy as well as after one day, one week, one month and two months. Gene expression was measured at the mRNA level by microarrays.

Results

More than 400 genes were identified as up-regulated or down-regulated in the course of therapy, and we analyzed their biological functions and regulatory interactions. Many of those genes are known to regulate lymphocyte activation and proliferation, but only a subset of genes was repeatedly differentially expressed at different time points during treatment.

Conclusions

Overall, the observed gene regulatory effects of GA on monocytes were modest and not stable over time. However, our study revealed several genes that are worthy of investigation in future studies on the molecular mechanisms of GA therapy.

Differential regulation of monocyte cytokine release by αV and β(2) integrins that bind CD23

The human soluble CD23 (sCD23) protein displays highly pleiotropic cytokine-like activity. Monocytic cells express the sCD23-binding integrins αVβ(3), αVβ(5), αMβ(2) and αXβ(2), but it is unclear which of these four integrins most acutely regulates sCD23-driven cytokine release. The hypothesis that ligation of different sCD23-binding integrins promoted release of distinct subsets of cytokines was tested. Lipopolysaccharide (LPS) and sCD23 promoted release of distinct groups of cytokines from the THP-1 model cell line. The sCD23-driven cytokine release signature was characterized by elevated amounts of RANTES (CCL5) and a striking increase in interleukin-8 (IL-8; CXCL8) secretion, but little release of macrophage inflammatory protein 1β (MIP-1β; CCL4). Antibodies to αVβ(3) or αXβ(2) both promoted IL-8 release, consistent with the sCD23-driven pattern, but both also evoked strong MIP-1β secretion; simultaneous ligation of these two integrins further increased cytokine secretion but did not alter the pattern of cytokine output. In both model cell lines and primary tissue, integrin-mediated cytokine release was more pronounced in immature monocyte cells than in mature cells. The capacity of anti-integrin monoclonal antibodies to elicit a cytokine release response is epitope-dependent and also reflects the differentiation state of the cell. Although a pattern of cytokine release identical to that provoked by sCD23 could not be elicited with any individual anti-integrin monoclonal antibody, αXβ(2) and αVβ(3) appear to regulate IL-8 release, a hallmark feature of sCD23-driven cytokine secretion, more acutely than αMβ(2) or αVβ(5).

Analysis of the CD23-αv integrin interaction: a study with model peptides

The human CD23 protein binds to αvβ3 and αvβ5 integrins. The integrins recognize a short tripeptide motif of arg-lys-cys (RKC) in CD23, and peptides containing this motif inhibit the binding of CD23 to B cells and monocytes; neither fibronectin, nor vitronectin, which contain arg-gly-asp motifs, inhibit binding of RKC-containing peptides to cells. RKC-containing peptides derived from CD23 show dose-dependent, biphasic binding profiles to both αvβ3 and αvβ5 that are cation-independent but sensitive to high chloride ion concentrations. Substitution of one basic residue in the RKC motif with alanine reduces but does not abolish integrin binding or the ability of peptides to stimulate pre-B cell growth or cytokine release by monocytes. Substitution of both basic residues abolishes both integrin binding and biological activity of CD23-derived peptides. These features indicate that binding of RKC-containing peptides to αv integrins has clearly distinct characteristics to those for binding of RGD-containing ligands.

Soluble CD23 controls IgE synthesis and homeostasis in human B cells

CD23, the low-affinity receptor for IgE, exists in membrane and soluble forms. Soluble CD23 (sCD23) fragments are released from membrane (m)CD23 by the endogenous metalloprotease a disintegrin and metalloprotease 10. When purified tonsil B cells are incubated with IL-4 and anti-CD40 to induce class switching to IgE in vitro, mCD23 is upregulated, and sCD23 accumulates in the medium prior to IgE synthesis. We have uncoupled the effects of mCD23 cleavage and accumulation of sCD23 on IgE synthesis in this system. We show that small interfering RNA inhibition of CD23 synthesis or inhibition of mCD23 cleavage by an a disintegrin and metalloprotease 10 inhibitor, GI254023X, suppresses IL-4 and anti-CD40-stimulated IgE synthesis. Addition of a recombinant trimeric sCD23 enhances IgE synthesis in this system. This occurs even when endogenous mCD23 is protected from cleavage by GI254023X, indicating that IgE synthesis is positively controlled by sCD23. We show that recombinant trimeric sCD23 binds to cells coexpressing mIgE and mCD21 and caps these proteins on the B cell membrane. Upregulation of IgE by sCD23 occurs after class-switch recombination, and its effects are isotype-specific. These results suggest that mIgE and mCD21 cooperate in the sCD23-mediated positive regulation of IgE synthesis on cells committed to IgE synthesis. Feedback regulation may occur when the concentration of secreted IgE becomes great enough to allow binding to mCD23, thus preventing further release of sCD23. We interpret these results with the aid of a model for the upregulation of IgE by sCD23.

Integrin-targeted imaging of inflammation in vascular remodeling

OBJECTIVE

Inflammation plays a key role in the development of vascular diseases. Monocytes and macrophages express α(v)β(3) integrin. We used an α(v) integrin-specific tracer, (99m)Tc-NC100692, to investigate integrin-targeted imaging for detection vessel wall inflammation.

METHODS AND RESULTS

The binding of a fluorescent homologue of NC100692 to α(v)β(3) on human monocytes and macrophages was shown by flow cytometry. Vessel wall inflammation and remodeling was induced in murine carotid arteries through adventitial exposure to CaCl(2). NC100692 micro single photon computed tomography/CT imaging was performed after 2 and 4 weeks and showed significantly higher uptake of the tracer in CaCl(2)-exposed left carotids compared with sham-operated contralateral arteries. Histological analysis at 4 weeks demonstrated significant remodeling of left carotid arteries and considerable macrophage infiltration, which was confirmed by real-time polymerase chain reaction. There was no significant difference in normalized α(v), β(3), or β(5) mRNA expression between right and left carotid arteries. Finally, NC100692 uptake strongly correlated with macrophage marker expression in carotid arteries.

CONCLUSIONS

NC100692 imaging can detect vessel wall inflammation in vivo. If further validated, α(v)-targeted imaging may provide a noninvasive approach for identifying patients who are at high risk for vascular events and tracking the effect of antiinflammatory treatments.

Soluble IgE receptors--elements of the IgE network

Soluble isoforms of three human IgE Fc receptors, namely FcεRI, FcεRII, and galectin-3, can be found in serum. These soluble IgE receptors are a diverse family of proteins unified by the characteristic of interacting with IgE in the extracellular matrix. A truncated form of the alpha-chain of FcεRI, the high affinity IgE receptor, has recently been described as a soluble isoform (sFcεRI). Multiple soluble isoforms of CD23 (sCD23), the low affinity IgE receptor also known as FcεRII, are generated via different mechanisms of extracellular and intracellular proteolysis. The second low affinity IgE receptor, galectin-3, only exists as a secretory protein. We here discuss the physiological roles of these three soluble IgE receptors as elements of the human IgE network. Additionally, we review the potential and current use of sFcεRI, sCD23, and galectin-3 as biomarkers in human disease.

Activation of CD47 receptors causes proliferation of human astrocytoma but not normal astrocytes via an Akt-dependent pathway

CD47 is a membrane receptor that plays pivotal roles in many pathophysiological processes, including infection, inflammation, cell spreading, proliferation, and apoptosis. We show that activation of CD47 increases proliferation of human U87 and U373 astrocytoma cells but not normal astrocytes. CD47 function-blocking antibodies inhibit proliferation of untreated U87 and U373 cells but not normal astrocytes, suggesting that CD47 may be constitutively activated in astrocytoma. CD47 expression levels were similar in our three cell types. CD47 couples to G-proteins in astrocytes and astrocytoma and especially to the Gβγ dimer. Downstream signaling following CD47 activation involves Gβγ dimer-dependent activation of the PI3K/Akt pathway in astrocytoma cells but not in normal astrocytes. This pathway is known to be deregulated in astrocytoma, leading to cell proliferation and enhanced survival signals. Putative PLIC-1 interaction with CD47 in astrocytoma cells but not astrocytes may contribute to the proliferative effect observed upon activation of CD47. Our data indicate that CD47 receptors have a stimulatory role in cell proliferation and demonstrate for the first time that CD47 signals via the PI3K/Akt pathway in cancerous cells but not normal cells.

CD23/FcεRII: molecular multi-tasking

CD23 is the low-affinity receptor for immunoglobulin (Ig)E and plays important roles in the regulation of IgE responses. CD23 can be cleaved from cell surfaces to yield a range of soluble CD23 (sCD23) proteins that have pleiotropic cytokine-like activities. The regions of CD23 responsible for interaction with many of its known ligands, including IgE, CD21, major histocompatibility complex (MHC) class II and integrins, have been identified and help to explain the structure-function relationships within the CD23 protein. Translational studies of CD23 underline its credibility as a target for therapeutic intervention strategies and illustrate its involvement in mediating therapeutic effects of antibodies directed at other targets.

SDF-1 and PDGF enhance alphavbeta5-mediated ERK activation and adhesion-independent growth of human pre-B cell lines

CD23 acts through the alphavbeta5 integrin to promote growth of human pre-B cell lines in an adhesion-independent manner. alphavbeta5 is expressed on normal B-cell precursors in the bone marrow. Soluble CD23 (sCD23), short CD23-derived peptides containing the arg-lys-cys (RKC) motif recognized by alphavbeta5 and anti-alphavbeta5 monoclonal antibodies (MAbs) all sustain growth of pre-B cell lines. The chemokine stromal cell-derived factor-1 (SDF-1) regulates key processes during B-cell development. SDF-1 enhanced the growth-sustaining effect driven by ligation of alphavbeta5 with anti-alphavbeta5 MAb 15F-11, sCD23 or CD23-derived RKC-containing peptides. This effect was restricted to B-cell precursors and was specific to SDF-1. The enhancement in growth was associated with the activation of extracellular signal-regulated kinase (ERK) and both these responses were attenuated by the MEK inhibitor U0126. Finally, platelet-derived growth factor also enhanced both alphavbeta5-mediated cell growth and ERK activation. The data suggest that adhesion-independent growth-promoting signals delivered to B-cell precursors through the alphavbeta5 integrin can be modulated by cross-talk with receptors linked to both G-protein and tyrosine kinase-coupled signalling pathways.

Molecular blocking of CD23 supports its role in the pathogenesis of arthritis

Background

CD23 is a differentiation/activation antigen expressed by a variety of hematopoietic and epithelial cells. It can also be detected in soluble forms in biological fluids. Initially known as the low-affinity receptor for immunoglobulin E (FcεRII), CD23 displays various other physiologic ligands such as CD21, CD11b/c, CD47-vitronectin, and mannose-containing proteins. CD23 mediates numerous immune responses by enhancing IgE-specific antigen presentation, regulating IgE synthesis, influencing cell differentiation and growth of both B- and T-cells. CD23-crosslinking promotes the secretion of pro-inflammatory mediators from human monocytes/macrophages, eosinophils and epithelial cells. Increased CD23 expression is found in patients during allergic reactions and rheumatoid arthritis while its physiopathologic role in these diseases remains to be clarified.

Methodology/Principal Findings

We previously generated heptapeptidic countrestructures of human CD23. Based on in vitro studies on healthy and arthritic patients' cells, we showed that CD23-specific peptide addition to human macrophages greatly diminished the transcription of genes encoding inflammatory cytokines. This was also confirmed by significant reduction of mediator levels in cell supernatants. We also show that CD23 peptide decreased IgE-mediated activation of both human and rat CD23⁺ macrophages. In vivo studies in rat model of arthritis showed that CD23-blocking peptide ameliorates clinical scores and prevent bone destruction in a dose dependent manner. Ex-vivo analysis of rat macrophages further confirmed the inhibitory effect of peptides on their activation. Taken together our results support the role of CD23 activation and subsequent inflammatory response in arthritis.

Conclusion

CD23-blocking peptide (p30A) prevents the activation of monocytes/macrophages without cell toxicity. Thus, targeting CD23 by antagonistic peptide decreases inflammatory markers and may have clinical value in the treatment of human arthritis and allergic reactions involving CD23.

Ghost cell odontogenic carcinoma of the mandible: a case report demonstrating expression of tartrate-resistant acid phosphatase (TRAP) and vitronectin receptor

INTRODUCTION

Ghost cell odontogenic carcinoma is a rare neoplastic variant of calcifying odontogenic cyst, with aggressive growth characteristics. A painful swelling in the jaws with local paraesthesia is the most common symptom. Although it often causes irregular destruction of the adjacent bone, immunohistochemical expression of tartrate-resistant acid phosphatase (TRAP) and vitronectin receptor has not previously been described in this carcinoma.

CASE REPORT

This article describes a ghost cell odontogenic carcinoma affecting the mandible of a 55-year-old man. The patient was treated by segmental mandibulectomy and there was no evidence of recurrence or metastasis for 1.8 years. Cytological features including the immunohistochemical expression of TRAP and vitronectin receptor were studied.

CONCLUSION

Specimens revealed varying sized islands of anucleate cell clusters with homogenous, pale eosinophilic cytoplasm, so called ghost cells, admixed with sheets of tumour. TRAP and vitronectin receptor were detected in the ghost cells, but they were not expressed in the tumour cells. Our findings suggest that some of the cytokines produced by ghost cells may play important roles in causing extensive bone resorption in the ghost cell odontogenic carcinoma.

IgE in allergy and asthma today

The spreading epidemic of allergies and asthma has heightened interest in IgE, the central player in the allergic response. The activity of IgE is associated with a network of proteins; prominent among these are its two principal receptors, FcepsilonRI (high-affinity Fc receptor for IgE) and CD23, as well as galectin-3 and several co-receptors for CD23, notably CD21 and various integrins. Here, we review recent progress in uncovering the structures of these proteins and their complexes, and in our understanding of how IgE exerts its effects and how its expression is regulated. The information that has emerged suggests new therapeutic directions for combating allergic disease.

αvβ5 Integrin Sustains Growth of Human Pre-B Cells through an RGD-independent Interaction with a Basic Domain of the CD23 Protein

CD23 is a type II transmembrane glycoprotein synthesized by hematopoietic cells that has biological activity in both membrane-bound and freely soluble forms, acting via a number of receptors, including integrins. We demonstrate here that soluble CD23 (sCD23) sustains growth of human B cell precursors via an RGD-independent interaction with the alphavbeta5 integrin. The integrin recognizes a tripeptide motif in a small disulfide-bonded loop at the N terminus of the lectin head region of CD23, centered around Arg(172), Lys(173), and Cys(174) (RKC). This RKC motif is present in all forms of sCD23 with cytokine-like activity, and cytokine activity is independent of the lectin head, an "inverse RGD" motif, and the CD21 and IgE binding sites. RKC-containing peptides derived from this region of CD23 bind alphavbeta5 and are biologically active. The binding and activity of these peptides is unaffected by inclusion of a short peptide containing the classic RGD sequence recognized by integrins, and, in far-Western analyses, RKC-containing peptides bind to the beta subunit of the alphavbeta5 integrin. The interaction between alphavbeta5 and sCD23 indicates that integrins deliver to cells important signals initiated by soluble ligands without the requirement for interactions with RGD motifs in their common ligands. This mode of integrin signaling may not be restricted to alphavbeta5.

Anti-inflammatory effects of alphav integrin antagonism in acute kidney allograft rejection

Integrin-mediated cell adhesion and signaling is essential to vascular development and inflammatory processes. Elevated expression of integrin alpha(v)beta(3) has been detected in ischemia-reperfusion injury and rejecting heart allografts. We thus hypothesized that the inhibition of alpha(v)-associated integrins may have potent anti-inflammatory effects in acute kidney allograft rejection. We studied the effects of a peptidomimetic antagonist of alpha(v) integrins in two rat models of renal allotransplantation, differing in degree of major histocompatibility complex mismatch. Integrin alpha(v)beta(3) was up-regulated in rejecting renal allografts. Integrin antagonist reduced the histological signs of acute rejection, the intensity of the mononuclear cell infiltration, and cell proliferation in the grafted kidneys. This could be correlated to a reduced leukocyte-endothelial interaction and an improved peritubular microcirculation observed by intravital microscopy. In vitro under laminar flow conditions, the arrest of monocytes to interleukin-1beta-activated endothelium was decreased. Furthermore, in co-culture models the proliferation and transmigration of monocytes/macrophages, endothelium, and fibroblasts induced by renal tubular epithelia was efficiently inhibited by alpha(v) integrin antagonism. These data reveal an important role of this integrin subclass in leukocyte recruitment and development and maintenance of acute rejection; blockade of alpha(v) integrins may provide a new therapeutic strategy to attenuate acute allograft rejection.

Soluble CD23 monomers inhibit and oligomers stimulate IGE synthesis in human B cells

The low affinity IgE receptor, CD23, is implicated in IgE regulation and the pathogenesis of allergic disease. CD23 is a type II integral membrane protein, comprising a lectin "head," N-terminal "stalk," and C-terminal "tail" in the extracellular sequence. Endogenous proteases cleave CD23 in the stalk and the tail to release soluble fragments that either stimulate or inhibit IgE synthesis in human B cells. The molecular basis of these paradoxical activities is not understood. We have characterized three fragments of CD23, monomeric derCD23, monomeric exCD23, and oligomeric lzCD23. We show that the monomers inhibit and the oligomer stimulates IgE synthesis in human B cells after heavy chain switching to IgE. CD23 fragments could be targets for therapeutic intervention in allergic disease.

P2Y2 receptors induced cell surface redistribution of alpha(v) integrin is required for activation of ERK 1/2 in U937 cells

Nucleotides released from cells due to stress, injury or inflammation, induce mitogenic effects in monocytes via activation of P2Y(2) nucleotide receptors (P2Y(2)Rs). Here we show that P2Y(2) nucleotide receptors in U937 monocytic cells regulate the activation of extracellular signal-regulated kinases 1 and 2 (ERK 1/2) by inducing the clustering of alpha(v) integrins. The activation of phosphatidylinositol 3-kinase by P2Y(2)R ligands was required for alpha(v) clustering, suggesting a means whereby two different classes of receptors communicate to induce mitogenic responses in monocytic cells. P2Y(2)R-induced alpha(v) clustering was also associated with a flattened phenotype of the U937 cells, consistent with the role of the P2Y(2)R in regulating early events in cell migration.

In vivo murine CD23 destabilization enhances CD23 shedding and IgE synthesis

To investigate the effects of in vivo CD23 destabilization on CD23 shedding and IgE production, an anti-CD23 stalk monoclonal (19G5), previously shown to enhance proteolysis of CD23 in vitro, was utilized. Compared to isotype control-treated mice, BALB/cJ mice injected with 19G5 displayed significantly enhanced serum soluble CD23 and IgE. Soluble CD23 and IgE levels were also increased in 19G5-treated C57BL/6J mice (intermediate IgE responders); however, the kinetics of the responses differed between the high (BALB/cJ) and intermediate responder mice, suggesting a potential role for CD23 in regulating IgE responder status. The 19G5-induced IgE response was dependent on IL-4 and independent of CD21 as demonstrated through use of IL-4Ralpha and CD21/35-deficient mice, respectively. Overall, the data provide a direct demonstration for CD23's role in regulating IgE production in vivo and suggest that therapies aimed at stabilizing cell surface CD23 would be beneficial in controlling allergic disease.

Structural changes in the lectin domain of CD23, the low-affinity IgE receptor, upon calcium binding

CD23, the low-affinity receptor for IgE (Fc epsilonRII), regulates IgE synthesis and also mediates IgE-dependent antigen transport and processing. CD23 is a unique Fc receptor belonging to the C-type lectin-like domain superfamily and binds IgE in an unusual, non-lectin-like manner, requiring calcium but not carbohydrate. We have solved the high-resolution crystal structures of the human CD23 lectin domain in the presence and absence of Ca2+. The crystal structures differ significantly from a previously determined NMR structure and show that calcium binding occurs at the principal binding site, but not at an auxiliary site that appears to be absent in human CD23. Conformational differences between the apo and Ca2+ bound structures suggest how IgE-Fc binding can be both calcium-dependent and carbohydrate-independent.

Role of phosphatidylinositol 3-kinase-gamma in mediating lung neutrophil sequestration and vascular injury induced by E. coli sepsis

We addressed the in vivo role of phosphatidylinositol 3-kinase-gamma (PI3K-gamma) in signaling the sequestration of polymorphonuclear leukocytes (PMNs) in lungs and in the mechanism of inflammatory lung vascular injury. We studied mice with deletion of the p110 catalytic subunit of PI3K-gamma (PI3K-gamma(-/-) mice). We measured lung tissue PMN sequestration, microvascular permeability, and edema formation after bacteremia induced by intraperitoneal Escherichia coli challenge. PMN infiltration into the lung interstitium in PI3K-gamma(-/-) mice as assessed morphometrically was increased 100% over that in control mice within 1 h after bacterial challenge. PI3K-gamma(-/-) mice also developed a greater increase in lung microvascular permeability after E. coli challenge, resulting in edema formation. The augmented lung tissue PMN sequestration in PI3K-gamma(-/-) mice was associated with increased expression of the PMN adhesive proteins CD47 and beta(3)-integrins. We observed increased association of CD47 and beta(3)-integrins with the extracellular matrix protein vitronectin in lungs of PI3K-gamma(-/-) mice after E. coli challenge. PMNs from these mice also showed increased beta(3)-integrin expression and augmented beta(3)-integrin-dependent PMN adhesion to vitronectin. These results point to a key role of PMN PI3K-gamma in negatively regulating CD47 and beta(3)-integrin expression in gram-negative sepsis. PI3K-gamma activation in PMNs induced by E. coli may modulate the extent of lung tissue PMN sequestration secondary to CD47 and beta(3)-integrin expression. Therefore, the level of PI3K-gamma activation may be an important determinant of PMN-dependent lung vascular injury.

Systemic Activation of Integrin αVβ3 in Donors with Spontaneous Intracerebral Hemorrhage is Associated with Subsequent Development of Vasculopathy in the Heart Transplant Recipient

BACKGROUND

Recipients of hearts from donors with spontaneous intracerebral hemorrhage (ICH) are at increased risk of allograft vasculopathy compared with trauma donors. We have recently shown that the vitronectin receptor (integrin alpha(V)beta3) is upregulated in transplant vasculopathy. We hypothesized that donor ICH is associated with systemic activation of alpha(V)beta3 in the donor before transplantation.

METHODS

We evaluated mRNA expressions of alpha(V)beta3 (TaqMan PCR) in endomyocardial biopsy samples at 1-week post-transplant in 20 recipients from ICH donors and 20 recipients from trauma donors. To investigate whether systemic activation of alpha(V)beta3 was present in the donor before transplantation, alpha(V)beta3 expression was also evaluated in the corresponding donor spleen lymphocytes. All patients underwent serial coronary intravascular ultrasound to evaluate for coronary vasculopathy. The baseline characteristics were similar except for increased donor age in the ICH Group.

RESULTS

The ICH Group showed significant increased mRNA expression of alpha(V)beta3 in the heart biopsy samples (3.8-fold, p = 0.012) and in the corresponding donor spleen lymphocytes (3.5-fold, p = 0.014) compared with the Trauma Group. At 1 year, the ICH Group also showed increased progression of coronary vasculopathy. Multivariate regression analysis found that donor lymphocytic alpha(V)beta3 mRNA expression was independently associated with increased risk of vasculopathy (odds ratio, 1.9; 95% CI, 1.21-3.98, p = 0.03).

CONCLUSIONS

Our report demonstrates the presence of systemic activation of alpha(V)beta3 in donors with spontaneous intracerebral hemorrhage and its association with the subsequent development of allograft vasculopathy in the recipient.

Tumour angiogenesis: a novel therapeutic target in patients with malignant disease

Angiogenesis refers to the formation of new blood vessels from an existing vasculature and is recognised as a necessary requirement for most tumours to grow beyond 1-2 mm in diameter. Factors established as playing a role in angiogenesis may be divided into two principal groups: (a) those that stimulate endothelial cell proliferation and/or elongation, migration and vascular morphogenesis including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet derived endothelial cell growth factor (PD-ECGF) and the tie and tek receptors, and (b) proteases and their receptors involved in the breakdown of basement membranes and the extracellular matrix (ECM) including the matrix metalloproteinases (MMPs), cathepsins and those involved in the plasmin cascade. Angiogenesis has been identified as a potential target for development of anticancer agents. The discovery of a range of naturally-occurring factors which negatively regulate angiogenesis, including the thrombospondins, angiostatin and endostatin, and the tissue inhibitors of MMPs (TIMPs), has given added impetus to this approach. Synthetic anti-angiogenic compounds have been developed, including TNP-470, carboxyamidotriazole, VEGF-tyrosine kinase inhibitors and MMP inhibitors (MMPI) which, like the naturally-occurring anti-angiogenic factors, inhibit angiogenesis in vitro and in vivo, and tumour development, growth and metastasis in vivo. Anti-angiogenic agents also enhance the antitumour activity of many conventional cytotoxic chemotherapeutic agents. Such combinations may have a particular role as adjuvant therapies following surgical resection of primary tumours. Unlike tumour cells, tumour associated endothelial cells do not develop resistance to anti-angiogenic agents. Furthermore, anti-angiogenic agents are generally cytostatic rather than cytotoxic. As such, these agents are, in general, likely to be administered over long periods of time. Therefore, as well as having proven antitumour efficacy, an anti-angiogenic compound will need to be well-tolerated if it is to become established in the clinical management of patients with malignant disease.

Myxoma virus M128L is expressed as a cell surface CD47-like virulence factor that contributes to the downregulation of macrophage activation in vivo

The M128L myxoma virus gene expresses a five-membrane spanning cell surface protein with significant amino acid homology to the cellular CD47 proteins. CD47, also called integrin-associated protein (IAP), is associated with the modulation of leukocyte adhesion, motility, activation, and phagocytosis. Creation of an M128L-deletion mutant myxoma virus strain and subsequent infection of the European rabbit demonstrated that M128L is necessary for the production of a lethal infection in susceptible rabbits, while it is fully dispensable for virus replication in vitro. Secondary sites of infection developed on the majority of rabbits infected with the M128L-deletion mutant (vMyx128KO), demonstrating that the M128L protein is nonessential for the dissemination of virus within the host. Although the size and severity of the primary lesions on vMyx128KO-infected rabbits were comparable to rabbits infected with the wild-type virus at the early stages of disease progression, by day 7 the reduced virulence of the vMyx128KO virus was clearly evident and all of the animals recovered from infection by the M128L-knockout virus. Histological analysis of the tissues of vMyx128KO-infected rabbits revealed greater activation of monocyte/macrophage cells in infected and/or lymphoid tissues when compared to those of wild-type myxoma-infected rabbits. We conclude that the M128L protein is a novel CD47-like immunomodulatory gene of myxoma virus required for full pathogenesis of the virus in the European rabbit and that its loss from the virus results in increased activation of monocyte/macrophage cells during infection.

Immunohistochemical localization of subtilisin/kexin-like proprotein convertases in human atherosclerosis

Integrins are heterodimeric alpha/beta receptors that link the cytoskeleton with the extracellular matrix, thereby regulating several cell functions important in atherosclerosis. In vitro, the subtilisin/kexin-like proprotein convertases (PCs), namely PC5 and furin, have been shown to be responsible for the endoproteolytic activation of the alpha(v) integrin subunit. Based on their cleavage activity, these PCs are potential targets in atherosclerosis. In the present study, we investigated the localization of furin and PC5 in different stages of human atherosclerosis. Immunohistochemical analysis of furin and PC5 revealed their presence in vascular smooth-muscle cells and endothelial cells in atherosclerotic and non-atherosclerotic lesions. However, in the more advanced lesions, furin and PC5 staining was significantly expressed in macrophages/foam cells. In vitro, THP-1 derived macrophages contained furin and PC5, and maturation of monocytes to macrophages was accompanied by enhanced alpha(v)beta3 cell-surface expression. Inhibition of furin/PC5 with the specific pharmacological furin-like PC-inhibitor dec-CMK inhibited alpha(v) endoproteolytic activation but did not abolish alpha(v)beta3 cell-surface expression. This indicates that furin/PC5 is required for alpha(v) endoproteolytic activation but not for alpha(v) routing and sorting to the cell surface. In conclusion, our study demonstrates that furin and PC5 are significantly expressed in mononuclear cells in advanced human atherosclerotic lesions, where they regulate alpha(v) endoproteolytic activation.

Oncothanin, a peptide from the alpha3 chain of type IV collagen, modifies endothelial cell function and inhibits angiogenesis

Previous studies from our group and the group of the Department of Biochemistry at the University of Rheims, France [corrected] have shown that basement membrane (BM) collagen from anterior lens capsule type IV collagen (ALC-COL IV) and peptides from the noncollagenous domain (NC1) of the alpha3(IV) [corrected] chain, corresponding to residues 185-203 and 179-208, inhibit tumor cell proliferation, specifically through the interaction of the -SNS- tripeptide (residues 189-191) with the CD47/alphavbeta3 integrin receptor complex. Data presented here demonstrate that the alpha3(IV)185-203 and the alpha3(IV)179-208 peptides, from here forward [corrected] designated as oncothanin, regulate endothelial cell (EC) proliferation, adhesion, and motility which [corrected] ultimately influence angiogenesis. The data also indicate that oncothanin, when used as a chemoattractant, greatly enhanced EC chemotaxis. In contrast, pretreatment of EC with oncothanin inhibited chemotaxis toward several different chemoattractants. When oncothanin was used as a substrate, it enhanced EC adhesion that was inhibited when pretreated with same. Analysis of angiogenesis by EC differentiation (tube formation), aortic ring microvessel formation [corrected] and the chorioallantoic membrane assay, [corrected] demonstrate that oncothanin, but not the control medium or peptides, inhibits angiogenesis. In the EC differentiation assay, oncothanin completely inhibited tube formation at 25 microg/ml, whereas peptides with comparable sequences, that lacked [corrected] the -SNS- sequence, from ALC-COL IV NC1 domains alpha1 and alpha2 chains failed to inhibit tube formation. The data support the hypothesis that ALC-COL IV and oncothanin inhibit angiogenesis by modulation of EC function.

Temperature effect on IgE binding to CD23 versus Fc epsilon RI

A chimeric soluble CD23, consisting of the extracellular domain of mouse CD23 and a modified leucine zipper (lz-CD23), has been shown to inhibit IgE binding to the FcepsilonRI. A similar human CD23 construct was also shown to inhibit binding of human IgE to human FcepsilonRI. In both systems, the inhibition was found to be temperature dependent; a 10-fold molar excess of lz-CD23 gave 90-98% inhibition at 4 degrees C, dropping to 20-30% inhibition at 37 degrees C. Surface plasmon resonance analysis of lz-CD23 binding to an IgE-coated sensor chip suggested that the effective concentration of lz-CD23 was lower at the higher temperatures. Analysis of (125)I-IgE binding to CD23(+)-Chinese hamster ovary cells also indicated that increased temperature resulted in a lower percentage of IgE capable of interacting with CD23. In contrast, IgE interacts more effectively with FcepsilonRI(+)-rat basophilic leukemia cells at 37 degrees C compared with 4 degrees C. The results support the concept that the open and closed IgE structures found by crystallography interact differently with the two IgE receptors and suggest that temperature influences the relative percentage of IgE in the respective structural forms. Changes in CD23 oligomerization also plays a role in the decreased binding seen at physiological temperatures.

Integrin alpha V beta 3 as a target for treatment of rheumatoid arthritis and related rheumatic diseases

A substantial and persuasive body of data now exists that supports the view that integrin alpha V beta 3 plays a critical part in activated macrophage dependent inflammation, osteoclast development, migration, and bone resorption, and inflammatory angiogenesis. All of these processes play an important part in the pathogenesis of rheumatoid arthritis (RA) and related arthropathies. Animal arthritis model data further support these concepts and also suggest that therapeutic antagonism of integrin alpha V beta 3 is worthy of further investigation in RA and related arthropathies. To this end, Vitaxin, also known as MEDI-522, has been developed. Vitaxin is a humanised monoclonal IgG1 antibody that specifically binds a conformational epitope formed by both the integrin alpha V and beta 3 subunits. It blocks the interaction of alpha V beta 3 with various ligands such as osteopontin and vitronectin. Clinical trials with Vitaxin in patients with RA are in progress.

Acute vascular rejection is associated with up-regulation of vitronectin receptor (alphavbeta3), increased expression of tissue factor, and activation of the extracellular matrix metalloproteinase induction system

BACKGROUND

A cascade of inflammatory reactions characterize acute vascular rejection after heart transplantation. This study was undertaken to test the hypothesis that acute vascular rejection is associated with up-regulation of vitronectin receptor (alphavbeta3), increased expression of tissue factor, and activation of the extracellular matrix metalloproteinase induction system.

METHODS

Acute vascular rejection developed in 14 heart transplant recipients within 2 weeks of transplantation, confirmed by immunofluorescence (AVR group). We compared these patients with 10 transplant recipients who had no evidence of acute vascular rejection or peritransplant ischemic injury (control group). We evaluated endomyocardial biopsy specimens for alphavbeta3, tissue factor, and extracellular matrix metalloproteinase inducer (EMMPRIN).

RESULTS

Compared with the control group, the AVR group demonstrated evidence of significantly increased expression of alphavbeta3 (1.9-fold, p < 0.001), tissue factor (1.8-fold, p < 0.001), and EMMPRIN (1.5-fold, p < 0.001). All patients in the AVR group received plasmapheresis; 11 of 14 patients had evidence of ischemic necrosis on biopsy specimens, and 3 of 14 patients experienced hemodynamic compromise and graft dysfunction and died within 3 weeks of transplant. Another patient died at 10 months after transplant.

CONCLUSIONS

Acute vascular rejection is associated with up-regulation of alphavbeta3, tissue factor, and activation of the matrix metalloproteinase induction system, which may contribute to the lethal morbidity associated with this disease.

Myocardial ischemic injury after heart transplantation is associated with upregulation of vitronectin receptor (alpha(v)beta3), activation of the matrix metalloproteinase induction system, and subsequent development of coronary vasculopathy

BACKGROUND

Myocardial ischemic injury after heart transplantation is associated with subsequent development of graft vasculopathy. Both vitronectin receptor (integrin alpha(v)beta3) and tissue factor play key roles in vascular endothelial cell injury. Matrix metalloproteinases (MMPs) are activated in ischemic injury models.

METHODS AND RESULTS

Thirteen patients developed myocardial ischemic injury within 2 weeks of cardiac transplantation (ischemia group). These were compared with 10 transplantation patients who had no evidence of ischemia (control group). Endomyocardial biopsies were evaluated within 2 weeks of transplantation for alpha(v)beta3, tissue factor, and extracellular MMP inducer (EMMPRIN). At 1 year, MMPs were evaluated, and interstitial myocardial fibrosis was quantified. All patients underwent intravascular ultrasound at 1 month and 1 year after transplantation. Compared with control, the ischemia group demonstrated evidence of significant increased expression of alpha(v)beta3 (3.2-fold, P<0.001), tissue factor (2.5-fold, P<0.001), and EMMPRIN (1.9-fold, P=0.01). At 1 year, the ischemia group had a significant increase in myocardial fibrosis (24+/-1.8% versus 14+/-1.1%, P<0.001) and zymographic activity of MMP-2 (1.4-fold, P<0.001), MMP-3 (1.2-fold, P<0.001), and MMP-9 (1.3-fold, P=0.01). Coronary vasculopathy progression was also more advanced in the ischemia group (change in coronary maximal intimal thickness over 1 year 0.54+/-0.1 versus 0.26+/-0.06 mm; P=0.031).

CONCLUSIONS

Myocardial ischemic injury after cardiac transplantation is associated with upregulation of alpha(v)beta3, tissue factor, and activation of the MMP induction system, which may contribute to the subsequent development of allograft remodeling and vasculopathy.

Signal transduction by cell adhesion receptors and the cytoskeleton: functions of integrins, cadherins, selectins, and immunoglobulin-superfamily members

Cellular interactions with the extracellular matrix and with neighboring cells profoundly influence a variety of signaling events including those involved in mitogenesis, survival, and differentiation. Recent advances have provided insights into mechanisms underlying the ability of integrins, cadherins, selectins, and other cell adhesion molecules to regulate signal transduction cascades. These mechanisms often involve the ability of cell adhesion molecules to initiate the formation of organized structures or scaffolds that permit the efficient flow of information in signaling pathways.

The role of vitronectin receptor (alphavbeta3) and tissue factor in the pathogenesis of transplant coronary vasculopathy

OBJECTIVES

This study was undertaken to test the hypothesis that transplant coronary vasculopathy (CV) is associated with increased myocardial protein expression of both tissue factor (TF) and integrin alphavbeta3.

BACKGROUND

The vitronectin receptor (integrin alphavbeta3) and TF have recently been found to play a key role in apoptotic cell death and vascular endothelial cell injury.

METHODS

A total of 77 heart transplant recipients underwent simultaneous endomyocardial biopsy and intravascular ultrasound (IVUS) at one year of transplant. Patients with pre-existing donor coronary atherosclerosis (n = 35) or with acute rejection (grade >1A, n = 10) at the time of the IVUS were excluded from the analysis. The remaining 32 patients constitute the cohort of the present study. A computerized biopsy score was derived based on the duration and severity of cellular rejection. Both TF and alphavbeta3 expression in the heart biopsy specimens were evaluated by immunoperoxidase histochemistry and Western blot analysis.

RESULTS

Patients with CV (n = 24) had increased expression of alphavbeta3 (2.7-fold, p = 0.003) and TF (7.9-fold, p = 0.04) compared with patients without evidence of vasculopathy (n = 8). In the absence of myocardial fibrosis, alphavbeta3 expression correlated significantly with the cellular rejection score (r = 0.58, p = 0.02).

CONCLUSIONS

Transplant vasculopathy is associated with increased expression of both TF and alphavbeta3. The significant correlation of alphavbeta3 with cellular rejection suggests an important role for this integrin in serving as a mechanistic link between cellular rejection and vasculopathy.

Acute cellular rejection following human heart transplantation is associated with increased expression of vitronectin receptor (integrin alphavbeta3)

The vitronectin receptor (integrin alphavbeta3), a cell-surface adhesion receptor, has been shown to play a significant role in endothelial cell migration, apoptosis, atherosclerosis, and T-lymphocyte activation. This study was undertaken to test the hypothesis that cardiac allograft rejection is associated with increased expression of alphavbeta3. We also determined whether fibronectin receptor (alpha5beta1) and tissue factor are up-regulated in the presence of acute cellular rejection. We evaluated endomyocardial biopsy specimens with histologic evidence of different degrees of acute cellular rejection (grade 0, n = 10; grade 1A, n = 10; grade 2, n = 10; grade 3A, n = 10). Biopsies were obtained 2-4weeks after cardiac transplantation. Immunoperoxidase staining was performed for alphavbeta3, tissue factor, and alpha5beta1, and protein levels were further determined by Western blot analysis. Specimens with grade 2 and grade 3A rejection showed positive staining of alphavbeta3 in lymphocytic aggregates and vascular endothelial cells. By immunoblotting, we identified significantly increased expression of alphavbeta3 in the presence of acute rejection, grade 2 (3-fold, p = 0.01) and grade 3A (3.6-fold, p = 0.005) compared to grade 0 and 1 A specimens. There was no evidence of increased expression of alpha5beta1 or tissue factor. Acute cellular rejection, a process characterized by T-lymphocyte activation and release of inflammatory cytokines, is associated with increased expression of alphavbeta3.

The role of human T-lymphocyte-monocyte contact in inflammation and tissue destruction

Contact-mediated signaling of monocytes by human stimulated T lymphocytes (TL) is a potent proinflammatory mechanism that triggers massive upregulation of the proinflammatory cytokines IL-1 and tumor necrosis factor-alpha. These two cytokines play an important part in chronic destructive diseases, including rheumatoid arthritis. To date this cell-cell contact appears to be a major endogenous mechanism to display such an activity in monocyte-macrophages. Since TL and monocyte-macrophages play a pivotal part in the pathogenesis of chronic inflammatory diseases, we investigated the possible ligands and counter-ligands involved in this cell-cell interaction. We also characterized an inhibitory molecule interfering in this process, apolipoprotein A-I. This review aims to summarize the state of the art and importance of contact-mediated monocyte activation by stimulated TL in cytokine production in rheumatoid arthritis and mechanisms that might control it.