Synthesis of Sialyl LewisX Mimetics with E- and P-Selectin Binding Properties and Immunosuppressive Activity.

E- and P-selectins are adhesion proteins implicated in immune cell recruitment at sites of infection, making them important drug targets for diseases involving excessive and uncontrolled inflammation. In this study, we developed an efficient strategy to synthesize bicyclic galactopyranosides through a key stereoselective equatorial C4-propiolate addition and TMSCN axial C-glycosidation. The nitrile group can then be converted to the carboxyl and different bioisosteres at a late stage in the synthesis, allowing for various derivatizations to potentially enhance biological activity. The sialyl LewisX glycomimetic featuring this rigidified bicyclic galactopyranoside moiety prevents neutrophil adhesion to endothelial cells in vitro by binding to both E- and P-selectins. We show here that the axial carboxyl analogue blocks immune cell recruitment in vivo, demonstrating its potential as an immunomodulator.

A Combined Activity of Thrombin and P-Selectin Is Essential for Platelet Activation by Pancreatic Cancer Cells.

Pancreatic cancer patients have an elevated risk of suffering from venous thrombosis. Among several risk factors that contribute to hypercoagulability of this malignancy, platelets possess a key role in the initiation of clot formation. Although single mechanisms of platelet activation are well-known in principle, combinations thereof and their potential synergy to mediate platelet activation is, in the case of pancreatic cancer, far from being clear. Applying an inhibitor screening approach using light transmission aggregometry, dense granule release, and thrombin formation assays, we provide evidence that a combination of tissue factor-induced thrombin formation by cancer cells and their platelet P-selectin binding is responsible for AsPC-1 and Capan-2 pancreatic cancer cell-mediated platelet activation. While the blockade of one of these pathways leads to a pronounced inhibition of platelet aggregation and dense granule release, the simultaneous blockade of both pathways is inevitable to prevent platelet aggregation completely and minimize ATP release. In contrast, MIA PaCa-2 pancreatic cancer cells express reduced levels of tissue factor and P-selectin ligands and thus turn out to be poor platelet activators. Consequently, a simultaneous blockade of thrombin and P-selectin binding seems to be a powerful approach, as mediated by heparin to crucially reduce the hypercoagulable state of pancreatic cancer patients.

Microwave Responsive Nanoplatform via P-Selectin Mediated Drug Delivery for Treatment of Hepatocellular Carcinoma with Distant Metastasis.

Hepatocellular carcinoma (HCC) with metastatic disease is associated with a low survival in clinical practice. Many curative options including liver resection, transplantation, and thermal ablation are effective in local but limited for patients with distant metastasis. In this study, the efficacy, specificity, and safety of P-selectin targeted delivery and microwave (MW) responsive drug release is investigated for development of HCC therapy. By encapsulating doxorubicin (DOX) and MW sensitizer (1-butyl-3-methylimidazolium-l-lactate, BML) into fucoidan conjugated liposomal nanoparticles (TBP@DOX), specific accumulation and prominent release of DOX in orthotopic HCC and lung metastasis are achieved with adjuvant MW exposure. This results in orthotopic HCC growth inhibition that is not only 1.95-fold higher than found for nontargeted BP@DOX and 1.6-fold higher than nonstimuli responsive TP@DOX but is also equivalent to treatment with free DOX at a 10-fold higher dose. Furthermore, the optimum anticancer efficacy against distant lung metastasis and effective prevention of widespread dissemination with a prolonged survival is described. In addition, no adverse metabolic events are identified using the TBP@DOX nanodelivery system despite these events being commonly observed with traditional DOX chemotherapy. Therefore, administering TBP@DOX with MW exposure could potentially enhance the therapeutic efficacy of thermal-chemotherapy of HCC, especially those in the advanced stages.

Circulating soluble P-selectin must dimerize to promote inflammation and coagulation in mice.

Leukocyte adhesion to P-selectin on activated platelets and endothelial cells induces shedding of the P-selectin ectodomain into the circulation. Plasma soluble P-selectin (sP-selectin) is elevated threefold to fourfold in patients with cardiovascular disease. Circulating sP-selectin is thought to trigger signaling in leukocytes that directly contributes to inflammation and thrombosis. However, sP-selectin likely circulates as a monomer, and in vitro studies suggest that sP-selectin must dimerize to induce signaling in leukocytes. To address this discrepancy, we expressed the entire ectodomain of mouse P-selectin as a monomer (sP-selectin) or as a disulfide-linked dimer fused to the Fc portion of mouse immunoglobulin G (sP-selectin-Fc). Dimeric sP-selectin-Fc, but not monomeric sP-selectin, triggered integrin-dependent adhesion of mouse leukocytes in vitro. Antibody-induced oligomerization of sP-selectin or sP-selectin-Fc was required to trigger formation of neutrophil extracellular traps. Injecting sP-selectin-Fc, but not sP-selectin, into mice augmented integrin-dependent adhesion of neutrophils in venules, generated tissue factor-bearing microparticles, shortened plasma-clotting times, and increased thrombus frequency in the inferior vena cava. Furthermore, transgenic mice that overexpressed monomeric sP-selectin did not exhibit increased inflammation or thrombosis. We conclude that elevated plasma sP-selectin is a consequence rather than a cause of cardiovascular disease.

Association of SELP Polymorphisms with Soluble P-Selectin Levels and Vascular Risk in Patients with Type 2 Diabetes Mellitus: A Case-Control Study.

P-selectin, an adhesion molecule, is encoded by SELP and known as biomarker of endothelial as well as platelet dysfunction. SELP polymorphisms (rs6136, rs6127, and rs6125) and raised levels of soluble P-selectin (sP-selectin) have been associated with several disease conditions. The present study was aimed to determine the association of SELP variants and sP-selectin levels as well as vascular risk in Type 2 diabetes mellitus (T2DM) patients. The frequency of rs6136, rs6127, and rs6125 was assessed by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR). sP-selectin levels were measured using commercially available kits. Haplotypes were constructed using PHASE software. The data obtained from the above-said analyses was subjected to suitable statistical analyses. sP-selectin levels (ng/ml) were significantly higher in patients as compared to controls (p < 0.001). Out of total, 22% of patients were found to have very high vascular risk, 43.2% with high vascular risk, while 34.4% with moderate vascular risk. For both rs6136 and rs6127, frequency of variant allele was found to be significantly higher in patients as compared to controls and accounted for 2.4- and 1.5-fold risk of disease development, respectively. CAG was found to be associated with 4.5-fold risk towards disease development. In contrast, AGG was conferring the protective effect. Significantly high sP-levels were observed in patients with homozygous wild genotype of rs6136, all genotypes of rs6127, and heterozygous genotype of rs6125 as compared to respective controls. Significant difference was observed in P-selectin levels within moderate-risk category for rs6136. When compared between the categories, significant difference was observed for rs6136 and rs6127. Furthermore, patients with haplotypes AAA, AGA, and AGG were found to have significantly high sP-selectin levels as compared to controls. Significant difference in sP-selectin levels was observed within very high-risk as well as high-risk category. When compared between the categories, significant difference was observed for AGA and AGG haplotypes. The studied polymorphisms of SELP have shown significant association with sP-selectin levels as well as vascular risk in T2DM patients.

Platelets activated by the anti-ß2GPI/ß2GPI complex release microRNAs to inhibit migration and tube formation of human umbilical vein endothelial cells.

BACKGROUND: Patients with anti-ß2GPI antibodies display significantly higher platelet activation/aggregation and vascular endothelial cell damage. The mechanism underlying the correlation between platelet activation, vascular endothelial cell dysfunctions and anti-ß2GPI antibodies remains unknown. METHODS: In this study, we derived miR-96 and -26a from platelets activated by the anti-ß2GPI/ß2GPI complex and explored their role in modulating human umbilical vein endothelial cell (HUVEC) migration and tube formation. RESULTS: Anti-ß2GPI/ß2GPI complex induces the release of platelet-derived microparticles (p-MPs). The amounts of miR-96 and -26a in these p-MPs were also higher than for the control group. Co-incubation of HUVECs with p-MPs resulted in the transfer of miR-96 and -26a into HUVECs, where they inhibited migration and tube formation. The targeting role of these miRNAs was further validated by directly downregulating targeted selectin-P (SELP) and platelet-derived growth factor receptor alpha (PDGFRA) via luciferase activity assay. CONCLUSION: Our study suggests that miR-96 and -26a in p-MPs can inhibit HUVEC behavior by targeting SELP and PDGFRA.

Replacing the Promoter of the Murine Gene Encoding P-selectin with the Human Promoter Confers Human-like Basal and Inducible Expression in Mice.

In humans and mice, megakaryocytes/platelets and endothelial cells constitutively synthesize P-selectin and mobilize it to the plasma membrane to mediate leukocyte rolling during inflammation. TNF-α, interleukin 1ß, and LPS markedly increase P-selectin mRNA in mice but decrease P-selectin mRNA in humans. Transgenic mice bearing the entire human SELP gene recapitulate basal and inducible expression of human P-selectin and reveal human-specific differences in P-selectin function. Differences in the human SELP and murine Selp promoters account for divergent expression in vitro, but their significance in vivo is not known. Here we generated knockin mice that replace the 1.4-kb proximal Selp promoter with the corresponding SELP sequence (Selp(KI)). Selp(KI) (/) (KI) mice constitutively expressed more P-selectin on platelets and more P-selectin mRNA in tissues but only slightly increased P-selectin mRNA after injection of TNF-α or LPS. Consistent with higher basal expression, leukocytes rolled more slowly on P-selectin in trauma-stimulated venules of Selp(KI) (/) (KI) mice. However, TNF-α did not further reduce P-selectin-dependent rolling velocities. Blunted up-regulation of P-selectin mRNA during contact hypersensitivity reduced P-selectin-dependent inflammation in Selp(KI) (/-) mice. Higher basal P-selectin in Selp(KI) (/) (KI) mice compensated for this defect. Therefore, divergent sequences in a short promoter mediate most of the functionally significant differences in expression of human and murine P-selectin in vivo.

Heparin-independent, PF4-dependent binding of HIT antibodies to platelets: implications for HIT pathogenesis.

Antibodies specific for platelet factor 4 (PF4)/heparin complexes are the hallmark of heparin-induced thrombocytopenia and thrombosis (HIT), but many antibody-positive patients have normal platelet counts. The basis for this is not fully understood, but it is believed that antibodies testing positive in the serotonin release assay (SRA) are the most likely to cause disease. We addressed this issue by characterizing PF4-dependent binding of HIT antibodies to intact platelets and found that most antibodies testing positive in the SRA, but none of those testing negative, bind to and activate platelets when PF4 is present without any requirement for heparin (P < .0001). Binding of SRA-positive antibodies to platelets was inhibited by chondroitinase ABC digestion (P < .05) and by the addition of chondroitin-4-sulfate (CS) or heparin in excess quantities. The findings suggest that although all HIT antibodies recognize PF4 in a complex with heparin, only a subset of these antibodies recognize more subtle epitopes induced in PF4 when it binds to CS, the major platelet glycosaminoglycan. Antibodies having this property could explain "delayed HIT" seen in some individuals after discontinuation of heparin and the high risk for thrombosis that persists for weeks in patients recovered from HIT.

Using affinity capillary electrophoresis and computational models for binding studies of heparinoids with p-selectin and other proteins.

A fast and precise affinity capillary electrophoresis (ACE) method has been developed and applied for the investigation of the binding interactions between P-selectin and heparinoids as potential P-selectin inhibitors in the presence and absence of calcium ions. Furthermore, model proteins and vitronectin were used to appraise the binding behavior of P-selectin. The normalized mobility ratios (∆R/Rf ), which provided information about the binding strength and the overall charge of the protein-ligand complex, were used to evaluate the binding affinities. It was found that P-selectin interacts more strongly with heparinoids in the presence of calcium ions. P-selectin was affected by heparinoids at the concentration of 3 mg/L. In addition, the results of the ACE experiments showed that among other investigated proteins, albumins and vitronectin exhibited strong interactions with heparinoids. Especially with P-selectin and vitronectin, the interaction may additionally induce conformational changes. Subsequently, computational models were applied to interpret the ACE experiments. Docking experiments explained that the binding of heparinoids on P-selectin is promoted by calcium ions. These docking models proved to be particularly well suited to investigate the interaction of charged compounds, and are therefore complementary to ACE experiments.

P-Selectin Targeted Dexamethasone-Loaded Lipid Nanoemulsions: A Novel Therapy to Reduce Vascular Inflammation.

Inflammation is a common process associated with numerous vascular pathologies. We hypothesized that targeting the inflamed endothelium by coupling a peptide with high affinity for P-selectin to the surface of dexamethasone-loaded lipid nanoemulsions will highly increase their specific binding to activated endothelial cells (EC) and reduce the cell activation. We developed and characterized dexamethasone-loaded lipid nanoemulsions directed towards P-selectin (PLN-Dex) and monitored their anti-inflammatory effects in vitro using cultured EC (EA.hy926 cells) and in vivo using a mouse model of acute inflammation [lipopolysaccharides (LPS) intravenously administered in C57BL/6 mice]. We found that PLN-Dex bound specifically to the surface of activated EC are efficiently internalized by EC and reduced the expression of proinflammatory genes, thus preventing the monocyte adhesion and transmigration to/through activated EC. Given intravenously in mice with acute inflammation, PLN-Dex accumulated at a significant high level in the lungs (compared to nontargeted nanoemulsions) and significantly reduced mRNA expression level of key proinflammatory cytokines such as IL-1ß, IL-6, and MCP-1. In conclusion, the newly developed nanoformulation, PLN-Dex, is functional in vitro and in vivo, reducing selectively the endothelium activation and the consequent monocyte infiltration and diminishing significantly the lungs' inflammation, in a mouse model of acute inflammation.

Structural determinants for binding of sorting nexin 17 (SNX17) to the cytoplasmic adaptor protein Krev interaction trapped 1 (KRIT1).

Sorting nexin 17 (SNX17) is a member of the family of cytoplasmic sorting nexin adaptor proteins that regulate endosomal trafficking of cell surface proteins. SNX17 localizes to early endosomes where it directly binds NPX(Y/F) motifs in the cytoplasmic tails of its target receptors to mediate their rates of endocytic internalization, recycling, and/or degradation. SNX17 has also been implicated in mediating cell signaling and can interact with cytoplasmic proteins. KRIT1 (Krev interaction trapped 1), a cytoplasmic adaptor protein associated with cerebral cavernous malformations, has previously been shown to interact with SNX17. Here, we demonstrate that SNX17 indeed binds directly to KRIT1 and map the binding to the second Asn-Pro-Xaa-Tyr/Phe (NPX(Y/F)) motif in KRIT1. We further characterize the interaction as being mediated by the FERM domain of SNX17. We present the co-crystal structure of SNX17-FERM with the KRIT1-NPXF2 peptide to 3.0 Å resolution and demonstrate that the interaction is highly similar in structure and binding affinity to that between SNX17 and P-selectin. We verify the molecular details of the interaction by site-directed mutagenesis and pulldown assay and thereby confirm that the major binding site for SNX17 is confined to the NPXF2 motif in KRIT1. Taken together, our results verify a direct interaction between SNX17 and KRIT1 and classify KRIT1 as a SNX17 binding partner.

Fucosylated chondroitin sulfates from the body wall of the sea cucumber Holothuria forskali: conformation, selectin binding, and biological activity.

Fucosylated chondroitin sulfate (fCS) extracted from the sea cucumber Holothuria forskali is composed of the following repeating trisaccharide unit: → 3)GalNAcß4,6S(1 → 4) [FucαX(1 → 3)]GlcAß(1 →, where X stands for different sulfation patterns of fucose (X = 3,4S (46%), 2,4S (39%), and 4S (15%)). As revealed by NMR and molecular dynamics simulations, the fCS repeating unit adopts a conformation similar to that of the Le(x) blood group determinant, bringing several sulfate groups into close proximity and creating large negative patches distributed along the helical skeleton of the CS backbone. This may explain the high affinity of fCS oligosaccharides for L- and P-selectins as determined by microarray binding of fCS oligosaccharides prepared by Cu(2+)-catalyzed Fenton-type and photochemical depolymerization. No binding to E-selectin was observed. fCS poly- and oligosaccharides display low cytotoxicity in vitro, inhibit human neutrophil elastase activity, and inhibit the migration of neutrophils through an endothelial cell layer in vitro. Although the polysaccharide showed some anti-coagulant activity, small oligosaccharide fCS fragments had much reduced anticoagulant properties, with activity mainly via heparin cofactor II. The fCS polysaccharides showed prekallikrein activation comparable with dextran sulfate, whereas the fCS oligosaccharides caused almost no effect. The H. forskali fCS oligosaccharides were also tested in a mouse peritoneal inflammation model, where they caused a reduction in neutrophil infiltration. Overall, the data presented support the action of fCS as an inhibitor of selectin interactions, which play vital roles in inflammation and metastasis progression. Future studies of fCS-selectin interaction using fCS fragments or their mimetics may open new avenues for therapeutic intervention.

Holothurian glycosaminoglycan inhibits metastasis via inhibition of P-selectin in B16F10 melanoma cells.

P-selectin-mediated tumor cell adhesion to platelets is a well-established stage in the process of tumor metastasis. Through computerized structural analysis, we found a marine-derived polysaccharide, holothurian glycosaminoglycan (hGAG), behaved as a ligand-competitive inhibitor of P-selectin, indicating its potential to disrupt the binding of P-selectin to cell surface receptor and activation of downstream regulators of tumor cell migration. Our experimental data demonstrated that hGAG significantly inhibited P-selectin-mediated adhesion of tumor cells to platelets and tumor cell migration in vitro and reduced subsequent pulmonary metastasis in vivo. Furthermore, abrogation of the P-selectin-mediated adhesion of tumor cells led to down-regulation of protein levels of integrins, FAK and MMP-2/9 in B16F10 cells, which is a crucial molecular mechanism of hGAG to inhibit tumor metastasis. In conclusion, hGAG has emerged as a novel anti-cancer agent via blocking P-selectin-mediated malignant events of tumor metastasis.

Protective effects of escin against indomethacin-induced gastric ulcer in mice.

Escin, a natural mixture of triterpenoid saponin isolated from the seed of the horse chestnut, is reported to have a potent antiulcer activity against ethanol-induced gastric mucosal lesions. This study investigated the possible mechanisms underlying the gastroprotective effect of escin against indomethacin-induced gastric ulcer in mice. Gastric ulceration was induced by a single intragastric administration of indomethacin (18 mg/kg). The mice underwent intragastric treatment with escin at doses of 0.45, 0.9 or 1.8 mg/kg. Gastric lesion was estimated morphometrically and histopathologically 6 h after the indomethacin administration. The antioxidative parameters in gastric mucosa were measured. Moreover, the activity of myeloperoxidase and the contents of TNF-α, P-selectin and VCAM-1 in gastric tissues were determined. The results showed that escin protected gastric tissues against indomethacin-induced gastropathy as demonstrated from a reduction in the ulcer index and an attenuation of histopathologic changes. Escin caused significant reductions of the contents of malondialdehyde, TNF-α, P-selectin, VCAM-1 and myeloperoxidase activity. The altered activities of superoxide dismutase, catalase and glutathione peroxidase in the stomach tissues were also ameliorated by escin treatment. The present study demonstrated that escin had a protective effect against indomethacin-induced gastric ulcer in mice, not only by virtue of its antioxidant potential, but also due to its anti-inflammatory effect.

Effect of extracellular pH on selectin adhesion: theory and experiment.

Selectins mediate circulatory leukocyte trafficking to sites of inflammation and trauma, and the extracellular microenvironments at these sites often become acidic. In this study, we investigated the influence of slightly acidic pH on the binding dynamics of selectins (P-, L-, and E-selectin) to P-selectin glycoprotein ligand-1 (PSGL-1) via computational modeling (molecular dynamics) and experimental rolling assays under shear in vitro. The P-selectin/PSGL-1 binding is strengthened at acidic pH, as evidenced by the formation of a new hydrogen bond (seen computationally) and the observed decrease in the rolling velocities of model cells. In the case of L-selectin/PSGL-1 binding dynamics, the binding strength and frequency increase at acidic pH, as indicated by the greater cell-rolling flux of neutrophils and slower rolling velocities of L-selectin-coated microspheres, respectively. The cell flux is most likely due to an increased population of L-selectin in the high-affinity conformation as pH decreases, whereas the velocities are due to increased L-selectin/PSGL-1 contacts. In contrast to P- and L-selectin, the E-selectin/PSGL-1 binding does not exhibit significant changes at acidic pH levels, as shown both experimentally and computationally.

The C-type lectin domain of CD62P (P-selectin) functions as an integrin ligand.

Recognition of integrins by CD62P has not been reported and this motivated a docking simulation using integrin αvß3 as a target. We predicted that the C-type lectin domain of CD62P functions as a potential integrin ligand and observed that it specifically bound to soluble ß3 and ß1 integrins. Known inhibitors of the interaction between CD62P-PSGL-1 did not suppress the binding, whereas the disintegrin domain of ADAM-15, a known integrin ligand, suppressed recognition by the lectin domain. Furthermore, an R16E/K17E mutation in the predicted integrin-binding interface located outside of the glycan-binding site within the lectin domain, strongly inhibited CD62P binding to integrins. In contrast, the E88D mutation that strongly disrupts glycan binding only slightly affected CD62P-integrin recognition, indicating that the glycan and integrin-binding sites are distinct. Notably, the lectin domain allosterically activated integrins by binding to the allosteric site 2. We conclude that CD62P-integrin binding may function to promote a diverse set of cell-cell adhesive interactions given that ß3 and ß1 integrins are more widely expressed than PSGL-1 that is limited to leukocytes.

Molecular dynamics simulation of shear- and stretch-induced dissociation of P-selectin/PSGL-1 complex.

By mediating the tethering and rolling of leukocytes on vascular surfaces, the interactions between P-selectin and the P-selectin glycoprotein ligand 1 (PSGL-1) play crucial roles during inflammation cascade. Tensile stretch produced by rolling leukocytes and shear stress exerted by blood flow constitute the two types of mechanical forces that act on the P-selectin/PSGL-1 bond. These forces modulate not only dissociation kinetics of this bond, but also the leukocyte adhesion dynamics. However, the respective contribution of the two forces to bond dissociation and to the corresponding microstructural bases remains unclear. To mimic the mechanical microenvironment, we developed two molecular dynamics approaches; namely, an approach involving the shear flow field with a controlled velocity gradient, and the track dragging approach with a defined trajectory. With each approach or with both combined, we investigate the microstructural evolution and dissociation kinetics of the P-LE/SGP-3 construct, which is the smallest functional unit of the P-selectin/PSGL-1 complex. The results demonstrate that both shear flow and tensile stretch play important roles in the collapse of the construct and that, before bond dissociation, the former causes more destruction of domains within the construct than the latter. Dissociation of the P-LE/SGP-3 construct features intramolecular destruction of the epidermal-growth-factor (EGF) domain and the breaking of hydrogen-bond clusters at the P-selectin-lectin/EGF interface. Thus, to better understand how mechanics impacts the dissociation kinetics of the P-selectin/PSGL-1 complex, we propose herein two approaches to mimic its physiological mechanical environment.

Proteomic screen identifies IGFBP7 as a novel component of endothelial cell-specific Weibel-Palade bodies.

Vascular endothelial cells contain unique storage organelles, designated Weibel-Palade bodies (WPBs), that deliver inflammatory and hemostatic mediators to the vascular lumen in response to agonists like thrombin and vasopressin. The main component of WPBs is von Willebrand factor (VWF), a multimeric glycoprotein crucial for platelet plug formation. In addition to VWF, several other components are known to be stored in WPBs, like osteoprotegerin, monocyte chemoattractant protein-1 and angiopoetin-2 (Ang-2). Here, we used an unbiased proteomics approach to identify additional residents of WPBs. Mass spectrometry analysis of purified WPBs revealed the presence of several known components such as VWF, Ang-2, and P-selectin. Thirty-five novel candidate WPB residents were identified that included insulin-like growth factor binding protein-7 (IGFBP7), which has been proposed to regulate angiogenesis. Immunocytochemistry revealed that IGFBP7 is a bona fide WPB component. Cotransfection studies showed that IGFBP7 trafficked to pseudo-WPB in HEK293 cells. Using a series of deletion variants of VWF, we showed that targeting of IGFBP7 to pseudo-WPBs was dependent on the carboxy-terminal D4-C1-C2-C3-CK domains of VWF. IGFBP7 remained attached to ultralarge VWF strings released upon exocytosis of WPBs under flow. The presence of IGFBP7 in WPBs highlights the role of this subcellular compartment in regulation of angiogenesis.

Self-assembled protein arrays from an Ornithodoros moubata salivary gland expression library.

Protein interactions play a critical role in the regulation of many biological events and their study in a high-throughput format has become a key area of proteomic research. Nucleid Acid Programmable Protein Arrays (NAPPA) technology allows the construction of protein arrays from cDNA expression libraries in high-throughput cell-free systems to study protein interaction and functions. Tick saliva contains antihemostatic, anti-inflammatory, and immunosuppressive proteins that counteract the host hemostatic, immune, and inflammatory responses allowing the ingestion of host blood and facilitating its infection by the tick-borne pathogens. Identification of such proteins and their functions could help in the selection of antigenic targets for the development of antitick and transmission-blocking vaccines. With that aim, we have prepared a cDNA expression library from the salivary glands of Ornithodoros moubata and subsequently produced a self-assembled protein microarray using 480 randomly selected clones from that library. The reproducibility of the array, its representativeness of the tick salivary protein repertoire, and the functionality of the in situ expressed proteins have been checked, demonstrating that it is a suitable tool for the identification and functional characterization of soft tick salivary molecules that interact with host proteins. Several clones in the array were shown to bind to human recombinant P-selectin. One of them was a likely secreted tick phospholipase A2, which may represent a potential new ligand for P-selectin. As these salivary molecules are likely involved in blood meal acquisition through the modulation of the host immune and hemostatic responses, this new high-throughput tool could open new avenues for development of new therapeutic agents and control strategies against ticks and tick-borne pathogens.

The effects of chemokine, adhesion and extracellular matrix molecules on binding of mesenchymal stromal cells to poly(l-lactic acid).

BACKGROUND AIMS: Mesenchymal stromal cells (MSC) are pluripotent adult stem cells capable of osteogenesis and chondrogenesis to form bone and cartilage. This characteristic gives them the potential for bone and cartilage regeneration. Synthetic polymers have been studied to examine whether they could be used as a scaffold for tissue engineering. In the current study a two-dimensional (2-D) poly(l-lactic acid) (PLLA) scaffold was treated with chemokine, adhesion and extracellular matrix molecules with the aim of using biologic molecules to improve the attachment of human MSC. METHODS: MSC were isolated from human bone marrow and applied to a 2-D PLLA scaffold. Chemokines ligand (CXCL12 and CXCL13), adhesion molecules [P-selectin, vascular cell adhesion molecule (VCAM)-1 and heparin] and extracellular matrix molecules (fibronectin and type IV collagen) were coated on the scaffold and their effects on the number of MSC that adhered were recorded. RESULTS: When used alone CXCL12 and CXCL13 enhanced MSC adhesion, as did VCAM-1, P-selectin, fibronectin and collagen, but not heparin. The effects of VCAM-1, P-selectin and heparin were enhanced by the addition of CXCL12. Incubation of MSC with antibodies to integrins α4 and α5ß1 inhibited their adhesion to VCAM-1 and fibronectin-treated PLLA respectively, suggesting that these integrins were involved in the MSC interactions. CONCLUSIONS: The use of certain chemokines and adhesion and extracellular matrix molecules, alone or in combination, is beneficial for the attachment of MSC to PLLA, and may be helpful as natural molecules in scaffolds for regenerative medicine.