Supplemental fibrinogen restores thrombus formation in cardiopulmonary bypass-induced platelet dysfunction ex vivo.

BACKGROUND: Major cardiac surgery related blood loss is associated with increased postoperative morbidity and mortality. Platelet dysfunction is believed to contribute to post-cardiopulmonary bypass (CPB)-induced microvascular bleeding. We hypothesised that moderately hypothermic CPB induces platelet dysfunction and that supplemental fibrinogen can restore in vitro thrombus formation. METHODS: Blood from 18 patients, undergoing first-time elective isolated aortic valve surgery was drawn before CPB, 30 min after initiation of CPB, and after CPB and protamine administration, respectively. Platelet aggregation was quantified by optical aggregometry, platelet activation by flow-cytometric detection of platelet surface expression of P-selectin, annexin V, and activated glycoprotein IIb/IIIa, thrombus formation under flow and effect of supplemental fibrinogen (4 mg ml-1) on in vitro thrombogenesis. RESULTS: Post-CPB adenosine-diphosphate and TRAP-6-induced aggregation decreased by 40% and 10% of pre-CPB levels, respectively (P<0.0001). Although CPB did not change glycoprotein IIb/IIIa receptor expression, it increased the percentage of unstimulated P-selectin (1.2% vs 7%, P<0.01) positive cells and annexin V mean fluorescence intensity (15.5 vs 17.2, P<0.05), but decreased percentage of stimulated P-selectin (52% vs 26%, P<0.01) positive cells and annexin V mean fluorescence intensity (508 vs 325, P<0.05). Thrombus area decreased from 6820 before CPB to 5230 after CPB (P<0.05, arbitrary units [a.u.]). Supplemental fibrinogen increased thrombus formation to 20 324 and 11 367 a.u. before CPB and after CPB, respectively (P<0.001), thereby restoring post-CPB thrombus area to levels comparable with or higher than pre-CPB baseline. CONCLUSIONS: Single valve surgery using moderately hypothermic CPB induces partial platelet dysfunction. Thrombus formation was restored in an experimental study design by ex vivo supplementation of fibrinogen.

Effect of pathological high shear exposure time on platelet activation and aggregation.

Circulating platelets are sometimes exposed to high shear rate environments due to vascular stenosis, and the effect of transiently elevated pathological high shear rates on platelet activation and aggregation function has not been clarified. The aim of this study was to investigate the effect of pathological high shear rate (8302s-1) exposure time (3.16-25.3 ms) on platelet activation and aggregation function. In addition, by adding active ingredients of antiplatelet drugs such as ASA (an active ingredient of aspirin), Ticagrelor, Tirofiban and GP1BA (platelet membrane protein GPIb inhibitor) in vitro, we studied TXA2, P2Y12-ADP, GPIIb/IIIa-fibrinogen and GPIb /IX/V-vWF receptor pathways to determine platelet activation function mediated by pathological high shear rate. In this study, we designed a set of microfluidic chips with stenosis lengths of 0.5 mm, 1 mm, 2 mm, 3 mm, and 4 mm, all with 80% stenosis, to generate pathological high shear forces that can act at different times. The whole blood flowing through the microchannels was collected by perfusion of sodium citrate anticoagulated whole blood at a physiological arterial shear rate (1500 s-1), and the expression levels of platelet surface activation markers (P-selectin and GP IIb/IIIa) and the degree of platelet aggregation were analyzed by flow cytometry; platelet aggregation patterns were observed by microscopic examination of blood smears. The results showed that shearing significantly increased platelet activation and aggregation levels compared to un-sheared whole blood, and the activation and aggregation levels increased with increasing duration of pathological high shear rate. In vitro inhibition studies showed that ASA barely inhibited the expression of P-selectin and PAC-1 on the platelet surface; Ticagrelor effectively inhibited the expression of both P-selectin and PAC-1; Tirofiban significantly inhibited the expression of PAC-1 on the platelet surface and slightly inhibited the expression of P-selectin; GP1BA significantly inhibited the expression of both. Our results suggest that transient pathological high shear rate (8302s-1) exposure can induce platelet activation in a time-dependent manner; however, the mechanism is more complex and may be due to the following reasons: transient elevated pathological high shear rate activates platelets through the GPIb/IX/V-vWF receptor pathway, and after platelet activation, its surface membrane protein GPIIb/IIIa receptors activate platelets through fibrinogen to form platelet-platelet aggregates, and further activation of active substances such as ADP and TXA2 released by platelet alpha particles, which contribute to the formation of irreversible platelet aggregation.

Therapy with high-dose statins reduces soluble P-selectin: The impact on plasma fibrin clot properties.

OBJECTIVE: Studies on the effect of statins on platelets in patients with coronary artery disease (CAD) yielded inconsistent results. We sought to investigate whether high-dose statin therapy reduces plasma concentrations of soluble P-selectin (sP-selectin), a well-established platelet activation marker and if such changes can affect fibrin clot properties, which are unfavorably altered in CAD patients. METHODS: We studied 130 consecutive patients with advanced CAD who did not achieve the target LDL cholesterol on statins. At baseline and after 6-12 months of treatment with atorvastatin 80 mg/day or rosuvastatin 40 mg/day, soluble plasma sP-selectin, along with plasma fibrin clot permeability (Ks), clot lysis time (CLT), thrombin generation and fibrinolysis proteins were determined. RESULTS: Before high-intensity statin treatment, lower Ks and longer CLT values were associated with increased sP-selectin (ß -0.27 [95% CI -0.44 to -0.10] and ß 0.21 [95% CI 0.01 to 0.41]; both p < 0.05, respectively) also after adjustment for potential confounders. sP-selectin, alongside fibrin features and other variables at baseline showed no association with lipid profile. On high-dose statin therapy, there was 32% reduction in sP-selectin levels (p < 0.001). On-treatment change (Δ) in sP-selectin correlated with ΔKs and ΔCLT (r = -0.32, p < 0.001 and r = 0.22, p = 0.011, respectively), but not with cholesterol and C-reactive protein lowering. We did not observe any associations between post-treatment sP-selectin levels and lipids, fibrin clot properties or thrombin generation. CONCLUSIONS: High-dose statin therapy reduces markedly sP-selectin levels in association with improved fibrin clot phenotype, which highlights the contribution of platelet-derived proteins to a prothrombotic state in hypercholesterolemia and statin-induced antithrombotic effects.

Effect of Single Housing on Innate Immune Activation in Immunodeficiency Virus-Infected Pigtail Macaques ( Macaca nemestrina ) as a Model of Psychosocial Stress in Acute HIV Infection.

OBJECTIVE: Simian immunodeficiency virus (SIV) infection of macaques recapitulates many aspects of HIV pathogenesis and is similarly affected by both genetic and environmental factors. Psychosocial stress is associated with immune system dysregulation and worse clinical outcomes in people with HIV. This study assessed the impact of single housing, as a model of psychosocial stress, on innate immune responses of pigtailed macaques ( Macaca nemestrina ) during acute SIV infection. METHODS: A retrospective analysis of acute SIV infection of 2- to si6-year-old male pigtailed macaques was performed to compare the innate immune responses of socially ( n = 41) and singly ( n = 35) housed animals. Measures included absolute monocyte count and subsets, and in a subset ( n ≤ 18) platelet counts and activation data. RESULTS: SIV infection resulted in the expected innate immune parameter changes with a modulating effect from housing condition. Monocyte number increased after infection for both groups, driven by classical monocytes (CD14 + CD16 - ), with a greater increase in socially housed animals (227%, p < .001, by day 14 compared with preinoculation time points). Platelet numbers recovered more quickly in the socially housed animals. Platelet activation (P-selectin) increased by 65% ( p = .004) and major histocompatibility complex class I surface expression by 40% ( p = .009) from preinoculation only in socially housed animals, whereas no change in these measures occurred in singly housed animals. CONCLUSIONS: Chronic psychosocial stress produced by single housing may play an immunomodulatory role in the innate immune response to acute retroviral infection. Dysregulated innate immunity could be one of the pathways by which psychosocial stress contributes to immune suppression and increased disease severity in people with HIV.

The effects of additive solutions on the development of storage lesions in canine platelet concentrates stored at 4°C.

OBJECTIVE: To assess platelet storage lesion development as evaluated by measurement of metabolic markers, platelet activation markers, and aggregometry, and determine the occurrence of bacterial growth in platelets stored in platelet additive solution (PAS) at 4°C for 7 days. DESIGN: Prospective, ex vivo experimental controlled study. SETTING: Research laboratory of a university veterinary teaching hospital. ANIMALS: Ten units of canine platelet concentrate collected from blood bank donations. INTERVENTIONS: Concentrates were aliquoted into 4 separate bags containing 100% plasma (control) or 30% plasma and 70% of a PAS (Plasma-Lyte A, Isoplate, or InterSol). Samples were stored at 4°C without agitation. At days 0, 3, 5, and 7, samples were analyzed for platelet count, mean platelet volume, glucose, lactate, lactate dehydrogenase, Po2 , Pco2 , degree of swirling, aggregate formation, aggregation via light aggregometry, surface P-selectin via flow cytometry, and bacterial contamination via culture. MEASUREMENTS AND MAIN RESULTS: Development of storage lesions was minimal, demonstrated by maintenance of a mean pH > 7.2 and mean lactate values <6 mmol/L at day 7 in all solutions. Glucose utilization did not vary significantly between any of the solutions. No significant difference was found between plasma and PAS for Po2 and Pco2 . P-selectin expression measured via flow cytometry showed a low platelet activation percent in all the solutions. InterSol had the lowest mean maximum percent aggregation (P < 0.001) and Isoplate the highest (P < 0.05). The mean maximum percent aggregation increased between day 0 and day 7 in all solutions. No bacterial growth was found in any of the solutions. CONCLUSIONS: Overall, PASs were comparable to plasma for the cold storage of platelets. Cold-stored platelets showed minimal storage lesion development with no bacterial growth. Plasma-, Plasma-Lyte A-, and Isoplate-stored platelets maintained function for up to 7 days at 4°C.

Combined effect of acute altitude exposure and vigorous exercise on platelet activation.

Exposure to high altitudes and exercise alters body's physiology and may cause acute cardiovascular events. Platelet activation is one of the key players in these events. Therefore, we investigated the effect of vigorous exercise at higher altitude (2650 m) on platelet aggregation and serum markers of platelet activation. 14 healthy subjects performed a step incremental ergometer test until exhaustion at the Environmental Research Station (UFS, 2650 m) at Zugspitze. Platelet aggregation and serum levels of endothelin-1, soluble p-selectin, platelet factor 4 and Chromogranin A were measured. Platelet activation was significantly enhanced after exercise at high altitude compared to measures immediately prior exercise. We detected significantly enhanced serum levels of endothelin-1 and soluble p-selectin whereas chromogranin A and platelet factor 4 remained unchanged. This effect might be due to increased endothelin-1 levels causing pulmonary vasoconstriction, rheological changes and direct platelet activation. This might be of clinical relevance, especially in patients with pre-existing diseases.

Effect of DDAVP on Platelet Activation and Platelet-Derived Microparticle Generation.

BACKGROUND: The way by which 1-deamino-8-D-arginine vasopressin (DDAVP) acts on platelets remains unclear. Data from the literature tend to show that there is no definite effect on platelet activation, but recent work has suggested that a subtype of platelets, activated by the combined action of collagen and thrombin, was triggered by DDAVP. Moreover, platelet microparticles (PMPs), which have been shown to be procoagulant, have rarely been studied in this context. The goal of this study was to analyze the effects of DDAVP on PMPs' release through platelet activation. METHODS: Fifteen out of 18 consecutive patients undergoing a therapeutic test with DDAVP were included. They were suffering from factor VIII deficiency or from von Willebrand disease. The expression of P-selectin and PAC-1 binding on platelets and the numbers of circulating PMPs were evaluated ex vivo before and after DDAVP infusion. Peripheral blood was collected on CTAD to limit artifactual platelet activation. RESULTS: DDAVP induced a significant decrease of platelet counts and volume. Only small changes of P-selectin expression and PAC-1 binding were observed. Considering PMPs, two populations of patients could be defined, respectively, with (120%, n = 6) or without (21%, n = 7) an increase of PMPs after DDAVP. The decrease in platelet counts and volume remained significant in the group of responders. CONCLUSION: This study shows that DDAVP induces the generation/release of PMPs in some patients with factor VIII deficiency and von Willebrand disease 1 hour after DDAVP infusion.

Tandem P-selectin glycoprotein ligand immunoglobulin prevents lung vaso-occlusion in sickle cell disease mice.

Sickle cell disease (SCD) is a monogenic disorder estimated to affect more than three million people worldwide. Acute systemic painful vaso-occlusive episode (VOE) is the primary reason for emergency medical care among SCD patients. VOE may also progress to acute chest syndrome (ACS), a type of acute lung injury and one of the primary reasons for mortality among SCD patients. Recently, P-selectin monoclonal antibodies were found to attenuate VOE in SCD patients and lung vaso-occlusion in transgenic humanized SCD mice, highlighting the therapeutic benefit of P-selectin inhibition in SCD. Here, we use quantitative fluorescence intravital lung microscopy (qFILM) to illustrate that tandem P-selectin-glycoprotein ligand-immunoglobulin (TSGL-Ig) fusion molecule containing four P-selectin binding sites, significantly attenuated intravenous (IV) oxyhemoglobin triggered lung vaso-occlusion in SCD mice. These findings highlight the therapeutic potential of TSGL-Ig in preventing VOE and ACS in SCD.

Molecular Requirements for the Expression of Antiplatelet Effects by Synthetic Structural Optimized Analogues of the Anticancer Drugs Imatinib and Nilotinib.

BACKGROUND: Platelets play important roles in cancer progression and metastasis, as well as in cancer-associated thrombosis (CAT). Tyrosine kinases are implicated in several intracellular signaling pathways involved in tumor biology, thus tyrosine kinase inhibitors (TKIs) represent an important class of anticancer drugs, based on the concept of targeted therapy. PURPOSE: The objective of this study is the design and synthesis of analogues of the TKIs imatinib and nilotinib in order to develop tyrosine kinase inhibitors, by investigating their molecular requirements, which would express antiplatelet properties. METHODS: Based on a recently described by us improved approach in the preparation of imatinib and/or nilotinib analogues, we designed and synthesized in five-step reaction sequences, 8 analogues of imatinib (I-IV), nilotinib (V, VI) and imatinib/nilotinib (VII, VIII). Their inhibitory effects on platelet aggregation and P-selectin membrane expression induced by arachidonic acid (AA), adenosine diphosphate (ADP) and thrombin receptor activating peptide-6 (TRAP-6), in vitro, were studied. Molecular docking studies and calculations were also performed. RESULTS: The novel analogues V-VIII were well established with the aid of spectroscopic methods. Imatinib and nilotinib inhibited AA-induced platelet aggregation, exhibiting IC50 values of 13.30 µΜ and 3.91 µΜ, respectively. Analogues I and II exhibited an improved inhibitory activity compared with imatinib. Among the nilotinib analogues, V exhibited a 9-fold higher activity than nilotinib. All compounds were less efficient in inhibiting platelet aggregation towards ADP and TRAP-6. Similar results were obtained for the membrane expression of P-selectin. Molecular docking studies showed that the improved antiplatelet activity of nilotinib analogue V is primarily attributed to the number and the strength of hydrogen bonds. CONCLUSION: Our results show that there is considerable potential to develop synthetic analogues of imatinib and nilotinib, as TKIs with antiplatelet properties and therefore being suitable to target cancer progression and metastasis, as well as CAT by inhibiting platelet activation.

Soluble P-selectin promotes retinal ganglion cell survival through activation of Nrf2 signaling after ischemia injury.

Retinal ischemic injuries play an important role in the pathogenesis of several eye disorders. Inflammation and oxidative stress are key players in ischemic injuries. Following retinal ischemia, vascular endothelial cells and leukocytes express several inflammatory adhesion receptors, such as selectins and cell adhesion molecules. P-selectin stimulates leukocyte recruitment to platelet aggregates and has an important role in vascular homeostasis and inflammatory leukocyte extravasation. Soluble P-selectin can be neuroprotective through competitive binding to the receptors of endogenous P-selectin molecules. Here, we demonstrate the neuroprotective effect of a recombinant P-selectin immunoglobin G (P-sel-IgG) chimeric fusion protein in a rat anterior ischemic optic neuropathy (rAION) model. rAION was induced by photodynamic therapy. P-sel-IgG treatment reduced optic nerve edema and stabilized the blood-optic nerve barrier (BONB) in the acute phase of rAION. Further, P-sel-IgG increased the retinal ganglion cell (RGC) survival rate, reduced RGC apoptosis, preserved visual function, maintained retinal nerve fiber layer thickness, and reduced macrophage infiltration in optic nerve tissue in the chronic phase (day 28). Increased NAD(P)H quinone dehydrogenase 1 (NQO1) and heme oxygenase 1(HO-1) expression levels, along with increased transcription factor Nrf2, suggesting an antioxidant role of P-sel-IgG via the Nrf2 signaling pathway. In conclusion, this study is the first to demonstrate that P-sel-IgG treatment promotes RGC survival by stabilizing the BONB and activating the Nrf2 signaling pathway in a rAION model.

Comparison of haemostatic function of PAS-C-platelets vs. plasma-platelets in reconstituted whole blood using impedance aggregometry and thromboelastography.

BACKGROUND AND OBJECTIVES: There are concerns about the haemostatic function of platelets stored in platelet additive solution (PAS). Aim of this study was to compare the haemostatic function of PAS-C-platelets to plasma-platelets in reconstituted whole blood. MATERIALS AND METHODS: In our experiment, whole blood was reconstituted with red blood cells, solvent-detergent (SD) plasma and either PAS-C-platelets or plasma-platelets (n = 7) in a physiological ratio. On storage days 2, 5, 8 and 13, the agonist-induced aggregation (multiple electrode aggregometry), clot formation (thromboelastography) and agonist-induced CD62P responsiveness (flow cytometry) were measured. RESULTS: Samples with PAS-C-platelets showed significantly lower aggregation than plasma-platelets when induced with adenosine diphosphate, -6 U (95% confidence interval: -8; -4) or thrombin receptor-activating protein, -15 U (-19; -10). Also when activated with collagen and ristocetin, the PAS-C-platelets showed less aggregation, although not statistically significant. All samples with PAS-C-platelets showed significantly lower agonist-induced CD62P responsiveness than samples with plasma-platelets. However, there was no difference regarding all TEG parameters. CONCLUSION: Our findings demonstrate that the function - aggregation and CD62P responsiveness - of PAS-C-platelets in reconstituted whole blood is inferior to that of plasma-platelets, which may have implications in the setting of massive transfusions.

Targeting P-selectin glycoprotein ligand-1/P-selectin interactions as a novel therapy for metabolic syndrome.

Obesity-induced insulin resistance and metabolic syndrome continue to pose an important public health challenge worldwide as they significantly increase the risk of type 2 diabetes and atherosclerotic cardiovascular disease. Advances in the pathophysiologic understanding of this process has identified that chronic inflammation plays a pivotal role. In this regard, given that both animal models and human studies have demonstrated that the interaction of P-selectin glycoprotein ligand-1 (PSGL-1) with P-selectin is not only critical for normal immune response but also is upregulated in the setting of metabolic syndrome, PSGL-1/P-selectin interactions provide a novel target for preventing and treating resultant disease. Current approaches of interfering with PSGL-1/P-selectin interactions include targeted antibodies, recombinant immunoglobulins that competitively bind P-selectin, and synthetic molecular therapies. Experimental models as well as clinical trials assessing the role of these modalities in a variety of diseases have continued to contribute to the understanding of PSGL-1/P-selectin interactions and have demonstrated the difficulty in creating clinically relevant therapeutics. Most recently, however, computational simulations have further enhanced our understanding of the structural features of PSGL-1 and related glycomimetics, which are responsible for high-affinity selectin interactions. Leveraging these insights for the design of next generation agents has thus led to development of a promising synthetic method for generating PSGL-1 glycosulfopeptide mimetics for the treatment of metabolic syndrome.

P-selectin promotes neutrophil extracellular trap formation in mice.

Neutrophil extracellular traps (NETs) can be released in the vasculature. In addition to trapping microbes, they promote inflammatory and thrombotic diseases. Considering that P-selectin induces prothrombotic and proinflammatory signaling, we studied the role of this selectin in NET formation. NET formation (NETosis) was induced by thrombin-activated platelets rosetting with neutrophils and was inhibited by anti-P-selectin aptamer or anti-P-selectin glycoprotein ligand-1 (PSGL-1) inhibitory antibody but was not induced by platelets from P-selectin(-/-) mice. Moreover, NETosis was also promoted by P-selectin-immunoglobulin fusion protein but not by control immunoglobulin. We isolated neutrophils from mice engineered to overproduce soluble P-selectin (P-selectin(ΔCT/ΔCT) mice). Although the levels of circulating DNA and nucleosomes (indicative of spontaneous NETosis) were normal in these mice, basal neutrophil histone citrullination and presence of P-selectin on circulating neutrophils were elevated. NET formation after stimulation with platelet activating factor, ionomycin, or phorbol 12-myristate 13-acetate was significantly enhanced, indicating that the P-selectin(ΔCT/ΔCT) neutrophils were primed for NETosis. In summary, P-selectin, cellular or soluble, through binding to PSGL-1, promotes NETosis, suggesting that this pathway is a potential therapeutic target for NET-related diseases.

P-selectin as a potential therapeutic target for endometriosis.

OBJECTIVE: To test the hypothesis that P-selectin plays a critical role in the development of endometriosis and that targeting P-selectin has therapeutic potential. DESIGN: Prospective, randomized study. SETTING: Academic facility. ANIMAL(S): The first experiment used 24 each of female adult P-selectin knockout mice and C57BL/6 wild-type mice, and 96 male green fluorescent protein (GFP) transgenic mice. The second experiment used 16 female adult C57BL/6 mice. INTERVENTION(S): In experiment 1, P-selectin knockout and wild-type mice alternately served as donors and recipients for the transplantation of endometrial tissue fragments into the peritoneal cavity to induce endometriosis. Two weeks later all four groups were each randomly divided into two equal-sized subgroups, receiving either green fluorescent protein-expressing platelets or saline infusion. In experiment 2, 2 weeks after the surgical induction of endometriosis, the mice were randomly divided into two groups, one receiving a 2-week treatment with a recombinant P-selectin protein and the other, non-immune IgG, both by intraperitoneal injection. MAIN OUTCOME MEASURE(S): Lesion size, hotplate latency, and immunohistochemistry analysis of platelet aggregation, angiogenesis, transforming growth factor ß1, α-smooth muscle actin, collagen I, and the extent of macrophage infiltration in ectopic implants. The extent of fibrosis also was evaluated in experiment 2. RESULT(S): P-selectin deficiency significantly retarded the development of endometriosis in a mouse model of endometriosis. In addition, soluble P-selectin treatment markedly reduced the lesion size in mouse through decreased platelet aggregation and angiogenesis, improved general hyperalgesia, and reduced the extent of macrophages infiltration, resulting in reduced fibrotic tissue content. CONCLUSION(S): Targeting P-selectin-mediated platelet adhesion onto endometriotic lesions holds promise as a novel therapeutics for treating endometriosis.

Benzophenone-based photochemical micropatterning of biomolecules to create model substrates and instructive biomaterials.

The extracellular matrix (ECM) is a dynamic and heterogeneous environment that controls many aspects of cell behavior. Not surprisingly, many different approaches have focused on creating model substrates that recapitulate the biomolecular, topographical, and mechanical properties of the ECM for in vitro studies of cell behavior. This chapter details a general, versatile method for the spatially controlled deposition of multiple biomolecules onto both planar and topographically complex support structures with micrometer resolution. This approach is based upon the well-understood photochemical UV crosslinking of benzophenone (BP) to solution-phase biomolecules. This is a molecularly general strategy that can be utilized to immobilize biomolecules onto any surface prefunctionalized with BP. Examples described herein include modification of planar and corrugated glass substrates as well as collagen-glycosaminoglycan biomaterials configured either as highly porous scaffolds or nonporous membranes with a variety of biomolecular targets, including proteins, glycoproteins, and carbohydrates.

Small-cell lung cancer (SCLC) cell adhesion on E- and P-selectin under physiological flow conditions.

Hematogenous metastasis is still a poorly understood phenomenon. The rate-limiting step within the metastatic cascade is not yet clear although it may be estimated that the extravasation of circulating tumor cells is a step of crucial importance, as most tumor cells that are shed into circulation undergo apoptosis. The process of extravasation includes a cascade of consecutive steps, starting with adhesion of tumor cells circulating in the bloodstream to endothelial cells, mimicking leukocyte adhesion and transmigration. Endothelial cell selectin-leukocyte glycan interaction occurs when leukocytes adhere to endothelial cells under conditions of shear stress. As there are parallels between cancer cell endothelial interactions with leukocyte endothelial cell systems an experimental setup has been developed in which adhesion of small cell lung carcinoma adhesive properties can be analyzed under physiological shear stress conditions during their attachment to E- and P-selection.

P-selectin-mediated platelet activation promotes adhesion of non-small cell lung carcinoma cells on vascular endothelial cells under flow.

Lung cancer is a severe disease threatening human health worldwide. Distant hematogenous metastasis results in poor prognosis and death of lung cancer patients. In the present study, we investigated the effect of circulatory platelets (PLTs) on hematogenous metastasis of non-small cell lung carcinoma (NSCLC). Laser scanning confocal microscopy was employed to assay the expression of P-selectin in lung cancer tissue, paracancerous tissue and distant tissue, respectively. Meanwhile, fluorescence-activated cell sorting (FACS) was used to determine P-selectin activation in peripheral blood. Purified PLTs were co-cultured with A549 cells and human vascular endothelial cells (HuvECs). Subsequently, the formation of PLT-lung cancer cell complexes and their effects on rolling and adhesion of A549 on the surface of vascular endothelium were assayed. Integrin α3, α5, ß1, ICAM-1 and VCAM-1 mRNAs and proteins were measured by reverse RT-PCR and western blot analysis, respectively. The expression of P-selectin in lung adenocarcinoma tissue was significantly stronger compared to that in paracancerous and distant tissues. P-selectin activation in peripheral blood in lung adenocarcinoma was markedly enhanced. The rolling rate of A549 on HuvECs was significantly slowed down after co-culture of activated PLTs and A549 cells. The mRNA and protein levels of integrin α3, α5, ß1, ICAM-1 and VCAM-1 were significantly increased after the co-culture. In conclusion, the PLT-lung cancer cell complexes protected the lung cancer cells from mechanical injury under blood flow. Furthermore, up-regulated integrin α3, α5, ß1 and endothelial cell adhesion molecules ICAM-1 and VCAM-1 promoted the adhesion of A549 on vascular endothelial cells, which may be responsible for hematogenous metastasis of lung cancer.

Variability in chemokine-induced adhesion of human mesenchymal stromal cells.

BACKGROUND AIMS. Intravenously applied mesenchymal stromal cells (MSC) are under investigation for numerous clinical indications. However, their capacity to activate shear stress-dependent adhesion to endothelial ligands is incompletely characterized. METHODS. Parallel-plate flow chambers were used to induce firm adhesion of MSC to integrin ligand vascular cell adhesion molecule (VCAM)-1. Human MSC were stimulated by chemokine (C-C motif) ligand (CCL15)/macrophage inflammatory protein (MIP-5), CCL19/MIP-3ß chemokine (C-X-C motif) ligand (CXCL8)/interleukin (IL)-8, CXCL12/ stromal derived factor (SDF-1) or CXCL13/B lymphocyte chemoattractant (BLC). RESULTS. Two MSC isolates responded to three chemokines (either to CCL15, CCL19 and CXCL13, or to CCL19, CXCL12 and CXCL13), two isolates responded to two chemokines (to CCL15 and CCL19, or to CCL19 and CXCL13), and one isolate responded to CCL19 only. In contrast, all tested MSC isolates responded to selectins (P-selectin and E-selectin) or integrin ligand VCAM-1, as visualized by a velocity reduction under flow. CONCLUSIONS. Inter-individual variability of chemokine-induced integrin activation should be considered when evaluating human MSC as cellular therapies.

Lysophosphatidylcholine pretreatment reduces VLA-4 and P-Selectin-mediated b16.f10 melanoma cell adhesion in vitro and inhibits metastasis-like lung invasion in vivo.

Lysophosphatidylcholine (LysoPC) is an important intermediate in degradation and biosynthesis of phosphatidylcholine (PC). Reduced plasma LysoPC levels observed in patients with advanced cancer indicate a deregulation of LysoPC metabolism in metastasis. Recent data showed strong antimetastatic effects of liposomes consisting of saturated PC in a murine pancreatic metastasis model. LysoPC, generated from saturated PC after accumulation of the liposomes in tumor tissue, might be contributing to these effects. Examining effects of high local concentrations of saturated LysoPC and investigating potential molecular mechanisms, fast removal of saturated LysoPC from medium by murine B16.F10 melanoma cells and radical shifts in tumor cell membrane fatty acid (FA) composition toward saturated FAs were observed in vitro. Scanning electron microscopy revealed remarkable morphologic surface changes of LysoPC-treated tumor cells, probably causing their impaired migratory ability on fibronectin. A LysoPC concentration exceeding a threshold of about 400 µmol/L, slightly above physiologic levels, strongly reduced VLA-4-mediated binding of B16.F10 cells to VCAM-1 as well as P-selectin-dependent interaction with activated platelets, although expression levels were not altered. These findings were reflected in a syngenic intravenous lung invasion model using repeatedly ex vivo LysoPC-treated (450 µmol/L) B16.F10 cells, resulting in significantly reduced lung metastasis-like lesions (-48.3%, P = 0.006). Prior application of 50 IU unfractionated heparin further reduced lung invasion (-81.6%, P = 0.043). Our work shows for the first time that saturated LysoPC in high concentrations reduces melanoma cell adhesion in vitro and hematogeneous dissemination in vivo by direct ex vivo tumor cell targeting.