Novel Approaches to Fine-Tune Therapeutic Targeting of Platelets in Atherosclerosis: A Critical Appraisal.

The pathogenesis of atherosclerotic vascular disease is driven by a multitude of risk factors intertwining metabolic and inflammatory pathways. Increasing knowledge about platelet biology sheds light on how platelets take part in these processes from early to later stages of plaque development. Recent insights from experimental studies and mouse models substantiate platelets as initiators and amplifiers in atherogenic leukocyte recruitment. These studies are complemented by results from genetics studies shedding light on novel molecular mechanisms which provide an interesting prospect as novel targets. For instance, experimental studies provide further details how platelet-decorated von Willebrand factor tethered to activated endothelial cells plays a role in atherogenic monocyte recruitment. Novel aspects of platelets as atherogenic inductors of neutrophil extracellular traps and particularities in signaling pathways such as cyclic guanosine monophosphate and the inhibitory adaptor molecule SHB23/LNK associating platelets with atherogenesis are shared. In summary, it was our intention to balance insights from recent experimental data that support a plausible role for platelets in atherogenesis against a paucity of clinical evidence needed to validate this concept in humans.

The endoplasmic reticulum protein SEC22B interacts with NBEAL2 and is required for megakaryocyte α-granule biogenesis.

Studies of inherited platelet disorders have provided many insights into platelet development and function. Loss of function of neurobeachin-like 2 (NBEAL2) causes gray platelet syndrome (GPS), where the absence of platelet α-granules indicates NBEAL2 is required for their production by precursor megakaryocytes. The endoplasmic reticulum is a dynamic network that interacts with numerous intracellular vesicles and organelles and plays key roles in their development. The megakaryocyte endoplasmic reticulum is extensive, and in this study we investigated its role in the biogenesis of α-granules by focusing on the membrane-resident trafficking protein SEC22B. Coimmunoprecipitation (co-IP) experiments using tagged proteins expressed in human HEK293 and megakaryocytic immortalized megakaryocyte progenitor (imMKCL) cells established binding of NBEAL2 with SEC22B, and demonstrated that NBEAL2 can simultaneously bind SEC22B and P-selectin. NBEAL2-SEC22B binding was also observed for endogenous proteins in human megakaryocytes using co-IP, and immunofluorescence microscopy detected substantial overlap. SEC22B binding was localized to a region of NBEAL2 spanning amino acids 1798 to 1903, where 2 GPS-associated missense variants have been reported: E1833K and R1839C. NBEAL2 containing either variant did not bind SEC22B coexpressed in HEK293 cells. CRISPR/Cas9-mediated knockout of SEC22B in imMKCL cells resulted in decreased NBEAL2, but not vice versa. Loss of either SEC22B or NBEAL2 expression resulted in failure of α-granule production and reduced granule proteins in imMKCL cells. We conclude that SEC22B is required for α-granule biogenesis in megakaryocytes, and that interactions with SEC22B and P-selectin facilitate the essential role of NBEAL2 in granule development and cargo stability.

Microvascular Mechanisms of Polyphosphate-Induced Neutrophil-Endothelial Cell Interactions in vivo.

BACKGROUND: Polyphosphates (PolyPs) have been reported to exert pro-inflammatory effects. However, the molecular mechanisms regulating PolyP-provoked tissue accumulation of leukocytes are not known. The aim of the present investigation was to determine the role of specific adhesion molecules in PolyP-mediated leukocyte recruitment. METHODS: PolyPs and TNF-α were intrascrotally administered, and anti-P-selectin, anti-E-selectin, anti-P-selectin glycoprotein ligand-1 (PSGL-1), anti-membrane-activated complex-1 (Mac-1), anti-lymphocyte function antigen-1 (LFA-1), and neutrophil depletion antibodies were injected intravenously or intraperitoneally. Intravital microscopy of the mouse cremaster microcirculation was used to examine leukocyte-endothelium interactions and recruitment in vivo. RESULTS: Intrascrotal injection of PolyPs increased leukocyte accumulation. Depletion of neutrophils abolished PolyP-induced leukocyte-endothelium interactions, indicating that neutrophils were the main leukocyte subtype responding to PolyP challenge. Immunoneutralization of P-selectin and PSGL-1 abolished PolyP-provoked neutrophil rolling, adhesion, and emigration. Moreover, immunoneutralization of Mac-1 and LFA-1 had no impact on neutrophil rolling but markedly reduced neutrophil adhesion and emigration evoked by PolyPs. CONCLUSION: These results suggest that P-selectin and PSGL-1 exert important roles in PolyP-induced inflammatory cell recruitment by mediating neutrophil rolling. In addition, our data show that Mac-1 and LFA-1 are necessary for supporting PolyP-triggered firm adhesion of neutrophils to microvascular endothelium. These novel findings define specific molecules as potential targets for pharmacological intervention in PolyP-dependent inflammatory diseases.

P-Selectin Is Critical for De Novo Pulmonary Arterial Thrombosis Following Blunt Thoracic Trauma.

BACKGROUND: Thromboembolic events within the pulmonary arterial vasculature are a troublesome complication of severe blunt thoracic trauma. Mechanisms underlying these events are currently in question as pulmonary thromboembolic events in this particular trauma population tend to be diagnosed more rapidly, more frequently and without an associated systemic thrombosis. This study investigates the role of P-selectin in thrombus formation through the use of in vivo blocking antibodies. We hypothesize that P-selectin plays a pivotal role in de novo pulmonary arterial thrombosis following blunt thoracic trauma. METHODS: A murine weight-drop model of lateral blunt thoracic trauma was used. Wild-type mice in the experimental group were given blocking antibodies against P-selectin prior to the trauma. All mice were euthanized at 24 hours for evaluation with hematoxylin-eosin staining or immunofluorescent staining for fibrin and P-selectin. RESULTS: Injured mice that did not receive the P-selectin antibody showed a robust fourfold to fivefold increase in fibrin accumulation in both coup and contrecoup tissues (fluorescence per um of arterial wall) compared to uninjured sham mice. In contrast, mice pretreated with P-selectin blocking antibody showed no significant increase in fibrin accumulation on either side of the lungs after blunt thoracic trauma. No difference in mean fibrin deposition was found between sham controls that received the P-selectin-blocking antibody and those that received an isotype control antibody. CONCLUSION: P-selectin expression increases at the pulmonary arterial luminal surface following blunt thoracic trauma. In addition, P-selectin-blocking in vivo prevents pulmonary arterial fibrin accumulation after blunt thoracic trauma, confirming that P-selectin is necessary for de novo pulmonary arterial thrombosis after traumatic injury.

Prevention of venous thromboembolism after resection of primary liver cancer with low molecular weight heparin and its association with P-selectin, lysosomal granule glycoprotein, platelet activating factor and plasma D-dimer.

OBJECTIVE: We aimed at analyzing the efficacy of low molecular heparin in the prevention of venous thromboembolism (VTE) after resection of primary liver cancer and at exploring the correlation of VTE with P-selectin (CD62P), lysosomal granule glycoprotein (CD63), platelet activating factor (PAF) and plasma D-dimer (D-D). PATIENTS AND METHODS: A total of 233 patients treated with primary liver cancer resection in our hospital from February 2014 to October 2016 were enrolled in this study. The patients were randomly divided into the observation group (n=117) and the control group (n=116). The observation group received a subcutaneous injection of low molecular weight heparin at 2-7 days after surgery, and the control group was not treated with anticoagulation. The prevalence of VTE and the changes of CD62P, CD63, PAF, and D-D before and after treatment were compared between the two groups. The VTE prevalence after surgery, the changes of CD62P, CD63, PAF, D-D before and after surgery and the correlation of the above indexes with VTE were analyzed. RESULTS: The prevalence of VTE in the observation group was 0.85% (1/117), which was lower than that of the control group (13.79%) (16/116); the difference was statistically significant (p<0.05). There was no significant difference in blood coagulation function between the two groups before and after operation (p>0.05). The CD62P, CD63, PAF, and D-D of the two groups were continuously decreased after the operation, and the serum CD62P, CD63 and plasma D-D of the observation group 6 d and 10 d after operation were lower than that of the control group; the difference was statistically significant (p<0.05). The serum CD62P, CD63 and plasma D-D in the VTE group 6 d and 10 d after operation were lower than those in the non-VTE group; the differences were statistically significant (p<0.05). CONCLUSIONS: Low molecular weight heparin can effectively prevent VTE after primary liver cancer resection. Regularly monitoring CD62P, CD63, PAF, and D-D in patients after the operation is pivotal for early diagnosis, evaluation and treatment of VTE.

Relationship of platelet microparticle CD62P and activated GP IIb/IIIa with hypercoagulable state after atrial fibrillation radiofrequency catheter ablation.

OBJECTIVE: The morbidity of atrial fibrillation (AF) is 1%-2% in clinic. Radiofrequency catheter ablation (RFCA) is a type of radical interventional therapy for AF, whereas it may lead to a hypercoagulable state. This study evaluated platelet particle CD62P and platelet activation biomarker GP IIb/IIIa expressions in AF patients treated by RFCA, and aimed to analyze their relationships with the hypercoagulable state after RFCA. PATIENTS AND METHODS: A total of 60 AF patients received RFCA in our hospital were enrolled. The patients were divided into group A as hypercoagulable state group and group B as non-hypercoagulable group. Healthy volunteers were selected as normal control. Serum D-Dimer, parathyroid activity index 1 (PAI-1), and tissue plasminogen activator (t-PA) content were tested by using enzyme-linked immunosorbent assay (ELISA), while peripheral CD62P and GP IIb/IIIa expressions were detected by using flow cytometry before, after, and seven days after RFCA. RESULTS: D-Dimer and PAI-1 levels increased, while t-PA reduced in group A compared with that in group B and control (p<0.05). D-Dimer and t-PA contents gradually elevated, whereas t-PA level gradually declined in group A before, after, and seven days after RFCA (p<0.05). Serum CD62P and GP IIb/IIIa expressions in group A were significantly higher compared to that in group B and control (p<0.05). CD62P and GP IIb/IIIa levels were significantly higher seven days after RFCA compared with immediate after RFCA in group A (p<0.05). CD62P showed a positive correlation with GP IIb/IIIa in hypercoagulable state patients after RFCA (p<0.05). CONCLUSIONS: AF patient may appear in hypercoagulable state after RFCA. CD62P and GP IIb/IIIa significantly increased and exhibited a positive correlation.

Tuning the endothelial response: differential release of exocytic cargos from Weibel-Palade bodies.

Essentials Endothelial activation initiates multiple processes, including hemostasis and inflammation. The molecules that contribute to these processes are co-stored in secretory granules. How can the cells control release of granule content to allow differentiated responses? Selected agonists recruit an exocytosis-linked actin ring to boost release of a subset of cargo. SUMMARY: Background Endothelial cells harbor specialized storage organelles, Weibel-Palade bodies (WPBs). Exocytosis of WPB content into the vascular lumen initiates primary hemostasis, mediated by von Willebrand factor (VWF), and inflammation, mediated by several proteins including P-selectin. During full fusion, secretion of this large hemostatic protein and smaller pro-inflammatory proteins are thought to be inextricably linked. Objective To determine if secretagogue-dependent differential release of WPB cargo occurs, and whether this is mediated by the formation of an actomyosin ring during exocytosis. Methods We used VWF string analysis, leukocyte rolling assays, ELISA, spinning disk confocal microscopy, high-throughput confocal microscopy and inhibitor and siRNA treatments to demonstrate the existence of cellular machinery that allows differential release of WPB cargo proteins. Results Inhibition of the actomyosin ring differentially effects two processes regulated by WPB exocytosis; it perturbs VWF string formation but has no effect on leukocyte rolling. The efficiency of ring recruitment correlates with VWF release; the ratio of release of VWF to small cargoes decreases when ring recruitment is inhibited. The recruitment of the actin ring is time dependent (fusion events occurring directly after stimulation are less likely to initiate hemostasis than later events) and is activated by protein kinase C (PKC) isoforms. Conclusions Secretagogues differentially recruit the actomyosin ring, thus demonstrating one mechanism by which the prothrombotic effect of endothelial activation can be modulated. This potentially limits thrombosis whilst permitting a normal inflammatory response. These results have implications for the assessment of WPB fusion, cargo-content release and the treatment of patients with von Willebrand disease.

Abacavir induces platelet-endothelium interactions by interfering with purinergic signalling: A step from inflammation to thrombosis.

The controversy connecting Abacavir (ABC) with cardiovascular disease has been fuelled by the lack of a credible mechanism of action. ABC shares structural similarities with endogenous purines, signalling molecules capable of triggering prothrombotic/proinflammatory programmes. Platelets are leading actors in the process of thrombosis. Our study addresses the effects of ABC on interactions between platelets and other vascular cells, while exploring the adhesion molecules implicated and the potential interference with the purinergic signalling pathway. The effects of ABC on platelet aggregation and platelet-endothelium interactions were evaluated, respectively, with an aggregometer and a flow chamber system that reproduced conditions in vivo. The role of adhesion molecules and purinergic receptors in endothelial and platelet populations was assessed by selective pre-incubation with specific antagonists and antibodies. ABC and carbovir triphosphate (CBT) levels were evaluated by HPLC. The results showed that ABC promoted the adherence of platelets to endothelial cells, a crucial step for the formation of thrombi. This was not a consequence of a direct effect of ABC on platelets, but resulted from activation of the endothelium via purinergic ATP-P2X7 receptors, which subsequently triggered an interplay between P-selectin and ICAM-1 on endothelial cells with constitutively expressed GPIIb/IIIa and GPIbα on platelets. ABC did not induce platelet activation (P-selectin expression or Ca2+ mobilization) or aggregation, even at high concentrations. CBT levels in endothelial cells were lower than those required to induce platelet-endothelium interactions. Thus, ABC interference with endothelial purinergic signalling leads to platelet recruitment. This highlights the endothelium as the main cell target of ABC in this interaction, which is in line with previous experimental evidence that ABC induces manifestations of vascular inflammation.

Deregulation of Soluble Adhesion Molecules in Resistant Hypertension and Its Role in Cardiovascular Remodeling.

BACKGROUND: Resistant hypertension (RHTN) and target organ damage are linked to increased inflammatory biomarkers, which may regulate adhesion molecules, such as intracellular adhesion molecule-1 (ICAM-1); vascular cell adhesion molecule-1 (VCAM-1); and the platelet (P-selectin) and endothelial (E-selectin) selectins. We investigated a previously unknown relationship between soluble P-selectin (sP-selectin), E-selectin (sE-selectin), ICAM-1 (sICAM-1) and VCAM-1 (sVCAM-1) with RHTN and target organ damage. METHODS AND RESULTS: We included 110 subjects diagnosed for true RHTN and 112 mild-moderate hypertensive (HTN) patients. Blood pressure parameters, pulse wave velocity and left ventricular mass index (LVMI) were measured. Adhesion molecules were measured on ELISA. Both sP-selectin and sE-selectin were increased; in contrast, sICAM-1 was reduced in RHTN compared with HTN patients, while similar sVCAM-1 was noted in the groups. sP-selectin and sVCAM-1 were elevated in the presence of arterial stiffness (sP-selectin: 104±47 vs. 89±45 ng/ml, P<0.05; sVCAM-1: 1,189±411 vs. 1,060±412 ng/ml, P<0.05) and cardiac hypertrophy (sP-selectin: 105±51 vs. 88±43 ng/ml, P<0.05; sVCAM-1: 1,170±433 vs. 1,040±383 ng/ml, P<0.05) in all HTN patients. sP-selectin was associated with target organ damage after adjustment for age and BP. Apart from potential confounders, sE-selectin was a significant indicator of RHTN. CONCLUSIONS: The adhesion molecule sP-selectin plays a role in cardiovascular damage, and sE-selectin in resistance to antihypertensive therapy. (Circ J 2016; 80: 1196-1201).

Platelet microparticles inhibit IL-17 production by regulatory T cells through P-selectin.

Self-tolerance and immune homeostasis are orchestrated by FOXP3(+)regulatory T cells (Tregs). Recent data have revealed that upon stimulation, Tregs may exhibit plasticity toward a proinflammatory phenotype, producing interleukin 17 (IL-17) and/or interferon γ (IFN-γ). Such deregulation of Tregs may contribute to the perpetuation of inflammatory processes, including graft-versus-host disease. Thus, it is important to identify immunomodulatory factors influencing Treg stability. Platelet-derived microparticles (PMPs) are involved in hemostasis and vascular health and have recently been shown to be intimately involved in (pathogenic) immune responses. Therefore, we investigated whether PMPs have the ability to affect Treg plasticity. PMPs were cocultured with healthy donor peripheral blood-derived Tregs that were stimulated with anti-CD3/CD28 monoclonal antibodies in the presence of IL-2, IL-15, and IL-1ß. PMPs prevented the differentiation of peripheral blood-derived Tregs into IL-17- and IFN-γ-producing cells, even in the presence of the IL-17-driving proinflammatory cytokine IL-1ß. The mechanism of action by which PMPs prevent Treg plasticity consisted of rapid and selective P-selectin-dependent binding of PMPs to a CCR6(+)HLA-DR(+)memory-like Treg subset and their ability to inhibit Treg proliferation, in part through CXCR3 engagement. The findings that ~8% of Tregs in the circulation of healthy individuals are CD41(+)P-selectin(+)and that distinct binding of patient plasma PMPs to Tregs was observed support in vivo relevance. These findings open the exciting possibility that PMPs actively regulate the immune response at sites of (vascular) inflammation, where they are known to accumulate and interact with leukocytes, consolidating the (vascular) healing process.

Anti-TNFα agents curb platelet activation in patients with rheumatoid arthritis.

BACKGROUND: Cardiovascular disease is important in rheumatoid arthritis (RA). Tissue factor (TF) is expressed upon platelet activation and initiates coagulation. Anti-tumour necrosis factor-α (TNFα) agents seem to decrease RA-associated cardiovascular events. We investigated whether (1) TNFα activates human platelets and (2) TNFα pharmacological blockade modulates the platelet-leucocyte reciprocal activation in RA. DESIGN: The expression of platelet TNFα receptors has been assessed by flow cytometry and immunogold electron microscopy. Platelet and leucocyte activation has been assessed also in the presence of antibodies against the TNFα receptors 1 and 2 and of infliximab. TF expression, binding to fibrinogen and phosphatidylserine exposure, has been assessed by flow cytometry, TF activity by coagulation time and by endogenous thrombin generation. Markers of platelet and leucocyte activation have been assessed in 161 subjects: 42 patients with RA, 12 with osteoarthritis, 37 age-matched and sex-matched patients with chronic stable angina and 70 age-matched and sex-matched healthy subjects. RESULTS: TNFα elicited the platelet activation and the expression of TF, which in turn prompted thrombin generation and clot formation. Inhibition of the TNFα-induced activation restricted platelet ability to activate leucocytes and to induce leucocyte TF. TNFα inhibition did not influence platelet activation induced by collagen, ADP or thrombin receptor activating peptide-6. Platelets of patients with RA were more activated than those of controls. Activation was reduced in patients treated with TNFα inhibitors. CONCLUSIONS: TNFα-dependent pathways control platelet activation and TF expression in RA. Further studies will verify whether the protective effect of TNFα inhibitors on cardiovascular events involves their ability to modulate platelet function.

Treatment with selectin blocking antibodies after lengthening contractions of mouse muscle blunts neutrophil accumulation but does not reduce damage.

P- and E-selectins are expressed on the surface of endothelial cells and may contribute to neutrophil recruitment following injurious lengthening contractions of skeletal muscle. Blunting neutrophil, but not macrophage, accumulation after lengthening contractions may provide a therapeutic benefit as neutrophils exacerbate damage to muscle fibers, while macrophages promote repair. In this study, we tested the hypothesis that P- and E-selectins contribute to neutrophil, but not macrophage, accumulation in muscles after contraction-induced injury, and that reducing neutrophil accumulation by blocking the selectins would be sufficient to reduce damage to muscle fibers. To test our hypothesis, we treated mice with antibodies to block P- and E-selectin function and assessed leukocyte accumulation and damage in muscles 2 days after lengthening contractions. Treatment with P/E-selectin blocking antibodies reduced neutrophil content by about half in muscles subjected to lengthening contractions. In spite of the reduction in neutrophil accumulation, we did not detect a decrease in damage 2 days after lengthening contractions. We conclude that P- and/or E-selectin contribute to the neutrophil accumulation associated with contraction-induced muscle damage and that only a portion of the neutrophils that typically accumulate following injurious lengthening contractions is sufficient to induce muscle fiber damage and force deficits. Thus, therapeutic interventions based on blocking the selectins or other adhesion proteins will have to reduce neutrophil numbers by more than 50% in order to provide a benefit.

Dimethyl Fumarate Reduces Inflammatory Responses in Experimental Colitis.

BACKGROUND AND AIMS: Fumaric acid esters have been proven to be effective for the systemic treatment of psoriasis and multiple sclerosis. We aimed to develop a new treatment for colitis. METHODS: We investigated the effect of dimethylfumarate [DMF, 10-30-100mg/kg] on an experimental model of colitis induced by dinitrobenzene sulphuric acid [DNBS]. We also evaluated the therapeutic activity of 7 weeks' treatment with DMF [30mg/kg] on 9-week-old IL-10KO mice that spontaneously develop a T helper-1 [Th1]-dependent chronic enterocolitis after birth, that is fully established at 8-10 weeks of age. The mechanism of this pharmacological potential of DMF [10 µM] was investigated in colonic epithelial cell monolayers [Caco-2] exposed to H2O2. The barrier function was evaluated by the tight junction proteins. RESULTS: The treatment with DMF significantly reduced the degree of haemorrhagic diarrhoea and weight loss caused by administration of DNBS. DMF [30 and 100mg/kg] also caused a substantial reduction in the degree of colon injury, in the rise in myeloperoxidase [MPO] activity, and in the increase in tumour necrosis factor [TNF]-α expression, as well as in the up-regulation of ICAM-1 caused by DNBS in the colon. Molecular studies demonstrated that DMF impaired NF-κB signalling via reduced p65 nuclear translocalisation. DMF induced a stronger antioxidant response as evidenced by a higher expression of Mn-superoxide dismutase. Moreover, DMF protected human intestinal epithelial cells against H2O2-induced barrier dysfunction, restoring ZO-1 occludin expression, via the HO-1 pathway. CONCLUSIONS: DMF treatment reduces the degree of colitis caused by DNBS. We propose that DMF treatment may be useful in the treatment of inflammatory bowel disease.

Adhesive Mechanisms of Histone-Induced Neutrophil-Endothelium Interactions in the Muscle Microcirculation.

BACKGROUND: Extracellular histones released during cell damage have the capacity to cause tissue injury associated with increased leukocyte accumulation. However, the molecular mechanisms regulating histone-induced leukocyte recruitment remain elusive. The objective of this study was to examine the role of adhesion molecules in histone-dependent leukocyte accumulation by use of intravital microscopy of the mouse cremaster microcirculation. METHODS: Histone 3 and TNF-α were intrascrotally administered, and anti-P-selectin, anti-P-selectin glycoprotein ligand-1 (PSGL-1), anti-membrane-activated complex-1 (Mac-1), anti-lymphocyte function antigen-1 (LFA-1) antibody and neutrophil depletion antibody were injected intravenously or intraperitoneally. RESULTS: Intrascrotal injection of histone 3 dose-dependently increased leukocyte recruitment. Neutrophil depletion abolished intravascular and extravascular leukocytes after histone 3 challenge, suggesting that neutrophils were the dominating leukocyte subtype responding to histone stimulation. Pretreatment with an anti-P-selectin and an anti-PSGL-1 antibody abolished histone-stimulated neutrophil rolling, adhesion and emigration. When the anti-P-selectin or the anti-PSGL-1 antibody was administrated after histone 3 stimulation, neutrophil rolling was reduced, whereas the number of firmly adherent and emigrated neutrophils were unchanged, suggesting that the inhibitory effect of blocking P-selectin and PSGL-1 on neutrophil adhesion and recruitment was due to the reduction in neutrophil rolling. Moreover, pretreatment with antibodies against Mac-1 and LFA-1 had no effect of neutrophil rolling but abolished adhesion and emigration evoked by histone 3. Thus, our data demonstrate that P-selectin and PSGL-1 play an important role in histone-induced inflammatory cell recruitment by mediating neutrophil rolling as a precondition for histone-provoked firm adhesion and emigration in vivo. Moreover, we conclude that both Mac-1 and LFA-1 are critical in supporting histone-provoked firm adhesion of neutrophils to endothelial cells. CONCLUSION: These novel findings define specific selectins and integrins as potential targets for pharmacological intervention in histone-dependent inflammatory diseases.

[Expression and significance of adhesion molecules CD62P and CD44 in peripheral blood of infants with bronchiolitis].

OBJECTIVE: To explore the expression and significance of the adhesion molecules CD62P and CD44 in the peripheral blood of infants with bronchiolitis. METHODS: Thirty-three infants with bronchiolitis in the acute phase and 19 infants with bronchiolitis in the recovery phase, who were hospitalized between November 2014 and May 2015, were enrolled. Thirty infants with bronchopneumonia and 26 infants without infection were enrolled as the bronchopneumonia group and the control group, respectively. The CD62P expression in the peripheral blood of each group was measured by flow cytometry, and the CD44 level in serum was determined using ELISA. RESULTS: The levels of the adhesion molecules CD62P and CD44 in the bronchiolitis group in the acute phase were significantly higher than those in the bronchiolitis group in the recovery phase, the bronchopneumonia group, and the control group (P<0.05). The levels of the adhesion molecules CD62P and CD44 in the bronchiolitis group in the recovery phase were also significantly higher than those in the control group (P<0.05). In the bronchiolitis group in the acute phase, there was a positive correlation between CD62P expression and serum CD44 level (r=0.91; P<0.05). CONCLUSIONS: The adhesion molecules CD62P and CD44 play an important role in the pathogenesis of bronchiolitis, and their levels can reflect the severity of inflammatory response in infants with bronchiolitis.

Spatiotemporal regulation of coagulation and platelet activation during the hemostatic response in vivo.

The hemostatic response requires the tightly regulated interaction of the coagulation system, platelets, other blood cells and components of the vessel wall at a site of vascular injury. The dysregulation of this response may result in excessive bleeding if the response is impaired, and pathologic thrombosis with vessel occlusion and tissue ischemia if the response is overly robust. Extensive studies over the past decade have sought to unravel the regulatory mechanisms that coordinate the multiple biochemical and cellular responses in time and space to ensure that an optimal response to vascular damage is achieved. These studies have relied in part on advances in in vivo imaging techniques in animal models, allowing for the direct visualization of various molecular and cellular events in real time during the hemostatic response. This review summarizes knowledge gained with these in vivo imaging and other approaches that provides new insights into the spatiotemporal regulation of coagulation and platelet activation at a site of vascular injury.

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-Mediated Adhesion between Platelets and Tumor Cells Promotes Intestinal Tumorigenesis in Apc(Min/+) Mice.

Studies have indicated that platelets play an important role in tumorigenesis, and an abundance of platelets accumulate in the ovarian tumor microenvironment outside the vasculature. However, whether cancer cells recruit platelets within intestinal tumors and how they signal adherent platelets to enter intestinal tumor tissues remain unknown. Here, we unexpectedly found that large numbers of platelets were deposited within human colorectal tumor specimens using immunohistochemical staining, and these platelets were fully associated with tumor development. We further report the robust adhesion of platelet aggregates to tumor cells within intestinal tumors, which occurs via a mechanism that is dependent on P-selectin (CD62P), a cell adhesion molecule that is abundantly expressed on activated platelets. Using spontaneous intestinal tumor mouse models, we determined that the genetic deletion of P-selectin suppressed intestinal tumor growth, which was rescued by the infusion of wild-type platelets but not P-selectin(-/-) platelets. Mechanistically, platelet adhesion to tumor cells induced the secretion of vascular endothelial growth factor (VEGF) to promote angiogenesis and accelerate intestinal tumor cell proliferation. Our results indicate that the adherence of platelets to tumor cells could promote tumor growth and metastasis. By targeting this platelet-tumor cell interaction, recombinant soluble P-selectin may have therapeutic value for the treatment of intestinal tumors.

Pentraxin 3 Induces Vascular Endothelial Dysfunction Through a P-selectin/Matrix Metalloproteinase-1 Pathway.

BACKGROUND: Pentraxin 3 (PTX3), the prototype of long pentraxins, has been described to be associated with endothelial dysfunction in different cardiovascular disorders. No study has yet evaluated the possible direct effect of PTX3 on vascular function. METHODS AND RESULTS: Through in vitro experiments of vascular reactivity and ultrastructural analyses, we demonstrate that PTX3 induces dysfunction and morphological changes in the endothelial layer through a P-selectin/matrix metalloproteinase-1 pathway. The latter hampered the detachment of endothelial nitric oxide synthase from caveolin-1, leading to an impairment of nitric oxide signaling. In vivo studies showed that administering PTX3 to wild-type mice induced endothelial dysfunction and increased blood pressure, an effect absent in P-selectin-deficient mice. In isolated human umbilical vein endothelial cells, PTX3 significantly blunted nitric oxide production through the matrix metalloproteinase-1 pathway. Finally, using ELISA, we found that hypertensive patients (n=31) have higher plasma levels of PTX3 and its mediators P-selectin and matrix metalloproteinase-1 than normotensive subjects (n=21). CONCLUSIONS: Our data show for the first time a direct role of PTX3 on vascular function and blood pressure homeostasis, identifying the molecular mechanisms involved. The findings in humans suggest that PTX3, P-selectin, and matrix metalloproteinase-1 may be novel biomarkers that predict the onset of vascular dysfunction in hypertensive patients.