Glioblastoma (GB) is a highly invasive type of brain cancer exhibiting poor prognosis. As such, its microenvironment plays a crucial role in its progression. Among the brain stromal cells, the ...microglia were shown to facilitate GB invasion and immunosuppression. However, the reciprocal mechanisms by which GB cells alter microglia/macrophages behavior are not fully understood. We propose that these mechanisms involve adhesion molecules such as the Selectins family. These proteins are involved in immune modulation and cancer immunity. We show that P-selectin mediates microglia-enhanced GB proliferation and invasion by altering microglia/macrophages activation state. We demonstrate these findings by pharmacological and molecular inhibition of P-selectin which leads to reduced tumor growth and increased survival in GB mouse models. Our work sheds light on tumor-associated microglia/macrophage function and the mechanisms by which GB cells suppress the immune system and invade the brain, paving the way to exploit P-selectin as a target for GB therapy.
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-selectinΔCT/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-selectinΔCT/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.
•NET formation is stimulated by platelet or soluble P-selectin.
Severe COVID-19 Is a Microvascular Disease Lowenstein, Charles J; Solomon, Scott D
Circulation (New York, N.Y.),
2020-October-27, Letnik:
142, Številka:
17
Journal Article
The up-regulation of P-selectin in endothelial cells and platelets contributes to the cell-cell interactions that are involved in the pathogenesis of vaso-occlusion and sickle cell-related pain ...crises. The safety and efficacy of crizanlizumab, an antibody against the adhesion molecule P-selectin, were evaluated in patients with sickle cell disease.
In this double-blind, randomized, placebo-controlled, phase 2 trial, we assigned patients to receive low-dose crizanlizumab (2.5 mg per kilogram of body weight), high-dose crizanlizumab (5.0 mg per kilogram), or placebo, administered intravenously 14 times over a period of 52 weeks. Patients who were receiving concomitant hydroxyurea as well as those not receiving hydroxyurea were included in the study. The primary end point was the annual rate of sickle cell-related pain crises with high-dose crizanlizumab versus placebo. The annual rate of days hospitalized, the times to first and second crises, annual rates of uncomplicated crises (defined as crises other than the acute chest syndrome, hepatic sequestration, splenic sequestration, or priapism) and the acute chest syndrome, and patient-reported outcomes were also assessed.
A total of 198 patients underwent randomization at 60 sites. The median rate of crises per year was 1.63 with high-dose crizanlizumab versus 2.98 with placebo (indicating a 45.3% lower rate with high-dose crizanlizumab, P=0.01). The median time to the first crisis was significantly longer with high-dose crizanlizumab than with placebo (4.07 vs. 1.38 months, P=0.001), as was the median time to the second crisis (10.32 vs. 5.09 months, P=0.02). The median rate of uncomplicated crises per year was 1.08 with high-dose crizanlizumab, as compared with 2.91 with placebo (indicating a 62.9% lower rate with high-dose crizanlizumab, P=0.02). Adverse events that occurred in 10% or more of the patients in either active-treatment group and at a frequency that was at least twice as high as that in the placebo group were arthralgia, diarrhea, pruritus, vomiting, and chest pain.
In patients with sickle cell disease, crizanlizumab therapy resulted in a significantly lower rate of sickle cell-related pain crises than placebo and was associated with a low incidence of adverse events. (Funded by Selexys Pharmaceuticals and others; SUSTAIN ClinicalTrials.gov number, NCT01895361 .).
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.
•Circulating sP-selectin shed from cell surfaces must dimerize to promote inflammation or coagulation.•Circulating sP-selectin is a consequence rather than a cause of cardiovascular disease.
P-selectin glycoprotein ligand-1 (PSGL-1/CD162) has been studied extensively for its role in mediating leukocyte rolling through interactions with its cognate receptor, P-selectin. Recently, PSGL-1 ...was identified as a novel HIV-1 host restriction factor, particularly when expressed at high levels in the HIV envelope. Importantly, while the potent antiviral activity of PSGL-1 has been clearly demonstrated in various complementary model systems, the breadth of PSGL-1 incorporation across genetically diverse viral isolates and clinical isolates has yet to be described. Additionally, the biological activity of virion-incorporated PSGL-1 has also yet to be shown.
Herein we assessed the levels of PSGL-1 on viruses produced through transfection with various amounts of PSGL-1 plasmid DNA (0-250 ng), compared to levels of PSGL-1 on viruses produced through infection of T cell lines and primary PBMC. We found that very low levels of PSGL-1 plasmid DNA (< 2.5 ng/well) were necessary to generate virus models that could closely mirror the phenotype of viruses produced via infection of T cells and PBMC. Unique to this study, we show that PSGL-1 is incorporated in a broad range of HIV-1 and SIV isolates and that virions with incorporated PSGL-1 are detectable in plasma from viremic HIV-1-infected individuals, corroborating the relevance of PSGL-1 in natural infection. Additionally, we show that PSGL-1 on viruses can bind its cognate selectin receptors, P-, E-, and L-selectins. Finally, we show viruses with endogenous levels of PSGL-1 can be captured by P-selectin and transferred to HIV-permissive bystander cells, highlighting a novel role for PSGL-1 in HIV-1 infection. Notably, viruses which contained high levels of PSGL-1 were noninfectious in our hands, in line with previous findings reporting the potent antiviral activity of PSGL-1.
Our results indicate that levels of PSGL-1 incorporation into virions can vary widely among model systems tested, and that careful tailoring of plasmid levels is required to recapitulate physiological systems when using pseudovirus models. Taken together, our data suggest that PSGL-1 may play diverse roles in the physiology of HIV-1 infection, particularly due to the functionally active state of PSGL-1 on virion surfaces and the breadth of PSGL-1 incorporation among a wide range of viral isolates.
The primary importance of tissue factor (TF) in blood coagulation and thrombus propagation has been recognized for many years. Nevertheless, our view about the origin of TF activity, necessary for ...normal hemostasis and found in pathologic conditions, needs to be revised in the light of recent observations. Pioneering work by Yale Nemerson's group showed that circulating TF on microparticles (MPs), could promote thrombus growth. The origin and characteristics of this ‘blood‐borne’ TF are targets of intense research as well as intense debate. Surprising observations now implicate the adhesion receptor P‐selectin (P‐sel), known for its role in inflammation, in these MPs’ generation. P‐sel, translocated from granules to the cell surfaces of activated platelets and endothelial cells, was recently found to play multiple roles in hemostasis. Expressed on endothelium, it can mediate platelet rolling. Signaling by P‐sel through its receptor on leukocytes, P‐selectin glycoprotein ligand 1 (PSGL‐1), induces the generation of TF‐positive, highly procoagulant MPs. In addition, P‐sel on activated platelets helps to recruit these MPs specifically to thrombi. In this review, we discuss the roles of P‐sel and TF‐positive MPs and highlight strategies to modulate hemostasis by modulating the P‐sel, TF, coagulation triad.
T‐cell migration across the blood‐brain barrier is a crucial step in the pathogenesis of EAE, an animal model for MS. Live cell imaging studies demonstrated that P‐selectin glycoprotein ligand‐1 ...(PSGL‐1) and its endothelial ligands E‐ and P‐selectin mediate the initial rolling of T cells in brain vessels during EAE. As functional absence of PSGL‐1 or E/P‐selectins does not result in ameliorated EAE, we speculated that T‐cell entry into the spinal cord is independent of PSGL‐1 and E/P‐selectin. Performing intravital microscopy, we observed the interaction of WT or PSGL‐1−/− proteolipid protein‐specific T cells in inflamed spinal cord microvessels of WT or E/P‐selectin−/− SJL/J mice during EAE. T‐cell rolling but not T‐cell capture was completely abrogated in the absence of either PSGL‐1 or E‐ and P‐selectin, resulting in a significantly reduced number of T cells able to firmly adhere in the inflamed spinal cord microvessels, but did not lead to reduced T‐cell invasion into the CNS parenchyma. Thus, PSGL‐1 interaction with E/P‐selectin is essential for T‐cell rolling in inflamed spinal cord microvessels during EAE. Taken together with previous observations, our findings show that T‐cell rolling is not required for successful T‐cell entry into the CNS and initiation of EAE.
Granulocyte colony-stimulating factor (G-CSF)-mediated mobilization of hematopoietic stem cells (HSCs) is a well-established method to prepare HSCs for transplantation nowadays. A sufficient number ...of HSCs is critical for successful HSC transplantation. However, approximately 2-6% of healthy stem cell donors are G-CSF-poor mobilizers for unknown reasons; thus increasing the uncertainties of HSC transplantation. The mechanism underlining G-CSF-mediated HSC mobilization remains elusive, so detailed mechanisms and an enhanced HSC mobilization strategy are urgently needed. Evidence suggests that P-selectin and P-selectin glycoprotein ligand-1 (PSGL-1) are one of the cell-cell adhesion ligand-receptor pairs for HSCs to keep contacting bone marrow (BM) stromal cells before being mobilized into circulation. This study hypothesized that blockage of PSGL-1 and P-selectin may disrupt HSC-stromal cell interaction and facilitate HSC mobilization.
The plasma levels of soluble P-selectin (sP-sel) before and after G-CSF administration in humans and male C57BL/6J mice were analyzed using enzyme-linked immunosorbent assay. Male mice with P-selectin deficiency (Selp
) were further employed to investigate whether P-selectin is essential for G-CSF-induced HSC mobilization and determine which cell lineage is sP-sel derived from. Finally, wild-type mice were injected with either G-CSF or recombinant sP-sel to investigate whether sP-sel alone is sufficient for inducing HSC mobilization and whether it accomplishes this by binding to HSCs and disrupting their interaction with stromal cells in the BM.
A significant increase in plasma sP-sel levels was observed in humans and mice following G-CSF administration. Treatments of G-CSF induced a decrease in the level of HSC mobilization in Selp
mice compared with the wild-type (Selp
) controls. Additionally, the transfer of platelets derived from wild-type mice can ameliorate the defected HSC mobilization in the Selp
recipients. G-CSF induces the release of sP-sel from platelets, which is sufficient to mobilize BM HSCs into the circulation of mice by disrupting the PSGL-1 and P-selectin interaction between HSCs and stromal cells. These results collectively suggested that P-selectin is a critical factor for G-CSF-induced HSC mobilization.
sP-sel was identified as a novel endogenous HSC-mobilizing agent. sP-sel injections achieved a relatively faster and more convenient regimen to mobilize HSCs in mice than G-CSF. These findings may serve as a reference for developing and optimizing human HSC mobilization in the future.
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