The Role of Sphingosine-1-Phosphate (S1P) in Thrombopoiesis

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. SCI-54-SCI-54
Author(s):  
Steffen Massberg
Keyword(s):  
Conflicts Of Interest ◽  
Multiphoton Microscopy ◽  
Lipid Mediator ◽  
Severe Thrombocytopenia ◽  
Time Loss ◽  
Sphingosine Kinase 2 ◽  
Sphingosine 1 Phosphate ◽  
S1p Receptor

Abstract Human megakaryocytes (MKs) release trillions of platelets each day into the circulation to maintain normal homeostatic platelet levels. However, the signals that control platelet biogenesis in vivo remain incompletely understood. We have recently identified that extracellular sphingosine 1-phosphate (S1P) plays a key role in thrombopoiesis. Using conditional mutants and intravital multiphoton microscopy, we demonstrate that the lipid mediator S1P serves as a critical directional cue guiding the elongation of megakaryocytic proplatelet (PP) extensions from the interstitium into bone marrow sinusoids and triggering the subsequent shedding of PPs into the blood. Correspondingly, mice lacking the S1P receptor S1pr1 develop severe thrombocytopenia caused by both formation of aberrant extravascular PPs and defective intravascular PP shedding. In contrast, activation of S1pr1 signaling leads to the prompt release of new platelets into the circulating blood. In addition to its role as an extracellular mediator, S1P can also function as a second messenger within the intracellular compartment. Correspondingly, we have demonstrated that MKs express the S1P-generating enzyme sphingosine kinase 2 (Sphk2). Sphk2 predominantly localizes to the nucleus and is the major source of intracellular S1P in MKs. Loss of Sphk2 significantly reduced intracellular S1P in MKs and downregulated the expression and activity of Src family kinases (SFKs). At the same time, loss of Sphk2 and inhibition of SFK activity resulted in defective intravascular PP shedding, the final stage of thrombopoiesis. Correspondingly, mice lacking Sphk2 in the hematopoietic system display thrombocytopenia. Collectively, our findings uncover a novel function of S1P as master regulator of efficient thrombopoiesis and might raise new therapeutic options for patients with thrombocytopenia. Disclosures No relevant conflicts of interest to declare.

scholarly journals A novel role of sphingosine 1-phosphate receptor S1pr1 in mouse thrombopoiesis

2012 ◽  
Vol 209 (12) ◽  
pp. 2165-2181 ◽  
Author(s):  
Lin Zhang ◽  
Martin Orban ◽  
Michael Lorenz ◽  
Verena Barocke ◽  
Daniel Braun ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Multiphoton Microscopy ◽  
Therapeutic Options ◽  
Lipid Mediator ◽  
Severe Thrombocytopenia ◽  
Master Regulator ◽  
Sphingosine 1 Phosphate ◽  
S1p Receptor

Millions of platelets are produced each hour by bone marrow (BM) megakaryocytes (MKs). MKs extend transendothelial proplatelet (PP) extensions into BM sinusoids and shed new platelets into the blood. The mechanisms that control platelet generation remain incompletely understood. Using conditional mutants and intravital multiphoton microscopy, we show here that the lipid mediator sphingosine 1-phosphate (S1P) serves as a critical directional cue guiding the elongation of megakaryocytic PP extensions from the interstitium into BM sinusoids and triggering the subsequent shedding of PPs into the blood. Correspondingly, mice lacking the S1P receptor S1pr1 develop severe thrombocytopenia caused by both formation of aberrant extravascular PPs and defective intravascular PP shedding. In contrast, activation of S1pr1 signaling leads to the prompt release of new platelets into the circulating blood. Collectively, our findings uncover a novel function of the S1P–S1pr1 axis as master regulator of efficient thrombopoiesis and might raise new therapeutic options for patients with thrombocytopenia.

scholarly journals Murine platelet production is suppressed by S1P release in the hematopoietic niche, not facilitated by blood S1P sensing

2019 ◽  
Vol 3 (11) ◽  
pp. 1702-1713 ◽  
Author(s):  
Hira Niazi ◽  
Nesrine Zoghdani ◽  
Ludovic Couty ◽  
Alexandre Leuci ◽  
Anja Nitzsche ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Lipid Mediator ◽  
Gradient Sensing ◽  
Platelet Production ◽  
Platelet Counts ◽  
Sphingosine Kinase 2 ◽  
Clinical Observations ◽  
Sphingosine 1 Phosphate ◽  
Hematopoietic Niche

Abstract The bioactive lipid mediator sphingosine 1-phosphate (S1P) was recently assigned critical roles in platelet biology: whereas S1P1 receptor-mediated S1P gradient sensing was reported to be essential for directing proplatelet extensions from megakaryocytes (MKs) toward bone marrow sinusoids, MK sphingosine kinase 2 (Sphk2)–derived S1P was reported to further promote platelet shedding through receptor-independent intracellular actions, and platelet aggregation through S1P1. Yet clinical use of S1P pathway modulators including fingolimod has not been associated with risk of bleeding or thrombosis. We therefore revisited the role of S1P in platelet biology in mice. Surprisingly, no reduction in platelet counts was observed when the vascular S1P gradient was ablated by impairing S1P provision to plasma or S1P degradation in interstitial fluids, nor when gradient sensing was impaired by S1pr1 deletion selectively in MKs. Moreover, S1P1 expression and signaling were both undetectable in mature MKs in situ, and MK S1pr1 deletion did not affect platelet aggregation or spreading. When S1pr1 deletion was induced in hematopoietic progenitor cells, platelet counts were instead significantly elevated. Isolated global Sphk2 deficiency was associated with thrombocytopenia, but this was not replicated by MK-restricted Sphk2 deletion and was reversed by compound deletion of either Sphk1 or S1pr2, suggesting that this phenotype arises from increased S1P export and S1P2 activation secondary to redistribution of sphingosine to Sphk1. Consistent with clinical observations, we thus observe no essential role for S1P1 in facilitating platelet production or activation. Instead, S1P restricts megakaryopoiesis through S1P1, and can further suppress thrombopoiesis through S1P2 when aberrantly secreted in the hematopoietic niche.

Sphingosine 1-phosphate signaling contributes to cardiac inflammation, dysfunction, and remodeling following myocardial infarction

2016 ◽  
Vol 310 (2) ◽  
pp. H250-H261 ◽  
Author(s):  
Fuyang Zhang ◽  
Yunlong Xia ◽  
Wenjuan Yan ◽  
Haoqiang Zhang ◽  
Fen Zhou ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Cardiac Remodeling ◽  
Dependent Manner ◽  
Cardiac Inflammation ◽  
Proinflammatory Responses ◽  
Sphingosine 1 Phosphate ◽  
S1p Receptor ◽  
S1p Lyase

Sphingosine 1-phosphate (S1P) mediates multiple pathophysiological effects in the cardiovascular system. However, the role of S1P signaling in pathological cardiac remodeling following myocardial infarction (MI) remains controversial. In this study, we found that cardiac S1P greatly increased post-MI, accompanied with a significant upregulation of cardiac sphingosine kinase-1 (SphK1) and S1P receptor 1 (S1PR1) expression. In MI-operated mice, inhibition of S1P production by using PF543 (the SphK1 inhibitor) ameliorated cardiac remodeling and dysfunction. Conversely, interruption of S1P degradation by inhibiting S1P lyase augmented cardiac S1P accumulation and exacerbated cardiac remodeling and dysfunction. In the cardiomyocyte, S1P directly activated proinflammatory responses via a S1PR1-dependent manner. Furthermore, activation of SphK1/S1P/S1PR1 signaling attributed to β1-adrenergic receptor stimulation-induced proinflammatory responses in the cardiomyocyte. Administration of FTY720, a functional S1PR1 antagonist, obviously blocked cardiac SphK1/S1P/S1PR1 signaling, ameliorated chronic cardiac inflammation, and then improved cardiac remodeling and dysfunction in vivo post-MI. In conclusion, our results demonstrate that cardiac SphK1/S1P/S1PR1 signaling plays an important role in the regulation of proinflammatory responses in the cardiomyocyte and targeting cardiac S1P signaling is a novel therapeutic strategy to improve post-MI cardiac remodeling and dysfunction.

scholarly journals Chemorepulsion by blood S1P regulates osteoclast precursor mobilization and bone remodeling in vivo

2010 ◽  
Vol 207 (13) ◽  
pp. 2793-2798 ◽  
Author(s):  
Masaru Ishii ◽  
Junichi Kikuta ◽  
Yutaka Shimazu ◽  
Martin Meier-Schellersheim ◽  
Ronald N. Germain
Keyword(s):  
Bone Remodeling ◽  
Lipid Mediator ◽  
Migratory Behavior ◽  
Bone Surface ◽  
Reciprocal Regulation ◽  
Sphingosine 1 Phosphate ◽  
S1p Receptor ◽  
Deficient Mice ◽  
High Inhibition

Sphingosine-1-phosphate (S1P), a lipid mediator enriched in blood, controls the dynamic migration of osteoclast (OC) precursors (OPs) between the blood and bone, in part via the S1P receptor 1 (S1PR1) which directs positive chemotaxis toward S1P. We show that OPs also express S1PR2, an S1P receptor which mediates negative chemotaxis (or chemorepulsion). OP-positive chemotaxis is prominent in gradients with low maximal concentrations of S1P, whereas such behavior is minimal in fields with high maximal S1P concentrations. This reverse-directional behavior is caused by S1PR2-mediated chemorepulsion acting to override S1PR1 upgradient motion. S1PR2-deficient mice exhibit moderate osteopetrosis as a result of a decrease in osteoclastic bone resorption, suggesting that S1PR2 contributes to OP localization on the bones mediated by chemorepulsion away from the blood where S1P levels are high. Inhibition of S1PR2 function by the antagonist JTE013 changed the migratory behavior of monocytoid cells, including OPs, and relieved osteoporosis in a mouse model by limiting OP localization and reducing the number of mature OCs attached to the bone surface. Thus, reciprocal regulation of S1P-dependent chemotaxis controls bone remodeling by finely regulating OP localization. This regulatory axis may be promising as a therapeutic target in diseases affecting OC-dependent bone remodeling.

Mutation-specific hemostatic variability in mice expressing common type 2B von Willebrand disease substitutions

Blood ◽  
2010 ◽  
Vol 115 (23) ◽  
pp. 4862-4869 ◽  
Author(s):  
Mia Golder ◽  
Cynthia M. Pruss ◽  
Carol Hegadorn ◽  
Jeffrey Mewburn ◽  
Kimberly Laverty ◽  
...  
Keyword(s):  
Ferric Chloride ◽  
Von Willebrand Disease ◽  
Expression Vectors ◽  
Severe Thrombocytopenia ◽  
Normal Platelet ◽  
Injury Model ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Type 2B von Willebrand disease (2B VWD) results from von Willebrand factor (VWF) A1 mutations that enhance VWF-GPIbα binding. These “gain of function” mutations lead to an increased affinity of the mutant VWF for platelets and the binding of mutant high-molecular-weight VWF multimers to platelets in vivo, resulting in an increase in clearance of both platelets and VWF. Three common 2B VWD mutations (R1306W, V1316M, and R1341Q) were independently introduced into the mouse Vwf cDNA sequence and the expression vectors delivered to 8- to 10-week-old C57Bl6 VWF−/− mice, using hydrodynamic injection. The resultant phenotype was examined, and a ferric chloride–induced injury model was used to examine the thrombogenic effect of the 2B VWD variants in mice. Reconstitution of only the plasma component of VWF resulted in the generation of the 2B VWD phenotype in mice. Variable thrombocytopenia was observed in mice expressing 2B VWF, mimicking the severity seen in 2B VWD patients: mice expressing the V1316M mutation showed the most severe thrombocytopenia. Ferric chloride–induced injury to cremaster arterioles showed a marked reduction in thrombus development and platelet adhesion in the presence of circulating 2B VWF. These defects were only partially rescued by normal platelet transfusions, thus emphasizing the key role of the abnormal plasma VWF environment in 2B VWD.

scholarly journals Impact of Platelet Count on Bleeding in the Setting of Anti-Platelet Therapy

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 18-18
Author(s):  
Robert Hugh Lee ◽  
Wolfgang Bergmeier
Keyword(s):  
Real Time ◽  
Conflicts Of Interest ◽  
Thrombotic Event ◽  
Platelet Inhibition ◽  
Intravital Imaging ◽  
Severe Thrombocytopenia ◽  
Platelet Counts ◽  
Anti Platelet Therapy ◽  
The Impact

Anti-platelet therapy (APT) is used for secondary prevention of thrombosis. The most commonly prescribed anti-platelet drugs are aspirin and P2Y12 inhibitors, including clopidogrel, prasugrel and ticagrelor. Dual anti-platelet therapy (DAPT) consisting of aspirin and a P2Y12 inhibitor is often used in the first 1-12 months after an initial thrombotic event and has a greater anti-thrombotic effect than single agents, but is also associated with a higher risk of bleeding. Due to this risk of hemorrhage, the appropriate use of DAPT in patients requiring percutaneous coronary intervention (PCI) with baseline or periprocedural thrombocytopenia remains unclear. To study the impact of thrombocytopenia on bleeding with APT, we used intravital imaging in a murine hemostasis model and adoptive platelet transfer to generate mice with specific platelet counts with or without platelet inhibition. To generate experimental mice, we used transgenic mice in which platelets express a chimeric GPIb receptor with the extracellular domain replaced with a domain of the human IL-4R (hIL-4R/GPIb-Tg). Endogenous platelets were depleted by injection of anti-hIL-4R antibody, and the recipient mice were then transfused with wild-type (WT) platelets from donor mice treated, or not, with single or dual APT (aspirin 20 mg/kg; clopidogrel 25 mg/kg) to achieve specific platelet counts ranging from 50,000 to 400,000 platelets/μL. We also compared these mice with WT mice (with normal platelet counts, ~1,200,000 platelets/μL) treated with APT. Platelet inhibition was confirmed prior to performing in vivo experiments. Hemostasis was determined by intravital imaging in our saphenous vein laser injury model, in which a 50 μm injury was induced by laser ablation. Real-time top-down epifluorescence imaging was used to determine time to initial hemostasis, rebleeding events, and platelet and fibrin accumulation. In each mouse, 3-5 injuries were induced at different sites and each injury was visualized for 10 minutes. Following real-time imaging, spinning disk confocal Z-stacks of platelet plugs were obtained for 3D reconstruction to compare platelet plug volume. In untreated WT mice, hemostasis was achieved in ~20 seconds. In WT mice treated with DAPT, initial hemostasis was often rapidly achieved but this was followed by significant rebleeding events. Paradoxically, platelet accumulation was increased in WT + DAPT mice due to extravascular accumulation of platelets which occurred during bleeding. However, in plugs that stabilized, plug volume was reduced in WT + DAPT mice. In hIL-4R/GPIb-Tg mice with reduced platelet counts, untreated platelets were able to form a stable hemostatic plug even at 50,000/μL, although time to hemostasis was slightly prolonged. However, as platelet counts decreased in mice with DAPT-treated platelets, initial hemostasis became more prolonged and many injuries never achieved initial hemostasis. These results suggest that DAPT may not be safe in the setting of severe thrombocytopenia. Disclosures No relevant conflicts of interest to declare.

scholarly journals Thrombocytopenia in septicemia: the role of disseminated intravascular coagulation

Blood ◽  
1980 ◽  
Vol 56 (1) ◽  
pp. 88-92 ◽  
Author(s):  
PB Neame ◽  
JG Kelton ◽  
IR Walker ◽  
IO Stewart ◽  
HL Nossel ◽  
...  
Keyword(s):  
Disseminated Intravascular Coagulation ◽  
Gel Chromatography ◽  
Severe Thrombocytopenia ◽  
Intravascular Coagulation ◽  
Platelet Counts ◽  
Normal Platelet ◽  
Platelet Survival ◽  
Possible Cause

Abstract The mechanism of isolated thrombocytopenia in septicemia is unknown, but compensated disseminated intravascular coagulation (DIC) has been suggested as a possible cause. To investigate this possibility, platelet counts and sensitive assays for in vivo thrombin and plasmin generation, including fibrinogen gel chromatography and fibrinopeptide A (FPA) assays, were obtained on 31 septicemic patients. Fifteen of 17 patients with gram-negative septicemia and 8 of 14 patients with gram- positive septicemia had thrombocytopenia. Platelet survival studied demonstrated a decreased platelet survival. In 11 of 12 patients with severe thrombocytopenia (platelet count less than 50,000mul), there was laboratory evidence of intravascular coagulation. In contrast, there was little evidence of intravascular coagulation in 8 of 11 patients with moderate thrombocytopenia (platelet counts 50,000 to less than 150,000/mul) or in 7 of 8 patients with normal platelet counts. This report indicates that while DIC accompanies thrombocytopenia in many patients with severe thrombocytopenia, there is frequently little evidence for intravascular coagulation in patients with moderate thrombocytopenia. It is apparent that factors other than intravascular thrombin must play a role in producing the thrombocytopenia of septicemia.

Sphingosine‐1‐phosphate (S1P) induces potent anti‐inflammatory effects in vitro and in vivo by S1P receptor 4‐mediated suppression of 5‐lipoxygenase activity

2018 ◽  
Vol 33 (2) ◽  
pp. 1711-1726 ◽  
Author(s):  
Jasmin Fettel ◽  
Benjamin Kühn ◽  
Nathalie A. Guillen ◽  
Duran Sürün ◽  
Marcus Peters ◽  
...  
Keyword(s):  
Lipoxygenase Activity ◽  
Sphingosine 1 Phosphate ◽  
S1p Receptor ◽  
Anti Inflammatory

Modulation of Mesenchymal Stem Cell MHC-I Complex Increases Engraftment In Vivo.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1457-1457
Author(s):  
Melisa Soland ◽  
Evan J Colletti ◽  
Mariana Bego ◽  
Chad Sanada ◽  
Christopher D Porada ◽  
...  
Keyword(s):  
Nk Cells ◽  
Conflicts Of Interest ◽  
Surface Expression ◽  
Large Animal ◽  
Specific Lysis ◽  
Fetal Sheep ◽  
Mhc I ◽  
Npt Ii

Abstract Abstract 1457 Mesenchymal stem cells (MSC) are good candidates for cell therapies due to their immunomodulatory properties, ability to home to/engraft damaged tissues, and potential to differentiate into different cell types. However, when transplanted (Tx) in an allogeneic setting, MSC can elicit an immune response, activating the recipient's cytotoxic T lymphocytes (CTL) and Natural Killer (NK) cells, resulting in rejection of the Tx cells and reduced therapeutic efficacy. Human cytomegalovirus (HCMV, has developed several strategies to evade CTL and NK cell recognition. HCMV avoids CTL attack by producing proteins that downregulate MHC-I surface expression. These proteins are coded for by the unique short regions (US) 2, 3, 6 and 11 of HCMV's genome. We have previously shown that when MSC are transduced with retroviral vectors encoding each one of these US proteins, US6 and US11 were the most effective in reducing MSC's HLA-I surface expression and allogeneic CTL recognition and proliferation. However, HLA-I downregulation may render MSC transduced with US6 (MSC-US6) and US11 (MSC-US11) more susceptible to NK killing, undermining MSC's inherent ability to inhibit function of allogeneic NK cells. Here, we first investigated the role of US6 or US11 on MSC allorecognition by NK cells, and on MSC in vivo engraftment capability. NK killing assays demonstrated that US11 generated the most protective effect at the highest NK concentration (E:T ratio 20:1) (% specific lysis for MSC-US6: 60.4 ± 5.7 %; MSC-US11: 45.5 ± 2.4 % vs. MSC: 88.5 ± 3.4 % respectively). However, at an E:T ratio of 10:1 and 5:1 US11 produced the same degree of protection as US6 (E:T ratio of 10:1; % specific lysis for MSC-US6: 30.1 ± 5.6 %; MSC-US11: 26.3 ± 1.9 % vs. MSC: 54.7 ± 1.9 %); (E:T ratio 5:1; % specific lysis for MSC-US6: 11.9 ± 4.2; MSC-US11: 13.4 ± 2.3; vs. MSC: 25.5 ± 4 respectively). Only at an E:T ratio of 1:1 were US6 and US11 similar to untransduced MSCs (% specific lysis for MSC-US6: 4.7 ± 1.6; MSC-US11: 2.1 ± 0.5; vs. MSC: 4.9 ± 1.8; respectively) in terms of inhibition of NK killing. We also studied the role of US6 and 11 on the expression of beta-2-microglobulin (b2m) and other HLA-I molecules, and we found that US6 reduced b2m by 87± 2 % and HLA-G1 by 44±4.7 %, while US11 reduced b2m by 70± 0.6 % but increased HLA-G1 expression by 176.6±1.9 %. Therefore, the increase in HLA-G1 expression induced by US11 may explain the decrease in NK killing observed in the MSC-US11 cells. Furthermore, we investigated whether US6 or US11 could play a role in mediating complement resistance. While US6 increased the expression of CD59 in transduced cells (Mean fluorescence intensity (MFI) increased by 123.3±1), US11 increased the number of cells expressing CD59 by 121.4 ± 0.8 %, but did not modify their MFI. We next compared the in vivo engraftment potential of MSC, MSC-US6 and MSC-US11 by Tx 5.6×10^4 of each cell population into fetal sheep at 60 days of gestation (n=6). Since we have previously reported the ability of MSC to generate liver cells, we first investigated whether the expression of US6 and 11 would allow higher levels of liver engraftment and hepatocyte formation when compared to MSC (MSC-E) transduced with a retroviral vector encoding only NPT-II. Two months after Tx, liver tissues were collected and stained with NPT-II antibody. This revealed that US6 and US11 increased engraftment efficiency by 241% for MSC-US6 and 277% for MSC-US11 (MSC-E: 5.3 ± 0.4 %, MSC-US6: 12.8 ± 0.9 % and MSC-US:11 14.7 ± 0.8 %). Despite the higher level of liver engraftment seen with MSC-US6 and MSC-US11, co-expression of NPT-II and albumin (MSC-US6: 57% MSC-US1: 50% MSC-E: 75%) or NPT-II and Ov-6 was found at significantly lower levels in MSC-US11 and MSC-US6 Tx animals than in those Tx with MSC-E. Nevertheless, similar numbers of NPT-II/CD34 double-positive cells were found in the liver of MSC-US6 and MSC-US11 Tx animals when compared to MSC-E alone. In conclusion, engineering MSC to over-express US6 or US11 is an effective way to reduce CTL proliferation, NK killing and destruction of engrafted cells by the complement membrane attack complex. In agreement with the in vitro studies, transplantation of these cells into a large animal sheep model resulted in significantly higher levels of overall cell engraftment, but not differentiation towards a hepatocytic phenotype. Studies are underway to determine the mechanism by which HCMV proteins are interfering with MSC differentiation. Disclosures: No relevant conflicts of interest to declare.

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