scholarly journals Procoagulant Platelets

Platelets ◽  
2020 ◽  
Author(s):  
Andaleb Kholmukhamedov
Keyword(s):  
Adhesive Properties ◽  
Protease Activated Receptors ◽  
Glycoprotein Vi ◽  
Activated Platelets ◽  
Functional Features ◽  
Phenotypic Features ◽  
Stimulation Of

There are two well-known subpopulations of activated platelets: pro-aggregatory and procoagulant. Procoagulant platelets represent a subpopulation of activated platelets, which are morphologically and functionally distinct from pro-aggregatory ones. Although various names have been used to describe these platelets in the literature (CoaT, CoaTed, highly activated, ballooned, capped, etc.), there is a consensus on their phenotypic features including exposure of high levels of phosphatidylserine (PSer) on the surface; decreased aggregatory and adhesive properties; support of active tenase and prothrombinase complexes; maximal generation by co-stimulation of glycoprotein VI (GPVI) and protease-activated receptors (PAR). In this chapter, morphologic and functional features of procoagulant platelets, as well as the mechanisms of their formation, will be discussed.

scholarly journals Lyn, PKC-δ, SHIP-1 interactions regulate GPVI-mediated platelet-dense granule secretion

Blood ◽  
2009 ◽  
Vol 114 (14) ◽  
pp. 3056-3063 ◽  
Author(s):  
Ramya Chari ◽  
Soochong Kim ◽  
Swaminathan Murugappan ◽  
Archana Sanjay ◽  
James L. Daniel ◽  
...  
Keyword(s):  
Human Platelets ◽  
Sh2 Domain ◽  
Dense Granule ◽  
Protease Activated Receptors ◽  
Inositol Phosphatase ◽  
Glycoprotein Vi ◽  
Dense Granule Secretion ◽  
Granule Secretion ◽  
Granule Release ◽  
Stimulation Of

Protein kinase C-δ (PKC-δ) is expressed in platelets and activated downstream of protease-activated receptors (PARs) and glycoprotein VI (GPVI) receptors. We have previously shown that PKC-δ positively regulates PAR-mediated dense granule secretion, whereas it negatively regulates GPVI-mediated dense granule secretion. We further investigated the mechanism of such differential regulation of dense granule release by PKC-δ in platelets. SH2 domain–containing inositol phosphatase-1 (SHIP-1) is phosphorylated on Y1020, a marker for its activation, upon stimulation of human platelets with PAR agonists SFLLRN and AYPGKF or GPVI agonist convulxin. GPVI-mediated SHIP-1 phosphorylation occurred rapidly at 15 seconds, whereas PAR-mediated phosphorylation was delayed, occurring at 1 minute. Lyn and SHIP-1, but not SHIP-2 or Shc, preferentially associated with PKC-δ on stimulation of platelets with a GPVI agonist, but not with a PAR agonist. In PKC-δ–null murine platelets, convulxin-induced SHIP-1 phosphorylation was inhibited. Furthermore, in Lyn null murine platelets, GPVI-mediated phosphorylations on Y-1020 of SHIP-1 and Y311 of PKC-δ were inhibited. In murine platelets lacking Lyn or SHIP-1, GPVI-mediated dense granule secretions are potentiated, whereas PAR-mediated dense granule secretions are inhibited. Therefore, we conclude that Lyn-mediated phosphorylations of PKC-δ and SHIP-1 and their associations negatively regulate GPVI-mediated dense granule secretion in platelets.

scholarly journals Differential Effects of Platelets Selectively Activated by Protease-Activated Receptors on Meniscal Cells

2019 ◽  
Vol 48 (1) ◽  
pp. 197-209 ◽  
Author(s):  
Hongyao Xu ◽  
Xiangjie Zou ◽  
Pengcheng Xia ◽  
Mohammad Ahmad Kamal Aboudi ◽  
Ran Chen ◽  
...  
Keyword(s):  
In Vivo Model ◽  
Enzyme Linked Immunosorbent Assay ◽  
Protease Activated Receptors ◽  
Activated Platelets ◽  
Meniscal Tissue ◽  
Vitro Model ◽  
High Level ◽  
Meniscal Cells

Background: Meniscal injury is very common, and injured meniscal tissue has a limited healing ability because of poor vascularity. Platelets contain both pro- and anti-angiogenic factors, which can be released by platelet selective activation. Hypothesis: Platelets release a high level of vascular endothelial growth factor (VEGF) when they are activated by protease-activated receptor 1 (PAR1), whereas the platelets release endostatin when they are activated by protease-activated receptor 4 (PAR4). The PAR1-treated platelets enhance the proliferation of meniscal cells in vitro and promote in vivo healing of wounded meniscal tissue. Study Design: Controlled laboratory study. Method: Platelets were isolated from human blood and activated with different reagents. The released growth factors from the activated platelets were determined by immunostaining and enzyme-linked immunosorbent assay. The effects of the platelets with different treatments on meniscal cells were tested by an in vitro model of cell culture and an in vivo model of wounded meniscal healing. Results: The results indicated that platelets contained both pro- and antiangiogenic factors including VEGF and endostatin. In unactivated platelets, VEGF and endostatin were contained inside of the platelets. Both VEGF and endostatin were released from the platelets when they were activated by thrombin. However, only VEGF was released from the platelets when they were activated by PAR1, and only endostatin was released from the platelets when they were activated by PAR4. The rat meniscal cells grew much faster in the medium that contained PAR1-activated platelets than in the medium that contained either PAR4-activated platelets or unactivated platelets. The wounds treated with PAR1-activated platelets healed faster than those treated with either PAR4-activated platelets or unactivated platelets. Many blood vessel–like structures were found in the wounded menisci treated with PAR1-activated platelets. Conclusion: The PAR1-activated platelets released high levels of VEGF, which increased the proliferation of rat meniscal cells in vitro, enhanced the vascularization of menisci in vivo, and promoted healing of wounded menisci. Clinical Relevance: Our results suggested that selective activated platelets can be used clinically to enhance healing of wounded meniscal tissue.

scholarly journals Effects of the stimulation of protease-activated receptors on Ca2+ signaling, cell morphology and proliferation in A172 human glioblastoma

1999 ◽  
Vol 79 ◽  
pp. 143
Author(s):  
Takahiro Okamoto ◽  
Masahiro Nishibori ◽  
Hiromi Iwagaki ◽  
Ken Sawada ◽  
Naoki Nakaya ◽  
...  
Keyword(s):  
Cell Morphology ◽  
Protease Activated Receptors ◽  
Human Glioblastoma ◽  
Stimulation Of

Role of Lipid Rafts in GPVI Agonist-Induced Platelet Signaling.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3576-3576
Author(s):  
Patricia G. Quinter ◽  
Todd M. Quinton ◽  
Carol A. Dangelmaier ◽  
Satya P. Kunapuli ◽  
James L. Daniel
Keyword(s):  
Platelet Aggregation ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Glycoprotein Vi ◽  
Activated Platelets ◽  
Low Concentrations ◽  
Multiple Receptors ◽  
Platelet Signaling ◽  
Collagen Receptor

Abstract The collagen receptor glycoprotein VI (GPVI), plays an essential role in platelet activation and the regulation of hemostasis. Microdomains within the plasma membrane, called lipid rafts, have been implicated in GPVI signaling. The GPVI receptor has been shown to associate with the lipid rafts in both resting and activated platelets. It has been reported that there is a reduction in GPVI signaling in raft-disrupted platelets following activation with various GPVI agonists, especially at low to moderate agonist concentrations. Since platelet aggregation is potentiated by secreted adenosine 5′-diphosphate (ADP) at low concentrations of convulxin and at all concentrations of collagen and collagen-related peptide (CRP), we wanted to determine whether the decrease in GPVI signaling found in platelets with disrupted rafts was due to the loss of agonist potentiation by ADP. We compared platelet aggregation, protein phosphorylation, and calcium mobilization in platelets with intact and disrupted lipid rafts following activation with the GPVI agonists, collagen, convulxin and CRP. We show that lipid raft disruption inhibits aggregation induced by collagen and convulxin, but this inhibition is no longer apparent in the presence of ADP feedback inhibitors. Furthermore, raft-disrupted platelets had the same level of phosphorylation of proteins involved in GPVI signaling (i.e. Syk, LAT, and PLCγ2) and the same ability to mobilize calcium following activation with collagen or convulxin. Therefore, the effects of lipid raft disruption on aggregation can be attributed to the loss of ADP feedback. Interestingly, however, raft disruption directly inhibited aggregation and Syk phosphorylation induced by CRP in the presence and absence of ADP feedback. We propose that these differences are due to the fact that CRP is a relatively small, synthesized peptide of 37 amino acids, while collagen and convulxin are large ligands. These agonists are all able to bind the GPVI receptor, but they may not have the same ability to simultaneously cluster multiple receptors due to their size differential. The lipid rafts may be important for CRP stimulation, but not for collagen or convulxin, because they may have a higher density of the GPVI receptor than nonraft membrane regions, allowing CRP to cluster multiple receptors and activate the GPVI signaling cascade. When we disrupt the lipid rafts, we are reducing the effective concentration of GPVI available for activation by CRP but not by collagen or convulxin.

Critical Role for Cyclophilin D and the Mitochondrial Permeability Transition Pore (MPTP) in Platelet Activation.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1508-1508 ◽  
Author(s):  
Shawn M. Jobe ◽  
Katina M. Wilson ◽  
Lori Leo ◽  
Jeffery D. Molkentin ◽  
Steven R. Lentz ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Mitochondrial Permeability Transition ◽  
Critical Role ◽  
In Vitro Tests ◽  
Cyclophilin D ◽  
Wild Type ◽  
Glycoprotein Vi ◽  
Stimulation Of

Abstract Dual stimulation of platelets with thrombin and collagen results in the formation of a unique subpopulation of highly activated platelets. Characteristics of the highly activated platelet subpopulation includeincreased surface retention of procoagulant alpha granule proteins,high-level phosphatidylserine (PS) externalization, andmodulation of the fibrinogen receptor αIIbβ3 as evidenced by their decreased recognition by antibodies to activated αIIbβ3 such as PAC-1 and JON/A. Formation of the highly activated platelet subpopulation is closely correlated with a rapid loss of mitochondrial transmembrane potential (ΔΨm), a marker of MPTP formation. To test whether formation of the MPTP might regulate the development of the highly activated platelet subpopulation, platelet activation responses were examined in the presence of inhibitors and activators of MPTP formation. Cyclosporine, an inhibitor of MPTP formation, inhibited both PS externalization and αIIbβ3 modulation following dual stimulation with thrombin and the glycoprotein VI agonist convulxin (58 ± 4% vs. 9 ± 3%, p<0.01). Conversely, thrombin stimulation of platelets in the presence of H2O2 (100μM), an MPTP activator, increased PS externalization and αIIbβ3 modulation relative to platelets stimulated with thrombin alone (11 ± 3% vs. 48 ± 6%, p<0.05). Platelet activation responses were examined in cyclophilin D null (CypD −/−) mice, which have marked impairment of MPTP formation. Following dual agonist stimulation with thrombin and convulxin, both αIIbβ3 modulation and platelet PS externalization were significantly abrogated in CypD −/− platelets relative to wild type (7 ± 1% vs. 69 ± 1%, p<0.01). Alpha granule release, however, was unaffected in the absence of CypD. In vitro tests of platelet function similarly demonstrated that CypD −/− platelets had marked impairment of platelet prothrombinase activity relative to wild-type platelets after stimulation with thrombin and convulxin, but normal platelet aggregation responses. We then tested the hypothesis that CypD −/− mice would have an altered thrombotic response to arterial injury. Following photochemical injury of the carotid artery endothelium, a stable occlusive thrombus formed more rapidly in CypD −/− than in wild-type mice (16 ± 2 vs. 32 ± 7 min, p<0.05). Tail-bleeding time was unaffected. These results strongly implicate cyclophilin D and the MPTP as critical regulators of the subset of platelet activation responses occurring in the highly activated platelet subpopulation and suggest that activation of this novel platelet mitochondrial signaling pathway might play an important role in the regulation of the thrombotic response in vivo.

scholarly journals Differential effects of reduced glycoprotein VI levels on activation of murine platelets by glycoprotein VI ligands

2002 ◽  
Vol 368 (1) ◽  
pp. 293-300 ◽  
Author(s):  
Daniel C. SNELL ◽  
Valerie SCHULTE ◽  
Gavin E. JARVIS ◽  
Kanako ARASE ◽  
Daiju SAKURAI ◽  
...  
Keyword(s):  
Marked Effect ◽  
Protein Tyrosine Phosphorylation ◽  
Wild Type ◽  
Glycoprotein Vi ◽  
Coated Surface ◽  
The Right ◽  
Static Conditions ◽  
Blocking Antibodies ◽  
Snake Toxin ◽  
Stimulation Of

We have investigated the effects of decreased levels of the complex between glycoprotein VI (GPVI) and the Fc receptor γ-chain (FcRγ) on responses to collagen and GPVI-specific ligands in murine platelets. We show that levels of GPVI—FcRγ of the order of 50% and 20% of wild-type levels caused 2- and 5-fold shifts to the right respectively in the dose—response curve for aggregation in response to collagen, the snake toxin convulxin and the monoclonal antibody JAQ1. In addition, there is a delay in the onset of aggregation in response to collagen. In contrast, the stimulation of protein tyrosine phosphorylation by collagen (as measured after 150s) and adhesion to a collagen-coated surface under static conditions were unaffected in platelets with 50% and 20% of wild-type levels of GPVI. In contrast, responses to a collagen-related peptide (CRP), made up of repeat glycine-proline-hydroxyproline motifs, were markedly inhibited and abolished in platelets expressing 50% and 20% of wild-type levels of GPVI respectively. We suggest that the marked effect of a reduction in GPVI levels on the CRP-induced activation of platelets is due to the multivalent nature of CRP and the fact that GPVI is its sole receptor on platelets. Thus it appears that the interaction of CRP with GPVI is determined by a combination of affinity and avidity. The observation that collagen does not behave like CRP in platelets expressing reduced levels of GPVI, even in the combined presence of blocking antibodies against integrin α2β1 and GPV, suggests that collagen has a greater affinity than CRP for GPVI, and/or that other receptors are involved in its binding to platelets. The clinical significance of these results is discussed.

scholarly journals Changes in the activity of ovine blood-derived macrophages stimulated with antimicrobial peptide extract (AMP) or platelet-rich plasma (PRP)

2019 ◽  
Vol 63 (2) ◽  
pp. 235-242
Author(s):  
Joanna Wessely-Szponder ◽  
Tomasz Szponder ◽  
Ryszard Bobowiec ◽  
Joanna Michalska
Keyword(s):  
Antimicrobial Activity ◽  
Growth Factors ◽  
Soft Tissue ◽  
Platelet Rich Plasma ◽  
Innate Immune ◽  
Ros Generation ◽  
Soft Tissue Healing ◽  
Tissue Healing ◽  
Functional Features ◽  
Stimulation Of

AbstractIntroduction: Antimicrobial peptides (AMP) are a large group of innate immune effectors, which apart from antimicrobial activity show immunomodulative properties. Platelet-rich plasma (PRP) is a source of autologous growth factors and is used for stimulation of bone and soft tissue healing. The purpose of this study was to assess the influence of PRP and AMP extract on ovine monocyte-derived macrophage cultures. Material and Methods: The study was conducted on ovine macrophages (Mfs) previously stimulated with LPS or dexamethasone and then with preparations of PRP or AMP. Following activation of the Mfs their morphological and functional features were assessed. Results: The study revealed pro-inflammatory influence of both examined preparations on Mfs cultures on the basis of morphology, ROS generation and arginase activity. Both preparations enhanced the pro-inflammatory response of cultured Mfs. Conclusion: This activity may intensify the antimicrobial action of Mfs, however, in cases of excessive and prolonged inflammation the use of these preparations should be limited.

scholarly journals Regulation of stimulated integrin surface expression in human neutrophils by tyrosine phosphorylation

Blood ◽  
1994 ◽  
Vol 84 (2) ◽  
pp. 616-624 ◽  
Author(s):  
PH Naccache ◽  
N Jean ◽  
NW Liao ◽  
JM Bator ◽  
SR McColl ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Tyrosine Phosphorylation ◽  
Essential Element ◽  
Surface Expression ◽  
Human Neutrophils ◽  
Adhesive Properties ◽  
Cd11b Expression ◽  
Necrosis Factor Alpha ◽  
In Vivo Models ◽  
Stimulation Of

Abstract The control of the adhesive properties of human neutrophils is an essential element of their defense function. One level at which this control is exerted involves the upregulation of the surface expression of beta 2-integrins. In this study, we have examined the potential involvement of tyrosine phosphorylation in the latter process. Two inhibitors of tyrosine kinases with differing modes of action, erbstatin and herbimycin A, were found to inhibit the expression of CD11b and CD18 stimulated by chemotactic factors (fMet-Leu-Phe or leukotriene B4) or growth factors (tumor necrosis factor alpha). This inhibition was not shared by an inactive analog of erbstatin or by the protein kinase C inhibitor Ro 31–8330. Erbstatin also inhibited the unveiling of activation-specific neoepitopes detected by antibody CBRM1/5. Pretreatment of neutrophils (but not of endothelial cells) with erbstatin inhibited the stimulation of neutrophils' adherence to endothelial cells induced by fMet-Leu-Phe. Augmentation of tyrosine phosphorylation by inhibiting tyrosine phosphatases using hydroperoxyvanadate led to an increased surface expression of CD11b and CD18 and enhanced the adhesion of neutrophils to endothelial cells. Finally, the leumedin NPC 15669, which had previously been shown to inhibit stimulated CD11b expression and neutrophil adherence to endothelial cells and to exhibit anti-inflammatory properties in various in vivo models of inflammation, inhibited the stimulation of tyrosine, phosphorylation induced by fMet-Leu-Phe. Taken together, these data establish a strong correlation between tyrosine phosphorylation and integrin upregulation in stimulated human neutrophils.

Surface expression and functional characterization of α-granule factor V in human platelets: effects of ionophore A23187, thrombin, collagen, and convulxin

Blood ◽  
2000 ◽  
Vol 95 (5) ◽  
pp. 1694-1702 ◽  
Author(s):  
L. Alberio ◽  
O. Safa ◽  
K. J. Clemetson ◽  
C. T. Esmon ◽  
G. L. Dale
Keyword(s):  
Functional Characterization ◽  
Factor Xa ◽  
Annexin V ◽  
Surface Expression ◽  
Human Platelets ◽  
Ionophore A23187 ◽  
Factor V ◽  
Glycoprotein Vi ◽  
Activated Platelets ◽  
Simultaneous Activation

Factor V (FV) present in platelet -granules has a significant but incompletely understood role in hemostasis. This report demonstrates that a fraction of platelets express very high levels of surface-bound, -granule FV on simultaneous activation with 2 agonists, thrombin and convulxin, an activator of the collagen receptor glycoprotein VI. This subpopulation of activated platelets represents 30.7% ± 4.7% of the total population and is referred to as convulxin and thrombin–induced-FV (COAT-FV) platelets. COAT-FV platelets are also observed on activation with thrombin plus collagen types I, V, or VI, but not with type III. No single agonist examined was able to produce COAT-FV platelets, although ionophore A23187 in conjunction with either thrombin or convulxin did generate this population. COAT-FV platelets bound annexin-V, indicating exposure of aminophospholipids and were enriched in young platelets as identified by the binding of thiazole orange. The functional significance of COAT-FV platelets was investigated by demonstrating that factor Xa preferentially bound to COAT-FV platelets, that COAT-FV platelets had more FV activity than either thrombin or A23187–activated platelets, and that COAT-FV platelets were capable of generating more prothrombinase activity than any other physiologic agonist examined. Microparticle production by dual stimulation with thrombin and convulxin was less than that observed with A23187, indicating that microparticles were not responsible for all the activities observed. These data demonstrate a new procoagulant component produced from dual stimulation of platelets with thrombin and collagen. COAT-FV platelets may explain the unique role of -granule FV and the hemostatic effectiveness of young platelets.

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