101
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Jackson SP, Schoenwaelder SM. PI 3-Kinase p110β regulation of platelet integrin α(IIb)β3. Curr Top Microbiol Immunol 2010; 346:203-24. [PMID: 20517720 DOI: 10.1007/82_2010_61] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hemopoietic cells express relatively high levels of the type I phosphoinositide (PI) 3-kinase isoforms, with p110δ and γ exhibiting specialized signaling functions in neutrophils, monocytes, mast cells, and lymphocytes. In platelets, p110β appears to be the dominant PI 3-kinase isoform regulating platelet activation, irrespective of the nature of the primary platelet activating stimulus. Based on findings with isoform-selective p110β pharmacological inhibitors and more recently with p110β-deficient platelets, p110β appears to primarily signal downstream of G(i)- and tyrosine kinase-coupled receptors. Functionally, inhibition of p110β kinase function leads to a marked defect in integrin α(IIb)β₃ adhesion and reduced platelet thrombus formation in vivo. This defect in platelet adhesive function is not associated with increased bleeding, suggesting that therapeutic targeting of p110β may represent a safe approach to reduce thrombotic complications in patients with cardiovascular disease.
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Affiliation(s)
- Shaun P Jackson
- Australian Centre for Blood Diseases, Alfred Medical Research and Education Precinct (AMREP), Monash University, Melbourne, VIC, 3004, Australia.
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102
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Gilio K, Munnix ICA, Mangin P, Cosemans JMEM, Feijge MAH, van der Meijden PEJ, Olieslagers S, Chrzanowska-Wodnicka MB, Lillian R, Schoenwaelder S, Koyasu S, Sage SO, Jackson SP, Heemskerk JWM. Non-redundant roles of phosphoinositide 3-kinase isoforms alpha and beta in glycoprotein VI-induced platelet signaling and thrombus formation. J Biol Chem 2009; 284:33750-62. [PMID: 19815551 PMCID: PMC2797144 DOI: 10.1074/jbc.m109.048439] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Revised: 09/11/2009] [Indexed: 11/06/2022] Open
Abstract
Platelets are activated by adhesion to vascular collagen via the immunoglobulin receptor, glycoprotein VI (GPVI). This causes potent signaling toward activation of phospholipase Cgamma2, which bears similarity to the signaling pathway evoked by T- and B-cell receptors. Phosphoinositide 3-kinase (PI3K) plays an important role in collagen-induced platelet activation, because this activity modulates the autocrine effects of secreted ADP. Here, we identified the PI3K isoforms directly downstream of GPVI in human and mouse platelets and determined their role in GPVI-dependent thrombus formation. The targeting of platelet PI3Kalpha or -beta strongly and selectively suppressed GPVI-induced Ca(2+) mobilization and inositol 1,4,5-triphosphate production, thus demonstrating enhancement of phospholipase Cgamma2 by PI3Kalpha/beta. That PI3Kalpha and -beta have a non-redundant function in GPVI-induced platelet activation and thrombus formation was concluded from measurements of: (i) serine phosphorylation of Akt, (ii) dense granule secretion, (iii) intracellular Ca(2+) increases and surface expression of phosphatidylserine under flow, and (iv) thrombus formation, under conditions where PI3Kalpha/beta was blocked or p85alpha was deficient. In contrast, GPVI-induced platelet activation was insensitive to inhibition or deficiency of PI3Kdelta or -gamma. Furthermore, PI3Kalpha/beta, but not PI3Kgamma, contributed to GPVI-induced Rap1b activation and, surprisingly, also to Rap1b-independent platelet activation via GPVI. Together, these findings demonstrate that both PI3Kalpha and -beta isoforms are required for full GPVI-dependent platelet Ca(2+) signaling and thrombus formation, partly independently of Rap1b. This provides a new mechanistic explanation for the anti-thrombotic effect of PI3K inhibition and makes PI3Kalpha an interesting new target for anti-platelet therapy.
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Affiliation(s)
| | | | - Pierre Mangin
- the Australian Centre for Blood Diseases, Monash University, Alfred Medical Research Centre and Education Precinct, Melbourne, 3800 Victoria, Australia
| | | | | | | | - Servé Olieslagers
- Cardiology, Cardiovascular Research Institute Maastricht, University of Maastricht, 6200 MD Maastricht, The Netherlands
| | | | - Rivka Lillian
- the Australian Centre for Blood Diseases, Monash University, Alfred Medical Research Centre and Education Precinct, Melbourne, 3800 Victoria, Australia
| | - Simone Schoenwaelder
- the Australian Centre for Blood Diseases, Monash University, Alfred Medical Research Centre and Education Precinct, Melbourne, 3800 Victoria, Australia
| | - Shigeo Koyasu
- the Department of Microbiology and Immunology, Keio University School of Medicine, 160–8582 Tokyo, Japan, and
| | - Stewart O. Sage
- the Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge CB2 3EG, United Kingdom
| | - Shaun P. Jackson
- the Australian Centre for Blood Diseases, Monash University, Alfred Medical Research Centre and Education Precinct, Melbourne, 3800 Victoria, Australia
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103
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Stalker TJ, Wu J, Morgans A, Traxler EA, Wang L, Chatterjee MS, Lee D, Quertermous T, Hall RA, Hammer DA, Diamond SL, Brass LF. Endothelial cell specific adhesion molecule (ESAM) localizes to platelet-platelet contacts and regulates thrombus formation in vivo. J Thromb Haemost 2009; 7:1886-96. [PMID: 19740102 PMCID: PMC4441405 DOI: 10.1111/j.1538-7836.2009.03606.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND In resting platelets, endothelial cell specific adhesion molecule (ESAM) is located in alpha granules, increasing its cell surface expression following platelet activation. However, the function of ESAM on platelets is unknown. OBJECTIVE To determine whether ESAM has a role in thrombus formation. METHODS AND RESULTS We found that following platelet activation ESAM localizes to the junctions between adjacent platelets, suggesting a role for this protein in contact-dependent events that regulate thrombus formation. To test this hypothesis we examined the effect of ESAM deletion on platelet function. In vivo, ESAM(-/-) mice achieved more stable hemostasis than wild-type mice following tail transection, and developed larger thrombi following laser injury of cremaster muscle arterioles. In vitro, ESAM(-/-) platelets aggregated at lower concentrations of G protein-dependent agonists than wild-type platelets, and were more resistant to disaggregation. In contrast, agonist-induced calcium mobilization, alpha(IIb)beta(3) activation, alpha-granule secretion and platelet spreading, were normal in ESAM-deficient platelets. To understand the molecular mechanism by which ESAM regulates platelet activity, we utilized a PDZ domain array to identify the scaffold protein NHERF-1 as an ESAM binding protein, and further demonstrated that it associates with ESAM in both resting and activated platelets. CONCLUSIONS These findings support a model in which ESAM localizes to platelet contacts following platelet activation in order to limit thrombus growth and stability so that the optimal hemostatic response occurs following vascular injury.
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Affiliation(s)
- T J Stalker
- Department of Medicine, The Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
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104
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Gui T, Reheman A, Ni H, Gross PL, Yin F, Monroe D, Monahan PE, Stafford DW. Abnormal hemostasis in a knock-in mouse carrying a variant of factor IX with impaired binding to collagen type IV. J Thromb Haemost 2009; 7:1843-51. [PMID: 19583826 DOI: 10.1111/j.1538-7836.2009.03545.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Factor IX binds to collagen type IV, but this binding has no known consequence. OBJECTIVES To determine the effect of reduced binding of FIX to collagen IV. METHODS We constructed and characterized 'knock-in' mice containing the mutation lysine 5 to alanine (K5A) in the Gla domain of their FIX. The K5A mutation dramatically reduced the affinity of FIX for collagen type IV, but had no measurable effect on platelet binding, phospholipid binding, or in vitro clotting activity. However, K5AFIX mice had a mild bleeding tendency, despite their in vitro clotting activity being normal. Hemostatic protection from delayed rebleeding was intermediate between wild-type and hemophilia B mice (which had no detectable clotting activity); moreover, survival of K5A FIX mice after nascent clot removal was dramatically improved as compared with hemophilia B mice. Importantly, there was no detectable difference between K5AFIX and wild-type mice in either a laser-induced thrombosis model or the chromogenic FIX activity assay. In contrast, after ferric chloride injury, which exposes collagen IV as well as other basement membrane proteins, intravital microscopy revealed that vessel occlusion was significantly slower in K5AFIX mice than in wild-type mice. CONCLUSIONS Our results indicate that the FIX molecule with decreased affinity for collagen IV has altered hemostatic properties in vivo and that the binding of FIX to collagen IV probably plays a significant functional role in hemostasis.
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Affiliation(s)
- T Gui
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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105
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Genetic evidence for a predominant role of PI3Kβ catalytic activity in ITAM- and integrin-mediated signaling in platelets. Blood 2009; 114:2193-6. [DOI: 10.1182/blood-2009-03-208074] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Abstract
Phosphatidylinositol 3-kinase (PI3K) isoforms PI3Kβ and PI3Kγ are implicated in platelet adhesion, activation, and aggregation, but their relative contribution is still unclear or controversial. Here, we report the first comparative functional analysis of platelets from mice expressing a catalytically inactive form of PI3Kβ or PI3Kγ. We demonstrate that both isoforms were similarly required for maximal activation of the small GTPase Rap1b and for complete platelet aggregation upon stimulation of G protein–coupled receptors for adenosine 5′-diphosphate (ADP) or U46619. Their contribution to these events, however, was largely redundant and dispensable. However, PI3Kβ, but not PI3Kγ, enzymatic activity was absolutely required for Akt phosphorylation, Rap1 activation, and platelet aggregation downstream of the immunoreceptor tyrosine-based activation motif (ITAM)–bearing receptor glycoprotein VI (GPVI). Moreover, PI3Kβ was a major essential regulator of platelet adhesion to fibrinogen and of integrin αIIbβ3-mediated spreading. These results provide genetic evidence for a crucial and selective role of PI3Kβ in signaling through GPVI and integrin αIIbβ3.
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106
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Abstract
The importance of the second messengers calcium (Ca(2+)) and diacylglycerol (DAG) in platelet signal transduction was established more than 30 years ago. Whereas protein kinase C (PKC) family members were discovered as the targets of DAG, little is known about the molecular identity of the main Ca(2+) sensor(s). We here identify Ca(2+) and DAG-regulated guanine nucleotide exchange factor I (CalDAG-GEFI) as a critical molecule in Ca(2+)-dependent platelet activation. CalDAG-GEFI, through activation of the small GTPase Rap1, directly triggers integrin activation and extracellular signal-regulated kinase-dependent thromboxane A(2) (TxA(2)) release. CalDAG-GEFI-dependent TxA(2) generation provides crucial feedback for PKC activation and granule release, particularly at threshold agonist concentrations. PKC/P2Y12 signaling in turn mediates a second wave of Rap1 activation, necessary for sustained platelet activation and thrombus stabilization. Our results lead to a revised model for platelet activation that establishes one molecule, CalDAG-GEFI, at the nexus of Ca(2+)-induced integrin activation, TxA(2) generation, and granule release. The preferential activation of CalDAG-GEFI over PKC downstream of phospholipase C activation, and the different kinetics of CalDAG-GEFI- and PKC/P2Y12-mediated Rap1 activation demonstrate an unexpected complexity to the platelet activation process, and they challenge the current model that DAG/PKC-dependent signaling events are crucial for the initiation of platelet adhesion.
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107
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Rivera J, Lozano ML, Navarro-Núñez L, Vicente V. Platelet receptors and signaling in the dynamics of thrombus formation. Haematologica 2009; 94:700-11. [PMID: 19286885 DOI: 10.3324/haematol.2008.003178] [Citation(s) in RCA: 257] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Hemostasis and pathological thrombus formation are dynamic processes that require a co-ordinated series of events involving platelet membrane receptors, bidirectional intracellular signals, and release of platelet proteins and inflammatory substances. This review aims to summarize current knowledge in the key steps in the dynamics of thrombus formation, with special emphasis on the crucial participation of platelet receptors and signaling in this process. Initial tethering and firm adhesion of platelets to the exposed subendothelium is mediated by glycoprotein (GP) Ib/IX/V complex and collagen receptors, GP VI and alpha(2)beta(1) integrin, in the platelet surface, and by VWF and fibrillar collagen in the vascular site. Interactions between these elements are largely influenced by flow and trigger signaling events that reinforce adhesion and promote platelet activation. Thereafter, soluble agonists, ADP, thrombin, TxA(2), produced/released at the site of vascular injury act in autocrine and paracrine mode to amplify platelet activation and to recruit circulating platelets to the developing thrombus. Specific interactions of these agonists with their G-protein coupled receptors generate inside-out signaling leading to conformational activation of integrins, in particular alpha(IIb)beta(3), increasing their ligand affinity. Binding of alpha(IIb)beta(3) to its ligands, mainly fibrinogen, supports processes such as clot retraction and platelet aggregation. Stabilization of thrombi is supported by the late wave of signaling events promoted by close contact between aggregated platelets. The best known contact-dependent signaling is outside-in signaling through alphaIb beta(3), but new ones are being clarified such as those mediated by interaction of Eph receptors with ephrins, or by Sema 4D and Gas-6 binding to their receptors. Finally, newly identified mechanisms appear to control thrombus growth, including back-shifting of activated integrins and actuation of compensatory molecules such as ESAM or PECAM-1. The expanding knowledge of thrombotic disease is expected to translate into the development of new drugs to help management and prevention of thrombosis.
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Affiliation(s)
- José Rivera
- Centro Regional de Hemodonación, Universidad de Murcia, C/ Ronda de Garay s/n., Murcia, Spain
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108
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Konopatskaya O, Gilio K, Harper MT, Zhao Y, Cosemans JMEM, Karim ZA, Whiteheart SW, Molkentin JD, Verkade P, Watson SP, Heemskerk JWM, Poole AW. PKCalpha regulates platelet granule secretion and thrombus formation in mice. J Clin Invest 2009; 119:399-407. [PMID: 19147982 DOI: 10.1172/jci34665] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 12/03/2008] [Indexed: 12/21/2022] Open
Abstract
Platelets are central players in atherothrombosis development in coronary artery disease. The PKC family provides important intracellular mechanisms for regulating platelet activity, and platelets express several members of this family, including the classical isoforms PKCalpha and PKCbeta and novel isoforms PKCdelta and PKCtheta. Here, we used a genetic approach to definitively demonstrate the role played by PKCalpha in regulating thrombus formation and platelet function. Thrombus formation in vivo was attenuated in Prkca-/- mice, and PKCalpha was required for thrombus formation in vitro, although this PKC isoform did not regulate platelet adhesion to collagen. The ablation of in vitro thrombus formation in Prkca-/- platelets was rescued by the addition of ADP, consistent with the key mechanistic finding that dense-granule biogenesis and secretion depend upon PKCalpha expression. Furthermore, defective platelet aggregation in response to either collagen-related peptide or thrombin could be overcome by an increase in agonist concentration. Evidence of overt bleeding, including gastrointestinal and tail bleeding, was not seen in Prkca-/- mice. In summary, the effects of PKCalpha ablation on thrombus formation and granule secretion may implicate PKCalpha as a drug target for antithrombotic therapy.
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Affiliation(s)
- Olga Konopatskaya
- Department of Physiology & Pharmacology, School of Medical Sciences, University of Bristol, Bristol, United Kingdom
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109
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Munnix ICA, Gilio K, Siljander PRM, Raynal N, Feijge MAH, Hackeng TM, Deckmyn H, Smethurst PA, Farndale RW, Heemskerk JWM. Collagen-mimetic peptides mediate flow-dependent thrombus formation by high- or low-affinity binding of integrin alpha2beta1 and glycoprotein VI. J Thromb Haemost 2008; 6:2132-42. [PMID: 18826391 DOI: 10.1111/j.1538-7836.2008.03167.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Collagen acts as a potent surface for platelet adhesion and thrombus formation under conditions of blood flow. Studies using collagen-derived triple-helical peptides have identified the GXX'GER motif as an adhesive ligand for platelet integrin alpha2beta1, and (GPO)(n) as a binding sequence for the signaling collagen receptor, glycoprotein VI (GPVI). OBJECTIVE The potency was investigated of triple-helical peptides, consisting of GXX'GER sequences within (GPO)(n) or (GPP)(n) motifs, to support flow-dependent thrombus formation. RESULTS At a high-shear rate, immobilized peptides containing both the high-affinity alpha2beta1-binding motif GFOGER and the (GPO)(n) motif supported platelet aggregation and procoagulant activity, even in the absence of von Willebrand factor (VWF). With peptides containing only one of these motifs, co-immobilized VWF was needed for thrombus formation. The (GPO)(n) but not the (GPP)(n) sequence induced GPVI-dependent platelet aggregation and procoagulant activity. Peptides with intermediate affinity (GLSGER, GMOGER) or low-affinity (GASGER, GAOGER) alpha2beta1-binding motifs formed procoagulant thrombi only if both (GPO)(n) and VWF were present. At a low-shear rate, immobilized peptides with high- or low-affinity alpha2beta1-binding motifs mediated formation of thrombi with procoagulant platelets only in combination with (GPO)(n). CONCLUSIONS Triple-helical peptides with specific receptor-binding motifs mimic the properties of native collagen I in thrombus formation by binding to both platelet collagen receptors. At a high-shear rate, either GPIb or high-affinity (but not low-affinity) GXX'GER mediates GPVI-dependent formation of procoagulant thrombi. By extension, high-affinity binding for alpha2beta1 can control the overall platelet-adhesive activity of native collagens.
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Affiliation(s)
- I C A Munnix
- Department of Biochemistry, CARIM, University of Maastricht, Maastricht, The Netherlands
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110
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Guidetti GF, Lova P, Bernardi B, Campus F, Baldanzi G, Graziani A, Balduini C, Torti M. The Gi-coupled P2Y12 receptor regulates diacylglycerol-mediated signaling in human platelets. J Biol Chem 2008; 283:28795-805. [PMID: 18755689 DOI: 10.1074/jbc.m801588200] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Stimulation of G(q)-coupled receptors activates phospholipase C and is supposed to promote both intracellular Ca(2+) mobilization and protein kinase C (PKC) activation. We found that ADP-induced phosphorylation of pleckstrin, the main platelet substrate for PKC, was completely inhibited not only by an antagonist of the G(q)-coupled P2Y1 receptor but also upon blockade of the G(i)-coupled P2Y12 receptor. The role of G(i) on PKC regulation required stimulation of phosphatidylinositol 3-kinase rather than inhibition of adenylyl cyclase. P2Y12 antagonists also inhibited pleckstrin phosphorylation, Rap1b activation, and platelet aggregation induced upon G(q) stimulation by the thromboxane A(2) analogue U46619. Importantly, activation of phospholipase C and intracellular Ca(2+) mobilization occurred normally. Phorbol 12-myristate 13-acetate overcame the inhibitory effect of P2Y12 receptor blockade on PKC activation but not on Rap1b activation and platelet aggregation. By contrast, inhibition of diacylglycerol kinase restored both PKC and Rap1b activity and caused platelet aggregation. Stimulation of P2Y12 receptor or direct inhibition of diacylglycerol kinase potentiated the effect of membrane-permeable sn-1,2-dioctanoylglycerol on platelet aggregation and pleckstrin phosphorylation, in association with inhibition of its phosphorylation to phosphatidic acid. These results reveal a novel and unexpected role of the G(i)-coupled P2Y12 receptor in the regulation of diacylglycerol-mediated events in activated platelets.
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Affiliation(s)
- Gianni F Guidetti
- Center of Excellence for Applied Biology, Department of Biochemistry, University of Pavia, via Bassi 21, 27100 Pavia, Italy
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111
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Judge HM, Buckland RJ, Sugidachi A, Jakubowski JA, Storey RF. The active metabolite of prasugrel effectively blocks the platelet P2Y12 receptor and inhibits procoagulant and pro-inflammatory platelet responses. Platelets 2008; 19:125-33. [PMID: 18297550 DOI: 10.1080/09537100701694144] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The aim of these studies was to investigate the extent of platelet P2Y(12) receptor inhibition by the thienopyridine active metabolite of prasugrel, R-138727. Blood was taken from healthy volunteers and pre-incubated with R-138727 or cangrelor (AR-C66931MX). Platelet aggregation was assessed in platelet rich plasma (PRP) and whole blood (WB). Vasodilator stimulated phosphoprotein (VASP) phosphorylation, platelet procoagulant activity (annexin V binding and microparticle formation) and calcium mobilisation were measured by flow cytometry. Platelet-leukocyte co-aggregate formation and sCD40L release, both pro-inflammatory responses of platelets, were measured by flow cytometry and ELISA, respectively. P2Y(12) receptor antagonism was determined using a radioligand binding assay ((33)P 2-MeSADP) in resting and stimulated platelets and the effects of clopidogrel administration were also assessed. R-138727 yielded concentration-dependent inhibition of platelet aggregation, VASP phosphorylation inhibition, procoagulant activity and pro-inflammatory responses. In the presence of R-138727 or cangrelor there was increased calcium reuptake following agonist stimulation. R-138727 30 micromol/L and cangrelor 1 micromol/L completely inhibited (33)P 2-MeSADP binding, compared to partial inhibition following clopidogrel administration. Platelet activation and granule secretion did not expose an additional pool of P2Y(12) receptors. Prasugrel's active metabolite effectively blocks the P2Y(12) receptor with the highest concentrations tested yielding complete inhibition of P2Y(12)-mediated amplification of several important platelet responses.
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112
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Cosemans JMEM, Iserbyt BF, Deckmyn H, Heemskerk JWM. Multiple ways to switch platelet integrins on and off. J Thromb Haemost 2008; 6:1253-61. [PMID: 18513212 DOI: 10.1111/j.1538-7836.2008.03041.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In the classical concept of platelet integrin activation, it is considered that unidirectional conformational changes of alpha(IIb)beta(3) and alpha(2)beta(1) regulate the adhesiveness of platelets for fibrin(ogen) and collagen, respectively. Here, we summarize recent evidence that these conformational changes: (i) can also occur in the reverse direction; and (ii) are not independent events. Platelet stimulation through the P2Y(12) receptors provokes only transient alpha(IIb)beta(3) activation via signaling routes involving phosphoinositide 3-kinases and Rap1b. Furthermore, alpha(IIb)beta(3) can be secondarily inactivated in platelets with prolonged high Ca(2+) rises, which expose phosphatidylserine and bind coagulation factors. Thus, platelet stimulation with strong agonists (collagen and thrombin) also results in transient integrin activation. Integrin alpha(2)beta(1) is found to be activated by a mechanism that is directly linked to alpha(IIb)beta(3) activation. Integrin alpha(2)beta(1) can adopt different activation states, depending on the trigger. Conclusively, reversibility and synchrony of platelet integrin activation are newly identified mechanisms to restrict thrombus growth and to allow optimal coagulation factor binding. Back-shifting of activated integrins towards their resting state may be a novel goal of antithrombotic medication.
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Affiliation(s)
- J M E M Cosemans
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands.
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113
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Mundell SJ, Barton JF, Mayo-Martin MB, Hardy AR, Poole AW. Rapid resensitization of purinergic receptor function in human platelets. J Thromb Haemost 2008; 6:1393-404. [PMID: 18513210 DOI: 10.1111/j.1538-7836.2008.03039.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Adenosine diphosphate (ADP) is a critical regulator of platelet activation, mediating its actions through two G protein-coupled receptors (GPCRs), the P2Y(1) and P2Y(12) purinergic receptors. Recently, we demonstrated that both receptors desensitize and internalize in human platelets by differential kinase-dependent mechanisms. OBJECTIVES To demonstrate whether responses to P2Y(1) and P2Y(12) purinergic receptors resensitize in human platelets and determine the role of receptor traffic in this process. METHODS These studies were undertaken either in human platelets or in cells stably expressing epitope-tagged P2Y(1) and P2Y(12) purinergic receptor constructs. RESULTS In this study we show for the first time that responses to both of these receptors can rapidly resensitize following agonist-dependent desensitization in human platelets. Further, we show that in human platelets or in 1321N1 cells stably expressing receptor constructs, the disruption of receptor internalization, dephosphorylation or subsequent receptor recycling is sufficient to block resensitization of purinergic receptor responses. We also show that, in platelets, internalization of both these receptors is dependent upon dynamin, and that this process is required for resensitization of responses. CONCLUSIONS This study is therefore the first to show that both P2Y(1) and P2Y(12) receptor activities are rapidly and reversibly modulated in human platelets, and it reveals that the underlying mechanism requires receptor trafficking as an essential part of this process.
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Affiliation(s)
- S J Mundell
- Department of Physiology and Pharmacology, School of Medical Sciences, University Walk, Bristol, UK
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114
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Zhou Y, Zhang L, Romaguera J, Delasalle K, Han X, Du X, Kwak L, Yi Q, Wang M. Immunotherapy in mantle cell lymphoma: anti-CD20-based therapy and beyond. Am J Hematol 2008; 83:144-9. [PMID: 17722077 DOI: 10.1002/ajh.21036] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Mantle cell lymphoma (MCL), an aggressive non-Hodgkin's lymphoma characterized by t(11; 14)(q13; q32) chromosomal translocation and overexpression of cyclin D1, has the worst prognosis among all lymphomas. Recent advances in biology, genetics, and immunology have supported the development of immunotherapy in MCL. Rituximab monotherapy in MCL has limited activity. It is more effective when used in combination with chemotherapy such as R-CHOP, R-hyperCVAD/MTX-Ara-C, or R-FCM as front-line or salvage therapy for mantle cell lymphoma. Maintenance with Rituximab was shown to prolong response duration. Although most results have suggested that combining autologous stem cell transplantation with Rituximab may lead to durable remission, the sample size was not sufficient to declare survival benefit. Anti-CD20 radioimmunoconjugates (RICs) (90)Yttrium-ibritumomab tiuxetan and (131)Iodine-tositumomab have been used in mantle cell lymphoma even when patients are relatively resistant to Rituximab-based therapy. Allogeneic stem cell transplantation is a treatment modality in advanced or relapsed MCL, particularly using reduced-intensity conditioning. MCL may have high response rates and sustained remissions after donor lymphocyte infusion. Dendritic cells (DCs) fused with MCL cells for immunostimulation have preliminarily shown anti-lymphoma effects as well. Idiotype vaccination in MCL patients following Rituximab-containing chemotherapy induced tumor-specific T-cell immunity in the absence of B cells. Other immunotherapy, such as the combination of thalidomide with Rituximab, has shown substantial antitumor activity. A Phase I/II study is ongoing to determine the maximum tolerated dose (MTD) and the efficacy of lenalidomide in combination with Rituximab for relapsed/refractory MCL. This review summarizes the latest and exciting advances in MCL.
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Affiliation(s)
- Yuhong Zhou
- Department of Oncology, Zhongshan Hospital, Fudan University, Shanghai, China
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115
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Hughes PJ, Lee JS, Reiner NE, Brown G. The vitamin D receptor-mediated activation of phosphatidylinositol 3-kinase (PI3Kα) plays a role in the 1α,25-dihydroxyvitamin D3-stimulated increase in steroid sulphatase activity in myeloid leukaemic cell lines. J Cell Biochem 2008; 103:1551-72. [PMID: 17879954 DOI: 10.1002/jcb.21545] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In this article we show that 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) stimulates the activity of the class IA phosphatidylinositol 3-kinase PI3Kalpha and its downstream target Akt in HL60, U937 and THP-1 myeloid leukaemic cell lines. Furthermore, we show that the classical nuclear vitamin D receptor (VDR(nuc)) is involved in this activation of the PI3K/Akt signalling in these cell lines. We have previously shown that the activity of steroid sulphatase is stimulated in HL60, U937 and THP-1 myeloid leukaemic cell lines by 1alpha,25(OH)(2)D(3) (Hughes et al., [2001] Biochem J 355:361-371; Hughes et al., [2005] J Cell Biochem 94:1175-1189; Hughes and Brown [2006] J Cell Biochem 98:590-617). In this article we show that the 1alpha,25(OH)(2)D(3)-stimulated increase in signalling via the PI3K/Akt pathway plays a role in the increase in steroid sulphatase activity in the HL60 U937 and THP-1 cell lines. We used a variety of pharmacological and biochemical approaches to show that activation of PI3Kalpha mediates the 1alpha,25(OH)(2)D(3)-stimulated increase in steroid sulphatase activity in myeloid leukaemic cells. We also show that the PI3K/Akt dependent activation of NF-kappaB plays a role in the 1alpha,25(OH)(2)D(3)-stimulated increase in steroid sulphatase activity in myeloid leukaemic cells.
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Affiliation(s)
- Philip J Hughes
- Division of Immunity and Infection, The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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116
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van der Meijden PEJ, Schoenwaelder SM, Feijge MAH, Cosemans JMEM, Munnix ICA, Wetzker R, Heller R, Jackson SP, Heemskerk JWM. Dual P2Y12 receptor signaling in thrombin-stimulated platelets - involvement of phosphoinositide 3-kinase β but not γ isoform in Ca2+ mobilization and procoagulant activity. FEBS J 2007; 275:371-85. [DOI: 10.1111/j.1742-4658.2007.06207.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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117
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Reséndiz JC, Kroll MH, Lassila R. Protease-activated receptor-induced Akt activation--regulation and possible function. J Thromb Haemost 2007; 5:2484-93. [PMID: 17883592 DOI: 10.1111/j.1538-7836.2007.02769.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Thrombin induces the activation of the platelet serine/threonine kinase Akt. Akt activation is dependent on its phosphorylation at Thr308 and Ser473. The mechanism by which thrombin induces Akt phosphorylation is controversial, as is the role of Akt in platelet function. OBJECTIVES To investigate how protease-activated receptors (PARs) stimulate Akt and the role that Akt plays in human platelet function. METHODS Platelets were stimulated through PAR1 or PAR4. Specific inhibitors were used to evaluate, by Western blotting, signaling pathways regulating Akt phosphorylation, and the role of activated Akt was evaluated by aggregometry and flow cytometry. RESULTS Phospholipase C (PLC) controls Akt phosphorylation elicited by PARs. Stimulation of PAR1 or PAR4 resulted in rapid Akt phosphorylation, independently of secreted ADP and phosphatidylinositol-3-kinase (PI3K) activation. Akt phosphorylation approximately 60 s after PAR1 stimulation became entirely dependent on the purinergic receptor P2Y(12) and the activation of PI3K. In contrast, PAR4 partially sustained Akt phosphorylation independently of P2Y(12) and PI3K for up to 300 s. Pharmacologic inhibition of Akt reduced P-selectin expression and fibrinogen binding in platelets stimulated through PAR1, and delayed platelet aggregation in response to submaximal PAR1 or PAR4 stimulation, although aggregation at 300 s was unaffected. CONCLUSIONS Platelet PAR stimulation causes rapid Akt phosphorylation downstream of PLC, whereas with continuous stimulation, ADP and PI3K are required for maintaining Akt phosphorylation. Activated Akt regulates platelet function by modulating secretion and alpha(IIb)beta(3) activation.
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Affiliation(s)
- J C Reséndiz
- Wihuri Research Institute, Kalliolinnantie 4, Helsinki, Finland.
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118
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Cauwenberghs S, van Pampus E, Curvers J, Akkerman JWN, Heemskerk JWM. Hemostatic and signaling functions of transfused platelets. Transfus Med Rev 2007; 21:287-94. [PMID: 17900490 DOI: 10.1016/j.tmrv.2007.05.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Metabolic studies have revealed a gradual impairment in platelet integrity during storage, a process termed the platelet storage lesion. Recent evidence shows that stored platelets also lose signaling responses to physiological agonists with impaired integrin activation, secretion, and aggregation of the cells. On the other hand, storage leads to a gain in platelet activation properties, such as release of microparticles and appearance of surface epitopes for their clearance by macrophages. New techniques for measuring flow-induced thrombus formation and platelet-dependent coagulation provide evidence that the hemostatic activity of platelets decreases during storage. Besides pharmacological inhibition, novel storage strategies, like metabolic suppression, should be considered to better preserve platelet functionality while limiting the expression of clearance markers. Understanding the changes that occur in association with the platelet storage lesion and the use of updated storage methods will help to generate platelets for transfusion with optimal hemostatic function and a long circulation time after transfusion.
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Affiliation(s)
- Sandra Cauwenberghs
- Department of Biochemistry (CARIM), Maastricht University and University Hospital, The Netherlands
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119
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120
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Hassan AE, Zacharatos H, Fareed M, Suri K, Qureshi AI. Drug evaluation of clopidogrel in patients with ischemic stroke. Expert Opin Pharmacother 2007; 8:2825-38. [DOI: 10.1517/14656566.8.16.2825] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Ameer E Hassan
- University of Minnesota, Zeenat Qureshi Stroke Research Center, Department of Neurology, 82 – 100 Phillips Wangensteen Building, 420 Delaware Street SE, Minneapolis, Minnesota 55455, USA
| | - Haralabos Zacharatos
- University of Minnesota, Zeenat Qureshi Stroke Research Center, Department of Neurology, 82 – 100 Phillips Wangensteen Building, 420 Delaware Street SE, Minneapolis, Minnesota 55455, USA
| | - M Fareed
- University of Minnesota, Zeenat Qureshi Stroke Research Center, Department of Neurology, 82 – 100 Phillips Wangensteen Building, 420 Delaware Street SE, Minneapolis, Minnesota 55455, USA
| | - K Suri
- University of Minnesota, Zeenat Qureshi Stroke Research Center, Department of Neurology, 82 – 100 Phillips Wangensteen Building, 420 Delaware Street SE, Minneapolis, Minnesota 55455, USA
| | - Adnan I Qureshi
- University of Minnesota, Zeenat Qureshi Stroke Research Center, Department of Neurology, 82 – 100 Phillips Wangensteen Building, 420 Delaware Street SE, Minneapolis, Minnesota 55455, USA
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121
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Schoenwaelder SM, Ono A, Sturgeon S, Chan SM, Mangin P, Maxwell MJ, Turnbull S, Mulchandani M, Anderson K, Kauffenstein G, Rewcastle GW, Kendall J, Gachet C, Salem HH, Jackson SP. Identification of a unique co-operative phosphoinositide 3-kinase signaling mechanism regulating integrin alpha IIb beta 3 adhesive function in platelets. J Biol Chem 2007; 282:28648-28658. [PMID: 17673465 DOI: 10.1074/jbc.m704358200] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoinositide (PI) 3-kinases play an important role in regulating the adhesive function of a variety of cell types through affinity modulation of integrins. Two type I PI 3-kinase isoforms (p110 beta and p110 gamma) have been implicated in G(i)-dependent integrin alpha(IIb)beta(3) regulation in platelets, however, the mechanisms by which they coordinate their signaling function remains unknown. By employing isoform-selective PI 3-kinase inhibitors and knock-out mouse models we have identified a unique mechanism of PI 3-kinase signaling co-operativity in platelets. We demonstrate that p110 beta is primarily responsible for G(i)-dependent phosphatidylinositol 3,4-bisphosphate (PI(3,4)P(2)) production in ADP-stimulated platelets and is linked to the activation of Rap1b and AKT. In contrast, defective integrin alpha(IIb)beta(3) activation in p110 gamma(-/-) platelets was not associated with alterations in the levels of PI(3,4)P(2) or active Rap1b/AKT. Analysis of the effects of active site pharmacological inhibitors confirmed that p110 gamma principally regulated integrin alpha(IIb)beta(3) activation through a non-catalytic signaling mechanism. Inhibition of the kinase function of PI 3-kinases, combined with deletion of p110 gamma, led to a major reduction in integrin alpha(IIb)beta(3) activation, resulting in a profound defect in platelet aggregation, hemostatic plug formation, and arterial thrombosis. These studies demonstrate a kinase-independent signaling function for p110 gamma in platelets. Moreover, they demonstrate that the combined catalytic and non-catalytic signaling function of p110 beta and p110 gamma is critical for P2Y(12)/G(i)-dependent integrin alpha(IIb)beta(3) regulation. These findings have potentially important implications for the rationale design of novel antiplatelet therapies targeting PI 3-kinase signaling pathways.
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Affiliation(s)
- Simone M Schoenwaelder
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Akiko Ono
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Sharelle Sturgeon
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Siew Mei Chan
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Pierre Mangin
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Mhairi J Maxwell
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Shannon Turnbull
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Megha Mulchandani
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Karen Anderson
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Gilles Kauffenstein
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1020, New Zealand
| | - Gordon W Rewcastle
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1020, New Zealand
| | - Jackie Kendall
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1020, New Zealand
| | | | - Hatem H Salem
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004
| | - Shaun P Jackson
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, Victoria, Australia 3004.
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Hashimoto M, Sugidachi A, Isobe T, Niitsu Y, Ogawa T, Jakubowski JA, Asai F. The influence of P2Y12 receptor deficiency on the platelet inhibitory activities of prasugrel in a mouse model: evidence for specific inhibition of P2Y12 receptors by prasugrel. Biochem Pharmacol 2007; 74:1003-9. [PMID: 17681285 DOI: 10.1016/j.bcp.2007.06.027] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2007] [Revised: 06/14/2007] [Accepted: 06/14/2007] [Indexed: 12/16/2022]
Abstract
Prasugrel is a novel orally active thienopyridine with faster, higher and more reliable inhibition of platelet aggregation than clopidogrel reflecting its metabolism in vivo to an active metabolite with selective P2Y(12) antagonistic activity. Several lines of evidence support the contention that prasugrel provides selective P2Y(12) receptor antagonistic activity. To date, however, direct evidence of P2Y(12) specific action by prasugrel in vivo is limited. In the present study, effects of prasugrel on ex vivo platelet aggregation were examined in wild type (WT) and P2Y(12)(-/-) mice. In WT mice, prasugrel showed platelet inhibition that was 8.2 times more potent than clopidogrel. In P2Y(12)(-/-) mice, ADP induced platelet aggregation was minimal, and its extent was similar to that in prasugrel-treated WT mice. In addition, no further inhibition of platelet aggregation was observed after administration of prasugrel to P2Y(12)(-/-) mice. Furthermore, prasugrel-treated WT mice showed similar aggregation patterns using collagen- and murine PAR-4 agonist peptide to those of P2Y(12)(-/-) mice treated with vehicle or prasugrel. Overall, these results clearly provide additional in vivo evidence that prasugrel has selective P2Y(12) antagonistic activity.
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123
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Affiliation(s)
- Andrew O Maree
- Division of Cardiology, Harvard Medical School and Massachusetts General Hospital, Boston, Mass, USA
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124
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Chiang TM, Postlethwaite AE. A cell model system to study regulation of phosphotidylinositol 3-kinase and protein kinase B activity by cytokines/growth factors produced by type I collagen stimulated immune cells from patients with systemic sclerosis. Biochim Biophys Acta Gen Subj 2007; 1770:1181-6. [PMID: 17524560 PMCID: PMC2083118 DOI: 10.1016/j.bbagen.2007.04.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Revised: 04/06/2007] [Accepted: 04/11/2007] [Indexed: 11/21/2022]
Abstract
We have reported that posttranslational modification of systemic sclerosis patients' platelet phosphoinositide 1,3,4,5 kinase (PI 3-K) and protein kinase B (Akt) altered their enzymatic activities. In the present investigation, we have established a cell line model to study further the effects of posttranslational modification and modification by cytokines or growth factors of these two enzymes. Results from these studies suggest that posttranslational modification by phosphorylation of Akt and nitrotyrosylation of PI 3-K increases enzymatic activities, as was observed from SSc patients' platelets. These two signaling components are controlled by a different mechanism, which alters platelet reactivity towards the matrix components of vascular walls. We have used a megakaryotic cell line to study these two enzymes in the presence of cultured supernatants from peripheral blood mononuclear cells (PBMC), which were isolated from blood of SSc patients compared to controls including culture medium, rheumatoid arthritis, systemic lupus erythematosus, and osteoarthritis. The effect of the supernatants from SSc CI-stimulated PBMC cultures on both PI 3-K and Akt is specific.
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Affiliation(s)
- Thomas M Chiang
- Veterans Affairs Medical Center, 1030 Jefferson Avenue, Memphis, TN 38104, USA.
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