Novel Platelet Antagonists

2006 ◽  
Author(s):  
Richard C. Becker ◽  
Frederick A. Spencer
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Adenosine Monophosphate ◽  
Stress Conditions ◽  
Platelet Glycoprotein ◽  
High Shear ◽  
High Shear Stress ◽  
Surface Receptor ◽  
Pharmacologic Agents

The development of pharmacologic agents that inhibit platelet performance could not have proceeded without a fundamental knowledge of normal biology and a clear understanding of the laws that govern cellular events in the circulatory system. The adhesion of platelets to a site of vessel wall injury is mediated by von Willebrand factor (vWF), which binds to the platelet glycoprotein (GP) Ib/IX-V complex receptor (and the GPIIb/IIIa receptor under high shear stress conditions). Monoclonal antibodies to vWF have been developed and tested in animal models, as has aurintricarboxylic acid (Strony et al., 1990), a triphenylmethyl compound that inhibits vWF binding. To date, investigation in humans has not taken place, perhaps because of concerns regarding the potential risk for hemorrhagic complications. Nevertheless, the scientific community remains interested in vWF and its platelet surface receptor as potential pharmacology-directed targets. Although the GPIIb/IIIa receptor antagonists are best known for their ability to inhibit platelet aggregation, under high shear stress conditions vWF can also bind the GPIIb/IIIa receptor, facilitating adhesion. As a result, GPIIb/IIIa antagonists may have an impact on both platelet adhesion and aggregation. As previously discussed, platelet activation is followed by a series of intracellular events that culminate in the release of calcium and substances that augment platelet aggregation and support coagulation protease binding. Thus, pharmacologic agents that inhibit initial surface receptor–mediated activation may also impair platelet aggregation. Several natural prostanoids (prostaglandin [PG] E1 and PGI2) can inhibit platelet activation and aggregation by elevating cyclic adenosine monophosphate (cAMP) levels. Although the mechanism is complex, the primary mode of inhibition is through the activation of adenylate cyclase (with a subsequent rise in cAMP concentrations), which in turn prevents calcium mobilization. The clinical application of PGE1 and PGI2 has been limited by their effect on vascular tone, producing substantial systemic hypotension (Emmons et al., 1967; Terres et al., 1989), and by extensive first-pass metabolism in the lungs (70% of the active compound is rapidly cleared) (Kleiman et al., 1994).

scholarly journals Antithrombotic Effects of Paeoniflorin from Paeonia suffruticosa by Selective Inhibition on Shear Stress-Induced Platelet Aggregation

2019 ◽  
Vol 20 (20) ◽  
pp. 5040 ◽  
Author(s):  
Thien Ngo ◽  
Keunyoung Kim ◽  
Yiying Bian ◽  
Hakjun Noh ◽  
Kyung-Min Lim ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Ex Vivo ◽  
Antiplatelet Agents ◽  
Human Platelets ◽  
Platelet Glycoprotein ◽  
High Shear ◽  
High Shear Stress ◽  
Paeonia Suffruticosa ◽  
Induced Aggregation

Antiplatelet agents are important in the pharmacotherapeutic regime for many cardiovascular diseases, including thrombotic disorders. However, bleeding, the most serious adverse effect associated with current antiplatelet therapy, has led to many efforts to discover novel anti-platelet drugs without bleeding issues. Of note, shear stress-induced platelet aggregation (SIPA) is a promising target to overcome bleeding since SIPA happens only in pathological conditions. Accordingly, this study was carried out to discover antiplatelet agents selectively targeting SIPA. By screening various herbal extracts, Paeonia suffruticosa and its major bioactive constituent, paeoniflorin, were identified to have significant inhibitory effects against shear-induced aggregation in human platelets. The effects of paeoniflorin on intraplatelet calcium levels, platelet degranulation, and integrin activation in high shear stress conditions were evaluated by a range of in vitro experiments using human platelets. The inhibitory effect of paeoniflorin was determined to be highly selective against SIPA, through modulating von Willebrand Factor (vWF)-platelet glycoprotein Ib (GP Ib) interaction. The effects of paeoniflorin on platelet functions under high shear stress were confirmed in the ex vivo SIPA models in rats, showing the good accordance with the anti-SIPA effects on human platelets. Treatment with paeoniflorin significantly prevented arterial thrombosis in vivo from the dose of 10 mg/kg without prolonging bleeding time or blood clotting time in rats. Collectively, our results demonstrated that paeoniflorin can be a novel anti-platelet agent selectively targeting SIPA with an improved safety profile.

Effect of a New Monoclonal Anti-Glycoprotein IX Antibody, KMP-9, on High Shear-Induced Platelet Aggregation

1997 ◽  
Vol 78 (02) ◽  
pp. 902-909 ◽  
Author(s):  
Tetsuya Miyake ◽  
Shosaku Nomura ◽  
Yutaka Komiyama ◽  
Yasuhiko Miyazaki ◽  
Hideo Kagawa ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Physiological Role ◽  
Inhibitory Effect ◽  
Platelet Glycoprotein ◽  
High Shear ◽  
High Shear Stress ◽  
Receptor Component ◽  
Induced Aggregation

SummaryHuman platelet glycoprotein Ib/IX complex acts as a receptor for von Willebrand factor. It is widely accepted that glycoprotein lb is the essential receptor component, but the role of glycoprotein IX is still unclear. We produced a new monoclonal anti-glycoprotein IX antibody (KMP-9) by the hybridoma technique using platelets from a patient with Glanzmann’s thrombasthenia. The epitope of KMP-9 was localized to the C-terminal 8 kD fragment of glycoprotein IX using ELISA analysis of polyethylene-pin-synthesized peptides, as well as Western blot analysis of platelets after digestion with N-glycosidase and Staphylococcus aureus V8 protease. KMP-9 partially inhibited high shear stress-induced platelet aggregation, but had no effect on aggregation induced by ristocetin or low shear stress. Its inhibitory effect on high shear stress-induced aggregation was weaker than that of antiglycoprotein lb or anti-glycoprotein Ilb/IIIa monoclonal antibodies. A 21-mer synthetic peptide (glycoprotein IX L110-G130) inhibited the binding of KMP-9 to platelets. It also competively inhibited the suppression of high shear stress-induced platelet aggregation by KMP-9, but had no direct effect on this aggregation. KMP-9 may be useful to clarify the physiological role of GPIX.

scholarly journals High shear stress can initiate both platelet aggregation and shedding of procoagulant containing microparticles

Blood ◽  
1996 ◽  
Vol 88 (9) ◽  
pp. 3456-3464 ◽  
Author(s):  
Y Miyazaki ◽  
S Nomura ◽  
T Miyake ◽  
H Kagawa ◽  
C Kitada ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Coagulation Cascade ◽  
Platelet Glycoprotein ◽  
High Shear ◽  
High Shear Stress ◽  
Microparticle Formation ◽  
High Level ◽  
Von Willebrand ◽  
Willebrand Factor

Previous studies have demonstrated that a high level of shear stress can produce platelet aggregation without the addition of any agonist. We investigated whether high shear stress could cause both platelet aggregation and shedding of microparticles from the platelet plasma membrane. A coneplate viscometer was used to apply shear stress and microparticle formation was measured by flow cytometry. It was found that microparticle formation increased as the duration of shear stress increased. Both microparticles and the remnant platelets showed the exposure of procoagulant activity on their surfaces. Investigation of the mechanisms involved in shear-dependent microparticle generation showed that binding of von Willebrand factor (vWF) to platelet glycoprotein lb, influx of extracellular calcium, and activation of platelet calpain were required to generate microparticles under high shear stress conditions. Activation of protein kinase C (PKC) promoted shear-dependent microparticle formation. Epinephrine did not influence microparticle formation, although it enhanced platelet aggregation by high shear stress. These findings suggest the possibility that local generation of microparticles in atherosclerotic arteries, the site that pathologically high shear stress could occur, may contribute to arterial thrombosis by providing and expanding a catalytic surface for the coagulation cascade.

Platelet Aggregation and Activation under Complex Patterns of Shear Stress

2002 ◽  
Vol 88 (11) ◽  
pp. 817-821 ◽  
Author(s):  
Jian-ning Zhang ◽  
Angela Bergeron ◽  
Qinghua Yu ◽  
Carol Sun ◽  
Larry McIntire ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Low Flow ◽  
High Shear ◽  
High Shear Stress ◽  
Fast Flow ◽  
Low Shear

SummaryArterial stenosis results in a complex pattern of blood flow containing an extremely fast flow in the throat of stenosis and a post-stenosis low flow. The fast flow generates high shear stress that has been demonstrated in vitro to activate and aggregate platelets. One potential problem of these in vitro studies is that platelets are invariably exposed to a high shear stress for a period that is significantly longer than they would have experienced in vivo. More importantly, the role of the poststenosis low flow in platelet activation and aggregation has not been determined. By exposing platelets to a shear profile that contains both high and low shear segments, we found that platelets aggregate when they are exposed to a high shear stress of 100 dyn/cm2 for as short as 2.5 s, a period that is significantly shorter than those previously reported (30–120 s). Platelet aggregation under this condition requires a low shear exposure immediately after a high shear pulse, suggesting that post-stenosis low flow enhances platelet aggregation. Furthermore, platelet aggregation under this condition is not activation-dependent because the CD62P expression of sheared platelets is significantly less than that of platelets treated with ADP. Based on these findings, we propose that shear-induced platelet aggregation may be a process of mechanical crosslinking of platelets, requiring minimal platelet activation. This process may function as a protective mechanism to prevent in vivo irreversible platelet activation and aggregation under temporary high shear.

Duration of exposure to high fluid shear stress is critical in shear-induced platelet activation-aggregation

2003 ◽  
Vol 90 (10) ◽  
pp. 672-678 ◽  
Author(s):  
Zhang Jian-ning ◽  
Angela Bergeron ◽  
Qinghua Yu ◽  
Carol Sun ◽  
Latresha McBride ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Whole Blood ◽  
Fluid Shear Stress ◽  
High Shear ◽  
Platelet Response ◽  
Short Pulses ◽  
Hydrodynamic Effects

SummaryPlatelet functions are increasingly measured under flow conditions to account for blood hydrodynamic effects. Typically, these studies involve exposing platelets to high shear stress for periods significantly longer than would occur in vivo. In the current study, we demonstrate that the platelet response to high shear depends on the duration of shear exposure. In response to a 100 dyn/cm2 shear stress for periods less than 10-20 sec, platelets in PRP or washed platelets were aggregated, but minimally activated as demonstrated by P-selectin expression and binding of the activation-dependent αIIbβ3 antibody PAC-1 to sheared platelets. Furthermore, platelet aggregation under such short pulses of high shear was subjected to rapid disaggregation. The disaggregated platelets could be re-aggregated by ADP in a pattern similar to unsheared platelets. In comparison, platelets that are exposed to high shear for longer than 20 sec are activated and aggregated irreversibly. In contrast, platelet activation and aggregation were significantly greater in whole blood with significantly less disaggregation. The enhancement is likely via increased collision frequency of platelet-platelet interaction and duration of platelet-platelet association due to high cell density. It may also be attributed to the ADP release from other cells such as red blood cells because increased platelet aggregation in whole blood was partially inhibited by ADP blockage. These studies demonstrate that platelets have a higher threshold for shear stress than previously believed. In a pathologically relevant timeframe, high shear alone is likely to be insufficient in inducing platelet activation and aggregation, but acts synergistically with other stimuli.

Numerical Study on Diastolic Left Ventricular Hemodynamics Using Motion Models of Mitral Valve With/Without Edge-to-Edge Repair

2010 ◽  
Author(s):  
Yingying Hu ◽  
Liang Shi ◽  
Siva Parameswaran ◽  
Sergey A. Smirnov ◽  
Zhaoming He
Keyword(s):  
Shear Stress ◽  
Mitral Valve ◽  
Left Ventricle ◽  
Platelet Activation ◽  
Numerical Study ◽  
Left Ventricular ◽  
High Shear ◽  
High Shear Stress ◽  
Orifice Area ◽  
Motion Models

Edge-to-edge repair (ETER) is a newly developed technique to correct such mitral valve (MV) malfunctions as regurgitation [1,2]. This technique changes MV geometric configuration by suturing the anterior and posterior leaflets at central or commissural edges, and consequently alters MV and left ventricle (LV) dynamics. For instance, stress in the MV elevated due to ETER may cause leaflets tearing near suture. Little has been known about shear stress on the MV and LV walls under MV ETER conditions, where high shear stress might cause platelet activation or hemolysis [3]. When ETER is done at the central leaflet edges, it generates two MV orifices, leads to two deflected jets, and completely changes vortices in the LV. ETER also reduces the orifice area, and increases jet velocity and transmitral pressure [1,2,4]. Flow patterns in the LV and ETER effects on the LV and MV functions have not been understood well.

A critical role for thrombin in platelet aggregation under high shear stress

2004 ◽  
Vol 113 (5) ◽  
pp. 311-318 ◽  
Author(s):  
Yoshihiko Sakurai ◽  
Midori Shima ◽  
John Giddings ◽  
Masahiro Takeyama ◽  
Shogo Kasuda ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Critical Role ◽  
High Shear ◽  
High Shear Stress

Shear Stress Initiates Cyclophilin D-Dependent Phosphatidylserine Exposure and Integrin αIIbβ3 Cleavage in Platelets

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3301-3301
Author(s):  
Fang Liu ◽  
Shawn M Jobe
Keyword(s):  
Shear Stress ◽  
Extracellular Calcium ◽  
Stress Conditions ◽  
High Shear ◽  
Cyclophilin D ◽  
High Shear Stress ◽  
Integrin Αiibβ3 ◽  
Platelet Accumulation ◽  
Platelet Formation

Abstract Abstract 3301 When platelets are simultaneously stimulated by multiple agonists, such as thrombin and collagen, a subpopulation of procoagulant platelets is formed that is characterized by phosphatidylserine (PS) exposure, integrin αIIbβ3 inactivation, and a rounded morphology in a process that is dependent on the mitochondrial permeability transition pore (mPTP) regulatory protein cyclophilin D (CypD). Recently, we have found that, in the absence of platelet CypD, platelet accumulation is markedly accentuated both in vitro and in vivo indicating that CypD-dependent procoagulant platelet formation may limit thrombus growth. Interestingly, the importance of CypD in limiting platelet accumulation was most evident in shear stress conditions consistent with arterial flow. In low (300 s−1) and high (1500 s−1) shear conditions, CypD null platelet accumulation was increased 1.5- and 4-fold compared to wild type platelets, respectively. Platelet activation and procoagulant platelet formation were examined in various shear conditions. In platelets subjected to increasing shear, PS exposure, but not P-selectin expression or integrin αIIbβ3 activation, was observed in a platelet subpopulation. When subjected to high shear in vitro as many as 70 % of platelets expressed high levels of PS on their surface within 5 min, and shear-dependent PS exposure was observed in as little as 30 seconds in high shear stress conditions. Previously we demonstrated that agonist-initiated PS exposure is closely associated with integrin αIIbβ3 cleavage and inactivation. In shear-treated, as in strongly-stimulated platelets, integrin αIIbβ3 cleavage was closely associated with PS exposure. PS exposure and integrin αIIbβ3 cleavage were not observed in the absence of VWF. In contrast to agonist-initiated PS exposure, shear stress-induced PS exposure was observed even in the absence of extracellular calcium. In a previous study, platelet PS exposure and apoptosis induced by ristocetin were found to be closely associated with an increase in the expression of the BH3-proteins, Bax and Bak. This finding, along with the observation that shear-stress dependent PS exposure occurred even in the absence of extracellular calcium led us to examine the role of Bax and Bak. However, shear stress-induced PS exposure was unaffected in Bax/Bak null platelets. In contrast, both shear stress-induced PS exposure and integrin αIIbβ3 cleavage were markedly blunted in CypD null platelets. Furthermore, shear stress induced-PS exposure was closely associated with loss of mitochondrial transmembrane potential, together indicating the importance of mPTP formation in the regulation of PS exposure in high shear stress conditions. These data identify a novel VWF- and CypD-dependent pathway that results in rapid PS exposure and integrin αIIbβ3 cleavage in high-shear stress conditions. This shear stress-initiated pathway of PS exposure, distinct from thrombin-collagen initiated PS exposure, does not require extracellular calcium and is not associated with P-selectin expression. Disclosures: Jobe: Baxter: Membership on an entity's Board of Directors or advisory committees.

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