120 results on '"Kroll, Michael H."'
Search Results
102. Magnesium maintains endothelial integrity, up-regulates proteolysis of ultra-large von Willebrand factor, and reduces platelet aggregation under flow conditions
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Dong, Jing-fei, Cruz, Miguel A., Aboulfatova, Khatira, Martin, Cecilia, Choi, Hiuwan, Bergeron, Angela L., Martini, Sheryl R., Kroll, Michael H., and Kent, Thomas A.
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- 2008
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103. Biochemical Mechanisms of Platelet Activation
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Kroll, Michael H. and Schafer, Andrew I.
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- 1989
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104. The Activation-Induced Decrease in the Platelet Surface Expression of the Glycoprotein Ib-IX Complex Is Reversible
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Michelson, Alan D., Benoit, Stephen E., Kroll, Michael H., Li, Jian-Ming, Rohrer, Michael J., Kestin, Anita S., and Barnard, Marc R.
- Abstract
Thrombin decreases the platelet surface expression of the glycoprotein (GP) Ib-IX complex. To determine whether this effect is reversible, flow cytometric studies were performed with GPIb-IX-specific monoclonal antibodies. In both whole blood and washed platelet systems, incubation of platelets with thrombin or a combination of adenosine diphosphate and epinephrine resulted in a maximal decrease of the platelet surface expression of GPIb-IX within 5 minutes, after which there was a time-dependent return of the platelet surface GPIb-IX complex, which was maximal by 60 minutes. Exposure of the same platelets to additional exogenous thrombin resulted in a second decrease in platelet surface GPIb-IX, followed by a second reconstitution of platelet surface GPIb-IX. Throughout these experiments there was no measurable release from the platelets of glycocalicin (a proteolytic fragment of GPIb). Experiments in which platelets were preincubated with a biotinylated GPIb-specific MoAb showed that the GPIb molecules that returned to the platelet surface were the same molecules that had been translocated to the intraplatelet pool. The GPIb molecules that returned to the platelet surface were functionally competent to bind von Willebrand factor, as determined by ristocetin-induced platelet agglutination and ristocetin-induced binding of exogenous von Willebrand factor. Inhibitors of protein kinase C and myosin light-chain kinase enhanced the reexpression of platelet surface GPIb. In summary, the activation-induced decrease in the platelet surface expression of the GPIb-IX complex is reversible. Inactivation of protein kinase C and myosin light-chain kinase are important mechanisms in the reexpression of the platelet surface GPIb-IX complex.
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- 1994
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105. Shear Stress-Induced von Willebrand Factor Binding to Platelet Glycoprotein lb Initiates Calcium Influx Associated With Aggregation
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Chow, Thomas W., Hellums, J. David, Moake, Joel L., and Kroll, Michael H.
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- 1992
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106. Thrombin Receptors Activate Potassium and Chloride Channels
- Author
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Sullivan, Richard, Kunze, Diana L., and Kroll, Michael H.
- Abstract
We used DAMI human megakaryocytic leukemia cells to study transmembrane ion currents activated through the G-protein-coupled thrombin receptor pathway. When the cells were stimulated by thrombin receptor-activating peptide, an increase in cytosolic Ca2+([Ca2+]i| developed as predicted by the known effect that thrombin exerts in the platelet. We then monitored the membrane potentials of individual DAMI cells during this response and observed complex, triphasic changes that could not be accounted for by Ca2+fluxes alone. These consisted of rapid hyperpolarization, followed by depolarization to values more positive than the resting potential and then by slow repolarization. For the purpose of this study, we focused on the hyperpolarizing current that developed immediately after thrombin receptor activation. This proved to be composed of (1) a Ca2+-independent, outwardly rectifying Cl-current and (2) a strongly hyperpolarizing, inwardly rectifying, Ba2+-sensitive K+current that required an increase of [Ca2+]i for activation. By analogy with their functions in other cell systems, it is logical to conclude that these prominent K+and CI-conductances may serve to regulate the complex volume changes that accompany thrombin receptor activation and/or to increase the electromotive drive that supports Ca2+influx under these conditions through hyperpolarization of the cell membrane.
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- 1996
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107. Hematological Complications of Immune Checkpoint Inhibitors
- Author
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Kroll, Michael H, Rojas-Hernandez, Cristhiam, and Yee, Cassian
- Abstract
Immune checkpoint inhibitors are a class of anti-neoplastic therapies that unleash immune cells to kill malignant cells. There are currently 7 medications FDA-approved for the treatment of 14 solid tumors and 2 hematological malignancies. These medications commonly cause immune-related adverse effects due to overactive T lymphocytes, autoantibody production, and/or cytokine dysregulation. Hematological toxicities are rare and of uncertain mechanism, and therefore management is often based on experiences with familiar conditions involving these perturbed immune responses, such as autoimmune hemolytic anemia, immune thrombocytopenia, and idiopathic aplastic anemia. Management is challenging because one must attend to the hematological toxicity while simultaneously attending to the malignancy, with the imperative that effective cancer therapy be maintained or minimally interrupted if possible. The purpose of this review is to assist clinicians by providing a clinical and pathophysiological framework in which to view these problems.
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- 2021
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108. Control of platelet protein kinase C activation by cyclic AMP
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Kroll, Michael H., primary, Zavoico, George B., additional, and Schafer, Andrew I., additional
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- 1988
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109. M r 6,400 aurin tricarboxylic acid directly activates platelets
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Guo, Zhaozeng, Weinstein, Mark J., Phillips, Martin D., and Kroll, Michael H.
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- 1993
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110. Platelets and Shear Stress
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Kroll, Michael H., Heliums, J.David, Mclntire, Larry V., Schafer, Andrew I., and Moake, Joel L.
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- 1996
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111. Regulation of the phosphoinositide cycle by Na +/H + exchange and intracellular pH in human platelets
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Luzzatto, Guido, Kroll, Michael H., Zavoico, George B., and Schafer, Andrew I.
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- 1991
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112. Shear Stress Directly Regulates Platelet aIIbß3 Signaling.
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Feng, Shuju, Lu, Xin, Resendiz, Julio C., and Kroll, Michael H.
- Abstract
Integrin mechanotransduction is a ubiquitous biological process. Mechanical forces are transduced by an integrin’s ligand-bound extracellular domain through its ß subunit’s cytoplasmic domain connected to the cytoskeleton. This often culminates in the activation of tyrosine kinases directing cell responses. The delicate balance between hemostasis and thrombosis requires exquisitely fine-tuned integrin function, and balance is maintained in vivo despite that the major platelet integrin aIIbß3 is continuously subjected to frictional or shearing forces generated by laminar blood flow. To test the hypothesis that platelet function is regulated by the direct effects of mechanical forces on aIIbß3, we examined aIIbß3/cytoskeletal interactions in human platelets exposed to shear stress in a cone-plate viscometer. We observed that a-actinin, myosin heavy chain and Syk co-immunoprecipitate with aIIbß3 in resting platelets, and that 120 dynes/cm2 shear stress leads to their disassociation from aIIbß3. Shear-induced disassociation of a-actinin and myosin heavy chain from the ß3 tail is unaffected by blocking VWF binding to GpIb-IX-V but abolished by blocking VWF binding to aIIbß3. Syk’s disassociation from ß3 is inhibited when VWF binding to either GpIb-IX-V or aIIbß3 is blocked. Shear stress-induced phosphorylation of SLP-76 and its association with tyrosine phosphorylated SLAP-130 are inhibited by blocking ligand binding to aIIbß3 but not by blocking ligand binding to GpIb-IX-V. Chinese hamster ovary (CHO) cells expressing human aIIbß3 demonstrate calcium and shear-dependent (1 and 10 dynes/cm2) attachment to glass cover slips coated with 20 µg/ml VWF. CHO cells expressing aIIbß3 with ß3 truncated of its cytoskeletal binding domains at C-terminal residue 716 demonstrate decreased VWF-dependent adhesion and cohesion in response to 1 dyne/cm2 shear stress. These results support the hypothesis that shear stress directly modulates aIIbß3 function, and suggest that shear-induced aIIbß3-mediated signaling regulates platelet aggregation by directing the release of a-actinin and myosin heavy chain from the ß3 tail.
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- 2005
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113. Durability of partial splenic artery embolization on platelet counts for cancer patients with hypersplenism-related thrombocytopenia.
- Author
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Hill, Ashley, Elakkad, Ahmed, Kuban, Joshua, Sabir, Sharjeel, Odisio, Bruno, Huang, Steven Y., Mahvash, Armeen, Miller, Ethan, Kroll, Michael H., Overman, Michael, Tam, Alda L., Gupta, Sanjay, and Sheth, Rahul A.
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SPLENIC artery , *PLATELET count , *CANCER patients , *THROMBOCYTOPENIA , *DURABILITY , *SYMPTOMS , *BLOOD platelets - Abstract
Purpose: Partial splenic artery embolization (PSAE) has shown promise in increasing platelet counts in cancer patients with hypersplenism-related thrombocytopenia. The purpose of this study was to identify response predictors and to longitudinally evaluate PSAE efficacy and durability in a large cohort of cancer patients with hypersplenism-related thrombocytopenia. Methods: A single-institution, IRB-approved, HIPAA-compliant retrospective review of all PSAEs for thrombocytopenia between 2012 and 2015 was performed. Patients were classified as complete responders (CR, no platelet value < 100 × 109/L following PSAE), partial responders (PR, initial increase in platelets but subsequent decrease in platelets < 100 × 109/L), and non-responders (NR, platelets never > 100 × 109/L following PSAE). Results: Of the 98 patients included in the study, 58 had CR (59%), 28 had PR (29%), and 12 patients had NR (12%). The percent splenic tissue embolized was significantly greater in the CR group compared to the PR group (P = 0.001). The percent volume of splenic tissue embolized was linearly correlated with the magnitude of platelet increase without a minimum threshold. At least one line of chemotherapy was successfully restarted in 97% of patients, and 41% of patients did not experience recurrence of thrombocytopenia for the duration of their survival. The major complication rate was 8%, with readmission following initial hospitalization for persistent "post-embolization syndrome" symptoms the most common. Conclusions: In cancer patients with hypersplenism-related thrombocytopenia, PSAE is a safe intervention that effects a durable elevation in platelet counts across a range of malignancies and following the re-initiation of chemotherapy. [ABSTRACT FROM AUTHOR]
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- 2020
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114. A pilot study of lower doses of ibrutinib in patients with chronic lymphocytic leukemia.
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Chen, Lisa S., Bose, Prithviraj, Cruz, Nichole D., Yongying Jiang, Qi Wu, Thompson, Philip A., Shuju Feng, Kroll, Michael H., Wei Qiao, Xuelin Huang, Nitin Jain, Wierda, William G., Keating, Michael J., and Gandhi, Varsha
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IBRUTINIB , *CHRONIC lymphocytic leukemia treatment , *PROTEIN-tyrosine kinases , *PHARMACOKINETICS , *PHARMACODYNAMICS - Abstract
Ibrutinib is highly efficacious and used at 420 mg/d for treatment of chronic lymphocytic leukemia (CLL). We previously demonstrated a decline in Bruton's tyrosine kinase (BTK) protein levels in CLL cells after 1 cycle of ibrutinib, suggesting ibrutinib dose could be lowered after the first cycle without loss of biological effect. To test this postulate, a pilot study (NCT02801578) was designed to systematically reduce ibrutinib dosing within the same patient with CLL over the course of three 28-day cycles. After an initial cycle of 420 mg/d, the dose was reduced to 280 mg/d in cycle 2, and then to 140 mg/d in cycle 3. Eleven patients began study treatment, and 9 completed the 3 cycles. Plasma and intracellular pharmacokinetics (PK), BTK occupancy, and pharmacodynamic (PD) response at different doses of ibrutinib were compared. Plasma and intracellular levels of ibrutinib were dose-dependent, and even the lowest dose was sufficient to occupy, on average, more than 95% of BTK protein. In concert, BTK downstream signaling inhibition was maintained with 140 mg/d ibrutinib in cycle 3, and there were comparable reductions in total and phospho-BTK (Tyr223) protein levels across 3 cycles. Reductions of plasma chemokine CCL3 and CCL4 levels, considered to be biomarkers of ibrutinib response, were similar during the 3 cycles. These PK/PD data demonstrate that after 1 cycle of ibrutinib at the standard 420 mg/d dose, the dose can be reduced without losing biological activity. Clinical efficacy of lower doses needs to be systematically evaluated. Such dose reductions would lower drug cost, lessen untoward toxicity, and facilitate rationale-based combinations. This trial was registered at www.clinicaltrials.gov as #NCT02801578 [ABSTRACT FROM AUTHOR]
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- 2018
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115. 3. - The Analysis of Ligand-Receptor Interactions in Platelet Activation
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Kroll, Michael H. and Schafer, Andrew I.
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- 1995
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116. Mechanical Venous Thrombectomy for Deep Venous Thrombosis in Cancer Patients: A Single-Center Retrospective Study.
- Author
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Patel RM, Pal K, Ahmed SH, Kuban JD, Patel M, Shah K, Habibollahi P, Metwalli Z, Gurusamy V, Gupta S, Rojas-Hernandez CM, Afshar-Kharghan V, Kroll MH, and Sheth RA
- Subjects
- Humans, Retrospective Studies, Female, Male, Middle Aged, Aged, Adult, Treatment Outcome, Aged, 80 and over, Venous Thrombosis diagnostic imaging, Venous Thrombosis therapy, Neoplasms complications, Thrombectomy methods
- Abstract
Purpose: Venous thromboembolism (VTE) is a major contributor to the mortality of cancer patients. Mechanical thrombectomy (MT) is an endovascular technique that physically removes a thrombus without thrombolytics. The purpose of this study was to evaluate safety, efficacy, and clinical outcomes following MT for lower extremity DVT in cancer patients., Methods: This single-center, retrospective study evaluated outcomes following MT of lower extremity DVT in cancer patients from November 2019 to May 2023. The primary outcome measure was clinical success, defined as a decrease in Villalta score by at least 2 points following the intervention. Secondary outcomes included repeat intervention-free survival and overall survival. Technical success was defined as restoring venous flow with mild (< 10%) or no residual filling defect., Results: In total, 90 patients and 113 procedures were included. Technical and clinical success was achieved in 81% and 87% of procedures performed. Repeat intervention-free survival at 1 month, 3 months, and 6 months post-procedure was 92%, 82%, and 77%, respectively. The complication rate was 2.7%. Pathologic analysis of the extracted thrombus revealed tumor thrombus in 18.4% (18/98) samples. Overall survival for the study cohort was 87% at 1 month, 74% at 3 months, and 62% at 6 months. Patients who were found to have tumor thrombi were noted to have a decreased overall survival compared to patients with non-tumor thrombi (P = 0.012)., Conclusion: MT is safe and efficacious in reducing cancer patients' VTE-related symptoms. The high rate of tumor thrombus in thrombectomy specimens suggests this phenomenon is more common than suspected., (© 2024. The Author(s).)
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- 2024
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117. Checkpoint inhibitors.
- Author
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Kroll MH
- Subjects
- Humans, Immunotherapy adverse effects, Cytokines, Immune Checkpoint Inhibitors, Neoplasms drug therapy, Neoplasms etiology, Antineoplastic Agents adverse effects
- Abstract
Immune checkpoint inhibitors are a class of antineoplastic therapies that unleash immune cells to kill malignant cells. These medications commonly cause immune-related adverse effects due to activated adaptive and innate immune cells, autoantibody production, and/or cytokine dysregulation. Hematologic toxicities are rare and of uncertain mechanism, and therefore management is often based on experiences with familiar conditions involving these perturbed immune responses. Management is challenging because one must attend to the hematologic toxicity while simultaneously attending to the malignancy, with the imperative that therapeutic effects be maintained or minimally interrupted when possible., (Copyright © 2023 by The American Society of Hematology.)
- Published
- 2023
- Full Text
- View/download PDF
118. Measurement of adherence and health-related quality of life during anticoagulation therapy in cancer-associated venous thromboembolism (VTE): a multicenter quantitative study.
- Author
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Font C, Gomez-Mesa JE, López-Núñez JJ, Calderón C, Galindo-Coral S, Wu CC, Ma J, Kroll MH, and Rojas-Hernandez CM
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- Adult, Humans, Anticoagulants therapeutic use, Quality of Life, Venous Thromboembolism drug therapy, Venous Thromboembolism etiology, Venous Thrombosis, Neoplasms complications
- Abstract
Purpose: Therapy for cancer-associated venous thromboembolism (VTE) includes long-term anticoagulation, which may have substantial impact on the health-related quality of life (HRQL) of patients. We assessed patient-reported outcomes to characterize the HRQL associated with VTE treatment and to begin to examine those HRQL elements impacting anticoagulation adherence (AA)., Methods: Participants were adult cancer patients with confirmed symptomatic acute lower extremity deep venous thrombosis. Patients were excluded if there was an indication for anticoagulation other than VTE, ECOG performance status >3, or life expectancy < 3 months. Participants were assessed with a self-reported adherence tool. HRQL was measured with a 6-domain questionnaire using a seven-point Likert scale. Evaluations were performed at 30 days and 3 months after enrollment. For the primary objective, an overall adherence rate was calculated at each time point of evaluation. For the HRQL domains, non-parametric testing was used to compare results between subgroups., Results: Seventy-four patients were enrolled. AA and HRQL at 30 days and 3 months were assessed in 50 and 36 participants, respectively. At 30 days the AA rate was 90%, and at 3 months it was 83%. In regard to HRQL, patients suffered frequent and moderate-severe distress in the domains of emotional and physical symptoms, sleep disturbance, and limitations to physical activity. An association between emotional or physical distress and AA was observed., Conclusion: Patients with VTE suffer a substantial impairment of their HRQL. Increased emotional distress correlated with better long-term AA. These results can be used to inform additional research aimed at developing novel strategies to improve AA., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)
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- 2023
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119. Hematologic complications of immune checkpoint inhibitors.
- Author
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Kroll MH, Rojas-Hernandez C, and Yee C
- Subjects
- Humans, Immune Checkpoint Inhibitors, Anemia, Hemolytic, Autoimmune chemically induced, Anemia, Hemolytic, Autoimmune drug therapy, Antineoplastic Agents adverse effects, Hematologic Neoplasms therapy, Neoplasms drug therapy
- Abstract
Immune checkpoint inhibitors are a class of antineoplastic therapies that unleash immune cells to kill malignant cells. There are currently 7 medications that have been approved by the US Food and Drug Administration for the treatment of 14 solid tumors and 2 hematologic malignancies. These medications commonly cause immune-related adverse effects as a result of overactive T lymphocytes, autoantibody production, and/or cytokine dysregulation. Hematologic toxicities are rare and of uncertain mechanism, and therefore management is often based on experiences with familiar conditions involving these perturbed immune responses, such as autoimmune hemolytic anemia, immune thrombocytopenia, and idiopathic aplastic anemia. Management is challenging because one must attend to the hematologic toxicity while simultaneously attending to the malignancy, with the imperative that effective cancer therapy be maintained or minimally interrupted if possible. The purpose of this review is to help clinicians by providing a clinical and pathophysiological framework in which to view these problems., (© 2022 by The American Society of Hematology.)
- Published
- 2022
- Full Text
- View/download PDF
120. Purinergic P2Y12 receptor blockade inhibits shear-induced platelet phosphatidylinositol 3-kinase activation.
- Author
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Reséndiz JC, Feng S, Ji G, Francis KA, Berndt MC, and Kroll MH
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- Blood Platelets enzymology, Chromones pharmacology, Enzyme Inhibitors, Enzyme Precursors metabolism, Humans, In Vitro Techniques, Intracellular Signaling Peptides and Proteins, Morpholines pharmacology, Phosphatidylinositol Phosphates metabolism, Phosphorylation, Platelet Glycoprotein GPIb-IX Complex metabolism, Protein-Tyrosine Kinases metabolism, Receptors, Purinergic P2Y12, Signal Transduction, Stress, Mechanical, Syk Kinase, Tyrosine metabolism, von Willebrand Factor metabolism, Blood Platelets drug effects, Membrane Proteins, Phosphatidylinositol 3-Kinases metabolism, Purinergic P2 Receptor Antagonists
- Abstract
Pathologically elevated shear stress triggers aspirin-insensitive platelet thrombosis. Signaling mechanisms involved in shear-induced platelet thrombosis are not well understood. To investigate these, we examined the hypothesis that functionally important platelet phosphatidylinositol 3-kinase (PI3-K) activity is stimulated by an in vitro shear stress of 120 dynes/cm(2) (shear rate of 6,000 sec(-1)). Phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) production was examined in washed human platelets subjected to pathological shear stress in a cone-plate viscometer. PIP(3) production peaks 30 s after shear begins and is initiated by von Willebrand factor (VWF) binding to the glycoprotein (Gp) Ib-IX-V complex. Inhibiting PI3-K with wortmannin or 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) results in the inhibition of shear-induced platelet aggregation. In resting platelets, class IA PI3-K associates with the tyrosine kinase Syk. Within 30 s of beginning shear, PI3-K-associated Syk becomes tyrosine phosphorylated. Inhibiting Syk activation with piceatannol results in the inhibition of PIP(3) production and aggregation. Selective blockade of the P2Y(12) receptor results in the inhibition of Syk phosphorylation, PIP(3) production, and aggregation. These results indicate that shear-induced VWF binding to platelet GpIb-IX-V stimulates functionally important PI3-K activity. PI3-K activation is signaled by rapid feedback amplification that involves P2Y(12) receptor-mediated activation of Syk.
- Published
- 2003
- Full Text
- View/download PDF
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