Browsing by Author "Paresh P. Kulkarni"

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Aerobic glycolysis fuels platelet activation: Small-molecule modulators of platelet metabolism as anti-thrombotic agents
(Ferrata Storti Foundation, 2019) Paresh P. Kulkarni; Arundhati Tiwari; Nitesh Singh; Deepa Gautam; Vijay K. Sonkar; Vikas Agarwal; Debabrata Dash
Platelets are critical to arterial thrombosis, which underlies myocardial infarction and stroke. Activated platelets, regardless of the nature of their stimulus, initiate energy-intensive processes that sustain thrombus, while adapting to potential adversities of hypoxia and nutrient deprivation within the densely packed thrombotic milieu. We report here that stimulated platelets switch their energy metabolism to aerobic glycolysis by modulating enzymes at key checkpoints in glucose metabolism. We found that aerobic glycolysis, in turn, accelerates flux through the pentose phosphate pathway and supports platelet activation. Hence, reversing metabolic adaptations of platelets could be an effective alternative to conventional anti-platelet approaches, which are crippled by remarkable redundancy in platelet agonists and ensuing signaling pathways. In support of this hypothesis, small-molecule modulators of pyruvate dehydrogenase, pyruvate kinase M2 and glucose-6-phosphate dehydrogenase, all of which impede aerobic glycolysis and/or the pentose phosphate pathway, restrained the agonist-induced platelet responses ex vivo. These drugs, which include the anti-neoplastic candidate, di ch loroacetate, and th e Food and Drug Administration-approved dehydroepiandrosterone, profoundly impaired thrombosis in mice, thereby exhibiting potential as anti-thrombotic agents. © 2019 Ferrata Storti Foundation.
Amine-modified graphene: Thrombo-protective safer alternative to graphene oxide for biomedical applications
(2012) Sunil K. Singh; Manoj K. Singh; Paresh P. Kulkarni; Vijay K. Sonkar; José J. A. Grácio; Debabrata Dash
Graphene and its derivatives have attracted significant research interest based on their application potential in different fields including biomedicine. However, recent reports from our laboratory and elsewhere have pointed to serious toxic effects of this nanomaterial on cells and organisms. Graphene oxide (GO) was found to be highly thrombogenic in mouse and evoked strong aggregatory response in human platelets. As platelets play a central role in hemostasis and thrombus formation, thrombotoxicity of GO potentially limits its biomedical applications. Surface chemistry of nanomaterials is a critical determinant of biocompatibility, and thus differentially functionalized nanomaterials exhibit varied cellular toxicity. Amine-modified carbon nanotubes have recently been shown to possess cytoprotective action, which was not exhibited by their relatively toxic carboxylated counterparts. We, therefore, evaluated the effect of amine modification of graphene on platelet reactivity. Remarkably, our results revealed for the first time that amine-modified graphene (G-NH 2) had absolutely no stimulatory effect on human platelets nor did it induce pulmonary thromboembolism in mice following intravenous administration. Further, it did not evoke lysis of erythrocytes, another major cellular component in blood. These findings contrasted strikingly the observations with GO and reduced GO (RGO). We conclude that G-NH 2 is not endowed with thrombotoxic property unlike other commonly investigated graphene derivatives and is thus potentially safe for in vivo biomedical applications. © 2012 American Chemical Society.
AMPK inhibition protects against arterial thrombosis while sparing hemostasis through differential modulation of platelet responses
(Elsevier Ltd, 2020) Paresh P. Kulkarni; Vijay K. Sonkar; Deepa Gautam; Debabrata Dash
AMP-activated protein kinase (AMPK) is a metabolic master switch that has critical role in wide range of pathologies including cardiovascular disorders. As AMPK-α2 knockout mice exhibit impaired thrombus stability, we asked whether pharmacological inhibition of AMPK with a specific small-molecule inhibitor, compound C, could protect against arterial thrombosis without affecting hemostasis. Mice pre-administered with compound C exhibited decreased mesenteric arteriolar thrombosis but normal tail bleeding time compared to vehicle-treated animals. Compound C potently restricted platelet aggregation, clot retraction and integrin activation induced by thrombin and collagen. It impaired platelet spreading on both immobilized fibrinogen and collagen matrices; it, however, had no significant effect on thrombin-induced phosphatidylserine exposure that is characteristic of procoagulant platelets. In parallel, compound C brought about significant drop in thrombin-induced phosphorylation of myosin light chain (MLC) and MLC phosphatase (MYPT1) as well as abrogated rise in level of RhoA-GTP in thrombin-stimulated platelets. Thus, effects of compound C on agonist-induced platelet responses could be at least in part attributed to modulation of cytoskeletal changes mediated by RhoA-MYPT1-MLC signaling. An ideal antithrombotic drug would spare hemostatic responses that maintain vascular integrity while preferentially protecting against thrombosis. The present study suggests that AMPK could be one such potential therapeutic target. © 2020 Elsevier Ltd
Amyloid β peptide stimulates platelet activation through RhoA-dependent modulation of actomyosin organization
(FASEB, 2014) Vijay K. Sonkar; Paresh P. Kulkarni; Debabrata Dash
Platelets contribute to 95% of circulating amyloid precursor protein in the body and have widely been employed as a "peripheral" model of neurons in Alzheimer's disease. We sought to analyze the effects of amyloid β (Aβ) on platelets and to understand the underlying molecular mechanism. The Aβ active fragment containing amino acid sequence 25-35 (Aβ25-35; 10-20 μM) was found to induce strong aggregation of human platelets, granule release, and integrin activation, similar to that elicited by physiological agonists. Platelets exposed to Aβ25-35 retracted fibrin clot and displayed augmented adhesion to collagen under arterial shear, reflective of a switch to prothrombotic phenotype. Exposure of platelets to Aβ peptide (20 μM) resulted in a 4.2- and 2.3-fold increase in phosphorylation of myosin light chain (MLC) and MLC phosphatase, respectively, which was reversed by Y27632, an inhibitor of Rho-associated coiled-coil protein kinase (ROCK). Aβ25-35- induced platelet aggregation and clot retraction were also significantly attenuated by Y27632. Consistent with these findings, Aβ25-35 elicited a significant rise in the level of RhoA-GTP in platelets. Platelets pretreated with reverse-sequenced Aβ fragment (Aβ35-25) and untreated resting platelets served as controls. We conclude that Aβ induces cellular activation through RhoA-dependent modulation of actomyosin, and hence, RhoA could be a potential therapeutic target in Alzheimer's disease and cerebral amyloid angiopathy. © FASEB.
Biomedical Applications of Carbon-Based Nanomaterials
(Blackwell Publishing Ltd., 2013) Sunil K. Singh; Paresh P. Kulkarni; Debabrata Dash
Carbon-based nanomaterials and their derivatives have triggered extensive research and promise to be some of the key materials in nanotechnology. Unlike other existing materials, carbon nanomaterials have found many scientific and technological applications in diverse areas. The wide range of superior properties (mechanical, electrical, optical and thermal) that are inherent in carbon nanostructures, specifically nanotubes and graphene, and the simplicity of their structures have played an important role in the current rapid expansion of fundamental studies of these materials and their potential use in nanotechnology. Based on their novel electronic and optical properties and their controllable chemical functionality, carbon nanostructures are expected to be used in several applications, including nanoelectronics and energy research, as well as biomedical areas such as biosensors, cellular imaging, drug delivery, photothermal therapy and diagnostics. Realizing the immense potential of carbon nanomaterials for applications in biology and medicine, we shall review recent advances in this field and discuss the outlook for the future. © 2013 John Wiley & Sons, Ltd.
Biomedical Applications of Nanomaterials: An Overview
(Blackwell Publishing Ltd., 2013) Sunil K. Singh; Paresh P. Kulkarni; Debabrata Dash
Within the short span of a decade, nanotechnology has evolved into a truly interdisciplinary field undergoing rapid expansion, with the promise of new developments in every traditional scientific discipline. At the nanometer scale, the self-ordering forces and properties of materials seem to be different from those at the macroscale. The application of nanotechnology in biomedical fields is one of the major thrust areas that are currently gaining momentum, as all biological systems embody the principles of nanotechnology. The nanoscience tools that are currently well understood and those that will be developed in future are likely to have an enormous impact on biology, biotechnology, and medicine. The comparable size scale of nanomaterials and biological materials, such as antibodies and proteins, facilitates their use in biological and medical applications. The biomedical community has recently discovered that the distinctive physical characteristics of nanomaterials, such as their extraordinarily high surface area to volume ratio, tuneable optical emission, unique electrical and magnetic behavior, and other novel properties can be exploited in a wide spectrum of biomedical utilities ranging from drug delivery to biosensors. Realizing the immense potential of nanomaterials for applications in diverse areas of biology and medicine, we review recent advances in this field and discuss future perspectives. © 2013 John Wiley & Sons, Ltd.
Correction to: Plasma fibrinogen is a natural deterrent to amyloid β-induced platelet activation and neuronal toxicity (Molecular Medicine (2016) 22 (224-232) DOI: 10.2119/molmed.2016.00003)
(BioMed Central Ltd., 2019) Vijay K. Sonkar; Paresh P. Kulkarni; Susheel N. Chaurasia; Ayusman Dash; Abhishek Jauhari; Devendra Parmar; Sanjay Yadav; Debabrata Dash
Following publication of the original article [1], the author reported an error in Figure 1. The correct version of Figure 1 is as follows: (Figure Presented). © 2019 The Author(s).
D-dimer, disease severity, and deaths (3D-study) in patients with COVID-19: a systematic review and meta-analysis of 100 studies
(Nature Research, 2021) Seshadri Reddy Varikasuvu; Saurabh Varshney; Naveen Dutt; Manne Munikumar; Shahir Asfahan; Paresh P. Kulkarni; Pratima Gupta
Hypercoagulability and the need for prioritizing coagulation markers for prognostic abilities have been highlighted in COVID-19. We aimed to quantify the associations of D-dimer with disease progression in patients with COVID-19. This systematic review and meta-analysis was registered with PROSPERO, CRD42020186661.We included 113 studies in our systematic review, of which 100 records (n = 38,310) with D-dimer data) were considered for meta-analysis. Across 68 unadjusted (n = 26,960) and 39 adjusted studies (n = 15,653) reporting initial D-dimer, a significant association was found in patients with higher D-dimer for the risk of overall disease progression (unadjusted odds ratio (uOR) 3.15; adjusted odds ratio (aOR) 1.64). The time-to-event outcomes were pooled across 19 unadjusted (n = 9743) and 21 adjusted studies (n = 13,287); a strong association was found in patients with higher D-dimers for the risk of overall disease progression (unadjusted hazard ratio (uHR) 1.41; adjusted hazard ratio (aHR) 1.10). The prognostic use of higher D-dimer was found to be promising for predicting overall disease progression (studies 68, area under curve 0.75) in COVID-19. Our study showed that higher D-dimer levels provide prognostic information useful for clinicians to early assess COVID-19 patients at risk for disease progression and mortality outcomes. This study, recommends rapid assessment of D-dimer for predicting adverse outcomes in COVID-19. © 2021, The Author(s).
Editorial: COVID-19 and thrombo-inflammatory responses
(Frontiers Media SA, 2023) Saravanan Subramaniam; Christoph Reinhardt; Paresh P. Kulkarni; Luca Spiezia
[No abstract available]
Energy metabolism in platelets fuels thrombus formation: Halting the thrombosis engine with small-molecule modulators of platelet metabolism
(W.B. Saunders, 2023) Paresh P. Kulkarni; Mohammad Ekhlak; Debabrata Dash
Platelets are circulating cells central to haemostasis that follows vessel injury, as well as thrombosis that ensues as a consequence of pathological stasis or plaque rupture. Platelet responses to various stimuli that mediate these processes are all energy-intensive. Hence, platelets need to adapt their energy metabolism to fulfil the requirements of clot formation while overcoming the adversities of the thrombus niche such as restricted access to oxygen and nutrient. In the present review, we describe the changes in energy metabolism of platelets upon agonist challenge and their underlying molecular mechanisms. We briefly discuss the metabolic flexibility and dependency of stimulated platelets in terms of choice of energy substrates. Finally, we discuss how targeting the metabolic vulnerabilities of stimulated platelets such as aerobic glycolysis and/or beta oxidation of fatty acids could forestall platelet activation and thrombus formation. Thus, we present a case for modulating platelet energy metabolism using small-molecules as a novel anti-platelet strategy in the management of vaso-occlusive disorders like acute myocardial infarction, ischemic stroke, deep vein thrombosis and pulmonary embolism. © 2023 Elsevier Inc.
Fatty acid oxidation fuels agonist-induced platelet activation and thrombus formation: Targeting β-oxidation of fatty acids as an effective anti-platelet strategy
(John Wiley and Sons Inc, 2023) Paresh P. Kulkarni; Mohammad Ekhlak; Vipin Singh; Vikas Kailashiya; Nitesh Singh; Debabrata Dash
Platelet mitochondria possess remarkable plasticity for oxidation of energy substrates, where metabolic dependency on glucose or fatty acids is higher than glutamine. Since platelets metabolize nearly the entire pool of glucose to lactate rather than fluxing through mitochondrial tricarboxylic acid cycle, we posit that majority of mitochondrial ATP, which is essential for platelet granule secretion and thrombus formation, is sourced from oxidation of fatty acids. We performed a comprehensive analysis of bioenergetics and function of stimulated platelets in the presence of etomoxir, trimetazidine and oxfenicine, three pharmacologically distinct inhibitors of β-oxidation. Each of them significantly impaired oxidative phosphorylation in unstimulated as well as thrombin-stimulated platelets leading to a small but consistent drop in ATP level in activated cells due to a lack of compensation from glycolytic ATP. Trimetazidine and oxfenicine attenuated platelet aggregation, P-selectin externalization and integrin αIIbβ3 activation. Both etomoxir and trimetazidine impeded agonist-induced dense granule release and platelet thrombus formation on collagen under arterial shear. The effect of inhibitors on platelet aggregation and dense granule release was dose- and incubation time- dependent with significant inhibition at higher doses and prolonged incubation times. Neither of the inhibitors could protect mice from collagen-epinephrine-induced pulmonary embolism or prolong mouse tail bleeding times. However, mice pre-administered with etomoxir, trimetazidine and oxfenicine were protected from ferric chloride-induced mesenteric thrombosis. In conclusion, β-oxidation of fatty acids sustains ATP level in stimulated platelets and is therefore essential for energy-intensive agonist-induced platelet responses. Thus, fatty acid oxidation may constitute an attractive therapeutic target for novel antiplatelet agents. © 2023 Federation of American Societies for Experimental Biology.
Graphene oxide: Characterization by flow cytometry and biomedical applications
(Nova Science Publishers, Inc., 2012) Sunil K. Singh; Paresh P. Kulkarni; Debabrata Dash
Graphene, a true 2-dimensional nanomaterial, has received increasing attention due to its unique physicochemical properties like large surface area, excellent conductivity, high mechanical strength and ease of bio-functionalization. Based on its unique optical, physical and electrical properties, graphene has found applications in a wide spectrum of biomedical utilities like imaging, sensing and therapeutics. Attempts are also being made to synthesize highly stable sheets of graphene, which can be easily ingested or injected into the body. Graphene can be characterized with various characterization tools like transmission electron microscopy (TEM) and atomic force microscopy (AFM). In a recent report, we have characterized graphene oxide (GO) sheets by flow cytometry, which stands out as a remarkable and versatile means for study of physical properties of graphene and graphene-cell interactions. Flow cytometry also provides rapid access to high-dimension statistical information on individual GO sheets that is not achievable with existing characterization tools. This review discusses latest advancements in graphene research highlighting its unique characteristics, potential biomedical applications, future prospective, as well as toxicity considerations. © 2012 Nova Science Publishers, Inc. All rights reserved.
Maternal serum irisin levels in normotensive and preeclamptic pregnancies: a systematic review and meta-analysis
(Taylor and Francis Ltd., 2022) Kumar Vivek; Balachandar Thangappazham; Alekya Vykunta; Paresh P. Kulkarni; Faustino R. Pérez-López; Seshadri Reddy Varikasuvu
Background: Altered irisin levels have been reported in pregnancy-associated disorders, such as preeclampsia. Objective: A systematic review and meta-analysis were conducted to evaluate the changes in maternal circulatory irisin levels in preeclampsia as compared to normotensive healthy pregnant controls. Methods: Relevant studies were identified by searching PubMed and other databases. Random-effects model was used to obtain standardized mean differences (SMDs) and its 95% confidence intervals (CIs). The sub-group meta-regression analyses were conducted to explore heterogeneity. The presence of publication bias and the study robustness was tested using funnel plot and sensitivity analyses, respectively. Results: This meta-analysis finally included 14 observations from eight studies. Compared with controls, preeclampsia patients showed significantly decreased serum irisin levels (SMD: −1.13; 95% CI: −1.63 to −0.62, p <.0001). The sub-group analysis showed that this decrease in irisin is regardless of body mass index (BMI) and gestational age of preeclampsia patients. The meta-regression analysis indicated that blood pressure is significantly associated with the observed results. There was no significant publication bias as indicated by the funnel plot analysis followed by Begg’s (p =.35) and Egger’s tests (p =.39). The sensitivity analysis indicated that no single study had a significant influence on the overall outcome, suggesting the robustness of this meta-analysis. Conclusions: This meta-analysis showed significantly decreased maternal serum irisin level in preeclampsia patients as compared to normotensive pregnant women. This study highlights the need for future studies evaluating the diagnostic utilities and associations of irisin with the fetal and neonatal outcomes in preeclampsia. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
Mitochondrial ATP generation in stimulated platelets is essential for granule secretion but dispensable for aggregation and procoagulant activity
(Ferrata Storti Foundation, 2022) Paresh P. Kulkarni; Mohammad Ekhlak; Vijay K. Sonkar; Debabrata Dash
[No abstract available]
Nanogold-coated stent facilitated non-invasive photothermal ablation of stent thrombosis and restoration of blood flow
(Royal Society of Chemistry, 2024) Nitesh Singh; Paresh P. Kulkarni; Prashant Tripathi; Vikas Agarwal; Debabrata Dash
In-stent restenosis (ISR) and stent thrombosis (ST) are the most serious complications of coronary angioplasty and stenting. Although the evolution of drug-eluting stents (DES) has significantly restricted the incidence of ISR, they are associated with an enhanced risk of ST. In the present study, we explore the photothermal ablation of a thrombus using a nano-enhanced thermogenic stent (NETS) as a modality for revascularization following ST. The photothermal activity of NETS, fabricated by coating bare metal stents with gold nanorods generating a thin plasmonic film of gold, was found to be effective in rarefying clots formed within the stent lumen in various in vitro assays including those under conditions mimicking blood flow. NETS implanted in the rat common carotid artery generated heat following exposure to a NIR-laser that led to effective restoration of blood flow within the occluded vessel in a model of ferric chloride-induced thrombosis. Our results present a proof-of-concept for a novel photothermal ablation approach by employing coated stents in the non-invasive management of ST. © 2024 RSC.
Necroptosis executioner MLKL plays pivotal roles in agonist-induced platelet prothrombotic responses and lytic cell death in a temporal order
(Springer Nature, 2023) Mohammad Ekhlak; Paresh P. Kulkarni; Vipin Singh; Susheel N. Chaurasia; Saroj Kant Mohapatra; Rameshwar Nath Chaurasia; Debabrata Dash
Necroptosis is a form of programmed cell death executed by receptor-interacting serine/threonine protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like (MLKL). Platelets are circulating cells that play central roles in haemostasis and pathological thrombosis. In this study we demonstrate seminal contribution of MLKL in transformation of agonist-stimulated platelets to active haemostatic units progressing eventually to necrotic death on a temporal scale, thus attributing a yet unrecognized fundamental role to MLKL in platelet biology. Physiological agonists like thrombin instigated phosphorylation and subsequent oligomerization of MLKL in platelets in a RIPK3-independent but phosphoinositide 3-kinase (PI3K)/AKT-dependent manner. Inhibition of MLKL significantly curbed agonist-induced haemostatic responses in platelets that included platelet aggregation, integrin activation, granule secretion, procoagulant surface generation, rise in intracellular calcium, shedding of extracellular vesicles, platelet-leukocyte interactions and thrombus formation under arterial shear. MLKL inhibition, too, prompted impairment in mitochondrial oxidative phosphorylation and aerobic glycolysis in stimulated platelets, accompanied with disruption in mitochondrial transmembrane potential, augmented proton leak and drop in both mitochondrial calcium as well as ROS. These findings underscore the key role of MLKL in sustaining OXPHOS and aerobic glycolysis that underlie energy-intensive platelet activation responses. Prolonged exposure to thrombin provoked oligomerization and translocation of MLKL to plasma membranes forming focal clusters that led to progressive membrane permeabilization and decline in platelet viability, which was prevented by inhibitors of PI3K/MLKL. In summary, MLKL plays vital role in transitioning of stimulated platelets from relatively quiescent cells to functionally/metabolically active prothrombotic units and their ensuing progression to necroptotic death. © 2023, The Author(s), under exclusive licence to ADMC Associazione Differenziamento e Morte Cellulare.
Non-canonical non-genomic morphogen signaling in anucleate platelets: a critical determinant of prothrombotic function in circulation
(BioMed Central Ltd, 2024) Paresh P. Kulkarni; Mohammad Ekhlak; Debabrata Dash
Circulating platelets derived from bone marrow megakaryocytes play a central role in thrombosis and hemostasis. Despite being anucleate, platelets express several proteins known to have nuclear niche. These include transcription factors and steroid receptors whose non-genomic functions are being elucidated in platelets. Quite remarkably, components of some of the best-studied morphogen pathways, namely Notch, Sonic Hedgehog (Shh), and Wnt have also been described in recent years in platelets, which regulate platelet function in the context of thrombosis as well as influence their survival. Shh and Notch pathways in stimulated platelets establish feed-forward loops of autocrine/juxtacrine/paracrine non-canonical signaling that helps perpetuate thrombosis. On the other hand, non-canonical Wnt signaling is part of a negative feedback loop for restricting platelet activation and possibly limiting thrombus growth. The present review will provide an overview of these signaling pathways in general. We will then briefly discuss the non-genomic roles of transcription factors and steroid receptors in platelet activation. This will be followed by an elaborate description of morphogen signaling in platelets with a focus on their bearing on platelet activation leading to hemostasis and thrombosis as well as their potential for therapeutic targeting in thrombotic disorders. © 2023, The Author(s).
Noncanonical Sonic Hedgehog signaling amplifies platelet reactivity and thrombogenicity
(American Society of Hematology, 2022) Arundhati Tiwari; Deepa Gautam; Paresh P. Kulkarni; Mohammad Ekhlak; Vijay K. Sonkar; Vikas Agrawal; Debabrata Dash
Sonic Hedgehog (Shh) is a morphogen in vertebrate embryos that is also associated with organ homeostasis in adults. We report here that human platelets, though enucleate, synthesize Shh from preexisting mRNAs upon agonist stimulation, and mobilize it for surface expression and release on extracellular vesicles, thus alluding to its putative role in platelet activation. Shh, in turn, induced a wave of noncanonical signaling in platelets leading to activation of small GTPase Ras homolog family member A and phosphorylation of myosin light chain in activated protein kinase-dependent manner. Remarkably, agonist-induced thrombogenic responses in platelets, which include platelet aggregation, granule secretion, and spreading on immobilized fibrinogen, were significantly attenuated by inhibition of Hedgehog signaling, thus, implicating inputs from Shh in potentiation of agonist-mediated platelet activation. In consistence, inhibition of the Shh pathway significantly impaired arterial thrombosis in mice. Taken together, the above observations strongly support a feed-forward loop of platelet stimulation triggered locally by Shh, similar to ADP and thromboxane A2, that contributes significantly to the stability of occlusive arterial thrombus and that can be investigated as a potential therapeutic target in thrombotic disorders. © 2022 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.
Plasma fibrinogen is a natural deterrent to amyloid β–induced platelet activation and neuronal toxicity
(Uninversity of Michigan, 2016) Vijay K. Sonkar; Paresh P. Kulkarni; Susheel N. Chaurasia; Ayusman Dash; Abhishek Jauhari; Devendra Parmar; Sanjay Yadav; Debabrata Dash
Alzheimer’s disease (AD) is a devastating neurodegenerative disorder, characterized by extensive loss of neurons and deposition of amyloid β (Aβ) in the form of extracellular plaques. Aβ is considered to have a critical role in synaptic loss and neuronal death underlying cognitive decline. Platelets contribute to 95% of circulating amyloid precursor protein that releases Aβ into circulation. We have recently demonstrated that the Aβ active fragment containing amino acid sequence 25–35 (Aβ25–35) is highly thrombogenic in nature and elicits strong aggregation of washed human platelets in a RhoA-dependent manner. In this study, we evaluated the influence of fibrinogen on Aβ-induced platelet activation. Intriguingly, Aβ failed to induce aggregation of platelets suspended in plasma but not in buffer. Fibrinogen brought about dose-dependent decline in aggregatory response of washed human platelets elicited by Aβ25–35, which could be reversed by increasing doses of Aβ. Fibrinogen also attenuated Aβ-induced platelet responses such as secretion, clot retraction, rise in cytosolic Ca+2 and reactive oxygen species. Fibrinogen prevented intracellular accumulation of full-length Aβ peptide (Aβ42) in platelets as well as neuronal cells. We conclude that fibrinogen serves as a physiological check against the adverse effects of Aβ by preventing its interaction with cells. © 2016, Uninversity of Michigan. All rights reserved.
Platelet HIF-2α promotes thrombogenicity through PAI-1 synthesis and extracellular vesicle release
(Ferrata Storti Foundation, 2019) Susheel N. Chaurasia; Geeta Kushwaha; Paresh P. Kulkarni; Ram L. Mallick; Nazmy A. Latheef; Jai K. Mishra; Debabrata Dash
Oxygen-compromised environments, such as high altitude, are associated with platelet hyperactivity. Platelets confined within the relatively impervious core of an aggregate/thrombus have restricted access to oxygen, yet they continue to perform energy-intensive procoagulant activities that sustain the thrombus. Studying platelet signaling under hypoxia is, therefore, critical to our understanding of the mechanistic basis of thrombus stability. We report here that hypoxia-inducible factor (HIF)-2α is translated from pre-existing mRNA and stabilized against proteolytic degradation in enucleate platelets exposed to hypoxia. Hypoxic stress, too, stimulates platelets to synthesize plasminogen-activator inhibitor-1 (PAI-1) and shed extracellular vesicles, both of which potentially contribute to the prothrombotic phenotype associated with hypoxia. Stabilization of HIF-a by administering hypoxia-mimetics to mice accelerates thrombus formation in mesenteric arterioles. In agreement, platelets from patients with chronic obstructive pulmonary disease and high altitude residents exhibiting thrombogenic attributes have abundant expression of HIF-2α and PAI-1. Thus, targeting platelet hypoxia signaling could be an effective anti-thrombotic strategy. © 2019 Ferrata Storti Foundation