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Blood Nov 2023Cardiovascular disease remains the primary cause of morbidity and mortality globally. Platelet activation is critical for maintaining hemostasis and preventing the...
Cardiovascular disease remains the primary cause of morbidity and mortality globally. Platelet activation is critical for maintaining hemostasis and preventing the leakage of blood cells from the vessel. There has been a paucity in the development of new drugs to target platelet reactivity. Recently, the oxylipin 12(S)-hydroxy-eicosatrienoic acid (12-HETrE), which is produced in platelets, was shown to limit platelet reactivity by activating the prostacyclin receptor. Here, we demonstrated the synthesis of a novel analog of 12-HETrE, known as CS585. Human blood and mouse models of hemostasis and thrombosis were assessed for the ability of CS585 to attenuate platelet activation and thrombosis without increasing the risk of bleeding. Human platelet activation was assessed using aggregometry, flow cytometry, western blot analysis, total thrombus formation analysis system, microfluidic perfusion chamber, and thromboelastography. Hemostasis, thrombosis, and bleeding assays were performed in mice. CS585 was shown to potently target the prostacyclin receptor on the human platelet, resulting in a highly selective and effective mechanism for the prevention of platelet activation. Furthermore, CS585 was shown to inhibit platelet function in human whole blood ex vivo, prevent thrombosis in both small and large vessels in mouse models, and exhibit long-lasting prevention of clot formation. Finally, CS585 was not observed to perturb coagulation or increase the risk of bleeding in the mouse model. Hence, CS585 represents a new validated target for the treatment of thrombotic diseases without the risk of bleeding or off-target activation observed with other prostaglandin receptor agonists.
Topics: Animals; Humans; Mice; Receptors, Epoprostenol; Oxylipins; Platelet Activation; Blood Platelets; Hemostasis; Thrombosis; Hemorrhage; Platelet Aggregation
PubMed: 37624927
DOI: 10.1182/blood.2023020622 -
Platelets May 2020Platelets are small, anucleated effector cells that play an important role in linking the hemostatic and inflammatory processes in the body. Platelet function is known... (Review)
Review
Platelets are small, anucleated effector cells that play an important role in linking the hemostatic and inflammatory processes in the body. Platelet function is known to be altered under various inflammatory conditions including aging. A gain in platelet function during aging can increase the risk of thrombotic events, such as stroke and acute myocardial infarction. Anti-platelet therapy is designed to reduce risk of serious cerebrovascular and cardiovascular events, but the adverse consequences of therapy, such as risk for bleeding increases with aging as well. Age-associated comorbidities such as obesity, diabetes, and hyperlipidemia also contribute to increased platelet activity and thus can enhance the risk of thrombosis. Therefore, identification of unique mechanisms of platelet dysfunction in aging and in age-associated comorbidities is warranted to design novel antiplatelet drugs. This review outlines some of the current areas of research on aging-related mechanisms of platelet hyperactivity and addresses the clinical urgency for designing anti-platelet therapies toward novel molecular targets in the aging population.
Topics: Aged; Aging; Animals; Blood Platelet Disorders; Blood Platelets; Comorbidity; Humans; Inflammation; Oxidative Stress; Platelet Activation; Risk Factors; Signal Transduction; Thrombosis
PubMed: 31524038
DOI: 10.1080/09537104.2019.1665641 -
Frontiers in Immunology 2021In 2019 10 million people developed symptomatic tuberculosis (TB) disease and 1.2 million died. In active TB the inflammatory response causes tissue destruction, which... (Review)
Review
In 2019 10 million people developed symptomatic tuberculosis (TB) disease and 1.2 million died. In active TB the inflammatory response causes tissue destruction, which leads to both acute morbidity and mortality. Tissue destruction in TB is driven by host innate immunity and mediated enzymes, chiefly matrix metalloproteinases (MMPs) which are secreted by leukocytes and stromal cells and degrade the extracellular matrix. Here we review the growing evidence implicating platelets in TB immunopathology. TB patients typically have high platelet counts, which correlate with disease severity, and a hypercoagulable profile. Platelets are present in human TB granulomas and platelet-associated gene transcripts are increased in TB patients versus healthy controls. Platelets most likely drive TB immunopathology through their effect on other immune cells, particularly monocytes, to lead to upregulation of activation markers, increased MMP secretion, and enhanced phagocytosis. Finally, we consider current evidence supporting use of targeted anti-platelet agents in the treatment of TB due to growing interest in developing host-directed therapies to limit tissue damage and improve treatment outcomes. In summary, platelets are implicated in TB disease and contribute to MMP-mediated tissue damage their cellular interactions with other leukocytes, and are potential targets for novel host-directed therapies.
Topics: Blood Platelets; Extracellular Matrix; Humans; Immunity, Innate; Inflammation; Leukocytes; Platelet Activation; Platelet Aggregation Inhibitors; Signal Transduction; Tuberculosis
PubMed: 34093524
DOI: 10.3389/fimmu.2021.631696 -
The Journal of Pharmacology and... May 2019Platelets are key mediators of thrombosis. Many agonists of platelet activation are known, but fewer endogenous inhibitors of platelets, such as prostacyclin and nitric...
Platelets are key mediators of thrombosis. Many agonists of platelet activation are known, but fewer endogenous inhibitors of platelets, such as prostacyclin and nitric oxide (NO), have been identified. Acetylcholinesterase inhibitors, such as donepezil, can cause bleeding in patients, but the underlying mechanisms are not well understood. We hypothesized that acetylcholine is an endogenous inhibitor of platelets. We measured the effect of acetylcholine or analogs of acetylcholine on human platelet activation ex vivo. Acetylcholine and analogs of acetylcholine inhibited platelet activation, as measured by P-selectin translocation and glycoprotein IIb IIIa conformational changes. Conversely, we found that antagonists of the acetylcholine receptor, such as pancuronium, enhance platelet activation. Furthermore, drugs inhibiting acetylcholinesterase, such as donepezil, also inhibit platelet activation, suggesting that platelets release acetylcholine. We found that NO mediates acetylcholine inhibition of platelets. Our data suggest that acetylcholine is an endogenous inhibitor of platelet activation. The cholinergic system may be a novel target for antithrombotic therapies.
Topics: Acetylcholine; Blood Platelets; Humans; Nitric Oxide; Platelet Activation; Receptors, Cholinergic
PubMed: 30765424
DOI: 10.1124/jpet.118.253583 -
Circulation Research Apr 2023
Topics: Humans; Platelet Activation; Thrombosis; Blood Platelets; Inflammation
PubMed: 37104561
DOI: 10.1161/CIRCRESAHA.123.322780 -
Blood Advances Oct 2023Blood platelets undergo several successive motor-driven reorganizations of the cytoskeleton when they are recruited to an injured part of a vessel. These reorganizations...
Blood platelets undergo several successive motor-driven reorganizations of the cytoskeleton when they are recruited to an injured part of a vessel. These reorganizations take place during the platelet activation phase, the spreading process on the injured vessel or between fibrin fibers of the forming clot, and during clot retraction. All these steps require a lot of energy, especially the retraction of the clot when platelets develop strong forces similar to those of muscle cells. Platelets can produce energy through glycolysis and mitochondrial respiration. However, although resting platelets have only 5 to 8 individual mitochondria, they produce adenosine triphosphate predominantly via oxidative phosphorylation. Activated, spread platelets show an increase in size compared with resting platelets, and the question arises as to where the few mitochondria are located in these larger platelets. Using expansion microscopy, we show that the number of mitochondria per platelet is increased in spread platelets. Live imaging and focused ion beam-scanning electron microscopy suggest that a mitochondrial fission event takes place during platelet activation. Fission is Drp1 dependent because Drp1-deficient platelets have fused mitochondria. In nucleated cells, mitochondrial fission is associated with a shift to a glycolytic phenotype, and using clot retraction assays, we show that platelets have a more glycolytic energy production during clot retraction and that Drp1-deficient platelets show a defect in clot retraction.
Topics: Platelet Activation; Blood Platelets; Clot Retraction; Oxidative Phosphorylation; Mitochondria
PubMed: 37624769
DOI: 10.1182/bloodadvances.2023010423 -
BioMed Research International 2016Beyond hemostasis and thrombosis, an increasing number of studies indicate that platelets play an integral role in intercellular communication, mediating inflammatory... (Review)
Review
Beyond hemostasis and thrombosis, an increasing number of studies indicate that platelets play an integral role in intercellular communication, mediating inflammatory and immunomodulatory activities. Our knowledge about how platelets modulate inflammatory and immunity has greatly improved in recent years. In this review, we discuss recent advances in the pathways of platelet activation and potential application of platelet activation biomarkers to diagnosis and prediction of disease states.
Topics: Animals; Biomarkers; Blood Platelets; Humans; Immunomodulation; Inflammation; Platelet Activation
PubMed: 27403440
DOI: 10.1155/2016/9060143 -
Methods in Molecular Biology (Clifton,... 2022Platelet activation and aggregation is implicated in all stages of inflammation-related atherosclerosis from the initial steps of endothelial dysfunction and plaque...
Platelet activation and aggregation is implicated in all stages of inflammation-related atherosclerosis from the initial steps of endothelial dysfunction and plaque formation, to plaque rupture and atherothrombotic events, such as acute coronary syndrome, myocardial infarction, and ischemic incidences. Platelet aggregometry assays are the mainstream for evaluating and monitoring platelet reactivity in such conditions and for the investigation of prophylactic and therapeutic approaches. The most established methodology is light transmittance aggregometry (LTA). Here we describe the appropriate preparation of platelet suspensions from human blood and the methodology of LTA-based assays that is used for basic and clinical research for monitoring and evaluating the activities of several thrombotic mediators, as well as determining the dose efficacy and safety of several pharmaceutical and nutraceutical compounds intended for therapeutic and prophylactic interventions for atherosclerosis.
Topics: Atherosclerosis; Blood Platelets; Humans; Platelet Activation; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Function Tests
PubMed: 35237975
DOI: 10.1007/978-1-0716-1924-7_21 -
Platelets Jun 2017Platelet adhesion and aggregation at sites of vascular injury are crucial for hemostasis; however, under pathological conditions, they can cause myocardial infarction... (Review)
Review
Platelet adhesion and aggregation at sites of vascular injury are crucial for hemostasis; however, under pathological conditions, they can cause myocardial infarction and stroke. Platelet adhesion is mediated by binding of the glycoprotein (GP)Ib-V-IX complex to immobilized von Willebrand factor (vWF), thereby enabling the interaction of GPVI with exposed collagen and subsequent platelet activation. This process is reinforced by locally produced thrombin and platelet-derived adenosine diphosphate (ADP) and thromboxane A2 (TxA2), leading to a conformational change of integrins from a low- to a high-affinity state, which allows firm platelet adhesion and aggregation. Stable platelet aggregation requires the formation of fibrin and the coordinated interaction of additional receptors on the adjacent platelets. Platelet surface receptor expression can partially be regulated by proteolytic cleavage, which may represent a mechanism to downregulate platelet reactivity toward extracellular matrix proteins and ligands. It is estimated that approximately 10% of platelet surface receptors are regulated by proteolytic cleavage. In this chapter of the review series we will summarize the platelet receptors that are known to be shed from the cell surface with a focus on the proteins GPIbα, GPV and GPVI, which are cleaved by members of the 'a disintegrin and metalloproteinase' (ADAM) family.
Topics: Blood Platelets; Humans; Models, Molecular; Platelet Activation; Platelet Adhesiveness
PubMed: 27337269
DOI: 10.1080/09537104.2016.1195491 -
Journal of Translational Medicine May 2021Due to mTOR (mammalian/mechanistic target of rapamycin) gene-loss mice die during embryonic development, the role of mTOR in platelets has not been evaluated using gene...
BACKGROUND
Due to mTOR (mammalian/mechanistic target of rapamycin) gene-loss mice die during embryonic development, the role of mTOR in platelets has not been evaluated using gene knockout technology.
METHODS
A mouse model with megakaryocyte/platelet-specific deletion of mTOR was established, and be used to evaluate the role of mTOR in platelet activation and thrombus formation.
RESULTS
mTOR platelets were deficient in thrombus formation when grown on low-concentration collagen-coated surfaces; however, no deficiency in thrombus formation was observed when mTOR platelets were perfused on higher concentration collagen-coated surfaces. In FeCl-induced mouse mesenteric arteriole thrombosis models, wild-type (WT) and mTOR mice displayed significantly different responses to low-extent injury with respect to the ratio of occluded mice, especially within the first 40 min. Additionally, mTOR platelets displayed reduced aggregation and dense granule secretion (ATP release) in response to low doses of the glycoprotein VI (GPVI) agonist collagen related peptide (CRP) and the protease-activated receptor-4 (PAR4) agonist GYPGKF-NH; these deficiencies were overcame by stimulation with higher concentration agonists, suggesting dose dependence of the response. At low doses of GPVI or PAR agonist, the activation of αβ in mTOR platelets was reduced. Moreover, stimulation of mTOR platelets with low-dose CRP attenuated the phosphorylation of S6K1, S6 and Akt Ser473, and increased the phosphorylation of PKCδ Thr505 and PKCε Ser729. Using isoform-specific inhibitors of PKCs (δ, ɛ, and α/β), we established that PKCδ/ɛ, and especially PKCδ but not PKCα/β or PKCθ, may be involved in low-dose GPVI-mediated/mTOR-dependent signaling.
CONCLUSION
These observations indicate that mTOR plays an important role in GPVI-dependent platelet activation and thrombus formation.
Topics: Animals; Blood Platelets; Mice; Mice, Knockout; Platelet Activation; Platelet Aggregation; Platelet Membrane Glycoproteins; TOR Serine-Threonine Kinases
PubMed: 33971888
DOI: 10.1186/s12967-021-02756-y