The dimeric platelet collagen receptor GPVI-Fc reduces platelet adhesion to activated endothelium and preserves myocardial function after transient ischemia in mice

Platelets play a critical role in the pathophysiology of reperfusion, sepsis, and cardiovascular diseases. In a multiple step process, they adhere to activated endothelium and release proinflammatory cytokines thereby promoting the inflammatory process. Glycoprotein VI (GPVI) is the major collagen receptor on the platelet surface and triggers platelet activation and primary hemostasis. Activation of GPVI leads to stable platelet adhesion and degranulation of platelet granules. However, GPVI is critically involved in platelet adhesion to activated endothelium without exposure of subendothelial matrix. Earlier studies show that the soluble GPVI-Fc binds to collagen and protects mice from atherosclerosis and decreases neointima proliferation after arterial injury. Here, we show for the first time that recombinant GPVI-Fc binds to activated endothelium mainly via vitronectin and prevents platelet/endothelial interaction. Administration of GPVI-Fc reduced infarct size and preserved cardiac function in a mouse model of myocardial infarction. This process was associated with reduced GPVI-induced platelet degranulation and release of proinflammatory cytokines in vitro and in vivo. Taken together, administration of GPVI-Fc offers a novel strategy to control platelet-mediated inflammation and to preserve myocardial function following myocardial infarction.

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Mice Lacking the Inhibitory Collagen Receptor LAIR-1 Exhibit a Mild Thrombocytosis and Hyperactive Platelets

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvbaha.117.309253 ◽

2017 ◽

Vol 37 (5) ◽

pp. 823-835 ◽

Cited By ~ 18

Author(s):

Christopher W. Smith ◽

Steven G. Thomas ◽

Zaher Raslan ◽

Pushpa Patel ◽

Maxwell Byrne ◽

...

Keyword(s):

Tyrosine Kinases ◽

Kinase Activity ◽

Thrombus Formation ◽

Physiological Role ◽

Src Family Kinase ◽

Glycoprotein Vi ◽

Collagen Receptor ◽

Deficient Mice

Objective— Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is a collagen receptor that belongs to the inhibitory immunoreceptor tyrosine-based inhibition motif–containing receptor family. It is an inhibitor of signaling via the immunoreceptor tyrosine-based activation motif–containing collagen receptor complex, glycoprotein VI-FcRγ-chain. It is expressed on hematopoietic cells, including immature megakaryocytes, but is not detectable on platelets. Although the inhibitory function of LAIR-1 has been described in leukocytes, its physiological role in megakaryocytes and in particular in platelet formation has not been explored. In this study, we investigate the role of LAIR-1 in megakaryocyte development and platelet production by generating LAIR-1–deficient mice. Approach and Results— Mice lacking LAIR-1 exhibit a significant increase in platelet counts, a prolonged platelet half-life in vivo, and increased proplatelet formation in vitro. Interestingly, platelets from LAIR-1–deficient mice exhibit an enhanced reactivity to collagen and the glycoprotein VI–specific agonist collagen-related peptide despite not expressing LAIR-1, and mice showed enhanced thrombus formation in the carotid artery after ferric chloride injury. Targeted deletion of LAIR-1 in mice results in an increase in signaling downstream of the glycoprotein VI–FcRγ-chain and integrin αIIbβ3 in megakaryocytes because of enhanced Src family kinase activity. Conclusions— Findings from this study demonstrate that ablation of LAIR-1 in megakaryocytes leads to increased Src family kinase activity and downstream signaling in response to collagen that is transmitted to platelets, rendering them hyper-reactive specifically to agonists that signal through Syk tyrosine kinases, but not to G-protein–coupled receptors.

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Local delivery of soluble platelet collagen receptor glycoprotein VI inhibits thrombus formation in vivo

Thrombosis and Haemostasis ◽

10.1160/th05-11-0731 ◽

2006 ◽

Vol 95 (05) ◽

pp. 763-766 ◽

Cited By ~ 31

Author(s):

Andreas Bültmann ◽

Christian Herdeg ◽

Zhongmin Li ◽

Götz Münch ◽

Christine Baumgartner ◽

...

Keyword(s):

Carotid Artery ◽

Vascular Injury ◽

Carotid Arteries ◽

Thrombus Formation ◽

Critical Role ◽

Local Delivery ◽

Computer Assisted ◽

Glycoprotein Vi ◽

Collagen Receptor

SummaryPlatelet-mediated thrombus formation at the site of vascular injury isa major trigger for thrombo-ischemic complications after coronary interventions. The platelet collagen receptor glycoprotein VI (GPVI) plays a critical role in the initiation of arterial thrombus formation. Endothelial denudation of the right carotid artery in rabbits was induced through balloon injury. Subsequently, local delivery of soluble, dimeric fusion protein of GPVI (GPVI-Fc) (n=7) or control Fc (n=7) at the site of vascular injury was performed with a modified double-balloon drugdelivery catheter.Thrombus area within the injured carotid artery was quantified using a computer-assisted image analysis and was used as index of thrombus formation.The extent of thrombus formation was significantly reduced in GPVI-Fc- compared with control Fc-treated carotid arteries (relative thrombus area, GPVI-Fc vs. Fc: 9.3 ± 4.2 vs. 2.3 ± 1.7, p<0.001). Local delivery of soluble GPVI resulted in reduced thrombus formation after catheter-induced vascular injury.These data suggest a selective pharmacological modulation of GPVI-collagen interactions to be important for controlling onset and progression of pathological arterial thrombosis, predominantly or even exclusively at sites of injured carotid arteries in the absence of systemic platelet therapy.

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Effects of Sodium Nitroprusside on Platelet Adhesion, Subsequent Aggregation and Vasoconstriction

10.1055/s-0039-1682743 ◽

1977 ◽

Author(s):

H.R. Baumgartner

Keyword(s):

Myocardial Infarction ◽

Acute Myocardial Infarction ◽

Sodium Nitroprusside ◽

Platelet Adhesion ◽

Ex Vivo ◽

Balloon Catheter ◽

Strong Inhibitor ◽

Induced Aggregation

Sodium nitroprusside (SNP), a potent vasodilator, has shown beneficial effects in acute myocardial infarction. Since platelets may play an important role in the pathogenesis of myocardial infarction, the effect of SNP on their interaction with rabbit aorta subendothelium was investigated in vivo and under controlled blood flow conditions ex vivo and in vitro.One iliac artery and the abdominal aorta were denuded of endothelium by balloon catheter injury during infusion of glucose, SNP at 6 or 12 μg/kg/min in groups of 12, 6 and 7 rabbits respectively. The aorta and their branches were perfuse-fixed under controlled pressure 10 min after denudation. Morphometric evaluation showed dose-dependent and significant (2p < 0.01 or 0.001) inhibition of platelet spreading, adhesion and aggregation. The latter was abolished at the higher dose of SNP. Denudation and subsequent platelet adhesion caused strong vasoconstriction (2p < 0.001) which was inhibited by SNP (2p < 0.01).By exposure of subendothelium to either citrated blood or native blood in a flow chamber (2000 sec-1 shear rate) strong inhibition of spreading and adhesion-induced aggregation was again demonstrated at 6 and 12 μg/kg/min SNP. In vitro, adhesion-induced aggregation was completely abolished after the addition of SNP to rabbit (at 20 μg/ml) or human blood (2 μg/ml). 1 μg/ml PGE1 was needed to induce a similar inhibitory effect.Thus SNP is a strong inhibitor of platelet function and of injury + platelet induced vasoconstriction. These findings may explain its beneficial effect in acute myocardial infarction.

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Critical Role for Cyclophilin D and the Mitochondrial Permeability Transition Pore (MPTP) in Platelet Activation.

Blood ◽

10.1182/blood.v108.11.1508.1508 ◽

2006 ◽

Vol 108 (11) ◽

pp. 1508-1508 ◽

Cited By ~ 1

Author(s):

Shawn M. Jobe ◽

Katina M. Wilson ◽

Lori Leo ◽

Jeffery D. Molkentin ◽

Steven R. Lentz ◽

...

Keyword(s):

Platelet Activation ◽

Mitochondrial Permeability Transition ◽

Critical Role ◽

In Vitro Tests ◽

Cyclophilin D ◽

Wild Type ◽

Glycoprotein Vi ◽

Stimulation Of

Abstract Dual stimulation of platelets with thrombin and collagen results in the formation of a unique subpopulation of highly activated platelets. Characteristics of the highly activated platelet subpopulation includeincreased surface retention of procoagulant alpha granule proteins,high-level phosphatidylserine (PS) externalization, andmodulation of the fibrinogen receptor αIIbβ3 as evidenced by their decreased recognition by antibodies to activated αIIbβ3 such as PAC-1 and JON/A. Formation of the highly activated platelet subpopulation is closely correlated with a rapid loss of mitochondrial transmembrane potential (ΔΨm), a marker of MPTP formation. To test whether formation of the MPTP might regulate the development of the highly activated platelet subpopulation, platelet activation responses were examined in the presence of inhibitors and activators of MPTP formation. Cyclosporine, an inhibitor of MPTP formation, inhibited both PS externalization and αIIbβ3 modulation following dual stimulation with thrombin and the glycoprotein VI agonist convulxin (58 ± 4% vs. 9 ± 3%, p<0.01). Conversely, thrombin stimulation of platelets in the presence of H2O2 (100μM), an MPTP activator, increased PS externalization and αIIbβ3 modulation relative to platelets stimulated with thrombin alone (11 ± 3% vs. 48 ± 6%, p<0.05). Platelet activation responses were examined in cyclophilin D null (CypD −/−) mice, which have marked impairment of MPTP formation. Following dual agonist stimulation with thrombin and convulxin, both αIIbβ3 modulation and platelet PS externalization were significantly abrogated in CypD −/− platelets relative to wild type (7 ± 1% vs. 69 ± 1%, p<0.01). Alpha granule release, however, was unaffected in the absence of CypD. In vitro tests of platelet function similarly demonstrated that CypD −/− platelets had marked impairment of platelet prothrombinase activity relative to wild-type platelets after stimulation with thrombin and convulxin, but normal platelet aggregation responses. We then tested the hypothesis that CypD −/− mice would have an altered thrombotic response to arterial injury. Following photochemical injury of the carotid artery endothelium, a stable occlusive thrombus formed more rapidly in CypD −/− than in wild-type mice (16 ± 2 vs. 32 ± 7 min, p<0.05). Tail-bleeding time was unaffected. These results strongly implicate cyclophilin D and the MPTP as critical regulators of the subset of platelet activation responses occurring in the highly activated platelet subpopulation and suggest that activation of this novel platelet mitochondrial signaling pathway might play an important role in the regulation of the thrombotic response in vivo.

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The Design and Synthesis of Small Molecule Inhibitors of Collagen Binding to Integrin α2β1 as Antithrombotic Agents.

Blood ◽

10.1182/blood.v110.11.306.306 ◽

2007 ◽

Vol 110 (11) ◽

pp. 306-306

Author(s):

Meredith W. Miller ◽

Soni Basra ◽

Paul C. Billings ◽

Jamie Gewirtz ◽

William F. DeGrado ◽

...

Keyword(s):

Small Molecule ◽

Platelet Adhesion ◽

Small Molecule Inhibitors ◽

Critical Event ◽

Platelet Activity ◽

Allosteric Site ◽

Collagen Binding ◽

Glycoprotein Vi

Abstract Vascular damage due to trauma or disease exposes circulating platelets to collagen in the subendothelial matrix. This is a critical event in the formation of a hemostatic plug or an occluding thrombus because collagen is not only a substrate for platelet adhesion but is also a strong platelet agonist. Platelets possess two physiologic collagen receptors: glycoprotein VI, a member of the immunoglobin superfamily, and the integrin α2β1. To design small molecule inhibitors of the interaction of platelets with collagen, we focused on α2β1 as a target because murine models of α2β1 deficiency display normal bleeding times and only a slight decrease in platelet activation by collagen and because the small number of reported patients with congenital α2β1 deficiency demonstrated only a mild bleeding diathesis. Thus, α2β1 antagonists could be effective anti-thrombotic agents with minimal toxicity, especially when combined with other anti-platelet drugs. We have developed a class of compounds that target the I-like domain of the β1 subunit, an allosteric site that regulates collagen binding to α2β1 by preventing the conversion of α2β1 from an inactive (low affinity) to an active (high affinity) conformation. This class of compounds is based on a proline-substituted 2,3-diaminopropionic acid scaffold. Structure-activity relationship studies of the scaffold have focused on optimization of the proline moiety, the urea functionality, and the sulfonyl group and have resulted in the development of potent inhibitors of α2β1-mediated platelet adhesion to collagen with IC50’s in the high picomolar to low nanomolar range. In particular, optimization of the proline moiety lead to compounds with high potency: transitioning from proline (DB496, IC50 of 29–62 nM) to a thiazolidine (SB68A) improved the IC50 to 2–8 nM; adding a methyl group at the 2 position of the thiazolidine (SB68B) slightly improved the IC50 to 1–12 nM; adding two methyl groups at the 5 position of the thiazolidine (SW4-161) resulted in a lead compound with an IC50 of 0.33–8 nM. As expected, the compounds had no effect on the binding of isolated α2 I-domains to collagen, consistent with their I-like domain mode of activity. Further, they were specific for α2β1-mediated platelet adhesion to collagen because they had no impact on ADP-stimulated platelet aggregation when added at 2 μM, a concentration more than 100-fold greater than the IC50 for inhibition of platelet adhesion to collagen. The compounds were also strong inhibitors of murine platelet adhesion to collagen and when tested in the ferric chloride-initiated murine carotid artery injury model, displayed activity similar to aspirin. Thus, 71% of untreated mice in this thrombosis model developed occlusive thrombi that remained stable for the 30 min duration of the assay, whereas stable thrombi developed in only 32% of mice treated with 1g/kg aspirin orally and in 41% of mice receiving 60 mg/kg CSW4-161intravenously. In summary, we have developed a class of potent inhibitors of the integrin α2β1 that demonstrate both in vitro and in vivo anti-platelet activity. Further development of this class of compounds may result in novel and relatively non-toxic anti-thrombotic agents.

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Targeting of the collagen-binding site on glycoprotein VI is not essential for in vivo depletion of the receptor

Blood ◽

10.1182/blood-2002-10-3242 ◽

2003 ◽

Vol 101 (10) ◽

pp. 3948-3952 ◽

Cited By ~ 46

Author(s):

Valerie Schulte ◽

Tamer Rabie ◽

Miroslava Prostredna ◽

Barsom Aktas ◽

Sabine Grüner ◽

...

Keyword(s):

Binding Site ◽

Ligand Binding Site ◽

Down Regulation ◽

Collagen Binding ◽

Glycoprotein Vi ◽

Dimeric Form ◽

Collagen Receptor

Abstract Glycoprotein (GP) VI is an essential collagen receptor on platelets and may serve as an attractive target for antithrombotic therapy. We have previously shown that a monoclonal antibody (mAb) against the major collagen-binding site on mouse GPVI (JAQ1) induces irreversible down-regulation of the receptor and, consequently, long-term antithrombotic protection in vivo. To determine whether this unique in vivo effect of JAQ1 is based on its interaction with the ligand-binding site on GPVI, we generated new mAbs against different epitopes on GPVI (JAQ2, JAQ3) and tested their in vitro and in vivo activity. We show that none of the mAbs inhibited platelet activation by collagen or the collagen-related peptide in vitro. Unexpectedly, however, injection of either antibody induced depletion of GPVI with the same efficacy and kinetics as JAQ1. Importantly, this effect was also seen with monovalent F(ab) fragments of JAQ2 and JAQ3, excluding the involvement of the Fc part or the dimeric form of anti-GPVI antibodies in this process. This indicates that anti-GPVI agents, irrespective of their binding site may generally induce down-regulation of the receptor in vivo.

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Abstract 15925: Newt Exosomes are Bioactive on Mammalian Heart, Enhancing Proliferation of Rat Cardiomyocytes and Improving Recovery After Myocardial Infarction

Circulation ◽

10.1161/circ.132.suppl_3.15925 ◽

2015 ◽

Vol 132 (suppl_3) ◽

Author(s):

Eleni Tseliou ◽

Liu Weixin ◽

Jackelyn Valle ◽

Baiming Sun ◽

Maria Mirotsou ◽

...

Keyword(s):

Myocardial Infarction ◽

Critical Role ◽

Dermal Fibroblasts ◽

Neonatal Rat ◽

Cardiomyocyte Proliferation ◽

Rat Cardiomyocytes ◽

Mesodermal Cell ◽

Wistar Kyoto

Introduction: Adult newts can regenerate amputated cardiac tissue (and whole limbs) without fibrosis, unlike adult mammals which lack such regenerative capacity. Exosomes are nanoparticles which mediate intercellular communication and play a critical role in therapeutic regeneration. Hypothesis: We isolated exosomes from a newt mesodermal cell line, and evaluated their bioactivity in rat models. Methods: A1 cells, derived from the amputated limb buds of Notopthalmus viridescense (Brockes JP, 1988), were expanded in culture. Exosomes were isolated by polyethylene glycol precipitation of A1-conditioned serum-free media (or media conditioned by human dermal fibroblasts [DF] as a control) followed by centrifugation. Bioactivity was tested in vitro on neonatal rat ventricular myocytes (NRVM), and in vivo on acute myocardial infarction in Wistar-Kyoto rats (250μg or 500μg of A1-exosomes or vehicle [placebo] injected intramyocardially). Functional and histological analyses were performed 3 weeks after therapy. Results: A1-conditioned media yielded ~2.8±1Billion particles/ml of 129±1.1 nm diameter. In vitro, A1-exosomes increased the proliferative capacity of NRVM compared to DF-exosomes (4.98±0.89% vs 0.77±0.33%, p=0.035). Priming of DFs with A1-exosomes increased SDF-1 secretion compared to DF-exosomes (755±117pg/ml vs.368±21pg/ml, p=0.03). In vivo, both A1-exosome doses increased cardiac function compared to placebo (EF= 46±1% in 250μg, 49±4% in 500μg vs 36±1% in placebo, p=0.045 by ANOVA). Scar size was markedly decreased (11±1% in 250μg, 9±2% in 500μg vs 18±2% in placebo, p=0.006 by ANOVA), and infarct wall thickness was increased after A1-exosome treatment (1.7±0.11mm in 250μg, 1.85±0.16mm in 500μg vs 1.17±0.11mm in Placebo, p=0.01 by ANOVA). Donor-specific antibodies were present at barely detectable levels in the serum of animals that had been injected with A1-exosomes. Conclusions: Newt exosomes stimulate rat cardiomyocyte proliferation and improve functional and structural outcomes in rats with myocardial infarction. Characterization of the RNA and protein content of newt exosomes, now in progress, may provide clues regarding conserved (or newt-unique) molecular mediators of therapeutic benefit.

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Non-invasive imaging of glycoprotein VI binding to injured arterial lesions

Thrombosis and Haemostasis ◽

10.1160/th04-10-0660 ◽

2005 ◽

Vol 93 (05) ◽

pp. 910-913 ◽

Cited By ~ 24

Author(s):

Ildiko Konrad ◽

Andrea Hauser ◽

Suzanne Sauer ◽

Zhongyan Li ◽

Hans-Jürgen Wester ◽

...

Keyword(s):

Ex Vivo ◽

Critical Role ◽

Vascular Lesions ◽

Glycoprotein Vi ◽

Non Invasive ◽

Arterial Lesions ◽

Ex Vivo Autoradiography ◽

Radiochemical Yields ◽

Collagen Receptor

SummaryGlycoprotein VI (GPVI) is the major platelet collagen receptor and plays a critical role in the process of thrombosis at sites of atherosclerotic lesions. This study evaluates the feasibility of radiolabeled soluble GPVI to identify injured arterial lesions. Radiolabeling was carried out using the iodogen method and resulted in the radioiodinated GPVI in radiochemical yields between 97–100%. The biodistribution of [125I]GPVI was determined in normal mice and demonstrated a blood clearance halftime of approximately 5.5 hours. Vascular lesions were induced in the carotid artery in wild type and ApoE -/- mice. Immediately after injury radioiodinated GPVI was injected intravenously. Binding of [123I]GPVI to carotid lesions was assessed by szinti-graphic in vivo imaging. Carotid arteries were explanted for ex vivo autoradiography and histological characterization of the lesion. In vivo and ex vivo imaging revealed substantial accumulation of radioiodinated GPVI in the injured artery wall, with a ratio of lesion to control vessel of 3:1 and 7:1, respectively. Because GPVI is the critical collagen receptor that mediates platelet adhesion to vascular lesions, soluble radiolabeled GPVI may be an agent for non-invasive imaging of thrombogenic thus, vulnerable atherosclerotic plaques.

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Differentially regulated GPVI ectodomain shedding by multiple platelet–expressed proteinases

Blood ◽

10.1182/blood-2010-06-289108 ◽

2010 ◽

Vol 116 (17) ◽

pp. 3347-3355 ◽

Cited By ~ 86

Author(s):

Markus Bender ◽

Sebastian Hofmann ◽

David Stegner ◽

Athena Chalaris ◽

Michael Bösl ◽

...

Keyword(s):

Myocardial Infarction ◽

Direct Evidence ◽

Ectodomain Shedding ◽

Therapeutic Implications ◽

Glycoprotein Vi ◽

Adam Family ◽

A Disintegrin And Metalloproteinase ◽

Normal Hemostasis

Abstract Glycoprotein VI (GPVI) mediates platelet activation on exposed subendothelial collagens at sites of vascular injury and thereby contributes to normal hemostasis, but also to the occlusion of diseased vessels in the setting of myocardial infarction or stroke. GPVI is an attractive target for antithrombotic therapy, particularly because previous studies have shown that anti-GPVI antibodies induce irreversible down-regulation of the receptor in circulating platelets by internalization and/or ectodomain shedding. Metalloproteinases of the a disintegrin and metalloproteinase (ADAM) family have been proposed to mediate this ectodomain shedding, but direct evidence for this is lacking. Here, we studied GPVI shedding in vitro and in vivo in newly generated mice with a megakaryocyte–specific ADAM10 deficiency and in Adam17ex/ex mice, which lack functional ADAM17. We demonstrate that GPVI cleavage in vitro can occur independently through either ADAM10 or ADAM17 in response to distinct stimuli. In contrast, antibody (JAQ1)–induced GPVI shedding in vivo occurred in mice lacking both ADAM10/ADAM17 in their platelets, suggesting the existence of a third GPVI cleaving platelet enzyme. This was supported by in vitro studies on ADAM10/ADAM17 double–deficient platelets. These results reveal that ectodomain shedding of GPVI can be mediated through multiple differentially regulated platelet–expressed proteinases with obvious therapeutic implications.

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Long noncoding RNA MALAT1 promotes cardiomyocyte apoptosis after myocardial infarction via targeting miR-144-3p

Bioscience Reports ◽

10.1042/bsr20191103 ◽

2019 ◽

Vol 39 (8) ◽

Cited By ~ 8

Author(s):

Xiaohong Gong ◽

Yun Zhu ◽

Haixia Chang ◽

Yongqin Li ◽

Feng Ma

Keyword(s):

Myocardial Infarction ◽

Noncoding Rna ◽

Ischemia Reperfusion Injury ◽

Ischemia Reperfusion ◽

Critical Role ◽

Underlying Mechanism ◽

Myocardial Apoptosis ◽

Injury Model

AbstractOur study aims to excavate the role of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in myocardial infarction (MI), especially in an ischemia/reperfusion injury model and the underlying mechanism involving the MALAT1-miR144 axis. Our results demonstrated that the expression of MALAT1 has a higher level, while miR-144 expression significantly reduced in myocardial tissue after MI and also in left anterior descending (LAD)-ligation mice. This result was confirmed in vitro studies in HL-1 cardiomyocytes followed with hypoxia/reoxygenation. In addition, overexpression of MALAT1 by MALAT1-pcDNA injection into the mice with LAD increased myocardial apoptosis in vivo, while this effect was attenuated by miR-144 mimic. Bioinformatics analysis exhibits that 3′-UTR of MALAT1 is targeted to the miR-144-3p. Up-regulation miR-144 blunted the hypoxia- or MALAT1-induced cell apoptosis. In conclusion, the expression of MALAT1 was increased, whereas miR-144 expression was down-regulated in the myocardium after AMI. MALAT1 up-regulation plays a critical role in promoting cardiomyocytes apoptosis via targeting miR-144.

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