Platelet-Specific p38α Deficiency Improved Cardiac Function After Myocardial Infarction in Mice

Qilong capsule prevents myocardial ischemia/reperfusion injury by inhibiting platelet activation via the platelet CD36 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Qilong capsule (QC) is developed from the traditional Chinese medicine formula Buyang Huanwu Decoction, which has been clinically used to invigorate Qi and promote blood circulation to eliminate blood stasis. Myocardial ischemia‒reperfusion injury (MIRI) can be attributed to Qi deficiency and blood stasis. However, the effects of QC on MIRI remain unclear.

AIM OF THE STUDY

This study aimed to investigate the protective effect and possible mechanism of QC on platelet function in MIRI rats.

MATERIALS AND METHODS

The left anterior descending artery of adult Sprague‒Dawley rats was ligated for 30 min and then reperfused for 120 min with or without QC treatment. Then, the whole blood viscosity, plasma viscosity, coagulation, platelet adhesion rate, platelet aggregation, and platelet release factors were evaluated. Platelet CD36 and its downstream signaling pathway-related proteins were detected by western blotting. Furthermore, the active components of QC and the molecular mechanism by which QC regulates platelet function were assessed via molecular docking, platelet aggregation tests in vitro and BLI analysis.

RESULTS

We found that QC significantly reduced the whole blood viscosity, plasma viscosity, platelet adhesion rate, and platelet aggregation induced by ADP or AA in rats with MIRI. The inhibition of platelet activation by QC was associated with reduced levels of β-TG, PF-4, P-selectin and PAF. Mechanistically, QC effectively attenuated the expression of platelet CD36 and thus inhibited the activation of Src, ERK5, and p38. The active components of QC apparently suppressed platelet aggregation in vitro and regulated the CD36 signaling pathway.

CONCLUSIONS

QC improves MIRI-induced hemorheological disorders, which might be partly attributed to the inhibition of platelet activation via CD36-mediated platelet signaling pathways.

Platelet transcription factors license the pro-inflammatory cytokine response of human monocytes

In humans, blood Classical CD14+ monocytes contribute to host defense by secreting large amounts of pro-inflammatory cytokines. Their aberrant activity causes hyper-inflammation and life-threatening cytokine storms, while dysfunctional monocytes are associated with 'immunoparalysis', a state of immune hypo responsiveness and reduced pro-inflammatory gene expression, predisposing individuals to opportunistic infections. Understanding how monocyte functions are regulated is critical to prevent these harmful outcomes. We reveal platelets' vital role in the pro-inflammatory cytokine responses of human monocytes. Naturally low platelet counts in patients with immune thrombocytopenia or removal of platelets from healthy monocytes result in monocyte immunoparalysis, marked by impaired cytokine response to immune challenge and weakened host defense transcriptional programs. Remarkably, supplementing monocytes with fresh platelets reverses these conditions. We discovered that platelets serve as reservoirs of key cytokine transcription regulators, such as NF-κB and MAPK p38, and pinpointed the enrichment of platelet NF-κB2 in human monocytes by proteomics. Platelets proportionally restore impaired cytokine production in human monocytes lacking MAPK p38α, NF-κB p65, and NF-κB2. We uncovered a vesicle-mediated platelet-monocyte-propagation of inflammatory transcription regulators, positioning platelets as central checkpoints in monocyte inflammation.

Platelets in Kawasaki disease: mediators of vascular inflammation

Kawasaki disease, a systemic vasculitis that affects young children and can result in coronary artery aneurysms, is the leading cause of acquired heart disease among children. A hallmark of Kawasaki disease is increased blood platelet counts and platelet activation, which is associated with an increased risk of developing resistance to intravenous immunoglobulin and coronary artery aneurysms. Platelets and their releasate, including granules, microparticles, microRNAs and transcription factors, can influence innate immunity, enhance inflammation and contribute to vascular remodelling. Growing evidence indicates that platelets also interact with immune and non-immune cells to regulate inflammation. Platelets boost NLRP3 inflammasome activation and IL-1β production by human immune cells by releasing soluble mediators. Activated platelets form aggregates with leukocytes, such as monocytes and neutrophils, enhancing numerous functions of these cells and promoting thrombosis and inflammation. Leukocyte-platelet aggregates are increased in children with Kawasaki disease during the acute phase of the disease and can be used as biomarkers for disease severity. Here we review the role of platelets in Kawasaki disease and discuss progress in understanding the immune-effector role of platelets in amplifying inflammation related to Kawasaki disease vasculitis and therapeutic strategies targeting platelets or platelet-derived molecules.

Aging-related alterations in mechanistic target of rapamycin signaling promote platelet hyperreactivity and thrombosis

BACKGROUND

Aging is an independent risk factor for the development of cardiovascular, thrombotic, and other chronic diseases. However, mechanisms of platelet hyperactivation in aging remain poorly understood.

OBJECTIVES

Here, we examine whether and how aging alters intracellular signaling in platelets to support platelet hyperactivity and thrombosis.

METHODS

Quantitative mass spectrometry with tandem mass tag labeling systematically measured protein phosphorylation in platelets from healthy aged (>65 years) and young human (<45 years) subjects. The role of platelet mechanistic target of rapamycin (mTOR) in aging-induced platelet hyperreactivity was assessed using pharmacologic mTOR inhibition and a platelet-specific mTOR-deficient mouse model (mTORplt-/-).

RESULTS

Quantitative phosphoproteomics uncovered differential site-specific protein phosphorylation within mTOR, Rho GTPase, and MAPK pathways in platelets from aged donors. Western blot confirmed constitutive activation of the mTOR pathway in platelets from both aged humans and mice, which was associated with increased aggregation compared with that in young controls. Inhibition of mTOR with either Torin 1 in aged humans or genetic deletion in aged mice reversed platelet hyperreactivity. In a collagen-epinephrine pulmonary thrombosis model, aged wild-type (mTORplt+/+) mice succumbed significantly faster than young controls, while time to death of aged mTORplt-/- mice was similar to that of young mTORplt+/+ mice. Mechanistically, we noted increased Rac1 activation and levels of mitochondrial reactive oxygen species in resting platelets from aged mice, as well as increased p38 phosphorylation upstream of thromboxane generation following agonist stimulation.

CONCLUSION

Aging-related changes in mTOR phosphorylation enhance Rac1 and p38 activation to enhance thromboxane generation, platelet hyperactivity, and thrombosis.

The Function of ASK1 in Sepsis and Stress-Induced Disorders

Apoptosis signal-regulating kinase 1 (ASK1) is a serine-threonine kinase that is ubiquitously expressed in nucleated cells and is responsible for the activation of multiple mitogen-activated protein kinases (MAPK) to regulate cell stress. Activation of ASK1 via cellular stress leads to activation of downstream signaling components, activation of transcription factors, and proinflammatory cytokine production. ASK1 is also expressed in anucleate platelets and is a key player in platelet activation as it is important for signaling. Interestingly, the mechanism of ASK1 activation is cell type-dependent. In this review we will explore how ASK1 regulates a variety of cellular processes from innate immune function to thrombosis and hemostasis. We will discuss how ASK1 influences FcγRIIA-mediated platelet reactivity and how that reactivity drives platelet clearance. Furthermore, we will explore the role of ASK1 in thromboxane (TxA2) generation, which highlights differences in the way ASK1 functions in mouse and human platelets.

Crosstalk between Platelets and SARS-CoV-2: Implications in Thrombo-Inflammatory Complications in COVID-19

The SARS-CoV-2 virus, causing the devastating COVID-19 pandemic, has been reported to affect platelets and cause increased thrombotic events, hinting at the possible bidirectional interactions between platelets and the virus. In this review, we discuss the potential mechanisms underlying the increased thrombotic events as well as altered platelet count and activity in COVID-19. Inspired by existing knowledge on platelet-pathogen interactions, we propose several potential antiviral strategies that platelets might undertake to combat SARS-CoV-2, including their abilities to internalize the virus, release bioactive molecules to interfere with viral infection, and modulate the functions of immune cells. Moreover, we discuss current and potential platelet-targeted therapeutic strategies in controlling COVID-19, including antiplatelet drugs, anticoagulants, and inflammation-targeting treatments. These strategies have shown promise in clinical settings to alleviate the severity of thrombo-inflammatory complications and reduce the mortality rate among COVID-19 patients. In conclusion, an in-depth understanding of platelet-SARS-CoV-2 interactions may uncover novel mechanisms underlying severe COVID-19 complications and could provide new therapeutic avenues for managing this disease.

Leonurine pretreatment protects the heart from myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion (I/R), an important complication of reperfusion therapy for myocardial infarction, is characterized by hyperactive oxidative stress and inflammatory response. Leonurine (4-guanidino-n-butyl syringate, SCM-198), an alkaloid extracted from Herbaleonuri, was previously found to be highly cardioprotective both in vitro and in vivo. Our current study aimed to investigate the effect of SCM-198 preconditioning on myocardial I/R injury in vitro and in vivo, respectively, as well as to decipher the mechanism involved. Rats were pretreated with SCM-198 before subjected to 45 min of myocardial ischemia, which was followed by 24 h of reperfusion. Primary neonatal rat cardiac ventricular myocytes (NRCMs) were exposed to hypoxia (95% N2 + 5% CO2) for 12 h, and then to 12 h reoxygenation so as to mimic I/R. The enzymatic measurements demonstrated that SCM-198 reduced the release of infarction-related enzymes, and the hemodynamic and echocardiography measurements showed that SCM-198 restored cardiac functions, which suggested that SCM-198 could significantly reduce infarct size, maintaining cardiomyocyte morphology, and that SCM-198 pretreatment could significantly reduce cardiomyocytes apoptosis. Moreover, we demonstrated that SCM-198 could exert a cardioprotective effect by reducing reactive oxygen species (ROS) level and Akt phosphorylation while reducing the phosphorylation of p38 and JNK. In addition, the upregulation of p-Akt, Bcl-2/Bax induced by SCM-198 treatment were blocked by PI3K inhibitor LY294002, and the total protein level of Akt was not affected by SCM-198 pretreatment. Our experimental results indicated that SCM-198 could have a cardioprotective effect on I/R injury, which confirmed the utility of SCM-198 preconditioning as a strategy to prevent I/R injury.

Saccharides from Arctium lappa L. root reduce platelet activation and thrombus formation in a laser injury thrombosis mouse model

Arctium lappa L., also known as burdock, is a popular medicinal plant in traditional Chinese medicine due to its potential therapeutic properties. Saccharides from Arctium lappa L. root (ALR-S) have been extensively studied for their anti-inflammatory and anti-diabetes effects. Platelets play a pivotal role in thrombosis. The present study describes the effects of ALR-S on platelet activation and thrombosis using a laser injury thrombosis in vivo model. The study also measured the effects of ALR-S on platelet activation by analysing aggregation, ATP release, platelet spreading, adhesion and clot retraction in vitro. Specifically, the effects were ALR-S concentration-dependent inhibition of platelet aggregation and ATP release. Activated platelets pretreated with ALR-S showed diminished CD62P expression levels and fibrinogen binding, as measured by flow cytometry. ALR-S inhibited platelet spreading on fibrinogen and adhesion on collagen under shear. ALR-S attenuated platelet activation by decreasing oxidative stress and thrombus formation. These results demonstrated the antiplatelet effects of ALR-S, suggesting the antithrombotic and cardiovascular protective activities of ALR-S as a functional food.

Decreased Human Platelet Activation and Mouse Pulmonary Thrombosis by Rutaecarpine and Comparison of the Relative Effectiveness with BAY11-7082: Crucial Signals of p38-NF-κB

Platelets play a critical role in arterial thrombosis. Rutaecarpine (RUT) was purified from Tetradium ruticarpum, a well-known Chinese medicine. This study examined the relative activity of RUT with NF-κB inhibitors in human platelets. BAY11-7082 (an inhibitor of IκB kinase [IKK]), Ro106-9920 (an inhibitor of proteasomes), and RUT concentration-dependently (1-6 μM) inhibited platelet aggregation and P-selectin expression. RUT was found to have a similar effect to that of BAY11-7082; however, it exhibits more effectiveness than Ro106-9920. RUT suppresses the NF-κB pathway as it inhibits IKK, IκBα, and p65 phosphorylation and reverses IκBα degradation in activated platelets. This study also investigated the role of p38 and NF-κB in cell signaling events and found that SB203580 (an inhibitor of p38) markedly reduced p38, IKK, and p65 phosphorylation and reversed IκBα degradation as well as p65 activation in a confocal microscope, whereas BAY11-7082 had no effects in p38 phosphorylation. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay shows that RUT and BAY11-7082 did not exhibit free radical scavenging activity. In the in vivo study, compared with BAY11-7082, RUT more effectively reduced mortality in adenosine diphosphate (ADP)-induced acute pulmonary thromboembolism without affecting the bleeding time. In conclusion, a distinctive pathway of p38-mediated NF-κB activation may involve RUT-mediated antiplatelet activation, and RUT could act as a strong prophylactic or therapeutic drug for cardiovascular diseases.

Roxadustat Does Not Affect Platelet Production, Activation, and Thrombosis Formation

Objective: Roxadustat is a new medication for the treatment of renal anemia. EPO (erythropoietin)-the current treatment standard-has been reported to enhance platelet activation and production. However, to date, the effect of roxadustat on platelets is unclear. To address this deficiency, herein, we have evaluated the effect of roxadustat on platelet production and function. Approach and Results: We performed several mouse platelet functional assays in the presence/absence of in vitro and in vivo roxadustat treatment. Both healthy and 5/6 nephrectomized mice were utilized. The effect of roxadustat on platelet function of healthy volunteers and chronic kidney disease patients was also evaluated. For platelet production, megakaryocyte maturation and proplatelet formation were assayed in vitro. Peripheral platelet and bone marrow megakaryocyte counts were also determined. We found that roxadustat could not stimulate washed platelets directly, and platelet aggregation, spreading, clot retraction, and P-selectin/JON/A exposure were similar with or without in vitro or in vivo roxadustat treatment among both healthy and 5/6 nephrectomized mice. In vivo mouse thrombosis models were additionally performed, and no differences were detected between the vehicle and roxadustat treatment groups. EPO, which was considered a positive control in the present study, promoted platelet function and production as reported previously. Megakaryocyte maturation and proplatelet formation were also not significantly different between control mice and those treated with roxadustat. After receiving roxadustat for 14 days, no difference in the peripheral platelet count was observed in the mice. Conclusions: Administration of roxadustat has no significant impact on platelet production and function.

Krüppel-like factor 15 reduces ischemia-induced apoptosis involving regulation of p38/MAPK signaling

Background Cardiomyocyte apoptosis is a characteristic of a variety of cardiac diseases including myocardial infarction (MI). Krüppel-like factor 15 (KLF15) is a transcription factor of Krüppel family that plays an important part in cardiovascular diseases. However, the function and the underlying mechanism of KLF15 in MI remain unknown. Methods and Results The expression of KLF15 was downregulated both in ischemic myocardium of MI mice model and hypoxia-treated neonatal rat ventricular myocytes (NRVCs). KLF15 overexpression mediated by adeno-associated virus significantly abrogated the ischemia-induced cardiac dysfunction, increased the survival rate and reduced infarct size after MI. Meanwhile, KLF15 overexpression dramatically reduced the myocardial apoptosis, regulated apoptosis-related genes such as Bcl2 and Bax, diminished the activities of caspase-9/3 and inactivated p38/MAPK signaling in the border zone. Similar results were observed in NRVCs exposed to hypoxia. Conclusions We demonstrated for the first time that KLF15 overexpression could reduce cardiomyocyte apoptosis and improve cardiac dysfunction in MI mice at least partially by inhibiting p38/MAPK signaling pathway.

Transcriptomic Profiling of Femoral Veins in Deep Vein Thrombosis in a Porcine Model

Deep vein thrombosis (DVT) is a severe disease affecting the human venous system, accompanied by high morbidity and mortality rates caused by early and late complications. The study aimed at analyzing the changes in the transcriptome of the femoral vein caused by DVT in the porcine model based on the formation of the thrombus in vivo. The study was performed on 11 castrated male pigs: A thrombus was formed in each left femoral vein in six animals; the remaining five served as a control group. Total RNA was isolated from the left femoral veins of the experimental and control animals. High-throughput RNA sequencing was used to analyze the global changes in the transcriptome of veins with induced DVT. Applied multistep bioinformatics revealed 1474 differentially expressed genes (DEGs): 1019 upregulated and 455 downregulated. Functional Gene Ontology annotated 1220 of DEGs into 225 biological processes, 30 molecular functions and 40 cellular components categories. KEGG analysis disclosed TNF, NF-κB and apoptosis pathways’ overexpression in DVT samples. A thorough analysis of the detected DEGs indicated that a dysregulated inflammatory response and disturbed balance between clotting and anti-clotting factors play a crucial role in the process of DVT.

Treating exuberant, non-resolving inflammation in the lung; Implications for acute respiratory distress syndrome and COVID-19

While COVID-19, the disease driven by SARS-CoV-2 has ignited interest in the host immune response to this infection, it has also highlighted the lack of treatment options for the damaging inflammatory responses driven by pathogens that precipitate the acute respiratory distress syndrome (ARDS). With the global prevalence of SARS-CoV-2 and the likelihood of a second winter spike alongside seasonal flu, the need for effective and targeted anti-inflammatory agents is even more pressing. Here we discuss the aetiology of COVID-19 and the common signalling pathways driven by SARS-CoV-2, namely p38 MAP kinase. We highlight that p38 MAP kinase becomes elevated with increasing age, thereby driving many of the inflammatory pathways that precipitate death in old people with the added drawback of impairing vaccine efficacy in this susceptible age group. Finally, we review drugs available to inhibit p38 MAP kinase, their risks-versus-benefits as well as suggested dosing regimen to combat over-exuberant innate immune responses and potentially reverse vaccine inefficacy in older patients.

Apoptosis signal-regulating kinase 1 regulates immune-mediated thrombocytopenia, thrombosis, and systemic shock

BACKGROUND

Immune complexes (ICs) bind to and activate platelets via FcγRIIA, causing patients to experience thrombocytopenia, as well as an increased risk of forming occlusive thrombi. Although platelets have been shown to mediate IC-induced pathologies, the mechanisms involved have yet to be fully elucidated. We identified that apoptosis signal-regulating kinase 1 (ASK1) is present in both human and mouse platelets and potentiates many platelet functions.

OBJECTIVES

Here we set out to study ASK1's role in regulating IC-mediated platelet functions in vitro and IC-induced pathologies using an in vivo mouse model.

METHODS

Using human platelets treated with an ASK1-specific inhibitor and platelets from FCGR2A/Ask1-/- transgenic mice, we examined various platelet functions induced by model ICs in vitro and in vivo.

RESULTS

We found that ASK1 was activated in human platelets following cross-linking of FcγRIIA using either anti-hCD9 or IV.3 + goat-anti-mouse. Although genetic deletion or inhibition of ASK1 significantly attenuated anti-CD9-induced platelet aggregation, activation of the canonical FcγRIIA signaling targets Syk and PLCγ2 was unaffected. We further found that anti-mCD9-induced cPla2 phosphorylation and TxA2 generation is delayed in Ask1 null transgenic mouse platelets leading to diminished δ-granule secretion. In vivo, absence of Ask1 protected FCGR2A transgenic mice from thrombocytopenia, thrombosis, and systemic shock following injection of anti-mCD9. In whole blood microfluidics, platelet adhesion and thrombus formation on fibrinogen was enhanced by Ask1.

CONCLUSIONS

These findings suggest that ASK1 inhibition may be a potential target for the treatment of IC-induced shock and other immune-mediated thrombotic disorders.

PCSK9 (Proprotein Convertase Subtilisin/Kexin 9) Enhances Platelet Activation, Thrombosis, and Myocardial Infarct Expansion by Binding to Platelet CD36

BACKGROUND

PCSK9 (proprotein convertase subtilisin/kexin 9), mainly secreted by the liver and released into the blood, elevates plasma low-density lipoprotein cholesterol by degrading low-density lipoprotein receptor. Pleiotropic effects of PCSK9 beyond lipid metabolism have been shown. However, the direct effects of PCSK9 on platelet activation and thrombosis, and the underlying mechanisms, as well, still remain unclear.

METHODS

We detected the direct effects of PCSK9 on agonist-induced platelet aggregation, dense granule ATP release, integrin αIIbβ3 activation, α-granule release, spreading, and clot retraction. These studies were complemented by in vivo analysis of FeCl₃-injured mouse mesenteric arteriole thrombosis. We also investigated the underlying mechanisms. Using the myocardial infarction (MI) model, we explored the effects of PCSK9 on microvascular obstruction and infarct expansion post-MI.

RESULTS

PCSK9 directly enhances agonist-induced platelet aggregation, dense granule ATP release, integrin αIIbβ3 activation, P-selectin release from α-granules, spreading, and clot retraction. In line, PCSK9 enhances in vivo thrombosis in a FeCl₃-injured mesenteric arteriole thrombosis mouse model, whereas PCSK9 inhibitor evolocumab ameliorates its enhancing effects. Mechanism studies revealed that PCSK9 binds to platelet CD36 and thus activates Src kinase and MAPK (mitogen-activated protein kinase)-extracellular signal-regulated kinase 5 and c-Jun N-terminal kinase, increases the generation of reactive oxygen species, and activates the p38MAPK/cytosolic phospholipase A2/cyclooxygenase-1/thromboxane A₂ signaling pathways downstream of CD36 to enhance platelet activation, as well. Using CD36 knockout mice, we showed that the enhancing effects of PCSK9 on platelet activation are CD36 dependent. It is important to note that aspirin consistently abolishes the enhancing effects of PCSK9 on platelet activation and in vivo thrombosis. Last, we showed that PCSK9 activating platelet CD36 aggravates microvascular obstruction and promotes MI expansion post-MI.

CONCLUSIONS

PCSK9 in plasma directly enhances platelet activation and in vivo thrombosis, and MI expansion post-MI, as well, by binding to platelet CD36 and thus activating the downstream signaling pathways. PCSK9 inhibitors or aspirin abolish the enhancing effects of PCSK9, supporting the use of aspirin in patients with high plasma PCSK9 levels in addition to PCSK9 inhibitors to prevent thrombotic complications.

Platelet MAPKs-a 20+ year history: What do we really know?

The existence of mitogen activated protein kinases (MAPKs) in platelets has been known for more than 20 years. Since that time hundreds of reports have been published describing the conditions that cause MAPK activation in platelets and their role in regulating diverse platelet functions from the molecular to physiological level. However, this cacophony of reports, with inconsistent and sometimes contradictory findings, has muddied the waters leading to great confusion. Since the last review of platelet MAPKs was published more than a decade ago, there have been more than 50 reports, including the description of novel knockout mouse models, that have furthered our knowledge. Therefore, we undertook an extensive literature review to delineate what is known about platelet MAPKs. We specifically discuss what is currently known about how MAPKs are activated and what signaling cascades they regulate in platelets incorporating recent findings from knockout mouse models. In addition, we will discuss the role each MAPK plays in regulating distinct platelet functions. In doing so, we hope to clarify the role for MAPKs and identify knowledge gaps in this field that await future researchers. In addition, we discuss the limitations of current studies with a particular focus on the off-target effects of commonly used MAPK inhibitors. We conclude with a look at the clinical utility of MAPK inhibitors as potential antithrombotic therapies with an analysis of current clinical trial data.

Redundant role of ASK1-mediated p38MAPK activation in human platelet function

Apoptosis signal-regulating kinase 1 (ASK1) is a member of mitogen-activated protein kinase kinase kinase (MAP3K) family, which recently has been implicated in the regulation of p38 MAPK/PLA2/thromboxane (TxA2) generation, as well as P2Y12 signalling in murine platelets. ASK1 has therefore been proposed as a potential target for anti-thrombotic therapy. At present it is unknown whether ASK1 also contributes to TxA2 formation and platelet function in human. In this study we therefore examined the role of ASK1 using the ASK1 inhibitor selonsertib (GS-4997). We established that ASK1 is responsible for p38 phosphorylation and TxA2 formation in murine platelets, with both GS4997 and p38 inhibitors reducing TxA2 formation. Similar to murine platelets, activation of human platelets resulted in the rapid and transient phosphorylation of ASK1 and the MAP2Ks MMK3/4/6. In contrast, phosphorylation of p38 and its substrate; MAPKAP-kinase2 (MAPKAPK2) was much more sustained. In keeping with these findings, inhibition of ASK1 blocked early, but not later p38/MAPKAPK2 phosphorylation. The latter was dependent on non-canonical autophosphorylation as it was blocked by the p38 inhibitor; SB203580 and the SYK inhibitor; R406. Furthermore, ASK1 and p38 inhibitors had no effect on PLA2 phosphorylation, TxA2 formation and platelet aggregation, demonstrating that this pathway is redundant in human platelets. Together, these results demonstrate that ASK1 contributes to TxA2 formation in murine, but not human platelets and highlight the importance of confirming findings from genetic murine models in humans.

Evidence of epigenetic alterations in thrombosis and coagulation: A systematic review

Thrombosis in the context of Cardiovascular disease (CVD) affects mainly the blood vessels supplying the heart, brain and peripheries and it is the leading cause of death worldwide. The pathophysiological thrombotic mechanisms are largely unknown. Heritability contributes to a 30% of the incidence of CVD. The remaining variation can be explained by life style factors such as smoking, dietary and exercise habits, environmental exposure to toxins, and drug usage and other comorbidities. Epigenetic variation can be acquired or inherited and constitutes an interaction between genes and the environment. Epigenetics have been implicated in atherosclerosis, ischemia/reperfusion damage and the cardiovascular response to hypoxia. Epigenetic regulators of gene expression are mainly the methylation of CpG islands, histone post translational modifications (PTMs) and microRNAs (miRNAs). These epigenetic regulators control gene expression either through activation or silencing. Epigenetic control is mostly dynamic and can potentially be manipulated to prevent or reverse the uncontrolled expression of genes, a trait that renders them putative therapeutic targets. In the current review, we systematically studied and present available data on epigenetic alterations implicated in thrombosis derived from human studies. Evidence of epigenetic alterations is observed in several thrombotic diseases such as Coronary Artery Disease and Cerebrovascular Disease, Preeclampsia and Antiphospholipid Syndrome. Differential CpG methylation and specific histone PTMs that control transcription of prothrombotic and proinflammatory genes have also been associated with predisposing factors of thrombosis and CVD, such us smoking, air pollution, hypertriglyceridemia, occupational exposure to particulate matter and comorbidities including cancer, Chronic Obstructive Pulmonary Disease and Chronic Kidney Disease. These clinical observations are further supported by in vitro experiments and indicate that epigenetic regulation affects the pathophysiology of thrombotic disorders with potential diagnostic or therapeutic utility.

Gut microbe-derived metabolite trimethylamine N-oxide accelerates fibroblast-myofibroblast differentiation and induces cardiac fibrosis

BACKGROUND

Trimethylamine N-oxide (TMAO), a gut microbe-derived metabolite of dietary choline and other trimethylamine-containing nutrients, has been associated with poor prognosis in coronary heart disease. However, the role and underlying mechanisms of TMAO in the cardiac fibrosis after myocardial infarction (MI) remains unclear.

METHODS

We used mouse MI models and primary cardiac fibroblasts cultures to study the role of TMAO in the heart and in cardiac fibroblasts. C57BL/6 mice were fed a control diet, high choline (1.2%) or/and DMB diet or a diet containing TMAO (0.12%) starting 3 weeks before MI. DMB, a structural analogue of choline, inhibited microbial TMA lyases and reduced the level of TMAO in mice. Cardiac function was measured 7 days after MI using echocardiography. One week post MI, myocardial tissues were collected to evaluate cardiac fibrosis, and blood samples were evaluated for TMAO levels. The expression of TGF-β receptor, P-Smad2, α-SMA or collagen I in myocardial tissues and fibroblasts were analyzed by western blot or immunocytochemistry.

RESULTS

We demonstrated that cardiac function and cardiac fibrosis were significantly deteriorated in mice fed either TMAO or high choline diets compared with the control diet, and DMB reversed the cardiac function damage of high choline diet (p < .05). Cardiomyocyte necrosis, apoptosis and macrophage infiltration after MI was significantly increased after treatment with TMAO or high choline diets. The size and migration of fibroblasts were increased after TMAO treatment compared with non-treated fibroblasts in vitro. Furthermore, TMAO increased TGF-β receptor I expression, which promoted the phosphorylation of Smad2 and up-regulated the expression of α-SMA and collagen I. The ubiquitination of TGF-βRI was decreased in neonatal mouse fibroblasts after TMAO treatment. TMAO also inhibited the expression of smurf2. Inhibition of TGF-β1 receptor with the small molecule inhibitor SB431542 decreased TGF-β receptor I expression, reduced the phosphorylation of Smad2, down-regulated TMAO-induced α-SMA and collagen I expression in cardiac fibroblasts.

CONCLUSIONS

Cardiac function and cardiac fibrosis were significantly exacerbated in mice fed diets supplemented with either choline or TMAO, probably through accelerating the transformation of fibroblasts into myofibroblasts, indicating activation of TGF-βRI/Smad2 pathway.

Role of Platelet Activation and Oxidative Stress in the Evolution of Myocardial Infarction

Myocardial infarction, commonly known as heart attack, evolves from the rupture of unstable atherosclerotic plaques to coronary thrombosis and myocardial ischemia–reperfusion injury. A body of evidence supports a close relationship between the alterations following an ischemia–reperfusion injury-induced oxidative stress and platelet activity. Through their critical role in thrombogenesis and inflammatory responses, platelets are fully (totally) implicated from atherothrombotic plaque formation to myocardial infarction onset and expansion. However, mere platelet aggregation prevention does not offer full protection, suggesting that other antiplatelet therapy mechanisms may also be involved. Thus, the present review discusses the integrative role of platelets, oxidative stress, and antiplatelet therapy in triggering myocardial infarction pathophysiology.

Network Pharmacology-Based Prediction and Verification of the Targets and Mechanism for Panax Notoginseng Saponins against Coronary Heart Disease

Coronary heart disease (CHD) is the worldwide leading cause for cardiovascular death. Panax notoginseng saponin (PNS), which is the main bioactive compound of panax notoginseng, has been generally accepted to exert a remarkable effect on CHD for a long time. However, to reveal the underlying treatment target and corresponding mechanism of PNS against CHD is still a substantial challenge. In this work, the targets and mechanism of PNS against CHD were successfully achieved by pharmacology-based prediction and experimental verification. 36 common targets were screened out through integrating the gene expression profile of CHD and the chemical-protein data of PNS. Then, two key nodes were further selected for verification by experiment after analyzing GO function, KEGG pathway, coexpression, and topology analysis. Results showed that PNS has protected the human umbilical vein endothelial cells from H₂O₂-induced oxidative stress by inhibiting early cell apoptosis via upregulating VEGFA mRNA expression. Therefore, our research has successfully pointed out one treatment target and apoptotic inhibition caused by PNS with method of integrating bioinformatics prediction and experimental verification, which has partially explained the pharmacological mechanism of PNS against CHD.

Echocardiographic Analysis of Cardiac Function after Infarction in Mice: Validation of Single-Plane Long-Axis View Measurements and the Bi-Plane Simpson Method

Although echocardiography is commonly used to analyze cardiac function in small animal models of cardiac remodeling after myocardial infarction, the different echocardiographic methods are validated poorly. End-diastolic volume, end-systolic volume and ejection fraction were analyzed using either standard single-plane analysis from parasternal long-axis B-mode views (PSLAX) or the bi-plane Simpson method (using PSLAX and three short-axis views) and validated using magnetic resonance imaging as standard. Ejection fraction measured by PSLAX was moderately correlated with a coefficient of R² = 0.49. The standard deviation of residuals was 9.91. Simpson analysis revealed an improved correlation coefficient of R² = 0.77 and a reduction in standard deviation of residuals by 45% (5.45 vs. 9.92, p = 0.014). Subgroup analysis revealed that the high variation in PSLAX is due to changes in ventricular geometry after myocardial infarction. Our results indicate that the bi-plane Simpson method is advantageous for the assessment of cardiac function after myocardial infarction.

Phosphoinositide 3-kinase p110α negatively regulates thrombopoietin-mediated platelet activation and thrombus formation

Phosphoinositide 3-kinase (PI3K) plays an important role in platelet function and contributes to platelet hyperreactivity induced by elevated levels of circulating peptide hormones, including thrombopoietin (TPO). Previous work established an important role for the PI3K isoform; p110β in platelet function, however the role of p110α is still largely unexplored. Here we sought to investigate the role of p110α in TPO-mediated hyperactivity by using a conditional p110α knockout (KO) murine model in conjunction with platelet functional assays. We found that TPO-mediated enhancement of collagen-related peptide (CRP-XL)-induced platelet aggregation and adenosine triphosphate (ATP) secretion were significantly increased in p110α KO platelets. Furthermore, TPO-mediated enhancement of thrombus formation by p110α KO platelets was elevated over wild-type (WT) platelets, suggesting that p110α negatively regulates TPO-mediated priming of platelet function. The enhancements were not due to increased flow through the PI3K pathway as phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P₃) formation and phosphorylation of Akt and glycogen synthase kinase 3 (GSK3) were comparable between WT and p110α KO platelets. In contrast, extracellular responsive kinase (ERK) phosphorylation and thromboxane (TxA₂) formation were significantly enhanced in p110α KO platelets, both of which were blocked by the MEK inhibitor PD184352, whereas the p38 MAPK inhibitor VX-702 and p110α inhibitor PIK-75 had no effect. Acetylsalicylic acid (ASA) blocked the enhancement of thrombus formation by TPO in both WT and p110α KO mice. Together, these results demonstrate that p110α negatively regulates TPO-mediated enhancement of platelet function by restricting ERK phosphorylation and TxA₂ synthesis in a manner independent of its kinase activity.

Platelet procoagulant phenotype is modulated by a p38-MK2 axis that regulates RTN4/Nogo proximal to the endoplasmic reticulum: utility of pathway analysis

Upon encountering physiological cues associated with damaged or inflamed endothelium, blood platelets set forth intracellular responses to ultimately support hemostatic plug formation and vascular repair. To gain insights into the molecular events underlying platelet function, we used a combination of interactome, pathway analysis, and other systems biology tools to analyze associations among proteins functionally modified by reversible phosphorylation upon platelet activation. While an interaction analysis mapped out a relative organization of intracellular mediators in platelet signaling, pathway analysis revealed directional signaling relations around protein kinase C (PKC) isoforms and mitogen-activated protein kinases (MAPKs) associated with platelet cytoskeletal dynamics, inflammatory responses, and hemostatic function. Pathway and causality analysis further suggested that platelets activate a specific p38-MK2 axis to phosphorylate RTN4 (reticulon-4, also known as Nogo), a Bcl-xl sequestration protein and critical regulator of endoplasmic reticulum (ER) physiology. In vitro, we find that platelets drive a p38-MK2-RTN4-Bcl-xl pathway associated with the regulation of the ER and platelet phosphatidylserine exposure. Together, our results support the use of pathway tools in the analysis of omics data sets as a means to help generate novel, mechanistic, and testable hypotheses for platelet studies while uncovering RTN4 as a putative regulator of platelet cell physiological responses.