Reversible Platelet Integrin αIIbβ3 Activation and Thrombus Instability

Conformational response of αIIbβ3 and αVβ3 integrins to force

As major adhesion receptors, integrins transmit biochemical and mechanical signals across the plasma membrane. These functions are regulated by transitions between bent and extended conformations and modulated by force. To understand how force on integrins mediates cellular mechanosensing, we compared two highly homologous integrins, αIIbβ3 and αVβ3. These integrins, expressed in circulating platelets vs. solid tissues, respectively, share the β3 subunit, bind similar ligands and have similar bent and extended conformations. Here, we report that in cells expressing equivalent levels of each integrin, αIIbβ3 mediates spreading on softer substrates than αVβ3. These effects correlate with differences in structural dynamics of the two integrins under force. All-atom simulations show that αIIbβ3 is more flexible than αVβ3 due to correlated residue motions within the α subunit domains. Single molecule measurements confirm that αIIbβ3 extends faster than αVβ3. These results reveal a fundamental relationship between protein function and structural dynamics in cell mechanosensing.

The immunopathology of coronary microembolization and the underlying inflammopathophysiological mechanisms

In coronary microembolization, inflammatory cell infiltration, patchy necrosis, and extensive intra-myocardial hemorrhage are dominant, which induce myocardial dysfunction with clinical symptoms of chronic ischemic cardiomyopathy. Microembolization can lead to obstruction of the coronary microvessels and result in the micro-infarction of the heart. The inflammation and elevated expression of the tumor necrosis factor in cardiomyocytes and the activation of extracellular ERK are involved in initiating the inflammatory response mechanism. The PI3K/Akt signaling pathway is the enriched pathway, and for controlling, inhibition of PI3K/Akt is necessary. Furthermore, the release of cytokines and the activation of inflammasomes contribute to the enhancement of vascular permeability, which results in edema within the myocardium. The immune response and inflammation represent the primary triggers in this process. The ability to control immune response and inflammation reactions may lead to the development of new therapies for microembolization.

Xuefu Zhuyu decoction alleviates deep vein thrombosis through inhibiting the activation of platelets and neutrophils via sirtuin 1/nuclear factor kappa-B pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Xuefu Zhuyu Decoction (XZD), a renowned traditional Chinese medicine prescription, is widely employed for the management of conditions characterized by qi-stagnation and blood stasis. Although its anti-thrombotic effect on deep vein thrombosis (DVT) patients has been clinically observed, the underlying mechanism remains largely unexplored.

AIM OF THE STUDY

Our aim was to investigate the mechanisms by which XZD exerted its effect on DVT.

MATERIALS AND METHODS

The ultra performance liquid chromatography (UPLC) technique was employed to evaluate quality of XZD. To examine the effect of XZD on DVT, a DVT rat model with inferior vena cava (IVC) stenosis was established. The 4D-label-free proteomics approach was then utilized to uncover the possible mechanisms of XZD against DVT. Based on proteomics, citrullinated histone H3 (CitH3), along with serum levels of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) were observed the inhibitory activity of XZD on neutrophil activation. Subsequently, the marker of platelet activation, specifically glycoprotein IIb (CD41) and glycoprotein IIIa (CD61), were assessed along with the secretion of von Willebrand factor (vWF) to investigate the inhibitory activity of XZD on platelet activation. Finally, we explored the impact of XZD on the sirtuin 1 (SIRT1)/nuclear factor kappa-B (NF-κB) pathway, which was associated with the activation of platelets and neutrophils.

RESULTS

Eight distinct components were identified for the quality control of XZD. XZD effectively reduced thrombus weight and length in DVT rats, without affecting the coagulation function or hematological parameters in the systemic circulation. Proteomics analysis revealed that XZD alleviated DVT by inhibiting the activation of platelets and neutrophils. The protein expression of CitH3, along with serum levels of TNF-α and IL-1β, were reduced in XZD-treated DVT rats. Similarly, protein expressions of CD41 and CD61, along with the release of vWF, were markedly down-regulated in XZD-treated DVT rats. Finally, treatment with XZD resulted in an up-regulation of SIRT1 protein expression and a down-regulation of both acetylated NF-κB/p65 and phosphorylated NF-κB/p65 protein expressions in endothelium.

CONCLUSIONS

XZD alleviates DVT by inhibiting the activation of platelets and neutrophils at the injured endothelium via the regulation of SIRT1/NF-κB pathway.

Suppressed ORAI1-STIM1-dependent Ca2+ entry by protein kinase C isoforms regulating platelet procoagulant activity

Agonist-induced rises in cytosolic Ca2+ control most platelet responses in thrombosis and hemostasis. In human platelets, we earlier demonstrated that the ORAI1-STIM1 pathway is a major component of extracellular Ca2+ entry, in particular when induced via the ITAM-linked collagen receptor, glycoprotein VI (GPVI). In the present article, using functionally defective platelets from patients with a loss-of-function mutation in ORAI1 or STIM1, we show that Ca2+ entry induced by the endoplasmic reticulum ATPase inhibitor, thapsigargin, fully relies on this pathway. We demonstrate that both the GPVI-induced and thapsigargin-induced Ca2+ entry are strongly suppressed by protein kinase C (PKC) activation while leaving intracellular Ca2+ mobilization unchanged. Comparing the effects of a PKC inhibitory panel pointed to redundant roles of beta and theta PKC isoforms in Ca2+-entry suppression. In contrast, tyrosine kinases positively regulated GPVI-induced Ca2+ entry and mobilization. Label-free and stable isotope phosphoproteome analysis of GPVI-stimulated platelets suggested a regulatory role of bridging integrator-2 (BIN2), known as an important mediator of the ORAI1-STIM1 pathway in mouse platelets. Identified were 25 to 45 regulated phospho-sites in BIN2 and 16 to 18 in STIM1. Five of these were characterized as direct substrates of the expressed PKC isoforms alpha, beta delta, and theta. Functional platelet testing indicated that the downregulation of Ca2+ entry by PKC resulted in suppressed phosphatidylserine exposure and plasmatic thrombin generation. Conclusively, our results indicate that in platelets multiple PKC isoforms constrain the store-regulated Ca2+ entry via ORAI1-BIN2-STIM1, and hence downregulate platelet-dependent coagulation.

Difluorinated thromboxane A2 reveals crosstalk between platelet activatory and inhibitory pathways by targeting both the TP and IP receptors

BACKGROUND AND PURPOSE

Thromboxane A2 (TXA2) is a prostanoid produced during platelet activaton, important in enhancing platelet reactivity by activation of TP receptors. However, due to the short half-life, studying TXA2 signalling is challenging. To enhance our understanding of TP receptor-mediated platelet biology, we therefore synthesised mono and difluorinated TXA2 analogues and explored their pharmacology on heterologous and endogenously expressed TP receptor function.

EXPERIMENTAL APPROACH

Platelet functional and signalling responses were studied using aggregometry, Ca2+ mobilisation experiments and immunoblotting and compared with an analogue of the TXA2 precursor prostaglandin H2, U46619. Gαq/Gαs receptor signalling was determined using a bioluminescence resonance energy transfer (BRET) assay in a cell line overexpression system.

KEY RESULTS

BRET studies revealed that F-TXA2 and F2-TXA2 promoted receptor-stimulated TP receptor G-protein activation similarly to U46619. Unexpectedly, F2-TXA2 caused reversible aggregation in platelets, whereas F-TXA2 and U46619 induced sustained aggregation. Blocking the IP receptor switched F2-TXA2-mediated reversible aggregation into sustained aggregation. Further BRET studies confirmed F2-TXA2-mediated IP receptor activation. F2-TXA2 rapidly and potently stimulated platelet TP receptor-mediated protein kinase C/P-pleckstrin, whereas IP-mediated protein kinase A/P-vasodilator-stimulated phosphoprotein was more delayed.

CONCLUSION AND IMPLICATIONS

F-TXA2 is a close analogue to TXA2 used as a selective tool for TP receptor platelet activation. In contrast, F2-TXA2 acts on both TP and IP receptors differently over time, resulting in an initial wave of TP receptor-mediated platelet aggregation followed by IP receptor-induced reversibility of aggregation. This study reveals the potential difference in the temporal aspects of stimulatory and inhibitory pathways involved in platelet activation.

Molecular Biomarkers for In Vitro Thrombogenicity Assessment of Medical Device Materials

To develop standardized in vitro thrombogenicity test methods for evaluating medical device materials, three platelet activation biomarkers, beta-thromboglobulin (β-TG), platelet factor 4 (PF4), soluble p-selectin (CD62P), and a plasma coagulation marker, thrombin-antithrombin complex (TAT), were investigated. Whole blood, drawn from six healthy human volunteers into Anticoagulant Citrate Dextrose Solution A was recalcified and heparinized over a concentration range of 0.5-1.5 U/mL. The blood was incubated with test materials with different thrombogenic potentials for 60 min at 37°C, using a 6 cm2/mL material surface area to blood volume ratio. After incubation, the blood platelet count was measured before centrifuging the blood to prepare platelet-poor plasma (PPP) and platelet-free plasma (PFP) for enzyme-linked immunosorbent assay analysis of the biomarkers. The results show that all four markers effectively differentiated the materials with different thrombogenic potentials at heparin concentrations from 1.0 to 1.5 U/mL. When a donor-specific heparin concentration (determined by activated clotting time) was used, the markers were able to differentiate materials consistently for blood from all the donors. Additionally, using PFP instead of PPP further improved the test method's ability to differentiate the thrombogenic materials from the negative control for β-TG and TAT. Moreover, the platelet activation markers were able to detect reversible platelet activation induced by adenosine diphosphate (ADP). In summary, all three platelet activation markers (β-TG, PF4, and CD62P) can distinguish thrombogenic potentials of different materials and detect ADP-induced reversible platelet activation. Test consistency and sensitivity can be enhanced by using a donor-specific heparin concentration and PFP. The same test conditions are applicable to the measurement of coagulation marker TAT.

Unlocking the intricacies: Exploring the complex interplay between platelets and ovarian cancer

Ovarian cancer, an aggressive malignancy of the female reproductive tract, is frequently linked to an elevated risk of thrombotic events. This association is manifested by a pronounced rise in platelet counts and activation levels. Current research firmly supports the pivotal role of platelets in the oncogenic processes of ovarian cancer, influencing tumor cell proliferation and metastasis. Platelets influence these processes through direct interactions with tumor cells or by secreting cytokines and growth factors that enhance tumor growth, angiogenesis, and metastasis. This review aims to thoroughly dissect the interactions between platelets and ovarian cancer cells, emphasizing their combined role in tumor progression and associated thrombotic events. Additionally, it summarizes therapeutic strategies targeting platelet-cancer interface which show significant promise. Such approaches could not only be effective in managing the primary ovarian tumor but also play a pivotal role in preventing metastasis and attenuating thrombotic complications associated with ovarian cancer.

The Molecular Mechanisms of Portal Vein Thrombosis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) represents the sixth most diagnosed cancer worldwide and is the second leading cause of cancer-related death in the world. The association of HCC and portal vein thrombosis (PVT) represents an advanced stage of the tumor. PVT has a prevalence of about 25-50% in HCC, determining poor prognosis and a remarkable reduction in therapeutic perspectives in these patients, leading to severe complications such as ascites, metastasis, an increase in portal hypertension and potentially fatal gastrointestinal bleeding. The aim of this review is to evaluate the molecular mechanisms that are at the basis of PVT development, trying to evaluate possible strategies in the early detection of patients at high risk of PVT.

USP15-Mediated Deubiquitination of FKBP 5 and Activation of the αIIbβ3 Signaling Pathway Regulate Thrombosis in Mice

BACKGROUND

Platelets have the hemostatic function, and their aberrant activation is associated with occlusive thrombus formation. Plasma exosomes are rich in platelets containing ubiquitin-specific peptidase 15 (USP15). Herein, we aim to explore the effect of USP15 on thrombosis, as well as expounding whether USP15 acts as an upstream target of FK506 binding protein 5 (FKBP5) to regulate occlusive thrombus formation.

METHODS

Washed human platelets were treated with thrombin for measurement of USP15 and FKBP5 expressions. USP15 loss/gain-of-function variant in HEK293 cells was performed by cell transfection, and the interaction between USP15 and FKBP5 was examined using immunoprecipitation and ubiquitination assays. Mice with USP15-knockout platelets (Plt USP15-/-) were modeled, and subjected to calculation of bleeding time, artery thrombosis imaging and clot retraction assay. FKBP5 expression and the inhibitor of nuclear factor kappa B kinase subunit epsilon (IKBKE)/phosphatidylinositol 3-kinase (PI3K)/Rap1 pathway in wild-type and Plt USP15-/- mice-derived platelets were detected using Western blot. The activation of αIIbβ3 in washed platelets was analyzed using flow cytometry.

RESULTS

USP15 and FKBP5 expressions were upregulated in platelets after thrombin treatment. Following transfection of USP15 knockdown and USP15 overexpression plasmids into HEK293 cells, FKBP5 protein expression was downregulated by USP15 knockdown while being upregulated by USP15 overexpression. USP15 bound to FKBP5 and protected FKBP5 against ubiquitination. Knockdown of platelet USP15 prolonged bleeding time, inhibited arterial thrombosis and delayed clot retraction in mice. Knockdown of platelet USP15 also decreased protein expressions of FKBP5, IKBKE and Rap1, p-PI3K/PI3K ratio, and activation of αIIbβ3 in mice.

CONCLUSION

USP15 knockdown in platelets affects thrombosis in mice by promoting the instability of FKBP5 to repress the activation of IKBKE/PI3K/Rap1 pathway-mediated αIIbβ3.

Skin Telocytes Could Fundament the Cellular Mechanisms of Wound Healing in Platelet-Rich Plasma Administration

For more than 40 years, autologous platelet concentrates have been used in clinical medicine. Since the first formula used, namely platelet-rich plasma (PRP), other platelet concentrates have been experimented with, including platelet-rich fibrin and concentrated growth factor. Platelet concentrates have three standard characteristics: they act as scaffolds, they serve as a source of growth factors and cytokines, and they contain live cells. PRP has become extensively used in regenerative medicine for the successful treatment of a variety of clinical (non-)dermatological conditions like alopecies, acne scars, skin burns, skin ulcers, muscle, cartilage, and bone repair, and as an adjuvant in post-surgery wound healing, with obvious benefits in terms of functionality and aesthetic recovery of affected tissues/organs. These indications were well documented, and a large amount of evidence has already been published supporting the efficacy of this method. The primordial principle behind minimally invasive PRP treatments is the usage of the patient's own platelets. The benefits of the autologous transplantation of thrombocytes are significant, representing a fast and economic method that requires only basic equipment and training, and it is biocompatible, thus being a low risk for the patient (infection and immunological reactions can be virtually disregarded). Usually, the structural benefits of applying PRP are attributed to fibroblasts only, as they are considered the most numerous cell population within the interstitium. However, this apparent simplistic explanation is still eluding those different types of interstitial cells (distinct from fibroblasts) that are residing within stromal tissue, e.g., telocytes (TCs). Moreover, dermal TCs have an already documented potential in angiogenesis (extra-cutaneous, but also within skin), and their implication in skin recovery in a few dermatological conditions was attested and described ultrastructurally and immunophenotypically. Interestingly, PRP biochemically consists of a series of growth factors, cytokines, and other molecules, to which TCs have also proven to have a positive expression. Thus, it is attractive to hypothesize and to document any tissular collaboration between cutaneous administered PRP and local dermal TCs in skin recovery/repair/regeneration. Therefore, TCs could be perceived as the missing link necessary to provide a solid explanation of the good results achieved by administering PRP in skin-repairing processes.

Myosin light chain 6 (Myl6) interacts with kindlin-3 and is required to support integrin αIIbβ3 activation in platelets in mice

BACKGROUND

Kindlin-3 in platelets plays an essential role in supporting integrin αIIbβ3 activation, platelet spreading, aggregation, and clot retraction by binding to the integrin β3 cytoplasmic tail. However, the mechanism by which kindlin-3 mediates the crosstalk between integrin αIIbβ3 and myosin in platelets remains unknown.

OBJECTIVES

To examine the role of myosin light chain 6 (Myl6) in supporting integrin αIIbβ3 activation in platelets.

METHODS

Myl6fl/flPF4-Cre mice with a deficiency of Myl6 in the megakaryocyte lineage were generated, and integrin αIIbβ3 activation in Myl6-deficient platelets was analyzed.

RESULTS

We identified a novel kindlin-3 binding protein, Myl6, an essential light chain of myosin in platelets. Myl6fl/flPF4-Cre mice exhibited significant macrothrombocytopenia resulting from defective proplatelet formation. In the absence of Myl6, integrin αIIbβ3 activation in platelets was significantly suppressed, and platelet aggregation was substantially impaired. Interestingly, the deficiency of Myl6 in platelets preferentially affected the binding of a multivalent ligand compared to a monovalent ligand to integrin αIIbβ3 upon activation, indicating that Myl6 may contribute to the avidity modulation of integrin αIIbβ3 by binding to kindlin-3. Furthermore, blood coagulation ability was impaired in Myl6fl/flPF4-Cre mice, and consistently, these mice exhibited defects in both hemostatic and thrombotic functions.

CONCLUSION

In summary, these results suggest that Myl6, as a novel kindlin-3 binding partner, is required to support integrin αIIbβ3 activation in platelets, which plays an important role in both hemostasis and thrombosis.

MRI-based microthrombi detection in stroke with polydopamine iron oxide

In acute ischemic stroke, even when successful recanalization is obtained, downstream microcirculation may still be obstructed by microvascular thrombosis, which is associated with compromised brain reperfusion and cognitive decline. Identifying these microthrombi through non-invasive methods remains challenging. We developed the PHySIOMIC (Polydopamine Hybridized Self-assembled Iron Oxide Mussel Inspired Clusters), a MRI-based contrast agent that unmasks these microthrombi. In a mouse model of thromboembolic ischemic stroke, our findings demonstrate that the PHySIOMIC generate a distinct hypointense signal on T2*-weighted MRI in the presence of microthrombi, that correlates with the lesion areas observed 24 hours post-stroke. Our microfluidic studies reveal the role of fibrinogen in the protein corona for the thrombosis targeting properties. Finally, we observe the biodegradation and biocompatibility of these particles. This work demonstrates that the PHySIOMIC particles offer an innovative and valuable tool for non-invasive in vivo diagnosis and monitoring of microthrombi, using MRI during ischemic stroke.

Renal Vein Thrombosis Secondary to Pyelonephritis: Targeting a Thrombo-Inflammatory Entity

Renal vein thrombosis (RVT) is a relatively uncommon condition that is most frequently observed in individuals with nephrotic syndrome. While rare, pyelonephritis (PN) may serve as a predisposing factor for secondary RVT. In such cases, one should consider the possibility of RVT when patients fail to respond to appropriate antibiotic treatment. Typically, these patients require additional anticoagulation therapy for a duration of 3 to 6 months, with a generally favorable prognosis. In this report, we present the case of a 74-year-old female who developed RVT due to Klebsiella pneumoniae PN. Additionally, we reviewed 11 cases of PN complicated by RVT, which were documented in the PubMed database over a span of 40 years, emphasizing key elements in diagnostic and therapeutic approaches. Lastly, we elaborated upon the role of thrombo-inflammation, especially in the context of sepsis.

Expression, Purification and Characterization of Recombinant Disintegrin from Gloydius Brevicaudus Venom in Escherichia Coli

Disintegrins, a family of snake venom protein, which are capable of modulating the activity of integrins that play a fundamental role in the regulation of many physiological and pathological processes. The main purpose of this study is to obtain the recombinant disintegrin (r-DI) and evaluate its biological activity. In this study, we explored a high-level expression prokaryotic system and purification strategy for r-DI. Then, r-DI was treated to assay effects on cell growth, migration, and invasion. The affinity for the interactions of r-DI with integrin was determined using Surface plasmon resonance (SPR) analyses. The r-DI can be expressed in Escherichia coli and purified by one-step chromatography. The r-DI can inhibit B16F10 cells proliferation, migration, and invasion. Also, we found that r-DI could interact with the integrin αIIbβ3 (GPIIb/IIIa). The r-DI can be expressed, purified, characterized through functional assays, and can also maintain strong biological activities. Thus, this study showed potential therapeutic effects of r-DI for further functional and structural studies.

Increase in venous thromboembolism in SARS-CoV-2 infected lung tissue: proteome analysis of lung parenchyma, isolated endothelium, and thrombi

AIMS

COVID-19 pneumonia is characterized by an increased rate of deep venous thrombosis and pulmonary embolism. To better understand the pathophysiology behind thrombosis in COVID-19, we performed proteomics analysis on SARS-CoV-2 infected lung tissue.

METHODS

Liquid chromatography mass spectrometry was performed on SARS-CoV-2 infected postmortem lung tissue samples. Five protein profiling analyses were performed: whole slide lung parenchyma analysis, followed by analysis of isolated thrombi and endothelium, both stratified by disease (COVID-19 versus influenza) and thrombus morphology (embolism versus in situ). Influenza autopsy cases with pulmonary thrombi were used as controls.

RESULTS

Compared to influenza controls, both analyses of COVID-19 whole-tissue and isolated endothelium showed upregulation of proteins and pathways related to liver metabolism including urea cycle activation, with arginase being among the top upregulated proteins in COVID-19 lung tissue. Analysis of isolated COVID-19 thrombi showed significant downregulation of pathways related to platelet activation compared to influenza thrombi. Analysis of isolated thrombi based on histomorphology shows that in situ thrombi have significant upregulation of coronavirus pathogenesis proteins.

CONCLUSIONS

The decrease in platelet activation pathways in severe COVID-19 thrombi suggests a relative increase in venous thromboembolism, as thrombi from venous origin tend to contain fewer platelets than arterial thrombi. Based on histomorphology, in situ thrombi show upregulation of various proteins related to SARS-CoV-2 pathogenesis compared to thromboemboli, which may indicate increased in situ pulmonary thrombosis in COVID-19. Therefore, this study supports the increase of venous thromboembolism without undercutting the involvement of in situ thrombosis in severe COVID-19.

Platelet Activation Pathways Controlling Reversible Integrin αIIbβ3 Activation

Background  Agonist-induced platelet activation, with the integrin αIIbβ3 conformational change, is required for fibrinogen binding. This is considered reversible under specific conditions, allowing a second phase of platelet aggregation. The signaling pathways that differentiate between a permanent or transient activation state of platelets are poorly elucidated. Objective  To explore platelet signaling mechanisms induced by the collagen receptor glycoprotein VI (GPVI) or by protease-activated receptors (PAR) for thrombin that regulate time-dependent αIIbβ3 activation. Methods  Platelets were activated with collagen-related peptide (CRP, stimulating GPVI), thrombin receptor-activating peptides, or thrombin (stimulating PAR1 and/or 4). Integrin αIIbβ3 activation and P-selectin expression was assessed by two-color flow cytometry. Signaling pathway inhibitors were applied before or after agonist addition. Reversibility of platelet spreading was studied by microscopy. Results  Platelet pretreatment with pharmacological inhibitors decreased GPVI- and PAR-induced integrin αIIbβ3 activation and P-selectin expression in the target order of protein kinase C (PKC) > glycogen synthase kinase 3 > β-arrestin > phosphatidylinositol-3-kinase. Posttreatment revealed secondary αIIbβ3 inactivation (not P-selectin expression), in the same order, but this reversibility was confined to CRP and PAR1 agonist. Combined inhibition of conventional and novel PKC isoforms was most effective for integrin closure. Pre- and posttreatment with ticagrelor, blocking the P2Y 12 adenosine diphosphate (ADP) receptor, enhanced αIIbβ3 inactivation. Spreading assays showed that PKC or P2Y 12 inhibition provoked a partial conversion from filopodia to a more discoid platelet shape. Conclusion  PKC and autocrine ADP signaling contribute to persistent integrin αIIbβ3 activation in the order of PAR1/GPVI > PAR4 stimulation and hence to stabilized platelet aggregation. These findings are relevant for optimization of effective antiplatelet treatment.

Study on the Mechanism of the Adrenaline-Evoked Procoagulant Response in Human Platelets

Adrenaline has recently been found to trigger phosphatidylserine (PS) exposure on blood platelets, resulting in amplification of the coagulation process, but the mechanism is only fragmentarily established. Using a panel of platelet receptors' antagonists and modulators of signaling pathways, we evaluated the importance of these in adrenaline-evoked PS exposure by flow cytometry. Calcium and sodium ion influx into platelet cytosol, after adrenaline treatment, was examined by fluorimetric measurements. We found a strong reduction in PS exposure after blocking of sodium and calcium ion influx via Na+/H+ exchanger (NHE) and Na+/Ca2+ exchanger (NCX), respectively. ADP receptor antagonists produced a moderate inhibitory effect. Substantial limitation of PS exposure was observed in the presence of GPIIb/IIIa antagonist, phosphoinositide-3 kinase (PI3-K) inhibitors, or prostaglandin E1, a cyclic adenosine monophosphate (cAMP)-elevating agent. We demonstrated that adrenaline may develop a procoagulant response in human platelets with the substantial role of ion exchangers (NHE and NCX), secreted ADP, GPIIb/IIIa-dependent outside-in signaling, and PI3-K. Inhibition of the above mechanisms and increasing cytosolic cAMP seem to be the most efficient procedures to control adrenaline-evoked PS exposure in human platelets.

Qihuang Zhuyu formula alleviates coronary microthrombosis by inhibiting PI3K/Akt/αIIbβ3-mediated platelet activation

BACKGROUND

Coronary microembolism (CME) is commonly seen in the peri-procedural period of Percutaneous Coronary Intervention (PCI), where local platelet activation and endothelial cell inflammation crosstalk may lead to micro thrombus erosion and rupture, with serious consequences. Qihuang Zhuyu Formula (QHZYF) is a Chinese herbal compound with high efficacy against coronary artery disease, but its antiplatelet mechanism is unclear.

HYPOTHESIS/PURPOSE

This study aimed to elucidate the effects and mechanisms of QHZYF on sodium laurate-induced CME using network pharmacology and in vitro and in vivo experiments.

METHODS

We employed high-performance liquid chromatography mass spectrometry to identify the main components of QHZYF. Network pharmacology analysis, molecular docking and surface plasmon resonance (SPR) were utilized to predict the primary active components, potential therapeutic targets, and intervention pathways mediating the effects of QHZYF on platelet activation. Next, we pretreated a sodium laurate-induced minimally invasive CME rat model with QHZYF. In vivo experiments were performed to examine cardiac function in rats, to locate coronary arteries on heart sections to observe internal microthrombi, to extract rat Platelet-rich plasma (PRP) for adhesion assays and CD62p and PAC-1 (ITGB3/ITGA2B) flow assays, and to measure platelet-associated protein expression in PRP. In vitro clot retraction and Co-culture of HUVECs with PRP were performed and the gene pathway was validated through flow cytometry and immunofluorescence.

RESULTS

Combining UPLC-Q-TOF/MS technology and database mining, 78 compounds were finally screened as the putative and representative compounds of QHZYF, with 75 crossover genes associated with CME. QHZYF prevents CME mainly by regulating key pathways of the inflammation and platelets, including Lipid and atherosclerosis, Fluid shear stress, platelet activation, and PI3K-Akt signaling pathways. Five molecules including Calyson, Oroxin A, Protosappanin A,Kaempferol and Geniposide were screened and subjected to molecular docking and SPR validation in combination with Lipinski rules (Rule of 5, Ro5). In vivo experiments showed that QHZYF not only improved myocardial injury but also inhibited formation of coronary microthrombi. QHZYF inhibited platelet activation by downregulating expression of CD62p receptor and platelet membrane protein αIIbβ3 and reduced the release of von Willebrand Factor (vWF), Ca2+ particles and inflammatory factor IL-6. Further analysis revealed that QHZYF inhibited the activation of integrin αIIbβ3, via modulating the PI3K/Akt pathways. In in vitro experiments, QHZYF independently inhibited platelet clot retraction. Upon LPS induction, the activation of platelet membrane protein ITGB3 was inhibited via the PI3K/Akt pathway, revealing an important mechanism for attenuating coronary microthrombosis. We performed mechanistic validation using PI3K inhibitor LY294002 and Akt inhibitor MK-2206 to show that QHZYF inhibited platelet membrane protein activation and inflammation to improved coronary microvessel embolism by regulating PI3K/Akt/αIIbβ3 pathways, mainly by inhibiting PI3K and Akt phosphorylation.

CONCLUSION

QHZYF interferes with coronary microthrombosis through inhibition of platelet adhesion, activation and inflammatory crosstalk, thus has potential in clinical anti-platelet applications. Calyson, Oroxin A, Protosappanin A, Kaempferol and Geniposide may be the major active ingredient groups of QHZYF that alleviate coronary microthrombosis.

The Effect of Leukocyte- and Platelet-Rich Fibrin on Central and Peripheral Nervous System Neurons-Implications for Biomaterial Applicability

Leukocyte- and Platelet-Rich Fibrin (L-PRF) is a second-generation platelet concentrate that is prepared directly from the patient's own blood. It is widely used in the field of regenerative medicine, and to better understand its clinical applicability we aimed to further explore the biological properties and effects of L-PRF on cells from the central and peripheral nervous system. To this end, L-PRF was prepared from healthy human donors, and confocal, transmission, and scanning electron microscopy as well as secretome analysis were performed on these clots. In addition, functional assays were completed to determine the effect of L-PRF on neural stem cells (NSCs), primary cortical neurons (pCNs), and peripheral dorsal root ganglion (DRG) neurons. We observed that L-PRF consists of a dense but porous fibrin network, containing leukocytes and aggregates of activated platelets that are distributed throughout the clot. Antibody array and ELISA confirmed that it is a reservoir for a plethora of growth factors. Key molecules that are known to have an effect on neuronal cell functions such as brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) were slowly released over time from the clots. Next, we found that the L-PRF secretome had no significant effect on the proliferative and metabolic activity of NSCs, but it did act as a chemoattractant and improved the migration of these CNS-derived stem cells. More importantly, L-PRF growth factors had a detrimental effect on the survival of pCNs, and consequently, also interfered with their neurite outgrowth. In contrast, we found a positive effect on peripheral DRG neurons, and L-PRF growth factors improved their survival and significantly stimulated the outgrowth and branching of their neurites. Taken together, our study demonstrates the positive effects of the L-PRF secretome on peripheral neurons and supports its use in regenerative medicine but care should be taken when using it for CNS applications.