Platelet integrin αIIbβ3: signal transduction, regulation, and its therapeutic targeting

BAD-Glucokinase Axis Regulates Platelet Activation and Thrombosis

BACKGROUND

BAD (Bcl2-associated death promoter), a member of the Bcl2 proapoptotic family, promotes cell apoptosis by sequestering the prosurvival proteins Bcl-XL and Bcl2 from the proapoptotic proteins BAK (Bcl2 homologous antagonist/killer) and BAX (Bcl2-associated X protein) in nucleated cells. BAD is also expressed in platelets, playing a role in regulating platelet lifespan, apoptosis, and clearance. However, whether BAD regulates platelet activation and arterial thrombosis remains unclear.

METHODS

The role of BAD in platelet activation and arterial thrombosis was investigated using BAD-deficient mice (Bad-/-), in vitro functional studies, and arterial thrombosis models. The regulatory effect of BAD on platelet energy metabolism was detected using a Seahorse Extracellular Flux Analyzer. The regulatory effect of BAD on glucokinase was investigated by coimmunoprecipitation and activity measurement. The glucokinase heterozygous knockout mice (Gck+/-) and activator were used to study its role in platelet activation.

RESULTS

BAD-deficient mice (Bad-/-) and wild-type mice transfused with Bad-/- platelets displayed prolonged tail bleeding and arterial occlusion times. Bad-/- platelets exhibited decreased aggregation in response to stimulations by proteinase-activated receptor 4-activating peptide, thrombin, and U46619. Furthermore, BAD ablation suppressed platelet integrin αIIbβ3 activation, granule secretion, and clot retraction induced by these agonists. Mechanistically, BAD interacted with glucokinase, and BAD deficiency resulted in decreased platelet glucokinase activity, mitochondrial oxidative phosphorylation, and mitochondrial ATP production. The partial loss of glucokinase (Gck+/-) phenocopied platelet function defects caused by BAD deficiency, and a glucokinase activator rescued the impaired mitochondrial ATP production and function of Bad-/- platelets. Additionally, the glucokinase activator enhanced human platelet activation.

CONCLUSIONS

Our findings demonstrate the critical role of the BAD-glucokinase axis in platelet activation and thrombosis, suggesting a potential target for antithrombotic therapy.

NR4A1 Acts as a Novel Regulator of Platelet Activation and Thrombus Formation

BACKGROUND

Mounting evidence indicates that nuclear receptors play a critical regulatory role in platelet pathophysiology and thrombotic disorders. Although NR4A (the nuclear receptor subfamily 4 group A) plays an important role in cardiovascular pathophysiology, the expression profile and biological function of NR4A member 1 (NR4A1) in platelets have never been reported.

METHODS

We evaluated the functions and the underlying mechanisms of NR4A1 in platelet activation and thrombus formation using platelet-specific NR4A1-deficient mice and NR4A1-specific agonists. Using a hyperlipidemic mouse model and platelets from patients with hypercholesterolemia, we explored the influence of hypercholesterolemia on NR4A1 expression and the effects of NR4A1-specific agonists on platelet hyperreactivity induced by hypercholesterolemia.

RESULTS

NR4A1 was expressed in both human and mouse platelets. Platelet-specific NR4A1 deletion accelerated FeCl3-induced carotid arterial occlusive thrombus formation, enhanced collagen/epinephrine-induced pulmonary thromboembolism, and exacerbated microvascular microthrombi obstruction and infarct expansion in an acute myocardial infarction model. NR4A1-deficient platelets exhibited enhanced agonist-induced aggregation responses, integrin αIIbβ3 activation, dense granule release, α-granule release, platelet spreading, and clot retraction. Consistently, pharmacological activation of NR4A1 by specific agonists decreased platelet activation in both mouse and human platelets. Mechanistically, CAP1 (adenylyl cyclase-associated protein 1) was identified as the direct downstream interacting protein of NR4A1. NR4A1 deletion decreased cAMP levels and phosphorylation of VASP (vasodilator-stimulated phosphoprotein), while NR4A1-specific agonists increased cAMP levels and phosphorylation of VASP in platelets. Importantly, NR4A1 expression in platelets was upregulated in the setting of hypercholesterolemia, which was derived from its upregulation in megakaryocytes in a reactive oxygen species-dependent manner. Platelets from hypercholesterolemic patients and mice exhibited hyperreactivity. However, NR4A1-specific agonists significantly inhibited the activation of hypercholesterolemic platelets to the levels of healthy control platelets.

CONCLUSIONS

We provide the first evidence that nuclear receptor NR4A1 negatively regulates platelet activation and thrombus formation. NR4A1 may serve as a novel therapeutic target for managing thrombosis-based cardiovascular diseases, especially with hypercholesterolemia.

Brolucizumab and Platelet Activation and Reactivity

PURPOSE

This study explores the potential interaction of brolucizumab with platelets and its effects on platelet activation and reactivity, crucial in retinal vasculitis and retinal vascular occlusion. Safety concerns remain of interest, although brolucizumab showed superior retinal efficacy and reduced injection frequency compared to other licensed anti-VEGF agents.

METHODS

Resting and activated platelets of healthy volunteers were pretreated with brolucizumab at the following concentrations 0.6 µg/mL, 3 µg/mL, 6 µg/mL, 300 µg/mL, and 3000 µ/mL or its solvent or PBS. The surface expression of platelet activation markers GPIIb/IIIa and P-selectin was determined by multispectral imaging flow cytometry, which combines flow cytometry and fluorescence microscopy. Two different methods were used to examine the interaction of brolucizumab with platelets: 1) A cross-pretreatment experiment was performed with FITC-labeled brolucizumab and bevacizumab; 2) Resting and activated platelets were pretreated with brolucizumab or its solvent or PBS, followed by anti-brolucizumab antibody generated by rabbit immunization.

RESULTS

Brolucizumab did not significantly affect platelet activation compared to solvent or PBS, across a range of concentrations. No significant upregulation of CD62P and no activation of the fibrinogen receptor (GPIIb/IIa) were observed in resting and TRAP-activated platelets. After pretreatment with PBS, the level of brolucizumab-FITC was significantly lower in comparison to bevacizumab-FITC (normalized MFI = 3.32, CI = 3.16-3.48 vs. normalized MFI = 7.19, CI = 7.04-7.35; p < 0.001). Both brolucizumab- and bevacizumab-FITC were downregulated after pretreatment with brolucizumab or bevacizumab compared to pretreatment with PBS. Antibodies against brolucizumab did not show any significant difference between pretreatment with brolucizumab and its solvent in resting and TRAP-activated platelets.

CONCLUSION

Brolucizumab does not appear to directly affect platelet activation or reactivity to thrombin receptor agonists. No platelet interaction was observed after increasing brolucizumab concentrations or anti-brolucizumab antibodies in resting and activated platelets. However, brolucizumab might be taken up in platelets.

Dendrobium nobile lindl extract modulates integrin αIIbβ3-mediated signaling pathways to inhibit platelet activation and thrombosis

ETHNOPHARMACOLOGICAL RELEVANCE

Dendrobium nobile Lindl. (DNL) is a promising medicinal plant. It has the traditional medicinal effects of promoting blood circulation and resolving stasis, as well as regulating the meridians and collaterals.

AIM OF THE STUDY

We studyed how DNL extract was involved in platelet activation and thrombosis and used network pharmacology and molecular docking analysis to help clarify the underlying mechanisms.

MATERIALS AND METHODS

The effect of DNL extract on platelet aggregation and ATP release function was examined by aggregometer; The effect of DNL extract on the binding of PAC-1 and fibrinogen to integrin was determined by flow cytometry; The effect of DNL extract on "outside-in" platelet signals was detected by platelet adhesion, spreading and clot retraction; Key compounds and major targets of platelet interactions with DNL extract were analyzed by network pharmacology and molecular docking and verified against related pathway proteins by western blotting; The effect of DNL extract on thrombosis was tested by mesenteric artery embolism model.

RESULTS

DNL extract exhibited inhibition of platelet function and PAC-1 and fibrinogen binding to integrin αIIbβ3. In addition, it delayed FeCl3-induced mesenteric artery thrombosis without affecting the clotting time and the hemostatic time of tail in mice. The detection of platelet "inside-out" and "outside-in" signaling by Western blot further confirmed the inhibitory effect of DNL extract on platelet activation.

CONCLUSIONS

DNL extract may affect the thrombosis process by inhibiting platelet activation via inhibiting integrin αⅡbβ3-mediated bidirectional signaling pathway proteins.

Pharmacological effects and mechanism of Ilexsaponin A1 in modulating platelet function

ETHNOPHARMACOLOGICAL RELEVANCE

Ilex pubescens Hook. & Arn. is a traditional Chinese medicine for promoting blood circulation. Ilexsaponin A1 (IsA), a monomer of the compound, exhibits pro-angiogenic, anti-apoptotic and anti-inflammatory activities. Nevertheless, the pharmacological effects and specific mechanisms by which IsA affects platelets remain unknown.

AIM OF THE STUDY

This study aims to investigate the antiplatelet effects of IsA and the underlying molecular mechanisms.

MATERIALS AND METHODS

Platelet aggregation and ATP release were assessed using platelet aggregometry. Flow cytometry was employed to evaluate the exposure of P-selectin, integrin αⅡbβ3 activation and calcium mobilization. Fluorescence microscopy was applied to observe platelet spreading. Clot retraction was imaged by digital camera. Protein phosphorylation regulation of major signaling pathways in platelets was determined by immunoblotting analysis. Doppler flowmetry was used to investigate the in vivo effect of IsA on FeCl3-induced carotid artery injury model. Tail vein transection was used to measure bleeding time.

RESULTS

IsA dose-dependently inhibited platelet aggregation and ATP release induced by collagen, U46619, thrombin and ADP. It also suppressed thrombin-induced P-selectin exposure and PAC-1 binding. Furthermore, IsA inhibited intracellular Ca2+ mobilization and the inward flow of extracellular Ca2+. It also influenced integrin αⅡbβ3 outside-in signaling pathways, including the inhibition of platelet spreading, clot retraction and phosphorylation of outside-in signaling molecules. In addition, IsA suppressed the phosphorylation of Syk-PLCγ2, PI3K-Akt-GSK3β and MAPKs proteins, which are downstream effectors of the collagen and thrombin receptors.

CONCLUSION

IsA inhibited platelet function and thrombus formation. This has potential to be developed into a novel therapeutic agent for the treatment of thrombotic diseases.

Harnessing native blueprints for designing bioinks to bioprint functional cardiac tissue

Cardiac tissue lacks regenerative capacity, making heart transplantation the primary treatment for end-stage heart failure. Engineered cardiac tissues developed through three-dimensional bioprinting (3DBP) offer a promising alternative. However, reproducing the native structure, cellular diversity, and functionality of cardiac tissue requires advanced cardiac bioinks. Major obstacles in CTE (cardiac tissue engineering) include accurately characterizing bioink properties, replicating the cardiac microenvironment, and achieving precise spatial organization. Optimizing bioink properties to closely mimic the extracellular matrix (ECM) is essential, as deviations may result in pathological effects. This review encompasses the rheological and electromechanical properties of bioinks and the function of the cardiac microenvironment in the design of functional cardiac constructs. Furthermore, it focuses on improving the rheological characteristics, printability, and functionality of bioinks, offering valuable perspectives for developing new bioinks especially designed for CTE.

Inflammation and platelet hyperresponsiveness in coronary artery disease and the influence of Talin-1/αIIbβ3-mediated bidirectional signaling pathway

Background

While platelet hyperreactivity constitutes an independent risk factor for major adverse cardiovascular events (MACEs) in coronary artery disease, its molecular underpinnings remain poorly characterized. Recent advances in transcriptomic profiling have revealed potential associations with specific RNA signatures. Through systematic bioinformatics analysis of differential gene expression patterns and pathway activation in CHD patients, this study aims to elucidate key molecular regulators of platelet hyperactivity, establishing a theoretical framework for developing precision therapeutic strategies to mitigate post-CHD complications.

Methods

This randomized controlled study included 16 CHD patients and 16 healthy controls. Inflammation markers, platelet aggregation function, and CD62p levels were assessed using flow cytometry. Mitochondrial morphology and organelles were observed using scanning electron microscopy and transmission electron microscopy. Genes related to symptom alteration between CHD patients and healthy controls were identified using the criteria of p < 0.05. The molecular correlations of these genes were analyzed using a comprehensive perspective that included Gene Ontology (GO) biological process and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Western blot and correlation analyses were also conducted to validate the expression and diagnostic value of the DEGs.

Results

CHD patients exhibited alterations in platelet organelles ultrastructure, heightened platelet activation and aggregation, and disturbance of the inflammatory equilibrium. RNA sequencing demonstrated distinct changes in the gene expression profiles of circulating platelets from CHD patients. The increase in platelet activation and aggregation could be partially associated with the upregulation of the Talin-1 and αIIbβ3 proteins expression.

Conclusion

Abnormal transcription and platelet activation occur after CHD onset, and upregulation of the Talin-1/αIIbβ3-mediated bidirectional signaling pathway are the primary pathological features.

Clinical Trial Registration

https://www.chictr.org.cn/, identifier ChiCTR2100041998.

High-dimensional analysis of injured patients reveals distinct circulating proteomic profiles in plasma vs. whole blood resuscitation

Early blood product resuscitation is often essential for optimal trauma care. However, the effects of different products on the underlying trauma-induced coagulopathy and immune dysfunction are not well described. Here, we use high-dimensional analysis and causal modeling in a longitudinal study to explore the circulating proteomic response to plasma as a distinct component versus low-titer O whole blood (LTOWB), which contains plasma. We highlight the differential impacts of plasma and LTOWB on immune mediator levels and the distinct capacity of plasma to modulate coagulation by elevating fibrinogen and factor XIII and reducing platelet factor 4. A higher proportion of plasma in prehospital resuscitation is associated with improved admission time coagulation parameters in patients with severe shock and elevated brain injury markers and reduced post-admission transfusion volumes in those suffering from traumatic brain injury (TBI) and blunt injury. While LTOWB offers broad hemostatic benefits, our findings demonstrate specific advantages of plasma and support individualized transfusion strategies.

Tryptanthrin impairs platelet function and thrombus formation by reducing Gp1bα expression

BACKGROUND

Tryptanthrin (Couroupitine A) is isolated from indigo-bearing traditional Chinese herbal medicines. It has a broad spectrum of pharmacological and biological activities. However, the potential effects of tryptanthrin on platelet function and thrombus formation remain elusive.

METHODS

Platelets were harvested from C57BL/6 mice and healthy individuals. Following incubation with tryptanthrin, various platelet functions were assessed. Thrombus formation in the presence of tryptanthrin was evaluated both in vitro, using a BioFlux 200 microfluidic system, and in vivo, through FeCl3-induced thrombosis and mouse deep venous thrombosis experiments. The closure times of the tryptanthrin-treated whole blood samples were determined using the PFA-200 system. Platelet proteomics sequencing was conducted to elucidate the underlying mechanisms by which tryptanthrin influences platelet function.

RESULTS

Tryptanthrin inhibited mouse platelet function and impaired carotid artery and deep venous thrombus formation. Tryptanthrin also inhibited human platelet spreading, aggregation and clot retraction. The signaling pathways related to platelet activation, aggregation, hemostasis, and the fibrin clotting cascade were significantly suppressed in platelets treated with tryptanthrin. Notably, the expression of Gp1bα in platelets was diminished by tryptanthrin.

CONCLUSIONS

Tryptanthrin impairs platelet function and thrombus formation.

α-Actinin-1 deficiency in megakaryocytes causes low platelet count, platelet dysfunction, and mitochondrial impairment

ABSTRACT

Cytoskeletal remodeling and mitochondrial bioenergetics play important roles in thrombocytopoiesis and platelet function. Recently, α-actinin-1 mutations have been reported in patients with congenital macrothrombocytopenia. However, the role and underlying mechanism of α-actinin-1 in thrombocytopoiesis and platelet function remain elusive. Using megakaryocyte (MK)-specific α-actinin-1 knockout (KO; PF4-Actn1-/-) mice, we demonstrated that PF4-Actn1-/- mice exhibited reduced platelet counts. The decreased platelet number in PF4-Actn1-/- mice was due to defects in thrombocytopoiesis. Hematoxylin and eosin staining and flow cytometry revealed a decrease in the number of MKs in the bone marrow of PF4-Actn1-/- mice. The absence of α-actinin-1 increased the proportion of 2 N-4 N MKs and decreased the proportion of 8 N-32 N MKs. Colony-forming unit-MK colony formation, the ratio of proplatelet formation-bearing MKs, and MK migration in response to stromal cell-derived factor-1 signaling were inhibited in PF4-Actn1-/- mice. Platelet spreading, clot retraction, aggregation, integrin αIIbβ3 activation, and CD62P exposure in response to various agonists were decreased in PF4-Actn1-/- platelets. Notably, PF4-Actn1-/- platelets inhibited calcium mobilization, reactive oxygen species (ROS) generation, and actin polymerization in response to collagen and thrombin. Furthermore, the PF4-Actn1-/- mice exhibited impaired hemostasis and thrombosis. Mechanistically, proteomic analysis of low-ploidy (2-4 N) and high-ploidy (≥8 N) PF4-Actn1-/- MKs revealed that α-actinin-1 deletion reduced platelet activation and mitochondrial function. PF4-Actn1-/- platelets and Actn1 KO 293T cells exhibited reduced mitochondrial membrane potential, mitochondrial ROS generation, mitochondrial calcium mobilization, and mitochondrial bioenergetics. Overall, in this study, we report that mice with α-actinin-1 deficiency in MKs exhibit low platelet count and impaired platelet function, thrombosis, and mitochondrial bioenergetics.

Advance in peptide-based drug development: delivery platforms, therapeutics and vaccines

The successful approval of peptide-based drugs can be attributed to a collaborative effort across multiple disciplines. The integration of novel drug design and synthesis techniques, display library technology, delivery systems, bioengineering advancements, and artificial intelligence have significantly expedited the development of groundbreaking peptide-based drugs, effectively addressing the obstacles associated with their character, such as the rapid clearance and degradation, necessitating subcutaneous injection leading to increasing patient discomfort, and ultimately advancing translational research efforts. Peptides are presently employed in the management and diagnosis of a diverse array of medical conditions, such as diabetes mellitus, weight loss, oncology, and rare diseases, and are additionally garnering interest in facilitating targeted drug delivery platforms and the advancement of peptide-based vaccines. This paper provides an overview of the present market and clinical trial progress of peptide-based therapeutics, delivery platforms, and vaccines. It examines the key areas of research in peptide-based drug development through a literature analysis and emphasizes the structural modification principles of peptide-based drugs, as well as the recent advancements in screening, design, and delivery technologies. The accelerated advancement in the development of novel peptide-based therapeutics, including peptide-drug complexes, new peptide-based vaccines, and innovative peptide-based diagnostic reagents, has the potential to promote the era of precise customization of disease therapeutic schedule.

NebulaPlate: a droplet microfluidic platform to analyze platelet aggregation

The accurate assessment of platelet activity is crucial in clinical practice and scientific research owing to the pivotal role of platelets in the progression of cardiovascular conditions, such as arterial thrombotic diseases. However, conventional platelet activity assessment methods are currently limited by their requirement of substantial blood samples and inadequate high-throughput capabilities, and therapeutic resistance induced by antiplatelet agents impedes treatment efficacy. In this study, we developed a microdroplet-based platelet function detection method, referred to as NebulaPlate, to achieve miniaturized and robust platelet activity assessment, thereby overcoming current challenges. NebulaPlate supports the merging of platelet samples with drugs confined in picoliter microdroplets and leverages an imaging-based analysis to automatically identify platelets, evaluate their aggregation, and determine P-selectin expression within the anchored microdroplets. We experimentally confirmed the feasibility of aggregation assays on NebulaPlate using various representative antiplatelet drugs. Requiring only 0.3 mL whole blood/chip, which corresponds to approximately 100 platelets/reaction, NebulaPlate reduced the consumption of platelet samples in a single assay. This represents a reduction of 10 times compared to that of conventional techniques. Moreover, our experimental results confirmed the validity and reproducibility of platelet function assays performed using NebulaPlate. Our research highlights important developments in the field of platelet activity assessment and provides fresh prospects for future antiplatelet therapies and personalized medicine. Moreover, it introduces new possibilities for research and clinical practice related to arterial thrombotic diseases.

Statins as an Adjunctive Antithrombotic Agent in Thrombotic Antiphospholipid Syndrome: Mechanisms and Clinical Implications

The thrombotic physiopathology of antiphospholipid syndrome (APS) is complex, heterogeneous, and dynamic. While venous thromboembolism (VTE) is the most common initial presentation, arterial thrombotic events (ATE) become more frequent in advanced stages and are associated with high morbidity and mortality. Despite the use of oral anticoagulants (OACs), thrombotic APS remains associated with a high risk of recurrent thrombosis. Given their potential antithrombotic effects capable of reducing the risk of both VTE and ATE, statins have been proposed as an adjunctive therapy to OACs for patients with APS and recurrent thrombosis. However, this recommendation is primarily based on studies not specifically conducted in APS populations, with only preclinical data or evidence from retrospective observational studies available from APS patients cohorts. For these reasons, this narrative review aims to synthesise the studies evaluating the potential antithrombotic effects of statins in patients with APS, highlighting the progress made and identifying areas for future research.

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.

Dual effects of DLG5 (disks large homolog 5 gene) modulation on chemotherapy-induced thrombocytopenia and nausea/vomiting via the hippo signalling pathway

BACKGROUND AND PURPOSE

The CAPEOX (combination of oxaliplatin and capecitabine) chemotherapy protocol is widely used for colorectal cancer treatment, but it can lead to chemotherapy-induced adverse effects (CRAEs).

EXPERIMENTAL APPROACH

To uncover the mechanisms and potential biomarkers for CRAE susceptibility, we performed whole-genome sequencing on normal colorectal tissue (CRT) before adjuvant chemotherapy. This is followed by in vivo and in vitro verifications for selected gene and CRAE pair.

KEY RESULTS

Our analysis revealed specific germline mutations linked to Grade 2 (or higher) chemotherapy-induced thrombocytopenia (CIT) and nausea/vomiting (CINV). Notably, both CRAEs were associated with mutations in the DLG5 gene. We found that DLG5 mutations related to CIT were associated with increased gene expression, while those associated with CINV were linked to suppressed gene expression, as indicated by the Genotype-Tissue Expression (GTEX) database. In megakaryocytes, overexpression of human DLG5 suppressed the hippo signalling pathway and induced YAP expression. In zebrafish, overexpression of human DLG5 not only reduced platelet production but also inhibited thrombus formation. Subsequent qPCR analysis revealed that DLG5 overexpression affected genes involved in cytoskeleton formation and alpha-granule formation, which could impact the normal generation of proplatelets.

CONCLUSION AND IMPLICATIONS

We identified a series of germline mutations associated with susceptibility to CIT and CINV. Of particular interest, we demonstrated that induced and suppressed DLG5 expression is respectively related to CIT and CINV. These findings shed light on the involvement of the hippo signalling pathway and DLG5 in the development of CRAEs, providing valuable insights into potential targets for therapeutic interventions.

Integrative Quantitative Analysis of Platelet Proteome and Site-Specific Glycoproteome Reveals Diagnostic Potential of Platelet Glycoproteins for Liver Cancer

The role of peripheral blood platelets as indicators of cancer progression is increasingly recognized, and the significance of abnormal glycosylation in platelet function and related disorders is gaining attention. However, the potential of platelets as a source of protein site-specific glycosylation for cancer diagnosis remains underexplored. In this study, we proposed a general pipeline that integrates quantitative proteomics with site-specific glycoproteomics, allowing for an in-depth investigation of the platelet glycoproteome. With this pipeline, we generated a data set comprising 3,466 proteins with qualitative information, 3,199 proteins with quantitative information, 3,419 site-specific glycans with qualitative information and 3,377 site-specific glycans with quantitative information from peripheral blood platelets of hepatocellular carcinoma (HCC) patients, metastatic liver cancer (mLC) patients, and healthy controls. The integrated analysis revealed significant changes in platelet protein N-glycosylation in liver cancer patients. Further systems biology analysis and lectin pull-down-coupled ELISA assays in independent clinical samples confirmed two N-glycoproteins with specific glycan types, complement C3 (C3) with oligomannose modification and integrin β-3 (ITGB3) with sialylation, as potential biomarkers distinguishing liver cancer patients from healthy individuals, without differentiating between HCC and mLC patient group. These findings highlight the potential of platelet protein glycosylation as biomarkers.

The Diagnostic Assessment of Platelet Function Defects - Part 2: Update on Platelet Disorders

Congenital platelet disorders are rare and targeted treatment is usually not possible. Inherited platelet function disorders (iPFDs) can affect surface receptors and multiple platelet responses such as defects of platelet granules, signal transduction, and procoagulant activity. If iPFDs are also associated with a reduced platelet count (thrombocytopenia), it is not uncommon to be misdiagnosed as immune thrombocytopenia. Because the bleeding tendency of the different platelet disorders is variable, a correct diagnosis of the platelet defect based on phenotyping, function analysis, and genotyping is essential, especially in the perioperative setting. In the case of a platelet receptor deficiency, such as Bernard-Soulier syndrome or Glanzmann thrombasthenia, not only the bleeding tendency but also the risk of isoimmunization after platelet transfusions or pregnancy has to be considered. Platelet granule disorders are commonly associated with either intrinsically quantitative or qualitative granule defects due to impaired granulopoiesis, or granule release defects, which can also affect additional signaling pathways. Functional platelet defects require expertise in the clinical bleeding tendency in terms of the disorder when using antiplatelet agents or other medications that affect platelet function. Platelet defects associated with hematological-oncological diseases require comprehensive information about the patient including the clinical implication of the genetic testing. This review focuses on genetics, clinical presentation, and laboratory platelet function analysis of iPFDs with or without reduced platelet number. As platelet defects affecting the cytoskeleton usually show thrombocytopenia, but less impaired or normal platelet functional responses, they are not specifically addressed.

The metastatic cascade through the lens of therapeutic inhibition

Metastasis is a main cause of cancer-related death, and a deeper understanding of the metastatic process will inform more targeted and mechanistic approaches that can abrogate challenges in treatment efficacy and toxicity. Several steps throughout the metastatic cascade, from angiogenesis to secondary tumor formation, offer specific vulnerabilities to therapies that can lead to the decline or cessation of metastatic progression. A deeper understanding of the metastatic cascade also allows combination systemic therapies to be used synergistically. In this review, we describe current treatment modalities in the context of multiple steps of the metastatic cascade. We highlight their mechanisms and present their efficacy across multiple cancers. This work also presents targets within the metastatic cascade in need of more research that can advance the landscape of treatments and lead to the goal of metastatic cancer remission.

From Blood to Therapy: The Revolutionary Application of Platelets in Cancer-Targeted Drug Delivery

Biomimetic nanodrug delivery systems based on cell membranes have emerged as a promising approach for targeted cancer therapy due to their biocompatibility and low immunogenicity. Among them, platelet-mediated systems are particularly noteworthy for their innate tumor-homing and cancer cell interaction capabilities. These systems utilize nanoparticles shielded and directed by platelet membrane coatings for efficient drug delivery. This review highlights the role of platelets in cancer therapy, summarizes the advancements in platelet-based drug delivery systems, and discusses their integration with other cancer treatments. Additionally, it addresses the limitations and challenges of platelet-mediated drug delivery, offering insights into future developments in this innovative field.

A Rare Case of Pyelonephritis With Methicillin-Resistant Staphylococcus aureus (MRSA) Bacteremia Complicated by Renal Vein Thrombosis

Pyelonephritis is a significant urinary tract infection (UTI) that can lead to serious complications, including bacteremia and renal vein thrombosis (RVT). This report presents a case of pyelonephritis caused by methicillin-resistant Staphylococcus aureus (MRSA), which progressed to RVT. We report a case of a 44-year-old male patient who presented with dysuria, increased urinary frequency, and urine retention over the past three days. His condition deteriorated, leading to reduced urine output and acute urinary retention. Notably, the patient did not report pyuria, hematuria, or fever, and there was no history of nephrolithiasis or recent urogenital procedures. Blood and urine cultures confirmed the presence of MRSA. A contrast-enhanced CT scan of the abdomen revealed left pyelonephritis complicated by abscess formation in both the left kidney and the prostate, as well as left RVT. This case highlights the potential complications of pyelonephritis, such as RVT, and underscores the importance of early diagnosis and intervention. Clinicians should maintain a high vigilance for RVT in patients with pyelonephritis and bacteremia, as timely management can significantly improve patient outcomes.

Olfactory Receptors and Aortic Aneurysm: Review of Disease Pathways

Aortic aneurysm, the pathological dilatation of the aorta at distinct locations, can be attributed to many different genetic and environmental factors. The resulting pathobiological disturbances generate a complex interplay of processes affecting cells and extracellular molecules of the tunica interna, media and externa. In short, aortic aneurysm can affect processes involving the extracellular matrix, lipid trafficking/atherosclerosis, vascular smooth muscle cells, inflammation, platelets and intraluminal thrombus formation, as well as various endothelial functions. Many of these processes are interconnected, potentiating one another. Newer discoveries, including the involvement of odorant olfactory receptors in these processes, have further shed light on disease initiation and pathology. Olfactory receptors are a varied group of G protein coupled-receptors responsible for the recognition of chemosensory information. Although they comprise many different subgroups, some of which are not well-characterized or identified in humans, odorant olfactory receptors, in particular, are most commonly associated with recognition of olfactory information. They can also be ectopically localized and thus carry out additional functions relevant to the tissue in which they are identified. It is thus the purpose of this narrative review to summarize and present pathobiological processes relevant to the initiation and propagation of aortic aneurysm, while also incorporating evidence associating these ectopically functioning odorant olfactory receptors with the overall pathology.

The natural flavonoid pinocembrin shows antithrombotic activity and suppresses septic thrombosis

Sepsis, an extreme host response to systemic infection, remains one of the leading causes of mortality worldwide. Platelets, which are integral to both thrombosis and inflammation, play a crucial role in the pathophysiology of sepsis. Excessive platelet activation and aggregation significantly increase the risk of thrombosis, thereby elevating mortality in septic patients. However, the etiology and treatment of this condition have not been comprehensively studied. This study identifies pinocembrin, a natural flavonoid compound derived from propolis, as a potential therapeutic agent for mitigating platelet activation and treating sepsis. In vivo, pinocembrin effectively inhibited FeCl3-induced carotid arterial occlusive thrombus formation and collagen/epinephrine-induced pulmonary thromboembolism in mouse models. In vitro, pinocembrin treatment suppressed multiple facets of platelet activation, including aggregation, secretion, and αIIbβ3-mediated signaling events. Mechanistically, pinocembrin repressed platelet functions by inhibiting Src/Syk/PLCγ2/MAPK signaling pathway. Using cecal ligation and puncture (CLP) mouse model to simulate human sepsis, pinocembrin reduced inflammatory cytokine release and septic thrombosis, thereby improving the survival rate of septic mice. Lipopolysaccharide (LPS)-induced model further substantiated these results. Overall, the inhibition of platelet activity by pinocembrin demonstrates significant therapeutic potential for managing life-threatening septic thrombosis.

Antiplatelet effects of the CEACAM1-derived peptide QDTT

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) restricts platelet activation via platelet collagen receptor GPVI/FcRγ-chain. In this study, screening against collagen-induced platelet aggregation was performed to identify functional CEACAM1 extracellular domain fragments. CEACAM1 fragments, including Ala-substituted peptides, were synthesized. Platelet assays were conducted on healthy donor samples for aggregation, cytotoxicity, adhesion, spreading, and secretion. Mice were used for tail bleeding and FeCl3-induced thrombosis experiments. Clot retraction was assessed using platelet-rich plasma. Extracellular segments of CEACAM1 and A1 domain-derived peptide QDTT were identified, while N, A2, and B domains showed no involvement. QDTT inhibited platelet aggregation. Ala substitution for essential amino acids (Asp139, Thr141, Tyr142, Trp144, and Trp145) in the QDTT sequence abrogated collagen-induced aggregation inhibition. QDTT also suppressed platelet secretion and "inside-out" GP IIb/IIIa activation by convulxin, along with inhibiting PI3K/Akt pathways. QDTT curtailed FeCl3-induced mesenteric thrombosis without significantly prolonging bleeding time, implying the potential of CEACAM1 A1 domain against platelet activation without raising bleeding risk, thus paving the way for novel antiplatelet drugs.

Optimizing Transmembrane Protein Assemblies in Nanodiscs for Structural Studies: A Comprehensive Manual

Membrane protein structures offer a more accurate basis for understanding their functional correlates when derived from full-length proteins in their native lipid environment. Producing such samples has been a primary challenge in the field. Here, we present robust, step-by-step biochemical and biophysical protocols for generating monodisperse assemblies of full-length transmembrane proteins within lipidic environments. These protocols are particularly tailored for cases where the size and molecular weight of the proteins align closely with those of the lipid islands (nanodiscs). While designed for single-span bitopic membrane proteins, these protocols can be easily extended to proteins with multiple transmembrane domains. The insights presented have broad implications across diverse fields, including biophysics, structural biology, and cryogenic electron microscopy (cryo-EM) studies. Key features • Overview of the sample preparation steps from protein expression and purification and reconstitution of membrane proteins in nanodiscs, as well as biobeads and lipids preparation. • Focus on single-span bitopic transmembrane proteins. • Includes protocols for validation procedures via characterization using biochemical, biophysical, and computational techniques. • Guide for cryogenic electron microscopy data acquisition from vitrification to image processing.

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.

SARS-CoV-2 spike protein potentiates platelet aggregation via upregulating integrin αIIbβ3 outside-in signaling pathway

Platelet hyperreactivity is one of the crucial causes of coagulative disorders in patients with COVID-19. Few studies have indicated that integrin αIIbβ3 may be a potential target for spike protein binding to platelets. This study aims to investigate whether spike protein interacts with platelet integrin αIIbβ3 and upregulates outside-in signaling to potentiate platelet aggregation. In this study, we found that spike protein significantly potentiated platelet aggregation induced by different agonists and platelet spreading in vitro. Mechanism studies revealed that spike protein upregulated the outside-in signaling, such as increased thrombin-induced phosphorylation of β3, c-Src. Moreover, using tirofiban to inhibit spike protein binding to αIIbβ3 or using PP2 to block outside-in signaling, we found that the potentiating effect of spike protein on platelet aggregation was abolished. These results demonstrate that SARS-CoV-2 spike protein directly enhances platelet aggregation via integrin αIIbβ3 outside-in signaling, and suggest a potential target for platelet hyperreactivity in patients with COVID-19. HIGHLIGHTS: • Spike protein potentiates platelet aggregation and upregulates αIIbβ3 outside-in signaling. • Spike protein interacts with integrin αIIbβ3 to potentiate platelet aggregation. • Blocking outside-in signaling abolishes the effect of spike protein on platelets.

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.

One immune cell to bind them all: platelet contribution to neurodegenerative disease

Alzheimer's disease (AD) and related dementias (ADRD) collectively affect a significant portion of the aging population worldwide. The pathological progression of AD involves not only the classical hallmarks of amyloid beta (Aβ) plaque buildup and neurofibrillary tangle development but also the effects of vasculature and chronic inflammatory processes. Recently, platelets have emerged as central players in systemic and neuroinflammation. Studies have shown that patients with altered platelet receptor expression exhibit accelerated cognitive decline independent of traditional risk factors. Additionally, platelets from AD patients exhibit heightened unstimulated activation compared to control groups. Platelet granules contain crucial AD-related proteins like tau and amyloid precursor protein (APP). Dysregulation of platelet exocytosis contributes to disease phenotypes characterized by increased bleeding, stroke, and cognitive decline risk. Recent studies have indicated that these effects are not associated with the quantity of platelets present in circulation. This underscores the hypothesis that disruptions in platelet-mediated inflammation and healing processes may play a crucial role in the development of ADRD. A thorough look at platelets, encompassing their receptors, secreted molecules, and diverse roles in inflammatory interactions with other cells in the circulatory system in AD and ADRD, holds promising prospects for disease management and intervention. This review discusses the pivotal roles of platelets in ADRD.

Differential Effect of Omega-3 Fatty Acids on Platelet Inhibition by Antiplatelet Drugs In Vitro

The omega-3 polyunsaturated fatty acids (PUFAs) Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA) exert multiple cardioprotective effects, influencing inflammation, platelet activation, endothelial function and lipid metabolism, besides their well-established triglyceride lowering properties. It is not uncommon for omega-3 PUFAs to be prescribed for hypertriglyceridemia, alongside antiplatelet therapy in cardiovascular disease (CVD) patients. In this regard, we studied the effect of EPA and DHA, in combination with antiplatelet drugs, in platelet aggregation and P-selectin and αIIbβ3 membrane expression. The antiplatelet drugs aspirin and triflusal, inhibitors of cyclooxygenase-1 (COX-1); ticagrelor, an inhibitor of the receptor P2Y12; vorapaxar, an inhibitor of the PAR-1 receptor, were combined with DHA or EPA and evaluated against in vitro platelet aggregation induced by agonists arachidonic acid (AA), adenosine diphosphate (ADP) and TRAP-6. We further investigated procaspase-activating compound 1 (PAC-1) binding and P-selectin membrane expression in platelets stimulated with ADP and TRAP-6. Both DHA and EPA displayed a dose-dependent inhibitory effect on platelet aggregation induced by AA, ADP and TRAP-6. In platelet aggregation induced by AA, DHA significantly improved acetylsalicylic acid (ASA) and triflusal's inhibitory activity, while EPA enhanced the inhibitory effect of ASA. In combination with EPA, ASA and ticagrelor expressed an increased inhibitory effect towards ADP-induced platelet activation. Both fatty acids could not improve the inhibitory effect of vorapaxar on AA- and ADP-induced platelet aggregation. In the presence of EPA, all antiplatelet drugs displayed a stronger inhibitory effect towards TRAP-6-induced platelet activation. Both omega-3 PUFAs inhibited the membrane expression of αIIbβ3, though they had no effect on P-selectin expression induced by ADP or TRAP-6. The antiplatelet drugs exhibited heterogeneity regarding their effect on P-selectin and αIIbβ3 membrane expression, while both omega-3 PUFAs inhibited the membrane expression of αIIbβ3, though had no effect on P-selectin expression induced by ADP or TRAP-6. The combinatory effect of DHA and EPA with the antiplatelet drugs did not result in enhanced inhibitory activity compared to the sum of the individual effects of each component.

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.

Dissecting the roles of dynamin and clathrin in platelet pinocytosis

Platelets endocytose many molecules from their environment. However, this process of pinocytosis in platelets is poorly understood. Key endocytic regulators such as dynamin, clathrin, CDC42 and Arf6 are expressed in platelets but their roles in pinocytosis is not known. Stimulated platelets form two subpopulations of pro-aggregatory and procoagulant platelets. The effect of stimulation on pinocytosis is also poorly understood. In this study, washed human platelets were treated with a range of endocytosis inhibitors and stimulated using different activators. The rate of pinocytosis was assessed using pHrodo green, a pH-sensitive 10 kDa dextran. In unstimulated platelets, pHrodo fluorescence increased over time and accumulated as intracellular puncta indicating constituently active pinocytosis. Stimulated platelets (both pro-aggregatory and procoagulant) had an elevated pinocytosis rate compared to unstimulated platelets. Dynamin inhibition blocked pinocytosis in unstimulated, pro-aggregatory and procoagulant platelets indicating that most platelet pinocytosis is dynamin dependent. Although pinocytosis was clathrin-independent in unstimulated and procoagulant populations, clathrin partially contributed to pinocytosis in pro-aggregatory platelets.

Myricetin reduces platelet PANoptosis in sepsis to delay disseminated intravascular coagulation

Sepsis is a severe inflammatory disease characterized by cytokine storm, often accompanied by disseminated intravascular coagulation (DIC). PANoptosis is a novel form of cell death triggered by cytokine storms, characterized by a cascade reaction of pyroptosis, apoptosis, and necroptosis. It exists in septic platelets and is closely associated with the onset and progression of DIC. However, there remains an unmet need for drugs targeting PANoptosis. The anti-PANoptosis effect of myricetin was predicted using network pharmacology and confirmed through molecular docking. In vitro platelet activation models demonstrated that myricetin significantly attenuated platelet particle release, integrin activation, adhesion, spreading, clot retraction, and aggregation. Moreover, in a sepsis model, myricetin reduced inflammatory infiltration in lung tissue and platelet activation while improving DIC. Additionally, whole blood sequencing samples from sepsis patients and healthy individuals were analyzed to elucidate the up-regulation of the PANoptosis targets. Our findings demonstrate the inhibitory effect of myricetin on septic platelet PANoptosis, indicating its potential as a novel anti-cellular PANoptosis candidate and therapeutic agent for septic DIC. Furthermore, our study establishes a foundation for utilizing network pharmacology in the discovery of new drugs to treat various diseases.

Heat stress-induced platelet dysfunction is associated with loss of fibrinogen and is improved by fibrinogen supplementation

INTRODUCTION

Heatstroke is a critical heat-related condition characterized by coagulopathy and multiple organ dysfunction. One of the most severe complications of heatstroke is disseminated intravascular coagulation. This condition manifests as excessive clot formation and bleeding that are primarily due to platelet depletion and dysfunction. Fibrinogen plays a crucial role in hemostasis because it links integrin αIIbβ3 on adjacent platelets, thereby promoting the platelet activation and aggregation necessary for clot formation. However, reduced fibrinogen levels may impair the formation of the initial platelet plug and increase the risk of bleeding. The current study explored the effect of fibrinogen on platelet dysfunction in a heatstroke model.

MATERIALS AND METHODS

Male Wistar rats were subjected to heat stress, and subsequent changes in hemodynamic, biochemical, and coagulation parameters were analyzed. Platelet viability, aggregation, adhesion, spreading and fibrin clot retraction were assessed.

RESULTS

The rats with heatstroke exhibited a variety of clinical symptoms, including hypotension, tachycardia, multiple organ dysfunction, and coagulopathy. Platelet viability in the heatstroke group was comparable to that in the healthy control group. However, the heatstroke group exhibited significant reductions in plasma fibrinogen levels and platelet aggregation, adhesion, spreading, and fibrin clot retraction. Notably, fibrinogen supplementation markedly augmented the aggregation responses of platelets in the heatstroke group. The impairment of platelet adhesion, spreading, and fibrin clot retraction in the rats with heatstroke was partially ameliorated by fibrinogen supplementation.

CONCLUSIONS

An early use of fibrinogen replacement may serve as a therapeutic intervention to alleviate platelet hyporeactivity and prevent the complications in patients with heatstroke.

From bench to bedside: Platelet biomimetic nanoparticles as a promising carriers for personalized drug delivery

In recent decades, there has been a burgeoning interest in cell membrane coating strategies as innovative approach for targeted delivery systems in biomedical applications. Platelet membrane-coated nanoparticles (PNPs), in particular, are gaining interest as a new route for targeted therapy due to their advantages over conventional drug therapies. Their stepwise approach blends the capabilities of the natural platelet membrane (PM) with the adaptable nature of manufactured nanomaterials, resulting in a synergistic combination that enhances drug delivery and enables the development of innovative therapeutics. In this context, we present an overview of the latest advancements in designing PNPs with various structures tailored for precise drug delivery. Initially, we describe the types, preparation methods, delivery mechanisms, and specific advantages of PNPs. Next, we focus on three critical applications of PNPs in diseases: vascular disease therapy, cancer treatment, and management of infectious diseases. This review presents our knowledge of PNPs, summarizes their advancements in targeted therapies and discusses the promising potential for clinical translation of PNPs.

Thrombotic events associated with immune checkpoint inhibitors and novel antithrombotic strategies to mitigate bleeding risk

Although immunotherapy is expanding treatment options for cancer patients, the prognosis of advanced cancer remains poor, and these patients must contend with both cancers and cancer-related thrombotic events. In particular, immune checkpoint inhibitors are associated with an increased risk of atherosclerotic thrombotic events. Given the fundamental role of platelets in atherothrombosis, co-administration of antiplatelet agents is always indicated. Platelets are also involved in all steps of cancer progression. Classical antithrombotic drugs can cause inevitable hemorrhagic side effects due to blocking integrin β3 bidirectional signaling, which regulates simultaneously thrombosis and hemostasis. Meanwhile, many promising new targets are emerging with minimal bleeding risk and desirable anti-tumor effects. This review will focus on the issue of thrombosis during immune checkpoint inhibitor treatment and the role of platelet activation in cancer progression as well as explore the mechanisms by which novel antiplatelet therapies may exert both antithrombotic and antitumor effects without excessive bleeding risk.

The Combination of Natural Compounds Escin-Bromelain-Ginkgo Biloba-Sage Miltiorrhiza (EBGS) Reduces Platelet Adhesion to TNFα-Activated Vascular Endothelium through FAK Signaling

Thrombosis is a key process that determines acute coronary syndrome and ischemic stroke and is the leading cause of morbidity and mortality in the world, together with cancer. Platelet adhesion and subsequent activation and aggregation are critical processes that cause thrombus formation after endothelial damage. To date, high hopes are associated with compounds of natural origin, which show anticoagulant action without undesirable effects and can be proposed as supportive therapies. We investigated the effect of the new combination of four natural compounds, escin-bromelain-ginkgo biloba-sage miltiorrhiza (EBGS), on the initial process of the coagulation cascade, which is the adhesion of platelets to activated vascular endothelium. Our results demonstrated that EBGS pretreatment of endothelial cells reduces platelet adhesion even in the presence of the monocyte-lymphocyte population. Our data indicate that EBGS exerts its effects by inhibiting the transcription of adhesion molecules, including P-selectin, platelet membrane glycoprotein GP1b, integrins αV and β3, and reducing the secretion of the pro-inflammatory cytokines interleukin 6, interleukin 8, and the metalloproteinases MMP-2 and MMP-9. Furthermore, we demonstrated that EBGS inhibited the expression of focal adhesion kinase (FAK), strictly involved in platelet adhesion, and whose activity is correlated with that of integrin β3. The results shown in this manuscript suggest a possible inhibitory role of the new combination EBGS in the reduction in platelet adhesion to activated endothelium, thus possibly preventing coagulation cascade initiation.

Biomedical application of TiO2NPs can cause arterial thrombotic risks through triggering procoagulant activity, activation and aggregation of platelets

BACKGROUND

Titanium dioxide nanoparticles (TiO2NPs) are widely used in medical application. However, the relevant health risk has not been completely assessed, the potential of inducing arterial thrombosis (AT) in particular.

METHODS

Alterations in platelet function and susceptibility to arterial thrombosis induced by TiO2NPs were examined using peripheral blood samples from healthy adult males and an in vivo mouse model, respectively.

RESULTS

Here, using human platelets (hPLTs) freshly isolated from health volunteers, we demonstrated TiO2NP treatment triggered the procoagulant activity of hPLTs through phosphatidylserine exposure and microvesicles generation. In addition, TiO2NP treatment increased the levels of glycoprotein IIb/IIIa and P-selectin leading to aggregation and activation of hPLTs, which were exacerbated by providing physiology-mimicking conditions, including introduction of thrombin, collagen, and high shear stress. Interestingly, intracellular calcium levels in hPLTs were increased upon TiO2NP treatment, which were crucial in TiO2NP-induced hPLT procoagulant activity, activation and aggregation. Moreover, using mice in vivo models, we further confirmed that TiO2NP treatment a reduction in mouse platelet (mPLT) counts, disrupted blood flow, and exacerbated carotid arterial thrombosis with enhanced deposition of mPLT.

CONCLUSIONS

Together, our study provides evidence for an ignored health risk caused by TiO2NPs, specifically TiO2NP treatment augments procoagulant activity, activation and aggregation of PLTs via calcium-dependent mechanism and thus increases the risk of AT.

Cancer progression and tumor hypercoagulability: a platelet perspective

Venous thromboembolism, which is common in cancer patients and accompanies or even precedes malignant tumors, is known as cancer-related thrombosis and is an important cause of cancer- associated death. At present, the exact etiology of the elevated incidence of venous thrombosis in cancer patients remains elusive. Platelets play a crucial role in blood coagulation, which is intimately linked to the development of arterial thrombosis. Additionally, platelets contribute to tumor progression and facilitate immune evasion by tumors. Tumor cells can interact with the coagulation system through various mechanisms, such as producing hemostatic proteins, activating platelets, and directly adhering to normal cells. The relationship between platelets and malignant tumors is also significant. In this review article, we will explore these connections.

Ultra-Hydrophobic Gauze Driving Super-Haemostasis

Controlling bleeding by applying pressing cotton gauze is the most facile treatment in prehospital emergencies. However, the wettable nature of cotton fibers leads to unnecessary blood loss due to excessive blood absorption, inseparable adhesion-induced pain, and pliable to infection. Here, a kind of ultra-hydrophobic haemostatic anti-adhesive gauze whose surface is loaded with polydimethylsiloxane (PDMS) and hydrophobic-modified cellulose nanocrystals (CNCs), achieving a water contact angle of ≈160° is developed. It is demonstrated that the mechanism by which hydrophobic CNCs promote blood clotting is associated with their ability to activate coagulation factors, contributing to fibrin formation, and promoting platelet activation. The blood-restricting effect results from the low surface energy layer formed by PDMS and then the alkyl chains of hydrophobic CNCs are combined. The produced ultra-hydrophobic gauze resists blood flow and diffusion, decreases blood loss, is effortlessly peelable, and minimizes pathogen adhesion. Compared to the commercial cotton gauze, this gauze achieved effective haemostasis and antiadhesion by reducing blood loss by more than 90%, shortening haemostasis time by more than 75%, lowering peeling force by more than 90% and minifying bacterium attachment by more than 95%. This work presents promising applications in terms of prehospital first aid.

Icaritin Sensitizes Thrombin- and TxA2-Induced Platelet Activation and Promotes Hemostasis via Enhancing PLCγ2-PKC Signaling Pathways

BACKGROUND

 Vascular injury results in uncontrollable hemorrhage in hemorrhagic diseases and excessive antithrombotic therapy. Safe and efficient hemostatic agents which can be orally administered are urgently needed. Platelets play indispensable roles in hemostasis, but there is no drug exerting hemostatic effects through enhancing platelet function.

METHODS

 The regulatory effects of icaritin, a natural compound isolated from Herba Epimedii, on the dense granule release, thromboxane A2 (TxA2) synthesis, α-granule release, activation of integrin αIIbβ3, and aggregation of platelets induced by multiple agonists were investigated. The effects of icaritin on tail vein bleeding times of warfarin-treated mice were also evaluated. Furthermore, we investigated the underlying mechanisms by which icaritin exerted its pharmacological effects.

RESULTS

 Icaritin alone did not activate platelets, but significantly potentiated the dense granule release, α-granule release, activation of integrin αIIbβ3, and aggregation of platelets induced by thrombin and U46619. Icaritin also shortened tail vein bleeding times of mice treated with warfarin. In addition, phosphorylated proteome analysis, immunoblotting analysis, and pharmacological research revealed that icaritin sensitized the activation of phospholipase Cγ2 (PLCγ2)-protein kinase C (PKC) signaling pathways, which play important roles in platelet activation.

CONCLUSION

 Icaritin can sensitize platelet activation induced by thrombin and TxA2 through enhancing the activation of PLCγ2-PKC signaling pathways and promote hemostasis, and has potential to be developed into a novel orally deliverable therapeutic agent for hemorrhages.

Advancements in precision nanomedicine design targeting the anoikis-platelet interface of circulating tumor cells

Tumor metastasis, the apex of cancer progression, poses a formidable challenge in therapeutic endeavors. Circulating tumor cells (CTCs), resilient entities originating from primary tumors or their metastases, significantly contribute to this process by demonstrating remarkable adaptability. They survive shear stress, resist anoikis, evade immune surveillance, and thwart chemotherapy. This comprehensive review aims to elucidate the intricate landscape of CTC formation, metastatic mechanisms, and the myriad factors influencing their behavior. Integral signaling pathways, such as integrin-related signaling, cellular autophagy, epithelial-mesenchymal transition, and interactions with platelets, are examined in detail. Furthermore, we explore the realm of precision nanomedicine design, with a specific emphasis on the anoikis‒platelet interface. This innovative approach strategically targets CTC survival mechanisms, offering promising avenues for combatting metastatic cancer with unprecedented precision and efficacy. The review underscores the indispensable role of the rational design of platelet-based nanomedicine in the pursuit of restraining CTC-driven metastasis.

Integrins as a bridge between bacteria and cells: key targets for therapeutic wound healing

Integrins are heterodimers composed of α and β subunits that are bonded through non-covalent interactions. Integrins mediate the dynamic connection between extracellular adhesion molecules and the intracellular actin cytoskeleton. Integrins are present in various tissues and organs where these heterodimers participate in diverse physiological and pathological responses at the molecular level in living organisms. Wound healing is a crucial process in the recovery from traumatic diseases and comprises three overlapping phases: inflammation, proliferation and remodeling. Integrins are regulated during the entire wound healing process to enhance processes such as inflammation, angiogenesis and re-epithelialization. Prolonged inflammation may result in failure of wound healing, leading to conditions such as chronic wounds. Bacterial colonization of a wound is one of the primary causes of chronic wounds. Integrins facilitate the infectious effects of bacteria on the host organism, leading to chronic inflammation, bacterial colonization, and ultimately, the failure of wound healing. The present study investigated the role of integrins as bridges for bacteria-cell interactions during wound healing, evaluated the role of integrins as nodes for bacterial inhibition during chronic wound formation, and discussed the challenges and prospects of using integrins as therapeutic targets in wound healing.

Current Advances in Nanomaterials Affecting Functions and Morphology of Platelets

Nanomaterials have been extensively used in the biomedical field due to their unique physical and chemical properties. They promise wide applications in the diagnosis, prevention, and treatment of diseases. Nanodrugs are generally transported to target tissues or organs by coupling targeting molecules or enhanced permeability and retention effect (EPR) passively. As intravenous injection is the most common means of administration of nanomedicine, the transport process inevitably involves the interactions between nanoparticles (NPs) and blood cells. Platelets are known to not only play a critical role in normal coagulation by performing adhesion, aggregation, release, and contraction functions, but also be associated with pathological thrombosis, tumor metastasis, inflammation, and immune reactions, making it necessary to investigate the effects of NPs on platelet function during transport, particularly the way in which their physical and chemical properties determine their interaction with platelets and the underlying mechanisms by which they activate and induce platelet aggregation. However, such data are lacking. This review is intended to summarize the effects of NPs on platelet activation, aggregation, release, and apoptosis, as well as their effects on membrane proteins and morphology in order to shed light on such key issues as how to reduce their adverse reactions in the blood system, which should be taken into consideration in NP engineering.

Potential Mechanism of Platelet GPIIb/IIIa and Fibrinogen on Retinal Vein Occlusion

PURPOSE

To explore the role of coagulation and fibrinolytic factors, and the potential mechanism of platelet aggregation in the pathogenesis of retinal vein occlusion.

METHODS

Coagulation and fibrinolytic parameters in patients with retinal vein occlusion were determined using hemagglutinin and HISCL-5000. Relationships between these elevated parameters and factors representing typical clinical manifestations of retinal vein occlusion were examined, and these parameters were analyzed using a STRING database to indicate the potential role of platelet aggregation. Platelet glycoprotein IIb/IIIa (GPIIb/IIIa) levels were evaluated by flow cytometry after antiplatelet treatment in patients and mouse models. Furthermore, the GPIIb/IIIa ligand fibrinogen in peripheral blood and retina of mouse models was assessed by the turbidimetric method and real-time PCR, respectively.

RESULTS

In patients, significant increases in peripheral blood fibrinogen and GPIIb/IIIa levels were observed (p = 0.0040, p < 0.0001, respectively). A positive correlation was observed between macular thickness (MT) and both fibrinogen and GPIIb/IIIa (r = 0.4528, p = 0.0063; r = 0.3789, p = 0.0427, respectively). After intravitreal injections of anti-vascular endothelial growth factor drugs, a significant reduction in fibrinogen levels was observed (p = 0.0072). In addition, the use of antiplatelet drugs resulted in a significant decrease in GPIIb/IIIa (p < 0.0001). In a mouse model, antiplatelet therapy significantly reduced both peripheral blood and retina fibrinogen levels and the overall rate of vein occlusion 3 days after occlusion (p < 0.0005). In addition, the reduction in GPIIb/IIIa levels after antiplatelet therapy was remarkable.

CONCLUSION

Fibrinogen and GPIIb/IIIa may be involved in retinal vein occlusion and blocking platelet aggregation may be a new therapeutic approach for retinal vein occlusion.

Nanoscale insights into hematology: super-resolved imaging on blood cell structure, function, and pathology

Fluorescence nanoscopy, also known as super-resolution microscopy, has transcended the conventional resolution barriers and enabled visualization of biological samples at nanometric resolutions. A series of super-resolution techniques have been developed and applied to investigate the molecular distribution, organization, and interactions in blood cells, as well as the underlying mechanisms of blood-cell-associated diseases. In this review, we provide an overview of various fluorescence nanoscopy technologies, outlining their current development stage and the challenges they are facing in terms of functionality and practicality. We specifically explore how these innovations have propelled forward the analysis of thrombocytes (platelets), erythrocytes (red blood cells) and leukocytes (white blood cells), shedding light on the nanoscale arrangement of subcellular components and molecular interactions. We spotlight novel biomarkers uncovered by fluorescence nanoscopy for disease diagnosis, such as thrombocytopathies, malignancies, and infectious diseases. Furthermore, we discuss the technological hurdles and chart out prospective avenues for future research directions. This review aims to underscore the significant contributions of fluorescence nanoscopy to the field of blood cell analysis and disease diagnosis, poised to revolutionize our approach to exploring, understanding, and managing disease at the molecular level.

Application of Funnel Metadynamics to the Platelet Integrin αIIbβ3 in Complex with an RGD Peptide

Integrin αIIbβ3 mediates platelet aggregation by binding the Arginyl-Glycyl-Aspartic acid (RGD) sequence of fibrinogen. RGD binding occurs at a site topographically proximal to the αIIb and β3 subunits, promoting the conformational activation of the receptor from bent to extended states. While several experimental approaches have characterized RGD binding to αIIbβ3 integrin, applying computational methods has been significantly more challenging due to limited sampling and the need for a priori information regarding the interactions between the RGD peptide and integrin. In this study, we employed all-atom simulations using funnel metadynamics (FM) to evaluate the interactions of an RGD peptide with the αIIb and β3 subunits of integrin. FM incorporates an external history-dependent potential on selected degrees of freedom while applying a funnel-shaped restraint potential to limit RGD exploration of the unbound state. Furthermore, it does not require a priori information about the interactions, enhancing the sampling at a low computational cost. Our FM simulations reveal significant molecular changes in the β3 subunit of integrin upon RGD binding and provide a free-energy landscape with a low-energy binding mode surrounded by higher-energy prebinding states. The strong agreement between previous experimental and computational data and our results highlights the reliability of FM as a method for studying dynamic interactions of complex systems such as integrin.

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.

An age-progressive platelet differentiation path from hematopoietic stem cells causes exacerbated thrombosis

Platelet dysregulation is drastically increased with advanced age and contributes to making cardiovascular disorders the leading cause of death of elderly humans. Here, we reveal a direct differentiation pathway from hematopoietic stem cells into platelets that is progressively propagated upon aging. Remarkably, the aging-enriched platelet path is decoupled from all other hematopoietic lineages, including erythropoiesis, and operates as an additional layer in parallel with canonical platelet production. This results in two molecularly and functionally distinct populations of megakaryocyte progenitors. The age-induced megakaryocyte progenitors have a profoundly enhanced capacity to engraft, expand, restore, and reconstitute platelets in situ and upon transplantation and produce an additional platelet population in old mice. The two pools of co-existing platelets cause age-related thrombocytosis and dramatically increased thrombosis in vivo. Strikingly, aging-enriched platelets are functionally hyper-reactive compared with the canonical platelet populations. These findings reveal stem cell-based aging as a mechanism for platelet dysregulation and age-induced thrombosis.

WY-14643, a novel antiplatelet and antithrombotic agent targeting the GPIbα receptor

BACKGROUND AND PURPOSE

Hypolipidemia and platelet activation play key roles in atherosclerotic diseases. Pirinixic acid (WY-14643) was originally developed as a lipid-lowering drug. Here we focused on its antiplatelet and antithrombotic abilities and the underlying mechanism.

EXPERIMENTAL APPROACH

The effects of WY-14643 on platelet aggregation was measured using a lumi-aggregometer. Clot retraction and spreading on fibrinogen were also assayed. PPARα-/- platelets were used to identify the target of WY-14643. The interaction between WY-14643 and glycoprotein Ibα (GPIbα) was detected using cellular thermal shift assay (CETSA), surface plasmon resonance (SPR) spectroscopy and molecular docking. GPIbα downstream signaling was examined by Western blot. The antithrombotic effect was investigated using mouse mesenteric arteriole thrombosis model. Mouse tail bleeding model was used to study its effect on bleeding side effects.

KEY RESULTS

WY-14643 concentration-dependently inhibits human washed platelet aggregation, clot retraction, and spreading. Significantly, WY-14643 inhibits thrombin-induced activation of human washed platelets with an IC50 of 7.026 μM. The antiplatelet effect of WY-14643 is mainly dependent of GPIbα. CESTA, SPR and molecular docking results indicate that WY-14643 directly interacts with GPIbα and acts as a GPIbα antagonist. WY-14643 also inhibits phosphorylation of PLCγ2, Akt, p38, and Erk1/2 induced by thrombin. Noteworthily, 20 mg/kg oral administration of WY-14643 inhibits FeCl3-induced thrombosis of mesenteric arteries in mice similarly to clopidogrel without increasing bleeding.

CONCLUSION AND IMPLICATIONS

WY-14643 is not only a PPARα agonist with lipid-lowering effect, but also an antiplatelet agent as a GPIbα antagonist. It may have more significant therapeutic advantages than current antiplatelet agents for the treatment of atherosclerotic thrombosis, which have lipid-lowering effects without bleeding side effects.

1,25-Dihydroxyvitamin D3 attenuates platelet aggregation potentiated by SARS-CoV-2 spike protein via inhibiting integrin αIIbβ3 outside-in signaling

Platelet hyperreactivity contributes to the pathogenesis of COVID-19, which is associated with a hypercoagulability state and thrombosis disorder. It has been demonstrated that Vitamin D deficiency is associated with the severity of COVID-19 infection. Vitamin D supplement is widely used as a dietary supplement due to its safety and health benefits. In this study, we investigated the direct effects and underlying mechanisms of 1,25(OH)2D3 on platelet hyperreactivity induced by SRAS-CoV-2 spike protein via Western blot and platelet functional studies in vitro. Firstly, we found that 1,25(OH)2D3 attenuated platelet aggregation and Src-mediated signaling. We further observed that 1,25(OH)2D3 attenuated spike protein-potentiated platelet aggregation in vitro. Mechanistically, 1,25(OH)2D3 attenuated spike protein upregulated-integrin αIIbβ3 outside-in signaling such as platelet spreading and the phosphorylation of β3, c-Src and Syk. Moreover, using PP2, the Src family kinase inhibitor to abolish spike protein-stimulated platelet aggregation and integrin αIIbβ3 outside-in signaling, the combination of PP2 and 1,25(OH)2D3 did not show additive inhibitory effects on spike protein-potentiated platelet aggregation and the phosphorylation of β3, c-Src and Syk. Thus, our data suggest that 1,25(OH)2D3 attenuates platelet aggregation potentiated by spike protein via downregulating integrin αIIbβ3 outside-in signaling.